Method for the production of glass components

Abstract

A method for the production of glass components, an apparatus for carrying out the method, and a glass component that is obtainable through the method are provided. The method is a drawing method wherein a forming zone of a preform is heated to a temperature that allows drawing of the glass. The method includes a forming zone of the preform that is very small. Thereby the width of the preform is decreased to a smaller extent than its thickness. The glass components that can be obtained by this method have very smooth surfaces.

Claims

1. A method for redrawing of glass, comprising the steps of: providing a blank of glass having an average thickness D and an average width B, wherein the width B of the blank is higher than the thickness D thereof; heating a deformation zone of the blank; and drawing of the blank to an average thickness d and an average width b, wherein the deformation zone is the part of the blank in which the blank has a thickness of between 0.95*D and 1.05*d and wherein the deformation zone has a height of at most 250 mm, and wherein the ratio B/b is at most 2.

2. The method according to claim 1, wherein the deformation zone has a height of at most 100 mm.

3. The method according to claim 2, wherein the glass of the blank has a viscosity .sub.2 of at most <10.sup.7.6 dPas in the deformation zone.

4. The method according to claim 1, wherein the glass of the blank has a viscosity .sub.2 of at most <10.sup.7.6 dPas in the deformation zone.

5. The method according to claim 1, wherein the glass is a technical glass or an optical glass.

6. The method according to claim 1, wherein the method further comprises the step of cooling the blank after leaving the deformation region such that the cooling results in a viscosity change of at least 10.sup.6 dPas/s.

7. The method according to claim 1, wherein the deformation zone of the blank is heated in a redrawing apparatus which at least comprises a heating facility being selected from the group consisting of a resistance heater, a burner arrangement, a radiation heater, a laser, and combinations thereof.

8. The method according to claim 1, wherein the ratio of width B to thickness D of the blank is at least 5.

9. The method according to claim 1, wherein the thickness d is at most D/10.

10. The method according to claim 1, wherein the blank is drawn in a region below the deformation zone with a drawing facility.

11. The method according to claim 1, wherein the blank is fed from a region above deformation zone into the direction of deformation zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows in a schematic manner a side view of an exemplary embodiment of a redrawing apparatus according to the present invention.

(2) FIG. 2 shows the schematic operating sequence of a method according to prior art.

(3) FIG. 3 shows in a schematic manner a blank.

(4) FIG. 4 shows in a schematic manner a mode of action of an optional radiation heater.

(5) FIG. 5 shows the dependency of the widths of a glass product on the height of the deformation zone in a redrawing process.

(6) FIG. 6 shows the distribution of thickness d of a flat glass product across width b of an example (example 3).

(7) FIG. 7 shows in an exemplary manner average width b (gross width) of the drawn glass component and the drawing force.

(8) FIG. 8 shows a plot of the ratio of average width b (gross width) to average thickness d (net thickness) of the drawn glass component and the drawing force which is necessary for drawing, each in dependency on the viscosity of the glass of the blank.

DETAILED DESCRIPTION OF THE DISCLOSURE

(9) FIG. 1 shows in a side view the schematic structure of an exemplary embodiment of a redrawing apparatus according to the present invention. In the redrawing apparatus a blank 1 is moved top down through the apparatus. The redrawing apparatus comprises two heating facilities 2 being arranged in a center region of the apparatus. In this embodiment the heating facilities are shielded by baffles 3 in such a manner that a deformation region 4 is formed. A part of blank 1 which is disposed in deformation region 4 is heated such that it reaches temperature T.sub.2. This part of the blank is the deformation zone 5 having height H. Blank 1 is drawn down with the help of a drawing facility 6 which here is realized in the form of two driven rolls. As a result that the feeding facility 7, here also designed in the form of rolls, feeds blank 1 in a speed which is lower than the speed of the drawing facility 6, blank 1 is deformed in deforming region 4. Because of that blank 1 becomes thinner; the thickness after the deforming step d is smaller than that prior the deforming step D. Prior to feeding blank 1 into deformation region 4 it is preheated to temperature T.sub.1 with the help of preheating facility 8, here symbolized by a burner flame. After passing the deformation region 4 blank 1 is fed into a cooling facility 9, here symbolized by an ice crystal.

(10) FIG. 2 shows the schematic operating sequence of a method according to prior art. A difference to FIG. 1 is that in this case the change of width B of the blank is shown. Blank 1 is moved into a deformation region 4. Deformation region 4 is heated with a heating facility 2here a resistance heater. Blank 1 is heated such that in the glass a deformation zone is formed, where the glass has low viscosity. But this deformation zone is much larger than the deformation zone according to the present invention due to the lack of any limitation and the height of heating facility 2. So a particularly distinct reduction of the width of blank 1 results. Also a drawing facility 6 is shown which draws blank 1 into the longitudinal direction.

(11) FIG. 3 shows in a schematic manner a blank with length L, thickness D and width B.

