JP3687593B2 - Stroke piston holding mechanism for compressed air driven impact tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a striking piston holding mechanism of a compressed air drive impact tool that holds a striking piston at a top dead center position in a striking cylinder in an impact tool such as a nailer driven by compressed air.
[0002]
[Prior art]
For example, in an impact tool such as a nail driver driven by compressed air, a striking piston in which a driver for striking a nail is integrally joined is slidably accommodated in a striking cylinder. It is held at the top dead center of the blow cylinder. Compressed air is supplied into the striking cylinder, the striking piston is driven in the direction of the bottom dead center in the striking cylinder, and a nail is driven by a driver integrally coupled to the striking piston. After the driving of the nail is finished, the striking piston is returned to the top dead center position by the return mechanism by the return mechanism and returned to the top dead center position. Retained.
[0003]
The striking piston holding mechanism holds the striking piston at the top dead center position until the pressure of the compressed air introduced into the striking cylinder becomes sufficiently high, and holds the striking piston when the pressure of the compressed air becomes sufficiently high. Is opened and the striking piston is driven with high pressure. In particular, a nailing machine that does not employ a head valve mechanism with a large opening area that opens and closes the air chamber and the inside of the striking cylinder without supplying an air chamber around the striking cylinder supplies compressed air into the cylinder. As the operating speed of the main valve for fluctuation changes, the rising speed of the air pressure supplied into the striking cylinder fluctuates, and the driving energy value of the striking piston fluctuates accordingly. A nailing machine requires a striking piston holding mechanism that reliably holds the striking piston at the top dead center position until the pressure of the compressed air supplied to the striking cylinder becomes sufficiently high.
[0004]
The conventional striking piston holding mechanism is formed with a convex portion projecting outward in a boss portion projecting upward from the striking piston, and this convex portion is a locking portion formed on a piston stop made of an elastic material. It was hooked and held. However, in this structure, when the striking piston returns from the bottom dead center to the top dead center, the momentum of the returning operation of the striking piston is required to insert the boss portion into the locking portion, and this engagement is easy. Therefore, if the shape of the locking part and the convex part is reduced, the holding force cannot be secured sufficiently, and the striking piston is driven in a state where the pressure of the compressed air supplied into the cylinder is low. There was a problem that energy could not be applied and the drive energy varied due to fluctuations in the operating speed of the main valve.
[0005]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, and can hold the striking piston at the top dead center position without great resistance when the striking piston returns, and when the striking piston is driven, the air supplied into the striking cylinder Holds the striking piston securely at the top dead center position until the pressure becomes sufficiently high, and holds the striking piston so that the striking piston can be completely released when the compressed air pressure in the striking cylinder reaches a predetermined pressure. It is an object to provide a mechanism.
[0006]
[Means for achieving the object]
In order to solve the above problems, the striking piston holding mechanism of the compressed air driven impact tool according to the present invention drives the striking piston slidably accommodated in the striking cylinder by the compressed air introduced into the striking cylinder. In the impact tool, a downward cylindrical portion and a piston stop integrally formed with a concave portion inside the cylindrical portion are arranged at the upper end portion of the striking cylinder, and the striking piston is made of an elastic material. When moving to the top dead center of the striking cylinder, the boss portion protruding from the top surface of the striking piston is accommodated and held in the recess, and the lower end surface of the cylindrical portion is tightly sealed to the top surface of the striking piston. the adhesive sealing surface is partitioned between inner and outer peripheral surface of the cylindrical portion by the percussion piston and the cylindrical outer peripheral surface of the compressed air supplied into the striking cylinder when starting To act on said contact sealing surface peripheral side surface, characterized in that so as to retain the boss portion which is accommodated in the recess by compressed air acting on the outer peripheral surface of the tubular portion.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings. FIG. 1 shows a nailing machine in which a striking piston holding mechanism according to the present invention is implemented. A striking cylinder 2 is arranged in a hollow housing 1 for striking a nail in the striking cylinder 2. A striking piston 4 in which the driver 3 is coupled to the lower surface is slidably accommodated. The upper part of the hitting cylinder 2 is covered with a cylinder cap 5 that forms a part of the housing 1, and a rubber piston stop 6 arranged inside the cylinder cap 5 causes the hitting piston 4 to be at the top dead center position. It is supposed 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 compressed air introduced into the striking cylinder 2 for driving the striking piston 4 is formed. The start valve mechanism 10 communicates with the air passage 8. The inside of the grip part 1a formed hollow integrally with the housing 1 is formed as an air chamber 9 for storing compressed air supplied from a compressed air source.
