Patent Publication Number: US-7895693-B2

Title: Lightweight modular footbridge and ladder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims benefit to U.S. Provisional Patent Application No. 60/920,436, filed Mar. 28, 2007, the content of which is hereby expressly incorporated by reference herein in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY-FUNDED RESEARCH 
     Not applicable. 
     NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not applicable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of a modular footbridge constructed in accordance with the present invention, shown in a ladder configuration. 
         FIG. 2  is a perspective view of a base segment of the footbridge of  FIG. 1 . 
         FIG. 3  is an enlarged perspective view of segments of the footbridge of  FIG. 1 . 
         FIG. 4  is a perspective view of one embodiment of a connection assembly for joining segments to form a modular footbridge or ladder and for adjusting the configuration thereof. 
         FIG. 4A  is a perspective view of another embodiment of a connection assembly constructed in accordance with the present invention. 
         FIG. 5  is a top plan view of one embodiment of a base plate for use with the modular footbridge of  FIG. 1 . 
         FIG. 6  is a perspective view of the modular footbridge of  FIG. 1 , shown in a footbridge configuration. 
         FIG. 6A  is a perspective view of a handrail connector assembly with a handrail support inserted therein. 
         FIG. 7  is a side elevational view of the modular footbridge of  FIG. 6 . 
         FIG. 8A  is a side elevational view of the modular footbridge of  FIG. 1  in a collapsed configuration for storage and transportation. 
         FIG. 8B  is an end elevational view of the modular footbridge of  FIG. 1  in a collapsed configuration. 
         FIG. 9  is a perspective view of a modular ladder and footbridge, in a collapsed configuration, positioned on a roof rack of a vehicle for transport. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present invention generally relates to means for crossing and/or overcoming obstacles such as waterways, ditches, canals, and walls. More specifically, but not by way of limitation, the present invention relates to a lightweight, modular footbridge that may also function as a ladder for climbing. 
     Numerous situations arise in which it is desirable to have an effective means for permitting individuals to traverse waterways such as streams, drainage channels, and the like. Similarly, numerous situations arise in which it is desirable to have an effective means for permitting individuals to ascend a wall or other elevated obstacle, such as to enter a second or third-story window of a building. Such needs arise in combat and urban-warfare situations where soldiers are often limited in the amount of equipment they can carry. Similar needs also arise in the case of emergency responders such as firemen, police, SWAT teams, and the like which are required to respond quickly to an emergency with only limited amounts of portable equipment. The inherent unpredictability of these situations further requires that such a means for overcoming obstacles be easily adaptable to various obstacles and also easily portable and deployable. 
     To this end, the present invention is directed to a modular footbridge that may be disassembled and/or collapsed for easy portability, and may be quickly and easily reassembled in a variety of configurations for adaptability and deployability for traversing a variety of obstacles such as streams and ditches. The modular footbridge of the present invention may further be utilized as a ladder for overcoming elevated obstacles such as walls and the like. In this way, the modular footbridge preferably has at least two configurations: a bridge configuration and a ladder configuration. In order to ensure its portability, the modular footbridge is preferably constructed of a durable and relatively lightweight material such as aluminum. In other embodiments, the footbridge may be constructed of any suitable polymer, composite, fiberglass, titanium, alloy, carbon fiber (including carbon nanotube materials), any other suitably durable material, or any combinations thereof. Portability may be of less importance in certain embodiments which may effectively utilize heavier materials such as steel and the like. 
     Referring now to the drawings, and in particular  FIG. 1 , shown therein is a perspective view of one preferred embodiment of the modular footbridge  10  constructed in accordance with the present invention and shown in a ladder configuration. The footbridge  10  is also preferably adapted to be selectively deployed in a footbridge configuration, as shown in  FIGS. 6 and 7 , and described in more detail below. The footbridge  10  preferably comprises two end segments  14  and two medial segments  18 . Other embodiments of the footbridge  10  may comprise any number of medial segments  18  and up to two end segments  14 . For example, to traverse a short wall, a footbridge  10  may be assembled with two end segments  14  and no medial segments  18 . Each segment  14  or  18  preferably has a ladder-like construction comprising a pair of longitudinal members  22  and a plurality of lateral members  26  extending between the longitudinal members  22 . In other embodiments, the segments  14  or  18  may comprise only one longitudinal member  22  with lateral members  26  extending from one or both sides of the longitudinal member  22 . Similarly, the segments  14  or  18  may comprise more than two longitudinal members  22  with lateral members  26  extending therebetween or therefrom. Each segment  14  or  18  preferably further includes an upper side  30  and a lower side  34 , which may also be referred to as the footbridge side  30  and ladder side  34 . 
