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FIELD OF THE INVENTION  
         [0001]    This application relates to stressed membrane structures and to opening or door assemblies for such enclosures.  
         BACKGROUND OF THE INVENTION  
         [0002]    Stressed membrane structures have been in use for many years and, in many situations, offer advantages over conventional structures. One area where such structures are very attractive is for use as aircraft hangars.  
           [0003]    In order to function effectively as aircraft hangars, it is necessary that wide opening doors be provided for ingress and egress of aircraft.  
           [0004]    There has been an ongoing need for doors which will meet this objective of wide opening doors for hangers and many other applications within the structural limitations of stressed membrane structures. It is preferable that such doors retain the relocatability which has been the hallmark of tensioned membrane structures, while meeting structural criteria such as wind resistance.  
           [0005]    The present invention arises against this background.  
         PRIOR ART  
         [0006]    Applicant&#39;s prior U.S. Pat. No. 5,283,993 illustrates a door arrangement for tensioned membrane structures.  
         SUMMARY AND OBJECTS OF THE INVENTION  
         [0007]    The present invention provides an opening or a door arrangement whereby an end of a stressed membrane structure can be partly or fully opened while maintaining a tensioned condition of the membrane of the opened part.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    In the drawings which illustrate embodiments of the invention:  
         [0009]    [0009]FIG. 1 is a plan view, partially cut away, of a stressed membrane structure, showing an airplane in ghost lines;  
         [0010]    [0010]FIG. 2 is a plan view of the structure of FIG. 1 with an opening assembly in an open position;  
         [0011]    [0011]FIG. 3 is a plan view of the structure of claim  1  with the opening assembly in a partially opened condition;  
         [0012]    [0012]FIG. 4 is a cross-section through the opening assembly of FIG. 1 with the tensioned membrane removed;  
         [0013]    [0013]FIG. 5 is a perspective view illustrating a support frame for the opening assembly;  
         [0014]    [0014]FIG. 6 illustrates detail of bracing for a part of the support frame of FIG. 5;  
         [0015]    [0015]FIG. 7 is an elevation of a pivot assembly for the opening assembly;  
         [0016]    [0016]FIG. 8 is a plan view of the pivot assembly of FIG. 7;  
         [0017]    [0017]FIG. 9 illustrates an inner tie-down for securing the opening assembly;  
         [0018]    [0018]FIG. 10 illustrates an outer tie-down for securing the opening assembly;  
         [0019]    [0019]FIG. 11 illustrates a closure lock plate for securing a pair of opening assemblies in a closed position;  
         [0020]    [0020]FIG. 12 illustrates the closure plate of FIG. 11 in a partially opened position;  
         [0021]    [0021]FIG. 13 is a plan view of a skid plate and alignment pipes for aligning a pair of opening assemblies during closing; and  
         [0022]    [0022]FIG. 14 is an elevation of the skid plate and alignment pipes of FIG. 13.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Stressed membrane structure  10  comprises a framework including structural members  12  which support tensioned membrane  14 .  
         [0024]    Various bracing arrangements, such as cable bracing  16 , may be utilized where required in structure  10 .  
         [0025]    Structure  10  may be provided with doors such as personnel doors  18  and sliding door  20 . Various other features, such as skylight  22 , may be included.  
         [0026]    Structure  10  will generally have a substantially semi-circular end  34 , and it is desirable that at least a part of end  34  can be opened to allow access to the structure for large objects. Thus end  34  is divided into two end parts  24  and  26 . In the preferred case, both end parts  24  and  26  are rotatable so that the entire end  34  of structure  10  can be opened to the full width of the structure  10 . For this purpose, end parts  24  and  26  are pivotally associated with but separated from structure  10  by pivot assemblies  28  and  30 .  
         [0027]    Stressed membrane structures normally have rounded or arcuate ends or ends which extend outwardly of the plane across the end of the normal full width of the structure. While this is not always true for these structures, the present invention is applicable to those which do have at least one such end.  
         [0028]    The rounded or arcuate end part has a number of advantages which include the ability to stress the membrane continuously around the structure without substantial special attention to the end treatment. As well, such end structures contribute to the very important ability of the structure to withstand wind and associated environmental effects.  
         [0029]    It is possible that other shapes might be used but all such protruding or extended ends are considered to be under the general heading of extended ends. Such extended shapes are to be contrasted specifically with a normal flat door configuration.  
         [0030]    In guiding the opening and closing of end parts  24  and  26 , pivot assemblies  28  and  30  are preferably positioning and guiding pivots only and are not intended to support any part of the weight of the associated end part.  
         [0031]    [0031]FIG. 3 illustrates the positioning of the main frame members  36  that would normally be a part of an end  34  of a structure  10 .  
         [0032]    The door arrangement of the present invention preferably provides a support structure  38  associated with each structural member  36 . As illustrated in FIG. 4, the support structure  38  comprises horizontal beam  40 , vertical beam  42  and diagonal beams  44  and  46 .  
         [0033]    Each support structure  38  is preferably provided with transport members which may be in the form of rollers which are preferably wheel assemblies and preferably at least two wheel assemblies  48  and  50  for each horizontal beam  40 .  
         [0034]    It is the combination of the support structures  38  and wheels  48  and  50  which support the weight of end parts  24  and  26  in opening and closing the end parts. Pivot assemblies  28  and  30  are non-weight bearing.  