[0008]
The start valve mechanism 10 includes a main valve 12 that selectively connects the inside of the impact cylinder 2 to an air chamber 9 and an exhaust path 11, and a trigger valve 13 that operates the main valve 12. Normally, the main valve 12 blocks the air passage 8 and the air chamber 9 so that the air passage 8 communicates with the exhaust passage 11. When the trigger valve 13 is manually operated, the main valve 12 is operated to connect the striking cylinder 2 and the air chamber 9 to supply compressed air into the striking cylinder. At this time, the blow cylinder 2 and the exhaust passage 11 are disconnected.
[0009]
As shown in detail in FIG. 2, a piston stop 6 made of an elastic material such as rubber is disposed at the upper end portion of the impact cylinder 2 so as to be sandwiched between the cylinder cap 5. The piston stop 6 is integrally formed with a cylindrical portion 14 that is formed downward so as to be fitted inside the upper end portion of the striking cylinder 2. Further, a concave portion 15 is formed inside the cylindrical portion 14. Is formed. A boss portion 16 fitted into the recess 15 of the piston stop 6 is formed on the upper surface of the striking piston 4 so as to protrude toward the upper surface, and when the striking piston 4 is arranged at the top dead center position, the boss The part 16 is accommodated in the recess 15. A flat annular seal surface 17 is formed on the outer upper end surface of the boss portion 16 of the striking piston 4, and the annular seal surface 17 is formed with a flat surface 18 formed at the downward tip of the tubular portion 14. It arrange | positions so that it may closely_contact | adhere. When the striking piston 4 is disposed at the top dead center position in the striking cylinder 2, the flat surface 18 of the cylindrical portion 14 tightly seals with the annular sealing surface 17 of the striking piston 4, and the inside of the recess 15 of the piston stop 6. The outer peripheral surface side of the cylindrical portion 14 is partitioned by the annular seal surface 17.
[0010]
An opening 19 continuous with the flow path 7 is formed in the peripheral wall near the upper end of the striking cylinder 2, and compressed air supplied from the starting valve mechanism 10 is introduced into the striking cylinder 2 through the opening 19. When the striking piston 4 is disposed at the top dead center position in the striking cylinder 2, the compressed air introduced into the striking cylinder 2 is separated from the outer peripheral surface of the tubular portion 14 of the piston stop 6 and the annular seal surface. It is made to act on the outer peripheral surface of the upper surface of the striking piston 4 defined by 17. The compressed air that acts on the outer peripheral surface of the cylindrical portion 14 deforms the cylindrical portion 14 from the outside in the direction of diameter reduction, and holds the boss portion 16 accommodated in the concave portion 15 in the concave portion 15. As shown in detail in FIG. 3, a convex strip 20 bulging in the outer diameter direction is formed on the outer peripheral surface of the upper end portion of the boss portion 16, and this convex strip 20 bites into the inner wall surface of the concave portion 15. Thus, the holding force of the striking piston 4 is increased. The size of the ridges 20 is set so that the driving energy value of the striking piston 4 is not less than a predetermined value.
[0011]
An enlarged diameter portion 21 having an inner diameter slightly enlarged is formed at the upper end portion of the impact cylinder 2, and an O-ring 22 attached to the impact piston 4 is accommodated in the expanded diameter portion 21, and the O A locking structure that prevents the striking piston 4 from moving in the direction of the bottom dead center by forming the ring 22 on the shoulder 21a at the lower end of the enlarged diameter portion 21 is formed. The locking structure formed between the striking cylinder 2 and the O-ring 22 of the striking piston 4 prevents the striking piston 4 from moving toward the bottom dead center when no compressed air is supplied into the striking cylinder 2. It works to stop.
[0012]
The operation of the above embodiment will be described below. When the starting valve mechanism 10 is not operated, the striking piston 4 is disposed at the top dead center position in the striking cylinder 2, and the boss portion 16 formed on the striking piston 4 is formed on the piston stop 6. The flat surface 18 at the lower end of the cylindrical portion 14 is in a state of being in close contact with the annular seal surface 17 on the upper surface of the striking piston 4. The main holding force of the striking piston 4 in this state is due to the enlarged diameter portion 21 at the upper end portion of the striking cylinder 2 and the O-ring 22 locked to the shoulder portion 21a of the enlarged diameter portion 21.
