WO2011007063A1 - Multipurpose mold - Google Patents

Abstract

The invention relates to a multipurpose device, illustrated very schematically in figure 5, consisting of a plate (3a) covered with insulation and working (4, 5, 6, and 7) layers, a working head (15) that is movable over said plate and capable of: working the surface (7) of said plate; depositing a material (2) thereon and working the latter; placing preexisting concave membranes (17, 18, 20) on said surface, or depositing materials capable of forming said membranes; and depositing the materials (19a, 19b, and 19c) that are capable of forming an auxiliary folding membrane (19).

Description

 POLYVALENT MOLD

 FIELD OF THE INVENTION The field of the invention is that of the manufacture on the ground of large membranous mirrors and means for their orbiting.

 PRIOR ART In the prior art there are descriptions of optical surfaces with steps, and molds and moldings of optical surfaces that can be used by transmission or reflection, molded lenses or concave or convex mirrors molded. German patent 1,050,223 of Feb. 5, 1959 describing the manufacture of a Fresnel lens, the article by Peter C. Chen and Robert C. Romeo (Proc of SPIE Vol 5382) describing molded mirrors multi-layered carbon composite, the application of MeIvMIe P. Ulmer and Michael E. Graham (US Application 2006/01 81 743 A1) describing molded mirrors consisting of several linked superimposed layers, and the patent of Robert M. Phillips ( US patent 3,61 3,659) describing the molding of Fresnel mirrors, linear or quasi-linear, with also the overlapping of several linked layers.

RESPONSE OF THE INVENTION TO THE PROBLEMS POSED. The satelliteization without deterioration of large membranous mirrors made on the ground was made possible by the use of a folding aid (Vernois, FR-A-2,744,244 of 01/08 / 1,997).

The folding aid practically eliminates the problems related to the diameter of the mirror and the mechanical stresses during the launch, but it still had to overcome the difficulties associated with the placement of the mirror membrane and the control membrane (Vernois FR 2 736 165 and FR 2 725 044) on this auxiliary.

The folding aid could be machined directly, but, according to the invention, it is manufactured by molding, which induces a significant saving for the manufacture of several auxiliaries, and also allows the prior deposition of materials that can constitute a membrane, or the prior placement on the mold of the membranous mirror and the control membrane manufactured elsewhere, largely eliminating the difficulties associated with the delicate placement of these membranes on the folding aid, since it is the folding aid which will be placed on these membranes by molding.

 By allowing the direct manufacture of the mirror or one or more control membranes on the multi-purpose mold, the invention eliminates the need for a large concave mold of large size to manufacture the mirror membrane and the control membrane (s), and also eliminates the devices necessary for the transfer of the membranes of these concave molds to the multi-purpose mold.

 In the case of very large mirrors, the invention solves the problem of a mold made by a conventional machine of sufficient size, but not dedicated, and which should be transported to its place of use.

This mold must be extremely precise and solid, and therefore rigid, to allow the placement or deposit of an undetermined number of membranes, and the molding of an indeterminate number of folding auxiliaries.

 For obvious efficiency reasons, from a certain size, this mold and its manufacture must be integrated in the operations of placement or membrane deposition and the final molding of the folding aid, or vice versa, and also in the optical deterioration or wear of this mold, and its restoration.

 The means involved in the construction of the mold are the same as the means participating in the deposition of materials to become a mirror membrane, a control membrane or a folding aid, Figure 5.

There is therefore unity of invention, from the manufacture of the mold to the placement or deposition of the membranes, and to the molding of the folding aid.

 PURPOSE OF THE INVENTION

The object of the invention is to manufacture a mold for molding a folding aid and allow before this molding the placement or the deposition of the mirror membrane and at least one control membrane on which or which will thus ideally be placed, ie molded, the auxiliary folding. SUMMARY OF THE INVENTION

 Mold - To obtain a mold 1 according to the invention, using a machinable thin film or surface film 2 at least a few millimeters thick, deposited in liquid or non-liquid form on a horizontal plate 3, for example a film of tin or lead, or a specific alloy, or polymerizable or thermosetting resins.

