Patent ID: 6918746

Claim:
A water pump of the centrifugal type adapted for use in engine cooling systems, the water pump comprising: a housing containing a shaft rotatable on an axis extending through the housing, the shaft mounting a drive member adjacent a drive end of the housing and a fluid impeller at an opposite impeller end of the housing; axially spaced roller bearings supporting the shaft in the housing, each bearing having an inner race fixed on the shaft and an outer race mounted in the housing, the outer race of one bearing being fixed in the housing and oriented to transmit major thrust forces from the shaft to the housing and the outer race of the other bearing being axially slidable in the housing and oriented to transmit minor thrust forces to the housing; and a biasing element disposed axially between the bearings and acting between the housing and the axially slidable outer race to preload the other bearing in a direction away from the one bearing with a selected preload force maintained on the other bearing, thereby preloading both bearings with a minimum preload force to maximize bearing life and concentric rotation of the shaft over all operating conditions of the pump.