JP2002307320A - Motor stop mechanism in pneumatic screw driving machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop the operation of an air motor even when a tip of a driver bit comes off an engaging groove in a head part of a driving screw. SOLUTION: In this motor stop mechanism in which a contact arm 18 slidable along a nose part 14 is arranged by protruding it from a tip of the nose part and a stop valve 22 is operated by the cooperative action of a pneumatic pressure supplied to an exhaust valve 35 operating the stop valve for stopping the air motor from a pneumatic cylinder when a piston 10 reaches the vicinity of a bottom dead center and the contact arm 18 to stop the motor 4, a small hole 49 communicating an air chamber 23a of the stop valve with the atmospheric air when the contact arm 18 is pushed into a screw driving machine main body side is formed, and the stop. valve 22 is operated by exhaust air from the small hole 49 when a fixed period of time elapses after the contact arm is pushed into irrespective of the cooperative action.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a case where the tip of a driver bit is disengaged from an engaging groove in the head of a driving screw immediately before the screwing is completed, and the driving screw floats with respect to a target member. The present invention relates to a motor stop mechanism in a screw driving machine which stops rotation of a motor of a driver bit.

[0002]

2. Description of the Related Art Generally, in a screw driving machine, a screw driving machine is pressed against a member to be screwed in, and the driving screw is lifted from the surface of the target member by a driver bit integrally connected to an actuated piston by pulling a trigger lever. A mechanism in which the driver bit is driven by an air motor and the screw is lifted by pressing the screw driving machine further toward the target member when the stopper holding the screw driving machine comes off, and then the screw is lifted. Has been adopted. A stop valve that operates to shut off the supply of compressed air to the air motor when the screw driving machine is pressed to the stroke end, and an exhaust valve that operates when the piston reaches the bottom dead center. The structure is such that the rotation of the air motor is automatically stopped by cooperation to control the tightening depth stably.

[0003] Such an automatic stop device is known from Japanese Patent Application Laid-Open No. 2000-326248.
This is because, as shown in FIGS. 3 to 8 of the publication, the piston 10 reaches the stroke end, the contact arm 18 is completely screwed in, and the piston 10
The exhaust valve 35 (exhaust valve) is operated by the compressed air when the exhaust hole 46 for exhausting the compressed air acting on the back surface of the valve is closed, and the compressed air in the pilot air chamber 23a of the open / close valve (stop valve) 22 is exhausted. By doing so, the opening / closing valve 22 is closed and the rotation of the air motor is thereby stopped.

[0004]

However, in an actual use mode, the screwing operation is completed even though the contact arm 18 hits the target member and its upper end is relatively raised with respect to the screw driving machine main body. Immediately before, the tip of the driver bit 11 may come off the engagement groove of the head of the driving screw. In this case, since the driving screw is not screwed into the target member, the driver bit 11 cannot reach the bottom dead center. In this case, of the two signs necessary for stopping the operation of the air motor, the sign from the contact arm 18 side is entered, but the sign from the piston side is not entered, so that the driving screw is floated from the target member. As it is, the driver bit will run idle forever. Therefore, a loss of compressed air is generated, and wear of the tip of the driver bit is promoted.

[0005] The present invention solves the above-mentioned problems, and can stop the operation of the air motor even when the tip of the driver bit is disengaged from the engagement groove of the head of the driving screw immediately before the screwing is completed. An object of the present invention is to provide a motor stop mechanism in a screwdriver.

[0006]

In order to solve the above-mentioned problems, a motor stop mechanism in a pneumatic screw driving machine according to the present invention uses a pneumatic driver bit having a bit formed at its tip to engage with the head of a driving screw. While being rotatably connected to the piston of the cylinder, the driver bit is operatively connected to the air motor, the piston of the pneumatic cylinder is driven, the driving bit is driven by the driver bit, and the driver bit is rotated by the air motor to drive the driving screw. A pneumatic screw driving machine to be screwed in, a pilot-operated stop valve is provided in a compressed air supply path to an air motor, and a contact arm slidable along the nose of the screw driving machine is projected from the tip of the nose. And the piston reaches near the bottom dead center In the motor stop mechanism for stopping the air motor by operating the stop valve by the cooperation of the air pressure supplied from the pneumatic cylinder and the contact arm when the contact arm is pushed into the screw driving machine body side, Forming a small hole for communicating the valve chamber of the valve with the atmosphere, and irrespective of the cooperative action, operating the stop valve by exhausting from the small hole when a certain time has elapsed after the contact arm is pushed in. It is characterized by.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIG. FIG. 1 shows a screw driving machine 1 in which a pneumatic cylinder 3 and an air motor 4 are accommodated in a housing 2, and a trigger valve 7 in a grip 5 is operated by a trigger lever 6 arranged in front of a grip portion 5 of the housing 2. Open and close. The inside of the grip 5 is an air chamber 8. An air hose is connected to an air hose connector 9 attached to the bottom of the grip 5 to supply compressed air from the air compressor to the air chamber 8.

