Title of Invention	AN AUTOMATIC SYSTEM FOR MEASUREMENT OF LENGTH OF MOVING PRODUCT
Abstract	The present invention is directed to an automatic online length measuring system for moving products including moving billets in rolling mills. The system automatically measures the various base lengths of billets, minimizing measuring error and reduce scrap. Moving billet length is measured by a single array of different phototransistors to sense the front end and dual phototransistors (DS) as reference/zero to sense the back end, placed at selective distances from centre of sensor stack(SS), favoring measurement of three base lengths with desired accuracy defined by selected range( R ) of 550mm and least count (Ic ) of 50mm. The front end(FP) pulse and the back end(BP) pulse from sensors are logically processed to get the length pulse(LP) that represents the length of moving billet, indicated on a display unit(DU) by LEDs. The speed of flying shear is adjusted by the operator directly from pulpit and limiting the error of measurement to 0 to 50mm or 0-0.3% reducing from about ± 250mm obtained in conventional methods.

Title of Invention

AN AUTOMATIC SYSTEM FOR MEASUREMENT OF LENGTH OF MOVING PRODUCT

Abstract

The present invention is directed to an automatic online length measuring system for moving products including moving billets in rolling mills. The system automatically measures the various base lengths of billets, minimizing measuring error and reduce scrap. Moving billet length is measured by a single array of different phototransistors to sense the front end and dual phototransistors (DS) as reference/zero to sense the back end, placed at selective distances from centre of sensor stack(SS), favoring measurement of three base lengths with desired accuracy defined by selected range( R ) of 550mm and least count (Ic ) of 50mm. The front end(FP) pulse and the back end(BP) pulse from sensors are logically processed to get the length pulse(LP) that represents the length of moving billet, indicated on a display unit(DU) by LEDs. The speed of flying shear is adjusted by the operator directly from pulpit and limiting the error of measurement to 0 to 50mm or 0-0.3% reducing from about ± 250mm obtained in conventional methods.

