A gas-liquid mixing action system suitable for a wide temperature range

Abstract

A gas-liquid mixing action system suitable for wide temperature range, comprising a first gas cylinder and a second gas cylinder, the first gas cylinder provides power for the extension and retraction of the gas cylinder, the second gas cylinder provides pressure compensation for the first gas cylinder, the first, second, fourth and fifth electromagnetic valves and the first check valve control the action of the gas cylinder, the fourth and fifth electromagnetic valves and the first check valve, the first and second hydraulic cylinders and the hydraulic pump recover the gas with pressure. The combination of the first and second hydraulic cylinders and the hydraulic pump forms a set of "pump" that alternately inhales and exhausts the gas, through the different switch state combinations of the second, third, fourth and fifth electromagnetic valves, the gas with pressure in the gas cylinder is recovered into the first gas cylinder to realize energy and gas recovery, the gas in the first gas cylinder is pumped out and discharged into the second gas cylinder to realize the "unloading" of the first gas cylinder, the gas in the second gas cylinder is pumped out and discharged into the first gas cylinder to realize the "pressure compensation" of the first gas cylinder, so that the application can be used in a wide temperature range and can also save energy for the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydraulic / pneumatic transmission technology, and particularly relates to a gas-liquid hybrid pneumatic system suitable for a wide temperature range. BACKGROUND

[0002] In a mobile device using a gas cylinder as a power source, especially in a mobile device in which the ambient temperature often changes greatly, the high-pressure gas in the gas cylinder will change greatly with the temperature, and at this time, an additional gas charging and discharging control unit needs to be installed to stabilize the gas pressure in the gas cylinder, so as to ensure the stability of the gas pressure in the gas cylinder. After the high-pressure gas drives the cylinder to complete the action, the gas remaining in the large-volume cavity will be directly discharged back to the low-pressure gas storage tank when the cylinder reverses, causing energy waste. In order to alleviate the influence of ambient temperature change on the gas pressure in the high-pressure gas cylinder, an additional gas charging and discharging control unit is often installed to stabilize the gas pressure in the gas cylinder, and the gas charging and discharging control unit makes the actuating system more complex, larger in size and heavier. SUMMARY

[0003] In order to overcome the above problems, the present application provides a gas-liquid hybrid pneumatic system suitable for a wide temperature range.

[0004] The technical scheme adopted by the present application is as follows: a gas-liquid hybrid pneumatic system suitable for a wide temperature range, comprising a first hydraulic control cylinder (61), a second hydraulic control cylinder (62) and a bidirectional hydraulic pump (7), the liquid chambers of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) are respectively connected with two oil ports of the bidirectional hydraulic pump (7), the bidirectional hydraulic pump (7) sucks out the hydraulic oil in one of the liquid chambers of the hydraulic control cylinders and discharges it into the other hydraulic cylinder; the bidirectional hydraulic pump (7) is connected with a motor, and the direction of the hydraulic oil sucked out or discharged is controlled by the rotation of the motor.

[0005] The gas chamber outlet of the first hydraulic control cylinder (61) and the gas chamber outlet of the second hydraulic control cylinder (62) are respectively connected with the first gas cylinder (51) through the right valve port of the fourth electromagnetic valve (44) and the right valve port of the fifth electromagnetic valve (45), and the left valve port of the second electromagnetic valve (42); the gas chamber outlet of the first hydraulic control cylinder (61) and the gas chamber outlet of the second hydraulic control cylinder (62) are respectively connected with the rodless chamber of the cylinder (2) through the left valve port of the fourth electromagnetic valve (44) and the left valve port of the fifth electromagnetic valve (45), and the first one-way valve (31); the gas chamber outlet of the first hydraulic control cylinder (61) and the gas chamber outlet of the second hydraulic control cylinder (62) are respectively connected with the second gas cylinder (52) through the left valve port of the fourth electromagnetic valve (44) and the left valve port of the fifth electromagnetic valve (45), and the left valve port of the third electromagnetic valve (43).

