Abstract:
A connection device for use with a blast-resistant container includes a frame with a recess, and a connecting member. An arcuate surface is formed on the outside of the opening of the recess. The connecting member is connected to the frame at one end with a head engaged in the recess and connected to a side panel at the other end. Thus, this connection device can transmit strong membrane force between each two panels of a container and meet the connection requirement of a blast-resistant container. When there is a blast, the connection device is able to confine the blast within the container for that the maximum strain of the plastic hinge in the connecting member can be controlled by the curvature of that arcuate surface formed on the frame.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a connection device of a container, and more particularly to a connection device for use with the blast-resistant container. The present invention connect one frame to its adjacent panels in this container, and it can not only transmit strong membrane force between two panels to meet the connection requirement of a blast-resistant container, but also especially admits one panel relatively moving to the frame.  
           [0003]    2. Description of Related Art  
           [0004]    A container is usually a box-shaped or nearly box-shaped structure. According to analysis and experiments, the blast-resistant container need to undertake the blast pressure much greater than the payloads of the conventional container overall. When the explosives explode inside, the container will deform tending to spherical shape unavoidably if its weight is limited for real use. Hence, they are very important both the extremely using the membrane strength of all panels of the container and the allowing of the bending rotation between the panels and their connectors(frames) on the surrounding edges of the container. Moreover, it may still make a serious problem if in practice one or some panels of a container have to be strongly supported or only one of two panels beside a frame can be expanded freely. The present invention is mainly to those important problems of a blast-resistant container.  
           [0005]    For example, an air cargo container must comprise strong and rigid enough frames, which can undertake the side restraint loadings for fixing the container on the deck of an airplane, on the perimeter of its bottom panel. The bottom perimeter frames are also a connection device between side panels and bottom panel of the container. And its bottom panel is strongly supported by the deck on an airplane, but the other panels of the container can expand freely.  
           [0006]    However, if the air cargo container does not have a strengthened design about the bottom perimeter frames connecting the side panels and bottom panel to resist an explosive blast, it is very easy to failure for the bottom panel separating with its adjacent side panels under the explosive blast. Even all the panels of the air cargo container are high membrane strength enough! There are two reasons to induce the former description. Firstly, the higher rigidity of bottom perimeter frames causes the difficult of relative rotation between the frame and side panel. Secondly, the explosive pressure cause all panels but bottom panel deform to outside, because it can be transmitted to the deck of an airplane or ground directly. Therefore, even the strengthened connection device, which can transmit membrane forces effectively between panels (except bottom panel and its adjacent panels), may not work well for bottom panel and its adjacent panels.  
           [0007]    Over a decade, airplanes have become a primary target for terrorist attack, and many people have lost their lives in plane crashes due to terrorist bombs attached in checked baggage. To prevent those tragedies from happening, a lot of efforts have been made in the field of blast-resistant containers. Recently, because of the bomb threat to the airliners by terrorists and the  911  suicide attack to the Twin Tower in New York City, U.S.A. Countries are devoting their researches on flight safety. Hence, a blast-resistant container becomes important and is extremely popular in the market. This kind of blast resistant container is also popular in the transportation and the storage business.  
           [0008]    According to the blast test of a blast-resistant air cargo container, it is one of the typical failure modes for the bottom panel separating with its adjacent side panels under the explosive blast. This is because of too great stress mainly contributed from the great bending stress happened in the concurrence of bottom frame and side panels.  
           [0009]    In order to overcome such problem, some blast-resistant container (U.S. Pat. Nos. 6,112,913 and 6,237,793) use the connecting members which extends upward some length directly from bottom perimeter frames to combine with the side panels of this container. It is a possible way to solve this problem; because the directly extended connecting members may soften the rotation stiffness between the bottom perimeter frames and the down edges of side panels. But it is not a reliable mechanism. The position and the quantity of the most seriously bending strain in the connecting member, which may cause the failure of a blast-resistant container, is not under control.  
           [0010]    To overcome those shortcomings, the present invention tends to provide an improved, more reliable connection device that can control the maximum strain of the plastic hinge in the connecting member to mitigate and obviate the aforementioned problems.  
         SUMMARY OF THE INVENTION  
         [0011]    For the blast-resistant container, the present connection device invention use a connecting member that is separated with a rigid frame, not extending directly from the rigid frame, such that the maximum strain of the plastic hinge in the connecting member can be controlled by the curvature of an arcuate surface formed on the frame under the explosive blast. Thus, this connection device can transmit strong membrane force between each two panels of a container and meet the connection requirement of a blast-resistant container.  
