WO2008142473A1

WO2008142473A1 - Wheelboard and wheel unit therefor

Info

Publication number: WO2008142473A1
Application number: PCT/IB2007/001550
Authority: WO
Inventors: Nigel Hansen
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-21
Filing date: 2007-05-21
Publication date: 2008-11-27
Anticipated expiration: 2009-11-21

Abstract

A wheelboard, such as a skateboard (10), may comprise a deck (12) having first, second and third wheels (14-18). The wheelboard may be configured to tip or pivot about the third wheel (18), such that when the wheelboard is on a planar surface (20) the third wheel (18) and one of the other two wheels (14 and 16) may contact the planar surface (20). The deck (12) may have a permanent, continuously curved shape that bulges towards the wheel unit side of the deck (12). The wheel units may comprise axially elongate wheels (62), with a camber defined by a smoothly curved profile. The wheel units may additionally comprise an undercarriage (84) carrying multiple wheel axles, the undercarriage pivoting about an axis parallel to the wheel exes. The features of the invention can provide the wheelboard with unique ride characteristics, enhanced versatility, and/or use as a snow or water surfboard trainer and/or a balance trainer.

Description

WHEELBOARD AND WHEEL UNIT THEREFOR

Field of the Invention

The present invention may relate to a wheelboard and/or to a wheel unit for a wheelboard.

The term wheelboard is especially intended to include a skateboard, but may also include any similar board on wheels, such as an off- road/mountain board, land kite board, land/sand wind surf board, land yacht, etc.

Background to the Invention

An optional aim of the present invention may be to provide a wheelboard that has one or more of the following characteristics: the wheelboard is more versatile than conventional wheelboard designs; the wheelboard has different handling characteristics from conventional wheelboards; the wheelboard can be used for training of a variety of skiing or surfing skills, such as wave surfing, water-kite surfing, windsurfing, snowboarding, water skiing, snow skiing, and/or sand skiing; the wheelboard can be used as a balance trainer The training characteristics may be especially advantageous because (i) current skateboards are not suitable as proper surfboard or balance trainers because the ride characteristics of conventional skateboards are quite different from those of surfboards; and (ii) there are not many low-cost options available to a rider wishing to practice surfboard or balance skills other than on snow or water. These characteristics may be illustrated later in the description of the preferred embodiments.

Summary of the Invention

Broadly speaking, a first aspect of the invention may provide a wheelboard comprising a first wheel unit at or near a first end of the board, a second wheel unit at or near a second end of the board, and a third wheel unit between the first and second wheel units.

The first, second and third wheel units may be spaced in the front-rear direction of travel of the wheelboard.

The wheelboard may be configured such that, when the wheelboard is placed on a generally planar surface, the third wheel unit and only one of the first and second wheel units touch the surface.

The wheelboard may tip or pivot, like a balance, about the third wheel unit.

The third wheel unit may be disposed generally at or near the centre of the board (in a longitudinal direction of the wheelboard), or it may be disposed nearer to one end than the other.

The third wheel unit may be disposed generally equidistant between the first and second wheel units, or it may be disposed generally closer to one of the first and second wheel units than to the other. The wheelboard may have a permanent, generally continuously curved shape. The curved shape may bulge towards the underside of the wheelboard.

One or more of the wheel units may be a multiple axis wheel unit, for example, as described later. Additionally or alternatively, one or more of the wheel units may comprise an elongate cambered wheel, as described later. Broadly speaking, a second aspect of the invention may provide a wheel unit for a wheelboard, the wheel unit including an axle carrying a single elongate cambered wheel.

The wheel may have an axial length that is longer than its maximum diameter.

The wheel may have a generally continuously curved profile in a cross- section through the axis of the wheel.

The wheel may have an axial length that is at least 50% of the width of the wheelboard in the region of the wheel unit, preferably at least 60%, more preferably at least 70%, more preferably at least 80% and more preferably at least 90%.

The wheel unit may comprise a truck suspension including one or more deformable and/or resilient members for permitting the wheel to bank with respect to the wheelboard. Broadly speaking, a third aspect of the invention may provide a wheelboard comprising at least two wheel units and a deck, the deck having a permanent, generally continuously curved shape in a longitudinal direction, and the deck having at least one valley or concave bulging on the wheel unit side of the deck. The deck may have a single valley, so that it has a generally U (or C or

V) configuration. Alternatively, the deck may have more than one valley, such as a W configuration.

Broadly speaking, a fourth aspect of the invention may provide a wheel unit for a wheelboard, the wheel unit comprising a chassis, a first axle carrying at least one first wheel and a second axle generally parallel to the first axle and carrying at least one second wheel, and a mounting portion for mounting the chassis to the wheelboard.

