U.S. patent application number 13/344138 was filed with the patent office on 2012-07-05 for multi-grommet retained slider for parachutes.
This patent application is currently assigned to AIRBORNE SYSTEMS NORTH AMERICA OF NJ, INC.. Invention is credited to Jean C. Berland.
Application Number | 20120168565 13/344138 |
Document ID | / |
Family ID | 39740671 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120168565 |
Kind Code |
A1 |
Berland; Jean C. |
July 5, 2012 |
MULTI-GROMMET RETAINED SLIDER FOR PARACHUTES
Abstract
A reefing slider for providing improved line management and
canopy deployment characteristics of a ram air inflated airfoil
type canopy. During initial descent of the parachute the slider,
secured by retaining elements, is held against the canopy in the
upper reefing position where it mechanically restricts canopy
deployment while giving the canopy time to achieve proper
orientation following the drop from the launching aircraft. Upon
sufficient air flow into the canopy cells, the retaining elements
separate, releasing the slider and enabling full opening of the
canopy.
Inventors: |
Berland; Jean C.;
(Wynnewood, PA) |
Assignee: |
AIRBORNE SYSTEMS NORTH AMERICA OF
NJ, INC.
|
Family ID: |
39740671 |
Appl. No.: |
13/344138 |
Filed: |
January 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12073206 |
Mar 3, 2008 |
8091834 |
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13344138 |
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11201186 |
Aug 11, 2005 |
7338016 |
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12073206 |
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Current U.S.
Class: |
244/146 ;
244/152 |
Current CPC
Class: |
B64D 17/343 20130101;
B64D 17/025 20130101; B64D 17/26 20130101 |
Class at
Publication: |
244/146 ;
244/152 |
International
Class: |
B64D 17/02 20060101
B64D017/02; B64D 17/62 20060101 B64D017/62 |
Claims
1-19. (canceled)
20. In combination with a ram air parachute canopy having a
wingspan with upper and lower airfoil surfaces separated by
chordwise-extending ribs to form cells inflated by inflow of air at
an open leading edge, and suspension lines connecting the lower
surface of the canopy to a load, the improvement comprising: a
reefing slider with a spanwise length and a chordwise width having
reinforced openings through which the suspension lines extend, said
slider further having a plurality of separate retaining devices
spaced along said spanwise length and secured to said canopy for
retarding descent of the slider relative to the canopy from an
upper reefing position in which inflation of the canopy is
restricted, said slider being releasable from said canopy to
descend along said suspension lines in response to release of said
retaining devices due to force created by said inflow of air to
said cells, a number of said retaining devices at a central area
along said slider spanwise length and secured to a central part of
said canopy wingspan being stronger than a number of said retaining
devices at outer edges of said slider spanwise length and secured
to wing tip portions of said canopy.
21. The combination as set forth in claim 20, wherein each of said
retaining devices includes a slider retaining element secured to
said slider, and a canopy retaining element secured to said canopy,
said slider retaining elements and said canopy retaining elements
being releasably secured to one another and calibrated so that the
force needed to separate the slider retaining elements from the
canopy retaining elements is greater at said central part of said
canopy wingspan than at said canopy wing tips.
22. The combination as set forth in claim 21, wherein each slider
retaining element is secured to said slider adjacent a reinforced
opening and said canopy retaining elements are secured to said
canopy in spaced relationship corresponding to a spacing of said
slider retaining elements so that said slider retaining elements
and said canopy retaining elements are releasably secured to one
another in corresponding pairs.
23. The combination as set forth in claim 21, wherein said slider
retaining elements and said canopy retaining elements are mating
magnetic elements.
24. The combination as set forth in claim 21, wherein said slider
retaining elements and said canopy retaining elements are mating
snap fastener elements.
25. The combination as set forth in claim 22, wherein said
corresponding pairs of slider retaining elements and said canopy
retaining elements are releasably secured to one another tie
elements.
26. The combination as set forth in claim 25, wherein said tie
elements are cable-tie type fasteners.
27. The combination as set forth in claim 25, wherein said tie
elements include cord or string.
28. The combination as set forth in claim 27, wherein each of said
slider retaining elements includes a slider retaining loop and each
canopy retaining element includes a canopy retaining loop, a tie
element being passed through the paired loops on said slider and
canopy and tied to join each corresponding pair.
29. The combination as set forth in claim 28, wherein said tie
element is passed through the loops of a corresponding pair of
retaining elements more than once before being tied.
30. The combination as set forth in claim 29, wherein tie elements
of corresponding pairs at the central part of the canopy are passed
through their associated loops a greater number of times than are
tie elements of corresponding pairs at said wing tips so that a tie
strength at the central part of the canopy is greater than a tie
strength at the wing tips.
31. The combination as set forth in claim 30, wherein a tie
strength of tie elements connecting loops of corresponding pairs
along the canopy wingspan between the central part and the wing
tips is intermediate between said central part tie strength and
said wing tip tie strength, said intermediate strength being
determined by a number of times the tie elements pass through their
associated pairs of loops before being tied.
32. The combination as set forth in claim 28, wherein a tie
strength of said tie elements incrementally increases from loop
pairs adjacent said wing tips to loop pairs at the center area of
the canopy.
33. A ram air parachute comprising: a canopy having a wingspan and
upper and lower airfoil surfaces separated by chordwise-extending
ribs to form cells inflated by inflow of air at an open leading
edge; suspension lines connecting the lower surface of the canopy
to a load; and a reefing slider with a spanwise length and a
chordwise width having reinforced openings through which the
suspension lines extend, said slider further having a plurality of
separate retaining devices spaced along said spanwise length and
secured to said canopy for retarding descent of the slider relative
to the canopy from an upper reefing position in which inflation of
the canopy is restricted, said slider being releasable from said
canopy to descend along said suspension lines in response to
release of said retaining devices due to force created by said
inflow of air to said cells, a number of said retaining devices at
a center along said slider spanwise length and secured to a central
part of said canopy wingspan being stronger than a number of said
retaining devices at outer edges of said slider spanwise length and
secured to wing tip portions of said canopy.
