Title of Invention

CONTROL SYSTEM FOR END CUTTING OF HOT ROLLED PRODUCTS USING FLYING SHEAR IN A HOT ROLLING MILL

Abstract

The control system for end cutting of hot rolled products using flying shear in a hot rolling mill which would enable automatic cutting of front end and/or back end of product and would be simple to operate comprises controller based system adapted to receive input signals from a pinch roll sensing control, hot metal detector, selector switch, means for measuring linear speed of metal and adapted to generate signals to activate an opto-coupler interface for the end cutting operation. The system can be used in a wire rod mill to cut the back of wire rod. The system would also provide for length of cut piece to be uniform in length and would serve as a cost effective system adapted for use in an existing rolling mill to have a facility of front end cutting and back end cutting.

Full Text

The present invention relates to a control system for end cutting of hot rolled products using flying shear in a hot rolling mill which would enable automatic cutting of front end and/or back end of product by a microcontroller based system and would thus be simple to operate. The system can be used in a wire rod mill to cut the back of wire rod. Normally in a rolling mill, when metal is rolled, the front end ana back end of a product is defective. To eliminate the defect the front end and back end is cut. In a wire rod mill, the last 2 meter and first 2 meter is cut to make the wire rod defect free. This cutting is to be done after 9th stand using a flying shear. In the presently known that the back end cutting is usually not done. After rolling the entire material the defective back end portion is cut manually by gas cut. Such conventional manually operated system for back end cutting and front end cutting operation suffers from drawbacks /disadvantages, which are discussed hereunder. A. Manual cutting is done at the end of rolling. In a wire rod mill comprising of 23 stands, manual cutting is to be done after 23rd stand and after the metal is taken to a safe place to enable the operator to cut the back end. This causes unnecessry rolling of the metal from 9th stand to 23rd stand and thereby consuming more electrical power, decreasing roll life. B. Some time is utilised to roll defective material. C. People have tried to implement the system using a programmable controller. The response of programmable controller will not be fast and therefore cutting accuracy will not be available with a programmable controller. It is thus basic object of the present invention to provide a control system for end cutting of hot rolled products using flying shear in a hot rolling mill. Another object of the present invention is to provide a system to provide a system to cut the back end and front end in the intermediate place using a flying shear in such a way that the length of cut piece will be uniform in length. 2 Yet anotner object of the present invention is to provide for a cost-effective system adapted for use in an existing rolling mill to have a facility of front end cutting and back end cutting. Summary of Invention Thus according to the present invention there is provided a control system for back and/or front cutting operation in a hot rolling mill comprising: a pinch roll sensing contact for feeding the billet into the rolling stand; hot metal detector adapted to view the presence of hot metal; means to measure the linear speed of the hot metal; selector switch means adapted to genarate time lag signals based on the desired cut and the linear speed of the metal in the stand; micro controller based board adapted to receive input signals from said pinch roll sensing control, hot metal detector, selector switch, means for measuring linear speed of metal and adapted to generate signals to activate an opto-coupler interface for the end cutting operation. The above system of the invention basically comprises of the micro controller board which is adapted to receive digital input signals from the said hot metal detector, pinch roll, selector switch through a relay interface and analog input signal from said means for measuring the linear speed of the metal which is preferably a tacho generator signal through an isolation amplfier. Importantly, the above control system is adapted for use in wire rod rolling line for end cutting of hot rolled products using flying shear in a hot rolling mill. Based on these inputs-the microprocessor board generates output digital signals to activate an opto-coupler interface which is operative connected to a flying shear to carry out said cutting of the hot metal. The processor is also adapted to generate delay output indication and a watch dog timer output. The watch dog timer output is such that as long as the CPU is running and executing the application program a pulse is available in a selected port in CPU. This pulse from port resets a counter. As long as the counter is reset cyclically, counter reading cannot