(12) FIG. 4 shows in a schematic manner the mode of action of an optional radiation heater which may be used as a heating facility 2. Dependent on its distance to blank 1 the height of deformation zone 5 is different. In this figure it is also shown, how by means of shadowing facility/baffle 3 the deformation zone can be limited to obtain a deformation zone 5 with a height which is as low as possible. Thus both, the distance and also the design of the heating facility 2 may serve for the adjustment of the height of deformation zone 5.

(13) FIG. 5 shows the dependency of the widths of a glass product on the height of the deformation zone in a redrawing process. It can be seen that a deformation zone with a lower height results in a reduction of the decrease of the width of the blank.

(14) FIG. 6 shows the distribution of thickness d of a flat glass product across width b of the product of example 3. Here can be seen that the sheet edges at the rims of the glass product are relatively small. The part with a homogenous low thickness can be used for the application of the glass product, but the sheet edges have to be removed. The use of the method according to the present invention results in a particularly high rate of yield.

(15) FIG. 7 shows in an exemplary manner average width b (gross width) of the drawn glass component and the drawing force which is required for drawing, each in dependency on the viscosity of the glass of the blank in the deformation zone, in the case of a blank having a thickness of 4 mm and a width of 400 mm which is fed into a muffle with a height of 40 mm with a speed of 5 mm/min. The glass is drawn with 200 mm/min. It can be clearly seen that the required drawing force increasingly increases with increasing viscosity. Furthermore it can be seen that average width b of the product obtained increasingly decreases with increasing viscosity.

(16) FIG. 8 shows in an exemplary manner the ratio of average width b (gross width) to average thickness d (net thickness) of the drawn glass component and the drawing force which is necessary for drawing, each in dependency on the viscosity of the glass of the blank in the deformation zone, in the case of a blank having a thickness of 4 mm and a width of 400 mm which is fed into the muffle with a height of 40 mm with a speed of 5 mm/min. The glass is drawn with 200 mm/min. It can be seen that the ratio b/d of the product obtained increasingly decreases with increasing viscosity. In comparison to the decrease of average width b with increasing viscosity shown in FIG. 7 the ratio b/d decreases in a relatively higher extent with increasing viscosity.

EXAMPLES

Example 1

Drawing of Optical Glass

(17) Here the optical glass (fluorophosphate glass) is cast into a bar form having dimensions of e.g. B=120 mm and D=14 mm. Then this bar is inserted into the redrawing apparatus and heated in a preheating zone to a temperature which corresponds to the glass-transition point (ca. 10.sup.13 dPas). By moving the blank downwards into a deformation region with a height of 40 mm and a temperature which at least corresponds to a viscosity of <10.sup.7.6 dPas and in the maximum a viscosity of ca. 10.sup.4 dPas. The leaving glass is guided through a cooling zone and fixed in a drawing facility and drawn faster than the blank is fed. So this results in a ribbon of glass having a width of 100 mm and an average thickness of 0.3 mm.

Example 2

Drawing of Flat Glass

(18) As a blank a flat glass (Borofloat) having a width of 300 and a thickness of 10 mm is provided. After passing a preheating zone (ca. Tg) this blank is moved into the deformation zone. This zone is heated over the whole width and a height of 20 mm to a minimum temperature which corresponds to a viscosity of 10.sup.4 dPas to <10.sup.7.6 dPas. After passing a cooling zone the leaving glass is fixed in a drawing facility. By a suitable selection of the speed of the blank and the speed of the product an average thickness of at most 100 m is adjusted and the product is coiled onto a cylinder. So this results in a product having a width of at least 250 mm.

Example 3

Drawing of Flat Glass

(19) A blank made of flat glass (Borofloat) having a width of 50 mm and a thickness of 1.1 mm is provided. After passing a preheating zone (ca. Tg) this blank is moved into the deformation zone. In the deformation zone the glass is heated over the whole width and a height of 3 mm to a temperature which corresponds to a viscosity of ca. 10.sup.7 dPas. After passing a cooling zone on the leaving glass a weight is attached (drawing facility). By a suitable selection of the speed of the blank and the size of the weight an average thickness of about 50 m is adjusted. So this results in a product having a width of at least 40 mm.

(20) TABLE-US-00001 TABLE 1 Examples and comparative examples U.S. Pat. No. U.S. Pat. No. According 3,635,687 3,635,687 to the without edge with present cooler edge cooler invention Length of deformation 508 508 30 region [mm] Width of blank B [mm] 508.0 508.0 120.0 Thickness of blank D [mm] 6.4 6.4 14.0 Ratio B/D 80.0 80.0 8.6 Width of component b 19.1 61.4 100.0 [mm] Average thickness of 0.1 0.1 0.3 component d [mm] Ratio b/d 250.0 853.3 333.3 (Ratio b/d)/(ratio B/D) 3.1 10.7 38.9

LIST OF REFERENCE SIGNS

(21) 1 blank 2 heating facility 3 baffle 4 deformation region 5 deformation zone 6 drawing facility 7 feeding facility 8 preheating facility 9 cooling facility