Patent Publication Number: US-2013228051-A1

Title: Telescopic hand tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 101203833, filed on Mar. 3, 2012, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a hand tool, more particularly to a telescopic hand tool. 
     2. Description of the Related Art 
     A conventional telescopic hand tool includes a main body, a tubular bar and a positioning device. The main body extends in an axial direction, and includes a tool head and a rod extending from the tool head in the axial direction into the tubular bar. 
     The positioning device is mounted between the main body and the tubular bar, and includes a cylindrical rotating knob that is sleeved on and fixed to a portion of the tubular bar and a torsion spring that has two ends connected fixedly and respectively to the rotating knob and the portion of the tubular bar. The torsion spring is in tight frictional contact with the rod so as to prevent movement of the rod in the axial direction relative to the tubular bar. 
     To adjust a length of the conventional telescopic hand tool, the rotating knob is twisted relative to the tubular bar against the biasing force of the torsion spring to expand the torsion spring radially and outwardly so as to release the rod from the frictional contact with the torsion spring, and then the rod can be moved relative to the tubular bar in the axial direction. 
     However, it is necessary for a user to continuously hold the rotating knob with one hand at the twisted state relative to the tubular bar so that only one hand is left for length adjustment of the telescopic rod. Once the rotating knob is released from twisting, the torsion spring would restore to position the rod immediately. Thus, it is inconvenient to adjust the length of the conventional telescopic rod. Additionally, replacement of the torsion spring is relatively cumbersome. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a length-adjustable telescopic hand tool that has a relatively simple structure and that can be easily operated. 
     According to this invention, a telescopic hand tool comprises an outer tube, an inner rod and a positioning unit. The outer tube extends in an axial direction, and has opposite first and second end portions in the axial direction, and an inner surface formed with first and second grooves that are respectively formed at the first and second end portions. The inner rod extends in the axial direction, is inserted in the outer tube, and is movable relative to the outer tube in the axial direction between retracted and extended positions. The inner rod has opposite interior and exterior end portions that are respectively surrounded by and exposed from the outer tube, and an outer surface. The exterior end portion is adapted to be connected to a tool head. The outer surface has a segment at the interior end portion, confronting the inner surface of the outer tube, and formed with a furrow portion. The positioning unit is disposed in the outer tube and includes a positioning block that corresponds in position to the furrow portion of the inner rod, and a resilient member that is disposed in the furrow portion for biasing the positioning block toward the inner surface of the outer tube. The positioning block engages the first groove when the inner rod is at the retracted position, and engages the second groove when the inner rod is at the extended position. The positioning block is biased to be in frictional contact with the inner surface of the outer tube for positioning the inner rod relative to the outer tube when the inner rod is between the retracted and extended positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which: 
         FIG. 1  is a fragmentary partly sectional view of a preferred embodiment of a telescopic hand tool according to the present invention, illustrating an inner rod at a retracted position; 
         FIG. 2  is a sectional view taken along line II-II in  FIG. 1 ; 
         FIG. 3  is a fragmentary partly sectional view of the preferred embodiment, illustrating the inner rod being moved relative to an outer tube of the telescopic hand tool; 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 3 ; 
         FIG. 5  is a fragmentary exploded perspective view of a positioning unit of the preferred embodiment; and 
         FIG. 6  is a sectional view of the preferred embodiment, illustrating the inner rod at an extended position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2 , the preferred embodiment of a telescopic hand tool according to the present invention is shown to include an outer tube  10 , an inner rod  20 , and a positioning unit  30 . 
     The outer tube  10  extends in an axial direction (L), and has opposite first and second end portions  11 ,  12  in the axial direction (L), and an inner surface  14  formed with first and second grooves  15 ,  17  that are respectively formed at the first and second end portions  11 ,  12 . 
     The first groove  15  is defined by a first groove defining surface  150  that has first and second annular surface sections  151 ,  152 . The first annular surface section  151  is disposed between the second groove  17  and the second annular surface section  152  and converges toward the second end portion  12 . The second groove  17  is defined by a second groove defining surface  170  that has first and second annular surface sections  171 ,  172 . The first annular surface section  171  is disposed between the first groove  15  and the second annular surface section  172  of the second groove defining surface  170  and converges toward the first end portion  11 . 
