WO1989009086A1

WO1989009086A1 - Motion system for simulating screen action to a cinema audience

Info

Publication number: WO1989009086A1
Application number: PCT/AU1989/000124
Authority: WO
Inventors: David William Bristow
Original assignee: BRISTOW ENGINEERING OF HASTINGS PTY Ltd
Current assignee: BRISTOW ENGINEERING OF HASTINGS PTY Ltd
Priority date: 1988-03-25
Filing date: 1989-03-23
Publication date: 1989-10-05
Anticipated expiration: 1990-09-25

Abstract

A motion system (10) has a base (12), a horizontal platform (20) spaced above the base (12) by central support means (18), drive means (32) operable to tilt the platform (20), and stabilizer means (46) for controlling movement of the platform (20) under the action of the drive means (32). The platform (20) may be circular and rotatable about the axis of the support means (18). The stabilizing means (46) includes at least one vessel (44) adjacent to, on, or defined by the base which holds liquid (48), and flotation means (66, 68) provided on and extending below the platform (20) so as to be at least partially within the liquid (48) thereby providing buoyancy to said platform (20). The motion system (10) may be used in a theatre complex to provide simulated action to a number of people seated on the platform (20).

Description

TO A CINEMA AUDIENCE

This invention relates to an improved motion system for a tiltable and vertically adjustable support platform, which also may be rotatable, and to a support platform having such motion system.

Over the years, there have been a number of proposals for motion systems for support platforms of theatrical systems. Examples of such proposals are provided by British patent specification 677383 and U.S. specifications 1,789,680 and 4,642,945. In these examples, a platform intended to support a number of people in a theatre complex is able to be tilted in at least some directions from the horizontal, or simultaneously tilted and rotated. The resultant motion is intended to be perceived by those people on the platform as attributable to action they are viewing on a cinema screen or other visual display system, or the like. That is, the intention is somewhat similar to that underlying aircraft flight deck simulators. However, for practical purposes, the platform needs to be relatively large so as to be able to hold a large number of people simultaneously, such as from 250 to £00 people, although for some applications a platform for a few as from 60 to 100 people can be provided. Particularly with platforms sufficiently large for such a number of people, there is difficulty providing a motion system having an appropriately large load carrying capacity, and yet having the versatility to provide a realistic range of movements. Also, with increasing size, it is difficult to isolate people on the platform from awareness of abrupt changes in motion and/or noise due to operation of the motion system, with these factors detracting from the ability to perceive the movement as attributable to cinema action. The present invention seeks to provide an improved motion system and, at least in a preferred form, such system having enhanced load carrying capacity and alternatively or additionally, facility for quieter and/or smoother operation.

According to the invention, there is provided a motion system having a base, a generally horizontally disposed platform spaced above the base by centrally disposed support means, drive means operable to tilt the platform from and back to the horizontal in at least some directions, and stabilizer means for controlling movement of the platform under the action of the drive means; the stabilizing means including at least one vessel adjacent, on or defined by the base for holding a body of liquid and flotation means provided on and extending below the platform so as to be at least partially within liquid in said vessel and for thereby providing a buoyancy action on said platform. The platform preferably is tiltable in any direction from the horizontal, such as through an angle of up to about 15° to 20°, while it preferably also is rotatable. The following description largely will be directed to a motion system in which the platform is so tiltable and rotatable, although it is to be understood that a lesser freedom of movement can be adopted in a more simple system.

The platform most preferably is circular, although other configurations can be used. The support means preferably includes a central column on which the platform is mounted. At the top of the column, at or below the platform, there may be a joint such as a gimbal joint which allows tilting of the platform relative to the column. The drive means for tilting the platform may comprise a plurality of hydraulic cylinders spaced around the column, and operable in unison to tilt the platform in a required direction.

In one arrangement, the column has a torque key at its lower end, with the torque key being located in a column sleeve mounted on the base. In that arrangement, the column is fixed against rotation but, due to location of its torque key in the sleeve, the column can be free to move vertically through a small distance. With such column, a gimbal joint preferably is provided at its upper end, above a transverse support plate. A series of hydraulic cylinders acting between the support plate, and a sub-platform flange of the column are adjustable for tilting the platform. Above the gimbal joint, the column has a turn-table on which the platform is fixed, with motors mounted on the support plate being operable to rotate the turn-table in a required direction and, hence, the platform. Where the platform is rotatable, the at least one vessel, for holding a body of liquid, extends circumferentially of the platform. If the platform is to be rotatable through 360°, there preferably is one vessel of annular form. The flotation means may include a plurality of flotation cells spaced circumferentially around the platform. The flotation cells may be of two types, the first being of a static load type and simply comprising sealed flotation cells and the second being of a live load type which enable addition or removal of ballast for varying their buoyancy effect.

