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Elliptic Glass Forming Process

IP.com Disclosure Number: IPCOM000075210D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Berger, CM: AUTHOR [+4]

Abstract

Elliptic cylinder mirror blanks are made by sagging a glass plate or sheet over a mold surface in a heated, evacuated chamber. To achieve perfect conformity with the mold surface, it is important that sagging occur progressively along the line of contact 4 between glass sheet 5 and mold 6, as in Fig. 3, rather than having the distal end droop into contact before the intermediate portion has contacted the mold, as in Fig. 2. This is accomplished by having the mold hotter than the glass so that the glass is hottest where it contacts the mold.

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Elliptic Glass Forming Process

Elliptic cylinder mirror blanks are made by sagging a glass plate or sheet over a mold surface in a heated, evacuated chamber. To achieve perfect conformity with the mold surface, it is important that sagging occur progressively along the line of contact 4 between glass sheet 5 and mold 6, as in Fig. 3, rather than having the distal end droop into contact before the intermediate portion has contacted the mold, as in Fig. 2. This is accomplished by having the mold hotter than the glass so that the glass is hottest where it contacts the mold.

As in Fig. 1, a glass plate 5 is secured by a graphite clamp 8 to a graphite mold 6, having a surface 7 to which it is desired to have the glass conform. The clamp 8 is retained by stainless steel screws 9 and assembly is placed in a vacuum furnace. The complete cycle is as follows: 1) Evacuate to 10/-4/ Torr or lower

2) Bring furnace up to 650 degrees C at 1300 degrees C/hr

3) Soak 10 minutes at 650 degrees C

4) Bring furnace to 670 degrees C at 850 degrees C/hr

5) Soak 10 minutes at 670 degrees C

6) Bring furnace to 760 degrees C at 1300 degrees C/hr

7) Soak 10 minutes at 670 degrees C

8) Shut off furnace, cool to 200 degrees C

9) Cool to 100 degrees C

10) Open furnace and remove mold.

In this cycle, the furnace temperature is programmed to read 650 degrees C in the shortest possible time (limited by power input) followed by a 10 minute soak to allow the mold to reach thermal equilibrium. The t...