GB1596192A - Method of conreolling the thickness of strip stock being rolled and a device for carrying same into effect - Google Patents

Description

(54) METHOD OF CONTROLLING THE THICKNESS OF STRIP STOCK BEING ROLLED AND A DEVICE FOR CARRYING SAME INTO EFFECT (71) We, CHELYABINSKY POLITEKHNICHESKY INSTITUT IMENI LENINSKOGO KOMSOMOLA, of prospekt V. I. Lenina, 76 Chelyabinsk, Union of Soviet Socialist Republics, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates generally to plastic metal working and more specifically to a method of controlling the thickness of the strip stock being rolled and to a device for carrying said method into effect.

The invention can find utility when applied in rolling mills for producing sheet and band stock.

According to one aspect of the present invention, there is provided a method of maintaining constant the thickness of strip stock being rolled between the rolls of a roll mill stand, comprising the following steps: setting up a force R causing the supports of one of the rolls to traverse, said force exceeding in magnitude the force P of rolling applied to roll the strip and being applied to the roll supports in such a way as to act against the force P of rolling, the difference between the force R and the force P of rolling tending to cause the roll supports to traverse; developing a balancing force Q proportional to the distance of traverse of the roll supports which acts to prevent the support of the rolls between which the strip stock is deformed from being brought together and to balance out the difference between the force R causing the roll supports to traverse and the force P of rolling; wherein the force R causing the rolls to traverse is regulated by means of a control circuit having no error feedback to be dependent upon the force P of rolling in accordance with the equation: R=k2P where k2 is a constant and wherein the factor of proportionality k, between the roll support traverse distance and the balancing force preventing the roll supports from being brought together is predetermined in dependence uporr the values of the said constant k2 and the mill stand stiffness factor k, the value of k1 satisfying the equation:: k1=k(k2-l) A second aspect of the invention provides a device located in the stand of a rolling mill, the mill having a roll housing which mounts a screwdown arrangement and mill rolls with supports accommodated in side recesses of said roll housing, at least one of the rolls being adapted to traverse along the direction of action of the force of rolling; the device comprising two assemblies situated one on each side of the roll mill stand, each assembly comprising: a hydraulic dynamometer interposed between the supports of one of the rolls and the roll mill stand housing and adapted to take up the force of rolling: at least one hydraulic cylinder provided between the supports of one of the rolls and the roll mill stand housing, the piston-end space of the hydraulic cylinder communicating with a source of hydraulic fluid under pressure to allow build-up of a force greater in magnitude than the force of rolling, the difference therebetween being large enough to cause said roll and associated supports to traverse during a rolling operation; elastic members adapted to determine the position of the supports of said traversable roll and so positioned as to take up the difference between the force developed by said hydraulic cylinder and the force of rolling; the force created by said hydraulic cylinder offering resistance to the force of rolling and at the same time inflicting deformation upon said elastic members, the ratio between the stiffness factor of said elastic members of the device and the stiffness factor of elastic members of the roll mill stand together with those members of the device adapted to take up the force of rolling being of a predetermined value; a valve adapted for regulating the pressure of hydraulic fluid in the interior space of-said hydraulic cylinder and comprising a valve body, a sliding spool accommodated in the body so as to define at least two chambers therein, one chamber being the control chamber of the valve and communicating with said hydraulic dynamometer to form therewith an enclosed fluid-filled space, the other chamber acting as the throttle chamber of said valve and communicating with the interior space of said hydraulic cylinder and with the source of hydraulic fluid to form with these an enclosed space for containing running hydraulic fluid.

The force of rolling developed during the rolling process, is taken up by the hydraulic dynamometer with the result that a pressure of power fluid proportionate to the force of rolling is built up in the hydraulic dynamometer chamber and in the control chamber of the pressure regulating valve, whereby the pumping unit develops a pressure of power fluid effective in the hydraulic cylinder and also proportionate to the force of rolling, said power fluid pressure developing a force in the hydraulic cylinder, proportionate to the force of rolling and aimed at traversing the supports of the movable roll.Part of said force overcomes the resistance to the force of rolling, while the difference between the force of the hydraulic cylinder and the force of rolling effects deformation of said elastic members of the device, whereby the movable roll supports traverse over a length equal to the magnitude of said deformation.It is due to the development of such a hydraulic cylinder force that the ratio between the force of deformation of the elastic members of the device and the force of rolling be equal to the ratio between said stiffness factor of said elastic members of the device and the stiffness factor of the mill stand elastic members, that the elastic members of the device are imparted deformation equal in its magnitude to the deformation undergone by the mill stand elastic members, whereby any effect of the mill stand deformation upon variation of the thickness of strip stock rolled between the work rolls is ruled out.

This solution enables one to dispense with electric and electronic circuits, thus rendering the device constructionally simple and reliable in operation. The device is inexpensive to manufacture. Provision is made for the use of power fluid (oil) featuring the degree of cleannes adopted in conventional hydraulic cylinders and for the device to be attended by low-skill personnel.

It is expedient that each of the hydraulic cylinders be provided with an enclosed piston-rod space confined within the cylinder barrel, cover, piston and piston rod and filled with power fluid which establishes, along with the hydraulic cylinder components defining said space, the elastic members of the device determining the position of the traversable roll supports, whereby the device can be made more compact and space-saving.

It is also practicable that the sliding spool of each valve for control of fluid pressure in the hydraulic cylinder interior be made stepped so as to form an additional control chamber along with the valve chest, and that said control chamber be communicated with the hydraulic cylinder rod space to establish an enclosed space together therewith, filled with power fluid, thus adding to the speed of response of the device and to the accuracy of the roll gap adjustment.

It is likewise reasonable that a spring be provided in the enclosed piston-rod space of the hydraulic cylinder, said spring resting with ends upon the cylinder piston and cover. and establishing, along with power fluid and the hydraulic cylinder components forming said enclosed piston-rod space and adapted to interact with said spring, the elastic members of the device, thus facilitating proper selection of a required stiffness factor of the elastic members of the device.

It is also appropriate that the chamber of the hydraulic dyanometer communicated with the valve control chamber, be combined with the hydraulic cylinder piston-end space, a feature that renders the device simpler and more space-saving.

It is likewise favourable that a spring be provided in the piston-end space of the hydraulic cylinder, communicated with the valve control and throttle chambers during the rolling process, said spring resting (under no-rolling conditions) upon the piston and barrel of the hydraulic cylinder and contributing to formation of an oil layer in the piston-end space "b", necessary for engaging the device into operation.

It is likewise advantageous that the device be provided with an additional hydraulic cylinder whose interior is communicated with the piston-rod space of the hydraulic cylinder to form an enclosed space along therewith, filled with power fluid, both said space and said fluid constituting an elastic member of the device, which makes it possible to provide a required ratio between the stiffness factors of the elastic members of both the device and the mill stand It is also advisable that the piston-end space of the hydraulic cylinder be communicated with a source of power fluid pressure through a directional-control sliding spool valve having two end control chambers, of which one is communicated with the valve throttle chamber and with the source of fluid pressure, while the other, with a source of constant pressure. a feature that enables the device to be simplified and more space-saving.

In what follows the device proposed in the present invention is illustrated in a number of exemplarv embodiments thereof with reference to the accompanying drawings, wherein: Fig. 1 illustrates schematically a roll mill stand according to the invention; Fig. 2 illustrates a further roll mill stand as viewed from the operator's side, showing the device for controlling the thickness of strip stock being rolled between rolls, made according to the invention, and a sectional view of the units of said device; Fig. 3 is a scaled-up sectional view of a hydraulic dynamometer, taken in an axial plane thereof; Fig. 4 is a scaled-up sectional view of a double-space hydraulic cylinder, taken in an axial plane thereof; FiR. 5 is a scaled-up sectional view of a valve for power fluid pressure control in the hydraulic cylinder interior, taken in an axial plane thereof;; Fig. 6 is a scaled-up sectional view of a volumetric oil regulator, taken in an axial plane thereof; Fig. 7 illustrates a roll mill stand as seen from the operator's side, showing the device for controlling the thickness of strip stock being rolled between rolls, wherein the valve sliding spool is made stepped, and a sectional view of the units of said device; Fig. 8 is a scaled-up sectional view of a valve for power fluid pressure control in the hydraulic cylinder interior as seen in Fig. 7, taken in an axial plane thereof; Fig. 9 is a sectional view of a hydraulic dynamometer and hydraulic cylinder made as a hydraulic unit, taken in an axial plane thereof; Fig. 10 is a sectional view of an embodiment of the hydraulic panel having three hydraulic dynamometers and three hydraulic cylinders, taken in an axial plane thereof;; Fig. 11 is a sectional view of another embodiment of the hydraulic unit having one hydraulic dynamometer and two hydraulic cylinders, wherein the axis of the hydraulic dynamometer coincides with that of one of the hydraulic cylinders, taken in the common plane of the axes of the hydraulic dynamometer and hydraulic cylinder, and in an axial plane of the other cylinder; Fig. 12 is a sectional view of still another embodiment of the hydraulic unit having a centrally situated hydraulic dynamometer and two peripherally disposed hydraulic cylinders, taken in a plane of the axes of the hydraulic dynamometer and hydraulic cylinders; Fig. 13 illustrates a roll mill stand as looked at from the operator's side, showing the device for controlling the thickness of strip stock being rolled between rolls, wherein a reversing spool valve is provided, shown in a longitudinal-section view;; Fig. 14 is a scaled-up view of the reversing spool valve of Fig. 13; Fig. 15 illustrates a roll mill stand as viewed from the operator's side, showing the device for controlling the thickness of strip stock being rolled between rolls, according to the invention featuring the chamber of the hydraulic dynamometer integrated with the piston-end space of the double-space hydraulic cylinder, and having a hydraulically piloted reversing spool valve; Fig. 16 is a scaled-up view of a valve for power fluid pressure control in the hydraulic cylinder interior as seen in Fig. 15; and Fig. 17 is a scaled-up view of the reversing spool valve of Fig. 15.

