Steel structure casting mold convenient to disassemble

Abstract

The invention discloses a steel structure casting mold convenient to disassemble, and relates to the technical field of casting forming. The problem of casting defects is solved. The mold specifically comprises an upper movable mold and a lower static mold which are matched with each other, a pouring gate is formed in the inner wall of the upper movable mold, a pouring gate is welded to the outer wall, located at the pouring gate, of the upper movable mold, a U-shaped channel is formed in the inner wall of the upper movable mold, steps are arranged at the two ends of the U-shaped channel, and sliding blocks are slidably connected to the inner walls of the steps; a through hole longitudinally staggered with the U-shaped channel is formed in the inner wall of the sliding block, a first spring is buckled to the end face of the sliding block, and the other end of the first spring is buckled to the inner wall of the step. By arranging the sliding block, the U-shaped channel and other components, on one hand, vibration of the upper movable mold can be achieved when pulse type gas is introduced, so that liquid metal is filled through vibration, defects of a casting are prevented, on the other hand, the functions of accelerated cooling and preheating can be achieved in cooperation with cooling liquid and hot liquid, and the casting efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of casting and molding, in particular to a steel structure casting mold which is easy to disassemble. Background Art

[0002] Steel structure buildings are widely used due to their advantages such as energy saving, environmental protection, reusability and short construction period. Most of the components of steel structure buildings are prefabricated parts, which include some castings. When castings are produced, high-temperature molten metal liquid is used in conjunction with a casting mold for casting, and then the metal is cooled and formed, and the burrs are repaired to obtain the finished product.

[0003] After searching, the Chinese patent publication number CN107671245A discloses a cylinder head casting mold and a casting method, including an upper template and a lower template, characterized in that: the top of the upper template is connected to a fixed plate, and a positioning ring is provided at the axis of the upper template and the fixed plate; the bottom end of the positioning ring is connected to the casting port, and the axis of the casting port is perpendicular to the plane where the upper template is located; a plurality of guide pillars are provided at the bottom end of the upper template, and the guide pillars are cooperated and connected with the guide pillar sleeves arranged at the top of the lower template; a male template is provided at the top of the lower template, and the cylinder head is connected between the male template and the upper template; a plurality of ejector pins are provided at the top of the male template, and the ejector pins pass through a plurality of cylinder head holes arranged on the cylinder head and are connected to the upper template; a drainage port is provided between the lower template and the male template; the bottom end of the lower template is connected to the bottom plate, and a support column is provided between the bottom plate and the lower template; an ejector plate is provided on one side of the support column.

[0004] The above patent has the following deficiencies: it directly performs casting, and since the fluidity of liquid metal is relatively poor, it is difficult to completely fill the corners of the cavity during the casting process, which will gradually cause defects.

[0005] To this end, the present invention provides a steel structure casting mold that is easy to disassemble. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to provide a steel structure casting mold that is easy to disassemble.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A steel structure casting mold that is easy to disassemble, comprising an upper movable mold and a lower static mold that cooperate with each other. A runner is provided on the inner wall of the upper movable mold, and a gate is welded on the outer wall of the upper movable mold at the runner. A "U"-shaped channel is provided on the inner wall of the upper movable mold, and steps are provided at both ends of the "U"-shaped channel. A sliding block is slidably connected to the inner wall of the step, and a through hole is provided on the inner wall of the sliding block that is longitudinally offset from the "U"-shaped channel. A spring 1 is buckled on the end face of the sliding block, and the other end of the spring 1 is buckled on the inner wall of the step.

[0008] Preferably: the bottom outer wall of the lower static mold is fixed to the base by bolts, the top outer wall of the base is fixed to the guide rod by bolts, the top outer wall of the guide rod is fixed to the top plate by bolts, the top outer wall of the top plate is fixed to the telescope by bolts, and the telescopic end of the telescope is fixed to the top outer wall of the upper movable mold by bolts.

[0009] Furthermore, a slider is fixed to the side wall of the upper movable mold by bolts, and the slider is slidably connected to the outer wall of the guide rod.

[0010] On the basis of the above solution: a demoulding mechanism is provided at the bottom of the lower static mold, and the demoulding mechanism includes a ejection plate and an ejection assembly, and the ejection plate is matched with the inner wall of the lower static mold.

