Method of controlling rolling speed
United States Patent Kamata et al.  
 METHOD OF CONTROLLING ROLLING SPEED Inventors:  
 Assignee:  
 Filed:  
 Appl. No.:  
 US. Cl. 72/6; 72/250; 226/44; 425/DIG. 235 Int. Cl B2lb 37/00 Field of Search 226/44. 118. 119; 72/9,  
 72/17. 26. 443. I83. 6, 250; 425/DlG. 23S  
 Masamoto Kamata; Masayuki lshida: Hiroshi Kuwamoto. all of Fukuyama. Japan Nippon Kokan Kabushiki Kaisha. Tokyo, Japan Apr. 18, 1973 References Cited UNITED STATES PATENTS Herr 226/1 l9 X 1 1 Apr. 8, 1975 3.583.619 6/1971 Shepherd 226/119 X 3.667.664 6/1972 Schroeder 226/44 X 3.680.753 8/1972 Shaw-Stewart 226/44 X 3.724.733 4/1973 Schaffcr et al 226/44 X 3.727.820 4/1973 Braun v 226/118 X 3.734.370 5/1973 Shumakcr 226/119 Primary Examiner-Francis S. Husar Assistant E.tulnim&#39;rR. .I. Charvat Attorney. Agent. or Firm-Flynn &amp; Frishauf {57] ABSTRACT In a rolling mill installation of the type wherein metal strips payed out from coils mounted on uneoilers are sequentially welded into a continuous strip and the continuous strip is stored in a variable quantity storage station including a loop car, the speeds of the uncoilers and the rolling mill are controlled in accordance with the quantity of the strip stored in the storage station.  
 8 Claims. 4 Drawing Figures PATENTEDAPR aims 3,875,774  
  0LT zzjm METHOD OF CONTROLLING ROLLING SPEED BACKGROUND OF THE INVENTION This invention relates to a method of controlling the rolling speed of a continuous cold mill installation.  
  In a modern continuous cold mill installation. metal strips are payed out from coils supported by uncoilers and successive strips are welded into a continuous strip. The continuous strip is stored in a storage station. In one form of the storage station. a loop car carrying a plurality of pulleys is used and the strip is continuously passed about the pulleys and stationary pulleys. Thus. by varying the position of the loop car with respect to the stationary pulleys, the quantity of the strip stored in the storage station can be controlled. The strip in the storage station is then supplied continuously to a tandem mill. The strip cold rolled by the tandem mill is severed by a flying shear and the cut length of the strip is wrapped on a coiler. In such an installation, the quantity of strip stored in the storage station is not large enough to supply strip to the mill running at normal speed during welding and the gauge of the rolled strip is changed frequently. For this reason. the quantity of the strip stored in the storage station varies greatly so that it is sometimes necessary to stop the mill stand, thereby reducing the production rate. Accordingly, the advantage of installing the storage station is reduced. Therefore it is highly desirable to provide a novel method of controlling the mill speed to fully enjoy the advantage of the storage station under all operating conditions of the continuous cold strip rolling mill installation.  
 SUMMARY OF THE INVENTION It is an object of this invention to provide an improved method of controlling the rolling speed so as to maintain the quantity of the strip stored in a predetermined range.  
  More particularly. the invention relates to a method of controlling the rolling speed wherein the control system is programmed to operate at two different schemes. one for a case wherein the quantity of the strip stored is small and the other for a case wherein the quantity of the strip stored is large. and wherein in the former case the constant position control of the loop car is effected whereas in the latter case the rolling speed of the mill is controlled.  
  The perfect continuous cold rolling technique is not yet practiced in any country so that the inventive concept of this invention is believed to be quite novel.  
  More particularly. according to one aspect of the invention. in a rolling mill installation ofthe type wherein metal strips payed out from coils mounted on uncoilers are sequentially welded into a continuous strip. the continuous strip is stored in a storage station including a loop car which is operated to vary the quantity of the strip stored in the storage station. and the strip is taken out from the storage station and then fed into a rolling mill. there is provided a method of controlling the rolling speed. characterized in that the speeds of the uncoilers and the rolling mill are controlled in accordance with the quantity of the strip stored in the storage station to a speed most suitable for the quantity of the strip stored in the storage station.  
