Abstract:
The present invention provides a power tool that can be used at a position away from the external power source. The power tool includes a housing, a motor, an end tool, a battery pack, and an inverter. The motor is supported by the housing and driven by alternate-current power. The end tool is supported by the housing and rotatably driven by the motor. The battery pack outputs direct-current voltage. The inverter is disposed outside the housing and is configured to convert the direct-current voltage outputted from the battery pack into alternate-current voltage and supplies the motor with alternate-current power.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2010-130970 filed Jun. 8, 2010. The entire content of this priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a power tool having a motor driven by an alternating-current power source. 
       BACKGROUND ART 
       [0003]    A power tool driven by an AC (alternating current) motor is conventionally known. Since the AC motor in such a power tool is supplied with electric power from an external power source, the power tool is used while being connected to the external power source via a power cord. This kind of power tool is described in Japanese Patent Application Publication No. 2009-219428. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PLT1: Japanese Patent Application Publication No. 2009-219428 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    According to the above-described configuration, however, there has been a problem that the power tool can only be used within the reach of the power cord connected to the external power source. 
         [0006]    In view of the above, it is an objective of the invention to provide a power tool that can be used even at locations away from an external power source. 
       Solution to Problem 
       [0007]    This and other objects of the present invention will be attained by a power tool including a housing, a motor, an end tool, a battery pack, and an inverter. The motor is supported by the housing and driven by alternate-current power. The end tool is supported by the housing and rotatably driven by the motor. The battery pack outputs direct-current voltage. The inverter is disposed outside the housing and is configured to convert the direct-current voltage outputted from the battery pack into alternate-current voltage and to supply the motor with alternate-current power. 
         [0008]    With this configuration, AC power can be supplied to the motor without connecting to an external AC power source via an extension cord. Hence, the power tool can be used even at locations away from an external AC power source. Additionally, the user is not bothered by an extension cord during work, thereby improving operability. 
         [0009]    It is preferable that the inverter is detachably provided to the housing. 
         [0010]    With this configuration, if the power tool is used near AC power source, AC voltage can be supplied directly from the external power source to the motor via the extension cord. Because the inverter is not used in this case, the entire power tool can be lightweight by detaching the inverter, thereby improving operability. 
         [0011]    It is preferable that the power tool includes a fixing unit configured to fix the inverter to the housing. 
         [0012]    With this configuration, it is possible to prevent the inverter from dropping off and from being electrically disconnected during use of the power tool. 
         [0013]    It is preferable that the fixing unit includes a latch section provided on one of the inverter and the housing and a latch receiving section provided on another one of the inverter and the housing. The inverter is attached to the housing upon connection between the latch section and the latch receiving section. 
         [0014]    With this configuration, because the latch mechanism by the latch section and the latch receiving section is adopted, the user can mount and dismount the inverter easily. 
         [0015]    It is preferable that the power tool includes a holding section configured to be held by a user and a pair of arm sections each having a base end pivotally connected to the housing and another end connected to the holding section so that the pair of arm sections is pivotally moved relative to the housing. Pivotal movement of the pair of arm section defines loci. A pair of imaginary planes includes the loci being defined. The inverter is disposed between the pair of imaginary planes. 
         [0016]    With this configuration, because the arm sections pivotally moves relative to the housing, the holding section can be oriented at a position that is easy for the user to work. Further, the inverter is disposed between the pair of imaginary planes containing the loci of the pair of arm sections, which prevents the inverter and the arm sections from contacting each other and being broken when the arm sections are pivotally moved. 
         [0017]    It is preferable that the inverter is disposed on the housing between the base ends of the pair of arm sections. 
         [0018]    With this configuration, when the arm sections are pivotally moved about the base ends relative to the housing, a cord extending from the terminal section to the holding section can be pivotally moved together with the arm sections, thereby preventing the cord from being broken or disconnected during the pivotal movement. 
         [0019]    It is preferable that the inverter is disposed at a position higher than the motor. 
         [0020]    With this configuration, the inverter is disposed at a position higher than the motor which prevents the inverter from being hit by another object during use. Further, when maintenance work is performed for the inverter, the motor does not get in the way. Further, if the inverter is detachable from the housing, mounting and dismounting of the inverter can be made easy. 
         [0021]    It is preferable that the battery pack is detachably mounted on the inverter. 
         [0022]    With this configuration, because the battery pack is detachable from the inverter, it is not necessary to carry the inverter together with the battery pack to a charging place when the charging-type battery pack is to be charged. In addition, the battery pack can be used for another power tool. 
