SWIVEL WHEEL

Abstract: A swivel wheel device (Fig. 1) is disclosed, designed to be mounted underneath a load bearing surface (21). The swivel wheel device (Fig. 1) comprises a substantially horizontal bar (2) adapted to pivotally turn about a vertical axle (20); at least one of a plurality of main wheels (3), provided at the bottom of the horizontal bar (2), so that the vertical axle (20) lies in the plane of rotation of the main wheel (3); and at least one of a plurality of support wheels (5), provided at the top of the horizontal bar (2), the axis of rotation of the at least one of a plurality of support wheels (5) is aligned radially with respect to the axis of rotation of the bar (2). When the swivel wheel device (Fig. 1) is positioned on a surface and moved in a predetermined direction, the load bearing surface (21) is supported by the at least one support wheel (5), and the bar (2) is caused to swivel about the vertical axle (20) and align the at least one of a plurality of main wheels' plane (see 3) of rotation in the predetermined direction, thus facilitating motion of the device (Fig. 1) in any desired horizontal direction.

Description: SWIVEL WHEEL FIELD OF THE INVENTION The present invention relates to wheels. More particularly it relates to a novel swivel wheel device. BACKGROUND OF THE INVENTION Swivel wheels are known for many years. Swivel wheels or casters are usually small wheels or casters installed in carts, boxes, wagons, chairs or items of furniture, to enable wheeling them around. A swivel wheel usually comprises a wheel, or several wheels, adapted to roll about a horizontal axle, which itself is rotatably attached to a vertical axle, so that the wheel may also swivel about the horizontal axle. When a load, such as a chair provided with swivel wheels, is pushed in order to move it in a particular direction, the swivel wheel swivels about its vertical axes to quickly assume a position where its horizontal axis of rotation is perpendicular to that particular direction, and revolves as the chair is progressed. The quick alignment of the wheel in the direction of motion enables swifter transportation of the load, thus prolonging the wheels effective life. However the vertical axle of convenient swivel wheels tends to break very often, as the load is positioned off the center of the wheel, providing a moment of force, which may be substantial depending on the dimensions of the axles and the weight of the load. The exist prior art swivel wheels that where designed to overcome this problem. Basically a good solution is to provide a wheel that can change its direction of rotation without disengaging from the surface on which it rolls. A known solution comprises a wheel whose horizontal axle on which it rolls is coupled to an annular ring that can rotate about a vertical axis. This is accomplished by providing a ball-bearing mechanism. However the known solutions usually refer to metallic casters provided with ball bearings to support the swivel wheel and withstand greater moment of force. Thus it is needed to provide a swivel wheel that is less prone to breakdown due to excess load, and surmounting moment of force. BRIEF DESCRIPTION OF THE INVENTION It is therefore thus provided, in accordance with a preferred embodiment of the present invention, a swivel wheel device designed to be mounted underneath a load bearing surface, the device comprising: a substantially horizontal bar adapted to pivotally turn about a vertical axle; at least one of a plurality of main wheels, provided at the bottom of said horizontal bar, so that said vertical axle lies in the plane of rotation of said main wheel; at least one of a plurality of support wheels, provided at the top of said horizontal bar, the axis of rotation of said at least one of a plurality of support wheels is aligned radially with respect to the axis of rotation of said bar; whereby when said device is positioned on a surface and moved in a predetermined direction, the load bearing surface is supported by said at least one support wheel, and said bar is caused to swivel about said vertical axle and align said at least one of a plurality of main wheels' plane of rotation in said predetermined direction, thus facilitating motion of said device in any desired horizontal direction. Furthermore, in accordance with a preferred embodiment of the present invention, said bar provided with vertical freedom to slide up and down so as to allow said load-bearing surface to rest on top of said at least one of a plurality of support wheels. Furthermore, in accordance with a preferred embodiment of the present invention, there is provided a swivel wheel device designed to be mounted underneath a load bearing surface, the device comprising: a substantially horizontal bar adapted to pivotally turn about a vertical axle; at least one of a plurality of main wheels, provided at the bottom of said horizontal bar, so that said vertical axle lies in the plane of rotation of said main wheel; two support wheels, provided at the top of said horizontal bar, the axis of rotation of said two support wheels is aligned radially with respect to the axis of rotation of said bar; whereby when said device is positioned on a surface and moved in a predetermined direction, the load bearing surface is supported by said two support wheel, and said bar is caused to swivel about said vertical axle and align said at least one of a plurality of main wheels' plane of rotation in said predetermined direction, thus facilitating motion of said device in any desired horizontal direction. Furthermore, in accordance with a preferred embodiment of the present invention, said at least one of a plurality of main wheels is partially sunken in a cavity