A planetary gear hole turning fixture resistant to centrifugal deformation

Abstract

This utility model relates to the field of planetary gear machining technology, and more particularly to a planetary gear inner hole turning fixture resistant to centrifugal force deformation. It includes: a base, a drive module on one side of the base, an anti-centrifugal force clamping assembly at the output end of the drive module, and shock-absorbing components around the bottom of the base. This utility model, by setting up the anti-centrifugal force clamping assembly, utilizes a 90-degree angle between two bidirectional lead screws, driven by motors one and two, to allow multiple arc-shaped anti-slip clamping seats to approach the center from different directions, achieving radial clamping of the planetary gear. Simultaneously, the combined use of a telescopic cylinder and an end face pressure plate achieves axial clamping of the planetary gear end face, increasing the effective clamping area and resisting the centrifugal force generated during machining. The addition of shock-absorbing components and a dual shock-absorbing mechanism effectively ensures the stability of the overall device during machining, reducing the impact of vibration on machining accuracy.

Description

Technical Field

[0001] This utility model relates to the field of planetary gear machining technology, and in particular to a planetary gear inner hole turning fixture that resists centrifugal deformation. Background Technology

[0002] Planetary gear internal turning fixtures are devices specifically designed to hold planetary gear workpieces in place for internal turning operations.

[0003] However, traditional planetary gear internal turning fixtures mostly use three-jaw chucks to hold the planetary gears. Due to the small contact area between the three-jaw chuck and the planetary gears, when the centrifugal force on the planetary gears is large during machining, local deformation is very likely to occur, which further aggravates the machining error caused by centrifugal force and seriously affects the machining accuracy of the planetary gear internal holes. Secondly, during machining, the centrifugal force not only acts on the planetary gears themselves, but also causes the entire device to vibrate. The vibration of the device will be directly transmitted to the machining process, resulting in machining instability and thus reducing the machining quality of the planetary gear internal holes.

[0004] Prior art 1 (Chinese patent application number CN202122443136.8, application date 2021-10-11) discloses a special fixture for turning planetary gear carriers. The special fixture for turning planetary gear carriers includes a flat plate, a box-shaped block fixedly installed at the bottom of the flat plate, the top of the box-shaped block being an opening, two movable holes being opened on the flat plate, two vertical plates being slidably installed in the corresponding movable holes, two arc-shaped blocks being installed on one side of the corresponding vertical plates, four clamping blocks being fixedly installed on the two arc-shaped blocks, and two fixing blocks being fixedly installed at the bottom of the flat plate. The special fixture for turning planetary gear carriers has the advantages of being easy to use, improving the service life of the fixture, and reducing cleaning steps during use.

[0005] Prior art 2 (Chinese patent application number CN202123263720.1, application date 2021-12-23) discloses a CNC lathe for planetary gears. Fixtures are fixed to both sides of the base surface, and a cutting tool assembly is fixedly installed on the rear of the base surface. A positioning rod is fixed between the inner walls of the recessed part of the base, and a rotating sleeve is movably connected to the outside of the positioning rod. A horizontal plate is fixed to the outside of the rotating sleeve, and a limit frame is fixed to the outer edge of the horizontal plate. A connecting block is movably connected inside the limit frame. A push rod is fixed to the inner wall of the recessed part of the base. By hollowing out the surface of the horizontal plate, when machining the planetary gears using the cutting tool assembly, most of the cutting chips can fall directly into the collection box through the hollowed-out holes on the surface of the horizontal plate. This effectively prevents chips from accumulating on the surface of the horizontal plate and affecting the normal cutting operation of the lathe, while also reducing the difficulty of cleaning the lathe surface and reducing the user's workload. Utility Model Content

[0006] The purpose of this invention is to provide a planetary gear inner hole turning fixture that resists centrifugal deformation, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: it includes a base, a drive module is provided on one side of the base, an anti-centrifugal force clamp assembly is provided at the output end of the drive module, and shock-absorbing components are provided around the bottom of the base.

