Abstract:
A nail gun has a free end  19   a  and central potion of a trigger arm  19  positioned within a trigger  11 , on an upper end  12   a  of a safety portion  12  and at a plunger  17 , respectively. When the trigger  11  is pivoted on its pivot end  16 , pivoting movement of the trigger  11  moves a pivot end  18  of the trigger arm  19  to press the central portion of the trigger arm  19  into contact with the plunger  17  and, with the plunger  17  serving as a fulcrum, to press the free end  19   a  downward against the upper end  12   a  of the safety portion  12 . If downward movement of the safety portion  12  is obstructed when the trigger  11  is pivoted, the upper end  12   a  contacted by the free end  19   a  of the trigger arm  19  serves as a fulcrum around which the trigger arm  19  pivots with movement of the trigger  11 , whereupon the central portion of the trigger arm  19  presses the plunger  17  inward so that an activation switch  10  activates a blade  7  to eject a nail through a nose piece  5.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a nail gun that drives a nail through, for example, the hole of a connection clasp and to a nail gun that can accurately drive nails into a desired drive position. 
     2. Description of the Related Art 
     A variety of different types of clasp fixing nail guns have been proposed. U.S. Pat. No. 5,193,730 discloses a nail gun that separates nails one at a time from a nail band and supplies the nail to a nail injection hole of the nosepiece. The nail tip is protruded from the end of the nosepiece before the nail gun drives the nail. 
     The nail gun further has a safety mechanism with a work-piece contact member, an intermediate lever, and an operation lever. The work-piece contact member extends from the nose of the nail gun to the base of the intermediate lever. When the trigger of the nail gun is pressed, the operation lever moves toward or away from an activation plunger, depending on the position of the work-piece contact member and the intermediate lever. That is, the work-piece contact member is raised into its lowermost position as long as the nose of the nail gun is not pressed against a work piece. If the trigger is pressed at this time, the intermediate lever pivots greatly and guides movement of the operation lever away from the activation plunger. On the other hand, when the nose of the nail gun is pressed against a work piece, the contact member is raised into its upper position. If the trigger is pulled at this time, pivoting movement of the intermediate lever is restricted so that the operation lever moves into contact with the activation plunger, thereby setting off a nail driving operation. In other words, the safety mechanism prevents the nail gun from firing when no work piece is present by changing the pivot path of the operation lever. 
     SUMMARY OF THE PRESENT INVENTION 
     It is conceivable to lengthen the stroke of the work-piece contact member, that is, the distance that the work-piece contact member can move, by increasing the length of the intermediate lever. However, the intermediate lever can only be lengthened within the movement range of the trigger. Therefore, it is difficult to lengthen the stroke of the work-piece contact member. As a result, the lower end of the work-piece contact member must always be positioned fairly near the nail ejection opening, even when the work-piece contact member is at its upper dead center. This makes it difficult to see the nail tip so that it is difficult to position the nail at the precise position where it is to be driven into the work piece. 
     Also, the intermediate lever and the operation lever are provided in a narrow space above the trigger and operate in a fairly complicated manner against urging force of springs. A slight error in component or position dimensions, abrasion caused by friction, or dust, dirt, and the like clinging to components could easily become the cause of misfires. As a result, reliability of the nail gun suffers. 
     It is an objective of the present invention to overcome the above-described problems and provide a nail gun that more easily allows visual confirmation of the nail tip location and that uses a simpler configuration, which improves reliability by helping prevent the danger of misfires. 
