BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded, isometric view of an electric fan in accordance with a preferred embodiment of the present invention;
FIG. 2 is an isometric view of a bearing of the electric fan of FIG. 1;
FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2;
FIG. 4 is an assembled, cross-sectional view of the electric fan of FIG. 1;
FIG. 5 is an isometric view of a bearing in accordance with a second embodiment of the present invention;
FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5;
FIG. 7 is a view similar to FIG. 5, but shown from an opposite bottom aspect;
FIG. 8 is an assembled, cross-sectional view of an electric fan incorporating the bearing of in accordance with the second embodiment of the present invention;
FIG. 9 is a cross-sectional view of a bearing in accordance with a third embodiment of the present invention; and
FIG. 10 is a cross-sectional view of an electric fan in accordance with related art.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates by way of example an electric fan in accordance with a preferred embodiment of the present invention. The fan comprises a fan base 10, a rotor assembly 20, a stator assembly 30 and a bearing 40. The rotor assembly 20 is pivotable with respect to the stator assembly 30.
The fan base 10 defines a cavity (not labeled) therein for receiving the rotor assembly 20 and the stator assembly 30 therein. A central tube 11 is formed at a central portion of the fan base 10. The central tube 111 has a hollow and cylindrical configuration. Referring also to FIG. 4, the bearing 40 is engagingly received in the central tube 11. The stator assembly 30 is attached around the central tube 11. A baffle element 110 bends inwardly from a top of a circumferential wall (not labeled) of the central tube 11 and engages with the bearing 40 so as to prevent lubricating oil from leaking from a top end of the bearing 40. The baffle element 110 comprises an annular connecting portion 111 extending perpendicularly, horizontally and inwardly from the top of the circumferential wall of the central tube 111 and a leg 112 extending perpendicularly and downwardly from an inner end of the connecting portion 111. A lubricant reservoir 14 is formed in the fan base 10 below the bearing 40, which supplies lubricant oil as the fan is operated.
The rotor assembly 20 comprises a generally cup-like fan hub 22 having a top wall (not labeled) and a periphery wall (not labeled). A plurality of fan blades 21 are formed around the periphery wall of the fan hub 22. A pivot axle 23 extends perpendicularly downwards from the top wall of the fan hub 22. A semispherical-shaped guiding portion 230 is formed at a distal, bottom end of the pivot axle 23. An annular slot 232 is defined adjacently above the guiding portion 230 for receiving a ring 50 (shown in FIG. 4) which holds the rotor assembly 20 on the fan base 10.
Referring to FIGS. 2-3, the bearing 40 has a cylindrical shape with a circumferential outer wall 41. A central hole 42 is defined in a central portion of the bearing 40 for receiving the pivot axle 23 therein. A plurality of evenly spaced protrusions 44 extend upwardly from a top end of the outer wall 41. A plurality of evenly spaced bulwarks 45 corresponding to the protrusions 44 are circumferentially formed on the outer wall 41. Each of the bulwarks 45 extends along an axial direction of the bearing 40. The hole 42 includes an upper contact hole 422 providing an entrance of the pivot axle 23, a lower contact hole 426 providing an exit of the pivot axle 23 and a partition hole 424 located between the upper and lower contact holes 422, 426. The partition hole 424 intercommunicates with the upper and lower contact holes 422, 426. The upper contact hole 422 has the same diameter as the lower contact hole 426. The pivot axle 23 has a diameter which is substantially equal to the diameters of the upper and lower contact holes 422, 426 to engage in the upper and lower contact holes 422, 426. The partition hole 424 has a diameter larger than that of the upper and lower contact holes 422, 426, to thereby separate the pivot axle 23 from a corresponding inner surface of the bearing 40. The partition hole 424 extends along the axial direction and has a length which is substantially equal to that of the bulwarks 45 of the bearing 40. The length of the partition hole 424 along the axial direction is much longer than that of the upper and lower contact holes 422, 426.
