U.S. patent number 3,599,218 [Application Number 04/759,136] was granted by the patent office on 1971-08-10 for lightweight collapsible dish structure and parabolic reflector embodying same.
This patent grant is currently assigned to TRW Inc.. Invention is credited to Michael E. Bochory, Clyde E. Williamson.
United States Patent |
3,599,218 |
Williamson , et al. |
August 10, 1971 |
LIGHTWEIGHT COLLAPSIBLE DISH STRUCTURE AND PARABOLIC REFLECTOR
EMBODYING SAME
Abstract
A collapsible lightweight, dish-shaped structure is provided for
use as a parabolic reflector and other uses. The structure has a
dish constructed of a lightweight, thin film membrane, such as an
aluminized polymeric plastic film selected from the class including
Mylar and Kapton. Lightweight elastic ribs or beams, which are
preferably slender tubes constructed of the same thin film material
as the dish, are bonded to the rear surface of the dish and are
preformed to cause the dish to normally assume a predetermined
geometric configuration, such as a parabolic shape. The structure
may be folded for stowage in a container, or the like, in such a
way that the structure, when released from the container, is
deployed to its predetermined configuration by the elastic strain
energy stored in the folded beams of the structure. Deployment of
the dish structure from its folded configuration may be aided by
auxiliary deployment means, such as leaf springs secured to the
inner ends of the beams, an inflatable ring secured about the rim
of the dish, guy wires extending between the rim and a telescopic
actuator at the center of the dish, and/or a separable thin film
cover defining with the dish an inflatable chamber.
Inventors: |
Williamson; Clyde E. (Los
Angeles, CA), Bochory; Michael E. (Los Angeles, CA) |
Assignee: |
TRW Inc. (Redondo Beach,
CA)
|
Family
ID: |
25054531 |
Appl.
No.: |
04/759,136 |
Filed: |
September 11, 1968 |
Current U.S.
Class: |
343/840; 343/915;
343/872 |
Current CPC
Class: |
H01Q
15/163 (20130101) |
Current International
Class: |
H01Q
15/14 (20060101); H01Q 15/16 (20060101); H01q
019/12 (); H01q 015/20 () |
Field of
Search: |
;343/840,912,915,872 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lieberman; Eli
Claims
What we claim as new in support of Letters Patent is:
1. A lightweight collapsible dish structure adapted to be folded
for storage and deployed for use, comprising:
a generally dish-shaped member constructed of a plastic film such
as Mylar or Kapton which is preformed to said normal dish
shape;
a number of individual elastic beams of tubular cross section
extending radially of and secured to said dish member and
constructed of a sheet-thin plastic film such as Mylar or
Kapton;
said beams being preformed to normally assume a configuration
wherein said dish member conforms to its normal dish shape;
said dish structure being adapted to be gathered and folded to a
compact stowage configuration wherein elastic strain energy is
stored within said beams for effecting deployment of said dish
structure when released;
an inflatable ring extending about and secured to the rim of said
dish structure; and
said ring being adapted to be deflated when said dish structure is
folded to its stowage configuration and to be inflated during
deployment of said dish structure for aiding such deployment,
stretching said dish structure radially and reinforcing said dish
structure against beam bending.
2. A lightweight collapsible dish structure adapted to be folded
for storage and deployed for use, comprising:
a generally dish-shaped member constructed of a plastic film such
as Mylar or Kapton which is preformed to said normal dish
shape;
a number of individual elastic beams of tubular cross section
extending radially of and secured to said dish member and
constructed of a sheet-thin plastic film such as Mylar or
Kapton;
said beams being preformed to normally assume a configuration
wherein said dish member conforms to its normal dish shape;
said dish structure being adapted to be gathered and folded to a
compact stowage configuration wherein elastic strain energy is
stored within said beams for effecting deployment of said dish
structure when released;
a rigid hub secured to the center of said dish structure; and
leaf springs secured to said hub and the inner ends of said beams
for aiding deployment of said dish structure.
