Abstract:
A combustion energy-operated setting tool for driving in fastening elements includes a setting piston ( 13 ) displaceable in a guide chamber ( 11 ) by reaction gases of a fuel, a bolt guide ( 20 ) for receiving and guiding the fastening elements and adjoining the guide chamber ( 11 ) in a setting direction, with the bolt guide ( 20 ) having a first region ( 21 ) with an inner diameter (D1) and a second region ( 21 ), extending in a direction toward an end ( 24 ) of the bolt guide ( 20 ) remote from the guide chamber ( 11 ), and having an inner diameter (D2) smaller than the inner diameter (D1) of the first region ( 21 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a combustion energy-operated setting tool including a guide chamber, a setting piston displaceable in the guide chamber by reaction gases of fuel and having a piston stem, and a bolt guide for receiving and guiding the fastening elements and adjoining the guide chamber in the setting direction.  
           [0003]    2. Description of the Prior Art  
           [0004]    In combustion energy-operated setting tools and, in particular, gas-operated setting tools an example of which is disclosed in German Publication DE 31 51 661 A1, there is provided a piston holder which directly engages the drive piston or directly acts thereon and which serves for stopping the piston. The piston holder holds the piston in its position at the start of combustion in the combustion chamber of the setting tool so that the piston can be driven with a sufficiently high energy in the main phase of the combustion by the expandable combustion gases. This principle is similar to that used in commercial aircrafts in which their turbines are brought to full power before brakes are released in order to be able to move from their stand-position with full power.  
           [0005]    The known holding or stopping device, which includes a ball acting on the piston stem, have a serious drawback that consists in that the device acts as a brake during displacement of the piston, which prevents the piston from a complete return to its initial position. During a following setting process, as a result of incomplete return of the piston, the setting energy acting thereon is noticeably reduced, resulting in a faulty process.  
           [0006]    Accordingly, an object of the present invention ins a setting tool of the type discussed above in which the drawback of the setting tools with a conventional piston holder is eliminated.  
         SUMMARY OF THE INVENTION  
         [0007]    This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a bolt guide having a first region with an inner diameter, and a second region adjoining the first region and extending in a direction toward an end of the bolt guide remote from the guide chamber, with the second region having an inner diameter smaller than the inner diameter of the first region.  
           [0008]    By reducing the cross-section of the bolt guide opening, during the setting process, a fastening element, which is displaced in the bolt guide and is provided on its stem with a plastic disc or washer that guides the fastening element, will be braked in the region of the reduced cross-section due to high frictional forces acting on the guide element and to the deformation of the guide element. This deceleration of the displacement of the fastening element also slows the piston for a certain time interval. Therefore, in the first phase of combustion in the combustion chamber, a sufficiently high energy can be built-up for a subsequent driving of the piston in the setting direction with a complete power. When the piston returns to its initial position, the stop means according to the present invention does not interfere with the return movement of the piston as they act on the piston indirectly, through the fastening element.  
           [0009]    It is advantageous, when the inner diameter of the first region is greater than an outer diameter of an at least partially elastic, guide element provided on a fastening element and formed, e.g., as a guide disc of a plastic material, and the inner diameter of the second region is smaller than the outer diameter of the guide element but greater than the outer diameter of the piston stem.  
           [0010]    The foregoing features insure an error-free, in particular, without tilting of the fasting element, functioning of the setting tool, with the piston slowing in the early phase of the combustion phase.  
           [0011]    For cost-effective manufacturing of the inventive setting tool, the second, reduced diameter region can extend up to the end of the bolt guide facing in the setting direction.  
           [0012]    According to a further advantageous embodiment of the present invention, a third region, which has an inner diameter substantially equal to that of the first region, adjoins the second region. In order to enable a friction-free transition of a fastening element and the guide element from one region in another region of the bolt guide, between the regions, inclined surfaces having different inner diameters can be provided.  
           [0013]    A reliable stoppage of the piston is achieved when the inner diameter of the second region is smaller than the outer diameter of the guide element, which is used with the fastening element, by from 0.5 mm to 0.5 mm.  
