Abstract:
A pneumatic tool includes a front handle section having an axial hole unit formed in a bifurcated front end, a bush unit extending into the axial hole unit, a driving head extending through the axial hole unit and obstructed by the bush unit, and a position limiting unit including at least one stop member disposed on an exposed section of the driving head, and a compression spring disposed between the bush unit and the driving head. The compression spring biases the stop member to contact the bush unit. As such, the driving head is fixed in the bifurcated front end of the front handle section, so as to prevent deformation of the bifurcated front end due to rotation of the driving head relative to the front handle section.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority of Taiwanese Application No. 101144493, filed on Nov. 28, 2012. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a pneumatic tool, and more particularly to a pneumatic tool capable of preventing deformation of a front handle section. 
         [0004]    2. Description of the Related Art 
         [0005]    Referring to  FIG. 1 , a conventional pneumatic tool  1  disclosed in U.S. Pat. No. 7,392,726 includes a front handle section  11 , a first guide bush  12 , a driving head  13 , a second guide bush  14 , two disc springs  15 , a C-shaped retaining ring  16 , a locking pin  17 , and a plurality of washers  18 ,  19 . The front handle section  11  has a bifurcated front end consisting of spaced-apart first and second annular hold portions  111 ,  112  each having axial hole  113  formed therethrough along an axis (X). During assembly, the first guide bush  12  and the driving head  13  are moved through the axial holes  113  in the second annular hold portion  112  to contact the first annular hold portion  111 . Subsequently, the second guide bush  14 , the disc springs  15 , and washers  10  are moved through the axial hole  113  in the second annular hold portion  112  until the second guide bush  14  comes into contact with the washer  18 , which is sleeved on the driving head  13  and abuts against a shoulder of the driving head  13 . The C-shaped retaining ring  16  is disposed in the axial hole  113  in the second annular hold portion  112 , so as to position the first and second guide bushes  12 ,  14 , the driving head  13 , and the washer  18  relative to the front handle section  11 . The locking pin  17  is inserted through the driving head  13  in a direction perpendicular to the axis (X) to limit the positions of the washers  19  and the disc springs  19 . 
         [0006]    As such, the disc springs  15  bias the driving head  13  away from the washers  19  until the locking pin  17  comes into contact with the washers  19 , so that the driving head  13  is positioned relative to the front handle section  11 , thereby preventing movement of free ends of the first and second annular hold portions  111 ,  112  away from each other. That is, deformation of the bifurcated front end of the front handle section  11  can be avoided. 
         [0007]    However, since the driving head  13  is moved into the first annular hold portion  111  through the axial hole  113  in the second annular hold portion  112  during assembly, the first annular hold portion  111  needs to have a shoulder portion for permitting the driving head  13  or the first guide bush  12  to abut thereon. In addition, during assembly of the driving head  13  to the front handle section  11 , before the locking pin  17  is assembled to the driving head  13 , the disc springs  15  and the washers  19  may drop from a space between the driving head  13  and the front handle section  11 . As such, the conventional pneumatic tool  1  has a complicated structure, and is difficult to assemble. Furthermore, the disc springs  15  serve as means for biasing the driving head  13 , and thus affect adversely smooth rotation of the driving head  13 . 
       SUMMARY OF THE INVENTION 
       [0008]    The object of this invention is to provide a pneumatic tool that can overcome the above-mentioned disadvantages associated with the prior art. 
