Patent Publication Number: US-2023158654-A1

Title: Dosing lever for fastener driving tool

Description:
PRIORITY 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/282,400, 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 specifically, to combustion powered fastener driving tools with improved dosing levers. 
     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 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 that is in fluid communication with the cylinder; and (2) a fuel supply assembly to dispense fuel from a fuel cell into the (now sealed) combustion chamber. 
     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. 
     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 needs to be carefully monitored to provide the desired combustion in a fuel efficient manner to prolong the working life of the fuel cell. Accordingly, various combustion powered fastener driving tools include a fuel supply assembly including a dosing lever that engages with certain other components of the fuel supply assembly and the tool before each combustion cycle to dispense the desired dose of fuel from the fuel cell. 
     Actuation of the tool causes the dosing lever to engage with certain other components of the tool and the fuel supply assembly to dispense the desired dose of fuel for the next combustion cycle. Certain known fuel supply assemblies of combustion powered fastener driving tools include dosing levers that can, in some circumstances, cause inconsistent amounts of fuel to be dispensed by the fuel supply assembly. For example, when certain known combustion powered fastener driving tools are actuated in relatively cold weather, the dosing lever can get stuck in an undesired position or otherwise cause undesirable engagement with one or more other components of the tool such that the fuel supply assembly dispenses inconsistent doses of fuel. There is a need for a combustion powered fastener driving tool with a fuel supply assembly that provides more consistent and stable doses of fuel in such circumstances. 
     SUMMARY 
     Various embodiments of the present disclosure provide a dosing lever for a combustion powered fastener driving tool that solves the above problems in part by eliminating or reducing the likelihood of causing inconsistent amounts of fuel to be dispensed by the fuel supply assembly. 
     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 fuel supply assembly includes a dosing lever that is configured, shaped, and sized to be better engaged by a combustion chamber ring during actuation of the dosing lever and dispensing of fuel for 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 cross-sectional view of a part of the known fuel supply assembly of the fastener driving tool of  FIG.  1   , showing the dosing lever in the non-actuated position. 
         FIG.  3    is an enlarged end perspective view of the known dosing lever of the fastener driving tool of  FIG.  1   . 
         FIG.  4    is an enlarged elevated perspective view of the known dosing lever of the fastener driving tool of  FIG.  1   . 
         FIG.  5    is a perspective view of a fastener driving tool of one example embodiment of the present disclosure. 
         FIG.  6    is an enlarged elevated perspective view of the dosing lever of the fastener driving tool of  FIG.  5   . 
         FIG.  7    is an enlarged side view of the dosing lever of  FIG.  6   . 
         FIG.  8    is an enlarged top view of the dosing lever of the fastener driving tool of  FIG.  6   . 
         FIG.  9    is an enlarged end view of the dosing lever of  FIG.  6   . 
         FIG.  10    is an enlarged perspective view of the dosing lever of  FIG.  6   . 
         FIG.  11    is an enlarged fragmentary cross-sectional view of part of the fastener driving tool of  FIG.  5   , showing part of the fastener driving assembly, and showing the fuel supply assembly including the dosing lever of  FIG.  6    mounted in the housing. 
         FIG.  12    is an enlarged fragmentary cross-sectional view of part of the fastener driving tool of  FIG.  5   , showing the dosing lever of  FIG.  6    in the non-actuated position, and showing the dosing lever engaged with the cylinder head. 
         FIG.  13    is an enlarged fragmentary cross-sectional view of part of the fastener driving tool of  FIG.  5   , showing the dosing lever in the partial actuated position, and showing the dosing lever engaged by with cylinder head and by the combustion chamber ring. 
         FIG.  14    is an enlarged fragmentary side cross-sectional view of part of the fastener driving tool of  FIG.  5   , showing the dosing lever of  FIG.  6    in the actuated position, and showing the dosing lever engaged by the combustion chamber ring. 
