Self-locking oil cylinder of hydraulic machine

Abstract

The invention relates to the technical field of hydraulic oil cylinders, in particular to a hydraulic machine self-locking oil cylinder which comprises a cylinder body, a middle end cover and a rear end cover are detachably connected to the two ends of the cylinder body, an oil inlet pipe is arranged on the inner wall of the middle end cover, an oil outlet pipe is arranged on the inner wall of the rear end cover, and an oil return pipe is connected to the inner wall of the cylinder body in a penetrating mode. The front end cover and the rear end cover are detachably matched, and the reducing self-locking assembly is installed in an inner cavity of the rear end cover, so that self-locking is achieved when the piston recovers the initial stroke, buffering of potential energy impact of the piston is achieved, and damage to the piston rod and the piston is reduced; the piston sleeve rod is matched with the locking block, so that double locking of the piston rod can be met, and meanwhile, the capacity of convenient unlocking is reserved; and the center oil channel designed at the end of the piston rod is matched with the transmission hole, and a lubricating channel is formed during self-locking, so that oil can enter a friction surface between the piston rod and the piston, and friction is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic cylinders, and particularly to a self-locking cylinder for a hydraulic press. Background Art

[0002] The self-locking cylinder of a hydraulic press is an important part of a hydraulic system, used to hold a load and prevent accidental movement at a specific position or under certain conditions. In a hydraulic system, when a hydraulic cylinder is used as an actuator, sometimes it is required to stay at any position or a certain fixed point position and bear a certain load force. Traditionally, this requirement is achieved through a hydraulic locking circuit, but this method may have problems such as insufficient stability or high complexity.

[0003] In the prior art, for example, a self-locking hydraulic cylinder installed on a lifting device with a publication number of CN107120333A includes a cylinder bottom, a piston, a cylinder barrel, a cylinder head, and a piston rod. The piston and the piston rod are both located inside the cylinder barrel. The piston is sleeved on the piston rod, and the cylinder head seals the piston rod inside the cylinder barrel. The cylinder bottom is welded to the cylinder barrel. An oil-free cavity and a rod cavity are respectively formed between the piston and the cylinder bottom and the cylinder head. A sleeve is provided on the piston rod. The sleeve is sleeved on the outer wall of the piston rod and can rotate around the axis of the piston rod. A locking groove is also provided on the sleeve. A second groove is provided on the inner wall of the cylinder barrel. A connecting element and a locking pin shaft matching the locking groove are provided in the second groove. One end of the connecting element is connected to the second groove, and the other end is connected to the locking pin shaft. And the locking pin shaft can move along the axis direction of the connecting element.

[0004] However, in the actual operation process, when the hydraulic cylinder completes a working cycle and the piston returns to the initial position, if the kinetic energy accumulated during its sliding process cannot be completely consumed, it will cause the piston to impact the cylinder head at a residual speed, reducing the service life of the hydraulic cylinder; and as the use time prolongs, the locking spring may gradually lose its elastic stress due to fatigue, corrosion, or material aging, resulting in the failure of the locking mechanism, and further causing accidental movement or detachment of the piston rod, resulting in serious consequences.

[0005] Therefore, the present invention proposes a self-locking cylinder for a hydraulic press to solve the problems of impact loss caused by improper management of piston kinetic energy and the risk of insufficient reliability of the locking mechanism in the traditional hydraulic cylinder system. It can achieve multiple self-lockings at the end of the piston rod stroke while retaining the ability of convenient unlocking, improving the compactness of the overall structure and the convenience of maintenance, and prolonging the overall service life. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a self-locking cylinder for a hydraulic press, which has the advantages of multiple self-lockings at the end of the piston rod stroke while retaining the ability of convenient unlocking, improving the compactness of the overall structure and the convenience of maintenance.