provided on said bar. Furthermore, in accordance with a preferred embodiment of the present invention, said two support wheels are each partially sunken in a cavity provided on said bar. Furthermore, in accordance with a preferred embodiment of the present invention, said at least on of a plurality of main wheels is provided with axle which is snapped in position inside matching carriers provided on the bar. Furthermore, in accordance with a preferred embodiment of the present invention, said bar has lateral opposite arcuate extensions, and wherein each of said support wheels is mounted in a cavity on one of said extensions. Furthermore, in accordance with a preferred embodiment of the present invention, each of said support wheels is provided with axle which is snapped in position inside matching bores provided on the sides of said cavity. Furthermore, in accordance with a preferred embodiment of the present invention, said vertical axle is provided with two opposite resilient flaps having a rim at their ends, so as to allow snapping of said rim into a bore provided on the load bearing surface. Furthermore, in accordance with a preferred embodiment of the present invention, said load bearing surface is a planar surface. Furthermore, in accordance with a preferred embodiment of the present invention, said load-bearing surface is provided with a round protrusion, so as to shorten the required length of said vertical axle, thus reducing the moment experienced by said axle. Furthermore, in accordance with a preferred embodiment of the present invention, said load bearing surface is further provided with an annular rim serving as protection against inadvertent jamming by external obstacles. Furthermore, in accordance with a preferred embodiment of the present invention, said device is made of plastic material. Furthermore, in accordance with a preferred embodiment of the present invention, said device is made of material selected from POM, polyamide, polypropylene or polybutylenetelphtalate. Furthermore, in accordance with a preferred embodiment of the present invention, said substantially horizontal bar is provided with voids so as to enhance its dimensional stability and reduce its overall weight. Finally, in accordance with a preferred embodiment of the present invention, said two support wheels are positioned so that an imaginary arc tangent to said support wheels planes of rotations is not tangential to the axis of rotation of the main wheel, so as to prevent flapping of said support wheels, due to instable balance of the forces acting on the support wheels. BRIEF DESCRIPTION OF THE FIGURES In order to better understand the present invention, and appreciate its practical applications, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention as defined in the appending Claims. Like components are denoted by like reference numerals. Figure 1 illustrates an isometric view of a swivel wheel device seen upside- down, having a pair of support wheels, in accordance with a preferred embodiment of the present invention, underneath a load-bearing surface. Figure 2 illustrates an elevated view of a swivel wheel device shown in Figure 1 , in accordance with a preferred embodiment of the present invention, detached from the load-bearing surface. Figure 3 illustrates another isometric view of the swivel wheel, seen in Figure 1. DETAILED DESCRIPTION OF THE INVENTION AND FIGURES A main aspect of the present invention is the provision of a swivel wheel comprising a main wheel having a horizontal axis of rotation, that is placed on a horizontal bar, positioned underneath a load-bearing surface and rotatble about a vertical axle. The swivel wheel partially or fully projects underneath the horizontal bar, away from its lower surface. The horizontal bar is also provided with at least one support wheel having a horizontal rotation axis which extends radially from the rotation axis of the bar, and is allowed to have contact with the lower part of the load-bearing surface. The horizontal bar is allowed to swivel substantially freely about the vertical axle, so that when the load bearing-surface is moved in a particular horizontal direction, the main wheel readily aligns behind the axle in the direction of motion. The support wheel bears the load of the load-bearing surface lying over it, sharing the load with the vertical axle, and thus balancing the moment of force and substantially eliminating the risk of a collapse of the axle. Besides sharing the load with the vertical axle, the support wheel also smoothes the rotation of the horizontal bar and its alignment with the vertical axle in the direction of motion. The horizontal bar is made to turn freely about the vertical axle. Moreover, the horizontal bar is allowed certain freedom of vertical motion in order to facilitate resting of the load bearing surface on the support wheel. This may be accomplished by providing a degree of freedom in the form of relative motion between the bar and the vertical axle, or between the vertical axle and the load bearing surface. The invention is better appreciated with reference to the accompanying Figures. Reference is made to Figure 1 , illustrating an isometric view of a swivel wheel seen upside-down, having a pair of support wheels, in accordance with a preferred embodiment of the present invention. A horizontal bar 2 is provided, here in the form of a frame, having a top side 15 and a bottom side 16. The horizontal bar 2 is provided with a vertical axle 20, which extends vertically from said bar's top side and is pivotally engaged to a load-bearing surface. The bar is allowed to turn substantially freely about that axle and has a small freedom to vertically slide up and down, though it