Abstract:
The present invention relates to an internal combustion-operated setting tool for driving fastener elements such as nails, bolts, pins into a substrate, having a fuel source, with a fuel feed line from a fuel source to a combustion chamber and having at least one dosing device ( 30 ), which is arranged between the fuel source and the combustion chamber. For improving such setting tools, a displacement body ( 50 ) is arranged in a chamber in the dosing device ( 30 ) for forcing fuel out of the chamber, whose displacement volume can be adjusted.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an internal combustion-operated setting tool for driving fastener elements such as nails, bolts, pins into a substrate, having a fuel source, with a fuel feed line from a fuel source to a combustion chamber and having at least one dosing device, which is arranged between the fuel source and the combustion chamber. A displacement body is arranged in a chamber in the dosing device for forcing fuel out of the chamber. This type of setting tool can be operated using gaseous or liquid fuels, that are burnt in a combustion chamber and wherein a drive piston for fastening elements is driven.  
           [0003]    2. Description of the Prior Art  
           [0004]    Generally, there is the problem of dosing the fuel for each work cycle with a calibrated quantity of a corresponding air or oxygen mix as the oxidation agent. The oxygen quantity available for the combustion process is heavily dependent on the ambient temperature as well as on the air pressure and humidity. The required fuel quantity therefore varies with the aforementioned parameters quite substantially—in the extreme case up to 40%. These variations can have adverse ramifications on the combustion of the air-fuel mixture if the air-fuel mixture is too rich or too lean in fuel. It is therefore desirable to match the fuel quantity to the respective ambient conditions.  
           [0005]    An internal combustion-operated setting tool of this general type is described in EP 0 597 241, wherein the metered feed of the fuel from the fuel source to the combustion chamber is done via a dosing device, which comprises a valve actuated by a solenoid, which is normally closed. The actuation is effected electronically by a switch circuit, which reacts to a switch and opens the valve for a controllable set time interval to enable a flow of the fuel from the fuel source to the combustion chamber.  
           [0006]    The drawback is that with varying upstream pressure in the fuel source, the flow rate of the fuel is variable and accordingly results in imprecise dose quantities.  
           [0007]    DE 42 43 617 A1 further discloses a setting tool, wherein a gas inlet valve is mechanically opened, in a work cycle,, such that fuel from a fuel source reaches a holding space, which communicates with the environmental air. A pressure or eventually a temperature equalization with the environmental air can take place via this connection, such that an adapted air-fuel mixture reaches the combustion chamber. From this holding space the fuel then reaches the combustion chamber at the appropriate time. The disadvantage is that a fuel loss can occur via the communication to the environmental air. In addition, the pressure in the dosing chamber cannot be regulated.  
         SUMMARY OF THE INVENTION  
         [0008]    The object of the present invention therefore resides in developing a setting tool of the aforementioned type, which prevents the aforementioned drawbacks and in which an exact dosing of the fuel is assured. This is achieved according to the invention when the dosing system comprises a displacement body arranged in a chamber, whose displacement volume and dosing quantity can be set or changed. The inside volumes of the dosing chamber or the reservoir space is constant in the start position of the displacement body. The dose quantity can thus be set in simple fashion by the volume displaced by the displacement body. The displacement body thus assumes simultaneous pushing out of the fuel dose quantity from the dosing device. A very simple construction and high functionality of the dosing device can be achieved by this double function and the fuel quantity can be matched to the environmental conditions.  
           [0009]    It can be advantageous if the displacement volume of the displacement body is adjustable using a control device. This control device can be mechanical or electronic. The user of the setting tool according to the invention no longer has to make the adjustment of the displacement volume himself since this adjustment is taken over by the control device. The device is thus very easy to operate.  
           [0010]    In an advantageous embodiment of the setting tool, a manually actuated setting means is provided on the setting tool, in which the displacement volume of the displacement body can be set by the user. Such a means is, for example, a knurled wheel on the outside of the device or a slider switch. In this fashion, a plurality of switch settings or even continuous setting can be done.  
           [0011]    In an advantageous further embodiment of the setting tool, sensor means are provided on the tool for picking of device and environmental parameters for forwarding the collected data to the control device. The control device can set the required fuel quantity for each work cycle of the setting tool as a factor of the parameters determined by the sensor means and correspondingly control the displacement volume of the displacement body. These parameters can include the air pressure, atmospheric humidity, air temperature and the device temperature.  
           [0012]    The sensor means advantageously comprise sensors for determining the air pressure, the temperature and the humidity of the ambient air. Furthermore, a sensor can also be provided for acquiring the internal temperature of the combustion chamber. Measured data can be collected by these sensors in sufficient quantity, that can be used for the determination of an ideal oxidation agent-fuel mixture.  
