Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FOLDABLE MEMBER
FIELD OF THE INVENTION
This invention relates to a foldable boom, truss, or longeron member,
collapsible truss
structures and other similar structures made of such members.
STATEMENT OF GOVERNMENT INTEREST
This invention was made with U.S. Govemment support under Contract no. F29601-
99-C-0010. The U.S. Government may have certain rights in the invention.
RELATED PATENT APPLICATIONS
This application is related to U.S. Patent Publication Number 20020056248
filed
January 11, 2002 entitled "Foldable Member" by the same inventor as the
subject application
which is a divisional application of application Serial No. 091436,514 filed
November 9, 1999
entitled "Foldable Member" now Patent No. 6,374,565, by the same inventor as
the subject
application. This application is also related to Patent No. 6,321,503.
BACKGROUND OF THE INVENTION
Key optical components of large aperture, space based optical instruments may
be
deployed on orbit to provide an aperture large enough to increase the
resolution and optical
performance by several orders of magnitude. The performance of such
instruments depends
on maintaining the precision and stability of the deployed structural
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geometry to within nanometers of an ideal shape. Nonlinear contact mechanics
and
freedom in the components of deployed structures mean that deployed
instruments will
have the capacity to change shape at the micron and nanometer level of
resolution.
Eliminating such nonlinearities as load path friction a.nd freeplay would
enable a deployed
structure to be as linear and precise as a monolithic block of material.
In most mechanically deployed structures, components are moved from their
stored positions into their final operational positions by some type of
actuator and then
locked into place with a deployment latch. For high precision structures, it
is critical that
the load paths and load predictable for the reliable operation of the
instrument.
Existing deployable structure joints have several limitations that either
completely
prevent them from being used in high precision deployable instruments or
require
complex analysis and additional launch mass to provide deployment actuation
and post
deployment locking. Hinge joints previously used in moderate precision
structures have
relied on high levels of preload and friction to eliminate freeplay and
geometric
ambiguity. These joints have been shown to be unstable at the micron level,
causing the
structure to "micro-lurch" or change shape and thus move the instrument's
optics far out
of alignment.
Existing joints for precision space structures relied on high levels of
preload
between the many components to eliminate gaps and free play that cause
inaccuracies in
the structure. Unfortunately, these high levels of preload introduce
correspondingly high
levels of friction both during the deployment and after deployment has been
completed.
Friction mechanisms are nonlinear and thus are more difficult to control and
less
predictable.
Other hinge designs such as latch and actuator type systems suffer from the
same
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disadvantages.
Recently, foldable truss members have been developed so that a truss structure
can be collapsed and compactly packaged to save space during delivery and then
released to expand and return to its original shape in orbit. All of these
mechanisms
add to the mass, expense and complexity of the structure and to the difficulty
and
expense of transporting it. These foldable members reduce the mass (and the
delivery
cost) of the structure by replacing the hinge, latch and actuator mechanisms
with one
single device. See, e.g., U.S. Patent No. 4,334,391.
Solid rods are joined on their ends forming a truss structure (a square frame
for a solar panel array or a superstructure for a communications satellite
antenna, for
example) and pre-selected rods are cut in sections to form a hinge between the
two
sections. The rod sections are joined with spring steel elements similar to if
not
actually lengths of a carpenter's tape measure.
The rod sections can be folded with respect to each other by imparting a
localized buckling force to one of the spring steel elements. Simply letting
go of one rod
section, returns the two rod sections to an end to end alignment due to the
potential
energy stored in the biased spring steel hinge elements.
In this way, a truss structure made up of several of these foldable rods can
be
designed on earth, collapsed for delivery to space, and then released once in
position
in space where the foldable rods flex back into position forming the truss
structure
designed and constructed on earth.
In use, this spring steel hinge design suffers from a number of shortcomings.
