A compact hydraulic cylinder

Abstract

This application relates to a compact hydraulic cylinder, comprising a cylinder body; a slide rod; a piston, fixedly connected to one end of the slide rod within the cylinder body, dividing the cavity into a first hydraulic chamber and a second hydraulic chamber that are not interconnected; a front end cap, fixedly connected to the extension end of the slide rod, having a first oil passage communicating with the first hydraulic chamber; a rear end cap, fixedly connected to the end of the cylinder body away from the front end cap, having a second oil passage communicating with the second hydraulic chamber; and a flange, fitted onto the outside of the slide rod and fixedly connected to one end of the cylinder body adjacent to the front end cap, used to constrain the axial displacement of the slide rod. Oil seals are provided on the outer circumferential surface of the piston, the inner surface of the flange, and between the flange and the inner wall of the cylinder body. Each oil seal has wear-resistant rings symmetrically arranged on both sides along the axial direction of the slide rod. This application, through the synergistic effect of the above components, effectively improves the shortcomings of existing hydraulic cylinders in terms of overall structure and sealing stability.

Description

Technical Field

[0001] This application relates to the technical field of hydraulic equipment, and in particular to a compact hydraulic cylinder. Background Technology

[0002] Hydraulic transmission technology, as an important component of modern industrial automation, is widely used in various industries such as engineering machinery, aerospace, metallurgy, automobile manufacturing, and intelligent equipment. As the core actuator in a hydraulic system, the performance of the hydraulic cylinder directly affects the overall system's operating efficiency, control precision, and reliability. In practical applications, hydraulic cylinders need to achieve efficient, stable, and precise linear reciprocating motion under complex working conditions, and their spatial arrangement is often strictly limited. Therefore, the structural design of hydraulic cylinders must not only meet basic hydraulic drive functions but also consider multiple performance indicators such as compactness, sealing, resistance to lateral loads, and safety.

[0003] Traditional hydraulic cylinder structures often employ external oil pipe connections, flange supports, and independent sealing of the slide rod. While these designs can meet basic usage requirements to some extent, they have numerous shortcomings in terms of space utilization, sealing stability, and bending stiffness. Especially in complex application scenarios such as space constraints, dusty environments, and high-frequency reciprocating motions, traditional hydraulic cylinder structures are prone to problems such as chaotic oil circuit layout, seal failure, slide rod sway, and insufficient lateral load, affecting the overall operational stability and service life of the equipment.

[0004] In recent years, as industrial equipment has developed towards higher precision, miniaturization, and intelligence, higher requirements have been placed on the integrated and compact design of hydraulic cylinders.

[0005] Chinese patent application CN202022588946.8 discloses a small hydraulic cylinder, including a cylinder body, an output shaft, and a rear cover. One end of the output shaft is disposed within the cylinder body, dividing the interior of the cylinder body into a first hydraulic chamber and a second hydraulic chamber. The other end of the output shaft extends out of the cylinder body. The rear cover has a first oil hole communicating with the first hydraulic chamber. The cylinder body has a second oil hole corresponding to the second hydraulic chamber. A sealing member is provided on the side of the rear cover near the cylinder body, and the sealing member is inserted into the cylinder body. A convex ring is provided on the side of the cylinder body near the sealing member. A groove adapted to the convex ring is formed on the surface of the sealing member. The cylinder body and the sealing member are interference-fitted by the convex ring and the groove, and a sealing ring is provided on the surface of the groove. This utility model provides a small hydraulic cylinder with good sealing effect, ensuring that the hydraulic cylinder can be used normally.

[0006] The aforementioned technologies have the following drawbacks:

[0007] Complex hydraulic circuit layout: This solution does not integrate the hydraulic circuit design and still relies on external oil pipe connections, resulting in redundant structure, risks of oil pipe entanglement and leakage, and a large amount of external space occupied, making it difficult to adapt to space-constrained application scenarios.

[0008] Single sealing system: Relying on a single sealing structure or local sealing components, lacking a multi-layer collaborative sealing design, it is difficult to meet the long-term sealing stability under high-frequency reciprocating conditions, and is prone to problems such as uneven wear and aging failure of sealing components.

[0009] Lack of extreme position protection: Without an effective mechanical limit and hydraulic buffer structure, when the piston moves to the extreme position, the sealing components are easily overloaded and compressed due to impact load, reducing the service life of the hydraulic cylinder.

