BACKGROUND ART A roulette wheel is required, by most gaming authorities, to spin unaided for a minimum time of twenty minutes from a starting speed of approximately 20 rpm (determined by when looking down on the rotating number ring, the numbers appear to be just going blurred) to rest.

To achieve this, a bearing system of minimum drag is required. Current practice to obtain this result is to use steel ball races with the thinnest of lubricant and the weight of the wheel is taken by either a ball race or a hardened pointed screw running on the hardened top of the axle (which also serves to adjust the height alignment between the wheel rim and bowl rim.

Current bearing systems have a major drawback in that regular re- lubrication of the bearing system is required. With oil in the bearings and the bearings unshielded dust is attracted. A lot of this dust is particles of the playing cloth released by the continual rubbing of the cloth with playing chips.

This dust can often make the bearing gritty and cause their frequent replacement. Whenever a roulette wheel is dismantled for service, it required checking by a relevant gaming authority being put back into operation.

It is an object of the present invention to provide a hub assembly for a roulette wheel which will be free of maintenance for a prolonged period so that the roulette wheel will be able to operate for that prolonged period without requiring rechecking by the relevant gaming authority.

SUMMARY OF THE INVENTION According to the invention there is provided a hub assembly for a roulette wheel comprising:-

(i) a housing defining a hollow body having first and second open ends, (ii) an axle within the housing supported by a first bearing seated in the first opening and a second bearing seated in the second opening o the housing, (iii) a plurality of spaced apart magnetic pairs within the body, each magnetic pair comprising an inner disc magnet and an outer ring magnet with an air gap therebetween, the inner disc magnets being fixed to the axle and the outer ring magnets being fixed to the housing, and (iv) a spacer pair between adjacent magnet pairs, each spacer pair comprising an inner disc spacer and an outer ring spacer with an air gap therebetween, the inner disc spacer being fixed to the axle and the outer ring spacer being fixed to the housing.

In a preferred form of the invention, the spacer pairs are magnetic spacer pairs. Preferably, each magnetic pair has a top face and a bottom face with the top face being one magnetic pole and the bottom face being the other magnetic pole.

Preferably, the magnetic pairs and spacer pairs are assembled on the axial and in the housing in a vertical disposition and wherein there is a top spacer pair between the top magnet pair and the first bearing and a bottom spacer pair between the lower magnet pair and the second bearing.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded view of a hub assembly for a roulette wheel according to one embodiment of the invention, Fig. 2 is a cross-sectional view of a roulette wheel incorporating the hub assembly of Fig. 1, Fig. 3 is a perspective view of a hub assembly for a roulette wheel according to a second embodiment of the invention, Fig. 4 is an exploded view of the hub assembly shown in Fig. 3, and

Fig. 5 is a schematic diagram of the magnetic pairs and spacer pairs of the hub assembly shown in Fig. 3.

MODES FOR CARRYING OUT THE INVENTION The hub assembly 10 shown in Fig. 1 includes a main housing 11 which defines a hollow body 12 having an open top 13 and an open bottom 14. The housing 11 has a skirt 15 and a tapered shoulder 16 which are adapted to engage the inner surface of a roulette wheel assembly.

An axle 17 located within the body 12 is axially supported by an upper ceramic bearing 18 which is positioned in the open top 13 that is closed by a plug 19 and a lower ceramic bearing 20 positioned in the bearing housing 21 that is a press fit in the open bottom 14 of the body 12.

The upper ceramic bearing 18 is secured to the upper end of the axle 17 by a countersunk screw 22 with a bearing keeper 23 therebetween and an acetal shim 24 beneath the upper ceramic 18.

Between the upper bearing 18 and the lower bearing 20 there is an array of magnet pairs 25, separated by spacer pairs 26. The magnetic pair 25 comprises an inner magnet disc 27 having a central aperture 27a and an outer ring magnet 28. The spacer pair 26 consists of an inner spacer disc 29 having a central aperture 29a and an outer spacer ring 30.

The inner disc magnet 27 of each magnet pair 25 is fixed to the axle 17 which passes through the central aperture 27a and the outer ring magnet 28 of each magnet pair 25 is a press fit within the body 12. Similarly, the inner spacer disc 29 of each spacer pair 26 is fixed to the axle 17 which passes through the central aperture 29a and the outer spacer ring 30 is a pres fit within the body 12.

Adjacent to the lower end of the axle 17 there is an integral collar 31 to which is fixed a mounting flange 32. Beneath the collar 31 there is a height

adjustment thread 33 adapted to engage a similarly threaded portion of the boss 39 of the flange 32. An acetal shim 34 is located between the lowest magnet 25 and the lower bearing 20.

The roulette wheel 40 shown in Fig. 2 includes a roulette wheel cylinder 41 which has a central housing 42 that seats on the shoulder 16 of the bearing housing 11 and the skirt 15.