The chassis may pivot about a third axis that may be generally parallel to the first and second axles. The third axis may be defined by a pivot axle. The mounting portion may include a truck suspension including one or more deformable members for permitting the wheel to bank with respect to the wheelboard.

The wheels may be conventional wheels, or the wheels may be the elongate cambered wheels defined above. In another aspect, a wheelboard may comprise a deck having first, second and third wheels. The wheelboard may be configured to tip or pivot about the third wheel, such that when the wheelboard is on a planar surface the third wheel and one of the other two wheels may contact the planar surface. The deck may have a permanent, continuously curved shape that bulges towards the wheel unit side of the deck. The wheel units may comprise axially elongate wheels, with a camber defined by a smoothly curved profile. The wheel units may additionally comprise an undercarriage carrying multiple wheel axles, the undercarriage pivoting about an axis parallel to the wheel axes. The features may provide the wheelboard with unique ride characteristics, enhanced versatility, and/or use as a snow or water surfboard trainer.

Although the above aspects have been defined independently, additional advantages may be achieved by using any two or three, or even all, of the above aspects in combination. The invention specifically contemplates any combination of any of the above aspects. Although the main features believed to be of importance have been defined above and in the appended claims, the Applicant claims protection for any novel feature or idea described herein and/or illustrated in the drawings whether or not emphasis has been placed thereon.

Brief Description of the Drawings

Non-limiting preferred embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of a first embodiment of a skateboard having a curved shape and three wheel units;

Fig. 2 is a schematic side view showing a rider using his weight to pivot the skateboard;

Fig. 3 is a schematic side view showing, in a comparative example, a rider of a conventional skateboard trying to mount a curb;

Figs. 4a-c are schematic side views showing a rider of the first embodiment mounting a curb;

Fig. 5 is a schematic side view of a second embodiment of a skateboard having a planar shape and three wheel units; Fig. 6 is a schematic side view of a third embodiment of a skateboard having a curved shape and four wheel units;

Fig. 7 is a schematic perspective underside view of a wheel unit having two wheels and a single axle;

Fig. 8 is a schematic section through a cambered elongate wheel unit of a fourth embodiment;

Fig. 9 is a schematic front view showing banking of the fourth embodiment;

Fig. 10 is a schematic front view of an elongate cambered wheel of a fifth embodiment; Fig. 11 is a schematic side view of the fifth embodiment;

Fig. 12 is a schematic side view of a multiple axle wheel unit of a sixth embodiment;

Fig. 13 is a schematic side view of a seventh embodiment of skateboard including a curved deck and two wheel units; and Fig. 14 is a schematic side view of an eighth embodiment of skateboard with a W-configuration;

Fig. 15 is a schematic perspective view of an elongate wheel unit of a ninth embodiment;

Fig. 16 is a schematic underside perspective view of a tenth embodiment of skateboard;

Fig. 17 is a front view of the wheel unit of Fig. 16;

Fig. 18 is a perspective view of a pivoting wheel unit of an eleventh embodiment;

Fig. 19 is a schematic front view of the wheel unit of Fig. 18; Fig. 20 is a schematic side view of a twelfth embodiment of skateboard;

Fig. 21 is an underside view of the wheel unit of Fig. 20; and

Fig. 22 is a schematic perspective view of a wheel unit of a thirteenth embodiment. Detailed Description of Preferred Embodiments

Referring to Fig. 1 , a first embodiment of wheelboard may be illustrated in the form of a skateboard 10. Although the embodiments illustrate skateboards, it will be appreciated that the same principles may be applied to other types of wheelboard, such as an off-road/mountain board, a land kite board, a land/sand wind surf board, a land yacht, etc.

The skateboard 10 may generally comprise a deck 12 on which a rider stands, and one or more wheel units indicated schematically at 14, 16 and 18. For the sake of brevity, the wheel units 14-18 may be illustrated as simple schematic wheels; however, as described later below, the wheel units may be much more elaborate according to the design desired for a particular skateboard 10. The present embodiment may employ three wheel units. A first wheel unit 14 may be provided at or near a first end of the deck 12, a second wheel unit 16 may be provided at or near a second opposite end of the deck 12, and a third wheel unit 18 may be provided at a position generally intermediate the first and second wheel units 14 and 16. As used herein, the term "near" is intended to mean that the respective wheel unit is nearer to the respective end of the deck 12 than to the opposite end.

