Skateboard truck assembly

Abstract: The present invention relates generally to an improved skateboard truck (3) for skateboards. The preferred skateboard truck (3) comprises a yoke (6) mounted by a king bolt (10) to a mounting base (21). The mounting base (21) comprises a socket hub (15) and a bracket (13). The yoke (6) comprises a hanger (7) and a pivot arm (14). The pivot arm (14) rotates freely in a bearing unit (18) supporting the pivot arm (14) in the socket hub (15). The king bolt (10) clamps the hanger (7) with a first grommet (20) and a second grommet (9). The first grommet (20) is flexible, preferably made of urethane rubber, and comprises an edge circumference and a center circumference (19). The center circumference (19) is narrower than the edge circumference. Preferably, the first and second grommets (20,9) are fluorescent.

Description: BACKGROUND OF THE INVENTION TECHNICAL FIELD The present invention relates generally to an improved truck assembly for skateboards and street luges and more particularly to provide speed and fast reaction maneuverability. BACKGROUND ART Skateboards have gained wide acceptance for recreational and sport activities. Competitions in skateboards have included downhill skateboard racing and slalom courses. Since the participants travel at relatively high speeds and require quick maneuverability in turns, the performance of the truck assembly is important. Additionally, such truck assemblies can also be utilized in street luges. A prior art skateboard and trucks are shown in Figures 11 through 14. Figure 11 is a perspective view that shows an assembled skateboard. Figure 12 is a front view of a prior art truck. Figure 13 is a side view of the prior art truck. Figure 14 is an expanded cross-sectional view of a prior art truck with a skateboard attached. Generally, a skateboard comprises a board 1and a set of wheels 2 that are attached to a bottom surface of the board 1. The wheels 2 are attached to the board using trucks 3. A truck 3 is mounted to the bottom surface of the board 1 by a mounting base 21 that comprises a socket hub 15 and a bracket 13. The mounting base 21 is generally mounted to the board 1 by bolts and nuts at mounting holes 17. The truck 3 comprises a right and left wheel axle 4 that extend perpendicularly to a side of the board 1 and the direction of the skateboard's travel. Each wheel axle 4 is mounted through a yoke 6 and affixed with an axle nut 5. The yoke 6 comprises a pivot arm 14 that is connected to the mounting base 21 at the socket hub 15. The pivot arm 14 is inserted into a rubber bushing mount 16, usually urethane, in a pivot hole 15a in the socket hub 15. The connection of the pivot arm 14 to the mounting base 21 at the socket hub 15 by using the rubber bushing 16 is usually done to reduce damage to the board 1 from vibration and positional change from any up and down motion of the yoke 6 during use. However, in a prior art truck, significant frictional forces can occur between the pivot arm 14 and the rubber bushing 16 and between the pivot hole 15a and the rubber bushing 16 when the board 1 inclines right or left during maneuvering, and in particular during slalom riding. The pivot arm 14 of the prior art skateboard truck may not rotate smoothly and therefore can reduce maneuverability. The yoke 6 further comprises a hanger 7 that is flexibly clamped by an upper grommet 8 and a lower grommet 9. A king bolt 10 passes through the lower grommet 9, the hanger 7 and the upper grommet 8 at the bolt holes 9a, 7a and 8a respectively and into the bracket 13 at bolt hole 13a. The king bolt 10 is affixed by a nut 11 and washer 12. The upper grommet 8 is generally shaped as a large, thick circular pillar. Though this structure absorbs impact, it may cause the wheel axle 4 to resist right or left movements when the user shifts his/her weight and may further reduce operating performance by hindering rotation of the wheel axle 4. French Patent Specification No. FR-A-2 586 619 discloses a steerable axle assembly whose steering is controlled by the displacement of the centre of gravity of the user and which comprises, on the one hand, a rigid balance arm carrying the linking pin of the load-bearing members, a pivot orthogonal to the pin and having a plate parallel to the linking pin and, on the other hand, a fixture on the lower face of the vehicle, consisting of a bolt with a head screwed to this face after having passed through a first tubular block made from deformable elastic material, the plate through an opening with a sufficient clearance, a second elastically deformable