BACKGROUND TO THE INVENTION Problems relating to flooring and other support surfaces include the fact that they may not always be even, level or flat. Even when laid to stringent specifications they may, in time, become uneven from unequal loading, subsidence and wear, for example. Objects with four rigidly assembled legs, for example a table, when placed on such an uneven floor may tend to wobble. Three legs of the object will rest on the floor, while the insufficient support of the fourth leg can cause the object to rock, pivoting on the two supported diagonally opposite legs and hence lifting the remaining leg.

Previous proposals for addressing these problems include placing shims underneath individual legs to compensate for the shortfall, but has frequently proved to be only a temporary solution. The table may be moved to a new position or the floor may settle under the subjected load and hence the table may become unstable again.

Adjustment screws attached to some or all legs are an alternative for shims and provide a more convenient means of adjustment, but customised settings are required for every situation. Depending on the application areas, frequent readjustment of the screws may become necessary.

Stabilising an object may require specialist knowledge and skilful adjustment if proper weight distribution is desired for example for heavy duty workbenches or machine supports.

A design for a floor-engaging leg assembly has been disclosed in U. S. Patent No. 3,844,517. This prior patent discloses disengaging a leg assembly connected to the main structure and thereby permitting a rotary oscillation about a generally horizontal axis and accomplishes self-adjusting floor-engagement before the assembly is locked in its current position with a series of teeth or friction pads. When all four legs are in contact with the support surface the table is firmly positioned even on an uneven floor. This design, however, requires manual intervention whenever the profile of the supporting surface changes.

Prior US Patent No. 5,690,303 discloses another design using a leg assembly with two opposing faces which rotate around a generally horizontal axis to enable floor- engaging positioning all four legs. Once a suitable configuration has been found, the leg assembly is locked into position by means of friction pads and a locking screw to prevent rotary motion of the leg assembly.

Consequently, wobbling of the table when a load is applied or shifted is prevented. Again, this mechanism requires manual readjustment whenever the table is subjected to changes of the floor due to relocation or settlement of the soil or deformation of the support surface.

Prior US Patent No. 3,954,241 provides a levelling assembly adapted to position and prevent"walking"of appliances such as washing machines on an'uneven floor.

Two mounting brackets with interconnected vertically movable floor-engaging leg members are attached to the appliance and ensure that each leg member is supporting its proportional share of the weight. The brackets can be frictionally engaged to prevent shifting movement of such appliances once all the legs are in normal contact with the floor. However, manual input is still required should the profile of the support surface change.

For structures requiring regular relocation, for example a mobile workbench, these prior proposals appear impractical. Frequent readjustment of the supporting legs can be time consuming and consequently is often neglected leading to a wobbling bench and therefore may pose unsuitable working conditions and safety hazards. In the case where the legs are replaced with wheels so that the bench is movable, continuous adjustment would be required which may not be practical.

This is particularly the case for trolleys or carts used for transport of materials on the shop floor. A course of

action to prevent wobbling is to utilise vehicles with only three wheels. Although such a vehicle will not wobble, the triangular shaped envelope within which the centre of gravity can be located before the vehicle overturns is restricted.

Four-wheeled carts often make use of two axles connected to the vehicle, with one wheel attached at each end of the axle. One of the axles is rigidly fixed, while the other is allowed to pivot around a horizontal axis to enable floor-engaging positioning of all four wheels.

This arrangement however, comprises in a mechanical sense, only a three-point support. Two points can be assumed between each of the wheels on the fixed axle and the support surface. The third point is located at the intersection of the virtual line connecting the contacts between the support surface and each of the wheels on the oscillating axles and the vertical plane through the pivot axis.

Prior German Patent No 28 36 494 discloses a two part rolling chassis whereby the front axle and the driver cabin is permitted to rotary oscillate about a generally horizontal longitudinal vehicle axis with respect to a fixed rear axle or axles. This patent discloses means to keep the wheels in contact with the road surface, by allowing limited rotational movement. As no provision to counteract such rotation is provided, it resembles a construction similar to the above four-wheeled cart, which provides non-overturning stability only within the triangular shaped envelopes.

