Abstract:
A caster assembly includes a wheel bracket, a wheel attached to the wheel bracket, a shaft about which the wheel bracket is free to rotate, and a cam assembly. The caster assembly is attached to the underside of a caster board, where the shaft is fixed perpendicular to the board, and the cam assembly comprises a cam track fixed to the board with the shaft at its center and a cam follower fixed to the wheel bracket. The cam track is geometrically formed to have a number of valleys and peaks along its circumference. As the wheel bracket rotates about the shaft, the cam follower engages the cam track and causes the board and the wheel assembly to move away and towards each other. The resulting forces generate or maintain a generally forward motion in the caster board, without the need for further efforts by a rider. The caster assembly further permits the rider to travel backwards as well as forwards. The cam track is easily changeable by the rider to accommodate various user preferences and skill levels.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of the following patent application which is hereby incorporated by reference: U.S. patent No. 60/971,257, filed Sep. 10, 2007 
     
    
       [0002]    A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the reproduction of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0003]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX 
       [0004]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0005]    The present invention relates generally to caster assemblies. More particularly, in various embodiments, the present invention relates to caster assemblies for use with ride-on devices. Even more specifically, this invention, in particular embodiments, pertains to an adjustable cam action assembly for improved performance of recreational skate boards, caster boards, and the like. 
         [0006]    There are numerous ride-on devices in the marketplace. Ride-on devices take many forms and may be used for exercise, entertainment or both. They may have a nondescript, mostly functional aesthetic form, like a skateboard or scooter, or they may be made to look like a vehicle, an animal or a fictional character as with many preschool toys. 
         [0007]    Conventional skate boards are generally supported by two-wheeled truck assemblies attached to the undersides of the boards. Such skate boards have long been popular, but are limited in the sense that the rider could realistically accelerate on a level or uphill surface only by removing one of his or her feet from the board and pushing off the ground. Typical such skate boards were also limited in the degree of steering that was possible, as where the turning radius reached a certain angle, the wheels would touch the board. 
         [0008]    There is a desire and need in the marketplace for ride-on products that can be propelled in a way that is more novel than simply pushing off, and that may provide sharper turns if desired. 
         [0009]    Caster boards were subsequently developed to address the limitations of skate boards. U.S. Pat. No. 7,195,259 provides certain examples of caster boards. Caster boards typically have comprised one or two boards, with at least one swivel caster wheel assembly in front and at least one in the rear of the caster board. The rider twists his or her body to the left and to the right to accelerate the caster board or to turn it within a relatively small turning radius. This is accomplished by having the wheels rotate around the wheel axis when the board is twisted in either direction, where the axis is angled with respect to the bottom of the caster board. 
         [0010]    In prior art caster boards, the board rises and falls at a rate predetermined by angle of attachment of the axis as the wheel bracket rotates. The angle can be made steep or slight or somewhere in between by the angle of the connection of the axis. Therefore the ease of operation and speed are inversely proportional to each other within this design and both must be compromised, in typical prior art designs, to achieve a balance between them. Moreover, in common prior art caster boards, the angle of the axis cannot be adjusted by the rider, according to his skill level, chosen activity or preference. In contrast, many sport type ride-on devices, such as BMX bicycles and common skateboards, retain the interest of the user partly due to the fact they can be customized to affect performance via changeable parts such as sprockets, trucks and other paraphernalia. 
         [0011]    Typical prior art caster boards with a fixed angle design are also limited in that propulsion is only unidirectional. This is because most caster boards use the lateral force against the supported weight and the rise of the board as the wheel caster rotates to propel the board. With the angled shaft design there is only one low point on the rotation of the wheel assembly. If the wheel assembly is rotated 180 degrees, the base of the ride-on device is at its highest point, no further rise is possible, and so it cannot be propelled in this direction. 
         [0012]    Some ride-on devices have used a spring to work against the rotation of the wheel assembly along the wheel axis, thus creating a force that replaces the gravitational force used in other prior art devices. This method still provides forward motion resulting from side-to-side, or twisting, forces applied by the rider. However, this does not allow full rotation of the wheel assembly which limits the maneuverability of the ride-on device. Moreover, the spring has a set tension so performance varies greatly with the weight of the rider. 
