Patent ID: 7464678

Claim:
1 . A hydraulic lash adjuster comprising: a cylindrical body having an annular oil groove for receiving oil from an oil gallery of an engine; a central cylindrical bore in the body and having a closed end; a first oil inlet passage through a side wall of the body into the bore; a hollow plunger reciprocable in the bore and having a reservoir chamber therein; a second oil inlet passage through a side wall of the plunger into the reservoir chamber; a high pressure chamber defined by the plunger and the closed end of the bore, the plunger having a close clearance with the bore to limit leakage of oil from the high pressure chamber; a second wall of the plunger separating the reservoir chamber from the high pressure chamber, the second wall including an orifice controlled by a check valve operative to allow oil flow through the orifice from the reservoir chamber to the high pressure chamber and to prevent oil flow from the high pressure chamber to the reservoir chamber; a plunger spring disposed in the high pressure chamber urging the plunger away from the closed end of the bore to draw oil into the high pressure chamber when unloaded; and a circumferential external groove around the side wall of the plunger between the second oil inlet passage and an end of the plunger distal from the high pressure chamber, the groove configured to restrict the passage of air through the plunger to body clearance into the reservoir chamber.