[0011] A better solution among the above solutions is: the bottom outer wall of the slider is fixed with a connecting frame by bolts, the side wall of the connecting frame is fixed with a hollow cylinder by bolts, the inner wall of the hollow cylinder is movably connected with a hollow shaft, and the hollow shaft is fixed to the bottom outer wall of the ejector plate.

[0012] As a further solution of the present invention: a spiral groove is provided on the outer wall of the hollow shaft, and a limiting protrusion is slidably connected to the inner wall of the hollow cylinder. The limiting protrusion is movably limited and fitted with the side wall of the spiral groove, and the side wall of the limiting protrusion is buckled with spring 2, and the other end of spring 2 is buckled to the inner wall of the hollow cylinder.

[0013] At the same time, the inner wall of the hollow shaft is rotatably connected to the multi-protrusion cam, and the radial inner wall of the hollow shaft is slidably matched with a collision block, which is movably contacted and matched with the side wall of the multi-protrusion cam.

[0014] As a preferred embodiment of the present invention: the inner cavity of the hollow shaft is rotatably connected to multiple planetary gears through a connecting shaft, the inner sides of the multiple planetary gears are engaged with the same sun gear, the outer sides of the multiple planetary gears are engaged with the same ring gear, and the top of the sun gear is fixedly connected to the end face of the multi-protrusion cam.

[0015] At the same time, the gear ring is rotatably connected to the inner wall of the hollow shaft, and a limiting cylinder is fixed to the bottom of the gear ring.

[0016] As a more optimal solution of the present invention: a key-shaped groove is opened on the inner wall of the limiting cylinder, a limiting shaft is fixed on the bottom inner wall of the hollow cylinder, and a key-shaped protrusion that is loosely matched with the key-shaped groove is welded on the outer wall of the limiting shaft.

[0017] The beneficial effects of the present invention are: 1. The present invention, by providing components such as a sliding block and a "U"-shaped channel, can, on the one hand, achieve vibration of the upper movable mold when pulsed gas is introduced, thereby utilizing vibration to fill the liquid metal and prevent defects in the casting; on the other hand, it can cooperate with coolant and hot liquid to achieve the functions of accelerated cooling and preheating, thereby increasing casting efficiency.

[0018] 2. The present invention provides a ejector plate, which can lift the casting, thereby achieving a demoulding effect and increasing ease of use. In addition, a connecting frame is provided, which can rise and fall along with the rise and fall of the upper movable mold, thereby increasing synchronous linkage.

[0019] 3. The present invention, through the spiral groove and the limiting protrusion, can use the vibration generated by the separation and combination of the limiting protrusion and the spiral groove to loosen the casting and the ejector plate. After loosening, it can use their cooperation to achieve the separation of the casting and the lower static mold, thereby avoiding the deformation of the casting caused by demolding using only static pressure.

[0020] 4. The present invention, through the arrangement of an ingenious mechanical structure combination, can realize the vibration of the ejector plate, the vibration of the lower static mold and the lifting and lowering of the ejector plate respectively, and each action is realized only by the lifting and lowering of the connecting frame, realizing power integration and increasing synchronous linkage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the overall structure of a steel structure casting mold that is easy to disassemble proposed by the present invention; Figure 2 This is a schematic cross-sectional view of an upper movable mold of a steel structure casting mold that is easy to disassemble, as proposed by the present invention; Figure 3 This is a schematic structural diagram of a demoulding mechanism of a steel structure casting mold that is easy to disassemble proposed by the present invention; Figure 4 This is a schematic diagram of the hollow cylinder and hollow shaft structure of a steel structure casting mold that is easy to disassemble proposed by the present invention; Figure 5 The invention proposes a steel structure casting mold that is easy to disassemble Figure 4 Schematic diagram of the structure of part A; Figure 6 This is a schematic diagram of the structure of a limiting shaft and a limiting cylinder of a steel structure casting mold that is easy to disassemble proposed by the present invention; Figure 7 The invention proposes a steel structure casting mold that is easy to disassemble Figure 6 Schematic diagram of the structure of part B; Figure 8 This is a schematic diagram of the key-shaped groove and key-shaped protrusion structure of a steel structure casting mold that is easy to disassemble proposed by the present invention; Figure 9 This is a schematic diagram of the sliding block structure of a steel structure casting mold that is easy to disassemble proposed by the present invention.

