[0001 ] This application claims convention priority from Australian provisional patent application 2016903091 filed on 5 August 2018. The contents of that application are incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to hangers and wheel assemblies for skateboards, particularly motorised skateboards having at least one electric motor that is controllable by a rider.

BACKGROUND OF INVENTION

[0003] Efforts to develop motorised skateboards have traditionally resulted in the adoption of complex and heavy additional apparatus, or custom-built parts and accessories, being added to conventional non-powered skateboards. This makes the motorised skateboards both heavy and expensive, and difficult to build and maintain. Also, most of the additional parts have tended to be mounted so as to be exposed to both a rider and the riders environment, usually resulting in safety concerns for a rider in potentially being injured when contacting these additional parts (such as gears, pulleys and motors, sometimes very hot motors), but also maintenance concerns due to the additional parts striking the ground or other surfaces and being damaged during use.

[0004] Additionally, motorisation has required the housing of electric motors and batteries in a piece of equipment (the skateboard) that has always been quite a simple and minimal piece of equipment. Indeed, there are not many places on a skateboard for the housing of such parts, and the normal cosmetics of such motorised skateboards have tended to be severely compromised, affecting their marketplace acceptance.

[0005] Further still, most traditional non-powered skateboards tend to be reasonably inexpensive, so the comparatively high increased cost of the motorised skateboards developed to date has also proven to be something of a barrier to the mass adoption of motorised skateboards.

[0008] It is an aim of the present invention to provide a skateboard wheel assembly for a motorised skateboard, and a hanger for such a wheel assembly, that simplifies the motorisation of skateboards, particularly motorised skateboards that use electric motors.

SUMMARY OF INVENTION

[0007] The present invention provides a skateboard hanger for a wheel assembly for a motorised skateboard, the wheel assembly including a pair of wheels, the hanger having opposed free ends for the wheels, at least one of which is a drive wheel having an in-wheel electric motor, and wherein the hanger includes a heat sink at or near each free end adjacent a drive wheel, the heat sink being capable of assisting with dissipation of heat from the in-wheel electric motor of an adjacent drive wheel.

[0008] The present invention also provides a wheel assembly for a motorised skateboard, the wheel assembly including a pair of wheels and a hanger of the abovementioned type.

[0009] The present invention further provides a motorised skateboard, the skateboard including a board mounted to front and rear wheel assemblies, at least one of the wheel assemblies being a wheel assembly of the abovementioned type, the skateboard also including a power source for the in-wheel electric motor and a controller such that a rider can control the operation of the in-wheel electric motor. In this respect, it will be appreciated that such an in-wheel electric motor will ideally be controllable to provide both acceleration and braking.

[0010] Such a motorised skateboard is advantageous over motorised skateboards with externally mounted motors for several reasons. Standard boards, standard base plates, standard bushings and standard connection pins may be used with the present invention, rather than having to use customised parts that add complexity, making the skateboards faster to assemble, easier to repair and maintain, and less expensive. Additionally, the use of in-wheel motors provides less resistance when rolling unpowered, providing more of a natural rolling feeling for the rider (like a non- powered skateboard). If is also safer due to there being no exposed gears, pulleys or motors, and is less likely to sustain mechanical damage to those parts for the same reason. Finally, the skateboard looks more like a normal skateboard, which (amongst other things) makes the motorised skateboard less likely to attract the attention of thieves and the like.

[001 1 ] An "in-wheel electric motor" is an electric motor that is incorporated into the hub of a wheel, driving the wheel directly. Any type of suitable in-wheel electric motor may be used. Regardless of the type of in-wheel electric motor adopted for use with the wheel assembly and hanger of the present invention, the motor will nonetheless preferably be a sealed motor (to prevent the entrance of debris and dirt), and will at least include a stationary core and a rotor, the core and rotor being separated by an air gap. During operation, current through the motor generates heat and the temperature of the core of the motor (at least) increases, particularly with sealed motors that do not otherwise allow for airflow therethrough and that do not utilise a fan for forced cooling.

[0012] Therefore, the hanger of the wheel assembly includes a heat sink at or near each free end adjacent a drive wheel to assist with the dissipation of heat from the in-wheel electric motor, and in particular from the core of the in-wheel electric motor, and more particularly from the exposed surface of the core (being the core surface exposed to the free end of the hanger). Given that an in-wheel electric motor will only generate excess heat when the motor is under load (namely, when the skateboard is moving), the location of the heat sink as a part of the hanger is advantageous as the hanger will therefore have air moving around it when the motor is most likely to be hot.

[0013] As will be understood by a skilled addressee, hangers function as axles in skateboards and are generally longitudinal, thus having two free ends and being connected to a base plate via a bushing (with a connecting pin) at a position between the two free ends, and generally centrally of the two free ends. Hangers are thus generally elongate (having a length similar to the width of a board), thus usually having an identifiable longitudinal axis. Having said that, there might not be symmetry about that axis, and the diameter or width of the hanger will often vary along its length depending upon its design. Nonetheless, hangers tend to narrow towards their free ends, and the ends themselves tend to have a lateral face for the mounting of wheels thereto (using known wheel mounting arrangements).

[0014] The heat sink of a hanger may be any suitable configuration of heat sink, such as fins, cavities (inverted fins) or apertures, and may be provided integrally in the hanger or as an addition to the hanger. In terms of location, the heat sink will ideally be located with the free end of a hanger, such as at the free end, adjacent to the free end, along the hanger towards and near the free end, about the full circumferential extent of the free end, or only about a portion of the circumferential extent of the free end, or across the lateral face of the free end. In one form, it is envisaged that the heat sink will be formed by a series of parallel cavities (grooves) formed in the surface of the hanger about a portion of the circumferential extent of the free end.

[0015] Of course, it will be appreciated that there will be a necessary balance to be struck between the heat transfer efficiency of such grooves (and indeed for any heat sink configuration) and structural integrity. For example, grooves and apertures should not be so deep or so prolific that the hanger is weakened and cannot carry the desired weight or resist breakage during normal (or extreme) use, but should not be so shallow or sparse that not enough heat is conducted away from the hanger and the motor.

[0018] Further, the thickness of any fin (or portion between grooves or apertures) should not be such that contact with the ground or debris might break parts of the heat sink. Further still, ideally there will be no sharp edges in the heat sink, given that riders will often carry a skateboard by its hanger.

[0017] Ideally, the free end of a hanger adjacent the drive wheel will be sized such that the area of its lateral face will at least approximately match the exposed area of the core of the in-wheel electric motor. In this form, heat transfer from the core to the free end of the hanger can be maximised, further maximising the heat dissipation provided by the heat sink.

[0018] In this respect, it is preferred for the heat sink configuration and location to be such that the surface temperature of the hanger does not increase above about 75°C. Preferably, the surface temperature of the hanger does not increase above about 65°C. More preferably, the surface temperature of the hanger does not increase above about 55°C. More preferably, the surface temperature of the hanger does not increase above about 45°C, Most preferably, the surface temperature of the hanger does not increase above about 40°C.

[0019] In a preferred form, the hanger will be manufactured from a strong but ductile material such as aluminium, which provides for relatively easy manufacture with the preferred form of heat sink, yet is strong enough for the expected use of a skateboard.

BRIEF DESCRIPTION OF DRAWINGS

[0020] The present invention will now be described with regard to a preferred embodiment illustrated in the accompanying drawings. It should be noted that the following description is not to limit the generality of the above description.

[0021 ] In the drawings:

[0022] Figure 1 is a side view of a motorised skateboard having a skateboard wheel assembly in accordance with a preferred embodiment of the present invention;

[0023] Figure 2a is a perspective view from one side of the preferred wheel assembly of Figure 1 , and Figure 2b is a perspective view from the other side of the preferred wheel assembly of Figure 1 ;

[0024] Figure 3 is a perspective view of the preferred wheel assembly of Figure 1 , showing only the hanger and the wheels of the wheel assembly;

[0025] Figure 4a is a perspective view of only the hanger of Figure 3, and Figure 4b is a side view of only the hanger of Figure 3.

[0028] Figure 5a is a side view of the preferred wheel assembly of Figure 1 , and Figure 5b is a section view through A-A in Figure 5a showing the in-wheel electric motor in the wheel assembly and its relationship to the hanger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] In Figure 1 there is illustrated a motorised skateboard 10, the skateboard 10 including a board 12 mounted to a front wheel assembly 14 and a rear wheel assembly 16. The rear wheel assembly 16 is in accordance with the present invention and includes a pair of wheels 18 (18a and 18b in later figures) mounted on a skateboard truck 20, with both wheels 18 including an in-wheel electric motor 19 (19a and 19b in later figures). The front wheel assembly 14 is a traditional non-powered wheel assembly having a skateboard truck 21 for its wheels 23.

