Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
82~
Background of the Invention
The present invention is directed toward the art of
support structures for parabolic reflectors, and more
particularly concerns a support structure for a large
parabolic reflector which is intended primarily for use as
a solar reflector and which is comprised of a large number
of small reflecting sections arranged into a paraboloid.
Large dimension parabolic reflectors, on the order
of twenty feet in diameter and larger, have historically
been proposed for use in a variety of applications, in-
cluding use in a solar collection system. However, large
dimension parabolic reflectors have always been difficult
and expensive to manufacture and hence are presently
considered impractical, except perhaps in special purpose
applications, such as large telescopes.
In addition to the cost involved in producing such a
parabolic reflector per se, the support structure for
such reflectors also is complicated and expensive. Add-
itionally, the support structure must be designed for the
particular reflector application, and a support structure
suitable for one application would not necessarily be suit-
able for any other reflector applications.
For instance, those support structures which have
been developed for parabolic reflector telescopes are not
suitable for solar collector applications, wherein the
reflective surface must be as open as possible to the sun,
and wherein the support structure must be capable of with-
standing harsh weather environments, including high winds
--2--
` ~";
.
4~:)823
and hail, without damage to either the support structure
or the reflector.
Other large-dimension curved structures besides para-
bolas have been constructed using a plurality of relatively
small size plane sections of various forms. An example
of using relatively small sections to construct a spherical
structure is shown in U. S. Patent No. 2,978,704, titled:
Random Structural Devices. As suggested herein, large
dimension parabolic reflectors can also be constructed with
small-size sections, at considerable cost savings over a
single surface reflector. ^
Although such a construction technique may sign-
ificantly reduce the cost of producing a parabolic reflect-
or per se, the problems of adequately supporting and protecting
that structure, especially under extreme weather conditions,
remain. To the best of the inventor's knowledge, there is
very little information available concerning support
structures for large-dimension parabolic reflectors intend-
ed for outdoor use, especially where the reflector comprises
a plurality of relatively small sections and is intended
for use as a solar collector.
Necessarily, such a support structure must have the
proper strength in order to support the plurality of re-
flecting sections without breakage during normal operation,
and must be capable of protecting the reflecting sections
in weather extremes. It must further interfere only
minimially, if at all, with the amount of sun reaching
the reflecting surfaces of the individual sections.
114~823
Additionally, such a support structure should be
relatively inexpensive, so that the combined support
structure-parabolic reflector may be economically prac-
tical as a solar collector. Further, the support structure
should be relatively simple and inexpensive to install on
site, and must be capable of accurately tracking the sun
in its movement across tne sky.
Accordingly, it is a general object of the present
invention to provide a support structure for a parabolic
reflector which overcomes one or more of the disadvantages
of the prior art noted above.
It is another object of the present invention to
provide such an apparatus which is relatively simple to
install on site.
It is a further object of the present invention to
provide such an apparatus which is capable of withstanding
the stresses of weather extremes.
It is another object of the present invention to
provide such an apparatus which is capable of supporting
a parabolic reflector without counterweights.
It is an additional object of the present invention to
provide such an apparatus which is capable of supporting
a large-dimension parabolic reflector comprised of a
plurality of relatively small-size reflecting sections.
It is yet another object of the present invention to
provide such an apparatus which is capable of supporting
a multiple-section parabolic reflector over an extended
period of time without damaging the individual sections.
It is a still further object of the present invention
to provide such an apparatus which permits the individual
ll~V8Z3
sections comprising the parabolic reflector to be sep-
arately focused.
It is another object of the present invention to
provide such an apparatus which is capable of tracking
the sun with the parabolic reflector.
Summary 3f the Invention
Accordingly, there is provided a special-purpose
support structure for supporting large-dimension reflectors
which exhibit a curved surface, such as a parabolic reflect-
or. The support structure includes a first rigid supportmatrix which comprises a plurality of strut-like members
which are joined together at matrix joints in such a manner
that the first rigid support matrix approximates the curved
shape of the large-dimension reflector which it is to
support. A plurality of standoff elements are provi~ed in
the support structure, with the standoff elements being
connected to the matrix joints and extending away there-
from. Additionally, there are securing member mounted on each
of the standoff elements for securing the curved reflector
in position away from the first rigid support matrix.
