U.S. patent application number 12/038793 was filed with the patent office on 2008-10-23 for method of bending sheet materials and sheet therefor.
This patent application is currently assigned to Industrial Origami, Inc.. Invention is credited to Max W. DURNEY, Alan D. Pendley.
Application Number | 20080257006 12/038793 |
Document ID | / |
Family ID | 36588370 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257006 |
Kind Code |
A1 |
DURNEY; Max W. ; et
al. |
October 23, 2008 |
Method of bending sheet materials and sheet therefor
Abstract
A sheet of material formed for bending along a bend line
including a sheet of material (30) includes a plurality of dividing
slits (37) and a plurality of strap slits (39) formed therethrough.
The dividing slits extending substantially along a desired bend
line (35) and divide the sheet of material into first and second
planar regions (32, 33). The strap slits intersect the desired bend
line and adjacent pairs of strap slits form a bending strap
therebetween. The bending strap has a longitudinal strap axis
intersecting the desired bend line. The sheet of material may be
formed of composite materials. A method of forming and using the
sheet of material is also disclosed.
Inventors: |
DURNEY; Max W.; (San
Francisco, CA) ; Pendley; Alan D.; (Petaluma,
CA) |
Correspondence
Address: |
MORGAN, LEWIS & BOCKIUS, LLP
ONE MARKET SPEAR STREET TOWER
SAN FRANCISCO
CA
94105
US
|
Assignee: |
Industrial Origami, Inc.
San Francisco
CA
|
Family ID: |
36588370 |
Appl. No.: |
12/038793 |
Filed: |
February 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11016408 |
Dec 16, 2004 |
7354639 |
|
|
12038793 |
|
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Current U.S.
Class: |
72/324 ; 428/136;
72/379.2 |
Current CPC
Class: |
H05K 1/028 20130101;
B21D 5/00 20130101; Y10T 428/24314 20150115; H05K 2203/302
20130101; Y10T 428/24198 20150115; H05K 1/0366 20130101; H05K
1/0278 20130101; Y10T 428/15 20150115; H05K 2201/09063 20130101;
Y10T 428/24264 20150115 |
Class at
Publication: |
72/324 ;
72/379.2; 428/136 |
International
Class: |
B21D 5/00 20060101
B21D005/00; B21D 28/00 20060101 B21D028/00 |
Claims
1. A sheet of material formed for bending along a bend line
comprising: a sheet of material having at least one dividing slit
extending substantially along a desired bend line dividing said
sheet of material into first and second planar regions, and at
least two strap slits formed through said sheet of material
intersecting said desired bend line, wherein said strap slits form
a bending strap therebetween, said bending strap having a
longitudinal strap axis intersecting said desired bend line.
2.-23. (canceled)
24. A method of forming a sheet of material for bending along a
bend line comprising the steps of: forming at least one dividing
slit through said sheet of material extending substantially along a
desired bend line thereby dividing said sheet of material into
first and second planar regions; and forming at least two strap
slits through said sheet of material intersecting said desired bend
line, thereby forming a bending strap between said strap slits,
said bending strap having a longitudinal strap axis intersecting
said desired bend line.
25. The method of claim 24, said method further comprising the step
of: after the forming steps but before the assembling step,
mounting at least one component to at least one of said first and
second planar regions.
26. A method of forming a sheet of material for bending along a
bend line comprising the steps of: forming a plurality of dividing
slits through said sheet of material extending substantially along
a desired bend line thereby dividing said sheet of material into
first and second planar regions; and forming a plurality of
substantially parallel strap slits through said sheet of material
intersecting said desired bend line, thereby forming a bending
strap between adjacent pairs of said strap slits, said bending
strap having a longitudinal strap axis intersecting said desired
bend line.
27. The method of claim 26, wherein prior to the forming steps,
selecting a sheet of elastically deformable material for
slitting.
28. The method of claim 26, said method further comprising the
step: prior to the forming steps, selecting a sheet of composite
material for slitting.
29. The method of claim 26, wherein said forming steps are
accomplished simultaneously.
30. The method of claim 26, wherein said forming steps are
accomplished by forming at least three dividing slits and at least
a pair of strap sets, and each strap set disposed between adjacent
ones of said dividing slits, each strap set having at least three
strap slits forming at least two substantially parallel bending
straps therebetween.
31. The method of claim 30, wherein said strap-slits forming step
is accomplished by forming at least a pair of said strap sets
parallel to one another such that the strap axis of a first of said
strap sets is parallel to the strap axis of a second of said strap
sets.
32. The method of claim 30, wherein said strap-slits forming step
is accomplished by forming at least a pair of said strap sets
nonparallel to one another such that the strap axis of a first of
said strap sets intersects the strap axis of a second of said strap
sets.
33. The method of claim 32, wherein said strap-slits forming step
is accomplished by forming strap sets symmetrically about a
transverse axis which extends substantially transverse to said
desired bend line.
34. The method of claim 26, wherein said strap-slits forming step
is accomplished by forming each said strap with a substantially
straight intermediate portion.
35. The method of claim 26, wherein said strap-slits forming step
is accomplished by forming an end of at least one of said strap
slits with a enlarged stress-relieving end opening.