block and a base dish. The load-bearing surfaces of two successive elements of the stack constituting the fastening, namely the head of the bolt, the two bearing surfaces of the block, the two bearing surfaces of the plate surrounding the opening and the bearing face of the block are frustoconical or in the form of spherical zones. US-A-4 109 925 discloses a skateboard truck including an axle assembly which is quickly detachable from the truck mounting pad by means of a tension bolt fitting within a slotted bracket in the mounting pad for quick detachment therefrom. The skateboard truck assembly is provided with tension screw assembly that is mounted at a less than 45° angle with respect to the skateboard and includes adjusting means for adjusting the pivot axis of the assembly with respect to the skateboard, totally independent of the adjustment of the tension in the assembly. A safety bracket includes a base portion with an arm having a cylindrical bore for receiving the cylindrical outer end of the tension bolt for reducing the stress on the board or tension bolt during the steering of the skateboard. US 4 194 752 discloses a skateboard comprising an elongated board and a pair of trucks mounted adjacent opposite ends of the board, each having a pair of rotatable wheels. Each truck consists of a tensile elastic suspension member and a pivot support consisting of a universally movable ball and socket joint. Thus, an improved skateboard truck is needed that allows for smoother pivot arm rotation associated with the right or left incline of the skateboard and increased operating performance of the wheel axis during such maneuvers. SUMMARY OF THE INVENTION The present invention relates generally to an improved skateboard truck for skateboards and luges. The preferred skateboard truck comprises a yoke mounted by a king bolt to a mounting base. The mounting base comprises a socket hub and a bracket. The yoke comprises a hanger and a pivot arm. The pivot arm can rotate freely in a ball bearing unit that supports the pivot arm in the socket hub. The king bolt clamps the hanger between a first grommet and a second grommet. The first grommet is flexible, preferably made of urethane rubber, and can comprise an edge circumference and a center circumference. The center circumference is narrower than the edge circumference. Preferably, the first and second grommets are fluorescent. BRIEF DESCRIPTION OF THE DRAWINGS The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings. Figure 1 is a cross-sectional view of the invention. Figure 2 is an oblique bottom view of the invention. Figure 3 is a front view of the invention. Figure 4 is a rear view of the invention. Figure 5 is a side view of the invention. Figure 6 is a bottom view of the invention. Figure 7 is a side cross-sectional view of the invention. Figure 8 is a side cross-sectional view of the pivot arm and bearing unit. Figure 9a is a front view of a preferred embodiment of the upper grommet inclined to the right. Figure 9b is a front view of a preferred embodiment of the upper grommet inclined to the left. Figures 10(a)-(f) are front views of alternative embodiments of the upper grommet. Figure 11 is an oblique view of a prior art skateboard. Figure 12 is a front view of a prior art truck. Figure 13 is a side view of the prior art truck. Figure 14 is an expanded cross-sectional view of a prior art truck with a skateboard attached. Figure 15 is a perspective view and diagram of a preferred embodiment of the invention in operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to provide an improved skateboard truck. Referring now to Figure 1, a preferred embodiment of the invention is illustrated. A skateboard comprises a board 1 and a set of wheels 2 that are attached to a bottom surface of the board 1. The wheels 2 are attached to the board using trucks 3. A truck 3 is mounted to the bottom surface of the board 1 by a mounting base 21 for example of aluminum or other appropriate metal that comprises a socket hub 15 and a bracket 13. Referring to Figures 2-8, the mounting base 21 is preferably mounted to the board 1 by bolts and nuts at mounting holes 17. The truck 3 comprises a right and left wheel axle 4 that extend perpendicularly to the board 1 and a direction of the skateboard's travel. Each wheel axle 4 is mounted through a yoke 6 and affixed with an axle nut 5. Referring to Figure 1, the yoke 6 includes an upper pivot arm 14 that is connected to the mounting base 21 at the socket hub 15. The pivot arm 14 is inserted into a ball bearing unit 18 mounted in a bushing 16, preferably