Patent Publication Number: US-2005121209-A1

Title: Transportable power tool

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a transportable (or handheld) power tool used for fastening a bolt, a nut, a screwnail, and so on, for drilling metalwork, woodwork, mortar, concrete, and so on, or for cutting metalwork, woodwork, and so on.  
      2. Description of the Related Art  
      A conventional transportable power tool is described with reference to  FIGS. 9A and 9B .  FIG. 9A  is a side view of the conventional transportable power tool. As can be seen from  FIG. 9A , in the conventional transportable power tool, a cylindrical shaped power unit  8  is provided at a top end of a grip  7  in a manner so that a center axis of the cylindrical shape of the power unit  8  crosses a center axis of the grip  7  at a predetermined angle near to right angle. A battery pack  6  is detachable provided at a bottom end of the grip  7 . Generally, a diameter of the cylindrical shape of the power unit  8  is larger than a width of the grip  7  in a direction perpendicular to a paper sheet of  FIG. 9A . The width of the battery pack  6  is similarly wider than that of the grip  7 .  
       FIG. 9B  is a plan view showing a part in the vicinity of a rear end the power unit  8 . A circular knob  11 ′ of an operation switch is rotatably provided on an outer face in the vicinity of the rear end of the power unit  8 , by which an operation mode (for example, a torque mode) of the power tool is selected among a plurality of the operation modes. Alternatively, in another conventional transportable power tool, a ring shaped finger grip (not shown) is rotatably provided around the center axis of the cylindrical shape of the power unit  8  on a front or rear end of the cylindrical shaped power unit  8 .  
      The conventional transportable power tool, however, has a possibility that the power tool is fallen from a hand of a user or toppled down due to careless handling. Because of the above-mentioned feature with respect to the shape of the power tool that the dimensions of the power unit  8  and the battery pack  6  are partially larger than those of the grip  7 , when the power tool is fallen or toppled down, a part of the cylindrical outer faces above the center axis of the cylindrical shape or the rear face of the power unit  8 , or a part of the side faces or the bottom face of the battery pack  6  could be bumped against the land surface or the floor face. Since the knob  11 ′ or the finger grip of the operation switch is provided on the outer face of the power unit  8 , the knob  11 ′ or the finger grip could be damaged due to the falling or toppling of the power tool.  
      On the other hand, still another conventional transportable power tool, for example, shown in laid open publication of Japanese patent application 7-161340 has a display device on the battery pack for indicating the capacity of the battery. A width of a rear end of the battery pack is narrowed, and the display device is provided on the narrowed rear end. Thus, the display device may not be damaged when the power tool is fallen or toppled down in sidewise. The display device, however, will be damaged, if the power tool is fallen or toppled down backend-to.  
     SUMMARY OF THE INVENTION  
      A purpose of the present invention is to provide a transportable power tool in which an operation member used for switching the operation mode may not be damaged due to bumping against the land surface or the floor face, even when the power tool is fallen or toppled down.  
      A transportable power tool in accordance with an aspect of the present invention comprises: a motor; a reducer-transmitter for reducing rotation speed of a driving shaft of the motor and for transmitting a driving force of the motor to an output shaft thereof; a control circuit for controlling driving of the motor; a housing for enclosing the motor, the reducer-transmitter and the control circuit; and a battery pack detachably coupled with the housing.  
      The power tool has a power unit in which at least the motor and the reducer-transmitter are contained, a grip and a coupler unit formed at an end of the grip opposite to the power unit with which battery pack is coupled. A center axis of the output shaft crosses a center axis of the grip around which a perm and fingers of a user grip at a predetermined angle near to right angle.  
      Maximum dimensions of the power unit and maximum dimensions of the battery pack in a direction perpendicular to both of the center axis of the output shaft and the center axis of the grip and in a direction parallel to the center axis of the output shaft are larger than those of the grip in the same directions.  
      At least an operation member used for selecting an operation mode of the motor is provided at a position near to the grip from a line binding contacting portions of the power unit and the battery pack when the power unit and the battery pack are simultaneously contacted with the same plane in each state.  
