JP4288596B2 - Relief valve for compressed air tool - Google Patents

Description

  The present invention relates to a compressed air-driven rotary tool in which an air motor is rotationally driven by compressed air to perform screw tightening, bolt tightening, or drilling, or a piston housed in a cylinder is impacted by compressed air to drive a nail. In particular, a compressed air tool such as a nail driver that is driven into the tool, in particular, automatically discharges the high pressure to the atmosphere when the pressure of the compressed air supplied to the tool becomes higher than a predetermined operating air pressure. The present invention relates to a relief valve for a compressed air tool.

  It consists of a pneumatic rotary tool that drives the air motor with compressed air supplied from a compressed air supply source and rotates the driver bit and drill bit to perform screw tightening and drilling, and a piston and cylinder with compressed air. In a compressed air tool such as a pneumatic nail driver that drives a driver rod through an impact mechanism and drives a nail, a compressed air supply source such as an air compressor and the compressed air tool are connected via an air hose. Thus, the compressed air is always stored in an air chamber formed in the compressed air tool. Then, by operating the throttle lever and trigger lever operated by the hand holding the tool, the compressed air supplied through the air hose and the compressed air in the air chamber are supplied to the air motor, the impact mechanism, etc. A drill bit, a driver rod, and the like are operated via these drive mechanisms.

In recent years, in these compressed air tools, in addition to the conventional normal pressure tools that are driven by compressed air in the normal pressure range of 10 kg / cm ² or less, the pressure in the conventional normal pressure range has been increased. In recent years, high-pressure dedicated compressed air tools that are driven by compressed air in a high pressure range that does not exceed 50 kg / cm ² have been used in recent years. By driving the tool with compressed air having a pressure in such a high pressure region, a high-power tool can be formed in a small size and light weight, so that there is an advantage that workability can be improved.

  As described above, compressed air is supplied from a dedicated compressed air source to a tool dedicated to normal pressure that operates with compressed air in the normal pressure region and a tool that operates with compressed air in the high pressure region. However, if both tools are used in the field, a tool dedicated to normal pressure is mistakenly connected to the compressed air source for the high pressure tool, and compressed air in the high pressure range is supplied to the normal pressure tool. There is a risk that it will happen. Moreover, even if it is a tool only for high pressure, there is a possibility that compressed air having a pressure higher than the operating air pressure (predetermined pressure or higher) may be supplied by mistakenly adjusting the supply pressure from the air compressor. When compressed air with a pressure higher than the original operating air pressure is supplied to the compressed air tool in this way, the operating parts such as the housing and valves that store the compressed air are damaged by high pressure, If the tool is operated with this high compressed air, the air motor rotates at high speed, causing bearing parts of the rotating part to burn in, or causing damage to the bumper that cushions the impact of the piston that is impacted. It is a factor to make.

  In a compressed air nailing machine in which a piston housed in a cylinder is shockedly actuated by the pressure of compressed air and a nail is driven by a driver rod coupled to the piston, it is formed in the nailing machine. It is already known that a relief valve is formed which automatically operates when the pressure of the compressed air in the air chamber becomes abnormally high and releases the high pressure to the atmosphere. In a relief valve formed in a conventional compressed air nailing machine or the like, a valve housing is integrally formed on the inner side of a grip portion of an end cap attached to an end portion of the grip portion, and the valve housing is formed in the valve housing. A piston valve whose pressure acting surface is directed into the grip is arranged by being biased by a spring, and this piston valve is operated by the compressed air pressure in the air chamber so as to communicate between the inside of the grip portion and the atmosphere. The discharge path that is being opened is opened.

Also, in a conventional rotary tool such as an impact driver that drives an air motor by compressed air to rotate the driver bit, a hollow sleeve valve is arranged along the inner peripheral surface of the grip portion inside the grip portion. A technique is known in which compressed air is supplied to an air motor via this sleeve valve. In this prior art, the sleeve valve is formed so as to slide through a safety lever operated by a hand holding the grip portion, and carelessly when the grip portion is not securely held. This constitutes a safety valve that prevents the tool from operating.
Japanese Patent Publication No. 60-31630

  In the relief valve formed in the conventional compressed air nailing machine or the like, the valve housing that accommodates the valve body is formed integrally with the end cap inside the end cap that is attached to the end of the grip portion. The compressed air supplied to the nailing machine through the air plug mounted on the outside of the cap is supplied via a supply passage formed so as to bypass the valve housing. For this reason, the flow resistance becomes large and the amount of compressed air supplied to the operating unit is limited, so that a rotary tool or the like that continuously supplies a large flow of compressed air to the air motor or the like is supplied to the air motor. The pressure of the compressed air may decrease, resulting in a decrease in output. Further, if the cross-sectional area of the flow path is increased in order to reduce the flow path resistance, there is a problem that the outer shape of the grip portion is increased and the tool is increased in size.

