Roll-up inflatable beam structure

Abstract

A sandwich beam including in one example first and second spaced walls, a core configured to maintain a predetermined spacing between the walls when the core is filled with pressurized gas and to resist shear when the beam is loaded in bending and a port for filling the core with gas biasing both walls in tension. The tension tends to increase in the second wall and decrease and cause a compression load in the first wall in response to a sufficiently large applied bending load. A compression element is fixed only with respect to the first wall and is configured (a) to support the compression load so that the beam is stronger at a given gas pressure and (b) to flex sufficiently to allow the beam to be rolled up when the gas is emptied from the core via the port.

1 . A sandwich beam comprising:
 first and second spaced walls;   a core configured to maintain a predetermined spacing between the walls when the core is filled with gas and to resist shear when the beam is loaded in bending;   a port for filling the core with gas, said gas biasing both walls in tension, said tension tending to increase in the second wall and decrease and cause a compression load in the first wall in response to a sufficiently large applied bending load; and   a compression element fixed only with respect to the first wall and configured (a) to support the compression load so that the beam is stronger at a given gas pressure and (b) to flex sufficiently to allow the beam to be rolled up when the gas is emptied from the core via the port.   
   
   
       2 . The sandwich beam of  claim 1  in which the beam has a load capacity X without the compression element and a load capacity of N times X when the compression element is added to the beam. 
   
   
       3 . The sandwich beam of  claim 2  in which N is greater than 1.5. 
   
   
       4 . The sandwich beam of  claim 1  in which the beam is at least 1.5× weaker when loaded in the reverse direction. 
   
   
       5 . The sandwich beam of  claim 1  in which the compression element is a sheet of material secured to the outer surface of the first wall. 
   
   
       6 . The sandwich beam of  claim 1  in which the first and second walls are fabric. 
   
   
       7 . The sandwich beam of  claim 1  in which the core includes a plurality of drop-stitches between the first and second walls. 
   
   
       8 . The sandwich beam of  claim 6  in which the drop-stitches are angled. 
   
   
       9 . The sandwich beam of  claim 1  in which the compression element is between 1/64 and 1/16 inches thick. 
   
   
       10 . The sandwich beam of  claim 1  in which the compression element is selected from materials including fiber reinforced polymers, polymer films, polymer sheets, metals, wood, and wood-based products. 
   
   
       11 . The sandwich beam of  claim 1  in which the compression element is flat. 
   
   
       12 . The sandwich beam of  claim 1  in which the compression element is curved concave. 
   
   
       13 . The sandwich beam of  claim 1  in which the compression element is curved convex. 
   
   
       14 . The sandwich beam of  claim 1  in which the core includes baffles. 
   
   
       15 . The sandwich beam of  claim 14  in which the baffles are angled. 
   
   
       16 . The sandwich beam of  claim 14  in which the baffles are angled and intersecting. 
   
   
       17 . The sandwich beam of  claim 14  in which the baffles are tube shaped. 
   
   
       18 . The sandwich beam of  claim 1  in which the core includes foam. 
   
   
       19 . The sandwich beam of  claim 1  in which there are a plurality of compression elements. 
   
   
       20 . The sandwich beam of  claim 19  in which each compression element is a flat strip. 
   
   
       21 . The sandwich beam of  claim 19  in which the compression elements are rods. 
   
   
       22 . The sandwich beam of  claim 19  in which the compression elements are tape springs. 
   
   
       23 . The sandwich beam of  claim 1  further including a skin over the compression element. 
   
   
       24 . The sandwich beam of  claim 1  in which the core includes baffles and there is a compression element associated with select baffles each including a top leaf hinged to a side leaf. 
   
   
       25 . The sandwich beam of  claim 1  in which there is a vacuum pocket about the compression element. 
   
   
       26 . The sandwich beam of  claim 1  in which the compression element includes multiple plies that are clamped together by pressure or vacuum force, but are allowed to slide when the beam is deflated, thus allowing the beam to be rolled up more easily. 
   
   
       27 . A waterboard comprising:
 upper and lower walls;   a core configured to maintain a predetermined spacing between the walls when the core is filled with gas and to resist shear when the waterboard is loaded in bending;   a port for filling the core with gas, said gas biasing both walls in tension, said tension tending to increase in the lower wall and decrease and cause a compression load in the upper wall in response to a sufficiently large applied bending load; and   a compression sheet secured about the upper wall and configured to support the compression load on the upper wall and to flex sufficiently to allow the waterboard to be rolled up when the gas is emptied from the core via the port.   
   
   
       28 . A method of making a sandwich beam, the method comprising:
 securing a first wall to a second wall via a core configured to maintain a predetermined spacing between the walls when the core is filled with a gas and to resist shear when the beam is loaded in bending; and   applying a compression element only to and fixed with respect to the first wall, the compression element configured to support the compression load on the first wall resulting from bending so that the beam is stronger at a given gas pressure and configured to flex sufficiently to allow the beam to be rolled up when the gas is emptied from the core via the port.   
   
   
       29 . The sandwich beam of  claim 1  having one or more second compression elements received by one or more sleeve pockets attached to the second wall. 
   
   
       30 . The sandwich beam of  claim 1  in which the compression element is pre-curled such that the beam rolls up when deflated and unrolls when inflated. 
   
   
       31 . A sandwich beam comprising:
 first and second spaced walls;   a core configured to maintain a predetermined spacing between the walls when the core is filled with pressurized gas and to resist shear when the beam is loaded in bending;   a port for filling the core with gas; and
 narrow compression elements fixed to both walls and configured (a) to support compression loads in the first and second walls due to bending loads applied to the beam in either direction (b) to flex sufficiently to allow the beam to be rolled up when the gas is emptied from the core via the port, and (c) to nest when deflated to allow each compression element to bend about its neutral axis.