Abstract:
A wheel assembly of luggage comprises a hollow cylindrical bearing for wheel of luggage wherein the bearing is of durable and has a lubrication nature. The hollow cylindrical bearing is further employed in conjunction with two short hollow shafts for prevention a rotational friction between metal axle and wheel to significantly decrease the heat generated between metal axle and plastic wheel when operated, thereby obtaining a number of advantages such as quiet in use, no wheel deformation, reduction in manufacturing cost, and ease of assembly.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a wheel assembly and more particularly to an improved bearing for wheeled luggage. 
     2. Description of Related Art 
     Conventionally, two metal bearings are provided in a wheel of luggage. But this is unsatisfactory because (1) it is relatively high in cost; and (2) it may produce loud sounds when operated. Typically, a metal bearing is not a high quality product required by luggage manufacturer because metal bearings for wheeled luggage do not operate so frequently as a machine bearing. Further, such metal bearings tend to become rusted after a long time of non-use. As such, wheeled luggage does not operate smoothly in most cases. Even worse, the loud sounds produced by a luggage rolling across a supporting surface in an airport often makes the traveler embarrassed. 
     A number of designs have been developed to eliminate the above deficiencies. For example, U.S. Pat. No. 5,134,753, entitled “Luggage Caster” and U.S. Pat. No. 5,295,565, entitled “Wheeled Luggage” both do not employ a metal bearing in the wheel assembly but rather wheel directly. Such designs are disadvantageous because a strong frictional resistance exists between the metal axle and the plastic wheel when luggage rolls across a supporting surface. worse, a considerable heat is generated between the metal axle and wheel when the luggage is loaded and transported a long distance which in turn tends to cause the bore to deform, thereby deactivating the wheel assembly. 
     An improved design that aims at solving the above problem is to mount two washers W on axle in either side of the wheel, i.e., between and attached to the wheel and the inner surface of the wheel mount as shown in FIG.  11 . As such, neither side of the wheel is not in contact with the inner surface of wheel mount. Such washers W aim at decreasing the frictional resistance between the wheel assembly and the wheel mount. However, the above high heat disadvantage still exists when operated. As a result, the problem of deformed plastic wheel is unsolved. 
     Thus, it is desirable to provide an improved bearing for wheeled luggage in order to overcome the above drawbacks of prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a bearing for wheeled luggage wherein a durable hollow cylindrical bearing unit is employed to replace conventional metal bearings for carrying out a rotational friction between axle and wheel, thereby obtaining a number of advantages such as quietness in use, no wheel deformation, reduction in manufacturing cost, and ease of assembly. 
     To achieve the above and other objects, the present invention provides a novel wheel assembly comprising a wheel mount having a central space, two holes on either side thereof; a wheel having a bore in the central portion; and an axle wherein a rotary hollow cylindrical bearing is inserted into the bore, a non-pivotable hollow shaft is further inserted into hollow cylindrical bearing, and axle is inserted through one side hole, bore, and the other side hole to mount wheel to the wheel mount such that no rotational friction between the wheel and axle occurs when wheel is rotating. 
     The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a wheel assembly in accordance with a first embodiment of the present invention; 
     FIG. 2 is a sectional view of FIG. 1; 
     FIG. 3 is an exploded sectional view of a wheel assembly in accordance with a second embodiment of the present invention; 
     FIG. 4 is a sectional view of FIG. 3; 
     FIG. 5 is an exploded sectional view of a wheel assembly in accordance with a third embodiment of the present invention; 
     FIG. 6 is a sectional view of FIG. 5; 
     FIG. 7 is an exploded view of a wheel assembly in accordance with a fourth embodiment of the present invention; 
     FIG. 8 is a sectional view of FIG. 7; 
     FIG. 9 is a perspective view of a hollow shaft in accordance with a fifth embodiment of the present invention; 
     FIG. 10 is an exploded view of a wheel assembly in accordance with a sixth embodiment of the present invention; and 
     FIG. 11 is a sectional view of prior art wheel assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown a wheel assembly constructed in accordance with the first embodiment of the invention comprising a wheel mount  10  having a central space  11 , two holes  12  on either side thereof; a wheel  20  having a bore  21  and an axle  50 . In one aspect of the invention a hollow cylindrical bearing  30  made of durable plastics is employed to replace conventional metal bearings for carrying out a rotational friction between axle  50  and wheel  20 . As shown, there are three slot-like recesses  33  formed from left to right and three slot-like recess  35  formed from right to left in the circumferential surface of hollow cylindrical bearing  30  in which each slot-like recess  33  is located between two slot-like recesses  35  and vice versa. It is seen that the length of each of recesses  33  and  35  is smaller than that of the bearing  30 . Further, such recesses  33  and  35  allow bearing  30  to change its diameter when a force is exerted on the surface thereof. Furthermore, three risers  32  are protruded on the left circumferential edge and three risers  34  are protruded on the right circumferential edge respectively in which each of risers  32  corresponds to a slot-like recess  33  and each of risers  34  corresponds to a slot-like recess  35 . The outer diameter of each of risers  32  and  34  is larger than the bore  21  and is equal to the inner diameter of the shoulder  210 . A circumferential flange  41  is formed on the external end of hollow shaft  40 . The outer diameter of circumferential flange  41  is larger than the bore  36  of hollow cylindrical bearing  30 . The outer diameter of the cylindrical body of hollow shaft  40  is equal to (or a little bit smaller than) the inner diameter of the bore  36  of hollow cylindrical bearing  30 . 
