CN112648182A

CN112648182A - Double-end-face shaft sealing device

Info

Publication number: CN112648182A
Application number: CN202110018567.1A
Authority: CN
Inventors: 谭在良
Original assignee: Zhejiang Huatai Bangwei Pump Co ltd
Current assignee: Zhejiang Huatai Bangwei Pump Co ltd
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-04-13

Abstract

Providing two independent double-end-face shaft sealing devices of two groups of moving rings and static rings, wherein a machine seal inner cavity 4 is provided with a first moving ring 5 and a first static ring 6, a machine seal seat 3 is externally provided with a second moving ring 7 and a second static ring 8, and the contact surfaces of the moving rings and the contact surfaces of the static rings are mutually attached to form a friction pair; the closed end of the mechanical seal seat 3 is provided with a radial inner wall 9, the first movable ring 5 and the first static ring 6 are arranged on the inner side of the radial inner wall 9 of the pump, and the second movable ring 7 and the second static ring 8 are arranged on the outer side of the radial inner wall 9 of the pump; the radial inner wall 9 is provided with more than 2 pin holes 10, the stop pin 11 penetrates through the pin holes 10, and the first stationary ring 6 and the second stationary ring 8 are respectively positioned on two sides of the radial inner wall 9; make two sets of quiet rings independent separately, its pressure spring manages respective rotating ring separately, and when one side sealed the problem, the opposite side was not influenced yet to the shaft seal performance of impeller pump and the sealed life of shaft have been promoted remarkably.

Description

Double-end-face shaft sealing device

Technical Field

The invention relates to a double-end-face shaft sealing device, in particular to a double-end-face shaft sealing device for a rotor pump.

Background

Various delivery pumps or mixers need to be provided with a shaft sealing device, such as a rotor pump for delivering fluid materials, a mechanical shaft sealing device utilizes a compression spring to force a movable ring which moves along with a shaft and a static ring which is relatively static to be mutually attached to form a sealed revolute pair, and a gap at the periphery is sealed by a sealing ring. The pump during operation rotating ring and quiet ring friction, the machine that includes rotating ring and quiet ring and sealing washer all need bear the wearing and tearing that generate heat. Usually, a set of dynamic and static rings and compression springs thereof, also called single-end-face shaft sealing device, are adopted, and in order to enhance the sealing performance, two sets of dynamic and static rings and compression springs thereof, also called double-end-face shaft sealing device, can be adopted. The shaft seal of the pump is very important, and the shaft seal of the pump is always one of the key technologies; the shaft sealing performance of the lift pump and the service life of the shaft seal reduce the pollution of leakage to the environment, which is a long-sought goal of the technicians in the field.

The existing double-end-face shaft sealing device for the rotor pump, such as the double-end-face shaft sealing device disclosed in chinese patent document CN108843614A, has the following problems: 1. two groups of moving and static rings and compression springs thereof are in linkage relation, one side is sealed to cause a problem, and the other side is also followed to cause a problem. 2. Because the compression spring of the dynamic and static ring group on the material side is positioned outside the pump, the elastic direction of the compression spring is opposite to the pressure direction borne by the material, the material side cannot bear high pressure, and the sealing performance to the material with high viscosity is poor. 3. Two sets of sound ring groups all are located the quick-witted seal intracavity, and the installation is comparatively difficult.

Disclosure of Invention

The invention aims to solve the technical problem of providing a double-end-face shaft sealing device with two independent sets of dynamic and static rings.

The technical scheme adopted by the double-end-face shaft sealing device is as follows:

a double-end-face shaft sealing device comprises a machine seal seat which is sleeved outside a rotating shaft and fixedly connected with a pump body, wherein the outer side of a pump of the machine seal seat is a closed end with a smaller inner diameter, and a machine seal inner cavity is formed between the inner wall of the machine seal seat and the rotating shaft; the closed end of the machine seal seat is provided with a radial inner wall, the first movable ring and the first static ring are arranged on the inner side of the pump of the radial inner wall, and the second movable ring and the second static ring are arranged on the outer side of the pump of the radial inner wall; a pin hole is formed in the radial inner wall, the stop pin penetrates through the pin hole, the first stationary ring and the second stationary ring are respectively positioned on two sides of the radial inner wall, and two ends of the stop pin are respectively inserted into connecting notches of the first stationary ring and the second stationary ring; the pump inner side of the first rotating ring is provided with a first compression spring and a first rotating ring seat for driving the first rotating ring, and the pump outer side of the second rotating ring is provided with a second compression spring and a second rotating ring seat for driving the second rotating ring.

