Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Reexamination Certificate
2000-05-22
2001-12-04
Sandy, Robert J. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
C277S387000, C277S412000
Reexamination Certificate
active
06325382
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a non-contact type mechanical seal that is mounted as a shaft seal on rotary equipment or machines such as wet-type compressors, mixers and pumps handling gases containing liquid or solid foreign matter such as oil, moisture and sludge.
DESCRIPTION OF THE PRIOR ART
It is known to provide a non-contact type mechanical seal configured to seal the internal or inside region within a rotary machine from the outside or atmospheric region. A rotary seal ring on the rotary shaft and a stationary seal ring on the seal case side are kept in a non-contact state by generating static pressure between opposed faces of the two seal rings, thereby creating a seal between the two regions. Unlike contact type mechanical seals in which the faces of the seals are in sliding contact as they rotate relative to each other, the non-contact type mechanical seal is free from such problems as seizing or burning up under dry operating conditions, and is suitable as a shaft seal for rotary equipment handling gases.
However, in applications where the gas to be sealed contains liquid foreign matter such as oil or solid foreign matter such as sludge, the foreign matter may creep into, stick to, or accumulate on, the seal faces. This could put the static pressure between the seal faces out of control, resulting in decreased or lost seal function.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a non-contact type mechanical seal (static pressure gas seal) for rotary machines, the seal preventing foreign matter in the gas being contained from creeping between the seal faces so that a good sealing function or performance is maintained for a long period.
This object is achieved by providing a non-contact type mechanical seal comprising a cylindrical seal case mounted horizontally on the rotary machine with one end opening into the inside region of the machine, a stationary seal ring held, relatively non-rotatable but movable in the axial direction, at the other end of the seal case, a rotary seal ring provided on the inside region side of the stationary seal ring and clamped on a rotary shaft passing through the seal case and the stationary seal ring, thrusting means that urges the stationary seal ring toward the rotary seal ring, and a static pressure generating mechanism to generate static pressure between the opposed seal faces of the two seal rings, wherein there is provided a labyrinth seal between the seal case and the rotary shaft, the labyrinth seal comprising a plurality of annular grooves provided side by side in the axial direction on the inner circumferential portion of one end of the seal case and a plurality of annular plates provided side by side in the axial direction on the outer circumferential portion of the rotary shaft, the annular plates extending into the annular grooves, thus separating the area on the outer circumferential side of the seal faces within the seal case from the inside region of the rotary machine.
The seal of the invention may be provided with a return passage that communicates with the bottom portions of the annular grooves and which opens into the inside region of the machine so that foreign matter entering the labryinth seal is returned to the inside region. The lower surface of the return passage may be tapered to slope down toward an opening into the inside region of the machine thus assisting in the return of the foreign material.
The seal case is preferably provided with a purge gas feed passage for supplying purge gas into the space on the outer circumferential side of the rotary and stationary seal faces, the purge gas being supplied at a pressure higher than the pressure on the inside region of the machine.
The seal case may also be provided with a foreign matter recovery passage that opens into the region on the outer circumferential side of the rotary and stationary seal faces. The recovery passage may be connected to a foreign matter recovery tank, the pressure in the recovery tank being maintained at the same level as the pressure in the outer circumferential side region. In equipment having a horizontal rotary shaft, it is desirable to provide the return passage under the rotary shaft and have the foreign matter recovery passage opening into the outer circumferential side region at a location under the rotary shaft.
The non-contact type mechanical seal of the present invention is especially suitable as a shaft seal for rotary equipment or machines such as wet-type compressors, mixers and pumps treating gases containing liquid or solid foreign matters such as oil, moisture and sludge. When the equipment is a compressor, it is preferable that the feeding pressure of the purge gas and the seal gas supplied between the rotary and stationary seal faces are controlled according to the pressure in the inside region of the compressor. This compensates for pressure changes in the inside region of the compressor such as might occur in the event of a power failure, or at the time of startup or stopping of the compressor. Also, the foreign matter collected in the foreign matter recovery tank may be returned to the inside region of the machine by using the discharge gas of the compressor.
REFERENCES:
patent: 5468002 (1995-11-01), Wasser
patent: 5700011 (1997-12-01), Bainachi et al.
patent: 5719560 (1998-02-01), Lorenzen
Furuya Masaaki
Ikehara Masahito
Iwamoto Yasutaka
Sekiya Yoshimitsu
Griffin & Szipl, P.C.
Nippon Pillar Packing Co. Ltd.
Sandy Robert J.
Schwing Karlena D.
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