An internally supported, flexible duct joint for use in conducting fluids under relatively high pressures in systems where relatively large deflection angles must be accommodated is presented. The joint includes a flexible tubular bellows and an elongated base disposed within the bellows. The base is connected through radiating struts to the bellows near mid-portion and to each of the opposite end portions of the bellows through a pivotal connecting body. A motion-controlling linkage is provided for linking the connecting bodies, whereby angular displacement of the joint is controlled and uniformity in the instantaneous bend radius of the duct is achieved as deflection is imposed

Kuhn, R. F., Jr.

English

NASA Technical Reports Server

REPLY TO
ATTN OF: GP
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
MAR 2 8 1975
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FROM
KSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Mor>gan
GP/Office of Assistant General ~?
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. -
 : 3
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent case No.
rp .
of ft
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "...with respect to
an invention of ..."
A/.X.--
Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19750011614 2020-03-19T20:48:43+00:00Z
United States Patent
Fletcher et al.
[in 3,869,151
[45] Mar. 4, 1975
[54] INTERNALLY SUPPORTED FLEXIBLE
DUCT JOINT
[76] Inventors: James Fletcher, Administrator of
the National Aeronautics and Space'
Administration with respect to an
invention by; Ralph F. Kuhn, Jr.,
24723 Mulholland Highway,
Calabasas. Calif.. 91302
[22] Filed: Apr. 16, 1974 '
[21] Appl. No.: 461,477
[52] U:S. Cl /. 285/114, 285/226
[51] Int. Cl F16I 27/04
[58] Field of Search 285/226, 227, 228, 229,
285/114, 299, 300, 301, 118; 403/50, 51;
74/18, 18.1
|56] References Cited
UNITED STATES PATENTS
2.103.988 12/1937 LcBus 285/118
2.901.272 8/1959 Anderson 285/227
3.070.387 12/1962 Peyton 285/114
3,659,879 5/1972 Stalph 285/227 X'
3.669,470 6/1972 Deuvloo 285/226 X
FOREIGN PATENTS OR APPLICATIONS
1.361,040 4/1964 France 285/227
10,321 7/1887 Great Britain 285/226
Primary Examiner—Thomas F. Callaghan
Attorney, Agent, or Firm—Wayland H. Riggins;
L, D. Woffard, Jr.; John R. Manning
[57] ABSTRACT
An internally supported, flexible duct joint for use in
conducting fluids under relatively high pressures in
systems where relatively large deflection angles must
be accommodated. The joint includes a flexible tubu-
lar bellows and an elongated base disposed within the
bellows. The base is connected through radiating
struts to the bellows near mid-portion thereof and to
each of the opposite end portions of the bellows
through a pivotal connecting body. A motion-
controlling linkage is provided for l ink ing the connect-
ing bodies, whereby angular displacement of the joint
is controlled and uniformity in the instantaneous bend
radius of the duct is achieved as deflection is imposed
thereto.
7 Claims, 7 Drawing Figures
y/e
PATENTEOHAR 41975 3,869,151
1 3,869,151
^.INTERNALLY SUPPORTED FLEXIBLE DUCT
JOINT
ORIGIN OF THE INVENTION
The invention described herein was made in the per-
formance of work under a NASA contract and is sub-
ject to the provisions of Section 305 of the National
Aeronautics and Space Act of 1958, Public Law
85-568 (72 Stat. 435; 42 U.S.C. 2457).
BACKGROUND OF THE INVENTION
The invention relates to flexible duct joints for high-
pressure systems, and more particularly to an internally
supported flexible duct joint adapted to be deflected
with a uniform bend radius, whereby bending stress is
reduced and fatigue life is increased.
The prior art is, of course, replete with flexible duct
joints of the type including tubular bellows and particu-
larly suited for use in uniting adjacent ends of angularly
related ducts. Often, the angular relationship estab-
lished between the ducts is varied periodically. Conse-
quently, the duct joints must be flexible enough to ac-
commodate such changes in angular relationship.
Where the duct joints are subjected, operationally, to
high operating pressures and large deflection angles,
special consideration must be given to problems relat-
ing to bending stress introduced as a result of pressur-
ization.
