Diaphragm pump with reversing structure

Abstract

The utility model is applicable to the technical field of diaphragm pumps, and provides a diaphragm pump with a reversing structure, which comprises a pump body and a reversing valve casing, the pump body consists of a main body and diaphragm cavity casings arranged at two ends of the main body, a shaft core cavity penetrating to two ends is arranged in the main body, a shaft core is arranged in the shaft core cavity in a reciprocating motion manner, and the reversing valve casing is arranged in the shaft core cavity. A piston cavity penetrating to the two ends is formed in the reversing valve shell. According to the diaphragm pump with the reversing structure, a plurality of air holes are formed in the reversing valve shell and the main body, and compressed air is communicated with the diaphragm pump main body through the air holes, so that the piston and the shaft core do reciprocating motion, automatic reversing is achieved, diaphragms at the two ends are driven to stir repeatedly, liquid suction and liquid discharge are achieved, and combined work is ingeniously achieved; the whole device is only provided with two movable parts, namely the piston and the shaft core, so that the whole mechanical structure is simple, the stability is high, faults are not prone to occurring, the number of quick-wear parts is small, the production and manufacturing cost is low, maintenance is convenient, and the fault rate is low.

Description

Technical Field

[0001] The utility model belongs to the technical field of diaphragm pumps, and particularly relates to a diaphragm pump with a commutation structure. Background Art

[0002] An air-operated diaphragm pump is a positive-displacement pump used for transporting fluids or powders. It uses compressed air as the power to push the diaphragm to move. Once it reaches the limit position, the compressed air distribution valve automatically changes the inlet and outlet directions of the compressed gas, thereby changing the movement direction of the diaphragm, making it continuously reciprocate. Then, with the cooperation of four one-way valves in the inlet and outlet pipes, the purpose of pumping the medium is achieved. It is a very widely used pump.

[0003] The working principle of the existing air-operated diaphragm pump is that after high-pressure gas enters the air valve chamber, it enters one of the two air chambers through the commutation valve slider, causing the diaphragm in this air chamber to bulge to the maximum stroke. The two diaphragms are connected by a connecting rod shaft. When one side reaches the maximum stroke, the other diaphragm is pulled to the minimum stroke. When the diaphragm is pulled to the minimum stroke, the pressing plate connected to it will push the assisting rod to drive the assisting rod slider, and the assisting rod slider is a commutation device that controls the commutation valve slider. It makes the commutation valve slider slide to change the connection of the high-pressure gas to the other air chamber, and this is taken as a cycle to achieve the purpose of continuously sliding left and right.

[0004] This commutation structure of the diaphragm pump has more components, and both the manufacturing cost and the installation cost are relatively high. At the same time, due to the complex mechanical structure and more moving parts, during the operation of the device, if any component fails, it will cause the diaphragm pump to not work properly, resulting in more complex equipment maintenance and higher failure rates. Summary of the Utility Model

[0005] The utility model provides a diaphragm pump with a commutation structure, aiming to solve the problems of more moving parts in the commutation mechanism of the existing diaphragm pump, relatively high manufacturing cost and installation cost, more complex equipment maintenance, and higher failure rates.

[0006] The utility model is realized as follows. A diaphragm pump with a commutation structure includes a pump body and a commutation valve housing, which are composed of a main body and diaphragm chamber shells arranged at both ends of the main body. An axial core cavity penetrating through both ends is arranged inside the main body, and an axial core that can reciprocate is arranged in the axial core cavity. The commutation valve housing is arranged on one side surface of the main body, and a piston cavity penetrating through both ends is arranged inside the commutation valve housing. A piston that can reciprocate is arranged in the piston cavity. The piston and the axial core are parallel to each other in space and their movement directions are perpendicular to each other.