3. A dish structure according to claim 2 wherein:
said leaf springs extend radially out from said hub into the inner
ends of said beams.
4. A lightweight collapsible dish structure adapted to be folded
for storage and deployed for use, comprising:
a generally dish-shaped member constructed of a plastic film such
as Mylar or Kapton which is preformed to said normal dish
shape;
a number of individual elastic beams of tubular cross section
extending radially of and secured to said dish member and
constructed of a sheet-thin plastic film such as Mylar or
Kapton;
said beams being preformed to normally assume a configuration
wherein said dish member conforms to its normal dish shape;
said dish structure being adapted to be gathered and folded to a
compact stowage configuration wherein elastic strain energy is
stored within said beams for effecting deployment of said dish
structure when released;
a front plastic film extending across the front side of and secured
to the rim of said dish structure; and
said front film and dish structure defining therebetween an
intervening hermetic chamber adapted to be pressurized for aiding
deployment of said dish structure.
5. A dish structure according to claim 4 including:
means for separating said front film said dish structure.
6. A dish structure according to claim 5 wherein:
said separating means comprises a hot wire secured to and extending
parametrically about said front film adjacent the rim of said dish
structure and adapted to be heated by an electrical current for
severing said front film said dish structure.
7. A lightweight collapsible dish structure adapted to be folded
for storage and deployed for use, comprising:
a generally dish-shaped member constructed of a plastic film such
as Mylar or Kapton which is preformed to said normal dish
shape;
a number of individual elastic beams of tubular cross section
extending radially of and secured to said dish member and
constructed of a sheet-thin plastic film such as Mylar or
Kapton;
said beams being preformed to normally assume a configuration
wherein said dish member conforms to its normal dish shape;
said dish structure being adapted to be gathered and folded to a
compact stowage configuration wherein elastic strain energy is
stored within said beams for effecting deployment of said dish
structure when released;
a rigid hub secured to the center of said dish structure;
a bag secured to said hub for containing said dish structure in its
folded configuration, said bag having a mouth remote from said hub
through which said dish structure is adapted to deploy; and
means for releasably closing said mouth.
8. A lightweight collapsible parabolic reflector for a
radiofrequency antenna adapted to be folded for stowage and
deployed for use comprising:
a parabolic reflector dish constructed of a lightweight sheet-thin
film having a front reflecting surface;
a number of individual elastic beams of tubular cross section
extending radially of and secured to the back side of said
parabolic dish and constructed of a sheet-thin plastic film such as
Mylar or Kapton;
said dish and beams being preformed to normally assume an
unstressed configuration wherein said reflector conforms to its
normal parabolic configuration;
said reflector being adapted to be gathered and folded to a compact
stowage configuration wherein elastic strain energy is stored
within said beams for effecting deployment of said reflector to its
normal parabolic configuration when released;
a rigid mounting hub secured to the center of said dish;
a telescoping actuator mounted on the front end of said actuator;
and
said actuator being adapted to be retracted to a position wherein
said element is situated adjacent said hub to facilitate folding of
said dish to its stowage configuration, and said actuator being
adapted to be extended to a position wherein said element is
situated adjacent the focal point of said dish when said dish
conforms to its normal parabolic configuration.
9. A parabolic reflector according to claim 8 including:
guy wires extending between the rim of said parabolic dish and the
front end of said telescoping actuator.
10. A lightweight collapsible parabolic reflector adapted to be
folded for stowage and deployed for use comprising:
a parabolic dish constructed of a lightweight sheet-thin film
having a front reflecting surface;
a number of individual elastic beams of tubular cross section
extending radially of and secured to the back side of said
parabolic dish and constructed of a sheet-thin plastic film such as
Mylar or Kapton;
said dish and beams being preformed to normally assume an
unstressed configuration wherein said reflector conforms to its
normal parabolic configuration;
said reflector being adapted to be gathered and folded to a compact
stowage configuration wherein elastic strain energy is stored
within said beams for effecting deployment of said reflector to its
normal parabolic configuration when released; and
an inflatable ring extending about and secured to the rim of said
parabolic dish.
