JP2000237971A - Silent clutch of thread tightening machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silent clutch of a tread tightening machine which is capable of improving the durability of a claw clutch and easily carrying out a so-called re-tightening, without a driving gear or a groove portion of an intermediate clutch member being damaged. SOLUTION: An intermediate clutch member 8 is displaced in a rotational direction with respect to a driving gear 4 by a tightening torque added when clutch teeth 8c-8c, and 11c-11c start being engaged with each other, which causes a square spring 10 interposed between the intermediate spring 8 and the driving gear 4 to be twisted to extend. Accordingly, the intermediate clutch member 8 advances in the engaging direction while reducing in speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silent clutch for transmitting and interrupting rotational power in a screw tightening machine.

[0002]

2. Description of the Related Art For example, an electric screw tightening machine has a built-in clutch for transmitting and shutting off the power of an electric motor to and from a spindle. An engagement clutch of a type that transmits power is employed. As a conventional meshing clutch, for example, a clutch disclosed in Japanese Patent Publication No. 3-5952 is known. The structure of this conventional screw tightening machine incorporating a meshing clutch will be described with reference to FIG. 8 which employs FIG. 2A of the publication. This screw tightening machine includes a housing, an electric motor, a clutch, a spindle 88 and a stopper sleeve 89. It has. An electric motor, a clutch and a spindle 88 are built in the housing. A stopper sleeve 89 is attached to the housing. The spindle 88 is provided with a driver bit 90 that is coupled to the screw and rotates the screw.
The driver bit 90 mounted on the spindle 88 rotates on the inner peripheral side of the stopper sleeve 89. Spindle 88
Is rotatably supported by the housing and slidable in the axial direction. Therefore, the driver bit 90 slides on the inner peripheral side of the stopper sleeve 89 together with the slide of the spindle 88.

The clutch includes a first disk 81 rotated by an electric motor and a second disk 81 facing the first disk 81.
It is mainly composed of a disk 84 and a third disk 87 fixed to an end face of a spindle 88. The first disk 81 is rotatably supported by the housing so as not to slide in the axial direction. Clutch teeth 82 are formed on the end surface of the first disk 81. Second disk 84
Is rotatably supported by the housing and slidable in the axial direction. On the upper end surface of the second disk 84, second clutch teeth 83 meshing with the clutch teeth 82 are formed. Further, the second disk 84 is urged by a compression spring (not shown) in a direction approaching the third disk 87, that is, in a direction away from the first disk 81. Grooves 85 and 86 are formed in the end faces of the second disk 84 and the third disk 87 facing each other.
The depth of 5,86 varies in the circumferential direction. That is, they are connected to the inclined surfaces 85b and 86b whose depths gradually become smaller from the deepest bottom surfaces 85a and 86a. Also, grooves 85, 86
Extends within a predetermined range in the circumferential direction, and its boundary is vertical surfaces 85c and 86c.

[0004] With the above configuration, this screw driving machine operates as follows. When the driver bit 90 is pressed against the screw, the driver bit 90, the spindle 88, and the third disk 87 are retracted integrally, and as a result, the second disk 84 is retracted. At this time, the clutch teeth 82 and the second clutch teeth 83
Are shallowly engaged with each other, and the grooves 85 and 86 are in contact with each other at the deepest bottom surfaces 85a and 86a. In this state, torque transmission from the electric motor to the driver bit 90 is performed. When the first disk 81 rotates the second disk 84 and the second disk 84 rotates the third disk 87, a contact pressure acts between the grooves 85 and 86. This force is
Since the depths 5 and 86 change in the circumferential direction, the second disk 84 acts to feed the first disk 81 along the inclined surfaces 85b and 86b.