Referring to FIG. 4, as the rotor assembly 20 with the bearing 40 is assembled on the fan base 10, the protrusions 44 of the bearing 40 abut against a bottom of the connecting portion 111 of the baffle element 110 of the central tube 11, and an inner surface (not labeled) of the circumferential wall (not labeled) of the central tube 11 abuts against the bulwarks 45. The central tube 11 exerts a radially inward pressure on the bearing 40 via the bulwarks 45. Since the bulwarks 45 are located corresponding to the partition hole 424 whose diameter is larger than that of the pivot axle 23, the radially inward pressure is not transferred to the pivot axle 23. Furthermore, since portions of the outer wall 41 of the bearing 40 corresponding to the upper and lower contact holes 422, 426 do not contact with the inner surface of the circumferential wall of the central tube 11, the radially inward pressure is not transferred to theses portions. Accordingly, the radially inward pressure exerted by the central tube 11 on the bearing 40 is not transferred to the pivot axle 23 via the bearing 40. Thus, the bearing 40 is so configured as to not only reduce the contact area between the pivot axle 23 and the bearing 40 but also prevent the radially inward pressure exerted by the central tube 11 on the bearing 40 from being exerted to the pivot axle 23 via the bearing 40, whereby a friction between the bearing 40 and the pivot axle 23 is reduced and the lifespan of the fan is prolonged accordingly. Moreover, the noise generated during operation of the fan is lowered.
Referring to FIGS. 5-8, in a second embodiment of the fan, the fan comprises a fan base, a rotor assembly, a stator assembly and a bearing 40a. The fan base, the rotor assembly and the stator assembly in this second embodiment have the same configuration as in the previous preferred embodiment. The bearing 40a has a cylindrical shape, and has a circumferential outer wall 41a. A central hole 42a is defined in a central portion of the bearing 40a for receiving the pivot axle 23 therein. The central hole 42a has a uniform diameter which is substantially equal to that of the pivot axle 23. A plurality of evenly spaced partition holes 43a communicating with the lubricant reservoir 14 are defined through the bearing 40a and circumferentially around the central hole 42a. The partition holes 43a are separated from the central hole 42a. A plurality of evenly spaced protrusions 44a corresponding to the partition holes 43a extend upwardly from a top end of the outer wall 41a and surround the partition holes 43a. A plurality of evenly spaced bulwarks 45a corresponding to the partition holes 43a are circumferentially formed on the outer wall 41a. A length of the bulwarks 45a along the axial direction is no longer than that of the partition holes 43a. Each of the partition holes 43a can have a uniform width. Alternatively, it can have a wedge-shaped cross section with a width increasing gradually from a top end to a bottom end thereof. The partition holes 43a can channel the lubricant oil flowing upwardly from a gag between the hole 42a and the pivot axle 23 to flow downwards back to the lubricant reservoir 14. The bearing 40a defines the partition holes 43a and the bulwarks 45a corresponding to the partition holes 43a, which effectively prevents the radially inward pressure exerted by the central tube 11 on the bearing 40 from being exerted to the pivot axle 23 via the bearing 40a, whereby a friction between the bearing 40a and the pivot axle 23 is reduced and the lifespan of the fan is prolonged accordingly.
FIG. 9 shows a bearing 40b in accordance with a third embodiment of the present invention. The bearing 40b is a combination of the features of the bearing 40 of the previous first embodiment and the bearing 40a of the previous second embodiment. The bearing 40b defines a central hole 42b and a plurality of evenly spaced slots 43b therein. The central hole 42b has the same configuration as the central hole 42 in the previous first embodiment and includes an upper contact hole 422b, a lower contact hole 426b and a partition hole 424b located between the upper and lower contact holes 422b, 426b. The partition hole 424b has a diameter larger than that of the upper and lower contact holes 422b, 426b, to thereby separate the pivot axle 23 from a corresponding inner surface of the bearing 40b. The slots 43b have the same configuration as the partition holes 43a in the previous second embodiment. The slots 43b communicating with the lubricant reservoir 14 are defined through the bearing 40b and circumferentially around the central hole 42b. The slots 43b are separated from the central hole 42b. A plurality of evenly spaced protrusions 44b corresponding to the slots 43b extend upwardly from a top end of an outer wall 41b. A plurality of evenly spaced bulwarks 45b corresponding to the slots 43b are circumferentially formed on the outer wall 41b. The bulwarks 45b are also located corresponding to the partition hole 424b. The design of the bearing 40b in accordance with the third preferred embodiment can more effectively prevent the friction between the bearing 40b and the pivot axle 23.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Patent Application
20080031737