[0007] An air inlet hole penetrating through to the piston cavity is formed at the top of the reversing valve housing. Air holes a, b, c, and d penetrating through to the piston cavity are formed at the bottom of the reversing valve housing. Air holes h and i penetrating through to the shaft core cavity are formed at the top of the main body. Air holes f and g extending inward are further formed at the top of the main body. When the reversing valve housing is fixedly installed on the main body, air hole a communicates with air hole f, air hole b communicates with air hole g, air hole i communicates with air hole c, and air hole d communicates with air hole h;

[0008] Air holes j and k are formed by inward indentation at the left end of the main body, and air holes m and r are formed by inward indentation at the right end of the main body. The inner end of air hole f communicates with the inner end of air hole j, air hole g communicates with the inner end of air hole r, the inner end of air hole k communicates with an air hole o extending to the right end of the main body, and the inner end of air hole m communicates with an air hole n extending to the left end of the main body.

[0009] Preferably, end caps are provided at both ends of the reversing valve housing, and a first elastic seal and a second elastic seal are respectively arranged between the two end caps and the end faces of the reversing valve housing.

[0010] Preferably, through holes are formed through the first elastic seal and the end cap at the same end, and a starting bolt capable of pushing the piston is slidably arranged in the through holes.

[0011] Preferably, first convex rings are respectively arranged at both ends of the piston. A first installation groove in the shape of a ring is formed on the outer ring surface of the first convex ring. A first O-ring and a first polytetrafluoroethylene ring are sleeved in the first installation groove from the inside to the outside.

[0012] Preferably, second convex rings are respectively arranged at both ends of the surface of the shaft core. A second installation groove in the shape of a ring is formed on the outer ring surface of the second convex ring. A second O-ring and a second polytetrafluoroethylene ring are sleeved in the second installation groove from the inside to the outside.

[0013] Preferably, shaft sleeves are respectively arranged at both ends of the surface of the shaft core. An inner O-ring is arranged between the shaft sleeve and the surface of the shaft core. An outer O-ring is arranged on the outer ring surface of the shaft sleeve. Annular grooves are respectively arranged at both ends of the inner cavity of the shaft core cavity, and elastic retaining rings for blocking the shaft sleeves are arranged in the annular grooves.

[0014] Preferably, a gasket is arranged between the bottom of the reversing valve housing and the top of the main body, and a plurality of ventilation holes are correspondingly formed on the gasket.

[0015] Preferably, an exhaust hole penetrating through to the shaft core cavity is formed in the middle of the bottom of the main body, and an exhaust silencer is arranged in the exhaust hole.

[0016] Beneficial effects

[0017] Compared with the prior art, the beneficial effects of the present utility model are as follows: A diaphragm pump with a commutation structure of the present utility model is provided with a plurality of air holes on the commutation valve housing and the main body. Compressed air is communicated with the diaphragm pump main body through the plurality of air holes, so that the piston and the shaft core reciprocate, realizing automatic commutation, driving the diaphragms at both ends to repeatedly agitate to realize liquid suction and liquid discharge, and ingeniously realizing combined work. There are only two moving parts, namely the piston and the shaft core, in the whole device. The overall mechanical structure is simple, with high stability, not easy to malfunction, very few vulnerable parts, low production and manufacturing costs. Due to the use of the Gleitring design for the shaft center and the piston, it can achieve oil-free self-lubrication, not get stuck when encountering water, self-compensate for wear, and the later maintenance cost is also very low, easy to maintain, and the failure rate is low. Description of the Drawings

[0018] Figure 1 It is a three-dimensional exploded view of the structure of the present utility model from the left front side perspective;

[0019] Figure 2 For the present utility model Figure 1 The structure schematic diagram after assembly from the perspective;

[0020] Figure 3 It is a three-dimensional distribution schematic diagram of the main body and the commutation valve housing of the present utility model from the right rear side perspective;

[0021] Figure 4 It is the left view of the present utility model;

[0022] Figure 5 It is the right view of the present utility model;

[0023] Figure 6 For Figure 5 The sectional view at A-A in;

[0024] Figure 7 For Figure 5 The sectional view at B-B in.