When the vertical surfaces 85c and 86c of the grooves 85 and 86 come into contact with each other, this feeding component disappears, and at this time, the clutch teeth 82 and the second clutch teeth 83 mesh most deeply.
Screw tightening proceeds in this state. FIG. 8 shows this state. The spindle 88 advances, and the stopper sleeve 8
After the abutment of the screw 9 with the material, when the screw is tightened to a predetermined depth, the engagement between the clutch teeth 82 and the second clutch teeth 83 is released. Then, since the second disk 84 does not act on the force for rotating the third disk 87,
The second disk 84 is formed with grooves 85, 8 by a spring (not shown).
6 along the inclined surfaces 85b, 86b, and the grooves 85, 8
6 abut each other at their deepest bottom surfaces 85a, 86a. As a result, a clearance is generated between the clutch teeth 82 and the clutch teeth 83 by the depth (distance in the axial direction) of the inclined surfaces 85b and 86b, and the meshing clutch keeps running idle quietly.

[0006]

However, in the above-described conventional configuration, the transmission of torque is limited to the clutch teeth 8.
Since the clutch teeth are engaged with each other, the durability of each clutch tooth itself is poor, and there is a problem that the clutch teeth are severely chipped or worn. In particular, in the initial stage of screw tightening, when the screw tightening machine is pressed in the screw tightening direction, the pressing force causes the spindle 88 to retreat together with the driver bit 90 and the rotating first disk 8.
Since the drive rotation is transmitted by the tooth surface of the first clutch tooth 82 abruptly contacting the tooth surface of the clutch tooth 83 of the second disk 84, there is a problem in durability and abrasion resistance at this meshing surface. there were.

Further, according to the above-mentioned conventional meshing clutch, when the screw tightening amount reaches a predetermined amount (length), the fixed-side clutch teeth 82 and the movable-side second clutch teeth 83 are positively and positively connected. When the stopper sleeve 89 is poorly adjusted due to the completely dissociated configuration, or when the screw to be tightened in the screw tightening work in a narrow place or a place with poor scaffolding is not enough for the originally desired tightening amount. However, there is a problem that further tightening is not performed as it is, that is, so-called retightening cannot be performed.

Accordingly, the present invention can improve the durability of the dog clutch, simplify the so-called retightening, and damage the groove of the drive gear or the intermediate clutch member provided to solve these conventional problems. It is an object of the present invention to provide a silent clutch for a screw tightening machine that does not suffer from the problem.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
A silent clutch having the configuration described in the claim is provided. According to the silent clutch of the first aspect, in a state where the electric motor is not rotated and the screwing machine is not pressed in the screw tightening direction (when the screw tightening machine is not used), the spindle clutch is not rotated. The clutch teeth of the intermediate clutch member and the clutch teeth of the intermediate clutch member are not engaged with each other, and therefore, no external force acts on the drive gear in a rotational direction with respect to the drive gear. Since the intermediate clutch member does not rotate relative to the drive gear, the coil spring is not twisted, and thus the clutch teeth of the intermediate clutch member and the clutch teeth of the spindle are in the most separated state.

In this state, when the electric motor is started to start screw tightening and the screw tightening machine is pressed in the screw tightening direction, first, the spindle retreats, and its clutch teeth are engaged with the clutch teeth of the intermediate clutch member. Start meshing. Then, a tightening resistance (rotation resistance) is added to the intermediate clutch member, whereby the intermediate clutch member rotates relative to the drive gear within a certain range. When the intermediate clutch member rotates relative to the drive gear, the coil spring is twisted and extended, thereby pushing the intermediate clutch member away from the drive gear, that is, in a direction in which the clutch teeth mesh more deeply (forward). In addition, the spindle is also pushed forward integrally. In this way, at the stage where the clutch teeth of the intermediate clutch member begin to mesh with the clutch teeth of the spindle, the intermediate clutch member rotates relatively to the drive gear, so that both clutch teeth can be meshed with less impact. As a result, damage or wear of both clutch teeth can be greatly reduced.

