Patent Publication Number: US-7712647-B2

Title: Driving machine

Description:
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 to  FIGS. 6 and 7 . 
     FIG. 6  is a broken section view of the main portions of a conventional driving machine, and  FIG. 7  is an enlarged section view of the main portions shown in  FIG. 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 chamber  2  formed in a driving machine main body  7 . Within the driving machine main body  7 , there is provided a tubular-shaped cylinder  5 ; and, into the cylinder  5 , there is fitted a piston  4  which can be slid in a reciprocating manner. 
   On the lower portion of the piston  4 , there is provided a driver  22  integrally therewith. Between a magazine (not shown) and a nose portion  23 , there is interposed fastening member feed means  25 . Fastening members  28  such as nails stored in the magazine are fed one by one into a shooting opening  24  formed in the nose portion  23  by the fastening member feed means  25 . 
   Here, the fastening member feed means  25  is composed of a fastening member feed cylinder  12  and a fastening member feed piston  11 . The fastening member feed piston  11  is fitted into the fastening member feed cylinder  12  in such a manner that it can be slid back and forth within the fastening member feed cylinder  12 . Also, on the leading end of the fastening member feed piston  11 , there is mounted a feed pawl  14  in such a manner that it can be rotated. When the fastening member feed cylinder  12  is operated, the feed pawl  14  can be moved reciprocatingly together with the feed piston  11  along a feed passage  29 . When the feed pawl  14  moves backward, it comes in contact with the shaft of the fastening member  28  within the feed passage  29  and is thereby rotated in such a manner as to retreat from the feed passage  29 , so that it moves beyond the fastening member  28 ; and, when the feed pawl  14  moves forward, it advances into the feed passage  29  and is engaged with the shaft of the fastening member  28  to thereby feed the fastening member  28 . 
   Next, when a trigger  1  is pulled, there is started a driving process in which a cylinder valve  3  sealing the upper end of the cylinder  5  is opened, and the compressed air of the pressure storage chamber pushes down the piston  4 , whereby the fastening member  28  fed into the shooting opening  24  of the nose portion  23  by the fastening member feed means  25  is driven by the leading end of the driver  22 . Also, after the fastening member  28  is driven, the piston  4  collides with a bumper  8 , whereby the remaining surplus energy of the piston  4  is absorbed by the bumper  8 . When the piston  4  passes through air holes  5   a , a portion of the compressed air is supplied through the air holes  5   a  and a check valve  50  to a return air chamber  6 . Further, a portion of the compressed air supplied to the return air chamber  6  flows from the return air chamber  6  and is stored through air passages  18  and  19  into the fastening member feed cylinder  12 , which pushes down the fastening member feed piston  11  that is tightly fitted with and is slid within the fastening member feed cylinder  12 , thereby causing the feed pawl  14  to move backward. 
   When the trigger  1  is released, the pressure of the return air chamber  6  pushes back the piston  4  and, at the top dead center of the piston  4 , the compressed air of the return air chamber  6  is exhausted from a lower exhaust port  21  existing downward of the bumper  8  or from an upper exhaust port  27  through a clearance formed upwardly of the cylinder  5 ; and, the feed pawl  14  is returned to its original position by a return spring  13 . 
   Also, between a main body side passage  18  communicating with the return air chamber  6  on the main body  7  side and an air passage  19  communicating with the inside of the fastening member feed cylinder  12 , there is interposed a plate-shaped filter portion  17  having a plurality of small holes  20  while the connecting portions of the passages  18  and  19  are sealed by packing  16   a ; and thus, an effective sectional area equal to the conventional passage area is secured by the plurality of small holes  20  (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 bumper  8  which is used to absorb the impact of the surplus energy, thereby forming a small broken piece  30  shown in  FIG. 7 . This small broken piece  30 , in most cases, is discharged from the lower exhaust port  21 . However, in some cases, the small broken piece  30  is moved from a return chamber passage hole  9  through the air passages  18  and  19  into the fastening member feed cylinder  12 , and is accumulated in the periphery of the fastening member feed piston  11 , which makes it impossible for the fastening member feed piston  11  to return to its normal position. As a result of this, the feeding operation of the fastening member feed piston  11  is incomplete, that is, the normal feeding of the fastening member  28  is 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 Claim  1 , 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 Claim  3 , the invention as set forth in Claim  2 , 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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a section view of the main portions of a driving machine according to an embodiment of the invention. 
       FIG. 2  is a perspective view of the driving machine according to an embodiment of the invention. 
