DE1442576A1 - Press mold for the production of optical elements - Google Patents

Description

Barr and Stroud Ltd., Anniesland, Glasgow / Scotland Press mold for the production of optical elements.

The invention relates to a mold for the production of optical elements from powder, in which the powder under high Pressure and high temperature is transformed into a solid polycrystalline body. Magnesium fluorine, among others, is suitable for this purpose id, zinc sulfide and zinc selenide.

According to the invention, relatively large optical ■ elements made from such powders by hot pressing without a particularly high pressure should apply.

With the mold of the invention it is possible to overcome the pressure to distribute the powder mass so evenly that there are no unwanted curvatures.

These advantages are achieved in the die of the invention the interaction of a Hinges with a fitting part is achieved, which deforms the -ttng when the pressure is applied, that the powder in the ring is compressed uniformly.

909810/06 5 0

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The fitting part has a conical dumbbell, which is the inner edge the .Ring is seated when pressing and the ring by wedge effect pushes apart, whereby the hi.agwand against> Buckling is protected.

In the mold of the invention can therefore be a relatively find thin-walled Hing use, and the pressure can be relatively small.

Therefore, relatively large. Elements in ver ■ relatively small presses are produced.

To produce curved optical "elements, the press mold the invention concave or convex projections and corresponding Hollow molds. Here are the projections with ring-expanding files and consist of a material, which becomes somewhat plastic and deformable under heat and pressure and = ο »β * strives i. @ a from the center outwards to deform and to distribute the pressure as evenly as possible over the curved mass of the powder.

The drawing shows, for example, schematically and partially in section two preferred embodiments of the -lürfindung

In the drawing is:

- ¹³ Ig. 1 a cross section through a - ^ ressfOrm for production

relatively large optical disks and . 2 shows a section through a junction for producing curved ones optical elements.

, -. ; . 90981070650

'Gohoim ■■ H42576

According to J? Ig, 1, magnesium fluoride powder X is wrapped in a ring 1 made of mild steel with relatively thin walls rectangular Cross-section poured. The press jaws of the form "order a pair of upper and lower steel plates 2 and 3 of each other opposing surfaces 2A and 3A are horizontal and flat.

The ring 1 lies on the surface 3A. There is one on the surface 2A Flussta Ischeibe 4 "attached, ie has on the surface 2A the same diameter as the outer jacket 5 cLes ring 1 and rests against the inner edge of the ring 1 with a conical surface 6. The ring 1 is placed on an aluminum plate 8 and also An aluminum plate 7 is placed on the poured powder χ placed. The surfaces of the aluminum plgtttea facing the powder 7 geiegt. And 8 are with difficult to melt plates 9 or Io occupied. The surface of the press jaw 3 and the surface of the disk 4- are covered with mica plates 4-A and 3A. Between the press jaw 2 and the washer 4- there is one Layer 11 made of hard-to-melt powder in the press jaw 2 a -JOhermoelement 12 is embedded, which is not on a The millivoltmeter shown shows the temperature of the press jaw., 13 denotes the coil of an induction furnace, which surrounds the - * ing 1 and the press jaws 2 and 3 and heats them. The described Contraption . ird in a not shown 80 t press inserted ^ The 'aluminum strips prevent sticking during the de isspress ens and the mica layers penetrate of the aluminum powder into the powder X. Between the press jaws 2 and 5 and the press itself are thick heat-insulating Plates I ^ and 15 einp: e slide en.

'^; * 909810/0650

BATH ORIGINAL

1ΛΛ2

The process of eating is as follows: - .. '. ^;

Stage A _: The agnosium fluoride powder, the; 3 weight percent LmoniuEifluori'd is added, is poured into the ring 1, Ler thereby protrude on the lower Pressplafcte 3 ruht.- ⁰ Ie bed must labei the annular rim. The upper press jaw 2 is then pushed over the ring 1 and a pressure of about 2 t / cm is exerted on the arrangement formed in this way at room temperature. The powder then forms a dense, compact mass in the ring is removed from the press.

> Level B: The thin layers 7 »8 and 11 are made of aluminum powder

Spread on the areas 4A, JA and 2A of the porosity, - by sieving the powder of the Llumfänium through Brönoegaze. The thin layers of mica 9 and 10 are placed on the aluminum layers and 8 and finally the ring 1 with the pressed powder is pushed in between, as shown in FIG. 1. The temperature is brought to about 75 ° G by the induction furnace 13 and at the same time a pressure of about 2t / cm air is exerted on the powder X. The pressure and temperature retention limits are maintained for 10 minutes. The pressure is then applied and the heating coil 13 is switched off. This treatment transforms the powder into a polycrystalline solid disk for infrared with a minimum of absorption and scattering

Is permeable. . . '. ; _;

After the hot-pressing process, the conical casing 6 of the disk 4 presses the ring 5 apart to form a truncated cone and penetrates it with uniform compression of the powder . a.