         [0009]    According to this invention, there is provided a pneumatic tool comprising: 
         [0010]    a front handle section having a first annular hold portion and a second annular hold portion that are spaced apart from each other, each of the first and second annular hold portions having an axial hole formed therethrough along an axis; 
         [0011]    a bush unit including a shoulder member, the shoulder member being disposed on the second annular hold portion of the front handle section and having an inner side surface facing the first annular hold portion, and an outer side surface opposite to the inner side surface; 
         [0012]    a driving head extending through the axial holes in the first and second annular hold portions and obstructed by the inner side surface of the shoulder member from removal from the front handle section through the axial hole in the second annular hold portion, the driving head having an exposed section extending outwardly from the outer side surface; and 
         [0013]    a position limiting unit including at least one stop member disposed on the exposed section, at least one compression spring disposed between the inner side surface of the shoulder member and the driving head, and at least one abutment member disposed between the compression spring and the inner side surface of the shoulder member, the compression spring biasing the driving head away from the second annular hold portion along the axis to allow the stop member to contact the bush unit, so as to prevent the driving head from removal from the front handle section through the axial hole in the first annular hold portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    These and other features and advantages of this invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
           [0015]      FIG. 1  is a sectional view of a conventional pneumatic tool disclosed in U.S. Pat. No. 7,392,726; 
           [0016]      FIG. 2  is an exploded perspective view of the first preferred embodiment of a pneumatic tool according to this invention; 
           [0017]      FIG. 3  is a sectional view of the first preferred embodiment; 
           [0018]      FIG. 4  is another sectional view of the first preferred embodiment; 
           [0019]      FIG. 5  is a sectional view of the second preferred embodiment of a pneumatic tool according to this invention; 
           [0020]      FIG. 6  is a sectional view of the third preferred embodiment of a pneumatic tool according to this invention; 
           [0021]      FIG. 7  is a sectional view of the fourth preferred embodiment of a pneumatic tool according to this invention; 
           [0022]      FIG. 8  is a sectional view of the fifth preferred embodiment of a pneumatic tool according to this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Before the present invention is described in greater detail in connection with the preferred embodiments, it should be noted that similar elements and structures are designated by like reference numerals throughout the entire disclosure. 
         [0024]    Referring to  FIGS. 2 ,  3 , and  4 , the first preferred embodiment of a pneumatic tool according to this invention includes a front handle section  2 , a bush unit  3 , a driving unit  4 , and a position limiting unit  5 . 
         [0025]    The front handle section  2  has a first annular hold portion  21  and a second annular hold portion  22  that are spaced apart from each other. Each of the first and second annular hold portions  21 ,  22  has an axial hole  23  formed therethrough along an axis (X). The axial holes  23  in the first and second annular hold portions  21 ,  22  cooperate to constitute an axial hole unit. The second annular hold portion  22  further ha a flange  231  extending into the axial hole  23 . 
         [0026]    The bush unit  3  includes an annular shoulder member  31  and a washer  32 . The shoulder member  31  has a small-diameter section  311  and a large-diameter section  312  that are interconnected. The large-diameter section  131  has an outer peripheral surface in contact with a wall of the second annular hold portion  22  defining the axial hole  23 . The small-diameter section  311  has a diameter smaller than that of the large-diameter section  312  so as to define an annular shoulder surface  316  (see  FIG. 3 ) therebetween. The annular shoulder surface  316  abuts against the flange  231 . The shoulder member  31  further has an inner side surface  313  facing the first annular hold portion  21 , and an outer side surface  314  opposite to the inner side surface  313 . The washer  32  abuts against the outer side surface  314  of the shoulder member  31 . 
         [0027]    The driving unit  4  includes a ratchet sleeve  41  disposed between the first and second annular hole portions  21 ,  22 , and a driving head  42  extending through the axial holes  23  in the first and second annular hold portions  21 ,  22  and the ratchet sleeve  41  and meshing with the ratchet sleeve  41 . The driving head  42  has a maximum diameter smaller than the diameter of the axial hole  23  in the first annular hold portion  21 , and extends through the axial hole  23  in the first annular hold portion  21  along the axis (X). The driving head  42  further has an exposed section  421  extending outwardly from the outer side surface  314  of the shoulder member  31  through the axial hole  23 , and a shoulder surface  422  facing the inner side surface  313  of the shoulder member  31  and formed with three blind holes  423 . As such, the driving head  42  is obstructed by the inner side surface  313  of the shoulder member  31  from removal from the front handle section  2  through the axial hole  23  in the second annular hold portion  22 . 