[0022] In the figure: 1. Base; 2. Slider; 3. Guide rod; 4. Top plate; 5. Telescope; 6. Upper movable mold; 7. Lower static mold; 8. Demolding mechanism; 9. Gate; 10. Runner; 11. Through hole; 12. Step; 13. Sliding block; 14. Spring 1; 15. "U"-shaped channel; 16. Ejector plate; 17. Ejector assembly; 18. Connecting frame; 19. Hollow cylinder; 20. Hollow shaft; 21. Spiral groove; 22. Limiting protrusion; 23. Spring 2; 24. Limiting shaft; 25. Limiting cylinder; 26. Multi-protrusion cam; 27. Impact block; 28. Connecting shaft; 29. ​​Planetary gear; 30. Ring gear; 31. Sun gear; 32. Key groove; 33. Key protrusion. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be further described in detail below in conjunction with specific implementation methods.

[0024] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention. Example

[0025] A steel structure casting mold that is easy to disassemble, such as Figures 1-8 As shown, it includes an upper movable mold 6 and a lower static mold 7 that cooperate with each other, the inner wall of the upper movable mold 6 is provided with a runner 10, and the outer wall of the upper movable mold 6 located at the runner 10 is welded with a gate 9, the inner wall of the upper movable mold 6 is provided with a "U"-shaped channel 15, both ends of the "U"-shaped channel 15 are provided with steps 12, the inner wall of the step 12 is slidably connected with a sliding block 13, the inner wall of the sliding block 13 is provided with a through hole 11 longitudinally offset from the "U"-shaped channel 15, the end face of the sliding block 13 is buckled with a spring 14, and the other end of the spring 14 is buckled to the inner wall of the step 12.

[0026] When the device is in use, molten liquid metal can be poured from the pouring gate 9 into the interior of the runner 10, thereby filling the mold cavity formed by the upper movable mold 6 and the lower static mold 7. During the casting process, pulsed gas can be introduced into one end of the "U"-shaped channel 15. When the gas enters, the through hole 11 in the sliding block 13 at the air inlet end is staggered with the "U"-shaped channel 15, thereby achieving the effect of end face sealing. At this time, the sliding block 13 moves downward under the air pressure, and the "U"-shaped channel 15 is connected. At the same time, the sliding block 13 at the other end moves upward. When the gas pressure disappears, the air pressure on the sliding block 13 is reduced, and the sliding block 13 moves to the end face of the step 12, thereby forming a collision and generating vibration. As the pulse gas circulates continuously, vibration is applied to the upper movable mold 6, and the liquid metal is filled by vibration. At the same time, in the cooling stage, coolant can be introduced into the "U"-shaped channel 15 to accelerate cooling. In the pre-casting stage, hot liquid can be introduced into the "U"-shaped channel 15 to achieve preheating.

[0027] This device, by providing components such as a sliding block 13 and a "U"-shaped channel 15, can, on the one hand, achieve vibration of the upper movable mold 6 when pulsed gas is introduced, thereby utilizing vibration to fill the liquid metal and prevent defects in the casting; on the other hand, it can also cooperate with coolant and hot liquid to achieve the functions of accelerated cooling and preheating, thereby increasing casting efficiency.

[0028] In order to solve the problem of mold opening and closing; Figure 1 As shown, the bottom outer wall of the lower static mold 7 is fixed to the base 1 by bolts, the top outer wall of the base 1 is fixed to the guide rod 3 by bolts, the top outer wall of the guide rod 3 is fixed to the top plate 4 by bolts, the top outer wall of the top plate 4 is fixed to the telescopic device 5 by bolts, the telescopic end of the telescopic device 5 is fixed to the top outer wall of the upper movable mold 6 by bolts, and the side wall of the upper movable mold 6 is fixed to the slider 2 by bolts, and the slider 2 is slidably connected to the outer wall of the guide rod 3.