Full Text	FIELD OF INVENTION: The present invention is directed to a very simple and low cost photosensor based automatic online length measuring system for moving products avoiding operator's involvement especially in hazardous/accident prone sites. The system is adapted to directly and automatically measure the various base lengths of moving billets at high temperatures, in the rolling mill in any steel plant, with higher accuracy for minimizing measuring error and also minimizing generation of scrap. The present new system controls the billet length by a single array(stack) of different photosensor/phototransistors to sense the front end and a dual phototransistors, which act as the reference/zero sensor, to sense the back end, being placed at selective distant locations from centre of sensor stack, favoring measurement of selective three base lengths of moving billets such as 5m, 6m and 12m with desired degree of accuracy, decided by end uses of such billets. The signal pulses generated by the front end and the back end sensors are logically processed to get another pulse that represents the length of moving billet. The length is finally indicated by said pulses on a display unit by means of selective LED indicators. The invention also provide means for faster adjustment of the speed of flying shear motor according to most recent measurement(from visual display unit) of a base length by the operator directly from pulpit, such that the error of measurement is limited to 0 to 50mm (or 0-0.3% that is further adjustable) in place of about ± 250mm obtained in conventional methods of similar measurements. Thus the present invention has the potential for wide scale industrial applications, particularly in measurement of base lengths of billets in rolling mill in steel plants. BACKGROUND AND PRIOR ART: The present invention relate to the development of the measuring system for a continuous rolling mill of blooms to billets. Usually, 5 meter long hot blooms of section 340mm x 300mm are rolled through ten numbers of rolling stands for successive reduction to the section of a billet. The blooms are converted to billets of 2 section 105 mm x105mm of varying continuous lengths ranging from 150 meter to 160 meter. For fulfilling the need of wire rod mill, merchant mill and other foreign customers, the long stream of billets are cut into smaller standard base lengths e.g. 12 meter, 6 meter and 5 meter, by means of two rotating blades, also called the flying shear which are coupled with separately excited DC drive motor with 1.1MW capacity. The conventional method of measuring the base lengths for the rolled out billets was achieved by the attending operator by crossing the 35 meter long cobble prone area to measure the billet length by using the mechanical measuring scale and running back to pulpit for adjusting the speed of flying shear motor depending on the direction of deviation from base length noted in the last measurements. Moreover, pneumatically operated stoppers used to stop the motion of billets to facilitate measurement, which itself incorporated some error due to play in said stopper in either direction. The operator was thus subjected to frequent accident in this crude method involving physical movements/running for measurement and adjustments in the hot cobble prone transfer zone. The conventional measuring process thus suffered from accidents, delay and inaccuracy in measurement, high volume of scrap and loss of productivity. A host of factors in the said conventional process were thus responsible for and led to variation/deviation in the standard base lengths intended to be cut from the continuous lengths rolled out from a bloom. This in turn led to increased scrap and loss of productivity. Such factors causing deviation of measurement of base lengths of billets included: Speed of flying shear motor could not be precisely adjusted as the angular velocity of flying shear blades could not be synchronized with the linear velocity of billets in particular ratio due to metallurgical and mechanical problems involved in rolling of billets from hot blooms. Parallax error in measuring cut billet length by using mechanical scale was another factor responsible for forced deviation in measured base length, the range of varying parallax being 30 to 50 mm. In the conventional method the billets were measured in stationary condition, after lifting the pneumatically operated flexible stopper which itself suffered from a play ranging from +50mm to -50mm from its normal position. 3 Yet another element of error causing forced deviation of measurement of base lengths in conventional method, was induced by delay in the measurement and also delay in applying the correction of speed of the flying shear motor lead to generate either longer or shorter billets, the number of such erroneous billet lengths obtained being 8 to 14 from each bloom. Loss of productivity was also caused in conventional method, due to the variation in base length in a sense that the longer length billets jammed the furnaces of the successive mills for longer times while the shorter length billets reduce the productivity/yield of the rolling mills. It was thus the long perceived need for developing a system of measurement of the various base lengths of the billets in the rolling mills where they are rolled out from blooms for continuous lengths of billet sections for required cutting by flying shear directed to more accurate measurement of various base lengths of billets standardized to meet the requirements of re-rolling in the wire rod mill and merchant mill and also the demand of outside customers including the overseas buyers. It was also the need to eliminate the limitations of the conventional measurement method as already discussed in order to achieve quality, productivity, safety and economy in billet rolling mill operations. Alternative measuring systems capable to measure length of moving billets and other similar products with precision and in a safe manner was explored in last few years. Measuring systems involving laser and charged coupled devices were tried during last 7-8 years in continuous casting shop with the involvement of some of the eminent instrument manufacturers including M/s American Sensor Manufacture Limited who tried such systems for measuring moving billet lengths but failed to establish an accurate method to measure the even length, although the systems were suitable for measuring dimensions of slab. The Charged Coupled Device (CCD) Camera which was installed in blooming mil! of steel plant was found to be not suitable for application in Continuous Casting Shop(CCS) because of fluctuation in surface temperature of slab. The system of measuring length of moving billet, according to the present invention was thus achieved by installing a single array of photosensors stack that takes care of wide length variation in three different base 4 lengths. Also a simple single array of Light Emitting Diodes (LED) displays the respective lengths by using few digital logic gates. The following comparative study of the present system as compared to the other expensive alternative means for such measurement of length of moving products like the Shaft Encoder, Laser Doppler, CCD based Camera etc. reveals its advantages, simplicity , cost effective yet an accurate means of measurement. A. Shaft Encoder: These instruments are capable of conducting two types of measurements -Incremental type and Absolute type. In either type of measurements, when applied to measure length of moving billets they are subjected to errors/constraints due to factors like wear and tear of rolls, non- contact/slip between rolls and billet, glitches unmeasured pulses, failure of coupling, hydraulically pressed roll needs continuous adjustment, it needs cooling. The error in measurement varies from 0.1% to more than 3% depending on interval of calibration. The cost of the instrument/system is about 0.06 million US dollars. B. Laser based systems :(i) Laser Doppler suffers from error incorporated due to tilting of reflecting plane of moving billet; (ii) Laser Interferometer is subjected to system failure due to dust deposition on lens; (iii) Laser Triangulation device needs continuous adjustments and complex circuitry has to be maintained;(iv) Pulse radar system based on (a) time of flight and (b) amplitude measurements, having the limitation that the object should be visible from the laser source without obstruction, there is hardly any gap between the two successive pieces and for accurate response the system needs (a) 0.001 nano seconds timer, (b) roughness of reflecting plane induces error. The Extent of error in Laser based systems ranges from 0.01% to over 0.3%. The cost including installation of a system in million US dollars is about 0.3 for laser Doppler/interferometer, about 0.05 for laser triangulation and about 0.01 for pulse radar device. C. CCD Camera: This system of measurement suffer from limitations like difficulty in sensing the edges of billets and its scaling, obstruction free area to view for the camera that is hardly possible to be maintained at shop floor. The system has further constraints like continuous supply of water is needed 5 to cool its electronic components, needs huge structure to install the system, images obtained in the scale of 1:100/1000, at least 200mm gap is required between two successive billets for distinctive measurement of dimensions. The error in measurement by the CCD camera varies from 0.1% to more than 0.3%, the threshold limit for the error percent can however be adjusted by means of software. The cost of installation for such CCD system is around 0.02 million US dollars. D. Load cell based system: these systems need major installation work where in the dimensions are calculated in an indirect way by dividing volume/weight by cross section, needing continuous calibration. The error in measurement is also on account of variation in cross section of rolled product by about ±10%. The magnitude of error in such systems ranges from 0.1% to more than 0.3% and the cost of installation is of the order of 0.2 million US dollars. E. Orbis coil : This system can measure the total cross section but not the height/width of the object; it is not capable to work at higher speed of moving product; this systems suffer from poor response time; it is difficult to install such systems in existing mills and need wide gap between edges of two pieces to be measured distinctively. In order to overcome the limitations of the above conventional methods, a low cost Photo-sensor based new system of the present invention is developed on the basis of completely blocking the view of focus object of sensors and is a distance based system that needs no calibration on working span of time. The system is a 1:1 scaling by putting sensors 50mm away from hot moving object and need no external cooling, no air purging for cleaning and its performance is unaffected by any vibration of the product/roll table; such system involves simple circuit using low cost components. The system has capability to measure dimension/length of moving hot billets within error limit of 0% to 0.3% depending upon the least count that is adjustable. The system is a low cost device, price of which is only about 60 US dollars. 6 It is thus evident from the aforesaid discussions, that the present invention is providing a simple and low cost system of measurement of dimension/length of hot moving billet in rolling mill of steel plants with high accuracy and reliability, maintaining safety of the operator attending to the rolling stands for the billets. The new system also eliminate the difficulty of measurement by the operator in the existing system wherein he needs to run in between high temperature cobble prone area to measure the billet lengths subsequently for its length correction thereby he was meeting frequent accidents. The new system according to the present invention is capable to display the base length of each billet right in the pulpit itself and thereby ensuring safety of the operator against hot cobbled metal/billet. The developed system also facilitate faster control on the billet length by quickly adjusting the speed of flying shear motor according to requirement and Thus limiting the measurement error within 0 to +50mm in place of existing level of +/-250mm. Also, web search on the prior art in related field of length/dimension measurement of moving product revealed, that such simple, safe, accurate and low cost system involving phototransistors/photo-sensor is novel and not available in any earlier publications/patent applications. The present invention is also capable to minimize scrap by adopting measurement with higher precision and thereby improving productivity/yield of the rolling mills and as such having potential for wide scale industrial application in steel and other industries, where the system can be applied with advantage. OBJECTS OF THE INVENTION: The basic object of the present invention is therefore directed to developing an automatic system using photosensors to measure the length of moving products in industry and in particular measuring hot moving billets in rolling mills of steel plants in. a safe, more accurate, reliable and economical method and thereby create 7 substantial financial saving running into a few crores over a year by way of savings on scrap only. A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants such that the prevailing practice of frequent unsafe hasty movement of the operator in the hot cobble prone zone in rolling mill for measurement/adjustments is avoided to ensure operator's safety and comfort. A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants wherein each of the said photo sensors are placed inside wooden blocks of dimension 200mmx 20mmx 16mm which are centrally drilled for focusing and pinpointing the edges of billets from a minimum distance of 50mm, making the device cheap yet safe even at high billet temperatures ranging from 550°C to 1200°C. Below 550°C, method of light interruption may be used. A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, wherein a selective numbers of photosensors are arranged in a single array for sensing the front end and a dual photosensor as reference to sense the back end, in 1:1 configuration for distance based measuring of said length of moving billets, on the basis of completely blocking the view of focus object except for only viewing the ends. A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, to ascertain the base lengths of moving billets on the basis of pulses generated by the front end and the back end sensors that are logically processed by means of an electronic processor comprising digital IC AIMD/Inverter, to get another pulse that represents the length of moving billet. 