Abstract:
A combustion-engined setting tool for driving fastening elements in constructional components includes a member ( 32 ) arranged in the combustion chamber ( 13 ) for generating turbulence of an oxidant-fuel mixture filling the combustion chamber ( 13 ), an ignition unit ( 23 ) for igniting the oxidant-fuel mixture, a drive for at least temporarily driving the turbulence generating member ( 32 ), and a switch ( 22 ) for actuating the ignition unit ( 23 ) and actuated by the turbulence generating member ( 32 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a combustion-engined setting tool for driving fastening elements such as, e.g., nails, bolts, pins, in a constructional components and which includes a combustion chamber, means arranged in the combustion chamber for generating turbulence of an oxidant-fuel mixture filling the combustion chamber, an ignition unit for igniting the oxidant-fuel mixture, and drive means for a least temporarily driving the turbulence generating means.  
         [0003]     2. Description of the Prior Art  
         [0004]     In the setting tools described above, a portion of the liquid gas or another vaporable fuel, which is mixed with an oxidant, e.g., environmental air, is combusted in the tool combustion chamber. In order to obtain as high as possible drive-in energy from the combustion process, it is important that the combustion of the gas or gas mixture takes place under turbulent flow conditions. Only a turbulent combustion permits to obtain a necessary drive-in energy from the combustion process, producing a sufficiently rapid pressure increase in the combustion chamber for accelerating the setting piston to a degree necessary for driving a fastening element in. With a laminar combustion, the combustion process and the resulting pressure increase take place so slow that only a fraction of the required mechanical energy can be obtained from the combustion process.  
         [0005]     European Patent EP-0 544471B1 discloses a combustion-engined setting tool having a combustion chamber for combusting a mixture of air and fuel gas and in which ventilator means is provided in the combustion chamber for generating turbulence therein. The ventilator means is driven by an electric motor which is supplied with electrical energy from a battery. The ventilator means is actuated by the head switch of the setting tool when the setting tool is pressed against a constructional component. The ignition unit is actuated for igniting the air-fuel mixture in the combustion chamber when an actuation switch is actuated, while the head switch is still closed.  
         [0006]     The drawback of the setting tool of the European Patent consist in complicated and costly electronics which actuates and controls the ventilator means and which also actuates ignition. A further drawback consists in that several accumulators are needed, which increases the tool weight.  
         [0007]     German Publication DE 199 62 711 A1 discloses a combustion-engined setting tool in which a separation plate with through-openings is arranged in the combustion chamber, dividing the combustion chamber in two chambers. An adjustment device is used for changing the distance between the separation plate and a rear wall that axially limits the combustion chamber, whereby the volumes of the forechamber and the main chamber change. In the forechamber, a first portion of the air-fuel mixture is ignited, with the flame jets penetrating into the main chamber through the openings in the separation plate, creating turbulence in the main chamber and igniting the air-fuel mixture therein.  
         [0008]     The drawback of the tool disclosed in DE 199 62 711 A1 consists in that the combustion process is sensible to the environmental conditions such as, e.g., temperature, scavenging ratio of the combustion chamber, or the environmental pressure. This results from the fact that the turbulence is generated as a result of the combustion process itself, i.e., when the combustion in the forechamber is poor, then the combustion in the main chamber is even worse.  
         [0009]     German Publication DE 102 26 878 A1 discloses a combustion-engined setting tool in which, as in the previously described case, the turbulence is generated by a perforated separation plate that remains static before and during the ignition process. After the combustion process ends, the separation plate and the rear wall are displaced in a direction toward the piston guide, so that the combustion chamber completely collapses. After the combustion chamber has collapsed, another, non-perforated plate is displaced as a result of application thereto a spring-biasing force from a location at the rear end of the setting tool remote from the piston guide up to the rear wall in order to scavenge the space before this plate with fresh air.  
         [0010]     Here, likewise, the drawback consists in that the combustion process is sensible to the fluctuation of the environmental conditions such as, e.g., temperature, scavenging ratio of the combustion chamber, or the environmental pressure.  
         [0011]     The object of the present invention is to provide a setting tool of the type described above and in which the drawbacks of the known tools are eliminated.  
         [0012]     Another object of the present invention is to provide a setting tool of the type described above which would have a high energy efficiency.  
       SUMMARY OF THE INVENTION  
       [0013]     These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a setting tool which would include switch means that actuates the ignition unit and that itself is actuated by the turbulence generating means.  
         [0014]     Thus, according to the present invention, the ignition unit is directly controlled by the turbulence generating means. When the ignition unit is actuated by the actuation switch means and all of safety switches are closed, then ignition is effected automatically. The ignition takes place during the displacement of the turbulence generating means or as a result of the displacement of the turbulence generating means.  
         [0015]     Thereby, ignition of the air-fuel mixture during a turbulent flow regime is insured, which permits to achieve a high energy efficiency of the combustion process. Complex electronics with separate switches for the ignition unit and the turbulence generating means is not any more necessary. Other switches or sensors can be provided, e.g., as safety switches in order to insure, e.g., that the setting tool is indeed pressed against a constructional component.  
         [0016]     Advantageously, the turbulence generating means is formed as a member axially displaceable in the combustion chamber and which is actuated by a mechanical device. This measure permits to provide, in a simple way, turbulence in the air-fuel mixture in the combustion chamber, without use of electrical energy from batteries or accumulators, and which is noticeably stronger than the turbulence created, e.g., by flame jets passing through openings formed in a separation plate. In particular, according to the present invention, the turbulence is created in the entire combustion chamber and not only in a sub-chamber, as it takes place when the turbulence is created by flame jets passing through the openings in a separation plate. The mechanical device permits to obtain a pulse acceleration which can provide for displacement of the turbulence generating means in a time period from 1 msec to 200 msec, preferably, from 5 msec to 100 msec. The displacement or operation of the turbulence generating means for such a short time does not require much energy. With a mass of the turbulence generating means from about 1 g to 200, only an energy from about 1 mJ to 1 J is needed. Because of the small energy requirement, it can be obtained, e.g., by pressing the setting tool against the construction component, with the press-on energy being transmitted to the mechanical device, without tiring the user too much.  
         [0017]     According to an advantageous embodiment of the present invention, the turbulence generating means is formed as a turbulence generating plate axially displaceable in the combustion chamber and provided, optionally, with openings. The turbulence generating plate can be displaced on a pipe or a rod, which is axially arranged in the combustion chamber, or be only connected with the force storing element, without any guidance. The openings in the turbulence generating plate can be formed as slots or holes. The turbulence generating plate can also be formed as a sieve plate. The turbulence generating plate can also be formed as an arched plate, with the concave side of the turbulence generating plate aligned preferably, in the direction of the pulsed movement. Such a turbulence generating plate has a high aerodynamic drag factor and, therefore, a strong turbulence when moving rapidly. It should be understood that with a collapsed combustion chamber, the displacement of the turbulence generating plate is possible or can take place only in at least partially expanded condition of the combustion chamber.  
         [0018]     It is beneficial, when the switch means is provided in the region of a cylindrical wall that radially limits the combustion chamber. With this arrangement, detection of the turbulence generating means passing, in its axial displacement in the combustion chamber, past the switch means is used for actuation of the ignition unit.  
         [0019]     Advantageously, the switch means is arranged on a combustion chamber wall that axially limits the combustion chamber. As the switch means, mounting wall, a front, in the setting direction, wall or an opposite rear wall can be used. With this arrangement, detection of engagement of the turbulence generating means with the combustion chamber wall or lifting of the turbulence generating means off the combustion chamber wall is used for the actuation of the ignition unit.  
         [0020]     It is beneficial when the switch means is formed as sensor means, which enables a contactless detection of the turbulence generating means or a contactless switching on. Suitable, to this end, sensors are Hall sensors, light-sensitive sensors, or capacitance sensors.  
         [0021]     The switch means can also be formed as mechanically actuated switch means, which reduces manufacturing costs of setting tool, without adversely affecting the inventive function. It is advantageous when there is provided time-delay means for delaying the ignition pulse of the switch means. Thereby, by arrangement of the switch means, in particular, in a region that adjoins the piston guide, it can be reliably determined that the turbulence generating means has been displaced by a sufficient amount before the ignition by the ignition unit takes place. As a result, a strong turbulence of the air-fuel mixture in the combustion chamber at the time of ignition prevails.  
         [0022]     When set means for adjusting the time delay of the time-delay means is provided, then, in a simple way, the drive-in energy of the inventive setting tool can be adjusted. It has been shown that the produced energy depends on the time the ignition takes-place after actuation of the turbulence generating means. The set means can include, e.g., an adjusting wheel connected with the time-delay means and with which the setting or drive energy can be preset by the user, e.g., there can be provided, on the adjusting wheel, a scale which would indicate the setting energy in absolute (e.g., in J) or relative (e.g., as a %) values.  
         [0023]     Instead of an adjusting wheel, the set means can include an adjusting lever or a pressure or sensor switch. Further, the set means can be formed as a sensor system or include such a sensor system. The sensor system can react, e.g., to the type of the constructional component or to the projecting length of a nail obtained from preceding nail settings, and adjust accordingly the setting energy by adjusting the time delay.  
         [0024]     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  
       [0025]     The drawing show:  
         [0026]      FIG. 1 a  longitudinal, partially cross-sectional view of a setting tool according to the present invention in an inoperative position;  
         [0027]      FIG. 2 a  longitudinal, partially cross-sectional view of the setting tool shown in  FIG. 1  in a position in which the tool is slightly pressed against a constructional component;  
         [0028]      FIG. 3 a  longitudinal, partially cross-sectional view of the setting tool shown in  FIG. 1  in a position in which the tool is completely pressed against a constructional component;  
         [0029]      FIG. 4 a  longitudinal, partially cross-sectional view of the setting tool shown in  FIG. 1  in a position in which the tool is completely pressed against a constructional component, the trigger is actuated, and ignition has taken place;  
         [0030]      FIG. 5 a  longitudinal, partially cross-sectional view of the setting tool shown in  FIG. 1 , in which the tool has been slightly lifted off the constructional component;  
         [0031]      FIG. 6 a  longitudinal, partially cross-sectional view of another embodiment of a setting tool according to the present invention in a position in which the tool is completely pressed against a constructional component, the trigger has been actuated, and ignition has taken place; and  
         [0032]      FIG. 7 a  diagram illustrating the influence of the time of ignition on the setting energy of the setting tool shown in  FIG. 6 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]     A setting tool  10  according to the present invention, which is shown in  FIGS. 1-5 , operates on a liquid or gaseous fluid.  
         [0034]     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.  
         [0035]     The setting mechanism includes, among others, a combustion chamber casing  12  in which a 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 fastening element can, e.g., be stored in magazine  27  on the setting tool  10 .  
         [0036]     The combustion chamber  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  shown in  FIG. 1 . The setting tool  10  further includes a press-on element  25  which is formed as a bar engaging with one of its end the combustion chamber casing  12 , with the opposite end projecting from the housing  11  and extending, in an inoperative position of the setting tool  10  according to  FIG. 1 , beyond the bolt guide  18 . The combustion chamber casing  12  is displaced, medium tight, with its rear wall  14  over a tubular element  20  in which an ignition element  23 , such as a spark plug, is arranged and in which a fuel conduit  21  is arranged. The fuel conduit  21  is connected with a fuel reservoir, not shown in the drawings, e.g., a liquid gas capsule. In the region of the ignition element  23 , the tubular element  20  has at least one opening  47  through which fuel  50  can flow into the combustion chamber  13  (please see  FIG. 2 ) and through which a air-fuel mixture can reach the ignition element  23 .  
         [0037]     An electrical conductor  45  connects the ignition element  23  with switch means  22 , which is formed as sensor switch means and with which an ignition process is actuated as it would be described more precisely below.  
         [0038]     The switch means  22  is formed, in the embodiment shown in the drawings, as a Hall sensor arranged on a cylindrical wall  54  of the combustion chamber casing  12 . Alternatively, the switch means  22  can also be formed, e.g., as an optical or capacitance switch. The switch means  22  can also be formed as a mechanical or electronic switch.  
         [0039]     Through an air inlet  51  in the housing  11  and an inlet opening  15  in the rear wall  14  of the combustion chamber  13 , air can be brought into the combustion chamber  13  (as shown with arrow  41 ) when the combustion chamber expands as a result of displacement of the combustion chamber casing  12  in the direction of arrow  40  (please see  FIG. 2 ).  
         [0040]     In the expanded condition of the combustion chamber casing  12  or the combustion chamber  13 , a mechanical device, which is generally designated with a reference numeral  30 , for a pulsed acceleration of turbulence generating means  32  is activated. The turbulence generating means  32  is formed as a turbulence generating plate  33  provided with openings  38 . The mechanical device  30  includes a force storing element  31  which is formed as a spring engaging, with one of its end, the turbulence generating plate  33  and with its other end, the rear wall  14  of the combustion chamber  13 . The turbulence generating means  32  or the turbulence generating plate  33  is displaced substantially friction-free along the tubular element  20  and is sufficiently spaced from the cylindrical wall  54  of the combustion chamber casing  12 , so that no friction losses occur during displacement of the turbulence generating plate  33  in an axial direction in the combustion chamber  13 .  
         [0041]     In the initial or inoperative position of the setting tool  10  shown in  FIG. 1 , the turbulence generating plate  33  and the rear wall  14  are locate directly adjacent to each other at an end of the piston guide  17  remote from the bolt guide  18 . The space of the combustion chamber  13  is reduced to a minimal gap, and the combustion chamber  13  is in collapsed condition.  
         [0042]     When the setting tool  10 , as shown in  FIG. 2 , is placed against a constructional component U, firstly, the free end of the press-on element  25  contacts the constructional component U. With the setting tool  10  being pressed against the constructional component U, the combustion chamber casing  12  is displaced in the direction of arrow  40  away from the piston guide  17 , whereby the combustion chamber  13  expands. However, the turbulence generating plate  33  is not yet displaced but remains rather at the end of the piston guide  17  where it is held by a locking member  39 . A switch rod  36  connects the locking member  39  with an actuation switch  35  provided on a handle  37  of the setting tool  10 .  
         [0043]     During the expansion process of the combustion chamber  13 , on one hand, air flows into the combustion chamber  13  through the air inlet  51  and the inlet opening  15  in the direction of arrow  41  and, on the other hand, fuel  50  is fed into the combustion chamber  13  through the fuel conduit  21 . The fuel conduit  21 , only a section of which is shown in  FIG. 2 , is connected with a fuel reservoir, not shown. Metering of the fuel can be effected with a metering device which can be controlled mechanically or electronically.  
         [0044]     When the setting tool  10 , as shown in  FIG. 3 , is completely pressed against the constructional component U, the inlet opening  15 , at the edge of which a sealing element  29  is provided, is closed by a seal  28 , which can be provided, e.g., in the housing  11 .  
         [0045]      FIG. 3  shows the combustion chamber  13  in a completely expanded condition. However, the actuation switch  35  is not yet actuated. Air and gaseous fuel fills the combustion chamber  13 .  
         [0046]     In the position of the setting tool  10  shown in  FIG. 4 , the actuation switch  35  is actuated (arrow  42 ). The locking member  39  is displaced by the switch rod  36  in its release position, and the turbulence generating plate  33  is displaced in the combustion chamber  13  in the direction of the rear wall  14  under the biasing force of the force storing element  31  with acceleration from 1 m/sec 2  to 5,000 m/sec 2  and is displaced through the combustion chamber  13 . As a result of the displacement of the turbulence generating plate  33 , the air-fuel mixture, which fills the combustion chamber  13  is subjected to a strong turbulence  46 . The acceleration forces, which are imparted by the force storing element  31  amounts to from about 1 N to 50 N. Alternatively or in addition to the mechanical switch rod, an electronic switching element can be provided for releasing the turbulence generating means  32  or the turbulence generating plate  33 .  
         [0047]     When the turbulence generating plate  33  reaches the switch means  22  or the Hall sensor, the later is actuated and communicates an ignition pulse to the ignition unit  23  through the conduit  45 . The ignition unit  23  ignites the air-fuel mixture, as shown with reference numeral  24 . If the switch means  22  is formed as a mechanical or electronic switch, it can likewise be actuated by the displaceable turbulence generating plate  33 , closing the ignition circuit. In every case, the ignition takes place automatically and is actuated by the turbulence generating means  32  or the turbulence generating plate  33 . Thereby, the ignition  24  always takes place during the displacement of the turbulence generating means  32  at a time when the air-fuel mixture in the combustion chamber  13  is subjected to a strong turbulence. Thereby, a very high energy yield during the combustion process is achieved.  
         [0048]     The setting piston  16  is displaced by the expandable gases in the direction of arrow  43  toward the bolt guide  18 , driving a fastening element in the constructional component U. At the end of the piston guide  17  adjacent to the bolt guide  18 , there is provided an annular damping element  26  that damps or prevents overrun of the setting piston  16  at this end of the piston guide  17 .  
         [0049]     In the wall of the piston guide  17 , there is provided an outlet opening  19  through which a major portion of the combustion gases can reach the exhaust opening  52  in the housing  11  and therethrough be released into environment when the piston plate  56  of the setting piston  16  is located between the outlet opening  19  and the damping element  26 .  
         [0050]     In  FIG. 5 , the setting piston  16  has already been displaced in the direction of arrow  48  to its initial position. This can take place, e.g., as a result of generation of under-pressure which is produced by cooling of residual combustion gases that remain in the combustion chamber  13 , or by a return mechanism, not shown.  
         [0051]      FIG. 5  shows a position in which the setting tool  10  is slightly lifted off the constructional component U. Thereby, an outlet opening  55 , which was sealed with a sealing element  59  against an annular wall  58  of the combustion chamber casing  12 , opens. The combustion gases, which remain in the combustion chamber  13 , can flow through the outlet opening  55  and then through openings, not shown, in the annular wall  58  to the outlet opening  52  in the housing  11  and therethrough into environment, as shown with arrow  44 . This process ends when the combustion chamber  13  completely collapses upon the setting tool  10  having been lifted form the constructional component  10 , and the setting tool  10  assumes its initial inoperative position shown in  FIG. 1 . Then again, the turbulence generating plate  33  becomes locked by the locking element  39  on the tubular element  20 , and the force storing element  31  becomes unloaded (the spring becomes released).  
         [0052]     The setting tool  10 , which is shown in  FIG. 6 , differs from the setting tool  10  shown in  FIGS. 1-5  in that the switch means  22  is formed as an electromechanical switch that is arranged on an annular combustion chamber wall  58  adjacent to the piston guide  17 . The conductor  45  connects the switch means  22  with the ignition unit  23 . However, in this embodiment, time delay means  48  is provided in the conductor  45 , which delays the further progression of the ignition pulse toward the ignition unit  23  or closing of the ignition circuit by about from 1 msec to 20 msec. Because of this time delay, the ignition  24  of the ignition unit  23  takes place not as soon as the turbulence generating plate  33  has been lifted off the combustion chamber wall  58  and the switch means  22  has been actuated but rather after the turbulence generating plate  33  has been displaced back a certain amount within the combustion chamber  13 . The time-delay ignition insures that the turbulence generating means  32  at the time of ignition is still displaceable, and a strong turbulence of the air-fuel mixture still occurs.  
         [0053]     In the setting tool  10  shown in  FIG. 6 , there is further provided set means  49  in form of an adjusting wheel which is manually operated by the user. The electrical conductor  53  connects the set means  49  with the time delay means  48 . The set means  49  is used for adjusting the setting energy by adjusting the time delay means  48  and thereby the time delay of the ignition. The set means  49  includes a scale  57  that can be graduated in absolute values, e.g., in joules (J) or in relative values, e.g., in %-readings for the setting energy. Thereby, the user can preset the setting or drive-in energy of the setting tool  10  with the adjusting wheel, using the scale  57 . This adjustment or presetting of the setting energy is possible because in the setting tools, such as the setting tool  10 , with a pulsed-driven turbulence generating means  32 , the setting energy depends on the time the ignition takes place after the turbulence generating means  32  or the turbulence generating plate  33  has been actuated. This dependence will now be described with reference to the diagram of  FIG. 7 . In  FIG. 7 , the graph  60  shows dependence of the setting energy in J on time, wherein t=0 at point  62  indicates the time at which the displacement of the turbulence generating plate  33  ended. As can be seen, the setting energy is minimal in the initial phase of the displacement of the turbulence generating plate  33  between about t=−25 to −20 msec and between t=5-17 msec. A maximal setting energy is achieved at t being about from −15 msec to −5 msec.  
         [0054]     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.