This invention relates to auditoriums of the amphitheatre type as used for concerts, theatrical, cinematograph and other public presentations.

A problem in the presentation of such performances is that, where they are presented in different cities, available facilities may vary greatly in physical layout and capacity. This may require modification of the performance or alter the artistic impression provided. The available facilities may be ill suited to the size of the expected audience, and usually do not combine facilities for all-season usage with the potential for an outdoor ambience.

An object of the invention is to provide an amphitheatre type auditorium providing standardized but widely adaptable facilities, suitable for all-season, all weather use, and capable of providing the ambience of an outdoor performance.

It has previously be=n proposed to provide auditoriums of this type having roof portions in the form of rotatable segmental leaves over a stage area, as shown for example in British Published Patent Application No. 2225360A, particularly Figures 13 to 15 showing prior art

structures. All such structures have required a central pillar, which is highly undesirable if an audience is to have an unobstructed view of the stage.

According to the invention, there is provided an auditorium comprising an amphitheatre partially surrounding a stage, a first fixed roof structure covering a majority of the amphitheatre area except for a segmental area above and including the stage, and second movable roof structure of segmental form movable between a first position in which it closes said segmental area, and a second position overlapping the first roof structure and leaving said segmental area open, said movable roof structure comprising segmental leaves rotatable in opposite directions about a common pivot point between a first closed position in which the leaves abut and a second open position in which they underlay the fixed roof structure, the first and second roof structures both being part-spherical shells, characterized in that the fixed roof structure is supported only at its periphery, and the movable roof structure is supported at its periphery and by said fixed roof structure, a vertical axis of the shell forming the fixed roof structure is above the stage, and a vertical axis of the shell forming the movable roof structure is at said common pivot point and is located horizontally spaced from the stage above a seating level of the amphitheatre. The auditorium may include means to partition off, by radially and/or circumferentially extending partitions, portions of seating provided by the amphitheatre to provide amphitheatres at different capacities. Retractable panels forming a curtain wall may be provided behind that portion of the stage not surrounded by the amphitheatre.

The above arrangement provides an all weather auditorium of flexible capacity which nevertheless is capable of providing an open-air ambience under suitable

weather conditions.

Further features of the invention will become apparent from the following description of a presently preferred embodiment of the invention with reference to the accompanying drawings in which:

Figure 1 is an elevation of the auditorium in accordance with the invention, facing the amphitheatre, with its roof closed and the wall behind its stage in place; Figure 2 is an end elevation of the auditorium;

Figure 3 is a vertical cross-section through the stage and amphitheatre;

Figure 4 is a plan view of the auditorium;

Figure 5 is a plan view of a lower seating level in the auditorium; and

Figure 6 is a plan view of an upper, gallery seating level in the auditorium.

The auditorium shown in the drawings comprises the following principal components; a banked amphitheatre comprising a main seating level 2 and a superposed gallery level 4, a stage 6, a fixed main roof 8, an opening auxiliary roof 10, a retractable curtain wall 12 behind the stage, and a foundation 14 supporting the amphitheatre, the curtain wall, supports 16 for the roofs, auxiliary structures 18 providing services such as restaurants, and service towers 20.

The main, fixed roof 8 comprises a part spherical shell supported solely at an approximately semicircular periphery 21 and having a vertical axis 7 above the stage 6, although that portion of the fixed roof above the stage is. segmentally. cut away along margins 22 converging, at an axis 24 above a control area 25, well in front of the stage

and over the amphitheatre. Sloped transitional portions 26 extend between the margins 22 and lines 28 extending between the point 24 towards the ends of the periphery 20. The roof 8 is supported at its periphery by the amphitheatre structure and by the service towers 18 which provides housings for mechanical and other services for the building and elevators 30, as well as support for telecommunications equipment 32.

The opening auxiliary roof 10 comprises two part- spherical segmental leaves 34 pivotally connected at their apices for rotation about the axis 24 between a first, closed, position (see Figures 1 and 2 and the solid line depiction in Figure 4) closing the segmental cutaway in the main roof defined by the margins 22 and a retracted position (see the broken line depiction in Figure 3) . The leaves 34 are supported at their outer peripheries by a track 36 carried by the supports 16 behind the stage 6. Since the greater portion of the roof structure is comprised by spherical shells, it can be constructed in modular fashion from rib components of only two different radii, thus simplifying construction. By situating the axis 24 which forms the common pivot point for the movable leaves 34 above the seating on level 2 and substantially spaced from the vertical axis of the shell forming the main roof 6 on the centre line of the amphitheatre a self- supporting structure can be provided, requiring no central pillar, and in which retraction of the leaves 34 will place the stage 6 in the open air and provide a substantial open air illusion to the auditorium as a whole, which can be greatly enhanced by withdrawing, into pockets 38, sliding panels 40 forming a curtain wall behind the stage 6. Deployment of the panels 40 and closing of the leaves 34 provides a wholly enclosed auditorium during inclement weather or to provide an enclosed environment. The lower surfaces of the leaves 34 may support baffles or reflectors

for acoustic control purposes, as may the main roof structure 8, as shown at 42. A frame 43 may be supported above the stage to support lighting and other equipment.

In order to accommodate different anticipated audience sizes, or different types of presentation, the internal configuration of the seating provided by the auditorium may be adjusted. For example, assuming total seating capacity of the auditorium as shown to be about 14000, movable partitions or curtain walls may be provided to reduce the seating capacity of the auditorium. Thus the gallery seating level may or may not be used, or circumferential partitions may be used to make available only lower portions such as 44 and 46 of the main seating level 2. Alternatively, radial partitions may be utilized to shut off wing portions of the auditorium. Advantageously, such an arrangement can be utilized to isolate central segments 48 of the gallery seating (see Figure 6) , with a screen being deployed, for example lowered and rotated from the structure 42 to a position to provide super wide screen cinema presentations.