The herein-proposed method of controlling the thickness of the strip stock being rolled is illustrated by a diagram of Fig. 1, wherein a roll mill stand 1 has a housing 2 the side recesses of which accommodate work rolls 3 and 4 adapted to rotate in chocks 5 and 6, strip stock deformation occurring between said work rolls.

The work rolls 3 and 4 are adapted to interact with backup rolls 7 and 8 which rest, through chocks 9 and 10 and a screwdown arrangement 11, upon the housing 2. To counterbalance the top work roll 3 and the top backup roll 7 with the respective chocks 5 and 9, hydraulic cylinders 12 and 13 are provided. A hydraulic dynamometer 14 is interposed between the screwdown arrangement 11 and the chock 9, adapted to take up the force P of rolling. A hydraulic cylinder 15 with a movable barrel 16 is provided for traversing the chocks 10 of the bottom backup roll 8. Provided between the movable barrel 16 and the housing 2 are springs A which develop the force Q preventing the rolls 3 and 4 between which the strip stock is deformed, from being brought together.

Situated between the hydraulic dynamometer 14 and the hydraulic cylinder 15 is a valve 17 adapted to control the pressure of power fluid fed from a pumping unit 18 to the hydraulic cylinder 15, in proportion to the force P of rolling.

When controlling the thickness h1 of the strip stock being rolled according to the method proposed herein, the force P of rolling is taken up by the fluid (oil) held in the chamber "a" of the hydraulic dynamometer 14 provided between the chock 9 of the top backup roll 7 and the screwdown arrangement 11.

The force R which causes the chock 10 of the bottom (movable) roll 8 to traverse, is set up by the hydraulic cylinder 15 whose interior space "b" is communicated with a pumping unit 18 which force-feeds the fluid. To satisfy the equation R=k2P, the delivery pressure of the pumping unit 18 and hence the fluid pressure effective in the interior of the hydraulic cylinder 15, is regulated in proportion to the force P of rolling by virtue of the valve 17. To this end the control chamber "d" of the valve 17 is communicated with the chamber "a" of the hydraulic dynamometer 14, and the throttle chamber "e" of that valve is communicated with the interior space "b" of the hydraulic cylinder 15 and with the pumping unit 18.

When strip stock is being rolled the fluid pressure q is built up in the control chamber "d" of the valve 17, equal to P q= (6) 2.Fa where F denotes the area of the piston of the hydraulic dynamometer 14.

Tíe pressure q actuates the sliding spool of the valve 17 so that the fluid pressure q2 is developed in the throttle chamber "e" thereof, equal to q2=q . k3; (7) where k3 stands for the boost pressure ratio of the valve 17.

As a result, the hydraulic cylinder 15 develops a force equal to R=2 . Fb q2 (8) where Fb means the area of the hydraulic cylinder piston-end space.

Substituting the values of the pressures q and q2 as taken from expressions (6) and (7), to equation (8), one can find the relationship between the forces R and P.

Fb R=k3. . --- . P=k2. P (9) Fa According to the herein-proposed method the parameters of the hydraulic dynamometer 14, the hydraulic cylinder 15 and the valve 17 are so selected as to obey the following expression Fb k2=k3. > 1 (10) Fa the force R being in excess of the force P of rolling by the value (k2- 1). P. As a result, when the force P of rolling is increased by aP the force R overcomes the force P and brings together the chocks 5 and 6 of the rolls 3 and 4, thus compensating for elastic deformation of the roll mill stand 1 accounted for by the variation of the force of rolling by AP > 0. When the force P of rolling decreases by the value aP > 0 the regulation process proceeds in a similar way but in the opposite direction.

The overall force Q preventing the supports of the rolls 3 and 4 from being brought together is established by, say, a set of springs A arranged between the movable barrel 16 of the hydraulic cylinder and the roll housing 2, due to compression of said springs resulting from the traversing of the movable hydraulic cylinder barrel 16 over a length expressed by the value ash2.

With the rate of the springs A equal to k, the force Q of the compression of the springs varies in response to traverse of the chocks 10 of the rolls 8 over a length 8h2 to obey the following relation Q=k1. Ah2 (11) With a view to ruling out any effect of elastic strain of the roll- mill stand 1 upon the strip stock thickness h1, the factor k2 is to be equal to k, k2= +1 (12) k While determining the force Q of deformation of the springs A proceeding from a static equilibrium of the movable barrel 16 of the hydraulic cylinder 15 with no account of losses for friction in the movable components thereof according to the relation Q=R-P=(k2-l).P (13) one can find the length of traverse of the chocks 10 of the movable roll 8 using the following expression R-P P ash2= =-=(3h1 (14) (k2-k1).k k Thus, according to the method proposed herein the chocks 10 always traverse, in the course of thickness control process, a length equal to the magnitude of deformation Ah, of the roll mill stand 1. Thereby the strip thickness h, remains unaffected at any fluctuations of the force P of rolling.

The essential object of the invention, i.e. increased accuracy of strip stock thickness control in the course of its deformation due to the provision of a simpler and cheaper device, is accomplished as follows.

Any variations of the force P of deformation as a result of, say, changed physico-chemical characteristics of the strip stock being rolled and, hence, a change of the force R=k2P developed by the hydraulic cylinder 15, causes the chocks 10 of the bottom backup roll 8 to traverse. This traversing occurs concurrently with the deformation of the roll mill stand 1, the values of both being equal to each other. It is due to this fact that the strip stock thickness h, remains invariable, i.e., the thickness variation value 5h equals zero throughout the strip length.

Given hereinbelow are some exemplary embodiments of the proposed method. Inasmuch as the device comprises two portions made to the same pattern, only one portion of the device is considered in the present disclosure and illustrated in the accompanying drawings. One side of the roll mill stand 1 incorporates, as has been mentioned hereinbefore, the roll housing 2 (Fig. 2) whose side recesses accommodate the work rolls 3 and 4 rotating in the chocks 5 and 6, and adapted to deform the strip stock therebetween. The work rolls 3 and 4 interact with the backup rolls 7 and 8 which rest upon the roll housing 2 through the chocks 9 and 10 and the screwdown arrangement 11. To balance the top work roll 3 and the top backup roll 7 with the chocks 5 and 9 the hydraulic cylinders 12 and 13 are provided.

The device for controlling the thickness of the strip stock being rolled shown in Figure 2 consists of a number of units.

Pertaining to the above units are: the hydraulic dynamometers 14 having the chamber "a" filled with a fluid to take up the force P of rolling, for which purpose it is interposed between the pressure screw 11 and the chock 9 of the backup roll 7 (Fig. 2); the double-space hydraulic cylinder 15 located on the roll housing 2 under the chock 10 of the backup roll 8, said cylinder having the piston-end space "b" for setting up the force R for traversing the chock 10 along with the rolls 4 and 8 and an enclosed piston-rod space "c" filled with the fluid adapted for developing the force Q preventing the movable barrel 16 of the hydraulic cylinder 15 from traversing.

Provided between the hydraulic dynamometer 14 and the hydraulic cylinder 15 is the valve 17 for regulating the pressure (flow-rate) of the fluid fed from the pumping unit 18 powered by a motor 19, to the piston-end space "b" of the doublespace hydraulic cylinder 15; said valve 17 having control chamber "d", throttle chamber "e" and drainback chamber "f'.

The device comprises also volumetric oil regulators 20 and 21 whose chambers "g" and "i" are communicated respectively to the piston-end space "b" and the piston-rod space "c" of the hydraulic cylinder 15, adapted for bringing the stiffness factor k1 of the members of the device (which are hereinafter more precisely defined) into correspondence with the stiffness factor k of the roll mill stand.

Provision is made in the hydraulic pipings of the device for check valves 22 and 23, stop valves 24 and 25 for air or oil to escape into a tank 26, a valve 27 (one for both sides of the roll mill stand 1) for restricting the minimum pressure developed by the pumping unit 18, and a pressure relief valve 28 to restrict the maximum pressure developed by the pumping unit 18. Common to the both sides of the roll mill stand 1 are an oil tank 26, a pumping unit 29 with a motor 30 and a valve 31 for keeping constant preliminary pressure in the spaces "c" of the hydraulic cylinders 15.

