A bounce roller hydraulic control circuit

Abstract

The application relates to a bounce roller hydraulic control circuit, which comprises a bounce roller, a hydraulic cylinder, a pressure oil pipe and an oil return pipe, a first overflow pressure relief valve is arranged on a branch between a rodless cavity of the hydraulic cylinder and the pressure oil pipe, and a second overflow pressure relief valve is arranged on a branch between a rod cavity of the hydraulic cylinder and the pressure oil pipe; the oil inlet of the first overflow pressure relief valve and the oil inlet of the second overflow pressure relief valve are communicated with the pressure oil pipe, the oil outlet of the first overflow pressure relief valve is communicated with the rodless cavity of the hydraulic cylinder, the oil outlet of the second overflow pressure relief valve is communicated with the rod cavity of the hydraulic cylinder, and the oil outlets of the first overflow pressure relief valve and the second overflow pressure relief valve are communicated with the oil return pipe; at least one of the first overflow pressure relief valve and the second overflow pressure relief valve is connected with a proportional overflow valve, the control port of the first overflow pressure relief valve or / and the control port of the second overflow pressure relief valve is communicated with the oil inlet of the proportional overflow valve, and the oil outlet of the proportional overflow valve is communicated with the oil return pipe. The bounce roller hydraulic control circuit disclosed by the application has lower cost and wider application range.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, and in particular to a hydraulic control circuit for a bouncing roller. Background Technology

[0002] As a commonly used metal processing technology, rolling refers to the plastic deformation of a metal billet passed through the gap between a pair of rotating rolls, resulting in the desired cross-sectional shape and altering its microstructure and properties. In the process of rolling a metal billet into a metal strip, the tension of the metal strip varies depending on the target thickness. Furthermore, for the same type of metal strip, a stable tension is essential to achieve a stable cross-sectional area. Therefore, tension control of the metal strip is a crucial aspect of metal processing.

[0003] A bouncing roller is a commonly used tension control device in the stainless steel industry. It is a bouncing roller that can move up and down suspended between two fixed rollers. By changing the position of the bouncing roller, the force exerted by the bouncing roller on the steel strip passing between the two fixed rollers can be adjusted, absorbing tension fluctuations of the steel strip and controlling the tension stability.

[0004] Early bouncing rollers adjusted the tension of the steel strip by suspending counterweights that could be increased or decreased on the bouncing roller. Although this structure was simple, it was inconvenient to operate. Moreover, due to the limited variety of counterweight specifications, the range of force that the bouncing roller could apply to the steel strip was discontinuous. Sometimes it was also difficult to ensure that the weight of the counterweight was just right. As a result, the bouncing roller was difficult to adapt to the tension control required for steel strips of different thicknesses, widths and performances, and the tension control accuracy was not high.

[0005] The later-stage bouncing roller uses the force exerted by the piston rod of a pneumatic or hydraulic cylinder on the bouncing roller as a counterweight. This mainly involves mounting the axle of the bouncing roller on the piston rod of a pneumatic or hydraulic cylinder. The cylinder body of the pneumatic or hydraulic cylinder is vertically fixed on the production line. An air pump or hydraulic station supplies compressed air or hydraulic oil to the upper and lower cavities of the piston inside the pneumatic or hydraulic cylinder through upper and lower pipelines. Pressure control valves, such as proportional pressure reducing valves, are installed on the upper and lower pipelines. These pressure control valves are controlled by a controller to adjust the pressure difference of the air or hydraulic oil in the upper and lower cavities of the piston, so that the pressure difference generated on the piston meets the tension requirements of the steel strip. The aforementioned bouncing roller tension control device is disclosed in Chinese Utility Model Patent No. ZL200920216578.5 (Authorization Announcement No. CN201482801U) entitled "Bouncing Roller Tension Control Device", Chinese Utility Model Patent No. ZL201020268425.8 (Authorization Announcement No. CN201778078U) entitled "Bouncing Roller Tension Control Device", and Chinese Invention Patent No. ZL201210012442.9 (Authorization Announcement No. CN102560072A) entitled "Pneumatic Automatic Counterweight Bouncing Roller".

