GARRA PARA VENTILADOR DE VEICULO A MOTOR

In a vehicle engine fan clutch 110 a driven member 24 comprises a pair of relatively rotatable, axially extensible portions 38-40, so that when a belt 66 carried by a driving member 12 is brought into driving engagement with the driven member, relative rotation between the portions extends the same so that engagement surfaces 56-58 on one of the portions and on the driving member are brought into engagement. A spring (72) (Fig. 1, not shown) holds the belt in driving engagement with the driven member when engine speeds are below a predetermined level, but yields to permit the belt to move out of engagement with the driven member when engine speed exceeds the predetermined level. A temperature responsive capsule (88) pivots a lever (78) which holds the belt engaged with the driven member when the temperature level exceeds a predetermined level, regardless of engine speed. The rotatable, axially extensible portions 38, 40 of the driven member may be connected by rollers 44 and co-operating camming surfaces, or by interengaged screw threads (Figs. 4 and 5, not shown) or by a ball and groove arrangement (Fig. 6, not shown).