     In order to achieve the above-described objective, a nail gun according to the present invention includes a body; a nail ejection portion connected to the body and having a tip formed with a nail ejection hole; a magazine connected to the nail ejection portion, the magazine feeding nails one at a time to the ejection portion; a blade supported in the body capable of reciprocal movement in opposing first and second directions and, when activated, driven in the second direction to the nail ejection portion to strike a nail in the nail ejection portion and to eject the nail through the nail ejection hole; an activation switch having a protruding plunger, the activating switch activating the blade when the plunger is pressed inward; a trigger having a trigger pivot end and a trigger free end, the trigger being supported pivotably on the body at the trigger pivot end; a trigger arm positioned within the trigger, the trigger arm having a trigger-arm pivot end, a central portion, and a trigger-arm free end, the trigger-arm pivot end being pivotably disposed at a position between the plunger and the trigger free end, the central portion being disposed at a position adjacent to the plunger; a safety portion having a first-side end disposed in contact with the trigger-arm free end and a second-side end positioned near the nail ejection hole, the safety portion being supported capable of reciprocal movement in the first and second directions between an upper dead center and a lower dead center; and urging means for urging the safety portion into the upper dead center; wherein when the trigger is pivoted on the trigger pivot end, pivoting movement of the trigger moves the trigger-arm pivot end to press the central portion of the trigger arm into contact with the plunger and, with the plunger serving as a fulcrum, to press the trigger-arm free end in the second direction against the first-side end of the safety portion. 
     With this configuration, a long stroke can be achieved for the safety portion. Therefore, the lower end of the safety portion can be separated from the nail tip in the initial condition, so that whether the nail tip is properly set in the clasp hole can be visually confirmed with ease. That is, the position where nails will be driven into the work piece can be accurately set. 
     Also, only the trigger arm is provided within the trigger and the safety portion is configured from only the upper safety portion and the lower safety portion. Operations are more reliable because the configuration is so simple. 
     If movement of the safety portion in the second direction is obstructed when the trigger is pivoted on the trigger pivot end, then the first-side end of the safety portion contacted by the trigger-arm free end serves as a fulcrum around which the trigger arm pivots with movement of the trigger, whereupon the central portion presses the plunger inward so that the activation switch activates the blade. 
     As a result, a nail driving operation can be reliably performed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the invention will become more apparent from reading the following description of the embodiments taken in connection with the accompanying drawings in which: 
     FIG. 1 is a cross-sectional side view showing a nail gun according to a first embodiment of the present invention; 
     FIG. 2 is a side view showing connected nails used in the nail gun of FIG. 1; 
     FIG. 3 is a cross-sectional view showing details of a safety portion and surrounding components of the nail gun in FIG. 1, while the trigger is not pulled; 
     FIG. 4 is front view showing a cam member of the safety portion; 
     FIG. 5 is a side view of the cam member of FIG. 4; 
     FIG. 6 is a back view of the cam member of FIG. 4; 
     FIG. 7 is a cross-sectional view taken along line VII—VII of FIG. 4; 
     FIG. 8 is a front view of the safety portion; 
     FIG. 9 is a cross-sectional view showing the trigger of the nail gun pulled while the nail gun is pressed against a work piece; 
     FIG. 10 is a cross-sectional view showing a nail driving operation; 
     FIG. 11 is a cross-sectional view showing the trigger of the nail gun pulled while no work piece obstructs downward movement of the safety portion; 
     FIG. 12 is a cross-sectional view showing the cam member pivoted by downward movement of the safety portion in the situation shown in FIG. 11; 
     FIG. 13 is a cross-sectional view showing a lower portion of the safety portion moving upward when pressed against a work piece while the cam member is pivoted as shown in FIG. 12; 
     FIG. 14 is a cross-sectional view showing a safety portion according to a second embodiment of the present invention; 
     FIG. 15 is a cross-sectional view showing disconnection of upper and lower portions of the safety portion of FIG. 14 when the trigger is pulled while nothing obstructs downward movement of the safety portion; and 
     FIG. 16 is a cross-sectional view showing the lower portion of the safety portion of FIG. 14 moving independently upward when pressed against a work piece while upper and lower portions are disconnected as shown in FIG.  15 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Next, a nail gun according to a first embodiment of the present invention will be provided while referring to FIGS. 1 to  13 . To facilitate explanation, the directional terms up, down, front, and rear will be used referring to orientation in which the nail gun is intended to be used and as indicated in FIG.  1 . 