 For corrugations of the order of one centimeter, a preliminary work of the surface layer can be performed, and the thin machinable layer deposited on the undulations thus created (Figure 5).

A decisive advantage of such a film 2 is that it is of easy and economical constitution, and is not limited in size as a very delicate and very expensive assembly of sheets.

A perfect surface diameter of 100 meters becomes feasible from the moment the tray 3 supporting it in the working conditions is achievable.

 Such a film 2, metallic, or simply conductive, is worked by the material removal methods of the prior art, including electroerosion, to a surface state of the order of Ra = 0.1, and can then be polished to optical quality.

 A non-conductive film 2 is worked by appropriate means, depending on its nature.

The plate 3 supporting this film 2 consists of a mechanical structure 3a supporting several specific layers or zones, in particular, from bottom to top, a constant temperature layer 4, a thermal insulating layer 5, a heating layer or that can be heated 6, a heatable and receptive layer 7 of the film 2, and an independent upper member 8 retractable, heated or simply protective (Figures 1 and 5).

 In the case where the plate 3 is rotating, it can be supported by floats 9 or laminar pneumatic or hydraulic cushions 10, according to the requirements imposed by its dimensions (Figure 2).

 At least one movable element 1 1, carrier of at least one movable carriage 12 provided with a vertical movement 1 3, sliding on a slide 14 integral with this movable element 1 1, and able to receive specific interchangeable working heads 1 5 , allows work on the entire surface of the plate 3 (Figure 5).

 Profile of the mold - According to the prior art, the profile of the folding aid is described by a set of arcs of circles of radius of curvature Rn centered on the cylinders projections of intersections of the mirror and intersecting planes, and tangentially connected.

In the prior art, the central part of this folding aid is concave.

For reasons that will be seen below, according to a first embodiment of the invention, the central portion of the folding aid will be convex.

 The profile of the mold is the negative of the profile of the folding aid that is to be obtained. The central part of the mold will be concave, according to Figures 3 and 4.

A set of equations 1 6 according to the invention makes it possible to determine the radii of curvature Rn and the centers of curvature zn, where R is the radius of curvature of the mirror membrane 1 7 and of the control membrane 1 8 in the case where they are spherical.

 These corrugations I b constituting the profile 1 a, are, according to the invention, at variable maxima and minima, or preferably at constant maxima z = 1.

Molding of the folding aid - According to the invention, the materials of the folding aid, polymerizable resin and anisotropic fabric are deposited on the mold 1 with the aid of specific working heads 1 5, and after polymerization, give a folding aid which can be used as in the prior art.

 The folding aid to be wound on itself for its orbiting, and to avoid deterioration of the mirror membrane by contact, the back of this auxiliary is covered with a protective layer of appropriate consistency

Placement and molding - According the invention, the mirror 1 membrane 7 alone, or the mirror membrane 1 at least 7 and a control membrane 1 8, separately manufactured, are placed on the mold I ₁ as they were on the folding aid in the prior art, possibly after the concave / convex reversal of these membranes 17 and 18.

The materials of the folding aid 1 9 are then deposited, partly with the aid of a specific working head 1 5, on the back of the mirror membrane 1 7, if it is alone, or on the back of the mirror. the control membrane 18 in the opposite case, resulting in a perfect adaptation of the folding aid 19 to the mirror membrane 1 7 if it is alone, or to the control membrane 18 if it has been placed. Deposition and molding - According to the invention, the constituent materials of the mirror membrane 1 7 are deposited on the mold 1, partly with the aid of a specific working head 1 5, and then, when these first materials are stabilized , those of the, or the control membranes 18 are optionally deposited, in part using the same specific working head 1 5, and partly with the aid of another specific working head 1 5 concerning the conductive and electronic elements.

 The materials of the folding aid 19 are then deposited.

 During the deposition of the materials constituting the membranes, an attempt is made, according to one embodiment of the invention, to reproduce the stresses existing in pre-existing membranes placed on the mold, so that, during separation into space from these deposited membranes, they tend to acquire the original form of these pre-existing membranes.

