# Patent

## Title
Pneumatic driving machine

## Abstract

The nailing machine (1) comprises an air passage (510) allowing communication between a cylinder (200) and a return air chamber (500) in which compressed air for returning a piston (300) to the initial position is accumulated. The air passage (510) is provided with a control valve (520) controlling entry of compressed air into the return air chamber (500) from the cylinder (200). The control valve (520) opens the air passage 510 and allows entry of compressed air into the return air chamber (500) in the case wherein the nailed object produces a small reaction force upon driving the nail, namely when the upward moving distance of the body (100) relative to the push lever (700) is smaller than a predetermined distance. The compressed air that has entered the return air chamber (500) further enters a below-the-piston chamber and serves as air damper, reducing excess energy absorbed by a piston bumper (360).

## Background
RELATED APPLICATIONS
This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2009/067965, filed on Oct. 13, 2009, which in turn claims the benefit of Japanese Application Nos. 2008-265124, filed on Oct. 14, 2008 and 2009-227229, filed on Sep. 30, 2009, the disclosures of which Applications are incorporated by reference herein.
TECHNICAL FIELD
The present invention relates to a pneumatic driving machine for driving fasteners such as nails and staples into an object.
BACKGROUND ART
It is a known technique in the prior art to adjust the distance between the tip of the push lever that abuts on an object into which a nail is driven (“the nailed object” hereafter) and the tip of the driver blade at the lower dead center from which a nail is ejected, namely the distance between the nailed object and driver blade in order to drive a nail into the nailed object in the manner that the head of the nail driven by the nailing tool is flush with the surface of the nailed object. For example, the driving machine disclosed in Patent Literature 1 below comprises a driving depth adjusting device in which the part of the push lever that makes contact with the driving machine body is threaded in the body using a screw. The operator shifts the knob in which the screw is housed in the axial direction of the screw to adjust the upper dead center of the push lever. In this way, the distance between the tip of the push lever and the tip of the driver blade at the lower dead center is adjusted.

    Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2003-136429


The pressure of the compressed air supplied to the nailing machine is generally set for a relatively wide range of values to cover a wide range of applications. When the adjusting device described in the above Patent Literature 1 is used for driving a short nail, the operator adjusts the position of the upper dead center of the push lever to increase the relative distance between the lower dead center of the driver blade tip and the push lever tip (the nailed object) in order to prevent the nail from being driven excessively deep. When the operator drives a nail into the nailed object in this state, the piston bumper absorbs excess energy after the nail is driven. In this way, the piston bumper receives a large load and has a short durability life. Consequently, a problem is that the nailing machine has short durability life.
SUMMARY OF INVENTION
The present invention is invented in view of the above problem and the purpose of the present invention is to improve the durability of the driving machine.
In order to achieve the above purpose, the pneumatic driving machine according to the first aspect of the present invention is characterized by comprising:
a housing;
a cylinder provided in the housing;
a piston reciprocating between a first position and a second position within the cylinder and dividing the interior of the cylinder into an above-the-piston chamber and a below-the-piston chamber;
a driver blade fixed to said piston and hitting and driving a fastener into a workpiece;
an accumulator accumulating compressed air for moving the piston from the first position to the second position;
a main valve sending the compressed air accumulated in the accumulator to the above-the-piston chamber to move the piston from the first position to the second position upon operation of a trigger;
a return air chamber communicating with the above-the-piston chamber while the piston is positioned at the second position, communicating with the below-the-piston chamber while the piston is positioned at the second position, and accumulating compressed air supplied from the above-the-piston chamber when the piston moves from the first position to the second position; and
a pressure control means controlling the pressure in the return air chamber.
Possibly, a push lever connected to the housing via a first resilient member and biased by the first resilient member to abut on the nailed object is further provided; and
the pressure control means controls the pressure in the return air chamber based on the moving distance of the housing relative to the push lever as a result of receiving a reaction force from the nailed object upon driving the fastener.
Possibly, the pressure control means increases the pressure in the return air chamber as the moving distance of the housing relative to the push lever is smaller.
Possibly, the pressure control means comprises a control valve allowing or blocking entry of compressed air into the return air chamber from the above-the-piston chamber via a check valve based on the moving distance of the housing relative to the push lever.
Possibly, the return air chamber communicates with the above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
the control valve comprises:
a valve member sliding within the control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of the reduced-diameter part and closing the control passage when engaging with the reduced-diameter part, and
a second resilient member biasing the one end of the valve member in the driving direction so that the one end engages with the reduced-diameter part; and
the push lever pushes the other end of the valve member in the direction opposite to the driving direction against the biasing force of the resilient member so that the one end of the valve member disengages from the reduced-diameter part when the moving distance of the housing relative to the push lever is smaller than a predetermined distance.
Possibly, the pressure control means comprises a control valve controlling the resistance to entry of compressed air from the above-the-piston chamber based on the moving distance of the housing relative to the push lever.
Possibly, the return air chamber communicates with the above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part; and
the control valve comprises:
a closing member placed in the control passage, having a diameter larger than the passage diameter of the reduced-diameter part, and closing the control passage when engaging with the reduced-diameter part,
a second resilient member biasing the closing member in the direction opposite to the driving direction so that the closing member engages with the reduced-diameter part,
a pin having one end abutting on the opposite end of the resilient member to the end abutting on the closing member so as to be biased in the driving direction, and
a moving means moving the pin within the control passage in the driving direction based on the moving distance of the housing relative to the push lever.
Possibly, the moving means comprises a locker arm that has one end pushing the other end of the pin in the direction opposite to the driving direction and the other end abutting on a third resilient member fixed to the housing at one end so as to be biased in the driving direction and abutting on the push lever so as to be pushed in the direction opposite to the driving direction, and that is rotatable about a rotation axis positioned between the two ends.
Possibly, the return air chamber consists of a first return air chamber communicating with the above-the-piston chamber and below-the-piston chamber and a second return air chamber communicating with the first return air chamber via an air passage; and
the pressure control means comprises a control valve controlling the opening/closing of the air passage based on the moving distance of the housing relative to the push lever.
Possibly, the air passage includes a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
the control valve comprises:
a valve member sliding within the control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of the reduced-diameter part and closing the control passage when engaging with the reduced-diameter part, and
a second resilient member having one end fixed to the housing and the other end abutting on the valve member to bias the valve member in the driving direction; and
the push lever pushes the other end of the valve member in the direction opposite to the driving direction against the biasing force of the second resilient member so that the one end of the valve member engages with the reduced-diameter part when the moving distance of the housing relative to the push lever is smaller than a predetermined distance.
Possibly, the pressure control means controls the pressure in the return air chamber based on the operation rate of an operation member.
Possibly, the pressure control means comprises a control valve allowing or blocking entry of compressed air into the return air chamber from the above-the-piston chamber via a check valve based on the operation rate of the operation member.
Possibly, the return air chamber communicates with the above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
the control valve comprises:
a valve member sliding within the control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of the reduced-diameter part and closing the control passage when engaging with the reduced-diameter part, and
a second resilient member biasing the one end of the valve member in the driving direction so that the one end engages with the reduced-diameter part;
the operation member has an abutting part abutting on the other end of the valve member;
the abutting part of the operation member pushes the other end of the valve member in the direction opposite to the driving direction against the biasing force of the resilient member so that the one end of the valve member disengages from the reduced-diameter part when the operation member is operated and the moving distance of the abutting part of the operation member in the driving direction is smaller than a predetermined distance.
Possibly, the pressure control means comprises a detection part detecting the length of a fastener and controls the pressure in the return air chamber based on the length of the fastener detected by the detection part.
Possibly, the pressure control means comprises a control valve allowing or blocking entry of compressed air into the return air chamber from the above-the-piston chamber via a check valve based on the length of the fastener detected by the detection part.
Possibly, the return air chamber communicates with the above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
the control valve comprises:
a valve member sliding within the control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of the reduced-diameter part and closing the control passage when engaging with the reduced-diameter part, and
a resilient member biasing the one end of the valve member in the driving direction so that the one end engages with the reduced-diameter part;
the detection part comprises a detection member that has one end abutting on the other end of the valve member and the other end abutting on a fastener longer than the predetermined length in the direction perpendicular to the driving direction, and that is rotatable about a rotation axis positioned between the two ends;
the one end of the detection member has:
a first abutting part abutting the other end of the valve member when the other end of the detection member does not abut on a fastener longer than the predetermined length, and
a second abutting part that abuts on the other end of the valve member when the other end of the detection member abuts on a fastener longer than the predetermined length and is closer to the rotation axis than the first abutting part; and
the one end of the valve member disengages from the reduced-diameter part when the other end of the valve member abuts on the first abutting part and engages with the reduced-diameter part when the other end of the valve member abuts on the second abutting part.
The present invention provides a pneumatic driving machine having an improved durability.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-sectional view of the nailing machine according to Embodiment 1.
FIG. 2 is a cross-sectional view of the nailing machine according to Embodiment 1 during the driving operation.
FIG. 3 is a cross-sectional view of the core part in FIG. 1.
FIG. 4 is a cross sectional view showing the piston operation of the nailing machine according to Embodiment 1.
FIG. 5 is a cross-sectional view of the nailing machine according to Embodiment 1 during the driving operation.
FIG. 6 is a cross-sectional view of the nailing machine according to Embodiment 2.
FIG. 7 is a cross-sectional view of the core part in FIG. 6.
FIG. 8 is a cross-sectional view of the core part in FIG. 6.
FIG. 9 is a cross-sectional view of the nailing machine according to Embodiment 3.
FIG. 10 is a cross-sectional view of the core part in FIG. 9.
FIG. 11 is a cross-sectional view of the core part in FIG. 9.
FIG. 12 is a cross-sectional view of the nailing machine according to Embodiment 4.
FIG. 13A is a cross-sectional view of the core part in FIG. 12.
FIG. 13B is a cross-sectional view of the core part in FIG. 12.
FIG. 13C is a cross-sectional view of the core part in FIG. 12.
FIG. 14A is a cross-sectional view of the core part at the section line A-A in FIG. 13A.
FIG. 14B is a cross-sectional view of the core part at the section line B-B in FIG. 13B.
FIG. 14C is a cross-sectional view of the core part at the section line C-C in FIG. 13C.
FIG. 15 is a cross-sectional view of the nailing machine according to Embodiment 5.
FIG. 16 is a cross-sectional view of the nailing machine according to Embodiment 5.
FIG. 17A is a cross-sectional view of the core part at the section line D-D in FIG. 15.
FIG. 17B is a cross-sectional view of the core part at the section line E-E in FIG. 16.



BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
A nailing machine 1 according to Embodiment 1 of the present invention will be described hereafter with reference to the drawings. For clarified explanation, the direction in which a fastener is ejected from the nailing machine 10 is defined as the ejection direction, and the ejection direction is termed downward and the direction opposite to it is termed upward in this embodiment.
FIG. 1 is a lateral cross-sectional view of a nailing machine 1 of this embodiment of the present invention. The nailing machine 1 of this embodiment of the present invention mainly consists of a body (housing) 100, a cylinder 200 provided inside the body 100, and a piston 300 sliding within the cylinder 200. These parts will be described in detail hereafter.
The body 100 has the cylinder 200 therein. The body 100 has a holding part 101 extending in the direction nearly perpendicular to the driving direction. An exhaust cover 110 is hermetically fixed to the top of the body 100 by not-shown multiple bolts to cover the upper opening of the cylinder 200. A nose 120 is fixed to the bottom of the body 100 by not-shown multiple bolts to cover the lower opening of the cylinder 200. The exhaust cover 110 has an exhaust passage 111 allowing an above-the-piston chamber 340 within the cylinder 200, which will be described later, to communicate with the atmosphere.
The cylinder 200 has a nearly cylindrical form and supports the piston 300 slidably (reciprocating) on the inner surface thereof. A cylinder plate 210 in the form of a ring is interposed between the outer surface of the cylinder 200 and the inner surface of the body 100. The cylinder 200 has air holes 220 and 230 and an air passage 510, which will be described later.
The piston 300 can slide (reciprocate) within the cylinder 200 in the nail driving direction. The piston 300 is formed by an integral piece consisting of a cylindrical large-diameter part 310 and a cylindrical small-diameter part 320 protruding downward from the large-diameter part 310. The upper end of a driver blade 330 in the form of a shaft is fitted in a through-hole formed in the center of the piston 300. The lower end of the driver blade 330 abuts on a nail upon driving. The piston 300 divides the interior of the cylinder 200 into an above-the-piston chamber 340 and a below-the-piston chamber 350 as shown in FIG. 4. A piston bumper 360 consisting of a resilient body such as rubber nearly in the shape of a tub having a through-hole in the center is provided at the lower end of the cylinder 200 to absorb shock upon downward movement of the piston 300.
The member supplying compressed air in the cylinder 200 will be described hereafter. As shown in FIG. 1, an air plug 410 connected to an air hose hooked to a not-shown air compressor for introducing compressed air into the nailing machine 1 is provided at the end of the holding part 101 of the body 100. An accumulator 420 accumulating the compressed air introduced through the air plug 410 is formed by the upper part of a cylindrical space enclosed by the cylinder 200, body 100, and cylinder plate 210. A cylindrical return air chamber 500, which will be described later, is formed by the lower part of it.
A head valve 430 serving to introduce or block the compressed air from the accumulator 420 into the cylinder 200 is provided above the cylinder 200. The head valve 430 is formed by an integral piece consisting of a nearly cylindrical lower member 431 having a through-hole in the center and a tubular upper member 432 provided above the lower member 431 coaxially with it. A flange 431a having a diameter larger than the other part so as to make contact with the exhaust cover 110 is formed at the upper end of the lower member 431 of the head valve 430. The underside of the flange 431a is normally pushed upward by the compressed air accumulated in the accumulator 420. On the other hand, the head valve 430 is biased downward (in the direction to abut on the cylinder 200) by a head valve spring 440 placed inside the upper member 432 and normally (in the driving standby state) positioned at the lower dead center. An above-the-head valve chamber 460 is formed between the top surface of the lower member 431 of the head valve 430 and the exhaust cover 110. The head valve 306 moves between the upper dead center and lower dead center described below depending on the pressure in an above-the-head valve chamber 450 described later, which the top surface of the lower member 431 of the head valve 430 receives, and the differential pressure between the pressure from the resilience of the head valve spring 440 and the pressure in the accumulator 420, which the underside of the flange 431a of the head valve 430 receives.
As shown in FIG. 1, when the head valve 430 is positioned at the lower dead center, the lower surface of the head valve 430 abuts on the top surface of the cylinder 200 to block entry of the compressed air in the accumulator 420 into the cylinder 200. Meanwhile, the upper member 432 of the head valve 430 opens the opening of the exhaust passage 111 of the exhaust cover 110 to allow the interior of the cylinder 200 to communicate with the atmosphere.
Furthermore, as shown in FIG. 2, when the head valve 430 is positioned at the upper dead center, the lower surface of the head valve 430 is spaced from the top surface of the cylinder 200, allowing the compressed air in the accumulator 420 to enter the cylinder 200. Furthermore, the upper member 432 of the head valve 430 closes the opening of the exhaust passage 111 of the exhaust cover 110 to prevent the compressed air from escaping into the atmosphere.
Furthermore, the body 100 is provided with a trigger 460 and a trigger valve 470 for initiating the driving of the nailing machine 1 in the driving standby state as shown in FIG. 1 and then returning to the driving standby state.
The trigger 460 is rotatably supported by the body 100 and has a plate-like trigger arm 461 rotatably supported at one end. The other end of the trigger arm 461 abuts on the upper end of a push lever 700, which will be described later, when the push lever 700 is positioned at the upper dead center. Therefore, when the trigger 460 is pressed upward while the push lever 700 is shifted upward in relation to the body 100, the trigger arm 461 pushes up the plunger 471 of a trigger valve 470, which will be described later.
The trigger valve 470 serves to change the position of the head valve 430 by supplying compressed air into the above-the-head valve chamber 450 or discharging compressed air from the above-the-head valve chamber 450. The trigger valve 470 is, as shown in FIG. 3, placed in the body 100 and mainly consists of a plunger 471 in the form of a shaft having a flange 471a having a diameter larger than the other part, a nearly cylindrical valve piston 472 surrounding the plunger 471, and a spring 473 abutting on the flange 471a of the plunger 471 for biasing it downward. When the plunger 471 is positioned at the lower dead center, the air tightness between the flange 471a and body 100 is maintained and the compressed air in the below-the-valve piston chamber 474 is supplied to the above-the-head valve chamber 450. On the other hand, when the plunger 471 is positioned at the upper dead center against the biasing force of the spring 473, the air tightness between the flange 471a and body 100 is broken and the compressed air in the below-the-valve piston chamber 474 is released into the atmosphere.
The member ejecting nails will be described hereafter. The member ejecting nails consists of a piston 300 sliding in the nail driving direction by way of compressed air, a driver blade 330 fixed to the piston 300, and a nose 120 guiding the nail to a desired driving point.
The nose 120 serves to guide the nail and driver blade 330 so that the driver blade 330 appropriately contacts the nail and drives it into a desired point on the nailed object 2. The nose 120 consists of a disk-shaped connection part 121 connected to the opening at the lower end of the body 100 and a tubular part 122 extending downward from the center of the connection part 121. Furthermore, the nose 120 has an ejection passage 123 formed through the center of the connection part 121 and tubular part 122. A magazine 610 housing multiple nails is mounted on the tubular part 122 of the nose 120. Nails are sequentially supplied to the ejection passage 123 in the nose 120 from the magazine 610 by a feeder 620 that can reciprocate by way of compressed air and resilient members.
A vertically slidable push lever 700 is provided along the outer surface of the nose 120. One end of the push lever 700 is connected to a spring 710 (compression spring) producing a biasing force in the nail driving direction. The push lever 700 is connected to the body 100 via the spring 710. The lower end of the push lever 700 protrudes from the lower end of the nose 120 in the driving standby state as shown in FIG. 1. On the other hand, receiving a reaction force from the nailed object 2, the push lever 700 moves upward relatively to the body 100 and nose 120 against the biasing force of the spring 710 during the driving operation on the nailed object 2 in which the body 100 is pressed against the nailed object 2 as shown in FIG. 2.
The driver blade 330 has a cylindrical column form and is integrally fixed to the piston 300 at the upper end. The driver blade 330 slides within the ejection passage 123 of the nose 120 to give the nail a driving force.
The structure for returning the piston 300 to the upper position in the cylinder 200 after the nail is driven will be described hereafter. The return air chamber 500 serves to return the piston 300 that has moved to the lower dead center after driving the nail to the initial position or upper dead center (the first position). The return air chamber 500 is formed by the lower part of a cylindrical space enclosed by the cylinder 200, body 100, and cylinder plate 210. The return air chamber 500 communicates with the cylinder 200 via air holes 220 and 230 each formed in the sidewall of the cylinder 200 in the circumferential direction. The air hole 220 is formed above the lower dead center, namely the point where the piston 300 abuts on the piston bumper 360 (the second position). The air hole 230 is formed below the point where the piston 300 abuts on the piston bumper 360. The air hole 220 is provided with a check valve 240 allowing one-way flow of compressed air from the above-the-piston chamber 340 to the return air chamber 500. When the piston 300 moves from the upper dead center to the lower dead center, the compressed air enters and accumulates in the return air chamber 500 via the air hole 220 having the check valve 240.
The pressure control means controlling the pressure in the return air chamber 500 will be described hereafter. The pressure control means of this embodiment consists of, as shown in FIG. 3, an air passage 510 and a control valve 520 controlling the opening/closing of the air passage 510.