[0008] As a preferred embodiment of this utility model, the anti-centrifugal force clamp assembly includes a rotary seat disposed at the output end of the drive module. The rotary seat has a cross-shaped mounting groove, and a pair of support seats are disposed in the cross-shaped mounting groove. A bidirectional lead screw is disposed between the two support seats. A motor is disposed in the cross-shaped mounting groove. One end of the bidirectional lead screw is connected to the transmission end of the motor. Guide rails are disposed on the inner walls of the rotary seat on both sides of the bidirectional lead screw.

[0009] In a preferred embodiment of this utility model, a pair of support seats are provided in the cross-shaped mounting groove, and a bidirectional lead screw is provided between the two support seats. The included angle between the bidirectional lead screw and the bidirectional lead screw is 90 degrees. The bidirectional lead screw is located on one side of the bidirectional lead screw. A motor is provided in the cross-shaped mounting groove, and one end of the bidirectional lead screw is connected to the transmission end of the motor. Guide rails are provided on the inner walls of the rotating seats on both sides of the bidirectional lead screw. A placement seat is provided in the middle of the cross-shaped mounting groove.

[0010] In a preferred embodiment of this utility model, a pair of driving blocks are helically sleeved on the outer side of the first bidirectional lead screw, and the two driving blocks are slidably mounted on the first guide rail. A pair of driving blocks are helically sleeved on the outer side of the second bidirectional lead screw, and the two driving blocks are slidably mounted on the second guide rail. Both the first and second driving blocks are provided with mounting plates. Each mounting plate has an arc-shaped anti-slip clamping seat on one side, and each arc-shaped anti-slip clamping seat has a pair of limiting blocks on one side. Limiting grooves are formed on the mounting plates corresponding to the positions of the limiting blocks. A pair of connecting members are symmetrically arranged on both sides of the arc-shaped anti-slip clamping seat. Fixing posts are provided on both sides of the mounting plates corresponding to the positions of the connecting members. The fixing posts pass through the connecting members, and a fixing cap is threaded to one end of the fixing posts.

[0011] As a preferred embodiment of this utility model, a pair of square slots are symmetrically opened on both sides of the rotating seat, and a telescopic cylinder is provided in each of the two square slots. The top of the telescopic rod of each of the two telescopic cylinders is provided with an end face pressure plate.

[0012] As a preferred embodiment of this utility model, the shock absorption component includes a support foot disposed at the bottom of the base, a large U-shaped frame disposed directly below the support foot, a small U-shaped frame disposed inside the large U-shaped frame, the bottom of the support foot being connected to the small U-shaped frame, a pair of guide posts symmetrically disposed on both sides of the top of the small U-shaped frame, and guide sleeves disposed on both sides of the large U-shaped frame corresponding to the positions of the guide posts.

[0013] As a preferred embodiment of this utility model, a pair of oil storage cylinders are symmetrically arranged on both sides of the bottom of the large U-shaped frame, and a piston rod and a piston are arranged on both sides of the small U-shaped frame corresponding to the positions of the oil storage cylinders. The piston is slidably arranged inside the oil storage cylinder, and a spring is arranged between the top of the piston rod and the bottom of the oil storage cylinder.

[0014] Compared with the prior art, the above-mentioned technical solution of this utility model has the following beneficial technical effects:

[0015] 1. This utility model, by setting up an anti-centrifugal force clamping assembly, utilizes a 90-degree angle between two bidirectional lead screws, driven by motors one and two, to allow multiple arc-shaped anti-slip clamping seats to approach the center from different directions, achieving radial clamping of the planetary gears. Simultaneously, the combined use of the telescopic cylinder and end-face pressure plate enables axial clamping of the planetary gear end faces, increasing the effective clamping area, resisting centrifugal force generated during processing, preventing deformation of the planetary gears due to centrifugal force, and ensuring processing accuracy. Furthermore, the arc-shaped anti-slip clamping seats are selected from... Made of nylon, it allows for flexible clamping, avoiding wear on the planetary gears caused by rigid clamping. This protects the planetary gears and ensures clamping stability. In addition, the limiting groove on the mounting plate cooperates with the limiting block on the arc-shaped clamping seat, which facilitates quick positioning when installing the arc-shaped anti-slip clamping seat. The combination of connectors, fixing posts and fixing caps makes the installation, disassembly and replacement of the arc-shaped anti-slip clamping seat extremely convenient. This allows for timely replacement of worn clamping seats, maintains clamping stability, and reduces processing errors caused by centrifugal force aggravated by clamping instability.