 This is done, according to the invention, by suitably dosing the components of the resin and the fillers to form the membranes, particularly in the direction of the thickness of these membranes, so as to obtain after shrinkage or polymerization, an extension reproducing the shrinkage and extension stresses of a preexisting membrane 17 or 18 placed on the mold 1.

 In another embodiment of the invention, to aid the preceding result, the shape of the corrugations of the mold 1 is modified so that these modifications take into account and compensate, as far as possible, the residual deformations after the separation of the membranes in space, and taking their concave forms.

Intermediate membrane - According to the invention, an additional inert membrane 20, or simply a specialized layer 20a of the control membrane 1 8, is interposed between the mirror membrane 1 7 and the control membrane 1 8.

This membrane 20, or specialized layer 20a of the control membrane, has a structure allowing its expansion in thickness in the vacuum, so as to macroscopically separate the mirror membrane 1 7 and the control membrane 1 8, the accidental direct contact in the membrane. space could be detrimental to their functional relationships. LIST OF ITEMS

 1 - Mold

l a - Mold profile

 1 b - Ripples of the mold 1

 2 - Machinable layer or film

3 - Support tray of the film 2

 3a - Supporting mechanical structure of the plate 3

 4 - Layer 3 constant temperature layer

 5 - Thermally insulating layer of the tray 3

 6 - Heating layer or heating layer 3

7 - Receiving layer of film 2

 8 - Protective mobile element and / or heating element

 9 - Float

 10 - Pneumatic or hydraulic laminar cushion

 1 1 - Mobile upper element carrying mobile carriages

12 - Mobile trolley

 13 - Vertical movement of the mobile carriage

 14 - Horizontal slide of the movable element 1 1

 15 - Set of specific interchangeable work heads

 16 - Equation giving the angle ê according to An and drn

16a - Equation giving the radius of curvature Rn as a function of

 17 - Mirror membrane

 17a - Materials constituting the mirror membrane

17b - Reflective deposit

 17c - Accessory Membrane Receiving Reflective Deposit

18 - Control membrane

19 - Folding aid

19a - Molding materials

19b - Fabric

19c - Protection layer Intermediate Expansive Membrane

 20a - Expansive layer of the control membrane

 21 - Work area

 21 a - Ring of deposit of the material constituting the machinable deposit

 BRIEF EXPLANATIONS OF FIGURES

Figure 1 - Plateau with its differentiated layers

Figure 2 - Large Floating Tray

Figure 3 - Schematic diagram of intersecting planes

Figure 4 - Curvature radius between r1 and r2; iterative values of maxima and minima

 Figure 5 - schematic summary of the invention showing all the hardware elements.

DETAILED DESCRIPTION

A - SUPPORT TRAY AND WORKING HEADS

a) Support plate 3

 The plate 3 consists of a plane mechanical structure 3a of the prior art thermostated to avoid dimensional variations.

 This flat structure 3a is covered according to the invention with working layers whose main function is to isolate this structure from the thermal flux resulting from the melting of the materials constituting the machinable layer 2, or from the exothermic polymerization reactions of the constituents of this machinable layer. 2.

 To obtain this dimensional stability in the presence of temporary heating of 300 or 400 degrees centigrade, the vertical layers or zones 4 and 5 consist of product of very low coefficient of expansion.

 This requirement of dimensional stability prevents the vertical layers or zones from slipping over each other to allow a clearance of expansion which may result in return differences inducing tensions and deformations that may appear only after the machining of the mold, and therefore virtually undetectable.

For this reason, the layers or zones 4 and 5 have sufficient thicknesses to allow non-destructive expansion having no dimensional residual impact, given the heated elementary surface, the thermal gradient obtained and the modulus of elasticity of the material. (Figure 5).

b) Machinable layer

According to the invention, the heating or heatable layer 6 and the receiving layer 7 of the machinable layer 2, this layer 7 being rough or machined to create corrugations, will be heated by local surface elements which will progressively extend, after melting or polymerization of the machinable local layer 2, and cooling, over the entire surface of this receiving layer 7.