36. The method of claim 35, wherein said strap-slits forming step
is accomplished by forming at least one of said strap slits with a
stress-relieving end radius to increase the cross-sectional area of
an adjacent bending strap as said adjacent bending strap merges
with a respective one of said planar regions.
37. The method of claim 26, wherein said strap-slits forming step
is accomplished by forming an adjacent pair of said strap slits
each with a stress-relieving end radius to increase the
cross-sectional area of an adjacent bending strap as said adjacent
bending strap meets a respective one of said planar regions.
38. The method of claim 37, wherein said forming steps are
accomplished by simultaneously forming said stress-relieving end
radius to interconnect said at least one of said strap slits and an
adjacent dividing slit.
39. The method of claim 26, wherein said forming steps are
accomplished by forming at least one interconnected dividing slit
and adjacent strap slit.
40. The method of claim 26, wherein said strap forming step is
accomplished by forming said strap slits such that said strap axis
is oblique to said desired bend line.
41. The method of claim 26, said method further comprising the
step: prior to the forming steps, selecting a sheet of composite
material having a substantially uniform thickness; wherein said
strap-slit forming step is accomplished by forming adjacent ones of
said strap slits such that each said bending strap includes a
minimum width dimension that is less than or substantially equal to
the thickness of said sheet of material.
42. The method of claim 26, said method further comprising the step
of: after the forming steps, bending the sheet of material about
said desired bend line.
43. The method of claim 26, said method further comprising the step
of: forming an assembly recess in each of said first and second
planar regions for locating and securing said sheet of material
during assembly.
44. The method of claim 43, said method further comprising the step
of: after the forming steps, bending the sheet of material about
said desired bend line; assembling said sheet of material with
another device such that a respective locating protrusion extends
through said each said assembly recess.
45. The method of claim 44, said method further comprising the step
of: after the forming steps but before the assembling step,
mounting a component to at least one of said first and second
planar regions.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 11/016,408 filed Dec. 16, 2004, entitled
METHOD OF BENDING SHEET MATERIALS AND SHEET THEREFOR, the entire
content of which is incorporated herein by this reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates, in general, to a method of folding
sheet materials and a sheet therefor.
[0004] 2. Description of Related Art
[0005] Currently, electronic equipment often includes several
discrete circuit boards disposed in a three-dimensional
configuration, that is, at an angle with respect to one another in
order to fulfill limited space requirements. For example,
electronic devices such as personal computers, stereo equipment,
television sets and the like often have a first circuit board
disposed on a base thereof, and a second circuit board disposed on
a side wall thereof and generally mounted perpendicularly to the
first circuit board. Such configuration requires relatively complex
connection systems to interconnect the components of the first
board with components of the second board.
[0006] Due to handling constraints, such connection systems are
often not installed until the circuit boards have been assembled to
a chassis of the electronic device or other internal frame
pre-assembly. Furthermore, electrically testing the components is
often difficult because the components are often not readily
accessible once the boards have been installed in the respective
electronic device. In the event that the boards include defective
components, replacing the defective components is often difficult
due to the limited accessibility, and may sometimes require
disassembly.
[0007] What is needed is method of bending sheet materials which
overcomes the above and other disadvantages. For example, it would
be advantageous to replace the several circuit boards with a single
circuit board that is capable of bending or folding, and in some
cases, is capable of unfolding.
BRIEF SUMMARY OF THE INVENTION
[0008] In summary, one aspect of the present invention is directed
to a sheet of material formed for bending along a bend line
including a sheet of material having at least one dividing slit
extending substantially along a desired bend line dividing the
sheet of material into first and second planar regions, and at
least two strap slits formed through the sheet of material
intersecting the desired bend line, wherein the strap slits form a
bending strap therebetween, the bending strap having a longitudinal
strap axis intersecting the desired bend line.
[0009] Another aspect of the present invention is directed to a
sheet of material formed for bending along a bend line including a
sheet of material having a plurality of dividing slits extending
substantially along a desired bend line dividing the sheet of
material into first and second planar regions, and a plurality of
substantially parallel strap slits formed through the sheet of
material intersecting the desired bend line, wherein adjacent pairs
of the strap slits form a bending strap therebetween, the bending
strap having a longitudinal strap axis intersecting the desired
bend line.
[0010] The sheet of material may be formed of a composite material.
The composite material may be selected from the group consisting of
polymer matrix composites, fiber reinforced composites, metal
matrix composites, ceramic composites, and aggregate composites.
The composite material may be, but not limited to, a fiber
reinforced composite selected from the group consisting of
fiberglass, polyaramid (Kevlar.RTM.), liquid crystal polymer,
phenolic, and carbon fiber composites.
[0011] The sheet of material may include at least three dividing
slits and at least a pair of strap sets, each strap set disposed
between adjacent ones of the dividing slits, and each strap set
having at least three strap slits forming at least two
substantially parallel bending straps. Optionally, at least a pair
of the strap sets are parallel to one another such that the strap
axis of a first of the strap sets is parallel to the strap axis of
a second of the strap sets. Alternatively, at least a pair of the
strap sets are nonparallel to one another such that the strap axis
of a first of the strap sets intersects the strap axis of a second
of the strap sets. The strap sets may be symmetric about a
transverse axis which extends substantially transverse to the
desired bend line.