The hydraulic dynamometer 14 (Fig. 3) has a casing 32 with a piston 33 and a cover 34 held by screws 35 to the casing 32. The casing 32 and the piston 33 establish a chamber "a" communicated with a port "a1" provided in the casing 32.

Hermetic tightness of the chamber "a" is carried out by seals (not shown). The hydraulic dynamometer 14 (Fig. 2) provided between the screwdown arrangement 11 and the chock 9, is adapted to interact with the screwdown arrangement 11 through its piston 33, and with the chock 9 of the top backup roll 7, through its casing 32.

The hydraulic cylinder 15 (Fig. 4) has a barrel 16, a piston 36 and a cover 37 held to the barrel 16 by screws 38. The piston 36 and the barrel 16 define the pistonend space "b"; whereas the piston 36, the barrel 16, the cover 37 and a rod 39 of the piston 36 form the piston-rod space "c". The spaces "b" and "c" are communicated with ports "b," and "C1", respectively. The spaces "b" and "c" are hermetically closed by virtue of seals (not shown). The hydraulic cylinder 15 (Fig.

2) is mounted under the chock 10 of the bottom backup roll 8 so as to interact with the chock 10 of the bottom backup roll 8 through its barrel 16, and with the roll housing 2 through the piston 36.

The valve 17 (Fig. 5) has a chest 40 with a sliding spool 41 and a cover 42 held to the chest 40 by screws 43. The sliding spool 41 forms the control chamber "d", along with the chest 40, the throttling gap "y" and the throttle chamber "e", along with the cover 42, and the drainback chamber "f', along with the chest 40 and the cover 42. Said chambers d, e, fare communicated respectively with ports dl, e1, and f1, and are hermetically closed by seals (not shown).

The volumetric oil regulators 20 and 21 (Fig. 6) are similar in construction, each having a chest 44 accommodating a piston 45 with a screw rod 46, and a cover 47 held to the chest 44 by screws 48. The piston 45 and the chest 44 define a chamber "g" communicated with the port "g1,, and hermetically closed by virtue of seals not shown).

All the remaining units of the device, viz., the valves 27 (Fig. 2) and 31, the stop valves 24 and 25, the check valves 22 and 23, the pressure relief valve 28, the pumping units 29 and 18 with the motors 30 and 19, and the tank 26 are commonly adopted in industrial practice. Therefore they are beyond the scope of the present disclosure to describe in detail.

Hydraulic communication of all the units based on the roll mill stand 1 of the herein-proposed device is effected as follows.

The chamber "a" of the hydraulic dynamometer 14 (Fig. 2) is communicated through hydraulic piping 49 with the control chamber "d" of the valve 17. For being filled with oil said chambers "a" and "d" communicate through hydraulic piping 50 and the check valve 22 with the chamber "f' of the valve 17. When the device is being operated said chambers "a" and "d" establish an enclosed space, wherein oil pressure is proportionate to the force P of rolling. Said pressure is applied to the sliding spool 41 of the valve 17 from the side of the chamber "d".

The piston-end space "b" of the hydraulic cylinder 15 is communicated simultaneously with the pumping unit 18 and with the chamber "e" of the valve 17 through respective hydraulic pipings 51 and 52. Pressure in said space and said chamber is built up by virtue of a hydraulic resistance to the flow of oil from the chamber "e" through the gap "y" to the drainback chamber "f' of the valve 17.

Said pressure actuates the sliding spool 41 from the side of the chamber "e" to balance the pressure applied to the sliding spool 41 from the side of the chamber "d". To change the stiffness factor of the double-space hydraulic cylinder 15 and, consequently, the stiffness factor "k" of the roll mill stand 1, the piston-end space "b" of said cylinder is communicated, through hydraulic pipings 51 and 53, with the chamber "g" of the volumetric oil regulator 20.

The piston-rod space "c" of the double-space hydraulic cylinder 15 is communicated, through hydraulic piping 54, with the chamber "i" of the volumetric oil regulator 21. For being filled with oil said space and said chamber are communicated, through hydraulic piping 55 and the check valve 23, with the pumping unit 29. When the device is operative, said space "c" and said chamber "i" define an enclosed space, wherein the oil pressure is proportionate to the length of traverse of the barrel 16 of the double-space hydraulic cylinder 15.

The components of the double-space hydraulic cylinder 15, the volumetric oil regulator 21 and the hydraulic piping 54 constitute an enclosed space which, with the oil contained therein, establish a group of elastic members of the device during its operation and control the stiffness factor k1.

The drainback chamber "f' of the valve 17 is communicated, via hydraulic pipings 56 and 57, with the tank 26. To build up a constant initial pressure q1 in an enclosed space defined by the chambers "a" and "d", the valve 27 is provided in the oil return line in between hydraulic pipings 56 and 57.

The device is adjusted in the following way.

An initial pressure is built up in the units of the device by switching on the motors 30 and 19 actuating the pumping units 29 and 18. Oil is gravity-fed to the pumping unit 29 from the oil tank 26 along a hydraulic piping 58, is delivered along the hydraulic piping 55 through the check valve 23 at a pressure q0 into the enclosed space formed by the space "c" and the chamber "i", the pressure q0 being set up by the valve 31 and kept thereby always constant. The surplus oil is drained back through the valve 31 and is returned along hydraulic piping 59 to the oil tank 26. Whenever necessary, air or oil from said spaces, chambers and hydraulic pipings is caused to escape to the tank 26 along the hydraulic piping (not shown) upon opening the stop valve 24.

Oil gravity-fed from the tank 26 to the pumping unit 18 along piping 60, is delivered along the hydraulic pipings 52 and 51 to the piston-end space "b" of the double-space hydraulic cylinder 15, and to the throttle chamber "e" of the valve 17. It then flows through the gap "y" between the sliding spool 41 and the cover 42 to the drainback chamber "f' and from there oil passes along the hydraulic pipings 56, 50 and through the check valve 22 to an enclosed space formed by the chambers "a" and "d" and the hydraulic piping 49. The surplus oil is drained back through the valve 27 to return along the piping 57 to the tank 26. Air and oil from said chambers, spaces and hydraulic pipings is vented, whenever necessary, to the tank 26 along hydraulic piping (not shown) upon opening the stop valve 25.

The pressure relief valve 28 is adjusted to the maximum permissible pressure developed by the pumping unit 18.

The pressure value q1 is set up by the valve 27 and is estimated so as to fix the piston 33 of the hydraulic dynamometer 14 and the piston 36 of the double-space hydraulic cylinder 15 in the initial position (i.e., before starting the rolling process).

In this connection the pressure value q1 must satisfy the following inequality Fc N0 q0 > q1 > (15) Fb 2.Fa where No is the force with which the top backup roll 7 and the top work roll 3 are forced against the hydraulic dynamometer 14 by the hydraulic cylinders 12 and 13; Fa is the area of the piston 33 of the hydraulic dynamometer 14; Fb is the area of the piston 36 of the hydraulic cylinder 15 on the side of the space "b"; Fc is the area of the piston 36 of the hydraulic cylinder 15 on the side of the space "c".

The pressure value q0 corresponds to the lower limit of the force of rolling, upon reaching of which the device starts controlling the strip stock thickness.

By changing appropriately the position of the piston 45 (Fig. 6) with respect to the chest 44 oft evolumetric oil regulator 20 one can set up the required stiffness factor k of the roll mill stand 1 (Fig. 2) which is a function of the elastic behaviour of the roll mill stand 1 and of other units of the device, viz., the hydraulic dynamometer 14 along with the oil contained in the chambers "a" and "d" and in the hydraulic piping 49, the hydraulic cylinder 15 complete with the oil contained in the spaces "b", "g" and "e" and in the pipings 51, 52 and 53.

Then the stiffness factor k1 of the group of elastic members of the device is set up by virtue of the volumetric oil regulator 21, said group incorporating the components of the hydraulic cylinder 15 and of the volumetric oil regulator 21, as well as the hydraulic piping 54 which constitute an oil-filled enclosed space.The stiffness factor k1 is brought into correspondence with the stiffness factor k of the roll mill stand according to the following equation k1=k.(k2-l) (16) where k2 is the factor of proportionality between the variation of the force P of rolling and the force R of the hydraulic cylinder 15 as results from the thickness control equation AP AR-AP #h = - = 0 (17) k k1 As a result of the effect made by the initial pressure in the units of the device, the piston 33 (Fig. 3) of the hydraulic dynamometer 14 is forced against the cover 34 by virtue of the difference between the force produced by the pressure q2 in the chamber "a" of the hydraulic dynamometer 14, and the force No of pressing of the chock 9 (Fig. 2) against the hydraulic dynamometer 14 by the hydraulic cylinders 12 and 13.The piston 36 of the double-space hydraulic cylinder 15 is forced against the bottom of the barrel 16 by virtue of the force Qo+G-R1 where Q,=2q,.F, (18) R1=2q1.F (19) G is the total weight of the rolls complete with the chocks, account being taken of the thrust developed by the hydraulic cylinders 12 and 13.