The following are further aspects of the double-ended shaft seal of the present invention:

the rotating shaft is fixedly connected with an impeller serving as a rotor, and the rotating shaft is characterized in that the first movable ring seat is connected with the impeller through at least 1 transmission pin, one end of the transmission pin is in tight fit connection, and the other end of the transmission pin is inserted in a floating mode.

One end of the transmission pin is tightly matched with the impeller, and the inner side of the pump of the first movable ring seat is provided with a corresponding number of driving notches for the transmission pin to be inserted in a floating mode.

The first rotating ring seat comprises a first rotating ring front seat and a first rotating ring rear seat, the impeller drives the first rotating ring front seat to operate through a driving notch on the inner side of the first rotating ring front seat pump, matching notches are respectively formed in the first rotating ring front seat and the first rotating ring rear seat, the first rotating ring front seat drives the first rotating ring rear seat to operate through matching notches of the first rotating ring front seat and the first rotating ring rear seat, and the first compression spring is arranged between the first rotating ring front seat and the first rotating ring rear seat.

The pump outside symmetry on the impeller is seted up 2 pinhole, and wherein one end of 2 driving pins tight fit inserts 2 pinholes on the impeller respectively, the pump inboard of first rotating ring front bezel is also seted up 2 drive gaps symmetrically and is supplied the floating formula of driving pin to insert.

In order to drive each movable ring, the pump outer side of the cylinder body of the first movable ring rear seat is provided with at least 2 convex ribs along the circumference of the inner wall of the pump outer side, and the first movable ring is provided with corresponding concave recesses along the circumference of the outer wall of the first movable ring. The pump of the barrel of the second rotating ring seat is provided with at least 2 convex ribs along the circumference of the inner wall of the pump, and the second rotating ring is provided with corresponding concave along the circumference of the outer wall of the second rotating ring seat.

The machine seal seat comprises a machine seal front seat and a machine seal rear seat, the inner side end of a pump of the machine seal front seat is fixedly connected with the pump body, the outer side end of the pump of the machine seal front seat is fixedly connected with the machine seal rear seat, the machine seal rear seat is provided with a closed end with a smaller inner diameter, and the first stationary ring and the second stationary ring are symmetrically positioned on two sides of the radial inner wall.

A radial positioning hole is formed in the outer side of the second movable ring seat pump, and a connecting pin is inserted into the radial positioning hole and is fixedly connected with the rotating shaft; and the second compression spring is arranged between the second movable ring seat and the second movable ring.

And the gaps among the first static ring, the second static ring and the closed end of the mechanical seal seat are respectively provided with a first seal ring, and the pump inner side of the first rotating ring and the pump outer side of the second rotating ring are respectively provided with a second seal ring for sealing the gaps between the respective rotating ring and the rotating shaft.

And a moving ring gasket is arranged on the outer side of the pump of the second moving ring, the second compression spring is arranged between the second moving ring seat and the moving ring gasket, and a second sealing ring of the second moving ring is arranged at a gap between the moving ring gasket and the second moving ring.

In the double-end-face shaft sealing device, one group of moving and static rings and a compression spring thereof are arranged in a machine sealing inner cavity, the other group of moving and static rings and a compression spring thereof are arranged outside a machine sealing seat, the sealing end of the machine sealing seat is provided with a radial inner wall, the first moving ring and the first static ring are arranged on the inner side of a pump of the radial inner wall, and the second moving ring and the second static ring are arranged on the outer side of the pump of the radial inner wall; a pin hole is formed in the radial inner wall, the stop pin penetrates through the pin hole, the first stationary ring and the second stationary ring are respectively positioned on two sides of the radial inner wall, and two ends of the stop pin are respectively inserted into connecting notches of the first stationary ring and the second stationary ring; the pump inner side of the first rotating ring is provided with a first compression spring and a first rotating ring seat for driving the first rotating ring, and the pump outer side of the second rotating ring is provided with a second compression spring and a second rotating ring seat for driving the second rotating ring. The two groups of dynamic and static rings are independent, the compression springs of the two groups of dynamic and static rings manage the respective dynamic rings, and when one side is sealed, the other side is not influenced. The compression spring of the dynamic and static ring group in the mechanical seal cavity is positioned at the inner side of the pump, and the elastic direction of the compression spring is the same as the pressure direction borne by the material, so that the sealing performance is better; the material side can bear high pressure, and the sealing performance to the material with high viscosity is better. Two groups of moving and static ring groups are respectively positioned inside and outside the inner cavity of the mechanical seal, and two moving ring seats are respectively positioned at two ends of the mechanical seal, so that the installation is more convenient.

