FR2505022A1 - HOLLOW CONCRETE FORMWORK BEAM COMPRESSED - Google Patents

Abstract

THE INVENTION RELATES TO A CONCRETE HOLLOW FORMWORK BEAM PUT UNDER COMPRESSION. THE COMPRESSION OF A LAYER 54 OF CONCRETE FORMING ONE OF THE BEAMS OF A FORMWORK IS CARRIED OUT BY USING BOLTS 69 AND NUTS 70 SCREWED ON PLATES 65 FIXED ON THE OPEN ENDS. FIELD OF APPLICATION: MANUFACTURING OF CONCRETE SUPPORTS FOR SOLAR REFLECTORS OR RADAR ANTENNAS.

Description

The invention relates to the manufacture of reflective surfaces for

  to be used as collectors

  The invention relates to solar energy or radar antennas.

  no longer particularly the framework supporting such reflective surfaces.

  Solar collectors of the type men-

  may be in the form of paraboloids of revolution.

  often referred to as "dome", which concentrate the light rays reflected on a single point constituting a focus and moving with the dome Two-axis heliostats concentrate the light rays reflected on a fixed focus located at the top of a tower such reflective surfaces may be in the form of a trough or parabolic section trough which

  reflects the sun's rays on a linear focus.

  The dome-type heliostat and the heliostat type

  segmented mirror are rotated around vertical axes

  cal and horizontal in order to track the sun's path both in azimuth and height Gutter-type solar collectors are rotated only around a vertical axis in order to follow either the azimuth, ie the height of the sun Sets of such two-axis reflectors are used to reflect the sun's rays on a fixed point focus Single-axis reflector sets can be used to reflect the sun's rays on a fixed linear focus formed on a row of towers En

  general, the heat released by the reflected light rays

  The heated fluid can then be used in a useful manner, for example for the production of steam for the drive.

a gas turbine generator.

  Radar antennas are of the dome type, that is to say paraboloids of revolution Their reflective surfaces are made of conductive material of the electric current, for example copper, aluminum, silver, and it is not necessary that they are

  specular as is the case with solar reflectors.

  Such reflective surfaces may have

  a laminated construction comprising a reflective layer

  A type of reflective surfaces includes an exposed and outer layer of glass, a reflective inner layer of silver, and one or more support layers such as a copper layer and a layer of plastic material. In another embodiment, a thin layer of aluminum is vacuum deposited on a thin film of acrylic polymer. As mentioned above with respect to the radar antennas,

  the material forming the reflective surface is conductive.

  Such reflective surfaces are thin, their thickness generally being about 0.038 to 1.5 mm, and they require the presence of a support to retain their shape and to allow their mounting and their implementation in a way to follow the sun or any other target Such a support or such a frame is generally made of plastic or steel, or else made of any other metal construction Because of the extremely large areas to be covered by such reflective surfaces

  and the large number of reflectors required,

  construction sites are an important part of

investment in capital.

  The subject of the invention is improvements made to the rear support structure of surfaces

  reflecting solar energy and radar antennas.

  Framing or surface support

  solar energy or radar surfaces can be real-

  made of inexpensive construction material, for example of reinforced fiberglass concrete, while assuming the

  function provided in a very convenient way.

  The invention will be described in more detail in

  FIGS. 1 is a perspective view of a trough-type reflector; Figure 2 is a perspective view of a formwork for the construction of the torsion beam of the reflector of Figure 1; Figure 3 is an elevation of a formwork for producing a cross member for the reflector of Figure 1; Figure 4 is a cross section of a mold for the manufacture of the reflector of Figure 1, this view showing the reflector partially manufactured; FIG. 5 is a section similar to that

  Figure 4, taken along line 5-5 of Figure 7, shows

  the finished reflector; Fig. 6 is a perspective view of the completed reflector (except for the end plates and mounting members), showing the back support; Figure 7 is a partial plan view of the rear face of the reflector of Figure 6; Fig. 8 is a partial section along the line 8-8 of Fig. 9, showing how the torsion beam of the reflector of Fig. 6 is placed under compression; Figure 9 is a partial end view of the reflector, showing one of the end plates which places the torsion beam under compression and which also serves to mount the reflector;

  Figure 10 is a cross section through

  showing the manufacture of a dome type reflector; FIG. 11 is a section similar to that

  of Figure 10, showing a dome reflector complete with

  manufactured; Figure 12 is a rear view of the reflector of Figures 10 and 11; Figure 13 is a rear perspective view of a two-axis heliostat manufactured in accordance with the invention;

  Figure 14 is a cross section through

  showing how a segmented type reflector is made for two-axis heliostat; Fig. 15 is an elevation, partly in section, showing the application of the invention to a radar antenna; Fig. 16 is a view similar to that of Fig. 15, but showing a different type of radar antenna; FIG. 17 is an axial section of a dome type reflector (which may be a solar reflector or a radar antenna), similar to the reflector of the

  Figure 11, but consisting of sections or sectors now

  naked assembled by a fret; Fig. 18 is a rear view of a sector of the reflector of Fig. 17; and FIG. 19 is a section along the line

19-19 of Figure 18.

