An automatic reciprocating hydraulic cylinder and its telescoping method

Abstract

The present invention discloses an automatic reciprocating hydraulic cylinder and its telescoping method, which relates to the technical field of hydraulic cylinders. It includes a hydraulic cylinder main body, and a piston chamber and a spool chamber are provided inside the hydraulic cylinder main body; a first piston and a second piston are slidably connected in the piston chamber, and a piston rod is provided at one end of the second piston away from the first piston; a spool body is slidably connected in the spool chamber; a spool oil inlet branch port, an oil outlet branch port, a spool connection port, a spool first pipe port, and a spool second pipe port are provided on the side wall of the spool chamber, and a piston oil inlet branch port, a piston connection port, a piston first pipe port, and a piston second pipe port are provided in the piston chamber. The spool oil inlet branch port and the piston oil inlet branch port are both connected to an oil inlet, the oil outlet branch port is connected to an oil outlet, the spool connection port is communicated with the piston connection port, the spool first pipe port is communicated with the piston first pipe port, and the spool second pipe port is communicated with the piston second pipe port. The present invention can control the telescopic movement of the piston rod without setting a reversing valve.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic cylinders, and particularly to an automatic reciprocating hydraulic cylinder and its telescoping method. Background Art

[0002] A hydraulic cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion (or oscillating motion). It has a simple structure and reliable operation.

[0003] Existing hydraulic cylinders generally need to be connected to a reversing valve. Through the reversing function of the reversing valve, the injection or inflow of two oil ports in the hydraulic cylinder is controlled, so as to adjust the oil circuit and control the telescoping of the hydraulic cylinder.

[0004] This setting will increase the installation cost and the operation is complex.

[0005] Therefore, there is an urgent need for a new type of automatic reciprocating hydraulic cylinder in the market to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide an automatic reciprocating hydraulic cylinder and its telescoping method to solve the technical problems existing in the above prior art, and the telescoping of the piston rod can be controlled without a reversing valve.

[0007] To achieve the above purpose, the present invention provides the following solutions:

[0008] The present invention discloses an automatic reciprocating hydraulic cylinder, including a hydraulic cylinder body, and a piston chamber and a valve core chamber are arranged in the hydraulic cylinder body;

[0009] A first piston and a second piston are slidably connected in the piston chamber. The first piston and the second piston are connected by a connecting rod. A piston rod is arranged at one end of the second piston away from the first piston, and the piston rod can penetrate through the hydraulic cylinder body. The first piston and the second piston divide the piston chamber into a rodless chamber, a transition chamber and a rod chamber;

[0010] A valve core body is slidably connected in the valve core chamber. The valve core body divides the valve core chamber into a large cross-section chamber and a small cross-section chamber. A first annular channel, a second annular channel and a third annular channel are arranged on the side wall of the valve core body. A T-shaped channel is arranged on the valve core body. One end of the T-shaped channel is communicated with the small cross-section chamber, and the other two ends of the T-shaped channel are both communicated with the third annular channel;

[0011] On the side wall of the spool cavity, there are a spool oil inlet branch port, an oil outlet branch port, a spool connection port, a first spool pipe orifice, and a second spool pipe orifice. In the piston cavity, there are a piston oil inlet branch port, a piston connection port, a first piston pipe orifice, and a second piston pipe orifice. The spool oil inlet branch port and the piston oil inlet branch port are both connected to an oil inlet. The oil outlet branch port is connected to an oil outlet. The spool connection port is in communication with the piston connection port. The first spool pipe orifice is in communication with the first piston pipe orifice. The second spool pipe orifice is in communication with the second piston pipe orifice;

[0012] The spool oil inlet branch port can be in communication with the second annular channel or the third annular channel. The oil outlet branch port can be in communication with the first annular channel or the second annular channel. The first spool pipe orifice is in communication with the large cross-section cavity. The second spool pipe orifice can be in communication with the first annular channel or the second annular channel. The spool connection port can be in communication with the second annular channel;

[0013] The first piston pipe orifice can be in communication with the transition cavity or the rod chamber. The second piston pipe orifice can be in communication with the transition cavity.

