Hydrodynamic lift seal for use with compressible fluids

A stationary seal member adapted to control and minimize the leakage of a compressible fluid along a path between a primary seal face on said seal member and a complementary surface on a movable member adjacent to which said seal member is adapted to be mounted, said seal face terminating at two spaced edges, one of said edges adapted to be exposed to a compressible fluid in a first region at relatively higher ambient pressure, the second of said edges being essentially continuous and being adapted to be exposed to a second region at a relatively lower ambient pressure, said stationary seal member being formed when in its operating position to isolate said first and second regions except along the aforementioned path, whereby the compressible fluid is adapted to pass between said seal face and the complementary movable surface from said one edge toward said second edge, said stationary seal member being adapted to be resiliently mounted such that said seal face is movable under resilient force toward said complementary surface and into engagement therewith and against such resilient force away from said complementary surface to vary the gap between said seal face and said complementary surface, said stationary seal member having:

• a. a sealing dam formed on said seal face adjacent said second edge and an elongated sealing dam groove in said seal face positioned adjacent to and parallel with said sealing dam;
• b. at least two equidistantly spaced transverse inlet plenums formed in said seal face and extending from said first edge thereof transversely across said seal face and terminating in said elongated sealing dam groove forming a plurality of pads on said seal face between adjacent ones of said sealing dam groove, said first edge and the adjacent transverse inlet plenums respectively;
• c. each of said pads having a plurality of equal depth parallel and co-extensive lift pockets formed therein and extending from one of said transverse inlet plenums into the respective pad and terminating in said pad short of but near the next transverse inlet plenum, each of said lift pockets being exposed to said complementary surface and being formed such that, when said movable surface moves relative to said seal face, compressible fluid is moved into each of said lift pockets from its inlet plenum to the leading edge thereof and, by virtue of the velocity shearing gradient between said movable and stationary members, an increased pressure is generated in said lift pockets to urge said seal face away from said movable surface, said lift pocket depth being between at least about 0.010 inches and no more than about 0.025 inches, even after moderate wear of the pad made by rubbing against said movable surface, so that it continues to be of sufficient size to maintain a velocity gradient induced pressure increase therein, said seal member being formed such that in the event of wear of said seal member pads to reduce the depth of said lift pocket, the velocity gradient in said lift pocket is increased to increase the pressure in said lift pocket, whereby said gap is increased to cause said gap to be self-regulating in size, and
• d) said pads each having all of the co-extensive shallow pockets therein connected with each other only by connection to said inlet plenum, respectively, and said shallow pockets each being otherwise effectively separate from an other shallow pocket and from said sealing dam groove in said sealing surface.