Patent Publication Number: US-6983808-B1

Title: Power tool with oil circulation apparatus

Description:
BACKGROUND OF INVENTION 
   1. Field of Invention 
   The present invention relates to a power tool with an oil circulation apparatus. 
   2. Related Prior Art 
   Referring to  FIG. 7 , a conventional power tool  110  includes a sleeve  120 , a bearing  128 , a ball  127 , a converter  130 , two pistons  150 , a retaining ring  140 , a striker  160  and a spring  170 . The sleeve  120  includes an aperture  121 , a small space  123  communicated with the aperture  121  and a large space  125  communicated with the small space  123 . A recess  126  is defined in the wall of the small space  123 . Two grooves  122  are defined in the wall of the large space  125 . The bearing  128  is put in the small space  123 . The ball  127  is put in the recess  126 . The ball  127  slides on the bearing  128 . The converter  130  is an annular element and includes an annular cam  134  formed with an inclined edge, an annular rib  133  formed on the annular cam  134  and teeth  135  formed on an internal face. Each piston  150  includes an annular groove  152  for receiving the annular rib  133 . The converter  130  is put in the large space  125  so that the pistons  150  are put in the grooves  122 . The annular retainer  140  includes two recesses  142  defined in the periphery thereof. The annular retainer  140  is put in the large space  125  so that the recesses  142  receive the pistons  150 . The spring  170  is put in the large space  125  and inserted through the annular retainer  140 . The striker  160  includes teeth  162  formed on a first section, two tabs  164  formed on a second section next to the first section and a square insert  165  formed on a third section next to the second section. The teeth  162  are engaged with the teeth  135 . The spring  170  is compressed between the tabs  164  and the annular rib  133 . In operation, the sleeve  120  is rotated. The ball  127  is rotated together with the sleeve  120 . The inclined edge of the annular cam  134  is pushed by the ball  127 . Thus, the rotation of the ball  127  is converted to rectilinear movement of the annular cam  134 . The pistons  150  are moved by the annular rib  133 . The tabs  164  are pushed by the pistons  150 . Thus, the striker  160  is moved. Lubrication for reducing the friction between the elements is important. To this end, oil is filled in the sleeve  120 . However, oil is expelled from the sleeve  120  easily when the pistons  150  and the tabs  164  are moved towards the exterior of the sleeve  120 . The friction between the elements thus rises so that the elements wear out one another. 
   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 power tool includes a sleeve, two pistons, a converter and a striker. The sleeve includes an axial aperture defined therein, a space communicated with the axial aperture, two grooves defined in the wall of the space and peripheral apertures communicated with the space. Oil flows into and from the space through the peripheral apertures. The pistons are put in the grooves. The converter is provided between the sleeve and the pistons for converting the rotation of the sleeve into rectilinear movement of the pistons. The striker is driven by the pistons. 
   The primary advantage of the power tool of the present invention is that it provides adequate lubrication. 
   Other objects, advantages and novel features of the invention will become more apparent from the following detailed description in conjunction with the attached drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention will be described via detailed illustration of the preferred embodiment referring to the drawings. 
       FIG. 1  is an exploded view of a power tool with an oil circulation apparatus according to the preferred embodiment of the present invention. 
       FIG. 2  is a front view, partially in cross-section, of the power tool with the oil circulation apparatus shown in  FIG. 1 . 
       FIG. 3  is an end elevational view, partially in cross section, of the power tool with the oil circulation apparatus shown in  FIG. 1 . 
       FIG. 4  is similar to  FIG. 2  but shows the oil circulation apparatus filled with oil. 
       FIG. 5  is similar to  FIG. 3  but shows the oil circulation apparatus filled with oil. 
       FIG. 6  is similar to  FIG. 5  but shows the oil circulation apparatus in a different position. 
       FIG. 7  is an exploded view of a conventional power tool. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 through 3 , according to the preferred embodiment of the present invention, a pneumatic tool  60  includes an axle  61 , a sleeve  50 , a bearing  40 , a ball  41 , a converter  20 , two pistons  30 , a striker  10  and a spring  15 . 
   The sleeve  50  includes an aperture  55  and a space  51  communicated with the aperture  55 . Teeth  53  are formed on the wall of the aperture  55 . A recess  56  is defined in the wall of the space  51 . Two grooves  52  are defined in the wall of the space  51 . Four apertures  54  are defined in the sleeve  50 . 
   The bearing  40  is put in the space  51 . The ball  41  is put in the recess  56 . The ball  41  slides on the bearing  40 . 
   The converter  20  is an annular element and includes an annular cam  22  formed with an inclined edge, an annular rib  21  formed on the annular cam  22  and teeth  23  formed on an internal face. Each piston  30  includes an annular groove  31  for receiving the annular rib  21 . The converter  20  is put in the space  51  so that the pistons  30  are put in the grooves  52 . 
   Two of the apertures  54  are located near an end of the movement of the pistons  30  and the other apertures  54  are located near another end of the movement of the pistons  30 . 
   The spring  15  is put in the space  51 . The striker  10  includes teeth  13  formed on a first section, two tabs  14  formed on a second section next to the first section and a square insert  11  formed on a third section next to the second section. The teeth  13  are engaged with the teeth  23 . The spring  15  is compressed between the tabs  14  and the annular rib  21 . 
   In operation, the sleeve  50  is rotated. The ball  41  is rotated together with the sleeve  50 . The inclined edge of the annular cam  22  is pushed by the ball  41 . Thus, the rotation of the ball  41  is converted to rectilinear movement of the annular cam  22 . The pistons  30  are moved by the annular rib  21 . The tabs  14  are pushed by the pistons  30 . Thus, the striker  10  is moved. 
   Referring to  FIG. 3 , some of the apertures  54  extend along radiuses of the sleeve  50 , some do not. When an aperture  54  does not extend along a radius of the sleeve  50 , it is angled from the radius so that when the pistons  30  are rotated in the space  51  oil can be drawn into the space  51  through the aperture  54 . 
   Referring to  FIG. 4 , when the sleeve  50  is rotated by the axle  61 , a centrifugal force causes a portion of the oil to flow from the space  51  through the apertures  54  that extend along radiuses of the sleeve  50 . 
   Referring to  FIG. 5 , a portion of the oil flows into the space  51  through the apertures  54  that do not extend along radiuses of the sleeve  50 . Thus, adequate oil is retained in the space  51  in order to lubricate the elements. 
   Referring to  FIG. 6 , when the rotation of the sleeve  50  is terminated, the centrifugal is gone. Thus, a portion of oil flows quickly into the space  51  through the apertures  54  that extend along radiuses of the sleeve  50 . A portion of oil flows slowly into the space  51  through the apertures  54  that do not extend along radiuses of the sleeve  50 . Again, the space  51  is filled with the oil. The sleeve  50  can be used in an electrical tool as well as in the pneumatic tool  60 . 
   The present invention has been described via detailed illustration 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. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.