11. A lightweight collapsible parabolic reflector adapted to be
folded for stowage and deployed for use, comprising:
a parabolic dish constructed of a lightweight sheet-thin film
having a front reflecting surface;
a number of individual elastic beams of tubular cross section
extending radially of and secured to the back side of said
parabolic dish and constructed of a sheet-thin plastic film such as
Mylar or Kapton;
said dish and beams being preformed to normally assume an
unstressed configuration wherein said reflector conforms to its
normal parabolic configuration;
said reflector being adapted to be gathered and folded to a compact
stowage configuration wherein elastic strain energy is stored
within said beams for effecting deployment of said reflector to its
normal parabolic configuration when released;
a rigid hub secured to the center of said dish; and
leaf springs secured to said hub and extending outwardly from said
hub into the inner ends of said beams.
12. A lightweight collapsible parabolic reflector adapted to be
folded for stowage and deployed for use, comprising:
a parabolic dish constructed of a lightweight sheet-thin film
having a front reflecting surface;
a number of individual elastic beams of tubular cross section
extending radially of and secured to the back side of said
parabolic dish and constructed of a sheet-thin plastic film such as
Mylar or Kapton;
said dish and beams being preformed to normally assume an
unstressed configuration wherein said reflector conforms to its
normal parabolic configuration;
said reflector being adapted to be gathered and folded to a compact
stowage configuration wherein elastic strain energy is stored
within said beams for effecting deployment of said reflector to its
normal parabolic configuration when released;
a front film extending across the front side of and secured to the
rim of said parabolic dish; and
said front film and parabolic dish defining an intervening hermetic
chamber adapted to be pressurized during deployment of said
dish.
13. A lightweight collapsible parabolic reflector adapted to be
folded for stowage and deployed for use, comprising:
a parabolic dish constructed of a lightweight sheet-thin film
having a front reflecting surface;
a number of individual elastic beams of tubular cross section
extending radially of and secured to the back side of said
parabolic dish and constructed of a sheet-thin plastic film such as
Mylar or Kapton;
said dish and beams being preformed to normally assume an
unstressed configuration wherein said reflector conforms to its
normal parabolic configuration;
said reflector being adapted to be gathered and folded to a compact
stowage configuration wherein elastic strain energy is stored
within said beams for effecting deployment of said reflector to its
normal parabolic configuration when released;
a rigid hub secured to the center of said dish;
a bag secured to said hub at the rear side of said dish for
containing said parabolic reflector in its folded configuration,
said bag having a mouth remote from said hub through which said
parabolic reflector is adapted to deploy; and
means for closing said mouth.
Description
REFERENCE TO RELATED APPLICATIONS
Reference is made herein to copending application Ser. No. 757,267
filed Sept. 4, 1968 under Docket -4060, and entitled "Light-Weight
Elastically Deformable Plastic Article of Manufacture and Method of
Forming Same."
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to lightweight collapsible
structures and more particularly to a novel lightweight, thin film
dish-shaped structure which may be folded to a compact stowage
configuration in such a way that the structure, when released, is
deployed to its normal dish shape by the elastic strain energy
stored within folded reinforcing beams of the structure. The
invention relates also to a parabolic reflector embodying the dish
structure.
2. Prior Art
Lightweight collapsible dish structures of the kind to which this
invention pertains may be used for various purposes. The dish
structure which constitutes the subject matter of the present
invention is intended primarily for use as a reflector for a
parabolic antenna and will be described in connection with such
use. However, the present dish structure may be utilized for other
applications so that the disclosed antenna application will be
understood to be purely illustrative and not limiting in
nature.
Parabolic antennas are well known in the art and are characterized
by the advantage of directional transmitting and receiving
capability. A typical parabolic antenna is equipped with a
parabolic dish or reflector constructed of a material having a high
degree of reflectivity to the radiofrequency energy to be
transmitted and/or received, and an antenna feed mechanism situated
on the antenna axis adjacent the focal point of the reflector.
