Abstract:
A folding, self-erecting ladder for use in the marine environment comprises two rigid side rails with holes for holding rungs. Bungee cord is thread through the rungs and rails to tension the rails toward each other top hold the rungs in the rail holes. The ladder can be folded by pulling the rails apart, allowing the rungs to leave the rail holes, and moving the rails closer to each other, trapping the rungs therebetween, and binding the folded ladder to hold it in the folded position.

Description:
BACKGROUND OF THE INVENTION 
     People in small boats end up in the water for a variety of reasons. Rowers in inherently unstable crew shells often work out in unfavorable conditions of cold weather and rough water made worse by wind and should get out of the water as quickly as possible when the boat swamps or turns over. Any boat presents difficulties when a swimmer tries to lift him or herself over the gunnels (gunwales) and back into the boat or into a rescue boat. 
     A number of so-called folding ladders have been designed to aid in this difficulty but a majority of them are non-rigid rope ladders that are tossed over the side and all have the inherent problem of becoming unstable and difficult to climb because they tend to be forced under the bottom of the boat as the swimmer puts weight on the bottom rung. Such a folding ladder can be seen at:
     (http://www.mysticmarinediscounts.com/sea-dog-corp-folding-ladder-5825011-ladder-five-step-rope.html)   

     A similar ladder is shown in  FIG. 8  with rungs  100 , rails  200 , and rope  300  threaded through the rungs and rails. When held by the rope ends  400  designed to attach the ladder to a boat, gravity will drop the rails and rungs to straighten the rope, forming a ladder with parallel rails  500  and parallel rungs perpendicular to the rails. Rope ladders have no “stand-off” feature and most of the straight rigid ladders that hook over the side rail of the hull do not have any such feature. Without this “stand-off,” the swimmers fingers and toes on the rungs of most such ladders are therefore jammed up against the hull, making it difficult or less secure to get a safe grip while attempting to climb into the boat. 
     Similarly, there are many folding ladders on the market that have mechanical hinges that have to be opened as the ladder is deployed. See U.S. Pat. No. 6,145,621 to Nye. Not only are these mechanical parts potentially subject to jamming (making them difficult and time-consuming to open), but alternatively they may become loosened and unstable once they are opened and such movement could eventually compromise the safety and reliability of the ladder. 
     Likewise, almost all of the boat ladders on the market have to have some external means of attaching them to the boat—such as a bracket screwed permanently into the hull at a particular location into which the ladder is fitted during use, or to which the ladder itself is permanently attached in its folded position when not deployed for rescuing an overboard swimmer. This prohibits the ladder from being deployed at the position on the boat where it is needed. If the water is cold, the swimmer should get into the boat quickly to avoid hypothermia. Indeed, even the simple rope ladders have to be tied onto a rail or some other structure on the boat, which only adds additional time and uncertainty during an emergency rescue. 
     As for those rigid ladders which do have some sort of stand-off feature, the stand-off feature usually consists of some short legs extending horizontally from the side rails to hold the ladder away from the side of the hull. See U.S. Pat. No. 5,113,782 (McCarty), U.S. Pat. No. 2,924,291 (Tunstead), Des. 185,212 and U.S. Pat. No. 2,992,697 (Klages), and U.S. Pat. No. 3,512,608 (Huntley). These short legs sometimes fold out from the rails. This mechanical feature adds to the complexity of the device, potentially increases the time for deployment, and may in fact prove to be totally useless if it is at the bottom of the ladder and below the bottom of the hull on a shallow-draft boat like a jonboat (usually termed a “launch”) used by a crew coach to follow the shell during practice sessions, etc. These launches or chase boats are required to carry a safety equipment bag including life vests. If a quickly deployable ladder were available to fit in the safety equipment bag carried by chase boats, the rowers&#39; safety would be enhanced in a simple and effective way. 