In one embodiment of the invention, the active heated elementary surface will be a circular or helical ring centered 21a extending progressively from the center of the working area 21 to its periphery, by the solidification of its concomitant internal portion to the fusion contribution of its external part, or vice versa.

At the same time, a plurality of these circular or helical rings 21a may exist, the principle being that the rings are sufficiently separated so that, given the width of these rings, the thickness of the layers or insulating zones and the modules of elasticity, the temporary deformations related to the expansion of the heated part of each ring remain strictly within the limits imposed by the modulus of elasticity.

The junctions between this plurality of rings will be according to the invention by the development of each ring which will necessarily reach the cooled edge of the next ring.

c) Diametral moving element 1 1

At least one movable mechanical element, for example a horizontal metal structure January 1, can be positioned above the working area 21, along a diameter of this area. This metal element January 1 has one or more slides 1 4 horizontal, that is to say parallel to the surface of the plate 3, which can each support a plurality of mobile carriages 1 2 and working heads 1 5, may participate, each according to its specificity, the shaping of the mold 1, the supply and melting of the materials constituting the machinable surface layer 2, the placement or deposition of the membrane membrane 17, the membrane 1 8, the intermediate membrane 20, and the deposition of the materials of the folding aid 1 9 (Figure 5).

d) Work heads 1 5

 These interchangeable work heads are specific and diverse given the various jobs they must perform.

 B - MANUFACTURE OF THE MOLD

 The receiving layer 7 of the machinable film 2, which can simply be the cleaning and horizontally of the heated or heatable surface 6, is worked by a mechanical head 1 5, which can make it horizontal or create meadow -ondulations.

 The machinable surface layer 2 is constituted, according to one embodiment of the invention, by the provision of a molten metal by a heating element, on the horizontal surface or on the pre-convolutions.

In one embodiment, the metal is provided in the form of a coil wire or ribbon carried by a specific working head having a means for melting the wire or ribbon, a heating means for the area where the wire will be melted or the ribbon so as to avoid excessive heating or too localized this layer 7, and a means of vertical movement.

In another embodiment, the wire or ribbon comes from one end of the movable element 1 1. The material removal work for machining the mold is carried out by specific heads 1 5 supporting mechanical means or means for removing material by thermal vaporization or electroerosion.

 Given the small vertical amplitude required for this machining, of the order of one centimeter, these heads are mounted on very light systems 1 3 of vertical displacement with two flexible blades superimposed without play and without friction of the prior art.

 This lightness allows the placement and the simultaneous work of a plurality of these heads 1 5. To minimize the very small parasitic lateral movement of these heads, this parasitic lateral movement is perpendicular to a radius of the working area 21.

The raw deposit constituting the machinable layer 2 is worked by a specific head 15 which will first give it a horizontal surface as perfect as possible, this horizontal surface becoming the working reference to give the mold the desired profile.

In the case of pre-corrugations, this reference surface will be made by placing in a plane the vertices of the pre-corrugations covered with the machinable layer 2.

For practical reasons we put the origin of the vertical ordinates at the top of the concave mirror, whose ordinate of the tangent plane will be z = 0.

 By choosing a unitary spacing between the intersecting planes of the spherical cap (FIG. 3), the first secant plane will therefore have the vertical ordinate z = 1.

 This secant plane will be physically represented by the preceding machined horizontal reference surface z = 1.

The surface of the machined layer 2 must be plane in the geometric sense, and not horizontal in the sense of a liquid surface that conforms to the local shape of the earth's geoid, the resulting gap resulting for a deposited mirror from the theoretical shape sought for at quarter-wavelength in the visible, as soon as the diameter of the mirror exceeds 1 0 m. C - PROFILE OF THE MOLD

a) General values of several elements of the profile in case of equidistant intersecting planes

 The profile of the mold is deduced from the length of the arcs intercepted by the equidistant intersecting planes, according to the prior art, FIG.

These lengths of the arches vary according to the shape of the mirror, spherical or other.

 In the case of a spherical surface, there is a simple conventional trigonometric approach.

 In the case of a parabolic or hyperbolic mirror, the approach is analytical.

