Metallic spring punching die

Abstract

The application discloses a metal spring punching die, which comprises a punch, a punching cylinder, an upper die base, a punch head, a lower die base, a cavity and a discharge port, wherein the punch is provided with an oil coating, oil discharging and discharge oil control assemblies; the oil coating assembly comprises two oil boxes which slide away from each other, and the oil boxes are provided with atomizing oil discharging holes; after the material is lubricated on both sides, the material directly falls into the cavity, thereby avoiding transfer and scraping; the oil discharging assembly supplies oil through a piston cylinder; the discharge oil control assembly comprises a discharge plate and an oil control mechanism; the discharge plate pushes out and recycles residual oil; when the discharge plate is retracted, an oil film is coated through capillary oil permeation holes; the application ensures the integrity of the oil film, realizes continuous lubrication and heat dissipation, reduces heat accumulation, and improves precision and stability.

Description

Technical Field

[0001] This invention relates to the field of stamping die technology, and in particular to a metal spring stamping die. Background Technology

[0002] In the stamping process of metal springs, lubrication of the blank surface is usually required to reduce friction and wear. Existing technologies mostly use fixed oil spray holes or pre-coating methods to supply oil to the material locally. For example, a stamping equipment for automotive metal parts disclosed in patent number CN120828091B sets up an oil spray structure in the flange area of ​​the mold and uses the cavity to wrap the oil.

[0003] However, in actual stamping processes, the blank undergoes sliding, stretching, and plastic deformation within the mold cavity, causing the pre-coated oil film to be easily scraped off the mold surface, squeezed out during mold closing, or lost through the oil drain hole. Simultaneously, after lubrication, the material often needs to undergo intermediate steps such as transfer and positioning before entering the mold cavity, a process that easily leads to oil film damage, evaporation, or contamination. These problems result in a lack of effective lubrication on the newly formed surface of the bending area, making it difficult to dissipate frictional heat. This easily leads to defects such as tearing, sintering, and dimensional drift, affecting the accuracy and consistency of the spring sheet forming. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a metal spring stamping die.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A metal spring stamping die includes a punch press, a stamping cylinder, an upper die base, a punch, a lower die base, a cavity, and a discharge port. The punch press is equipped with an oiling assembly for lubricating the upper and lower surfaces of the material. The punch press is also equipped with an oil outlet assembly for supplying oil to the oiling assembly. The punch press is also equipped with a discharge oil control assembly for ejecting the stamped material from the cavity.

[0007] The oiling assembly includes two oil boxes, an atomizing oil outlet, an oil cavity, and a sliding mechanism. The sliding mechanism is used to drive the two oil boxes to slide in opposite directions. The two oil boxes are located above the cavity. Several atomizing oil outlets are provided and distributed in the upper and lower layers of the oil boxes. The positions of the atomizing oil outlets in the two oil boxes are close to each other. The oil cavity is located inside the oil box.

[0008] Preferably, the sliding mechanism includes an electric telescopic rod, a first pressing block, a second pressing block, a slider, and a sliding groove. The second pressing block is fixedly connected to the side wall of the oil box away from the discharge port. The electric telescopic rod is installed on the upper mold base. The upper end of the first pressing block is fixedly connected to the telescopic end of the electric telescopic rod. The wedge-shaped surfaces of the first pressing block and the second pressing block are arranged opposite to each other.

[0009] Preferably, the slider is fixedly connected to the lower end of the oil box, the slide groove is provided on both sides of the cavity, the slider slides in the slide groove, and a transmission cavity is provided below the slide groove.

[0010] Preferably, the oil outlet assembly includes an oil tank, an oil inlet pipe, an oil outlet pipe, a piston cylinder, and an oil outlet mechanism, wherein the oil outlet mechanism is used to pump the lubricating grease in the oil tank into the piston cylinder and then pump it out.

[0011] Preferably, the oil drum is installed inside the punch press, a base plate is installed on the side wall of the punch press, the piston cylinder is installed on the base plate, one end of the oil inlet pipe is connected to the oil outlet of the oil drum, and the other end is connected to the oil inlet of the piston cylinder, one end of the oil outlet pipe is connected to the oil outlet of the piston cylinder, and the other end is connected to the oil inlet of the oil box.