The air passage 510 is a passage allowing communication between the cylinder 200 and return air chamber 500. The air passage 510 consists of an influx passage 511, a control passage 512, and an outflux passage 513.
The influx passage 511 is a passage guiding the compressed air in the cylinder 200 to the control passage 512. The influx passage 511 opens to the peripheral surface of the cylinder 200 at one end, where an opening 511a is formed, and extends outward in the radial direction of the cylinder 200 from the opening 511a. The other end of the influx passage 511 is connected to one end the control passage 512. The opening 511a of the influx passage 511 is formed in the peripheral surface of the above-the-piston chamber 340 when the piston 300 is positioned at the second position.
The control passage 512 allows or blocks entry of compressed air coming through the influx passage 511 into the return air chamber 500. The control passage 512 extends in the driving direction, namely in the sliding direction of the piston. The control passage 512 consists of a first control passage 512a and a second control passage 512b. A partition 530 having a through-hole allowing entry of the compressed air is placed at the connection part between the first and second control passages 512a and 512b. 
The first control passage 512a is connected to the influx passage 511 at one end and to the second control passage 512b at the other end. A check valve 540 allowing only the entry of compressed air from the influx passage 511 and blocking entry of compressed air into the influx passage 511 from the first control passage 512a is provided at the one end of the first control passage 512a that is connected to the influx passage 511. The check valve 540 consists of a closing member 541 closing the opening of the first control passage 512a that makes connection to the influx passage 511, and a spring 542 that is a resilient member biasing the closing member 541 in the direction opposite to the driving direction, namely in the direction the closing member 541 closes the opening. Therefore, the compressed air coming from the influx passage 511 is allowed to enter the first control passage 512a by pushing down the closing member 541 in the driving direction against the biasing force of the spring 542. However, the compressed air in the first control passage 512a cannot enter the influx passage 511 because the closing member 541 closes the opening.
The second control passage 512b is connected to the first control passage 512a at one end and has at the other end an opening 512c opening in the driving direction from the body 100. Furthermore, the second control passage 512a has an opening 512d opening inward in the radial direction of the cylinder 200, where it is connected to the outflux passage 513. Furthermore, a reduced-diameter part 512e protruding inward in the radial direction of the second control passage 512b and having a passage diameter smaller than the other part is formed along the peripheral surface of the second control passage 512b between the connection part to the first control passage 512a and the opening where it is connected to the outflux passage 513. A control valve 520 allowing or blocking entry of compressed air coming from the above-the-piston chamber 340 into the return air chamber 500 via the influx passage 511 and first control passage 512a based on the moving distance of the body 100 relative to the push lever 700 is provided in the second control passage 512b. 
The control valve 520 consists of a valve member 521 sliding within the second control passage 512b and a spring 522 that is a resilient member biasing the valve member 521 in the driving direction. The valve member 521 has at one end a flange 521a protruding outward in the radial direction of the second control passage 521b from the other part of the valve member 521. The flange 521a has a diameter larger than the passage diameter of the reduced-diameter part 512e of the second control passage 512b and engages with the reduced-diameter part 512e to close the second control passage 512b. Furthermore, the valve member 521 has at the other end an abutting part 521b protruding outside the body 100 through the opening 512c of the second control passage 512b and abutting on the push lever 700. The abutting part 521b is provided with a sealing member 523 to prevent leakage of compressed air from the opening 512c. The spring 522 abuts on the flange 521a at one end and abuts on the partition 530 at the other end. Then, the spring 522 biases the flange 521a of the valve member 521 in the driving direction, namely in the direction the flange 521a engages with the reduced-diameter part 512e. Therefore, when the push lever 700 does not abut on the abutting part 521b, the biasing force of the spring 522 causes the flange 521a to engage with the reduced-diameter part 512e and close the second control passage 512b, whereby the control valve 520 blocks entry of compressed air from the first control passage 511. When the push lever 700 abuts on the abutting part 521b and pushes it upward, the flange 521a of the valve member 521 moves upward against the biasing force of the spring 522 and disengages from the reduced-diameter part 512e. Therefore, the control valve 520 allows entry of compressed air from the first control passage 511.
The outflux passage 513 is a passage guiding the compressed air in the control passage 512 to the return air chamber 500. The outflux passage 513 opens to the peripheral surface of the second control passage 512b at one end, where an opening 512d is formed, and extends inward in the radial direction of the cylinder 200 from the opening 512d. 
The operational behavior of the nailing machine 1 having the above structure will be described hereafter.
First, the nailing machine 1 of this embodiment in the driving standby state will be described. As shown in FIG. 1, first, the air plug 410 of the nailing machine 1 is connected to an air hose hooked to a not-shown compressor that supplies compressed air as power source of the nailing machine 1. Then, the compressed air is supplied into the accumulator 420 provided in the body 100 of the nailing machine 1 via the air plug 410. The accumulated compressed air is partly supplied to the below-the-valve piston chamber 474 shown in FIG. 3 so that the plunger 471 is pushed down to the lower dead center. Meanwhile, the compressed air pushes up the valve piston 472 and enters the above-the-head valve chamber 450 via the gap created by the raised valve piston 474, body 100, and air passages 480a and 480b shown in FIG. 1. The compressed air supplied in the above-the-head valve chamber 450 pushes down the head valve 430 so that the head valve 430 and cylinder 200 make close contact with each other, whereby the compressed air does not enter the cylinder 200. In this way, the piston 300 and driver blade 330 remain in the driving standby state in which they stand still at the upper dead center (the first position).
The behavior of the nailing machine 1 of this embodiment during the driving operation will be described hereafter. As shown in FIG. 2, when the operator presses the push lever 700 against the nailed object 2, the top of the push lever 700 abuts on the abutting part 521b of the valve member 521 provided in the control passage 512 shown in FIG. 3 to move the valve member 521 to the upper dead center. Then, the flange 521a of the valve member 521 disengages from the reduced-diameter part 512e to open the air passage 510.
Then, as shown in FIG. 2, the operator pulls the trigger 460 while pressing the push lever 700 against the nailed object 2. Consequently, the plunger 471 of the trigger valve 470 shown in FIG. 3 is pushed up to the upper dead center so that the compressed air in the below-the-valve piston chamber 474 is discharged. Furthermore, the difference in pressure between the air passage 480a and below-the-valve piston chamber 474 serves to push down the valve piston 472. Then, the compressed air in the above-the-head valve chamber 450 is discharged into the atmosphere via the air passage 480b of the exhaust cover 110 and the air passage 480a provided in the body 100. After the compressed air in the above-the-head valve chamber 450 is discharged, the pressure of the compressed air in the accumulator 420 serves to push up the head valve 430 to make a gap between the head valve 430 and cylinder 200. The compressed air enters the above-the-piston chamber 340 within the cylinder 200 through the gap. With the compressed air entering the above-the-piston chamber 340, the piston 300 and driver blade 330 quickly move to the lower dead center. Consequently, the tip of the driver blade 330 hits the nail and drives it into the nailed object 2. Here, the piston 300 bumps against the piston bumper 360 at the lower dead center and the deformed piston bumper 360 absorbs excess energy.
Meanwhile, as the piston 300 moves from the upper dead center to the lower dead center, the air in the below-the-piston chamber 350 enters the return air chamber 500 via the air hole 230 and air passage 510. Furthermore, after the piston 300 passes the air hole 220 as shown in FIG. 4, the compressed air in the above-the-piston chamber 340 partly enters the return air chamber 500 via the air hole 220. Furthermore, after the piston 300 passes the opening 511a of the air passage 510, the compressed air in the above-the-piston chamber 340 partly enters the return air chamber 500 via the air passage 510. Here, during the driving operation, the pressures in the accumulator 420 and above-the-piston chamber 340 are nearly equal and the pressure in the return air chamber 500 is lower than the pressure in the above-the-piston chamber 340. This is because the compressed air enters the return air chamber 500 from the above-the-piston chamber 340 via the air hole 220 and air passage 510 where the check vales 240 and 540 cause resistance to entry.
The restoring action of the nailing machine 1 of this embodiment after driving the nail will be described hereafter. When the operator returns the trigger to the initial position or releases the push lever 700 from the nailed object 2, the plunger 471 of the trigger valve 470 shown in FIG. 3 returns to the lower dead center. Then, the compressed air in the accumulator 420 enters the trigger valve 470 and further enters the above-the-head valve chamber 450 via the air passages 480a and 480b shown in FIG. 2. The pressure of the compressed air in the above-the-head valve chamber 450 serves to return the head valve 430 to the lower dead center as shown in FIG. 1. Then, the lower surface of the head valve 430 abuts on the top surface of the cylinder 200 to block entry of compressed air into the above-the-piston chamber 340 from the accumulator 420. Meanwhile, when the head valve 430 is lowered to the lower dead center, the opening of the exhaust passage 111 provided in the exhaust cover 110 is opened, allowing the above-the-piston chamber 340 to communicate with the atmosphere. Therefore, the pressure in the below-the-piston chamber 350, namely the pressure in the return air chamber 500 where the compressed air is accumulated becomes higher than the pressure in the above-the-piston chamber 340. Then, the differential pressure between the below-the-piston chamber 350 and above-the-piston chamber 340 serves to quickly raise the piston 300 within the cylinder 200 toward the upper dead center together with the driver blade 330 and return it to the initial position (the first position). Here, the check valve 540 in the air passage 510 prevents the compressed air in the return air chamber 500 from entering the above-the-piston chamber 340 via the air passage 510.