         [0023]    It is preferable that the battery pack has a rail section, and that the inverter includes a mount section on which the battery pack is mounted, the mount section including a rail receiving section that receives the rail section. 
         [0024]    With this configuration, the battery pack can be mounted on the inverter easily. 
         [0025]    It is preferable that the power tool includes a cover covering the mount section. 
         [0026]    With this configuration, the battery pack and the mount section can be protected from dusts and the like. 
         [0027]    It is preferable that the mount section is configured to mount a plurality of battery packs thereon. 
         [0028]    With this configuration, the power can be supplied for a longer period by using the plurality of battery packs sequentially, compared with the case where the single battery pack is mounted. 
         [0029]    It is preferable that the inverter is portable as a result of detachment inverter from the housing. 
         [0030]    With this configuration, when the user picks up and uses the power tool, it is possible to make the weight of the housing lighter and improve operability. For example, if the power tool is a compact hedge cutter, the user can operate cutting operations by gripping the housing provided with a cutting blade and putting the inverter on the user&#39;s shoulder. Additionally, the inverter can be used by itself. 
         [0031]    It is preferable that the inverter includes a belt hook section for carrying the inverter separate from the housing. 
         [0032]    With this configuration, the belt or the like can be attached to the inverter when the inverter is used by itself, which improves operability. 
         [0033]    It is preferable that the inverter includes a power-source supply section that supplies the motor with a power source, and that the inverter has a first surface on which the fixing unit is disposed and a second surface on which the power-source supply section is provided, the first surface being different from the second surface. 
         [0034]    With this configuration, because the power-source supply section of the inverter is provided on a surface different from the fixing unit, a cord of the power tool does not hinder mounting and dismounting of the inverter. 
         [0035]    It is preferable that the power-source supply section is located between the pair of arm sections. 
         [0036]    With this configuration, it is possible to suppress an unexpected detachment of cords of the power tool from the power-source supply section. 
         [0037]    It is preferable that the inverter includes a belt hook section for carrying the inverter separate from the housing and a power-source supply section that supplies the motor with a power source. The inverter has a first surface on which the belt hook section is provided and a second surface on which the power-source supply section is provided, the first surface being different from the second surface. 
         [0038]    With this configuration, when the user carries and uses only the inverter, the belt and cords connected to the power-source supply section do not get in the way each other. Specifically, by arranging the power-source supply section at a position lower than the inverter when the separated inverter is carried by the user, the power cord connected to the power supply section does not get in the way. 
         [0039]    It is preferable that the power-source supply section is detachably provided with a first power cord that outputs the alternate-current power. Further, it is preferable that the power-source supply section is detachably provided with a second power cord connected to an external power source. 
         [0040]    With this configuration, the power cords can be connected and disconnected depending on usage conditions of the inverter, and the user is not bothered by the power cords, thereby improving operability. For example, if the second power cord is not necessary, the second power cord can be detached from the inverter. Hence, the user is not subject to restrictions on work area. 
       Advantageous Effects of Invention 
       [0041]    As described above, it is possible to provide a power tool that can be used at a position away from the external power source. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0042]    In the drawings; 
           [0043]      FIG. 1  is a side view of a power tool according to an embodiment of the present invention; 
           [0044]      FIG. 2  is a front view of the power tool according to the embodiment; 
           [0045]      FIG. 3  is a plan view of the power tool according to the embodiment in a state where a pair of arm sections of the power tool are in a rearward inclining state; 
           [0046]      FIG. 4  is a plan view of the power tool according to the embodiment in a state where the pair of arm sections is in a front folding state; 
           [0047]      FIG. 5  is a side view of the power tool according to the embodiment in a state where an inverter unit separates from a housing; 
           [0048]      FIG. 6  is a front view of a part of the power tool according to the embodiment in a state where the inverter unit separates from the housing; 
           [0049]      FIG. 7  is a plan view showing the power tool according to the embodiment in a state where the inverter separates from the housing in the rearward inclining state; 
           [0050]      FIG. 8(   a ) is a plan view showing the inverter unit of the power tool according to the embodiment in a state where a battery pack, a power cord, and a charging cord separate from the inverter unit; 
           [0051]      FIG. 8(   b ) is a side view showing the inverter unit of the power tool according to the embodiment in a state where the battery pack separates from the inverter unit; 
           [0052]      FIG. 8(   c ) is a rear view of the inverter unit of the power tool according to the embodiment; 
           [0053]      FIG. 9(   a ) is a plan view showing the inverter unit of the power tool according to the embodiment in a state where a belt is attached to the inverter unit and when the power cord and charging cord are connected to the inverter; 
           [0054]      FIG. 9(   b ) is a side view showing the inverter unit of the power tool according to the embodiment in a state where the belt is attached to the inverter unit; 
           [0055]      FIG. 10(   a ) is a plan view of an inverter provided on a power tool according to a first modification of the present invention; 
           [0056]      FIG. 10(   b ) is a rear view of the inverter of the power tool according to the first modification; 
           [0057]      FIG. 10(   c ) is a side view of the inverter provided on the power tool according to the first modification; 
           [0058]      FIG. 10(   d ) is a side view of the inverter provided on the power tool according to the first modification showing open/cover operations of a cover of the inverter; 
           [0059]      FIG. 11  is a side view of a power tool according to a second modification of the present invention; 
           [0060]      FIG. 12(   a ) is a plan view of a power tool according to a third modification; and 
           [0061]      FIG. 12(   b ) is a side view of the power tool according to the third modification. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0062]    A power tool according to an embodiment of the invention will be described with reference to  FIGS. 1 through 8(   c ). As shown in  FIG. 1 , a power tool  1  is specifically a lawn mower in this example. The power tool  1  includes a housing  2 , a grass-collecting bag  3  detachably provided on the housing  2 , a handle  4  extending from the housing  2 , an inverter unit  5 , front wheels  6 A and rear wheels  6 B rotatably supported by the housing  2 , and a motor  7 . 