The at least one vessel for holding a body of liquid preferably has control means for enabling the volume of liquid to be varied. In one arrangement, there is a transfer tank to which liquid can be withdrawn from the vessel on opening an outlet control valve, and a supply tank from which liquid can pass to the vessel on opening an inlet control valve. Preferably there is a pump for passing liquid from the transfer tank to the supply tank, to provide a closed liquid circulation system. In an alternative form, the flotation means comprises at least one flotation member secured to the underside of the platform, and extending downwardly into the at least one vessel for holding a body of liquid. When the platform is not rotatable, there may be a plurality of angularly spaced vessels into each of which a respective such flotation member extends. However, where the platform is rotatable, a single annular vessel is provided, and the flotation means can comprise a single, circumferentially continuous flotation member. The or each flotation member may be of a hollow construction, or it may be of a foamed plastics material.

The or each flotation member preferably is arcuate such that it curves downwardly and inwardly below the platform. Preferably such member is so curved by defining part of a spherical form, and has a centre of curvature substantially co-incident with the axes of tilting of the platform. While tilting of the platform may be under the action of hydraulic cylinders, with its rotation provided by drive to a column structure on which the platform is supported. However, where there is an annular flotation member which extends downwardly into an annular trough, an alternative arrangement is possible. Thus, the flotation member may co-operate with a fixed baffle to deviate the trough into two concentric trough sections, with water flowing in opposite directions around each trough section. The flotation member can be provided with angularly spaced vane means which are selectively pivotable to provide tilting, rotation or braking of the flotation member, and hence the platform, under the action of the water flow.

In use of the motion system, the platform initially is horizontal and at a datum level. At that level, the upper surface of the platform preferably is substantially flush with surrounding flooring. The platform may be retained at that datum level by at least one locking and support leg which may, for example, be hydraulically engageable and releaseable. Movement of the platform to the datum level can be by variation of the level of liquid in the at least one vessel and, hence, variation in the buoyance effect provided by the flotation means. The platform is retained at its datum level until a number of people are assembled, and preferably seated, on the platform, after which the locking and support leg can be released.

Prior to releasing the locking and support leg, the increased load resulting from the live load being added to the dead load, is compensated for by altering the level of liquid in the at least one vessel and/or altering the ballast supplied to the live load flotation cells. The platform then can be tilted and/or rotated, with its resultant movement being controlled by the stabilizing means. The arrangement is such that rotation and/or tilting can be smooth, as can changes in the direction or rate of rotation and/or tilting. Also, power requirements for rotation and/or tilting are reduced, enabling use of smaller and quieter actuators and/or motors. This is due to both the dead and live loads being carried by the buoyancy action of the stabilizing means, with minimum force being required for rotation and/or tilting and only friction and inertia needing to be overcome.

As will be appreciated, the total of dead and live load need not be uniformly distributed on the platform, while resultant out of balance forces can vary with time. To compensate for this, the flotation cells of the live load type preferably are spaced around the circumference of the platform, and the quantity of ballast supplied to each is controlled so as to counter-balance such forces. Typically the ballast is a liquid and, in one convenient arrangement, the live load flotation cells are inter-connected by conduit means by which ballast can be added to or withdrawn from each; with pump or pneumatic means being operable to circulate ballast and control valve means at each live load cell being operable to enable selective adjustment of the ballast of each cell. The motion system preferably has load sensing means, operable to determine the level of the live load and out of balance forces. The system preferably also has a micro- computer control means, responsive to output signals of the load sensing means, and operable to control actuation of valves and pumps for varying the level of liquid in the vessel for containing a body of liquid and the distribution of ballast to the live load flotation cells. Reference now is directed to the accompanying drawings, in which:

Figure 1 is a part vertical section of a motion system according to a first embodiment of the invention; Figure 2 is a partial plan view of the system of Figure 1;

Figure 3 is a plan view of a motion system according to a second embodiment of the invention;

Figure 4 is a vertical section taken on line IV-IV of Figure 3;

Figure 5 is a plan view of a motion system according to a third embodiment of the invention;

Figure 6 is a vertical section taken on line VI-VI of Figure 5; Figure 7 is a vertical section of a motion system according to a fourth embodiment of the invention;

Figure 8 is a schematic representation of part of the structure of the system of Figure 7, as seen in plan view; Figure 9 is a schematic representation, showing at A, B and C, respective operating positions for rotation control elements of the system of Figure 7;

Figure 10 is a sectional schematic representation of a preferred form of flotation control member according to the invention; and

Figure 11 is a perspective view of an alternative form of control member.