         [0013]    It is desirable therefore to provide a caster assembly that permits full rotation of the wheel for improved maneuverability. This improved performance may include sharper turns, bi-directional travel, and user-adjustable components for various preferences and/or skill levels as examples. Other needs and potential areas for benefit may be apparent to persons of skill in the art having studied this document. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    It is an object of some embodiments of this invention to provide a caster assembly for ride-on devices such as caster boards that uses a cam to permit bidirectional motion, improve performance, or both, for example, for riders of all sizes. Some embodiment may have other objects or benefits, some of which may be apparent from this document. 
         [0015]    In accordance with some embodiments of the invention, a caster assembly includes a wheel bracket, a wheel attached to the wheel bracket, a shaft about which the wheel bracket is free to rotate, and a cam assembly, for example. In some embodiments, the caster assembly is attached to the underside of a caster board, for instance where the shaft is fixed perpendicular to the board, and the cam assembly may comprise a cam track fixed to the board with the shaft at its center, for example, and a cam follower may be fixed to the wheel bracket in some embodiments. The cam track is geometrically formed to have a number of valleys and peaks along its circumference, in various embodiments. Oscillating lateral forces applied by the rider may cause the wheel bracket to rotate about the shaft and the cam follower to engage and track the valleys and peaks in the cam track, for example. The resulting forces may operate to cause the wheels to roll and maintain a generally forward motion in the caster board, without the need for further efforts by a rider. 
         [0016]    Through the use of various embodiments of the invention, forward motion may be easier to maintain than it is to initiate. Further, in a number of embodiments, the caster assembly further permits the rider to travel backwards as well as forwards. In different embodiments, the cam track may comprise a wide variety of configurations and some embodiments may be easily changeable by the rider to accommodate various user preferences and skill levels, for example. As used herein, “changeable”, when referring to a part such as a cam track, means that the part can be removed and replaced without damaging the part using the skill and tools ordinarily found in homes of most riders of skateboards, caster boards, scooters, and the like. 
         [0017]    In accordance with other embodiments of the caster assembly, the cam track may be attached to the wheel bracket and may actually rotate with the wheel bracket. In some such embodiments, the cam follower(s) is/are fixed to the underside of the caster board, for example, and thus continue(s) to engage the cam track as it rotates around the shaft. In this manner the caster assembly may allow for a variety of cam configurations where aesthetically desirable or functionally necessary, while still maintaining some or all of the improved capabilities of the previously disclosed embodiments. 
         [0018]    While many ride-on devices as contemplated by this invention may require more than one wheel to operate, only one propulsion caster assembly as described may be required. However, the various caster assemblies of the present invention may be used in a variety of combinations with a variety of ride-on devices in some embodiments. The caster assembly may, in addition, comprise a blade instead of a wheel where the ride-on device is to be used on ice. Further, the caster assembly may conceivably be used with devices that are not intended to be ridden such as carts or wagons, as examples. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0019]      FIGS. 1A and 1B  contain a side view and an end view of one embodiment of a caster assembly of the present invention as associated with a caster board. 
           [0020]      FIG. 2  is an end view of one embodiment of a caster assembly of the present invention (no caster wheel attached). 
           [0021]      FIG. 3  contains an exploded perspective view of the caster assembly of  FIG. 2  (no caster wheel included). 
           [0022]      FIGS. 4A to 4C  contain side, perspective, and front views of a wheel, wheel bracket and cam assembly used in one embodiment of the invention. 
           [0023]      FIGS. 5A to 5C  contain side, perspective and front views of another embodiment of the invention. 
           [0024]      FIG. 6  is a side view of another embodiment of a caster assembly in accordance with the present invention (without a wheel attached). 
           [0025]      FIGS. 7A to 7C  contain top, side, and end views of one embodiment of a cam track used with a caster assembly of the present invention. 
           [0026]      FIGS. 8A and 8B  contain side and rear views of another embodiment of a caster assembly in accordance with the present invention. 
           [0027]      FIG. 9  is an exploded perspective view of another embodiment of a caster assembly in accordance with the present invention. 
           [0028]      FIG. 10  is a perspective view of another embodiment of a caster assembly in accordance with the present invention. 
           [0029]      FIG. 11  is a perspective view of another embodiment of a caster board using the caster assembly of the present invention. 
