Abstract:
A combustion-engined setting tool ( 10 ) for driving in fastening elements such as bolts, nails, and the like in a constructional components includes an inlet/outlet valve arrangement ( 20 ) that connects the combustion chamber ( 13 ) of the setting tool ( 10 ), which is filled with an air-fuel mixture, with at least two tool openings ( 33, 34 ), has an inlet ( 21 ) connectable with a first tool opening ( 33 ) and an outlet ( 22 ) connectable with the second tool opening ( 34 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a combustion-engined setting tool for driving fastening elements such as nails, bolts, and the like in a constructional component and that includes a combustion chamber which is being filled with an air-fuel mixture, and an inlet/outlet valve arrangement that connects the combustion chamber with tool openings which communicate with the environment. 
   2. Description of the Prior Art 
   In setting tools described above, fuel, such as, e.g., fuel gas, is combusted with an environmental air in the combustion chamber. Before each setting process, fresh air should be fed into the combustion chamber, and after each setting process, flue gases, which are produced during a combustion process, should be expelled from the combustion chamber. 
   In a conventional combustion-engined setting tool, such as Hilti GX 100 of the assignee herein, a setting piston is displaced in a piston guide that is adjoined, in the setting or drive-in direction, by a bolt guide. At the end of the piston guide remote from the bolt guide, there is provided a combustion chamber. The combustion chamber has a rear wall coaxially displaceable in the combustion chamber. When the setting tool is pressed against a constructional component, the rear wall is displaced away from the end of the combustion chamber adjacent to the piston guide up to the end of the combustion chamber remote from the piston guide, loading the return springs. The combustion chamber assumes an expanded position. Simultaneously with the expansion of the combustion chamber, fresh air is fed thereinto through the inlet/outlet valve. After completion of the setting process and lifting of the setting tool off the constructional component, the rear wall is displaced to its initial position by the biasing force of the return springs. As the combustion chamber collapses, the flue gases are expelled through the inlet/outlet valve. The advantage of the setting tool, which is described above, consists in that no accumulator or battery is needed, as the flushing of the combustion chamber is effected mechanically. 
   In this setting tool, the flue gas can be expelled from the setting tool in the same volume of the environment from which the fresh air is aspirated. This can result in contamination of the aspirated fresh air with the flue gas which can reduce the energy efficiency of the combustion process. 
   Accordingly, an object of the present invention is to provide a setting tool in which the drawback of the conventional 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 an inlet/outlet valve arrangement having separated from each other, inlet connectable with the first tool opening and outlet connectable with the second tool opening that is spatially spaced from the first tool opening. 
   With an inlet/outlet valve arrangement according to the present invention, the fresh air for a combustion process can be aspirated from an environmental volume different from an environmental volume the flue gas is discharged into. 
   It is advantageous when the combustion chamber is connected with the first tool opening by the inlet of the inlet/outlet valve arrangement in a first operational phase or position of the inlet/outlet valve arrangement, is closed in a second operational phase or position of the inlet/outlet valve arrangement, and is connected with the second tool opening by the outlet of the inlet/outlet valve arrangement in the third operational phase or position of the inlet/outlet valve arrangement. Thus, the combustion chamber is connectable with different environmental volumes during aspiration of the fresh air and during discharge of the flue gas, respectively. By separation of the operational phases or positions of the inlet/outlet valve arrangement according to the present invention, a clear separation of the incoming air from the outgoing flue gas is achieved. Advantageously, the inlet/outlet valve arrangement is formed as a shuttle valve. 
   Advantageously, the inlet/outlet valve arrangement includes a closure member for closing the inlet, a closure member for closing the outlet, and a closure member for closing a combustion chamber opening of the inlet/outlet valve arrangement, with the closing member for the combustion chamber opening being actuated by a press-on element of the setting tool. The foregoing measures insure a technically simple association of the operational phases of the inlet/outlet valve arrangement with the setting process. 
   The provision of a first channel for connecting the inlet of the inlet/outlet valve arrangement with the first tool opening and a second channel for connecting the outlet with the second tool opening permits to further improve separation of the incoming air from the flue gases that are removed from the setting tool. 
   Further, the provision of the second channel for connecting the outlet with the second tool opening prevents accumulation of the flue gases in the setting tool housing and an uncontrolled discharge of the flue gas. 
