Patent Publication Number: US-8118203-B2

Title: Hammer-drive powder-actuated tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 098207118, filed on Apr. 28, 2009. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a hammer-drive powder-actuated tool, and more particularly to a hammer-drive powder-actuated tool that has a high success rate in ignition of a primer and that is safe to use. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional hammer-drive powder-actuated tool  1  includes a tubular tool body  11 , an inner tube  12  movable forwardly and rearwardly within the tool body  11 , a sleeve  13  connected to a rear end of the inner tube  12  and formed with an accommodating chamber  131  for receiving a powder cartridge (not shown), a piston  14  movable forwardly and rearwardly within the inner tube  12 , and a firing device  15 . 
     The firing device  15  includes a pin holder  151  disposed within the tool body  11  and abutting against a rear end of the sleeve  13 , a firing pin  152  extending into the pin holder  151 , a coiled compression spring  153  sleeved on the firing pin  152  and abutting against the pin holder  151 , a nut  154  engaging an externally threaded rear end of the firing pin  152  and abutting against a rear end  157  of the coiled compression spring  153 , and a positioning pin  158  extending through the nut  154  and the externally threaded rear end of the firing pin  152  to fix the nut  154  relative to the firing pin  152 . The pin holder  151  has a front end formed with a cavity  156 . The firing pin  152  has a head  155  disposed within the cavity  156 . 
     During use, a hammer (not shown) is operated to strike the externally threaded rear end of the firing pin  152  to move the head  155  of the firing pin  152  into contact with the powder cartridge so as to ignite the powder cartridge to thereby drive forward movement of the piston  14 . 
     The abovementioned conventional hammer-drive powder-actuated tool l  1  suffers from the following disadvantages:
     (1) The head  155  of the firing pin  152  has a diameter much larger than that of the rear end of the powder cartridge. As such, when the powder cartridge is stricken by the firing pin  152 , if the central axis of the firing pin  152  is inclined relative to that of the powder cartridge, misfire may occur.   (2) To prevent accidental removal of the powder cartridge from the chamber  131  when the tool  1  is in an upright state such that the cartridge is disposed above the firing pin  152 , a reed spring  159  is disposed on a front end of the pin holder  151  and between the head  155  of the firing pin  152  and the powder cartridge. In case of accidental dropping of the tool  1 , however, the powder cartridge may hit the reed spring  159  by virtue of the gravity of the inner tube  12  and the sleeve  13  to result in ignition of a primer of the powder cartridge, thereby affecting safety during use.   

     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a hammer-drive powder-actuated tool that has a high success rate in ignition of a primer. 
     Another object of this invention is to provide a hammer-drive powder-actuated tool that is safe to use. 
     According to this invention, a hammer-drive powder-actuated tool is adapted for activating ignition of a rimfire cartridge. The rimfire cartridge has a rear end and an annular primer disposed at the rear end of the rimfire cartridge. The tool includes a hollow tool body extending along a front-to-rear direction; and a firing device disposed within a rear end portion of the tool body. The firing device includes a pin holder and a firing pin. The pin holder has a through hole extending along the front-to-rear direction. The firing pin is movable forwardly and rearwardly relative to the pin holder, and has a firing end portion that is disposed at a front end thereof and that extends into the through hole in the pin holder, and a central axis adapted to be aligned with that of the rimfire cartridge along the front-to-rear direction, a front end of the firing end portion of the firing pin having a diameter adapted to be larger than an inner diameter of the annular primer and smaller than an outer diameter of the annular primer. 
     Preferably, the through hole in the pin holder has a front hole section. The front hole section has a front distal end, a rear distal end, and a diameter that reduces gradually from the front distal end to the rear distal end so that the front section has a minimum diameter at the rear distal end. The minimum diameter of the front hole section is adapted to be smaller than that of the rear end of the rimfire cartridge. 
     Preferably, the front section of the through hole in the pin holder further has a maximum diameter at the front distal end, which is adapted to be slightly larger than that of the rear end of the rimfire cartridge. 
     Preferably, the firing end portion of the firing pin has a large-diameter section and a small-diameter section disposed in front of the large-diameter section, having a diameter smaller than that of the large-diameter section, and adapted to be movable into contact with the annular primer of the rimfire cartridge. 