[0016] 2. This utility model, by setting up a shock-absorbing component, allows the support feet to transmit the vibration of the device to the small U-shaped frame. Through the cooperation of the guide column and guide sleeve, it provides precise guidance for the movement of the small U-shaped frame relative to the large U-shaped frame, ensuring its stability during movement. Secondly, the spring can quickly deform when the small U-shaped frame moves, initially absorbing vibration energy and playing a first-level shock-absorbing role. At the same time, through the combined use of the oil reservoir, piston rod, and piston one, when the small U-shaped frame drives the piston rod and piston one to slide in the oil reservoir, the hydraulic oil flows repeatedly between the two chambers. The friction between the orifice wall and the hydraulic oil, as well as the internal friction between the hydraulic oil molecules, generates a damping force, reducing the spring's rebound speed and preventing the spring from rebounding too quickly and aggravating the vibration. This achieves further absorption and dispersion of vibration energy. The dual shock-absorbing mechanism effectively ensures the stability of the overall device during processing, reduces the impact of vibration on processing accuracy, and improves processing quality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0018] Figure 2 This is a schematic diagram of the anti-centrifugal force clamp assembly of this utility model;

[0019] Figure 3 This is a schematic diagram of the arc-shaped anti-slip clamping seat structure in the anti-centrifugal force clamping assembly of this utility model;

[0020] Figure 4 This is a schematic diagram of the shock absorption component structure of this utility model;

[0021] Figure 5 This is a schematic diagram of the small U-shaped frame structure in the shock absorption component of this utility model.

[0022] Reference numerals: Base 1, Drive Module 2, Anti-centrifugal Force Clamp Assembly 3, Cross-shaped Mounting Slot 31, Support Base 1 32, Bidirectional Lead Screw 1 33, Motor 1 34, Guide Rail 1 35, Support Base 2 36, Bidirectional Lead Screw 2 37, Motor 2 38, Guide Rail 2 39, Rotary Seat 310, Drive Block 1 311, Drive Block 2 312, Mounting Plate 313, Arc-shaped Anti-slip Clamping Seat 314, Limiting Block 315, Limiting Slot 316, Connector 318, Fixing Column 319, Fixing Cap 320, Square Slot 321, Telescopic Cylinder 322, End Face Pressure Plate 323, Placement Seat 324, Shock Absorption Assembly 4, Support Foot 41, Large U-shaped Frame 42, Small U-shaped Frame 43, Guide Column 44, Guide Sleeve 45, Oil Storage Cylinder 46, Piston Rod 47, Piston 1 48, Spring 49. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this utility model. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of this utility model.

[0024] like Figures 1-5 As shown, the present invention proposes a planetary gear inner hole turning fixture that resists centrifugal deformation. It includes a base 1, a drive module 2 is provided on one side of the base 1, an anti-centrifugal force fixture assembly 3 is provided at the output end of the drive module 2, and shock-absorbing components 4 are provided around the bottom of the base 1.

[0025] The anti-centrifugal force clamp assembly 3 includes a rotary seat 310 disposed at the output end of the drive module 2. The rotary seat 310 provides a mounting base for other components in the anti-centrifugal force clamp assembly 3. A cross-shaped mounting groove 31 is provided on the rotary seat 31. A pair of support seats 32 are disposed in the cross-shaped mounting groove 31. A bidirectional lead screw 33 is disposed between the two support seats 32. The support seats 32 provide support for the bidirectional lead screw 33 to ensure the stability of the bidirectional lead screw 33 during rotation. A motor 34 is disposed in the cross-shaped mounting groove 31. One end of the bidirectional lead screw 33 is connected to the transmission end of the motor 34. The motor 34 provides rotational power for the bidirectional lead screw 33, converting the rotational motion of the bidirectional lead screw 33 into the linear motion of the drive block 311. Guide rails 35 are provided on the inner walls of the rotary seat 310 on both sides of the bidirectional lead screw 33.

