The present invention relates to position adjustment apparatus, and more particularly to position adjustment apparatus for use in lowering and raising a heavy object.

In this regard, as described in my earlier application WO 03/024272, I have previously devised a position adjustment mechanism for holding two cylindrical members at longitudinally spaced positions, where one of the memloers is provided with a cam circuit and the other with a cam follower or peg, the cam follower being directed around the cam circuit on relative longitudinal movement of the members, for moving the members between the spaced positions.

In my earlier application, an example of use of the position adjustment mechanism was in the context of a snooker, billiards or pool table, where the mechanism formed part of each leg, the mechanism allowing the table to be used as a games table at first height and as a dining table at a lower height.

The mechanism as described in my earlier application works extremely well, but nevertheless has certain drawbacks. Firstly where only one person is available to adjust the table's height, in order to operate the mechanism they will in practice have to lower or raise the table in two stages, so that they first raise or lower one end, and then move to the opposite end of the table to raise or lower that end.

Raising or lowering the table in two stages in this way is not ideal in that there results an intermediate position where the table top is at an angle, with one end relatively high with respect to the other. This results in off-axis forces on the table and legs which are to be avoided.

Further, to operate the mechanism from a low to a high position, the table needs to be lifted a height of up to around 95 mm. Such tables are generally very heavy because of the use of a slate bed in their construction, and this can be problematic, particularly for larger tables.

Hence, an object of the present invention is to provide a mechanism which seeks to alleviate such known problems.

According to an aspect of the present invention there is provided apparatus for holding two elements at two longitudinally spaced positions, the apparatus comprising:- a cam circuit provided to a first one of said elements; a cam follower provided to a second one of the elements; wherein the cam circuit directs the cam follower around the circuit as a result of alternating relative longitudinal movements of the first and second elements, relative longitudinal movements between the elements in one direction being effected through pressurising or depressurising a chamber formed between the elements.

With such an arrangement, the need to manually lift an object being supported by the apparatus is avoided. Preferably, the first and second elements comprise respective first and second cylindrical portions, the first one of which disposed inside the second. In this manner, the first and second cylindrical portions can function as a piston/cylinder arrangement.

Preferably, an end of the first cylindrical portion together an internal bore of the second cylindrical portion form said chamber between the elements. Said chamber conveniently has a combined fluid inlet/outlet. A plurality of fluid inlet/outlets may be provided where suitable.

The apparatus preferably has a plurality of cam circuit/cam follower combinations positioned non-diametrically opposite around the circumference of the cylindrical portions. Conveniently, three such cam circuit/cam follower combinations and are provided at equal intervals around the circumference of the cylindrical portions.

Examples of the present invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 shows a cut away perspective view of a height adjustment mechanism of the present invention;

Figure 2 shows a cut away perspective view of a height adjustment mechanism of a second embodiment of the present invention;

Figure 3 shows a part cross-sectional view of a height adjustment mechanism of a third embodiment of the present invention; and

Figure 4 shows a cam circuit for use with the present invention.

As shown in Figure 1, the position adjustment mechanism comprises a first element in the form of an outer cylindrical portion 200 and a second element in the form of an inner cylindrical portion 201 which is slidably received in the outer cylindrical portion.

The outer cylindrical portion 200 is provided with one or more cam followers in the form of pegs 202 which are received within a cam circuit 203 provided on an outer face of the inner cylindrical portion 201. The cam circuit may be machined (milled) or otherwise formed into the outer surface of the inner cylindrical portion 201.

As is described in my earlier application WO 03/024272, relative longitudinal movement of the inner and outer cylindrical portions causes each peg to move around its cam circuit. In this respect, each cam circuit includes a lower detent 204 and an upper detent 205 in which the pegs can seat.

The cam circuit is configured for directing each peg between these detents.

In use, the outer cylindrical portion 200 is attached to an object requiring raising and lowering via bolts or the like in flange 217. The inner cylindrical portion is attached to a foot 216 for engaging the ground or other support surface. Hence the pegs 202 are naturally urged downwardly together with the outer cylindrical portion so that they will seat in one of detents 204 or 205.

The means of attachment to the object need not be provided at the top of the outer cylindrical portion but can be provided at any suitable position on the outer cylindrical portion 200. Moreover whilst a disc like foot 216 is shown in the drawings, any suitable means may be used for engaging the ground or other support surface.

With the peg positioned in the lower detent 204, moving the inner and outer cylindrical portions substantially longitudinally away from one another will result in the peg moving upwardly in the cam circuit. Slight deviations in vertical movement will be accommodated by the inclined surface 208, so that the peg will ultimately engage surface 209 and be directed into detent 214, above inclined surface 210 of detent 205. Hence on a further substantially longitudinal relative movement, this time in a direction moving the inner and outer cylindrical portions together, the peg will fall into detent 205. Movement of the peg from detent 205, back to detent 204 is conducted in a similar fashion.

Hence, in the embodiment shown in Figure 1, in order to raise and then lower the object through 1 complete cycle of the cam circuit, the inner and outer cylindrical portions are moved in alternating longitudinal directions, i.e. apart then together, then apart and then together.