  Referring now to the drawings and all

  first in Figure 1, the latter represents a

  trough type or trough type, generally indicated at 10 and comprising a mirror or reflector 11 which is

  carried by vertical supports 13 in order to be able to

  around a horizontal axis A linear focus is

  represented at 14 and is supported by bars 15

  the rear support or the frame of the

  reflector 11, this framework and its manufacturing process

  cation being described below in relation to the others

FIGS.

  FIG. 4 represents a formwork or male mold generally indicated by numeral 20 and can be mounted on wheels 21, if desired, in order to be easily transported from one place to another. The formwork or mold 20 comprises end walls, one of which is represented at 22, and a vault or dome 23 which may be made of wood, metal or any suitable material and whose shape corresponds to that of the mirror, except that it is convex whereas the mirror is concave As shown in Figure 4 and on others

  figures, it is assumed that the mirror is placed on the

  face 23 of the mold and that a support element or rear support is applied directly to the rear surface

  In this case, the mirror becomes an integral part of

  However, as described hereinafter, in some cases it is advantageous to form the rear support separately, in which case the upper surface of the bare mold is used, the rear support being formed on the bare mold, and then removed from it. last and glued on the back surface of the mirror It is also obvious that the mirror 11 may consist of segments that are

assembled on the mold.

  The exposed rear surface of the mirror is coated with an adhesive that exhibits good adhesion characteristics to wet concrete and behaves like a sealant that impairs the moisture of wet concrete

  during manufacture, or the moisture can

  pour the finished hardened coating, to reach the back surface of the mirror and in particular the joints between the

  segments of the mirror The adhesive is compatible with the

  backside of the mirror and with the concrete.

  nable is an epoxy resin known under the trade name "AQUATAPOXY", registered trademark of the American Chemical Corporation, 81 Encina Avenue, Palo Alto, California, 94301 This is an epoxy system in two

  parts, curing at room temperature.

  The surface 23 of the mold is solid and imperforate except for the presence of openings 24 in which suction cups 25 are fixed, these suction cups being connected by conduits 26 to a source 27 of vacuum This vacuum keeps the segments 11 of the mirror tightly and uniformly

on the surface of the mold.

  A coating or a layer, indicated generally by the reference numeral 30, is applied to the sealed rear surface of the mirror, this coating possibly consisting of a mixture of concrete or mortar composed of sand, hydraulic cement, for example cement

  Portland, and water, in suitable proportions.

  Ordinary Portland cement, for example of the type "ASTM Type 1 2", weakly alkaline, or a Portland cement not producing clear expansion (compensated shrinkage cement), such as that described in the US Pat. No. 3,155,526, can be used Suitable proportions of sand and cement are 0.66 / 1, by weight, respectively Water is added to obtain a mixture

  wet suitable for spraying.

  This material is applied by means of a spray gun of a type well known to those skilled in the art such as those used for spraying coatings on swimming pool walls. Such a pistol ejects the mixture of mortar or concrete to high speed and it is equipped with a fiberglass reel (fiberglass wick) and the device has a chopper that cuts the wick in short lengths during the spraying of the mortar mixture, so that the ends of fibers of glass

  cut are intimately mixed with mortar or concrete.

  The glass fibers are produced from zirconia sands and are available under the trademark "Cem-FIL AR". In general, a layer of

4.8 mm thick.

  Then, a perforated formwork (not shown) for example of expanded metal, having a suitable shape, is applied to the upper surface of the freshly applied layer, the form of the formwork being such

  that it causes the formation of a flat and superelevated part

  31 and rounded side portions 32 connected by shoulders 33 When this perforated formwork has been applied and shaped the layer 30 so that it has the configuration shown in FIG. 4, an agitator or vibrator device (not shown ) is applied to agitate the perforated formwork, this stirring device being well known to those skilled in the art and not

  therefore not requiring a more detailed description.

