Title of Invention

"A SYSTEM FOR MEASUREMENT OF PLATE WIDTH IN A PLATE MILL"

Abstract

A system for measurement of plate width in a plate mill comprising at least one set of a left and a right manipulator being moveable towards and away from each other so as to provide there between an adjustable space to receive a plate and to define a predetermined width of the plate, said manipulators being adapted to press and/or guide the plates along the said space. At least two digital encoders each mounted on said left and right manipulators so as to generate signals representative of the linear motion of the manipulator, said encoders being adapted to generate plurality of pulses such that the number of pulses is proportional to the angular motion of the rack pinion of the said manipulators. A logic controller is connected to said encoders and comprising digital input and output cards to receive the signals generated by the encoders and to provide data representing the width of the plate comprising means to calculate the linear distance traveled by said left and right manipulators from the said signals from the said encoders and means to calculate the width of the plate from the said linear distance traveled by the said left and right manipulators. At least one display unit is connected to the logic controller and adapted to display the plate width calculated dynamically.

Full Text

SYSTEM FOR MEASUREMENT OF PLATE WIDTH IN A PLATE MILL Field of invention The present invention relates to a system for the measurement of plate width in a plate mill. The present invention, particularly relates to a system for accurate width measurement of metal/steel plates at the roughing stand of a pate mill thus facilitating excellent width control and consistency of plates production The system is widely applicable particularly in processes requiring very accurate control of dimension measurement of plates manufactured in a plate mill Background of the invention In the manufacture of plates, the steel manufactured is brought from the continuous casting to re-heating furnaces in a Plate Mill Here, the slabs are first re-heated to pre-determined temperature and rolled into the stands in the mill. In a typical plate mill there are three stands namely vertical stand, rolling stand and finishing stands The rolling is such that it only reduces the thickness of the stock in the rolling direction while the width is kept constant Under the currently practiced process the control of width is effected by the use of manipulators in between the vertical and the roughing stands The function of the manipulators is to manipulate the plates for rotations, centering, tilting etc during the rolling for achieving desired width and length The centering of the plate before the slabs are rolled into the roughing stand is of great importance and the manipulators play a vital role in centering the plates as well Before the slab enters the roughing stand the manipulators hold the plate/slab and at the time of holding, the width of the slab is measured and corrections are made Conventionally, the device for slab/plate measurement is an analog device based on single potentiometer This potentiometer is mounted on one of the manipulators Since the movement of the manipulators is theoretically identical, the measurement 2- from one side of the manipulator is sufficient to calculate the slab/plate width by doubling the result obtained from one potentiometer The conventional system for slab/plate measurement has many drawbacks Firstly, this system is based on a single encoder measuring upto 270° rotation only For rotations of 270° to 360° the measurement is manipulated As a result the complete span of the plate width is not covered with the device Secondly, over the years the hydraulic coupling of the two manipulators did not remain identical The rack-pinion motion also starts giving back lasses in the manipulator movements due to wear and tear of moving machine parts Thus a varying amount of error in plate width measurement gets added continuously in the width measurement This error forces operators to increase the side trimming allowances for the pates and thereby the overall yield of the product decreases However, in most situations, an error tolerance of ±20mm is very acceptable for both heavy and light plates But when the error tolerance band increases to more than ±40mm it becomes very difficult to process the plates with such high inaccuracy The other known methods /devices for plate width measurement include pan view methods, CCD camera based width measurement and LASER based non-contact width measurement, which are in vogue in modern steel plants these days But such advanced measurement systems are not cost-effective and require very high development and installation costs Thus, there is a need for a plate width measuring system, which provide very accurate results at a very low development cost Objects of the invention The object of the invention is to provide a system for the measurement of plates in a plate mill for the accurate control of the width of plates and excellent consistency in the measurement of rolled plates Another object of the present invention is to provide for a system for the measurement of plates in a plate mill that is cost-effective and requires lower installation cost Another object of the present invention is to provide for a system for the measurement of plates in a plate mill that measures the plate width over the complete span to avoid any manipulation in width measurement Summary of the invention Thus according to the present invention there is provided a system for measurement of plate width in a plate mill comprising. at least one set of a left and a right manipulator being moveable towards and away from each other so as to provide therebetween an adjustable space to receive a plate and to define a predetermined width of the plate, said manipulators being adapted to press and/or guide the plates along the said space, at least two digital encoders each mounted on said left and right manipulators so as to generate signals representative of the linear motion of the manipulator, said encoders being adapted to generate plurality of pulses such that the number of pulses is proportional to the angular motion of the rack pinion of the said manipulators, a logic controller connected to said encoders and comprising digital input and output cards to receive the