     
    
    
     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 ,  2 ,  3 , and  4    illustrate an example known combustion powered fastener driving tool  50  (that is sometimes referred to herein as “known tool” for brevity).  FIGS.  1 ,  2 ,  3 , and  4    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, in part: (1) a cylinder head  210 ; (2) a combustion chamber  220  suitably connected to the cylinder head  210 ; (3) a fan motor  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 ; and (5) a combustion chamber ring  250  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, in part: (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  400  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 dosing lever  400  includes: (1) a dosing lever body  410 ; (2) a first dosing lever leg  430  connected to and extending from a first end of the dosing lever body  410 ; (3) a second dosing lever leg  440  connected to and extending from a second end of the dosing lever body  410 ; (4) a first lever pivot  450  pin connected to and extending from the first dosing lever leg  430 ; and (5) a second lever pivot  460  pin connected to and extending from the second dosing lever leg  440 . 
     In the illustrated known tool  50 , the first dosing lever leg  430  includes a foot  432  that includes: (1) a toe  434 ; (2) a heel  435 ; and (3) a sole  436  extending between and connected to the toe  434  and the heel  435 . The sole  436  defines a first contact surface  437  and the toe  434  defines a second contact surface  438 . In the known tool  50 , the second contact surface  438  has a completely curved and arcuate profile (having a radius of curvature of about 0.08 inches (0.2032 cms)) configured to engage one of the ring fingers  252  of the combustion chamber ring  250 . This engagement between the ring fingers  252  of the combustion chamber ring  250  and the foot  432  causes an actuation of the known dosing lever  400 . For brevity, only the foot  432  of the first dosing lever leg  430  is described herein; however, it will be understood that the second dosing lever leg  440  includes a foot  442  that is substantially identical to the foot  432 . 
     In certain circumstances, actuation of the known dosing lever  400  can cause the curved and arcuate profile of the second contact surface  438  of the foot  432  to temporarily stick to the ring fingers  252  of the combustion chamber ring  250 . In certain circumstances, this sticking between the known dosing lever  400  and the combustion chamber ring  250  can cause the fuel supply assembly  300  to dispense an improper amount of fuel to the fastener driving assembly  200 . As a result, the improper amount of fuel delivered to the fastener driving assembly  200  can cause variation in the combustion and operation of the known fastener driving tool  50 . The apparatus of the present disclosure overcomes these problems. 
     In the illustrated known fastener driving tool  50 , the dosing lever body  410  includes a fuel cell door facing section  414  that includes a beveled portion  422  along the width of the fuel cell door facing section  414 . However, the dosing lever body  410  of the dosing lever  400  of this illustrated known fastener driving tool  50  can interact with the fuel cell door  310  as the dosing lever body  410  pivots between the non-actuated position and the actuated position. This interaction between the dosing lever  400  and the fuel cell door  310  can inhibit movement during actuation of the dosing lever  400  such that the fuel supply assembly  300  does not dispense a full dose of fuel to the fastener driving assembly  200 . In certain circumstances, for each actuation cycle of the known dosing lever  400 , the interaction between the dosing lever  400  and the fuel cell door  310  causes the fuel supply assembly  300  to deliver a different amount of fuel to the fastener driving assembly  200 . As a result, the variation of fuel delivered to the fastener driving assembly  200  can cause variation in the combustion and operation of the known fastener driving tool  50 . The apparatus of the present disclosure overcomes these problems. 
       FIGS.  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13 , and  14    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 actuation 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, in part: (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, in part: (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 , parts of the fuel supply assembly  1300 , and other components of the tool  1050 . 
     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 fan motor  1230  suitably mounted to the cylinder head  1210  and projecting into the combustion chamber  1220 ; (4) a cylinder  1240  suitably connected to the combustion chamber  1220 ; (5) a driving blade  1250  suitably connected to the cylinder  1240 ; (6) a piston  1260  positioned in the cylinder  1240  and suitably connected to the driving blade  1250 ; and (7) a combustion chamber ring  1270  positioned between the combustion chamber  1220  and the cylinder head  1210 . The combustion chamber ring  1270  suitably connects the cylinder head  1210  to an upper portion of the combustion chamber  1220 . 
