JP3622190B2 - Nailing machine return air discharge mechanism - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a return air discharge mechanism of a nail driver that discharges return air of a drive piston and maintains the drive piston at a bottom dead center position when an air hose leading to an air supply source is removed from the nail driver. .
[0002]
[Prior art]
Generally, a pneumatically driven nail driver is connected to an air supply source via an air hose. And when attaching an air hose from an air supply source to a nailing machine, in many cases, the grip of the nailing machine is held with one hand and the end of the hose is attached to the nailing machine with the other hand. Do. At this time, the finger of the hand holding the handle often touches the trigger lever unintentionally.
[0003]
However, the type of start valve that has a pilot valve in the start valve that is actuated by the trigger lever has the advantage that the main valve can be switched reliably even by an unstable operation of the trigger lever. Since the structure is operated by the air pressure, if the supply of air is cut off in the on state, it remains in the on operation position until the next moment when the air is supplied.
[0004]
For example, in the off state, as shown in FIG. 4A, the start valve is closed so that the compressed air in the main chamber 44 is not supplied to the drive cylinder in the on state. ), The main valve 42 is opened and compressed air in the main chamber 44 is supplied to the drive cylinder to operate the drive piston for driving the nail, but the nail driving operation is completed, that is, the start valve When the air hose is disconnected and the supply air is shut off with the valve 41 turned on (main valve 42 opened with the main chamber 44 open to the drive cylinder), the pilot valve 45 is turned on (bottom dead center). If the trigger valve is inadvertently operated at the moment when air is supplied to the nailer again, the main valve 42 opens and the drive pin is turned on. Phenomenon that drives the tons occurs. That is, the pilot valve 45 moves to the off position (top dead center position) by releasing the operation of the trigger lever 40 and the air in the main chamber 44 acting on the lower end surface of the pilot valve 45, but includes a contact arm. A single nailing machine, that is, the contact arm is activated by pressing the contact arm against the material to be driven and then the trigger lever is operated, and if the contact arm is pressed again while the trigger lever is pulled, the activation is not performed. In the type of nailing machine, when the air hose is connected to the nailing machine, if the trigger lever 40 is unintentionally touched and operated, the trigger stem 47 moves as shown in FIG. The trigger stem 47 blocks the air passage between the lower end surface of the main chamber 45 and the main chamber 44, and the pilot valve 45 is turned off. Returning to the h position will be impossible. As a result, the control air is not supplied to the upper end of the main valve 42, the main valve 42 is opened by the air pressure in the main chamber 44, and the air is supplied into the drive cylinder to surely cause an explosion. .
[0005]
As described above, in addition to the case where the trigger lever 40 is operated unintentionally, the return operation of the pilot valve 45 to the OFF position is delayed due to the grease cut of the pilot valve 45 or the diameter of the air passage due to dust or the like. The above phenomenon may occur.
[0006]
In order to prevent such an explosion at the time of air connection, when the air is shut off while the start valve 41 is in an ON state, a mechanism that keeps the drive piston at the bottom dead center position that is operated is effective. If the drive piston remains at the bottom dead center position even when the start valve 41 is turned on, the compressed air only flows into the drive cylinder, and this compressed air urges the drive piston toward the bottom dead center side. Because there is no problem at all.
[0007]
However, the drive piston at the bottom dead center position normally discharges the compressed air in the return chamber configured to store the compressed air during the operation stroke, and the upper air of the drive cylinder is discharged to the atmosphere. At this time, it can be returned to the top dead center by acting on the lower surface side of the drive piston, but the air hose was pulled out with the drive piston operating at the bottom dead center, and the supply air from the air supply source was shut off. In this case, the pressure on the upper surface of the drive piston is reduced, but the compressed air accumulated in the return chamber acts on the lower surface side of the drive piston, so that the drive piston returns to the top dead center in the same manner. As soon as the air hose is connected, the compressed air from the air supply source is directly supplied to the drive cylinder, causing a phenomenon of explosion.
[0008]
Therefore, even when the air hose is pulled out, the driving piston must be maintained at the bottom dead center position. As a technique for that purpose, as shown in FIG. 5, the drive cylinder 43 is movable up and down, and the drive cylinder 43 is mounted on the housing by air pressure from the main chamber 44 acting on the cylinder ring 50 fixed to the flange portion 49 in the normal state. When the air hose is pulled out while being pressed and fixed downward and the drive piston 46 is operated, the drive cylinder 43 is moved upward using the air pressure in the return chamber 48 as shown in FIG. In this way, the passage between the return chamber 48 and the main chamber 44 is opened, and the air in the return chamber 48 is discharged to the main chamber 44 side so that the drive piston 46 stopped at the bottom dead center position cannot be returned. There is.
