Title of Invention	SYSTEM TO MEASURE THE LENGTH OF SLAB
Abstract	A system for measuring the length of slabs for cutting into desired different base lengths. Basically the system involves low cost silicon photo sensor based slab length measuring system which would be adapted to directly and effectively measure the slab length at continuous casting unit thereby minimizing the generation of plate scrap in plate mills of steel plants. Importantly, the sensor system is housed within a wooden box having a silicon phototransistor operatively connected to optical amplification means and a cooperative wooden focusing tube which surprisingly favours pin pointing hot and cold slabs without any adverse effects of the wooden housing at the high operative temperatures of about 1100°C. The invention would make the measurement and cutting of slab in steel plants more reliable, user friendly and also cost effective.

Title of Invention

SYSTEM TO MEASURE THE LENGTH OF SLAB

Abstract

A system for measuring the length of slabs for cutting into desired different base lengths. Basically the system involves low cost silicon photo sensor based slab length measuring system which would be adapted to directly and effectively measure the slab length at continuous casting unit thereby minimizing the generation of plate scrap in plate mills of steel plants. Importantly, the sensor system is housed within a wooden box having a silicon phototransistor operatively connected to optical amplification means and a cooperative wooden focusing tube which surprisingly favours pin pointing hot and cold slabs without any adverse effects of the wooden housing at the high operative temperatures of about 1100°C. The invention would make the measurement and cutting of slab in steel plants more reliable, user friendly and also cost effective.

