Hydraulic tappet for IC engine - has piston sealed to cylinder with air vent above piston

摘要

The tappet has a cylindrical body with a crown piece which has an internally projecting cylinder. A piston (2) fits tightly in the cylinder. Oil is admitted to the inside of the piston through a radial passage (2). A plate (5) is held above the piston by a spring. The piston is sealed (3) to the cylinder but the plate has a small clearance (6) to it. Air passes through the clearance easily while oil flows through it very slowly. The air is thus vented and is discharged through an annular channel (7) surrounding the plate (5) in the crown. There is a radial outlet (8) from the channel.