The driving force control by the pressure control means of the nailing machine 1 of this embodiment will be described hereafter.
Generally, the nailing machine receives a small reaction force from the nailed object when the pressure of compressed air accumulated in the accumulator is high, when the nailed object is soft, or when the nail to be driven is thin or short. Therefore, in such cases, the upward movement of the nailing machine as a result of the reaction force from the nailed object is small and the nail is driven deep into the nailed object. Conversely, the nailing machine receives a large reaction force from the nailed object when the pressure of compressed air accumulated in the accumulator is low, when the nailed object is hard, or when the nail to be driven is thick or long. Therefore, in such cases, the upward movement of the nailing machine as a result of the reaction force from the nailed object is large and the nail is driven shallowly into the nailed object. As just stated, the nail is driven into the nailed object to different depths depending on the nailing machine, nail, nailed object, or compressed air used. The pressure control means of the nailing machine 1 of this embodiment detects the magnitude of reaction force the nailing machine 1 receives from the nailed object 2 as the distance of the nailing machine 1 moving upward from the nailed object 2 and controls the driving force based on the distance.
First, the behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 will be described. While the operator drives a nail, the push lever 700 stays abutting on the nailed object 2 because of the biasing of the spring 710. When the nailed object 2 produces a small reaction force, as shown in FIG. 2, the nose 120 continues to abut on the nailed object 2 or slightly moves upward. Then, the push lever 700 continues to push the valve member 521 upward; therefore, the air passage 510 stays open. Hence, the compressed air in the above-the-piston chamber 340 enters the return air chamber 500 via the air passage 510. Then, the pressure in the above-the-piston chamber 340 is decreased and the pressure in the return air chamber 500 is increased. Furthermore, the compressed air entering the below-the-piston chamber 350 from the return air chamber 500 via the air hole 230 serves as air damper, reducing the driving force of the driver blade 330. In this way, the nail is not driven excessively deep into the nailed object 2 even in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2.
The behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a large reaction force from the nailed object 2 will be described hereafter. When the nailed object 2 produces a large reaction force, as shown in FIG. 5, the reaction force from the nailed object 2 causes the nose 120 to move away and further upward from the nailed object 2 compared to the case of a small reaction force. Since the push lever 700 continues to abut on the nailed object 2 because of the biasing force of the spring 710, the body 100 moves upward relatively to the push lever 700. Here, the valve member 521 is less pushed by the push lever 700 and moves downward relatively to the body 100 because of the biasing force of the spring 522. Then, the flange 521a of the valve member 521 engages with the reduced-diameter part 512e to close the air passage 510. Consequently, the compressed air is not allowed to enter the return air chamber 500 from the above-the-piston chamber 340 via the air passage 510. Therefore, the driving force of the driver blade 330 is not reduced by the compressed air entering the below-the-piston chamber 350 from the above-the-piston chamber 340 via the air passage 510 and return air chamber 500 and serving as air damper as in the case of a small reaction force. In this way, the nailing machine 1 can drive a nail into the nailed object 2 with its maximum driving force in the case wherein the nailing machine 1 receives a large reaction force from the nailed object 2.
As described above, the nailing machine 1 of this embodiment of the present invention reduces the driving force of the driver blade 330 to prevent the nail from being driven excessively deep into the nailed object 2 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 during the driving operation. Furthermore, the compressed air in the below-the-piston chamber 350 serves as air damper and reduces the driving energy of the piston 300 from the beginning to end (when the piton 300 bumps against the piston bumper 360) of driving. Therefore, the shock caused by excess energy of the piston 300 on the piston bumper 360 can be reduced, improving the durability of the piston bumper 360, namely the durability of the nailing machine 1.
Furthermore, the nailing machine 1 of this embodiment of the present invention detects the moving distance of the body 100 relative to the nailed object 2 as a result of the reaction force the nailing machine 1 receives from the nailed object 2 to control the driving force. Therefore, there is no need of test driving and manual control of the driving force, improving the working efficiency.
Embodiment 2
A nailing machine 1 according to Embodiment 2 of the present invention will be described hereafter with reference to the drawings. The pressure control means of the nailing machine 1 of Embodiment 1 controls the opening/closing of the air passage 510 based on the moving distance of the body 100 relative to the push lever 700 as a result of the reaction force from the nailed object 2 so as to control the pressure in the return air chamber 500. On the other hand, the pressure control means of the nailing machine 1 of this embodiment changes the resistance to entry of compressed air into the return air chamber 500 from the above-the-piston chamber 340 based on the moving distance of the body 100 relative to the push lever 700 as a result of the reaction force from the nailed object 2 so as to control the pressure in the return air chamber 500. The pressure control means of the nailing machine 1 of this embodiment will be described in detail hereafter. The same structures as in the nailing machine 1 of Embodiment 1 are referred to by the same reference numbers and their explanation will be omitted.
FIG. 6 is a cross-sectional view of the nailing machine 1 of this embodiment of the present invention. The pressure control means of the nailing machine 1 of this embodiment of the present invention comprises an air passage 810, a control valve 820 controlling the resistance to entry of compressed air into the return air chamber 500 from the above-the-piston chamber 340 via the air passage 810, and a detection part 830 detecting the movement of the push lever 700 relative to the body 100.
The air passage 810 is a passage allowing communication between the cylinder 200 and return air chamber 500. As shown in FIG. 7, the air passage 810 consists of a influx passage 511, a control passage 812, and an outflux passage 513. Here, the influx passage 511 and outflux passage 513 have the same structures as those of Embodiment 1 and their explanation is omitted.
The control passage 812 is a passage for controlling the resistance to entry of compressed air coming through the influx passage 511 into the return air chamber 500. The control passage 812 extends in the driving direction, namely in the sliding direction of the piston. The control passage 812 is connected to the influx passage 511 at one end and has at the other end an opening 812c opening in the driving direction from the body 100. The control passage 812 also has an opening 812d opening inward in the radial direction of the cylinder 200 and is connected to the outflux passage 513 via the opening 812d. 
The control valve 820 allows only the entry of compressed air from the influx passage 511 and blocks the entry of compressed air into the influx passage 511 from the control passage 812. The control valve 820 also controls the resistance to entry of compressed air coming from the influx passage 511, in other words controls the difficulty level of entry of compressed air into the control passage 812 from the influx passage 511. The control valve 820 consists of a closing member 821, a spring 822, and a pin 823.
The closing member 821 is a spherical member formed at the connection part between the influx passage 511 and control passage 812 and having a diameter larger than the opening 812f. The closing member 821 is placed in the control passage 812 and biased upward by the spring 822. The closing member 821 engages with the opening 812f by way of the biasing force of the spring 822 to close the control passage 812.
The spring 822 is a member biasing the closing member 821 upward, namely to close the opening 812f. The spring 822 abuts on the closing member 821 at one end and abuts on one end of the pin 823 at the other end.
The pin 823 is a member sliding within the control passage 812 based on the moving rate of the push lever 700 relative to the body 100 that is detected by the detection part 830. The pin 823 abuts on the spring 822 at one end. The other end of the pin 823 protrudes outside the body 100 through the opening 812c of the control passage 812 and abuts on one end of a locker arm 831 of the detection part 830, which will be described later. The pin 823 slides within the control passage 812 and changes the compression of the spring 822 as the locker arm 831 rotates. Furthermore, the pin 823 is provided with a sealing member 824 for preventing leakage of compressed air to the outside through the opening 812c of the control passage 812.
The detection part 830 serves to detect the movement of the push lever 700 relative to the body 100. The detection part 830 consists of a locker arm 831 and a spring 832.
The locker arm 831 consists of a body 831a having a rotation axis in the center, a first protrusion 831b protruding radially outward from the body 831a, and a second protrusion 831c protruding radially outward from a position on the body that is nearly opposite to the position where the first protrusion 831b protrudes. The underside of the first protrusion 831b abuts on the push lever 700 and the top surface abuts on one end of the spring 832. The top surface of the second protrusion 831c abuts on the end of the pin 823.