[0026] A pair of support seats 36 are provided in the cross-shaped mounting groove 31. A double-acting lead screw 37 is provided between the two support seats 36. The included angle between the double-acting lead screw 33 and the double-acting lead screw 37 is 90 degrees. The double-acting lead screw 37 is located on one side of the double-acting lead screw 33. The support seats 36 provide support for the double-acting lead screw 37 to ensure the stability of the double-acting lead screw 37 during rotation. A motor 38 is provided in the cross-shaped mounting groove 31. One end of the double-acting lead screw 37 is connected to the transmission end of the motor 38. The motor 38 provides rotational power for the double-acting lead screw 37, converting the rotational motion of the double-acting lead screw 37 into the linear motion of the drive block 312. Guide rails 39 are provided on the inner walls of the rotating seats 310 on both sides of the double-acting lead screw 37. A placement seat 324 is provided in the middle of the cross-shaped mounting groove 31. The placement seat 324 provides a preliminary placement position for the planetary gear to be processed, making it convenient for the operator to position the planetary gear.

[0027] A pair of drive blocks 311 are helically sleeved on the outer side of the double-acting screw 33. The two drive blocks 311 are slidably mounted on the guide rail 35. A pair of drive blocks 312 are helically sleeved on the outer side of the double-acting screw 37. The two drive blocks 312 are slidably mounted on the guide rail 39. The guide rails 35 and 39 provide guidance for the drive blocks 311 and 312, respectively, to ensure the stability of the drive blocks 311 and 312 during movement. Mounting plates 313 are provided on both drive blocks 311 and 312. The mounting plates 313 provide a mounting base for the arc-shaped anti-slip clamping seats 314. An arc-shaped anti-slip clamping seat 314 is provided on one side of each mounting plate 313. The arc-shaped anti-slip clamping seats 314 are made of nylon, which allows for flexible clamping and avoids direct contact between rigid clamping and the planetary gears. The wear caused by the wheels achieves stable radial clamping of the planetary gears. Each arc-shaped anti-slip clamping seat 314 has a pair of limiting blocks 315 on one side. The mounting plate 313 has limiting grooves 316 at the corresponding positions of the limiting blocks 315. The limiting blocks 315 and the limiting grooves 316 cooperate to facilitate quick positioning when installing the arc-shaped anti-slip clamping seat 314. A pair of connecting parts 318 are symmetrically arranged on both sides of the arc-shaped anti-slip clamping seat 314. The mounting plate 313 has fixing posts 319 at the corresponding positions of the connecting parts 318 on both sides. The fixing posts 319 pass through the connecting parts 318. One end of the fixing posts 319 is threaded to a fixing cap 320. The combination of connecting parts 318, fixing posts 319 and fixing caps 320 is used to fix the arc-shaped anti-slip clamping seat 314, which facilitates the installation, disassembly and replacement of the arc-shaped anti-slip clamping seat 314.

[0028] A pair of square slots 321 are symmetrically opened on both sides of the rotating seat 310. Each square slot 321 is equipped with a telescopic cylinder 322. The top of the telescopic rod of each telescopic cylinder 322 is equipped with an end face pressure plate 323. By extending and retracting the telescopic rod of the telescopic cylinder 322, the end face pressure plate 323 is driven to move, thereby releasing or pressing the end face of the planetary gear.

[0029] The vibration damping assembly 4 includes a support foot 41 at the bottom of the base 1. The support foot 41 transmits the vibration of the device to the small U-shaped frame 43. A large U-shaped frame 42 is located directly below the support foot 41. The small U-shaped frame 43 is located inside the large U-shaped frame 42. The bottom of the support foot 41 is connected to the small U-shaped frame 43. The large U-shaped frame 42 and the small U-shaped frame 43 provide the mounting base for other components in the vibration damping assembly 4. A pair of guide posts 44 are symmetrically arranged on both sides of the top of the small U-shaped frame 43. Guide sleeves 45 are arranged on both sides of the large U-shaped frame 42 at the positions corresponding to the guide posts 44. The guide posts 44 and guide sleeves 45 cooperate to provide guidance for the movement of the small U-shaped frame 43 relative to the large U-shaped frame 42, ensuring stability during movement.

