Abstract:
An exercise and/or play hoop, made of semi-rigid plastic tubing, is partially filled with water ( 30 ) to between ⅙ and ½ full, most preferably ¼ full. The water improves the dynamics of the hoop and makes keeping the hoop elevated by gyration easier. The hoop is preferably made of a length of hoop tube ( 10 ) bent into a circle. A coupling tube ( 20 ) is inserted where the ends ( 11, 12 ) abut, spanning over the joint. The coupling tube includes a bore ( 25 ) through which the liquid flows circumferentially around inside the hoop, and past the joint. To seal the water in O-rings ( 41, 42 ) are used. A decorative, preferably iridescent cover ( 18 ) may cover the hoop. Tape ( 50 ) keeps the joint together. The hoop may be scented.

Description:
FIELD OF THE INVENTION 
     The present invention relates to play and/or exercise hoops of the type known as HULA HOOPS. 
     DESCRIPTION OF THE RELATED ART 
     Play hoops are widely known. They are used for rolling and gyrating about the hips and other parts of the body. Hoops are typically made from a length of plastic tubing by bending the length into a circle and joining the ends. 
     Such hoops do not have any internal damping, which restricts their efficiency. To gyrate a conventional hoop about the hips requires considerable work because the needed rotational speed is quite high. 
     Another drawback of previous hoops is that they are too light. The conventional hoops can be made of heavier-walled plastic tubing, but this is expensive and makes for difficult bending into the required circular form. 
     One previous hoop designed by the present applicant had contained water in an attempt to solve these problems, but this earlier liquid-filled hoop was not successful. The water leaked out and the hoop did not function properly. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a play and/or exercise hoop which has internal damping. Another object is to make a hoop which has greater mass without the use of heavier and more expensive materials. Still another object is to provide a hoop with internal inertia shifting. 
     These objects are met by partially filling a hollow tubular hoop with water or some other liquid, preferably one at least as heavy as water. The trapped water increases the mass, provides internal damping of any motion (especially axial acceleration or deceleration), and leads to novel motions because of the shifting of the water inside. 
     Unlike the previous water-containing hoop, the circular hoop of the present invention allows the trapped water or liquid to freely circulate all the way around the hoop circumferentially; thus if the hoop is rolled slowly, the liquid remains in the lower part and the rolling motion of the hoop is smooth. The flow of the water around the circumference of the hoop must not be blocked if desirable toy dynamics are to be achieved. 
     The water filling of the present invention makes the typical HULA-HOOP hip gyration in which the hoop remains elevated, and similar gyrations, easier. This is because the water decreases the rotational speed needed in the hip motion. Centrifugal force causes the water to shift as the circular hoop is rotated or gyrated about the hips, permitting a slower, easier and less tiring rotation. 
     The water-tight hoop joint of the present invention includes a coupling tube, disposed inside the outer main hoop tube at the joint, having a large bore through which the liquid can freely flow. The coupling tube is preferably adapted for a seal, such as an O-ring, to be placed between the outer wall of the inner coupling and inner wall of the outer hoop tube. 
     The present invention also contemplates a method of making such a hoop and the construction of such a hoop, so that the hoop is both inexpensive and leak-proof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects and the nature and advantages of the present invention will become more apparent from the following detailed description of an embodiment [s] taken in conjunction with drawings, wherein: 
     FIG. 1 is an exploded perspective view of the invention. 
     FIG. 2 is a perspective view of an alternative coupling. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows two ends of a circular hoop tube  10 , the ends being labeled as  11  and  12 . The ends are shown in exploded view, separated to show the internal coupling tube  20 , which is covered when the two ends  11  and  12  are butted together and the hoop is completed in the form of a hoop tube joint. The hoop tube  10  extends in a full circle (not shown) between its two ends  11  and  12 , as is conventional in hoops. 
     The hoop tube  10  is semi-rigid and is preferably made of extruded polyethylene or polyethylene terephthalate glycol (PETG), a type of saturated (i.e. thermoplastic) polyester, having a wall thickness for example of 1 mm. Preferably, the outside is covered with a decorative pattern such as iridescent sparkles  17 , of the type employing diffraction rulings to cause scintillating colors. This decoration  17  may be applied in the form of a plastic film  18  wrapped around the hoop tube  10  and adhered to its outside surface. Such films having diffraction rulings may be produced by holographic printing. Other types of exterior decorations are also possible, but the iridescent-like effect produced by the diffraction rulings is particularly striking and therefore most desirable. 
     A liquid  30  partially fills the interior space  15  of the hoop. Preferably the interior space  15  is filled more than ⅙ full, and less than half full, of the liquid by volume. Still more preferably, the hoop is between ⅙ and ⅖ full of liquid; and an optimum amount of liquid is approximately ¼ full. Less full than ⅙ provides an insufficient effect, and more full than ½ overcomes the desirable inertial shifting effect. 
     The liquid  30  is preferably water, which may be treated to resist bacterial or fungal growth, to resist freezing, and/or the like. Preferably, the water  30  is scented with a perfume or the like so that the hoop emits a pleasant odor; or the pleasant scent-producing chemical may instead be incorporated into the film  18  or the hoop tube  10  itself. 
     Other freely flowable materials may be used in place of the liquid  30 , although water is preferred as indicated above. For example, ball bearings, most desirably relatively small ball bearings, either alone or together with a liquid, can replace the use of water alone. Other freely flowable materials can be routinely tested for suitability, with the objective that the freely flowing material will flow sufficiently quickly to that part of the hoop opposite, i.e. roughly 180° from, the part of the hoop which is in contact with the user&#39;s body during rotation, and with the further objective that the freely flowable material be able to pass quickly through the coupling tube, described below. 
     To couple the two ends  11  and  12  of the hoop tube  10  together, an inner coupling  20  is provided, preferably in the form of a hard, rigid tube. When the joint is made (not shown), the coupling  20  is roughly centered in the joint, so that the hoop tube ends  11  and  12  abut adjacent the approximate mid-point of the coupling  20 . In this position each of the two illustrated O-rings  41 ,  42  is on one side of the gap where the ends  11  and  12  abut. These O-rings prevent the water  30  from passing from the interior  15  to the joint where it can escape, so that the hoop is maintained watertight. The O-rings  41 ,  42  are preferably set into annular grooves  21 ,  22  in the exterior of the coupling  20 . However, the coupling tube  20  may be fashioned merely by cutting a short length of preferably hard plastic tubing having the appropriate outer diameter, and sliding O-rings over the ends to be held in place by friction. 
     An important feature of the present invention is that the water  30  is free to pass through the coupling  20 , and so a large diameter through-bore  25  is provided and the coupling  20  takes the form of a coupling tube. The bore  25  allows the water to flow circumferentially around inside the hoop past the joint, so that it does not pile up and ruin the dynamics of the finished hoop. In one embodiment, the inner diameter of the hoop tube  10  is 1.5 cm, and the diameter of the bore  25  is 1.1 cm, and in general the bore  25  should have a cross-sectional area no less than about half the cross-sectional area of the interior of the hoop tube  10  to provide sufficient pass-through of water past the bore  25 , especially in the case of hoop tubes having diameter bores no greater than 1.5 cm. However, as the hoop tube diameter increases, this rule becomes increasingly less important. 
     In those cases where the freely flowable material comprises or consists of solid particles, e.g. ball bearings, it may be desirable to increase the diameter of the bore  25  to more closely approach the inner diameter of the hoop tube  10 . If no liquid is present, then the problem of leakage is considerably diminished and there is no need to maintain the hoop water tight, which thus facilitates an increase in size of the bore  25  of the inner coupling  20 . In such a case, the wall thickness of the coupling  20  can also be more safely reduced. To further facilitate flow of solid particles into the inner coupling  20  so that such particles can then more freely flow therethrough, the ends of the coupling  20  can be tapered instead of extending radially as shown in FIGS. 1 and 2. 
     Once the joint is assembled (not shown) the ends  11  and  12  are preferably wrapped with tape  50  all around the joint, to assist in preventing joint separation. To cover the tape  50 , a label  60  may be applied. 
     FIG. 2 shows an alternative embodiment of the coupling tube  20  in which ridges  28  are molded into the exterior so that the seal and the coupling may be unitary. (Here, and in the following claims, “unitary” means formed in one piece, although possibly of more than one material.) These ridges  28 , co-molded of elastomeric material with the preferably hard coupling tube, act as liquid seals in place of the O-rings  41 ,  42 . The ridges  28  may be multiplied to form a labyrinth seal, and may also provide mechanical support to align the hoop tube ends  11  and  12  precisely, to avoid a lumpy hoop exterior; one wider central ridge (not shown) may be provided for this purpose. The ridges may be sloped to ease assembly and resist separation of the joint. The ridges may be used in conjunction with O-rings or other sorts of separate gaskets. 
     The hoop tube  10  and the coupling tube  20  may be glued, welded, or otherwise fastened, and such fastening may comprise a liquid seal. 
     The cross-sectional shape of the hoop tube may be other than circular, e.g. octagonal, rectangular, ellipsoidal, etc., without departing from the invention. The diameters of both the hoop and the hoop tube may also vary. 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means and materials for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention. 
     Thus the expressions “means to . . . ” and “means for . . . ” as may be found. in the specification above and/or in the claims below, followed by a functional statement, are intended to define and cover whatever structural, physical, chemical or electrical element or structure may now or in the future exist which carries out the recited function, whether or not precisely equivalent to the embodiment or embodiments disclosed in the specification above; and it is intended that such expressions be given their broadest interpretation.