Abstract:
The present invention relates to a method and apparatus for providing a flexible ladder for traversing a structure that addresses problems common with conventional rope ladders.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to rope ladders. 
     2. Description of Related Art 
     Ladders that have flexible stiles—colloquially “rope ladders” or in nautical usage “pilot ladders”—are better suited to certain applications than are ladders that have rigid stiles. 
     Rope ladders are particularly well adapted for: (a) compact storage between uses; (b) suspension, including from great height, and (c) conformance around surfaces. Thus, for example, rope ladders may be well suited for escaping from buildings, climbing into rescue helicopters, and embarking on or disembarking from large ships. 
     Conventional rope ladders do however present challenges; perhaps most significantly, they can be very precarious. When ascending or descending one, a user typically grasps the stiles on either side of the rungs. Problematically, although a line of force runs vertically through each stile above the point grasped, the line of force below the point grasped is redirected by the user&#39;s lower body as his legs drive the supporting rung forward. This effect can leave the user in an inverse position, with his back to the ground. 
     Furthermore, if one of the user&#39;s hands loses its grip on a stile, both the user and the conventional rope ladder are likely to twist away from each other, further raising the risk that the user will fall. 
     Additionally, when using a conventional rope ladder, it is possible for a user&#39;s hands to become pinched between the rungs and a hard surface adjacent the ladder, for example a ship or a building. Alternatively, where the adjacent surface is soft, for example the gunwale of an inflatable rubber watercraft, a conventional rope ladder may become enveloped and thereby inaccessible. 
     Finally, a conventional rope ladder is challenging to mount for descent, for example from a high-rise building roof or window or from a buffeted vessel such as a ship or helicopter. A user has to swing his weight backwards out over the top of the ladder and then reach down with his legs to feel for the closest rung, precariously shifting more weight outside until—hopefully—his foot securely finds a rung. 
     Accordingly, what is needed is a rope ladder that addresses these challenges. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to this need. 
     According to one aspect of the present invention, there is provided a ladder having flexible first, second and third stiles and first, second and third crosspieces, respectively extending between the first and second stiles, the first and third stiles, and the second and third stiles. The three stiles are all substantially longitudinally parallel, but not all coplanar. At least one of the crosspieces resists extension and/or compression. 
     One end of the first crosspiece and one end of the second crosspiece might be positioned coplanar. In fact, the ends of the first, second and third crosspieces might be positioned coplanar. So positioned, the first, second and third crosspieces could form at least part of a frame. 
     In such a ladder having a plurality of such frames extending between the stiles and distributed along the length of the stiles, inclucing a proximate frame relatively proximate the top end of the stiles and a distal frame relatively distant from the top end of the stiles, the distal frame might have a perimeter greater than or equal to the perimeter of the proximate frame, such that the frames in effect taper larger from the top to the bottom of the ladder. 
     The ladder might further have a floor connected to the frame and covering at least a portion of the region bounded by the frame. This floor might be flexible pocket or a rigid platform for example, in which latter case the frame and the floor might be integral. 
     The frame might also include a coupler at its perimeter, adapted to engage a surface adjacent the ladder. This coupler might be a magnet for example. 
     The ladder might be configured such that a least one of: a) the rungs; b) the reinforcement; c) the frame; and d) the floor is flexible. 
     The ladder might be configured such that a least one of: a) the rungs; b) the reinforcement; c) the frame; and d) the floor is rigid. 
     According to another aspect of the present invention, there is provided a method of climbing such a ladder apparatus, comprising grasping the first stile, placing a foot on the first crosspiece and placing a foot on the second crosspiece. 
     According to yet another aspect of the present invention, there is provided a method of creating a ladder, comprising: arranging flexible first, second and third stiles substantially longitudinally parallel but not all coplanar; extending a first crosspiece between the first and second stiles; extending a second crosspiece between the first and third stiles; and extending a third crosspiece extending between the second and third stiles. 