[0030] A pair of oil reservoirs 46 are symmetrically arranged on both sides of the bottom of the large U-shaped frame 42. The oil reservoirs 46 are used to store hydraulic oil. Piston rods 47 and pistons 48 are arranged on both sides of the small U-shaped frame 43 corresponding to the positions of the oil reservoirs 46. Pistons 48 are slidably arranged inside the oil reservoirs 46. The piston rods 47 and pistons 48 slide inside the oil reservoirs 46 under the drive of the small U-shaped frame 43, separating the space inside the oil reservoirs 46, allowing the hydraulic oil to flow between the two chambers and generating a damping force. A spring 49 is arranged between the top of the piston rod 47 and the bottom of the oil reservoir 46. The spring 49 deforms when the small U-shaped frame 43 moves, initially absorbing vibration energy. At the same time, in conjunction with the damping force, it prevents the spring 49 from rebounding too quickly and aggravating the vibration, further absorbing and dispersing the vibration energy.

[0031] In operation, the operator first places the planetary gear to be processed against the placement seat 324, then starts motor 34 and motor 38. Motor 34 drives the bidirectional lead screw 33 to rotate, converting its rotational motion into the linear motion of drive block 311. This causes the drive blocks 311 on both sides to move other components mounted on them closer together along guide rail 35. Simultaneously, motor 38 drives the bidirectional lead screw 37 to rotate, converting its rotational motion into the linear motion of drive block 312. The drive blocks 312 on both sides drive other components mounted on them to move closer to each other along the guide rail 39. Since the angle between the two-way lead screw 33 and the two-way lead screw 37 is 90 degrees, several arc-shaped anti-slip clamping seats 314 can move closer to the center from different directions, thereby clamping the planetary gear and completing radial clamping. Then, the telescopic cylinder 322 is activated. The telescopic rod of the telescopic cylinder 322 retracts, driving the end face pressure plate 323 to move and press the end face of the planetary gear, thereby achieving axial clamping. Then, the drive module 2 is activated to start the turning of the inner hole of the planetary gear.

[0032] During processing, the entire device will vibrate. The support foot 41 transmits the vibration to the small U-shaped frame 43. With the cooperation of the guide post 44 and the guide sleeve 45, the small U-shaped frame 43 moves relative to the large U-shaped frame 42. The spring 49 deforms and initially absorbs the vibration energy. At the same time, the small U-shaped frame 43 drives the piston rod 47 and piston 48 to slide in the oil reservoir 46. The piston 48 divides the space inside the oil reservoir 46 into two chambers. The hydraulic oil in the oil reservoir 46 will repeatedly flow from one chamber to another through different small holes on the piston 48. The friction between the hole wall and the hydraulic oil and the internal friction between the hydraulic oil molecules will hinder the flow of hydraulic oil, thereby generating a damping force, reducing the rebound speed of the spring 49, and preventing the spring 49 from rebounding too quickly and aggravating the vibration. This further absorbs and disperses the vibration, ensuring the stability of the entire device.

[0033] In addition, the arc-shaped anti-slip clamping seat 314 will show wear after a period of use. If wear is found, a new anti-slip clamping seat should be replaced in time to ensure clamping stability and avoid clamping instability caused by wear, which will aggravate the processing error caused by centrifugal force. When replacing, the operator only needs to loosen and remove the fixing cap 320 to remove the old arc-shaped anti-slip clamping seat 314. Then, align the limiting block 315 on one side of the new arc-shaped anti-slip clamping seat 314 with the limiting groove 316 on the mounting plate 313, and align the connecting parts 318 on both sides of the arc-shaped anti-slip clamping seat 314 with the fixing post 319, so that the fixing post 319 passes through the connecting part 318. Finally, align the fixing cap 320 with the fixing post 319 and tighten it to complete the replacement of the arc-shaped anti-slip clamping seat 314.