Description of the Drawings
A more thorough understanding of the invention may
be obtained by a study of the following detailed des-
cription taken in connection with the accompanying drawings
in which:
)823
Figure 1 is a diagram showing the principal components
of a solar collection system, including the support apparatus
of the present invention.
Figure 2 is a perspective view of one embodiment of
the present invention, with a single support structure.
Figure 3 is an exploded view of one portion of the
embodiment of Figure 2.
Figure 4 is a partial perspective view of another
embodiment of the present invention, with a double support
structure.
Figure 5 is an exploded view of a portion of the
embodiment of Figure 4.
Figure 6 is a perspective view of a standoff element,
a connecting hub, and a securing member which connect the
two support structures and the reflecting sections of the
embodiment of Figure 4.
Figure 7 is a perspective view showing the axis structure
between the support structure for the parabolic reflector
and apparatus for tracking the sun.
Figure 8 is a perspective view showing the structure
for securing the individual reflecting sections in place
to form a parabolic reflector.
Description of the Preferred Embodiment
Referring now to Figure 1, the reflector support
structure of the present invention is shown in the conte~t
of a complete solar energy collection system. A parabolic
reflector is shown generally at 10, and is comprised of a
--6--
1:14~ Z3
plurality of triangular sections 11-11 of conventional
mirrored glass. Triangular sections 11-11 may be plane or
slightly curved or dished. Triangular sections 11-11 are
arranged and positioned such that their respective apex
points lie on the surface of a true parabola. Reflector
10 thus is substantially parabolic.
In the embodiment shown in Figure 1, a first re-
flector support matrix, also of generally parabolic con-
figuration, shown generally at 12, is provided inside para-
bolic reflector 10. Reflector support matrix 12 comprisesa plurality of elongated rod-like elements 13-13 which are
joined together at their ends, at joints 14-14, to form a
plurality of intersecting open triangles in a generally
parabolic arrangement. The joints 14-14, in the con-
lS figuration shown, lie substantially on the surface of atrue imaginary parabola.
Extending outwardly from each joint 14, and fixedly
connected thereto, is an elongated standoff element 15 which
has located therealong positioning elements (not shown in
Figure 1) which may be moved longitudinally along stand-
off elements 15, and which hold triangular sections 11-
11 at their apexes in a parabolic arrangement 10.
In Figure 1, four triangular sections 11-11 are shown
for each triangular portionof support matrix. This is
shown most clearly in Figure 3. In an even more simple
embodiment, the triangular sections 11-11 could be the same
size as the triangular support matrix portions. A more
complicated embodiment, using two support matrixes, wherein
16 triangular sections 11-11 are used for each triangular
portion of the first support matrix is shown in Figures
--7--
-
1~4~823
4 and 5.
A boiler 16 of conventional design and of a size
which is commensurate with parabolic reflector 10, is
located substantially at the focal point of parabolic
reflector 10 and parabolic support matrix 12. An elong-
ated support element 18 connects boiler 16 and the back
center of the parabolic support matrix 12, and supports boiler
16 at the focal point thereof. The boiler 16 may take
various configurations, and may be a mercury heat exchanger.
An example of a boiler which may be useful is described in
U. S. Patent No. 4,019,868 issued to Sebacher, et al, on
April 26, 1977 and titled: Solar Hydrogen Generator.
Encircling parabolic reflector 10 and parabolic
support matrix 12 is a terrain support apparatus which .
includes first and second support rings 20 and 22. The
first support ring 20 is stationary and is supported off
the ground at a selected angular orientation to the terrain
by a plurality of upright posts 24-24. The second support
ring 22, which is of substantially the same configuration
and size as the first support ring 20, is positioned on
top of the first support ring and rotates relative to
the first support ring by means of rollers or similar
conventional devices 26 through a motor 31.
Parabolic reflector 10 and parabolic support matrix
12 are secured to an axis structure 27 which is in turn
rotatably connected to second support ring 22 through
conventional means, such as a motor-driven gear arrange-
ment 29. This arrangement permits parabolic reflector
10 to be rotated within support rings 20 and 22.
--8--
140823
In operation, second support ring 22 is rotated relative
to first support ring 20 at specified time intervals to
maintain the correct reflector azimuth for the parabolic
reflector 10, while parabolic reflector 10 itself is period-
ically rotated, through axis structure 27, to maintain acorrect reflector altitude. Hence, parabolic reflector 10
follows the path of the sun as it moves from horizon to
horizon.