[0006] Compared to earlier models, later-generation bouncing rollers can control the pressure of compressed air supplied to the cylinder or hydraulic oil supplied to the hydraulic cylinder by a proportional pressure reducing valve via a current signal from the controller. This allows for stepless adjustment of the pressure difference between the upper and lower sides of the piston, making operation more convenient and faster, and providing higher precision in steel belt tension control. However, the following shortcomings still exist: ① The proportional pressure reducing valve is expensive and has a small flow rate, which cannot support large flow operations, thus limiting the application of the aforementioned bouncing roller device in steel belt tension control; ② The bouncing roller is mounted on the piston rod, which not only makes the piston rod prone to shaking due to the rotation of the bouncing roller, affecting the sealing effect and tension control precision of the cylinder or hydraulic cylinder, but also makes it difficult to adjust the position of the cylinder or hydraulic cylinder according to the actual tension control requirements of the production line, resulting in low flexibility. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a hydraulic control circuit for bouncing rollers that is lower in cost and has a wider range of applications, in light of the above-mentioned technical situation.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a hydraulic control circuit for a bouncing roller, including a hydraulic cylinder for changing the degree of compression of the strip by the bouncing roller, characterized in that: it further includes a pressure oil pipe and a return oil pipe, the rodless chamber of the hydraulic cylinder is connected to the pressure oil pipe through a first branch, the rod chamber of the hydraulic cylinder is connected to the pressure oil pipe through a second branch, a first overflow pressure reducing valve is provided on the first branch, and a second overflow pressure reducing valve is provided on the second branch;

[0009] Both the first and second relief pressure reducing valves have an oil inlet, an oil outlet, a control port, and a drain port. The oil inlets of both the first and second relief pressure reducing valves are connected to the pressure oil pipe. The oil outlet of the first relief pressure reducing valve is connected to the rodless chamber of the hydraulic cylinder. The oil outlet of the second relief pressure reducing valve is connected to the rod chamber of the hydraulic cylinder. The drain ports of both the first and second relief pressure reducing valves are connected to the return oil pipe.

[0010] At least one of the first and second relief pressure reducing valves is connected to a proportional relief valve, the proportional relief valve having an inlet and an outlet, the control port of the first and / or second relief pressure reducing valve being connected to the inlet of the proportional relief valve, and the outlet of the proportional relief valve being connected to the return oil pipe.

[0011] To facilitate control of the pressure difference between the rod-side and rodless chambers of the hydraulic cylinder, only the first relief pressure reducing valve is connected to a proportional relief valve. The control port of the first relief pressure reducing valve is connected to the inlet of the proportional relief valve, and the control port of the second relief pressure reducing valve is connected to the return oil pipe. By setting the pressure in the rod-side chamber of the hydraulic cylinder to a constant value, the pressure difference between the rod-side and rodless chambers can be changed by adjusting the pressure in the rodless chamber. This eliminates the need to simultaneously adjust the pressure in both chambers, simplifying tension control. Alternatively, only the second relief pressure reducing valve can be connected to a proportional relief valve, with the control port of the first relief pressure reducing valve connected to the return oil pipe and the control port of the second relief pressure reducing valve connected to the inlet of the proportional relief valve.

[0012] Further design details include a vertically positioned hydraulic cylinder with its piston rod independent of the bouncing roller. This allows the piston rod to press down on or support the bouncing roller. Firstly, the rotation of the bouncing roller has minimal impact on the piston rod, minimizing disruption to the cylinder's sealing performance. Secondly, the piston rod primarily responds to vertical position changes in the bouncing roller, improving strip tension control accuracy. Thirdly, the hydraulic cylinder's position can be adjusted according to the production line's strip tension control requirements, resulting in greater flexibility in strip tension control.

[0013] To save energy, the bouncing roller is positioned above the strip, and the hydraulic cylinder is also positioned above the bouncing roller, so that the piston rod of the hydraulic cylinder can only press down on the bouncing roller. This design ensures that the pressure difference between the rodless and rod chambers of the hydraulic cylinder exerts a downward force on the bouncing roller, in the same direction as the weight of the hydraulic cylinder piston and the weight of the bouncing roller. This allows the combined force of all three forces to act on the strip, reducing the energy required by the hydraulic system. If the hydraulic cylinder were positioned above the bouncing roller, the pressure difference between the rodless and rod chambers would exert a force on the bouncing roller in the opposite direction to the weight of the hydraulic cylinder piston and the weight of the bouncing roller. The piston rod of the hydraulic cylinder would then need to overcome the weight of the hydraulic cylinder piston and the weight of the bouncing roller to act on the strip, resulting in higher energy consumption of the hydraulic system.

