| 摘要 |
A chain saw is provided with a saw chain cassette and a releasable clamping cover for holding the cassette against the side of the chain saw frame. The clamping cover, together with the cassette and the chain saw frame, have aligning surfaces extending in a direction longitudinal of the cassette saw bar for preventing relative rotation between the saw bar and the frame. A tightening mechanism for the cassette is used for urging the saw bar forwardly with respect to its drive sprocket and a further mechanism is provided within the cassette comprising a spring biased shoe for urging the cassette sprocket in a direction for tightening the chain when the cassette is removed from the chain saw frame. A camming device on the frame engages the shoe when the cassette is installed on the frame for holding the shoe away from the sprocket such that the latter can be driven by the chain saw motor drive shaft.
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