8 A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, wherein photo sensor based measurement of moving billet is carried out with an accuracy of 0 to + 50 mm (or 0 to 0.3%) for three base length of billets for example 5m, 6m and 12m cut of section 105mm x 105mm, from continuous lengths of 150m/160m rolled out from blooms, to suit the intended end use. A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, by said photosensor means and the signals/pulses processed electronically to favor displaying the measured length on a display unit in the pulpit itself and thereby facilitating faster adjustments of speed of flying shear to control the deviations in length of billet observed to be within the desired accuracy limit. A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants, and the three base lengths measured with higher accuracy reducing scrap and thereby improving productivity. SUMMARY OF THE INVENTION: The basic aspect of the present invention is directed to an automatic system of measurement of length of moving product, such as of hot moving billets of various base lengths in rolling mills of stee! plants comprising: photosensor/phototransistor means to measure length of moving product; said photosensors adapted to sense the light radiation from hot billet ends, the front and the back end of the moving billet, to favor said automatic measurement of lengths; said photosensors means comprising a single array of photo sensors/ phototransistors (sensor stack) in selective numbers to sense the front end and a 9 dual photosensor/phototransistors to sense the back end of moving product to facilitate said length measurement; said automatic system of length measurement comprising, said sensor adapted to generate electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor and these pulses finally generate length pulse, combining the two end pulses using logic gates, a pulse width enlarger circuit adapted to receive said length pulse , output of which is displayed as the length of billet in the LED based display unit. A further aspect of the present invention directed to an automatic system of measurement of length of moving product wherein said photosensors are selectively disposed away from the hot product/billet to favor distance based measurement of length of the said hot moving billet without need of calibration in the span of time with the system adapted to conduct 1:1 scaling between coordinate of slab and the array of photo sensors; the number of said photo sensors "n" required for a particular base length of billet in said automatic system of length measurement is based on: where PSO0 and PSO1 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements. the number of said photo sensors 'n' required for measuring 'x' number of base lengths of moving billets in said automatic system of length measurement based on: 10 said automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoretical measuring error , is given by: Where 'a' is the serial number/position of a particular sensor in the sensor stack with respect to the central sensor, that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack; said dual sensor is selected/connected by means of selector switch corresponding to a particular base length. According to a preferred aspect of the present invention, said automatic system of measurement of length of moving product wherein said photo sensors are preferably placed inside soft wooden blocks adapted for independent focusing and pinpointing of the ends of billets and to protect the sensors from high billet temperature. said automatic system of length measurement involving comprising, a sensor unit generating electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor, comprising simple AND and inverter digital IC and these pulses are finally generate length pulse, combining the two end pulses, the length pulse in turn is sent to pulse width enlarger circuit, output of which is displayed as the length of billet in the LED based display unit. According to an important aspect of the present invention, each of said photo sensors are advantageously placed inside soft wooden blocks preferably of dimension 200mmx 20mmx 16mm which are centrally drilled for independent 11 focusing and pinpointing of the edges of billets from a minimum distance of 50mm, making the device cheap yet safe and accurate, avoiding expensive bakelite or metal tube used conventionally, even at billet temperatures up to 1200°C and without the need for cooling of the sensing unit. According to another aspect of the present invention, in a particular embodiment of the said automatic system of measurement of length of moving product, particularly of hot moving billets in steel plants, to measure the base lengths of 5m, 6m and 12m, the dual photosensors were kept at a distance of 4.65m, 5.65m and 11.65m respectively to ascertain a range of 550mm in measured values of each base lengths i.e the corresponding ranges for the three base lengths being 4.95m to 4.4m, 5.95m to 5.4m and 11.95m to 11.4m, respectively; in a particular embodiment of the present automatic system of length measurement the position/location number V varies from -5 to +5 in a step of 1, the total number of sensors in the sensor stack being 11 and said zero/reference/dual sensors are three paires in numbers selectively located to measure three base lengths of moving billets and all its variations by involving said at least total 17 phototransistors, said dual sensor is selected/connected by means of selector switch corresponding to a particular base length. In said particular embodiment of the present invention for automatic measuring of moving billet length, the least count is 50mm for the present system ensuring the limit of measuring error to lie between 0 to 50mm and can be adjusted based on the accuracy desired by increasing the number of sensors for a given range, thus minimizing further the present level of measuring error of 0 to 0.3%; said photosensor based automatic system of length measurement of hot moving billet in said particular embodiment, 18 phototransistors have been used for measuring 33 different billet lengths, as process variants to three selective base lengths e.g. 5m, 6m and 12m. 12 According to a further aspect of the present invention of automatic system of measuring length of moving product, particularly of moving hot billets in steel plants, said photosensor based measurement and subsequent signal analysis to display the measured length, is achieved by interactive and cooperative functions of five separate electronic circuits e.g. sensing unit, signal processing and forming end pulses, length pulse detection circuit, output pulse width enlarger and LED length display unit. According to a preferred aspect of the present invention, said sensing unit of the auotomatic measuring system having sensor stack with selective numbers of photosensors/sensor stack for sensing the front end and said dual photosensors sensing the back end of the moving billet of selective base lengths, comprising n-p-n silicon phototransistors to sense light radiation from hot billet end which is collected at the collector-base junction; said emitter voltage from the phototransistors is sent to a signal processor wherein it is amplified and compared with a set voltage in the respective comparator circuits for eliminating the background light radiation and thereby favor formation of end pulses; said signal processor of the automatic length measuring system generate the front end pulse by AND-ing the output of one phototransistors, with the inverted output of the successive one in the respective quad section of logic AND gate; and the Back end pulse is formed by processing the inverted signal of zero sensor PS00 with non inverted signal of its pair PS01 in one of the quad section of logic AND gate, corresponding to dual photosensor for sensing particular base length selected by selector switch i.e. any one of three dual sensors put at 4.65m, 5.65m, 11.65m respectively from the centre of sensor stack to measure base lengths of 5m, 6m, 12m. 13 said signal processor circuit of the automatic system of measuring length of moving billets, said simultaneous occurrence of any one of front end puise of sensor stack is AND-ed with a back end pulse derived from dual reference/zero sensors of particular base length such that the output of this logic AND gate produces 'Length Pulse' which represents length of moving billet measured. Said length pulse that represent the length of billet needing widthwise enlargement prior to recognizable/readable display of measured length by display unit to favor display of output of pulse width enlarger in visually distinguishable form, as the width of the said 'length pulse' so derived depend on the rolling speed of a particular base length of billet and the time needed to cover the distance equal to the least count lc in mm with a rolling speed of Sm m/sec is given by: t = (lc/Sm) milliseconds(ms), and that the value of Y for lc = 50mm and maximum rolling speed of Sm = 4 m/sec comes out to be 12.5 ms which is beyond the limit of recognition response of retina by human eye which is 20 ms. According to a further aspect of the present invention, a simple single array of light emitting diodes(LEDs) displays the respective billet lengths by using few digital logic gates, activated by the said width wise enlarged length pulse, the display unit being located in the pulpit itself for ready viewing by the operator, acting as an interface between the measuring system and the operator. said display unit comprise of number of LEDs needed to display a range of V base lengths is given by: x = d + x; where 'd' is a particular base length. According to yet another aspect of the present invention, in a particular embodiment for measuring length of hot moving billets, the number of LEDs in display unit is 14 for displaying 36 numbers of different billet lengths within the range (550mm) of variability of measured dimensions corresponding to three base lengths 5m, 6m and 12m by the system having specified least count of 50mm. 14 The present invention and its various objects and advantages are described in further details herein below with reference to accompanying figures and non-limiting exemplary illustrations. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES: Figure 1: is a schematic illustration of the layout arrangement of various elements of a billet mill in a steel plant, showing the location of photosensors according to the present invention. Figure 2: is the illustration of cutting operation of billets by flying shear blades. Figure 3: is the illustration of conventional method of measuring billet length by the operator. Figure 4: is the schematic circuit diagram for signal processor unit illustrating formation of front end and back end pulses. Figure 5: is the schematic circuit diagram illustrating logic gates for generation of length pulse. Figure 6: is the schematic circuit diagram for length pulse display unit representing measured length of billet. DETAILED DESCRIPTION WITH REFERENCE TO ACCOMPANYING FIGURES: Reference is first invited to the Figure 1 that illustrates the layout configuration of the billet mill in a steel plant with particular illustration of the elements of the automatic length measuring system of the present invention as well as the mechanical scale measurement done conventionally. The figure shows the physical distance (shown with an double headed arrow) measuring about 35 m, that an operator has to move in conventional measurement for checking length on a mechanical scale and simultaneously to control/adjust the speed of the fly sheer from pulpit, as and when necessary to rectify large deviations observed in length of billets cut on most recent occasions. The old system also made use of pneumatically operated stoppers to stop the billets to carry out said measurement by taking the reading on mechanical scale with the billet at a stationary condition as 15 illustrated in figure 3. Thus the human error like parallax in taking readings on mechanical scale amounting to 30-50mm and amount of play on the stoppers ranging from + 50mm to -50mm and a total error in such measurement was accumulated to about ±250mm. Moreover, the delay in measurement for time taken to cover the distance by the operator to adjust the speed of flying sheer(FS) according to requirement resulted in length variations, the said cutting operation being illustrated in accompanying figure 2, longer or shorter than selected base length, numbering about 8-14 billets per each bloom rolled into billets. The operator also had to run the risk of moving rapidly/running in a hot cobble prone zone and subjected to frequent accidents, apart from suffering from unnecessary fatigue affecting his physical performance. The automatic system of measuring the length of moving product such as moving billets in a rolling mill in steel plants, of the present invention involving photosensor based measurement of lengths eliminate the perceived limitations and disadvantages of the conventional system. Figure 1 illustrates the preferred location of such photosensors/phototransistors to favor said automatic measurement directly by the operator from the pulpit itself. This in turn facilitate the adjustments in speed of flying sheer(FS) for cutting the billets, as necessary, from the control panel in the same pulpit. The principle of said automatic measurement of hot moving billets is achieved in the present invention by involving a selective number of photosensors/ phototransistors adapted to carry out a distance based measurement of billet lengths needing no calibration in the span of time since it involves 1:1 scaling between coordinate of billet and photosensor array, without stopping its motion and irrespective of speed of rolling/progress. The front end of a moving billet is sensed gradually by different phototransistors that are kept in a single array in selective numbers depending on base lengths to be measured and the desired accuracy of the system, called a sensor stack(SS), while the back end of the billet is sensed by a dual phototransistor(DS) also called the zero or reference sensor located selectively at a distance of 4.65m, 5.65m, 11.65m respectively from the center of said sensor stack for measuring the intended base length of 5m, 6m, 12m of billets 16 within a range of variation of 550mm and with a least count of 50mm as illustrated in figure 6. The photosensors sense the light radiation from the front end and the back end of the hot billet by means of said phototransistors, that are basically high gain two bipolar n-p-n silicon phototransistors. They generate front end pulse(FP) and back end pulses(BP) that are logically processed to get another pulse i.e. length pulse(LP) that represents the length of moving billet. The width of resultant pulse depend upon the rolling speed and it varies in the range of 6 ms to 12.5 ms and is very difficult to be detected by operator because the retina of human eye can only recognize the signals that are at least 20 ms wide. Therefore, the resultant length pulse need width wise enlargement for its distinctive detection and is finally displayed by means of glowing selective combination of LEDs in a display unit(DU) comprising an array of LEDs in selective numbers, to represent the said enlarged length pulse signal corresponding to a billet length, within the range and accuracy level specified for the system. Reference is now invited to accompanying figures 4 to 6 that illustrates the schematic circuit diagrams for different functional units of the automatic measuring system of the present invention. The total system is composed of five electronic circuits/units namely (1) sensing unit, (2) signal processing and formation of end pulses, (3) length pulse detection circuit,(4) Output pulse-width enlarger, (5) LED display circuit/unit. The cooperative functions and interdependence of various units to transform the light radiation sensed by the phototransistors for the two ends of a billet length to be converted to measurement of length in a LED display unit adaptable to display 36 different lengths corresponding to three base lengths with their selected range of variability and least count for the system, are described below: The sensing Unit has the design