     Preferably, the through hole in the pin holder further has a small-diameter hole section disposed behind and connected to the front hole section and having a diameter the same as that of the rear distal end of the front hole section and smaller than the diameter of the large-diameter section of the firing end portion of the firing pin, and a large-diameter hole section disposed behind and connected to the small-diameter hole section and having a diameter larger than that of the small-diameter hole section. The large-diameter section of the firing end portion of the firing pin is disposed within the large-diameter hole section of the through hole in the pin holder. The small-diameter section of the firing end portion of the firing pin is disposed within the large-diameter and small-diameter hole sections of the through hole in the pin holder. 
     Preferably, the firing pin further has a rod portion disposed behind and formed integrally with the firing end portion and extending along the front-to-rear direction, a head disposed behind and formed integrally with the rod portion and adapted to permit application of an external force thereto, and a shoulder defined between the firing end portion and the rod portion. The firing device further includes a retaining member sleeved on the rod portion of the firing pin, and a resilient member disposed between the retaining member and the head of the firing pin for biasing the retaining member to abut against the shoulder of the firing pin and a rear end of the pin holder, thereby allowing the firing end portion of the firing pin to be spaced apart from the rear end of the rimfire cartridge by a predetermined distance when no external force is applied to the firing pin. 
     Preferably, the tool body has an annular inner wall surface, and the retaining member is generally U-shaped, and has an outer periphery in contact with the annular inner wall surface of the tool body. 
     Preferably, the retaining member is configured as a generally U-shaped plate. 
     Preferably, the resilient member is configured as a coiled compression spring. 
     Preferably, the firing device further includes a rigid washer sleeved on the rod portion of the firing pin between the retaining member and the resilient member. 
     Preferably, the tool body includes a tubular portion having a rear end portion, and a grip portion having a front end portion sleeved fixedly on the rear end portion of the tubular portion. The tubular portion has a first stop flange extending radially and inwardly from an intermediate portion of the tubular portion, and a second stop flange extending radially and inwardly from a rear end of the tubular portion. The pin holder has a small-diameter holder portion and a large-diameter holder portion disposed behind and connected to the small-diameter holder portion and having an outer diameter larger than that of the small-diameter holder portion. The large-diameter holder portion has a front end surface abutting against the first stop flange of the tool body, and a rear end surface abutting against the retaining member. The washer has a front side surface abutting against the retaining member, and a rear side surface abutting against the second stop flange of the tool body. As such, the pin holder, the retaining member, and the washer are fixed within the tool body. 
     Since the diameter of the front end of the firing end portion of the firing pin is larger than the inner diameter of the annular primer and smaller than the outer diameter of the annular primer, the firing end portion of the firing pin can strike the primer of the rimfire cartridge even when the central axis of the firing pin is somewhat misaligned or inclined from that of the rimfire cartridge during striking of the firing pin against the rimfire cartridge. As a result, the success rate in ignition of the primer of the rimfire cartridge can be increased significantly. 
     Furthermore, since the minimum diameter of the front hole section is adapted to be smaller than that of the rear end of the rimfire cartridge, accidental dropping of the rimfire cartridge and accidental firing of the tool can be prevented. Thus, the tool is safe to use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of this invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a conventional hammer-drive powder-actuated tool; 
         FIG. 2  is an assembled perspective view of the first preferred embodiment of a hammer-drive powder-actuated tool according to this invention; 
         FIG. 3  is a fragmentary exploded perspective view of the first preferred embodiment, illustrating a firing device; 
         FIG. 4  is a sectional view of the first preferred embodiment; 
         FIG. 5  is a fragmentary sectional view of the first preferred embodiment, illustrating a firing pin in a non-striking position; 
         FIG. 6  is a rear view of a rimfire cartridge of the first preferred embodiment; 
         FIG. 7  is a fragmentary sectional view of the first preferred embodiment, illustrating the firing pin in a striking position; and 
         FIG. 8  is a fragmentary sectional view of the second preferred embodiment of a hammer-drive powder-actuated tool according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the present invention is described in greater detail in connection with the preferred embodiments, it should be noted that similar elements and structures are designated by like reference numerals throughout the entire disclosure. 
