JP2004017206A - Starting valve mechanism for compressed-air drive impact tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of a shortage of power and a bad return of an impact piston 51 by surely moving a pilot valve 64 down to a lower dead point. <P>SOLUTION: A main valve 12 is formed to be hollow. Further, a pilot valve 22 formed to be hollow is slidably disposed inside the hollow space of the main valve 12. A trigger stem 23 is slidably and concentrically arranged within the hollow space of the pilot valve 22. The supply and cut-off of air to a valve chamber 21 is carried out by means of the pilot valve 22 and the trigger stem 23. Also, the pilot valve 22 is moved down to the lower dead point by setting the position of the lower dead point in the sliding direction through bringing the pilot valve 22 into contact with a valve housing 15 and bringing the main valve 12 into contact with the pilot valve 22 while the main valve is operating. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an impact tool such as a nailing machine driven by compressed air, in which compressed air is introduced into a striking cylinder to impactably drive a striking piston slidably accommodated in a striking cylinder. The present invention relates to a starting valve mechanism of a compressed air driven impact tool for driving a tool.
[0002]
[Prior art]
In a nailing machine driven by compressed air, as shown in FIG. 6, a striking piston 51 is slidably accommodated in a striking cylinder 50, and compressed air is supplied into the striking cylinder 50 to strike. In order to drive the piston 51, a starting valve mechanism 53 including a trigger valve operated by a trigger lever 52 and a main valve 56 operated by the trigger valve is formed.
[0003]
A hollow main valve 56 for selectively connecting the inside of the impact cylinder 50 to an air chamber 54 and an exhaust passage 55 is slidable in a valve housing 57 formed at the base of the grip of the nailing machine. An air supply O-ring 60 that is housed in the valve housing 57 and opens and closes between an air chamber 54 and an air passage 59 that is communicated with the striking cylinder 50 by coming into contact with and separating from an air supply valve seat 58 formed in a valve housing 57; An exhaust O-ring 62 is attached to and separated from the valve seat 61 to open and close the inside of the impact cylinder 50 and the exhaust path 55. A valve chamber 63 is defined at a lower portion of the valve housing 58, and a lower end of the main valve 56 faces the valve chamber 63.
[0004]
A trigger valve for operating the main valve 56 includes a hollow pilot valve 64 concentrically disposed inside the main valve 56 and a trigger stem slidably disposed in the hollow of the pilot valve 64. 65. The pilot valve 64 is accommodated in the hollow inner peripheral side of the main valve 56 and is slidably guided, and the lower end surface faces the valve chamber 63 similarly to the main valve 56. The main valve 56 and the pilot valve 64 are moved to a non-operating position, that is, a top dead center position by a compressed air pressure acting on the respective lower ends facing the valve chamber 63. When the compressed air pressure in 63 decreases, the main valve 56 and the pilot valve 64 are moved to the bottom dead center position, which is the operating position, by the compressed air pressure in the air chamber 54 acting on the respective upper surfaces.
[0005]
The trigger stem 65 includes a first O-ring 66 that flows into or shuts off compressed air from the air chamber 54 into the valve chamber 63 through the hollow of the pilot valve 64 by entering the hollow of the pilot valve 64, and a valve housing. A second O-ring 69 is attached and protruded and retracted in a cylindrical portion 67 formed in 57 and communicates and shuts off between the inside of the valve chamber 63 and the exhaust port 68, as shown in FIG. Before the trigger stem 65 is operated, the second O-ring 69 is fitted into the cylindrical portion 67, and the first O-ring 66 is protruded from the hollow portion of the pilot valve 64. As a result, compressed air from the air chamber 54 is introduced into the valve chamber 63, and the pilot pressure and the main valve 56 are operated to the non-operating position by the air pressure.
