Patent ID: 8002285

Claim:
A seal for sealing a circumferential gap between a first machine component and a second machine component which is rotatable relative to the first machine component about a longitudinal axis, comprising: at least one shoe having a first surface and a second surface spaced from said first surface, said first surface extending along one of said first and second machine components in a position to create a non-contact seal therewith, said first surface being formed with a first area which extends longitudinally at a substantially constant radial spacing between first and second ends thereof relative to one of said first and second machine components, a second area which extends longitudinally at a substantially constant radial spacing between third and fourth ends thereof relative to one of said first and second machine components, said second area being substantially parallel to and radially spaced from said first area, a flow contraction area connected between said second end of said first area and said third end of said second area, and a converging area extending in a longitudinal direction from said forth end of said second area of substantially constant radial spacing and in a direction toward one of said first and second machine components; at least one spring element adapted to connect to one of the first and second machine components and being connected to said second surface of said at least one shoe, said at least one spring element being effective to deflect and move with said at least one shoe in response to the application of fluid pressure to said at least one shoe in such a way as to assist in the creation of a primary seal of the circumferential gap between the first and second machine components; at least one secondary seal acting on said second surface of said at least one shoe and being effective to deflect and move with said at least one shoe in response to the application of fluid pressure to said at least one shoe in such a way as to assist in the creation of a secondary seal of the circumferential gap between the first and second machine components.