[0006] The first outlet of the first gas cylinder (51) is connected with the rod cavity of the gas cylinder (2), and the first outlet of the first gas cylinder (51) is connected with the rodless cavity of the gas cylinder (2) through the first electromagnetic valve (41), and the second pressure sensor (12) is installed at the first outlet of the first gas cylinder (51); the second outlet of the first gas cylinder (51) is connected with the inflation port A through the second one-way valve (32), and the external gas source inflates the first gas cylinder (51) through the inflation port A;

[0007] The hydraulic pump (7) controls the liquid cavity pressure of the first liquid control cylinder (61) and the second liquid control cylinder (62) by forward and reverse rotation, when the interface with the increased gas cavity volume in the first liquid control cylinder (61) and the second liquid control cylinder (62) is communicated with the rodless cavity of the gas cylinder (2), and the interface with the reduced gas cavity volume is communicated with the gas cylinder (51), the gas in the gas cylinder can be transferred to the gas cylinder (51), and the gas and energy are recovered for the system;

[0008] When the interface with the increased gas cavity volume in the first liquid control cylinder (61) and the second liquid control cylinder (62) is communicated with the gas cylinder (52), and the interface with the reduced gas cavity volume is communicated with the gas cylinder (51), the gas in the gas cylinder (52) can be transferred to the gas cylinder (51), and the gas cylinder (51) is pressurized;

[0009] When the interface with the increased gas cavity volume in the first liquid control cylinder (61) and the second liquid control cylinder (62) is communicated with the gas cylinder (51), and the interface with the reduced gas cavity volume is communicated with the gas cylinder (52), the gas in the gas cylinder (51) can be transferred to the gas cylinder (52), and the gas cylinder (51) is unloaded.

[0010] Further, the bidirectional hydraulic pump (7) can be replaced by a quantitative pump or an external oil source, and the volume change of the liquid cavity of the first liquid control cylinder (61) and the second liquid control cylinder (62) is controlled through the reversing valve, so that the volume change of the gas cavity of the first liquid control cylinder (61) and the second liquid control cylinder (62) is controlled.

[0011] Further, the gas cylinder can be replaced by a spring return type single rod cylinder, at this time the reset spring is installed in the rod cavity of the gas cylinder, and the reset power is provided for the gas cylinder piston by the spring.

[0012] Further, the gas cylinder can be replaced by a double-acting double-rod cylinder, at this time the on-off of the two side cavities of the gas cylinder piston is controlled by the electromagnetic valve, and the side with smaller stress area in the two cavities of the gas cylinder is communicated with the one-way valve.

[0013] Further, when the system is in gas or energy recovery, pressure charging, unloading and other actions, when any one of the first pressure sensor (11) or the third pressure sensor (13) at the suction port of the bidirectional hydraulic pump (7) is zero, the hydraulic pump quickly reverses rotation to continuously perform the above actions. Further, the controller, the signal input end of the controller is respectively connected with the first pressure sensor (11), the second pressure sensor (12), the third pressure sensor (13); the signal output end of the controller is respectively connected with the first hydraulic cylinder (61), the second hydraulic cylinder (62), the bidirectional hydraulic pump (7), the first electromagnetic valve (41), the second electromagnetic valve (42), the third electromagnetic valve (43), the fourth electromagnetic valve (44), the fifth electromagnetic valve (45);

[0014] When the controller issues the extension command, the first electromagnetic valve is opened, and the cylinder piston is extended;

[0015] When the controller issues the retraction command, the second electromagnetic valve is opened, the fourth and fifth electromagnetic valves are alternately opened and closed, and the bidirectional hydraulic pump is started. When the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the first hydraulic cylinder cavity needs to be connected with the low-pressure oil. When the second pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed, and the second hydraulic cylinder cavity needs to be connected with the low-pressure oil. When the third pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed again, and the fourth and fifth electromagnetic valves and the hydraulic pump rotation direction are alternately opened and closed until the cylinder piston moves to the upper limit, and the hydraulic pump and all electromagnetic valves are closed.

[0016] When the controller issues the pressure charging signal, the second and third electromagnetic valves are opened, the fourth and fifth electromagnetic valves are alternately opened and closed, and the bidirectional hydraulic pump is started. When the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the first hydraulic cylinder cavity needs to be connected with the low-pressure oil. When the second pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed, and the second hydraulic cylinder cavity needs to be connected with the low-pressure oil. When the third pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed again, and the fourth and fifth electromagnetic valves and the hydraulic pump rotation direction are alternately opened and closed until the first cylinder reaches the rated pressure, and the hydraulic pump and all electromagnetic valves are closed.

