U.S. patent application number 10/906442 was filed with the patent office on 2008-06-12 for stretched membrane device.
Invention is credited to Douglas Evan Simmers.
Application Number | 20080137221 10/906442 |
Document ID | / |
Family ID | 39387530 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080137221 |
Kind Code |
A1 |
Simmers; Douglas Evan |
June 12, 2008 |
STRETCHED MEMBRANE DEVICE
Abstract
An improved device for reflecting, radiating, or receiving
electromagnetic radiation, acoustic waves, or other energy forms
through the use of a membrane stretched across a lightweight,
round, frame structure. A near perfectly round and flat semi-rigid
backplane surface (1) and a near perfectly round ring or stack of
rings (2) are mutually reinforced, forming a raised circumferential
planar surface, and a cavity within. A membrane (3) is attached to
the top of the rings, forming one wall of a sealed chamber. A
source of sub-ambient pressure (4) is applied to the chamber,
causing a primary uniform deformation in the membrane for the
purpose of manipulating electromagnetic radiation, acoustic waves,
or other energy. The backplane surface also deforms uniformly,
increasing the strength of the structure. A flat, rigid floating
batten (5) prevents waves or wrinkles from forming in the membrane
material. A circumferential heating element (6) and insulation (7)
provides tensioning of the membrane by slightly controlling the
circumference of the device.
Inventors: |
Simmers; Douglas Evan;
(Massillon, OH) |
Correspondence
Address: |
DOUGLAS EVAN SIMMERS
7485 CHERYL LN. NW
MASSILLON
OH
44646
US
|
Family ID: |
39387530 |
Appl. No.: |
10/906442 |
Filed: |
February 20, 2005 |
Current U.S.
Class: |
359/847 |
Current CPC
Class: |
G02B 7/1815 20130101;
G02B 26/0825 20130101; G02B 5/10 20130101 |
Class at
Publication: |
359/847 |
International
Class: |
G02B 5/08 20060101
G02B005/08 |
Claims
1. An improved design for a reflector, radiator, or receiver of
electromagnetic, acoustic, or other energy, comprising a frame
structure that provides a near-perfectly round shape with a raised
planar circumferential surface, and creating an internal cavity
within, a non-porous reflective, transmissive, translucent, or
opaque membrane or plurality of membranes, a means of attaching and
sealing said membrane material to said raised planar surface, and
to each other in the case of multiple membranes, such that a sealed
cavity results between said frame structure and said membrane or
membranes, a means of applying sub-ambient or super-ambient
pressure to said sealed cavity, deforming said membrane or
membranes thereby resulting in membrane deformations which are
capable of manipulating electromagnetic, acoustic, or other energy,
wherein improvements are comprised of a near perfectly flat and
round semi rigid planar structural surface element of foam board,
cardboard, plywood, honeycombed laminate, or other material having
parallel opposed major faces with a predetermined distance between
them, and a predetermined fill material contained within a near
perfectly round ring element or plurality of ring elements that
provide circumferential reinforcement, having a predetermined
cross-sectional shape, being of a predetermined material, and
having a predetermined rigidity, means of attaching said planar
surface to said ring, and said rings to each other, thus forming a
near-perfect raised circumferential planar surface with an internal
cavity, the walls and bottom of which are sealed, and non-porous a
means of attaching and sealing said membrane or plurality of
membranes to said circumferential planar surface and also to each
other in an opposing orientation to said near perfectly flat and
round semi rigid planar structural surface element a means of
applying sub ambient or super ambient pressure thereby resulting in
membrane deformations which are capable of manipulating
electromagnetic, acoustic, or other energy, and thereby also
inducing a lesser convex or concave deformation into the semi-rigid
structural planar backplane material A means of inhibiting wrinkles
in said non-porous membrane elements A means of dynamically
tensioning said non-porous membrane or plurality of membranes.