When the intermediate clutch member is displaced over the entire allowable range for the drive gear, the two cannot displace any more, so that the intermediate clutch member rotates integrally with the drive gear. The rotational force transmitted to the drive gear in this integrally rotating state is transmitted to the spindle through the engagement of the intermediate clutch member and the clutch teeth, whereby the screw set at the tip of the spindle is tightened. During the screw tightening, a tightening torque is applied to the intermediate clutch member, so that the intermediate clutch member is maintained in a state of being maximally displaced in the rotational direction and the axial direction with respect to the drive gear, and is thus transmitted to the drive gear. The state in which the rotational force is directly transmitted to the intermediate clutch member is maintained. After the stopper sleeve comes into contact with the screw tightening member as the screw tightening progresses, the spindle relatively advances, so that the engagement of the clutch teeth gradually becomes shallower.

When the screwing is completed and the clutch teeth are disengaged, no tightening torque is applied to the intermediate clutch member, so that the torsion of the coil spring is returned and the coil spring is contracted, whereby the intermediate clutch member is reduced. When retracted, a clearance occurs between the clutch teeth of the spindle and the clutch teeth of the intermediate clutch member, so that the clutch idles gently. If the screw tightening operation is interrupted even though the screw tightening amount is insufficient due to an operator error or the like, the electric motor is stopped. When the electric motor is started again with the screwing machine pressed against the screw tightening member, the intermediate clutch member starts rotating with a slight delay with respect to the drive gear even when the clutch teeth are not engaged. Therefore, the intermediate clutch member is displaced in the rotational direction with respect to the drive gear. This extends the coil spring and pushes the intermediate clutch member forward, thereby re-engaging the clutch teeth and returning to a properly tightened condition. That is, so-called retightening can be performed without performing a troublesome operation such as adjusting the position of the stopper sleeve, unlike a conventional tool.

Further, in the case of the retightening, at the moment when the clutch teeth start to mesh, the intermediate clutch member starts to be displaced with respect to the drive gear, and the rotation of the intermediate clutch member becomes lower than the rotation of the drive gear. (The rotation speed of the intermediate clutch member is later than the rotation of the drive gear.) For this reason, when the meshing of the clutch teeth starts, the meshing is performed at a rotation speed lower than the rotation speed of the drive gear, so that the impact applied to the clutch teeth is reduced, and the durability of the clutch teeth can be improved. .

[0014]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. In this example, an electric screwdriver 1 will be described as an example of the screwdriver. FIG.
Indicates almost half of the tip side of the screwing machine 1.
An electric motor 3 is mounted inside the housing 2. The electric motor 3 is started and stopped by turning on and off a trigger-type main switch (not shown) provided in the screw tightening machine main body. A pinion gear 3 a formed on the output shaft of the electric motor 3 meshes with the drive gear 4. The drive gear 4 is rotatably supported on the drive shaft 5. However, the drive gear 4 does not move in the axial direction because it is supported by the thrust bearing 7 or the like. A rear end side (right end side in the figure) of the drive shaft 5 is supported by a bearing 6 so as to be rotatable with respect to the housing 2 and movable in the axial direction. On the front side (left side in the figure) of the drive gear 4, an intermediate clutch member 8 is rotatably supported on the drive shaft 5 independently of the drive gear 4. However, three engagement teeth 4a to 4a and 8a to 8a are formed on the front surface of the drive gear 4 and the rear surface of the intermediate clutch member 8, respectively. Each of the engaging teeth 4a to 4a and 8a to 8a is formed radially radially at three equally spaced positions in the circumferential direction as shown in FIG. For this reason, the intermediate clutch member 8 has approximately 12 movable engagement teeth 8a between the engagement teeth 4a, 4a of the drive gear 4.
It is rotatable relative to the drive gear 4 within the range of 0 °.

