Abstract:
An improved wheel is disclosed which is capable of traversing small obstacles easily without having to mount over the obstacle. The wheel design includes a wheel hub having an axis of rotation and a wheel rim coupled to the hub by a plurality of spokes. The wheel rim is formed in the shape of an annular sinusoidal wave having a plurality of alternating crests and troughs extending away from a center line by an amplitude. The wheel rim is configured such that the spokes couple to the rim at the center line at an intersection of the crests and troughs. The spokes are separated from each other by a space extending from the wheel rim to the hub.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to wheels for traversing rough terrain. 
     BACKGROUND OF THE INVENTION 
     The basic function of the wheel has remained unchanged for centuries. Wheels are generally designed to propel a device in a direction dictated by the direction of the rotation of the wheel. Generally, a smooth, regular and even surface is required for the proper function and smooth running of the wheel. 
     Many prior attempts have been made (see prior art) to improve the wheels ability to overcome common obstacles such as stairs, curves, and rugged terrain. The most common approach has been to arrange multiple wheels in a circular fashion. All of the wheels are able to rotate around a common centre, when the wheel encounters a regularly shaped obstacle. All these wheels are rotating in the same plain. Although the prior art serves the basic function of allowing the wheel to mount a curve or ascend stairs the action is a hit, stop and then roll kind of movement. Essentially the wheel hits the obstacle and stops before the next wheel can be rotated around to make contact with the next elevation. This is not a smooth transfer from wheel to wheel. This approach also limits the size of the wheels as multiple wheels are needed. Therefore, what is required is a wheel design which permits the wheel to overcome obstructions in an entirely different way. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, there is provided an improved wheel design which is capable of traversing small obstacles easily without having to mount over the obstacle. The wheel design includes a wheel hub having an axis of rotation and a wheel rim coupled to the hub by a plurality of spokes. The wheel rim is formed in the shape of an annular sinusoidal wave having a plurality of alternating crests and troughs extending away from a center line by an amplitude. The wheel rim is configured such that the spokes couple to the rim at the center line at an intersection of the crests and troughs. The spokes are separated from each other by a space extending from the wheel rim to the hub. 
     In accordance with another aspect of the present invention, there is provided a drive train for driving a load over rough terrain, the drive train including first and second wheels in locked rotational relationship with each other. Each wheel has a wheel hub and a wheel rim. The wheel rim being formed in the shape of an annular sinusoidal wave having a plurality of alternating crests and troughs extending away from a center line by an amplitude. The wheel rim is configured such that the spokes couple to the rim at the center line at an intersection of the crests and troughs. The wheels are configured such that the first and second wheels are biased towards parallel rotational planes. The wheel hubs are configured to pivot such that the first and second wheels can pivot out of the parallel rotational planes. 
     In accordance with another aspect of the present invention, there is provided wheel configured to traverse small obstacles with ease, the wheel including a wheel hub having an axis of rotation and a wheel rim coupled to the hub by a plurality of spokes. The wheel rim is formed in the shape of an annular sinusoidal band having a plurality of alternating crests and troughs extending away from a center line by an amplitude, the band having a width less than the amplitude. Finally, the wheel rim is configured such that the spokes couple to the rim at the center line at an intersection of the crests and trough. 
     With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is side view of a wheel made in accordance with the present invention showing the hub portion at an angle from the rotational plane of the wheel. 
         FIG. 2  is a front view of the wheel shown in  FIG. 1  showing the hub portion in the same plane as the rotational plane of the wheel. 
         FIG. 3  is an isometric view of the wheel shown in  FIG. 1  showing the parts of the hub portion. 
         FIG. 4  is a top view showing the ban portion of the rim portion of the wheel shown in  FIG. 1 . 
         FIGS. 5   a  through  5   e  are side views showing a wheel made in accordance with the present invention traversing over an obstacle. 
         FIG. 6   a  through  6   e  are front views showing the wheel of  FIG. 5  traversing over the obstacle shown in  FIGS. 5   a  through  5   e.    
         FIG. 7  is a side view of a wheel made in accordance with the present invention having six spokes. 
         FIG. 8  is a side view of a wheel made in accordance with the present invention having only three spokes. 
         FIG. 9  is an isometric view of the hub portion of a wheel made in accordance with the present invention. 
         FIG. 10  is a front view of a drive train made in accordance with the present invention. 