Full Text	Field of the invention The present invention is directed to measurement of length of slab for cutting into different base length in continuous casting units and in particular to a cost effective system for measuring the length of slabs for cutting into desired different base lengths. Importantly, the system of the invention involves low cost silicon photo sensor based slab length measuring system which would be adapted to directiy and effectively measure the slab length at continuous casting unit thereby minimizing the generation of plate scrap in plate mills of steel plants. Thus the invention is directed to make the measurement and cutting of slab in steel plants user friendly, cost effective and reliable. BACKGROUND ART It is well known that in steel plants molten steet is continuously cast into slabs. Usually after passing through accelerated water spray system, the slabs are gradually dragged and rolled down to ground level where they are art into 170 different base lengths, ranging from 5.5 m to 10.5m by means of gas cutting torches to meet the varying needs of the plate mills. At SBS stage slabs of CCS are further cut into three pieces (base lengths) in the range of 1.8m to 3.6m. The above process of cutting of slabs Involving gas cutting torches suffers from several inherent drawbacks /deficiencies. In particular, in this process (i) from 5.5m to 7.5m there, is no measuring system at all because of the movement of the gas flame which destroys the sensing device, and (if) from 7.5m onwartfs, the slabs use the contact type sensors which have additional problems of (a) metaflic rod gets damaged due to hitting of front end of bent slab, b) deposition of carbon particles on metallic rod which breaks the continuity of circuit, (c) it needs about minimum 500mm. gap between two successive slabs, For the above reasons, it is difficult to change the slab length after every half art hour by adjusting existing hanging metallic contact. Other measuring devices such as shaft encoder have further limitations which in dude tear and wear of rolls, non-contact / slip between roll and slab, glitches and unmeasured pulses, failure of couplings, hydraulically pressed rom requiring continuous adjustment and the necessity of cooling. Moreover, the laser based systems have limitations which include tilting of reflecting plane of moving slab, dust on tens causing system failure. The laser measuring system 2 based on time of flight principle need for continuous adjustment, complex circuitry to be maintained, requirement of the front end of the slab to be visible from the laser source, but hardly any gap between two successive pieces and it needs firstly 0.001 nano second timer for measuring slab length in mm and secondly it needs reflective surface which is not possible in steel product at semi finished stage- The CCD camera system also has its own limitation which includes the difficulty to sense the edges of slab and its scaling factor ranging from l:100/1000 need obstruction free area to view which fs not possible en the shop floor, and other [imitations are continuous supply of water to cool its electronics components, requirement of huge structure for installing and the need at least 500mm gap between two slabs. The roads cell based measuring system are also in use whfch again have problems such as requiring major installation work, requiring continuous calibration, indirect method calculate length by dividing weight / volume by its cross section, the cross section which itself varies +/- 10%. The Orbis Coll based measurement is found bo be not complete and reliable since while total cross section can be measured. However, the height or width of the object can not be measured. Also, the system does not work at higher speed, have poor response type and ft Is difficult to install and maintain existing mills and need huge gap between two pieces. Apart from the respective drawback / deficiency of the existing measuring devices made available to the art discussed about, all such conventional systems suffer from above said problems which tend to affect quality of the measurement apart from also being cost extensive. OBJECTS OF THE INVENTION It is thus basic object of the present invention to provide a system for measuring of the length of the slab and its cutting into different base lengths which would be reliable in the variable slab surface temperature range of 30C°C to 1100ºC as compared to other measuring systems and Importantly also be cost effective for wide scale application and use. 3 Another obiect of the present invention is directed to a system for measuring the length of slab and its catting in desired different base lengths involving a selective cost effective and rellable sensor assembly. Another object of the present Invention is directed to a system for measuring the length of the slab and Its cutting Into different desired length which would have the facility of pin pointing the movement of hot as west cold slab by selective sensor means which would have provision for suppressing and as such awowfans the light of the incoming hot slab which is directly / reflected from the rolled table and surrounding structure generating false measurement. Yet further object of the present invention is directed to a silicon photo transistor based sensor means which would enable sensing of slab whose surface temperature varies ranging form 400ºC to 1I00°C thereby providing for effective advantageous and reliable manner of slab sensing. A further of the present invention is directed to system for measuring the length of a slab and its cutting into desired length which would not require calibration and in the span of time and thereby make the process of slab measurement and cutting user friendly and with no complexity. A further object of the present Invention is directed to a system of measuring the slab and its cutting into desired length which would not require any cooling for the sensing unit though the measurement is carried from only lm from hot slab. Further object is directed to a low cost nighty reliable contact less dimensional measuring and controlling system of slabs wherein the operator can select any slab length from the pulpit itself without the need for going out every 20 minutes or heat change whichever is lesser for seeing the slab length. Anotner object of the present invention is directed to a system for measuring a length of slab and cutting toto desired different levels wherein less count Of measurement tan be adjusted as per accuracy desired by increasing the number of sensors which would favour bringing down the measuring error by possible increasing number of sensors. Yet another object of the present invention is directed to sensor means adapted to sense the slab for measurement and cutting which would enable effective focusing the sensor 4 lor length measurement and automatic length control and even sustain high degree of vibration requiring practically zero maintenance. A further object of the present invention is directed to a system for measuring the length of slab and cutting into different lengths wtiich would enable apart from improving the yield, would also favour upliftng the working conditions by relieving from excessive heat, dust and also accidents from fatigue operations involved in different processes. Yet another object of present invention is directed to optimization of apparatus for cutting slabs of desired lengths with minimum length of pFaEe scrap in cutting a strand slab into separate pieces. A further object is directed to impart accuracy in slab length measurement, reduce the tolerance of slab length and increase reliability significantly wherein the system would be effective even in minute gap in order of 500mm. In between two successive Slabs. A further object of the present Invention is directed to a safe, reliable and cost effective system for measuring the length of the slab and cutting into desired lengths which would also favour immediately correction in case of any required adjustment especially, in the bouncing of trolley thereby ensuring the accuracy and friability of the system, SUMMARY OF THE INVENTION Thus according to the basic aspect of the present invention there is provided a system for measuring the length of 3 stab and its cutting into desired different base lengths comprising: sensor stacks comprising plurality of photo sensor assemblies each said photo sensor assembly housed within an ordinary wooden block having a silicon phototransistor operatively connected bo a convex lens based optical amplification means and a cooperative wooden focusing tube said sensor assemblies arranged along a desired variable length for the monitoring and cutting of the slabs ; said sensor stacks operatively connected to corresponding LED display for indicating the length of the advancing slab through glowing of the LEPs upon sensing of the slab length by the multipte /170 nos. sensors; 5 each said LED in the length display unit having an associated length indication switches for selecting the desired slab length for cutting; means for selectivity positioning a gas cutting trolley for slab cutting based on the selected desired length of the steb as per the length selecting switch. In the above system the said convex lens based optical amplification means comprises a convex lens having + 45 optical amplification for sensing even little radiation from low temperature slabs. It is possible by way of me above system to cover about 5000 mm variation in slab length by arranging 170 numbers silicon photo transistors at an intervals of about 30mm in a sensor stack.The photoelectric current is sent through heat resistant cable to electronic processing unit wherein the weak signals of the photo sensors are amplified, a comparator circuit dips the photo voltage due to the surrounding light, the output current of the comparator circuit of operational amplifier iliuminate the different LEDs in the length display and control unit. The system ensures that on arrival of slab before respective photo sensor charme? (tube) , it Is displayed by means of the glowing LEDs which are installed in the slab length display unit in the pulpit. The photo sensor used in the system selectively comprises of slicon photo sensors configured in darlington pair with in built convex lens of +2 mm focal length. The light ray of the front end of moving slab gradually advances over photo translstor stack and the same is indicated by the glowing of different light emitting diodes of length display unit after processing through operabonai amplifiers and filter circuit.Each said light emitting diode and associated