First, hinges formed of spring steel elements require joining the ends of each
spring
steel element to a rod section. These joints and the spring steel elements
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themselves add significantly to the overall weight of the truss structure
which is an
undesired factor in space launch capability.
The spring steel elements also result in dimensionally unstable truss
structures.
The dimensional instability is caused by the relative motion of the internal
components
including the joints between the spring elements and the rod sections and
permanent
yielding of different areas of the spring elements themselves.
The result is that the shape of the truss structure may change when it is
erected in
space from the shape of the truss structure before it was collapsed on eartli.
This can have
disastrous effects on instrument performance as even a ten nanometer to ten
micrometer
displacement can severely affect the performance of primary and secondary
optics
attached to the truss structure.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a foldable member and a
collapsible structure made of a number of foldable members that is lighter
than prior art
foldable members and collapsible structures.
It is a further object of this invention to provide such a member and such a
structure which is more dimensionally stable.
It is a fiu-ther object of this invention to provide such a foldable member
which
eliminates numerous sources of iinprecision.
It is a further object of this invention to provide such a member and such a
structure which eliminates the need for deployment actuators and mechanical
latches to
further reduce systein mass.
It is a further object of this invention to provide such a member and such a
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structure which have tailorable thermal expansion and conductivity properties
and which
thus can be designed for a multitude of performance requirements.
It is a further object of this invention to provide such a member which can be
made of a variety of different types of materials.
It is a further object of this invention to provide such a member which is
simple to
manufacture and use.
It is a further object of this invention to provide a collapsible tube useful
in variety
of applications.
This invention results from the realization that a lighter and more
dimensionally
stable foldable member can be constructed by forming longitudinal slots in a
tube around
the perimeter thereof at a location where the member is designed to bend
thereby forming
separated, longitudinal strips of material at that location which easily
buckle allowing the
member to fold without adding a separate hinge which would add weight to the
member
and which would also result in dimensional instability.
This invention features a method of manufacturing a foldable member, the
method
comprising forming a plurality of C-section member plies, assembling a first
set of the C-
section member plies, assembling a second set of the C-section meniber plies,
arranging
two sections of a tube in an end-to-end manner defining a gap therebetween,
securing the
first set of C-section member plies to one side of the two tube sections to
bridge the gap
therebetween, and securing the second set of C-section member plies to an
opposing side
of the two tube sections to bridge the gap therebetween thus forming opposing
elongated
slots in the tube separated by longitudinal strips of C-section member plies
material
between the slots which fold when subjected to localized buckling forces and
which
unfold when released.
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In one example, the step of assembling the first and second sets of C-section
member plies includes securing all the plies of each set together first before
the sets of
plies are attached to the two tube sections. Preferably, the plies are made of
composite
material pultruded into a C-section cross sectional shape and the two tube
sections are
also made of composite material.
If other materials are used, it is preferred that the material of the first
and second
set of C-section members is the same as the material of the two tube sections.
In another embodiment, a third tube section is arranged in an end-to-end
manner
with the two tube sections to define a gap therebetween and third and fourth
sets of C-
section member plies are secured to opposing sides of the third tube section
and the two
tube sections thus forming sets of longitudinally adjacent opposing elongated
slots.
This invention also features a foldable member comprising two sections of a
tube
arranged in an end-to-end manner defining a gap tlzerebetween, and opposing
conforming
meinbers each made of multiple plies attached to both tube sections and
bridging the gap
therebetween defining opposing elongated slots and separated longitudinal
strips of
material between the slots which fold when subjected to localized buckling
forces and
which unfold when released. Typically, the conforming members have a C-cross
sectional shape and the material of the conforming members is the same as the
material of
the two tube sections. Preferably, the conforming members are made of
composite
material and the two tube sections are also made of composite material.
In one example, both sections of the tube comprise a plurality of layers.
There
may be two diametrically opposing elongated slots and two diametrically
opposing
longitudinal strips or even three opposing elongated slots and three opposing
elongated
strips wherein each longitudinal strip diametrically opposing an elongated
slot.
