A square aluminum shell semi-solid battery pack

Abstract

The present invention relates to the technical field of square aluminum shell battery packs, and specifically relates to a square aluminum shell semi-solid battery pack, which includes a battery box frame. A battery pack inner core with a square appearance is arranged in the battery box frame. Aluminum plate assemblies are arranged at the positions of the four vertical side surfaces between the battery box frame and the battery pack inner core. The aluminum plate assembly includes a hard plate square frame in the shape of a square plate frame, square aluminum plates distributed in the hard plate square frame, a row of limiting units in contact with each edge of the square aluminum plates, and a column square frame in contact with and driving all the limiting units. The adjustment and control of the deformed square aluminum plates will cause the power-off of the battery pack, avoiding safety problems caused by the energization of overheated or damaged square aluminum plates. By arranging a plurality of limiting units at the four edges of the square aluminum plates, the deformation of the square aluminum plates can be monitored in a timely and sensitive manner. Once any limiting unit monitors the deformation of the square aluminum plates, subsequent transmission will cause final power-off.

Description

Technical Field

[0001] The present invention relates to the technical field of square aluminum shell battery packs, and particularly to a square aluminum shell semi-solid battery pack. Background Art

[0002] The aluminum shell is prone to deformation, which is mainly caused by the characteristics of aluminum materials and possible problems during the processing. Aluminum has low rigidity and a large coefficient of thermal expansion, which means that the aluminum shell is easily affected by thermal stress and mechanical stress, resulting in deformation. Common deformation forms include bending, bulging, and denting. The outer shell of the square aluminum shell semi-solid battery pack is made of aluminum material. The aluminum shell battery is lighter than the steel shell battery, which helps to reduce the weight of the entire battery pack. At the same time, aluminum has good thermal conductivity, which helps the battery to dissipate heat quickly, extend the service life of the battery, and improve safety. The aluminum shell battery also has excellent corrosion resistance and can effectively intercept the corrosive materials leaked from the battery.

[0003] The aluminum plate of the battery pack housing will also undergo significant volume changes when the temperature changes. In practical applications, due to excessive temperature differences, the aluminum plate expands when heated or contracts when cooled, resulting in obvious deformation. Based on the solutions to the thermal expansion deformation and impact deformation of the aluminum shell, the present invention provides a square aluminum shell semi-solid battery pack. Summary of the Invention

[0004] The purpose of the present invention is to provide a square aluminum shell semi-solid battery pack to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A square aluminum shell semi-solid battery pack, including a battery box frame. A battery pack inner core with a square appearance is arranged in the battery box frame. Isolated aluminum plate assemblies are arranged at the four vertical side positions between the battery box frame and the battery pack inner core. The aluminum plate assembly includes a hard board square frame in the shape of a square plate frame, square aluminum plates distributed in the middle of the hard board square frame, a row of limiting units in contact with each edge of the square aluminum plates, and a column square frame in contact with and driving all the limiting units. The column square frame is parallelly distributed at one side position of the hard board square frame. Plate holes for heat dissipation are opened on the housing of the battery box frame on one side of the square aluminum plate. A square frame is horizontally placed above the battery pack inner core. Multiple groups of conductive metal sheets are fixed in the middle of the square frame, and the conductive metal sheets realize current transmission by contacting the electrode sheet ends on the battery pack inner core. Springs are connected to the four corners of the square frame. Two hard board square frames at the corner positions of the battery pack inner core are vertically fixed to form an L-shaped vertical plate, and the springs are arranged on the L-shaped vertical plate. A control tool is connected to the upper end of each column square frame. The control tool pushes up the frame on the square frame to raise the square frame, and the square frame is raised to disconnect the electrode sheet ends of the battery pack inner core and the wire metal sheets.

[0006] The limiting unit props up one side edge of the square aluminum plate. On the other side edge of the square aluminum plate, there is also a square frame thin plate integrally connected. And the limiting unit and the back plate fixed on the hard board square frame cooperate to clamp the square frame thin plate of the square aluminum plate.

[0007] The spring group includes an intercepting body fixed on the hard board square frame, an angular position rod fixedly connected to the square frame, and a spring sleeved on the angular position rod. The angular position rod slides through a through hole opened on the intercepting body, and the spring is supported between the square frame and the intercepting body.