lengtfi selector switches are provided for their respective slab length with reference to the gas cutting touch.Preferably the sensor stack is put dose to the slab for minimiztng the measuring error. Importantly in accordance with an aspect tfte means for selectively positioning a gas cutting trottey comprises means for sensing the deviation of trolley from Its initial position including a sensor stack comprising of plurality of sensors preferably about 10 sensors arranged at intervals preferably about 10 mm from one side of the shadow provider ,preferably a metallic strip projected from the trolley, and a bunch of LEDs are 6 kept at the other side, such that in case of any deviation of trolley from its initial position is observed in the glowing of the LEDs the same is indicative for the operator to activated corrective measures by selecting the corresponding stab length selection switch. The velocity of the gas cuffing torches in the cutting trolley are synchronized with casting velocity by means of a gripper mechanism adapted to grip the stab and force trolley to move, after cutting the slab, the gripper mechanism is adapted to be released from the streams of cast slabs and the gas cutting trolley returns to its initial position to grip and wait for incoming stream of slab for storing cutting process. in accordance with another aspect of the invention there is provided a photo sensor assembly for measuring steb length having temperature m the range of 400ºC to 1100°C comprising a wooden rectangular shaped block housing havlng a silicon phototransistor operatively connected to a convex lens based optical amplification means to sense slab of Power temperature and a cooperative long wooden focusing tube for sensing stab of higher temperatures. The said convex lens based optical amplification means comprises a convex lens having + 45 optical amplification for sensing even little radiation from low temperature slabs. The stated said wooden tube comprises of a wooden tube preferably mare length but having smaller diameter. It is thus possible by way of the above disclosed system to carry out the measurement of length of slab and cutting into desired lengths involving multiple discreet sensors avoiding the normally optical sensor are used for sensing the presence of luminous / non-luminous object. The system of the invention and the method for measurement and stab cutting aivd using the same enables achieving measuring error less than 0.l% which is comparable with other measuring system. Importantly, also the system of the invention advantageously provides for selective use of sensors which would be cost effective and the soft wooden block provided to keep accessories like photo transistor sensor, lens and light emitting diodes and focusing tube Is made in wood itsetf by drilling entire wooden block centrally. This is a compfete deviation from the cost extensive and extremely hard bakelite block used for photo sensing elements known in the art. More importantly, it is unexpectedly and surprisingly found try way of the present invention that wooden block used to keep the accessories 7 does not suffer from any adverse effect even at high hot slab temperature of about 1100°C. Moreover, the system of the invention would favour pin pointing the movement of the hot as well as cold slab by the same sensor by way of tts fabrication in long wooden tubes and avoids problems of false measurement. Moreover advantageously by way of the selective silicon photo transistor in combination with tive bi- convex lens of magrifyinig power +45° it is possible to measure slabs having temperature even of the onder of the 400º by collecting the very weak radiation from slab by using bl-convex lens. Thus the above defective combination avoids limitations of conventional silicon sensor which are sensitive to only red / higher intensity of infrared energy 550°C above temperature range). The system does not require arty calibration in me span of time since it ?s 1:1 scaling between coordinate of slab and photo sensor array. There 15 also no n£ed for cooling of the sensing unit. It is thus possible to provide a low cost, highly reliable contact less dimensional measuring and controlling system since operator can select any slab length from the pulpit Itself without requirement going outside after every 20 minutes or heat change (whichever is lesser) for seeing the stab length. The least count of measurement can also be adjusted as per accuracy desired by Increasing me number of sensor. Presently, measuring error found in the art of upto 0.3% can be advantageousily reduced by further increasing the number of sensors. The system therefore utifces Independent sensors to focus arid sense the stab along with possible automatic length control. Advantageously the use of the wooden housing for the sensor provides the system with the ability to sustain high degree of vibration and requires pjacticalty zero maintenance. Besides improving the yields, the system of the invention is further directed to uplift the working condition by relieving the excessive heat, dust and also from accidents from fatigue operations involved in different processes. The system and method achieves optimization for cutting of the slab of desired levels with minimum amount plate scrap in cutting a strand of slab into separate pieces. 8 The reliability and accuracy of the system is such that there is no variation in accuracy in the slab measurement over period of time, importantly to the system reduces the tolerances of the slab length as well as it reduces the slab / plate scrap. The system of the invention is safe since it is usually installed 1m away from the hot slab and work satisfactorily even a minute gap of the order of 50mm, possible in between successive slabs. The selector switches enabte selecting of the slab length such as between. 5.5m to 10.57m. in comibination with multiple photo sensor. Advantageously, considering the bouncing of troltey have been displayed before the operator thereby immediate correction can be taken by length selector switches as there is no need of the operator for manually shifting the metallic contact as in the case of the earlier installed system. The details of the invention its object and advantages are explained hereunder in greater details in relation to norHimitfng exemplary illustration of the system and the method of measurement of sfab length and cutting of slab as per the following accompanying figures: BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Figure 1: is a schematic illustration of a slab caster; Figure 2: is a schematic illustration for conversion of continuous cast slab into plate; Figure 3: is an illustration of the manner of stab cutting through gas flame. Figure 4: is 3 representation of the relative sensitivity of Ge / Si photo sensors; Figure S: is a photo sensor assembly; (Intermediate development) Figure 6: is an illustration of an electronic circuit: used in combination with the photo sensors in the system; Figure 7: illustrate the electronic circuit for photo sensors; Figure 8: is an illustration of the final sensor for slab length measurement; and Figure 9: is a slab length display unit. Reference is, first invited to accompanying figures 1 to 3 which is a schematic representation of a slab caster. As shown in said figure the slab caster is adapted to continuously cast the molten steel into slabs of desired dimension. After passing through accelerated water spray system the slabs are gradually dragged and rolled down to ground level where they are cut into 170 different base length ranging from 5-5m to 10.5m long by means of gas cutting torches so as to meet the diverged needs of plate 9 mills. Customer of all over world at slafc storage stage, slabs or CCS are further cut into three pieces, base length of the range 1.8m to 3.6m. It would toe apparent from the above that in the system as above between 5.5m to 7.5m. there is no measuring system at all because of the movement of the gas flame. From 7.5m. onwards there is use of contact type of sensor which has accompanying problems such as frequent metallic rod damages, deposition of carbon particles and need for a 500m gap between two successive slabs. Importantly, usually a wide variation in temperature (400°C to 11OO°C) at slab surface is known due to coating of casting powder, scale formation and fluctuation of casting speed. It is thus known bo be belter to detect the slab of low temperature by using the Germanian photo sensor which is usually sensitive to low temperature radiation but their electrical behavior is unstable at higher temperature. On the other hand the presently available silicon photo sensors are stable at a higher operative temperature. But Its sensitivity is limited in visible and higher intensity of infra red radiation regions only. Normally, such silicon sensors sense object whose temperature is more than 550°C. In the backdrop of the above limitations, it is possible by way of the present invention to pTtrffde for a lov# tost photo sensor which would be effective in the wide temperature range of slab surfaces usually in the range of 4O0°c to 1100%. Reference, is nom invited to accompanying figure 4 which further illustrates the relative responses of the available Germanium photo sensor, silicon photo sensor and the modified convex lens accompanying silicon photo sensor of the present invention. As dearly illustrated in the said figure, by introducing optics the radiation fn the lower region of infra red region can be sensed even through the silicon photo transistor based sensor assembly of the invention vis-a-vis Germanium photo sensor which although can sence such radiation but is extremely cost extensive. Reference is Invited to accompanying figure 5 which illustrate photo sensor assembly (intermediate stage) in accordance with the present invention. As illustrated in the said figure, the photo sensor assembly Is specificaPFy adopted to suit measurement in wide temperature range. Thus while the silicon photo transistor (SPT) is shown provided in the sensor assembly which by itself is usually capable of sensing temperature more than 550ºCAdvantageously, however, the photo sensor assembly of the invention selectively uses along witfi the silicon photo transistor a convex lens (CL) having +45 optical amplification whereby it is possible to also sense whatever little radiation emerged out 10 from the low temperature slab. Thus by introducing optics in the sensing process it is possible to sense the slab even of 400°C (radiation in the lower range of infra region) through sllicon photo transistor. Importantly, also as apparent