Figure 4 showing two _gaps' between two odd values ri and r3 illustrates the method for calculating the radii of curvature Rn of the invention.

 It can be seen in this FIG. 4 that the horizontal bottom tangential connection in fn for the two successive dr intervals can not be done on z = 0 if the high tangential connection has been made in ri on the z = 1 plane, in the case of a mold with concave central part.

It is made to a non-zero positive fn value If we now consider an interval infinite infinite, we see that there will be confusion between the two arcs B described by the infinite rays Rb and Rh and the infinite arc An, and that in this extreme situation, fn is zero.

 We therefore deduce that fn increases when dr decreases, and that the successive maxima of the profile are decreasing by a value gn = dfn, here g3 = df3 = f3 - f2, given the horizontal tangential connection at fn, this value gn being very weak, and not representable in scale.

 The interval ri; r2 is processed by the computation, and the values y are on the scale, in particular f2.

The interval r2; r3 is purely demonstrative and pedagogical, and none of the elements appearing in it is to scale, the difference df3 between f3 and f2 being of the order of 1/1000 of f2, so that g3 , absolutely unrepresentable, as will be seen later in a numerical example for a mirror of about 1000 mm in diameter and numerical aperture close to F: 2.

 We can also simply consider that the interval r2; r3 is the peripheral interval of the mirror, rn-1; rn.

 This pedagogical view makes it possible to show that the presence of intermediate intervals would not change the peripheral value of gn, where gn represents the maximum deviation of the peaks of the undulation at the z = 1 plane.

b) equations 16: calculation of radii of curvature and centers of curvature

We see in Figure 4 that there is a low radius Rn, Rnb, and a radius Rn high, Rnh.

 Equations 16 according to the invention give the angle θ with the vertical of the straight line joining the centers of low curvature zb and high zh in an interval dr.

 The successive arc elements moved directly or after reversal on the z = 0 plane in FIG. 3 are shown in FIG. 4.

Taking the high radii of curvature Rnh and low Rnb equal, we can write by definition dnn = 2nn, being the arc described by the end of a radius Rn pivoting from the angle in with the vertical.

 We have En = 2pi / 360 Rn.ên, and 2ên = An = 2pi / l 80 Rn.ên.

 From where 2 Rn = 1 80 / ft x dnn / ln.

On the other hand, we have: 2Rn sinen = drn.

 So it comes: 2Rn = drn / sinen = 1 80 / pi dnn / ln

 Equation 16 is finally obtained: ên / sinên = 180 / pi dnn / drn.

since dn and drn are known from elsewhere, this equation makes it possible to calculate the angle in and thus Rn which is worth, equation 16a: Rn = 180 / 2pi x dnn / ln

We call hn the height of the right triangle of hypotenuse 2Rn and base drn = rn - rn-1. hn is the vertical distance between the center of curvature low znb and the center of curvature high z (n + 1) h, always in any interval drn.

 In these conditions we see that the values of the ordinates z of the centers of curvature and radii of curvatures are iterative since they depend on the values of fn and gn in the preceding interval.

 It can be seen in FIG. 3 that the tangential connection between the first direct section rθ; rl and the second inverted section ri; r2 is along the plane z = 1.

 The first section rθ; rl is naturally constituted by two arcs of circle of radius Rl =

R / 2 and angle λ1 = λ1, centered on the vertical lines r0 and r1, where R is the radius of curvature of the mirror.

 The R / 2 value is optimal, the possible increase without interest of one of the rays being able to lead only to the decrease without interest also of the other.

 The radius of curvature Rn is limited in a lower value by the alteration that would result from the mechanical properties of the membrane, or the impossibility of placing conductors, electrodes or electronic elements therein.

 The minimum radius of curvature depends on the numerical aperture and pitch of the intersecting planes, but not on the diameter of the mirror.

c) constant decreasing constant iterative profile with Rnb = Rnh

Magnitude

Example of a mirror of radius of curvature R = 4000 mm and numerical aperture close to 2

 A distance of 1 mm is chosen between the secant planes.

