Self-tailing winch

In a self-tailing winch for a sheet of the kind having in combination a stationary frame, a rotatable input shaft supported by said frame, a rotatable drum supported by said frame, a reduction gear train connecting said input shaft to said drum so that said drum is driven by said shaft, sheet gripping means attached to and axially aligned with the upper end of said drum for rotation therewith, said gripping means having inner annular surfaces defining an annular groove between them, whereby said groove defines a constant winding diameter for said sheet, said groove having an effective root diameter substantially equal to or less than the winding diameter of said drum, a stationary member anchored to said frame near the top of said drum, and sheet deflector means supported by said stationary member and adapted to feed a sheet from said drum to said groove, the improvement wherein said gripping means comprises a pair of juxtaposed toroidal gripping diaphragms each composed substantially of elastomeric material, said diaphragms abutting respectively, at least in part, a surface of said stationary member and a surface of support means co-extensive with said upper end of said drum, with a free space interposed between each said diaphragm and a respective one of said last-mentioned surfaces, whereby the initial feeding of said sheet to said groove deflects said diaphragms into the respective free spaces against a lesser reactive force, and whereby upon the resultant filling of said spaces the further motion of said sheet towards the root of said groove distorts said diaphragms against a greater reactive force.