The double-end-face shaft sealing device is particularly suitable for rotor pumps and also for other liquid material conveying pumps or mixers.

Drawings

FIG. 1 is a schematic cross-sectional view of a shaft seal assembly of a rotor pump according to an embodiment of the present invention.

Fig. 2 is a perspective view of the front seat of the rotating ring.

Fig. 3 is a perspective view of the movable ring rear seat.

Fig. 4 and 5 are schematic perspective views of the movable ring of the present invention, which respectively show different orientations.

Fig. 6 and 7 are schematic perspective views of the stationary ring of the present invention, which respectively show different orientations.

Fig. 8 and 9 are schematic perspective views of the second rotating ring seat of the present invention, which respectively show different orientations.

Fig. 10 is a front view of a two-bladed impeller adapted for use with the present invention.

FIG. 11 is a schematic cross-sectional view of a two-bladed impeller adapted for use with the present invention.

FIG. 12 is a schematic sectional view of a shaft seal device of a two-rotor pump according to an embodiment of the present invention.

Fig. 13 is a perspective view of the front seat of the mechanical seal.

Fig. 14 is a perspective view of the rear seat of the mechanical seal.

Reference numbers in the figures: 1. a rotating shaft; 2. a pump body; 3. a machine seal seat; 4. mechanically sealing the inner cavity; 5. a first rotating ring; 6. a first stationary ring; 7. a second rotating ring; 8. a second stationary ring; 9. a radially inner wall; 10. a pin hole; 11. a retaining pin; 12. a connecting gap; 13. a first compression spring; 14. a first movable ring seat; 15. a second compression spring; 16. a second movable ring seat; 17. an impeller; 18. a drive pin; 19. a first rotating ring front seat; 20. a first rotating ring rear seat; 21. a drive notch; 22. a pin hole; 23. a rib is protruded; 24. recessing; 25. a mechanical seal front seat; 26. a machine seal rear seat; 27. a first seal ring; 28. a second seal ring; 29. a moving ring washer; 30. and (7) positioning the holes.

Detailed Description

The following describes a specific embodiment of the present invention, as shown in fig. 1 to 14.

Example one, externally mounted double-ended shaft seal

As shown in fig. 1, an externally-mounted double-end-face shaft sealing device comprises a machine seal seat 3 which is sleeved outside a rotating shaft 1 and is fixedly connected with a pump body 2, the outer side of a pump of the machine seal seat 3 is a closed end with a smaller inner diameter, a machine seal inner cavity 4 is formed between the inner wall of the machine seal seat 3 and the rotating shaft 1, the machine seal inner cavity 4 is provided with a first movable ring 5 and a first stationary ring 6, the machine seal seat 3 is externally provided with a second movable ring 7 and a second stationary ring 8, and the contact surface of each movable ring and the contact surface of the stationary ring are mutually attached to form a friction pair; the closed end of the mechanical seal seat 3 is provided with a radial inner wall 9, the first movable ring 5 and the first static ring 6 are arranged on the inner side of the pump of the radial inner wall 9, and the second movable ring 7 and the second static ring 8 are arranged on the outer side of the pump of the radial inner wall 9. More than 2 pin holes 10 are formed in the radial inner wall 9, more than 2 stop pins 11 penetrate through the pin holes 10, and the first stationary ring 6 and the second stationary ring 8 are respectively located on two sides of the radial inner wall 9. As shown in fig. 6 and 7, the first stationary ring 6 and the second stationary ring 8 are provided with 2 or more connection notches 12. The two ends of the stop pin 11 are respectively inserted into the connecting notches 12 of the first stationary ring 6 and the second stationary ring 8. The pump inner side of the first rotating ring 5 is provided with a first pressure spring 13 and a first rotating ring seat 14 for driving the first rotating ring 5, and the pump outer side of the second rotating ring 7 is provided with a second pressure spring 15 and a second rotating ring seat 16 for driving the second rotating ring 7. As shown in fig. 1, the first stationary ring 6 and the second stationary ring 8 may be embedded stationary rings, which are made of hard alloy or ceramic and stainless steel.