[0025] In the figure: 1 - main body, 2 - diaphragm chamber housing, 3 - reversing valve housing, 4 - piston, 5 - first convex ring, 6 - first O-ring, 7 - first polytetrafluoroethylene ring, 8 - shaft core, 9 - second convex ring, 10 - second O-ring, 11 - second polytetrafluoroethylene ring, 12 - bushing, 13 - outer O-ring, 14 - inner O-ring, 15 - snap ring, 16 - exhaust hole, 17 - exhaust muffler, 18 - gasket, 19 - first elastic seal cover, 20 - end cover, 21 - starting bolt, 22 - air inlet hole, 23 - air hole a, 24 - air hole b, 25 - air hole c, 26 - air hole d, 27 - air hole f, 28 - air hole g, 29 - air hole h, 30 - air hole i, 31 - air hole j, 32 - air hole k, 33 - air hole m, 34 - air hole n, 35 - air hole o, 36 - air hole r, 37 - second elastic seal cover. Detailed implementation mode

[0026] In order to make the objectives, technical solutions and advantages of the present utility model clearer and more understandable, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0027] Please refer to Figures 1-7 , the present utility model provides a technical solution: a diaphragm pump with a reversing structure, including a pump body composed of a main body 1 and diaphragm chamber housings 2 arranged at both ends of the main body 1 and a reversing valve housing 3. A shaft core cavity penetrating through both ends is arranged in the main body 1, and a shaft core 8 that can reciprocate is arranged in the shaft core cavity. The reversing valve housing 3 is arranged on one side surface of the main body 1, a piston cavity penetrating through both ends is arranged in the reversing valve housing 3, and a piston 4 that can reciprocate is arranged in the piston cavity. The piston 4 and the shaft core 8 are parallel to each other in space and the movement directions are perpendicular to each other.

[0028] The diaphragm chamber housing 2 is disc-shaped, and an outer shell can be installed on the outside to form a diaphragm air chamber for accommodating a diaphragm. The diaphragm is reciprocally pushed, and thus reciprocating motion can be achieved, and reciprocating suction and discharge of liquid can be realized. The diaphragm air chambers a and b are respectively at the left and right ends.

[0029] Both ends of the shaft core 8 are respectively connected to a diaphragm and move synchronously.

[0030] An air inlet hole 22 penetrating through to the piston cavity is formed at the top of the reversing valve housing 3. Air holes a23, b24, c25, and d26 penetrating through to the piston cavity are formed at the bottom of the reversing valve housing 3. An air hole h29 and an air hole i30 penetrating through to the core cavity are formed at the top of the main body 1. Air holes f27 and g28 extending inward are further formed at the top of the main body 1. When the reversing valve housing 3 is fixedly installed on the main body 1, the air hole a23 communicates with the air hole f27, the air hole b24 communicates with the air hole g28, the air hole i30 communicates with the air hole c25, and the air hole d26 communicates with the air hole h29; the positions of the air hole c25 and the air hole i30 are misaligned, but there is a ventilation groove formed in the reversing valve housing 3, and the ventilation groove covers the position of the air hole i30, so that the air hole i30 communicates with the air hole c25, and the way that the air hole d26 communicates with the air hole h29 is the same.

[0031] The air inlet hole 22 is located at the middle position of the top of the reversing valve housing 3.

[0032] An air hole j31 and an air hole k32 are formed by inwardly opening at the left end of the main body 1, and an air hole m33 and an air hole r36 are formed by inwardly opening at the right end of the main body 1. The inner end of the air hole f27 communicates with the inner end of the air hole j31, the air hole g28 communicates with the inner end of the air hole r36, the inner end of the air hole k32 communicates with an air hole o35 extending to the right end of the main body 1, and the inner end of the air hole m33 communicates with an air hole n34 extending to the left end of the main body 1.

[0033] In this embodiment, the lengths of the air holes k32 and m33 are slightly less than the length of the main body 1, and the inner ends extend to the inside of the other end of the main body 1. The air holes n34 and o35 are respectively located at both ends of the main body 1.

[0034] The lengths of the air holes j31 and r36 are about half of the length of the main body 1, and the air holes g28 and f27 are respectively located at the middle positions of the main body 1.

[0035] The axes of the air holes k32 and m33 are respectively at both ends of a straight line where a diameter of the core cavity is located, and the axes of the air holes j31 and r36 are respectively at both ends of a straight line where a diameter of the core cavity is located.

[0036] First convex rings 5 are respectively arranged at both ends of the piston 4. An annular first installation groove is formed on the outer ring surface of the first convex ring 5. A first O-ring 6 and a first polytetrafluoroethylene ring 7 are sleeved from the inside to the outside in the first installation groove. The first O-ring 6 and the first polytetrafluoroethylene ring 7 form a first Gleitring. The Gleitring is a double-acting piston seal, with low friction, no creep, small starting force, and high pressure resistance.