         [0035]    [0035]FIG. 5 illustrates an essentially complete frame for each of end parts  24  and  26 . This consists of the normal structural members  36  of structure  10  and, as well, usual structural members  52 , extending between structural members  36 .  
         [0036]    In addition, FIG. 5 illustrates transverse bracing arrangements  54  between vertical beams  42  and shown consisting of horizontal members  56  and diagonal structure  58 . Diagonals  58  may comprise cables and the cables may be adjustable in tension.  
         [0037]    End parts  24  and  26  are thus each self-supporting structures and each maintains its membrane in a stressed condition at all times.  
         [0038]    It is noted that bracing structure is required to provide rigidity and tension to the end parts  24  and  26 , and variations on the support structure are therefore permissible so long as those criteria are maintained. Thus the bracing structure may vary for different environments.  
         [0039]    [0039]FIGS. 7 and 8 illustrate details of pivot assemblies  28 ,  30 . Pivot post  60  comprises pipe  62  which passes through the structure&#39;s concrete pad  64  and is embedded in concrete pile  66 . Pipe  62  may be filled with concrete  68 .  
         [0040]    Brackets  74  and  76  are fixed to structure member  36 . Each bracket includes a cylindrical sleeve  78 .  
         [0041]    In assemblies structure  10 , the sleeves  78  are slid over post  60  to form the pivot.  
         [0042]    Each horizontal structural beam  40  is provided with wheel assemblies  48  and  50 . The wheel assemblies support the weight of the end parts so that the pivot assemblies do not carry the weight of the end parts. Additional wheel assemblies may be used if required.  
         [0043]    Connecting and/or sealing means (not shown) are preferably provided between beams  39  and  41  in the closed position and between beams  37  and  43  and beam  45  main part  32  of structure  10  when the end parts are in the closed position.  
         [0044]    In order to actually activate opening or closing of the assemblies  24  and  26  around pivot assemblies  28  and  30 , tow-bar attachments are provided at the bases  80  and  82  of the central arches  39  and  41 , which are the arches which will be adjacent when the door is in the closed position. An aircraft tug or other small motorized vehicle may then be used to open and close the assemblies.  
         [0045]    As well, an integral drive arrangement (not shown) may be mounted on the opening assemblies for opening and closing parts  24  and  26 .  
         [0046]    [0046]FIGS. 13 and 14 illustrate alignment pipe and skid plate assemblies  84  and  85 . The assemblies are mounted at selected locations between the arches  39  and  41 , which are located adjacent each other when the opening assemblies are in the closed position, and also between the end rib  45  of the stationary part of the stressed membrane structure and the adjacent ribs  37  and  43  of the opening assemblies when in the closed position.  
         [0047]    Assemblies  84  and  85  comprise skid plates  86  and  88  and respective pairs of alignment pipes  90  and  92 . As the opening assembly is moved into the closed position, the camming angles  94  on pairs of pipes  90  and  92  ride alone skid plates  86  and  88  to align the adjacent beams.  
         [0048]    The effect of the alignment is to transfer some of the load from the rolling sections of the assemblies to the overall structure to thus provide greater structural stability of the system. The skid plates also provide some friction between the opening assemblies and the stressed membrane structure to further facilitate load transfer from the opening assembly to the stationary structure.  
         [0049]    [0049]FIGS. 11 and 12 illustrate a lock plate assembly  96  for holding doors in a locked position. The assembly  96  comprises fixed plates  98  and  100  from which project pins  102  and  104 . Lock plate  106  rotates on pin  104 . Lock plate  106  includes camming surface  108  which, during closing of the assemblies, rides up and over pin  102 . Recess  110  at the end of surface  108  then drops over pin  102  to lock the assemblies in the closed position.  
         [0050]    Parts  24  and  26  are preferably additionally stabilized in the open and closed positions by the use of conventional aircraft tie-down systems.  
         [0051]    [0051]FIGS. 9 and 10 illustrate inner and outer tie-down assemblies  112  and  114  respectively. Tie-down assemblies  112  and  114  include earth anchors  116  and  118  implanted below surface  119 . Cables  120  and  122  project from earth anchors  116  and  118  above surface  119 . The opening assemblies are provided with brackets  124  and  126  to correspond in positioning with projecting cables  120  and  122  respectively. When the opening assemblies are in position and ready for tie down in either the open or the closed position, load binders  128  or  130  are installed between the brackets and the projecting cable ends.  
         [0052]    The inner tie-down is intended for installation on interior beam members while the outer tie-down is intended for installation on the outer arches.  
         [0053]    Clearly, the tie-downs will vary in size, type, location, and quantity depending on door size and environmental conditions. In short, any kind of tie-down may be used depending on circumstances.  
         [0054]    Suitable flashing will be installed along the line where the two halves of the opening assembly meet in the closed position and along the line between the two parts of the opening assembly and the stationary structure in the closed position.

Summary:
There is provided an opening assembly for an extended end of a stressed membrane structure having a fixed part, said opening assembly comprising: at least a part of said end separated from said fixed part and moveable relative to said fixed part; a pivot assembly for permitting movement of said at least a part of said extended end between an open and a closed position relative to said structure; a support frame for maintaining the integrity of said part in stressed membrane condition at all times during said movement and when in said open and closed position; rolling transport means for supporting said frame and said assembly during said movement.