In recent years projection onto non-flat fields of projection has shown an enormous increase. There are for instance cinemas where films are projected onto a partly cylindrical or even spherical"screen"in order to give spectators the feeling that they are part of the projected environment. The"screen"or field of projection is herein formed by a wall of the desired form. Such cinemas generally require a large investment as a result of the special shape of the field of projection. Nor are they easy to embody in displaceable manner, for instance for use as attraction at events, since the shape of the"screen"requires a stable and therefore voluminous and heavy construction.

Non-flat fields of projection are also applied in simulators. Simulators are increasingly being used to simulate specific situations and to thus train behaviour in these situations. Compared to practical training, training in a simulator has the advantage of being relatively inexpensive, while there is no risk of damage and physical injury in the case of mistakes.

Known simulators are often based on relatively simple equipment, for instance PCs and simple software, with which images are projected onto a number of flat screens placed at angles to each other. These simple

simulators do not provide a very lifelike image, whereby the usefulness of the simulation is limited. On the other hand, simulators are also known which are built specially for a particular purpose and a particular target group, and which provide an exceptionally lifelike training situation but also entail very high costs. Examples of these are type-specific flight simulators, sailing simulators and driving simulators, which are used by large companies or by the defence ministry. These simulators often make use of curved fields of projection which are formed, just as in cinemas, by fixed walls or panels and thus have the same drawbacks as set forth above.

The invention has for its object to provide a projection apparatus with a non-flat, for instance partly cylindrical or spherical field of projection which can be manufactured simply and at relatively low cost, which can be transported with little effort and can be constructed quickly and easily. According to the invention this is achieved in the case of a projection apparatus of the above described type by a frame which supports the at least one screen and the reproducing means and which is provided with means for tensioning the screen in an at least partly curved shape.

The screen can be brought into the desired shape in simple manner when the screen tensioning means comprise at least one at least partly curved support which is connected to the frame and extends along at least a part of an edge of the at least one screen. In order to hold the screen in this form the at least one support preferably has means for fixing the at least one screen thereto.

A fixing which can be formed and released again rapidly is obtained when the fixing means comprise strips of hook or loop tape for co-action with

corresponding strips of loop or hook tape along the edge of the at least one screen.

It is however also conceivable for the fixing means to comprise at least one recess for receiving a part of the edge of the at least one screen. For an optimum support of the screen in the curved shape, the at least one recess can extend over substantially the whole length of the support so as to receive a piping connected to the edge of the at least one screen.

In order to allow rapid and easy construction and dismantling of the projection apparatus, the support can be releasably connected to the frame.

When the screen is manufactured from a relatively flexible and light material the screen tensioning means preferably comprise at least one weighting element connected to an edge of the screen located opposite the edge of the at least one screen connected to the at least one support. This weighting element can also comprise at least one recess for receiving a part of the edge of the at least one screen.

When the at least one weighting element has a shape corresponding with the at least one support, the projection apparatus can be formed with a relatively small number of different components.

A robust yet still light and therefore easily transportable projection apparatus is obtained when the frame is at least partly formed by a space frame. With a view to transporting thereof, the frame, which can preferably be manufactured at least partly from a metal, in particular aluminium, advantageously comprises a number of parts connected releasably to each other.

When the reproducing means comprise at least one projector, the frame preferably has means for releasably connecting the at least one projector thereto. In this manner the projector (s) can be transported separately

and, after construction of the frame, be mount thereon in simple manner. The connecting means then advantageously comprise rapid-action couplings.

In order to enable presentation of an optimal image the projection apparatus preferably has a single seamless screen. With a view to a good reproduction of images projected by a projector in a high position, the at least one screen is further preferably adapted to reflect a projected image at an angle differing from the angle of incidence.

The invention also relates to the frame, the screen tensioning means and the screen which are intended for application in a projection apparatus as described above.

The invention is now elucidated on the basis of two embodiments, with reference to the drawing, in which: Fig. 1 is a partially broken-away schematic perspective view of the frame, the screen tensioning means and the screen of a first embodiment of the projection apparatus, prior to assembly thereof, Fig. 2 is a view corresponding with fig. 1 of the frame and the screen tensioning means in assembled state, Fig. 3 and 4 are perspective detail views according to arrows III and IV respectively in fig. 2, Fig. 5 is a schematic perspective view of the frame with screen and a support according to an alternative embodiment of the invention, Fig. 6 is a perspective detail view as according to arrow VI in fig. 5, wherein an edge of the screen is received in the support, Fig. 7 is a schematic perspective view of a weighting element as according to yet another embodiment of the invention, and

Fig. 8 is a schematic perspective view of a rapid- action coupling for mounting a projector on the frame of the projection apparatus according to the invention.