     As shown in FIG. 1, a nail gun  1  includes a nail ejection portion  5 , a magazine  6 , a drive portion  8 , a trigger  11 , and a safety portion  12 . The magazine  6  houses connected nails  3  that are supplied to the nail ejection portion  5 . As shown in FIG. 2, the connected nails  3  are arranged on a single plane, separated by a fixed distance, and connected by a connection band  3   a . Each nail  4  typically has a circular head  4   a  at its upper end, a cylindrical body  4   b , and an acutely pointed tip  4   c . As shown in FIG. 1, the magazine  6  includes a feeder  14  and a feeder spring (not shown). The feeder  14  receives pressure from the feeder spring and feeds the nails  4  to the nail ejection portion  5 , which is formed by a nosepiece  13  of the nail gun  1 . 
     The nail ejection portion  5  is formed at its lower end with a nail ejection hole  5   a . The tip  4   c  of the lead nail  4  within the nail ejection portion  5  protrudes downward out of the nail erection hole  5   a , so that the position of the nail tip  4   c  can be visually confirmed with ease. 
     The drive portion  8  houses a blade  7 . The blade  7  is capable of reciprocal movement in the drive portion  8  to drive nails supplied to the nail ejection portion  5  out from the ejection hole  5   a.    
     The nail gun  1  also includes a handle  9  and an activation switch  10 . The handle  9  is held by the user to support the nail gun  1 . The activation switch  10  is for controlling a nail driving operation of the nail gun  1 . As shown in FIG. 3, the activation switch  10  includes a downward-protruding plunger  17  substantially at its center. The plunger  17  is supported capable of reciprocal movement in the vertical direction. While the plunger  17  is positioned at its lower dead center, the activation switch  10  is maintained OFF, so the nail gun  1  remains in a non-activated condition. However, as the plunger  17  moves from its lower dead center to its upper dead center, the activation switch  10  is turned ON, so that the nail gun  1  starts a nail driving operation. 
     As shown in FIG. 3, the trigger  11  is supported adjacent to the activation switch  10  on a pivot shaft  16  so as to be capable of pivotable movement centered on the pivot shaft  16 . The user uses a finger of the hand he or she uses to hold the handle  9  to pull the trigger  11 . The trigger  11  is provided with a support portion  18  that pivotably supports a trigger arm  19 . The trigger arm  19  is supported in a posture with the central portion in contact with the tip of the plunger  17  and with the other end  19   a  in contact on an upper end  12   a  of the safety portion  12 . 
     The safety portion  12  is supported capable of reciprocal movement, in parallel with the reciprocal movement direction of the blade  7 , between upper and lower dead centers as guided by a nose  13 , which configures the nail ejection portion  5 . The safety portion  12  is configured from an upper safety portion  20 , a cam member  21 , and a lower safety portion  22 . 
     The upper safety portion  20  has a substantial reversed L-shape, and includes the upper end  12   a , a vertical section  20   c , and a horizontal section  20   d . The upper end  12   a  is disposed in contact with the underside of the free end  19   a  of the trigger arm  19 . A spring  15  is disposed beneath the horizontal section  20   d  for constantly urging the safety portion  12  toward its upper dead center. 
     The lower safety portion  22  is supported capable of reciprocal movement in parallel with the reciprocal movement direction of the blade  7 , as guided by pins  23 ,  24  provided in the nose  13 . The lower safety portion  22  includes a lower end  12   b  and an engagement recess portion  22   a . The lower end  12   b  is located near the ejection opening  5   a  of the nail ejection portion  5 . When the safety portion  12  is in its upper dead center following the urging of the spring  15 , the lower end  12   b  is retracted above the nail tip  4   c  as shown in FIG.  3 . On the other hand, when the safety portion  12  is in its lower dead center, the lower end  12   b  protrudes beyond the nail tip  4   c  of the nail  4  in the nail ejection portion  5  as shown in FIG.  11 . The engagement recess portion  22   a  is provided in the upper portion of the lower safety portion  22  and includes an upper plate  22   b  and a lower plate  22   c , wherein the upper plate  22   b  protrudes further than the lower plate  22   c . A spring  25  is provided for constantly urging the lower safety portion  22  downward when the nail gun  1  is oriented as in the drawings. Said differently, when the nail gun  1  is oriented for driving a nail upward, for example, into a ceiling fixture, the spring  25  prevents the lower safety portion  22  from sagging downward. 
