Torsion Shaft Bending Machine with Off-Center Load Protection Function

Abstract

The present invention discloses a torsion shaft bending machine with an eccentric load protection function, which includes a frame, a slider and a workbench. The oil cylinders drive the left and right sides of the slider respectively; the upper die is connected to the lower end of the slider, presses above the plate, and cooperates with the lower die to bend the plate; the lower die is located below the plate and is fixed on the workbench; the rear stop mechanism is used to limit the rear edge of the plate; the eccentric load protection mechanism triggers shutdown and alarm when the slider tilts in the left and right directions. The eccentric load protection mechanism includes: a striker block, which is fixed to the upper part of the back surface of the slider and extends along the vertical axis of the slider; a horizontal bracket is fixed on the front side wall of the fuel tank; the lower end of the vertical bracket is fixedly connected to the front end of the horizontal bracket; eccentric load protection travel switches, one is fixed at each of the upper and lower ends of the vertical bracket. When the striker block tilts and triggers any one of the travel switches, the bending machine shuts down and alarms. That is, when the slider has an eccentric load, it can be prevented from continuing to descend, which can meet the bending requirements of special-shaped parts.

Description

Technical Field

[0001] The present invention relates to a bending machine, and in particular to a torsion shaft bending machine with an off-load protection function, belonging to the technical field of numerical control machine tools. Background Art

[0002] The slider of the bending machine is made of a whole steel plate, and both ends are connected to the piston rod of the slider cylinder. The cylinder body is fixed on the left and right side plates of the machine frame. By sequentially controlling the hydraulic system, the piston rod of the cylinder can be driven to drive the slider to move up and down. During the up and down movement of the slider of the torsion shaft bending machine, the movement of the piston rods of the left and right cylinders must be kept synchronous, and usually a balance arm device is used to force synchronization.

[0003] During the downward movement of the slider, since the system pressure is small, at this time, the position deviation of the two piston rods can be easily synchronized through the balance arm device. At this time, placing the plate to be processed in the middle of the slider for bending or symmetrically bending under the two cylinders on both sides will not cause the failure of the balance arm to be twisted and broken due to off-load. However, when the plate is placed on one side of the slider for bending, when the slider moves downward to contact the plate, because a certain pressure is required for the plate to bend and deform, the piston of the cylinder at the end where the plate is placed will not continue to move downward, while the piston of the other cylinder will continue to move downward because there is no plate to press, and at the same time, the lower die opening has a certain depth. When the pressure at both ends is not balanced, the piston in this cylinder will continue to move downward, and when the off-load reaches a certain level, it will cause the failure of the balance arm to be twisted and broken.

[0004] Normally, the slider of the torsion shaft bending machine stops at the upper limit position. When a failure of the balance arm to be twisted and broken occurs, it will cause the slider to slide downward. Once the slider disengages from the upper limit travel switch, the control system will display an alarm message. If the machine tool is continued to be operated, the slider return stroke action needs to be carried out first. After the slider presses the upper limit travel switch, the positioning work of the back gauge or the slider can be started.

[0005] Another example is the use of a multi-step bending process. When the slider returns to the upper limit, it will slide downward and disengage from the upper limit travel switch, and it will not be possible to perform step change operation. Therefore, solving the problem of slider downward sliding is a top priority issue for the bending machine. It is not required to achieve 100% non-downward sliding, but to achieve that the slider stops in the middle for 5 minutes and the downward sliding amount ≤ 0.5 mm.

[0006] In summary, the existing bending machines have the following defects: 1. The slider ensures synchronization through the torsion shaft, and it is extremely easy to cause the balance arm to break when there are operation errors, resulting in a large amount of maintenance service;

[0007] 2. When the slider stops at the upper limit, the downward sliding amount is too large, which not only affects the operation of the machine tool, but also has certain potential safety hazards;

[0008] 3. The back gauge is not easy to adjust up and down, and it is impossible to position some special-shaped parts formed by continuous bending;

[0009] 4. The torsion shaft bending machine usually only has X / Y axis control. The X / Y axis positioning uses the forward and reverse control of the jogging motor, which is not only time-consuming and laborious, but also cannot guarantee the accuracy and requires multiple manual calibration adjustments.

[0010] The Chinese utility model patent with the publication number CN 206139677U discloses a control precision system for the frequency converter of a torsion shaft bending machine, including a motor Ⅰ that drives the rear stop of the X axis of the bending machine and a motor Ⅱ that drives the slider of the Y axis of the bending machine. The motor Ⅰ and the motor Ⅱ are controlled by a frequency converter, the frequency converter is connected to a numerical control system, the motor Ⅰ and the motor Ⅱ are respectively connected with an encoder Ⅰ and an encoder Ⅱ for detecting the rear stop of the X axis and the slider of the Y axis, and the encoder Ⅰ and the encoder Ⅱ are respectively connected to the numerical control system. It is described in this patent that "the power of the frequency converter is greater than the sum of the powers of the motor Ⅰ and the motor Ⅱ". On the one hand, this results in an overly large selection of the frequency converter, and on the other hand, because the power of the motor Ⅰ is much greater than that of the motor Ⅱ, the frequency converter cannot provide overload protection for the motor Ⅱ.

[0011] The Chinese utility model patent with the publication number CN 214366942U discloses a hydraulic system for a bending machine to prevent the slider from falling, including an oil tank, a fixed-displacement gear pump, a control valve block, a main cylinder, an auxiliary cylinder, and a pressure gauge; the suction port of the fixed-displacement gear pump is connected to the hydraulic oil tank, and the outlet port is connected to the P port of the control valve block; the T port of the control valve block is connected to the hydraulic oil tank, the B port is connected to the lower cavity of the cylinder, the M port is connected to the pressure gauge, the A port is connected to the upper cavity of the main cylinder, and the F port is connected to the control port of the filling valve. When the slider changes from fast descent to working feed, "the oil in the lower cavity of the cylinder returns to the oil tank only through the third two-position four-way solenoid directional valve 10 (YV1) and the slow-flow throttle valve 9; therefore, the oil resistance is relatively large, the back pressure in the lower cavity of the cylinder is relatively high, and thus the descending speed of the slider becomes slower". By adjusting the slow-flow throttle valve 9 to control the descending speed of the slider, on the one hand, it is difficult to adjust accurately, and on the other hand, even if it is adjusted accurately, it will still change due to the influence of the rising oil temperature. In addition, for this system, "when unloading, the fifth two-position four-way solenoid directional valve 14 (YV5) loses power and the system unloads". In addition to YV5 losing power, the YV2 / YV3 / YV4 solenoid valves are still in the powered-on working state to achieve unloading. If the solenoid valve gets stuck or the equipment loses power, unloading cannot be achieved, and the high-pressure oil is trapped in the cylinder and the oil circuit, posing a certain danger to the maintenance personnel and causing abnormal noise to affect the normal operation of the workshop.

