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

Abstract

The utility model 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, the 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 the third cartridge valve and / or the servo proportional valve, and the power unit is communicated with the first cartridge valve and the second cartridge valve at the same time. The power unit supplies oil to a rodless cavity of the mold locking oil cylinder through the first cartridge valve, oil returns to a rod cavity of the mold locking oil cylinder 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, and the micro mold opening action of the injection molding machine can be achieved through one set of power unit. Cost can be saved, and the size of the injection molding machine can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of injection molding machine micro open mould, especially a two-plate type injection molding machine micro open mould hydraulic control system. BACKGROUND

[0002] In the manufacturing process of plastic products, injection molding is a widely used technology, in which injection molding machines play a key role. Injection molding machines inject molten plastic into a mold and open the mold after cooling to remove the finished product. With the development of plastic product technology, chemical foaming technology, which can effectively reduce product weight, is increasingly widely used. The completion of chemical foaming technology is mainly based on the micro open mould function of injection molding machines. In the traditional, injection molding machines are divided into three-plate type and two-plate type, and two-plate type injection molding machines are favored for their compact structure, high efficiency, and easy maintenance.

[0003] In the prior art, there are micro open mould systems for two-plate type injection molding machines. For example, patent number 2016100490211 discloses an improved injection molding machine micro open mould system and its oil circuit control method, which discloses precise control of the hydraulic oil in the rod cavity of the locking oil cylinder through a servo valve, thereby controlling the precision of the mold opening and achieving micro open mould of the moving mold. However, it has the following defects: 1. It needs to use at least two power units, which are the rodless cavity and the rod cavity of the locking oil cylinder. However, using two sets of hydraulic power units to complete the micro open mould function of the injection molding machine will result in high implementation cost and energy consumption, and 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 factory building is low. 2. The oil inlet and outlet of the rod cavity of the locking oil cylinder are through the servo valve, but the opening of the conventional servo valve is small, and in the process of high-pressure locking, the locking efficiency is low. SUMMARY

[0004] The utility model considers the foregoing problem and is made, the utility model aims at providing a two-plate type injection molding machine micro open mould hydraulic control system, which only needs a set of power unit to realize the micro open mould action of the two-plate type injection molding machine, and has low cost and small occupied area. At the same time, when supplying oil to the rod cavity of the locking oil cylinder, the second plug-in valve can be freely switched to the third plug-in valve and the second plug-in valve to the servo valve, which can ensure rapid locking.

[0005] In order to achieve the above object, the utility model provides a kind of two-plate injection molding machine micro-opening mold hydraulic control system, and the injection molding machine is equipped with movable mould, fixed mould and mould locking oil circuit, and the micro-opening mold control system includes oil tank, power unit, first plug-in valve, multiple mould locking oil cylinders and multiple micro-opening mold units corresponding to multiple mould locking oil cylinders, and the micro-opening mold unit includes second plug-in valve, third plug-in valve and servo proportional valve, the piston rod of the mould locking oil cylinder is connected with the movable mould, and the movable mould can be driven to translate, and the power unit can be used to supply oil for the mould locking oil circuit;

[0006] When the first plug-in valve is closed, the second plug-in valve is opened, and the third plug-in valve is opened, the mould locking oil circuit can supply oil for the rod cavity of the mould locking oil cylinder through the second plug-in valve and the third plug-in valve to provide mould locking force.

[0007] When the first plug-in valve is opened, and the second plug-in valve is closed, the power unit can supply oil for the rodless cavity of the mould locking oil cylinder through the first plug-in valve, and the rod cavity of the mould locking oil cylinder can be communicated with the oil tank through the servo proportional valve to control the movable mould to open a preset distance.

[0008] When the actual opening distance of the movable mould is greater than the preset distance, the first plug-in valve can be controlled to be closed, the second plug-in valve can be controlled to be opened, and the third plug-in valve can be controlled to be closed, and the power unit can supply oil for the rod cavity of the mould locking oil cylinder through the second plug-in valve and the servo proportional valve.

[0009] According to the above-mentioned two-plate injection molding machine micro-opening mold hydraulic control system, 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 plug-in valve and the oil inlet of the second plug-in valve, and the oil outlet of the first plug-in valve is communicated with the rodless cavity of the multiple mould locking oil cylinders.

[0010] The servo proportional valve and the third plug-in valve are arranged in parallel between the oil outlet of the second plug-in valve and the rod cavity of the mould locking oil cylinder.

[0011] According to the above-mentioned two-plate injection molding machine micro-opening mold hydraulic control system, the servo proportional valve is equipped with first oil inlet, first oil outlet and 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 plug-in valve, the first oil outlet is communicated with the oil tank, and the first variable oil port is communicated with the rod cavity of the mould locking oil cylinder.

[0012] The two-plate injection molding machine micro-opening mold hydraulic control system, the first electromagnetic iron is arranged on the servo proportional valve, when the first electromagnetic iron is powered, the first variable oil port is communicated with the first oil outlet, when the first electromagnetic iron is powered off, the first variable oil port is communicated with the first oil inlet.

[0013] The two-plate injection molding machine micro-opening mold hydraulic control system, the oil outlet of the locking oil way is communicated with the oil inlet of the second plug-in valve.

[0014] The two-plate injection molding machine micro-opening mold hydraulic control system, further comprising a fourth plug-in valve, the oil inlet of the fourth plug-in valve is communicated with the oil outlet of the power unit, the oil outlet of the fourth plug-in valve is communicated with the oil inlet of the second plug-in valve through a first pipeline, and the oil outlet of the locking oil way is communicated with the first pipeline.

[0015] The two-plate injection molding machine micro-opening mold hydraulic control system, further comprising a first pilot valve for controlling the opening or closing of the fourth plug-in valve, a second pilot valve for controlling the opening or closing of the second plug-in valve, and a third pilot valve for controlling the opening or closing of the third plug-in valve, when the first pilot valve is powered, the fourth plug-in valve is opened, when the second pilot valve is powered, the second plug-in valve is closed, and when the third pilot valve is powered, the third plug-in valve is opened.

[0016] The two-plate injection molding machine micro-opening mold hydraulic control system, further comprising an overflow valve, the oil outlet of the first plug-in valve is communicated with the rodless cavity of the locking oil cylinder through a second pipeline, the oil inlet of the overflow valve is communicated with the second pipeline, and the oil outlet of the overflow valve is communicated with the oil tank.

[0017] The two-plate injection molding machine micro-opening mold hydraulic control system, further comprising a fourth pilot valve for controlling the opening or closing of the first plug-in valve, when the fourth pilot valve is powered, the first plug-in valve is opened.

[0018] The two-plate injection molding machine micro-opening mold hydraulic control system, the power unit comprises a hydraulic pump and a motor, the oil inlet of the hydraulic pump is communicated with the oil tank, the oil outlet of the hydraulic pump is communicated with the oil inlet of the first plug-in valve and the oil inlet of the second plug-in valve at the same time, and the motor is used for providing power for the hydraulic pump.

[0019] The utility model has the following beneficial effects: compared with prior art, a set of power unit can realize the micro -open mould action of two -plate injection molding machine, it can save a set of power unit, and can reduce the injection molding machine size, improve the workshop utilization rate, and through the power unit can carry out micro -open mould size adjustment, improve micro -open mould precision, simultaneously in the mould -clamping process, the oil supply in the rod cavity of the mould -clamping cylinder can be carried out through the oil way of the second plug -in valve and the third plug -in valve with large flow, and the oil supply in the rod cavity of the mould -clamping cylinder can be carried out through the oil way of the second plug -in valve and the servo valve with high precision in the adjustment process, which can meet the large flow demand in the mould -clamping process, and can meet the high precision requirement in the micro -open mould size adjustment process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the whole oil circuit schematic diagram of example.

[0021] In the drawing:

[0022] 1, oil tank;2, power unit;21, hydraulic pump;22, motor;3, first plug-in valve;31, fourth pilot valve;4, mould -clamping cylinder;5, second plug-in valve;51, second pilot valve;6, third plug-in valve;61, third pilot valve;7, servo proportional valve;71, first electromagnet;8, fourth plug-in valve;81, first pilot valve;9, overflow valve;10, mould -clamping oil circuit. DETAILED DESCRIPTION

[0023] The following is a specific embodiment of the utility model and is further described in conjunction with the drawings, but the utility model is not limited to these embodiments.

[0024] As Figure 1 Indicated, a two -plate injection molding machine micro -open mould hydraulic control system, including oil tank 1, power unit 2, first plug-in valve 3, multiple mould -clamping cylinders 4 and multiple micro -open mould units corresponding to multiple mould -clamping cylinders 4.

[0025] Among them, the injection molding machine is equipped with movable die, fixed die and mould -clamping oil circuit 10, and the movable die and fixed die form a mould, and the mould -clamping oil circuit 10 is used for oil supply to the rod cavity of the mould -clamping cylinder 4, so that the piston rod of the mould -clamping cylinder 4 can tighten the movable die, and high-pressure mould -clamping is realized.

[0026] Specifically, the micro -open mould unit includes second plug-in valve 5, third plug-in valve 6 and servo proportional valve 7, the piston rod of the mould -clamping cylinder 4 is connected with the movable die and can drive the movable die to translate, the second plug-in valve 5 is communicated with the rod cavity of the mould -clamping cylinder 4 through the third plug-in valve 6 and / or servo proportional valve 7, and the power unit 2 is communicated with the first plug-in valve 3 and the second plug-in valve 5 simultaneously.

[0027] In the present embodiment, during the process of high-pressure clamping, the power unit 2 supplies oil to the clamping 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 clamping oil circuit 10 can supply oil to the rod cavity of the clamping cylinder 4 through the second cartridge valve 5 and the third cartridge valve 6 to provide clamping force and achieve high-pressure clamping. During this process, since the flow capacities of the second cartridge valve 5 and the third cartridge valve 6 are very large, the oil inlet speed of the rod cavity of the clamping cylinder 4 can be improved. Of course, in order to further improve the oil inlet speed, the servo proportional valve 7 can be opened during this process to supply liquid to the rod cavity of the clamping cylinder 4 together with the third cartridge valve 6.

[0028] When micro-clamping action needs to be performed, the first cartridge valve 3 is opened and the second cartridge valve 5 is closed, and the oil in the power unit 2 can supply oil to the rodless cavity of the clamping 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 away from the fixed mold. During this process, the rod cavity of the clamping cylinder 4 needs to be drained, which can be communicated with the oil tank 1 through the servo proportional valve 7. Since the servo proportional valve 7 can accurately control the size of the passage and thus control the discharge amount of the oil, small-scale discharge can be achieved, thereby achieving micro-clamping of the movable mold and clamping the movable mold to a preset distance. However, in general, the movable mold cannot be clamped to the preset distance at one time, which can be divided into two cases. One is that the actual clamping distance of the movable mold is less than the preset distance, and the movable mold can be continuously clamped by the above steps. The other is that the actual clamping distance of the movable mold is greater than the preset distance, and 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 cavity of the clamping 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 precision is higher and the oil supply is slower, so the clamping distance of the movable mold can be slowly controlled to reduce the clamping distance, thereby achieving size adjustment of micro-clamping. The same power unit 2 can be used, which can reduce the cost, the size of the injection molding machine, and improve the utilization rate of the factory space.

[0029] Specifically, the oil inlet of the power unit 2 is communicated with the oil tank 1, the oil outlet of the power unit 2 is communicated with the oil inlet of the first cartridge valve 3 and the oil inlet of the second cartridge valve 5, the oil outlet of the first cartridge valve 3 is communicated with the rodless cavity of the plurality of clamping 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 cavity of the clamping cylinder 4. That is, the power unit 2 can suck hydraulic oil from the oil tank 1, which can be discharged into the first cartridge valve 3 or the second cartridge valve 5. When the oil is discharged through the first cartridge valve 3, the hydraulic oil can enter the rodless cavity of the clamping cylinder 4 to drive the piston rod to extend and drive the movable mold to perform micro-clamping. When the oil is discharged through the second cartridge valve 5, the oil is supplied to the rod cavity of the clamping cylinder 4 through the servo proportional valve 7 to adjust the clamping size.

[0030] In the embodiment, the oil outlet of the mold locking oil line 10 is communicated with the oil inlet of the second cartridge valve 5, and the mold locking oil line 10 supplies oil for the second cartridge valve 5 in the high-pressure mold locking process. The oil flows to the third cartridge valve 6 and the servo proportional valve 7 after passing through the second cartridge valve 5, and finally flows into the rod cavity of the mold locking cylinder 4 to realize high-pressure mold locking.

[0031] In order to prevent the hydraulic oil in the mold locking oil line 10 from flowing into the power unit 2, a fourth cartridge valve 8 is further included. The oil inlet of the fourth cartridge valve 8 is communicated with the oil outlet of the power unit 2, and the oil outlet of the fourth cartridge valve 8 is communicated with the oil inlet of the second cartridge valve 5 through a first pipeline. The oil outlet of the mold locking oil line 10 is communicated with the first pipeline. Therefore, when the mold locking oil line 10 supplies oil, the fourth cartridge valve 8 can be in a closed state, and the hydraulic oil can only flow to the second cartridge valve 5. When the power unit 2 supplies oil for the second cartridge valve 5, the fourth cartridge valve 8 is opened.

[0032] In order to realize the opening and closing control of the second cartridge valve 5, the third cartridge valve 6 and the fourth cartridge valve 8, 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 are further included. When the first pilot valve 81 is powered, the fourth cartridge valve 8 is opened. When the first pilot valve 81 is de-energized, the fourth cartridge valve 8 is closed. When the second pilot valve 51 is powered, the second cartridge valve 5 is closed. When the second pilot valve 51 is de-energized, the second cartridge valve 5 is opened. When the third pilot valve 61 is powered, the third cartridge valve 6 is opened. When the third pilot valve 61 is de-energized, the third cartridge valve 6 is closed. Therefore, the power-on and power-off of the pilot valve can realize the separate control of the multiple cartridge valves.

[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 cavity of the mold locking cylinder 4. The first electromagnet 71 is further arranged on the servo proportional valve 7. When the mold locking cylinder 4 is in a micro-opening mold state, the power unit 2 supplies oil for the rodless cavity of the mold locking cylinder 4 through the first cartridge valve 3. At this time, the rod cavity of the mold locking cylinder 4 needs to be drained. At this time, the first electromagnet 71 is powered, the first variable oil port is communicated with the first oil outlet, and the hydraulic oil in the rod cavity is drained into the oil tank 1 through the first oil outlet. When the mold locking cylinder 4 is in a micro-opening size adjustment process, the power unit 2 needs to supply oil for the rod cavity of the mold locking cylinder 4 through the servo proportional valve 7. At this time, the first electromagnet 71 is de-energized, the first variable oil port is communicated with the first oil inlet, and the power unit 2 supplies oil for the rodless cavity of the mold locking cylinder 4 through the first variable oil port.

[0034] In order to control the oil discharging speed in the rodless cavity of the mold locking cylinder 4 and improve the safety performance, the overflow valve 9 is further included, the oil outlet of the first cartridge valve 3 is communicated with the rodless cavity of the mold locking cylinder 4 through the second pipeline, the oil inlet of the overflow valve 9 is communicated with the second pipeline, the oil outlet of the overflow valve 9 is communicated with the oil tank 1, and the rodless cavity of the mold locking cylinder 4 is provided with an oil discharging pressure through the overflow valve 9, so that the oil discharging speed of the rodless cavity of the mold locking cylinder 4 is not too fast, and the safety performance is improved when the oil pressure in the second pipeline is too large.

[0035] Specifically, in order to control the first cartridge valve 3, the fourth pilot valve 31 for controlling the opening or closing of the first cartridge valve 3 is further included, when the fourth pilot valve 31 is powered on, the first cartridge valve 3 is opened, and when the fourth pilot valve 31 is powered off, the first cartridge valve 3 is closed.

