Abstract:
The outstanding tensile strength of some materials are used in compression applications by using air pressure to supply the outward force on an enclosure and by using interior tension members to maintain the geometry of the air-pressurized structure. The air pressure on each face of the structure is balanced by the tension in the tension members. Due to the high modulus of the tension members, the air-pressurized structures are very rigid. It is the air pressure that actually supports any load placed on the structure, but it is the tension members that maintain the geometry when the load is removed, and the strength of the tension members determine how much air pressure can be sustained. The mass of tension material required in such a structure is roughly equivalent to the amount of filament material required in a cable to support the same load. The Compressed-air Rigid Building Blocks can be stacked like bricks to form strong, lightweight walls, buildings, towers, and other structures.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This claims priority to and the benefit of U.S. Patent Provisional Application No. 61/046,878, filed Apr. 22, 2008, the entirety of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    For load-bearing structures, we normally need materials with high compressive strength. However, in order to use these materials effectively, large masses are required. A filament, a wire, or a cable of the material would be useless in the compressive mode. There are materials that have very high tensile strengths that can support large loads as a cable, if the support is supplied from above the load. Unfortunately in practice, most loads are supported from below. I propose herein a method for using the high tensile strengths of some materials to support loads in the compressive mode. This means that building blocks could be much lighter than the standard load-bearing materials such as masonry bricks, concrete, or steel beams. (Since “wire” connotes a metal, “string” connotes a collection of fibers, “yarn” means a large string, and “cable” is usually applied to a large metal rope, “filament” will be used in this document refer to the elongated support member). 
         [0003]    U.S. Patents such as U.S. Pat. Nos. 3,854,253, 4,004,380, 4,676,032, 5,675,938, and 6,584,732 show inflatable structures that have interior braces, cables, and films to maintain the geometry of the structure, but they are not constructed to form building blocks for larger structures. Between the connecting points of the cables to the outer surfaces, the outer surface material typically bulges out, due to the air pressure. If these were used as building blocks, when one block is placed upon another, the bulges would be springy and would compress so that there would not be sufficient rigidity for effective building blocks. 
         [0004]    This description also includes the use of the building blocks for the construction of convection towers, for which I have four patents with the U.S. Pat. Nos. 5,284,628, 5,395,598, 5,477,684, and 5,483,798. 
       SUMMARY OF THE INVENTION 
       [0005]    High air pressure in an air bag can support heavy loads, but they are very compressible (spongy). Now suppose that we have a bag in the shape of a rectangular box and each face of the box is maintained in position by air pressure and an array of high tensile strength, high modulus filaments that run from one face to the opposite face. The load-bearing surfaces can be rigid or can have external washers that connect to the filaments. The air pressure pushes outward, while the filaments pull in. The pressure can be high inside such a box since the forces on the faces are borne by the filaments. When a heavy load is placed on the top face, the tension on the filaments that run from the top face to the bottom face of the box is reduced, and the load is supported by the air pressure. Since the filaments are made of a high modulus material such as Vectran, S-glass, graphite yarn, carbon-reinforced plastic, or even steel, there will be almost no depression of the box. It would be quite rigid as long as the external pressure on the top face did not exceed the pressure of the air inside the box. 
         [0006]    This invention provides a method of utilizing the high tensile strength of some materials to provide large compression forces to support loads. 
         [0007]    A box shape is appropriate for many building blocks, but the use of air pressure in an enclosed surface with internal filaments or thin films to maintain the shape can take many shapes. This invention concerns pressurized containers that can be stacked to make larger structures. They would be quite rigid as long as the external pressure on the top face did not exceed the pressure of the air inside the box. We may call it a “Compressed-Air Rigid Building Block” (CARBB), and it may be much larger than a standard brick or a building block. 
         [0008]    To prevent gradual deflation by possible small leaks, each CARBB could have a small-diameter hose attached to it through a one-way valve. The hose is attached to a pressure tank. Actually, if it is properly built, it should hold its pressure for years, just like car tires. If one CARBB is accidentally damaged, it can be deflated and removed, and another one can be inserted and inflated. The CARBB&#39;s are laid like ordinary bricks with the middle of each brick placed over the joint of the two bricks below it. See  FIG. 8 . For applications in which a narrow column is required, the CARBB&#39;s can be stacked one above the other. 