[0012] Preferably, the oil outlet mechanism includes a first pressure plate, a second pressure plate, a piston, and a spring. The first pressure plate slides in the groove, and a limiting block is provided on the side wall of the punch press. The second pressure plate slides in the limiting block. Both the outer end of the first pressure plate and the second pressure plate are provided with wedge-shaped surfaces, and the wedge-shaped surfaces are arranged opposite to each other.

[0013] Preferably, the piston slides inside the piston cylinder, the lower end of the second pressure plate is fixedly connected to the piston, one end of the spring is fixedly connected to the piston, and the other end is fixedly connected to the bottom of the piston cylinder.

[0014] Preferably, the discharge oil control assembly further includes an oil control mechanism, which is used to recover residual lubricating grease at the bottom of the cavity and to uniformly apply a thin oil film to the bottom of the cavity when the discharge plate retracts. The oil control mechanism includes an oil storage tank, capillary oil seepage holes, and a pump plate. The oil storage tank is disposed inside the discharge plate. Several capillary oil seepage holes are opened at the front end of the bottom of the discharge plate and communicate with the oil storage tank. An installation plate is provided inside the punch press. A fixing plate is provided on the installation plate. One end of the pump plate is fixedly connected to the side wall of the fixing plate, and the other end is sealed and inserted into the oil storage tank.

[0015] Preferably, the lower surface of the first pressure plate is provided with gear teeth, which mesh with the gear. Both the oil inlet pipe and the oil outlet pipe are provided with one-way valves, and two sets of oiling components and oil outlet components are provided.

[0016] The present invention has the following beneficial effects:

[0017] 1. In this invention, by setting a double oil box structure that can slide backwards, the upper and lower surfaces of the material are simultaneously atomized and lubricated in the closed state, avoiding damage to the oil film caused by scraping during transfer. After lubrication, the oil box is opened immediately so that the material falls directly into the cavity, ensuring that the oil film is completely preserved until the moment of stamping.

[0018] 2. The discharge oil control component sucks up and recovers residual oil when ejecting the workpiece, and re-coats a uniform oil film through capillary oil seepage holes during retraction, thereby realizing the dynamic renewal of lubricating grease.

[0019] 3. During the stamping process, the blank collapses and contacts the bottom oil surface. Under high pressure, the oil rises and wets the surface, providing real-time lubrication and heat dissipation for the newly drawn surface. This effectively suppresses dry friction, heat accumulation and dimensional drift, thereby significantly improving the forming accuracy, surface quality and production stability of the metal spring sheet. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a metal spring stamping die proposed in this invention;

[0021] Figure 2 This is a schematic diagram of the internal cross-sectional structure of the punch press in this invention;

[0022] Figure 3 This is a schematic diagram of the connection structure of the stamping cylinder, upper die holder, and punch in this invention;

[0023] Figure 4 This is a schematic diagram of the external connection structure of the oiling assembly, the oil outlet assembly, and the oil discharge control assembly in this invention;

[0024] Figure 5 This is a cross-sectional structural diagram of the oil box in this invention;

[0025] Figure 6 This is a schematic cross-sectional view of the lower mold base and piston cylinder in this invention;

[0026] Figure 7 This is a schematic diagram of the connection structure of the second pressing block, oil box, and slider in this invention;

[0027] Figure 8 This is a schematic diagram of the specific structure of the first pressure plate in this invention;

[0028] Figure 9 for Figure 3 Enlarged view of point A in the middle;

[0029] Figure 10 for Figure 4 Enlarged view at point B in the middle;

[0030] Figure 11 for Figure 5 Enlarged view at point C;

[0031] Figure 12 for Figure 7 Enlarged view at point D;

[0032] Figure 13 This is a schematic diagram of the cross-sectional structure of the discharge plate.