[0013]
When the start valve mechanism 10 is operated and the main valve 12 communicates between the impact cylinder 2 and the air chamber 9, the air in the air chamber 9 opens into the impact cylinder 2 via the air passage 8 and the flow path 7. 19 is introduced. Compressed air when introduced into the striking cylinder 2 from the opening 19 acts on the outer peripheral surface of the cylindrical portion 14 of the piston stop 6 to press and deform the cylindrical portion 14 in the inner diameter direction, and is formed inside the cylindrical portion 14. The recessed portion 15 is deformed in the direction of diameter reduction, and the boss portion 16 of the striking piston 4 accommodated in the recessed portion 15 is nipped and held. At this time, the compressed air also acts on the upper surface of the striking piston 4, but the flat surface 18 at the lower end of the cylindrical portion 14 is in close contact with the annular sealing surface 17 on the upper surface of the striking piston 4, so that the compressed air is in this annular shape. It acts only on the outer peripheral side of the seal surface 17. Accordingly, since the compressed air pressure at the moment of introduction into the striking cylinder 2 from the opening 19 is not sufficiently high, the holding force of the boss portion 16 by the concave portion 15 is larger than the driving force acting on the outer peripheral portion of the striking piston 4. The piston 4 is held at the top dead center position.
[0014]
When the compressed air pressure introduced into the striking cylinder 2 increases, the force acting on the top surface of the striking piston 4 to act in the direction of the bottom dead center increases, and the boss 16 is held by the recess 15. The striking piston 4 is driven in the direction of the bottom dead center in the striking cylinder 2 overcoming the force. At this time, the flat surface 18 of the cylindrical portion 14 and the annular seal surface 17 of the striking piston 4 are separated from each other, so that the compressed air pressure acts on the entire upper end surface of the striking piston 4, and the sufficiently high compressed air pressure is applied. Since the piston 4 acts on the entire surface and is driven, a large driving energy is given to the striking piston 4.
[0015]
When the striking piston 4 driven to the bottom dead center is returned to the top dead center, the compressed air in the striking cylinder 2 is exhausted through the exhaust passage 11, and the inner surface and the inner surface of the cylindrical portion 14 of the piston stop 6 are exhausted. Since the same pressure acts on the peripheral surface, the cylindrical portion 14 is not deformed, and therefore the boss portion 16 of the striking piston 4 is accommodated in the recess 15 without resistance. The striking piston 4 is held at the top dead center position by the enlarged diameter portion 21 at the upper end portion of the striking cylinder 2 and the O-ring 22 locked to the shoulder portion 21a of the enlarged diameter portion.
[0016]
【The invention's effect】
According to the present invention, a cylindrical portion is formed in the piston stop and a concave portion is formed inside the cylindrical portion, the boss portion of the striking piston is accommodated in the concave portion, and the pressure of the compressed air supplied into the striking cylinder is used. By deforming the cylindrical portion in the inner diameter direction, the boss portion is held, and further, the cylindrical portion seals tightly with the upper surface of the striking piston, thereby partitioning the outer peripheral portion and the inner side of the striking piston to the striking cylinder. Since the area where the supplied compressed air acts on the upper surface of the striking piston is limited, the striking piston can be reliably held at the top dead center position until the compressed air pressure becomes sufficiently high. Also, when the striking piston returns, the same pressure is applied to the inside and outside of the cylindrical portion, so that the cylindrical portion is not deformed and the striking piston is held at the top dead center position without any significant resistance. Even if the operating speed of the main valve of the valve mechanism varies and the pressure rise speed of the compressed air supplied into the cylinder varies, the piston is surely dead until the pressure in the striking cylinder becomes sufficiently high. The striking piston can be driven with a sufficiently high compressed air pressure, and the striking piston can be driven with a stable energy value.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a nailing machine in which a striking piston holding mechanism according to the present invention is implemented. FIG. 2 is a detailed cross-sectional view of an upper end of a striking cylinder of the same nailing machine as in FIG. Detailed cross-sectional view showing an enlarged view [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Stroke cylinder 4 Stroke piston 5 Cylinder cap 6 Piston stop 14 Cylindrical part 15 Recess 16 Boss part 17 Annular seal surface 18 Flat surface 19 Opening 20 Projection 21 Expanded part 22 O-ring

Claims (1)

An impact tool in which a striking piston slidably accommodated in a striking cylinder is driven impactively by compressed air introduced into the striking cylinder. A piston stop integrally formed with a recess inside the cylindrical portion is arranged at the upper end of the striking cylinder, and when the striking piston moves to the top dead center of the striking cylinder, it is formed to project on the upper surface of the striking piston. The boss portion is accommodated and held in the concave portion, and the lower end surface of the cylindrical portion is tightly sealed with the upper surface of the impact piston, and the outer peripheral surface side and the inside of the cylindrical portion are partitioned by this tightly sealed surface to start. by the action of compressed air during fed into the striking cylinder and the outer side of the contact seal surface of the striking piston top surface and the outer peripheral surface of the cylindrical portion compression, it acts on the outer peripheral surface of the tubular portion Striking piston holding mechanism of the compressed air-driven impact tool being characterized in that so as to retain the boss portion which is accommodated in the recess by vapor.

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