The third wheel unit 18 may be disposed generally symmetrically or equidistant between the first and second wheel units 14 and 16, or it may be closer to one of the wheel units 14 and 16 than the other. The third wheel unit 18 may be disposed generally symmetrically or equidistant with respect to the opposite ends of the deck 12, or it may be closer to one end of the deck 12 than the other. A characteristic of the first embodiment may be that, as illustrated in

Fig. 1 , when the skateboard 10 is placed on a generally planar surface 20, the skateboard may tip or pivot about the third wheel unit 18, like a balance. The third wheel unit 18 and only one of the first and second wheel units 14 and 16 may contact the planar surface 20. The skateboard 10 may be designed to have an asymmetrical characteristic such that the skateboard is more stable when a particular one end of the skateboard may normally be touching the surface 20, or the skateboard 10 may be designed to have a generally symmetrical characteristic such that the skateboard 10 may be generally equally stable with either end touching the surface 20. The skateboard 10 may have significantly different ride characteristics compared to a conventional skateboard. A rider may stand and use the skateboard 10 in a style more similar to surfing than conventional skateboarding. For example, in Fig. 1 , a rider 22 may stand towards the rear of the skateboard 10 (compared to a forward direction of movement indicated by arrow 24). Referring to Fig. 2, the rider 22 may alternatively stand with one foot on either side of the third wheel unit 18, and control the pivot attitude of the skateboard 10 about the third wheel unit 18 by applying or transferring more weight to one side than the other. The skateboard 10 may be used as a surfing trainer. The skateboard 10 may also enable the rider more easily to accomplish certain ride tricks than a conventional skateboard. For example, referring to Fig. 3, when using a conventional skateboard 30, it is generally quite difficult, especially for an inexperienced rider, to mount a curb 32. The manoeuvre requires skill to coordinate a combination of (i) the rider "lifting" the front end 34 of the conventional skateboard by kicking down more weight at the rear of the skateboard such that the skateboard pivots about the rear wheels 36, thus allowing the front wheels 38 more easily to mount the curb; (ii) the rider jumping up (or at least removing his weight) from the skateboard in order to allow the skateboard to complete mounting the curb; and (iii) the rider landing again on the moving skateboard. Such a manoeuvre is difficult for inexperienced riders, and is problematic even for experience riders, often leading to a fall and possible injury. The conventional skateboard 30 is stable only when both its front wheels 38 and rear wheels 36 are both on the ground. The position of the rear wheels 36 near the rear of the skateboard also makes it difficult to apply weight to lift the front wheels 38.

In contrast, the skateboard 10 of the first embodiment can enable a rider, even an inexperienced rider, to accomplish this trick more easily and with much less risk of falling. Referring to Fig. 4a, with the rider 22 applying more weight to the rear of the skateboard 10, the skateboard 10 may approach the curb 30 with the front wheel unit 14 already lifted from the ground. In this state, the skateboard 10 is perfectly stable, and there is little risk of the rider falling. Referring to Fig. 4b, at the appropriate moment, when the front wheel unit 14 touches, or is about to touch, the curb 32, the rider may transfer his weight to the front of the skateboard 10, thus pivoting the weight on the skateboard 10 about the third wheel unit 18, and allowing the skateboard 10 easily to mount the curb 30 (Fig. 4c). Such a manoeuvre relies mainly on the rider choosing the appropriate moment to transfer his weight between the skateboard's two stable positions, and thus is considerably easier for a rider to learn, and is also much safer to perform than with a conventional skateboard.

Similarly, referring again to Fig. 3, with a conventional skateboard 30, practising a "wheelie" is extremely difficult, even for an experienced or advanced level rider. A wheelie involves the rider placing his weight behind the rear wheel unit 36 in order to lift the front wheel 38 off the ground, while the skateboard 30 is moving forwards. If the rider looses balance such that the front wheel 38 drops down, the rider is saved from a fall and can still continue without falling off the board. However, if the rider looses balance such that the front wheel 38 lifts too high, the rider will inevitably fall off as the board tips or flips backwards. However, referring to Figs. 1 and 2, with the skateboard 10 of the first embodiment, the rider can easily practise a wheelie by balancing the weight on the third wheel 18, with both the first and second wheel units 14 and 16 off the ground. This involves the same balancing skills as with a conventional skateboard. However, should the rider loose balance such that either the first wheel unit 14 or the second wheel unit 16 drops down, the skateboard 10 will remain stable without the rider falling off. In essence, the wheelie is balancing between the two stable positions shown in Figs. 1 and 2. In the event of a loss of balance, the skateboard can still continue in one of the stable positions, without the rider falling off.