         [0009]    Large CARBB&#39;s would be useful in building large structures such as convection towers, cooling towers, housings for blimps, airplanes, military equipment, and farm products such as wheat, and temporary buildings for special events. Since they are light and foldable, they can be shipped in the deflated state and inflated at the site where they will be used. They could be used as temporary bridge supports in dry streambeds in military applications. 
         [0010]    To give an idea of the kind of load that can be borne by a CARBB, suppose it is constructed in the form of a cube that is 10 feet on each side and then a pressure of 100 psi is applied inside. The filaments can be made of Vectran, which has a tensile strength of 3.2 Giga Pascals (464,000 psi). It would require 235 lbs. of Vectran for the filaments (with a safety factor of 4) and 600 lbs of other materials, for a total of 835 lbs. Yet it could support 700 tons (1.4 million pounds) of weight on top of it. Imagine stacking 14 military tanks on top of an 835 lb. box! Of course, the compressed air inside the air box weighs 490 lbs., so the total weight is 1,325 lbs. Its average density of the CARBB is 0.021 gm/cc, including the air. That compares to 0.69 for cardboard and 0.12 gm/cc for balsa wood. The CARBB is much stronger than cardboard or balsa. 
         [0011]    We could stack such boxes on top of each other to a height of about 11,000 feet, before the bottom box would begin to collapse. By tapering the weight (that is, by having the higher boxes have less mass and less air pressure), they could theoretically be stacked to over 30,000 feet. We can also increase the air pressure and put in heavier filaments in order to support heavier loads. Replacing air with helium allows the construction of taller towers. For the moment, we are neglecting such things as wind forces and guy wires. 
         [0012]    For many applications, the CARBB would be much smaller than 10 feet on each side. The advantage of having them large is the fact that their density is less. A 10 by 10 by 10 foot CARBB would occupy 1,000 cubic feet. It would require 125 blocks that were two feet on each side to construct a building block that that occupied 1,000 cubic feet. It would weigh much more, because there would be much more face material. 
         [0013]    To provide a perspective, we can make a comparison to a steel cable. An ordinary steel cable, one square inch in cross sectional area, can safely support 10 tons of weight. If it is suspended from a crane 100 meters high, the cable will weigh 1,116 lbs. It can support 17.9 times its own weight. Compare this with the 10 by 10 by 10 foot CARBB. The unit can support 1,080 times its own weight. 
         [0014]    The U.S. military could use CARBB&#39;s as structural material, since military units often have to move quickly into an area to set up large temporary buildings. For military purposes, the boxes might be six feet on each side and weigh 240 lbs. The CARBB&#39;s are transported flat and then inflated on site. They can be stacked to make walls. What about the roof? Calculations show that if the CARBB&#39;s are designed with sufficient diagonal filaments, they can be placed on top of the walls to stretch across a 200-foot opening on the top to form a roof. Rather than having to build CARBB&#39;s that are 200 feet long, shorter bodies can be designed so that they can be placed end-to-end, and sliding connectors can hold them together. 
         [0015]    Of course, for building moderate size structures, such as the military might need, it is not necessary to design the CARBB&#39;s for 100 psi. For example, a CARBB that is 6 by 6 by 12 feet long that has only 10 psi pressure inside would be able to support 50 tons. If the CARBB&#39;s were used to build a wall 60 feet tall, the weight on the top of each bottom CARBB due to the CARBB&#39;s above it would be a little over one ton. The extra support capacity can be used to support the roof and possibly intermediate floors. If heavier loads are required, the pressure can be increased. 
         [0016]    Another application would be tall convection towers. A company in Australia plans to build a 1,000-meter tall solar power tower to produce electricity. The tower would be 130 meters in diameter and would be built of reinforced concrete that is one meter thick at the bottom. The glass-covered greenhouse around the base is to be 7 kilometers in diameter, incorporating 38 square kilometers (15 square miles) of glass to heat the air with solar energy. The tower will be very heavy (requiring a massive foundation) and expensive. By stacking CARBB&#39;s around in a circle at the base and continuing to stack CARBB&#39;s on top of those, the tower could be less expensive and far lighter. The proposed concrete tower would weigh more than 600,000 tons. A tower built of CARBB&#39;s (3 meter wide walls at the bottom) would weigh about 25,000 tons. 
         [0017]    Downdraft convection towers that spray water across the open top to cool the air can clean air pollution from the atmosphere while producing electric power. They can be built with CARBB&#39;s. These will be discussed below. 