For practical reasons, it is necessary to have an integer number of secant planes. A simple calculation shows that for a calotte radius of 500 mm, there are 31 intersecting planes, which brings the radius of the concave cap to r31 = 497.0301 801 mm.

 Under these conditions, the angle α31 of the radius of curvature R with the vertical is:

 sinâ31 = r31 / R = 497.0301801 / 4000 = 0.1 242575 hence 31 = 7.1 378909 degrees

 An identical calculation gives r30 = 488.9785271 mm, and therefore dr31 = r31 - r30 = 8.0551 653.

The angle with the vertical â30, from sinâ30 = r30 / / R = 488.9785271 / 4000 = 0.1222446, is 3030 = 7.0216644.

 It comes from 31 to 30 = 0.1 162265.

The length of the arc d31 then becomes d31 = d31 pi R / 1 80 = 8.1 141416.

 We can then calculate the angle 31 31 such that 31 31 / sin 31 31 = 1 80 / d d 31 / dr 31 = 57.7404505.

It comes to 31 = 1 2,330,494 degrees.

 From this we deduce R31 = 1 8,851 8834, h31 = 36,83401 86, and f 31 = 0,1 30251 mm

 If one makes the same calculations for r1 and r2, it comes f2 = 0.1 297506, value lower than the previous value of 0.1 30251 - 0.1 297506 = 0.000501, that is 5/10 of micron.

 Since the values are iterative, it can be deduced that the maxima of the generating profile of the undulation will remain smaller than the z = 1 plane of this value dfn = gn of the order of 1/10 micron.

The minima will remain above the z = 0 plane by a value between f2 = 0, 1297506 mm and f31 = 0.1 30251 mm.

It should be noted that regardless of the diameter of the concave membranes, the maximum value of fn will always remain extremely close to f 31 = 0.1 30 mm, for a pitch of the secant planes of 1 mm, and a numerical aperture close to F: 2 .

 The weakness of these values shows that the equations 16 according to the invention very satisfactorily give a wave generating profile that can be used for diameters of any size.

 In particular, the deviation on the z = 1 plane is not likely to modify the behavior of the folding auxiliary during the orbiting.

d) constant maxima profile, gn = O and z = 1

 In a first variant of the invention, in order to avoid the iterative influence of the variable ordinates z of the variable maxima lower than z = 1, the distances of the even secant planes are increased to adapt the values of fn so as to obtain maxima with gn = 0, always located in the theoretical plane of ordinate z = 1.

 In a second variant of the invention, for the same purpose, the arcs of circle described by the ends of the radii Rb and Rh are replaced by arcs of ellipses or arcs of specific curves.

e) convex central section

 In this variant of the invention, FIG. 4 shows that the profile would be tangent to the z = 0 plane instead of being at the z = 1 plane, but that the magnitudes of the various elements, e2, R2, R3, f2, f3, g3 would be preserved.

The values of the minima of the corrugations of the profile will be very close to z = 0, and the maxima will be close to z = 1.

 D - MOLDING A FOLDING AUXILIARY

 In all that follows, the anti-adhesion techniques of the prior art are used whenever necessary.

 A folding aid is constituted according to the invention of a first part comprising the relief of the profile of the mold 1, whose thickness is equal to the depth of the undulations of the mold, and a second part, on the back of this relief. , consisting of a bidirectional fabric of small thickness compared to the depth of the corrugations.

To obtain this result, according to the invention, a suitable polymerizable resin is deposited on the mold, to a level equal to or slightly greater than the peaks of the undulations of this mold, and then, according to a particular embodiment, the fabric previously under form of a roll, is unrolled on the mold and impregnated with the polymerizable resin exceeding the mold.

Once the polymerized resin the fabric becomes integral with the molded footprint and gives it its mechanical properties.

In another embodiment of the invention, the threads constituting the fabric are individually deposited by specialized working heads 15. For a good realization, and to prohibit that the tissue does not penetrate in the hollow parts of the mold and lose the flatness necessary for a good winding and a good behavior during the launching, the material constituting this fabric is according to the invention of lesser density or equal to that of the molding resin, so that the fabric floats on this resin. A specific working head 15 pours the polymerizable resin onto the mold to the proper height, and once the fabric is deposited, a specific working head 15 imparts a slight vibratory motion to the floating fabric to allow it to move freely. impregnate properly.