[0014] Preferably, the spool oil inlet branch port is connected to the oil inlet through a second oil inlet branch;

[0015] The piston oil inlet branch port is connected to the oil inlet through a first oil inlet branch;

[0016] The oil outlet branch port is connected to the oil outlet through an oil outlet pipeline;

[0017] The spool connection port is in communication with the piston connection port through a connection channel;

[0018] The first spool pipe orifice is in communication with the first piston pipe orifice through a first pipeline;

[0019] The second spool pipe orifice is in communication with the second piston pipe orifice through a first pipeline.

[0020] Preferably, an oil circuit block is provided on the side wall of the hydraulic cylinder body. The oil inlet and the oil outlet are both arranged on the oil circuit block.

[0021] Preferably, a plurality of piston sealing rings are provided on the side walls of the first piston and the second piston.

[0022] Preferably, the hydraulic cylinder body includes a cylinder block and a cylinder head. The cylinder head is fixed at the opening of the piston cavity. The piston rod passes through the cylinder head.

[0023] Preferably, a plurality of piston sealing rings are provided on the cylinder head.

[0024] Preferably, the cross-sectional area of the rodless cavity is larger than that of the rod cavity.

[0025] The present invention also discloses a telescoping method for an automatic reciprocating hydraulic cylinder, including an extending method and a retracting method;

[0026] Extending method:

[0027] S1. Inject hydraulic oil into the oil inlet. Part of the hydraulic oil will enter the valve core cavity through the valve core oil inlet branch and enter the small cross-sectional cavity through the T-shaped channel;

[0028] S2. Another part of the hydraulic oil will enter the rod cavity through the piston oil inlet branch, then enter the large cross-sectional cavity through the first piston pipe orifice and the first valve core pipe orifice, and push the valve core body in the direction of the small cross-sectional cavity;

[0029] S3. The valve core oil inlet branch is connected to the valve core connection port, and the second valve core pipe orifice is connected to the oil outlet. The hydraulic oil will enter the rodless cavity through the valve core connection port. The pressure in the rodless cavity is greater than that in the rod cavity, thereby pushing the piston rod to extend;

[0030] Retracting method:

[0031] S1. When the first piston pipe orifice and the second piston pipe orifice are both located in the transition cavity, at this time, the second valve core pipe orifice is connected to the oil outlet branch;

[0032] S2. The hydraulic oil in the large cross-sectional cavity will flow into the transition cavity through the first valve core pipe orifice and the first piston pipe orifice, then flow out from the transition cavity through the second piston pipe orifice and the second valve core pipe orifice, and finally flow out from the oil outlet, thereby completing the pressure relief of the large cross-sectional cavity and pushing the valve core body towards the large cross-sectional cavity;

[0033] S3. The valve core connection port is also connected to the oil outlet. The hydraulic oil entering from the oil inlet enters the rod cavity through the piston oil inlet branch. The hydraulic oil in the rodless cavity flows out from the oil outlet after passing through the piston connection port and the valve core connection port, thereby pushing the piston rod to retract.

[0034] The present invention has achieved the following technical effects compared with the prior art:

[0035] By continuously injecting hydraulic oil into the oil inlet, the present invention can control the telescoping of the piston rod without setting a reversing valve to change the oil injection pipeline, and the operation is simple and convenient. Description of the Drawings

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0037] Figure 1 This is the initial state diagram of the automatic reciprocating hydraulic cylinder in the embodiment of the present invention;

[0038] Figure 2 For Figure 1 Schematic diagram of the spool cavity in the state;

[0039] Figure 3 This is the state diagram of the piston rod extending in the automatic reciprocating hydraulic cylinder in the embodiment of the present invention;

[0040] Figure 4 For Figure 3 Schematic diagram of the spool cavity in the state;

[0041] Figure 5 This is the initial state diagram of the automatic reciprocating hydraulic cylinder in the embodiment of the present invention when the piston rod needs to be retracted;

[0042] Figure 6 For Figure 5 Schematic diagram of the spool cavity in the state;

[0043] Figure 7 This is the state diagram of the piston rod retracting in the automatic reciprocating hydraulic cylinder in the embodiment of the present invention;

[0044] Figure 8 For Figure 7 Schematic diagram of the spool cavity in the state;