           [0014]    According to a still further advantageous embodiment of the present invention, within the second region, there are provided elements movable in and out of the bolt guide. Preferably, the penetration depth of the elements in the bolt guide is steplessly controlled. This feature permits to drive, with the setting tool, fastening elements and guide elements, which are arranged thereon, having different diameters. Thus, the piston slowing can be adjusted by adjusting the cross-section of the opening in the second region.  
           [0015]    For automatic displacement of the elements out of the bolt guide, spring means can be provided between the elements and the bolt guide and which biases the elements in the direction in which they displace out of the bolt guide.  
           [0016]    According to a preferred embodiment of the invention, the elements can be steplessly displaced in the bolt guide with an adjusting member formed, e.g., as a knurled screw. Upon release of the knurled screw, the elements can be pressed out of the bolt guide by the biasing force of the spring means.  
           [0017]    The novel features of the present invention, which are considered as characteristics for the invention, are set forth in the appended claims. The invention itself, however both as to its construction and its mode 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 DRAWING  
       [0018]    The drawing show:  
         [0019]    [0019]FIG. 1 a side, partially cross-sectional view of a setting tool according to the present invention with a fastening element located in the bolt guide;  
         [0020]    [0020]FIG. 2 a cross-sectional view of the bolt guide of the setting tool shown in FIG. 1 with the fastening element in an initial position (shown with dash line) and a first intermediate position (solid lines);  
         [0021]    [0021]FIG. 3 a cross-sectional view of the bolt guide shown in FIG. 2 with the fastening element in the second intermediate position;  
         [0022]    [0022]FIG. 4 a cross-sectional view of another embodiment of a bolt guide with a fastening element in the intermediate position;  
         [0023]    [0023]FIG. 5 a cross-sectional view of a further embodiment of the bolt guide with an adjustable reduction of the inner diameter in its first position with a fastening element in the initial position; and  
         [0024]    [0024]FIG. 6 a cross-sectional view of the bolt guide shown in FIG. 5 with the fastening element in the second position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    As discussed above, FIG. 1 shows a side, partially cross-sectional view of a gaseous fuel-driven setting tool  10  according to the present invention. The setting tool  10  has a one-or multi-piece housing  15  with a handle  16  provided with an actuation switch  17  with which a setting process can be initiated. In the housing  15 , there is provided a combustion chamber  12  in which an air-fuel mixture can be ignited with an ignition device (not shown). A setting piston  13  with a piston stem  14  is axially displaceable in a guide chamber  11  that adjoins the combustion chamber  12 . The guide chamber  11  opens into a bolt guide  20  arranged at the front of the setting tool  10 . In the bolt guide  20 , there are arranged fastening elements  30 , which are driven by a free end of the piston stem  14 , upon actuation of the setting process, in a constructional component (not shown). For guiding the fastening elements  30  in the bolt guide  20 , they are provided with guide elements  31  such as, e.g., disc-shaped elements.  
         [0026]    The bolt guide  20  is shown in detail in FIGS. 2-3. As shown in FIGS. 2-3, the bolt guide  20  has a first region  21  which is provided, in the embodiment of the bolt guide  20  shown in the drawings, somewhat in the middle of the bolt guide  20 . In the direction of the front end  24  of the bolt guide  20 , a second region  22  adjoins the first region  21 . The inner diameter D1 of the first region  21  is larger than the inner diameter D2 of the second region  22 . Between the front end  24  of the bolt guide  20  and the second region  22 , there is provided a third region  23  of the bolt guide  20  the inner diameter D3 of which substantially corresponds to the inner diameter D1 of the first region  21 . In the bolt guide  20  shown in FIG. 2, a fastening element  30  is shown in its initial position  32  (with dash-dot lines). The guide element  31  of the fastening element  30 , e.g., a plastic disc-shaped element, is located in the first region  21  of the bolt guide  20 . The fastening element  30  can be manually inserted in the bolt guide  20 , e.g., through a side opening or be inserted from a magazine (not shown) with fastening elements that can be attached to the bolt guide  20 . As shown in FIG. 2 the outer diameter D F1  of the guide element  31  is larger than the inner diameter D2 of the second region  22  of the bolt guide  20  but is somewhat smaller, within a backlash, than the inner diameter D1 of the first region  21  of the bolt guide  20  in which the guide element  31  is located. When the fastening element  30  is driven by the piston stem  14  of the piston  13  (not shown in FIG. 2) forward, the guide element  31  should pass the reduced diameter region  22  of the bolt guide  20 . Upon passing, the outer diameter of the guide element  31  is reduced to a diameter D F2 , as shown in intermediate position  33  of the fastening element  30 . The reduction of the outer diameter of the guide element  31  by the narrower region  22  leads to slowing of the setting piston  13  which, in turn, leads to generation of high setting energy in the combustion chamber  12  as a result of a progressive combustion of the fuel therein. The high setting energy insures a complete setting of the fastening element  30 .  
         [0027]    [0027]FIG. 3 shows the bolt guide  20  being set against a constructional component  40 , with the fastening element  30  being partially driven in the constructional component  40 . As can be seen in FIG. 3, the guide element  31  has already passed the second region  22  of the bolt guide  20  and has its initial diameter D F1  restored. The fastening element  30  can be completely driven in the constructional component by the piston stem  14  of the setting piston  13  only with the use of all of the generated setting energy.  
         [0028]    A further embodiment of the bolt guide  20  is shown in FIG. 4. The bolt guide  20  shown in FIG. 4 differs from that shown in FIGS. 2-3 in that the second region  22  extend to the front end  24  of the bolt guide  20 . In all other respects, reference is made to the description of the bolt guide  20  and the fastening element  30  shown in FIGS. 1-3.  
         [0029]    A still further embodiment of the bolt guide  20  is shown in FIGS. 5-6. The bolt guide  20 , which is shown in FIGS. 5-6 differs from that shown in FIGS.  1 - 3  in that displaceable elements  22 . 1 , which can be drawn in or pulled out of the bolt guide  20 , are provided in the second region of the bolt guide  20 . The displaceable elements  22 . 1  are supported in the bolt guide  20  by springs  25 . The springs  25  preload the displaceable elements  22 . 1  in their pull-out direction. The ends of the displaceable elements  22 . 1 , which project from the bolt guide  20  are provided with control surfaces  22 . 2 . And adjusting member  26 , which is formed, in the embodiment shown in FIGS. 5-6 as a knurled screw, serves for adjusting the position of the elements  22 . 1  and has control surfaces  26 . 2  that cooperate with control surfaces  22 . 2  of the displaceable elements  22 . 1 . In the embodiment shown in FIGS. 5-6, the control surfaces  22 . 2  and  26 . 2  are formed as inclined surfaces. The knurled screw, the adjusting member  26 , is displaced along a thread  26 . 1  provided on the bolt guide. Upon rotation of the adjusting member  26  clockwise, the adjusting member  26  is displaced in the direction of arrow  18 , applying pressure, with the control surfaces  26 . 2 , to opposite control surfaces  22 . 2  of the elements  22 . 1 . As a result, the elements  22 . 1  are displaced against the biasing forces of the springs  25  in the direction of arrow  19  in the interior of the bolt guide, as shown in FIG. 6. When the adjusting member  26  is rotated in the counter-clockwise direction, the elements  22 . 1  are displaced, as a result of application of the biasing force of springs  25  thereto, out of the bolt guide  20 .  
         [0030]    In order to prevent tilting of the guide element  31  when the fastening element  30  passes the region  22 , an inclined surfaces  27  are provided on the edge regions of the elements  22 . 1 . The inclined surfaces  27  facilitate entry of the guide elements  31  in the reduced diameter region  22  of the bolt guide  20 . Other elements of the bolt guide  20  and the fastening element  30  are the same as those of the bolt guides  20  shown in FIGS. 1-4.  
         [0031]    Though the present invention was shown and descried with references to the preferred embodiments, such are merely illustrative of the present 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.