go high. If pulse is not available from 3 said selected port and the counter reading goes to high value and this high value resets the CPU. Each of said micro controller board, relay interface, isolation amplifier and opto coupler are operatively connected to power supply. The output from the opto-coupler is fed into a transistor, which in turn drives a relay. The NO contact of relay drives a contactor such that when contactor is on its NO contact is used to drive the shear mechanism. When contactor is dropped, the shear is Off. Preferably, the selector switch is provided with 3 position and is mounted with control pulpit. Position 1 indicative of required one cut, position 2 indicative of required two cut and position 3 indicative of selector switch in control cabin in OFF position. The system also includes means to square the operation of the flying shear based on the selector switch portions and the speed of the metal. Also, the system including means for continuously sensing the flow of the billets one after another such that in respect of each said billet the desired front and/or back end cutting is effected properly. The details of the invention, its objects and advantages are explained in great detail in relation to non limiting exemplary embodiments of the control system of the invention in relation to the accompanying figures wherein. Fig. 1 shows the mill layout where front end and back end cutting operation is done. Fig. 2 is a general arrangement of the control system with all its components in relation thereto; Fig. 3 is the diagram which shows various indications provided in the equipment for smooth operation of the system. Fig. 4 is the Timing diagram of operation. Fig. 5 is the basic flow chart of the process. 4 Reference is first invited to Fig. 1, where general arrangement of wire rod rolling line is shown. The roughing group consists of 9 rolling stands. After 9th stand there is a flying shear where the provision for back end cutting has been introduced. After the flying shear there are another 14 rolling stands to obtain the first product. Hot billet of size 110 mm x 110 mm x 11800 mm are discharged from reheat furnace. Billet is fed into 1st rolling stand by the pinch roll. There is a hot metal detector placed after 7th rolling stand (HMD-7). The HMD-7 operates a relay whenever a hot metal is seen in the viewing line of HMD-7. Stand 9 is the last stand of the roughing group. After 9th stand metal's front end and back end is cut by the flying shear. The linear speed of the metal is proportional to the 9th stand roll diameter and speed of 9th stand. One analog tacho generator is fitted with the 9th stand motor to obtain the speed feed back. The flying shear cuts the metal in every rotation. Whenever the blade comes in contact, the metal is cut. The cut portion of the metal is collacting in the crop-collecting bucket. Whenever the bucket is filled up, an empty bucket using an overhead crane replaces it. Fig. 2 shows the scheme of implementation of back end cutting system and front end cutting system. The following are the components of the control system. (i) Microcontroller board based on 89C52 (ii) Relay interface (iii) Isolation amplifier (iv) Opto-coupler and contractor driver with contractor K1 (v) Digital indications (vi) Regulated DC power supply PS1 (vii) Regulated DC power supply PS2 (viii) Regulated DC power supply PS3 Microcontroller board The microcontroller board is based on 89C52 processor (ATMEL make) where there is on chip 8K EEPROM to store the application program. This processor is more suitable for industrial applications. There is on chip 128 KB of data memory to store intermediate values. The four digital inputs are directly 5 connected with the port 1 of 89C52. The processor is having 3 internal timer, out of which 2 are used in the program. When the processor is working, it communicates with a PC regarding all the calculations performed within it. The microcontroller board is having one RS 232 output using IC MAX 232. The board communicates with PC using RS 232 type communication Microcontroller board is having one analog to digital converter (ADC) using integrated Circuit (IC) AD 574 (Analog Device make). This IC is a 12 bit successive approximation type analog to digital converter. The board is having capacity of 8 channel analog input in the range of 0 to 10 V DC. The analog input is multiplexed using IC 4051 and fed to AD 574. The purpose of selecting AD 574 is for its fast response time (in the order of 36 usec). Out of the 8 channel analog input only one channel is used. The linear speed of the metal is fed into this channel. The microcontroller board is having three independent Digital to Analog Converters (DAC). These DACs are of type AD 7541A, make Analog Device and are of 12 bit resolution. Output voltage from the DACs are 0 to 10V DC. The digital input pins of AD 7541A are obtained from two numbers of programmable peripheral interface (PPI) of type 8255, INTEL make. The analog output can be