[0037] Two first convex rings 5 make the piston 4 form a barbell shape, with a gap between the middle part and the inner wall of the piston chamber, forming an intake chamber communicating with the intake hole 22. Both ends of the intake chamber are closed by the first convex rings 5. When the piston 4 moves to the end where the first elastic seal 19 is located, the air hole a23 is in this intake chamber and communicates with the intake hole 22. When the piston 4 moves to the end where the second elastic seal 37 is located, the air hole b24 is in this intake chamber and communicates with the intake hole 22.

[0038] The first Glide ring plays a sealing role, with its outer ring surface closely attached to the inner wall surface of the piston chamber, making the spaces on both sides of the first convex ring 5 not communicate with each other, and forming cavities respectively between the two ends of the piston 4 and the inner cavity of the piston chamber. When compressed air enters one end of the cavity, it will push the piston 4 to move to the other side.

[0039] The air hole c25 is at one end of the piston chamber close to the first elastic seal 19. When air flows in from the air hole c25, it will push the piston 4 towards the end of the second elastic seal 37. The air hole d26 is at one end of the piston chamber close to the second elastic seal 37. When air flows in from the air hole d26, it will push the piston 4 towards the end of the first elastic seal 19.

[0040] When the piston 4 moves to the maximum stroke, both ends will not completely block the air holes c25 and d26, which can ensure that spaces are formed at both ends for the intake of air through the air hole c25 or d26 to push the piston 4 to move.

[0041] At the same time, with the cooperation of the first O-ring 6 and the first polytetrafluoroethylene ring 7, the piston 4 can move smoothly in the piston chamber while maintaining sealing, with oil-free self-lubrication and no jamming in the presence of water, making the movement of the piston 4 more flexible.

[0042] End caps 20 are provided at both ends of the reversing valve housing 3. There are a first elastic seal 19 and a second elastic seal 37 respectively between the two end caps 20 and the end faces of the reversing valve housing 3.

[0043] Second convex rings 9 are provided at both ends of the surface of the shaft core 8. An annular second installation groove is provided on the outer ring surface of the second convex ring 9. A second O-ring 10 and a second polytetrafluoroethylene ring 11 are sleeved in the second installation groove from the inside to the outside.

[0044] The second O-ring 10 and the second polytetrafluoroethylene ring 11 form a second Glide ring, which has the same effect as the first Glide ring composed of the above-mentioned first O-ring 6 and the first polytetrafluoroethylene ring 7. Similarly, two cavities are formed in the shaft core chamber by the two groups of second convex rings 9. When compressed air enters one cavity, it will push the shaft core 8 to the other end.

[0045] Shaft sleeves 12 are respectively arranged at both ends of the surface of the shaft core 8. An inner O-ring 14 is arranged between the surface of the shaft sleeve 12 and the surface of the shaft core 8. An outer O-ring 13 is arranged on the outer ring surface of the shaft sleeve 12. Annular grooves are respectively arranged at both ends of the inner cavity of the shaft core cavity. Elastic retaining rings 15 for positioning the shaft sleeve 12 are arranged in the grooves.

[0046] The diameters at both ends of the shaft core cavity are increased to accommodate the shaft sleeve 12. The second polytetrafluoroethylene ring 11 is in close contact with the inner wall surface of the shaft core cavity and can move, achieving the effects of sealing and sliding. The elastic retaining ring 15 fixes the position of the shaft sleeve 12, making it unable to move.

[0047] The shaft sleeves 12 are arranged at both ends of the inner cavity of the shaft core cavity to support the shaft core 8, enabling the shaft core 8 to move freely within the shaft sleeves 12. At the same time, the outer ends of the air holes n34 and o35 are respectively located inside the two shaft sleeves 12. The gas discharged from the air holes n34 and o35 will be blocked by the shaft sleeves 12 and will not enter the diaphragm air cavities at both ends, but enter the shaft core cavity and the cavities at both ends of the shaft core 8, pushing the shaft core 8 to move towards the other end.

