Abstract:
The invention concerns a free fall simulator, characterized in that it comprises: a lower compression chamber ( 22 ) proximate the lower periphery wherefrom emerge the outputs of a plurality of ventilators ( 24 ) arranged in centripetal configuration, and the tapered upper part of which is arranged a compression grid ( 30 ), a cylindroid chamber ( 36 ) defining a displacement space, which is located just above the compression chamber ( 22 ), and which is designed to be traversed by a homogeneous rising air stream having a gradient of constantly decreasing upward speeds.

Description:
The present invention relates to a free fall simulator, in other words an installation for keeping a person in equilibrium in a free fall position in a controlled flow of rising air which passes through a maneuvering chamber. 
   A free fall simulator of this type has been designed for multiple purposes, including training and education of parachutists or sports enthusiasts, and has even been applied in theme parks. Clearly, this type of free fall simulator makes it possible to avoid all the problems of cost and meteorological uncertainties associated with the obligation regarding normal practice when diving from an aircraft at altitude. 
   The object of the present invention was therefore to provide an improved free fall simulator which is capable of generating a rising air flow at decreasing speed. Such an air flow has to be as homogeneous as possible to enable any user, regardless of his weight and build, to move through his equilibrium positions and free fall configurations at different equilibrium heights. To enable the user to learn effectively how to change the attitude and orientation of his body to control the speed and direction of motion of his fall, it is essential to generate a rising air flow which is as homogeneous as possible within the maneuvering chamber. Such an installation must of course also meet a number of other constraints relating to environmental protection, and more particularly relating to soundproofing. 
   SUMMARY OF THE INVENTION 
   This is why the present invention relates to a free fall simulator which is characterized in that it comprises:
         a lower compression chamber:
           in the vicinity of whose lower periphery there open the outlets of a plurality of fans arranged in a centripetal configuration, and   in whose upper tapered part there is placed a compression grid;   
           a cylindroid chamber delimiting a maneuvering space, which is located immediately above the compression chamber, and which is designed to be traversed by a homogenous flow of rising air having a speed gradient decreasing regularly from the bottom to the top; and   a generally cylindrical superstructure which encloses at least the maneuvering chamber of the simulator, which terminates in its upper part in a dome covering said maneuvering chamber of the simulator, and which is arranged to promote a downward circulation of the air leaving the maneuvering chamber toward the fan inlets.       

   According to the present invention, the inner surface of the compression chamber must be shaped to generate a homogeneous air flow which is essential to ensure the stability of the operator in the maneuvering chamber. 
   A certain number of specific characteristics relating to the design of this compression chamber will become clear from reading the detailed description provided below, particularly with reference to the attached drawings showing schematically a free fall simulation installation of this type. 
   Further characteristics relating to the maneuvering chamber of the simulator will also become clear from reading the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The FIGURE shows a free fall simulator according to one embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The free fall simulation installation according to the invention comprises a superstructure part  10  comprising a dome  12  protecting the maneuvering cylinder itself  14 . 
   In the attached drawing, the superstructure part is extended by a schematic representation of attached buildings  16  designed to house changing rooms, sanitary facilities and access corridors for the maneuvering chamber  14 , an extension which can be provided equally well on either side of the dome  10 . In the attached drawing, the line  18  indicates schematically the approximate ground level. 
   Below this level  18 , the installation comprises an substructure part essentially consisting of an annular machine room  20  for the introduction of air, together with the lower compression chamber  22 . 
   The lower compression chamber  22  has in the vicinity of its lower periphery a plurality of apertures into which there open the outlets of centrifugal fans  24  arranged in a centripetal configuration. This lower part of the compression chamber  22  is advantageously made in the general shape of a cylindrical solid of revolution  26  extended upward by a truncated conical part  28 . 
   To generate a homogenous air flow both in the compression chamber  22  and especially in the maneuvering chamber  14  subsequently, it is advantageous to arrange the propeller fans  24  with a constant angular spacing. 
   In practice, it has been found satisfactory to use twelve centrifugal fans installed in the annular machine room  20  with a constant angular spacing. 