     The footbridge side  30  is provided with a walking surface  38  that generally faces up when the footbridge  10  is in use in its bridge configuration. The walking surface  38  is preferably constructed from expanded metal, that has been cut and/or stretched to provide a number of substantially-equivalent protrusions so as to make a non-slip surface. In other embodiments, the walking surface  38  may be constructed with a rigid or flexible solid sheet of material, a plurality of slats or wires, or any combination of materials and structures which provide a surface or equivalent that is capable of supporting an individual or small vehicle while traversing the footbridge  10  in its bridge configuration. For example, the walking surface  38  may be constructed or formed from strap, fabric, netting, or the like which may be fastened and/or stretched to or about a portion of the footbridge  10 . In other embodiments of the present invention, the footbridge  10  may comprise any combination of end segments  14  and medial segments  18  that permit the footbridge  10  to function as a bridge, a ladder, a scaffold, or any other secondary purposes to which the invention lends itself. 
     Each of the segments  14  or  18  preferably attaches to, connects to, or otherwise engages the immediately-adjacent segment  14  or  18  via a pair of connection assemblies  42 . It should be understood that embodiments comprising less or more longitudinal members  22  will likely utilize a correspondingly smaller or greater number of connection assemblies  42 . Each longitudinal member  22  of a segment  14  or  18  will preferably be attached to the corresponding longitudinal member  22  of the adjacent segment  14  or  18  via a single connection assembly  42 . For example, adjacent segments having only a single longitudinal member  22  will preferably attach to one another via only a single connection assembly  42 . In addition to connecting adjacent segments  14  or  18 , the connection assemblies  42  are preferably used to adjust the configuration of the footbridge  10 . The footbridge  10  in  FIG. 1  is depicted in the ladder configuration. That is, all segments  14  or  18  are arranged in a substantially co-planar manner such that the length  46  of the footbridge  10  is maximized for the given number of segments  14  or  18 . 
     The end segments  14  preferably have a connection assembly  42  attached to a medial end  50  and a terminal connector  54  attached to a distal end  58 . The terminal connector  54  shown is merely exemplary and other embodiments of the terminal connector  54  may be constructed with any suitable shape or connection means for attaching objects or devices to the end of the footbridge  10 . For example, the terminal connector  54  may be adapted to bolt directly to a vehicle (not shown) or to fit over a standard ball hitch, such as on a vehicle. In the embodiment shown, the footbridge  10  is provided with a base plate  62  that pivotally attaches to the distal end  58  via the terminal connector  54 . 
     Referring now to  FIGS. 2 and 3 , enlarged perspective views of an end segment  14  and of the lateral supports  26  are depicted. The lateral supports  26  extend between the longitudinal supports  22 . The lateral supports  26  preferably provide or function as “steps” or “rungs” to permit an individual to climb the footbridge  10  when in a ladder configuration. To this end, the lateral supports  26  are incrementally spaced at preferably equal distances  66 . The distance  66  can be any suitable length that permits an individual to climb effectively and adequately supports the longitudinal supports  22  and the walking surface  38 . For example, the distance  66  may be 8″, 12″, or 18″. In other embodiments, the distance  66  may vary between lateral supports  26 . As best shown in the exemplary embodiment of  FIG. 3 , the lateral supports  26  are preferably deeper than the longitudinal supports  22  so as to provide a larger area for climbing when the footbridge  10  is in a ladder configuration. The lateral supports  26  also preferably include openings  70  ( FIG. 3 ) sized to permit a human hand to grasp the lateral support  26  so as to facilitate climbing the footbridge  10  in its ladder configuration or carrying the footbridge  10 . In other embodiments, the lateral supports may be constructed so as to be flush with the longitudinal supports  22 , for example, to reduce the weight of the footbridge  10 . Similarly, the openings  70  may be modified or omitted entirely in other embodiments, as desired for various applications. For example, a lip (not shown) could be provided on one or more lateral supports  26  or one or more longitudinal supports  22  to facilitate grasping a segment  14  or  18 . 
