JP2545728Y2 - Mechanical seal for cryogenic liquid - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical seal for sealing a cryogenic liquid such as liquid oxygen, liquid nitrogen or liquid argon.

[0002]

2. Description of the Related Art Conventionally, there is a mechanical seal for a cryogenic liquid as shown in FIG. In other words, the mechanical seal is provided with a metal bellows on a case 104 which is airtightly fixed to the housing 101 with respect to an end surface of a cemented carbide mating ring 103 which rotates integrally with a rotating shaft 102 inserted into a housing 101 of the fuselage. 105
Seal ring 1 elastically supported via
The sliding projection 106a at the tip of the reference numeral 06 performs a shaft sealing function by airtight sliding contact, and prevents the cryogenic liquid L such as liquid oxygen existing in the outer peripheral space from leaking from the shaft circumference.

[0003]

However, in the mechanical seal for cryogenic liquid having the above-mentioned conventional structure, when the bellows 105 and the seal ring 106 are displaced in the radial direction due to vibration or the like, the inner peripheral edge of the bellows 105 made of metal is formed. There is a risk that the rotating shaft 102 may be damaged by contact with the outer peripheral surface thereof or sparks may be generated.

[0004] Further, a cemented carbide mating ring 10
If the sliding projection 106a of the carbon-made seal ring 106 is worn out due to sliding with the third ring 3, the wear of the seal ring 106 tends to progress until the bellows 105 extends to a free length. In the process, the metal retainer 107 that fits and holds the seal ring 106 at the free end of the bellows 105 comes into metallic contact with the cemented carbide mating ring 103, and the sliding load increases rapidly. The cryogenic liquid L may suddenly leak in large quantities, or a situation such as ignition may occur due to the scattering of the seal ring 106 including the seal ring 106 and the damage of the bellows 105 accompanying the scattering.

In view of the above problems, the present invention prevents the metal bellows from being damaged by contact with the rotating shaft and the metal retainer from contacting with the cemented carbide mating ring due to excessive wear of the carbon seal ring. Thus, a mechanical seal for a cryogenic liquid with improved safety is provided.

[0006]

In order to solve the above problems, a mechanical seal for a cryogenic liquid according to the present invention has a baffle sleeve extending from an inner peripheral space of a bellows to an inner peripheral space of a seal ring on a case side. At the tip of the baffle sleeve located on the inner periphery of the seal ring, a bent portion protruding to the outer diameter side is provided, while the inner diameter end of the rear end flange portion of the retainer is moved from the inner periphery of the seal ring to the outer diameter end of the bent portion. Than the axial height of the sliding protrusion with the mating ring formed on the seal ring, extending to the inner diameter position, and the axial distance between the bent surface and the opposing surface of the inner end of the rear flange end of the retainer. Is set to be small.

[0007]

In the above construction, the baffle sleeve prevents the inner peripheral edge of the metal bellows from contacting the outer peripheral surface of the rotating shaft, and slides on the carbon seal ring by sliding with the cemented carbide mating ring. As the wear of the dynamic projections progresses, the distance between the opposing surfaces of the inner end of the rear flange portion of the metal retainer and the bent portion of the front end of the baffle sleeve gradually decreases, and the two eventually interfere. At this point, the axial biasing force from the metal bellows to the seal ring is cut off, and the wear of the sliding protrusion is stopped.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the mechanical seal for a cryogenic liquid according to the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a housing of the body, and 2 denotes a rotary shaft inserted through a shaft hole of the housing 1. The mechanical seal of this embodiment is mounted on the outer peripheral surface of the rotary shaft 2 in an airtight manner, and a key 3 is provided. And a mating ring 4 made of cemented carbide, which is prevented from rotating relative to the rotating shaft 2. The mating ring 4 is elastically supported by the housing 1 via a metal bellows 5 and slides on the mating ring 4. And a carbon-made seal ring 6 in contact therewith.

An annular adapter 7 is provided at the fixed end 5 a of the metal bellows 5, and the adapter 7 is attached to a fitting portion on the inner periphery of the housing 1 via an O-ring 9. The free end 5b of the metal bellows 5 is airtightly fixed to the rear end flange 10a, and the rear end flange 8 is attached to the free end 5b.
An annular retainer 8 made of metal, comprising an outer diameter supporting portion 82 extending in the axial direction from the outer diameter of the seal ring 1, is provided. The seal ring 6 is fitted and held in the retainer 8.

On the surface of the seal ring 6 facing the mating ring 4, double sliding projections 6 extending at the same height in the axial direction and extending concentrically with each other are provided.
1, 62 are provided, and a required number of notches 63 penetrating in the radial direction are provided in the outer peripheral side sliding protrusion 61. In addition, an end face of the mating ring 4 facing the seal ring 6 is provided between the sliding protrusions 61 and 62.
Correspondingly, an annular groove 41 is provided.
A required number of radiation holes 42 penetrate from the inside toward the outer peripheral surface of the mating ring 4.