The first movable ring seat 14 is connected with the impeller 17 through at least 1 driving pin 18, one end of the driving pin 18 is tightly matched and connected, and the other end is inserted in a floating manner. This can be generally set up as follows: as shown in fig. 10 and 11, one end of the driving pin 18 is tightly fitted on the impeller 17, and the inner side of the first rotating ring seat 14 is provided with a corresponding number of driving notches 21 for the driving pin 18 to be inserted in a floating manner.

As shown in fig. 1, 2 and 3, the first rotating ring seat 14 includes a first rotating ring front seat 19 and a first rotating ring rear seat 20, the impeller 17 drives the first rotating ring front seat 19 to operate through a driving notch 21 on the inner side of the first rotating ring front seat 19, the first rotating ring front seat 19 and the first rotating ring rear seat 20 are respectively provided with a matching notch, the first rotating ring front seat 19 drives the first rotating ring rear seat 20 to operate through the matching notches of both sides, and the first compression spring 13 is disposed between the first rotating ring front seat 19 and the first rotating ring rear seat 20. The first compression spring 13 is preferably a single large spring.

As shown in fig. 10 and 11, the following steps may be specifically provided: the pump outer side of impeller 17 is symmetrical to be seted up 2

pinhole

22, and 2 drive pin 18 wherein one end closely matches the 2 pinhole 22 of inserting on impeller 17 respectively. As shown in fig. 2, the pump inner side of the first rotating ring front seat 19 is also symmetrically provided with 2 driving notches 21 for the floating insertion of the driving pin 18.

In order to drive the first rotating ring 5, as shown in fig. 3, at least 2 ribs 23 are arranged on the pump outer side of the cylinder of the first rotating ring rear seat 20 along the circumference of the inner wall; as shown in fig. 4 and 5, the first rotating ring 5 is provided with corresponding recesses 24 along the circumference of the outer wall thereof; the first rotating ring rear seat 20 drives the first rotating ring 5 by the matching of the convex ribs 23 and the concave 24. As shown in fig. 8 and 9, the pump inner side of the cylinder of the second rotating ring seat 16 is provided with at least 2 ribs 23 along the circumference of the inner wall thereof, and referring to fig. 4 and 5, the second rotating ring 7 is provided with corresponding recesses 24 along the circumference of the outer wall thereof; the second rotating ring seat 16 drives the second rotating ring 7 by the matching of the convex ribs 23 and the concave grooves 24.

As shown in fig. 1, the pump inside end of the mechanical seal holder 3 is fixedly connected to the pump body 2, the mechanical seal holder 3 is provided with a closed end having a smaller inside diameter, and the first stationary ring 6 and the second stationary ring 8 are symmetrically located on two sides of the radial inner wall 9. As shown in fig. 1, 8 and 9, a radial positioning hole 30 is formed on the outer side of the second rotating ring seat 16, and a connecting pin is inserted into the radial positioning hole and fixedly connected with the rotating shaft 1. As shown in fig. 1, a second compression spring 15 is disposed between the second moving ring seat 16 and the second moving ring 7.

As shown in fig. 1, first sealing rings 27 are respectively disposed at the gaps between the first stationary ring 6 and the closed end of the mechanical seal holder 3, and second sealing rings 28 for sealing the gaps between the respective moving rings and the rotating shaft 1 are respectively disposed at the pump inner side of the first moving ring 5 and the pump outer side of the second moving ring 7.

To facilitate the installation of the second rotating ring 7 and the second compression spring 15, as shown in fig. 1, a rotating ring gasket 29 is disposed on the pump outer side of the second rotating ring 7, the second compression spring 15 is disposed between the second rotating ring seat 16 and the rotating ring gasket 29, and the second seal ring 28 of the second rotating ring 7 is disposed at the gap between the rotating ring gasket 29 and the second rotating ring 7. The second compression spring 15 may be a bellows spring.

