U.S. patent application number 10/188721 was filed with the patent office on 2003-01-30 for foldable member.
Invention is credited to O'Reilly, Sean, Rosenberg, Sara E., Warren, Peter A..
Application Number | 20030019180 10/188721 |
Document ID | / |
Family ID | 30114014 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030019180 |
Kind Code |
A1 |
Warren, Peter A. ; et
al. |
January 30, 2003 |
Foldable member
Abstract
A method of manufacturing a foldable member. A plurality of
C-section member plies are formed. First and second sets of the
C-section member plies are assembled. Two sections of a tube are
arranged in an end-to-end manner defining a gap therebetween. The
first set of the C-section member plies is secured to one side of
the two sections of the tube to bridge the gap therebetween and the
second set of C-section member plies is secured to an opposing side
of the two tube sections to also bridge the gap therebetween thus
forming opposing elongated slots separated by longitudinal strips
of material between the slots which fold when subjected to
localized buckling forces and which unfold when released. A
foldable member manufactured in accordance with this method is also
disclosed. Also disclosed is a structure made of one or more such
foldable members.
Inventors: |
Warren, Peter A.; (Newton,
MA) ; Rosenberg, Sara E.; (Natick, MA) ;
O'Reilly, Sean; (East Boston, MA) |
Correspondence
Address: |
IANDIORIO & TESKA
INTELLECTUAL PROPERTY LAW ATTORNEYS
260 BEAR HILL ROAD
WALTHAM
MA
02451-1018
US
|
Family ID: |
30114014 |
Appl. No.: |
10/188721 |
Filed: |
July 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10188721 |
Jul 2, 2002 |
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10044434 |
Jan 11, 2002 |
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10044434 |
Jan 11, 2002 |
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09436514 |
Nov 9, 1999 |
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6374565 |
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Current U.S.
Class: |
52/646 ;
135/143 |
Current CPC
Class: |
E04C 3/28 20130101; E04C
2003/0434 20130101; E04C 2003/043 20130101; E04B 1/3441 20130101;
B64G 9/00 20130101; E04C 3/005 20130101; B64G 1/222 20130101; E04C
2003/0417 20130101; E04C 2003/0413 20130101; E04C 2003/0495
20130101; E04C 3/08 20130101; E04C 2003/0447 20130101; E04C 3/07
20130101; E04C 2003/0421 20130101; E04C 3/291 20130101 |
Class at
Publication: |
52/646 ;
135/143 |
International
Class: |
E04H 015/48; E04H
012/18 |
Goverment Interests
[0002] This invention was made with U.S. Government support under
Contract no. F29601-99-C-0010. The Government may have certain
rights in the invention.
Claims
What is claimed is:
1. 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 member 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 of the tube 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.
2. The method of claim 1 in which assembling the first set of
C-section member plies includes securing all the plies of the first
set together.
3. The method of claim 1 in which assembling the second set of
C-section member plies includes securing all the plies of the
second set together.
4. The method of claim 1 in which the plurality of C-section member
plies are made of composite material.
5. The method of claim 1 in which the two tube sections are made of
composite material.
6. The method of claim 1 in which the plurality of C-section member
plies are pultruded into a C-section cross sectional shape.
7. The method of claim 1 in which the material of the first and
second set of C-section members is the same as the material of the
two tube sections.
8. The method of claim 1 further including the steps of arranging a
third tube section in an end-to-end manner with the two tube
sections to define a gap therebetween and securing third and fourth
sets of C-section member plies to opposing sides of the third tube
section and the two tube sections thus forming sets of
longitudinally adjacent opposing elongated slots.
9. A foldable member comprising: 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.
10. The foldable member of claim 9 in which the conforming members
have a C-cross sectional shape.
11. The foldable member of claim 9 in which the material of the
conforming members is the same as the material of the two tube
sections.
12. The foldable member of claim 11 in which the conforming members
are made of composite material and the two tube sections are made
of composite material.
13. The foldable member of claim 9 in which both sections of the
tube comprise a plurality of layers.
14. The foldable member of claim 9 in which there are two
diametrically opposing elongated slots and two diametrically
opposing longitudinal strips.
15. The foldable member of claim 9 in which there are a plurality
of hinge areas longitudinally spaced from each other along the
length of the tube, each hinge area including opposing elongated
slots.
16. The foldable member of claim 9 in which there are three
opposing elongated slots and three opposing elongated strips each
longitudinal strip diametrically opposing an elongated slot.
17. The foldable member of claim 9 further including a third tube
section and sets of longitudinally adjacent opposing elongated
slots.
18. The foldable member of claim 9 in which the conforming members
have a neck down region.
