JPH0314086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a clutch mechanism for determining the tightening torque of a power tool for automatically tightening a screw, bolt or nut.

Conventional configuration and its problems Conventional power tools have a shut-off type clutch mechanism that tightens screws with a constant torque, and when the screw tightening torque reaches a set value, the clutch mechanism moves away, but on the rotating side (motor side) This causes the clutch mechanism to shift in the rotational direction on the fixed side (bit side).

In the conventional clutch mechanism shown in Fig. 2, when the driving force is cut off at the highest point of disengagement (top dead center), the motor suddenly stops at this point and enters the state shown in Fig. 3, unable to recover by itself. It had the disadvantage of disappearing.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a clutch mechanism that provides a space for rotational deviation to one side of the disengaged portion of the shutter-off clutch and provides a force, thereby eliminating the possibility of stopping at top dead center. It is something.

Structure of the Invention The present invention relates to a camshaft that directly receives torque from a drive source, a ring cam that fits into this shaft and has a structure in which rotational directions are connected by claws that engage with each other, but has rotational play, and a camshaft. A torque-responsive clutch consisting of a hammer ring that is slidably fitted into the ring cam and rotatably connected to the ring cam with a steel ball interposed between the parts allows the hammer ring to stop at a neutral point when it separates from the ring cam. It has the unique effect of preventing things from happening.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 shows an outline of a power tool including an embodiment of the present invention, in which A is a clutch portion including the mechanism of the present invention, B is a reducer portion, C is a motor, and bit 1 at the tip of clutch portion A is shown. When pressed against the screw, the limit switch 3 is activated by the switch rod 2 interposed in the center hole of the clutch part A, reducer part B, and motor C, and the power supplied from the power cord 4 is supplied to the motor, causing the motor C to rotate. It is something. 5 is a switch for changing the rotation direction of the motor C, and 6 is an exterior cover.

A first example is shown. In FIG. 4, 7 is a camshaft, and a ring cam 8 is fitted onto this. Ball 9 climbing up and down cam mountain 8a of ring cam 8
The hammer ring 10 having a groove in its groove is attached to the camshaft 7.
is slidably fitted to the A bit holder 11 fits into the center hole of the camshaft 7, and a return spring 12 is interposed between it and the camshaft 7. The bit holder 11 has a pawl receiver 14 that slides in the axial direction but whose rotational direction is regulated by a steel ball 13, and a pawl 14a at one end engages with a pawl 10a at one end of the hammer ring 10. There is. Claw receiver 1
4 and the retaining ring 15 near the center of the bit holder 11.
A reset spring 16 is biased in between. A lock spring 19 is enclosed between the camshaft 7 and a camshaft bushing 18 press-fitted into the camshaft 7 on the left end surface of the lock cam 17 which is inserted into the center hole of the camshaft 7 and the bit holder 11, and a switch rod is inserted into the center of the lock spring 19. It extends to the limit switch 3 in FIG. A steel ball 20 interposed in a side hole of the bit holder 11 partially peeks out from the neck 17a of the lock cam 17. Reference numeral 21 designates a clutch case that covers the clutch portion A, and a torque spring 24 is biased between the inner surface of the clutch case and the hammer ring via a thrust bearing 22 and spring seats 23 and 23'. 25 is a torque adjuster nut screwed into the clutch case, 2
Reference numeral 6 denotes a ring fitted on the left end thereof, and is structured so that several pins 27 in the clutch case 21 press against the spring seat 23' as the torque adjuster nut moves. 28 is clutch case 2
1, with a knob spring 29 interposed between the clutch case 21 and the steel ball 30.
It is stopped from rotating, and the bushing 31 is press-fitted into the tip.
A retaining ring 32 of the bush 31 is fitted. 33 is a retaining ring on the knob 28, 3
4 is a ring on the camshaft 7, 35 is a bit 1
This is a steel ball to prevent it from falling out. When the bit 1 is pressed against the screw, the claw 14a of the claw holder and the hammer ring 1
The claws 10a of 0 engage with each other. At this time, the limit switch 3 is activated by the movement of the switch rod 2, and the motor C is rotated.

In Fig. 5, when the screw (not shown) reaches a certain torque, the bit 1, bit holder 11, and pawl receiver 14 stop, but since the motor C still tries to continue rotating, the torque is transmitted through the reducer part B. The generated driving force is transmitted to the camshaft 7, which also rotates the ring cam 8, causing the steel ball 9 to climb the cam ridge 8a of the ring cam 8, and the hammer ring 10 to move in the direction of arrow a. The hammer ring 10 has a claw receiver 1 at its right end.
Push back 4. At this time, the steel ball 20 is locked into the lock cam 17.
It is moved by the pressure of the lock spring 19 that presses and enters the hole in the pawl receiver 14. At this time, the switch rod 2 returns to its original position and the limit switch 3 is turned off, stopping the motor C. As shown in FIG. 6, when the hammer ring 10 is moved over the cam ridge 8a, it returns to the direction indicated by the arrow b.
move in the direction. On the other hand, since the claw receiver 14 cannot return to its original position due to the action of the steel ball 20, the claw 1
The mesh between 0a and 14a is out of alignment. In this state, the transmission of the driving force to bit 1 is completely cut off.

