A hydraulic jack

Abstract

The utility model relates to the technical field of oil cylinder, especially relates to a hydraulic jack, including cylinder body, piston rod, locking mechanism and anti -rotation mechanism, the piston rod coaxial is established in the cylinder body, the locking mechanism includes locking block and motor, the locking block is set on the piston rod and is connected with its screw thread, the locking block outside processing step is connected with the motor inboard, the anti -rotation mechanism includes the shaft sleeve and the key, the shaft sleeve is set on the piston rod, its outside is connected with the cylinder body, the shaft sleeve inboard is set up and the key fixed connection of key groove, the piston rod outside has been set up recess groove is used to accommodate the key and with its sliding fit. Through structural improvement makes locking mechanism and piston rod mutual cooperation, and reasonable utilization jack internal space places anti -rotation mechanism in the cylinder body and reaches the effect of piston rod circumferential location to simple integrated stable while of hydraulic jack overall structure, saves the labor high -efficient locking reliable and can remote control.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic cylinder technology, and in particular to a hydraulic jack. Background Technology

[0002] As a key component of the support system, the stability and safety of hydraulic jacks are of paramount importance. However, during lifting operations, hydraulic jacks rely on oil pressure to support heavy objects for extended periods, making them highly susceptible to sudden failure and damage, or oil backflow causing relative displacement, posing significant safety hazards.

[0003] Traditional mechanical self-locking hydraulic jacks are mostly operated manually, which consumes a lot of manpower and has low operating efficiency. They are difficult to meet the needs of some emergency or high-intensity operations and are prone to the following problems during use: The locking structure is too simple and is prone to loosening under long-term load or vibration, which poses a great safety risk of instability of the load. To enhance the self-locking capability of the locking structure, more components are used, making the overall structure of the hydraulic jack cumbersome and complex. This not only increases the space occupied by the hydraulic jack itself, but also increases its cost and the difficulty of assembly.

[0004] In some dangerous, inaccessible, or space-constrained work scenarios, the inability of existing hydraulic jack operators to operate them remotely increases safety risks. Utility Model Content

[0005] The technical problem to be solved by this utility model is to address the issues of existing hydraulic jacks, such as the difficulty of manual operation, unreliable locking, suboptimal structure, and inability to be remotely controlled.

[0006] Therefore, this utility model provides a hydraulic jack. Through structural improvements, the locking mechanism and piston rod cooperate with each other, achieving reliable self-locking and remote control of the hydraulic jack while maintaining overall structural stability. By making reasonable use of the internal space of the jack, the anti-rotation mechanism is placed in the cylinder body through a bushing. This not only cooperates with the piston rod to achieve the function of circumferentially limiting the piston rod, but also increases the self-locking capability of the locking mechanism, thereby improving the convenience, safety and work efficiency of the hydraulic jack operation.

[0007] The technical solution adopted by this utility model to solve its technical problem is: a hydraulic jack, characterized in that it includes a cylinder body, a piston rod, a locking mechanism, and an anti-rotation mechanism. The piston rod is coaxially disposed within the cylinder body; The locking mechanism includes a locking block and a motor. The locking block is sleeved on the piston rod and threadedly connected to it. A step is machined on the outer side of the locking block and connected to the inner side of the motor. The anti-rotation mechanism includes a bushing and a retaining key. The bushing is sleeved on the piston rod and its outer side is connected to the cylinder body. A keyway is provided on the inner side of the bushing to be fixedly connected to the retaining key. A groove is provided on the outer side of the piston rod to accommodate the retaining key and slide with it.

[0008] Furthermore, it also includes a remote control module. The motor is interference-fitted with the locking block, and the motor rotor is located inside it. The motor can adjust the position of the locking block relative to the piston rod by controlling the forward and reverse rotation of the rotor. The remote control module controls the motor through electrical signals.

[0009] Furthermore, the piston rod includes an integrally formed rod body section and a piston section, the surface of the rod body section is provided with threads, and the locking block is threadedly connected to the rod body section.

[0010] Furthermore, it also includes a guide structure, which includes a connecting plate, a guide rod, a small bushing, and a locking nut. The connecting plate is sleeved on the motor and has an interference fit with the outside of the motor.

[0011] Furthermore, one end of the guide rod is fixedly connected to the connecting plate by the locking nut, and the other end of the guide rod is fitted to the cylinder body through a small bushing with clearance.

[0012] Furthermore, it also includes a bottom cover, which is connected to the end of the cylinder body away from the bushing and forms a seal.

