US3389588A - Apparatus for controlling the position of work rolls - Google Patents

Description

June 25, 1968 A. D. REINHARDT ET AL 3,389,588

APPARATU FOR CONTROLLING THE POSITION OF WORK ROLLS Filed March 9, 1965 Lg/ I For" sauna:

INVENTORS ANTHONY D. RE/lV/IARDT and ROBERT C. SL/F/(A United States Patent 3,389,588 APPARATUd FQR CGNTROLLING THE. PGSHTEUN OF WGRK ROLLS Anthony D. Reinhardt, South Holland, and Robert C.

Slifha, Cicero, ill assignors to United States Steel Corporation, a corporation of Delaware Filed Mar. 9, 1965, Ser. No. 433,274 3 Claims. (Cl. 72-3) ABSTRACT tlF THE DESQLOSURE An apparatus for controlling the position of work rolls in a mill is disclosed which includes means to obtain a signal related to the spacing between the work rolls, means to provide a command signal proportional to desired roll spacing and means to operate a fluid system responsive to a signal related to the deviation between actual and desired roll spacing so as to adjust the roll spacing.

The present invention relates to an apparatus for controlling the position of work rolls in a rolling mill. More particularly, the invention involves adjusting the spacing between the work rolls so as to maintain an approximate desired roll gap.

In recent years, there has been emphasis on improving the quality of rolled products. As a result, greater efforts have been made to more accurately control product thickness during rolling. Conventionally, the thickness of the product has been determined by measuring the product after rolling and making mill adjustments as needed. The present invention contemplates maintaining continuous surveillance of the roll gap and making instantaneous mill adjustments to compensate for undesirable deviations.

An outstanding advantage of the invention is the relative simplicity of the equipment to measure the position of work rolls in a rolling mill. The invention is particularly useful in slab mills and in other mills where relatively thick product is rolled. The system employed for measuring and controlling the roll position can maintain roll spacing within a tolerance of $0.025. Although not sufliciently accurate for thin gauge strip, the system according to the invention is well-suited for use on rolling mills in which relatively thick product such as slabs are rolled.

.In addition to the above, the invention is particularly useful in conjunction with continuous metal casting oper ations. In continuous casting, a continuous metal column of metal is produced which is passed through rolls which should be maintained at a preselected roll spacing. In spite of continual variation in the roll separating forces caused by changes in the thickness and temperature of the metal column entering the rolls, the present invention can be employed to maintain the preselected roll gap with sufficient accuracy to produce a more uniform product.

Other advantages of the invention will be made more apparent by the following description in conjunction with the drawing which is a schematic diagram illustrating a preferred embodiment of the invention.

In the drawing, a Z-high rolling stand is shown, comprising top and bottom rolls l2 and M, respectively, having shafts mounted in roll chocks 12a and 12b and 14a and 141), respectively. The roll checks in turn are supported in a mill housing It) wherein they may be moved vertically to adjust the roll gap, i.e. spacing, between the rolls l2 and M. in the preferred embodiment illustrated, the position of top roll 12. is fixed within the mill housing lti, but the roll chochs 14a and ltd!) of the bottom roll are supported by fluid-operated assemblies Zita and Z lb to raise and lower the bottom roll.

3,339,588 Patented June 25, 1968 The spacing between the rolls is controlled by means of an electrical system which measures the roll gap and energizes the hydraulic system to affect movement of bottom roll 14 as needed (up or down) so as to maintain the desired roll spacing. This is accomplished in the preferred embodiment by means of a transducer 22 connected to a recorder 50 whose indicator arm 51 is mechanically linked to the slider arm 52 of a retransmitting potentiometer '2 which is in turn connected to a device 54 which compares the magnitude of two electrical signals and energizes the proper fluid system to raise or lower the bottom work roll to maintain the desired roll gap. Also connected to device 54-, which may be a bridgebalance relay as herein after described, is a set-point potentiometer 56 whose slider arm 56' may be manually set to issue a signal to device 54 proportional to the desired roll spacing.

The roll gap is varied by moving roll 14 by means of the fiuidoperated cylinder-ram assemblies 29a and 201). To operate the cylinder-ram assemblies, a pump 24 continuously circulates fluid to the storage reservoir 26 through a control valve 28 which is positioned in fluid line Stl. The control valve 28, which is preferably an air-actuated valve produced by Republic Mfg. Co., model No. 831-1, is normally open to permit the circulation of fluid to the reservoir 26 and is closed by introducing air through line 32 via solenoid valve 34 (connected to an air supply not shown). The air-actuated control valve 28 may be closed by solenoid-operated valve 34. The solenoid valves used herein may be model CC20025A made by Hannifin. When valve 23 is closed, fluid from pump 24 is forced to flow through line 36 and through check valve 38 into the flow divider 4d which distributes the fluid flow into two equal components which are diverted to the two fluid-operated ram assemblies a and 20b to cause the roll 14 to move upwardly and thereby decrease the roll gap.

The bottom roll is lowered by energizing solenoid-operated valves 48a and dtib thereby permitting pump 60 to force pilot fluid through lines 49a and 4912 thereby applying force to hydraulic actuators which. in turn open decompression valves Ma and 44b to allow fluid from ram assemblies 201: and 20b to escape through lines 46a and 46b to the reservoir 26, thus lowering roll 14. The solenoids 47a and 47b of solenoid-operated valves 48a and 48b together with the solenoid of solenoid-operated valve 34 are energized and de-energized by control relays and 57 which are contained within the bridge-balance relay 54. Relays 55 and 57 are energized by power from a transistorized amplifier also contained within bridgebalance relay 54.

In operation, the roll gap measuring device 22 which may be any suitable transducer but in the preferred embodiment is a spring-loaded reel-type precision potentiometer, with its wire connected between the roll chocks, receives a constant input signal and produces an output signal approximately proportional to the existing roll gap. The signal sent by device 22 is only approximately proportional to the roll spacing because it actually measures the spacing between the roll chocks which may be slightly different than the spacing between the rolls. Spacing be tween the rolls will vary largely due to rolling forces which change the relative positions of the roll chocks which changes are proportional to changes in the roll gap but, in addition, because of roll Wear, deflection, etc; these latter changes will not be reflected in the signal issued by the potentiometer 22. However, it has been found that an arrangement as illustrated can be satisfactorily operated within $0.625 of actual roll spacing. This tolerance is more than satisfactory for a relatively large roll gap such as would be used in rolling slabs. The signal issued from potentiometer 22 which is therefore approximately proportional to the roll gap, is received by a strip recorder 50 which provides a continuous record of changes in the roll spacing. Any suitable recorder may be employed such as the Minneapolis-Honeywell continuous-balance potentiometer type. As the roll gap and the relative positions of the roll chocks 12a and 14a vary, the reel of the potentiometer 22 is likewise rotated by the wire connection between the chocks to change the valve of the signal to the recorder. Simultaneously actuated is a circuit comprising a set-point potentiometer 56 and a retransmitting potentiometer 52 both of which are connected to a suitable device 54- for comparing values and algebraically summarizing two electrical signals. One preferred such device for comparing values of two electrical signals is a bridge-balance relay produced by the Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., identified as R7103C and described in a publication by the manufacturer identified as 95-5420.

The set-point potentiometer 56 has an adjustable slider arm and dial 56' to permit a manual setting of potentiometer 56 so as to provide an electrical signal to the bridge-balance relay 54 proportional to the desired roll spacing. The potentiometer is properly calibrated for this purpose. The retransmitting potentiometer 52 has a slider arm 52' that is mechanically linked with the arm or pen of the recorder 50 so that it assumes a position in accordance with the existing roll gap as indicated on the recorder. Any suitable recorder may be used such as the continuous-balance potentiometer type made by Minneapolis-Honeywell. In this way, the potentiometer 52 provides a signal to the relay 54 approximately proportional to the existing roll gap. The bridge-balance control relay contacts receive an input from a power source through lines L and L and compare the signal from the set-point potentiometer 56 to the signal from the retransmitting potentiometer 52. These signals are of equal value when the roll spacing conforms with the desired roll gap. In that event, the bridge-balance relay 54 Will have both of its control relays, 55 and 57 and their respective circuits 54x and 54z, each of which include common line 54y deenergized, thereby causing no change in the roll gap. If, however, the roll gap is greater than that desired, the bridge-balance relay will be unbalanced and will energize control relay 57 which, when closed, connects the solenoid 35 associated with solenoid-operated valve 34 with the line source and the solenoid is energized to operate the valve. When valve 34 is opened, it permits air to enter through line 32 closing the air-actuated control valve 28.