FIG. 7 shows a state in which the steel ball 9 has climbed the cam ridge 8a of the ring cam 8. The ring cam 8 and the camshaft 7 are engaged with each other with some play in the rotational direction, and the camshaft 7 is When rotating in the direction of arrow C, the surface 7a of the camshaft 7 and the surface 8b of the ring cam 8
contacts and moves the steel ball 9 along the cam ridge 8a. At the moment when the steel ball 9 finishes climbing the cam mountain 8a, the rotational force that has been applied to the steel ball 9 until now is released, and the reaction force given by the inertia force causes the ring cam 8 to move as shown by the arrow d.
being swung in a direction. On the other hand, steel ball 9 is ring cam 8
The steel ball 9 tries to roll in the direction of arrow e in the opposite direction.
It becomes impossible to stop at the top dead center position.

This prevents the clutch from stopping at its neutral point.

Next, a second example will be shown. In Figure 8, 3
Reference numeral 6 denotes a spring stretched between the cam shaft 7 and the ring cam 8. When tightening the screw, the spring 36 is pulled so that the surfaces 7a and 8b come into contact with each other, and the cam ridge 8a of the steel ball 9 is brought into contact with the cam ridge 8a at the position shown by the dashed line. The cam 36 moves over the top, but the moment the cam 36 climbs over the top, the elastic force of the spring 36 returns to its original state and causes the steel ball 9 to come off the top of the cam crest. This prevents the clutch from stopping at the neutral point.

In the conventional example shown in FIGS. 2 and 3, the camshaft 7' has a cam ridge 8'a on its circumferential surface and moves the steel ball 9' in the radial direction. Since the steel ball 9' is integrated with the cam ridge 8'a, the steel ball 9' is integrated with the cam ridge 8'a.
When it reaches the apex of point a, it cannot move away from the drive source, and when the drive source is stopped, the steel ball 9' remains trapped between it and the hammer ring 10'.

For this reason, a neutral point stop occurs.

Effects of the Invention As described above, a conventional camshaft is divided into a ring-shaped cam having cam ridges in the axial direction and a shaft that holds this, and a margin is provided between the ring-shaped cam and the shaft in the direction of rotation. By interlocking or applying the elastic force of a spring between the two, we eliminate the need for a torque-responsive clutch to stop at a neutral point, which disengages according to the torque when tightening a screw, thereby providing a highly reliable power tool. This has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is an overall view of a power tool showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing a conventional torque-responsive clutch section, Fig. 3 is a - cross-sectional view of Fig. 2, and Fig. 4 is Fig. 1 is a full sectional view of the clutch part A, Fig. 5 is a sectional view showing the torque responsive clutch when it is disengaged, Fig. 6 is a sectional view when the torque is cut off, and Fig. 7 is a partial view showing the neutral point stop position. 8 is a cross-sectional view of a portion of a torque responsive clutch showing a second embodiment. 7...Cam shaft, 8...Ring cam, 9...Steel ball, 10...Hammer ring, 11...Bit holder, 12...Return spring, 14...Claw holder,
16...Reset spring, 17...Lock cam, 1
9... Lock spring, 20... Steel ball, 21... Clutch case, 24... Torque spring, 36... Spring.

Claims (1)

[Scope of Claims] 1. A camshaft, a link cam having a cam ridge shape that fits on the camshaft and rotates integrally with the camshaft while regulating the rotational direction, and a link cam that fits on the camshaft and rotates integrally with the camshaft. a movable hammer ring rotatably coupled to the ring cam via a steel ball; a bit holder that fits into the cam shaft center hole and holds a tip tool;
a pawl receiver rotatably coupled to the bit holder and slidable and capable of engaging with the hammer ring; a lock cam inserted into the center hole of the cam shaft and the bit holder; and a lock cam that is open in the radial direction of the bit holder. A steel ball interposed in the horizontal hole, a lock spring that presses one end of the lock cam, a reset spring that presses one end of the pawl receiver, a return spring stretched between the cam shaft and the bit holder, and a lock spring that presses one end of the lock cam, a return spring stretched between the cam shaft and the bit holder, and a lock spring that presses one end of the lock cam. A clutch device for a power tool, comprising: a torque spring that presses the clutch case; 2. Claim 1, wherein a spring is provided between the camshaft and the ring cam to bias the camshaft and the ring cam in a direction in which the camshaft and the ring cam move relative to each other in the rotational direction.
A clutch device for a power tool as described in Section 1.