Patent Publication Number: US-7588094-B2

Title: Power hand tool

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to power hand tools, and more particularly, to a power hand tool capable of adjusting torsion and impacting a workpiece. 
   2. Description of the Related Art 
   A conventional power impact wrench is primarily composed of an electric motor, a transmission gear set, and an impact device. The transmission gear set is to decelerate the rotary motion of an output shaft of the electric motor down to a predetermined rotary speed and then to output it via the output shaft. The impact device is to apply a rapid discontinuous impact having the same rotary direction as the output shaft does to the output shaft so as to enable the output shaft to overcome the resistance and to keep working. 
   A conventional power screwdriver is primarily composed of an electric motor, a transmission gear set, and a torsion regulator. The transmission gear set is to decelerate the rotary motion of the output shaft of the electric motor down to a predetermined rotary speed and then to output it. The torsion regulator is to adjust the maximum torsion outputted by power hand tool to avoid damage to a workpiece. 
   The above-mentioned impact device and torsion regulator are applicable to users&#39; needs to the contrary separately because these two devices generally do not exist in the same power hand tool. However, under few special circumstances, the two devices are needed at the same time. For example, when the user operates a power wrench to dismantle a tire from a car, to overcome the obstacle resulted from rusty bolts or other causes, the power wrench needs the impact device; when the user installs the tire onto the car, to prevent overgreat torsion output of the power hand tool from damage to the bolts provided for fastening the tire onto the car, the power hand tool needs the torsion regulator. However, if the two devices are combined into the same power hand tool, the number of elements and the size of the power hand tool will be inevitably increased to be defective. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide a power hand tool, which includes a torsion regulator and an impact device at the same time, wherein the torsion regulator and the impact device share some elements or components to decrease required elements and size of the power hand tool. 
   The foregoing objective of the present invention is attained by the power hand tool composed of a housing, an electric motor, a transmission gear set, a torsion control device, an impact device, and a locating device. The electric motor is mounted in the housing for provide a rotary motion. The transmission gear set is mounted in the housing and connected in transmission with the electric motor, for decelerating the rotary motion output of the electric motor down to a predetermined speed and then outputting it via an output shaft. The torsion control device includes a base, a rotary disk, and a first rotary knob. The base is connected with the transmission gear set and located in the housing. The rotary disk is mounted to the base, rotatable on a rotary center of the output shaft and axially movable along the output shaft. The axial movement of the rotary disk can adjust the maximum torsion output of the output shaft. The first rotary knob is mounted to the housing, rotatable on the rotary center of the output shaft, and connected with the rotary disk for driving rotation of the rotary disk while being turned. The first rotary knob has an internal periphery and a plurality of first dents formed on the internal periphery thereof. The impact device includes a switch and a second rotary knob. The switch is mounted in the housing, of reciprocating rotation on the rotary center of the output shaft. One reciprocating rotation of the switch can switch on or off an impact motion against the output shaft. The second rotary knob is mounted to the housing, rotatable on the rotary center of the output shaft. The second rotary knob is connected with the switch for driving rotation of the switch while being rotated. The second rotary knob further has an internal periphery and a plurality of second dents formed on the internal periphery thereof. The locating device includes a holder and a locating member. The holder is fixed to the base of the torsion control device. The locating member has two separate base portions and two resilient portions parallel connected between the two base portions respectively. Each of the resilient portions has a convexity. The base portions of the locating member are mounted to the holder, the two resilient portions facing internal peripheries of the first and second rotary knobs respectively, the convexities of the two resilient portions engaging with the first dents or the second dents when the first rotary knob or the second rotary knob is turned. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of a preferred embodiment of the present invention. 
       FIG. 2  is a side view of the preferred embodiment of the present invention. 
       FIG. 3  is a sectional view taken from a line  3 - 3  indicated in  FIG. 2 . 
       FIG. 4  is a sectional view taken from a line  4 - 4  indicated in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1-4 , a power hand tool  100  of a preferred embodiment of the present invention is composed of a housing  10 , an electric motor (not shown), a battery pack (not shown), a transmission gear set (not shown), a torsion control device  30 , an impact device  40 , and a locating device  50 . 
   The housing  10  includes a first semi-shell  11 , a second semi-shell  12 , a washer  13 , and a C-shaped Ring  14 . The first and second semi-shells  11  and  12  are butted with each other. 
   The electric motor is fixed in the housing for providing a rotary motion. 
   The battery pack is detachably mounted to the housing  10  for providing power for the electric motor. 
