Patent Publication Number: US-2020276692-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 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 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 being in its initial position and 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 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, is achieved in that the control device is connected to the main combustion chamber by control pressure. By way of the control pressure connection, the control device is actuated by the main combustion chamber pressure during operation of the setting tool. After the pressure in the main combustion chamber has reached a certain pressure level, at least one passage opening of the passage opening is then automatically opened. The control pressure connection may be implemented in different ways. 
     A preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control device has at least one control pressure surface which is applied with the main combustion chamber pressure. This has the advantage that no additional sensor device is needed to detect the main combustion chamber pressure. 
     Moreover, the main combustion chamber pressure acting on the control pressure surface may be directly used, for example via a suitable mechanical coupling, to control or affect the opening or the releasing and closing of the passage opening of the prechamber. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control pressure surface of the control device is mechanically coupled to a control sleeve. For example, the control sleeve substantially has the shape of a circular cylinder jacket, which relative to a housing or a 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 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 as a function of the main combustion chamber pressure. The movement of the control sleeve advantageously is controlled by the main combustion chamber pressure acting on the control pressure surface. 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 cylinder delimiting the prechamber. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control pressure surface of the control device is mechanically coupled to the control sleeve via a coupling element. The coupling element may be a slider, for example. Advantageously, the control pressure surface is formed at an end of the slider facing the main combustion chamber. Advantageously, the slider is coupled to the control sleeve at an end of the slider facing away from the main combustion chamber. Advantageously, the slider serves to transfer a pressure force generated by the main combustion chamber pressure acting on the control sleeve surface to the control sleeve. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control pressure surface is braced by at least one spring device at a stop fixedly joined with the housing. The stop fixedly joined with the housing, for example, is attached in the housing or the cylinder delimiting the prechamber. The spring device pretensions the control pressure surface, in particular in combination with the control sleeve, into the closed position, in which the passage opening of the prechamber is closed by the control sleeve. 
     A further preferred exemplary embodiment of the combustion-powered setting tool is characterized by the fact that the control pressure surface is configured as an annular surface and is situated radially outside of a piston guide space. The drive piston is guided moveably back and forth in the piston guide space. In this instance, the drive piston can be guided directly in the piston guide space. It is however also possible to guide a piston rod or a piston plunger of the drive piston in an additional piston guide within the piston guide space. Depending on the configuration, the piston guide space coincides with the prechamber. 
     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 previously described setting tool can only be operated by an ignition device which is 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 undesireable wear of the setting tool when in use may be reduced. Moreover, controlling the passage opening of the prechamber by the main combustion chamber pressure can ensure a significantly increased service life of the setting tool. 
     The present invention further relates to a control device, in particular a control sleeve and/or a coupling element, 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 after an ignition in a prechamber; 
         FIG. 2  shows the setting tool from  FIG. 1  shortly after an ignition in the main combustion chamber; 
         FIG. 3  shows the setting tool from  FIGS. 1 and 2  shortly after the ignition in the main combustion chamber having open passage openings of the prechamber for ventilation; 
         FIG. 4  shows the setting tool from  FIGS. 1 through 3  having a drive piston in a bottom dead center; 
         FIG. 5  shows the setting tool from  FIGS. 1 through 4  having a drive piston in the bottom dead center having a closed control sleeve; 
         FIG. 6  shows the setting tool from  FIG. 1  according to a further exemplary embodiment having a further ignition device, which is assigned to the main combustion chamber; and 
         FIG. 7  shows partially a longitudinal section of a combustion-powered setting tool having a control device after an ignition in a prechamber. 
     
    
    
     EXEMPLARY EMBODIMENTS 
       FIGS. 1 through 5  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  through  5  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 through 5 , 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 also referred to as bolts. In  FIGS. 3, 4, 5 , setting end  14  of piston rod  11  of drive piston  10  is shown in a cut-off manner. 
     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 (also not shown) of setting tool  1 . 
     In  FIGS. 1 through 5 , 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  FIG. 1 , which corresponds to a top dead center, into an end position, which is shown in  FIG. 4 , for example, and corresponds to a bottom dead center. 
     A movement of drive piston  10 , in the upward direction in  FIGS. 1 through 5 , is limited by a piston stop  16  fixedly joined with the housing. 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  FIG. 1 . A movement of drive piston  10  in the downward direction is limited by stop 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 is facing 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  or is rigidly connected to housing  3 . 
     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 , such as it is indicated in  FIG. 1  by a symbol  60 . 
     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, as can be seen in  FIGS. 2, 3, 4 . In  FIGS. 1 and 5 , 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 through 5  is moveable in the upward and downward directions. 
     Two 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 are open in  FIG. 1 , to enable that the fuel-air mixture passes from prechamber  25  into main combustion chamber  6 . In  FIGS. 2 and 5 , valve devices  43 ,  44  are closed. 
     Control device  30  includes a control pressure surface  45 , which is connected in terms of control pressure to main combustion chamber  6 . Control pressure surface  45  is configured as annular surface  46 , which is facing main combustion chamber  6  radially outside of prechamber cylinder  24 . Control pressure surface  45  is mechanically coupled via a coupling element  48  to control sleeve  34 . Coupling element  48  is configured as slider  50 , which in  FIGS. 1 through 5  is guided moveably back and forth in the upward and downward directions at prechamber cylinder  24 . At an upper end  51  of slider  50  in  FIGS. 1 through 5 , a control pressure surface  45  configured as annular surface  46  is provided. Control sleeve  34  is attached at a lower end  52  of slider  50  in  FIGS. 1 through 5 . 
     Control device  30  further includes spring devices  54 ,  55 , which are designed as helical compression springs, for example. Respectively one stop  56 ,  57 , fixedly joined with the housing in  FIGS. 1 through 5 , is assigned to the lower end of spring devices  54 ,  55 . Stops  56 ,  57  fixedly joined with the housing are provided at prechamber cylinder  24 . Spring devices  54 ,  55  together with control pressure surface  45  are clamped between stops  56 ,  57  fixedly joined with the housing and upper end  51  of slider  50 . In so doing, slider  50  is braced at stops  56 ,  57  fixedly joined with the housing via spring devices  54 ,  55 . 
     In  FIG. 1 , setting tool  1  is shown shortly after ignition  60  in prechamber  25 . Arrows  61 ,  62  indicate that the ignited mixture enters main combustion chamber  6  via open valve devices  43 ,  44  through overflow openings  41 ,  42 . Passage openings  31 ,  32  of prechamber  25  are closed by control sleeve  34 . 
     In  FIG. 2 , setting tool  1  is shown shortly after ignition in main combustion chamber  6 . The ignition in main combustion chamber  6  is indicated by a symbol  65 . Ignition  65  in main combustion chamber  6 , for example, is triggered via a flame front from prechamber  25  (not shown). The increased pressure in main combustion chamber  6  closes valve devices  43 ,  44 . At the same time, control device  30  opens passage openings  31 ,  32  so that exhaust gas can escape from prechamber  25 . 
     The release of passage openings  31 ,  32  of prechamber  25  by control sleeve  34  is triggered by the increased pressure in main combustion chamber  6 , which acts on control pressure surface  45  and which is transferred via the slider  50  to control sleeve  34 . By the movement of control sleeve  34  in the downward direction in  FIG. 2 , passage openings  37 ,  38  of control sleeve  34  are positioned to overlap with passage openings  31 ,  32  in prechamber cylinder  24 . 
     In  FIG. 3 , setting tool  1  is shown shortly after ignition  65  in main combustion chamber  6 . Main combustion chamber  6  is also referred to shortly as main chamber  6 . In  FIG. 3 , arrows  66  and  67  indicate that the increased pressure in or from main combustion chamber  6  acts on first piston surface  21  of drive piston  10  facing main combustion chamber  6 , as a result of which the drive piston in  FIG. 3  is moved downwards in setting direction  15 . Arrows  68  and  69  indicate that when drive piston  10  is moved downwards in setting direction  15 , exhaust gas from prechamber  25  discharges through open passage openings  31 ,  32 . 
     In  FIG. 4 , drive piston  10  is shown in its bottom dead center. Piston head  12  of drive piston  10  comes into contact with stop and/or damping elements  28 ,  29 . In the bottom dead center, piston head  12  of drive piston  10  in  FIG. 4  is situated below open passage openings  31 ,  32  of prechamber  25 . Arrows  71 ,  72  indicate that exhaust gases or hot gases escape from main combustion chamber  6  via open passage openings  31 ,  32 . 
     In  FIG. 5 , drive piston  10  is still located in its bottom dead center. When the hot gases escape, the pressure of main combustion chamber or main chamber  6  decreases. The decreasing pressure in main combustion chamber  6  together with the spring force of spring devices  54 ,  55  of control device  30  affects that control sleeve  34  closes passage openings  31 ,  32  in prechamber cylinder  24 . The return of drive piston  10  subsequently takes place thermically (not shown) by the cooling of the hot gases in main combustion chamber  6 , a vacuum resulting in the main combustion chamber. 
     Such as illustrated in  FIGS. 1 through 5 ,  FIG. 6  shows a similar combustion-powered setting tool  74 . Setting tool  74  differs from setting tool  1  illustrated in  FIGS. 1 through 5  in that additionally a valve device  75  and also a further ignition device  76  are assigned to main combustion chamber  6 . 
     Valve device  75  enables a ventilation of main combustion chamber  6 , for example for flushing purposes. Via further ignition device  76 , a gas mixture can be ignited in main combustion chamber  6  independent from whether an ignition has been already taken place in prechamber  25 . In so doing, further operating modes of setting tool  74  become possible. Otherwise, setting tool  74  in  FIG. 6  does not differ from setting tool  1  shown in  FIGS. 1 through 5 . 
     As a further exemplary embodiment,  FIG. 7  partially shows a setting tool  101  operated by a combustion gas or by a vaporizable liquid fuel. Setting tool  101  includes a main cylinder  105  rigidly connected to different elements, which is illustrated by the same hatching as main cylinder  105 . In main cylinder  105 , a drive piston  110  is guided moveably back and forth downwards and upwards in setting direction  115 . Drive piston  110  includes a piston rod  111 , which emanates from a piston head  112 . 
     When setting a fastening element, drive piston  110  is greatly accelerated in setting direction  115  by piston rod  111 , starting from the initial position shown in  FIG. 7 , to drive a not shown fastening element into an also not shown substrate. A movement of drive piston  110  in the downward direction is dampened by buffer  128 . A piston stop  116  for upwardly delimiting drive piston  110  has a magnetic device  117 , which keeps drive piston  110  by a predetermined holding force in its initial position illustrated in  FIG. 7 . 
     A main combustion chamber  106  is substantially delimited by piston head  112  (in setting direction  115 ), by a back-wall plate  170  (against setting direction  115 ) and by combustion chamber sleeve  180  (transverse to setting direction  115 ). Main combustion chamber  106  can be flushed with fresh air by displacing combustion chamber sleeve  180  vis-a-vis main cylinder  105  and back wall plate  170  in setting direction  115 .  FIG. 7  shows a closed position of combustion chamber sleeve  180 , in which the annular flushing openings are closed and are sealed with the aid of sealing rings  171 ,  172 . A ventilator  173  actuated by a ventilation motor  174  serves fresh air purging and a swirling or generating of turbulence within main combustion chamber  106 . 
     A prechamber  125  is substantially delimited by piston head  112  (against setting direction  115 ), by a not shown end face of main cylinder  105  (in setting direction  115 ) and by main cylinder  105  (transverse to setting direction  115 ). Prechamber  125  represents a pre-combustion chamber, to which a not shown ignition device and an also not shown inlet device for fuel are assigned. Moreover, the buffer is situated in prechamber  125 . 
     Main cylinder  105  includes two passage openings  131 ,  132 , which, for example, enable the discharge of exhaust gases from prechamber  125 . Passage openings  131 ,  132  are closeable on demand by a control device  130 . Control device  130  includes a control sleeve  134 , which has two passage openings  137 ,  138 . If passage openings  137 ,  138  of control sleeve  134  are positioned to overlap with passage openings  131 ,  132 , then passage openings  131 ,  132  are open. In  FIG. 7 , passage openings  131 ,  132  are closed by control sleeve  134 . Control sleeve  134  substantially has the shape of a straight circular cylinder jacket and in  FIG. 7  is moveable in the upward and downward directions. 
     Two not shown overflow openings provided with valve devices are provided between prechamber  125  and main combustion chamber  106  to enable a passage of the ignited fuel-air mixture from prechamber  125  into main combustion chamber  106 . 
     Control device  130  includes a control pressure surface  145 , which is connected in terms of control pressure to main combustion chamber  106 . Control pressure surface  145  is configured as an annular surface, which with the aid of one or a plurality of borings  175  in main cylinder  105  is facing main combustion chamber  106  within main cylinder  105 , and which is exposed to a vacuum in main combustion chamber  106 . Control pressure surface  145  via a coupling element  148  is mechanically coupled, in particular rigidly coupled, to control sleeve  134 . Control pressure surface  145  and borings  175  are situated radially inside of the combustion chamber sleeve and, in particular, of sealing ring  171 . 
     Control device  30  further includes not shown spring devices for pretensioning control sleeve  134  and control pressure surface  145  into the respective position shown in  FIG. 7 . 
     The mode of operation of control device  130  corresponds substantially with the mode of operation of control device  30  of the first exemplary embodiment ( FIGS. 1 through 5 ).