Abstract:
A flotation device carries two or more people down a waterslide on shaped flotation tubes, coupled by flexible straps into a train. The bows and the sterns of adjacent buoyant bodies are complementarily shaped, preferably the bow being circularly convex and the stern concave as viewed in plan. The straps hold the bow and stern together at a minimal gap, constraining relative rotation by the convex/concave engagement of the bow and stern. In addition, lateral shoulders on the bow abut against the ends of the concave stern to prevent rotation beyond a predetermined angle, for example wherein the bodies in the train are relatively rotated to a bend having about a ten foot radius. This structure provides sufficient flexibility to traverse relatively tight turns in the waterslide course while preventing buckling or accordion-fold collapse when the train of buoyant bodies encounter an obstruction such as a splash down pool.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of aquatic recreation apparatus and in particular concerns a flotation tube that is nestably coupleable to other similar tubes to form a semi-rigid elongated train. Laterally spaced flexible straps hold successive tubes together at complementary convex/concave abutting surfaces that allow the train to bend around a curve but the structure is such that the train cannot collapse or buckle, for example, when the front tube(s) encounter an obstruction such as a splash down pool. 
     2. Prior Art 
     A waterslide typically involves a path with an elongated trough or sluice in which water flows, in an amount at least sufficient to wet the surfaces and in many instances moving a substantial volume of water per unit time. The trough usually defines a continuously downward flow path and drains water that is pumped upwardly from a splash down pool at the end of the course to an entry point at the entrance. 
     There are various known configurations. A deep water ride may carry a flow on which riders float, or the riders may skim over a thin layer of water, or a gush of water may carry the riders along turbulently. A course may be relatively steep or have a mild gradient. In an uphill/downhill course the water may pool in the valleys and require draining or the course may have some places where the water is relatively deep and/or fast flowing and other places that are merely wetted, such as uphill runs. For excitement, the course often has banked turns. 
     The nature of the flow of water is determined by the contour of the sluice, including its width, curvature and vertical gradient, and by the amount of water flowing in the sluice at any particular point. Sluices or slides can lead to intermediate pools, and outlets or alternative outlets from intermediate pools can lead to further slides, etc. 
     The sluice can define a sinuous path, and the curves are correspondingly banked such that the flow of water due to inertia is not restricted to the lowest cross-sectional portion of the sluice, but rather rises along the sides of the sluice. Accordingly, in traversing turns the riders become canted to an angle defined by the surface of the water flowing around the turn. 
     Waterslide riders can traverse the slides with or without flotation devices or sliding mats, however such devices are preferred due to their ability to protect the rider from friction with the sluice. Flotation devices also support the riders in relatively deep water. Whether a particular waterslide sluice is apt for persons alone or for persons with flotation devices is a matter of the width of the sluice, the character of its surfaces, the rider&#39;s speed and the flow of water. The sluice width is such that the rider or the rider&#39;s flotation apparatus is confined between the sidewalls. The sluice may be correspondingly narrow to prevent the rider or flotation device from turning laterally to the flow and obstructing flow and traffic or subjecting the rider to friction along the sluice sidewalls. 
     Air mattresses have been used for flotation in waterslide parks, as have vehicle inner tubes. However, an air mattress or inner tube of the type often used for placid floating may not be suitable for riding a waterslide. Accordingly, reinforced and adapted versions of such flotation devices have been developed. For example, U.S. Pat. No. 5,020,465--Langford discloses a variation on an inner tube, having a relatively sharper prow and blunt stern with complementary couplings permitting the attachment of several such devices in lines or arrays. U.S. Pat. Nos. 5,011,134 and 5,230,662 disclose sliding mat variations having toboggan-like fronts and handles. U.S. Pat. No. 5,453,054--Langford discloses a different tube variation with couplings that, like Langford &#39;465 are pivotable on a vertical axis. The foregoing patents disclose various details of flotation devices as well as waterslides, and their disclosures are hereby incorporated. 
     Tubes are comfortable and convenient flotation devices because a person can sit comfortably upright in the central opening defined by the tube, with the user&#39;s legs hanging over the sides. Durable versions of the tubes having fabric surfaces resist damage from friction, for example the friction occurring between the tube and the sides of waterslide sluices. Such tubes are typically made of resin embedded in a fiber as the wear-resistant external skin of an inflatable tube. The tubes can have handles on the top surface, to steady a rider when sitting upright, and back rests, etc. Due to these beneficial attributes, tubes have become a preferred form of flotation device for waterslide parks wherein the riders traverse a sluice on an individual flotation device. 
