US3648496A

US3648496A - Apparatus for controlling rolling mill

Info

Publication number: US3648496A
Application number: US833286A
Authority: US
Inventors: Henry Alfred Petry; Francis Rerecich; Gerhard Spangenberg
Original assignee: MAROTTA VALVE CORP
Current assignee: MAROTTA VALVE CORP
Priority date: 1969-06-16
Filing date: 1969-06-16
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14
Also published as: DE2204489A1

Abstract

A system for controlling rolling mills, especially roll contour, has hydraulic motors supplied with working fluid through a pressure regulator. The downstream pressure of the working fluid from the pressure regulator is adjusted by selectively supplying and venting fluid from a loading chamber of the pressure regulator. The loading and unloading controls are of a nature that permits remote location, and they are operated by an attendant in accordance with signals from the mill indicating errors in the dimensions of metal being rolled by the mill. Automatic operation can be substituted for the manual operation and programmed control of the pressure can also be used. Loading and unloading valves have actuators providing dither for the valve to prevent the difference in flow rates when flow is increasing as compared to conditions when flow is decreasing.

Description

etry et all.

APPARATUS TU "CUNTUILTJING UTJLTNG MllTslls lllenry ATred lPetry, Sparta; Francis Rerecicli, Dover; Gerhard Spangenlberg, Boonton, all of NJ.

Assignee: Mlnrottn Valve Corporation, Boonton, NJ.

Filed: June 16, 1969 Appl. No: 033,286

Inventors:

US. Cl ..72/16, 72/28, 72/245 lint. Cl. ..]Hl2lllr 37/02, B21b 37/06, B2lb 31/32 lFielld at Search ..72/8, 9, 16, 28, 246, 245,

References Cited UNlT ED STATES PATENTS 3,024,679 3/1962 Fox ..72/245 Primary Examiner-Milton S. Mehr Attorney-Sandoe, Hopgood & Calimafde [5 7] ABSTRACT A system for controlling rolling mills, especially roll contour, has hydraulic motors supplied with working fluid through a pressure regulator. The downstream pressure of the working fluid from the pressure regulator is adjusted by selectively supplying and venting fluid from a loading chamber of the pressure regulator. The loading and unloading controls are of a nature that permits remote location, and they are operated by an attendant in accordance with signals from the mill indicating errors in the dimensions of metal being rolled by the mill. Automatic operation can be substituted for the manual operation and programmed control of the pressure can also be used. Loading and unloading valves have actuators providing dither for the valve to prevent the difference in flow rates when flow is increasing as compared to conditions when flow is decreasmg.

7 lawn 1111 Drawing Patented March 14, 1972 7 3,648,496

3 Sheets-Sheet 1 GAUGE INVENTORS ATTORNEYS.

APPARATUS FOR CONTROLLING ROLLING MILL BACKGROUND AND SUMMARY OF THE INVENTION One of the problems encountered in rolling mills involves variations in the dimensions of the work piece along its length and transverse of its width. Particularly with mills for rolling sheet metal, the gauge of the metal is often greater toward the center of the strip than near the edges.

Efforts have been made to overcome this variation in gauge by providing the work rolls of the mill with a crown and applying pressure to the axles of the work rolls to change the contour of the rolls by bending them slightly to compensate any errors in gauge during a rolling operation.

This invention combines with the pressure-applying apparatus of the work rolls an improved system for applying pressure to change the contour of the work rolls. In its broadest aspects, the invention provides an improved system for applying constant pressure to an element and assures the degree of pressure necessary in response to error signals from the work to which the pressure is applied.

In the case of rolling mills, the invention supplies working fluid to the motors or other means that exert the pressure which is to be controlled; this pressure being applied to the axles of the work rolls of the mill to bend the rolls with a maximum diameter crown as the center fulcrum. The working fluid for the motors is supplied by a pressure regulator having a chamber that is subject to the pressure of the working fluid supply to the motors, i.e., the downstream pressure of the regulator, and this pressure acts against a movable wall of the regulator having a loading chamber on its other side.

The loading chamber is loaded and unloaded by valve means that supply the same kind of working fluid to the loading chamber as is controlled by the main valve of the regulator in the preferred construction.

The valves that supply the fluid to the loading chamber have actuators that provide dither to the valves to reduce static friction so that the fluid flow for a particular valve operating force is substantially the same whether the valve is moving toward open or closed position.