     In this method, extending the second crosspiece might include extending the second crosspiece coplanar with the first crosspiece and extending the third crosspiece might extending the third crosspiece coplanar with the first and second crosspieces. The method might further include forming the first, second and third crosspieces into a frame and might include forming a floor from the frame. 
     Further aspects and advantages of the present invention will become apparent upon considering: the following drawings, description, and claims. 
     DESCRIPTION OF THE INVENTION 
     The invention will be more fully illustrated by the following detailed description of non-limiting specific embodiments in conjunction with the accompanying drawing figures. In the figures, similar elements and/or features may have the same reference label. Further, various elements of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar elements. If only the first reference label is identified in a particular passage of the detailed description, then that passage describes any one of the similar elements having the same first reference label irrespective of the second reference label. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric top-front-right view of a first embodiment of a ladder according to one aspect of the present invention; 
         FIG. 2  is an isometric top-rear-left view of the ladder of  FIG. 1 ; 
         FIG. 3  is an isometric top-front-right view of a second embodiment of a ladder according to another aspect of the present invention; 
         FIG. 4  is an isometric top-front-right view of a third embodiment of a ladder according to another aspect of the present invention; 
         FIG. 5  is an isometric top-front-right view of a fourth embodiment of a ladder according to another aspect of the present invention; 
         FIG. 6  is an isometric top-front-right view of a fifth embodiment of a ladder according to another aspect of the present invention; 
         FIG. 7  is an isometric top-front-right view of a sixth embodiment of a ladder according to another aspect of the present invention; 
         FIG. 8  is an isometric top-front-right view of a seventh embodiment of a ladder according to another aspect of the present invention; 
         FIG. 9  is an top elevational view of an eighth embodiment of a ladder according to another aspect of the present invention; and 
         FIG. 10  is an isometric top-front-right view of a ninth embodiment of a ladder according to another aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     (a) Structure of Specific Embodiments 
     The structure of the invention will now be illustrated by explanation of specific, non-limiting, exemplary embodiments shown in the drawing figures and described in greater detail herein. 
     (i) First Embodiment 
       FIGS. 1 and 2  show a rope ladder according to a first embodiment of the present invention, generally illustrated at  20 . The ladder  20  has more than two stiles  22 , and in this particular embodiment has a first stile  22   a , a second stile  22   b , and a third stile  22   c . The stiles  22  are strong and flexible and can be formed from cable, chain, natural or synthetic rope, plastic, rubber or the like. 
     The ladder  20  further includes crosspieces  24  that extend between two or more of the stiles  22 . A crosspiece  24  may function as a rung  24   a  adapted to support a person and/or a payload, a reinforcement  24   b  adapted to reinforce a relative position between adjacent stiles  22 , or both. The rungs  24   a  and reinforcements  24   b  may thus be similar or identical crosspieces  24  or else may differ according to the requirements of their different functions. For example, reinforcements  24   b  may offer resistance in compression, tension or both. In this regard, the crosspieces  24  may be fashioned from rigid materials including wood, metal, rubber, plastic and composites or flexible materials including chain, cable and rope as necessary to support a person and/or payload, to reinforce a relative position between stiles  22 , or both. Rungs  24   a  must be constructed sufficiently to support a load against gravity. 
     The crosspieces  24  might be connected to the stiles  22  in any suitable conventional way, whether removably, semi-permanently, or permanently. For example, a stile  22  might be passed through a hole in a crosspiece  24  and then tied into a knot larger than the hole below—and perhaps above—the crosspiece  24 . Instead of a hole, the crosspiece  24  might include a notch that positively bites into the stile  22  and retains the stile  22  within. The stile  22  might be connected to the crosspiece  24  with hardware fasteners or adhesives. The stile  22  might be fused to or otherwise integrated with the crosspiece; for example, a rope or wire crosspiece  24  might be braided into a rope or wire stile  22 . 
     Crosspieces  24  might be of various shapes. They might be elongate. They might be polygonal or polyhedral for example. Portions of a crosspiece  24  might extend radially outside a perimeter defined by the stiles  22 . 
