A manual screw shaft driving device, comprising:
- a screw shaft, which is a rod-shaped member extending on an axis, being formed with screw threads around an outer peripheral surface of the screw shaft;
- a driving member, which has a tubular shape, being formed with driving threads on an internal surface of the driving member, the driving threads being corresponding in shape and spirally fitted to the screw threads to enable the driving member to relatively slidably and rotatably fit around the screw shaft along the axis;
- a front one-way bearing, wherein an inner ring of the front one-way bearing is fixedly fitted around the driving member to support the driving member on the axis, the inner ring of the front one-way bearing is rotatable in a first rotation direction in relation to an outer ring of the front one-way bearing, and the inner ring of the front one-way bearing is not rotatable in a second rotation direction, whose rotating direction is opposite to the first rotation direction, in relation to the outer ring of the front one-way bearing;
- a rear one-way bearing, which is provided behind the front one-way bearing, wherein an inner ring of the rear one-way bearing is fixedly fitted around the driving member to support the driving member on the axis, the inner ring of the rear one-way bearing is rotatable in the second rotation direction in relation to an outer ring of the rear one-way bearing, and the inner ring of the rear one-way bearing is not rotatable in the first rotation direction in relation to the outer ring of the rear one-way bearing;
- a front teeth member, fixed to the outer ring of the front one-way bearing;
- a rear teeth member, fixed to the outer ring of the rear one-way bearing;
- a gripping member, which has a tubular shape, being formed with a sliding and rotating space inside the gripping member, wherein the driving member, the front one-way bearing and the rear one-way bearing are rotatably disposed in the sliding and rotating space such that the driving member is rotatable in the first rotation direction in a manner that the inner ring of the front one-way bearing, the inner ring of the rear one-way bearing and the outer ring of the rear one-way bearing rotate integrally with the driving member, and the driving member is rotatable in the second rotation direction in a manner that the inner ring of the front one-way bearing, the outer ring of the front one-way bearing and the inner ring of the rear one-way bearing rotate integrally with the driving member;
- and
- a driving direction switching member, disposed at the gripping member and having a front pawl portion corresponding to the front teeth member and a rear pawl portion corresponding to rear teeth member, wherein the driving direction switching member is disposed to switch between a first switching position and a second switching position;
- wherein while the driving direction switching member is switched to the first switching position, the front pawl portion engages to the front teeth member so that the outer ring of the front one-way bearing is fixed to the gripping member through the front teeth member such that the driving member becomes a first state in which the driving member is not rotatable in the second rotation direction and is rotatable in the first rotation direction,
- in the first state, when the gripping member slides forwardly and backwardly in relation to the screw shaft, the screw shaft is driven to rotate in the first rotation direction in relation to the gripping member by a screw mechanism between the screw threads and the driving threads of the driving member since the driving member is not rotatable in the second rotation direction and the driving member rotates in the first rotation direction in relation to the screw shaft, thereby not driving the screw shaft to rotate in the second rotation direction,
- wherein while the driving direction switching member is switched to the second switching position, the rear pawl portion engages to the rear teeth member so that the outer ring of the rear one-way bearing is fixed to the gripping member through the rear teeth member such that the driving member becomes a second state in which the driving member is not rotatable in the first rotation direction and is rotatable in the second rotation direction,
- in the second state, when the gripping member slides forwardly and backwardly in relation to the screw shaft, the screw shaft is driven to rotate in the second rotation direction in relation to the gripping member by the screw mechanism between the screw threads and the driving threads of the driving member since the driving member is not rotatable in the first rotation direction and the driving member rotates in the second rotation direction in relation to the screw shaft, thereby not driving the screw shaft to rotate in the first rotation direction.