JP2014124713A - Driving tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving tool that can prevent air pressure in a piston lower chamber from increasing than necessary and ensure prompt and sure fastening with simple and low-cost structure, which can solve the problems that in a screw driving machine, in which a screw is driven and rotated to be fastened using compressed air as a driving source, air pressure in the piston lower chamber, if increased more than necessary during screw fastening, offers opposition to the fastening direction, thereby making prompt and sure fastening difficult.SOLUTION: An air vent portion 7b with smaller radius is provided at a middle position in a shaft line direction of a driver bit 7, and a clearance between an inner peripheral hole 50a of a guide sleeve 50 and the air vent portion is enlarged so that during screw fastening, compressed air in a piston lower chamber 25 is let out to the outside.

Description

  The present invention relates to a driving tool such as a screw driving machine that operates using compressed air as a power source.

For example, the above-described compressed air type screw driving machine performs tightening of the bit by rotating the head of one screw (screw) supplied to the driving guide portion with a driver bit in the tightening direction. The tool main body is provided with a piston that reciprocates using compressed air as a power source and a rotating air motor. The driving guide portion is provided at the tip of the tool main body in the driving direction. The air motor reciprocates integrally with the piston, and a driver bit is attached to its output shaft. The tip portion of the driver bit reaches the driving guide portion. The driving guide section is provided with a screw supply section that operates in conjunction with the driving operation of the tool main body section and a magazine that stores a large number of screws.
A handle portion that is gripped by the user is provided on a side portion of the tool body portion, and a trigger type switch lever that is operated by the user with a fingertip is provided near the base portion of the handle portion. When the switch lever is pulled, compressed air is supplied to the piston upper chamber of the tool body, the piston moves downward, and the air motor rotates to make a screw. When the pulling operation of the switch lever is released, the compressed air supplied to the piston upper chamber side flows into the piston lower chamber side, and the piston and the air motor are integrally returned to the top dead center.
Conventionally, as a technique related to this screw driving machine, the following patent document discloses a technique for increasing the output of the screw driving machine by increasing the exhaust passage to increase the exhaust efficiency.

JP 2012-71369 A

However, the conventional screw driving machine has the following problems to be solved. At the stage of tightening in which the screw is hit by the downward movement of the piston and rotated by the air motor while pressing in the tightening direction as it is, the volume of the piston lower chamber decreases as the piston and the air motor move downward, resulting in the air pressure being reduced. It will gradually increase. The air pressure in the piston lower chamber acts in a direction to push back to the top dead center side of the piston and the air motor, and acts in a direction to reduce thrust for screw tightening (force to press the screw in the tightening direction). For this reason, if the air pressure in the piston lower chamber becomes higher than necessary compared to the air pressure in the piston upper chamber, the thrust in the screw tightening direction is not sufficiently secured, and quick tightening is not performed. It becomes easy to generate.
It is an object of the present invention to further improve the workability of the driving tool by avoiding that the air pressure in the piston lower chamber becomes higher than necessary.

The above problems are solved by the following invention.
A first invention is a driving tool for rotating and tightening a screw set at the tip of a driver bit by rotating an air motor while lowering a piston using compressed air as a driving source. The driving tool has a configuration in which an air escape portion is provided in a part in the axial direction and compressed air in the piston lower chamber is released to the outside of the piston lower chamber through the air escape portion in a part of the screw tightening process.
According to the first invention, the air under the piston lower chamber is released at an appropriate timing through the air releasing portion provided for a part of the driver bit in the axial direction. It is avoided that a part of the tightening process becomes higher than necessary, thereby suppressing an increase in the downward movement resistance (air pressure) of the piston and the driver bit, and the screw can be tightened quickly.
In addition, by reducing the downward resistance of the driver bit by releasing the air from the piston upper chamber, it is possible to secure an appropriate pressing force of the tip of the driver bit against the head of the screw. Can be prevented.
According to a second invention, in the first invention, the air bleeding part is a driving tool provided in a range excluding the tip part of the driver bit.
According to the second aspect of the invention, at the beginning of the downward movement of the driver bit and at the initial stage of tightening the screw, the air bleeding portion is not functioned, and the air pressure in the piston lower chamber (the downward movement resistance of the piston) ) Is appropriately increased, the reaction in the anti-tightening direction received by the driving tool when the screw is hit is reduced.
According to a third invention, in the first or second invention, the air bleeding portion is a driving tool provided in a range excluding the base end portion of the driver bit.
According to the third invention, a sufficient amount of return air can be secured in the piston lower chamber by avoiding the air release of the piston lower chamber in the stage just before the piston reaches the lower moving end.
A fourth invention is a driving tool according to any one of the first to third inventions, wherein a piston lower chamber side is set larger than a piston upper chamber side with respect to a pressure receiving area of the piston.
According to the fourth invention, it is possible to reduce the reaction in the counter-tightening direction received by the driving tool at the time of hitting the screw.
A fifth invention is a driving tool according to any one of the first to fourth inventions, wherein a small-diameter portion having a small diameter is provided as a part of the driver bit in the axial direction as an air bleeding portion.
According to the fifth aspect, the air vent can be provided with a low cost and simple configuration.
In a sixth aspect of the invention according to any one of the first to fifth aspects of the invention, the piston is a two-stage piston that moves down in two stages with a time difference. This is a driving tool configured to allow the air vent to function.
According to the sixth aspect of the present invention, the tip of the driver bit is struck by the head of the screw by the downward movement of the upper piston, which is first moved downward, and the screw is driven into the screw fastening material. Thereafter, when the lower piston moves downward, a pressing force in the tightening direction is applied to the screw. The screw is tightened by the lead of the screw by rotating around the screw shaft by the rotation of the air motor while receiving a pressing force accompanying the downward movement of the lower piston.
Since the piston is a two-stage piston that is divided into two parts, an upper piston and a lower piston that move downward with a time difference from each other, a reliable driving of the screw into the screw tightening material and subsequent screw lead Fast and reliable tightening can be realized.