[0006]
As shown in FIG. 8B, the trigger lever 52 is operated to fit the first O-ring 66 of the trigger stem 65 into the hollow of the pilot valve 64, and the second O-ring 69 is connected to the cylinder of the valve housing 57. By being operated to the ON position where the valve chamber 63 is removed, the flow of the compressed air into the valve chamber 63 is shut off and the inside of the valve chamber 63 is communicated with the exhaust port 68, whereby the pressure in the valve chamber 63 is reduced. The main valve 56 is lowered to move to the lower operating position by the compressed air pressure acting from the upper end surface, thereby blocking the striking cylinder 50 from the exhaust path 55 and communicating with the air chamber 54 to introduce the compressed air into the striking cylinder 50. Then, the striking piston 51 is driven. At this time, the pilot valve 64 also moves toward the bottom dead center due to the difference in diameter due to the absence of the pressure in the valve chamber 63. As a result, the fitting depth between the first O-ring 66 and the pilot valve 64 increases, and the trigger stem The ON state is maintained during a distance H from 65 to the OFF position below the ON position.
[0007]
The distance H can be set even if the trigger stem 65 operates in an unstable manner due to a reaction caused by driving of an impact tool such as a nail driver or an impact at the time of nail driving, etc. Is reliably maintained in the operating position, and the compressed air is sufficiently supplied to the striking piston 51 to reliably operate to the bottom dead center, and the compressed air is sufficiently stored in the return chamber of the striking piston 51. This is to ensure that the striking piston 51 returns to the top dead center.
[0008]
[Problems to be solved by the invention]
As shown in FIGS. 6 and 7, the conventional pilot valve 64 has an enlarged diameter portion 70 formed at the lower end accommodated in the valve chamber 63. A plurality of slits 71 are formed radially to communicate with the inside of the member, and are configured in a shape that does not have sufficient margin in strength. Therefore, when the main valve 56 is operated in the bottom dead center position so that the main valve 56 does not collide with the pilot valve 64 when the main valve 56 is operated in the direction of the bottom dead center, It is arranged so that a gap S (see FIG. 8B) is formed.
[0009]
Further, since the pilot valve 64 is formed in a hollow cylindrical shape, a diameter difference area for applying a compressed air pressure for operating the pilot valve 64 in the direction of the bottom dead center cannot be sufficiently obtained. 8, the sliding resistance of the pilot valve 64 increases, and the pilot valve 64 may not operate to the bottom dead center position as shown in FIG. In such a state, when the dimension h between the ON position and the OFF position of the trigger stem 65 is reduced, and the position of the trigger stem 65 is slightly lowered due to vibration or reaction of the nail driver, the trigger stem 65 is compressed into the valve chamber 63. The introduction of air causes the main valve 56 to rise. As a result, sufficient compressed air cannot be supplied to the striking piston 51, resulting in insufficient power, or sufficient compressed air cannot be stored in the return chamber, and the striking piston 51 cannot be returned to the top dead center position. In some cases, a defective resin may occur.
[0010]
The present invention solves the above-mentioned conventional problems, and ensures that the pilot valve 64 is operated to the bottom dead center position so as to prevent insufficient power of the striking piston 51 and poor return from occurring. It is an object to provide a starting valve mechanism.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, a starting valve mechanism for a compressed air driven impact tool according to the present invention includes a striking cylinder, a striking piston housed in the striking cylinder, and an air chamber storing compressed air. A main valve for opening and closing between the cylinders is disposed facing the valve chamber, and the compressed air pressure in the valve chamber is controlled based on the operation of a manually operable trigger stem. The main valve is operated between an operating position and a non-operating position by pressure, and compressed air in the air chamber is supplied to the striking cylinder to drive the striking piston by the main valve actuated to the operating position. In the compressed air driven impact tool, the main valve is formed in a hollow shape and the main valve is formed. A pilot valve formed in a hollow shape is slidably disposed in the hollow of the pilot valve, and the trigger stem is slidably disposed concentrically in the hollow of the pilot valve, and the pilot valve and the trigger stem are used to move to the valve chamber. The pilot valve is brought into contact with the valve housing to set the bottom dead center position in the sliding direction, and the main valve is brought into contact with the pilot valve when the main valve is operated. The pilot valve is actuated to the bottom dead center position by contacting the pilot valve.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings. FIG. 1 shows a nailing machine as an example of a compressed air driven impact tool in which a starting valve of the present invention is implemented. A nailing cylinder 2 is disposed in a housing 1, and a nailing nail is provided in the nailing cylinder 2. A striking piston 4 in which a driver 3 for striking the ball is coupled to the lower surface is slidably accommodated. The upper part of the striking cylinder 2 is covered with a cylinder cap 5 forming a part of the housing 1, and a rubber piston stop 6 arranged inside the cylinder cap 5 moves the striking piston 4 to a top dead center position. It is to be received at. Between the inner peripheral surface of the housing 1 and the outer peripheral surface of the striking cylinder 2, a flow path 7 for introducing compressed air into the striking cylinder 2 to drive the striking piston 4 is formed. Are communicated via an air passage 8 to a starting valve mechanism 10 described later. The inside of the grip portion 1a formed integrally with the housing 1 so as to be hollow is formed as an air chamber 9 for storing compressed air supplied from a compressed air source.