  The purpose of the agitation is to cooperate with the perforated formwork to ensure an intimate contact between the small

  lengths of fiberglass and concrete as well as elimi-

  to remove air bubbles, so that no large amounts of voids remain in the layer formed of concrete and chopped glass fibers Other forms of internal reinforcing means such as organic polymers under fiber form can be

  used, but glass fibers are preferred.

  FIG. 2 generally shows at 40 a formwork or core that can be made quite satisfactorily of corrugated board, a surface of which is coated with a water-impermeable material. Paraffin is suitable as water-proofing material. So

  as can be seen, the formwork 40 is of triangular section

  gullet and has inclined lateral walls 41,

  a bottom wall 42 and a top or edge 43.

  Other cheap materials can be used at

the place of the cardboard.

  Figure 3 shows another formwork indicated

  overall by reference numeral 50 and which is also

  made of corrugated cardboard or any other material

  this formwork being treated in a similar way

  it has a triangular section and has lateral walls 51 which

  converge, as shown, to a point 52, and it pre-

feels a peak or ridge 53.

  Figure 5 shows the formwork 20 on which-

  a layer 30 of concrete is applied, this layer having

  Shaped and shaken as described previously.

  The formwork 40 is then applied to the layer 30, the formwork being in particular applied to the flat portion 31 of the layer 30 of concrete As indicated below, with reference to FIGS. 8 and 9, stoppers (not shown)

  are placed in the open ends of the formwork 40.

  Then, the sides 41 and the crest 43 of the formwork 40 are spray coated with an additional amount of the same fiberglass-reinforced concrete or mortar and using the same type of equipment to form a layer. 54 of concrete A dorsal beam is thus obtained

  or torsion 55 which can be modified as described above.

  after The thickness of the layer 54 of concrete applied to the formwork 40 may be about 4.8 mm This layer is shaped and agitated in the same way

than the layer 30.

  Transverse ribs are then applied

  in the following way: so many forms are laid

  50 as desired, depending on the dimensions of the structure.

  It appears that the lower edges of these forms are

  configured to match the shape of the side walls

  54 of the torsion beam and that of the curved lateral portions 32 of the concrete layer 30

  are compressed against the concrete of the lateral parts 32.

  A layer of concrete and glass fibers is then applied as before, using the same equipment,

  to form a layer 56 on the transverse ribs.

  Expanded metal formwork is then applied and vibrated to ensure intimate contact of the fibers

  of glass with the concrete and also to expel the air.

  Additional ribs, indicated globally

  60, are also

  these ribs being tubular and comprising a cardboard inner casing and an outer layer of fiberglass-reinforced concrete. They are formed in the same way on the dorsal or torsion beam 55, but are smaller in size and have a shape.

  adapted to that of the inclined sides of the frame.

  The result of this method is a mirror, a reflector or a collector of solar energy, indicated generally by the reference numeral 61, having a reflecting surface 11 and made in one piece with a monolithic support made of concrete, indicated overall.

  in 62 The monolithic and integral character of this

  The formwork 40 and 50 made of cardboard and the cardboard formwork used in the ribs 60 remain in the concrete and increase a little, if necessary, the strength of the support Their permanent presence is not annoying

  necessary resistance is ensured by the monolithic mass

  This resistance is increased

  by the compression of the torsion beam,

as described below.

  Referring now to FIGS. 8 and 9,

  it can be seen that FIG. 9 represents in elevation a

  that 65 end of metal, for example steel, triangular shape As shown in Figure 8, because of the presence of the plugs mentioned above, introduced into the open ends of the formwork 40 before laying the plates 65 (these plugs having a shape suitable for closing the open ends), the layers 31 and 54 of cement project or protrude at both ends of the formwork 40. These projecting or cantilevered parts constitute tabs 66 on which joints 67 are nested Seals 67 are made of

  suitable, for example rubber or plastic

  tick, and they serve to seal the ends of the layers 31 and 54 of concrete and to hold clamps

  68 formed along the three edges of each plate 65.

  Bolts 69 are threaded into holes in

  the plates 65 and nuts 70 are screwed onto the ends

  threaded bolts of these bolts at an appropriate time after

  that layers 31 and 54 of concrete have taken and hardened sufficiently

  The nuts are actuated to urge against the plates 65. This places the bolts under tension and applies compression to the concrete layers 31 and 54. Thus, a beam under stress is obtained. Concrete is very resistant to compression Therefore, the torsion beam 55 is strong Despite its hollow and relatively light construction, it considerably strengthens

the rear support 62 in concrete.

  The plates 65 are also used for the assembly of the ends of the axes 72 in the following manner: a mounting plate 73, having a hole 73 has access, 1 O is bolted to each plate 65 A console 74 is welded to the Bottom end of the plate 73 An axis 72 is fitted into the aligned holes of the plate 73

  and console 74 and is welded to these two elements.

  The ends of the pins are mounted so that they can be

  lonner in bearings 75 arranged on uprights 76.

  The end rods 15 can also be mounted, as shown in FIG. 8, on the plate 73. The bolts 69 can be energized while the mirror is still in position on the mold, and it can be continued after it was set up

on the amounts 76.

  FIGS. 10, 11 and 12 show a dome type reflector, generally indicated at 80 and whose reflective surface <see FIG. 11) has the shape of a paraboloid of revolution As in the case of FIGS. 4 and 5, the reflective surface (designated 81) is placed on the complementary surface 23 of a

  The reflective surface 81 has an opening

  the central axial axis 82 which is placed above an

  83 is formed in the surface of the mold and which, like the opening 82, is circular, but of a substantially smaller radius. A formwork 84 is fitted into the opening 82 and held vertically in the recess 83. The upper end is provided with a stopper 85 The formwork is held in the appropriate position by any suitable means and the glass fiber reinforced concrete is sprayed on the rear surface of the reflector and on the surface. As it appears, the concrete forms a layer 86 on the rear surface of the reflector and a layer 87 on the sides of the formwork 84, and it also penetrates in 88 in the annular space between the bottom of the formwork and the edge of the opening 82 These layers of concrete are vibrated, one after the other or together, if preferred and as described above, in order to be shaped, it favors r the contact of the glass fibers with the concrete and to expel the air, all these operations being carried out as described previously

  and using the same equipment as indicated above.

  The tubular layer 87 of concrete forms a beam 89 whose

  the manufacturing continues as described below.

  Radiant ribs 90 are then applied

  said ribs having the shape shown and being made by means of corrugated cardboard forms 91 on which layers of glass fiber reinforced concrete are applied by spraying, using the same technique as that described above.

is removed.

  Then, the beam 89 receives seals 93, end plates 94, bolts 95 and nuts 96 as previously described for the torsion beam 55, except that a cylindrical shape is obtained instead of a triangular shape. The nuts are tightened to place the beam 89 under compression and an axle end 92 is attached to the end plate 94 remote from the reflective surface 81, so as to allow mounting of the reflector Gussets 93 are welded to the plate 94 to reinforce it (see FIG. 12) Transverse ribs 95 are applied in the same manner as

the radial ribs 90.

  FIG. 13 represents another form of heli

  tat, indicated overall in 110 and comprising two

  segmented fliers 111 which are mounted on a horizontal axis 112 and on a vertical axis 113 to follow the sun

  both in azimuth and height The reflective surface

  111 is of known construction and is

  killed from a number of mirror facets that are each oriented to focus the reflected light

  on a punctual focus at the top of a tall tower.

  Figure 14 shows how the present invention

  is applied to this type of reflector Figure 14

  presents in particular at 120 a fragment of mold having a segmented upper surface which consists of

  facets 121 These facets have shapes and

  such that, when mirror facets 122 are assembled as shown, each of them concentrates the reflected light rays to a single point focus, i.e. to a receiving element at the top

  The rear surfaces of the facets

  bending agents receive, by spraying, an adhesive and

  a layer 123 of fiberglass reinforced concrete is

  verified on the rear face of the facets of the mirror

  layer is vibrated and shaped as described previously

  and a torsion beam 124 and cross members 125

  are applied as described with reference to Figure 5.

  Triangular plates 126 and bolts 127 are placed and the bolts are placed under tension so that the torsion beam is placed under compression, as described above with reference to FIGS. 8 and 9 Axis ends (not shown) are fixed to the inner plates 126 to allow mounting of the mirror on

a vertical support 128.

  As indicated above, in the various figures, the mirror is placed on the mold and the concrete is sprayed on its rear surface. This method has the advantage of eliminating the additional operation of pouring the rear support in advance. remove it from

  mold and stick it to the reflective surface.

  is favored by the use of a non-shrinking cement, that is to say a cement which, during the drying and curing of concrete or mortar, does not exhibit

  net withdrawal or only a minimal withdrawal.

  trait may cause unacceptable deformation of the

  reflective surface or mirror.

  Another method can be used to solve this problem The surface of the mold can be coated with a release agent that allows the concrete support to be

  easily separated from the mold after it has set and hardened.

