Abstract:
The present invention refers to a dry firing prevention device, especially for use in a nail gun with a drawer type magazine, in which the main body of the nail gun is equipped with a safety apparatus and a dry firing prevention device near a trigger. The dry firing prevention device is disposed on the magazine. When a nail pusher pushes nails until where last few nails are left, the nail pusher will contact with one end of the dry firing prevention device and the other end of the dry firing prevention device blocks the safety apparatus, so that the safety apparatus retains in a safety status to prevent the nail gun from dry firing, so as to prolong the lifetime of the nail gun.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to the field of nail guns, and more particularly to a dry firing prevention device for use in nail guns with drawer type magazines. 
   BACKGROUND OF THE INVENTION 
   Conventional depth adjusting devices of nail guns are generally installed inside the safety devices, for example, U.S. Pat. No. 6,170,729, U.S. Pat. No. 6,427,896 and US 2003/0019901 disclose that the adjusting devices and the safety devices are disposed on the outside of the barrels. The addition of other adjusting devices makes the whole structures more complicated and limited in stabilization. Besides, it is more inconvenient to make adjustment because of its vicinity to the muzzle of the barrel. 
   Such structure has shortcomings, such as unstable structure, inconvenience for use and complicated manufacture. Because the safety device is assembled by pieces, an adjustment assembly is additionally attached in the middle thereof, which will cause the safety device to shake while the adjustment assembly acts, so as to make the structure unstable and unable to locate precisely. Besides, the adjustment assembly is near the muzzle, it is unable to make an adjustment by one hand that presses the trigger while use. If it needs to adjust the depth of nailing frequently, which is inconvenient for use. Moreover, the connection between the adjustment assembly, the safety device and the trigger uses corresponding connection structure, it needs to design the corresponding connection structure individually for application of different safety devices and triggers, which is complicate to manufacture. 
   As for the shortcomings mentioned above, the inventor has a TW Appl. No. 93133904 adjustable safety device approved, which discloses that a main body of a nail gun is equipped with an adjusting assembly and a moving assembly between a trigger and a magazine. One end of an acting piece of the adjusting assembly is connected with the trigger. The acting piece is connected with a supporting piece, and the acting piece and one end of the supporting piece are coupled with a moving piece of the moving assembly. Meanwhile, the moving piece is connected with one end of an interlocking assembly of a safety device via a compressing piece. When adjusting the supporting piece, the distance between the acting piece and the moving piece can be controlled precisely, so as to precisely adjust the depth between the actuation point of the safety device and the muzzle. However this case does not consider that the nail gun is still dry firing while the nail is insufficient, which causes the damage of the structure of the nail gun and the firing device. 
   SUMMARY OF THE INVENTION 
   The objective of the present invention is to provide a dry firing prevention device for use with a nail gun with a drawer type magazine, which is equipped with a safety apparatus and a dry firing prevention device between a trigger and a fixed magazine, wherein the dry firing prevention device has an interlocking piece pivotally connected with the magazine, one end of the interlocking piece is pushed by a nail pusher and the other end is inserted into the safety apparatus or the trigger, so that the nail gun will stop firing while the nail is insufficient, so as to protect the driving device and the inner structure of the nail gun from damage. 
   The other objective of the present invention is to provide a safety apparatus that is disposed between a trigger and a magazine, by cooperating with the dry firing prevention device, the safety apparatus is simplified and the depth between an actuation point and a muzzle is precisely adjusted, in addition, it is easy to operate the trigger and the adjusting assembly by one hand so as to promote the convenience. 
   Another objective of the present invention is to provide a structure that is simplified and stable. Because the components of the safety apparatus are all formed as one-piece structure and connect each other, which does not affect the structure of the safety apparatus, so as to improve the stabilization of the whole structure of the nail gun. Moreover, the adjusting assembly is near the trigger, so that it can use one hand that press the trigger to adjust the adjusting piece of the adjusting assembly, while it needs to adjust the depth of nailing frequently, which is convenient for use. In addition, the pushing part of the interlocking piece of the dry firing prevention device is able to stop the trigger to fire while the nail is insufficient, so as to protect the driving device and the inner structure of the nail gun from damage, thus, the lifetime of the nail gun can be prolonged. Because the safety apparatus and the dry firing prevention device are all formed as one-piece structure and use elements to simplify the structure, so as to simplify the maintenance and manufacture of the nail gun, then the objective of convenience of maintenance and low cost of manufacture are achieved. 