[0007] To achieve the above object, the present invention provides the following technical solution: A self-locking oil cylinder for a hydraulic press, comprising a cylinder block, with an intermediate end cover and a rear end cover detachably connected to both ends of the cylinder block. An oil inlet pipe is provided on the inner wall of the intermediate end cover, and an oil outlet pipe is provided on the inner wall of the rear end cover. A return oil pipe is connected through the inner wall of the cylinder block. The outer side of the intermediate end cover is detachably connected with a front end cover. A reserved groove is provided on the central inner wall of the intermediate end cover. A support ring seat and a return groove plate are fixedly installed on the inner surface of the reserved groove. A piston rod is arranged at the center of the return groove plate. A central oil passage is provided on the inner wall of one end of the piston rod. A piston sleeve rod is sleeved and connected on the outer surface of the piston rod. A pressure increasing hole is provided on the inner wall of the piston sleeve rod. One end of the piston rod is fixedly connected with a piston. A variable diameter self-locking assembly is arranged on the side of the piston close to the intermediate end cover for locking and braking after the piston rod resumes its stroke. A buffer groove is provided on the inner wall of the cylinder block, and a buffer ring is movably embedded in the buffer groove. The buffer ring is fixedly installed on the surface of the piston. A touch switch is arranged between the buffer groove and the buffer ring for starting the variable diameter self-locking assembly.

[0008] Preferably, a controller is fixedly installed on the inner surface of the support ring seat. The controller is electrically connected to the touch switch. A hollow shaft rod is fixedly connected to the output shaft of the controller. The hollow shaft rod is of a hollow columnar structure. Oil inlet holes are evenly provided on the inner wall of the hollow shaft rod, and an electromagnetic valve is arranged on the inner wall of the hollow shaft rod.

[0009] Preferably, the variable diameter self-locking assembly includes a rotating plate and a base plate. The base plate is rotatably installed inside the rotating plate. The diameter of the base plate is larger than that of the rotating plate. A protective cover is fixedly connected to the outer surface of the rotating plate. An arc-shaped groove is provided on the inner wall of the rotating plate, and a sliding groove for auxiliary limiting is provided on the inner wall of the base plate. There are nine groups of both the arc-shaped groove and the sliding groove.

[0010] Preferably, a locking rod is slidably connected to the inner surface of the sliding groove. A convex column is fixedly installed on the surface of the locking rod, and the outer surface of the convex column is movably connected to the inner surface of the arc-shaped groove.

[0011] Preferably, two support wing arms are fixedly connected to the outer surface of the base plate close to the rotating plate. The two support wing arms are in an overall "L"-shaped plate structure. The two support wing arms are mirror-symmetrically distributed about the central axis of the base plate, and one end of each support wing arm is fixedly connected to the inner wall of the reserved groove.

[0012] Preferably, a rod end limit ring is fixedly connected to one end of the piston rod. Locking grooves are equally spaced on the inner wall of the rod end limit ring, and the inner surface of the locking grooves is movably inserted with the outer surface of the locking rod.

[0013] Preferably, the figure-eight groove plate is in the shape of a hollow annular plate structure. An annular cavity is arranged inside the figure-eight groove plate. An abutting spring is fixedly connected to the inner surface of the annular cavity. The other end of the abutting spring is fixedly connected to a pressing block. One side of the pressing block away from the abutting spring is provided with a rounded corner. The rounded corner end of the pressing block is in movable abutment with the outer surface of the piston rod.

[0014] Preferably, transfer holes are formed through the inner wall of the central oil passage for the transfer of lubricating oil. A plurality of groups of transfer holes are provided and are circularly arrayed about the central axis of the central oil passage.

[0015] Preferably, a plurality of groups of boosting holes are provided and are equidistantly arrayed about the central axis of the piston sleeve rod.

[0016] Preferably, locking grooves are formed on the inner wall of the cylinder block. Locking blocks are movably connected to the inner surfaces of the locking grooves. Two groups of locking blocks are provided and are symmetrically distributed about the central axis of the piston rod. A spring is fixedly connected to the inner side surface of the locking block. A receiving groove is formed on the surface of the piston rod. The spring is arranged inside the receiving groove. One end of the spring is fixedly connected to the inner wall of the receiving groove.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] A self-locking oil cylinder for a hydraulic press proposed by the present invention realizes self-locking when the piston returns to the initial stroke through the detachable cooperation between the front end cover and the rear end cover, and installs a variable-diameter self-locking component in the inner cavity of the rear end cover, and meets the buffering of the potential energy impact on the piston, reducing the damage to the piston rod and the piston; the cooperation between the piston sleeve rod and the locking block can meet the double locking of the piston rod while retaining the ability of convenient unlocking; and through the cooperation between the central oil passage designed at the end of the piston rod and the transfer holes, a lubricating channel is formed during self-locking, enabling the oil to enter the friction surface between the piston rod and the piston, thereby reducing friction; further solving the problems of impact loss caused by improper management of piston kinetic energy and the risk of insufficient reliability of the locking mechanism in the traditional hydraulic cylinder system, and can realize multiple self-lockings at the end of the piston rod stroke while improving the overall structural compactness and maintenance convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a three-dimensional structural diagram of the present invention;

[0020] Figure 2 is a half-sectional structural diagram of the present invention;

[0021] Figure 3 is of the present invention Figure 2 magnified structural diagram at A;

[0022] Figure 4 is of the present invention Figure 3Schematic diagram of the enlarged structure at A1;

[0023] Figure 5 Schematic diagram of the partial cross-sectional structure of the cylinder block of the present invention;

[0024] Figure 6 Schematic diagram of the connection structure between the piston rod and the piston of the present invention;

[0025] Figure 7 Schematic diagram of the sectional view of the connection between the piston rod and the piston of the present invention;

[0026] Figure 8 For the present invention Figure 7 Schematic diagram of the enlarged structure at B;

[0027] Figure 9 Schematic diagram of the structure of the variable-diameter self-locking assembly of the present invention;

[0028] Figure 10 Schematic diagram of the disassembled structure of the rotating plate and the base plate of the present invention.

[0029] In the figure: 1. Cylinder block; 11. Intermediate end cover; 13. Front end cover; 12. Rear end cover; 110. Reserved groove; 2. Piston rod; 3. Piston; 31. Buffer ring; 10. Buffer groove; 4. Oil inlet pipe; 5. Oil outlet pipe; 8. Oil return pipe; 21. Rod end limit ring; 210. Locking groove; 6. Support ring seat; 61. Controller; 611. Hollow shaft rod; 6110. Oil inlet hole; 612. Rotating plate; 6121. Protective cover; 6120. Arc-shaped groove; 613. Base plate; 614. Support wing arm; 6130. Sliding groove; 6131. Convex column; 6132. Locking rod; 7. Return groove plate; 71. Abutting spring; 72. Pressing block; 20. Central oil passage; 200. Transfer hole; 22. Piston sleeve rod; 220. Boosting hole; 230. Receiving groove; 23. Locking block; 231. Spring; 24. Locking groove. Detailed implementation manners

[0030] In order to clearly and completely describe the objectives, technical solutions of the present invention and make the advantages more clear, the following further elaborates on the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, not to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0031] Embodiment 1, please refer to Figure 1-10, the present invention provides a technical solution: a self-locking oil cylinder for a hydraulic press, including a cylinder block 1, with an intermediate end cover 11 and a rear end cover 12 detachably connected to both ends of the cylinder block 1. An oil inlet pipe 4 is provided on the inner wall of the intermediate end cover 11, and an oil outlet pipe 5 is provided on the inner wall of the rear end cover 12. A return oil pipe 8 is connected through the inner wall of the cylinder block 1. The outer side of the intermediate end cover 11 is detachably connected with a front end cover 13. A reserved groove 110 is provided on the central inner wall of the intermediate end cover 11. A support ring seat 6 and a return groove plate 7 are fixedly installed on the inner surface of the reserved groove 110. A piston rod 2 is arranged at the center of the return groove plate 7. One end of the piston rod 2 is fixedly connected with a piston 3. A variable-diameter self-locking assembly is provided on one side of the piston 3 close to the intermediate end cover 11 for locking and braking after the piston rod 2 resumes its stroke.

[0032] Embodiment 2, referring to the attached Figure 1-10 , on the basis of Embodiment 1, in order to realize the self-locking trigger of the variable-diameter self-locking assembly after the piston 3 resumes its stroke: a buffer groove 10 is provided on the inner wall of the cylinder block 1, and a buffer ring 31 is movably embedded in the buffer groove 10. The buffer ring 31 is fixedly installed on the surface of the piston 3. A touch switch is provided between the buffer groove 10 and the buffer ring 31 for starting the variable-diameter self-locking assembly; a controller 61 is fixedly installed on the inner surface of the support ring seat 6. The controller 61 is electrically connected to the touch switch. A hollow shaft rod 611 is fixedly connected to the output shaft of the controller 61. The hollow shaft rod 611 is in a hollow cylindrical structure. Oil inlet holes 6110 are evenly provided on the inner wall of the hollow shaft rod 611. An electromagnetic valve is provided on the inner wall of the hollow shaft rod 611.

[0033] A buffer groove 10 is provided on the inner wall of one end of the cylinder block 1, and a touch switch is arranged inside it for starting the variable-diameter self-locking assembly. When the piston rod 2 drives the piston 3 to reset to the initial position, the kinetic energy accumulated during the sliding process cannot be completely consumed. At this time, the buffer ring 31 connected to one end of the piston 3 first enters the buffer groove 10. The piston 3 will not directly contact the cylinder block 1 through the blockage of the buffer ring 31. In this way, the dynamic potential energy of the piston 3 is reduced by the elastic force of the buffer ring 31; when the buffer ring 31 touches the touch switch inside the buffer groove 10, the piston 3 completely reaches the initial position, and at this time, the variable-diameter self-locking assembly is turned on in time.

[0034] Embodiment 3, referring to the attached Figure 1-10, on the basis of the second embodiment, in order to achieve automatic locking of the piston 3 that returns to the initial position: the variable-diameter self-locking assembly includes a rotating plate 612 and a base plate 613. The base plate 613 is rotatably installed inside the rotating plate 612. The diameter of the base plate 613 is larger than that of the rotating plate 612. A protective cover 6121 is fixedly connected to the outer surface of the rotating plate 612. An arc-shaped groove 6120 is opened on the inner wall of the rotating plate 612. A sliding groove 6130 for auxiliary limiting is opened on the inner wall of the base plate 613. Both the arc-shaped groove 6120 and the sliding groove 6130 are provided with nine groups; A locking rod 6132 is slidably connected to the inner surface of the sliding groove 6130. A convex column 6131 is fixedly installed on the surface of the locking rod 6132. The outer surface of the convex column 6131 is movably connected to the inner surface of the arc-shaped groove 6120; A support wing arm 614 is fixedly connected to the outer surface of the base plate 613 close to the rotating plate 612. There are two groups of support wing arms 614 and the overall shape is an "L"-shaped plate structure. The two groups of support wing arms 614 are mirror-symmetrically distributed about the central axis of the base plate 613. One end of the support wing arm 614 is fixedly connected to the inner wall of the reserved groove 110; One end of the piston rod 2 is fixedly connected with a rod end limit ring 21. Locking grooves 210 are equally opened on the inner wall of the rod end limit ring 21. The inner surface of the locking groove 210 is movably inserted with the outer surface of the locking rod 6132;

[0035] When the controller 61 is started by receiving a driving signal, its output shaft rotates to drive the hollow shaft rod 611 to rotate. It should be noted that at this time, the oil inlet pipe 4 is in a state of stopping oil supply, and one end of the piston 3 plugs one end of the reserved groove 110. When the hollow shaft rod 611 rotates, it synchronously drives the rotating plate 612 and the protective cover 6121 to rotate. The reason for adding the protective cover 6121 outside the rotating plate 612 is to prevent the hydraulic oil flowing through the oil inlet pipe 4 from impacting the rotating plate 612; At this time, the arc-shaped grooves 6120 evenly opened on the rotating plate 612 drive the internal convex columns 6131 to move. In this way, multiple groups of locking rods 6132 move with variable diameters synchronously, and finally match with the locking grooves 210 opened on the rod end limit ring 21 to achieve mechanical locking of the entire piston rod 2.

[0036] Embodiment 4, referring to the attached Figure 1-10 , on the basis of the third embodiment, in order to enable the oil to penetrate into the friction surface between the piston rod 2 and the piston 3 during the self-locking process: a central oil passage 20 is opened on the inner wall of one end of the piston rod 2. A transfer hole 200 is opened through the inner wall of the central oil passage 20 for the transfer of lubricating oil. Multiple groups of transfer holes 200 are opened and are circularly arrayed about the central axis of the central oil passage 20;