In this connection, a fluid inlet/outlet 211 allows fluid to be introduced into and released from a chamber 212 formed between a top end face 213 of the inner cylindrical portions 201 and an upper internal portion of the outer cylindrical portions 200. Multiple inlet/outlets may be provided where suitable.

With the arrangement shown, the inner cylindrical portion effectively becomes a piston within the outer cylindrical portion.

When it is desired to raise the object in question, fluid is introduced under pressure into the chamber 212, so that the inner cylindrical portion is forced downwardly within the outer cylindrical portion. Hence the peg moves with the outer cylindrical portion from detent 204, into engagement with surface 209 and then into detent 214. At this point, pressure is released from the chamber so that the outer cylindrical portion, under the weight of the object being supported, is urged downwardly. The peg thus moves via engagement surface 209 and detent 214 into detent 205. This represents a high position of the object being supported.

The process is repeated to move the peg from detent 205 back to detent 204 and complete one circuit of the cam circuit. In other words, the chamber is again pressurised until the peg is at position 207, whereupon the pressure is released — O such that the peg drops down and is directed to detent 204.

Sensors may be positioned at suitable locations such that the position of the peg in detents 207 and 214 is detected for enabling the pressure to be released from chamber 212 at the appropriate time. Also suitable seals, such as an 0-ring seal 215 are provided to ensure effectiveness of the pressurized fluid in chamber 212. The pressure can be released slowly for a controlled lowering of the object.

In the context of a table, with such an arrangement all four legs can be connected to a common fluid source so that they are raised and lowered at the same time, with ease and without any requirement for manual physical lifting by a user.

Three non-diametrically opposed cam circuits and pegs are provided around the circumference of the inner and outer cylindrical portions. Three equi-spaced cam circuits and pegs is particularly preferred as this offers a highly stable support construction. In this respect, not having the pegs diametrically opposite one another is advantageous in that otherwise an axle is effectively formed on which the inner cylindrical portion will tend to rock.

In this regard, it is preferred for there to be an odd number of cam circuits and a corresponding number of pegs, greater than 1.

Further, the detents may be aligned in the longitudinal axis of the cylindrical portions as shown in Figure 4. In other words, a lower detent 400 is vertically below an upper detent 401. This means that the process of moving the member from one detent to another does not leave the inner and outer cylindrical portions relatively twisted. The cam follower is shown in Figure 4 in many positions to illustrate how it moves around the cam circuit.

The fluid for use in the system may be a liquid or gas or a combination of the two. In this regard, whilst gases tend to present greater sealing problems, should there be a leakage then less damage is likely to occur, compared with a liquid leak.

The means for moving the inner and outer cylindrical portions apart is hence provided in the form of a hydraulic or pneumatic arrangement. Separate inlets and outlets for the fluid may be provided where this is more suitable.

In an alternative arrangement, the means for moving the outer cylindrical portion and peg upwardly with respect to the inner cylindrical portion may comprise a vacuum arrangement, as shown in Figure 2, a chamber 220 in this regard being formed by extending the outer cylindrical portion below a base of the inner cylindrical portion, with suitable seals 221 provided around an extended foot section 222. A vent 218 is provided in the upper part of the outer cylindrical portion.

The mechanism is not limited to use with tables and may for example be incorporated into other systems which require raising and lowering of a substantial load.

A further example is within the context of vehicles, that can have different ride heights. In this regard, vehicles for use in off-road conditions are arranged such that their ride height is raised in comparison with road only going vehicles.

The present invention can be incorporated, as shown in Figure 3, into for example, a shock absorber system for adjusting the ride height of a vehicle between road and off-road configurations.

As shown, an upper part of a height adjustment assembly for a vehicle 300 is attached at one end to a vehicle frame 301 and at another end houses a shock absorber 302. The assembly includes inner and outer cylindrical portions 303, 304 as before with associated cam circuits 305 and pegs 306. In order to raise the ride height of the vehicle, a pressure of fluid in chamber 307 is increased by introducing fluid through inlet/outlet 309 and then released to direct the peg 306 into detent 308 in the cam circuit. To further increase the ride height, the pressure of fluid in chamber 307 is again increased by introducing fluid through inlet/outlet 309 and then released to direct the peg in an upper detent 311.

To reduce the ride height the pressure in the chamber is again increased and then released.

The shock absorber mounting can be provided further into the body of the inner cylindrical portion in order to enhance the compactness of the assembly.

It has been calculated that in order to raise the vehicle ride height by around 100 mm, 4 such assemblies (one on each wheel for a car with four wheels), each having a diameter of around 65 mm would raise a car of 3000 Kg in 7.5 seconds, using 0.49 Kw or 0.66 Hp rated pump. Current pumps for vehicle power steering units are rated considerably higher than this.

It will be appreciated that a number of variations can be made to the height adjusting apparatus. For example, the arrangement of the pegs and cam circuits could be reversed, so that the pegs are carried on the inner cylindrical portion and the cam circuits are formed on the outer cylindrical portion.