The roulette wheel 40 also includes a wooden bowl 43 having a central recess 44 which supports an aluminium bowl 45 having a central opening 46 to receive the lower end of the axle 17. The mounting flange 32 is supported on the bowl 45 by screws 47.

The weight of the rotating part of the roulette wheel 40 is supported by the array of ring and disc magnets 25 arranged as a stack of rings 28 separated by the rings 30 of the non-magnetic spacers 26 within the non- magnetic housing 11 and a stack of discs of similar thickness separated by the discs of the non-magnetic spacers of similar thickness fitted on the hardened steel axle 17. The running clearance between the discs and rings is approximately 0.5mm giving an immensely strong axial coupling between them. As magnets in this configuration are not stable, a fixed force is required to provide stabilisation in a radial direction. This is achieved by using the ceramic single row deep groove ball bearings with Teflon cages 18 and 20 located above and below the array of magnets 25. Dust is excluded from this assembly by the sealing plug 19 in the top of the body 12 and the close seal of the bearing housing in the bottom of the body 12.

The hardened steel axle 17 is a light press fit into to the mounting flange 32. When pressed and the thread engaged a couple of turns, the position of the axle and therefore the wheel rim and bowl alignment can be adjusted by

turning the protruding hexagonal axle section clockwise to raise or anti- clockwise to lower the wheel.

The embodiment of the invention shown in Figs 3 and 4 is substantially similar to that shown in Figs 1 and 2. Thus, like components carry the same numerals. One difference between the embodiments is that the non-magnetic spacer pairs 26 of the first embodiment are replaced by magnetic spacer pairs of the second embodiment.

The axle 17 is axially supported by the upper ceramic bearing 18 which is located by a glass reinforced teflon sleeve 50 retained in the open top 13 of the housing 11 by a press sleeve 51 and is closed by the plug 19 and the lower ceramic bearing 20 located by a glass reinforced teflon sleeve 52 retained in the lower bearing housing 21 by a pressed sleeve and flange 53.

Resistance to unwanted rotation of the axle 17 is achieved by two brass friction pads 54 radially disposed around the boss 55 of the upper mounting flange 56, the brass pads 54 being 90 degrees apart. The brass pads 54 are located in apertures formed in the boss 54 and are adjusted by grub screws 57 threadingly engaged in the apertures. The required amount of friction to prevent unwanted rotation is achieved by fine adjustment of the screws 57. A lower mounting flange 58 is coupled to the upper mounting flange 56.

In this instance, the magnet pairs are formed of rare earth magnets.

When the rare earth magnet 27 is forced (against the various magnetic fields) into the rare earth outer ring magnet 28, the redirection of the various magnetic fields creates a very strong magnetic bond between the inner disc magnet 27 and the outer ring magnet 28 both in a radial and an axial direction. Without a mechanical device to keep the inner disc magnet 27 and outer ring magnet 28 separated, the inner disc magnet 27 will be pulled radially into contact with the outer ring magnet 28. In this instance, the mechanical device consists of the

housing 11 and the axle 17 which is supported by the ceramic bearings 18 and 20 which prevents any axial contact between the inner disc magnet 27 and the outer ring magnet 28.

If an axial force is applied to either the axle 17 or the housing 11 whilst the other is prevented from moving, then the force needed to insert the inner disc magnet 27 into the outer ring magnet 28 is initially applied in the opposite manner-that is, opposite to the force needed to separate the components.

In this instance, there is a stack consisting of four layers of magnetic pairs interposed between five layers of spacer pairs. The interposing of the steel spacer pairs enables the stack of magnetic pairs and spacer pairs to be assembled with north pole to north pole and south pole to south pole as shown in Fig. 5. This arrangement allows the forces needed to separate an inner disc from an outer ring (axially) to be cumulative or in series-that is, if the force to separate one magnetic disc from its associated ring is say 20 kg then the force needed to separate the stack of four magnetic discs of Fig. 5 is four times that or 80 kg.

In the hub assembly of the present invention, this characteristic of the stack is utilised as a load carrying device and supports the weight of the roulette wheel thus taking any axial load of the ceramic bearings and consequently removing the drag or friction in the ceramic bearing to a very low value thus providing very long run times for the roulette wheel.

When the roulette wheel is placed onto the hub assembly, the weight of the wheel (approximately 30 kg) causes a slight deflection in the axial relationship between the magnetic discs and rings to a position where the reactive forces of the attempted separation equals the weight of the wheel.

When this deflection occurs, there is an axial load applied to the ceramic bearings to remove any effects of the drag caused in the ceramic bearings by

the axial deflection. The ceramic bearings are located circumferentially within the glass filled teflon sleeve (at each end of the housing 11) which, having a very low coefficient defriction, allows the ceramic bearings to axially relocate themselves to a position of minimum axial loading. The glass filled teflon bearing retaining sleeves have an internal diameter of. 01 mm less than the outside diameter of the ceramic bearings. Thus, the ceramic bearing is held firmly in a radial plane but can slide relatively freely in an axial plane.