Driving machine

A driving machine

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a driving machine for driving a fastening member such as a nail using compressed air as a power source.

2. Background Art

Description will be given below of an example of a conventional driving machine with reference toFIGS. 6 and 7.

FIG. 6is a broken section view of the main portions of a conventional driving machine, andFIG. 7is an enlarged section view of the main portions shown inFIG. 6. In the illustrated driving machine, compressed air, which is supplied from a compressor (not shown), is accumulated through an air hose (not shown) into a pressure storage chamber2formed in a driving machine main body7. Within the driving machine main body7, there is provided a tubular-shaped cylinder5; and, into the cylinder5, there is fitted a piston4which can be slid in a reciprocating manner.

On the lower portion of the piston4, there is provided a driver22integrally therewith. Between a magazine (not shown) and a nose portion23, there is interposed fastening member feed means25. Fastening members28such as nails stored in the magazine are fed one by one into a shooting opening24formed in the nose portion23by the fastening member feed means25.

Here, the fastening member feed means25is composed of a fastening member feed cylinder12and a fastening member feed piston11. The fastening member feed piston11is fitted into the fastening member feed cylinder12in such a manner that it can be slid back and forth within the fastening member feed cylinder12. Also, on the leading end of the fastening member feed piston11, there is mounted a feed pawl14in such a manner that it can be rotated. When the fastening member feed cylinder12is operated, the feed pawl14can be moved reciprocatingly together with the feed piston11along a feed passage29. When the feed pawl14moves backward, it comes in contact with the shaft of the fastening member28within the feed passage29and is thereby rotated in such a manner as to retreat from the feed passage29, so that it moves beyond the fastening member28; and, when the feed pawl14moves forward, it advances into the feed passage29and is engaged with the shaft of the fastening member28to thereby feed the fastening member28.

Next, when a trigger1is pulled, there is started a driving process in which a cylinder valve3sealing the upper end of the cylinder5is opened, and the compressed air of the pressure storage chamber pushes down the piston4, whereby the fastening member28fed into the shooting opening24of the nose portion23by the fastening member feed means25is driven by the leading end of the driver22. Also, after the fastening member28is driven, the piston4collides with a bumper8, whereby the remaining surplus energy of the piston4is absorbed by the bumper8. When the piston4passes through air holes5a, a portion of the compressed air is supplied through the air holes5aand a check valve50to a return air chamber6. Further, a portion of the compressed air supplied to the return air chamber6flows from the return air chamber6and is stored through air passages18and19into the fastening member feed cylinder12, which pushes down the fastening member feed piston11that is tightly fitted with and is slid within the fastening member feed cylinder12, thereby causing the feed pawl14to move backward.

When the trigger1is released, the pressure of the return air chamber6pushes back the piston4and, at the top dead center of the piston4, the compressed air of the return air chamber6is exhausted from a lower exhaust port21existing downward of the bumper8or from an upper exhaust port27through a clearance formed upwardly of the cylinder5; and, the feed pawl14is returned to its original position by a return spring13.

Also, between a main body side passage18communicating with the return air chamber6on the main body7side and an air passage19communicating with the inside of the fastening member feed cylinder12, there is interposed a plate-shaped filter portion17having a plurality of small holes20while the connecting portions of the passages18and19are sealed by packing16a; and thus, an effective sectional area equal to the conventional passage area is secured by the plurality of small holes20(see the patent reference 1 Japan Utility Model Application No. 2510176).

In the above-mentioned conventional driving machine, when the above-mentioned driving operation is carried out repeatedly tens of thousands times, owing to the impact fatigue, there are caused cracks on the upper surface of the bumper8which is used to absorb the impact of the surplus energy, thereby forming a small broken piece30shown inFIG. 7. This small broken piece30, in most cases, is discharged from the lower exhaust port21. However, in some cases, the small broken piece30is moved from a return chamber passage hole9through the air passages18and19into the fastening member feed cylinder12, and is accumulated in the periphery of the fastening member feed piston11, which makes it impossible for the fastening member feed piston11to return to its normal position. As a result of this, the feeding operation of the fastening member feed piston11is incomplete, that is, the normal feeding of the fastening member28is impossible.