configuration providing a linear array of phototransistors/photodiodes that are for the first time in industrial application is housed inside soft wooden block, instead of costly and hard bakelite block conventionally used, with advantageous easy workability for shaping the block to requirement and safe operation in measurement of hot moving product, such as billets in rolling mifls, from a minimum distance with desired accuracy. Such 17 wooden blocks are centrally drilled for focusing and pin pointing the edges of billet. By using wood in sensing assembly unit, the cost of overall system has been reduced significantly. The photosensor based automatic measuring system of the present invention is designed to ensure a selective range of variations in different base lengths and accuracy in measurements. Supposing the system has the range 'R' meter, related to variations in lengths of billets in different base lengths and the desired measuring accuracy is 'lc'(in mm), the numbers of photosensors 'n' required for measuring a particular base length is given as follows: where PS00 and PSO1 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where Lbx is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements. The number of said photo sensors 'n' required for measuring V number of base lengths of moving billets in said automatic system of length measurement is given by: In the automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoreticalmeasuring error , is given by: Where 'a' is the serial number/position of a particular sensor in the sensor stack that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack. 18 In a particular embodiment of the present invention for demonstrating said automatic system of measurement of length of moving product, particularly of hot moving billets in steel plants, to measure the base lengths of 5m, 6m and 12m, the dual photosensors were kept at a distance of 4.65m, 5.65m and 11.65m respectively adapted to incorporate a range of 550mm in measured length data for each base lengths i.e the corresponding ranges for the three base lengths being 4.95m to 4.4m, 5.95m to 5.4m and 11.95m to 11.4m, respectively; In this embodiment of the present invention, only 18 phototransistors have been used for measuring 33 different billet lengths. In said particular embodiment of the present automatic system of length measurement the position/location number 'a' varies from -5 to +5 in a step of 1, the total number of sensors in the stack being 11 and said zero/reference/dual sensors are three in numbers selectively located to measure three base lengths of moving billets, said dual sensor is selected/connected by means of selector switch corresponding to a particular base length. The photosensors in the preferred embodiment for measuring different base lengths of hot moving billets, are in particular high gain, two bipolar, n-p-n silicon phototransistors (type 14 LF-32 Qualimatrix of USA make or equivalent of any other make) are configured to a darlington-pair and works as an emitter follower with its open base as shown in figure 5. The light radiation of billet is concentrated at the collector-base junction of phototransistors and generates enough electrons. The variation in the signal in light and dark state is sent to electronic processing unit, kept in a control pulpit at an electrical distance of 150 meters. The Signal processing unit receive the signal from the phototransistors and transform the into end pulses. The emitter voltage of respective phototransistors is amplified in quad sections of linear operational amplifiers(IC type LM-324) in electronic processing unit. The signals are compared with set voltage of respective comparator circuits for eliminating the background light radiation as shown in figure 5. Subsequently, the output of comparator goes to high state. In this way, the states of all the eleven number phototransistors in the sensor stack gradually changes. There are six numbers operational amplifiers IC LM 324 used for eleven number amplifier circuits and the eleven number comparator circuits. 19 The front end pulses(FP) are formed by processing the output of a pair of successively placed photosensors in the sensor stack(SS), wherein the out put of the first photosensor is processed with the inverted output of second photosensors in one of the section of quad sections logic AND gate (IC TTL type 7408). In this way other front end pulses(FP) gradually formed by AND-ing the output of a phototransistor with inverted output of succeeding phototransistors in other sections of quad AND gates as shown in figure 5. The dual photosensors(DS) PSO0 and PSO1 in pairs, have been put at 4.65m, 5.65m and 11.65m respectively from the mid of sensor stack for 5m, 6m/ 12m base lengths to sense the back end of billet. The back end pulse(BP) is formed by processing the inverted signal of PSOo with non-inverted signal of PSOi in one of the section of quad AND gate(IC 7408). After selecting the appropriate base length out of three different options through the selector switch provided for the purpose, as illustrated in figure 6, the end pulse signals are sent to the length pulse detection unit/circuit. The length pulse detection unit is adapted to convert the front and back end pulses corresponding to a particular billet length into a representative 'Length-pulse'(LP), using simple logic gates. The simultaneous occurrence of any one of front end pulse(FP) of sensor stack(SS) is AND-ed with a back end pulse derived from dual reference/zero sensors(DS) of particular base length such that the output of this logic AND gate produces 'Length Pulse' (LP) which represents length of moving billet measured. The length pulse thus obtained is sent to pulse width enlarger circuit. The pulse width enlarger unit simply enlarges the width of length pulse formed compatible with signals corresponding to least count of measurement into recognizable by human eye. The output at the length pulse detection unit has a pulse width depending on the speed of rolling and said length pulse that represent the length of billet needing widthwise enlargement prior to recognizable/readable display of measured length by display unit(DU) to favor display of output of pulse width enlarger in visually distinguishable form. The width of the said length pulse' is related to rolling speed of a particular base length of billet and the time needed 20 to cover the distance equal to the least count Ic in mm with a rolling speed of Sm m/sec is given by: t = (Ic/Sm) milliseconds(ms), and that the value of 't' with least count lc = 50mm and maximum rolling speed of Sm = 4 m/sec for 12m base length, comes out to be 12.5 ms, which is much less than the limit of minimum recognition response of retina of human eye which is 20 ms. This is why a width wise enlargement of length pulse is needed and the same is carried out by latching this signal by J-K type flip-flop IC 7474 till the arrival of next length pulse. The width wise enlarged length pulse signal now comes to an electronic display unit(DU) that serves as an important interface between the operator and the measuring system of this invention. The output pulse width enlarger is fed to LED based billet length display unit(DU) which is installed in the operator pulpit to guide him about the length of that billet which is recently cut. The concept of redundancy is also applied in the use of different light emitting diodes(LEDs) as illustrated in figure 6. A simple single array of LEDs displays the respective billet lengths by using few digital logic gates. In the particular embodiment of the measuring system for three selective base lengths e.g. 5m, 6m, 12m comprised 14 numbers LEDs for displaying 36 numbers of different billet lengths, as variations for the three base lengths within the selected range and precision of measurement. The number of LEDs needed for display of the base lengths V is given by (d+x), where 'd' is the number of LEDs needed to display a particular base length, as illustrate in figure 6. 21 We claim: 1. An automatic system of measurement of length of moving product, such as of hot moving billets of various base lengths in rolling mills of steel plants comprising: photosensor/phototranststor means to measure length of moving product; said photosensors adapted to sense the light radiation from hot billet ends, the front and the back end of the moving billet, to favor said automatic measurement of lengths; said photosensors means comprising a single array of photo sensors/ phototransistors (sensor stack) in selective numbers to sense the front end and a dual photosensor/phototransistors to sense the back end of moving product to facilitate said length measurement; said automatic system of length measurement comprising, said sensor adapted to generate electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor and these pulses finally generate length pulse, combining the two end pulses using logic gates, a pulse width enlarger circuit adapted to receive said length pulse , output of which is displayed as the length of billet in the LED based display unit. 2. An automatic system of measurement of length of moving product as claimed in claim 1 wherein said photosensors are selectively disposed away from the hot product/billet to favor distance based measurement of length of the said hot moving billet without need of calibration in the span of time with the system adapted to conduct 1:1 scaling between coordinate of slab and the array of photo sensors; the number of said photo sensors wnw required for a particular base length of billet in said automatic system of length measurement is based on: where PS and PS01 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements. 22 the number of said photo sensors xn' required for measuring V number of base lengths of moving billets in said automatic system of length measurement based on :n = (R/ lc +1 +2x) said automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoretical measuring error , is given by: Where'a' is the serial number/position of a particular sensor in the sensor stack that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack; said dual sensor is selected/connected by means of selector switch corresponding to a particular base length. 3. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 or 2 wherein said photo sensors are preferably placed inside soft wooden blocks adapted for independent focusing and pinpointing of the ends of billets and to protect the sensors from high billet temperature. 4. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 3 comprising, measurement of the base lengths with said dual photosensors, three pairs acting as reference/zero sensors selectively distanced respectively from the center of sensor stack, comprising independently focusing sensors, to ascertain a selective range in measured values of each base lengths. a selective least count maintained in said system of measurement, ensuring the limit of measuring error is limited to between 0 to 50mm and can be adjusted based on the accuracy desired by increasing the number of sensors for a given range, thus minimizing further the level of measuring error . 5. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 4, comprising interactive and cooperative functions of separate electronic circuits preferably including sensing unit, signal processing and forming end pulses, length pulse detection circuit, output pulse width enlarger and length display unit. 23 6. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 5, wherein said photosensor based measurement comprises n-p-n silicon phototransistors to sense light radiation from hot billet ends, being concentrated at the collector-base junction that in turn emits enough electrons; the emitter voltage from said phototransistors being sent to a signal processor wherein it is amplified and compared with a set voltage in the respective comparator circuits for eliminating the background light radiation and thereby favor formation of front end and back end pulses; 7. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 6 wherein said signal processor of the automatic length measuring system generate the 'front end pulse' by AND-ing the output of one phototransistors, with the inverted output of the successive one in the respective quad section of logic AND gate; and the 'back end pulse' is formed by processing the inverted signal of PS0o with non inverted signal of PSoiin one of the quad section of logic AND gate, corresponding to dual photosensor for sensing particular base length selected by selector switch. 8. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 7 wherein said length pulse that represent the length of billet needing widthwise enlargement prior to recognizable/readable display of measured length by the display unit to favor display of output of pulse width enlarger in visually distinguishable form, as the width of the said 'length pulse' so derived depend on the rolling speed of a particular base length of billet and the time needed to cover the distance equal to the least count lc in mm with a rolling speed of Sm m/sec is given by: t = (Ic/Sm) milliseconds(ms)/ and that the value of 't' for lc - 50mm and maximum rolling speed of Sm = 4 m/sec comes out to be 12.5 ms which is beyond the limit of recognition response of retina by human eye which is 20 ms. 9. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 8 wherein said simple single array of light emitting diodes(LEDs) displays the respective billet lengths by using few digital logic gates, activated by the said display located in the pulpit itself for display of billet lengths to the operator, acting as an interface between the measuring system and the operator. 24 said display unit comprising of selective number of LEDs needed to display a range of 'x' base lengths is given by: x = d + x; where 'd' is a particular base length. 25 10. An automatic system of measurement of length of moving product as claimed in anyone of claims 1 to 9 wherein for automatic measuring of lengths of hot moving billets, the number of LEDs in display unit is selectively provided preferably 14 for displaying 36 numbers of different billet lengths within the range (550mm) of variability of measured dimensions corresponding to three base lengths 5m, 6m and 12m by the system having specified least count of 50mm. 11. An automatic system of measurement of length of moving product such as hot moving billets as substantially herein described and illustrated with reference to accompanying figures. The present invention is directed to an automatic online length measuring system for moving products including moving billets in rolling mills. The system automatically measures the various base lengths of billets, minimizing measuring error and reduce scrap. Moving billet length is measured by a single array of different phototransistors to sense the front end and dual phototransistors (DS) as reference/zero to sense the back end, placed at selective distances from centre of sensor stack(SS), favoring measurement of three base lengths with desired accuracy defined by selected range( R ) of 550mm and least count (Ic ) of 50mm. The front end(FP) pulse and the back end(BP) pulse from sensors are logically processed to get the length pulse(LP) that represents the length of moving billet, indicated on a display unit(DU) by LEDs. The speed of flying shear is adjusted by the operator directly from pulpit and limiting the error of measurement to 0 to 50mm or 0-0.3% reducing from about ± 250mm obtained in conventional methods.