         [0063]    Hereinafter, for the description purposes, the left side in the drawing sheet of  FIG. 1  is defined as the rear side, the right side in the drawing sheet is defined as the front side, the upper side in the drawing sheet is defined as the upper side, and the lower side in the drawing sheet is defined as the lower side. Further, the top surface side of the drawing sheet of  FIG. 1  is defined as the right side, and the bottom surface side of the drawing sheet is defined as the left side. Also, the direction from the rear side to the front side is defined as the traveling direction. 
         [0064]    The housing  2  includes a lower section  21  that confronts the ground surface when the power tool  1  is used, an upper section  22  located vertically upward from the lower section  21  when the power tool  1  is used, a rear wall section  23  located at the rear side, a front wall section  24  located at the front side, a left wall section  25  located at the left side ( FIG. 2  etc.), and a right wall section  26  located at the right side. The lower section  21  and the upper section  22  are connected by the rear wall section  23  and the front wall section  24 , the left wall section  25 , and the right wall section  26 . The upper section  22  has a top flat surface (uppermost surface)  22 A and a curved surface section  22 B. The top flat surface  22 A forms the topmost part of the housing  2 , and is formed by a flat surface. The curved surface section  22 B is located forward from the top flat surface  22 A, and is formed by a surface curving gradually from the horizontal direction to the vertical direction. As shown in  FIG. 2 , an adjustment knob  22 C is provided on the curved surface section  22 B. The adjustment knob  22 C is for adjusting height of the front end of the lower section  21  from the ground surface by pivotally moving the housing  2  about a rear-wheel rotational axis (not shown) to be described later, thereby adjusting cutting depth of a rotary blade (reel)  7 A into lawn. Here, the rotary blade  7 A serves as an end tool which is an end section to which a driving force is transmitted from the motor  7  as will be described later. 
         [0065]    The housing  2  rotatably supports both of the large-diameter front wheels  6 A that are provided as a left and right pair and the small-diameter rear wheels  6 B that are also provided as a left and right pair. The housing  2  is capable of travelling on the ground surface (lawn) by the front wheels  6 A and the rear wheels  6 B. The pair of front wheels  6 A is rotatable about a front-wheel rotational axis (not shown), and the pair of rear wheels  6 B is rotatable about the rear-wheel rotational axis (not shown). 
         [0066]    A discharge opening  23   a  is formed on the rear wall section  23  of the housing  2 . The grass-collecting bag  3  is detachably mounted on the rear wall section  23  of the housing  2  so as to close the discharge opening  23   a . A handle  3 A is attached to the front upper end of the grass-collecting bag  3 . 
         [0067]    The housing  2  accommodates therein the motor  7  serving as the driving source and the rotary blade  7 A serving as the end tool rotatably driven by the motor  7 . The motor  7  is supported by the housing  2  so that an output shaft (not shown) extends in the left-right direction. The output shaft (not shown) of the motor  7  is located further rearward than the front-wheel rotational axis (not shown). The motor  7  is a so-called AC motor that is driven by AC voltage. A pulley (not shown) is provided coaxially on the output shaft (not shown) so as to be rotatable together with the output shaft. 