       FIG. 3  is an enlarged section view of a filter portion of the driving machine according to an embodiment of the invention. 
       FIG. 4  is an enlarged section view of a filter portion of a driving machine according to another embodiment of the invention. 
       FIG. 5  is an enlarged section view of a filter portion of the driving machine according to another embodiment of the invention. 
       FIG. 6  is a broken section view of a filter portion of a conventional driving machine. 
       FIG. 7  is an enlarged section view of the main portions of the conventional driving machine shown in  FIG. 6 . 
   

   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 in  FIGS. 6 and 7  and, therefore, description will be given below of the basic structure of the driving machine according to the invention with reference to  FIGS. 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 chamber  2  formed within the driving machine main body  7 . Within the driving machine main body  7 , there is disposed a tubular-shaped cylinder  5 ; and, into the cylinder  5 , there is fitted a piston  4  in such a state that it can be slid in a reciprocating manner. And, on the lower portion of the piston  4 , there is provided a driver  22  integrally therewith. When a trigger  1  is actuated, a cylinder valve  3 , which seals the upper end of the cylinder  5 , is opened and thus the compressed air of the pressure storage chamber  2  pushes down the piston  4 , whereby a fastening member  28  fed into the shooting opening  24  of a nose portion  23  is driven by the leading end of the driver  22 . 
   Also, between the nose portion  23  and a magazine (not shown), there is interposed fastening member feed means  25 ; and, a plurality of fastening members  28  stored in the magazine can be fed out one by one into the shooting opening  24  of the nose portion  23  by the fastening member feed means  25 . 
   The fastening member feed means  25  is composed of a fastening member feed cylinder  12  and a fastening member feed piston  11 . The fastening member feed piston  11  is fitted into the fastening member feed cylinder  12  in such a manner that it can be slid back and forth within the fastening member feed cylinder  12 . Also, on the leading end of the fastening member feed piston  11 , there is mounted a feed pawl  14  in such a manner that it can be rotated. When the fastening member feed cylinder  12  is operated to thereby reciprocate the feed pawl  14  together with the feed piston  11  along a feed passage  29 , the feed pawl  14 , in the backward movement thereof, comes in contact with the shaft of the fastening member  28  within the feed passage  29  and is thereby rotated in such a manner to retreat from the feed passage  29 , so that it moves beyond the fastening member  28 ; and, when the feed pawl  14  moves forward, it advances into the feed passage  29  and is engaged with the shaft of the fastening member  28  to thereby feed the fastening member  28 . 
   Here, description will be given below of the subject matter of the invention with reference to  FIGS. 1˜3 . 
     FIG. 1  is a section view of the main portions of the driving machine according to the invention,  FIG. 2  is a perspective view of a filter portion formed in the driving machine, and  FIG. 3  is an enlarged section view of the filter portion of the present driving machine. 
   As shown in  FIG. 1 , between the air passage  19  and return air chamber  6 , there is formed a main body side passage  18  which is used to allow the communication of the compressed air; and, in the main body side passage  18 , there is formed a filter portion  17  which includes a plurality of small holes  20 . This filter portion  17  is formed in such a manner that its projection-shaped portion  17   b  projects within the return air chamber  6  of a housing  26  in the form of a chimney; and, in the vicinity of the upper portion of the projection-shaped portion  17   b , there are opened up the plurality of small holes  20  which are used to allow the air passage  19  to communicate with the filter portion  17  from the main body side passage  18 . 
   The filter portion  17  is made of resin such as plastic, while the small holes  20  opened up in the outer periphery of the upper portion of the filter portion  17  are formed of a thin-film-shaped mesh  17   a . This mesh  17   a  is welded to the filter portion  17  from the inside thereof to thereby form the filter portion  17  as an integral body. Between the filter portion  17  and air passage  19 , there are interposed two or more pieces of packing  16   a ,  16   b  which are used to prevent the compressed air from leaking to the air. The filter portion  17  is mounted in such a manner that it penetrates from the outside of the housing  26  and into the return air chamber  6 , the small holes  20  of the filter portion  17  are opened in the return air chamber  6 , and the filter portion  17  can be separated from the housing  26 . 
   By the way, the housing  26  includes a stepped portion  26   a  which is used to prevent the filter portion  17  from moving into the inside of the housing  26  when the filter portion  17  is mounted from the nose portion  23  side of the housing  26 . Also, even when the filter portion  17  is inserted from the return air chamber  6  side of the housing  26 , in order to prevent the filter portion  17  from being removed due to pressure, there is additionally provided a structure for prevention of removal of the filter portion  17 , for example, a structure for holding the filter portion  17  using 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 trigger  1  is pulled, the cylinder valve  3  on the upper end of the cylinder  5  is opened, the compressed air of the pressure storage chamber  2  pushes down the piston  4  suddenly, and the fastening member within the shooting opening  24  is driven by the leading end of the driver  22 . 