     In the subject embodiment, all of the crosspieces  24  function as both rungs  24   a  and reinforcements  24   b , and in fact extend between all three of the first stile  22   a , the second stile  22   b  and the third stile  22   c , to retain the stiles  22  in relative position and to provide a broad platform  24   c  there between. 
     The ladder  20  further includes couplers  26  to couple the ladder  20  to a structure S to be traversed (not shown), for example a ship, or the ground G (not shown). Depending on the nature of the coupling desired—fixed, flexible, slideable, rotatable, permanent, temporary, safety, primary, secondary, redundant, etc.—the particulars of the coupler  26  will vary. A coupler might, for example, include a shackle, lug, eye, fastener, magnet, tie, clasp, grapple, adhesive, bushing, bearing, or the like. 
     The couplers may be stile-couplers  26   a  or crosspiece-couplers  26   b . A stile-coupler 26   a  is adapted to couple an end or an intermediate section of a stile  22  to the structure S or the ground G. A crosspiece-coupler  26   b  is adapted to couple a crosspiece  24  to the structure S. 
     (ii) Second Embodiment 
       FIG. 3  shows a ladder  20  according to a second embodiment of the present invention, wherein rungs  24   a  extending between the first stile  22   a  and the second stile  22   b  are not coplanar with rungs  24   a  extending between the first stile  22   a  and the third stile  22   c , and neither are coplanar with reinforcements  24   b  extending between the second stile  22   b  and the third stile  22   c.    
     (iii) Third Embodiment 
       FIG. 4  shows a ladder  20  according to a third embodiment of the present invention, wherein rungs  24   a  extending between the first stile  22   a  and the second stile  22   b  are coplanar with rungs  24   a  extending between the first stile  22   a  and the third stile  22   c , but neither are coplanar with reinforcements  24   b  extending between the second stile  22   b  and the third stile  22   c.    
     (iv) Fourth Embodiment 
       FIG. 5  shows a ladder  20  according to a fourth embodiment of the present invention, wherein rungs  24   a  extending between the first stile  22   a  and the second stile  22   b  are coplanar with rungs  24   a  extending between the first stile  22   a  and the third stile  22   c  and coplanar with reinforcements  24   b  extending between the second stile  22   b  and the third stile  22   c . In this embodiment, the coplanar rungs  24   a  and reinforcements  24   b  may cooperate or otherwise be connected together or formed integrally to create a frame  24   d  to better retain crosspieces  24  and stiles  22  in a desired relative configuration. 
     (v) Fifth Embodiment 
       FIG. 6  shows a ladder  20  according to a fifth embodiment of the present invention, wherein a frame  24   d  extending between the three stiles  22  supports a flexible pocket  28 , for example a mesh pocket  28 , adapted to support a person and/or a payload. Those skilled in the art will note that a user might traverse the ladder  20  through the center of the frame  24   d    
     (vi) Sixth Embodiment 
       FIG. 7  shows a ladder  20  according to a sixth embodiment of the present invention, wherein the rungs  24   a  and reinforcements  24   b  are fashioned from a flexible material, for example rope, wire, chain, or rubber or plastic extrusion, either solid or tubing. 
     (vii) Seventh Embodiment 
       FIG. 8  shows a ladder  20  according to a seventh embodiment of the present invention, wherein the crosspieces  24  are configured differently at different positions along the length of the ladder  20 , for example being selected as an assortment of some crosspieces  24  of the previous six embodiments. Such variation might better support specific tasks correlated to elevation, either absolute over the ground G or relative to the structure S, or correlated to a position along the ladder  20 . 
     (viii) Eighth Embodiment 
       FIG. 9  shows a ladder  20  according to an eighth embodiment of the present invention, wherein the span between the stiles  22  tapers larger from top to bottom, so that the crosspieces  24  increase in length and the platforms  24   c  increase in area. Alternatively, successively lower crosspieces  24  might increase in length and platforms  24   c  might increase in area independently of the span between stiles  22 . 