19. The foldable member of claim 18 in which the conforming members
are secured together only at the neck down region.
20. The foldable member of claim 9 in which the conforming members
are secured together only where they attach to the tube
sections.
21. The foldable member of claim 20 in which the conforming members
are centrally secured together only where they attach to the tube
section.
22. The foldable member of claim 9 further including an
intermediate rigid member interconnecting the conforming members
with a tube section.
23. The foldable member of claim 22 in which the intermediate
member has spaced fingers, each conforming member received between
two spaced fingers.
24. A structure comprising: a plurality of joined truss members; a
selected number of said truss members each including a foldable
member comprising: 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.
25. The structure of claim 24 in which the conforming members have
a C-cross sectional shape.
26. The structure of claim 24 in which the material of the
conforming members is the same as the material of the two tube
sections.
27. The structure of claim 26 in which the conforming members are
made of composite material and the two tube sections are made of
composite material.
28. The structure of claim 24 in which both sections of the tube
comprise a plurality of layers.
29. The structure of claim 24 in which there are two diametrically
opposing elongated slots and two diametrically opposing
longitudinal strips.
30. The structure of claim 24 in which there are a plurality of
hinge areas longitudinally spaced from each other along the length
of the tube, each hinge area including opposing elongated
slots.
31. The structure of claim 24 in which there are three opposing
elongated slots and three opposing elongated strips each
longitudinal strip diametrically opposing an elongated slot.
32. The structure of claim 24 in which the multiple plies are
secured together before the conforming members are attached to the
tube sections.
33. The structure of claim 24 in which the plies are pultruded into
a C-section cross sectional shape.
34. The structure of claim 24 further including a third tube
section and longitudinally adjacent slots opposing each other
around the circumference of the foldable member.
Description
RELATED PATENT APPLICATIONS
[0001] This application is a continuation-in-part application of
patent application Ser. No. 10/044,434 filed Jan. 11, 2002 entitled
"Foldable Member" by the same inventor as the subject application
which is a divisional application of application Ser. No.
09/436,514 filed Nov. 9, 1999 entitled "Foldable Member" now U.S.
Pat. No. 6,374,565, by the same inventor as the subject
application. This application is also related to U.S. Pat. No.
6,321,503.
FIELD OF THE INVENTION
[0003] This invention relates to a foldable boom, truss, or
longeron member, collapsible truss structures and other similar
structures made of such members.
BACKGROUND OF THE INVENTION
[0004] 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 instruments depends on maintaining the precision and
stability of the deployed structural 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 and freeplay would enable a deployed structure to be as
linear and precise as a monolithic block of material.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] Other hinge designs such as latch and actuator type systems
suffer from the same disadvantages.
[0009] 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. Pat. No. 4,334,391 incorporated herein by this reference.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] In use, this spring steel hinge design suffers from a number
of shortcomings.
[0014] 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 themselves add
significantly to the overall weight of the truss structure which is
an undesired factor in space launch capability.
[0015] 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.
[0016] 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 earth. 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
[0017] 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.
[0018] It is a further object of this invention to provide such a
member and such a structure which is more dimensionally stable.
[0019] It is a further object of this invention to provide such a
foldable member which eliminates numerous sources of
imprecision.
[0020] 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
system mass.
[0021] It is a further object of this invention to provide such a
member and such a structure which have tailorable thermal expansion
and conductivity properties and which thus can be designed for a
multitude of performance requirements.
[0022] 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.
[0023] It is a further object of this invention to provide such a
member which is simple to manufacture and use.
[0024] It is a further object of this invention to provide a
collapsible tube useful in variety of applications.
[0025] 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.
[0026] 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 member 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] This invention also features a foldable member comprising
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. 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.
[0031] 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.
[0032] 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 where they attach to the tube sections. In
another embodiment, an intermediate rigid member is provided
interconnecting the conforming members with a tube section. The
intermediate member typically has spaced fingers and each
conforming member is received between two spaced fingers.
[0033] 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 may be a third tube section and sets of
longitudinally adjacent opposing elongated slots.