BATH

As a result, the disc 4 hinderb the ring 1 a., An uneven Buckling under the pressure. As a result, the wall thickness of the ri.in.5e3 1 can be reduced to a minimum. However, this means that the pressure required for the production of both small and large disks from the same relatively small press can be produced-. As a result the deformation of the ring 1 to a truncated cone is about it In addition, the powder X on the surface of the disk is only slightly stressed, so that the finished optical disc is easier to tfing can be removed.

Before the extrusion process, the aluminum fluoride reacts with the magnesium oxide present as an impurity and forms magnesium fluoride, Ammonium and water, which both escape:

i? + ■ IgO »MgF ₂ . + 2NH ₅ +

this ./eise the impurities are removed from the powder, without causing any harmful substance to the product needs to be added.

iJie optical ocheibe in the ring 1 is datwi to about 25o ° C and cooled - ing ^L and öcaeibe be removed from the -Press, • IENN the optical Jctieibe is cooled to Haumtemperatur is the \ in ··; 1 is found by dissolving it in nitric acid. The optisctie jchöibe is ground to the desired disc and polished.

909810/0650

BATH ORIGINAL

In the case of the press mold, according to. - ⁰ Ig. 2 "the upper part is made of *. A convex projection 16 aas iflus steel with a curved." _ Surface, the projection is conical at its -ö'uss. This conical part 17 rests on the inner edge of the thin-walled steel ring 18 during the pressing. The foot of the Vorsprun. ^ 16 it sits on the Uhterfläclie 2.X the pressing jaw 2 consists of the lower part of the -Pressform aas -fressbacke 3 with the concave recess 19 which rests above the ^ ing 18th The mutually facing surfaces of the projection 16 and the recess 19 are lined with low-melting aluminum powder, so that the optical element is better released from the Eorm.

In the ^ -eisspressung the optical item generated v / ith the ^ 18 = -ing expressed uniformly to a truncated cone and the projection 16 penetrates into the recess: 19 under compression of the powder a -λ-. The projection 16 is made of J? Luss steel and becomes somewhat plastic under the pressure-sensitive conditions, so that it is pressed outwards from the center. Due to this lateral deformation of the projection 16, the pressure is uniform over the entire curve. ^ & Bse of the powder & distributed. There is a tendency of the projection 16 to press more at the edges than in the middle, so that the optical element would become thinner at the edges. This disadvantage can, however, be eliminated by the fact that the protrusion 16 on the outside has a smaller radius than the recess, so that when the protrusion penetrates into the powder JC, the parts of the shape near the edge are better filled. · ·

G-ekrüaimte i) ^v eiister else can as shown similarly in i'ig // "2 by i'-teisspressen generated; will.

Claims (8)

Patent claims: Press mold for the production of solid polycrystalline optical elements by pressing »powder, characterized by a hing for receiving the powder and a fitting part which cooperates with the hing and which forms the ring formed by each action, the powder in it is uniformly primes and prevents it from kinking. 2. Press mold naoh claim ^ 1, d ^ Ldu ^ ch characterized,; _4th that the fitting part rests on the edge when you - ^ res'sen. 3. Press mold according to claim 1 or 2, characterized in that that the fitting part has a conical jacket that corresponds to the Ring mouth stands up on the inside so that the fiing comes out when pressed stretches and is thus prevented from kinking 4. Press mold according to one of claims 1 to 3 »thereby characterized in that the ring has a rectangular cross-section and the fitting part has a flat washer with a conical side wall that sets up the inner edge of the ring during pressing. 5 »Press mold according to claim 3 with opposite convex Projections and concave recesses for manufacture optical cements with curved surfaces » 8098! 0 / 06EO BAD ORfGlNAL η c «- indicates that the gate jump at its o'out a conlibehe Ring surface and in, the recess has a Hing with a rectangular ' cross section lies. 6. Press mold according to claim 5j, characterized in that the projection is a dome and the recess accordingly is designed concave dome-shaped. 7. Press mold according to claim 5 or 6, characterized in that that the projection is made of material that is exposed to heat and pressure becomes plastic and deformable and strives under pressure is to expand from the ^ entrum to the outside in order to thereby to produce a relatively uniform distribution of the pressure on the curved mass of the powder. 8. Press mold according to one of the preceding claims, characterized characterized in that the mutually facing surfaces of the pressing parts of difficult-to-melt powder e.g. Aluminum powders have to facilitate the removal of the elements from the surfaces and also flexible difficult to sciaielzbaren Foils e.g. made of axIimmer on the difficult-to-melt powder layers have to prevent the powder from being melted in to prevent the 'material of the optical element., ■ ». 9098 10/0650