[0008] The limiting unit includes a rubber plate padded between the hard board square frame and the square aluminum plate, unit straight plates distributed on one side of the rubber plate, a limiting plate seat that confines the unit straight plates, a boosting elastic sheet connected between the limiting plate seat and the unit straight plates, and a transmission group in contact with and driving the unit straight plates. On the column square frame, a vertical fixed orientation column slides through a through hole opened at one end of the limiting plate seat.

[0009] The edge of the square frame thin plate on the square aluminum plate is snapped into a groove opened at one end of the rubber plate, and the other end of the rubber plate is inserted into a plate groove opened on the hard board square frame. On the unit straight plate, a convex block is arranged to contact the outer edge of the square aluminum plate.

[0010] The limiting plate seat is fixed on the hard board square frame, and the unit straight plate slides through a plate hole opened on the limiting plate seat. One end of the boosting elastic sheet is fixed on the unit straight plate, and the other end is fixed on the limiting plate seat.

[0011] The transmission group includes a secondary plate frame fixed at one end on the limiting plate seat, a commutation seat padded between the unit straight plate and the column square frame, and a pressing cover elastic sheet that supports the commutation seat. One end of the pressing cover elastic sheet is fixed on the secondary plate frame. The commutation seat includes a concave block and a slider fixed on one side of the concave block. On the unit straight plate, a semi-cylindrical body is arranged to be snapped into the inside of the concave block of the commutation seat. The slider of the commutation seat passes through a square hole opened on the secondary plate frame and then contacts the column square frame.

[0012] The control tool includes an L-shaped push-pull plate fixed on the column square frame, a flat plate group connected to one end of the L-shaped push-pull plate, and a top position frame that supports the flat plate group. The end of the top position frame is fixed on the hard board square frame, and the flat plate group is in contact with and drives the square frame.

[0013] The flat plate group includes an L-shaped flat plate in contact with the square frame, a U-shaped elastic sheet fixedly connected between the L-shaped flat plate and the L-shaped push-pull plate, a piston column arranged on the L-shaped flat plate, a cylinder barrel slidably sleeved at one end on the piston column, and an elastic sheet door that seals the other end port of the cylinder barrel. On the top position frame, two symmetric concave blocks are arranged to clamp the L-shaped flat plate.

[0014] One end of the L-shaped flat plate pushes the frame of the square frame by setting an inclined plane. A triangular plate is arranged on the L-shaped flat plate to support and fix the piston column. The elastic sheet door includes a disc body and a C-shaped elastic sheet fixed on one side of the disc body. One end of the C-shaped elastic sheet is fixed on the top frame, and an air supplement pore is formed in the middle of the disc body of the elastic sheet door.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. By monitoring the thermal expansion deformation or impact deformation of the square aluminum plate, the present invention further controls the power on and off of the battery pack. The adjustment and control after the deformation of the square aluminum plate will cause the battery pack to power off, avoiding the safety problems caused by the energization of the overheated or damaged square aluminum plate. By arranging a plurality of limiting units at the four peripheral edges of the square aluminum plate to monitor the deformation of the square aluminum plate in a timely and sensitive manner, once any limiting unit detects the deformation of the square aluminum plate, subsequent transmissions will cause the final power off.

[0017] 2. By setting a delay mechanism in the flat plate group, the present invention can effectively avoid the power off problem caused by vibration. Only the deformation of the square aluminum plate will cause power off. The temporary vibration influence of the square aluminum plate ends before the L-shaped flat plate makes an effective translation, so it will not cause the subsequent rise of the square frame, avoiding the power off problem, and thus ensuring the stable charge and discharge operation of the battery pack. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the present invention.

[0019] Figure 2 It is a schematic structural diagram of the aluminum plate assembly.

[0020] Figure 3 It is a schematic structural diagram of the battery box frame.

[0021] Figure 4 It is a schematic diagram of the position of the control tool.

[0022] Figure 5 It is a schematic structural diagram of the spring group.

[0023] Figure 6 It is a schematic structural diagram of the square frame.

[0024] Figure 7 It is a schematic diagram of the position of the back plate.