  The present invention solves the above-mentioned problems in the prior art, and can form a sufficiently large cross-sectional flow path for supplying compressed air to the drive part of the compressed air tool, and the length and outer diameter of the grip part. It is an object of the present invention to provide a relief valve for a compressed air tool capable of forming an outer shape such as a small size.

In order to solve the above problems, a relief valve for a compressed air tool according to the present invention has a grip portion integrally formed in a housing incorporating an air motor, and a supply passage for supplying compressed air to the air motor is formed in the grip portion, at both ends. A hollow valve body formed with a difference in effective area on which compressed air acts is slidably disposed on an inner peripheral surface of a supply path formed in the housing, and the valve body having a smaller effective area is disposed. It is arranged on the air motor side and is urged by a spring so that it slides toward the larger effective area , and the discharge path that communicates the inside of the supply path to the atmosphere is blocked at the position of the valve body that is urged by the spring. together, effective surface against the valve body to the spring bias by the action of the predetermined pressure or more compressed air to the end portion having a larger effective area of the valve body Slide operate the smaller, along with discharging compressed air of more than the predetermined pressure to the atmosphere through the supply passage communicated with said discharge passage, together to open the discharge passage on the outer surface side of the grip portion, the grip A concave groove having one end continuous with the discharge path and having the other end opened in the rear end surface of the grip portion on the outer surface of the grip portion; and a grip cover attached to the grip portion by the concave groove and an outer peripheral surface of the grip portion; A discharge passage is formed between the two.

According to the relief valve of the present invention, the hollow valve body having an effective area difference is slidably disposed on the inner peripheral surface of the supply path formed in the grip portion of the housing incorporating the air motor. The valve body is spring-biased in one of the sliding directions, and the discharge path that connects the supply path to the atmosphere is blocked at the spring-biased position of the valve body, and the effective area of the valve body Compressed air of a predetermined pressure or more acts on the difference portion to cause the valve body to slide against the spring biasing force, and the supply path is communicated with the discharge path to exceed the predetermined pressure in the supply path. The compressed air supplied to the rear end of the grip part can be used as a compressed air supply passage. Use of a tool that uses a large amount of compressed air since it is possible to supply to without driver to receive flow resistance by the relief valve to become possible. In addition, since it is not necessary to form the relief valve integrally with the end cap as in the conventional case, it is possible to incorporate the relief valve into the grip part without increasing the outer diameter or length of the grip part.・ Weight reduction is possible.

Further, the compressed air into the grip portion to form a supply passage for supplying to the drive unit to form a grip portion integrally to housings, is disposed the valve body to the supply path, the actuation of the valve body A discharge passage for exhausting compressed air to the atmosphere is opened on the outer surface side of the grip portion, and one end side is continuous with the discharge passage on the outer surface of the grip portion, and the other end side is opened on the rear end surface of the grip portion. Since the drainage passage is formed between the grip cover attached to the grip part and the outer peripheral surface of the grip part by the concave groove, the exhaust port is gripped even if the grip part is covered with the grip cover. High pressure compressed air can be reliably discharged to the atmosphere without being closed by the cover.

  It is an object of the present invention to form a flow path having a sufficiently large cross-sectional area for supplying compressed air to a drive unit of a compressed air tool and to reduce the outer shape such as the length and outer diameter of the grip portion. A hollow valve body having a difference in effective area on which compressed air acts is slidably disposed on an inner peripheral surface of a supply path formed in the housing, and the valve body is moved in one direction of the sliding direction. The valve body is biased to block the supply passage and the exhaust passage at the spring-biased position of the valve body, and compressed air of a predetermined pressure or more acts on the effective area difference portion of the valve body. In this way, the valve body is configured to slide against the spring biasing force, and a more specific embodiment will be described below.