         [0018]    For wind turbines in the U.S. and around the world, taller heights mean higher wind speeds and greater power production. CARBB&#39;s could be used to inexpensively build taller wind turbine towers. The towers could be constructed by laying the CARBB&#39;s like bricks in a circular fashion, or they could be built with circular CARBB&#39;s like that shown in  FIG. 10 . 
         [0019]    Homes, factories, warehouses, and office buildings can be built with CARBB&#39;s that are especially designed for the purpose. Hangers at airports represent another application. 
         [0020]    It is therefore an object of the present invention to provide a rigid box-like structure that is caused to retain its shape by internal air pressure (or other gas pressure) and by high strength, high modulus filaments that are attached to opposite faces of the structure. 
         [0021]    It is another object of the present invention provide a rigid cylindrical structure that is caused to retain its shape by internal air pressure (or other gas pressure) and by high strength, high modulus filaments that are attached to the top and bottom of the structure and by filaments attached to the outside of the structure. 
         [0022]    It is another object of the present invention to provide a rigid box-like structure that is caused to retain its shape by internal air pressure (or other gas pressure) and by high strength, high modulus films that are attached to the interior faces of the structure. 
         [0023]    It is another object of the present invention to utilize rigid structures for inexpensive construction of convection towers for the generation of electric power. 
         [0024]    Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The accompanying drawings illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings: 
           [0026]      FIG. 1  is a cross-sectional side-view schematic of one embodiment of the present invention showing a structure that is held rigid by air pressure pushing outward and tension filaments pulling inward. 
           [0027]      FIG. 2  is an isometric drawing of the CARBB invention showing a structure that is held rigid by air pressure and internal tension filaments and showing diagonal filaments on the outside faces that resist shearing forces. 
           [0028]      FIG. 3  is a schematic side view showing a method of inserting filaments between the top and bottom faces of a CARBB. 
           [0029]      FIG. 4  is a schematic side view showing a method of inserting filaments between the side faces of a CARBB. 
           [0030]      FIG. 5  is a cross-sectional side-view schematic of a single frame on which tension filaments are wound. 
           [0031]      FIG. 6  is an end view and a top view of part of the frame of  FIG. 5 . 
           [0032]      FIG. 7  illustrates a method of inserting filaments into a CARBB. 
           [0033]      FIG. 8  shows how the CARBB&#39;s are laid to form a wall. 
           [0034]      FIG. 9A  is a cross-sectional side-view schematic of another embodiment of the present invention showing a structure that is cylindrical. 
           [0035]      FIG. 9B  is an isometric view of the cylindrical embodiment of  FIG. 9A . 
           [0036]      FIG. 10  is an isometric view of another embodiment of the present invention, which provides a circular geometry with a cylindrical hollow inside. 
           [0037]      FIG. 11  is a top view schematic showing how the circular configurations of  FIGS. 9A and 9B  or  FIG. 10  can be arranged on a flat sheet. 
           [0038]      FIG. 12  is a cross-sectional side-view schematic of another embodiment of the present invention showing a structure that contains horizontal sheets and vertical filaments as tension members. 
           [0039]      FIG. 13  is an isometric schematic of another embodiment of the present invention showing a structure that contains horizontal, vertical, and diagonal sheets as tension members. 
           [0040]      FIG. 14  is a cross-sectional side-view schematic of a convection tower that uses CARBB modules to construct the walls of the tower. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]      FIG. 1  shows one design of a CARBB  1  in cross sectional side view. The faces  2 ,  3 ,  4  and  5  of the CARBB can be made of thin, tough composite plastic material or other airtight material. The top face  2  and bottom face  4  can be somewhat rigid. Side faces  3  and  5 , as well as the front and back faces (not shown) should be flexible so that the box can be folded down for shipping. Horizontal filaments  8  and vertical filaments  9  are shown. The dots  10  represent filaments that run in the third dimension (perpendicular to the page). The filaments hold the faces in place against the inside air pressure. In this design, the filaments  9  and  10  run through the side faces and are attached to rectangular plastic or metal washers, which distribute the force from the filaments to the face material. Filaments  8  pass through the top and bottom faces and are attached to the outside of those faces. On the side faces  3  and  5  (as well as the front and back faces), there should be small gaps between the rectangular washers so that the side faces can fold inward to allow the box to be collapsed. 