[0012] The Chinese utility model patent with the publication number CN 210196159 discloses a torsion shaft bending machine. The upper chamber of the slider oil cylinder is connected to the oil tank through a filling valve. The outlet of the oil pump is connected to the P port of the first electromagnetic directional valve. The A port of the first directional valve is connected to the upper chamber of the slider oil cylinder. The B port of the first directional valve is connected to the hydraulic control port of the filling valve and the B port of the third electromagnetic directional valve. The B port of the third directional valve is connected to the inlet of the cartridge valve through the first throttle port. The outlet of the first throttle port is also connected to the lower chamber of the slider oil cylinder through the first check valve and the fifth throttle port. The inlet of the cartridge valve is connected to the P port of the third directional valve through the second throttle port. The outlet of the cartridge valve is connected to the lower chamber of the slider oil cylinder. The hydraulic control port of the cartridge valve is connected to the A port of the fourth electromagnetic directional valve. The P port of the fourth directional valve is connected to the outlet of the cartridge valve. The outlet of the cartridge valve is connected to the oil tank through the fourth throttle port and the third pressure regulating valve. The upper chamber of the slider oil cylinder is also connected to the B port of the fifth electromagnetic directional valve. The T ports of each directional valve are connected to the oil tank. The unloading of the upper chamber of this system is controlled by the fifth electromagnetic directional valve YV5 of the electromagnetic directional valve. When the fifth electromagnetic directional valve YV5 of the electromagnetic directional valve loses power, the upper chamber unloads. After all, the solenoid valve has a neutral position and a time delay during operation, and the response speed is slow. In addition, the unloading of the oil pump is realized by the P port to the T port of the three-position four-way solenoid valve. In this way, the displacement of the oil pump is limited by the diameter of the three-position four-way solenoid valve.

[0013] There is also a bending machine hydraulic system that uses a three-position four-way solenoid valve with a Y-type neutral function. That is, when in the neutral position, the P port, B port, and T port communicate with each other, and the B port is connected to the upper chamber of the oil cylinder. When the three-position four-way solenoid valve is in the neutral position, the outlet of the oil pump returns to the oil tank through the P port to the T port of the three-position four-way solenoid valve. When the displacement of the oil pump is large, the diameter of the three-position four-way solenoid valve is small, or the diameter of the connected pipeline is small, the T port is too late to drain oil, resulting in unexpected back pressure at the B port. Some of the oil discharged from the oil pump will enter the upper chamber of the oil cylinder through the B port, causing the slider to slide down unexpectedly. Summary of the Invention

[0014] The purpose of the present invention is to overcome the problems existing in the prior art and provide a torsion shaft bending machine with an off-center load protection function, which can prevent the slider from continuing to descend when an off-center load occurs and can meet the bending requirements of special-shaped parts.

[0015] To solve the above technical problems, a torsion shaft bending machine with an off-center load protection function of the present invention includes a frame, a slider, and a workbench, and also includes: an oil cylinder that drives the left and right sides of the slider respectively; an upper die connected to the lower end of the slider, pressing on the upper side of the plate, and cooperating with the lower die to bend the plate; a lower die located below the plate and fixed on the workbench; a rear stop mechanism for limiting the rear edge of the plate; and an off-center load protection mechanism that triggers shutdown and alarm when the slider tilts in the left and right directions.

[0016] As an improvement of the present invention, the off-center load protection mechanism includes: a bumper block fixed to the upper part of the back surface of the slider and extending along the vertical axis of the slider; a transverse bracket fixed to the front side wall of the fuel tank and protruding towards the back surface of the slider; a vertical bracket, the lower end of which is fixedly connected to the front end of the transverse bracket; off-center load protection travel switches, one fixed at each of the upper and lower ends of the vertical bracket, and the contacts of the two off-center load protection travel switches are respectively attached to the side walls of the bumper block. When the bumper block tilts to trigger any one of the off-center load protection travel switches, the bending machine stops and alarms.

[0017] As a further improvement of the present invention, the upper chambers of the two oil cylinders (1a) are respectively connected to the fuel tank through filling valves (DZ), the inlet of the oil pump (B1) is connected to the fuel tank, the outlet of the oil pump (B1) is connected to the P port of the three-position four-way solenoid valve, the T port of the three-position four-way solenoid valve is connected to the fuel tank, and the A port of the three-position four-way solenoid valve is connected to the upper chambers of the two oil cylinders (1a); the A port of the three-position four-way solenoid valve is also connected to the outlet oil circuit of the oil pump (B1) through a one-way valve one (D1) and a regulating valve one (J1);

[0018] The B port of the three-position four-way solenoid valve is connected to the lower chamber oil circuit of the two oil cylinders (1a) through a one-way valve two (D2), and the B port of the three-position four-way solenoid valve is also connected to the hydraulic control port of the filling valve (DZ) and the B port of the electromagnetic ball valve (YV3). The A port of the electromagnetic ball valve (YV3) is connected to the lower chamber oil circuit of the two oil cylinders (1a) through a regulating valve three (J3);

[0019] The lower chamber oil circuits of the two oil cylinders (1a) are also connected to the B port of the three-position four-way solenoid valve through a regulating valve two (J2) and a support valve (F4), and the neutral position function of the three-position four-way solenoid valve is of the O type.

[0020] As a further improvement of the present invention, the outlet of the oil pump (B1) is also connected to the inlet of the cartridge valve (C1), the outlet of the cartridge valve (C1) is connected to the fuel tank, the hydraulic control port of the cartridge valve (C1) is connected to the P port of the two-position four-way electromagnetic reversing valve (YV4), and the A port of the two-position four-way electromagnetic reversing valve (YV4) is connected to the fuel tank.

[0021] As a further improvement of the present invention, the back gauge mechanism includes: an X-axis drive mechanism for adjusting the front and back positions of the R-axis drive mechanism; an R-axis drive mechanism for adjusting the height of the back gauge finger; and a back gauge finger located on the R-axis mechanism and abutting against the rear edge of the sheet.