[0017] When the controller sends the unloading signal, the second and third electromagnetic valves open, the fourth and fifth electromagnetic valves open / close alternately, and the hydraulic pump starts to rotate. When the fourth electromagnetic valve opens, the fifth electromagnetic valve closes, and the second hydraulic cylinder needs to be connected with the low-pressure oil. When the pressure of the third pressure sensor is zero, the fourth and fifth electromagnetic valves change direction, and the first hydraulic cylinder needs to be connected with the low-pressure oil. When the pressure of the second pressure sensor is zero, the fourth and fifth electromagnetic valves change direction again. The fourth and fifth electromagnetic valves and the hydraulic pump rotate alternately until the first gas cylinder reaches the rated pressure, and then the hydraulic pump, the first electromagnetic valve (41), the second electromagnetic valve (42), the third electromagnetic valve (43), the fourth electromagnetic valve (44) and the fifth electromagnetic valve are closed.

[0018] The beneficial effects of the present application are:

[0019] (1) The problem of energy waste and pressure deviation can be solved. The present application can recover high-pressure gas in the cylinder and supplement or unload high-pressure gas in the gas cylinder.

[0020] (2) Two hydraulic cylinders reciprocate alternately to realize continuous suction and exhaust;

[0021] (3) Energy saving by recovering gas under pressure;

[0022] (4) Wider temperature range and more accurate pressure control; BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the present application.

[0024] Reference signs: 11-first pressure sensor, 12-second pressure sensor, 13-third pressure sensor, 2-cylinder, 31-first one-way valve, 32-second one-way valve, 33-third one-way valve, 41-first electromagnetic valve, 42-second electromagnetic valve, 43-third electromagnetic valve, 44-fourth electromagnetic valve, 45-fifth electromagnetic valve, 51-first gas cylinder, 52-second gas cylinder, 61-first hydraulic cylinder, 62-second hydraulic cylinder, 7-hydraulic pump. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" appear only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, terms such as "mounting", "connection", "connection" should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0028] Referring to the drawings, a gas-liquid mixing action system suitable for a wide temperature range includes a first hydraulic gas cylinder 61, a second hydraulic gas cylinder 62 and a bidirectional hydraulic pump 7, the liquid chambers of the first hydraulic gas cylinder 61 and the second hydraulic gas cylinder 62 are connected with two oil ports of the bidirectional hydraulic pump 7 respectively, the bidirectional hydraulic pump 7 sucks out the hydraulic oil in one of the liquid chambers of the hydraulic gas cylinders and discharges it into the other hydraulic gas cylinder; the bidirectional hydraulic pump 7 is connected with a motor, and the rotation of the motor controls the direction of the hydraulic oil suction or discharge;

[0029] The first oil port of the first hydraulic gas cylinder 61 and the first oil port of the second hydraulic gas cylinder 62 are connected with the rodless chamber of the cylinder 2 through a first one-way valve 31, at the same time, the first oil port of the first hydraulic gas cylinder 61 and the first oil port of the second hydraulic gas cylinder 62 are connected with the second gas cylinder 52 through a third electromagnetic valve 43; the second oil port of the first hydraulic gas cylinder 61 and the second oil port of the second hydraulic gas cylinder 62 are connected with the outlet of the first gas cylinder 51 through a second electromagnetic valve 42;

[0030] The outlet of the first gas cylinder 51 is connected with the rod chamber of the cylinder 2 through a second pressure sensor 12, and the outlet of the first gas cylinder 51 is connected with the rodless chamber of the cylinder 2 through a first electromagnetic valve 41; the inlet of the first gas cylinder 51 is connected with the charging port A through a second one-way valve 32, and the external gas source is connected with the first gas cylinder 51 to charge the gas; when the second pressure sensor displays that the system reaches the rated pressure, the external gas source is removed. The second gas cylinder outlet is communicated with the charging port B through a third one-way valve, and the external gas source is connected with the second gas cylinder through the interface B to charge the gas, and when the pressure reaches the preset pressure, the external gas source is removed.

