Abstract:
A setting tool assembly for driving fastening elements in constructional components includes a combustion energy-operated setting tool ( 10 ), a fuel source ( 11 ), a metering head ( 20 ) for metering a predetermined amount of liquid fuel or gaseous fuel stored in the fuel source ( 11 ) into the combustion chamber ( 12 ) of the setting tool ( 10 ), the metering head ( 20 ) having an inlet ( 23 ) communicating with the fuel source ( 11 ), at least two outlets ( 42, 52, 62, 72 ), and at least two metering valves ( 40, 50, 60, 70 ) which connect the inlet ( 23 ) with respective outlets and which have different volumes of metering chambers ( 41, 51, 61, 71 ), and a device for selectively connecting the outlets of the metering head ( 20 ) with the combustion chamber ( 12 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a setting tool assembly for driving fastening elements in constructional components and including a combustion energy-operated setting tool having at least one combustion chamber, a fuel source, a metering head for metering a predetermined amount of liquid fuel or gaseous fuel stored in the fuel source into the at least one combustion chamber of the setting tool, with the metering head having at least one inlet communicating with the fuel source, at least two outlets, and at least two metering valves connected with the at least one inlet and respective outlets and having different volumes of their metering chambers.  
           [0003]    2. Description of the Prior Art  
           [0004]    The setting tool of setting tool assemblies of the type described above can be driven with liquid or gaseous fuels which are combusted in a combustion chamber of the setting tool in form of a mixture with an oxidant (e.g., air), with combustion energy driving the drive piston that drives a fastening element in a constructional component. The metering of fuel is effected, e.g., with a metering head having at least one metering valve with at least one metering chamber.  
           [0005]    The drive energy, which is used for driving the fastening element, directly depends on the chemically bonded energy introduced into the combustion chamber of the setting tool and on possibility to convert it into kinetic energy. The problem consists in admixing to the fuel, for each operational cycle, an appropriate amount of the oxidant, air or oxygen. The fuel-air ratio λ is retained, in an ideal case, constant and has a value of λ=1.  
           [0006]    The amount of oxygen, which is available for combustion, strongly depends on the outside temperature, air pressure, and air humidity. Therefore, the amount of fuel varies significantly with changes in the above-mentioned parameters, up to 40% in extreme cases.  
           [0007]    German Publication DE 19950350 A1 discloses a metering head which is pinned on a union for metering of a metered amount of a liquified fuel gas in different combustion chambers of a setting tool. The metering head has an inlet, at least two outlets, and two or more metering valves which connect the inlet with respective outlets. The metering valves can have metering chambers having different volumes. Each metering valve supplies with fuel a different chamber of the setting tool. The fuel is metered via appropriate metering chambers associated with respective combustion chambers. The drawback of the described metering head consists in that it is not possible to adapt the fuel volume for a particular chamber to particular environmental conditions. The resulting change of λ at changing environmental conditions leads to change of the setting energy at delivery of a constant amount of fuel.  
           [0008]    German Publication DE 4243 617 A1 discloses a setting tool in which for an operational cycle, a gas inlet valve is mechanically opened, and fuel is fed from a fuel source into an intermediate chamber that is connected with the environment. The connection of the intermediate chamber with the environment permits to equalize the pressure and, if needed, the temperature with the surrounding air, whereby an adaptable air-fuel mixture is fed into a combustion chamber. The fuel is fed from the intermediate chamber to the combustion chamber at a predetermined time. The drawback of this solution consists in high technical expanses associated with maintaining of the air-fuel ratio λ which, in turn, is associated with high manufacturing costs.  
           [0009]    European Publication EP 0 597 241 B1 discloses a setting tool in which fuel for admixing is delivered from a fuel source to the combustion chamber via a normally-closed solenoid-actuated valve. The actuation is effected electronically by a switching circuit in response to actuation of a switch, with the valve opening after a predetermined time period for enabling flow from the fuel source into the combustion chamber. There, likewise the drawback consists in high technical expenses, which are associated with maintaining of the air-fuel ratio λ, and the resulting high manufacturing costs.  
           [0010]    Accordingly, an object of the present invention is to provide a setting tool assembly of a type described above in which the drawbacks of the prior art setting tools and assemblies are eliminated.  
           [0011]    Another object of the present invention is to provide a setting tool assembly of a type described above which would enable an easy adaptation of the fuel metering.  
         SUMMARY OF THE INVENTION  
         [0012]    These and other objects of the present invention, which will become apparent hereinafter are achieved by providing a device for selectively connecting the two outlets of the two metering valves with the at least one combustion chamber.  
           [0013]    According to the invention, there is provided a setting tool assembly that in addition to the setting tool and a metering head, includes a device for selectively connecting outlets of the metering valves of the metering head with the combustion chamber. The provision of the selectively connecting device permits to activate predetermined metering chambers or the metering chamber-containing valves so that upon actuation of the metering head, the fuel contained in these metering chambers flows in the combustion chamber or chambers. In this Way, at low temperatures those metering valves are connected with the combustion chamber which have a relatively large metering chamber volume, to provide for a relatively rich air-fuel mixture in the combustion chamber. When the setting tool becomes heated after performing several setting processes, the device permits to associate another set of metering valves of the metering head with the combustion chamber(s), the set of metering valves having a smaller volume metering chambers to provide a less rich air-fuel mixture in the combustion chamber(s). The device for selectively connecting sets of metering valves having metering chambers with different volumes with the combustion chamber, permits to technically easy change the fuel-air ratio in the combustion chamber(s).  
           [0014]    Advantageously, the selectively connecting device has an operational member associated with at least one of metering head and the combustion chamber and having fuel passages with stops for supporting at least one of the at least two outlets of the metering head and blind bores for receiving another one of the at least two outlets without actuating, respective metering valves. The selectively connecting device is displaceable between different indexing positions in which respective ones of the fuel passages and the blind bores are associated with each of the at least two metering valves.  
           [0015]    The operational member permits to easily activate those metering valves or their outlets that are associated with the fuel passages, and to keep inactive those metering valves or their outlets that are associated with the blind bores.  
           [0016]    According to an advantageous embodiment of the present invention, for each indexing position of the selectively connecting device, a number of fuel passages and blind bores, which corresponds to a respective indexing position, is operationally associated with the metering valves. This measure permits to activate and de-activate one or several metering valves and, thereby, to be able to obtain a large number of possible combination of metering valves for metering fuel in the combustion chamber(s).  
           [0017]    Advantageously, the operational member is formed as a slide displaceably supported on a combustion chamber wall for displacement, relative to the outlets, from one indexing position of the selectively connecting device to its another indexing position. The slide can be arranged either on the setting tool or on the metering head. The formation of the operational member as a slide provides for a simple and cost-effective formation of the selectively connecting device.  
           [0018]    When the operational member is formed as an integral part of the combustion chamber wall, the metering head with the metering valves is displaceably arranged opposite the operational member. This arrangement also can be easily executed.  
           [0019]    For metering a predetermined volume, the metering head can be displaced by an actuation device from its off-position in which the metering head is spaced from the member and the metering valves are closed, to its operational position in which the outlets extend into respective fuel passage(s) and blind bore(s) in a predetermined indexing position of the selectively connecting device, with the metering valve(s), the outlet of which extend into the fuel passage(s) being activated. The foregoing measures permit, by using the selectively connecting device, to select the to-be-activated metering valves and to activate the selected metering head with the actuation device.  
           [0020]    Advantageously, the metering valves are arranged on the metering head in a row, with the fuel passages and the blind bores being likewise arranged in a row located opposite the row of metering valves.  
           [0021]    Advantageously, there is provided an electromechanical device for displacing the member or the metering head from one indexing position into another indexing position. The use of the electromechanical device facilitates handling of the setting tool assembly and the setting tool itself, as the user does not need anymore to manually adjust the selectively connecting device. Rather, with a control device that controls the operation of the electromechanical device, it is possible, by displacing the selectively connecting device or the metering head, to select the to-be-activated metering valves dependent on measured pressure and temperature of the surrounding air and/or of the combustion chamber.  
           [0022]    According to a further development of the present invention, the metering head itself can be provided with the device for connected the outlets of the metering valves with the combustion chamber of the setting tool. The metering head, which is usually pinned on a fuel container, can be easily removed from the setting tool, together with the fuel container, which provides for an easy monitoring of the selectively connecting device. In case of malfunction, the selectively connecting device can be easily removed and repaired or replaced.  
           [0023]    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 DRAWINGS  
       [0024]    The drawing show:  
         [0025]    [0025]FIG. 1 a longitudinal cross-sectional view of a setting tool assembly including a setting tool, a fuel container, a metering head, and a device for selectively connecting the metering head with the setting tool in an off-position of the setting tool and a first indexing position of the selectively connecting device;  
         [0026]    [0026]FIG. 2 a cross-sectional view of a portion of the setting tool assembly shown in FIG. 1 at an increased, in comparison with FIG. 1 scale, in a press-on-position of the setting tool and in the first indexing position of the selectively connecting device;  
         [0027]    [0027]FIG. 3 a cross-sectional view similar to that of FIG. 2 but in a second indexing position;  
         [0028]    [0028]FIG. 4 a cross-sectional view of another embodiment of a setting tool assembly including a setting tool, a fuel container, a metering head, and a device for selectively connecting the metering: head with the setting tool in an off-position of the setting tool and in a first indexing position of the selectively connecting device;  
         [0029]    [0029]FIG. 5 a cross-sectional view of a further embodiment of a setting tool assembly including a setting tool, a fuel container, a metering head, and a device for selectively connecting the metering head with the setting tool in an off-position of the setting tool and in a first indexing position of the selectively connecting device.  
         [0030]    [0030]FIG. 6 a cross-sectional view of a portion of the setting tool assembly shown in FIG. 5 at an increased, in comparison with FIG. 1 scale, in a press-on position of the setting tool and in the first indexing position of the selectively connecting device; and  
         [0031]    [0031]FIG. 7 a cross-sectional view similar to that of FIG. 6 but in a second indexing position of the selectively connecting device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    [0032]FIGS. 1 through 3 show a first embodiment of a setting tool assembly according to the present invention and including a setting tool  10 , shown in a very simplified manner, a metering head  20 , a fuel container  11 , and a device  25  for selectively connecting the metering head  20  with the setting tool  10 . In FIG. 1, the inventive setting tool assembly is shown in its initial or off-position and in FIGS. 2-3 the setting tool assembly is shown in its operational position.  
         [0033]    In the embodiment of the setting tool assembly shown in FIGS. 1-3, the setting tool  10  is driven by a fuel gas. The setting tool  10  has a housing in which a setting mechanism is located with which a fastening element (not shown) is driven in a constructional component (likewise not shown) when the setting tool  10  is pressed against the constructional component and is actuated.  
         [0034]    The setting mechanism includes, among others, a combustion chamber  12  and a piston guide  14  in which a drive piston  13  is displaceably arranged. Usually, a bolt guide (not shown) adjoins the piston guide  14 . The bolt guide receives a fastening element that can be driven in the constructional component by movable forward, setting direction end of the drive piston  13 . The fastening elements can be stored in a magazine (not shown) attachable to the setting tool  10 .  
         [0035]    In the embodiment shown in the drawings, the combustion chamber  12  is formed of two sub-chambers  15  and  17  which are separated by an intermediate plate  16  displaceable in the combustion chamber  12  and provided with through-openings. With an ignition device, e.g., a spark plug, a fuel-air mixture, which fills the combustion chamber  12 , can be ignited upon actuation of a trip switch (not shown).  
         [0036]    The fuel container  11  is located, in the operational condition of the setting tool  10 , in a receptacle (not shown) provided on the setting tool  10 . The fuel container  11 , which is shown in the drawings, is formed as a separate container that can be removed and replaced with another fuel container when the fuel in the full container is used. However, a fuel container can be permanently secured on the setting tool, forming an integral component of the setting tool. In the later case, the container can be filled with fuel a new after the fuel, which was contained therein, has been used. On the container  11 , a metering head  20  is pinned. The metering head  20 , which is shown in the drawings, has three metering valves  40 ,  60 ,  70  having respectively, metering chambers  41 ,  61 ,  71  of different size.  
         [0037]    The structure of the metering valves  40 ,  60 ,  70  will be described with reference to the metering valve  40 . The metering valve  40  includes a valve spool  44  that is supported by a spring  43  against a wall of the metering head  20 . At the end of the valve spool  44  remote from the spring  43 , there is provided a discharge pipe  45  that forms an outlet  42  of the metering valve  40 . In the rear region of the discharge pipe  45 , there is provided a connection channel  46  which is formed in the wall of the discharge pipe  45 . The connection channel  46  connects the outlet  42  with the metering chamber  41  when the valve spool  44  is actuated and is pressed into the metering head  20  against a biasing force of the spring  43 . Upon actuation of the metering valve  40  by pressing the valve spool  44  into the metering head  20 , as shown in FIG. 2 (metering valves  40  and  70 ) and FIG. 3 (metering valves  40  and  60 ), the valve spool  44  simultaneously interrupts connection of the inlet  23  of the metering head  20 , which connects the metering head  20  with the fuel container  11 , with the metering chamber  41  (the same with the metering valve  60 / 70 ). Air, which is necessary for a combustion process in the combustion chamber  12  (or another oxidant) is described into the combustion chamber  12  or sub-chambers  15  and through separate inlets (not shown) formed therein.  
         [0038]    A wall  18  of the combustion chamber  12 , which is located opposite outlets  42 ,  62 ,  72  of the metering valves  40 ,  60 ,  70 , is provided with the openings  19 . 1 ,  19 . 2  and  19 . 3  through which fuel can be delivered into the combustion chamber  12  or the subchambers  15 ,  17 . Between the metering head  20  and the combustion chamber wall  18 , there is provided a device  25  that selectively connects the outlets  42 ,  62 ,  72  of the metering head  20  with the openings  19 . 1 ,  19 . 2  and  19 . 3  in the combustion chamber wall  18 . The device . 25  includes, to this end, a displaceable operational member formed as a slide  30 . 1  that in the embodiments shown in the drawings, is arranged on the combustion chamber wall  18 . The slide  30 . 1  is provided at one of its end with actuation means  26 . 1  accessible from outside of the setting tool  10  and with which the slide  30 . 1  can be manually displaced by the user from a position  27  (FIGS. 1, 2) in the direction of arrow  81  in a further position  28  (FIG. 3) and vice versa (in the direction of the arrow  82 , FIG. 3). The slide  30 . 1  is held on the combustion chamber wall  18  in the positions  27 ,  28  by locking means  24  provided on the wall,  18  and engaging matching locking means  31  on the slide  30 . 1 . The slide  30 . 1  has a row of recesses  32  a part of which forms fueled passages  33 ,  34 ,  35  which are provided with stops  39 , and a part of which forms blind bores  36 ,  37 .  
         [0039]    In the off-position  21  of the metering head  20 , none of the metering valves  40 ,  60 ,  70  is actuated, and the outlets  42 ,  62 ,  72  are spaced from the slide  30 . 1  so that the slide  30 . 1  can be displaced by a user.  
         [0040]    In FIG. 2, the metering head  20  is displaced by an adjusting cam  91  of an actuation device  90  from its off-position  21  to its operational position  22 . The actuation device  90  is provided with a rotary device for rotating the adjusting cam  91  that presses the metering head  20  against the slide  30 . 1 . In the actuation position  22  of the metering head  20  and in the first indexing position  27  of the slide  30 . 1 , the inlets  42  and  72  are pressed against the respective stops  39  in the full passages  33 ,  35 . In this position of the inlets  42 ,  72  the metering valves  40  and  70  are actuated, and fuel can flow from the respective metering chambers  41 ,  71  in the associated sub-chambers  15 ,  17 . The metering valve  60 , the metering chamber  61  of which has a smaller volume than the metering chamber  71  of the metering valve  70 , is not actuated, having its outlet  62  located in the blind bore  36 . The indexing position  27  corresponds, e.g., to cold start position of the setting tool  10  when a rich, i.e., a fuel-rich fuel air mixture should be present in the sub-chamber  17 . With appropriate marking provided on the setting tool  10  or the slide  30 . 1 , the user can switch the setting tool  10  between cold and hot start position.  
         [0041]    In FIG. 3, the setting tool  10  or the metering head  20  occupies an operational position  22 , and the device occupies an indexing position  28  which corresponds to a hot operation of the setting tool  10  at which the sub-chamber  17  needs to be supplied with a fuel-poor fuel-air mixture. In this case, it is the outlet  62  of the metering valve  62  which is connected with the fuel passage  35 . The metering valve  70  is not actuated, having its outlet extending into the blind bore  37 .  
         [0042]    A setting tool assembly shown in FIG. 4 differs from that shown in FIGS. 1-3 in that the device  25  includes an electromechanical adjusting device  80  for, the slide  30 . 1 . With the adjusting device  80 , the slide can be displaced between the indexing positions  27 ,  28  in accordance with the requirements and environmental conditions. The device  25  is displaced automatically in the directions  81 ,  82  between indexing positions  27 ,  28  according to a control command of a control device. In all other respects, reference is made to the previous description.  
         [0043]    [0043]FIGS. 5-7 show a further embodiment of the device  25 . In FIGS. 5-6, the device  25  is shown in its first indexing position  27 , and in FIG. 7, the device  25  is shown in its second indexing position  28 . In the embodiment shown in FIGS. 5-7, the operational member  30 . 2  remains stationary and is formed by the combustion chamber wall  18 . The wall  18  has a row of recesses  32  a part of which is formed of a blind bore  37  and recesses  36 ,  38 , and a part of which is formed as fueled passages  33 ,  34 .  
         [0044]    In the embodiment shown in FIGS. 5-7, the metering head  20  has four metering valves  40 ,  50 ,  60 ,  70  of which the metering valves  50  and  70  have a greater metering chamber volume than the metering valves  40  and  60 . The metering head  20 , together with the fuel container  11 , is displaced between the first  27  and second  28  indexing positions by an adjusting member  26 . 2  of the device  25 . The adjusting member  26 . 2  is provided, in its lower region, with a cavity  85  for the fuel container  11  and includes an actuation member  29 . 1  that can be actuated manually or mechanically, and an actuation member  29 . 2  that engages an end of the fuel container  11  remote from the metering head  20 .  
         [0045]    In FIG. 5, the metering head  20  is in its off or initial position  21  in which the metering head  20 , together with the fuel container  11 , is displaceable by the adjusting member  26 . 2  from the indexing position  27 ,  28  so to the next indexing position  28 ,  27 , and all of the metering values  40 ,  50 ,  60 ,  70  are not actuated. The adjusting member  26 . 2  is fixed in the indexing positions  27 ,  28  with appropriate locking means.  
         [0046]    In FIG. 6, as in FIG. 2, the metering head  20  is displaced by the adjusting cam  91  of the actuation device  90  in its operational position  22 . The metering valves  50 ,  70 , which have a larger metering chamber volume, are actuated and are connected with sub-chambers  15 ,  17  of the combustion chamber  12  by fuel passages  33 ,  34 , so that respective fuel amounts are fed in the sub-chambers  15 ,  17 .  
         [0047]    The outlets  42 ,  62  of the metering values  40 ,  60  extend into the blind bore  37  and the units  46  are not actuated.  
         [0048]    In FIG. 7, the fuel container  11 , together with the metering head  20 , are displaced in the second indexing position  28  by a pivotal movement of the adjusting member  26 . 2 . In the indexing position  28 , only metering valves  40 ,  60  with a smaller metering chamber volume are located opposite the fuel passages  33 ,  34 . In all other aspects, reference is made to description with reference to FIGS. 1-4.  
         [0049]    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 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.