           [0013]    It is of further advantage if the chamber that is configured as a dosing chamber has an inlet and an outlet through which the dosing chamber is connected to the fuel source, on the one hand, and with the combustion chamber, on the other hand. Advantageously, valve means such as non-return valves are arranged both at the inlet and at the outlet, which allow fuel transport only in the direction of the combustion chamber. Incorrect quantities at the time of dosing of the fuel are thereby prevented since it is assured that the total displaced fuel is supplied to the combustion chamber.  
           [0014]    In an advantageous further embodiment of the invention, the displacement body is configured as a piston that is displaceable guided in an optionally cylindrical chamber. The piston stroke, which can be adjusted via the control device or the adjustment means, defines the displacement volume of the displacement body configured as a piston.  
           [0015]    In an advantageous alternative embodiment, the displacement body is configured as a membrane, which is arranged in an opening of the dosing chamber that it seals impermeable to the media. The membrane can be moved into the chamber using an appropriate admission means, wherein the membrane stroke, which defines the displacement volumes is adjustable via the control device. The membrane can accordingly be loaded hydraulically using air or an appropriate fluid or using a displaceable plunger. The advantage in the embodiment as a membrane is the easily achieved seal at the interface between the membrane and the chamber.  
           [0016]    It can also be advantageous if the displacement body can be loaded using an electrical actor such as a solenoid, a piezo-element or a motor drive. The displacement body can be moved at a specific displacement such that a fuel quantity with defined volumes is pushed out of the dosing chamber and supplied to the combustion chamber. The actor then moves the displacement body with an adjustable displacement that corresponds to a certain displacement volume.  
           [0017]    The displacement body can, however, be operated mechanically as well. For example, if a compression movement of the setting tool on a substrate can be utilized to move the displacement body into the dosing chamber and to withdraw a fuel quantity that corresponds to the displacement volume from the dosing chamber. The displacement volume is advantageously preset using the setting means or using the control device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    Other advantages and features of the invention are apparent from the following description with reference to the drawings, wherein:  
         [0019]    [0019]FIG. 1 shows a first embodiment of a setting tool according to the invention, in a partial longitudinal section;  
         [0020]    [0020]FIG. 2 shows a cutout of the setting tool of FIG. 1 with the dosing system;  
         [0021]    [0021]FIG. 3 shows a second embodiment of a setting tool according to the invention, in a partial longitudinal section;  
         [0022]    [0022]FIG. 4 shows a cutout of the setting tool of FIG. 3 with the dosing device; and  
         [0023]    [0023]FIG. 5 shows a cutout of a third embodiment of a setting tool according to the invention with the dosing device.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    [0024]FIGS. 1 and 2 show the setting tool  10  according to the invention, in a first embodiment, in its starting or resting position. In this first embodiment, the setting tool  10  is operated using a fuel gas. The setting tool  10  has a housing  14 , in which a setting mechanism is arranged, by which a fastener element (not shown) can be driven into a substrate (not shown), when the setting tool is urged against a substrate and triggered.  
         [0025]    The setting mechanism comprises inter alia a combustion space or a combustion chamber  13 , a piston guide  17 , in which a driving piston  16  is displaceable arranged and a bolt guide  18 , in which the fastener element can be guided and where a fastener element moves over end of the driving piston moving forward towards the setting end and can be driven into a substrate. The fasteners can be supplied in a magazine  19  on the tool.  
         [0026]    In the first embodiment, there is an ignition element in the combustion chamber  13  such as a spark plug  23  for firing a fuel gas - air mixture supplied to the combustion chamber  13 . The supply of the fuel gas into the combustion space or the combustion chamber  13  is achieved over a fuel feed line  12  from the fuel reservoir or a fuel source  11 . The supply direction of the fuel gas from the fuel reservoir  11  to the combustion chamber  13  is indicated with the reference  26  in FIG. 1.  
         [0027]    In addition, the setting tool  10  has an electronic control device  20 , which is connected via electrical lines  47  to a power source  27  such as a battery or a battery pack. The control device  20  controls the point in time of firing and accordingly controls the firing unit or the spark plug  23  via the electrical line  43 . A setting operation is triggered by the operator by pressing the setting tool  10  against a substrate and by actuating a switch means  25  on a hand grip  15  of the setting tool  10 , which forwards the trigger command via an electrical line  45  to the control device  20 . When this is done, the setting tool  10  can also be configured without a control device.  
         [0028]    In addition, a manually adjustable dosing device  30  is arranged in the fuel feed  12 . The dosing device  30  is reproduced in more detail in FIG. 2. The dosing device  30  has a chamber  31  arranged in a housing  54 . The chamber  31  is connected via an inlet  32  with the fuel feed  12  from the fuel source  11  (not shown here). The chamber  31  is further connected with the section of the fuel feed  12  leading to the combustion chamber  13  via an outlet  33 .  
         [0029]    A valve  34  is arranged at the inlet  32 , which merely enables an entry/inflow of fuel into the chamber  31 . A valve  35  is arranged at the outlet  33 , which merely enables exit/outflow of fuel from the chamber  31 . A displacement body  50 , which is configured as a piston, is glided into an opening  36  to the chamber  31  and sealed against the side wall of the opening  36  using at least one seal element  53 . The displacement body  50  is fixed, at its end facing away from the chamber  31 , on an actuating means  24 , such as a pressure rod (compare also FIG. 1). The maximum stroke of the displacement body  50  in the chamber  31  can be manually set by the user by a setting means  52 , such as a knurled screw.  
         [0030]    [0030]FIG. 2 shows the displacement body  50  initially in its starting position  50 . 1 . If the setting tool  10 , in a first position of the setting means  24  is urged against a substrate, then the displacement body  50  is moved in the direction of the arrow  56  to an end position  50 . 2 . With this stroke of the displacement body  50 , a fuel volume is forced out of the chamber  31  and guided via the opening spring biased valve  35  through the outlet  33  and the fuel feed line  13  of the combustion chamber.  
         [0031]    In another position of the setting means  24 , for example, for the operation of the setting tool  10  under cold conditions, the displacement body  50  moves in the direction of the arrow into the end position  50 . 3 , upon urging the setting tool  10 . In this longer stroke of the displacement body  50 , a fuel volume larger than that described herein is now forced out of the chamber  31  and led off to the combustion chamber  13 . In addition, a means for temporarily holding the displacement body  50  in its end position can be provided such that with an intended lifting and urging the setting tool  10 , prior to triggering the setting tool  10 , prevents a repeat supply of fuel to the combustion chamber  13 .  
         [0032]    The setting tool  10  shown in FIGS. 3 and 4 differs essentially from the setting tool of FIGS. 1 and 2 in that the control device  20  also controls dosing system  30  and the displacement volume of the displacement body  50 . In addition, the control device  20  can be equipped with a microprocessor, in which a control program for one or several device functions can run.  
         [0033]    The control device  20  is connected via an electrical line  44  with the dosing device  30  using an electrical actor  55 . The control device  20  is connected with the spark plug  23  via the electrical line  43 . The switching means  25  or the trigger switch on the hand grip  15  of the setting tool  10  switches electronically and is connected via an electrical line  45  with the control device  20 . In addition, in the control device  20 , measurement data and parameters from sensors, such as a sensor for acquiring the temperature of the combustion chamber and a sensor  21  for acquiring the temperature and pressure of the ambient air, can be analyzed and converted to control signals. The sensor  22  is connected via the electrical line  42  and the sensor  21  via the electrical line  41  with the control device  20 . The electrical lines or connections  41 ,  42 ,  43 ,  44 ,  43 ,  47  can be used for the electrical energy supply and for electronic data transfer. Along with the sensors  22 ,  21 , other sensors can transfer measurement data to the control device  20 .  
         [0034]    Concerning the principal architecture of the dosing device  30 , reference is made to the entirety of the above description relative to FIG. 1 and  2 . Here, the control of the displacement body  50  is changed, which can be actuated in the direction of the arrow using the electrical actor  55 . The displacement body  50  can be moved dependent on the acquired parameters and the respective control command from the control device  20  to different end positions  50 . 1 ,  50 . 2 ,  50 . 3  such that a quantity of fuel corresponding to the displacement volume is supplied in the described manner to the combustion chamber.  
         [0035]    A variant of an electronically controlled dosing device  30  is shown in FIG. 5. The displacement body  51  is configured as a membrane that closes the one opening  36  of the chamber  31 . In this example, the displacement body  51  or the membrane can be actuated by an electrical actor  55  and is moveable in the direction  56  from a starting position  51 . 1  into different end positions  51 . 2 ,  51 . 3 .  
         [0036]    With regard to FIG. 5, reference is made to the preceding description relative to FIGS.  1  to  4  in their entirety. In addition, it is true that actuation of the displacement body  50 ,  51  in the exemplary embodiments pursuant to FIG. 3 can be done pulse-like, so that a high flow or current rate of the fuel to the combustion chamber  13  can be achieved. This can be used on an injection nozzle at the end of the fuel feed  12  on the combustion chamber  13  for fine atomization of the fuel.