In the first embodiment, the deck 12 may have a permanent, generally continuously curved shape in a longitudinal direction. The deck may have a valley or concave bulging on the wheel unit side of the deck. Such a shape may be very ergonomic, and may enable the relative positions or "heights" of the wheel units 14, 16 and 18 to be achieved merely as a result of the shape of the deck 12. This may advantageously enable the wheel units 14, 16 and 18 to be the same as each other. It may also allow the deck 12 to be relative close to the ground at the positions where the rider may stand, thus giving a desirably low centre of gravity. In one form, it may be preferred that the curvature of the deck 12 be greater than the curvature of quarter-pipe and half-pipe ramps used in skateboard parks, so that the curved shape of the deck 12 does not restrict use of the skateboard 10. For example, the curvature may be sufficient to produce a deviation (namely a difference in height between the middle wheel 18 and the end wheels 14 and 16) of at least 25mm (i.e. at least about 1 inch), or at least 31mm, or at least 37mm, or at least 44 mm, or at least 50 mm, or at least 56 mm, or at least 63 mm, or at least 68 mm, or at least 75 mm (i.e. at least about 3 inches). Such a deviation may be associated with a board length of about 610mm (about 24 inches). It will be appreciated that, for a board that is longer or shorter than 610 mm, a given curvature will result in a respectively greater or lesser height deviation between the wheels. Although a curved shape of the deck 12 is preferred, this is not essential in all embodiments. For example, referring to Fig. 5, the deck 12 may have a more conventional generally planar shape. The ends 40 of the deck 12 may be angled upwardly, if desired. The third wheel unit 18 may either include a longer support 42, or may be mounted with an appropriate spacer 44, to provide the configuration in which the third wheel unit 18 is more distant from the deck 12 than the first and second wheel units 14 and 16.

Fig. 14 illustrates a further alternative form of deck 12, which may offer the possibility of a lower centre of gravity. The deck 12 has a generally "W" shape, with first and second bulges 12a and 12b towards the wheel side of the deck 12. The first and second bulges 12a and 12b are located at positions between the wheel units. The third wheel unit 18 is located at an apex or cusp 12c between the first and second bulges 12a and 12b. The deck 12 has a curvature, as explained above, to ensure that the board 10 may pivot about the third wheel unit 18 even when the board 10 is used in a half- pipe or quarter pipe ramp.

In the first embodiment, the skateboard 10 may include three wheel units 14, 16 and 18, which may give the skateboard 10 two stable ride positions. The term "stable" may mean a ride position with at least two wheel units (or wheels on at least two different axes) contacting the planar surface 20 (Fig. 1). Although three wheel units are currently preferred, the invention contemplates more wheel units if desired. For example, Fig. 6 may illustrate a skateboard 10 including four wheel units 14, 16, 18 and 46. The wheel units may be configured to give the skateboard three stable ride positions, each in which an adjacent pair of wheel units 14+18, 18+46, 46+16, respectively, may be in contact with the planar surface 20. This may further increase the versatility of the skateboard 10, and its use as a surfing trainer.

Referring to Fig. 7, one or more (or each) of the wheel units 14, 16, 18 (and 46) may be of a type comprising first and second wheels 50 mounted on a common axis or axle 54, and coupled to the deck 12 by means of a suspension mechanism 56 that may allow at least some relative banking movement of the wheels 50 and 52 with respect to the deck 10 (as indicated by arrows 58b). For example, the suspension mechanism 56 may comprise a ball-and-socket pivoting joint 52a, and a resilient stabilizer 52b, such as an elastomeric block. The joint 52a and the stabilizer 52b may be arranged in line, in a direction that is generally perpendicular to the axis 54. Such a combination may allow limited front-rear rocking of the axis 54 (indicated by arrows 58a), to absorb wheel vibrations, in addition to banking movement (arrows 58b). Yet at the same time, the in-line arrangement of the joint 52a and the stabilizer 52b may keep the axis 54 generally perpendicular to the longitudinal direction of the board 12, for straight steering. The wheel unit may further comprise a mounting portion 60 for fitting against the underside of the deck 12 and by which the wheel unit is secured to the deck 12 by suitable fixings, for example, nuts and bolts.

Referring to Figs. 8 and 9, in a further preferred form, one or more (or each) of the wheel units may be of a type comprising a single wheel 62 per axle or axis 66. The single wheel 62 may be axially elongate such that it has an axial length greater than its maximum diameter. The single wheel 62 may be an elongate roller. The axial length may be at least 50% of the corresponding width of the deck 12. The wheel 62 may be cambered. The camber may be smooth. The camber may be curved. The camber may be symmetrical on either side of the wheel. The wheel may have a minimum diameter at one or both of its ends that is less than 80% of the maximum diameter at or near the axial centre, more preferably less than 70%, more preferably less than 60%. The wheel 62 may be made of high density rubber mounted around a support tube 64, for example of metal. The tube 64 may extend continuously through the wheel, or the support tube may be substituted by tube segments or stubs at the opposite ends of the wheel. In the form illustrated in Fig. 8, the wheel 62 may be generally solid, apart from a central aperture for receiving the support tube 64. In an alternative lightweight form, the wheel 62 may be generally hollow, and moulded around a solid or hollow internal support structure of lighter weight than a solid rubber wheel. The wheel may include synthetic and/or natural polymers. The support tube 64 may be omitted if the wheel material provides sufficient self support. The wheel 62 may be mounted on an axle 66 by means of bearings 68.