used if the controller is hooked up with any analog drive for the flying shear. The board is having 16 digital input and 16 digital outputs. The digital inputs are taken from relay interface module. The digital outputs from the board are taken to opto-coupler module. The inputs to the board are shown in Table 1. Table 1 Sl.No. Input Description Input Type Voltage level Connecting point 1. HMD-7 Digital Input DI-1 TTL P1.0 of 89C52 2. Pinch Roll Digital Input DI-2 TTL Pl.l of 89C52 3. Selector switch in position-1 Digital Input Di-3 TTL P1.4of 89C52 4. Selector switch in position-2 Digital Input DI-4 TTL P1.5 of 89C52 5. Tacho Generator signal Analog Input AI-1 0 to 10V DC ADC Channel 0 The first digital input is obtained from a hot metal detector(HMD). In this particular case HMD is installed after 7th stand in the rolling line. The HMD gives a contact input to the processor. 6 The second digital input is obtained from a pinch roll, which pushes the metal which are discharged from the reheat furnace into 1st stand. The outputs from the board are shown in Table 2 Table 2 SI.No. Output Description Output Type Voltage level Connecting point 1. Shear ON Contact Digital Output DO-1 TTL, P1.2 of 89C52 2. Delay Output Indication Digital Output DO-2 TTL P1.3 of 89C52 3. Watch Dog Timer Output Digital Output DO-3 TTL P1.7 of 89C52 The processor is having a watch dog timer. As long as the CPU is running and executing the application program a pulse is available in port 1.7 of the CPU. This pulse from port 1.7 resets a counter. As long as the counter is reseted cyclically, counter reading cannot go high. If pulse is not available from port 1.7 then counter reading goes to high value and this high value resets the CPU 89C52. The reset pin of 89C52 processor is pin # 9. This pin is normally kept at low value by a pull down resistance of 8.2 KO A High, Logic '1', on this pin resets the processor. While the application program is running, if CPU halts or if it is in an infinite loop then the processor gets reseted by a Logic '1' pulse available from counter. The microcontroller board is having a 12 MHz crystal which generates the clock for this IC. From this basic clock processor generates time delays. Relay Interface The relay interface module converts a contact input to 5 V level TTL (Transistor Transfer logic) pulse. There are four digital inputs as shown in Table 1. HMD-7 contact is available from HMD-7 monitor unit and is brought to relay interface module through cable. Pinch roll contact is available from a contactor, driving the pinch roll solenoid. A selector switch, having three position is mounted in the control pulpit (Control room). Position 2 indicates that only two cuts are required in the back end. Neutral position indicates that no cutting is required. Using these contacts, four numbers of 12 V OEN make relays are energised. Each of these OEN relays are having three change over contacts. One NO contact 7 is used to fed TTL level input to the Microcontroller board. The digital inputs are shorted to PS-1 Common through a IK O resistance. The purpose of this resistance is that if the contact is open, input will be TTL logic "0". In Fig 2 of the Relay interface the contact and resistance is shown only for DI-3. The same is existing for all the digital inputs. Isolation amplifier The isolation amplifier isolates the voltage obtained from the tacho generator of 9th stand. This voltage is a measure of linear speed of the metal after 9th stand. The voltage available from tacho generator is of the order of 0 to 150V DC corresponding to angular speed of 0 to 1000 RPM of 9th stand. The isolation amplifier used here converts 0 to 300 V DC to 0 to 10V DC with an solation voltage of 2.5kV.The isolation amplifier requires + 12V DC supply for its operation which is obtained from Regulated DC power supply PS-3. Power supply common of PS-1 and PS-3 are shorted. Opto-coupler and contactor driver with contactor K 1 The digital output for shear ON is obtained from Port 1.2 of 89C52. This output is of TTL level. This output is fed to a opto-coupler MCT2E. This device provides an electrical isolation between microcontroller board and the power circuit. Opto-coupler drives a transistor and which in turns drive a OEN relay. The NO contact of OEN relay drives a contactor K 1. When K 1 is ON, its NO contact is used to drive the shear mechanism. When K 1 is dropped, the shear is OFF. The contactor K 1 is a power contactor operated by 230V AC coil. Its contact rating is 32A DC. Digital Indications There are two digital indicators from the microcontroller board. First LED indicated a delay. After HMD-7 relay drops, a delay routine is executed and after that the flying shear is made ON. This delay is a function of selector switch in control cabing and the linear speed of the metal. As long as the processor is executing the delay routine, this LED glows. The second LED indication is for RUN mode indication. As long as the processor is working and executing the application