     (ix) Ninth Embodiment 
       FIG. 10  shows a ladder  20  according to a ninth embodiment of the present invention that further includes a fourth stile  22   d , wherein crosspieces  24  extend between the four stiles  22 , creating platforms  24   c , portions of which function as rungs  24   a  and portions of which function as reinforcements  24   b.    
     (b) Operation of Specific Embodiments 
     With reference now to  FIGS. 1-10 , the operation of these specific embodiments of the invention will now be described. 
     The ladder  20  may be created by arranging more than two stiles  22  substantially in parallel but not all of them coplanar, having regard to their respective longitudinal axes. Adjacent stiles  22  may then be connected with crosspieces  24 , for example in any of the forms or arrangements described above, at least some of the crosspieces  24  functioning as reinforcements  24   b  to urge at least some of the stiles  22  into a particular relative arrangement. 
     The crosspieces  24  may be so connected either removably, semi-permanently, or permanently. Depending on the nature of this connection, the ladder  20  may be furled as a fully-assembled whole for convenient storage and transportation to a job site or else the stiles  22  can be furled and the crosspieces bundled or stacked, for convenient storage and transportation but subsequent assembly at a job site. 
     In use, the ladder  20  may be connected with couplers  26  to a structure S to be traversed. In this regard, the stiles  22  would typically be so coupled, but at least some of the crosspieces  24  might also be coupled to further resist movement. For further support, some of the stiles  22  might be coupled to the ground G. 
     A user would generally grasp one stile  22  and step on the crosspieces  24  extending from that stile  22 , using such crosspieces  24  as rungs  24   a . Where the crosspieces form a platform  24   c  or support a pocket  28 , the user might rest a payload either to pause in his traverse or to provide a storage or work surface. 
     Once the ladder  20  is no longer needed, the couplers  26  can be disengaged from the structure S and the ground G, and the ladder  20  furled, after perhaps being disassembled, for convenient storage until its next use 
     (c) Description Summary 
     Thus, it will be seen from the foregoing embodiments and examples that there has been described a way to provide a flexible ladder  20  for traversing a structure S that addresses problems common with pilot ladders. 
     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims. In particular, all quantities described have been determined empirically and those skilled in the art might well expect a wide range of values surrounding those described to provide similarly beneficial results. 
     It will be understood by those skilled in the art that various changes, modifications and substitutions can be made to the foregoing embodiments without departing from the principle and scope of the invention expressed in the claims made herein. For example, although in many of the embodiments the crosspieces  24  have been arranged in a generally triangular configuration, other configurations could be equally well or better adapted for various applications. 
     While the invention has been described as having particular application for shipping and evacuation, those skilled in the art will recognize it has wider application. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 TABLE OF REFERENCES 
               
             
          
           
               
                 Element(s) 
                 Reference 
                 Total count 
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                 ladder 
                 20 
                 21 
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                 stiles 
                 22 
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                 stile 
                 22 
                 34 
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                 first stile 
                  22a 
                 8 
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                 second stile 
                  22b 
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                 third stile 
                  22c 
                 8 
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                 fourth stile 
                  22d 
                 1 
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                 crosspieces 
                 24 
                 19 
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                 crosspiece 
                 24 
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                 rungs 
                  24a 
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                 rung 
                  24a 
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                 reinforcements 
                  24b 
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                 reinforcement 
                  24b 
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                 platform 
                  24c 
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                 platforms 
                  24c 
                 3 
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                 frame 
                  24d 
                 3 
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                 couplers 
                 26 
                 5 
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                 coupler 
                 26 
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                 stile-couplers 
                  26a 
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                 stile-coupler 
                  26a 
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                 crosspiece-coupler 
                  26b 
                 1 
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                 crosspiece-couplers 
                  26b 
                 1 
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                 pocket 
                 28 
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                 ground 
                 G 
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                 structure 
                 S 
                 7 
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