[0014] In order to facilitate the hydraulic cylinder piston pressing down on the bouncing roller by the pressure difference between the rodless chamber and the rod chamber of the hydraulic cylinder, the set pressure of the first relief pressure reducing valve is not less than the set pressure of the second relief pressure reducing valve.

[0015] Further improvements include an electromagnetic directional valve on the first branch line for controlling the connection between the pressure oil pipe and the rodless chamber of the hydraulic cylinder. When the electromagnetic directional valve is de-energized, the pressure oil pipe is blocked from the rodless chamber of the hydraulic cylinder, preventing oil from entering the rodless chamber while oil enters the rod chamber. This causes the piston rod to retract under the pressure in the rod chamber, moving it away from the bouncing roller. When the electromagnetic directional valve is energized, the pressure oil pipe is connected to the rodless chamber. As the pressure in the rodless chamber gradually increases to a set value, the piston overcomes the pressure in the rod chamber and moves downwards until it presses down on the bouncing roller. Simultaneously, the volume of the rod chamber decreases, and excess oil in the rod chamber overflows from the drain port of the second relief valve into the return pipe, maintaining a constant pressure in the rod chamber. Since the electromagnetic directional valve only has on / off functionality, a two-position, two-way directional valve is sufficient.

[0016] Further design features a double one-way throttle valve located downstream of the first overflow pressure reducing valve on the first branch. The double one-way throttle valve allows hydraulic oil to enter the rodless chamber of the hydraulic cylinder at an accelerated speed, while simultaneously slowing down the flow of hydraulic oil out of the rodless chamber.

[0017] To facilitate monitoring of the pressure in the rodless chamber of the hydraulic cylinder, a pressure sensor is installed on the first branch, located after the first relief pressure reducing valve.

[0018] In order to enable hydraulic oil to quickly enter the rod chamber of the hydraulic cylinder, a one-way valve is provided on the second branch, and the inlet of the one-way valve is connected to the pressure oil pipe, and the outlet of the one-way valve is connected to the oil inlet of the second relief pressure reducing valve.

[0019] Compared with existing technologies, the advantages of this invention are as follows: The combination of a proportional relief valve and a relief pressure reducing valve achieves pressure regulation of the rodless and / or rod-side chambers of the hydraulic cylinder, which is less expensive than a proportional pressure reducing valve. Furthermore, the relief pressure reducing valve has a large flow rate, enabling it to support high-flow-rate operations and thus expanding its application range. By independently configuring the piston rod of the hydraulic cylinder and the bouncing roller, the rotation of the bouncing roller has a smaller impact on the piston rod, minimizing the impact on the sealing effect of the hydraulic cylinder. This also allows the piston rod to primarily respond to changes in the position of the bouncing roller, improving the accuracy of strip tension control. On the other hand, the hydraulic cylinder can be adjusted in position according to the strip tension control requirements of the production line, resulting in greater flexibility in strip tension control. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the hydraulic cylinder and the bouncing roller in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the hydraulic principle of the piston rod of the hydraulic cylinder in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] like Figure 1-2 As shown, the hydraulic control circuit of the bouncing roller involved in this embodiment includes a hydraulic cylinder 1, a bouncing roller 2, a pressure oil pipe 31, and a return oil pipe 32.

[0024] like Figure 1 As shown, in this embodiment, the strip travels between two sets of pinch rollers. Each set of pinch rollers includes a fixed roller located below the strip and a movable roller located above the strip. The spring roller 2 for extruding the strip is located horizontally between the two sets of pinch rollers and vertically above the strip.