2. The apparatus of claim 1 wherein said round frame structure for
use in supporting said membrane is comprised of a near perfectly
flat and round semi rigid planar surface element, a near perfectly
round ring or stack of ring elements that provides circumferential
reinforcement, being of any material, being hollow or solid, and
with any cross sectional shape, a means of attaching said planar
surface to said ring or rings, thus forming a near-perfect raised
circumferential planar surface with an internal cavity, a means of
attaching and sealing a membrane to said circumferential planar
surface, a means of applying sub ambient or super ambient pressure
for the purposes of inducing a uniform concave or convex
deformation to the membrane surface for the purpose of reflecting,
radiating, receiving or other manipulations of said
electromagnetic, acoustic, or other energy, and also inducing a
strengthening uniform convex or concave deformation into the
semi-rigid backplane material.
3. The apparatus of claim 1 wherein said round frame structure for
use in supporting said membrane is comprised of a near perfectly
flat and round semi rigid planar surface element, a near perfectly
round ring or stack of ring elements with any cross sectional shape
that provides circumferential reinforcement, a means of attaching
said planar surface to said ring or rings, thus forming a raised
circumferential planar surface with an internal cavity, a means of
attaching and sealing two membranes to said circumferential planar
surface, a means of applying super ambient pressure between the
inboard and outboard membranes for the purpose of inducing a
uniform convex deformation in the outboard membrane, and for
inducing a concave deformation to the inboard membrane surface for
the purpose of said reflecting, radiating, or receiving or other
manipulations of said electromagnetic, acoustic, or other energy,
and providing a means of venting the area between the inboard
membrane and the backplane material.
4. A circular floating batten for the purpose of inhibiting the
propagation of waves or wrinkles formed at the circumference of a
membrane and radiating inward as the said membrane is tensioned in
multiple directions, comprised of an annular, flat, rigid batten of
slightly less circumference than the membrane, constructed as one
piece, or in sections, a means for firmly attaching said batten to
the membrane, such that the batten is solely supported by said
membrane and that it may float in or out as the membrane is
tensioned.
5. A thermal size adjuster for uniformly adjusting the
circumference of a round structure with minimal distortion,
comprised of a circumferential heater, a method of attaching said
heater to the circumferential ring or rings, an insulating material
to minimize the heat loss from said heater.
6. The apparatus of claim 4, wherein the method of applying heat is
solar, comprising a solar absorbing material attached to the outer
face of the membrane material, a means of attaching said solar
absorbing material, an underlying heat conductive material to
conduct heat from the solar absorbing material to the ring or stack
of rings, n insulating layer covering the circumferential heater
and underlying layers, but not covering the solar absorbing
material, or the portion of conducting material underlying the
solar absorbing layer.
7. The apparatus of claim 4, wherein the method of applying heat is
an electrical resistance heater, comprised of a circumferential
resistance heater, a means of attaching said circumferential heater
to the circumference of the said round frame structure, an
insulating layer covering the circumferential heater and underlying
layers
8. An improved design for a reflector, radiator, or receiver of
electromagnetic, acoustic, or other energy, comprising a frame
structure that provides a near-perfectly round shape with a raised
planar circumferential surface, and creating an internal cavity
within, a non-porous reflective, transmissive, translucent, or
opaque membrane or plurality of membranes, a means of attaching and
sealing said membrane material to said raised planar surface, and
to each other in the case of multiple membranes, such that a sealed
cavity results between said frame structure and said membrane or
membranes, a means of applying sub-ambient or super-ambient
pressure to said sealed cavity, deforming said membrane or
membranes thereby resulting in membrane deformations which are
capable of manipulating electromagnetic, acoustic, or other energy,
wherein improvements are comprised of a near perfectly flat and
round semi rigid planar structural surface element, having parallel
opposed major faces with predetermined distance between them, and
predetermined fill material contained within a near perfectly round
ring element or plurality of ring elements that provide
circumferential reinforcement, having a predetermined
cross-sectional shape, being of a predetermined material, and
having a predetermined rigidity, a means of attaching said planar
surface to said ring, and said rings to each other, thus forming a
near-perfect raised circumferential planar surface with an internal
cavity, a means of attaching and sealing said membrane or plurality
of membranes to said circumferential planar surface, and also to
each other, a means of applying sub ambient or super ambient
pressure, thereby resulting in membrane deformations which are
capable of manipulating electromagnetic, acoustic, or other energy,
and thereby also inducing a lesser convex or concave deformation
into the semi-rigid structural planar backplane material a means of
inhibiting wrinkles in said non-porous membrane elements comprising
a circular floating batten element, formed inside the circumference
of said membrane element comprised of an annular, flat, batten of
slightly less circumference than the membrane, of a predetermined
material, of a predetermined width and thickness, with a
predetermined rigidity, and constructed as one piece, or in
sections, a means of attaching said batten to said membrane or
membrane elements with a predetermined strength and flexibility,
such that said batten is solely supported by said non-porous
membrane element a means of dynamically tensioning said non-porous
membrane or plurality of membranes.
