JPH01295768A - Clamp torque control mechanism for power tool - Google Patents

Abstract

PURPOSE:To shut off surely transmission torque from a drive unit to a bit with set torque and prevent power from superfluous consumption by providing the drive side can means parting axially from each other when clamp torque reaches a set value and a drive force from the drive unit acts. CONSTITUTION:When clamp torque reaches a set value, a clutch ring 8 forcibly moves a clutch sleeve 20 through a stop shaft 5 similarly toward the bit end against a force of a torque spring 16 urging the clutch sleeve to the clutch shaft 3 side with the cam means 3a, 8a immediately after said cam means 3a, 8a part from each other so that a portion of the clutch sleeve 20 contacting a parting ball 11 provides a stepped small diameter portion 20''. Thus, the parting ball 11 fitted in a cam ring groove 9' is removed therefrom and the cam ring 9 is urged by a spring 7 to be moved until it engages a stopper ring 10. The transmission of a drive force to the bit 19 is shut off by the parting of the cam means 3a, 8a from each other to stop clamping of a screw.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a tightening torque control mechanism used in power tools such as air screwdrivers and electric screwdrivers that can adjust the tightening torque used to tighten screws or nuts. It is something.

(Prior art and its problems) Conventional tightening torque control mechanisms are: 1) When the target torque is reached, the torque is regulated by causing a slip on the drive side and the driven side, 2) When the target torque is reached, an air screwdriver etc. is used to control the torque. 3. When this happens, the air circuit that is the power source is cut off.
) There is a method in which a hollow hole is provided in the rotation center shaft of the bit spindle and a cam means fitted into the hole is used to engage and engage the clutch.

Among the above conventional techniques, 1) causes slippage.

In methods that regulate torque, the tightening torque fluctuates depending on the length of time that slippage occurs, and unless the driving force is interrupted in some way, it takes a large reaction force and driving source to hold the tool. A large load continued to be applied to the machine, which had a negative impact on workability. Furthermore, in the method of 2), which shuts off the air, the shutoff of the driving force may become unstable due to a defect in the shutoff mechanism (or locking mechanism) or improper spring selection. Furthermore, in the method of 3) in which a cam is provided within the bit spindle, the cam naturally has a small diameter, and although it is an important component, it is prone to premature wear, which is undesirable from the viewpoint of longevity.

(Means for solving problems according to the invention) By disengaging the clutch, the tightening torque does not fluctuate, the reaction force for holding the tool after tightening is completed, and the consumption of unnecessary power is reduced. The problem was solved by not machining a hollow hole in the bit spindle, that is, by discontinuing the use of a cam means that fits into the hollow hole, and by using a tightening torque control mechanism with a new structure.

In other words, it has drive-side cam means that act to move away from each other in the axial direction when a driving force is applied from the drive part, and a bit that is fixed in the axial direction with respect to the main body casing and tightens a screw or nut at the rotation center. It has a clutch shaft with an inner hole for holding and biasing the attached bit spindle, and a cam means on the driven side, and is rotatably slidable relative to the main body casing and is engaged by a nut screwed into the main body casing. A clutch ring that is stopped, is biased in the clutch axial direction by a torque spring whose pressing force is adjustable, and has a clutch pawl on a part of its inner circumference that can engage with a clutch pawl provided on the outer circumference of the clutch sleeve, and a bit spindle. There is a clutch pawl on a part of the outer periphery that is inserted into the shaft part of the clutch so that it can freely slide in the axial direction and transmit rotational force, and that can engage with the clutch pawl of the clutch ring.
a clutch sleeve having a stepped portion on the outer periphery of the opposite side that allows changing the position of the separation ball from the center of rotation;
Several separation balls are attached to the bit spindle and are held so as to be movable radially within the same plane, and the stepped portion of the clutch sleeve is inserted inside the balls to make them movable in the axial direction, and the clutch sleeve is attached. A ball holder that locks one end of the spring for the sleeve to be pressed, and a ball holder that is inserted inside the clutch ring so that it can slide in the axial direction. The power tool is tightened by the cam ring, which has a circumferential groove on the inner circumference into which a part of the separation ball can fit. A torque control mechanism was constructed.

