US2693924A - Parachute canopy structure - Google Patents

Description

Nov. 9, 1954 Filed Oct. 22, 1949 P. FRIEDER ET AL 2,693,924

PARACHUTE CANOPY STRUCTURE 5 Sheets-Sheet 1 FIG. 2

INVENTORS. LEONARD R F RIEDER By WALTER S. FINKEN W 8. MM

ATTORNEY.

Nov. 9, 1954 L. P. FRIEDER ET AL 2,693,924

PARACHUTE CANOPY STRUCTURE Filed Oct. 22, 1949 5 Sheets-Sheet 2 INVENTORS. LEONARD n FRIEDER BY WALTER s. FINKEN WSW ATTORNEY.

1954 L. P. FRIEDER ET AL 2,693,924

PARACHUTE CANOPY STRUCTURE Filed Oct. 22, 1949 s Sheets-Sheet :5

INVENTORS. LEONARD F. F RIEDER BY WALTER S. F'INKEN WSW ATTORNEY.

1-954 7 l. P. FRIEDER ETAL 2,693,924

PARACHUTE CANOPY STRUCTURE Filed Oct. 22, 1949 5 Sheets-Sheet 4 FIG. I6

INVENTORS. I LEONARD P. FRIEDER I40 I35 WALTER S. FINKEN' BYW 3W ATTORNEY United States Patent 3, 2 PARA'CHUIE 'CANOPY STRUCTURE Leonard 7].. 'LErieder, Great Neck, and "Walter *S. =Finken, ;Brooklyn, Y., tassignors, by mesne assignments, to :General Cilextile Mills, Inc., New York, N. Y., 'a cor- ,porafion ;of dhelaware Application .Octoher 22, r1949, aSerial. 1N0. 122,9 62 15 Claims. v(c1. 24,4 1 45.

.Thisinvention relates to-parac'hutes andtingan important spec1fic :aspect, ;to parachutes of 'a truly "hemispherical shape, 1. .e. wherein :the load-retarding canopy is .ifashioned that :when extended and operative *to retard -a descending load brother-object moving through'a fluid med1um,l1t.;assumes asubstantially hemispherical contour. A particularly important :object of the invention is to ing more useful control -:of the forces ari'sin'g in the adeployment and operation-"of the parachute, -and especially, amore effective utilization of such r'orces, --to assure the prompt :and complete opening of the canopy "upon its release. :By way of example of a hemispherical parachute .construction,suitable for embodimentoftheinveution,; reference :is vmade PIO -the convenient andeasily manufactured devices which are described and claimed in United States ;PatentfNo. 2,412,392grantedDecember 130, 194.6, on'the'applicatiomof'W. *S. Einken.

Parachutes with substantially hemispherical canopies have a number of importantadvantages,including 'certainty and stability ofsopening:anda remarkable stability and freedom :from oscillation-during :actual use e'. g. in descent with.loads:.of :any :character, animate :or inanimate. Although the ;princip'lestof the present invention may be'applied'to parachutesiofsany size :or (material, a specific object ;is :to .aiford .asstructure that lias improved operating characteristics (an'd'yetis comparatively-simple to manufacture) :in the icasetoftcloth :parachutes of'c onsiderable size, e. g. as distinguished fromasmall paper canopies or vthe like :used Ito zdrop ili-ght objects. Par-achutesdesigned :to .retard heavy loads or fspecifically to etfectsafe .dCSCBIItZOfYPLeISOIIIIl, .vehiclesaandseven aircraft (and including parachutes used to EIBtEII'd OI rest-abilize aircraft in rapidadownwardmotiom), have .a considerable range of diameters up to extremely large sizespand have a canopy which .is :customarilymadecf woven-textile r suitably selected .for lightness :of weight, strength and durability. As will .be more-;fully explainedlhereinbelow, special problems 'have :been discovered .to :be involved in obtaining optimum results with .a;canopy of truly hemisphericalshape, notablyiimthe larger sizes, and thevpresent invention is specifically designed zto overcome such problems.

Further. objects 2 are to, provide new, -strongert and more eifective parachute structure particularly when 2manufactored froma multiplicityofXpiecestof textile-or other fabric; and to afford a greater security of .opening ..or.a more rapid opening oftheparac'hutecauopy [when lit-is released, yet toavoid undue. shocknszsuc'hitimes.

Another specific object is .to aiford (improvements canopy structures of the sort ,enibracedhylthe aboveeited Patent No. 24121392, especiallylfor;thesituationofllarger sizes of parachutes and for the more ready adaptabilitytof the canopy'tomeet any of a variety o'frequirementsas-to porosity, weight of .fabric and wother,factonsgoverned;lqy the intendeduse.

To these and other ends an embodiment :of .the ,present invention is shown, purely by .way of example, .in .the accompanying drawings and .is described .hereinbelow, it being believed that the principles .and strueturahfeatures of the invention may .be teffectivelytdisclosed Lin -.an.illustrative manner, v.bysuch embodiment.

Referring to the'drawings:

Fig. 1 shows,somewhatdiagrammatically a hemishperical parachute-just releasedlhutnot lyetopenedtataall;

Fig. 2 shows tsucha parachutein.a arIiminasy.stage afford animprovedcanopy of=the type-described, embody- 2,693,924 Patented .Nov. .9 19.54

2 of opening, and in diagrammatic form, in the opening cycleg iEig. 3 is 1 an'enlar-ged, simplified view of the parachute, to illustrate certain pressure ;and velocityefiects;

Fig. -4 is perspective view-of aparachute canopy embodying the=present invention;

Fig. 5 is a.-fragmentaIy vertica1section showing various features act the fabric canopyin an enlarged, diagrammatictmanner;

:I- ig. 6 iis :adiagram :of the 'crown -partsof -the parachute o'fJFiga l, :before final assembly;

Figs. 7 ;and '8'are views of-the shroud line-connections which may beused.With:devicesof-thepresent invention, respectively showing such connections for the preliminary stageaoflFig. Z and the fullydeployed condition of Figs. 3 am: -4;

"Figs. .9 and .10 arediagrammatic verticalsecticns of the canopy :of Eigsa izand 5, :andtaken on the great circles marked "-/9-%9 and -1()--'10 .respectively in Fig. *4;

fig. 1 1 iis atdiagrammati'c, perspective view of another form :of parachute .canopvembodying .the invention;

Fig. '12 is an enlarged, :fragmentary plan viewcf "the crown.andadjacent-regionof the canopyof Fig. 11;

Fig. 51-3 'isra iview-similarto that of Fig. .12, .but showing an example :of "a rfurther istructural modification;

.:Fig. 514 :is aidiagrammaticuvertical section of .the; canopy of Big. ill'lntakenloniline 14-44 of Fig. 12;

ig. :15 is:a:view,.like 'Pig.:-8,. showing.:another arrangementcofsshroudilineeonnections; and

Fig. 16 is a diagram of a sequentiallymeleased arrangement :IOf parachutes, embodying .featuresof .the invention.