  According to another aspect of the invention. in the continuous rolling mill installation of the type described above there is provided a method of controlling the rolling speed. characterized in that the speed of the uncoiler is controlled such that the loop car is maintained within a definite range when the quantity of the strip stored in the storage station exceeds a predetermined quantity. that the rolling speed of the rolling mill is controlled in relation to the speed of the uncoilers when the quantity of the strip stored in the storage station is less than the predetermined quantity and that the rolling speed is preferentially reduced to a speed below a normal rolling speed when the strip rolled by the rolling mill is cut by a flying shear. when the gauge of the rolled strip is to be changed and when the strips are welded together.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic representation showing a continuous cold mill installation including five tandem mill stands. a welder and a strip storage station in the form of a loop car;  
  FIG. 2 is a diagram showing the relationship among the uncoiler speed. the mill speed and the quantity of strip stored in the storage station;  
  FIG. 3 is a flow diagram of an uncoiler speed analogue control system. (System for controlling the speed of the uncoiler so as to maintain the loop car in a definite zone when the quantity of strip stored in the storage station lies in the A range shown in FIG. 2.); and  
  FIGv 4 is a flow diagram ofa mill speed analogue control system. (System for controlling the speed of the mill in relation to the speed of the uncoiler when the quantity of strip stored in the storage station is in the B range shown in FIG. 2.).  
 DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a diagram of a continuous cold mill installation to which the invention is applicable and comprises a five stand cold tandem mill 1, and a strip storage apparatus or station 2 including a loop car 3 which is moved along rails. The metal strip is passed about a set of stationary pulleys and a set of movable pulleys carried by the loop car 3 so that the quantity of the strip stored in the storage station 2 is increased or decreased as the loop car 3 is moved to the left or right. Thus. a sufficient quantity of the strip can be stored so that even when the supply of the strip to the storage station is interrupted temporarily, continuous supply of the strip to the mill can be assured. On the input side of the storage station are installed a pair of uncoilers 4 which are operated alternately. The trailing end of a preceding coil and the leading end ofa succeeding coil are cut by a shear 5 and are then welded into a continuous strip by means of a welder 6. On the output side of the mill are disposed a pair of coilers 7 which are also operated alternately to take up continuously rolled strip into coils ofa predetermined diameter. When the gauge of the rolled strip is changed. strips of different gauges are wrapped on different coilers.  
  A flying shear 8 is positioned at a suitable position between the rolling mill and the coilers for severing the rolled strips into a predetermined length. As the rolling speed of a modern cold rolling mill is extremely high. at the time of operating the shear it is necessary to reduce the rolling speed. as in the case of welding.  
  In the accompanying drawings and following description. following symbols are used:  
 MSP: mill speed (in terms of the input speed to the first mill stand) MSPN: normal rolling speed (same as above] MSPH: reduced rolling speed (same as above) MSPC: rolling speed during cutting [same as above) MSPA: rolling speed during gauge change (same as above) MSPWP: rolling speed when the weld is passing through the mill stand (same as above) MSPW. rolling speed when the strips are welded together (same as above) MSPMIN: the lower limit of the mill speed below which off-gauge strips are produced (same as above] STRG: the quantity of the strip stored USP: uncoiler pay off speed SLl: the quantity of the strip stored at a time when the operating scheme of the speed control system is switched SLMAX: quantity of strip stored at the time of emergency stop of the uncoiler SLMIN1 quantity of the strip stored at the time when the mill is to be applied with the emergency stop First, the method of controlling the uncoiler speed will be described with reference to FIG. 3. When the quantity of the strip stored is in range A (FIG. 2) which shows a condition in which the quantity of the strip stored is large, the loop car constant position control is performed, More particularly. the uncoiler pay off speed USP is controlled such that the loop car assumes a definite position whereas the mill speed MSP is not controlled in accordance with the position of the loop car,  
  When the quantity of the strip mounted on the uncoiler reduces as a result of pay&#39;off until the following equation holds true, deceleration of the uncoiler is commenced and then stopped for welding.  