The sun's rays, when they strike the inside reflecting
surface of parabolic reflector 10, are focused by the ind-
ividual triangular sections 11-11 to the boiler 16. The
boiling medium in boiler 16 is raised to a temperature
between 600F and 1000F when plane triangular sections are
used, and between 3000F and 6000F, when curved triangular
sections are used, resulting in superheated steam which can
then be utilized to drive conventional steam generators or
similar means.
Figure 2 shows in more detail the parabolic reflector
lO and parabolic support matrix 12 shown in Figure 1.
Parabolic support matrix 12 comprises a plurality of elongated
struts or rods 13 joined together at their ends, at joints
14, in such an arrangement as to form the parabolic support
matrix shown in Figure 2.
The arrangement of struts 13-13 form a plurality of
open triangles, with each strut 13, except for those in the
top row, Eorming one side of 2 adjacent triangles. The
specific arrangement of the triangles and their relative
sizes can be obtained in a number of ways, but in the instant
case was achieved by projecting the lower half of a sub-
divided isohedron onto a true parabolic surface.
_ g_
,
114~823
Each of the joints l4-14 lies substantially on the
surface of a true parabola, while struts 13-13 extend in a
straight line between joints 14-14. The upper row of struts
13-13 all lie in the same plane and form rim 30 of the support
matrix, as shown in Figure 2, while the remainder of support
matrix 12 extends downward therefrom in a parabolic con-
figuration. The individual struts 13-13 are of varying length,
depending upon their location in the support matrix.
In the embodiment shown, struts 13-13 are lengths of
1 1/2" galvanized pipe, since galvanized pipe offers relatively
high strength at a low cost. Other materials, however, such
as aluminum tubing, can be effectively used.
Stabilizing rim 30 are a plurality of guidewires 34
(shown in Figure 2 but not Figure 1) which run cross-ways of
rim 30 from each joint 14 on the rim to an opposing joint
on the opposite side of the rim. Hence, each joint 14 or
rim 30 is connected by stiff wire, or small-diameter tubing,
to an opposing joint on the rim. Guide wires 34 provide ;
necessary support structure rigidity.
The structure of the joints 14-14 is shown more
clearly in Figure 6. The construction of each joint 14 will
vary depending upon its location, and whether there is
more than one support matrix provided. Each joint will
include a full hub or collar element which is shown generally
at 35, a triangular section securing element, shown gen-
erally at 42, and a standoff element 15. When two support
matrixes are used a modified hub 36 is included at
each joint. A full hub 35 is used wherever the struts
forming either the first or second matrixes are joined.
--10--
. . .
nsz3
A modified hub 36 is used for attaching a standoff element
15 to a strut 13 intermediate of its ends.
Joint 14 shown in Figure 6 is the joint structure
shown as 38 in Figure 4. It includes a tubular T shaped
modified hub 36, having a cross member 36a which is secured
to a single strut 13 in the first support structure, and a
base member 36b, into which one end of standoff element 15
is inserted. The modified hub 36 is positioned intermediate
of the strut 13 and is used both on the first and second
support structures to permit subdivision of each structural
support portion.
Midway along standoff element 15 in Figure 6 is a
full hub 35 which receives the ends of various numbers of
struts 13, depending upon location, in a second support
matrix. Hub 35 includes a central ring 35a, through the
center of which standoff element 15 extends, and a plurality
of fins 35b-35b which extend radially outward from central
ring 35a and which receive the ends of struts 13.
Standoff element 15 in Figure 6 is a rod-like strut
~hich extends perpendicularly from modified hub 36 and
through full hub 35 so that it hence extends perpendicularly
from a plane which is tangent to an imaginary parabolic
surface connecting each joint of the parabolic support matrix.
The length of standoff element 15 depends upon the
number of parabolic support matrixes used. In the embodiment
of Figure 2, for instance, only one support matrix is shown,
and the length of standoff element 15 is approximately 2
inches. In the embodiment of Figure 4, standoff element 15
might be approximately 4 inches.
--11--
40823
Located near the end of standoff element 15 is
securing element 42, which holds one apex of several
triangular reflecting sections ll-ll firmly in place. ~ -
Positioning element 42 of Figure 6 comprises two relatively
thin members 44a, 44b of a flexible but stiff material,
such as a stiff rubber or teflon, which, when moved close
together, hold the apexes of several triangular reflecting
sections 11-ll in place to form the parabolic reflector 10.