[0025] Figure 8 It is a schematic structural diagram of the limiting unit.

[0026] Figure 9 It is a schematic structural diagram of the transmission group.

[0027] Figure 10 It is a schematic diagram of the position of the unit straight plate.

[0028] Figure 11 Schematic diagram of the control tool structure

[0029] Figure 12 Schematic diagram of the position of the L-shaped push-pull plate

[0030] Figure 13 Schematic diagram of the flat plate group structure

[0031] In the figure: battery box frame 1, battery pack inner core 2, aluminum plate assembly 3, hard plate square frame 4, square aluminum plate 5, limit unit 6, column square frame 7, square frame 8, spring group 9, control tool 10, back plate 11, interceptor 12, spring 13, corner bar 14, rubber plate 15, booster spring piece 16, transfer group 17, limit plate seat 18, unit straight plate 19, auxiliary plate frame 20, pressure cover spring piece 21, commutation seat 22, orientation column 23, flat plate group 24, L-shaped push-pull plate 25, top position frame 26, spring piece door 27, cylinder barrel 28, piston column 29, L-shaped flat plate 30, U-shaped spring piece 31. Specific implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the technical solutions in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] Please refer to Figures 1 to 13 , the present invention provides a technical solution: a square aluminum shell semi-solid battery pack, including a battery box frame 1, in which a battery pack inner core 2 with a square appearance is arranged. Isolated aluminum plate assemblies 3 are provided at the positions of the four vertical side surfaces between the battery box frame 1 and the battery pack inner core 2. The aluminum plate assembly 3 includes a hard plate square frame 4 in the shape of a square plate frame, square aluminum plates 5 distributed in the middle of the hard plate square frame 4, a row of limit units 6 in contact with each edge of the square aluminum plates 5, and a column square frame 7 in contact with and driving all the limit units 6. The column square frame 7 is parallelly distributed on one side of the hard plate square frame 4. A plate hole for heat dissipation is opened on the shell of the battery box frame 1 on one side of the square aluminum plate 5. A square frame 8 is horizontally placed above the battery pack inner core 2. Multiple groups of conductive metal sheets are fixed in the middle of the square frame 8, and the conductive metal sheets are used to realize current transmission by contacting the electrode sheet ends on the battery pack inner core 2. Spring groups 9 are connected to the four corners of the square frame 8. Two hard plate square frames 4 at the corner positions of the battery pack inner core 2 are vertically fixed to form an L-shaped vertical plate, and the spring groups 9 are arranged on the L-shaped vertical plate. One control tool 10 is connected to the upper end of each column square frame 7. The control tool 10 makes the square frame 8 rise by pushing the side frame on the square frame 8 upward, and the square frame 8 makes the electrode sheet ends of the battery pack inner core 2 and the wire metal sheets cut off power and separate by rising.

[0034] The present invention protects through the square aluminum plates 5 on the four sides around the inner core 2 of the battery pack. At the same time, the heat generated during the charging and discharging of the inner core 2 of the battery pack can be quickly conducted out through the square aluminum plates 5, so as to quickly dissipate heat from the inner core 2 of the battery pack. When a malfunction occurs in the operation of the inner core 2 of the battery pack and too much heat is generated during operation, heat transfer causes the temperature of the square aluminum plates 5 themselves to be too high, and the square aluminum plates 5 undergo thermal expansion and deformation. In addition, an accidental impact outside the battery pack that hits the square aluminum plates 5 will also directly cause the deformation of the square aluminum plates 5. The above-mentioned two deformations will automatically trigger subsequent power-off, that is, the square aluminum plates 5 will power off when they overheat during operation, or they will also power off when subjected to a strong external impact, avoiding safety problems during the charging and discharging of the battery pack. Timely power-off can prevent the expansion of accidental safety problems.

[0035] Reference Figure 7 Understand that the limiting unit 6 props up one side edge of the square aluminum plate 5, and a square frame thin plate is integrally connected to the other side edge of the square aluminum plate 5, and the limiting unit 6 and the back plate 11 fixed on the hard board square frame 4 cooperate to clamp the square frame thin plate of the square aluminum plate 5.