  FIG. 1 is a longitudinal side view showing an impact driver as an example of a compressed air tool in which a relief valve of the present invention is implemented. The impact driver 1 is integrally formed with a grip portion 2 for gripping the impact driver 1 during work. A housing 3 is formed, and an air motor 4 that is rotationally driven by compressed air supplied into the impact driver 1 and an impact mechanism 6 that is driven by the air motor 4 are accommodated in the housing 3. Yes. The output shaft 5 of the air motor 4 is connected to the impact hammer 7 of the impact mechanism 6, the impact hammer 7 is rotated by the air motor 4, and the impact hammer 7 is rotationally driven to be disposed on the central axis of the impact mechanism 6. The anvil 9 formed on the outer peripheral surface on the base side of the drive shaft 8 is struck and an impulsive rotational force is transmitted to the drive shaft 8 through the anvil 9. The front end of the drive shaft 8 is disposed so as to protrude from the end on the other end side of the housing 3 to the outside of the housing 3, and a chuck for detachably attaching a driver bit to the front end of the drive shaft 8. Part 10 is formed.

The grip portion 2 formed integrally with the housing 3 is formed in a hollow shape, and a supply path 11 for compressed air supplied to the air motor 4 and the air motor 4 are driven inside the hollow portion of the grip portion 2. After that, an exhaust passage 12 for exhausting exhaust air exhausted from the air motor 4 to the atmosphere is formed in parallel. An end of the supply path 11 is opened at the rear end surface of the grip portion 2, and an air plug for connecting the impact driver 1 to the other end of the air hose whose one end is connected to the compressed air supply source. 13 is attached, and compressed air is supplied from the compressed air supply source into the supply path 11 through the air plug 13. The impact driver 1 of this embodiment is set so as to be operated by compressed air in a high pressure range higher than the pressure in the normal pressure range of 10 kg / cm ² or less. Therefore, the air plug 13 is compressed air in the high pressure range. It is designed for high pressure systems that can only be connected to the supply system.

  An end portion of the exhaust passage 12 is also opened at the rear end surface of the grip portion 2, and an exhaust portion 14 for exhausting exhaust air exhausted from the air motor 4 to the atmosphere is formed in the opening portion. The exhaust unit 14 is provided with a filter case 16 containing an exhaust filter 15 for reducing the flow rate of compressed air exhausted from the air motor 4 to prevent the exhaust air from blowing up dust and wood chips and reducing exhaust noise. The exhaust air exhausted from the air motor 4 is guided by the exhaust passage 12, passes through the exhaust filter 15, and is exhausted to the atmosphere from the exhaust port 17 formed in the filter case 16. Has been.

  A throttle valve 18 for supplying the compressed air supplied to the supply passage 11 to the air motor 4 is formed at the base of the grip 2 and is rotatably supported by the base of the grip 2. By operating the throttle lever 19 with the fingers of the hand holding the grip portion 2, the throttle valve 18 is operated to supply compressed air to the air motor 4 to rotate the air motor 4. In the throttle valve 18 according to this embodiment, the amount of compressed air supplied to the air motor 4 can be adjusted by adjusting the amount of rotation of the throttle lever 19 to thereby adjust the throttle lever 19. The number of rotations of the air motor 4 can be adjusted as appropriate by adjusting the amount.

  In the supply path 11 formed in the hollow of the grip portion 2, when the pressure of the compressed air in the supply path 11 is higher than the pressure for driving the impact driver 1 (above a predetermined pressure), A relief valve 20 is formed for discharging the compressed air to the atmosphere so that the pressure in the supply passage 11 does not become higher than a predetermined driving pressure. As shown in detail in FIG. 2, the relief valve 20 includes a guide sleeve 21 that is mounted along the inner peripheral surface of the supply path 11, and a valve body that is slidably accommodated inside the guide sleeve 21. 22 and an urging spring 23 for urging the valve body 22 in the sliding direction, and the guide sleeve 21, the valve body 22 and the urging spring 23 are all hollow in the center. The central part of the valve body 22 is formed as a compressed air supply path by combining these members concentrically and arranging them on the inner peripheral surface of the supply path 11.