A coil spring 10 wound in a coil shape is interposed between the intermediate clutch member 8 and the drive gear 4. The coil spring 10 is formed of a wire having a rectangular cross section. The coil spring 10 extends in the axial direction while reducing the coil diameter when twisted, and returns to its original length by its elastic force when the twist is released. And both ends 10a, 1
It has a function of converting the displacement in the rotation direction between 0b into a change in the length in the axial direction. This coil spring 10 itself
It is a conventionally known one and does not need to be changed in this embodiment. The front end 10b of the coil spring 10 is hooked and fixed to the notch 8b of the intermediate clutch member 8, and the rear end 10a is hooked and fixed to a hook hole 4b formed in the drive gear 4. ing. For this reason, when the intermediate clutch member 8 is displaced in the rotational direction with respect to the drive gear 4, the coil spring 10 is twisted and extended, so that the intermediate clutch member 8 is displaced axially forward. The engagement state of the engagement teeth 8a, 4a is always maintained even when the intermediate clutch member 8 moves in the axial direction.
Rubber rings 9 and 9 are mounted on the boss of the drive gear 4 and the boss of the intermediate clutch member 8, and the two ends of the rings 9 and 9 form the front end 10b and the rear end 10a of the coil spring 10. The other parts are prevented from contacting the drive gear 4 or the intermediate clutch member 8 and the coil spring 10
Is prevented from shifting in the radial direction.

On the front surface of the intermediate clutch member 8, clutch teeth 8c to 8c are formed along the same circumference, and in front of the clutch teeth 8c to 8c, a flange 1 of the spindle 11 is provided.
The clutch teeth 11c to 11c formed in 1a are arranged to face each other. Therefore, when the intermediate clutch member 8 is displaced forward in the axial direction due to the extension of the coil spring 10, the clutch teeth 8c to 8c become the clutch teeth 1 on the spindle 11 side.
1c to 11c are engaged with each other, whereby the intermediate clutch member 8 and the spindle 11 are integrated in rotation (clutch connection state). On the other hand, when the screw tightening is completed and the meshing state between the clutch teeth 8c and the clutch teeth 11c is released, an external force (twisting the coil spring 10) for rotating the intermediate clutch member 8 relative to the drive gear 4 is released. Is removed, the torsion of the coil spring 10 is eliminated, and the coil spring 10 contracts. This coil spring 10
The intermediate clutch member 8 retreats rearward in the axial direction by the reduction of the pressure and the urging force of the compression spring 14 described later, and the clutch teeth 8c
-8c and the clutch teeth 11c-11c generate an appropriate clearance (clutch disengaged state). From the above, the clutch teeth 8c to 8c and the clutch teeth 11c to
11c, the intermediate clutch member 8 for moving the two close or apart, the coil spring 10, and the like constitute the silent clutch CL in this embodiment.

Next, the spindle 11 is supported via the front and rear bearing cylinders 12 and 13 so as to be rotatable about the same axis as the drive shaft 5 and movable in the axial direction. The flange portion 11a is formed at the rear end of the spindle 11,
The clutch teeth 11c to 11c-
11c is formed. A support hole 11b is formed at the center of the rear surface of the spindle 11 at a constant depth. The front end of the drive shaft 5 is inserted into the support hole 11b so as to be relatively rotatable and axially movable. I have. A compression spring 14 is interposed between the drive shaft 5 and the bottom surface of the support hole 11b, and the compression spring 14 urges the spindle 11 forward in the axial direction. On the other hand, a rubber stopper ring 21 is attached to the housing 2, and the axially forward moving end of the spindle 11 is regulated by pressing the flange 11 a against the stopper ring 21. In addition, the flange 11a is pressed against the stopper ring 21 by the compression spring 14, so that the spindle 11 is prevented from idling. or,
The drive shaft is formed with a flange portion 5a. The flange portion 5a is pressed against the front surface of the intermediate clutch member 8 by the compression spring 14, whereby the axial movement of the drive shaft 5 is restricted. Further, a flat surface 5b is formed at the front portion of the drive shaft 5, and the flat surface 5b bleeds the air from the support hole 11b, whereby the spindle 11 can move smoothly in the axial direction. ing. Here, when the spindle 11 is slightly retracted to separate the flange portion 11a from the stopper ring 21, the drive shaft 5 and the spindle 11 rotate integrally by the action of the compression spring 14. That is, the flange portion 1
1a is separated from the stopper ring 21 to make the spindle 11 rotatable. When the electric motor 3 is started and the drive gear 4 is rotated in this state, the flange portion 5a is pressed by the intermediate clutch member 8. As a result, the drive shaft 5 also rotates, and this is transmitted to the spindle 5 by the action of the compression spring 14. Therefore, even when the clutch teeth 8c to 8c and the clutch teeth 11c to 11c are not meshed, the spindle 11 runs idle when the electric motor 3 is started. However, when the retreating operation of the spindle 11 is stopped and the flange portion 11a is pressed against the stopper ring 21, the rotation resistance due to this becomes larger, so that the spindle 11 does not idle.