[0013] Furthermore, an oil port is provided on the side of the cylinder near the bottom cover or on the bottom cover, through which the medium provides a hydraulic environment for the extension and retraction of the piston rod.

[0014] Furthermore, an annular groove is provided at the front end of the piston section, and oil is stored between the piston section and the cylinder through the annular groove.

[0015] Furthermore, an annular notch is provided on the piston section, and a sealing element is provided between the piston section and the cylinder body through the annular notch to facilitate sealing.

[0016] Furthermore, a small hole is provided on the end face of the bushing opposite to the locking block to facilitate the installation of the bushing.

[0017] Based on the above technical solution, the technical effect of this utility model is as follows: This utility model of a hydraulic jack integrates a locking block with a piston rod threadedly connected to the inner side, and a stepped outer side with an interference fit to the motor. This integrated structure achieves self-locking and strong anti-loosening capabilities. The motor drive replaces manual operation, reducing labor intensity. Operators can remotely operate the jack via a remote control module that controls the motor through electrical signals, making it more suitable for use in dangerous or high-altitude work scenarios, thus reducing operational risks. The piston section and rod body section of the piston rod are integrally formed, making the jack less prone to wear and fluid leakage, and more stable and durable. When the piston section reciprocates in the cylinder, the rod body section, as its extension, can effectively transmit motion and force, ensuring synchronous movement and improving operating efficiency. This utility model of a hydraulic jack makes reasonable use of the internal space of the jack to place the anti-rotation mechanism inside the cylinder and connect it to the cylinder. The outer side of the piston rod has a groove to accommodate the locking key in the anti-rotation mechanism and slide with it to achieve the function of limiting the circumferential movement of the piston rod. The structure of the hydraulic jack is optimized by the locking mechanism, which increases the self-locking ability of the locking mechanism to a certain extent. The lifting height can be quickly adjusted according to actual needs by using the locking mechanism to improve work efficiency. This utility model of a hydraulic jack cleverly integrates a connecting plate fitted onto the motor with an interference fit. The connecting plate and a guide rod with a clearance fit to the cylinder body easily achieve circumferential positioning and guidance for the motor, improving the ease of operation, safety, and efficiency of the hydraulic jack. Compared to traditional jacks with internal guide components on the piston rod, this design is simpler, requires lower machining precision, is easier to assemble, and has a lower failure rate. Combined with other structural improvements, this utility model of a hydraulic jack not only achieves labor-saving, efficient, reliable locking, and remote control, but also boasts a simple, integrated, and stable overall structure. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the hydraulic jack of this utility model; Figure 2 This is a side view of the hydraulic jack of this utility model; Figure 3 for Figure 2 A cross-sectional view of the hydraulic jack's cross-section BB; Figure 4 This is a cross-sectional view of the piston rod of the hydraulic jack of this utility model; Figure 5 This is a cross-sectional view of the hydraulic jack of this utility model during assembly; In the diagram: 1-Cylinder block; 2-Piston rod; 21-Rod section; 211-Groove; 22-Piston section; 221-Annular groove; 222-Annular notch; 3-Locking block; 4-Motor; 5-Anti-rotation mechanism; 51-Sleeve; 511-Keyway; 512-Small hole; 52-Key; 6-Connecting plate; 61-Locking nut; 7-Guide rod; 8-Small sleeve; 9-Bottom cover; 10-Oil port. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0022] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0023] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0024] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0025] like Figures 1-3 As shown, this embodiment proposes a hydraulic jack, including a cylinder body 1, a piston rod 2, a locking mechanism, and an anti-rotation mechanism 5. The piston rod 2 is coaxially disposed inside the cylinder body 1. The locking mechanism includes a locking block 3 and a motor 4. The locking block 3 is sleeved on the piston rod 2 and threadedly connected to it. A step is machined on the outer side of the locking block 3 and connected to the inner side of the motor 4. The anti-rotation mechanism 5 includes a bushing 51 and a retaining key 52. ​​The bushing 51 is sleeved on the piston rod 2 and its outer side is connected to the cylinder body 1. A keyway 511 is formed on the inner side of the bushing 51 and fixedly connected to the retaining key 52. ​​A groove 211 is formed on the outer side of the piston rod 2 parallel to the axis of the piston rod 2 to accommodate the retaining key 52 and slide with it.