Thus, the bottom rolls 4 and 8 which rest upon the hydraulic cylinder 15 through the chock 10, and the top rolls 3 and 7 resting on the hydraulic dynamometer 14 through the chock 9, are fixed in the initial position.

Then the initial gap h0 is set between the work rolls 3 and 4 using the screwdown arrangement 11.

The amount of said gap is to be taken from the following equation: 2q0.F-G ho=h - (20) k where h is the preset outgoing thickness of the finished strip stock.

The device operates as follows.

When the strip stock enters the work rolls 3 and 4 (Fig. 2), a force P of rolling arises in the roll mill stand 1.

The components of the roll mill stand 1, including the hydraulic dynamometer 14 and the hydraulic cylinder 15, acted upon by said force, undergo elastic strain, thus changing the gap between the rolls 3 and 4.

The incremental value Aho of the gap between the rolls 3 and 4 due to deformation of the roll mill stand 1 depends upon the value of the initial pressure of of oil contained in the space formed by the chambers "c" and "i", and is equal to the deformation of the roll mill stand 1 caused by the force P of rolling which corresponds to the pressure q0 of oil effective in the hydraulic dynamometer 14 q0 . 2FaG AhQ= - - (21) k Further increment of the value Ah1 of deformation of the roll mill stand which may be due to variation AP of the pressure P exerted by the metal upon the roll with respect to the value 2qO.FaG is compensated for by a corresponding traversing of the chocks 10 of the roll 8, said traversing being hereinafter referred to as the traversing of the barrel 16 of the hydraulic cylinder 15.

Thus, the thickness of the strip stock leaving the roll mill stand I is equal to 2to . FaG h,=ho+ (22) k (22) As soon as-the oil pressure in the chamber "a" of the hydraulic dynamometer 14 and in the control chamber "d" of the valve 17 rises, the check valve 22 is closed to form an enclosed space made up by the chamber "a" of the hydraulic dynamometer 14 and the control chamber "d" of the valve 17, 'wherein the pressure q of oil is effective, proportionate to the force P of rolling, i.e.

P No + (23) 2Fa 2Fa As a result of action of said pressure in the control chamber "d" of the valve 17, the state of balance of the sliding spool 41 (Fig. 5) thereof is upset, and the latter is displaced towards the cover 42, thus reducing the gap "y" between the sliding spool 41 and the cover 42, with the result that the resistance to the oil flow passing from the throttle chamber "e" through the gap "y" to the drainback chamber "f' is increased, and thence the pressure developed by the pumping unit 18 (Fig. 2) rises accordingly.

Once the pressure developed by the pumping unit 18 exceeds the value q2, the force R=2q2. Fb arises in the piston-end space "b" of the double-space hydraulic cylinder 15, which actuates the piston 36 and the barrel 16. Part of said force (q . 2Fa) provides for the force P of rolling and balances the weight G of the rolls and chocks, whereas the difference between forces (R-P-G) is applied to the group of- elastic members of the device.

As soon as the force R gets in excess of the force P of rolling and the force Q0 created by the oil pressure q0 effective in the piston-rod space "c" of the hydraulic cylinder 15, the barrel 16 starts travelling with respect to the piston 36. This, in turn, reduces the volume of the piston-rod space "c", whereby the oil contained therein is compressed and, hence, the oil pressure in the piston-rod space "c" of the hydraulic cylinder 15 and in the chamber "i" of the volumetric oil regulator 21 is raised. As a result, the check valve 23 is closed to form an enclosed space made up by the piston-rod space "c" of the hydraulic cylinder 15 and the chamber "i" of the volumetric oil regulator 21.

Thus, the barrel 16 of the hydraulic cylinder 15 traverses along with the chock 10 of the bottom backup roll 8 for a length corresponding to the value of the oil compression effective in said enclosed space. Said traverse is due to a change of the oil pressure in the piston-end space "b" and, hence, due to a change in the pressure developed by the pumping unit 18.

A pressure raise of the pumping unit 18 when controlling the ?thickness of the strip stock being rolled is accounted for by two reasons: firstly, inadequacy of the pressure developed by the pumping unit 18 and the pressure in the enclosed space made up by the chambers "a" and "d"; secondly, a resistance offered to the force P of rolling and to the force Q of oil compression in the enclosed space made up by the chambers "c" and "i", which prevents the piston from traversing under the effect of the force R proportionate to the pressure of the pumping unit 18.

That is why the barrel 16 travels with respect to the piston 36 until the sliding spool 41 is balanced by the oil pressure effective in the control chamber "d" and the throttle chamber "e" of the valve 17, and until the barrel 16 of the hydraulic cylinder 15 is balanced from one side by the force R and from other side, by the force P of rolling and by the force Q of oil compression effective in the enclosed space made up by the chambers "c" and "i".In this case, the length of traverse of the barrel 16 from its initial position (before the rolling process), resulting from its balanced state at the stiffness factor kl of the enclosed space made up by the chambers "c" and "i", is equal to R-P-Q6G Sh2= (24) k 1 Substituting the value Q0 to equation (24), whose magnitude is found proceeding from the balanced state of the barrel 16 of the hydraulic cylinder 15 at the moment of application of the force of rolling, at which p0=2q0. FaG and the force RO=2qO .Fb Q0=R0-P0-G (25) one can find the amount of traverse of the barrel 16 of the hydraulic cylinder 15 as the function of the increment values aR and aP aR-aP ash2= k (26) 1 In this case the aggregate change of the roll gap and hence the change of the strip stock thickness with due account of the traverse S h2 can be described by equation (17) AP aR-aP Sh= - =0 (17) k k1 whereas the thickness h, of the strip stock leaving the roll mill stand 1 is expressed by the following equation 2to .FaG AP aR-aP ha=ho+ + - (27) k k k, When realizing relation (16) between the factors k and k1 the right-hand member of equation (17) equals zero. Hence any change of the gap ah between the rolls 3 and 4 and of the thickness h, of the strip stock due to deformation of the roll mill stand 1 is ruled out.

As a result operation of the device according to thickness control equation (17), absolutely stiff mechanical characteristics of the system "stand-device" is attained at soh=0, whereby the effect of the elastic deformation if the roll mill stand upon the strip thickness in response to a change in the force of rolling within the interval P > 2qO. FaG (28) is completely eliminated.

With the sliding spool 41 of the valve 17 in the balanced state oil delivered by the pumping unit 18 flows from the throttle chamber "e" through the gap "y" (Fig.

5) to the drainback chamber "f' and further on through the valve 27 to the tank 26 (Fig. 2).

Upon discharging the strip stock from the mill stand rolls oil pressure effective in the enclosed space made up by the chambers "a" and "d" drops to the initial value q,. The same pressure is developed by the pumping unit 18.

As a result, the piston 36 of the hydraulic dynamometer 14 and the barrel 16 of the double-space hydraulic cylinder return to the initial position, and the pressure in the enclosed space made up by the chambers "c" and "i" gets equal to zero as well.

Thus, the device is ready for the next operating cycle.

In order to add to the stiffness of the elastic members of the device, a spring 61 (Fig. 4) is provided in the enclosed piston-rod space "c" of the hydraulic cylinder 15, said spring resting with its ends upon the piston 36 and the cover 37 to establish, along with the pressure fluid and the components constituting the enclosed pistonrod space "c", the elastic members of the device.

Provision of said spring 61 in the piston-rod space "c" of the hydraulic cylinder 15 is instrumental in proper matching of a required value ol the stiffness factor k, of the elastic members of the device. As to all the rest of the operating particulars these remain just the same as described above.

An embodiment of the device for controlling the thickness of the strip stock being rolled, as illustrated in Figs. 7 and 8, differs from the device shown in Figs. 2 to 6 in that the valve 17a (Fig. 7) thereof is provided with an additional control chamber "1" which is communicated through hydraulic pipings 62 and 54 with the enclosed space formed by the chambers "c" and "i".

The remaining units of the device, such as the hydraulic dynamometer 14, the double-space hydraulic cylinder 15, the pumping units 18 and 29 with the motors 19 and 30, the volumetric oil regulators 20 and 21, the valves 27 and 31, the pressure relief valve 28, the check valves 22 and 23, the stop valves 24 and 25, the oil tank 26, as well as the hydraulic pipings 49 through 60 perform the same functions as in the embodiment disclosed hereinbefore and have the identical reference numerals.

As to the modified valve 17a, its chambers and ports which perform the similar functions as in the device of Figs. 2 and 5 of the embodiment considered hereinbefore, have the same reference numerals, while its components are indicated at the same numerals followed by letter indexes.

The valve 17a (Fig. 8) comprises a chest 40a, a stepped sliding spool 41a having a step 63, and a cover 42a held to the chest 40a by screws 43a.

The sliding spool 41a along with the chest 40a establishes the main control chamber "d" communicated with the port d1, with its step 63 along with the cover 42a, the control chamber "1" communicated with the port 1" and the throttle chamber "e" communicated with the port "e,", while along with the chest 40a and the cover 42a said sliding spool forms the drainback chamber f communicated with the port f,. The sliding spool 41a and the cover 42a define the throttling gap "y".