[0036] Specifically, the power unit 2 includes the hydraulic pump 21 and the motor 22, the oil inlet of the hydraulic pump 21 is communicated with the oil tank 1, the oil outlet of the hydraulic pump 21 is communicated with the oil inlets of the first cartridge valve 3 and the second cartridge valve 5, and the motor 22 is used for providing power for the hydraulic pump 21.

[0037] The technical scheme of the utility model is described in detail above in combination with the drawings, and the described embodiments are used to help understand the idea of the utility model. The specific embodiments described in the text are only examples of the spirit of the utility model. Those skilled in the art to which the utility model belongs can make various modifications or supplements to the described specific embodiments or replace them with similar ways, but will not deviate from the spirit of the utility model or exceed the range defined by the attached claims.

[0038] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the utility model are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0039] In addition, the description of "first", "second", "one" and the like in the utility model is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the utility model, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0040] In the utility model, unless another definite provision and limitation, the term "connect", "fix" and so on should do the broad sense understanding, for example, "fix" can be fixed connection, also can be detachable connection, or be integrated;Can be mechanical connection, also can be electric connection;Can be directly connected, also can be indirectly connected through the intermediate medium, can be two element inside's intercommunication or two element's mutual action relation, unless another definite limitation.For the ordinary skill in the art, the specific meaning of the above-mentioned term in the utility model can be understood according to the specific circumstances.

[0041] In addition, the technical solutions of various embodiments of the present application can be combined with each other, but must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, also not within the protection scope required by the present application.

Claims

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

2. A two-plate injection molding machine micro-open mold hydraulic control system according to claim 1, characterized by, 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 cavity of the plurality of locking oil cylinders. The servo proportional valve is arranged in parallel with the third cartridge valve between the oil outlet of the second cartridge valve and the rod cavity of the locking oil cylinder.

3. A two-plate injection molding machine micro-open mold hydraulic control system according to claim 2, characterized by, 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 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, the first oil outlet is communicated with the oil tank, and the first variable oil port is communicated with the rod cavity of the locking oil cylinder.

4. The two-plate injection molding machine micro-opening 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 powered, the first variable oil port is communicated with the first oil outlet, and when the first electromagnet is de-energized, the first variable oil port is communicated with the first oil inlet.

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

6. A two-plate injection molding machine micro-open mold hydraulic control system according to claim 5, characterized by, Further comprising a fourth cartridge valve, the oil inlet of the fourth cartridge valve is communicated with the oil outlet of the power unit, the oil outlet of the fourth cartridge valve is communicated with the oil inlet of the second cartridge valve through a first pipeline, and the oil outlet of the locking oil circuit is communicated with the first pipeline.

7. A two-plate injection molding machine micro-open mold hydraulic control system according to claim 6, characterized by, Further comprising 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 powered, the fourth cartridge valve is opened, when the second pilot valve is powered, the second cartridge valve is closed, and when the third pilot valve is powered, the third cartridge valve is opened.

8. A two-plate injection molding machine micro-open mold hydraulic control system according to claim 1, characterized by, Further comprising an overflow valve, an oil outlet of the first spool valve is communicated with a rodless cavity of the locking oil cylinder through a second pipeline, an oil inlet of the overflow valve is communicated with the second pipeline, and an oil outlet of the overflow valve is communicated with the oil tank.

9. The two-plate injection molding machine micro-open mold hydraulic control system according to claim 1, characterized in that, Further comprising a fourth pilot valve for controlling the first spool valve to open or close, when the fourth pilot valve is powered, the first spool valve is opened.

10. The two-plate injection molding machine micro-open mold hydraulic control system of claim 1, wherein, The power unit comprises a hydraulic pump and a motor, an oil inlet of the hydraulic pump is communicated with the oil tank, an oil outlet of the hydraulic pump is communicated with an oil inlet of the first spool valve and an oil inlet of the second spool valve, and the motor is used for powering the hydraulic pump.

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