Patent ID: 7182059

Claim:
An oil pump mechanism, which is incorporated in a chain saw having a centrifugal clutch and a saw chain adapted to be driven through said centrifugal clutch, and which is activated in synchronization with said centrifugal clutch to supply a lubricating oil to said saw chain, including: a crankshaft; a clutch shoe being mounted on said centrifugal clutch and being connected in driven relation to said crankshaft; a clutch drum disposed coaxially around said crankshaft; a worm fitted on said crankshaft by insertion in a freely rotatable manner, and connected in driven relation to said clutch drum so as to be integrally rotated with said clutch drum; a driven gear engaged with said worm; and a movable pumping element for pumping said lubricating oil, wherein said worm has an inner portion located opposed to said crankshaft and an outer portion including a tooth region, said inner portion being made of self-lubricating resin, and said outer portion being made of wear-resistant metal.