from said figure 5 for focused sensing by the sensor (intermediate stage) a focusing tube (FT) is also provided. Further, in order to effectively sense the slab of higher temperature the said wooden tube is provided in the sensor assembly as otherwise it would have sensed the light which is reflected from the rolled table and other surrounding structure and lead to false sensing. The manner of slab measurement and slab cutting using the system of the invention is discussed hereunder in greater details in relation to the further accompanying figures 6 to 9. The system for such stab length measurement and cutting of the present invention thus basically involves the following units; a) sensors stack, b) LED based slab length displaying units, c) Gas cutting trolley position sensing. The various units involved, in the system are further detailed hereunder. a) Sensor stack - By providing for the sensor stack it is possible to achieve 5000mm. variation of slab length which is covered by putting 170 nos. sEflcon photo transistors at an interval of 30mm. in a sensor stack . The photo transistor as explained above are put in the wooden blocks. Normally to protect Che sensor's heat from hot object costiy bakelite material is used. However, for the first time by way of present invention it is proposed to provide a low cost wooden block for mounting me sensing unit (Photo transistor). Also as dearly illustrated in Figure 5 in the same wooden block low cast powerful tens (+45 magnification) and also focusing tube are assembled and housed (in intermediate development of sensor). The photo electric current is sent through 0.2 sq. mm2 heat resistant cable to electronic processing unit in which big signal of photo sensor are amplified. Comparator's circuit is adapted to dick the photo voltage which is due to surrounding light (fig. 6). The output current of comparator circuit LM 324 operational amplifier illuminate the LSJs (Light Emitting Diodes). On arrival of bloom before respective photo sensor channel (tube), its shadow is displayed by means or glowing the LEDs which are installed in the pulpit. Photo sensor type 11 can be preferably 14 LF= 32 silicon photo transistors configured in Darlington pair within bulit convex lens of +2mm. focal length. b) LED based slab length display unit: Light ray of front end of moving slab gradually advances over photo transistor slack and same is indicated by glowing different light emitting diodes of length display unit after processing through operational amplifiers and filter circuit as shown in figure 6 to 9. Each light emitting diodes and associated length selector switches meant for their respective length with reference to gas cutting torch. For minimum measuring error, sensors stack is disposed closed to the stack preferably about 170 nos. LED alternate colours green / red can be put in display unit. Below each LED the measured bloom length is written such as 5.5m., 5.530m, 10.570m. each LED is incorporated with length selecting switch for selecting the desired bloom length c) Gas cutting trolley position sensing ; for sensing the deviation of trolley from its initial position, a sensor stack consisting of preferably about 10 sensors are kept at an Interval of 10mm. from one side of shadow provider (a metallic strip Is projected from the trolley) while a bunch of LED kept on the other side. If any deviation of trolley from its initial position is observed in the glowing of LEDs of display unit the operator can immediately take correcting action by selecting the corresponding selection switch (Figure 9). it is thus possible by way of the above disclose system of the invention to measure slab length in the accuracy of 0 to +30mm. in the range of 5.5m. to 10. 57m. Importantly, the accuracy in measurement favours better productivity per strands apart from being cost effective and reliable, importantty, the invention provides for the required system for measuring of the length of the slab and its cutting into different base lengths which would be reliable in the variable slab surface temperature range of 400°C to I100°Cas compared to other measuring systems and importantly also be cost effective for wide scale application and use. 12 WE CLAIM: l.A system for measuring the length of a sfab and its cutting into desired different base lengths compotising: sensor stacks comprising plurality of photo sensor assemblies each said photo sensor assembly housed within a wooded block, having a silicon phototransistor operatively connected to a convex lens based optical amplification means and a cooperative wooden focusing tube ,said sensor assemblies arranged along a desired variable length for the monitoring and cutting of the slabs ; said sensor stacks operativety connected to corresponding LED display for indicating the length of the advancing slab through glowing of the LEOs upon sensing of the slab length by the sensors; each said LED having an associated length indication switch for selecting the desired slab length for cutting; means for selectively positioning a gas cutting trolley for slab cutting based on the selected desired length of the slab as per the length selecting switch. 2. A system for measuring the length of a slab for cutting into desired different lengths as datmed in claim 1 wherein said convex lens based optical amplification means comprises a convex lens having + 45 optical amplification for sensing even little radiation from low temperature slabs. 3. A system for measuring the length of a slab for cutting into desired different lengths as claimed in anyone of Claims 1 to 2 wherein about 5000 mm variation in slab length is covered by arranging about: 170 numbers silicon photo transistors at intervals of about 30mm in a sensor stack. 4. A system for measuring the length of a slab for cutting into desired different lengths as daimed in anyone of daims 1 to 3 wherein the photoelectric current Is sent through heat resistant cable to electronic processing unit wherein the weak signals of tne photo sensors arc amplified, a comparator circuit dips the photo voltage due to tne surrounding light , the output current of the comparator circuit operational amplifier illuminating the LEDs. 13 5. A system for measuring the length of a slab for cutting into desired different lengths as claimed in anyone of claims 1 to 4 wherein on arrival of stab before respective photo I sensor channel (tube) , its shadow is displayed by means of the glowing LEDs which are installed in the pulpit. 6. A system for measuring the length of a slab for culling into desired different lengths as claimed in anyone of claims 1 to 5 wherein the photo sensor comprises silicon photo sensors as configured in darlington pair with in built convex lens of +2 mm focal length. 7. A system for measuring the length of a slab for cutting into desired different lengths as claimed in anyone of claims 1 to 6 wherein the light ray of the front end of moving slab gradually advances over photo transistor stack and the sarrvc is indicated by the glowing of different light emitting diodes of length display unit after processing through operational amplifiers and fitter circuit. 8. A system for measuring the length of a Slab for cutting into desired different lengths as claimed in anyone of dalrns 1 to 7 wherein each said light emitting diode and associated length selector switches are provided for their respective length with reference to the gas cutting torch. 9. A system for measuring the length of a siab for cutting into desired different lengths as daimed in anyone of daims 1 to 8 wherein preferably the sensor stack fs disposed dose to the Slab. 10. A system for measuring the length of a Stab for cutting into desired different lengths as claimed in anyone of claims I to 9 wherein means for selectively positioning a gas cutting trolley comprises means for sensing the deviation of trolley from its initial position including a sensor stack comprising of plurality of sensors preferably about 10 sensors arranged at intervals preferably about 10 mm from one side of the shadow provider ,preferably a metallic strip projected from the troley, and a bunch of LEDs are kept at the other side, such that in case of any deviation of brolley from Its initial positron is observed in the glowing of the LEDs the same is indicative for the operator to activated corrective measures by selecting the corresponding selection switch. 11. A photo sensor assembly for measuring slab length having temperature in the range of 400°C to H00°C comprising a wooden block sensor housing having a silicon photptransistpr operattvely connected to a convex lens based optical amplification means 14 to sense slab of lower temperature and a cooperative wooden focusing tube for sensing slab of higher temperatures. 12. A photo sensor assembly as claimed in anyone of claims 11 wherein said wooden tube is very long but smaller diameter tube is used for amplifying the weak radiations. 13. A photo sensor assembly as daimed in anyone of daims 11 or 12 comprising soft wooden box adapted to keep accessories including photo sensors,lens,LED and focusing tube obtained of wood by drilling entire wooden block centrally by different bit (different diameter) which is surprisingly free of any adverse effects at hot slab temperature of about 1100°C. 14. A photo sensor as claimed in anyone of claims 1 to 13 to favour pin-pointing of the movement of hot as well as cold slab wherein the sensor is adapted and fabricated in long wooden tube with smaller cross section such as to avoid the probfem of false measurement and cutting of slabs. 15. A system for measuring the length of a stab for cutting into desired different lengths and a photo sensor assembly substantially as herein described and illustrated with reference to the accompanying figures. 15 A system for measuring the length of slabs for cutting into desired different base lengths. Basically the system involves low cost silicon photo sensor based slab length measuring system which would be adapted to directly and effectively measure the slab length at continuous casting unit thereby minimizing the generation of plate scrap in plate mills of steel plants. Importantly, the sensor system is housed within a wooden box having a silicon phototransistor operatively connected to optical amplification means and a cooperative wooden focusing tube which surprisingly favours pin pointing hot and cold slabs without any adverse effects of the wooden housing at the high operative temperatures of about 1100°C. The invention would make the measurement and cutting of slab in steel plants more reliable, user friendly and also cost effective.