[0031] The hydraulic pump 7 controls the liquid chamber pressure of the first and second hydraulic cylinders 61 and 62 by forward and reverse rotation, and when the interfaces with the increased gas chamber volume of the first and second hydraulic cylinders 61 and 62 are communicated with the cylinder 2 non-rod cavity and the interfaces with the decreased gas chamber volume are communicated with the gas cylinder 51, the gas in the cylinder can be transferred to the gas cylinder 51 to recover the gas and energy of the system;

[0032] When the interfaces with the increased gas chamber volume of the first and second hydraulic cylinders 61 and 62 are communicated with the gas cylinder 52 and the interfaces with the decreased gas chamber volume are communicated with the gas cylinder 51, the gas in the gas cylinder 52 can be transferred to the gas cylinder 51 to supplement the pressure of the gas cylinder 51.

[0033] When the interfaces with the increased gas chamber volume of the first and second hydraulic cylinders 61 and 62 are communicated with the gas cylinder 51 and the interfaces with the decreased gas chamber volume are communicated with the gas cylinder 52, the gas in the gas cylinder 51 can be transferred to the gas cylinder 52 to unload the gas cylinder 51.

[0034] In some embodiments of the application, the bidirectional hydraulic pump 7 can be replaced by a constant displacement pump or an external oil source, and the volume change of the liquid chambers of the first and second hydraulic cylinders 61 and 62 is controlled by a reversing valve, so as to control the volume change of the gas chambers of the first and second hydraulic cylinders 61 and 62.

[0035] In some embodiments of the application, the cylinder is a spring return single rod cylinder, and a return spring is installed in the rod cavity of the cylinder to provide return power for the cylinder piston.

[0036] In some embodiments of the application, the cylinder is a double-acting double-rod cylinder, and the on-off of the cavities on both sides of the cylinder piston is controlled by a solenoid valve, and the side with smaller stress area in the two cavities of the cylinder is communicated with the one-way valve 31.

[0037] In some embodiments of the application, when the gas pressure in the gas cylinder 51 is higher than the safe pressure due to temperature rise or other reasons, the first and second hydraulic cylinders 61 and 62 can transfer the gas in the gas cylinder 51 to the gas cylinder 52 to unload the gas cylinder 51,

[0038] In some embodiments of the application, when any one of the first pressure sensor (11) or the third pressure sensor (13) at the oil suction port of the bidirectional hydraulic pump (7) is zero during the gas or energy recovery, pressure charging, unloading and other actions of the system, the hydraulic pump quickly reverses to continuously perform the above actions.

[0039] In some embodiments of the application, the bidirectional hydraulic pump can be replaced by a constant displacement pump or an external oil source, and the volume change of the liquid chambers of the first and second hydraulic cylinders is controlled by a reversing valve, so as to control the volume change of the two gas chambers.

[0040] In some embodiments of the present application, the air cylinder can be replaced by any form, when selected as a spring return single rod cylinder, a return spring is installed in the rod cavity, and the spring provides the return power for the piston; when selected as a double-acting double rod cylinder, the on-off of the cavity on both sides of the piston needs to be controlled by the electromagnetic valve, and the gas recovery needs to be communicated with the side with smaller stress area.

[0041] In addition, when the control system issues an "extension" instruction, the first electromagnetic valve is opened, and the cylinder piston is extended; when the control system issues a "retraction" instruction, the second electromagnetic valve is opened, the fourth and fifth electromagnetic valves are alternately opened / closed, and the bidirectional hydraulic pump is started; when the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the first hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the second pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed, and the second hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the third pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed again, and the fourth and fifth electromagnetic valves and the hydraulic pump rotation direction are alternately opened / closed until the cylinder piston moves to the upper limit, the hydraulic pump and all electromagnetic valves are closed; when the control system issues a "pressure compensation" signal, the second and third electromagnetic valves are opened, the fourth and fifth electromagnetic valves are alternately opened / closed, and the bidirectional hydraulic pump is started; when the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the first hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the second pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed, and the second hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the third pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed again, and the fourth and fifth electromagnetic valves and the hydraulic pump rotation direction are alternately opened / closed until the first gas cylinder reaches the rated pressure, the hydraulic pump and all electromagnetic valves are closed; when the control system issues a "unloading" signal, the second and third electromagnetic valves are opened, the fourth and fifth electromagnetic valves are alternately opened / closed, and the bidirectional hydraulic pump is started; when the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the second hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the third pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed, and the first hydraulic cylinder liquid cavity needs to be communicated with the low-pressure oil; when the second pressure sensor pressure is zero, the fourth and fifth electromagnetic valves are reversed again, and the fourth and fifth electromagnetic valves and the hydraulic pump rotation direction are alternately opened / closed until the first gas cylinder reaches the rated pressure, the hydraulic pump and all electromagnetic valves are closed.

