Patent Publication Number: US-2020282536-A1

Title: Fuel-powered setting device and method for operating such a setting device

Description:
TECHNICAL FIELD 
     The present invention relates to a combustion-powered setting tool for driving fastening elements into a substrate, having at least one main combustion chamber for a fuel, having a drive piston actuatable by way of expandable gases from the main combustion chamber in the setting direction, and having a prechamber, to which an ignition device is assigned and in which a pressure acting on the main combustion chamber is buildable before the ignition of a fuel-air mixture in the main combustion chamber, the prechamber being connected or connectable to the surroundings of the prechamber by at least one passage opening, which is closeable by a control device. The present invention further relates to a method for operating such a combustion-powered setting tool. 
     BACKGROUND OF THE INVENTION 
     German patent publication DE 10 32 035 A1 discloses a combustion-powered setting tool for driving fastening elements into a substrate, which has at least one main combustion chamber for a fuel, one drive piston mounted in a piston guide actuatable in the setting direction by way of expandable gases from the main combustion chamber, and which has a prechamber, in which a pressure acting on the main combustion chamber is buildable prior to the ignition of a fuel-air mixture in the main combustion chamber, the prechamber being formed within the piston guide by a space connecting to the bottom side of the drive piston, which is in its initial position, facing away from the main combustion chamber, and the prechamber at least temporarily being connected via a passage opening to the main combustion chamber, and in the main combustion chamber a means for detecting the pressure being provided, which acts together with the ignition device for the main combustion chamber. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to improve the effectiveness and/or functionality when in-driving fastening elements using a combustion-powered setting tool, having at least one main combustion chamber for a fuel, having a drive piston actuatable by way of expandable gases from the main combustion chamber in the setting direction, and having a prechamber, to which an ignition device is assigned and in which a pressure acting on the main combustion chamber is buildable prior to the ignition of a fuel-air mixture in the main combustion chamber, the prechamber being connected or connectable to the surroundings of the prechamber by at least one passage opening, which is closeable by a control device. 
     The object of the present invention for a combustion-powered setting tool for driving fastening elements into a substrate, having at least one main combustion chamber for a fuel, having a drive piston actuatable in the setting direction by way of expandable gases from the main combustion chamber, and having a prechamber, to which an ignition device is assigned and in which a pressure acting on the main combustion chamber is buildable prior to the ignition of a fuel-air mixture in the main combustion chamber, the prechamber being connected or connectable to the surroundings of the prechamber by at least one passage opening, which is closeable by a control device, is achieved in that the control device includes an electronic controller. Undesireable frictional losses during operation of the combustion-powered setting tool can be significantly reduced by the use of the electronic controller for closing or releasing the passage opening of the prechamber. As a result, the service life of the combustion-powered setting tool can be extended. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the electronic controller is connected to an electronic actuator. Via the electric actuator, the passage opening of the prechamber can be quickly closed or released in a simple manner. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the electric actuator includes an electric motor. Via the electronic controller, the electric motor can be actuated in a fast and simple manner. For the representation of the electric actuator, the electric motor, for example, is mounted on the outside of a housing, in particular a prechamber cylinder. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the electric actuator is mechanically coupled to a control sleeve. The mechanical coupling between the electric actuator and the control sleeve includes, for example, a type of gear mechanism. For example, the control sleeve substantially has the shape of a circular cylinder jacket, which relative to a housing, in particular the prechamber cylinder delimiting the prechamber, is moveable between an open position, in which the passage opening is released or open, and a closed position, in which the passage opening of the prechamber is released. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control sleeve has a toothing, which is coupled to the electric actuator via a gear wheel. For example, the toothing can be provided at a toothed rod, which is fastened to the outside of the control sleeve. Advantageously, the gear wheel using the toothing meshes with the toothed rod. In so doing, a gear mechanism can be embodied in a simple manner, via which the control sleeve can be moved by the electric motor, which is actuated by the electronic controller. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control sleeve is configured in such a manner that, and is moveable in relation to the passage opening of the prechamber so that the passage opening of the prechamber is released or closed by the control sleeve via the electronic controller by way of the electric actuator. For example, the movement of the control sleeve between the open position and the closed position is enabled by guiding the control sleeve at the housing or the prechamber cylinder delimiting the prechamber. Given a complete overlapping between a passage opening in the control sleeve and the passage opening of the prechamber, a passage cross section or outlet cross section of the prechamber is maximized. In the closed position, the passage opening of the prechamber preferably is completely closed by the control sleeve. Via the electronic controller, any intermediate positions of the control sleeve can be represented in a simple manner. Thus, with the aid of the electronic controller and the electric actuator, the passage cross section can be infinitely varied between the open position and the closed position. In so doing, particularly advantageously a power adjustment or setting becomes possible during operation of the setting tool. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the electronic controller is connected to at least one sensor device, which is assigned to the main combustion chamber. The sensor device, for example, can be a pressure sensor, which detects a pressure in the main combustion chamber. The signal of the pressure sensor is processed in the electronic controller of the control device. The sensor device can include further sensors, which detect an ambient pressure, a pressure in the prechamber, an acceleration of the setting tool and/or a temperature at any location of the setting tool, for example. 
