EP0071605A1 - Ebauche de miroir - Google Patents

Ebauche de miroir

Info

Publication number
EP0071605A1
EP0071605A1 EP19810902946 EP81902946A EP0071605A1 EP 0071605 A1 EP0071605 A1 EP 0071605A1 EP 19810902946 EP19810902946 EP 19810902946 EP 81902946 A EP81902946 A EP 81902946A EP 0071605 A1 EP0071605 A1 EP 0071605A1
Authority
EP
European Patent Office
Prior art keywords
fibres
shell
glass
support structure
blank according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19810902946
Other languages
German (de)
English (en)
Inventor
Gustav Bernhard Rennerfelt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0071605A1 publication Critical patent/EP0071605A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors

Definitions

  • the present invention refers to a mirror blank, and more particularly to a mirror blank of the type which includes a shell the shape of which substantially corresponds to the shape of the finished mirror and a support structure which is fastened to the shell and which fills the latter.
  • a mirror blank of this type is known from my Swedish patent application No. 79.04584-5 which is referred to for a more thorough understanding of the shell and the way in which this is formed.
  • the support structure of the prior mirror blank consists of micro spheres which are caused to adhere to each other and to the shell.
  • PCT/SE80/00151 a support structure is described including foam glass which, if desired, may be mixed with micro spheres.
  • the present invention refers to a new material for the support structure, more precisely a fibre material the coefficient of thermal expansion of which is adapted to that of the shell.
  • the support structure forms a three-dimensional network of fibre and binder which fixedly connects the fibres with each other and with the shell so that the entire support structure is fastened to the shell.
  • the filled shell shape is covered with a flat or convex plate of glass or a mat of fibres.
  • a silver-plated thin glass-plate is glued on to the concave or flat surface thus obtained.
  • the plate of glass covering the support structure may be ground, polished and have a reflecting coating applied to it directly.
  • the support structure may consist, instead of fibre material, of micro spheres coated with a dust of sealing glass, lead glass or ceramics, or else the support structure may consist of foam glass or of mixtures of micro spheres and foam glass.
  • a shell 1 of a normally solid material mouldable in heat, for example glass or ceramics, has been produced in a master die 2 in the way described in either of the patent applications mentioned above. It may suffice here to mention that the shell 1 is produced from a flat plate which by heat treatment and with the use of vacuum or nitrogen has been formed under overpressure against the master die 2. After controlled cooling the finished shell 1 is obtained which, according to the invention, is filled with fibres of a material the coefficient of thermal expansion of which is adapted to that of the shell. Preferably, the coefficients of the thermal expansion of the fibre material and the shell are chosen to be as equal as possible.
  • the fibres are designated by the reference numeral 3 , and they may either be short and have an unarranged orientation in the shell 1 or else they may be present in the form of fibre mats which fill the shell 1 in several layers.
  • the fibres 3 are of glass, polymer material or any other material which has the suitable coefficient of thermal expansion.
  • a binder not shown in the drawing firmly connects the fibres with each other to form a firm stiff three-dimensional net-work.
  • the binder is a dust, i.e. very small particles, of glass or ceramics the melting temperature of which is lower than that of the fibres.
  • the fibres are provided with a coating of this dust before they are introduced into the shell 1.
  • the fibres thus dusted are allowed to fill the shell mould 1 with good measure, whereupon they are compressed by placing a mould part 4 having a moulding surface 5 which may be convex or flat over and in contact with the master die 2.
  • the fibres After the compression or simultaneously therewith the fibres are subjected to a heat treatment up to the melting temperature of the dust serving as binder which then melts and wets the fibres as well as the inside surface of the shell mould 1.
  • the whole assembly is then subjected to a controlled cooling, a three-dimensional network being thereby formed the knots of which consist of the contact point between two fibres crossing each other.
  • the support structure produced in this way imparts dimensional stability, i.e. stiffness, to the shell mould. If the mirror blank is to be used for sun collectors a silver-plated thin glass plate not shown is thereupon glued on to the concave or flat surface of the support structure.
  • a thin plate 6 may be placed between the fibres and the moulding surface 5 in which case the plate compresses the fibres 3.
  • the plate 6 may be releasably fixed to the moulding surface, for example by vacuum which is applied through channels not shown in the mould part 4.
  • the thin plate 6 is preferably of the same material as the shell 1 and the plate is either flat or preformed to the desired curved form.
  • the compression may be carried out before or simultaneously with the heat treatment of the dusted fibres.
  • the thin glass plate fused-on in this way may be ground, polished and have a reflecting coating applied to it for simple optical applications of the mirror.
  • the fibres may be provided with the said coating with ceramics or glass powder dust either by being mixed together with the dust in a drum, so called tumbling, or by emulsifying the fibres in a liquid together with the powder dust, whereupon the liquid is removed.
  • the fibres 3 may consist of mats of glass fibres, said mats being provided with a coating of the said dust.
  • the shell mould filled in this way with several layers of mats is heat treated to the melting temperature of the glass dust which then melts and wets the fibres of the mats. After a controlled cooling the said three-dimensional network is obtained, which may be regarded as a closed framework construction which imparts optimum dimensional stability to the shell 1.
  • a mixture of mats of glass fibre and unarranged short er fibres may occur, it being presupposed that the mats and the fibres, respectively, are provided with said dust coating.
  • the uppermost material layer of the shell mould consists of a fibre mat on to which the thin plate 6 is either glued or fastened by melting during the heat treatment.
  • glue may be used, for example UV-hardening glue, which is allowed to wet the fibres and the fibre mats, respectively.
  • the finished mirrors are to be used in an environment where they are subjected to bending stresses it is suitable to reinforce the support structure with long fibres which are placed in close connection with at least one of the two principal surfaces of the finished mirror.
  • the long fibres are orientated such that their direction agrees with the direction in which the stresses act.
  • These long fibres are preferably of the same material as the rest of the fibre material of the support structure.
  • the long fibres may either be provided with a coating of said dust of glass or ceramics powder or be wetted with said glue, and they are baked into the support structure together with the other fibres of the support structure in connection with the three- dimensional network being produced.
  • the said long fibres to which the said orientation is imparted consist of a material the coefficient of thermal expansion of which is greater than that of the shell.
  • These long fibres are placed near the principal surfaces of the shell, i.e. the external surfaces, whcre owing to the wind forces the stress is greatest.
  • the whole assembly is subjected to a controlled cooling, a contraction strain being then created to a particularly marked degree in the long fibres since their coefficient of thermal expansion is greater than that of the shell.
  • the long fibres shrink and thereby cause a tensile stress in the fibre and a corresponding compressive stress in the shell along its principal surfaces.
  • each principal surface is compressed in the direction in which the long fibres are orientated.
  • the rest of the support structure may, instead of fibres or glass fibre mats or glass fibre felts, consist of micro spheres of the type mentioned in the said patent applications which have been provided in the abovementioned way with a coating of dust of glass the melting temperature of which is lower than that of the shell 1, or of foam glass produced in the way described in the said patent applic ations .