[0013]
The starting valve mechanism 10 includes a main valve 12 for selectively connecting the inside of the impact cylinder 2 to an air chamber 9 and an exhaust passage 11 formed in the grip portion 1a, and a manual valve for operating the main valve 12. And a trigger valve 14 operated by a trigger lever 13 which is operated. As shown in FIG. 2, the hollow main valve 12 is slidably accommodated in a valve housing 15 formed at the base of the grip portion 1a. An air supply O-ring 17 that opens and closes between the air chamber 9 and the air passage 8 that is connected to and separates from the air valve seat 16 and that continues to the inside of the striking cylinder 2. An exhaust O-ring 19 that opens and closes the gap is mounted. An enlarged diameter portion 12a is formed at the lower portion of the main valve 12, and the enlarged diameter portion 12a is slidably guided by slidingly contacting the peripheral surface of the valve housing 15 via a sliding ring 20. A valve chamber 21 is defined below the valve housing 15, and the lower surface of the enlarged diameter portion 12 a of the main valve 12 faces the inside of the valve chamber 21.
[0014]
The trigger valve 14 includes a hollow pilot valve 22 concentrically disposed inside the main valve 12 and a trigger stem 23 slidably disposed in the pilot valve 22 hollow. . The pilot valve 22 is housed on the inner peripheral surface of the main valve 12 and is slidably guided. The lower end surface faces the valve chamber 21 similarly to the main valve 12. The main valve 12 and the pilot valve 22 are moved to the non-operating top dead center position by the compressed air pressure acting on the respective lower ends facing the valve chamber 21. When the compressed air pressure in the valve chamber 21 decreases, the main valve 12 and the pilot valve 22 are operated to the bottom dead center position, which is the operating position, by the compressed air pressure in the air chamber 9 acting on the respective upper surfaces.
[0015]
A cylindrical portion 24 extending upward is formed at the center of the bottom of the valve housing 15, and an exhaust port 25 for communicating the inside of the valve chamber 21 with the atmosphere is formed at the bottom inside the cylindrical portion 24. Is formed. A first O-ring 26 for flowing into or shutting off compressed air from the air chamber 9 into the valve chamber 21 through the hollow of the pilot valve 22 by entering the hollow of the pilot valve 22; A second O-ring 27, which is disposed in the cylindrical portion 24 and communicates and shuts off the inside of the valve chamber 21 and the exhaust port 25, and a third O-ring 28, which is always disposed in the hollow of the pilot valve 22, are mounted. The lower end of the trigger stem 23 protrudes downward from the exhaust port 25 and can be operated by a manually operated trigger lever 13. A hole 22a is formed at the upper end of the pilot valve 22, and the upper portion inside the hollow of the pilot valve 22 is always connected to the atmosphere via a hole formed at the upper end of the valve housing 15. The third O-ring 28 divides the inside of the hollow of the pilot valve 22 into an upper part and a lower part.