A projection apparatus 1 (fig. 1) comprises a frame 2 which here consists of a number of arcuate segments 3 and uprights 4. These components, which each take the form of an aluminium space frame, are releasably connected to each other at coupling points 5.

The upper arcuate segments 3 define a closed circle while the lower arcuate segments 3 define a semi-circle.

Projection apparatus 1 can hereby be used as simulator, wherein a car can be placed in the space defined by frame 2.

Frame 2 is provided with means 6 for tensioning at least one screen 7 therein in a curved shape. In the shown embodiment use is made of a single, seamless screen 7 which here extends through an angle of 180.

Larger or smaller angles can however also be envisaged.

In the shown embodiment the screen tensioning means 6 are formed by a number of curved horizontal and straight vertical supports 8,9 which are mutually connected to form a number of sub-frames 10, which are each connected releasably to frame 2. In the shown embodiment straps 12, each provided with an eye 13, are arranged at different positions around tubes 11 of frame 2 (fig. 3,4). Brackets 14 are formed close to the top and bottom of vertical supports 9. Sub-frames 10 are fixed to frame 2 by arranging connecting elements 15, here in the form of springs, between straps 12 and brackets 14.

Supports 8,9 further have means 16 for fastening the screen 7, in the shown embodiment in the form of strips of hook tape 17 glued thereon, which co-act with strips of loop tape 18 arranged along upper edge 19, lower edge 20 and side edges 21 of screen 7. This manner

of fastening the screen 7, which acts very rapidly and simply, is particularly suitable when the screen is manufactured from a relatively thick and heavy material and thus has some stiffness. It is possible here to envisage a projection screen fabric with a thickness of several tenths of a millimetre, for instance 0.58 mm, and with a back reinforced with a fibre material such as glass fibre. Such projection screen fabric is commercially available under the name Datalux-M.

In an alternative embodiment of the invention, which is more suitable for a lighter and more flexible screen 107 which can be rolled up, use is made of a horizontal curved support 108 mounted close to the upper side of frame 2. This support 118 is provided with a continuous recess 117 for receiving a piping 118 which is fixed to the upper edge 119 of screen 107. Piping 118, which can be manufactured from plastic, herein ensures that the upper edge 119 of screen 107 follows the. form of support 108 and does not have any undulations.

Support 108 can here also take a divided form, for instance in the form of segments, which are each fixed to one of the arcuate segments 3 of the frame, for instance by welding. In the shown embodiment the support 108 otherwise has a symmetrical form with a corresponding recess 125 opposite recess 117. Support 108 can hereby be mounted on frame 2 in any random position.

In this embodiment the lower edge 120 of screen 107 can be held in place by a weighting element 121. As support 108, this weighting element 121 can have a recess 122 in which a piping 123 can be received along the lower edge 120 of screen 107. In order to limit the number of different components as much as possible, weighting element 121 can have the same form as support

108, with a corresponding recess 124 opposite recess 122. Weights can be arranged in this recess 124 in order to increase the tension in screen 107 if this is deemed necessary.

Projection apparatus 1 is further provided with reproducing means which can be formed by one or more projectors (not shown here). Frame 2 is provided for this purpose with means 22 for mounting those projectors. In the shown embodiment these mounting means 22 are formed on the upper ring of frame 2. In order to still provide an audience situated in the space defined by frame 2 with a clear image during a projection from this upper ring, use can be made of a special screen which reflects the image projected thereon at an angle which differs from the angle of incidence. The image projected from above can thus be reflected horizontally.

With a view to separate transport of the (fragile) projectors, mounting means 22 can be adapted to form a releasable connection. Mounting means 22 here take the form of rapid-action couplings, each consisting of a female part 23 on the outer end of a tube 24 welded to frame 2 and a male part 25 which is fixed onto a mounting plate 26 connected to the relevant projector.

The outer periphery of male part 25 and the inner periphery of female part 24 herein have shapes fitting precisely into each other, for instance a conical shape, whereby a form-fitting and force-transmitting connection is obtained. This connection is tensioned and secured by a tapered pin 26 which is pressed through a tapered bore 27 in parts 24,25 and is secured in turn by a split pin 28.

The projection apparatus according to the invention can be applied in many fields. It is possible for instance to envisage placing at driving schools to allow learners a practice"dry-run"of the first driving

lessons. Owing to its compact form and simple construction the device is also suitable for displacing, and thus for use at for instance trade fairs and similar events.

Although the invention is elucidated above on the basis of a number of embodiments, it can be varied in many ways. Other forms of the frame and the screen tensioning means could thus be envisaged, while the method of fixing the screen to the supports and mounting the projector (s) on the frame could be adapted. The scope of the invention is therefore defined solely by the following claims.