         [0042]      FIG. 2  shows a perspective view of the box. The encasing composite material on the faces has diagonal filaments  12  cemented to the outside of the faces to resist shear forces. 
         [0043]    In order to fabricate such a building block, one method would be to construct a plastic CARBB with the six faces sealed together at the edges of each face sheet and hold it in place by slight inside air pressure against the inside a jig. A rod passes a filament through holes in one face and continues on to holes in opposite faces of the box, and the filament is fastened to the rectangular, tapered washers on the outside of the faces. An appropriate adhesive seals the washers to the box. This would work for small boxes, but it would be difficult for large boxes. 
         [0044]    The question is, how are the filaments installed in the box of  FIG. 1  and  FIG. 2 , if the box is large? There are several ways in which it may be done. One method is described here. The top face  2  and the bottom face  4  have small holes drilled in them at appropriate locations for the filaments to pass through. Both faces are placed in a jig with the top face  2  lying on the bottom face  4 , as shown in  FIG. 3 . This is just a schematic drawing, showing only a few spools and filaments. A machine  13  that has many spools  14  of filaments across top area of the top face  2  and needles (not shown) pointed downward toward the holes in the top and bottom faces with the filaments  9  threaded through the eyes of the needles, which descend so that the needles pass through the holes in the top and bottom faces. Mechanisms below the bottom face  4  would intercept the needles and filaments and attach the filaments to the bottom face, similar to the operation of a sewing machine. The upper part of the machine would then rise. The top sheet would be raised the appropriate distance. 
         [0045]    We now have two rigid sheets at the top and bottom and rows of vertical filaments  9  extending between the two sheets. The whole assembly is then rotated 90 degrees to the left, and the faces  2  and  4  are separated further. See  FIG. 4 . Note that the machine  13  is now on the left. Face  3  is placed below the filaments  9 , and face  5  is placed above the filaments  9 . Face  3  is raised as face  5  is lowered. The filaments  9  are pressed between the two faces  3  and  5  as the spools  14  allow the filaments to be extended. Faces  3  and  5  have holes in them for the passage of the filaments. Face  3  has rectangular washers cemented to its bottom matching the position of the holes. Face  5  has rectangular washers cemented to its top over the holes. While faces  3  and  5  are pressed together, machine  15 , which is similar to machine  13 , and spools  16  holding filaments pass the filaments  8  through holes in faces  3  and  5  by needles (not shown). The filaments are attached to the bottom of face  3 . Then face  3  is lowered while machine  15  and face  5  are raised. 
         [0046]    The process of the preceding paragraph is repeated, except that the whole assembly is rotated into the page of the drawing, and the front and back faces of the CARBB are placed above and below all the filaments. The front and back faces are moved together to press all the filaments  8  and  9  between them. Another machine then passes filaments through the front and back faces, the filaments are connected to one of the faces, and the faces are moved apart. All of the faces are moved into the appropriate positions, and all the filaments are tightened and cemented to the outside of the faces. The faces are sealed along all the edges. The finished BARBB can then be inflated. 
         [0047]    Each CARBB has an inflation connection and valve, and a connection for a small diameter hose to maintain pressure (not shown). 
         [0048]    Another way of positioning the filaments is to wind the filaments onto a plastic (or metal) frame  20  as shown in  FIG. 5 . The frames are constructed of narrow strips that might be two inches wide (in the direction normal to the page of the drawing) and perhaps 3/16 of an inch thick. Vertical  9 , horizontal  8 , and diagonal filaments  7  are wound around the frames. Many of these frames are then placed adjacent to each other. The top, bottom, and sides of the plastic casing (faces) of the CARBB are then epoxied to the outside of the frames and sealed at the corners. That will take care of four faces of the box. Filaments will need to be passed through the other faces by rods. If each rod has a streamlined body at its front end, it will be guided through rows and columns of filaments as it presses against those filaments. Finally the end plastic sheets are sealed to the side sheets. The whole process can be automated in a factory. 
         [0049]    The advantage of having the diagonal filaments is that they provide resistance to shear forces about the axis normal to the page. The CARBB&#39;s can be oriented so that the probable direction of greatest shear forces will be resisted. Shear forces in other directions can be resisted by diagonal filaments on the outside of the box. 
         [0050]    The frames  20  have hinges  21  on side strips  25  and  26  so that the CARBB&#39;s can be folded down for transporting to the location of use or for storage. The side encasing material must be flexible in order to permit the folding of the box. The top and bottom of the box can be rigid. Alternatively, in order to make side strips easily foldable, side strips  25  and  26  can be made of flexible material that have rigid rectangular washers where the filaments are attached. 
         [0051]      FIG. 6  shows detail of part of the frame. The filaments  7 ,  8 , and  9  are wrapped into slots  22  in the frames and tightened to specified tension while the frames are held in a jig. When the frames are stacked adjacent to each other, they fit together with overlaps  23  and  24 . 
         [0052]    Another way to put the filaments into the CARBB is illustrated in  FIG. 7 . The top face  2  and the bottom face  4  of CARBB can be put together as shown in  FIG. 3 . The filaments are passed through and attached to the bottom face. Then the two faces are moved to their normal finished positions, and the filaments  9  are cemented to the outside of the top face. In  FIG. 7 , the left face  3  is then placed on the left. A vertical row of shuttles  80  attached to rods  82  are inserted from the right and pass down between the rows of vertical filaments  9 . The rods  82  are moved by support  83 . For the first pass through, horizontal filaments  8  are attached to the first vertical catch rod  84 . There is one vertical catch rod  84  at the right of each row of vertical filaments  9 . From there filaments  8  pass through the eye of the needles  81  and then go back to spools  87 . Alternatively, the shuttles  80  could contain the spools of filaments. The shuttles  80  are supported by supports  86  and roller  89 . 
         [0053]    When the shuttles  80  reach the left side, an inserted guide  85  guides the needles into the holes  88  in the left face  3 . After the needles pass through left face, a mechanism (not shown) seizes the filament above the needle and attaches it to the surface of face  3 . Then the shuttles are withdrawn to the right. The support  83 , along with the rods, shuttles, and the spools, move one row toward the viewer in the drawing. As it moves toward the viewer, the filament passes around the next catch rod  84 . On the left, the guide  85 , which has slots in the side to let the filaments pass through, also moves toward the viewer to line up with the next row of holes  88 . Then the shuttles move again to the left to install the next row of horizontal filaments  8 . This process continues until all the horizontal filaments are installed. The guide  85  is removed, and the left face  3  is moved into contact with the top face  2  and bottom face  4  and cemented to them. 
         [0054]    On the right, the shuttle mechanism ( 80 ,  82 ,  83 , and  87 ) is removed. The right face  5  (shown in  FIG. 1 ) is put into place, and a mechanism from the right side of the right face inserts hooks through the holes and seizes the filaments that are held by the catch rod  84  and pulls them through the holes. The catch rods have grooves in the right side so that it is easy to snag the filaments. After all the filaments  8  have been drawn through the holes, the catch rods  84  are removed, and the right face  5  is moved against the top face  2  and bottom face  4  and sealed into place. The filaments  8  are drawn tight and attached to the right surface of face  5 . 
         [0055]    The assembly is then rotated about the vertical axis 90 degrees counterclockwise. The back face is placed to the left along with the guide  85 . The supports  86  are removed from between the shuttles, because they would interfere with the filaments  8 . The shuttles are guided by moving down the channels, which are surrounded by the vertical and horizontal filaments. The catch rods  84  are put in place on the right. The shuttles are inserted from the right, and the process described in the proceeding paragraphs insert the remaining filaments. Finally the front and back faces are cemented in place. 
         [0056]    This method would work for the design shown in  FIG. 1 . It would also work for the design in which filaments  7 ,  8 , and  9  are put in place by the frames of  FIG. 5 . In some cases, the diagonal filaments would be pushed out of the way by the shuttles. 
         [0057]      FIG. 8  shows one method of building a wall or other supporting structure with CARBB&#39;s. The CARBB&#39;s  1  can be stacked like bricks. 
         [0058]    Another embodiment ( 30 ) of a CARBB is shown in  FIG. 9A  and  FIG. 9B .  FIG. 9A  shows a cross sectional side view of a cylindrical enclosure that has filaments  9  running in the axial direction to support the circular faces  33  and  34  against internal air pressure.  FIG. 9B  gives an isometric view of the outside of this embodiment. Filaments  32  are wrapped around the cylinder  35  in a circumferential direction to support the side pressure. Diagonal filaments (not shown) cemented to the outside of cylinder  35  resist shear forces. The cylinder  35  should be made of flexible material so that the CARBB can be folded down for shipping. Cylinder  35  is sealed to the rigid top  33  and the rigid bottom  34 . 