[0042] The content described in the embodiments of the present application is only a list of implementation forms of the inventive concept, and the protection scope of the present application should not be regarded as limited to the specific forms stated in the embodiments, and the protection scope of the present application also includes equivalent technical means that can be thought of by those skilled in the art according to the inventive concept.

Claims

1. A gas-liquid mixing action system suitable for a wide temperature range, characterized by: It includes a first hydraulic control cylinder (61), a second hydraulic control cylinder (62) and a bidirectional hydraulic pump (7), the liquid cavity of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) is connected with the two oil ports of the bidirectional hydraulic pump (7), the bidirectional hydraulic pump (7) sucks out the hydraulic oil in one of the liquid control cylinder oil cavities and discharges it into the other liquid control cylinder; the bidirectional hydraulic pump (7) is connected with the motor, and the direction of the hydraulic oil suction or discharge is controlled by the rotation of the motor; The gas cavity outlet of the first hydraulic control cylinder (61) and the gas cavity outlet of the second hydraulic control cylinder (62) are respectively connected with the second outlet of the first gas cylinder (51) through the right valve port of the fourth electromagnetic valve (44) and the right valve port of the fifth electromagnetic valve (45), the left valve port of the second electromagnetic valve (42); the gas cavity outlet of the first hydraulic control cylinder (61) and the gas cavity outlet of the second hydraulic control cylinder (62) are respectively connected with the rodless cavity of the cylinder (2) through the left valve port of the fourth electromagnetic valve (44) and the left valve port of the fifth electromagnetic valve (45), the first one-way valve (31); the gas cavity outlet of the first hydraulic control cylinder (61) and the gas cavity outlet of the second hydraulic control cylinder (62) are respectively connected with the second gas cylinder (52) through the left valve port of the fourth electromagnetic valve (44) and the left valve port of the fifth electromagnetic valve (45), the left valve of the third electromagnetic valve (43); The first outlet of the first gas cylinder (51) is connected with the rod cavity of the cylinder (2), and the first outlet of the first gas cylinder (51) is connected with the rodless cavity of the cylinder (2) through the first electromagnetic valve (41), and a second pressure sensor (12) is installed at the first outlet of the first gas cylinder (51); the second outlet of the first gas cylinder (51) is connected with the charging port A through the second one-way valve (32), and an external gas source charges the first gas cylinder (51) through the charging port A; The bidirectional hydraulic pump (7) controls the liquid cavity pressure of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) by forward and reverse rotation, when the interface with the increased gas cavity volume of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) is communicated with the rodless cavity of the cylinder (2), and the interface with the reduced gas cavity volume is communicated with the first gas cylinder (51), the gas in the cylinder can be transferred to the first gas cylinder (51), and the gas and energy of the system are recovered; When the interface with the increased gas cavity volume of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) is communicated with the second gas cylinder (52), and the interface with the reduced gas cavity volume is communicated with the first gas cylinder (51), the gas in the second gas cylinder (52) can be transferred to the first gas cylinder (51), and the first gas cylinder (51) is pressure compensated; When the interface with the increased gas cavity volume of the first hydraulic control cylinder (61) and the second hydraulic control cylinder (62) is communicated with the first gas cylinder (51), and the interface with the reduced gas cavity volume is communicated with the second gas cylinder (52), the gas in the first gas cylinder (51) can be transferred to the second gas cylinder (52), and the first gas cylinder (51) is unloaded.

2. A gas-liquid mixing system suitable for a wide temperature range according to claim 1, characterized in that: The bidirectional hydraulic pump (7) can be replaced by a quantitative pump or an external oil source, and the volume changes of the first hydraulic cylinder (61) and the second hydraulic cylinder (62) are controlled by a reversing valve, so as to control the volume changes of the air chambers of the first hydraulic cylinder (61) and the second hydraulic cylinder (62).