[0029] The telescopic device 5 can drive the upper movable mold 6 to move up and down, thereby realizing the opening and closing of the upper movable mold 6 and the lower static mold 7. In addition, the upper movable mold 6 can be guided by the slider 2 during the lifting process, thereby increasing the lifting accuracy and stability.

[0030] When this embodiment is in use, molten liquid metal can be poured from the pouring gate 9 into the interior of the runner 10, thereby filling the mold cavity formed by the upper movable mold 6 and the lower static mold 7. During the casting process, pulsed gas can be introduced into one end of the "U"-shaped channel 15. When the gas enters, the through hole 11 in the sliding block 13 at the air inlet end intersects with the "U"-shaped channel 15, thereby achieving an end face sealing effect. At this time, the sliding block 13 moves downward due to the air pressure, and the "U"-shaped channel 15 is connected. At the same time, the sliding block 13 at the other end moves upward. When the gas pressure disappears, the air pressure on the sliding block 13 is reduced. , the sliding block 13 moves to the end face of the step 12, thereby forming a collision and generating vibration. As the pulse gas circulates continuously, vibration is applied to the upper movable mold 6, and the liquid metal is filled with vibration. At the same time, in the cooling stage, coolant can be introduced into the "U"-shaped channel 15 to accelerate cooling. In the pre-casting stage, hot liquid can be introduced into the "U"-shaped channel 15 to achieve preheating. The telescopic device 5 can drive the upper movable mold 6 to move up and down, thereby realizing the opening and closing action of the upper movable mold 6 and the lower static mold 7. In addition, the upper movable mold 6 can also be guided by the slider 2 during the lifting process to increase the lifting accuracy and stability. Example

[0031] A steel structure casting mold that is easy to disassemble, such as Figures 1-9 As shown, in order to solve the demoulding problem, this embodiment makes the following improvements on the basis of embodiment 1: a demoulding mechanism 8 is provided at the bottom of the lower static mold 7, and the demoulding mechanism 8 includes a ejection plate 16 and a ejection assembly 17, and the ejection plate 16 is matched with the inner wall of the lower static mold 7.

[0032] After cooling and forming, the ejector plate 16 can be lifted by the ejector assembly 17 to lift the casting.

[0033] In order to solve the reliability of demoulding, such as Figures 1-8 The problem is that the bottom outer wall of the slider 2 is fixed with a connecting frame 18 by bolts, and the side wall of the connecting frame 18 is fixed with a hollow cylinder 19 by bolts. The inner wall of the hollow cylinder 19 is movably connected with a hollow shaft 20, and the hollow shaft 20 is fixed to the bottom outer wall of the ejection plate 16. The outer wall of the hollow shaft 20 is provided with a spiral groove 21, and the inner wall of the hollow cylinder 19 is slidably connected with a limiting protrusion 22, and the limiting protrusion 22 is movably limited and matched with the side wall of the spiral groove 21, and the side wall of the limiting protrusion 22 is buckled with a spring 23, and the other end of the spring 23 is buckled with the inner wall of the hollow cylinder 19.

[0034] The inner wall of the hollow shaft 20 is rotatably connected to a multi-protrusion cam 26 , and the radial inner wall of the hollow shaft 20 is slidably fitted with a collision block 27 , which is movably contacted and fitted with the side wall of the multi-protrusion cam 26 .

[0035] The inner cavity of the hollow shaft 20 is rotatably connected to multiple planetary gears 29 through a connecting shaft 28. The inner sides of the multiple planetary gears 29 are engaged with the same sun gear 31, and the outer sides of the multiple planetary gears 29 are engaged with the same ring gear 30. The ring gear 30 is rotatably connected to the inner wall of the hollow shaft 20. The top of the sun gear 31 is fixedly connected to the end face of the multi-protrusion cam 26, and the bottom of the ring gear 30 is fixed to the limiting cylinder 25.

[0036] The inner wall of the limiting cylinder 25 is provided with a key-shaped groove 32 , the bottom inner wall of the hollow cylinder 19 is fixed with a limiting shaft 24 , and the outer wall of the limiting shaft 24 is welded with a key-shaped protrusion 33 that is clearance-matched with the key-shaped groove 32 .