Full Text

Field of the invention
The present invention is directed to measurement of length of slab for cutting into
different base length in continuous casting units and in particular to a cost effective
system for measuring the length of slabs for cutting into desired different base lengths.
Importantly, the system of the invention involves low cost silicon photo sensor based
slab length measuring system which would be adapted to directiy and effectively
measure the slab length at continuous casting unit thereby minimizing the generation of
plate scrap in plate mills of steel plants. Thus the invention is directed to make the
measurement and cutting of slab in steel plants user friendly, cost effective and reliable.
BACKGROUND ART
It is well known that in steel plants molten steet is continuously cast into slabs. Usually
after passing through accelerated water spray system, the slabs are gradually dragged
and rolled down to ground level where they are art into 170 different base lengths,
ranging from 5.5 m to 10.5m by means of gas cutting torches to meet the varying needs
of the plate mills. At SBS stage slabs of CCS are further cut into three pieces (base
lengths) in the range of 1.8m to 3.6m.
The above process of cutting of slabs Involving gas cutting torches suffers from several
inherent drawbacks /deficiencies. In particular, in this process (i) from 5.5m to 7.5m
there, is no measuring system at all because of the movement of the gas flame which
destroys the sensing device, and (if) from 7.5m onwartfs, the slabs use the contact type
sensors which have additional problems of (a) metaflic rod gets damaged due to hitting
of front end of bent slab, b) deposition of carbon particles on metallic rod which breaks
the continuity of circuit, (c) it needs about minimum 500mm. gap between two
successive slabs, For the above reasons, it is difficult to change the slab length after
every half art hour by adjusting existing hanging metallic contact.
Other measuring devices such as shaft encoder have further limitations which in dude
tear and wear of rolls, non-contact / slip between roll and slab, glitches and unmeasured
pulses, failure of couplings, hydraulically pressed rom requiring continuous adjustment
and the necessity of cooling.
Moreover, the laser based systems have limitations which include tilting of reflecting
plane of moving slab, dust on tens causing system failure. The laser measuring system
2

based on time of flight principle need for continuous adjustment, complex circuitry to be
maintained, requirement of the front end of the slab to be visible from the laser source,
but hardly any gap between two successive pieces and it needs firstly 0.001 nano second
timer for measuring slab length in mm and secondly it needs reflective surface which is
not possible in steel product at semi finished stage-
The CCD camera system also has its own limitation which includes the difficulty to sense
the edges of slab and its scaling factor ranging from l:100/1000 need obstruction free
area to view which fs not possible en the shop floor, and other [imitations are continuous
supply of water to cool its electronics components, requirement of huge structure for
installing and the need at least 500mm gap between two slabs.
The roads cell based measuring system are also in use whfch again have problems such
as requiring major installation work, requiring continuous calibration, indirect method
calculate length by dividing weight / volume by its cross section, the cross section which
itself varies +/- 10%.
The Orbis Coll based measurement is found bo be not complete and reliable since while
total cross section can be measured. However, the height or width of the object can not
be measured. Also, the system does not work at higher speed, have poor response type
and ft Is difficult to install and maintain existing mills and need huge gap between two
pieces.
Apart from the respective drawback / deficiency of the existing measuring devices made
available to the art discussed about, all such conventional systems suffer from above
said problems which tend to affect quality of the measurement apart from also being
cost extensive.
OBJECTS OF THE INVENTION
It is thus basic object of the present invention to provide a system for measuring of the
length of the slab and its cutting into different base lengths which would be reliable in
the variable slab surface temperature range of 30C°C to 1100ºC as compared to other
measuring systems and Importantly also be cost effective for wide scale application and
use.
3

Another obiect of the present invention is directed to a system for measuring the length
of slab and its catting in desired different base lengths involving a selective cost effective
and rellable sensor assembly.
Another object of the present Invention is directed to a system for measuring the length
of the slab and Its cutting Into different desired length which would have the facility of
pin pointing the movement of hot as west cold slab by selective sensor means which
would have provision for suppressing and as such awowfans the light of the incoming hot
slab which is directly / reflected from the rolled table and surrounding structure
generating false measurement.
Yet further object of the present invention is directed to a silicon photo transistor based
sensor means which would enable sensing of slab whose surface temperature varies
ranging form 400ºC to 1I00°C thereby providing for effective advantageous and reliable
manner of slab sensing.
A further of the present invention is directed to system for measuring the length of a
slab and its cutting into desired length which would not require calibration and in the
span of time and thereby make the process of slab measurement and cutting user
friendly and with no complexity.
A further object of the present Invention is directed to a system of measuring the slab
and its cutting into desired length which would not require any cooling for the sensing
unit though the measurement is carried from only lm from hot slab.
Further object is directed to a low cost nighty reliable contact less dimensional measuring
and controlling system of slabs wherein the operator can select any slab length from the
pulpit itself without the need for going out every 20 minutes or heat change whichever is
lesser for seeing the slab length.
Anotner object of the present invention is directed to a system for measuring a length of
slab and cutting toto desired different levels wherein less count Of measurement tan be
adjusted as per accuracy desired by increasing the number of sensors which would
favour bringing down the measuring error by possible increasing number of sensors.
Yet another object of the present invention is directed to sensor means adapted to sense
the slab for measurement and cutting which would enable effective focusing the sensor
4

lor length measurement and automatic length control and even sustain high degree of
vibration requiring practically zero maintenance.
A further object of the present invention is directed to a system for measuring the length
of slab and cutting into different lengths wtiich would enable apart from improving the
yield, would also favour upliftng the working conditions by relieving from excessive heat,
dust and also accidents from fatigue operations involved in different processes.
Yet another object of present invention is directed to optimization of apparatus for
cutting slabs of desired lengths with minimum length of pFaEe scrap in cutting a strand
slab into separate pieces.
A further object is directed to impart accuracy in slab length measurement, reduce the
tolerance of slab length and increase reliability significantly wherein the system would be
effective even in minute gap in order of 500mm. In between two successive Slabs.
A further object of the present Invention is directed to a safe, reliable and cost effective
system for measuring the length of the slab and cutting into desired lengths which would
also favour immediately correction in case of any required adjustment especially, in the
bouncing of trolley thereby ensuring the accuracy and friability of the system,
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a system
for measuring the length of 3 stab and its cutting into desired different base lengths
comprising:
sensor stacks comprising plurality of photo sensor assemblies each said photo sensor
assembly housed within an ordinary wooden block having a silicon phototransistor
operatively connected bo a convex lens based optical amplification means and a
cooperative wooden focusing tube said sensor assemblies arranged along a desired
variable length for the monitoring and cutting of the slabs ;
said sensor stacks operatively connected to corresponding LED display for indicating the
length of the advancing slab through glowing of the LEPs upon sensing of the slab length
by the multipte /170 nos. sensors;
5