When stiff members 44 and 46 are held close enough together
by plate 46 and by nut and washer arrangement 45, several
triangular reflecting sections ll-ll may be held firmly in
position, as shown in Figures 6 and 8. Members 44a and 44b
are sufficiently flexible, however, to permit a slight
movement of reflecting sections ll-ll to take up a
certain amount of environmental stresses, particularly
changes in temperature, without breakage.
At no time will securing element 42, and hence re-
flecting sections ll-ll, come into contact with the
parabolic support matrix 12, and hence, no stress will
be placed on reflecting sections ll-ll by the parabolic
reflector structure itself.
A further ~ey structural advantage of securing
element 42 is that it may be moved a ways longitudinally
along standoff element 15, permitting individual focusing
of each reflecting sections 11-ll onto boiler 16. In
this manner, the parabolic reflector 10 may be tuned
to maximum effectiveness.
Reflecting sections ll-ll may be comprised of a
number of different materials, among them being glass and
11~ 8Z3
polished metal, such as aluminum. It has been found, how-
ever, that the conventional double-sided mirror, silvered on
the backside, is the best when both cost and reflective
quality are considered. The support structure of the
present invention permits the use of this relatively
inexpensive material.
The reflecting sections 11-11 may be plane, which
is a relatively easy and inexpensive shape to manufacture,
or they may be slightly curved. If reflecting sections
11-11 are curved, the total reflecting quality of the
complete parabolic reflector 10 will be better than with
plane reflecting sections, and the solar collector
operation will improve. The National Aeronautics and Space
Administration has developed a method of fabricating
curved silvered glass which is suitable for use with the
present nvention. It is available on microfilm under
the number NTIS-N75-328~4/8ST in engineering libraries
of several universities, under the title "Light Weight
Reflector Assembly and Method." It should be understood,
however, that the present invention is capable of function-
ing efficiently with plane reflecting sections.
In the embodiment shown in Figure 2, the support
matrix 12 is provided inside the reflector 10. This
configuration has been found to reduce the amount of
reflected sunlight to the boiler by approximately 15%, which
is acceptable in view of the cost savings produced in
construction of large parabolic reflectors by use of
the support structures disclosed herein.
. '
-
`` 11~8Z3
Referring again to Figure 1, the combination of
parakolic reflector 10 and parabolic support matrix 12 is
encircled by first and second support rings 20 and 22.
Support ring 22 rides on top of suppport ring 20, by
means of conventional rollers 26 or similar devices.
Support rings 20 and 22 are substantially circular in
configuration, and have diameters slightly greater than
the diameter of parabolic reflector 10. In the case of
a 30 foot diameter parabolic reflector, for instance, the
diameter of support rings 20 and 22 is approximately
31.82 feet.
First and second support rings 20, 22 may be con-
structed of a variety of materials, but in the embodi-
ment shown are aluminum tubing, approximately 4 inches
thick and 9 inches wide. It should be understood, how-
ever, that rings 20 and 22 may take various configurations.
They may be square or rectangular in cross-section or
they may be two iron~girders formed into circles.
Support ring 20 is supported off the terrain by
means of a plurality of posts 24, at an angle 52 from
the vertical which is equal to the latitude of the part-
icular terrain location of the collector. Hence, the
angle 52 of the support rings will vary, depending upon
the latitude of the location of the apparatus.
Hence, first support ring 20 is fixedly supported
by means of a plurality of support posts 24, while
second support ring 22 is rotatably connected to support
ring 20 by means of rollers or the like, driven by means
of motor-driven gearing 31.
-14-
823
Figure 7 shows in more detail the axis structure 27
by which the combination of parabolic reflector 10 and
parabolic support matrix 12 is rotatably connected to
support ring 22. A series of struts 60 are connected
between (1) the ends of a number of standoff elements which
extend from hubs 35, and (2) a common joint 62, which in
turn extends into a short axle and gear arrangement 64,
which controls rotation of the combination relative to
first and second support rings 20 and 22. Axis structure
27 extends through reflector 10 and support matrix 12
at approximately their combined center of gravity, and
hence, no counterweights are needed to stabilize the
reflector during rotation.
