Patent ID: 7249768

Claim:
A pressure-actuated shaft seal assembly for controlling the flow of a fluid adjacent a rotatable shaft between first and second fluid chambers of the assembly, the seal assembly comprising: a first seal member extending circumferentially around the rotatable shaft to define a fluid passage between the seal member and the shaft, the seal member being adjustable in an axial direction between open and closed positions, the seal member in the open position configured to define a space fluidly connecting the first fluid chamber to the passage between the seal member and the shaft, and the seal member in the closed position configured to close the space to substantially seal the fluid passage and prevent the fluid from flowing from the first chamber of the assembly through the passage; and a housing extending circumferentially around the shaft and extending between the first and second fluid chambers, the housing being configured to at least partially receive the first seal member such that the housing defines third and fourth fluid chambers on opposite sides of a portion of the first seal member; wherein the third and fourth chambers are fluidly connected to first and second fluid sources, respectively, such that the seal member is configured to be adjusted axially between the open and closed positions by a pressure differential between the first and second fluid sources.