US 3410511 A
Description (OCR text may contain errors)
A. P. COPPA 3,410,511
INFLATABLE BAG FOR DISSIFATING IMPACT ENERGY Nov. 12, 1968 Filed Dec. 12, 1966 o owvooooo s 6 INVENTOR. ANT ONY P COPPA, BY Q AGENT United States Patent 3,410,511 INFLATABLE BAG FOR DISSIPATING IMPACT ENERGY Anthony Patrick Coppa, Merion Station, Pa., assignor to General Electric Company, a corporation of New York Filed Dec. 12, 1966, Ser. No. 601,141 5 Claims. (Cl. 244138) ABSTRACT OF THE DISCLOSURE Inflatable bags for energy absorption systems include a plurality of pores or openings, which are distributed over the surfaces of the bags and covered with a nonporous material having a preselected burst pressure. Upon impact, internal pressure exceeds this preselected burst pressure and the pores or openings become discharge ports. Since these ports are distributed over the surface of a bag, partial deflation of the bag will cause the ports located in the deflated portion at the impact surface to cease to be effective as discharge ports. Thus rate of deflation is retarded and the rate of retardation is directly related to the degree of deflation. Variable rate discharge ports may also be used.
Introduction The present invention relates to a system for absorbing impact energy at a controlled rate and more particularly to an inflatable bag system in which landing impact energy is dissipated at a preselected rate.
Background Impact energy absorption and, specifically, non-destructive landing of aerospace hardware may be accomplished in a variety of ways. Usually, however, devices for absorbing impact energy are complex and heavy. One of the common types of devices used to dissipate impact energy is that which includes an inflatable bag as the primary energy dissipating means. The effectiveness of this type of device may be due to compression of gas in the inflatable bag, bursting of the bag or a combination of these. In any event, the uniform distribution of decelerating force on the payload achieved in an inflatable bag system and the excellent storability characteristics of such a system are well-known advantages of these devices. Under certain conditions, inflatable bag systems are also more efficient, with regard to weight required versus energy dissipation, than other alternative systems, such as honeycombs.
One of the primary disadvantages of inflatable bag systems heretofore has been the inability to control rate of energy absorption and therefore deceleration loading, without complex mechanical systems to regulate the re lease of compressed gas. The complexity of these mechanical gas release systems increases with the degree of sophistication required to obtain a desired degree of gas release at each stage of the deflation stroke.
Objects It is an object of the present invention to provide an inflatable bag landing system having a simple deflationcontrolling means.
It is also an object of this invention to provide an inflatable bag landing system with an integral gas release controlling means.
Another object of this invention is to provide a means for controlling the deceleration stroke of an inflatable bag landing system.
Still another object of this invention is to provide a means for controlling the rate of gas release from an 3,410,511 Patented Nov. 12, 1968 'ice inflatable bag through each stage of deflation thereof, which means is simple and further is an integral and easily manufacturable part of the inflatable bag.
Brief summary of the invention These and other objects are met, in accordance with the present invention, by an inflatable bag for dissipating impact energy which includes a plurality of distributed segments, each having a preselected burst strength below that of the bag generally. These segments may be discrete openings or pores in the main portion of the inflatable bag, which are covered with a non-porous material designed to burst upon impact of the bag.
In one of the preferred forms of the present invention, the main portion of the bag comprises a strong, semiporous fabric of synthetic resin, glass, metal, or other suitable material combined with a non-porous film, having a preselected burst pressure. Upon impact, gas contained in the inflatable bag first is compressed to the limit of the pressure-sustaining capability of the non-porous covering material and this material then bursts. This leads to the second stage of the deflation stroke wherein high volume gas release takes place through the openings previously covered. As deflation of the bag proceeds, a progressively greater proportion of bag area is gathered at the impact surface and progressively less of the discharge openings remain in high volume gas transport communication with the main interior portion of the inflatable bag. This retards the rate of deflation progressive- 1y through the deflation stroke.
Detailed description of the invention While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, this invention may be better understood from the following description, taken in conjunction with the following drawings, in which:
FIGURE 1 is a sketch of a generally spherical inflatable bag landing system in which the payload is disposed at the center of the sphere;
FIGURE 2 is a detailed view of a section of the inflatable bag shown in FIGURE 1; and
FIGURES 3 and 4 depict another form of the inflatable bag landing system of the present invention and its operation.
Referring more specifically to FIGURE 1, there is shown a partially cut-away spherical inflatable bag 1, comprised of twelve pyramidal segments radiating from a common origin at the center of the sphere, each having a pentagonal cross-section perpendicular to its axis and containing a compressed gas, not shown. Disposed at the center thereof is a payload capsule 2. A segmented structure, as shown, is preferred over a non-segmented structure because of its ability to withstand side load and the fact that payloads may be better secured within the inflatable bag. However, non-segmented structures may also be used.
In FIGURE 2, a section of the bag used in the embodiment shown in FIGURE 1 is shown in detail. In particular, the inflatable bag, segmented or otherwise, is comprised of a fabric made of interwoven individual fibers 3, combined with or adjacent to a non-porous film 4. In the preferred form of the present invention, fabric fibers 3 are composed of a polyester, such as linear polyethylene terephthalate, commmercially available in fiber form from Du Pont under the trademark Dacron. Other synthetic resin fibers, such as nylon, as well as glass and metallic materials may also be used. Polyvinyl chloride film is typical of the non-porous films which may be used in the present invention.
In one example, the semi-porous fabric used comprises Dacron polyester fibers 0.14 inch in diameter, having a tensile strength of 40,000 pounds per square inch and a density of 0.050 pound per cubic inch, interwoven in perpendicular directions with a spacing of about 4 fibers per inch. The porous fabric thus formed is then combined with a flexible polyvinyl chloride film having an ultimate tensile strength of 3000 pounds per square inch and density of 0.050 pound per cubic inch. This combination has an overall weight per unit area of 0.901 pound per square foot. Utilizing this combination in a system based on a segmented sphere, 105 inches in diameter with a 150% safety factor on bag strength and a 300% safety factor on helium gas containers, a payload 4 feet in diameter, weighing 12,800 pounds with a landing speed of 128 feet per second may he landed with a maximum deceleration of 100 Gs. This overall system weighs 2460 pounds. An operating helium pressure within the inflatable bag of 47.5 pounds per square inch absolute is assumed for the time just prior to impact. By comparison, a system using the best available honeycomb as the energy absorbing medium, would weigh 9600 pounds.
As an alternative to the porous fabric in the above embodiment, a spherical inflatable bag, comprised of a nonporous material, may also be used. In this alternative, discrete openings or discharge ports are provided throughout the surface area of the non-porous bag material. These discharge ports are covered with a non-porous material having a burst strength lower than that of the bag genorally and preselected for operation in the same manner as that described with reference to the first embodiment.
In the form of the present invention shown in FIGURE 3, a non-porous material is used as the main portion 6 of a cylindrical inflatable bag 7. Distributed vertically along the inflatable bag 7 are openings 8 in the main portion 6 of the inflatable bag 7 covered by a non-porous material 9 having a burst pressure below that of the bag generally. Upon impact and gas compression to a pressure exceeding the burst pressure of the material 8, the openings in the bag form discharge ports for the compressed gas. High volume gas release may then take place through these discharge ports as long as the port remains in high volume gas transport communication with the interior portion of the bag 6. By vertically distributing the openings, the rate of gas release is controlled through-out the deflation stroke of the bag. Further control may be attained by varying the size of these openings to otbain the desired amount of pressure released at each point of the deflation stroke or by using a multiplicity of bags of either the same or diflerent shapes.
It will be noted that while the embodiment of the present invention shown in FIGURE 1 is omnidirectional, that is, it is non-specific as to the orientation of the landing system upon impact, the embodiment shown in FIG- URE 3 requires placement of the payload at the top of the inflatable bag and vertical orientation of the system upon impact in order to obtain the desired control over. pressure release during the deflation stroke. Operation of the device of FIGURE 3 is illustrated in FIGURE 4, showing the bag in partially deflated form. At the instant shown, the inflatable bag is partially deflated and a substantial proportion of the discharge openings, being in the lower deflated portion of the bag near the impact surface, not shown, have been withdrawn from high volume gas transport communication with the interior of the bag.
At this point, in accordance the rate of deflation has been partially retarded by the decrease in effective discharge area. Further retardation will occur as deflation proceeds. This retardation of all embodiments of the present invention depends upon the distribution of the gas discharge ports along substantially the entire axial length of thebag. In any of the embodiments of the'present invention in which gas discharge ports or openings are used, two types of ports may be used. In the simplest form, these ports may be fixed area openings providing a constant discharge area per port. The second type is a variable area port, the area of which varies with pressure fluctuations and provides further means to control the rate of deflation following the initial compression and bursting of the non-porous covering on the discharge ports.'
What I claim as new and desire to secure by Letters Patent of the United States is:
1. An inflatable bag for dissipating landing impact-energy which begins deflation at a preselected over-pressure; said bag including integral controlled deflation means; said means consisting of a plurality of openings in said bag covered by a non-porous material, said non-porous material having a preselected burst strength below that of the bag generally, said openings being distributed substantially along the entire axial length of'said bag, the flow through some of the openings being impeded by collapse of the bag around these openings upon impact on a surface, thereby reducing the rate of gas release flow as the bag is deflated.
.2. An inflatable bag, as recited in claim 1, wherein said bag is comprised primarily of non-porous material and said integral controlled deflation means consists of a relatively limited number of discrete openings in the primary material of said bag, said openings having a covering, said covering having a burst strength belo that of the primary material of the bag. i
3. An inflatable bag, as recited in claim 2, wherein each of said openings is of preselected size so that rate of deflation is controlled during deflation by. the cross-sectional area of the openings remaining in effective high volume gas transport communication with the main interior space ofsaid bag. i
4. An inflatable bag, as recited in claim 1, wherein said bag comprises a porous fabric. V
5. An inflatable bag, as recited in claim 4, wherein said porous fabric comprises a plurality of interwoven fibers spaced sufiiciently far apart so that controlled pressure release may occur through said spacing upon bursting' of said non-porous covering material.
References Cited UNITED STATES PATENTS 2,713,466 7/1955 Fletcher et a1 244%138 2,887,055 5/1959 Bagdanovich et al. 244-138 X FOREIGN PATENTS 1,230,569 4/1960 France.
1,234,194 5/1960 France.
. MILTON BUCHLER, Primary Examiner.
R, A. DORNON, Assistant Examiner.