Abstract:
A gas combustion-powered apparatus includes a piston chamber housing a driveable piston, and a combustion chamber having a generally flat wall assembly and a cup-shaped wall defining at least one combustion volume therebetween. The cup-shaped wall is moveable in relation to the piston chamber, and has a generally flat portion opposing, and generally parallel to, the generally flat wall assembly. An ignition source is in operable relationship to the combustion volume, which can ignite a combustible gas within the combustion volume. The piston forms at least a portion of the generally flat wall assembly when the piston is in an undriven state.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a gas combustion-powered apparatus, and more specifically to a gas combustion-powered fastener-driving apparatus having a collapsible combustion volume for displacing a gas volume within a combustion chamber.  
         [0002]     Gas combustion devices are known in the art. A practical application of this technology is found in combustion-powered fastener driving tools. One type of such tools, also known as IMPULSE          brand tools for use in driving fasteners into workpieces, is described in commonly assigned patents to Nikolich, U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162, 4,483,473, 4,483,474, 4,403,722, 5,197,646, and 5,263,439, all of which are incorporated by reference herein. Similar combustion powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE          brand.  
         [0003]     Such tools incorporate a generally pistol-shaped tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and the engine also includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body. When a work contact element is pressed against a workpiece, a fuel-metering valve introduces a specified volume of fuel into a combustion chamber of the engine.  
         [0004]     Upon pulling a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber, the piston and the driver blade are shot downward to impact a positioned fastener and drive it into a workpiece. The piston then returns to its original, or “ready,” position through differential gas pressures within the cylinder. Fasteners are fed magazine-style into a nosepiece, where the fasteners are held in a properly positioned orientation for receiving the impact of the driver blade. The charge of gas is a combustible fuel/air mixture, and the combustion in the chamber causes an acceleration of the piston/driver blade assembly and a resulting penetration of the fastener into the workpiece if the fastener is present in the nosepiece.  
         [0005]     Combustion pressure in the chamber is an important consideration because such pressure affects the amount of force with which the piston may drive the fastener. Combustion pressure increases the more rapidly the fuel/air mixture within the combustion chamber can be ignited. The fuel/air mixture in the combustion chamber may be more rapidly ignited when the mixture is in a turbulent state. The ability to rapidly complete processes ancillary to this combustion operation of the tool is another important consideration. Such ancillary processes include: inserting the fuel into the combustion chamber; mixing the fuel and air within the chamber; and removing, or scavenging, combustion by-products remaining in the chamber after a combustion event.  
         [0006]     One known method of scavenging the residual combustion by-products between combustion events is by dilution. Dilution scavenging is performed by sending fresh air flowing through the combustion chamber between combustion events to displace combustion by-products. An example of dilution scavenging is described in commonly assigned, copending application Ser. No. ______ (Attorney Docket No. 13696), which is incorporated by reference herein. A fan is located within the combustion chamber to create the turbulence for a more rapid, higher-energy combustion, and also to drive fresh air through the combustion chamber between combustion events. Although this process is effective to achieve rapid, high-energy combustions and scavenging, the scavenging is not always performed efficiently. Typically, a volume of air required to scavenge the combustion by-products after a combustion event is equal to approximately two and one half times the volume of the combustion chamber itself.  
         [0007]     Another known method of scavenging, which is more efficient than the dilution method, is the displacement method. Displacement scavenging is performed by eliminating, or otherwise effectively reducing to zero, the volume within the combustion chamber itself, thereby removing all air within the volume, including that containing combustion by-products. Examples of displacement scavenging are described in patents to Cotta, U.S. Pat. No. 4,721,240, and to Gschwend, U.S. Pat. No. 5,181,495.  
         [0008]     Cotta requires the displacement of moveable parts at the front of the combustion chamber toward a rear wall of the chamber. Displacement is thus performed by the movement of a second piston assembly through the combustion chamber in a direction opposite to the piston in the piston chamber. The second piston displaces the entire volume of gas from the combustion chamber, but does not actually reduce the volume to zero. Although reasonably efficient, the complexity of this configuration greatly increases the cost of the tool. The cost and complexity are both significantly increased by the number of extra components required for the second piston assembly, as well as a host additional electrical components (motors, batteries, control circuits, etc.) to operate the complex construction.  
         [0009]     Gschwend displaces the combustion chamber volume by requiring that a moveable section at the rear of the combustion chamber move toward the front of the chamber to mostly collapse the chamber from behind, and reduce its volume to near zero. Force from an operator in back of the tool moves the moveable section to toward the front of the combustion chamber, thereby having the moveable section operate like Cotta&#39;s piston, but only in the reverse direction. Gschwend also separates the combustion chamber into first volume and a second combustion volume by use of a divider plate configured as a multiple-volume system, as is known in the art, to increase the energy of combustion.  
         [0010]     To operate the tool as a multiple volume system though, Gschwend requires a complicated system of collapsing guide rods throughout the moveable section and the divider plate between the volumes. The tool&#39;s trigger also must be located at an awkward position at the rear of the tool where the operator must be positioned to push the moveable section toward the front of the tool, thereby making the tool itself cumbersome to operate. And similar to Cotta&#39;s tool as well, this tool is significantly complex, and requires a great deal of additional electrical and mechanical components to guide the opposing structures of the combustion chamber together and apart at appropriate timings.  
         [0011]     There is a need therefore for a commercially available combustion gas fastener-driving tool having a simplified construction that reduces the need for expensive mechanical and electrical components in its construction. Such expensive components limit the availability of cordless combustion gas technology to a range of high cost applications only. A simplified single or multiple combustion volume construction, which can achieve substantially the same performance as the higher cost tools, would greatly extend the availability of combustion gas technology to more affordable, lower cost applications.  