(Example) An explanation will be given based on the drawings. First, in FIG. 1, which shows the state before the bit 19 is pressed against the screw, the clutch shaft 3 to which the driving force is directly connected is a cam that has the effect of separating from the clutch ring 8 in the axial direction when the driving force is applied. Means 3a, 8
It meshes with a.

The clutch ring 8 is urged toward the clutch shaft 3 via a pin 12 by a torque spring 16 whose pressing force can be adjusted by rotation of a nut 18 . However, the clutch pawl 8b of the clutch ring 8 and the clutch pawl 20b of the clutch sleeve 20 do not mesh with each other.

No driving force can be transmitted to the clutch sleeve 20.

The bit spindle 22 is urged toward the tip of the bit 19 by a return spring 4 and is locked by a stopper ring 17, and the bit spindle 22 and clutch sleeve 20 can transmit instantaneous force in the rotational direction by a rotation stopper ball 13. Although it is stopped, it is slidable in the axial direction, and is urged toward the clutch [3 by a sleeve spring 21 and locked by a stopper 23. The cam ring 9 is urged toward the tip of the bit by the cam ring spring 7,
It is locked by a stopper ring 1o.

The separation ball 11 has a spherical body partially fitted into a groove 9' provided on the inner periphery of the cam ring 9.

The balls 11 are held down by the stepped large-diameter portion 20'' of the clutch sleeve 20. In this state, the balls 11 cannot move radially. The structure is such that independent axial movement of only one member is impossible.

When the bit 19 is pressed against the mating screw in this state, the bit spindle 22 is pushed in and the ball holder 14 also moves, pushing the cam ring 9 through the separation ball 11. Further, in this case, the clutch sleeve 20 is urged toward the retaining ring 23 by the sleeve spring 21 and is locked, so it moves in the axial direction together with the movement of the bit spindle 22, and the ball holder clutch sleeve 2o 1 bit is pushed in without changing the positional relationship.

Figure 2 shows the bit pressed against the screw and the bit spindle 2.
This is the state immediately after the stepped portion 22a of No. 2 has been pushed in until it hits the clutch shaft 3, and the clutch sleeve 2o is pushed by the bit spindle 22 via the sleeve spring 21, and pushed as far as the clutch ring 8 side. At this time, the clutch pawls 8b and 20b are naturally engaged, and the driving force from the driving section can be transmitted to perform the tightening operation.

Fig. 3 shows cam means 3a and 8 which have the effect of separating from each other in the axial direction when a driving force is applied due to reaching the set torque.
Immediately after the clutch ring a is released, the clutch ring 8 overcomes the force of the torque spring 16 biased toward the clutch shaft 3 by the cam means 3a and 8a and moves toward the tip of the bit.

As a result, the clutch sleeve 20 is also forcibly moved toward the tip of the bit via the stop @5, and the portion of the clutch sleeve 20 that is in contact with the separating ball 11 becomes the small diameter portion 20'' of the stepped portion. , because the cam ring 9 is biased by the cam ring spring 7.

The action of the cam ring groove 9' generates a force that pushes the separation ball 11 toward the center of rotation, and as a result, the separation ball 11 is disengaged from the cam ring groove 9'.
The cam ring 9 is urged by the cam ring spring 7 and moves to a position where it is locked to the stopper ring 10. Further, as a matter of course, since the cam means 3a, 8a are separated, the transmission of driving force is interrupted, and the screw cannot be tightened.

Further thereafter, the engagement between the cam means 3a and 8a returns to the original state shown in FIG. 4, that is, when the clutch ring 8 is pushed by the torque spring 16 and returns to its original position, the clutch sleeve 2
0 is also pushed by the sleeve spring 21 and tries to move toward the clutch shaft 3 side. However, as described above, the cam ring 9 has moved toward the tip of the bit, and the separating ball 11 is pressed against the small diameter portion 20' of the stepped portion of the clutch sleeve 20, and the stepped portion 20' causes the clutch slippage to occur.
- The sleeve 20 is stopped from being biased by the sleeve spring 21, and the clutch pawls 8b, 20b are kept in a disengaged state, thereby continuing to cut off the transmission of the driving force.