Therefore, according to the patent reference 1, in a structure in which, between the air passages, there is interposed a plate-shaped filter portion for preventing the entrance of the broken piece of the bumper, in order to prevent the broken pieces of the bumper from entering the fastening member feed cylinder, they are accumulated on the air passages using the compressed air; and, the broken pieces, which have entered the air passages once, are crammed into the air passages and are thus hard to be discharged into the return air chamber, with the result that the broken pieces close the air passages respectively formed between the return air chamber and feed cylinder. This raises the following problems: that is, a sufficient amount of compressed air cannot be supplied to the fastening member feed cylinder, and the compressed air supplied to the fastening member feed cylinder cannot be exhausted, whereby the forward and backward movements of the feed piston are made incomplete and, therefore, the fastening members such as connected nails cannot be fed properly.

SUMMARY OF THE INVENTION

The present invention aims at solving the above problems and thus it is an object of the invention to provide a driving machine which, even when a bumper is broken and broken pieces are produced, can prevent the broken pieces from entering an air passage to thereby always be able to feed a fastening member properly.

In attaining the above object, according to the invention, there is provided a driving machine which uses compressed air as a power source and comprises: a cylinder; a piston fitted into the cylinder such that it can be reciprocated; a driver connected to the piston; a bumper provided on the bottom portion of the cylinder; a housing disposed so as to cover the cylinder from outside and including therein a pressure storage chamber for storing compressed air; a return air chamber formed in the outer periphery of the cylinder for storing the return compressed air that is used to move up and return the piston; an exhaust port, after the piston is returned, for discharging compressed air existing downwardly of the piston to the air; a fastening member feed piston movable backward or movable forward by supplying the compressed air of the return air chamber from the passage hole of the return air chamber through an air passage into the fastening member feed cylinder or by discharging such compressed air from the fastening member feed cylinder; a return spring for energizing the fastening member feed piston in one direction; and, a feed pawl mounted on the leading end of the fastening member feed piston, wherein, within the air passage formed between the return air chamber and the fastening member feed cylinder, there is formed a filter portion and, in the vicinity of the leading end of the projection-shaped portion of the filter portion, there is formed the passage hole.

According to the invention, in the invention as set forth in Claim1, the passage hole opened up in the vicinity of the leading end of the projection-shaped portion of the filter portion is made of a thin-film-shaped mesh, and the passage hole is opened in the return air chamber by mounting the mesh from the outside of the housing into the return air chamber.

According to the invention as set forth in Claim3, the invention as set forth in Claim2, the filter portion is made of plastic, and the filter portion and the mesh are formed as an integral body.

According to the invention, even when the broken pieces of the bumper enter the return air chamber and, with the flow of the compressed air into the fastening member feed means, the broken pieces of the bumper are going to move through the main body side passage into the air passage, since the projection-shaped filter portion projecting into the return air chamber is formed in the vicinity of the main body side passage, the filter portion prevents the broken pieces from moving into the air passage, whereby the feeding operation of the fastening member can be carried out properly. And, since there can be secured a large opening area in the filter portion, in the filter portion, there can be sufficiently secured a flow-in area equal to or larger than the air passage; and, therefore, even when the bumper is slightly broken and the broken pieces thereof stick to the filter portion, the feeding operation of the fastening member can be always carried out properly.

Also, since the filter portion is structured separately from the housing, the filter portion can be taken out from the housing easily and thus the broken pieces sticking to the filter portion can be cleaned simply.

DETAILED DESCRIPTION OF THE INVENTION

Now, description will be given below of a driving machine according to an embodiment of the invention with reference to the accompanying drawings.

