Engine cooling system viscosity clutch - has primary disc with fluid-transporting groove on outer disc surface

The arrangement consists of a primary disc (1) keyed on to a shaft driven by the engine. The disc has a U-shaped cross section at the perimeter area and rotates within the secondary disc designed as a closed housing (2). The perimeter surface of the primary disc is provided with a threadlike groove (8) which during its rotation transports continuously fluid from the rear of the disc towards the front. This fluid flow represents the connecting link between the two discs and the secondary disc is carried along. The primary disc is fitted on its perimeter part with an opening (3) which can be closed by a spring loaded valve (4). At relatively low speed the opening remains uncovered, so that the fluid circulation can take place.