Patent Publication Number: US-2006011367-A1

Title: Electric hand tool

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an electric hand tool and more particularly, to such an electric hand tool, which is practical for use in a narrow place for enabling the user to conveniently change the direction of rotation of the electric hand tool.  
      2. Description of the Related Art  
      A commercially available electric hand tool essentially comprises a housing, a driving mechanism installed in the housing, a chuck coupled to the driving mechanism and partially extended out of the housing to hold a bit, a battery pack for providing electricity to the driving mechanism, and a switch unit. The switch unit comprises an ON/OFF switching button for operation by the user to determine whether the electricity provided by the battery pack is supplied to the driving mechanism, and a direction switching member for operation by the user to determine the direction of electric current provided by the battery pack and to further determine the rotation direction of the driving mechanism that drivers the chuck.  
      The conventional direction switching member has a switching rod having an end coupled to a switch that controls the direction of the supplied electric current, and the other end connected to an operation member. The operation member has two ends extended respectively out of two opposite lateral sidewalls of the housing of the electric hand tool for operation by the user such that the switch is controlled to determine the direction of electric current provided by the battery pack by the operation member through the switching rod.  
      This design of electric hand tool is functional; however, it is not convenient for use in a narrow place. When wishing to reverse the direction of rotation of the electric hand tool during working of the electric hand tool in a narrow place that has no room for the user&#39;s hand to operate the operation member, the user shall have to stop the operation, and remove the electric hand tool out of the narrow place, and then to adjust the operation member to change the direction of electric current provided by the battery pack, and then to insert the electric hand tool into the narrow place again. This inconvenient operation situation lowers the working efficiency. In addition, the conventional electric hand tool has no indication to tell the direction of rotation thereof. The user must press the ON/OFF switching button to power the electric hand tool so as to learn the direction of rotation thereof whenever the electric hand tool is not operated. This is inconvenient.  
     SUMMARY OF THE INVENTION  
      It is the primary objective of the present invention to provide an electric hand tool, which is practical for use in a narrow place for enabling the user to conveniently change the direction of rotation of the electric hand tool.  
      To achieve this objective of the present invention, the electric hand tool comprises a housing, a driving mechanism installed in the housing, a chuck, a battery pack for providing electricity to the driving mechanism, and a switch unit installed in the housing. The housing has a front portion provided with an opening, and a rear portion. The chuck is coupled to the driving mechanism and extends out of the opening of the housing to hold a bit for turning by the driving mechanism. The switch unit has a switch, an operating member connected to the switch for switching on/off the switch to control supply of electricity from the battery pack to the driving mechanism, and a switching lever for driving the switch to change the direction of electric current provided by the battery pack. The switching lever has a switching portion at one end thereof. The rear portion of the housing has a through hole through which the switching portion of the switching lever extends for operation by a user. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of an electric hand tool according to a first preferred embodiment of the present invention.  
       FIG. 2  is a partial sectional view of the electric hand tool according to the first preferred embodiment of the present invention.  
       FIG. 3  is a rear view of the electric hand tool according to the first preferred embodiment of the present invention.  
       FIG. 4  is a partial sectional view of an electric hand tool according to a second preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 1-3 , an electric hand tool  10  in accordance with the first preferred embodiment of the present invention is shown comprised of a housing  20 , a driving mechanism  30 , a chuck  40 , a battery pack  50 , and a switch unit  60 .  
      The housing  20  comprises a first part  21  and a second part  22 . The first part  21  has a first end  23  and a second end  24 . The first end  23  has a front portion  25  and an opening  26  in the front portion  25 . The second part  22  extends from the second end  24  of the first part  21  at an angle. The second part  22  has a rear portion  27  opposite to the front portion  25  of the first end  23  of the first part  21 , and a through hole  28  in the rear portion  27 . The second part  22  further has an opening  29 .  
      The driving mechanism  30  is installed in the first part  21  of the housing  20 , comprising a motor  31 .  
      The chuck  40  is installed in the first part  21  of the housing  20  and coupled to the driving mechanism  30 , having a chuck shell  41  extending out of the opening  26  of the housing  20  to hold a bit (not shown) for working.  
      The battery pack  50  is detachably fastened to the rear end of the second part  22  of the housing  20  to provide electricity to the motor  31  of the driving mechanism  30 .  
      The switch unit  60  is installed in the second part  22  of the housing  20 , comprising an operating rod  61 , a switching lever  62 , and a switch  63 . The operating rod  61  has one end connected to the switch  63  and the other end connected to a button  64  that extends out of the housing  20  through the opening  29 . The user can press the button  64  to control the switch  63 . The switching lever  62  is comprised of a first link  65  and a second link  66 . The first link  65  is pivoted to the top of the switch  63 , and forwardly backwardly turnable relative to switch  63  to control the switch  63  to change the direction of electric current provided by the battery pack  50 . The second link  66  has one end pivoted to the free end  67  of the first link  65  and the other end extended out of the through hole  28  in the rear portion  27  of the housing  20  and forming a switching portion  68  for pushing by the user. The user can push the switching portion  68  to force the second link  66  to pivot the first link  65 , thereby causing the switch  63  to change the direction of electric current provided by the battery pack  50 . In addition, the switching portion  68  has an indication zone  69  on which letters of “R” (not shown) and “L” are marked for indicating the right-handed and left-handed rotation direction. As shown in  FIG. 3 , when the switching portion is pushed to left end of the through hole  28 , the indication letter of “L” can be seen by the user such that the user can learns that the hand tool is under a left-handed rotation status.  
      When using the electric hand tool  10 , the user can hold the second part  22  of the housing  20  with the hand and press the button  64  with the forefinger to drive the operating rod  61  and to further switch on the switch  65 , thereby causing the battery pack  50  to provide electricity to the motor  31 . Further, the user can move the switching portion  68  of the switching lever  62  with the thumb, causing the second link  66  to bias the first link  65  and to further drive the switch  63  to change the direction of electric current provided by the battery pack  50 , and therefore the direction of rotation of the bit of the electric hand tool  10  is revered.  
      As indicated above, the switching portion  68  for controlling the direction of rotation of the bit of the electric hand tool  10  is set in the rear portion  27  of the housing  20 . Therefore, the user can conveniently drive the switching portion  68  with the thumb to change the direction of electric current when using the electric hand tool  10  in a narrow work place. Further, the indication zone  69  of the switching portion  68  provides directly the direction of rotation of the hand tool to the user, thereby enhancing the working convenience.  
      The switching lever is not limited to the aforesaid design.  FIG. 4  shows a second preferred embodiment of the present invention. According to this embodiment, the electric hand tool  70  is comprised of a housing  71 , a driving mechanism  72 , a battery pack  73 , and a switch unit  74 . The housing  71 , the driving mechanism  72 , and the battery pack  73  are similar to the corresponding members of the aforesaid first embodiment. The switch unit  74  comprises a switching lever  75  and a switch  76 . The switching lever  75  has one end pivoted to the switch  76 , and the other end extended out of a through hole  78  of the housing  71  and forming a switching portion  77 . The user can directly drive the switching portion  77  to switch the switch  76 , causing the switch  76  to change the direction of electric current provided by the battery pack  50 .