In the preferred embodiment, the invention has separate operating means for different sides of the mill and this provides greater flexibility of adjustment to correct errors in gauge that may not be symmetrical about the center line of the strip or other work piece; and the rate of correction is responsive to the extent of displacement of the controls.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

BRIEF DESCRIPTION OF DRAWING In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIG. I is a diagrammatic view of a rolling mill equipped with roll pressure controls made in accordance with this invention;

FIG. 2 is an enlarged diagrammatic view of one of the roll passes of FIG. I;

FIG. 3 is a diagrammatic wiring and piping diagram for the rolling mill control shown in FIG. 1',

FIG. 4 is a schematic view showing the correlation of the control valves for the system shown in FIG. 3;

FIG. 5 is a greatly enlarged sectional view through one of the regulators shown in FIG. 3;

FIG. 5a is an enlarged, fragmentary view of the main valve element shown in FIG. 5;

FIG. 6 is a fragmentary and partly diagrammatic end view of the regulator shown in FIG. 5;

FIG. 7 is a wiring diagram for the control connections shown diagrammatically in FIG. 3;

FIG. 8 is a graph showing the principle of operation of the electrical controls shown in FIG. 7;

FIG. 9 is a chart showing the effect of friction on the operation of the pilot valves and the resulting fluid flow; and

FIG. 10 is a chart similar to FIG. 9 but showing the improved results obtained when the control means provides dither for the pilot valves.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. I shows a rolling mill having successive roll stands I6 and 118 through which a metal strip 20 passes. Each of the roll stands 16 and 18 is a four-high mill having an upper work roll 22 and a lower work roll 24. These work rolls 22 and 24 have

backup rolls

26 and 28, respectively.

The roll stands 16 and I8 have long rolls for rolling sheet metal, and this invention is particularlly concerned with and will be described in connection with, the control of roll stands for sheet metal. However, in its broader aspects, the strip 20 is representative of metal which is rolled by passing it between work rolls that operate upon the metal to change its shape or dimensions.

FIG. 2 shows the roll stand 16. The

rolls

22 and 24 are crowned and the roll 24 has axle extensions at its opposite ends extending into chocks 30 which are movable up and down in a frame 32 of the roll stand in order to shift the lower roll 24 toward and from the upper roll 22. These chocks 36 are urged upward by cylinder-and-piston motors located under the chocks 30. Each motor includes a piston 34 attached to the chock 3th and a cylinder 36 supported from a lower chock 33 which provides a bearing for the backup roll 28.

Working fluid is supplied to the cylinders 36 from a pressure regulator which will be described. The introduction of additional working fluid into each of the cylinders 36 causes the piston 34 to lift its associated chock 38 and this bends the roll 24 about the upper center region of the roll 28 where the roll 28 contacts with the work piece with maximum pressure, this location serving as a fulcrum during the bending of the roll 24.

Both of the hydraulic devices, comprising the pistons 34 and cylinders 36, can be operated simultaneously to bend the roll 24 symmetrically, or the hydraulic devices can be operated separately or with less pressure supplied by one than the other where the roll is to be bent unsymmetrically because of unsymmetrical errors in the gauge of the strip passing between the

work rolls

22 and 24.

It will be understood that the upper work roll 22 can also be provided with hydraulic devices for thrusting it toward the lower work roll 24. In some installations the rolls are bent by pushing the crown portion of the roll against the backup roll. The rolling mill structure thus far described and illustrated diagrammatically is conventional and this invention includes new combinations with a rolling mill of apparatus for controlling the operation of the hydraulic devices so as to obtain better results, and more especially more unifonn results, in correcting for errors in the rolling of metal, especially errors in the gauge of sheet metal. The invention will be described as applied to a single roll stand of a mill; but it will be understood that it can be applied in similar fashion to any or to all of the roll stands.

FIG. 3 shows the cylinders 36 and pistons 34, and these hydraulic pressure devices are indicated generally in FIG. 3 by the reference characters 40. Working fluid passes to and from the respective hydraulic devices 40 through

tubing

42 and 43. The tubing 42 leads to a pressure regulator 46 and the tubing 43 leads to a pressure regulator 48. The pressure regulator 46 and its controls will be described, and it will be understood that the pressure regulator 48 and its controls are of similar construction.