program, the processor gives a pulse and the LED blinks. If the 8 processor halts, this LED will be either ON or OFF state continuously indicating the halting stage of the processor. Regulated DC power supply PS 1 This regulated DC power supply feeds DC power to the microcontroller board. This gives +5V with a capacity of 5A and +/- 12V with a capacity of 1A. Input to this regulated power supply is 230V AC. Regulated DC power supply PS 2 This regulated DC power supply feeds DC power to the Relay module and Opto-coupler module. This gives +12 V with a capacity of 1A. Input to this regulated power supply is 230V AC. Regulated DC power supply PS 3 This regulated DC power supply feeds DC power to the isolation amplifier module. This gives +12 V with a capacity of 1A. Input to this regulated power supply is 230V AC. Fig.3 is the diagram which shows various indications provided in the equipment for smooth operation of the system. Using this indications, the sequence of operation can be seen to ensure fault free operation. There are 12 LEDs in the front panel. Each LED is 5mm in size. Table 4 below shows the functions of the LEDs. Table 4 SI. No. LED Number Indicating Function 1. LED L1 Selector switch in control cabin in OFF position. 2. LED L2 Selector switch in control cabin in 1 cut position 3. LEDL3 Selector switch in control cabin in 2 cut position 4. LEDL4 +5 V DC in PS-1 is present 5. LEDL5 +12V DC in PS-1 is present 6. LED L6 -12V DC in PS-1 is present 7. LEDL7 Pinch Roll ON 8. LED L8 HMD-7 ON 9. LEDL9 Delay T' ON 10. LED L10 Shear ON 11. LED LI 1 Not used 12. LED L12 Not used 9 There are six switches for functioning of the controller. The functions of the switches are indicated in Table 5. Table 5 S1. No. Switch Number Indicating Function 1. S1 To simulate 1 cut position from the local board 2. S2 To reset the processor manually 3. S3 Not used 4. S4 Not used 5. S5 To simulate Pinch roll input i.e. without operating the pinch roll the input can be pulled to logic '1' 6. S6 To simulate HMD-7 input i.e. without a hot billet near HMD-7, the input can be pulled to logic'1' Fig. 4 shows the timings diagram for operation of the system. When back end of the billet leaves 7th stand, flying shear is made ON after a time lag "T" This time lag depends on the selector switch setting in control cabing for 1 cut or 2 cut and the linear speed of the metal derived from 9th stand tacho generator signal. The linear speed signal of the billet helps to keep the last cut piece length constant. Once HMD-7 signal goes from ON to OFF a time lag "T" is generated. This "T" depends on three components T = T1 + T2 + T3 T1= 500 m Sec T2=400mSec for 1 cut, 200mSec for 2 cut T3=depends on speed of rolling. If Speed increases, T3 decreases. After flying shear has started, it will remain ON for 3 Sec if no billet is discharged in that strand as shown in case I. If any billet is discharged, sensed by pinch roll, while the flying is cutting the back end of the billet as shown in case II, the flying shear shall remain ON till the arrival of next meal. Shear will stop after cutting the front end., However, if metal does not arrive in stand 7 with in 65 sec. Then flying shear stops automatically (This happens if there is any cobble between stand #1 to stand #9). Fig 5 shows the flow chart of the system. The processor is programmed to perform in this manner. Initially all the memory locations which stores the 10 inputs and outputs are cleared (i.e. all are made to logic "O"). The system waits for a transition from logic "1" to logic "O". This indicates that the billet has just crossed the 7th stand. Once this event takes place, the time delay 'T' is calculated based on the linear speed of the billet and the selector switch position. During the time delay 'T' one output LED is made ON, indicating that delay is being executed. After this delay shear is made ON by energizing K 1 contactor. The processor then checks whether a new billet has been fed into rolling line or not. If a new billet has been fed then the shear is kept ON till the arrival of next billet and the shear is made OFF only after front end cutting. The sensing of new billet is done through the pinch roll contact. If no billet is discharged, the shear remain ON for 3 sec and then it stops. The information is passed to a PC. The processor then clear all the input and output from memories and waits for the next transition from logic '1' to logic '0'. Thus as detailed herein before the control system of the invention basically utilizing (I) Hot Metal Detector (ii) Pinch Roll operation signal (iii) 9th stand speed signal from tacho generator (iv) Selector switch to select number of pieces to be cut in the back end of the billet (v) Relay interface Module (vi) Microcontroller board (vii) Output contactor driving circuit, to achieve automatic back end cutting operation as per the length requirement and without any human interference. The Relay interface module comprising (i) Relays with 12V DC coil and 3 change over contacts. Relays are energised whenever the external contacts are closed. (ii)One side of the contact is connected with 5V DC obtained from the same power supply feeding the microcontroller board and other side connected to processors port. Each of the processor is pulled down to OV through 1KO resistance. The Microcontroller board comprising (i) Processor 89C52 with 12 MHz crystal, 8 channel Analog to digital converter, RS 232 communication link, (ii) Watch dog timer for automatic reseting. (iii) Indication for RUN mode of the application program. 