US Patent 7399001 Rotary fluid-feed coupling with temperature compensation

A rotary coupling has a nonrotatable stator having a stator passage with an end opening along an axis and a rotor rotatable on the stator about the axis and having a rotor passage with an end axially confronting the stator end. A rotor seal is rotatable with the rotor end about the axis, and a stator seal is rotationally fixed to the stator end and bears axially on the rotor seal. Thus the rotor seal rotates on the stator seal on rotation of the rotor. A strain element that changes size in response to temperature in the stator adjacent the seals is coupled to one of the seals for shifting the one seal relative to the other seal in response to temperature changes adjacent the seals.