The spring 832 abuts on the body 100 at one end and abuts on the top surface of the first protrusion 831b of the locker arm 831 at the other end. The spring 832 biases the first protrusion 831b in the driving direction, namely downward.
The driving force control by the pressure control means of the nailing machine 1 of this embodiment will be described hereafter.
First, the behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 will be described. While the operator drives a nail, the push lever 700 stays abutting on the nailed object 2 because of the biasing of the spring 710. When the nailed object 2 produces a small reaction force, in the same manner as in Embodiment 1, as shown in FIG. 2, the nose 120 continues to abut on the nailed object 2 or slightly moves upward. Here, as shown in FIG. 7, the push lever 700 continues to push the first protrusion 831b of the locker arm 831 upward against the biasing force of the spring 832; therefore, the pin 823 abutting on the second protrusion 831c of the locker arm 831 is placed at the lower dead center by the biasing force of the spring 822. In this state, the spring 822 is least compressed and gives the closing member 821 the minimum biasing force. Therefore, the resistance to entry of compressed air into the return air chamber 500 from the above-the-piston chamber 340 via the air passage 810 is minimized. Then, the compressed air in the above-the-piston chamber 340 can easily enter the return air chamber 500 via the air passage 810. The pressure in the above-the-piston chamber 340 is decreased and the pressure in the return air chamber 500 is increased. Furthermore, the compressed air entering the below-the-piston chamber 350 from the return air chamber 500 via the air hole 230 serves as air damper and reduces the driving force of the driver blade 330. In this way, the nail is not driven excessively deep into the nailed object 2 even in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2.
The behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a large reaction force from the nailed object 2 will be described hereafter. When the nailed object 2 produces a large reaction force, in the same manner as in Embodiment 1, as shown in FIG. 5, the reaction force from the nailed object 2 causes the nose 120 to move away and further upward from the nailed object 2 compared to the case of a small reaction force. Since the push lever 700 continues to abut on the nailed object 2 because of the biasing force of the spring 710, the body 100 moves upward relatively to the push lever 700. Here, as shown in FIG. 8, the first protrusion 831b of the locker arm 831 rotates because of the biasing force of the spring 832 and the second protrusion 831c pushes the pin 823 upward against the biasing force of the spring 822. Pushed by the second protrusion 831c, the pin 823 moves within the control passage 812 upward. Then, the spring 822 is compressed by the pin 823 and biases the closing member 821 with a larger biasing force. Therefore, the resistance to entry of compressed air into the return air chamber 500 from the above-the-piston chamber 340 via the air passage 510 is increased compared to the case of a small reaction force. Then, the amount of compressed air entering the return air chamber 500 from the above-the-piston chamber 340 via the air passage 510 is reduced compared to the case of a small reaction force. The difference in pressure between the above-the-piston chamber 340 and the return air chamber 500, namely the below-the-piston chamber 350 is increased. Consequently, the compressed air that has entered the below-the-piston chamber 350 from the above-the-piston chamber 340 via the return air chamber 500 has less effect as air damper; therefore, the driving force of the driver blade 330 is not reduced. In this way, when the nailing machine 1 receives a large reaction force from the nailed object 2, the nailing machine 1 can drive a nail into the nailed object 2 with a large driving force compared to the case of a small reaction force.
As described above, the nailing machine 1 of this embodiment of the present invention reduces the driving force of the driver blade 330 to prevent the nail from being driven excessively deep into the nailed object 2 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 during the driving operation. Furthermore, the compressed air in the below-the-piston chamber 350 serves as air damper and reduces the driving energy of the piston 300 from the beginning to end (when the piton 300 bumps against the piston bumper 360) of driving. Therefore, the shock caused by excess energy of the piston 300 on the piston bumper 360 can be reduced, improving the durability of the piston bumper 360, namely the durability of the nailing machine 1.
The nailing machine 1 of this embodiment of the present invention detects the moving distance of the body 100 relative to the nailed object 2 as a result of the reaction force the nailing machine 1 receives from the nailed object 2 to control the driving force. Therefore, there is no need of test driving and manual control of the driving force, improving the working efficiency.
Embodiment 3
A nailing machine 1 according to Embodiment 3 of the present invention will be described hereafter with reference to the drawings. The pressure control means of the nailing machine 1 of Embodiment 1 controls the opening/closing of the air passage 510 based on the moving distance of the body 100 relative to the push lever 700 as a result of the reaction force from the nailed object 2 so as to control the pressure in the return air chamber 500. On the other hand, the pressure control means of the nailing machine 1 of this embodiment changes the capacity of the return air chamber 500 based on the moving distance of the body 100 relative to the push lever 700 as a result of the reaction force from the nailed object 2 so as to control the pressure in the return air chamber 500. The pressure control means of the nailing machine 1 of this embodiment will be described in detail hereafter. The same structures as in the nailing machine 1 of Embodiment 1 are referred to by the same reference numbers and their explanation will be omitted.
FIG. 9 is a cross-sectional view of the nailing machine 1 of this embodiment of the present invention. The return air chamber 500 of the nailing machine 1 of this embodiment of the present invention consists of a first return air chamber 501 and a second return air chamber 502. The pressure control means of the nailing machine 1 of this embodiment of the present invention consists of a control passage 910 allowing communication between a first return air chambers 501 and a second return air chamber 502, and a control valve 920 controlling the opening/closing of the control passage 910 based on the moving rate of the push lever 700 relative to the body 100.
The first return air chamber 501 is formed by the lower part of a cylindrical space enclosed by the cylinder 200, body 100, and cylinder plate 210. The first return air chamber 501 communicates with the cylinder 200 via air holes 220 and 230 each formed in the sidewall of the cylinder 200 in the circumferential direction. The air holes 220 and 230 have the same structures as those in Embodiment 1 and their explanation is omitted. The first return air chamber 501 has an opening 501a for communicating with the control passage 910.
The second return air chamber 502 is formed by the upper part of a cylindrical space enclosed by the cylinder 200, body 100, and cylinder plate 210. In other words, the second return air chamber 502 is provided above the first return chamber 501 and communicates with the first return air chamber 501 via the control passage 910.
The control passage 910 is a passage allowing communication between the first and second return air chambers 501 and 502. The control passage 910 extends in the driving direction, namely in the sliding direction of the piston 300. As shown in FIG. 10, the control passage 910 is connected to the first return air chamber 501 at one end and has at the other end an opening 910a opening in the driving direction from the body 100. The control passage 910 also has an opening 910b opening inward in the radial direction of the cylinder 200 and is connected to the first return air chamber 501 via the opening 910b. The peripheral surface of the control passage is tapered at the part above the opening 910b so as to have a reduced-diameter part 911 having a passage diameter smaller than the other part for closing the control passage 910 with a closing part 921a of a valve member 921, which will be described later.
The control valve 920 allows or blocks entry of compressed air into the second return air chamber 502 from the first return air chamber 501. The control valve 920 consists of a valve member 921 and a spring 922.
The valve member 921 slides within the control passage 910 based on the moving rate of the push lever 700 relative to the body 100 so as to close or open the control passage 910. The valve member 921 is tapered at one end to have a closing part 921a having a diameter larger than the passage diameter of the reduced-diameter part 911. The other end of the valve member 921 protrudes outside the body 100 through the opening 910a of the control passage 910 and has an abutting part 921b abutting on the push lever 700. A sealing member 923 is provided to the closing part 921a of the valve member 921 to close the control passage 910 at the upper dead center. Furthermore, a sealing member 924 is provided to the abutting part 921b to prevent leakage of compressed air to the outside through the opening 910a of the control passage 910.
The spring 922 is a member biasing the valve member 921 downward, namely in the manner that the closing part 921a disengages from the reduced-diameter part 911 to open the control passage 910. The spring 922 abuts on the valve member 921 at one end and engages with an engaging part 912 formed on the peripheral surface of the control passage 910 at the other end.
The driving force control by the pressure control means of the nailing machine 1 of this embodiment will be described hereafter.
First, the behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 will be described. While the operator drives a nail, the push lever 700 stays abutting on the nailed object 2 because of the biasing of the spring 710. When the nailed object 2 produces a small reaction force, in the same manner as in Embodiment 1, as shown in FIG. 2, the nose 120 continues to abut on the nailed object 2 or slightly moves upward. Here, as shown in FIG. 10, the push lever 700 continues to push the valve member 921 upward against the biasing force of the spring 922 so that the closing part 921a of the valve member 921 engages with the reduced-diameter part 911 to close the control passage 910. In this state, the first and second return air chambers 501 and 502 do not communicate with each other. Therefore, the compressed air enters the first return air chamber 501 from the above-the-piston chamber 340. The pressure in the above-the-piston chamber 340 is decreased and the pressure in the return air chamber 500 is increased. Furthermore, the compressed air entering the below-the-piston chamber 350 from the first return air chamber 501 via the air hole 230 serves as air damper, reducing the driving force of the driver blade 330. In this way, the nail is not driven excessively deep into the nailed object 2 even in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2.