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In one embodiment, the conforming members have a neck down region and the
conforming members are secured together only at the neck down region. Also,
the
conforming members may be centrally secured together only wlZere they attach
to the tube
sections. In another embodiment, an intermediate rigid member is provided
interconnecting the conforming meinbers with a tube section. The intermediate
member
typically has spaced fingers and each conforming meinber is received between
two spaced
fingers.
In lengthy foldable members, there may be a plurality of hinge areas
longitudinally
spaced from each other along the length of the tube, each hinge area including
opposing
elongated slots. Further included maybe a third tube section and sets of
longitudinally
adjacent opposing elongated slots.
A truss type structure in accordance with this invention features a plurality
of
joined truss members wherein a selected number of said truss members each
include a
foldable member as discussed above: two sections of a tube arranged in an end-
to-end
manner defining a gap therebetween and opposing conforming members each made
of
multiple plies attached to both tube sections and bridging the gap
therebetween defining
opposing elongated slots and separated longitudinal strips of material between
the slots
which fold when subjected to localized buckling forces and which unfold when
released.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages will occur to those skilled in the art
from
the following description of a preferred embodiment and the accompanying
drawings, in
which:
Fig. 1 is a perspective view of a structure made of a number of foldable
members
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in accordance with the subject invention;
Fig. 2 is a schematic view of the structure shown in Fig. 1 in a collapsed
state;
Fig. 3 is a perspective view of the structure of Fig. 2 after it expands from
the
collapsed condition;
Fig. 4 is a front elevational view of a prior art foldable device;
Fig. 5 is a view of the prior art device shown in Fig. 4 in the folded
position;
Fig. 6 is a side elevational view of the foldable member of the subject
invention;
Fig. 7 is a front elevational view of the foldable member shown in Fig. 6;
Fig. 8 is a schematic view of the foldable member shown in Figs. 6 and 7 in a
folded position;
Fig. 9 is a front elevational view of another embodiment of the foldable
member
of this invention;
Fig. 10 is a side elevational view of another embodiment of the foldable
member
of the subject invention;
Fig. 11 is a view similar to Fig. 11 showing the interior rear side wall of
the
foldable member of the subject invention;
Fig. 12 is a front elevational view of a single elongated foldable member with
multiple hinge areas in accordance with this invention;
Fig. 13 is a schematic view of the member of Fig. 13 in folded position;
Fig. 14 is a schematic view of another embodiment of a foldable member in
accordance with the subject invention;
Fig. 15 is a schematic view of still another embodiment of a foldable member
in
accordance with the subject invention;
Fig. 16 is a schematic exploded view of still another einbodiment of a
foldable
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member in accordance with the subject invention showing the use of conforming
members connected between two tube sections;
Fig. 17 is a schematic view showing the embodiment of the foldable member of
Fig. 16 in the assembled state;
Fig. 18 is a schematic partially exploded view showing another embodiment of
the
subject invention;
Fig. 19 is a schematic view showing an assembled foldable member in accordance
with the embodiment shown in Fig. 18;
Fig. 20 is a schematic partially exploded view of still another embodiment of
the
foldable member of this invention;
Fig. 21 is a schematic view showing an assembled foldable member in accordance
with the embodiment of Fig. 20;
Figs. 22-23 are schematic views showing conforming members in accordance with
this invention having neck down regions;
Fig. 24 is a schematic view showing one method of securing the conforming
members to the two tube sections in accordance with this invention;
Fig. 25 is a cross sectional view of a portion of Fig. 24; and
Fig. 26 is a schematic view showing the use of an intermediate member used to
join the conforming members of this invention to a tube section.
DISCLOSURE OF THE PREFERRED EMBODIMENT
Truss structure 10, Fig. 1, of this invention includes a plurality of joined
truss
members 12 and 14 as shown. Truss structure 10, for example, may be 1.25
meters tall
but collapsible to a height of 27 centimeters as shown in Fig. 2 due to the
foldable nature
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of truss member 12 (and other selected truss members) which includes hinge
areas 16, 18,
and 20 along its length.
