Patent ID: 7351169

Claim:
A power transmission device for utility machinery, the transmission device including: (a) a hub supporting a first sheave member having a first face; (b) a sleeve received on and supported only by said hub and moveable axially and rotationally in relation to said hub, said sleeve supporting a second sheave member having a second face that opposes said first face such that said first and second faces define therebetween a groove adapted to receive a belt and relative axial movement therebetween being adapted to vary at least one of the pitch and grip of said belt; and (c) a torque dependent pressure device comprising at least one wedge member disposed on one of said sleeve and said hub and an associated wedge track disposed on the other of said sleeve and said hub, said wedge member being arranged in use in the event of belt slippage to move along said wedge track so as to rotate said sheave members relative to each other and to simultaneously force said sheave members axially towards each other and thereby to increase grip on said belt, wherein said wedge member and said wedge track are substantially enclosed in a casing defined within said power transmission device by one or more of said sheave members, hub and sleeve.