Full Text

FIELD OF INVENTION:
The present invention is directed to a very simple and low cost photosensor based automatic online length measuring system for moving products avoiding operator's involvement especially in hazardous/accident prone sites. The system is adapted to directly and automatically measure the various base lengths of moving billets at high temperatures, in the rolling mill in any steel plant, with higher accuracy for minimizing measuring error and also minimizing generation of scrap. The present new system controls the billet length by a single array(stack) of different photosensor/phototransistors to sense the front end and a dual phototransistors, which act as the reference/zero sensor, to sense the back end, being placed at selective distant locations from centre of sensor stack, favoring measurement of selective three base lengths of moving billets such as 5m, 6m and 12m with desired degree of accuracy, decided by end uses of such billets. The signal pulses generated by the front end and the back end sensors are logically processed to get another pulse that represents the length of moving billet. The length is finally indicated by said pulses on a display unit by means of selective LED indicators. The invention also provide means for faster adjustment of the speed of flying shear motor according to most recent measurement(from visual display unit) of a base length by the operator directly from pulpit, such that the error of measurement is limited to 0 to 50mm (or 0-0.3% that is further adjustable) in place of about ± 250mm obtained in conventional methods of similar measurements. Thus the present invention has the potential for wide scale industrial applications, particularly in measurement of base lengths of billets in rolling mill in steel plants.
BACKGROUND AND PRIOR ART:
The present invention relate to the development of the measuring system for a continuous rolling mill of blooms to billets. Usually, 5 meter long hot blooms of section 340mm x 300mm are rolled through ten numbers of rolling stands for successive reduction to the section of a billet. The blooms are converted to billets of
2

section 105 mm x105mm of varying continuous lengths ranging from 150 meter to 160 meter. For fulfilling the need of wire rod mill, merchant mill and other foreign customers, the long stream of billets are cut into smaller standard base lengths e.g. 12 meter, 6 meter and 5 meter, by means of two rotating blades, also called the flying shear which are coupled with separately excited DC drive motor with 1.1MW capacity. The conventional method of measuring the base lengths for the rolled out billets was achieved by the attending operator by crossing the 35 meter long cobble prone area to measure the billet length by using the mechanical measuring scale and running back to pulpit for adjusting the speed of flying shear motor depending on the direction of deviation from base length noted in the last measurements. Moreover, pneumatically operated stoppers used to stop the motion of billets to facilitate measurement, which itself incorporated some error due to play in said stopper in either direction. The operator was thus subjected to frequent accident in this crude method involving physical movements/running for measurement and adjustments in the hot cobble prone transfer zone. The conventional measuring process thus suffered from accidents, delay and inaccuracy in measurement, high volume of scrap and loss of productivity.
A host of factors in the said conventional process were thus responsible for and led to variation/deviation in the standard base lengths intended to be cut from the continuous lengths rolled out from a bloom. This in turn led to increased scrap and loss of productivity. Such factors causing deviation of measurement of base lengths of billets included:
Speed of flying shear motor could not be precisely adjusted as the angular velocity of flying shear blades could not be synchronized with the linear velocity of billets in particular ratio due to metallurgical and mechanical problems involved in rolling of billets from hot blooms.
Parallax error in measuring cut billet length by using mechanical scale was another factor responsible for forced deviation in measured base length, the range of varying parallax being 30 to 50 mm.
In the conventional method the billets were measured in stationary condition, after lifting the pneumatically operated flexible stopper which itself suffered from a play ranging from +50mm to -50mm from its normal position.
3

Yet another element of error causing forced deviation of measurement of base lengths in conventional method, was induced by delay in the measurement and also delay in applying the correction of speed of the flying shear motor lead to generate either longer or shorter billets, the number of such erroneous billet lengths obtained being 8 to 14 from each bloom.
Loss of productivity was also caused in conventional method, due to the variation in base length in a sense that the longer length billets jammed the furnaces of the successive mills for longer times while the shorter length billets reduce the productivity/yield of the rolling mills.
It was thus the long perceived need for developing a system of measurement of the various base lengths of the billets in the rolling mills where they are rolled out from blooms for continuous lengths of billet sections for required cutting by flying shear directed to more accurate measurement of various base lengths of billets standardized to meet the requirements of re-rolling in the wire rod mill and merchant mill and also the demand of outside customers including the overseas buyers. It was also the need to eliminate the limitations of the conventional measurement method as already discussed in order to achieve quality, productivity, safety and economy in billet rolling mill operations.
Alternative measuring systems capable to measure length of moving billets and other similar products with precision and in a safe manner was explored in last few years. Measuring systems involving laser and charged coupled devices were tried during last 7-8 years in continuous casting shop with the involvement of some of the eminent instrument manufacturers including M/s American Sensor Manufacture Limited who tried such systems for measuring moving billet lengths but failed to establish an accurate method to measure the even length, although the systems were suitable for measuring dimensions of slab. The Charged Coupled Device (CCD) Camera which was installed in blooming mil! of steel plant was found to be not suitable for application in Continuous Casting Shop(CCS) because of fluctuation in surface temperature of slab. The system of measuring length of moving billet, according to the present invention was thus achieved by installing a single array of photosensors stack that takes care of wide length variation in three different base
4

lengths. Also a simple single array of Light Emitting Diodes (LED) displays the respective lengths by using few digital logic gates.
The following comparative study of the present system as compared to the other expensive alternative means for such measurement of length of moving products like the Shaft Encoder, Laser Doppler, CCD based Camera etc. reveals its advantages, simplicity , cost effective yet an accurate means of measurement.
A. Shaft Encoder: These instruments are capable of conducting two types of
measurements -Incremental type and Absolute type. In either type of
measurements, when applied to measure length of moving billets they are
subjected to errors/constraints due to factors like wear and tear of rolls, non-
contact/slip between rolls and billet, glitches unmeasured pulses, failure of
coupling, hydraulically pressed roll needs continuous adjustment, it needs
cooling. The error in measurement varies from 0.1% to more than 3%
depending on interval of calibration. The cost of the instrument/system is
about 0.06 million US dollars.
B. Laser based systems :(i) Laser Doppler suffers from error incorporated
due to tilting of reflecting plane of moving billet; (ii) Laser Interferometer is
subjected to system failure due to dust deposition on lens; (iii) Laser
Triangulation device needs continuous adjustments and complex circuitry has
to be maintained;(iv) Pulse radar system based on (a) time of flight and (b)
amplitude measurements, having the limitation that the object should be
visible from the laser source without obstruction, there is hardly any gap
between the two successive pieces and for accurate response the system
needs (a) 0.001 nano seconds timer, (b) roughness of reflecting plane
induces error. The Extent of error in Laser based systems ranges from
0.01% to over 0.3%. The cost including installation of a system in million US
dollars is about 0.3 for laser Doppler/interferometer, about 0.05 for laser
triangulation and about 0.01 for pulse radar device.
C. CCD Camera: This system of measurement suffer from limitations like
difficulty in sensing the edges of billets and its scaling, obstruction free area
to view for the camera that is hardly possible to be maintained at shop floor.
The system has further constraints like continuous supply of water is needed
5

to cool its electronic components, needs huge structure to install the system, images obtained in the scale of 1:100/1000, at least 200mm gap is required between two successive billets for distinctive measurement of dimensions. The error in measurement by the CCD camera varies from 0.1% to more than 0.3%, the threshold limit for the error percent can however be adjusted by means of software. The cost of installation for such CCD system is around 0.02 million US dollars.
D. Load cell based system: these systems need major installation work where
in the dimensions are calculated in an indirect way by dividing
volume/weight by cross section, needing continuous calibration. The error in
measurement is also on account of variation in cross section of rolled product
by about ±10%. The magnitude of error in such systems ranges from 0.1%
to more than 0.3% and the cost of installation is of the order of 0.2 million
US dollars.
E. Orbis coil : This system can measure the total cross section but not the
height/width of the object; it is not capable to work at higher speed of
moving product; this systems suffer from poor response time; it is difficult to
install such systems in existing mills and need wide gap between edges of
two pieces to be measured distinctively.
In order to overcome the limitations of the above conventional methods, a low cost Photo-sensor based new system of the present invention is developed on the basis of completely blocking the view of focus object of sensors and is a distance based system that needs no calibration on working span of time. The system is a 1:1 scaling by putting sensors 50mm away from hot moving object and need no external cooling, no air purging for cleaning and its performance is unaffected by any vibration of the product/roll table; such system involves simple circuit using low cost components. The system has capability to measure dimension/length of moving hot billets within error limit of 0% to 0.3% depending upon the least count that is adjustable. The system is a low cost device, price of which is only about 60 US dollars.
6