         [0068]    The rotary blade  7 A has a substantially cylindrical shape, and is rotatably supported by the housing  2  so that its axial center extends in the left-right direction. The axial center of the rotary blade  7 A is located at a position further rearward than the output shaft (not shown) of the motor  7  and further frontward than the rotational shaft (not shown) of the rear wheels  6 B. A pulley (not shown) is coaxially provided on the rotary blade  7 A so as to be rotatable together with the rotary blade  7 A. A belt (not shown) is looped around the pulley (not shown) of the motor  7  and the pulley (not shown) of the rotary blade  7 A, so that rotation of the output shaft (not shown) of the motor  7  is transmitted to the rotary blade  7 A via the belt (not shown) for rotating the rotary blade  7 A. 
         [0069]    As shown in  FIG. 7 , a terminal section  22 D is provided on the top flat surface  22 A of the housing  2 . The terminal section  22 D is connected to another end  44 B of a second cord  44  to be described later. The terminal section  22 D is located between one end sections  42 A that are lower end sections of a pair of arm sections  42  to be described later. Further, a pair of engaging members  22 E is provided on the top flat surface  22 A so as to confront each other in the left-right direction. The engaging members  22 E serve as latch receiving sections for engaging engaged sections  53  serving as latch sections provided on the inverter unit  5  as will be described later. Each of the engaging members  22 E is a plate member extending in the front-rear direction. A through hole  22   c  is formed to penetrate each of the engaging members  22 E in the plate thickness direction, so that a hook (a pressing piece  54  described later) of the engaged section  53  can catch the through hole  22   c.    
         [0070]    Further, the handle  4  is provided on the upper rear part of the housing  2 . The handle  4  includes a holding section  41  held by a user of the power tool  1  and the pair of arm sections  42  extending in parallel with each other. The one end (base end)  42 A of each of the arm sections  42  is coupled and connected to a part near the rear end of the upper section  22  of the housing  2 . The arm sections  42  are pivotally movable about the coupled point between a rearward inclining state shown in  FIG. 1  and a frontward folding state shown in  FIG. 4 , while maintaining parallel relationship with each other. Trajectories (loci) defined by pivotal movements of the pair of arm sections  42  are included in a pair of imaginary planes. Respective another ends  42 B of the pair of arm sections  42  are coupled to the both ends of the holding section  41  in the lengthwise direction. 
         [0071]    As shown in  FIG. 2 , the holding section  41  is provided with a main switch  41 A and a safety lock switch  41 B. Also, a first cord  43  and the second cord  44  are provided as a part of wiring connected to the main switch  41 A and the safety lock switch  41 B. One end  43 A of the first cord  43  is connected to the holding section  41  so that the first cord  43  is electrically connected to the main switch  41 A and the safety lock switch  41 B. Another end  43 B of the first cord  43  is selectively connected either one of: a power cord  81  ( FIG. 1  etc.) serving as a first power cord extending from the inverter unit  5 ; and an extension cord (not shown) extending from an outlet of a commercial power source (not shown).  FIG. 2  shows a state in which the another end of the first cord  43  is connected to the power cord  81 . One end  44 A of the second cord  44  is connected to the terminal section  22 D provided at the housing  2 . The another end  44 B of the second cord  44  is connected to the holding section  41 , and is electrically connected to the motor  7  and the first cord  43  via the main switch  41 A and the safety lock switch  41 B. If the main switch  41 A becomes a pushed state by a user, the motor  7  is electrically connected to either the inverter unit  5  connected to the first cord  43  or the commercial power source (not shown) so that AC power is supplied. In order to protect the motor  7 , the safety lock switch  41 B automatically stops the motor  7  if foreign matters or the like twine around the rotary blade  7 A and the rotary blade  7 A stops. When starting work, the user operates (turns on) the safety lock switch  41 B, and subsequently operates the main switch  41 A to rotate the motor  7 . If foreign matters twine around the rotary blade  7 A, load will increase. At this time, the safety lock switch  41 B is turned off (the power supply route to the motor  7  is shut off), thereby stopping the motor  7 . After the safety lock switch  41 B is operated, the motor  7  can be driven again by turning off the main switch  41 A temporarily, turning on the safety lock switch  41 B again, and operating the main switch  41 A. In a state where the safety lock switch  41 B is off, the main switch  41 A cannot be operated (turned on) mechanically. 
         [0072]    The inverter unit  5  is provided outside the housing  2  and on the top flat surface  22 A so as to be detachable from the housing  2 . In a state where the inverter unit  5  is fixed to the upper section  22 , the inverter unit  5  is located at a position on the top flat surface  22 A of the upper section  22  and directly above the rotary blade  7 A during use of the power tool  1  shown in  FIG. 1 , that is, in a normal posture of the power tool  1 . This position is further upward than the motor  7 , further forward of the rear wall section  23 , and further forward than the rear-wheel rotational axis (not shown). The projected position of the inverter unit  5  in the vertical direction is in a range from the rear-wheel rotational axis (not shown) to the front-wheel rotational axis (not shown). The position at which the inverter unit  5  is fixed to the top flat surface  22 A is between the pair of imaginary planes including the trajectories formed when the pair of arm sections  42  is pivotally moved. 
