Patent ID: 8057199

Claim:
A centrifugal drainage pump, comprising: a rotor chamber and a pump cover chamber which are separated from one another, wherein the rotor chamber includes a pump body, a permanent magnet rotor, a rotor shaft, a bearing, a bearing seat and an impeller washer being installed on the rotor shaft; and the pump cover chamber includes a pump cover with a water-inlet, a shaft sleeve and an impeller provided with a holding chamber in its center for holding the shaft sleeve; wherein the shaft sleeve is provided with a tubular body, and a starting rib which is integral with the shaft sleeve that extends outwardly from the tubular body; the impeller is provided with a stopping rib projecting inwardly from an internal wall of the holding chamber, and the starting rib interferes with the stopping rib after it rotates for a certain distance; the impeller washer is arranged on one end of the shaft sleeve and located inside of the impeller and outside of the holding chamber; the stopping rib of the impeller has a interference contact surface into which a notch extending axially is recessed and an open-end of the notch is narrower than an inner space of the notch; and a shock absorbing pad having a convex ridge extending from its side that contacts with the interference contact surface, and the convex ridge can be embedded in the notch in order that the pad tightly contacts with the stopping rib and the convex ridge of the shock absorbing pad is integrated firmly with the notch of the stopping rib which prevents separation of the shock absorbing pad from the stopping rib under frequent impacts between the starting rib and the stopping rib during start-up of clockwise and counterclockwise rotation of the impeller.