In Figures 1 and 2 of the drawings, the motion system 10 includes a base structure 12 which defines a surrounding floor level 14. Within cavity 16 of base structure 12, there is a support column structure 18 on which is mounted a circular platform 20. Structure 18 includes a column 22 having a torque key 24 on its lower end, and a column sleeve 26 in which column 22 and its key 24 is vertically, but non-rotatably, adjustable.

At its upper end, column 22 has a gimbal or other universal joint 28 which enables reversible tilting of associated upper plate 30 in any direction from the horizontal. Tilting of plate 30 is by operation of circumferentially spaced hydraulic cylinders 32 mounted on sub-platform 34 of column 22 and connected to plate 30. Above joint 28, there is a turn-table 36 rotatable on bearing 38, such as a ball-race. Diametrically opposed reversible hydraulic motors 40 on plate 30 drivingly engage turn-table 36 by drive means 42, such as a friction or toothed belt, sprocket chain, gears or friction drive, for rotation of turn-table 36. As platform 20 is fixed on turn-table 36, platform 20 rotates on axis X of structure 18, and/or tilts, with turn-table 36.

Around column structure 18, base structure 12 defines an annular trough or vessel 44 of a stabilizer system 46. Vessel 44 holds a body of liquid such as water, of which the upper level 48 is shown. An outlet conduit 50 enables discharge of liquid from vessel 44 on opening of high volume gate valve 52; the discharged liquid passing to transfer tank 54. Liquid can pass from tank 54, via conduit 56, to supply tank 58 under the action of transfer pump 60. Also, liquid can return from tank 58 to vessel 44, through conduit 62, on opening of high volume gate valve 64.

System 46 also includes a plurality of flotation cells 66,68, each mounted on support members 70 depending from platform 20. Cells 66,68 are in alternating series, with each cell 66 being a sealed vessel, or made of a block of suitable buoyant material such as foamed plastics, arranged to support static load, and each cell 68 being a vessel enabling ballast liquid to be added or withdrawn. It is to be noted that cells 66,68 can be arranged other than in an alternating series. Around the series of cells 66,68, there is a ballast loading pipe 72 and a ballast unloading pipe 74. Each pipe 72, 74 communicates with the interior of each cell 68, via a respective conduit 72a.,74a., under the action of respective gate valves 72b,74b. Liquid, drawn from vessel 44, is able to pass along pipe 72 under the action of ballast loading pump 72c and to pass, as required, to one or more of cells 68 by selective and timed actuation of the respective valve 72b.. Similarly, liquid is able to be drawn into pipe 74 under the action of ballast unloading pump 74c, from one or more cells 68, by selective and timed actuation of the respective valve 74b; the liquid discharging from pump 74c. passing back to vessel 44. The level of ballast liquid in one cell 68 is shown at 76 in Figure 1.

In Figure 1, one half of platform 20 is depicted in its horizontal position to the left of the centre-line. To the right of that line, tilting of the platform 20 is depicted. However, as indicated above, platform 20 is circular and it is centrally located on column structure 18. When in its horizontal position, platform 20 can be held at a datum level in which its upper surface is flush with level 14. Platform 20 is vertically adjustable to such datum level by varying the level 48 of liquid in vessel 44 and/or by varying the ballast in cells 68, with adjustment of actuators 32. When at its datum level, platform 20 can be locked by a plurality of circumferentially spaced locking and support legs 78, each movable under the action of a hydraulic cylinder 80, and having a projection 82 engageable in a peripheral groove 84 of platform 20.

In the arrangement illustrated, the dead load of platform 20 (and any structure thereon) is carried by the buoyancy effect of cells 66. The difference between the dead load, and the total of the live load due to people on platform 20 and the dead load, is compensated by the ballasting of cells 68 and/or by altering level 48 of liquid in vessel 44, with adjustment of actuators 32. Selective ballasting of cells 68 enables any out of balance load forces to be compensated. The arrangement enables variation in the live load to be accommodated and, as both dead and live loads are offset by the buoyancy effect of cells 66,68, minimum force is required to rotate platform 20 by motors 40 or to tilt platform 20 by cylinders 32. Variation of the height of platform 20 with change in liquid level 48 and/or ballasting of cells 68 is permitted by sliding of column 22 in sleeve 26.

To maintain a sufficient buoyancy effect on platform 20, cells 66,68 must be submerged throughout the range of tilting. Vessel 44 needs to be configured to accommodate the full range of movement of cells 66,68 as shown in the right half of Figure 1.