The outer peripheral surface of the driver bit 11 connected to the piston 10 of the pneumatic cylinder 3 is formed with a spline groove. The driver bit is inserted into the spline groove hole at the center of the gear 12 mounted in the front part of the housing 2. Bit 11 is inserted, piston 10 and driver bit 1
1 is slidable with respect to the guide member 12. The power of the air motor 4 that rotationally drives the driver bit 11 is transmitted to a final gear provided on the guide member 12 via a plurality of reduction gears 13 arranged at the front of the housing 2.

The screw feeder 15 provided on the side surface of the nose portion 14 is constituted by a pneumatic cylinder and a ratchet type feed claw which are not shown in the drawing, similarly to a general pneumatic nailer.
The connection type screws stored in the screw magazine 16 are sequentially supplied into the nose portion 14.

A swingable free arm 17 is attached to the trigger lever 6. A contact arm 18, one end of which is opposed to the front surface of the free arm 17, passes through the back side of the pneumatic cylinder 3 in FIG. And protrudes from the nose portion 14 in the screw injection direction. A freely openable and closable chuck 20 is pivotally mounted on a screw guide 19 at the front end of the contact arm 18 that can slide back and forth, and the chuck 20 is closed by a spring (not shown).

By pressing the screw guide 19 against an object 51 such as a building material and pushing the contact arm 18,
When the contact arm 18 contacts the distal end of the free arm 17 and the trigger lever 6 is turned in this state, the stem of the trigger valve 7 is pushed through the free arm 17 and the trigger valve 7 is switched. A known miss-fire prevention mechanism in which the pneumatic cylinder 3 and the air motor 4 are not activated by the operation of only 6 is constituted.

A motor stop mechanism 21 composed of two stop valves for opening and closing an air supply path to the air motor 4 is provided on a side surface of the housing 2 shown in FIG. 2 (the back surface of the pneumatic cylinder 3 in FIG. 1). Built-in.

Next, the motor stop mechanism 21 will be described with reference to FIGS. Note that, in the same figure, the right from the center line is a vertical cross section of the screw pit as in FIG. 1, and the left from the center line is a horizontal cross section.

FIG. 3 shows the motor stop mechanism 21 in a standby state. The stop valve 22 constituting the motor stop mechanism 21 is constituted by a cylindrical main stem 24 inserted into a valve sleeve portion 23 and a small-diameter pilot stem 25 inserted below the main stem 24. An O-ring 26 is mounted around the periphery.

The main stem 24 is in the raised position by the bias of the compression spring 27, and as shown in FIG.
The upper port 3 has an inlet port 28 and an outlet port 29 which are always in communication. The pilot stem 25 is the main stem 2
The lower vent port 31 of the valve sleeve 23 is closed by being urged downward by the compression spring 30 inserted into the inside 4. A slide member 33 having a shutter 45 is attached to a lower end portion of the pilot subtle 25, and is opposed to an upper end of the contact arm 18. The compressed air in the air chamber 8 is supplied to the pilot air chamber 23a on the lower surface of the main stem 24 through the inside of the main stem 24.

The inlet port 2 above the stop valve 22
8 is connected to the air chamber 8, and the outlet port 29 is connected to the air motor 4.

The exhaust valve 3 is arranged in parallel with the stop valve 22.
5 are arranged. The exhaust valve 35 is provided with a valve stem 37 that is slidable in a valve sleeve portion 36, and the valve stem 37 is urged downward by a compression spring 38 to constantly shut off the vent ports 31 and 40 of the stop valve 22. I have.

The pneumatic cylinder 3 has an air passage 41 for discharging compressed air acting on the back surface of the piston 10 when the piston 10 reaches the vicinity of the bottom dead center. One end of the air passage 41 faces the opening port 3b,
At the other end, a valve chamber 47 for operating an exhaust valve 35 for opening and closing the pilot air chamber 23a to the atmosphere is formed, and an exhaust hole 46 is formed in the valve chamber 47.