It is a side view of the internal structure of the driving tool which concerns on embodiment of this invention. This figure has shown the non-operation state (initial state). It is a side view of the internal structure of the driving tool of this embodiment. This figure shows the state at the moment when the trigger valve is turned on by pulling the switch lever. It is a side view of the internal structure of the driving tool of this embodiment. This figure shows a state at the time when the head valve is opened, compressed air is supplied to the piston upper chamber, the piston and the air motor move down integrally, and the piston reaches its bottom dead center. The air motor is moving downward. It is a side view of the internal structure of the driving tool which concerns on this embodiment. In this figure, the lower part of a tool main-body part and a driving guide part are shown. This figure shows the stage where the air vent part of the driver bit has entered the inner peripheral hole of the guide sleeve. It is a side view of the internal structure of the driving tool of this embodiment. This figure shows the state at the time when the screw has been tightened by reaching the bottom dead center while the air motor is rotating. It is a side view of the internal structure of the driving tool of this embodiment. This figure has shown the state in the middle of returning a piston and an air motor to a top dead center.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the overall internal structure (initial state) of the driving tool 1 according to the present embodiment. The illustrated driving tool 1 is a so-called screw driving machine, and is an air tool having a function of rotating a screw B in the tightening direction while striking one screw B to tighten the screw B into the tightening material W. The fastening material W is, for example, a wall surface of a two-layer structure in which a gypsum board W1 is attached to a wood ground W2. By screwing the screws B to B into the wood ground W2 through the gypsum board W1, the gypsum board W1 is made of wood. Affixed to the ground W2.
The driving tool 1 includes a tool body 2, a handle 3, a driving guide 4, and a driving tool supply device 5. The tool main body 2 has a configuration in which each mechanism such as an impact mechanism 10 and an air motor 30 described below is housed in a substantially cylindrical main body case 2a. A handle portion 3 for a user to grip from the side portion of the tool main body portion 2 is provided in a state of protruding sideways. Illustration of the distal end side of the handle portion 3 is omitted. Compressed air is stored inside the handle portion 3 through an air hose connected to the tip of the handle portion 3 via a coupler. Hereinafter, a section inside the handle portion 3 in which compressed air as a power source is stored is referred to as a reservoir 3a. The reservoir 3a is always in communication with the pressure accumulating chamber 2b that is divided inside the main body case 2a and around the striking mechanism 10 and the air motor 30.
A trigger-type switch lever 6 that is pulled by a fingertip of a hand held by the user and a trigger valve 40 that is operated by the operation are provided near the base of the handle portion 3. Compressed air is supplied to and exhausted from the tool main body 2 side by turning on and off the trigger valve 40 accompanying the operation of the switch lever 6.
The driving guide portion 4 has a function of guiding one screw B supplied into the driving passage 4a to the fastening material W by being struck by the driver bit 7, and is downward (tightened) from the lower portion of the tool body portion 2. It is provided in a state of protruding to the stuffing material W side. A contact arm 8 is provided at the tip of the driving guide portion 4. Only when the contact arm 8 is pressed against the screw driving portion, the pulling operation of the switch lever 6 becomes effective, and the driving operation in the tool body 2 is performed, thereby preventing the inadvertent driving operation. ing. A detailed description of the erroneous operation prevention mechanism, which is conventionally known, is omitted.