[0045] In the figure: 1 - Hydraulic cylinder main body; 2 - Piston cavity; 3 - Spool cavity; 4 - First piston; 5 - Second piston; 6 - Connecting rod; 7 - Piston rod; 8 - Spool body; 801 - First annular channel; 802 - Second annular channel; 803 - Third annular channel; 804 - T-shaped channel; 9 - Oil circuit block; 10 - Cylinder head; 11 - Connecting channel; 1101 - Piston connection port; 1102 - Spool connection port; 12 - First pipeline; 1201 - First piston pipe orifice; 1202 - First spool pipe orifice; 13 - Second pipeline; 1301 - Second piston pipe orifice; 1302 - Second spool pipe orifice; 14 - Oil outlet pipeline; 1401 - Oil outlet; 1402 - Oil outlet branch port; 15 - Oil inlet; 1501 - Piston oil inlet branch port; 1502 - First oil inlet branch; 1503 - Spool oil inlet branch port; 1504 - Second oil inlet branch. Detailed implementation manners

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] The object of the present invention is to provide an automatic reciprocating hydraulic cylinder and its telescoping method, which are used to solve the technical problems existing in the above-mentioned prior art, and can control the telescoping of the piston rod without a reversing valve.

[0048] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Embodiment 1

[0050] As Figures 1 - 8 shown, this embodiment provides an automatic reciprocating hydraulic cylinder, which includes a hydraulic cylinder body 1. A piston chamber 2 and a valve core chamber 3 are arranged in the hydraulic cylinder body 1;

[0051] Among them, a first piston 4 and a second piston 5 are slidably connected in the piston chamber 2. The first piston 4 and the second piston 5 are connected by a connecting rod 6. One end of the second piston 5 away from the first piston 4 (i.e., Figure 1 the right side in Figure 1 shown) is provided with a piston rod 7. The piston rod 7 can penetrate the hydraulic cylinder body 1. The first piston 4 and the second piston 5 divide the piston chamber 2 into a rodless chamber, a transition chamber, and a rod chamber. Specifically, as

[0052] shown, the left side of the first piston 4 is the rodless chamber, the space between the first piston 4 and the second piston 5 is the transition chamber, and the right side of the second piston 5 is the rod chamber; Figure 1 the left chamber in Figure 1In the right cavity on the right side), the cross-sectional area of the large cross-section cavity is larger than that of the small cross-section cavity. On the side wall of the valve core body 8, there are a first annular channel 801, a second annular channel 802, and a third annular channel 803. Among them, both the second annular channel 802 and the third annular channel 803 are annular groove structures opened on the side wall of the valve core body 8, while the first annular channel 801 is an annular space formed between the left end of the valve core body 8 and the inner wall of the valve core cavity 3. When the valve core body 8 moves to the leftmost end, the first annular channel 801 will disappear. In addition, on the valve core body 8, there is a T-shaped channel 804. One end of the T-shaped channel 804 is connected to the small cross-section cavity, and the other two ends of the T-shaped channel 804 are both connected to the third annular channel 803;

[0053] On the side wall of the valve core cavity 3, there are a valve core oil inlet branch port 1503, an oil outlet branch port 1402, a valve core connection port 1102, a valve core first pipe orifice 1202, and a valve core second pipe orifice 1302. The piston cavity 2 is provided with a piston oil inlet branch port 1501, a piston connection port 1101, a piston first pipe orifice 1201, and a piston second pipe orifice 1301. The valve core oil inlet branch port 1503 and the piston oil inlet branch port 1501 are both connected to an oil inlet 15 through pipes. The oil outlet branch port 1402 is connected to an oil outlet 1401 through a pipe. The valve core connection port 1102 is connected to the piston connection port 1101 through a pipe. The valve core first pipe orifice 1202 is connected to the piston first pipe orifice 1201 through a pipe. The valve core second pipe orifice 1302 is connected to the piston second pipe orifice 1301 through a pipe;

[0054] The valve core oil inlet branch port 1503 can be connected to the second annular channel 802 or the third annular channel 803. The oil outlet branch port 1402 can be connected to the first annular channel 801 or the second annular channel 802. The valve core first pipe orifice 1202 is connected to the large cross-section cavity. The valve core second pipe orifice 1302 can be connected to the first annular channel 801 or the second annular channel 802. The valve core connection port 1102 can be connected to the second annular channel 802;

[0055] The piston first pipe orifice 1201 can be connected to the transition cavity or the rodless cavity. The piston second pipe orifice 1301 can be connected to the transition cavity.