The basic structure of a driving machine according to the invention is similar to that of the conventional driving machine shown inFIGS. 6 and 7and, therefore, description will be given below of the basic structure of the driving machine according to the invention with reference toFIGS. 6 and 7.

In the driving machine according to the invention, compressed air from a compressor (not shown) is accumulated through an air hose (not shown) into the pressure storage chamber2formed within the driving machine main body7. Within the driving machine main body7, there is disposed a tubular-shaped cylinder5; and, into the cylinder5, there is fitted a piston4in such a state that it can be slid in a reciprocating manner. And, on the lower portion of the piston4, there is provided a driver22integrally therewith. When a trigger1is actuated, a cylinder valve3, which seals the upper end of the cylinder5, is opened and thus the compressed air of the pressure storage chamber2pushes down the piston4, whereby a fastening member28fed into the shooting opening24of a nose portion23is driven by the leading end of the driver22.

Also, between the nose portion23and a magazine (not shown), there is interposed fastening member feed means25; and, a plurality of fastening members28stored in the magazine can be fed out one by one into the shooting opening24of the nose portion23by the fastening member feed means25.

The fastening member feed means25is composed of a fastening member feed cylinder12and a fastening member feed piston11. The fastening member feed piston11is fitted into the fastening member feed cylinder12in such a manner that it can be slid back and forth within the fastening member feed cylinder12. Also, on the leading end of the fastening member feed piston11, there is mounted a feed pawl14in such a manner that it can be rotated. When the fastening member feed cylinder12is operated to thereby reciprocate the feed pawl14together with the feed piston11along a feed passage29, the feed pawl14, in the backward movement thereof, comes in contact with the shaft of the fastening member28within the feed passage29and is thereby rotated in such a manner to retreat from the feed passage29, so that it moves beyond the fastening member28; and, when the feed pawl14moves forward, it advances into the feed passage29and is engaged with the shaft of the fastening member28to thereby feed the fastening member28.

Here, description will be given below of the subject matter of the invention with reference toFIGS. 1˜3.

FIG. 1is a section view of the main portions of the driving machine according to the invention,FIG. 2is a perspective view of a filter portion formed in the driving machine, andFIG. 3is an enlarged section view of the filter portion of the present driving machine.

As shown inFIG. 1, between the air passage19and return air chamber6, there is formed a main body side passage18which is used to allow the communication of the compressed air; and, in the main body side passage18, there is formed a filter portion17which includes a plurality of small holes20. This filter portion17is formed in such a manner that its projection-shaped portion17bprojects within the return air chamber6of a housing26in the form of a chimney; and, in the vicinity of the upper portion of the projection-shaped portion17b, there are opened up the plurality of small holes20which are used to allow the air passage19to communicate with the filter portion17from the main body side passage18.

The filter portion17is made of resin such as plastic, while the small holes20opened up in the outer periphery of the upper portion of the filter portion17are formed of a thin-film-shaped mesh17a. This mesh17ais welded to the filter portion17from the inside thereof to thereby form the filter portion17as an integral body. Between the filter portion17and air passage19, there are interposed two or more pieces of packing16a,16bwhich are used to prevent the compressed air from leaking to the air. The filter portion17is mounted in such a manner that it penetrates from the outside of the housing26and into the return air chamber6, the small holes20of the filter portion17are opened in the return air chamber6, and the filter portion17can be separated from the housing26.

By the way, the housing26includes a stepped portion26awhich is used to prevent the filter portion17from moving into the inside of the housing26when the filter portion17is mounted from the nose portion23side of the housing26. Also, even when the filter portion17is inserted from the return air chamber6side of the housing26, in order to prevent the filter portion17from being removed due to pressure, there is additionally provided a structure for prevention of removal of the filter portion17, for example, a structure for holding the filter portion17using a cylinder.

Now, description will be given below of the operation of the above-structured driving machine according to the invention.