In the diagrammatic illustration of FIG. 3, working fluid is withdrawn from a reservoir or sump 50 through tubing 52 leading to the inlet side of a pump 54 driven by a motor 56. The pump 54 supplies pressure through

tubing

58 and 59 leading to the

regulators

46 and 48, respectively. The regulator 46 has a return line 60 consisting of tubing leading back to the sump 50.

A controller 62 has a handle 64 which moves angularly about an axis into different positions, as indicated by the dotted lines in FIG. 3. When the handle is in the center position, the regulator 46 remains in its last adjusted position. In order to change the delivery pressure of the regulator 46, the handle 64 is moved to load or unload a loading chamber of the regulator 46. This apparatus will be described in connection with the other figures, but for the present it is sufficient to understand that movement of the handle 64 counterclockwise increases the loading of the loading chamber of the regulator 46; and movement of the handle 64 clockwise from its middle position vents fluid from the loading chamber of the pressure regulator 46.

In the control apparatus shown in FIG. 3 there is another controller 62' having a handle 64 which is operated to control the pressure regulator 48 in the same way that the handle 64 controls the pressure regulator 46.

These

controllers

62 and 62 with their

handles

64 and 64 are manually operated controls which are manipulated by an attendant in response to signal indications from gauge detectors 68 (FIG. 1) located at different locations across the width of the strip 20. If one gauge detector shows an increase in the gauge of the strip at the center region and the other gauge detectors indicate that the error is symmetrical, then the attendant operates both of the

handles

64 and 64 to cause the hydraulic devices on the rolling mill to apply additional pressure at both ends of the work roll. If the gauge detectors 68 show the error to be unsymmetrical, then the attendant operates only one of the controllers 62 or 62' to change the roll contour on whichever side is necessary in order to minimize the error; or he may operate the controllers 62 and 62' in opposite directions so as to increase the pressure at one end of the work roll and decrease it at the other, in order to minimize the error.

The manual controllers 62 and 62' illustrate the invention in its simplest aspects and it will be understood that the operation can be made automatic by having the

controllers

62 and 62 responsive to signals from the gauge detectors 68; and in more elaborate systems the controls can be combined with quality control computers which program the operation and take into consideration other factors such as pressure and temperature, in addition to the localized gauge readings of the detectors 68.

FIG. 4 is a schematic showing of the piping connections for controlling the operation of the pressure regulator 46. The pressure regulator has a main valve element 70 which controls flow of fluid from the inlet tubing 58 through the regulator 46 to the outlet tubing 42 which leads to the hydraulic pressure device. The pressure regulator 46 also contains a vent valve element 72 which controls the discharge of fluid from the regulator through the return line 60 to the sump 50. This fluid flowing from the regulator through the return line 60 may be either fluid vented from the loading chamber of the regulator, or it may be fluid exhausting from the hydraulic pressure device, as will be more fully explained in connection with FIGS. and 6.

The pressure regulator 46 has the supply of fluid for loading and unloading its chamber controlled by

valves

74 and 76, respectively. The valve 74 is operated by a solenoid 78 and the valve 76 is operated by a solenoid 80. The energy supplied to the solenoids comes from the controller 62; and in the preferred construction, which will be described in connection with FIG. 7, the amount of energy supplied to the

solenoids

78 and 80 depends upon the displacement of the controller 62 so that the extent of opening of the

valves

74 and 76, and the resultant flow, is proportional to the displacement of the controller 62.

When the solenoid 78 is energized, fluid flows from the inlet tubing 58 through a passage 82 in the regulator body, and past the open valve 74 to a passage 84 which leads to the loading chamber of the pressure regulator. When the valve 74 is closed and the valve 76 is open, fluid flows from the loading chamber through a passage 86, past the open valve 76, and through a passage 88 of the regulator to the return line 60.

FIG. 5 shows the internal construction of the regulator 46. The relation of some of the passages is not so clearly shown as in the schematic illustration of FIG. 4 because of the fact that the solenoid-operated

pilot valves

74 and 76 are located in different planes, one behind the other. The inlet tubing 58 connects with an inlet passage 90 which leads to a main valve chamber 92. The main valve element 70 is located in this valve chamber 92 and the portion of the valve chamber 92 beyond the main valve element 70 is indicated by the reference character 94. This portion 94 of the valve chamber has a passage 96 leading to the outlet tubing 42. When the main valve 70 is in open position, fluid flows from the inlet 58 through the passage 90 and valve chamber 92 to the passage 96 which leads to the outlet tubing 42 that communicates with the hydraulic pressure device.