All the aforesaid chambers are hermetically closed by virtue of seals (not shown).

Hydraulic communication between the chambers "d", "e" and "f' with the other units of the device is effected in the same way as in the embodiment described hereinabove. The control chamber "1" of the valve 17a is communicated, through the hydraulic pipings 62 and 54 (Fig. 7) with the enclosed space made up by the chambers "c" and "i".Such a communication enables one to control the pressure and flow-rate of the oil in the piston-end space "b" of the double-space hydraulic cylinder 15 in additional proportion to the stress applied to the group of elastic members of the device, constituted by the piston-rod space "c" of the double-space hydraulic cylinder 15, the chamber "i" of the volumetric oil regulator 21 and the control chamber "1" of the valve 17a, whereby the speed of response of the device according to said embodiment, is higher as compared to the device according to the embodiment disclosed hereinbefore.

Indeed, the amount aV of oil fed to the piston-end space "b" of the hydraulic cylinder 15 according to the first embodiment of the present invention, is equal to aV=k4. AP (29) where k4 is the factor of proportionality between the change in the force of rolling and the amount of oil fed to the piston-end space "b" of the hydraulic cylinder 15.

Let us find the relationship between the parameters aV and AP holding true of the device made to the second embodiment of the present invention.

Taking into account the sluggishness of the device in response to a change in the force of rolling by the value AP, the barrel 16 of the hydraulic cylinder 15 is sunk due to the deformation ah3 of the oil contained in the piston-end space "b", by the value equal to AP #h3= (30) k5+k, where k5 is the stiffness factor of the oil contained in the piston-end space "b" of the hydraulic cylinder 15 and in the hydraulic pipings 51 through 53, as well as in the chambers "g" and "e".

In this case the variation of the stress value of the group of elastic members of the device obey the following equation aQ=Sh3. k, (31) Substituting expression (30) to equation (31) one can find the relationship between the value AQ of variation of the stress applied to the group of elastic members of the device and the value AP of change in the force of rolling AP AQ= (32) k5 1+ k, Taking account of expression (32) the resultant signal controlling the oil flow-rate is equal to aP+aQ=aP . (1+ ) (33) k5 1+ k, The amount of oil fed to the hydraulic cylinder 15 in response to a change of the force P of rolling by the value hP, equals to 1 AV=k4 - hP(I + ) (34) k5 1+ k1 While comparing expressions (29) and (34) one can easily be sure that the amount AV1 of the oil fed to the hydraulic cylinder space in response to a change in the force P of rolling by the value nP, according to the second embodiment of the invention is greater than that according to the first embodiment thereof by the value 1 EV2=k4. .AP. (35) k5 + k1 and hence the control time is shorter.

It is easy to evidence that the accuracy of control in the second embodiment is higher than in the first one.

If, according to device of the first embodiment of the invention the force F1 of friction arising between the movable components of the hydraulic cylinder 15.

affects the length of traverse thereof, one can record that the elastic members of the device take up the force equal to aQ=hRaP+F1 (36) while the length of said traverse itself equals AQ AR-APiF1 ah2 = (37) k1 k1 the inaccuracy of traversing of the barrel 16 of the hydraulic cylinder 15, according to the first embodiment, equals to F1 + k1 According to the second embodiment of the invention the amount of oil fed to the hydraulic cylinder 15 is proportionate to the value aP by which the force P of rolling is changed and to the value AQ by which the force Q of deformation is varied, obeying the equation AP AQ --- - ah (38) k k, Once the equation aP AQ k k, has been satisfied, oil feed to the hydraulic cylinder 15 ceases.

In this case the length of traverse ofthe barrel 16 of the hydraulic cylinder 15 is equal to AQ AP ash2= = (39) k, k being independent of the forces of friction in the movable components of the hydraulic cylinder 15.

The device is adjusted before the strip stock rolling process and put into operation upon entering the strip into the roll mill stand 1 in a way similar to that described with reference to the first embodiment of the invention.

Now let us consider the operation of the device during the rolling process in the case where the thickness of the strip stock at the entrance to the rolls of the mill stand 1 increases.

With a larger thickness of the strip stock being rolled, the force P of rolling increases by the value AP and hence the pressure q of the oil in the enclosed space made up by the chambers "a" and "d" is increased by the value aq, while the pressure in the enclosed space made up by the chambers "c", "i" and "I" falls. As a result, the balanced state of the sliding spool 41a (Fig. 8) is upset and the latter is made to displace, thus reducing the gap "y" between itself and the cover 42a, with the resultant increase in resistance to the oil flow from the pumping unit 18 (Fig. 7) and, consequently, a higher pressure q2 of said pumping unit by the value Aq2.As a result of pressure increment by the value Aq2, an additional force is developed in the piston-end space "b" of the hydraulic cylinder 15 equal to aR=2 aq2 Fb, part of said pressure offering resistance to the increment aP of the force P of rolling, whereas the difference between the force R created by the hydraulic cylinder 15 under the effect of oil pressure effective in the piston-end space "b" and by the force of rolling P, compresses the oil contained in an enclosed space made up by the chambers "c", "i" and "1". Thus, the barrel 16 of the hydraulic cylinder 15 traverses along with the chock 10 of the bottom backup roll 8 for a length corresponding to the magnitude of compression of the oil in said enclosed space.

Traversing of the barrel 16 with respect to the piston 36 (Fig. 4) of the hydraulic cylinder 15 occurs due to a change in the oil pressure effective in the piston-end space "b" and hence due to a change in the pressure produced by the pumping unit 18.

The pressure of the pumping unit 18 changes until the sliding spool 41a (Fig. 8) of the valve 17a gets balanced by the oil pressure effective in the enclosed spaces made up by the chambers "a", "d" and "c", "i", "I", and due to the pressure of the Pumping unit 18 (Fig. 7), and until the barrel 16 of the double-space cylinder 15 gets balanced by the force R provided by the hydraulic cylinder 15 under the effect of the pressure in the piston-end space "b" established by the pumping unit 18, by the force Q of oil compression in the enclosed space made up by the chambers "c", "i" and "1", and by the force P of rolling.

The amount of traverse of the roll till balancing the sliding spool 41 a (Fig. 8) of the valve 17a and the barrel 16 (Fig. 7) of the hydraulic cylinder 15, is equal to AQ #h2= (37) k1 where AQ is the value of variation of compression force of the enclosed space made up by the chambers "c", "i", "1".

In this case a total change of the gap between the rolls 3 and 4 and, hence, of the strip thickness with account of the traverse of the chocks 10 of the bottom roll 8 for a length #h2, is equal to aP AQ ah", - ---- (38) k k1 while the thickness of the strip leaving the roll mill stand 1 is expressed by the following equation 2qO. FaG aP aQ h1=h0 + + - (27) k k k1 When realizing relation (16) the right-hand member of equation (38) equals zero.Hence, any variation of the gap between the rolls 3 and 4 and of the outgoing strip thickness h1 due to deformation of the roll mill stand 1 is ruled out.

With the sliding spool 41a (Fig. 8) of the valve 17a and the barrel 16 (Fig. 7) of the hydraulic cylinder 15 being in the balanced state, as well as upon discharging the strip stock from the rolls 3 and 4 of the roll mill stand 1, the device operates in a similar way as in the first embodiment of the invention.

It is advantageous that the hydraulic dynamometer 14 and the hydraulic cylinder 15 be fashioned as a compact hydraulic unit 64 (Fig. 9).

Fig. 9 illustrates the bottom portion of the recess of the roll mill stand 2, showing the hydraulic unit 64 situated between the chock 10 of the bottom backup roll 8 and the roll mill stand 2.

The components of the hydraulic dynamometer 14 (Fig. 3), i.e., the piston 33, the cover 34 and the screws 35, and those of the hydraulic cylinder 15 (Fig. 4), i.e.

the piston 36 with the rod 39, the cover 37 and the screws 38, form part of the constructional arrangement of the hydraulic unit 64 (Fig. 9). Their respective chambers "a", "b" and "c" perform similar functions and are indicated by the same reference numerals as in Figs. 3 and 4.

The hydraulic unit 64 has a casing 65 and a piston 33, to form a hydraulic dynamometer 14 having a chamber "a" communicating with a port "a," and filled with oil. Cover 34 is held to the casing 65 by screws 35. Piston 36 and cover 37 are held to casing 65 by screws 38. Piston 36 and its rod 39 establish, along with casing 65 and cover 37, double-space hydraulic cylinder 15 which has a piston-end space "b" and a piston-rod space "c" in communication with ports "b," and "c,", respectively.

The hydraulic unit 64 is adapted to interact, through the piston 33 of the hydraulic dynamometer, with the chock 10 of the bottom backup roll 8, and through the rod 39 of the piston 36 of the double-space hydraulic cylinder 15, to interact with the mill separator of the roll housing 2.

To reduce overall height, the hydraulic unit 64 may have a plurality of the hydraulic dynamometers 14 and double-space hydraulic cylinders 15.