     Single and multiple tubes and tube connections are possible. Riders of waterslides frequently attend in or form groups. Members of a group find it enjoyable to traverse the slide together. Although traversing the sluice one after another is in a sense traversing the sluice together, riders may join hands and traverse the slide single file. Of course, when joining hands makes it difficult to maintain a hold on any handles that may be provided on the rider&#39;s tube. To serve the users&#39; desires, park operators may supply an integrally double tube or &#34;double doughnut&#34; wherein an inflatable body in a figure eight shape provides apertures for two riders to sit. Such a device is relatively rigid and is impractical in units of more than two rider positions. The long longitudinal axis causes wear on the tube when traversing curves or limits the minimum radius of curves, or cause wear at vertical diversions and changes in slope, or causes problems in wider areas such as pools. 
     US Pat. No. 5,507,674--Yeung discloses a plurality of tubes that are coupleable in a single file by pairs of mating connectors on opposite sides of the tubes. The connectors in the pairs are spaced on the tube and the round shape of the tube causes the tube to protrude between the connectors. Thus, connected tubes bear relatively tightly against one another between the connectors, providing a train of tubes that is substantially as rigid as a double doughnut type. The Yeung patent is also hereby incorporated. 
     The coupled single rider tubes of the Langford &#39;465 and &#39;054 patents, which pivot on a vertical coupling axis, ameliorate the difficulty with rigidity and permit a line of two or more connected tubes to bend to follow a curve. However, other problems are presented. The couplings permit a certain longitudinal play or slack in the train. The couplings also are quite free to pivot, both on a vertical axis and a horizontal axis. As a result, when a line of coupled tubes encounters an obstruction, the train of tubes can be longitudinally compressed and may tend to collapse into an accordion fold. This can occur at points such as a splash down pool when the leading tube(s) of a fast moving tube train encounter the obstruction of deep water, and is undesirable. 
     To deal with accordion fold collapse, a designer may choose to reduce the gradient of the course so that obstructions such as the splash down pool do not produce the sudden braking that causes such collapse. However, this reduces the speed and excitement of the ride. Alternatively the designer may choose an integral multi-rider tube or another rigid train arrangement. However, all the curves along the course then are required to have a minimum turning radius that will accommodate the longest rigid tube train, which also reduces the excitement of the ride. What is needed is a tube train structure that balances the need for flexibility, for negotiating turns and gradient changes, with the need for structural integrity and rigidity of the train of coupled tubes. 
     SUMMARY OF THE INVENTION 
     In its broadest aspects, the invention provides a flotation device comprising at least two buoyant bodies each having a bow and a stern, and preferably a central aperture for the rider, wherein the bows and the sterns are shaped to complement one another such that the bodies nest longitudinally. Means are provided for flexibly fastening together the buoyant bodies in their nested relationship, so as to constrain each bow and stern to a movement complementary to their abutting surfaces. 
     In one embodiment, one of the bow and the stern is convex in plan view and the other is concave. A pair of attachment structures are disposed adjacent to each of the bow and the stern of the buoyant bodies in arcuately spaced relation to their respective concave or convex outer surfaces. In this embodiment, the arcuate spacing between the pair of attachment structures on the convex side can be less than the spacing of the attachment structures on the concave side. Flexible straps, preferably having mating male and female fasteners at their free ends, are affixed to each attachment structure and join the stern of one of the buoyant bodies with the bow of the next following body. Preferably, the bows of the tubes are convex and the sterns are concave, causing the straps to flare laterally outwardly in the forward direction. 