[0012] Each strap slit may have a substantially straight
intermediate portion. Also, an end of at least one of the strap
slits may include a enlarged stress-relieving end opening. Also, at
least one of the strap slits may include a stress-relieving end
radius to increase the cross-sectional area of an adjacent bending
strap as the adjacent bending strap merges with a respective one of
the planar regions. Optionally, the at least one of the strap slits
and an adjacent dividing slit may be connected by the
stress-relieving end radius. Furthermore, an adjacent pair of the
strap slits may each include a stress-relieving end radius to
increase the cross-sectional area of an adjacent bending strap as
the adjacent bending strap meets a respective one of the planar
regions. At least one dividing slit and an adjacent strap slit may
be interconnected.
[0013] The strap axis may be oblique to the desired bend line. The
strap axis may extend less than 45.degree. with respect to the
desired bend line. Alternatively, the strap axis may extend within
the range of approximately 5-45.degree. with respect to the desired
bend line, an in the case that the strap are utilized as an
in-plane actuator, approximately 5-60.degree.. Further still, the
strap axis may extend within the range of approximately
7-45.degree. with respect to the desired bend line.
[0014] The sheet of material may have a substantially uniform
thickness, and each bending strap may include a minimum width
dimension that may be less than or substantially equal to the
thickness of the sheet of material. At least one bending strap may
include a continuous surface extending between the first and second
planar regions. The sheet of material may include an electrical
connector extending along the continuous surface between the first
and second planar regions. Optionally, each of the first and second
planar regions may include an assembly recess for locating and
securing the sheet of material during assembly with another
device.
[0015] Still another aspect of the present invention is directed to
a method of forming a sheet of material for bending along a bend
line including the steps of: forming at least one dividing slit
through the sheet of material extending substantially along a
desired bend line thereby dividing the sheet of material into first
and second planar regions; and forming at least two strap slits
through the sheet of material intersecting the desired bend line,
thereby forming a bending strap between the strap slits, the
bending strap having a longitudinal strap axis intersecting the
desired bend line. The method may further include the step, after
the forming steps but before the assembling step, mounting at least
one component to at least one of the first and second planar
regions.
[0016] Yet another aspect of the present invention is directed to a
method of forming a sheet of material for bending along a bend line
including the steps of: forming a plurality of dividing slits
through the sheet of material extending substantially along a
desired bend line thereby dividing the sheet of material into first
and second planar regions; and forming a plurality of substantially
parallel strap slits through the sheet of material intersecting the
desired bend line, thereby forming a bending strap between adjacent
pairs of the strap slits, the bending strap having a longitudinal
strap axis intersecting the desired bend line.
[0017] The method may include, wherein prior to the forming steps,
the step of selecting a sheet of elastically deformable material
for slitting. The method may include, prior to the forming steps,
selecting a sheet of composite material for slitting.
[0018] The forming steps may be accomplished simultaneously. The
forming steps may be accomplished by forming at least three
dividing slits and at least a pair of strap sets, and each strap
set disposed between adjacent ones of the dividing slits, each
strap set may have at least three strap slits forming at least two
substantially parallel bending straps therebetween.
[0019] The strap-slits forming step may be accomplished by forming
at least a pair of the strap sets parallel to one another such that
the strap axis of a first of the strap sets is parallel to the
strap axis of a second of the strap sets. The strap-slits forming
step may be accomplished by forming at least a pair of the strap
sets nonparallel to one another such that the strap axis of a first
of the strap sets intersects the strap axis of a second of the
strap sets. Furthermore, the strap-slits forming step may be
accomplished by forming strap sets symmetrically about a transverse
axis which extends substantially transverse to the desired bend
line. The strap-slits forming step may be accomplished by forming
each strap with a substantially straight intermediate portion.
[0020] The strap-slits forming step may be accomplished by forming
an end of at least one of the strap slits with a enlarged
stress-relieving end opening. The strap-slits forming step may be
accomplished by forming at least one of the strap slits with a
stress-relieving end radius to increase the cross-sectional area of
an adjacent bending strap as the adjacent bending strap merges with
a respective one of the planar regions. The strap-slits forming
step may be accomplished by forming an adjacent pair of the strap
slits each with a stress-relieving end radius to increase the
cross-sectional area of an adjacent bending strap as the adjacent
bending strap meets a respective one of the planar regions.
[0021] The forming steps may be accomplished by simultaneously
forming the stress-relieving end radius to interconnect the at
least one of the strap slits and an adjacent dividing slit. The
forming steps may be accomplished by forming at least one
interconnected dividing slit and adjacent strap slit.
[0022] The strap forming step may be accomplished by forming the
strap slits such that the strap axis is oblique to the desired bend
line.