     According to a further exemplary embodiment, the electronic controller of the control device can have a user interface. Via the user interface, the user of the setting tool can individually modify or adjust a power setting. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the electronic controller is connected to the ignition device, which is assigned to the prechamber. As a result, a time-oriented sequential control can be enabled in a simple manner during operation of the combustion-powered setting tool. Opening and closing the passage opening of the prechamber can be carried out in a time-controlled manner after a specific period of time has elapsed following an ignition in the prechamber. For this purpose, for example a time interval, which begins with the ignition in the prechamber, is measured in the electronic controller of the control device. According to the previously set time interval, the electric actuator for opening the passage opening of the prechamber can, also via the electronic controller, be then automatically activated with the aid of the control sleeve. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that a further ignition device is assigned to the main combustion chamber. The setting tool previously described can be operated by only one ignition device assigned to the prechamber. Following an ignition in the prechamber, the reaction gases from the prechamber expand into the main combustion chamber having a spreading flame front. Via the flame front spreading into the main combustion chamber, the ignition of a pre-compressed fuel-air mixture included in the main combustion chamber then occurs in the main combustion chamber. The ignition of the fuel-air mixture in the main combustion chamber may however also take place via the further ignition device in the main combustion chamber. 
     In a method for operating a combustion-powered setting tool described previously, the above indicated object is alternatively or additionally achieved in that the control of the passage opening of the prechamber is carried out by the main combustion chamber pressure. In so doing, a combustion-powered or gas-powered setting tool, which has a substantially higher energy density, can be implemented in a simple manner. The previously described measures enable to control a ventilation of the prechamber in a particularly simple manner. For this purpose, an undesirable wear of the setting tool when in use may be reduced. Moreover, by controlling the passage opening of the prechamber by the main combustion chamber pressure, a significantly increased service life of the setting tool can be ensured. 
     A preferred exemplary embodiment of the method is characterized by the fact that the control of the passage opening of the prechamber is carried out as a function of the ignition time and the sensor. In so doing, the control of a prechamber ventilation when operating the combustion-powered setting tool can be implemented in a simple manner. 
     Optionally, the present invention also relates to a computer program product having a program code for carrying out a previously-described method, in particular if the program is executed in the control of the setting tool. 
     The present invention further relates to a control device, in particular an electronic controller, an electric actuator and/or a control sleeve for a previously-described setting tool. The mentioned parts are optionally separately negotiable. 
    
    
     
       Further advantages, features and details of the present invention result from the subsequent description, in which different exemplary embodiments are described in greater detail on the basis of the drawing. In the figures, 
         FIG. 1  shows a longitudinal section of a simplified illustration of a combustion-powered setting tool including a control device prior to an ignition in a prechamber; 
         FIG. 2  shows a similar setting tool as in  FIG. 1  in a longitudinal section, having a different control device, shortly before an ignition in a prechamber. 
     
    
    
     EXEMPLARY EMBODIMENTS 
       FIGS. 1 and 2  show a setting tool  1  in a greatly simplified manner in a longitudinal section in different operating states. Setting tool  1  illustrated in  FIGS. 1 and 2  can be operated by a combustion gas or by a vaporizable liquid fuel. Setting tool  1  includes a housing  3  having a main cylinder  5 , which delimits a main combustion chamber  6 . Gas and/or air can be supplied to main combustion chamber  6  via an inlet device  8 . 
