GAP SEAL WITH THERMAL AND PRESSURE DISTORTION COMPENSATION

• US 3,804,424 A
• Filed: 04/24/1972
• Issued: 04/16/1974
• Est. Priority Date: 04/24/1972
• Status: Expired due to Term

• Current Assignee: John Crane Incorporated (Smiths Group International Holdings Ltd.)
• Original Assignee: James F. Gardner
• Inventors: Gardner, James F.
• Primary Examiner(s): Rothberg, Samuel B.
• Application Number:
  US05/246,823
• Time in Patent Office: 722 Days
• Field of Search: 277/3,27,74,75,96
• US Class Current: 277/360
• CPC Class Codes: F16J 15/3412 with cavities F16J15/3424 takes precedence
• CPC Class Codes: F16J 15/342 with means for feeding fluid directly to the face
• CPC Class Codes: Y10S 277/91 O-ring seal

Abstract

The disclosure is of a rotary mechanical seal of the gap type, particularly for large diameter shafts, which is designed to reduce or eliminate entirely distortions in the sealing washer thereof caused by thermal expansion of the washer or by a change in the pressure profile across the sealing face of the washer. Thermal deflection is counteracted by providing a chamber on a cylindrical section behind the sealing washer face, and subjecting the chamber to the pressure existing between the opposing faces of the seal. Shallow spiral grooves formed in one of the opposing faces and directed to produce a pressure across the faces in opposition to the normal pressure gradient thereacross serve to provide a variety of pressures one of which is tapped as the source of pressure for the chamber.

Claims

1. In combination, a housing defining a chamber for the reception of a fluid under pressure, a shaft in the chamber, said housing having an opening through which said shaft extends to the exterior of the housing, and a rotary mechanical seal for effectIng a seal between the shaft and housing, said seal comprising a sealing washer fixed to and rotatable with the shaft, a non-rotatable sealing washer adjacent the rotatable sealing washer, said rotatable and non-rotatable sealing washers having opposed radially extending sealing faces, said nonrotatable washer being subject under operating conditions to thermal coning such that the radially inner portion of its sealing face is closer to the sealing face of the rotating washer than is the radially outer portion of its sealing face, an axially disposed support for the non-rotatable sealing washer, and means establishing a pressure chamber between the support and non-rotatable sealing washer acting in opposition to the thermal coning of said non-rotating washer resulting from heat generated between said faces by the relative rotation thereof.

2. The combination defined in claim 1, said means establishing a pressure chamber comprising spaced sealing means between the non-rotatable washer and the axially disposed support therefor, fluid means for producing a gap between said faces, and means for conducting fluid under pressure from between said faces to said pressure chamber, said non-rotatable washer being subjected to an axially increasing temperature gradient in the direction of said faces tending to distort the washer by turning it about its centroid in its radial cross section in one direction of rotation about said centroid and said fluid under pressure in said pressure chamber acting upon said washer eccentrically of said centroid to rotate said washer about its centroid in the opposite direction, whereby to minimize said thermal coning of said washer under operating conditions.

3. The combination defined in claim 2, said means for producing a gap between said faces comprising a plurality of shallow spiral grooves formed in one of said faces and of an angularity with respect to a radius on said one of said faces to pump fluid toward the first said chamber for the reception of fluid under pressure and thereby create a pressure between said faces tending to separate said faces, and said means for conducting fluid under pressure from between said faces to said pressure chamber comprising orifices in said one of said faces at the radial location of said pressure between said faces tending to separate said faces, said shallow spiral grooves establishing a decreasing pressure gradient from the chamber for the reception of fluid under pressure to the atmospheric side of said non-rotatable washer face which varies in form and magnitude in accordance with the relative speed of rotation of said faces, and means for introducing fluid under pressure from between said faces to said pressure chamber at a point between said faces at which the pressure is greater than the pressure in the first said chamber.

4. The combination defined in claim 2, said axially disposed support for the non-rotatable sealing washer comprising a cylindrical extension on the housing, said non-rotatable sealing washer encircling said extension, and said spaced sealing means comprising a pair of O-rings compressed between said non-rotatable sealing washer and said extension.