Because of their directional transmitting and receiving capability,
parabolic antennas are commonly employed on space vehicles for
receiving radio signals from control stations on the earth and/or
transmitting radio signals back to monitoring stations on the
earth. However, the design of parabolic antennas for space vehicles
poses a problem for the reason that the antenna reflector is often
so large as to require the reflector to be collapsible for stowage
within the spacecraft body during the launch phase. When final
orbit is achieved, the reflector is deployed to its normal
parabolic configuration.
A variety of collapsible parabolic reflectors have been devised for
this purpose. These existing parabolic reflectors are generally
characterized, respectively, by rigid petals, inflatable
rigidizable shells, spin stabilized membranes, and rib-stiffened
membranes. While the existing reflectors are satisfactory to some
degree, they have several inherent disadvantages which detract from
their usefulness, particularly for space applications. Among the
foremost of these disadvantages are excessive weight, excessive
stowage volume requirements, excessive cost and complexity, the
necessity of using mechanical latching means for retaining the
reflectors in their collapsed condition and active or powered
deployment mechanisms for deploying the reflectors, and a tendency
to malfunction.
SUMMARY OF THE INVENTION
According to one of its narrower aspects, the present invention
provides an improved parabolic reflector which avoids the above
noted and other disadvantages of the existing reflectors of this
type. In general terms, the present parabolic reflector is
characterized by a lightweight parabolic reflector dish constructed
of a thin radiofrequency reflective film reinforced with slender
elastic ribs or beams. These beams are prestressed or preformed to
cause the reflector dish to assume a normally generally parabolic
dish shape. While various thin film materials may be used for the
reflector dish, the latter preferably comprises an aluminized
polymeric film selected from the class including Mylar and Kapton.
The reflector beams are preferably tubular in cross section and
constructed of the same thin film material as the reflector dish.
If desired the reflector dish and beams may have a laminated
construction including two outer thin film layers bonded to
opposite sides of an intervening reinforcing layer, such as
metallic screen. Mounted on the axis of the parabolic reflector,
adjacent at its focal point, is an antenna feed mechanism.
The thin film construction of the present parabolic reflector
provides the latter with several unique and highly important
advantages. By way of example, two primary advantages of the
reflector from the standpoint of space use reside in the fact that
the reflector is extremely light in weight and may be folded to a
very compact configuration for stowage within a minimum stowage
volume, as within a spacecraft body during launch. In this regard,
it will become evident from the ensuing description that the
reflector may be folded in various ways but is preferably folded in
generally serpentine fashion, in a manner similar to a parachute,
for packaging within a bag or other stowage container which may be
opened on command to release the reflector for deployment to its
normal parabolic configuration. Folding of the reflector for
stowage creates strain energy within the elastic beams of the
reflector which is utilized to unfold or deploy the reflector when
the container is opened. To this end, the reflector dish and beams
are prestressed or preformed to assume a normally generally
parabolic curvature when deployed. Additional advantages of the
present invention, therefore, reside in the fact in that complex
mechanical latching means to retain the parabolic reflector in its
folded configuration and complex mechanical deployment mechanisms
for deploying the reflector to its parabolic configuration are not
required.
According to a further feature of the invention, the present
parabolic reflector may be equipped with auxiliary means to aid its
deployment to the proper parabolic shape, and/or to adjust the
parabolic curvature of the reflector. The disclosed embodiments of
the invention, for example, are equipped with an inflatable ring
about the rim of the reflector dish which acts to stretch the
reflector radially and resist beam bending of the reflector. This
ring cooperates with the reflector beams to eliminate wrinkles in
the film of the reflector dish, thereby to assure a reflector with
an accurate parabolic reflective surface. The ring also provides
the reflector with sufficient structural rigidity in its deployed
configuration to resist distortion due to thermal radiation, solar
pressure, material degradation, drag and other factors. The
reflector may be equipped with guy wires which extend radially
between the rim and center of the reflector dish to aid the above
function of the inflatable ring. Means may be provided for
adjustably tensioning these wires and shifting the antenna feed
mechanism along the reflector axis to adjust the parabolic
curvature of the reflector and/or locate the feed mechanism in
optimum transmitting and receiving relation to the reflector.