[0022] As a further improvement of the present invention, the X-axis drive mechanism includes: an X-axis motor that drives two X-axis synchronous pulleys to rotate through an X-axis synchronous belt; X-axis synchronous pulleys that are respectively installed at the shaft ends of two X-axis ball screws; X-axis ball screws that are symmetrically located on the left and right sides of the frame and extend in the front-rear direction; X-axis screw nuts that are respectively screwed onto the two X-axis ball screws; X-axis guide blocks that are respectively fixedly connected to the two X-axis screw nuts and translate along the X-axis guide rails; X-axis guide rails that are respectively fixed on the left and right sides of the frame; and an X-axis slide plate that is fixedly connected to the X-axis guide block or the X-axis screw nut and bears the R-axis drive mechanism.

[0023] As a further improvement of the present invention, the R-axis drive mechanism includes: R-axis guide seats that are respectively fixed on the X-axis guide blocks; R-axis guide rails whose middle sections are respectively embedded in the R-axis guide seats for lifting movement; R-axis brackets that are respectively fixedly connected to the R-axis guide rails and lift synchronously; R-axis racks that are respectively fixed on the front sides of the R-axis brackets and lift synchronously; R-axis gears that are respectively installed on the R drive shafts to drive the R-axis racks and drive the R-axis brackets to lift; an R-axis motor that drives two R drive shafts to rotate synchronously through an R-axis speed reducer and an R-axis synchronous rod; a rear material stop frame that is connected to the tops of the two R-axis brackets to form a gantry shape; and rear material stop fingers that are fixed on the upper part of the rear material stop frame and are symmetrically provided with two.

[0024] As a further improvement of the present invention, the control system includes: a Y-axis motor that drives a stroke adjustment screw to rotate. The stroke adjustment screw is arranged in the piston of the oil cylinder and cooperates with a screw sleeve to control the lifting stroke of the slider. A Y-axis encoder is installed at the rotor shaft end of the Y-axis motor; an X-axis motor with an X-axis encoder installed at its rotor shaft end; a frequency converter that supplies power to the X-axis motor and the Y-axis motor and adjusts the speed. And a thermal overload relay is connected in series in the power supply circuit of the Y-axis motor for overload protection; a controller whose communication interface is connected to the frequency converter through a MODBUS bus; the output ends of the X-axis encoder and the Y-axis encoder are respectively connected to the encoder interface of the controller, and the step change, speed change point, mode selection, and main motor start contact switches are respectively connected to the action signal input end of the controller; the contact switch of the thermal overload relay is connected in series to the fault signal input end of the controller to realize the overload protection of the Y-axis motor.

[0025] As a further improvement of the present invention, the two offload protection limit switches are connected in parallel and then connected to the fault signal input end of the controller. The signal input end of the frequency converter is connected in series with the normally closed contacts of the upper and lower limit switches of the slider and the normally closed contacts of the front and rear limit switches of the stop finger.

[0026] As a further improvement of the present invention, the main contact of the main contactor KM1 is connected in series in the power supply circuit of the X-axis motor, and the coil of the main contactor KM1 is controlled by the contact of the relay KA6.

[0027] The main contact of the main contactor KM2 is connected in series in the power supply circuit of the Y-axis motor, and the coil of the main contactor KM2 is controlled by the contact of the relay KA7;

[0028] The coil of the relay KA6 and the normally closed contact of the relay KA7 are connected in series to a certain output port of the controller, and the coil of the relay KA7 and the normally closed contact of the relay KA6 are connected in series to another output port of the controller.

[0029] As a further improvement of the present invention, the working steps are as follows:

[0030] S1. After the oil pump is started, the two-position four-way electromagnetic directional valve YV4 is powered on, and pressure is built up at the outlet of the oil pump;

[0031] S2. The slider moves down quickly: the right coil YV2 of the three-position four-way solenoid valve is powered on, and the pressure oil enters the upper cavity of the oil cylinder. Part of the oil in the lower cavity of the oil cylinder returns to the oil tank through the regulating valve J2, the support valve F4, and the T port of the three-position four-way solenoid valve; another part returns to the oil tank through the regulating valve J3, the electromagnetic ball valve YV3, and the T of the three-position four-way solenoid valve;

[0032] S3. The slider moves forward during processing: when the slider moves quickly down to the speed change point, the electromagnetic ball valve YV3 is de-energized, closing the direct return oil tank channel of the lower cavity of the oil cylinder. The oil in the lower cavity of the oil cylinder can only return to the oil tank through the support valve F4. The slider changes from moving quickly down to moving slowly forward during processing until the sheet metal is bent and formed;

[0033] S4. The slider holds pressure;

[0034] S5. The slider releases pressure: all solenoid valves are de-energized; the pressure oil in the upper cavity of the oil cylinder returns to the oil tank through the one-way valve D1 and the regulating valve J1, realizing rapid internal leakage;

[0035] S6. The slider returns: the left coil YV1 of the three-position four-way solenoid valve is powered on, and the pressure oil enters the lower cavity of the oil cylinder through the electromagnetic ball valve YV3, the regulating valve J3, and the one-way valve D2. Most of the oil in the upper cavity of the oil cylinder returns to the oil tank through the filling valve DZ; a small amount of oil returns to the oil tank through the T port of the three-position four-way solenoid valve. The slider returns to the upper limit travel switch to send a signal, and all solenoid valves are de-energized.

[0036] As a further improvement of the present invention, when the slider tilts, the normally open contact of one of the off-load protection travel switches closes. The input switch quantity port of the controller receives the signal, which is sent to the CPU through the optoelectronic coupling circuit. The stop signal sent by the CPU after calculation is output through the optoelectronic isolation circuit. The output end of the switch quantity port of the controller causes the coils of each relay to be de-energized, and the solenoid valves of each hydraulic system to be de-energized; at the same time, the communication port of the controller sends a signal to the frequency converter through the MODBUS bus to stop the X-axis motor and the Y-axis motor.

[0037] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. An anti-off-center load travel switch is added. The striker is fixed on the back of the slider, the bracket is fixed to the fuel tank, and the travel switch is fixed on the bracket. When the slider has an off-center load, it will trigger the action of the travel switch on one side, and the switch contact signal is strung in the control circuit to prevent the slider from continuing to descend.

[0038] 2. A two-position four-way solenoid valve YV4 is added at the oil outlet of the oil pump to control the opening and closing of the cartridge valve. At the same time, the three-position four-way solenoid valves YV1 / YV2 are changed from the original middle-position Y type to O-type valves, which can prevent the oil from the oil pump from entering the upper cavity of the oil cylinder through the middle position of the three-position four-way solenoid valve and causing a downward slide.

