Abstract:
A fuel cell includes a spark initiator configured to initiate spark events, and a fuel level monitoring system configured for monitoring the fuel level in the fuel cell and indicating the monitored fuel level to a user. Included in the fuel level monitoring system is a programmable control unit configured to control the spark initiator and to count the spark events initiated by the spark initiator, to compare a number of spark events with at least two predetermined ranges of spark events, and to determine the fuel level in the fuel cell based on the determinations. An indicator controlled by the programmable control unit is supplied for providing the user with an indication of the fuel level in the fuel cell.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to handheld power tools, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools or combustion nailers. More specifically, the present invention relates to such combustion tools using replaceable fuel cells, also called fuel canisters. 
         [0002]    Combustion-powered tools are known in the art, and 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; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill. under PASLODE® brand. As exemplified in the above-listed patents, it is known to use a disposable fuel cell for dispensing a pressurized hydrocarbon fuel to a combustion gas-powered tool. In particular, a suitable fuel cell is described in Nikolich U.S. Pat. No. 5,115,944, which is incorporated by reference herein. 
         [0003]    Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by the fuel cell, a canister of pressurized fuel gas. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body. 
         [0004]    Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original, or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade. 
         [0005]    As the combustion tool is operated, the fuel in the cell is progressively depleted. As this occurs, the internal fuel cell pressure drops until the cell is empty, or has insufficient fuel for further fastener-driving combustion events. 
         [0006]    When the tool fails to fire, the first impulse is typically for the user to remove the fuel cell from the tool to determine whether an empty fuel cell is the cause. However, it is often difficult to gauge how much fuel remains in the fuel cell. In some instances, the tool fails to misfire for reasons unrelated to the fuel cell, and otherwise usable fuel cells are disposed of. 
       BRIEF SUMMARY 
       [0007]    The present combustion tool employing a fuel cell includes a spark initiator configured to initiate spark events, and a fuel level monitoring system configured for monitoring the fuel level in the fuel cell and indicating the monitored fuel level to a user. Included in the fuel level monitoring system is a programmable control unit configured to control the spark initiator and to count the spark events initiated by the spark initiator, to compare a number of spark events with at least two predetermined ranges of spark events, and to determine the fuel level in the fuel cell based on the determinations. An indicator controlled by the programmable control unit is supplied for providing the user with an indication of the fuel level in the fuel cell. 
         [0008]    More specifically, a fuel level monitoring system for monitoring the fuel level in a fuel cell, and for indicating the monitored fuel level to a user, is provided. The system includes a programmable control unit configured to count spark events initiated by a spark initiator of the tool. The system compares a number of spark events with at least two predetermined ranges of spark events, and determines the fuel level in the fuel cell based on the determinations. An indicator is controlled by the programmable control unit for providing the user with an indication of the fuel level in the fuel cell. A reset device is configured to reset the number of spark events counted by the programmable control unit to zero. 
         [0009]    In another embodiment, a method of monitoring and indicating a fuel level of a fuel cell in a combustion tool includes providing at least two predetermined ranges of spark events, counting the number of spark events in the tool, and comparing the number of spark events with the at least two predetermined ranges of spark events. The method further includes indicating the fuel level in the fuel cell with an indicator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a front perspective view of a combustion tool suitable for use with the present fuel level monitoring system; 
           [0011]      FIG. 2  is a fragmentary vertical cross-section of the combustion tool of  FIG. 1 ; 
           [0012]      FIG. 3  is a fragmentary perspective view of the rear of the combustion tool having an indicator and a reset device; and 
           [0013]      FIG. 4  is a schematic of the connection of the indicator, the reset device and a programmable control unit of the present fuel level monitoring system. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring now to  FIGS. 1 and 2 , a combustion-powered, fastener-driving tool suitable for incorporating the present handle housing is generally designated  10 . While the tool  10  is depicted as being of the type described in the patents listed above, other types of combustion tools are contemplated as having the potential of incorporation of the present fuel level monitoring system. 
         [0015]    A housing  12  of the tool  10  encloses a self-contained internal power source  14 , within a housing main chamber  16 . As in conventional combustion tools, the power source  14  is powered by internal combustion and includes a combustion chamber  18  that communicates with a cylinder  20 . A piston  22  reciprocally disposed within the cylinder  20  is connected to the upper end of a driver blade  24 . As shown in  FIG. 2 , an upper limit of the reciprocal travel of the piston  22  is referred to as a top dead center or pre-firing position, which occurs just prior to firing, or the ignition of the combustion gases which initiates the downward driving of the driver blade  24  to impact a fastener (not shown) to drive it into a workpiece. 