  Outer peripheral surfaces having different outer diameters are formed on one end side and the other end side along the longitudinal direction of the valve body 22. The outer diameter of the outer peripheral surface 22a on the right end side in the figure is larger than the outer diameter of the outer peripheral surface 22b on the left end side, with the approximate center in the longitudinal direction of the valve body 22 as a boundary. On the other hand, on the inner peripheral surface of the guide sleeve 21 that accommodates the valve main body 22, two O-rings 24 and 25 that are in sliding contact with the outer peripheral surfaces 22a and 22b having different diameters of the valve main body 22 are spaced apart in the longitudinal direction. Is installed. Further, a plurality of openings 26 are formed in the wall portion between the two O-rings 24 and 25 of the guide sleeve 21 so as to communicate the inside and outside of the guide sleeve 21 with a circumferential interval therebetween. The opening 26 is continued to the outer peripheral surface of the grip part 2 through a discharge path 27 formed in the grip part 2. The supply path 11 formed inside the grip portion 2 is communicated with the atmosphere through the opening 26 and the discharge path 27.

  By accommodating the valve main body 22 inside the guide sleeve 21 and fitting the outer peripheral surfaces 22a and 22b having different outer diameters of the valve main body 22 to the two O-rings 24 and 25 of the guide sleeve 21, respectively. The valve body 22 blocks the inside of the supply path 11 and the opening 26 formed in the guide sleeve 21. As described above, the outer diameters of both ends of the valve main body 22 are formed to be different from each other, and the two O-rings 24 and 25 attached to the guide sleeve 21 are brought into sliding contact with the outer peripheral surfaces 22a and 22b. Therefore, an effective area difference in which compressed air acts is formed on both end surfaces of the valve body 22, and the compressed air supplied into the supply path 11 on both end surfaces of the valve body 22 mounted in the guide sleeve 21. When the pressure is applied, the valve body 22 is slid in the left direction in the figure by the compressed air pressure acting on the portion of the effective area difference.

  The valve body 22 is slid and urged to the right in the figure by the urging spring 23 so as to oppose the direction in which the valve body 22 operates by the compressed air acting on the diameter difference portion. The spring force of the urging spring 28 is such that when compressed air having a normal pressure for operating the impact driver 1 is supplied into the supply path 11, the compressed air has a difference in effective area of the valve body 22. It is set to be larger than the pressing force that acts on the portion and presses the valve body 22 toward the left end in the figure. When compressed air of normal operating pressure is supplied, the urging force of the urging spring 23 applies the valve body 22. Is pushed in the right direction in the figure. Accordingly, the valve main body 22 is normally disposed at the right end position in the drawing in contact with the washer 28 disposed at the end portion of the guide sleeve 21 by the urging force of the urging spring 23, and the supply body is provided at this position. The inside of the path 11 is blocked from the opening 26 and the discharge path 27.

  An opening 29 is formed in the outer peripheral portion 22a of the valve main body 22 which is formed to have a large outer diameter on the right side in the drawing, and the hollow main body 22 communicates with the outer peripheral surface side. In a state where the biasing spring 23 is arranged on the right end side in the figure, the opening 29 is arranged on the right side in the figure of the O-ring 24 which is in sliding contact with the outer peripheral surface 22a having a large outer diameter of the valve body 22. The space between the hollow of the valve body 22 and the discharge passage 27 is blocked by the O-ring 24. When the valve body 22 is actuated leftward in the figure against the biasing force of the biasing spring 23, the opening 26 is disposed between the two O-rings 24, 25 of the guide sleeve 21. The inside of the supply path 11 is connected to the atmosphere via the opening 29 of the valve body 22, the opening 26 of the guide sleeve 21, and the discharge path 27.

  A discharge passage 27 formed in the grip portion 2 continuously with the opening 26 formed in the guide sleeve 21 is opened on the surface side of the grip portion 2, and a grip portion is formed on the outer surface of the clip portion 2. A concave groove 30 for guiding exhaust air is formed along the outer surface 2, one end side of the concave groove 30 is continuous with the discharge path 27, and the other end side opens to the rear end surface side of the grip portion 2. Has been. Further, a rubber grip cover 31 is attached to the grip portion 2 so as to easily grip the grip portion 2 so as to cover the surface of the grip portion 2, and the grip cover 31 and the outer peripheral surface of the grip portion 2 are arranged. A discharge passage is formed by a concave groove 30 that is continuous with the discharge passage 27. The discharge passage is opened 32 at the rear end surface of the grip portion, and the grip cover 31 is attached to the grip portion 2. The opening of the discharge passage 27 is not closed by the grip cover 31.