Fig. 10 illustrates an embodiment of the hydraulic unit provided with three hydrauicdynamometers 14 and three hydraulic cylinders 15. It is quite possible that the number of the hydraulic dynamometers 14 and the hydraulic cylinders 15 in the device may also be more or less than three.

The hydraulic unit components illustrated in Fig. 10 are indicated by the same reference numerals as in Fig. 9 but followed by letter suffixes.

The hydraulic panel 64a (Fig. 10) has three pistons 33a which forms, along with the casing 66, the hydraulic dynamometer 14 which has chambers "a" in communication with one another and with the port "at" provided in the casing 66.

Cover 34a is held to casing 66 by screws 35a. The cover 37a is held to casing 66 by screws 38a. The three pistons 36a and the rods 39a thereof form, along with the casing 66 and the cover 37a, the double-space hydraulic cylinders 15 which has piston-end spaces "b" and piston-rod spaces "c". The like spaces of the doublespace hydraulic cylinders 15 are in communication with each other and with the respective ports "b," and "c," in the casing 66.

The hydraulic unit 64a provided according to said embodiment of the invention, is adapted to interact, through all the pistons 33a of the hydraulic dynamometers 14, with the chock 10 of the bottom backup roll 8; and to interact through all the rods 39a of the pistons 36a of the double-space hydraulic cylinders 15 with the mill separator of the roll stand 2.

In both of the embodiments of the hydraulic unit, the axes of the hydraulic dynamometers 14 coincide with the axes of the hydraulic cylinders 15.

Fig. I I shows a further embodiment of the hydraulic unit having one hydraulic dynamometer 14 and two hydraulic cylinders 15. The axis of the hydraulic dynamometer 14 coincides with the axis of either of the hydraulic cylinders 15.

Such a constructional arrangement of the hydraulic unit is simpler than the abovedescribed ones.

The hydraulic unit 64b has a casing 67 with a footstep 68. Piston 33b forms, along with the casing 67, the hydraulic dynamometer 14 which has the chamber "a" in communication with the port "at". Cover 34b is held to casing 67 by screws 35b, and cover 37b is held to casing 67 by screws 38b. The two pistons 36b and their rods 39b form, along with the casing 67 and the cover 37b, the hydraulic cylinders 15 which each have a piston-end space "b" and piston-rod space "c". The like spaces of the hydraulic cylinders 15 communicate with each other and with the respective ports "b," and "c,".

The hydraulic unit 64b is adapted to interact, through the piston 33b of the hydraulic dynamometer 14 and the footstep 68 of the casing 67, with the chock 10 of the backup roll 8; and to interact through rods 39b of pistons 36b of the hydraulic cylinders 15 with the bottom mill separator of the roll housing 2.

During the rolling process the hydraulic dynamometer 14 takes up the force proportionate to the force P of rolling, in a way similar to the embodiments described above. Such an embodiment of the hydraulic unit makes it possible to simplify the construction of the device.

The hydraulic unit may have one hydraulic dynamometer 14 and a plurality of the hydraulic cylinders 15 spaced apart round the hydraulic dynamometer 14. Such an embodiment enables it to be located between the pressure screw 11 (Fig. 2) and the chock 9 of the top backup roll 7.

Fig. 12 shows an embodiment of the hydraulic unit 64c having one hydraulic dynamometer 14 and two hydraulic cylinders 15.

Said hydraulic unit 64c has a casing 69 and a piston 33c establishing the hydraulic dynamometer 14 which has a chamber "a" communicating with a port "at". Cover 34c is held to casing 69 by screws 35c and covers 37c are held to the casing 69 by the screws 38c. The two pistons 36c and rods 39c form, along with the casings 69 and covers 37c the double-space hydraulic cylinders 15 which have piston-end space "b" and piston-rod space "c". The like spaces of the hydraulic cylinders 15 communicate with each other and with the respective ports "b," and c1 The hydraulic unit 64c interacts with pressure screw 11 through the piston 33c, and interacts with the chock 9 of the top backup roll 7 through the rods 39c of the pistons 36c.

The chamber "a" and the spaces "b" and "c" of the hydraulic units illustrated in Figs. 9 through 12, are hermetically closed by virtue of seals (not shown).

Hydraulic communication of said chamber and said spaces with the units of the device is carried out in the same way as in the above-described embodiments of the device, viz., through the respective ports "a,", "b," and "c,".

A further embodiment of the device for controlling the thickness of the strip stock being rolled between the rolls of a mill stand is illustrated in Figs. 1 3.and 14. It differs from the devices shown in Figs. 2 through 6 and 7-8 in that provision is made therein for a reversing spool valve 70 (Fig. 13) which is adapted, upon putting the device in operation, to connect the piston-end space "b" of the hydraulic cylinder 15 with the pumping unit 18, and upon discharging the strip stock from the rolls, to connect said space with the oil tank 26.

Provision of the reversing spool valve 70 in the hydraulic circuit of the device enables the latter to be simplified. In particular, such units as the pumping unit 29 with the motor 30, the valve 31 and the hydraulic pipings 58 and 59 can be dispensed with. The other units of the device, i.e., the hydraulic dynamometer 14, the double-space hydraulic cylinder 15, the pumping unit 18 with the motor 19, the volumetric oil regulators 20 and 21, the valve 27, the pressure relief valve 28, the check valve 22 and 23, the stop valves 24 and 25 and the oil tank 26, as well as the hydraulic pipings 49 through 57, 60 and 62 perform the same functions as in the first and second embodiments of the device and are indicated by the same reference numerals.

The reversible spool valve 70 (Fig. 14) has a chest 71 accommodating a spool 72 loaded at the end of a tailpiece 73 by a spring 74 which rests upon a cover 75 held to the chest 71 by screws 76. The spool 72 along with the chest 71 form a chamber "m" communicated with ports "met" and "m,", an end chamber "n" communicated with a port "not", and along with the chest 71 and the cover 75 the spool 72 defines a chamber "p" communicated with a port "put".

Hydraulic communication of the reversible spool valve 70 (Fig. 13) is effected as follows. The chamber "m" is communicated with the pumping unit 18 via the port "m," (Fig. 14) and by way of a hydraulic piping 77 (Fig. 13) connected to the hydraulic piping 52, while through the port "m2" and the hydraulic piping 51 (Fig.

13) said chamber "m" is communicated with the piston-end space "b" of the hydraulic cylinder 15; the chamber "p" is communicated with the hydraulic piping 56 through the port "put" (Fig. 14) and a hydraulic piping 78 (Fig. 13). The end chamber "n" of the reversing spool valve 70 is communicated with the tank 26 (Fig.

13) through the port "not" (Fig. 14) by the hydraulic pipings 78a and 57.

In the herein-described embodiment of the invention the way by which the space established by the piston-rod space "c" of the double-space hydraulic cylinder 15, the chamber "i" of the volumetric oil regulator 21 and the control chamber "1" of the pressure valve 17a, is communicated with the source of power fluid (oil), is modified, i.e., said space is communicated with the hydraulic piping 56 through the hydraulic piping 55a and the check valve 23, the pressure in said hydraulic piping 56 being created and kept always constant with the use of the valve 27 when oil flows therethrough.

The device according to the embodiment described above is adjusted before the rolling process, but in operation and operated in the course of thickness control of the strip stock being rolled in a way similar to that described in the two embodiments discussed hereinbefore.

An embodiment of the device as shown in Figs. 15 through 17 differs from the device according to the second embodiment thereof as seen in Fig. 7 in that the chamber "a" of the hydraulic dynamometer 14 is combined with the space "b" of the double-space hydraulic cylinder 15 (Fig. 15) which adds substantially to the simplicity of the device.

With a view to automatically engaging said device in operation, a hydraulically piloted reversing spool valve 79 is incorporated into the circuit thereof. With the same view the construction of the valve 17 and of the double-space hydraulic cylinder 15, as well as hydraulic communication of the units of the device are modified, while the units of the device, viz., the pumping units 18 and 28 with the motors 19 and 30, the volumetric oil regulators 20 and 21, the valves 27 and 31, the pressure relief valve 28, the check valves 22 and 23, the stop valves 24 and 25 and the tank 26 remain invariable, perform the same functions as in the second embodiment and bear the same reference numerals.

As to the hydraulic cylinder 15b and the valve 17b whose construction is modified but partly, their components, spaces, chambers and ports performing the same functions as in the second embodiment of the device, are indicated with the same reference numerals but followed by other suffixes.

The valve 17b (Fig. 16) comprises the chest 40b which accommodates the stepped sliding spool 41b having the step 63, a floating piston 80 loaded by a spring 81, cover 42b held to the chest 40b by the screws 43b.

The sliding spool 41b forms along with the chest 40b a control chamber which is subdivided into two subchambers "d" and "r" which are communicated with the respective ports "d," and "rut" in the chest 40b, while along with the cover 42b the sliding spool 41b defines two chambers, i.e., the control chamber "1" communicated with the port "11" and the throttle chamber "e" communicated with the port "e1", as well as the throttling gap "y". The drainback chamber "f" is established by the sliding spool 41b and is communicated with the port "f," provided in the chest 40b.