   The transmission gear set is mounted in the housing  10  and connected in transmission with the electric motor, for decelerating the rotary motion provided by the electric motor down to a predetermined speed and then outputting it via an output shaft  21 . 
   The torsion control device  30  includes a base  31 , a rotary disk  32 , and a first rotary knob  33 . The base  31  is located in the housing  10  and connected with the transmission gear set. The rotary disk  32  is mounted to the base  31 , axially movable along the output shaft  21  and rotatable on a rotary center of the output shaft  21 , for adjusting the maximum torsion of the output shaft  21  via the axial movement of the rotary disk  32 . The base  31  has an annular groove  311  formed on an external periphery thereof. The rotary disk  32  has a plurality of recesses  321  formed axially on an external periphery thereof. The first rotary knob  33  is mounted to the housing  10  and rotatable on the rotary center of the output shaft  21 . The first rotary knob  33  has an internal periphery  331 , a retaining wall  331  protruding outward from the internal periphery thereof, and a plurality of ribs  332  corresponding to the recesses  321  respectively and formed on the internal periphery thereof at one side of the retaining wall  331 . The ribs  332  can be axially inserted in the recesses  321 , so the rotary disk  32  can be axially moved, with respect to the first rotary knob  33 , via the recesses  321  along the ribs  332  and be driven for rotation together while the first rotary knob is turned. A plurality of first dents  333  are annularly formed on the internal periphery at the other side of the retaining wall  331 . 
   The impact device  40  includes a switch  41  and a second rotary knob  42 . The switch  41  is mounted in the housing  10  and can be operated for reciprocating motion on the rotary center of the output shaft  21 . One of the reciprocating motion of the impact device  40  can switch on or off an impact motion generated on the output shaft  21 . The second rotary knob  42  has a coordinating hole  421  and a receiving hole  422 . The coordinating hole  421  is located at an axis of the second rotary knob  42 , corresponding to the shape of the switch  41 . The receiving hole  422  is located around the coordinating hole  421 . The second rotary knob  42  is mounted to the housing  10 , allowing the switch  41  to be engaged with the coordinating hole  421  for driving rotation of the switch  41  while the second rotary knob  42  is turned on the rotary center of the output shaft  21 . The base  31  of the torsion control device  30  is inserted into the receiving hole  422 . Because the diameter of the receiving hole  422  is larger than the profile of the base  31 , i.e. there is a predetermined gap formed between the base  31  and the sidewall of the receiving hole  422 , it prevents the sidewall of the coordinating hole  422  from driving motion of the base  31  or from interference with the base  31  while the second rotary knob  42  is turned to drive rotation of the switch  41 . The second rotary knob  42  has an internal periphery and a plurality of second dents  423  annularly formed on the internal periphery thereof. In addition, the C-shaped ring  14  of the housing  10  is jammed in the annular groove  311  of the base  31 , and the washer  13  is closely mounted between the C-shaped ring  14  and an external end face of the second rotary knob  42 , so the C-shaped ring  14  restricts the axial motion of the first and second rotary knobs  33  and  42 . 
   The locating device  50  includes a holder  51  and a locating member  52 . The holder  51  has a locating hole  511  formed at an axis thereof and corresponding in shape to the base  31  of the torsion control device  30 . The holder  51  is located between the first and second knobs  33  and  42 , the base  31  mounted in the locating hole  511  and the holder  51  fixedly connected with the base  31 . The holder  51  has two slots  512  formed on an external periphery thereof and spaced from each other. The locating member  52  has two base portions  521  separate from each other, and two resilient portions  522  parallel located between the two base portions  521 . Each of the two resilient potions  522  has a first convexity  523  and a second convexity  524 . The two base portions  521  of the locating member  52  are inserted in the two slots  512  of the holder  51  respectively. The two resilient portions  522  face the internal peripheries of the first and second rotary knobs  33  and  42  respectively. The first and second convexities  523  and  524  of the two resilient portions  522  are engaged with the first dents  333  or the second dents  423 . Accordingly, while the first rotary  33  or the second rotary knob  42  is turned, the first and second convexities  523  and  524  of the two resilient portions  522  are engaged in the associated first dents  333  or the associated second dents  423  respectively, thus adjusting the torsion output and switching on or off the impact motion. 
   In conclusion, the power hand tool of the present invention not only provides the torsion control and the impact functioned by the torsion control device and the impact device respectively at the same time, but also shares the same locating device for the torsion control and impact devices to decrease required elements and size thereof. 
   Although the present invention has been described with respect to a specific preferred embodiment thereof, it is no way limited to the details of the illustrated structures but changes and modifications may be made within the scope of the appended claims.