Explosion-proof motor shell

Abstract

The utility model provides an explosion-proof motor housing, and belongs to the technical field of motors. The utility model solves the technical problem that the installation of the motor and the whole machine is affected because the positions of the junction box and the output end of the rotating shaft cannot be adjusted in the conventional explosion-proof motor shell. An explosion-proof motor housing comprises a left end cover, a housing body and a right end cover which are fixedly connected in sequence, the housing body is fixedly connected with a junction box, a rotating shaft is arranged in the housing body, one end of the rotating shaft extends out of the left end cover and is used for outputting power, and the other end of the rotating shaft extends out of the right end cover and is connected with heat dissipation fan blades. The left portion of the shell is provided with a left explosion-proof joint face matched with the left end cover, the right portion of the shell is provided with a right explosion-proof joint face matched with the right end cover, the left explosion-proof joint face and the right explosion-proof joint face are consistent in size, and the lower portion of the shell is detachably and fixedly connected with a machine foot base which is provided with a left through hole and a right through hole. The distance L1 between the left through hole and the left end face of the shell is equal to the distance L2 between the right through hole and the right end face of the shell. According to the utility model, the positions of the output end of the rotating shaft and the junction box can be adjusted to adapt to more installation positions.

Description

Technical Field

[0001] The utility model belongs to the technical field of motors, in particular to a flameproof motor casing. Background Art

[0002] The flameproof enclosure of a flameproof motor is composed of various flameproof components, including the housing, end caps, shaft, and junction box. The gaps between these components are formed by the flameproof joints, significantly reducing the spread of flames and lowering the temperature, preventing the explosive mixture outside the enclosure from igniting. To ensure flameproof performance, the maximum gap or diameter difference between the flameproof joints, the minimum effective length of the flameproof joints, the minimum effective length from the edge of the flameproof joint to the edge of the screw hole, and the smoothness of the flameproof joints are all subject to specified dimensional and precision requirements. However, in the prior art, the positional relationship between the junction box and the output end of the rotating shaft of the flameproof enclosure cannot be adjusted. This sometimes requires adjustment to meet different requirements. This adjustment requires the manufacture of a new flameproof enclosure, which is relatively expensive. If the installation of the motor and the entire machine is affected simply because the position of the junction box and the output end of the rotating shaft cannot be adjusted, the flameproof enclosure must be remade, which increases manufacturing costs. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a flameproof motor housing with adjustable positions of the shaft output end and the junction box.

[0004] The purpose of the utility model can be achieved through the following technical solutions: a flameproof motor casing, comprising a left end cover, a shell and a right end cover fixedly connected in sequence, a junction box fixedly connected to the shell, a rotating shaft arranged in the shell, one end of the rotating shaft extending out of the left end cover for outputting power, the other end of the rotating shaft extending out of the right end cover and connected to the heat dissipation fan blades, the left part of the shell having a left flameproof joint surface cooperating with the left end cover, the right part of the shell having a right flameproof joint surface cooperating with the right end cover, the sizes of the left flameproof joint surface and the right flameproof joint surface are consistent, the bottom of the shell is detachably fixedly connected to an organic foot, the machine foot has a left through hole and a right through hole, the distance L1 between the left through hole and the left end face of the shell is equal to the distance L2 between the right through hole and the right end face of the shell. The left and right end surfaces of the shell are set to be equal to the center distance of the left through hole and the right through hole on the machine foot respectively, so that both the left and right ends of the shell can be used as the output ends of the rotating shaft. Without re-making the mold to manufacture the motor housing, only the installation direction of the shell and the rotating shaft needs to be changed according to the scene requirements. The position of the output end of the rotating shaft and the junction box can be adjusted to adapt to more installation positions. This can save costs and ensure the stable installation of the overall structure.

[0005] Furthermore, the bottom of the housing is formed with a fixing block 1, a cylindrical block protruding downward from the lower portion of the fixing block, and a T-shaped block protruding upward from the side of the machine foot near the housing. The T-shaped block is provided with a fixing square hole that cooperates with the fixing block 1, and a stepped circular hole is passed through the middle of the fixing square hole. The fixing block 1 abuts against the bottom surface of the fixing square hole, and the cylindrical block is embedded in the stepped circular hole. A fastener passes through the stepped circular hole from the bottom and is threadedly connected to the cylindrical block. This makes it easier to manufacture the housing and the machine foot, and ensures that the housing is firmly fixed to the machine foot.