       SUMMARY OF THE INVENTION  
       [0012]     The above-listed concerns are addressed by the present gas combustion-powered apparatus, which features a simplified solid chamber structure for igniting a combustible gas to drive a piston. A combustion volume is defined between the piston and a moveable wall of a combustion chamber, and an ignition device ignites the combustible gas in or into the combustion volume to drive the piston. Turbulence is created within the combustion volume to increase the speed and energy of combustion in a single volume by either the movement of the moveable wall, or by a high speed fuel injected into the combustion chamber shortly prior to ignition, or in a second volume by a high speed flame jet exiting the first volume.  
         [0013]     More specifically, the present invention provides a gas combustion-powered apparatus includes a driveable piston chamber housing a piston and a combustion chamber having a generally flat wall assembly and a cup-shaped wall defining at least one combustion volume therebetween. The cup-shaped wall is moveable in relation to the piston chamber, and has a generally flat portion opposing, and generally parallel to, the generally flat wall assembly. An ignition source is in operable relationship to the combustion volume, which can ignite a combustible gas within the combustion volume. The piston forms at least a portion of the generally flat wall assembly when the piston is in an undriven state.  
         [0014]     In a gas combustion-powered apparatus, the simplified structure of the present invention is effective for generating high-energy combustion to drive a piston, and for a broader cost range of applications than other types of combustion-powered devices. The present invention is also effective in either single-, or multiple-volume combustion apparatuses.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a vertical schematic sectional view of an embodiment of the present gas combustion-powered apparatus;  
         [0016]      FIG. 2  is vertical schematic sectional view illustrating an operation of the apparatus shown in  FIG. 1 ;  
         [0017]      FIG. 3  is a partial sectional schematic view of the apparatus shown in  FIG. 1 ;  
         [0018]      FIG. 4  illustrates an alternative configuration of the apparatus illustrated in  FIG. 1 ;  
         [0019]      FIG. 5  is a vertical schematic sectional view of another embodiment of the present gas combustion-powered apparatus;  
         [0020]      FIG. 6  is vertical schematic sectional view illustrating an operation of the apparatus shown in  FIG. 5 ;  
         [0021]      FIG. 7  is an expanded partial sectional view illustrating the moveable plug structure of the embodiment shown in  FIG. 5 ;  
         [0022]      FIG. 8  is an alternative configuration of the apparatus illustrated in  FIG. 5 ;  
         [0023]      FIG. 9  is a vertical schematic sectional view of still another embodiment of the present gas combustion-powered apparatus;  
         [0024]      FIG. 10  illustrates an operation of the apparatus illustrated in  FIG. 9 ; and  
         [0025]      FIG. 11  illustrates a further operation of the apparatus illustrated in  FIG. 9 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     Referring now to  FIGS. 1-4 , a combustion-powered apparatus is generally designated  10 , and includes a combustion chamber  12  in communication with a piston chamber  14 . Such an apparatus  10  is preferably intended for use in a combustion-powered tool of the type described above and disclosed in the patents incorporated by reference herein. Both of the chambers  12  and  14  are preferably rigid metal bodies, but may also be formed from other strong, combustion-resistant solid materials as are known in the art. The piston chamber  14  houses a piston  16  and driver blade  18  within a main body  20 , which is preferably generally cylindrical.  
         [0027]     When the piston  16  is in a “ready” position prior to firing, as best seen in  FIG. 1 , a generally flat surface  22  of the piston substantially aligns with outer surface  24  of a flanged end  26  of the piston chamber  14  to create a substantially continuous and generally flat wall assembly  28 . A piston stop  30 , which is preferably one or more protrusions, or a continuous ring, around an inner surface  32  of the main body  20  of the piston chamber  14 , is preferably positioned near the flange outer surface  24  against which the piston  16  aligns. Air is preferably prevented from flowing between the piston  16  and the piston chamber inner surface  32  by a piston seal  34 . The piston seal is preferably an o-ring around an outer circumference  36  of the piston  16 , but may also be any type of combustion-resistant seal known in the art.  
         [0028]     The flat wall assembly  28 , together with a cup-shaped wall  38 , defines the combustion chamber  12 . Referring now to  FIG. 1 , the combustion chamber  12  is shown in a fully closed, or “collapsed,” position. The cup-shaped wall  38  includes a generally flat rear surface  40  that opposes, and is generally parallel to, the flat wall assembly  28 , and a continuous sleeve body  42  joining to an outer periphery  44  of the flat rear surface. The cup-shaped wall  38  is preferably formed as single piece, or as several pieces solidly joined together, and is slidingly moveable in a direction A about the piston chamber flanged end  26 . A chamber seal  46  preferably prevents air from flowing between the flanged end  26  and an internally extending portion  48  of the sleeve body  42  when the cup-shaped wall  38  is in a fully opened position, as best seen in  FIG. 3 . The sleeve body  42  is preferably cylindrical, but may be of any shape to conform to a shape of the flanged end  26 , and the flat rear surface  40 .  
         [0029]     Although moveable, the cup-shaped wall  38  is preferably held in the fully closed position by a first pawl  50 . The first pawl  50  is configured as well known in the art to be preferably located directly, or by a linkage, in association with a housing (not shown) of the tools described above. The first pawl  50  is preferably also a beveled rod, or any solid shape known in the art which is moveable to hold the cup-shaped wall  38  firmly. When in the fully closed position, the flat rear surface  40  of the cup-shaped wall  38  approaches very near to, or contacts, the flat wall assembly  28 , which includes the flange outer surface  24  and the piston flat surface  22 . When the cup-shaped wall  38  is in the fully closed position therefore, there is preferably no effective volume of air between the flat rear surface  40  and the flat wall assembly  28 .  
         [0030]     Referring now to  FIG. 2 , a work contact element  52  is pressed against a workpiece (not shown), pushing the work contact element in the direction A. The work contact element  52  is connected directly to the cup-shaped wall  38 , but is more preferably operably linked to the cup-shaped wall by a first spring  54 . A first end  56  of the first spring  54  is connected to a first stop  58  located on the work contact element  52 , and a second end  60  of the first spring is connected to an extending portion  62  of the cup-shaped wall  38 . The movement of the work contact element  52  and the first stop  58  in the direction A compresses the first spring  54  to create pressure against the cup-shaped wall  38 , which is still held in place by the first pawl  50 . A second spring  64  is similarly compressed between a second stop  66  and an extending portion  68  of the piston chamber  14 . The compression of the second spring  64  moves the work contact element  52  back to its original ready position when released from the workpiece. The extending portion  68  also preferably serves as a guide for the moving work contact element  52 .  
         [0031]     Referring now to  FIG. 3 , when a trigger (not shown) is activated, the pawl  50  retracts in the direction B, thereby allowing the pressure from the compressed first spring  54  to rapidly move the cup-shaped wall  38  in the direction A to the fully opened position, thereby creating a combustion volume between the flat wall assembly  28  and the open cup-shaped wall. In this embodiment, fuel is preferably injected from a fuel line  70  into the combustion volume through a fuel port  72  when the trigger releases the first pawl  50 . However, fuel may also be injected at any time while the flat wall assembly  28  and the rear surface  40  of the cup-shaped wall are still moving apart. A suitable fuel is MAPP gas of the type used in combustion-powered fastener driving tools, but may also be any of a number of known combustible fuels practiced in the art. As the cup-shaped wall  38  moves in the direction A, a vacuum pressure from the opening combustion volume draws air into the combustion chamber  12  along and through an unsealed periphery  74  between the cup-shaped wall  38  and the piston chamber  14 . The vacuum pressure also facilitates holding of the piston  16  against the piston stop  30 .  
         [0032]     The rapid movement of the cup-shaped wall  38  toward the fully opened position creates turbulence within the combustion chamber  12  and the opening combustion volume therein. The turbulence in turn mixes the fuel and the air in the volume. Ideally, when the cup-shaped moving wall  38  reaches its fully opened position, but before the turbulence with the volume subsides, an ignition source  76  (which is preferably a spark plug) ignites the turbulent air/fuel mixture within the combustion chamber  12 . The turbulence within the combustion chamber  12  also increases the speed at which the air/fuel mixture ignites, thereby also increasing the combustion pressure. The rapid increase in combustion pressure drives the piston  16  in the direction C, which in turn drives the driver blade  18  to drive the fastener into the workpiece.  
         [0033]     Excess combustion pressure in the piston chamber  14  is expelled through an exhaust port  78 , and the piston  16  comes to a stop against a resilient member  80  after the piston passes the exhaust port in the direction C. Although the resilient member  80  is preferred to act as a brake for the piston  16 , air pressure between the piston and a generally closed end  82  of the piston chamber  14  may also be utilized to provide a braking force for the piston. Additionally, when the cup-shaped wall  38  reaches its fully opened position, by a linkage with the tool housing and trigger (not shown) similar to that of the first pawl  50 , a second pawl  84  moves in the direction D to contact the cup-shaped wall and fixedly hold it in the fully opened position, and thus also fixedly sealing the piston chamber flanged end  26  to the internally extending sleeve portion  48  at the chamber seal  46 .  
         [0034]     As residual gas within the combustion chamber  12  and the piston chamber  14  cools, a vacuum develops in the chambers, which closes a valve  86  over the exhaust port  78 , and draws the piston  16  back to the initial ready position aligning with the flange outer surface  24  ( FIG. 1 ). When the trigger is released, the second pawl  84  retracts in the direction B, thereby allowing the vacuum to also pull the cup-shaped wall  38  toward its initial fully closed position. As the cup-shaped wall  38  closes, the volume within the combustion chamber  12  is effectively reduced to zero, and all of the residual combustion gases from the volume are expelled through the unsealed periphery  74  ( FIG. 1 ). Additionally, force from the compressed second spring  64  causes a catch  88  on an end  90  of the work contact element  52  to pull the cup-shaped wall  38  toward the initial fully closed position after the second pawl  84  retracts, and after the work contact element is removed from the workpiece.  
         [0035]     Referring now to  FIG. 4 , an alternative configuration of the apparatus  10  is configured without the first pawl  50 . This alternative configuration is otherwise identical to the configuration shown in  FIG. 1 , except for the positioning of the fuel line  70  and fuel port  72  along the flanged end  26  of the piston chamber  14 . According to this configuration, the turbulence in the combustion chamber  12  is created by injecting the fuel into the combustion volume as a high-speed fuel jet. The present inventors have discovered that, when properly configured within the combustion volume, the high-speed fuel jet will have sufficient energy to create the necessary turbulence to produce a rapid, high-energy combustion. The fuel jet itself thus serves as the mixing element for the fuel and the air. The air still is drawn into the combustion chamber  12  through the unsealed periphery  74  as the cup-shaped wall  38  is pushed open. Mixing occurs as the air is entrained into the jet as the jet courses through the open combustion chamber  12 .  
