Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1983-12-22
1985-03-12
Smith, Robert I.
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277 27, 277 53, F16J 1538, F16K 4100
Patent
active
045040699
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a sealing device for sealing in one direction between the surface of a cylindric cavity and in co-operation therewith the shell surface of a spindle movable in the cavity, either of the surfaces provided with an annular groove, in which a sealing ring is laid, which can move slightly in axial and radial direction and is intended to minimize fluid leakage in axial direction between said co-operating surfaces, of which ring at its positioning in a groove in the cylindric cavity the sealing surface is located about the inside of the ring, and at its positioning in a groove in the spindle the sealing surface is located about the outside of the ring.
It was tried since long to solve the problems of leakage and slide friction in hydraulic valves comprising a valve housing and a slide axially movable therein. The efforts were directed to the co-operating sealing surfaces formed by the housing and slide and to designing said surfaces with tolerances so narrow as to form the smallest possible sealing gap. Too small clearance yields low leakage, but involves the risk of increased friction to such an extent that the slide is locked completely. Too great clearance yields unacceptable leakage, but reduced risk of slide locking. As the pressure increases the size of the gap and even can bend the valve housing and yields so-called hydraulic locking due to non-uniform pressure distribution in the sealing gap, both the leakage and the friction are affected in a negative way. The temperature and temperature deformation, too, have a negative effect on the leakage and friction. The leakage increases due to reduced viscosity and gap deformation, and the friction increases due to the bending of the valve housing and the shrinking of the gap, especially at high temperatures. The problems are overcome passibly well for small valves by a very exacting precision manufacture, where the slide as well as the slide aperture of the valve housing must be within ca. two thousandths of one millimeter. For large valves and at high tightness requirements the slide principle must be replaced by valve functions of seat type. Seat valves, however, have restricted controllability and, therefore, it has always been desired to have a tight and friction-less controlled sliding valve. The hydraulic valve with sealing rings is not in use to-day, because its known embodiments yield unacceptable friction forces. One essential, though scarcely noticed disadvantage with the gap-sealed sliding valve is that the problem of reducing the leakage and slide friction so entirely dominates the stuctural design, that substantially no freedom of design is left any more. The result are bulky, heavy and expensive valves which, besides, are neither tight nor can be controlled by small forces. The aforementioned disadvantages and problems also exist with piston pumps, because also they operate with gap sealing. Also swivel structures can be pointed out, where gap sealing is required to permit rotary mobility while an axial position is to be maintained by a hydraulic pressure, which must not escape out through the gap sealing.
The present invention has the object to eliminate the aforesaid and other known disadvantages by permitting a certain small leakage past the sealing surfaces and by utilizing the hydraulic conditions then prevailing for eliminating friction. The characterizing features of the invention are that the ring has small cross-sectional dimensions in relation to the spindle and surrounding cavity. that the ring is so slim that the dimensioning fluid pressure over the ring is capable to change the diameter of the ring, but that the ring is of such rigid material that the deformation of the cross-section of the ring is negligible along with the change in diameter of the ring, that the sealing surface of the ring is slightly conic and provided with at least one overall groove, that the ring is located so that the sealing surface at co-operation with either sealing surface of the cavity and spindle forms a gap which has decreasing h
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Hep Products AB
Smith Robert I.
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