Fluid coupling with movable vanes

A fluid clutch of the kind specified comprising power input and output means (11, 13), a pump element (10) and a turbine element (12) connected respectively to the power input and power output means for rotation thereby and providing respectively cooperating pump and turbine chambers rotatable about the same axis and constituting a working chamber, a quantity of working liquid in the working chamber, each element comprising a respective annular element shell (10, 12) and a respective set of radially-extending vortex producing vanes (14, 16), the pump element having an axial extension (19) thereof surrounding the turbine element shell to form a compartment between the extension and the turbine element shell, the turbine element comprising another annular shell (30) fixed thereto, disposed within the said compartment axially spaced from and rotatable with the turbine element shell to form a corresponding enclosure of constant volume therebetween, at least a portion of some of the vanes of said turbine element being movable axially through slots formed in the wall of the respective turbine element shell out of and into the turbine element chamber and respectively into and out of the last-mentioned constant volume enclosure for movement of the movable vanes or vane portions into and out of vortex-producing operative cooperation with the vanes of the pump element, and means operatively connected to the said movable vanes or vane portions for moving them through the slots from a clutch-engaged position in the turbine element chamber in which the pump and turbine vanes cooperate to produce power-transmitting vortices, to a clutch-disengaged position in which the pump and turbine vanes cannot cooperate to produce such vortices.