CN217621302U - Core mould of engine shell - Google Patents

Abstract

The utility model provides an engine housing mandrel, include: a mold body; the mandrel is installed on the mandrel, the shaft diameter of the first end of the mandrel is larger than that of the second end of the mandrel, the second end of the mandrel is provided with a positioning flange, the positioning flange is connected with the die body, and the mandrel penetrates through the die body. The utility model provides a current major diameter engine housing gypsum shaping back, the inconvenient technical problem of gypsum mandrel drawing of patterns realizes the convenient technological effect of mandrel drawing of patterns.

Description

Core mold of engine shell

Technical Field

The utility model relates to an engine technical field particularly, relates to an engine housing mandrel.

Background

With the development of aerospace, higher requirements on carrying weight and range are met, the demand on large-diameter engine shells is increasing day by day, a simple gypsum core mold with high structural strength can be adopted for a short large-diameter engine, and the existing gypsum core mold shell or the existing gypsum core mold with large diameter can be released into the shell by an operator to complete demolding; or the diameter is small, the total length is short, and the split mold with the same total length can realize connection and demolding of the shell by virtue of positioning at two ends.

There is a problem in that: after the gypsum of the large-diameter engine shell is formed, the gypsum core mold is inconvenient to demold.

SUMMERY OF THE UTILITY MODEL

The utility model provides a current major diameter engine housing gypsum shaping back, the inconvenient technical problem of gypsum mandrel drawing of patterns realizes the convenient technological effect of mandrel drawing of patterns.

In order to solve the above problem, the utility model provides an engine housing mandrel, include: a mold body; the mandrel is installed on the mandrel, the shaft diameter of the first end of the mandrel is larger than that of the second end of the mandrel, the second end of the mandrel is provided with a positioning flange, the positioning flange is connected with the die body, and the mandrel penetrates through the die body.

Compared with the prior art, the technical scheme has the following technical effects: when the core mould of the engine shell is assembled, the positioning flange is arranged at the second end of the core mould and is used as the starting point for installing each installing plate of the mould body, so that the assembly is more convenient. After the die body and the mandrel are assembled, the mandrel penetrates through the die body, then the mandrel rotates at a constant speed, and the die body rotates along with the mandrel, so that slurry is conveniently blade-coated on the outer surface of the die body. When the core mold of the engine case is to be released, an operator enters the mold from the end having the larger axial diameter. The mounting flange on the mandrel is removed, the second end is disconnected from the die body, and the diameter of the shaft of the first end is larger than that of the second end, so that the second end moves towards the direction of the first end when the shaft is pulled out, the diameter of the shaft of the second end is smaller, the inner part of the die body can be quickly pulled out, and then the shaft is taken out more conveniently and quickly, time and labor are saved, and the demolding speed is improved.

The utility model discloses an in the example, the flange includes the first portion, the second portion, third portion and fourth part, the first portion, the second portion, third portion and fourth part pass through the lock sleeve and connect, and the lock sleeve cup joints in flange.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: compare in the flange of ordinary complete shape, it need take out from the outermost end of axle when dismantling, and other connecting pieces are still installed to the epaxial, just so need demolish other connecting pieces earlier this moment, just can take out the flange from the epaxial, and is comparatively troublesome. The positioning flange of the embodiment is divided into four halves, namely a first part, a second part, a third part and a fourth part, which are spliced to form a flange in a complete shape, and a connecting screw with the mandrel can be screwed off when the mandrel is pulled out, so that the friction with the mandrel is reduced, and the mandrel is pulled out and the die is removed more easily. The lock sleeve is sleeved on the positioning flange, so that the first part, the second part, the third part and the fourth part are connected more stably and are not easy to shift.

In an example of the present invention, the positioning flange is mounted to the core shaft by radial screws.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the positioning flange is installed on the mandrel through radial screws, and the positioning flange is simple in structure, convenient to install and stable in connection.

The utility model discloses an in the example, the axle sleeve is installed to the second end, and the spacing ring is installed to the both sides of axle sleeve.