is prevented from disengaging from the load-bearing surface completely. The load-bearing surface is preferably provided with a round protrusion 25, so as to shorten the required length of the vertical axle 20, thus reducing the moment experienced by said axle. A main wheel 3 is provided on the horizontal bar 2, partially sunken in a cavity 33 provided on the horizontal bar, with its plane of rotation parallel to the vertical axle, and partially protruding from horizontal bar 2 downwardly. The axle 12 of the main wheel is engaged on both sides to matching carriers 30 provided on the bar. Reference is now made to Figure 2 illustrating an elevated view of a swivel wheel device shown in Figure 1 , in accordance with a preferred embodiment of the present invention, detached from the load-bearing surface. Bar 2 is provided with lateral opposite arcuate extensions 31 , and on the top side of these extensions two support wheels 5 are provided, one support wheel on each extension, each partially sunken in a cavity 7 and protruding from that cavity. The axis of rotation of the support wheels 5 is aligned radially with respect to the vertical axle (and hence the bar's) axis of rotation. The rotation axle 6 of each of the support wheels 5 is snapped in position inside matching bores 32 provided on the side walls of each cavity 7. a protrusion 34, which is in fact the wall of cavity 33 (see Fig. 1), bulges from bar 2, but does not interfere with the smooth operation of the swivel wheel device, as it is comfortably accommodated between the support wheels. Note, however that protrusion 34 has to be lower than support wheels 5 so that they may come in contact with the load-bearing surface. It is noted that the arrangement of the support wheels in an arcuate arrangement, allows bar 2 to comfortably turn about the vertical axle 20 axis of rotation, facilitating a smooth ride. This is accomplished because the support wheels axis of rotation in the device of the present invention is aligned radially to the vertical axis of rotation of the bar. Note also that while the embodiment disclosed in the Figures is provided with lateral arcuate extensions, support wheels may be provided in an arcuate arrangement on a bar that is wide enough to accommodate these wheels laterally. In this case there would be no need for lateral extensions, and yet this embodiment would still remain within the scope of the present invention. The vertical axle 20 is preferably provided with two opposite resilient flaps 36, with a rim 37 at their ends, so that they can be snapped into a bore provided on the load bearing surface, and remain engaged. However other methods of engagement of the vertical axle to the load-bearing surface may be used, yet still remain within the scope of the present invention. Figure 3 illustrates another isometric view of the swivel wheel, seen in Figure 1. The bottom of the load bearing surface 21 is preferably a planar surface so that it presents no obstacle to the swiveiing horizontal bar. It may be provided with a defined track 35 (sunk or elevated) for the support wheels. An optional annular rim 22 may provide the swivel wheel device of the present invention some protection against inadvertent jamming caused by external obstacles. The swivel wheel of the present invention is in particular appealing to the plastic industry, suitable to be made of plastic products and components, as all its parts may be manufactured from plastic materials, such as POM, polyamide, polypropylene, polybutylenetelphtalate and the like. The device of the present invention may be therefore be manufactured in various plastic manufacturing processes, such as injection molding. The swivel wheel of the present invention may therefore be made to posses a light weight which is another advantage rendered when using plastic materials. The voids 10 provided on the horizontal bar, as shown in the embodiment presented in the figures, are material releases, a fairly standard procedure in plastic injection molding, aimed at reducing the susceptibility of the molded bar to distortion during manufacture, and hence enhancing its dimensional stability and reducing its overall weight. In the swivel wheel of the present invention the support wheels substitute ball bearings to provide the main wheel the maneuverability it needs to be able to swiftly rotate in 360° degrees and quickly assume the desired direction. Configuration with at least two support wheels is recommended as providing at least two supporting points release the vertical axle from the moment of force applied on it by the load-bearing surface above it. However providing the swivel wheel device of the present invention with a single support wheel would suffice to allow it to perform. Provision of more than two support wheels is also possible, and allows the swivel wheel device of the present invention to bear heavier loads, yet it seems that two support wheels would do for most tasks anticipated. It is recommended to position the support wheels so that the imaginary arc tangent to their planes of rotations is not tangential to the axis of rotation of the main wheel, as that may cause the support wheels to flap, presenting jittery motion, due to instable balance of the forces acting on the wheels. Note also that although the embodiments shown in the accompanying Figures have only one main wheel, it is possible to add more main wheels on the bottom of the horizontal bar 2 provided they are properly aligned. It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following Claims. It should also be clear that a person skilled in the art, after reading the present specification could make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the following Claims.