The axle 66 may be coupled to a forked support frame 70 including a mounting portion 60 for fitting against the underside of the deck 12 for securing to the deck 12. In the embodiment shown in Fig. 8, the support frame 70 may be rigid and/or rigidly mounted to the deck 12. In that case (as illustrated in Fig. 9), even though the wheel 62 might not bank with respect to the deck 12, the cambered shape of the wheel may still allow relative banking movement between the deck 12 and the surface 20 on which the skateboard 10 is riding. One significant feature of such banking is that the effective pivot point 72 about which the deck banks may be lower than the surface 20, such that the point of contact between the wheel 62 and the surface 20 may move axially as the deck 12 banks. The wheel 62 may roll transversely on the surface with banking movement. Such behaviour may give an entirely different ride "feel" than the wheel type of Fig. 7, in which the pivot point about which the surfboard banks is fixed by the suspension 56, and is above the surface 20. The banking action of the elongate cambered wheel can make the deck 10 feel much more like a surfboard than a conventional skateboard, and can greatly increase the usefulness of the skateboard 10 as a surfboard trainer, for example, for simulating toe-side turns and heel-side turns. When a surfer turns on the toe-side, he can stay centred more easily because he can make small adjustments at his ankles, knees and hips while keeping weight on the balls of his feet. A heel-side turn requires weight transfer further back on the foot. This makes it more difficult to coordinate for the novice surfer, as the sensation is that of falling backward. The present invention can replicate such sensations during turns, making it an ideal surf trainer, whereas a conventional skateboard cannot. The wheel unit and/or the board, can mimic movement of the "sweetspot" and/or contact point with respect to a surfing medium. The aspect of balance and a movable "sweetspot" of the board provides a very different ride experience from a conventional board.

Also, with the present embodiment, since there is generally only a single point of contact between the cambered wheel and the ground, this may allows the rider to perform additional tricks such as a pirouette, which would be extremely difficult with a conventional skateboard having two wheels in contact with the ground at spaced apart positions on each wheel axis.

In the modified form illustrated in Figs. 10 and 11 , the support frame 70 of the elongate cambered wheel 62 may additionally comprise a movable suspension 56 of a similar type to that of Fig. 7. The movable suspension 56 may provide a degree of additional banking movement to extend the banking range achievable by just the cambered wheel 62 alone. For example, the banking angle θ achieved by the deck 12 in Fig. 10 may include a first component Θ1 provided by the cambered shape of the wheel 62, and a second component Θ2 provided by the suspension mechanism 56. The first component Θ1may correspond to the angle between the axle 66 and the surface 20. The second component Θ2 may correspond to the angle between the axle 66 and the deck 12. Combining both the banking actions of the cambered wheel 62 and the suspension mechanism 56 may enable the skateboard 10 to achieve a much higher range of banking angles than may be attainable by a conventional skateboard. The increased banking angles may enable the skateboard 10 to feel much more like a surfboard on water or snow, and may enhance the usefulness of the skateboard 10 as a surfboard trainer and/or a balance trainer. As explained above, the banking action of the elongate cambered wheel 62 may further add to the realistic "feel" of a surfboard.

The elongate cambered wheel 62 may generally have a maximum diameter that is larger than a conventional skateboard wheel. Although the suspension mechanism 56 may be located above the wheel 62 (e.g. between the wheel 62 and the deck 12), it may preferred to locate the suspension mechanism 56 to one side of the wheel in order to reduce the overall height of the wheel unit. For example, as illustrated in Fig. 11, the suspension mechanism 56 may be located in front of, or behind, the wheel 62. If desired, two suspension mechanisms 56 may be used, one in front and one behind the wheel 62. Each suspension mechanism 56 may be coupled to a respective mounting portion 60 for securing to the deck 12, or the two suspension mechanisms 56 may be joined to a common mounting portion 60. Alternatively, a single suspension mechanism 56 may be used, with the joint 52a and the stabilizer 52b placed one in front, and one behind, the wheel 62.

Referring to Fig. 15, an alternative support frame or fork 92 for mounting the elongate wheel 62. The frame 92 may be made of a forged metal/aluminium alloy. The frame 92 may be stiffly resilient to support the wheel 62, while permitting a degree of deformation for banking. This leads to a simpler, integral construction of the support for each wheel unit, instead of the wheel unit support being an assembly of multiple pieces.