9. The means of dynamically tensioning said non-porous membrane or
plurality of membranes of claim 1, comprising A thermal size
adjuster for uniformly adjusting the circumference of said round
structure, comprised of a circumferential heating element, a means
of attaching said heater to said circumferential ring or rings, an
insulating material to minimize the heat loss from said heater a
means of attaching said insulating material to ring or rings.
10. The apparatus of claim 9, wherein the method of applying heat
is solar, comprising a solar absorbing material attached to the
outer face of the membrane material, a means of attaching said
solar absorbing material, an underlying heat conductive material to
conduct heat from the solar absorbing material to the ring or stack
of rings, an insulating layer covering the portion of said
underlying heat conductive material not already covered by the
solar absorbing material.
11. The apparatus of claim 9, wherein the method of applying heat
is an electrical resistance heater, comprised of a circumferential
resistance heater, a means of attaching said circumferential heater
to the circumference of the said round frame structure, a means of
applying and controlling electricity to said resistance heater an
insulating layer covering the circumferential heater and underlying
layers.
Description
[0001] U.S. patent Documents
TABLE-US-00001 2,300,251 1941 Flint 2,952,189 1960 Pajes 3,031,928
1962 Kopitko 3,056,131 1962 Mcreary 3,610,738 1971 Bochmann
3,687,524 1972 Martinez 3,757,479 1973 Martinez 3,877,139 1975
Martinez 3,880,500 1975 Kojabashian 4,033,676 1977 Brantley, Jr. et
al 4,046,462 1977 Fletcher et al 4,068,777 1978 Humphrey, et al.
4,130,234 1978 Schmidt 4,352,112 1982 Leonhardt, et al 4,741,609
1988 Sallis 4,987,826 1991 Deppert, et al. 5,590,497 1997 Moore
5,680,262 1997 Soliday, et al. 5,813,830 1998 Smith, et al.
5,990,851 1999 Henderson, et al. 6,332,687 2001 Carreras, et al
6,716,017 2004 Papadopoulas
BACKGROUND OF THE INVENTION, AND PRIOR ART
[0002] Membranes, esp. polymeric membranes, provide an economical
method of presenting large surfaces to electromagnetic, acoustic,
or other energy, for the purpose of absorbing, reflecting,
focusing, or other manipulation of this energy.
[0003] Flint (U.S. Pat. No. 2,300,251, 1941) describes fabricating
a lens by using two transparent membranes with a clear fluid
between. Focal adjustment is made by mechanically adjusting the
frame, or by varying the fluid pressure between the membranes, or
diaphragms.
[0004] Membranes have also enabled the design of inexpensive
mirrors when a membrane is coated with a reflective coating, and
then are stretched over a suitable frame.
[0005] Martinez (U.S. Pat. Nos. 3,687,524, 3,757,479, and 3,877,139
1972-1975) described a flat "glassless" mirror stretched over a
sheet metal "pan".
[0006] Additionally, the shaping of such stretched reflective
membrane mirrors into a concave or convex lens shape enables the
mirror surface to now become a reflective lens with an approximate
spherical/parabolic shape useful for radiating, receiving,
reflecting or focusing electromagnetic radiation or acoustic waves.
A concave shape may be established by applying a vacuum within the
sealed chamber formed by the membrane and it's supporting frame. A
convex shape can be established by applying a positive pressure
within the sealed chamber. For space-based applications where near
vacuum ambient conditions exist, a second clear membrane may be
placed over the reflective membrane, and positive pressure
introduced between the two membranes to induce a concave shape into
the reflective inner membrane.