In the arrangement illustrated, motors 40 are mounted on upper plate 30 which is tiltable relative to column structure 18 under the action of cylinders 32. While gimbal joint 28 is suitable in that system, it may be necessary to use another form of universal joint instead of the gimbal joint if it is required to replace motors 40 with a rotary drive on column structure 18, as a gimbal joint does not have sufficient capacity to transmit rotational movement.

In the arrangement of Figures 1 and 2, support members 70 are shown as being at right angles to platform 20. As platform 20 tilts, the cells 66, 68 which are raised as a consequence in vessel 44 move radially outwardly with respect to the pivot axes at joint 28, while the radially opposite cells 66, 68 are lowered and move radially inwardly with respect to that axis. However resultant out of balance forces can be substantially offset by adjusting ballast loading between cells 68.

Figures 3 and 4 show a motion system 110 according to a second embodiment. In system 110, there is a base structure 112 above which a circular platform 114 is mounted on a column structure 118. An annular disc 120 of structure 118 is fixed on base structure 112 and has rotatable thereon a turn-table 122 having an upstanding column 124 rotatable therewith. A reversible electric or hydraulic motor 126 is mounted on turn-table 122 and has an output shaft provided with a friction wheel 128 bearing against the inner circumferential surface 130 of disc 120. Operation of motor 126 rotates wheel 128 and friction between surface 130 and wheel 128 causes the latter to ride around disc 120. As a consequence, turn-table 122 and column 124 are caused to rotate on axis X of column 124.

Column 118 also includes a sleeve 132 coupled to platform 114 by a gimbal or other form of universal joint 134, with sleeve 132 being received on and rotatable with column 124 by a spline coupling 136 therebetween. Also, structure 118 includes a plurality of hydraulic actuators 138 spaced circumferentially around column 124 and connected between sub-frame 115 of platform 114 and turn-table 122 by respective ball joints 115a, 122a. The arrangement of structure 118 is such that rotation of turn-table 122 and column 124, by motor 126, rotates sleeve 132 and platform 114, due to spline coupling 136 and gimbal joint 134. Also, selective operation of actuators 138 provides required reversible tilting of platform 114 relative to the axis of column 124; with joint 134 enabling such tilting on one or both of two horizontally disposed axes of joint 134 which are at right angles and intersect at axis X of column 124.

Simultaneous operation of actuators 138 provides required vertical adjustment of sleeve 132 and platform 114 permitted by spline coupling 136.

Below platform 114 and around column structure 118, base structure 112 has formed therein an annular trough

140. Depending from sub-frame 115 of platform 114, there is an annular flotation member 142 which has the lower portion thereof within trough 140. Water is provided in trough 140 as indicated by water line 141, while member 142 is of a material or of a form which displaces water in trough 140 and thereby provides a buoyant lift on platform 114. Member 142 thus can be defined by a hollow rigid shell, such as thin metal or reinforced plastics material. Alternatively, member 142 can be formed from foamed plastics material such as polystyrene or polyurethane, most preferably with a water impermeable - outer skin or membrane. Where such foamed material is used, it can be strengthened or made less water permeable by being provided in such shell.

Around the underside of platform 114 and supported by sub-frame 115 thereof, an annular array of liquid ballast cells 144 is provided. Each of cells 144 is a vessel able to hold suitable ballast. At least some cells 144 are inter-connected by ballast loading and unloading pipes, conduits and gate valves not shown but similar to pipes 72, 74, conduits 72a, 74a and valves 72b, 74b of Figures 1 and 2. Thus, liquid ballast can be adjusted around platform 114, as required, under the action of ballast loading and unloading pumps or pneumatic devices which also are not shown but can be as depicted in Figure 2 for pumps 72c, 74c. Where such adjustment is possible for only some of cells 144, the ballast in the remaining cells can be liquid or of a suitable solid form.

Cells 144 provide a static load for platform 114, additional to that of the platform itself and its sub-frame 115. Those cells between which ballast is able to be adjusted enable the overall balance of platform 114 to be achieved while also enabling fixed, variable or movable loads provided on platform 114 to be allowed for while maintaining such balance.

Flotation member 142, as shown in schematic form in Figure 10, can be regarded as comprising two principal parts, viz. the main body or panel portion 142a and the toroidal lower rim portion 142b. The volume of panel portion 142a below the level of water line 141 provides the bulk of water displacement and produces a positive centering action on platform 114. The spacing between surfaces 142c and also the vertical extent of portion 142a provide the main factors controlling that action. The volume of rim portion 142b produces a negative centering action on platform 114, with the projected area of the external surface 142d of that portion onto a horizontal plane controlling that action. The positive and negative centering actions most preferably are substantially balanced under the ballasted, in use load conditions for platform 114. That is, platform 114 most preferably has neutral characteristics under such conditions in that it tends neither to tilt from the horizontal and, at a given angle of tilt, preferably returns to the horizontal, unless moved in response to the action of actuators 138. For platform 114 to be neutral, panel portion 142a preferably is curved, such that its surfaces 142c are part spherical and have a substantially common centre of curvature. Also, that common centre of curvature most preferably is substantially at the point of intersection of axis X of column 124 and the axes of gimbal joint 128, with that centre of intersection also substantially at the centre of gravity of platform 114 when the latter is in its ballasted, in use load conditions.

The ballasted, in use load conditions for platform 114, and the height of its centre of gravity under such conditions, can vary substantially. The load of course includes members of an audience to be accommodated on platform 114, as well as any seating provided for the audience and apparatus provided on platform 114. It may not be possible to achieve ideal neutral characteristics for platform 114 at all times, but it is preferable for this to be obtained at least under average operating load conditions such that departure from the ideal can be minimized. Factors to be taken into account are the respective radii of curvature R*, R" of surfaces 142c of panel portion of 142a, the vertical extent of the spacing of the axes of gimbal joint 128 from platfrom 114, and the volume of portion 142a relative to that of rim portion 142b. The flotation member profile most preferably is determined by the following factors:

(a) the overall platform, superstructure and live load mass;

(b) the location of the tilt axes for the platform in relation to the centre of gravity of the mass of

(a) ; and

(c) dynamic requirements.

These factors determine the centering or non- centering tilting movement. The tilting movement can be increased, neutralised or decreased, subject to system requirements, by both the volume and position relationship of the flotation member submerged and flotation value. The basic flotation member value variations are: (i) increased submerged value gives increased non-centering movement; (ii) decreased flotation value gives increased centering movement. Due to the dynamic requirements, the flotation member preferably is curved, such as to be of part spherical form, to minimise water turbulence and subsequent drag, providing maximum dynamic efficiency. These considerations apply both to the system of Figures 3 and 4, as well as those of Figurs 5 and 6, Figures 7 to 9, and Figure 12.

With tilting of platform 114 under the action of actuators 138 under such ideal conditions or a reasonable approximation thereto, the volume of flotation member 142 below the level of water line 141 remains substantially constant. Also, out of balance forces are substantially avoided due to the surfaces 142c having a centre of curvature substantially co-incident with the axes of gimbal joint 128. However where, for a given installation of motion system 110, such ideal conditions can not be achieved in the overall form depicted in Figures 4 and 10, the volume of rim portion 142b can be increased or decreased relative to that of panel portion 142a, such as to provide a rim portion having a diameter greater or less than the radial thickness of panel portion of 142a.

However, with such increase or decrease, it is highly desirable that portions 142a, 142b merge smoothly so as to avoid resultant water drag resisting tilting of platform 114. Also, the junction of flotation member 142 and platform 114 can be above or below the centre of curvature of surfaces 142c.

Figures 5 and 6 show a simplified form of motion system 110 of Figures 3 and 4, with corresponding parts having the same reference numerals plus 100. In system 210 of Figures 5 and 6, platform 214 is square rather than circular in plan view and, while tiltable, it is not rotatable. Thus, column structure 218 simply comprises a base 260 having an integral sleeve 262 fixed thereon, and in which a column 264 is received, but is fixed against rotation by spline coupling 266. Platform 214 is tiltable on gimbal or other form of pivot joint 228 on column 264, while the height of column 264 and platform 214 is adjustable under the action of extendable and retractable actuators 238 and is permitted by coupling 266. While Figures 5 and 6 show a gimbal joint 228, any simple ball or other suitable pivot joint can be used, with platform 214 preferably being constrained against rotation by a Panhard rod 229 connected between platform 214 and fixed structure 231 relative to which platform 214 is pivotable. Sub-frame 215 of platform 214 has a triangular frame portion defined by beams 268. On the underside of platform 214, sub-frame 215 supports concentric, arcuate arrays of ballast cells 244. Similar arrays of cells 244 are provided adjacent each beam 268 but, for simplicity of illustration, these are shown adjacent only one of the three beams 268. Cells 244 are for the same purpose as cells 144 of Figures 3 and 4, and at least some of them can enable ballast adjustment similar to that described with reference to Figures 3 and 4.