     In the preferred embodiment, the connection assemblies  42  are provided with one handrail attachment member  74  and a pair of anchor members  78 . The terminal connector  54  is also preferably provided with at least one anchor member  78 . Alternatively, or in addition, anchor members  74  may be provided nearly anywhere on the footbridge that may be advantageous for specific applications. The handrail attachment member  74  provides a connection point for selective attachment of a handrail support, which will be described in more detail below. The anchor members  78  provide connection points for numerous possible purposes, for example: anchoring the footbridge  10  to a building in a ladder configuration, anchoring the footbridge  10  to a vehicle for transport, or anchoring a safety line to the footbridge  10 . The anchor members  78  preferably have a hole  82  formed therethrough such that a rope or clip can be fastened to the anchor member  78 . In the preferred embodiment, the anchor members  78  are fastened to the footbridge  10  with one or more bolts or rivets to facilitate easily assembly and replacement. The anchor members  78  may also be attached to the footbridge  10  with any other suitable fastening means such as welds, screws, adhesives, clips, or the like. In addition, the footbridge  10  may be provided with additional clips or mounts (not shown) as desired to mount or attach equipment, supplies, accessories, or the like. For example, the footbridge  10  may be provided with clips or mounts for affixing light sources for night crossings and the like. 
     Referring now to  FIG. 4 , one preferred embodiment of the connection assembly  42  is depicted in greater detail. Each connection assembly  42  comprises a pair of connection members  100 , each engaging a corresponding longitudinal support  22  of an adjacent segment  14  or  18 . Each connection member  100  preferably includes an attachment portion  104  and an adjustment portion  108 . The attachment portion  104  is shown attached to the corresponding longitudinal support  22  with a pair of standard bolts  112 . Such attachment methods are well known in the art and the bolts  112  may be replaced with any suitable attachment means, including but not limited to: welds, adhesives, screws, interlocking or engaging grooves or protrusions, magnets, tabs, snaps, or the like, or any combination thereof. In the preferred embodiment, the adjustment portion  108  comprises a pivot hole  116 , a ladder configuration hole  120 , and a bridge configuration hole  124 . As shown, the pivot hole  116  is preferably offset from the axis of the longitudinal member  22  such that connected segments  14  or  18  may be pivoted about the axis of the pivot hole  116  in such a way to as be proximal to one another, as shown in  FIGS. 8A and 8B  and described in more detail below. 
     As shown, when the footbridge  10  is in either of the ladder and bridge configurations, the adjustment portions  108  are preferably secured relative to one another via two axial connectors  128  such as, for example, pins  128 : one pin  128  extending through the pivot hole  116  and one pin  128  extending through one of the configuration holes  120  or  124 . As shown in  FIG. 3 , when one pin  128  is inserted through the pivot hole  120  and one pin is inserted through the ladder hole  120 , the adjacent segments  14  or  18  are substantially aligned. As shown in  FIG. 4 , when one pin  128  is inserted through the pivot hole  120  and one pin  128  is inserted through the bridge hole  124 , the adjacent segments  14  or  18  are in a bridge position in which the segments are still expanded relative to one another, but are disposed at an angle  132  relative to one another. The angle  132  in the bridge position is preferably between about 90 degrees and about 175 degrees, and in some embodiments, the connection assembly  42  may be adapted such that the angle  132  is adjustable. When in the bridge position, the angle  132  is always less than 170 degrees, and more preferably less than 170 degrees such that the adjacent segments  14  or  18  are angularly disposed relative to one another and are not substantially aligned or coplanar, as they are in the ladder configuration. In this bridge position, the segments  14  or  18  in held in this expanded angularly-disposed relationship with one another in which the segments  14  or  18  are not coplanar, but are still expanded relative to one another. 
     In other embodiments, the connection assembly  42  may be constructed without the ladder hole  120 , such that connection assembly  42  has only a pivot hole  116  and a bridge hole  124 . In such embodiments, the angle between the segments  14  or  18  when in the bridge position may be 180 degrees such that the segments  14  or  18  are substantially coplanar and aligned. In such embodiments, there would only be two positions or configurations when segments  14  or  18  are connected by a connection assembly  42 : a collapsed position and a bridge position. However, when the bridge position results in the segments  14  or  18  being substantially coplanar or aligned, the bridge position may be suitable for use a ladder as well. 
     Referring now to  FIG. 4A , another embodiment of a connection assembly  42   a  constructed in accordance with the present invention is shown. The connection assembly  42   a  is a single-piece member having attachment portions  100  adapted to be inserted into the corresponding longitudinal supports  22  of the adjacent segments  14  or  18 . As with the connection assembly  42  above, the connection assembly  42   a  may be constructed in an aligned ladder configuration, an angled footbridge configuration, or any other configuration which may enable practical implementation of the present invention. 