     FIG. 2 illustrates the assembly process of the wheel shown in FIG.  1 . First, apply a contraction force on the circumferential surface of hollow cylindrical bearing  30  to make the outer diameter of risers  32  slightly smaller than the bore  21  if the assembly process begins from right side of wheel as shown. Then insert hollow cylindrical bearing  30  into bore  21  until risers  32  and  34  engage against the inner surfaces of shoulders  210  respectively. As shown, the shoulders  210  are flush with risers  32  and  34 . Then insert hollow shafts  40  into the hollow cylindrical bearing  30  from both sides. Then put wheel  20  in the space  11 . Then insert axle  50  through one side hole  12 , bore  21 , and the other hole  12  to mount wheel  20  to the wheel mount  10  until the head  51  of axle  50  engages against one outer surface of wheel mount  10 . Finally, hammer the other recessed end  52  into an enlarged portion  52 A to lock axle  50  into place in order to form a complete wheel assembly. 
     As shown, hollow cylindrical bearing  30  is secured to hollow shafts  40 . Further, there is a small gap between hollow cylindrical bearing  30  and bore  21  as such there is a rotational friction between hollow cylindrical bearing  30  and bore  21  as well as a rotational friction between hollow cylindrical bearing  30  and hollow shafts  40  and no rotational friction between the wheel  20  and axle  50  when wheel  20  is rotating. Additionally, hollow cylindrical bearing  30  and hollow shafts  40  are made of hard durable thermoplastic and have a lubrication nature. It is found by the inventor that hollow cylindrical bearing  30  and hollow shafts  40  nearly have the same performance as the conventional metal bearing. 
     Referring to FIGS. 3 and 4, there is shown a wheel assembly constructed in accordance with the second embodiment of the invention. This embodiment is generally configured the same as the first embodiment and thus only the difference therebetween is described below. The difference is that two short hollow shafts  40  are replaced by a single hollow shaft  40 A having the same length as hollow shafts  40 . The assembled wheel assembly is shown in FIG. 4 in which hollow shaft  40 A has the same functionality as hollow shafts  40  shown in FIG.  2 . 
     Referring to FIGS. 5 and 6, there is shown a wheel assembly constructed in accordance with the third embodiment of the invention. This embodiment is generally configured the same as the second embodiment and thus only the difference therebetween is described below. The difference is that axle  50  is replaced by a novel axle  50 A consisting of a left axle section  501 , a spring  502 , and a right axle section  503 . Thus, no riveting operation is required for the axle  50 A thus easing assembly. 
     Referring to FIGS. 7 and 8, there is shown a wheel assembly constructed in accordance with the fourth embodiment of the invention. This embodiment is generally configured the same as the first embodiment and thus only the difference therebetween is described below. The difference is that the slot-like recesses  32  and  34  oh the circumferential surface  37  of hollow cylindrical bearing  30  in the first embodiment are replaced by two smooth circumferential surfaces  37  of hollow cylindrical bearings  30 A. Thus, two separate insertions of hollow cylindrical bearing  30 A into bore  21  are required. If necessary, a number of axial grooves  35  are provided on the circumferential surface  37  of hollow cylindrical bearings  30 A as shown in FIG.  7 . These grooves  35  may be filled with lubricating oil so as to further reduce rotational friction between wheel  20  and hollow cylindrical bearing  30 A. As the rest of assembly process and the functionality of such wheel assembly are generally the same as the first embodiment, a detailed description thereof will be omitted herein for the sake of brevity. 
     Referring to FIG. 9, there is shown a hollow shaft constructed in accordance with the fifth embodiment of the invention. Other components of the wheel assembly of this embodiment are omitted herein for the sake of brevity. This embodiment is general configured the same as fourth embodiment and only a different therebetween is described below The difference is that a number of axial grooves  43  are provided on the circumferential surface of hollow shaft  40 A. These grooves  43  are filled with lubricating oil so as to further reduce rotational friction between the hollow shaft  40 A and the hollow cylindrical bearing  30 . Moreover, if available, a number of annular cavities  44 - 44  may be further provided on the inner side of circumferential flange  41  of hollow shafts  40 . These cavities  44 - 44  may be filled with lubricating oil (or served as a dust collector) so as to further reduce rotational friction between the hollow shaft  40 A and the hollow cylindrical bearing  30  and  30 A. 
     Referring to FIG. 10, there is shown a wheel assembly constructed in accordance with the sixth embodiment of the invention. This embodiment is generally configured the same as the fourth embodiment and thus only the differences therebetween are described below The differences are that a number of grooves  35  on the hollow cylindrical bearing  30 A of fourth embodiment are replaced by a number of axial elongate projections  38  provided on the circumferential surface  37  of hollow cylindrical bearing  30 B and the same number of corresponding axial elongate recesses  211  provided on the inner surface of bore  21  of wheel  20 A for receiving the projections  38  when assembled. As such, the wheel  20 A and the hollow cylindrical bearings  30 B are combined with one unit and the hollow shafts  40 A and the axle  50  firmly fixed together as another one unit, the only rotational friction relationship is existed between the hollow cylindrical bearings  30 B and the hollow shafts  40 A obtaining a same function of the first embodiment as mentioned above. Of course a number of axial grooves  43  may be further provided on the outer surface of cylindrical portion of the hollow shaft  40 A and the grooves  43  may be filled with lubricating oil so as to further reduce rotational friction between the hollow shaft  40 A and the hollow cylindrical bearing  30 B as mentioned above. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.