AUTOMATIC OIL RETURN STRUCTURE

Abstract

The automatic oil return structure comprises a piston assembly (20) and a main body assembly (30), which includes a first main section (3112), a control device (370), an actuating locking element, and a switching channel (34) that is fluid-connected to the first main section (3112), a pressurizing channel (35), and an oil return channel (36). When the pressure of the first main section (3112) reaches a maximum pressure, the pressure forces the control device (370) and the actuating locking element, and the oil reservoir (10) is fluid-connected to the first main section (3112), thereby reducing the pressure of the first main section (3112).A switching device (343) is moved to isolate the switching channel (34) from the first main section (3112), so that the switching channel (34) is in fluid communication with the oil return channel (36) and the hydraulic oil continues to return to the oil storage reservoir (10).

Description

1. Field of the invention

[0001] The present invention relates to a piston pump, in particular a piston pump which is designed to be installed in a clamping tool. 2. Description of the state of the art

[0002] The conventional piston pump comprises an oil reservoir, a drive mechanism, and a piston. The drive mechanism pumps the hydraulic oil from the oil reservoir and pressurizes the hydraulic oil to pump it into the piston, setting it in motion. To quickly push the piston into a working position and to precisely control and adjust the piston as it approaches the working position, the piston is pushed by means of an inner tube and an outer tube.

[0003] When the piston pump is activated, the drive unit pumps hydraulic oil into the inner tube to quickly push the piston. Due to the smaller diameter of the inner tube, the inner tube can be pushed a long distance with a small amount of hydraulic oil, allowing the piston to move quickly. As the piston approaches the working position, the drive unit pumps hydraulic oil into both the inner and outer tubes, allowing the piston's movement speed to be precisely controlled and adjusted.

[0004] As long as the piston, along with its constant movement, collides with an object to be compressed, the pressures in the inner and outer tubes increase and amplify with the increasing compression the piston exerts on the object. A safety valve is forced open when the pressure rises to a preset value, indicating that the required compression has been achieved by the piston, and the hydraulic oil in the inner and outer tubes flows back into the oil reservoir via a safety channel.

[0005] However, once the safety valve opens, the pressure would suddenly drop to zero. Therefore, the safety valve can only be opened at a certain moment, and the safety valve would soon close again as long as the pressure drops to zero. Therefore, only a small amount of hydraulic oil can flow back from the safety channel to the oil storage tank via the safety valve. In this case, the user needs to operate another oil release lever to open an oil return channel, and they need to constantly operate the oil release lever until all the hydraulic oil from the inner tube and outer tube flows back into the oil storage tank via the oil return channel. Thus, the hydraulic oil flows from the piston back to the oil storage tank. However, the aforementioned process is extremely cumbersome.

[0006] DE 10 2022 131 012 B3 discloses an automatic oil return structure comprising a piston and a main body assembly. The automatic oil return structure is capable of automatically returning the hydraulic oil using the pressure acting on the control-locking device and the actuating device to temporarily maintain the return channels connected to the reservoir.

[0007] DE 10 2023 122 022 A1 discloses another automatic oil return structure comprising a main body assembly and a piston. The automatic oil return structure is capable of returning the hydraulic oil with the engagement unit engaged with the pressure regulating blocking unit.

[0008] DE 10 2020 112 217 A1 discloses a hydraulic clamping device comprising a main body assembly and a piston. The main body facilitates the flow of hydraulic oil into the piston, and the hydraulic clamping device must manually return the hydraulic oil by means of a pressing mechanism.

[0009] WO 2014 / 063 182 A1 discloses a hydraulically operated tool and a shuttle valve assembly. The hydraulically operated tool must recirculate the hydraulic oil by constantly pressing the release trigger.

[0010] US 6 276 186 B1 discloses a method for actuating a hydraulic pressure device having a stationary part and a movable part, and the movable part is capable of automatically and completely returning to the initial position thereof when a predetermined pressure is reached with a valve piston which is connected to a compression spring.

[0011] The main object of the present invention is to provide an automatic oil return structure adapted to be installed in a piston pump having an inner tube and an outer tube and capable of returning all the hydraulic oil to an oil storage tank as long as a pressure of the hydraulic oil is higher than a predetermined value.

[0012] The automatic oil return structure includes an oil storage tank, a piston device, and a main body device.

[0013] The oil storage tank contains hydraulic oil in it, with the hydraulic oil in the oil storage tanks maintaining a static pressure.