As platform 214 is not rotatable, an annular trough into which a flotation member extends is not necessary. Rather, there is provided a plurality of angularly spaced troughs 240 of which three are shown. Troughs 240 are inter-connected by conduits 250 such that water in each is at a common level 141. Similarly, for each trough 240, platform 214 is provided with a respective flotation member 242. In radial section, each member 242 is of a similar general form to the annular member 242- of Figures 3, 4 and 10 apart from being of limited extent circumferentially of column structure 218. However, as shown in Figures 5, and the related schematic perspective representation of Figure 11, each member 242 is of limited arcuate extent in plan view, that is around column 264, (as shown for two members 242) or of substantially linear extent in plan view (as shown for one member 242) . However each member 242 also has rounded end surfaces 242e to avoid turbulence of water in troughs 240.

Apart from platform 214 not being rotatable, motion system 210 operates in a similar fashion to system 110 of Figures 3 and 4, and further description thereof is not warranted. However, each flotation member 242 preferably is shaped and is of a construction as shown in Figure 11 as described above for member 142 of Figures 3, 4 and 10.

Figures 7 to 9 illustrate a motion system 310 similar in overall form to system 110 of Figures 3 and 4, and corresponding parts thereof therefore have the same reference numeral plus 200. However, the description of system 310 principally will be limited to additional features not present in system 110.

In system 310, platform 314 is rotatable, as well as tiltable and liftable. Trough 340 therefore is of annular form. Also, a single, circumferentially continuous, annular flotation member 342 is provided, as with member 142 of Figures 3 and 4, although only two angularly spaced sections of member 342 are depicted in Figure 8 for ease of illustration.

Column structure 318 has a base plate 320 fixed on base structure 312 and, journalled in plate 320, an upstanding fixed column 324. Platform 314 is mounted on column 324 by a sleeve 332 coupled to platform 314 by a gimbal joint 334, with sleeve 332 being received on and rotatable relative to column 324. This simple coupling enables vertical adjustment of sleeve 332 and platform 314 relative to column 324. However, structure 318 does not include hydraulic actuators similar to actuators 138 of Figures 3 and 4, the need for such actuators being obviated due to further structure described in the following.

As shown in Figure 7, the lower portion of each flotation member 342 is bifurcated to define a groove 370. In radial section, each groove has a curvature corresponding to that of surfaces 342c while in horizontal section groove 370 has an arcuate form around column structure 318. Also, trough 340 has an upwardly extending baffle 372 which corresponds in vertical and circumferential curvature to groove 370 and is slidably received therein. Thus, member 342 and baffle 372 together divide trough 340 into inner and outer trough sections 340a, 340b. Also, the curvature and sliding fit of baffle 372 in groove 370 is such that flotation member 342 can rotate and tilt with platform 314, relative to baffle 372, while retaining baffle 372 in groove 370. As shown in Figure 8, trough sections 340a, 340b have respective tangential, but oppositely directed, water inlet conduits 374, 375. Each trough section also has a respective outlet conduit 376, 377 forming a closed loop with its inlet. A pump 378, 379 in each loop is operable to circulate a flow of water around each trough section, with the flow in one section being in the opposite direction to that in the other.

Figure 8 is of a simple schematic form and, as a practical matter, a more complex arrangement would be used. Thus, each trough section 340a, 340b more typically would have a plurality of tangential inlets 374, 375 spaced around its periphery. Also, rather than have outlet conduits 376, 377, the oppositely circulating flow of water in sections 340a, 340b would be allowed to overflow a wier portion 340c, 340d of the upper edge of each section, with the overflow being received in a holding tank (not shown) and recycled via pumps 378, 379. In each trough section 340a, 340b, flotation member 342 is provided with respective circumferentially spaced pairs of adjustable vanes 342a, 342b. The vanes of each pair include an upper and lower vane, each of which projects laterally of member 342 in the water flow in the respective trough section. The vanes in each trough section are pivotable under the action of a drive system (not shown) such as small electric servodrives provided in member 342, so that the vanes are movable in unison or independently as required. In Figure 9, one pair of vanes 342a in trough section 340a are indicated in respective operating positions A, B, C. In position A, the vanes 342a are parallel to each other and to the water flow in section 340a, in which case they are neutral and simply stabilise system 310. The vanes 342b in trough section 340b may be simultaneously in position A, or in position B or C, depending on the effect required.

In position B, vanes 342a still are parallel but are inclined with respect of water flow in section 340a. The inclination illustrated is such that the water flow exerts a force on vanes 342a, with that force being resolved in the vanes to provide an upward force component F on member 342 and, hence, on platform 314. Similarly, the inclination could be opposite to that shown, such that the water flow provides a downward force component F. With selective positioning of pairs of vanes 342a (and also vanes 342b), tilting of platform 314 is possible in a required direction; the vanes therefore obviating the need for actuators such as hydraulic actuators 138 as provided in Figures 3 and 4.