each said LED in the length display unit having an associated length indication switches
for selecting the desired slab length for cutting;
means for selectivity positioning a gas cutting trolley for slab cutting based on the
selected desired length of the steb as per the length selecting switch.
In the above system the said convex lens based optical amplification means comprises a
convex lens having + 45 optical amplification for sensing even little radiation from low
temperature slabs.
It is possible by way of me above system to cover about 5000 mm variation in slab
length by arranging 170 numbers silicon photo transistors at an intervals of about 30mm
in a sensor stack.The photoelectric current is sent through heat resistant cable to
electronic processing unit wherein the weak signals of the photo sensors are amplified, a
comparator circuit dips the photo voltage due to the surrounding light, the output
current of the comparator circuit of operational amplifier iliuminate the different LEDs in
the length display and control unit.
The system ensures that on arrival of slab before respective photo sensor charme?
(tube) , it Is displayed by means of the glowing LEDs which are installed in the slab
length display unit in the pulpit.
The photo sensor used in the system selectively comprises of slicon photo sensors
configured in darlington pair with in built convex lens of +2 mm focal length.
The light ray of the front end of moving slab gradually advances over photo translstor
stack and the same is indicated by the glowing of different light emitting diodes of length
display unit after processing through operabonai amplifiers and filter circuit.Each said
light emitting diode and associated lengtfi selector switches are provided for their
respective slab length with reference to the gas cutting touch.Preferably the sensor stack
is put dose to the slab for minimiztng the measuring error.
Importantly in accordance with an aspect tfte means for selectively positioning a gas
cutting trottey comprises means for sensing the deviation of trolley from Its initial
position including a sensor stack comprising of plurality of sensors preferably about 10
sensors arranged at intervals preferably about 10 mm from one side of the shadow
provider ,preferably a metallic strip projected from the trolley, and a bunch of LEDs are
6

kept at the other side, such that in case of any deviation of trolley from its initial position
is observed in the glowing of the LEDs the same is indicative for the operator to
activated corrective measures by selecting the corresponding stab length selection
switch.
The velocity of the gas cuffing torches in the cutting trolley are synchronized with
casting velocity by means of a gripper mechanism adapted to grip the stab and force
trolley to move, after cutting the slab, the gripper mechanism is adapted to be released
from the streams of cast slabs and the gas cutting trolley returns to its initial position to
grip and wait for incoming stream of slab for storing cutting process.
in accordance with another aspect of the invention there is provided a photo sensor
assembly for measuring steb length having temperature m the range of 400ºC to 1100°C
comprising a wooden rectangular shaped block housing havlng a silicon phototransistor
operatively connected to a convex lens based optical amplification means to sense slab
of Power temperature and a cooperative long wooden focusing tube for sensing stab of
higher temperatures.
The said convex lens based optical amplification means comprises a convex lens having
+ 45 optical amplification for sensing even little radiation from low temperature slabs.
The stated said wooden tube comprises of a wooden tube preferably mare length but
having smaller diameter.
It is thus possible by way of the above disclosed system to carry out the measurement
of length of slab and cutting into desired lengths involving multiple discreet sensors
avoiding the normally optical sensor are used for sensing the presence of luminous /
non-luminous object. The system of the invention and the method for measurement and
stab cutting aivd using the same enables achieving measuring error less than 0.l% which
is comparable with other measuring system.
Importantly, also the system of the invention advantageously provides for selective use
of sensors which would be cost effective and the soft wooden block provided to keep
accessories like photo transistor sensor, lens and light emitting diodes and focusing tube
Is made in wood itsetf by drilling entire wooden block centrally. This is a compfete
deviation from the cost extensive and extremely hard bakelite block used for photo
sensing elements known in the art. More importantly, it is unexpectedly and surprisingly
found try way of the present invention that wooden block used to keep the accessories
7

does not suffer from any adverse effect even at high hot slab temperature of about
1100°C. Moreover, the system of the invention would favour pin pointing the movement
of the hot as well as cold slab by the same sensor by way of tts fabrication in long
wooden tubes and avoids problems of false measurement.
Moreover advantageously by way of the selective silicon photo transistor in combination
with tive bi- convex lens of magrifyinig power +45° it is possible to measure slabs having
temperature even of the onder of the 400º by collecting the very weak radiation from
slab by using bl-convex lens. Thus the above defective combination avoids limitations of
conventional silicon sensor which are sensitive to only red / higher intensity of infrared
energy 550°C above temperature range).
The system does not require arty calibration in me span of time since it ?s 1:1 scaling
between coordinate of slab and photo sensor array. There 15 also no n£ed for cooling of
the sensing unit.
It is thus possible to provide a low cost, highly reliable contact less dimensional
measuring and controlling system since operator can select any slab length from the
pulpit Itself without requirement going outside after every 20 minutes or heat change
(whichever is lesser) for seeing the stab length.
The least count of measurement can also be adjusted as per accuracy desired by
Increasing me number of sensor. Presently, measuring error found in the art of upto
0.3% can be advantageousily reduced by further increasing the number of sensors.
The system therefore utifces Independent sensors to focus arid sense the stab along with
possible automatic length control. Advantageously the use of the wooden housing for the
sensor provides the system with the ability to sustain high degree of vibration and
requires pjacticalty zero maintenance.
Besides improving the yields, the system of the invention is further directed to uplift the
working condition by relieving the excessive heat, dust and also from accidents from
fatigue operations involved in different processes. The system and method achieves
optimization for cutting of the slab of desired levels with minimum amount plate scrap in
cutting a strand of slab into separate pieces.
8

The reliability and accuracy of the system is such that there is no variation in accuracy in
the slab measurement over period of time, importantly to the system reduces the
tolerances of the slab length as well as it reduces the slab / plate scrap.
The system of the invention is safe since it is usually installed 1m away from the hot slab
and work satisfactorily even a minute gap of the order of 50mm, possible in between
successive slabs. The selector switches enabte selecting of the slab length such as
between. 5.5m to 10.57m. in comibination with multiple photo sensor. Advantageously,
considering the bouncing of troltey have been displayed before the operator thereby
immediate correction can be taken by length selector switches as there is no need of the
operator for manually shifting the metallic contact as in the case of the earlier installed
system.
The details of the invention its object and advantages are explained hereunder in greater
details in relation to norHimitfng exemplary illustration of the system and the method of
measurement of sfab length and cutting of slab as per the following accompanying
figures:
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is a schematic illustration of a slab caster;
Figure 2: is a schematic illustration for conversion of continuous cast slab into plate;
Figure 3: is an illustration of the manner of stab cutting through gas flame.
Figure 4: is 3 representation of the relative sensitivity of Ge / Si photo sensors;
Figure S: is a photo sensor assembly; (Intermediate development)
Figure 6: is an illustration of an electronic circuit: used in combination with the photo
sensors in the system;
Figure 7: illustrate the electronic circuit for photo sensors;
Figure 8: is an illustration of the final sensor for slab length measurement;
and
Figure 9: is a slab length display unit.
Reference is, first invited to accompanying figures 1 to 3 which is a schematic
representation of a slab caster. As shown in said figure the slab caster is adapted to
continuously cast the molten steel into slabs of desired dimension. After passing through
accelerated water spray system the slabs are gradually dragged and rolled down to
ground level where they are cut into 170 different base length ranging from 5-5m to
10.5m long by means of gas cutting torches so as to meet the diverged needs of plate
9

mills. Customer of all over world at slafc storage stage, slabs or CCS are further cut into
three pieces, base length of the range 1.8m to 3.6m.
It would toe apparent from the above that in the system as above between 5.5m to
7.5m. there is no measuring system at all because of the movement of the gas flame.
From 7.5m. onwards there is use of contact type of sensor which has accompanying
problems such as frequent metallic rod damages, deposition of carbon particles and need
for a 500m gap between two successive slabs.
Importantly, usually a wide variation in temperature (400°C to 11OO°C) at slab surface is
known due to coating of casting powder, scale formation and fluctuation of casting
speed. It is thus known bo be belter to detect the slab of low temperature by using the
Germanian photo sensor which is usually sensitive to low temperature radiation but their
electrical behavior is unstable at higher temperature. On the other hand the presently
available silicon photo sensors are stable at a higher operative temperature. But Its
sensitivity is limited in visible and higher intensity of infra red radiation regions only.
Normally, such silicon sensors sense object whose temperature is more than 550°C.
In the backdrop of the above limitations, it is possible by way of the present invention to
pTtrffde for a lov# tost photo sensor which would be effective in the wide temperature
range of slab surfaces usually in the range of 4O0°c to 1100%.
Reference, is nom invited to accompanying figure 4 which further illustrates the relative
responses of the available Germanium photo sensor, silicon photo sensor and the
modified convex lens accompanying silicon photo sensor of the present invention. As
dearly illustrated in the said figure, by introducing optics the radiation fn the lower
region of infra red region can be sensed even through the silicon photo transistor based
sensor assembly of the invention vis-a-vis Germanium photo sensor which although can
sence such radiation but is extremely cost extensive.
Reference is Invited to accompanying figure 5 which illustrate photo sensor assembly
(intermediate stage) in accordance with the present invention. As illustrated in the said
figure, the photo sensor assembly Is specificaPFy adopted to suit measurement in wide
temperature range. Thus while the silicon photo transistor (SPT) is shown provided in
the sensor assembly which by itself is usually capable of sensing temperature more than
550ºCAdvantageously, however, the photo sensor assembly of the invention selectively
uses along witfi the silicon photo transistor a convex lens (CL) having +45 optical
amplification whereby it is possible to also sense whatever little radiation emerged out
10

from the low temperature slab. Thus by introducing optics in the sensing process it is
possible to sense the slab even of 400°C (radiation in the lower range of infra region)
through sllicon photo transistor.
Importantly, also as apparent from said figure 5 for focused sensing by the sensor
(intermediate stage) a focusing tube (FT) is also provided. Further, in order to effectively
sense the slab of higher temperature the said wooden tube is provided in the sensor
assembly as otherwise it would have sensed the light which is reflected from the rolled
table and other surrounding structure and lead to false sensing.
The manner of slab measurement and slab cutting using the system of the invention is
discussed hereunder in greater details in relation to the further accompanying figures 6
to 9.
The system for such stab length measurement and cutting of the present invention thus
basically involves the following units; a) sensors stack, b) LED based slab length
displaying units, c) Gas cutting trolley position sensing. The various units involved, in the
system are further detailed hereunder.
a) Sensor stack - By providing for the sensor stack it is possible to achieve
5000mm. variation of slab length which is covered by putting 170 nos. sEflcon
photo transistors at an interval of 30mm. in a sensor stack . The photo transistor
as explained above are put in the wooden blocks. Normally to protect Che
sensor's heat from hot object costiy bakelite material is used. However, for the
first time by way of present invention it is proposed to provide a low cost
wooden block for mounting me sensing unit (Photo transistor). Also as dearly
illustrated in Figure 5 in the same wooden block low cast powerful tens (+45
magnification) and also focusing tube are assembled and housed (in
intermediate development of sensor).
The photo electric current is sent through 0.2 sq. mm2 heat resistant cable to
electronic processing unit in which big signal of photo sensor are amplified.
Comparator's circuit is adapted to dick the photo voltage which is due to
surrounding light (fig. 6). The output current of comparator circuit LM 324
operational amplifier illuminate the LSJs (Light Emitting Diodes). On arrival of
bloom before respective photo sensor channel (tube), its shadow is displayed by
means or glowing the LEDs which are installed in the pulpit. Photo sensor type
11

can be preferably 14 LF= 32 silicon photo transistors configured in Darlington pair
within bulit convex lens of +2mm. focal length.
b) LED based slab length display unit: Light ray of front end of moving slab
gradually advances over photo transistor slack and same is indicated by glowing
different light emitting diodes of length display unit after processing through
operational amplifiers and filter circuit as shown in figure 6 to 9. Each light
emitting diodes and associated length selector switches meant for their
respective length with reference to gas cutting torch. For minimum measuring
error, sensors stack is disposed closed to the stack preferably about 170 nos.
LED alternate colours green / red can be put in display unit. Below each LED the
measured bloom length is written such as 5.5m., 5.530m, 10.570m. each LED is
incorporated with length selecting switch for selecting the desired bloom length
c) Gas cutting trolley position sensing ; for sensing the deviation of trolley from its
initial position, a sensor stack consisting of preferably about 10 sensors are kept
at an Interval of 10mm. from one side of shadow provider (a metallic strip Is
projected from the trolley) while a bunch of LED kept on the other side. If any
deviation of trolley from its initial position is observed in the glowing of LEDs of
display unit the operator can immediately take correcting action by selecting the
corresponding selection switch (Figure 9).
it is thus possible by way of the above disclose system of the invention to measure slab
length in the accuracy of 0 to +30mm. in the range of 5.5m. to 10. 57m. Importantly,
the accuracy in measurement favours better productivity per strands apart from being
cost effective and reliable, importantty, the invention provides for the required system
for measuring of the length of the slab and its cutting into different base lengths which
would be reliable in the variable slab surface temperature range of 400°C to I100°Cas
compared to other measuring systems and importantly also be cost effective for wide
scale application and use.
12