Compared with the prior art, the technical scheme has the following technical effects: because the shaft diameter of the second end is small, in order to strengthen the connection strength of the second end, the shaft sleeve is arranged at the second end and is sleeved on the mandrel, the limiting rings are arranged on two sides of the shaft sleeve, the inner diameter of each limiting ring is matched with the shaft diameter of the mandrel, the limiting rings can be sleeved on the mandrel, the mounting is convenient, and the shaft sleeve can be fixed by the limiting rings to prevent the shaft sleeve from shifting.

In an example of the present invention, the stop collar includes a first stop collar and a second stop collar, and the first stop collar and the second stop collar are connected by a hoop nut.

Compared with the prior art, the technical scheme has the following technical effects: through the staple bolt nut, realize connecting first spacing ring and second spacing ring for it can be close lock on the dabber, and the staple bolt nut is connected firmly, and simple to operate just is difficult for droing, and then has improved the steadiness of spacing ring and axle sleeve structure.

In one example of the present disclosure, the mold body includes a first valve component, a partition and a second valve component, the partition is installed between the first valve component and the second valve component, the first valve component is installed at the first end, the second valve component is installed at the second end, and the positioning flange is connected with the second valve component.

Compared with the prior art, the technical scheme has the following technical effects: the second valve assembly is sequentially mounted on the positioning flange around the positioning flange, the partition board is tightly attached to the second valve assembly and sequentially mounted until the second valve assembly is mounted on the first valve assembly, the mounting of the mounting plate at the innermost part of the die body is completed, the mounting is simple, and errors are not prone to occurring in the mounting process.

In one embodiment of the present invention, the positioning rings are installed at intervals on the mandrel, the connecting ring is installed on the positioning rings, and the first valve component, the partition plate and the second valve component are installed on the connecting ring.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the positioning rings are arranged at intervals on the mandrel, the mounting positions of the first valve assembly, the partition plate and the second valve assembly are positioned, the connecting rings are arranged on the positioning rings and play a role in connecting the die body and the mandrel, an operator can directly install the first valve assembly, the partition plate and the second valve assembly on the connecting rings, and the valve assembly positioning device is convenient to mount and not prone to error.

The utility model discloses an in the example, the die body still includes head assembly and coverboard, and head assembly includes head body and connecting piece, and the head body is connected with the coverboard, and the head body is installed in one side of connecting piece, and the connecting piece cup joints in positioning flange.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the end enclosure assembly and the shell plate are arranged outside the first valve assembly, the partition plate and the second valve assembly, so that the inner structure of the die body is firmer and is not easy to loosen when in use. The connecting piece cup joints in the locating flange, and the head body is installed in one side of connecting piece, and the head body card is between locating flange and connecting piece, and then it is firm that the head body is installed in spindle structure.

The utility model discloses an in an example, the externally mounted of head body has the shell, and the shell is installed in the opposite side of connecting piece, and the shell is connected with the coverboard.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the shell is installed in the opposite side of connecting piece, simple to operate, and the shell can prevent that the head body from droing for the structure steadiness is better.

The utility model discloses an in the example, the dabber includes first axis body, the second shaft body, and the third axis body, first axis body is connected with the one end of the second shaft body, and the third axis body is connected with the other end of the second shaft body, and the diameter of axle of first axis body is greater than the diameter of axle of third axis body.

Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the first shaft body and the third shaft body are respectively arranged at two ends of the second shaft body, so that a finished mandrel is formed, and the assembly is simple. After the gypsum of the surface of the engine shell core mold is formed, demolding is carried out on the gypsum, the core shaft is drawn out from the mold body towards the direction of the first end, the shaft diameter of the first shaft body is larger than that of the third shaft body, the third shaft body can be drawn out quickly, the shaft is drawn out more conveniently, and demolding speed is improved.

Drawings

Fig. 1 is a schematic structural diagram of an engine case core mold according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of fig. 1.

Fig. 3 is a partially enlarged view of the area a in fig. 2.

Fig. 4 is a schematic structural view of a positioning flange provided by an embodiment of the present invention.

Fig. 5 is a schematic structural view of the positioning flange installed on the mandrel according to an embodiment of the present invention.

Fig. 6 is a schematic structural view illustrating a mold body mounted on a mandrel according to an embodiment of the present invention.

Fig. 7 is a partially enlarged view of the area B in fig. 6.