[0028] The board 12 of the skateboard 10 includes a housing 26 on its underside (either an integral housing or, as in this case, a housing that is secured to a traditional board) that is capable of housing a power source (such as a battery) and whatever electronic controllers are required or desired.

[0029] Referring now to Figures 2a and 2b, the truck 20 of the rear wheel assembly 16 includes a hanger 22 with opposed free ends 24a,24b for the wheels 18a, 18b, the opposed free ends being more readily visible in Figures 4a and 4b. The truck 20 also includes a base plate 30 for mounting the wheel assembly 16 to the board 12, and a bushing 32, the base plate 30 being connected to the hanger 22 with a connecting pin 34 via the bushing 32.

[0030] The in-wheel electric motors 19a, 19b are incorporated into the hub of a respective wheel, driving the wheel directly. As can be seen in Figures 5a and 5b, the preferred in-wheel electric motor is a sealed motor that includes (in both motors in both rear wheels) a stationary core (stator) 40 and a rotor 42, the core 40 and the rotor 42 being separated by an air gap 41 . During operation, current through the motor generates heat and the temperature of the core 40 of the motor (at least) increases.

[0031 ] Referring to each of Figures 4a, 4b, 5a and 5b, the hanger 22 of the rear wheel assembly 16 includes a heat sink 50a, 50b at or near each free end 24a,24b, adjacent to a respective wheel 18a, 18b (in Figure 3). As mentioned above, the heat sinks 50a,50b assist with the dissipation of heat from the in-wheel electric motors 19a, 19b, and in particular from the cores 40 of those motors, and more particularly from the exposed surfaces 44 of the cores 40 (being the core surface exposed to the free end of the hanger). As can also be seen in Figure 5, in this embodiment, the size of the end 56 of the hanger 22 is such that a reasonable portion of the exposed surfaces 44 of the core 40 of the motor is cioseiy adjacent thereto, to assist with maximising heat transfer from the core 44 to the hanger 22,

[0032] The heat sinks 50a, 50b shown in Figures 4a and 4b are best described as a series of cavities (inverted fins) or grooves 52, provided integrally in the surface of the hanger 22. In this embodiment, the heat sink sinks 50a, 50b are located at the free ends 24a, 24b of the hanger 22, including cioseiy adjacent to the free ends and slightly along the hanger 22 towards the free ends 24a, 24b. The grooves 52 extend about the full circumferential extent of the free ends 24a, 24b at the free ends 24a, 24b, but are only located at the top portions of the hanger 22 away from the free ends 24a,24b.

[0033] The hanger 22 additionally includes apertures 54a, 54b, the apertures serving to assist with heat dissipation, but also to assist with weight reduction and cosmetics.

[0034] A motorised skateboard of the type illustrated need only use standard boards, standard base plates, standard bushings and standard connection pins, rather than having to use customised parts that add complexity, making the skateboards faster to assemble, easier to repair and maintain, and less expensive. In-wheei motors provide less resistance when roiling unpowered, providing more of a natural rolling feeling for the rider (like a non-powered skateboard). The in-wheel configuration of the motor also makes these motorised skateboards safer due to there being no exposed gears, pulleys or motors, and less likely to sustain mechanical damage to those parts for the same reason. Finally, as can be seen from the figures, the skateboard also looks more like a normal skateboard.

[0035] The hanger of the wheel assembly of the type illustrated assists with dissipation of heat from the in-wheei electric motor, and given that an in-wheei electric motor will only generate excess heat when the motor is under load (namely, when the skateboard is moving), the location of the heat sink as a part of the hanger is advantageous as the hanger will therefore have air moving around it when the motor is most likely to be hot. [0036] While the invention has been described in conjunction with a single preferred embodiment, if will be appreciated by those skilled in the art that many alternative, modifications and variations in light of the foregoing description are possible. Accordingly, the present invention is intended to embrace all such alternative, modifications and variations as may fail within the spirit and scope of the invention as disclosed.