[0023] The method may further include the step, prior to the
forming steps, selecting a sheet of composite material having a
substantially uniform thickness, wherein the strap-slit forming
step may be accomplished by forming adjacent ones of the strap
slits such that each bending strap may include a minimum width
dimension that is less than or substantially equal to the thickness
of the sheet of material. The method may further include the step
of, after the forming steps, bending the sheet of material about
the desired bend line. The method may further include the step of
forming an assembly recess in each of the first and second planar
regions for locating and securing the sheet of material during
assembly. Furthermore, the method may include the steps of, after
the forming steps, bending the sheet of material about the desired
bend line, and assembling the sheet of material with another device
such that a respective locating protrusion extends through each
assembly recess. Further still, the method may further include the
step of, after the forming steps but before the assembling step,
mounting a component to at least one of the first and second planar
regions.
[0024] The method of bending sheet materials and the sheets used
therefor in accordance with the present invention have other
features and advantages which will be apparent from or are set
forth in more detail in the accompanying drawings, which are
incorporated in and form a part of this specification, and the
following Detailed Description of the Invention, which together
serve to explain the principles of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a top plane of a sheet material sheet in
accordance with the present invention.
[0026] FIG. 2 is an enlarged detail of the sheet material of FIG. 1
taken within circle 2-2 of FIG. 1.
[0027] FIG. 3 is a cross-sectional view of sheet material of FIG.
1.
[0028] FIG. 4 is a perspective view of the sheet material of FIG. 1
in a bent configuration.
[0029] FIG. 5 is a cross-sectional view, similar to, FIG. 3 of the
sheet material in the bent configuration of FIG. 4.
[0030] FIG. 6 is a top plane view of another sheet material similar
to that shown in FIG. 1 but having a modified strap
configuration.
[0031] FIG. 7 is a top plane view of another sheet material similar
to that shown in FIG. 1 but having a modified strap
configuration.
[0032] FIG. 8 is a cross-sectional view, similar to FIG. 5, of the
sheet material of FIG. 1 shown installed about a component.
[0033] FIG. 9 is a cross-sectional view, similar to FIG. 5, of the
sheet material of FIG. 1 shown installed within a chassis and
having components installed thereon.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Reference will now be made in detail to the preferred
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. While the invention will be described in
conjunction with the preferred embodiments, it will be understood
that they are not intended to limit the invention to those
embodiments. On the contrary, the invention is intended to cover
alternatives, modifications and equivalents, which may be included
within the spirit and scope of the invention as defined by the
appended claims.
[0035] The present invention is directed to relatively stiff sheet
materials and methods of bending the same. For example, the present
invention is particularly suited for fabricating electronic circuit
boards, however, one will appreciate that the methods and sheet
materials of the present invention are equally suited for other
uses including, but not limited to in-plane springs and expansion
joints, fiber optic devices, nanostructures, radiofrequency
shields, wireless antennae and other devices.
[0036] As noted above, prior electronic devices often include
several discrete circuit boards disposed in a three-dimensional
configuration and require relatively complex connection systems to
interconnect the components of a first board with components of a
second board. The present invention overcomes the associated
disadvantages of the multiple discrete circuit boards of the prior
art, namely in that the present invention provides for a sheet of
material that is capable of bending or folding and that is capable
for serving as a single circuit board that replaces the multiple
circuit boards of the prior art.
[0037] Such a foldable circuit board would save component count,
system complexity, and space. As the components that are to be
installed on the foldable circuit board may be installed and
electrically connected before folding, and before the foldable
circuit board is installed in an electronic device, the resulting
circuit may be tested while it is still easily accessible to test
equipment. Any defective components may be fixed or replaced at
this stage, as such components would be readily accessible as the
foldable circuit board has not yet been installed into the
electronic device. Significantly, the above manufacturing, assembly
and testing steps are simplified as they are performed on a
substantially two-dimensional (2D) structure (e.g., a flat
structure). The flat structure could be shipped flat for folding at
a remote location. Later, the 2D structure can be folded into a
three-dimensional (3D) structure (e.g., a folded structure) for
more efficient space utilization or to allow the 3D structure to
fit inside a specific volume.
[0038] Turning now to the drawings, wherein like components are
designated by like reference numerals throughout the various
figures, a sheet of material, generally designated by the numeral
30 is illustrated in FIG. 1. Sheet 30 is configured such that,
despite being formed of a relatively stiff material, first and
second planar regions 32, 33 of the sheet may be bent about a bend
line 35. To facilitate bending, sheet 30 is provided with a
plurality of dividing slits 37, and with a plurality of strap slits
39 forming bending straps therebetween 40 as seen in FIG. 2.
[0039] Such a bendable sheet is particularly suited for electronic
circuit boards or other applications where multiple layers of board
would be useful in that it would be possible to populate the boards
with components (e.g., component 42; FIG. 9) while the boards are
flat 2D structures and easily accessible using conventional
equipment including, but not limited to, automated pick and place
equipment, wave solder and other suitable manufacturing and
assembly equipment. Once populated, the foldable boards can be
folded to achieve more efficient packaging without the need for
incorporating connectors or having to plug connectors into sockets,
as would normally be the case.
[0040] In some aspect, the forming and bending of sheet materials
in accordance with the present invention are similar to the methods
and devices described in copending U.S. patent application Ser. No.
10/795,077 entitled SHEET MATERIAL WITH BEND CONTROLLING
DISPLACEMENTS AND METHOD FOR FORMING THE SAME and now U.S. Pat. No.
7,152,450, U.S. patent application Ser. No. 10/672,766 entitled
TECHNIQUES FOR DESIGNING AND MANUFACTURING PRECISION-FOLDED, HIGH
STRENGTH, FATIGUE-RESISTANT STRUCTURES AND SHEET THEREFOR and now
U.S. Pat. No. 7,152,449, U.S. patent application Ser. No.
10/256,870 entitled METHOD FOR PRECISION BENDING OF SHEET
MATERIALS, SLIT SHEET AND FABRICATION PROCESS and now U.S. Pat. No.
6,877,349, and described in U.S. Pat. No. 6,481,259 entitled METHOD
FOR PRECISION BENDING OF A SHEET OF MATERIAL AND SLIT SHEET
THEREFOR, the entire contents of which applications and patent is
incorporated herein by this reference. For example, the methods and
devices used for forming slits described in the above applications
and patent may be adapted to be used to form slits in accordance
with the present invention.
[0041] One will appreciate, however, that some fold requirements of
the present sheet materials vary from the fold requirements of the
sheet materials described in the above-mentioned applications and
patent. For example, the folds of sheet 30 need not snap into place
and stay folded by themselves, The folds need not be load bearing,
as the sheet, once installed in or on an electronic device as a
circuit board, would be supported by the chassis or other frame
work of the electronic device. The folds need not provide
geometrical precision so that the folded sections of the sheet line
up with attachment points as necessary, as the sheet, once
installed in an electronic device, would be positioned by the same
means which supports the sheet in or on the electronic device.
[0042] In contrast, the fold configuration of the present sheet is
conducive for use with relatively brittle sheet materials
including, but not limited to, polymer matrix composites, fiber
reinforced composites such as fiberglass, phenolic or carbon fiber
composites, metal matrix composites (MMC), ceramic composites and
aggregate composites (where the reinforcing phase consists of
particles rather than fibers). Also the fold configuration of the
present sheet is also conducive to reducing the folding force
(i.e., force necessary to fold sheet 30 about bend line 35),
especially as compared to folding a sheet of material not provided
with the dividing and strap slits of the present invention.
[0043] One will appreciate that the folds of sheet 30 do provide
various other features and advantages not found in prior fold
configurations. For example, bending straps 40 provide continuity
between the first and second planar regions of sheet 30,
particularly in the unfolded state, so that the whole sheet can be
handled as one piece.
[0044] Turning now to the configuration of the sheet of material,
sheet 30 includes a plurality of dividing slits 37 which extend
substantially along a desired bend line 35, as shown in FIG. 1.
Although the bend line appears to be coplanar or coincident with
the sheet in FIG. 1, one will appreciate that the radius of
curvature of the bent sheet will likely be greater than the
thickness of the sheet, in which case the actual axis of about
which the materials bend will likely be parallel to but offset from
the sheet (see, e.g., bend axis BA in FIG. 5).
[0045] The dividing slits also divide the sheet of material into
first and second planar regions 32, 33 on either side of the bend
line (e.g., portions of sheet 29 which remain substantially flat).
One will appreciate that two, three or more dividing slits may be
utilized to divide the sheet into the first and second planar
regions. One will also appreciate that dividing slits may extend
along a plurality of bend lines in order to divide the sheet into
three, four, five, six or more planar regions as desired (e.g., to
form a triangular 3D structure, a square 3D structure, an open-box
3D structure, a closed-cube 3D structure, or other 3D
structures).
[0046] Sheet 30 also includes a plurality of substantially parallel
strap slits 39 formed therethrough. The strap slits intersect bend
line 35 and adjacent pairs of the strap slits (e.g., 39', 39'', see
FIG. 2) form a bending strap 40 therebetween.
[0047] Preferably, the slits are formed by the use of computer
numerically controlled (CNC) devices which control a slit forming
apparatus, such as a laser, water jet, punch press, knife or other
tool. One will appreciate that other suitable means may be used to
form slits in accordance with the present invention including, but
not limited to, casting and molding. As the configuration of all
slits, dividing slits and strap slits, can be preprogrammed and
effected at once on or at a single workstation, it is considered
that the slits may be formed substantially simultaneously.
[0048] Returning now to the strap slits, each adjacent pair of
strap slits 39 form a bending strap 40 therebetween. The bending
strap has a longitudinal strap axis 44 intersecting the desired
bend line as seen in FIG. 2.
[0049] Preferably, each strap slit has substantially straight
intermediate portion 46 which extends across the bend line. The
intermediate portion provides a length of the strap slit which has
a substantially uniform cross-section along which torsion (e.g.,
twist about the strap axis) may be distributed fairly uniformly
along the length. In the illustrated embodiment, the sheet of
material has a substantially uniform thickness (T) (see, e.g., FIG.
3), however, one will appreciate that the sheet need not be
uniformly thick. Preferably, the bending strap may have a minimum
width dimension (w) (see, FIG. 2) that is less than or
substantially equal to the thickness (T) of the sheet of material
in order to minimize the torsional resistance of the strap.
