BACKGROUND TO THE INVENTION Turntables for turning vehicles in confined spaces have been well- known for many years. Most people would be familiar with the use of turntables to turn locomotives at the ends of railway yards. Typically, such an installation is a complex mechanical construction requiring heavy engineering to build a turntable able to support the weight of a locomotive and yet be easy to turn.

Turntables have also be devised for turning motor vehicles in confined spaces, such as driveways, garages and parking stations. One example can be found in Australian Patent Number 222855 granted to J & E Ledger Pty Ltd. In broad terms, this patent describes a turntable for motor vehicles wherein the table is provided with one or more driving rollers adapted to be engaged by the driving wheels of a vehicle positioned on the table to rotate the table. The Ledger device had a large diameter and involved a complex transmission assembly.

Another form of motor vehicle turntable is described in Australian Patent Number 582246 granted to K.G. Coles & Co Pty Ltd. The Coles device comprises a rotatable vehicle support means that is mounted on slew rings with its axis of rotation inclined relative to orthogonal vertical planes. The weight of the vehicle is utiiised to effect rotation of the vehicle. Although clever in its operation, this device includes a complex assembly that is expensive to make and difficult to install. Furthermore, the operation of the turntable requires careful positioning of the vehicle that can be inconvenient.

More recently, an attempt has been made to provide a vehicle turntable somewhat simpler in construction than those described above.

Australian Patent Number 654633 granted to Campbell describes a driveway turntable having a base, a platen rotatable on the base and a locking means. The platen comprises a network of decking support beams under a plate. Wheels are provided at the periphery of the platen for rotation. Although simpler in construction than earlier arrangements, the Campbell assembly requires a heavy platen to support the vehicle.

Furthermore, the network of decking support beams add to the cost and complexity of the turntable.

OBJECT OF THE INVENTION It is an object of the present invention to provide a vehicle turntable that is simple in construction and economic to produce.

It is a further object to overcome one or more of the identified deficiencies in the known prior art.

Further objects will be evident from the following description.

DISCLOSURE OF THE INVENTION In one form, although it need not be the only or indeed the broadest form, the invention resides in a turntable comprising a base plate; a top plate rotatable with respect to the base plate; a central bearing locating the top plate with respect to the base plate; and an array of support bearings between the base plate and the top plate to facilitate rotation of the top plate with respect to the base plate; wherein a load on the top plate is distributed across the base plate by the array of support bearings.

In one preferred form the support bearings are fixed to the base plate and the top plate rotates on the support bearings. In an alternate

preferred form the support bearings are fixed to the top plate and the support bearings rotate with the top plate.

The support bearings are suitably stainless steel ball bearings of 250kg load capacity. The central bearing suitably has a load capacity of 2500kg. The top plate and base plate may conveniently be made from 350 grade mild steel.

In preference, the support bearings are arranged in an array having an outer ring of bearings adjacent a periphery of the turntable and an inner ring of bearings displaced radially inward from the outer ring of bearings. In an alternate arrangement the support bearings are arranged in an array having four sets of four bearings located at wheel positions of a vehicle positioned on the turntable. Additional bearings may be located at intermediate positions to help stabilise the top plate of the turntable.

In a further form, the invention resides in a turntable as described above with the addition of means for automated rotation of the top plate.

In preference the means for automated rotation of the top plate comprises a motor mounted below the base plate and means for transmission of rotational power from the motor to the top plate, which is suitably a gearbox.

Alternatively, the invention may reside in a turntable with the addition of means for mechanical rotation of the top plate. The means for mechanical rotation suitably consists of a cable attached at each end to a periphery of the top plate that passes over a crank and pulley arrangement such that operating the crank causes the pulley to pull on the cable to rotate the top plate.

A number of tabs and stops can be provided to stop rotation of the top plate at desired positions. A catch means may also be provided that is releasably engageable with the top plate to prevent rotation.

To assist with correct alignment of a vehicle on the turntable an optical guide means may be provided.

BRIEF DETAILS OF THE DRAWINGS To assist in understanding the invention preferred embodiments will now be described with reference to the following figures in which FIG 1 is a sketch of a first embodiment of a vehicle turntable.

