DE1938642U - PRESS FORM FOR MANUFACTURING OPTICAL ELEMENTS. - Google Patents

Description

Patent Attorneys HM. 1 ] k 3 O 2 * "2, 3" 66 ₅ 1 ₂ 1965

Dft. RUDOLF BAUER © pforzheim, ^ * · ^?

Westliche 31 at Leopoldplatz Dipl.-Ing. Telephone 2429O

HELMUTHUBBUCH

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

The innovation "relates to a mold for manufacture optical elements made of powder, in which the powder under high pressure and high temperature into a solid polycrystalline - body is transformed. Magnesium fluoride, among others, are suitable for this purpose. Zinc sulfide and. Zinc selenide,

According to the innovation, relatively large optical Elements can be produced by hot pressing from such powders without having to use a “particularly high pressing pressure would have to apply.

With the compression mold of the innovation, it is possible to reduce the pressure over the . Distribute powder mass so evenly that no unwanted Curvatures arise.

'These advantages' are used in the press form of the innovation by the Cooperation between a ring and a fitting part that deforms the ring when the pressure is applied so that the

-. Powder in the ring is compressed uniformly. The fitting part has a conical shell, which is attached to the inner wheel of the ring

Press seated and presses the ring apart by wedge action, whereby the ring wall is protected against kinking.

In the compression mold of the innovation, a relatively thin-walled ring can therefore be used and also the compression ■ pressure can be relatively small.

Therefore, relatively large elements can also be relatively large small presses.

To produce curved optical elements, the mold of the invention has concave or convex projections and corresponding Hollow molds. Here, the projections are equipped with ring-expanding wedges and consist of a material, which under Heat and pressure are something plastic and deformable - and strive for is to deform from the center outwards and the pressure over the curved mass of the powder as evenly as possible to distribute.

The drawing shows, for example, schematically and partially in section, two preferred embodiments of the innovation. In the drawing is:

Fig. 1 is a cross section through a mold for the production of relatively large optical disks and ver

2 shows a section through a mold for producing curved optical elements.

-According to Fig. 1, magnesium fluoride powder X is made into a ring 1 Mild steel with relatively thin walls of rectangular cross-section poured. The die jaws consist of a pair of upper and lower steel plates 2 and 3 each other opposing surfaces 2A and 3A are horizontal and flat.

The ring 1 lies on the surface 3A. A mild steel disk 4- is attached to the surface 2A. On the surface 2A it has the same diameter as the outer jacket 5 of the 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 an aluminum plate 7 is also placed on the poured powder X. The surfaces of the aluminum plates 7 and 8 facing the powder are covered with difficult-to-melt plates 9 and 10, respectively. The surface of the press jaw 3 and the surface of the disk ^L \ - are covered with mica plates 4-A and 3A. Between the press jaw 2 and the disk 4- there is a layer 11 made of powder that is difficult to melt. A thermocouple 12 is embedded in the press jaw 2, which shows the temperature of the press jaw on a millivoltmeter (not shown). 13 denotes the coil of an induction furnace which surrounds the ring 1 and the pressing jaws 2 and 3 and heats them. The device described is inserted into an 80 t press, not shown. The aluminum layers prevent sticking during hot pressing and the mica layers prevent the aluminum powder from penetrating into the powder X. Between

_ Il _

the press jaws 2. and 3 and the press itself are thick, heat-insulating Plates 14 and 15 inserted. The pressing process is as follows:

Grade A: The magnesium fluoride powder X, the 3 percent by weight

Amonium fluoride is added, is poured into the ring 1, which rests on the lower press plate 3. The bulk material must protrude beyond the edge of the ring. The upper press jaw 2 is then pushed over the ring 1 and a pressure of about is now applied to the arrangement formed in this way at room temperature 2t / cm exercised. The powder then forms a dense compact mass in the ring. The ring with the mass comes out of the press removed.

Level B: The thin layers 7 _? 8 and 11 of aluminum powder are applied to surfaces 4A, 3A and 2A of the mold by sifting the aluminum powder through bronze gauze. The thin mica layers 9 and 10 are placed on the aluminum layers 7 and 8 and finally the ring 1 with the pressed powder is pushed in between, as shown in FIG. 1. The temperature is now used by the induction furnace 13 to about 75O ⁰ C and simultaneously a pressure of from about 2t / cm applied to the powder X. The pressure and temperature conditions are maintained for 10 minutes. The pressure is then released and the heating coil 13 is switched off. This treatment turns the powder into a polycrystalline solid disk

is transparent to infrared with a minimum of absorption and scattering.