11 The Opto-coupler interface module comprising (i) Opto-coupler MCT2E and a driving transistor, driving a relay. (ii) A contactor driven by the relay. The control system of the invention thus provides (i) Automatic cutting of back end and front end of wire rod or any hot rolled product (ii) Communicating with a PC for the events that are taking place in the process It is thus possible by way of the above discussed system of the inventiaon to precisely carry out back end and front end cutting operation as per the set value of the operator, to reduce the defect from the rolled product. Also the system provides information in a PC for better monitoring of the process. The system avoids manual cutting of the ends after the rolling is over. The system avoids rolling of defective materials The system of the invention is thus a cost effective solution for back end cutting and front cutting system for hot rolled products in a hot rolling mill. 12 WE CLAIM : 1. A control system for end cutting of hot rolled products in a hot rolling mill comprising - a pinch roll sensing contact for feeding the billet into the rolling stand; hot metal detector adapted to view the presence of hot metal; - means to measure the linear speed of the hot metal; - selector switch means adapted to generate time lag signals based on the desired cut and the linear speed of the metal in the stand; micro controller based board adapted to receive input signals from said pinch roll sensing control, hot metal detector, selector switch, means for measuring linear speed of metal and adapted to generate signals to activate an opto-coupler interface for the end cutting operation. 2. A control system as claimed in claim 1 wherein said micro controller board comprise of 89C52 processor with analog input, digital input, digital outputs and communication facility with PC. 3. A control system as claimed in anyone of claims 1 or 2 wherein said hot metal detector is adapted to sense the metal position after 7th stand in the rolling line. 4. A control system as claimed in anyone of claims 1 to 3 wherein said pinch roll contact is adapted to an output whether a new billet has been discharged into the rolling line or not. 5. A control system as claimed in anyone of claims 1 to 4 wherein the selector switch comprise of 3 position indicting 1 cut, 2 cut or no cut required in the metal. 6. A control system as claimed in anyone of claims 1 to 5 wherein said opto coupler is adapted to give electrical isolation and drive a contactor for running the shear mechanism. 5. -13- 7. A control system as claimed in anyone of claims 1 to 6 wherein the back end cutting operation and its duration of time is based on said selector switch setting and the linear speed of the metal. 8. A control system as claimed in claim 7 wherein when the back end of the billet leaves 7th stand, flying shear is activated after said duration of time based on the selector switch position and the linear speed of the metal. 9. A control system as claimed in anyone of claims 7 or 8 wherein said hot metal detector does not detect any metal it is put off, a time lag is generated based on T=T1+T2+T3 wherein T1 = 400 to 600 m Sec preferably 500 m Sec. T2 = 300 to 500 m Sec preferably 400 m Sec. for 1 cut, T3 = 100 to 300 m Sec preferably 200 m Sec for 2 cut. T3 = speed of rolling when if speed increases T3 decreases. 10. A control system as claimed in anyone of claims 7 to 9 adapted such that after flying shear is in operation, it is maintained ON for a period of 2 to 4 sec preferably 3 Sec, if no billet is discharged in that stand and when the billet is discharged, sensed by the pinch roll while the flying is cutting the back end of the billet, the flying shear is adapted to remain ON till arrival of the next billet, the shear will stop after cutting the front end, if metal does not arrive in stand 7 within 40 to 70 sec preferably 60 sec, then the flying shear is adapted to stop automatically. 11. A control system as claimed in anyone of claims 1 to 10 wherein said relay interface module comprise: (i) relays with 12 V DC coil and 3 change over contacts said relays are energised whenever the external contacts are closed, (ii) One side of the said contact being connected with 5 V DC obtained from the same power supply feeding the micro controller board, and other side connected to processor port, each port of the processor is pulled down to 0 V through a 1K O resistance. -14- 12. A control system as claimed in anyone of claims 1 to 11 wherein said micro controller board comprise: (i) processor 89C52 with 12 MHz crystal, 8 channel analog to digital converter, RS 232 communication link. (ii) watch dog timer for automatic resting, (iii) Indication for RUN mode of the application program. 