[0026] In other words, the surface of the piston rod 2's rod section 21 is threaded, and the locking block 3 is threadedly connected to the piston rod 2. In this embodiment, a trapezoidal thread is preferably used. In addition to its advantages of long wear resistance and life, the trapezoidal thread has high precision and small repeatability error. Its strong load-bearing capacity and impact resistance are also more suitable for heavy-duty applications. The locking block 3 has a stepped outer side for easy direct connection to the inner side of the motor 4, making the structure more integrated. An anti-rotation mechanism 5 is added inside the cylinder 1. The outer side of the anti-rotation mechanism 5's bushing 51 is threadedly connected and fixed to the cylinder 1. The bushing 51 is fitted onto the piston rod 2 and leaves a certain gap with the piston rod 2. It can help support the piston rod 2 and limit its radial rotation when it has a large radial swing tendency, avoiding excessive radial rotation and deflection pressure on the piston rod 2, and playing a role in timely correction to prevent the piston rod 2 from bending. In this embodiment, the bushing 51 is preferably made of copper, which is soft and can prevent the piston rod 2 from scratching when it provides auxiliary support. A keyway 511 is provided on the inner side of the bushing 51 to facilitate the placement and fixed connection of the retaining key 52. ​​The retaining key 52 and the groove 211 on the outer side of the piston rod 2, parallel to the axis of the piston rod 2, form a sliding fit. When the piston rod 2 extends or retracts, the retaining key 52 and the piston rod 2 slide relative to each other. Figure 2 As shown, the groove 211 of the rod segment 21 is machined in a simple way, such as... Figure 3 The bushing 51 and key 52 of the anti-rotation mechanism 5 shown can be mass-produced and are easy to replace and repair in case of failure. The anti-rotation mechanism 5 is cleverly fixed to the cylinder body 1 to restrict the rotation of the piston rod 2, so that the piston rod 2 only makes linear motion. At the same time, it avoids the drawbacks of traditional mechanical self-locking jacks, which have unstable locking position and unreliable locking due to the tendency of the piston rod 2 to rotate.

[0027] This utility model of a hydraulic jack features an optimized structure and enables remote control. For example, the rotor of the motor 4 is located inside the motor 4 and is interference-fitted with the locking block 3. An adhesive can be added to further strengthen the fixation. The motor 4 can directly adjust the position of the locking block 3 relative to the piston rod 2 by rotating the rotor forward and backward, achieving precise adjustment. The motor 4 can be connected to a remote control module (not shown in the figure). In hazardous, high-altitude, or confined work environments, the operator can control the remote control module to issue commands, which in turn control the rotation of the motor 4 via electrical signals to drive the locking block 3, achieving mechanical self-locking of the hydraulic jack and adjustment of the piston rod 2's position.

[0028] In this embodiment, the piston rod 2, which is slidably disposed in the cylinder 1, includes a piston section 22 and a rod section 21. The piston section 22 and the rod section 21 are integrally formed. This structure is not easy to wear and is stable and durable. When the piston section 22 moves in extension and retraction within the cylinder 1, the rod section 21, as its extension, can effectively transmit force and motion, realize the function of lifting and lowering heavy objects, and ensure the synchronous movement of the piston section 22 and the rod section 21 to improve operating efficiency.

[0029] Specifically, this embodiment also includes a guide structure, which comprises a connecting plate 6, a guide rod 7, a small bushing 8, and a locking nut 61. The connecting plate 6 is sleeved on the motor 4 and has an interference fit with the outer side of the motor 4. One end of the guide rod 7 is fixedly connected to the connecting plate 6, and the other end of the guide rod 7 is clearance-fitted to the cylinder 1 through the small bushing 8, allowing the guide rod 7 to slide relative to the cylinder 1, thus playing a guiding role. In this embodiment, the connecting plate 6 and the guide rod 7 are preferably fixed with threads and the locking nut 61. The connecting plate 6 and the guide rod 7 achieve the function of restricting the rotation of the outer side of the motor 4 and guiding it. Compared with the traditional method of setting a guide post inside the piston rod, this embodiment has lower machining accuracy requirements, simpler process, lower failure rate, and more stable mechanism operation. The small bushing 8 is also preferably made of copper. The surface roughness of copper can be very low, reducing friction, and its low hardness can also effectively reduce the noise generated by sliding with the guide rod 7.

