Patent Publication Number: US-7213500-B2

Title: Pneumatic tool

Description:
BACKGROUND OF INVENTION  
   1. Field of Invention 
   The present invention relates to a pneumatic tool and, more particularly, to an inexpensive pneumatic tool. 
   2. Related Prior Art 
   In Taiwanese Patent Publication No. 513992, there is disclosed an air-directing device of a pneumatic tool. This pneumatic tool includes a shell  20  defining spaces  21  and  26 , a cylinder  23  put in the space  21 , a rotor  22  put in the cylinder  23 , a sleeve  32  put in the space  26 , and a rotational switch  33  put in the sleeve  32  except an end by which the rotational switch  33  can be rotated. The air-directing device is made of the sleeve  32  and the rotational switch  33 . The rotational switch  33  includes blocks  331 – 334 . The sleeve  32  includes aperatures  321 – 325 . As the rotational switch  33  is rotated in the sleeve  32 , the blocks  331 – 334  are rotated relative to the apertures  321 – 325 . Thus, the direction and rate of the rotation of the rotor  22  is changed. It is, however, troublesome and, hence, expensive to independently make the sleeve  32  and then to fit it in the space  26 . Moreover, it is difficult and, hence, expensive to make the apertures  321 – 325  in the sleeve  32  and form the blocks  331 – 334  on the rotational switch  33 . 
   In Taiwanese Patent Publication No. 367926, there is disclosed a controlling and regulating device for a pneumatic tool. This pneumatic tool includes a shell  40  defining spaces  41  and  45 , a rotor (not shown) put in the space  41 , and a rotational switch  70  put in the space  45  except an end by which the rotational switch  70  can be rotated. The rotational switch  70  includes two channels  711  and  712  and two slots  714  and  715 . The channels  711  and  712  are communicated with and extended perpendicular to each other. As the rotational switch  70  is rotated, the channels  711  and  712  and the slots  714  and  715  are rotated. Thus, the direction and rate of the rotation of the rotor is changed. However,it is difficult and, hence, expensive to make the channel  711  and  712  that are communicated with and extended perpendicular to each other. Furthermore, it entails a cost to make the slots  714  and  715 . 
   The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art. 
   SUMMARY OF INVENTION  
   According to the present invention, a pneumatic tool includes a shell defining a first space, a second space communicated with the first space, a third space communicated with the second space, a fourth space communicated with the second space, a channel communicated with the second space, an inlet communicated with the channel, and an outlet communicated with the second space. A cylinder is put in the first space and defines first, second and third ports. Pressurized air drives a rotor in the cylinder in a direction while entering the cylinder through the first port and leaving the cylinder through the third port. Pressurized air drives the rotor in an opposite direction while entering the cylinder through the second port and leaving the cylinder through the third port. A cover is connected to the shell and defines an aperture communicated with the second space, a first channel communicated with the third space on one hand and the first port on the other hand, a second channel communicated with the fourth space on one hand and the second port on the other hand. A rotational switch extends into the second space the aperture and defines two cutouts. Different portions of the channel open to selective one of the cutouts as the axle is rotated in the second space so that the rotor is driven at different speeds. 
   The primary advantage of the pneumatic tool according to the present invention is a low cost of the rotational switch, since the cutouts can easily be made in the axle. 
   Other advantages and novel features of the invention will become more apparent from the following detailed description in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS  
     The present invention will be described through detailed description of the preferred embodiment referring to the drawings. 
       FIG. 1  is an exploded view of a pneumatic tool according to the preferred embodiment of the present invention. 
       FIG. 2  is a cross-sectional view of the pneumatic tool shown in  FIG. 1 . 
       FIG. 3  is a cross-sectional view taken along a line  3 — 3  in  FIG. 2 . 
       FIG. 4  is a cross-sectional view taken along a line  4 — 4  in  FIG. 2 . 
       FIG. 5  is a cross-sectional view taken along a line  5 — 5  in  FIG. 2 . 
