Patent ID: 8206083

Claim:
A force balanced seal for use in connection with a rotor in a turbomachine, comprising: a) an annular sealing member in opposed facing disposition to the rotor, comprising: i) a face dam defining a radially outboard portion of the sealing member and having a surface parallel with a sealing surface of the rotor; ii) a groove radially inboard of the face dam and also facing the rotor; iii) an air bearing surface, located radially inboard of the groove, and being parallel with the face dam surface and therefore parallel with the sealing surface of the rotor; iv) at least one first passageway through the sealing member having a first entrance formed in the groove and a second entrance formed in a surface of the sealing member facing oppositely from the air bearing surface such that the first passageway is in fluid communication with a low pressure compartment of the turbomachine; v) a second passageway through the sealing member having at least one orifice formed in the air bearing surface and an inlet formed in a radially outwardly facing surface of the member such that the second passageway is in fluid communication with a high pressure compartment of a turbomachine; b) a spring connected to a housing of the turbomachine, for biasing the sealing member towards the rotor; wherein the combination of a first force exerted by the spring and a second force resulting from outward flow of high pressure air from the orifice in the air bearing surface maintains a desired operating clearance between the sealing member and the rotor.