The behavior of the nailing machine 1 in the case wherein the nailing machine 1 receives a large reaction force from the nailed object 2 will be described hereafter. When the nailed object 2 produces a large reaction force, in the same manner as in Embodiment 1, as shown in FIG. 5, the reaction force from the nailed object 2 causes the nose 120 to move away and further upward from the nailed object 2 compared to the case of a small reaction force. Since the push lever 700 continues to abut on the nailed object 2 because of the biasing force of the spring 710, the body 100 moves upward relatively to the push lever 700. Here, as shown in FIG. 11, the valve member 921 moves to the lower dead center because of the biasing force of the spring 922. Then, the closing part 921a of the valve member 921 disengages from the reduced-diameter part 911 of the control passage 910 to open the control passage 910. Therefore, the first and second return air chambers 501 and 502 communicate with each other and the return air chamber has a larger capacity compared to the case of a small reaction force. Consequently, the compressed air in the above-the-piston chamber 340 enters the first return air chamber 501 and then the second return air chamber 502 via the control passage 910. Then, the pressures in the first and second return air chambers 501 and 502 are low compared to the case of a small reaction force and the difference in pressure between the above-the-piston chamber 340 and the first and second return air chambers 501 and 502, namely below-the-piston chamber 350 is increased. Consequently, the compressed air that has entered the below-the-piston chamber 350 from the first and second return air chambers 501 and 502 has less effect as air damper compared to the case of a small reaction force; therefore, the driving force of the drive blade 330 is not reduced. In this way, when the nailing machine 1 receives a large reaction force from the nailed object 2, the nailing machine 1 can drive a nail into the nailed object 2 with a large driving force compared to the case of a small reaction force.
As described above, the nailing machine 1 of this embodiment of the present invention reduces the driving force of the driver blade 330 to prevent the nail from being driven excessively deep into the nailed object 2 in the case wherein the nailing machine 1 receives a small reaction force from the nailed object 2 during the driving operation. Furthermore, the compressed air in the below-the-piston chamber 350 serves as air damper and reduces the driving energy of the piston 300 from the beginning to end (when the piston 300 bumps against the piston bumper 360) of driving. Therefore, the shock caused by excess energy of the piston 300 on the piston bumper 360 can be reduced, improving the durability of the piston bumper 360, namely the durability of the nailing machine 1.
The nailing machine 1 of this embodiment of the present invention detects the moving distance of the body 100 relative to the nailed object 2 as a result of the reaction force the nailing machine 1 receives from the nailed object 2 to control the driving force. Therefore, there is no need of test driving and manual control of the driving force, improving the working efficiency.
Embodiment 4
A nailing machine 1 according to Embodiment 4 of the present invention will be described hereafter with reference to the drawings. The pressure control means of the nailing machine of Embodiments 1 to 3 controls the opening/closing of the air passage based on the moving distance of the body relative to the push lever as a result of reaction so as to control the pressure in the return air chamber 500. On the other hand, the pressure control means of the nailing machine 1 of this embodiment controls the pressure in the return air chamber 500 based on the operation rate of an operation part 1030 that is effected by the operator. The pressure control means of the nailing machine 1 of this embodiment will be described in detail hereafter. The same structures as in Embodiment 1 are referred to by the same reference numbers and their explanation will be omitted.
FIG. 12 is a cross-sectional view of the nailing machine 1 of this embodiment of the present invention. The pressure control means of this embodiment consists of an air passage 510, a control valve 520 controlling the opening/closing of the air passage 510, and an operation part 1030. The air passage 510 of this embodiment has the same structure as in Embodiment 1 and its explanation is omitted.
The control valve 520 of this embodiment is different from the control valve 520 of Embodiment 1 in that the abutting part 521b of the valve member 521 abuts on an operation member 1032 of the operation part 1030, which will be described later. Therefore, as shown in FIG. 13C, when the operation member 1032 of the operation part 1030 is located at the lowest position, the flange 521a engages with the reduced-diameter part 512e because of the biasing force of the spring 522 to close the second control passage 512b; therefore, the control valve 520 blocks entry of compressed air from the first control passage 512a. On the other hand, as shown in FIG. 13A, when the operation member 1032 of the operation part 1030 is located at the highest position, the flange 521a of the valve member 521 moves upward against the biasing force of the spring 522 and disengages from the reduced-diameter part 512e. Therefore, the control valve 520 allows entry of compressed air from the first control passage 512a. Furthermore, as shown in FIG. 13B, when the operation member 1032 of the operation part 1030 is located between the position in FIG. 13A and the position in FIG. 13C, the flange 521a of the valve member 521 moves upward against the biasing force of the spring 522 and disengages from the reduced-diameter part 512e. However, the moving rate is lower than that in FIG. 13A. Therefore, the control valve 520 allows entry of a smaller amount of compressed air than that in FIG. 13A.
The operation part 1030 consists of a knob 1031 rotatably supported by the body 100 and an operation member 1032 fixed to the knob 1031 and vertically moving as the knob is rotated. As shown in FIGS. 14A, 14B, and 14C corresponding to FIGS. 13A, 13B, and 13C, respectively, the operation member 1032 abuts on the abutting part 521b of the valve member 521. As the knob 1031 is rotated, the operation member 1032 rotates and vertically moves so as to slide the valve member 521 within the second control passage 512b. 
The driving force control by the pressure control means of the nailing machine 1 of this embodiment will be described hereafter.
First, the behavior of the nailing machine 1 when the operator operates the operation part 1030 for a small driving force will be described. Before pulling the trigger 460, the operator operates the knob 1031 of the operation part 1030 to move the operation member 1032 to the highest position as shown in FIG. 13A. Here, the operation member 1032 continues to push the valve member 521 upward to keep the air passage 510 open. Then, as the operator pulls the trigger 460, the compressed air in the above-the-piston chamber 340 enters the return air chamber 500 via the air passage 510. Consequently, the pressure in the above-the-piston chamber 340 is decreased and the pressure in the return air chamber 500 is increased. Furthermore, the compressed air entering the below-the-piston chamber 350 from the return air chamber 500 via the air hole 230 serves as air damper, reducing the driving force of the driver blade 330. In this way, when the nailing machine 1 receives a small reaction force from the nailed object 2 such as the case of driving a short nail, the operator can operate the operation part 1030 to prevent the nail from being driven excessively deep into the nailed object 2.
Next, the behavior of the nailing machine 1 when the operator operates the operation part 1030 for a large driving force will be described. Before pulling the trigger 460, the operator operates the knob 1031 of the operation part 1030 to move the operation member 1032 to the lowest position as shown in FIG. 13C. Here, the spring 522 biases the valve member 521 downward so that the flange 521a of the valve member 521 engages with the reduced-diameter part 512e to close the air passage 510. In this state, as the operator pulls the trigger 460, the compressed air is not allowed to enter the return air chamber 500 from the above-the-piston chamber 340 via the air passage 510. Consequently, the driving force of the driver blade 330 is not reduced by the compressed air entering the below-the-piston chamber 350 from the above-the-piston chamber 340 via the air passage 510 and return air chamber 500 and serving as air damper. In this way, when the nailing machine 1 receives a large reaction force from the nailed object 2 such as the case of driving a long nail, the operator can operate the operation part 1030 to drive the nail into the nailed object 2 with the maximum driving force of the nailing machine 1 itself.
As described above, the nailing machine 1 of this embodiment of the present invention allows the operator to operate the operation part 1030 so as to reduce the driving force of the drive blade 330 to prevent the nail from being driven excessively deep into the nailed object 2 in the case wherein a small driving force is desired during the driving operation. Furthermore, the compressed air in the below-the-piston chamber 350 serves as air damper and reduces the driving energy of the piston 300 from the beginning to end (when the piton 300 bumps against the piston bumper 360) of driving. Therefore, the shock caused by excess energy of the piston 300 on the piston bumper 360 can be reduced, improving the durability of the piston bumper 360, namely the durability of the nailing machine 1.
Embodiment 5
A nailing machine 1 according to Embodiment 5 of the present invention will be described hereafter with reference to the drawings. The pressure control means of the nailing machine 1 of Embodiment 1 controls the opening/closing of the air passage 510 based on the moving distance of the body 100 relative to the push lever 700 as a result of reaction force so as to control the pressure in the return air chamber 500. On the other hand, the pressure control means of the nailing machine 1 of this embodiment controls the opening/closing of the air passage 510 based on the length of a fastener so as to control the pressure in the return air chamber 500. The pressure control means of the nailing machine 1 of this embodiment will be described in detail hereafter. The same structures as in Embodiment 4 are referred to by the same reference numbers and their explanation will be omitted.