[0007] Such designs have been suggested for use in solar
concentrating dishes, radio antennas and also for imaging
applications such as telescopes and holographic projection.
[0008] Prior art with reference to utilizing a stretched membrane
material as a lens, or reflective lens include:
[0009] Pajes (U.S. Pat. No. 2,952,189, 1960) designed a drum which
is evacuated to induce a concave shape.
[0010] Kopitko (U.S. Pat. No. 3,031,928, 1962) described a dual
diaphragm system and a controlling method to maintain
curvature.
[0011] Bochmann (U.S. Pat. No. 3,610,738, 1971) depicted an
arrangement whereby a diaphragm was pulled by a cam to induce a
vacuum, and hence concave shape.
[0012] Brantley, Jr. et al, (U.S. Pat. No. 4,033,676 1977) depicted
two hoops separated by vertical strut members. The two membranes
form a cavity inside the circumference, and membranes also form a
pressure barrier around the strut members. The frame function is
separate from the sealing pressure barrier.
[0013] Kojabashian (U.S. Pat. No. 3,880,500, 1975) described a
frame design and a method utilizing two films that equalize the
pneumatic forces on the supporting structure.
[0014] Soliday, et al. (U.S. Pat. No. 5,680,262 1997) utilizes a
tubular frame of square cross section, and describes a tensioning
method for the stretched membrane utilizing a plurality of
pneumatic cylinders.
[0015] Carreras, et al (U.S. Pat. No. 6,332,687, 2001) describe
utilizing a vacuum for primary deformation, and also using an outer
mechanical ring and central plunger to achieve a more parabolic
shape.
[0016] Each of these designs utilized some type of frame over which
the reflective membrane is stretched:
[0017] Pajes (U.S. Pat. No. 2,952,189, 1960) and Bochmann (U.S.
Pat. No. 3,610,738, 1971) utilized a drum design.
[0018] Kopitko (U.S. Pat. No. 3,031,928, 1962) utilized two
parallel plates, with the film stretched at the midpoint.
[0019] One problem with previous designs is that although the
reflective membrane affords an inexpensive method of presenting and
manipulating large surfaces for the purpose of directing
electromagnetic radiation or other energy, the framework for the
membrane must be very strong to withstand the considerable
pneumatic forces required to establish the membrane shape with
minimal distortion. The primary aim of the frame is to establish a
nearly perfect round shape with a circumferential raised portion
that establishes a near perfect plane for the attachment and
sealing of a non-porous membrane to the frame structure. An
internal cavity is required to allow for the deformation of the
membrane material. These past designs often utilized heavy and
expensive frames.
[0020] Kopitko (U.S. Pat. No. 3,031,928, 1962), and Brantley, Jr.
et al, (U.S. Pat. No. 4,033,676 1977), Kojabashian (U.S. Pat. No.
3,880,500, 1975), Leonhardt, et al (U.S. Pat. No. 4,352,112 1982),
and Soliday, et al. (U.S. Pat. No. 5,680,262 1997) all address this
problem by utilizing two membranes with the vacuum or pressure
within, thus equalizing much of the resulting forces. This has the
disadvantage in that since both membranes stretch, the frame needs
to be of considerable width to prevent the two membranes from
touching in the middle when a vacuum is applied. Also, the sole
structural element becomes the outer ring or drum, which can still
oval and warp, distorting the desired focus or other manipulation
of the directed electromagnetic or other radiation. The ovaling
stress is non-uniform, and also tends to exacerbate the formation
of wrinkles or waves in the membrane surface.
[0021] Inflatable systems eliminate much of the weight problem, and
add a portability function, but tend to experience more
distortion.
[0022] Mcreary (U.S. Pat. No. 3,056,131, 1962) circumvents the
frame with an inflatable dish with reflective material on the back
side, and transparent material at the front.
[0023] Wladimir von Maydell et al. (U.S. Pat. No. 3,326,624)
describes an inflatable mirror for use in space-based
applications.