Referring to Figs. 16 and 17, an alternative wheel unit 100 may be illustrated. The wheel unit 100 provides a camber effect similar to that described above, but by implementing multiple small wheels 102 on a camber axis 104. The wheels 102 may be carried on a single axle defining the camber axis 104, of the wheels may be carried on respective separate supports which are in a splayed arrangement to present the wheels 102 as in on a single camber axis 104. The arrangement of wheels 102 may either be fixed relative to the deck 12 (in a similar manner to the embodiment of Figs. 8 and 9) such that the banking action results solely from the camber shape. Alternatively, a suspension mechanism (not shown) may optionally be provided, in order to extend the range of banking angles, in a similar manner to the suspension mechanism 56 of the embodiment of Fig. 10. Fig. 12 may illustrate a modified form of wheel unit usable as one or more (or each) of the wheel units 14, 16, 18 (and 46). In the preceding embodiments, each wheel unit may comprise a single wheel axle or axis. In the embodiment of Fig. 12, the wheel unit may comprise first and second wheel axles or axes 80 and 82 supported in a common chassis or undercarriage 84. The undercarriage 84 may be pivot about a pivot axis 86 that may be generally parallel to the wheel axes 80 and 82. Such an undercarriage carrying plural wheel axles or axes 80 and 82, can enable the deck 12 to pivot in its longitudinal direction, while still maintaining the wheels on both wheel axles or axes 80 and 82 in contact with the ground (or other surface 20). This may enhance the stability of the skateboard, particularly when the skateboard is balanced on only one wheel unit (for example, during a transition between the two stable positions using the skateboard 10 of the first embodiment).

Each wheel axle or axis 80 and 82 may carry a single elongate cambered wheel 62 as described above, or more conventional pairs of wheels 50 also as described above.

The undercarriage 84 may be mounted on a support 86 comprising a pivot axle 88 defining the pivot axis 86 of the undercarriage 84. The support 86 may include a suspension mechanism 56 for permitting banking movement between the undercarriage 84 and the deck 12. The support 86 may further include a mounting portion 60 for attachment to the underside of the deck 12 by suitable fixings.

In the form illustrated in Fig. 12, the undercarriage 84 may be freely pivotable about the pivot axis 86. In alternative form, one or more bias members 90 (shown in phantom in Fig. 12) may be provided for biasing the undercarriage to a rest position with respect to the deck. For example, each bias member 90 may comprise a spring or other resilient member that extends between the undercarriage and the support 86 (such as the mounting portion 60 of the support 86). A single bias member 90 may be provided, or a pair of bias members 90 may be provided one on either side of the pivot axis 86. The or each bias member 90 may act in compression or expansion, or a combination of both. (As illustrated later, the bias members 90 may define a further stable or semi-stable position of the board 10).

Bump stops 94 may be provided on the undercarriage 84 and/or on the underside of the deck 12 and/or on the mounting portion 60, for limiting the pivoting movement of the undercarriage 84, and preventing the hard material of the undercarriage from colliding with the deck 12 should the undercarriage 84 pivot too far. The bump stops 94 may, for example, be made of an elastomeric or other shock absorbing material. In the form illustrated in Fig. 12, the undercarriage 84 may be bifurcated, such that the wheels 50/62 are carried on axles between the bifurcated portions of the undercarriage. In an alternative form illustrated in Figs. 18 and 19, conventional wheels 50 may be carried on axles 110 supported in bearings 112 in a single chassis arm 114. The chassis arm 114 may be angled to define two limb portions 116 on either side of an apex 118 at which the pivot axle 88 is located. The mounting portion 60 may comprise a U-shaped bracket 120 supporting the pivot axle 88.

Figs. 20 and 21 may illustrate a further embodiment employing a pivoting undercarriage 84 as the third wheel unit 18. The third wheel unit 18 includes two elongate wheels 62 as described above. The third wheel unit 18 also includes two bias members 90 for biasing the pivoting undercarriage 84 to a central, or neutral position, illustrated in Fig. 20. This provides the board 10 with a further stable, or at least semi-stable, dynamic ride position even with the first and second wheel units 14 and 16 not touching the ground. Thus the board 10 has the same number of stable (or at least semi-stable) ride positions as it has wheel units, namely three in the illustrated embodiment. The ride position illustrated is a self-balanced or glide position, similar to the rider performing a wheelie on a single wheel unit, but with additional self-correction provided by the bias members 90. The resistance or resilience of the bias members 90 may determine the characteristics of the board 10, in particular how resistant the board 10 is to tilting forwards or backwards to engage the first or second wheel unit 14 or 16 on the ground. The bias members 90 may additionally or alternatively comprise electronically controlled actuators, giving the board 10 a form of active suspension. An electronic control unit (not shown) may, for example, monitor the attitude of the board and/or the application of weight, and/or a centre of gravity, in order to control the application of appropriate forces by means of the actuators.