     In  FIGS. 1 and 2 , a drive piston  10  is guided moveably back and forth in the downward and upward directions in housing  3  of setting tool  1 . Drive piston  10  includes a piston rod  11 , which emanates from a piston head  12 . A setting end  14  of piston rod  11  facing away from piston head  12  is situated in a bolt guide (not shown), which serves the purpose of guiding fastening elements which are also referred to as bolts. 
     The bolt guide including piston rod  11  of drive piston  10  situated therein is also referred to as a setting mechanism. Via the setting mechanism, a fastening element such as a nail, bolt or the like can be driven into a substrate (not shown). Before setting the fastening element, setting tool  1  is pressed by its bolt guide against the substrate, and is triggered. For example, a switch (not shown), which is also referred to as a trigger switch, serves to trigger a setting procedure. The switch, for example, is provided at a handlebar of setting tool  1  (also not shown). 
     In  FIGS. 1 and 2 , a setting direction is indicated by an arrow  15 . When setting the fastening elements, drive piston  10  is greatly accelerated by piston rod  11  in setting direction  15  to drive the fastening element into the substrate. During the setting procedure, drive piston  10  is moved from its initial position shown in  FIGS. 1 and 2 , which corresponds to a top dead center, into an end position, which corresponds to a bottom dead center. 
     A movement of drive piston  10 , in  FIGS. 1 and 2  in the upward direction, is limited by a piston stop  16  fixedly joined with the cylinder. Piston stop  16  defines the top dead center of drive piston  10 . Piston stop  16  may be combined with a magnetic device  17 . Magnetic device  17 , for example, serves to keep drive piston  10  by a predetermined holding force in its initial position shown in  FIGS. 1 and 2 . 
     A movement of drive piston  10  in the downward direction is limited by one or a plurality of stops and/or damping elements  28 ,  29 . Stop and/or damping elements  28 ,  29  are configured as a buffer, for example. 
     Piston head  12  includes a first piston surface  21 , which faces main combustion chamber  6 . A second piston surface  22 , which is facing away from main combustion chamber  6 , delimits a prechamber  25  in a prechamber cylinder  24 . Prechamber cylinder  24  is part of housing  3  of setting tool  1 . 
     Prechamber  25  represents a pre-combustion chamber, to which an ignition device  26  and an inlet device  27  are assigned. Moreover, stop and/or damping elements  28 ,  29  are situated in prechamber  25 . Via inlet device  27 , a fuel-air mixture is supplied to prechamber or pre-combustion chamber  25 , which is ignited in prechamber  25  with the aid of ignition device  26 . 
     Prechamber cylinder  24  includes two passage openings  31 ,  32 , which, for example, enable the discharge of exhaust gases from prechamber  25 . Passage openings  31 ,  32  are closeable on demand by a control device  30 . Control device  30  includes a control sleeve  34 , which has two passage openings  37 ,  38 . 
     If passage openings  37 ,  38  of control sleeve  34  are positioned to overlap with passage openings  31 ,  32 , then passage openings  31 ,  32  are open. In  FIGS. 1 and 2 , passage openings  31 ,  32  are closed by control sleeve  34 . Control sleeve  34  substantially has the shape of a straight circular cylinder jacket and in  FIGS. 1 and 2  is moveable in the upward and downward directions. 
     Two or a plurality of overflow openings  41 ,  42  are provided between prechamber  25  and main combustion chamber  6 . Respectively one valve device  43 ,  44  is assigned to overflow opening  41 ,  42 . Valve devices  43 ,  44 , for example, may be valve flaps, which open as a function of pressure, to enable the passage of the fuel-air mixture from prechamber  25  into main combustion chamber  6 . In  FIGS. 1 and 2 , valve devices  43 ,  44  are closed. 
     The exemplary embodiments of setting tool  1 ;  121  illustrated in  FIGS. 1 and 2  for the representation of control device  30  include an electronic controller  100 . A control line  102  connects electronic controller  100  in terms of control to an electric actuator  104 . Electric actuator  104  includes an electric motor  105  having a shaft  106 . At an end of shaft  106  facing away from electric motor  105 , a gear wheel  108  is indicated, which can be rotatably actuated by electric motor  105 . 
     Gear wheel  108  meshes with a toothing  110 , which is configured as a straight toothing. For example, toothing  110  can be configured at a toothed rod provided at the outside of control sleeve  34 . When gear wheel  108  rotates counterclockwise, control sleeve  34  in  FIGS. 1 and 2  moves in the downward direction, thus, in setting direction  15 . When gear wheel  108  rotates clockwise, control sleeve  34  in  FIGS. 1 and 2  moves in the upward direction, thus, against setting direction  15 . 
     Electric motor  105  of electric actuator  104  may be a linear motor, for example. Instead of electric motor  105 , electric actuator  104  may also include a different actuator, for example a piezo actuator. Different from the illustrations, control sleeve  34  for opening and closing passage openings  31 ,  32  of prechamber  25  can also be differently moved, for example twisted. The movement of control sleeve  34  can occur in any manner by applying a voltage. 
     For setting tool  1  illustrated in  FIG. 1 , a sensor device  112  is assigned to main combustion chamber  6 . Sensor device  112  is connected in terms of control to the electronic controller of control device  30  via a control line  101 . Sensor device  112  includes a pressure sensor, by which the pressure in main combustion chamber  6  is detected. When operating setting tool  1 , sensor device  112  issues a signal, which is processed in electronic controller  100 . 
     Electronic controller  100  can have further sensor inputs which are connected to further sensor devices (not shown). The further sensor devices may detect, for example, an ambient pressure or a pressure in prechamber  25 . Alternatively or additionally, the further sensor devices may detect an acceleration and/or a temperature in different locations during operation of setting tool  1 . 
     Moreover, the electronic controller advantageously includes a user interface. Via this user interface, a user of setting tool  1  can individually set the desired power for operating setting tool  1 . With the aid of electronic controller  100 , inter alia on the basis of the sensor data and user data, the following processes are controlled during operation of setting tool  1 : an electronic control of a dosing amount, a control of ignition device  26  in prechamber  25  and/or of a further ignition device (not shown in  FIG. 1 ), which may be assigned to main combustion chamber  6 . Moreover, a not-shown ventilator for forming a mixture prior to combustion and/or for flushing is controlled after combustion by electronic controller  100 . 
     With the aid of electric actuator  104 , an effective passage cross section in passage openings  31 ,  32  of prechamber  25  may be infinitely variably adjusted in a simple manner via control sleeve  34 . Particularly advantageously, a power setting or power adjustment by the user is enabled by the flexible control of the passage cross section. If the user of setting tool  1  chooses a low power setting, the prechamber ventilation only opens partially, later or not at all. This results in that when operating setting tool  1 , an air cushion or a cushion of combustion gases is built up in prechamber  25 . This cushion enables that drive piston  10  can be slowed in a significantly more gentle manner than slowing drive piston  10  suddenly, when the drive piston impacts stops and/or damping elements  28 ,  29  in prechamber  25 . As a result, the wear of the tool can be reduced and the lifespan of the tool can be extended. 
     With the aid of electric actuator  104 , the closing and release of passage openings  31 ,  32  of prechamber  25  can be controlled via electronic controller  100  in a simple manner as a function of the ambient air temperature and the ambient pressure. For both mentioned parameters, the density of air or of the fuel-air mixture changes prior to combustion in prechamber  25  and in main combustion chamber  6 . This influences the combustion chamber pressure in main combustion chamber  6 . In order to ensure constant power in a simple manner, the effective passage cross section of passage openings  31 ,  32  can be adapted. 
     For setting tool  121  illustrated in  FIG. 2 , it is illustrated that a further ignition device  126  can be assigned to main combustion chamber  6 . Via further ignition device  126 , a gas mixture can be ignited in main combustion chamber  6  independent from whether an ignition already has occurred in prechamber  25 . In so doing, further operating modes of setting tool  121  become possible. 
     Different from setting tool  1  shown in  FIG. 1 , a control line  141  is provided for setting tool  121  shown in  FIG. 2 , which connects electronic controller  100  of control device  30  to ignition device  26  of prechamber  25 . As a result, a time-oriented sequential control of the prechamber ventilation is enabled in a simple manner. In this instance, the opening and closing of passage openings  31 ,  32  of prechamber  25  by control sleeve  34 , for example, is triggered after a specific period of time has elapsed after the ignition in the prechamber. 
     For example, electronic controller  100  measures a time interval which begins with the ignition in the prechamber. After the previously set time interval has elapsed, passage openings  31 ,  32  of prechamber  25  are released by control sleeve  34  via electric actuator  104 , that is the passage openings are opened. Inter alia, this has the advantage that a sensor device ( 112  in  FIG. 1 ) can be omitted.