Patent ID: 7434502

Claim:
A chain saw having a retaining assembly for a tensioning arrangement for adjusting the tension of a cutting chain, the chain saw having an engine chassis, a clutch cover, and a guide bar for the cutting chain, the retaining assembly comprising: a rotatable knob operatively cooperative with the engine chassis, the clutch cover, and the guide bar, wherein the knob may be rotated about a rotational axis between a tightened position, in which the guide bar is fixed in place between the engine chassis and the clutch cover, and a loosened position, in which the guide bar is loosened and may be repositioned using the tensioning arrangement so as to adjust the tension of the cutting chain on the guide bar; a plurality of engagement points fixed relative to the clutch cover; and a locking mechanism connected to the rotatable knob for alternatively locking the rotatable knob against rotation about its rotational axis and unlocking the rotatable knob to enable the rotatable knob to be rotated about its rotational axis, the locking mechanism including a plurality of moveable engagement points and means for moving the movable engagement points alternatively outwardly and inwardly of the confines of the rotatable knob into and out of engagement, respectively, with the engagement points fixed relative to the clutch cover; wherein the means for moving the movable engagement points moves the movable engagement points alternatively radially outwardly and inwardly of, and substantially perpendicularly to, the rotational axis of the rotatable knob into and out of engagement, respectively, with the engagement points fixed relative to the clutch cover; and wherein the locking mechanism includes a lock on which the moveable engagement points are located, the lock being slidably mounted within the rotatable knob for alternative movement radially outwardly and inwardly of, and substantially perpendicularly to, the rotational axis of the rotatable knob, whereby the movable engagement points are, respectively, extended beyond the confines of the rotatable knob and into engagement with the engagement points fixed relative to the clutch cover and retracted within the confines of the rotatable knob and out of engagement with the engagement points fixed relative to the clutch cover.