:13 or z-purposescof illustration, it will be assumed in Figs. 1'.to 4 iinclusivetthat aiload'lilis being dropped from an airplane or the :like silt a :considerable :altitude, .the load being suspended :by ishroud .lines .21 .from a parachute canopy ,ZZ ;oflhemispherical shape, viz. a canopy :formed ofta'spltnrility ofx-pieees-ofiabriossoiashioned and secured together iasto provide a substantially.hemispherical:shape when the canopy-has fullybloomed. Thus in Fig. .1 the loadrhas :justrbeenrreleasedand :the ;canopy .22 .ingaimore or less collapsed condition is vtrailing .above the load. In actualpractice, the canopyat .once begins to open, ;in some :part by virtue 'of entering the opening defined .by the chottom edge .24 lot ;the canopy, and in considerable part ,:as explained ;below, by virtue of the reduced or subatmosp'heric pressure created immediately above the canopyzasiit falls.

:luvthe'usualtcase. ofr'hemispherical' canopies ofv the character ito which ;the present invention is directed, the opening :action ainvolves deployment ;of ;the parachute through successive. shapes @to its final, hemispherical configuration shown ;at -26 in Figs. ,2 and 3. At first the parachute'openstot'a verticallywelongated, somewhat pearshapedarrangementas:shown.in solid lines designated 28:in:Fig..2. :Frorntthisconfiguration,wherein the upper or crown :portion fithhas :a ;more or less bulbous shape and =the hem'or Ebottom edge-24 ;is ;pulled together into a small circle, tthetcanopy-passes through intermediate stages'such as illldiCfltddiBt 32, wherein the bulbous part enlarges "and ithe :throat 34 (that leads to the edge 24) also sbegins ato-enlarge, :until the tfinal, fully open shape 2-6 :is ereached. EIn ttherabsence of ;proper .design of the hemispherical canopy, however, and notably Where the principles; of ;the :present :invention have not been utilized, a tendency {has :been meted for parachutes ;of this :type, particularly large ones, :to delay in "opening beyond the preliminary ;stages 12.8 or 52, :or sometimes even to remain in such :condition.

whileztheipresent improvements .are not necesarily restricted to zany-particular :theory v or rationaleof the various' phenomena Einvolved, reference may be now made 'to what we believe are the conditionsof pressurean'dother forces acting ..on such a :canopy, and to the manner in whichfthe structures. of the-inventiomis-understoodto control such forces for improved. and eminentl-y satisfactory results.

Referring more particularly to Figs. L2 and i3, Eit z-has been found ithatithfi ifabric at 1diiferent localities ;of ."the canopy .is subjected {to substantially didering .forces ;as the parachute :tends tocopen whileitiisbeing drawntdownwardl-y, through the .air, by the .action :of gravity on the successive stages load. Thus the fabric at the pole or center of the crown, designated A, appears to be subjected to the greatest stress by reason of the relatively large difference of barometric pressure between the inside and outside of the canopy at this place, in that the pressure outside, i. e. just above the canopy, falls to a much lower value than that which characterizes the air through which the parachute is dropping. That is to say, the rapid downward movement of the canopy, displacing the air, produces a very low barometric pressure above the crown location A. The circular or annular locality B, constituting what may be termed the lower boundary of the crown section, is subjected to similar stress, but of less magnitude than at location A, because the drop of barometric pressure is counterbalanced by the relative velocity head of the air through which the canopy is passing, i. e. considering such air as if it were moving upward past the canopy.

The portion of the canopy below the crown region BAB may be considered to be composed of an intermediate zone C and a lower or hem zone D, meeting at a horizontal circle 36 spaced above the bottom edge 24. In regions C and D there is also internal pressure in the canopy, especially when the latter is fully deployed, and there is also some stress on the fabric at the region C by reason of the aspirating or suction effect of the rapidly moving outer air (indicated by arrows 38 in Fig. 3), which may be considered to travel upward past the canopy. It is also understood that a region of somewhat high barometric pressure, schematically indicated at 39 in Fig.

3, eventually builds up at the mouth of the canop extending cone-like beneath it and functioning somewhat as the bow wave of a ship. The low pressure area above the canopy, i. e. over the crown BA--B, is also schematically indicated at 40 in Fig. 3.

At the outset of inflation, the downward displacement of the canopy forms the area 40 of lower barometric pressure than the air within the canopy. The region 40 thus causes, in effect, a suction lifting the fabric varying distances, in proportion to the extent of such suction or low pressure adjacent the outer surface of the canopy. The limitation to the bulbous shape is influenced by the gradu ation of the low pressure area 40 from a maximum at the center A to a minimum at position B where there is a velocity head due to the air streaming past the outer skin of the canopy. Within the bulbous section so formed, i. e. indicated at 28 in Fig. 2, the air is or at least tends to be of sub-atmospheric pressure itself; although there may be a tendency for air to enter thereafter through the equatorial opening of the canopy, it may not necessarily, or at once, be sufficient (in constructions not embodying the present invention) to complete the opening of the canopy. The requirement is not merely that the pressure inside the canopy equal or even slightly exceed the external pressure, but that there be a relatively considerable excess.

That is to say, it has been found that outward force must be exerted at regions below the crown, i. e. in regions C and D, in order to expand the structure to the full form 26. In performing this operation, a definite amount of work must be accomplished, since the extension of the hem or lower edge involves an elevation of the load relative to the canopy. Thus in Fig. 2 the load must be moved up, so to speak, from its solid line position to the dotted line position 20. This mutual re-positioning of the canopy and load is in part represented by the work in terms of friction which is done in drawing up the lateral supporting lines (or hem structure itself) at the lower edge of the canopy, for instance as illustrated in Figs. 7 and 8, and in part by the geometrical shortening of the theoretical center line 42 (extending from the canopy to the load) as the angle E between the shroud lines and the line 42 increases to the maximum value corresponding to full inflation. In an approximate or general sense, the work done in so displacing the shroud lines, and especially in lifting the load toward the canopy as required by the geometrical shortening of the center distance 42, varies in accordance with the sine of the angle E.

It will now be seen that since the energy required to complete the opening of the canopy is governed by sine B, such energy or load decreases with an increase of the length of the shroud lines, i. e. with a corresponding decrease in the maximum value of the angle E. While benefit to the rapid and effective blooming of the parachute is thus achieved by the use of relatively long shroud lines, there are limitations of space, weight and the like, as to the length of such lines for practical parachute assemblies,

and in any event there is a substantial minimum amount of work required by the second or later stages of the deployment of the parachute. T0 that end, i. e. of accomplishing such work, one particular problem is to provide suflicient outward force or pressure at regions C and D of the canopy to overcome the velocity head'of the air streaming upward past the outer skin of the canopy as designated by the arrows 44 in Fig. 2, it being remembered that the formation of the bulbous section 28 at the top is occasioned by the suction effect of reduced barometric pressure above it and that under such circumstances the inherent tendency of the interior of such bulbous section (far from affording a large super-atmospheric pressure) is to be characterized by a pressure condition which though higher than the region 40 is sub-atmospheric.

In accordance, therefore, with paramount features of the present invention, flow of air into and thence through the canopy is promoted and controlled, selectively in point of locality, so as to effectuate exertion of opening force upon the regions of the canopy below the crown, and preferably so as to coordinate the function of the conditions described above (which occasion or accompany the blooming of the bulbous portion 28) with subsequent etfects of air flow and displacement for most efficient performance in respect to the completion of the opening cycle. Under these circumstances, the parachute may have optimum characteristics of light weight and economy of manufacture yet possess fully adequate strength for the load it is designed to support at the desired speed of descent, while complete opening of the canopy is positively assured, preferably in accordance with the cycle described in connection with Fig. 2, and thus in a progressive fashion which though prompt affords a minimum of shock on all parts, including the shroud lines 21 and connections to the load 20.

Specifically (see Fig. 3), the presently preferred construction comprises a zone of relatively considerable permeability to air flow (i. e. fabric of corresponding porosity) at or within the central region C, a hem zone D of not more than relatively low permeability (e. g. fabric of low or in some cases, practically zero porosity), and a crown area A having a permeability or porosity substantially lower than that of the stated zone in re- I gion C but substantially greater than that of the hem zone D. A notably preferred embodiment of the invention further embraces, as an important element of the combination, a special plural-fabric structure in the crown portion, affording (under the transient conditions of canopy deployment) a ratio or relationship of internal pressure to air flow through the crown which is of an advantageous magnitude (i. e., preventing a high velocity of air flow through the crown) for the subsequent parts of the opening cycle.

As may be apparent from the foregoing, it has been found that in order to provide the initial stage of deployment to the bulbous configuration 28 of Fig. 2 and likewise in order to afford the desired structural strength of the canopy at all times, the fabric at the crown area cannot have a porosity or permeability greater than a value readily determinable for given conditions of size, load and speed of descent. At the same time, it has also now been found that where the remainder of the canopy, particularly at zone C, is of essentially the same character as the crown region, difficulty is encountered in attempting to build up the necessary pressure or force to advance the deployment cycle from the initial bulbous stage or stages. By utilizing, however, a fabric structure of greater porosity in the zone C an increased flow of air is obtained outwardly, through the fabric, at this region, such flow being generally as indicated by the dotted arrows 46 in Fig. 2. More particularly, it is understood that when the openings in the fabric are too small, the outer air stream 44 produces an aspirator effeet at each of such openings, to an extent that reduces the pressure within the canopy at this region, or prevents such pressure from rising as a velocity head of air entering the mouth of the canopy. Indeed the effect of a low porosity in the region C may alternatively or additionally be described as impeding sufficient movement of air up into the canopy, to build up a velocity head that will suffice to open the parachute, against the force (exerted by the shroud lines 21) that keeps the lower edge 24 in a contracted position.

By enlarging the apertures in the region C, e. g. by

atthe sametime; exertsoutwardiorce against the.thr,eads

defining or surrounding such openings, so as to. displace the entire fabric radially in. a lateral direction. andthus. to open the canopy toward the; final condition indicated. at 26 in Fig. 2. Of course, excessive porosity at; the zone C wouldnot. only permit a; correspondinglyexcessive flow of. air relative to the actual. effective. area. of the.

solid part of the fabric, but would afford. insufficient. physical. surface upon. which. outward. force could. be exerted; however, avoidance of such. excessive porosity isa. matter of ready determination, as. by simplev test, for a parachute having any given size, load rating and speed of. descent.

Having thusa region. at orwithin. the. zone: C, extending circumferentially aroundthe. canopy, which is of. substantially greater permeability than. the. crown area. and which is effective to build up.a1.suitablevelocity'head. of the air following the paths 46 (in Figs. 2' and 3.) while providing suflicient. fabric surface. or barrier to convert the outward pressure into outward: displacement of the fabric, the cycles of deployment. beyond. theoriginalbulbous condition 28 of- Fig. 2. are greatly facilitated. At

the; same time, the low (or even zero). porosity of the hem zone D serves important, cooperating purposes. In. the; first place, during. the. opening cycle, the. relatively large inflow of air through the mouth ofthe. canopy and out; through the region C contributes. materially to the conversion of the interior space of the canopy. from a. low pressure region (when the top is. first! opening as explained. above) to a locality of super-atmospheric-pressure, particularly of higher pressureimmediat'ely. outside the structure at the zones. Cand' D. In consequence this greater pressure isaalso materially efiective against the inner surface of the. hemzone D, to exert direct force on the latter, and urge it outward, along with the region C as explained above.

Furthermore, after the parachute has completely deployed, the described structure. of the hemor lowermost zone. D promotes the stability of the parachute. That. is to. say, during subsequent. descent in. the condition of Fig. 3, a high pressure condition. ismaintained: Within the canopy and indeed throughout a space: which is understood to. project below (ahead. ofthe canopy in its direction of descent) as indicated at 39 and: already explained. By virtue of the relatively non-porous characterof the zone D and by reason of the downward and inward component of force exerted by the shroud lines 21, the zone D assumes an. incurving' shape as shown at 47 in. Fig. 3, instead of following the-lowermost extension of a strictly hemispherical configuration as in dicated by the dotted lines 47a. The practical effect, asatpresent understood, of this inward curvature of the hem: region is to impede actual flow of air between the inside and outside of the canopy (the upward air stream beingthus guided around the exterior of thefabr-ic), and especially to prevent air from spilling around the lower edge. As an ultimate consequence, the region 39 becomes a relatively static cushion, andithere-is no periodic or other spilling of air at the bottom edges of the-canopy such as might cause oscillation, swinging or other instability. In practice, the inward bowing or curving of this lowermost region may be only of a relatively small extent, yet suliicient for highly favorable influence on the stability of the entire structure.

As' indicated above, thepreferred crown construction is such as to cooperate effectively: in thedeployment beyond the first or bulbous: stage. More specifically, the crown section A-B, as shown in: Fig; 5,. is made of a double layer of fabric 48, e..g; two separate, superimposed pieces, joined together -by seams 49=-or tlie like: only at their common, lower edges. This doublerfabricstructure is also illustrated in Fig. 2, the separate 'Iayersbeing designated 48a, 4812, at the top-regionof.the'intermediate, bulbouscanopy state 32. It is particularly to-benoted. that the two fabric layers thus constituting the crown piece are entirely separable except at their peripheral, bottomedge. line, Not only does this construction afford adesirably lower porosityor permeability thanin the regionC (which may, for instance, be. constructed of. fabric having aporosity of the. order ofv one of. thelayers; 48a, 4817.),but.

than: the regions.

the. structure has: an iinportanttransient eifect as the can opy' deploys.

According to: present-understanding, the reduced: or; greatly sub-atmospheric: pressure region. 40. appearing above. the. canopy when the. parachute has just been re leased occasions a. larger. pressure diiference; between. the inside. and. outside. of; the. canopy at. the crown: region. There is a correspondingtendency for airvto flow through. the crown region, andi'indeed there:v must be. a certain. amount of. flow for: proper. relief: of strain-. v However, the: eifect. of; layer of fabric is .to effectuate acorrespondingly. rapid drop. in the pressure on: the. inside, e.v g.. .to. sub-atmospheric value as the canopy blooms; Bymaking the. crown. portion of a double character, theinitnrl result of the suction. (soto speak) ontheiuppen, outer surface is.that the. presv sure drop, between inside. and outside is. divided. into two. successive elementsof components,.i. e. azdrop betweenthe interior. across the fabric; 4% to. the locality between: the fabrics, and a further drop. between that locality and? the exterior of the-canopy, i.. e;. across the other fabric 48a.

Since the drop across each fabric. layer-ris. thusmaterially less than the; entire; drop,.the flowthrough each is correspondingly. lessened, andin consequence the flow from the; inside to theoutside is. lessened-in exactly the same way. The resistancesv of thetwo. fabric layers being; in series, the flow-must be or becomethe samethrough both and; will thus haveza considerably smaller; value than. if the entire drop Were; across a singlepiece; of fabric. While it is conceivable thatc'thea same reduction of flow might be achieved; with a single layen'ofi very dense-or closely woven fabric,.the double layen structureis of. ma?- terial advantagein promoting a rapid; establishment of the desired conditions: under the. almost. tion of expanding or. deploying force on the canopy crown. Indeed during; the; initial. stages, the twofabrics actually separate, to bring; about. the. equalization of flow throughthem and thus ina. sense,:to:.provide; an airlook, so to speak, which promply controls the rate of. air flow (despite the high pressure. difference); without excessive strain on the crown region. It wilhbe: appreciated that; the avoidance of undue strain is .amatter, of, great importance, for the security of theentirestructure, asiwell as for lightness of weight and economy.-

Functioning in the. describedimannen, the; specific crown structure eliectively retards the; flowr of; airthrough the crown and. prevents as great. a: falliinzthe internal; pressure, under the crown, as might otherwise occur. Atan early. stage in the rapid deployment. cycle, the. air accumulating under. the crown thus begins, to'build. up inpressure, forming a higher basis upon. WhiChl the velocity head, achieved at the intermediate region: 6, is; then. supen imposed. In'other words,thewconjointt-efiectof the.- crown and. intermediate areas is to buildup; a'high': and eifective pressure within the canopy at; adesirably rapid: rate, the specific crown arrangement contributing peculiarly to the rapidity of such result, without; undue and. danger.- gusi strain on the. crown or any-otherw-part of the canopy.

Thus by the cooperation; of; theseveral partsdescribed; the parachute promptly andzsurelydeployst frotnthe ini tial, shapeless arrangementof Fig. 1'. through thGXSHCCflSe sive stages indicated in-Fig; 2', tothe final, hemispherical shape designated inFigi 3 Theseveral partslfunction; to-. gether in promoting the progressiveexpansion of: the body, and also in the; stable and secure conditions during the subsequent flight or' descent of theiparachute. Indeed, while the foregoing explanation is: believed to represent an accurate functional analysis of thestructure and its operation, extensive tests have demonstrated that-regardless of theory, the described arrangement in fact yield'sthe desired results, making certain that the parachute will bloom quickly to the full: hemispherical shape, without undue shock. and without dangerous strain onany part of its own structure. The subsequent stability of the device in flight: has also been. fully demonstrated.

As indicated, Fig; 5' illustrates; a. presently preferred structure in accordancev with; the invention, including the double layer fabric 48 at the :crownregionA, Baa: section C composed of fabric 5.0:having: moderate. porosity, andv a lowermost or hem-zoneYDrembodyinga textilezwith. little or no porosity.

By way; of more specific illustration, .Fig. 4. shows; a canopy. made of a. multiplicity.- of pieces :of: fabric, which havecertain. featuresof. construct-ion,- embraced by;

a. sudden. and rapid flow through a. single.

instantaneous creae 7 the cited U. S. Patent No. 2,412,392 and which may embody the present invention. Thus the crown area comprises a central section 60 of generally polygonal shape (see also Fig. 6), having inwardly curved sides 61 and attached segmental sections 62, so cut and fitted that the whole is adapted to inflate, with substantially uniform tension, to a spherical shaped cap having a circular lower edge 63. The central section 60 and preferably also each of the cooperating sections 62, is of the double construction illustrated at 48 in Fig. 5, i. e. consisting of one piece of fabric superimposed on another, and joined to the other only at the edges 61, 63. The construction is further illustrated in the diagrammatic sectional views of Figs. 9 and 10, wherein the pieces 60a, 60b constitute the two layers of the central crown section 60, while the corresponding pieces 62a, 62b are the-layers of the adjoining panels which complete the crown area bounded by the seams 63. It will be noted that in accordance with the preferred arrangement shown, each separately cut section is itself composed of two layers which are nevertheless joined at the edges of the section; by this construction equalization of tension is assured, yet the full advantage of the separable layer arrangement, as explained above, is well realized. For optimum structural security and balance, each of the separate pieces 60a, 60b and 62a,

62b, is preferably cut on the bias relative to its edges.

The zone C consists of a plurality of gores or panels 64, joined at their side edges and cut to provide an upper circular edge fitting the edge 63, and to provide a lower circular edge 65. The lowermost zone D is similarly fashioned of a plurality of gores or panels 66 similarly arranged for attachment to the edge 65 of the zone C and to provide a hem edge 67 constituting the bottom of the hemispherical canopy. Preferably each of the panels 64, 66 is also cut on the bias, for greater strength, uniformity of stress and like advantages under tension. It will also be appreciated that the panels 64 and 66 may be cut with a fullness, so to speak, along their side or vertical edges 68, 70 respectively, in the manner disclosed and claimed in the cited Patent No. 2,412,392, so that when the parachute is inflated, the chief areas of stress will extend up across central regions of the panels 64, 66, rather than along the seams at their vertical edges 68, 70. Although the seams at 68, 70 may be aligned with each other and with the intersections of the seams 61 of the crown structure, it will be noted that no special alignment of such edges of the pieces is ordinarily necessary.

As will now be appreciated, the panels or .other structure of the hem zone section 66 are constructed of relatively dense fabric or other material, e. g. having not more than a very low porosity. The panels or gores 64 have a substantially higher porosity than the net or over-all porosity of the crown area, and by the same token, a much greater porosity than the hem zone 66. While in some cases the region C, i. e. between the horizontal circular boundary 63 and 65 may involve a series of zones of mutually differing porosity (for instance of a porosity which decreases from the top edge 63 to the lower edge 65 of this intermediate zone) a simple construction involves employing the same fabric throughout the entirety of the panel 64, and having a porosity, for example (as measured in volume of flow per unit area for unit difference of pressure) which is usually at least not much less than that of a single layer of the crown area (or of the least porous of such layers where their porosities are not equal), or is at the very least no less permeable than is represented by a porosity value intermediate that of the combined crown layers and that of a single one of such layers.

The relative extents of the several zones will be determined, as will now be appreciated, by the circumstances of size, load-supporting characteristics and rate of descent of the canopy structure. For most purposes, the crown region should be such that its projected area in the plane of the equatorial circle 67 is at least 6 of the last-mentioned, circular area and more preferably at least ,4. The relative dimensions of the crown and other zones depend somewhat on the porosity characteristics; for example, a somewhat larger crown area is usually desirable where the entire region C is of uniform porosity (higher, as explained above, than the over-all porosity of the crown). More generally stated, the crown area may comprise from s to /2 of the total projected area of the canopy, under the more usual conditions encountered. The hem zone D of little or no porosity may often be of relatively small extent, e. g.

having its upper boundary elevated not more than 5" to 10 from the lower, circular edge of the hemispherical canopy. As explained, these and other characteristics of the structure differ with conditions and purposes of the parachute, in a manner which will now be readily understood or will be readily determinable in the light of the foregoing explanation.

As indicated, other shapes and arrangements of the pieces which are joined by appropriate seams to constitute the fabric canopy, may in some cases differ substantially from the arrangement of Fig. 4, but are preferably so cut and joined that the canopy will assume a truly or essentially hemispherical shape upon its complete deployment. Thus the polygonal piece 60 shown at the very cap or crown of the canopy may have four sides as shown, or may have a greater or less number of sides, providing it extends integrally from the crown center A in all directions for a considerable distance and thus aifords an essentially seamless area 60 of substantial extent centered about the crown.

Although other shroud line attachments may be employed, a peculiarly desirable structure includes a cord 80 (Figs. 7 and 8), conveniently continuous and extending peripherally around the lower edge of the canopy in a suitable sleeve or hem-pocket as shown. At spaced intervals part of the fabric is cut away permitting access to the cord 80, so that it may be encircled by the attaching loops 82 of the shroud lines 21. In the partially deflated condition such as at 28 of Fig. 2, the shroud lines then tend to pull depending loops 84 (of the cord 80) down, and out of the openings, but when the canopy springs out to its full shape, completely stretching the hem to the desired circumferential value, the cord 80 is tightened to an essentially horizontal position as shown in Fig. 8, drawing up the shroud lines 21 to the level of the bottom edge 24. To insure proper positioning of the shroud lines, stitching or other fastening may be provided as at 86, securing the cord 80 at intermediate localities between the openings, so that it will not creep laterally inside the hem. Fig. 7 thus not only shows the condition of these parts at preliminary stages of inflation, but also illustrates the compacted condition or pleat-like folding of the lower part of the canopy before it snaps out to full shape.

Although other configuration of the separate pieces of nylon, silk, cotton or other textile may be employed in the canopy (including shapes such that the high porosity zone C has edges that are circular only in an average sense, being of zig-zag or other irregular outline) and although the porosity characteristics may be obtained by special or varying weave of vertically long gores or the like, structure such as illustrated in Figs. 4, 5 and 6 represents a peculiarly convenient and durable type of canopy. In all instances where the features of the present invention are employed, specifically having the described high porosity zone intermediate the hem region and the crown area and the very low porosity hem zone, and also preferably in combination with the plural-layer construction at the crown, the advantages of prompt and sure opening are obtained, together with improved stability and freedom from oscillation or other derangement in flight, as well as an effectively smooth retardation of load.

Figs. 11 and 12 illustrate another example of canopy structure preferably embodying features described above in connection with Figs. 4, 5, 6, 9 and 10, and illustrating certain further relationships which may also be constituted or obtained in the canopy, for instance, of Fig. 4. Like the structure of Fig. 4, the canopy of Figs.ll and l2 involves a multiplicity of pieces of fabric and at the same time affords realization of certain features embraced by the cited Patent No. 2,412,392. The crown area comprises a central, polygonal section having a small number of inwardly curved sides 91 (peculiar advantage being had with a regular, four-sided figure as shown), and segmental sections 92 attached to the cap 90 by seams along the sides 91, the entire crown being shaped as a portion of a sphere and having a generally circular lower edge 93.

A multiplicity of side or gore panels 94 are arranged circumferentially to constitute the main body of the canopy below the crown, each panel being essentially a vertically elongated trapezoid having somewhat curved escapes sides, and having its upper edge joined toa corresponding :portion f the adjacent segment by .a suitable seam along the line 93. Each gore panel has a lower edge 95 where it is joined by a suitable seam to a complementary section 96, of short vertical extent, which may have a much lower porosity and which terminates at its lower side :in the hem edge '97 of the canopy. Although in some cases, as where the feature of a low porosity hem section is not desired, .the gore panels 94 may extend completely to the .edge 97, the illustrated structure is of special advantage for reasons explained above. :By way of further example, .the :upper edges 95 of the lowermost sections 96 are .shown as inclined at differently inclined small angles to the horizontal, thereby affording .a strong seam connection to the main panels 94 while still maintaining .an approximately circular boundary for the low .POIOSltYsZOIR.

It will be appreciated :that the fabric of the crown section 90-92 .may be constructed of .a double thickness as described above andshown in Figs. 9 and 10, the latter figures thus in effect representing views of the structure of Figs. 11 and 12, .forythe sections '90, 92 instead of the sections 60, 62. Indeed, other features and relationships set forth respecting Figs. 4 to 6 may be understood to be embodied :in the corresponding elements of Figs. 1,1 and 12,including the provision of fullness along the vertical scams 9.8, 100, as shown .in Fig. :14, where the .dot-and-dash lines .102 .represent the relative situation of the medial part of each :gore panel 94-96, included also .in Fig. 12. For example, by cutting the gores :94 (and in a similar way, if desired, the secti0ns'96) so that the central vertical line of each falls along :a truly hemispherical surface corresponding to the diameter of the canopy opening and so that the edges of-each gore occupy a longer distance between the upper circle 93 and the bottom edge 95 than would be constituted by an arc of .a great circle on the same hemisphere, the greatest strain is carried by and about the central line 102 of each gore, .and .a desirable minimum of strain is imposed on the seams 98, all as explained in the cited patent.

A particularly important feature of the present structure is thateach of the sections, segments or panels 90, 92 and 94 and also the sections 96 when used, is cut on a bias with respect 'to each other piece to which it is joined by a seam. For example, as illustrated in Fig. 12, the lowermost gore '94 has its threads running nonrectangularly (e. g. by a substantial angle, as of at-least about 15 and preferably .at least 25 or 30) relative to the adjacent gores 94 and to the segment '92 abut-ted at the upper edge. Similarly the 'cap section 90, which provides a seamless central piece over the top of the canopy, has its threads at :an angle to those in each of the segments 92. More specifically, too, each fabric portion is cut with its threads at a like bias to the direction of principal stress, e. g. the threads of .each of the sections 90, 92 and 94 being at an acute angle to a great circle which extends from the pole of the canopy through a central part of the given fabric portion. In this way strain of the fabric is carried on avbias relative to the threads throughout each section or panel and a similar bias connection is afforded at all of the seams 91, 93, 98 with consequent maximum resistance to rupture of the fabric or the seams.

Bearing .in mind that in the inflated and operative state, the strain in the canopy extends radially from and to the center of the crown, i. e. at least to a zone lying approximately one-third of the peripheral distance between the hem and the crown, and that the strain in the fabric below such point is both vertical, and circumferential in a horizontal direction, it will be seen that the described structure affords an effective equalization of strains throughout the canopy, while promoting maximum resistance to ripping or tearing. In .Fig. 1.2, the arrows 1104 represent roughly the direction and magnitude of force exerted on the seam '93 by the gores 94, the greatest pull in each gore being .at the .center of its upper edge by reason of the feature illustrated in .Fig. 14. Similarly the arrows v1.06 represent the forces on one of theseams 91, such forces being carried across the segment 92 to the seam .93, while theopposing forces sustained by the cap section 90 are indicated :by -the arrows 108. As will be apparent, the forces arewell distributed along the several'seams, indeed preferably with a minimum at the .apices of tthctcapsection 90, and with greatest concentration of forces, i. e. at the center of the crown, traversing a completely strong and seamless area of fabric centered about the pole of the parachute, viz. the cap whichma ypreferably-cover at least one or ifpossible several percent of the total'canopy surface, for example an area centered over the pole and having a diameter in everydirect-ionof at least a major fraction of one foot.

Moreover, by making the cap 90 of double thickness fabric as shown in Figs. 5,9 and 10, and preferably also the segments 92, the=greatest strength is achieved in the crown region, while-at the same time accomplishing the important functional results explained above, i. e. with respect to the opening characteristics and stability of the parachute. itwill now be appreciated that by the structure of Figs. ii and 12 important :features of the cited patentare realized to full advantage, yet thecanopy may be manufactured in very large sizes (each gore :panel being governed in dimensions by the width of commercially available textiles and :the number of gore panels 94 being increased or diminished .as necessary for a given size); at the same time :the .imultiple-piece structure provides great flexibility .of design, for utilization of the principles of pressure and air flow control hereinabove explained.

The essential features :of the arrangement are susceptible of.modification, i. e. as to the shape, number and disposition of the constituent pieces of textile. For .instance, while the alignment of the .apices of the cap 90 with certain of .the gore seams 9.8 "is not necessary in many cases (as indicated above) and is thus absent in Fig. 4,such alignment as in l2lhas some advantage (forparticularly heavy duty with minimum fabric weight) in the reduction of stress .along these narrow, pointed regions of the cap, ire. as shown by the smaller arrows of force in Fig. 12. Simply .as an example of another structural arrangement, Fig. 13 shows the centralportion of a canopy having a cap 1-10and'main'gore panels 112 corresponding generally to the cap 90 and panels 94 of Fig. 12,.buthaving enlarged segmental pieces 114 shaped notonly-to abut thepolygon-al'edges 115 ofthe cap 110, but to project downwardly somewhat in the canopy surface as along the edges 116.. This is one of various alternative arrangements which nevertheless realize the same essential principles, of strain equalization and of mutual bias-cutrelation, which have been described in connection with preceding figures. .Here (Fig. 13) although .the crownsection has .a-merging orserrated lower boundary, departing from a true circle 117, it nevertheless -affords substantial realization of the advantages described above. Preferably, eachof the segments 114 is made of double thickness fabric like the segments -62 of :Fig. 5, although in some cases, .-as where less complete advantage of suchstructure ,isrequired, the cap section :may .alone be so fashioned.

.As explained above, the parachutes are preferably so designed thatan incurving or skirting effect is obtained, in use, at the .hem region as shown at-47 in Fig. 3 A greater stability of thedeployed canopy is found to occur, e. .g. .as evidenced .by theapparentrnaintenance of a high prcssureregion-39 projecting ahead of the canopy mouth during its .descent. Indeed it is believed that optimum conditions of maintained inflation :and stability are in many cases accompanied and promoted-by the extension of the lowpressure region40 all the-way to the hem line 24, the depth or radial extent of .such region, and its departure below theatmosphericpressure, decreasing gradually from the crown to the hem. Itis believed that the upward current of air .38,.deflected by the head wave 39 andthe .incurved zone 47, travels rapidly past the hem zone and produces .a siphon .or suction effect upon the air immediately outside the surface of the canopy section C. in this manner, it is thought :thatthe barometric pressure over the section C is reduced below that of the surrounding atmosphere, so that inactual use, i. e. after full deployment, the canopy may'in a sense be deemed to be covered with a blanket of low pressure air, i. e. over a much greater portion of the surface "than the minimal condition-indicated at 40 in Fig. 3. The result of such effect is auniformityof air flow .46 through the pores of the fabric and thereby or more directly, a greater distribution of pressure drop across the fabric .andthroughout the canopy, with superior buoyancyand stability'for the latteraas it descends carrying the :load.

While "in many cases the opening-of the canopy will be accompanied by a withdrawal of the protruding hem cord loops 84 from the position of Fig. 7 to the situation of shroud line connections shown in Fig. 8, superior control of deployment at the hem line during opening, and specifically accurate control of the shape and extent of the incurving zone 47, may be attained, especially under severe use conditions, by special disposition of the stitching or bar-tacking which is otherwise illustrated at 86 in Figs. 7 and 8.

Thus in Fig. 15 the bar-tacking 86a, whereby the hem cord is locally secured against longitudinal displacement in the hem sleeve, is located immediately adjacent each of the openings 120 in the hem sleeve. Under circumstances where the weight of the load or the drag characteristics of the canopy would impede or would fail to permit the retraction of hem cord loops into the hem sleeve (i. e. "by pulling the load up relative to the canopy), the structure of Fig. 15 permits efiective deployment of the hem to nearly complete opening, yet permits the hem and adjacent canopy section to remain shirred over relatively small regions at the openings 120. Thus where heavy loads or high speeds, or both, are involved, the arrangement of Fig. 15 avoids the necessity of overcoming friction between the cord and the hem sleeve in order to obtain a desirably wide mouth opening (and avoids the.

additional work of elevating the load in order to retract long loops 84) yet at the same time provides an accurately controlled dimension for the bottom edge of the fully deployed parachute. Fig. 15 thus shows the condition of such a canopy at its ultimate stage of opening, with the cord 80 pulled slightly downward at each aperture 120 and with the degree of incurving 47 (Fig. 3) thus controlled and maintained by the continuing, gathered condition 122 of the canopy hem region in peripherally very short areas. It will thus be seen that the location of the bar-tacking 86a alfords means for accurate control of the skirting or incurving effect, i. e. under load and speed conditions which would prevent full retraction of hem cord loops, so as to achieve a skirted structure of sufiicient extent for high stability yet insufficient to impair the desired drag or supporting function of the canopy.

It will be apparent from all of the foregoing that a number of factors should be properly correlated in order to obtain best results with parachutes such as herein described, not only as to strength and stability, but especially as to sureness of opening, e. g. under higher air speeds. As explained, full opening of the canopy is facilitated by a high ratio of shroud line length to canopy diameter, and also by securing the floating hem cord to the hem at points next to the shroud line attachments. The combination of the double layer (or other reduced porosity) crown with a very low porosity hem zone below a major canopy portion or body of intermediate porosity is of unusually beneficial effect, for rapidity and completeness of deployment. In a more general sense, and indeed in cases where the special hem zone either cannot or need not be used, as well as in the specified combination, the degree of porosity of the main portion or body of the canopy is found to be especially significant. This and related criteria are of notable importance when the parachute is released at high air speed (c. g. of several hundred miles an hour or more) or when it is employed with a so-called infinite load, an example of the latter situation being a parachute released for braking effect upon a falling alrplane, the relatively great weight of the latter being such that it is always controlling the parachute rather than coming under the control or absolute support of the parachute. As a somewhat general rule although not to a point where there is insufficient permeability at central portions of the hemisphere for the desirable outward flow of an, decrease of fabric porosity (e. g. sidewall fabric porosity) mproves the opening characteristics; yet a very low porosity throughout the sidewall may sometimes adversely affect the stability of the canopy in subsequent flight. The weight of the fabric has also been found material, in that for a given porosity, the opening or inflation of the parachute is better when its fabric is of greater Weight. A possible explanation is that the inflation of the canopy is enhanced by a venturi-like effect of rather larger apertures between heavy threads as distmguished from an orifice-like efiect of smaller apertures between fine threads, but in any event, the described ultimate significance of fabric weight has been confirmed by many tests. For example, in one instance of the peculiarly severe, infinite-type load, a 3Q-inch hemispherical canopy having a sidewall structure of 2.14 oz. nylon of porosity 407 failed to open satisfactorily at an air speed of 200 M. P. H., yet prompt and efiective opening was had with a like canopy of 4.81 oz. nylon of porosity 404, these porosities being measured on the standard basis of cubic feet of air capable of escaping per minute per square foot of fabric under a pressure difference of one-half inch of water. The Weight of the fabric of the canopy must also, of course, be related to the magnitude of the load or the ratio of load to canopy size; briefly stated, the fabric should be heavy enough to resist weakening or rupture under the conditions of opening and use. In that respect, and since carrying capacity is almost always at a premium in the vehicle that carries the packed parachute aloft, structures such as illustrated in Figs. 9 to 12 and 14 are advantageous in providing a canopy of maximum strength for its weight and for the space it occupies when packed.

More specifically, the satisfactory example of a 30- inch hemispherical canopy mentioned above had a structure essentially as shown in Fig. 11, the crown section of elements 90, 92 being a double thickness of the same woven nylon cloth (4.81 oz., porosity 404) used singly for the side wall (intermediate) panels 94; the bottom edge zone of segments 96 was of very low porosity, viz. 2.18 oz. nylon cloth of porosity 137.

Another satisfactory example of a parachute had a 5 ft. diameter canopy constructed as hereinabove described, using 4 oz. woven nylon fabric; the porosity over the crown region was 105, and was likewise at the hem or equatorial zone, the substantially higher porosity in the central or intermediate zone being 308. An effective 22 ft. diameter nylon parachute (hemispherical) had a crown area of two ply 2 oz. nylon, each ply being of 157 porosity; the large central zone was single ply 1.3 oz. fabric of porosity 325, and the bottom zone of 1.5 oz. fabric of porosity 225. In a satisfactory 50 ft. nylon canopy, both the lowest zone and a large crown area had a porosity of about 70, the intermediate zone being fabric having porosity of about 140.

By way of a specific application of the above general principles it appears that if a heavy load is to be released at a high speed and if requirements of stability and strength make it desirable to use a canopy wall fabric of high porosity (which involves little sacrifice of buoyancy), such fabric should be relatively heavy, i e. to promote full opening. If packing space is not available for a large canopy of heavy textile, a sequential parachute system as embraced in our U. S. Patent No. 2,478,758, granted August 9, 1949, may be employed so that the load is first slowed down to a slow speed which will permit a light weight, main parachute to take the load. In accordance with the principles herein explained, it is found that unusually superior results for a minimum of parachute packing space may be obtained by a particular relation of the successively larger, sequentially released canopies, i. e. by making them, in their order of increasing size, of progressively (and substantially) lower porosities and lighter weights.

For example (although the number of canopies in the sequence may be two or more, depending on the need) Fig. 16 shows diagrammatically a series of four hemispherical parachutes 130, 131, 132 and 133 which may have suitable means (not shown) such as described in Patent No. 2,478,758, to release them in. succession for support of the load 135. There may be a common load line 137, with branch lines 140, 141, and 142 extending from it to the respective parachutes 130, 131 and 132 at spaced localities such that each of the three upper canopies (released or deployed only after the preceding lower one has fully deployed and assumed control of the load) takes a position where the apex of its shroud lines is well above or beyond the top of the canopy below it. Indeed, in practice, the successive sections of the line 137 are longer than as here shown, it being also noted that each canopy is connected only at the apex of its shroud lines and thus deploys wholly clear and at one side of the line to the canopy above it. All of the parachutes, and preferably at least the main device 133, may if desired embody the structural features of parachutes of preceding figures herein, although for simplicity such details are omitted from Fig. 16.

By way of further example, to decelerate a load of the order of 1000 pounds or more traveling at a speed upwards of 1000 miles per hour, the first-released canopy may have a diameter of 18 inches and have its wall all made of low of a 12 oz. fabric (say, :nylon) withngporosity'approachmg 1000. The next-.deployedcanopies 1'31 and..132, with progressively larger .diameters, may be :made 20f :8 (oz. and 4 oz. nylon cloth, :of .porosities about .600 :and 39:0 respectively. The final .or main load carrying rparachute 153, which is released-when the load has reached .a much lower speed, 'is of suitably .large size-and may have its sidewall of 1 /2 oz. or 2 oz.nylon'havinga porosity even as low as 150 or so. In this way, the .loadus finally dropped .at a safe and very low terminal velocity, -yet by the described relationship of canopy characteristics (as to .porosity and fabric Weight) excessive shock and undue strains are avoided while permitting exceptional economy of. space'and-weight for the parachuteassembly as folded and packed. It .will be appreciated that the above numerical values are recited approximately, andsimply as an example, and thatthe exact structure .and number of canopies in any given .system will be governed by the specific conditions of use, under the principles hereinabove explained.

Referring back to the specificcanopyshown'in Fig. 13, it may be noted-that structures involving [this and similar arrangements of canopy segments .around vthe crown region, particularly when the portions .110 and .-11-4are porosity material or preferably of a double layer of material, are of advantage in situations where it isdesired to cause .a-defiection of air within the canopy in such manner that the (low porosity effect occurs over a greater crown area than in smaller =circular regions (such :as bounded bythe .seam 93 in Fig. 12). The parachute of the present invention, when embodied in the arrangement of .Fig. 13, thusachieves this further result, while it may cooperatively afford a desirably controlled value of barometric pressure .over the crown area during flight. Another advantage of structures such as in Fig. 13 is that there is no .continuous, circumferential crown seam, and thus no hazard that by lack of attention in making such a seam, there will be stressed stitching and undesirable gathering .of the fabric under threads drawn .too tightly. More ,generally stated, arrangements .ofthesort shown in Fig. 13 provide an exceptionally flexible crown and minimize local crownstresses.

This application is a continuation in part of our copending patent application Serial 'No. 88,976, filed April 22, 1949, for Parachute Canopy Structure, now .abandoned.

It is to be understood that the invention is notlimited to the specific devices herein shown .and described, but may be carried out in other ways without departure from its spirit.

What is claimed is:

1. In-aparachute, a substantially hernispheric-al'loadretarding cloth fabric .canopy which is adapted, upon release in non-expanded condition, .to expand progressively, first through a bulbous shape adjacent its crown and subsequently to a substantially complete hemispherical shape .by lateral displacement of portions below the crown, comprising a bottom zone of very low porosity, a crown section of greater porosity than the bottom zone, said crown section completely covering the crown, and a zone intermediate said crown section and bottom zone, having porosity substantially greater than said crown section and inducing flow of air into the bottom opening of the canopy and out through said intermediate zone to create force against the fabric thereof for laterally expanding the canopy after initial expansion to said bulbous shape.

2. In a parachute, a substantially hemispherical loadretarding canopy having a Zone of not more than very low porosity adjacent its bottom edge, a crown section of greater porosity than said bottom edge zone, said crown section completely covering the crown, and a zone of substantially greater porosity than said crown section, disposed intermediate the crown section and bottom edge zone.

3. In a parachute, a substantially hemispherical loadretarding fabric canopy comprising a crown section of fabric completely covering the crown and having a projected area, in the plane of the equator of the canopy, equal to at least about one-fifth of the total projected area, a bottom zone section having its lower edge constituting the lower edge of the canopy at the equator thereof and having a peripheral extent of at least about measured angularly from said lower edge, and an .intermediater'zone section betweenwsaidtcrown land bottom. :zone tsections, :said intermediate zone 'section cornprisingazzone ofssubstantially greater porosity than said crown section, said bottom zone section having a substantially lower porosity Ethan said crownsection, and said crown section including :a cap .portioncentered at the pole of the canopyzand occupying at least the major part of the total area of the crown section, said cap portion consisting .of continuous fabric free of connecting .seams intermediate its edges.

4. :In auparachute a substantially hemispherical canopy comprising a polygonal :cap portion, -a plurality of segment-shaped portions corresponding "to, and each having an :uppercurved edge-connected with, oneside of said polygonal :portion, said. segment-shaped portions extending predominantly thorizontal ly about the upper part of the .parachute and .together substantially completely encircling the cap 'port-ion,"and.a multiplicity of side panel portions disposed. in 1a horizontally circumferential array below .said segment-shaped portions, said panel portions having side edges connected to each other successively around :the canopy'and :upperedges connected to lower edgesef the segment-shaped portions, said canopy "havingabottomedge defining its bottom opening, and said panel -;portions :extending from the :said segment-shaped portions .atleast nearly .to said bottom edge, .and each of said cap, segment-shaped:and panel portions comprising :textile fabric .cut on a bias with respect to-each of the other of the :aforesaid portions with which it is directly connected, said cap portion comprising .a fabric piece extending .OVCI' the'vpole of the canopy and pro viding .a continuous, seamless fabric portion .centered over said pole, and each of said segment-shaped portions being-defined essentially by its upper curved edge and its lower edge extending tozmeet the upper .curved edge at apexes at opposite ends tof the segmentwshaped portion.

5. Aparachute rcanopyas described in .claim.4, where- 'n the :cap portion and the segment-shaped portions cooperatively constitute a crown section for the canopy, and wherein-the segment-.shapedzportions have. respective, curved lower edges :shapedtand disposed to constitute, together, asubstantially circular lower boundary for said crown section, said :lower .edges of thezsegment-shaped portions being connected with :the .upper edges of the panel portions as .aforesai 6. A para-chute canopy as described in lclairn 4, wherein reap portion comprises plural, separable :layers .of fabric each having the polygonal configuration of said cap portion, said layers. of fabric being joined only at their :edges.

7. :In .a parachute canopy as described :in claim 5, whereinthe :cap and segment-shaped portions constituting :the crown section :each comprise a fabric structure having so stantially less porosity than thepanel portions.

8. Amarachute-canopy as described ineclaim .6, wherein the panel portions are constituted by respectivepieces of fabric all having the same, predetermined "porosity, and wherein the cap portion consists of two layers of fabric arranged and joined as aforesaid, each of said layers consisting of a piece of fabric having the same predetermined porosity as the panel portions.

9. In a parachute, a substantially hemispherical canopy comprising a polygonal cap portion having its boundary consisting of four incurving sides with their points of intersection in a substantially rectangular configuration, sa1d polygonal cap portion comprising a fabric piece extending over the pole of the canopy and providing a continuous, seamless fabric portion centered over said pole, a multiplicity of side panel portions disposed in a horizontally circumferential array at a zone of the canopy below said cap portion, said panel portions having side edges connected to each other, successively around the canopy, and having upper edges, and segmental fabric portions oining the cap portions and the panel portions and connected to the sides and upper edges of said cap and panel portions respectively, said cap fabric portion being cut on a bias relative. to the central locality of each of its aforesaid sides, and each of said panel portions comprising fabric cut on a bias relative to a great circle of the canopy which extends from the pole thereof through a central part of each such panel portion.

10. A parachute canopy as described in claim 9, wherein each of the segmental portions comprises a fabric piece cut on a bias relative to a great circle which extends from the pole of the canopy through a central part of such segmental portion, and wherein each of said cap, segmental and panel portions comprises fabric cut on a bias with respect to each of the other of the aforesaid portions with which it is directly connected.

11. In a parachute, a substantially hemispherical loadretarding canopy comprising a plurality of separate sections of fabric joined by seam structure extending in a substantially horizontal direction around the canopy, one of said sections constituting a bottom zone section with its lower edge providing the bottom edge of the canopy and another of said sections comprising a crown section. and said crown section having a circular lower edge and being constituted of a plurality of pieces of fabric, one of said last-mentioned pieces of fabric being a cap piece in the shape of a polygon having a predetermined small number of sides, centered over the pole of the canopy and providing a continuous, seamless fabric portion occupying an area, centered as aforesaid having a diameter in every direction of at least a major fraction of one foot, said crown section consisting of said polygonal cap portion and an equal predetermined number of horizontal segment-shaped portions corresponding to, and each having an upper curved edge connected with, one side of said polygonal portion, the lower edges of said segment-shaped portions being disposed to constitute, together, the circular lower edge of the crown section.

12. The parachute of claim 11 wherein the canopy includes a side zone section intermediate the crown section and the bottom zone section, the crown section having a lower porosity than said side zone section and said bottom zone section having a lower porosity than the crown section.

13. In a parachute, a substantially hemispherical canopy constructed of fabric and comprising a crown section and a side wall section extending from said crown section to the bottom edge of the canopy, a hem sleeve around the bottom edge of the canopy, a floating hem cord disposed in said sleeve, said sleeve having openings at spaced localities around the bottom edge, shroud lines respectively corresponding to said openings and connected to the hem cord through the latter, and means immediately adjacent each opening, at localities respectively on each side thereof, for securing the hem cord to the hem sleeve to prevent lateral movement of the hem cord relative to the sleeve at each side of each opening, the said localities of hem cord attachment for each opening being spaced by a short distance along the hem, said hem being of uniform construction throughout its circumferential extent and being free of reinforcement localized adjacent said openings, and said distance between hem cord attachments at each opening being sufficient, so that upon full deployment of the parachute the hem cord will be drawn down by each shroud line at each opening, gathering the sleeve into shirred relation throughout each said distance, and thereby imparting a substantially incurving configuration to the canopy through a vertically short region at the hem edge.

14. Parachute apparatus comprising a plurality of parachutes each having a fabric canopy and shroud lines extending from the bottom edge thereof to an apex of convergence, load line means extending from the apices of the shroud lines and adapted to be connected to a load, for support of the load successively by said parachutes upon successive deployment of the same, said load line means being adapted for deployment of each parachute wholly clear of attachment to said load line means except at the apex of the shroud lines of such parachutes, said load line means including successive load line sections extending to the shroud lines of the successive parachutes, and said load line means for other than the last released of said parachutes being adapted for deployment of each such other parachute Wholly at one side of the load line section extending to the next parachute in succession, said canopies being graduated in size in increasing magnitude in order of succession of release, each of said canopies having side wall structure extending around the canopy and occupying at least a major part of the surface thereof, the side wall structures of the canopies being respectively composed of fabric of decreasing weight and decreasing porosity in the order of successive release.

15. Parachute apparatus comprising a main parachute having a canopy and shroud lines therefor, a smaller parachute comprising a canopy, line means for connecting said parachutes to the load, including a long line extending from the shroud lines of the main canopy to the load, and including line means between said smaller canopy and the load, arranged for deployment of the smaller canopy wholly at one side of the said long line and with the upper end of said smaller canopy substantially nearer to the load than the shroud lines of the main parachute, each of said canopies comprising fabric side panel structure extending around such canopy and occupying at least a major part of its surface area, the said side wall structure of the main canopy being composed of fabric having substantially less weight and substantially less porosity than the fabric of said side wall structure of the smaller canopy.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,712,296 Dapp May 7, 1929 2,358,582 Little Sept. 19, 1944 2,409,562 Hastings Oct. 15, 1946 2,411,868 Brown Dec. 3, 1946 2,412,392 Finken Dec. 10, 1946 2,478,758 Frieder Aug. 9, 1949 2,501,670 Fogal Mar. 28, 1950 FOREIGN PATENTS Number Country Date 271,488 Great Britain July 14, 1927

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