[0033] In the diagram: 1. Punch press, 2. Punch cylinder, 3. Upper die base, 4. Punch head, 5. Lower die base, 6. Cavity, 7. Discharge port, 8. Electric telescopic rod, 9. First pressing block, 10. Second pressing block, 11. Oil box, 12. Atomizing oil outlet, 13. Slider, 14. Slide groove, 15. First pressing plate, 16. Gear, 17. Second pressing plate, 18. Limiting block, 19. Piston, 20. Spring, 21. Piston cylinder, 22. Oil inlet pipe, 23. Oil outlet pipe, 24. Oil tank, 25. Transmission cavity, 26. Screw, 27. L-shaped mounting plate, 28. L-shaped sliding plate, 29. Discharge plate, 30. Oil cavity, 31. Base plate, 32. Oil storage tank, 33. Capillary seepage hole, 34. Pump plate, 35. Mounting plate, 36. Fixing plate. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] Example 1

[0036] Reference Figures 1-7 and Figure 9 , Figure 11 , Figure 12 A metal spring stamping die includes a punch press 1, a stamping cylinder 2, an upper die base 3, a punch 4, a lower die base 5, a cavity 6, and a discharge port 7. The punch press 1 is equipped with an oiling component for lubricating the upper and lower surfaces of the material. The punch press 1 is also equipped with an oil outlet component for supplying oil to the oiling component. The punch press 1 is equipped with a discharge oil control component for ejecting the stamped material from the cavity 6.

[0037] The oiling assembly includes two oil boxes 11, atomizing oil outlets 12, an oil cavity 30, and a sliding mechanism. The sliding mechanism is used to drive the two oil boxes 11 to slide in opposite directions. The two oil boxes 11 are located above the cavity 6. Several atomizing oil outlets 12 are provided and distributed in the upper and lower layers inside the oil boxes 11. The positions of the atomizing oil outlets 12 in the two oil boxes 11 are close to each other. The oil cavity 30 is located inside the oil box 11.

[0038] The sliding mechanism includes an electric telescopic rod 8, a first pressing block 9, a second pressing block 10, a slider 13, and a sliding groove 14. The second pressing block 10 is fixedly connected to the side wall of the oil box 11 away from the discharge port 7. The electric telescopic rod 8 is installed on the upper mold base 3. The upper end of the first pressing block 9 is fixedly connected to the telescopic end of the electric telescopic rod 8. The wedge-shaped surfaces of the first pressing block 9 and the second pressing block 10 are arranged opposite to each other.

[0039] The slider 13 is fixedly connected to the lower end of the oil box 11. The slide groove 14 is set on both sides of the cavity 6. The slider 13 slides in the slide groove 14. The transmission cavity 25 is provided below the slide groove 14.

[0040] The oil outlet assembly includes an oil tank 24, an oil inlet pipe 22, an oil outlet pipe 23, a piston cylinder 21, and an oil outlet mechanism. The oil outlet mechanism is used to pump the lubricating grease in the oil tank 24 into the piston cylinder 21 and then pump it out.

[0041] Oil drum 24 is installed inside punch press 1. A base plate 31 is installed on the side wall of punch press 1. Piston cylinder 21 is installed on base plate 31. One end of oil inlet pipe 22 is connected to oil outlet of oil drum 24, and the other end is connected to oil inlet of piston cylinder 21. One end of oil outlet pipe 23 is connected to oil outlet of piston cylinder 21, and the other end is connected to oil inlet of oil box 11.

[0042] The oil outlet mechanism includes a first pressure plate 15, a second pressure plate 17, a piston 19, and a spring 20. The first pressure plate 15 slides in the slide groove 14. A limiting block 18 is provided on the side wall of the punch press 1. The second pressure plate 17 slides in the limiting block 18. Both the outer end of the first pressure plate 15 and the second pressure plate 17 are provided with wedge-shaped surfaces, and the wedge-shaped surfaces are arranged opposite to each other.

[0043] The piston 19 slides inside the piston cylinder 21. The lower end of the second pressure plate 17 is fixedly connected to the piston 19. One end of the spring 20 is fixedly connected to the piston 19, and the other end is fixedly connected to the bottom of the piston cylinder 21.

[0044] The metal spring stamping die in this embodiment includes a punch press 1, a stamping cylinder 2, an upper die base 3, a punch 4, a lower die base 5, a cavity 6, and a discharge port 7. The punch press 1 integrates an oiling assembly, an oil outlet assembly, and an atomizing oil outlet 12, which are evenly distributed in two layers to ensure that the material is simultaneously oiled on both sides.