13. A control system as claimed in anyone of claims 1 to 12 wherein said opto coupler interface module comprise: (i) opto-coupler MCT2E and a driving transistor, driving a relay, (ii) a contactor driven by the relay. 14. A control system as claimed in anyone of claims 1 to 13 adapted for use in a wire rod rolling line wherein the roughing group consists of 9 rolling stands, after 9th stand there is a flying shear where the provision for back end cutting is introduced, after the flying shear there are provided another 14 rolling stands to obtain the final product, hot billet are discharged from reheat furnace and fed into 1st rolling stand by the pinch roll, the hot metal detector placed after 7th rolling stand (HMD-7), said HMD-7 operates a relay whenever a hot metal is viewed in line of HMD-7, stand 9 being the last stand of the roughing group, after 9lh stand metal's front end and back end is cut by the flying shear, the linear speed of the metal is proportional to the 9th stand roll diameter and speed of 9th stand, an analog tacho generator fitted with the 9th stand motor to obtain the speed feed back with said flying shear cutting the metal in every rotation. 15. A control system as claimed in anyone of claims 1 to 14 wherein the cut portion of the metal is collected in the crop collecting bucket preferably adapted such that the bucket is filled up, an empty bucket using an overhead crane replaces it. 16. A control system as claimed in anyone of claims 1 to 15 wherein the relay interface module converts a contact input to 5 V level TTL (Transistor logic) pulse. 15. -15- 17. A control system as claimed in anyone of claims 1 to 16 wherein the voltage available from tacho generator is of the order of 0 to 150 V DC corresponding to angular speed of 0 to 1000 RPM of 9th stand, said isolation amplifier adapted to convert 0 to 300 V DC to 0 to 10 V DC with an isolation voltage of 2.5 KV. 18. A control system as claimed in anyone of claims 1 to 17 wherein said opto coupler is adapted to drive a transistor and which in turns drives a OEN relay, the NO contact of OEN relay drives a contactor K1 such that when K1 is ON, its NO contact is used to drive the shear mechanism, when K1 is dropped, the shear is OFF. The contactor K1 is a power contactor operated by 230 V AC coil. Its contact rating is 32 A DC. 19. A control system as claimed in anyone of claims 1 to 18 comprising digital/LED indication means of stands of various operating systems. 20. A control system as claimed in anyone of claims 1 to 19 wherein said micro controller board indicates a delay routine for executing the flying shear by a LED means and a further LED means to indicate the RUN mode. 21. A control system as claimed in anyone of claims 1 to 20 wherein regulated DC power supply feeds DC power to the micro controller board, relay module and opto coupler module and isolation amplifier module. 22. A control system for automatic cutting of back end and front end of wire rod or any hot rolled product substantially as herein described and illustrated with reference to the accompanying figures. 22. Dated this 14th day of January 2002. The control system for end cutting of hot rolled products using flying shear in a hot rolling mill which would enable automatic cutting of front end and/or back end of product and would be simple to operate comprises controller based system adapted to receive input signals from a pinch roll sensing control, hot metal detector, selector switch, means for measuring linear speed of metal and adapted to generate signals to activate an opto-coupler interface for the end cutting operation. The system can be used in a wire rod mill to cut the back of wire rod. The system would also provide for length of cut piece to be uniform in length and would serve as a cost effective system adapted for use in an existing rolling mill to have a facility of front end cutting and back end cutting.

Documents:

00021-cal-2002-abstract.pdf

00021-cal-2002-claims.pdf

00021-cal-2002-correspondence.pdf

00021-cal-2002-description(complete).pdf

00021-cal-2002-drawings.pdf

00021-cal-2002-form-1.pdf

00021-cal-2002-form-18.pdf

00021-cal-2002-form-2.pdf

00021-cal-2002-form-3.pdf

00021-cal-2002-pa.pdf

21-cal-2002-granted-abstract.pdf

21-cal-2002-granted-claims.pdf

21-cal-2002-granted-correspondence.pdf

21-cal-2002-granted-description (complete).pdf

21-cal-2002-granted-drawings.pdf

21-cal-2002-granted-examination report.pdf

21-cal-2002-granted-form 1.pdf

21-cal-2002-granted-form 18.pdf

21-cal-2002-granted-form 2.pdf

21-cal-2002-granted-form 3.pdf

21-cal-2002-granted-letter patent.pdf

21-cal-2002-granted-pa.pdf

21-cal-2002-granted-reply to examination report.pdf

21-cal-2002-granted-specification.pdf