     Referring to  FIGS. 2 ,  3 , and  4 , the first preferred embodiment of a hammer-drive powder-actuated tool  2  according to this invention is used for activating ignition of a rimfire cartridge  9 . The tool  2  includes a hollow tool body  21  extending along a front-to-rear direction, an inner tube  22  movable forwardly and rearwardly within the tool body  21 , a sleeve  23  disposed within and engaging threadably a rear end portion of the inner tube  21  and having a rear end formed with an accommodating chamber  231  for receiving the rimfire cartridge  9 , a piston  24  movable forwardly and rearwardly within the inner tube  22  and driven by the rimfire cartridge  9  when the rimfire cartridge  9  is ignited, and a firing device  3  disposed within a rear end portion of the tool body  21  for igniting the rimfire cartridge  9  within the chamber  231  in the sleeve  23 . 
     With further reference to  FIGS. 5 and 6 , the rimfire cartridge  9  has a rear end  91  and an annular primer  92  disposed at the rear end  91 . 
     The tool body  21  has a tubular portion  211 , and a grip portion  212  having a front end portion sleeved fixedly on a rear end portion of the tubular portion  211 . The tubular portion  211  has a first stop flange  213  extending radially and inwardly from an intermediate portion of the tubular portion  211 , and a second stop flange  214  extending radially and inwardly from a rear end of the tubular portion  211 . In this embodiment, the second stop flange  214  is formed by a rolling process. 
     The firing device  3  includes a pin holder  4 , a firing pin  5 , a retaining member  6 , a rigid washer  7 , and a resilient member  8 . 
     The pin holder  4  is disposed behind the sleeve  23 , and has a small-diameter holder portion  43 , a large-diameter holder portion  44  disposed behind and connected to the small-diameter holder portion  43  to define a shoulder  42  therebetween, and a through hole  41  formed through the large-diameter and small-diameter holder portions  44 ,  43  and extending along the front-to-rear direction. The large-diameter holder portion  44  has a front end surface abutting against the first stop flange  213  of the tool body  21 . The through hole  41  has a front hole section  413 , a small-diameter hole section  412 , and a large-diameter hole section  411 . The front hole section  413  has a diameter that reduces gradually from a front distal end thereof to a rear distal end thereof. As such, the front hole section  413  has a maximum diameter at the front distal end thereof, and a minimum diameter at the rear distal end thereof. The maximum diameter of the front hole section  413  is slightly larger than the diameter of the rear end  91  of the rimfire cartridge  9 . The minimum diameter of the front hole section  413  is smaller than that diameter of the rear end  91  of the rimfire cartridge  9 . 
     The small-diameter hole section  412  is disposed behind and connected to the front hole section  413 , and has a diameter the same as that of the rear distal end of the front hole section  413 . The large-diameter hole section  411  is disposed behind and connected to the small-diameter hole section  412 , and has a diameter larger than that of the small-diameter hole section  412 . The through hole  41  can be formed easily by a lathe, thereby reducing the manufacturing costs of the pin holder  4 . 
     The firing pin  5  is movable forwardly and rearwardly relative to the pin holder  5 , and has a firing end portion  53  that is disposed at a front end thereof, that extends into the through hole  41  in the pin holder  4 , and that is movable forwardly into contact with the annular primer  92  of the rimfire cartridge  9 . The firing pin  5  further has a rod portion  52  disposed behind and connected to the firing end portion  53  and extending along the front-to-rear direction, a head  51  disposed behind and connected to the rod portion  52  and permitting application of an external force thereto by a hammer (not shown), and a shoulder  54  defined between the firing end portion  53  and the rod portion  52 . In this embodiment, the firing end portion  53 , the rod portion  52 , and the head  51  are integrally formed with each other. The head  51  has a diameter larger than those of the rod portion  52  and the firing end portion  53 . 
     The central axis of the firing pin  5  is aligned with that of the rimfire cartridge  9  along the front-to-rear direction. A front end of the firing end portion  53  has a diameter that is larger than the inner diameter of the annular primer  92  of the rimfire cartridge  9  and smaller than the outer diameter of the annular primer  92  of the rimfire cartridge  9 . The firing end portion  53  of the firing pin  5  has a large-diameter section  531  and a small-diameter section  532  disposed in front of the large-diameter section  531 , having a diameter smaller than that of the large-diameter section  531 , and movable in contact with the annular primer  92  of the rimfire cartridge  9 . 