[0045] When the stamping cylinder 2 starts to move downward, it drives the upper die base 3 and the punch 4 to move downward synchronously. At the same time, the electric telescopic rod 8 installed on the upper die base 3 extends synchronously, pushing the first pressing block 9 to move downward. The wedge end of the first pressing block 9 contacts the wedge end of the second pressing block 10 fixed to the side wall of the oil box 11 and presses against each other, forcing the two oil boxes 11 to slide back to back along the slide groove 14.

[0046] During the sliding process of the oil box 11, the slider 13 fixed at its bottom synchronously pushes the first pressure plate 15 located in the slide groove 14 to move outward. The wedge surface at the outer end of the first pressure plate 15 interacts with the wedge surface of the second pressure plate 17 sliding in the limiting block 18, driving the second pressure plate 17 to move downward, thereby driving the piston 19 fixedly connected to it to move downward in the piston cylinder 21.

[0047] The piston 19 compresses the spring 20 downwards, pumping the lubricating grease in the piston cylinder 21 into the oil chamber 30 of the oil box 11 via the oil outlet pipe 23. Since both the oil inlet pipe 22 and the oil outlet pipe 23 are equipped with one-way valves, unidirectional flow of the grease is ensured, preventing backflow. After entering the oil chamber 30, the lubricating grease is evenly sprayed into the upper and lower surfaces of the material in a fine mist form through the atomizing oil outlet hole 12, completing double-sided pre-lubrication.

[0048] The two oil boxes 11 slide open in opposite directions, forming a centering guide channel that allows the lubricated material to fall directly and smoothly into the lower cavity 6 without lateral transfer or intermediate transport, thus avoiding scratching or contamination of the oil film. Subsequently, the punch 4 continues to descend, applying punching pressure to the material and forming it into a metal spring within the cavity 6.

[0049] During the stamping process, the blank collapses downwards and contacts the bottom of cavity 6. Because an oil film is pre-stored at the bottom, under high pressure, the oil rises and wets the surface of the blank. This process provides real-time lubrication and heat dissipation for the newly stretched surface at the bend, effectively suppressing scratches or sintering caused by dry friction.

[0050] Example 2

[0051] Reference Figure 8 , Figure 10 , Figure 13 The discharge oil control assembly includes a gear 16, a screw 26, an L-shaped mounting plate 27, an L-shaped sliding plate 28, and a discharge plate 29. The gear 16 is fixedly connected to one end of the screw 26 and is installed in the transmission cavity 25. The L-shaped mounting plate 27 is installed on the side wall of the lower mold base 5 away from the discharge port 7. The other end of the screw 26 extends through the transmission cavity 25 to the outside of the lower mold base 5 and is rotatably connected to the side wall of the L-shaped mounting plate 27. One end of the L-shaped sliding plate 28 is threadedly connected to the screw 26, and the other end is fixedly connected to the upper end of the discharge plate 29. The side wall of the cavity 6 away from the discharge port 7 has an opening, and the discharge plate 29 slides in the opening.

[0052] The discharge oil control assembly also includes an oil control mechanism, which is used to recover residual lubricating grease at the bottom of the cavity 6 and to evenly apply a thin layer of oil film to the bottom of the cavity 6 when the discharge plate 29 retracts. The oil control mechanism includes an oil storage tank 32, capillary oil seepage holes 33, and a pump plate 34. The oil storage tank 32 is located inside the discharge plate 29. Several capillary oil seepage holes 33 are opened at the front end of the bottom of the discharge plate 29 and are connected to the oil storage tank 32. The punch press 1 is provided with an installation plate 35. A fixing plate 36 is provided on the installation plate 35. One end of the pump plate 34 is fixedly connected to the side wall of the fixing plate 36, and the other end is sealed and inserted into the oil storage tank 32.

[0053] The lower surface of the first pressure plate 15 is provided with gear teeth, which mesh with the gear 16. One-way valves are provided in both the oil inlet pipe 22 and the oil outlet pipe 23. Two sets of oiling components and oil outlet components are provided.

