METHOD IN PRODUCING GLASS OBJECTS BY USING A BLOW PIPE

Abstract: Glass is gathered on the pipe from the glass melt by means of a navel provided on the pipe, which navel is of a metal which is substantially resistant to oxidation at the temperatures to which the navel can be exposed on contact with the glass melt. After production of a glass object and separation of this from the pipe, this is left to cool with an attached lump of glass on the navel. The lump of glass cracks and falls off the navel leaving a thin film of glass on the navel. This is then shock-heated before fresh gathering takes place from the glass melt for the production of a new glass object. The invention also relates to a blow pipe with a navel for carrying out the method, the navel being made of metal or metal alloy with the said characteristics.

Description: METHOD IN PRODUCING GLASS OBJECTS BY USING A BLOW PIPE The present invention relates to a method in produc¬ ing glass objects by using a blow pipe. When glass objects are produced by using a blow pipe, a lump of glass, the so-called attachment, remains on the navel of the pipe after the finished glass object has been separated from the pipe. The attachment must be removed from the pipe before this can be used again. It has always been usual and it is still so, that the attachment is removed by knocking it off the navel. Apart from the fact that a noisy environment is caused in the glass factory through the perpetual knocking against the pipes made of iron or steel, this method of procedure means that the pipes are exposed to heavy stress so that they repeatedly have to be repaired because they have been deformed or crack when the attachment is knocked off the navel. In order to make the glass come loose from the navel more easily, it is usual to dip the navel in a clay mixture before the pipe- is used, but the said inconven ences of noise in the glass factory and damage to the pipes are not avoided in this manner. Another important disadvantage of the present method of procedure lies on the economic plane and consists in that the glass which is knocked off the navel is completely unfit for direct re-use, since oxide from the navel remains on the bits of glass removed. If glass with iron oxide is introduced into the glass melt, the iron oxide causes bubbles and dark cords (discolour- ing) in the glass, as a result of which the product pro¬ duced from such glass is defective. In addition, the crucible in which the glass is melted is easily destroyed due to the fact that the iron oxide tends to eat through the refractory material of the crucible; this is why an attempt is always made to remove by magnets any iron O PI particles which may occur in the batch material for the glass melt. The amount of glass which it is necessary to reject in this manner as valueless waste, since it cannot be re-used, involves a not inconsiderable loss ' for glass factories, which is all the greater since the remelting of glass can take place with less energy consumption tha the new production of glass from batch material and the necessary removal of the waste glass from the glass factory also involves costs. Whereas it has hitherto not been possible to over¬ come the disadvantages with regard to the working environment and tool costs, which the knocking off of the attachment from the navel on the pipes involves, nevertheless more progress has been made with regard to the re-using of the bits of glass covered with iron oxide knocked off the navel. Thus, Gl asforsknings- institutet (the Glass Research Institute) in Vaxjδ, Sweden, has worked out a method of removing the iron oxide by acid treatment of the bits of glass, but the gain achieved by the glass being re-usahle after the acid treatment is considerably reduced by the fact that the treatment is expensive and moreover is not particularly favourable to the environment in view of the use of acid which constantly has to be replaced. According to the invention it has surprisingly been found that through a certain method of procedure in handling the blow pipes in combination with a suit¬ able selection of the material in the navel, it is poss- ible to achieve that the glass in the attachment, which remains on the navel after the separation of the finishe object from the pipe, can be fully re-used without any aftertreatment whatsoever and without causing any deteri ration in the quality of the glass, while at the same time an atmosphere favourable to the environment is created in the glass factory as a result of the fact that there is no need to suffer from the noise from the harmful treatment of the pipes to remove the attachment from the navel. This is achieved in that the method according to the invention has obtained the characteristics appear¬ ing from claim !. According to the invention, a blow pipe is also provided for carrying out the method with the charac- teristics appearing from claim 2. To illustrate the invention, this will be described in more detail below with reference to some examples of embodiment. A conventional blow pipe comprises a tube of iron or stainless steel with a navel in one end which is shaped like a long and narrow cone which is connected to the tube at its small end and which is slightly convexly curved at its large end. A passage communicat¬ ing with the interior of the tube may be provided through the navel (blowing navel) in case of a blow pipe. The navel according to the invention is made of a material which does not oxidize or form scale to any great extent at the temperature to which it may be exposed on contact with the glass melt. Normally, the temperature of the glass melt in the crucible is about 1200°C and during the gathering of glass on the navel as a result of the fact that this is dipped in the glass melt and the pipe is turned round, the navel comes up to a maximum temperature of about 1000°C. The selection of material in the navel and the method of using the blow pipe is illustrated by the following examples. Example 1 The production of glass objects, for example hand-. made objects of art of crystal glass, is effected by OMPI using a blow pipe, the navel of which is made of stainless steel alloyed with molybdenum under the name UHB 8825 (SIS 2361) from Uddeholm Svenska AB , Sweden. After molten glass has been gathered on the navel by dipping this in the glass melt while turning the pipe, the desired glass object is produced and then separated from the pipe leaving a lump of glass, the so-called attachment, on the navel. The pipe is then left to cool, and it has been found that the attachment gradually cracks away of its own accord and falls off the navel leaving a thin film of glass on the navel. Before the pipe is used again, the navel is introduced into a special furnace for shock heating for about 5 seconds at a temperature of the order of 1000 - 1200°C, during which the thin film of glass on the navel cracks and mainly falls off the navel. If traces of oxide should occur in the glass which has fallen off, this does not matter because it is a question of small amounts of glass which it is not worth taking for re-use by mixing in the glass melt. The shock-heated navel is then preheated to 300 - 500°C and then introduced into the glass melt while being turned to gather glass for the production of a new object. The continued process is the same as described above. The navel can be welded to the tube or be other¬ wise fixed to this but it is also conceivable and economical to make the blow pipe as a whole of the same material as the navel. Example 2 The nave! is made of HASTALLOY C, which is marketed by Messrs. Harald Pihl, Stockholm, Sweden. Apart from this, the procedure is the same as in Example 1. Example 3 The navel is made substantially of pure titanium. Apart from this the procedure is the same as in Example 1. In all three examples above, the bits of glass which, in practising the invention, fallen off the navel, when the attachment cracked to pieces during the cooling of the blow pipe, were completely free of oxide which could be harmful to the glass melt, and no other coating occurred on the bits of glass ' so that these could be melted down to be used again for the manufacture of high-quality glass objects of art. CMPI

