US 2398745 A
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April 5- Q D. c. JALBERT I 2,398,745
KITE BALLOON Filed Aug. 51, 1945 4 V 3nbentor DQMINA C. JALBERT I attorney.
Patented Apr. 16, 1946 KITE BALLOON Domina C. Jalbert,,Belmont,. Mass, assignor to Dewey and Almy Chemical Company, North Cambridge, sctts Application August Mass., a corporation of Massachu- 31, 1945,;S erial 116,613,887
This state. relates to kite balloons Al- -though, as will be apparent, the balloonmay be adaptedformany uses and can be made in nu-' merous sizes, it is particularly designed for use wherebconservation of weight in l the balloon structure is of paramount importance. Weight conservation is an absolute necessity insea-res "cue balloons, since the hydrogen capacity of any, generatorcthat may be apart of an aviators -ditching kit is strictly limited. The largest practical size of the sea-rescue gas generator is 40 cubic feet of hydrogen. Considering the-gross lifting capacity of hydrogen as 32 grams per cubic footjthe static or hydrogen-created lift is but 1280 grams. Therefore, for the balloon to rise at all the weight'of the flying line and all of the balloon structure cannot exceed 1280 grams and should not exceed more than 65% of the figure because residual or free lift-of.
the balloon is required for effective service.
vSince the instant invention successfully meets ;the weight requirements of sea-rescue balloons,
that model will be described as the preferred example.
One of the most important requirements in searescue balloons is that they shall fly independently of weather conditions for a long time, for
it frequently happens that the occupant of a life it to act like a kite, and the lifting or kite effect,
which conveniently is called the dynamic lift, of even light Winds is greater than the static lift due to the gas. The pressure of the wind on the balloon envelope not equipped with lifting-fins and anchored (i. e., flying captive) forces it progressively down toward the sea as the wind rises.
A'forty cubic foot spherical balloon is blown down to'the sea in winds of about 35 to 45 miles an hour. But when the balloons are equipped with lifting-fins, the blow-down effect of wind pressure is counteracted by wind lift, or kite effect, and the balloons may ride even higher in E'stiff winds than in a light breeze.
The most common kite balloon, the barrage balloon, conserves its hydrogen supply and maintains its shape while flying by means of a balloonette, a gas-proof diaphragm, which is at- "tached to the lower interior walls of the balloon in' such a manner that air may be scooped into 'theballoonette', which swells up inside the balloon envelope and compresses the hydrogen gas in the balloonzabove the diaphragm. When the temperature rises or the external pressure falls and the hydrogen gas-expands, the balloonette .is pushed downwardly by the hydrogen andsome ,airis expelled, In this manner, fixed volumes of hydrogen are used to lift the balloon, yet the danger that a fixedvolume of hydrogen will build up such-a pressure that the balloon envelope will be'ruptured iseliminated;
..; i-The weight limitations imposed on sea-rescue balloons makedt impossible to use this effective --in flight,
device. .A further difliculty has been that when ajbarrage balloon'has been reduced in dimensions'to 40 cubic feet capacity its stability practicallyjvanishes; it lunges wildly in'the air in all but the very lightest of winds, makingit unsuitable for an antenna support.
My present kite balloon avoids these difficulties. It will fly without lunging or yaw; it will rise indead calmsand fly in any wind up to a violentblow'; itis not forced down by thewind like a balloon, but will climb into the wind like -a kite andconsistently will maintain a high angle to the horizontal, independent of the wind, It 'may'be packed in a package of approximately cubic inches; and its total weight, is below '750grams. It will support a metallic antenna 400 or 500 feet long weighing 300 grams for sending, and receiving signals on the international distress wave length and, even when so loaded, will exert a net free lift of more than 250 grams. This is sufficient to launch the balloonstraight up between trees, a very valuable feature in jungle or tropic rescue work.
The invention will be apparent from the specification and from the drawing in which: t
Figure 1 is a perspective viewof the balloon Figure 2yis atop view of the balloon, and Figure 3, is a section through the balloon on the line-3-3 of Figure 2.
In carrying out my invention, I provide a balloon envelope I 0 which is approximately ovoid in which are sewn to the casing along certain of the lune seams 2!. These fins form the horizontal lifting surfaces and thevertical stabilizing surfaces and are held extended by light struts 22, of wood or light metal tubing, which are anchored at their outer ends in small tape pockets 23 sewn on the tips of the fins and havetheir inner ends held on the envelope by cloth ockets 24 sewn on the lune seams. To prevent an air pocket forming, thestruts 22 which support the lifting-fins i1 and I9 should be located on the under side of the fin, as shown in Figure 3.- Cloth rigging loops 25 are sewn on certain lun'e seams between the vertical and horizontal fins to provide anchorage for the guys 26-26, which are stretched between the loops 25 and the tips of the fins. Each strut 22 is of a'length equal to the radial extension of the adjacent fin, but the guys are so proportioned that the pair of guys supporting one fin are not long enough to permit'the end of the strut'to move out to the normal periphery of the envelope. Instead, the base of the strut lies at a point well inside the normal periphery and the envelope swells out on each side. The fin, therefore, springs from the envelope along a substantial crease or depression when the envelope is fully expanded. If, for example, the diameter of the balloon is 39" when fully inflated, the radial dimension from the central axis to the base of any strut is preferably about 17 inches.
This kite balloon flies on the lifting-fins I! and I9 and is held on course by vertical stabilizingfins l8 and 20. It is quite necessary that the lifting-fins l1 and I9 be symmetrical/but it is not necessary, although it is convenient, to make the stabilizing-fins the same size as the lifting-fins. Furthermore, it is not necessary that stabilizingfin l8 be the same size as stabilizing-fin 26, the requirement being merely that sufficient vertical fin expanse be given to prevent yawing and to hold the nose of the balloon into the Wind.
The balloon'is attached to the antenna or to the flying line by means of a harness 2'! which is made up of six cords extending from small loop patches 28 sewn on the lune seams 2| to a concentration ring 29 located beneath the balloon. The longest pair of cords stretches from the concentration ring to symmetrically spaced loops located beneath the fins near the stern of the bal-' loon. The second pair stretches between the rin and loops located forward of the fin struts and adjacent the maximum diameter of. the envelope. A third and the shortest pair: of cords stretches from'loops adjacent the nose to the'concentration as" follows.
After hydrogen has been admitted through the valve I6 by inserting the nozzle of the sea-generator into the valve and the balloon has been inflated to assume the cross-section shape shown in Figure 3, the externally directed pressure of the hydrogen puts the balloon envelope under tension and pushes the struts out radially, thus maintaining the fins straight, stiff, and in flight condition. The hydrogen diffuses :through the envelope slowly during flight. Until the hydrogen has diffused to such a degree that the guys 26 become slack and consequently the gas can exert no effective outward thrust upon the struts, the fins remain taut. The balloon will be lifted by the wind until the fins go slack; consequently, once the rate of diffusion of hydrogen through the bladder is known, the time during which the balloon is capable of wind-borne flight may be preadjusted by the length of the guys. This determines the amount by which the struts are pushed inward radially in the initial inflation.
The valuable feature of the invention is that only the lightest of struts and guys are necessary to hold the fins extended (the struts and guys have a total weight of no more than grams) the gas itself is made to hold the fins out stiff and extended for a very long time.
When the hydrogen has diffused to a point where the guys slacken and the fins are no longer stiff, the balloon may be hauled down. If more hydrogen is available, the original flight characteristics of the balloon are completely restored by an additional hydrogen charge; but if, as is more usual, no hydrogen is available, the balloon may be inflated with air. Obviously, inflation with air does not change the residual static. lift due to the hydrogen, but it will restore the dynamic lift because the fins will then be held in taut condition again. Since these balloons will fly as very effective kites in winds of two or three miles an hour and upwards, and since winds .of this force are almost always encountered at sea, the effective life of the antenna support is extended well beyond the life of the hydrogen charge.
The balloons are stable in flight, maintain the antenna at a high angle to the horizontal independent of wind velocities from 2 or 3 miles an hour to storm violence and have much greater free lifts than other kite-balloons of the same capacity, which must depend on heavier structure to support the lifting and stabilizing surfaces. These advantages are in addition to their long service life, for a volume of hydrogen represented by the volume of the depressions in the envelope must diffuse through the envelope before the flight of the balloons is affected, and diffusion of this large quantity is a matter of many hours.
1. An inflated kite balloon having a flexible envelope, on which rest radially outwardly extending lifting-fins the outer ends of which are positioned by flexible guys of such length that some portion of the radial extent of the fin lies inside the normal circumference of the inflated balloon envelope so that the fin restsiina depression when the envelope is fully inflatedjand loss of inflation will not cause the guys toslacken.
2. An inflated kite balloon having a flexible envelope, on which rest radially outwardlyextendinglifting-fins the outer ends of whioham positioned by flexible guys of such. lQn th-that some portion ofthe radial extent ofxthafinp es inside the normalcircumferejnce of the? inflated balloon envelope so that the fin rests in a depression when the envelope is fully inflated, the gas pressure within said balloon acting to push the fins outwardly and to hold the guys tight until the gas pressure drops below a predetermined point.
3. An inflated kite balloon having a flexible 4. An inflated kite balloon having a flexible envelope provided with radially outwardly extending flexible fins for lifting and stabilizing the balloonin captive flight, struts holding the fins extended which are positioned by flexible guys, some portion of the radial extent of the strut lying inside the normal circumference of the inflated envelope so that the fin springs from a depression when the envelope is fully inflated, the gas pressure within said balloon acting to push the struts outwardly and to hold the guys taut until the gas pressure drops below a predetermined point.
DOMINA C. JALBERT.