[0024] One object of this invention that is believed to solve many
of these problems is an improved frame design, utilizing a
combination of two basic geometric shapes (a ring and a flat plane)
which are mutually reinforced to arrive at a lightweight, rigid and
true structure for supporting the stretched membrane.
[0025] Leonhardt, et al (U.S. Pat. No. 4,352,112 1982) describe
utilizing a circumferential ring or rings with a vertical member to
increase height in a drum-like arrangement. The ring or rings,
however are described with two membrane surfaces forming the top
and bottom walls of the structure.
[0026] Ring reinforcement has been applied in the past for a wide
variety of unrelated applications, such as rolling a lip into the
rim of a paper cup, a formed lip of ajar lid, and as with the
molded lip on a container or with flying discs:
[0027] Schmidt (U.S. Pat. No. 4,130,234, 1978) and others discuss
improved methods of rolling a lip surface into a cup design for
greater strength. The goal here is to economically increase the
strength of the rim.
[0028] Sassak (U.S. Pat. No. 5,116,275, 1992) discusses a flying
toy with a reinforcing lip, but molded in.
[0029] Weiss (U.S. Pat. No. 5,366,403, 1994) discusses utilizing a
reinforcing ring to convert a disposable plate into a flying
toy.
[0030] Gilliam, et al. 6,761,283 2004 and others describe molding a
lip, or "brow ridge" into a container and closure for same as a way
of increasing the strength.
[0031] The primary function of the ring in this invention is
unique--to provide mutual reinforcement along with a backplane
element for the purpose of establishing a nearly perfect round
shape with a circumferential raised portion that establishes a near
perfect planar surface for the attachment and sealing of the
membrane. Further, the application of negative or positive pressure
inside the proposed structure causes a uniform warpage of the
backplane element, increasing the strength of the structure without
distortion of the manipulated electromagnetic, acoustic, or other
energy.
[0032] Another object of this invention are methods of preventing
wrinkles when a stretched membrane (esp. of polymeric material) is
tensioned in multiple directions, as when it is stretched over a
frame in a uniform manner, and then pneumatically deformed.
[0033] Sail battens have been utilized for minimizing wrinkling of
sails, and also for shaping sails into an ideal aerodynamic form.
Also similar to this invention, sail battens float on (are solely
support by) the stiffened sail surface.
[0034] Mauney (U.S. Pat. No. 2,743,510 1956) describes an
inflatable batten, and also one that forms an arc, but not a
complete circle
[0035] Leonhardt, et al (U.S. Pat. No. 4,352,112 1982) describes
prestressing a diaphragm in order to eliminate folds, and also
discusses various reinforcing strips for the purpose of altering
the stressed membrane configuration. The reinforcing ring depicted
forms only an arc, and is not completely annular.
[0036] Henderson (U.S. Pat. No. 5,333,569 1994) describes an
inflatable sail batten
[0037] Baird (U.S. Pat. No. 5,095,837 1992) describes a ram air
inflatable form for a spinnaker sail, again with a curved surface,
but not a completely round surface.
[0038] None of this prior art relates to preventing wrinkles in 360
degree round structure through the use of a circumferential
batten.
[0039] Another object of this invention is to provide a means of
uniformly tensioning the reflective membrane without inducing
distortion via the application of heat to the circumference of the
ring. Ambient temperature changes may affect the membrane material
in a different way than the supporting structure, due to
differences in thermal coefficient of expansion. The membrane may
remain tightly stretched at one ambient temperature, but become
loose when the ambient temperature is lowered, or vica versa. This
problem increases as the size of the structure increases.
[0040] Martinez (U.S. Pat. No. 3,687,524, 3,757,479, and 3,877,139
1972-1975) described a method of tensioning a membrane mirror
surface through the application of heat to shrink the film. This is
a one-time manufacturing process, however, as opposed to a method
of controlling the tension to accommodate changing ambient
temperatures.
[0041] Sallis, (4,741,609 1988) described a tensioning method for a
membrane reflector utilizing an inflatable bladder, but no thermal
component is mentioned.