Prior US Patent No. 4,071,. 259 discloses a pair of unsprung pivotally connected axle structures connected to a rigid frame on a pair of laterally spaced longitudinally extending axes. This suspension system establishes an effective pivot or roll centre, which is at a higher elevation than the centre of gravity of the vehicle, hence mimicking a suspended mass. When the wheels traverse uneven ground the suspension system permits the axle assemblies to shift laterally, around the elevated pivot point, so that all wheels remain in ground contact, thus ensuring proper support and traction. This arrangement resembles in a mechanical sense an oscillating axle. The vehicle remains stable (i. e. not overturning), so long as the centre of gravity remains in lateral direction within the virtual vertical triangle formed by the elevated virtual pivot axis and the two laterally spaced wheel contacts. In order to prevent the axle structure to swivel outwards excessively, end stops are required to allow only a small lateral displacement and therefore limits its effective range. Using a similar approach an axle suspension system for rigid axles on utility vehicles has been disclosed in Patent No. W097/00176 and W097/00177 with variations on the implemented levers to accomplish lateral shift motion to enable compensation for uneven support surfaces.

A vehicle with variable length banking links is disclosed in U. S. Patent No 2,689,747. This invention employs springs in order to increase the banking range and the maximal permissible unevenness of the support surface

before individual wheels loose road contact.

Springs suspension of axles and individual wheels are commonly used in today's vehicles, mobile and fixed structures to ensure floor engagement. The main shortcomings of passive suspension systems are that the height of the system varies dependent on the payload.

Furthermore, roll and bank movements are inevitable when the load shifts and above all the load distribution on the contact points is directly dependent on the unevenness of the support surface. Active suspension systems can overcome some of the limitations of their passive counterparts, but introduce unnecessary complexity and add to the costs.

SUMMARY OF THE INVENTION According to the present invention there is provided a self-stabilising article having a plurality of support members together providing four contact points for contacting a reference surface, the support members being constrained by a mechanical linkage such that rotation of the line joining any two adjacent contact points relative to the article is accompanied by rotation of the line joining the other two adjacent contact points relative to the article in the opposite sense.

In a practical embodiment of the invention, there are two support members pivotally attached to the article about substantially parallel axes, each support member providing two contact points for contacting a reference surface and being constrained by the mechanical linkage

such that rotation of one support member about its axis is accompanied by corresponding rotation of the other support member in the opposite sense.

Likewise, the contact points are preferably so constrained by a mechanical linkage that comprises the plurality of support members. The mechanical linkage may include a first linking member pivotally attached to the body about an axis substantially normal to the axes about which the support members are pivotally attached to the article, each of the two ends of the first linking member being articulated to a respective support member. A second linking member may also be provided, pivotally attached to the body about an axis substantially parallel to the axis about which the first linking member is pivotally attached to the article, each of the two ends of the second linking member being articulated to a respective support member.

Each support member may have legs, wheels, chain crawlers or pontoons taking real support from a fixed or varying uneven support surface or floor for stationary, mobile or moving support of the support surface.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an exploded view of components of the support assembly according to embodiment of the invention;

Figure 2 is a perspective view of the assembled components of Figure 1 as they would appear when placed on an uneven surface; Figure 3 is a top view of a support assembly according to one embodiment of the invention; Figure 4 is a perspective view of a support assembly according to a further embodiment of the invention, which details an implementation of the stabilising support assembly incorporating three radially positioned levers; Figure 5 is a perspective view of an'embodiment of the invention comprising a staggered multi-lever assembly; Figure 6 is a perspective view of an embodiment of the invention comprising a trapezoidal arrangement of the levers; Figure 7 is a perspective view of an embodiment of the invention comprising a chain crawler assembly with a single level arrangement; Figure 8 is a perspective view of an embodiment of the invention incorporated within a vehicle chassis; Figure 9 is a perspective view of a further embodiment of the present invention as applied to a domestic appliance or white good, not showing the connection of the support members and linkage to the body of the appliance; Figure 10 is a cross-section of the coupling between the support members and the linkage; Figures 11 and 12 show an adjustable coupling for use in connecting the support members and linkage to the body of the appliance; and Figures 13 and 14 show an alternative adjustable

coupling for light loads, for use in connecting the support members and linkage to the body of the appliance.

DETAILED DESCRIPTION The components of a self-stabilising support assembly 1 according to one embodiment of the invention are illustrated in an exploded view in Figure 1 which details how the parts are assembled together. Two longitudinally spaced support members 11 and 13 are connected via cylindrical joints 15 to a support surface 9. This allows rotary oscillation about a generally horizontal axis. In this embodiment, two laterally spaced levers or linking means 3 and 5 are connected via cylindrical joints 7 to the support surface 9 permitting generally rotary oscillation about a generally horizontal axis. Each of the levers 3 and 5 are connected at their longitudinal opposite ends to the support members 11 and 13 by means of generally spherical joints 17. This arrangement constrains the two support members to opposite rotary oscillation about a generally horizontal axis with respect to the superstructure.

