Patent Publication Number: US-2004042918-A1

Title: Fan assembly with lubricant-containing bearings

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a fan assembly, more particularly to a fan assembly which is provided with lubricant-containing bearings so as to prolong the service life thereof.  
       [0003] 2. Description of the Related Art  
       [0004] Referring to FIGS. 1 and 2, a conventional fan assembly is shown to include a mounting member  11 , a stator  12 , a rotor  13 , and a tubular bearing  122 . The mounting member  11  defines an axially extending bore  112 , and includes an annular mounting plate Ill disposed in the bore  112 , a plurality of ribs  113  extending radially and outwardly from the mounting plate  111  to connect with a bore-defining wall surface that confines the bore  112  so as to form a plurality of ventilation holes  112 ″, and a mounting tube  115  that extends axially from the mounting plate  111  and that has an inner wall surface to confine a bearing-receiving space. The stator  12  is sleeved securely on the mounting tube  115 , and has a plurality of coils  123 . The rotor  13  includes a generally U-shaped rotor casing  131 , a rotor shaft  134 , and a plurality of blades  133 . The rotor casing  131  is disposed in the bore  123 , and surrounds the stator  12 . The rotor shaft  134  extends axially from the rotor casing  131 , and is inserted rotatably and co-axially into the bearing-receiving space of the mounting tube  115 . The blades  133  extend radially and outwardly from the rotor casing  131 . A magnetic sleeve  132  is disposed within the rotor casing  131  around the stator  12 . A tubular bearing  122  is disposed in the bearing-receiving space of the mounting tube  115 , and is sleeved on the rotor shaft  134 . A C-shaped fastener clip  135  is mounted on the rotor shaft  134  to prevent disengagement of the rotor  13  relative to the stator  12 .  
       [0005] Some disadvantages resulting from the use of the aforementioned conventional fan assembly are as follows:  
       [0006] (1) The service life of the conventional fan assembly is short, because the lubricant disposed in the tubular bearing  122  gradually diminishes since no covering means is provided to prevent loss of the lubricant.  
       [0007] (2) Provision of such covering means results in increased manufacturing costs.  
       [0008] (3) Since the entire inner wall surface of the bearing  122  slidably contacts the rotor shaft  134 , the force of friction therebetween is relatively large.  
       SUMMARY OF THE INVENTION  
       [0009] Therefore, the object of this invention is to provide a fan assembly with lubricant-containing bearings of a simple construction so as to eliminate the aforesaid disadvantages of the prior art.  
       [0010] Accordingly, a fan assembly according to the present invention includes: a mounting frame, a stator, a rotor, first and second bearings, and first and second annular bearing-covering caps. The mounting frame includes a mounting plate, and a hollow mounting tube extending transversely from the mounting plate. The mounting tube has an inner wall surface confining a bearing-receiving space, and an annular flange that projects inwardly and radially from the inner wall surface into the bearing-receiving space, and that has two opposite sides and two opposite annular side faces. The stator is sleeved securely on the mounting tube. The rotor includes an annular rotor casing, a rotor shaft, and a plurality of blades. The rotor casing surrounds the stator. The rotor shaft extends axially from the rotor casing, and is inserted rotatably into the mounting tube. The blades extend radially and outwardly from the rotor casing. The first and second bearings are respectively disposed at the opposite sides of the annular flange within the bearing-receiving space in the mounting tube, and are sleeved on the rotor shaft. Each of the first and second bearings has a U-shaped cross section, an annular abutment plate that abuts against a respective one of the annular side faces of the annular flanges of the mounting tube, and a peripheral flange that extends axially from the abutment plate, that slidably contacts the inner wall surface of the mounting tube, and that cooperates with the rotor shaft and the abutment plate to define a lubricant-receiving reservoir thereamong. The first and second annular bearing-covering caps are snugly fitted into the bearing-receiving space in the mounting tube, are sleeved on the rotor shaft, and respectively and sealingly cover the lubricant-receiving reservoirs in the first and second bearings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which:  
     [0012]FIG. 1 is an exploded perspective view of a conventional fan assembly;  
     [0013]FIG. 2 is a sectional view of the conventional fan assembly, illustrating how a lubricant is spilled outwardly from a bearing during rotation of a rotor;  
     [0014]FIG. 3 is an exploded perspective view of the first preferred embodiment of a fan assembly according to the present invention;  
     [0015]FIG. 4 is a sectional view of the first preferred embodiment, illustrating how two lubricant-containing bearings are disposed in a mounting tube;  
     [0016]FIG. 5 is a sectional view of the second preferred embodiment of the fan assembly; and  
     [0017]FIG. 6 is an enlarged perspective view of a lubricant-containing bearing employed in the second preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0018] Referring to FIGS. 3 and 4, the first preferred embodiment of a fan assembly according to the present invention is shown to include a mounting frame  2 , a stator  3 , a rotor  5 , first and second bearings  31 , and first and second annular bearing-covering caps  4 . As illustrated, the mounting frame  2  includes a mounting plate  21  with opposing front and rear sides  211 ,  212 , a hollow mounting tube  24  extending transversely and rearwardly from an annular central portion  22  of the mounting plate  21 , a surrounding wall  26  extending transversely and rearwardly from the mounting plate  21 , surrounding the mounting tube  24 , and cooperating with the annular central portion  22  to define a chamber  222  therebetween, and a plurality of ribs  23  extending radially and outwardly from a periphery  221  of the annular central portion  22  to connect with the surrounding wall  26  so as to define a plurality of ventilation holes  25 . The mounting tube  24  defines a bearing-receiving space  244 , and has an inner wall surface  241  confining the bearing receiving space  244 , and an annular flange  243  that projects inwardly and radially from the inner wall surface  241  into the bearing-receiving space  244  and that has two opposite sides and two opposite annular side faces  245 .  