     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 pathway between the fuel cell  1320  and the combustion chamber  1220 ; and (7) a dosing lever  1400  pivotally supported in the housing  1100  and engaged to the fuel cell receiving block  1350 . The dosing lever  1400  is further described below. 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 channel  1610  configured to hold a plurality of fasteners (e.g., nails, or staples); and (2) a fastener channel  1610  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  1610 , 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  1610 . 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 dosing lever  1400  of the present disclosure is now further described.  FIGS.  6  to  14    illustrate the example dosing lever  1400  of the example fastener driving tool  1050 . The dosing lever  1400  includes: (1) a body  1410 ; (2) a first leg  1430  connected to and extending from the body  1410  along a first longitudinal axis (L 1 ); (3) a second leg  1440  connected to and extending from the body  1410  along a second longitudinal axis (L 2 ); (4) a first lever pivot pin  1450  connected to and extending from the first leg  1430 ; and (5) a second lever pivot pin  1460  connected to and extending from the second leg  1440 . 
     The body  1410  includes: (1) a leg connection section  1412 ; (2) a fuel cell door facing section  1414 ; and (3) a fuel block contact section  1416 . The leg connection section  1412  (that is sometimes referred to herein as the “front section”) incudes: (1) a first leg connection portion  1418  connected to the first leg  1430 ; and (2) a second leg connection portion  1420  connected to the second leg  1440 . The fuel cell door facing section  1414  (that is sometimes referred to herein as the “rear section”) includes: (1) a first beveled portion  1422 ; (2) a second beveled portion  1424 ; (3) a third beveled portion  1426 ; and (4) an upright portion  1428  that connects the fuel cell door facing section  1414  to the fuel block contact section  1416 . The fuel block contact section  1416  (that is sometimes referred to herein as the “bottom section”) is configured to engage the fuel cell receiving block  1350  upon actuation of the dosing lever  1400 . 
     The first dosing lever leg  1430  includes: (1) a connection portion  1431  suitably connected to the first leg connection portion  1418  of the body  1410 ; (2) a foot  1432  opposite the connection portion  1431 ; and (3) a central portion  1433  extending between and connected to the connection portion  1431  and the foot  1432 . In the illustrated example embodiment, the first lever pivot pin  1450  is connected to and transversely extends outward from the connection portion  1431  of the first dosing lever leg  1430 . 
     The foot  1432  of the first dosing lever leg  1430  includes: (1) a toe  1434 ; (2) a heel  1435 ; and (3) a sole  1436  extending between and connected to the toe  1434  and the heel  1435 . In the illustrated example embodiment, the sole  1436  includes a substantially flat surface (within manufacturing tolerances) that defines a first contact surface  1437  of the foot  1432 . The toe  1434  includes a sloped surface with respect to the sole  1436  that defines a second contact surface  1438  of the foot  1432 . In this illustrated example embodiment, the second contact surface  1438  can be completely flat or can have a slight curvature such as a having a radius of curvature of about 1 inch (2.54 cms). In the illustrated example embodiment, the foot  1432  forms or otherwise defines an angle (α 1 ) of approximately 32 degrees between the first contact surface  1437  of the sole  1436  and the second contact surface  1438  of the toe  1434 . The foot  1432  thus includes two flat or generally flat separate contact surfaces  1436  and  1438  that function for different purposes as described below. 
     The second leg  1440  includes: (1) a connection portion  1441  suitably connected to the second leg connection portion  1420  of the body  1410 ; (2) a foot  1442  opposite the connection portion  1441 ; and (3) a central portion  1443  extending between the connection portion  1441  and the foot  1442 . In the illustrated example embodiment, the second lever pivot pin  1460  is connected to and transversely extends outward from the connection portion  1441  of the second dosing lever leg  1440 . 