           [0030]      FIG. 12  is a perspective view of still another embodiment of a caster board using a caster assembly of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    One embodiment of the invention is disclosed in  FIGS. 1A and 1B . In this embodiment, a cam action caster assembly  10  is presented for use with a ride-on device  12  having at least one base  14 . Each base  14  has a top side  16  for supporting the feet of a rider and a bottom side  18  to which the caster assembly  10  is attachable. 
         [0032]    Referring now to  FIGS. 2 and 3 , in the embodiment illustrated, the caster assembly  10  includes a wheel  20  supported by a wheel bracket  22 . The wheel  20  is attached so as to rotate freely along its entire circumference. In this embodiment, the wheel bracket  22  is rotatably connected to a shaft  24  that is fixed perpendicular to the bottom side  18  of the base  14 . In this manner the wheel  20  and the wheel bracket  22  are free to rotate around the shaft  24  and about an axis generally forming a right angle with respect to the base  14 . The benefits of this axis of rotation will be discussed below. 
         [0033]    In some embodiments, friction on the shaft  24  may be reduced, for example, by the use of shaft radial bearings  26  engaging both wheel bracket  22  and shaft  24 . Bearings  26  may be secured to wheel bracket  22  by a bushing  28  having a flange or lip  30  on one side (e.g., on the top) and an external snap ring  32  on the other side (e.g., on the bottom), for example. Once so secured, the bushing  28  may then slide on shaft  24 , for instance. 
         [0034]    Referring to  FIG. 1 , in the embodiment illustrated, cam track  34  is attached to the bottom side  18  of base  14  with shaft  24  at its center. In various embodiments, cam track  34  is shaped such that it has at least on valley  36  and one peak  38 . In the embodiment shown, the two lowest points or valleys  36  of the cam track  34  face to the left and to the right of the ride-on device  12  with respect to motion or a direction in which the device  12  is normally ridden, for example, the long axis or long horizontal dimension of the device  12 . Likewise, the two highest points or peaks  38  of the cam track  34  face forward and to the back of the ride-on device  12  with respect to the normal direction of motion. In other embodiments, the valleys  36  of the cam track  34  may be in front of and behind shaft  24  or at other locations along cam track  34 . 
         [0035]    In the embodiment shown, a cam follower is attached to the wheel bracket  22  by cam bolts  42 . In some embodiments, the cam follower comprises roller followers or cam track radial bearings  40 . The cam track bearings  40  may be secured to the wheel bracket  22  so as to be parallel to each other and to the wheel  20  at all times. The cam track bearings  40  are also equidistant from the center of the wheel bracket  22  at a distance equal to the radius of the cam track  34  in the embodiment shown. Upon rotation of the wheel bracket  22 , each of the cam track bearings  40  engages the cam track  34 . In the embodiment shown, as the cam track bearings  40  engage and trace the cam track  34  from a low point  36  to a high point  38 , a distance between the wheel  20  and the base  14  subsequently increases. Likewise, as the cam track  34  is followed by cam track bearings  40  from the high point  38  back to a low point  36 , the distance between the wheel  20  and the base  14  decreases. As such, the more pronounced the difference between the valleys  36  and peaks  38  of the geometry of the cam track  34 , the greater the effect on the distance between the wheel  20  and the base  14 , with results that will become apparent below. 
         [0036]    In some embodiments of the caster assembly  10 , for example, a helical spring  44  is positioned over the end of shaft  24  and may be secured in place by subsequently threading a shaft bolt  46  into the end, for instance. As the wheel bracket  22  rotates around cam track  34 , in this embodiment spring  44  is compressed by wheel bracket  22  traveling down or away from bottom side  18  of base  14 . In this embodiment, spring  44  acts to keep wheel  20  and wheel bracket  22  from rotating freely (i.e., around shaft  24 ) when wheel  20  is not making contact with a riding surface, such as during an airborne maneuver, for example. 
         [0037]      FIGS. 4A to 4C  illustrate another embodiment of a caster assembly having a cam. Other embodiments of the caster assembly  10  of the present invention can be viewed in  FIGS. 5A to 6 .  FIGS. 7A to 7C  demonstrate an embodiment of the cam track  34  specifically. Although not shown in  FIG. 7B , in a number of embodiments cam track  34  may contain holes for fasteners to secure cam track  34  to base  14 , for example (e.g., as shown in  FIG. 3 ). 
