U.S. patent number 3,840,922 [Application Number 05/303,324] was granted by the patent office on 1974-10-15 for landing cushion for falling objects.
This patent grant is currently assigned to Thermo-Flex, Inc.. Invention is credited to Richard L. Morrison, Venard C. Webb.
United States Patent |
3,840,922 |
Morrison , et al. |
October 15, 1974 |
LANDING CUSHION FOR FALLING OBJECTS
Abstract
A device for decelerating an object in motion is provided with a
first cushion body that is positioned within the path of travel of
the object. This is a hollow, flexible and inflatable cushion
provided with sidewalls, a supported surface, and a first surface.
The supported and first surfaces are opposed, spaced apart and are
disposed transversely of the path when the first cushion has been
inflated. A hollow flexible and inflatable second cushion body is
disposed in advance of the first cushion and has an impact surface
and a second surface. The second cushion is supported by the first
surface of the first cushion and has a higher gas pressure than the
first cushion. The first surface of the first cushion and the
impact surface of the second cushion are movable inwardly of the
first and second cushions, respectively, when the bodies have been
inflated, in response to the force of an object thereagainst.
However, the second body is constructed to impede the rapid escape
of gas upon the inward movement, thereby becoming relatively firm
when the object strikes the impact surface. Thus, the area over
which the force of the object is applied is greater on the first
surface of the first cushion than the force area applied at the
impact surface of the second cushion. Due to the relatively large
force area, the gas pressure within the first body necessary to
decelerate the object is decreased.
Inventors: |
Morrison; Richard L. (Salina,
KS), Webb; Venard C. (Salina, KS) |
Assignee: |
Thermo-Flex, Inc. (Solina,
KS)
|
Family
ID: |
23171538 |
Appl.
No.: |
05/303,324 |
Filed: |
November 3, 1972 |
Current U.S.
Class: |
482/15; 182/137;
5/420 |
Current CPC
Class: |
A63B
6/02 (20130101); A63B 2225/62 (20130101) |
Current International
Class: |
A47C
27/08 (20060101); A63B 6/00 (20060101); A63B
6/02 (20060101); A47c 027/08 () |
Field of
Search: |
;5/348,349,350
;182/137,139 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gilliam; Paul R.
Assistant Examiner: Calvert; Andrew M.
Attorney, Agent or Firm: Lowe, Kokjer, Kircher, Wharton
& Bowman
Claims
Having thus described our invention, we claim:
1. A device for decelearating a person falling from an elevated
height comprising:
a hollow, flexible, inflatable first body disposed within the path
of travel of said person and adapted to have a gas pressure,
said first body including a supported surface and a first surface
in opposed spaced apart relationship transversely of said path;
and
a hollow, flexible, inflatable second body independent of the first
body, disposed on said first surface and adapted to have a gas
pressure at least three times the gas pressure in said first
body,
said second body including an impact surface and a second surface
in opposed spaced apart relationship and independent of said
supported surface and said first surface;
whereby when a person impacts on said second body the impacting
force is distributed over a relatively large area thereby
decreasing the pressure needed in the first body to complete
decelearation of the person.
2. The invention of claim 1, including alternating elastic and
inelastic spacing members tying said supporting surface to said
first surface from within said first body when the latter is
inflated to control movement of said first surface in response to
the force of a person thereagainst.
3. The invention of claim 1, wherein is included means for creating
said gas pressures in said first and second bodies
respectively.
4. The invention of claim 3, including a first conduit for
communicating said first body with the gas pressure creating means;
and means for controlling the flow of gas through the first conduit
to maintain said first body in an inflated condition and preventing
gas from leaving the body when a person impacts against it.
5. The invention of claim 4, wherein the gas pressure creating
means comprises a first air blower communicating with the
atmosphere with the first conduit, and said flow control means
comprises a one way flap valve disposed downstream from said air
blower.
6. The invention of claim 5, wherein is included a second conduit
for communicating said second body with said gas pressure creating
means, and the gas pressure creating means comprises a second air
blower communicating with the atmosphere and disposed in
communication with the second conduit.
7. The invention of claim 1, wherein said impact surface and said
second surface are recurrently joined together to form a plurality
of intercommunicated chambers in the second body.