   In the illustrated embodiment, the compression chamber  22  has a radius of 7.75 m and a height of 7.5 m. The shape of this chamber makes it possible, in particular, to generate air speed curves which are as homogeneous as possible. 
   In order to avoid the separation of the air stream along the inner wall of the truncated conical part  28  near the compression grid  30  arranged in the upper tapered part of the truncated conical part  28 , it was found useful to equip the inner wall with an annular bend  32  projecting toward the inside of the compression chamber  22 . In the illustrated embodiment, the annular bend has a radius of 1 m. This characteristic profile of the inner wall of the compression chamber  22  makes it possible to channel the air flow and to efficiently convert the static pressure of the chamber to dynamic pressure without causing the separation of the air stream after its passage through the annular bend  32 . This bend has a radius of approximately 1 m and is preferably made in the form of a galvanized sheet steel component which is perfectly matched to the structure of the concrete walls of the lower compression chamber. 
   The fans placed in the room can consist of centrifugal fans of the type having an inlet funnel protected with a grid, for introducing air which travels through apertures formed in the periphery of the annular machine room  20 . In the conditions of embodiment of the illustrated installation, the air flow speed in this annular section and at the fan inlet will preferably remain less than 7 m/s. 
   The propeller fans will advantageously be mounted on pedestals and anti-vibration blocks. The characteristics of the fans which have been used successfully in practice can be, for example, as follows:
     unit air flow rate: 66 m 3 /s;   fan pressure: 2,260 Pa.   

   The air outflow speed from this type of fan should advantageously be in the vicinity of 40 m/s. 
   The compression grid  30  fitted after the annular bend  32  has the principal function of maintaining the pressure of the lower compression chamber  22  and distributing as uniformly as possible the air speeds at the outlet of this compression chamber. 
   Advantageously, the compression grid  30  which is mounted in the upper part of the lower compression chamber  22  is designed to generate a pressure drop of approximately 150 Pa. In practice, a grid having a mesh size of 500 mm×500 mm and, for example, a wire diameter of approximately 2 mm has been found entirely satisfactory. 
   To complete the description of the lower substructure part of the installation according to the invention, we should mention that there must be constant air renewal  24 , principally in order to counteract the overheating of the air due to the operation of the fans and to supply clean air regularly. For this purpose, in a particular embodiment, the upper part of the dome  12  has at least one fresh air intake fitted with a sound trap. Furthermore, air extraction is provided mechanically by a plurality of extractor fans which also enable the temperature of the whole flight simulator to be controlled. 
   Sound traps can advantageously also be provided at the outlets of the extractor fans. 
   In all circumstances, fresh air inlets and outlets should be provided in this installation and should be arranged for operation in opposition. 
   The compression grid  30  is surmounted by a cylindroid chamber  36  delimiting a maneuvering space, located immediately above the compression chamber  22 . This cylindroid chamber  36  is designed to be traversed by a homogeneous rising air flow having a speed gradient decreasing regularly from the bottom to the top. 
   Advantageously, this cylindroid maneuvering chamber  36  comprises a generally cylindrical bottom part  38  which is extended upward by a diverging conical part  40 . 
   Advantageously, the angle formed by the walls of the diverging conical part  40  with the vertical is less than approximately 6°. 
   In the embodiment schematically shown, the total maneuvering height is of the order of 7 m. This total maneuvering height extends between the two safety nets  42  and  44  fitted, respectively, to the bottom and top parts of the cylindroid maneuvering chamber  36 , when the intermediate comfort net  43  is removed. 
   The bottom part of this cylindroid maneuvering chamber  36  consists, in the installation shown in the attached FIGURE, of a cylinder 3.80 m in diameter with a height of 2 m. The diverging conical part  40  has a height of 8.50 m with an angle of divergence from the vertical of approximately 3.6°. in practice, this angle has made it possible to avoid the wall effects and the separation of the air stream along the cylindroid maneuvering chamber  36 . 