     The foot  1442  of the second dosing lever leg  1440  includes: (1) a toe  1444 ; (2) a heel  1445 ; and (3) a sole  1446  extending between and connected to the toe  1444  and the heel  1445 . In the illustrated example embodiment, the sole  1446  includes a substantially flat surface (within manufacturing tolerances) that defines a first contact surface  1447  of the foot  1442 . The toe  1444  includes a sloped surface with respect to the sole  1446  that defines a second contact surface  1448  of the foot  1442 . In this illustrated example embodiment, the second contact surface  1448  can be completely flat or can have a slight curvature such as a having a radius of curvature of about 1 inch (2.54 cms). In the illustrated example embodiment, the foot  1442  forms an angle (α 2 ) (not shown) that is the same or substantially the same as the angle (α 1 ). Angle (α 2 ) is approximately 32 degrees and formed between the first contact surface  1447  of the sole  1448  and the second contact surface  1448  of the toe  1444 . The foot  1442  thus includes two flat or generally flat separate contact surfaces  1446  and  1448  that function for different purposes as described below. 
     In the illustrated example dosing lever  1400 , the different beveled portions of the body  1410  define sloped surfaces of the fuel cell door facing section  1414 . More specifically, the first beveled portion  1422  includes a substantially rectangular surface  1471  defined by: (1) a first edge  1472 ; (2) a second edge  1473  opposite the first edge  1472 ; (3) a third edge  1474  connecting the first edge  1472  and the second edge  1473 ; and (4) a fourth edge  1475  opposite the third edge  1474  and connecting the first edge  1472  and the second edge  1473 . 
     The second beveled portion  1424  includes a substantially trapezoidal surface  1476  defined by: (1) the third edge  1474 ; (2) a fifth edge  1477  opposite the third edge  1474 ; (3) a sixth edge  1478  connecting the third edge  1474  and the fifth edge  1477 ; and (4) a seventh edge  1479  opposite the sixth edge  1478  and connecting the third edge  1474  and the fifth edge  1477 . 
     The third beveled portion  1426  includes a substantially trapezoidal surface  1480  defined by: (1) the fourth edge  1475 ; (2) an eighth edge  1481  opposite the fourth edge  1475 ; (3) a ninth edge  1482  connecting the fourth edge  1475  and the eighth edge  1481 ; and (4) a tenth edge  1483  opposite the ninth edge  1482  and connecting the fourth edge  1475  and the eighth edge  1481 . 
     In the illustrated example embodiment, the rectangular surface  1471  is a downwardly sloping surface that extends downward from the first edge  1472  to the second edge  1473  of the first beveled portion  1422 . The trapezoidal surface  1476  is defined at one end of the rectangular surface  1471 . The trapezoidal surface  1476  is a downwardly sloping surface that extends downward from the third edge  1474  to the fifth edge  1477  of the second beveled portion  1424 . The trapezoidal surface  1480  is defined at the other end of the rectangular surface  1471 . The trapezoidal surface  1480  is a downwardly sloping surface that extends downward from the fourth edge  1475  towards the tenth edge  1483 . 
     In the illustrated example embodiment, the downwardly sloping surfaces of the rectangular surface  1471 , the trapezoidal surface  1476 , and the trapezoidal surface  1480  reduce a height or thickness of the fuel cell door facing section  1414  of the body  1410  (as compared to the known dosing lever described above). As discussed in more detail below, the beveled portions  1422 ,  1424 , and  1426  are configured such that the body  1410  of the dosing lever  1400  does not engage or otherwise contact the fuel cell door  1310  during actuation of the dosing lever  1400 . 
     As best shown in  FIGS.  11   , the dosing lever  1400  engages the fuel cell receiving block  1350  to dispense a dose of fuel from the fuel cell  1320 . The fuel cell receiving block  1350  is mounted on and connected to a valve stem  1332  of the fuel cell adapter  1330 . The fuel cell receiving block  1350  includes an internal fuel passageway (not labeled) aligned with an internal fuel passageway (not labeled) of the valve stem  1332  to fluidly couple the fuel cell  1320  to the fuel cell receiving block  1350 . 