34. The ram air parachute as set forth in claim 33, wherein each of
said retaining devices includes a slider retaining element secured
to said slider and a canopy retaining element secured to said
canopy, said slider retaining elements and said canopy retaining
elements being aligned in corresponding pairs and calibrated so
that the force needed to separate the slider retaining elements
from the canopy retaining elements is greater at said central part
of said canopy wingspan than at said canopy wing tips.
35. The ram air parachute as set forth in claim 34, wherein said
slider retaining elements and said canopy retaining elements are
mating magnetic elements.
36. The ram air parachute as set forth in claim 34, wherein said
slider retaining elements and said canopy retaining elements are
mating snap fastener elements.
37. The ram air parachute as set forth in claim 34, wherein said
corresponding pairs of slider retaining elements and said canopy
retaining elements are releasably secured to one another by tie
elements including cable-tie type fasteners, cord or string.
38. The ram air parachute as set forth in claim 37, wherein each of
said slider retaining elements includes a slider retaining loop and
each canopy retaining element includes a canopy retaining loop, a
tie element being passed through the pair loops on said slider and
canopy at least once and tied to join each corresponding pair.
39. The ram air parachute as set forth in claim 38, wherein said
tie elements are cords, the tie element cords of corresponding
pairs at the central part of the canopy being passed through their
associated loops a greater number of times than are tie element
cords of corresponding pairs at said wing tips so that a tie
strength at the central part of the canopy is greater than a tie
strength at the wing tips.
40. A method of securing a reefing slider to a ram air parachute
canopy having a wingspan and upper and lower airfoil surfaces
separated by chordwise-extending ribs to form cells inflated by
inflow of air at an open leading edge, and suspension lines
connecting the lower surface of the canopy to a load, said reefing
slider having a plurality of reinforced openings spaced from one
another through which the suspension lines extend, said slider
further having slider retaining elements adjacent at least some of
said reinforced openings and said canopy having canopy retaining
elements in spaced relationship corresponding to a spacing of said
slider retaining elements, the method comprising the steps of:
aligning the canopy retaining elements with said slider retaining
elements to form a plurality of retaining element pairs; and
releasably securing the slider retaining elements and the canopy
retaining elements of each respective retaining element pair to one
another along the wingspan of said canopy, said step of securing
including securing retaining element pairs near a central area of
said canopy with a mechanical connection having a first connection
strength and securing retaining element pairs near the wing tips of
the canopy with a mechanical connection having a second connection
strength, said first connection strength being greater than said
second connection strength, said releasably secured pairs of
retaining elements securing said slider to said canopy to retard
descent of the slider relative to the canopy from an upper reefing
position in which inflation of the canopy is restricted, said
slider being released from said canopy to descend along said
suspension lines to a lowered position in response to release of
said retaining elements from one another due to force created by
said inflow of air to said cells.
41. The method as set forth in claim 40, wherein each of said
slider retaining elements includes a slider retaining loop and each
canopy retaining element includes a canopy retaining loop, said
step of releasably securing including passing a tie element through
the canopy retaining loop and the slider retaining loop of each
retaining element pair and tying the tie element, tie elements that
secure retaining element pairs near a central area of said canopy
being passed through the respective loop pairs more than once
before tying to obtain said first connection strength, and tie
elements that secure retaining element pairs near the wing tips of
said canopy being passed through the respective loop pairs a fewer
number of times before tying as compared with said central area
pairs to obtain said second connection strength.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of copending application
Ser. No. 12/073,206, filed Mar. 3, 2008, issuing as U.S. Pat. No.
8,091,834 on Jan. 10, 2012, which was a continuation-in-part of
application Ser. No. 11/201,186, filed Aug. 11, 2005, which issued
as U.S. Pat. No. 7,338,016 on Mar. 4, 2008, and hereby claims the
priority thereof to which it is entitled.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates in general to delaying the
opening of parachute canopies and, more particularly, to a slider
type reefing device that is secured to the canopy during initial
parachute deployment.
[0004] 2. Description of the Related Art
[0005] A known problem with the use of parachutes to lower
personnel and unmanned cargo to the ground from airplanes and other
airborne craft is the sudden shock when the parachute opens and
fills quickly with air. This is especially serious at high speeds
where the canopy fills more rapidly, as may occur during the
deployment of parafoils designed to fly at high wing loadings.
[0006] The mechanical reefing of parachute canopies by sliders on
the canopy suspension lines for the purpose of delaying canopy
opening and/or reducing canopy opening shock is already well known
as representatively disclosed in U.S. Pat. No. 5,005,785 to Puskas.
According to such prior art arrangement, opening of a ram-air
inflated, airfoil gliding parachute canopy (hereinafter "ram air
parachutes" or "ram air canopies") is physically restricted to a
decreasing extent as the reefing slider is displaced downwardly
from an upper reefing position along converging suspension lines
under canopy opening forces.
[0007] The reefing system disclosed in the Puskas patent achieves
aerodynamic delay by means of a flow deflecting flap extending from
the slider beyond the suspension lines so as to be positioned in
alignment with the leading edge portion of the canopy in the upper
reefing position. However, because the slider is not physically
connected to the canopy, heavier payloads can render the flap
insufficient to withstand the force of the air flowing into the
canopy upon deployment. Hence, under heavy loading of the parachute
canopy, the slider may descend too rapidly such that adequate
retarding of the canopy opening process is not achieved.
[0008] One system has been developed by Pioneer Aerospace
Corporation that is directed to a large forward-gliding parachute
canopy bearing a heavy payload such as spacecraft returning from
orbit. This system relies upon pyrotechnic connections between
adjacent chords of the canopy which are activated to release one
section of the canopy at a time. However, the system is highly
complex and very expensive, making it unsuitable for routine and
repeated airborne delivery of equipment and supplies such as is
needed for troop support during military operations, particularly
during periods of war and foreign occupation.
[0009] Therefore, a need exists for a reefing device suitable for
large and very large ram air canopies that produces a retarded rate
of slider descent while also providing suspension line management
capabilities. A need also exists for a reefing device that is
released based upon actual forces imposed on the canopy, making it
more responsive to dynamic deployment or opening conditions and
appropriate for use with heavy payloads being delivered by forward
gliding parachute canopies of the ram-air inflated airfoil
type.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, and the need to overcome the
difficulties of undesirable inflation characteristics in ram air
parachutes supporting large payloads, the present invention is
directed to a generally rectangular slider type reefing device that
is physically secured to the ram air canopy to retard its initial
descent along the suspension lines. Retention of the slider
prolongs the physical restriction of the ram air canopy opening
process, producing delay in the inflation of the canopy by reducing
the inflow of inflating air to the cells of the canopy.
[0011] The generally rectangular slider is provided with multiple,
appropriately spaced grommets for managed segregation of the
suspension lines, and is retained against the canopy by retaining
devices positioned adjacent to at least the edge grommets. The
retaining devices include slider retaining loops secured adjacent
to at least the slider edge grommets, canopy retaining loops
secured to the canopy, and breakable fastening elements to secure
the slider retaining loops and the canopy retaining loops together
in respective pairs. To compensate for varying load on different
portions of the canopy, the strength of the breakable fastening
elements can vary at each grommet location according to distance
from the wing tip so as to preferably obtain a uniformly timed
release of the fastening elements and the subsequent even release
of the slider retaining loops from their corresponding canopy
retaining loops.
[0012] It is therefore an object of the present invention to
provide a retained slider system in which the slider is secured to
at least the leading edge portion of the ram air canopy with
breakaway fastening elements that delay initial descent of the
slider from the upper reefing position.
[0013] Another object of the present invention is to provide a
relatively simple, force-activated system for securing and then
releasing the edges of a forward gliding parachute canopy of the
ram-air inflated airfoil type to regulate the opening thereof.
[0014] A further object of the present invention is to provide a
slider system with retaining devices having variable retention
strength which is both reliable and effective for modulating the
canopy inflation and opening process during chute deployment.
[0015] A still further object of the present invention is to
provide a retained slider system that can be readily adapted to fit
and work effectively with a wide range of commercially available
ram air parachutes while requiring minimal adaptation of the
existing parachute structure.
[0016] It is yet another object of the invention to provide a
slider type reefing device that is not complex in structure and
which will conform to conventional forms of manufacture so as to
provide a canopy inflation control system that is economically
feasible, long-lasting and relatively trouble free in
operation.
[0017] These together with other objects and advantages which will
become subsequently apparent reside in the details of construction
and operation as more fully hereinafter described and claimed,
reference being had to the accompanying drawings forming a part
hereof, wherein like numerals refer to like parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a ram-air inflated
airfoil-type parachute with the retained slider reefing system of
the present invention installed thereon, shown with the slider in
the upper reefing position prior to release from the canopy.
[0019] FIG. 2 is a perspective view of the ram air parachute of
FIG. 1, shown as fully deployed, with the slider in a lower
position.
[0020] FIG. 3 is a more detailed view of a portion of the bottom
surface of the parachute taken along line 3-3 of FIG. 2.
[0021] FIG. 4 is an enlarged view of detail "4" of FIG. 1.
[0022] FIG. 5 is an enlarged view of detail "5" of FIG. 1.
[0023] FIG. 6 is a plan view of the slider of FIGS. 1 and 2.
[0024] FIG. 7 is an enlarged view of detail "7" in FIG. 6, showing
a corner grommet with adjacent slider retaining loop.
[0025] FIG. 8 depicts a suspension line extending from its
attachment point on the canopy through a slider grommet during
packing in accordance with the present invention.
[0026] FIG. 9 shows four upper cascaded lines from a suspension
line gathered through a slider grommet during packing, with the
shortest cascaded line provided with a detachable slider stop and
the corresponding canopy portion fitted with a canopy retaining
loop.
[0027] FIG. 10 depicts an alternative arrangement in accordance
with the present invention in which the slider stop is secured to
the canopy and the canopy retaining loop is attached directly to
the slider stop.
[0028] FIG. 11A shows a calibrated break cord with one turn around
an aligned pair of slider and canopy retaining loops in accordance
with the present invention.
[0029] FIG. 11B shows the calibrated break cord of FIG. 11A with
two turns around the aligned pair of retaining loops.
[0030] FIG. 11C shows the calibrated break cord of FIGS. 11A and
11B with three turns around the aligned pair of retaining
loops.
[0031] FIG. 12 illustrates the securing of the retaining loops on
the slider and canopy with multiple turns of a calibrated break tie
in accordance with the present invention.
[0032] FIG. 13 illustrates knotting of the calibrated break tie or
cord of FIG. 12.
[0033] FIG. 14 is an enlarged view of detail "14" of FIG. 2.
[0034] FIG. 15 shows a first alternative fastening mechanism
embodiment using magnetic elements in accordance with the present
invention.
[0035] FIG. 16 shows the magnetic elements of FIG. 15 in a fastened
configuration.
[0036] FIG. 17 shows a second alternative fastening mechanism
embodiment using a snap fastener in accordance with the present
invention.
[0037] FIG. 18 shows the snap fastener elements of FIG. 17 in a
fastened configuration.
[0038] FIG. 19 is another view of the snap fastener elements of
FIG. 16 in a fastened configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] In describing a preferred embodiment of the invention
illustrated in the drawings, specific terminology will be resorted
to for the sake of clarity. However, the invention is not intended
to be limited to the specific terms so selected, and it is to be
understood that each specific term includes all technical
equivalents which operate in a similar manner to accomplish a
similar purpose.
[0040] Referring now to the drawings in detail, FIGS. 1 and 2
illustrate a ram air parachute, generally designated by the
reference numeral 10, in a partially deployed and a fully deployed
condition, respectively. The parachute includes a canopy generally
designated by the reference numeral 12, shown fully inflated in
FIG. 2, from which a payload 15 is suspended by means of a
plurality of suspension lines 16 connected at their upper ends to
the bottom surface of the canopy at suspension line attachment
points 56, as shown in FIG. 3. Groups of adjacent suspension lines
16 are anchored at their lower ends to the airborne guidance unit
20. A generally rectangular reefing slider device, generally
designated by reference numeral 24, slides or descends from an
upper operative reefing position, as shown in FIG. 1, to a lower
position, as shown in FIG. 2.
[0041] The ram air canopy 12 has upper and lower flexible airfoil
surfaces 26 and 28 which, together with chordwise extending ribs
32, form ram air inflated cells 30. The airfoil shaped surfaces 26
and 28 thus extend chordwise from an open leading edge portion 34
to a trailing edge portion 36 in the direction of forward glide.
When the parachute 10 is deployed, the canopy 12 is normally
inflated by inflow of air into the cells 30 between ribs 32 at the
open leading edge portion 34, as is already well known in the art.
Such inflation causes the canopy 12 to become fully extended in
both the chordwise and spanwise directions, the former extending
front to back and the latter extending from wing tip 35 to wing tip
35, to rapidly assume the shape shown in FIG. 2. However, in
accordance with the present invention, inflation of the canopy 12
is delayed and modulated during initial descent of the parachute 10
by the reefing slider device 24.
[0042] The slider device 24 is initially retained against the
bottom surface 28 of the canopy 12 by retaining devices generally
designated by the reference numeral 80, as shown in FIGS. 4 and 5.
As will be discussed more fully hereinafter, each retaining device
80 includes a canopy retaining loop 82 secured to the canopy, a
slider retaining loop 84 secured to the slider 24, and a breakable
fastening element 86 for securing the two loops together. When the
fastening element 86 breaks, the slider is released from the canopy
bottom surface 28 so that the slider 24 can descend, relative to
the canopy, from its upper retained position as shown in FIG. 1 to
its lower position as shown in FIG. 2.
[0043] As evident from FIG. 2, the airfoil gliding parachute 10
with which the retained slider 24 of the present invention is
intended to operate can be very large, on the order of 3500 square
feet with a wing span of about 100 feet. A chute of this size is
designed to be able to operate effectively with a payload of up to
30,000 pounds and is greatly benefitted by the retained slider of
the present invention which reduces the opening force on the
payload by delaying the full opening of the chute.
[0044] Somewhat smaller ram air parachutes, but supporting payloads
down to about 2,000 pounds, are also benefitted by the retained
slider of the present invention. Further, even with the smaller
design, ram air canopies 12 of this type having the size necessary
to support loads of the foregoing magnitude, i.e., of from about
1,000 pounds to about 30,000 pounds, require a large number of
suspension lines 16 to distribute the load. As best shown in FIG.
3, each suspension line 16 cascades from one lower main line rising
from the risers into four upper cascaded lines 40 prior to spaced
attachment of the upper cascaded lines 40 to the bottom surface 28
of the canopy 12 at the suspension line attachment points 56. This
multiplication of lines creates a heightened risk, as compared with
smaller and simpler chute designs, for crossing and tangling of the
suspension lines 16 prior to and during deployment which can
produce catastrophic results.
[0045] To address this line management problem, the slider of the
present invention includes a plurality of individual grommets 42
through which the suspension lines pass in controlled groups. The
number of upper cascaded lines to be passed through each grommet is
adjustable according to design choice requirements. As shown in
FIG. 4, according to a preferred embodiment, the two centermost
forward edge grommets 42a each accommodate only the four upper
cascaded lines from one of the two centermost suspension lines.
Limiting the number of upper cascaded lines in the center grommets
to four facilitates opening of the center cells, which provides
stability to the canopy. Edge grommets closer to the wing tips, by
contrast, typically accommodate eight upper cascaded lines each
(rising from two lower main suspension lines), as shown in FIG. 5.
By organizing and spacing the lines in this way, the slider assists
in ensuring that the lines remain segregated and unobstructed, and
that the canopy material 44 does not become twisted or bunched
within a tangle of lines.
[0046] As shown particularly in FIG. 6, the slider 24 is
constructed as a rectangular sheet 46 made of a relatively low
porosity, flexible material. The sheet 46 is bounded on the edges
by reinforcing strips or tapes 48. More specifically, the edges of
the sheet 46 are bounded by a forward edge reinforcing tape 48a, a
rear edge reinforcing tape 48b, and two wing tip edge reinforcing
tapes 48c, 48d. These are preferably made of highly rip-resistant
nylon fabric as well known in the parachute art.
[0047] Unlike prior art rectangular slider designs which typically
included only four corner grommets, each of the edge reinforcing
tapes 48a, 48b, 48c, 48d includes a plurality of intermediate edge
slider grommets 42a, 42b, 42c, 42d which are interconnected in
spaced relation to each other along the edge tapes 48a, 48b, 48c,
48d, and bounded by corner grommets 42e. According to the
embodiment shown in FIG. 6, and including the corner grommets 42e
in each of the following totals, the forward edge reinforcing tape
48a is provided with a total of ten grommets, the rear edge
reinforcing tape 48b with a total of six grommets, and each wing
tip edge reinforcing tape 48c, 48d with a total of four
grommets.
[0048] Spaced between the forward edge reinforcing tape 48a and the
rear edge reinforcing tape 48b, and generally parallel therewith,
are two longitudinally extending inner reinforcing tapes 49a, 49b.
Each of these tapes corresponds with the forward edge tape 48a in
having a total of eight internal grommets 43a, 43b spaced
equivalently therealong, with the outermost grommets on either end
of such longitudinally extending inner tapes 49a, 49b being the
intermediate grommets 42c, 42d on the wing tip edges 48c, 48d, for
a total of ten grommets along each inner reinforcing tape 49a,
49b.
[0049] Similarly, spaced between the wing tip edge reinforcing
tapes 48c, 48d and generally parallel therewith are eight laterally
extending inner reinforcing tapes 49c, 49d, 49e, 49f, 49g, 49h,
49i, 49j. These tapes cross over the longitudinally extending inner
tapes 49a, 49b at respective internal grommet locations 43a, 43b
therealong and similarly join the forward and rear edges 48a, 48b
at aligned grommet locations 42a, 42b.
[0050] The laterally extending inner reinforcing tapes 49c-49j are
preferably not equidistantly spaced, but are preferably closer to
one another nearest the wing tip edges 48c, 48d. This spacing
generally corresponds with the narrowing of the cells nearest the
wing tips of the ram air canopy as compared with the wider center
cells. The center cell is widest to encourage its initial opening,
while the wing tip cells are narrower to rigidify the wing and
thereby prevent inadvertent collapse when incoming air is reduced
during turning maneuvers.
[0051] The ratio of the span to the chord length of the slider 24
is generally the same as that of the wingspan to chord length of
the corresponding canopy 12. In terms of absolute size, if the
slider is too big it will not be efficient as the canopy will be
allowed to spread too much at the outset, negating the
effectiveness of the slider reefing function. Conversely, if the
slider is too small, it will produce insufficient drag. For use
with a ram air parachute canopy of the type shown in FIGS. 1 and 2,
being on the order of 100 feet in wingspan with a chord length of
about 30 feet, the slider is preferably about 20 feet spanwise and
7 feet chordwise. Hence, the ratio of the wingspan of the canopy to
the span of the slider is about 5:1. With smaller parachutes of the
same style construction, the ratio of the wingspan of the canopy to
the span of the slider should remain substantially the same.
[0052] When the slider 24 is functioning with the parachute 10, the
suspension lines 16 respectively extend slidably through the
grommets 42, 43 to guide the slider upon its descent following the
release of the fastening elements 86. The number of suspension
lines 16 passing through each grommet 42, 43 depends upon the
number of grommets, which can be used to effect the desired opening
behavior of the canopy. For example, as the number of grommets is
increased, the number of suspension lines and corresponding upper
cascaded lines 40 per grommet is reduced while the force necessary
to release the slider from the canopy is increased, assuming all of
the grommets are retained.
[0053] As previously noted, the number of upper cascaded lines 40
per grommet 42, 43 depends upon the particular outcome desired. For
example, if fewer total grommets are provided in the slider, the
number of cascaded lines per grommet may be increased to twelve, or
even more. However, this can make line management somewhat unwieldy
and is ultimately limited by the size of the grommet. Conversely,
if the total number of grommets is increased, then each grommet is
required to retain fewer cascaded lines, such as only four cascaded
lines per grommet throughout the slider. However, as the number of
grommets is increased, the complexity of the slider is also
increased, as is the time required to pack the parachute in
preparation for air drop, as will be discussed more fully
hereinafter.
[0054] As shown particularly by the corner grommet 42e of FIG. 7,
each grommet of the slider that is to be secured to the canopy has
a corresponding slider retaining loop 84, or 84e in FIG. 7. If not
all grommets are to be retained, then the unretained grommets do
not have to have an associated retaining loop. As used herein,
"retaining" a grommet means securing the slider retaining loop
adjacent such grommet to a corresponding canopy retaining loop on
the canopy; similarly, the slider is "retained" in that it is
secured to the canopy.
[0055] The slider retaining loops 84 are preferably made of
reinforced nylon, although any lightweight, high-strength material
could be used. The loops 84 are sewn or otherwise secured to the
reinforcing tapes 48, 49, or 48b and 48d in FIG. 7.
[0056] Whether or not all of the grommets are to be retained will
depend upon design requirements. Any number of grommets may be
retained. For example, every grommet can be retained, or only those
grommets on the edges of the slider, or alternate grommets, or any
other combination of grommets. According to a preferred embodiment,
the grommets 42 located at the periphery or edges of the slider are
retained while the center or internal grommets 43, which are used
to segregate and organize the corresponding suspension lines
stemming from the center areas of the canopy, are not necessarily
retained and, if not, do not have associated retaining loops.
[0057] The suspension line attachment points 56 where the upper
cascaded lines 40 are secured to the canopy typically are placed
along the chord ribs as can be seen in FIG. 3. At each suspension
line attachment point 56, the cascaded line is secured to the
canopy in accordance with conventional line attachment techniques.
When the canopy is being packed, or prepared for air drop, the four
upper cascaded lines of each suspension line are gathered together
to be run through an appropriate grommet. When the lines are
gathered and passed through the grommet, they will have slightly
different lengths according to their individual attachment points
on the canopy, as depicted in FIG. 9. To prevent the canopy fabric
44 from being drawn through the grommet 42 with the lines, the
shortest line 58 within each grommet group of lines is provided
with a slider stop 60. The canopy retaining loops 82 are also
placed adjacent the shortest suspension lines as shown.
[0058] The slider stop 60 is an element that is sized so as to be
unable to fit through the grommets and is preferably made of
reinforced nylon although other lightweight materials could also be
used. The material itself, or the material in combination with a
contained object or other material, must be sufficiently rigid to
prevent folding or crushing thereof that would allow the slider
stop to be pulled through the grommet.
[0059] As shown in FIGS. 8 and 9, the slider stop 60 is preferably
a separate component that can be tied to the desired line and then,
if necessary, untied and retied to a different line. This allows
adjustments to be made to the canopy while in the field, as no
sewing is required to secure the slider stop and no damage occurs
to the chute upon removal of the slider stop. In the embodiment
shown in FIG. 9, the slider stop is constructed with a hard object,
such as a rigid disc 62, encased within a nylon sleeve 64. An
attachment loop 66, used to secure the slider stop 60 to the
cascaded suspension line 40, is sewn to the nylon sleeve 64. Any
sufficiently rigid and lightweight object could be encased within
the nylon sleeve 64 to provide the slider stop function.
[0060] In an alternative embodiment, the slider stop 60 may be sewn
into the fabric 44 of the canopy 12 at the suspension line
attachment point 56, as shown in FIG. 10. With this configuration,
the canopy retaining loop 82 can be advantageously secured to the
slider stop itself as shown. As with the embodiment of FIGS. 8 and
9, the slider retaining loop 84 adjacent the grommet 42 and the
canopy retaining loop 82 on the shortest associated suspension line
58 are then secured together by the fastening element 86 as shown
in FIGS. 4 and 5. As with the slider retaining loops, the canopy
retaining loops 82 are preferably made of reinforced nylon or other
lightweight, high-strength material.
[0061] As already discussed, the number of grommets provided on any
given slider will depend on the canopy size and construction, as
well as the degree of canopy opening restriction that is desired.
However, for the purposes of explanation, the particular slider
embodiment of FIG. 6, in conjunction with a parachute of the type
shown in FIGS. 1 and 2, will be described in the following
explanation of the process for packing a parachute with a retained
slider according to the present invention.
[0062] Returning to the specific construction of the slider 24
illustrated in FIG. 6, according to the preferred embodiment shown,
the grommets 42 along the periphery of the slider are retained.
Therefore, counting so as to include the corner grommets 42e in
each total, there are ten leading edge grommets 42a, eight wing tip
grommets 42c, 42d, and six rear edge grommets 42b which must be
secured to the canopy. This equates to an absolute total of twenty
grommets to be retained.
[0063] In preparation for securing the slider 24 to the canopy 12,
the canopy must be equipped with sufficient canopy retaining loops
82 to correspond with the slider retaining loops 84 on the slider
24. Hence, ten canopy retaining loops 82 are attached to the
leading edge 34 of the canopy, four to each wing tip 35, and six to
the trailing edge 36 of the canopy 12. As with the slider, the
corner retaining loops on the leading edge 34 of the canopy are the
same as the forward-most corner retaining loops of the canopy wing
tips 35. Similarly, the corner retaining loops on the canopy
trailing edge 36 of the canopy are the same as the rear corner
retaining loops of the wing tips 35. Accordingly, the total number
of retaining loops 82 on the canopy is twenty.
[0064] The process by which the slider is retained against the
canopy is undertaken as follows. First, the ten forward edge slider
retaining loops 84a, 84e are secured to the ten leading edge canopy
retaining loops 82; the retaining loops on the corners are
designated 84e for clarity given their shared membership with the
group of wing tip retaining loops 84c, 84d.
[0065] Starting from either the left or the right slider wing tip
with loop 84e and working toward the center, corresponding pairs of
slider and canopy retaining loops 84a, 82 are brought into
alignment with one another. Upon reaching the center, the aligning
process is repeated beginning from the opposite wing tip corner
loop 84e. Once all of the retaining loop pairs of slider loops 84a,
84e and canopy loops 82 are aligned, the loops of each pair are
secured to one another using appropriate fastening elements 86.
[0066] The fastening elements can include string, cord, cable-tie
type fasteners, etc. Any fastening element 86 having a set or
calibrated break strength within a required range and a
configuration making it suitable to join two loops of fabric may be
used. According to a preferred embodiment as shown in FIGS. 11A,
11B, 11C, 12 and 13, the fastening element 86 is embodied as a
calibrated break tie or cord 78 such that each aligned pair of
retaining loops is fastened together by tying.
[0067] To tie each aligned pair of loops, the calibrated break tie
or cord 78 is passed through each of the two retaining loops 82, 84
at least once, i.e., for one turn, as shown in FIG. 11A, and then
tied. For increased tie strength, the cord 78 is passed through the
two retaining loops 82, 84 a second time, i.e., for two turns, as
shown in FIG. 11B, and then tied. Similarly, the cord 78 may be
passed through the two retaining loops 82, 84 a third time, i.e.,
for three turns, as shown in FIG. 11C; this process may be
continued with as many turns as desired. The turns are pulled
tightly, as shown in FIG. 12, and then a knot 79 is formed with the
cord ends to complete the tie, as shown in FIG. 13. When fastened
in this manner, the slider 24 is retained against the canopy 12 as
in FIG. 1.
[0068] Using calibrated break ties or cord, it has been determined
that desirable chute opening performance is achieved with an
incremental pattern of tie strength beginning from the wing tips 35
and edge tapes 48c and 48d and increasing toward the center. More
particularly, and still referring to the forward edge 48a of the
slider, the process of tying the aligned loops begins from either
the left or the right slider wing tip 48c, 48d and working toward
the center. First, the wing tip corner loops are secured together
using one turn of the cord. The next pair of loops is secured using
two turns of cord, the next pair using three turns of cord, and the
next pair using four turns of cord. Finally, the centermost pair of
loops is secured using four turns of cord. Upon completing this
centermost pair of loops, the process is repeated beginning from
the opposite wing tip.
[0069] Once the ten pairs of retaining loops 82, 84 on the forward
and leading edges 48a, 34 of the slider and canopy, respectively,
have been retained in the manner just described, the eight wing tip
retaining loops on the slider, which include four intermediary
loops 84c, 84d and four corner loops 84e, are secured to the
corresponding eight wing tip retaining loops on the canopy (not
shown). Since the loops 84e on the forward corners of the wing tips
48c, 48d have already been secured as part of the securing of the
retaining loop pairs on the forward/leading edges of the
slider/canopy, there remain only six pairs of wing tip retaining
loops 84c, 84d, 84e to be secured, three on each side.
[0070] Beginning on either side and working front to rear, the wing
tip retaining loops 84c, 84d, 84e on the slider are aligned with
the corresponding wing tip retaining loops on the canopy. Once
aligned, each pair is secured by one turn of the calibrated break
cord, as shown in FIG. 11A, and knotted, as shown in FIG. 13. The
process is repeated on the opposite wing tip.
[0071] The remaining six rear edge slider retaining loops and
trailing edge canopy retaining loops are then similarly secured
using the same tying technique. Beginning on either side and
working from the wing tip corner loops 84e on the rear corner
toward the center, the respective pairs of loops are aligned with
one another. Since the wing tip corner loops 84e by the rear corner
grommets 42e have already been secured as part of the securing of
the retaining loop pairs on the wing tip edges 48c, 48d of the
slider/canopy, there remain only four pairs of rear edge retaining
loops 84b to be secured. The next inward pair is secured by two
turns of the calibrated break cord, as shown in FIG. 11B, and
knotted, as shown in FIG. 13. Finally, the innermost pair is
secured by three turns of the cord, as shown in FIG. 11C, and
knotted. The process is repeated on the opposite side working from
the opposite wing tip inward.
[0072] To help prevent the possibility of a "line over", a
situation in which the suspension lines attached to the trailing
edge of the canopy get crossed over to the leading edge prior to
deployment, often with serious results upon deployment, the process
of retaining the slider may conclude with the final step of
gathering the rear edge slider stops together and securing them in
a bundle with a single turn of calibrated tie cord. The cord is
passed through each of the trailing edge retaining loops, which are
located adjacent the slider stops, with the ends of the cord then
being drawn snugly together, but without drawing up the canopy
material, and then knotted as with the other ties.
[0073] As is evident from the example just given, the higher stress
to which the center of the canopy is subjected necessitates that
the fastening elements retaining the centermost edge grommets be
stronger than those used to retain the wing tip grommets. The goal
in defining the different strengths of the fastening elements is to
have all of the fastening elements break simultaneously in response
to air flow forces encountered during parachute descent.
Simultaneous breaking of the fastening elements releases the canopy
evenly so that its pressurization is regular across the span. The
rear edge also needs to break evenly with the front edge and thus
is secured with weaker tie strength reflective of the lower level
of stress imposed on the rear edge relative to that on the
front.
[0074] A range of other fastening materials may be used to retain
the slider as has already been stated. The calibrated break cord
used in the representative example is preferably one that is
readily available to military users from existing supply stocks
such as, for example, MIL-T-5660-Style A Ticket 5. Use of such a
standard supply stock material, with varying strength obtained
through variation in the number of turns, allows a single material
supply source to be used to secure all of the retaining loops,
increasing the efficiency of military operations by simplifying the
equipment requirements and avoiding complexity in the packing
procedure. However, any connecting element or combination of
connecting elements may be used. For example, cable ties of
different strengths may be secured to different retaining loop
pairs, i.e., with stronger cable ties in the center and weaker
cable ties on the wing tips. Alternatively, cords of different
strengths could be used for specific retaining loop pairs.
[0075] Other fastening mechanisms of various types that will
release when subjected to a specified amount of force may also be
used while retaining the advantages already described in connection
with the break ties. For example, magnets, snaps, calibrated wires,
clips, etc. could all be effectively adapted to retain the slider
until sufficient force is applied thereto in accordance with the
present invention.
[0076] A first alternative embodiment using magnetic retaining
devices is set forth in FIGS. 15 and 16. As shown in FIG. 15, a
magnet 100 is positioned within a fabric housing 102 that is sewn
onto or otherwise secured to the slider 24; preferably, the fabric
housing is adjacent a slider grommet 42. A mating magnet 104 is
secured within a similar fabric housing 106 that is sewn or
otherwise connected to the canopy 12 at the point where the slider
stop 60 comes in contact with the slider grommet 42. The fabric
housings protect and secure the magnets against the respective
slider or canopy portion to which they are attached.
[0077] During the packing process, the two magnets 100, 104 are
coupled to one another as shown in FIG. 16 and thereby hold the
slider 24 against the canopy 12. When the canopy deploys, the
slider is retained against the bottom of the canopy by the magnetic
force until enough pressure builds up inside the canopy to pull the
two magnets 100, 104 apart. Once the magnets are separated, the
slider is free to move down the suspension lines 16.
[0078] A second alternative embodiment using snap fasteners 110 as
retaining devices is set forth in FIGS. 17, 18 and 19. As shown in
FIG. 17, each snap fastener 110 includes a stud 112 and a mating
socket 114. The stud 112 is preferably positioned on the slider 24
adjacent to a grommet 42, while the socket 114 is installed on a
piece of webbing 116 that is sewn or otherwise connected to the
canopy 12 at the point where the slider stop 60 comes in contact
with the slider grommet 42. As would be understood by persons of
ordinary skill in the art, the positions of the stud 112 and socket
114 could be reversed, and a material other than webbing could be
used to hold the socket 114.
[0079] During the packing process, the stud 112 and socket 114 are
snapped together to hold the slider 24 against the canopy 12, as
shown in FIGS. 18 and 19. When the canopy deploys, the slider is
retained against the bottom of the canopy by the mechanical
connection of the snap fastener elements 112, 114 until enough
pressure builds up inside the canopy to pull the socket 114 from
the stud 112 and unfasten the snap. Once the socket and stud have
been pulled apart, the slider is free to move down the suspension
lines.
[0080] Clips having a determined strength may also be used to
secure a portion of the canopy to the slider, preferably adjacent a
grommet location. The clips may be attached with a string tie or
other mechanism to either the slider or the canopy so that, once
they have been forced to release the fabric they were holding, the
clips will be retained and can be reused. However, clips represent
a less preferred embodiment as the clip structure tends to be bulky
and can become caught on other portions of the canopy or slider
during the packing process.
[0081] In addition to the use of different fastening mechanisms,
tie materials and related methods, the relative strength of the
ties or other fastening mechanisms used to secure the center
retaining loop pairs as opposed to the wing tip pairs may also be
varied to suit the particular size parachute and payload. For
example, as the weight of the payload is reduced within a moderate
range, the fastening elements will take slightly longer to release,
whether by breaking as in the case of ties or calibrated wires, or
by element separation as in the case of magnets or snaps, but the
delay will not be unduly extended. When the weight of the payload
is substantially reduced, as from 10,000 pounds to 5,000 pounds,
however, a different fastening element arrangement may be necessary
to ensure timely fastening element release.
[0082] In addition to varying the strengths of a particular
fastening mechanism to accommodate the varying loads placed upon
different areas of the canopy during deployment, more than one type
of fastening mechanism may be utilized on the same canopy. For
example, in certain parachute payload conditions, break ties may be
used in the center of the canopy where the force is greatest, while
magnets are used on the wing tips where a reduced force is
experienced. This is advantageous in that the ease of the magnetic
closure is obtained in those areas of the canopy where the
retaining power of smaller magnets is sufficient, while avoiding
the use of large heavier magnets as would otherwise be needed to
accommodate the greater center loading were only magnetic fastening
mechanisms to be used.
[0083] Any of the fastening mechanisms discussed herein, as well as
other comparable fastening mechanisms that are structured to
release when subjected to a level of force as described herein, may
be used together in various combinations on a single canopy to best
suit the particular load and force requirements thereof. In
accommodating these combinations, the canopy may be equipped with
both a magnetic and a retaining loop device at a particular
grommet, or with both a snap fastener and retaining loops at a
particular grommet. In this way, the magnetic connection (or the
snap fastener) can be used when their retaining force is
sufficient, as with a smaller payload, reducing the time needed for
packing of the parachute. The same canopy configuration can
thereafter be used with a heavier payload by securing the retaining
loop device, which is at the same grommet formerly secured by the
magnets or snap fastener, with appropriate break ties. This use of
alternate fastening mechanisms provides significant versatility and
variability in load capability using a single canopy.
[0084] The speed at which the chute is to be deployed must also be
taken into consideration when planning fastening element strength.
Stronger fastening elements are needed to withstand the greater
opening forces experienced at higher altitudes where higher air
drop speeds are required to sustain lift. Weaker fastening elements
may be advisable at lower altitudes to ensure adequate flight time
for the parachute.
[0085] The retained slider according to the present invention
requires only conventional materials, making it cost-effective and
relatively simple to employ. Upon chute deployment, the fastening
elements break or are separated when sufficient force is created by
the inflow of air into the cells of the canopy, allowing the slider
24 to descend to the position shown in FIG. 2. However, in the case
of the break ties, the canopy retaining loops 82 remain secured to
the canopy 12, as shown in FIG. 14, just as the slider retaining
loops 84 are still affixed to the slider 24, thus enabling both
loops to be reused with only a new fastening element being
required. In the case of magnets or snaps, or course, the fastening
mechanism elements remain respectively secured to one of the canopy
and slider and can be reused almost indefinitely; all that is
required is to refasten the mating components during the packing
process.
[0086] The slider retention design according to the present
invention also facilitates chute preparation. As compared with
prior art designs for the controlled opening of large canopies
which could take multiple persons several days or more to pack
preparatory to air drop, the retained slider system of the present
invention can be folded and packed by two people in about four
hours using conventional parachute packing techniques.
[0087] In sum, the retained slider according to the present
invention provides not only for greater regularity in the expansion
of the chute through delay in the opening thereof, the duration of
which is directly responsive to actual forces on the chute, but
also provides improved line management capability through
segregation and retention of groups of lines within the plurality
of individual grommets for greater organization and increased
deployment safety.
[0088] The foregoing descriptions and drawings should be considered
as illustrative only of the principles of the invention. The
invention may be configured in a variety of shapes and sizes and is
not limited by the dimensions of the preferred embodiment. Numerous
applications of the present invention will readily occur to those
skilled in the art. Therefore, it is not desired to limit the
invention to the specific examples disclosed or the exact
construction and operation shown and described. Rather, all
suitable modifications and equivalents may be resorted to, falling
within the scope of the invention.
* * * * *