       FIG. 6  is an enlarged partial view of the pneumatic shown in  FIG. 3  in order to show open positions of a channel related to operative rates. 
       FIG. 7  is an enlarged partial view of the pneumatic tool of  FIG. 4  in an idle position. 
       FIG. 8  is a cross-sectional view of the pneumatic tool shown in  FIG. 7 . 
       FIG. 9  is an enlarged partial view of the pneumatic tool of  FIG. 8 . 
       FIG. 10  is similar to  FIG. 7  but shows the pneumatic tool operated in a reversed direction at a low speed. 
       FIG. 11  is a cross-sectional view of the pneumatic tool of  FIG. 10 . 
       FIG. 12  is an enlarged partial view of the pneumatic tool of  FIG. 11 . 
       FIG. 13  is similar to  FIG. 10  but shows the pneumatic tool operated at a high speed. 
       FIG. 14  is a cross-sectional view of the pneumatic tool of  FIG. 13 . 
       FIG. 15  is an enlarged partial view of the pneumatic tool of  FIG. 14 . 
       FIG. 16  is similar to  FIG. 13  but shows the pneumatic tool operated in a forward direction. 
       FIG. 17  is a cross-sectional view of the pneumatic tool of  FIG. 16 . 
       FIG. 18  is an enlarged partial view of the pneumatic tool of  FIG. 17 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
   Referring to  FIG. 1 , there is shown a pneumatic tool according to the preferred embodiment of the present invention. The pneumatic tool includes a shell  10 , a handle  12  extended from the shell  10 , a cylinder  20 , a cover  30 , and a rotational switch  40 . 
   Referring to  FIGS. 2 and 3 , the shell  10  defines spaces  11 ,  13 ,  14 , and  15 . The space  11  is communicated with the space  13  through a channel  111  near an end and through two channels  112  near an opposite end. The space  13  is communicated with the space  14  through a channel  141 . The space  13  is communicated with the space  15  through a channel  151 . 
   The handle  12  defines an inlet  121  and an outlet  122 . The inlet  121  is communicated with the space  13  through a channel  131  with a cruciform profile. However, the channel  131  may include another profile such as a rhombus. The outlet  122  is communicated with the space  13  through the channels  112 . 
   The cylinder  20  is put in the space  11 . The cylinder  20  defines two ports  21  and  22  in an end thereof and a plurality of ports  23  in a periphery thereof. Although not shown, a rotor is put in the cylinder  20 . While entering the cylinder  20  through the port  21  and leaving the cylinder  20  through the ports  23 , pressurized air drives the rotor in a forward direction. While entering the cylinder  20  through the port  22  and leaving the cylinder  20  through the ports  23 , pressurized air drives the rotor in a reversed direction. 
   Referring to  FIG. 5 , the cover  30  is connected to the shell  10 . The cover  30  defines an aperture  31 , a plurality of recesses  311  in the wall of the aperture  31 , and two channels  32  and  33  in an internal side thereof. The aperture  31  is communicated with the space  13 . The cover  30  is put against the end of the cylinder  20  so that the channels  32  and  33  become two separate channels. The channel  32  includes an end communicated with the space  14  and another end communicated with the port  21 . The channel  33  includes an end communicated with the space  15  and another end communicated with the port  22 . Marks “F”, “O” and “R” are made on an external side of the cover  30  in order to indicate the status of the pneumatic tool. 
   The rotational switch  40  includes a knob  41  and an axle  43  extended from the knob  41 . The axle  43  is put in the space  13  through the aperture  31 . The axle  43  defines two separate cutouts  431  and  432 . A positioning device is connected to the axle  43 . The positioning device includes a detent  421  and a spring  422 . The detent  421  is biased by the spring  422  that is put in a recess  42  defined in the axle  43  near the knob  41 . The knob  41  facilitates the rotation of the axle  43 . The detent  421  can be put partially in one of the recesses  311  in order to keep the axle  43  in one of several positions in the space  13 . Two seals  44  are  45  are put around the axle  43  for sealing. The channel  111  is separated from the channels  112  by the seal  44 . A ring  46  is put around the axle  43  and engaged with the cover  30  in order to keep the axle  43  in the space  13 . 