   After the above driving operation, the piston  4  collides with the bumper  8  at the lower-most point thereof, and the remaining surplus energy of the piston  4  is absorbed by the bumper  8 , whereby the piston  4  is caused to stop. When the piston  4  passes through the air hole  5   a , a portion of the compressed air is supplied through the air hole  5   a  and a check valve  50  to the return air chamber  6 . Further, a portion of the compressed air supplied to the return air chamber  6  is stored from the return air chamber  6  through the air passage  19  into the fastening member feed cylinder  12 ; and, this compressed air pushes down the fastening member feed piston  11  sliding within the fastening member feed cylinder  12  to thereby retreat the feed pawl  14  from the shooting opening  24 . 
   Next, when the trigger  1  is released, the piston  4  is moved backward. Specifically, the piston  4  is pushed up to the top dead center thereof by the pressure of the return air chamber  6 , whereby the compressed air existing in the lower chamber of the piston  4  and in the return air chamber  6  is discharged from either a lower exhaust port  21  through a clearance between the leading end of the driver  22  and the piston  4 , or an upper exhaust port  27  through a clearance formed upwardly of the cylinder  5 . Also, simultaneously with this, the air existing within the fastening member feed cylinder  12  is also discharged therefrom. Thus, owing to the force of a return spring  13  which is provided on the back surface of the driving machine, the fastening feed piston  11  and feed pawl  14  existing within the fastening member feed cylinder  12  are returned within the feed passage  29  to feed the fastening member  28  again into the shooting opening  24 , thereby ending  1  driving cycle. 
   When the above-mentioned driving cycle is repeated tens of thousands times, the upper surface of the bumper  8  to absorb the surplus energy is gradually caused to crack, resulting in the formation of such broken pieces  30  as shown in  FIG. 3 . These broken pieces  30  are carried from the return chamber hole  9  into the return air chamber  6  by the force of the compressed air and are going to move from the main body side passage  18  into the air passage  19  which communicates with the fastening member feed cylinder  12 . However, since, between the air passage  19  and the main body side passage  18  that communicates with the return chamber  6  on the main body  7  side, there is interposed the filter portion  17  including a large number of small holes  20  which are made of the mesh  17   a  and are situated in the vicinity of the leading end of the projection-shaped portion  17   b , not only small-size broken pieces  30  but also large-size broken pieces  30  can be prevented from moving into the air passage  19 . 
   Also, even when the broken pieces  30  happen to move into the main body side passage  18  and stick to and cover the small holes  22  of the mesh  17   a  in the leading end of the projection-shaped portion  17   b  of the filter portion  17  entirely, since the projection-shaped portion  17   b  of the filter portion  17  projects in a chimney shape, the broken pieces  30  can be easily diffused due to the force of the compressed air discharged or the broken pieces  30  are easy to slip down in the downward direction within the return air chamber  6  due to the own mass of the broken pieces and are thus easy to accumulate in the lower portion of the return air chamber  6 , thereby eliminating a possibility that the whole of the small holes  20  can be covered completely by the broken pieces  30 . This makes it possible for the filter portion  17  to sufficiently secure an effective section area equal to the passage area. Also, when the filter portion  17  is formed separately from the housing  26 , the filter portion  17  can be taken out from the housing  26  easily, so that the broken pieces  30  sticking to neighboring portion of the upper portion of the filter portion  17  can be cleaned easily. 
   In the above-described embodiment, there is employed a structure in which the filter portion  17  including the small holes  20  is disposed within the air passage  19  to the fastening member feed piston  11  on the return air chamber  6  side of the housing  26 , and the mesh  17   a  is welded to the filter portion  17  to thereby provide an integral body. However, as shown in  FIGS. 4 and 5 , even in another structure in which the filter portion  17  has a chimney-like projection shape similar to the above-mentioned embodiment, small holes  31  are formed in the vicinity of the upper portion of the leading end of the projection-shaped portion  17   b , and the filter portion  17  is formed removably from the housing  26  or integrally with the housing  26 , the broken pieces  30  of the cracked bumper  8  are easy to accumulate on the lower portion of the housing  26 . Therefore, in this structure as well, there can be obtained effects similar to the above-mentioned structure.