[0025] like Figure 1As shown, the hydraulic cylinder 1 is vertically positioned and is used to apply different forces to the bouncing roller 2 during strip operation to control the strip tension. Due to force balance, the strip tension is equal to the resultant force of the force applied by the hydraulic cylinder 1 to the bouncing roller 2 and the weight of the bouncing roller 2. The hydraulic cylinder 1 has a rodless chamber 11 and a rod chamber 12 located on both sides of the piston, and a piston rod 13 is provided on the piston. The force applied by the hydraulic cylinder 1 to the bouncing roller 2 is the resultant force F exerted by the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of the hydraulic cylinder 1 on the bouncing roller 2 and the weight of the piston of the hydraulic cylinder 1. This resultant force causes the piston rod 13 of the hydraulic cylinder 1 to drive the bouncing roller 2 to move in the vertical direction, thereby adjusting the squeezing action of the bouncing roller 2 on the strip, that is, realizing the tension control of the strip. Since the weight of the piston in hydraulic cylinder 1 and the bouncing roller 2 is constant, the change in the tension of the strip depends on the change in the force F exerted by the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of hydraulic cylinder 1 on the bouncing roller 2. In this embodiment, hydraulic cylinder 1 is located above bouncing roller 2, and the force F exerted by the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of hydraulic cylinder 1 on the bouncing roller 2 satisfies the formula: F=F1-F2=P1·S1-P2·S2, where F1 is the oil pressure in the rodless chamber 11 of hydraulic cylinder 1, F2 is the oil pressure in the rod chamber 12 of hydraulic cylinder 1, P1 is the pressure of the hydraulic oil in the rodless chamber 11 of hydraulic cylinder 1, S1 is the area of ​​the rodless chamber 11 of hydraulic cylinder 1, P2 is the pressure of the hydraulic oil in the rod chamber 12 of hydraulic cylinder 1, and S2 is the area of ​​the rod chamber 12 of hydraulic cylinder 1. In the above formula, the area S1 of the rodless chamber 11 of the hydraulic cylinder 1 and the area S2 of the rod chamber 12 of the hydraulic cylinder 1 are both constant values. Therefore, the magnitude of the force F exerted by the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of the hydraulic cylinder 1 on the bouncing roller 2 is determined by the difference between the hydraulic oil pressure P1 in the rodless chamber 11 and the hydraulic oil pressure P2 in the rod chamber 12 of the hydraulic cylinder 1.

[0026] like Figure 2 As shown, the rodless chamber 11 of the hydraulic cylinder 1 is connected to the pressure oil pipe 31 via a first branch 51, which is used to control the pressure P1 of the hydraulic oil in the rodless chamber 11 of the hydraulic cylinder 1; the rod chamber 12 of the hydraulic cylinder 1 is connected to the pressure oil pipe 31 via a second branch 52, which is used to control the pressure P2 of the hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1.

[0027] like Figure 2As shown, a first relief pressure reducing valve 61 is provided on the first branch 51, and a proportional relief valve 7 for adjusting the oil pressure in the rodless chamber 11 of the hydraulic cylinder 1 is connected to the first relief pressure reducing valve 61. The first relief pressure reducing valve 61 has an oil inlet, an oil outlet, a control port, and a drain port. The oil inlet of the first relief pressure reducing valve 61 is connected to the pressure oil pipe 31, the oil outlet of the first relief pressure reducing valve 61 is connected to the rodless chamber 11 of the hydraulic cylinder 1, and the drain port of the first relief pressure reducing valve 61 is connected to the return oil pipe 32. The proportional relief valve 7 has an oil inlet and an oil outlet. The oil inlet of the proportional relief valve 7 is connected to the control port of the first relief pressure reducing valve 61, and the oil outlet of the proportional relief valve 7 is connected to the return oil pipe 32. The pressure at the outlet of the first relief pressure reducing valve 61 is the sum of the set pressure of the first relief pressure reducing valve 61 and the pressure at the control port of the first relief pressure reducing valve 61. The pressure at the control port of the first relief pressure reducing valve 61 is equal to the pressure at the inlet of the proportional relief valve 7. The pressure at the inlet of the proportional relief valve 7 is the set pressure of the proportional relief valve 7. The pressure P1 of the hydraulic oil in the rodless chamber 11 of the hydraulic cylinder 1 is controlled by steplessly adjusting the set pressure of the proportional relief valve 7.

[0028] In this embodiment, the pressure regulation of the rodless chamber 11 in the hydraulic cylinder 1 is achieved by using a combination of the first proportional relief valve 61 and the relief pressure reducing valve 7. This method is less expensive than the proportional pressure reducing valve commonly used in the prior art, and the relief pressure reducing valve 7 has a larger flow rate, which can support large flow rate actions, making the application range of the bouncing roller hydraulic control circuit more extensive.

[0029] like Figure 2 As shown, a second relief valve 62 is provided on the second branch 52. The second relief pressure reducing valve 62 has an oil inlet, an oil outlet, a control port, and a drain port. The oil inlet of the second relief pressure reducing valve 62 is connected to the pressure oil pipe 31, the oil outlet of the second relief pressure reducing valve 62 is connected to the rod chamber 12 of the hydraulic cylinder 1, and the control port and drain port of the second relief pressure reducing valve 62 are both connected to the return oil pipe 32. Because the pressure at the control port of the second relief pressure reducing valve 62 is 0, the pressure at the oil outlet of the second relief pressure reducing valve 62 is the set pressure of the second relief pressure reducing valve 62, that is, the pressure P2 of the hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1 is a constant value.