   The present invention will become more obvious from the following description when taken in connection with the accompanying drawings that show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the present invention; 
       FIG. 2  is a perspective view of the assembly of the present invention; 
       FIG. 3  is an exploded view of the present invention; 
       FIG. 4  is a plan view showing the motion of the present invention; 
       FIG. 5  is a plan view showing the status of use of the present invention; 
       FIG. 6  is a flow chart of the present invention; and 
       FIG. 7  is a plan view of another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the present invention refers to a typical nail gun, a main body A of the nail gun is equipped with a safety apparatus D and a dry firing prevention device E between a trigger B and a fixed magazine C. The safety apparatus D includes an adjusting assembly  10  that is disposed near the trigger B and is interlocked by the dry firing prevention device E. The dry firing prevention device E is disposed on a locking area C 1  of the fixed magazine C near the trigger B. With the cooperation of the trigger B and the safety apparatus D together with the dry firing prevention device E, when a nail pusher C 3  inside a removable nail loading assembly C 2  disposed on one side of the fixed magazine C pushes the nails until where last few nails are left, on end of the dry firing prevention device E props against the trigger B so that the trigger B is unable to be pressed to fire the nail. As a result, the inner structure of the nail gun and the firing device can be protected from damage. 
   Referring to  FIGS. 2 and 3 , the fixed magazine C includes a locking area C 1 , a removable nail loading assembly C 2  and a nail pusher C 3 . The locking area C 1  is equipped with a threaded hole of fixing part C 10  and an engaging hole of receiving part C 11  for fixing the dry firing prevention device E. The removable nail loading assembly C 2  urges elastically the nail pusher C 3  and is engaged with the fixed magazine C. 
   The adjusting assembly  10  of the safety apparatus D includes an acting piece  11 , an adjusting piece  12 , a safety piece  13  and a spring of elastic piece  14 . The acting piece  11  has a cylindrical threaded locking part  110  with thread inside for receiving the adjusting piece  12 , two lateral setting parts  111  in the shape of triangle for engaging with one end of the dry firing prevention device E, an inserting end  112  that is disposed at the other end from the setting parts  111  and cut in the center for insertion of the elastic piece  14 , and a C-shaped penetrating part  113  disposed between the inserting part  112  and the threaded locking part  110 . The acting piece  11  is locked in position near the trigger B by a fastener  15  received through the penetrating part  113 . 
   The adjusting piece  12  includes an adjusting element  120 , a threaded part  121  and a locking part  122 . The adjusting element  120  is a round gear wheel, in which the threaded part  121  is installed in the center. The location of the adjusting element  120  can be adjusted with cooperation of the threaded part  121 . The threaded part  121  would match in thread with the threaded locking part  110  of the acting piece  11 . The locking part  122  that has surrounding groove would penetrate through the safety piece  13 . 
   The safety piece  13  is unitarily formed in the shape of L, which has a round aperture  130  disposed on the top end thereof for receiving the locking part  122  of the adjusting piece  12  that is locked by a C-shaped locking element  16 . 
   The dry firing prevention device E, which has an interlocking piece  20  that is unitarily formed in the shape of a dolphin, is pivotally connected to the fixing part C 10  inside the locking area C 1  of the fixed magazine C. The interlocking piece  20  includes a hooking part  21 , a retaining part  22 , a pushing part  23  and a protruding part  24 . The hooking part  21  is a lateral plate and able to hook with one of the setting parts  111  of the adjusting assembly  10 . The retaining part  22  is propped against the fixed magazine C to retain the position of releasing the adjusting assembly  10 . The pushing part  23 , which is a lateral plate, is inserted into the receiving part C 11  of the fixed magazine C and able to be pushed by the nail pusher C 3 . The protruding part  24  is inserted into a spring of elastic element  25 , which is compressed against the fixed magazine C to enable the interlocking piece  20  to have a prestressing force, so as to retain the position of releasing the adjusting assembly  10 . 