Fig. 8 is a first schematic structural diagram of a mold body according to an embodiment of the present invention.

Fig. 9 is a partially enlarged view of the region C in fig. 8.

Fig. 10 is a schematic structural diagram of a mold body according to an embodiment of the present invention.

Fig. 11 is a partially enlarged view of a region D in fig. 10.

Fig. 12 is a schematic structural diagram of a mandrel according to an embodiment of the present invention.

Description of reference numerals:

10-a mold body; 11-a first valve component; 12-a separator; 13-a second valve component; 20-a mandrel; 20 a-a first end; 20 b-a second end; 21-a first shaft body; 22-a second shaft body; 23-third shaft body; 30-a positioning flange; 31-a first part; 32-a second part; 33-a third part; 34-fourth section; 35-a first via; 36-a second via; 40-a locking sleeve; 50-shaft sleeve; 60-a limit ring; 61-a first stop collar; 62-a second stop collar; 63-anchor ear nuts; 70-a positioning ring; 70 a-a first positioning ring; 70 b-a second positioning ring; 71-a connecting ring; 72-a connecting rod; 80-a head assembly; 81-end enclosure body; 82-a connector; 83-a housing; 84-a fixed ring; 90-shell plate; 100-engine housing core mold.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below.

The first embodiment is as follows:

referring to fig. 1 to 3, the present invention provides an engine case core mold 100, including: a mold body 10; the mold body 10 is mounted on the mandrel 20, the axial diameter of the first end 20a of the mandrel 20 is larger than that of the second end 20b of the mandrel 20, the second end 20b is provided with the positioning flange 30, the positioning flange 30 is connected with the mold body 10, and the mandrel 20 penetrates through the mold body 10.

Specifically, when the core mold 100 of the engine housing is assembled, the core shaft 20 is firstly placed on the installation table, and the positioning flange 30 is installed at the second end 20b of the core shaft 20, so as to serve as a starting point for installing each installation plate of the mold body 10, thereby facilitating the assembly. After the die body 10 and the mandrel 20 are assembled, the mandrel 20 penetrates through the die body 10, the mandrel 20 is rotated at a constant speed, and the die body 10 rotates along with the mandrel 20, so that gypsum slurry which is uniformly stirred is conveniently blade-coated on the outer surface of the die body 10. When the core mold 100 of the engine case is demolded, the operation of the case exterior is performed first, and the operator removes the connecting member of the first end 20a close to the mold body 10, and then removes the mounting plate of the mold body 10 close to the first end 20a, so that the operator can enter the interior of the mold body 10 to perform the removal operation. The positioning flange 30 installed on the mandrel 20 is removed, the second end 20b is disconnected from the die body 10, and the shaft diameter of the first end 20a is larger than that of the second end 20b, so that the second end 20b moves towards the first end 20a when the shaft is drawn out, the shaft diameter of the second end 20b is smaller, the second end can be drawn out from the inside of the die body 10 quickly, the shaft can be taken out more conveniently and quickly, time and labor are saved, and the demolding speed is increased.

Example two:

referring to fig. 4 and 5, the positioning flange 30 includes a first portion 31, a second portion 32, a third portion 33 and a fourth portion 34, wherein the first portion 31, the second portion 32, the third portion 33 and the fourth portion 34 are connected by a locking sleeve 40, and the locking sleeve 40 is sleeved on the positioning flange 30.

Specifically, compare in the flange of ordinary complete shape, it need take out from the outermost end of axle when dismantling, and other connecting pieces still are installed to the epaxial, just need demolish other connecting pieces earlier this moment, just can take out the flange from the axle, and is comparatively troublesome. The positioning flange 30 of the embodiment is divided into four halves, namely a first part 31, a second part 32, a third part 33 and a fourth part 34, which are spliced to form a flange with a complete shape, and the flange can be directly separated from a shaft during disassembly, so that the shaft can be more conveniently pulled out. The locking sleeve 40 is sleeved on the positioning flange 30, so that the connection among the first part 31, the second part 32, the third part 33 and the fourth part 34 is more stable and is not easy to shift.