The reversing spool valve 79 (Fig. 17) has a chest 82, wherein mounted coaxially are a sliding spool 83 loaded by a spring 84 and a plunger 85 loaded by a spring 86 which rests upon a cover 87 held to the chest 82 by screws 88. On the side of the sliding spool 83 the reversible spool valve 79 is closed by a cover 89 held to the chest 82 by screws 90.

The sliding spool 83 forms along with the chest 82 and the cover 89 the chamber s communicated with the port "s,", and with the chest 82, the annular chambers "t" and "u" communicated with the respective ports "t1,, and "u1,,.

The plunger 85 defines along with the chest 82 the annular chamber "v", and along with the chest 82 and the cover 87, the chamber "w", both of said chambers being intercommunicated through the respective ports "v," and "w,", and communicated with the annular chamber "u" through the port "U1".

The annular- chamber "z" is defined between the sliding spool 83 and the plunger 85, communicated with the chamber "t" by way of the ports "Z1" and "t1,,.

The chest 82 of the reversible spool valve 79 is provided with the ports "s2" and "t2,'.

Hydraulic communication of the units of the device is carred out as follows.

The space formed by the piston-end space "b" of the hydraulic cylinder 15b (Fig.

15) and the chamber "g" of the volumetric oil regulator 20 is communicated through the hydraulic piping 51 and the port "S1" with the chamber "s", and through the check valve 22 and the hydraulic pipings 51 a and 51 b, with the valve 27 and the annular chamber "t". The control chamber "d" and the throttle chamber "e" of the valve 17b as well as the pumping unit 18 are communicated through the hydraulic piping 52, 52a, 52b with the port "s2" of the reversible spool valve 79 which is adapted to communicate with the chamber "s" during the rolling process, and when no strip stock is between the rolls, the valve 79 is communicated with the annular chamber "t" and, through the port "t1,, and the hydraulic pipings 51b and 91, with the tank 26.The chamber "r" of the valve 17b is communicated via a hydraulic piping 92 with the port "t2" which is adapted to communicate, during the rolling process, with the tank 26 through the annular chamber "t", the port "t," and the hydraulic pipings 51b and 91, and when no strip stock is between the rolls, said chamber "r" is communicated, through the annular chamber "u", the ports "U1" and "V1", hydraulic pipings 93 and 55, with the pumping unit 29 creating constant oil pressure. With the sliding spool 83 (Fig. 17) assuming the neutral position the port "t2, is closed, and the chambers "v" and "w" are communicated with the pumping unit 29 through the hydraulic pipings 93 (Fig. 15) and 55.

Hydraulic communication of the rest of the units of the device, such as the piston-rod space "c" of the hydraulic cylinder 15b, the chamber "i" of the volumetric oil regulator 21, the other control chamber "1" of the valve 17b, the drainback chamber "f,', is similar to that described with reference to the second embodiment of the device (Fig. 7).

The device is adjusted for operation in the same way as in the device according to the second embodiment, the only difference residing in that the tension of the spring 84 (Fig. 17) is selected to be lower than that of the spring 86.

An initial pressure is built up in the units of the device by putting the pumping units 18 and 29 (Fig. 15) in operation, with the result that the pressure q0 is developed in the space formed by the chambers "c", "i" and "1" of the pumping unit 29, the same pressure being established in the chambers "v", "w" and "u" of the reversing spool valve 79, as well as in the chamber "r" of the valve 17b and in the hydraulic pipings 55, 92, 93 communicating the pumping unit with said chambers. It should be noted in this connection that the plunger 85 (Fig. 17) is in the leftmost position so that its piston 94 thrusts against the chest 82, whereas the sliding spool 83 is likewise in the leftmost position and thrusts against the cover 89.

The result is that the annular chamber "u" communicates the ports "t2" and u1 , the annular chamber "t" communicates the ports "s," and "t,", and the pumping unit 18 (Fig. 15), the first control chamber "d" and the throttle chamber "e" of the valve 17b are communicated with the tank 26 through the annular chamber "t,', the hydraulic pipings 51b, 91 and the valve 27. The pressure qO, effective in said chambers and in the hydraulic pipings 52, 52a, 52b is above the atmospheric, and is adjusted by the valve 27. The same pressure is developed in the space defined by the chambers "b", "g", s , the amount of pressure being selected obeying to the following inequalities P.

q01 < (40) F3 where P, is the force exerted by the spring 84 (Fig. 17); F3 is the area of the end face of the sliding spool 83 in the chamber "s"; and Fc q01 < q0. ---- (41) Fb where Fc and Fb are the areas of the hydraulic cylinder piston in its respective spaces "c" and "b The sliding spool 41b of the valve 17b is forced against the cover by the floating piston 80 being exerted by the initial pressure q0 effective in the chambers "1" and 'r", the pressure q01 effective in the chambers "d" and "e", and by virtue of the tension of the spring 81 (Fig. 16).

The balanced state of the sliding spool 41b of the valve 17b can be expressed as follows q0. F+qot . Fe+T(Fr . qO+F)=0 (42) from whence one can find the force T with which the sliding spool 41b is pressed against the cover 42b T=qO . (Fr-F1)+F-q01 . Fe (43) where Fr is the area of the floating piston 80 in the chamber "r".

As a result of action of said force the amount of the gap "y" between the sliding spool 41b and the cover 42b equals zero.

The hydraulic cylinder piston rests through the spring 95 (Fig. 15) upon the bottom of the barrel 16, an oil layer being formed in between the ends of the piston 36 and the barrel 16. Thus, the bottom rolls 4 and 8 which rest through the chock 10 upon the barrel 16 of the hydraulic cylinder 15b, are locked in a definite position.

The required gap between the work rolls 3 and 4 is set by the pressure screw 11.

The device operates as follows.

As soon as the strip stock enters the rolls of the mill stand 1 the force of rolling arises, whereby the components of the mill stand 1 and the double-space hydraulic cylinder 15b are subject to strain.

The result is a pressure rise in the piston-end space "b" due to the ends of the piston 36 and the barrel 16 being brought together which results also in an oil pressure rise also in the chamber "s" of the reversing spool valve 79.

Once the pressure has reached the value q in the piston-end space "b" of the hydraulic cylinder 15b P.

q0 > q > (44) Fs the sliding spool 83 (Fig. 17) is urged to displace, thus communicating the port "s2" with the chamber "s". At the same time the port "t2" is closed, whereby the pistonend space "b" of the double-space hydraulic cylinder 15b (Fig. 15) gets communicated with the pumping unit 18 and with the chambers "d" and "e" of the valve 17b. This causes a pressure rise in the pumping unit 18, as well as in the piston-end space "b" of the hydraulic cylinder 15b and in said chambers of the valve 17b, as amount of the gap "y" equals zero no oil flow from the throttle chamber "e" into the drainback chamber "f" occurs.

At a pressure of the pumping unit equal to q > qO the sliding spool 83 (Fig. 17) along with the plunger 85 is urged to travel to the rightmost position so that the plunger thrusts against the cover 87, the sliding spool 83 thrusts against the plunger 85 and the chamber "r" of the valve 17b gets communicated with the tank 26 (Fig.

15) through the port "t2" and the annular chamber "t".

The piston 80 (Fig. 16) of the valve 17b moves away from the sliding spool 41b to thrust against the bottom of the drilling in the chest 40b, while the sliding spool 41b of the valve 17b is forced against the cover 42 by the force T=q(FdFe)qO. F, (45) where Fd, Fe, F, are the areas of the sliding spool 41b in the chambers "d", "e" and "1", respectively, of the pressure valve 17b.

That is why the throttling gap "y" is closed and no oil flows therethrough to the oil tank 26 (Fig. 15).

A pressure rise of the pumping unit 18 occurs until the force R created under the effect of the pressure q produced by the pumping unit, urges the barrel 16 to displace with respect to the piston 36, while part of the force R developed by the hydraulic cylinder 15b under the effect of the pressure in the piston-end space "b", offers resistance to the force P of rolling, and the difference between the force R and the force P of rolling is effective in an enclosed space formed by the chambers "c", "i", "1".

The barrel 16 starts travelling under the following conditions R-P > q0. Fc (46) Thus, the oil pressure therein rises due to said enclosed space being reduced.

As soon as the sliding spool 41b (Fig. 16) of the valve 17b gets balanced by the oil pressure effective in the chambers "d", "e" and "1", the gap "y" between the sliding spool 41b and the cover 42b opens so that the oil delivered by the pumping unit 18 (Fig. 15) is free to completely flow from the throttle chamber "e" through the gap "y" to the drainback chamber "f" and therefrom to the oil tank 26, whereby the barrel 16 of the hydraulic cylinder 15b stops moving.

The length of travel run by the barrel 16 is equal to Q-Qo AQ #h2= =(47) k, k, Taking into account of said length of travel a total change of the strip stock thickness equals AR-AQ AQ Ah= - --- (48) .

while the outgoing thickness of the strip stock is equal to 2q0 . FaG nR-aQ aQ h1=h0+ + - (49) k k k, When realizing relation (16) between the stiffness factors k, and k, the righthand member of equation (48) equals zero, therefore no change of the roll gap and hence of the outgoing strip stock thickness due to deformation of the roll mill stand occurs.