The external shaft seal device is a shaft seal device that is generally used for a pump having a small size, and is mounted outside the pump when the shaft seal device is mounted. In this embodiment, the externally mounted double-end-surface shaft seal device needs to be mounted on the outside of the pump after the pump body 2 and the impeller 17 are assembled. As shown in fig. 1, the flange end of the mechanical seal holder 3 is provided with a plurality of connecting holes along the circumference thereof, the pump body 2 is provided with corresponding threaded holes, and the flange end of the mechanical seal holder 3 is attached to the outer wall of the pump body 2 and fixedly connected with the outer wall of the pump body 2 by a plurality of bolts.

During operation, the rotating shaft 1 drives the first rotating ring 5 to rotate relative to the first stationary ring 6 through the impeller 17, the transmission pin 18, the first rotating ring front seat 19 and the first rotating ring rear seat 20 in sequence, and simultaneously, the rotating shaft 1 drives the second rotating ring 7 to rotate relative to the second stationary ring 8 through the second rotating ring seat 16.

EXAMPLE II built-in double-ended shaft seal

The built-in shaft seal device is a shaft seal device that can be mounted inside a pump when the shaft seal device is mounted, and is generally used for a large-sized pump.

As shown in fig. 12, in the second built-in double-ended shaft seal device according to the first embodiment, the machine seal holder 3 includes a front machine seal holder 25 and a rear machine seal holder 26, and the machine seal holder 3 is an assembly formed by assembling the front machine seal holder 25 and the rear machine seal holder 26. The pump inside end of the mechanical seal front seat 25 is fixedly connected with the pump body 2, and the pump outside end of the mechanical seal front seat 25 is fixedly connected with the mechanical seal rear seat 26. As shown in fig. 14, a closed end with a smaller inner diameter is provided on the rear seal seat 26, that is, the radially inner wall 9 is provided, and the first stationary ring 6 and the second stationary ring 8 are symmetrically located on both sides of the radially inner wall 9. As shown in fig. 13, a flange end is provided on the pump inner side of the mechanical seal front seat 25, and a plurality of connection holes are formed along the circumference of the flange end. As shown in fig. 12, a flange mounting cavity is formed in the inner cavity of the pump body 2, the flange end of the front mechanical seal seat 25 is embedded into the flange mounting cavity, and the front mechanical seal seat 25 is fixedly connected with the pump body 2 through a plurality of bolts from the inner cavity of the pump body 2. The difference from the first embodiment is that the pump outer side of the flange end of the mechanical seal front seat 25 is jointed with the pump body 2. The pump outer side of the mechanical seal front seat 25 is provided with a plurality of threaded holes along the circumference of the wall thickness. The pump inner side of the machine seal rear seat 26 is also provided with a flange end, a plurality of connecting holes are arranged along the circumference of the flange end, and the machine seal front seat and the machine seal rear seat are fixedly connected through a plurality of bolts.

The other steps are carried out by adopting the scheme of the first embodiment.

The machine seal piece of the second embodiment is installed from the inside of the pump body, and the inlet and outlet pipelines of the pump do not need to be disassembled when the machine seal piece is replaced, so that convenience is brought to maintenance of a rotor pump user.

Claims

1. A double-end-face shaft sealing device comprises a machine seal seat (3) which is sleeved outside a rotating shaft (1) and fixedly connected with a pump body (2), wherein the outer side of the pump of the machine seal seat (3) is a closed end with a smaller inner diameter, and a machine seal inner cavity (4) is formed between the inner wall of the machine seal seat (3) and the rotating shaft (1), and is characterized in that the machine seal inner cavity (4) is provided with a first movable ring (5) and a first stationary ring (6), a second movable ring (7) and a second stationary ring (8) are arranged outside the machine seal seat (3), and the contact surface of each movable ring and the contact surface of the stationary ring are mutually clung to form a friction pair; the closed end of the machine seal seat (3) is provided with a radial inner wall (9), the first movable ring (5) and the first static ring (6) are arranged on the inner side of the pump of the radial inner wall (9), and the second movable ring (7) and the second static ring (8) are arranged on the outer side of the pump of the radial inner wall (9); a pin hole (10) is formed in the radial inner wall (9), a stop pin (11) penetrates through the pin hole (10), the first stationary ring (6) and the second stationary ring (8) are respectively located on two sides of the radial inner wall (9), and two ends of the stop pin (11) are respectively inserted into connecting notches (12) of the first stationary ring (6) and the second stationary ring (8); the inner side of the pump of the first rotating ring (5) is provided with a first pressure spring (13) and a first rotating ring seat (14) for driving the first rotating ring (5), and the outer side of the pump of the second rotating ring (7) is provided with a second pressure spring (15) and a second rotating ring seat (16) for driving the second rotating ring (7).