Hereinafter, each mechanism such as the striking mechanism 10 of the tool main body 2 and the air motor 30 will be described from the upstream side along the flow of the compressed air supplied to the reservoir 3a. First, the trigger valve 40 is accommodated in a valve case portion 3 b provided at the base portion of the handle portion 3. In a non-operating state in which the switch lever 6 is not pulled, the trigger valve 40 is off. In the OFF state of the trigger valve 40, the compressed air is supplied to the head valve upper chamber 11a through the working air passage 2c.
The head valve 11 has a function of opening and closing the inside of the piston upper chamber 12 a with respect to the pressure accumulating chamber 2 b, and is biased to the closing side by the compression spring 13. For this reason, in a state where compressed air is supplied to the head valve upper chamber 11a via the working air passage 2c, the air pressure cancels out with the compressed air in the pressure accumulating chamber 2b acting on the opening side. 11 is held on the closing side by a compression spring 13. As a result of the head valve 11 being held in the closed state, compressed air is not supplied to the piston upper chamber 12a, and thus the tool body 2 is held in the non-operating state (initial state).

As shown in FIG. 2, when the switch lever 6 is pulled upward, the trigger valve 40 is turned on and the operating air passage 2c is shut off from the reservoir 3a while being released to the atmosphere. When the working air passage 2c is opened to the atmosphere, the head valve upper chamber 11a is opened to the atmosphere, so that the head valve 11 is opened upward against the compression spring 13 by the air pressure in the pressure accumulating chamber 2b. When the head valve 11 is opened, the compressed air in the pressure accumulating chamber 2b flows into the piston upper chamber 12a, which acts on the inner peripheral upper surface of the piston 12 and the compressed air acts on the piston 12 in the downward movement direction. . In FIG. 3, the flow of compressed air (supply / exhaust) is indicated by white arrows.
The piston 12 starts to move downward by the compressed air flowing into the piston upper chamber 12a. When the piston 12 starts to move downward, the air motor 30 starts to move downward together with the piston 12. The lower side (end plate 34a) of the air motor 30 is airtightly accommodated in the cylinder 18 attached to the main body case 2a. A front cushion 19 is attached to the lower portion of the cylinder 18. The driver pit 7 is inserted into the inner peripheral side of the front cushion 19. The lower side of the air motor 30 on the inner peripheral side of the cylinder 18 corresponds to the piston lower chamber 25.
As shown in the figure, the pressure receiving area of the piston lower chamber 25 (the area on the lower surface side of the air motor 30) is larger than the pressure receiving area of the piston upper chamber 12a (the area on the inner peripheral side of the head valve 11).
Since the pressure receiving area on the piston lower chamber 25 side is set large, the reaction in the anti-tightening direction received by the driving tool 1 at the time of hitting the screw is reduced.
The piston lower chamber 25 communicates with the atmosphere side through the inner peripheral side of the front cushion 19 and the exhaust passage 26. The exhaust passage 26 reaches the upper part of the main body case 2a. As shown in the figure, an exhaust valve 20 is interposed in the exhaust passage 26. The exhaust valve 20 has a function of reducing the exhaust efficiency by narrowing the effective ventilation area of the exhaust passage 26 at the time of return.

A stroke shaft portion 31 of the air motor 30 is inserted into the inner peripheral side of the piston 12 so as to be relatively movable up and down. A stopper flange portion 32 is provided at the upper end portion of the stroke shaft portion 31. Four motor air inlets 33 to 33 are provided below the stopper flange portion 32. The compressed air that has flowed into the piston upper chamber 12 a when the head valve 11 is opened also flows into the inner peripheral side of the stroke shaft portion 31 through the motor air inlets 33 to 33.
The air motor 30 starts to rotate due to the compressed air flowing into the inner peripheral side of the stroke shaft portion 31 through the motor air inlets 33 to 33. The air motor 30 includes a motor case portion 34 that is eccentric with respect to the stroke shaft portion 31, and an output base 36 and a plurality of fins 35 to 35 can be displaced radially on the inner peripheral side of the motor case portion 34. The well-known structure accommodated in is provided. The output base 36 is accommodated so as to be rotatable with respect to the motor case 34 via bearings 36a and 36b. When compressed air flows into the motor case portion 34 through the inner peripheral side of the stroke shaft portion 31, the fins 35 receive the compressed air, whereby the output base 36 rotates, whereby the fins 35 reciprocate in the radial direction. Air supply and exhaust are made. As shown in FIG. 3, the motor air is exhausted through an exhaust port 2d provided on the side of the main body case 2a.
An output gear 36 c is formed at the lower end of the output base 36 of the air motor 30. The output gear 36c is connected to a planetary gear train 37 for reduction. A driver bit 7 is attached to the carrier 37 a of the planetary gear train 37. The carrier 37a is rotatably held with respect to the end plate 34a of the motor case part 34 via a bearing 38.
While the piston 12 and the air motor 30 are moved downward integrally by the compressed air flowing into the piston upper chamber 12a, the air motor 30 is rotated so that the driver bit 7 is driven downward while rotating in the driving passage 4a in the screw tightening direction. Thus, one screw B supplied into the driving passage 4a is struck by the driver bit 7 and rotated in the tightening direction to be tightened to the tightening material W.

