| 摘要 |
A clutch mechanism adapted to facilitate disengageable manual operation of a roller door or shutter comprising a chain pulley wheel journalled for rotation about the axis of a first shaft permanently engaged with or common with the main shaft about which the door or shutter is stored but not constrained to rotate with the first shaft at times when such shaft is driven other than manually; a clutch disc journalled alongside the chain pulley wheel on the same axis and similarly free to rotate independently of the first shaft; a linking pin on the chain pulley wheel between the chain pulley wheel and the clutch disc to link the chain pulley wheel to the clutch disc such that rotation of one causes rotation of the other about their common axis; biasing springs on the clutch disc constraining the free end of the linking pin to bias the linking pin into an equilibrium linked position; the biasing springs being sufficiently weak that a light tug on the chain about the chain pulley wheel will allow limited relative rotational movement of the chain pulley wheel relative to the clutch disc out of the equilibrium linked position; a driven disc interposed between the chain pulley wheel and the clutch disc and keyed to the first shaft so as to preclude independent rotation of the driven disc with respect to the shaft; a drive pawl mounted to the clutch disc about a pivot on the disc at a point non-concentric with the axis about which the clutch disc rotates.
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