      By such a configuration, the operation member may not be damaged due to bumping against the land surface or the floor face even when the power tool is fallen or toppled down on the land surface or the floor face. Consequently, the transportable power tool can be used stably over the long term. Furthermore, it is no need to reinforce the mechanical strength of the operation member and so on, so as not to be damaged due to the bumping. Thus, it is possible to reduce the cost of the transportable power tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view showing an appearance and a configuration of a transportable power tool in accordance with an embodiment of the present invention;  
       FIG. 2  is a schematic sectional view showing an arrangement of elements of the transportable power tool in the embodiment;  
       FIG. 3  is a partial sectional view showing a detailed configuration of a main portion of the transportable power tool in the embodiment;  
       FIG. 4  is a block diagram showing a circuit configuration of the transportable power tool in the embodiment;  
       FIG. 5  is a side view showing an example of toppling down of the transportable power tool;  
       FIG. 6  is a side view showing another example of toppling down of the transportable power tool;  
       FIG. 7  is a front view showing still another example of toppling down of the transportable power tool;  
       FIG. 8  is a perspective view showing an appearance and a configuration of a modified transportable power tool in accordance with an embodiment of the present invention;  
       FIG. 9A  is a side view showing an appearance and a configuration of a conventional transportable power tool; and  
       FIG. 9B  is a partial plan view of the conventional transportable power tool. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT  
      A transportable power tool in accordance with an embodiment of the present invention is described with reference to drawings.  
      An appearance and a configuration of a transportable power tool (hereinafter, abbreviated as “power tool”)  10  in accordance with the embodiment are shown in  FIG. 1 . The transportable power tool  10  is, for example, an impact power tool, a power drill/driver, or the like. A block configuration of the power tool  10  is shown in  FIG. 2 . A detailed configuration of a main portion of the power tool  10  in the embodiment is shown in  FIG. 3 .  
      The power tool  10  comprises a motor  1 , a reducer-transmitter  2  for reducing rotation speed of a driving shaft of the motor  1  and for transmitting a driving force of the motor  1  to an output shaft  3  of the reducer/transmitter  2 , a switching circuit  4 , a trigger lever  16  for switching on and off of the driving of the motor  1 , a rotation switch lever  22  for switching the rotation direction of the motor  1  between normal and reverse directions, a control circuit  14  for controlling driving of the motor  1 , operation members  11  ( 11   a  and  11   b ) used for selecting an operation mode of the motor  1 , a display device  12 , a housing  5  for enclosing the above-mentioned components and a battery pack  6  detachably coupled with the housing  5 . The operation members  11  are, for example, buttons made of resin molding, which are movably held on the housing  5 .  
      The power tool  10  has a power unit  8  and a grip  7 . The motor  1  and the reducer-transmitter  2  including the output shaft  3  are contained in a portion of the housing  5  corresponding to the power unit  8 . A center axis of the output shaft  3  crosses a center axis of the grip  7  around which a perm and fingers of a user grip at a predetermined angle near to right angle. The predetermined angle, however, is not necessarily right angle. The power tool  10  further has a coupler unit  9  having a coupler structure with which battery pack  6  is coupled at a lower end of the grip  7  opposite to the power unit  8 . A pair of detaching operation members  25  is provided on sidewalls of the battery pack  6 . When the user pushes the detaching operation members  25 , the battery pack  6  can be detached from the coupler unit  9 . When the battery pack 6  is forcibly pushed toward the coupler unit  9 , the battery pack  6  is coupled with the coupler unit  9 .  
      The portion of the housing  5  corresponding to the power unit  8  has, for example, a substantially cylindrical shape. Cross-section of the power unit  8  in a direction perpendicular to the center axis of the output shaft  3  is circular, elliptic, round triangular, or the like. The motor  1  and the reducer-transmitter  2  are provided in the power unit  8 . A switching circuit  4  is provided in the grip  7 . A trigger lever  16  is slidably provided at a neck portion between the power unit  8  and the grip  7  in a manner so that a rear end portion of the trigger lever  16  can be moved in and out with respect to the inside of the grip  7 . Similarly, the rotation switch lever  22  is movably provided at the neck portion between the power unit  8  and the grip  7  in a manner so that a normal/reverse rotation switch  22 A (see  FIG. 4 ) is switched for varying a direction of a current flowing in windings of the motor  1  is reversed corresponding to the position of the rotation switch lever  22 . The operation members  11 , the display device  12  and the control circuit  14  are provided in a portion of the housing  5  corresponding to the coupler unit  9 , as shown in  FIG. 3 .  