FIGS. 15 and 16 are cross-sectional views of the nailing machine 1 of this embodiment of the present invention. The pressure control means of this embodiment consists of an air passage 510, a control valve 520 controlling the opening/closing of the air passage 510, and a detection part 1130 detecting the length of a nail or a fastener. Here, the air passage 510 of this embodiment has the same structure as that in Embodiment 1 and its explanation is omitted.
The control valve 520 of this embodiment is different from the control valve 520 of Embodiment 1 in that the abutting part 521b of the valve member 521 abuts on a detection member 1131 of the detection part 1130, which will be described later. As shown in FIG. 17A, when the abutting part 521b of the valve member 521 abuts on a first abutting part 1131d of the detection member 1131, the flange 521a of the valve member 521 moves upward against the biasing force of the spring 522 and disengages from the reduced-diameter part 512e. Therefore, the control valve 520 allows entry of compressed air from the first control passage 512a. On the other hand, as shown in FIG. 17B, when the abutting part 521b of the valve member 521 abuts on a second abutting part 1131e of the detection member 1131, the flange 521a engages with the reduced-diameter part 512e because of the biasing force of the spring 522 to close the second control passage 512b. Therefore, the control valve 520 blocks entry of compressed air from the first control passage 512a. 
The detection part 1130 serves to detect the length of nails supplied from the magazine 610. The detection part 1130 is provided below the control valve 520 and consists of a detection member 1131, a pin 1132, and a spring 1133.
The detection member 1131 consists of, as shown in FIGS. 17A and 17B, a body 1131a having an rotation axis in the center, a first protrusion 1131b protruding radially outward from the body 1131a, and a second protrusion 1131c protruding radially outward from a position on the body 1131a that is nearly opposite to the position where the first protrusion 1131b protrudes. The body 1131a is rotatably supported at the connection part 124 between the nose 120 and integrally formed magazine 610 as shown in FIGS. 15 and 16. The first protrusion 1131b abuts on the pin 1132 at the end. The second protrusion 1131c has at the end a first abutting part 1131d and a second abutting part 1131e that is closer to the rotation center of the detection member 1131 than the first abutting part 1131d. 
The pin 1132 slides within a passage 1134 formed at the connection part 124 and extending in the direction perpendicular to the driving direction. When the nail has a length not larger than a predetermined length, as shown in FIG. 17A, one end of the pin 1132 protrudes from an opening 1134a of the passage as a result of being pushed by the second protrusion 1131c of the detection member 1131. Furthermore, in order to prevent the pin 1132 from coming off the passage 1134, the pin 1132 has a protrusion 1132a engaging with the end of the peripheral wall of the passage 1134. When the nail has a length larger than a predetermined length, as shown in FIG. 17B, part of the nail is located next to the opening 1134a and the pin 1132 abuts on the nail at one end and pushes the second protrusion 1131c of the detection member 1131 against the biasing force of the spring 1133 at the other end.
The spring 1133 abuts on the connection part 124 at one end and is fixed to the first protrusion 1131b of the detection member 1131 at the other end. The spring 1133 biases the first protrusion 1131b of the detection member 1131 so that the first abutting part 1131d abuts on the abutting part 521b of the valve member 521.
The driving force control by the pressure control means of the nailing machine 1 of this embodiment will be described hereafter.
First, the case wherein the nail has a length not larger than a predetermined length will be described. In such a case, the nail does not make contact with the pin 1132. The detection member 1131 is positioned as shown in FIG. 17A because of the biasing force of the spring 1133, whereby the first abutting part 1131d pushes the valve member 521 upward against the spring 522. Therefore, the air passage 510 is opened. Then, as the operator pulls the trigger 460, the compressed air in the above-the-piston chamber 340 enters the return air chamber 500 via the air passage 510. Consequently, the pressure in the above-the-piston chamber 340 is decreased and the pressure in the return air chamber 500 is increased. Furthermore, the compressed air entering the below-the-piston chamber 350 from the return air chamber 500 via the air hole 230 serves as air damper, reducing the driving force of the driver blade 330. In this way, the nail is not driven excessively deep into the nailed object 2 when the nail having a length not larger than a predetermined length is driven into the nailed object 2.
Next, the case wherein the nail has a length larger than a predetermined length will be described. In such a case, the nail is located next to the opening 1134a of the passage 1134. Therefore, the pin 1132 abuts on the nail at one end and moves into the passage 1134. Then, pushed by the other end of the pin 1132, the second protrusion 1131c of the detection member 1131 is positioned as shown in FIG. 17B. Then, the second abutting part 1131e of the detection member 1131 abuts on the abutting part 521b of the valve member 521. Here, the spring 522 biases the valve member 521 downward, whereby the flange 521a of the valve member 521 engages with the reduced-diameter part 512e to close the air passage 510. Then, as the operator pulls the trigger 460 in this state, the compressed air is not allowed to enter the return air chamber 500 from the above-the-piston chamber 340 via the air passage 510. Consequently, the driving force of the driver blade 330 is not reduced by the compressed air entering the below-the-piston chamber 350 from the above-the-piston chamber 340 via the air passage 510 and return air chamber 500 and serving as air damper. In this way, when the nail having a length larger than a predetermined length is driven into the nailed object 2, the nailing machine 1 can drive the nail into the nailed object 2 with the maximum driving force of the nailing machine 1 itself.
As described above, the nailing machine 1 of this embodiment of the present invention reduces the driving force of the driver blade 330 to prevent the nail from being driven excessively deep into the nailed object 2 in the case wherein the nail to be driven has a length not larger than a predetermined length during the driving operation. Furthermore, the compressed air in the below-the-piston chamber 350 serves as air damper and reduces the driving energy of the piston 300 from the beginning to end (when the piton 300 bumps against the piston bumper 360) of driving. Therefore, the shock caused by excess energy of the piston 300 on the piston bumper 360 can be reduced, improving the durability of the piston bumper 360, namely the durability of the nailing machine 1.
Furthermore, the nailing machine 1 of this embodiment of the present invention detects the length of nails to control the driving force. Therefore, there is no need of test driving and manual control of the driving force, improving the working efficiency.
The present invention is not confined to the above embodiments and various modifications and applications can be made thereto.
In the nailing machine 1 of Embodiment 1, the valve member 521 of the control valve 520 opens/closes the air passage 510 to control the amount of compressed air supplied to the below-the-piston chamber 350 and accordingly control the driving force. A method of controlling the driving force by another behavior of the valve member 521 will be described below.
When the pressure of compressed air supplied to the nailing machine 1 through the air plug 410 is excessively high during the nail driving, the compressed air entering through the opening of the cylinder 200 applies an excessive pressure on the top surface of the flange 521a of the valve member 521. This pressure causes the abutting part 521b of the valve member 521 to push the push lever 700 downward. The pushed push lever 700 receives a vertical reaction force from the nailed object 2 shown in FIG. 5 and, conversely, moves the body 100 upward via the valve member 521. Since the body 100 moves upward, consequently, the lower dead center of the driver blade 330 shifts away from the nailed object 2, preventing the nail from being driven deep into the nailed object 2.
In the nailing machine 1 of the above described embodiments, the opening area of the opening 511a of the cylinder 200 leading to the air passage 510 can be adjusted on an arbitrary basis or the closing member 541, spring 542, and valve member 521 can be selected according to the nailed object, fastener, or compressed air used so as to adjust the resistance to entry and inlet velocity and accordingly adjust the effect of the air damper. For example, the flange 521a of the valve member 521 can be spherical or tapered.
Furthermore, in the above embodiments, the closing member 541 provided in the air passage 510 is spherical. It can be wafer-shaped or tapered as long as the air passage 510 is closed.
Furthermore, in the above embodiments, the nailing machine 1 working with nails as fastener is explained. The present invention is not confined to the nailing machine 1 and similarly applicable to, for example, a driving machine working with staples as fastener.
Furthermore, in the above embodiments, the air passage 510 allows communication between the air hole 220 and return air chamber 500. However, the air passage 510 can be connected to the air hole 230 to guide compressed air directly to the below-the-piston chamber 350 instead of communicating with the return air chamber 500.
In the above embodiments, the nailing machine 1 having the head valve 430 as the main valve is explained. Needless to say, the main valve can be a different type of valve such as a sleeve valve.
Various embodiments and changes may be made thereunto without departing from the broad spirit and scope of the invention. The above-described embodiments are intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiments. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention.
The present application is based on Japanese Patent Application No. 2008-265124 and Japanese Patent Application No. 2009-227229. Their specifications, scope of patent claims, and drawings are entirely incorporated in this specification by reference.
INDUSTRIAL APPLICABILITY
The present invention is preferably utilized in applications in which fasteners such as nails or staples are driven in an object.