 USP uncoiler speed upon completion of the deceleration,  
 a rate deceleration D outer diameter of the coil D,, inner diameter of the coil l1 strip gauge L the length ofthe strip remaining after completion of deceleration.  
  When the welding operation of the strips is finished, the uncoiler is operated at a high speed until the quan tity of the strip stored reaches SL1 (see steps 7 to 10, in FIG. 3). When the uncoiler is accelerated to a maximum speed, this speed is maintained during succeeding operation. When the quantity of the strip stored exceeds SL1, the operating scheme of the control system is switched so as to control the uncoiler speed in a manner to maintain the loop car within a definite range. The level SLo shown in FIG. 2 corresponds to the quantity of the strip, SLO showing the center of said range.  
  Where it is necessary to temporarily decrease the uncoiler speed due to inadequate operation of the apparatus or for inspecting the coil while the quantity of the strip stored lies in range A the uncoiler is temporarily decelerated. But when the normal operation of the apparatus is resumed or the inspection of the coil is finished, the uncoiler is accelerated to the normal running speed in the same manner as the acceleration of the uncoiler when the welding operation is completed. In these cases the speed of the uncoiler is sometimes not reduced to zero.  
  In the absence of an order for decreasing the uncoiler speed, if the loop car is positioned such that the quantity of the strip stored lies in range B which shows a condition wherein the quantity of the strip stored is small, the uncoiler speed is increased until the quantity of the strip reaches a level SL1. If the quantity of the strip stored exceeds SLMAX, an emergency stop will be applied to the uncoiler.  
  Turning now to FIG. 4 illustrating the control of the rolling mill, the mill is generally controlled to operate at a speed between the normal rolling speed MSPN and a reduced rolling speed MSPH, the former being determined by the size of the product, Generally the mill speed is set by a computer.  
  It is necessary to reduce the rolling speed when the operation mode is changed, that is, when flying shearing is conducted, when the size of the strip changes while running, or when the welded portion of the strip enters the roll stand, etc., and such reduced rolling speed is designated herein as MSPH. Accordingly, the reduced rolling speed MSPH varies dependent upon the operation mode and is controlled by a command signal calculated by the computer. When an order for changing the operation mode is given in accordance with an order of rolling and coil tracking information, the rolling speed is changed to a speed corresponding to the content of the order. Thus for instance, when the order relates to the operation of the flying shear, the rolling speed is changed to that required for performing cutting MSPC. The deceleration of the mill speed is commenced at a distance Lm which is equal to the distance in which the strip travels between an interval during which the mill speed is reduced from MSPN to MSPH. Where two or more mode changing orders are given at a time, the reduced rolling speed is made to coincide with the smallest one, and when one of the mode changing orders has been executed but the others are yet to be met, the smaller one of the remaining orders is substituted for the reduced rolling speed MSPH. Upon complete execution of all mode changing orders, the mill speed is accelerated to the normal rolling speed MSPN. At the commencement of such acceleration the reduced rolling speed MSPH is substituted by the lower limit of the rolling mill speed MSPMIN. This is because the lower limit of the rolling mill speed is generally much smaller than the rolling speed during rolling MSPC, the rolling speed when the weld is passing through the mill stand MSPWP and the rolling speed when the strips are welded together MSPW. Thus when the MSPH is substituted by MSPMIN before acceleration, according to this invention when all mode changing orders have been executed the mill speed is reduced to the lower limit MSPMIN.  
  According to this invention, said acceleration control is effected according to the following schemes in accordance with (i.e., as a function of) the quantity of the strip stored in the storage station.  
  i. Where the quantity of the strip stored lies in region A, the rolling speed is increased to the normal rolling speed MSPN.  
  ii. Where the quantity of the strip stored lies in region if USP (uncoiler pay off speed) is larger than the mill speed MSP, the mill speed MSP is increased, if USP MSP, the MSP is maintained and if USP MSP, the MSP is reduced.  