As can readily be appreciated by those familiar with
the design and fabrication of flexible duct joints, there
is an attendant increase in bending stress as internal
pressures within the bellows is increased. As a conse-
quence, the joint often experiences lateral shift or
change in bend radius in a manner not unlike that expe-
rienced by an axially loaded curved beam supported
with the ends thereof restrained. Of course, a reduction
in fatigue life attends increased stress resulting from a
reduction of the bend radius.
Heretofore, attempts have been made to overcome
the aforementioned disadvantages by providing a plu-
rality of coaxially aligned bellows assemblies to accom-
modate the angulation requirements or, alternatively,
to employ bellows having higher inherent stiffness re-
sulting from an increased mass. Such design practices
have resulted in complex, massive, and expensive joints
often totally impractical for use in environments
wherein reduction of weight and simplicity in design
are of utmost concern.
It therefore is the purpose of the instant invention to
provide an improved flexible duct joint of the type in-
cluding a flexible tubular bellows having particular util-
ity in an operational environment wherein the joint is
subjected to relatively high internal pressures and large
angles of deflection.
OBJECTS AND SUMMARY OF THE INVENTION"
An object of the instant invention is to provide an im-
proved flexible duct joint which overcomes the afore-
mentioned disadvantages.
It is another object to provide an improved flexible
duct joint of the type including an internally supported
flexible, tubular bellows.
It is another object to provide in a flexible duct joint
of the type including a flexible, tubular bellows, im-
proved means for controlling angular deflection im-
parted to the tubular bellows, when the joint is sub-
jected to both high internal pressures and large deflec-
tion angles.
It is another object to provide a lightweight flexible
duct joint, the midspan of which is restrained by an in-
5 ternal tie and the deflection thereof is controlled for
imposing uniformity on the bend radius of the bellows
as deflection occurs, whereby lateral shift in the mid-
span of the bellows is precluded.
These and other objects and advantages are achieved
10 through a lightweight flexible duct joint including a tu-
bular, flexible bellows having a pair of opposite end
portions, an elongated base disposed internally of the
bellows and having an end portion disposed adjacent to
each of the opposite end portions of the bellows, a plu-
15 rality of angularly related struts projected radially from
the elongated base and connected with the side walls of
the bellows, a pair of annular supports, each being rig-
idly affixed to one end portion of the bellows in a con-
centric relationship therewith, a pair of elongated con-
20 necting bodies, each including a plurality of angularly
related struts extended radially from the body and af-
fixed to the internal surfaces of one of the annular sup-
ports, a universal joint for coupling each of the con-
necting bodies with one end of the elongated base', a
25 pair of lever arms, each being projected axially from
one of the connecting bodies and concentrically related
to the elongated base, and a ball-and-socket coupling
. joint interconnecting the distal ends of the lever arms
within the base, whereby angular motion imparted to
30 one of the lever arms is transmitted to the other lever
arm through the coupling joint, as will become more
readily apparent by reference to the following descrip-
tion and claims in light of the accompanying drawings.
35 BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of an improved lightweight,
flexible duct joint embodying the principles of the in-
stant invention.
FIG. 2 is an end view of the joint shown in FIG. 1.
40
 FIG. 3 is a cross sectional view taken generally along
line 3-3 of FIG. 1.
FIG. 4 is a cross sectional view taken generally along
line 4-4 of FIG. 3.
FIG. 5 is a cross sectional view taken generally along
45
 line 5—5 of FIG. 3.
FIG. 6 is a cross sectional view taken generally along
line 6—6 of FIG. 3.
FIG. 7 is a cross sectional view, similar to FIG. 4, with
the joint being angularly deflected.50
DESCRIPTION OF THE PREFERRED
EMBODIMENT
Referring now with more specificity to the drawings
wherein like reference characters designate like or cor-
responding parts throughout the several views, there is
shown in FIG. 1 a flexible duct joint, generally desig-
nated 10, which embodies the principles of the instant
invention.
0 It is to be understood that the joint 10 is, in opera-
tion, subjected to both relatively high internal pressures
and large deflection angles. Such pressures and angles
often are common to propulsion systems provided for
spacecraft and the like.
65 The duct joint 10 is of a tubular configuration and is
provided with a support 12, of an annular configura-
tion, at each of its opposite ends. The supports 12,
where so desired, include a tapered external surface for
3,869,151
20
facilitating a mating of the joint 10 with an adjacent
segment of a pressurizable duct. Extended between the
supports 12 there is a tubular, convoluted bellows 14.