[0036] Reference Figure 5 Understand that the spring group 9 includes an intercepting body 12 fixed on the hard board square frame 4, an angular position rod 14 fixedly connected to the square frame 8, and a spring 13 sleeved on the angular position rod 14. The angular position rod 14 slides through a through hole opened on the intercepting body 12, and the spring 13 is supported between the square frame 8 and the intercepting body 12.

[0037] Reference Figure 8 Understand that the limiting unit 6 includes a rubber plate 15 cushioned between the hard board square frame 4 and the square aluminum plate 5, unit straight plates 19 distributed on one side of the rubber plate 15, a limiting plate seat 18 that restricts the unit straight plates 19, a boosting elastic piece 16 connected between the limiting plate seat 18 and the unit straight plates 19, and a transmission group 17 that contacts and transmits with the unit straight plates 19. A vertical fixing orientation column 23 on the column square frame 7 slides through a through hole opened at one end of the limiting plate seat 18.

[0038] The edge of the square frame thin plate on the square aluminum plate 5 is snapped into a groove opened at one end of the rubber plate 15, the other end of the rubber plate 15 is inserted into a plate groove opened on the hard board square frame 4, and the unit straight plates 19 contact the outer edge of the square aluminum plate 5 by arranging protrusions.

[0039] The limiting plate seat 18 is fixed on the hard board square frame 4, the unit straight plates 19 slide through plate holes opened on the limiting plate seat 18, one end of the boosting elastic piece 16 is fixed on the unit straight plates 19, and the other end is fixed on the limiting plate seat 18.

[0040] The transmission group 17 includes a secondary plate frame 20 with one end fixed to the limit plate seat 18, a reversing seat 22 padded between the unit straight plate 19 and the column square frame 7, and a gland spring piece 21 supporting the reversing seat 22. One end of the gland spring piece 21 is fixed to the secondary plate frame 20. The reversing seat 22 includes a concave block and a slider fixed on one side of the concave block. A semi-cylindrical body is arranged on the unit straight plate 19 to be clamped into the concave block inside the reversing seat 22. The slider of the reversing seat 22 passes through the square hole opened on the secondary plate frame 20 and then contacts the column square frame 7.

[0041] The control tool 10 includes an L-shaped push-pull plate 25 fixed to the column square frame 7, a flat plate group 24 connected to one end of the L-shaped push-pull plate 25, and a top position frame 26 supporting the flat plate group 24. The end of the top position frame 26 is fixed to the hard plate square frame 4. The flat plate group 24 and the square frame 8 are in contact transmission.

[0042] The flat plate group 24 includes an L-shaped flat plate 30 in contact with the square frame 8, a U-shaped spring piece 31 fixedly connected between the L-shaped flat plate 30 and the L-shaped push-pull plate 25, a piston column 29 arranged on the L-shaped flat plate 30, a cylinder barrel 28 with one end slidably sleeved on the piston column 29, and a spring piece door 27 blocking the other end port of the cylinder barrel 28. Two symmetric concave blocks are arranged on the top position frame 26 to clamp the L-shaped flat plate 30.

[0043] One end of the L-shaped flat plate 30 pushes the frame edge of the square frame 8 by arranging an inclined surface. A triangular plate is arranged on the L-shaped flat plate 30 to support and fix the piston column 29. The spring piece door 27 includes a disc body and a C-shaped spring piece fixed on one side of the disc body. One end of the C-shaped spring piece is fixed to the top position frame 26. An air supplement fine hole is opened in the middle of the disc body of the spring piece door 27.