           [0012]    For example, the blast-resistant air cargo container comprises bottom perimeter frames which are connectors of bottom panel and its adjacent side panels and must be strong and rigid enough to undertake the side restraint loadings for fixing the container on the deck of an airplane. The present connection device includes bottom perimeter frame and a connecting member for connecting down edge of the side panel to the bottom panel. The bottom perimeter frame has a recess and an arcuate surface formed outside the recess.  
           [0013]    By means of these, we provide a “soft connection” between the side panels and the bottom panel which can be “opened” by the mechanism of plastic hinge on the connecting member under a blast. When the blast-resistant container is experiencing a blast, the connection device is able to confine the blast within the container for that the maximum strain of the plastic hinge in the connecting member can be controlled by the curvature of that arcuate surface formed on the frame.  
           [0014]    Besides, being a connection device between side panels and bottom panel, it can not only transmit strong membrane force between them to meet the connection requirement of a blast-resistant container, but also especially admits side panel sliding along the bottom frame. Hence, base on this feature, the side panel above this frame can be used as a sliding door for a blast-resistant container.  
           [0015]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of the connection device applied to an air cargo blast-resistant container;  
         [0017]    [0017]FIG. 2 is a side plan view of the large-curvature bottom perimeter frame corresponding to the head of L shaped extended outwardly;  
         [0018]    [0018]FIG. 3 is a schematic view showing the engagement between the bottom perimeter frame in FIG. 2 and distal edges of side panels before and after the blast;  
         [0019]    [0019]FIG. 4 is a side plan view of the small-curvature bottom perimeter frame corresponding to the head of L shaped extended outwardly;  
         [0020]    [0020]FIG. 5 is a schematic view showing the engagement between the bottom perimeter frame in FIG. 4 and distal edges of side panels before and after the blast;  
         [0021]    [0021]FIG. 6 is a side plan view of the bottom perimeter frame corresponding to the head of a L shaped extended inwardly; and  
         [0022]    [0022]FIG. 7 is a schematic view showing the engagement between the bottom perimeter frame in FIG. 6 and distal edges of side panels before and after the blast. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    With reference to FIG. 1, an air cargo blast-resistant container includes bottom perimeter frames ( 10 ) formed on a peripheral edge of a bottom panel (not shown) of the blast-resistant container. The bottom perimeter frames ( 10 ) are used to connect the bottom panel to side panels ( 30 ). Each of the side panels ( 30 ) has a connecting member ( 20 ) formed on a lower portion of the side panel ( 30 ) to connect with the bottom perimeter frame ( 10 ).  
         [0024]    With reference to FIG. 2, the bottom perimeter frame ( 10 ) has a recess ( 12 ). An arcuate surface ( 122 ) is formed the outside of the opening ( 120 ) of the recess ( 12 ). Besides, the bottom perimeter frame ( 10 ) has an engaging portion ( 126 ) extending from a side of the bottom perimeter frame ( 10 ) to connect with the bottom panel of the blast-resistant container. In order to reduce the weight of the connection device, multiple reinforced ribs ( 128 ) are formed inside the bottom perimeter frame ( 10 ) instead of the solid frame.  
         [0025]    With reference to FIG. 3, the bottom perimeter frame ( 10 ) is combined with the side panel ( 30 ) through a connecting member ( 20 ). One edge of the connecting member ( 20 ) connects to side panel ( 30 ), and the other edge of this connecting member ( 20 ) is formed a head to be held in the recess ( 12 ). The head of the connecting member can be L shaped, T shaped (not shown), or the likes which embed in the recess ( 120 ). The connection between the connecting member ( 20 ) and the side panel ( 30 ) must transmit great tensile force therein. The using of high strength bolts is preferable. The arrangement of the bolts is the same as conventional method and well known in the art. Detailed description thereof is omitted hereinafter. The frame and connecting member can be manufactured by extrusion. The frame is made of metal; aluminum alloy is preferred for lightweight. The connecting member is made of high toughness metal, like stainless steel, aluminum alloy with high toughness, for it can take loading under a long-range plastic state without failure until its maximum strain over its elongation strength.  
         [0026]    When the blast-resistant container is experiencing a blast and the side panel ( 30 ) is deformed relative to a bottom panel ( 40 ), the blast pressure (P 1 ) applied on a top surface of the bottom panel ( 40 ) is counterbalanced by a counter-reaction force (P 2 ) on a bottom surface of the bottom panel ( 40 ). The side panel ( 20 ) will be pushed by the blast pressure (P 3 ) to engage with the arcuate surface ( 122 ) and is bent according to the arcuate surface ( 122 ). A plastic hinge is thus formed on controlled position and the maximum deformation is controlled to prevent destruction of overly bending. After the plastic deformation of the connecting member, the membrane force between two panels on different sides of connector, including bottom perimeter frame and connecting member, can be transmit effectively.  
