Abstract:
An air cushioned bearing includes: a cylindrical arbor; and an axial bushing formed as a hollow cylindrical tube for rotationally accepting the arbor; wherein a spiral groove or a spiral flange rib is formed between the arbor and the axial bushing. Therefore, the arbor rotates in high speed to form an air cushion between the axial bushing and the arbor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a bearing, and more particularly, to an air cushioned bearing suitable for ultra-high speed, low operating noise environments, such as hard disk drives, optical disk drives or computer cooling fans.  
         [0003]     2. Description of the Related Art  
         [0004]     Please refer to  FIG. 1 .  FIG. 1  shows a prior art bearing, which comprises an arbor  11  and an axial bushing  12 . The axial bushing  12  is hollow for internally accepting the arbor  11  so that the arbor  11  can rotate at high speeds. However, during rotation of the arbor  11 , friction between the arbor  11  and the axial bushing  12  leads to excessive heating and material fatigue. In order to avoid these problems, friction between the arbor  11  and the axial bushing  12  must be reduced.  
         [0005]     Ball bearings are one of the most popular bearings, in which balls are placed between the arbor and the axial bushing to reduce friction between the arbor and the axial bushing. However, ball bearings are not suitable for environments that demand high rotational speeds, small sizes, low noise, or low costs, which are all frequently desired in high-tech products.  
         [0006]     Greased bearing is another popular bearing, which utilizes a porous greased metallic material in the fabrication of the axial bushing so that lubricating oil from the axial bushing reduces friction between the arbor and the axial bushing. However, the high rotational speed of the arbor causes loss of the lubricating oil, or heat generated by friction between the arbor and the axial bushing vaporizes the lubricating oil so that the lubricating oil must be refilled regularly to avoid dry friction between the arbor and the axial bushing, which can otherwise cause serious wear and tear. But this is not practical for many applications, such as hard disk drives, optical disk drives or computer cooling fans.  
         [0007]     Therefore, it is desirable to provide an air cushioned bearing to mitigate and/or obviate the aforementioned problems.  
       SUMMARY OF THE INVENTION  
       [0008]     A main objective of the present invention is to provide an air cushioned bearing that provides advantages such as low polluting characteristics, a low coefficient of friction, a long lifetime, a low operating noise and a high operating efficiency.  
         [0009]     In accordance with one aspect of the present invention, the air cushioned bearing comprises: a cylindrical arbor; and an axial bushing formed as a hollow cylindrical tube for rotationally accepting the arbor; wherein a spiral groove is formed between the arbor and the axial bushing.  
         [0010]     In accordance with another aspect of the present invention, the air cushioned bearing comprises: a cylindrical arbor; and an axial bushing formed as a hollow cylindrical tube for rotationally accepting the arbor; wherein a spiral flange rib is formed between the arbor and the axial bushing.  
         [0011]     The spiral groove or the spiral flange rib is formed between the arbor and the axial bushing. Therefore, the arbor rotates in high speed to form an air cushion between the axial bushing and the arbor.  
         [0012]     In accordance with a further aspect of the present invention, the air cushioned bearing comprises: a cylindrical arbor; and an axial bushing formed as a hollow cylindrical tube with a plurality of circularly arranged saw-teeth on an inner wall, with one end of the saw-teeth being more narrow than another end.  
         [0013]     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a prior art bearing  FIG. 2  shows a first embodiment of an air cushioned bearing in accordance with the present invention.  
         [0015]      FIG. 3  is a cross-sectional view of an air stream forming when an arbor is rotating in accordance with the first embodiment.  
         [0016]      FIG. 4  shows an air cushioned bearing comprising a carrying body in the first embodiment in accordance with the present invention.  
         [0017]      FIG. 5  shows an air cushion forming when an arbor is rotating in the first embodiment in accordance with the present invention.  
         [0018]      FIG. 6  shows a second embodiment of an air cushioned bearing in accordance with the present invention.  
         [0019]      FIG. 7  shows a third embodiment of an air cushioned bearing in accordance with the present invention.  
         [0020]      FIG. 8  shows a fourth embodiment of an air cushioned bearing in accordance with the present invention.  
         [0021]      FIG. 9  shows a fifth embodiment of an air cushioned bearing in accordance with the present invention.  
         [0022]      FIG. 10  shows an air cushion forming when an arbor is rotating in the fifth embodiment in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     Please refer to  FIG. 2 .  FIG. 2  shows a first embodiment of an air cushioned bearing in accordance with the present invention. The air cushioned bearing comprises an arbor  21  and an axial bushing  22 . The axial bushing  22  is a hollow cylindrical tube for holding and permitting rotation of the arbor. The arbor  21  is cylindrical, and a spiral groove  211  is formed on the surface of the arbor  21 .  
         [0024]     The spiral groove  211  of the arbor  21  winds counterclockwise around the arbor  21 , from top to bottom. Therefore, as shown in  FIG. 3 , when the arbor  21  rotates counterclockwise, air in the spiral groove  211  is pushed by the groove wall and flows down and counterclockwise to form a downward moving air steam.  