Reference numeral 11 denotes a baffle sleeve which is fixed to the inner periphery of the adapter 7 and extends in the axial direction, and reaches from the inner peripheral space of the metal bellows 5 to the inner peripheral position of the seal ring 6 due to eccentricity or bending of the metal bellows 5. The inner peripheral edge of the bellows 5 is prevented from contacting the outer peripheral surface of the rotating shaft 2 and being damaged. Reference numeral 12 denotes a tapered PTFE damper whose diameter gradually decreases toward the anti-mating ring side. The large-diameter end is fixed to the case 10 and the inner peripheral surface is formed at the rear end flange of the retainer 8. The eccentricity of the seal ring 6 is suppressed by elastically contacting the outer peripheral edge of the seal ring 6.

A bent portion 13 protruding toward the outer diameter side is provided at the tip of the baffle sleeve 11, while the inner diameter end 81 a of the rear end flange portion 81 of the retainer 8 projects from the inner periphery of the seal ring 6. The axial distance A between the inner diameter end 81a and the opposing surface of the bent portion 13 is larger than the outer diameter end of the bent portion 13 by an axial distance A.
It is set smaller than the axial heights B of 1,62.

In the above configuration, when the mating ring 4 rotates integrally with the rotating shaft 2, the pumping action of the radiation hole 42 provided in the mating ring 4 causes
Space 64 between the mechanical seal the outer periphery of the cryogenic liquid L Both slides from the notch 63 projecting portions 61 and 62, since it is again returned to the mechanical seal periphery from the radiation hole 42 through the annular groove 41, both sliding The dynamic projections 61 and 62 are cooled and lubricated to have high wear resistance.

Here, when the sliding projections 61 and 62 of the carbon seal ring 6 are worn out over a long period of use, the seal ring 6 urged by the bellows 5 causes the mating ring to move as the wear progresses. 4, the inner diameter end 8 of the rear end flange portion 81 of the metal retainer 8.
The distance A between the surface 1a and the opposing surface of the bent portion 13 at the tip of the baffle sleeve 11 gradually decreases. Since this distance A is smaller than the axial height B of the sliding protrusions 61 and 62, the inner end 81a and the bent portion 13 interfere with each other in the axial direction before the sliding protrusions 61 and 62 are worn out. At this point, the follow-up movement of the seal ring 6 toward the mating ring 4 is prevented, and the seal ring 6
Since the surface pressure of the sliding protrusions 62 becomes zero, the amount of leakage increases, but the progress of wear of the sliding protrusions 61 and 62 is prevented, so that the outer diameter supporting portion 82 of the metal retainer 8 is Metal contact with the cemented carbide mating ring 4 cannot occur.
As shown in the example of the drawing, the outer diameter of the seal ring 6 is made larger than the outer diameter of the mating ring 4 and the eccentricity of the seal ring 6 is suppressed by the damper 12. This is effective in preventing metal contact between the outer diameter supporting portion 82 and the cemented carbide mating ring 4.

[0016]

As described above, according to the mechanical seal for cryogenic liquid of the present invention, the inner peripheral edge of the metal bellows is prevented from contacting the outer peripheral surface of the rotating shaft with the baffle sleeve, and the sliding of the carbon seal ring is performed. When the wear of the protrusion reaches a certain amount, the inner end of the rear flange portion of the metal retainer and the bent portion of the tip of the baffle sleeve interfere in the axial direction to prevent the wear of the slide protrusion from progressing. So
A sudden accident such as scattering of the retainer and the seal ring, breakage of the bellows, or fire due to contact between the cemented carbide mating ring and the metal retainer can be prevented.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of the same.

FIG. 3 is a half sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Rotating shaft 4 Mating ring 5 Bellows 6 Seal ring 8 Retainer 10 Case 11 Baffle sleeve 13 Bending part 61, 62 Sliding projection part 81 Rear end flange part 81a Inner diameter end L Cryogenic liquid

Claims (1)

(57) [Scope of request for utility model registration] 1. A carbon seal ring slidingly contacting a rotating side cemented carbide mating ring is held by a metal retainer at a free end of a metal bellows provided on an inner periphery of a non-rotating case, and a cryogenic liquid is discharged. In the mechanical seal to be sealed, a baffle sleeve that extends from the inner peripheral space of the bellows to the inner peripheral space of the seal ring is fixed to the case side, and protrudes outward at the tip of the baffle sleeve located on the inner periphery of the seal ring. While providing the bent portion, the inner diameter end of the rear end flange portion of the retainer extends from the inner periphery of the seal ring to the inner diameter position than the outer diameter end of the bent portion, and the mating ring formed on the seal ring. The axial distance between the bent portion and the opposed surface of the inner end of the rear flange portion of the retainer is set smaller than the axial height of the sliding protrusion. Mechanical seal for cryogenic liquids.