     The invention is advantageously applied to a systern of aquatic recreation comprising a waterslide amusement including down-hill and optionally up-hill runs, as well as a plurality of curved sections. The convex/concave nested tubes preferably are coupled sufficiently closely by the flexible straps that at least a portion of their facing surfaces come into contact when traversing curves. By providing a slight longitudinal clearance between tubes when the tubes are straight in line, for example about 0.75 inch, or by use of resiliently extensible material for the straps, the train of tubes can readily conform to a minimum radius of curvature, preferably about ten feet. However, the structure limits the extent to which successive tubes can pivot and thereby prevents an accordion collapse of the tube train when the leading tube(s) encounter an obstruction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will be apparent from the following detailed description of preferred embodiments, which are to be considered together with the accompanying drawings, wherein like numbers refer to like parts, as well as the appended claims. In the drawings, 
     FIG. I is a top view of a flotation train formed in accordance with the invention; 
     FIG. 2 is a top view of an individual flotation device from the flotation train shown in FIG. 1; 
     FIG. 3 is a top view of a typical waterslide amusement of the type for which the invention is contemplated for use; 
     FIG. 4 is a top view of the invention, similar to that shown in FIG. 1, but showing the relative orientation of the individual floatation devices of a train when subjected to a curved section of a typical waterslide amusement; and 
     FIG. 5 is a top view of a flotation train formed in accordance with an alternative embodiment of the invention 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A flotation train 5 as shown in FIG. 1 is made up of two or more bodies 10, each preferably shaped generally as a tube, and each comprising a bow 15, a stern 20, a central rider&#39;s compartment 25, and a plurality of attachment structures 30. For convenience in describing the invention, the nautical terms &#34;bow&#34; and &#34;stern&#34; are used herein, and should be considered to have their usual meanings, i.e., the front and rear ends of a boat in the normal direction of travel. Bodies 10 are preferably buoyant, but the invention is also applicable to similarly shaped rider supporting structures that slide over wetted surfaces or the like as opposed to floating. Bodies 10 may comprise a flexible inflated envelope or may comprise solid or foamed buoyant material such as kapok, foamed polystyrene or the like, or they may be hollow. Preferably bodies 10 are hollow, flexible and inflated, having a structure comparable to that of a vehicle tire inner tube, with an external covering of resinous fiber or fabric to resist wear. 
     Bow 15 and stern 20 define opposite longitudinal ends, with central aperture 25 disposed between them and centered relative to a longitudinal axis through body 10. Central aperture 25 is typically circular and about a foot wide at its minimum inside diameter, widening upwardly due to the generally toroidal shape of body 10. 
     Bow 15 and stern 20 form complementary curved contours. In the embodiment shown, each bow 15 comprises a convexly curved portion 32 and each stern 20 comprises a concavely curved portion 34 (FIG. 2) as viewed in plan. Bow 15 and stern 20 can also be complementarily convex and concave as viewed in side elevation, but preferably both are convexly rounded as so viewed. The terms &#34;complement,&#34; &#34;complementary&#34; and the like, as used herein to describe the contour of buoyant bodies 10, have the ordinary meaning to fill-in, complete or match. However the advantages of the invention can be obtained if the bow and stern are partly complementary as opposed to being precise mirror images in three dimensions, and in addition, the forward facing contour of the bows preferably have lateral shoulders extending laterally outwardly relative to the curved concavity of the stern as discussed below. Nevertheless, when two or more buoyant bodies 10 are placed in line bow to stern (FIGS. 1, 3 and 4), the convexly curved portions 32 of the rearward bodies 10 substantially fit the concavely curved portion 34 of stern 20 of the next adjacent buoyant body 10. 
     Convexly curved portion 32 can form a substantially circular section of arc extending, for example, over about 90 degrees as shown and having a radius from about one to 2.5 feet. Insofar as the bow is toroidal in shape, the torus has an outside diameter in plan of about five feet, forming a doughnut shaped tube having a section about one foot in diameter. 
     A pair of concave recesses 38 are formed between each side of convex portion 32 and the front corners 40 of bow 15, thus providing lateral shoulders on bow 15, against which the rear corners of the stern of the next body 10 abut at a predetermined pivot angle relative to the first body. Concave recesses 38 join concave portion 32 smoothly around the shoulders with the sides 42 of buoyant body 10. Comers 44 of stern 20 are rounded so as to complement the recesses 38 of an adjacent bow 15. Stern 20 can have a radius of curvature equal to that of bow 15, but preferably has a slightly larger radius of curvature. For example, stern 20 can have a radius one inch longer than the radius of bow 15 so that when the coupled bodies 10 are spaced by a one inch longitudinal gap, the convex and concave surfaces are evenly spaced all along the junction. 
     Each body 10 preferably comprises front and rear attachment structures for receiving flexible straps 50 that attach the successive bodies together. The attachment structures can comprise, for example, surface-attached receptacles having an annular bezel attached to the surface of body 10 with a bridge member extending across the central opening, around which a strap 50 can be passed. Alternatively, the attachment structures can comprise open-ended passageway members forming through holes that extend through the body in a vertical direction, the strap 50 extending therethrough. Other connections for straps 50 are also possible, the object being to form a flexible coupling between bodies 10 with sufficient clearance that bodies 10 can be relatively rotated until the stern comers 44 abut against the shoulders of bow 15 at recesses 38, thereby permitting free relative rotation but only over a limited angle. 