[0048] An exhaust hole 16 penetrating through to the inner cavity of the shaft core is opened in the middle of the bottom of the main body 1. An exhaust silencer 17 is arranged in the exhaust hole 16.

[0049] In the initial state, the piston 4 is at one end close to the first elastic seal cover 19, and the air hole a23 is located between the first convex rings 5 at both ends of the piston 4. This position forms an intake chamber a communicating with the intake hole 22. The air hole a23 communicates with this intake chamber a. After the compressed air enters the reversing valve housing 3 through the intake hole 22, it enters the air hole f27 of the main body 1 from the intake chamber a through the air hole a23 of the reversing valve housing 3, and then enters the air hole j31, thereby entering the diaphragm air chamber a at the left end of the main body 1, pushing the diaphragm at the left end to move outward, driving the shaft core 8 to move simultaneously. At the same time, the compressed air continuously entering the diaphragm air chamber a is blocked by the diaphragm, enters the air hole k32 at the left end of the main body 1 and then enters the air hole o35, and enters the right end cavity of the inner cavity of the shaft core chamber through the air hole o35, pushing the second convex ring 9 on the right side of the surface of the shaft core 8. Under the sliding effect between the second O-ring and the inner wall of the shaft core chamber, the shaft core 8 moves to the left to the maximum stroke. At this time, the second convex ring 9 on the right has moved leftward past the air hole i30, making the air hole i30 communicate with the right end cavity of the inner cavity of the shaft core chamber. The compressed air then enters the air hole c25 from the air hole i30 of the main body 1, pushing the piston 4 to move towards the second elastic seal cover 37. During this process, since the diaphragm air chamber a on the left side of the main body 1 contains compressed air and enters the air hole c25, the piston 4 will keep moving until it reaches the second elastic seal cover 37 and then stops. At this time, the air hole b24 is located between the first convex rings 5 at both ends of the piston 4. This position forms an intake chamber b communicating with the intake hole 22. The air hole b24 communicates with the intake chamber b. At this time, the intake hole 22 and the air hole b24 are conducted, and the compressed air enters the intake chamber b from the intake hole 22 of the reversing valve housing 3, passes through the air hole b24 to the air hole g28 of the main body and then enters the air hole r36 to push the diaphragm at the right end to move outward. At the same time, relying on the second O-ring installed on the shaft core 8, the shaft core 8 moves simultaneously. And the compressed air continuously entering the diaphragm air chamber b at the right end will enter the air hole m30 at the right end of the main body 1, and enter the left end of the shaft core chamber through the air hole n34, pushing the second convex ring 9 on the left side of the surface of the shaft core 8. Under the sliding effect between the second O-ring and the inner wall of the shaft core chamber, the shaft core 8 moves to the right to the maximum stroke, and the diaphragm on the left will move to the right. And at the same time during the process of the shaft core 8 moving to the right, the space of the diaphragm air chamber a decreases, and the stored compressed air passes through the air hole j31 and the air hole f27 of the main body 1 and comes to the air hole a23 of the reversing valve housing 3. At this time, since the piston 4 is at one end of the second elastic seal cover 37, the air hole a23 and the air hole c25 are both in a cavity at one end of the piston 4 and are connected. Since when the shaft core 8 moves to the right, the second O-ring on it also moves, the air hole i30 of the main body is conducted through the shaft core chamber and the exhaust hole 16. The compressed air enters the air hole i30 of the main body 1 from the air hole c25 of the reversing valve housing 3 and is discharged from the exhaust hole 16 of the main body 1. Under the continuous supply of compressed air, the above action process will regularly repeat continuously, realizing reciprocating motion and automatic commutation.

[0050] Through holes are formed in the first elastic cover 19 and the end cover 20 at the same end in a penetrating manner, and a starting bolt 21 capable of pushing the piston 4 is slidably arranged in the through holes.

[0051] The through hole in the first elastic cover 19 is a stepped hole, the inner end diameter of which is larger than the outer end diameter. A bolt head is arranged at the inner end of the starting bolt 21. Under normal circumstances, the bolt head is embedded in the inner end of the through hole under the action of compressed air and the piston 4 to achieve sealing. Since there is a small amount of moisture in the compressed air, when winter comes and the temperature drops, the moisture in the compressed air freezes, blocking the air holes of the reversing valve housing 3 and the main body 1, and the diaphragm pump may freeze. At this time, the starting bolt 21 can be pressed to forcibly push the piston 4 to move for manual forced start.