3. A gas-liquid mixing system suitable for a wide temperature range according to claim 1, characterized in that: The cylinder is a spring return type single rod cylinder, and a return spring is arranged in the rod cavity of the cylinder, so that the spring provides a return power for the cylinder piston.

4. The gas-liquid mixing system suitable for wide temperature range according to claim 1, characterized in that: The cylinder is a double-acting double rod cylinder, and the on-off of the cavities on both sides of the cylinder piston is controlled by an electromagnetic valve. The side with a smaller force area in the two cavities of the cylinder is communicated with the first one-way valve (31).

5. A gas-liquid mixing system suitable for a wide temperature range according to claim 1, characterized in that: When the system performs gas or energy recovery, pressure charging, and unloading actions, when any one of the first pressure sensor (11) or the third pressure sensor (13) at the oil suction port of the bidirectional hydraulic pump (7) is zero, the bidirectional hydraulic pump quickly reverses to continuously perform the above actions.

6. A gas-liquid mixing system suitable for a wide temperature range according to any one of claims 1, 3-5, characterized in that: The controller is further provided, and signal input ends of the controller are electrically connected with the first pressure sensor (11), the second pressure sensor (12), and the third pressure sensor (13) respectively; signal output ends of the controller are electrically connected with the first hydraulic cylinder (61), the second hydraulic cylinder (62), the bidirectional hydraulic pump (7), the first electromagnetic valve (41), the second electromagnetic valve (42), the third electromagnetic valve (43), the fourth electromagnetic valve (44), and the fifth electromagnetic valve (45) respectively; When the controller issues an extension instruction, the first electromagnetic valve is opened, and the cylinder piston is extended; When the controller issues a retraction instruction, the second electromagnetic valve is opened, the fourth electromagnetic valve and the fifth electromagnetic valve are alternately opened and closed, and the bidirectional hydraulic pump is started. When the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the liquid cavity of the first hydraulic cylinder needs to be communicated with low-pressure oil. When the pressure of the second pressure sensor is zero, the fourth and fifth electromagnetic valves are reversed, and the liquid cavity of the second hydraulic cylinder needs to be communicated with low-pressure oil. When the pressure of the third pressure sensor is zero, the fourth and fifth electromagnetic valves are reversed again, and the opening and closing of the fourth and fifth electromagnetic valves and the rotating direction of the bidirectional hydraulic pump are alternated until the cylinder piston moves to the upper limit, and the bidirectional hydraulic pump and all the electromagnetic valves are closed. When the controller issues a pressure charging signal, the second and third electromagnetic valves are opened, the fourth and fifth electromagnetic valves are alternately opened and closed, and the bidirectional hydraulic pump is started. When the fourth electromagnetic valve is opened, the fifth electromagnetic valve is closed, and the liquid cavity of the first hydraulic cylinder needs to be communicated with low-pressure oil. When the pressure of the second pressure sensor is zero, the fourth and fifth electromagnetic valves are reversed, and the liquid cavity of the second hydraulic cylinder needs to be communicated with low-pressure oil. When the pressure of the third pressure sensor is zero, the fourth and fifth electromagnetic valves are reversed again, and the opening and closing of the fourth and fifth electromagnetic valves and the rotating direction of the bidirectional hydraulic pump are alternated until the first cylinder reaches the rated pressure, and the bidirectional hydraulic pump and all the electromagnetic valves are closed. When the controller sends the unloading signal, the second and third solenoid valves open, the fourth and fifth solenoid valves open / close alternately, and the bidirectional hydraulic pump starts. When the fourth solenoid valve opens, the fifth solenoid valve closes, and the second hydraulic cylinder chamber needs to be connected with the low-pressure oil. When the third pressure sensor pressure is zero, the fourth and fifth solenoid valves reverse, and the first hydraulic cylinder chamber needs to be connected with the low-pressure oil. When the second pressure sensor pressure is zero, the fourth and fifth solenoid valves reverse again, and the fourth and fifth solenoid valves and the bidirectional hydraulic pump rotate direction alternately open / close. Until the first cylinder reaches the rated pressure, the bidirectional hydraulic pump, the first solenoid valve, the second solenoid valve, the third solenoid valve, the fourth solenoid valve and the fifth solenoid valve are closed.

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