US2696959A - Parachute canopy structure - Google Patents

Description

Dec. 14, 1954 J. A. AILEO PARACHUTE CANOPY STRUCTURE 2 Sfieeis-Sheet 1 Filed Jan. 26, 1952 IN VEN TOR.

Dec. 14, 1954 J. A. AILEO PARACHUTE CANOPY STRUCTURE 2 Sheetg-Sheet 2 Filed Jan. 26, 1952 9 INVEN TOR.

Jar/(son fl fllka BY Mam United States Patent ranacnurn CANOPY STRUCTURE vJackson A. Aileo, Carbondale, Pa., assignor to Leonard P. Frieder, Great Neck, N. Y.

Application January 26, 195.2, Serial No. 268,401

4 Claims. ((31.24'4-142') This invention pertains to load-carrying canopies and more particularly relates 'to a novel and improved parachute canopy structure in which the canopy is preformed substantially in the shape of the polar zone of a hemisphere, the altitude .of the polar zone being less than the spherical radius. Such a canopy will be often referred to herein as a polar zone canopy.

Reference herein to the preformed shape of a canopy signifies that if properly supported (but without inflation), the canopy will assume .the described special configuration even when there is essentially .no tension in the fabric at any place.

The most widely used type of parachute (at least until very recently) has involved a so-called flat canopy, i. e. preformed to a flat shape. The assembly usually has a circular edge to which shroud lines are connected, for convergence to the point of load attachment. When such a parachute blooms in use, the downward pull of the shroud lines and the upward or inward force of air cup the fabric into a shallow, more or less parabolic shape.

More recently, use has been made of canopies preformed to a hemispherical shape, for example as described in the prior U. S. Patents No. 2,412,392, granted December '10, 1946, on the application of Walter S. Finken, and No. 2,426,926, granted September 2, 1947, on the application of Leonard P. Frieder and Walter S. Fink-en. Hemispherical canopies have been found specially advantageous, particularly in having much greater stability in flight than the older flat type parachutes which have a strong tendency to oscillate during descent; the hemispherical canopies also generally exhibit improved strength, especially against the sudden shock of opening at high speeds. Furthermore, in the case of a flat-type canopy, large and unequal stresses are developed in the fabric to pull the canopy into the desired, shallow parabolic contour. some degree of stability, a crown or polar opening is usually provided (in a flat-type canopy) to relieve a considerable part of the so-called velocity head of air enter ing the mouth of the canopy and moving upward against the fabric.

A parachute having a canopy of the hemispherical type provides a much more stable descent than where a flattype canopy is used, and. the fabric in the hemispherical canopy is not subjected to any unequal stresses and other forces.

The present invention embraces the discovery that a canopy having the above-described novel, polar zone configuration affords several marked advantages over either or both of the flat and the hemispherical canopies. For example, the polar zone canopy: is faster opening than the hemispherical canopy; is more stable than the flat canopy, i. e. does not oscillate as much during descent; produces less unequal fabric strains and stresses than the flat canopy; requires considerably less cloth area than the hemispherical canopy to support a given load; and is relatively easy to manufacture, i. e. in that the gores or other sections making up the canopy may conveniently be made of the same shape as for a hemispherical canopy, but of shorter dimension toward the hernline or mouth opening. The retarding effect of the polar zone canopy is good, because of the fairly large low-pressure area which is found to be present above the crown during flight. Important objects of this invention are therefore to attain the above-mentioned advantages, and generally, to provide improved parachute and like structures.

A further feature of the invention is the discovery that To avoid undue strain on the fabric and to promote 2,696,959 Patented Dec. 14, 1954 it is advantageous to provide .a :polar zone canopy (and in some cases, other types of canopies) with an arrangement in the crown area for relieving internal pressure to ease the initial shock of inflation. Such an arrangement may most conveniently comprise a venting crown of overlapping flaps or panels, which will permit air to pass therethrough as the parachute is being inflated, but which will be closed and so held by the velocity head of air as and after the canopy is .fully opened. Such improved structure thus advantageously differs from the parachutes of the prior art which have been equipped with crown holes that remain open in flight, e. g. as in the case of the flattype canopies described above.

It is accordingly a further object of the invention to provide a canopy having novel means for relieving the initial shock occasioned by the sudden opening of the parachute.

The above and other objects and advantages will appear more clearly from the following description, taken with the accompanying drawings in which:

Fig. 1 is a somewhat diagrammatic perspective view of an example of a parachute having the improved polar zone dcanopy, shown in expanded form, as for support of a loa Fig. 2 is a diagram showing the preformed canopy of Fig. l in vertical section, with certain geometric relationships;

Fig. 3 is a top view :of a self-sealing crown vent, with portions broken away;

Fig. 4 is a sectional view on line 44 of Fig. 3;

Fig. 5 is a perspective view of the vent arrangement with the canopy fully opened; and

Fig. 6 is a perspective view of the vent arrangement with the canopy partially opened.

Like reference numerals denote like parts in the various views.

Fig. 1 shows diagrammatically .a parachute having a polar zone canopy 10 in expanded form, supporting a load 12 by means of a plurality of shroud lines 14. The canopy 10 has a crown section 15 and a circular mouth or hem edge 16 circumferentially terminated by a hemmed sleeve 18 looped over a running cord 20, which may if desired be bartacked at suitable localities to limit its movement relative to the hem. The sleeve 18 is provided with evenly spaced holes 22 (there being .as many holes 22 as there are shroud lines 14), and the upper end of each shroud line 14 is passed through one of the holes 22 and looped around the cord 20, thus to connect the lines 14 to the canopy l0. Hem cord arrangements of this type are now well known and need not here be described in greater detail.

The canopy 10 is composed essentially of flexible sheet material, preferably woven textile fabric. Its configuration, i. e. as a polar zone canopy, can be best seen in and understood from Fig. 2, which is a diagram showing the preformed canopy in vertical section, i. e. in a section perpendicular to the mouth 16 and passing through the top or crown 15. In this section, the canopy 10 appears as a circular are 26 of radius R extending outward and downward an equal distance on each side of the top 15 of the canopy 10 and being terminated by the mouth 16. The dimensions are such that the depth h of the are 26 is less than R. More specifically, a canopy having satisfactory characteristics of stability, load-retarding effect,

- and minimum weight of fabric is believed to result where h is substantially in the range from 30% to of R. At present it is greatly preferred to limit the range to from 40% to 70%, a particularly useful arrangement being one in which h has a value about 60% of K As shown, the canopy 19 is made up (except at its crown area) of gores 28, which, as will now be apparent, are readily cut in essentially the same way as for true hemispherical canopies, with the exception that for this polar zone canopy, the gores 28 are shorter at the bottom. The amount by which they are shorter is essentially determined by the desired ratio of h to R.

It is further preferred to provide the top 15 of the polar zone canopy 10 with a venting arrangement 30, designed and adapted to provide an air escape to ease the initial shock which occurs when the canopy 10 opens. This shock is particularly severe when the parachute is reunder such circumstances the initial velocity head of air entering the canopy through its mouth 16 is abnormally large. Although providing the initial relief of shock, the arrangement 30 is also self-sealing after the canopy 10 is fully opened, so that in effect no more air can pass therethrough.

In the example of crown structure shown, the arrangement 30 is substantially circular at its outer boundary 31, with its center corresponding to the top of the canopy 10, and may conveniently be constituted by two pieces of fabric 32 and 34. The ends of the pieces 32 and 34 are substantially circular arcs, each corresponding to and embracing approximately 90 of the circle 31. The pieces 32 and 34, which are preferably considerably narrower at their central portions than at their ends, are affixed to the gores 28, for instance by suitable stitching such as shown at 36 (Fig. 4), with the lengthwise center lines of the pieces 32 and 34 intersecting each other at right angles. Thus the piece 32 lies above the piece 34, and the pieces 32 and 34 cooperate in overlapping relationship to cover the crown area of the canopy 10 comgletely, when the canopy is in its deployed or open conition.

The pieces 32 and 34 are preferably hemmed at their sides as shown at 38, and may if desired be cut to have a little fullness across the circular area bounded by the upper ends of the gores 28; specifically, the crown assembly can thus be preformed to constitute (when the piece 32 smoothly and fully overlies the piece 34) a part of the polar zone shape of Fig. 2.

Fig. 5 shows, in perspective, the vent arrangement 30 with the canopy 10 in its fully deployed or opened position. Under these conditions, the air velocity head inside the canopy 10 exerts upward and outward pressure to force the pieces 32 and 34 together in smoothly abutting relation and thus to prevent outward passage of air through the vent arrangement 30.

Fig. 6 shows, also in perspective, the arrangement 30 with the canopy 10 part way open, as it will be during the opening of the parachute and before the fabric of the gore assembly has assumed full, uniform tension. It will be apparent that when this condition prevails (during the opening of the canopy 10) air can freely pass be tween the pieces 32, 34, from the inside of the canopy as shown by the arrows, to ease the initial shock of the opening.

Suitable means, such as lines 40 which are joined together at an eye 42 at the top and at their lower ends are joined by suitable loops to tabs 44 on the canopy at the crown boundary, are adapted for attaching a pilot parachute (not shown) to the top of the canopy 10; it will be understood that other pilot chute attachments may be employed if desired, as well as further structural features sometimes found advantageous, such as a hem zone of relatively low porosity thereby providing the intermediate zone between hem zone and crown as by a region of comparatively high porosity.

It may be explained, i. e. in further detail, that by reason of the novel crown construction, the velocity head of incoming air, in conjunction with an increasing effect of canopy expansion by volumetric displacement of air into and within the canopy, results in effective ballooning of the parachute, so that it inflates promptly and positively but in a cushioned manner. That is to say, at the outset as the parachute falls under the weight of its load, and as it then commences to expand, the mouth or open end of the canopy tends to scoop up a greater amount of air than will pass through the valve-like crown. In consequence, the enlarging volume of air expands the canopy more rapidly; as such expansion progresses to maximum radius, the fabric is increasingly stressed, and indeed sufficiently stressed to tighten the overlaps of the crown to the point where further escape of air is prevented. Thereafter, the parachute continues its descent as a completely closed canopy, with full retarding force.

As illustrated in Figs. 1 and 2, and conveniently as embodying the flap crown construction of Figs. 3 to 6, the polar Zone canopy provides efiective load-retarding action and accomplishes the several objects set forth above. To some special advantage, notably of stability, the parachute preferably is such that when fully deployed, its hem region is pulled slightly inward (at 24, Fig. l), i. e. in a slightly incurving distortion from the shape as actually preformed.

It is to be understood that the invention is not limited to the specific details herein shown and described, but may be embodied in other forms without departure from its spirit.

What is claimed is:

1. A load carrying canopy having a crown region and including a crown vent structure occupying the crown region and effective to ease the initial shock when said canopy is opened, said crown vent structure including overlapping pieces of flexible material extending across said crown region and having ends shaped to conform to the boundary of said crown region and affixed thereto, said pieces being arranged and constructed so that when said canopy is fully opened, said pieces will seal said crown region in substantially air-tight relationship, and when said canopy is not fully opened, said pieces will permit air to escape between them.

2. A canopy as described in claim 1, wherein said crown region is circular, and the ends of said pieces are circular arcs of radii substantially equal to the radius of said crown region.

3. A vent structure as described in claim 1, wherein said crown region is circular, the ends of said pieces are circular arcs of radii substantially equal to the radius of said crown region, the sides of the pieces are similar 90 arcs, and the lengthwise center lines of said pieces intersect each other at right angles.

4. A load-carrying canopy having a crown region and a peripheral portion encircling said crown region, including crown vent means to ease the initial shock when the canopy opens, said vent means including overlapping pieces of flexible material extending generally diametrically across said crown region and fixed only at their ends to said peripheral portion, said pieces having longitudinal dimensions substantially equal to the diameter of said crown region when the canopy is fully open, so that the pieces are slack during the opening of the canopy until the peripheral portion is fully open, said pieces when slack providing pressure-relieving vent openings between them, said pieces being placed under tension only by said full opening, said pieces having lateral dimensions sufficient so that when all the pieces are under tension, the pieces cooperate to close the crown region substantially completely.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,319,553 Ziegenfuss Oct. 21, 1919 1,328,425 Duffy Ian. 20, 1920 2,127,895 Tingle Aug. 23, 1938 2,410,207 Frieder Oct. 29, 1946 2,412,392 Finken Dec. 10, 1946 FOREIGN PATENTS Number Country Date 250,330 Italy Sept. 28, 1926 640,891 France Apr. 7, 1928 678,946 France Ian. 2, 1930

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