Patent Publication Number: US-2023158652-A1

Title: Combustion chamber ring for fastener driving tool

Description:
PRIORITY 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/282,525, filed Nov. 23, 2021, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates to fastener driving tools, and specifically to combustion powered fastener driving tools with improved combustion chamber rings. 
     BACKGROUND 
     Powered fastener driving tools use one of several types of power sources to carry out a fastener driving cycle to drive a fastener (such as a nail or a staple) into a workpiece. More specifically, a powered fastener driving tool uses a power source to force a driving assembly, such as a piston carrying a driver blade, through a cylinder from a pre-firing position to a firing position. As the driving assembly moves to the firing position, the driver blade travels through a nosepiece, which guides the driver blade to contact a fastener housed in the nosepiece. Continued movement of the driving assembly through the cylinder toward the firing position forces the driver blade to drive the fastener from the nosepiece into the workpiece. The driving assembly is then forced back to the pre-firing position in a way that depends on the tool&#39;s construction and power source. A fastener advancing device forces another fastener from a magazine into the nosepiece, and the tool is ready to fire again. 
     Combustion powered fastener driving tools are one type of powered fastener driving tools that typically use a small internal combustion assembly as their power source. To operate various known combustion powered fastener driving tools, an operator depresses a workpiece contact element of the tool onto a workpiece. This moves the workpiece contact element from an extended position to a retracted position, which causes one or more mechanical linkages to cause: (1) a valve sleeve to move to a sealed position to seal a combustion chamber; and (2) a fuel supply assembly to dispense fuel from a fuel cell into the (now sealed) combustion chamber. The fuel supply assembly is configured to dispense only a desired amount of fuel to the combustion chamber for each combustion event. The amount of fuel is carefully determined to provide the desired combustion in a fuel efficient manner to prolong the working life of the fuel cell. 
     The operator then pulls the trigger to actuate a trigger switch, thereby causing a spark generator to deliver a spark and ignite the fuel/air mixture in the combustion chamber to start the fastener driving cycle. This generates high-pressure combustion gases that expand and act on the piston to force the driving assembly to move through the cylinder from the pre-firing position to the firing position, thereby causing the driver blade to contact a fastener housed in the nosepiece and drive the fastener from the nosepiece into the workpiece. 
     Certain known driving assemblies of combustion powered fastener driving tools include combustion chamber rings that can, in some circumstances, cause inconsistent or incomplete combustion of fuel in the combustion chamber. For example, when certain known combustion powered fastener driving tools are actuated in relatively cold weather, certain known combustion chamber rings can cause the turbulence in the combustion chamber to be directed toward the ignition tip of the spark plug that extends into the combustion chamber. This turbulence directly toward the ignition tip can inhibit or deter sparks from occurring and thus cause inconsistent or incomplete combustion of the fuel. There is a need for a combustion powered fastener driving tool that overcomes such issues such that the driving assembly can consistently and completely combust the fuel during each combustion cycle of the tool. 
     SUMMARY 
     Various embodiments of the present disclosure provide a combustion powered fastener driving tool that solves the above problems in part by changing the direction of the turbulence in the combustion chamber and eliminating or reducing the likelihood of causing inconsistent or incomplete combustion of the fuel. 
     In various example embodiments of the present disclosure, the fastener driving tool includes a housing, a fastener driving assembly at least partially positioned in, connected to, and supported by the housing, a handle assembly connected to the housing, a fastener magazine assembly connected to the housing and the handle assembly, a workpiece contact assembly connected to the housing, and a fuel supply assembly at least partially positioned in, supported by, and connected to the housing. The fastener driving assembly includes a combustion chamber ring that is configured, shaped, and sized to reduce turbulence and velocity of vaporized fuel in the combustion chamber at and around the injection tip of the spark plug just prior to and during combustion of the fastener driving tool. 
     Other objects, features, and advantages of the present disclosure will be apparent from the following detailed disclosure and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is an enlarged fragmentary cross-sectional view of part of a known fastener driving tool showing the fuel supply assembly mounted in the housing and showing part of the fastener driving assembly. 
         FIG.  2    is an enlarged fragmentary side cross-sectional view of a part of the known fastener driving assembly of the fastener driving tool of  FIG.  1   , showing the cylinder head, the combustion chamber ring, and part of the combustion chamber. 
         FIG.  3    is a perspective view of an example embodiment of a fastener driving tool of the present disclosure. 
         FIG.  4    is an enlarged perspective view of the combustion chamber ring of the fastener driving tool of  FIG.  3   . 
         FIG.  5    is an enlarged bottom perspective view of the combustion chamber ring of  FIG.  4   . 
         FIG.  6    is an enlarged side perspective view of the combustion chamber ring of  FIG.  4   . 
         FIG.  7    is an enlarged top perspective view of the combustion chamber ring of the  FIG.  4   . 
         FIG.  8    is an enlarged cross-sectional view of the combustion chamber ring of  FIG.  4   . 
         FIG.  9    is an enlarged fragmentary cross-sectional view of part of the fastener driving tool of  FIG.  3   , showing the fuel supply assembly, and showing part of the fastener driving assembly including the combustion chamber ring of  FIG.  4   . 
         FIG.  10    is an enlarged fragmentary cross-sectional view of part of the fastener driving tool of  FIG.  3   , showing part of the fastener driving assembly, and showing the combustion chamber ring connected to the combustion chamber and the cylinder head. 
         FIG.  11    is an enlarged bottom perspective view of the cylinder head of the fastener driving tool of  FIG.  3   , showing the spark plug receiver defined by the cylinder head. 
     
    
    
     DETAILED DESCRIPTION 
     While the systems, devices, and methods described herein may be embodied in various forms, the drawings show, and the specification describes certain exemplary and non-limiting embodiments. Not all of the components shown in the drawings and described in the specification may be required, and certain implementations may include additional, different, or fewer components. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of connections of the components may be made without departing from the spirit or scope of the claims. Unless otherwise indicated, any directions referred to in the specification reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. Further, terms that refer to mounting methods, such as mounted, connected, etc., are not intended to be limited to direct mounting methods but should be interpreted broadly to include indirect and operably mounted, connected, and like mounting methods. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the present disclosure and as understood by one of ordinary skill in the art. 
     For a better understanding of the present disclosure, an example known combustion powered fastener driving tool is first partially described. 
       FIGS.  1  and  2    illustrate an example known combustion powered fastener driving tool  50  (that is sometimes referred to herein as “known tool” for brevity).  FIGS.  1  and  2    show selected components of the example known tool  50  including: (1) a housing  100 ; (2) a fastener driving assembly  200  partially positioned in, supported by, and connected to the housing  100 ; and (3) a fuel supply assembly  300  partially positioned in, supported by, and connected to the housing  100 . 
     In the illustrated known fastener driving tool  50 , the fastener driving assembly  200  includes: (1) a cylinder head  210 ; (2) a combustion chamber  220  suitably connected to the cylinder head  210 ; (3) a circulating fan  230  suitably mounted to the cylinder head  210  and projecting into the combustion chamber  220 ; (4) a sleeve  240  suitably connected to the combustion chamber  220 ; (5) a driving blade  250 ; (6) a piston  260  positioned in the sleeve  240  and suitably connected to the driving blade  250 ; and (7) a combustion chamber ring  400  suitably connected to an upper portion of the combustion chamber  220  and the cylinder head  210 . 
     In the illustrated known fastener driving tool  50 , the fuel supply assembly  300  includes: (1) a fuel cell door  310  pivotally connected to the housing  100 ; (2) a fuel cell  320  receivable in and at least partially supported by the housing  100 ; (3) a fuel cell adapter  330  suitably connected to the fuel cell  320 ; (4) a fuel cell metering valve  340  connected to the fuel cell adapter  330  and extending into a portion of the fuel cell  320 ; (5) a fuel cell receiving block  350  mounted on, connected to, and in fluid communication with the fuel cell adapter  330 ; (6) a fuel line  360  suitably connected between the fuel cell receiving block  350  and the cylinder head  210  to define a fuel pathway between the fuel cell  320  and the combustion chamber  220 ; and (7) a dosing lever  370  pivotally supported by the cylinder head  210  and engaged to the fuel cell receiving block  350 . The fuel cell  320  and the adapter  330  are described as part of the fuel supply assembly for ease of description but are separate components receivable by the tool  50 . 