Specifically, the positioning flange 30 is provided with a plurality of first through holes 35, the positioning flange 30 is connected with the die body through screws, the positioning flange 30 is provided with an annular structure and a cylindrical structure after being assembled, the annular structure surrounds the cylindrical structure, the first through holes 35 are formed in the annular structure, and the annular structure is located in the die body. When the shaft is drawn out, the connecting screws of the positioning flange 30 and the mandrel 10 can be screwed off, so that the friction between the shaft and the mandrel 10 is reduced, and the shaft is drawn out and the mold is removed more easily.

Further, the positioning flange 30 is provided with a key groove, and correspondingly, the joint of the mandrel 20 and the positioning flange 30 is provided with a key groove, so that the two can be connected through a flat key, and the connection stability is further enhanced.

Example three:

referring to fig. 5, the positioning flange 30 is mounted to the spindle 20 by radial screws.

Specifically, on the basis of the second embodiment, the positioning flange 30 is provided with a plurality of second through holes 36, the second through holes 36 are arranged on the cylindrical structure, and the radial screws are arranged in the second through holes 36, so that the positioning flange 30 is arranged on the mandrel 20, and the second embodiment is simple in structure, convenient to install and stable in connection.

Example four:

referring to fig. 5, the second end 20b is provided with a bushing 50, and both sides of the bushing 50 are provided with a retainer ring 60.

Specifically, because the shaft diameter of the second end 20b is small, in order to enhance the connection strength thereof, the shaft sleeve 50 is installed at the second end 20b, the shaft sleeve 50 is sleeved on the mandrel 20, the limiting rings 60 are installed on two sides of the shaft sleeve 50, the inner diameter of the limiting ring 60 is matched with the shaft diameter of the mandrel 20, and then the limiting ring 60 can be sleeved on the mandrel 20, so that the installation is convenient, the limiting ring 60 can fix the shaft sleeve 50, and the displacement of the shaft sleeve 50 is prevented.

Example five:

referring to fig. 5, the stop collar 60 includes a first stop collar 61 and a second stop collar 62, and the first stop collar 61 and the second stop collar 62 are connected by a hoop nut 63.

Specifically, the inner diameter of the retainer ring 60 is adapted to the shaft diameter of the mandrel 20, and the inner diameters of the retainer rings 60 on both sides of the shaft sleeve 50 are not the same. First spacing ring 61 and second spacing ring 62 are installed in the relative both sides of dabber 20, first spacing ring 61 and second spacing ring 62 adaptation, first spacing ring 61 and second spacing ring 62 are provided with the through-hole respectively, through the staple bolt nut, realize connecting first spacing ring 61 and second spacing ring 62, make it can be close lock on dabber 20, staple bolt nut 63 connects firmly, simple to operate and be difficult for droing, and then improved the steadiness of spacing ring 60 and the 50 structures of axle sleeve.

Example six:

referring to fig. 6 and 7, the mold body 10 includes a first valve component 11, a partition 12 and a second valve component 13, the partition 12 is installed between the first valve component 11 and the second valve component 13, the first valve component 11 is installed at the first end 20a, the second valve component 13 is installed at the second end 20b, and the positioning flange 30 is connected with the second valve component 13.

Specifically, on the basis of the second embodiment, the first valve assembly 11 is an eight-valve, the second valve assembly is an eight-valve, the positioning flange 30 is connected with the second valve assembly 13 through screws, the second valve assembly 13 is sequentially mounted on the positioning flange 30 around the positioning flange 30, the partition plate 12 is sequentially mounted close to the second valve assembly 13 until the partition plate is mounted on the first valve assembly 11, namely, the mounting of the innermost mounting plate of the die body 10 is completed, the mounting is simple, and errors are not prone to occurring in the mounting process.

Specifically, the locking sleeve 40 is installed at both ends of the mandrel 20, a through hole is formed in one side, close to the locking sleeve 40, of the first valve component 11 and the second valve component 13, the locking sleeve 40 is correspondingly provided with a through hole, the locking sleeve 40 is connected with the first valve component 11 and the second valve component 13 through screws, and the connection strength between the mandrel 20 and the die body 10 is further enhanced.

Example seven:

referring to fig. 6 and 7, the mandrel 20 is spaced apart by a positioning ring 70, the positioning ring 70 is mounted by a connecting ring 71, and the first valve assembly 11, the separator plate 12 and the second valve assembly 13 are mounted to the connecting ring 71.