[0006] Furthermore, a plurality of fixing blocks 2 are symmetrically provided at the left and right ends of the shell, the left end cover is fastened to the fixing block 2 by bolts, and the right end cover is fastened to the fixing block 2 by bolts.

[0007] Furthermore, the end of the second fixing block away from the end face of the shell has a fixed T-slot, a nut is provided in the fixed T-slot, and the nut is restricted from rotating in the fixed T-slot.

[0008] Furthermore, the right end cover has a heat sink 2 at the end away from the shell, the heat dissipation blades are arranged relative to the heat sink 2, the right end cover is fixedly connected with a blade cover, and the outer periphery of the right end cover is protruding with several fixing blocks 3, the fixing blocks 3 are arranged corresponding to the fixing blocks 2 and are fixed by bolts and nuts, and the inner periphery of the blade cover is abutted and fixed to the outer periphery of the fixing block 3.

[0009] Furthermore, the housing is formed with a square seat on its upper portion, and a wiring bucket is provided on its side. The square seat has a mounting hole, the bottom of which communicates with the interior of the housing. A junction box is fixedly connected to the square seat. The lower end surface of the junction box is a second flameproof surface, and the upper end surface of the square seat is a first flameproof surface. The second flameproof surface abuts against the first flameproof surface. The abutment between the second flameproof surface and the first flameproof surface provides a better flameproof effect. Furthermore, since the cable is introduced into the junction box through the cable inlet, after the cable is connected, the rubber gasket is installed, and then the wiring bucket is installed and screwed, so that the end surface of the wiring bucket presses against the rubber ring, fully enclosing the cable. The cable inlet is generally located on one side of the motor relative to the radial direction of the motor shaft. To accommodate a wider range of cable installation positions, changing the shaft's installation orientation also changes the orientation of the cable inlet relative to the shaft's output end, allowing for more installation space.

[0010] Furthermore, a door cover is fixedly connected to the upper portion of the junction box. An annular flange 1 protrudes outward from the upper portion of the junction box. The upper end surface of the annular flange 1 serves as a flameproof surface 3. The inner circumference of the junction box near the annular flange 1 serves as a flameproof surface 4. The door cover has an annular flange 2 that cooperates with the annular flange 1. The lower end surface of the annular flange 2 serves as a flameproof surface 5. A cylindrical portion protrudes downward from the lower end surface of the annular flange 2. The outer circumference of the cylindrical portion serves as a flameproof surface 6. The cylindrical portion is embedded in the junction box. The flameproof surface 5 abuts against the flameproof surface 3, and the flameproof surface 6 abuts against the flameproof surface 4. This provides a better flameproof effect.

[0011] Furthermore, a cylindrical boss protrudes downward from the second explosion-proof surface of the junction box, and the cylindrical boss is embedded in the mounting hole.

[0012] Furthermore, a coaxial annular seat and a bearing seat are protruding inward from the middle of the left end cover, an annular groove is provided between the bearing seat and the annular seat, the inner circumference of the annular seat is in contact with the rotating shaft, an annular hole is protruding outward from the middle of the left end cover, the annular hole is connected to the annular seat on the same axis, and a seal is provided in the annular hole.

[0013] Furthermore, a coaxial annular seat 2 and a bearing seat 2 are protruding inward from the middle of the right end cover, an annular groove 2 is provided between the bearing seat 2 and the annular seat 2, the inner circumference of the annular seat 2 is in contact with the rotating shaft, and an annular hole 2 is protruding outward from the middle of the right end cover, the annular hole 2 is coaxially connected to the annular seat 2, and a seal 2 is provided in the annular hole 2.

[0014] Compared with the prior art, the technical effect of the present invention is as follows: the left and right end surfaces of the shell are set to be equal to the center distance of the left through hole and the right through hole on the machine foot, so that both the left and right ends of the shell can be used as the output ends of the rotating shaft. The installation direction of the shell and the rotating shaft can be changed according to the scene requirements. Without re-making the mold to manufacture the motor housing, the junction box can be adapted to more installation positions, which can save costs and ensure the stable installation of the overall structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This utility model is a cross-sectional view Figure 1 .