FIG. 5a shows the construction of the main valve element 70. It comprises a stem 98 having a flange with a tapered face 100 behind which there is a shoulder 102 against which a plastic facing washer 104 is clamped by a bushing 106, threaded on the stem 98 with a thread lock 108, and an O-ring to prevent leakage of pressure behind the facing washer 104.

When the valve element 70 is in closed position, the facing washer 104 contacts with a seat 112 which fits with a press fit into a counterbore and against a shoulder 114 of the counterbore. An O-ring 116 prevents leakage of pressure behind the seat 112.

One end of the valve stem 98 slides in a guide 118 (FIG. 5) in a fitting 120 held in a counterbore of the pressure regulator housing by a threaded fitting 122. The end of the guide 118 is closed but the space within the guide communicates with the portion 94 of the valve chamber through drilled passages 124 so as to avoid compression of fluid beyond the left-hand end of the valve stem. A spring 126 urges the main valve element 70 toward closed position.

The right-hand end of the valve stem 98 slides in a cylindrical guide 128 (FIG. 5a). There is a tapered frustoconical face 130 on the right-hand end of the valve stem 98 and this face 130 surrounds a recess 132 which communicates through a passage 134 with the portion 94 of the main valve chamber.

A movable element 136 slides in various guides in the housing of the regulator with O-rings to prevent leakage of fluid around the outside of the movable element 136. This movable element 136 has a piston portion 138 which is a movable wall on the left-hand side of a loading chamber 140 of the regulator. The movable element 136 is also an auxiliary valve stem for transmitting motion of the piston portion 138 to the main valve element 70 when the movable element 136 moves toward the left in FIG. 5. When the movable element moves toward the right, the spring 126 moves the main valve element 70 into contact with the seat 112.

The movable element 136 also has a plastic valve element 142 that contacts with the frustoconical face 130 at the righthand end of the valve stem 98. This plastic valve element 142 is in closed position in contact with the face 130 whenever the main valve element 70 is open as a result of pressure in the loading chamber 140 holding the piston portion 138 far enough to the left to open the main valve element.

When the main valve element 70 moves into closed position, any further movement of the movable element 136 toward the right causes the plastic valve element 142 to move away from the frustoconical face 130 and this shifting of the valve element 142 into open position permits fluid in the portion 94 of the valve chamber to flow through the passage 134 into the recess 132, past the valve element 142 into a chamber 144 which communicates with a passage 146 leading to the return line 60. Thus the valve element 142 serves as a relief valve for pressure in the downstream portion 94 of the main valve chamber. The movable element 136 is moved to the left by pressure in the loading chamber 140 of the regulator, as previously explained; and it is moved toward the right by pressure in another chamber 148 which communicates with the downstream portion 94 of the main valve chamber through

passages

150 and 151. In the illustrated construction, the fluid supplied to the loading chamber 166 is the same hydraulic fluid as is regulated by the pressure regulator 16 and since this is not a compressible fluid, the loading chamber of the pressure regulator has to have resilient means for maintaining a load on the substantially incompressible fluid. This resilient means includes a stack of Belleville washers 152 held in stacked relation by an elastomeric sleeve 15 1 and housed in a cap 156 which screws into the end of the regulator along threads 158. A conventional spring can be substituted for the Belleville washers 152 but the washers have the advantage of providing more force and travel within a smaller space. The stack of washers 152 contacts with a fitting 1611 at one end of the cap 156 and this fitting 161]! extends through an opening 162 in the cap and has an axial opening 161 for free flow of air into and out ofthe cap 156.

The other end of the stack of washers 152 contacts with a plunger 166 which slides as a piston in a cup 1611 threaded into a holder 1711 in a counterbore of the regulator housing.

The space in the holder 1711 between the piston portion 136 of the movable element 136 and the end face of the plunger 166 is the loading chamber of the regulator. The end of the cup 1611 is open so that the piston portion 136 confronts the end face of the plunger 166 across the loading chamber. rings 172 prevent leakage of liquid around the outside of the plunger 166 and cup 169 into the space that holds the stack of washers 1152.