signals generated by the encoders and to provide data representing the width of the plate comprising means to calculate the linear distance traveled by said left and right manipulators from the said signals from the said encoders and means to calculate the width of the plate from the said linear distance traveled by the said left and right manipulators at least one display unit connected to the logic controller and adapted to display the output of the logic controller 4 According to a preferred embodiment two digital encoders are mounted on the each of the two left and right manipulators When the plate width varies or the plate shifts from the centrally aligned position, the manipulator arms move linearly The arms are connected to racks that have teeth which couples with the teeth of the pinion with axis of rotation parallel to the motion of the plate Due to the coupling, any linear motion of the arms is transmitted to the pinion which is made to rotate This in turn rotates the encoders The digital encoders have 360° rotations and even multiple rotations can be accounted for using the encoders The encoders generate pulses such that the number of pulses generated is proportional to the rotation of the pinion and linear motion of the manipulator arms The output from the encoders is fed into the logic controller, preferably a PLC via an input card The PLC calculates the linear distance traveled by the manipulators from the pulses generated dynamically by the encoders from which the width of the plate is calculated The resting position of the manipulators is considered as the zero position of the encoders and is determined when the manipulators are fully apart The zero position reference is obtained by installing two inductive type proximity sensors (switches) on either side of the manipulators The linear distance is measured from this initial position and till the point at which the arms hold the process slab/plate All distances are measured with respect to the centerline of the mill be the center of the roll table in between the manipulators The slab/plate width is calculated dynamically and is send to the display unit via the output card The present system takes into account the non-uniform motion of the manipulators and does not assume that the motion of the two manipulators to be identical Thus, even if there are some variations from the centerhne on either side, it is measured very accurately by either encoder The system of the invention measures the plate width very accurately The accuracy depends on the number of pulses the encoders generate for one single rotation and diameter of the pinion Standard values of the same are 1024 and 416mm respectively Using such encoders lengths as less as 1 276mm can be measured which is much less than the usual tolerance acceptance of 10mm of 5 most steel manufacturers In other words, any width or alignment variation of the plates in excess of 1 276mm can be detected by the present system. The linearity of measured results depends on the proper calibration of the manipulators Calibration here is the measurement of the distances between the two arms of the manipulators when the are fully apart and fully closed respectively This measurement should be done from the centerline of the mill for each of the manipulators Normally, this calibration is a one-time affair, provided the manipulators settings are not disturbed However, this calibration will be required for each major disturbance in the manipulators In addition to this, a pitch factor is calculated based on the calibration readings for both encoders This pitch factor theoretically should be constant but due to slippage in the rack-pinion arrangement the same should be calculated from time to time by the above calibration method Description of preferred embodiments The invention will now be described with reference to non-limiting embodiments illustrated by figures Figure 1 shows the assembly consisting of roughing stand, manipulators, roll table and the encoders Figure 2 shows the arrangement of components in the width measurement system Figure 3 shows the methodology for plate width measurement of the system As shown in Figure 1, a plate mill comprises a roughing stand (1) The hot steel slabs (2) move over the roll table (3) and towards the roughing stand Before the slab enters the stand the left and right manipulators (4) push and/or guide the slabs The encoders (10) and the left and right proximity sensors (5) are mounted on the left and right manipulators as shown in the figure 6 Figure 2 shows the arrangement of components in the width measurement system The arms of the manipulators (6) are connected to the rack (7) having teeth (8) which couples with the teeth of the respective pinions (9) The encoders (10) are mounted on the pinion (9) As the racks (7) of the manipulators move, the arms (6) move and this linear movement is transmitted to angular motion of the pinion (9) via the coupling The encoders (10), are 10 bit absolute encoders They generate plurality of pulses, the number of such pulses being proportional to the amount of angular motion of the pinion The encoders (10) and the proximity sensors (5) are connected to the logic controller which is a PLC (11). The proximity sensors are inductive type and help in measuring the distance between the arms of the manipulators when they are fully apart The PLC (11) is a small logic controller having two 16 channel digital input cards and two 16 channel digital output cards. The PLC has a 8K RAM processor which converts the signals received from the encoders into signals representing the width of the plate The output of the PLC is fed to the display (12) which is a 4 digit, 7 segment LED type digital display unit The methodology followed for the plate width measurement is demonstrated in Figure 3 The figure shows the top view of the plate and manipulators The plate or slab (2) is pushed or guided by the manipulator arms (6) The encoders (10) rotate as the arms move linearly away or towards the plate All measurements are based on the centerline (13) of the mill As discussed earlier the encoders generate a number of pulses, the number being proportional to the linear distance traveled by the arms of the manipulators This distance is represented by X1 and X2 for the left, and right arms respectively X1 and X2 are calculated by the PLC from the number of pulses generated by the encoders For this, the