         [0059]    This cylindrical embodiment can be easily fabricated in a factory. The top face  33  and the bottom face  34  should have small holes for the filaments at appropriate locations. Both are placed in a jig with the top face lying on the bottom face. A machine that has many spools of filaments across a circular area and needles pointed downward toward the holes in the top and bottom faces with the filaments threaded through the eyes of the needles can descend so that the needles pass through the holes in the top and bottom faces. Mechanisms below the faces would intercept the needles and filaments and attach the filaments to the bottom face. The upper part of the machine would then rise. The top sheet would be raised the appropriate distance, and the filaments would be attached to the top face. The holes would be sealed and the filaments would be cemented to the top face  33  and bottom face  34 . The side enclosure  35  would then be sealed to the top and bottom sheets. 
         [0060]    For narrow towers, like those that support wind turbines, the CARBB&#39;s could be constructed in a circular design  36  as shown in  FIG. 10 . The interior would be constructed of frames like that in  FIG. 5 , but the outer part of each frame would be wider than the inner part, since the radius and the circumference of the circular design are larger on the outside. There would be vertical, horizontal, and diagonal filaments inside. The horizontal filaments run radially. Since the outside cylinder  37  has a larger area than the inside cylinder  38 , there might be concern that the radial filaments would pull more strongly towards the outside, but there will be filaments wrapped circumferentially around the outside cylinder  37  that will counter this extra force. 
         [0061]      FIG. 11  shows a method of grouping CARBB modules such as design  30  in  FIG. 9  or design  36  in  FIG. 10 . The modules can be attached to a bottom rigid sheet  39 . In this way, the circular CARBB&#39;s can be assembled to function as building blocks similar to those of  FIG. 2  and can be stacked like those of  FIG. 8 . 
         [0062]    Another design that makes it easy to fold the CARBB flat is shown in side view cross section in  FIG. 12 . The air pressure on the CARBB&#39;s sides is countered by horizontal thin film sheets  41  of material with high tensile strength. The internal air pressure on the top  44  and bottom  45  are supported by filaments  42 . The outer edges of the sheets are sealed together by end sheets  43  that are cemented to the horizontal sheets  41 . Air pressure forces them to curve outward. This design is fabricated by laying the bottom face  45  of the CARBB on the factory assembly mechanism and then laying the first horizontal sheet  41  on the bottom face  45  and sealing the first sheet  41  to the bottom face with the end sheets  43 . While that sheet lays flat on the bottom, the second horizontal sheet  41  is laid on top of the first sheet  41  and sealed to the first horizontal sheet with other end sheets  43 . This process is continued until the last horizontal sheet  41  is sealed to the top face  44  of the CARBB with end sheets  43 . The top face  44  and the bottom face  45  can be somewhat rigid and have many small holes in them for the attachment of the filaments  42 . With the whole assembly lying flat, needles pass through the holes in the top face  44  and are forced down through the horizontal sheets  41  with filaments  42  in the eyes of the needles. Mechanisms below the bottom face catch the filaments  42  and attach them to the bottom face  45 . When this process is finished, air pressure raises the top to full height while spools reel out the filaments. The filaments are then attached to the top, and the holes where the filaments pass through are sealed. 
         [0063]    An alternative to the design shown in  FIG. 12  would be to use sets of filaments in place of the horizontal sheets. The sets of filaments would be laid upon the bottom face  45  and attached to the end sheets  43  in a manner similar to the description in the previous paragraph. An advantage of the horizontal sheets  41  is that they provide resistance to shear forces about the vertical axis. 
         [0064]    Another alternative embodiment similar to  FIG. 12  is shown in  FIG. 13 . The tension support is provided by vertical  51 , horizontal  52 , and diagonal sheets  53  of strong plastic film. This configuration of sheets can be formed by extrusion of the plastic through a die. The isometric drawing shows the direction of extrusion. When the plastic exits the die, it already has the vertical, horizontal, and diagonal sheets. Only two diagonal sheets are shown, but diagonal sheets can actually be placed to meet all the intersections of the vertical and horizontal sheets. The extrusion units are cemented to the top rigid face  55  and bottom rigid face  56 . If the end sheets  54  are not part of the extrusion, they can be added by cementing onto the horizontal sheets  51 . 