[0010] Insufficient dust protection and installation flexibility: It does not provide a dynamic dustproof structure design, making it susceptible to dust intrusion that affects its sealing performance; at the same time, it does not provide standardized, multi-angle installation interfaces, which limits its flexible installation and application in complex spatial structures. Utility Model Content

[0011] In order to improve the shortcomings of existing hydraulic cylinders in terms of overall structure and sealing stability, this application provides a compact hydraulic cylinder.

[0012] The compact hydraulic cylinder provided in this application adopts the following technical solution:

[0013] A compact hydraulic cylinder includes:

[0014] The cylinder block has an axially continuous cavity inside;

[0015] A sliding rod is slidably disposed within the cavity of the cylinder body, with one end located in the cavity and the other end extending out of the cylinder body;

[0016] The piston is fixedly connected to one end of the slide rod located inside the cylinder, and divides the cavity into a first hydraulic cavity and a second hydraulic cavity that are not interconnected.

[0017] The front end cover is fixedly connected to the extension end of the slide rod and has a first oil passage communicating with the first hydraulic chamber;

[0018] The rear end cover is fixedly connected to the end of the cylinder body away from the front end cover, and has a second oil passage that connects to the second hydraulic chamber;

[0019] The flange is fitted onto the outside of the slide rod and fixedly connected to one end of the cylinder body near the front end cover, and is used to constrain the axial displacement of the slide rod;

[0020] Oil seals are provided on the outer circumferential surface of the piston, the inner bore surface of the flange, and between the flange and the inner wall of the cylinder. Wear-resistant rings are symmetrically arranged on both sides of each oil seal along the axial direction of the slide rod.

[0021] Furthermore, a guide ring and a step seal are sequentially provided on the inner surface of the flange facing the first hydraulic chamber, and the step seal is located between the guide ring and the adjacent wear-resistant ring.

[0022] Furthermore, the outer circumferential surface of the piston protrudes outward along its axial direction to form an annular convex ring; on the inner circumferential surface of the flange facing the first hydraulic chamber, corresponding to the position of the annular convex ring, an annular groove is provided to cooperate with the annular convex ring.

[0023] Furthermore, the slide rod is a hollow tubular structure, and a radially penetrating oil inlet hole is provided on the tube wall of the slide rod in the area adjacent to the annular convex ring in the first hydraulic cavity;

[0024] It also includes an oil inlet pipe disposed in the hollow cavity of the slide bar, one end of which is connected to the oil inlet hole and the other end of which is connected to the first oil passage.

[0025] Furthermore, the outer side of the front end cover is provided with a first oil connector that communicates with the first oil passage, and the outer side of the rear end cover is provided with a second oil connector that communicates with the second oil passage.

[0026] Furthermore, the front end cover is provided with a first plug, which is detachably disposed in the first oil passage between the first oil connector and the slide rod; the rear end cover is provided with a second plug, which is detachably disposed in the second oil passage between the second oil connector and the slide rod.

[0027] Furthermore, a corrugated telescopic shield is fitted between the outer peripheral surfaces of the front end cover and the cylinder body that are close to each other; both the front end cover and the rear end cover are provided with mounting holes for installation.

[0028] In summary, the beneficial technical effects of this application are as follows:

[0029] 1. Through the integrated design of flange and cylinder body, built-in oil inlet pipe structure and integrated layout of oil passage, the external space occupied by external oil circuit connection and support structure in traditional hydraulic cylinder is reduced. At the same time, the slide rod adopts a hollow structure and cooperates with the oil inlet pipe, making the hydraulic oil circuit layout simpler, avoiding the risk of entanglement and leakage of external pipes, and further improving the compactness of the overall structure, which is suitable for application scenarios with limited installation space.

[0030] 2. By integrating the support structure through the flange, additional support points are provided for the slide bar, enhancing its bending stiffness and effectively suppressing radial runout and bending deformation of the slide bar in the extended state, thereby improving its lateral load capacity;

[0031] 3. Wear-resistant rings are symmetrically arranged on both sides of the oil seal, which reduces the risk of uneven wear of the seal while achieving a sealing effect and extends the service life. Furthermore, through the layered sealing combination (guide ring + step seal + wear-resistant ring + oil seal + wear-resistant ring), dynamic sealing and low-wear operation of the slide rod are achieved in synergy, making it suitable for high-frequency reciprocating working conditions.