[0037] When in the mold separation state, the slider 2 rises, thereby pulling the hollow cylinder 19 up through the connecting frame 18. Since the ejector plate 16 also has an adhesive force with the casting at this time, the ejector plate 16 has a rotational resistance. At this time, the limiting protrusion 22 is subject to a large resistance from the spiral groove 21. Since the end face of the limiting protrusion 22 is in a curved state, a component force along the axial direction of the limiting protrusion 22 is generated, causing the limiting protrusion 22 to shrink inward. During the continuous shrinkage and contact process, the hollow shaft 20 will vibrate, thereby using the vibration to loosen the ejector plate 16 and the casting. After the loosening is completed, the rotational resistance of the hollow shaft 20 is greatly reduced, so that the limiting protrusion 22 can move along the spiral groove 21. The path of the groove 21 slides, and the hollow shaft 20 rotates. At this time, the bonding force between the hollow shaft 20 and the lower static mold 7 is still maintained. When the hollow shaft 20 rotates relative to the hollow cylinder 19, the transmission action of the ring gear 30, the sun gear 31, and the planetary gear 29 will also cause the multi-protrusion cam 26 to rotate relative to the hollow shaft 20, so that the multi-protrusion cam 26 can continuously limit the impact block 27, so that the impact block 27 can move outward periodically, so as to use the impact block 27 to periodically impact the lower static mold 7, apply vibration to the lower static mold 7, and then use the vibration to loosen the lower static mold 7 and the casting. After reaching the maximum relative motion stroke of the hollow cylinder 19 and the hollow shaft 20, the ejector plate 16 rises and gradually lifts the loose parts.

[0038] When the present embodiment is in use, when in the mold separation state, the slider 2 rises, thereby pulling the hollow cylinder 19 up through the connecting frame 18. Since the ejector plate 16 also has an adhesive force with the casting at this time, the ejector plate 16 has a rotational resistance. At this time, the limiting protrusion 22 is subject to a greater resistance from the spiral groove 21. Since the end face of the limiting protrusion 22 is in a curved state, a component force along the axial direction of the limiting protrusion 22 is generated, causing the limiting protrusion 22 to contract inwardly. In the continuous contraction and contact process, the hollow shaft 20 will vibrate, thereby utilizing the vibration to loosen the ejector plate 16 and the casting. After the loosening is completed, the rotational resistance of the hollow shaft 20 is greatly reduced, thereby making the limiting protrusion 22 The hollow shaft 20 slides along the path of the spiral groove 21 and rotates. At this time, the bonding force between the hollow shaft 20 and the lower static mold 7 is still maintained. When the hollow shaft 20 rotates relative to the hollow cylinder 19, the transmission action of the ring gear 30, the sun gear 31 and the planetary gear 29 will also cause the multi-lobed cam 26 to rotate relative to the hollow shaft 20. The multi-lobed cam 26 continuously limits the impact block 27, so that the impact block 27 moves outward periodically, thereby using the impact block 27 to periodically impact the lower static mold 7, applying vibration to the lower static mold 7, and then using the vibration to loosen the lower static mold 7 and the casting. After reaching the maximum relative motion stroke of the hollow cylinder 19 and the hollow shaft 20, the ejector plate 16 rises and gradually lifts the loose parts.

[0039] This device, by providing a ejector plate 16, can lift the casting, thereby achieving a demoulding effect and increasing ease of use, and by providing a connecting frame 18, it can rise and fall with the rise and fall of the upper movable mold 6, increasing synchronous linkage.

[0040] In addition, the present device, through the spiral groove 21 and the limiting protrusion 22, can, on the one hand, utilize the vibration generated by the separation and combination of the limiting protrusion and the spiral groove to loosen the casting and the ejector plate 16, and after loosening, it can utilize their cooperation to achieve the separation of the casting and the lower static mold 7, thereby avoiding the deformation of the casting caused by demolding using only static pressure.

[0041] At the same time, the device is equipped with an ingenious mechanical structure combination, which can realize the vibration of the ejector plate 16, the vibration of the lower static mold 7, and the lifting and lowering of the ejector plate 16 respectively, and each action is realized only by the lifting and lowering of the connecting frame 18, realizing power integration and increasing synchronous linkage.