Claims: C L A I M S 1. A swivel wheel device designed to be mounted underneath a load bearing surface, the device comprising: a substantially horizontal bar adapted to pivotally turn about a vertical axle; at least one of a plurality of main wheels, provided at the bottom of said horizontal bar, so that said vertical axle lies in the plane of rotation of said main wheel; at least one of a plurality of support wheels, provided at the top of said horizontal bar, the axis of rotation of said at least one of a plurality of support wheels is aligned radially with respect to the axis of rotation of said bar; whereby when said device is positioned on a surface and moved in a predetermined direction, the load bearing surface is supported by said at least one support wheel, and said bar is caused to swivel about said vertical axle and align said at least one of a plurality of main wheels' plane of rotation in said predetermined direction, thus facilitating motion of said device in any desired horizontal direction. 2. The device as claimed in Claim 1 , said bar provided with vertical freedom to slide up and down so as to allow said load-bearing surface to rest on top of said at least one of a plurality of support wheels. 3. A swivel wheel device designed to be mounted underneath a load bearing surface, the device comprising: a substantially horizontal bar adapted to pivotally turn about a vertical axle; at least one of a plurality of main wheels, provided at the bottom of said horizontal bar, so that said vertical axle lies in the plane of rotation of said main wheel; two support wheels, provided at the top of said horizontal bar, the axis of rotation of said two support wheels is aligned radially with respect to the axis of rotation of said bar; whereby when said device is positioned on a surface and moved in a predetermined direction, the load bearing surface is supported by said two support wheel, and said bar is caused to swivel about said vertical axle and align said at least one of a plurality of main wheels' plane of rotation in said predetermined direction, thus facilitating motion of said device in any desired horizontal direction. 4. The device as claimed in Claim 3, wherein said at least one of a plurality of main wheels is partially sunken in a cavity provided on said bar. 5. The device as claimed in Claim 3, wherein said two support wheels are each partially sunken in a cavity provided on said bar. 6. The device as claimed in Claim 4, wherein said at least on of a plurality of main wheels is provided with axle which is snapped in position inside matching carriers provided on the bar. 7. The device as claimed in Claim 3, wherein said bar has lateral opposite arcuate extensions, and wherein each of said support wheels is mounted in a cavity on one of said extensions. 8. The device as claimed in Claim 7, wherein each of said support wheels is provided with axle which is snapped in position inside matching bores provided on the sides of said cavity. 9. The device as claimed in Claim 3, wherein said vertical axle is provided with two opposite resilient flaps having a rim at their ends, so as to allow snapping of said rim into a bore provided on the load bearing surface. 10. The device as claimed in Claim 3, wherein said load bearing surface is a planar surface. 11. The device as claimed in Claim 10, wherein said load-bearing surface is provided with a round protrusion, so as to shorten the required length of said vertical axle, thus reducing the moment experienced by said axle. 12. The device as claimed in Claim 10, wherein said load bearing surface is further provided with an annular rim serving as protection against inadvertent jamming by external obstacles. 13. The device as claimed in Claim 1 wherein it is made of plastic material. 14. The device as claimed in Claim 13 wherein it is made of material selected from POM, polyamide, polypropylene or polybutylenetelphtalate. 15. The device as claimed in Claim 3 wherein it is made of plastic material. 16. The device as claimed in Claim 15 wherein it is made of material selected from POM, polyamide, polypropylene or polybutylenetelphtalate. 17. The device as claimed in Claim 3, wherein said substantially horizontal bar is provided with voids so as to enhance its dimensional stability and reduce its overall weight. 18. The device as claimed in Claim 3, wherein said two support wheels are positioned so that an imaginary arc tangent to said support wheels planes of rotations is not tangential to the axis of rotation of the main wheel, so as to prevent flapping of said support wheels, due to instable balance of the forces acting on the support wheels.

Inventors: BEN MEIR ILAN, BEN MEIR, ILAN
Applicants: BEN MEIR ILAN, PRACTIMA LTD, BEN MEIR, ILAN, PRACTIMA LTD.
Application year: 2000
Main classification: B65G
IPC codes: B60B33