GB2225004A

GB2225004A - Process and apparatus for the production of multiple-layer hollow glass objects

Info

Publication number: GB2225004A
Application number: GB8923129A
Authority: GB
Inventors: Franz Gunthner
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1988-10-15
Filing date: 1989-10-13
Publication date: 1990-05-23
Also published as: GB8923129D0; DE3835228A1

Description

2d- 2 z 5004 PROCESS AND APPARATUS FOR THE PRODUCTION OF MULTIPLE-LAYER

HOLLOW GLASS OBJECTS The invention relates to a process for the production of multiple-layer hollow glass objects and to an apparatus for performing the process.

Hollow glass objects, such as, for example, bottles or flasks, are usually produced with relatively great wall thicknesses and exhibit a correspondingly high weight. This large wall thickness is required for safety reasons in order to obtain adequate strength because the conventional methods of producing hollow glass articles, for example by blowing or vacuum blowing, result in hollow glass objects showing a relatively high fluctuation in wall thickness. Since the strength of hollow glass objects is determined by their weakest point, a relatively large average wall thickness must be provided.

Reduction of the wall thickness and/or raising the strength of the glass is desirable in order to save costs of material and to diminish the danger of glass fracture.

A conventional possibility for.increasing the strength of hollow glass objects is the use of multiplelayer glass exhibiting a surface layer, placed under compressive stress during cooling, made of a glass type having a smaller coefficient of thermal expansion than the glass located therebeneath.

Other conventional processes for increasing glass strength are thermal or chemical (ion exchange) hardening methods. However, these procedures are not well suited for hollow glass objects. Thermal hardening is possible effectively only in case of wall thicknesses larger than about 3 mm, and can be performed in the interior of a bottle having a narrow neck only with difficulties, or not at all. Chemical hardening yields merely a very thin compressive stress layer on the sur- face, readily penetrated by deeper scratches whereby the glass then again becomes prone to fracturing. Besides, chemical hardening takes several hours and is expensive.

The principle of multiple-layer glass has been described in German Patent 61,573. A more recent process for the production of multiple-layer glass is known from DAS 1,926,824 and DAS 1,954,423. In accordance with this more recent procedure, a multiple-layer glass ribbon is produced; a process for the forming of blown hollow glass articles has not been known there- from.

The production of multiple-layer hollow glass objects from a gob has been disclosed in U.S. Patent 2,500,105 and in East German Patent 124,295. In accordance with U.S. Patent 2,500,105, a multiple-layer glass gob is withdrawn from a revolving funnel-shapedfeeder pot into which various glass streams are introduced, is fed into a mold, and the hollow glass object is formed by pressing with the aid of a ram. Since the various glass streams intermix to relatively great extents, no constant layer thickness proportion is obtained. Besides, it is impossible to manufacture narrow-necked hollow glass articles, such as bottles, for example. These drawbacks are mitigated according to the process in East German Patent 124,295, but here again the hollow glass object is produced from a 1 1 multiple-layer gob. The required degrees of deformation are so great herein that there is still the possibility of relatively extensive deviations from the desired layer thicknesses and layer thickness proportions.

EP 0 075 445 discloses a process usable for press-molding thin-walled hollow glass articles. This process also lends itself to the manufacture of hollow glass items of multiple-layer glass. According to this method, a glass ribbon is placed over the press mold, the glass ribbon partially shapes itself to the press mold and is then pressed into its final shape. With the use of this process, narrow-necked hollow glass items, such as bottles, for example, cannot be manufactured.

It is an object of the invention to provide a process for the production of multiple-layer hollow glass objects wherein the deviation from the desired layer thicknesses and layer thickness proportions is to be minor. Furthermore, it is an object of the invention to provide an apparatus for performing the process.

According to this invention, this object has been attained with respect to the process by means of a method for producing multiple-layer hollow glass items by blowing wherein an approximately square multiple-layer glass ribbon section is plAced in an essentially horizontal orientation over an opening of, a mold and is shaped into the mold by blowing.

