Overhead camshaft engine valve train with slack take up means

Claim 1

A valve train of an overhead camshaft engine comprising: a valve stem; a valve operating cam; a rocker arm operatively engaged with said valve stem and said cam for transferring motion from the cam to the valve stem and having at a part where it is operatively engaged with the cam a hole; a tappet reciprocatingly mounted in said hole in a manner to define an oil pressure chamber variable in volume in accordance with actual movement of said tappet and having an end protruding from said rocker arm to contact said cam; a source of pressurized oil; passageway means for providing communication between said source of pressurized oil and said oil pressure chamber; check valve means operatively connected with said passageway means for preventing a return flow out of said oil pressure chamber; a spring disposed in said oil pressure chamber to urge said tappet in the direction causing the oil pressure chamber to increase in volume to thereby take up slack in the valve train; and an oil releasing passageway having one end opening directly into the uppermost part of the oil pressure chamber and another end opening to the outside of said rocker arm and providing direct, constant communication between the uppermost part of said pressure chamber and the outside of said rocker arm for constantly effecting a limited release of oil from said oil pressure chamber to permit said tappet to move in the direction causing the oil pressure chamber to decrease sufficiently in volume in order to make an effective take up adjustment during each cycle of valve operation; wherein said tappet is in the form of a cup having a hollow, cylindrical plunger portion slidably received in said hole and a bottom constituting said protruding end, said bottom being enlarged in diameter to provide an outward flange having an annular flat surface disposed in a spaced parallel relationship opposite a flat surface provided on said rocker arm, and wherein said oil releasing opening is constructed so that said opposing flat surfaces are brought into contact with each other to transfer motion from said cam to said valve stem.