Valve system for overhead valve type four-cycle engine

Claim 1

A valve system for the overhead valve type four-cycle engine disposing the intake and exhaust valves substantially symmetrically to each other with respect to the cylinder center line, wherein the valve stems are so tilted in the cylinder head that the valve bodies are in juxtaposition close to the cylinder center line, comprising; for each cylinder, two guide cams disposed around the circumferential surfaces of two crank shafts extending on each side of a crank pin, each cam having a shape of a "figure-eight" folding around the crank shaft while returning back to the starting point in two turns, and also having one projection in the course of said turn; two sliding pieces each having an arm extending sideways at the lower end of a stem thereof and engaging at the other end of said arm with one of said guide cams, and said stem of said sliding piece being able to slide parallel to the cylinder center line along a guide hole disposed in the cylinder as well as to rotate about its own axis; two push rods each engaging at the lower end thereof with the top end of one of said sliding pieces and said two push rods extending essentially parallel to and symmetrical with respect to the cylinder center line; and two rocker arms being supported at the center thereof by a common rocker shaft disposed in the center of the cylinder head, and each engaging at one end with the top end of one of said push rods and at the other end with the top end of one of said valve stems of said intake or exhaust valve; and said projection on said guide cam for the intake or exhaust valve being disposed at such a place as to engage with said sliding piece at the rotational angle of the crank shaft corresponding to the opening timing of the intake or exhaust valve.