[0016]
As shown in FIGS. 2 and 3, an enlarged diameter portion 29 is formed at the lower end of the pilot valve 22, and an upwardly facing shoulder 30 is formed at the upper end of the enlarged diameter portion 29. The shoulder 30 is brought into contact with a downwardly facing surface in the enlarged diameter portion 12 a of the main valve 12. A plurality of openings 31 are formed in the circumferential surface of the enlarged diameter portion 29 of the pilot valve 22 in the circumferential direction to communicate the inside and the outside of the pilot valve 22. As shown in FIG. 4, when the pilot valve 22 is operated to the bottom dead center, the bottom dead center position of the pilot valve 22 is set by contacting the upper end surface of the tubular portion 24 formed in the valve housing 15. On the other hand, the main valve 12 has a lower dead center by contacting a downwardly facing surface in the enlarged diameter portion 12a with a shoulder 30 of the pilot valve 22 operated at the lower dead center position. The position is set.
[0017]
The operation of the above embodiment will be described with reference to FIG. As shown in FIG. 5A, in an initial state in which the trigger lever 13 is not operated, the second O-ring 27 of the trigger stem 23 is fitted in the cylindrical portion 24, and thereby the valve chamber 21 and the exhaust port 25 spaces are closed. The first O-ring 26 is separated from the inside of the hollow portion of the pilot valve 22 arranged at the top dead center position, and supplies the compressed air in the air chamber 9 into the valve chamber 21. Therefore, the compressed air in the valve chamber 21 is maintained at a high pressure, and the main valve 12 is disposed at the non-operating position to shut off the connection between the air chamber 9 and the striking cylinder 2.
[0018]
When the trigger stem 23 is operated upward by the operation of the trigger lever 13, the second O-ring 27 of the trigger stem 23 separates from the cylindrical portion 24 as shown in FIG. And the compressed air in the valve chamber 21 leaks from the exhaust port 25. Further, the first O-ring 26 of the trigger stem 23 fits into the hollow of the pilot valve 22 to shut off the supply of compressed air from the air chamber 9 to the valve chamber 21. Thereby, the compressed air in the valve chamber 21 is discharged through the exhaust port 25, and the pressure in the valve chamber 21 drops rapidly.
[0019]
When the pressure in the valve chamber 21 drops, as shown in FIG. 5 (c), the acting force acting on the lower end faces of the main valve 12 and the pilot valve 22 upward disappears, so that these valves have an upper surface. The compressed air in the air chamber 9 is rapidly moved downward by the compressed air pressure in the air chamber 9 acting on the air valve 9, and the air supply O-ring 17 of the main valve 12 separates from the air supply valve seat 16, thereby compressing the compressed air in the air chamber 9. The striking piston 4 is driven by being introduced into the striking cylinder 2. At this time, even if the sliding resistance of the pilot valve 22 is so large that the pilot valve 22 does not reach the bottom dead center, the shoulder 30 formed on the enlarged diameter portion 29 of the pilot valve 22 comes into contact with the main valve 12. The main valve 12 reliably operates to the bottom dead center position. Since the main valve 12 has a sufficiently large diameter difference, the main valve 12 operates reliably together with the pilot valve 22 to the bottom dead center, which is the operating position.
[0020]
When the pilot valve 22 is actuated by the main valve 12, the main valve 12 abuts on a shoulder 30 formed on the upper surface of an enlarged diameter portion 29 formed at the lower end of the pilot valve 22 to apply an impact. Since an opening communicating the inside and outside is formed in the enlarged diameter portion 29 of the pilot valve 22, the strength of the enlarged diameter portion 29 can be increased as compared with a conventional slit having a slit formed. Even if the main valve 12 is brought into contact with the shoulder portion 30, the pilot valve 22 will not be damaged.
[0021]
As shown in FIG. 5D, even if an unstable operation such that the trigger stem 23 is slightly returned downward from the ON position is performed due to a recoil at the time of operation of the striking piston 4 or the like, the pilot valve can be used. 22 is located at the bottom dead center position, the fitting depth between the first O-ring 26 of the trigger stem 23 and the hollow portion of the pilot valve 22 is increased, and the second O-ring 27 of the trigger stem 23 is Even if the first O-ring 26 is fitted into the hollow of the pilot valve 22 even if it is returned to the position where the valve chamber 21 and the exhaust port 25 are shut off by fitting into the cylindrical portion 24, the air chamber 9 and the valve Since the shielded state between the chambers 21 is maintained, compressed air is not supplied into the valve chamber 21 and the main valve 12 is not operated instable.