Once the polymerization has been carried out, the folding aid obtained is then wound up and can be moved to the place of use where it is unwound to receive a mirror membrane 17 and possibly a control membrane 1 8 as in the prior art. .

 The folding aid supporting the mirror and the control membrane or membranes will be wound on itself and then subjected to the constraints of the launch, ie to a strong acceleration and to strong vibrations.

 In this winding on itself, the resistant fabric of the folding aid will be in contact with the mirror membrane and could deteriorate it.

 To avoid this, according to the invention, a protective layer 19c of appropriate consistency is deposited on the back of the fabric of this folding aid.

 According to the invention, the total mass of this protective layer 19c and its distribution are such that the fabric of the folding aid is always at the center of gravity of the auxiliary assembly and membranes so that this tissue, and therefore the folding aid and the membranes are not deformed by the acceleration and the vibrations of the launch (figure

5).

 According to the invention, electrical circuits, electrodes and semiconductors and microprocessors are integrated in this protection layer 19c.

 E - PLACEMENT AND MOLDING

 The invention adds the possibility of placing a preexisting mirror membrane 17 no longer directly on the folding aid 19, but on the mold 1 itself, and to mold the folding aid 19 on the back of this mirror membrane. 1 7.

The invention also makes it possible to place at least one preexisting control membrane 1 8 on the back of the mirror membrane 1 7 and then to mold the folding aid 1 9 on the back of this control membrane 1 8.

 This supposes a manufacture of the mirror membrane 17 on a concave specific mold.

1 7a not far from the mold 1, and also the complete clearance of the surface of the mold 1 and the existence of a handling means.

 Likewise for the control membrane (s) 1 8.

 F - DEPOT AND MOLDING

 Instead of placing on the mold 1 a preexisting mirror membrane 1 7, on the mold 1, according to the invention, using specific working heads 1 5, materials 17a of appropriate thickness and consistency are deposited. will form after solidification a concave membrane just by their deposition on the mold 1 whose profile is suitable, when removing the mold or the folding aid.

According to the invention these materials are polymerizable resins, or fuse materials deposited hot, in liquid phase or vapor phase, and appropriate charges.

 In order to obtain, after separation of the bending auxiliary, the sought-after spherical, parabolic, hyperbolic or other shape, the stresses existing in a membrane of the desired shape when it is placed on the mold 1 are reproduced in the deposited membrane.

These constraints exist on both sides of a medium neutral surface, a contraction of the concave side and an extension of the convex side.

 This is achieved, according to the invention, by suitably dosing the polymerizable mixture, or simply solidifiable, and the distribution of the charges, in the direction of the thickness of the membrane, the middle or neutral portion of this membrane having the suitable developed length in relation to which there will be extension or contraction.

On this mean or neutral part will be deposited, according to the invention, parallel to the surface, thin fibers so as to ensure a particular strength of this neutral layer of the membrane.

 The mixture of resins and catalysts will be such that, after the total deposition of the membrane, this neutral layer polymerizes the first and acquires sufficient rigidity, and then

8 the outer layers polymerize by creating tension or extension stresses with respect to this already solidified middle layer, recreating the tension and extension stresses of a pre-existing membrane placed on the mold.

 In order for this concave membrane obtained to be a concave mirror 17, a reflective deposit 17b prior to or after the deposition of the polymerizable resins or of the fusible materials 17a is made, the reflective deposit 17b being designed so that it adheres only to the membrane. concave created.

 This preliminary reflective deposit 17b is made according to the invention on a first transparent deposit 17c very thin, and the materials 17a of the mirror membrane 17 will adhere to this first reflecting membrane 17c

 The materials 18a constituting a control membrane 18 are optionally deposited in the same manner on the back of the preceding membrane, and the materials of the folding aid 19 are then deposited (FIG. 5).

G - INTERMEDIATE MEMBRANE 20

 According to the prior art, the mirror membrane and the control membrane interact electromagnetically.