[0016] Figure 2 It is a bottom view of the housing and the machine base of the utility model.

[0017] Figure 3 It is a three-dimensional diagram of the machine foot of the utility model.

[0018] Figure 4 This utility model is a three-dimensional Figure 1 .

[0019] Figure 5 This utility model is a three-dimensional Figure 2 .

[0020] Figure 6 This utility model is a cross-sectional view Figure 2 .

[0021] Figure 7 It is a cross-sectional view of the junction box of the present utility model.

[0022] Figure 8 This utility model is a cross-sectional view Figure 3 .

[0023] Figure numbers: 1. Left end cap; 101. Annular seat 1; 102. Bearing seat 1; 103. Annular groove 1; 104. Annular hole 1; 2. Housing; 201. Left flameproof joint surface; 202. Right flameproof joint surface; 21. Heat sink 1; 22. Fixing block 1; 221. Cylindrical block; 23. Square seat; 231. Mounting hole; 232. Flameproof surface 1; 24. Fixing block 2; 241. Fixed T-slot; 3. Right end cap; 301. Annular seat 2; 302. Bearing seat 2; 303. Annular groove 2; 304. Annular hole 2; 305. Heat sink 2; 306 , fixing block three; 4, junction box; 401, explosion-proof surface two; 402, explosion-proof surface four; 41, cylindrical boss; 42, door cover; 43, circular flange one; 431, explosion-proof surface three; 44, circular flange two; 441, explosion-proof surface five; 45, cylinder; 451, explosion-proof surface six; 46, wiring bucket; 5, rotating shaft; 6, heat dissipation fan blade; 7, machine foot; 701, left through hole; 702, right through hole; 71, T-block; 711, fixing square hole; 712, step round hole; 8, seal one; 9, seal two; 10, fan blade cover; 11, nut; 12, wiring bucket. DETAILED DESCRIPTION

[0024] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0025] It should be noted that the descriptions of the present invention regarding directions such as "up", "down", "left", "right", "top" and "bottom" are all defined based on the relationship between the orientations or positions shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0026] Example 1: According to Figures 1 to 7As shown, a flameproof motor housing includes a left end cover 1, a shell 2, and a right end cover 3 fixedly connected in sequence, with a junction box 4 fixedly connected to the shell 2. A rotating shaft 5 is provided in the shell 2, one end of the rotating shaft 5 extends out of the left end cover 1 for outputting power, and the other end of the rotating shaft 5 extends out of the right end cover 3 and is connected to a heat dissipation fan 6. The left part of the shell 2 has a left flameproof joint surface 201 that cooperates with the left end cover 1, and the right part of the shell 2 has a right flameproof joint surface 202 that cooperates with the right end cover 3. The left flameproof joint surface 201 and the right flameproof joint surface 202 are both located at the two ends of the inner circumference of the shell 2, and the left flameproof joint surface 201 and the right flameproof joint surface 202 are of the same size, that is, the left flameproof joint surface 201 can be matched with the left end cover 1 or the right end cover 3, and the right flameproof joint surface 202 can also be matched with the left end cover 1 or the right end cover 3. Then, according to the external installation conditions, the output end of the rotating shaft 5 (the end for outputting power) can be selected to be set at the left end or the right end of the housing 2. Since the junction box 4 is fixed, the position of the junction box 4 can be changed with the different directions of the rotating shaft 5, which is conducive to the use in multiple scenarios and saves production costs. However, the machine feet of the housing 2 have strict size regulations, so the machine foot seat 7 is detachably fixed and connected below the housing 2, and a left through hole 701 and a right through hole 702 are set on the machine foot seat 7. A through hole can also be set between the left through hole 701 and the right through hole 702. The distance L1 between the left through hole 701 and the left end face of the housing 2 is equal to the distance L2 between the right through hole 702 and the right end face of the housing 2. This solution sets the housing 2 to be equal to the distance between the left through hole 701 and the right through hole 702 on the machine foot seat 7 and the left and right end faces of the housing 2, so that both the left and right ends of the housing 2 can serve as the output ends of the rotating shaft 5, so that the motor can be applied to multiple occasions and save production costs.