[0056] During actual use, it includes the following three processes:

[0057] Process 1: As Figures 1 - 4As shown, the hydraulic oil enters through the oil inlet 15 and then is divided. After division, one path enters the valve core cavity 3 through the valve core oil inlet branch 1503, and then enters the small cross-section cavity through the T-shaped channel 804; the other path enters the rodless cavity through the piston oil inlet branch 1501, and then enters the large cross-section cavity through the first piston pipe orifice 1201 and the first valve core pipe orifice 1202. Since the cross-sectional area of the left end of the valve core body 8 is larger than that of the right end (i.e., the cross-sectional area of the large cross-section cavity is larger than that of the small cross-section cavity), at this time, the valve core body 8 moves differentially to the right. At this time, both the valve core connection port 1102 and the valve core oil inlet branch 1503 are communicated with the second annular channel 802, and the second valve core pipe orifice 1302 is connected to the oil outlet branch 1402 through the first annular channel 801. The hydraulic oil from the valve core oil inlet branch 1503 will enter the rodless cavity through the valve core connection port 1102 and the piston connection port 1101. At the same time, since the cross-sectional area of the rodless cavity is larger than that of the rodless cavity and the pressures of the two are the same, the pressure in the rodless cavity is less than the pressure in the rodless cavity at this time, and the piston rod 7 extends outwards due to the differential movement generated.

[0058] Process two: As Figures 5 - 8 shown, as the piston rod 7 continues to move, when both the first piston pipe orifice 1201 and the second piston pipe orifice 1301 are in the transition cavity at the same time (as Figure 5 shown), at this time, the valve core connection port 1102 and the second valve core pipe orifice 1302 are connected to the oil outlet branch 1402 through the second annular channel 802. The hydraulic oil in the large cross-section cavity flows into the transition cavity through the first valve core pipe orifice 1202 and the first piston pipe orifice 1201, and then flows into the oil outlet branch 1402 through the second piston pipe orifice 1301 and the second valve core pipe orifice 1302, so that the large cross-section cavity is depressurized while the pressure in the small cross-section cavity is maintained. Under the action of the pressure, the valve core body 8 moves to the left. At this time, the hydraulic oil can only enter the rodless cavity through the piston oil inlet branch 1501, and the hydraulic oil in the rodless cavity passes through the piston connection port 1101 and the valve core connection port 1102 and then is discharged from the oil outlet branch 1402. The piston rod 7 automatically changes the movement direction and starts to retract inward.

[0059] Process three: When the piston rod 7 retracts until both the piston oil inlet branch 1501 and the first piston pipe orifice 1201 are located in the rodless cavity at the same time, repeat step 1, and the piston rod 7 automatically changes direction again and extends outwards. It should be noted here that if it is necessary to keep the piston rod 7 in a certain position, only stop oil supply and maintain pressure.

[0060] In this embodiment, each oil port is connected through pipelines, and the respective pipelines are as follows:

[0061] The valve core oil inlet branch 1503 is connected to the oil inlet 15 through the second oil inlet branch 1504, and the second oil inlet branch 1504 passes through the side wall of the hydraulic cylinder body 1;

[0062] The piston oil inlet branch port 1501 is communicated with the oil inlet port 15 through the first oil inlet branch 1502, and the first oil inlet branch 1502 is located outside the hydraulic cylinder body 1;

[0063] The oil outlet branch port 1402 is communicated with the oil outlet port 1401 through the oil outlet pipeline 14, and the oil outlet pipeline 14 is an internal channel of the hydraulic cylinder body 1;

[0064] The spool connection port 1102 is communicated with the piston connection port 1101 through the connection channel 11, and the connection between the spool cavity 3 and the piston cavity 2 is realized through the connection channel 11;

[0065] The first spool pipe orifice 1202 is communicated with the first piston pipe orifice 1201 through the first pipeline 12, and the first pipeline 12 is an external pipe fitting of the hydraulic cylinder body 1;

[0066] The second spool pipe orifice 1302 is communicated with the second piston pipe orifice 1301 through the first pipeline 12, and the second pipeline 13 is an external pipe fitting of the hydraulic cylinder body 1.

[0067] In this embodiment, an oil circuit block 9 is provided on the side wall of the hydraulic cylinder body 1. The oil circuit block 9 is fixed to the side wall of the hydraulic cylinder body 1 by screws. The oil inlet port 15 and the oil outlet port 1401 are both arranged on the oil circuit block 9, which facilitates the arrangement and connection of the oil inlet port 15 and the oil outlet port 1401.