     In the illustrated known fastener driving tool  50 , the combustion chamber ring  400  is positioned between the cylinder head  210  and the combustion chamber  220 . The combustion chamber ring  400  is supported by and suitably connects the combustion chamber  220  to the cylinder head  210 . The combustion chamber ring  400  includes: (1) a body  410  that has an upwardly angled bottom surface  432  that is positioned, at least in part, in the combustion chamber  220 . During operation, vaporized fuel (shown in phantom as arrow  222 ) is injected into the combustion chamber  220 , via the fuel supply assembly  300 . A spark plug  216  is supported by and connected to the cylinder head  210  such that the spark plug  216  can ignite the vaporized fuel  222  in the combustion chamber  220  to cause a driving blade  250  to move downwardly through the cylinder  240 . 
     However, the upwardly angled bottom surface  432  of the combustion chamber ring  400  of this illustrated known fastener driving tool  50  can interact with the vaporized fuel  222  as it is injected into the combustion chamber  220 . This interaction between the vaporized fuel  222  and upwardly angled bottom surface  432  of the combustion chamber ring  400  causes turbulence of the vaporized fuel  222  in the combustion chamber  220  directed at the ignition tip of the spark plug  216 . In certain cases, this directed turbulence, combined with environmental conditions such as relatively low temperatures can cause the spark plug to fail to consistently create sparks and thus can cause the fastener driving tool  50  to not operate optimally. The apparatus of the present disclosure overcomes these problems. 
       FIGS.  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 , and  11    illustrate the combustion powered fastener driving tool of one example embodiment of the present disclosure that is generally indicated by numeral  1050  (that is sometimes referred to herein as the “tool” for brevity). The illustrated example shows selected components of the tool  1050  during operation of the tool  1050  to drive a fastener (not shown) into a workpiece. Other components of the tool  1050  not discussed herein will be readily understood by those skilled in the art. 
     The illustrated example tool  1050  includes: (1) a housing  1100 ; (2) a fastener driving assembly  1200  at least partially positioned in, supported by and connected to the housing  1100 ; (3) a fuel supply assembly  1300  partially positioned in, supported by, and connected to the housing  1100 ; (4) a handle assembly  1500  supported by and connected to the housing  1100 ; (5) a fastener magazine assembly  1600  supported by and connected to the housing  1100  and the handle assembly  1500 ; (6) a workpiece contact assembly  1700  supported by and connected to the housing  1100 ; and (7) a nosepiece assembly  1800  supported by and connected to a lower portion of the housing  1100 . The illustrated example combustion powered fastener driving tool  1050  in this example is known in the industry as is a mid-range combustion powered fastener driving tool; however, it should be understood that the present disclosure can also be applied to what is known in the industry as framing combustion powered fastener driving tools, what is known in the industry as trim combustion powered fastener driving tools, and other combustion powered tools. 
     The housing  1100  includes: (1) a first wall  1110 ; (2) a second wall  1120  opposite of the first wall; and (3) a housing cap  1130  suitably connected to the first and second walls  1110  and  1120  of the housing  1100 . The housing  1100  thus provides a suitable protective enclosure for the fastener driving assembly  1200 , the fuel supply assembly  1300 , and other components of the tool 
     The fastener driving assembly  1200  includes, in part: (1) a cylinder head  1210  connected to the housing cap  1130 ; (2) a combustion chamber  1220  suitably connected to the cylinder head  1210 ; (3) a circulating fan  1230  suitably mounted to the cylinder head  1210  and projecting into the combustion chamber  1220 ; (4) a sleeve  1240  suitably connected to the combustion chamber  1220 ; (5) a driving blade  1250 ; (6) a piston  1260  positioned in the sleeve  1240  and suitably connected to the driving blade  1250 ; and (7) a combustion chamber ring  1400  disposed between the combustion chamber  1220  and the cylinder head  1210 . The combustion chamber ring  1400  suitably seals the cylinder head  1210  to an upper portion of the combustion chamber  1220 . The combustion chamber ring  1400  (that is sometimes herein referred to as “chamber ring” for brevity) is further described below. 