[0014] The piston assembly is spaced apart from the oil storage container. The piston assembly includes an inner tube, a displacement unit, a first oil reservoir, an outer tube, and a second oil reservoir. The inner tube includes an inner channel. The displacement unit is mounted on the inner tube, and the displacement unit is sealed to an outer wall surface of the inner tube. The first oil reservoir is formed within the displacement unit and fluidly connected to the inner channel. The outer tube is mounted on the displacement unit. The displacement unit is sealed to an inner wall surface of the outer tube, and the displacement unit is capable of movement relative to the inner tube and the outer tube. The second oil reservoir is formed at (e.g., between, midway between, below) the outer tube, the inner tube, and the displacement unit.

[0015] The main body assembly is disposed between the oil storage tank and the piston assembly. The main body assembly includes a first main portion, a second main portion, a first one-way interlocking means, a second one-way interlocking means, a switching channel, a switching means, a pressurizing channel, an oil return channel, a control channel, a control means, an actuating channel, a first actuating closure member, and a second actuating closure member. The first main portion is in fluid communication with the oil storage tank. The second main portion is in fluid communication with the first oil reservoir and the second oil reservoir. The first one-way interlocking means is operable to prevent hydraulic oil from flowing from the first main portion into the oil storage tank.The second one-way blocking device is capable of preventing the hydraulic oil from flowing from the second main section into the second oil reservoir. The switching channel is in fluid communication with the first main section. The switching device is mounted in the switching channel and selectively blocks the switching channel. The pressurization channel has one end in fluid communication with the switching channel and another end in fluid communication with the first oil reservoir. The oil return channel has one end in fluid communication with the switching channel and another end in fluid communication with the oil storage container. The control channel is in fluid communication with the first main section. The control device is mounted in the control channel and selectively blocks the control channel.The actuation channel has a first actuation portion and a second actuation portion, one end of the first actuation portion being in fluid communication with the control channel and another end of the first actuation portion being in fluid communication with the oil storage container and the second actuation portion. The first actuation closure member is movably mounted in the first actuation portion of the actuation channel, with positions where the control channel is in fluid communication with the first actuation portion and where the oil storage container is in fluid communication with the first actuation portion being arranged on two respective sides of the first actuation closure member. The second actuation closure member is mounted in the actuation channel and selectively isolates the first actuation portion from the second actuation portion.

[0016] When a pressure of the first main section is higher than a starting pressure, the pressure of the first main section drives the switching device to move and isolate the switching channel from the oil return channel, and the switching channel remains in fluid communication with the first main section and the pressurizing channel, so that the hydraulic oil flows into the first oil reservoir via the inner channel; the starting pressure is higher than the static pressure.

[0017] When the pressure of the first main section reaches a maximum pressure, the pressure of the first main section pushes the control device, and thus the first main section is in fluid communication with the first actuating section; the pressure of the first main section also drives the first actuating closure member to push the second actuating closure member to move, and thus the second actuating section is in fluid communication with the first actuating section and the oil storage container; when the second actuating section is in fluid communication with the oil storage container, the pressure of the first main section drops to the static pressure; the maximum pressure is higher than the starting pressure.

[0018] When the pressure of the first main section drops to the static pressure, the switching device moves and isolates the switching channel from the first main section, and the switching channel remains in fluid communication with the pressurization channel and the oil return channel, and then the hydraulic oil flows through the inner channel, the pressurization channel, and the oil return channel from the first oil reservoir to the oil storage tank; the hydraulic oil in the second oil reservoir pushes the second one-way blocking device and enters the second main section, and the hydraulic oil flows through the pressurization channel and the oil return channel toward the oil storage tank.

[0019] Therefore, when the pressure of the first main section reaches the maximum pressure, the pressure pushes on the control device and the actuating closure element, causing the oil storage tank, the first actuating section, the second actuating section, and the first main section to be in fluid communication, and the pressure of the first main section to decrease. Meanwhile, the switching device moves to isolate the switching channel and the first main section and establishes fluid communication between the switching channel and the oil return channel, thus enabling the first oil reservoir and the second oil reservoir to maintain fluid communication with the oil storage tank to reduce the pressure and return the hydraulic oil.