In position C, vanes 342a are mutually inclined towards each other in the direction of water flow in trough section 340a, producing a positive force F' on the vanes to cause rotation of member 342 and platform 314 in the direction of such flow. With vanes 342a oppositely inclined to that shown in position C, force F' provides a braking action on such rotation. However, it is preferred that a braking action is achieved by having vanes 342a in position A or B, and to place vanes 342b in position C relative to water flow in trough section 340b.

The vanes 342b in trough section 340b, while not shown in Figure 9, are similarly pivotable. In use, vanes 342b would be inclined so as to assist or enable tilting, rotation or braking of platform 314. Thus, with vanes 342a in position B, vanes 342b could also be in position B, as required for tilting in a required direction. Similarly, with vanes 342a in position C, vanes 342b would be in position A or B, and vice versa. Also, as will be appreciated, it may be vanes 342b, rather than vanes 342a, which are provided in position C to provide rotation of platform 314, with that rotation being in the direction of water flow in trough 340b. Similarly, with vanes 342a in the opposite inclination to that shown for position C, they provide a braking action; that action being able to be assisted by appropriate mutual inclination of vanes 342b to provide a reverse driving action.

Thus, motion system 310 utilises vanes 342a, 342b to provide tilting of its platform 314 in a required direction, or to provide rotation of platform 314 in either direction for braking or reveral of such direction. Also, while such rotation can be simultaneous with tilting of platform 314, tilting and rotation can be at respective time intervals, rather than simultaneous. Variation of water level 341 in trough 340 enables variation in the height of platform.314, with such vertical adjustment of platform 314 being permitted by corresponding adjustment^' of sleeve 332 on column 324. Such adjustment of platform, of course, causes a corresponding adjustment of flotation member 342 and resultant adjustment of baffle 372 in groove 370 of member 342. This adjustment of baffle 372 necesssitates use of a flexible baffle 372 in order that it can accommodate a variation in the vertical location of slot 370, although use of a flexible baffle which still has a degree of stiffness if highly desirable in any event.

Figure 12 schematically illustrates an amusement centre 400 having a motion system 410 substantially in accordance with that of Figures 3 and 4. Centre 400 is within a building 401 while platform 414 thereof is provided with seating 402 for members of an audience, a cinematic projector 403 rearwardly of seating 402 and a screen 404 forwardly of seating 402. Platform 414 is mounted on a support column structure 418, of which only the lower power thereof is shown for simplicity of illustration. However, structure 418 may be similar to structure 118 of Figures 3 and 4, or structure 318 of Figures 7 to 9. The system 410 differs principally in the form of annular flotation member 442 which extends into annular through, and further description principally is directed to member 442.

In member 442, portions 442a, 442b differ in relative volume, while portion 442a also differs in form. Thus, portion 442b is of relatively large volume compared with portion 442a, while the latter is relatively thin radially of structure 418 but is tapered at its lower edge so as to merge with portion 442b so as to minimise water drag. Also, member 442 is supported by a plurality of angularly spaced depending arms 443 secured to sub-frame 415 of platform 414. However, arms 443 are curved downwardly and inwardly such that each andd portions 442a. has a centre of curvature centered on the intersection of the pivot axes of joint 428. In use, system 410 enables rotation and tilting of platform 414 as members of an audience view a cinematic programme projected onto screen 404 by projector 403. Such rotation and tilting preferably is synchronised with action viewed by those members, thereby creating an enhanced perception of being present in that action. In the foregoing, reference is made to various components enabling or providing rotation or tilting of the platform of the motion system. However, it is to be understood that other components can be used. Thus, the gimbal joints enabling tilting of the platform can be replaced by other forms of universal joint. Also, actuators other than hydraulic cylinders can be used for such tilting, while other motor drive systems can be used to rotate the platform. Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

Claims

1. A motion system having a base, a generally horizontally disposed platform spaced above the base by centrally disposed support means, drive means operable to tilt the platform from and back to the horizontal in at least some directions, and stabilizer means for controlling movement of the platform under the action of the drive means; the stabilizing means including at least one vessel adjacent, on or defined by the base for holding a body of liquid, and flotation means provided on and extending below the platform so as to be at least partially within liquid in said vessel and for thereby providing a buoyancy action on said platform.

2. A system according to claim 1, wherein the support means includes a column structure which extends upwardly from the base and centrally locates the platform; a joint of the column structure allowing tilting of the platform under the action of the drive means.

3. A system according to claim 2, wherein the joint is a universal joint.

4. A system according to claim 2 or claim 3, wherein the column structure has upper and lower inter-fitted parts, with the upper part being vertically adjustable on the upper part to .enable vertical adjustment of the platform relative to the base.

5. A system according to any one of claims 1 to 4, wherein the platform is rotatable on said support means and able to rotate simultaneously with tilting and also independently of tilting.

6. A system according to any one of claims 1 to 4, wherein the platform is non-rotatably supported by said support means.

7. A system according to any one of claims 1 to 6, wherein the drive means for tilting the platform comprises a plurality of hydraulic cylinders spaced around the support means and operable in unison to tilt the platform in a required direction.

8. A system according to claim 5, or to claim 7 when appended to claim 5, wherein the at least one vessel comprises an annular trough which extends around the support means.

9. A system according to claim 8, wherein the flotation means comprises a plurality of flotation cells spaced around, and supported from the underside of, the platform.

10. A system according to claim 9, wherein the flotation cells are of two types, including static load cells comprising sealed flotation cells and live load cells between which ballast can be transferred for varying their buoyancy effect.

11. A system according to any one of claims 8 to 10, wherein said platform is rotatable under the action of a drive motor operable to rotate the platform on said support means.

12. A system according to any one of claims 8 to 10, wherein said platform is rotatable under the action of a drive motor operable to rotate at least part of the support means and the platform.

13. A system according to claim 8, wherein the flotation means comprises a single flotation member which is of annular form and extends around the support means, the flotation member being secured to the underside of the platform.

14. A system according to claim 13, wherein the flotation member comprises a water impermeable body of foamed plastics material.

15. A system according to claim 13, wherein the flotation member comprises a water impermeable body of foamed plastics material.

16. A system according to any one of claims 13 to 15, wherein the flotation member curves downwardly and inwardly from the platform.

17. A system according to claim 16, wherein said flotation member is of part spherical form.

18. A system according to claim 16 or claim 7 wherein said flotation member has an upper panel portion of substantially uniform radical thickness which extends into liquid in said annular trough around it full circumferential extent, and a lower rim portion defining a curved lower surface with which surfaces of the panel portion merge smoothly; the panel portion providing a positive centering action on the platform and the rim portion providing a negative centering action.

19. A system according to claim 16, wherein said panel portion has a centre of curvature which is substantially co-incident with axes about which the platform is tiltable during in use load conditions for the platform.

20. A system according to any one of claims 13 to 19, wherein an array of ballast vessels is mounted on the platform, the ballast vessels being disposed around the support structure and having associated therewith transfer means by which liquid ballast is able to be transferred between respective vessels to offset out of balance forces on the platform due to a load acting thereon.

21. A system according to any one of claims 13 to 20, wherein said flotation member is bifurcated in a lower region thereof to define a circumferentially slot, the annular trough having a circumferential baffle which in part is received in said slot, such that the baffle is retained in said slot during rotation and tilting of the flotation member with the platform, the flotation member and baffle dividing said trough into radially inner and outer trough sections.

22. A system according to claim 21, wherein each trough section forms part of a liquid circuit in which liquid can be recycled such that a respective annular flow of liquid can be generated in each trough section, the flow in one trough section being in the opposite direction to that in the other trough section; the flotation means, in each trough section, having adjustable vanes by the flotation member and platform can be caused to rotate and tilt under the action of forces applied to the vanes by the annular flow of liquid in at least one trough section.

23. A system according to claim 6, wherein said at least one vessel comprises an array of vessels spaced around the support means, the flotation means comprising a plurality of flotation members each secured to the platform and each extending therefrom downwardly into a respective said vessel.

24. A system according to claim 23, wherein each flotation member comprises a rigid hollow shell.

25. A system according to claim 23, wherein each flotation member comprises a water impermeable body of foamed plastic material.

26. A system according to any one of claims 23 to 25, wherein each flotation member curves downwardly and inwardly from the platform.

27. A system according to claim 26, wherein each flotation member has an upper panel portion which is of substantially uniform thickness in a direction radially of the support means and which extends into liquid in said respective vessel, and a lower rim portion defining a curved lower surface with which surfaces of the panel portion merge smoothly; the panel portions providing a positive centering action on the platform and the rim portions providing a negative centering action.

28. A system according to any one of claims 23 to 27, wherein an array of ballast vessel is mounted on the platform, the ballast vessels being disposed around the support structure and having associated therewith transfer means by which liquid ballast is able to be transferred between respective vessels to offset out of balance forces on the platform due to a load acting thereon.

29. A system according to any one of claims 1 to 27, wherein seating for members of an audience is provided on said platform, a cinematic screen being positioned on the platform forwardly of the seating with a cinematic projection being provided rearwardly of the seating, the arrangement being such that movement can be imparted to the platform to enhance the perception of members of the audience of being present in action depicted on the screen.