[0009]
Details of such technology are disclosed in Japanese Utility Model Publication No. 62-40774.
[0010]
[Problems to be solved by the invention]
However, in the above conventional technique, the structure is complicated because the drive cylinder is movable, and a flange portion 49 that protrudes from the outer peripheral surface of the drive cylinder 43 is required to move the drive cylinder 43 with air pressure. Since such a flange portion 49 must be formed by cutting away a thick drive cylinder material, there is a problem that the processing cost is increased and the cost becomes high.
[0011]
Further, since the O-ring 51 is soft at a high temperature, a part of the driving cylinder 43 is easily detached from the groove of the cylinder 50 when the driving cylinder 43 is moved upward. In order to prevent this, the width of the vertical groove If the value is reduced, a sufficient air outflow area for preventing the drive piston from returning can not be obtained, and the initial purpose cannot be achieved.
[0012]
The present invention solves the above problems, and even in a drive cylinder in which a molding upper flange portion cannot be formed, the air in the return chamber is discharged when shut off from the air supply source, and the drive piston is stopped at the bottom dead center position. It is an object of the present invention to provide a return air discharge mechanism for a nailing machine that can be kept.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the return air discharge mechanism of the nailer according to the present invention communicates with the air supply source around the upper outer periphery of the drive cylinder in which the drive piston for nailing is slidably accommodated. A main chamber is provided, a return chamber is provided around the lower periphery of the drive cylinder, and the drive piston is driven by nailing with compressed air supplied from the main chamber to the upper end of the drive cylinder. The compressed air compressed in step 1 is supplied to the return chamber through a communication hole formed in the lower part of the drive cylinder, and after the nail driving operation is finished, the compressed air in the return chamber is applied to the lower surface of the drive piston to return the drive piston. in striking machine, the outer periphery of the upper driving cylinder of said return chamber cylinder And a space between the upper end of the cylinder ring and the drive cylinder is formed between the lower end of the cylinder ring and the drive cylinder. The intermediate portion of the cylinder ring is formed with a through hole through which the space portion and the main chamber communicate with each other, and an air passage is formed between the return chamber and the main air chamber by the space portion and the through hole. And is opened outside the through hole so that the compressed air in the return chamber is discharged into the main chamber only when the internal pressure of the return chamber becomes larger than the internal pressure of the main chamber. A possible check valve is arranged.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cross section of a nailing machine. Reference numeral 1 denotes a body, and 2 denotes a grip. The end of the grip 2 is configured so that an air hose 4 leading to an air supply source 3 can be connected. A nose portion 5 is continuously arranged below the body 1.
[0015]
The body 1 is provided with a cylindrical drive cylinder 6. A main valve 7 is disposed above the drive cylinder 6, and the main valve 7 is operatively connected to an activation valve 8 at the base of the grip 2. The start valve 8 is actuated by operating the trigger lever 9. When the actuating valve 8 is actuated to the on position (bottom dead center), the upper end opening of the drive cylinder 6 is opened to the main chamber 10 and opened to the atmosphere at the off position (top dead center). Thus, the mechanism is selectively opened and closed, and is the same known mechanism as that shown in FIG.
[0016]
Next, the drive piston 11 is slidably accommodated in the drive cylinder 6, and a nail driver 12 is integrally coupled to the drive piston 11. The main chamber 10 is provided around the upper periphery of the drive cylinder 6. The main chamber 10 is also continuously connected to the inside of the grip 2 through the air hose 4 to the air supply source 3, and compressed air is stored when the air hose 4 is connected. A return chamber 13 is provided around the lower outer periphery of the drive cylinder 6 and communicates with the drive cylinder 6 through upper and lower communication holes.
[0017]
In the above configuration, when the main valve 7 is operated to open the upper end opening of the drive cylinder 6 by pulling the trigger lever 9 and turning on the start valve 8, the compressed air is discharged from the main chamber 10. Is supplied from the upper end of the drive cylinder 6 to drive the drive piston 11. As a result, the nail supplied to the nose portion 5 is struck by the driver 12 and driven into a material to be driven (not shown).