     In the illustrated example embodiment, the dosing lever  1400  is engaged to the fuel cell receiving block  1350  and actuation of the dosing lever  1400  transfers axial force from the dosing lever  1400  to the fuel cell receiving block  1350 . More specifically, actuation of the dosing lever  1400  causes the fuel block contact section  1416  to move downward and engage the fuel cell receiving block  1350 . This downward movement of the fuel cell receiving block  1350  causes a corresponding downward movement of the valve stem  1332  of the fuel cell adapter  1330  and the fuel cell metering valve  1340 . As the fuel cell metering valve  1340  moves downward, the valve draws a fuel dose from the fuel cell  1320  into the fuel cell metering valve  1340 . Non-actuation of the dosing lever  1400  causes an upward movement of the fuel block contact section  1416  and a corresponding upward movement of the fuel cell receiving block  1350 . This upward movement of the fuel cell receiving block  1350  causes a corresponding upward movement of the valve stem  1332  and the fuel cell metering valve  1340 . As the fuel cell metering valve  1340  moves upward, the valve dispenses the fuel dose from the fuel cell  1320  into the combustion chamber  1220 . 
     Part of the operation of the example fastener driving tool  1050  is also partially shown in  FIGS.  11  to  14   . In the illustrated example embodiment, the fastener driving tool  1050  is configured to sequentially drive a plurality of fasteners (not shown) into a workpiece. Prior to actuation of the tool  1050 , the dosing lever  1400  is in a non-actuated position. As best shown in  FIGS.  12 ,  13   , and  14 , the combustion chamber ring  1270  includes a plurality of ring fingers  1272  configured to selectively engage the feet  1432  and  1442  of the first and second legs  1430  and  1440 , respectively. As shown in  FIG.  12   , when the dosing lever  1400  is in the non-actuated position, the combustion chamber ring  1270  is in the non-actuated position and the plurality of ring fingers  1272  are in a non-engaged position with respect to the feet  1432  and  1442  of the dosing lever  1400 . 
     In the illustrated example embodiment, when the dosing lever  1400  is in the non-actuated position, the dosing lever  1400  is pivoted about the first and second lever pivot pins  1450  and  1460  such that the first and second dosing lever legs  1430  and  1440  angle downward towards the combustion chamber ring  1270  and the body  1410  angles upward towards the fuel cell door  1310 . More specifically, when the dosing lever  1400  is in the non-actuated position, the first contact surfaces  1437  and  1447  of feet  1432  and  1442  are engaged to and supported by the cylinder head  1210  and the beveled portions  1422 ,  1424 , and  1426  of the fuel cell door facing section  1414  are adjacent the fuel cell door  1310 . The beveled portions  1422 ,  1424 , and  1426  are configured such that the body  1410  of the dosing lever  1400  does not contact or otherwise engage the fuel cell door  1310  when the dosing lever  1400  is in the non-actuated position. In other words, the beveled portions  1422 ,  1424 , and  1426  define a gap between the fuel cell door facing section  1414  of the body  1410  and the inner surface of the fuel cell door  1310  when the dosing lever  1400  is in the non-actuated position. 
     When the operator is ready to actuate the tool  1050 , the operator can cause the compression of the workpiece contact element  1710  against a workpiece (not shown). This compression of the workpiece contact element  1710  causes the combustion chamber ring  1270  to move axially upwardly which causes the dosing lever  1400  to pivot which causes the fuel cell receiving block  1350  to push on the adapter  1330  and causes the adapter  1330  to push on the fuel cell metering valve  1340  to cause a release of a dose of fuel from the fuel cell into the closed combustion chamber. At that point, subsequent compression of the trigger  1530  that causes a spark in the closed combustion chamber can ignite the dose of fuel in the combustion chamber and drive the fastener (not shown) into the workpiece. Thus, as best shown in  FIGS.  13  and  14   , engaging the workpiece contact element  1710  from the workpiece closes the combustion chamber and causes movement of the combustion chamber ring  1270 , and the plurality of ring fingers  1272 , in an axially upward direction towards the housing cap  1130 . After driving the fastener into the workpiece, disengagement of the workpiece contact element  1710  from the workpiece causes the combustion chamber to open and causes the downward axial movement of the combustion chamber ring  1270  (including its plurality of fingers  1272 ) and thus disengagement of the dosing lever  1400 . This disengagement of the dosing lever  1400  causes the dosing lever  1400  to pivot downwardly to be in a position ready for the next actuation of the workpiece contact element  1710  and thus for the next combustion cycle of the tool  1050 . 