The exhaust hole 46 is configured to open and close in conjunction with the vertical movement of the contact arm 18.
That is, the L-shaped shutter 45 is formed so as to open and close the exhaust hole 46 in conjunction with the vertical movement of the contact arm 18.

The vent port 31 of the stop valve 22 is connected to the exhaust valve 35. When the exhaust valve 35 is opened, the pilot air chamber 23a on the lower surface of the main stem 24 of the stop valve 22 vents through the vent port 31. The port 40 communicates with the atmosphere.

A small hole 49 is formed through the valve housing 48 of the exhaust valve 35. The pilot air chamber 23a and the vent port 31
It communicates with the atmosphere through 9. Accordingly, the air in the pilot air chamber 23a leaks little by little from the small holes 49 into the atmosphere and is exhausted. Note that the small hole 49 may be one that allows the pilot air chamber 23a to communicate with the atmosphere, and is not necessarily formed in the valve housing 48.

Next, the operation of the screw driving machine will be described.
The tip of the screw guide 19 shown in FIG.
1 until the contact arm 18 comes into contact with a contact arm stopper (not shown) and the trigger lever 6 is actuated.
Is opened, and the head valve 42 of the pneumatic cylinder 3 is operated, whereby compressed air flows into the pneumatic cylinder 3 from the air chamber 8 on the outer periphery of the pneumatic cylinder 3, and the piston 10 and the driver bit 11 descend to lower the nose portion 1.
The screw 32 in 4 is hit, and the driving screw 32 is driven into the screwing target 51.

When the driving screw 32 is driven into the object 51 to be driven, the driver bit 11 is rotated by the air motor 4. Since its tip is engaged with the engaging groove on the upper surface of the head of the driving screw 32, the driving screw 3
2 is screwed. As the screw 32 is screwed in, the piston 10 moves toward the bottom dead center, the screwing machine approaches the screwing target 51, and the contact arm 18 is further pushed into the screwing machine main body.

The piston 10 is connected to the pneumatic cylinder 3
When the air passes through the opening port 3b of the pneumatic cylinder 3 acting on the back surface of the piston 10,
From the valve chamber 47. However, the compressed air is discharged to the atmosphere through the exhaust holes 46 as shown in FIG.

At the end of the screwing, the contact arm 18 pushes up the slide member 33 to slide the pilot stem 25 of the stop valve 22 upward as shown in FIG. When the pilot stem 25 moves upward, the pilot air chamber 23a on the lower surface of the main stem 24 is moved.
And the vent port 31 are opened. Then, when the screw driving machine is pushed to the stroke end, the pilot arm 25 of the stop valve 22 is pushed up by the contact arm 18 as shown in FIG. Close the hole 46. As a result, the compressed air in the dripping state is filled in the valve chamber 47, and the internal pressure increases. At this time, the pilot air chamber 23a communicates with the small hole 49 at the same time. However, since the amount of discharge from the small hole 49 is small, the pressure does not decrease so that the stop 22 is actuated immediately. When the internal pressure of the valve chamber 47 increases, the exhaust valve 35
, The compressed air in the pilot air chamber 23a of the stop valve 22
1 communicates with the atmosphere through a vent port 40. Therefore, the pilot pressure acting on the lower surface of the main stem 24 is exhausted from the vent port 31 to the atmosphere through the vent valve 40 through the exhaust valve 35. As a result, a difference occurs in the pressures acting on the upper and lower surfaces of the main stem 24, and the main stem 24 descends as shown in FIG.
6, the inlet port 28 and the outlet port 29 are shut off, and the air supply to the air motor 4 is cut off.
Stops.

When the screwing machine 1 is lifted from the screwing target 51 after the air motor 4 stops, the contact arm 18 descends and separates from the pilot stem 25.
As shown in FIG. 4, the L-shaped valve body 45 opens the exhaust hole 46, and the compressed air in the valve chamber 47 is discharged again. Therefore, the stem 37 of the exhaust valve 35 returns to the initial position, and Is drained to the atmosphere, and the vent ports 31 and 40 are shut off. When the pilot stem 25 descends, the pilot air chamber 23a and the vent port 31 are shut off, and at the same time, the air chamber 8 communicates with the pilot air chamber 23a to supply compressed air from the inlet port 28 to the pilot air chamber 23a. Then, the main stem 24 floats and returns to the initial position.

When the operation of the trigger lever 6 is released, the trigger valve 7 is closed and the head valve 42 is lowered to return to the initial position shown in FIG. The pressure rises and returns to the initial position due to the pressure of the formed blowback chamber 44. Then, when the piston 10 rises from the bottom dead center and passes through the opening port 3b in the pneumatic cylinder 3, the pressure supply from the inside of the pneumatic cylinder 3 to the air passage 41 of the exhaust valve 35 is cut off. The motor stop mechanism 21 also returns to the initial position.

Next, immediately before the piston 10 reaches the bottom dead center, when the head of the driving screw 32 is still slightly floating from the object 51, the tip of the driver bit is positioned at the head of the driving screw 32. Fig. 8
As shown in the figure, the upper end of the contact arm 18 also rises relatively to the screw driving machine main body, and the valve body 45
However, since the compressed air in the pneumatic cylinder 3 cannot pass through the air passage 41, the compressed air does not flow into the valve chamber 47. Therefore, even if the exhaust hole 46 is closed, the exhaust valve 35 does not operate, and the stop valve 22 does not operate. Meanwhile, the air motor 4
Will continue to rotate without stopping.

However, since the small hole 49 is formed through the valve housing 48 of the exhaust valve 35,
The air in the pilot air chamber 23a leaks to the atmosphere from the small holes 49 and continues to be exhausted. For this reason, even though the exhaust valve 35 does not operate, the internal pressure of the pilot air chamber 23a decreases after a certain period of time, so that the main stem 24 moves down and the stop valve 22 also operates, as shown in FIG. The air motor 4 stops automatically.

As described above, in the normal case, the signature is entered from the two sides of the contact arm side and the piston side, so that the air motor 4 is stopped. In contrast, the signature from the contact arm 18 side is entered. Despite this, when the head of the driving screw 32 is still slightly floating from the object 51, the tip of the driver bit 11 is disengaged from the engaging groove at the tip of the head of the driving screw 32, Even if the sign from the driving piston side of the driver bit does not enter, the operation of the air motor 4 is stopped after a certain period of time, so that the driver bit 11 remains forever while the driving screw 32 is floating from the object 51. There is no idling. Therefore, no loss of the compressed air occurs, and the inconvenience of abrasion of the tip of the driver bit 11 is effectively prevented.

In the motor stop mechanism, the small hole 49 is simply formed in the valve housing 48, so that the size of the tool can be reduced.

Since the size of the small hole 49 and the volume of the valve chamber differ depending on the size of the small hole 49 and the volume of the pilot air chamber 23a, the delay time until the operation of the air motor 4 is stopped is adjusted. It can be done by changing.

[Brief description of the drawings]

FIG. 1 is a sectional view of a screw driving machine.

FIG. 2 is a side view of the screw driving machine.

FIG. 3 is a sectional view showing a motor stop mechanism in an initial state.

FIG. 4 is a cross-sectional view showing a state in which compressed air on the back surface of a piston is supplied to a valve chamber of an exhaust valve.

FIG. 5 is a partial cross-sectional view when driving a screw;

FIG. 6 is a cross-sectional view showing a state where the pilot stem is operated.

FIG. 7 is a sectional view showing a state where the main stem is operated.

FIG. 8 is a partial sectional view of the screw driving machine at the time of abnormality.

FIG. 9 is a partial cross-sectional view of the screw driving machine in a state where the air motor stops when an abnormality occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw driving machine 3 Pneumatic cylinder 4 Air motor 10 Piston 18 Contact arm 22 Stop valve 35 Exhaust valve 49 Small hole

Claims (1)

[Claims] A driver bit having a bit engaged with the head of a driving screw at the tip is rotatably coupled to a piston of a pneumatic cylinder, and the driver bit is operatively connected to an air motor to connect the piston of the pneumatic cylinder. A pneumatic screw driving machine that drives and drives a driving screw with a driver bit, and rotationally drives the driver bit with an air motor to screw the driving screw, wherein a pilot-operated stop valve is provided in a compressed air supply path for the air motor. A contact arm slidable along the nose of the screw driving machine is disposed so as to protrude from the tip of the nose, and when the piston reaches near the bottom dead center, the air pressure supplied from the pneumatic cylinder and the contact arm A stop valve is created in cooperation with In the motor stop mechanism for stopping the air motor, the contact arm is formed into a small hole that allows the valve chamber of the stop valve to communicate with the atmosphere when the contact arm is pushed into the screw driving machine main body, regardless of the cooperative action, A motor stop mechanism in a pneumatic screw driving machine, wherein a stop valve is operated by exhaustion from the small hole when a predetermined time has elapsed after the contact arm is pushed in.