[0037] Just as Figure 3As shown, after the piston 3 is self-locked, a small amount of oil exists in the lubrication channel formed by the central oil passage 20 and the transfer hole 200 through the oil inlet hole 6110 opened on the hollow shaft rod 611. At this time, the oil will penetrate between the friction surfaces of the piston rod 2 and the piston 3 through multiple small channels, thus realizing dynamic lubrication, greatly reducing the running resistance and wear. Lubrication can reduce the loss of energy during the friction process, improve the mechanical transmission efficiency, enable the hydraulic cylinder to work more efficiently, and further extend the service life of the hydraulic cylinder. It should be noted that by designing the central oil passage 20 at one end of the piston rod 2 close to the oil inlet pipe 4 and penetrating the dispersive transfer holes 200, when the piston rod 2 and the piston 3 are self-locked, they can be adaptively docked through the input port of the central oil passage 20 and the hollow shaft rod 611. After the two are connected, it not only meets the limit support when the piston rod 2 and the piston 3 are self-locked, but also can guide a small amount of oil between the friction surfaces of the piston rod 2 and the piston 3 to form a dynamic lubrication effect.

[0038] Embodiment Five. Refer to the appendix Figure 1-10 , on the basis of Embodiment Four, in order to achieve double locking of the piston rod 2: The return groove plate 7 has a hollow annular plate structure. An annular cavity is provided inside the return groove plate 7. An abutting spring 71 is fixedly connected to the inner surface of the annular cavity. The other end of the abutting spring 71 is fixedly connected to a pressing block 72. The side of the pressing block 72 away from the abutting spring 71 is provided with a rounded corner. The rounded corner end of the pressing block 72 is movably abutted against the outer surface of the piston rod 2;

[0039] Just as Figure 7 and Figure 8 As shown, when the piston rod 2 passes through the central position of the abutting spring 71, the rounded corner position of the pressing block 72 contacts the surface of the piston rod 2. During the process of the piston rod 2 returning to its initial position, the pressing block 72 is always pushed by the surface of the piston rod 2, and at this time, the abutting spring 71 is in a compressed state. When the piston 3 completely reaches the locking position, the elastic potential energy of the abutting spring 71 drives the pressing block 72 to clamp the surface of the piston rod 2. While realizing double-layer locking of the piston rod 2, it avoids the fluctuation of the piston rod 2 and the piston 3, maintains the overall stability when the piston 3 resets, and further solves the problems of impact loss caused by improper management of the piston kinetic energy and the risk of insufficient reliability of the locking mechanism in the traditional hydraulic cylinder system.

[0040] Embodiment Six. Refer to the appendix Figure 1-10, on the basis of the fifth embodiment, in order to achieve the convenient unlocking ability of the piston rod 2 and the piston 3: a piston sleeve rod 22 is sleeved and connected to the outer surface of the piston rod 2, and a pressurizing hole 220 is formed in the inner wall of the piston sleeve rod 22. A plurality of groups of pressurizing holes 220 are provided and are arranged in an equidistant array about the central axis of the piston sleeve rod 22; a locking groove 24 is formed in the inner wall of the cylinder block 1, and a locking block 23 is movably connected to the inner surface of the locking groove 24. Two groups of locking blocks 23 are provided and are symmetrically distributed about the central axis of the piston rod 2. A spring 231 is fixedly connected to the inner side surface of the locking block 23. A receiving groove 230 is formed in the surface of the piston rod 2. The spring 231 is arranged inside the receiving groove 230, and one end of the spring 231 is fixedly connected to the inner wall of the receiving groove 230;

[0041] As Figure 5 and Figure 6 shown, a piston sleeve rod 22 is installed on the surface of the piston rod 2. Through the pressurizing holes 220 uniformly formed in the inner wall of the piston sleeve rod 22, it is used for the introduction and circulation of hydraulic oil when the oil return pipe 8 returns oil. Specifically, the oil return pipe 8 is externally connected to an oil return channel. At this time, the hydraulic oil flows through the pressurizing holes 220 in the direction of the locking block 23. When the pressure in the inner cavity of the cylinder block 1 increases, the locking groove 24 is filled with hydraulic oil, and the locking block 23 is pushed outwards. At this time, the spring 231 is squeezed by an external force and generates a compressive deformation. The locking block 23 and the spring 231 are received inside the receiving groove 230, and the locking groove 24 releases the restriction on the locking block 23. In this way, the rapid unlocking of the piston rod 2 is realized. The pressurizing holes 220 formed in the piston sleeve rod 22 can guide part of the oil fluid, so that the hydraulic oil flows through the pressurizing holes 220 in the direction of the locking block 23. Here, the piston sleeve rod 22 can not only meet the structural support during the use of the piston rod 2, but also meet the guiding flow of the hydraulic oil, and achieve the auxiliary unlocking effect on the locking block 23, realizing the effect of multi-purpose use of one object; it should be noted that when the spring 231 gradually loses its elastic stress due to fatigue, corrosion or material aging during long-term use and causes the locking mechanism to fail, the piston rod 2 can be automatically unlocked through the reverse drive of the variable-diameter self-locking component. In this way, the normal use of the piston rod 2 and the piston 3 can be restored.