[0034] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this utility model and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this utility model should be included within its protection scope. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A planetary gear inner bore turning fixture resistant to centrifugal deformation, comprising: A base (1) is provided with a drive module (2) on one side of the base (1), characterized in that: the output end of the drive module (2) is provided with an anti-centrifugal force clamp assembly (3), and the bottom of the base (1) is provided with shock-absorbing components (4) around the perimeter.

2. The planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 1, characterized in that: The anti-centrifugal force clamp assembly (3) includes a rotating seat (310) disposed at the output end of the drive module (2). The rotating seat (310) has a cross-shaped mounting groove (31). A pair of support seats (32) are disposed in the cross-shaped mounting groove (31). A bidirectional lead screw (33) is disposed between the two support seats (32). A motor (34) is disposed in the cross-shaped mounting groove (31). One end of the bidirectional lead screw (33) is connected to the transmission end of the motor (34). Guide rails (35) are disposed on the inner walls of the rotating seat (310) on both sides of the bidirectional lead screw (33).

3. The planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 2, characterized in that: A pair of support seats (36) are provided in the cross-shaped mounting groove (31), and a two-way lead screw (37) is provided between the two support seats (36). The included angle between the two-way lead screw (33) and the two-way lead screw (37) is 90 degrees. The two-way lead screw (37) is located on one side of the two-way lead screw (33). A motor (38) is provided in the cross-shaped mounting groove (31). One end of the two-way lead screw (37) is connected to the transmission end of the motor (38). Guide rails (39) are provided on the inner walls of the rotating seats (310) on both sides of the two-way lead screw (37). A placement seat (324) is provided in the middle of the cross-shaped mounting groove (31).

4. The planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 3, characterized in that: The outer side of the first bidirectional lead screw (33) is helically fitted with a pair of first drive blocks (311), and the two first drive blocks (311) are slidably mounted on the first guide rail (35). The outer side of the second bidirectional lead screw (37) is helically fitted with a pair of second drive blocks (312), and the two second drive blocks (312) are slidably mounted on the second guide rail (39). Each first drive block (311) and second drive block (312) is provided with a mounting plate (313), and each mounting plate (313) is provided with an arc-shaped anti-slip clamping seat (314) on one side. A pair of limiting blocks (315) are provided on one side of the arc-shaped anti-slip clamping seat (314). Limiting grooves (316) are provided on the mounting plate (313) at the positions corresponding to the limiting blocks (315). A pair of connecting parts (318) are symmetrically provided on both sides of the arc-shaped anti-slip clamping seat (314). Fixing posts (319) are provided on both sides of the mounting plate (313) at the positions corresponding to the connecting parts (318). The fixing posts (319) penetrate the connecting parts (318), and a fixing cap (320) is threaded to one end of the fixing posts (319).

5. A planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 4, characterized in that: The rotating seat (310) has a pair of square slots (321) symmetrically opened on both sides. Each of the two square slots (321) is equipped with a telescopic cylinder (322), and the top of the telescopic rod of each of the two telescopic cylinders (322) is equipped with an end face pressure plate (323).

6. A planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 5, characterized in that: The shock absorption assembly (4) includes a support foot (41) at the bottom of the base (1), a large U-shaped frame (42) is provided directly below the support foot (41), a small U-shaped frame (43) is provided inside the large U-shaped frame (42), the bottom of the support foot (41) is connected to the small U-shaped frame (43), a pair of guide posts (44) are symmetrically provided on both sides of the top of the small U-shaped frame (43), and guide sleeves (45) are provided on both sides of the large U-shaped frame (42) corresponding to the guide posts (44).

7. A planetary gear inner hole turning fixture resistant to centrifugal deformation according to claim 6, characterized in that: A pair of oil reservoirs (46) are symmetrically arranged on both sides of the bottom of the large U-shaped frame (42). Piston rods (47) and pistons (48) are arranged on both sides of the small U-shaped frame (43) corresponding to the positions of the oil reservoirs (46). Pistons (48) are slidably arranged inside the oil reservoirs (46). A spring (49) is arranged between the top of the piston rod (47) and the bottom of the oil reservoir (46).

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