[0030] In this embodiment, the hydraulic oil pressure P2 in the rod chamber 12 of the hydraulic cylinder 1 is set to a constant value, and the hydraulic oil pressure P1 in the rodless chamber 11 of the hydraulic cylinder 1 is adjusted steplessly to change the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of the hydraulic cylinder 1. This eliminates the need to simultaneously adjust the hydraulic oil pressure P1 in the rodless chamber 11 and the hydraulic oil pressure P2 in the rod chamber 12 of the hydraulic cylinder 1, making the tension control of the strip simpler.

[0031] like Figure 2As shown, to reduce the impact of the rotation of the bouncing roller 2 on the sealing effect of the hydraulic cylinder 1 and the accuracy of strip tension control, the piston rod 13 of the hydraulic cylinder 1 and the bouncing roller 2 are set independently, so that the piston rod 13 of the hydraulic cylinder 1 can only press down on the bouncing roller 2 and cannot pull it up. To facilitate the downward pressing of the bouncing roller 2 by the piston rod 13 of the hydraulic cylinder 1, the set pressure of the first overflow pressure reducing valve 61 is not less than the set pressure of the second overflow pressure reducing valve 62. In this embodiment, the set pressure of the first overflow pressure reducing valve 61 is 35 bar, and the set pressure of the second overflow pressure reducing valve 62 is 30 bar.

[0032] like Figure 2 As shown, the first branch 51 is also equipped with an electromagnetic directional valve 4, a double one-way throttle valve 81, and a pressure sensor 9. The electromagnetic directional valve 4 is used to control whether the pressure oil pipe 31 is connected to the rodless chamber 11 of the hydraulic cylinder 1. In this embodiment, the electromagnetic directional valve 4 is located after the first overflow relief valve 61. The double one-way throttle valve 81 is located after the electromagnetic directional valve 4. This double one-way throttle valve 81 can accelerate the hydraulic oil into the rodless chamber 11 of the hydraulic cylinder 1, and decelerate the hydraulic oil flowing out of the rodless chamber 11 of the hydraulic cylinder 1. The pressure sensor 9 is located after the double one-way throttle valve 81 and is used to monitor the oil pressure in the rodless chamber 11 of the hydraulic cylinder 1.

[0033] like Figure 2 As shown, a check valve 82 is provided on the second branch 52, and the inlet of the check valve 82 is connected to the pressure oil pipe 31, and the outlet of the check valve 82 is connected to the oil inlet of the second relief pressure reducing valve 62.

[0034] like Figure 1-2 As shown, the working principle of this embodiment is as follows:

[0035] The set pressure of the proportional relief valve 7 is preset according to the target tension of the strip, so that the force F exerted by the oil pressure difference between the rodless chamber 11 and the rod chamber 12 of the hydraulic cylinder 1 on the bouncing roller 2 is a constant value, thereby maintaining a constant tension of the strip.

[0036] When the solenoid directional valve 4 is de-energized, the pressure oil pipe 31 is blocked from the rodless chamber 11 of the hydraulic cylinder 1, and no oil enters the rodless chamber 11. Oil enters the rod chamber 12 of the hydraulic cylinder 1, causing the piston rod 13 of the hydraulic cylinder 1 to retract under the pressure P2 of the hydraulic oil in the rod chamber 12. At this time, the piston rod 13 of the hydraulic cylinder 1 moves away from the bouncing roller 2. When the solenoid directional valve 4 is energized, the pressure oil pipe 31 is connected to the rodless chamber 11 of the hydraulic cylinder 1, and oil begins to enter the rodless chamber 11 of the hydraulic cylinder 1. As the pressure P1 of the hydraulic oil in the rodless chamber 11 of the hydraulic cylinder 1 gradually increases to the set value, the piston 13 of the hydraulic cylinder 1 moves downward against the pressure P2 of the hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1 until it presses down on the bouncing roller 2. At the same time, the volume of the rod chamber 12 of the hydraulic cylinder 1 decreases, and the excess oil in the rod chamber 12 of the hydraulic cylinder 1 overflows from the drain port of the second overflow relief valve 62 into the return oil pipe 32, so that the hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1 maintains a constant pressure P2.