One illustrative embodiment of the invention is equipped with a
second thin film which is situated in front of and parametrically
sealed to the rim of the parabolic reflector. This front film and
the reflector define therebetween a hermetic chamber which may be
pressurized to aid deployment of the reflector to its proper
parabolic shape. The front film may be transparent to the
radiofrequency energy to be transmitted and received by the antenna
so as to permit the film to remain in position in front of the
antenna reflector during the operation of the antenna.
Alternatively, the front film may be severed from the antenna
reflector after deployment.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a parabolic antenna embodying a
parabolic reflector according to the invention;
FIG. 2 is an enlarged fragmentary perspective view of the rear side
of the reflector;
FIG. 3 is an enlarged fragmentary perspective view of one of the
reflector beams;
FIG. 4 is an enlarged section taken on line 4-4 in FIG. 2;
FIG. 4a is an enlarged section of a reinforcing ring embodied in
the antenna;
FIGS. 5--8 illustrate one method of folding the reflector for
stowage;
FIG. 9 is a perspective view of a modified parabolic reflector;
and
FIG. 10 is an enlarged perspective view of the reflector in FIG. 9
with a front cover film thereof severed from the reflector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIGS. 1--8 of these drawings, there is illustrated a
lightweight collapsible dish structure 10 according to the
invention. In this instance, the dish structure forms the parabolic
reflector of a parabolic antenna 12. The reflector has a parabolic
dish 14, proper, and a number of preformed reinforcing ribs or
beams 16 secured to the back side of the dish. In accordance with
an important feature of the invention, dish 14 is fashioned from a
lightweight sheet-thin film, and the ribs or beams 16 are provided
with a slender, elastic construction, such that the parabolic
reflector may be packaged for stowage within a minimum stowage
volume by folding the reflector in the manner illustrated in the
drawings. The folded parabolic reflector may then be contained
within a storage container 18. This folding action creates elastic
strain energy within the reflector beams 16. When the reflector is
released from the container, the strain energy in the beams causes
return of the latter and the parabolic dish 14 to their original
parabolic configuration.
The parabolic dish 14 and its reinforcing beams 16 may be
constructed of various materials. According to the preferred
practice of the invention, however, these parts are fashioned from
a polymeric plastic film material, selected from the class
including Mylar and Kapton. In the particular embodiment of the
invention which has been selected for illustration, for example,
the parabolic reflector 10 is a radiofrequency reflector, wherein
the reflector dish 14 is constructed of a metallic coated plastic
film, such as aluminized Mylar or Kapton. The dish may have a
single layer or a multiple layer laminated construction depending
upon the required structural rigidity of the dish. The reflector
beams 16 have a slender thin-walled tubular configuration and are
fabricated from sheet-thin film material which is preferably the
same plastic film material as that of the reflector dish 14. The
beams extend radially of the reflector dish between its center and
rim and are bonded or otherwise secured to the back side of the
dish. The dish and beams are prestressed or preformed to normally
assume a parabolic curvature.
It will be immediately evident to those versed in the art that the
parabolic dish 14 and beams 16 may be fabricated in various ways.
The illustrated dish, for example, is composed of a number of
gore-shaped sections 20 which are individually preshaped to a
parabolic curvature by stretch-forming or heat-forming the sections
over a suitable parabolically curved mold. The several parabolic
gore sections are then joined edge-to-edge by aluminized pressure
sensitive Mylar tape or other suitable means. The reflector beams
16 are preferably heat formed in the manner disclosed in the
aforementioned copending application, Ser. No. 757,267. Since the
beam forming method is fully disclosed in the copending
application, it is unnecessary to treat the method in detail in
this disclosure. Suffice it to say that the beams are fabricated,
either from strips of plastic film material which are
ultrasonically welded or otherwise bonded along their longitudinal
edges to form thin-walled sleeves or tubes, or from sleeves or
tubes of plastic film material whose walls are squeezed flat and
bonded face-to-face along diametrically opposite sides of the
tubes. In either case, the completed plastic tubes have
diametrically opposed, longitudinally extending flanges 22. These
tubes are then heat-formed to normally assume a parabolic curvature
by insertion of a parabolically curved rod or mandrel through each
tube and exposure of the latter to a suitable forming temperature.
