Abstract:
A setting tool for driving fastening elements into constructional components and parts and including a guide tube ( 3 ) for guiding a fastening element out, a device for displacing the fastening element through the side cut-out ( 13 ) formed in the guide tube ( 3 ) into interior of the guide tube ( 3 ), and a feeler element extending into the interior of the guide tube ( 3 ) opposite the side cut-out ( 13 ) with a depth by which the feeler element extends into the interior of the guide tube ( 3 ) being determined by a fastening element to-be-displaced into the interior of the guide tube ( 3 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a setting tool for driving-in fastening elements and, in particular, to a portable, internal combustion engine-driven setting tool including a guide tube for guiding a fastening element out of the tool and having a side cut-out through which a fastening element is displaced into the guide tube interior. 
     2. Description of the Prior Art 
     For pushing a fastening element out of a guide tube, a piston rod of a piston is driven into the guide tube for impacting the fastening element. A piston plate, which is secured on the piston rod is connected with a combustion chamber in which a driving power is generated upon ignition of a suitable combustible gas mixture, e.g., air/fuel gas mixture. 
     For safety reasons, in this type of setting tools often, there is provided a pressing sleeve displaceable over the guide tube. The pressing sleeve insures that the setting process, i.e., driving of a fastening element in an object can only then take place when the setting tool is pressed against the object. Upon the setting tool being pressed against an object, the pressing sleeve is displaced rearward with respect to the guide tube against a biasing force. The pressing sleeve, upon being displaced interact with mechanical and/or electrical switches which actuate an actuation element or trigger and/or provide for release of the drive energy only then when the pressing sleeve is depressed by a certain minimal amount. 
     The setting tools of this type are often equipped with magazines containing fastening elements and further include additional elements for determining, before initiating the setting process, if a magazine is mounted on the tool, if the number of fastening elements in the magazine is sufficient, if the fastening elements are correctly positioned in the magazine or the guide tube. Preferably, the fastening elements are arranged in strips in belt-like manner and in this condition are mounted in a tool magazine. The displacement of the magazine is effected under action of a biasing force for successively displacing the fastening elements in the interior of the guide tube so that they can be driven in an object. 
     An object of the present invention is to provide simple means for effecting one or several of the above-listed determining functions. 
     SUMMARY OF THE INVENTION 
     This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a feeler element extending into the interior of the guide tube opposite the side cut-out formed in the guide tube, with a depth by which the feeler element extends into the interior of the guide tube being determined by a fastening element to-be-displaced into the interior of the guide tube. 
     The depth, by which the feeler element extends into the interior of the guide tube permits to determine whether a fastening element has be displaced into the guide tube and whether, if displaced, is correctly positioned therein. If there is no fastening element in the guide tube or it has not been pushed into the guide tube out of the magazine sufficiently far, the feeler element would extend into the interior of the guide tube only so far that an initiation of the setting process and of the ignition of the combustible mixture in the combustion chamber would not be possible. In other words, the operation of the setting tool would be blocked until a fastening element is properly positioned in the guide tube in a position corresponding to a minimal depth by which the feeler element can extend into the interior of the guide tube. 
     According to one embodiment of this invention, the feeler element is formed as a section of a pawl pivotable in a plane containing the central axis of the guide tube, with pawl being pivotable about an axis extending transverse to the plane containing the central axis and having a locking edge which prevents displacement of a pressing sleeve displaceable over the guide tube in absence of a fastening element in the guide tube. 
     The feeler element according to the present invention provides simple means for blocking operation of the setting tool. If there is no fastening element in the setting tool or the fastening element is improperly positioned, the depth, by which the feeler element extends into the interior of the guide tube, exceeds a predetermined minimal depth. In this position of the feeler element, the locking edge lies in the displacement path of the pressing sleeve, preventing its displacement inside the tool when the tool is pressed against an object. The ignition of the combustible mixture is not possible until the pressing sleeve reaches its end position in which the ignition can take place. 
     Only when a fastening element is correctly positioned in the guide tube, the feeler element extends into the interior of the guide tube by a predetermined minimal depth and enables a rearward displacement of the pressing sleeve to its end position upon pressing the tool against an object so that ignition of the combustible mixture or firing of the tool becomes possible. 
     According to a further embodiment of the present invention, the pawl has an adjusting edge located between the locking edge and the feeler section and extending at an angle relative to the guide tube. The pressing sleeve is displaced along the adjusting edge for pivoting the feeler section out of the interior of the guide tube. Before the pressing sleeve reaches its rearward end position which provides for firing of the tool, the pawl is pivoted further away from the guide tube, and the feeler section is completely displaced out of the guide tube. As a result, a piston rod, displaceable, upon firing of the tool, into the guide tube, would not have any contact with the feeler section, whereby damage of the feeler section and/or the piston rod is prevented. 