         [0073]    The inverter unit  5  includes a box-shaped casing  51 , and also includes a well-known inverter (not shown) accommodated within the casing  51  and a battery pack  52 . The inverter converts DC voltage outputted from the battery pack  52  to AC voltage, and supplied the motor  7  with AC power. A rail section  52 A ( FIG. 8(   b )) extending in the vertical direction is provided at the front-side of the battery pack  52  in a state where the battery pack  52  is mounted on the inverter unit  5  shown in  FIG. 1 . 
         [0074]    As shown in  FIGS. 8(   a ) through  8 ( c ) etc., the casing  51  is provided, at its rear part, with a mount section  51 A for inserting and detaching the battery pack  52 , and an input plug  51 B and an output plug  51 C for supplying the motor  7  with power serving as parts of power-source supply section. The input plug  51 B and the output plug  51 C are arranged to be located between the arm sections  42  during use of the power tool  1 , that is, at normal times. The mount section  51 A includes a rail receiving section  51 D for guiding the rail section  52 A of the battery pack  52 . The mount section  51 A is provided with a terminal connecting to the terminal of the battery pack  52 . 
         [0075]    In order to mount the battery pack  52  on the casing  51 , as shown in  FIGS. 8(   a ) through  8 ( c ), the user slidably moves the battery pack  52  downward in the mount section  51 A so that the rail section  52 A moves along the rail receiving section  51 D, and pushes the battery pack  52  further downward in the mount section  51 A until the battery pack  52  is fixed in the mount section  51 A by a latch mechanism (not shown). By this operation, the inverter (not shown) and the battery pack  52  are electrically connected to each other. In this state, by connecting one end  83 A of a charging cord  83  serving as a second power cord to the input plug  51 B, and by connecting another end  83 B of the charging cord  83  to the external power source (not shown), the battery pack  52  is supplied with power and charging is performed. Further, when one end  81 A of the power cord  81  is connected to the output plug  51 C, and also another end  81 B of the power cord  81  is connected to the first cord  43 , the motor  7  can be supplied with AC power obtained by converting DC power from the battery pack  52 . 
         [0076]    The engaged sections  53  are provided on both of the left and right side surfaces of the casing  51  at center portions in the front-rear direction. As shown in  FIG. 6 , each of the engaged sections  53  includes the pressing piece  54 , a side wall  55 , a lever pivot section  56  extending from the casing  51 , a lever  57  provided to be pivotally movable about the lever pivot section  56 , and a restricting section  58  that restricts pivotal movement of the lever  57 . 
         [0077]    The pressing piece  54  is a substantially squared-U shaped member, and has an upper end section  54 B and a lower end section  54 C both protruding from a base body  54 A. The distance between the base body  54 A and the side wall  55  is larger than the plate thickness of the engaging member  22 E, whereas the distance between the lower end section  54 C and the side wall  55  is smaller than the plate thickness of the engaging member  22 E. In a state where the inverter unit  5  is detached from the housing  2  as shown in  FIG. 6 , the pressing piece  54  is pressed outwardly in the left-right direction by a spring (not shown), and the pressing piece  54  is supported by abutment of the base body  54 A against a protruding section  55 A protruding toward the base body  54 A from the side wall  55 . The lever  57  is pressed outwardly in the left-right direction by a spring (not shown) or the restricting section  58 , and is supported by the casing  51  at a position away from the pressing piece  54  and the restricting section  58 . 
         [0078]    In order to mount the inverter unit  5  on the housing  2 , the user presses the inverter unit  5  against the housing  2  in a state where the engaging member  22 E and the engaged sections  53  confront each other, and then the engaging member  22 E causes the lower end section  54 C to move toward the center in the left-right direction against the pressing force of the spring (not shown), and enters a space between the base body  54 A and the side wall  55 . Then, the lower end section  54 C fits in the through hole  22   c  ( FIG. 5 ) of the engaging member  22 E, and the inverter unit  5  is fixed onto the top flat surface  22 A of the upper section  22 . If the user (operator) pushes the lever  57  inwardly in the left-right direction against the pressing force of the spring (not shown) in a state where the inverter unit  5  is mounted on the housing  2 , the pressing piece  54  moves inwardly in the left-right direction in conjunction with pivotal movement of the lever  57  or the restricting section  58 , and the lower end section  54 C comes out of the through hole  22   c  so as to release engagement with the engaging member  22 E. 
