Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1987-04-30
1989-01-24
Ward, Robert S.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277 93SD, 277168, F16J 1534
Patent
active
047996935
DESCRIPTION:
BRIEF SUMMARY
This invention relates to face seals, for preventing fluid leakage between relatively rotatable members, such as a shaft and its housing.
Face seals have a sealing ring mounted, on one sealed member, for a transverse radial face of the ring to bear axially against a transverse radial counter-face, of the other member, to prevent leakage of sealed fluid between the opposed faces.
Probably the widest use of face seals is in the water-circulating pumps of the cooling systems of automobile engines, the sealing ring being mounted in the pump body, such as in the housing of the pump shaft bearing, to bear against a counter-face of the impeller hub. The sealed space in which the water circulates is called the sealed side "S" and the other side of the seal, open to atmosphere or ambient pressure, is called the air side "A".
Face sealing rings are usually made of a hard material, such as carbon, ceramic material or a plastics equivalent material, so that corrosion is resisted and the sealing face conforms to the counter-face to maintain a plane circular sealing contact band. The existing practice is to make the face and counterface surfaces as plane as possible.
Leakage at face seals occurs from causes such as uneven wear or grit becoming trapped in the interface of the contact band, spoiling the maintenance of plane face contact.
The present invention introduces for face seals a positive action to promote return to the sealed space of fluid tending to leak across the contact band to the air side.
According to one aspect of the invention, in a face seal having a sealing ring with an axially-directed annular sealing face to bear, under axial spring load, by a circular sealing contact band against a circular counter-face of a sealed relatively rotatable member, a peripheral margin of the contact band is made of frusto-conical form, to diverge from the plane of the contact band so as to define an annular sealing region which enlarges in circumferential area radially towards the sealed side of the seal, and the sealing ring is provided at the sealed side with a peripheral shoulder which is designed to have non-constant axial clearance from the counter-face so that, on relative rotation, liquid pulsation is produced in the clearance to cause slight variation in the axial load of the sealing ring against the counter-face and consequent displacement pumping in the sealing region towards the sealed side.
The term "contact" is of course used to include nominal or effective contact, with an interposed fluid film, to maintain a seal between the contact band and its counter-face.
The non-constant axial clearance of the sealing ring shoulder can be achieved by any suitable variation of the axial dimension of the shoulder. For example, the shoulder may have a lobed or sinuous configuration or be slightly canted across the rotational axis.
The invention is illustrated by way of example on the accompanying drawings, in which:
FIG. 1 is a somewhat diagrammatic half axial section, on a much enlarged scale, of a typical water pump face seal,
FIG. 2 is a fragmentary axial section generally corresponding to part of FIG. 1 but showing one embodiment of a face seal in accordance with the invention, and
FIG. 3 is a plan view, on the line III--III of FIG. 2, showing the face of the sealing ring.
The known kind of face seal shown by FIG. 1 comprises a casing cup 1 which is set, statically sealed in an annular recess around the pump shaft 2, in the bearing housing 3 of a water pump of which part of the impeller hub is shown as 4.
A circumferentially corrugated rubber sleeve 5 has one end clamped fluid-tight in the base of the cup 1 by a helical compression spring 6 which constantly loads axially towards the impeller hub 4 a face sealing ring 7 seated in the other end of the sleeve 5.
The sealing ring 7 bears axially under its spring-loading to seal by a circular contact band 8 against a plane machined counterface 9 of the impeller hub 4.
To permit the sealing ring 7 to move axially and to restrain the ring against becoming entrained in rotat
REFERENCES:
patent: 3499653 (1970-03-01), Gardner
patent: 3738667 (1973-06-01), Symons
patent: 4407512 (1983-10-01), Trytek
George Angus & Company Limited
Hinds William R.
Ward Robert S.
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