   Referring to  FIGS. 3 ,  4  and  6 , as the axle  43  is rotated in the space  13 , different portions of the channel  131  open to the cutout  431  or  432 . As a small portion (A) of the channel  131  opens to the cutout  431  or  432 , the rotor is rotated at a low speed. As a medium portion (A plus A) of the channel  131  opens the cutout  431  or  432 , the rotor is rotated at a medium speed. Because the medium portion is twice as large as the small portion, the medium speed is twice as fast as the low speed. As a large portion (A plus A plus  2 A) of the channel  131  opens to the cutout  431  or  432 , the rotor is rotated at a high speed. Because the large portion is twice as large as the medium portion, the high speed is twice as fast as the medium speed. 
   Referring to  FIGS. 7 through 9 , the pneumatic tool is in an idle position. The channel  131  is blocked by the axle  43 . 
   Referring to  FIGS. 10 through 12 , the rotor is rotated in the reversed direction at the low speed. As indicated with thin arrowheads, pressurized air goes to the port  22  from the inlet  121  through the channel  131 , the cutout  432 , the channel  151 , the space  15  and the channel  33 . The pressurized air enters the cylinder  20  through the port  22  in order to rotate the rotor in the reversed direction. As a small portion of the channel  131  opens to the inlet  121 , the rotor is rotated at the low speed. 
   A portion of the pressurized air leaves the cylinder  20  through the ports  23 , and goes to the outlet  122  through the space  11 , the channels  112  and the space  13 . As indicated with thick arrowheads, the other portion of the pressurized air leaves the cylinder  20  through the port  21 , and goes to the outlet  122  through the channel  32 , the space  14 , the channel  141 , the cutout  431 , the channel  111 , the space  11  and one of the channels  112 . 
   Referring to  FIGS. 13 through 15 , the rotor is rotated in the reversed direction at a high speed. Pressurized air goes to the port  22  from the inlet  121  through the channel  131 , the cutout  432 , the channel  151 , the space  15 , and the channel  33 . The pressurized air enters the cylinder  20  through the port  22  in order to rotate the rotor in the reversed direction. As a large portion of the channel  131  opens the inlet  121 , the rotor is rotated at the high speed. 
   Referring to  FIGS. 16 through 18 , the rotor is rotated in the forward direction at a high speed. Pressurized air goes to the port  21  from the inlet  121  through the channel  131 , the cutout  431 , the channel  141 , the space  14 , and the channel  32 . The pressurized air enters the cylinder  20  through the port  21  in order to rotate the rotor in the forward direction. As a large portion of the channel  131  opens to the inlet  121 , the rotor is rotated at the high speed. 
   A portion of the pressurized air leaves the cylinder  20  through the ports  23 , and goes to the outlet  122  through the space  11 , the channels  112  and the space  13 . As indicated with thick arrowheads, the other portion of the pressurized air leaves the cylinder  20  through the port  22 , and goes to the outlet  122  through the channel  33 , the space  15 , the channel  151 , the cutout  432 , the channel  111 , the space  11  and one of the channels  112 . 
   Compared with the conventional pneumatic tools discussed in the Related Prior Art, the pneumatic tool of the present invention is advantageous in several aspects. Firstly, the cutouts  431  and  432  can easily be made in the axle  43  so that the cost of the rotational switch  40  is low. Secondly, since the cutouts  431  and  432  form part of a discharge route, the rotational switch  40  is saved from any auxiliary venting device so that the cost of the rotational switch is low. Thirdly, the channel  131  and the cutouts  431  and  432  render the differences between the speeds large so that the performance of the pneumatic tool is good. 
   The present invention has been described through the detailed description of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. The preferred embodiment shall not limit the scope of the present invention defined in the claims.