         [0079]    As shown in  FIGS. 9(   a ) and  9 ( b ), belt hook sections  51 E are provided on front parts of the left and right side surfaces of the casing  51 . The belt hook sections  51 E are for using the inverter unit  5  in a state separated from the housing  2 . By connecting hooks etc. of a belt  84  to the belt hook sections  51 E, the user can carry the inverter unit  5  with the belt  84  on his shoulder or waist. 
         [0080]    According to above-described the power tool  1 , AC power can be supplied from the battery pack  52  to the motor  7  by connecting the first cord  43  to the power cord  81 , without connecting to an external AC power source via an extension cord (not shown). Hence, the power tool  1  can be used even at locations away from an external AC power source. Additionally, even in a situation where work is done near the external power source, if the first cord  43  is connected to the power cord  81 , the user is not bothered by the extension cord (not shown) during work, thereby improving operability. 
         [0081]    If the power tool  1  is used near AC power source, the first cord  43  may be connected to the extension cord (not shown) so that AC voltage can be supplied directly from the external power source to the motor  7 . Because the inverter unit  5  is not used in this case, the entire power tool  1  can be lightweight by detaching the inverter unit  5 , thereby improving operability. In this case, the inverter unit  5  and the battery pack  52  can be used with another power tool. 
         [0082]    The inverter unit  5  is fixed to the housing  2  by the engaging member  22 E and the engaged sections  53 , thereby preventing the inverter unit  5  from dropping off and from being electrically disconnected during use of the power tool  1 . Because the latch mechanism by the engaging member  22 E and the engaged sections  53  is adopted, the user can mount and dismount the inverter unit  5  easily. 
         [0083]    Because the arm sections  42  pivotally moves relative to the housing  2 , the holding section  41  can be oriented at a position that is easy for the user to work. Further, the inverter unit  5  is arranged between the pair of imaginary planes including the trajectories formed when the pair of arm sections  42  is pivotally moved, which prevents the inverter unit  5  and the arm sections  42  from contacting each other and being broken when the arm sections  42  are pivotally moved. 
         [0084]    The inverter unit  5  is arranged between the one end sections  42 A of the pair of arm sections  42  on the top flat surface  22 A. Thus, when the arm sections  42  are pivotally moved about the one end sections  42 A relative to the housing  2 , the second cord  44  extending from the terminal section  22 D to the holding section  41  can be pivotally moved together with the arm sections  42 , thereby preventing the second cord  44  from being broken or disconnected during the pivotal movement. 
         [0085]    Because the battery pack  52  is detachable from the inverter unit  5 , it is not necessary to carry the inverter unit  5  together with the battery pack  52  to a charging place when the charging-type battery pack  52  is to be charged. In addition, the battery pack  52  can be used for another power tool. 
         [0086]    Because the mount section  51 A has the rail receiving section  51 D that receives the rail section  52 A of the battery pack  52 , the battery pack  52  can be mounted on the inverter unit  5  easily. 
         [0087]    The user can carry the inverter unit  5  separate from the housing  2 . Hence, the inverter unit  5  can be carried in a detached state from the housing  2 , thereby making the weight of the housing  2  and its attachment lighter and improving operability. For example, mowing work can be performed by putting the inverter unit  5  on the user&#39;s shoulder. Additionally, the inverter unit  5  can be used by itself. 
         [0088]    The inverter unit  5  is provided with the belt hook sections  51 E for using the inverter unit  5  separate from the housing  2 . Thus, the belt  84  or the like can be attached to the inverter unit  5  when the inverter unit  5  is used by itself, which improves operability. 
         [0089]    Because the output plug  51 C of the inverter unit  5  is provided on a surface different from the engaged sections  53 , the power cord  81  of the power tool  1  does not hinder mounting and dismounting of the inverter unit  5 . 
         [0090]    The output plug  51 C is positioned between the arm sections  42  when the arm sections  42  are at the normal state, which suppresses an unexpected detachment of the power cord  81  from the output plug  51 C. 