It is thus evident from the aforesaid discussions, that the present invention is providing a simple and low cost system of measurement of dimension/length of hot moving billet in rolling mill of steel plants with high accuracy and reliability, maintaining safety of the operator attending to the rolling stands for the billets. The new system also eliminate the difficulty of measurement by the operator in the existing system wherein he needs to run in between high temperature cobble prone area to measure the billet lengths subsequently for its length correction thereby he was meeting frequent accidents. The new system according to the present invention is capable to display the base length of each billet right in the pulpit itself and thereby ensuring safety of the operator against hot cobbled metal/billet. The developed system also facilitate faster control on the billet length by quickly adjusting the speed of flying shear motor according to requirement and Thus limiting the measurement error within 0 to +50mm in place of existing level of +/-250mm.
Also, web search on the prior art in related field of length/dimension measurement of moving product revealed, that such simple, safe, accurate and low cost system involving phototransistors/photo-sensor is novel and not available in any earlier publications/patent applications. The present invention is also capable to minimize scrap by adopting measurement with higher precision and thereby improving productivity/yield of the rolling mills and as such having potential for wide scale industrial application in steel and other industries, where the system can be applied with advantage.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to developing an automatic system using photosensors to measure the length of moving products in industry and in particular measuring hot moving billets in rolling mills of steel plants in. a safe, more accurate, reliable and economical method and thereby create
7

substantial financial saving running into a few crores over a year by way of savings on scrap only.
A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants such that the prevailing practice of frequent unsafe hasty movement of the operator in the hot cobble prone zone in rolling mill for measurement/adjustments is avoided to ensure operator's safety and comfort.
A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants wherein each of the said photo sensors are placed inside wooden blocks of dimension 200mmx 20mmx 16mm which are centrally drilled for focusing and pinpointing the edges of billets from a minimum distance of 50mm, making the device cheap yet safe even at high billet temperatures ranging from 550°C to 1200°C. Below 550°C, method of light interruption may be used.
A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, wherein a selective numbers of photosensors are arranged in a single array for sensing the front end and a dual photosensor as reference to sense the back end, in 1:1 configuration for distance based measuring of said length of moving billets, on the basis of completely blocking the view of focus object except for only viewing the ends.
A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, to ascertain the base lengths of moving billets on the basis of pulses generated by the front end and the back end sensors that are logically processed by means of an electronic processor comprising digital IC AIMD/Inverter, to get another pulse that represents the length of moving billet.
8

A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, wherein photo sensor based measurement of moving billet is carried out with an accuracy of 0 to + 50 mm (or 0 to 0.3%) for three base length of billets for example 5m, 6m and 12m cut of section 105mm x 105mm, from continuous lengths of 150m/160m rolled out from blooms, to suit the intended end use.
A further object of the present invention directed to an automatic system of measuring length of moving billets in steel plants, by said photosensor means and the signals/pulses processed electronically to favor displaying the measured length on a display unit in the pulpit itself and thereby facilitating faster adjustments of speed of flying shear to control the deviations in length of billet observed to be within the desired accuracy limit.
A further object of the present invention is directed to an automatic system of measuring length of moving billets in steel plants, and the three base lengths measured with higher accuracy reducing scrap and thereby improving productivity.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is directed to an automatic system of measurement of length of moving product, such as of hot moving billets of various base lengths in rolling mills of stee! plants comprising:
photosensor/phototransistor means to measure length of moving product;
said photosensors adapted to sense the light radiation from hot billet ends, the front and the back end of the moving billet, to favor said automatic measurement of lengths;
said photosensors means comprising a single array of photo sensors/ phototransistors (sensor stack) in selective numbers to sense the front end and a
9

dual photosensor/phototransistors to sense the back end of moving product to facilitate said length measurement;
said automatic system of length measurement comprising, said sensor adapted to generate electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor and these pulses finally generate length pulse, combining the two end pulses using logic gates, a pulse width enlarger circuit adapted to receive said length pulse , output of which is displayed as the length of billet in the LED based display unit.
A further aspect of the present invention directed to an automatic system of measurement of length of moving product wherein said photosensors are selectively disposed away from the hot product/billet to favor distance based measurement of length of the said hot moving billet without need of calibration in the span of time with the system adapted to conduct 1:1 scaling between coordinate of slab and the array of photo sensors;
the number of said photo sensors "n" required for a particular base length of billet in said automatic system of length measurement is based on:

where PSO0 and PSO1 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements.
the number of said photo sensors 'n' required for measuring 'x' number of base lengths of moving billets in said automatic system of length measurement based on:

10

said automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoretical measuring error , is given by:

Where 'a' is the serial number/position of a particular sensor in the sensor stack with respect to the central sensor, that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack; said dual sensor is selected/connected by means of selector switch corresponding to a particular base length.
According to a preferred aspect of the present invention, said automatic system of measurement of length of moving product wherein said photo sensors are preferably placed inside soft wooden blocks adapted for independent focusing and pinpointing of the ends of billets and to protect the sensors from high billet temperature.
said automatic system of length measurement involving comprising, a sensor unit generating electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor, comprising simple AND and inverter digital IC and these pulses are finally generate length pulse, combining the two end pulses, the length pulse in turn is sent to pulse width enlarger circuit, output of which is displayed as the length of billet in the LED based display unit.
According to an important aspect of the present invention, each of said photo sensors are advantageously placed inside soft wooden blocks preferably of dimension 200mmx 20mmx 16mm which are centrally drilled for independent
11

focusing and pinpointing of the edges of billets from a minimum distance of 50mm, making the device cheap yet safe and accurate, avoiding expensive bakelite or metal tube used conventionally, even at billet temperatures up to 1200°C and without the need for cooling of the sensing unit.
According to another aspect of the present invention, in a particular embodiment of the said automatic system of measurement of length of moving product, particularly of hot moving billets in steel plants, to measure the base lengths of 5m, 6m and 12m, the dual photosensors were kept at a distance of 4.65m, 5.65m and 11.65m respectively to ascertain a range of 550mm in measured values of each base lengths i.e the corresponding ranges for the three base lengths being 4.95m to 4.4m, 5.95m to 5.4m and 11.95m to 11.4m, respectively; in a particular embodiment of the present automatic system of length measurement the position/location number V varies from -5 to +5 in a step of 1, the total number of sensors in the sensor stack being 11 and said zero/reference/dual sensors are three paires in numbers selectively located to measure three base lengths of moving billets and all its variations by involving said at least total 17 phototransistors, said dual sensor is selected/connected by means of selector switch corresponding to a particular base length.
In said particular embodiment of the present invention for automatic measuring of moving billet length, the least count is 50mm for the present system ensuring the limit of measuring error to lie between 0 to 50mm and can be adjusted based on the accuracy desired by increasing the number of sensors for a given range, thus minimizing further the present level of measuring error of 0 to 0.3%;
said photosensor based automatic system of length measurement of hot moving billet in said particular embodiment, 18 phototransistors have been used for measuring 33 different billet lengths, as process variants to three selective base lengths e.g. 5m, 6m and 12m.
12

According to a further aspect of the present invention of automatic system of measuring length of moving product, particularly of moving hot billets in steel plants, said photosensor based measurement and subsequent signal analysis to display the measured length, is achieved by interactive and cooperative functions of five separate electronic circuits e.g. sensing unit, signal processing and forming end pulses, length pulse detection circuit, output pulse width enlarger and LED length display unit.
According to a preferred aspect of the present invention, said sensing unit of the auotomatic measuring system having sensor stack with selective numbers of photosensors/sensor stack for sensing the front end and said dual photosensors sensing the back end of the moving billet of selective base lengths, comprising n-p-n silicon phototransistors to sense light radiation from hot billet end which is collected at the collector-base junction;
said emitter voltage from the phototransistors is sent to a signal processor wherein it is amplified and compared with a set voltage in the respective comparator circuits for eliminating the background light radiation and thereby favor formation of end pulses;
said signal processor of the automatic length measuring system generate the front end pulse by AND-ing the output of one phototransistors, with the inverted output of the successive one in the respective quad section of logic AND gate; and the Back end pulse is formed by processing the inverted signal of zero sensor PS00 with non inverted signal of its pair PS01 in one of the quad section of logic AND gate, corresponding to dual photosensor for sensing particular base length selected by selector switch i.e. any one of three dual sensors put at 4.65m, 5.65m, 11.65m respectively from the centre of sensor stack to measure base lengths of 5m, 6m, 12m.
13

said signal processor circuit of the automatic system of measuring length of moving billets, said simultaneous occurrence of any one of front end puise of sensor stack is AND-ed with a back end pulse derived from dual reference/zero sensors of particular base length such that the output of this logic AND gate produces 'Length Pulse' which represents length of moving billet measured.
Said length pulse that represent the length of billet needing widthwise enlargement prior to recognizable/readable display of measured length by display unit to favor display of output of pulse width enlarger in visually distinguishable form, as the width of the said 'length pulse' so derived depend on the rolling speed of a particular base length of billet and the time needed to cover the distance equal to the least count lc in mm with a rolling speed of Sm m/sec is given by: t = (lc/Sm) milliseconds(ms),
and that the value of Y for lc = 50mm and maximum rolling speed of Sm = 4 m/sec comes out to be 12.5 ms which is beyond the limit of recognition response of retina by human eye which is 20 ms.
According to a further aspect of the present invention, a simple single array of light
emitting diodes(LEDs) displays the respective billet lengths by using few digital
logic gates, activated by the said width wise enlarged length pulse, the display unit
being located in the pulpit itself for ready viewing by the operator, acting as an
interface between the measuring system and the operator.
said display unit comprise of number of LEDs needed to display a range of V base
lengths is given by:
x = d + x;
where 'd' is a particular base length.
According to yet another aspect of the present invention, in a particular embodiment for measuring length of hot moving billets, the number of LEDs in display unit is 14 for displaying 36 numbers of different billet lengths within the range (550mm) of variability of measured dimensions corresponding to three base lengths 5m, 6m and 12m by the system having specified least count of 50mm.
14