[0068] In this embodiment, a plurality of piston sealing rings are provided on the side walls of the first piston 4 and the second piston 5. The use of the piston sealing rings can further improve the sealing performance between the first piston 4 and the second piston 5 and the piston cavity 2 respectively.

[0069] In this embodiment, the hydraulic cylinder body 1 includes a cylinder block and a cylinder head 10. The cylinder head 10 is fixed to the opening of the piston cavity 2 ( Figure 1 on the right side of the piston cavity 2 in the figure) by screws, and the piston rod 7 passes through the cylinder head 10.

[0070] In this embodiment, a plurality of piston sealing rings are provided on the cylinder head 10. The use of the piston sealing rings can ensure the sealing performance between the piston rod 7 and the cylinder head 10, and between the cylinder head 10 and the cylinder block.

[0071] In this embodiment, the cross-sectional area of the rodless cavity is larger than that of the rod cavity. When the pressure of the hydraulic oil is the same, the larger the cross-sectional area, the greater the pressure.

[0072] Embodiment Two

[0073] This embodiment provides a telescopic method for an automatic reciprocating hydraulic cylinder, including an extending method and a retracting method;

[0074] Among them, the extending method is as follows:

[0075] S1. Hydraulic oil is introduced into the oil inlet 15. A part of the hydraulic oil will enter the spool cavity 3 through the second oil inlet branch 1504 and the spool oil inlet port 1503, and enter the small cross-section cavity through the T-shaped channel 804;

[0076] S2. Another part of the hydraulic oil will enter the rod chamber through the first oil inlet branch 1502 and the piston oil inlet port 1501, and then enter the large cross-section cavity through the piston first pipe orifice 1201 and the spool first pipe orifice 1202 (i.e., the first pipeline 12), and push the spool body 8 in the direction of the small cross-section cavity;

[0077] S3. The spool oil inlet port 1503 is connected to the spool connection port 1102 through the second annular channel 802, and the spool second pipe orifice 1302 is connected to the oil outlet 1401 through the first annular channel 801. The hydraulic oil will enter the rodless cavity through the spool connection port 1102 and the connection channel 11. The pressure in the rodless cavity is greater than the pressure in the rod chamber, thereby pushing the piston rod 7 to extend;

[0078] The retraction method is as follows:

[0079] S1. When the piston first pipe orifice 1201 and the piston second pipe orifice 1301 are both located in the transition cavity, at this time, the spool second pipe orifice 1302 is connected to the oil outlet branch 1402;

[0080] S2. The hydraulic oil in the large cross-section cavity will flow into the transition cavity through the spool first pipe orifice 1202 and the piston first pipe orifice 1201, then flow out from the transition cavity through the piston second pipe orifice 1301 and the spool second pipe orifice 1302, and finally flow out from the oil outlet 1401, thereby completing the pressure relief of the large cross-section cavity, and the pressure in the small cross-section cavity remains unchanged, thereby pushing the spool body 8 towards the large cross-section cavity;

[0081] S3. The spool connection port 1102 is also connected to the oil outlet 1401. The hydraulic oil entering from the oil inlet 15 enters the rod chamber through the piston oil inlet port 1501. The hydraulic oil in the rodless cavity flows out from the oil outlet 1401 after passing through the piston connection port 1101 and the spool connection port 1102, thereby pushing the piston rod 7 to retract.