     The firing end portion  53  of the firing pin  5  has an axial length smaller than that of the through hole  41  in the pin holder  4 . The large-diameter section  531  of the firing end portion  53  of the firing pin  5  has an axial length smaller than that of the large-diameter hole section  411  of the through hole  41  in the pin holder  4  so as to permit the large-diameter section  531  of the firing end portion  53  to be received within the large-diameter hole section  411 . The large-diameter section  531  of the firing end portion  53  of the firing pin  5  has a diameter larger than that of the small-diameter hole section  412  of the through hole  41  in the pin holder  4  so as to prevent movement of the large-diameter section  531  into the small-diameter hole section  412 . A portion of the small-diameter section  532  of the firing pin  5  is disposed within the large-diameter hole section  411  of the through hole  41  in the pin holder  4 . The remaining portion of the small-diameter section  532  of the firing pin  5  is disposed within the small-diameter hole section  412  of the through hole  41 . As such, the travel distance of the firing pin  5  is limited. 
     The rod portion  52  of the firing pin  5  has a first section  521  having a rear end connected to the head  51 , and a second section  522  connected between the first section  521  and the firing end portion  53  and having a diameter smaller than that of the first section  521 . In this embodiment, the second section  522  has a diameter smaller than that of the large-diameter section  531  of the firing end portion  53  to form the shoulder  54  between the second section  522  and the large-diameter section  531 . The first section  521  and the large-diameter section  531  have the same diameter such that an annular groove is formed therebetween. The annular groove can be formed easily by lathing. 
     The retaining member  6  is sleeved on the rod portion  52  of the firing pin  5 , and has a front side surface abutting against the large-diameter holder portion  44  of the pin holder  4  and the shoulder  54  of the firing pin  5 . In this embodiment, the retaining member  6  is configured as a generally U-shaped plate, and a radially extending slot  61  having an open end  611 , a closed end  612 , and a width (I) approximate to the diameter of the second section  522  of the rod portion  52  of the firing pin  5  so as to prevent removal of the retaining member  6  from the firing pin  5  along the front-to-rear direction. 
     The washer  7  is sleeved on the rod portion  52  of the firing pin  5  between the retaining member  6  and the resilient member  8 . The washer  7  has a front side surface abutting against the retaining member  6 , and a rear side surface abutting against the second stop flange  214  of the tool body  21 . Since the large-diameter holder portion  44  of the pin holder  4  is disposed between and abuts against the first stop flange  213  of the tool body  21  and the retaining member  6 , and since the washer  7  is disposed between and abuts against the second stop flange  214  of the tool body  21  and the retaining member  6 , the pin holder  4 , the retaining member  6 , and the washer  7  are fixed within the tool body  21 . The washer  7  has an inner diameter larger than the diameter of the large-diameter section  531  of the firing end portion  53  of the firing pin  5 , and hence can be sleeved onto the rod portion  52  of the firing pin  5  via the front end of the firing pin  5 . 
     The resilient member  8  is configured as a coiled compression spring, is sleeved on the rod portion  52  of the firing pin  5 , and has a front end abutting against the retaining member  6 , and a rear end abutting against the head  51  of the firing pin  5 . As such, the firing pin  5  is biased by the resilient member  8  to move rearwardly away from the rimfire cartridge  9  to thereby allow the firing end portion  53  of the firing pin  5  to be spaced apart from the rear end  91  of the rimfire cartridge  9  by a predetermined distance when no external force is applied to the firing pin  5 . 
     During assembly, the resilient member  8  is first sleeved onto the rod portion  52  of the firing pin  5  via the front end of the firing pin  5  to allow the rear end of the resilient member  8  to abut against the head  51  of the firing pin  5 . Next, the washer  7  is sleeved onto the rod portion  52  via the front end of the firing pin  5 , and is moved rearwardly to and maintained in a position located behind the shoulder  54  of the firing pin  5  by a positioning means (not shown). The retaining member  6  is sleeved onto the second section  522  of the rod portion  52  between the washer  7  and the shoulder  54 . Subsequently, the positioning means is removed. Hence, the retaining member  6  and the washer  7  are pushed forwardly by the resilient member  8  until the retaining member  6  abuts against the shoulder  54 . 