Specifically, on the basis of the sixth embodiment, the positioning rings 70 are uniformly installed on the mandrel 20 at intervals, the positioning rings 70 include a first positioning ring 70a and a second positioning ring 70b, and the first positioning ring 70a and the second positioning ring 70b are connected by a hoop nut, so that the positioning rings 70 are convenient to install and detach.

Specifically, the positioning ring 70 further includes a connecting rod 72, the connecting rod 72 is connected to the connecting ring 71 through a screw, and the positioning ring 70 is connected to the connecting ring 71.

Specifically, the first valve component 11, the partition plate 12 and the second valve component 13 are provided with through holes, and the connection ring 71 is provided with through holes in a matching manner, so that the first valve component 11, the partition plate 12 and the second valve component 13 are mounted on the connection ring 71 through screws, and the valve assembly is convenient to mount and stable in structure.

The positioning rings 70 are arranged on the mandrel 20 at intervals, so that the mounting positions of the first valve assembly 11, the partition plate 12 and the second valve assembly 13 are positioned, the connecting ring 71 is arranged on the positioning rings 70, the connecting ring 71 plays a role in connecting the die body and the mandrel 20, an operator can directly mount the first valve assembly 11, the partition plate 12 and the second valve assembly 13 on the connecting ring 71, and the mounting is convenient and is not prone to error.

Example eight:

referring to fig. 8 and 9, the die body further includes a sealing head assembly 80 and a shell plate 90, the sealing head assembly 80 includes a sealing head body 81 and a connecting member 82, the sealing head body 81 is connected with the shell plate 90, the sealing head body 81 is installed on one side of the connecting member 82, and the connecting member 82 is sleeved on the positioning flange 30.

Specifically, the sealing head assembly 80 and the shell plate 90 are mounted outside the first valve assembly 11, the partition plate 12 and the second valve assembly 13, so that the inner structure of the mold body is firmer and is not easy to loosen in use. The connecting piece 82 is sleeved on the positioning flange 30, the end socket body 81 is installed on one side of the connecting piece 82, the end socket body 81 is clamped between the positioning flange 30 and the connecting piece 82, and the end socket body 81 is installed on the mandrel 20 and is firm in structure.

Specifically, the head body 81 is installed outside the first valve assembly 11 and the second valve assembly 13, the shell plate 90 is installed outside the partition plate 12, the connecting piece 82 is installed between the positioning flange 30 and the locking sleeve 40, the connecting piece 82 is provided with a plurality of through holes in a surrounding manner, correspondingly, one side of the locking sleeve 40, which is close to the first valve assembly 11 and the second valve assembly 13, is provided with a plurality of through holes, the connecting piece 82 is connected with the first valve assembly 11 and the second valve assembly 13 through screws, the locking sleeve is connected with the connecting piece 82 and the second valve assembly 13, and the connection between the die body and the positioning flange 30 is more stable.

Example nine:

referring to fig. 9 to 11, the shell 83 is mounted on the exterior of the head body 81, the shell 83 is mounted on the other side of the connecting member 82, and the shell 83 is connected to the shell plate 90.

Specifically, on the basis of the eighth embodiment, the connecting piece 82 is of a boss structure, the edge of the connecting piece extends outwards, the shell 83 can be buckled with the extending part and is connected with the shell plate 90, the installation is convenient, and the shell 83 can prevent the end socket body 81 from falling off, so that the structural stability is better.

Further, referring again to fig. 1, a fixing ring 84 is installed at the joint of the outer shell 83 and the shell plate 90, and the fixing ring 84 can further enhance the connecting strength of the two.

Example ten:

referring to fig. 12, the mandrel 20 includes a first shaft body 21, a second shaft body 22, and a third shaft body 23, the first shaft body 21 is connected to one end of the second shaft body 22, the third shaft body 23 is connected to the other end of the second shaft body 22, and the diameter of the first shaft body 21 is greater than the diameter of the third shaft body 23.