[0020] In the drawings: Fig. 1 is a side view of an automatic oil return structure according to the present invention, shown mounted in a piston pump, Fig. 2 is a cross-sectional view of the automatic oil return structure taken along line 2-2 in Fig. 15, which shows a cross section of a piston device, Fig. 3 is a cross-sectional view of the automatic oil return structure taken along line 3-3 in Fig. 16, which shows a cross-section of a first primary channel, Fig. 4 is a cross-sectional view of the automatic oil return structure taken along line 4-4 in Fig. 16, which shows a cross-section of a second primary channel, Fig. 5 is a cross-sectional view of the automatic oil return structure taken along line 5-5 in Fig. 16, which shows a cross-section of a connecting channel, Fig. 6 is a cross-sectional view of the automatic oil return structure taken along line 6-6 in Fig. 18, which shows a cross-section of a switching channel, Fig. 6A is a cross-sectional view of the automatic oil return structure in Fig. 1, which shows a switching device blocking a first switching opening, Fig. 6B is a cross-sectional view of the automatic oil return structure in Fig. 1, which shows a switching device blocking a second switching opening, Fig. 7 is a cross-sectional view of the automatic oil return structure taken along line 7-7 in Fig. 17, which shows a cross-section of an actuating channel, Fig. 7A is a cross-sectional view of a first actuating closure element of the automatic oil return structure in Fig. 1, Fig. 8 is a cross-sectional view of the automatic oil return structure taken along line 8-8 in Fig. 17, Fig. 9 is a cross-sectional view of the automatic oil return structure taken along line 9-9 in Fig. 16, which shows a cross-section of a control channel, Fig. 10 is a cross-sectional view of the automatic oil return structure which line 10-10 in Fig. 15, Fig. 11 is a cross-sectional view of the automatic oil return structure taken along line 11-11 in Fig. 16, which shows a section of an actuating channel, Fig. 12 is a cross-sectional view of the automatic oil return structure taken along line 12-12 in Fig. 17, which shows a section of an actuating channel, Fig. 13 is a cross-sectional view of the automatic oil return structure taken along line 13-13 in Fig. 18, which shows cross sections of a switching channel, a pressurization channel and an oil return channel, Fig. 14 is a cross-sectional view of the automatic oil return structure taken along line 14-14 in Fig. 17, which shows a pressurization channel in fluid communication with a second main section, Fig. 15 is a front view of the automatic oil return structure in Fig. 1, Fig. 16 is a side view of the automatic oil return structure in Fig. 1, Fig. 17 is a plan view of the automatic oil return structure in Fig. 1, and Fig. 18 is an enlarged partial view of the automatic oil return structure in Fig. 1.

[0021] With reference to Fig. 1, an automatic oil return structure according to the present invention includes an oil storage tank 10, a piston assembly (hereinafter referred to as "piston assembly") 20, a main body assembly (hereinafter referred to as "main body assembly") 30, and a drive assembly (hereinafter referred to as "drive assembly") 40. The piston assembly 20 is spaced apart from the oil storage tank 10, and the main body assembly 30 is disposed between the piston assembly 20 and the oil storage tank 10. The drive assembly 40 is connected to the main body assembly 30. The drive assembly 40 drives the hydraulic oil in the oil storage tank 10 to flow through the main body assembly 30 and then be forced toward the piston assembly 20.

[0022] The hydraulic oil is stored in the oil storage tank 10, and the hydraulic oil in the oil storage tank 10 is under static pressure. If the channels of the automatic oil return structure in this disclosure communicate with the oil storage tank 10, the hydraulic oil in the channels would also reach static pressure due to the very large volume of the oil storage tank 10.

[0023] With reference to Fig. 2 and Fig. 15, the piston device 20 comprises an inner tube 21, a displacement unit 22, and an outer tube 23, and a first oil reservoir 201 and a second oil reservoir 202 are formed in the piston device 20. The piston device 20 can selectively comprise an elastic return unit 24. The inner tube 21 has an inner channel 210. The displacement unit 22 is mounted on the inner tube 21 (e.g., slid onto it) and seals an outer wall surface of the inner tube 21. The outer tube 23 is mounted on the displacement unit 22 (e.g., slid onto it), and the displacement unit 22 seals an inner wall of the outer tube 23. The displacement unit 22 is capable of moving relative to the inner tube 21 and the outer tube 23. The first oil reservoir 201 is formed in the displacement unit 22 and is in fluid communication with the inner channel 210, and the second oil reservoir 202 is at (e.g.between, in the middle of, under) the outer tube 23, the inner tube 21, and the displacement unit 22. The volumes of the first oil reservoir 201 and the second oil reservoir 202 change with the movement of the displacement unit 22. The elastic return unit 24 is configured to return the displacement unit 22. More specifically, the elastic return unit 24 returns the displacement unit 22 to a position in which the volumes of the first oil reservoir 201 and the second oil reservoir 202 are at a minimum.

[0024] With reference to the Fig. 3 to 18, the main body device 30 has two primary channels (as in Fig. 3, Fig. 4 and Fig. 16), a connecting channel 32 (as shown in Fig. 5 and Fig. 16), two secondary channels 33 (as shown in Fig. 3, Fig. 4 and Fig. 16), a switching channel 34 (as shown in Fig. 13 and Fig. 18), a pressurization channel 35 (as in Fig. 13 and Fig. 18), an oil return channel 36 (as shown in Fig. 13 and Fig. 18), a control channel 37 (as shown in Fig. 9 and Fig. 16) and an actuating channel 38 (as shown in Fig. 11, Fig. 12, Fig. 16 and Fig. 17 shown).