[0032] 4. When the piston moves to its limit position, the annular convex ring on the piston and the annular groove on the flange form a mechanical engagement to achieve rigid limiting, effectively absorb axial impact force, and avoid damage to the sealing components due to overload compression. At the same time, the shielding design between the oil inlet and the inner wall of the flange forms a hydraulic buffer pad when the piston approaches the limit position, achieving uniform deceleration braking, further improving the safety and stability of the hydraulic cylinder under extreme working conditions.

[0033] 5. The corrugated telescopic dust cover dynamically seals the protruding slide bar, avoiding sealing failure caused by dusty environments and extending the maintenance cycle; the integrated modular installation interface reserved on the end cover solves the installation problem of hydraulic cylinders in space-constrained situations. Attached Figure Description

[0034] Figure 1 This is a partial sectional view of the overall structure of an embodiment of this application;

[0035] Figure 2 yes Figure 1 A magnified view of part A in the middle;

[0036] Figure 3 This is a schematic diagram of the overall structure from another perspective of an embodiment of this application.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Cylinder body; 11. First hydraulic chamber; 12. Second hydraulic chamber; 13. Shield;

[0039] 2. Slide rod; 21. Oil inlet hole; 22. Oil inlet pipe;

[0040] 3. Piston; 31. Annular convex ring; 32. Wear ring; 33. Oil seal;

[0041] 4. Front end cover; 41. First oil passage; 42. First oil connector; 43. First plug; 44. Mounting hole;

[0042] 5. Rear end cover; 51. Second oil passage; 52. Second oil connector; 53. Second plug;

[0043] 6. Flange; 61. Step seal; 62. Guide ring; 63. Annular groove. Detailed Implementation

[0044] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] This application discloses a compact hydraulic cylinder. (Refer to...) Figure 1 It includes a cylinder body 1, which has an axially penetrating cavity inside. A slide rod 2 is slidably disposed within the cavity of the cylinder body 1, with one end located within the cavity and the other end extending out of the cylinder body 1. A piston 3 is fixedly connected to the end of the slide rod 2 located within the cylinder body 1, dividing the cavity into a first hydraulic chamber 11 and a second hydraulic chamber 12 that are not interconnected. This allows the two hydraulic chambers to form relatively independent spaces, providing a basis for hydraulic drive.

[0046] The front cover 4 is fixedly connected to the extension end of the slide rod 2, and has a first oil passage 41 communicating with the first hydraulic chamber 11. The rear cover 5 is fixedly connected to the end of the cylinder body 1 away from the front cover 4, and has an integrally extended sealing member on the side of the rear cover 5 facing the cylinder body 1, which is inserted into the end of the cylinder body 1. The rear cover 5 has a second oil passage 51 communicating with the second hydraulic chamber 12. The flange 6 is sleeved on the outside of the slide rod 2 and fixedly connected to the end of the cylinder body 1 adjacent to the front cover 4 by multiple fixing bolts, integrating guiding and sealing functions, eliminating the installation space of an independent guide sleeve, and shortening the axial length of the cylinder body 1.

[0047] Oil seals 33 are provided between the outer circumferential surface of the piston 3 and the inner wall of the cylinder 1, between the inner bore surface of the flange 6 and the slide rod 2, and between the flange 6 and the inner wall of the cylinder 1. The main function of the oil seals 33 is to prevent hydraulic oil leakage, thereby achieving a seal between the two hydraulic chambers. Wear-resistant rings 32, such as Glyd rings, are symmetrically arranged on both sides of each oil seal 33 along the axial direction of the slide rod 2.

[0048] Thus, when the external hydraulic system delivers pressurized oil to the first hydraulic chamber 11 through the first oil passage 41, while simultaneously causing the pressurized oil in the second hydraulic chamber 12 to flow back (depressurize) through the second oil passage 51, the pressure in the first hydraulic chamber 11 will be higher than the pressure in the second hydraulic chamber 12. This pressure difference acts on both sides of the piston 3, driving the piston 3 and its rigidly connected slide rod 2 to move against the load towards the second hydraulic chamber 12 (i.e., the retraction direction). Conversely, when the external hydraulic system delivers pressurized oil to the second hydraulic chamber 12 through the second oil passage 51, while simultaneously depressurizing the first hydraulic chamber 11, the pressure difference drives the piston 3 and slide rod 2 towards the first hydraulic chamber 11 (i.e., the extension direction). By alternately delivering pressurized oil to different hydraulic chambers, the reciprocating linear motion of the piston 3 and slide rod 2 can be achieved; by precisely controlling the pressure, flow rate, and direction of the hydraulic oil in the input and output hydraulic chambers, precise closed-loop control of the slide rod 2's movement direction, speed, and output force can be achieved.