[0042] Deppert, et al. (U.S. Pat. No. 4,987,826 1991) describes a
dynamic thermal tensioning method for a piston rod-to-cylinder
sealing ring, but utilizing a fluid filling medium.
[0043] Moore (U.S. Pat. No. 5,590,497 1997) discussed mechanical
circumferential tensioning of prestress cables in a concrete
tank.
[0044] Smith, et al. (U.S. Pat. No. 5,813,830 1998) utilizes
springs for circumferential tensioning of a carbon seal containment
barrier system inside a turbine engine.
[0045] Henderson, et al. (U.S. Pat. No. 5,990,851 1999) discusses
circumferential tensioning of a space-based antennae, but not by
thermal means.
[0046] Papadopoulas (U.S. Pat. No. 6,716,017 2004) discusses
circumferential tensioning of an embossing roll, but not by thermal
means.
BRIEF DESCRIPTION OF THE INVENTION
[0047] The principle object of this invention is to provide an
improved device for reflecting, radiating, or receiving
electromagnetic radiation, acoustic waves, or other energy forms
through the use of a membrane stretched across a lightweight,
round, frame structure. The primary purpose of the structure is to
establish a nearly perfect round shape with a circumferential
raised portion that establishes a near perfect plane for the
attachment of a membrane. The structure primarily consists of two
basic geometric shapes--a flat semi rigid planar surface attached
to a circumferential ring or stack of rings. The flat planar
surface and circumferential ring(s) provide mutual reinforcement,
and result in an internal cavity which may be utilized for
clearance to permit the deformation of the said stretched membrane
covering the cavity.
[0048] Further, the resulting shape becomes more rigid as vacuum or
pressure is placed inside the sealed area between the structure and
the reflective membrane. The primary concave or convex deformation
is induced into the reflective membrane, but the semi-rigid
backplane will also warp slightly and uniformly into a near-perfect
concave or convex shape that is stronger and more rigid than the
unstressed structure without causing significant distortion of the
desired membrane manipulation. Further, the minimal concavity
induced on a semi-rigid backplane minimizes the depth required of
the supporting structure.
[0049] Another object of the invention comprises a unique method of
preventing wrinkles that typically form in the periphery of the
reflective membrane surface as it is deformed. Many planar
materials, and especially polymeric materials, will develop large
wrinkles or waves when tensioned into a concave or convex shape
about a circular frame. These large wrinkles or waves scatter the
object radiation, acoustic, or other energy away from the desired
direction. This invention inhibits the propagation of these
wrinkles or waves through the attachment of a flat, rigid "floating
batten". This stiffening batten has a circumference slightly less
than that of the main structure, is solely supported by the
membrane itself, and inhibits the wrinkles from propagating from
the outside circumference inward.
[0050] Another object of the invention provides a unique method of
thermally tensioning the stretched film membrane by applying heat
circumferentially around the ring or rings. The ring heats up,
expanding in a uniform manner, while the film remains at ambient
temperature. Circumferential tensioning is uniform, minimizing the
distortion of the desired manipulation of electromagnetic, acoustic
or other energy. Method of circumferential heating may be via solar
radiation, resistance heating, or other method of generating
heat.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0051] FIG. 1 is a drawing depicting cross-sectional view the
overall preferred embodiment of the invention.
[0052] FIG. 2 depicts a near-perfect ring, which may be constructed
of any material, may be solid or hollow, and it may have a round,
square, or any other cross sectional shape
[0053] FIG. 3 depicts a typical deformation or ovaling of said ring
into an out of round condition, due to it's own weight, unbalanced
forces of a mechanical, pneumatic, hydraulic, electromagnetic, or
other nature.
[0054] FIG. 4 depicts a planar backplane material that forms a
near-perfect flat surface.
[0055] FIG. 5--Again, stresses of a gravitational, mechanical,
pneumatic, hydraulic, electromagnetic, or other source can easily
cause this backplane material to warp or "potato chip" out of the
near perfect flat shape.
[0056] FIG. 6 depicts an assembly whereby a near-perfect ring is
attached to a near-perfect flat structure, or backplane whereby the
backplane prevents ovaling of the ring, and the ring inhibits
warping of the backplane, creating a near-perfect circumferential
raised planar surface, and also resulting in an internal
cavity.
[0057] FIG. 7 depicts the same assembly as in FIG. 6, but with a
stack of reinforcing rings, and a non-porous membrane stretched
across it, and sub-ambient pressure applied to the interior of the
assembly, causing a primary deformation into the membrane, and a
slight secondary but uniform deformation into the semi rigid
backplane material.
[0058] FIG. 8 depicts the same assembly as FIG. 7, but with a
super-ambient pressure applied, causing a convex deformation of the
membrane, and a slight uniform concave deformation of the backplane
element.
[0059] FIG. 9 depicts a dual membrane assembly with super-ambient
pressure applied between the two membranes.
[0060] FIG. 10 depicts large radial wrinkles or waves that
typically form when a stretched membrane is tensioned in more than
one direction, as, for example, when a sub or super-ambient
pressure is applied.
[0061] FIG. 11 depicts a method for minimizing the large wrinkles
or waves depicted in FIG. 7 via a round, flat, rigid batten
attached to, and wholly supported by the stretched membrane.
[0062] FIG. 12 depict a thermal circumference adjuster, utilizing
the application of heat circumferentially to the ring surface with
a solar absorbing material, a heat conductive layer, and an
insulating layer on top.
[0063] FIG. 13 illustrates another thermal circumferential adjuster
utilizing a resistance heater around the circumference, again with
an insulating layer above to retain heat.
DETAILED DESCRIPTION OF THE INVENTION
[0064] As shown in the drawings, the preferred embodiment in
accordance with the present invention is an improved stretched
membrane device for reflecting, radiating, or receiving
electromagnetic radiation, acoustic waves, or other energy forms
through the use of a membrane stretched across a lightweight,
round, frame structure. The preferred embodiment, depicted in FIG.
1 comprises a round frame consisting of (1) a near perfectly round
and flat semi rigid foamboard backplane element attached to (2) a
stack of near perfectly round circumferential reinforcing ring
elements. A reflective membrane element (3) consisting of a
non-porous reflective material is stretched across the cavity
formed by the structure, and attached to the circumferential ring,
thereby forming one wall, and sealing said cavity. A vacuum (4) is
placed into to cavity, causing a primary uniform concave
deformation of the reflective membrane for the object of
manipulating said forms of electromagnetic, acoustic, or other
energy. The vacuum also induces a slight, uniform convex shape into
the semi-rigid backplane material that increases the total strength
of the frame structure with minimal distortion of the object
manipulations of energy. An annular floating batten element (5) of
slightly less diameter than the frame is attached to and solely
supported by the reflective membrane, and prevents the propagation
of large wrinkles or waves that form in the reflective membrane as
it is tensioned by the application of vacuum. A circumferential
heater (6) of solar or other source is provided to induce a uniform
growth or shrinkage to the reinforcing ring, thereby evenly
tensioning the reflective film, again with minimal distortion.
Insulation (7) is applied over the heated rings for the purpose of
retaining heat.
[0065] FIGS. 2-7 provide an understanding of the problems of
fabricating a large supporting frame structure for the embodiment,
and also the advantages of this improvement.
[0066] FIG. 2 depicts a typical ring element. The ring may
constructed of any material, may be hollow or solid, and may be of
any cross sectional area. FIG. 3 depicts an oval distortion typical
of a ring when gravitational, mechanical, pneumatic or other forces
are applied to it.
[0067] FIG. 4 depicts a round, flat planar surface which may be
constructed of foamboard, cardboard, plywood, or honeycombed
material with backing.
[0068] FIG. 5 depicts typical distortion, non-uniform warpage, or
"potato chipping" that can occur from gravitational, mechanical,
pneumatic or other forces are applied to it, and also by the
absorption of moisture or other fluids into the material.
[0069] FIG. 6 depicts an assembly whereby a near perfectly round
ring (2) as depicted in FIG. 2 is solidly attached to a near
perfectly flat backplane surface (1) as depicted in FIG. 4. The
circumferential rigidity imparted by the ring inhibits the
distortion in the backplane element noted in FIG. 4, and the
backplane material inhibits ovaling of the ring or rings element as
shown in FIG. 2. The resulting assembly results in a nearly perfect
round shape with a circumferential raised portion that establishes
a near perfect plane (4) for the attachment and sealing of a
membrane. An internal cavity (3) is formed by this assembly, which
provides clearance for the uniform deformation of the said
membrane.
[0070] FIG. 7 depicts an assembly with a stack of rings (4) with a
means of attaching them to the backplane and to each other,
providing additional depth to the cavity, and a non-porous membrane
(1) attached and sealed to the circumferential plane established
across the top, forming a sealed cavity into which a sub-ambient
pressure (2) may be applied and held. Said sub-ambient pressure
causes a primary uniform concave deformation in the membrane
material, and also causes a slight but uniform convex deformation
in the semi rigid backplane material (3), which increases the
strength of the total assembly without inducing significant
distortion to the membrane or to the object manipulation of the
said electromagnetic, acoustic, or other energy.
[0071] FIG. 8 depicts an assembly with a stack of rings (4)
providing additional depth to the cavity, and a non-porous membrane
attached and sealed across the top, forming a sealed cavity into
which a super-ambient pressure (1) may be applied and held. Said
super-ambient pressure causes a primary uniform convex deformation
in the membrane material (2), and also causes a slight but uniform
concave deformation in the semi rigid backplane material (3), which
increases the strength of the total assembly without inducing
significant distortion to the membrane, or to the object
manipulation of the said electromagnetic, acoustic, or other
energy.
[0072] FIG. 9 depicts an assembly with a stack of rings (6)
providing additional depth to the cavity, and two non-porous
membranes attached and sealed across the top. Super-ambient
pressure (3) may be applied and held between the two membranes,
causing a convex manipulation of the outboard membrane (1), and a
concave manipulation of the inboard membrane(2). The cavity between
the inboard membrane and the backplane element is vented(4).
Backplane element (5) remains flat in this instance. Such an
arrangement would be advantageous in forming an optical lens by
using two transmissive membranes. Another use would be for a
space-based reflective lens with an outboard transmissive membrane,
and a reflective inboard membrane.
[0073] FIG. 10 depicts large wrinkles or waves (1) that form in
membrane films when tensioned in multiple directions, such as in
FIG. 7, when a sub-ambient pressure is applied inside the sealed
cavity. Many membrane materials display some small amount of
elasticity when tensioned uniformly in one direction. When tension
is simultaneously applied to said membrane in more than one
direction, however, large wrinkles or waves form at the
circumference of the membrane, and radiate inward. These waves or
wrinkles display maximum amplitude (2) just inside the
circumference, and decreasing amplitude as the deformation
progresses toward the center. Said wrinkles or waves in the
membrane material direct the object electromagnetic, acoustic, or
other energy away from the desired manipulation.
[0074] FIG. 11 depicts a unique circular, flat, rigid annular
batten (1) of slightly less diameter than the structure that it is
firmly attached to, and solely supported by the reflective membrane
(2). This floating annular batten inhibits the propagation of said
waves or large wrinkles.
[0075] FIG. 12 depicts a unique method of thermally tensioning the
stretched film membrane by applying heat circumferentially around
the ring or rings. The ring(s) (1) heat up, expanding in a uniform
manner, while the film (2) remains at ambient temperature.
Circumferential tensioning minimizes deformation of the reflective
membrane and also of the desired manipulation of electromagnetic,
acoustic or other energy. FIG. 12 depicts a solar absorbing
material (3)attached to the outer face of the reflective membrane.
A conducting material (4) underneath carries the heat generated to
the outer diameter of the rings. An insulating layer(5) is applied
on top to prevent heat loss.
[0076] FIG. 13 depicts another method of applying circumferential
heat via an electrical heating element. An electrical resistance
heater element (1) is attached circumferentially to the ring(s),
electricity is applied and controlled (2), and an insulating layer
(3) is provided to prevent heat loss.
[0077] The foregoing description of the preferred embodiment of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of the above teaching. It is
intended that the scope of the invention be limited not by this
detailed description, but rather by the claims appended hereto.
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