     Referring now to  FIG. 5 , a top plan view of one embodiment of a base plate  62  is shown. The base plate  62  is preferably provided with a generally-rectangular shape having a width  200  and a length  204 . In the preferred embodiment, the base plate  62  is provided with a pair of footbridge connectors  208  corresponding to the terminal connectors  54  of the end segments  14  ( FIG. 2 ). The footbridge connectors  208  preferably protrude upwards from the base plate  62  to provide a pivoted connection to permit the base plate  62  to be easily adjusted to adapt, for example, to uneven terrain. Additionally, the base plate  62  is preferably provided with a plurality of holes  212  near the peripheral edge  216 . The holes  212  provide a means for stabilizing the base plate  62 , such as by staking it into the ground, bolting it to the bed of a truck, or by any other suitable methods. The base plate  62  may also be constructed in any other shape that provides a suitable base for the footbridge  10  in either of a ladder configuration or a footbridge configuration. In other embodiments, the base plate  62  may also be omitted entirely. 
     Referring now to  FIGS. 6 and 6A , a perspective view of the footbridge  10  is shown in a footbridge configuration, as well as an enlarged view of a handrail attachment member  74 . When deployed in the footbridge configuration, the footbridge  10  preferably includes a handrail  300 . The handrail  300  generally comprises a plurality of handrail supports  304  and a handrail cord  308 . The handrail supports  304  are connected to the footbridge  10  at the handrail attachment members  74 . Each handrail support  304  preferably includes a base portion  316 , an extension portion  320 , and a guide portion  324 . The handrail cord  308  may be constructed of any suitably durable cord, such as a cable, rope, wire, chain, or the like. 
     The base portion  316  preferably inserts into the handrail attachment member  74 . As best shown in  FIG. 6A , the handrail connection member  74  includes a retention slot  328 . In the preferred embodiment, the base portion  316  of the handrail support  304  is provided with a corresponding retention pin  332 . In this way, assembly is accomplished by inserting the base portion  316  into the handrail attachment member  74  with the retention pin  332  aligned with the retention slot  328 . As the base portion  316  is inserted, the handrail support  304  is rotated to seat the retention pin  332  and thereby substantially secure the handrail support  304  in the handrail attachment member  74 . The extension portion  320  extends from the base portion  316  to the guide portion  324  to elevate the handrail to a functional height. The guide portion  324  is a preferably hollow member through which the handrail cord  308  is threaded to create the functional handrail  300  as shown. In other embodiments, the guide portion  324  may be provided with a slot through which the handrail cord  308  may be passed without having to thread it through the guide member  324 . 
     To assemble handrail  300 , the handrail supports  304  are connected to the footbridge  10 , as described above, and the handrail cord  308  is sequentially threaded through each of the guide portions  324 . Each end of the handrail cord  308  is then fastened to a corresponding anchor member  78  at each end of the footbridge  10 . The handrail cord  308  is preferably tensioned prior to or concurrently with being fastened to the anchor members  78  such that a downward force is provided to the handrail supports  304  and the handrail  300  will be stable enough to provide support to individuals crossing the footbridge  10 . 
     When the preferred embodiment of the footbridge  10  is deployed in a footbridge configuration, it can be provided with one or more stiffener straps  328 . Two stiffener straps  328  are shown by way of example. The stiffener straps  328  are preferably selectively connected to the anchor points  78  at either end of the footbridge  10 , via a connection means such as snap-rings, carabiners, snap hooks, or the like. In other embodiments, the stiffener straps  328  may be tied to the anchor points  78  by hand as necessary. The stiffener straps  328  preferably extend from one end of the footbridge  10  to the next, preferably at an angle or across the width of the bridge  10  as well as the length. For example, a first stiffener strap would extend from the right side of the first end to the left side of the second end of the footbridge  10 , and a second stiffener strap  328  would extend from the left side of the first end to the right side of the second end of the footbridge  10 . In this way, the straps provide tension between the two ends of the footbridge  10 , as well as provide resistance to torsional loads that may be created by uneven terrain or uneven load distribution upon the footbridge  10 . The stiffener straps  328  may be constructed of any suitably-durable cord-like material, for example chain, strap, rope, cable, wire, or the like. In other embodiments, the stiffener straps  328  may extend from a segment  14  or  18  to the next sequential segment  14  or  18 ; from an end segment  14  to a medial segment  18 ; or in any other suitable configuration. 