     The cam member  21  is pivotably supported on a shaft  20   a  provided to a lower portion of the upper safety portion  20 . As shown in FIGS. 4 to  8 , the car portion  21  includes a lower end  21   a  and two guide protrusions  21   b . As shown in FIG. 3, the lower end  21   a  fits in the engagement recess portion  22   a  of the lower safety portion  22 . As shown in FIG. 4, the guide protrusions  21   b  are provided symmetrically on either side of the cam portion  21 . As shown in FIGS. 1 and 12, the guide protrusions  21   b  fit in guide grooves  5   b  provided in the side surfaces of the nail ejection portion  5 . The guide grooves  5   b  are formed in a diagonally extending shape, so that when the guide protrusions  21   b  move downward in the guide grooves  5   b , the cam member  21  separates from the engagement recess portion  22   a  as shown in FIG.  11 . 
     Next, an explanation will be provided for operation of the nail gun  1 . In this example, the nail gun  1  is used to fix in place a connection clasp  2  shown in FIG.  9 . The connection clasp  3  is preformed with a hole  2   a . First, the nail tip  4   c  protruding from the nail ejection hole  5   a  is set directly into the hole  2   a  of the connection clasp  2 . Because the nail tip  4   c  protrudes from the nail ejection hole  5   a , the nail tip  4   c  can be easily aligned with the clasp hole  2   a . Once the nail tip  4   c  is set, the lower end  12   b  of the lower safety portion  22  presses against an upper surface  2   b  of the clasp  2 , so the safety portion  12  is prevented from moving downward. 
     Next, the user pulls the trigger  11  of the nail gun  1 . When the user pulls the trigger  11 , the trigger  11  pivots centered on the pivot shaft  16  toward the activation switch  10 , that is, from the orientation shown in FIG. 1 to the orientation shown in FIG.  9 . The support portion  18  of the trigger arm  19  moves upward so that the central portion of the trigger arm  19  abuts against the tip of the plunger  17  of the activation switch  10 . As a result, the plunger  17  serves as a fulcrum so that force from the support portion  18  presses the other end  19   a  of the trigger arm  19  down against the upper end  12   a  of the safety portion  12 . However, the upper end  12   a  remains in place because the upper surface  2   b  of the clasp  2  prevents the safety portion  12  from moving. Therefore, the upper end  12   a  serves as a fulcrum so that force from the support portion  18  presses the central portion of the trigger arm  19  upward against the plunger  17  when the trigger  11  is pulled. When the plunger  17  is pressed in, the activation switch  10  is turned ON, thereby starting operation of the nail gun  1  so that the nail  4  in the nail ejection portion  5  is driven downward as shown in FIG.  10 . 
     The above explanation is for the situation wherein the trigger  11  is pulled after the nail tip  4   c  protruding from the nail ejection hole  5   a  was set in the clasp hole  2   a . Next, with reference to FIGS. 11 to  13 , an explanation will be provided for operations performed when the nail tip  4   c  is not set in the clasp hole  2   a , that is, when the nail ejection port is not located in abutment with a work piece. 
     In the same manner as described above, when the trigger  11  is pulled in this case, the support portion  18  of the trigger arm  19  moves so that the central portion of the trigger arm  19  abuts against the tip of the plunger  17 . Accordingly, the tip of the plunger  17  functions as a fulcrum so that force from the support portion  18  presses the other tip  19   a  of the trigger arm  19  down against the upper end  12   a . However, because there is no work piece to prevent downward movement of the safety portion  12  in this case, the safety portion  12  moves from its upper dead center to its lower dead center against the urging force of the spring  15 . The plunger  17  remains positioned at its lower dead center so the activation switch  10  does not turn ON. 