With respect to the apparatus, the object has been attained by means of a device serving for performing the process with a part exhibiting a round opening with an upwardly oriented pointed edge, this part being mountable over a mold and accommodating an approximately square multiple-layer glass ribbon section in a substantially centered way above the opening, with a blowing pipe placeable above the opening onto the glass ribbon section and being the means for blowing a parison forming from the glass ribbon section into the mold.

4 - In contrast to the state of the art prevailing thus far, the invention makes it possible to produce hollow glass objects with a high uniformity and accuracy of the wall thicknesses and layer thicknesses because there are considerably lower degrees of deformation than in the manufacture from gob material. This holds true, in particular, for the manufacture of bottles and corresponding hollow glass items having a certain height, such as, for example, drinking glasses, 10. vases, etc.; with the aid of the process of this invention, these articles can also be mass produced. For this reason, the thus- manufactured hollow glass objects, while exhibiting identical strength, can have a smaller wall thickness as compared with conventional hollow glass items.

Practically all glasses that can be shaped by blowing can be utilized in the multiple-layer glass ribbon. It is thus possible, for example, to produce, after the forming step, by means of a tempering procedure also multiple-layer glass ceramic articles or laminated glasses from glass-glass ceramic material.

Owing to the externally located layers, it is not only possible to generate differences in expansion but also to improve other properties, for example the color (flashed glas) or chemical resistance. I - The glass ribbon which suitably has a width of 40 - 300 mm can be made up of any desired multiplelayer glass ribbons as they can be prepared, for example, according to DAS 1,954,423. Glass ribbons that have been subsequently coated can likewise be utilized.

The glass ribbon is severed without interference with the stratified structure in areas governing for the strength of the hollow glass object to be produced since the severing site lies outside of the glass ribbon region from which the parison is formed.

1 - Separation of the cap from the useful portion of the hollow glass object, as well as the possible necessary treatment of the cutting site at the useful portion in order to cover the inner layr with outer-layer glass take place according to known methods, such as, for example, the method described in DOS 2,635,354. If needed, the useful portion can be provided, during a further operating step, with a formed-on thread or rim for a seal, e.g. a crown cork seal.

The invention as well as embodiments of the invention will be described in greater detail below with reference to an example in conjunction with the drawings wherein:

Figure 1 shows the multiple-layer glass ribbon from the narrow side; Figure 2 shows the multiple-layer glass ribbon from the broad side; Figure 3 shows a section through the multiple layer glass ribbon along line III-III of Figure 1; Figure 4 shows the severing of the glass ribbon (section) and the turning of the glass ribbon section into the horizontal; Figure 5 shows a sectional vLc---w of the parison along line V-V of Figure 6, and I Figure 6 shows a top view of the parison., r_ A multiple-layer glass ribbon 1 illustrated in Figures 1 and 2 leaves a slot-shaped outlet 2 of a feeder (not shown herein) in the viscous condition. Blades 3 for severing the glass ribbon 1 are opened and allow the glass ribbon 1 to flow downwardly.

Figure 3 shows the specially configured blades 3 and the multiple-layer structure of the glass ribbon 1 with an inner layer 4 and outer layers 5. The laterally projecting edges of the blades3 permit a clean cut without spreading of the glass ribbon 1.

In Figures 4 and 5, an approximately square section 8 of glass ribbon is severed from the downwardly exiting glass ribbon 1 by means of the blades 3; this section is deflected via a curved chute 6 into the horizontal and is placed on a bottom part 15 of a bipartite rough press mold 15 and 16. By means of the top part 16, the glass ribbon section 8 is rough-formed by pressing, emplaced by suction, brought over an opening 9 of a conveyor plate 10, and deposited on the latter.

