Patent ID: 8006820

Claim:
A torsional damper, comprising: a hub assembly rotatable about an axis of rotation and having a hub; a disc assembly centered with respect to the axis of rotation; a first plate having a plurality of circumferentially distributed first apertures and fixed to one of the disc assembly and the hub assembly for rotation therewith; a pair of facing cover plates with the cover plates having a plurality of aligned circumferentially distributed cover plate apertures defining spring pockets at least partially aligned with the disc apertures and the cover plates fixedly secured to the other of the disc assembly and the hub assembly to which the first plate is not fixed, the cover plates radially overlapping and sandwiching the first plate therebetween; and a plurality of coil springs with one spring disposed in each of the spring pockets and the plate apertures and the spring pockets retaining the coil springs therein, the coil springs being compressed with relative rotation between the hub assembly and the disc assembly; wherein the cover plate apertures have parallel inner and outer edges and end portions of the otherwise parallel outer edge defined at least in part by an arc eccentric to the axis of rotation and having a radius of approximately one half the radius of the cover plate and the parallel outer edge defining a chord across the arc and the end portions providing deflection relief near the ends of the coil springs.