     As the safety portion  12  moves from its upper dead center to its lower dead center, the cam member  21  moves downward with the upper safety portion  20 . As shown in FIG. 12, the two guide protrusions  21   b  provided on the side surface of the cam member  21  are fitted in the guide grooves  5   b  provided on the outer side of the nail ejection portion  5 . Therefore, the cam member  21  follows the slanted shape of the guide grooves  5   b  in association with downward movement of the guide protrusions  21   b  in the guide grooves  5   b  and pivots on the pivot shaft  20   a . As shown in FIG. 11, when the safety portion  12  moves downward to near its lower dead center, the cam member  21  separates from the lower safety portion  22 . Described in more detail, the lower end  21   a  of the cam member  21  pulls away from the lower plate  22   c  of the engagement recess portion  22   a , but remains in contact with the upper plate  22   b . The downward urging force of the spring  25  urges the upper plate  22   b  into abutment with the lower end  21   a  of the cam member  21 . At this time, the lower end  12   b  protrudes beyond the nail tip  4   c . In this situation, if the lower end  12   b  is pressed against a work piece, or for some other reason the lower safety portion  22  is raised upward from its lower dead center, then all that will happen is that as shown in FIG. 13 the lower safety portion  22  will move upward against the urging force of the spring  25 . That is, neither the cam member  21  nor the upper safety portion  20  will move upward. Accordingly, activation switch  10  will not be turned ON, because the trigger arm  19  will not be raised upward. 
     According to the present embodiment, no other components besides the trigger arm  19  are provided within the trigger  11  and supported pivotably on the trigger  11 . Moreover, when the safety portion  12  can move into its lower dead center without obstruction, the plunger  17  serves as a fulcrum when the other tip  19   a  of the trigger arm  19  presses the upper safety portion  12   a  down toward its lower dead center. With this configuration the safety portion  12  can have a long stroke, that is, the safety portion  12  moves a long distance from its upper dead center into its lower dead center. Therefore, the lower end  12   b  of the safety portion  12  can be raised up further above the nail tip  4   c , thereby making it easier to visually confirm the position of the nail tip  4   c  so that the nail will be driven into the work piece with greater positional accuracy. 
     Also, because the trigger arm  19  pivots with the tip of the plunger  17  serving as a fulcrum, the force at which the safety portion  12  can be pressed downward can be increased. As a result, the following effects can be achieved. It will be possible to move the safety portions  20 ,  22  downward, even if the safety portions  20 ,  22  become difficult to move downward because dirt and the like cling to the safety portions  20 ,  22 , the cam member  21 , or other components. This enhances reliability of the nail gun. Also, the safety portions  20 ,  22  can be reliably lowered, even if the load on the spring  15 , which is for supporting the safety portions  20 ,  22  in the upper dead center, is increased because the weight of the safety portions  20 ,  22  is increased for some reason, for example to increase the strength of, or to lengthen, the safety portions  20 ,  22 . 
     Next, a second embodiment will be explained while referring to FIGS. 14 to  16 . According to the second embodiment, a safety portion  120  includes an upper safety portion  200 , a lower safety portion  220 , and a connector  30 . The upper safety portion  200  and the lower safety portion  220  are formed with holes  200   e  and  220   e , respectively The connector  30  is slidably engaged in the holes  200   e ,  220   e , thereby connecting the safety portions  200 ,  220  together. The connector  30  includes pins  31  on its inside tip. Downward slanting grooves  5   e  are formed in the inner surfaces of the nail ejection portion  5 . The pins  31  are fitted in the grooves  5   e.    
     When the safety portion  120  is in its upper dead center as shown in FIG. 14, the safety portions  200 ,  220  are connected together by the connector  30 , and so move vertically in an integral manner. However, when the lower safety portion  220  moves downward without obstruction, the pin  31  slides inward following the guide groove  5   e . Once the safety portions  200 ,  220  move downward by a predetermined amount or more, then as shown in FIG. 15 the connector  30  pulls out of the hole  220   e  of the lower safety portion  220 . As a result, there is no danger that the nail gun will fire. Also, even if after this the lower safety portion  220  is raised upward for some reason, then as shown in FIG. 16 the lower safety portion  220  alone will merely move vertically. Again, there is no danger that the nail gun will fire.