GB2097779A - Method of heat polishing pattern cut glassware - Google Patents

Abstract

The invention relates to treatment of glassware. Polishing of glassware is carried out by a beam of concentrated heat flow with sequential movement thereof along the entire surface of the glassware being polished, the selectable effective width of the concentrated heat flow being substantially less than the circumference of the ware being processed, each element of the cut pattern being exposed to equal heat stress and subjected to a single- acting pass of the concentrated heat flow. At least two beams of the concentrated heat flow are employed for polishing. The invention can find application in the glass industry for manufacturing richly ornamented glassware, mostly of lead glass. <IMAGE>

Description

SPECIFICATION Method of heat polishing pattern cut glassware This invention relates to the treatment of glassware, and more particularly to methods of heat polishing the surface of cut patterned glassware obtained by grinding the surface after glass forming or in any combination of the two operations.

The present invention can find application in the glass industry for manufacturing richly ornamented glass tableware predominantly from lead glass, such as tumblers, goblets, flower vases, illuminating glassware, such as wall fittings, luminaries, chandelier components, etc., the surface of which needs to be perfected.

The invention resides in that in a method of heat polishing pattern cut glassware through the application of high heat against the surface thereof, according to the invention, the polishing is effected by a beam of concentrated heat flow moving sequentially along the entire surface area of the ware, the effective width of the heat flow being substantially less than the circumference of the ware being polished, each element of the cut pattern being exposed to equal heat stress.

Preferably, for heat polishing various glassware having dissimilar designs cut on the surface thereof the selectable width of the concentrated heat flow ranges between 0.5 and 6.0 mm.

Preferably, each element of the cut pattern is subjected to a single-acting pass of the concentrated heat flow.

Glassware polishing according to the invention may be carried out through the application of at least two beams of the concentrated heat flow.

Disclosed hereinbelow is the essence of the present invention.

A flow of heat of sufficient intensity causes the surface of the glassware being polished as well as the pattern cut thereon to fuse to thereby smooth out the surface irregularities under the action of the surface tension forces.

When polishing glassware from lead containing glass the heat flow must contain no reducing gases, since under the action of the latter the lead oxide of the glass surface tends to reduce to metallic lead which leads to the appearance of dullness and consequently to defective end products.

In order to improve the efficiency of application of the gas flow against the pattern cut surface of the glassware being polished, the flow is preferably concentrated into a beam, the effective width of the beam being substantially less than the circumference of the glassware being polished.

The application of the burner gases as heat carriers acts to facilitate the heat transfer throughout the entire depth of the cut pattern in the course of heat polishing which ensures a uniform polishing all the pattern cut elements.

The use of alternative concentrated heat flows provides, accordingly, for a strictly limited portion on the generatrix of the ware to be heated.

Each given portion of the surface area of the glassware being polished is subjected to the concentrated heat flow only once, which prevents structural deformations to occur as a result of low heat conductivity of glass.

By virtue of the fact that only a limited portion of the glassware is affected by heat at any given time in the course of operation, a concentrated heat flow of substantially higher temperature can be applied, which affords to increase the efficiency of the whole process.

Gas burners, plasma generators, radiation heaters or any other suitable means can be used as the sources of high heat.

Conforming to the aforedesclosed operating conditions will result in a highly efficient method of heat polishing pattern cut glassware.

Other objects and advantages of the present invention will become apparent from the following detailed description of the embodiments thereof taken in conjunction with the accompanying drawings, in which: Figure 1 illustrates the general principle for carrying out a method of heat polishing glassware according to the invention; and Figures 2 and 3 are schematic representations of the effect of the heat flow on various elements of a cut pattern.

Referring now to Fig. 1, there is shown a means for heat polishing glassware embodying the principles and features of the present invention.

The means comprises a burner 1, a nozzle 2 producing a heat beam 3, and a turntable 4 with a glassware 5 fixed thereon.

Figs. 2 and 3 show schematically, by way of illucidating the method according to the invention, the effect of the heat flow on the elements of the cut pattern.

Disclosed hereinbelow are specific examples for practising the method according to the invention.