[0054] In this embodiment, combined with Embodiment 1, after stamping is completed, the stamping cylinder 2 moves upward to reset. At this time, the spring 20 releases its stored energy, pushing the piston 19 and the second pressing plate 17 upward to reset. The wedge surface of the second pressing plate 17 presses against the wedge surface of the first pressing plate 15 in the opposite direction, causing it to slide inward.

[0055] The lower surface of the first pressure plate 15 is provided with gear teeth, which mesh with the gear 16 in the transmission cavity 25. When the first pressure plate 15 slides inward, it drives the gear 16 to rotate, thereby driving the screw 26, which is coaxially fixed with it, to rotate. The screw 26 passes through the transmission cavity 25 and is rotatably connected to the L-shaped mounting plate 27. The L-shaped sliding plate 28 is threadedly engaged with the screw 26 and fixed to the upper end of the discharge plate 29.

[0056] The rotation of screw 26 causes L-shaped slide plate 28 to move axially into cavity 6, pushing discharge plate 29 to slide into the opening on the side wall of cavity 6, and pushing the molding spring sheet out to discharge port 7.

[0057] During this process, the discharge plate 29 has an oil storage tank 32 inside, and several capillary oil seepage holes 33 are opened at the front end of the bottom surface and are connected to the oil storage tank 32. The punch press 1 has a fixing plate 36 fixed on the mounting plate 35 inside, and one end of the pump plate 34 is fixed to the fixing plate 36, and the other end is sealed and inserted into the oil storage tank 32.

[0058] When the discharge plate 29 is pushed outward, it moves away from the pump plate 34, the volume of the oil storage tank 32 increases, and a negative pressure is formed inside, which draws in excess residual oil at the bottom of the cavity 6 through the capillary oil seepage hole 33. When the discharge plate 29 retracts and resets, it moves closer to the pump plate 34, squeezing the grease in the oil storage tank 32 and squeezing it out evenly from the capillary oil seepage hole 33, re-coating a thin oil film at the bottom of the cavity 6, providing pre-lubrication for the next stamping.

[0059] In this embodiment, two sets of oiling and oil dispensing components are provided, corresponding to the front and rear sides of the material feeding direction, respectively, to ensure uniform lubrication of the long-length spring sheet throughout the process. The oil tank 24 is installed inside the punch press 1 and the piston cylinder 21 is supported by the base plate 31, which has a compact structure and is easy to maintain.

[0060] As can be seen from the above technical solution, the metal spring stamping die provided in this embodiment of the invention achieves oil film integrity assurance, dynamic residual oil recovery, and real-time lubrication of the new surface through a three-in-one design of closed-loop double-sided atomized lubrication, non-transferable material feeding, and controlled oil discharge. This significantly reduces heat accumulation and dimensional drift, improving product consistency and die life. Simultaneously, the oil supply and discharge mechanisms are driven by the stamping action, eliminating the need for an additional power source. The structure is simple and efficient, suitable for high-frequency continuous stamping production scenarios.

[0061] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A metal spring stamping die, comprising a punch press (1), a stamping cylinder (2), an upper die base (3), a punch (4), a lower die base (5), a cavity (6), and a discharge port (7), characterized in that, The punch press (1) is provided with an oiling component, which is used to lubricate the upper and lower surfaces of the material. The punch press (1) is also provided with an oil outlet component, which is used to supply oil to the oiling component. The punch press (1) is provided with a discharge oil control component, which is used to eject the stamped material from the cavity (6). The oiling assembly includes two oil boxes (11), an atomizing oil outlet (12), an oil cavity (30), and a sliding mechanism. The sliding mechanism is used to drive the two oil boxes (11) to slide in opposite directions. The two oil boxes (11) are located above the cavity (6). There are several atomizing oil outlets (12), which are distributed and arranged in the upper and lower layers inside the oil boxes (11). The positions of the atomizing oil outlets (12) in the two oil boxes (11) are close to each other. The oil cavity (30) is located inside the oil box (11).

2. The metal spring stamping die according to claim 1, characterized in that, The sliding mechanism includes an electric telescopic rod (8), a first pressing block (9), a second pressing block (10), a slider (13), and a sliding groove (14). The second pressing block (10) is fixedly connected to the side wall of the oil box (11) away from the discharge port (7). The electric telescopic rod (8) is installed on the upper mold base (3). The upper end of the first pressing block (9) is fixedly connected to the telescopic end of the electric telescopic rod (8). The wedge-shaped surfaces of the first pressing block (9) and the second pressing block (10) are arranged opposite to each other.