[0025] As in Fig. 3, Fig. 4 and Fig. 16, one end of each primary channel is in fluid communication with the oil storage container 10 and another end is in fluid communication with the second oil reservoir 202. A plurality of one-way blocking devices are attached to the two ends of the primary channel, whereby the one-way blocking devices limit the hydraulic oil flowing into or out of the primary channel.

[0026] More specifically, the two primary channels may include a first primary channel 311 and a second primary channel 312. In this embodiment, a primary channel blocking unit 3111 is mounted in the first primary channel 311, thereby dividing the first primary channel 311 into a first main section 3112 and a second main section 3113, and the first main section 3112 is not in fluid communication with the second main section 3113. However, in another embodiment, the first main section 3112 and the second main section 3113 may be two independent channels instead of being formed in the same channel. The first main section 3112 is in fluid communication with the oil storage container 10, and the second main section 3113 is in fluid communication with the inner channel 210 and the second oil reservoir 202.The connecting channel 32 is in fluid communication with the second primary channel 312 and the first main section 3112, so that the pressure in the first main section 3112 remains equal to the pressure in the second primary channel 312.

[0027] The one-way blocking device may include a first one-way blocking device 3131, a second one-way blocking device 3132, a third one-way blocking device 3133, and a fourth one-way blocking device 3134. The first one-way blocking device 3131 is configured to prevent the hydraulic oil from flowing from the first main portion 3112 to the oil storage tank 10, and the second one-way blocking device 3132 is configured to prevent the hydraulic oil from flowing from the second main portion 3113 to the second oil reservoir 202. The third one-way blocking device 3133 is configured to prevent the hydraulic oil from flowing from the second primary channel 312 to the oil storage tank 10, and the fourth one-way blocking device 3134 is configured to prevent the hydraulic oil from flowing from the second oil reservoir 202 to the second primary channel 312.

[0028] One end of each of the secondary channels 33 is in fluid communication with the oil storage container 10, and another end of each of the secondary channels 33 is in fluid communication with the second oil reservoir 202, thereby maintaining the pressures in the secondary channels 33 equal to the static pressure in the oil storage container 10. A secondary channel one-way blocking device 330 is configured to prevent the hydraulic oil from flowing from the second oil reservoir 202 to the secondary channel 33. In another embodiment, the main body device 30 may have only one secondary channel 33.

[0029] As in Fig. 5, Fig. 6 and Fig. 13, the switching channel 34 is in fluid communication with the first main portion 3112, the pressurizing channel 35, and the oil return channel 36. In other words, the first main portion 3112, the pressurizing channel 35, and the oil return channel 36 are fluidly connected to each other via the switching channel 34. More specifically, one end of the pressurizing channel 35 is fluidly connected to the switching channel 34, and another end is fluidly connected to the inner channel 210. One end of the oil return channel 36 is fluidly connected to the switching channel 34, and another end is fluidly connected to the oil storage container 10. In this embodiment, the switching channel 34 has a first switching opening 341 and a second switching opening 342. The first switching opening 341 is fluidly connected to the first main portion 3112.The pressurization channel 35 is fluidly connected to a position between the first switching opening 341 and the second switching opening 342 of the switching channel 34. The second switching opening 342 is fluidly connected to the oil return channel 36.

[0030] Referring to Fig. 6A and Fig. 6B, a switching device 343 is mounted in the switching channel 34 and selectively blocks the switching channel 34, whereby only two of the first main section 3112, the pressurizing channel 35 and the oil return channel 36 can communicate with each other at the same time.

[0031] The switching device 343 comprises a switching closure element or switching pin or switching plug (hereinafter also referred to as: switching closure element) 3431, a switching seal 3432, and a switching spring unit 3433. The switching closure element 3431 is movably mounted in the switching channel 34 and can selectively block the first switching opening 341 or the second switching opening 342. The switching closure element 3431 has an annular projection 3434, and a gap is formed between an outer annular surface of the annular projection 3434 and an inner annular surface of the switching channel 34.

[0032] The switching seal 3432 is mounted in the switching channel 34 and is movably mounted (e.g., slidably mounted) on the switching closure element 3431. An outer annular surface of the switching seal 3432 abuts an inner annular surface of the switching channel 34, and a gap is formed between an inner surface of the switching seal 3432 and the switching closure element 3431. An inner diameter of the switching seal 3432 is shorter than an outer diameter of the annular projection 3434, whereby the switching seal 3432 selectively abuts one side of the annular projection 3434 and the switching channel 34 is blocked as long as the switching seal 3432 abuts the annular projection 3434. The switching spring unit 3433 abuts the switching seal 3432 and presses the switching seal 3432 so that it is adapted to abut the annular projection 3434.