In the driving machine according to the invention, when the trigger1is pulled, the cylinder valve3on the upper end of the cylinder5is opened, the compressed air of the pressure storage chamber2pushes down the piston4suddenly, and the fastening member within the shooting opening24is driven by the leading end of the driver22.

After the above driving operation, the piston4collides with the bumper8at the lower-most point thereof, and the remaining surplus energy of the piston4is absorbed by the bumper8, whereby the piston4is caused to stop. When the piston4passes through the air hole5a, a portion of the compressed air is supplied through the air hole5aand a check valve50to the return air chamber6. Further, a portion of the compressed air supplied to the return air chamber6is stored from the return air chamber6through the air passage19into the fastening member feed cylinder12; and, this compressed air pushes down the fastening member feed piston11sliding within the fastening member feed cylinder12to thereby retreat the feed pawl14from the shooting opening24.

Next, when the trigger1is released, the piston4is moved backward. Specifically, the piston4is pushed up to the top dead center thereof by the pressure of the return air chamber6, whereby the compressed air existing in the lower chamber of the piston4and in the return air chamber6is discharged from either a lower exhaust port21through a clearance between the leading end of the driver22and the piston4, or an upper exhaust port27through a clearance formed upwardly of the cylinder5. Also, simultaneously with this, the air existing within the fastening member feed cylinder12is also discharged therefrom. Thus, owing to the force of a return spring13which is provided on the back surface of the driving machine, the fastening feed piston11and feed pawl14existing within the fastening member feed cylinder12are returned within the feed passage29to feed the fastening member28again into the shooting opening24, thereby ending1driving cycle.

When the above-mentioned driving cycle is repeated tens of thousands times, the upper surface of the bumper8to absorb the surplus energy is gradually caused to crack, resulting in the formation of such broken pieces30as shown inFIG. 3. These broken pieces30are carried from the return chamber hole9into the return air chamber6by the force of the compressed air and are going to move from the main body side passage18into the air passage19which communicates with the fastening member feed cylinder12. However, since, between the air passage19and the main body side passage18that communicates with the return chamber6on the main body7side, there is interposed the filter portion17including a large number of small holes20which are made of the mesh17aand are situated in the vicinity of the leading end of the projection-shaped portion17b, not only small-size broken pieces30but also large-size broken pieces30can be prevented from moving into the air passage19.

Also, even when the broken pieces30happen to move into the main body side passage18and stick to and cover the small holes22of the mesh17ain the leading end of the projection-shaped portion17bof the filter portion17entirely, since the projection-shaped portion17bof the filter portion17projects in a chimney shape, the broken pieces30can be easily diffused due to the force of the compressed air discharged or the broken pieces30are easy to slip down in the downward direction within the return air chamber6due to the own mass of the broken pieces and are thus easy to accumulate in the lower portion of the return air chamber6, thereby eliminating a possibility that the whole of the small holes20can be covered completely by the broken pieces30. This makes it possible for the filter portion17to sufficiently secure an effective section area equal to the passage area. Also, when the filter portion17is formed separately from the housing26, the filter portion17can be taken out from the housing26easily, so that the broken pieces30sticking to neighboring portion of the upper portion of the filter portion17can be cleaned easily.

In the above-described embodiment, there is employed a structure in which the filter portion17including the small holes20is disposed within the air passage19to the fastening member feed piston11on the return air chamber6side of the housing26, and the mesh17ais welded to the filter portion17to thereby provide an integral body. However, as shown inFIGS. 4 and 5, even in another structure in which the filter portion17has a chimney-like projection shape similar to the above-mentioned embodiment, small holes31are formed in the vicinity of the upper portion of the leading end of the projection-shaped portion17b, and the filter portion17is formed removably from the housing26or integrally with the housing26, the broken pieces30of the cracked bumper8are easy to accumulate on the lower portion of the housing26. Therefore, in this structure as well, there can be obtained effects similar to the above-mentioned structure.