Abstract:
A combustion power-operated setting tool has a propellant-driven setting mechanism, ( 12 ) an ignition device ( 18 ) for igniting a propellant, a receptacle ( 15 ) for receiving a propellant holder ( 20 ) and a device ( 30 ) for sensing presence of the propellant holder ( 20 ) in the receptacle ( 15 ) and which blocks ignition of the propellant by the ignition device in absence of the propellant holder in the receptacle ( 15 ) and provides for the ignition of the propellant by the ignition device upon sensing the presence of the propellant holder ( 20 ) in the receptacle ( 15 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a combustion power-operated setting tool including a propellant-operated setting mechanism, an ignition device for igniting the propellant, and a receptacle for a propellant holder. The present invention also relates to a propellant holder for a combustion power-operated setting tool. 
   2. Description of the Prior Art 
   Setting tools of the type described above can be operated with liquid or gaseous fuels that act as propellants and are generally stored in propellant holders. 
   German Publication DE-42 43 617 A1 discloses a combustion power-operated setting tool in which during an operational cycle, a gas inlet valve mechanically opens to provide for flow of fuel from a propellant holder into a storage chamber. From the storage chamber, the fuel flows into a combustion chamber before an ignition process is initiated. The propellant holder is formed as a cartridge with a liquefied gas and which is replaceably received in a receptacle of the setting tool. 
   The drawback of the disclosed setting tool consists in that in case of absence of the propellant holder in the receptacle, the residual fuel in the storage chamber can be still available, and an unintended actuation of a setting process by the tool user can take place, while the user believes that the setting tool is not operation-ready because of the absence of the propellant holder in the tool receptacle. 
   Accordingly, an object of the present invention is a setting tool of the type described above in which the foregoing drawback of the known setting tool is eliminated. 
   SUMMARY OF THE INVENTION 
   This and other objects of the present invention, which will become apparent hereinafter are achieved by providing in a setting tool a device for sensing presence of the propellant holder in the receptacle and which blocks ignition of the propellant by the ignition device in absence of the propellant holder in the receptacle and provides for the ignition of the propellant by the ignition device upon sensing the presence of the propellant holder in the receptacle. 
   Blocking of the ignition mechanism prevents an unintended ignition of propellant or fuel gas that still remains in the setting tool. 
   Advantageously, the sensing device includes switching means that opens the ignition current circuit in the absence of the propellant holder in the receptacle and closes the ignition current circuit when the presence of the propellant holder in the receptacle is detected. The switching means insures a very rapid and substantially disturbance-free blocking of the ignition mechanism or of the ignition device. 
   Advantageously, the sensing device includes a sensor. With a sensor, the presence or absence of a propellant holder in the tool receptacle can be determined in a simple manner, contact-free and reliably. The sensor can be formed, e.g., as a Hall sensor, capacitance sensor, or a light barrier sensor. 
   It is advantageous when the sensing device includes a touch contact switch which is deflected or pressed by the propellant holder when it is located in the tool receptacle. With a touch contact switch, a cost-effective construction of the sensing device can be obtained. 
   Advantageously, the sensor and/or the touch contact switch of the sensing device is arranged in the region of the receptacle, which makes a disturbance-free detection of the presence of a propellant holder in the tool receptacle possible. 
   It is further advantageous when the propellant holder such as, e.g., a fuel pressure vessel, has sensor means that can be easily recognized by the setting tool sensing device. The sensor means can be formed, e.g., as a permanent magnet, which insures a good detectability of the propellant holder when the sensing device sensor is formed as a Hall sensor. 