[0033] As in Fig. 9 and Fig. 16, the control channel 37 is in fluid communication with the first main portion 3112, and a control device 370 is mounted in the control channel 37 and selectively blocks the control channel 37.

[0034] As in Fig. 7, Fig. 11, Fig. 12, Fig. 16 and Fig. 17, the actuating passage 38 includes a first actuating portion 381 and a second actuating portion 382. One end of the first actuating portion 381 is fluidly connected to the control passage 37, and another end of the first actuating portion 381 is fluidly connected to the oil storage container 10 and the second actuating portion 382. A first actuating plug (hereinafter referred to as actuating plug) 383 is movably mounted in the first actuating portion 381, and the position at which the control passage 37 is in fluid communication with the first actuating portion 381 and the position at which the first actuating portion 381 is in fluid communication with the oil storage container 10 are respectively disposed on two sides of the first actuating plug 383.A second actuating closure element 384 is mounted in the actuating channel 38 and selectively isolates the first actuating portion 381 from the second actuating portion 382.

[0035] Next, Fig. 7A. In this embodiment, the first actuating closure member 383 includes a first portion 3831 and a second portion 3832 that are fluidly connected to each other. An outer annular surface of the first portion 3831 seals and abuts against an inner annular surface of the first actuating portion 381, so that the first actuating portion 381 is divided into two parts. The second portion 3832 is capable of passing through a position where the first actuating portion 381 is connected to the second actuating portion 382, ​​and thereby the second portion 3832 is capable of moving into the second actuating portion 382. A gap is formed between an outer annular surface of the second portion 3832 and an inner wall surface at the position where the first actuating portion 381 is connected to the second actuating portion 382.

[0036] The first actuating closure element 383 has an inner flow channel 3833, a first opening 3834, and a second opening 3835. The inner flow channel 3833 is formed by the first portion 3831 and the second portion 3832 of the first actuating closure element 383, and the first opening 3834 and the second opening 3835, which are respectively located at two opposite ends of the inner flow channel 3833, connect the inner flow channel 3833 to the outside. The outer annular surface of the first portion 3831 is arranged between the first opening 3834 and the second opening 3835. More specifically, the first opening 3834 can be formed on the first portion 3831 and is fluidly connected to the inner flow channel 3833, the first actuating channel 381, and the control channel 37.The second opening 3835 may be formed on the first actuating closure member 383 and is fluidly connected to the internal flow channel 3833, the first actuating portion 381 or the second actuating portion 382, ​​and the oil storage container 10. More specifically, the second opening 3835 may be formed on an end surface of the second portion 3832, and the end surface of the second portion 3832 is adjacent to the second actuating closure member 384. The second opening 3835 enters the second actuating portion 382 when the second portion 3832 of the first actuating closure member 383 enters the second actuating portion 382. In this embodiment, a cross-sectional area of ​​the second opening 3835 is much smaller than a cross-sectional area of ​​the internal flow channel 3833.

[0037] Furthermore, the first actuating closure element 383 may include a third opening 3836 formed on the first portion 3831 of the first actuating closure element 383. As a result, the third opening 3836 is disposed in the first actuating portion 381 and thus fluidly connected to the internal flow channel 3833 and the first actuating portion 381. In this embodiment, the third opening 3836 is formed on a side surface of the first actuating closure element 383. A cross-sectional area of ​​the third opening 3836 is much smaller than the cross-sectional area of ​​the internal flow channel 3833.

[0038] However, in another embodiment, the first actuating closure member 383 may be solid and therefore the first actuating closure member 383 may not include the inner flow channel 3833, the first opening 3834, the second opening 3835, and the third opening 3836.

[0039] The pressure of the first main section 3112 is lower than a starting pressure in a static state before launch via the aforementioned structures. As in Fig. As shown in Figure 6A, the switching closure element 3431 blocks the first switching opening 341 by the engagement of the switching spring unit 3433, and the switching seal 3432 abuts the annular projection 3434. Furthermore, the control device 370 blocks the control channel 37, and the second actuating closure element 384 isolates the first actuating portion 381 from the second actuating portion 382.