[0049] During this process, the flange 6, through its fixed connection with the cylinder body 1, provides a front-end support point for the slide rod 2 away from the piston 3, effectively constraining the radial degree of freedom of the slide rod 2, improving its bending stiffness and ability to resist lateral loads, and reducing the risk of bending deformation of the slide rod 2 in its extended state. This ensures that the slide rod 2 can only perform high-precision linear motion along the axis of the cylinder body 1 within a set stroke, greatly reducing radial runout and yaw. At the same time, the flange 6 can also withstand a portion of the hydraulic force, reducing the load on the cylinder body 1 and improving the overall strength and reliability of the hydraulic cylinder.

[0050] Furthermore, during hydraulic cylinder operation, the oil seal 33 prevents hydraulic oil from leaking from the high-pressure chamber to the low-pressure chamber or to the outside, maintaining stable pressure within both hydraulic chambers to achieve the hydraulic drive effect. Simultaneously, the oil seal 33 effectively prevents external impurities from entering the hydraulic chambers, avoiding wear and damage to hydraulic components and extending the service life of the hydraulic cylinder. Moreover, during the reciprocating motion of the slide rod 2, the wear-resistant ring 32 reduces friction and wear between the slide rod 2 and the flange 6, and between the piston 3 and the cylinder body 1, reducing energy loss and improving the working efficiency of the hydraulic cylinder. The wear-resistant ring 32 also provides support and guidance, improving the straightness of the slide rod 2 during movement and further enhancing the motion accuracy and stability of the hydraulic cylinder. Through the synergistic effect of the aforementioned components, this hydraulic cylinder effectively addresses the shortcomings of existing hydraulic cylinders in terms of overall structure and sealing stability.

[0051] Specifically, refer to Figure 1 and Figure 2 On the inner surface of the flange 6 facing the first hydraulic chamber 11, a guide ring 62 and a step seal 61 are sequentially provided, and the step seal 61 is located between the guide ring 62 and the adjacent wear-resistant ring 32.

[0052] The guide ring 62 is made of materials with good wear resistance and self-lubricating properties, such as bronze and polyoxymethylene. When the slide rod 2 reciprocates linearly within the cylinder 1, the guide ring 62 directly contacts the slide rod 2. It provides precise guidance for the slide rod 2, ensuring that the slide rod 2 moves along the axis of the cylinder 1 and preventing wobbling or jamming during movement. The step seal 61 is a high-performance sealing element consisting of a rubber O-ring and a polytetrafluoroethylene (PTFE) retainer ring, effectively preventing high-pressure oil from leaking from the first hydraulic chamber 11 to the outside of the flange 6. Through a layered sealing structure design, each component can fully perform its specific function while cooperating and protecting each other. The guide ring 62 improves the movement accuracy of the slide rod 2 and reduces damage to the seals caused by movement deviations; the wear-resistant ring 32 reduces wear between the slide rod 2 and the flange 6, extending the service life of the components; and the step seal 61 further improves the sealing performance of the hydraulic cylinder, preventing hydraulic oil leakage. The combined effect of these three factors further optimizes the overall performance of the hydraulic cylinder, improves its reliability, stability, and service life, enabling it to operate normally under various complex working conditions.

[0053] Furthermore, referring to Figure 1 The outer circumferential surface of the piston 3 protrudes outward along its axial direction to form an annular convex ring 31; on the inner circumferential surface of the flange 6 facing the first hydraulic chamber 11, corresponding to the position of the annular convex ring 31, an annular groove 63 is provided to cooperate with the annular convex ring 31. When the piston 3 moves to its limit position, the annular convex ring 31 is embedded in the annular groove 63 to form a mechanical engagement.

[0054] When the slide bar 2 moves to its maximum extension stroke, the annular convex ring 31 is embedded in the annular groove 63 to form a rigid metal engagement. The axial impact force is transmitted to its bolt connection through the flange 6, avoiding the risk of overload compression of the sealing assembly.

[0055] Furthermore, referring to Figure 1 and Figure 2 The slide rod 2 is a hollow tubular structure. A radially penetrating oil inlet hole 21 is provided on the tube wall of the slide rod 2 in the area corresponding to the annular convex ring 31 in the first hydraulic cavity 11. It also includes an oil inlet pipe 22 provided in the hollow cavity of the slide rod 2. One end of the oil inlet pipe 22 is connected to the oil inlet hole 21, and the other end is connected to the first oil passage 41.

