Decompression device for an engine

Claim 2

A decompression device for an engine having a crankshaft rotated by a recoil starter, a gear securely mounted on said crankshaft, a camshaft synchronously rotated by said crankshaft, a cam gear supported on said camshaft and meshed with said gear, and a push rod mechanically lifted for opening and closing a valve, the decompression device comprising: a cam portion formed integrally on a periphery of said cam gear including an intake cam and an exhaust cam, a decompression element slidably and rotatable inserted in a hole of said cam portion in parallel with said crankshaft; a decompression cam exposed from a groove with a semicircular section provided in said hole; an annular groove provided at one of sides of said cam gear; a weight provided in said annular groove and at an end of said decompression element; and a spring provided in the annular groove for urging said weight to said camshaft in hand-starting operation and moved apart from the camshaft by centrifugal force, thereby projecting said decompression cam in a compression stroke of the engine so as to open said valve.

Claim 3

The decompression device according to claim 1, wherein the spring is a wire spring provided between an inside wall of the annular groove and a back of the weight, and wherein all of the wire of the spring is disposed in said annular groove.

Claim 4

The decompression device according to claim 1, wherein said annular groove has a groove provided in a peripheral inside wall thereof for insertion of a part of said wire spring.

Claim 5

A decompression device for an engine having a crankshaft, a camshaft synchronously rotated by said crankshaft, a gear provided on said crankshaft, and a cam gear mounted on said camshaft, comprising: an intake cam and an exhaust cam formed on the cam gear for operating an intake valve and an exhaust valve of the engine; the cam gear provided with an annular groove at one of sides thereof and a cylindrical hole parallel with the camshaft; the cylindrical hole being provided to form an exposed groove with a semicircular section; a decompression device having a shaft portion rotatably mounted in the cylindrical hole of the cam gear; a decompression cam exposed from the groove; a weight provided in the annular groove and tangentially extending from the shaft portion; a spring provided in the annular groove for urging the weight to the camshaft in hand-starting operation and moved apart from the camshaft by centrifugal force, thereby projecting the decompression cam in the compression stroke of the engine as to open the corresponding valve; wherein the spring is a wire spring provided between an inside wall of the annular groove and a back of the weight; and a part of the wire spring is engaged in a groove in a peripheral inside wall of the annular groove.

Claim 6

A decompression device for an engine having a crankshaft, a camshaft synchronously rotated by said crankshaft, a gear provided on said crankshaft, and a cam gear mounted on said camshaft, comprising: an intake cam and an exhaust cam formed on the cam gear for operating an intake valve and an exhaust valve of the engine; the cam gear provided with an annular groove at one of sides thereof and a cylindrical hole parallel with the camshaft; the cylindrical hole being provided to form an exposed groove with a semicircular section; a decompression device having a shaft portion rotatably mounted in the cylindrical hole of the cam gear; a decompression cam exposed from the groove; a weight provided in the annular groove and tangentially extending from the shaft portion; a spring provided in the annular groove for urging the weight to the camshaft in hand-starting operation and moved apart from the camshaft by centrifugal force, thereby projecting the decompression cam in the compression stroke of the engine as to open the corresponding valve; wherein the spring is a wire spring provided between an inside wall of the annular groove and a back of the weight; and a part of the wire spring is engaged in a groove in a peripheral inside wall of the annular groove.