[0052] A gasket 18 is arranged between the bottom of the reversing valve housing 3 and the top of the main body 1. A plurality of ventilation holes are correspondingly formed in the gasket 18. The gasket 18 is a nylon gasket to improve the sealing effect at the joint.

[0053] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diaphragm pump with a reversing structure, characterized in that: The invention comprises a pump body and a reversing valve housing (3) composed of a main body (1) and a diaphragm chamber housing (2) arranged at both ends of the main body (1); the main body (1) is provided with an axial core chamber extending to both ends, and an axial core (8) is arranged in the axial core chamber so as to be reciprocatingly movable; the reversing valve housing (3) is arranged on one side of the main body (1); the reversing valve housing (3) is provided with a piston chamber extending to both ends, and a piston (4) is arranged in the piston chamber so as to be reciprocatingly movable; the piston (4) and the axial core (8) are parallel to each other in space and their movement directions are perpendicular to each other; The top of the reversing valve housing (3) is provided with an air inlet hole (22) penetrating into the piston cavity; the bottom of the reversing valve housing (3) is provided with air holes a (23), air holes b (24), air holes c (25), and air holes d (26) penetrating into the piston cavity; the top of the main body (1) is provided with air holes h (29) and air holes i (30) penetrating into the shaft core cavity; the top of the main body (1) is also provided with air holes f (27) and air holes g (28) extending inward; when the reversing valve housing (3) is fixedly mounted on the main body (1), the air holes a (23) are connected to the air holes f (27), the air holes b (24) are connected to the air holes g (28), the air holes i (30) are connected to the air holes c (25), and the air holes d (26) are connected to the air holes h (29); The left end of the main body (1) is provided with an air hole j (31) and an air hole k (32) inwardly, and the right end is provided with an air hole m (33) and an air hole r (36) inwardly, the inner end of the air hole f (27) is connected to the inner end of the air hole j (31), the air hole g (28) is connected to the inner end of the air hole r (36), the inner end of the air hole k (32) is connected to an air hole o (35) extending to the right end of the main body (1), and the inner end of the air hole m (33) is connected to an air hole n (34) extending to the left end of the main body (1).

2. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: End covers (20) are provided at both ends of the reversing valve housing (3), and a first elastic sealing cover (19) and a second elastic sealing cover (37) are respectively provided between the two end covers (20) and the end surface of the reversing valve housing (3).

3. A diaphragm pump with a reversing structure as claimed in claim 2, characterized in that: A through hole is formed through the first elastic sealing cover (19) and the end cover (20) at the same end, and a starter bolt (21) capable of pushing the piston (4) is provided in the through hole in a drawable manner.

4. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: The two ends of the piston (4) are respectively provided with a first convex ring (5), the outer ring surface of the first convex ring (5) is provided with a first annular installation groove, and the first installation groove is provided with a first O-ring (6) and a first polytetrafluoroethylene ring (7) from the inside to the outside.

5. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: A second convex ring (9) is provided at both ends of the surface of the shaft core (8), and an annular second mounting groove is provided on the outer ring surface of the second convex ring (9). A second O-ring (10) and a second polytetrafluoroethylene ring (11) are provided in the second mounting groove from the inside to the outside.

6. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: Axle sleeves (12) are respectively arranged at both ends of the surface of the shaft core (8), an inner O-ring (14) is arranged between the shaft sleeve (12) and the surface of the shaft core (8), and an outer O-ring (13) is arranged on the outer ring surface of the shaft sleeve (12).

7. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: A gasket (18) is provided between the bottom of the reversing valve housing (3) and the top of the main body (1), and a plurality of ventilation holes are correspondingly provided on the gasket (18).

8. A diaphragm pump with a reversing structure as claimed in claim 1, characterized in that: An exhaust hole (16) is provided in the middle of the bottom of the main body (1) and is connected to the shaft core cavity. An exhaust muffler (17) is provided in the exhaust hole (16).

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