8. The invention of claim 3, wherein said first body includes
sidewalls combined with said supported and first surfaces; and
including weight means coupled with said second body adjacent the
sidewalls of the first body for generating a downward force near
said sidewalls opposed to the force of a person moving against said
first and impact surfaces whereby to provide increased resistance
to the forces of the person.
9. The invention of claim 1, including:
a hollow, flexible, protective element combined with and projecting
to one side of said first body and having a gas pressure, an
impinging surface, and a support surface;
said impinging surface being movable toward said support surface in
response to the force of a person moved thereagainst;
a hollow, flexible, inflatable support member underlying said
impinging surface and having a gas pressure normally equal to the
gas pressure in said element; and
means for causing the gas pressure in said member to become greater
than the pressure in said element upon a person moving against the
impinging surface of the element.
10. The invention of claim 9, wherein said means for causing a
greater gas pressure in said protective element comprises a first
opening communicating said element with said first body and a
second opening communicating said element with said support member
and having a smaller cross-sectional area than the first
opening.
11. The invention of claim 10, wherein said support member is of
circular cross-sectional configuration whereby to cause any
deformation of the member to create a pressure increase
therewithin.
12. The invention of claim 11, wherein a vertical bisector of said
member extends along a line adjacent an edge of said impinging
surface.
13. The invention of claim 1, wherein said device includes a
hollow, flexible, inflatable edge support underlying said first
surface at opposite edges of the latter to either side of the
direction in which a person is jumping, said support having a
normal gas pressure equal to the pressure in said first body; and
means for causing the gas pressure in said support to become
greater than the pressure in said first body upon a person moving
against said first surface in the area of said support.
14. The invention of claim 13, wherein said support underlies said
supported surface and is of circular cross-sectional
configuration.
15. The invention of claim 14, wherein said means for causing a
greater gas pressure in the support comprises a restricted opening
communicating the interior of said support with said first
body.
16. The invention of claim 15, wherein a vertical bisector of said
support extends along a line adjacent to the edge of said first
surface.
Description
Support cylinders are provided at the edges of the first cushion
body, supported surface. These support cylinders are hollow
inflatable bodies in communication with the first body through
restricted orifices. This assures that when an object pushes
against the first body in the area of the support cylinders, a
higher gas pressure will be present in the cylinders than in the
first body. Accordingly, the edges of the body will be supported
and will not collapse.
It is well known that it is desirable to cushion the fall of pole
vaulters and high jumpers in athletic contests without subjecting
the athletes to shock or injury. Also, it has been found a
desirable characteristic of these cushions to be portable,
permitting quick and easy removal from the location of use to
storage areas. Normally, this type air cushion applies a low
initial gas pressure, with the pressure rapidly increasing as the
athlete penetrates deeper into the cushion. It has therefore been
thought desirable to have such an initial low gas pressure to
softly cushion the initial shock of the falling vaulter and then
increase the pressure to be sure the vaulter stops before
"bottoming out."
One such prior art device is shown in U.S. Pat. No. 3,399,407
issued Sept. 3, 1968. However, there are many characteristics of
this type air cushion that make it unsatisfactory for use in
athletic contests. One such characteristic is: if the electricity
supplying the blower which provides the air pressure inside the
cushion is removed, the cushion will lose pressure within
approximately 3 seconds. Due to this rapidity of pressure loss, the
cushion could fail to build sufficient pressure to completely
decelerate the vaulter if the power is removed during a valt. Thus,
serious injury could occur to the vaulter because of his impact
with the ground. Another undesirable feature of this type of air
cushion is the relatively far distance that the vaulter has to
penetrate into the cushion before a sufficient air pressure is
created therein for decelerating the vaulter. This deep penetration
by the body of the vaulter with the corresponding sudden stop causd
by the decelerating air pressure may generate a "whiplash" effect
to the vaulter. This effect could be injurious or at best
frightening to the vaulter. It has also been found that the safety
wedges at the front of the air cushions of the patented device tend
to twist a vaulter's feet out from under him should he fall onto a
wedge instead of onto the air cushion.
Accordingly, it is one of the primary objects of this invention to
provide apparatus for decelerating moving objects using a
relatively high pressure air cushion in advance of a lower pressure
air cushion to widen the impact area of the object on the lower
pressure cushion thus distributing the force of the object over a
larger area and allowing the decelerating gas pressure to be
relatively low at the moment of completion of the deceleration of
the object.