         FIG. 11  is a front view of the drive train of  FIG. 10  traversing an obstacle. 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , the present invention consists of a wheel, shown generally as item  10 , which consists of a rim  12  mounted to a hub portion  14  via a plurality of spokes  16 . As seen in  FIG. 2 , rim  12  consists of a sinusoidal shaped band  18  having a width  20  and having a plurality of alternating crests  22  and troughs  24  which extend away from a center line  26  by an amplitude  28 . Width  20  is less than amplitude  28  so that an inner lip  22   a  of each crest and an inner lip  24   a  of every trough is spaced away from center line  26  so as to leave a space wherein an obstacle may pass. Hub  14  has a rotational axis  11  which is the natural rotational axis of the hub. 
     As best seen in  FIG. 3 , hub portion  14  includes an inner (or central) hub portion  32 , a middle portion  34  surrounding the central/inner hub portion  32  and an outer hub portion  36  surrounding the middle portion. Central hub portion  32  has the rotational axis  11 , while middle portion  34  is pivotally coupled to central hub portion  32  at a first pivotal axis  38  and the outer hub portion  36  is pivotally coupled to middle portion  34  at a second pivotal axis  40 . Pivotal axis  36  and  38  are 90° from each other, and rotational axis  11  is 90° from both axis  36  and  38 . Essentially, hub portions  32 ,  34  and  36  form a universal joint (U joint) allowing wheel rim  12  to pivot into a plurality of different positions. 
     As best seen in  FIG. 4 , band  18  consists of a ribbon of rigid material which is in the shape of a sinusoidal wave which is joined at opposite ends  3  and  5  to form wheel rim  12 . Crests  22  and troughs  24  are formed on band  18  and are spaced away from center line  26  by amplitude  28 . As mentioned above, band  18  has a width  20  which is less than amplitude  28  so as to leave spaces between the center line  26  and inner lips  22   a  and  24   a . Spokes  16  attach to band  18  at the intersection points  30  on the center line  26  which are formed at the junction of the crests and troughs. In the example shown in  FIGS. 1 through 4 , band  18  has a “wavelength” of three, meaning it has three pairs of troughs and crests; therefore, there are six intersection points  30 . The preferred number of spokes for the particular embodiment shown in  FIGS. 1 through 4  is therefore six. However, it is possible to build a wheel in accordance with the present invention which has a “wavelength” of either more or less than three, in which case the number of intersecting points will be either more or less than six, respectively. Furthermore, it is possible to attach a spoke to the rim at every intersecting point (as seen in  FIG. 7 ) or at every other intersecting point, therefore making a wheel with only three spokes (as seen in  FIG. 8 ). 
     Referring now to  FIG. 9 , central hub portion  32  has a rotational axis  11 . For the wheel to operate, central hub portion  32  will be rotatably mounted to an axel  15  which is coaxial with the axis of rotation. Essentially, middle portion  32  of the hub is perpendicular to axel  15  and axis of rotation  11 . Middle portion  34  is pivotally attached to central portion  32  by axis  38  and outer portion  36  is pivotally attached to middle portion  34  by axis  40 . Preferably, portions  32 ,  34  and  36  are configured such that they are biased into an aligned position where all three are co-planar so that the wheel maintains a rotation in the same plane (a rotational plane) which is perpendicular to the axis of rotation  11 . This aligned position (or orientation) can be seen in  FIGS. 2 and 6   a  where there is a plane of rotation wherein the wheel rim and the parts of the hub are all on the same plane. In this aligned position, first pivotal axis  36  and second pivotal axis  38  are co-planar (i.e. in the same plane). Since the various parts of the hub are configured to form a flexible connection between the central hub portion and the rim, it is possible for the wheel, and in particular the wheel rim, to pivot out of this aligned position and into a plurality of other positions. Hence, as seen in  FIGS. 5   c  and  6   c , the wheel can be pivoted into a position wherein the wheel rim is at an angle from the axis of rotation of the hub. Preferably, springs or resilient members can be incorporated into pivotal axis  36  and  38  so as to bias the wheel into its aligned orientation. 
     Alternatively, it is possible to build hub  14  as a single piece of deformable yet resilient material such as rubber or elastic plastic which would naturally bias the wheel into the position wherein the axis of rotation for the entire wheel is aligned with the axis of rotation of the hub (i.e. the rotational axis of the wheel is perpendicular to the axis of rotation of the hub), but yet the wheel could be forced into a plurality of positions wherein the rotational plane of the wheel (particularly the rim of the wheel) is not perpendicular to the rotational axis of the hub. A disc of this resilient and flexible material could be used to form a continuous piece extending from the hub to the spokes. Several suitable rubber and plastic compositions exist for making a one piece hub having the property of biasing the wheels rotational plane into a perpendicular orientation relative to the axis of rotation of the hub yet allowing the wheels rotational plane to be moved out of the perpendicular angle with respect to the rotational axis of the hub. It is possible that the same resiliently flexible material could be used to form both the hub and the spokes—provided the structure of the hub and spokes allowed for pivotal movement out of the aligned position and biasing towards the aligned position. 