     The fuel supply assembly  1300  includes, in part: (1) a fuel cell door  1310  pivotally connected to the housing cap  1130  of the housing  1100 ; (2) a fuel cell receiving assembly  1316  positioned in and at least partially supported by the housing  1100  and configured to receive a removable fuel cell  1320 ; (3) a fuel cell adapter  1330  suitably connected to the fuel cell  1320 ; (4) a fuel cell metering valve  1340  connected to the fuel cell adapter  1330  and extending into a portion of the fuel cell  1320 ; (5) a fuel cell receiving block  1350  connected to and in fluid communication with the fuel cell adapter  1330 ; (6) a fuel line  1360  suitably connected between the fuel cell receiving block  1350  and the cylinder head  1210  to define a fuel passageway between the fuel cell  1320  and the combustion chamber  1220 ; and (7) a dosing lever  1370  pivotally supported in the housing  1100  and engaged to the fuel cell receiving block  1350 . It should be appreciated that while the fuel cell  1320  and the fuel cell adapter  1330  of the present disclosure are described herein as part of the fuel supply assembly  1300  of the tool  1050  for ease of description, that these components will typically be provided separately from the tool  1050  and insertable in the tool  1050 , and thus to a certain extent are not part of the fuel supply assembly  1300 , but rather connectable to and operable with the fuel supply assembly  1300  of the tool  1050 . 
     The handle assembly  1500  includes, in part: (1) a gripping portion  1510 ; (2) a trigger mount  1520  defined on the gripping portion  1510 ; and (3) a trigger  1530  suitably connected to the trigger mount  1520  via a trigger pin (not shown) such that a portion of the trigger  1530  can move relative to the gripping portion  1510 . The handle assembly  1500  is suitably connected to the housing  1100 . 
     The fastener magazine assembly  1600  includes, in part: (1) a fastener cannister  1610  configured to hold a plurality of fasteners (e.g., nails, or staples); and (2) a fastener channel  1620  suitably connected to the nosepiece assembly  1800  and to the handle assembly  1500 . During operation of the tool  1050 , a fastener is delivered, via the fastener channel  1620 , to the nosepiece assembly  1800  and driven into the workpiece by the fastener driving assembly  1200 . 
     The workpiece contact assembly  1700  includes, in part, a workpiece contact element  1710  suitably connected to the nosepiece assembly  1800  and to the fastener magazine assembly  1600 . The workpiece contact element  1710  contacts the location where the fastener is driven into the workpiece by the tool  1050 . The nosepiece assembly  1800  is suitably connected to the fastener magazine assembly  1600  and to the cylinder  1240 . The nosepiece assembly  1800  receives a fastener from the fastener channel  1620 . During operation of the tool  1050 , the piston  1260  is driven downward via the driving blade  1250  in the cylinder  1240 , contacts the fastener positioned in the nosepiece assembly  1800  and drives the fastener into the workpiece. 
     The example chamber ring  1400  of the present disclosure is now further described.  FIGS.  4  to  10    illustrate the example chamber ring  1400  of the example fastener driving tool  1050 . The illustrated chamber ring  1400  includes an annular body  1410  that defines a ring like structure configured to suitably seal the combustion chamber  1220  and cylinder head  1210  of the fastener driving assembly  1200 . More specifically, the body  1410  includes: (1) a chamber connector  1420 ; (2) a chamber fuel mixer  1430  suitably connected to the chamber connector  1420 ; (3) a cylinder head connector  1440  suitably connected to the chamber connector  1420  and the chamber fuel mixer  1430 ; and (4) a dosing lever engager  1450  suitably connected to the cylinder head connector  1440 . 
     In the illustrated example, the chamber ring  1400  is fabricated from a suitable metal or metal alloy such as aluminum that is configured to withstand the operational conditions of the tool  1050 . As such, the chamber ring  1400  can be cast, machined, or otherwise fabricated to form a monolithic structure including the chamber connector  1420 , the chamber fuel mixer  1430 , the cylinder head connector  1440 , the dosing lever engager  1450 , and other such castable and/or machinable features and components of the chamber ring  1400 . It should be understood that the chamber connector  1420 , the chamber fuel mixer  1430 , the cylinder head connector  1440 , and the dosing lever engager  1450  can alternatively be formed as two or more separate components that are suitably connected or that are fastened to the body  1410  during fabrication of the chamber ring  1400 . 
     In the illustrated example embodiment, the chamber connector  1420  of the body  1410  includes; (1) an outer portion  1421  defining an outer circumference of the body  1410 ; (2) a plurality of fastening flanges  1422 ,  1423 ,  1424 , and  1425  extending radially outward from the outer portion  1421 ; (3) a chamber engagement surface  1426  configured as an annular surface circumferentially defined around a bottom of the chamber connector  1420 ; (4) a cylindrical surface  1427  connected to the chamber engagement surface  1426 ; and (5) an annular surface  1428  connected to the cylindrical surface  1427  and the chamber fuel mixer  1430 . In the illustrated example embodiment, the cylindrical surface  1427  and the annular surface  1428  define an annular groove  1429  between the chamber connector  1420  and the chamber fuel mixer  1430 . 
     In the illustrated example embodiment, the chamber ring  1400  is mounted on and connected to an upper portion of the combustion chamber  1220 . More specifically, the chamber engagement surface  1426  is aligned with and engaged to an upper surface of the combustion chamber  1220 . The plurality of fastening flanges  1422 ,  1423 ,  1424 , and  1425  are each configured to receive a fastener (not shown) such as a threaded bolt that is threadably received in a portion of the combustion chamber  1220  to fixedly connect the chamber ring  1400  to the combustion chamber  1220 . 
     In the illustrated example embodiment, the chamber fuel mixer  1430  includes: (1) an outer cylindrical surface  1431  connected to the annular surface  1428  of the chamber connector  1420 ; (2) a bottom annular surface  1432  connected to the outer cylindrical surface  1431 ; (3) an inner cylindrical surface  1433  connected to the bottom annular surface  1432 ; and (4) a top annular surface  1434  connected to the inner cylindrical surface  1433  and the cylinder head connector  1440 . In the illustrated example embodiment, the bottom and top annular surfaces  1432  and  1434  are downwardly sloping surfaces. For example, the bottom annular surface  1432  slopes downward from the outer cylindrical surface  1431  to the inner cylindrical surface  1433 , and the top annular surface  1434  slopes downward from the cylinder head connector  1440  to the inner cylindrical surface  1433  to define the downwardly sloping profile of the chamber fuel mixer  1430 . 
     In the illustrated example embodiment, an angle α 1  formed between the bottom annular surface  1432  and the inner cylindrical surface  1433  defines a desired slope of the bottom annular surface  1432 . For example, the angle α 1  can be configured to form a 77° angle between the bottom annular surface  1432  and the inner cylindrical surface  1433  such that the bottom annular surface slopes downward a desired amount between the outer cylindrical surface  1431  and the inner cylindrical surface of the chamber fuel mixer  1430 . It will be understood that other angle values are possible to define the bottom annular surface slope. For example, α 1  can be up to approximately a 90 degree angle in various other embodiments. It should thus be appreciated that the surface should not extend upwardly toward the central axis of the chamber ring  1400  in accordance with the present disclosure. 
     In the illustrated example embodiment, an angle α 2  formed between the top annular surface  1434  and the inner cylindrical surface  1433  defines a desired slope of the top annular surface  1434 . For example, the angle α 2  can be configured to form approximately 105 degree angle between the top annular surface  1434  and the inner cylindrical surface  1433  such that the top annular surface slopes downward a desired amount between the cylinder head connector  1440  and the inner cylindrical surface  1433  of the chamber fuel mixer  1430 . It will be understood that other angle values are possible to define the top annular surface slope. 
     In the illustrated example embodiment, the cylinder head connector  1440  includes a plurality of connector portions  1441 ,  1442 ,  1443 ,  1444 ,  1445 ,  1446 ,  1447 , and  1448  suitably connected to and extending from the body  1410  of the chamber ring  1400 . In the illustrated example, the connector portions  1441 ,  1442 ,  1443   1444 ,  1445 ,  1446 ,  1447 , and  1448  extend upwards from a top surface of the body  1410  and are configured to mate with and engage with a chamber ring receiver  1212  of the cylinder head  1210 . 
     As best shown in  FIGS.  9  to  11   , the chamber ring receiver  1212  of the cylinder head  1210  is configured such that the connector portions  1441 ,  1442 ,  1443 ,  1444 ,  1445 ,  1446 ,  1447 , and  1448  of the cylinder head connector  1440  extend into the chamber ring receiver  1212  to suitably connect the combustion chamber ring  1400  to the cylinder head  1210 . The cylinder head  1210  also includes a spark plug receiver  1214  configured to receive a spark plug  1216 . The spark plug receiver  1214  is configured to removably securely receive the spark plug  1216  partly in the cylinder head  1210  such that an ignition tip of the spark plug  1216  in the combustion chamber  1220  can selectively cause combustion or ignition of a vaporized fuel dose (somewhat shown in phantom as arrow  1222 ) in the combustion chamber  1220 . 
     In the illustrated example embodiment, the dosing lever engager  1450  includes a plurality of fingers  1451 ,  1452 ,  1453 ,  1454 ,  1455 ,  1456 ,  1457 , and  1458  suitably connected to and extending from the body  1410  of the chamber ring  1400 . In the illustrated example embodiment, finger  1451  is connected to connector portions  1448  and  1441 , finger  1452  is connected to connector portions  1441  and  1442 , finger  1453  is connected to connector portions  1442  and  1443 , finger  1454  is connected to connector portions  1443  and  1444 , finger  1455  is connected to connector portions  1444  and  1445 , finger  1456  is connected to connector portions  1445  and  1446 , finger  1457  is connected to connector portions  1446  and  1447 , and finger  1458  is connected to connector portions  1447  and  1448 . 
     In the illustrated example embodiment, during operation of the tool  1050  the chamber ring  1400  engages with the dosing lever  1370  to cause the fuel supply assembly  1300  to dispense the fuel  1222  into the combustion chamber  1220 . More specifically, actuation of the tool  1050  causes at least one of the fingers  1451 ,  1452 ,  1453 ,  1454 ,  1455 ,  1456 ,  1457 , and  1458  of the dosing lever engager  1450  to engage with and cause the dosing lever  1370  to pivot between a non-actuated position and an actuated position. In the illustrated example embodiment, actuation of the dosing lever  1370  causes a subsequent depression of the fuel cell receiving block  1350  and fuel cell metering valve  1340  such that the fuel supply assembly  1300  delivers the dose of fuel from the fuel cell  1320  to the combustion chamber  1220 . 
     In the illustrated example embodiment, and as shown in  FIGS.  9  and  10   , the fuel supply assembly  1300  delivers the fuel dose  1222  into the combustion chamber  1220  via the fuel line  1360  and a fuel passageway  1218  defined in the cylinder head  1210 . In the illustrated example embodiment, the fuel supply assembly  1300  dispenses the fuel dose  1222  in vaporized form and the circulating fan  1230  mixes the vaporized fuel dose  1222  with the air inside the combustion chamber  1220  to create a desired an air/fuel mixture of the tool  1050 . In the illustrated example embodiment, the chamber ring  1400  is connected to the cylinder head  1210  and the combustion chamber  1220  such that the chamber fuel mixer  1430  extends into at least a portion of the combustion chamber. 
     In the illustrated example embodiment, and as shown in  FIGS.  9  and  10   , the top annular surface  1434  of the chamber fuel mixer  1430  is adjacent the cylinder head  1210  and the bottom annular surface  1432  faces the circulating fan  1230  and extends through at least a portion of the combustion chamber  1220 . The top annular surface  1434  slopes downward from the cylinder head connector  1440  to the inner cylindrical surface  1433  and the bottom annular surface  1432  slopes downward from the outer cylindrical surface  1431  to the inner cylindrical surface  1433  to define the downwardly sloping profile of the chamber fuel mixer  1430 . As such, when the fuel supply assembly  1300  dispenses the vaporized fuel dose  1222  into the combustion chamber  1220 , the circulating fan  1230  mixes the fuel dose  1222  in the combustion chamber  1220  and the chamber fuel mixer  1430  generates a desired flow or circulation pattern of the vaporized fuel dose  1222  in the combustion chamber  1220 . 
     In the illustrated example embodiment, the downward sloping profile of the chamber fuel mixer  1430  is configured to cause the vaporized fuel dose  1222  to be directed away from the ignition tip of the spark plug to reduce the turbulence and velocity of the vaporized fuel dose  222  at the ignition tip of the spark plug as it circulates within the combustion chamber  1220 . Thus, even certain operating conditions, such as when the temperature is relatively low, the vaporized fuel dose  1222  is substantially less likely to prevent sparks at the ignition tip of the spark plug. Thus, the downward sloping profile of the chamber fuel mixer  1430  reduces the vaporized fuel directed at the tip of the spark plug within the combustion chamber such that even if the temperature is relatively low, the fuel dose  1222  at the tip of the spark plug is more likely to ignite. Accordingly, the combustion chamber ring  1400  produces the desired flow or circulation pattern around the spark plug  1216  such that there is more likely to be complete and consistent combustion of the fuel  1222 . 
     Various changes and modifications to the present embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.