         [0038]    With one or more caster assemblies  10  as described mounted to a ride-on device  12 , in this example a caster board, motion may be started with a push by the rider. The supported weight on cam bearings  40  causes them to seek the valleys  36  of the cam track  34 . As a sufficient twisting and/or side-to-side force is applied, e.g., swizzling, the cam bearings  40  overcome this tendency in proportion to the twisting and/or the side to side force applied. As a result, the cam bearings  40  travel from the valley  36  of the cam track  34  toward the peak  38  of same. 
         [0039]    With the cam action of this embodiment of the invention as described, the rise and fall of the base  14  is not limited to a predetermined rate by the axis angle of attachment as the wheel bracket  22  rotates. Using a cam allows more control over the rise and fall of the device, and therefore more control over performance when compared to an angled caster without a cam. By its shape, the cam track  34  can cause the base  14  to rise and fall modestly at first and accelerate the angle of action as the caster assembly  10  rotates further around the cam track  34  and its axis. This means that a cam track  34  can make the ride-on device  12  easy to set into beginning motion, yet still offer the potential for greater speed within a single configuration. Therefore a cam track  34  effectively reduces the opposition of these two characteristics of performance in a ride-on device  12  using such a caster assembly  10 . 
         [0040]    For example, a cam track  34  having a steeper angular incline with respect to the base  14  may raise the base  14  higher and more quickly, and permit the rider to move the device at greater speeds when side to side force is applied, with the caveat that such an angle may make the ride-on device  12  more difficult to set in motion and control. A cam track  34  with a flatter angular incline with respect to the base  14  will facilitate easier starts and enable turns and tricks such as a 180 or 360 degree spin, for example. However, a flatter angular incline will decrease the ability to accelerate to higher speeds. 
         [0041]    A cam track  34  having a wider radius also allow greater speeds with a lower profile cam track. As such, some embodiments of the invention offer a variety of configurations of cam tracks  34  that may easily be changeable by the rider, for example, to adjust the performance of the ride-on device  12  to match skill level, chosen activity or preference. In some embodiments, a cam track  34  may be changeable simply be detaching it from the base  14  using conventional fasteners and may be interchangeable with other shape or height cam tracks  34 , for example. Where a wider radius for the cam track  34  is desired for improved leverage and greater response by the caster assembly  10  to lateral forces, other components such as the cam bearings  40  may also be detachable and interchangeable. 
         [0042]    In various embodiments of ride-on devices  12 , the most stable positions of the device  12  are where the caster  10  is at its low points  36 . This is because gravity always causes the device  12  to seek its lowest point. The higher the base  14  is pushed by the rotation of the caster  10 , the more it gravitates toward a lower position. With the cam track  34  of certain embodiments, including the embodiments shown, complementing low positions  36  are available in both the forward and back positions of the cam track  34  relative to normal motion of ride-on device  12 . This makes changing the direction of the ride-on device  12  (e.g., going backwards) a more stable activity than was possible previously, e.g., with angle-axis caster devices. This opens up a variety of tricks that can be better executed by various embodiments of the invention. 
         [0043]    In another embodiment of the invention, a specialty “trick track” cam track  34  with smaller valleys  36  every ninety degrees rather than merely in the front and rear of the ride-on device  12  can be attached to the caster assembly  10  by the rider, for example. This will make the ride-on device  12  more stable north, south, east and west and able to propel itself in each of these directions. This opens up more possibilities for dancing or freestyle activities, for example. 
         [0044]    Another significant advantage of some embodiments of the invention resides in the integrity of the attachment of the caster assembly  10  to bottom side  18  of base  14 . Cam track  34  allows a vertical attachment as opposed to an angled attachment. Therefore less bending moment is exerted on the connection point when a downward force is applied (such as the weight of the rider, particularly during some sort of landing as from a trick). Because of the bending moment an angle creates, an angled attachment actually acts as a lever to increase force on the single attachment point of the caster. Conversely, the disclosed cam track  34  serves as an additional support for the caster assembly  10 , in some embodiments. This relieves stress placed upon the connection point when a downward force is applied by distributing the force over an exponentially wider area. 
         [0045]    Referring now to  FIGS. 8A and 8B , in another embodiment of the invention, the caster assembly  10  further includes pivot hinge  48  on wheel bracket  22  such that wheel bracket  22  no longer needs to travel up and down shaft  24 . A helical or other shape spring may be affixed to the pivot hinge  48  in this embodiment for the same reason that the helical spring  44  was positioned over the shaft  24  in other embodiments. 
         [0046]    In another embodiment of the invention as displayed in  FIG. 9 , cam track  34  is attached to, or is integral with, wheel bracket  22  and rotates with wheel bracket  22 . In this embodiment, cam follower or cam bearing  40  is fixed (from rotating about shaft  24 , although cam bearings  40  are free to rotate about their own axes) to the bottom side  18  of the base  14 , and engages cam track  34  as it rotates around shaft  24 . In other embodiments, shaft  24  may rotate with cam track  34 . In this manner, caster assembly  10  allows for a variety of cam configurations where aesthetically desirable or functionally necessary, while still maintaining, in some embodiments, some or all of the improved capabilities of the previously disclosed embodiments. 
         [0047]    In the particular embodiment of the invention specifically illustrated in  FIGS. 1A and 1B , the ride-on device  12  comprises two bases  14  connected to each other with a connecting element  50  and having one caster assembly  10  attached to the bottom side  18  of each base  14 . In various embodiments, boards  14  may be adapted to support a rider&#39;s feet. For example, boards  14  may be of sufficient strength to support a rider and may be made of a material having a relatively high coefficient of friction with the sole of a typical shoe that may be worn when riding a ride-on device  12  of the embodiment. The caster assembly  10  may also work with numerous other embodiments of ride-on devices  12 . 
         [0048]      FIG. 10  illustrates a ride-on device  12  having a front board  14   a  and a rear board  14   b  with a connecting element  50  having elastic properties connected between the two boards  14   a, b . In this embodiment, the front board  14   a  is attached to a steering column  52  having a wheel bracket  22  such that the wheel  20  is able to pivot about the axis of the steering column  52 . A cam action caster assembly  10  is attached to the underside  18  of the rear board  14   b , in the embodiment shown, and permits the rider to sustain a forward motion in the ride-on device  12  without taking his or her feet off of the boards  14   a, b.    
         [0049]      FIG. 12  shows a ride-on device  12  having one board  14  with two cam action caster assemblies  10  attached to either end of a rear portion of the underside of the board  14 . In the rear center portion of the underside of the board  14  there is attached a fixed third wheel  20  to provide support during riding maneuvers conventionally known as “wheelies.” The front end of the board  14  is attached to a steering column  52  having a wheel bracket  22  such that a front wheel  20  is able to pivot about the axis of the steering column  52 . The cam action caster assemblies  10  permit the rider to sustain a forward motion in the ride-on device  12  without taking his or her feet off of the board  14 . 
         [0050]      FIG. 11  illustrates a ride-on device  12  having a left member  15  and a right member  15 , each member  15  having a foot platform  54  to support a rider. In particular, one of skill in the art will recognize that each platform  54  should have sufficient surface area and structural rigidity so as to support a rider&#39;s feet during use of the device  12 . The members  14  are each attached to a bracket  56 , in this embodiment, the attachments being pins or hinges  48  that permit the members  15  to pivot to the left and to the right while steering column  52  remains at the same nearly-vertical angle. There is also a support element  58 , in this embodiment, pivotably attached on one end to a central portion of the left member  15  and on the other end to a central portion of the right member  15 . The bracket  56  also is attached to a steering column  52 , in this embodiment, and a wheel  20  that is able to rotate about the axis of the steering column  52 . There are two cam action caster assemblies  10 , in this embodiment, one attached to the underside of each foot platform  54 , to permit the rider to sustain a forward motion in the ride-on device  12  without taking his or her feet off of the platforms  54 . 
         [0051]    A number of embodiments of the present invention have been presented herein. However, the invention may be used in the context of a device that is not ridden, such as a cart or wagon. In other embodiments, the invention could provide for a caster assembly using blades for use on ice rather than wheels. This disclosure is not intended to limit the invention in any way to the particular embodiments described, understanding that there are numerous alternative constructions. The invention is intended to cover the full scope of the subject matter as presented in the following claims.