[0056] The internal oil inlet pipe 22 simplifies the structure of the hydraulic circuit and avoids the problem of external oil pipe entanglement. It also reduces the risk of oil pipe leakage and makes the overall structure of the hydraulic cylinder more compact, saving installation space. The coupling design of the engagement area of ​​the convex ring groove and the oil inlet hole 21 allows the hydraulic oil to act directly on the front section of the piston 3, which is the most critical part bearing pressure. When the piston 3 approaches the end of its extension stroke, as the annular convex ring 31 enters the annular groove 63, the oil inlet hole 21 is gradually blocked by the inner wall of the flange 6, and the return oil cross-sectional area decreases. The pressure oil in the first hydraulic chamber 11 forms a hydraulic buffer pad, realizing uniform deceleration braking.

[0057] Furthermore, referring to Figure 1 and Figure 3 The outer side of the front cover 4 is provided with a first oil connector 42 that communicates with the first oil passage 41, and the outer side of the rear cover 5 is provided with a second oil connector 52 that communicates with the second oil passage 51. Through the first oil connector 42 and the second oil connector 52, the hydraulic cylinder can be easily connected to external hydraulic pumps, control valves and other hydraulic components to form a complete hydraulic circuit.

[0058] At the same time, refer to Figure 1 and Figure 3 The front cover 4 is provided with a first plug 43, which is detachably installed in the first oil passage 41 between the first oil connector 42 and the slide rod 2. The front cover 4 also has a first test branch connected to the first oil passage 41, and the first plug 43 is used to seal the outlet of the first test branch. The rear cover 5 is provided with a second plug 53, which is detachably installed in the second oil passage 51 between the second oil connector 52 and the slide rod 2. The rear cover 5 also has a second test branch connected to the second oil passage 51, and the second plug 53 is used to seal the outlet of the second test branch. Through the integration of oil passage interfaces and the reuse of plug functions, the synergistic optimization of testing, maintenance, and safety is achieved while meeting the sealing requirements.

[0059] Additionally, refer to Figure 1 A corrugated telescopic shield 13 is fitted between the outer peripheral surfaces of the front cover 4 and the cylinder body 1, which are close to each other. The shield 13 is made of EPDM rubber or polyurethane-nylon fabric composite material and is used to dynamically seal the protrusion of the slide rod 2. Both the front cover 4 and the rear cover 5 have mounting holes 44 for multi-angle installation and positioning. Through the integration of dynamic dustproof sealing and modular installation interfaces, the problems of sealing failure and space-constrained installation of hydraulic cylinders in dusty environments are solved.

[0060] The implementation principle of a compact hydraulic cylinder according to an embodiment of this application is as follows:

[0061] When the external hydraulic system delivers pressurized oil to the first hydraulic chamber 11 through the first oil passage 41, and simultaneously causes the pressurized oil in the second hydraulic chamber 12 to flow back (depressurize) through the second oil passage 51, the pressure in the first hydraulic chamber 11 will be higher than the pressure in the second hydraulic chamber 12. This pressure difference acts on both sides of the piston 3, driving the piston 3 and its rigidly connected slide rod 2 to move against the load towards the second hydraulic chamber 12 (i.e., the retraction direction). Conversely, when the external hydraulic system delivers pressurized oil to the second hydraulic chamber 12 through the second oil passage 51, and simultaneously depressurizes the first hydraulic chamber 11, the pressure difference drives the piston 3 and slide rod 2 towards the first hydraulic chamber 11 (i.e., the extension direction). By alternately delivering pressurized oil to different hydraulic chambers, the reciprocating linear motion of the piston 3 and slide rod 2 can be achieved; by precisely controlling the pressure, flow rate, and direction of the hydraulic oil in the input and output hydraulic chambers, precise closed-loop control of the slide rod 2's movement direction, speed, and output force can be achieved.

[0062] During this process, the flange 6, through its fixed connection with the cylinder body 1, provides a front-end support point for the slide rod 2 away from the piston 3, effectively constraining the radial degree of freedom of the slide rod 2, improving its bending stiffness and ability to resist lateral loads, and reducing the risk of bending deformation of the slide rod 2 in its extended state. This ensures that the slide rod 2 can only perform high-precision linear motion along the axis of the cylinder body 1 within a set stroke, greatly reducing radial runout and yaw. At the same time, the flange 6 can also withstand a portion of the hydraulic force, reducing the load on the cylinder body 1 and improving the overall strength and reliability of the hydraulic cylinder.