As liquid is pumped into the loading chamber 1410, the plunger 166 is moved to the right in FIG. against the pressure of the washers 152 and this compression of the washers increases the pressure on the fluid in the loading chamber and consequently increases the pressure on the piston portion 138 of the movable element 136. The fluid in the loading chamber is, in effect, a hydraulic link transmitting pressure of the stack of Belleville washers 152 to the piston portion 136 of the movable element 136.

The main valve element has the diameter of its contact with its seat correlated with the diameters of the portions of the stem that slide in the guides so that the main valve element is a balanced poppet and its movement is subject only to the balance of forces between the spring 126 and the downstream fluid pressure in the chamber 149 acting against the annular face of the element 136 which is exposed to fluid pressure in the chamber 1411], which forces urge the parts toward the right, and the pressure of the fluid in the loading chamber 140 acting against the piston portion 136 and urging the movable parts toward the left.

The space at the left of the piston portion 1311 is vented to the ambient atmosphere through a vent passage 17d, past the end of the holder 1711 and through an opening 175 in the side of the regulator housing.

The flow of fluid to and from the loading chamber 140 is through an axial passage 1811 in the movable element 136 and through a radial bore 1132 to a chamber 1134. These passages 11311 and 192 and the chamber 181 are portions of the passage 841 from the valve '7 1 to the loading chamber. The passage 92 that supplies fluid to the valve 7 1 is shown in dotted lines in FIG. 5. In practice, it is provided by drillings and crossdrillings in the block that comprises the housing of the pressure regulator 16; but these drillings and cross-drillings cannot be shown as such in FlG. 5 and the dotted line for passage 82 is the effective course of the passage.

When the valve 7 1 is in open position, fluid flows from the inlet 90 through chamber 92, passage 82, past the open valve 7 1 and through passage 8 1 to the loading chamber 1411 re gardless of whether the main valve element 711 is open or closed.

The other valve 76 (FlG. t) operated by the solenoid 80 is similar to the valve 7 which is operated by the solenoid 76. It controls flow of fluid from the from the loading pressure chamber through passages 11111, 182, and the chamber 184, and through the passage 86 (FIGS. 1 and 6), past the open valve 76 and through the passage 1111 to the return line 60. The extent to which valves 741 and 76 are open determines the rate of flow to and from the loading chamber of the regulator and thus determines the rate of change of the delivery pressure of the regulator.

FIG 7 shows, diagrammatically, the controller 62. The other controller 62 is of similar construction. The handle 641 is secured to a shaft 169. There are two switches 191 and 192 urged into closed positions by springs 19 1 and actuated into open positions by a plunger 196 for the switch 191 and by a plunger 197 for the other switch 192. Both of the plungers 196 and 197 bear against a cam 198 on the shaft 196, and this cam is shaped to let one or the other of the switches 191 and 192 close when the cam 199 operates one or the other of the plungers 196 and 197.

Power is supplied to the controller 62 from an alternating current power line 2011. For some controllers a combination of alternating current and direct current is used, but the illustrated controller 62 uses alternating current power only. The power passes from a radiofrequency choke 202 and then through a delaying network 21141 to a solid state trigger 2116. A solid state switch 266 is provided for the main current flow.

The delay network 2941 includes an iinductance potentiome ter 210. A brush 212 wipes along the curved potentiometer to change the inductance of the circuit of the delaying network. The wiper brush 212 is secured to the shaft 1119 in such position that the wiper is at the midpoint of the potentiometer when the handle 641 is in its mid or off position which does not close either of the switches 191 and 192. Changes in the delaying network change the point in each cycle at which the switch 208 closes to supply power to one side of each of the switches 191 and 192. The switch 191 closes to supply power to the solenoid 78 to open the valve 76 which increases the pressure in the loading chamber of the regulator. The closing of the switch 192 supplies power to the solenoid to open the valve 76 which decreases the pressure in the loading chamber of the regulator.

FIG. 9 shows the principle of operation of the controller shown in FIG. 7. With the delaying network adjusted for a long delay, the switch 298 (FIG. 7) closes late in the current cycle as indicated by the line 216, and the only power supplied to the solenoid is that represented by the area under the alternating current curve 218 to the right of line 216. Reducing the delay of the delaying network moves the time of closing of the switch forward to the time represented by the line 2211, and the power represented by the area under the curve 218 to the right of the line 220 is substantially greater than the power to the right ofline 216.

