GB2220626A - Parachutes - Google Patents

Abstract

A parachute canopy (1) has a skirt (5) extending around its lower peripheral region. The upper portion of the skirt (5) is secured directly to the canopy (1) and its lower free edge portion (6) is connected to the peripheral hem (3) of the canopy (1) by a plurality of tie elements (7). During deployment of the canopy, the skirt (5) inflates to force the lower region of the canopy (1) radially outwardly to aid its opening. The ties (7) may be such that they fail at a critical deployment velocity allowing inversion of the skirt so as to avoid excessive opening shock loads. For example, the ties (7) may be connected to the rigging lines (4) in such a way that they will be snapped by the tension in the rigging lines (4) when this exceeds a critical value. <IMAGE>

Description

PARACHUTES This invention relates to parachutes, and relates in particular to parachutes incorporating means intended to increase the rate of inflation, i.e. "opening", of the parachute canopy after deployment.

Where a parachute is to be deployed at low speeds and low heights, it is desirable that the canopy inflation time be as short as possible, and to this end, various means have been proposed to improve the rate of inflation. These include inflatable air pockets sewn on the outside of the canopy, inflatable hoses sewn around the outer periphery of the canopy, flaps arranged to seal or restrict an upper vent of the canopy during inflation, and "taschengurts" i.e. short lengths of tape or webbing extending between adjacent gores around the outer periphery of the canopy.

It is an object of a first aspect of this invention to provide a parachute incorporating improved means for increasing the speed of inflation.

In known parachutes incorporating means to reduce the inflation time problems can arise if the parachute is required to operate over a wider range of operating conditions since, if deployed at higher velocities, the enhanced inflation characteristics can result in unacceptably high shock loads being imparted to the person or store being dropped, or to the parachute itself.

It is an object of a further aspect of this invention to provide a parachute where this drawback may be avoided.

Viewed from a first aspect the invention provides a parachute having means for increasing the inflation rate of the canopy, such means comprising a skirt extending around the canopy adjacent a lower, peripheral region thereof, the skirt having an upper portion secured directly to the canopy and a lower, free edge portion connected to or adjacent the peripheral edge of the canopy by means of a plurality of peripherally spaced tie elements, whereby the skirt is arranged to inflate during deployment in such a way as to define with said lower region of the canopy a generally annular region of increased air pressure the effect of which is to urge said lower region outwardly to assist in inflating the canopy.

In accordance with the invention, inflation time is decreased whilst stability of the parachute is maintained. The effect of the annular region of higher pressure defined by the skirt and lower region of the canopy is to force the lower region or "mouth" of the canopy radially outwardly during inflation which prompts faster filling of the canopy as a whole. This effectively reverses the inflation sequence as compared with a traditional canopy wherein the upper, central region opens first and only subsequently is the lower region urged outwardly following inflation of the upper parts of the canopy.

The arrangement in accordance with the invention provides an improvement both as regards inflation time and stability over known proposals for causing rapid inflation such as discrete inflatable pockets which do not define an annular region of increased pressure.

In a preferred embodiment the upper portion of the skirt forms a substantial air tight seal with the region of the canopy to which it is secured, although it is envisaged that if necessary suitable vents could be provided to reduce the shock loading upon inflation of the skirt. The tie elements connecting the lower edge of the skirt to or adjacent the peripheral edge of the canopy can take any convenient form, e.g. tapes, ribbons, cords or any suitable sections of sheet material. The height of the skirt in relation to the lower, peripheral edge of the canopy, and the dimensions of the skirt and of the tie elements are not critical and will vary in accordance with the size and configuration of the canopy and with the intended operating conditions thereof. The skirt is conveniently formed of the same material as the canopy.

The present invention is particularly applicable to emergency escape parachutes for aircraft where often it may be necessary to deploy the parachute at a low height and rapid inflation at a relatively low deployment speed is therefore essential. The present invention is also applicable to the low level dropping of stores where there is a requirement that the speed variation and stock loads be limited.

However, in conditions where the parachute is subject to higher deployment velocities the rapid inflation characteristics could introduce an undesirable and excessive opening shock load. In a preferred embodiment, therefore, the tie elements are adapted or arranged to fail at a critical loading resulting from the inflation pressure of the skirt, whereby the skirt is rendered ineffective and the canopy reverts to its conventional inflation characteristics.

The tie elements may themselves be adapted to break at the critical loading, or alternatively could be secured to the skirt and/or to the canopy by suitable frangible means.

In a particularly preferred such embodiment each tie element or frangible means is also coupled to a rigging line. Thus, if an excessive shock loading is being produced by the rapid development of the parachute then the resultant tension in the rigging lines acts directly on the tie elements or frangible means to cause them to fail.

Viewed from a second aspect the invention provides a parachute comprising a canopy having means associated therewith for increasing the rate of inflation of the canopy at relatively low deployment velocities, such means being adapted to be disabled or rendered less effective at least in the latter stages of inflation of the canopy if deployment of the parachute occurs above a critical maximum deployment velocity.

This aspect of the invention is applicable independently of the first aspect, to other arrangements for increasing the canopy inflation rate.

For example, the canopy may include discrete inflatable air pockets adjacent its lower peripheral edge, such pockets either including vents adapted to open at a critical pressure or being frangibly connected to the canopy so as to be partly or wholly released therefrom at higher development speeds.

An alternative embodiment may comprise a canopy with discrete inflatable flaps adjacent its lower peripheral edge, the lower edge of each flap being secured to or adjacent the lower peripheral edge of the canopy by one or more frangible tie elements.

Each of the tie elements may be coupled to a respective rigging line so that the tension in the rigging line acts directly on the tie element. Thus, if the canopy is deployed above a maximum critical velocity, the tension in the rigging lines will break the tie elements and disable the flaps.

This embodiment has the advantage of a more positive disabling action since the excessive tension in the rigging lines acts directly on the frangible tie elements. In the case of parachutes in accordance with the first aspect of the invention, whilst in the presently preferred embodiments tie elements are provided which are adapted to fail at the critical deployment velocity, an alternative arrangement for rendering the skirt ineffective or less effective might include vents associated with the skirt and adapted to open at a critical pressure.

The point during inflation (in the event of deployment at high velocities) when the means for disabling or rendering less effective the inflation increasing means will vary depending on various factors, including the actual deployment velocity although it will be appreciated that the means should be adapted to be disabled by the time the latter stages of inflation are reached if significant shock loads are to be avoided. For example, in the case of frangible pockets or elements discussed above, the relevant components may be adapted to fail at an appropriate time which may be immediately after deployment as a result of the shock loads produced by the drogue or may be when the shock loads produced by the opening of the main canopy occur. In either case the relevant elements fail when the stresses due to inflation reach a predetermined value.If the inflation aiding means are disabled by the deployment of the drogue, then they will be ineffective throughout substantially the complete development.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view showing schematically an inflated canopy; Figure 2 shows schematically in cross-section the canopy of Figure 1 during inflation thereof at a relatively low deployment velocity; Figure 3 is a view similar to Figure 2, but illustrating inflation of the canopy at a higher deployment velocity.

Figure 4 shows an arrangement for disabling a flap, the flap being used to increase the rate of inflation of a canopy.

Referring to the drawings, a parachute canopy 1 is formed of a plurality of gores and is secured at its lower, peripheral edge or hem 3 to a plurality of rigging lines 4 which carry the person or cargoe being dropped.

Adjacent the lower, peripheral region of the canopy 1 is provided a skirt 5 which at its upper edge is sewn directly to the canopy and which has a lower free edge 6 connected to the peripheral hem 3 of the canopy via a plurality of tapes 7.

As shown in Figure 2 during deployment of the canopy at relatively low deployment velocities the skirt inflates and defines with the lower region of the canopy an annular region or ring of increased air pressure. This causes the lower region of the canopy to be forced radially outwardly which in turn causes the canopy as a whole to open very rapidly and subsequently inhibits any tendency to collapse.

As shown in Figure 3, if deployment occurs above a certain critical maximum velocity the tapes 7 connecting the free edge of the skirt 5 to the peripheral hem 3 of the canopy are arranged to fail, allowing inversion of the skirt 5. This nullifies the effectiveness of the skirt, so that the canopy can revert to its conventional inflation characteristics.

The dimensions of the skirt and of the tapes, and the location of the skirt relative to the peripheral edge of the canopy may vary depending on the size of the canopy and the intended operating conditions.

Thus, in the case of a 32' parachute (gore length 16') the skirt depth may vary, for example, between 9" and 2' 6", whilst the length of the tapes 7 might vary between 6" and 1'. The tapes are preferably secured to the peripheral hem 3 of the canopy, although in an alternative arrangement the tapes could be secured above the hem, or alternatively to the rigging lines. The lower edge of the skirt must be in the region of the base of the canopy to be effective to force the canopy open, although need not be exactly level with the peripheral edge.

In the case of a steerable parachute which would include a vent on one side of the canopy the skirt 5 should be located below such vent.

In a preferred embodiment, rapid opening of a canopy in accordance with the invention has been achieved at a deployment velocity of 30 knots, which is substantially lower than deployment velocities at which successful inflation can be achieved with conventional parachutes. The tapes 7 are preferably arranged to fail at a critical deployment velocity of between 60 and 90 knots and this value can be adjusted according to requirements.

Figure 4 shows an arrangement for disabling a flap. The upper edge of flap 8 is sewn to the canopy 1. The lower edge of the flap 8 is joined by the tie element 9 to hem 3. The rigging line 4 is also joined to the tie element 9 via an anchor loop 10. The distance along the rigging line 4 between the hem 3 and the anchor loop 10 is chosen to be sufficiently large that the tension in the rigging line 4 acts on the tie element 9 rather than on the portion of the rigging line 4 between the anchor loop 10 and the hem 3. The breaking strain of the tie element 9 is chosen so that the tie element 9 will snap when the tension in the rigging line 4 exceeds a predetermined value.

When the tie element 9 fails, the lower edge of the flap 8 is no longer secured to the hem 3 and the flap is disabled as a means of causing the rate of inflation of the parachute to be increased.

The breaking strain of the tie element 9 can be altered so as to alter the critical deployment velocity above which the tie element will break.

The depth of the flaps and the length of the tie element are not restricted to any particular value and will generally be of the same order as the skirt depth and tape length discussed above. The preferred disabling means illustrated in Figure 4 may be applied to the skirt configuration shown in Figure 1, or to other forms of inflation means such as individual pockets and may be used on its own or in conjunction with any other means for disabling the inflation aiding means.

Whilst certain broad aspects and more specific exemplary features of this invention have been described, modifications may be apparent to those of relevant skill which retain one or more of the advantages envisaged. The disclosure hereof is intended to encompass such modifications, even if certain features presently described and/or illustrated are omitted.

Claims (12)

CLAIMS:

1. A parachute having means for increasing the inflation rate of the canopy, such means comprising a skirt extending around the canopy adjacent a lower, peripheral region thereof, the skirt having an upper portion secured directly to the canopy and a lower, free edge portion connected to or adjacent the peripheral edge of the canopy by means of a plurality of peripherally spaced tie elements, whereby the skirt is arranged to inflate during deployment in such a way as to define with said lower region of the canopy a generally annular region of increased air pressure the effect of which is to urge said lower region outwardly to assist in inflating the canopy.

2. A parachute according to claim 1 wherein the upper portion of the skirt forms a substantial air tight seal with the region of the canopy to which it is secured.

3. A parachute according to claim 1 or 2 wherein the tie elements are adapted or arranged to fail at a critical loading resulting from the inflation pressure of the skirt.

4. A parachute according to claim 3 wherein said tie elements are adapted to break at said critical loading.

5. A parachute according to claim 3 wherein said tie elements are secured to the skirt and/or to the canopy by frangible means.

6. A parachute acording to any one of claims 3 to 5 wherein each tie element or frangible means is also coupled to a rigging line.

7. A parachute according to claims 1 or 2 wherein vents are associated with the skirt and are adapted to open at a critical pressure.

8. A parachute comprising a canopy having means associated therewith for increasing the rate of inflation of the canopy at relatively low deployment velocities, such means being adapted to be disabled or rendered less effective at least in the latter stages of inflation of the canopy if deployment of the parachute occurs above a critical maximum deployment velocity.

9. A parachute according to claim 8 wherein said canopy includes discrete inflatable air pockets adjacent its lower peripheral edge, such pockets either including vents adapted to open at a critical pressure or being frangibly connected to the canopy so as to be partly or wholly released therefrom at higher development speeds.

10. A parachute according to claim 8 wherein said canopy is provided with discrete inflatable flaps adjacent its lower peripheral edge, the lower edge of each flap being secured to or adjacent the lower peripheral edge of the canopy by one or more frangible tie elements.

11. A parachute according to claim 10 wherein each of said tie elements is coupled to a respective rigging line so that the tension in the rigging line acts directly on the tie element.

12. A parachute substantially as hereinbefore described with reference to the accompanying drawings.