Example 1 A glassware from lead glass, such as a tumbler, having a design pattern cut at the surface thereof, the width of the ground elements of the design being essentially 3 mm, is heated in a conventional lehr or kiln to a temperature essentially below the softening point of glass, e.g. to 480"C. The ware being fixed to a turntable is then subjected to a flow of concentrated heat, the width of the flow being within from 1.0 to 2.5 mm, the temperature thereof amounting to 1 580 C. While maintaining a preset rate of rotation, heat polishing is conducted by turning the ware by 360'-390'.

One gas burner is used as a source of the heat flow.

The heat flow covers the entire height of the ware along the generatrix thereof.

By heating a portion of the surface area of the ware which is substantially less than the total surface area thereof the concentrated heat flow acts to heat that portion to a temperature at which flowing begins.

The shape of the heat flow and duration of its application against a limited portion of the surface area of the ware are such that the wall structure or the rest of the ware is never heated throughout its entire thickness to the temperature attained at the surface area subjected to the heat flow, which prevents deformation of the ware and distortion of the cut pattern to occur.

Inasmuch as the heat flow is commensurable with the elements making up the cut pattern, each element of the cut pattern is subjected to a thermal stress of equal value.

Shown schematically in Figs. 2 and 3 is the effect of the heat flow on the elements of the cut pattern.

After sequential passing of the concentrated heat flow throughout the entire surface area of the pattern cut glassware, a smooth, glazed surface free of deformations and distortions of the design is obtained, the definition of the pattern being preserved.

The thus polished ware is then conveyed into a conventional lehr or kiln to anneal or remove the strains therefrom.

Example 2 A lead glass ware, such as a goblet, having a design pattern ground at the outer surface thereof, the width of the cut pattern elements being essentially within the range of from 1.0 to 2.5 mm, is subjected to heat polishing conforming to the operating conditions described heretofore in Example 1, the width of the heat flow being between 0.5 and 1.5 mm. The stem and base of the ware are not subjected to the heat treatment.

Example 3 A larger lead glass articie, such as a flower or fruit vase, having a design at the surface thereof cut by grinding, the width of the design elements being within the range of from 4 to 1 2 mm, is heated in a conventional lehr or kiln to a temperature not in excess of the glass softening point, e.g., to 460"C. The ware being fixed on a turntable is then subjected to a concentrated heat flow, the width thereof ranging from 3 to 6 mm. Two or three gas burners serve as sources of the heat flow.

When two burners are used, the ware is turned by 180 , whereas with three burners the ware is turned 120 . Heat polishing conditions must conform to those referred to in Example 1.

Example 4 Lead or soda lime glass articles, such as formed commercial ware, not being ground but yet having design indentations within the range referred to in Examples 1 to 3, are subjected to heat polishing essentially conforming to the operating conditions disclosed in said examples. Heat polishing is carried out here to improve the surface quality as well as to increase the mechanical and thermal strength of the glassware.

Therefore, the method of heat polishing pattern cut glassware features, as compared with the prior art methods, substantial technological, economical and ecological advantages, among which are the following: simplification of the technology of the process; improvement in the quality of the end product; saving on the material, energy and labor expenditures; reduction of the cost of the equipment required; improvement of the sanitary conditions for the operators and protection of the environment; and creating potential conditions for automated processing.

Claims (5)

1. A method of heat polishing pattern cut glassware by subjecting the surface thereof to high heat, wherein the heat polishing is carried out by a beam of concentrated heat flow with sequential movement thereof along the entire surface of the glassware being heat polished, the selectable effective width of the concentrated heat flow bieng substantially less than the circumference of the ware being processed, each element of the cut pattern being exposed to equal heat stress.

2. A method according to claim 1, wherein the width of the concentrated heat flow ranges from 0.5 to 6.0 mm.

3. A method according to claim 1, wherein each element of the cut pattern is subjected to a single-acting pass of the concentrated heat flow.

4. A method according to claim 1, wherein heat polishing glassware is carried out by at least two beams of the concentrated heat flow.

5. A method according to any of the preceding claims substantially as heretofore described with reference to and as illustrated in the accompanying drawings.