         [0065]    For large assemblies, the extrusions can be made in smaller units and can then be cemented together. For example, each extrusion unit might be one foot square in cross section with two-inch spacing between the vertical sheets and two-inch spacing between the horizontal sheets. If the CARBB is to be six feet long by three feet wide by three feet tall, it would require nine of the extruded units (each six feet long) to fill the interior. Holes in the interior sheets would allow air to flow throughout the interior. 
         [0066]    The advantage of the design of  FIG. 13  is that, in addition to the strong tension forces applied to the outside faces of the box by the interior sheets, there are strong forces to resist any shear stresses. The end sheets  54  on the side allow the unit to collapse downward when the air pressure is removed. To attach end sheets to the front (nearest the viewer in the drawing) and back, the extrusion is allowed to extend a little beyond the intended face of the box, the vertical and the diagonal sheets are cut back slightly, and end sheets are cemented to the horizontal sheets. Since interior sheets are thin, heavier and more rigid sheets  55  and  56  are cemented to the top and bottom. The end sheets should be thicker and tough to prevent abrasive objects from damaging the unit. 
         [0067]    If the sheets in a 6 by 3 by 3 feet CARBB are 5 mils thick with two-inch spacing between sheets and the material has a density similar to Spectra 2000, the weight on the interior sheets would be 41 lbs. If the tensile strength is 30,000 psi, the maximum allowable air pressure would be 150 psi. With a safety factor of three (air pressure=50 psi), the CARBB could support 129,600 lbs. A warehouse wall 120 feet long could support 1,296 tons. The complete 6 by 3 by 3 foot CARBB would weigh 100 lbs. With the compressed air at 60 psi, it would weigh 120 lbs. It can support 1,300 times its own weight. 
         [0068]    Since the CARBB&#39;s are so light, there might be a concern that CARBB&#39;s might be blown off a wall built with CARBB&#39;s by the wind. For some applications, Velcro could be applied to the top, bottom, and ends of the CARBB&#39;s to secure them together. For other applications, straps can tie them together and anchor them to a concrete foundation. 
         [0069]    Rigid CARBB&#39;s that use air pressure to provide support and internal filaments that have high tensile strength and high modulus can be used to build towers, such as those that support wind turbines. 
         [0070]    One of the important applications of CARBB technology is the construction of convection towers, either downdraft or updraft. A downdraft convection tower, such as that shown schematically in side view cross-section in  FIG. 14 , works well in low-humidity areas where water is available. Water is sprayed across the open top of the tower by a water spraying system  61 . That cools the air and makes it dense. The air falls down the inside of the tower and turns air turbines  62  at the bottom of the tower to generate electricity. The diffuser  63  improves the efficiency of the turbines. 
         [0071]    The cylindrical wall  60  is made by stacking CARBB&#39;s in brick-like manner ( FIG. 8 ). Guy wires  65  and radial cables  66  add to the rigidity of the tower wall. These can be steel cables, or they can be made of some of the new lightweight, high-strength filament materials. Structural supports  67  are built to support the wall above the turbines. 
         [0072]    A downdraft convection tower that is 1,000 meters tall and 500 meters in diameter can generate 1,000 megawatts of electric power when the relative humidity is 20% or less. But building a tower of that size is quite expensive by using the standard materials and methods. The value of CARBB can be illustrated by comparing it with concrete and steel construction. Consider the CARBB&#39;s to be 10 by 10 by 10-foot cubes, as described above with air pressure of 100 psi. The cube would weigh 1,325 lbs, including the compressed air. A cube of the same size made of concrete would weigh 150,000 lbs. The foundation for a 1,000-meter tall concrete tower would be enormous. 
         [0073]    As mentioned above, with a CARBB top face force of 1,440,000 lbs, it could support CARBB&#39;s that are stacked to a height of 10,000 feet. Since the tower is only 3,280 feet tall, the pressure can be lowered considerably. 
         [0074]    Whereas a 1,000 meter tall concrete and steel tower would require several years to complete. Such a tower that is built with CARBB would require about five months. The blocks can be inflated at the base of the tower. Lightweight lifting units on top of the wall can raise the CARBB to the top and quickly place it on top of the wall. A number of crews of three workers each can make the tower grow rapidly. When one row is finished, the lifting unit can be placed on an uninflated CARBB, and the inflation of the CARBB will lift the lifting unit to the next level. For concrete towers, it requires a lot of energy to lift the concrete, and then after the concrete is poured, time must be allowed for it to harden. After that, the concrete forms must be dismantled and reset.