US2988309A - Inflatable kite - Google Patents

Description

June 13, 1961 R. A. POHL INFLATABLE KITE Filed March 5, 1958 IN VEN TOR.

RUSSELL A. POHL ATTORNEY United States Patent 2,988,309 INFLATABLE KITE Russell A. Pohl, St. Paul, Minn., assignor to General Mills, Inc., a corporation of Delaware Filed Mar. "3, 1958, Ser. No. 718,821 8 Claims. (Cl. 244-153) The instant invention relates to kites, and more specifically to inflatable kites of non-rigid construction. Kites may be constructed of numerous materials which when inflated possess relative rigidity without the employment of added stiffening or support members. Such kites may be transported to a flight site in an uninflated condition, filled with air or lifting gas, and sent aloft.

In my. invention the kite is constructed of a thin plastic sheet material sealed to produce an inflatable outer circular portion. The kite is shaped by inflation which forms the entire structure into an airfoil section which upon exposure to a wind stream has aerodynamic lift and stability.

'It is therefore an object of my invention to provide San inflatable kite having an integral stress beam construction which imparts suflicient strength and rigidity .to its kite to produce aerodynamic characteristics without the employment of rigid stiffening or support members.

Another object of my invention is to provide a substantially circular kite formed of a plurality of plastic sheets and provided with an inflatable circumferentially shaped stress beam for providing substantial rigidity for the kite.

An object of my invention is to provide a circumferentially shaped inflatable plastic kite having at least two concentric seams within the outer edges of the kite to provide an outer inflatable portion, and an inner membrane section.

Another object of my invention is to provide a circular plastic kite having at least two concentric compartments and providing at least one of said compartments with means therein to admit air thereto.

An object of my invention is to provide an inflatable plastic kite having improved flight characteristics by the i provision of an airfoil surface formed by the inflation of a portion of said kite. 1 Other objects and advantages will become apparent in the subsequent specification and the appended drawings -in which:

. FIGURE 1 is an elevation view of the circular kite; FIG. 2 is a perspective view of the inflated kite of FIG. 1 in flying position;

. FIG. '3 is a sectional view taken along line 3-3 of FIG. 2; FIG. 4 is an elevation view of a modified kite of FIG.

FIG. 5 is an elevation view of a further modification of the kite of FIG. 1;

FIG. 6 is a sectional view of the kite taken along line together at their outer edges by a heat seal 16. The tabs 8, 10, and 12 are formed by sheets 4 and 6 and are also sealed along their outer edges. The inflation tube 14 is sealed only on each side to provide on opening 18 for .ef the kite ismaintained.

Patented June 13, 1961 inflating the kite. A seam 20 continuous and concentric to seam 16 separates the kite into an inflatable portion B and an uninflatable portion A.

Gas admitted through the opening .18 of the inflation tube 14 fills compartment B causing it to inflate. When compartment B is fully inflated, the inflation tube 14 is tied or sealed off to retain the gas within the kite.

The kite 2 when inflated does not necessarily assume a planar configuration but rather assumes a shape with camber and dihedral as seen in FIGS. 2 and 3. It is this camber and dihedral that provides an elfective airfoil for the kite.

Upon inflation the kite deforms into a configuration forming an air foil section and thereby imparting flight characteristics to the embodiment. By way of further explanation, gas is admitted to the inflation tube 14 to inflate compartment B to form a circular stress beam of relative rigidity.

The inflated compartment B exerts radial force through seal 20 on compartment A. These forces are held in restraint by compartment A and in so doing compartment A becomes taut. The radial forces in compartment A are relatively uniform circumferentially providing the inflated member B maintains its circular shape. Since the balance of forces of compartments A and B is critical and the entire embodiment is in a semirigid state, the circumferential stress beam B will deform somewhat .elliptically and yield in both directions normal to the plan view. This deformation normal to the plan view is a result of the entire embodiment being unable to maintain radial forces in compartment A in a steady state. Upon deformation of compartment B in a direction normal to the plan view the stress is partially relieved in one direction in compartment A. When the stress is maintained along the theoretical line 30, which .is the roll axis of the kite the stress is partially relieved normal to line 30 and the inflated compartment B is deformed as shown in FIG. 2. It can be seen that areas 32 and 34 of compartment B are deformed normal to the plan view toward the attached bridle. Furthermore the areas adjacent to the tie tabs 8 and 12 deform in a normal direction to plan view away from. the bridles of attachment. The deformation in compartment B results in the formation of material folds adjacent to tie tabs 8, 10, 12 and the inflation tube.

Thus the aerodynamic characteristics are established by inflation which deforms compartment B. Improved lift is provided by the camber of the kite. The camber is realized by passing an imaginary straight line through tab 10 and inflation tube 14 and the camber will be the bowing away of the kite from the said imaginary line.

Aerodynamic stability is obtained from the dihedral angle of the kite. This dihedral can be seen in FIG. 2 wherein the fold at tab 10 is the vertex of the dihedral angle D formed by the deformation of compartment B upwardly from the bridle attachments 8 and .12.

The present kite, inflated to the position shown in FIGS. 2 and 3, could be pressurized until it again lies fully inflated within a substantially flat plane. However to inflate the kite 2 sufiiciently to effect its return to a normally flat plane requires a higher internal pressure and greater stresses are created in the material than in the present kite with loss of flight characteristics.

Considering now the manner in which the kite is to be flown. The kite 2 is flown by attaching a bridle 24 to the tabs 8, 10 and 12 and the inflation tube 14. A tail 26 is also secured to the inflation tube 14 and may be used to. seal ofi the end thereof when the kite 2 is fully inflated. By adjusting the angle of attachment of the bridle 24, and by controlling the dimensions of the tail 26 stability 'tube 14a.

Asstated previously the kite 2 does not require a high internal pressurization. This allows inflation of the kite in the simple manner of merely blowing into tube 14 and no bulky inflation equipment is required. Additionally the-kite requires no rigid I stiffening members and-.the resultant deformation by inflation imparts an efficient airfoil to the kite.

-According to conventional wind'lift wing theory the lift created is 'due partially to flat plane lift and partially to venturi-effect. The lift caused by'flat plane theory is the impaction of flight stream air on the front surface of the kite which is inclined at an angle to the wind stream. When flying a kite at an angle to the wind, the wind stream vector direction is broken into two components, 'a vertical and a horizontal vector. It is the vertical vector which imparts lift to the structure. 7

The lift caused by venturi action is due to the partial vacuum created on the upper (back) surface of'the kite due to the higher velocity of the air stream over the back surface compared to the velocity of the air stream on the front of the kite.

The camber which is formed by the circumferential stress beam deformation increases the venturi action thereby increasing the width of the kite. Stability is maintained about the roll axis 30 such that when the kite tends to roll in one direction the down side of the kite has a greater lift area than the up side lift area in relation to the wind stream therefore causing counter rotation about the roll axis to return the kite to normal position.

The deformation of the inflated circumferential stress 'beam to impart dihedral to the air foil improves the stability by reducing the up side lift area and increasing the down side lift area during a roll.

Referring now to FIG. 4. The kite 30 is somewhat identical in construction to the previous embodiment except for a plurality of perforations indicated by the numeral 32. These perforations provide air spillout when 1 the kite 30 is flown during adverse wind conditions and assist in maintaining the stability of the kite. For example, while the previous embodiment canbe flown during wind conditions of from 6 mph. to 8 mph, the present embodiment can be flown during fluctuating wind conditions of up to 12 mph. since greater air spillout is provided.

In addition to the above embodiments the kite may be constructed as shown in FIGS. 5 and 6, wherein inflatable compartments A and B are provided.

Referring first toFIG. 5, the kite 32a is substantially the same as in the previous embodiments except that the total area of the kite is inflated. For example, seams 16a and 18a divide the sheets 4a and 6a into two compartments A and B which are inflatable through the inflation The only difference in the seams 16a and 18a and those of the kite 2 of FIG. 1 is that an opening 17a is provided in seam 16a adjacent the inflation tube 14a. Thus both compartments are inflated from a single opening. As will be noted from the drawing, tabs 8a, 10a, and 12a are also provided on the kite 32a and facilitate attachment of a bridle to the kite.

.Referring now to FIG. 6, the kite 30a when inflated assumes generally the configuration of the kite 2 of FIG. 3. It will be noted, however, that compartment A, when inflated, extends slightly forward at 6a somewhat more than the previous embodiment. While this slightly reduces the efficiency of the airfoil, greater over-all strength is afiorded to the kite 3001 by this inflation.

As stated earlier the general line of tensioning which occurs in the central compartment of the kite of my invention does not always occur in the relationship indicated by the line 35 of FIG. 1. For example, the line of tensioning may occur in an angular relationship relative to the inflationtube. Therefore in the previous embod'iments it would be necessary, in some instances, to manually bias the deformation in" the desired direction in order to achieve the configuration shown. However in the ensuing embodiment I provide a means which will positively assure the desired configuration of the kite.

Referring now to FIG. 7 the kite 40 of FIG. 7 is constructed of plastic sheets 42 and 44 which are seamed together to form a'circular kite substantially identical to the previous embodiment. The kite 40' also has integral therewith tabs 46, '48, and 50 and an inflation tube'52. Circular seams 54'and 5'6 secure the sheets 42 and 44 together to form compartments C and D and a radial slot 43 is provided in compartment 0 to allow for adequate "air spillout when the kite '42 is flown. As will be noted from FIGS. 7 and 8 the sheet 42 is only a partial sheet being generally of a doughnut shape suflicient to form the circular compartment D. By constructing sheet 42 in this manner a resultant savings in material is achieved and a much lighter kite is produced.

Looking now at the outer seam 56. The seam 56 secures the sheets 42 and 44 together along their outer peripheral edges and is provided with concave seams or indentations 58 adjacent the tabs 46, 48, and 50. These indentations perform an essential function in the: present embodiment for as pressure is admitted to compartment D they tend to effect the bending of the material of sheet 42 along the dotted lines 60 to control the configuration of the kite 40. By positioning a third concave indentation adjacent tab 48 as shown a third bending occurs on the rear surface of the kite and a shouldered effect is created generally along line 60 adjacent the tab 48.

Thus I have in the drawings and specification presented a detailed disclosure of my invention; while I have described particular embodiments it is to be understoodthat modifications and changes will occur to those skilled in the art, and therefore I intend to be limited only by the scope of the appended claims.

Now, therefore, I claim:

1. In an inflatable kite, two normally flat circular similar sections of flexible plastic sheet material, each such sheet having the same area, a first airtight seam securing the sheets together along their outer-matching edges, a second airtight seam securing said sheets together concentric of said first seam providing an inflatable portion between said seams and an uninflated portion in the center of said kite, an inflation tube integral with said sheets for admitting a fluid to said inflatable portion, whereby admission of the fluid to said inflatable portion produces an air foil having both dihedral and camber.

2. In an inflatable kite, a plurality of normallyflat circular sections of flexible plastic sheet material of equal size including tab portions secured together at their outer edges by a first airtight seam extending around the outer edges of said sheets, a second airtight circular seam spaced from said first seam concentric therein .dividing the kite into an inflatable portion and an uninflatable portion, an inflation tube integral with said inflatable portion for inflating said inflatable portion, whereby inflation of said inflatable portion produces a dihedral and a'camber in the inflatable portion and tensions in said uninflatable portion.

3. In a circular inflatable kite, a' first sheet of normally flat circular flexible plastic material, a second normally flat circular flexible plastic sheet alignable circumferentially with said first sheet and provided with a circular opening concentric of said sheets, the outside diameter of said second sheet being the same as the diameter of said first sheet, a first airtight seam securing said sheetstogether at their outer circumference, a second air tight seam securing the inner edge of said second sheet to said first sheet to provide a circular inflatable portion anda singlesheet uninflatable portion, and an inflation tube integral with said circular inflatable portion for'in'flating said inflatable portion with a gas, whereby inflation of said inflatable portion produces an air foil on saidkite having'a compound curvature.

provided at the outer matching edges of said first and second sheets, one of said tabs being located at the front of the longitudinal axis of said kite, the other two said tabs located on the transverse axis of said kite, said transverse axis tabs being partly defined by said first seam to provide a seamed surface inward of said outer matching edges to facilitate forming a camber when said inflatable portion is inflated.

5. The combination of claim 4 including an attachable tail means for closing of said inflation tube for maintaining inflation of said inflatable portion.

6. An inflatable kite constructed of a plurality of substantially circular normally flat flexible plastic sheets of equal size, a first air tight circular seam securing the sheets together along their outer circumferential edges, a second air tight circular seam spaced interior of said first seam and concentric therewith forming a stress beam compartment, an inflation tube integral with said stress beam compartment for inflating said stress beam compartment, the relative diameters and locations of said first and second seams insuring inflation of said stress beam to a curved shape and providing for said kite having an aerodynamic shape with both camber and dihedral.

7. An inflatable circular kite constructed of similar circular sections of normally flat flexible plastic sheet material, a first air tight circular seam securing the sheets together along their outer matching edges, a second air tight circular seam within said first seam concentric therewith dividing the kite into a first inflatable compartment and a second uninflated compartment, an inflation tube integral with said sheets for inflating said first compartment and a plurality of perforations in said second Compartment adapted to provide air spillout when said kite is flown, the relative diameters and locations of said first and second seams insuring inflation of said inflatable compartment to a curved shape and providing both camher and dihedral in said kite.

8. An inflatable circular kite constructed of similar circular sections of normally flat flexible plastic sheet material of equal size, a plurality of tabs integral with said sheets and spaced apart around the circumference thereof, a first air tight circular seam securing the sheets together at their outer matching edges, a second air tight circular seam within said first seam concentric therewith dividing the kite into two compartments, a concave seam adjacent each of said tabs extending inwardly toward said second seam, and an inflation tube integral with said sheet material for inflating said kite, the relative diameters and locations of said first and second seams insuring inflation of said kite to aerodynamic shape having both camber and dihedral.

References Cited in the file of this patent UNITED STATES PATENTS 1,328,848 Ramauge Jan. 27, 1920 1,529,076 Marchessault Mar. 10, 1925 1,572,187 Cooper Feb. 9, 1926 1,929,005 Rolkerr Oct. 3, 1933 2,486,158 Haas Oct. 25, 1949 2,733,880 Burrell et a1 Feb. 7, 1956 2,743,510 Mauney et a1 May 1, 1956 2,769,605 Sparkman Nov. 6, 1956 2,824,589 Neisler et al Feb. 25, 1958 FOREIGN PATENTS 215,241 Germany Oct. 23, 1909

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