made of urethane rubber. A circular flange about the pivot arm 14 seats an annular ball bearing housing which provides a low frictional rotational movement of the pivot arm 14 and the corresponding yoke 6 in the socket hub 15. The bushing 16 and bearing unit 18 are friction mounted in a pivot hole 15a in the socket hub 15. The pivot arm 14 can rotate freely in the ball bearing unit 18 when the board 1 is inclined to the right or left during maneuvers such as a slalom course. The pivot arm 14 has reduced contact with the bushing 16 and therefore friction is reduced. The ball bearing unit 18 is preferably a ball bearing unit. The bearing unit 18 can also be a socket joint bearing as long as there is no obstructions to the support of the pivot arm 14. When the pivot arm 14 extending from the upper surface of the yoke 6 rotates, the axles 4 can also rotate to provide steering direction to the skateboard. The yoke 6 further includes an extended hanger 7 that is flexibly clamped by a first grommet 20 and second grommet 9, an upper grommet 20 and a lower grommet 9. A king bolt 10 passes through the lower grommet 9, the hanger 7 and the upper grommet 20 at the bolt holes 9a, 7a and 8a respectively and into the bracket 13 at bolt hole 13a. The king bolt 10 is affixed by a nut 11 and a conical washer 12 and tightens the grommets 20 and 9 to the hanger 7. To further increase the responsiveness of the truck assembly to steering movements by the rider, it is desirable for the extended hanger 7 to be responsive to control and movement when the rider shifts his weight on the board 1. Accordingly, it has been found desirable to provide greater flexing or movement to the bracket 13 by providing an upper grommet 20 that will facilitate such movement. The grommet 20 can be of a single or double piece construction and has a combined cross-sectional configuration of a reduced center relative to the upper and lower surfaces that contact respectively an indented grommet seat in the lower surface of the bracket 13 and an indented grommet seat in the upper surface of the hanger 7. Preferably, the upper grommet 20 is pulley-shaped. The upper grommet 20 comprises a center circumference or constriction 19. The constriction 19 can also be described as a forming a V-shaped groove around the central circumference of the upper grommet 20. Preferably, the center circumference 19 is narrower than the upper and lower surface edges of the upper grommet 20. The upper grommet 20 does not have to be pulley-shaped. Referring to Figure 10, six alternative preferred embodiments of upper grommets 20 comprising reduced center circumferences 19 are shown. Additionally, the upper grommet 20 can be a pair of sub-grommet parts each having a semi-spherical configuration. Preferably, the upper grommet 20 and the lower grommet 9 are flexible and made of urethane rubber. Referring to Figure 9(a) and (b), another alternative embodiment of the upper grommet 20 is shown. The upper grommet 20 resists compression along an axis 22. However, the upper grommet 20 can turn easily right or left about the center circumference 19 as shown. Alternatively, the constriction 19 does not have to be located at the center of the upper grommet 20. Instead, the constriction 19 can be located closer to one of the upper or lower edge circumferences as long as skateboard maneuverability is maintained. The upper grommet 20 in addition to the bearing unit 18 allow the skateboard 1 to maintain vertical stability and flexibility while also allowing the board 1 to quickly and easily change direction during maneuvers such as slalom-riding. This improved skateboard truck also reduces or eliminates possible interruption of rotation of the wheel axis 4. Preferably, the upper grommet 20 and the lower grommet 9 are treated with a fluorescent coating or doping to emit fluorescent light. The fluorescent substance can also be added to material from which the grommets are made, extruded or molded prior to formation. The fluorescent light should be bright enough to be seen by others at night while the skateboard 1 is being ridden. This feature provides added safety for riders and is an aesthetic feature as well. The upper grommet 20 is preferably a single body construction. However, as noted above, the upper grommet 20 can also consist of two pieces that join at the center circumference 19 and are held together on the king bolt 10 between the hanger 7 and the bracket 13. Referring now to Figure 15, a preferred embodiment of the invention is shown in action. Reference numeral 100 refers to the inclining force applied by