Depending on its specific design, hinge area 16 may fold downward, hinge area
20
may fold upward, and hinge area 18 may fold in the direction out of the plane
of the
drawing.
When collapsed as shown in Fig. 2, the volume of truss structure 10 is sharply
reduced resulting in significant space savings for space flight.
Upon deployinent in outer space, however, truss structure 10 automatically
expands as shown in Fig. 3 to its original configuration and may be used as a
frame for
solar panels, various optical devices, or as a part of a superstructure when
joined to
similar structures.
As shown in Fig. 3, the truss structure is strong under compression and can
support several hundred pounds. Its also strong against bending and torque
since the
individual hinge areas can only be actuated by intentional localized buckling
force applied
directly to the hinge areas.
In the prior art, hinges are formed in a truss member by cutting the truss
members
at the desired hinge area and attaching single clam shell shaped steel spring
elements 40,
42, and 44, Fig. 4 to truss member sections 46 and 48.
The spring steel elements are similar to lengths of carpenter's tape from a
tape
measure. When a localized buckling force is imparted to one spring element as
shown at
50 and the two truss member sections are subjected to a bending force, the
spring
elements readily bend, collapsing the truss member as shown in Fig. 5. If one
truss
member section is released, the clam shell shape of the spring steel elements
spring the
truss members into the configuration shown in Fig. 4.
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However, these and other such truss members suffer from numerous shortcomings
as discussed in the Background of the Invention above, including the fact that
they are not
thermally stable. Also, the joints between each spring steel element and the
truss member
sections can shift slightly and/or a spring steel element may yield while the
truss structure
is in the collapsed condition. When this truss structure is deployed in space
it may not
return to its original shape, resulting in dimensional instability which can
severely affect
the performance of sensitive equipment and optical devices. Other prior art
devices added
significantly to the overall weight of the system, were not dimensionally
stable, and/or
were complex, and/or costly.
In contrast, the subject invention solves these problems in part by a foldable
member with a hinge preferably constructed of the same material as the member.
In one
example, foldable member 60, Fig. 6, includes tube 62 having at least one
predetermined
hinge area 64. Hinge area 64 includes opposing, elongated slots 66 and 67 (see
Fig. 7)
forming separate longitudinal strips 70 and 72 of material between the slots.
These strips
70 and 72 fold when subjected to localized buckling forces as shown in Fig. 8,
thereby
allowing the member to fold at the hinge area about axis 74, Fig. 7. "Slots"
as used herein
means openings, slits, and cuts of any configuration.
Member 60 is dimensional stable and extremely reliable. In addition, by
tailoring
the material of tube 62, the thermal expansion and/or conductivity of member
60 can be
precisely tailored to meet various performance requirements. At the same time,
member
60 is sufficiently strong with respect to torsion, shear, and buckling for
numerous
applications.
Slots 66 and 67, as shown in Figs. 6 and 7, are diametrically opposing but
this is
not a limitation of the present invention. For example, in the embodiment
shown in Fig.
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9, there are three opposing elongated slots 90, 92, and 94 and three opposing
longitudinal
strips 96, 98, and 100 (see also Fig. 10). Longitudinal strip 96 is
diametrically opposed to
elongated slot 94, longitudinal strip 98 is diametrically opposed to slot 90
and
longitudinal slot 100 diametrically opposes slot 92. Therefore, the slots are
spaced around
the circumference of the tube in a generally opposing configuration, but a
given slot may
not diametrically oppose another slot even if there are only two slots. Also,
although the
slots are each shown to be of the same construction, this is not a limitation
of the present
invention as the length and opening width of the slots at a given hinge area
may be
different depending on the specific design. Furthermore, the slots may vary
from a mere
slit to a wide elongated opening. For exainple, slots 66 and 67, Figs. 6 and
7, are simply a
4 inch long formed in a 1 3/4 inch tube. Slots 90, 92, and 94, Fig. 9, on the
other hand,
are elliptically shaped and approximately 11/16 inches wide at their widest
point.