         [0091]    The output plug  51 C and the belt hook sections  51 E are provided on different surfaces. Hence, when the user carries and uses only the inverter unit  5 , the belt  84  and the power cord  81  do not get in the way each other. Specifically, the output plug  51 C is located at a lower position of the inverter unit  5 . Hence, when the belt  84  is attached to the belt hook sections  51 E for carrying the inverter unit  5 , the power cord  81  connected to the output plug  51 C does not get in the way. Further, the power cord  81  for outputting AC power is detachably connected to the output plug  51 C, and the charging cord  83  connected to the external power source is detachably connected to the input plug  51 B. Thus, the power cord  81  and the charging cord  83  can be connected and disconnected depending on usage conditions of the inverter unit  5 , and the user is not bothered by the power cord  81  and the charging cord  83 , thereby improving operability. For example, if the charging cord  83  is not necessary, the charging cord  83  can be detached from the inverter unit  5 . Hence, the user is not subject to restrictions on work area. 
         [0092]    The inverter unit  5  is disposed at an upper position higher than the motor  7 , which prevents the inverter unit  5  from being hit by another object during use. Especially, in a case of a lawnmower, the lower section  21  confronts the ground surface during use of the lawnmower. Thus, if the inverter unit  5  is provided on the lower section  21 , there is possibility that the inverter unit  5  hits the ground surface, stones, and the like. This can be avoided according to the above-described embodiment. Further, when maintenance work is performed for the inverter unit  5 , the motor  7  does not get in the way. Further, if the inverter unit  5  is detachable from the housing  2 , mounting and dismounting of the inverter unit  5  can be made easy. In addition, if the motor  7  and the rotary blade  7 A have relatively large weight, weight balance can be improved with a relatively large weight of the inverter unit  5 . 
         [0093]    Because the inverter unit  5  is located directly above the rotary blade  7 A, the rotary blade  7 A can be urged downward by the inverter unit  5  having a relatively large weight. Especially, in a case of a lawnmower, this can prevent the rotary blade  7 A from lifting from the ground surface, and prevent the rotary blade  7 A from becoming unstable during lawn mowing. 
         [0094]    The inverter unit  5  is located at a position further forward than the rear wall section  23  and further forward than the rear-wheel rotational axis (not shown). The projected position of the inverter unit  5  in the vertical direction is in a range from the rear-wheel rotational axis (not shown) to the front-wheel rotational axis (not shown). 
         [0095]    This feature can suppress falling over of the power tool  1  rearward due to a relatively large weight of the inverter unit  5 . Especially, in a case of a lawnmower, the power tool  1  is sometimes leaned rearward in order to adjust cutting depth into lawn. In such a situation, the above-described feature can effectively suppress falling over of the power tool  1  rearward. 
         [0096]    The inverter unit  5  is fixed on the top flat surface  22 A of the upper section  22 . Thus, the inverter unit  5  can be arranged at a position away from a part where the adjustment knob  22 C for adjusting cutting depth is provided, which enables effective utilization of dead space. 
         [0097]    The part of the upper section  22  at which the engaging member  22 E is provided is further forward than the pivotal axis of the one end section  42 A of the arm section  42 . Hence, when engagement/disengagement of the engaging member  22 E to/from the engaged section  53  during use of the power tool  1 , the arm sections  42  can be prevented from hindering engagement/disengagement work. 
         [0098]    While the invention has been described in detail with reference to the above aspects thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the claims. For example, in a first modification of the embodiment as shown in  FIGS. 10(   a ) through  10 ( d ), the inverter unit  5  may include a cover  100  that covers the battery pack  52  and the mount section  51 A. The cover  100  is provided at an upper part of the casing  51 . According to the first modification, the battery pack  52  and the mount section  51 A can be protected from dusts and the like. In  FIGS. 10(   a ) through  10 ( d ), the cover  100  is configured to pivotally move about pivotal supports  100 A. Further, for example, a latch mechanism for fixing the cover  100  to the casing  51  of the inverter unit  5  may be provided, so that the cover  100  does not open due to vibrations or the like during use of the power tool and the battery pack  52  can be maintained in a covered state by the cover  100 . 
         [0099]    In the above-describe embodiment and the first modification, a single battery pack  52  is mounted on the mount section  51 A. However, the mount section may be so configured that a plurality of battery packs  52  can be mounted thereon. According to this configuration, power can be supplied for a longer period by using the plurality of battery packs  52  sequentially, compared with the case where the single battery pack  52  is mounted. 
         [0100]    In the above-describe embodiment and the first modification, the latch mechanism including the engaging member  22 E and the engaged section  53  is adopted as fixing means for fixing the inverter unit  5  to the housing  2 . However, another configuration may be adopted. For example, a latch section may be provided on the housing  2  and a latch receiving section may be provided on the inverter unit  5 . Further, the inverter unit  5  and the housing  2  may be fixed by a band, or a locking switch for restricting movement of the pressing piece  54  may be provided on the holding section  41 . Further, the inverter unit  5  may be fixed to the housing  2  by a sliding mechanism, or may be fixed to the housing  2  by an insertion mechanism. 