  In each case, however, where the condition of MSP MSPN is reached, the normal mill speed MSPN is maintained so as not to accelerate to a speed above this value and when the condition of MSP MSPl-l is reached. the speed is not permitted to become lower than this value.  
  Even under this condition, upon receipt of a mode change order, the mill speed is controlled in the same manner as above described. Where the quantity of the strip stored decreases below the level at which the mill is to be applied with the emergency stop SLMlN, the mill is preferentially applied with the emergency stop.  
  As above described, according to this invention it is possible to prevent unreasonable stoppage of the uncoiler and rolling mill thereby improving production rate. Further, as the mill speed is not decreased below a predescribed value, the quantity of the offgauge product can be reduced.  
  Further, the method enables full automatic operations thus decreasing the number of operators. Any control system may be used for carrying out the method of this invention.  
 We claim:  
  1. A method of controlling a continuous rolling mill installation of the type wherein metal strips payed out from coils mounted on uncoilers are sequentially welded into a continuous strip, comprising the steps of:  
 storing a quantity of said continuous strip payed out from said uncoilers in a variable-quantity storage station including a loop car which is operable to vary the quantity of the strip stored in said storage station;  
 controlling the position of said loop car to vary the quantity of the strip stored in said storage station; feeding the strip out from said variable-quantity storage station and into a rolling mill;  
 detecting the quantity of the strip stored in said storage station; and  
 selectively controlling the speeds of said uncoilers and of the rolling mill as a function of the quantity of the strip stored in said storage station to a speed most suitable for the quantity of the strip stored in said storage station.  
  2. The method according to claim 1 comprising controlling the rolling speed to a speed which is not below a given minimum speed.  
  3. A method of controlling a continuous rolling mill installation of the type wherein metal strips payed out from coils mounted on uncoilers are sequentially welded into a continuous strip, comprising the steps of:  
 storing a quantity of said continuous strip payed out from said uncoilers in a variable-quantity storage station including a loop car which is operable to vary the quantity of the strip stored in said storage station:  
 controlling the position of said loop car to vary the quantity of the strip stored in said storage station;  
 feeding the strip out from said variable-quantity storage station and into a rolling mill;  
 detecting the quantity of the strip stored in said storage station;  
 controlling the pay-out speed of said uncoilers such that said loop car is maintained within a definite range when the quantity of the strip stored in said storage station exceeds a predetermined quantity; controlling the rolling speed of said rolling mill as a function of the speed of said uncoilers when the quantity of the strip stored in said storage station is less than said predetermined quantity; and  
 preferentially reducing the rolling speed of said rolling mill to a speed below a normal rolling speed (i) when cutting the strip rolled by said rolling mill by means of a flying shear, (ii) when the gauge of the rolled strip is to be changed and (iii) when the strips are welded together.  
  4. The method according to claim 3 comprising applying an emergency stop to the uncoiler when the quantity of the strip stored in said storage station exceeds a predetermined maximum.  
  5. The method according to claim 3 comprising applying an emergency stop to the rolling mill when the quantity of the strip stored in said storage station becomes less than a predetermined minimum.  
  6. The method according to claim 3 comprising controlling the rolling speed to a speed which is not below a given minimum speed.  
  7. A method of controlling a continuous rolling mill installation of the type wherein metal strips payed out from coils mounted on uncoilers are sequentially welded into a continuous strip, comprising the steps of:  
 storing a quantity of said continuous strip payed out from said uncoilers in a variable-quantity storage station including a loop car which is operable to vary the quantity of the strip stored in said storage station;  
 controlling the position of said loop car to vary the quantity of the strip stored in said storage station; feeding the strip out from said variable-quantity storage station and into a rolling mill;  
 detecting the quantity of the strip stored in said storage station;  
 controlling the pay-out speed of said uncoilers such that said loop car is maintained within a definite range when the quantity of the strip stored in said storage station exceeds a predetermined quantity; and  
 controlling the rolling speed of said rolling mill as a function of the speed of said uncoilers when the quantity of the strip stored in said storage station is less than said predetermined quantity.  
  8. The method according to claim 7 comprising controlling the rolling speed to a speed which is not below a given minimum speed.