Abstract:
A combustion-engined setting tool for driving fastening elements such as, e.g., nails, blots, etc. in constructional components includes a combustion chamber ( 13 ) for combusting therein an oxidant-fuel mixture, a turbulence generating element, arranged in the combustion chamber ( 13 ) for creating turbulence of the oxidant-fuel mixture, and a drive for at least partially driving the turbulence generating element ( 32 ) and including a mechanical device ( 30 ) for a pulsed acceleration of the turbulence generating element ( 32 ) and which is activated by the actuation switch ( 35 ) that actuates the setting process.

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, e.g., nails, bolts, and the like and includes an actuation switch for actuating a setting process, a combustion chamber for combusting therein an oxidant-fuel mixture, turbulence generating means arranged in the combustion chamber for creating turbulence of the oxidant-fuel mixture, and drive means for at least partially driving the turbulence generating means. 
   2. Description of the Prior Art 
   In the setting tools of the type described above, a portion of 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 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. 
   European Patent EP 0 711 634B1 discloses a combustion-engined setting tool having a combustion chamber for combusting an air-fuel gas mixture and in which there is provided ventilator means for creating turbulence. The ventilator means is driven by an electric motor that is supplied with electrical energy from a battery. 
   The drawbacks of the described tool consists in an increased weight because of addition of the battery or accumulator, and in a need to replace them when their electrical energy expires. 
   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. 
   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 of the environmental pressure. This results from the fact that the turbulence generation takes place 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. 
   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. 
   Here, likewise, the drawback consists in that the combustion process is sensible to the fluctuations of the environmental conditions such as, e.g., temperature, scavenging ratio of the combustion chamber or environmental pressure. 
   The object of the present invention is to provide a setting tool of the type described in above and in which the drawbacks of the known tools are eliminated. 
   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 
   These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a setting tool the drive means of which includes a mechanical device for a pulsed acceleration of the turbulence generating means and which is actuated by the actuation switch that actuates the setting process. 
   The present invention permits to create turbulence in the combustion chamber without using the electrical energy and which is noticeably stronger than the turbulence which is generated by the passage of flame jets through the openings in the separation plate. In particular, according to the invention, the turbulence is generated in the entire combustion chamber and not only in a portion of the combustion chamber. Further, there is no noticeable time delay between actuation of the actuation switch and the setting process. The pulsed acceleration provides for displacement of the turbulence generating means within a range from 1 to 200 msec, preferably from 5 to 100 msec. Further, the displacement or the operation of the turbulence generating means for a such short period of time does not require much energy. With a mass of the turbulence generating means from about 1 to 200 g the energy of only from about 1 mJ to 1 J is needed. Because of the low energy requirement, it can be obtained by conversion of the press-on movement of the setting tool against a constructional component in to a mechanical energy of the mechanical device, without excessively tiring the setting tool operator. 
   A further advantage of the selling tool according to the present invention consists in that it provides for carrying out rapidly following one another setting processes. 
   It is beneficial when the mechanical device imparts a pulsed acceleration in a range from 1 m/s 2  to 5,000 m/s 2  to the turbulence generating means. This permits to achieve very short acceleration time periods and high displacement speeds of the turbulence generating means. It is particularly advantageous when the mechanical device imparts to the turbulence generating means a pulsed acceleration of at least 25 m/s 2 , in particular, of about 60 m/s 2 . 
   Advantageously, the mechanical device includes a force storing element that can be loaded when the setting tool is pressed against a constructional component. Advantageously, the force storing component is formed as a spring element. Such a spring element only slightly increases the necessary press-on force, producing no inconvenience for the setting tool operator. 
   It is beneficial when the force storing element applies an acceleration force from 1 to 50 N to the turbulence generating means. With such a force storing element, the inventive acceleration values can be easily achieved, without any additional measures. 
   Advantageously, the press-on element is formed as a rod with which the force storing element is loaded. With such press-on element, the force or energy, which is produced by the press-on movement, can be easily introduced mechanically into the force storing element. 
   Advantageously, the turbulence generating means is displaced in the combustion chamber substantially friction-free. Thereby, no energy losses or braking of the turbulence generating means occurs because of friction during the displacement of the turbulence generating means in the combustion chamber. In order to obtain a substantially friction-free guidance, a sufficiently large clearance can be provided in all of support/sliding locations and/or special materials with low friction coefficients can be used. There also exists a possibility of using stationary turbulence generating means. 
   According to one of advantageous embodiments of the present invention the turbulence generating means is formed as a turbulence generating plate provided with through-openings and axially displaceable in the combustion chamber. The turbulence generating plate can be guided along an axially extending tube or rod arranged in the combustion chamber or be connected with the force storing element, without any displacement. The through-openings can be formed as slots or holes. The turbulence generating plate can be formed also as a mesh plate. Further, the turbulence generating plate can be formed as a bulged plate, with the concave tide of the turbulence generating plate falling, preferably, in the direction of the pulsed movement. Such a turbulence generating plate has a high aerodynamic drag value and thereby produces a large turbulence at a rapid displacement. It should be understood that with a collapsed combustion chamber, the displacement of the turbulence generating plate only possible at least in the partially expanded condition of the combustion chamber. 
   According to a further advantageous embodiment of the present invention, the turbulence generating means is formed as a rotatable stirring element. This stirring element is driven, e.g., by a mechanical device formed, e.g., as a spring drive with a free run, with the spring drive being formed by a spring element which also functions as the force storing element. Such stirring element has a high aerodynamic drag value and has an advantage that consists in that the stirring element still runs after the pulsed acceleration has ended. 
   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 drawing show: 
       FIG. 1  a longitudinal, partially cross-sectional view of a setting tool according to the present invention in an inoperative position; 
       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; 
       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; 
       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, and the trigger is actuated; 
       FIG. 5  a longitudinal, partially cross-sectional view of the setting tool shown in  FIG. 1 , in which the tool is completely pressed against a constructional component, with the ignition having taking place; 
       FIG. 6  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; and 
       FIG. 7  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 and the trigger has been actuated. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A setting tool  10  according to the present invention, which is shown in  FIGS. 1–6 , operates on a liquid or gaseous fluid. 
   In  FIG. 1 , the setting tool  10  is shown in its initial or inoperative position. 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. 2–6 ) when the setting tool  10  is pressed against the constructional component U and is actuated. 
   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 a 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 . 
   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 in the combustion chamber  13  (please see  FIG. 2 ) and through which a air-fuel mixture can reach the ignition element  23 . 
   An electrical conductor  45  connects the ignition element  23  with switch means  22 , such as a conventional switch or with a piezoelectrical element which an ignition process is actuated. 
   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 in to 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 ). 
   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 means  32  or plate  33  in an axial direction in the combustion chamber  13 . 
   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 located 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. 
   When the setting tool  10 , as shown in  FIG. 2 , is put 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  and is held there 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 . 
   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. 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 . 
     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. 
   In the position of the setting tool  10  shown in  FIG. 4 , the actuation switch is actuated. 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 an acceleration from 1 m/s 2  to 5,000 m/s 2 . The displacement of the turbulence generating plate  33  causes a strong turbulence  46  of the air-fuel mixture that fills the combustion chamber  13 . The acceleration forces imparted by the force storing element  41  amounts to about from 5 to 30 N. 
   As the turbulence generating plate  33  approaches the combustion chamber rear wall  14 , it actuates the switch means  22 . The switch means actuates the ignition element  23 , whereby the ignition  24  of the air-fuel mixture takes place. The actuation is effected, e.g., by closing an ignition current circuit or by ignition pulse generated by the switch means  22 . The ignition of an air-or other oxidant means-fuel mixture in the combustion chamber can also be effected, e.g., during the pulsed displacement of the turbulence generating means, e.g., by a switch provided at the other location. 
   At the time of ignition, the air-fuel mixture is subjected to a strong turbulence, whereby a high energy yield of the combustion process is achieved. The setting piston  16  is displaced by expanding combustion gases in the direction of arrow  43  towards 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 . 
   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 . 
   In  FIG. 6 , the setting piston  16  has already been displaced in the direction of arrow  48  in its initial position. This can take place, e.g., as a result of generation of underpressure which is produced by cooling of residual combustion gases that remain in the combustion chamber, or by a return mechanism, not shown. 
     FIG. 6  shows a position in which the setting tool  10  is slightly lifted off the constructional component  10 . 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 from 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 loaded (the spring becomes compressed). 
   The setting tool  10 , which is shown in  FIG. 7 , differs from the setting tool  10  shown in  FIGS. 1–6  in that the turbulence generating means  32  is formed as a stirring element  34  or a rotor element with a very steeply extending rotor blades  66 . Further, the mechanical device  30  for accelerating the turbulence generating means  32  is formed as a gear drive  65  that includes the force storing element  31  which is formed as a spring. The gear drive  65  includes a transmission member  61  arranged on the rear wall  14  of the combustion chamber  13  and which is formed as a tooth sack displaceable together with the combustion chamber casing  12 . The transmission member  61  engages a receiving member  62 , which is formed as a tooth gear, for transmission of a press-on movement. The receiving member  62  converts the translatory movement of the transmission member  61  in a rotary movement, transmitting the rotary movement into the force storing element  31 . Thereby, the press-on displacement of the setting tool  10  against the constructional component U tensions and loads the force storing element  31 . 
   The output side of the force storing element  31  is connected with an output member  63  formed as a tooth gear. The output member  63  engages a receiving member  64  of the stirring element  34  which is formed as a tooth rim provided on a hollow shaft  60 . The hollow shaft  60  carries, at its end opposite the tooth rim, rotor blades  66  of the stirring element  34 . The hollow shaft  60  is rotatably supported on a support pin  57  that also carries the ignition unit  23 . The hollow shaft  60  extends through the rear wall  14  or is additionally supported in the rear wall  14 . In the region of the ignition unit  23 , there is provided in the hollow shaft  60  at least one opening  67  that performs the same function as the opening  47  in the previously described embodiment of the inventive setting tool  10  (ignition, flow of fuel into the combustion chamber). 
   As in the previous embodiment, a locking member  39  is provided on the switch rod  36  and which in non-actuated condition of the actuation switch  35 , engages the receiving member  64 , preventing rotation of the stirring element  34 . 
   When the setting tool  10  is completely pressed against the constructional component U, as shown in  FIG. 7 , the force storing element  31  is, as it has already been discussed before, completely loaded. When, as shown in  FIG. 7 , the actuation switch is actuated, by being displaced in the direction of the arrow  42 , the locking member  39  is displaced from its engagement position with the receiving member  64 , releasing the hollow shaft  60 . The force storing member  31  can now be unloaded, with the output member  63  imparting a rotational movement to the stirring element  34 . With the stirring element  34 , a large turbulence  46  is imparted to the air-fuel mixture which by that time has been delivered into the combustion chamber  13 . The switch means  22  can be formed as a flow sensor that would actuate the ignition unit  23  for igniting the air-fuel mixture when a predetermined degree of turbulence is reached. 
   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.