Patent ID: 7178651

Claim:
A thermal clutch assembly for rapidly de-coupling one rotatable member from another rotatable member when the temperature of the surrounding medium goes to or above a predetermined temperature and for rapidly re-coupling the two rotatable members when the temperature of the surrounding medium returns to below the predetermined temperature, the assembly comprising: a radially inner rotatable member; a radially outer rotatable member; a pair of axially spaced apart ring structures which are both affixed to and rotate with one of the rotatable members, the ring structures each having at least one substantially axial surface which may contact substantially axial surfaces of the other rotatable member; and a thin tension web which has high tensile strength, a high surface area to volume ratio, a thermally efficient flow arrangement to the surrounding medium, and high thermal conductivity, and which is secured to each of the two ring structures and substantially spans the space between the substantially axial surfaces of the ring structures, the web having a significantly higher thermal coefficient of expansion than the material between the substantially axial surfaces of the other rotatable member such that the web is in tension at temperatures of the surrounding medium below the predetermined temperature thereby causing the substantially axial surfaces of the ring structures to engage the substantially axial surfaces of the other rotatable member for coupling the two rotatable members for rotating together, and is not in tension at temperatures of the surrounding medium at or above the predetermined temperature thereby causing the substantially axial surfaces of the ring structures to disengage from the substantially axial surfaces of the other rotating structure for de-coupling the two rotatable members so they do not rotate together.