The bellows 14 includes annular corrugations and is se-
cured at each of its opposite ends to the external sur-
faces of the supports 12.
Within the bellows 14, near the mid-portion thereof,
there is provided an annulus 16 to which is rigidly se-
cured the bellows 14 by suitable means including weld
beads, not shown. Hence, it can be appreciated that the
bellows 14 is supported, internally, at each of its oppo-
site ends by the supports 12 and at its mid-portion by
the annulus 16.
The annulus 16, in turn, is seated in circumscribing
relation with a sleeve 18. Disposed within the sleeve 18,
in concentric relation therewith, there is an elongated
base, generally designated 20, including a tubular body
21. From the body 21 there is a plurality of radially ex-
tended, angularly related struts 22. The struts 22 are
fixed to the external surface of the mid-portion of the
elongated base 20 and to the internal surface of the
sleeve 18 so that the struts serve to support the base 20
in its concentric relationship with the sleeve 18.
As a practical matter, the struts 22 are disposed in or-
thogonally related planes and serve to unite the body 25
21 with the sleeve 18. Thus, the mid-portion of the bel-
lows 14 is supported by the struts 22 radiating from the
base 20.
Each of the supports 12 is pivotally connected with
one end of the base 20 through an elongated connect-
ing body, generally designated 24. Each of the connect-
ing bodies 24 is of an elongated configuration and in-
cludes a pedestal 26 from which also radiates a plural-
ity of orthogonally related struts 28. In practice, the
struts 28, for each of the connecting bodies 24, are dis-
posed in a coplanar relationship with the struts 22 and
are united at their distal ends with the internal annular
surface of one of the supports 12. The pedestal 26, for
each of the struts 28, is further connected to the body
21 of the base 20 through a knuckle joint generally des-
ignated 30.
Each knuckle joint 30 functions as a universal joint
and includes a socket 32 formed in one end of the body
21 and a ball 34 seated within the socket. A knuckle
pin 36 is extended through coaxially aligned bores, not
designated, formed in the body 21 and the ball 34 for
securing the ball 34 within the socket 32.
The knuckle joint 30 further includes a truncated
segment of a socket 38 formed in a relieved portion,
note that the knuckle joints are interposed between the
motion restraining arms 40 and 42 and opposite ends'
of the duct joint 10f Therefore, the distal ends of the
motion restraining arms 40 and 42 are caused to move
5 in a direction opposite to that in which the ends of the
duct joint 10 are moved as deflection is imparted
thereto. As a consequence, the knee joint 44 serves to
stabilize the instantaneous length of the bend radius for
thus assuring that as angular displacement is imparted
10 to one end of the duct joint 10, angular motion, similar
in direction and magnitude, uniformly is imparted to
the opposite end portion of the duct joint. As a practi-
cal matter, the internal surface of the tubular bore 46
circumscribes the knee joint 44 and serves as a stop
IS surface for limiting angular motion imparted to the dis-
tal ends of the arms 40 and 42 as deflection of the duct
joint 10 occurs. It should readily be apparent that the
bend radius for the duct joint 10 always is uniform, for
any given angle of deflection.
In practice, a sleeve segment 48 is fixed to each of the
supports 12, as by welding or the like, and extends into
telescoped engagement with the adjacent end of the
sleeve 18. Thus, the sleeve segments 48 and the sleeve
18 cooperate and serve to prevent flow impingement
on the surface of the convolutions of the bellows 14
and thus inhibit flow-induced vibration fatigue in the
bellows.
OPERATION
30
35
It is believed that in view of the foregoing descrip-
tion, the operation of the device will readily be under-
stood and it will be briefly reviewed at this point.
With the flexible duct joint 10 fabricated in the man-
ner hereinbefore described, it is to be understood that
the joint is adapted to be united with adjacent segments
of pressurizable ducts, not shown, through supports 12.
Of course, as deflection of the duct joint 10 occurs, as
the angular relationship of the ducts is varied, in any
direction, the knee joint 44 becomes effective for caus-
ing the opposite end portions of the duct joint 10 to de-
flect uniformly because of the uniform pivotal motion
imparted to the arms 40 and 42. Hence, the instanta-
neous bend radius of the duct joint 12 is at any instant
uniform, throughout the length thereof, due to the sta-
bilizing effect of the knee joint 44.