[0039] 3. Ordinary torsion shaft bending machines usually only have X / Y axis control. This bending machine adds R axis control for the up and down movement of the back gauge for the operation of some special-shaped parts, which can make the application of the bending machine more extensive. In addition, the lifting mechanism uses a rack and pinion to achieve synchronous operation, which can effectively prevent the back gauge from sliding down, and the speed is controlled by a worm and worm gear.

[0040] 4. Using a frequency converter can improve the positioning accuracy and the convenience of machine operation; one frequency converter is used to drive the X-axis motor of the bending machine and the Y-axis motor that drives the slider. The position detection is detected by the X-axis encoder and the Y-axis encoder respectively and connected to the control system. Since the X-axis motor and the Y-axis motor do not work simultaneously, and since the power of the Y-axis motor is less than the power of the X-axis motor, the power of the frequency converter only needs to match the power of the X-axis motor, and there is no need to increase the configuration. A thermal overload relay is provided in the Y-axis motor circuit, and the contact switch of the thermal overload relay is connected in series in the control circuit of the Y-axis motor to achieve overload protection of the Y-axis motor; the X-axis motor is provided with overload protection by the frequency converter.

[0041] 5. It changes the conventional way of controlling the frequency change of the frequency converter by the contacts of the high and low speed relays, and adopts direct communication connection between the control system and the frequency converter, which simplifies the control circuit, has a low line failure rate, and at the same time simplifies the electrical components and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The following further describes the present invention in detail with reference to the drawings and specific embodiments. The drawings are only for reference and illustration, and are not intended to limit the present invention.

[0043] Figure 1 It is the left view of the torsion shaft bending machine with off-center load protection function of the present invention;

[0044] Figure 2 It is the structural schematic diagram of the off-center load protection mechanism in the present invention;

[0045] Figure 3 For Figure 2 The top view;

[0046] Figure 4 Rear view of the torsion shaft bending machine with off-center load protection function of the present invention;

[0047] Figure 5 Top view of the torsion shaft bending machine with off-center load protection function of the present invention;

[0048] Figure 6 For Figure 4 Left view;

[0049] Figure 7 Schematic diagram of the hydraulic system in the present invention;

[0050] Figure 8 Schematic diagram of the control system in the present invention;

[0051] Figure 9 Schematic diagram of the electrical system in the present invention;

[0052] In the figure: 1. Frame; 2. Slide block; 3. Oil cylinder; 4. Bumper block; 5. Horizontal bracket; 6. Vertical bracket; 6a. Vertical long slot; 7. Oil tank; 8. Upper die; 9. Lower die; 10. Workbench; 11. X-axis motor; 12. X-axis synchronous belt; 13. X-axis synchronous pulley; 14. X-axis ball screw; 15. X-axis screw nut; 16. X-axis slide plate; 17. X-axis guide block; 18. X-axis guide rail; 19. R-axis reducer; 20. R-axis synchronous rod; 21. R drive shaft; 22. R-axis gear; 23. R-axis rack; 24. R-axis guide seat; 25. R-axis guide rail; 26. R-axis bracket; 27. Rear stop; 28. Rear stop finger; B1. Oil pump; DZ. Liquid filling valve; F1. Pressure valve 1; F2. Pressure valve 2; F3. Pressure valve 3; F4. Support valve; C1. Cartridge valve; YV3. Electromagnetic ball valve; YV4. Two-position four-way electromagnetic directional valve; D1. Check valve 1; D2. Check valve 2; J1. Regulating valve 1; J2. Regulating valve 2; J3. Regulating valve 3. Detailed implementation manners

[0053] In the following description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating that the device must have a specific orientation.

[0054] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below with reference to specific drawings.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0056] As Figures 1 to 6 shown, the torsion shaft bending machine of the present invention includes a frame 1, a slider 2 and a workbench 10. The left and right sides of the slider 2 are respectively driven by oil cylinders 3. An upper die 8 is fixed to the lower end of the slider 2, a lower die 9 is fixed to the workbench 10, a backgauge mechanism is provided at the rear side of the workbench 10, and the two sides of the slider 2 are driven by two symmetrically arranged oil cylinders 3 to move up and down. A partial load protection mechanism is provided at the rear side of the slider 2. When the slider 2 tilts in the left-right direction, it triggers shutdown and alarms.

[0057] As Figure 2 、 Figure 3 shown, the partial load protection mechanism includes a bumper 4, a transverse bracket 5, a vertical bracket 6 and a partial load protection travel switch SQ3. A bumper 4 is fixed to the upper part of the back surface of the slider 2 by screws, and the bumper 4 extends along the vertical axis of the slider 2.

[0058] A forward-extending transverse bracket 5 is fixed to the front side wall of the fuel tank 7, and the front end of the transverse bracket 5 is fixedly connected to an upward-extending vertical bracket 6. The vertical bracket 6 is a channel steel, and the opening of the channel steel faces the back surface of the slider 2.

[0059] The bumper 4 is a C-shaped steel, the C-shaped steel is located in the inner cavity of the channel steel and faces the opening of the channel steel, and the bottom wall of the C-shaped steel is fixed to the upper part of the back surface of the slider 2 by screws.

[0060] A vertical long groove 6a is provided on one side wall of the vertical bracket 6, and partial load protection travel switches SQ3 are respectively fixed to the upper and lower ends of the vertical long groove 6a, which is convenient for adjusting the distance between the two partial load protection travel switches SQ3. After the normally open contacts of the partial load protection travel switches SQ3 are connected in parallel, they are jointly connected to the alarm input port of the controller.

[0061] The sheet material is placed above the lower die 9. When the sheet material is bent using only half of the width of the slider 2, the slider 2 moves downward. The upper die 8 fixed to the lower part of the slider 2 first contacts the sheet material, and then continues to move downward, causing the sheet material to be bent and deformed in the lower die 9, and the slider 2 is subjected to a partial load pressure.

[0062] The sheet metal bending deformation requires a certain amount of pressure. The piston of the oil cylinder 3 at the end where the sheet metal is placed will not continue to move downward. While for the oil cylinder 3 at the other end, since there is no sheet metal to press and the lower die opening has a certain depth, when the pressures at both ends are not balanced, the piston in this oil cylinder 3 will continue to move downward, causing the slider 2 to tilt by a certain amount. The striker 4 on the back of the slider 2 tilts along with the slider 2. When the left side of the slider 2 is higher, the striker 4 presses the contact of the off-center load protection travel switch SQ3 below, sending a shutdown signal to the controller and alarming. When the right side of the slider 2 is higher, the striker 4 presses the contact of the off-center load protection travel switch SQ3 above, also triggering the bending machine to stop and alarm. In this way, the off-center load of the slider 2 can be controlled to avoid the failure of the balance arm being broken.