When implemented according to the preferred embodiments, all legs of the assembly can be brought into floor- engaging contact and support their proportional amount of weight. Hence, objects can be positioned on a support surface without wobbling when loaded, the load shifts or the profile of the support changed.

The embodiment of the invention is suitable, but not limited to provide supports for, appliances such as

refrigerators, washing machines, work benches, trolleys, carts, mobile platforms, agricultural vehicles and devices, earth moving appliances, utility vehicles, floating structures and the like. When the contacts on the support surface are not level, the assembly stabilises objects by bringing the support members into floor-engaging contact without any manual intervention and hence minimises problems associated with the unevenness of the support surface. Means may be included to adjust the elevation of some or all individual legs or wheel assemblies for levelling the superstructure when placed on an uneven or slope support surface.

Although the embodiments illustrated in Figure 1 to 7 show a support surface 9 mounted internally, in the support assembly, it is also envisaged that the support surface could be mounted externally.

Figure 2 illustrates the components as assembled according to an embodiment of the invention. The assembly is suspended above a surface and is then gradually lowered vertically. Each end of the support members 11 and 13 comprises vertically extending legs 19,21,23, 25. Further lowering of the assembly causes leg 19 to move upwards relative to the support surface and simultaneously, pivotal action of the support member 11 around the cylindrical joint 15 causes the opposite leg 21 to be lowered. Rotary oscillation of the support member 11 is transmitted via levers 3 and 5 and imposes opposite rotary oscillation on the support member 13.

This rotation results in the lowering of the adjacent leg

25 and a simultaneous upward movement of the diagonally opposite leg 23. Assuming both legs 19 and 21 are now floor engaging, the further lowering of the assembly a rotating motion of the whole assembly about a virtual axis joining the contacts on the leg 25 and leg 23. When leg 23 becomes a third floor engaging leg, further lowering of the assembly causes simultaneous rotation of both support members 11 and 13 in opposite direction until the remaining leg 25 is in floor engagement.

When all four legs are in contact with the floor, the gravitational force exerted on the support surface 9 is transmitted through the cylindrical joints 15 to the two support members 11 and 13, to the legs and then to the support surface only one of the two levers 3 or 5 is required to prevent the otherwise free rotation of the support surface 9 around the longitudinal axis. However, for symmetrical movement of both support members 11 and 13 and a balanced load distribution, an arrangement with two moveable levers may be beneficial.

In use assuming the centre of gravity is located at the geometric centre of the support assembly, each leg 19, 21,23,25 will, on a flat and level surface carry equal weight. Unevenness of a generally level surface has within limit only marginal influence on the distribution of the weight carried by each leg. When the assembly is subjected to unequal loading e. g. the centre of gravity is not coincident with the geometr4ic centre or when positioned on a slope sufficiently steep to cause the vertical projection of the centre of gravity to shift,

each leg will carry its proper share of the weight. The envelope within which no danger of overturning of the assembly is to be expected is indicated by the dotted line 10 shown in figure 3 which essentially connects the cylindrical joints 7 and 15.

When placed on a horizontal and even surface the ideal implementation would provide all joints located on a generally horizontal plane with the cylindrical joints 7 and 15 positioned midway between the spherical joints 17.

In an embodiment of the invention where parallel movement of the vertically extended support members is important.

Figure 4 shows a further embodiment of the self- stabilising assembly incorporating three,. levers 3,5, and 14. In the embodiment illustrated in figure 4, it is preferred to locate the third lever 14 such that the distances between the cylindrical joints 15 and adjacent spherical joint 17 are matched on the support members 3 and 5 for all levers 3,5 and 14. More levers may be distributed radially to the longitudinal axis which connects the cylindrical joints 15 of the support members 16.

In all the embodiments, provision for marginal longitudinal and lateral movement of the support members 11,13 and 16 and levers 3,5 and 14 respectively is provided by the cylindrical joints 7, and 15. Other embodiments of the invention may feature a revolving joint for the support members, which would prevent such longitudinal contraction. In this case means would be

required for the levers to facilitate such contraction when the support members 11 and 13 rotate. This may be implemented by allowing a lever to slide through the spherical joint 17 or by telescopic, folding or other means of the lever to adjust for the variation of the length as the lever 11,13 and support members 3,5 rotate.

Further embodiments of the invention are indicated in figures 5 and 6. Figure 5 illustrates vertically extended 20 whilst figure 6 illustrates a trapezoidal shaped support surface 24 for different lengths if the support members 26, and 28 and unequal distances between the spherical joint 17 and the cylindrical joint 7 on the levers 25. The function of the embodiments of the invention shown in figures 5 and 6 is similar to that for previous embodiments.