[0063] Furthermore, during hydraulic cylinder operation, the oil seal 33 prevents hydraulic oil from leaking from the high-pressure chamber to the low-pressure chamber or to the outside, maintaining stable pressure within both hydraulic chambers to achieve the hydraulic drive effect. Simultaneously, the oil seal 33 effectively prevents external impurities from entering the hydraulic chambers, avoiding wear and damage to hydraulic components and extending the service life of the hydraulic cylinder. Moreover, during the reciprocating motion of the slide rod 2, the wear-resistant ring 32 reduces friction and wear between the slide rod 2 and the flange 6, and between the piston 3 and the cylinder body 1, reducing energy loss and improving the working efficiency of the hydraulic cylinder. The wear-resistant ring 32 also provides support and guidance, improving the straightness of the slide rod 2 during movement and further enhancing the motion accuracy and stability of the hydraulic cylinder. Through the synergistic effect of the aforementioned components, this hydraulic cylinder effectively addresses the shortcomings of existing hydraulic cylinders in terms of overall structure and sealing stability.

[0064] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A compact hydraulic cylinder characterized by, include: The cylinder (1) has an axially penetrating cavity inside; The slide bar (2) is slidably disposed in the cavity of the cylinder (1), with one end located in the cavity and the other end extending out of the cylinder (1). The piston (3) is fixedly connected to one end of the slide rod (2) located inside the cylinder (1) and divides the cavity into a first hydraulic cavity (11) and a second hydraulic cavity (12) that are not connected to each other. The front end cover (4) is fixedly connected to the extension end of the slide bar (2) and has a first oil passage (41) that communicates with the first hydraulic chamber (11). The rear end cover (5) is fixedly connected to the end of the cylinder body (1) away from the front end cover (4) and has a second oil passage (51) that connects to the second hydraulic chamber (12). The flange (6) is sleeved on the outside of the slide rod (2) and fixedly connected to one end of the cylinder body (1) near the front end cover (4) to constrain the axial displacement of the slide rod (2); Oil seals (33) are provided on the outer circumferential surface of the piston (3), the inner bore surface of the flange (6), and between the flange (6) and the inner wall of the cylinder (1). Each oil seal (33) is symmetrically provided with wear-resistant rings (32) on both sides along the axial direction of the slide rod (2).

2. A compact hydraulic cylinder according to claim 1, characterized in that, The inner surface of the flange (6) facing the first hydraulic chamber (11) is also provided with a guide ring (62) and a step seal (61) in sequence, and the step seal (61) is located between the guide ring (62) and the adjacent wear-resistant ring (32).

3. A compact hydraulic cylinder according to claim 1, characterized in that The outer peripheral surface of the piston (3) protrudes outward along its axial direction to form an annular protrusion (31); on the inner peripheral surface of the flange (6) facing the first hydraulic chamber (11), corresponding to the position of the annular protrusion (31), an annular groove (63) is provided to cooperate with the annular protrusion (31).

4. A compact hydraulic cylinder according to claim 3, characterized in that The slide bar (2) is a hollow tubular structure. A radially penetrating oil inlet hole (21) is provided on the tube wall of the slide bar (2) in the area adjacent to the annular convex ring (31) in the first hydraulic cavity (11). It also includes an oil inlet pipe (22) disposed in the hollow cavity of the slide bar (2), one end of the oil inlet pipe (22) is connected to the oil inlet hole (21), and the other end is connected to the first oil passage (41).

5. A compact hydraulic cylinder according to claim 1, characterized in that The front end cover (4) is provided with a first oil connector (42) communicating with the first oil passage (41) on the outside, and the rear end cover (5) is provided with a second oil connector (52) communicating with the second oil passage (51) on the outside.

6. A compact hydraulic cylinder according to claim 5, characterized in that The front end cover (4) is provided with a first plug (43), which is detachably disposed in the first oil passage (41) between the first oil connector (42) and the slide rod (2); the rear end cover (5) is provided with a second plug (53), which is detachably disposed in the second oil passage (51) between the second oil connector (52) and the slide rod (2).

7. A compact hydraulic cylinder according to claim 1, characterized in that A corrugated telescopic shield (13) is fitted between the outer peripheral surfaces of the front end cover (4) and the cylinder body (1) that are close to each other; both the front end cover (4) and the rear end cover (5) are provided with mounting holes (44) for installation.

Images