Automatic clutch

An automatic clutch for effecting engagement between rotatable driving and driven members in response to rotation of said driving member, said driving member including means defining straight and helical splines, said clutch comprising first and second clutching means respectively rotatable with said driving and driven members, said first clutching means being axially movable relative to said driving member to first and second positions respectively out of and in clutching engagement with said second clutching means, said first clutching means being guided in its axial movement by said straight spline, means biasing said first clutching means for axial movement to its first position in the absence of rotation of said driving member, and means for moving said first clutching means axially to its second position, said moving means including an actuator rotatable with and axially movable relative to said driving member, said actuator being guided in its axial movement by said helical spline, means tending to retard rotation of said actuator thereby effecting said axial movement of said actuator relative to said driving member, and means coupling said actuator with said first clutching means for effecting said axial movement of said first clutching means to its second position in response to said axial movement of said actuator.