Another aim of this invention is to eliminate a hard or slapping
sensation caused by the tension in the material due to its
relatively large radius of curvature as characterize the prior art
devices. The construction of the second body of the present
invention creates "tufts" of small radius, thereby reducing the
tension and increasing its shock absorbing qualities. A body of
this construction has been found to be far superior to pads of
foamed rubber or polyurethane, or air cushions of the prior
art.
Another primary object of this invention is to provide apparatus to
decelerate moving objects when impacting an air cushion even upon
removal of the electricity supplying the power to blowers providing
the air pressure to inflate the cushions.
A further object of this invention is to provide a sufficiently
high gas pressure within the first, bottom air cushion to assist a
vaulter in a relatively easy exit from the vaulting pit.
As a further object of this invention, an air cushion is
constructed to cause a relatively high gas pressure to decelerate
an object on initial impact thereby reducing the required pressure
as the object penetrates deeper into the cushion.
Another aim of this invention is to provide front safety wedges in
combination with an air cushion that will allow an object striking
upon the impinging surfaces of these wedges to be impelled onto the
impact surface without causing the vaulter's feet to go out from
under him.
As another aim of this invention, apparatus is provided to apply a
relatively uniform decelerating force against an object striking an
air cushion with a corresponding prevention of "bounce" to the
object by controlling the variation in spacing between the top and
bottom of the cushion.
Still another object of the invention is to provide support
cylinders at the edges of the first cushion body, which cylinders
are caused to have a higher gas pressure than the body when a force
acts against the latter whereby the cylinder will support the edges
of the body.
IN THE ACCOMPANYING DRAWINGS
FIG. 1 is a front perspective view of the device of this
invention;
FIG. 2 is an enlarged, fragmentary side elevational view of the
device, a portion of the first inflatable body being broken away
and appearing in cross-section to reveal details of
construction;
FIG. 3 is an enlarged, fragmentary, vertical sectional view taken
on line 3--3 of FIG. 2;
FIG. 4 is a fragmentary, vertical sectional view through the fan
unit of the second body on a scale enlarged of FIG. 3, the fan
blade and motor appearing in elevation;
FIG. 5 is a fragmentary, vertical sectional view through the blower
unit in the same scale as FIG. 3, the one-way flap valve appearing
in elevation;
FIG. 6 is an enlarged, fragmentary, elevational sectional view of a
safety wedge and support, and showing the relationship between the
orifice sizes communicating with a safety wedge;
FIG. 7 is a fragmentary, vertical sectional view taken on line 7--7
of FIG. 6 and on the same scale as FIG. 6;
FIG. 8 is fragmentary, vertical sectional view taken on line 8--8
of FIG. 6 and on the same scale as FIG. 6;
FIG. 9 is an enlarged, fragmentary, plan view of a portion of the
second body;
FIG. 10 is an enlarged, fragmentary, vertical sectional view taken
on line 10--10 of FIG. 9.
FIG. 11 is a perspective view of an alternative form of the
invention showing the edge support cylinders;
FIG. 12 is an enlarged fragmentary end elevational view of the
embodiment of FIG. 11 looking in the direction of arrows 12--12 and
showing further details of the edge supports; and
FIG. 13 is a fragmentary vertical cross-sectional view of the
cushion bodies and edge support taken along line 13--13 of FIG.
11.
Referring initially to FIGS. 1-3, a device 20 includes a first
inflatable body 22 in the nature of a hollow collapsible bag of
flexible material. Body 22 has a bottom supported wall 24, a front
wall 26 with forward extending walls 28 and front closing wall 30,
a rear wall 32, sidewalls 34 and 36, and a first surface 38 the
latter providing the top of body 22. The material from which body
22 is constructed is relatively impervious to the flow of air. A
material such as nylon or the like which has been impregnated with
rubber, neoprene, plastic or other synthetic material, is
well-suited for this purpose. The joining of the walls to the
individual surfaces may be by any suitable process such that the
seam formed will be impervious to the flow of air.
A plurality of tabs 40 are secured in spaced intervals to the
underside of top 38 and the upper surface of bottom 24. It may be
seen from FIGS. 2 and 3 of the drawing that the tabs 40 for top 38
are located immediately above the corresponding tabs 40 for bottom
24. Cords 42 (constructed of inelastic material) and cords 44
(constructed of elastic material) are alternately secured to
grommets 46 in tabs 40. When body 22 is inflated, cords 42 and 44
will stand substantially vertical between bottom 24 and top 38,
thus the shape of body 22, when inflated with air, is substantially
as shown in the drawings. A plurality of sandbag weights secured to
walls 26, 30, 32 and 34 provide an anchoring system for the device
20.
A pair of auxiliary wedge shaped cushions 48 are secured to front
closing wall 30 in mutually spaced relationship. As illustrated in
FIGS. 6 and 7, each wedge 48 includes an impinging surface 50, a
front wall 52, a backwall 54, an outside wall 56, an inside wall
57, and a support surface 58. Outside wall 56 of each wedge 48 is
positioned substantially in a coplanar relation with forward
extending wall 28, as shown in FIG. 1, and back wall 54 is secured
to front extending wall 30. The spacing between the inside walls 57
will be discussed in greater detail hereinafter.
A cord 60 is secured similarly to cords 42 and 44 in a relatively
vertical position extending between impinging surface 50 and
support surface 58 of each wedge 48. The relative spacing between
surfaces 50 and 58 upon inflation of wedge 48 is maintained by cord
60. Each wedge 48 communicates with the interior of body 22 through
orifices 62 for receiving air pressure.
Wedges 48 are each upheld by supporting cylinders 64, as
illustrated in FIGS. 6 and 8. Each cylinder 64 comprises a hollow,
inflatable, flexible, elongated member secured to support surface
58 of each respective wedge 48. Each cylinder 64 has an outside
surface 66 and closing ends 68. Closing ends 68 and walls 56 and 57
of wedges 48 are in substantial alignment when viewed in a front,
vertical direction (FIG. 8). Each supporting cylinder 64
communicates with the interior of the respective wedge 48 through
surfaces 58 and 66 by means of relatively restricted orifices 70.
Restrictive orifices 70 are substantially smaller than orifices 62
in back 54 of wedge 48 for purposes to be explained
hereinafter.
Rear wall 32 of body 22 is provided with a port 72 which
communicates with an elongated conduit 74, the latter having one
end secured to the angular rim of port 72 as best illustrated in
FIG. 2. Conduit 74 may be of any convenient length and extends from
rear wall 32 to an outlet 78 of blower unit 76. As seen in FIG. 5,
blower 76 is of a conventional squirrel cage type with a protective
casing 80 and an electric motor (not shown) providing the power to
turn the blower blades (not shown). A one-way flap valve 82 is
secured by its upper edge to blower outlet 78, such that, as long
as air is being expelled from blower 76 through conduit 74, and
into bag 22 the valve is open, as illustrated at 86. However,
should the electricity to the motor of blower 76 be removed, the
blower will cease to run and as the air tries to return through
conduit 74, valve 82 closes and the air is prohibited from passing.
Thus, the gas pressure within body 22 will be maintained for an
extended period of time.
A second hollow, flexible, and inflatable body 86 is positioned
atop and supported by first body 22. Second body 86 may be
constructed of materials substantially similar to that used for the
construction of first body 22. However, second body 86 is
constructed differently from that of first body 22. That is, an
impact surface 88 is used to form the top of second body 86 and is
secured to a second surface 90, the latter providing the bottom for
second body 86. Impact surface 88 and second surface 90 are secured
to a recurrent "tufted" pattern, such that a plurality of chambers
94, each characterized by an outer wall formed by surface 88 which
is of a relatively small radius of curvature, are interconnected by
air passages 96, as best seen in FIGS. 9 and 10. Second body 86 is
held in a relatively fixed position to first surface 38 of body 22
by ties 98 and sandbag weights 106.
A conduit 100 is secured to the back portion of second body 86, as
illustrated in FIGS. 1 and 2. Conduit 100 extends between second
body 88 and a fan casing 102 mounted on the protective casing 80 of
blower 76. Air is forced through conduit 100 by a blower fan 104 to
inflate second body 86. The blower 104 is constructed to produce
and maintain a relatively constant gas pressure in second body 86
higher than the gas pressure in first body 22.
Although, the device 20 has many applications for cushioning
falling objects, it is particularly useful for athletic events such
as pole vaulting and high jumping contests. When device 20 is to be
used as a vaulting pit, the vaulting standards are placed on the
outside of walls 28 and 56. Wedges 48 are positioned on either side
of the vaulting box for placing the pole when the vaulter is
vaulting, thus determining the distance between inside walls 57.
Electrical wiring is run to the motors for fans 76 and 104. The
fans are activated and bodies 22 and 86 are inflated to their
respective gas pressures. First body 22 is inflated until spacers
42 and 44 limit the distance between support surface 24 and first
surface 38, depending on the gas pressure produced by blower
76.
Upon activation of blower fan 104, air will be supplied through
conduit 100, gas passages 96 and into the chambers 94, thus
inflating second body 86. The fans 76 and 104 are controlled to
provide a greater gas pressure in second body 86 than in first body
22. In general, it has been found that a satisfactory result is
obtained when the pressure in second body 86 is from 5 to 10 inches
water column and the pressure in first body 22 is from 11/4 to 11/2
inches, of water column. Thus, when a vaulter impacts upon impact
surface 88, impact surface 88 is compressed toward second surface
90. Because gas passages 96 are not continuous, the movement of gas
from the impact area is delayed and only a minor amount of gas
escapes through conduit 100 and blower 104 to the atmosphere.
Therefore, second body 88 is essentially an enclosed air container
with the air pressure acting within chamber 94 as a support to
provide a relatively firm body. This distributing effect of the
high pressure body 86 causes the force of the impacting object to
be distributed over a larger area on first surface 38 than the
actual contact area of the object on impact surface 88. Since
second body 86 results in the force applied to body 22 being
applied through a greater area, the gas pressure in first body 22
does not have to be as great to achieve the necessary deceleration
as would be the case if an object were to strike first body 22
directly without first striking second body 86. This relatively
fast application of a decelerating force aids in preventing the
vaulter being rolled "into a ball" and becoming "buried" in the
cushion. Also, the "whiplash" effect caused by a vaulter's head
penetrating substantially deeper into a low pressure cushion than
the rest of his body is prevented. Since the distance the head lags
behind the body is minor with bodies 22 and 86, movement of the
head relative to the body is substantially eliminated.
As second surface 90 of second body 86 is compressed against first
surface 38 of first body 22 through the force of the object on the
impact surface 88, the gas pressure within first body 22 is
increased and the flow of gas through conduit 74 tends to flow
toward blower 76. This causes valve 82 to be closed, as illustrated
in solid line on FIG. 5, thus prohibiting gas from leaving first
body 22. Manifestly, valve 82 will close in a like manner when the
electricity supplying the power to blowers 76 and 104 is removed.
Since spacing cords 42 and 44 permit relative movement of surfaces
24 and 38, thus the force of an object impacting against body 22
causes only a relatively small pressure rise within body 22 even
though it is essentially a "closed" container.
It has been found highly desirable to have spacing cords 42 and 44
alternately constructed of inelastic and elastic material,
respectively. When all the cords are constructed of elastic
material, first body 22 merely expands in the areas away from the
impact area and sufficient pressure to completely decelerate the
object is not developed, thus it may "bottom out." When all the
cords are constructed of relatively inelastic material, the
surfaces 24 and 38 cannot move relatively and an undesired increase
in pressure occurs as the object penetrates into the body. This may
result in the object being decelerated too quickly for safety
and/or comfort. However, it has been found by alternating inelastic
and elastic cords, the undesired pressure increase is minimized
without causing the object to be thrown or "bounced" from the
impacting surface.
The weight of sandbags 106 acting at edges 92 of second body 86 act
in an inertial moment when the object impacts upon surface 88. That
is, taking the sum of the moments about the contact area where the
object impacts, the weights will tend to resist movement of impact
surface 88 toward the impact area. This resistance aids in
providing the second body 86 with relatively firm resistance to
penetration by the object. Thus, through the use of these weights,
a greater decelerating force is applied to the object more quickly
to an object impacting on first surface 38.
Should the object miss the normal impact surface 88 of second body
86, and strike impinging surface 50 of wedges 48, impinging surface
50 will move inwardly toward support surface 58. The gas within
wedge 48 is forced outwardly through orifices 62 and 70. The force
of the object is then transmitted to supporting cylinder 64, which
will accordingly cause a greater pressure within supporting
cylinder 64 and there will be some tendency for gas to move from
the cylinder into wedge 48. However, since orifice 70 connecting
the wedge with the cylinder is of much smaller diameter than
orifice 62 connecting the wedge with body 22, a much larger amount
of gas will escape from wedge 48 into first body 22 than will move
from supporting cylinder 64 into wedge 48. Thus, the wedge 48 will
move downwardly at the point of impact while the end of the wedge
above cylinder 64 will remain substantially "upright" supported by
the cylinder. The cylindrical cross-sectional configuration of the
wedge supports is highly desirable since any deformation of the
cylinder will decrease the volume and increase the pressure, thus
further contributing to support of wedge 48. This assures that a
vaulter landing on a wedge and rolling toward bodies 22 and 86 will
fall toward the cushion bodies rather than being thrown backwards
onto the ground.
Referring now to FIGS. 11-13 where an alternative embodiment of the
invention is shown, a device designated generally by the numeral
120 is substantially identical to the device 20 described above
except in the respects noted hereinafter. First cushion body 122 is
provided with a supported surface 124 which is tapered upwardly at
the edges of the body to present side wedges 108 of generally the
same configuration as forward wedges 48 previously described.
As shown in FIG. 13, a plurality of auxiliary tie cords 142 (only
one of which is visible in the drawing) hold supported surface 124
relative to the first or top surface 38 in the same manner as
previously described for ties 42. It is to be understood that a
plurality of ties 142 are spaced along the length of each side of
body 122 other than the side from which wedges 48 project.
Disposed in underlying relationship to surfaces 38 and 124 at each
side of body 122 other than the side from which wedges 48 project,
is an elongated, hollow, flexible, inflatable edge support cylinder
164 of generally the same construction as cylinders 64 previously
described. Cylinder 164 is in communication with the interior body
122 through one or more restricted orifices 110 and will thus be
inflated to a pressure normally equal to the pressure within the
body 122 by blower 76.
While there have been previous attempts to provide high pressure
areas around the perimeter of an air cushion to prevent collapse of
the edges of the cushion such prior art devices have not been
entirely satisfactory. A typical example of a prior art device of
this type is shown in the patent to D. W. Gordan, Pat. No.
3,391,414, issued July 9, 1968. While this patentee proposed to
have a high pressure area at the edge of his cushion, it was
contemplated that this area would be maintained at a high pressure
at all times thus necessitating an auxiliary air supply to maintain
the high pressure. Since the air supply means is one of the major
cost factors in constructing an air cushion, the high pressure area
at the edge of this patentee's cushion is achieved only at a
substantial increase in cost. Also, the configuration of the high
pressure areas which has characterized the prior art has resulted
in their being deficient. When a configuration other than
cylindrical is utilized, any deformation of the chamber defining
the high pressure area will first result in an increase in volume
of the area with no accompanying increase in pressure. Finally, the
prior art devices have heretofore been characterized by completely
underlying the cushion surface thus having little or no tendency to
throw a person landing in the high pressure area toward the center
of the cushion.
The foregoing disadvantages of the prior art devices are eliminated
with the present invention. Since cylindrical supports 164 are in
direct communication with the interior of body 122 and are inflated
by blower 76 at the same gas pressure normally attributable to the
first cushion body, no auxiliary blower is required to maintain the
cylinder supports at a high pressure. On the other hand, because of
the relatively restricted orifices between cylinders 164 and the
interior of body 122, whenever an object moves against first
surface 38 and thus exerts a force against cylinder 164, it will be
much more difficult for air to escape from the cylinder than is the
case from the impact area of body 122. Accordingly, a substantial
pressure differential will develop between the support cylinders
and the interior of the cushion body. This will cause the surface
38 to collapse while the cylinders 164 remain relatively firm and
any object moving against the surface 38 in the vicinity of the
cylinders will be thrown inwardly toward the center of body
122.
Another advantage of cylinders 164 is that they are located so that
a vertical bisector through the cylinder extends along a line
adjacent to the edge of first surface 38. Thus, substantially
one-half of the total area of each cylinder 164 is outside of the
perimeter of top surface 38 further enhancing the support of the
surface at its edges and assuring that an object striking the edge
will actually be turned inwardly toward the center of the cushion.
This is a substantial improvement in an air landing cushion which
largely avoids the problem of collapsing edges.
While the invention has been described with particular reference to
a pole vaulter's landing cushion, it is to be understood that the
invention can be utilized equally well in a high-jumping contest or
other athletic events, as well as a safety device, and in fire
rescue work.
* * * * *