[0018]
When the drive piston 11 operates toward the bottom dead center, the air below the drive piston 11 is compressed and supplied to the return chamber 13 through the upper and lower communication holes 14 and 15 formed in the lower part of the drive cylinder 6 and stored. The Then, after the trigger lever 9 is released after the nail driving operation is finished, the start valve 8 is turned off as shown in FIG. 1, and the main valve 7 is operated to open the upper end opening of the drive cylinder 6 to the atmosphere. The compressed air supplied into the cylinder 6 is discharged to the atmosphere, and the air pressure with respect to the upper surface of the drive piston 11 is reduced. On the other hand, since the compressed air in the return chamber 13 flows back into the drive cylinder 6 from the lower communication hole 15 and acts on the lower surface of the drive piston 11, the drive piston 11 returns to the top dead center.
[0019]
By the way, the drive cylinder 6 is formed into a cylindrical shape having a circular or elliptical cross section by extrusion molding of aluminum, and is fixed to the body 1. As shown in detail in FIG. 2, an upper cylinder ring 16 is provided around the outer periphery of the upper end of the drive cylinder 6, and a lower cylinder ring 17 is provided thereunder via an O-ring 18. These cylinder rings may be made of a synthetic resin or a metal such as aluminum. An engaging portion 19 that engages with the upper end surface of the drive cylinder 6 is formed at the upper end of the upper cylinder ring 16, and a step portion 20 is also formed on the outer peripheral surface thereof, and the step portion 20 and the inner wall of the body 1 are formed. A cylinder presser cylinder 22 is attached between the cylinder 21 and the drive cylinder 6. The drive cylinder 6 is pressed and fixed downward by the cylinder presser cylinder 22. Further, the lower end of the lower cylinder ring 17 is also engaged with a step portion 23 formed on the inner wall of the body 1 together with the O-ring 24, and is fixed between the upper cylinder ring 16 and the step portion 23 of the body 1.
[0020]
The upper inner diameter of the lower cylinder ring 17 is substantially the same as the outer diameter of the drive cylinder 6, but the lower inner diameter is formed to be larger than the outer diameter of the drive cylinder 6, and the lower cylinder ring 17 and the drive cylinder A space (air passage) S is formed between the two.
[0021]
Incidentally, a belt-like check valve 25 having elasticity is attached to the outside of the upper communication hole 14 formed in the drive cylinder 6. As shown in FIG. 3A, a plurality of protruding pieces 26 are formed on the upper end of the check valve 25 outward. On the other hand, a short cylindrical protruding edge 27 protruding to the other is formed at the lower end of the lower cylinder ring 17, and the engaging edge 28 larger than the protruding piece 26 is formed on the protruding edge 27 at a position corresponding to the protruding piece 26. Are formed at equal intervals. As shown in FIG. 2B, the protruding piece 26 of the check valve 25 is engaged with and engaged with the engaging port 28 of the lower cylinder ring 17. Since the engagement port 28 is larger than the projecting piece 26, the return chamber 13 communicates with the space S between the lower cylinder ring 17 and the drive cylinder 6 via the engagement port 28.
[0022]
Next, through holes 29 are formed in the lower cylinder ring 17 at intervals in the circumferential direction. And the outer side of these through-holes 29 is covered with the strip | belt-shaped check valve 30 which has elasticity. For this reason, the return chamber 13 communicates with the space S between the lower cylinder ring 17 and the drive cylinder 6 through the engagement port 28 and further communicates with the main chamber 10 through the check valve. In short, the return chamber 13 and the main chamber 10 are connected via the check valve 30. The check valve 30 opens and operates so that the compressed air in the return chamber 13 is discharged to the main chamber 10 only when the internal pressure of the return chamber 13 becomes larger than the internal pressure of the main chamber 10. Therefore, when the air hose 4 is connected for the first time when the nailing machine is started, or when the air below the driving piston 11 is compressed and supplied to the return chamber 13 and stored when the driving piston 11 is operated. When the air pressure in the chamber 10 is equal to or higher than the air pressure in the return chamber 13, the check valve 30 is not opened.