3. The metal spring stamping die according to claim 2, characterized in that, The slider (13) is fixedly connected to the lower end of the oil box (11), the slide groove (14) is provided on both sides of the cavity (6), the slider (13) slides in the slide groove (14), and a transmission cavity (25) is provided below the slide groove (14).

4. The metal spring stamping die according to claim 3, characterized in that, The oil outlet assembly includes an oil tank (24), an oil inlet pipe (22), an oil outlet pipe (23), a piston cylinder (21), and an oil outlet mechanism. The oil outlet mechanism is used to pump the lubricating grease in the oil tank (24) into the piston cylinder (21) and then pump it out.

5. A metal spring stamping die according to claim 4, characterized in that, The oil drum (24) is installed inside the punch press (1). A base plate (31) is installed on the side wall of the punch press (1). The piston cylinder (21) is installed on the base plate (31). One end of the oil inlet pipe (22) is connected to the oil outlet of the oil drum (24), and the other end is connected to the oil inlet of the piston cylinder (21). One end of the oil outlet pipe (23) is connected to the oil outlet of the piston cylinder (21), and the other end is connected to the oil inlet of the oil box (11).

6. A metal spring stamping die according to claim 5, characterized in that, The oil outlet mechanism includes a first pressure plate (15), a second pressure plate (17), a piston (19), and a spring (20). The first pressure plate (15) slides in the slide groove (14). The side wall of the punch press (1) is provided with a limiting block (18). The second pressure plate (17) slides in the limiting block (18). The outer end of the first pressure plate (15) and the second pressure plate (17) are both provided with wedge-shaped surfaces, and the wedge-shaped surfaces are arranged opposite to each other.

7. A metal spring stamping die according to claim 6, characterized in that, The piston (19) slides inside the piston cylinder (21), the lower end of the second pressure plate (17) is fixedly connected to the piston (19), one end of the spring (20) is fixedly connected to the piston (19), and the other end is fixedly connected to the bottom of the piston cylinder (21).

8. A metal spring stamping die according to claim 7, characterized in that, The discharge oil control assembly includes a gear (16), a screw (26), an L-shaped mounting plate (27), an L-shaped sliding plate (28), and a discharge plate (29). The gear (16) is fixedly connected to one end of the screw (26). The gear (16) is installed in the transmission cavity (25). The L-shaped mounting plate (27) is installed on the side wall of the lower mold base (5) away from the discharge port (7). The other end of the screw (26) extends through the transmission cavity (25) to the outside of the lower mold base (5) and is rotatably connected to the side wall of the L-shaped mounting plate (27). One end of the L-shaped sliding plate (28) is threadedly connected to the screw (26), and the other end is fixedly connected to the upper end of the discharge plate (29). The cavity (6) has an opening on the side wall away from the discharge port (7), and the discharge plate (29) slides in the opening.

9. A metal spring stamping die according to claim 8, characterized in that, The discharge oil control assembly also includes an oil control mechanism, which is used to recover residual lubricating grease at the bottom of the cavity (6) and to uniformly coat a thin layer of oil film at the bottom of the cavity (6) when the discharge plate (29) retracts. The oil control mechanism includes an oil storage tank (32), capillary oil seepage holes (33) and a pump plate (34). The oil storage tank (32) is located inside the discharge plate (29). Several capillary oil seepage holes (33) are opened at the front end of the bottom of the discharge plate (29) and are connected to the oil storage tank (32). The punch press (1) is provided with an installation plate (35). A fixing plate (36) is provided on the installation plate (35). One end of the pump plate (34) is fixedly connected to the side wall of the fixing plate (36), and the other end is sealed and inserted into the oil storage tank (32).

10. A metal spring stamping die according to claim 9, characterized in that, The lower surface of the first pressure plate (15) is provided with gear teeth, which mesh with the gear (16). The oil inlet pipe (22) and the oil outlet pipe (23) are both provided with one-way valves. The oiling assembly and the oil outlet assembly are provided with two sets.

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