   Referring to  FIGS. 4 and 5 , an operator places the safety apparatus D against a work object and presses the trigger B to drive the nails inside the fixed magazine C into the work object. Due to the nail pusher C 3  urging the nails toward the barrel of the nail gun, when the nails inside the fixed magazine C are getting low, the pushing part  23  of the interlocking piece  20  of the dry firing prevention device E would be pushed by the nail pusher C 3  making the hooking part  21  to hook on the setting part  111  of the adjusting assembly  10 . As a result, the adjusting assembly  10  is unable to move namely the safety piece  13  is unable to push back so that the trigger B is unable to be pressed and fire the nail. The operator has to open the removable nail loading assembly C 2  on the fixed magazine C to load nails, and then the nail pusher C 3  is away from the pushing part  23  of the interlocking piece  20 . The adjusting assembly  10  is returned to the normal position by means of the elasticity of the elastic element  25  mounted on the protruding part  24  pushing the hooking part  21  of the interlocking piece  20  away from the setting part  111  of the acting piece  11 . When the nail gun is placed against the work object, the safety apparatus D would be pushed back and the adjusting assembly  10  would be not in the position of blocking the trigger B, then the trigger B can be pressed and fire the nail. 
   Referring to  FIG. 6 , the dry firing prevention flow chart  40  depicts a procedure as follows. 
   Loading  41 : the operator opens the removable nail loading assembly C 2  and loads nails therein, then pushes the removable nail loading assembly C 2  back to the fixed magazine C, the nails are urged by the nail pusher C 3 . 
   Adjusting  42 : the operator places the safety apparatus D against a work object by means of the safety piece  13  of the adjusting assembly  10  of the safety apparatus D pushing the work object, and then adjusts the adjusting piece  12  to the need depth of the work object. 
   Firing  43 : the operator presses the trigger B continuing to drive the nails out of the fixed magazine C into the work object. 
   Dry firing prevention  44 : when the nails inside the fixed magazine C are getting low, the nail pusher C 3  on the removable nail loading assembly C 2  urges the pushing part  23  of the interlocking piece  20  that is pivotally connected to the locking area C 1  of the fixed magazine C to cause the hooking part  21  to hook on the setting part  111  of the adjusting assembly  10 , so that the trigger B is unable to be pressed and the nail gun will be protected from dry firing. 
   Reloading  45 : the operator pulls the removable nail loading assembly C 2  together with the nail pusher C 3  out of the fixed magazine C and reloads nails, and then pushes the removable nail loading assembly C 2  together with the nail pusher C 3  back to the fixed magazine C to make the fixed magazine C full with nails. 
   Continue firing  46 : the operator can readjust and reuse the nail gun. 
   Referring to  FIG. 7 , which is another embodiment of the prevent invention. A main body A of a nail gun is equipped with a dry firing prevention device E between a trigger B and a fixed magazine C. The trigger B includes a pressing part B 1  that is a device that can be activated by fingers and a propping part B 2  that is able to prop against the dry firing prevention device E. The dry firing prevention device E is disposed on a locking area C 1  of the fixed magazine C near the trigger B. With the cooperation of the propping part B 2  of the trigger B and the dry firing prevention device E on the locking area C 1 , when a nail pusher C 3  inside the fixed magazine C pushes the nails until where last few nails are left, on end of the dry firing prevention device E props against the propping part B 2  of the trigger B, so that the pressing part B 1  of the trigger B is unable to be pressed to fire the nail. As a result, the inner structure of the nail gun and the firing device can be protected from damage. 
   The fixed components, nails and the firing device are all conventional mechanisms and instruments, so that further description is superfluous. 
   While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.