The increase in the power supplied to the solenoids increases the pull of each solenoid and increases the extent to which the valve is opened by the solenoid for greater flow of liquid to the loading chamber of the regulator with resulting increase in the rate at which the regulator adjusts to a higher delivery pressure, or to a lower delivery pressure in the case of the vent valve.

FIG. 8 shows power supplied to the solenoids for both the plus and minus halves of the alternating current wave. In prac' tice, this power can be rectified at the solenoid either by half wave or full wave rectification. One of the advantages of the pulse power supply to the solenoids is that the pulsing force applied to the valves provides dither so that there is substan tially no static friction to be overcome in the operation of the valves.

The important advantage of providing dither for the

pilot valves

74 and 76 is brought out clearly by a comparison of FIGS. 9 and 10. FIG. 9 shows a curve 2241 which plots flow of fluid past an open pilot valve against the voltage applied to the solenoid that operates the valve. The voltage used for FlG. 9 was direct current voltage without pulses and without dither of the valves. lt is apparent that when the valve is opened to increase the rate of flow there is much less flow for a given voltage on the solenoid as compared with the condition where the valve is closed. The difference in flow rate at voltage Y-ll is represented by the distance from 74-1 to X-2 on the chart, and it is of substantial magnitude.

In FIG. a curve 226 corresponds to the curve 224 of FIG. 9, but the voltage applied to the valve-operating solenoid was a pulsing power supplied as shown in FIG. 8 with resulting dither of the valve. The decreasing flow portion of the curve of FIG. 10 is close to the increasing flow portion and at some points the two portions of the curve intersect indicating identical fluid flow for a given solenoid voltage regardless of whether the flow is increasing or decreasing, that is, whether the valve is opening or closing. This makes the rate of change substantially uniform for a given position of the control handles and is especially important when automatic control is substituted for manual.

The preferred embodiment of the invention has been illustrated and described and the invention is described in the appended claims.

What is claimed is:

l. The combination with a roll mill having rolls forming a pass through which a metal workpiece travels and having pressure operated motor means for moving one roll with respect to the other roll of the roll pass to change the pressure of the roll on the workpiece, of means for supplying working fluid to said motor means including a pressure regulator having an inlet for receiving high pressure working fluid from a working fluid source at fixed or variable pressure and an outlet connected with the motor means, valve means in the pressure regulator commanding flow from the inlet to the outlet, a valve chamber in the pressure regulator supplied with pressure from the outlet and from the downstream side of the valve means, an actuator for the valve means exposed to the chamber pressure for closing the valve means when the chamber pressure reaches a predetermined pressure, and adjustable means movable into different positions to change the downstream pressure at which the actuator operates the valve means.

2. The combination described in claim 1 characterized by the pressure regulator including a loaded relief valve through which working fluid escapes from said valve chamber when the pressure of the working fluid at the outlet exceeds a predetermined value.

3. The combination described in claim 2 characterized by the working fluid being a liquid and the motor means including two cylinder-and-piston hydraulic motors, a different one of which is connected with each end of the roll, a sump from which working fluid is supplied to the pressure regulator and to which the working fluid flows from said relief valve, and a pump that delivers liquid from the sump to the inlet of the pressure regulator.

4. A pump system for correcting errors in the thickness of metal being rolled in a rolling mill including in combination pressure devices for changing the pressure of rolling mill rolls on the metal, a transducer for detecting errors in the thickness of the metal as it comes from the roll pass, separate pressure regulators that supply working fluid to each of the pressure devices, each of the regulators having an inlet for receiving high pressure working fluid from a working fluid source at fixed or variable pressure and an outlet connected with the pressure devices, valve means in the pressure regulator commanding flow from the inlet to the outlet, a valve chamber in the pressure regulator supplied with pressure from the outlet and from the downstream side of the valve means, an actuator for the valve means exposed to the chamber pressure for closing the valve means when the chamber pressure reaches a predetermined maximum pressure, each of the actuators including a movable wall exposed on one side to the pressure of the valve chamber, each of the regulators also having a loading chamber on the other side of the movable wall, other valve means for supplying fluid to and exhausting fluid from the loading chambers of the regulators, and devices for operating said other valve means in accordance with errors detected by the transducer.

