Hydraulic power transmission device with centrifugally actuated clutch override

Claim 1

A hydraulic power transmission device with a centrifugally actuated clutch override, comprising: first and second coaxially arranged independently rotatable shaft assemblies, said shaft assemblies being provided respectively with first and second wall members defining a chamber adapted to contain a viscous fluid; first and second mutually spaced discs alternately arranged in said chamber, said first and second discs being respectively connected to and rotatable with said first and second shaft assemblies, with the viscous resistance of the fluid in said chamber providing a rotational driving connection between said first and second discs and their respective shaft assemblies; and clutch means arranged between said shaft assemblies, said clutch means including at least one clutch member carried on said first shaft assembly at a location surrounded by a circumferential surface on said second shaft assembly, said clutch member being movable radially outwardly into engagement with said circumferential surface in response to centrifugal forces developed during rotation of said first shaft assembly above a selected angular velocity, thereby establishing a rotational driving connection between said first and second shaft assemblies which overrides the rotational driving connection derived from the viscous resistance of the fluid in said chamber.