[0050] Preferably, the strap axis is oblique to the bend line. The
strap axis may extend less than approximately 45.degree. with
respect to the desired bend line, more preferably, within the range
of approximately 5-40.degree. with respect to the desired bend
line, and still more preferably within the range of approximately
15-30.degree. with respect to the desired bend line. To this end,
one will appreciate that a sheet of material may bend to a certain
minimum radius of curvature before the sheet will fail. This
minimum radius of curvature is dependent, among other things, on
the material and thickness of the sheet. For example, a solid sheet
of phenolic having a thickness of approximately 0.060 inches may
have a minimum radius of curvature which the sheet can be bent
about a bend line to a minimum radius of several inches, if not
feet, beyond which minimum the phenolic sheet will fail.
[0051] Skewing the strap axis with respect to the bend line serves
to reduce the effective minimum radius of curvature. Firstly,
skewing the strap axis subjects the strap to a certain amount of
torsion that is distributed along a length of the strap. The
effective minimum of radius about the bend line may be reduced as a
certain amount of angular displacement about the bend line is
accommodated by such torsion. Furthermore, skewing the strap axis
at an angle with respect to the fold line also skews the actual
minimum radius of curvature (Rmin.sup.a) angle with respect to the
fold line. Thus, the effective minimum radius of curvature
(Rmin.sup.e) may be further reduced by the sine of angle thereby to
reducing the radius of curvature as follows:
Rmin.sup.e=Sin e( )*Rmin.sup.a
[0052] In the embodiment of FIG. 1, sheet 30 has three dividing
slits 37, 37', 37'' effectively separating the sheet into first and
second planar regions 32, 33 on either side of bend line 35. A pair
of strap sets 47, 49' are disposed between respective ones of the
dividing slits. One will appreciate that two, three, four or more
dividing slits may be utilized to form one, two, three or more
straps sets.
[0053] In this embodiment, each strap set includes four strap slits
39 thereby forming three bending straps 40 as shown in FIG. 2 (only
one bending strap 40 is shown). Again, one will appreciate that
two, three, four or more strap slits may be utilized to
respectively form one, two, three or more straps there between.
Preferably, each strap set includes two or more straps in order to
distribute torsion over a greater number of straps, and/or to
accommodate a greater amount of torsion.
[0054] With continued reference to FIG. 1, the strap sets 47, 47'
are not parallel to one another and are instead symmetrically
arranged about a transverse axis 51 such that the strap axis 44 of
the first strap set intersects the strap axis 44' of the second
strap set. Such a symmetric arrangement is advantageous in that it
tends to effectively cancel axial shifting of first planar region
32 relative to second planar region 33 along bend line 35.
[0055] One will appreciate that the strap sets may be
asymmetrically oriented and even parallel to one another in the
event that axial shift along the bend line is desired. For example,
FIG. 6 illustrates a sheet 30a that includes a pair of strap sets
47a, 47a' that are parallel to one another. As will be apparent
from FIG. 6, the geometric configuration of strap sets 47a,
47a'would allow a limited amount of axial shift of first planar
region 32 relative to second planar region 33 as illustrated by
arrows A, A' in FIG. 6.
[0056] Returning to FIG. 1, the strap slits 39 are provided with
stress reducing structures at ends thereof, namely, enlarged
stress-relieving end openings 53. The end openings are provided so
as to effect a reduction in the stress concentration in the bending
straps. The end openings will tend to cause any stress cracks to
propagate back into the strap slits, depending on the loading
direction of the sheet. It will be understood, however, that stress
reducing structures, such as the enlarged end openings are not
required for realization of the benefits of the bending method of
the present invention. In the illustrated embodiment, the end
openings have a circular configuration having a diameter that is
larger than the width or kerf of the strap slits, as best seen in
FIG. 2.
[0057] The strap slits may also be provided with other
stress-reducing structures. For example, the strap slits may be
provided with stress-relieving end radii 54 which cause the ends of
the strap slits to diverge away from bend line 35. In particular,
each end radius diverges away from the bend line and thus gradually
increases the width and cross-sectional area of an adjacent bending
strap as the strap meets or merges with a respective planar region.
As best seen in FIG. 2, the terminal width dimension (w.sup.t) of
each bending strap is significantly larger than the minimum width
dimension wm. For example, the terminal width may be two, three, or
more, times larger than the minimum width dimension of the strap.
Moreover, larger terminal width dimension may cause the deformation
of bending straps to be more gradual during bending and torsion so
that stress concentration will be reduced. This, of course,
combines with increasing strap width to transfer loading forces and
bending forces more evenly into the remainder of the sheet with
lower stress concentration
[0058] As illustrated in FIG. 1, adjacent ones of dividing slits 37
and strap slits 39 may be interconnected end-to-end with a stress
reducing structure such as connecting radius 56. One will
appreciate that the dividing slits may extend to and terminate
intersecting a respective strap slit, however, connecting radius 56
provides several advantages.
[0059] Firstly, interconnecting adjacent dividing slits and strap
slits end-to-end simplifies the manufacturing process. For example,
in the event that the slits are formed by the use of computer
numerically controlled (CNC) devices which control a slit forming
apparatus, such as a laser, water jet, punch press, knife or other
tool, the end-to-end configuration eliminates the need to power
down and/or remove the cutting element from the sheet between the
steps of forming a dividing slit and an adjacent strap slit.
Similarly, since the dividing slit and adjacent strap slit form one
continuous slit, there is no need to reverse or backtrack the tool
to complete the strap slit.
[0060] Secondly, connecting radius 56 eliminates the sharp point
which would otherwise be formed if the dividing slit linearly
continued to intersect the adjacent strap slit, namely, the sharp
point that would be formed on the acute-angle side of such
intersection.
[0061] The materials being considered in the present invention are
capable of elastic deformation without failure but may fail
catastrophically when a substantial amount of plastic deformation
occurs. Consequently, the torsion straps are designed to maintain
the materials in a state of substantially elastic-only deformation.
The substantially elastic-only torsion straps can be considered
torsion springs. Each strap contributes a finite amount of
resistance force as the two planes are rotated about the bend.
Three-dimensional structures can be held into position by the
fastening or closure methods that prevent the rotational degrees of
freedom of each bend from springing open. Printed circuits boards
that incorporate the torsion joints of the present invention can be
held closed in the desired bend angle by the temporary or permanent
docking of components that are assembled onto the surface of each
plane.
[0062] These elastic bend joints can be designed with a large
degree of spring-back force if the bend joint will be subject to
mechanical stresses in service or conversely the joints may be
designed with a negligible amount of spring-back force if a
surrounding chassis supports the folded structure. Another
consideration in the design choice of how stiff to make the elastic
bend joint is the ability to handle the unfolded sheet in a planar
form prior to and after assembly of attached components but prior
to folding. A very low force elastic bend joint with negligible
spring-back force may be unable to resist the gravitational forces
of the slit sheet itself or in combination with the attached
components. Therefore, a sheet may be designed with additional
rigidity at each elastic bend joint which must be overcome by
fastening to a supporting chassis, through temporary or permanent
docking of components attached to the surface of each articulated
plane, through three dimensional closure of three or more planes,
or through compression or tensile members that temporarily or
permanently define the angular degree of freedom of the elastic
bend joint. At least one bending strap may include a continuous
surface 58, that is, an uninterrupted surface extending between the
first and second planar regions as shown in FIG. 2. As the
continuous surface extends obliquely to the bending line, and as
the continuous surface is not subject to creasing as sheet 30 is
folded about bend line 35, the continuous surface provides a path
upon which an electrical connector 60 may be located between the
first and second planar regions. The electrical connector may take
the form of a portion of a printed circuit connector or otherwise
applied directly to the surface of the sheet. One will appreciate
that other suitable electrical conduit means may be applied
directly to the sheet such that the conduit means extends along the
continuous surface.
[0063] For example, the electrical connection may make use of
conductive electrical traces that pass between the first and second
planar regions along one or more straps, occurring on one or more
layers of a multi-layer printed circuit board. The purpose of these
conductive electrical traces running along the straps can be the
provision of power from one planar region to another. Another
purpose for these conductive electrical traces is the communication
of electrical signals or logic switching from one planar region to
another. Yet another purpose for providing conductive electrical
traces across articulated elastic bend joints is electrical or
capacitive continuity between ground plane structures which
provide, among other things, electromagnetic shielding.
[0064] Because the process of forming the electrically conductive
traces is separate from the process of forming the strap-defining
slits, provisions must be made for registering the two fabrication
steps in close registration. If the automated process for forming
the boards and slitting them is inline, connected, and maintains
rotational and translated position of the board throughout the
process, then co-registration of the two processes will be
automatically embedded in the manufacturing process. However, if
the position of the board is not maintained between the
trace-forming steps and the slitting steps, for example because the
two processing steps are in different locations, the design of the
printed circuit board most preferably contains registration marks
that can be use by the slit forming process to recall the
positional registration of the board prior to slitting.
[0065] One will appreciate that the foldable configuration of sheet
30 allows the sheet to be populated with one or more components 42
while the sheet is in its flat configuration. In the event that the
components are electronic and located on opposing planar regions,
electrical connector 60, shown in FIG. 4, may be used to operably
connect the components.
[0066] Optionally, each of the first and second planar regions are
provided with one or more assembly recesses 61 for locating and
securing the sheet of material during assembly with another device.
In one embodiment, the assembly recess takes the form of a
plurality of assembly apertures 61 located adjacent the corners of
sheet 30. One will appreciate that one, two, three or more assembly
recesses may be used and that the locations of the assembly
recesses may vary depending upon various design parameters
including, but not limited to, the arrangement of components
populated on the sheet, whether the sheet is installed on and about
a subassembly 63 or other suitable device in an external-corner
configuration (see FIG. 8), whether the sheet is installed within a
chassis 65 or other suitable device in an internal-corner
configuration (see FIG. 9), and/or the inherent spring coefficient
of the sheet of material. For example, if the sheet of material has
a relatively high spring coefficient which tends to return the
sheet to its flat configuration when bent, the assembly recesses
may be more numerous and provided closer or further to the bend
line to maximize leverage in holding sheet in place.
[0067] For example, in the case of an external-corner
configuration, the sheet may include one or more assembly apertures
61 located proximal the corners thereof to cooperate with assembly
fastener 67 in order to minimize the likelihood of the outer
extremities of first and second planar regions 32, 33 from
springing back away from subassembly 63 such that sheet 30 returns
to its flat configuration, as illustrated by Arrow S in FIG. 8.
Similarly, in the case of an internal-corner configuration,
assembly apertures 61a may be located proximal the bend line to
cooperate with assembly fastener 68a in order to minimize the
likelihood of the inner extremities of first and second planar
regions 32a, 33a from buckling up away from the internal corner of
chassis 65 such that sheet 30 returns to its flat configuration, as
illustrated by Arrow B in FIG. 9.
[0068] The various embodiments of the present invention allow
designing manufacturing and fabrication advantages to be achieved
which have not heretofore been realized. Thus, the full benefits of
such design and fabrication techniques as CAD design, Rapid
Prototyping and "pick and place" assembly can be realized by using
single 2D sheets of material to replace 3D structures which
heretofore required the use of multiple discrete 2D structures.
[0069] The configuration of the bendable sheet of the present
invention may also be suitable for manufacturing circuit boards
which conform to non-orthogonal device packages. Generally,
industrial designs are often limited by the need for flat or
connectored printed circuit board assemblies ("PCBA's"). The
bendable configuration of sheet 30 would facilitate artistically
shaped devices having compact designs with high circuit density.
For example, wearable electronics, conformal automotive or airborne
electronics and other products may require complex-shaped housings
that require circuit boards to be oblique to one another. The
configuration of the present invention would allow a single circuit
board take the place of two or more obliquely oriented circuit
boards.
[0070] Furthermore, the bendable configuration of the sheet may be
utilized to provide a hinged PCBA, that is, a PCBA that may be bent
back and forth repeatedly. For example, the sheet of the present
invention may be adapted for use within a folding mobile phone or
other device which presently requires two or more circuit boards
that must pivot relative to one another. Such a bendable
configuration avoids the need for inelegant hot bar soldering
and/or expensive connectors between two discrete circuit
boards.
[0071] Another advantage of the present invention is that one may
be able to fold a circuit board into its own RF shield and isolate
RF circuits from digital circuits cleanly and cheaply. The device
could be tested flat to verify functionality and repair any
defective or missing components without removing RF cans prior to
folding.
[0072] An advantage of the interconnected straps is the bendable
sheet of the present invention may also be used with fiber optic
technologies. For example, an embedded light pipe may extend along
one or more straps to optically couple the first and second planar
regions of the sheet. Such embedded light pipes would be capable of
transferring optic signals between the first and second planar
regions without having to resort to optical fibers and their high
cost.
[0073] One will appreciate that the geometries of the sheet of the
present invention may also be utilized on nanostructures in order
to produce articulated micro-mirrors, biomimetic cilia,
piezoelectric drive motors and other nanotechnology devices.
[0074] One will also appreciate that the configuration of the sheet
material may also serve as an in-plane spring which allows linear
displacement of the first and second planar regions with respect to
one another. For example, the slit/strap configuration of sheet 30
would allow first planar region 32 to displace in the direction of
arrow C (FIG. 1) relative to second planar region 33 and/or the
second planar region to displace in the direction of arrow D (FIG.
1) relative to the first planar region to displace in the direction
of arrow D. Such a configuration allows the sheet to accommodate
expansion and contraction of materials for various reasons
including, but not limited to, heat. Furthermore, the configuration
of sheet 30 allows the material to absorb a significant amount of
linear force (e.g., in the direction of arrows C and D) with
relatively little linear displacement. Such a configuration may be
utilized in the manufacture of strain gauges and other devices.
Additionally, the spaces created by the slit forming process may be
filled with viscoelastic material to act as an inherent vibration
dampener for the in-plane spring of the present invention.
[0075] In another embodiment of the present invention, sheet of
material 30a is similar to sheet 30 described above but includes
parallel strap sets 47a as shown in FIG. 6. In yet another
embodiment of the present invention, sheet of material 30b is
similar to sheets 30 and 30a described above but includes a single
strap set 47b including eleven bending straps 40 as shown in FIG.
7. Like reference numerals have been used to describe like
components of sheets 30, 30a and 30b. In operation and use, sheets
30a and 30b are used in substantially the same manner as sheet 30
discussed above.
[0076] One will appreciate that the number and configuration of
strap sets may vary in accordance with the present invention. For
example, each strap set may be parallel with one another,
symmetrically arranged, asymmetrically, arranged and so forth.
Similarly, each strap set may have one, two, three or more bending
straps contained therein.
[0077] For convenience in explanation and accurate definition in
the appended claims, the terms "up" or "upper", "down" or "lower",
"inside" and "outside" are used to describe features of the present
invention with reference to the positions of such features as
displayed in the figures.
[0078] In many respects the modifications of the various figures
resemble those of preceding modifications and the same reference
numerals followed by subscripts "a" and "b" designate corresponding
parts.
[0079] The foregoing descriptions of specific embodiments of the
present invention have been presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teaching. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
application, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
claims appended hereto and their equivalents.
* * * * *