Patent ID: 7134416

Claim:
A valve seal mechanism for a rotary valve comprising a first cylindrical valve element and a second cylindrical valve element each formed with a respective valve port, the first cylindrical valve element being rotatable relative to the second cylindrical valve element to a position in which the ports in each cylindrical valve element are aligned, the seal mechanism comprising a substantially rigid sealing frame adapted to substantially surround the periphery of the valve port of the first cylindrical valve element to rotate with the first cylindrical valve element, the arrangement being such that, in use, an outer curved surface of the sealing frame sealingly engages a radially inner surface of the second cylindrical valve element, a sealing element being provided to effect a seal between the sealing frame and the first cylindrical valve element, a predetermined surface area of the sealing frame being exposed to an internal chamber of the first cylindrical valve element such that the pressure within the internal chamber acts on a predetermined surface area of the sealing frame to bias the sealing frame into sealing engagement with the second cylindrical valve element.