     SUMMARY OF THE INVENTION 
     There is a need for a small, rigid-when-deployed, quickly deployable ladder capable of easy attachment to the gunnels of a watercraft in an emergency situation to allow a swimmer to lift him or herself out of the water into the craft as quickly as possible. Instant deployment is important for obvious safety reasons. U.S. Pat. No. 5,329,873 to Tiballi recognizes the need for quick deployment of a safety dive flag from a folded position. The flag is folded in a small, convenient bundle in FIG. 5 of Tiballi and is quickly erected using tube sections joined by elastic cord 30 of FIG. 4 in Tiballi. 
     The ladder of the invention has rigid side rails and will maintain its vertical (or even slightly inclined away from the boat) position against the boat hull as the swimmer climbs up the rungs, which provides a far more secure and safe operation than the instability of a swinging rope ladder. 
     The ladder of the invention has no mechanical hinges connecting the rungs to the rails. Rather, the rungs automatically insert into the rails when opened to form a secure and fool-proof connection that is not subject to movement during use. Bungee cord (shock cord) is threaded through the rails and rungs and held under tension when the ladder is folded. The assembly remains under tension when the folded ladder is released to allow the rungs to be positioned between the rails and nest in the rails to form a rigid ladder. 
     The ladder of the invention snaps open instantly from its folded storage state and can immediately be hung over the gunnels of a water craft when needed, and can be positioned at any position on the boat gunnels to be deployed closest to the swimmer in need of help. The hooks at the top of the rails of the inventive ladder are intended to be compatible with the gunnels of a standard jonboat, but will also work on a canoe. These hooks can easily be modified to present a more universal geometry to fit any boat rail or gunnel. A second set of different shaped hooks on the bottom end of the ladder rails can be provided so that the device could be deployed on boats with various shaped gunnels or transoms simply by turning it upside down and hanging it using whichever set of hooks best fit a particular gunnel. 
     The inventive ladder has a built in “stand-off”, projection, or protrusion to engage the hull on each rail that keeps it hanging at least vertically or slightly inclined away from the hull during deployment, making it far easier for a swimmer to climb up the rungs. The ladder of this invention is designed with a bulge at the top of the device just below the hooks that serves to hold the rails away from the side of the boat so that the swimmer&#39;s fingers and toes have room to securely grab onto the rungs without hitting the hull. Moreover, since this stand-off bulge is at the top of the ladder, it will properly function even on very shallow-draft hulls, unlike the stand-off legs that are at the bottom of many rigid ladders. Finally, that the design of the bulge is intended to press the rails against the hull when the swimmer&#39;s weight is on the ladder, which makes sure the hooks stay fully engaged on the gunnel and the ladder remains firmly in place as the swimmer ascends into the boat. 
     The inventive ladder is constructed to float if it is accidentally dropped overboard, which most likely is not true with the prior art rigid mechanical ladders, most of which are made of aluminum or stainless steel. The present design using plywood rails floats naturally. 
     These and other features and advantages will be evident from the drawings and detailed description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the inventive ladder in the erected state; 
         FIG. 2  is a side view of the erected ladder; 
         FIG. 3  is a vertical section through a rail hole showing the relationship of the hole, the rung and the elastic cord; 
         FIG. 4  is a plan view of the ladder in the folded state; 
         FIG. 5  is a side view of the ladder in the folded state; 
         FIG. 6  shows the ladder mounted on the side of a jonboat; 
         FIG. 7  shows the ladder mounted to the side of a canoe; the ladder having mounting means on each end, one end mounted to a canoe rail; 
         FIG. 8  shows a conventional collapsing ladder. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  show the folding ladder of the invention. Single piece rails  1  comprise a top end  50 , a bottom end  60 , a series of holes  2  into which rungs  3  fit snuggly to form the ladder. The rungs  3  and holes  2  are tapered to mate snuggly to form a rigid connection when tensioned together by bungee cord  4 . The bungee cord is held in tension by appropriate knots  5 . Any means can be employed to prevent the knot  5  from passing through hole  4 . The tension of the bungee is sufficient to bring the rungs and rails into alignment to mate the rungs  3  with the holes  2 , forming a rigid ladder when the ladder is released from its folded orientation, described below. 
       FIG. 3  shows the rungs  3  and hole  2 . The rung  3  in the figure has tapered ends  6  (only one end shown) pulled into tapered hole  7  of rail  1  by the tension of bungee cord  2  (in the direction of the arrow in  FIG. 3 ) but the holes and rungs preferably have straight walls. A straight walled rung end  3  will properly seat in a straight walled hole. The rung entry end of hole  2  will have a larger diameter than the bungee cord exit end of the hole. When the hole is straight walled, a shoulder between the larger and small diameters will stop the rung at an intermediate position in the hole to seat it securely, held by the tension of bungee cord  4 . 
     The ladder is assembled by threading a bungee cord  4  through one of the top or bottom-most rail holes  2  with a knot  5  on the end of the cord. Cord  4  is then passed through a rung  3  and through the opposite rail, passed up to the next hole on the same rail, through a rung and so on until the cord  4  exits the last unfilled hole  2 , following the dotted line with arrows of  FIG. 1 ). The cord  4  is tensioned and a second knot is tied to keep the cord from passing through the last hole. The tension is sufficient to hold the ladder in its “use” configuration but loose enough to allow folding of the ladder as described below. Sufficient cord if left beyond the knot  5  at the top of the ladder to hold the ladder in the folded orientation of  FIG. 4 . An additional knot or other enlargement  9  is placed on the end of cord  4  to maintain the cord in slot  8  when the ladder is folded. 
       FIGS. 4 and 5  show the ladder of the invention in its folded orientation. The ladder is folded by forcing the rails  1  slightly apart to allow the tapered rungs ends  6  to move out of tapered holes  7  and forcing one of the rails  1  downwardly with respect to the other rail. This allows the rails  1  to trap the rungs  3  in a position parallel to the rails  1  as the rails are moved closer to each other with the rungs lying therebetween as shown in  FIGS. 4 and 5 . Once positioned as in figured  4  and  5 , the bungee cord enlargement  9  is manually pulled so cord end  4  is drawn into and held by slot  8  thereby holding the rails closed on the rungs maintaining the ladder in the folded position of  FIGS. 4 and 5 . In the folded orientation, the ladder can be stowed anywhere on the craft, preferably in the required safety equipment bag (in the case where the ladder is employed by a crew launch). The cord enlargement  9  can be of any construction capable of keeping the cord from passing through the slot  8  when the ladder is folded. A simple knot or the combination of a knot and apertured element could be used. A cane tip with a hole therethrough with a knotted bungee has proved effective. 
     Folding the ladder can be a bit awkward but it is important to note that folding is accomplished at a non-critical time. Assuming the ladder is used to rescue a swimmer, the ladder has been instantly erected for use when pulled from its stowed position (described below), hooked to the gunnel of the launch boat, used by the swimmer to get in the launch, and removed from the gunnel as the swimmer is taken to safely either on shore or on a bigger boat. The ladder can be re-folded any time prior to re-use of the launch or the safety equipment bag, in the case of crew use. 
     The folded ladder of  FIGS. 4 and 5  can be instantly erected for use simply by pulling enlarged end  9  to removed cord end  4  from slot  8 . When released, the tension of the bungee cord  4  draws the tapered rungs ends  6  into the tapered holes  7  of the rails forcing the ladder into the position of  FIGS. 1 and 2 . Since the force of a swimmer on the rungs is vertical with the ladder in a vertical orientation on the boat, the ladder maintains its  FIGS. 1 and 2  orientation to allow the swimmer to climb into the boat to which it is attached. 
     A critical element of the invention is the means by which the ladder attached to the boat gunnels.  FIG. 6  shows boat  20  (a jonboat boat, in this figure) having gunnels  21 . The inventive ladder has hooks at the ends of rails  1 . Hooks  22  have openings 23 sized to fit over gunnels  21 . The hooks can be sized for any boat gunnel and are optimally sized to fit many common gunnels. The ladder ends also include a protrusion or bulge  24  to provide the stand-off feature of the ladder. Protrusion  24  lies against the boat hull sidewall  25  at point X to act with the hooks  22  to keep the ladder from moving with respect boat sidewall when under the load of a swimmer exiting the water. Since the protrusion  24  is at the top of the ladder, it will properly function on very shallow-draft hulls, unlike the previously mentioned stand-off legs at the bottom of many rigid ladders. The relationship between hooks  22 , opening  23 , and protrusion  24  orients the ladder at least vertically and optimally at an angle away from the boat (a canoe) as shown in  FIG. 7 . The important point here is that the swimmers can&#39;t force the ladder under the boat, preventing injury to feet and hands that would be trapped between the ladder and the boat sidewall and allowing easier exit from the water because of the positive angle of the ladder with respect to the boat. Of course, some boat hulls/gunnels are dimensioned such that the protrusions  24  are unnecessary for maintaining the ladder in the optimal position of at least vertical and, preferably, angled away from the boat hull as described elsewhere in this specification. 
     Hooks  22  can be provided on either end of the ladder as shown in  FIG. 7  and be of different configuration on each end to allow a single ladder to be attached to various boat gunnels/sidewalls. The protrusion can be of any size or shape to mate with any sidewall. Hooks  26  on end  60  of the rails  1  can face in either direction (shown in  FIG. 7  oriented in the same direction as hooks  22 ) to be attached to boat structure when the ladder is rotated 180 degrees such that hooks  26  are at the top of the ladder. Hooks  26  and/or protrusion/projection  25  are of different dimension than hooks  22  and/or projections  24 .  FIG. 7  clearly show the inventive ladder positioned at a positive angle from vertical making climbing much easier than if the ladder were allowed to move past vertical and under the boat hull. 
     Some boats will not accept the hooks described herein. It is anticipated that other attaching means can be used with the hooks. Knotted rope can mate with a variety of boat structures. The important aspect of this invention is that the ladder stand off from the boat sidewall to be near vertical and preferable angled away from the boat for easy use. Also, the ladder hooks can mount to any boat structure that will accept it such as existing fixed ladders, rear transoms, motor mounts or hand rails above gunnels. The ladder could be securely hung from a cleat, or a railing, or even the bracket for the outboard motor on some sailboats. Inasmuch as the ladder can be an emergency device, the means of hanging it on the boat within reach of the stranded swimmer in the water does not have to be particularly elegant, only quick and reasonably secure. It could be used even on boats that had gunwales too wide for the hooks and the user could attach a short (e.g. 3 foot) knotted rope to one of the hooks, with the free end of this rope looped inboard around a cleat, stanchion, winch, railing, or other nearby structure on the boat and then brought back to be inserted into the slot  8  in the other hook. If this short rope were already knotted at 6 inch intervals, the height of the ladder as it hung over the side of the hull could be easily and quickly adjusted simply by choosing which knot on the rope to insert in the slot  8  in the ladder. In fact, although it would be desirable for stability purposes that the hooks actually “grabbed” over the top of the gunwale. On sailboats and other boats like the Boston Whaler™ this might not always be possible because of their “smooth gunwale” design, the ladder would still be held securely in position by the looped rope in any event—and it would be far quicker to deploy and more stable to use than the non-rigid rope ladders that are presently on the market which need to be individually tied the boat&#39;s structure in some fashion before they are deployed overboard. 
     It is envisioned the ladder will float if dropped into the water. The rails  1  of the preferred embodiment are constructed from plastic or plywood and the rungs  3  of PVC. Materials are not critical to the invention provided they possess the required strength and desired characteristics (floatable, for one). 
     The dimension shown in the drawings are not meant to be limiting in any way. The invention is limited only by the claims.