A guide sleeve 50 for guiding the driver bit 7 is attached to the lower surface of the main body case 2a. A driver bit 7 is supported in the inner peripheral hole 50a of the guide sleeve 50 so as to be movable up and down and rotatable about an axis. The inner peripheral hole 50a of the guide sleeve 50 is set to have an inner diameter sufficient to allow the driver bit 7 to be smoothly inserted without rattling. As shown in FIG. 1, in the initial state of the driving tool 1, the tip (bit portion) 7a of the driver bit 7 is located in the inner peripheral hole 50a.
The driving guide 4 is coupled to the lower surface of the main body case 2a with the guide sleeve 50 interposed therebetween.
The driver bit 7 is a long rod member for striking the head of the screw B supplied into the driving passage 4a and pressing the screw B in the tightening direction as it is. have. In the present embodiment, a narrow diameter portion having an outer diameter of 4.75 mm is provided as the air bleeding portion 7 b with respect to the outer diameter of the driver bit 7 of 5.0 mm. The air vent 7b is provided by reducing the outer diameter by 0.25 mm within a certain axial range of the driver bit 7.
The driver bit 7 moves up and down while rotating in the inner peripheral hole 50 a of the guide sleeve 50, so that the air vent 7 b passes through the inner peripheral hole 50 a of the guide sleeve 50 during the tightening process of the screw B. To do. As shown in FIG. 4, in a state where the air bleeding portion 7b has entered the inner peripheral hole 50a of the guide sleeve 50, an annular gap (clearance) between the driver bit 7 and the inner peripheral hole 50a is zero on one side. Increased by 125 mm. For this reason, during the tightening process of the screw B, the compressed air in the piston lower chamber 25 flows out to the outside (inside the driving passage 4a) through the air vent 7b.
In the middle of the tightening process of the screw B (while the air motor 30 is moving downward), the piston lower chamber 25 is vented through the air vent 7b, so that the air pressure in the piston lower chamber 25 is increased more than necessary. Absent. Since the air pressure in the piston lower chamber 25 acting as a resistance in the anti-tightening direction does not increase more than necessary, the air motor 30 moves down smoothly while rotating, and the tightening of the screw B proceeds quickly and reliably. To do.
In addition, since the air pressure in the piston lower chamber 25 does not increase more than necessary, the resistance in the anti-tightening direction acting on the air motor 30 and thus the driver bit 7 is suppressed, whereby the tip 7a of the driver bit 7 is screwed. A so-called come-out is prevented by being pressed against the head of B with an appropriate pressing force.
The position and length of the air bleeding part 7b in the axial direction are appropriately set. As a result, the timing of entering and exiting the inner peripheral hole 50a of the air vent 7b accompanying the downward movement of the driver bit 7 is set appropriately. Hereinafter, along the process of tightening the screw B, the timing of entering and exiting the inner peripheral hole 50a of the air bleeding part 7b will be described.

First, as shown in FIG. 1, in an initial state where the switch lever 6 is not pulled, the tip 7 a of the driver bit 7 is located in the inner peripheral hole 50 a of the guide sleeve 50. Accordingly, the air vent 7b is located in the piston lower chamber 25 and has not yet entered the inner peripheral hole 50a.
As described above, when the trigger valve 40 is turned on by pulling the switch lever 6, the head valve 11 is opened and the piston 12 starts to move downward. When the piston 12 starts to move downward, the air motor 30 starts to move downward together with the piston 12, and thus the driver bit 7 starts moving downward. When the piston 12 starts to move downward, the air pressure in the piston lower chamber 25 is gradually increased.
When the head valve 11 is opened and compressed air flows into the piston upper chamber 12a, the air motor 30 starts to rotate by the compressed air flowing into the inner peripheral side of the stroke shaft portion 31.
Further, the stroke shaft portion 31 and the air motor 30 are integrally moved downward when the compressed air that has flowed into the piston upper chamber 12 a by opening the head valve 11 acts on the upper surface of the stroke shaft portion 31.
The distal end portion 7a of the driver bit 7 that moves downward integrally by the downward movement of the piston 12 is struck by the head of one screw B supplied into the driving passage 4a, whereby the screw B is tightened W ( It is driven mainly into gypsum board W1). At this stage, the air vent 7b of the driver bit 7 has not yet reached the inner peripheral hole 50a of the guide sleeve 50. For this reason, the air pressure in the piston lower chamber 25 is increased by the downward movement of the air motor 30 accompanying the downward movement of the piston 12, and the reaction at the time of driving the screw is reduced.