[0022]
When the trigger lever 13 is released and the trigger stem 23 returns to the non-operating position, the first O-ring 26 of the trigger stem 23 descends to a position where the first O-ring 26 separates from the hollow of the pilot valve 22. After that, compressed air is supplied from the air chamber 9 into the valve chamber 21, and the pressure of the compressed air supplied into the valve chamber 21 causes the main valve 12 and the pilot valve 22 to return to the non-operating positions and return to the initial state.
[0023]
【The invention's effect】
According to the present invention, the pilot valve is brought into contact with the main valve, and the main valve is forcibly operated to the bottom dead center position. The pilot valve can be reliably operated to the bottom dead center position by the main valve, even when the pilot valve does not operate, or when the sliding resistance increases during work in cold climates and the pilot valve malfunctions. Thereby, the fitting depth between the first O-ring of the trigger stem and the pilot valve can be maintained at a predetermined set value, and the main valve can be operated stably even by the unstable operation of the trigger stem, so that the striking piston can be operated. It is possible to supply sufficient compressed air, and to prevent the occurrence of poor return of the striking piston. It is possible.
[Brief description of the drawings]
FIG. 1 is a sectional view of a part of a nailing machine in which a starting valve mechanism according to the present invention is implemented.
FIG. 2 is an enlarged sectional view of the same starting valve mechanism of the nailing machine as in FIG. 1;
FIG. 3 is a perspective view of a trigger stem.
FIG. 4 is a cross-sectional view showing a part of the starting valve mechanism in an activated state.
FIGS. 5A and 5B are cross-sectional views showing an operating state of the starting valve mechanism. FIG. 5A is a state before the operation, FIG. 5B is a state in which the trigger stem is operated to the ON position, and FIG. (D) shows a state in which the nail driving machine is driven, and (d) shows a state in which the trigger stem is slightly returned after starting.
FIG. 6 is a sectional view showing the configuration of a starting valve mechanism employed in a conventional nailing machine.
FIG. 7 is a perspective view of a trigger stem of a conventional starting valve mechanism.
8A and 8B are cross-sectional views illustrating an operation state of a conventional start valve mechanism, in which FIG. 8A is a state before operation, FIG. 8B is a state in which a trigger stem is operated to an ON position and a nail driver is driven, c) shows a state in which the trigger stem is slightly returned after activation.
[Explanation of symbols]
Reference Signs List 10 Start valve mechanism 11 Exhaust path 12 Main valve 13 Trigger lever 14 Trigger valve 15 Valve housing 16 Air supply valve seat 17 Air supply O-ring 18 Exhaust valve seat 19 Exhaust O-ring 21 Valve chamber 22 Pilot valve 23 Trigger stem 24 Cylindrical part 25 exhaust port 26 first O-ring 27 second O-ring 28 third O-ring

Claims (1)

A striking cylinder, a striking piston housed in the striking cylinder, and an air chamber storing compressed air; a main valve for opening and closing the air chamber and the striking cylinder facing the valve chamber; Configured to control the compressed air pressure in the valve chamber based on a possible actuation of the trigger stem, and actuating the main valve to an activated position and a non-activated position by the compressed air pressure in the valve chamber to an activated position; In a compressed air driven impact tool, the compressed air in the air chamber is supplied into the striking cylinder by an actuated main valve to drive a striking piston.
The main valve is formed in a hollow shape, and a pilot valve formed in a hollow shape is slidably disposed in the hollow of the main valve, and the trigger stem is slidably and concentrically disposed in the hollow of the pilot valve. With the arrangement, while supplying and shutting off the valve chamber by the pilot valve and the trigger stem, and setting the bottom dead center position of the sliding direction by contacting the pilot valve with the valve housing, A starting valve mechanism for a compressed air driven impact tool, wherein the main valve is brought into contact with the pilot valve when the main valve is operated, and the pilot valve is operated to the bottom dead center position.

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