Patent ID: 7153227

Claim:
A decoupler, comprising: a hub structure capable of being mounted on a shaft; a pulley mounted on said hub structure and capable of relative rotational movement with respect to said hub structure; a coil spring extending between said pulley and said hub structure resiliently coupling said pulley with said hub structure, said coil spring transmitting driven rotational movements of said pulley to said hub structure; an inner spring engaging structure comprising a slip ring in contact with a portion of said coil spring and rotatably mounted on said hub structure and rotationally fixed with respect to said pulley, said inner spring engaging structure engaging volutes of said coil spring as a result of radial contraction of said coil spring, whereby as said coil spring engages said inner spring engaging structure, a spring rate of said coil spring increases before directly coupling said pulley to said hub structure; a C-shaped sleeve surrounding said coil spring said sleeve limiting radial expansion of said coil spring, whereby as said coil spring engages said sleeve, said spring rate increases before directly coupling said pulley to said hub structure; and wherein said coil spring is radially spaced from said inner spring engaging structure by a first predetermined clearance gap and said sleeve is radially spaced from said pulley by a second predetermined clearance gap.