[0027] Several heat sinks 21 are protruded outward from the outer periphery of the shell 2. The heat sinks 21 are arranged horizontally and vertically. The maximum outer diameter of the heat sink 21 is greater than the maximum width between the two machine feet 7, which reduces the size of the entire machine. The detachable machine feet 7 and the shell 2 are easy to process. In order to make the shell 2 and the machine foot 7 more firmly connected. A fixed block 22 is formed at the bottom of the shell 2. A cylindrical block 221 protrudes downward from the lower part of the fixed block 22. A T-shaped block 71 protrudes upward from the side of the machine foot 7 close to the shell 2. A fixed square hole 711 is provided on the T-shaped block 71 to cooperate with the fixed block 22. A stepped circular hole 712 is passed through the middle of the fixed square hole 711. The fixed block 22 rests on the bottom surface of the fixed square hole 711. The cylindrical block 221 is embedded in the stepped circular hole 712. The fastener passes through the stepped circular hole 712 from the bottom and is threadedly fixed to the cylindrical block 221. The fastener can be a bolt.

[0028] An annular seat 101 and a bearing seat 102 protrude coaxially from the center of the left end cap 1. Bearing seat 102 is a stepped ring shaped housing for the bearing. An annular groove 103 is located between bearing seat 102 and annular seat 101. The inner circumference of annular seat 101 contacts the rotating shaft 5. An annular hole 104 protrudes outward from the center of the left end cap 1 and is coaxially connected to annular seat 101. A seal 8 is located within annular hole 104. A heat sink 3 protrudes outward from the exterior of the left end cap 1. The inner circumference of annular seat 101, where it contacts the rotating shaft 5, also serves as the first flameproof joint surface of the rotating shaft 5.

[0029] A coaxial annular seat 301 and a bearing seat 302 protrude inward from the center of the right end cap 3. The bearing seat 302 is a stepped ring shape, housing the bearing. An annular groove 303 is defined between the bearing seat 302 and the annular seat 301. The inner circumference of the annular seat 301 contacts the rotating shaft 5. A coaxial annular hole 304 protrudes outward from the center of the right end cap 3. The annular hole 304 is coaxially connected to the annular seat 301 and contains a seal 9. A heat sink 305 protrudes outward from the end of the right end cap 3 facing away from the housing 2. The heat dissipation blades 6 are positioned relative to the heat sink 305. The inner circumference of the annular seat 301, where it contacts the rotating shaft 5, also serves as the second flameproof joint surface of the rotating shaft 5.

[0030] Several fixing blocks 24 are symmetrically arranged at the left and right ends of the housing 2. The left end cover 1 is fastened to the fixing block 24 by bolts, and the right end cover 3 is fastened to the fixing block 24 by bolts. That is to say, when the output end of the rotating shaft 5 changes direction, it can also ensure that the left end cover 1 and the right end cover 3 can be fixed to the left and right ends of the housing 2. In addition, a fixing T-slot 241 is provided at the end of the fixing block 24 away from the end face of the housing 2. A nut 11 is provided in the fixing T-slot 241, and the nut 11 is restricted from rotating in the fixing T-slot 241. Bolts of different sizes axially pass through the left end cover 1 and the right end cover 3 as well as the fixing block 24 and are fixed to the nut 11. The fixing nut 11 can be restricted by the fixing T-slot 241, making it convenient to tighten the bolts.

[0031] Preferably, several fixing blocks 306 are formed protruding from the outer periphery of the right end cap 3. The fixing blocks 306 are arranged corresponding to the fixing blocks 24. Bolts axially pass through the fixing blocks 306 and 24 and are secured with nuts 11. The inner periphery of the fan cover 10 abuts against the outer periphery of the fixing blocks 306. Bolts of different sizes radially pass through the fan cover 10 and are threadedly secured to the fixing blocks 306. Of course, a fourth protruding block can also be formed protruding from the outer periphery of the right end cap 3. Bolts of different sizes radially pass through the fan cover 10 and are threadedly secured to the fourth protrusion.