[0030] In addition, the hydraulic jack in this embodiment also includes a bottom cover 9, which is connected to the end of the cylinder body 1 away from the bushing 51 and forms a seal (e.g. Figure 3 The embodiment shown preferably employs welding, which provides high rigidity, simple structure, and better sealing. An oil port 10 is provided on the side of the cylinder body 1 near the bottom cover 9 or on the bottom cover 9. When the piston rod 2 retracts, it is pressed back by an external load. The oil port 10 is not limited and can be designed as multiple or one. In this embodiment, one oil port 10 is preferably used, which allows for both oil inlet and outlet, and also saves processing costs. The medium provides a hydraulic environment for the extension and retraction of the piston rod 2 through the oil port 10.

[0031] like Figures 3-4 As shown, an annular groove 221 is provided on the outer circumferential surface of the piston section 22. When the piston rod 2 is adjusted to rise to the target position, the hydraulic jack is filled with oil. The oil fills the cylinder 1, allowing the piston rod 2 to move under oil pressure load. The annular groove 221 between the piston section 22 and the cylinder 1 allows a portion of the oil to be stored in the annular groove 221 when the oil pressure is released after the locking mechanism self-locks. In this embodiment, the piston section 22 preferably adopts a welding technique on the outside to enhance the wear resistance, corrosion resistance, and load-bearing capacity of the piston section 22, thereby extending its service life. Copper is further preferred for welding, which not only ensures the strength of the piston section 22 itself, but also provides good sliding on its working surface, thus playing a guiding role. Moreover, the welded copper itself has the physical and chemical properties of copper and steel, and also has cost advantages. The annular groove 221 for oil storage increases the lubrication between the piston section 22 and the cylinder 1, and also promotes the guidance of the piston rod 2.

[0032] It is worth mentioning that an annular notch 222 is also provided on the piston section 22. A sealing element (not shown in the figure) is provided between the piston section 22 and the cylinder body 1 through the annular notch 222 to facilitate sealing. A small hole 512 is also provided on the end face of the bushing 51 opposite to the locking block 3. The small hole 512 can usually be set as a hexagonal hole or a dodecagonal hole. Auxiliary parts such as wrenches can be easily fitted into the small hole 512 regardless of whether the bushing 51 is in a narrow position, thereby facilitating the installation, disassembly and maintenance of the bushing 51 and improving the convenience and efficiency of operation.

[0033] like Figure 5 As shown, in this preferred embodiment, the locking block 3 and the motor 4 are circular, and the motor 4, bushing 51, connecting plate 6, and bottom cover 9 are coaxially arranged along the axis of the piston rod 2. During assembly, preferably the piston rod 2, bushing 51, key 52, locking block 3, motor 4, and connecting plate 6 can be installed sequentially, resulting in simple integrated assembly.

[0034] The working process of this utility model: When piston rod 2 needs to extend, hydraulic oil enters cylinder 1 from oil port 10. Anti-rotation mechanism 5 is fixedly connected to cylinder 1 to restrict piston rod 2 from rotating. The hydraulic oil pushes piston rod 2 to slide relative to key 52 and rise to the target position. After that, the operator sends a command through the remote control module to control motor 4 to rotate. Since the circumferential limit of connecting plate 6 and guide rod 7 does not rotate, the rotor inside motor 4 drives locking block 3 to move towards cylinder 1, where locking block 3 is threaded onto piston rod 2. It also serves as a guide, moving in conjunction with the locking mechanism towards the cylinder 1. The guide rod 7 slides relative to the small bushing 8, and the anti-rotation mechanism 5 is fixedly connected to the cylinder 1 and remains stationary. At this time, it also restricts the piston rod 2 from rotating until the locking block 3 contacts the cylinder 1. The connecting plate 6 and the guide rod 7 also stop moving. At this time, the oil pressure can be released. The hydraulic jack can achieve mechanical self-locking by relying on the locking mechanism and the anti-rotation mechanism 5 to prevent the piston rod 2 from sliding down and rotating. It has strong anti-loosening ability and can still stably lock the position of the piston rod 2 under heavy load, ensuring operational safety.

[0035] When the position of piston rod 2 needs to be readjusted, hydraulic oil is injected into cylinder 1 through oil port 10 to increase the oil pressure. When the oil pressure and load reach equilibrium, there is no contact force between locking block 3 and cylinder 1. At this time, the operator sends a command through the remote control module to control the rotor of motor 4 to drive locking block 3 to rotate in the opposite direction. The locking mechanism, connecting plate 6, and guide rod 7 move together away from cylinder 1, releasing the self-lock. Continue to inject oil to increase the oil pressure and push piston rod 2 upward, or slowly release the oil pressure to make piston rod 2 descend, thereby adjusting the position of piston rod 2. The anti-rotation mechanism 5 remains fixed throughout. The locking block 3, which is fixed to the cylinder 1, restricts the rotation of the piston rod 2. The final position of the piston rod 2 depends on the relative position of the locking block 3 and the piston rod 2, thus enabling easy adjustment of the locking position via remote control. When the piston rod 2 reaches its final position, the remote control module controls the motor 4 to rotate as needed via an electrical signal. The motor 4 moves towards the cylinder 1 together with the locking block 3, the connecting plate 6, and the guide rod 7. After the locking block 3 is adjusted to the designated position, it abuts against the cylinder 1 again, and the oil pressure is slowly released to achieve self-locking again. The position adjustment of the piston rod 2 is then complete.

