US 4,484,753 A · Rotary shaft seal

Abstract

The present invention is directed to a rotary shaft seal assembly and, more particularly, to an assembly including a continuous, annular, but axially variable seal for providing hydrodynamic lubrication between the seal and rotating shaft. The seal assembly uses differential pressures to maintain the seal compressed as it wears. The present system is particularly useful in drilling motors utilizing the movement of drilling fluid under pressure to operate the motor parts and thereby to drive a drill bit. The abrasive drilling fluid environment in a borehole is detrimental to the moving parts in such a system, and especially destructive to the bearings and seals. The present system utilizes a sealing member arranged in a continuous, annular, but axially variable path between the rotating shaft and housing of such a motor. Annular seal mounting members are positioned above and below the seal and have surfaces to matingly engage the seal member. The mounting elements are arranged to move relative to one another. A pressure differential developed across the motor is communicated to the respective mounting elements to urge the elements toward one another and thereby compress the seal member therebetween to accommodate wear take-up on the seal member. An oil chamber above the upper mounting element communicates drilling fluid pressure inside the drill pipe to the upper mounting element. The pressure of the annular space below the motor housing is communicated to the lower mounting element by means of a lower chamber.

Claims25

Dependent claims

A rotary shaft seal system for sealing an annular space between a rotating shaft and its housing, comprising:

annular seal means having upper and lower engaging surfaces and having an axially variable configuration about a rotating shaft so that one sealing surface of said seal means slidably engages said rotating shaft;
first and second means for matingly engaging the upper and lower engaging surfaces of said seal means and arranged to permit relative longitudinal movement with respect to one another;
means actuated by a differential fluid pressure for biasing said first and second engaging means toward one another;
and
means for substantially preventing contact of said seal means with the fluid in the environment of said housing.

2 more elements

In a borehole tool suitable for incorporation in a drill string in which a drilling fluid is pumped down the bore of the drill string and out the bottom of the drill string, said tool including a housing capable of incorporation on the lower end of the drill string, a rotating shaft carried within the housing, bearings positioned between the housing and the shaft for supporting the rotary movement of the shaft within the housing, the bearings being maintained within an oil bath, and a shaft rotation system connected to the shaft to cause the shaft to rotate within the housing when drilling fluid is pumped downwardly through the drill string, a sealing system for sealing the lower end of the housing and shaft to prevent drilling fluids from entering into the oil bath, a seal system comprising:

annular seal means having an axially variable configuration about said rotating shaft so that one surface of said seal means slidably engages said rotating shaft;
first and second means engaging the top and bottom surfaces of said seal means and arranged for relative longitudinal movement with respect to one another;
means actuated by a differential fluid pressure urging said first and second engaging means toward one another;
and
means for substantially preventing contact of said seal means with the fluid in the environment of said housing.

2 more elements

Dependencies are inferred from the claim text.

Rotary shaft seal

Life of this patent

Rotary shaft seal

Life of this patent

Abstract

Claims25