[0032] A square seat 23 is formed on the upper portion of the housing 2. A wiring hopper 46 is fixedly attached to the side of the seat 23. A mounting hole 231 is formed within the seat 23. The bottom of the mounting hole 231 communicates with the interior of the housing 2. A small semicircular hole is drilled at the bottom of the mounting hole 231 where it connects to the interior of the housing 2 for threading the wiring. A junction box 4 is fixedly attached to the seat 23. The lower end of the junction box 4 forms a second flameproof surface 401. The upper end of the seat 23 forms a first flameproof surface 232. Flameproof surface 201 abuts against flameproof surface 232.

[0033] A door cover 42 is fixedly connected to the upper part of the junction box 4, and a circular flange 1 43 protrudes outward from the upper part of the junction box 4, and the upper end surface of the circular flange 1 43 is a flameproof surface 3 431, and the inner circumference of the junction box 4 near the circular flange 1 43 has a flameproof surface 402, and the door cover 42 has a circular flange 2 44 cooperating with the circular flange 1 43, and the lower end surface of the circular flange 2 44 is a flameproof surface 5 441, and a cylindrical portion 45 protrudes downward from the lower end surface of the circular flange 2 44, and the outer circumferential surface of the cylindrical portion 45 is a flameproof surface 6 451, and the cylindrical portion 45 is embedded in the junction box 4, and the flameproof surface 5 441 abuts against the flameproof surface 3 431, and the flameproof surface 6 451 abuts against the flameproof surface 402.

[0034] Example 2: According to Figure 8 As shown, a square seat 23 is formed on the upper portion of the housing 2, with a mounting hole 231 formed therein. The bottom of the mounting hole 231 communicates with the interior of the housing 2. A small semicircular hole is drilled at the bottom where the mounting hole 231 communicates with the interior of the housing 2 for threading. A junction box 4 is fixedly connected to the square seat 23 using bolts. A cylindrical boss 41 is integrally formed downwardly protruding from the lower end surface of the junction box 4, i.e., the second flameproof surface 401. The cylindrical boss 41 is inserted into the mounting hole 231 until the second flameproof surface 401 of the junction box 4 rests against the first flameproof surface 232 of the square seat 23.

[0035] The left and right end surfaces of the shell 2 are set to be equal to the center distance of the left through hole 701 and the right through hole 702 on the machine foot seat 7, so that both the left and right ends of the shell 2 can serve as the output ends of the rotating shaft 5. The installation direction of the shell 2 and the rotating shaft 5 can be changed according to the scene requirements. Without re-making the mold to manufacture the motor housing, the junction box 4 can be adapted to more installation positions. This is convenient for installation and saves costs, and can also ensure the stable installation of the overall structure.

[0036] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection defined by the claims of the present invention.

Claims

1. A flameproof motor housing, comprising a left end cover (1), a housing (2) and a right end cover (3) fixedly connected in sequence, a junction box (4) fixedly connected to the housing (2), a rotating shaft (5) provided in the housing (2), one end of the rotating shaft (5) extending out of the left end cover (1) for outputting power, and the other end of the rotating shaft (5) extending out of the right end cover (3) and connected to a heat dissipation fan blade (6), characterized in that: The left portion of the shell (2) has a left flameproof joint surface (201) that cooperates with the left end cover (1), and the right portion of the shell (2) has a right flameproof joint surface (202) that cooperates with the right end cover (3). The left flameproof joint surface (201) and the right flameproof joint surface (202) have the same size. An organic foot (7) is detachably fixedly connected below the shell (2). The organic foot (7) has a left through hole (701) and a right through hole (702). The distance L1 between the left through hole (701) and the left end face of the shell (2) is equal to the distance L2 between the right through hole (702) and the right end face of the shell (2).

2. The flameproof motor housing according to claim 1, characterized in that: The bottom of the shell (2) is formed with a fixing block (22), and a cylindrical block (221) protrudes downward from the lower part of the fixing block (22). A T-shaped block (71) protrudes upward from the side of the machine foot (7) close to the shell (2). The T-shaped block (71) is provided with a fixing square hole (711) that matches the fixing block (22). A stepped circular hole (712) is passed through the middle of the fixing square hole (711). The fixing block (22) is against the bottom surface of the fixing square hole (711), and the cylindrical block (221) is embedded in the stepped circular hole (712). A fastener passes through the stepped circular hole (712) from the bottom and is threadedly fixed to the cylindrical block (221).