In view of the foregoing, it is believed to be apparent
that through the instant invention, the perplexing prob-
lem of providing for lateral stability near the center
span of an internally pressurized bellows has been
45
_ __ »»j»«-«« v
not designated, of the pedestal 26, in spaced relation solved.
with the struts 28. The segment also receives the ball Although the invention has been herein shown and
34 in a manner such that the internal surface of the
truncated segment of the socket 38 has a radius pro-
jected from the symmetric center of the knuckle pin
36. It is here important to note that the relieved portion
of the pedestal 26 has a thickness substantially less than
the diameter of the ball 34 so that omnidirectional os-
cillatory motion of the connecting body 24 relative to
any axes diametrically related to the ball 34 is accom-
 6Q
modated.
The connecting bodies • 24 are interconnected
through motion restraining arms, designated 40 and 42,
which junction at a knee joint, generally designated 44.
The motion restraining arms 40 and 42 are projected ^
axially from the connecting bodies 24, along the longi-
tudinal axis of symmetry of the base 20, when the bel-
lows 14 is in a linear configuration. It is important to
described in what is conceived to be the most practical
and preferred embodiment, it is recognized that depar-
tures may be made therefrom within the scope of the
invention, which is not to be limited to the illustrative
details disclosed.
I claim:
1. In a lightweight, flexible duct joint of the type in-
cluding a convoluted, tubular bellows having opposite
end portions adapted to be connected with adjacent
segments of a pressurizable duct, whereby the duct
joint operatively is subjected to internal pressure and
angular deflections, the improvement comprising:
means for controlling angular deflection imparted to
said tubular bellows including:
A. an elongated, rigid base disposed internally of the
bellows and having an end portion disposed adja-
3,869,151
cent to each of the opposite end portions of said
-*"•" bellows,
B. means including a plurality of angularly related
struts projected from said base for connecting the
bellows with the base, and
C. means for interconnecting the opposite end por-
tions of said bellows with the adjacent end portions
of said elongated base including a pair of annular
supports, each being affixed to one end portion of
said bellows in concentric relation therewith, a pair
of connecting bodies, each being rigidly affixed to
one of said annular supports and pivotally con-
nected to one end portion of said elongated base,
and motion control means affixed to said connect-
ing bodies for limiting angular motion imparted to
said annular supports relative to said base.
2. The improvement of claim 1 wherein each con-
necting body of said pair of connecting bodies includes
a plurality of angularly related struts extended radially
with respect to one of said annular supports and rigidly
affixed thereto, and means defining a pair of universal
joints for coupling said pair of connecting bodies to
said elongated base.
3. The improvement of claim 2 wherein said motion
control means includes a pair of lever arms, each being
projected axially from one of said connecting bodies
with the distal ends thereof being disposed in a contigu-
ous relationship, a ball-and-socket coupling intercon-
necting the distal ends of said lever arms, and stop
means including a surface of an annular configuration
circumscribing the distal ends of said lever arms.
4. The improvement of claim 3 wherein the base is of
a tubular configuration and said pair of lever arms are
connectrically related thereto.
S. A lightweight, flexible duct joint comprising:
A. a tubular, convoluted bellows having a pair of op-
posite end portions;
B. an elongated base, disposed internally of said bel-
5 lows and having an end portion disposed adjacent
to each of the opposite end portions of the bellows;
C. means for connecting said base to said bellows in-
cluding a first plurality of angularly related struts
projected radially from the base;
10 D. a pair of annular supports, each being rigidly af-
fixed to one end portion of said bellows in a con-
centric relationship therewith, a pair of elongated
connecting bodies, each including a further plural-
ity of angularly related struts extended radially
15 therefrom and affixed to the internal surfaces of
one of said annular.supports;
E. means including a pair of universal joints for cou-
pling said connecting bodies with said elongated
base; and
20 .F. motion control means including a pair of lever
arms, each being projected axially from one of said
connecting bodies, and a ball-and-socket joint in-
terconnecting the distal ends of the lever arms in-
ternally of said base.
25 6. The duct joint of claim 5 further including a sleeve
concentrically related to said base and supported by
said first plurality of struts for preventing flow impinge-
ment on said bellows.
7. The duct of claim 6 wherein said means for con-
30 necting said base to said bellows further includes an an-
nulus affixed to said sleeve in circumscribing relation
therewith and affixed to the internal surface of said bel-
lows near the mid-portion thereof.
35
40
45
50
55
60
65


Internally supported flexible duct joint

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