The finished parabolically curved beams are then ultrasonically
welded or otherwise bonded to the back side of the parabolic dish
14 in such a way that the beam flanges 22 parallel the dish as
shown.
At the center of the parabolic dish 14 is an antenna mounting hub
24. This hub has a generally cylindrical housing 26 which projects
rearwardly from the dish on its central axis. Integrally formed on
the front end of the housing 26 is a flange 28. Flange 28 is
parametrically secured to the parabolic dish 14 about a central
opening 30 in the dish.
Coaxially mounted on and extending forwardly from the hub 24 is a
telescoping antenna feed mechanism or horn 32. This feed mechanism
includes a telescoping fluid pressure actuator 34 having a cylinder
36 centered on the axis of the reflector dish 14 and rigidly
secured at its rear end to the hub 24. Guy wires 38 may be secured
between the hub flange 28 and the actuator cylinder 36 to brace the
cylinder in the lateral direction. Movable in the cylinder is a
telescoping plunger 40 which mounts the receiving and/or radiating
element 42 of the antenna. When the antenna is in its normal
operating configuration, this element is located at the focal point
of the parabolic dish 14. Accordingly, radiofrequency waves
incident on the front reflective surface of the dish are reflected
to the element 42, and radiofrequency waves emanating from the
element are reflected forwardly from the dish parallel to its axis,
depending upon whether the antenna is operating in a receiving or
transmitting mode.
As noted earlier, the parabolic dish structure or reflector 10 is
adapted to be folded for stowage in the manner illustrated in the
drawings and to be later released for deployment by the elastic
strain energy stored within the folded reflector beams 16. The
particular embodiment of the invention under discussion includes
three additional deployment means 46, 48, and 50 for aiding proper
deployment of the reflector. The deployment means 46 comprises leaf
springs 52 which are fixed at one end to the antenna hub flange 28.
The opposite, free ends of these leaf springs extend into the
adjacent inner ends of the reflector beams 16 and mount resilient
pads 54 for engaging the inner walls of the beams. When the
parabolic reflector 10 is folded for stowage, the leaf springs 52
are bent or bowed in the manner illustrated so that elastic strain
energy is stored in the springs. When the reflector is released for
deployment, this elastic strain energy returns the springs to their
original or normal unstressed conditions. It will be understood,
therefore, that the springs aid deployment of the parabolic
reflector 10 from its collapsed or stowed configuration to its
deployed parabolic configuration.
The deployment means 48 comprises an inflatable torus or ring 56
which is secured to the parabolic dish 14 about its rim. When the
parabolic reflector 10 is folded for stowage, the ring is deflated.
During deployment of the reflector, the ring is inflated in any
convenient way. In the drawings, for example, the ring is inflated
through a tube 58 which extends from the ring, radially inward
along the back side of the parabolic dish 14, to a pressurized
fluid source (not shown). When inflated, the ring tends to stretch
the parabolic reflector 10 radially in such a way as to cause the
reflector to assume its normal parabolic shape. The inflated ring
also reinforces the reflector against beam bending. The torus ring
56 may be a simple plastic tube or a laminate. In the latter case,
there is interposed between two plastic layers 56a (FIG. 4a) a
screen metal mesh 56b. Upon inflation of the torus ring 56, the
metal mesh is prestressed to assume a torus shape. In the event the
inflatable ring 56, deflates itself, or the plastic material starts
degrading in the space environment, the metal mesh would have
enough structural rigidity to restrain the deflection of the beams
due to solar pressure. Upon degradation of the plastic surface of
the ring, the guy wires will remain attached to the metal mesh, as
will the ends of the beams to which the ring is attached.