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Laminated Bodies (AREA)

Abstract

Ebauche de miroir comprenant une coquille (1) en verre ou ceramique, dont la forme correspond sensiblement a celle du miroir fini, et une structure de support formant un reseau tridimensionnel fixee a la coquille et remplissant celle-ci. La nouveaute de l'invention consiste en ce que la structure de support comprend des fibres (3) d'un materiau dont le coefficient de dilatation thermique est adapte a celui de la coquille, ainsi qu'un liant qui relie solidement les fibres entre elles et a la coquille. En utilisant des fibres dont le coefficient de dilatation thermique est superieur a celui de la coquille on peut conferer une precontrainte a l'ebauche de miroir.
EP19810902946 1980-10-22 1981-10-21 Ebauche de miroir Withdrawn EP0071605A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8007420 1980-10-22
SE8007420A SE8007420L (sv) 1980-10-22 1980-10-22 Spegelemne

Publications (1)

Publication Number Publication Date
EP0071605A1 true EP0071605A1 (fr) 1983-02-16

Family

ID=20342057

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810902946 Withdrawn EP0071605A1 (fr) 1980-10-22 1981-10-21 Ebauche de miroir

Country Status (4)

Country Link
EP (1) EP0071605A1 (fr)
JP (1) JPS57501894A (fr)
SE (1) SE8007420L (fr)
WO (1) WO1982001421A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3225566C2 (de) * 1982-07-08 1987-03-19 Flabeg GmbH, 8510 Fürth Spiegel für Solar-Reflektoren
US4554197A (en) * 1984-06-18 1985-11-19 Corning Glass Works Fiber reinforced glass/glass-ceramic mirror blanks
FR2574953B1 (fr) * 1984-12-19 1988-09-02 Centre Nat Rech Scient Substrat de miroir, notamment pour optique de precision, et procede pour sa fabrication

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1451397A (en) * 1974-04-11 1976-09-29 Wingard Ltd Mirrors
FR2345736A1 (fr) * 1976-01-28 1977-10-21 Commissariat Energie Atomique Reflecteur de construction legere
US4256378A (en) * 1979-07-02 1981-03-17 United Technologies Corporation Graphite-glass composite laser mirror
DE3007097C2 (de) * 1980-02-26 1982-05-19 Messerschmitt-Bölkow-Blohm GmbH, 8000 München Verfahren zum Herstellen eines Bauteils mit einer hochgenauen Oberfläche

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8201421A1 *

Also Published As

Publication number Publication date
SE8007420L (sv) 1982-04-23
WO1982001421A1 (fr) 1982-04-29
JPS57501894A (fr) 1982-10-21

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Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19821012

AK Designated contracting states

Designated state(s): AT CH DE FR GB LI LU NL SE

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19840229