         [0025]     The air steam reduces the friction between the arbor  21  and the axial bushing  22 . As shown in  FIG. 4 , the air cushioned bearing further comprises a carrying body  23 , which is a hollow cylindrical body with one open end and one closed end, and which is used for containing the axial bushing  22  and the arbor  21 .  
         [0026]     As shown in  FIG. 5 , when the axial bushing  22  and the arbor  21  are placed in the carrying body  23 , the lower end of the axial bushing  22  is sealed. Please refer again to  FIG. 3 . When the arbor  21  rotates counterclockwise, air moves down while more air enters from the upper end of the axial bushing  22 . However, the lower end of the axial bushing  22  is sealed so that the air is compressed between the axial bushing  22  and the arbor  21 , forming an air cushion. When the arbor  21  rotates faster, the air is even further compressed. The air cushion is used as a friction buffer layer between the axial bushing  22  and the arbor  21  to efficiently reduce the friction between the axial bushing  22  and the arbor  21 .  
         [0027]     The spiral groove  211  of the arbor  21  can also be wound clockwise around the inner wall surface of the axial bushing  22  from top to bottom, and the arbor  21  correspondingly rotates clockwise so that an air cushion is formed between the axial bushing  22  and the arbor  21 .  
         [0028]      FIG. 6  shows a second embodiment of an air cushioned bearing according to the present invention. The second embodiment is similar to the first embodiment, but the spiral groove  211  is formed on the inner wall surface of the axial bushing  22 . The spiral groove  211  is wound counterclockwise around the inner wall surface of the axial bushing  22  from top to bottom, and the arbor  21  rotates counterclockwise, thus creating an air cushion between the axial bushing  22  and the arbor  21 ; or alternatively, the spiral groove  221  is wound clockwise around the inner wall surface of the axial bushing  22  from top to bottom, and the arbor  21  rotates clockwise to form an air cushion between the axial bushing  22  and the arbor  21 .  
         [0029]      FIG. 7  shows a third embodiment of an air cushioned bearing according to the present invention. The third embodiment is similar to the first embodiment. The difference is that a spiral flange rib  711  is formed on the inner wall surface of the axial bushing  22 . The spiral flange rib  711  is wound counterclockwise around the surface of arbor  21  from top to bottom, and the arbor  21  rotates counterclockwise to create an air cushion between the axial bushing  22  and the arbor  21 ; or alternatively, the spiral flange rib  711  is wound clockwise around the surface of the arbor  21  from top to bottom, and the arbor  21  rotates clockwise to form an air cushion between the axial bushing  22  and the arbor  21 .  
         [0030]      FIG. 8  shows a fourth embodiment of an air cushioned bearing according to the present invention. The fourth embodiment is similar to the first embodiment. The difference is that a spiral flange rib  711  is formed on the surface of the arbor  21 . The spiral flange rib  711  is wound counterclockwise around the inner wall surface of the axial bushing  22  from top to bottom, and the arbor  21  rotates counterclockwise to form an air cushion between the axial bushing  22  and the arbor  21 ; or alternatively, the spiral flange rib  711  is wound clockwise around the inner wall surface of the axial bushing  22  from top to bottom, and the arbor  21  rotates clockwise to form an air cushion between the axial bushing  22  and the arbor  21 .  
         [0031]     Accordingly, the spiral groove or the spiral flange rib are formed on the surface between the axial bushing  22  and the arbor  21 , so that when the arbor  21  rotates at high speeds, the surrounding air streaming between the axial bushing  22  and the arbor  21  forms the air cushion to reduce the friction between the axial bushing  22  and the arbor  21 .  
         [0032]     In the above-mentioned embodiments, the carrying body  23  is used for sealing the lower end of the axial bushing  22  to form the air cushion; however, when the axial bushing  22  is actually part of an assembly within a machine, the lower end of the axial bushing  22  may be blocked by other parts, and therefore there may be no need to provide for the carrying body  23  to form the air cushion.  
         [0033]      FIG. 9  shows a fifth embodiment of an air cushioned bearing according to the present invention. The fifth embodiment is similar to the first embodiment. The arbor  21  is cylindrical, and the axial bushing  22  is a hollow cylindrical tube with a plurality of circularly arranged saw-teeth  91  on the inner wall, and one end of the saw-teeth  91  is narrower than the other end. Therefore, as shown in  FIG. 10 , since the saw-teeth  91  are circularly arranged, a gap in the saw-teeth  91  between the axial bushing  22  and the arbor  21  becomes narrower in the clockwise direction (in this embodiment). When the arbor  21  rotates clockwise, the air flows from the wider gap to the narrower gap, and so forms an air cushion between the axial bushing  22  and the arbor  21  to reduce the friction between the axial bushing  22  and the arbor  21 .  
         [0034]     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.