The remaining deployment means 50 comprises a number of slender guy
wires 60 of fiberglass or other suitable material which extend
between the rim of the parabolic dish 14 and the front end of the
actuator plunger 40. These wires are arranged in a uniformly spaced
array, as shown, and aid in deploying the parabolic reflector to
and retaining the reflector in its parabolic configuration. The
parabolic curvature of the reflector may be adjusted within limits
by extending and retracting the plunger 40.
The additional deployment means 46, 48, 50 may not be required in
all applications of the invention. Accordingly, it should be
understood that any one or more of these deployment means may be
omitted.
It will be observed in FIGS. 5--8 that the parabolic reflector 10
may be stowed by first gathering the reflector inwardly toward its
axis in a manner similar to that involved in closing an umbrella.
The gathered reflector is then folded laterally of its beams 16 in
serpentine fashion, preferably with the aid of packaging rolls 62
placed between the adjacent folds, to a final stowage configuration
within the stowage container 18. In this instance, the container is
a pleated bag secured about the edge of the antenna hub flange 28.
After the reflector is properly folded, the bag is gathered about
the reflector and the mouth of the bag is closed by a suitable
release mechanism 64. In the case of the parabolic antenna for a
space vehicle, this release mechanism may be designed for release
on command by radio signals from a ground station. When released,
the bag opens to release, in turn, the folded parabolic reflector
10 which then deploys to its normal parabolic configuration under
the action of the elastic strain energy in the beams 16. It should
be understood that the illustrated manner of folding the reflector
for stowage is purely illustrative and that the reflector may be
stowed by folding it in other ways.
As described earlier, the antenna feed mechanism 32 comprises a
telescoping actuator 34. This actuator is retracted to its
contracted condition when the parabolic reflector 10 is folded for
stowage. The actuator is extended to its operating position after
deployment of the reflector to its normal parabolic configuration.
The ring 56 on the parabolic dish 14 is inflated during deployment
as explained earlier, to aid proper deployment of the reflector to
its parabolic shape and reinforce the reflector against beam
bending.
Reference is now made to the drawing FIGS. 9 and 10 which
illustrate a modified parabolic antenna 100 according to the
invention. The modified antenna is identical to the antenna just
described except that a cover film 102 is disposed in front of and
sealed about its edge to the rim of the parabolic reflector 10.
This front film may be preformed to normally assume a parabolic
curvature and is folded with the reflector for stowage in the
manner explained earlier. In this case, means 104 are provided for
pressurizing or inflating, during deployment, the hermetic chamber
106 defined between the parabolic reflector 10 and the front film
102. Inflation of the chamber 106 aids deployment of the reflector
to its proper parabolic configuration. The front film 102 may be
constructed of a material, such as uncoated Mylar or Kapton, which
is transparent to radiofrequency waves, in which case the front
film may remain in position on the reflector 10 during operation of
the antenna 100. Alternatively, the front film may be separated
from the reflector after deployment of the latter to its parabolic
configuration. In the particular embodiment of the invention
illustrated, for example, a hot wire 108 is bonded to the front
cover film 102 about its edge and immediately adjacent to the rim
of the reflector. After deployment, this wire is electrically
heated with sufficient current to sever the film from the
reflector. The modified parabolic antenna 100 is otherwise
identical to and is folded, deployed, and operated in the same
manner as the first described parabolic antenna of the
invention.
At this point, it will be evident to those versed in the art that
while the invention is disclosed in connection with a parabolic
antenna, the parabolic dish structure of the invention may be used
for other purposes. For example, the dish structure could
conceivably be employed as an optical reflector, a cover or
shelter, or other lightweight collapsible structure.
Accordingly, while the invention has been disclosed in connection
with certain physical embodiments thereof, various modifications of
the invention are possible within the spirit and scope of the
following claims.
* * * * *