WE CLAIM:
l.A system for measuring the length of a sfab and its cutting into desired different base
lengths compotising:
sensor stacks comprising plurality of photo sensor assemblies each said photo sensor
assembly housed within a wooded block, having a silicon phototransistor operatively
connected to a convex lens based optical amplification means and a cooperative wooden
focusing tube ,said sensor assemblies arranged along a desired variable length for the
monitoring and cutting of the slabs ;
said sensor stacks operativety connected to corresponding LED display for indicating the
length of the advancing slab through glowing of the LEOs upon sensing of the slab length
by the sensors;
each said LED having an associated length indication switch for selecting the desired slab
length for cutting;
means for selectively positioning a gas cutting trolley for slab cutting based on the
selected desired length of the slab as per the length selecting switch.
2. A system for measuring the length of a slab for cutting into desired different lengths
as datmed in claim 1 wherein said convex lens based optical amplification means
comprises a convex lens having + 45 optical amplification for sensing even little
radiation from low temperature slabs.
3. A system for measuring the length of a slab for cutting into desired different lengths
as claimed in anyone of Claims 1 to 2 wherein about 5000 mm variation in slab length is
covered by arranging about: 170 numbers silicon photo transistors at intervals of about
30mm in a sensor stack.
4. A system for measuring the length of a slab for cutting into desired different lengths
as daimed in anyone of daims 1 to 3 wherein the photoelectric current Is sent through
heat resistant cable to electronic processing unit wherein the weak signals of tne photo
sensors arc amplified, a comparator circuit dips the photo voltage due to tne
surrounding light , the output current of the comparator circuit operational amplifier
illuminating the LEDs.
13

5. A system for measuring the length of a slab for cutting into desired different lengths
as claimed in anyone of claims 1 to 4 wherein on arrival of stab before respective photo
I sensor channel (tube) , its shadow is displayed by means of the glowing LEDs which are
installed in the pulpit.
6. A system for measuring the length of a slab for culling into desired different lengths
as claimed in anyone of claims 1 to 5 wherein the photo sensor comprises silicon photo
sensors as configured in darlington pair with in built convex lens of +2 mm focal length.
7. A system for measuring the length of a slab for cutting into desired different lengths
as claimed in anyone of claims 1 to 6 wherein the light ray of the front end of moving
slab gradually advances over photo transistor stack and the sarrvc is indicated by the
glowing of different light emitting diodes of length display unit after processing through
operational amplifiers and fitter circuit.
8. A system for measuring the length of a Slab for cutting into desired different lengths
as claimed in anyone of dalrns 1 to 7 wherein each said light emitting diode and
associated length selector switches are provided for their respective length with
reference to the gas cutting torch.
9. A system for measuring the length of a siab for cutting into desired different lengths
as daimed in anyone of daims 1 to 8 wherein preferably the sensor stack fs disposed
dose to the Slab.
10. A system for measuring the length of a Stab for cutting into desired different lengths
as claimed in anyone of claims I to 9 wherein means for selectively positioning a gas
cutting trolley comprises means for sensing the deviation of trolley from its initial
position including a sensor stack comprising of plurality of sensors preferably about 10
sensors arranged at intervals preferably about 10 mm from one side of the shadow
provider ,preferably a metallic strip projected from the troley, and a bunch of LEDs are
kept at the other side, such that in case of any deviation of brolley from Its initial positron
is observed in the glowing of the LEDs the same is indicative for the operator to
activated corrective measures by selecting the corresponding selection switch.
11. A photo sensor assembly for measuring slab length having temperature in the range
of 400°C to H00°C comprising a wooden block sensor housing having a silicon
photptransistpr operattvely connected to a convex lens based optical amplification means
14

to sense slab of lower temperature and a cooperative wooden focusing tube for sensing
slab of higher temperatures.
12. A photo sensor assembly as claimed in anyone of claims 11 wherein said wooden
tube is very long but smaller diameter tube is used for amplifying the weak radiations.
13. A photo sensor assembly as daimed in anyone of daims 11 or 12 comprising soft
wooden box adapted to keep accessories including photo sensors,lens,LED and focusing
tube obtained of wood by drilling entire wooden block centrally by different bit (different
diameter) which is surprisingly free of any adverse effects at hot slab temperature of
about 1100°C.
14. A photo sensor as claimed in anyone of claims 1 to 13 to favour pin-pointing of the
movement of hot as well as cold slab wherein the sensor is adapted and fabricated in
long wooden tube with smaller cross section such as to avoid the probfem of false
measurement and cutting of slabs.
15. A system for measuring the length of a stab for cutting into desired different lengths
and a photo sensor assembly substantially as herein described and illustrated with
reference to the accompanying figures.

15

A system for measuring the length of slabs for cutting into desired different
base lengths. Basically the system involves low cost silicon photo sensor
based slab length measuring system which would be adapted to directly and
effectively measure the slab length at continuous casting unit thereby
minimizing the generation of plate scrap in plate mills of steel plants.
Importantly, the sensor system is housed within a wooden box having a
silicon phototransistor operatively connected to optical amplification means
and a cooperative wooden focusing tube which surprisingly favours pin
pointing hot and cold slabs without any adverse effects of the wooden
housing at the high operative temperatures of about 1100°C. The invention
would make the measurement and cutting of slab in steel plants more
reliable, user friendly and also cost effective.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=EMXHVs7zMFT1sGRmqikSPA==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

271489

Indian Patent Application Number

185/KOL/2006

PG Journal Number

09/2016

Publication Date

26-Feb-2016

Grant Date

23-Feb-2016

Date of Filing

06-Mar-2006

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA, RANCHI-834002 STATE OF JHARKHAND, INDIA

Inventors:

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

PCT International Classification Number

G21C21/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA