Glass manufacturing – Processes – Utilizing parting or lubricating layer
Patent
1991-02-08
1994-11-15
Woodard, Joye L.
Glass manufacturing
Processes
Utilizing parting or lubricating layer
65 24, 65170, 106 382, 264338, 184 614, C03B 948
Patent
active
RE0347850
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for lubricating a surface such as a mould, a conveyor belt, etc., for the manufacture of a glass article such as a receptacle, in which there is periodically deposited a layer of lubricant on the surface. The manufacture of glass objects, in particular hollow glass objects such as bottles, flasks, etc. . . . is usually carried out in accordance with two methods:
The first method, termed "blown-blown", in which a blank is formed by blowing in a first mould, this blank being then transferred to a second mould in which it is blown so as to assume its final shape.
The second method, termed, "pressed-blown", in which a blank is formed by pressing a drop of glass or parison issuing from a hopper in a mould, this blank being then transferred to a blowing mould in which the hollow blank is blown so as to assume its final shape.
Flat glass objects are usually produced by pressing.
Irrespective of the method employed, the internal walls of the moulds in which the blanks are formed are regularly lubricated to permit an improved penetration of the glass and avoid [cetain] certain surface defects of the blank, which defects subsist on the finished receptacle. The technique still frequently employed at the present time in glassworks is a technique involving the manual lubrication of the moulds, which is not without danger for the handlers. This lubrication is usually carried out with an oil containing graphite in suspension.
In such a manual method, the operator has a tendency to deposit a large quantity of oil so as to reduce the frequency of the lubrications. This results in a soiling of the first blanks produced after each lubrication and considerably increases the losses in the manufacturing line. Further, a large amount of smoke in the working area is created.
It has been for a long time attempted to substitute for the manual lubrication an automatic lubrication in manufacturing lines of glass receptacles, without much success up to the present time.
French Pat. No. 1,285,586 discloses an automatic lubricating process for a closed mould in which the moulding apparatus is provided with lubricating passageways through which oil is injected into the mould before introducing the parison in the latter.
The introduction of oil by a manual or automatic process results in a great local pollution, since the oil burns upon contact with the moulds and gives off a thick black smoke charged with polyaromatic hydrocarbons. Now this pollution is found on the glass articles, the latter being coated with residues of incomplete combustion of the oil which do not burn in the air not-withstanding the high temperature at which the blank leaves the mould, which in practice forbids the lubrication before each introduction of a parison. If this lubrication is not effected before each introduction, there is a rapid decrease in the pollution but a corresponding increase in the surface defects of the glass article.
A solution has been proposed in U.S. Pat. No. 4,165,974 which comprises coating the internal surface of the moulds with a carbon fluoride so as to produce an anti-adherent layer on this surface. This process necessiates the disassembly of each mould, the treating thereof, and then its submission to a heat treatment before placing it back on the machine. Although the mentioned duration of lubrication is several hours, such a process requires a practically permanent human presence around the manufacturing machine with the obligation to frequently stop this machine for disassembling the moulds, lubricating them, remounting them, etc., which results in prohibitive manufacturing costs.
U.S. Pat. No. 4,409,010 discloses a process for lubricating moulds by a spaying of liquid oil onto the internal surfaces of the moulds, but the disclosed process does not avoid the drawbacks relating to the use of oil for the lubrication.
There is also another problem when using one of the processes described hereinbefore: when the glass receptacles leave the mould without a trace of
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L'Air Liquide, Societe Anonyme Pour L'Etude et L'Exploitation de
Woodard Joye L.
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