      Hereupon, a direction parallel to the center axis of the output shaft  3  is defined X-direction, as shown in  FIG. 1 . A direction perpendicular to both of the center axis of the output shaft  3  and a line binding the power unit  8  and the battery pack  6  which is substantially parallel to the center axis of the grip  7  is defined Y-direction. A direction perpendicular to both of the center axis of the output shaft  3  and the center axis of the grip  7  is defined Z-direction. Furthermore, in X-direction, a part of the output shaft  3  is called “front”, and the opposite part is called “rear”. In Z-direction, a part of the power unit  8  is called “upper”, and a part of the battery pack  6  is called “bottom”.  
      A maximum dimension (length) of the power unit  8  in X-direction is larger (longer) than that of the grip  7 , and a maximum dimension (width) of the power unit  8  in Y-direction is larger (wider) than that of the grip  7 . In other words, the profile of the grip  7  in X-direction and Y-direction is smaller than the profile of the power unit  8  in the same directions, and the profile of the grip  7  is positioned inside the profile of the power unit  8 , when the power tool  10  is projected on X-Y plane.  
      Maximum dimensions (length and width) of the coupler unit  9  provided on the lower end of the grip  7  in X-direction and Y-direction are larger (longer and wider) than those of the grip  7  in the same directions. The profile of the grip  7  in X-direction and Y-direction is smaller than the profile of the coupler unit  9  in the same directions, and the profile of the grip  7  is positioned inside the profile of the coupler unit  9 , when the power tool  10  is projected on X-Y plane.  
      Maximum dimensions (length and width) of the battery pack  6  in X-direction and Y-direction are substantially the same as those of the coupler unit  9  in the same directions. Thus, the maximum dimensions (length and width) of the battery pack  6  in X-direction and Y-direction are larger (longer and wider) than those of the grip  7  in the same directions. The profile of the grip  7  in X-direction and Y-direction is smaller than the profile of the battery pack  6  in the same directions, and the profile of the grip  7  is positioned inside the profile of the battery pack  6 , when the power tool  10  is projected on X-Y plane.  
      In this embodiment, the operation members  11  and the display device  12  are provided at positions near to the grip  7  from a line binding contacting portions of the power unit  8  and the battery pack  6  when the power unit  8  and the battery pack  6  are simultaneously contacted with the same plane in each state, as shown in  FIGS. 5, 6  and  7 .  
      As can be seen from FIGS.  1  to  3 , the operation members  11  and the display device  12  are provided on an upper face of a protruded portion  24  of the coupler unit  9 , which is protruded forward from the grip  7 . Since the profiles of the power unit  8  and the battery pack  6  are larger than the profile of the grip  7 , when the power tool is toppled down, a part of the power unit  8  and a part of the battery pack  6  are simultaneously contacted with the same plane such the land surface or the floor face. Thus, the grip  7  is departed from the land surface or the floor face.  
       FIG. 5  shows an example of toppling down of the power tool  10  forward. In the case shown in  FIG. 5 , a lower front edge of the output shaft  3  which is included in the power unit  8  and a lower front edge of the battery pack  6  are contacted with the land surface or the floor face.  FIG. 6  shows another example of toppling down of the power tool  10  backward. In the case shown in  FIG. 6 , the most protruded rear edge, for example, a lower rear edge of the power unit  8  and a lower rear edge of the battery pack  6  are contacted with the land surface or the floor face.  FIG. 7  shows still another example of toppling down of the power tool  10  sideway. In the case shown in  FIG. 7 , the most protruded side portion or line of the power unit  8  and the most protruded side portion or line of the battery pack  6  are contacted with the land surface or the floor face. In each case, the upper face of the protruded portion  24  of the coupler unit  9 , on which the operation members  11  and the display device  12  are provided, is departed from the land surface or the floor face. In other words, the operation members  11  and the display device  12  are provided at a positions near to the grip  7  from a line binding contacting portions of the power unit  8  and the battery pack  6  when the power unit  8  and the battery pack  6  are simultaneously contacted with the same plane in each state. By such a configuration, the operation members  11  and the display device  12  may not be damaged due to bumping against the land surface or the floor face even when the power tool  10  is fallen or toppled down on the land surface or the floor face.  