After the piston 12 and the air motor 30 move downward integrally, and the piston 12 reaches its lower moving end position, the air motor 30 continues to rotate and further moves downward alone. A piston stopper portion 12b provided on the outer periphery of the upper portion of the piston 12 abuts against the upper surface of the intermediate base portion 2e of the main body case 2a, whereby the lower end position of the piston 12 is regulated.
As shown in FIG. 3, when the piston 12 reaches the lower moving end, a plurality of auxiliary ventilation holes 12c to 12c provided around the piston 12 and a plurality of auxiliary ventilation holes 2f to 2f provided around the intermediate base portion 2e Therefore, the supply amount of compressed air to the inner peripheral side of the head valve 11 and the piston 12 increases at a stretch, and thereby the air motor 30 starts to rotate at a higher torque while moving down alone.
Accordingly, the piston 12 and the stroke shaft portion 31 located on the inner peripheral side thereof constitute a two-stage piston that strokes in the axial direction in two stages. The piston 12 first moves down, and then the stroke shaft portion 31 moves down. By the downward movement of the two-stage piston, the air motor 30 is integrally moved downward, and the air pressure in the piston lower chamber 25 is gradually increased accordingly.
After the piston 12 reaches the lower moving end, when the stroke shaft portion 31 starts to move downward relative to the piston 12, tightening of the tightening material W (mainly wood ground W <b> 2) with the lead of the screw B is performed. Is made.
On the other hand, when tightening of the wood ground W <b> 2 by the lead of the screw B rotating by the air motor 30 is started, the air bleeding portion 7 b of the driver bit 7 starts to enter the inner peripheral hole 50 a of the guide sleeve 50. As shown in FIG. 4, when a finer air bleeding portion 7b enters the inner peripheral hole 50a of the guide sleeve 50, a gap (between the driver bit 7 and the inner peripheral hole 50a of the guide sleeve 50 ( Clearance) increases by 0.125 mm on one side. For this reason, the compressed air in the piston lower chamber 25, which has been gradually increased at this stage, begins to flow to the outside through the gap between the air vent 7b and the inner peripheral hole 50a. The increase in the internal air pressure is suppressed or reduced.

At the stage where the lead of the rotating screw B is tightened to the wood ground W2, the compressed air in the piston lower chamber 25 is vented to the outside through the air vent 7b, so that the air in the piston lower chamber 25 is discharged. It is avoided that the pressure is increased more than necessary, thereby reducing the reaction force (tightening resistance) in the anti-tightening direction against the air motor 30 and thus the driver bit 7, and exerting an appropriate pressing force against the screw B of the driver bit 7. As a result, the screw B is quickly and smoothly tightened by the lead.
The air release from the piston lower chamber 25 is performed while the air release portion 7b passes through the inner peripheral hole 50a of the guide sleeve 50 downward.
As shown in FIG. 3, after the piston 12 stops moving downward, the air motor 30 moves downward alone, so that the stopper flange portion 32 provided at the upper end portion of the stroke shaft portion 31 touches the upper surface on the inner peripheral side of the piston 12. The air motor 30 comes into contact with the lower moving end position.
During the downward movement before the air motor 30 and thus the driver bit 7 reaches the lower end position, the air bleeding portion 7b of the driver bit 7 is withdrawn from the inner peripheral hole 50a of the guide sleeve 50, and thereafter the outer diameter is 5.0 mm. The base end portion 7c enters the inner peripheral hole 50a, and the inner peripheral hole 50a is almost airtightly closed, and the air venting in the piston lower chamber 25 is stopped. For this reason, at the stage where the air motor 30 reaches the lower end and the tightening of the bit B is completed, the air pressure of the compressed air that flows into the piston lower chamber 25 thereafter is increased. The compressed air in the piston lower chamber 25 in which the air pressure is sufficiently increased is used as return air for returning the piston 12 and the air motor 30 to the top dead center (initial position) thereafter.
When the stopper flange portion 32 comes into contact with the upper surface on the inner peripheral side of the piston 12, the supply of compressed air from the piston upper chamber 12a to the air motor 30 is stopped, and the rotation of the air motor 30 is stopped. At this point, the fastening of the screw B to the fastening material W is completed.

