Process and Apparatus for the Manufacture of Glass Sheets, Glass Tubes, and Cylinders for the Production of Glass Sheets and other Articles
Year: 1896

page_text: Date of Application, 6th Aug., 1896-Accepted, 26th Sept., 1896
COMPLETE SPECIFICATION.
Process and Apparatus for the Manufacture of Glass Sheets, Glass
Tubes, and Cylinders for the Production of Glass Sheets and
other Articles.
•
I PAUL THEODOR SIEVERT, of Lindenaustrasse, 32, Dresden, Saxony,
Germany, Glass Manufacturer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
In order to produce sheets of glass, many attempts have been made to force the
molten glass or metal, by pressure, out of the end or side opening of a suitable
vessel, thereby dispensing with the ordinary methods of blowing and rolling, the
disadvantages of which are well known.
As one of the causes of failure in these attempts, may be cited the difficulty of
obtaining a constant thickness of glass issuing from the said vessel, because the
walls of the slot, which usually consist of refractory material, become eaten away,
and even fused by the heat of the fluid metal.
According to the present invention, not only the production of glass sheets
without blowing, rolling, or pressing, is effected, but also round or angular hollow
forms, such as cylinders to be used for the manufacture of sheet glass, or tubes.
A known property of glass is here made use of, viz., that while in a fluid or
molten state it is capable of being drawn, at a certain speed, into determined forms
of uniform thickness, as, for example, in glass spinning or drawing rods and tubing
by means of the blow pipe.
The mechanical drawing of masses of molten glass into sheets and cylinders has
also been attempted; thus, a bar of iron has been dipped into the molten glass,
and the glass adhering thereto in a sheet has been then drawn upwards.
Nothing has, however, resulted from this method, because the glass does not
adhere to the iron uniformly, and the glass plate, on cooling, separates from the
iron bar.
Again, it has been proposed to produce sheets and cylinders of glass, by
introducing a plunger into a vessel filled with molten glass. This plunger was
intended either to draw the glass adhering to its surface, as a sheet, up or down,
or, by means of loose grippers, to draw it upwards in either sheet or cylinder form.
This process afforded no practical result, because the moving iron machinery partly
attached to, and partly within the furnace, was rapidly rendered useless by the
heat. Also, it was not possible to close the opening for the introduction of the
plunger sufficiently tightly to prevent its becoming choked by the glass cooling as
it issued therefrom.
It is also impossible to prevent the formation of bubbles, which arise through
the repeated introduction of the plunger, and the receding of the detached portions
of glass, and which must prevent the production of a good quality of window glass.
Again, the separation of the glass bodies produced from the plunger is attended
with considerable difficulty, and is almost impracticable.
Now the present invention consists of a method or process unknown up to the
present time, which renders possible the production, in the simplest way, of sheets,
cylinders, etc., and in which the above enumerated disadvantages are avoided.
In carrying out the present invention for the production of the sheets of glass,
the ordinary hopper-shaped holders are employed, having a straight slit in the
bottom thereof.