         [0027]    When either different material or different thickness is used on the connecting member ( 20 ), the curvature of the arcuate surface ( 122 ) would be different. The smaller the elongation strength or the larger the thickness, the smaller the curvature is needed. And doing that can avoid the failure happened. Therefore, FIG. 2 and FIG. 3 show the connecting member ( 20 ′) uses highly elongation steel and the curvature is obviously smaller than the design of aluminum with smaller elongation strength, shown in FIG. 4 and FIG. 5.  
         [0028]    The head in the FIG. 3 has to be held in the recess ( 12 ) and keeps the connecting member away from failure. Therefore, the design of the head is very important. With reference to FIG. 3, the head is L shaped with a lip and the lip of the L shaped extends outwardly from its elbow. This is because when the blast is happened, the pressure faces outward and makes the upper of L shaped deform to outward and that lets the tip of the lip contact the bottom of the recess tighter and tighter. This avoids the head to be stretched straightly automatically and the head would be kept in the recess safely. Besides, the elbow of the connecting member would be pulled up to contact the upper of the recess by the great tensile force transmitted from a side panel. Comparing two contact forces: the upper contact force is with smaller arm and greater magnitude of force, the direction of the lower contact force is on the contrary with the upper contact force, results that the bending moment in the neighbor of elbow is not very great. Therefore, the thickness of the lip is not necessary great and can be designed nearly the thickness of its upper of L shaped. When the head is L shaped which lip extends inwardly, it would be drawn out without strengthened design. Because the lip extends inwardly, the blasting pressure would pull the connecting member( 20 ″) straightly, like a wire, which makes the connecting member drawn out. In order to avoid this problem, the lip has to become a big block which is much thicker than original design in order to avoid to be stretched straightly, shown in FIG. 7. This block can help the connecting member to securely hold in the recess. This type of head would not touch the bottom of the recess, rather than L outwardly type, when the blast is happened. Because the great membrane forces of panels will pull up the connecting member and the head will contact tightly to the upper of the recess. Therefore, it is allowable to install roller on the frame (not shown) and the side panel above this frame can be used as a door.  
         [0029]    The bottom perimeter frame ( 10 ″) corresponding to the head of a big block is shown in FIG. 6. The bottom perimeter frame ( 10 ″) has a recess ( 12 ″). An arcuate surface ( 122 ″) is formed the outside of the opening ( 120 ″) of the recess ( 12 ″). Besides, the bottom perimeter frame ( 10 ″) has an engaging portion ( 126 ″) extending from a side of the bottom perimeter frame ( 10 ″) to connect with the bottom panel of the blast-resistant container. In order to reduce the weight of the connection device, multiple reinforced ribs ( 128 ″) are formed inside the bottom perimeter frame ( 10 ″) instead of the solid frame.  
         [0030]    When the blast-resistant container is experiencing a blast and the side panel ( 30 ″) is deformed relative to a bottom panel ( 40 ″), the blast pressure (P 1 ″)) applied on a top face of the bottom panel ( 40 ″) is counterbalanced by a counter-reaction force (P 2 ″) on a bottom surface of the bottom panel ( 40 ″). The side panel ( 20 ″) will be pushed by the blast pressure (P 3 ″) to engage with the arcuate surface ( 122 ″) and is bent according to the arcuate surface ( 122 ″). A plastic hinge is thus formed and the maximum deformation is controlled to prevent destruction by overly bending.  
         [0031]    It is concluded from the foregoing that the connection between the distal edges of the side panels (through the connecting members) and the bottom perimeter frame ( 12 ) provides a clearance and low rotation stiffness of the connecting member to allow the cside panel to rotate relatively to the rigid frame when experiencing a blast. Therefore, damage from the rotation destruction is prevented. I.e., the adaptable deformable plastic hinge of the connecting member avoids the direct failure of over stress (including the bending stress) due to the overly stiffness of rotation.  
         [0032]    The connecting member is made of stainless steel or aluminum with high toughness. The radius of the arcuate surface ( 122 ) of the frame ( 10 ) is depends on the strength of the blast and which material the connecting member ( 20 ) is made of. The stronger of a blast, the more thick of connecting member ( 20 ) is needed to take the greater tensile force. So, the smaller curvature or the larger curvature radius of the arcuate surface ( 122 ) is needed. When there is a blast, the connecting member is bent according to the arcuate surface ( 122 ) so as to form a plastic hinge. Its maximum deformation is controlled so that the blast-resistant container is protected from damage of overly bending deformation.  
         [0033]    Furthermore, the connection device of the present invention not only can be applied to the blast-resistant container with vertical side panels ( 30 ), but also applied to a sliding door frame. It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.