  Hereinafter, the operating state of the relief valve 20 according to the above embodiment will be described. As shown in FIG. 3, in a state in which compressed air having a normal pressure for operating the impact driver 1 is supplied to the impact driver 1, the impact driver 1 is supplied into the supply path 11 in the grip portion 2 through the air plug 13. The compressed air thus applied is applied to both end faces of the valve body 22. Compressed air presses the valve body 22 leftward in the figure due to the effective area difference formed in the valve body 22, but the pressing force of the biasing spring 23 acting on the valve body 22 is formed larger. Therefore, the valve main body 22 is slid in the right direction in the drawing by the spring biasing force, and is disposed at a position in contact with the washer 28 disposed at the end of the guide sleeve 21. By arranging the valve main body 22 at this position, the O-rings 24 and 25 attached to the inner peripheral surface of the guide sleeve 21 are brought into close contact with the outer peripheral surfaces 22a and 22b of the valve main body 22, so The space between the discharge paths 27 is blocked. The compressed air supplied through the air plug 13 attached to the end portion side of the grip portion 2 is supplied to the air motor arranged in the left end direction in the drawing through the hollow portion of the valve body 22.

  When the pressure of the compressed air supplied from the compressed air supply source reaches a predetermined high pressure exceeding the normal pressure for operating the impact driver 1, the high pressure compressed air forms the effective area difference. The pressing force that acts on both ends of the valve main body 22 and presses the valve main body 22 in the left direction in the drawing is larger than the spring force of the biasing spring 23 that slidably biases the valve main body 22. As a result, the valve body 22 is slid in the left direction in the figure against the spring force of the biasing spring 23. As shown in FIG. 4, when the valve main body 22 is operated in the left end direction, an opening 29 formed in the valve main body 22 is disposed between the two O-rings 24 and 25 attached to the inner peripheral surface of the guide sleeve 21. The supply passage 11 is communicated with the discharge passage 27 through the opening 29 formed in the valve body 22 and the opening 26 formed in the guide sleeve 21, and high-pressure compression in the supply passage 11 is performed. Air is discharged to the atmosphere, and the pressure in the supply path 11 is reduced.

In the above embodiment, a compressed air tool is described which is driven by compressed air in a high pressure range where the working air pressure is higher than the pressure in the normal pressure range and does not exceed 50 kg / cm ^2. However, the present invention is not necessarily limited to a tool that operates with compressed air in a high pressure region, and can be implemented with a tool for normal pressure that is driven with compressed air in a normal pressure region of 10 kg / cm 2 or less, which has been conventionally used. is there.

Longitudinal side view of impact driver implementing the relief valve of the present invention 1 is a longitudinal side view showing in detail the relief valve in the impact driver of FIG. Longitudinal side view of relief valve showing operating condition where compressed air with normal operating pressure is supplied Longitudinal side view of the relief valve showing an operating state in which compressed air of a predetermined high pressure exceeding the operating pressure is supplied

Explanation of symbols

1 Impact driver (compressed air tool)
2 Grip part 11 Supply path 13 Air plug 20 Relief valve 21 Guide sleeve 22 Valve body 23 Biasing spring 27 Discharge path

Claims (1)

A hollow valve body in which a grip portion is integrally formed in a housing incorporating an air motor and a supply path for supplying compressed air to the air motor is formed in the grip portion, and an effective area difference in which the compressed air acts on both ends is formed. The valve body is slidably disposed on the inner peripheral surface of the supply path formed in the housing, and the valve body is disposed with the smaller effective area on the air motor side and slid toward the larger effective area. a is spring-loaded, the supply path at a position which is spring biased in the valve body as well as so as to shut off the discharge passage communicating with the atmosphere, a predetermined pressure to the end which is the effective area of the valve body is large and towards the slide operation effective area against the valve body to the spring bias is less by the action of the above compressed air, communicates with the discharge passage through the supply passage The predetermined pressure or more compressed air with discharges to the atmosphere, causes opening the discharge passage on the outer surface side of the grip portion, the other end a grip portion with one end on the outer surface of the grip portion is continuous with the discharge passage Te A relief valve for a compressed air tool, wherein a recessed groove opened in the rear end surface is formed, and a discharge passage is formed between the grip cover attached to the grip portion by the recessed groove and the outer peripheral surface of the grip portion. .

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