   Advantageously, the first and/or second channel has an elastic section. The elastic section insures a medium tight connection of the inlet and/or outlet of the inlet/outlet valve arrangement with the tool openings even for the displaceably arranged combustion chamber casing and/or the rear wall of the combustion chamber. The elastic section or sections can be formed, e.g., as bellows. 
   It is advantageous when the second channel extends, at least regionwise, past the outlet of the setting tool. This permits to use so-called “jet effect” (as in injection pumps) which is produced by suction of the outlet and which improves the discharge of the flue gases in the second channel. 
   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 cross-sectional view of a setting tool according to the present invention in a press-on position; 
       FIG. 2  a cross-sectional view of a detail of the setting tool shown in  FIG. 1 , at an increase, in comparison with  FIG. 1 , scale, during a process of pressing the setting tool against a constructional component; 
       FIG. 3  a cross-sectional view of the detail shown in  FIG. 2  during a setting process; and 
       FIG. 4  a cross-sectional view of the detail shown in  FIG. 2  during lifting of the setting tool off the constructional component. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A setting tool  10  according to the present invention, which is shown in  FIGS. 1–4 , operates on a liquid or gaseous fluid which is stored in a fuel reservoir (not shown). 
   The setting tool  10  has a housing  11  in which there is arranged a setting mechanism with which a fastening element such as a nail, a bolt or the like can be driven in a constructional component U ( FIGS. 2–5 ) when the setting tool  10  is pressed against the constructional component U and is actuated by an actuation switch  36  arranged on a handle  35  of the setting tool  10 . The actuation switch  36  also actuates an ignition device (not shown), that ignites an air-fuel mixture contained in a combustion chamber  13 . 
   The setting mechanism includes, among others, a combustion chamber casing  12  in which the combustion chamber  13  is expandable, a piston guide  17  in which a setting piston  16  is displaceably arranged, and a bolt guide  18  in which a fastening element can be displaced by setting direction end of the forward movable setting piston  16  and, thereby, be driven in a constructional component. The combustion chamber casing  12 , the piston guide  17 , and the bolt guide  18  are preferably arranged coaxially with each other. At the end of the piston guide  17  adjacent to the bolt guide  18 , there are provided outlet openings  19  through which a portion of flue gases can flow out of the piston guide  17  when the setting piston  16  is located in its end position remote from the combustion chamber  13 . 
   In the embodiment shown in the drawings, the combustion chamber casing  12  is displaceably arranged with respect to the piston guide  17  and is elastically biased by a spring (not shown in the drawings), in a direction toward the bolt guide  18  or in a direction of a collapsed position of the combustion chamber  13 . The setting tool  10  further includes a press-on element  30  that engages with one of its end the combustion chamber casing  12 , while its opposite end projects from the housing  11  and extends, in an inoperative position of the setting tool  10  (not shown in the drawings) beyond the bolt guide  18 . The combustion chamber casing  12  has, at its end remote from the piston guide  17 , a combustion chamber rear wall  14  with which, the combustion chamber casing  12  is securely connected. The rear wall  14  of the combustion chamber  13  can, meanwhile, be displaced medium tight in the combustion chamber casing  12 . The rear wall  14  is supported for a medium tight displacement on at least one guide member  39  during a medium tight displacement of the combustion chamber casing  12  over the rear end of the piston guide  17 . 
   Feeding of air into the combustion chamber  13  and removal of flue gases from the combustion chamber  13  take place through openings  15  formed in the combustion chamber rear wall  14 . An inlet/outlet valve arrangement, which is generally designated with a reference numeral  20  and is arranged outside of the combustion chamber  13  in the region of the rear wall  14 , controls flow of air into the combustion chamber  13  and flow of flue gases therefrom. An inlet  21  of the inlet/outlet valve arrangement  20  is connected by a channel  31  or a first conduit with a first tool opening  33  formed in the section of the housing  11  of the setting tool  10  remote from the bolt guide  18 . The channel  31  has an elastic section  37  that is formed as a bellows. At the inlet  21 , there is provided a closure member  24  which is formed as a flap valve that functions as an inlet check valve. The closing member  24  provides for flow of air in the inlet/outlet valve arrangement  20  but prevents flow of the flue gas out of the inlet/outlet valve arrangement  20  and into the channel  31 . 
   An outlet  22  of the inlet/outlet valve arrangement  20  is connected by an outlet channel  29  and a second channel  32  or the second conduit, which is connected with the outlet channel  29 , with a second tool opening  34  of the setting tool  10  which is formed in the section of the housing  11  located between the bolt guide  18  and the first tool opening  33 . The second channel  32  has an elastic section  38  formed as a bellows. At the outlet  22 , there is provided a closure member  25  which s formed as a flap valve that functions as an outlet check valve that provides for flow of the flue gas from the inlet/outlet valve arrangement  20  in the channel  32  but prevents flow of air into the inlet/outlet valve arrangement  20 . The channel  32  extends past an outlet (not shown) that starts from outlet openings  19 , whereby a “jet effect”, which is produced by suction from the outlet is used in order to improve the flow of the flue gases in the channel  32 . The tool openings  33  and  34  communicate, because of their spacing from each other, with different volumes of the surrounding air. Therefore, the suction of the fresh air and the ejection of the flue gas cannot be based on the same volume of the surrounding air. 
   The inlet/outlet valve arrangement  20  also includes a closure member  26  which is actuated during a press-on process and with which a combustion chamber opening  23  of the inlet/outlet valve arrangement  20 , which communicates with the combustion chamber  13  or its opening  15 , is closed (see  FIG. 3 ). The combustion chamber opening  23  of the inlet/outlet valve arrangement  20  and the closure member  26  form together a pass valve. The closure member  26  is arranged at the end of a plunger  28  that is supported by a return member  27 , which is formed as a spring, on a wall  42  of the housing of the inlet/outlet valve arrangement  20 . The return member  27  elastically biases the closing member  26  to a position in which the combustion chamber opening  23  is at least partially open (see  FIGS. 2 and 4 ). During a press-on displacement of the setting tool  10  in the direction of arrow  43  ( FIG. 1 ), the combustion chamber casing  12  and the rear wall  14  move way from the piston guide  17 , and the combustion chamber  13  expands ( FIG. 1 ). 
   During expansion of the combustion chamber  13 , on one hand, air flows into the combustion chamber  13  through the tool opening  33  and the opening  15  in the direction of arrow  40 , and on the other hand, fuel flows through a fuel conduit (not shown) out of the fuel reservoir and into the combustion chamber  13 . 
   As shown in  FIG. 2 , during the press-on process, the inlet/outlet valve arrangement  20  provides a connection between the first channel  31  and the combustion chamber  13 , so that fresh air can be aspirated in the direction of arrow  40  by the expanding combustion chamber  13 . The closing member  24 , which is formed as a flap valve, releases the inlet  21 , and the closing member  26  releases the combustion chamber opening  23 . The closing member  25  closes the outlet  22  of the inlet/outlet valve arrangement  20 . 
   When the setting tool  10  is completely pressed against the constructional component, as shown in  FIG. 1 , the inlet/outlet valve arrangement  20  assumes a position shown in  FIG. 3 . In this position, the closing member  26 , which is retained in its closed position against the biasing force of the return member  27  by a stop  44 , closes the combustion chamber opening  23  of the inlet/outlet valve arrangement  20 . The closing members  24  and  25  close the inlet  21  and the outlet  22 . In this position of the inlet/outlet valve arrangement  20 , the combustion chamber  13  is completely sealed and is ready for a setting process. 
   After the setting process has been completed, and the setting tool  10  is lifted of the constructional component U, the closing member  26  is lifted from the combustion chamber opening  23  under the action of the return member  27 , opening the opening  23  of the inlet/outlet valve arrangement  20 . Because of the overpressure in the collapsible combustion chamber  13 , the flue gas flows under pressure in the inlet/outlet valve arrangement  20 , displacing the closing member  25 , which is formed as valve flap, opening the outlet  22 . The flue gas can only flow from the combustion chamber  13  in the direction of arrow  41  through the outlet  22  of the inlet/outlet arrangement  20 , the outlet channel  29 , the second channel  32 , and toward the second tool opening  34 . 
   With a new setting process, the above-described cycle is repeated. 
   Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is 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 embodiment 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.