Abstract:
A cordless power tool system includes a power tool including with a motor disposed in the tool housing, and a variable speed circuit for controlling the speed of the motor. A power tool battery pack is electrically connectable to the power tool. The battery pack has an electric/electronic component connectable to the variable speed circuit. The variable speed circuit and/or the power tool are disabled if the variable speed circuit fails to detect the electric/electronic component.

Description:
FIELD 
       [0001]    This specification relates to cordless power tools and more specifically to a lockout arrangement for locking out certain power tool battery packs from certain power tools. 
       BACKGROUND 
       [0002]    Referring to  FIGS. 1-2 , a cordless power tool, such a drill  100 , typically has a housing  101 , a motor M for driving a cutting tool, such as drill bit DB, and a power tool battery pack  10  electrically connected to motor M. Drill  100  may have a variable speed feature allowing the user to select the rotational speed of motor M. Typically such variable speed feature is integrated into trigger assembly TA, allowing the user to adjust the desired speed by pulling trigger assembly TA a certain distance. 
         [0003]    A typical power tool battery pack  10  has a housing  13 , cells  11  disposed in the housing  13  and connected between first and second terminals A, B, and a thermistor  12  disposed in the housing  13  and connected between first and third terminals A, C. Such power tool battery pack  10  can be connected to drill  100  via terminals A, B. 
         [0004]    Typically trigger assembly TA has a first switch S 1 , a second switch S 2  and a potentiometer R 1 . Accordingly, when the operator closes the trigger assembly, first switch S 1  closes, thereby powering up integrated circuit IC 1 . Integrated circuit IC 1  is a device such as a 555 timer, micro controller, or other device capable of controlling the voltage or current or power control to motor M. After first switch S 1  is closed, potentiometer R 1  provides a voltage signal to integrated circuit IC 1  relative to trigger position. As the position of potentiometer R 1  varies, the voltage presented to integrated circuit IC 1  varies. Integrated circuit IC 1  responds by activating FET Q 1  with on/off pulses allowing current to flow from terminal A through switch S 1  through motor M through FET Q 1  (when FET Q 1  is directed to be on by integrated circuit IC 1 ). By directing FET Q 1  on and off with a variable duty cycle, motor speed can be controlled. As previously stated, as the trigger assembly TA is fully engaged, FET Q 1  is bypassed by second switch S 2  allowing full connection to the power tool battery pack  10  for maximum power capability. 
         [0005]    It is preferable to ensure that certain power tools can only be used with certain battery packs, and to lock out undesirable battery packs, which may not meet quality requirements, etc. 
       SUMMARY 
       [0006]    A cordless power tool system comprising a power tool including a tool housing, a motor disposed in the tool housing, and a variable speed circuit for controlling the speed of the motor, and a power tool battery pack electrically connectable to the power tool, the power tool battery pack including a pack housing, cells disposed within the pack housing, and an electric/electronic component disposed within the pack housing and connectable to the variable speed circuit, wherein at least one of the variable speed circuit and the power tool is disabled if the variable speed circuit fails to detect the electric/electronic component. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0007]    The accompanying drawings illustrate preferred embodiments according to the practical application of the principles thereof, and in which: 
           [0008]      FIG. 1  illustrates a typical cordless power tool. 
           [0009]      FIG. 2  is a schematic diagram of the prior art power tool/power tool battery pack system. 
           [0010]      FIG. 3  is a schematic diagram of the power tool/power tool battery pack system according to the invention. 
           [0011]      FIG. 4  is a partial schematic diagram of the power tool/adapter/power tool battery pack system according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The present invention will now be described more fully hereinafter. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0013]    Referring first to  FIGS. 1 and 3 , where like numerals refer to like parts. A cordless power tool, such a drill  100 , preferably has a housing  101 , a motor M for driving a cutting tool, such as drill bit DB, and a power tool battery pack  10  electrically connected to motor M. Drill  100  may have a variable speed feature allowing the user to select the rotational speed of motor M. Typically such variable speed feature is integrated into trigger assembly TA, allowing the user to adjust the desired speed by pulling trigger assembly TA a certain distance. 
         [0014]    Power tool battery pack  10  preferably has a housing  13 , cells  11  disposed in the housing  13  and connected between first and second terminals A, B, and a thermistor  12  disposed in the housing  13  and connected between first and third terminals A, C. Such power tool battery pack  10  can be connected to drill  100  via terminals A, B. 
         [0015]    Trigger assembly TA preferably has a first switch S 1 , a second switch S 2  and a potentiometer R 1 . Accordingly, when the operator closes the trigger assembly, first switch S 1  closes, thereby powering up integrated circuit IC 1 . Integrated circuit IC 1  is a device such as a 555 timer, micro controller, or other device capable of controlling the voltage or current or power control to motor M. After first switch S 1  is closed, potentiometer R 1  provides a voltage signal to integrated circuit IC 1  relative to trigger position. As the position of potentiometer R 1  varies, the voltage presented to integrated circuit IC 1  varies. 