         [0036]     To maximize the mixing effect, the fuel line  70  and fuel port  72  should be positioned at the flanged end  26  of the piston chamber  14  to fire the jet of fuel in a direction E toward the flat rear surface  40  of opened cup-shaped wall  38 , and more preferably toward a center point  92  of the flat rear surface. The ignition source  76  should also be located ideally on the flanged end  26 , and generally in the same plane as the fuel port  72  and the piston surface  22 , but at a maximum distance from the fuel port along the flanged end. By this preferred configuration, the fuel jet travels a maximum distance from the fuel port  72  toward the center  92  of the rear surface  40 , and then toward the ignition source  76  before igniting. This extended distance allows for better mixing of the fuel with air in the combustion volume.  
         [0037]     Also according to this configuration, the first spring  54  is preferably eliminated, and the cup-shaped wall  38  can be directly fixed to the work contact element  52 , thereby moving to the fully opened position directly when the work contact element is placed against the workpiece. The fuel need not be injected when the combustion chamber  12  opens, but instead is preferably introduced into the already-open chamber whenever firing is desired. Ideally then, when the trigger is activated, the second pawl  84  moves in the direction D to lock the cup-shaped wall  38  into the fully opened position, as described above ( FIG. 3 ), the fuel jet is injected into the combustion volume, and the ignition source  76  ignites the resultant fuel/air mixture. The ignition source  76  is preferably timed to allow the fuel jet sufficient time to travel across the combustion volume before ignition occurs. The remaining sequence of operation for this alternative configuration is as described above for  FIGS. 1-3 .  
         [0038]     According to these embodiments of the present invention, a combustion volume is created from a simplified construction of an expanding collapsible chamber by moving apart two generally opposing walls of the chamber. Turbulence for a rapid combustion is thus created by one of two methods described above. According to the first method, components of the chamber move apart immediately prior to igniting the fuel/air mixture, to expand the combustion volume. The turbulence created by the moving components is adequate to produce the rapid combustion needed for a practical tool if ignition occurs early enough. According to the second method though, a fuel jet both creates the turbulence, and also is the mixing element for the air and fuel. Both turbulence generation methods produce adequate fuel/air mixtures for rapid, high-energy combustions.  
         [0039]     Referring now to  FIGS. 5-8 , a combustion-powered apparatus is generally designated  100 , but features of the apparatus  100  that are the same as those described above with reference to  FIGS. 1-4  are identified by the same numerical designations.  
         [0040]     The apparatus  100  includes a combustion chamber  102  in communication with a piston chamber  104 , and is formed of materials as described above with respect to the apparatus  10 . The piston chamber  104  is preferably cylindrical, and is located partially within the combustion chamber  102 , which is also preferably cylindrical and has a larger outer diameter than the piston chamber, however, non-cylindrical shapes are also contemplated. A moveable plug  106  is located within the combustion chamber  102 . In this embodiment, the combustion chamber  102  is preferably a rigid structure, and does not move relative to the piston chamber  104 .  
         [0041]     The moveable plug  106  includes a generally flat base portion  108 , which preferably is shaped as a round disk having an outer periphery  110 , which generally corresponds to an inner wall  112  of the combustion chamber  102 . Connected to the base portion  108  is a generally ring-shaped wall  114 , which has a ring inner wall  116  that preferably corresponds to an outer wall  118  of the piston chamber  104 , and a ring outer wall  120  that generally corresponds to the inner wall  112  of the combustion chamber  102 . As best seen in  FIG. 7 , the ring-shaped wall  114  has a height H that preferably corresponds to a length L of a portion  122  of the piston chamber  104  which is located within the combustion chamber  102 . In this embodiment, the flat base portion  108  and the ring-shaped wall  114  together preferably form a cup shape similar to the cup-shaped wall  38  of the apparatus  10  ( FIGS. 1-4 ). The cup-shaped portion  108 ,  114  of the plug  106  therefore functions, with respect to the portion  122  of the piston chamber  104 , similarly to the function of the cup-shaped wall  38  with respect to the piston chamber  14  of the apparatus  10  ( FIGS. 1-4 ).  
         [0042]     Connected to the base portion  108 , and on a side  124  of the base portion opposite to the ring-shaped wall  114 , is a stem portion  126 . The stem portion  126  is preferably centered relative to the base portion  108 , and preferably generally aligns with the driver blade  18  of the piston  16 . The stem portion preferably extends through an opening  128  in a rear wall  130  of the combustion chamber  102 , and is fixedly attached to an attaching member  132 , which in turn is operably linked to the work contact element  52  directly, by spring tension, or other linking methods known in the art. Although the moveable plug  106  is preferably formed from separate and/or hollow pieces, the base portion  108 , the ring-shaped wall  114 , and the stem portion  126  are more preferably formed together as a single, solid piece, and of generally rigid, combustion-resistant materials as are known in the art.  
         [0043]     The base portion  108  and the ring-shaped wall  114  have a cup-like shape, and move and function in relation to the piston chamber  104  similarly to the way the cup-shaped wall  38  moves and functions in relation to the piston chamber  14  of the apparatus  10 , as described above. As best seen in  FIG. 5 , the moveable plug  106  is fixedly held in the fully closed, or ready, position by a pawl  134 , which is associated or linked with a tool housing (not shown) similar to the pawls  50 ,  84  described above. In this embodiment, when the moveable plug  106  is fully closed, a single mixing volume Vm is defined within the combustion chamber  102  between the side  124  of the base portion  108  and the rear wall  130  of the combustion chamber. All other volume of air within the combustion chamber  102 , but outside of the dimensions of the mixing volume Vm, is effectively reduced to zero. As the work contact element  52  is pushed against the workpiece, a first spring  136 , which connects the attaching member  132  to the work contact element at a first spring stop  138 , is stretched to create a pulling tension against the attaching member in the direction A.  