     Preferably, the pawl is spring-biased in a direction toward the guide tube so that upon the fastening element leaving the guide tube and the piston rod moved to its initial position, the pawl is also pivoted into its initial position. 
     The novel feature of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both s 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 view of a setting tool according to the present invention; 
     FIG. 2 a side view similar to that of FIG. 1 with a cross-sectional view of the front region of the tool; 
     FIG. 3 an axial cross-sectional view of the guide tube and the pressing sleeve in the fastening element feed region with incorrect positioning of the fastening element; 
     FIG. 4 a view similar to that of FIG. 3 with correct positioning of the fastening element; and 
     FIG. 5 a view similar to that of FIG. 4 with correct positioning of the fastening element and with a feeler section of the locking pawl being completely withdrawn form the inner channel of the guide tube. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A setting tool  1  according to the present invention, which is shown in FIG. 1, includes a housing  2 , a guide tube  3  and a pressing sleeve  4  projecting out of the housing  2 . The pressing sleeve  4  is concentrically slidably mounted on the guide tube  3  and is displaceable into the interior of the housing  2  against a biasing force when is pressed against an object into which a fastening element is to be driven-in. When the pressing sleeve  4  reaches its rear end position, the setting tool is unlocked and the drive-in process of a fastening element can begin upon actuation of a trigger  5 . Upon actuation of the trigger  5 , a combustion mixture, e.g., air/fuel gas mixture, which fills a combustion chamber, can be ignited with an electrical ignition device for driving a piston plate which is connected with a piston rod. Thereby, the piston rod is driven into the guide tube  3  for pushing a fastening element located there-in out. The fastening elements are located in a magazine  6  in strips in a bell-like manner, with fastening elements. The magazine  6  extends from a front section of the tool to a handle  7 . 
     As shown in FIG. 2 which, as discussed above, shows a cross-section of the front region of the inventive setting tool, an inner channel  8  of the guide tube  3  is aligned with the piston rod  9  which is being driven into the inner channel  8 . At its rear end, the piston rod  9  is connected with a piston plate which in turn is connected with a combustion chamber (not shown), whereby the piston plate is subjected to a pressure force generate upon the combustion of the air/fuel gas mixture in the combustion chamber. As discussed above, upon actuation of the trigger  5 , the air/fuel gas mixture in the combustion chamber is ignited with the electrical ignition device, with the generated pressure acting on the piston plate which results in displacement of the piston rod  9  into the inner channel  8  of the guide tube  3 , with the piston rod  9  pushing a fastening element  10 , which is located in the inner channel  8 , out of the channel  8 . This, however, is only then possible when the pressing sleeve  4  has been sufficiently pressed against the object, into which the fastening element is being driven in, and has been displaced, as a result, to it rear end position. Only then, actuation of the trigger  5  results in the release of an electrical or mechanical lock. 
     As discussed above, the fastening elements  10  are arranged in the magazine  6  in strips of fastening elements. Here, the fastening elements  10  are nails carrying in their head regions a collar  11  formed of a plastic material. The plastic collars  11  connect the fastening elements  10  with each other. A spring-biased pressing device  12 , which is located in the magazine  6 , biases the fastening element strip in a direction toward the guide tube  3  so that a front-most fastening element  10  is always pressed into the guide tube  3  through as cut-out  13  in the guide tube wall. A head member  14  is arranged in the cut-out  13 , with the fastening elements  10  reaching the channel  8  there past. There is further provided a stop for the pressing device  12  and which absorbs the biasing force acting on the pressing device  12 . In this case, a small number of fastening elements is still located between the guide tube  3  and the pressing device  12  which, at that stage, cannot be pushed further in the direction toward the guide tube  3 . This is necessary in case when for the release of the pressing sleeve  4 , a certain minimal number of the fastening elements  10  need be present in the magazine  6 . In the embodiment shown in FIG. 2, the minimal number of the fastening elements  10 , which need be present in the magazine  6 , is four. 
     FIG. 2 shows that in the wall of the guide tube  3 , there is provided, opposite the cut-out  13 , another cut-out  15 . The cut-out  15  is located opposite the collars  11  of the fastening elements  10 . The cut-out  15 , thus, is located in the rear region of the guide tube  3  or the head member  14 . The tool  1  further includes a plate-shaped locking pawl  16  lying in a plane of the central axis of the guide tube  3 . The locking pawl  16  pivots about a pivot axis  17  which extends perpendicular to the plane of the locking pawl  16  which coincides with the plane of the central axis  8   a  of the guide tube  3 . The separate fastening elements  10  are displaced toward the inner channel  8  also in the plane of the central axis of the guide tube  3 , with the fastening elements  10  extending parallel to the central axis of the guide tube  3 . In FIG. 2, this plane is the plane of the drawing. The pivot axis  17  is located outside of the guide tube  3 , on a radial shoulder  18  connected with the guide tube  3 . Thus, the locking pawl  16  is located outside of the guide tube  3  and has a free end facing the cut-out  15  of the guide tube  3 . At its lower edge facing the guide tube  3 , the locking pawl  16  has a feeler section  19 . The feeler section  19  projects into the inner channel  8  when the free end of the locking pawl  16 , e.g., lies on the circumferential edge of the cut-out  15  formed in the guide tube  3 . A compression spring  20  constantly biases the locking pawl  16  toward the guide tube  3  about the pivot axis  17 . 
     When there is no fastening element  10  in the inner channel  8  of the guide tube  3 , the compression spring  20  biases the locking pawl  16  abuts the pivot axis  17  in counter clockwise direction toward the  9  guide tube  3 , and the free end of the locking pawl  16  abuts the edge limiting the cut-out  15 . The feeler section  19  does not encounter any object in the inner channel  8  which would obstruct the movement of the feeler section  19 . The free end of the locking pawl  16 , in the case, lies in the displacement path of the pressing sleeve  4  and prevents the pressing sleeve  4  from reaching its inner or rear end position when the setting tool  1  is pressed with the pressing sleeve  4  against an object. The operation of the setting tool  1  or its drive mechanism is not possible. As a result, the pressing sleeve  4  cannot rotate the locking pawl  16  about the pivot axis  17  in the clockwise direction even when being forcefully pressed against the object as, in this case, self-locking takes place. In this case, the pressing sleeve  4  impacts the locking pawl at a point which is located in FIG. 2 beneath the pivot axis  17 . 
     FIGS. 3-5 show different positions of the locking pawl  16  and the pressing sleeve  4  when a fastening element  10  is located in the inner channel  8 . 
     FIG. 3 show respective positions when the fastening element  10  has not penetrated in the inner channel  8  of the guide tube  3  sufficiently far under the action of the pressing device  12  in the magazine  6 . The locking pawl  16 , in this case, can pivot about the pivot axis  17  in the clockwise direction so far that the free end of the locking pawl  16  facing the mount of the guide tube  3  lies in the displacement path of the pressing sleeve  4 . In other words, the edge of the free end of the locking pawl  16  lies in the displacement path of the sleeve  4 . This edge, which is designated with a reference numeral  21 , in this case, extends somewhat transverse to the guide tube  3 . The pressing sleeve  4  still cannot be displaced to its rear or unlocking position, and actuation of the tool is still not possible. 
     In FIG. 4, the fastening element  10  is located in the inner channel  8  so that it lies along the central axis  8   a  of the guide tube  3 . The feeler section  19  of the locking pawl  16  is pressed by the collar  11  on the fastening element  10  upward against a biasing force of the spring  20 , and the locking pawl  16  is pivoted about the pivot axis  17  in the counter clockwise direction. Thereby, the front edge  21  is pivoted out of the displacement path of the pressing sleeve  4 , and the sleeve  4  can be displaced to its rear end position. 
     FIG. 5 shows a position shortly before the pressing sleeve  4  reaches its rear end or unlocking position. The sleeve  4  presses the inclined adjusting edge  22  in the front region of the locking pawl  16  and further pivots the locking pawl  16  in the counter clockwise direction to an extend that the feeler section  19  is completely lifted of the inner channel  18  and does not contact the collar  11  on the fastening element  10 . In the end position of the pressing sleeve  4 , actuation of the ignition mechanism becomes possible. The piston rod  9 , upon ignition of the explosive powder charge, is displaced into the inner channel  8  and drives the fastening element  10  out of the guide tube  3 , without contacting the feeler section  19  of the locking pawl  16 . In this manner the feeler section  19  and the piston rod  9  are both protected from damage. The adjusting edge  22  extends approximately at an angle of 45 to the front edge  21  and is lifted by the rear portion  23  of the pressing sleeve  4 . 
     Though the present invention was shown and described 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 modification of the present invention will be apparent to those skilled n 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.