This embodiment also illustrates a modified form of the first and second wheel units 14 and 16 (and which could also be used for the third wheel unit if desired instead of the twin-axle type of wheel unit)., As illustrated in Fig. 21 , each of these wheel units comprises an elongate wheel 62 supported in a bifurcated undercarriage 84. The undercarriage 84 comprises suspension lever arms 122 that pivot about a pivot axis 124, and are resiliency supported at a spring axis 126. As illustrated, the springs act in tension. However, if desired, the positions of the pivot axis 124 and the spring axis 126 could be interchanged such that the springs act in compression. The arms 122 may be joined together by bridges 128, to form a forked or wishbone structure. The structure may be an integral piece if desired.

Fig. 22 shows, by way of example, a combination of the embodiment of Figs. 16 and 17, with the embodiment of Fig. 12. The resulting hybrid wheel unit includes a pivoting undercarriage 84 carrying two sets of multiple wheels 102 on matching or complementary camber axes 104. This can provide the same combination of camber banking and undercarriage pivoting as the embodiment of Fig. 12, but without using an elongate wheel. Although the features of the curved shaped deck 12, the elongate cambered wheel 62, the multiple wheel 102 camber wheel unit, and the undercarriage 84 of the wheel unit, have been described in association with a skateboard 10 including at least three wheel units, these features are not limited only to such a skateboard, and may be used independently or in combination with a skateboard including just two wheel units.

For example, Fig. 13 may illustrate a skateboard 10 comprising a generally curved shaped deck 12, and two wheel units 14 and 16. Each of the wheel units 14 and 16 may as illustrated in any of Figs. 7 to 12 and/or 15- 22. The curved shape of the deck 12 may enable the centre of gravity at the standing position of the rider 22 to be desirably lower than that of conventional, planar deck.

Fig. 14 may illustrate a skateboard comprising a generally planar shaped deck 12, and two wheel units 14 and 16. Each of the wheel units may be as illustrated in any of Figs. 8 to 12. The ends 40 of the deck 12 may be angled upwardly, if desired.

It will be appreciated that the present invention, particularly as illustrated in the preferred embodiments, can provide a novel skateboard and/or novel wheel units, that may be more versatile than conventional designs, and/or may give the skateboard different handling characteristics, and/or may enhance the usefulness of the skateboard as a surfboard trainer.

The foregoing description is merely illustrative of preferred forms of the invention. Many modifications, improvements and equivalents may be used without departing from the scope and/or principles of the invention.

Claims

1. A wheelboard comprising: a deck; a first wheel unit at or near a first end of the deck; a second wheel unit at or near a second end of the deck; and a third wheel unit between the first and second wheel units; the wheelboard being configured such that, when the wheelboard is placed on a generally planar surface, the third wheel unit and no more than one of the first and second wheel units may touch the surface.

2. The wheelboard of claim 1, wherein the wheelboard is configured to pivot about the third wheel unit.

3. The wheelboard of claim 1 or 2, wherein the third wheel unit is disposed between the first and second wheel units in a direction of travel of the wheelboard in use.

4. The wheelboard of claim 1, 2 or 3, wherein the third wheel unit is disposed generally at or near the centre of the wheelboard in a longitudinal direction of the wheelboard.

5. The wheelboard of claim 1, 2 or 3, wherein the third wheel unit is disposed nearer to one end of the deck than the other end of the deck.

6. The wheelboard of any preceding claim, wherein the third wheel unit is disposed generally equidistant between the first and second wheel units.

7. The wheelboard of any of claims 1 to 5, wherein the third wheel unit is disposed generally closer to one of the first and second wheel units than to the other.

8. The wheelboard of any preceding claim, wherein the deck has a permanent, generally continuously curved shape, the curved shape presenting a valley near or at the third wheel unit.

9. The wheelboard of any of claims 1 to 7, wherein the deck has two valleys, one valley on either side of the third wheel unit.

10. A wheelboard comprising a deck and a plurality of wheel units attached to the deck, the deck having a permanent, generally continuously curved shape that bulges towards the wheel unit side of the deck.

11. The wheelboard of any preceding claim, wherein at least one of the wheel units comprises an at least one axially elongate, cambered wheel.

12. The wheelboard of claim 11 , wherein the wheel has an axial dimension greater than its maximum diameter.

13. The wheelboard of claim 11 or 12, wherein the camber is defined by a generally continuously curved profile in a cross-section parallel to the axis of the wheel.