         [0044]     Referring now to  FIG. 6 , activation of the trigger releases the pawl  134  in the direction B, and the pulling tension from the first spring  136  rapidly moves the plug  106  in the A direction toward the rear wall  130  of the combustion chamber  102 . This movement of the plug  106  is preferably terminated when the side  124  of the base portion  108  contacts a resilient stop  140  at the fully open position of the plug. In addition to acting as a brake for the movement of the plug  106 , the resilient stop  140  is preferably a hollow cylinder, which also preferably serves as a guide for the movement of the stem portion  126  through the hollow cylinder, as well as a seal against potential airflow into the mixing volume Vm through the opening  128 . When the moveable plug  106  reaches its fully open position, the mixing volume Vm partially collapses, and first and second combustion volumes V 1  and V 2  respectively are created within the combustion chamber  102 , which now contains at least three separate and distinct volumes.  
         [0045]     When the plug  106  is fully open, the first and second combustion volumes V 1  and V 2  together contain approximately the amount of volume by which the mixing volume Vm is reduced. In other words, the distinct volumes within the combustion chamber  102  preferably generally satisfy the equation V 1 +V 2 +Vm open =Vm closed . Although the mixing volume Vm is not entirely collapsed in this configuration, the present inventors contemplate that the moveable plug  106  and chambers  102 ,  104  are configurable so that the resilient stop  140  is alternatively removed, and the base portion  108  then will open all of the way to the rear wall  130  of the combustion chamber  102 . The formula described above would then still be satisfied as Vm open  becomes equal to zero.  
         [0046]     The first combustion volume V 1  is preferably annular, and the second combustion volume V 2  is cylindrical. A diameter of the cylindrical volume V 2  will then preferably be approximately equal to an inner diameter of the annular volume V 1 . The cylindrical volume V 2  also ideally conforms to the shape of the cylindrical portion  122  of the piston chamber  104  located within the combustion chamber  102 . The mixing volume Vm is basically cylindrical, but can also be considered annular when movement of the plug  106  is effected by the central inclusion of the stem portion  126  through the mixing volume Vm. One skilled in the art, however, will be aware that movement of the plug  106  may instead be operably linked to the movement of the work contact element  52 , without the inclusion of the stem portion  126 , through many other linkage methods known in the art, without departing from the present invention.  
         [0047]     As best seen in  FIG. 5 , when the work contact element  52  is pressed against the workpiece, fuel is preferably injected into the mixing volume Vm of the combustion chamber  102  through a first fuel port  142 , to mix with air in the mixing volume. Although fuel is preferably injected at this time, it can also be injected at any time prior to movement of the moveable plug, such as in coordination with an activation of the trigger. As described above, the trigger activation will also preferably move the pawl  134  in the direction B to release the attaching member  132  to begin a rapid movement of the moveable plug in the direction A.  
         [0048]     Referring now to  FIG. 6 , as the first combustion volume V 1  and the second combustion volume V 2  begin to open and expand, the fuel/air mixture in the mixing volume Vm is drawn into the combustion volume V 2  through a fuel valve  144  located in the base portion  108 , and then from the combustion volume V 2  into the combustion volume V 1  through at least one combustion port  146  located in the ring-shaped wall  114 . The fuel valve  144  is preferably a reed valve, but may be any type of valve known in the art which allows one-way communication from the mixing volume Vm into the combustion volume V 2 . The combustion port  146  is ideally located on the ring-shaped wall  114  at a location that is a maximum distance on the wall  114  from the ignition source  76 . Vacuum pressure, caused by the expansion of the combustion volumes V 1  and V 2 , will then fill the two combustion volumes with the fuel/air mixture. The vacuum and rapid expansion of the combustion volumes V 1  and V 2  will also create a sufficient turbulence within both of the combustion volumes V 1  and V 2  to provide a rapid, high-energy combustion when the fuel/air mixture is ignited.  
         [0049]     Referring now to  FIG. 7 , the chambers  102 ,  104  and the ring-shaped wall  114  are configurable to allow even greater airflow between the several volumes within the combustion chamber, to provide additional filling, mixing, and turbulent properties to the several volumes. The ring-shaped wall  114  is preferably formed to include an extending portion  148  on the ring inner wall  116  which approaches, but does not contact, the portion  122  of the piston chamber  104  inside the combustion chamber  102 . In this preferred configuration, when the plug  106  reaches the fully opened position, the extending portion  148  will contact a combustion seal  150 , thereby sealing airflow between the two combustion volumes V 1  and V 2 , except for the combustion port  146 . The combustion seal  150  is preferably an o-ring located around an outermost periphery  152  of the piston chamber portion  122 , but may be any type of combustion-resistant seal known in the art. The air/fuel mixture in the second combustion chamber V 2  then flows around the combustion seal  150  and across the ring inner wall  116  into the first combustion chamber V 1  while the plug  106  is moving, but is blocked when the plug reaches the fully opened position. This increased airflow further increases turbulence in the first combustion volume V 1  shortly prior to ignition.  
         [0050]     To further increase the turbulence in V 1  caused by the structure of the moving plug  106 , a recess  154  is preferably provided on the inner wall  112  of the combustion chamber  102 , and located in the vicinity of the ring-shaped wall  114  when the plug  106  is in the fully closed position. The recess  154  thus allows additional airflow between the combustion chamber inner wall  112  and the outer wall  120  of the ring-shaped wall  114 . A first ring seal  156  is preferably located on the ring outer wall  120  opposite to the extending portion  148  of the ring inner wall  116 . Airflow is then sealed between the ring outer wall and the combustion chamber inner wall  112  when the first ring seal  156  moves past the recess  154  and the plug  106  reaches the fully opened position.  
         [0051]     Before the first ring seal  156  passes the vicinity of the recess  154 , however, the ring outer wall  120  and the combustion chamber inner wall  112  are configurable to allow additional airflow between the mixing volume Vm and the first combustion volume V 1  while the plug  106  is moving, but before first ring seal contacts the combustion chamber inner wall. A second ring seal  158  is optionally included on the ring outer wall  120 , and near the base portion  108 , to prevent any direct airflow between the mixing volume Vm and the first combustion volume V 1  by having the second ring seal be always in contact with the combustion chamber inner wall  112  away from the recess  154 , and regardless of whether the plug  106  is in the fully opened or fully closed positions. The present inventors contemplate that it may desirable in some circumstances to prevent direct airflow into the first combustion volume V 1  from the mixing volume Vm.  
         [0052]     Referring now to  FIG. 6 , activation of the trigger causes the pawl  134  to move in the direction B, thereby allowing the plug  106  to rapidly move in the direction A. The moving plug  106  reduces the mixing volume Vm and opens first and second combustion volumes V 1  and V 2  respectively. The fuel/air mixture in the mixing volume Vm flows into combustion volumes V 1  and V 2 , and a spark from the ignition source  76  ignites the fuel/air mixture in the first combustion volume V 1 , and preferably when the plug  106  reaches the fully opened position and turbulence within the combustion volume V 1  still exists from the movement of the plug. A flame front of the ignited fuel/air mixture then progresses through dual arcs of the annular combustion volume V 1 , until reaching combustion port  126 . The moving flame front passes through the combustion port  126  and into the second combustion volume V 2  as an ignited gas jet, thereby also igniting the fuel/air mixture within the volume V 2 . The ignited gas jet also creates turbulence in the volume V 2 , and in addition to the turbulence caused by movement of the plug  106 .  
         [0053]     As the air/fuel mixture in the second combustion volume V 2  is ignited, the increased pressure in the volume V 2  rapidly pushes the piston  16  and driver blade  18  to drive the fastener into the workpiece. Similarly to the operation of the apparatus  10  described above, excess pressure in the piston chamber  104  is exhausted through the exhaust port  78  as and after the piston  16  passes the exhaust port. As the gas remaining within the piston chamber  104  and combustion volumes V 1  and V 2  cools, a vacuum develops which acts to pull the piston  16  back to the initial ready position. When the tool  100  is removed from the workpiece, the work contact element  52  is returned to its original ready position as well by compression force of a second spring  160 , which is ideally compressed between a second spring stop  162  located on the work contact element  52 , and either of the combustion chamber  102  or the piston chamber  104 .  
         [0054]     The combination of the return movement of the work contact element  52  to its ready position, together with the vacuum created in the combustion volumes V 1  and V 2  from the cooling gas, causes the plug  106  to move to its original closed position, thereby collapsing both of the combustion volumes V 1  and V 2 , while also effectively scavenging the remaining combustion gases from both combustion volumes as well. The movement of the plug  106  to its fully closed position also reduces the pressure in the mixing volume Vm, which in turn draws fresh air into the volume Vm through an air check valve  164 . The air check valve  164  is preferably a reed valve, but can be any combustion-resistant one-way valve as is known in the art. When the trigger is released, the pawl  134  moves in the direction D to lock the attaching member  132  near the combustion chamber  102  ( FIG. 5 ), in preparation for a next combustion/firing cycle.  
         [0055]     Because the mixing volume Vm is not utilized in the actual combustion (the air/fuel mixture in the volume Vm is not ignited), it is not an important consideration for combustion purposes to displace the entire volume Vm, or scavenge its unignited contents. The present inventors do contemplate, however, that other considerations may make it desirable to completely displace the mixing volume Vm ( FIGS. 9-11 , below). The present inventors also contemplate that it may be preferable in some circumstances to inject the fuel into the mixing chamber Vm at this time (trigger release), which will also be in preparation for the next cycle.  
         [0056]     Referring now to  FIG. 8 , an alternative configuration of the apparatus  100  uses a fuel jet, similar to that described above for the tool  10  ( FIG. 4 ), to generate turbulence in the combustion volume V 1  immediately prior to ignition. The present inventors have discovered that, for this configuration, only a moderate amount of turbulence is required in the first combustion volume V 1  to rapidly and sufficiently ignite the air/fuel mixture drawn into the volume. A second fuel port  166  is preferably located along the combustion chamber  102 , to allow a high-speed fuel jet to be injected directly into the first combustion volume V 1 . The second fuel port  166  is preferably located on the combustion chamber  102  in the same plane as, but at a maximum distance from, the ignition source  76 , to allow a maximum amount of mixing of air and gas throughout the volume V 1  before the fuel/air mixture reaches the ignition source. Except for the addition of the second fuel port  166 , and the elimination of the pawl  134  and the spring  136 , this alternative configuration is preferably the same as that shown in  FIGS. 5-7 .  
         [0057]     For this configuration, the attaching member  132  is connected directly to the work contact element  52 , thereby opening the first and second combustion volumes to the fully opened position when the work contact element  52  is pressed against the workpiece. For this particular configuration then, the fuel jet is preferably injected upon activation of the trigger, and the ignition source  76  is timed to spark after a brief delay to allow the air and fuel to fill and mix in both combustion volumes. The air/fuel mixture enters the second combustion volume V 2  through the combustion port  146  from the first combustion volume V 1 , or through the fuel valve  144  from the mixing volume Vm, or both.  
         [0058]     When the mixing volume Vm is used as an air/fuel mixture source for the second combustion volume V 2 , fuel is preferably injected into the mixing volume Vm through the first fuel port  142 , when the work contact element  52  opens the plug  106  to the fully opened position. The present inventors also contemplate, however, that because no fuel is actually required in the mixing chamber Vm for combustion, the first fuel port  142  may be entirely eliminated from the structure, leaving the mixing volume Vm as a source for fresh air only into the combustion volumes V 1 , V 2 , and the second fuel port  166  as the only fuel source for the three volumes. In this configuration, it is also preferable to eliminate the second ring seal  158  from the structure in order to allow direct airflow between the mixing volume Vm and the first combustion volume V 1  while the combustion volume V 1  is expanding.  
         [0059]     For this configuration, the first combustion volume V 1 , into which the fuel is injected, is defined between a preferably flat portion  168  of the ring-shaped wall  114  and an opposing region  170  of the combustion chamber  102 . The flat portion  168  is preferably generally parallel to both the base portion  108  and the opposing region  170 , and located on an end of the ring-shaped wall  114  opposite to the base portion  108 . The opposing region  170  also preferably defines the plane in which the ignition source  76  and the fuel port  166  are preferably located. The moveable flat portion  168  thus performs, with respect to the opposing region  170 , similarly to how the flat rear surface  40  ( FIG. 4 ) performed with respect to the flat wall assembly  28  of the apparatus  10 . Turbulence is created in the combustion volume V 1  by the unignited fuel jet, in a manner similar to the configuration shown in  FIG. 4 .  
         [0060]     Once the air/fuel mixture in the first combustion volume V 1  is ignited, the flame front travels rapidly across the annular volume V 1  and into the second combustion volume V 2  through the combustion port  146  as a high-energy flame jet. Directing a separate, unignited fuel jet into the second combustion volume V 2  is not an important consideration because the high-energy flame jet itself from the first combustion volume V 1  is a sufficient source of turbulence to create an adequate high-energy combustion in the volume V 2 , which then resultantly fires the piston  16 . For the second combustion volume V 2  therefore, the ignited high-energy flame jet performs the turbulence function of the unignited fuel jet into the first combustion volume V 1 . The rest of the operation of this configuration of this embodiment is as described above with respect to  FIGS. 5-7  (without the use of the fuel jet as the turbulence source).  
         [0061]     Referring now to  FIGS. 9-11 , a combustion-powered apparatus is generally designated  170 , but features of the apparatus  170  that are the same as those described above with reference to  FIGS. 1-8  are identified by the same numerical designations.  
         [0062]     The apparatus  170  includes a combustion chamber  172  in communication with the piston chamber  104 . The piston chamber of the apparatus  170  is preferably the same as that of the apparatus  100 , described above ( FIGS. 5-8 ). Preferably, no portion of the piston chamber  104  is located within the combustion chamber  172 , and the flat surface  22  of the piston  16  is preferably in the general plane of an annular wall  174  of the combustion chamber when in the ready position. The combustion chamber  172  is preferably cylindrical and does not move relative to the piston chamber  104 .  
         [0063]     A moveable cup  176  moves relative to both the combustion chamber  172  and the piston chamber  104 . The moveable cup includes a generally flat plate  178  and a ring wall  180  attached to flat portion along one entire edge  182  of the ring wall. The ring wall  180  is preferably tubular, and has a cylindrical diameter slightly larger than the outer wall  118  of the piston chamber  104 . The flat plate  178  is generally parallel to the annular wall  174 , and includes an annular portion  184  that extends from the ring wall  180  toward an inner wall  186  of the combustion chamber  172 . The inner wall  186  is also preferably a tube, and the annular portion  184  is configured to have an outer periphery  188  slightly smaller than a diameter of the inner wall. A mixing seal  190 , which is preferably a combustion-resistant o-ring, prevents airflow between the outer periphery  188  of the flat plate  178  and the inner wall  186 .  
         [0064]     As best seen in  FIG. 9 , when in the ready position, a volume of air between the flat plate  178  and both the annular wall  174  and the piston flat surface  22  is practically zero. The mixing volume Vm is therefore defined within the combustion chamber  172  between the flat plate  178  and a rear wall  192  of the combustion chamber. The rear wall  192  is preferably generally flat, and also generally parallel to both the annular wall  174  and the plate  178 . The moveable cup  176  is preferably held in the ready position by a spring  194  attached to both a fixed portion  196  of the apparatus  170  and an extension  198  of the ring wall  180 . The ring wall extension  198  is preferably also a tube formed together with, or attached to, the ring wall  180 , but may also be a single rod, or a plurality of rods.  
         [0065]     When in the ready position, fuel is preferably injected into the mixing volume Vm through a fuel valve  200  located on the inner wall  186  of the combustion chamber  172 , to mix with air that enters the mixing volume Vm through a first air intake port  202 . A first air check valve  204  prevents backflow through the air intake port  202 .  
         [0066]     Referring now to  FIG. 10 , when a work contact element  206  is pressed against the workpiece, the work contact element pushes the ring wall extension  198  in the direction A, thereby moving the moveable cup  176  toward the rear wall  192  of the combustion chamber  172 , and effectively reducing to zero the mixing volume Vm when in the fully opened position. The fuel/air mixture from the mixing volume Vm enters the first combustion volume V 1  through a second air intake port  208  and a one-way second air check valve  210 , and into the second combustion volume V 2  through a third air intake port  212  and a one-way third air check valve  214 .  
         [0067]     A flange  216  is located on the ring wall  180  between the ring wall and the ring wall extension  198 , and generally conforms to the shape of the ring wall, but extends outward from either side of the ring wall. When the moveable cup  176  is in the fully opened position, the flange  216  contacts a first purging seal  218  and a second purging seal  220 , to close airflow through a first purging opening  222  between the annular wall  174  of the combustion chamber  172  and the ring wall  180 , and through a second purging opening  224  between the ring wall and the outer wall  118  of the piston chamber  104 , respectively. The first and second purging seals  218 ,  220  are preferably constructed similarly to the seals described above.  
         [0068]     In this embodiment, when the moveable cup is in the fully opened position, the combustion chamber is divided into two effective combustion volumes V 1  and V 2 , and the third mixing volume Vm is effectively eliminated. Also in this embodiment, the annular first combustion volume V 1  preferably surrounds the cylindrical second combustion volume V 2  instead of the piston chamber  104 , and both combustion volumes align along their respective planar borders parallel to the annular wall  174  and the rear wall  192  of the combustion chamber  172 . And except for this different structural placement, the combustion volumes V 1  and V 2  otherwise function the same as described above with respect to the apparatus  100 .  
         [0069]     When in the fully opened position, activation of a trigger (not shown) causes a spark from the ignition source  76  to ignite the fuel/air mixture in the first combustion volume V 1 . The ignition source is preferably located on the annular wall  174  of the combustion chamber  172 . The ignited flame front travels through the first combustion volume V 1  until reaching, and exiting through, a combustion port  226 . The combustion port  226  may be located on the ring wall  180  to directly connect the first and second combustion volumes V 1  and V 2 , but more preferably the combustion port is located on the annular portion  184  of the flat plate  178  facing the rear wall  192  of the combustion chamber  172 . The present inventors further contemplate that, for some circumstances, it may also be preferable to inject fuel directly into the first combustion volume V 1  from the fuel valve  200 , and particularly if and when there is a significant delay between the movement of the moveable cup to the fully opened position, and the activation of the trigger.  
         [0070]     When the combustion port  226  is located on the annular portion  184 , a combustion recess  228  is preferably formed in the rear wall  192  of the combustion chamber  172  to create a path for the high-energy flame jet to travel. The third air intake port  212  is therefore preferably located near the combustion recess  228  and the combustion port  226  such that the combustion recess can provide a continuous path for the flame jet to travel from the first combustion volume V 1  through the combustion port  226  into the combustion recess  228 , and then from the combustion recess  228  through the third air intake port  212  into the second combustion volume V 2  to ignite that volume as well. To allow for a maximum distance for the flame front to travel, it is preferable that the combustion port  226 , the combustion recess  228 , and the third air intake port  212  be located at a distance farthest away from the ignition source  76 . The present inventors also contemplate that it can be advantageous to locate the second air intake port  208 , where the most airflow turbulence is created, on the annular portion  184  nearest the ignition source  76 , and to located the first air check valve  204  within the combustion recess  228  to allow a maximum displacement of the mixing volume Vm.  
         [0071]     Similar to with the apparatus  100 , described above, the flame jet into the second combustion volume V 2  provides both the desired turbulence and ignition of the air/fuel mixture within that volume to create a high-energy combustion. This combustion in the second combustion volume V 2  then drives the piston  16  in the direction C, as best seen in  FIG. 11 .  
         [0072]     Referring now to  FIG. 11 , excess ignited gas exits the piston chamber  104  through the exhaust port  78 , and the combustion by-products within the piston chamber and the combustion volumes V 1  and V 2  cool. The cooling gases within the apparatus  170  create a vacuum effect that pulls the piston  16  back toward the combustion chamber  172 . The relative volumes of the piston chamber  104  and the second combustion volume V 2  are preferably configured so as to allow the vacuum effect to fully return the piston  16  to the original, ready position (best seen in  FIG. 10 ) without requiring separate, mechanical tension on the piston. As the work contact element  206  is removed from the workpiece, tension from the spring  194  moves the moveable cup  176  back to its original, ready position as well (best seen in  FIG. 9 ) for the next combustion event. Residual combustion by-products within the two combustion volumes are purged through the first and second purging openings  222  and  224  that reappear as the flange  216  moves in the direction C.  
         [0073]     According to this embodiment of the present invention, the need for pawls can be entirely eliminated, and the need for springs reduced to a minimum. This embodiment provides a “cup within a cup” (moveable cup within a combustion chamber) configuration which gives all of the advantages described above for multiple-volume apparatuses, but at the same time also allows for the significantly more compact geometry closer to that of single volume apparatuses.  
         [0074]     Utilization of moveable plugs and or cup-shaped walls therefore, allow combustion-powered tools according to the present invention to adapt the turbulence generation methods, described above for a single-volume combustion chamber, to multiple-volume combustion apparatuses. The present invention can thus be adapted to both lower- and higher-energy combustion-powered fastener-driving operations. Furthermore, although the present invention has been described in relation to single-, dual-, and triple-volume combustion apparatuses, those skilled in the art will know that the basic principles of the present invention may be utilized in combustion apparatuses employing any number of volumes in their structure, with departing from the present invention.  
         [0075]     Those skilled in the art are further apprised that combustion apparatuses, such as in the present invention, may also be effectively employed in other devices which drive a piston, or devices that may be powered by combustion in general. While particular embodiments of the combustion-powered apparatus of the present invention have been shown and described, it will also be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects, and as set forth in the following claims.