[0040] When a piston pump having the automatic oil return structure described in this disclosure is actuated, the drive device 40 drives the hydraulic oil from the oil storage tank 10 into the first main section 3112 via the first one-way blocking device 3131 and into the second primary passage 312 via the third one-way blocking device 3133. The first one-way blocking device 3131 and the third one-way blocking device 3133 are capable of preventing backflow of the hydraulic oil, therefore, the pressure of the first main section 3112 and the pressure of the second primary passage 312 are higher than the pressure of the oil storage tank 10.

[0041] When the pressure of the first main section 3112 increases and becomes higher than the starting pressure, the pressure of the first main section 3112 presses on the switching device 343 and drives the switching device 343 to move to isolate the switching channel 34 from the oil return channel 36, and the switching channel 34 remains in fluid communication with the first main section 3112 and the pressurizing channel 35.

[0042] More specifically, when the pressure of the first main section 3112 is higher than the starting pressure, the pressure of the first main section 3112 will cause the switching closure element 3431 to move to open the first switching opening 341, and thereby the first main section 3112 remains in fluid communication with the pressurizing channel 35. At the same time, the switching closure element 3431 also blocks the second switching opening 342, thus isolating the switching channel 34 from the oil return channel 36. Next, as shown in Fig.6B, the pressure of the first main portion 3112 separates the switching seal 3432 and the annular projection 3434 and opens the switching channel 34, whereby the first main portion 3112 is in fluid communication with the pressurizing channel 35, and thereby the hydraulic oil is able to flow from the first switching opening 341 via the gap between the switching seal 3432 and the annular projection 3434 to the pressurizing channel 35. Thus, the hydraulic oil flows sequentially via the first main portion 3112, the switching channel 34, the pressurizing channel 35, and the inner channel 210, and then flows into the first oil reservoir 201.

[0043] The first oil reservoir 201 expands with the further pumping of hydraulic oil into the first oil reservoir 201 by the drive device 40, and then the displacement unit 22 moves. The volume of the second oil reservoir 202 increases along with the movement of the displacement unit 22, so that the pressure of the second oil reservoir 202 is lower than the static pressure, whereby the hydraulic oil in the oil storage tank 10 is able to pass through the secondary channel one-way blocking device 330, and then the hydraulic oil flows through the secondary channel 33 and is sucked into the second oil reservoir 202. In this case, all the hydraulic oil pumped by the drive device 40 enters the first oil reservoir 201, and consequently the displacement unit 22 moves faster.

[0044] As long as the pressure of the first main section 3112 becomes higher than a pressurizing pressure, the hydraulic oil is able to push the fourth one-way locking device 3134 and then flows from the second primary channel 312 into the second oil reservoir 202. In this case, the hydraulic oil pumped by the drive device 40 enters both the first oil reservoir 201 and the second oil reservoir 202, and thus the displacement unit 22 moves more slowly, but the user can control the position of the displacement unit 22 more precisely.

[0045] Since the drive device 40 does not pump the hydraulic oil evenly and constantly into the first main section 3112 and the second primary channel 312, the pressures of the first main section 3112 and the second primary channel 312 would be subject to periodic fluctuations. Under the periodic pressure fluctuation, together with the pressure of the first main section 3112, which increases and at a certain moment becomes higher than a maximum pressure, the pressure of the first main section 3112 pushes the control device 370 and ensures that the first main section 3112 is fluidly connected to the first actuating section 381. Then, the pressure of the first main section 3112 would drop slightly under the periodic pressure fluctuation. Since the first main section 3112 is in constant communication with the second actuating section 382, ​​the pressure of the first main section 3112 is equal to the pressure of the second actuating section 382.In other words, as long as the control device 370 is pushed away, the pressure of the first actuating portion 381 is higher than the pressure of the second actuating portion 382 and the first main portion 3112, and consequently, the first actuating closure member 383 is able to move to push the second actuating closure member 384, thereby fluidly connecting the second actuating portion 382 to the first actuating portion 381 and the oil storage container 10. If the second actuating portion 382 is fluidly connected to the oil storage container 10, the first main portion 3112 would drop to the static pressure.

[0046] As long as the pressure of the first main section 3112 drops to the static pressure, the switching closure element 3431 of the switching device 343 is pushed back to an initial position by the switching spring unit 3433, that is, the switching closure element 3431 is pushed back to block the first switching opening 341 and open the second switching opening 342. Therefore, the switching device 343 isolates the switching channel 34 from the first main section 3112, and the switching channel 34 remains in fluid communication with the pressurization channel 35 and the oil return channel 36. Thereafter, the displacement unit 22 moves toward the initial position via the elastic return unit 24 and compresses the first oil reservoir 201 and the second oil reservoir 202 to return oil.Meanwhile, the hydraulic oil from the first oil reservoir 201 flows to the oil storage tank 10 via the inner passage 210, the pressurizing passage 35, and the oil return passage 36; the hydraulic oil in the second oil reservoir 202 also pushes the second one-way valve 3132 to flow into the second main portion 3113 and then flows to the oil storage tank 10 via the pressurizing passage 35 and the oil return passage 36.

[0047] Additionally, the user can perform oil return to relieve pressure before the maximum pressure is reached. Specifically, the user can press a pressure release button that cooperates with the first actuating closure member 383, moving the first actuating closure member 383 to press the second actuating closure member 384, thereby fluidly connecting the second actuating portion 382 to the first actuating portion 381 and the oil storage container 10, and reducing the pressure of the first main portion 3112 to the static pressure.

Claims

[1] An automatic oil return structure comprising: an oil storage tank (10) containing hydraulic oil, the hydraulic oil in the oil storage tank (10) remaining at a static pressure, a piston device (20) arranged at a distance from the oil storage container (10), the piston device (20) comprising: an inner tube (21) with an inner channel (210); a displacement unit (22) mounted on the inner tube (21), the displacement unit (22) being sealed to an outer wall surface of the inner tube (21), a first oil reservoir (201) formed within the displacement unit (22) and fluidly connected to the inner channel (210), an outer tube (23) mounted on the displacement unit (22), wherein the displacement unit (22) is sealed to an inner wall surface of the outer tube (23) and the displacement unit (22) is movable relative to the inner tube (21) and the outer tube (23), and a second oil reservoir (202) formed in the outer tube (23), the inner tube (21) and the displacement unit (22), a main body means (30) disposed between the oil storage container (10) and the piston means (20) and comprising: a first main section (3112) which is in fluid communication with the oil storage container (10), a second main section (3113) which is in fluid communication with the first oil reservoir (201) and the second oil reservoir (202), a first one-way blocking device (3131) capable of preventing the hydraulic oil from flowing from the first main section (3112) to the oil storage tank (10), a second one-way blocking device (3132) capable of preventing the hydraulic oil from flowing from the second main section (3113) to the second oil reservoir (202), a switching channel (34) which is in fluid communication with the first main section (3112), a switching device (343) which is mounted in the switching channel (34) and selectively blocks the switching channel (34), a pressurization channel (35) having one end fluidly connected to the switching channel (34) and another end fluidly connected to the first oil reservoir (201), an oil return channel (36) having one end fluidly connected to the switching channel (34) and another end fluidly connected to the oil storage container (10), a control channel (37) which is in fluid communication with the first main section (3112), a control device (370) mounted in the control channel (37) and selectively blocking the control channel (37), an actuating channel (38) having a first actuating portion (381) and a second actuating portion (382), one end of the first actuating portion (381) being fluidly connected to the control channel (37) and another end of the first actuating portion (381) being fluidly connected to the oil storage container (10) and the second actuating portion (382); a first actuating closure element (383) which is movably mounted in the first actuating section (381) of the actuating channel (38), wherein positions where the control channel (37) is in fluid communication with the first actuating section (381) and where the oil storage container (10) is in fluid communication with the first actuating section (381) are arranged on two respective sides of the first actuating closure element (383), a second actuating closure element (384) mounted in the actuating channel (38) and selectively isolating the first actuating portion (381) from the second actuating portion (382); wherein, when a pressure of the first main section (3112) is higher than a starting pressure, the pressure of the first main section (3112) drives the switching device (343) to move and isolate the switching channel (34) from the oil return channel (36), and the switching channel (34) remains in fluid communication with the first main section (3112) and the pressurizing channel (35), and thus the hydraulic oil flows into the first oil reservoir (201) via the inner channel (210), the starting pressure being higher than the static pressure, when the pressure of the first main section (3112) reaches a maximum pressure, the pressure of the first main section (3112) presses the control device (370) and thus the first main section (3112) is in fluid communication with the first actuating section (381), the pressure of the first main section (3112) also drives the first actuating closure element (383) to press the second actuating closure element (384), and thus the second main section (382) is in fluid communication with the first actuating section (381) and the oil storage container (10); wherein, when the second actuating section (382) is in fluid communication with the oil storage container (10), the pressure of the first main section (3112) drops to the static pressure, wherein the maximum pressure is higher than the starting pressure, when the pressure of the first main section (3112) drops to the static pressure, the switching device (343) moves and isolates the switching channel (34) from the first main section (3112) and the switching channel (34) remains in fluid communication with the pressurization channel (35) and the oil return channel (36), and then the hydraulic oil flows through the inner channel (210), the pressurization channel (35) and the oil return channel (36) from the first oil reservoir (201) to the oil storage tank (10), the hydraulic oil in the second oil reservoir (202) pushes the second one-way blocking device (3132) and enters the second main section (3113), and the hydraulic oil flows via the pressurization channel (35) and the oil return channel (36) to the oil storage tank (10). [2] The automatic oil return structure according to claim 1, wherein the main body means (30) comprises a first primary passage (311) and a primary passage blocking unit (3111), and the primary passage blocking unit (3111) is mounted in the first primary passage (311), and thus the first primary passage (311) isolates the first main portion (3112) from the second main portion (3113). [3] The automatic oil return structure according to claim 1, wherein the main body means (30) comprises: a primary channel having one end in fluid communication with the oil storage container (10) and another end in fluid communication with the second oil reservoir (202), a third one-way blocking device (3133) capable of preventing the hydraulic oil from flowing from the primary channel to the oil storage tank (10), and a fourth one-way blocking device (3134) capable of preventing the hydraulic oil from flowing from the second oil reservoir (202) to the primary channel. [4] The automatic oil return structure according to claim 3, wherein the main body means (30) has a communication passage (32) in fluid communication with the primary passage and the first main portion (3112), when the pressure of the first main portion (3112) is higher than a pressurizing pressure, the hydraulic oil flows from the primary passage into the second oil reservoir (202), the maximum pressure being higher than the pressurizing pressure and the pressurizing pressure being higher than the starting pressure. [5] The automatic oil return structure according to any one of claims 1 to 4, wherein the main body means (30) comprises a secondary channel (33) having one end in fluid communication with the oil storage container (10) and another end in fluid communication with the second oil reservoir (202), and a secondary channel one-way blocking device (330) capable of preventing the hydraulic oil from flowing from the second oil reservoir (202) to the secondary channel (33). [6] The automatic oil return structure according to any one of claims 1 to 4, wherein the first actuating closure member (383) comprises: an inner flow channel (3833) formed in the first actuating closure element (383), a first opening (3834) which is fluidly connected to the inner flow channel (3833) and the control channel (37), a second opening (3835) formed on an end surface of the first actuating closure element (383), the end surface being adjacent to the second actuating closure element (384), the first opening (3834) being in fluid communication with the inner flow channel (3833) and the oil storage container (10), and an outer annular surface which abuts and seals against an inner surface of the first actuating portion (381), the outer annular surface being arranged between the first opening (3834) and the second opening (3835). [7] The automatic oil return structure according to any one of claims 1 to 4, wherein: two ends of the switching channel (34) are a first switching opening (341) and a second switching opening (342), the first switching opening (341) is in fluid communication with the first main section (3112), a position at which the switching channel (34) is in fluid communication with the pressurizing channel (35) is arranged between the first switching opening (341) and the second switching opening (342), the second switching opening (342) is in fluid communication with the oil return channel (36), the switching device (343) comprises: a switching closure element (3431) which is movably mounted in the switching channel (34) and selectively blocks the first switching opening (341) or the second switching opening (342); wherein the switching closure element (3431) comprises: an annular projection (3434) arranged in the switching channel (34), and a gap formed between an outer annular surface of the annular projection (3434) and an inner annular surface of the switching channel (34), a switching seal (3432) which is mounted in the switching channel (34) and is movably mounted on the switching closure element (3431), and an outer annular surface of the switching seal (3432) which abuts the inner annular surface of the switching channel (34), wherein a gap is formed between an inner annular surface of the switching seal (3432) and the switching closure element (3431), an inner diameter of the switching seal (3432) is smaller than an outer diameter of the annular projection (3434), whereby the switching seal (3432) selectively abuts the annular projection (3434) and the first switching opening (341) is blocked as long as the switching seal (3432) abuts the annular projection (3434), and a switching spring unit (3433) which bears against the switching seal (3432) and presses the switching seal (3432) such that the switching seal (3432) is adapted to bear against the annular projection (3434), wherein, when the pressure of the first main section (3112) is lower than the starting pressure, the switching closure element (3431) blocks the first switching opening (341) and the switching seal (3432) abuts the annular projection (3434), when the pressure of the first main section (3112) is higher than the starting pressure, the pressure of the first main section (3112) drives the switching closure element (3431) to move to open the first switching opening (341) and block the second switching opening (342), thereby isolating the switching channel (34) from the oil return channel (36), wherein the pressure of the first main section (3112) then separates the switching seal (3432) and the annular projection (3434) from each other and opens the first switching opening (341), whereby the first main section (3112) is fluidly connected to the pressurizing channel (35), when the pressure of the first main section (3112) drops to the static pressure, the switching closure element (3431) moves to block the first switching opening (341) of the switching channel (34) and opens the second switching opening (342), whereby the pressurizing channel (35) is fluidly connected to the oil return channel (36).

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