      A block configuration of the control unit of the power tool  10  is shown in  FIG. 4 . The control circuit  14  has a torque setting switch  11 A, an over-fastening switch  11 B, a main processor  13 , an impact sensor  17 , a torque calculator  18  and a rotation sensor  19 . The main processor  13 , the impact sensor  17  and the torque calculator  18  are constituted by, for example, a CPU (central processing unit), a ROM (read only memory) and a RAM (random access memory) and so on, which are commonly used. The rotation sensor  19  is, for example, an encoder provided on the driving shaft of the motor  1  for sensing the rotation speed and the rotation direction of the driving shaft of the motor  1 . As shown in  FIG. 3 , the torque setting switch  11 A and the over-fastening switch  11 B are mounted at positions facing the operation members  11  ( 11   a  and  11   b ) on a printed circuit board of the control circuit  14 .  
      When the user operates (for example, pushes) the operation members  11  ( 11   a  and  11   b ), the torque setting switch  11 A and the over-fastening switch  11 B are switched on. The main processor  13  counts numbers of switching on of the torque setting switch  11 A and the over-fastening switch  11 B. The main processor  13  selects a torque for fastening a fastening member such as a bolt, a nut or a screwnail, and so on, corresponding to the number of switching on of the torque setting switch  11 A. The main processor  13  switches on and off the over-fastening mode corresponding to the number of switching on of the over-fastening switch  11 B.  
      The switching circuit  4  has a main switch  20  operated by the trigger lever  16 , a switching element  21  and the normal/reverse rotation switch  22 A operated by the rotation switch lever  22 . In  FIG. 4 , a numerical reference  23  designates a rechargeable secondary battery contained in the battery pack  6 .  
      The example shown in  FIG. 4  is a control circuit of an impact power tool such as an impact driver, since it has the impact sensor  17 . When the over-fastening mode is switched on, the impact sensor  17  senses an impact of a hammer on an anvil fixed on the output shaft  3  of the power tool  10  corresponding to, for example, a variation of the rotation speed of the motor  1  sensed by the rotation sensor  19 . The torque calculator  18  calculates a torque for fastening the fastening member with using, for example, the rotation angle of the driving shaft of the motor  1  and the reduction ratio of the reducer/transmitter  2  in an impact of the hammer on the anvil, or the like. The main processor  13  controls the driving of the motor  1  (starting and stopping the rotation of the driving shaft of the motor) via the switching circuit  4  with using the calculated torque or the like corresponding to the driving mode set by the user with using the operation members  11 .  
      The switching on or off of the over-fastening mode, the selected operation mode, the remained capacity of the battery, or the like is displayed on the display device  12 . The display device  12  is, for example, an LCD (liquid crystal display) device, which is directly mounted on the printed circuit board of the control circuit  14 . It is possible to use an LED illumination device for illuminating the display on the display device  12  from the back face thereof.  
      A modification of the power tool  10  in accordance with this embodiment is shown in  FIG. 8 . In this modification, an LCD device with a touch panel serving as operation members  11  is used as the display device  12 . By such a modification, substantially the same effect as the above-mentioned embodiment can be obtained.  
      In the above-mentioned description, the display device  12  is provided on the protruded portion  24  of the coupler unit  9 . It, however, is not necessary to provide the display device. In the present invention, at least an operation member used for selecting an operation mode of the motor is provided at a position near to the grip from a line binding contacting portions of the power unit and the battery pack when the power unit and the battery pack are simultaneously contacted with the same plane in each state. Furthermore, the position of the operation member or the display device is not limited to the above-mentioned description and the illustration in the drawings. Still furthermore, it is possible to use a plurality of LEDs and indications provided in the vicinity of respective LEDs as the display device instead of the LCD.  
      According to the present invention, the operation member may not be damaged due to bumping against the land surface or the floor face even when the power tool is fallen or toppled down on the land surface or the floor face. Consequently, the transportable power tool can be used stable over the long term. Furthermore, it is no need to reinforce the mechanical strength of the operation member and so on, so as not to be damaged due to the bumping. Thus, it is possible to reduce the cost of the transportable power tool.  
      This application is based on Japanese patent application 2003-381458 filed Nov. 11, 2003 in Japan, the contents of which are hereby incorporated by references.  
      Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.