Patent ID: 8177669

Claim:
A pulley structure comprising: a first rotating member that is rotatable around a first axis; a second rotating member that is rotatable around the first axis and in at least partial axial coincidence with the first rotating member; a spring containing chamber defined between the first and second rotating members; and a spring comprising axially spaced first and second ends defined by coils extending around the first axis, at least one coil at each of the first and second axially spaced ends of the spring radially biased relative to the first axis thereby to be frictionally held against each of the first and second rotating members to thereby allow forces generated by relative rotation between the first and second rotating members to be transmitted through the spring, the spring comprising one plurality of coils extending between the coils at the first and second spring ends, another plurality of coils within the one plurality of coils changing in diameter as the first and second rotating members are relatively rotated, the spring and first and second rotating members configured so that coils in the another plurality of coils, over a substantial axial extent of the spring, between the first and second spring ends, remain at all times unsupported by and out of contact with the first and second rotating members as the first and second rotating members are rotated relative to each other in operation, wherein the first member has an axially opening recess with radially inwardly and outwardly facing surfaces defined by the first member and spaced by a first distance and the at least one coil at the first end of the spring extends into the axially opening recess.