   It will be noted that, in these conditions, the bottom safety net  42 , fitted approximately 1.5 m from the compression grid  30  and above the latter, contributes to a total pressure drop for the compression grid and safety net of the order of 400 Pa. 
   Users of the installation can therefore maneuver through a height of approximately 7 m between the bottom protective net  42  and the lift limit located approximately 50 cm below the upper protective net  44 . 
   In order to facilitate the outflow of air at the outlet of the cylindroid chamber  36  and thus enable it to be correctly recycled, the upper free edge of the cylindroid chamber  36  is provided with a peripheral collar  46  which can also be made from galvanized steel sheet in the form of a conversion component. Clearly, the annular bend  32  and the peripheral collar  46 , made for example from galvanized steel sheet, together with the safety nets  42  and  44  and the compression grid  30 , will be installed without the use of any fixing devices which might perturb the outflow of the fluid. 
   In the illustrated embodiment, the speeds are distributed within the cylindroid maneuvering chamber  36  as follows:
     bottom part: approximately 70 m/s   median part: approximately 50 m/s   top part: near the limit lift speed of approximately 45 m/s.   

   It should be noted that the air speed generated in the bottom part, namely approximately 70 m/s, allows most free fall maneuvers to be carried out by experienced operators. Beyond this region, the speed decreases to the limit lift speed in the upper section of this chamber  36 . The intermediate section corresponds in fact to the most widely used speed for operators with an average level of experience. This speed, of approximately 50 m/s (180 km/hr), will in particular be complied with at the top point of the platform  48  for access to the cylinder, which is located at the level numbered  48  on the attached drawing. 
   At this level of the cylindroid chamber, the invention has a certain number of characteristics which are not shown in greater detail, and which are intended, in particular, to allow access to the maneuvering chamber. 
   Thus, the cylindroid maneuvering chamber is provided with an additional comfort net  43 , fixed removably to its periphery. 
   According to another characteristic of the invention, the wall of the median part of the cylindroid maneuvering chamber has at least one aperture opening into a closed access chamber  52  in the dome and delimiting an access platform  48 , preferably having the shape of a cylindrical solid of revolution. 
   According to another characteristic of the invention, the upper part of the access chamber  52  has a curved connecting profile  54 , with an inward concavity to promote the circulation of the air flows. 
   According to another characteristic of the invention, the additional comfort net  43  is positioned substantially at the level of said access platform  48 . 
   According to another characteristic of the invention, at least one peripheral net  56  allowing the operators to remain in the air flow is stretched over said aperture in the extension of the wall of the diverging conical part  40 . 
   According to another characteristic of the invention, two peripheral nets  56  overlap each other at least partially in order to allow the operators to access the maneuvering chamber. 
   According to another characteristic of the invention, the inner wall of the conical chamber  40  comprises a take-off and damping border  58  whose inner face extends in the extension of said inner wall of the conical chamber  40 . 
   The homogeneity of the rising air flow in the cylindroid chamber  36  is also promoted by good recirculation of the air flow within the superstructure and substructure of the installation, the air flow passing through the annular chamber  20 . This air circulation is indicated schematically by different arrows on the attached drawing. To promote this air circulation, the superstructure is provided with a profiled central projection in the form of a solid of revolution  50  which is centered on the axis of revolution of the cylindroid maneuvering chamber  36 . Advantageously, this profiled central projection in the form of a solid of revolution  50  takes the general shape of a cone whose lateral surface is concave with a concavity directed toward the interior of said projection. 
   This arrangement promotes changes in the direction of the air at the outlet of the cylindroid chamber  36 . 
   Clearly, the simulator described above can also comprise a certain number of modifications and/or additions without thereby departing from the scope of the present invention. 
   Thus, it is possible to provide for the presence of ventilation openings and/or devices to reduce the internal temperature of the installation. 
   The use of extractors to suppress noise inside and outside the installation can also be envisaged for certain conditions of use. 
   The use of any additional grids for diffusing and/or stabilizing the air flow can also be envisaged within the scope of certain specific applications of the simulator according to the invention.