  Then, the concrete or mortar is sprayed directly onto the mold and the following operations such as the manufacture of a torsion beam, etc., are performed exactly as described above when the finished back support has taken and cured sufficiently for removed from the mold, it is lifted from the mold and is stuck on the reflecting surface of the mirror The latter can actually be placed on the mold, a bonding agent being sprayed on its rear surface and the

  rear concrete support being applied to it.

  Demoulders include oil or sawdust, and suitable bonding agents include the aforementioned "AQUATAPOXY" adhesive or the "3 M" type adhesive.

Company's No. 77 ".

  As typical dimensions of the structures according to the invention, the diameter of the dome may be 3 to 15 m; the length of the reflectors in the trough can be 4.5 to 9 m; the thickness of the mirrors can be from 0.025 to 1.5 mm; the thickness of the concrete layers (including applied or bonded layers on the rear surface of the mirror and the layers applied to the torsion beams and other reinforcing elements) may be 4.8 to 6.5 mm; and the global dirensions of the structures in

  concrete can match the dimensions of the mirror.

  As mentioned above, FIGS. 15 and 16 show different types of radar antennas, the antenna shown in FIG. 16 being known as the Cassegrain antenna. In both figures,

  the antenna is indicated overall by the numerical reference

  130 and it is mounted on a support 131 and can rotate about an axis 132 so that it can be adjusted in height, and around a vertical axis in order to be able to be adjusted in azimuth In FIG. 15, a receiver 133 is mounted in the focal point by means of bars 134 In FIG. 16, a receiver 135 is located at the top of the dish and a reflector 136 is supported at the fireplace by

  These embodiments are conventional.

  The application of the invention to the antennas of the figures and 16 is the same, except that in the case of FIG.

  16, the receiver 135 is mounted on the beam 89.

  The same construction steps are carried out

  and we obtain the same results as those described above.

  with regard to Figures 10, 11 and 12, except that the

  reflecting surface 81 is made of a suitable conductive material

  In addition, in the case of Figure 16, the receiver

  is fixed to the beam 89, for example by subjugation

  at the inner end 94, in particular by means of the bolts 95 and nuts 96.

  FIGS. 17, 18 and 19 show a split-type reflector which, when its sections or sectors are assembled, is substantially identical to the reflector of FIGS. 11 and 12. This reflector is indicated overall by reference numeral 145. The individual sectors, in the form of circle sector, are indicated in 146 and 1 S the joints connecting them are indicated in 147 Each sector can cover, for example an arc of 600 or any other arc if it is more convenient, considering the dimension of the reflector These sectors are manufactured substantially in the same manner as the cupola of Figure 11 Figure 19 shows a formwork 148 which has a flange 149 defining its upper surface 150 whose size, shape and curvature correspond to the size and shape provided for the sector 146 of dome and for

  a sector 154 of beam, and the curvature of the dome.

  Reinforced fiberglass concrete is applied to the surface 150 to form a layer 151 A core 152 is applied to the concrete layer before it hardens, this core can be made of cardboard.

  when the concrete is applied, a rib 153.

  The sectors of the reflector are then assem-

  for example, on a tray or on the ground so that their concave faces are facing downward. A beam 154 is obtained by the application of end plates 160, bolts 161 and nuts 162. An axis 163 is also realized apart from the fact that this beam

  consists of sections, it is formed as the

  shown in Figure 11 and it performs the same function as the latter A seal 164 surrounds the peripheral edge of the dome and a hoop 165 is also used, this hoop can be any suitable material, for example sheet metal, its ends being fixed and tightened properly, for example by means of a tensioner (not shown). The invention thus makes it possible to obtain a complete reflector of the dome type, which can be used as a

  radar antenna or as a solar reflector, and

  For example, individual sections or sectors can be realized at the factory,

  stored until it is necessary to use them, trans-

  brought to the place of use and assembled at this place of use Such a practice is much more convenient and less expensive than the manufacture of the whole

  reflector at the place of use, or its manufacturer

  one place and its transport to the place of use.

  lisation. It therefore appears that the frame or the rear support for solar reflectors and radar antennas according to the invention has the required strength and rigidity and is inexpensive both with regard to the materials (concrete and inexpensive formwork / and the

assembly methods.

  It goes without saying that many modifications can be made to the reflector described and shown

  without departing from the scope of the invention.

Claims (2)

  1 beam characterized in that it comprises a hollow interior formwork (40) at least a portion of the outer surface is coated with a layer (54) of concrete which extends from one end to the other of the formwork , elements (65, 69, 70) applying compression to this layer of concrete.   2 beam according to claim 1, characterized in that it comprises plates (65) fixed at its open ends and bolts (69) which pass through these plates and which are intended to place the beam under compression.