As shown in Fig. 1, a given truss member may include a plurality of hinge
areas
such as hinge areas 16, 18, and 20 along the length of truss member 12.
Therefore, any
one member may include a number of hinge areas, each hinge area including two
or more
opposing elongated slots.
Tube 62, Figs. 6-9 may be made of plastic material such as a polycarbonate
material, but polyurethane, Delrin, or nylon tubes may also be constructed.
Also, for
space applications in particular, composite materials inay be used including a
braided
fiber structure embedded in a resin matrix. In one early example, carbon
fibers were
braided using a round braider to form a triaxial braid in a tubular shape
which was then
impregnated with a polycarbonate resin. A thin wall aluminum tube was wrapped
in
Teflon and over wrapped with a sheet of Lexan material. A triaxial carbon
braid was
formed over the Lexan sheet and additional layers of Lexan were added over
triaxial
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braid. A combination of pressure and elevated temperature was used to
consolidate the
Lexan material into the fibers. The slots were then formed in the tube in the
desired
configuration. The tube may also be made of metal.
When structure 10, Fig. 1 was constructed of 1.5 inch diameter tubes similar
to
those shown in Fig. 9, it weighed 3.9 lbs. and supported a static load of more
than 2001bs.
This 4 ft. tall structure is collapsible to an 11 inch tall folded package.
Therefore, a 100
foot long structure could be packaged into a "Delta class" space vehicle for
space
deployment and would weigh less than 100 lbs. Since material is actually
removed from
each foldable member when the opposing slots are formed, the resulting
structure weighs
significantly less than prior art structures constructed of members including
spring steel
elements 40, 44, and 42, Fig. 4 or prior art structures with mechanical
hinges.
In another embodiment, member 120, Fig. 10 includes opposing sets 122 and 124
of elongated slots. Thus, set 122 includes two slots, slot 126 and slot 128
separated by
bridge element 130; and set 124 includes two slots, slot 132 and slot 134
separated by
bridge element 136. Each slot was about 1/8" wide and about 5/8" long in a 1%
inch
diameter Lexan tube. Each bridge element was about 3/16 inches long.
In one embodiment, slot 126 is diametrically opposed from slot 132 and slot
128
is diametrically opposed from slot 134 although this is not a limitation of
the present
invention.
Also, stress relieving member 138 (e.g. a dowel) may be attached to each
bridge
element 130 and 136 on the inside of the tube for relieving the stress of each
bridge
member and to prevent them from tearing or cracking when the tube is folded.
The foldable member shown in Figs. 10 and 11 proved to be generally stronger
in
and torsion than the members shown in Figs. 6-9.
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By including the hinges of this invention in a longeron twenty feet in length,
it
may be collapsed to a three foot long package, convenient for storage. A 3-4
inch
diameter tube would typically have about a 1/16th inch wall thickness while a
1 1/2 inch
diameter tube would typically have a .020 inch wall thickness, although many
different
combinations of wall thickness and diameters are possible over a wide variety
of tube
lengths and tube materials for specific applications.
The result is a foldable truss member, or longeron, or tube with no moving
parts or
joints and thus a lighter and more dimensionally stable structure. The hinge
means or
elements are preferably made of the same material as the tube unlike the
spring steel
elements of the prior art.
The members shown in Figs. 6-11 could be a component of truss structure 10,
Fig.
1 made of like truss members joined together as shown or instead could be a
longeron of a
frame or bulkhead or even a solitary boom or portion of an arnn or other
member.
In addition, the members shown in Fig. 6-11 could be a part of other
mechanical
structures such as collapsible mobile bridges, erectable civil engineering
structures for
emergency response and disaster relief, tent poles, police barricades, and the
like.
Figs. 12 and 13 show foldable structural member 150 with elongated slots
placed
at different locations to allow the member to be folded at different angles of
bend to
accommodate unique storage and/or deployment requirements or sequencing.
Foldable member 300, Fig. 14 includes tube 302 made of layers 303, 304, 306,
etc. of material, plastic (e.g. Lexan or composite material), for example,
formed by
wrapping a sheet of the material around itself several perhaps even 20 or more
times. An
adhesive, for example a double sided tape, may be used to secure the layers of
plastic
material to each other at selected locations along the length of the tube for
example at
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locations 310 and 312, shown in phantom. If the sheet of material comes off a
round roll
of stock material, it will have a tendency to roll up into a tube due to
memory, an
advantageous feature of this embodiment of the subject invention.
As with the other embodiments, slot 314 and an opposing slot (not seen in Fig.
14)
is formed through all of layers 303, 304, and 306 forming longitudinal strips
of layers of
material 318 and 320 which fold when subjected to localized buckling forces.
In this
embodiment, additional strength is provided by virtue of the many individual
columns of
tube material.
In the embodiment shown in Fig. 15, the individual tube layers are laminated
to
each other in areas A and B but not at hinge area C. As such, the layers of
material may
be made of plastic or composite materials subjected to conventional lamination
processes.
There is yet another method of forming opposing elongated slots in accordance
with this invention to achieve a configuration similar to that of Figs. 14 or
15. Fig. 16
shows two sections 400 and 402 of a composite material tube arranged in an end-
to-end
manner defining gap 403 therebetween.
One set 404 of C-section member plies 408 and 410 is assembled and ply 408 is
bonded or otherwise secured to ply 410 but typically only at the ends thereof.
Set 406 of
C-section member plies 412 and 414 is likewise assembled. Then, as shown in
Fig. 17,
set 404 is bonded or otherwise secured to one side of tube sections 400 and
402 to bridge
the gap therebetween and set 406 is secured to an opposite side of tube
sections 400 and
402 to also bridge the gap therebetween.
This construction results in opposing elongated slots such as slot 420 (and a
slot,
not shown, opposite slot 420) separated by longitudinally running strips of
material, i.e.,
the material of ply set 404 and 406 which fold when subjected to localized
buckling
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forces and which unfold, typically, automatically, when released.
In Fig. 16, only two plies for each set of C-section meinbers are shown for
clarity
but typically numerous (e.g., 8 or more) plies are used for increased strength
and stiffness
as shown in Fig. 17. The C-cross sectional shape is typically obtained by
pultrusion
tecluliques. Preferably, the material of plies 408, 410, 412, and 414 are the
same as the
material of tube sections 402 and 400 although this is not a necessary
limitation of the
subject invention. In this way, all of the components of Figs. 16-17 discussed
above may
be made of composite materials (e.g., carbon/PEEK compositions). In other
examples,
tube sections 400, 402 and plies 408, 410, 412, and 414 are made of plastic
such as
Lexan. It is also preferred that the tube sections 400, 402, Fig. 16 each
include a plurality
of layers or plies 430, 432, 434 as shown for tube section 400. See also Figs.
14-15.
As with the designs discussed above with reference to Figs. 6-15, there may be
two diametrically opposing slots, three opposing slots, and many hinge areas
in a given
foldable member.
For example, as shown in Figs. 18-19, there are three sets 340, 342, 344 of
conforming members each made of three plies as shown and another set (not
shown) on
the side opposite ply set 344 resulting in foldable member 350, Fig. 19 with
four slots two
of which are shown at 352 and 354 in Fig. 19.