In the center of the front surface of the spindle 11, a bit mounting hole 11d for inserting a driver bit 20 for screw fastening is formed at a constant depth. In the bit mounting hole 11d, a plurality of steel balls 16 to 16 elastically urged radially inward by a leaf spring 15 are arranged at regular intervals in the circumferential direction. The rear end side of the driver bit 20 is inserted into the bit mounting hole 11d, and the steel balls 16 to 16 are pushed in while being displaced radially outward against the elastic force of the leaf spring 15 so as to be pushed. Can be mounted in the bit mounting hole 11d. When the driver bit 20 is pushed down to a certain position, the steel balls 16 to 16 are fitted into the engagement grooves 20a of the driver bit 20, whereby the mounted state of the driver bit 20 is maintained.

An adjust sleeve 17 is mounted on the front end of the housing 2 via a screw portion 17a, and a stopper sleeve 18 is detachably mounted on the front end of the adjust sleeve 17. The front end of the driver bit 20 protrudes from the front end of the stopper sleeve 18. By rotating the adjustment sleeve 17 in the axial direction, the position of the front end (stopper surface 18a) of the stopper sleeve 18 with respect to the driver bit 20 can be arbitrarily adjusted, thereby adjusting the screwing depth of the screw. can do. This is the same as the conventional configuration.

According to the silent clutch CL of the present embodiment configured as described above, the screw tightening machine 1 operates as follows. As shown in FIG. 1, the spindle 11 is pushed forward by the compression spring 14 in a non-use state in which the screwing machine 1 is not pressed in the screw tightening direction.
Further, each engagement tooth 8a of the intermediate clutch member 8 is
The intermediate clutch member 8 and the drive gear 4 are not relatively displaced in the rotational direction by engaging with the respective engagement teeth 4a, and in this state, the two 4 and 8 are integrally rotating. Since the intermediate clutch member 8 and the drive gear 4 are not relatively displaced in the rotation direction, the coil spring 10 is not twisted, and is therefore in the shortest state. Coil spring 10
Is the shortest, the intermediate clutch member 8 is most retracted. Thus, in the non-use state of the screw tightening machine 1,
Since the spindle 11 moves forward and the intermediate clutch member 8 moves backward, an appropriate gap is generated between the clutch teeth 11a to 11a and the clutch teeth 8a to 8a, and both clutch teeth 11a to 11a, 8a to 8a is not engaged,
Accordingly, the silent clutch CL is in a state of idling quietly (clutch disengaged state).

Next, from the non-use state, a screw S is set at the tip of the driver bit 20 as shown in FIG. 3, and the screw tightening machine 1 is set in the screw tightening direction (left side in the figure) in the set state. When the screw S is pressed against the material W by a pressing operation, the driver bit 20 and the spindle 11 are relatively moved.
Retreats rightward in the figure against the compression spring 14. When the spindle 11 retreats, its flange portion 11a separates from the stopper ring 21. Therefore, the spindle 11 starts idling, and when the spindle 11 is further retracted in this idling state, the clutch teeth 11a to 11a become the clutch teeth 8a of the intermediate clutch member 8. Start to engage with ~ 8a. Both clutch teeth 11a ~
When the gears 11a and 8a to 8a start to mesh with each other, the screw tightening force is applied as rotational resistance to the intermediate clutch member 8, so that the rotational speed of the intermediate clutch member 8 decreases instantaneously, and The clutch member 8 and the drive gear 4 are relatively displaced in the rotational direction. As shown in FIGS. 4 and 5, when the intermediate clutch member 8 and the driving gear 4 are relatively displaced by about 120 ° in the rotational direction, each of the engaging teeth 8a
And the respective engagement teeth 4a are engaged, and the intermediate clutch member 8 and the drive gear 4 are integrated again with respect to rotation.