[0063] As Figure 7 shown, the hydraulic system includes the oil cylinder 3, the filling valve DZ, the three-position four-way solenoid valve, the electromagnetic ball valve YV3 and the two-position four-way electromagnetic directional control valve YV4. The neutral position function of the three-position four-way solenoid valve is of type O, that is, when in the neutral position, the P port, T port, A port and B port are not interconnected; the electromagnetic ball valve YV3 is a two-position two-way valve, and the electromagnetic ball valve YV3 is a pilot-operated check valve. The upper chambers of the two oil cylinders 3 are respectively connected to the oil tank through the filling valve DZ, and the inlet of the oil pump B1 is connected to the oil tank.

[0064] The outlet of the oil pump B1 is connected to the inlet of the cartridge valve C1, the outlet of the cartridge valve C1 is connected to the oil tank, the pilot port of the cartridge valve C1 is connected to the P port of the two-position four-way electromagnetic directional control valve YV4, and the A port of the two-position four-way electromagnetic directional control valve YV4 is connected to the oil tank. The two-position four-way electromagnetic directional control valve YV4 is set at the pump port to control the cartridge valve C1, and the outlet of the oil pump does not need to return to the oil tank through the P port to T port of the three-position four-way solenoid valve, expanding the application range of the hydraulic system.

[0065] The pilot port of the cartridge valve C1 is also connected to the oil tank through the pressure valve two F2, and the maximum pressure of the system is adjusted by the pressure valve two F2, usually set at 25 MPa.

[0066] The outlet of the oil pump B1 is also connected to the oil tank through the pressure valve one F1. The pressure valve one F1 is used as a remote pressure regulating valve for adjusting the working pressure during bending, and the pressure regulating range is 0 - 25 MPa.

[0067] The lower chamber oil circuits of the two oil cylinders 3 are also connected to the oil tank through the pressure valve three F3. The pressure valve three F3 is the safety valve for the lower chamber of the oil cylinder, set at 25 MPa, playing a protective role.

[0068] The outlet oil circuit of the oil pump B1 is connected to the P port of the three-position four-way solenoid valve, the T port of the three-position four-way solenoid valve is connected to the oil tank, and the A port of the three-position four-way solenoid valve is connected to the upper chambers of the two oil cylinders 3; the A port of the three-position four-way solenoid valve is also connected to the outlet oil circuit of the oil pump B1 through the check valve one D1 and the regulating valve one J1.

[0069] The B port of the three-position four-way solenoid valve is connected to the lower chamber oil circuit of the two oil cylinders 3 through the one-way valve two D2. The B port of the three-position four-way solenoid valve is also connected to the hydraulic control port of the filling valve DZ and the B port of the electromagnetic ball valve YV3. The A port of the electromagnetic ball valve YV3 is connected to the lower chamber oil circuit of the two oil cylinders 3 through the regulating valve three J3. The lower chamber oil circuit of the two oil cylinders 3 is also connected to the B port of the three-position four-way solenoid valve through the regulating valve two J2 and the support valve F4.

[0070] As Figure 8 shown, the automatic control system of the torsion shaft bending machine of the present invention includes an X-axis motor 11, a Y-axis motor, an inverter, and a controller.

[0071] A stroke adjustment screw is installed inside the piston of the oil cylinder. The stroke adjustment screw cooperates with the screw sleeve to control the lifting stroke of the slider and determine the bending angle of the sheet. The stroke adjustment screw is driven by the Y-axis motor, and a Y-axis encoder is installed at the rotor shaft end of the Y-axis motor.

[0072] The X-axis motor 11 is used to drive the stop finger of the back gauge mechanism to translate along the X-axis, and an X-axis encoder is installed at the rotor shaft end.

[0073] The L1, L2, and L3 ports of the inverter are connected to a 380VAC power supply. The U / T1, V / T2, and W / T3 ports of the inverter supply power to the main circuits of the X-axis motor 11 and the Y-axis motor. The main contacts of the main contactor KM1 are connected in series in the power supply circuit of the X-axis motor 11, and the main contacts of the main contactor KM2 are connected in series in the power supply circuit of the Y-axis motor. The inverter controls the rotational speeds of the X-axis motor 11 and the Y-axis motor according to the control signals of the controller.

[0074] Since the power of the X-axis motor 11 is 550W and the power of the Y-axis motor is 250W, and the two do not work simultaneously, the power of the inverter in this system only needs to match the power of the X-axis motor 11 and does not need to be increased to 750W. Because the Y-axis motor is smaller than the X-axis motor 11, in this solution, an overload protection for the Y-axis motor is achieved by adding a thermal overload relay FR1 to the main circuit of the Y-axis motor; the X-axis motor 11 is provided with overload protection by the inverter.

[0075] A step-changing contact switch SQ1 is connected between the I1 port of the controller and +24V. A variable-speed point contact switch SQ2 is connected between the I2 port of the controller and +24V. A foot-down contact switch SF1 is connected between the I3 port of the controller and +24V. A foot-up contact switch SF2 is connected between the I4 port of the controller and +24V. A mode selection contact switch SA2 is connected between the I5 port of the controller and +24V; after the off-center protection travel switches SQ3 and SQ4 are connected in parallel, they are jointly connected to the I6 port of the controller; a main motor start contact KM3 is connected between the I7 port of the controller and +24V; a normally closed contact of the thermal overload relay FR1 is connected between the I8 port of the controller and +24V.

[0076] A coil of a relay KA1 is connected between the Y1 port of the controller and 0V, and the contact of the relay KA1 controls the left coil YV1 of the three-position four-way solenoid valve; a coil of a relay KA2 is connected between the Y2 port of the controller and 0V, and the contact of the relay KA2 controls the right coil YV2 of the three-position four-way solenoid valve; a coil of a relay KA3 is connected between the Y3 port of the controller and 0V, and the contact of the relay KA3 controls the coil circuit of the electromagnetic ball valve YV3; a coil of a relay KA4 is connected between the Y4 port of the controller and 0V, and the contact of the relay KA4 controls the coil of the two-position four-way electromagnetic reversing valve YV4; a coil of a relay KA5 is connected between the Y5 port of the controller and 0V for standby.