     The inner rod  20  extends in the axial direction (L), is inserted in the outer tube  10 , and is movable relative to the outer tube  10  in the axial direction (L) between a retracted position (see  FIG. 1 ) and an extended position (see  FIG. 6 ). The inner rod  20  has an outer surface  24  and opposite interior and exterior end portions  21 ,  22  that are respectively surrounded by and exposed from the outer tube  10 . The exterior end portion  22  is connected to a tool head. The outer surface  24  of the inner rod  20  has a segment  241  at the interior end portion  21 , confronting the inner surface  14  of the outer tube  10 , and formed with a furrow portion  25 . 
     In this embodiment, the positioning unit  30  is disposed in the outer tube  10  and includes two positioning blocks  31  and a resilient member  32 . Further referring to  FIG. 5 , the inner rod  20  is formed with a through hole  26  that extends in a direction (R) perpendicular to the axial direction (L) and that extends through the furrow portion  25 . The positioning blocks  31  correspond in position to the furrow portion  25  of the inner rod  20 . Each of the positioning blocks  31  has a semi-circular block body that has an outer face  311  confronting the inner surface  14  of the outer tube  10  and an inner face  312  radially opposite to the outer face  311 , and a projection  313  that projects from the inner face  312 . In this embodiment, the resilient member  32  is a compression spring that extends through the through hole  26  of the inner rod  20  and that has opposite ends connected respectively to the projections  313  of the positioning blocks  31  for biasing the positioning blocks  31  toward the inner surface  14  of the outer tube  10 . 
     As illustrated in  FIGS. 1 and 2 , when the inner rod  20  is at the retracted position, the positioning blocks  31  are biased by the resilient member  32  to engage the first groove  15 . At this time, the outer faces  311  of the positioning blocks  31  abut against the first groove defining surface  150  so as to position the inner rod  20  stably relative to the outer tube  10 . 
     Referring to  FIGS. 3 and 4 , in order to adjust a length of the telescopic rod, the inner rod  20  is moved from the retracted position toward the extended position in the axial direction (L). The positioning blocks  31  are driven to be disengaged from the first groove  15  against a biasing force of the resilient member  32  to enable the interior end portion  21  of the inner rod  20  to move toward the second end portion  12  of the outer tube  10 . The inclined first annular surface section  151  of the first groove defining surface  150  facilitates disengagement of the positioning blocks  31  from the first groove  15 . When a force exerted on the inner rod  20  is released, the resilient member  32  is compressed and the positioning blocks  31  are biased by a restoring force of the resilient member  32  to be in frictional contact with the inner surface  14  of the outer tube  10  for positioning the inner rod  20  relative to the outer tube  10  at a desired position between the retracted and extended positions. It should be noted that static friction between the outer faces  311  of the positioning blocks  31  and the inner surface  14  is sufficient to provide resistance to the movement of the inner rod  20  relative to the outer tube  10  in the axial direction (L) when no external force is exerted on the inner rod  20  and the outer tube  10 . 
     Referring to  FIG. 6 , when the inner rod  20  is further moved toward the second end portion  12  to the extended position, the positioning blocks  31  are driven to slide over the first annular surface section  171  of the second groove defining surface  170  and are biased by the restoring force of the resilient member  32  to engage the second groove  17 . At this time, the outer faces  311  of the positioning blocks  31  abut against the second groove defining surface  170  so as to position the inner rod  20  stably relative to the outer tube  10 . The inclined second annular surface section  171  of the second groove defining surface  170  facilitates disengagement of the positioning blocks  31  from the second groove  17  in the next length-adjustment action of the preferred embodiment. 
     Additionally, in this embodiment, the second end portion  12  of the outer tube  10  terminates at an end of the second annular surface section  172  of the second groove defining surface  170 . The outer tube  10  further includes a cap  19  sleeved on a portion of the second end portion  12  of the outer tube  10  and cooperating with the second end portion  12  to define a shoulder portion  191  (see  FIG. 6 ) that abuts against the positioning blocks  31  so as to prevent removal of the inner rod  20  from the outer tube  10  when the inner rod  20  is at the extended position. 
     When it is desired to replace the resilient member  32 , the cap  19  is first removed from the outer tube  10 , and the inner rod  20  together with the positioning unit  30  are pulled out of the outer tube  10  so that the resilient member  32  can be accessed for replacement. 
     To sum up, by virtue of the first and second grooves  15 ,  17 , the inner rod  20  can be stably positioned relative to the outer tube  10  at the retracted and extended positions. Further, the configuration of the annular surface sections  151 ,  171  facilitates smooth length adjustment of the telescopic hand tool by moving the inner rod  20  relative to the outer tube  10  in the axial direction (L). Finally, it is convenient to replace the resilient member  32 . 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.