Dimpled bimetal temperature responsive fan drive coupling

Claim 1

A temperature controlled fluid coupling adapted to couple a radiator cooling fan of an internal combustion engine to the engine to thereby rotate the fan, the fluid coupling being of the type including a housing having a drive chamber into which a rotor extends and is positioned, a shear liquid reservoir chamber in the housing, the reservoir chamber communicating with the drive chamber through a temperature controlled valve, the amount of valve opening determining the degree of fluid coupling between the engine and the fan, the valve in one position establishing maximum rotary coupling, a bi-metal laminate mounted on the housing and actuating the valve by an elongated rod, bowing of the bi-metal laminate in one direction due to changes in its ambient temperature causing the valve to open and bowing of the laminate in the opposite manner causing the valve to close, the improvement comprising, the bi-metal laminate having a dimple to thereby define a convex zone on one surface and a concave zone on its other surface, the said elongated rod normally engaging one of said zones in a predetermined orientation of the bi-metal laminate relative to the valve, whereby mounting of the bi-metal laminate in an other orientation relative to the valve causes the valve to be fully open at all temperatures.