[0023]
According to the above configuration, after the nail driver is driven into the nail, the trigger lever 9 is operated unconsciously (the start valve 8 and the main valve 7 are turned on), and the drive piston 11 is at the bottom dead center. If the air hose 4 is removed from the grip 2 as it is, the air in the main chamber 10 is released to the atmosphere and decompressed. As a result, a differential pressure is generated between the air pressure in the main chamber 10 and the air pressure in the return chamber 13, and the latter becomes higher, so that the check valve 30 is opened and the compressed air in the return chamber 13 is It is discharged from the through hole 29 to the main chamber 10 and further released to the atmosphere. Accordingly, the air pressure in the main chamber 10 and the return chamber 13 is both atmospheric pressure. For this reason, since sufficient air pressure is not supplied from the return chamber 13 to the lower surface of the drive piston 11, the drive piston 11 cannot return to the top dead center and is maintained at the bottom dead center position.
[0024]
Thereafter, when the air hose 4 is connected to the air supply source 3 while operating the trigger lever 9, compressed air is supplied into the main chamber 10, but the drive piston 11 is operated at the bottom dead center position. Never do. This compressed air is supplied into the drive cylinder 6 and further supplied into the return chamber 13 from the upper communication hole. At this time, the check valve 30 is not opened due to the balance with the air pressure in the main chamber 10, so the compressed air is stored in the return chamber 13.
[0025]
When the trigger lever 9 is further released, the start valve 8 and the main valve 7 return to the off state, so that the air in the drive cylinder 6 is discharged to the atmosphere. As a result, the air pressure from the return chamber 13 to the lower surface of the drive piston 11 increases, and the drive piston 11 returns to the top dead center for the first time, and the next nail driving is prepared.
[0026]
Therefore, according to the return air discharge mechanism of the nail driver configured as described above, when the air supply between the air supply source 3 and the nail driver is cut off, the air in the return chamber 13 is discharged from the air chamber to the atmosphere. End up. Therefore, even if the starting valve 8 remains in the ON state at this time, the drive piston 11 can be stopped at the bottom dead center position, so that the nail driver and the air supply source 3 can be connected in this state. Even when connected, the drive piston 11 does not operate. Therefore, it is possible to effectively prevent unexpected bursts regardless of whether the start valve 8 is turned on or off.
[0027]
Further, the drive cylinder 6 may be a cylindrical one obtained by extrusion molding of aluminum or the like, and there is no need to process a flange portion or the like. Therefore, the cost can be kept low.
[0028]
Further, since it is not necessary to make the drive cylinder 6 movable, the structure can be simplified, and there is no inconvenience that the O-ring is detached. Therefore, the outflow amount from the check valve 30 can be accurately grasped, and the failure is reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a nailing machine according to the present invention. FIG. 2 is an enlarged view of a driving cylinder of the nailing machine and its surroundings. FIGS. 3A and 3B are a check valve and a lower cylinder, respectively. Plan view before and after assembly of ring engagement holes [Fig. 4] (a) and (b) are illustrations of operation modes when the start valve is turned on and off, respectively [Fig. 5] For conventional return Fig. 6 is a longitudinal sectional view of the air discharge mechanism.
3 Air supply source 6 Drive cylinder 10 Main chamber 11 Drive piston 13 Return chamber 30 Check valve

Claims (1)

A main chamber that communicates with the air supply source is provided around the upper outer periphery of the drive cylinder that slidably accommodates a drive piston for driving a nail, and a return chamber is provided around the lower outer periphery of the drive cylinder. The driving piston is driven into the nail by the compressed air supplied to the upper end of the cylinder, and compressed air compressed below the driving piston when the driving piston is operated is supplied to the return chamber from the communication hole formed in the lower part of the driving cylinder. In the nailing machine for returning the driving piston by causing the compressed air in the return chamber to act on the lower surface of the driving piston after the driving operation is completed,
A cylinder ring is provided on the outer periphery of the drive cylinder at the top of the return chamber, seals between the upper end of the cylinder ring and the drive cylinder, and between the lower part of the upper end of the cylinder ring and the drive cylinder. A space portion that opens at the upper end of the return chamber is formed, and a through hole that allows the space portion and the main chamber to communicate with each other is formed through the intermediate portion of the cylinder ring.
An air passage is formed between the return chamber and the main air chamber by the space portion and the through hole , and the internal pressure of the return chamber is larger than the internal pressure of the main chamber in the air passage outside the through hole. A return air discharge mechanism for a nailing machine, wherein a check valve that can be opened and operated so that the compressed air in the return chamber is discharged to the main chamber only when

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