[0044] During the thermal expansion and deformation of the square aluminum plate 5, the edge of the square aluminum plate 5 diffuses and deforms outward. In this way Figure 10 the edge of the square aluminum plate 5 in moves to the right, causing the rightward translation of the unit straight plate 19. When an external impact acts on the square aluminum plate 5, the middle of the square aluminum plate 5 sinks, causing the edge of the square aluminum plate 5 to move relatively closer to the middle, that is Figure 10 the edge of the square aluminum plate 5 in moves to the left. The unit straight plate 19 is pushed to move leftward by the pressurizing spring piece 16. The rubber plate 15 is a hard rubber material in the prior art. Although it restricts and limits the square aluminum plate 5, it does not affect the deformation of the square aluminum plate 5. The translation of the unit straight plate 19 in both directions will cause the semi-cylindrical body to push the concave block of the reversing seat 22. In this way, the reversing seat 22 moves overcoming the elastic force of the gland spring piece 21. The slider on the reversing seat 22 moves to lift the column square frame 7. There are multiple reversing seats 22 in contact with the column square frame 7. The translation of any reversing seat 22 will cause the movement of the column square frame 7, that is, the column square frame 7 moves away from the hard plate square frame 4. Figure 11 During the process of the column square frame 7 moving away from the hard plate square frame 4 in it drives the L-shaped push-pull plate 25. Figure 13The L-shaped push-pull plate 25 translates to the right, and then the L-shaped flat plate 30 is pulled by the U-shaped spring piece 31. The inclined surface of the L-shaped flat plate 30 translates to the right and pushes up the frame of the square frame 8, causing the square frame 8 to rise, so that the electrode sheet ends of the battery pack core 2 and the wire metal sheet are disconnected and separated.

[0045] The flat plate group 24 also has a delay mechanism. If only a short impact causes the vibration displacement of the square aluminum plate 5, rather than the complete deformation of the square aluminum plate 5 itself, the delay mechanism will work and will not cause subsequent power outages. The principle is that the shaking of the square aluminum plate 5 caused by the vibration is short-lived. After the shaking, the square aluminum plate 5 is quickly reset by the contact and pressure of the unit straight plate 19. The unit straight plate 19 quickly resets after moving the reversing seat 22. The reversing seat 22 lifts up the column frame 7 and then resets. The distance between the column frame 7 and the hard plate frame 4 increases briefly and then quickly shrinks and recovers. That is, Figure 13 The L-shaped push-pull plate 25 briefly translates to the right and then translates to the left to reset. Although the L-shaped push-pull plate 25 pulls the U-shaped spring sheet 31, it does not cause the L-shaped flat plate 30 to translate quickly. The speed of the L-shaped flat plate 30 to translate to the right is limited because the piston column 29 fixed on the L-shaped flat plate 30 is affected by the negative pressure environment in the cylinder barrel 28 during the axial movement to the right. It takes time for the external air to pass through the fine holes in the middle of the spring sheet door 27. The negative pressure environment affects the translation speed of the L-shaped flat plate 30. The L-shaped flat plate 30 does not effectively respond to the right translation. The L-shaped push-pull plate 25 has been reset, so the L-shaped flat plate 30 is close to motionless for a short time, and there is no subsequent rise of the square frame 8. The delay mechanism can avoid the problem of power failure due to vibration of the battery pack. Only when the external impact force is sufficient to cause the impact deformation of the square aluminum plate 5, or the overheating of the battery pack core 2 causes the thermal expansion deformation of the square aluminum plate 5, will the final safe power failure occur.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A square aluminum shell semi-solid battery pack, comprising a battery box frame (1), characterized in that: The battery box frame (1) is provided with a battery pack core (2) having a square appearance. Four vertical side positions between the battery box frame (1) and the battery pack core (2) are provided with isolated aluminum plate assemblies (3). The aluminum plate assembly (3) comprises a square plate frame-shaped hard plate frame (4), a square aluminum plate (5) distributed in the middle of the hard plate frame (4), a row of limit units (6) on each edge of the square aluminum plate (5) in contact with each other, and a column frame (7) in contact with all the limit units (6). The column frame (7) is distributed in parallel at one side of the hard plate frame (4). A plate hole for heat dissipation is provided on the shell of the battery box frame (1) on one side of the square aluminum plate (5). The battery pack core (2) is placed flat on the top. A square frame (8) is provided, wherein a plurality of groups of conductive metal sheets are fixed in the middle of the square frame (8), and the conductive metal sheets realize current transmission by contacting with the ends of the electrode sheets on the inner core (2) of the battery pack, and the four corners of the square frame (8) are connected to spring groups (9), and two hard plate square frames (4) at the corners of the inner core (2) of the battery pack are vertically fixed to form an L-shaped vertical plate, and the spring groups (9) are arranged on the L-shaped vertical plate, and the upper end of each column square frame (7) is connected to a control device (10), and the control device (10) causes the square frame (8) to rise by pushing the frame on the square frame (8) upward, and the square frame (8) causes the ends of the electrode sheets of the inner core (2) of the battery pack to be disconnected and separated from the metal sheets of the conductor by rising; The limiting unit (6) supports one side edge of the square aluminum plate (5), and the other side edge of the square aluminum plate (5) is also integrally connected with a square frame thin plate, and the limiting unit (6) and the back plate (11) fixed on the hard plate square frame (4) cooperate to clamp the square frame thin plate of the square aluminum plate (5); The spring group (9) comprises an interception body (12) fixed on the hard plate frame (4), a corner rod (14) fixedly connected to the frame frame (8), and a spring (13) sleeved on the corner rod (14), the corner rod (14) slidingly passes through a through hole formed on the interception body (12), and the spring (13) is supported between the frame frame (8) and the interception body (12); The limiting unit (6) comprises a rubber plate (15) padded between the hard plate frame (4) and the square aluminum plate (5), a unit straight plate (19) distributed on one side of the rubber plate (15), a limiting plate seat (18) for restraining the unit straight plate (19), a booster spring (16) connected between the limiting plate seat (18) and the unit straight plate (19), and a transmission group (17) for contact transmission with the unit straight plate (19); the column frame (7) is slidably connected to the through hole opened at one end of the limiting plate seat (18) by means of a vertically fixed directional column (23); The control device (10) comprises an L-shaped push-pull plate (25) fixed on the column frame (7), a flat plate group (24) connected to one end of the L-shaped push-pull plate (25), and a top frame (26) supporting the flat plate group (24), the end of the top frame (26) being fixed on the hard plate frame (4), and the flat plate group (24) and the frame frame (8) are in contact transmission.

