Reinforcing bar binding machine

1. A reinforcing bar binding machine comprises:

a main sleeve having a tip end on which a hook is pivotally mounted;

a tip end shaft fitted in an inside of the main sleeve;

a spiral screw groove formed on the tip end shaft;

a fitting opening that penetrates from an outside to the inside of the main sleeve;

a key fitted in the fitting opening and brought in mesh engagement with the screw groove;

a short sleeve provided on an outer periphery of the main sleeve and covering the key; and

engaging means formed on the short sleeve and controlling a rotation of the main sleeve.

2. The reinforcing bar binding machine according to claim 1 , wherein the short sleeve comprises a short sleeve main body and a stopper sleeve, and an outer side of the key is covered by the stopper sleeve.

3. The reinforcing bar binding machine according to claim 2 , wherein front and rear ends of the stopper sleeve respectively engage with a rib formed on the outer periphery of the main sleeve and the short sleeve.

4. The reinforcing bar binding machine according to claim 1 , wherein the main sleeve and the short sleeve are engaged with each other by key coupling.

5. The reinforcing bar binding machine according to claim 1 , further comprising a cutter ring which fits on the outer periphery of the main sleeve and actuates a cutter of a wire, wherein the cutter ring is sandwiched and fixed between the short sleeve and a stopper ring attached on the main sleeve.

6. The reinforcing bar binding machine according to claim 1 , further comprising:

a spring collar fitting on the tip end shaft; and

a compression spring provided between a planet cage coupled to a rear end of the tip end shaft for rotatably supporting a planet gear configuring a speed reduction mechanism of a drive motor and a rear end of the main sleeve, and disposed on an outer side of the spring collar.

7. The reinforcing bar binding machine according to claim 6 , wherein the planet cage and the tip end shaft are coupled by a parallel pin, and

the parallel pin is prevented from coming out by a bearing portion of the planet cage.

8. The reinforcing bar binding machine according to claim 6 , further comprising a bumper provided between the planet cage and a rear spring collar.

9. A reinforcing bar binding machine comprising:

a sleeve having a tip end on which a hook is pivotally mounted;

a long fin which is long in an axial direction of the sleeve and a short fin which is short in the axial direction, the long and short fins being formed on the sleeve at intervals in a circumferential direction of the sleeve;

a tip end shaft fitted in an inside of the sleeve;

a spiral screw groove formed on the tip end shaft;

a fitting opening that penetrates from an outside to the inside of the sleeve;

a key fitted in the fitting opening and brought in mesh engagement with the screw groove;

a rotation stopper provided on a binding machine body and engageable with the long and short fins; and

a bumper provided between a jutting part provided on a base portion of the tip end shaft and an end face of the sleeve;

wherein, when the long fin engages with the rotation stopper, the sleeve advances with respect to the tip end shaft by a rotation of the tip end shaft so that the hook grasps a wire,

wherein, when the sleeve retreats to a standby position by a reverse rotation of the tip end shaft and the short fin disengages from the rotation stopper, the tip end shaft and the sleeve integrally rotate so that the long fin engages with the rotation stopper to set the hook in a predetermined orientation,

wherein, when the sleeve retreats, by a frictional force between the spiral screw groove and the key caused by colliding the sleeve with the bumper, the tip end shaft and the sleeve integrally rotate.

10. The reinforcing bar binding machine according to claim 9 , wherein, after the short fin and the rotation stopper are disengaged when the sleeve retreats, the sleeve is collided with the bumper at a controlled fixed number of rotations, and

a drive motor is stopped based on a change in current or number of rotations when the bumper is compressed by the collision.

11. The reinforcing bar binding machine according to claim 9 , wherein, after the short fin and the rotation stopper are disengaged when the sleeve retreats, a drive motor is controlled to rotate at a low speed immediately before the sleeve is collided with the bumper, and

the drive motor is stopped, based on a change in current or number of rotations when the bumper is compressed by the collision.

12. The reinforcing bar binding machine according to claim 9 , wherein when the sleeve collides with the bumper, a change in current or number of rotations when the bumper is compressed is monitored, and the drive motor is rotated at a fixed number of rotations and then stopped.