When the user releases the pulling operation of the switch lever 6 after the screw B has been tightened, the trigger valve 40 is turned off and the working air passage 2c is communicated with the reservoir 3a. When the working air passage 2c communicates with the reservoir 3a, the compressed air flows into the head valve upper chamber 11a through the working air passage 2c, and the head valve 11 is moved downward by the compression spring 13, thereby causing the piston upper chamber 12a to move downward. Is cut off from the pressure accumulating chamber 2b side, and the supply of compressed air to the piston upper chamber 12a is stopped. When the head valve 11 is thus closed, the compressed air confined in the piston upper chamber 12a is used as return air for returning the piston 12 and the air motor 30 to the top dead center. Therefore, the driving tool 1 of the present embodiment is an exhaust return type driving tool.
A cylindrical upper base portion 2g is provided on the upper portion of the main body case 2a. The upper base portion 2g defines a head valve upper chamber 11a. On the inner peripheral side of the upper base portion 2g, a stroke shaft portion 11b provided on the upper portion of the head valve 11 is held so as to be vertically movable and airtight. A valve stopper 14 is attached above the stroke shaft portion 11b and above the upper base portion 2g. A plurality of exhaust holes 15 to 15 are provided below the valve stopper 14 and on the side of the upper base portion 2g. Ring-shaped check valves 16 are attached to the outer peripheral sides of all the exhaust holes 15 to 15. A return air passage 17 communicates with the upper base portion 2g. The check valve 16 allows the flow of compressed air from the inner peripheral side of the upper base portion 2g through the exhaust holes 15 to 15 to the return air passage 17, and blocks the flow of compressed air in the reverse direction.
As shown in FIGS. 2, 3, and 5, when the head valve 11 is moved upward and the piston upper chamber 12 a is opened with respect to the pressure accumulating chamber 2 b, the stroke shaft portion 11 b of the head valve 11 projects against the valve stopper 14. The piston upper chamber 12a is in a state of being airtightly blocked from the exhaust holes 15 to 15 by being applied. On the other hand, as shown in FIG. 1, when the head valve 11 is moved downward and the piston upper chamber 12a is shut off from the pressure accumulating chamber 2b, the stroke shaft portion 11b of the head valve 11 is separated from the valve stopper 14. The piston upper chamber 12a is in communication with the exhaust holes 15 to 15 side. For this reason, the compressed air confined in the piston upper chamber 12 a by the downward movement of the head valve 11 flows into the return air passage 17 through the exhaust holes 15 to 15 and the check valve 16.

The return air passage 17 communicates with the piston lower chamber 25 through a return hole 18 a provided in the lower part of the cylinder 18 and on the outer peripheral side of the front cushion 19. Therefore, the compressed air that has flowed into the return air passage 17 from the piston upper chamber 12a through the exhaust holes 15 to 15 and the check valve 16 flows into the cylinder lower chamber 25 through the return air passage 17 and the return hole 18a. To do. Compressed air (return air) flowing into the piston lower chamber 25 from the piston upper chamber 12a through the return air passage 17 acts on the end plate 34a of the air motor 30, thereby finally causing the piston 12 and the air motor 30 to move from the bottom dead center. Returned to top dead center. Immediately after the air motor 30 starts to move upward, a part of the return air flows into the exhaust passage 26 through the inner peripheral side of the front cushion 19 and is exhausted.
When the head valve 11 is closed and the compressed air confined in the piston upper chamber 12 a flows into the return air passage 17 through the exhaust holes 15 to 15 and the check valve 16, the air pressure passes through the operation hole 23 and the exhaust valve. When the exhaust passage 26 is throttled by operating the throttle 20 toward the throttle side, the exhaust efficiency is suppressed.
In this way, by forming the exhaust passage 26 with a larger diameter than before and increasing its exhaust efficiency, it is possible to output a large striking force that could not be obtained in the past. Therefore, most of the return air that has flowed into the piston lower chamber 25 is consumed to return the piston 12 and the air motor 30 to the top dead center. Returned to top dead center.
When return air flows into the piston lower chamber 25, this acts on the end plate 34 a of the air motor 30. Due to the area difference between the end plate 34 a and the upper surface of the stroke shaft portion 31, the air motor 30 first moves up by the air pressure on the return air chamber 25 side. When the air motor 30 moves upward with respect to the piston 12, the stopper flange portion 32 is separated from the upper surface on the inner peripheral side of the piston 12, so that the piston upper chamber 12 a is connected to the inner periphery of the stroke shaft portion 31 via the motor air inlets 33 to 33. As a result, the piston upper chamber 12a is opened to the atmosphere via the motor air supply path and the exhaust port 2d. On the other hand, the return air flowing into the piston lower chamber 25 through the return air passage 17 is prevented from flowing back into the piston upper chamber 12a by the check valve 16. In this way, the piston upper chamber 12a is opened to the atmosphere, and the return air flows into the piston lower chamber 25, whereby the air motor 30 further moves up.