During the hot pressing, the conical jacket 6 of the disk 4- pushes the ring 5 apart to form a truncated cone and penetrates into it insert it while compressing the powder Z evenly. As a result, the disk 4- prevents the ring 1 from being uneven Buckling under the pressure. As a result, the wall thickness of the ring 1 can be reduced to a minimum. this means but that the pressure necessary to produce both small and large disks is relatively small Press can be generated »As a result of the deformation of the ring 1 to form a truncated cone, the powder X at the edge of the disk is also only slightly stressed, so that the finished Easier to remove the optical disc from the ring Read.

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

^ P + MgO -> MgF ₂ + 2NH-, + H _p 0

In this way the impurities are removed from the powder, without any harmful substance being added to the product. needs to be.

The optical disc in ring 1 is then set to about 250 ° C cooled and the ring and washer are removed from the press.

When the optical disc has cooled to room temperature, the ring 1 is removed by dissolving it in nitric acid. The optical disc is ground and polished to the desired thickness.

In the mold according to FIG. 2, the upper part consists of a convex projection 16 made of mild steel with a curved surface. The protrusion on his puss is conical. This conical part 17 sits on the inner edge of the thin-walled mild steel ring when pressed 18 on. The puss of the projection 16 sits on the lower surface 2A of the press jaw 2. The lower part of the press mold consists from the press jaw 5 with the concave recess 19, the top of the Ring 18 is seated. The mutually facing surfaces of the projection 16 and the recess 19 are made of low-melting aluminum powder lined so that the optical element can be released more easily from the mold.

When the optical element is hot-pressed, the ring "B expressed evenly to a truncated cone and the protrusion 16 penetrates into the recess 19 with the powder X being compressed. The projection 16 is made of plus steel and is under the hot pressing conditions somewhat plastic, so that it pushes itself outwards from the center. This lateral deformation of the projection 16 the pressure is evenly over the whole curved Mass of powder X distributed. There is a tendency

of the projection 16 to press harder at the edges than in the Middle, so that the optical element would be thinner at the edges. However, this disadvantage can be eliminated by that the projection 16 at the foot has a smaller radius than the recess, so that when the projection penetrates into the Powder X the parts of the mold near the edges are better filled,

Curved windows can be shown in a manner similar to that shown in FIG can be produced by hot pressing.

Claims (8)

You. RUDOLF BAUER na, -M / nno ®rfF9R? ÄEIM 'Dipl.-Ing. s «H. || 4 abZ * & J & d $ & HELMUT HUBBUCH Protection claims: 1.) Press mold for the production of solid -po ^ crystalline optical elements by hot pressing of powder, characterized by a ring for receiving the powder and a fitting part cooperating with the input, which deforms the ring by wedge action, compresses the powder uniformly in it and attaches it to Prevents kinking. j ""'· 2.) Press mold according to claim 1, characterized in that the fitting part rests on the ring edge during pressing. 3.) Press mold according to claim 1 or 2, characterized in that that the fitting part has a conical jacket that rises up on the inside of the ring edge, so that the ring moves when it is pressed expands and is thus prevented from kinking. Ά.) Press mold according to one of claims 1 to 3, characterized in that that the ring has a rectangular cross-section and the fitting part has a flat disc with a conical side wall is, which stands up when pressing the inner edge of the ring. 5.) Press mold according to claim 3 with opposite convex Projections and concave recesses for the production of optical elements with curved surfaces, thereby marked net that the projection at its foot is a koiic ring surface and a ring with a rectangular cross-section is located in the recess. 6.) Press mold according to claim 5, characterized in that the projection is a dome and the recess is designed in a correspondingly concave dome-shaped manner. 7.) Press mold according to claim 5 or 6, characterized in that that the projection is made of material that becomes plastic and deformable under heat and pressure and strives under pressure is to expand from the center outwards, thereby making it a proportionate one uniform distribution of pressure on the curved To produce mass of powder. 8.) Press mold according to one of the preceding claims, characterized in that characterized in that the facing surfaces of the press have layers of powder that is difficult to melt, e.g. aluminum powder have to facilitate the removal of the elements from: the surfaces and also flexible, difficult-to-melt foils e.g. from Mica on the weld "fusible powder layers have to allow penetration to prevent the difficult-to-melt powder in the material of the optical element.