     [0019] The stator  3  is disposed in the chamber  222 , is sleeved securely on the mounting tube  24 , and has a plurality of coils  32 . Since the stator  3  is not a characterizing feature of the present invention, a detailed description of the same will be omitted herein for the sake of brevity.  
     [0020] The rotor  5  includes a rotor casing  52 , a rotor shaft  55 , and a plurality of blades  54 . The rotor casing  52  is disposed in the chamber  222 , and surrounds the stator  3 . The rotor shaft  55  extends axially from the rotor casing  52 , and is inserted rotatably into the mounting tube  24 . The blades  54  extend radially and outwardly from the rotor casing  52 . A magnetic sleeve  53  is disposed within the rotor casing  52  around the stator  3 .  
     [0021] The first and second bearings  31  are respectively disposed at the opposite sides of the annular flange  243  within the bearing-receiving space  244  in the mounting tube  24 , and are sleeved on the rotor shaft  55 . Each of the first and second bearings  31  has a U-shaped cross section, an annular abutment plate  311  that abuts against a respective one of the annular side faces  245  of the annular flanges  243  of the mounting tube  24 , and a peripheral flange  312  that extends axially from the abutment plate  311 , that slidably contacts the inner wall surface  241  of the mounting tube  24 , and that cooperates with the rotor shaft  55  and the abutment plate  311  to define a lubricant-receiving reservoir  57  thereamong. A proper amount of Lubricating grease is disposed in the lubricant-receiving reservoir  57 .  
     [0022] The first and second annular bearing-covering caps  4  are snugly fitted into the bearing-receiving space  244  of the mounting tube  24 , are sleeved on the rotor shaft  55 , and respectively and sealingly cover the lubricant-receiving reservoirs  57  in the first and second bearings  31 .  
     [0023] A C-clip  56  is disposed around the rotor shaft  55 , engages a base plate of the stator  3  to prevent disengagement of the rotor  5  relative to the stator  3 .  
     [0024] The abutment plates  311  of the first and second bearings  31  cooperate with the annular flange  243  of the mounting tube  24  and the rotor shaft  55  to define an auxiliary lubricant-receiving reservoir  58  thereamong. A proper amount of lubricating grease is disposed within the auxiliary lubricating-receiving reservoir  58 .  
     [0025] The rotor shaft  55  contacts slidably a small portion of the abutment plates  311  of the first and second bearings  31  during rotation. As such, little friction force is generated, which is contrast to the prior art.  
     [0026] Note that the first and second bearings  31 , and the annular bearing-covering caps  4  are simple and inexpensive to manufacture. The object of the present invention is thus achieved.  
     [0027] Referring to FIGS. 5 and 6, the second preferred embodiment of the fan assembly according to the present invention is shown to have a structure similar to the previous embodiment. The main difference resides in that each of first and second bearings  6  includes an inner flange  62  that extends axially from the abutment plate  61  of a respective one of the first and second bearings  6 , that is sleeved on the rotor shaft  55 ″ of the rotor  5 ″, and that cooperates with the abutment plate  61  and the peripheral flange  63  of a respective one of the first and second bearings  6  to define the lubricant-receiving reservoir  64  thereamong.  
     [0028] 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 the invention be limited only as indicated in the appended claims.