     Subsequent to the assembly of the firing pin  5 , the retaining member  6 , the washer  7 , and the resilient member  8 , the pin holder  4  is inserted forwardly into a rear end of the tubular portion  211  of the tool body  21  (since the second stop flange  214  has not been formed at this time, the pin holder  4  can be inserted into the tubular portion  211 ) until the shoulder  42  (i.e., the front end surface of the large-diameter holder portion  44  of the pin holder  4 ) abuts against the first stop flange  213 . Afterwards, the assembly of the firing pin  5 , the retaining member  6 , the washer  7 , and the resilient member  8  are also inserted forwardly into the rear end of the tubular portion  211  such that the firing end portion  53  of the firing pin  5  is extended into the through hole  41  in the pin holder  4  until the retaining member  6  abuts against the large-diameter holder portion  44  of the pin holder  4 . At this time, the rear end of the tubular portion  211  is rolled with the assistance of a jig (not shown) to form the second stop flange  214  such that the second stop flange  214  abuts against the washer  7 . As such, any two adjacent ones of the first stop flange  213 , the large-diameter holder portion  44  of the pin holder  4 , the retaining member  6 , and the washer  7  abut against each other, so that the pin holder  4 , the retaining member  6 , and the washer  7  are fixed within the tool body  21 . Thus, the firing device  3  can be assembled quickly and conveniently to the tool portion  211  of the tool body  21 . 
     It should be noted that, the washer  7  is disposed between the coiled compression spring  8  and the retaining member  6  to result in convenience when the jig is placed into the tubular portion  211  of the tool body  21  to compress the coiled compression spring  8 . The washer  7  may be omitted from the firing device  3  to allow the coiled compression spring  8  to press directly against the retaining member  6 . 
     The firing pin  5  is movable within the tool body  21  between a non-striking position shown in  FIGS. 4 and 5  and a striking position shown in  FIG. 7 . When the firing pin  5  is disposed in the non-striking position, the firing end portion  53  of the firing pin  5  is spaced apart from the rimfire cartridge  9  by the predetermined distance, as described above. 
     In this position, since the rear end  91  of the rimfire cartridge  9  is larger than the minimum diameter of the front section  413  of the through hole  41  in the pin holder  4  and slightly smaller than the maximum diameter of the front section  413 , as described above, a wall of the pin holder  5  defining the front section  413  of the through hole  41  can prevent removal of the rimfire cartridge  9  from the chamber  231  when the tool  2  is upright. Furthermore, in case of accidental downward dropping of the tool  2 , the primer  92  of the rimfire cartridge  9  cannot hit the firing pin  5 . As a consequence, accidental firing of the tool  2  can be substantially eliminated, thereby promoting safety during use of the tool  2 . Alternatively, the diameter of the rear end  91  of the rimfire cartridge  9  may be equal to the maximum diameter of the front section  413 . 
     During use, when the head  51  of the firing pin  5  is hammered to move the firing pin  5  from the non-striking position to the striking position, the primer  92  of the rimfire cartridge  9  is ignited to drive forward movement of the piston  24 . 
     It also should be noted that, since the diameter of the small-diameter section  532  of the firing end portion  53  of the firing pin  5  is larger than the inner diameter of the primer  92  and smaller than the outer diameter of the primer  92 , as described above, effective striking of the firing pin  5  against the primer  92  of the rimfire cartridge  9  can be ensured even when the central axis of the firing pin  5  is somewhat inclined relative to that of the rimfire cartridge  9  during striking of the firing pin  5  against the rimfire cartridge  9 . That is, the success rate in ignition of the primer  92  can be increased significantly. 
       FIG. 8  shows the second preferred embodiment of a hammer-drive powder-actuated tool according to this invention, which is similar in construction to the first preferred embodiment. Unlike the first preferred embodiment, the maximum diameter of the front hole section  413  of the through hole  41  in the pin holder  4  is equal to the diameter of the rear end  91  of the rimfire cartridge  9 . 
     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.