The design of Figs. 10-11 wherein there are sets of longitudinally adjacent
opposing slots may be effected by tube sections 360 and 362, Figs. 20-21 and
intermediate tube section 364. Sets 368 and 370 of conforming C-section plies
secure the
bottom of tube section 360 to the intermediate bridge element section 364
wlule sets 372
and 374 secure the top of tube section 362 to intermediate section 364 to form
a set of
longitudinally adjacent slots 380 and 382, Fig. 21 separated by bridge element
364 and a
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similar set of circumferentially located axially adjacent slots (not shown)
opposite slot set
380, 382. As shown for ply 371, it may be preferential that select or even all
the
individual plies of sets 368 and 370 be continuous.
In accordance with the designs and method of Figs. 16-21, the number,
thickness,
length, width and material used for the conforming plies which ultimately form
the slots
can be tailored to the specific implementation. Similar variations exist with
the respect to
the material used for, the length and diameter of, and the number of plies or
layers of the
tube sections.
The curvature of the cross section of each member relative to its thickness is
governed by the tensile and compression yield strength of the material. The
maximum
amount of stress is seen by the material at the surface of the cross section.
For this reason,
the surface of the cross section should be as free from defects as possible.
The amount of strain seen is given as:
t
2R (1)
where t is the thickness of the cross-section and R and the radius of
curvature
either of the curved cross-section that is to be flattened or of the cross-
section to which a
flat element is to be curved.
For completely elastic storage, the value of the strain may be selected to be
below
the yield strength of the material in the direction of the curvature.
In the case of shape memory or super-elastic materials, the strain value is
selected
so that the value R is below the limit of elongation and compression recovery
of those
materials.
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For precision applications, these values of t and R should be selected so the
strain
R is sufficiently below the yield strain so that creep, stress relaxation and
micro-yield
are reduced to acceptable limits. The acceptable limits are defined by the
material section
and the specific needs of the application.
In Fig. 22, set 404a of conforming members 410a and 408a between tube sections
400 and 402 includes neck down regions 502, 504 designed to control the
location of the
folding of the conforming members and to prevent delamination or deformation
of the
conforming members. The saine result is shown in Fig. 23 by neck down regions
506,
508, 510, and 512. Preferably, it is only at these neck down regions that the
individual
confortning members are adhered together and the set of conforming members are
then
adhered and optionally fastened using fastener 516 to the tube sections at the
neck down
region.
In Fig. 24, conforming members 410c and 408c are secured together only at
central end regions 520 where they attached to the tube sections 400, 402 and
central end
regions 520 is capped with plate 522, which may be made of metal, through
which
fastener 516 extends. In cross section, film adhesive 526, as shown in Fig.
25, centrally
secures cap 522 to conforming member 408c, film adhesive 528 centrally secures
conforming member 408c to conforming member 410c and film adhesive layer 530
centrally secures conforming member 410c to the outer wall of tube section
400.
Typically, tube section 400 includes multiple plies or layers as shown in
Figs. 14 and 16.
In Fig. 26, intermediate rigid (e.g., metal) member 540 is used and has spaced
fingers 542, 544, and 546. One end of conforming member 410d is received and
secured
(e.g., adhered) between fingers 542 and 544 and one end of conforming member
408d is
CA 02491693 2004-12-31
WO 2004/005645 PCT/US2003/020541
19
secured between fingers 546 and 544. Intermediate member 540 is then attached
to the
outer wall of tube section 400. A similar rigid member, not shown, is secured
between
the adjacent spaced tube section and the opposite ends of conforming members
408d and
410d. In still another embodiment, intermediate member fingers 542, 544, and
546 are
integral layers of the tube sections theinselves.
Although specific features of the invention are shown in some drawings and not
in
others, this is for convenience only as each feature may be combined with any
or all of the
other features in accordance with the invention. The words "including",
"comprising",
"having", and "with" as used herein are to be interpreted broadly and
comprehensively
and are not limited to any physical interconnection. Moreover, any embodiments
disclosed in the subject application are not to be taken as the only possible
einbodiments.
Other embodiments will occur to those skilled in the art and are within the
following claims:
What is claimed is:
