IMPROVEMENTS IN THE PRODUCTION OF TOUGHENED GLASS AND IN APPARATUS THEREFOR " to be ass
Year: 1884

page_text: I, CHARLES DENTON ABEL of N° 28 Southampton Buildings Chancery Lane
in the county of Middlesex, Consulting Engineer and Patent Agent do hereby
declare the nature of the said invention for ." IMPROVEMENTS IN THE PRODUCTION
OF TOUGHENED GLASS AND IN APPARATUS THEREFOR " to be as follows:---
This invention relates to the production of toughened glass by first reheating the
glass articles after being formed in the usual manner and then plunging them in a
heated liquid such as oil or melted grease, whereby they are rendered of a tough
nature.
•
In these operations, as at present couducted, unreliable results are frequently
obtained, firstly because the glass is not uniformnly reheated, and secondly because
the liquid bath in which the glass is tempered is not of a uniform temperature.
The present invention has for its object to effect both the uniform reheating and
the uniform tempering of the glass, whereby a uniformly successful result is
obtained. In carrying out this process heretofore, the glass article, after manu-
facture, has been held by means of the pontil in the opening or mouth of the glass
melting furnace in order to reheat it to the requisite degree before plunging it
into the tempering bath. The glass being generally of unequal thickness becomes
very unequally heated by this means, more particularly as the thickest part, which
requires most heat, is held by the pontil in the coolest part of the furnace mouth.
In order to obviate this inconvenience there is employed, according to this
invention, a small separate reheating furnace consisting either of a chamber heated
by an open fire, or of a muffle heated externally by the fire.
According to one mode of operating with such reheating furnace, this is provided
with two opposite openings, so that the glass article being introduced by the pontil
through the one opening, can be pushed forward thereby, until the end of the glass
article which is opposite that held by the poutil, and which is consequently the
thinnest, projects out through the opposite opening, so that only the thicker part of
the glass is subjected to the heat of the furnace. When this part of the glass haa

page_text: become sufficiently heated, the article is drawn back, so as to submit the thin part
of the glass to the action of the heat for a shorter time, after which it is entirely
withdrawn and plunged into the tempering bath.
The opening through which the glass article is partly protruded may either be
open to the atmosphere or it may be surrounded by an enclosure which partly or
wholly excludes the outer air.
According to another mode of operating, a muffle is employed, divided hori-
zontally into two compartments, both of which are open at both ends, the muffle
being heated externally by a fire. The glass articles, removed from the pontil, are
introduced into the one compartment, being first placed close to the one open end
thereof, and the compartment is then successively filled in up to the other end after
which the second compartment is filled in like manner. While this compartment
is being filled, the articles are removed from the first compartment, beginning with
those which were first introduced and are plunged into the tempering bath. By
this means all the articles will be submitted uniformly to the action of the heat,
and as the one compartment of the muffle is always being filled while the other is
being emptied, the operation is rendered continuous. It is essential that the bath
of liquid into which the glass articles are plunged after being reheated should be
of a very uniform temperature throughout, as otherwise the glass being cooled at
different temperatures at different parts, will be under unequal tension and will be
liable to fracture. In the baths as at present employed however, the central part
of the liquid' is generally at the requisite temperature, while that situated at the
sides of the vat is considerably cooled by conduction.
In order to obviate this defect, the vat or receptacle containing the liquid is,
according to this invention, prevented from contact with the outer air either by
placing it, after receiving the heated liquid, in a casing of brickwork or other bad
conductor of heat, or by constructing the vat with double sides, the spaces between
which are filled with a bad conductor of heat.
Thus the liquid bath not being cooled by its contact with the sides of the vat, is
retained of a uniform temperature throughout.

page_text: "
I, CHARLES DENTON ABEL, of No 28 Southampton Buildings, Chancery Lane in
the County of Middlesex, Consulting Engineer and Patent Agent, do hereby
declare the nature of my invention for IMPROVEMENTS IN THE PRODUCTION OF
TOUGHENED GLASS AND IN APPARATUS THEREFOR and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement:―
"
This invention relates to the production of toughened glass by first reheating the
glass articles after being formed in the usual manner and then plunging them in a
heated liquid such as oil or melted grease, whereby they are rendered of a tough
nature. In these operations as at present conducted, unreliable results are
frequently obtained, firstly, because the glass is not uniformly reheated, and
secondly because the liquid bath in which the glass is tempered is not of a uniform
temperature. The present invention has for its object to effect both the uniform
reheating and the uniform tempering of the glass, whereby a uniformly successful
result is obtained.
In carrying out this process heretofore, the glass article after manufacture has
been held by means of the pontil in the opening or mouth of the glass melting
furnace in order to rebeat it to the requisite degree before plunging it into the
tempering bath. The glass, being generally of unequal thickness becomes very
unequally heated by this means, more particularly as the thickest part, which
requires most heat, is held by the pontil in the coolest part of the furnace
mouth.
In order to obviate this inconvenience, there are employed, according to the
present invention, small reheating furnaces in which the heat is raised to a degree
corresponding to the articles to be treated. These small furnaces have in addition
the advantage of not interfering in any way with the process of manufacture, tho
toughening process being a second operation independant of the actual manufacture
of the glass article. When this has been formed in the usual manner a boy, instead
of taking it to the annealing furnaces, hands it to a workman, who introduces it
into the reheating furnace and then toughens it as soon as it is in the proper
condition. The reheating furnace is very simple; it is either constructed as an
open hearth furnace or as a muffle, the latter being preferable on account of not
permitting any contact between the flame and the glass. The advantage of this
furnace is that the heat can be regulated with nicety according to the nature and
position and the thickness of the glass articles to be toughened so that these
objects, when heated to a degree when they become slightly soft can remain an
indefinite time in the furnace without fear of being melted down or even losing
their shape.
As shewn at Figs. 1 and 2 of the drawings one of the essential arrangements for
this purpose consists in providing two opposite holes A and B which permit the
workmen, after having introduced the glass article into the furnace, to extrude the
same at will on the opposite side in order to cool down one part thereof while the
other part continues to be heated in the furnace. It has been stated above that an