a user to turn the skateboard 1. The user inclines the skateboard 1 by applying a force 100 to one side of the board 1. The flexible upper grommet 20 inclines about the center circumference 19. The constriction or center circumference 19 of the flexible upper grommet 20 allows the board 1, socket hub 15 and bracket 13 to more quickly and easily incline with the force 100. The inclination of the board 1, socket hub 15 and bracket 13 places increased pressure on the wheel 2 beneath the force 100. The wheel 2 beneath the force 100 therefore turns slower then the outer wheel 2a and the skateboard 1 turns toward the force 100 about the axis 22 through the hanger 7 and upper grommet 20. During the turn, the pivot arm 14 rotates in the ball bearing unit 18 around a pivot arm axis 25 within the socket hub 15. The ball bearing unit 18 allows the pivot arm 14 to more freely rotate and thus allows the truck 3 and wheel 2 assembly to more quickly and freely turn the skateboard 1. Therefore, the present invention has several advantages over the prior art. The improved skateboard truck reduces friction between the pivot arm 14 and the bushing 16. The improved skateboard truck allows the board 1 to quickly and easily change direction during maneuvers such as slalom-riding. This invention also reduces or eliminates possible interruption of rotation of wheel axis 4 when the board 1 is inclined to the right or left. Thus, turns are smoother and operating performance is increased. In each of the above embodiments, the different positions and structures of the present invention are described separately in each of the embodiments. However, it is the full intention of the inventor of the present invention that the separate aspects of each embodiment described herein may be combined with the other embodiments described herein. Those skilled in the art will appreciate that adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein. Reference Numbers 1. Skateboard 2. Wheel 2a. Outer Wheel 3. Truck 4. Wheel Axle 5. Axle Nut 6. Yoke 7. Hanger 7a. Bolt Hole 8. Prior art grommet 8a. Bolt Hole 9. Lower grommet 9a. Bolt Hole 10. King bolt 11. Nut 12. Washer 13. Bracket 13a. Bolt Hole 14. Pivot arm 15. Socket Hub 15a. Pivot Hole 16. Bush 17. Mounting Hole 18. Bearing unit or Ball Bearing Unit 19. Constriction or Center Circumference 20. Upper grommet 21. Mounting Base 22. Axis 25. Pivot Ann Axis 100. Inclining Force

Claims: A skateboard truck (3) comprising a mounting base (21) with a socket hub (15) and a yoke (6), supporting a wheel axis (4), having a pivot arm (14) mounted in the socket hub (15) and a hanger (7) operatively attached to the mounting base (21), and an upper grommet (20) and a lower grommet, characterized in that the upper grommet (20) comprises an elastic grommet (20) resiliently mounting the yoke (6) at the hanger (7), the upper elastic grommet (20) comprising an interior circumference (19) disposed between two exterior segments wherein the interior circumference (19) has a circumference narrower than the circumference of each exterior segment to facilitate control movement by the user through the hanger (7) to the wheel axis (4). The skateboard truck of Claim 1 wherein the socket hub (15) includes a bearing unit (18). The skateboard truck of Claim 2 wherein the bearing unit (18) is a ball bearing unit. The skateboard truck of Claim 3 wherein the socket kub (15) includes a urethane rubber bushing (16) frictionally mounting the ball bearing unit. The skateboard truck of Claim 1 wherein the hanger (7) is further mounted with a lower elastic grommet (9) so that the hanger (7) is resiliently clamped between the upper and lower elastic grommets (20, 9). The skateboard truck of Claim 1 wherein the upper elastic grommet (20) is fluorescent. The skateboard truck of Claim 1 wherein the upper elastic grommet (20) can be formed of two separate pieces. The skateboard truck of Claim 1 further including a bolt (10) connected to the mounting base (21) and extending through the hanger (7) and upper elastic grommet (20). The skateboard truck of Claim 8 wherein the hanger (7) is further mounted with a lower elastic grommet (9) having the bolt (10) extending therethrough so that the hanger (7) is resiliently clamped between the upper and lower elastic grommets (20, 9). The skateboard truck of Claim 9 wherein the socket hub (15) contains a rubber urethane bush (16).

Inventors: HIRANUMA TAKAYUKI, YAMADA TOSHIHIRO, HIRANUMA, TAKAYUKI, YAMADA, TOSHIHIRO
Applicants: UNICOMM CORP, UNICOMM CORPORATION
Application year: 2000
Main classification: A63C17
IPC codes: A63C17