14. The wheelboard of any preceding claim, wherein at least one of the wheel units comprises: an undercarriage carrying wheels that rotate about at least two different wheel rotation axes, and a pivot coupling between the undercarriage and the deck for permitting the undercarriage to pivot with respect to the deck about a pivot axis that is generally parallel with the wheel rotation axes.

15. A wheel unit for a wheelboard, the wheel unit comprising a wheel that has an axial dimension greater than its maximum diameter, the wheel having a camber defined by a generally continuously curved profile in a cross-section parallel to the axis of the wheel.

16. The wheel unit of claim 15, further comprising a mounting portion for fitting against the under side of a wheelboard, for securing the wheel unit to the wheelboard.

17. The wheel unit of claim 16, further comprising a suspension mechanism for permitting banking inclination between the mounting portion and the axis of the wheel.

18. The wheel unit of claim 15, 16 or 17, comprising at least one wheel rotation axis, wherein the wheel unit comprises a single wheel per wheel rotation axis.

19. The wheel unit of any of claims 15 to 18, wherein the wheel comprises bearings at its opposite ends.

20. The wheel unit of any of claims 15 to 19, further comprising a forked or bifurcated frame for supporting the wheel at its opposite ends.

21. A wheelboard comprising a wheel unit as defined in any of claims 15 to 20.

22. The wheelboard of claim 21 , wherein each wheel unit of the wheelboard as a wheel unit as defined in any of claims 15 to 20.

23. A wheel unit for a wheelboard, the wheel unit comprising: an undercarriage carrying wheels that rotate about at least two different, non-coaxial, wheel rotation axes, a mounting portion for fitting against the underside of a wheelboard for securing the wheel unit to the wheelboard; and a pivot coupling between the undercarriage and the mounting portion for permitting the undercarriage to pivot about at least a pivot axis that is generally parallel with the wheel rotation axes.

22. The wheel unit of claim 21 , wherein the undercarriage has first and second different wheel rotation axes that are generally parallel with other.

23. The wheel unit of claim 21 or 22, wherein a single wheel is used for each rotation axis.

24. The wheel unit of claim 21 or 22, wherein plural wheels are used for each rotation axis.

25. The wheel unit of any of claims 21 to 24, wherein the undercarriage comprises at least one angled member for carrying the wheels.

26. The wheel unit of claim 25, wherein the pivot axis is at or near the apex of the angled member.

27. The wheel unit of any of claims 21 to 26, further comprising a suspension mechanism for permitting banking inclination of the undercarriage with respect to the mounting portion.

28. A wheelboard comprising a wheel unit as defined in any of claims 21 to 27.

29. A wheel unit for a wheelboard, the wheel unit comprising: an undercarriage comprising comprising bifurcated arms; at least one wheel unit disposed between and supported by the bifurcated arms; a pivot joint permitting the undercarriage to pivot about at least a pivot axis that is generally parallel with the wheel rotation axis

30. The wheel unit of claim 29, further comprising a mounting portion for mounting to a wheelboard, further comprising a suspension mechanism for permitting banking inclination of the undercarriage with respect to the mounting portion.

31. A wheelboard comprising a wheel unit as defined in claim 29 or 30.

32. A wheelboard as defined in any of claims 1 to 14, 21 , 22, 28 or 31 , wherein the wheelboard is a skateboard.

33. A kit of parts for a wheelboard as defined in any of claims 1 to 14, the kit comprising: a deck; a first wheel unit for mounting at or near a first end of the deck; a second wheel unit for mounting at or near a second end of the deck; and a third wheel unit for mounting between the first and second wheel units; the wheelboard being configured such that, when the wheelboard is constructed and placed on a generally planar surface, the third wheel unit and no more than one of the first and second wheel units touch the surface.

34. A deck for a wheelboard, the deck being configured to accept a first wheel unit for mounting at or near a first end of the deck, a second wheel unit for mounting at or near a second end of the deck; and a third wheel unit for mounting between the first and second wheel units.

35. The deck of claim 34, wherein the deck has a shape to present the third wheel unit at a position such that, when the wheelboard is constructed and placed on a generally planar surface, the third wheel unit and no more than one of the first and second wheel units touch the surface.

36. The deck of claim 35, wherein the deck is has a generally continuously curved shape that bulges one or more times towards the wheel unit side of the deck.

37. The deck of claim 36, wherein the deck has a first bulge at or near the position for the third wheel unit.

38. The deck of claim 36, wherein the deck has first and second bulges, one bulge on either side of the position for the third wheel unit.

39. A wheelboard substantially as hereinbefore described with reference to any of the accompanying drawings.

40. A wheel unit for a wheelboard, the wheel unit being substantially as hereinbefore described with reference to any of the accompanying drawings.