 These electromagnetic interactions, in particular the electrostatic interactions, are not very controllable at too short distances, which can be the case in case of accidental contact, given the very small thickness of these membranes.

 To overcome this drawback according to the invention, a separation membrane 20 is placed between the mirror membrane 17 and the control membrane 1 8.

 The purpose of this membrane is not only to prohibit direct contact between the mirror membrane and the control membrane, but also to maintain the greatest possible gap between these two membranes in case of accidental approach.

 To maintain this larger gap, this membrane 20 according to the invention has a structure trapping air during its manufacture so that in vacuum, this air swells in thickness said membrane 20.

 After swelling, the membrane will finish its natural polymerization in time, or accelerated under the effect of ultraviolet solar radiation.

 Swelling by a factor of 10 would result in a 10 micron membrane at a thickness of

100 microns, ie 1/1 0 mm, sufficient to allow good control of electrostatic effects.

 In order to make it possible to eliminate any parasitic electrical charges, this membrane will be very slightly conducting and connected to the mass of the telescope, this very slight conductivity not disturbing the electrostatic effects between the conducting layer 17c of the mirror 17 and the membrane of the telescope. control 18.

 H - UNIT OF INVENTION - FIGURE 5

This figure shows the essential elements of the invention, and their necessary and sufficient interconnections.

 The layers or zones 4, 5, 6 and 7 are necessary to allow heating of the layer 7 without introduction of defects.

 The working head 15 may surface the layer 7 to prepare the deposition of the layer 2, deposit this layer 2, and give it the profile l a suitable.

 This working head 1 5 can also deposit the constituent materials of the mirror membrane 1 7 and the control membrane 1 8, the materials 19a filling the corrugations of the machined layer 2, the tissue 19b the back deposit 19c of the auxiliary folding

1 9, and the deposition of the materials of the intermediate membrane 20.

None of the elements presented in this figure 5 are on any scale compared to another, since this figure mixes microns, millimeters, centimeters and meters, and that each element must appear clearly whatever its size.

Claims

. claims 1) Method of manufacturing a molding folding aid  characterized in that the molding of the folding aid is made interposed, between the mold and the materials to constitute the folding aid, of one or more separable independent membranes, said mold having the profile of a folding aid or its negative. 2) A method of manufacturing a molding folding aid according to claim 1, characterized in that the interposed separable independent membrane (s) is (are) previously manufactured outside the mold and then placed on the mold whose shape they perfectly match, by definition profile mold, profile of a folding aid or its negative.  3) Process for manufacturing a molding folding aid according to claim 1, characterized in that the interposed separable independent membrane or membranes are manufactured on the mold by one or more deposits of materials. 4) A method of manufacturing a molding folding auxiliary according to claim 1, characterized in that the separable independent membrane in contact with the mold is a mirror membrane, manufactured outside the mold, or by depositing materials on the mold. 5) Process for manufacturing a molding folding aid according to claim 1, characterized in that the different membranes and the folding aid are separated by deposits of materials which allow the separations of these membranes and the auxiliary folding in space.  6) A method of manufacturing a molding folding aid according to claim 1, characterized in that the folding aid is constituted, on the one hand, of a material filling the circular hollow portions of the mold covered with one or of several separable independent membranes, and secondly of a fabric covering this material and tangent the vertices of the circular undulations of said mold covered with said membranes.  7) A method of manufacturing a molding folding aid according to claim 3, characterized in that when an interposed membrane is formed by depositing materials on the mold, the deposit consists of a mixture of hardenable materials and fillers whose proportions are variable in the direction of the thickness of said deposit, on either side of the average neutral surface of said deposit.  8) A method of manufacturing a molding folding aid according to claim 3, characterized in that when an interposed membrane is formed by depositing material on the mold, the average neutral surface of said deposit is reinforced by fibers arranged parallel to said average neutral surface.  9) A method of manufacturing a molding folding aid according to claim 3, characterized in that when an interposed membrane is formed by depositing solidifying materials on the mold, the average neutral surface solidifies before the rest of the deposit . 1 0