[0042] Working principle and usage process of the present invention: First, the self-locking oil cylinder of the hydraulic press is in a non-working state, and the piston 3 and its piston rod 2 are located at a certain working position in the oil cylinder. When the hydraulic cylinder starts to work, hydraulic oil enters the oil cylinder through the oil supply system such as the oil inlet pipe 4, pushing the piston 3 and the piston rod 2 to move in the working direction to complete the work task. After the work is completed, the piston 3 and the piston rod 2 need to return to the initial position. During this process, the piston 3 enters the inside of the buffer groove 10 through the buffer ring 31, and the dynamic potential energy of the piston 3 is reduced by the elastic force of the buffer ring 31. Subsequently, when the buffer ring 31 touches the touch switch inside the buffer groove 10, the touch switch sends a signal to the controller 61, and the controller 61 is activated upon receiving the drive signal. At the same time, the hollow shaft rod 611 starts to rotate. At this time, since the oil supply through the oil inlet pipe 4 stops and the piston 3 seals one end of the reserved groove 110, it is ensured that the rotation of the hollow shaft rod 611 will not be interfered by the hydraulic oil. As the hollow shaft rod 611 rotates, the rotating plate 612 and the base plate 613 in the variable-diameter self-locking assembly start to work. The arc-shaped groove 6120 drives the convex column 6131 to move, causing multiple locking rods 6132 to change diameter synchronously, and finally matching with the locking groove 210 opened on the rod-end limit ring 21 to achieve mechanical locking of the piston 3 and its connected component, the piston rod 2. During the variable-diameter self-locking process, due to the structure of the abutting spring 71 and the pressing block 72 inside the loop-shaped groove plate 7, when the piston rod 2 returns to the initial position, the rounded end of the pressing block 72 abuts against the outer surface of the piston rod 2 and further clamps the piston rod 2 through the elastic potential energy of the abutting spring 71 to achieve double locking. During the self-locking process, a small amount of oil enters the lubrication channel formed by the central oil passage 20 and the transfer hole 200 through the oil inlet hole 6110 opened on the hollow shaft rod 611, and penetrates between the friction surfaces of the piston rod 2 and the piston 3 to achieve dynamic lubrication, reducing friction and wear. When unlocking is required, the inside of the locking groove 24 is filled with hydraulic oil through external control or pressure change of the hydraulic system, pushing the locking block 23 to move outward. At the same time, the spring 231 generates a compressive deformation, and the locking block 23 and the spring 231 are received into the receiving groove 230, thereby releasing the restriction on the piston rod 2 to achieve rapid unlocking. If the spring 231 loses its elastic stress due to long-term use, automatic unlocking can also be achieved through the reverse drive of the variable-diameter self-locking assembly.

[0043] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A self-locking oil cylinder for a hydraulic press, comprising a cylinder block (1), both ends of the cylinder block (1) are detachably connected with an intermediate end cover (11) and a rear end cover (12), an oil inlet pipe (4) is provided on the inner wall of the intermediate end cover (11), and an oil outlet pipe (5) is provided on the inner wall of the rear end cover (12), and it is characterized in that: An oil return pipe (8) is connected through the inner wall of the cylinder block (1). The outer side of the middle end cover (11) is detachably connected with a front end cover (13). A reserved groove (110) is formed in the central inner wall of the middle end cover (11). A support ring seat (6) and a return groove plate (7) are fixedly installed on the inner surface of the reserved groove (110). A piston rod (2) is arranged at the center of the return groove plate (7). A central oil passage (20) is formed in the inner wall of one end of the piston rod (2). A piston sleeve rod (22) is sleeved and connected on the outer surface of the piston rod (2). A boosting hole (220) is formed in the inner wall of the piston sleeve rod (22). One end of the piston rod (2) is fixedly connected with a piston (3). A variable-diameter self-locking assembly is arranged on one side of the piston (3) close to the middle end cover (11) for locking and braking after the piston rod (2) resumes its stroke. A buffer groove (10) is formed in the inner wall of the cylinder block (1). A buffer ring (31) is movably embedded in the buffer groove (10). The buffer ring (31) is fixedly installed on the surface of the piston (3). A touch switch is arranged between the buffer groove (10) and the buffer ring (31) for starting the variable-diameter self-locking assembly.

2. The self-locking oil cylinder of a hydraulic press according to claim 1, wherein: A controller (61) is fixedly installed on the inner surface of the support ring seat (6). The controller (61) is electrically connected with the touch switch. A hollow shaft rod (611) is fixedly connected to the output shaft of the controller (61). The hollow shaft rod (611) has a hollow cylindrical structure. Oil inlet holes (6110) are uniformly formed in the inner wall of the hollow shaft rod (611). An electromagnetic valve is arranged on the inner wall of the hollow shaft rod (611).

3. A self-locking oil cylinder of a hydraulic press according to claim 1, characterized in that: The variable-diameter self-locking assembly includes a rotating plate (612) and a base plate (613). The base plate (613) is rotatably installed inside the rotating plate (612). The diameter of the base plate (613) is larger than that of the rotating plate (612). A protective cover (6121) is fixedly connected to the outer surface of the rotating plate (612). An arc-shaped groove (6120) is formed in the inner wall of the rotating plate (612). A sliding groove (6130) for auxiliary positioning is formed in the inner wall of the base plate (613). Both the arc-shaped groove (6120) and the sliding groove (6130) are provided with nine groups.

4. The self-locking oil cylinder of a hydraulic press according to claim 3, wherein: A locking rod (6132) is slidably connected to the inner surface of the sliding groove (6130). A convex column (6131) is fixedly installed on the surface of the locking rod (6132). The outer surface of the convex column (6131) is movably connected to the inner surface of the arc-shaped groove (6120).

5. The self-locking oil cylinder of a hydraulic press according to claim 3, characterized in that: Two support wing arms (614) are fixedly connected to the outer surface of the base plate (613) close to the rotating plate (612). The support wing arms (614) are in an overall "L"-shaped plate structure. The two support wing arms (614) are mirror-symmetrically distributed about the central axis of the base plate (613). One end of the support wing arm (614) is fixedly connected to the inner wall of the reserved groove (110).

6. A self-locking oil cylinder of a hydraulic press according to claim 1, characterized in that: One end of the piston rod (2) is fixedly connected with a rod end limit ring (21). Locking grooves (210) are equally arranged on the inner wall of the rod end limit ring (21), and the inner surface of the locking groove (210) is movably inserted with the outer surface of a locking rod (6132).

7. A self-locking oil cylinder of a hydraulic press according to claim 1, characterized in that: The return groove plate (7) has a hollow annular plate-like structure. An annular cavity is arranged inside the return groove plate (7). An abutting spring (71) is fixedly connected to the inner surface of the annular cavity. The other end of the abutting spring (71) is fixedly connected with a pressing block (72). One side of the pressing block (72) away from the abutting spring (71) is provided with a rounded corner. The rounded corner end of the pressing block (72) is movably abutted against the outer surface of the piston rod (2).

8. A self-locking oil cylinder of a hydraulic press according to claim 7, characterized in that: Transfer holes (200) are formed through the inner wall of the central oil passage (20) for the transfer of lubricating oil. A plurality of groups of transfer holes (200) are provided and are circularly arrayed about the central axis of the central oil passage (20).

9. A self-locking oil cylinder of a hydraulic press according to claim 8, characterized in that: A plurality of groups of boosting holes (220) are provided and are equally spaced and arrayed about the central axis of the piston sleeve rod (22).

10. A self-locking oil cylinder of a hydraulic press according to claim 1, characterized in that: Locking grooves (24) are formed on the inner wall of the cylinder block (1). The inner surface of the locking groove (24) is movably connected with locking blocks (23). Two groups of locking blocks (23) are provided and are symmetrically distributed about the central axis of the piston rod (2). A spring (231) is fixedly connected to the inner side surface of the locking block (23). A receiving groove (230) is formed on the surface of the piston rod (2). The spring (231) is arranged inside the receiving groove (230), and one end of the spring (231) is fixedly connected with the inner wall of the receiving groove (230).

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