Fluid is then forced by pump 24 through line 36, passed the spring-loaded check valve 38 into the flow divider 40 and then into lines 40a and 40b. The fluid passes check valves 41a and 41b to enter the cylinder-ram assemblies 20a and 20b, thereby raising roll chocks 14a and 14b and work roll 14. This action continue-s until the desired roll gap is achieved at which time the slider arm 52 of the retransmitting potentiometer 52 is at a setting such that the signals from this potentiometer and the set-point potentiometer will balance in the relay 54 and the control relay 57 becomes de-energized. De-energizing control relay 57 causes the solenoid-operated valve 34 to shift, permitting air to open valve 28 and resumes the flow of fluid through line 30 to the reservoir 26, thereby halting the flow of fluid into the cyinder-ram assemblies 20a and 20b.

If the existing roll gap is less than the desired roll spacing established by the slider arm of the set-point potentiometer 56, the bridge-balance relay energizes the normally opened relay 55. 'In so doing, solenoids 47a and 47b of solenoid-operated valves 48a and 4%!) are electrically connected with the line source and the valves 48a and 48b are operated to open pilot-operated decompression valves 44a and 44b. This, as previously described, causes fluid to be exhausted from the cylinder-ram assemblies 20a and 20b, thereby causing the cylinder-rams and bottom roll to lower and increase the roll spacing. This action continues until the selected roll gap is achieved as indicated by the slider arm of the retransmitting potentiometer 52. The signals from the retransmitting potentiometer and set-point potentiometer then balance in the bridge-balance relay, and no signal is produced across 54x and S-tz. As these signals become equal, bridge 54 is balanced and relay 55 is opened and the solenoids 47a and 47b are de-energized, closing valves 811 and 48b. This directs pilot flow from motor-operated pump 69 to the reservoir and allows lines 49a and 49b to drain and stops the flow of fluid from the cylinderram assemblies 20a and 20b to the reservoir '26 and the roll gap is thereby maintained at the preselected setting.

It is apparent from the above that various changes and modifications may be made without departing from the invention. The fluid-operating system employed in conjunction with the circuitry for sensing the approximate position of the Work rolls with respect to each other has been found to be effective for instantaneous mill adjustments. The term fluid-operated system, of course, refers generally to hydraulic systems. Although one type of valve responsive to electrical signals has been shown, i.e. the solenoid-operated valves, other valves operating under the same principle may be similarly employed, preferably other low torque rotary directional valves. In this connection it should be noted that alternate equipment performing similar functions may be readily substituted throughout the system described herein. Thus, for example, summing or bi-stable amplifiers may be used in lieu of the bridge-balance relay. Similarly other transducers, or indeed, any device which translates mechanical displacement into a proportional signal, electrical or otherwise, may be used in place of the spring-loaded potentiometer 22.

In the preferred embodiment described herein, a recorder is used to maintain a record of roll changes. However, it is apparent that the recorder may be omitted and, moreover, the potentiometer 22 may be directly connected to the bridge-balance relay 54, thereby also omitting, if desired, retransmitting potentiometer 52.

We claim:

1. Apparatus for controlling the position with respect to each other of work rolls in a rolling mill comprising means to obtain a first signal approximately proportional to the spacing between work rolls in a rolling mill, means to provide a command signal proportional to the desired roll spacing, means to compare said first signal and said command signal, a fluid-operated system responsive to said last-named means for increasing and decreasing roll spacing so that a desired approximate roll spacing may be maintained.

2. An apparatus for controlling the position with respect to each other of work rolls in a rolling mill comprising upper and lower work rolls, support means for said work rolls, fluid-operated rams positioned at the supports of at least one work roll in said rolling mill adapted to raise and lower said roll, means to provide a controlled supply of fluid to said fluid-operated rams, means to evacuate a controlled quantity of fluid from said fluid-operated rams, means to obtain a signal approximately proportional to the spacing between the rolls, means responsive to said signal for energizing and de-energizing said means to supply fluid to said rams and said means to evacuate fluid from said rams whereby a desired roll spacing is maintained.

3. An apparatus for controlling the position with respect to each other of work rolls in a rolling mill having upper and lower work rolls with the roll ends mounted in roll chocks and supported in a mill housing comprising a fluid-actuated cylinder-ram assembly positioned beneath the roll chock at each end of the bottom roll for raising and lowering said roll chocks and roll, first means to supply a controlled quantity of fluid to said cylinderram assemblies to raise said bottom roll and second means to withdraw a controlled quantity of fluid from said cylinder-ram assemblies to lower said bottom roll, means to obtain a first signal proportional to thespacing between the roll chocks of the top and bottom rolls, means to provide a command signal proportional to the desired roll spacing, means to compare said first signal and said command signal and to energize one of said first means and said second means to raise or lower the bottom work roll until said first signal and said command signal balance.

References Cited UNITED STATES PATENTS 0 GERALD A. DOST, Primary Examiner.

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