2. A square aluminum shell semi-solid battery pack according to claim 1, characterized in that: The edge of the square frame thin plate on the square aluminum plate (5) is inserted into a groove formed at one end of the rubber plate (15), and the other end of the rubber plate (15) is inserted into a plate groove formed on the hard plate square frame (4). The unit straight plate (19) is provided with a protrusion to contact the outer edge of the square aluminum plate (5).

3. The square aluminum shell semi-solid battery pack according to claim 1, characterized in that: The limit plate seat (18) is fixed on the hard plate frame (4), the unit straight plate (19) slides through the plate hole opened on the limit plate seat (18), and one end of the booster spring (16) is fixed on the unit straight plate (19) and the other end is fixed on the limit plate seat (18).

4. The square aluminum shell semi-solid battery pack according to claim 1, characterized in that: The transmission group (17) includes a sub-plate frame (20) having one end fixed on the limit plate seat (18), a reversing seat (22) padded between the unit straight plate (19) and the column frame (7), and a pressure cover spring sheet (21) supporting the reversing seat (22), one end of the pressure cover spring sheet (21) is fixed on the sub-plate frame (20), the reversing seat (22) includes a concave block and a slider fixed on one side of the concave block, a semi-cylinder is arranged on the unit straight plate (19) to be inserted into the concave block of the reversing seat (22), and the slider of the reversing seat (22) passes through the square hole opened on the sub-plate frame (20) and contacts with the column frame (7).

5. The square aluminum shell semi-solid battery pack according to claim 1, characterized in that: The plate group (24) comprises an L-shaped plate (30) in contact with the square frame (8), a U-shaped spring piece (31) fixedly connected between the L-shaped plate (30) and the L-shaped push-pull plate (25), a piston column (29) arranged on the L-shaped plate (30), a cylinder barrel (28) with one end slidingly sleeved on the piston column (29), and a spring piece door (27) blocking the other end port of the cylinder barrel (28), and the top frame (26) is provided with two symmetrical concave blocks to clamp the L-shaped plate (30).

6. A square aluminum shell semi-solid battery pack according to claim 5, characterized in that: One end of the L-shaped plate (30) is provided with an inclined surface to push the frame of the square frame (8), and a triangular plate is provided on the L-shaped plate (30) to support and fix the piston column (29). The spring door (27) comprises a disk body and a C-shaped spring fixed to one side of the disk body, and one end of the C-shaped spring is fixed to the top frame (26). A fine air replenishing hole is provided in the middle of the disk body of the spring door (27).

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