Specifically, the diameter of the second shaft 22 is greater than the diameters of the first shaft 21 and the third shaft 23, mounting holes are formed at two ends of the second shaft 22, the diameter of the second shaft 22 is matched with the diameters of the first shaft 21 and the third shaft 23, so that the first shaft 21 and the third shaft 23 are respectively mounted in the mounting holes, and the first shaft 21 and the third shaft 23 are respectively mounted at two ends of the second shaft 22, thereby forming the finished spindle 20, and the assembly is simple.

Further, the first shaft body 21, the second shaft body 22 and the third shaft body 23 are respectively provided with a key groove, the first shaft body 21 is connected with the second shaft body 22 through a flat key, and the third shaft body 23 is connected with the second shaft body 22 through a flat key, so that a complete mandrel 20 is formed.

Or, the first shaft body 21, the second shaft body 22 and the third shaft body 23 are integrally formed, so that the processing is convenient, the connection is stable, the installation among the three parts is not needed, and the installation steps of the mandrel 20 are reduced.

Referring to fig. 1 again, after the gypsum on the outer surface of the engine case core mold 100 is formed, to remove the gypsum, the core shaft 20 is removed from the mold body 10, and at this time, the core shaft 20 is removed from the mold body 10 toward the first end 20a, and since the shaft diameter of the first shaft body 21 is greater than that of the third shaft body 23, the third shaft body 23 can be removed quickly, the shaft can be removed more conveniently, and the mold removal speed is increased.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected by one skilled in the art without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims (10)

1. An engine case core mold, comprising:

a mold body (10);

the die body (10) is arranged on the mandrel (20), the shaft diameter of a first end (20 a) of the mandrel (20) is larger than that of a second end (20 b) of the mandrel, a positioning flange (30) is arranged at the second end (20 b), the positioning flange (30) is connected with the die body (10), and the mandrel (20) penetrates through the die body (10).

2. The engine housing core mold of claim 1, wherein the locating flange (30) comprises a first portion (31), a second portion (32), a third portion (33) and a fourth portion (34), the first portion (31), the second portion (32), the third portion (33) and the fourth portion (34) being connected by a locking sleeve (40), the locking sleeve (40) being sleeved to the locating flange (30).

3. The engine housing core mold of claim 1, wherein the locating flange (30) is mounted to the core shaft (20) by radial screws.

4. The engine housing core mold of claim 1, wherein the second end (20 b) mounts a bushing (50), and stop rings (60) are mounted on either side of the bushing (50).

5. The engine housing core mold as set forth in claim 4, characterized in that the retainer ring (60) comprises a first retainer ring (61) and a second retainer ring (62), the first retainer ring (61) and the second retainer ring (62) being connected by a hoop nut (63).

6. The engine housing core mold of claim 1, wherein the mold body (10) comprises a first valve component (11), a spacer (12) and a second valve component (13), the spacer (12) being mounted between the first valve component (11) and the second valve component (13), the first valve component (11) being mounted at the first end (20 a), the second valve component (13) being mounted at the second end (20 b), the positioning flange (30) being coupled to the second valve component (13).

7. The engine housing core mold of claim 6, wherein the mandrel (20) is spaced apart by a retaining ring (70), the retaining ring (70) is mounted by a connecting ring (71), the first valve assembly (11), the baffle plate (12) and the second valve assembly (13) are mounted by the connecting ring (71).

8. The engine shell core mold as recited in claim 6, wherein the mold body (10) further comprises a head assembly (80) and a shell plate (90), the head assembly (80) comprises a head body (81) and a connecting piece (82), the head body (81) is connected with the shell plate (90), the head body (81) is mounted on one side of the connecting piece (82), and the connecting piece (82) is sleeved on the positioning flange (30).

9. The engine housing core mold as set forth in claim 8, characterized in that an outer shell (83) is installed to an outside of the head body (81), the outer shell (83) is installed to the other side of the connecting member (82), and the outer shell (83) is connected to the shell plate (90).

10. The engine housing core mold according to claim 1, characterized in that the mandrel (20) comprises a first shaft body (21), a second shaft body (22), and a third shaft body (23), the first shaft body (21) is connected with one end of the second shaft body (22), the third shaft body (23) is connected with the other end of the second shaft body (22), and the shaft diameter of the first shaft body (21) is larger than the shaft diameter of the third shaft body (23).

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