[0042] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A steel structure casting mold that is easy to disassemble, comprising an upper movable mold (6) and a lower static mold (7) that cooperate with each other, characterized in that: The inner wall of the upper movable mold (6) is provided with a runner (10), and the outer wall of the upper movable mold (6) at the runner (10) is welded with a gate (9), and the inner wall of the upper movable mold (6) is provided with a "U"-shaped channel (15), and steps (12) are provided at both ends of the "U"-shaped channel (15), and the inner wall of the step (12) is slidably connected to a sliding block (13), and the inner wall of the sliding block (13) is provided with a through hole (11) longitudinally offset from the "U"-shaped channel (15), and the end face of the sliding block (13) is buckled with a spring (14), and the other end of the spring (14) is buckled to the inner wall of the step (12).

2. The easily disassembled steel structure casting mold according to claim 1, characterized in that: The bottom outer wall of the lower static mold (7) is fixed to a base (1) by bolts, the top outer wall of the base (1) is fixed to a guide rod (3) by bolts, the top outer wall of the guide rod (3) is fixed to a top plate (4) by bolts, the top outer wall of the top plate (4) is fixed to a telescopic device (5) by bolts, and the telescopic end of the telescopic device (5) is fixed to the top outer wall of the upper movable mold (6) by bolts.

3. The easily disassembled steel structure casting mold according to claim 2, characterized in that: The side wall of the upper movable mold (6) is fixed with a slider (2) via bolts, and the slider (2) is slidably connected to the outer wall of the guide rod (3).

4. The easily disassembled steel structure casting mold according to claim 1, characterized in that: A demoulding mechanism (8) is provided at the bottom of the lower static mold (7), and the demoulding mechanism (8) comprises a ejection plate (16) and an ejection assembly (17), wherein the ejection plate (16) is fitted to the inner wall of the lower static mold (7).

5. The easily disassembled steel structure casting mold according to claim 3, characterized in that: The bottom outer wall of the slider (2) is fixed with a connecting frame (18) by bolts, the side wall of the connecting frame (18) is fixed with a hollow cylinder (19) by bolts, the inner wall of the hollow cylinder (19) is movably connected with a hollow shaft (20), and the hollow shaft (20) is fixed to the bottom outer wall of the ejector plate (16).

6. The easily disassembled steel structure casting mold according to claim 5, characterized in that: The outer wall of the hollow shaft (20) is provided with a spiral groove (21), and the inner wall of the hollow cylinder (19) is slidably connected to a limiting protrusion (22), the limiting protrusion (22) is movably limited and matched with the side wall of the spiral groove (21), and the side wall of the limiting protrusion (22) is buckled with a spring 2 (23), and the other end of the spring 2 (23) is buckled with the inner wall of the hollow cylinder (19).

7. The easily disassembled steel structure casting mold according to claim 5, characterized in that: The inner wall of the hollow shaft (20) is rotatably connected to a multi-protrusion cam (26), and the radial inner wall of the hollow shaft (20) is slidably fitted with a bump block (27), which is movably contacted with the side wall of the multi-protrusion cam (26).

8. The easily disassembled steel structure casting mold according to claim 5, characterized in that: The inner cavity of the hollow shaft (20) is rotatably connected to a plurality of planetary gears (29) via a connecting shaft (28); the inner sides of the plurality of planetary gears (29) are meshed with a common sun gear (31); the outer sides of the plurality of planetary gears (29) are meshed with a common ring gear (30); and the top of the sun gear (31) is fixedly connected to the end face of the multi-protrusion cam (26).

9. The easily disassembled steel structure casting mold according to claim 8, characterized in that: The gear ring (30) is rotatably connected to the inner wall of the hollow shaft (20), and a limiting cylinder (25) is fixed to the bottom of the gear ring (30).

10. The easily disassembled steel structure casting mold according to claim 9, characterized in that: The inner wall of the limiting cylinder (25) is provided with a key-shaped groove (32), the bottom inner wall of the hollow cylinder (19) is fixed with a limiting shaft (24), and the outer wall of the limiting shaft (24) is welded with a key-shaped protrusion (33) that is clearance-matched with the key-shaped groove (32).

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