[0036] In summary, the hydraulic jack of this utility model achieves reliable self-locking and remote control while maintaining overall structural stability through the threaded connection between the inner side of the locking block 3 and the piston rod 2, and the interference fit between the outer side of the machined step and the motor 4. By making reasonable use of the internal space of the jack, the anti-rotation mechanism 5 is placed in the cylinder 1 through the bushing 51, which not only cooperates with the piston rod 2 to achieve the function of circumferentially limiting the piston rod 2, but also increases the self-locking capability of the locking mechanism. The lifting height can be quickly adjusted according to actual needs by matching the locking mechanism, which improves the convenience, safety and work efficiency of the hydraulic jack operation. The hydraulic jack not only meets the requirements of labor-saving, efficient, reliable locking and remote control, but also achieves the advantages of simple overall structure and stable integration.

[0037] The embodiments of this utility model have been described in detail above with reference to the accompanying drawings. However, this utility model is not limited to the above embodiments. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A hydraulic jack, characterized in that, It includes a cylinder body (1), a piston rod (2), a locking mechanism, and an anti-rotation mechanism (5). The piston rod (2) is coaxially disposed inside the cylinder body (1); The locking mechanism includes a locking block (3) and a motor (4). The locking block (3) is sleeved on the piston rod (2) and threadedly connected to it. The outer side of the locking block (3) is machined with a step and connected to the inner side of the motor (4). The anti-rotation mechanism (5) includes a bushing (51) and a retaining key (52). The bushing (51) is sleeved on the piston rod (2) and its outer side is connected to the cylinder (1). A keyway (511) is opened on the inner side of the bushing (51) and fixedly connected to the retaining key (52). A groove (211) is opened on the outer side of the piston rod (2) to accommodate the retaining key (52) and slide with it.

2. The hydraulic jack according to claim 1, characterized in that, It also includes a remote control module. The motor (4) is interference-fitted with the locking block (3). The rotor of the motor (4) is located inside it. The motor (4) can adjust the position of the locking block (3) relative to the piston rod (2) by rotating the rotor forward and backward. The remote control module controls the motor (4) through electrical signals.

3. The hydraulic jack according to claim 1, characterized in that, The piston rod (2) includes an integrally formed rod section (21) and a piston section (22). The surface of the rod section (21) is provided with threads, and the locking block (3) is threadedly connected to the rod section (21).

4. The hydraulic jack according to claim 1, characterized in that, It also includes a guide structure, which includes a connecting plate (6), a guide rod (7), a small bushing (8) and a locking nut (61). The connecting plate (6) is sleeved on the motor (4) and has an interference fit with the outside of the motor (4).

5. The hydraulic jack according to claim 4, characterized in that, One end of the guide rod (7) is fixedly connected to the connecting plate (6) through the locking nut (61), and the other end of the guide rod (7) is in clearance fit with the cylinder body (1) through the small bushing (8).

6. The hydraulic jack according to claim 1, characterized in that, It also includes a bottom cover (9), which is connected to the end of the cylinder body (1) away from the bushing (51) and forms a seal.

7. The hydraulic jack according to claim 6, characterized in that, The cylinder (1) has an oil port (10) on the side near the bottom cover (9) or on the bottom cover (9), through which the medium provides a hydraulic environment for the extension and retraction of the piston rod (2).

8. The hydraulic jack according to claim 3, characterized in that, The piston section (22) has an annular groove (221) at its front end, and the piston section (22) and the cylinder (1) store oil through the annular groove (221).

9. The hydraulic jack according to claim 8, characterized in that, The piston section (22) is provided with an annular notch (222), and a sealing element is provided between the piston section (22) and the cylinder (1) through the annular notch (222) to facilitate sealing.

10. The hydraulic jack according to claim 1, characterized in that, A small hole (512) is also provided on the end face of the bushing (51) opposite to the locking block (3).

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