page_text: article introduced into the opening of the melting furnace is generally held by its
thickest part and consequently it is the thinnest part which is situated in the
hottest part of the furnace. This is not the case with a reheating furnace used
according to this invention. Taking for instance, a glass having a foot. This glass
is fixed to the pontil by means of the foot which is the thickest part and which,
consequently, should be most heated in order that the whole article may assume a
uniform temperature throughout. But it is impossible to obtain this result in an
ordinary furnace. According to the present invention, the workman introduces the
said glass into the furnace on one side, and causes the chalice thereof to be extruded
at the opposite side so that the foot is alone subjected to the heat and after this has
been raised to the temperature of the furnace the workman draws the glass back
again so as to subject the chalice to the furnace heat simultaneously with the foot
by which means the entire glass becomes uniformly heated throughout, after which
it is subjected to the toughening process. By this means all breaking of the glass
articles in the toughening bath is avoided as is also any spontaneous breaking of
the glass subsequently. In cases where it may be objectionable to extrude the part
of the glass directly into the outer atmosphere as described, the said opening may
be surrounded by means of a screen of brick work or sheet metal so as to form a
sort of chamber external to the furnace, but which receives a small amount of heat
therefrom. By forming one or more openings in this chamber so as to admit the
outer air, its temperature may be regulated according to the nature of the article to
be treated.
The present invention consequently consists, firstly, of an arrangement of reheating
furnace specially designed for reheating glass objects before the toughening process;
secondly, the use in such reheating furnaces of two opposite openings for the purpose
described; thirdly, the surrounding of the second opening by means of a chamber
or screen as described. In addition to providing for the uniform reheating of the
glass articles as described, it is also essential that the tempering bath should possess
a uniform temperature. In the tempering baths usually employed it generally
happens that the central part of the liquid is heated to the requisite degree while
its temperature decreases towards the side of the bath where it often happens that
the heat is sufficiently low to allow the grease to solidfy. From this it results that
a long article such as the chimney of a lamp or a glass with a stem does not become
immersed in the uniformly heated liquid and consequently the cooling effect is not
carried out uniformly throughout the article. It is from this that the breakages
so frequently occur in the bath as also the spontaneous fracture that sometimes
takes place subsequently. It is very essential that the heat should be uniformly
distributed throughout the glass article before steeping, and that the cooling should
also be effected in a perfectly uniform manner. In order to obtain this result, the
following arrangements may be employed.
Firstly, a movable vat which is placed by means of a screen into a brickwork or
other casing having a corresponding configuration. This casing protects the sides
of the vat from the cooling effect of the outer air. Secondly, a vat with double
sides, the space between which is filled with a bad conductor of heat. This arrange-
ment has the advantage of not requiring a permanent structure against the side of
the reheating furnace.
In order to avoid the attachment of a pontil to some part of the glass article,
whereby the action of the heat upon such part is interfered with, the use of the
pontil may in some cases be entirely dispensed with, by effecting the heating of the
glass articles in a muffle furnace as shewn in Figs. 3 and 4 of the drawings. It
consists of a mufle divided into two compartments A and A' and heated by a
surrounding furnace F, the flames from which, after heating the bottom of the
muffle, pass round the sides thereof and escape through the chimney C.
The symmetrical arrangement of the apparatus ensures a uniform heating. The
mode of operating with this furnace is as follows:-
The glass articles are first introduced at P into the compartment A and are first
placed at the end P¹ after which the compartment is gradually filled up towards P.

page_text: This compartment being filled, the same operation is carried out in the com-
partment A' introducing them at P, and placing them towards P¹. While this is
being done, the articles first introduced into A, are removed from the end P' and
taken to the tempering bath. By this arrangement, the glass articles are not
subjected to currents of air and each article is maintained at a constant temperature
for the same length of time. Besides these advantages the operation is rendered
continuous as the time required for filling one compartment is equal to that for
removing the articles from the other compartment so that while one is being filled
the other is always being emptied.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1, The herein described improved method of treating glass for the toughening
process.
2, The use for reheating and toughening glass articles of apparatus constructed
and operating substantially as herein described.
Dated this 28th day of April 1885.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.