Furthermore, although the embodiments disclose 1-6 only feature stationary objects, the invention is not restricted to stationary implementations. The legs may easily be replaced with wheel assemblies to provide an unsprung running gear, which generally enables continuous road to tyre contact even on an uneven support surface.

Additionally, each support member is not limited to distinct contact points such as legs or wheels, but one element such as a chain crawler for example for earth moving equipment. Such an embodiment of the invention is illustrated in figure 7.

In figure 7 a surface 9 or platform forming the base of a

vehicle body is connected to two laterally spaced tracks 27 via revolving joints 37. Lever 11 is attached to the platform 29 via cylindrical joint 15 and attached at each of its ends to tacks 27 via generally spherical joints 38 with sliding means to allow for the variation in the effective length of the lever. The support surface or platform 29 self-stabilises any object or vehicle body, for example placed, thereon.

Figure 8 illustrates the wheeled undercarriage of the vehicle. The base for the support surface in this embodiment is provided by support elements 32, each attached to support members 33 and 34 and levers or linking means 3 and 5 by the cylindrical joints 15 and 7 respectively. The support members in this embodiment form the front axle 33 and rear axle 34 to the levers 3 and 5 via the spherical joint 17.

It is envisaged that the present invention may incorporate a ratchet and pawl mechanism or other suitable device for levelling the support surface after stabilisation of the structure has been achieved.

It is also envisaged that one support assembly may be mounted on another so as to provide a tiered arrangement.

Figure 9 is a perspective view of a further embodiment of the present invention as applied to a domestic appliance or white good, not showing the connection of the support members and linkage to the body of the appliance. In this case, each end of the support members 11 and 13 comprises

a moulded plastics foot 19', 21', 23', 25'. One end of each support member 11,13 is coupled to a respective end of a linkage or lever 3. The coupling is shown in detail in figure 10. At the medial point of each of the support members and the linkage is a bracket 10,12,14. One end of each bracket includes a"T"-shaped extension that is retained in a slot in the support member or linkage; the other end is secured by a screw or bolt. The brackets provide a journal for the connecting pins 16,18,20, that are secured to the body of the appliance (not shown).

Figure 10 is a cross-section of the coupling between the support members and the linkage. Briefly, as can be seen, the lever 3 and support member 13 are formed into a dish or dome shape at corresponding points. The dish or dome includes a central aperture for passage of a connecting bolt 22, secured at its lower end by a nut 24. Part- spherical washers or collars 26,28 are located on the bolt and/or the nut, or threaded onto the bolt, to co- operate with the dish-or dome-shaped regions. A spacer 30 maintains a proper spacing between the lever 3 and the support member 13. It will be appreciated that relative movement between the shaped washers or collars 26,28 and the dished or domed regions of the lever 3 and the support member 13 allows limited relative rotation of the support member 13 and the lever 3 about any axis.

As explained extensively above, pivoting movement of the support member 11 is transmitted via the lever 3 and causes opposite pivoting movement of the support member

13. This stabilises the appliance. When placed on a horizontal and even. surface the ideal implementation would provide all connecting pins 16,18,20 to be located in a horizontal plane. Whilst this cannot be achieved if the points at which the pins 16,18,20 attach to the body of the appliance are fixed relative to it, some degree of adjustment of those points can allow an appliance that has been stabilised to be levelled as well.

Figures 11 and 12 show an adjustable coupling for use in connecting the support members and linkage to the body of the appliance. The concept is a simple one. A plate 50 to which the pin 16 is perpendicularly attached is provided at each end with a threaded bolt hole. A bolt 52,54 passes first through a washer 56,58, then through a slot 60,62 in the body 64 of the appliance, allowing the position of the plate 50 to be adjusted vertically relative to the body of the appliance. This adjustable coupling may be used for all three pins 16,18,20 or for just one, typically the centre pin 18.

In this case, for example, if the appliance were to lean forward, the bolts 52,54 locating the pin 18 on the body of the appliance may be loosened and the appliance pushed into the desired position before tightening the bolts 52, 54 again. During adjustment, the weight of the appliance would rest mainly on the two centre mountings of the support members and would hence allow easy levelling of the appliance.

Figures 13 and 14 show an alternative adjustable coupling for light loads, for use in connecting the support members and linkage to the body of the appliance. In this case, the plate 50 is absent. Instead, a bolt 52 passes first through a washer 56, then through a slot 60 in the body 64 of the appliance and into the pin 16, allowing the position of the pin 16 to be adjusted vertically relative to the body of the appliance. Again, this adjustable coupling may be used for all three pins 16, 18,20 or for just one, typically the centre pin 18.