Upon discharging the strip stock from the rolls the device resumes the initial position to be ready for a next operating cycle.

Thus, the specific object of the invention aimed at increasing the accuracy of control and its carrying into effect in a cheaper and simpler device is achieved, according to the invention due to the fact that in a method of controlling the thickness of the strip stock being rolled the force causing the roll supports to traverse is changed in the course of the strip stock deformation between the rolls proportionate to the force of rolling, for which purpose in a device for carrying into effect said method use is made of hydraulic dynamometers having their interior chamber fully filled with a fluid adapted for taking up the force of rolling, valves for pressure control of said fluid, having the control chamber communicated with the chamber of the hydraulic dynamometer, and the throttle chamber communicated with the hydraulic cylinder and with the source of fluid, whereby the afore-stated object is attained.

WHAT WE CLAIM IS: 1. A method of maintaining constant the thickness of strip stock being rolled between the rolls of a roll mill stand, comprising the following steps: setting up a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. T=q(FdFe)qO. F, (45) where Fd, Fe, F, are the areas of the sliding spool 41b in the chambers "d", "e" and "1", respectively, of the pressure valve 17b. That is why the throttling gap "y" is closed and no oil flows therethrough to the oil tank 26 (Fig. 15). A pressure rise of the pumping unit 18 occurs until the force R created under the effect of the pressure q produced by the pumping unit, urges the barrel 16 to displace with respect to the piston 36, while part of the force R developed by the hydraulic cylinder 15b under the effect of the pressure in the piston-end space "b", offers resistance to the force P of rolling, and the difference between the force R and the force P of rolling is effective in an enclosed space formed by the chambers "c", "i", "1". The barrel 16 starts travelling under the following conditions R-P > q0. Fc (46) Thus, the oil pressure therein rises due to said enclosed space being reduced. As soon as the sliding spool 41b (Fig. 16) of the valve 17b gets balanced by the oil pressure effective in the chambers "d", "e" and "1", the gap "y" between the sliding spool 41b and the cover 42b opens so that the oil delivered by the pumping unit 18 (Fig. 15) is free to completely flow from the throttle chamber "e" through the gap "y" to the drainback chamber "f" and therefrom to the oil tank 26, whereby the barrel 16 of the hydraulic cylinder 15b stops moving. The length of travel run by the barrel 16 is equal to Q-Qo AQ #h2= =(47) k, k, Taking into account of said length of travel a total change of the strip stock thickness equals AR-AQ AQ Ah= - --- (48) . while the outgoing thickness of the strip stock is equal to 2q0 . FaG nR-aQ aQ h1=h0+ + - (49) k k k, When realizing relation (16) between the stiffness factors k, and k, the righthand member of equation (48) equals zero, therefore no change of the roll gap and hence of the outgoing strip stock thickness due to deformation of the roll mill stand occurs. Upon discharging the strip stock from the rolls the device resumes the initial position to be ready for a next operating cycle. Thus, the specific object of the invention aimed at increasing the accuracy of control and its carrying into effect in a cheaper and simpler device is achieved, according to the invention due to the fact that in a method of controlling the thickness of the strip stock being rolled the force causing the roll supports to traverse is changed in the course of the strip stock deformation between the rolls proportionate to the force of rolling, for which purpose in a device for carrying into effect said method use is made of hydraulic dynamometers having their interior chamber fully filled with a fluid adapted for taking up the force of rolling, valves for pressure control of said fluid, having the control chamber communicated with the chamber of the hydraulic dynamometer, and the throttle chamber communicated with the hydraulic cylinder and with the source of fluid, whereby the afore-stated object is attained. WHAT WE CLAIM IS:

1. A method of maintaining constant the thickness of strip stock being rolled between the rolls of a roll mill stand, comprising the following steps: setting up a

force R causing the supports of one of the rolls to traverse, said force exceeding in magnitude the force P of rolling applied to roll the strip and being applied to the roll supports in such a way as to act against the force P of rolling, the difference between the force R and the force P of rolling tending to cause the roll supports to traverse: developing a balancing force Q proportional to the distance of traverse of the roll supports which acts to prevent the supports of the rolls between which the strip stock is deformed from being brought together and to balance out the difference between the force R causing the roll supports to traverse and the force P of rolling; wherein the force R causing the rolls to traverse is regulated by means of a control circuit having no error feedback to be dependent upon the force P of rolling in accordance with the equation:: R=k2P where k2 is a constant and wherein the factor of proportionality kl between the roll support traverse distance and the balancing force preventing the roll supports from being brought together is predetermined in dependence upon the values of the said constant k2 and the mill stand stiffness factor k, the value of k1 satisfying the equation: k1=k(k2-1)

2.A device for carrying out the method as claimed in Claim I, located in the stand of a rolling mill, the mill having a roll housing which mounts a screwdown arrangement and mill rolls with supports accommodated in side recesses of said roll housing, at least one of the rolls being adapted to traverse along the direction of action of the force of rolling; the device comprising two assemblies situated one on each side of the roll mill stand, each assembly comprising: a hydraulic dynamometer interposed between the supports of one of the rolls and the roll mill stand housing and adapted to take up the force of rolling; at least one hydraulic cylinder provided between the supports of one of the rolls and the roll mill stand housing, the piston-end space of the hydraulic cylinder communicating with a source of hydraulic fluid under pressure to allow build-up of a force greater in magnitude than the force of rolling, the difference therebetween being large enough to cause said roll and associated supports to traverse during a rolling operation; elastic members adapted to determine the position of the supports of said traversable roll and so positioned as to take up the difference between the force developed by said hydraulic cylinder and the force of rolling, the force created by said hydraulic cylinder offering resistance to the force of rolling and at the same time inflicting deformation upon said elastic members, the ratio between the stiffness factor of said elastic members of the device and the stiffness factor of elastic members of the roll mill stand together with those members of the device adapted to take up the force of rolling being of a predetermined value; a valve adapted for regulating the pressure of hydraulic fluid in the interior space of said hydraulic cylinder and comprising a valve body, a sliding spool accommodated in the body so as to define at least two chambers therein, one chamber being the control chamber of the valve and communicating with said hydraulic dynamometer to form therewith an enclosed fluid-filled space, the other chamber acting as the throttle chamber of said valve and communicating with the interior space of said hydraulic cylinder and with the source of hydraulic fluid to form with these an enclosed space for containing running hydraulic fluid.

3. A device as claimed in Claim 2, wherein each hydraulic cylinder has an additional enclosed piston-rod space defined by the cylinder walls, cylinder end cover, piston and piston rod, said additional space being filled with fluid and constituting along with said components of the hydraulic cylinder defining the space, the elastic members of said device which provide the required magnitude of the force determining the position of the traversable roll supports.

4. A device as claimed in Claim 2 or 3, wherein the sliding spool of each valve adapted for hydraulic fluid pressure control in the interior space of said hydraulic cylinder, is stepped so as to form along with the body of said valve an additional control chamber, said additional control chamber communicating with the pistonrod space of said hydraulic cylinder to establish an enclosed space along therewith for containing running hydraulic fluid.

5. A device as claimed in Claim 3, wherein a spring is provided in the enclosed piston-rod space of said hydraulic cylinder filled with power fluid, said spring being operative between the piston and end cover of the cylinder and constituting along with said fluid and the components of said hydraulic cylinder which form the enclosed piston-rod space therein and are adapted to interact with said spring, the elastic members of the device.

6. A device as claimed in Claim 2, wherein the chamber of said hydraulic dynamometer communicating with the control chamber of said valve for hydraulic fluid pressure control in the interior of the hydraulic cylinder, is combined with the piston-end space of said hydraulic cylinder.

7. A device as claimed in Claim 6, wherein a spring is located in the piston-end space of said hydraulic cylinder, which space is adapted to communicate, during the rolling process with the control and throttle chambers. of said valve for hydraulic fluid pressure control in the hydraulic cylinder interior, said spring resting (when no strip stock is in between the rolls of the mill stand) upon the piston and barrel of said hydraulic cylinder so as to prevent the supports of said rolls from being moved apart.

8. A device as claimed in any of Claims 3 to 7, wherein there is additionally provided a regulator cylinder whose interior communicates with the piston-rod space of said hydraulic cylinder to form along therewith an enclosed space filled with hydraulic fluid, both said space and said fluid constituting an elastic member of the device.

9. A device as claimed in any of Claims 2, 4 and 6, wherein the piston-end space of said hydraulic cylinder communicates with the source of pressurised fluid via a directional-control sliding spool valve which has two end control chambers of which one chamber is adapted to communicate, during the rolling process, with said throttle chamber of said fluid pressure control valve in the interior of said hydraulic cylinder, and also with the piston-end space of said hydraulic cylinder and with the source of pressurised fluid, while the other end of the control chamber communicates with the source of constant pressure.

10. A method of maintaining constant the thickness of strip stock when being rolled between rolls, substantially as hereinbefore described with reference to, and as shown in accompanying drawings.

11. A device for maintaining constant the thickness of strip stock being rolled between rolls, substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.