While the intermediate clutch member 8 and the drive gear 4 are relatively displaced in the rotational direction, the coil spring 10 is twisted and expanded, whereby the intermediate clutch member 8 moves forward to the left in the drawing and the clutch teeth 8a ~ 8a and clutch teeth 11a
11a is deepened at a stretch, so that the connection of the silent clutch CL is completed within a short time.
During the progress of the screw tightening, a tightening torque is applied to the intermediate clutch member 8, so that the intermediate clutch member 8
And the drive gear 4 are held in a state of being relatively displaced with respect to rotation (the state shown in FIGS. 4 and 5), so that the coil spring 10 is held in a twisted state, and the intermediate clutch member 8 is advanced. That is, the clutch teeth 8a to 8a and the clutch teeth 11a to 11a are held in a deeply meshed state, whereby the intermediate clutch member 8
Tightening torque is reliably transmitted to the motor.

When the screw tightening reaches the final stage, the stopper surface 18a of the stopper sleeve 18 comes into contact with the material W as shown in FIG. 6, so that only the spindle 11 and the driver bit 20 move in the screw tightening direction thereafter. Screw tightening proceeds. Therefore, at this stage, the engagement of the clutch teeth 11c to 11c of the spindle 11 with the clutch teeth 8c to 8c of the intermediate clutch member 8 gradually becomes shallower. When the screw is tightened to a predetermined depth and screw tightening is completed, the clutch teeth 1 for the clutch teeth 8c to 8c are
The meshes 1c to 11c are disengaged. Then, since the tightening torque from the spindle 11 is not applied to the intermediate clutch member 8, an external force for twisting the coil spring 10 does not act, and as a result, the torsion of the coil spring 10 is returned and the coil spring 10 10 shrinks to its original length,
Accordingly, the intermediate clutch member 8 retreats to the right in the figure. When the intermediate clutch member 8 retreats in this way, the clutch teeth 8c to 8c and the clutch teeth 11c to
An appropriate gap is instantly generated between the silent clutch CL and the silent clutch CL.

Next, the case of retightening the screw will be described. For example, since the tightening is interrupted on the way due to the carelessness of the operator or the like, the clutch teeth 11c with respect to the clutch teeth 8c to 8c before the screw is completely closed.
11c is disengaged, and as a result, the silent clutch CL is disconnected, the main switch of the screw tightening machine 1 is once turned off and the electric motor 3
Is stopped, it is possible to re-tighten the remaining portion. That is, with the electric motor 3 stopped, the tip of the driver bit 20 is set to the unfastened screw, and the screw tightening machine 1 is pressed in the screw tightening direction. The motor 3 is started. Then, since the drive gear 4 meshes with the pinion gear 3a of the electric motor 3, the electric motor 3
Starts spinning at the same time as starting. On the other hand, the intermediate clutch member 8 is configured to rotate integrally with the drive gear 4 through the engagement state of the engagement teeth 4a to 4a and the engagement teeth 8a to 8a. About 12
Relative rotation is possible within the range of 0 °. For this reason,
The drive gear 4 starts rotating at the same time as the activation of the electric motor 3, but the intermediate clutch member 8 starts rotating with a slight delay,
As a result, the intermediate clutch member 8 is displaced in the rotational direction with respect to the drive gear 4.

As described above, after the drive gear 4 starts to rotate and before the intermediate clutch member 8 starts to rotate, the two members 4, 8 rotate relatively, so that the coil spring 10 is twisted and extended. As a result, the intermediate clutch member 8 is displaced forward. When the intermediate clutch member 8 is displaced forward, the clutch teeth 8c to 8c and the clutch teeth 11c to 11c
c engages again, thereby starting to retighten the remaining screw. As described above, according to the silent clutch CL of the present embodiment, the screws can be retightened without re-adjusting the position of the stopper sleeve 18.