         [0016]    Integrated circuit IC 1  is preferably connected to thermistor  12  via third terminal C. If integrated circuit IC 1  does not detect thermistor  12 , it will not turn on FET Q 1 , effectively disabling cordless drill  100 . Alternatively, if integrated IC 1  does not detect thermistor  12 , it can just turn on FET Q 1  full-time, effectively disabling the variable speed feature and the operator&#39;s ability to vary the speed of motor M. Disabling the variable speed feature may also be accomplished by never turning on FET Q 1  such that the motor will only run full speed via closure of second switch S 2 . Alternately FET Q 1  could be turned off and on in such a way to create an undesirable, counter-intuitive, or difficult to control behavior from the motor speed control. 
         [0017]    On the other hand, if integrated circuit IC 1  detects thermistor  12 , it would activate FET Q 1  with on/off pulses allowing current to flow from terminal A through switch S 1  through motor M through FET Q 1  (when FET Q 1  is directed to be on by integrated circuit IC 1 ). By directing FET Q 1  on and off with a variable duty cycle, motor speed can be controlled. As previously stated, as the trigger assembly TA is fully engaged, FET Q 1  is bypassed by second switch S 2  allowing full connection to the power tool battery pack  10  for maximum power capability. 
         [0018]    Persons skilled in the art will recognize that such arrangement can be used to render undesirable the use of power tool battery packs  10  that do not have a thermistor  12 , thus encouraging operators to use power tool battery packs that have a thermistor  12 . In addition, persons skilled in the art will recognize that thermistor  12  may replaced by other electric and/or electronic components, such as resistors, capacitors, inductors, transistors, integrated circuits, etc., which can be recognized by integrated circuit IC 1 . 
         [0019]    A second embodiment of the present invention is shown in  FIG. 4 , where like numerals refer to like parts. All the teachings of the first embodiment discussed above are incorporated herein by reference. The only difference between the first and second embodiments is that an adapter  20  is disposed on battery pack  10  and/or cordless drill  100 . Persons skilled in the art are referred to U.S. Pat. No. 6,525,511, which is fully incorporated herein by reference, for further information on adapter  20 . 
         [0020]    Adapter  20  may interface one type of power tool battery pack with a cordless drill  100  that accepts a different type of power tool battery pack. For example, adapter  20  may interface a tower-style power tool battery pack with a cordless drill  100  that accepts only slide-style power tool battery packs, and/or a tower-style power tool battery pack having a first terminal configuration with a cordless drill  100  that accepts only tower-style power tool battery packs having a second terminal configuration, where the cordless drill  100  would not accept the power tool battery pack having the first terminal configuration. 
         [0021]    Adapter  20  may also interface a power tool battery pack  10 ′ that does not have a thermistor  12  with a cordless drill  100  that requires the presence of thermistor  12  in order to activate cordless drill  100  and/or the variable speed circuit. Such result can be accomplished as follows. Adapter  20  may be electrically connected to power tool battery pack  10  via first and second terminals A, B. Adapter  20  may in turn have third and fourth terminals A′, B′ that electrically connect to cordless drill  100 , in the same manner the first and second (power) terminals A,B would have been connected to cordless drill  100 . 
         [0022]    In addition, adapter  20  may have a fifth terminal C′, and a thermistor  12  connected to such terminal C′. Terminal C′ would preferably be connected to cordless drill  100  so that the presence of thermistor  12  could be detected by integrated circuit IC 1 . 
         [0023]    Persons skilled in the art will recognize that if an adapter  20  lacking thermistor  12  is used to interface power tool battery pack  10 ′ with cordless drill  100 , integrated circuit IC 1  cannot detect a thermistor  12 . Thus, integrated circuit IC 1  will not turn on FET Q 1  in a desirable manner, effectively disabling cordless drill  100 , or turn on FET Q 1  full-time, effectively disabling the variable speed feature and the operator&#39;s ability to vary the speed of motor M. 
         [0024]    It should be understood that the adapter preferably acts as a pass-through for battery terminals A and B to connect the battery and terminal to the power tool motor. Adapter  20  may also have a pass-through terminal for a thermistor in battery pack  10 . 
         [0025]    Alternately instead of passing through the thermistor signal, the adapter  20  may not pass through the thermistor signal by not connecting to the thermistor terminal in battery pack  10  or terminating such line within the adapter  20 . Rather the connection to the integrated circuit IC 1  could be made by an electronic/electrical element in the adapter  20  itself (taking the place of the thermistor in the battery pack  10 ) thereby impersonating the thermistor lock-out feature of the circuit. The electronic/electrical element could be a thermistor, resistor, or other element that would signal the variable speed circuit to operate in a normally desirable manner. 
         [0026]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.