[0034] 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
[0035] 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:
[0036] FIG. 1 is a perspective view of a structure made of a number
of foldable members in accordance with the subject invention;
[0037] FIG. 2 is a schematic view of the structure shown in FIG. 1
in a collapsed state;
[0038] FIG. 3 is a perspective view of the structure of FIG. 2
after it expands from the collapsed condition;
[0039] FIG. 4 is a front elevational view of a prior art foldable
device;
[0040] FIG. 5 is a view of the prior art device shown in FIG. 4 in
the folded position;
[0041] FIG. 6 is a side elevational view of the foldable member of
the subject invention;
[0042] FIG. 7 is a front elevational view of the foldable member
shown in FIG. 6;
[0043] FIG. 8 is a schematic view of the foldable member shown in
FIGS. 6 and 7 in a folded position;
[0044] FIG. 9 is a front elevational view of another embodiment of
the foldable member of this invention;
[0045] FIG. 10 is a side elevational view of another embodiment of
the foldable member of the subject invention;
[0046] FIG. 11 is a view similar to FIG. 11 showing the interior
rear side wall of the foldable member of the subject invention;
[0047] FIG. 12 is a front elevational view of a single elongated
foldable member with multiple hinge areas in accordance with this
invention;
[0048] FIG. 13 is a schematic view of the member of FIG. 13 in
folded position;
[0049] FIG. 14 is a schematic view of another embodiment of a
foldable member in accordance with the subject invention;
[0050] FIG. 15 is a schematic view of still another embodiment of a
foldable member in accordance with the subject invention;
[0051] FIG. 16 is a schematic exploded view of still another
embodiment of a foldable member in accordance with the subject
invention showing the use of conforming members connected between
two tube sections;
[0052] FIG. 17A is a schematic view showing the embodiment of the
foldable member of FIG. 16 in the assembled state;
[0053] FIG. 17B is a schematic view showing the embodiment of FIG.
17A in the folded configuration;
[0054] FIG. 18 is a schematic partially exploded view showing
another embodiment of the subject invention;
[0055] FIG. 19 is a schematic view showing an assembled foldable
member in accordance with the embodiment shown in FIG. 18;
[0056] FIG. 20 is a schematic partially exploded view of still
another embodiment of the foldable member of this invention;
[0057] FIG. 21 is a schematic view showing an assembled foldable
member in accordance with the embodiment of FIG. 20;
[0058] FIGS. 22-23 are schematic views showing conforming members
in accordance with this invention having neck down regions;
[0059] FIG. 24 is a schematic view showing one method of securing
the conforming members to the two tube sections in accordance with
this invention;
[0060] FIG. 25 is a cross sectional view of a portion of FIG. 24;
and
[0061] 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
[0062] 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 of truss member 12 (and other selected truss
members) which includes hinge areas 16, 18, and 20 along its
length.
[0063] 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.
[0064] When collapsed as shown in FIG. 2, the volume of truss
structure 10 is sharply reduced resulting in significant space
savings for space flight.
[0065] Upon deployment 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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. 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
example, slots 66 and 67, FIGS. 6 and 7, are simply a 4 inch long
formed in a 13/4 inch tube. Slots 90, 92, and 94, FIG. 9, on the
other hand, are elliptically shaped and approximately {fraction
(11/16)} inches wide at their widest point.
[0073] 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.
[0074] 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 may 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 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.
[0075] 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 200 lbs. 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.
[0076] 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 {fraction (3/16)} inches long.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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 {fraction (1/16)}th inch wall thickness
while a 11/2 inch diameter tube would typically have a 0.020 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.
[0081] 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.
[0082] 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 arm or other
member.
[0083] In addition, the members shown in FIGS. 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.
[0084] 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.
[0085] 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 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.
[0086] 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.
[0087] 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.
[0088] There is yet another method of forming opposing elongated
slots in accordance with this invention to achieve a configuration
similar to that of FIG. 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.
[0089] 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 FIGS.
17A-17B, 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.
[0090] 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
forces (See FIG. 17B) and which unfold, typically, automatically,
when released.
[0091] In FIG. 16, only two plies for each set of C-section members
are shown for clarity but typically numerous (e.g., 8 or more)
plies are used for increased strength and stiffness as shown in
FIG. 17B. The C-cross sectional shape is typically obtained by
pultrusion techniques. 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.
[0092] 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.
[0093] 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.
[0094] 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 while 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 similar set of circumferentially located axially adjacent
slots (not shown) opposite slot set 380, 382. As shown for ply 371,
it may be preferrential that select or even all the individual
plies of sets 368 and 370 be continuous.
[0095] 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.
[0096] 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.
[0097] The amount of strain seen is given as: 1 = t 2 R ( 1 )
[0098] 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.
[0099] 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.
[0100] In the case of shape memory or super-elastic materials, the
strain value is selected so that the value 2 t 2 R
[0101] is below the limit of elongation and compression recovery of
those materials.
[0102] For precision applications, these values of t and R should
be selected so the strain 3 t 2 R
[0103] 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.
[0104] 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 same 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 conforming 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.
[0105] 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.
[0106] 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 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
themselves.
[0107] 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
embodiments.
[0108] Other embodiments will occur to those skilled in the art and
are within the following claims:
* * * * *