         [0016]    Through depression of a trigger  26 , an operator induces combustion within the combustion chamber  18 , causing the driver blade  24  to be forcefully driven downward through a nosepiece  28  ( FIG. 1 ). The nosepiece  28  guides the driver blade  24  to strike a fastener that had been delivered into the nosepiece via a fastener magazine  30 . 
         [0017]    Included in the nosepiece  28  is a workpiece contact element  32 , which is connected, through a linkage  34  to a reciprocating valve sleeve  36 , an upper end of which partially defines the combustion chamber  18 . Depression of the tool housing  12  against the workpiece contact element  32  in a downward direction as seen in  FIG. 1  (other operational orientations are contemplated as are known in the art), causes the workpiece contact element to move from a rest position to a pre-firing position. This movement overcomes the normally downward biased orientation of the workpiece contact element  32  caused by a spring  38  (shown hidden in  FIG. 1 ). 
         [0018]    Through the linkage  34 , the workpiece contact element  32  is connected to and reciprocally moves with, the valve sleeve  36 . In the rest position ( FIG. 2 ), the combustion chamber  18  is not sealed, since there is an annular gap  40  including an upper gap  40 U separating the valve sleeve  36  and a cylinder head  42 , which accommodates a chamber switch  44  and a spark initiator  46 , such as a spark plug, and a lower gap  40 L separating the valve sleeve  36  and the cylinder  20 . The spark initiator  46  is in fluid communication with the combustion chamber  18 . 
         [0019]    In the preferred embodiment of the present tool  10 , the cylinder head  42  also is the mounting point for at least one cooling fan  48  and the associated fan motor  49  which extends into the combustion chamber  18  as is known in the art and described in the patents which have been incorporated by reference above. In the rest position depicted in  FIG. 2 , the tool  10  is disabled from firing because the combustion chamber  18  is not sealed at the top with the cylinder head  42  and the chamber switch  44  is open. 
         [0020]    Firing is enabled when an operator presses the workpiece contact element  32  against a workpiece. This action overcomes the biasing force of the spring  38 , causes the valve sleeve  36  to move upward relative to the housing  12 , closing the gap  40 , sealing the combustion chamber  18  and activating the chamber switch  44 . This operation also induces a measured amount of fuel to be released into the combustion chamber  18  from a replaceable fuel cell  50  (shown in fragment). 
         [0021]    In a mode of operation known as sequential operation, upon a pulling of the trigger  26 , the spark initiator  46  is energized, igniting the fuel and air mixture in the combustion chamber  18  and sending the piston  22  and the driver blade  24  downward toward the waiting fastener for entry into the workpiece. The ignition of the fuel and air mixture by the spark initiator  46  is known as a “spark event”. As the piston  22  travels down the cylinder  20 , it pushes a rush of air which is exhausted through at least one petal, reed or check valve  52  and at least one vent hole  53  located beyond the piston displacement ( FIG. 2 ). At the bottom of the piston stroke or the maximum piston travel distance, the piston  22  impacts a resilient bumper  54  as is known in the art. With the piston  22  beyond the exhaust check valve  52 , high pressure gasses vent from the cylinder  20 . Due to internal pressure differentials in the cylinder  20 , the piston  22  is drawn back to the pre-firing position shown in  FIG. 1 . 
         [0022]    Referring now to  FIGS. 3 and 4 , a fuel level monitoring system suitable for use with the tool  10  is generally designated  56  and is configured for monitoring the level of fuel in the fuel cell  50  and for indicating the monitored condition to a user. In the present application, the condition of the fuel cell  50  will generally relate to the amount or level of fuel remaining in the fuel cell  50 . As described in U.S. Pat. No. 6,722,550, incorporated by reference herein, it is known to monitor fuel levels by determining the pressure of the fuel emitted from the fuel cell  50 , or by determining the flow of the fuel as it is emitted from the fuel cell  50  to the combustion chamber  18 . 
         [0023]    In the present fuel level monitoring system  56 , the amount of the fuel in the fuel cell  50  is determined by the number of shots fired or “spark events” in the combustion chamber  18  of the tool  10 . Typically, each fuel cell  50  has fuel for about 1,200 spark events. As is known in the art, one spark event is needed each time a fastener is driven by the tool  10 . By counting the number of spark events or the number of shots fired, the fuel level monitoring system  56  can estimate the amount of fuel that remains in the fuel cell  50 . 
         [0024]    An indicator  58  is disposed at a visible location on the tool  10 , for example the rear of the tool, however it is contemplated that the indicator may be placed anywhere on the housing  12  that is convenient and easy for the user to read. In the present embodiment, the indicator  58  is at least one LED. The indicator  58  is configured for indicating the amount of fuel remaining in fuel cell  50  or whether the fuel cell requires replacement, for example by the number or color of LED&#39;s. While the present fuel level monitoring system  56  uses LEDs as indicators  58 , it should be appreciated that other indicators can be used. 