[0082] In this specification, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An automatic reciprocating hydraulic cylinder, characterized in that: It includes a hydraulic cylinder body, and a piston chamber and a spool chamber are provided inside the hydraulic cylinder body; A first piston and a second piston are slidably connected in the piston chamber. The first piston and the second piston are connected by a connecting rod. A piston rod is provided at one end of the second piston away from the first piston, and the piston rod can penetrate through the hydraulic cylinder body. The first piston and the second piston divide the piston chamber into a rodless chamber, a transition chamber, and a rod chamber; A spool body is slidably connected in the spool chamber. The spool body divides the spool chamber into a large-section chamber and a small-section chamber. A first annular channel, a second annular channel, and a third annular channel are provided on the side wall of the spool body. A T-shaped channel is provided on the spool body. One end of the T-shaped channel communicates with the small-section chamber, and the other two ends of the T-shaped channel both communicate with the third annular channel; A spool oil inlet branch port, an oil outlet branch port, a spool connection port, a spool first pipe orifice, and a spool second pipe orifice are provided on the side wall of the spool chamber. A piston oil inlet branch port, a piston connection port, a piston first pipe orifice, and a piston second pipe orifice are provided in the piston chamber. The spool oil inlet branch port and the piston oil inlet branch port are both connected to an oil inlet. The oil outlet branch port is connected to an oil outlet. The spool connection port communicates with the piston connection port. The spool first pipe orifice communicates with the piston first pipe orifice. The spool second pipe orifice communicates with the piston second pipe orifice; The spool oil inlet branch port can communicate with the second annular channel or the third annular channel. The oil outlet branch port can communicate with the first annular channel or the second annular channel. The spool first pipe orifice communicates with the large-section chamber. The spool second pipe orifice can communicate with the first annular channel or the second annular channel. The spool connection port can communicate with the second annular channel; The piston first pipe orifice can communicate with the transition chamber or the rod chamber. The piston second pipe orifice can communicate with the transition chamber.

2. The automatic reciprocating hydraulic cylinder according to claim 1, wherein: The spool oil inlet branch port is connected to the oil inlet through a second oil inlet branch; The piston oil inlet branch port is connected to the oil inlet through a first oil inlet branch; The oil outlet branch port is connected to the oil outlet through an oil outlet pipeline; The spool connection port is connected to the piston connection port through a connection channel; The spool first pipe orifice is connected to the piston first pipe orifice through a first pipeline; The spool second pipe orifice is connected to the piston second pipe orifice through a first pipeline.

3. The automatic reciprocating hydraulic cylinder according to claim 1, wherein: An oil circuit block is provided on the side wall of the hydraulic cylinder body. The oil inlet and the oil outlet are both arranged on the oil circuit block.

4. The automatic reciprocating hydraulic cylinder according to claim 1, characterized in that: A plurality of piston sealing rings are provided on the side walls of the first piston and the second piston.

5. The automatic reciprocating hydraulic cylinder according to claim 1, characterized in that: The hydraulic cylinder body includes a cylinder block and a cylinder head. The cylinder head is fixed at the opening of the piston chamber, and the piston rod passes through the cylinder head.

6. The automatic reciprocating hydraulic cylinder according to claim 5, wherein: A plurality of piston sealing rings are provided on the cylinder head.

7. The automatic reciprocating hydraulic cylinder according to claim 1, characterized in that: The cross-sectional area of the rodless chamber is larger than that of the rod chamber.

8. A telescopic method of the automatic reciprocating hydraulic cylinder according to any one of claims 1-7, characterized in that: It includes an extending method and a retracting method; Extending method: S1. Inject hydraulic oil into the oil inlet. A part of the hydraulic oil will enter the valve core cavity through the valve core oil inlet branch, and enter the small cross-section cavity through the T-shaped channel; S2. Another part of the hydraulic oil will enter the rod chamber through the piston oil inlet branch, then enter the large cross-section cavity through the first piston pipe orifice and the first valve core pipe orifice, and push the valve core body in the direction of the small cross-section cavity; S3. The valve core oil inlet branch is connected to the valve core connection port, and the second valve core pipe orifice is connected to the oil outlet. The hydraulic oil will enter the rodless cavity through the valve core connection port. The pressure in the rodless cavity is greater than the pressure in the rod chamber, thereby pushing the piston rod out; Retraction method: S1. When the first piston pipe orifice and the second piston pipe orifice are both located in the transition cavity, at this time, the second valve core pipe orifice is connected to the oil outlet branch; S2. The hydraulic oil in the large cross-section cavity will flow into the transition cavity through the first valve core pipe orifice and the first piston pipe orifice, then flow out from the transition cavity through the second piston pipe orifice and the second valve core pipe orifice, and finally flow out from the oil outlet, thereby completing the pressure relief of the large cross-section cavity, and pushing the valve core body towards the large cross-section cavity; S3. The valve core connection port is also connected to the oil outlet. The hydraulic oil entering from the oil inlet enters the rod chamber through the piston oil inlet branch, and the hydraulic oil in the rodless cavity flows out from the oil outlet after passing through the piston connection port and the valve core connection port, thereby pushing the piston rod to retract.

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