     In the illustrated example embodiment, engagement between the combustion chamber ring fingers  1272  and the dosing lever feet  1432  and  1442  causes the dosing lever  1400  to pivot about the first and second lever pivot pins  1450  and  1460  from the non-actuated position into the actuated position. More specifically, when the dosing lever  1400  pivots between the non-actuated position to the actuated position, the ring fingers  1272  engage the respective second contact surfaces  1438  and  1448  of feet  1432  and  1442 . As such, the second contact surfaces  1438  and  1448  slide along the outer surface of the ring fingers  1272  and the first contact surfaces  1437  and  1447  slide along the outer surface of the cylinder head  1210 . As best shown in  FIG.  14   , when the dosing lever  1400  is in its fully actuated position, the second contact surfaces  1438  and  1448  are engaged with and supported by the ring fingers  1272 . 
     In the illustrated example embodiment, as the combustion chamber ring moves the dosing lever  1400  between the non-actuated and actuated position the first contact surfaces  1437  and  1447  and second contact surfaces  1438  and  1448  of the feet  1432  and  1442  are configured to slide smoothly along the ring fingers  1272 . This engagement between the ring fingers  1272  and the feet  1432  and  1442  causes a consistent and repeatable actuation of the dosing lever  1400 , which in turn causes the fuel supply assembly  1300  to deliver a consistent and repeatable dose of fuel from the fuel cell  1320  to the combustion chamber  1220  even in circumstances of extremely cold weather. 
     In the illustrated example embodiment, actuation of the dosing lever  1400  also causes downward movement of the body  1410  from the fuel cell door  1310  towards the fuel cell  1320 . This downward movement of the body  1410  causes depression of the fuel cell receiving block  1350 , the valve stem  1332 , and the fuel cell metering valve  1340 . As such, the fuel cell metering valve  1340  draws a dose of fuel from the fuel cell  1320  for delivery to the combustion chamber  1220 . The first contact surfaces  1437  and  1447  and second contact surfaces  1438  and  1448  of the feet  1432  and  1442  are configured to slide smoothly along the ring fingers  1272  as the combustion chamber ring moves the dosing lever  1400  between the non-actuated and actuated position. This engagement between the ring fingers  1272  and the feet  1432  and  1442  causes a consistent and repeatable actuation of the dosing lever  1400 , which in turn causes the fuel supply assembly  1300  to deliver a consistent and repeatable dose of fuel from the fuel cell  1320  to the combustion chamber  1220 . 
     In the illustrated example embodiment, as the dosing lever  1400  moves between the non-actuated position (as shown in  FIG.  12   ) and the actuated position (as shown in  FIG.  14   ), the interaction between the dosing lever  1400  and the fuel cell receiving block  1350  causes the fuel metering valve to draw a dose of fuel from the fuel cell  1320 . In the illustrated example embodiment, the beveled portions  1422 ,  1424 , and  1426  of the fuel cell door facing section  1414  of the body  1410  are configured to form a gap between the body  1410  and the inner surface of the fuel cell door  1310 . Accordingly, the beveled portions  1422 ,  1424 , and  1426  of the dosing lever  1400  ensure that the dosing lever  1400  can fully pivot between the non-actuated position and the actuated position without contacting the inner surface of the fuel cell door  1310 . As such, each actuation cycle of the dosing lever  1400  delivers a consistent and repeatable amount of fuel from the fuel cell  1320  to the combustion chamber  1220  even in circumstances of extremely cold weather. 
     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.