In addition, since a part of the compressed air (motor exhaust) flowing into the motor air supply path from the piston upper chamber 12a through the motor air inlets 33 to 33 acts on the lower surface of the piston 12, the piston 12 also starts to move up at this time. .
A stopper washer 39 provided around the stroke shaft portion 31 of the air motor 30 comes into contact with the lower surface of the intermediate base portion 2e, and the air motor 30 reaches the top dead center. Thus, the air motor 30 is returned to the top dead center, and the piston 12 is moved upward by exhausting the motor. Finally, the piston 12 is pushed by the air motor 30 that moves upward while the stopper washer 39 of the air motor 30 is in contact with the lower surface. Returned to dead point.
The air passage 5 a of the driving tool supply device 5 is communicated with the return air passage 17. For this reason, after the completion of driving, a part of the compressed air flowing into the return air passage 17 from the piston upper chamber 12a is supplied to the driving tool supply device 5 through the air passage 5a. The feed piston 5b moves backward against the compression spring 5c by the compressed air supplied through the air passage 5a. When the return air in the piston lower chamber 25 is exhausted, the feed piston 5b moves forward by the compression spring 5c. The feed piston 5b is provided with feed claws 5d and 5d. When the feed piston 5b moves forward, one screw B is supplied into the driving passage 4a by the feed claws 5d and 5d.

According to the driving tool 1 of the present embodiment configured as described above, the air release from the piston lower chamber 25 is performed at an appropriate timing via the air relief portion 7b provided for a part of the driver bit 7 in the axial direction. As a result, it is avoided that the air pressure in the piston lower chamber 25 becomes higher than necessary for a part of the screw tightening process, thereby suppressing an increase in the downward movement resistance (air pressure) of the piston 12 and the driver bit 7. Thus, the screw B can be fastened quickly, and an appropriate pressing force of the driver bit tip 7a against the head of the screw B can be secured to prevent so-called cam-out.
The timing of entry of the air vent 7b into the inner peripheral hole 50a is set to a stage where the stroke shaft portion 31 as the second stage piston starts to move downward relative to the piston 12 as the first stage piston. . Further, the timing for the air vent 7b to leave the inner peripheral hole 50a is set before the air motor 30 reaches its lower end position. For this reason, the air vent 7b passes through the inner peripheral hole 50a from the time when the screw B starts to pass through the gypsum board W1 and before it is completely tightened into the wood base W2. Then, the air in the piston lower chamber 25 is released. By appropriately releasing the air in the piston lower chamber 25, it is avoided that the air pressure in the piston lower chamber 25 becomes excessively high, and the lowering resistance of the air motor 30 and thus the driver bit 7 is reduced. Screw B is quickly and reliably tightened by the lead.
Thereafter, just before the tightening of the screw B is completed, the base end portion 7c enters the inner peripheral hole 50a of the guide sleeve 50, and the inner peripheral hole 50a is almost airtightly closed. The compressed air is stored in the piston lower chamber 25, and the piston 12 and the air motor 30 are reliably returned to the top dead center.
In addition, according to the illustrated embodiment, the air vent portion 7b is configured by providing the narrow portion having a small diameter with respect to a certain range in the axial direction of the driver bit 7 so that the air vent portion 7b is simple and low. Can be provided at cost.

Further, since the air vent 7b is provided between the distal end 7a and the base end 7c so that the air is released from the piston lower chamber 25 in the middle of tightening the bit B, the tip is initially tightened. The reaction at the time of driving can be reduced by closing the inner peripheral hole 50a with the portion 7a to increase the air pressure in the piston lower chamber 25, and the inner peripheral hole 50a is closed again with the base end portion 7c just before the tightening is completed. Thus, compressed air having a sufficient pressure can be stored in the piston lower chamber 25 and used as return air.
Further, the reaction in the anti-tightening direction that the driving tool 1 receives when the screw is hit also by the fact that the pressure receiving area on the piston lower chamber 25 side of the air motor 30 is larger than the pressure receiving area on the piston upper chamber 12a side of the piston 12. Can be reduced.
Further, in the present embodiment, the air motor 30 is moved downward by the piston 12 and the stroke shaft portion 31 constituting the two-stage piston. The tip portion 7a of the driver bit 7 is struck by the head of the screw B by the downward movement of the piston 12 on the upper stage, which is first moved down, and the screw B is driven into the fastening material W (mainly gypsum board W1). Thereafter, the lower-stage stroke shaft portion 31 moves downward relative to the piston 12 to apply a pressing force in the tightening direction to the screw B.
The screw B is pressed in the tightening direction through the distal end portion 7a of the driver bit 7 by the relative downward movement of the stroke shaft portion 31. In this pressed state, the screw B is rotated in the tightening direction by the air motor 30, so that the screw B is securely and quickly tightened by the lead of the screw.
In this way, the piston is a two-stage piston divided into an upper piston (piston 12) and a lower piston (stroke shaft portion 31) that move downward with a time difference from each other. It is possible to realize reliable driving and subsequent fast and reliable tightening of the screw B by the lead of the screw.