[0037] During the operation of the strip, when the strip slacks, the strip tension is less than the resultant force of the force exerted by the hydraulic cylinder 1 on the bouncing roller 2 and the weight of the bouncing roller 2. The piston rod 13 of the hydraulic cylinder 1 moves downward, causing the volume of the rodless chamber 11 of the hydraulic cylinder 1 to increase and the volume of the rod chamber 12 of the hydraulic cylinder 1 to decrease. Excess hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1 overflows from the drain port of the second overflow relief valve 62 into the return oil pipe 32, maintaining a constant pressure P2 in the hydraulic oil in the rod chamber 12 of the hydraulic cylinder 1. Simultaneously, the strip tension increases until the resultant force of the strip tension, the force exerted by the hydraulic cylinder 1 on the bouncing roller 2, and the weight of the bouncing roller 2 reaches a certain value. When the strip is taut, the strip tension is greater than the resultant force of the force exerted by the hydraulic cylinder 1 on the bouncing roller 2 and the weight of the bouncing roller 2. The piston rod 13 of the hydraulic cylinder 1 moves upward, causing the volume of the rodless chamber 11 of the hydraulic cylinder 1 to decrease and the volume of the rod chamber 12 of the hydraulic cylinder 1 to increase. The excess hydraulic oil in the rodless chamber 11 of the hydraulic cylinder 1 overflows from the drain port of the first overflow relief valve 61 into the return oil pipe 32, so that the hydraulic oil in the rodless chamber 11 of the hydraulic cylinder 1 maintains a constant pressure P1. At the same time, the strip tension decreases until the strip tension and the resultant force of the force exerted by the hydraulic cylinder 1 on the bouncing roller 2 and the weight of the bouncing roller 2 reach equilibrium.

Claims

1. A hydraulic control circuit for a bouncing roller, comprising a hydraulic cylinder (1) for changing the degree of compression of the bouncing roller (2) onto the strip, characterized in that: It also includes a pressure oil pipe (31) and a return oil pipe (32). The rodless chamber (11) of the hydraulic cylinder (1) is connected to the pressure oil pipe (31) through a first branch (51). The rod chamber (12) of the hydraulic cylinder (1) is connected to the pressure oil pipe (31) through a second branch (52). A first relief pressure reducing valve (61) is provided on the first branch (51), and a second relief pressure reducing valve (62) is provided on the second branch (52). The first overflow pressure reducing valve (61) and the second overflow pressure reducing valve (62) both have an oil inlet, an oil outlet, a control port and a drain port. The oil inlets of the first overflow pressure reducing valve (61) and the second overflow pressure reducing valve (62) are connected to the pressure oil pipe (31). The oil outlet of the first overflow pressure reducing valve (61) is connected to the rodless chamber (11) of the hydraulic cylinder (1). The oil outlet of the second overflow pressure reducing valve (62) is connected to the rod chamber (12) of the hydraulic cylinder (1). The drain ports of the first overflow pressure reducing valve (61) and the second overflow pressure reducing valve (62) are both connected to the return oil pipe (32). At least one of the first overflow pressure reducing valve (61) and the second overflow pressure reducing valve (62) is connected to a proportional overflow valve (7), the proportional overflow valve (7) having an oil inlet and an oil outlet, the control port of the first overflow pressure reducing valve (61) or / and the second overflow pressure reducing valve (62) being connected to the oil inlet of the proportional overflow valve (7), and the oil outlet of the proportional overflow valve (7) being connected to the return oil pipe (32); The bouncing roller (2) is located above the strip, and the hydraulic cylinder (1) is located above the bouncing roller (2), so that the piston rod (13) of the hydraulic cylinder (1) can only press down on the bouncing roller (2); The first branch (51) is equipped with an electromagnetic directional valve (4) for controlling whether the pressure oil pipe (31) and the rodless chamber (11) of the hydraulic cylinder (1) are connected or not.

2. The hydraulic control circuit for the bouncing roller according to claim 1, characterized in that: Only the first overflow pressure reducing valve (61) is connected to the proportional overflow valve (7). The control port of the first overflow pressure reducing valve (61) is connected to the oil inlet (71) of the proportional overflow valve (7), and the control port of the second overflow pressure reducing valve (62) is connected to the return oil pipe (32).

3. The hydraulic control circuit for the bouncing roller according to claim 2, characterized in that: The first branch (51) is provided with a double one-way throttle valve (81) located after the first overflow pressure reducing valve (61).

4. The hydraulic control circuit for the bouncing roller according to claim 2, characterized in that: The first branch (51) is equipped with a pressure sensor (9) located after the first overflow pressure reducing valve (61).

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