5. The system described in claim 4 characterized by the pressure devices being hydraulic motors on different sides of the rolling mill, there being a plurality of transducers at different locations across the width of the metal being rolled, there being different valve means for each pressure regulator for supplying fluid to and exhausting fluid from the loading chambers of the pressure regulators, and the devices for operating said valve means including a different manually actuated element for each valve means for selectively operating the valve means in accordance with the errors detected by the transducer.

6. A pump for correcting errors in the thickness of metal being rolled in a rolling mill including in combination pressure devices for changing the pressure of rolling mill rolls on the metal, a transducer for detecting errors in the thickness of the metal as it comes from the roll pass, separate pressure regulators that supply working fluid to each of the pressure devices, each of the regulators having a loading chamber, valve means for supplying fluid to the loading chambers of the regulators,

and devices for operating said valve means in accordance with errors detected by the transducer, characterized by the pressure devices being hydraulic motors on different sides of the rolling mill, there being a plurality of transducers at different locations across the width of the metal being rolled, there being different valve means for supplying fluid to the loading chambers of the pressure regulators, and the devices for operating said valve means including a different manually actuated element for each valve means for selectively operating the valve means in accordance with the errors detected by the transducer, and further characterized by the rolling mill having long rolls for rolling metal sheets, and the rolling mill being a four high mill with crowned work rolls and a backup roll behind each of the work rolls, the valve means that supply fluid to the loading chambers of the pressure regulators also including means for venting the loading chambers to reduce the loading on the pressure regulators, the loading chambers being loaded with liquid and having two movable walls, one of which has spring means on the side opposite the loading chamber which are compressed by displacement of the movable wall to increase the pressure of the liquid in the loading chamber, and the other of which connects with a main valve of the regulator for controlling the flow of liquid through the pressure regulator.

7. The system described in claim 6 characterized by the connection between one of the movable walls of the loading chamber and the main valve of the regulator being made in two parts in end-to-end abutment for displacing the main valve, a relief valve on one of said parts, a seat for the relief valve on the other of said parts, the relief valve being opened by continued movement of its connected movable wall of the loading chamber after the main valve of the pressure regulator has moved into closed position, and a pressure chamber exposed to the outlet pressure of the regulator and located on the side of said other wall, which side is the one away from the loading chamber of the regulator.

Claims

1. The combination with a roll mill having rolls forming a pass through which a metal workpiece travels and having pressure operated motor means for moving one roll with respect to the other roll of the roll pass to change the pressure of the roll on the workpiece, of means for supplying working fluid to said motor means including a pressure regulator having an inlet for receiving high pressure working fluid from a working fluid source at fixed or variable pressure and an outlet connected with the motor means, valve means in the pressure regulator commanding flow from the inlet to the outlet, a valve chamber in the pressure regulator supplied with pressure from the outlet and from the downstream side of the valve means, an actuator for the valve means exposed to the chamber pressure for closing the Valve means when the chamber pressure reaches a predetermined pressure, and adjustable means movable into different positions to change the downstream pressure at which the actuator operates the valve means.

6. A pump for correcting errors in the thickness of metal being rolled in a rolling mill including in combination pressure devices for changing the pressure of rolling mill rolls on the metal, a transducer for detecting errors in the thickness of the metal as it comes from the roll pass, separate pressure regulators that supply working fluid to each of the pressure devices, each of the regulators having a loading chamber, valve means for supplying fluid to the loading chambers of the regulators, and devices for operating said valve means in accordance with errors detected by the transducer, characterized by the pressure devices being hydraulic motors on different sides of the rolling mill, there being a plurality of transducers at different locations across the width of the metal being rolled, there being different valve means for supplying fluid to the loading chambers of the pressure regulators, and the devices for operating said valve means including a different manually actuated element for each valve means for selectively operating the valve means in accordance with the errors detected by the transducer, and further characterized By the rolling mill having long rolls for rolling metal sheets, and the rolling mill being a four high mill with crowned work rolls and a back-up roll behind each of the work rolls, the valve means that supply fluid to the loading chambers of the pressure regulators also including means for venting the loading chambers to reduce the loading on the pressure regulators, the loading chambers being loaded with liquid and having two movable walls, one of which has spring means on the side opposite the loading chamber which are compressed by displacement of the movable wall to increase the pressure of the liquid in the loading chamber, and the other of which connects with a main valve of the regulator for controlling the flow of liquid through the pressure regulator.