Foldable conduit capable of springing back as self erecting structural membe

Dunn, J. H.

Gertsma, L. W.

English

NASA Technical Reports Server

an; 3, 1967 L. W. GERTSMA ETAL 3,295,55 
FOLDABLE CONDUIT 
_. Filed Aug. 26, 1963 
i 
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FIG. 2 
IO 
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INVENTORS 
LAURENCE W. GERTSMA 
JAMES H. DUNN 
/ d o ?  
BY 
/&Al.-7Md 
ATTORNEYS 
https://ntrs.nasa.gov/search.jsp?R=19700032263 2020-03-17T02:10:14+00:00Z
United States Patent Office Patented Jan. 3, 1967 
1 
3,295,556 
FOLDABLE CONDUIT 
Laurence W. Gertsma. Berea. and James 
wood, Ohio, assignors to the United States of America 
as represented by the Administrator of the National 
Aeronautics and Space Administration 
Filed Aug. 26,1963, Ser. No. 304,698 
1 Claim. (C1. 138-119) 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
This invention relates generally to conduits and, more 
particularly, to a conduit which may be folded or bent 
without the walls thereof permanently deforming. 
In  order to achieve optimum efficiency in carryilng cap- 
ability and ease of storing of space vehicles at launch, it 
has been observed that it is desirable to retain as many 
components as possible within the confines of the space 
vehicle itself. There are many instances wherein items 
such as nuclear reactors, antennae, radiators and extensi- 
ble legs for lunar landings must be projected or injected 
out into space after the vehicle has left the confines of 
the launching pad. Some !of the techniques of confining 
an element to be subsequently erected when in orbit, or 
in other space flight paths, is the utilization of a coiled 
tube, for example, which is partially uncoiled for erection 
or utilization of a large bellows-type joint to provide for 
the flexibility of right angle curvature. Some of the dis- 
advantages associated with such techniques are that the 
coiled tube becomes very large and heavy for 90" of 
movement, and the bellows is large and must be made 
of thin material if it is to be bent with a small force 
which thereby lowers the reliability with corrosive fluids. 
Also, the bellows will trap fluid in the folds and, further, 
the folds will cause large pressure drops in flowing fluids. 
Additionally, when one applies a bending force to the 
conventional tubular conduit the risk is always present 
that the conduit will collapse at the point of bending 
thus eliminating any spring or resilient force necessary 
to urge the conduit into the unbent position. 
Accordingly, it is an object of this invention to pro- 
vide a foldable conduit having the characteristic of spring- 
ing back into a rigid position. 
Another object of the instant invention is to provide 
a 'new and novel self-erecting structural member. 
Still another object of this invention is to provide a 
new and improved method for making a nonpermanent- 
deforming-foldable-conduit. 
A still further object of the present invention is the 
provision of a self-erecting foldab!e conduit. 
According to the present invention, the foregoing and 
other objects are obtained by providing a conduit having 
a cross-sectional contour defined by opposing arcs of 
circles having substantially equal radii so that when 
flattened the contour will provide a fairly uniform stress 
at all points in the flattened position. To provide the 
aforementioned foldable conduit, two opposing elements 
of the conduit are formed; each one having three changes 
of curvilinear shape associated therewith comprised of 
the arcs of circles having substantially equal radii. The 
elements are fastened or secured at the ends thereof so 
that the curvilinear ends of the elements are in juxta- 
position tangentially at the point of fastening. 
A more complete appreciation of the invention and 
many of the attmdant advantages thereof will be greatly 
appreciated as the same becomes better understood with 
reference to the following detailed description when con- 
sidered in connection with the accompanying drawing 
wherein: 
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2 
FIG. 1 is a perspective view illustrating a conduit made 
in accordance with this invention. 
FIG. 2 is an end section of the conduit shown in 
FIG. 1. 
FIG. 3 is an elevation of the conduit of FIG. 1 shown 
iD a collapsed and bent position. 
Referring now to the drawings wherein like reference 
materials designate identical or corresponding parts 
throughout the several views and, more particularly, to 
FIGS. 1 and 2 wherein the foldable conduit 10 is shown 
as consisting of a first side 12 and a second side 14 
fastened together at the ends 16. As better shown in 
FIG. 2, the first and seuond side has a curvilinear shape 
defined by opposing arcs having substantially equal radii 
r. Material chosen for the sides 12 and 14 and the thick- 
ness thereof should be with regard to a number of prac- 
tical considerations taking into account the environment 
within which the conduit 10 is to be utilized and par- 
ticularly that the sides be fabricated of a material hav- 
ing some degree of flexibility. A material having a 
characteristic of high yield strength has been found to be 
satisfacfiory. The sides 12 and 14 may be formed or 
stamped by any conventional method to provide a con- 
tour generally described as a middle arc continuing on 
each side thereof as substantially equal arcs tangentially 
and of an opposing direction thereof terminating as 
ends tangentially in the same plane 18; all arcs having 
substantially equal radii. The ends are secured by weld- 
ing or any other conventional technique so that the 
ends of the opposing sides are parallel and in juxtapo- 
sition to each other. To provide for additional structural 
strength, the parts may be extended beyond the initial 
point of tangential contact parallel to the same plane 18. 
In FIG. 3, the general shape of the conduit invention 
is shown when it is flexed in a partially folded position. 
In actual practice, it has been determined that a conduit 
constructed in acuordance with the invention can be bent 
to a radius of curvature up to 1% inches. Radius of 
curvature is defined as a radius of a circle about which a 
tube can be wrapped. Upon removal of the stress caus- 
ing retention (not shown) of the conduit in the position 
shown in FIG. 3, the conduit will immediately straighten 
and become a light, strongly rigid structural member. 
Because of the smooth inner surface, any pressure drop 
associated with the flowing of fluid through the conduit 
is negligible. Simplicity of the invention increases the 
reliability of structural integrity when cycling the conduit 
through the stress-unstress positions as exemplified by 
the fact that an invention constructed in accordance with 
the teachings herein has been flexed over a hundred 
times with no apparent structural deterioration. 
Quite obviously, applicants' invention can be utilized 
in all applicat3ons wherever tubular members have to be 
folded for one purpose or another. I;n addition to  en- 
abling compact foldable construction of radiators for 
space power systems, the foldable conduit or tube con- 
cept can be employed as rigid legs of nonsurface to sur- 
face vehicles for landing purposes which legs are coiled 
up within the vehicle itself and deployed before settling 
down on a surface. 
Another application for the foldable tube exists whm a 
space propulsion system is powered by a nuclear reactor. 
For example, one end of each of two tubes would be 
rigidly attached to the vehicle structure and the other 
ends attached to the reactor. The reactor would then 
be rolled in the collapsed tubes and secured in the vehicle 
for launch. Prior to system startup, the reactor would 
be deployed out in front and away fmm the vehicle by 
unrolling the reactor and tubes. Positioning the reactor 
out in front of the vehicle would reduce the required area 
of reactor shadow shield. The expanded tubes would 
carry the reactor coolant to and from the vehicle. 
3,295,558 
3 
Obvi'ously, numerous other modifications and varia- 
tions of the present invention are possible in the light of 
the above teachings. 
It is, therefore, to be understood that within the scope 
of the appended claim, the invention may be practiced 
otherwise than as specifically described herein. 
What is claimed is: 
In a bendable tubular support of the type having 
two flexible parts with mating marginal surface portions 
of each joined to the other along the length thereof and 
central sections traversely bowed outwardly from the 
plane of the marginal surface portions, the improvement 
comprising, 
an inwardly curved portion between each of the cen- 
tral sections and the marginal surface portions, 
one edge of said inwardly curved portion being tan- 
gent 90 the central section to provide a smooth, grad- 
ual, reversal of curvature whereby high stress con- 
centrations are prevented when said central sections 
are forced towards one another, 
4 
the opposite edge of said inwardly curved portion be- 
ing tangent to the marginal surface portion whereby 
said inwardly curved portion merges smoothly with 
said marginal surface portion thereby preventing 
high stress areas between said inwardly curved por- 
tion and said marginal portion when said support 
is bept, - 
the radius of each inwardly curved portion being sub- 
stantially equal to the radius of the traverse bow in 
tion so that stresses in the flexible parts 
prevent kinking or rupture of the 
5 
es Cited by the Examiner 
NITED STATES PATENTS 
_ _ _ _ _ _  138-119 X 
EIGER, Primary Examiner. 


Foldable conduit Patent

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