pitch factor for the manipulators have to be measured The pitch factor is defined as the amount of linear motion of the manipulator arms generating a single encoder pulse and is calculated by dividing the circumference of the pinion by the number of pulses in one rotation The pitch factor for left and right manipulators are represented by L and R respectively Here, the diameter (D) of the pinion is 416mm and the encoders 7 generate 1024 pulses for one complete rotation Thus, the pitch factor is calculated as L = Circumference of pinion / Number of absolute pulses in one rotation = D/1024 = 3 141 X 416/1024 = 1.276 mm/pulse. Since theoretically L = R, therefore R = 1 276 mm/pulse Now, let at any time the number of absolute pulses for left manipulator be NL and number of absolute pulses for right manipulator be NR Before starting, the left and right proximity sensors (5) are used to calculate the maximum opening and initial reference The maximum openings of left and right manipulators are represented as YL and YR with reference to the centerline (13) Now, let at any time the number of absolute pulses for left manipulator be NL and number of absolute pulses for right manipulator be NR Let at any time X1 and X2 be the distances of the manipulators from the initial reference They are calculated dynamically from the number of pulses generated by the encoders at that time as follows X1=NLX L, and X2 = NR X R. Let WL and WR be the distance between the centerline and the left and right sides of the plate respectively such that the sum of WL and WR gives the width (W) of the plate WL and WR are calculated as follows WL = YL-X1, WR = YR-X2, and W = WL + WR 8 Thus by the present system the width of the plate is measured dynamically and with great accuracy. Besides the width, the system can also detect the whether the plate is aligned centrally on the roll table by comparing WL and WR. We claim: 1. A system for measurement of plate width in a plate mill comprising: at least one set of a left and a right manipulator (4) being moveable towards and away from each other so as to provide therebetween an adjustable space to receive a plate (2) and to define a predetermined width of the plate, said manipulators being adapted to press and/or guide the plates along the said space; at least two digital encoders (10) each mounted on said left and right manipulators (4) so as to generate signals representative of the linear motion of the manipulator, said encoders being adapted to generate plurality of pulses such that the number, of pulses is proportional to the angular motion of the rack pinion (9) of the said manipulators; a logic controller (11) connected to said encoders (10) and comprising digital input and output cards to receive the signals generated by the encoders and to provide data representing the width of the plate comprising means to calculate the linear distance traveled by said left and right manipulators from the said signals from the said encoders and means to calculate the width of the plate from the said linear distance traveled by the said left and right manipulators. at least one display unit (12) connected to the logic controller (11) and adapted to display the plate width calculated dynamically. 2. A system according to claim 1 which measures plate width at roughing stand of a plate mill. 3. A system according to any of claims I or 2, wherein the said encoders are 10 bit absolute encoders. 4. A system according to any of the preceding claims, wherein the said manipulators comprise arms (6) which press and/or guide the plates, the arms being connected to a rack (7) having teeth (8) thereof, 5 A system according to any of the preceding claims, wherein the said teeth (8) of rack (7) are coupled to teeth of pinion (9) having axis of rotation parallel to the direction of motion of plate (2). 10 6. A system according to any of the preceding claims, wherein the said logic controller (11) comprises 8K RAM processor. 7. A system according to any of the preceding claims, wherein the said digital input and said digital output cards are 16 digital channel cards. 8. A system according to any of the preceding claims, wherein the said display unit (12) is of 4 digit, 7 segment LED type. 9. A system according to any of the preceding claims, further comprising atleast two proximity sensors (5) mounted on each of the said left and right manipulators (4). 10. A system according to claim 8, wherein the said proximity sensors (5) are of inductive type. 11. A system according to any of the preceding claims, wherein the said encoders (10) generate 1024 pulses for a single rotation. 12. A system according to any of the preceding clams wherein the diameter of the said pinion is 416mm. A system for measurement of plate width in a plate mill comprising at least one set of a left and a right manipulator being moveable towards and away from each other so as to provide there between an adjustable space to receive a plate and to define a predetermined width of the plate, said manipulators being adapted to press and/or guide the plates along the said space. At least two digital encoders each mounted on said left and right manipulators so as to generate signals representative of the linear motion of the manipulator, said encoders being adapted to generate plurality of pulses such that the number of pulses is proportional to the angular motion of the rack pinion of the said manipulators. A logic controller is connected to said encoders and comprising digital input and output cards to receive the signals generated by the encoders and to provide data representing the width of the plate comprising means to calculate the linear distance traveled by said left and right manipulators from the said signals from the said encoders and means to calculate the width of the plate from the said linear distance traveled by the said left and right manipulators. At least one display unit is connected to the logic controller and adapted to display the plate width calculated dynamically.

Documents:

00044-kol-2003 abstract.pdf

00044-kol-2003 claims.pdf

00044-kol-2003 correspondence.pdf

00044-kol-2003 description(complete).pdf

00044-kol-2003 drawings.pdf

00044-kol-2003 form-1.pdf

00044-kol-2003 form-18.pdf

00044-kol-2003 form-2.pdf

00044-kol-2003 form-3.pdf

00044-kol-2003 letters patent.pdf

00044-kol-2003 p.a.pdf

44-KOL-2003-(01-02-2012)-FORM-27.pdf

44-KOL-2003-FORM 27.pdf