[0077] A coil of a relay KA6 and a normally closed contact of a relay KA7 are connected in series between the Y6 port of the controller and 0V, and a coil of a relay KA7 and a normally closed contact of a relay KA6 are connected in series between the Y7 port of the controller and 0V. The relay KA6 controls the loop of the main contactor KM1 coil, and the relay KA7 controls the loop of the main contactor KM2 coil.

[0078] The communication interface of the controller is connected to the frequency converter through the MODBUS bus. The control system uses the YLD600 controller combined with the SS2-043 Shilin frequency converter to meet the high and low speed positioning requirements of the positioning axis. The high speed is used to control the rapid operation of the axis, and the low speed is used to control the precise positioning of the axis. The control system and the frequency converter abandon the previous contact connection control method and adopt the MODBUS communication method for connection, reducing the cable connection and improving the communication rate; simplifying the control circuit, making the distribution of the electrical cabinet more convenient, with fewer contacts and lower line failure rate. The system has intuitive hardware diagnosis and monitoring, making the machine tool more convenient for maintenance and use.

[0079] The output ends of the X-axis encoder and the Y-axis encoder are respectively connected to the encoder interface of the controller, and the position signal of the stop finger of the rear stock stop and the stroke signal of the slider are fed back to the controller. After internal processing by the system, the forward and reverse and high and low speed control of the X-axis motor 11 and the Y-axis motor are realized, and at the same time, the solenoid valve group is logically controlled according to the requirements of the machine tool actions.

[0080] A normally closed contact of a slider upper limit travel switch SQ5 is connected between the STR input end of the frequency converter and 0V, and a normally closed contact of a slider lower limit travel switch SQ6 is connected between the STF input end of the frequency converter and 0V. When the slider upper limit travel switch SQ5 or the slider lower limit travel switch SQ6 is pressed, the Y-axis motor stops running.

[0081] A normally closed contact of the front limit travel switch SQ7 for the finger stop is connected between the MO input terminal of the frequency converter and 0V, and a normally closed contact of the rear limit travel switch SQ8 for the finger stop is connected between the M1 input terminal of the frequency converter and 0V. When the front limit travel switch SQ7 for the finger stop or the rear limit travel switch SQ8 for the finger stop is pressed, the X-axis motor 11 stops running.

[0082] The working cycle of the bending machine is as follows:

[0083] 1. The oil pump runs idly

[0084] Start the motor, and its rotation direction should be in the direction of the arrow on the oil pump B1. The oil in the fuel tank is sucked into the oil pump B1, and the oil provided by the oil pump B1 returns to the fuel tank through the cartridge valve C1. At this time, all solenoid valves do not work.

[0085] 2. The slider moves down quickly

[0086] The output of the high level at the Y4 port of the controller makes the two-position four-way electromagnetic directional valve YV4 energized, and the pressure is built at the outlet of the oil pump B1; the output of the high level at the Y2 port of the controller makes the right coil of the three-position four-way solenoid valve YV2 energized, the P port is communicated with the A port, and the B port is communicated with the T port; the output of the high level at the Y3 port of the controller makes the electromagnetic ball valve YV3 energized, and the P port is communicated with the A port.

[0087] The oil at the outlet of the oil pump B1 enters the upper cavity of the oil cylinder 3 through the A port of the three-position four-way solenoid valve. At this time, a part of the oil in the lower cavity of the oil cylinder 3 returns to the fuel tank through the regulating valve J2, the support valve F4, and the T port of the three-position four-way solenoid valve; another part returns to the fuel tank through the regulating valve J3, the electromagnetic ball valve YV3, and the T of the three-position four-way solenoid valve. Due to the self-weight of the slider, a large amount of oil is sucked into the upper cavity of the oil cylinder 3 due to negative pressure through the filling valve DZ. Since the oil return circuit of the lower cavity of the oil cylinder 3 directly returns to the fuel tank, the slider can move down quickly.

[0088] 3. The slider feeds slowly

[0089] When the slider moves down quickly to the speed change point and keeps pressing the speed change point travel switch, the output of the low level at the Y3 port of the controller makes the electromagnetic ball valve YV3 de-energized, and the three-position four-way solenoid valve and the two-position four-way electromagnetic directional valve YV4 continue to be energized, closing the direct return oil channel of the lower cavity of the oil cylinder. The oil in the lower cavity of the oil cylinder can only return to the fuel tank through the support valve F4. The oil passing area of the oil return circuit decreases, and the filling valve DZ closes. The slider changes from moving down quickly to feeding slowly. Decelerating in advance can reduce the impact of the upper die on the sheet metal and also reduce the impact vibration of the machine tool itself, thereby improving the bending accuracy. When the slider feeds slowly, the support valve F4 keeps the back pressure of the lower cavity of the oil cylinder at 3MPa.

[0090] When the upper die contacts the sheet metal, the system pressure rises, which then pushes the slider to continue moving downward until the sheet metal is bent and formed. After the pressure continues to rise and reaches the pressure value set by the first pressure valve F1, a part of the oil fluid at the outlet of the oil pump B1 returns to the fuel tank through the first pressure valve F1, and most of the oil fluid overflows back to the fuel tank through the cartridge valve C1.

[0091] 4. Slider pressure holding

[0092] The pressure holding process of the bending machine is actually a working feed pressure holding process, and the overflow pressure holding method is adopted.

[0093] 5. Slider pressure relief

[0094] The slider pressure relief is an internal pressure relief method. After the pressure holding delay sends a signal, all solenoid valves lose power to ensure reliable unloading; the pressure oil in the upper cavity of the oil cylinder returns to the fuel tank through the one-way valve D1 and the regulating valve J1, realizing rapid internal leakage. The pressure relief shock is achieved by adjusting the opening degree of the regulating valve J1.

[0095] 6. Slider return stroke

[0096] After the pressure relief delay time arrives, the left coil YV1 of the three-position four-way solenoid valve is energized when the Y1 port of the controller outputs a high level, the P port communicates with the B port, and the A port communicates with the T port. At the same time, the two-position four-way electromagnetic directional valve YV4 is energized when the Y4 port of the controller outputs a high level. The oil fluid at the outlet of the oil pump B1 flows out from the B port of the three-position four-way solenoid valve, passes through the electromagnetic ball valve YV3, the regulating valve J3, and the one-way valve D2 and enters the lower cavity of the oil cylinder. The oil pump B1 runs idly. At the same time, the control oil opens the filling valve DZ. Most of the oil fluid in the upper cavity of the oil cylinder returns to the fuel tank through the filling valve DZ; a small amount of oil fluid returns to the fuel tank through the T port of the three-position four-way solenoid valve, and the slider performs a return stroke action. When the return stroke reaches the upper limit travel switch and sends a signal, all solenoid valves lose power.