FIG 2 is a schematic cross-section view of the vehicle turntable of FIG 1; FIG 3 is a schematic cross-section view of a second embodiment of a vehicle turntable; FIG 4 is a top view of the base plate of FIG 1 showing the bearing array; FIG 5 is a sketch of a motor and transmission assembly applied to the first embodiment of FIG 1; FIG 6 is a bottom view of the top plate of FIG 3 showing an alternate bearing array; FIG 7 is a sketch of an alternate embodiment of a motor and transmission assembly applied to the second embodiment of FIG 3; FIG 8 is a sketch of a mechanical means for rotating the turntable; FIG 9 depicts the operation of the embodiment of FIG 8; FIG 10 is a sketch of a stop to control rotation of the turntable; FIG 11 is a sketch of a manual means for rotating the turntable; FIG 12 is a top view of a catch for locking the position of the turntable; FIG 13 is a side view of the catch of FIG 12; FIG 14 is a sketch of an alignment means for use with the method depicted in FIG 14; FIG 15 depicts a method of positioning a vehicle on the turntable; FIG 16 further depicts the method of FIG 14; and FIG 17 shows the vehicle correctly positioned on the turntable.

DETAILED DESCRIPTION OF THE DRAWINGS In the drawings, like reference numerals refer to like parts.

Referring to FIG 1, there is shown a concept drawing of a vehicle turntable 1 that is useful for turning a vehicle 30 in a confined space. As depicted in FIG 1 and described in detail below, the turntable is able to be easily turned by application of moderate force to the vehicle.

A cross-sectional view of a first embodiment of the vehicle turntable 1 is shown in FIG 2. The turntable 1 comprises a base plate 2 seated on an underlying support structure 3, such as concrete. A central bearing support 4 is set in the support structure to extend through and above the base plate 2. A central bearing 5 comprises a fixed part 5a attached to the central bearing support 4 and a rotatable part 5b attached to a top plate 6. A gear 7 is optionally attached to the top plate 6 by bolts 8. The gear 7 is used for a motorised embodiment described below with reference to FIG 5 and FIG 7.

The top plate 6 is supported by an array of support bearings, such as 9. The support bearings 9 are set in the base plate 2 as depicted in FIG 4. In a typical embodiment there are sixteen support bearings arranged so as to evenly distribute a load placed on the top plate 6. The array of sixteen bearings avoids any problem with tilt of the top plate.

Furthermore, a relatively lightweight top plate can be used since the array of bearings mitigates the possibility of buckling or bending of the top plate.

As shown in FIG 4, the support bearings 9 are arranged with an outer ring of bearings close to the periphery of the top plate and an inner ring of bearings spaced such that the wheels of a typical vehicle would be located between the outer ring and the inner ring of bearings when parked on the turntable. The outer ring of bearings provide support for the edge of the top plate when a vehicle is driven onto the turntable. A

bevel 10 is provided around the circumference of the top plate to further facilitate a vehicle being driven onto the turntable.

The inventor has found that lOmm thick, 350 grade mild steel is suitable for the top plate and the base plate in this embodiment. This is considerably lighter and cheaper than top plates required in prior art turntables.

A second embodiment of the turntable 1 is shown in FIG 3. The second embodiment varies from the first embodiment by the bearings 9 being located in the top plate 6 rather than the base plate 2. This allows the base plate 2 to lay flat on the support structure 3 without the need for preparatory work as required with the first embodiment. To achieve this the central bearing support 4 is machined to fit into the base plate 2.

Screws 22 are used to fix the central bearing support 4 to the base plate.

An alternate arrangement of support bearings applied to the second embodiment of the turntable is shown in FIG 6. In this case the bearings 9 are clustered in groups of four at a location that would be occupied by the wheels of the vehicle when the vehicle is on the turntable. Two additional bearings 9a are located intermediate the wheel locations to stabilise the top plate 6. The embodiment of FIG 6 is well suited to applications where the vehicle will always be rotated through 180 degrees. The embodiment of FIG 4 is better suited to applications where the vehicle may be driven onto the turntable from any direction and be rotated to any direction.

The inventor has found that the embodiment of FIG 3 with the bearing arrangement of FIG 6 can be constructed from a 6mm mild steel base plate and an 8mm mild steel top plate.

Suitable support bearings 9 are sealed unit stainless steel bearings having a rated load capacity of 250kg. The array of sixteen support bearings is therefore able to support a load of four tonne on the top plate and yet be easily rotatable.

The turntable may be automated in the manner shown in FIG 5.

An electric motor 11 is bolted to the underside of base plate 2. A gearbox <BR> <BR> <BR> <BR> 12 2 transfers the rotation of the horizontal motor shaft to a vertical shaft 13 having a gear 14 on the end. The gear 14 drives gear 7 to rotate the top plate 6. An aperture 15 is provided in the base plate 2 for the shaft 13. The motor 11 is an induction motor providing electronic braking to stop the top plate at the desired position.

A similar arrangement can be employed with the second embodiment as shown in FIG 7. The motor 11 is again bolted to the base plate 2. To make room for the motor 11, the base plate 2 is elevated on legs 23. The number of legs required will depend on the size of the turntable and the weight of the heaviest vehicle expected to use the turntable.

As with the arrangement shown in FIG 5, the motor 11 drives a vertical shaft 13 through gearbox 12. A gear 14 on the end of the shaft 13 drives a gear 7 that rotates the top plate 6. A ramp 24 is provide for the vehicle to access the turntable 1.

A further arrangement for effecting rotation of the top plate of the turntable is shown in FIG 8. In this arrangement, the top plate is rotated mechanically by a crank and pulley system. Each end of a cable 25 is attached to the periphery of the top plate 6 of the turntable 1. The cable 25 passes over a pulley 26 that is rotated by crank 27. When the crank 27 is turned the pulley 26 pulls on one end of cable 25 to rotate the top plate 6. Turning the crank 27 in the opposite direction will cause the pulley 26 to pull on the opposite end of the cable and thereby rotate the top plate 6 back to the starting position. The operation of the mechanical arrangement is depicted in FIG 9.

In order to achieve correct alignment of the top plate 6 with the expected vehicle position, a stop 28 can be provided to engage a tab 29 projecting from the top plate 6. Two such tabs can be provided at

diametrically opposed positions to correctly stop the top plate 180 degrees from a starting position.

As shown in FIG 1, the vehicle can be rotated on the turntable by simply applying pressure to an extremity of the vehicle. In FIG 11, a tool 31 is shown for assisting with rotation of the turntable when there is no vehicle. It will be appreciated that if manual rotation of the top plate is required it may be difficult. The tool 31 assists with manual rotation by engaging a stub 32 on the top plate 6. The tool then provides a convenient handle for rotation of the top plate.

A catch 16, may be provided to lock the top plate 6 in a stationary position, as shown in FIG 12. In one embodiment the catch 16 is a foot pedal having a base 17 that is fixed to the support structure 3. A tongue 18 engages a slot 19 formed in the side of the top plate 6. There may be a number of slots each corresponding to a desired position of rotation of the top plate. In many applications there will be two slots separated by 180°.

The catch 16 also has foot plate 20 biased to an engaged position by spring 21. When the foot plate is depressed the tongue is disengaged from the slot thereby allowing rotation of the top plate.

For manual operation in the manner of FIG 1, a vehicle is driven onto the turntable 1 and stopped so as to be approximately centred on the top plate 6. In this position the wheels of the vehicle will be between or close to the support bearings 9. A person depresses the foot plate 20 of the catch 16 and applies pressure to commence rotation of the vehicle.

The person then walks with the vehicle allowing the tongue 18 to press against the bevel 10 of the top plate 6 under influence of the spring 21.

When the top plate 6 has rotated to a position where another slot 19 becomes aligned to the tongue 18 the spring will urge the tongue 18 into the slot 19, thereby ceasing rotation. The vehicle will then be in position for driving back in the direction from which it arrived.

For mechanical operation in the manner shown in FIG 9, the foot plate 20 of the catch 16 is depressed and the crank 27 is turned to rotate the top plate 6 and therefore the vehicle 30. The vehicle 30 will be oriented to drive from the turntable when the tab 29 engages the stop 28.

For automated operation the catch 16 may not be required. The electric motor 11 is operated to rotate the top plate 6. When the vehicle is pointing in the desired direction the motor is stopped. Control of the motor may be effected by a conventionai control box having a start button and stop button. Activation of the start button commences rotation of the top plate which is stopped by depression of the stop button. Alternatively, a more sophisticated system can be employed that automatically rotates the top plate a set angle (such as 180 degrees).

Correct positioning of the vehicle is required for efficient operation of the turntable. The vehicle can be positioned by judging the location based on the bump of the wheels running on to the top plate however a more positive guidance is useful. An optical guide 33 is shown in FIG 14.

The optical guide 33 consists of a pair of slots 34 from which a light is visible as the vehicle 30 approaches the turntable 1, as seen in FIG 15.

If the vehicle is off line to the right or left, one or both of the lights will seek to be visible. The driver will then correct the alignment of the vehicle till both lights are visible, thereby coming into alignment for correct positioning on the turntable. When the vehicle is on the turntable the line of vision to the lights will be cut by the top of the slot (or the vehicle bonnet), thereby indicating that the vehicle is correctly positioned and should be stopped, as shown in FIG 17.

It will be appreciated that variations of the preferred embodiment are possible, for example, a lateral displacement catch could be employed. By lateral displacement is meant a catch which moves in the plane of the top plate rather than out of the plane of the top plate. The advantage of such a catch is that it presents a lower profile and is

therefore less likely to provide an obstruction to a person walking around the turntable.

It will also be appreciated that the turntable is not limited to the application of turning vehicles. The turntable can be usefully employed in any situation where distributed support of a load is required during rotation. Furthermore, the simple, lightweight and economic construction of the turntable mean that it could replace existing heavy duty systems.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features.