US Patent 8434236 Chain saw with tension adjustment

A chain saw apparatus has a body, a guide bar extending from the body, a drive sprocket rotatably mounted to the body, a chain affixed to the drive sprocket and to the guide bar, an engagement device positioned on the body and cooperative with the guide bar so as to allow the guide bar to move toward and away from the body, and pushing device for automatically moving the guide bar away from the drive sprocket. The pushing device has a slide and an elastic component. The slide bears against a rear end of the guide bar. The elastic component urges between the body and the slide.