Abstract:
A spring lock for interconnecting adjacent walls of a shipping container having foldable walls, said spring lock including a mounting portion and a clamping portion, and a shipping container with foldable walls wherein at least one pair of adjacent walls is interconnected with a spring lock.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/822,523 filed on 13 May 2013, which is hereby incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention generally relates to shipping containers, and more specifically to a shipping container having sidewalls that can be rotated from a horizontal, stowed position, which minimizes storage and transportation costs of empty containers, to a vertical position allowing containers to be loaded and stacked two or more containers high. 
         [0006]    2. General Background of the Invention 
         [0007]    For many years, industries dealing in bulk goods have utilized returnable containers featuring folding sidewalls that minimize the cost associated with storing and transporting empty containers. In general, such containers include a first pair of opposing sidewalls (“primary sidewalls”) that must be the first two walls raised to an upright position. Such primary sidewalls typically have edge portions that wrap around toward the other primary sidewall. Such containers also generally contain a second pair of opposing sidewalls (“secondary sidewalls”) that can be raised to an upright position only after the primary sidewalls have been raised to their upright position. The edge portions of the secondary sidewalls will typically engage the “wrap around” edge portions of the primary sidewall to add rigidity to the container. Frequently, the edge portions of the primary sidewall and the secondary sidewall are designed to mate together, for example by providing recesses in the edge portion of the primary sidewalls to receive protuberances extending from the edge portions of the secondary sidewalls. 
         [0008]    In many applications, such configurations provide the necessary strength and resiliency. But when loaded containers are transported while stacked, problems can arise when the bottom container is brought to an abrupt stop. This results in the momentum of the upper container applying an outward force to the sidewall of the lower container that is facing the direction in which it had previously been moving. Such containers are generally able to withstand such force when applied to one of the secondary sidewalls, especially when the edge portions of the primary and secondary sidewalls are design to mate together so long as the length of the wrap around portion of the primary sidewalls is kept to a minimum to minimize the moment applied to the primary sidewalls. 
         [0009]    When such an outward force is applied to one of the primary sidewalls, failures occur on a much more frequent basis. The reason for this is that the latching mechanism and the mating of the sides through recesses and fingers do not collectively have the strength to resist a large outward force applied to the upper portion of the primary sidewall. The primary means of trying to overcome this is by extending the length of the wrap around edge portions of the primary sidewalls to make the primary sidewall more rigid. This, however, has the effect of increasing the moment resulting from an outward force applied to a secondary sidewall and leads to more failures resulting from the application of this type of force. Extending the wrap around edge portion also has the drawback of reducing the width available for a drop-down access panel or door in the secondary sidewall (such drop-down panels are frequently provided to facilitate access to goods stored within such containers). 
         [0010]    What is needed then is a container with folding sidewalls that is capable of resisting the outward force applied to any one of its sidewalls resulting when a stack of loaded containers is being moved and the bottom container is brought to an abrupt stop. Such container should also be capable of passing the standard industry inclined impact test that involves placing two loaded containers (the load for each container can be as much as 2000 pounds) with one container stacked on the other. The loaded containers are then allowed to slide down an inclined surface, and at the terminal point of the test the bottom container is impacted and brought to an abrupt halt, resulting in the momentum of the upper container placing an outward force on the upper portion of the downhill sidewall of the bottom container. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention relates to a shipping container having folding sidewalls, the sidewalls further comprising a pair of primary sidewalls, each said primary sidewall having an edge portion that wraps around and extends toward the opposing sidewall, and a pair of secondary sidewalls having edge portions designed to mate with the wrap around edge portions of the primary sidewalls when the sidewalls are in their vertical positions, and a spring lock further interconnecting each primary sidewall to each secondary sidewall to enable such container to resist the outward force applied to a primary sidewall when the bottom container is brought to an abrupt stop when a stack of loaded containers is being transported. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the attached figures, wherein like reference numerals denote like elements. 
           [0013]      FIG. 1  is a perspective view of an embodiment of a container using an embodiment of the spring lock described herein. 
           [0014]      FIG. 2  is a perspective view of the Detail A portion of the container from  FIG. 1 . 
           [0015]      FIG. 3  is an exploded perspective view of Detail A. 
           [0016]      FIG. 4  is an exploded perspective view of Detail A from an alternate angle. 
           [0017]      FIG. 5  is a horizontal sectional view of the perspective view of Detail A. 
           [0018]      FIG. 6  is vertical sectional view of the perspective view of Detail A. 
           [0019]      FIG. 7  is a perspective view of an embodiment of the spring lock. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The present invention is a shipping container for bulk goods. Referring now to  FIG. 1 , container  1  comprises rectangular base  10 , opposing pair of primary sidewalls  100 , opposing pair of secondary sidewalls  200 , and spring locks  50 . Except as expressly noted herein, for purposes of the elements and limitations of the present invention each of primary sidewalls  100  are considered to be identical and each of secondary sidewalls  200  are considered to be identical. In practice, each sidewall may have differing features unrelated to the elements and limitations of the present invention such as secondary access panels or doors. 
         [0021]    Secondary sidewalls  100  are rotatably connected to opposing side portions of base  10  such that secondary sidewalls  100  can be folded flat onto base  10  with one of secondary sidewalls  100  resting on the upper surface of base  10  and the other secondary sidewall  100  resting on the first secondary sidewall  100 . 