   The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings show: 
       FIG. 1  a side partially cross-sectional view of a setting tool according to the present invention with a propellant holder located in the tool receptacle; 
       FIG. 2  a side, partially cross-sectional view similar to that of  FIG. 1  but without the propellant holder being located in the tool receptacle; 
       FIG. 3  a side, cross-sectional view showing the receptacle section of the setting tool shown in  FIG. 1  with the propellant holder located in the receptacle; 
       FIG. 4  a cross-sectional view similar to that of  FIG. 3  and showing the receptacle section of another embodiment of a setting tool according to the present invention with the propellant holder located in the receptacle; and 
       FIG. 5  a cross-sectional view similar to that of  FIG. 3  and showing the receptacle section of yet another embodiment of a setting tool according to the present invention with the propellant holder located in the receptacle. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 through 3  show a setting tool  10  according to the present invention which is driven by a liquid or gaseous fuel that forms a propellant stored in a propellant holder  20 . The setting tool  10  has a housing  11  with a handle  16  formed thereon and which is provided with an actuation switch  17  with which a setting process can be initiated. The setting tool further has a setting mechanism  12  that includes a piston guide  14 , a drive piston  13  displaceable in the piston guide  14  which is formed as a cylinder, and a combustion chamber  38  adjoining the piston guide  14 . The propellant holder  20  is replaceably arranged in a receptacle  15  of the setting tool  10 . In the embodiment shown in  FIGS. 1-3 , the propellant holder  20  is formed as a pressure vessel. A fuel conduit  29  connects the propellant holder  20  with a metering device  25  that includes, e.g.; first and second valves  26 ,  28  and a chamber  27  arranged between the valves  26 ,  28 . Another section of the fuel conduit connects the metering device  25  with the combustion chamber  38 . In this way, the propellant or fuel is fed from the propellant holder  20  through the fuel conduit  29  and the metering device  25  into the combustion chamber  38  of the setting tool  10 . In the combustion chamber  38 , there is provided an ignition device  18  for igniting an air-propellant mixture located in the combustion chamber  38 . 
   The setting tool  10  further includes a sensing device  30  having a sensor  32 , which is formed as a Hall sensor, and switching means  31 , e.g., an electronic switch. The sensor  32  is arranged on the receptacle  15 , projecting partially into the receptacle interior. The switching means  31  can form part of the sensor  32  or be formed as a separate part, as shown in  FIGS. 1 and 2 . The switching means  31  forms part of an ignition current circuit  19  and closes or opens the same. 
   The propellant holder  20 , which is formed as pressure vessel, has a housing  21  in an interior  22  of which the propellant in form of gaseous and/or liquid fuel, e.g., a liquefied gas is stored. The propellant holder  20 , which is shown in  FIGS. 1 and 3 , has, at its side adjacent to the fuel conduit  29 , sensor means  24  formed as a permanent magnet. The sensor means  24  cooperates with the sensor  32 , which is formed as a Hall sensor, of the sensing device  30  of the setting tool  10 . By sensing the presence of the sensor means  24 , the sensing device  30  ascertains presence of the propellant holder  20  in the receptacle  15  and closes, with the switching means  31 , the ignition current circuit  19  as shown in  FIG. 1 , so that the ignition device  18  can be actuated by the actuation switch  17  when the setting tool  10  is pressed against a constructional component. 
     FIG. 2  shows the setting tool  10  without a propellant holder located in the receptacle  15  and connected with the fuel conduit  29 . However, the propellant can still be located in the conduit  29  and in the chamber  27  of the metering device in particular. However, the sensor  32  would only register the absence of the propellant holder  20  in the receptacle  15 , and the switching means  31  would open the ignition current circuit  19 . Therefore, an accidental actuation of the setting tool  10  is not possible. 
   The setting tool, the receptacle section of which is shown in  FIG. 4 , differs from the setting tool, which was described above with reference to FIGS.  1 - 3 , in that the sensing device  30  includes, instead of a sensor and switching means, a touch contact switch  33  integrated directly into the ignition current circuit  19 . A pure mechanical presence of the propellant holder  20  is detectable by the touch contact switch  33  that opens the ignition current circuit  19  in the absence of the propellant holder  20  in the receptacle  15 . Other particularities of this embodiment of the inventive setting tool are the same as of the setting tool  10 , which were described with reference to  FIGS. 1-3 . 
   The setting tool, the receptacle section of which is shown in  FIG. 5 , differs from the setting tool shown in  FIGS. 1-3  in that the sensing device  30  has, instead of a Hall sensor, a capacitance sensor  32 . The sensor  32  is connected with switching means in the same way as it was described with reference to  FIGS. 1-3 . In the absence of a propellant holder  20  in the receptacle  15 , the capacitance field in front of the capacitance sensor  32  changes. The switching means of the sensing deice  30  opens the ignition current circuit, so that actuation of the setting tool is not possible. All other particularities of the setting tool shown in  FIG. 5  are the same as those of the setting tool  10 , which were described with reference to  FIGS. 1-3 . invention and are not to be construed as a limitation thereof, and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.