3. The flameproof motor housing according to claim 2, characterized in that: A plurality of fixing blocks (24) are symmetrically provided at the left and right ends of the shell (2); the left end cover (1) is fastened to the fixing block (24) by bolts; and the right end cover (3) is fastened to the fixing block (24) by bolts.

4. The flameproof motor housing according to claim 3, characterized in that: The second fixed block (24) has a fixed T-slot (241) at one end away from the end surface of the housing (2). A nut (11) is provided in the fixed T-slot (241), and the nut (11) is restricted from rotating in the fixed T-slot (241).

5. The flameproof motor housing according to claim 4, characterized in that: The right end cover (3) has a heat sink 2 (305) at one end away from the housing (2), and the heat dissipation blades (6) are arranged relative to the heat sink 2 (305). The right end cover (3) is fixedly connected with a blade cover (10), and the outer periphery of the right end cover (3) is protruding with a plurality of fixing blocks 3 (306). The fixing blocks 3 (306) are arranged corresponding to the fixing blocks 2 (24) and are fixed by bolts and nuts (11). The inner periphery of the blade cover (10) abuts against and is fixed to the outer periphery of the fixing blocks 3 (306).

6. The flameproof motor housing according to any one of claims 1 to 5, characterized in that: A square seat (23) is formed on the upper part of the shell (2), and a wiring bucket (46) is also provided on the side of the square seat (23). A mounting hole (231) is provided in the square seat (23), and the bottom of the mounting hole (231) is connected to the interior of the shell (2). A junction box (4) is fixedly connected to the square seat (23), and the lower end surface of the junction box (4) is a second explosion-proof surface (401). The upper end surface of the square seat (23) is a first explosion-proof surface (232), and the second explosion-proof surface (401) is in contact with the first explosion-proof surface (232).

7. The flameproof motor housing according to claim 6, characterized in that: The upper portion of the junction box (4) is fixedly connected to a door cover (42), the upper portion of the junction box (4) is provided with an annular flange 1 (43) protruding outward, the upper end surface of the annular flange 1 (43) is a flameproof surface 3 (431), the inner circumferential surface of the junction box (4) close to the annular flange 1 (43) is provided with a flameproof surface 4 (402), the door cover (42) is provided with an annular flange 2 (44) matched with the annular flange 1 (43), The lower end surface of the annular flange 2 (44) is the explosion-proof surface 5 (441), and a cylindrical portion (45) protrudes downward from the lower end surface of the annular flange 2 (44). The outer peripheral surface of the cylindrical portion (45) is the explosion-proof surface 6 (451). The cylindrical portion (45) is embedded in the junction box (4), and the explosion-proof surface 5 (441) is in contact with the explosion-proof surface 3 (431), and the explosion-proof surface 6 (451) is in contact with the explosion-proof surface 4 (402).

8. The flameproof motor housing according to claim 6, characterized in that: A cylindrical boss (41) protrudes downward from the second explosion-proof surface (401) of the junction box (4), and the cylindrical boss (41) is embedded in the mounting hole (231).

9. The flameproof motor housing according to claim 1, characterized in that: The left end cover (1) has a coaxial annular seat (101) and a bearing seat (102) protruding inward from the middle portion thereof, an annular groove (103) being provided between the bearing seat (102) and the annular seat (101), the inner circumference of the annular seat (101) being in contact with the rotating shaft (5), an annular hole (104) protruding outward from the middle portion thereof, the annular hole (104) being coaxially connected to the annular seat (101), and a sealing member (8) being provided in the annular hole (104).

10. The flameproof motor housing according to claim 1, characterized in that: The middle part of the right end cover (3) protrudes inwardly with a coaxial annular seat 2 (301) and a bearing seat 2 (302), and an annular groove 2 (303) is provided between the bearing seat 2 (302) and the annular seat 2 (301). The inner circumference of the annular seat 2 (301) contacts the rotating shaft (5). The middle part of the right end cover (3) protrudes outwardly with an annular hole 2 (304), and the annular hole 2 (304) is coaxially connected to the annular seat 2 (301). A sealing member 2 (9) is provided in the annular hole 2 (304).

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