Fan impeller automatic clutch - uses mechanical friction for lower speed range d viscosity friction with speed limiting

摘要

The impeller (3) is bolted onto the composite hub (1) consisting of a split housing (2) and the extended hub (5). The latter is shaped to form a radially extended gap (6) filled with silicon oil. At normal speed the two legs of the extended radial hub, being pre-stressed in outward direction engage against the walls of the housing by means of a step-shaped surface of the extension. At higher speeds, when the shaft input is increasing, at a certain point a slip develops between the extended hub and the housing walls. At this point the oil particles trapped between the stepped surface of the extension and the housing wall limit, due to viscosity friction, the amount of slip to a level which prevents the fan impeller from becoming too noisy.