After the driving force is cut off, the bit 19 is stopped being pressed against the screw, and in the process of the bit spindle 22 being pushed by the return spring 4 and moving to the farthest end of the bit, the clutch sleeve 2o moves its stepped portion 20'. The pushing separation ball 11 moves the bit spindle 22 at the same time, but at the position where the bit spindle 22 has returned to the farthest end of the bit, or at the position just before that, the separation ball 11 moves into the circumferential groove 9' of the cam ring 9. It will be the same as the position. At this time, the separation ball 11 is pushed by the sleeve spring 21 via the clutch sleeve 20, and the circumference? g9', thereby allowing the large diameter portion 20- of the clutch sleeve 20 to pass through, and the clutch sleeve 20 is pushed by the sleeve spring 21 and moves until it is locked by the retaining ring 23. The state shown in FIG. 1 is restored.

(Effects) According to the tightening torque control mechanism of the present invention, a double clutch structure is used to reliably cut off the transmitted torque at the set torque, and the tightening torque control mechanism is always stable regardless of whether the operator changes. Operates with torque, minimizes recoil after tightening,
A good working environment can be provided without consuming extra power.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a tightening torque control mechanism in an embodiment of the present invention. FIGS. 2 and 3 are cross-sectional views of the same tightening torque control mechanism in different operating states. FIG. 4 is a front view of the cam means section. FIG. 5 is a sectional view taken along the line V-V in FIG. 1. In the figure; 1! ! Moving parts 2 Body casing 3 Clutch shaft 4 Return spring 5 Retaining ring 6 Bearing 7 Cam ring spring 8 Clutch ring 9 Cam ring IO stopper ring 11 Separation ball
12 Pin 13 Rotation stop ball 14 Ball holder 15 Set screw 16 Torque spring 17 Stopper ring 18 Nut 19 Bit 2o Clutch sleeve 21 Sleeve spring 22 Bit spindle 23 Stop shaft and above Applicant Shinano Engineering Co., Ltd. Agent Patent attorney Isamu Ohashi

Claims (1)

[Claims] It has drive side cam means (3a) that act so as to move away from each other in the axial direction when a driving force is applied from the drive part (1), and a screw is fixed in the rotation center in the axial direction with respect to the main body casing (2). Alternatively, a clutch shaft (3) provided with an inner hole for holding and biasing a bit spindle (22) equipped with a bit (19) for tightening nuts, etc., and a cam means (also on the driven side)
A nut (18
) and has an adjustable torque spring (1
A clutch ring (6) is biased toward the clutch shaft (3) and has a clutch pawl (8b) on a part of its inner circumference that can engage with a clutch pawl (20b) provided on the outer periphery of the clutch sleeve (20). 8), and a clutch claw (8b) of a clutch ring (8) is attached to a part of the outer periphery of the bit spindle (22) so that it can slide freely in the axial direction and transmit rotational force.
) and a clutch pawl (20b) that can engage with the clutch sleeve (20), and a stepped portion (20') on the outer periphery of the opposite side that can change the position of the separation ball (11) from the center of rotation. Several separation balls (11) are attached to the bit spindle (22) and held movably radially within the same plane, and the stepped portion (20) of the clutch sleeve (20) is attached to the inside of the balls (11). A ball holder (14) that locks one end of a sleeve spring (21) that inserts a sleeve spring (20') and makes it movable in the axial direction and biases a clutch sleeve (20), and Although it is inserted and can slide in the axial direction, the stopper ring (10) provided inside is biased toward the tip of the bit (19) by the cam ring spring (7) also fitted inside the cam ring spring (7). ), and a cam ring (9) having a circumferential groove (9') in which a part of the separation ball (11) can fit into a part of the inner circumference. Tightening torque control mechanism for power tools.