page_text: .
For producing cylinders, a circular or other shaped vessel or holder is employed,
having a suitably-shaped slit in the bottom.
In the accompanying drawing :-
Figs. 1 and 2 shew side and plan views, partly in section, of a machine for
making sheets ;
Figs. 3 and 4 are similar views of a machine for making cylinders.
Referring now to Figs. 1 and 2, a is the holder or vessel to contain the molten
glass, and is preferably exposed to the action of heat in a suitable chamber.
From the slit in the base of this vessel, the molten glass issues, and the strip is
caught by some suitable device and is drawn out, so as to form a sheet of the
desired length and thickness, at a speed exceeding that of the natural flow of
the glass.
The molten glass issuing from the slit of the vessel a, may be gripped between
fillets of wood or other suitable material, and be drawn in a downward direction by
band, or by a mechanical device, such as will hereafter be explained with reference
to Figs. 3 and 4; or it may be caught by a carriage on rails upon which the molten
glass is directed to be laid upon a fillet on the carriage, and a second fillet put over
it, to grip the glass, so that when the carriage is moved, the drawing of the glass
in a sheet of desired thickness will take place.
For the production of hollow glass articles, holders of truncated cone or funnel
shape in cross section are most preferable. The outlet aperture may be circular,
angular, uninterrupted, or interrupted. Holders of this kind have not yet been
employed in the glass trade.
The cylinders produced are cut longitudinally, and opened out into sheets, which
have hitherto only been obtained by the blowing process.
The conversion of cylinders into glass sheets is well known in the art of glass
making, and requires no further explanation. For, producing these cylinders from
which the glass sheet is made, and for other purposes, I employ the apparatus shown
at Figs. 3 and 4. a is the truncated cone-shaped holder, in which, by means of a
conical core a', an annular slit or outlet is formed. This annular aperture may be
interrupted or continuous, the latter by making the holder and core in one at the
top, or by connecting the same together at the upper part. The aperture, which
may be circular or polygonal (see Fig. 5), allows the liquid glass to issue, and it is
gripped by devices h corresponding to the contour of the slot, and drawn down-
wards, so that a hollow article is produced, the thickness of the walls and length
thereof depending, however, on the drawing process.
The drawing apparatus may be operated by hand or by mechanical means, an
example of which is shown in Fig. 3. The devices or grippers h, which grasp the
end of the hollow glass body, press it against the periphery of a block i, which is
secured to the bars k, carrying on their inner ends the grippers h. The bars are
provided with internal screw threads, into which the screwed rods enter, which
screwed rods are rotated by means of mitre wheels. By turning the spindles l, the
bars k with the grippers are drawn downward, so that, by this drawing, the glass
article seized by the grippers is produced in any desired thickness and length,
and of the form of the slot used.
In the above mentioned process, the width of the slot is but of slight importance.
The thickness of the walls of the glass articles produced in this way depends upon
the tension put upon it by the grippers.
Under the old plan of working, it is absolutely impossible, for example, to
produce, say, a sheet of glass of good quality, of a thickness equal to the width of
the slot in the vessel. Either the enlargement of the slot, as before described
'soon takes place, or, if this be prevented, the mere flow of the molten metal from
such aperture would never produce a sheet fit for a window pane or other
'purpose.
In the present new mode of manufacture, the alteration of the width of slot, due
to the effects of the molten glass, is of as little importance as its actual origina
size

page_text: Generally speaking, for certain thicknesses of glass articles to be produced,.
regulated widths of slot are used, so as not to have too copious an outflow of glass
from too wide a slot. Nevertheless, I do not coufine myself, in this invention, to
any particular width of slot. The glass issues from the aperture partly by its
own weight, and partly by the tension put upon it. It can, however, be subjected
to pressure, pneumatic, for example, either by compresse.l air or gas. The tension
may, as above mentioned, be effected by hand, or by mechanical means.
case, the metal, in whatever form it issues from the slot, will be gripped, and drawn
out to such length as it is desired to give to the article. After being drawn out,
the article thus formed has to be separated from the fluid mass at the proper
moment, when the glass has become sufficiently rigid to allow of the mechanical
separation. Naturally the speed of drawing must exceed that with which the glass
issues from the slot.
As an important advantage accruing from this invention, it may be mentioned,
that the glass, with the exception of its edge, where it is gripped by the bars
during the drawing process, need not come into contact with metal or any other
material, and therefore will retain its original "fire polish," which is considerably
increased by the drawing, so that glass articles of high lustre are produced by the
new process.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that, what I
claim is :-
1. A process for producing glass sheets from molten glass issuing from the slot
or aperture of a holder, either by its own weight or by pressure, as is well known,.
and consisting in seizing the molten glass after issue, or during issue, with suitable
travelling devices, and drawing the same forward at a speed in excess of the
natural flow of the glass, in order to form the sheet of the required thickness and
length as set forth."
2. The process for the production of glass cylinders and tubes, consisting in
allowing the molten glass to flow from a holder through an annular or polygonal
slot or aperture, seizing the glass with suitable travelling devices, and drawing out
the glass to form the cylindrical or other shaped hollow body, of the required
thickness and length, as set forth.
3. As means for producing cylindrical or other shaped hollow glass bodies by a
drawing operation, the vessel a a¹ described with reference to Figs. 3 and 4, having
a slot at bottom for the issuing of the molten glass, of a shape corresponding to
that of the body it is desired to produce, as set forth.
4. The combination with a vessel a, described with reference to Figs. 1 and 2,
or with a vessel a a', described with reference to Figs. 3 and 4, of means for
gripping and drawing the molten glass issuing from the slots or apertures of said
vessels, as set forth.
Daand this ch dom of August 1806
NEWTON & SON,
Agents for the Applicant.