[0097] As Figures 3 to 6 shown, the back gauge mechanism includes an X-axis drive mechanism, an R-axis drive mechanism, and a back gauge finger 28. The X-axis drive mechanism includes an X-axis motor 11, an X-axis synchronous belt 12, X-axis synchronous pulleys 13, an X-axis ball screw 14, an X-axis screw nut 15, an X-axis guide block 17, an X-axis guide rail 18, and an X-axis slide plate 16.

[0098] The X-axis ball screw 14 is symmetrically located on the left and right sides of the frame 1 and extends in the front-rear direction. The rear ends of the two X-axis ball screws 14 are respectively equipped with X-axis synchronous pulleys 13, and X-axis screw nuts 15 are respectively screwed on the two X-axis ball screws 14. The X-axis guide block 17 and the X-axis slide plate 16 are connected to the X-axis screw nut 15.

[0099] After the X-axis motor 11 starts, its driving pulley drives two X-axis synchronous pulleys 13 to rotate through the X-axis synchronous belt 12. The two X-axis synchronous pulleys 13 respectively drive two X-axis ball screws 14 to rotate synchronously. The two X-axis screw nuts 15 translate back and forth along the X-axis ball screws 14 respectively. The X-axis screw nuts 15 drive the X-axis guide blocks 17 and the X-axis slide plates 16 to translate synchronously. An R-axis driving mechanism is installed between the X-axis slide plates 16 on both sides. When the X-axis slide plates 16 translate back and forth, the R-axis driving mechanism drives the rear stop fingers 28 to translate back and forth to provide a limit for the rear edge of the plate.

[0100] The R-axis driving mechanism includes an R-axis motor, an R-axis synchronous rod 20, an R driving shaft 21, an R-axis gear 22, an R-axis rack 23, an R-axis bracket 26, a rear stop frame 27, an R-axis guide seat 24 and an R-axis guide rail 25. The R-axis guide seats 24 are respectively fixed on the X-axis guide blocks 17 and remain stationary. The middle sections of the R-axis guide rails 25 are respectively embedded in the R-axis guide seats 24. The cross section of the R-axis bracket 26 is L-shaped. The outside is fixed on the R-axis guide rail 25. The R-axis rack 23 is fixed on the front side of the R-axis bracket 26. The R-axis bracket 26 and the R-axis rack 23 lift and lower synchronously with the R-axis guide rail 25.

[0101] The input end of the R-axis speed reducer 19 is driven by the R-axis motor. One side of the output end of the R-axis speed reducer 19 is connected to the R driving shaft 21, and the other side is connected to the R driving shaft 21 through the R-axis synchronous rod 20. Driven by the R-axis motor and the R-axis speed reducer 19, the two R driving shafts 21 rotate synchronously. The R-axis gears 22 at both ends respectively drive the R-axis racks 23 to lift and lower. The R-axis racks 23 drive the R-axis brackets 26 to lift and lower. The tops of the two R-axis brackets 26 are connected by the rear stop frame 27 to form a gantry shape. The two rear stop fingers 28 are fixed on the upper part of the rear stop frame 27 and are symmetrically provided with two. In this way, through the drive of the R-axis motor, the height of the rear stop fingers 28 can be adjusted.

[0102] The above is only the preferred feasible embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention. It does not limit the patent protection scope of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. Except for the above embodiments, without departing from the spirit and scope of the present invention, the present invention can also have other implementation manners. The present invention will also have various changes and improvements. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention. The protection scope required by the present invention is defined by the appended claims and their equivalents. The technical features not described in the present invention can be realized by or adopted the existing technologies and will not be elaborated here.

Claims

1. A torsion shaft bending machine with an eccentric load protection function, comprising a frame, a slider and a workbench, characterized in that, It also includes: An oil cylinder that drives the left and right sides of the slider respectively; An upper die that is connected to the lower end of the slider, presses above the plate, and cooperates with the lower die to bend the plate; A lower die that is located below the plate and fixed on the workbench; A rear stop mechanism used to limit the rear edge of the plate; An off-center load protection mechanism that triggers shutdown and alarms when the slider tilts in the left-right direction; The off-center load protection mechanism includes: A striker that is fixed to the upper part of the back surface of the slider and extends along the vertical axis of the slider; A horizontal bracket that is fixed on the front side wall of the fuel tank and extends towards the back surface of the slider; A vertical bracket whose lower end is fixedly connected to the front end of the horizontal bracket; An off-center load protection travel switch, with one fixed at each of the upper and lower ends of the vertical bracket. The contacts of the two off-center load protection travel switches are respectively attached to the side wall of the striker. When the striker tilts and triggers any one of the off-center load protection travel switches, the bending machine shuts down and alarms; The upper chambers of the two oil cylinders (1a) are respectively connected to the fuel tank through a filling valve (DZ). The inlet of the oil pump (B1) is connected to the fuel tank. The outlet of the oil pump (B1) is connected to the P port of a three-position four-way solenoid valve. The T port of the three-position four-way solenoid valve is connected to the fuel tank. The A port of the three-position four-way solenoid valve is connected to the upper chambers of the two oil cylinders (1a). The A port of the three-position four-way solenoid valve is also connected to the outlet oil circuit of the oil pump (B1) through a check valve one (D1) and a regulating valve one (J1); The B port of the three-position four-way solenoid valve is connected to the lower chamber oil circuit of the two oil cylinders (1a) through a check valve two (D2). The B port of the three-position four-way solenoid valve is also connected to the hydraulic control port of the filling valve (DZ) and the B port of the electromagnetic ball valve (YV3). The A port of the electromagnetic ball valve (YV3) is connected to the lower chamber oil circuit of the two oil cylinders (1a) through a regulating valve three (J3); The lower chamber oil circuits of the two oil cylinders (1a) are also connected to the B port of the three-position four-way solenoid valve through a regulating valve two (J2) and a support valve (F4). The neutral position function of the three-position four-way solenoid valve is of the O type.

2. The torsion shaft bending machine with off-center load protection function according to claim 1, characterized in that: The outlet of the oil pump (B1) is also connected to the inlet of the cartridge valve (C1). The outlet of the cartridge valve (C1) is connected to the fuel tank. The hydraulic control port of the cartridge valve (C1) is connected to the P port of the two-position four-way electromagnetic reversing valve (YV4). The A port of the two-position four-way electromagnetic reversing valve (YV4) is connected to the fuel tank.