The present invention and its various objects and advantages are described in further details herein below with reference to accompanying figures and non-limiting exemplary illustrations.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is a schematic illustration of the layout arrangement of various elements
of a billet mill in a steel plant, showing the location of photosensors according to
the present invention.
Figure 2: is the illustration of cutting operation of billets by flying shear blades.
Figure 3: is the illustration of conventional method of measuring billet length by the
operator.
Figure 4: is the schematic circuit diagram for signal processor unit illustrating
formation of front end and back end pulses.
Figure 5: is the schematic circuit diagram illustrating logic gates for generation of
length pulse.
Figure 6: is the schematic circuit diagram for length pulse display unit representing
measured length of billet.
DETAILED DESCRIPTION WITH REFERENCE TO ACCOMPANYING FIGURES:
Reference is first invited to the Figure 1 that illustrates the layout configuration of the billet mill in a steel plant with particular illustration of the elements of the automatic length measuring system of the present invention as well as the mechanical scale measurement done conventionally. The figure shows the physical distance (shown with an double headed arrow) measuring about 35 m, that an operator has to move in conventional measurement for checking length on a mechanical scale and simultaneously to control/adjust the speed of the fly sheer from pulpit, as and when necessary to rectify large deviations observed in length of billets cut on most recent occasions. The old system also made use of pneumatically operated stoppers to stop the billets to carry out said measurement by taking the reading on mechanical scale with the billet at a stationary condition as
15

illustrated in figure 3. Thus the human error like parallax in taking readings on mechanical scale amounting to 30-50mm and amount of play on the stoppers ranging from + 50mm to -50mm and a total error in such measurement was accumulated to about ±250mm. Moreover, the delay in measurement for time taken to cover the distance by the operator to adjust the speed of flying sheer(FS) according to requirement resulted in length variations, the said cutting operation being illustrated in accompanying figure 2, longer or shorter than selected base length, numbering about 8-14 billets per each bloom rolled into billets. The operator also had to run the risk of moving rapidly/running in a hot cobble prone zone and subjected to frequent accidents, apart from suffering from unnecessary fatigue affecting his physical performance.
The automatic system of measuring the length of moving product such as moving billets in a rolling mill in steel plants, of the present invention involving photosensor based measurement of lengths eliminate the perceived limitations and disadvantages of the conventional system. Figure 1 illustrates the preferred location of such photosensors/phototransistors to favor said automatic measurement directly by the operator from the pulpit itself. This in turn facilitate the adjustments in speed of flying sheer(FS) for cutting the billets, as necessary, from the control panel in the same pulpit.
The principle of said automatic measurement of hot moving billets is achieved in the present invention by involving a selective number of photosensors/ phototransistors adapted to carry out a distance based measurement of billet lengths needing no calibration in the span of time since it involves 1:1 scaling between coordinate of billet and photosensor array, without stopping its motion and irrespective of speed of rolling/progress. The front end of a moving billet is sensed gradually by different phototransistors that are kept in a single array in selective numbers depending on base lengths to be measured and the desired accuracy of the system, called a sensor stack(SS), while the back end of the billet is sensed by a dual phototransistor(DS) also called the zero or reference sensor located selectively at a distance of 4.65m, 5.65m, 11.65m respectively from the center of said sensor stack for measuring the intended base length of 5m, 6m, 12m of billets
16

within a range of variation of 550mm and with a least count of 50mm as illustrated in figure 6.
The photosensors sense the light radiation from the front end and the back end of the hot billet by means of said phototransistors, that are basically high gain two bipolar n-p-n silicon phototransistors. They generate front end pulse(FP) and back end pulses(BP) that are logically processed to get another pulse i.e. length pulse(LP) that represents the length of moving billet. The width of resultant pulse depend upon the rolling speed and it varies in the range of 6 ms to 12.5 ms and is very difficult to be detected by operator because the retina of human eye can only recognize the signals that are at least 20 ms wide. Therefore, the resultant length pulse need width wise enlargement for its distinctive detection and is finally displayed by means of glowing selective combination of LEDs in a display unit(DU) comprising an array of LEDs in selective numbers, to represent the said enlarged length pulse signal corresponding to a billet length, within the range and accuracy level specified for the system.
Reference is now invited to accompanying figures 4 to 6 that illustrates the schematic circuit diagrams for different functional units of the automatic measuring system of the present invention. The total system is composed of five electronic circuits/units namely (1) sensing unit, (2) signal processing and formation of end pulses, (3) length pulse detection circuit,(4) Output pulse-width enlarger, (5) LED display circuit/unit. The cooperative functions and interdependence of various units to transform the light radiation sensed by the phototransistors for the two ends of a billet length to be converted to measurement of length in a LED display unit adaptable to display 36 different lengths corresponding to three base lengths with their selected range of variability and least count for the system, are described below:
The sensing Unit has the design configuration providing a linear array of phototransistors/photodiodes that are for the first time in industrial application is housed inside soft wooden block, instead of costly and hard bakelite block conventionally used, with advantageous easy workability for shaping the block to requirement and safe operation in measurement of hot moving product, such as billets in rolling mifls, from a minimum distance with desired accuracy. Such
17

wooden blocks are centrally drilled for focusing and pin pointing the edges of billet. By using wood in sensing assembly unit, the cost of overall system has been reduced significantly.
The photosensor based automatic measuring system of the present invention is designed to ensure a selective range of variations in different base lengths and accuracy in measurements. Supposing the system has the range 'R' meter, related to variations in lengths of billets in different base lengths and the desired measuring accuracy is 'lc'(in mm), the numbers of photosensors 'n' required for measuring a particular base length is given as follows:

where PS00 and PSO1 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where Lbx is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements.
The number of said photo sensors 'n' required for measuring V number of base lengths of moving billets in said automatic system of length measurement is given by:

In the automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoreticalmeasuring error , is given by:
Where 'a' is the serial number/position of a particular sensor in the sensor stack that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack.
18

In a particular embodiment of the present invention for demonstrating said automatic system of measurement of length of moving product, particularly of hot moving billets in steel plants, to measure the base lengths of 5m, 6m and 12m, the dual photosensors were kept at a distance of 4.65m, 5.65m and 11.65m respectively adapted to incorporate a range of 550mm in measured length data for each base lengths i.e the corresponding ranges for the three base lengths being 4.95m to 4.4m, 5.95m to 5.4m and 11.95m to 11.4m, respectively; In this embodiment of the present invention, only 18 phototransistors have been used for measuring 33 different billet lengths. In said particular embodiment of the present automatic system of length measurement the position/location number 'a' varies from -5 to +5 in a step of 1, the total number of sensors in the stack being 11 and said zero/reference/dual sensors are three in numbers selectively located to measure three base lengths of moving billets, said dual sensor is selected/connected by means of selector switch corresponding to a particular base length.
The photosensors in the preferred embodiment for measuring different base lengths of hot moving billets, are in particular high gain, two bipolar, n-p-n silicon phototransistors (type 14 LF-32 Qualimatrix of USA make or equivalent of any other make) are configured to a darlington-pair and works as an emitter follower with its open base as shown in figure 5. The light radiation of billet is concentrated at the collector-base junction of phototransistors and generates enough electrons. The variation in the signal in light and dark state is sent to electronic processing unit, kept in a control pulpit at an electrical distance of 150 meters.
The Signal processing unit receive the signal from the phototransistors and transform the into end pulses. The emitter voltage of respective phototransistors is amplified in quad sections of linear operational amplifiers(IC type LM-324) in electronic processing unit. The signals are compared with set voltage of respective comparator circuits for eliminating the background light radiation as shown in figure 5. Subsequently, the output of comparator goes to high state. In this way, the states of all the eleven number phototransistors in the sensor stack gradually changes. There are six numbers operational amplifiers IC LM 324 used for eleven number amplifier circuits and the eleven number comparator circuits.
19

The front end pulses(FP) are formed by processing the output of a pair of successively placed photosensors in the sensor stack(SS), wherein the out put of the first photosensor is processed with the inverted output of second photosensors in one of the section of quad sections logic AND gate (IC TTL type 7408). In this way other front end pulses(FP) gradually formed by AND-ing the output of a phototransistor with inverted output of succeeding phototransistors in other sections of quad AND gates as shown in figure 5.
The dual photosensors(DS) PSO0 and PSO1 in pairs, have been put at 4.65m, 5.65m and 11.65m respectively from the mid of sensor stack for 5m, 6m/ 12m base lengths to sense the back end of billet. The back end pulse(BP) is formed by processing the inverted signal of PSOo with non-inverted signal of PSOi in one of the section of quad AND gate(IC 7408). After selecting the appropriate base length out of three different options through the selector switch provided for the purpose, as illustrated in figure 6, the end pulse signals are sent to the length pulse detection unit/circuit.
The length pulse detection unit is adapted to convert the front and back end pulses corresponding to a particular billet length into a representative 'Length-pulse'(LP), using simple logic gates. The simultaneous occurrence of any one of front end pulse(FP) of sensor stack(SS) is AND-ed with a back end pulse derived from dual reference/zero sensors(DS) of particular base length such that the output of this logic AND gate produces 'Length Pulse' (LP) which represents length of moving billet measured. The length pulse thus obtained is sent to pulse width enlarger circuit.
The pulse width enlarger unit simply enlarges the width of length pulse formed compatible with signals corresponding to least count of measurement into recognizable by human eye. The output at the length pulse detection unit has a pulse width depending on the speed of rolling and said length pulse that represent the length of billet needing widthwise enlargement prior to recognizable/readable display of measured length by display unit(DU) to favor display of output of pulse width enlarger in visually distinguishable form. The width of the said length pulse' is related to rolling speed of a particular base length of billet and the time needed
20

to cover the distance equal to the least count Ic in mm with a rolling speed of Sm m/sec is given by: t = (Ic/Sm) milliseconds(ms),
and that the value of 't' with least count lc = 50mm and maximum rolling speed of Sm = 4 m/sec for 12m base length, comes out to be 12.5 ms, which is much less than the limit of minimum recognition response of retina of human eye which is 20 ms. This is why a width wise enlargement of length pulse is needed and the same is carried out by latching this signal by J-K type flip-flop IC 7474 till the arrival of next length pulse.
The width wise enlarged length pulse signal now comes to an electronic display unit(DU) that serves as an important interface between the operator and the measuring system of this invention. The output pulse width enlarger is fed to LED based billet length display unit(DU) which is installed in the operator pulpit to guide him about the length of that billet which is recently cut. The concept of redundancy is also applied in the use of different light emitting diodes(LEDs) as illustrated in figure 6. A simple single array of LEDs displays the respective billet lengths by using few digital logic gates. In the particular embodiment of the measuring system for three selective base lengths e.g. 5m, 6m, 12m comprised 14 numbers LEDs for displaying 36 numbers of different billet lengths, as variations for the three base lengths within the selected range and precision of measurement. The number of LEDs needed for display of the base lengths V is given by (d+x), where 'd' is the number of LEDs needed to display a particular base length, as illustrate in figure 6.
21

We claim:
1. An automatic system of measurement of length of moving product, such as of hot moving
billets of various base lengths in rolling mills of steel plants comprising:
photosensor/phototranststor means to measure length of moving product;
said photosensors adapted to sense the light radiation from hot billet ends, the front and the back end of the moving billet, to favor said automatic measurement of lengths;
said photosensors means comprising a single array of photo sensors/ phototransistors (sensor stack) in selective numbers to sense the front end and a dual photosensor/phototransistors to sense the back end of moving product to facilitate said length measurement;
said automatic system of length measurement comprising, said sensor adapted to generate electrical signals by sensing variation in the signal reception for light and dark state that are converted to front end and back end pulses by means of a signal processor and these pulses finally generate length pulse, combining the two end pulses using logic gates, a pulse width enlarger circuit adapted to receive said length pulse , output of which is displayed as the length of billet in the LED based display unit.
2. An automatic system of measurement of length of moving product as claimed in claim 1
wherein said photosensors are selectively disposed away from the hot product/billet to
favor distance based measurement of length of the said hot moving billet without need of
calibration in the span of time with the system adapted to conduct 1:1 scaling between
coordinate of slab and the array of photo sensors;
the number of said photo sensors wnw required for a particular base length of billet in said automatic system of length measurement is based on:

where PS and PS01 are dual phototransistors used for sensing the back end of the billet and are kept at a distance of (Lbx+R/2) meter from the centre of sensor stack sensing the front end of billet, where is the minimum base length of a billet and 'R' is the range of variability of a particular base length and lc is the least count of measurements.
22

the number of said photo sensors xn' required for measuring V number of base lengths of moving billets in said automatic system of length measurement based on :n = (R/ lc +1 +2x)
said automatic system of length measurement involving photosensors/phototransistors, the length of moving billet incorporating the theoretical measuring error , is given by:
Where'a' is the serial number/position of a particular sensor in the sensor stack that is activated by an approaching billet edge within proximity of at least 50mm when the other end of the billet is leaving the sensing range of the dual /reference/zero sensor; said serial number/location of particular sensor sensing the characteristic dimension of a moving billet is decided by its relative position from the centre of sensor stack; said dual sensor is selected/connected by means of selector switch corresponding to a particular base length.
3. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 or 2 wherein said photo sensors are preferably placed inside soft wooden blocks
adapted for independent focusing and pinpointing of the ends of billets and to protect the
sensors from high billet temperature.
4. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 3 comprising,
measurement of the base lengths with said dual photosensors, three pairs acting as reference/zero sensors selectively distanced respectively from the center of sensor stack, comprising independently focusing sensors, to ascertain a selective range in measured values of each base lengths.
a selective least count maintained in said system of measurement, ensuring the limit of measuring error is limited to between 0 to 50mm and can be adjusted based on the accuracy desired by increasing the number of sensors for a given range, thus minimizing further the level of measuring error .
5. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 4, comprising interactive and cooperative functions of separate electronic
circuits preferably including sensing unit, signal processing and forming end pulses, length
pulse detection circuit, output pulse width enlarger and length display unit.
23

6. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 5, wherein said photosensor based measurement comprises n-p-n silicon
phototransistors to sense light radiation from hot billet ends, being concentrated at the
collector-base junction that in turn emits enough electrons;
the emitter voltage from said phototransistors being sent to a signal processor wherein it is amplified and compared with a set voltage in the respective comparator circuits for eliminating the background light radiation and thereby favor formation of front end and back end pulses;
7. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 6 wherein said signal processor of the automatic length measuring system
generate the 'front end pulse' by AND-ing the output of one phototransistors, with the
inverted output of the successive one in the respective quad section of logic AND gate; and
the 'back end pulse' is formed by processing the inverted signal of PS0o with non inverted
signal of PSoiin one of the quad section of logic AND gate, corresponding to dual
photosensor for sensing particular base length selected by selector switch.
8. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 7 wherein said length pulse that represent the length of billet needing
widthwise enlargement prior to recognizable/readable display of measured length by the
display unit to favor display of output of pulse width enlarger in visually distinguishable
form, as the width of the said 'length pulse' so derived depend on the rolling speed of a
particular base length of billet and the time needed to cover the distance equal to the least
count lc in mm with a rolling speed of Sm m/sec is given by:
t = (Ic/Sm) milliseconds(ms)/
and that the value of 't' for lc - 50mm and maximum rolling speed of Sm = 4 m/sec comes out to be 12.5 ms which is beyond the limit of recognition response of retina by human eye which is 20 ms.
9. An automatic system of measurement of length of moving product as claimed in anyone
of claims 1 to 8 wherein said simple single array of light emitting diodes(LEDs) displays the
respective billet lengths by using few digital logic gates, activated by the said display
located in the pulpit itself for display of billet lengths to the operator, acting as an interface
between the measuring system and the operator.
24

said display unit comprising of selective number of LEDs needed to display a range of 'x'
base lengths is given by:
x = d + x;
where 'd' is a particular base length.
25
10. An automatic system of measurement of length of moving product as claimed in
anyone of claims 1 to 9 wherein for automatic measuring of lengths of hot moving billets,
the number of LEDs in display unit is selectively provided preferably 14 for displaying 36
numbers of different billet lengths within the range (550mm) of variability of measured
dimensions corresponding to three base lengths 5m, 6m and 12m by the system having
specified least count of 50mm.
11. An automatic system of measurement of length of moving product such as hot moving
billets as substantially herein described and illustrated with reference to accompanying
figures.

The present invention is directed to an automatic online length measuring system for moving products including moving billets in rolling mills. The system automatically measures the various base lengths of billets, minimizing measuring error and reduce scrap. Moving billet length is measured by a single array of different phototransistors to sense the front end and dual phototransistors (DS) as reference/zero to sense the back end, placed at selective distances from centre of sensor stack(SS), favoring measurement of three base lengths with desired accuracy defined by selected range( R ) of 550mm and least count (Ic ) of 50mm. The front end(FP) pulse and the back end(BP) pulse from sensors are logically processed to get the length pulse(LP) that represents the length of moving billet, indicated on a display unit(DU) by LEDs. The speed of flying shear is adjusted by the operator directly from pulpit and limiting the error of measurement to 0 to 50mm or 0-0.3% reducing from about ± 250mm obtained in conventional methods.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=kqbm4zyfD0IMPB/FlO6Jmg==&loc=wDBSZCsAt7zoiVrqcFJsRw==

« Previous Patent

Next Patent »

Patent Number

268332

Indian Patent Application Number

1260/KOL/2006

PG Journal Number

35/2015

Publication Date

28-Aug-2015

Grant Date

26-Aug-2015

Date of Filing

22-Nov-2006

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA,RANCHI-834002

Inventors:

#	Inventor's Name	Inventor's Address
1	KHARE MALAYA RANJAN	RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, STEEL AUTHORITY OF INDIA LTD., RANCHI-834002. JHARKHAND, INDIA

PCT International Classification Number

G01B

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA