Platform with several ground effect pads and plenum chamber

Blaise, H. T.

Dane, D. H.

English

NASA Technical Reports Server

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DAN H. DANE 
HERMAN T. BLAISE 
INVEAI TORS 
https://ntrs.nasa.gov/search.jsp?R=19710006214 2020-03-17T02:41:35+00:00Z
[72] Inventors 
[ 2 1 ] Appl. No. 
[22] Filed 
[45] Patented 
1731 Assignee 
UNITED STATES PATENTS , 
2,780,826 2/1957 Coonset al. ................. 180/116 
2,889,570 6/1959 Duff ............................. 180/116X 
3,195,665 7/1965 Beardsley .................... 180/116 
Primury Examiner- A. Harry Levy 
Attorneys- L. D. Wofford,Jr., G. J.  Porter and G. T. McCoy 
9 Claims, 4 Drawing Figs. 
[52] U.S.B;rk ....................................................... 180/1 18, 
1801 12 I 
.............................................. i 
h ............................................ 18Ol116. 1 
125,121,118 \ 
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ACT: A platform having several ground effect pads is 
supported in a substantially frictionless manner over a surface. 
Each pad has a plenum chamber with an open bottom which 
enables pressurized air to support the pad above the surface. 
The load of the platform is applied to the top center of each 
pad. The upper wali of the pad converges downwardly from 
the side wall of the plenum chamber whereby the center of lift 
of the resultant pressure is above the point of application of 
the load. 
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effect and more specifically to those utilizing an air cushion of 
pressurized air to support the device above a surface. 
2. Description of the Prior Art 
There are two distinct air cushion techniques for supporting 
a device such as a vehicle over a surface One is to utilize an 
air cushion which supports a device over a prepared surface 
with very close clearances in the manner of an air bearing. in 
the other, an air cushion of low pressure air supports the 
device over an unprepared surface sufficiently to clear obsta- 
cles thereon by the use of a plenum chamber, peripheral jets 
andlor flexible skirts. 
The use of precision air bearing system for providing a 
device with random horizontal movement over a large work- 
ing area is very costly because of the need to grind large floor 
areas to precision tolerances. However, the air bearing 
techniques did result in a stable device with substantially no 
flutter, vibration, or pitching so long as the air flow did not 
raise the airgap over a few thousandths of an inch thick. A very 
thin film of air was required for good stability characteristics, 
The low pressure air cushion system while operating in a 
generally satisfactory manner over a rough or unprepared sur- 
face has heretofore been subject to motions such as heaving, 
pitching, and yawing. 
To overcome the disadvantage of the prior air cushion 
techniques, the present invention has been devised which ena- 
bles an air cushion device to be inherently stable while operat- 
ing with a substantial air gap over an unprepared surface. 
MARY OF THE INVENTION 
In the present invention a pad has a plenum chamber 
defined by an enclosing side wall skirt and an upper wall con- 
verghg downwardly to form an inverted truncated cone. The 
load supported by the pad is applied to the upper wall at the 
truncated cone center so that the load application to the pad is 
below the resultant of the air lift forces. 
Accordingly, it is an object of this invention to provide an 
improved air cushion device with superior stability. 
Another object is to provide an improved air cushion vehi- 
cle which operates on ordinary surfaces with great stability. 
Other objects and advantages of the present invention will 
become more apparent from the following detailed descrip- 
tion when taken in conjunction with the accompanying 
drawings. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a side view of a test type platform supported by 
FIG. 2 is a perspective view of an air cushion pad being used 
FIG. 3 is an elevational cross-sectional view of the air 
FEG. 4 is a schematic view of the air cushion pad of FIG. 2 il- 
several air cushion pads of the present invention; 
in FIG. 1; 
cushion pad of FIG. 2; and 
lustrating the forces acting thereon. 
DESCRIPTION OF THE PRESENTLY PREFERRED 
1 EMBODIMENT 
FIG. 1 illustrates a platform ‘simulator 11 used to perform 
certain mechanical space simulation experiments. The plat- 
form 11 carries a seat 13 for a human 15 and is adapted to 
move in random horizontal movements over a surface 17 in 
accordance with a force applied by a connecting link 19. The 
platform 11 is provided with several air cushion pads 21, con- 
structed in accordance with the present invention, which al- 
3,534,826 
AIR C U S ~ I O ~  LIFT PAD 
The invention described herein was made by employees of 
the US. Government and may be manufactured and used by 
or for the Government for governmental purposes without the 
payment of any royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
lows the platform 11 to move in a substantiatly frictionless 
manner on a rough finished surface 17. 
one  Of the air cushion pads 21 is shown in perspective in 
FIG. 2 and in cross section in FIG. 3. The pad 21 has an en- 
s closing (circular) vertical side wall 23 and an upper wall 25 
converging downwardly from the upper end of the side wall SO 
as to form an inverted truncated cone within a plenum 
chamber 27. The center portion 29 of the upper wall, i.e. trun- 
Cone, is flat and orientated Perpendicular, (horizontal) 
to the vertical side wall 23. 
1. Field of the lnvention I 
n e  present invention relates to devices utilizing a ground, 
A tubular fitting 31 extends through the upper wail 25 SO 
that a conventional type hose (not shown) may detiver pres- 
surized air into the plenum chamber 27. While only one fitting 
15 is shown, others could be provided if additional air flow was 
desired. Further, the fitting 31 could be integral with the wall 
25, if desired. 
As indicated by FIG. 1. the weight of the platform 111 IS 
placed upon the depressed Pat center 29 of the upper air 
20 cushion pad surface 25 by struts 33. The struts 33 may be 
secured by any suitable means such as welding or adhesively 
bonding to the pads 21. Also, the struts 33 may be pivotally 
joined to the center 29 of the pads 21 to enable a pad to tilt in- 
dependently of the other pads. in FIG. 4, the load (L) placed 
25 upon the flat center 29 of the air cushion pad 21 by the plat- 
form 11 is shown as an arrow. The air pressure exerted on the 
bottom surface of the upper inverted truncated cone shaped 
wall 25 is represented by numerous small arrows. All the pres- 
sure forces are focused by the shape of the upper wall 25 
30 toward a center which is above the load (L)  application to the 
air cushion pad 2 1. This results in a very stable air cushion pad 
21 which unlike a conventional air bearing will not flutter or 
vibrate when floated a significant distance from the floor. For 
example, an air cushion pad constructed of plastic and having 
35 a diameter of 24 inches, a vertical side wall of 4 inches, a 
center flat portion with a diameter of 3 inches and wall 
thicknesses of 0.13 inches lifted 0.02 inches from the floor 
with an air flow 70 c.f.m. with no significant vibrations. The 
pad 21 is designed to float 0.125 inches off the floor under a 
40 20 pound load with an air flow of 41 5 c.f.m. 
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The superior horizontal stability of the pad 21 is not entirely 
explained because the load acting on the pad is below its 
center of lift. Since the vertical lift is perpendicular to the sur- 
face L7, the tilting of the pad 21 will cause the vertical lift 
component acting on the inner surface of the upper wall 25 to 
decrease on the high side and increase on the low side thereby 
causing a corrective torque tending to stabilize the pad along 
the horizontal. In reference to the angle CP between the 
horizontal and the inner surfaces of the upper wall 25, the ver- 
tical lift will decrease by the change in the cosine function of 
the angle on the high side and increase by the change in the 
cosine function of the angle @ on the low side. 
Further, the normal stability achieved by air cushion 
devices because of pressure differentials in a tilting attitude is 
present, which adds to the inherent stability caused by the 
specific design of the present invention. The stability achieved 
by the present invention is that normally associated with preci- 
sion air bearings on precision surfaces under designed air flow. 
Obviously, many modifications and variations o€ the present 
invention are possible in light of the above teachings. It is, 
therefore, to be understood that within the scope of the ap- 
pended claims the invention may be practiced other than as 
specifically descnbed. 
We claim: 
1. A vehicle adapted to be supported in a substantially fric- 
tionless manner over an unprepared surface, compeising: 
a platform adapted for carrying a load thereon; 
an air cushion pad adapted to support said platform; 
said air cushion pad having an upper wall and an enclosing 
side wall defining an open bottom plenum chamber; 
said upper wall sloping upwardly from a central portion to 
the surrounding upper edge of said enclosing side wall; 
inlet means extending through the sloping portion of said 
upper wall between said central portion and said side wall 
3 ,534 ,824  
for blowing pressurized air into said plenum chamber so 
as to cause the pad to hover over the surface; and 
said central portion serving as a load bearing portion for a 
strut secured at its lower end thereto, said strut being 
secured at its upper end to the platform whereby the load 5 
of the platform is applied to the central portion of said 
pad so as to be below the resultant pressure force caused 
by the air in the plenum chamber. 
2. A vehicle as defined by claim 1 including a plurality of 
3. The vehicle as defined by claim 1 wherein said central 
portion of the upper wall of said air cushion pad is located 
contiguous to the open bottom level defined by the surround- 
ing lower edge of the enclosing side wall whereby the plenum 
chamber is effectively compartmented so to slow the air flow I5 
between air pressure differentials caused by a tilting of the pad 
relative to the unprepared surface so as to tend to prevent 
pitching and vibration of the pad. 
4. A vehicle as defined by claim 3 wherein said enclosing 
side wall has a smooth, even interior surface which is adapted 2o 
to be substantially perpendicular to the surface the vehicle 
operates over, and the interior surface of said sloping upper 
wall being smooth and even between said central portion and 
the surrounding upper edge of said enclosing side wall. 
air cushion pads supporting said platform. 
side wall is circular. 
such air cushion pads supporting said platform. 10 
5. A vehicle as defined by claim 4 including several of such 25 
4. A vehicle as defined by claim 4 wherein said enclosing 
'7. An air cushion pad adapted to operate over an un- 
prepared surface without heaving. pitching, and yawing, com- 30 closing side 
prising: 
is 
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a housing having an upper wall and an enclosing side wall ' 
defining an open bottom plenum chamber; 
P 
said upper wall sloping upwardly from a central portion to 
the surrounding upper edge of said enclosing side wall; 
said central portion being located contiguous to the open 
bottom level defined by the surrounding lower edge of the 
enclosing side wall so the plenum chamber is effectively 
compartmented so as to slow the air flow between air 
pressure differentials caused by a tilting of the pad rela- 
tive to the unprepared surface whereby the pad does not 
tend to vibrate; 
inlet means extending through the sloping portion of said 
upper wall between said central portion and said side wall 
for blowing pressurized air into said plenum chamber so 
as to cause the pad to hover over the unprepared surface; 
and 
said central portion having a load applying means adapted 
to support the entire load placed on the pad so that load 
application is below the resultant pressure force caused 
by the air in the plenum chamber acting on the interior 
surface of the sloping wall of said housing. 
8. An air cushion pad as defined by claim 7 wherein: 
the interior surface of said sloping upper wall being smooth 
and even between said central portion and the surround- 
ing upper edge of said enclosing side wall; and 
said enclosing side. wall having a smooth and even interior 
surface which is adapted to be substantially perpendicular 
to the unprepared surface the pad operates over. 
9. An air cushion pad as defined by claim 7 wherein said en- 
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Air cushion lift pad Patent

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