         [0022]    Primary sidewalls  200  are rotatably connected to base portion  10  such that primary sidewalls  200  can be folded flat onto secondary sidewalls  100  with one of primary sidewalls  200  resting on the upper secondary sidewall  100  and the other primary sidewall  200  resting on the first primary sidewall  200 . Each primary sidewall  200  includes support portions  210  that extend inward from the inner surface of primary sidewall  200  along opposing edge portions  220  of primary sidewall  200 . In certain embodiments, when primary sidewalls  200  and secondary sidewalls  100  are rotated to their upright position, at least the portion of outer surface  212  of each support portion  210  adjacent to a secondary sidewall  100  aligns with the outer surface the adjacent secondary sidewall. 
         [0023]    Each secondary sidewall  100  includes opposing mating portions  110  that engage support portions  210  of the primary sidewalls  200 . Said engagement may simply be an abutment of two flat surfaces (not shown). Alternatively, support portions  210  and mating portions  110  can have complementary designs allowing the portions to be physically interlocked. One example would be keyways  214  defined in support portions  210  to receive mating protuberances  114  extending from mating portions  110 . 
         [0024]    Each primary sidewall  200  is further connected to secondary sidewall  100  using one or more spring locks  50 . If a single spring lock  50  is used to connect a primary sidewall  200  to a secondary sidewall  100  (as shown in the illustrations), spring lock  50  is preferably located toward an upper portion of primary sidewall  200  and secondary sidewall  100 . Mounting portion  60  of each spring lock  50  is affixed to primary sidewall  200 . In the illustrated embodiment, mounting portion  60  comprises wedge-shaped portion  62  to be inserted in recess  202  defined in primary sidewall  200 . To facilitate the retention of mounting portion  60  by recess  202 , nubs  64  extending outward from wedge-shaped portion  62  to contact the upper and lower surfaces defining recess  202  may be provided. Nubs  64  may be chamfered to ease the insertion of mounting portion  60  into recess  202 . To further enhance retention while easing assembly, wedge-shaped portion  62  may further define slot  66  to permit easier compression of mounting portion  60  as it is inserted into recess  202  provided that the material used for spring lock  50  is sufficiently resilient to maintain a compressive force against the upper and lower surfaces defining recess  202  through nubs  64 . Retention may also be enhanced by defining depressions  204  in the upper and lower surfaces defining recess  202  for receiving nubs  64  when mounting portion  60  is inserted in recess  202  (best seen in  FIG. 6 ). The foregoing and illustrated embodiments of mounting portion  60  are exemplary in nature. Affixation of spring lock  50  to primary sidewall  200  and the configuration of mounting portion  60  can, however, occur in many ways that would be known to those of skill in the art. For example, in an alternative embodiment, mounting portion  60  could be a flat portion that is screwed to primary sidewall  200 . 
         [0025]    Connecting portion  70  of spring lock  50  extends from mounting portion  60  along the outer surface of primary sidewall  200  to the edge portion of primary sidewall  200  adjacent to secondary sidewall  100 . Alternatively, primary sidewall  200  may define recessed area  204  to receive connecting portion  70  of spring lock  50  to keep spring lock  50  in alignment and to avoid having the outer surface of spring lock  50  extend proud of the outer surface of primary sidewall  200 . 
         [0026]    Binder portion  80  of spring lock  50  extends beyond connecting portion  70  of spring lock  50  and turns to be received into mating recess  102  defined in secondary sidewall  100  in part by surface  104  of rib  106 . Binder portion  80  is configured such that clamping surface  82  of the clamping section  81  applies a compressive force against inner surface  104  of mating recess  102  that is defined by rib  106 , mating recess  102  being adjacent to primary sidewall  200 . (This arrangement is best seen in  FIG. 5 .) In the illustrated embodiment, binder portion  80  is configured such that the gap between the edge portion of primary sidewall  200  and clamping surface  82  is less than the thickness of rib  106 . The compressive force may be enhanced by providing binder portion  80  of spring lock  50  with curved section  84  intermediate connecting portion  70  and clamping surface  82 . To facilitate rotation of secondary sidewall  100  to its vertical position, binder portion  80  may further comprise upturned lip portion  86 . 
         [0027]    The foregoing is merely one illustrative embodiment. One of skill in the art would be familiar with any number of configurations that would make the invention operative. The key design considerations, especially in selecting the material for spring lock  50 , are twofold. First, to avoid increasing the moment applied to primary sidewall  200  in the event of a force applied outward against secondary sidewall  100 , the compressive force generated by spring lock  50  against inner surface  104  of rib  106  of secondary sidewall  100  should not prevent inner surface  104  from sliding relative to spring lock  50  in the direction of such a force. Second, the compressive force of spring lock  50  against inner surface  104  should be sufficient to allow primary sidewalls  200  and the secondary sidewall  100  interconnecting primary sidewalls  200  to resist an outward force applied to an upper portion of one of primary sidewalls  200  that is greater than or equivalent to the outward force that would be applied if a second fully loaded container  1  (the weight of the load can be as much as 2000 pounds) were stacked on top of a first fully loaded container and the stacked containers allowed to slide down a standard inclined impact tester with the stacked containers being impacted at the bottom of first container, bringing the first container to an abrupt halt. 
         [0028]    Subject to the foregoing performance considerations, spring lock  50  can be formed from any suitable semi-rigid material that provides sufficient spring force to enable spring lock  50  to exert the requisite amount of compressive force for the particular container size and container loading capacity. Suitable materials include metals, fiberglass, carbon fiber, plastics, and other materials that meet the above requirements. 
         [0029]    The foregoing described embodiments are exemplary in nature and are not intended to limit the scope of the invention.