2. Double-ended shaft seal according to claim 1 for a rotor pump, said shaft (1) being fixedly connected to an impeller (17) as a rotor, characterized in that said first rotating ring seat (14) is connected to the impeller (17) via at least 1 driving pin (18), one of the ends of said driving pin (18) being tightly fitted and the other end being inserted in a floating manner.

3. Double-ended shaft seal according to claim 2, characterised in that one end of the drive pin (18) is tightly fitted on the impeller (17), and the pump inner side of the first moving ring seat (14) is provided with a corresponding number of drive notches (21) for the floating insertion of the drive pin (18).

4. The double-end-face shaft sealing device according to claim 2, wherein the first rotating ring seat (14) comprises a first rotating ring front seat (19) and a first rotating ring rear seat (20), the impeller (17) drives the first rotating ring front seat (19) to operate through a driving notch (21) on the inner side of the first rotating ring front seat (19) and the first rotating ring rear seat (20), the first rotating ring front seat (19) and the first rotating ring rear seat (20) are respectively provided with a matching notch, the first rotating ring front seat (19) drives the first rotating ring rear seat (20) to operate through the matching notches of the first rotating ring front seat and the first rotating ring rear seat (20), and the first compression spring (13) is arranged between the first rotating ring front seat (19) and the first rotating ring rear seat (20).

5. The double-end-face shaft sealing device according to claim 4, wherein the pump outer side of the impeller (17) is symmetrically provided with 2 pin holes (22), one end of each of the 2 driving pins (18) is tightly inserted into the 2 pin holes (22) of the impeller (17), and the pump inner side of the first movable ring front seat (19) is also symmetrically provided with 2 driving notches (21) for the driving pins (18) to be inserted in a floating manner.

6. The double-ended shaft seal arrangement according to claim 4, characterized in that the pump outer side of the cylinder of the first rotating ring back seat (20) is provided with at least 2 ribs (23) along its inner wall circumference, and the first rotating ring (5) is provided with corresponding recesses (24) along its outer wall circumference; the pump inner side of the cylinder body of the second movable ring seat (16) is provided with at least 2 convex ribs (23) along the circumference of the inner wall, and the second movable ring (7) is provided with corresponding concave recesses (24) along the circumference of the outer wall.

7. The double-end-face shaft sealing device according to claim 1, wherein the mechanical seal seat (3) comprises a mechanical seal front seat (25) and a mechanical seal rear seat (26), the pump inside end of the mechanical seal front seat (25) is fixedly connected with the pump body (2), the pump outside end of the mechanical seal front seat (25) is fixedly connected with the mechanical seal rear seat (26), the mechanical seal rear seat (26) is provided with the closed end with the smaller inner diameter, and the first stationary ring (6) and the second stationary ring (8) are symmetrically located on two sides of the radial inner wall (9).

8. The double-ended shaft seal according to claim 1, wherein the second rotating ring seat (16) is provided with a radial positioning hole (30) at the outside of the pump, and a connecting pin is inserted to be fixedly connected with the rotating shaft (1); the second compression spring (15) is arranged between the second movable ring seat (16) and the second movable ring (7).

9. The double-end-face shaft sealing device as claimed in claim 1, wherein first sealing rings (27) are respectively arranged at the gaps between the first stationary ring (6) and the second stationary ring (8) and the closed end of the machine sealing seat (3), and second sealing rings (28) for sealing the gaps between the respective moving rings and the rotating shaft (1) are respectively arranged at the pump inner side of the first moving ring (5) and the pump outer side of the second moving ring (7).

10. Double-ended shaft sealing device according to claim 9, characterised in that a moving ring gasket (29) is arranged outside the second moving ring (7) on the pump side, that the second compression spring (15) is arranged between the second moving ring seat (16) and the moving ring gasket (29), and that the second sealing ring (28) of the second moving ring (7) is arranged at the gap between the moving ring gasket (29) and the second moving ring (7).