## Claims

1. A pneumatic driving machine comprising:
a housing;
a cylinder provided in said housing;
a piston reciprocating between a first position and a second position within said cylinder and dividing the interior of said cylinder into an above-the-piston chamber and a below-the-piston chamber;
a driver blade fixed to said piston and hitting and driving a fastener into a workpiece;
an accumulator accumulating compressed air for moving said piston from said first position to said second position;
a main valve sending said compressed air accumulated in said accumulator to said above-the-piston chamber to move said piston from said first position to said second position upon operation of a trigger;
a return air chamber communicating with said above-the-piston chamber while said piston is positioned at said second position, communicating with said below-the-piston chamber while said piston is positioned at said second position, and accumulating compressed air supplied from said above-the-piston chamber when said piston moves from said first position to said second position; and
a pressure control means controlling the pressure in said return air chamber.

2. The pneumatic driving machine according to claim 1,
characterized in that a push lever connected to said housing via a first resilient member and biased by the first resilient member to abut on said nailed object is further provided; and
said pressure control means controls the pressure in said return air chamber based on the moving distance of said housing relative to said push lever as a result of receiving a reaction force from said nailed object upon driving said fastener.

3. The pneumatic driving machine according to claim 2,
characterized in that said pressure control means increases the pressure in said return air chamber as the moving distance of said housing relative to said push lever is smaller.

4. The pneumatic driving machine according to claim 2,
characterized in that said pressure control means comprises a control valve allowing or blocking entry of compressed air into said return air chamber from said above-the-piston chamber via a check valve based on the moving distance of said housing relative to said push lever.

5. The pneumatic driving machine according to claim 4,
characterized in that said return air chamber communicates with said above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
said control valve comprises:
a valve member sliding within said control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of said reduced-diameter part and closing said control passage when engaging with said reduced-diameter part, and
a second resilient member biasing said one end of said valve member in the driving direction so that said one end engages with said reduced-diameter part; and
said push lever pushes the other end of said valve member in the direction opposite to the driving direction against the biasing force of said resilient member so that said one end of said valve member disengages from said reduced-diameter part when the moving distance of said housing relative to said push lever is smaller than a predetermined distance.

6. The pneumatic driving machine according to claim 2,
characterized in that said pressure control means comprises a control valve controlling the resistance to entry of compressed air from said above-the-piston chamber based on the moving distance of said housing relative to said push lever.

7. The pneumatic driving machine according to claim 6,
characterized in that said return air chamber communicates with said above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part; and
said control valve comprises:
a closing member placed in said control passage, having a diameter larger than the passage diameter of said reduced-diameter part, and closing said control passage when engaging with said reduced-diameter part,
a second resilient member biasing said closing member in the direction opposite to the driving direction so that said closing member engages with said reduced-diameter part,
a pin having one end abutting on the opposite end of said resilient member to the end abutting on said closing member so as to be biased in the driving direction, and
a moving means moving said pin within said control passage in the driving direction based on the moving distance of said housing relative to said push lever.

8. The pneumatic driving machine according to claim 7,
characterized in that said moving means comprises a locker arm that has one end pushing the other end of said pin in the direction opposite to the driving direction and the other end abutting on a third resilient member fixed to said housing at one end so as to be biased in the driving direction and abutting on said push lever so as to be pushed in the direction opposite to the driving direction, and that is rotatable about a rotation axis positioned between the two ends.

9. The pneumatic driving machine according to claim 2,
characterized in that said return air chamber consists of a first return air chamber communicating with said above-the-piston chamber and below-the-piston chamber and a second return air chamber communicating with said first return air chamber via an air passage; and
said pressure control means comprises a control valve controlling the opening/closing of said air passage based on the moving distance of said housing relative to said push lever.

10. The pneumatic driving machine according to claim 9,
characterized in that said air passage includes a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
said control valve comprises:
a valve member sliding within said control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of said reduced-diameter part and closing said control passage when engaging with said reduced-diameter part, and
a second resilient member having one end fixed to said housing and the other end abutting on said valve member to bias said valve member in the driving direction; and
said push lever pushes the other end of said valve member in the direction opposite to the driving direction against the biasing force of said second resilient member so that said one end of said valve member engages with said reduced-diameter part when the moving distance of said housing relative to said push lever is smaller than a predetermined distance.

11. The pneumatic driving machine according to claim 1,
characterized in that said pressure control means controls the pressure in said return air chamber based on the operation rate of an operation member.

12. The pneumatic driving machine according to claim 11,
characterized in that said pressure control means comprises a control valve allowing or blocking entry of compressed air into said return air chamber from said above-the-piston chamber via a check valve based on the operation rate of said operation member.

13. The pneumatic driving machine according to claim 12,
characterized in that said return air chamber communicates with said above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
said control valve comprises:
a valve member sliding within said control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of said reduced-diameter part and closing said control passage when engaging with said reduced-diameter part, and
a second resilient member biasing said one end of said valve member in the driving direction so that said one end engages with said reduced-diameter part;
said operation member has an abutting part abutting on the other end of said valve member;
said abutting part of said operation member pushes said other end of said valve member in the direction opposite to the driving direction against the biasing force of said resilient member so that said one end of said valve member disengages from said reduced-diameter part when said operation member is operated and the moving distance of said abutting part of said operation member in the driving direction is smaller than a predetermined distance.

14. The pneumatic driving machine according to claim 1,
characterized in that said pressure control means comprises a detection part detecting the length of a fastener and controls the pressure in said return air chamber based on the length of said fastener detected by the detection part.

15. The pneumatic driving machine according to claim 14,
characterized in that said pressure control means comprises a control valve allowing or blocking entry of compressed air into said return air chamber from said above-the-piston chamber via a check valve based on the length of said fastener detected by said detection part.

16. The pneumatic driving machine according to claim 15,
characterized in that said return air chamber communicates with said above-the-piston chamber via a control passage extending in the driving direction and having a reduced-diameter part having a passage diameter smaller than the other part;
said control valve comprises:
a valve member sliding within said control passage in the driving direction and provided with one end having a diameter larger than the passage diameter of said reduced-diameter part and closing said control passage when engaging with said reduced-diameter part, and
a resilient member biasing said one end of said valve member in the driving direction so that said one end engages with said reduced-diameter part;
said detection part comprises a detection member that has one end abutting on the other end of said valve member and the other end abutting on a fastener longer than said predetermined length in the direction perpendicular to the driving direction, and that is rotatable about a rotation axis positioned between the two ends;
said one end of said detection member has:
a first abutting part abutting said other end of said valve member when the other end of said detection member does not abut on a fastener longer than said predetermined length, and
a second abutting part that abuts on said other end of said valve member when the other end of said detection member abuts on a fastener longer than said predetermined length and is closer to said rotation axis than said first abutting part; and
said one end of said valve member disengages from said reduced-diameter part when said other end of said valve member abuts on said first abutting part and engages with said reduced-diameter part when said other end of said valve member abuts on said second abutting part.