         [0101]    In the above-describe embodiment and the first modification, the battery pack  52  is guided to the mount section  51 A by sliding along the rail. However, the battery pack  52  may be guided to the mount section  51 A by an insertion mechanism. Further, connection between the battery pack  52  and the inverter unit  5  (the mount section  51 A) may be done only by sliding, without using the latch mechanism. 
         [0102]    The position at which the inverter unit  5  is arranged is not limited to the position of the inverter unit  5  in the above-describe embodiment and the first modification. For example, the inverter unit  5  is arranged directly above the rotary blade  7 A in the above-describe embodiment, but the position of the inverter unit  5  is not limited to directly above the rotary blade  7 A. For example, the projected position of the inverter unit  5  in the vertical direction may be in a range from the motor  7  to the rotary blade  7 A. 
         [0103]    The lever  57  and the pressing piece  54  of the engaged section  53  shown in  FIG. 6  may be formed as an integral part. In this case, the engaged section  53  is urged outwardly in the left-right direction by a spring (not shown). It is so configured that the lever  57  pivotally moves about the lever pivot section  56  when the engaged section  53  (the lever  57 ) is pressed against the urging force of the spring. Further, a tapered section may be provided at the lower end section  54 C of the pressing piece  54 . In this case, the tapered section can be provided so that, when the inverter unit  5  is mounted on the housing  2 , the tapered section abuts on the engaging member  22 E without operating the engaged section  53  and the lower end section  54 C moves inwardly in the left-right direction. 
         [0104]    In the above-describe embodiment and the first modification, the through hole  22   c  is formed in the engaging member  22 E. However, another shape may be used as long as the above-described pressing piece  54  can engage. For example, a concave and convex shape may be used instead of the through hole. 
         [0105]    The pair of arm sections  42  may be so configured that its lengthwise size can be adjusted. For example, as shown in  FIG. 11 , an arm section  142  of a power tool  101  according to a second modification may include an adjustment member  142 C. The length of the arm section  142  can be fixed by adjusting the pair of arm section  142  to a desired length and subsequently rotating the adjustment member  142 C. Here, it may be also configured such that the length of the arm section  142  can be adjusted finely by rotating the adjustment member  142 C. 
         [0106]    The invention can be applied to power tools such as hedge trimmers (cutters), lawn trimmers (cutters), brushcutters, etc. For example, as shown in  FIGS. 12(   a ) and  12 ( b ), the invention can be applied to a hand-held hedge trimmer (cutter)  201  serving as a power tool according to a third modification. The hedge trimmer  201  includes a housing  202 , handles  203  and  204  each extending from the housing  202  and provided for being gripped by a user, an inverter unit  205  provided detachably on a lower side of the handle  204 , a motor  207  driven by power supplied from the inverter unit  205 , and a cutting blade  208  for performing trimming (cutting) work in conjunction with rotation of the output shaft of the motor  207 . The inverter unit  205  has a rail section (not shown), and is mounted while being slid along a rail receiving section (not shown) provided on the handle  204 . 
       INDUSTRIAL APPLICABILITY 
       [0107]    A power tool of the invention is especially useful in a field of mowers and the like that are used at outdoor places away from outlets. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 ,  101 , power tool 
           2 ,  202  housing 
           3  grass-collecting bag 
           3 A,  4 ,  104 ,  203 ,  204  handle 
           5 ,  205  inverter unit 
           6 A front wheel 
           6 B rear wheel 
           7 ,  207  motor 
           7 A rotary blade 
           21  lower section 
           22  upper section 
           22 A top flat surface 
           22 C adjustment knob 
           22 D terminal section 
           22 E engaging members 
           23  rear wall section 
           23   a  discharge opening 
           24  front wall section 
           25  left wall section 
           26  right wall section 
           41  holding section 
           42 ,  142  arm sections 
           42 A one end of arm section 
           42 B another end of arm section 
           43  first cord 
           43 A one end of first cord 
           43 B another end of first cord 
           44  second cord 
           44 A one end of second cord 
           44 B another end of second cord 
           51  casing 
           51 A mount section 
           51 B input plug 
           51 C output plug 
           51 D rail receiving section 
           51 E belt hook sections 
           52  battery pack 
           52 A rail section 
           53  engaged sections 
           54  pressing piece 
           54 A base body 
           54 B upper end section 
           54 C lower end section 
           55  side wall 
           55 A protruding section 
           56  lever pivot section 
           57  lever 
           58  restricting section 
           81  power cord 
           83  charging cord 
           100  cover 
           201  hand-held hedge trimmer 
           208  cutting blade