         [0028]    The position limiting unit  5  includes a stop member  51  extending through the exposed section  421  of the driving head  42  along a direction perpendicular to the axis (X) and abutting against the washer  32  of the bush unit  3 , three compression springs  52  disposed respectively within the blind holes  423  in the driving head  42 , and three abutment members  53  each disposed between and abutting against the corresponding compression spring  52  and the inner side surface  313  of the shoulder member  31 . In this embodiment, the stop member  51  is configured as a pin, and each of the abutment members  3  is configured as a rolling member, such as a ball. As such, the compression springs  52  bias the driving head  42  away from the second annular hold portion  22  along the axis (X) to allow the stop member  51  to contact the washer  32  of the bush unit  3 , so as to prevent the driving head  42  from removal from the front handle section  2  through the axial hole  23  in the first annular hold portion  21 . 
         [0029]    During assembly, the front handle section  2  is first rotated about its central axis to an angular position whereat the first annular hold portion  21  is disposed under the second annular hold portion  22 . Next, the small-diameter section  311  of the shoulder member  31  is inserted into the axial hole  23  in the second annular hold portion  22  until the annular shoulder surface  316  comes into contact with the flange  231  of the second annular hold portion  22 . The washer  32  is also placed into the axial hole  23  in the second annular hold portion  22  until it abuts against the outer side surface  314  of the shoulder member  31 . Thereafter, the driving head  42  is inserted upwardly through the axial hole  23  in the first annular hold portion  21  and the ratchet sleeve  41  and into shoulder member  31  and the washer  32  until the shoulder surface  422  comes into contact with the inner side surface  313  of the shoulder member  31 , so that the exposed section  421  projects outwardly from the second annular hold portion  22 . Finally, an external force is applied to the driving head  42  along the X-axis to compress the compression springs  52 , and the stop member  51  is inserted through the driving head  42 . 
         [0030]    When the external force is released, the stop member  51  is biased by the compression springs  52  to abut against the washer  32 , so as to prevent removal of the driving head  42  from the front handle section  2  through the axial hole  23  in the first annular hold portion  21 . In addition, since the shoulder surface  422  of the driving head  42  is obstructed by the inner side surface  313  of the shoulder member  31 , removal of the driving head  42  from the front handle section  2  through the axial hole  23  in the second annular hold portion  22  is prevented. Furthermore, since the abutment members  53  are pressed against the inner side surface  313  of the shoulder member  31 , the driving head  42  can be positioned relative to the front handle section  2 . Further, since the abutment members  53  are configured as balls, smooth rotation of the driving head  42  is allowed, and the driving head  42  and the shoulder member  31  experience less wear. 
         [0031]      FIG. 5  shows the second preferred embodiment of a pneumatic tool according to this invention, which differs from the first preferred embodiment in the following. 
         [0032]    The small-diameter section  311  has the outer side surface  314 , and abuts against the washer  32 . The large-diameter section  312  has the inner side surface  313 , and abuts against the shoulder surface  422 . 
         [0033]    The exposed section  421  of the driving head  42  has an outer surface formed with an annular groove  424 . The stop member  54  is configured as a C-shaped retaining ring, and is received within the annular groove  424 . 
         [0034]      FIG. 6  shows the third preferred embodiment of a pneumatic tool according to this invention, which differs from the first preferred embodiment in the following. 
         [0035]    The shoulder member  24  is formed integrally with the second annular hold portion  22 , defines the axial hole  23 , and has an inner side surface  241  facing the first annular hold portion  21 , and an outer side surface  242  opposite to the inner side surface  241 . 
         [0036]      FIG. 7  shows the fourth preferred embodiment of a pneumatic tool according to this invention, which is similar to the third preferred embodiment except that the outer side surface  242  of the shoulder member  24  is formed with a recess  243 , within which the washer  32  is disposed, so that, during rotation of the driving head  42 , the shoulder member  24  and the second annular hold portion  22  cannot be scratched by the stop member  51 . 
         [0037]      FIG. 8  shows the fifth preferred embodiment of a pneumatic tool according to this invention, which is similar to the fourth preferred embodiment except that the front handle section  2  further includes two washers  25 . 
         [0038]    One of the washers  25  is disposed between and abuts against the inner side surface  241  of the shoulder member  24  and the abutment members  53 , so as to prevent contact between the shoulder member  24  and the abutment members  53 . The other of the washers  25  is disposed between the outer side surface  242  of the shoulder member  24  and the stop member  51 , so as to prevent contact between the stop member  51  and the shoulder member  24 . 
         [0039]    With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.