Micro mold opening hydraulic control system of two-plate type injection molding machine

Abstract

The invention relates to the technical field of injection molding machines, and particularly discloses a two-plate injection molding machine micro-mold-opening hydraulic control system which comprises an oil tank, a power unit, a first cartridge valve, a plurality of mold locking oil cylinders and a plurality of micro-mold-opening units in one-to-one correspondence with the mold locking oil cylinders, and each micro-mold-opening unit comprises a second cartridge valve, a third cartridge valve and a servo proportional valve. The second cartridge valve is communicated with a rod cavity of the mold locking oil cylinder through a third cartridge valve and / or a servo proportional valve, the power unit is communicated with the first cartridge valve and the second cartridge valve at the same time, in the micro mold opening process, the power unit supplies oil to a rodless cavity of the mold locking oil cylinder through the first cartridge valve, and the rod cavity of the mold locking oil cylinder returns oil through the servo proportional valve; in the mold opening size adjusting process, the power unit supplies oil to the rod cavity of the mold locking oil cylinder through the servo proportional valve, the micro mold opening action of the injection molding machine can be realized by adopting one set of power unit, the cost can be saved, and the size of the injection molding machine can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of micro-mold opening of an injection molding machine, in particular to a hydraulic control system for micro-mold opening of a two-platen injection molding machine. Background Art

[0002] Injection molding is a widely used technology in the manufacturing process of plastic products, in which injection molding machines play a key role. Injection molding machines inject molten plastic into the mold and open the mold to take out the finished product after cooling. With the development of plastic product technology, chemical foaming processes that can effectively reduce product weight have become more and more widely used. The completion of chemical foaming processes is mainly based on the micro-mold opening function of injection molding machines. Traditionally, injection molding machines are divided into two types: three-platen and two-platen. The two-platen injection molding machine is favored for its compact structure, high efficiency and easy maintenance.

[0003] In the prior art, there is a micro-mold opening system for a two-platen injection molding machine. For example, patent No. 2016100490211 discloses an improved micro-mold opening system for an injection molding machine and its oil circuit control method, which discloses the precise control of the hydraulic oil in the rod chamber of the locking cylinder by a servo valve, thereby controlling the accuracy of its mold opening and realizing micro-mold opening of the movable mold. However, it has the following defects: First, it requires at least two power units, which are respectively for supplying oil to the rodless chamber and the rod chamber of the locking cylinder. However, two sets of hydraulic power units are used to complete the micro-mold opening function of the injection molding machine, which will result in high implementation costs and energy consumption. In addition, due to the large number of hydraulic power systems, the overall size of the injection molding machine is large and the utilization rate of the plant is low. Second, the inlet and outlet oil of the rod chamber of the locking cylinder passes through the servo valve, but the opening of the conventional servo valve is small, and its locking efficiency is low during high-pressure mold locking. Summary of the invention

[0004] The present invention is made in consideration of the above-mentioned problems. The purpose of the invention is to provide a micro-mold opening hydraulic control system for a two-platen injection molding machine, which only requires one set of power units to realize the micro-mold opening action of the two-platen injection molding machine. It has low cost and occupies a small area. At the same time, when supplying oil to the rod chamber of the locking cylinder, the two oil circuits from the second cartridge valve to the third cartridge valve and from the second cartridge valve to the servo valve can be freely switched, which can ensure rapid locking.

[0005] To achieve the above-mentioned object, the present invention provides a two-platen injection molding machine micro-mold hydraulic control system, the injection molding machine is provided with a movable mold, a fixed mold and a mold locking oil circuit, the micro-mold control system comprises an oil tank, a power unit, a first cartridge valve, a plurality of mold locking cylinders and a plurality of micro-mold units corresponding to the plurality of mold locking cylinders one by one, the micro-mold units comprise a second cartridge valve, a third cartridge valve and a servo proportional valve, the piston rod of the mold locking cylinder is connected to the movable mold and can drive the movable mold to translate, and the power unit can be used to supply oil to the mold locking oil circuit;

[0006] When the first cartridge valve is closed, the second cartridge valve is opened, and the third cartridge valve is opened, the mold locking oil circuit can supply oil to the rod chamber of the mold locking oil cylinder through the second cartridge valve and the third cartridge valve to provide a mold locking force;

[0007] When the first cartridge valve is opened and the second cartridge valve is closed, the power unit can supply oil to the rodless chamber of the clamping cylinder through the first cartridge valve, and the rod chamber of the clamping cylinder can be connected to the oil tank through the servo proportional valve to control the preset distance of the movable mold opening;

[0008] When the actual opening distance of the movable mold is greater than the preset distance, the first cartridge valve can be controlled to close, the second cartridge valve can be controlled to open, and the third cartridge valve can be controlled to close. The power unit can supply oil to the rod chamber of the locking cylinder through the second cartridge valve and the servo proportional valve.

[0009] According to the above-mentioned two-platen injection molding machine micro-mold hydraulic control system, the oil inlet of the power unit is connected to the oil tank, the oil outlet of the power unit is simultaneously connected to the oil inlet of the first cartridge valve and the oil inlet of the second cartridge valve, and the oil outlet of the first cartridge valve is connected to the rodless chambers of the plurality of clamping cylinders;

[0010] The servo proportional valve and the third cartridge valve are arranged in parallel between the oil outlet of the second cartridge valve and the rod chamber of the clamping cylinder.

[0011] According to the above-mentioned hydraulic control system for micro-opening of a two-platen injection molding machine, the servo proportional valve is provided with a first oil inlet, a first oil outlet and a first variable oil port, the first variable oil port is connected to the first oil inlet or the first oil outlet, the first oil inlet is connected to the oil outlet of the second cartridge valve, the first oil outlet is connected to the oil tank, and the first variable oil port is connected to the rod chamber of the locking cylinder.

[0012] According to the above-mentioned two-platen injection molding machine micro-mold hydraulic control system, a first electromagnet is provided on the servo proportional valve. When the first electromagnet is energized, the first variable oil port is connected to the first oil outlet. When the first electromagnet is de-energized, the first variable oil port is connected to the first oil inlet.

[0013] According to the above-mentioned hydraulic control system for micro-mold opening of a two-platen injection molding machine, the oil outlet of the mold locking oil circuit is communicated with the oil inlet of the second cartridge valve.

[0014] According to the above-mentioned two-platen injection molding machine micro-opening mold hydraulic control system, it also includes a fourth cartridge valve, the oil inlet of the fourth cartridge valve is connected to the oil outlet of the power unit, the oil outlet of the fourth cartridge valve is connected to the oil inlet of the second cartridge valve through a first pipeline, and the oil outlet of the locking oil circuit is connected to the first pipeline.

[0015] According to the above-mentioned two-plate injection molding machine micro-mold hydraulic control system, it also includes a first pilot valve for controlling the opening or closing of the fourth cartridge valve, a second pilot valve for controlling the opening or closing of the second cartridge valve, and a third pilot valve for controlling the opening or closing of the third cartridge valve. When the first pilot valve is energized, the fourth cartridge valve opens, when the second pilot valve is energized, the second cartridge valve closes, and when the third pilot valve is energized, the third cartridge valve opens.

[0016] According to the above-mentioned two-platen injection molding machine micro-opening mold hydraulic control system, it also includes a relief valve, the oil outlet of the first cartridge valve is connected to the rodless chamber of the locking cylinder through the second pipeline, the oil inlet of the relief valve is connected to the second pipeline, and the oil outlet of the relief valve is connected to the oil tank.

[0017] According to the above-mentioned two-platen injection molding machine micro-mold hydraulic control system, it also includes a fourth pilot valve for controlling the opening or closing of the first cartridge valve. When the fourth pilot valve is energized, the first cartridge valve opens.

[0018] According to the above-mentioned two-platen injection molding machine micro-mold hydraulic control system, the power unit includes a hydraulic pump and a motor, the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is simultaneously connected to the oil inlet of the first cartridge valve and the oil inlet of the second cartridge valve, and the motor is used to provide power for the hydraulic pump.

[0019] The present invention has the following beneficial effects: compared with the prior art, a set of power units can be used to realize the micro-mold opening action of a two-plate injection molding machine, which can save a set of power units, reduce the size of the injection molding machine, and improve the utilization rate of the factory building. The power unit can be used to adjust the size of the micro-mold opening and improve the accuracy of the micro-mold opening. At the same time, during the clamping process, the second cartridge valve and the third cartridge valve can be used to supply oil to the rod cavity of the clamping cylinder through the oil circuit with a larger flow rate. During the adjustment process, the second cartridge valve and the servo valve can be used to supply oil to the rod cavity of the clamping cylinder through the oil circuit with a higher accuracy. This can meet the large flow demand during the clamping process and the high precision requirement during the micro-mold opening size adjustment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the overall oil circuit of the embodiment.

[0021] In the figure:

[0022] 1. Oil tank; 2. Power unit; 21. Hydraulic pump; 22. Motor; 3. First cartridge valve; 31. Fourth pilot valve; 4. Locking cylinder; 5. Second cartridge valve; 51. Second pilot valve; 6. Third cartridge valve; 61. Third pilot valve; 7. Servo proportional valve; 71. First solenoid; 8. Fourth cartridge valve; 81. First pilot valve; 9. Overflow valve; 10. Locking oil circuit. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0024] like Figure 1 As shown, a two-platen injection molding machine micro-mold hydraulic control system includes an oil tank 1, a power unit 2, a first cartridge valve 3, a plurality of mold locking cylinders 4, and a plurality of micro-mold units corresponding to the plurality of mold locking cylinders 4 one by one.

[0025] Among them, the injection molding machine is provided with a movable mold, a fixed mold and a clamping oil circuit 10. The movable mold and the fixed mold are combined to form a mold, and the clamping oil circuit 10 is used to supply oil to the rod chamber of the clamping cylinder 4, so that the piston rod of the clamping cylinder 4 can tighten the movable mold to achieve high-pressure clamping.

[0026] Specifically, the micro-opening mold unit includes a second cartridge valve 5, a third cartridge valve 6 and a servo proportional valve 7. The piston rod of the locking cylinder 4 is connected to the movable mold and can drive the movable mold to translate. The second cartridge valve 5 is connected to the rod chamber of the locking cylinder 4 through the third cartridge valve 6 and / or the servo proportional valve 7. The power unit 2 is connected to the first cartridge valve 3 and the second cartridge valve 5 at the same time.

[0027] In this embodiment, during the high-pressure mold locking process, the power unit 2 supplies oil to the mold locking oil circuit 10, that is, when the first cartridge valve 3 is closed, the second cartridge valve 5 is opened, and the third cartridge valve 6 is opened, the mold locking oil circuit 10 can supply oil to the rod chamber of the mold locking cylinder 4 through the second cartridge valve 5 and the third cartridge valve 6 to provide a clamping force and achieve high-pressure mold locking. In this process, since the flow rates of the second cartridge valve 5 and the third cartridge valve 6 are very large, the oil inlet speed of the rod chamber of the mold locking cylinder 4 can be increased. Of course, in order to further increase its oil inlet speed, the servo proportional valve 7 can be opened in this process, and the servo proportional valve 7 and the third cartridge valve 6 can be used together to supply liquid to the rod chamber of the mold locking cylinder 4.

[0028] When a micro-opening action is required, the first cartridge valve 3 is opened and the second cartridge valve 5 is closed, and the oil of the power unit 2 can supply oil to the rodless chamber of the locking cylinder 4 through the first cartridge valve 3. At this time, the oil can drive the piston rod to extend and drive the movable mold to move to the side away from the fixed mold. In this process, the rod chamber of the locking cylinder 4 needs to be drained, which can be connected to the oil tank 1 through the servo proportional valve 7. Since the servo proportional valve 7 can accurately control the size of its channel, the discharge amount of the oil can be controlled to achieve small-scale discharge, thereby achieving micro-opening of the movable mold and opening the movable mold to a preset distance. However, under normal circumstances, the movable mold cannot be micro-opened in one go, which can be divided into two situations. First, when the actual mold opening distance of the movable mold is less than the preset distance, it can continue to open the mold through the above steps. Second, when the actual mold opening distance of the movable mold is greater than the preset distance, the first cartridge valve 3 can be controlled to be closed, the second cartridge valve 5 can be controlled to be opened, and the third cartridge valve 6 can be controlled to be closed. At this time, the power unit 2 can supply oil to the rod chamber of the locking cylinder 4 through the second cartridge valve 5 and the servo proportional valve 7. Since the servo proportional valve 7 is used to supply oil, the oil supply accuracy is higher and the oil supply is slower. Therefore, the movable mold can be slowly controlled to reduce the mold opening distance to achieve the size adjustment of the micro mold opening. It also only needs to use the same power unit 2, which can reduce costs, reduce the size of the injection molding machine, and improve the utilization rate of the plant space.

[0029] Specifically, the oil inlet of the power unit 2 is connected to the oil tank 1, and the oil outlet of the power unit 2 is connected to the oil inlet of the first cartridge valve 3 and the oil inlet of the second cartridge valve 5 at the same time. The oil outlet of the first cartridge valve 3 is connected to the rodless chambers of multiple locking cylinders 4, and the servo proportional valve 7 and the third cartridge valve 6 are arranged in parallel between the oil outlet of the second cartridge valve 5 and the rod chamber of the locking cylinder 4, that is, the power unit 2 can inhale hydraulic oil from the oil tank 1, which can be discharged into the first cartridge valve 3 or the second cartridge valve 5. When it discharges oil through the first cartridge valve 3, its hydraulic oil can enter the rodless chamber of the locking cylinder 4, drive the piston rod to extend, and drive the movable mold to open slightly. When it discharges oil through the second cartridge valve 5, it supplies oil to the rod chamber of the locking cylinder 4 through the servo proportional valve 7 to adjust its opening size.

[0030] In this embodiment, the oil outlet of the clamping oil circuit 10 is connected to the oil inlet of the second cartridge valve 5. During the high-pressure clamping process, the clamping oil circuit 10 supplies oil to the second cartridge valve 5. After passing through the second cartridge valve 5, the oil flows to the third cartridge valve 6 and the servo proportional valve 7, and finally flows into the rod chamber of the clamping cylinder 4 to achieve high-pressure clamping.

[0031] In order to prevent the hydraulic oil in the mold locking oil circuit 10 from flowing back into the power unit 2, a fourth cartridge valve 8 is also included. The oil inlet of the fourth cartridge valve 8 is connected to the oil outlet of the power unit 2, and the oil outlet of the fourth cartridge valve 8 is connected to the oil inlet of the second cartridge valve 5 through the first pipeline. The oil outlet of the mold locking oil circuit 10 is connected to the first pipeline. When the mold locking oil circuit 10 supplies oil, the fourth cartridge valve 8 can be in a closed state, and its hydraulic oil can only flow to the second cartridge valve 5. When the power unit 2 supplies liquid to the second cartridge valve 5, the fourth cartridge valve 8 is opened.

[0032] In order to realize the control of opening and closing of the second cartridge valve 5, the third cartridge valve 6 and the fourth cartridge valve 8, it also includes a first pilot valve 81 for controlling the opening or closing of the fourth cartridge valve 8, a second pilot valve 51 for controlling the opening or closing of the second cartridge valve 5 and a third pilot valve 61 for controlling the opening or closing of the third cartridge valve 6. When the first pilot valve 81 is energized, the fourth cartridge valve 8 is opened, and when the first pilot valve 81 is de-energized, the fourth cartridge valve 8 is closed; when the second pilot valve 51 is energized, the second cartridge valve 5 is closed, and when the second pilot valve 51 is de-energized, the second cartridge valve 5 is opened; when the third pilot valve 61 is energized, the third cartridge valve 6 is opened, and when the third pilot valve 61 is de-energized, the third cartridge valve 6 is closed, and the individual control of multiple cartridge valves can be realized by whether the pilot valves are energized or not.

[0033] Specifically, the servo proportional valve 7 is provided with a first oil inlet, a first oil outlet and a first variable oil port, the first variable oil port is communicated with the first oil inlet or the first oil outlet, the first oil inlet is communicated with the oil outlet of the second cartridge valve 5, the first oil outlet is communicated with the oil tank 1, the first variable oil port is communicated with the rod chamber of the clamping cylinder 4, and the servo proportional valve 7 is also provided with a first electromagnet 71. When the clamping cylinder 4 is in a slightly open mold state, the power unit 2 supplies oil to the rodless chamber of the clamping cylinder 4 through the first cartridge valve 3. At this time The rod chamber of the locking cylinder 4 needs to be drained. At this time, the first electromagnet 71 is energized, and the first variable oil port is connected to the first oil outlet. The hydraulic oil in the rod chamber is discharged into the oil tank 1 through the first oil outlet. When the locking cylinder 4 is in the process of micro-opening the mold size, the power unit 2 needs to supply oil to the rod chamber of the locking cylinder 4 through the servo proportional valve 7. At this time, the first electromagnet 71 loses power, and the first variable oil port is connected to the first oil inlet. The power unit 2 supplies oil to the rodless chamber of the locking cylinder 4 through the first variable oil port.

[0034] In order to control the oil discharge speed in the rodless chamber of the locking cylinder 4 and improve the safety performance, a relief valve 9 is also included. The oil outlet of the first cartridge valve 3 is connected to the rodless chamber of the locking cylinder 4 through the second pipeline, the oil inlet of the relief valve 9 is connected to the second pipeline, and the oil outlet of the relief valve 9 is connected to the oil tank 1. The relief valve 9 provides an oil discharge pressure for the rodless chamber of the locking cylinder 4 so that it will not be discharged too quickly. At the same time, when the oil pressure in the second pipeline is too high, the pressure can be relieved through the relief valve 9 to improve the safety performance.

[0035] Specifically, in order to realize the first cartridge valve 3, a fourth pilot valve 31 is also included for controlling the opening or closing of the first cartridge valve 3. When the fourth pilot valve 31 is energized, the first cartridge valve 3 is opened, and when the fourth pilot valve 31 is de-energized, the first cartridge valve 3 is closed.

[0036] Specifically, the power unit 2 includes a hydraulic pump 21 and a motor 22. The oil inlet of the hydraulic pump 21 is connected to the oil tank 1, and the oil outlet of the hydraulic pump 21 is connected to the oil inlet of the first cartridge valve 3 and the oil inlet of the second cartridge valve 5 at the same time. The motor 22 is used to provide power for the hydraulic pump 21.

[0037] The technical solution of the present invention is described in detail above in conjunction with the accompanying drawings, and the described embodiments are used to help understand the concept of the present invention. The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art of the invention may make various modifications or supplements to the described specific embodiments or replace them in a similar manner, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

[0038] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0039] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0040] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A two-platen injection molding machine micro-mold hydraulic control system, the injection molding machine is provided with a movable mold, a fixed mold and a clamping mold oil circuit, characterized in that: The micro-opening mold control system includes an oil tank, a power unit, a first cartridge valve, a plurality of mold locking cylinders, and a plurality of micro-opening mold units corresponding to the plurality of mold locking cylinders one by one. The micro-opening mold units include a second cartridge valve, a third cartridge valve, and a servo proportional valve. The piston rod of the mold locking cylinder is connected to the movable mold and can drive the movable mold to translate. The power unit can be used to supply oil to the mold locking oil circuit. When the first cartridge valve is closed, the second cartridge valve is opened, and the third cartridge valve is opened, the mold locking oil circuit can supply oil to the rod chamber of the mold locking oil cylinder through the second cartridge valve and the third cartridge valve to provide a mold locking force; When the first cartridge valve is opened and the second cartridge valve is closed, the power unit can supply oil to the rodless chamber of the clamping cylinder through the first cartridge valve, and the rod chamber of the clamping cylinder can be connected to the oil tank through the servo proportional valve to control the preset distance of the movable mold opening; When the actual opening distance of the movable mold is greater than the preset distance, the first cartridge valve can be controlled to close, the second cartridge valve can be controlled to open, and the third cartridge valve can be controlled to close. The power unit can supply oil to the rod chamber of the locking cylinder through the second cartridge valve and the servo proportional valve.

2. A two-platen injection molding machine micro-mold hydraulic control system according to claim 1, characterized in that: The oil inlet of the power unit is communicated with the oil tank, the oil outlet of the power unit is communicated with the oil inlet of the first cartridge valve and the oil inlet of the second cartridge valve, and the oil outlet of the first cartridge valve is communicated with the rodless chambers of the plurality of clamping cylinders; The servo proportional valve and the third cartridge valve are arranged in parallel between the oil outlet of the second cartridge valve and the rod chamber of the clamping cylinder.

3. A two-platen injection molding machine micro-mold hydraulic control system according to claim 2, characterized in that: The servo proportional valve is provided with a first oil inlet, a first oil outlet and a first variable oil port, the first variable oil port is connected to the first oil inlet or the first oil outlet, the first oil inlet is connected to the oil outlet of the second cartridge valve, the first oil outlet is connected to the oil tank, and the first variable oil port is connected to the rod chamber of the locking cylinder.

4. A two-platen injection molding machine micro-mold hydraulic control system according to claim 3, characterized in that: The servo proportional valve is provided with a first electromagnet. When the first electromagnet is energized, the first variable oil port is connected with the first oil outlet. When the first electromagnet is de-energized, the first variable oil port is connected with the first oil inlet.

5. A two-platen injection molding machine micro-mold hydraulic control system according to claim 2, characterized in that: The oil outlet of the mold locking oil circuit is communicated with the oil inlet of the second cartridge valve.

6. A two-platen injection molding machine micro-mold hydraulic control system according to claim 5, characterized in that: It also includes a fourth cartridge valve, the oil inlet of the fourth cartridge valve is connected to the oil outlet of the power unit, the oil outlet of the fourth cartridge valve is connected to the oil inlet of the second cartridge valve through a first pipeline, and the oil outlet of the locking oil circuit is connected to the first pipeline.

7. A two-platen injection molding machine micro-mold hydraulic control system according to claim 6, characterized in that: It also includes a first pilot valve for controlling the opening or closing of the fourth cartridge valve, a second pilot valve for controlling the opening or closing of the second cartridge valve, and a third pilot valve for controlling the opening or closing of the third cartridge valve. When the first pilot valve is energized, the fourth cartridge valve opens, when the second pilot valve is energized, the second cartridge valve closes, and when the third pilot valve is energized, the third cartridge valve opens.

8. A two-platen injection molding machine micro-mold hydraulic control system according to claim 1, characterized in that: It also includes a relief valve, the oil outlet of the first cartridge valve is connected to the rodless chamber of the clamping cylinder through a second pipeline, the oil inlet of the relief valve is connected to the second pipeline, and the oil outlet of the relief valve is connected to the oil tank.

9. A two-platen injection molding machine micro-mold hydraulic control system according to claim 1, characterized in that: The invention also includes a fourth pilot valve for controlling the first cartridge valve to be opened or closed. When the fourth pilot valve is energized, the first cartridge valve is opened.

10. A two-platen injection molding machine micro-mold hydraulic control system according to claim 1, characterized in that: The power unit includes a hydraulic pump and a motor. The oil inlet of the hydraulic pump is connected to the oil tank, and the oil outlet of the hydraulic pump is connected to the oil inlet of the first cartridge valve and the oil inlet of the second cartridge valve at the same time. The motor is used to provide power for the hydraulic pump.

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