     On a level surface a wheel made in accordance with the present invention behaves much like a standard circular wheel. To better understand how this invention responds to an obstacle please refer to  FIGS. 5   a  through  5   e  and  FIGS. 6   a  through  6   e . From  FIGS. 5   a  and  6   a , we can see that as the wheel encounters an obstacle  100  the sinusoidal rim  12  catches on the obstacle  100 . The primary rotation of the wheel continues in its original direction. This forward movement causes the wheel to pivot on its hub out of the aligned position as seen in  FIGS. 5   a  and  6   a  and into a position wherein the plane of rotation of the wheel is at an angle from axis  11  and axel  15 . The primary momentum of the wheel causes the wheel, which is now pivoted out of its aligned position, to essentially tumble over obstacle  100  (see  FIGS. 5   b  and  6   b  to  FIGS. 5   d  and  6   d ). The interior curve of the sinusoidal member steps smoothly over or on to the obstacle. The unique combination of the sinusoidal rim and the pivoting hub allow the pivoting, and recovering action to happen smoothly. The wheel simply roles along the continuous curve of the sinusoidal rim regardless of the angle it has pivoted too as it continues in its original direction as dictated by the primary direction of rotation. Once the wheel is again on an even surface and there is no longer pivoting pressure on the sinusoidal rim, the wheel recovers to its original aligned orientation ( FIG. 5   e  and  FIG. 6   e ). This recovery is aided by the means of biasing the wheel into its aligned position. 
     Referring now to  FIGS. 10 and 11 , a pair of wheels made in accordance with the present invention, namely wheels  210  and  212  can be combined to form a drive train  200  wherein the wheels have a common axis of rotation (either in the form of a continuous axel as illustrated or by separate aligned axels). Wheels  210  and  212  are preferably held in locked rotational relationship so that as one wheel rotates, the other wheel rotates in the same way. Wheels  210  and  212  are also preferably aligned so as to be “in phase” meaning that the crests and troughs of the two wheels are horizontally aligned. Wheels  210  and  212  are identical to the wheels discussed previously and each includes a sinusoidal rim  214  and a rotating hub portion  216  which biases the wheels into an aligned position wherein the wheels are biased towards parallel rotational plains oriented perpendicular to the axis of rotation  218 . Hubs  214  of each wheel also has the ability to permit the rim portion of the wheel to pivot relative to the rotational axis of the hub (i.e. pivot away from being perpendicular to axis  218 ). As discussed above, when rim portions  214  of the wheels contact obstacle  220 , the wheels can tilt out of their aligned positions as shown in  FIG. 10  and into a pivoted position as shown in  FIG. 11 . In this pivoted position, the rotational plane of the wheels (particularly of the rim of the wheels) is not perpendicular to the axis of rotation of the hubs (axis  218 ), allowing the rim to traverse obstacle  220  easily. 
     Several factors ensure the smooth functioning of the wheel. The larger the interior curve ( 22   a  and  24   a  of  FIG. 2 ) the larger the obstacle it can overcome. To accommodate this, the width  20  of the sinusoidal member may be reduced. In addition the interior curve ( 22   a  and  24   a ) must pass centerline  26  of the wheel. In the current embodiment, the sinusoidal member is made of a durable, somewhat flexible material such as plastic or rubber. Other materials may also be used separately or in conjunction, in order to improve grip or function. Additionally, a surface texture on the edge of the sinusoidal member, may also aid in gripping surfaces. Preferably, the sinusoidal member is made with a rounded or oval cross section to allow the wheel to roll from a primary surface at the center of the sinusoidal member to the edge of the sinusoidal member and back seamlessly. 
     The unique combination of the sinusoidal rim and the pivoting hub allows the wheel to smoothly traverse obstacles better than a standard wheel. As pressure due to an irregular surface or obstacle is applied to the sinusoidal rim, the hub pivots in the appropriate direction allowing the wheel to traverse the irregularities on the surface with fewer bumps and less jarring on the axel. These wheels can be of particular benefit on robotic or autonomous devices designed to traverse rough terrain; however, if suitable biasing means are adopted, even larger vehicles capable of carrying people can be built using the wheels of the present invention. 
     A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims