Ultra lightweight segmented ladder/bridge system

A dual-use ladder and bridge modular system preferably includes tubes, gussets, flanges, and/or joints. In a preferred embodiment, the tubes, gussets, flanges, and/or joints are made of carbon fiber. A method connects and disconnects modular carbon fiber ladder segments. Another method creates a lightweight carbon-fiber beam with exceptionally high stiffness and strength using a combination of carbon-fiber braid material, uni-directional cloth, and pultruded carbon-fiber strips. A carbon fiber ladder segment and tube connectors are also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to the field of ladders and bridges. More particularly, the invention pertains to a segmented ladder and bridge system.

2. Description of Related Art

The use of ladders and small bridges is commonplace in commercial and military applications. Unfortunately, long ladders tend to be heavy and difficult to transport. In addition, units designed as ladders are not strong enough to be laid flat and used as a walking bridge or scaffolding. One solution to improve portability is to use a segmented ladder.

Segmented ladders are comprised of several smaller ladder sections, which are aligned and secured together to form a longer ladder at the time of use. The benefit of such a design is that, instead of transporting, for example, a single 20-foot long ladder, one can separately transport four five-foot sections, which are assembled only when needed. This allows ladders to be carried within cars, trucks, helicopters, and other vehicles with relative ease.

Several patents exist for segmented ladder designs. Leavitt and Whitehurst, U.S. Pat. No. 2,900,041, entitled “SECTIONAL LADDERS”, issued Aug. 18, 1959, discloses a simple, inexpensive sectional ladder that includes telescoping sleeve-type joints with a snap-action locking mechanism. Brookes et al., U.S. Pat. No. 3,995,714, entitled “MULTI-SECTION LADDER FOR SCALING POLES”, issued Dec. 7, 1976, discloses a multi-section ladder specifically for scaling poles. In this design, the main support rail runs along the center of the ladder, and the rungs are supported mid-span. Extending the work by Leavitt, U.S. Pat. No. 4,917,216, Kimber, entitled “SEGMENTED LADDER CONSTRUCTION”, issued Apr. 17, 1990, discloses a multi-step ladder construction unit with side rails, cross members joined at the ends, and telescopic ends for insertion into additional segments. A primary goal of this patent was to develop a system that was manufacturable at low cost.

Several segmented ladders are available commercially, including the Bauer Corporation Series 333 fiberglass parallel section ladder and Series 339 fiberglass tapered sectional ladder (Bauer Corporation, Wooster, Ohio), the S7900 series fiberglass sectional ladder from Werner Corporation (Werner Co., Greenville, Pa.), and the six-section surveyors ladder from Midland Ladder Co. Ltd (Birmingham, UK).

In addition to segmented ladders where the individual segments detach from one another, telescopic ladders are now widely available. One such example was disclosed by James and Richard Weston, U.S. Pat. No. 5,494,915, entitled “COLLAPSIBLE LADDER”, issued Mar. 5, 1996. In this patent, the entire ladder is comprised of individual sections that collapse and nest within one another for storage and transport. Although useful for certain applications, the entire ladder remains a single unit; hence the weight cannot be distributed amongst multiple separate units. In addition, this type of design does not work well for bridges, since the segments that are meant for use at the top of the ladder are inherently smaller and weaker than those intended for use at the bottom of the ladder. This configuration may be acceptable for a ladder, since the stresses while in use will typically be much less at the top than at the bottom; however, in a bridge or scaffold configuration, the segments must be equally rigid across the entire length for sufficient structural rigidity. Commercially available telescopic ladders include the Telesteps® telescoping ladder, the Up Up® ladder (Core Distribution, Inc., Minneapolis, Minn.), and the Xtend & Climb® ladder (Core Distribution, Inc., Minneapolis, Minn.).

Carbon fiber has been used in a limited basis for ladder fabrication. GMT Composites (Bristol, R.I.) offers a folding carbon-fiber ladder for use on boats. Cima Ladder (www.cimaladder.com, Spain) has produced a 1-piece carbon-fiber ladder for light duty use. Neither of these ladders is designed for easy disassembly into individual segments. There is a need in the art for a portable, lightweight segmented ladder that is also strong enough to utilize as a horizontal walking surface.

SUMMARY OF THE INVENTION

A dual-use ladder and bridge modular system preferably includes tubes, gussets, flanges, and/or joints. In a preferred embodiment, the tubes, gussets, flanges, and/or joints are made of carbon fiber. A carbon fiber ladder segment includes a pair of tubular carbon fiber side rails, where each rail has a first end and a second end, at least one carbon fiber rung perpendicular to the carbon fiber side rails, where the carbon fiber rung connects the side rails of the ladder segment, and a joint connector located at least one of the first end and the second end of each carbon fiber side rail. The joint connector on an end of a first carbon fiber side rail of a first ladder segment mates with the joint connector on a second carbon fiber side rail of a second ladder segment. When at least two ladder segments are joined by the joint connectors, they form a structure.

A method of the present invention forms at least one carbon fiber ladder segment by permanently connecting a pair of carbon fiber side rails to at least one carbon fiber rung and adding a joint connector to at least one of the ends of each carbon fiber side rail.

The present invention also includes modular systems utilizing carbon fiber tubes. In one embodiment, the system includes a plurality of carbon fiber tubes having ends, and a joint connector located at least one of the ends of each carbon fiber tube. The modular system also preferably includes at least one modular element. The joint connectors mate with joint connectors on adjoining carbon fiber tubes or the modular elements to form a structure.

One preferred modular system is a modular ladder/bridge system which includes at least two ladder segments and at least one joint connector located at least one of the ends of each ladder segment. Each ladder segment includes a pair of carbon fiber side rails and at least one carbon fiber rung perpendicular to the carbon fiber side rails. The carbon fiber rung connects the carbon fiber side rails of the ladder segment. The joint connectors mate with joint connectors on adjoining carbon fiber side rails or the modular elements to form the structure.

Tube connectors of the present invention join a first tube and a second tube. Each tube has ends and an interior hollow portion. The tube connector includes a pair of male joint connectors having a first end connected to an interior surface of the first tube and a second end protruding from an end of the first tube, the second end of the male joint connector having at least one hole formed therein such that, when the second end of the male joint connector is inserted into an interior surface of the second tube, it is secured in place by insertion of pins through the second end of the male joint connector and mating holes in the second tube. In a preferred embodiment, the first tube and the second tube are made of carbon fiber.

DETAILED DESCRIPTION OF THE INVENTION

Carbon-fiber (CF) tubes and gusset plates can be used to create various structures, including trusses, bridges, supports for equipment, and many others. By fabricating a segmented ladder from carbon-fiber composites and metal or composite joints, the result is a unit that is both portable, as well as strong enough to utilize as a horizontal walking surface. The present invention includes a dual-use ladder and bridge structure preferably composed of carbon-fiber tubes, gussets, flanges, and/or joints. In particular, this design lends itself well to a segmented carbon-fiber ladder and bridge, but could be used for other designs as well. Within the framework of the design, the joint connectors (or splices) are an important component.

The present invention also includes a method for joining carbon-fiber tubes that is applicable where one needs the ability to both connect, as well as disconnect, the tubes. Another method creates a lightweight carbon-fiber beam with exceptionally high stiffness and strength using a combination of carbon-fiber braid material, uni-directional cloth, and pultruded carbon-fiber strips.

The structure includes modular construction of multiple pieces that are assembled into one or more ladders, bridges or other structures at the time of use, and then disassembled for storage or travel when the obstacle is cleared. The obstacles could include both vertical obstacles and horizontal obstacles. Some vertical obstacles include, but are not limited to, walls, trees, and rocks. Some horizontal obstacles include, but are not limited to, moving from rooftop to rooftop, moving from window to window, or crossing a river.

In a preferred embodiment, the carbon-fiber structures of the present invention are composed of a combination of carbon fiber tubes, carbon fiber gussets, carbon fiber flanges, and/or carbon fiber splices. Some uses for this carbon fiber assembly include a climbing ladder, when an individual needs to scale an obstacle vertically, and a bridge, when an individual needs to cross an obstacle horizontally.

The modular devices of the present invention, which preferably include multiple identical segments, can be built and used as a ladder, a bridge, or any other segmented structure, including, but not limited to, a scaffold or truss structure. While the structure preferably includes pieces made of carbon fiber, the modular ladder/bridge system of the present invention could alternatively be manufactured out of other lightweight materials, such as fiberglass, aluminum, or titanium, or any combination of these and other materials. The obstacles could include both vertical obstacles and horizontal obstacles. A ladder, as defined herein, is a structure that includes steps which include two parallel members connected by rungs. A bridge, as defined herein, is any structure that spans and provides passage over a gap, barrier, or other obstacle, thus allowing people, animals, vehicles or other objects to bypass the obstacle. These two terms will be used interchangeably herein.

An embodiment of the present invention is shown inFIG. 1, which depicts an assembled segmented ladder/bridge structure100. The ladder/bridge100includes main support beams, which are preferably tubes1, and perpendicular rungs2that act as hand and foot supports. The main support tubes are permanently connected to the rungs2. In a preferred embodiment, the main support tubes1and the perpendicular rungs2are made of carbon fiber. The rungs are preferably permanently connected by bonding them with an adhesive to the side support tubes with gussets3. Bonding, as used herein, is the use of an adhesive layer placed at the mating surfaces between two components that results in a permanent connection. In a preferred embodiment, the gussets3are made of carbon fiber. A precision fixture is used to hold the assembly in the correct position during fabrication while the adhesive cures.

FIG. 1shows a six-rung version of the structure100. However, a structure100with any alternative number of rungs2and segments could be manufactured, depending upon the intended use of the structure100. The rungs2are preferably evenly spaced when the structure100is assembled.

FIG. 2shows a close-up view of an example of carbon fiber gusset plate construction. In this example, 1-inch square carbon fiber tubes are used for both the tubes1and the rungs2in the entire structure. However, other sizes for the carbon fiber tubes, including, but not limited to, 0.75 inch square and 2 inch square, as well as other shapes for the carbon fiber tubes, including, but not limited to, carbon fiber tubes that are round, rectangular, or rectangular with rounded ends, in cross-section, could alternatively be used. In addition, the carbon fiber tubes may be braided carbon fiber tubes. Preferred materials in the embodiments where carbon fiber tubes are used in the ladder/bridge are DragonPlate™ Engineered Carbon Fiber Composites (Allred & Associates Inc., Elbridge, N.Y.). In other embodiments, the segments of the ladder in the modular system may be made of other lightweight materials, or a combination of materials.

FIG. 3shows the ladder/bridge100pulled apart, to show splice joint, rung, and flange construction of the ladder/bridge100. Splice connections4are shown inFIG. 3. The splices4slide into the outer tubes1and are bonded into place. In this case, a splice4is bonded approximately half-way into one of the support tubes. Opposite splices4are lined up with the mating tubes1and pressed together at the time of use. A pin, clip, or other fastener can optionally be used to guarantee the splice4does not come apart during use.

Often, added structural stiffness is necessary, for example for greater weight loads or if the ladder is longer.FIG. 4shows an alternative construction for the structure40, which is preferably constructed as a ladder or a bridge. In this figure, instead of the square side supports1, the tubes41are now preferably rectangular. By doing this, the stiffness of the main supports is greatly increased without substantially increasing the weight. In a preferred embodiment, the tubes41are carbon fiber tubes. In embodiments where carbon fiber tubes are used, any usable size for the carbon fiber tubes41(as well as the rungs42), including, but not limited to, 0.75 inch square, 1 inch square, and 2 inch square, as well as other shapes for the carbon fiber tubes, including, but not limited to, carbon fiber tubes that are square, round, or rectangular with rounded ends, in cross-section, could alternatively be used. In addition, the carbon fiber tubes may be braided carbon fiber tubes. Preferred materials for the carbon fiber tubes and other components of the ladder/bridge are DragonPlate™ Engineered Carbon Fiber Composites (Allred & Associates Inc., Elbridge, N.Y.).

In addition, a core material45, typically foam, is preferably added inside the splice joint44to increase rigidity and damage tolerance. The core45could alternatively be made of any lightweight material able to increase the structural stiffness of the ladder/bridge40, including, but not limited to, a lightweight wood, for example balsa wood. The core material45may also optionally be included in the tubes41, and/or the rungs42, to further increase stability.

FIG. 4also shows the rungs42, which are preferably a rectangular shape with rounded ends, although they could alternatively be other shapes including, but not limited to, square, round, or rectangular. Reinforcement plates46may optionally be added on the side beams41on the side opposite the internal splice44for additional strength. Note that the core material45and/or the reinforcement plates46may alternatively be included in the ladder/bridge100shown inFIGS. 1-3. For example, the core material45may be incorporated inside any or all of the main support tubes1, the rungs2, and or the splice connections4of the ladder/bridge100shown inFIGS. 1-3.

FIG. 5shows two rungs42of the ladder/bridge40with one side-rail hidden. The rungs42in this embodiment may include a core material45. A portion48of the rungs42carries through the inside surface of the side support tubes41and is bonded to the interior of the opposite face. This ties the entire assembly together and prevents the rungs42from shearing off. To further increase bonding surface area and strength, flanges47are preferably fabricated to match the contour of the rungs42. In preferred embodiments, the flanges47are carbon fiber flanges. The structure40is assembled by first sliding the rung42through the left side support41, then sliding on the flanges47, and finally attaching the right side support tube41.

An assembled three-section structure40is shown inFIG. 6in a vertical ladder use configuration, and inFIG. 7in a horizontal bridge use configuration.

The structures of the present invention are particularly useful because of the segmentation of the components. The entire modular structure is composed of smaller pieces, each one a separate ladder/bridge section (also described as a ladder segment herein), which are put together at the time of use. While the structure includes pieces made of carbon fiber in some preferred embodiments, the modular ladder/bridge system of the present invention could alternatively be manufactured out of other lightweight materials, such as fiberglass, aluminum, or titanium, or any combination of these and other materials. The individual pieces, or any combination of them, may be used as a ladder, a bridge, or another structure. For ease of fabrication and assembly, all components can be made identical. For assemblies with greater than two sections, the only difference is elimination of the splices at the terminal ends.

One example of a ladder/bridge of the present invention is a five-section, 32-foot ladder weighing approximately 35 pounds. For scaling vertical obstacles, the user can choose to use 1, 2, 3, 4, or all 5 sections, depending on the height of the obstacle. This unit could also be used as two or more smaller ladders simultaneously by multiple individuals. The individual sections could then be used either alone or with any combination of other sections, and be placed horizontally across a gap, for example between buildings or over a small ravine or canal. Once all users are safely across, the bridge can be pulled up by a single individual due to its light weight carbon-fiber tubular construction.

A novel method fabricates the main support beams80, shown inFIG. 8. Pultruded carbon-fiber strips88are placed within carbon-fiber tubes to add significant tensile and bending strength. In a preferred embodiment, the pultruded carbon-fiber strips88are preferably approximately rectangular in shape, although other shapes are also possible. The strips88are placed within the composite layup and sandwiched between layers81,89, and90of carbon-fiber woven material. In a preferred embodiment, a layer of braided or plain-weave material is used for the inside surface89(inner carbon fiber layer) of the tube80, followed by layers of uni-direction carbon-fiber fabric90(uni-directional carbon fiber), and then a layer of braided material for the outside layer81(outer carbon fiber layer) of the tube80. Pultruded carbon fiber strips88are preferably placed between the braided carbon fiber layers90and81(or, in the embodiments where there is no uni-directional carbon-fiber fabric layer90, between the braided carbon fiber layers89and81) and held in place once the adhesive cures. In one embodiment, the adhesive is epoxy, but any adhesives that could be applied to carbon fiber tubes and efficiently adhere the layers could alternatively be used.

In applications where bending strength is needed about a single axis (for example, bending of the carbon-fiber ladder/bridge), pultruded carbon fiber strips88can be placed along only the top and bottom beam surfaces, but excluded from the sides. In some preferred embodiments, the uni-direction carbon-fiber fabric90wrapped around the inner carbon-fiber layer89is excluded, leaving only the outer81and inner carbon-fiber material89and the pultruded carbon-fiber strips88. During fabrication, the pultruded carbon-fiber strip88may be one solid piece on each side, or composed of two or more pieces for ease of fabrication. Also, by stacking the strips88on top of one another, additional wall thickness can be easily accomplished, resulting in higher beam stiffness and strength. This method of construction results in a lightweight beam with exceptionally high stiffness and strength along a single bending axis.

FIG. 9shows a close-up near a joint of a ladder/bridge40, depicting the rungs42and reinforcement gussets92.FIG. 10shows a portion of the ladder/bridge40with one side-wall tube made transparent, revealing the internal joint connectors93bonded within the side-beam tube41. The joint connectors93are preferably made of fiberglass, but they could alternatively be made of other lightweight, strong materials, including, but not limited to, aluminum or titanium.FIG. 11shows a basic assembly of this type of joint110. The gussets92are placed on the opposite (female) side of the joint for added wall strength. Pins94are inserted to hold the joined components together when in use. The complete female ladder segment connection95is shown inFIG. 12.FIG. 13shows the mating male segment side93. The individual ladder/bridge segments are assembled by sliding the internal joint connectors93into the mating end95of the adjoining segment, lining up the joint connector holes, and inserting two pins94.

An alternative internal joint connector140with ridge guides96is shown inFIG. 14. The ridge guides96are preferably fabricated as part of the internal joint connector140. This joint connector140would replace the male segment side93of the joint connector110shown inFIG. 11. The joint connector140allows proper spacing of the internal connector piece away from the tube inner wall to maintain sufficient adhesive thickness. In one embodiment, the joint connector140is preferably made of fiberglass. Alternatively, the joint connector140may be made from any other lightweight, strong material including, but not limited to, aluminum or titanium.

One embodiment of a pin joint connector is a dual-pin connector117, as shown inFIG. 15. This design includes two pins114rigidly connected to a metal or composite bracket118. In the center of the connector is a fastener119, which engages with a hole120in the side of the outer surface of the main ladder beam41, as shown inFIG. 16. In a preferred embodiment, the fastener119is a Zeus-type turn fastener. When the fastener119is fully engaged and turned, the pin connector117locks in place to prevent the ladder segments from sliding apart.

An alternative female internal connector121is also shown inFIG. 16. The outer reinforcement bracket112can optionally be used here; however, the primary load path now goes through the female internal connector121.

Insertion and final placement of the two-pin connector117in the assembly is shown inFIG. 17. Here, the side-beams are hidden to show only the male and female internal connectors113and121, and the dual-pin connector117. When the structure is disassembled, the pin connector117can be stored in place in the segment holes, or retained by a tie or line affixed to the structure.

FIGS. 18 through 22show an alternative embodiment of internal joint connectors.FIG. 18shows the complete joint180. Here, additional mounting hardware (for example, bolts, washers, and/or nuts)122are permanently mounted to each side beam41through the internal joint connectors for added safety. Pins184make the connection through holes185between the two joining segments.FIG. 19shows the female segment end190for the joint connector180andFIG. 20shows the male segment end200. The male123and female124internal joint connectors are preferably fabricated from multiple machined flat plates, as shown inFIG. 21. By using a flat-plate construction, volume machining costs are reduced. In between the male123and female124internal connectors are shear support pieces125. These pieces act as the web of an I-beam, reducing the shear stresses in the side-walls of the carbon fiber tubes41.FIG. 22shows a single male internal connector123and a single female internal connector124before the connection is made.

FIGS. 23 through 27show another embodiment for the internal joint connectors.FIG. 23shows the complete joint230.FIGS. 24 and 25show the female240and male250connector ends, respectively.FIG. 26shows the male263and female264internal joint connectors connected to each other.FIG. 27shows a male internal connector263and a female internal connector264with brackets (which are made of carbon-fiber in a preferred embodiment) and front components hidden. In this embodiment, the joints are again made up of flat-plate machined components. Unlike the design shown inFIG. 21, however, where the shear web125is a separate piece, the flat components265and266on the outer walls in this embodiment include the top and bottom components, as well as the shear web. This reduces the number of machined parts.

While the joint connectors93,140,117,180,230discussed herein are preferably used in the modular ladder/bridge system of the present invention, any of the joint connectors93,140,117,180,230could alternatively be used in any structure or modular system that required connections between two separate pieces with interior portions, for example a beam including but not limited to, a rail, an I-beam, or a tube. In one preferred embodiment, the joint connectors connect two tubes with interior hollow portions or more specifically, two composite tubes. More preferably, the tubes are carbon fiber tubes. A tube, as defined herein, is a long hollow object. As an example, any of the joint connectors could be used to connect pieces of a truss structure.

At the two terminal ends of the structure, either permanently mounted feet or removable base pieces are used.FIG. 28shows one example of permanent feet126, which preferably take the form of molded plastic or rubber inserts bonded into the inside of the main beams41with adhesive. Alternatively, removable pieces can be pinned in place. One embodiment of a removal and adjustable foot assembly127is shown inFIG. 29. These pieces may be adjustable to vary the height of the two side beams, for example in the event of uneven ground. Multiple mounting hole positions128in the foot support bracket129allow the pin117to be placed in the most desirable position for each application. This also allows the foot290to be completely removed from the end of the structure if necessary.FIG. 30shows a terminal ladder segment500with removable/adjustable feet290installed.

At the other terminal end of the structure, instead of feet290, a modular element, such as a ladder hook130, can optionally be inserted and pinned into place, as shown inFIG. 31, for example, using the pin117shown inFIG. 15. Alternatively, other joint connectors, including, but not limited to those discussed herein, could be used to connect the hook to the structure. The hook130is another modular piece of the ladder/bridge system of the present invention.

In addition to ladders and bridges, the basic building blocks of this system can be utilized to construct a myriad of other structures. For example, scaffolding, look-out stands, and tables can also be made by connecting multiple pieces together to form legs and platforms. To facilitate this, special modular elements, such as angle connector pieces, are preferably used.FIG. 32shows an angle connector modular element131used to combine the ladder segments into a step ladder600, as shown inFIG. 33. In this case, four segments330(two on each side) are used to form the step ladder600, with the step ladder connector131in place at the top. The connector131is preferably pinned in place and easily removable for disassembly. Alternatively, any number of ladder segments330can be used to form smaller or taller step ladders600.FIG. 34shows a close-up of the step ladder connector131in place on the ladder600. The pin joint connector shown inFIGS. 16 and 17is used to connect the angle connector131shown inFIG. 34. Alternatively, other joint connectors, including, but not limited to, the joint connectors discussed herein, could be used in combination with the angle connector131.

In order to form other structures, modular elements, connectors, of different angles are preferably used.FIG. 35shows a 90 degree angle connector132. Using this connector, structures with vertical and horizontal components can be constructed. A close-up of the 90 degree angle connector132in use is shown inFIG. 36. This connector is similar to the one shown inFIGS. 15-17, with the addition of the 90 degree angle portion132. An assembled L-shaped structure700with four segments370is shown inFIG. 37.FIG. 38shows a scaffold structure800with 90 degree connectors132and six segments380. Both of these structures700and800are made possible by the ladder/bridge connector system discussed herein. In a preferred embodiment, to facilitate greater stability for the user, a solid panel133is preferably added over top of the rungs on the horizontal components, as shown in the scaffold structure900inFIG. 39This provides better footing when standing on the top of the structure900.