3. The torsion shaft bending machine with off-center load protection function according to claim 1, characterized in that, The rear stop mechanism includes: An X-axis drive mechanism that adjusts the front and rear positions of the R-axis drive mechanism; An R-axis drive mechanism that adjusts the height of the rear stop finger; A rear stop finger that is located on the R-axis mechanism and abuts against the rear edge of the plate.

4. The torsion shaft bending machine with an off-center load protection function according to claim 3, characterized in that, The X-axis drive mechanism includes: An X-axis motor that drives two X-axis synchronous pulleys to rotate through an X-axis synchronous belt; X-axis synchronous pulleys that are respectively installed at the shaft ends of two X-axis ball screws; X-axis ball screws that are symmetrically located on the left and right sides of the frame and extend in the front-rear direction; X-axis screw nuts that are respectively screwed onto the two X-axis ball screws; X-axis guide blocks that are respectively fixedly connected to the two X-axis screw nuts and translate along the X-axis guide rail; X-axis guide rails that are respectively fixed on the left and right sides of the frame; An X-axis slide plate that is fixedly connected to the X-axis guide block or the X-axis screw nut and carries the R-axis drive mechanism.

5. The torsion shaft bending machine with off-center load protection function according to claim 4, characterized in that, The R-axis drive mechanism includes: R-axis guide seats that are respectively fixed on the X-axis guide blocks; The R-axis guide rails are respectively embedded in the R-axis guide seats in the middle section and perform lifting movements; The R-axis brackets are respectively fixedly connected to the R-axis guide rails and lift synchronously; The R-axis racks are respectively fixed on the front sides of the R-axis brackets and lift synchronously; The R-axis gears are respectively installed on the R drive shafts, drive the R-axis racks and drive the R-axis brackets to lift; The R-axis motors drive the two R drive shafts to rotate synchronously through the R-axis speed reducers and R-axis synchronizing rods; The rear stock stop frame is connected to the tops of the two R-axis brackets to form a portal shape; The rear stock stop fingers are fixed on the upper part of the rear stock stop frame and two are symmetrically provided.

6. The torsion shaft bending machine with off-center load protection function according to claim 3, characterized in that The control system includes: The Y-axis motor drives the stroke adjustment screw to rotate. The stroke adjustment screw is arranged in the piston of the oil cylinder and cooperates with the screw sleeve to control the lifting stroke of the slider. The rotor shaft end of the Y-axis motor is equipped with a Y-axis encoder; The X-axis motor has an X-axis encoder installed at its rotor shaft end; The frequency converter supplies power to the X-axis motor and the Y-axis motor and adjusts the speed. And a thermal overload relay is connected in series in the power supply circuit of the Y-axis motor for overload protection; The controller, its communication interface is connected to the frequency converter through the MODBUS bus; the output ends of the X-axis encoder and the Y-axis encoder are respectively connected to the encoder interface of the controller, the step change, speed change point, mode selection, and main motor start contact switches are respectively connected to the action signal input ends of the controller; the contact switch of the thermal overload relay is connected in series in the fault signal input end of the controller to realize the overload protection of the Y-axis motor.

7. The torsion shaft bending machine with off-center load protection function according to claim 6, characterized in that The two partial load protection travel switches are connected in parallel and then connected to the fault signal input end of the controller. The signal input end of the frequency converter is connected in series with the normally closed contacts of the upper and lower limit travel switches of the slider and the normally closed contacts of the front and rear limit travel switches of the stock stop fingers.

8. The torsion shaft bending machine with off-center load protection function according to claim 6, characterized in that, The main contact of the main contactor KM1 is connected in series in the power supply circuit of the X-axis motor, and the coil of the main contactor KM1 is controlled by the contact of the relay KA6; The main contact of the main contactor KM2 is connected in series in the power supply circuit of the Y-axis motor, and the coil of the main contactor KM2 is controlled by the contact of the relay KA7; The coil of the relay KA6 and the normally closed contact of the relay KA7 are connected in series at a certain output port of the controller, and the coil of the relay KA7 and the normally closed contact of the relay KA6 are connected in series at another output port of the controller.

9. The torsion shaft bending machine with off-center load protection function according to claim 8, characterized in that, The working steps are as follows: S1. After the oil pump is started, the two-position four-way electromagnetic directional valve YV4 is energized, and pressure is built at the outlet of the oil pump; S2. The slider quickly descends: the right coil YV2 of the three-position four-way solenoid valve is energized, and the pressure oil enters the upper cavity of the oil cylinder. Part of the oil in the lower cavity of the oil cylinder returns to the oil tank through the regulating valve J2, the support valve F4, and the T port of the three-position four-way solenoid valve; another part passes through the regulating valve J3, the electromagnetic ball valve YV3, and the T of the three-position four-way solenoid valve returns to the oil tank; S3. The slider advances during work: when the slider quickly descends to the speed change point, the electromagnetic ball valve YV3 is de-energized, closing the direct return oil tank channel of the lower cavity of the oil cylinder. The oil in the lower cavity of the oil cylinder can only return to the oil tank through the support valve F4. The slider changes from quickly descending to slowly advancing during work until the sheet metal is bent and formed; S4. The slider holds pressure; S5. Slide block pressure relief: All solenoid valves are de-energized; the pressure oil in the upper chamber of the oil cylinder returns to the oil tank through check valve D1 and regulating valve J1, achieving rapid internal leakage. S6. Slide block return stroke: The left coil YV1 of the three-position four-way solenoid valve is energized, and the pressure oil enters the lower chamber of the oil cylinder through electromagnetic ball valve YV3, regulating valve J3, and check valve D2. Most of the oil in the upper chamber of the oil cylinder returns to the oil tank through the filling valve DZ; a small amount of oil returns to the oil tank through the T port of the three-position four-way solenoid valve. The slide block returns to the upper limit travel switch to send a signal, and all solenoid valves are de-energized.

10. The torsion shaft bending machine with off-center load protection function according to claim 8, characterized in that, When the slide block tilts, the normally open contact of one of the off-load protection travel switches closes. The input digital quantity port of the controller receives the signal, which is sent to the CPU through the opto-coupler circuit. The shutdown signal sent by the CPU after calculation is output through the opto-isolation circuit. The output terminal of the digital quantity port of the controller de-energizes the coils of each relay, causing the solenoid valves of each hydraulic system to be de-energized; at the same time, the communication port of the controller sends a signal to the frequency converter through the MODBUS bus, causing the X-axis motor and Y-axis motor to stop operating.

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