The conveyor plate 10 is moved on for the subsequent forming of the glass ribbon section 8, and another conveyor plate is brought into position in front of the rough press mold 15 and 16. The glass ribbon 1 can in this way be continuously severed and delivered.

The glass ribbon section 8 is retained, as_ illustrated in Figures 5 and 6, by means of a pointed edge 11. on account of gravity, the glas.s ribbon section 8 sags over the opening 9 and constitutes a tubular parison 12. In addition to gravity, the parison 12 can also be created by applying a blast of air via a blowing pipe 13 to the opening 9.

n', i i 1 7 - During formation of the parison 12, the conveyor tray 10 is rotated about its vertical axis and arranged above a mold 14 shortly before termination of parison formation. Thereafter, the mold is closed and the parison finished by blowing. In this arrangement, the mold 14 can be polished to be smooth at the contact points with the glass (fixed blow mold) or it can be provided with a water-absorbing coating (rotational mold). When using the rotational mold, the parison is turned relatively to the mold during the finishing blowing step, while no rotation takes place when using the fixed blow mold. After the finishing blowing step is completed, the mold 14 is opened, the semifinished article is taken off the conveyor plate 10, and the cap is separated from the useful portion, the finished article. This separating step is executed, for example, as described in DOS 2,635,354.

The apparatus is not restricted to the illustrated embodiment. Thus, the glass ribbon section 8 can also be placed directly over the opening of a mold.

If necessary, heating units can also be included in order to bring or maintain the glass ribbon section to or at a suitable processing temperature. In addition to the described multiple-layer glass ribbon, it is also possible to utilize coated glass 'panes, such as, for example, flashed glasses. The glass plates need not be used -- as described -directly upon manufacture. Also intermediately stored glass plates, for example from other production facilities or after having been coated, can be employed after an appropriate heating step (for example on a conveyor belt by means of an oven).

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Claims

CLAIMS:

1. A process for the production of multiplelayer hollow glass objects by blowing, characterized in that an approximately square, multiple-layer glass ribbon section is placed in essentially horizontal orientation over an opening of a mold and is shaped by being blown into the mold.

2. A process according to claim 1, characterized in that the glass ribbon section is severed from a multiple-layer glass ribbon discharged continu ously from an outlet of a feeder in the downward direction and is turned into the horizontal orientation.

3. A process according to claim 2, characterized by using a continuously downwardly delivered glass ribbon exhibiting an inner layer and an outer layer surrounding this inner layer, the outer layer consisting of a different type of glass from that of the inner layer.

4. A process according to one of the preceding claims, characterized by using a glass ribbon exhibiting an outer layer of a type of glass having a smaller coefficient of thermal expansion than an inner layer.

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5. A process according to one of the preceding claims, characterized in that the glass ribbon section is preformed by means of a rough press- molding die.

6. Apparatus for performing the process according to one of the preceding claims, with a part exhibiting a round opening oriented pointed edge above a mold with an upwardly which part can be mounted and receives an approximately square multiple-layer glass ribbon section essentially centered above the oDenina with a blowing pipe placeable above the opening onto the glass ribbon section and being the means for blowing a parison forming from the glass ribbon section into the mold

7. Apparatus according to claim 6, characterized in that a multiple-layer glass ribbon can be withdrawn continuously from a slot-shaped outlet of a feeder for the production of multiple-layer glass, and that controllable blades are provided underneath the slot-shaped outlet ribbon sections.

severing the multiple-layer glass into approximately square glass ribbon

8. Apparatus according to claim 6 or 7, characterized in that the part exhibiting the opening is a conveyor tray

9. Apparatus according to one of claims 6-8, characterized in that the part exhibiting the opening is rotatable and turns the parison relatively to the mold

10. Apparatus according to claim 6, substantially as hereinbefore described with reference to the accompanying drawings.

11. A process according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

12. A multiple-layer hollow glass object when produced by a process as claimed in any one of claims 1 to 5 or claim 11.

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