Claims: CLAIMS 1. A method in producing glass objects by using a blow pipe, c h a r a c t e r z e d in that glass is gathered on the pipe from the glass melt by means of a navel of a metal or metal alloy which is provided on the pipe and which is substantially resistant to oxidation at the temperature to which the navel is heated on contact with the glass melt, that after production of a glass object and separation of this from the navel, the pipe is left to cool with an attached lump of glass on the navel, the lump of glass cracking and falling off the navel leaving a thin film of glass thereon and that the navel is shock-heated before glass is again .gathered on the navel from the glass melt for the production of a new glass object. 2. A method as claimed in claim 1, c h a r a c ¬ t e i z e d in that the navel is shock-heated for about 5 seconds at 1000 - 1200°C. 3. A method as claimed in claim 2, c h a r a c - t e r i z e d in that, after the shock-heating, the navel is preheated to 300 - 500°C before glass is again gathered. 4. A blow pipe with a navel for carrying out the method as claimed in claim 1, wherein the navel con- sists of a metal or metal alloy which is substantially resistant to oxidation at the temperatures to which the navel can be exposed on contact with the glass melt, c h a r a c t e r i z e d in that the navel consists of stainless steel alloyed with molybdenum, or of sub- stantially pure titanium. * Uϊifc

Inventors: MARCOLIN J
Applicants: FAERE MARCOLIN KONSTGLAS AB, MARCOLIN J
Application year: 1980
Main classification: C03B9
IPC codes: C03B9