Various modifications can be made to the embodiment described above. For example, engaging teeth 4a-4a, 8a-8
a is provided at three equally divided positions and the maximum displacement of the drive gear 4 and the intermediate clutch member 8 is about 120 °.
The range in which the coil spring 10 can be displaced may be set based on the required torsional angle of the coil spring 10 and the amount of extension thereof. Accordingly, it is possible to increase the amount of extension of the coil spring 10 by providing the engaging teeth at two equally-divided positions in the circumferential direction and setting the torsion angle of the coil spring 10 to 180 ° at the maximum. Alternatively, the engagement teeth may be provided at positions equal to or more than four in the circumferential direction, and the extension amount of the coil spring may be set small.

In the illustrated embodiment, a screw tightening machine is exemplified as an example of the screw tightening machine. However, the present invention can be widely applied as a clutch in a screw tightening machine in which a spindle of a tool body is pressed against a material side and rotated. it can.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, and is a longitudinal sectional view of a front portion of a screw tightening machine. In this figure, although the spindle is slightly retracted, the engagement teeth 4a to 4a and the engagement teeth 8a to 8a
8a shows a clutch disengaged state in which the clutch is not engaged.

FIG. 2 is a sectional view taken along line (2)-(2) of FIG.
It is a figure which shows the positional relationship of the engagement teeth 8a-8a with respect to 4a.

FIG. 3 is a longitudinal sectional view of a front portion of the screw tightening machine. This figure is
The spindle retreats and the clutch teeth are engaged,
This shows a state in which the intermediate clutch member has not yet advanced.

FIG. 4 is a longitudinal sectional view of a front portion of the screw tightening machine. This figure is
This shows a state in which the coil spring is twisted and the intermediate clutch member advances.

FIG. 5 is a view taken in the direction of arrows (5)-(5) in FIG. 4, and as a result of displacement of the intermediate clutch member with respect to the drive gear, engagement teeth 4a to 4
The state where the positional relationship of the engaging teeth 8a to 8a with respect to a has changed is shown.

FIG. 6 is a side view showing the internal structure of the front part of the screw tightening machine. This figure shows a state immediately before the disengagement of the clutch teeth. At this stage, the coil spring is still twisted and the intermediate clutch member is moving forward.

FIG. 7 is a side view showing the internal structure of the front part of the screw tightening machine. This figure shows a clutch disengaged state in which the spindle advances and the intermediate clutch member retreats.

FIG. 8 is a view showing a conventional silent clutch, and is a view in which FIG. 2a of Japanese Patent Publication No. 3-5952 is used.

[Explanation of symbols]

CL: Silent clutch 1: Screw tightener 3: Electric motor, 3a: Pinion gear 4: Drive gear, 4a: Engaging teeth 5: Drive shaft 8: Intermediate clutch member, 8a: Engaging teeth, 8c: Clutch teeth 10: Coil Spring 11 ... Spindle, 11c ... Clutch tooth 14 ... Compression spring 17 ... Adjust sleeve 18 ... Stopper sleeve 20 ... Driver bit

Claims (1)

[Claims] When the screwing machine body is pressed toward a material via a screw set at the tip of a spindle, the spindle retreats and a silent clutch is engaged, while a stopper sleeve contacts the material during screwing. The silent clutch of the screw tightener, wherein the silent clutch is disengaged when the spindle advances in contact with the drive shaft, the drive shaft being coaxially arranged with the spindle, and a drive rotatably supported by the drive shaft and rotated by an electric motor. A gear, an intermediate clutch member supported on the drive shaft so as to be rotatable and axially movable within a certain range with respect to the drive gear, and provided on the intermediate clutch member and the spindle; A clutch tooth for transmitting rotation of a clutch member to the spindle; A coil spring that is interposed between the drive gear and extends when twisted, and moves the intermediate clutch member in the axial direction by expansion and contraction of the coil spring due to relative rotation of the intermediate clutch member with respect to the drive gear. A silent clutch of a screw tightening machine configured to engage or disengage the clutch teeth.