Self-locking type hydraulic die clamping device capable of maintaining pressure

Abstract

The self-locking type hydraulic die clamping device comprises a body, a pressing plate and an oil cylinder and further comprises a pressure retaining valve, the pressure retaining valve is arranged on the body, an oil inlet, an oil outlet and an air inlet are formed in the pressure retaining valve, an upper valve chamber and a lower valve chamber are formed in the pressure retaining valve, the upper valve chamber is communicated with the lower valve chamber, the oil inlet and the oil outlet are communicated with the lower valve chamber, and the oil cylinder is arranged on the pressing plate. The air inlet is communicated with the upper valve chamber, a pressure relief assembly is arranged in the upper valve chamber in a sliding fit mode, a non-return assembly is arranged in the lower valve chamber in a sliding fit mode, a valve sleeve is arranged at the top of the non-return assembly, a through hole is formed in the outer wall of the valve sleeve and communicated with the oil inlet, and an oil channel is formed in the body and communicated with the oil outlet. According to the technical scheme, when faults such as all oil pipes are fractured or all oil pressure is lost occur, the positioning function of the pressing plate can still be played continuously, it is ensured that mold parts can be effectively pressed, and therefore the self-locking effect is good, and safety is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mold clamping devices, and more particularly to a self-locking hydraulic mold clamping device capable of maintaining pressure. BACKGROUND

[0002] The mold clamping device is an important component of an injection molding machine, which is installed on the platen of the clamping unit to fix and press the mold parts, so as to ensure that the mold parts remain tightly closed during the injection molding process and prevent the mold parts from moving or leaking under high pressure, thereby ensuring production efficiency.

[0003] The mold clamping device disclosed in the Chinese patent with the publication number CN218018043U and the name "hydraulic mold clamping device with large stroke" includes a clamp body, the bottom of the clamp body is provided with a base, the front and rear ends of the clamp body are provided with shaft holes, the inner cavities of the shaft holes are connected with connecting shafts, the outer walls of the connecting shafts are connected with pressing plates, the rear end of the top of the clamp body is connected with an oil cylinder, the top of the oil cylinder is provided with a piston, and the rear end of the clamp body is provided with an oil inlet hole. The problem of this mold clamping device is that when faults such as complete rupture of the oil pipe or complete loss of oil pressure occur, the positioning function of the pressing plate will fail, the mold parts will not be correctly pressed, and the mold parts are prone to move or even fall during the injection molding process, thereby causing a great safety hazard. This is also a common problem of conventional mold clamping devices.

[0004] To this end, a self-locking mold clamping device has appeared on the market, which can maintain the pressing of the mold parts by the pressing plate when faults such as complete rupture of the oil pipe or complete loss of oil pressure occur. For example, the Chinese patent with the publication number CN215661465U discloses a self-locking mold clamping device, which includes a mold clamping device body and a pressure maintaining valve. The pressure maintaining valve is in communication with the mold clamping device body. The pressure maintaining valve includes a pressure maintaining block. The pressure maintaining block is provided with an oil inlet and an oil outlet, and the oil outlet of the pressure maintaining block is in communication with the hydraulic oil inlet of the mold clamping device body. A cavity is arranged between the oil inlet and the oil outlet, and the oil inlet, the cavity and the oil outlet are sequentially connected. A pressure relief rod, a check seat and a plug are arranged in the cavity. The pressure relief rod is arranged in the cavity and is movably connected with the pressure maintaining block. The pressure relief rod is used to push the check seat to move, and the check seat and the plug are connected by a spring.

[0005] The pressure relief rod of the above-mentioned mold clamping device is lifted upward by the inlet oil pressure, and the check seat is also compressed under the action of the inlet oil pressure. When the inlet oil pressure is insufficient, it is difficult to overcome the gravity of the hydraulic rod. The pressure relief rod can push the check seat downward to ensure that the check seat can be normally compressed, so that the hydraulic oil can enter the mold clamping device, the pressure can be maintained, the pressing plate can maintain the pressing of the mold parts, but it also means that the oil inlet and the oil outlet on both sides of the check seat are in communication. Obviously, this can easily cause the hydraulic oil entering the mold clamping device to flow backward. At this time, the self-locking structure will fail, and the mold parts cannot be correctly pressed by the pressing plate, so there is still a considerable safety hazard. SUMMARY

[0006] In view of the above, in order to overcome the problem that the existing self-locking mold clamping device is prone to cause the hydraulic oil to flow backward when the oil inlet and the oil outlet on both sides of the reverse stopping seat are kept in communication in the pressure maintaining state, the self-locking structure will fail, the mold parts cannot be correctly pressed by the pressing plate, and the safety hazard still exists, the utility model aims at providing a self-locking hydraulic mold clamping device which can still play the positioning role of the pressing plate when faults such as complete rupture of the oil pipe or complete loss of oil pressure occur, ensure that the mold parts can be effectively pressed, and has good self-locking effect and high safety.

[0007] In order to achieve the above object, the technical solution of the present application is:

[0008] The self-locking hydraulic mold clamping device capable of maintaining pressure comprises a body, a pressing plate and an oil cylinder, further comprises a pressure maintaining valve, the pressure maintaining valve is arranged on the body, the pressure maintaining valve is provided with an oil inlet, an oil outlet and an air inlet, and is internally provided with an upper valve chamber and a lower valve chamber, the upper valve chamber and the lower valve chamber are in communication, the oil inlet and the oil outlet are in communication with the lower valve chamber, the air inlet is in communication with the upper valve chamber, a pressure relief assembly is slidably arranged in the upper valve chamber, a reverse stopping assembly is slidably arranged in the lower valve chamber, the top of the reverse stopping assembly is provided with a valve sleeve, a through hole is formed in the outer wall of the valve sleeve and in communication with the oil inlet, an oil channel is formed in the body and in communication with the oil outlet.

[0009] Preferably, the pressure relief assembly comprises a sliding cover and a thimble, the sliding cover is slidably arranged in the upper valve chamber, and the thimble is arranged on the sliding cover, the lower end of the thimble penetrates into the valve sleeve and is slidably arranged in the valve sleeve.

[0010] Preferably, the pressure relief assembly further comprises a pressure relief spring, and the pressure relief spring is arranged at the bottom of the sliding cover.

[0011] Preferably, the reverse stopping assembly comprises a steel ball and a steel ball seat, the steel ball seat is slidably arranged in the lower valve chamber, and the steel ball is arranged on the steel ball seat and abuts against the lower end of the valve sleeve.

[0012] Preferably, an oil passage is formed between the steel ball seat and the lower valve chamber.

[0013] Preferably, the reverse stopping assembly further comprises a reverse stopping spring, and the reverse stopping spring is arranged at the bottom of the steel ball seat.

[0014] Preferably, the pressure maintaining valve comprises an upper valve body and a lower valve body, the air inlet and the upper valve chamber are formed in the upper valve body, and the oil inlet, the oil outlet and the lower valve chamber are formed in the lower valve body.

[0015] Preferably, the top of the body is formed with a mounting seat, the pressing plate is hinged to the mounting seat through a rotating shaft, the front end of the pressing plate extends out of the body, the bottom of the body is further formed with a receiving groove, the oil passage is communicated with the receiving groove, and the oil cylinder is arranged in the receiving groove and opposite to the rear end of the pressing plate.

[0016] Preferably, the bottom of the body is formed with a T-shaped guide rail.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] When the oil inlet pressure of the pressure retaining valve is insufficient, the reverse stopping assembly is reset under the hydraulic oil floating force in the lower valve chamber, the pressure relief assembly driven by the compressed gas does not interfere with the reset process of the reverse stopping assembly, the lower end of the valve sleeve is closed again to prevent the hydraulic oil in the lower valve chamber from flowing back to the oil inlet when faults such as complete rupture of the oil pipe or complete loss of oil pressure occur, the positioning effect of the pressing plate is still effective in this unexpected situation, and the mold parts can be correctly pressed, the safety of injection molding production is improved, and when the mold parts need to be removed from the platen, compressed gas can be injected into the upper valve chamber to drive the pressure relief assembly to slide in the direction of the lower valve chamber until the pressure relief assembly abuts against the valve sleeve and moves away from the valve sleeve, the lower end of the valve sleeve is opened, and the hydraulic oil in the pressure retaining valve and the body can be emptied. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the overall structure schematic diagram of the pressing plate of the mold clamping device of the utility model when the pressing plate is not pressed down;

[0020] Figure 2 is the overall structure schematic diagram of the mold clamping device of the utility model when the pressing plate is pressed down;

[0021] Figure 3 is the exploded structure schematic diagram of the mold clamping device of the utility model;

[0022] Figure 4 is the overall structure schematic diagram of the lower valve body and the steel ball seat of the reverse stopping assembly of the pressure retaining valve of the mold clamping device of the utility model when the two are matched;

[0023] Figure 5 is the cross-sectional structure schematic diagram of the mold clamping device of the utility model when no hydraulic oil is injected and the oil pipe is completely ruptured or the oil pressure is completely lost;

[0024] Figure 6 is the A part enlarged structure schematic diagram of the mold clamping device of the utility model; Figure 5

[0025] Figure 7 is the cross-sectional structure schematic diagram of the mold clamping device of the utility model when the hydraulic oil is injected into the pressure retaining valve;​

[0026] Figure 8 is the B part enlarged structure schematic view of the utility model Figure 7

[0027] Figure 9 is the sectional structure schematic view of the utility model when the ejector is used, the plunger of the pressure relief assembly pushes the steel ball of the non-return assembly downward;

[0028] Figure 10 is the C part enlarged structure schematic view of the utility model Figure 9

[0029] Figure 11 is the overall structure schematic view of the utility model when the ejector is connected with the table plate and the pressing plate is pressed on the mold part;

[0030] Figure 12 is the overall structure schematic view of the utility model when the ejector is connected with the table plate and the body is moved to be far away from the mold part along the guide groove of the table plate.

[0031] As shown in the figure:

[0032] 1, body; 101, oil passage; 102, mounting seat; 103, storage groove; 104, T-shaped guide rail; 2, pressing plate; 3, oil cylinder; 4, pressure maintaining valve; 4a, upper valve body; 4b, lower valve body; 401, oil inlet; 402, oil outlet; 403, air inlet; 404, upper valve chamber; 405, lower valve chamber; 405a, oil passage groove; 5, pressure relief assembly; 501, sliding cover; 502, plunger; 503, pressure relief spring; 6, non-return assembly; 601, steel ball; 602, steel ball seat; 603, non-return spring; 7, valve sleeve; 701, through hole; 8, rotating shaft; 9, table plate; 901, guide groove; 10, mold part. DETAILED DESCRIPTION

[0033] The application will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0034] In the description of the application, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the application is usually placed, and are only for the convenience of simplifying the description, and do not indicate or imply that the orientation is a specific orientation and a specific orientation configuration and operation, and therefore cannot be understood as a limitation on the application.

[0035] As Figures 1 to 3 and Figures 5 to 10 ​​The utility model relates to a self-locking hydraulic mold clamp ware of pressure maintaining, it includes body 1, pressing plate 2 and oil cylinder 3, especially, it still includes pressure maintaining valve 4, pressure maintaining valve 4 is located on body 1, pressure maintaining valve 4 is set up and opens oil inlet 401, oil outlet 402 and air inlet 403, one end of oil inlet 401, oil outlet 402 and air inlet 403 and pressure maintaining valve 4 outer wall are through, the inside of pressure maintaining valve 4 is set up and opens upper valve chamber 404 and lower valve chamber 405, upper valve chamber 404 and lower valve chamber 405 are linked together, oil inlet 401 and oil outlet 402 and lower valve chamber 405 are communicated, air inlet 403 and upper valve chamber 404 are communicated, specifically, oil inlet 401 is located in the left side of lower valve chamber 405, oil outlet 402 is located in the right side of lower valve chamber 405, air inlet 403 is close to the top of upper valve chamber 404, the upper valve chamber 404 is slidably fitted with pressure relief assembly 5, pressure relief assembly 5 can slide up and down in upper valve chamber 404, and can enter lower valve chamber 405 when sliding, the power for driving pressure relief assembly 5 to move to lower valve chamber 405 is the compressed gas that injects upper valve chamber 404 from air inlet 403, pressure relief assembly 5 moves to lower valve chamber 405 direction under the action of compressed gas propelling force, lower valve chamber 405 is slidably fitted with check assembly 6, check assembly 6 can slide up and down in lower valve chamber 405, the top of check assembly 6 is equipped with valve sleeve 7, check assembly 6 is in initial position and is abutted with the lower end of valve sleeve 7 to close it, the outer wall of valve sleeve 7 is set up and opens through -hole 701, through -hole 701 and oil inlet 401 are communicated, so that the hydraulic oil can enter valve sleeve 7, at this time, check assembly 6 will slide and open the lower end of valve sleeve 7 under the action of oil pressure, allow the hydraulic oil to enter lower valve chamber 405, the body 1 is set up and opens oil passage 101, oil passage 101 and oil outlet 402 are communicated, the hydraulic oil that enters lower valve chamber 405 finally passes through oil outlet 402 to oil passage 101 and enters the inside of body 1, and drive oil cylinder 3 to make pressing plate 2 press the mold part 10 installed on injection molding machine table disc 9, the utility model mold clamp ware when the oil inlet pressure of pressure maintaining valve 4 side is insufficient, check assembly 6 will reset under the buoyancy of the hydraulic oil that has entered lower valve chamber 405, pressure relief assembly 5 driven by compressed gas will not interfere during the reset of check assembly 6, ensure that check assembly 6 can close the lower end of valve sleeve 7 again smoothly, thereby prevent the hydraulic oil in lower valve chamber 405 from flowing back to oil inlet 401 when faults such as all oil pipes are broken or all oil pressure is lost occur, ensure that the positioning effect of pressing plate 2 is still effective under this unexpected situation, and the mold part 10 can also be correctly pressed, improve the safety of injection molding production, and in the closed state, if the mold part 10 needs to be removed from table disc 9, can inject compressed gas to upper valve chamber 404, drive pressure relief assembly 5 to slide to lower valve chamber 405 direction through compressed gas, until entering valve sleeve 7 and abutting with check assembly 6, and push check assembly 6 away from valve sleeve 7 and move, open the lower end of valve sleeve 7,Thus, the hydraulic oil in the pressure retaining valve 4 and the body 1 can be emptied.

[0036] As shown in Figure 3 and Figures 5 to 10 , the pressure relief assembly 5 includes a sliding cover 501 and a thimble 502, the sliding cover 501 is slidingly fitted in the upper valve chamber 404, the air inlet 403 is located above the sliding cover 501, the thimble 502 is installed on the sliding cover 501, and the thimble 502 will move synchronously when the sliding cover 501 slides, the lower end of the thimble 502 penetrates into the valve sleeve 7 and is slidingly fitted with the valve sleeve 7, in the utility model, the sliding cover 501 is used as the force receiving part of the pressure relief assembly 5, when the pressure relief assembly 5 needs to move downward to the lower valve chamber 405, compressed air is injected from the air inlet 403 into the upper valve chamber 404 to drive the sliding cover 501 to move, and the thimble 502 is driven to move in the valve sleeve 7 until it abuts against the reverse stopping assembly 6 abutting at the lower end of the valve sleeve 7, and the reverse stopping assembly 6 is pushed to move away from the valve sleeve 7, the lower end of the valve sleeve 7 is opened, so that the hydraulic oil in the pressure retaining valve 4 and the body 1 can be emptied.

[0037] As shown in Figure 3 and Figures 5 to 10 , the pressure relief assembly 5 further includes a pressure relief spring 503, the pressure relief spring 503 is arranged at the bottom of the sliding cover 501 and is supported by the pressure relief spring 503, so that when the pressure relief assembly 5 does not need to move downward to the lower valve chamber 405, it can be kept at the high position of the upper valve chamber 404, avoiding self-moving downward due to gravity, ensuring that the reverse stopping assembly 6 can stably cooperate with the lower end of the valve sleeve 7, when the pressure relief assembly 5 needs to move downward to the lower valve chamber 405, the driving force generated by the compressed air injected into the upper valve chamber 404 will overcome the supporting force of the pressure relief spring 503, so that the sliding cover 501 drives the thimble 502 to move downward.

[0038] As shown in Figure 3 and Figures 5 to 10 , the reverse stopping assembly 6 includes a steel ball 601 and a steel ball seat 602, the steel ball seat 602 is slidingly fitted with the lower valve chamber 405, the steel ball 601 is placed on the steel ball seat 602 and abuts against the lower end of the valve sleeve 7, so as to close the lower end of the valve sleeve 7, the steel ball seat 602 supports the steel ball 601 to constrain the movement path of the steel ball 601, avoiding free rolling of the steel ball 601 in the lower valve chamber 405.

[0039] As shown in Figure 4As shown, the oil passage 405a is formed between the steel ball seat 602 and the lower valve chamber 405, that is, the cross section of the steel ball seat 602 and the lower valve chamber 405 is not a uniform shape, so that a gap is formed between the steel ball seat 602 and the lower valve chamber 405, which is the oil passage 405a. It can be understood that, when the lower valve chamber 405 is communicated with the oil passage 101 in the body 1, the oil passage 405a is also communicated with the oil passage 101, and the hydraulic oil injected from the oil inlet 401 and passing through the valve sleeve 7 can enter the oil passage 405a, and finally enter the oil passage 101 in the body 1 through the oil passage 405a.

[0040] As shown in Figure 3 and Figures 5 to 10 As shown, the check assembly 6 further comprises a check spring 603 arranged at the bottom of the steel ball seat 602 to provide support for the steel ball seat 602, so as to avoid the steel ball seat 602 and the installed steel ball 601 from moving downward by gravity, thereby ensuring that the lower end of the valve sleeve 7 can be normally closed by the steel ball 601. When the steel ball 601 is affected by the hydraulic oil entering the valve sleeve 7, the elastic force of the check spring 603 will be overcome, the steel ball seat 602 will move downward along the lower valve chamber 405, and the check spring 603 will be compressed. When the oil pressure on the oil inlet 401 side is insufficient, it will not be enough to overcome the elastic force of the check spring 603 to restore the deformation, and the steel ball seat 602 will drive the steel ball 601 to quickly reset under the action of the buoyancy of the hydraulic oil in the lower valve chamber 405 and the elastic force of the check spring 603, thereby ensuring that the check assembly 6 can smoothly close the lower end of the valve sleeve 7 again, so as to prevent the hydraulic oil in the lower valve chamber 405 from flowing back to the oil inlet 401 when the oil pipe is completely broken or the oil pressure is completely lost.

[0041] As shown in Figure 3 and Figures 5 to 10 As shown, the pressure maintaining valve 4 comprises an upper valve body 4a and a lower valve body 4b, the oil inlet 401, the oil outlet 402 and the lower valve chamber 405 are arranged on the lower valve body 4b, and the oil inlet 401, the oil outlet 402 and the lower valve chamber 405 are arranged on the lower valve body 4b.

[0042] As shown in Figures 1 to 3As shown, the top of the body 1 is formed with a mounting seat 102, the pressing plate 2 is hinged on the mounting seat 102 through a rotating shaft 8, the front end of the pressing plate 2 extends out of the body 1, thereby forming a step position with the outer wall of the body 1, through the step position, the step cooperation between the mold part 10 to be fixed and the mold part 10 is formed, so that the mold part 10 is clamped between the pressing plate 2 and the injection molding machine table 9, and the mold part 10 can be stably fixed on the table 9 without the help of a screw rod, thereby improving the efficiency, safety and consistency of mold installation and injection molding production, the bottom of the body 1 is also provided with a receiving groove 103, the oil channel 101 is communicated with the receiving groove 103, the oil cylinder 3 is arranged in the receiving groove 103, and the rear end of the oil cylinder 3 is opposite to the pressing plate 2, the hydraulic oil input by the pressure maintaining valve 4 enters the oil cylinder 3 through the oil channel 101, and drives the oil cylinder 3 to press the mold part 10 installed on the injection molding machine table 9 by the pressing plate 2.

[0043] As shown in the drawings, Figures 1 to 3 As shown, the bottom of the body 1 is formed with a T-shaped guide rail 104, the T-shaped guide rail is used for sliding cooperation with the guide groove 901 on the injection molding machine table 9, so that the mold clamp of the utility model can slide along the injection molding machine table 9, through the sliding, the body 1 can drive the pressing plate 2 to move away from the mold mounting position on the injection molding machine table 9, at this time, the limitation of the pressing plate 2 above the mold part 10 is released, the mold part 10 can be installed and removed vertically, and it is more beneficial to the installation and removal of the mold part 10 with large size and large thickness.

[0044] In combination with Figures 1 to 12The utility model discloses a clamp mould ware, first input hydraulic oil from the oil inlet 401 of self -preserving valve 4, and the hydraulic oil enters inside through the through -hole 701 on the outer wall of valve bush 7, at this moment, the steel ball 601 of valve bush 7 lower end check subassembly 6 is under the oil pressure and will be together with steel ball seat 602 and move down, and steel ball seat 602 makes check spring 603 compression, at this moment, the lower end of valve bush 7 opens, and the hydraulic oil can enter the oil -passing groove 405a between lower valve chamber 405 and steel ball seat 602, and then enters oil passage 101 to the body 1, and finally injects oil cylinder 3, and oil cylinder 3 will push the pressing plate 2 rotation and clamps the mould part 10 installed on injection molding machine table disc 9, at this moment, if the oil pressure of oil inlet 401 side is insufficient, steel ball seat 602 will be driven steel ball 601 fast reset under the buoyancy of lower valve chamber 405 hydraulic oil and check spring 603 elastic force, ensure that check subassembly 6 can smoothly again close the lower end of valve bush 7, to prevent the hydraulic oil in lower valve chamber 405 from flowing back to oil inlet 401 when the fault such as oil pipe is all broken or oil pressure is all lost, if the mould part 10 needs to remove from table disc 9, can inject compressed gas to upper valve chamber 404, and the sliding cover 501 of pressure relief assembly 5 is slid to the direction of lower valve chamber 405 by compressed gas drive, at this moment, sliding cover 501 will drive the thimble 502 synchronous movement, and check spring 503 is compressed, and the thimble 502 moves in valve bush 7 until and check subassembly 6 abuts at the lower end of valve bush 7, and check subassembly 6 moves away from valve bush 7, and the lower end of valve bush 7 is opened, to be able to empty the hydraulic oil in self -preserving valve 4 and body 1, at this moment, the pressing plate 2 can rotate and remove the pressing of mould part 10, finally push the body 1 away from the mould installation position on injection molding machine table disc 9, and the restriction of pressing plate 2 is released, and the mould can be smoothly removed.

[0045] The above embodiments and descriptions are only to illustrate the principles and best embodiments of the present application, and the present application can have various changes and improvements without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A self-locking hydraulic clamp capable of maintaining pressure, comprising a body (1), a pressure plate (2) and an oil cylinder (3), characterized in that: The pressure maintaining valve (4) is provided on the main body (1), and is provided with an oil inlet (401), an oil outlet (402) and an air inlet (403). The pressure maintaining valve (4) is provided with an upper valve chamber (404) and a lower valve chamber (405) inside. The upper valve chamber (404) and the lower valve chamber (405) are connected. The oil inlet (401) and the oil outlet (402) are both connected to the lower valve chamber (405). The air inlet (403) is connected to the upper valve chamber (404). 04), a pressure relief assembly (5) is slidably fitted in the upper valve chamber (404), a check assembly (6) is slidably fitted in the lower valve chamber (405), a valve sleeve (7) is provided on the top of the check assembly (6), a through hole (701) is provided on the outer wall of the valve sleeve (7), the through hole (701) is communicated with the oil inlet (401), an oil channel (101) is provided on the body (1), and the oil channel (101) is communicated with the oil outlet (402).

2. A self-locking hydraulic clamp capable of maintaining pressure according to claim 1, characterized in that: The pressure relief assembly (5) includes a sliding cover (501) and a ejector pin (502). The sliding cover (501) is slidably engaged in the upper valve chamber (404). The ejector pin (502) is mounted on the sliding cover (501). The lower end of the ejector pin (502) penetrates into the valve sleeve (7) and is slidably engaged with the valve sleeve (7).

3. A self-locking hydraulic clamp capable of maintaining pressure according to claim 2, characterized in that: The pressure relief assembly (5) further comprises a pressure relief spring (503), and the pressure relief spring (503) is arranged at the bottom of the sliding cover (501).

4. A self-locking hydraulic clamp capable of maintaining pressure according to any one of claims 1 to 3, characterized in that: The anti-return assembly (6) includes a steel ball (601) and a steel ball seat (602), wherein the steel ball seat (602) is slidably matched with the lower valve chamber (405), and the steel ball (601) is placed on the steel ball seat (602) and abuts against the lower end of the valve sleeve (7).

5. A self-locking hydraulic clamp capable of maintaining pressure according to claim 4, characterized in that: An oil groove (405a) is formed between the steel ball seat (602) and the lower valve chamber (405).

6. A self-locking hydraulic clamp capable of maintaining pressure according to claim 5, characterized in that: The anti-return assembly (6) further comprises an anti-return spring (603), and the anti-return spring (603) is arranged at the bottom of the steel ball seat (602).

7. A self-locking hydraulic clamp capable of maintaining pressure according to any one of claims 1, 2, 3, 5 or 6, characterized in that: The pressure-maintaining valve (4) comprises an upper valve body (4a) and a lower valve body (4b); the air inlet (403) and the upper valve chamber (404) are both provided on the upper valve body (4a); and the oil inlet (401), the oil outlet (402) and the lower valve chamber (405) are all provided on the lower valve body (4b).

8. A self-locking hydraulic clamp capable of maintaining pressure according to claim 7, characterized in that: A mounting seat (102) is formed on the top of the body (1), the pressure plate (2) is hinged to the mounting seat (102) via a rotating shaft (8), the front end of the pressure plate (2) extends outside the body (1), and a receiving groove (103) is also provided at the bottom of the body (1), the oil channel (101) is connected to the receiving groove (103), the oil cylinder (3) is arranged in the receiving groove (103), and the oil cylinder (3) is opposite to the rear end of the pressure plate (2).

9. A self-locking hydraulic clamp capable of maintaining pressure according to claim 8, characterized in that: A T-shaped guide rail (104) is formed at the bottom of the body (1).

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