Torque limit drive transmission

Roller friction gearing comprising a driving shaft, a driven shaft, the center lines of said shafts being parallel but offset radially of one another, an external annular roller-engaging surface secured to one of said shafts, means secured to the other of said shafts and having an internal annular roller-engaging surface, the spacing between said surfaces varying due to the offset of the center lines of said shafts and providing a narrowing pocket between said surfaces in the direction of rotation of the driving shaft, a plurality of rollers between said surfaces and acting to transmit torque from said driving shaft to said driven shaft, one of said rollers being a wedging roller mounted in said pocket and capable of moving further into said pocket as torque transmitted between said shafts causes relative deformation thereof, said wedging roller having an inner annular surface and disposed loosely about an axle, a cross-pin disposed in said axle in substantially tangential orientation with a first end oriented toward said pocket and a second end oriented away from said pocket, said cross-pin having a notch therein formed by a first surface relatively toward said first end and having a relatively large angle relative to the axis of said wedging roller and a second surface relatively toward said second end and having a relatively shallow angle relative to said axis, an axial pin having a tapered end received in said notch and having first and second surfaces complementary to said notch first and second surface, and spring means urging said axial pin end into said notch, said first surfaces initially engaging to bias said wedging roller into said pocket, said cross-pin following said roller until said axial pin end bottoms in said notch, the opposite end of said cross-pin subsequently engaging said inner annular surface to limit movement of said wedging roller into said pocket to limit torque transmitted by said gearing.