Such an arrangement permits support matrix 12 and
hence, parabolic reflector 10 as well, to follow the
path of the sun as it moves across the sky. It also
permits reflector support matrix 12 and reflector 10
to be rotated so that they face the terrain. Typically,
a fairly rigid lightweight protective covering (not
shown) may be provided over the exterior of the reflector
10 so that when the support matrix 12 and reflector 10
are rotated upside down, the protective covering is
exposed to the weather. The protective covering serves
to protect the reflector during extreme weather conditions,
in particular, hail, dust storms, and high winds.
Referring now to Figures 4 and 5, there is shown
another embodiment of the present invention which is some-
what more complicated than the embodiment of Figures 2
and 3. In the embodiment of Figures 4 and 5, an inter-
,
114~8Z3
mediate parabolic support matrix 70 is provided between a
base parabolic support matrix 72 and a parabolic reflector
74. A substantial portion of the complete structure is
shown in Figure 4.
The arrangement of this embodiment is shown most
clearly in Figure 5, wherein ihe relationshp between a
single portion of the base parabolic support matrix is
shown with its corresponding intermediate support matrix
and corresponding reflector structure. As with the embodi-
ment of Figures 2 and 3, the more complex embodiment
includes a first set of standoff elements 76 located at
each joint 78 of each triangular portion 80 of the base
parabolic support structure, and a second set of standoff
elements 82 intermediate of each pair of joints 78-78.
Hubs (not shown) such as hubs 35 in Figure 6, are located
at each joint 78 while modified hubs (not shown) , such as
hubs 36 in Figure 6, are used intermediate of joints 78.
The intermediate parabolic support matrix 70 comprises
a plurality of struts 86 which are approximately half as
long as the struts comprising base parabolic support matrix
68. Each strut 86 is connected between hubs (not shown)
which are similar to hubs 35 in Figure 6, which are
positioned on standoff elements 76 and 82, as shown in
Figure 5. This results in a four triangle section of inter-
mediate support matrix for each portion 80 of base supportmatrix. Struts 86 may be lighter in weight than those
struts comprising the base parabolic support matrix. For
example, struts having a diameter of 1/2 inch and a wall
-16-
~ )823
thickness of l/16th inch have been found to be useful for
a 30 foot diameter reflector. In addition to standoff
elements 78 and 82 which extend through the hubs which
support struts 86, further standoff elements g2 are pro-
vided, located intermediate each strut 86 and connectedthereto by a modified hub (not shown) similar to hub 36
shown in Figure 6.
At the end of standoff elements 78, 82 and 92, a
securing element (not shown) similar to element 42 in
Figure 6 is provided to hold the reflecting sections
which fit together to comprise the parabolic reflector
10 .
Because standoff elements 78, 82 and 92 all
support individual reflecting sections 94i94, there are
four reflecting sections for each intermediate support
matrix section, and hence sixteen reflecting sections for
each portion 80 of the base support matrix 72. This
arrangement is shown most clearly in Figure 5. In the
embodiment of Figure 4, which was developed by projecting
a subdivided isohedron onto a parabolic surface, there are
40 triangular shaped portions which comprise the base
parabolic support matrix. Hence, a total of 640 reflecting
sections will comprise the parabolic reflector 10.
The support structure described above is advantageous,
as it has sufficient strength to support the reflecting
sections, and to take up environmental stress, so as to
minimize possible damage to the reflecting sections. In
addition, such a structure permits the reflecting sections
, ~ '
V823
to be individually focused on to a boiler, increasing the
potential efficiency of the reflector. In the arrangement
shown above, each reflecting section reflects substantially
the same amount of light to the boiler when the
reflector is properly oriented with respect to the sun.
The above-described support structure permits,
in practical terms, the use of plane triangles to construct
a large-dimension parabolic reflector. Such a complete
structure can be used advantageously in solar collection
systems. The support structure is relatively inexpensive,
as it can be made from commercially available, relatively
inexpensive, materials and can be assembled quickly and
easily on site. It has extremely high strength, and can
protect the reflector structure against weather extremes,
particularly high winds and hail, without blocking a sub-
stantial amount of light from the reflector.
Although a preferred embodiment of the invention has
been disclosed for purposes of explanation, it should be
understood that various changes, and modifications can be
made to the embodiment shown without departing from the
spirit of the invention. It should be understood, for
instance, that although the support matrix is shown as being
interior of the reflecting sections, the same principles
could be used to provide an exterior support matrix.
Additionally, it should be understood that the particular
hub configuration shown is not critical. Various con-
figurations may be successfully used. The invention is
defined by the claims, which follow.
-18-
