US 3797788 A
Kite structure in which the airfoil surface is supported by integrally formed ribs and foam backing material against waving or flapping of the surface in flight.
Description (OCR text may contain errors)
United States Patent 1 1 1111 3,797,788 Beljer 1 Mar. 19, 1974 KITE STRUCTURE 3,284,033 11/1966 Ventre 244/154 3,292,883 12/1966 Curtis et a1. 244/153 R [761 Invent: Jan Bell", 9 3,357,660 12/1967 Condrashoff 244/153 R Pasadena, Callf- 91104 2,767,436 10/1956 Noland 61 a1. 244/154 ux  Filed y 17 1972 3,110,460 11/1963 Koonce et a1 244/153 R  Appl. No.: 272,130 Primary Examiner-Duane A. Reger Assistant Examiner-Paul E. Sauberer 52 us. c1. 244/153 R, 1334/15 AF Attorney, g r Fir i J Bachand  Int. Cl. 1364c 31/06  Field of Search... 244/153 R, 154; D3:6//1759A8l-3  ABSTRACT Kite structure in which the airfoil surface is supported 5 References Cited by integrally formed ribs and foam backing material UNITED STATES PATENTS against waving or flapping of the surface in flight.
3,128,974 4/1964 4 Claims, 5 Drawing Figures Teague, Jr. 244/153 R KITE STRUCTURE BACKGROUND OF THE INVENTION This invention has to do with kite structures.
Kite flying is an ancient pastime and many types of kites have been known. To my knowledge, kites have been built of fabric or paper stretched over a supporting frame.
The causes of kite failure to fly well are often subtle; one cause is the turbulent air flow condition at the airfoil surface of the kite, generated by surface discontinuities and, particularly waving or flapping portions of the airfoil surface. These are most often encountered at the long lateral edges of the airfoil material, between the ribs. Ribs being heavy, only a limited number and size can be employed. In the past, therefore, such edges have been supported with string which thus forms a perimetrical support for the airfoil material, but the central fabric area between the ribs remains free to flap.
SUMMARY OF THE INVENTION It is a major objective of this invention to provide a new kite structure, one in which the airfoil surface is universally supported, against wrinkling, undulation and other localized turbulence-inducing movements of the airfoil in the wind-carried condition of the kite.
There is provided, in accordance with the invention, to meet the foregoing and other objectives to become apparent hereinafter, a lightweight kite structure in which the airfoil surface is rib-supported and between the ribs supported by a plastic foam backing, integrally formed with the surface.
DETAILED DESCRIPTION FIG. I is a front view of the kite of the invention.
FIG. 2 is a side cross-section view of the kite taken along line 22 of FIG. 1.
FIG. 3 is a rear view of the kite showing the rib construction.
FIG. 4 is a transverse view of the kite taken along line 44 of FIG. 1.
FIG. Sis a view taken along line 5-5 of FIG. 3 showing details of the surface backing portion and storing attachment means.
With reference to the drawings. in FIGS. 1 and 2 lightweight kite structure 1 according to the invention is shown comprising sheet material 2 defining at one side an airfoil surface 3 which is held into the wind to effect flying of the kite, controlled by string 4 connected to bridle 5-which is anchored to the kite by upper and lower connectors 6 and 7 spaced along the center rib 8 (FIG.3). With reference to FIGS. 2, 3 and 4, the kite structure 1 comprises plural intersecting ribs. namely center rib 8, upper cross rib 9 having right and left portions 91, and 92, respectively and lower cross rib 10 having right-and left portions 101 and 102 respectively. The upper and lower cross rib portions 91, 92, 101 and 102 intersect the center rib 8, e.g., in a cruciform relation, or more particularly, these rib portions intersect the center rib at acute angles, e.g., upper rib cross portions at angle a equal to about 70 and lower cross rib portions at angle b equal to about 45. both to the major length 11 of the center cross rib. The ribs 9 and 10 may be-edge and end beveled, e.g.. at 12 to reduce weight. 7
The sheet material 2 is laterally and longitudinally extended. supported by the ribs 8, 9 and 10. Sheet material 2 has a surface portion 3 (FIG. 1, FIG. 5) identified above defining the kite airfoil surface at 13 and a surface backing portion 14 (FIG. 5) integrally formed with the surface portion and the ribs as well, and comprising a foamed plastic. The surface backing portion 14 as shown, is coextensive with the sheet material surface portion 3 and having a stiffener, as described below, it is adapted to support the surface portion 3 and thus airfoil surface 13 between the rib locations against wrinkling, undulation, and similar localized turbulenceproducing movement when the kite is flying.
The sheet material surface portion 3 and backing portion 14 may be formed to have the kite airfoil surface curved longitudinally and transversely of the center rib, See FIGS. 3 and 5, as is typical in kite structures.
The specific shape of kite structure 1, Le, the shell effect, is merely illustrative. Circles, diamonds, ovals and other regular and irregular shapes as well as traditional skewed diamond shapes may be used. When the lower end is narrow, the lower rib 10 may be foreshortened or omitted altogether.
The kite structure I is designed to be readily molded by injection molding from pellets or compression molding or vacuum molding techniques from sheet, or a combination of these techniques. In a preferred mode. styrene polymer beads impregnated with a blowing agent are confined in a mold and heated to both expand and fuse to one another in a manner known per se. Suitable densities of the resulting foam will be between 3 and 25 pounds per cubic foot. A final sheet material thickness of 50 to mils will be sufficient. The surface portion of such sheet material will typically be from 10 to 25 percent of the sheet material thickness e.g., from 5 to 15 mils in a structure having a sheet material of 50 m 150 mils, or more or less,
The essential feature is the provision of a suitable airfoil surface 13 backed with a suitably rigid backing portion 14. Because of its foamed nature, the backing material is lightweight, and quite rigid for its weight. This is due to the beam effect realized from the low density, relatively thick core of the sheet material, bonded to the skin portions, the outer of which defines the airfoil surface.
Suitable plastics for formation of the kite structure include the polyolefins, e.g., polymers and copolymers of ethylene, propylene, butene-l styrenes, vinyl esters, e.g., vinyl acetate, propionate, or butyrate and vinyl chlorides, and like thermoplastic resins having sheet forming capabilities, which can be foamed in molding by inclusion of blowing agents such as pentane, and various of the azo blowing agents known 'tothe art.
1. A lightweight kite structure carrying a string connector and comprising an integral molding of plastic foam generally cruciform ribs and plastic foam sheet material laterally and longitudinally extended in ribsupported relation. said ribs including a center rib adapted to support said string connector, a first cross rib and a second cross rib in spaced, opposed relation to the first cross rib, said first and second ribs each having left and right portions intersecting the center rib at an acute angle to the center rib major length, said sheet material having a surface portion curved longitudinally and transversely of the center rib and defining the kite a density between 3 and 25 pounds per cubic foot.
3. Kite structure according to claim 2 in which the sheet material has a thickness of from 50 to I50 mils.
4. Kite structure according to claim 3 in which said sheet material surface portion has a thickness from 5 to 15 mils.