The embodiment described above can be implemented with various modifications. For example, a configuration in which a narrow-diameter portion with a reduced diameter is provided as the air vent portion 7b of the driver bit 7 over the entire circumference around the axis, but instead, for example, a groove portion along the axial direction on the outer surface of the driver bit 7 is provided. May be provided as an air vent, or a flat surface may be provided as an air vent. The gap between the guide sleeve 50 and the inner peripheral hole 50a is also increased by these grooves and flat surfaces, and the compressed air in the piston lower chamber 25 can be released.
Further, the position of the air bleeding portion 7a in the axial direction of the driver bit 7 or the range (length) in the axial direction in which the air bleeding portion is provided should be changed appropriately depending on factors such as the length of the screw B that can be tightened. Can do.
Further, the configuration in which the air bleeding portion 7b is provided in the middle of the axial direction of the driver bit 7 and between the distal end portion 7a and the proximal end portion 7c having a larger diameter is illustrated, but either one is omitted. You can also. The point is that in the process of tightening the screw B, the inner peripheral hole 50a is almost airtightly closed and the air pressure in the piston lower chamber 25 is increased moderately, and the air in the piston lower chamber 25 passes through the air vent. What is necessary is just to set it as the structure switched to the state by which compressed air is escaped outside. The former state is preferable at the stage where it is desired to increase the air pressure in the piston lower chamber 25 to reduce the reaction at the time of driving the screw, and the latter state reduces the downward resistance of the driver bit 7 to quickly tighten the bit. And it is preferable at the stage where it is desired to proceed reliably.
Moreover, although the screw driving machine which incorporates the air motor 30 was illustrated as the driving tool 1, it is a driving tool only of the hammering action which does not have this kind of air motor, and can be similarly applied to a nailing machine.

B ... Screw W ... Fastening material 1 ... Driving tool 2 ... Tool main body 2a ... Main body case, 2b ... Accumulation chamber, 2c ... Working air passage, 2d ... Exhaust port 2e ... Intermediate base part, 2f ... Auxiliary vent hole, 2g ... Upper base part 3 ... Handle part 3a ... Reservoir, 3b ... Valve case part, 3c ... Valve case hole 4 ... Driving guide part, 4a ... Driving tool supply unit 5a ... Driving tool supply device 5a ... Air path, 5b ... Feeding piston, 5c ... Compression spring, 5d ... Feed claw 6 ... Switch lever 7 ... Driver bit, 7a ... Tip part, 7b ... Air vent part, 7c ... Base end part 8 ... Contact arm 10 ... Blowing mechanism part 11 ... Head valve, 11a ... Head Valve upper chamber 12 ... Piston 12a ... Piston upper chamber, 12b ... Piston stopper portion, 12c ... Auxiliary vent hole 13 ... Compression spring 14 ... Valve stopper 15 ... Exhaust hole 16 ... Reverse Valve 17 ... Return air passage 18 ... Cylinder, 18a ... Return hole 19 ... Front cushion 20 ... Exhaust valve 21 ... Exhaust piston 22 ... Compression spring 23 ... Actuation hole 25 ... Piston lower chamber 26 ... Exhaust passage 30 ... Air motor 31 ... Stroke shaft Portion 32 ... Stopper flange portion 33 ... Motor air inlet 34 ... Motor case portion 34a ... End plate 35 ... Fin 36 ... Output base 36a, 36b ... Bearing 36c ... Output gear 37 ... Planet gear 37a ... Carrier 38 ... Bearing 39 ... Stopper washer 40 ... Trigger valve 50 ... Guide sleeve, 50a ... Inner peripheral hole

Claims (6)

A driving tool for rotating and tightening a screw set at the tip of a driver bit by rotating the air motor while moving the piston downward using compressed air as a driving source, and a part of the driver bit in the axial direction A driving tool having a structure in which an air vent portion is provided, and compressed air in the piston lower chamber is released to the outside of the piston lower chamber through the air vent portion in a part of the screw tightening process. The driving tool according to claim 1, wherein the air bleeding portion is provided in a range excluding a tip portion of the driver bit. The driving tool according to claim 1 or 2, wherein the air bleeding part is provided in a range excluding a base end part of the driver bit. 4. The driving tool according to claim 1, wherein a piston lower chamber side is set larger than a piston upper chamber side with respect to a pressure receiving area of the piston. 5. The driving tool according to claim 1, wherein a small-diameter portion having a small diameter is provided as a part of an axial direction of the driver bit as the air bleeding portion. The driving tool according to any one of claims 1 to 5, wherein the piston is a two-stage piston that moves down in two stages with a time difference, and a lowering process of the lower piston that moves down later A driving tool configured to allow the air vent to function.

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