US 7,044,025 B2 · Rim sprocket for chain saw

Abstract

Batch casting of rim sprockets for chain saws as particularly applied to larger rim sprockets experience undesired high scrap rate resulting from porosity and chip-out. The solution is to ensure flow of molten steel throughout solidification of the molten steel in the sprocket mold while retaining molten steel portals or gates of a size that permits breakaway of portal stems. Such enhances the cooling rate of the molten steel in the sprocket mold which was found beneficial. The objective of reduced scrap rate is thus accomplished by maintaining a ratio of mass to surface area of the sprockets being cast to no greater than about 4 grams of material to each square inch of surface area and alternatively provide through bores through the rim sprockets which additionally assist in wood chip removal. This design also reduces the material content which reduces the cost and weight of the product.

Claims6

Dependent claims

A rim sprocket for driving a saw chain of a chain saw, which rim sprocket is cast from molten steel in a batch casting process, said sprocket comprising:

spaced apart side walls connected together by circumferentially spaced teeth, said side walls having an outer periphery for supporting side links of the saw chain and the circumferentially spaced apart teeth receiving and engaging center drive link tangs of the saw chain, and said side walls having an inner periphery configured to receive a splined drive shaft of the chain saw for rotatably driving the sprocket, and through engagement of the teeth with the drive link tangs thereby driving the saw chain of the chain saw;
said side walls having continuous peripheral rings of metal defining said inner and outer peripheries and said side walls and teeth cooperatively configured to provide through bores between said teeth and extended through both side walls, said cooperatively configured side walls and teeth having a desired mass of material as compared to the outer surface area of the sprocket that is no greater than about 4 to 1 as measured in grams of weight to square inches of surface area.

Dependencies are inferred from the claim text.

Rim sprocket for chain saw

Life of this patent

Rim sprocket for chain saw

Life of this patent

Abstract

Claims6