         [0025]    In one embodiment, the indicator  58  has a green LED  60  that is illuminated to indicate a first predetermined range of spark events of the tool  10  with the fuel cell  50 , for example 0 to 1,000 spark events. An illuminated green LED indicates to the user that the fuel cell  50  has ample fuel. When a second predetermined range of spark events is reached, for example 1,001 to 1,200 spark events, a yellow LED  62  is illuminated to indicate that the fuel in the fuel cell  50  is low. When a third predetermined range of spark events is reached, for example 1,201 and up, a red LED  64  is illuminated to indicate that the fuel in the fuel cell  50  is currently depleted or will soon be depleted. 
         [0026]    The indicator  58  indicates at least two different fuel levels that correspond to the at least two predetermined ranges of spark events. It should be appreciated that the amount of LEDs and predetermined ranges can vary. Further, it should be appreciated that other colors of LED, the flashing of LED, and the brightness of LED can be used as distinguishing indicators, among others. A legend  59  may be provided on the tool  10  to provide instruction to the user on what the indicator  58  is indicating, such as a color-coded chart corresponding to the colors of the LEDs. 
         [0027]    The spark events or shots fired are counted by a programmable control unit  66  of the tool  10 . The programmable control unit  66 , preferably including a microprocessor, is preferably already employed in the tool  10  for coordinating combustion, as is known in the art in the patents made of record above. Upon the user pulling the trigger  26  ( FIG. 1 ), among other things, the programmable control unit  66  energizes the spark plug  46 , igniting the fuel and air mixture in the combustion chamber  18  (the “spark event”). The resulting combustion sends the piston  22  and the driver blade  24  downward toward the waiting fastener for entry into the workpiece ( FIG. 2 ). A battery  65  ( FIG. 4 ) powers the programmable control unit  66 , which also includes a counter  67  that counts the amount of spark events. The counter  67  is preferably a software function within the programmable control unit  66 , and the programmable control unit compares the number of spark events accumulated by the counter  67  with the above-identified predetermined stored ranges. 
         [0028]    The counter  67  of the programmable control unit  66  is reset to zero by a reset device  68 . In the present embodiment, the reset device  68  is a button or other switch  70  that is electrically connected to the programmable control unit  66 . Each time a new fuel cell  50  is inserted into the tool  10 , the user activates the reset device  68  to reset the counter of the programmable control unit  66 , for example by pressing the button  70 . It is possible that the reset device  68  can require activation by the user for a predetermined period of time, for example 3-seconds, to reset the counter  67 . In this configuration, unintentional resetting of the counter  67  is avoided or reduced. Further, with the manual resetting of the reset device  68 , the fuel cell  50  can be removed from the tool  10  and then placed back into the tool without interrupting the count. Alternatively, it is possible that automatic resetting of the reset device  68  can occur whenever a fuel cell  50  is placed into the tool  10 . 
         [0029]    Referring now to  FIG. 4 , while other circuits or connections are contemplated, it is preferred that a first wire  72  from the programmable control unit  66  provides power to the reset device  68 , and a second wire  74  between the reset device and the programmable control unit grounds the reset device. A third wire  76  extends between the reset device  68  and the indicator  58  to ground the indicator. 
         [0030]    The programmable control unit  66  also controls the indicator  58 . A fourth wire  78  extends between the programmable control unit  66  and the green LED  60 , a fifth wire  80  extends between the programmable control unit  66  and the yellow LED  62 , and a sixth wire  82  extends between the programmable control unit  66  and the red LED  64 . A seventh wire  84  extends between the programmable control unit  66  and the power source  14 . It should be understood that the fuel level monitoring system  56  is not limited to the wiring described above. 
         [0031]    Thus, it will be seen that the present fuel level monitoring system  56  provides a way for the user to easily monitor the level of fuel in the fuel cell  50 . In this manner, tool  10  malfunctions may be more easily diagnosed, since time is not wasted on checking the fuel cell fuel level when that is not the cause for malfunction. In addition, users will not be forced to discard usable fuel cells  50  in the mistaken belief that they are empty. Further, the present system  56  is a less complex method of monitoring the fuel cell  50  fuel level than monitoring the pressure or flow of the fuel emitted from the fuel cell. In addition, fastener-driving production is made more efficient, in that the user knows precisely when to change the fuel cell  50 . 
         [0032]    While particular embodiments of the present fuel cell level monitoring system  56  and mechanism for a combustion-powered tool  10  have been described herein, it will 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.