     A first pair of attachment structures 30a are arcuately spaced from one another adjacent to bow 15. A second pair of attachment structures 30b are arcuately spaced from one another adjacent to stern 20. As best shown in FIGS. 1 and 2, the spacing between the first pair of attachment members 30a is less than the spacing between the second pair 30b. A third pair of members 30c are disposed on the upper surface of body 10 and form or receive handle grips for use by a rider to maintain a hold on an individual body 10. 
     First and second pairs of attachment members 30a, 30b are sized and shaped so that each may receive an end or an intermediate length of strap 50 for securing two adjacent buoyant bodies 10 together. Straps 50 include mating fasteners such as spring clip male and female fasteners 55, 60, that are disposed on the free ends of each strap. Separate short straps can be affixed at one end to a respective attachment member 30a, 30b with fasteners for attachment to a complementary fastener on its opposed strap. In the event the straps are continuous loops, the opposite ends of each strap have complementary fasteners and pass through the attachment members 30a, 30b to affix the bodies together via a closed circle of strap. Straps 50 have a length sufficient to affix bodies 10 together at a slight clearance or gap 65, for example from 0.75 to 1.5 inches and preferably about 1.0 inch measured longitudinally, when bodies 10 are in line. 
     As illustrated in FIGS. 1 and 4, once assembled to adjacent buoyant bodies 10, straps 50 are aligned radially to central aperture 25 and subtend an angle between them of about 60 degrees. This angle can be somewhat higher or lower, for example between 45 and 90 degrees. However, the straps diverge outwardly, away from the bow due to the difference in spacing of attachment structures 30a and 30b. This angular arrangement of straps 50 provides for freedom of complementary movement between adjacent buoyant bodies 10. 
     More particularly, each bow 15 is capable of sliding along the surface of the abutting stern 20, thereby relatively rotating the adjacent bodies 10. Such rotation preferably is about the center axis of central aperture 25 and perpendicular to the longitudinal axis of the buoyant bodies, allowing flotation train 5 to bend laterally when traversing curved sections of a typical waterslide amusement (FIGS. 3 and 4). However, due to the angular arrangement of straps 50 and the eventual abutment of comers 44 and the shoulders at recesses 38, excessive bending or buckling of the flotation train 5 is prevented. This feature of the present invention is unlike prior art structures in which substantial stress is placed on the straps (when bending stresses are present) that would fold the train accordianwise. The present invention&#39;s convex/concave shape provides mechanical engagement, as discussed hereinabove, which substantially reduces the propensity of the train to fold accordianwise. If, in addition to the use of the aforementioned mechanically engaging structures, the specific structures are inflatables, the resistance to accordianwise folding is further enhanced. Thus, with inflatable bodies 10, the resilient compression of each body 10 bears the stresses rather than using straps as the primary means to bear the stress. With this construction, the shoulders of the following bow 15 bearing against the stern receptacles of the stern of the leading tube are particularly effective to resiliently bear stress in a manner that is more durable than would be possible if relying on straps. 
     Bodies 10 are symmetric about the longitudinal axis. Thus the limit on relative rotation and the ability to traverse a turn or bend is equal whether the flotation train 5 is traversing a &#34;right-handed&#34; curve 75 or &#34;left-handed&#34; curve 85 on a waterslide 90 (FIGS. 3 and 4). The extent of permitted bending is variable by suitable adjustment of the relative dimensions of the bow, stern, straps, etc. In the embodiment shown and using the dimensions discussed above, a four-tube train can readily traverse a waterslide curve having a radius as little as ten feet. 
     Various changes and modifications may be made to the foregoing preferred embodiments without departing from the scope of the invention. For example, as shown in FIG. 5, bow 95 of a leading body 100 may have an entirely convex shape. Stem 20 of body 100 has a concave shape identical to that disclosed in connection with body 10. The convex shape of bow 95 helps flotation train 5 cut through the water of waterslide 90 by decreasing the amount of drag experienced on body 100. A convex bow also contains substantially more air than a toroidal shape, which improves flotation at the front and minimizes the extent to which the bow can submerge and cause deceleration. Instead, the device is more prone to skimming and less prone to hydraulic drag. 
     The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art. The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.