     In some embodiments, it is desirable to construct the connection assemblies  42  such that the connection assemblies alone are not sufficiently strong to alone support the footbridge  10  or a weight on the footbridge  10  when in the bridge configuration or position. For example, this may be desirable to reduce the weight of the footbridge  10 . However, in such embodiments, the stiffener straps  328  preferably cooperate with the connection assemblies  42  and the segments  14  or  18  to provide sufficient strength to support both the footbridge  10  and a suitable weight or working load on the footbridge  10  to enable it to function in the bridge configuration or position. 
     Referring now to  FIG. 7 , a side elevational view of the footbridge  10  deployed across an obstacle is shown. The footbridge is shown deployed across a channel  400  having a first side  404 , a second side  408 , and a width  412 . As shown, the width  412  of the channel  400  is nearly as large as the span of the footbridge  10 . It will be appreciated by those skilled in the art that the footbridge  10  having four segments  14  or  18  as shown will be sufficient to cross a channel narrower than width  412 . However, the footbridge  10  may also be modified by adding additional medial segments  18  so as to increase the span of the footbridge  10 . It will also be appreciated by those skilled in the art that adding additional segments may decrease the load capacity of the footbridge  10 . Additionally, for channels  400  narrower than width  412 , it may be desirable to assemble the footbridge  10  with only one medial segment  18  or with no medial segments  18 , as needed. 
     As shown, when deployed in the footbridge configuration, the footbridge  10  preferably has a base plate  62  attached to each end segment  14  so as to stabilize both ends of the footbridge  10 . The base plates  62  can be positioned and staked to the ground with one or more stakes  416  to provide additional stability to the footbridge  10 . In one preferred method of deployment, the footbridge  10  is assembled on a first side  404  of the channel  400 . A first base plate  62   a  is then staked to the ground with one or more stakes  416 , and the footbridge is pivoted, relative to the staked base plate  62   a , into position across the channel  400 . An individual may then cross the footbridge  10  and stake the second base plate  62   b  with one or more stakes  416  to secure the footbridge  10  in position for additional individuals to cross the channel  400 . Once all individuals have crossed the channel  400 , the stakes  416  can be removed to free the first base plate  62   a  and the footbridge  10  can be pivoted, relative to the second base plate  62   b , across to the second side  408  of the channel  400 . The stakes  416  can then be removed to free the second base plate  62   b  and the footbridge  10  disassembled or collapsed to be transported with the individuals or stored for a later return. 
     Referring now to  FIGS. 8A and 8B , one half of the footbridge  10  of  FIG. 1  is shown in a collapsed position for transport or storage. As shown, the connection assembly  42  is designed such that a pin  128  can be left in the pivot hole  116  such that adjacent segments  14  or  18  may be folded flat against one another to facilitate transport or storage of the footbridge  10 . In the collapsed position, two segments  14  or  18  preferably remain connected by the connection assembly  42 , and more particularly by the axial connector  128  extending through the pivot hole  116  ( FIG. 4 ), but are pivoted relative to one another such that the segments  14  or  18  are proximal to one another, and more preferably such that the segments  14  or  18  are substantially parallel to one another. 
     Referring now to  FIG. 9 , shown therein is the footbridge  10 , in the collapsed configuration of  FIGS. 8A and 8B , positioned on the roof rack  500  of a vehicle  504 . As shown, the modular design of the preferred embodiment of the footbridge  10  is well-suited for easy storage and transportation. The roof rack  500  is exemplary and is not the only roof rack  500  that will conveniently carry the footbridge  10  in its collapsed configuration. For example, U.S. patent application Ser. Nos. 11/010,457, filed Dec. 13, 2005, and 11/511,161, filed Aug. 28, 2006; the entire content of both patent applications is hereby incorporated by reference disclose other exemplary roof racks  500  capable of carrying the footbridge  10 . With some embodiments of the footbridge  10 , it will be desirable to distribute the footbridge  10  with a roof rack  500  that is well-suited to its transportation. Some such roof racks  500  may even be specially-modified to carry a specific embodiment of a footbridge  10 . In other embodiments, a roof rack  500  may not be necessary to transport the footbridge. For example, the footbridge  10  could be placed in the bed of a truck or the like. Similarly, the vehicle  504  is shown as a Humvee, but numerous other vehicles can be used to transport the footbridge  10 . 
     Changes may be made in the construction and the operation of the various components, elements and assemblies described herein or in the steps or the sequence of steps of the methods described herein without departing from the spirit and scope of the invention.