Improvements in the Production of Ruled Metal Writing Tablets.
Year: 1891

page_text: Date of Application, 12th May, 1891
Complete Specification Left, 12th Feb., 1292-Accepted, 12th Mar., 1892
.
PROVISIONAL SPECIFICATION.
Improvements in the Production of Ruled Metal Writing Tablets.
I, THEODOR BERGMANN Gaggenau Iron Works Gaggenau Germany Director
do hereby declare the nature of this invention to be as follows :-
My invention relates to the manufacture of writing tablets of sheet metal
covered with an enamel and ruled with lines for writing thereon.
Numerous inventors have already attempted the manufacture of metal writing
tablets covered with a glass flux, but although several succeeded more or less in
producing such tablets, all had again to desist for the reason that they were not
able to produce a proper ruling on such tablets, which is indispensable in order to
make such tablets fit for school purposes. What they could produce were tablets
ruled but with the high gloss of the glass flux. Glossy tablets being injurious to
the eyes of the children, and the ruling indispensable, everybody had to give up
the attempt. It is absolutely impossible to produce enameled surfaces of any
kind at high temperatures without any gloss.
If again a great proportion of flux is admixed, which renders the enamel soft and
easily melted, the surface produced has the great disadvantage of not being
homogeneous enough and too porous, which forms an obstruction to the easy erasing
or wiping away of the writing.
I have made it my object to produce dulled or glossless surfaces of the hardest
possible enamel provided with indelible ruling.
After great trouble and thousands of experiments I have succeeded in producing
indelible coloured lines upon dim enameled surfaces of metal plates without having
to subject them to a second glossing heat.
To carry my invention into practice I provide a plate of sheet iron suitably
prepared for enameling with a good rather hard glossing enamel, burn it in,
and treat it after any of the well known processes for deadening or dimming it.
With a suitable ruling machine provided with elastic pens or styles of a material
not attacked by acids, I rule the plates thus enameled with saturated mineral acid.
The lines drawn by these acids are visible, but for most purposes too pale. In
order to obtain lines of a deeper colour, I dissolve metallic salts as for instance, iron
copper, nickel or cobalt salts in the acids, which after entering into the enamel
produces a durable and sharply defined line.
I thereby obtain the great advantage that this ruling does not require a glossing
heat for melting in but that the lines are fixed at a moderate temperature without
glossing. In this way the enamel is prevented from melting again and the dim
surface is thereby preserved.
.lהו'תנית
E. EATON,
Agent for Applicant.
COMPLETE SPECIFICATION.
Improvements in the Production of Ruled Metal Writing Tablets.
1, THEODOR BERGMANN Gaggenau Ironworks Gaggenau Germany Director of
Ironworks 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 :-
My invention relates to the manufacture of writing tablets of sheet metal covered
with an enamel and ruled with lines for writing thereon. Numerous inventors have

page_text: already attempted the manufacture of metal writing tablets covered with a glass
flux, but although several succeeded more or less in producing such tablets, all had
again to desist for the reason, that they were not able to produce a proper ruling on
such tablets which is indispensable in order to make such tablets fit for school
purposes. What they could produce were tablets, ruled, but with the high gloss of
the glass flux. Glossy tablets however being injurious to the eyes of the children,
and the ruling being indispensable, everybody had to give up the attempt. 'It is
absolutely impossible to produce enameled surfaces of any kind at high temperatures
without any gloss. If, in order to avoid this, a great proportion of flux is admixed,
which renders the enamel soft and easily melted, the surface produced has the great
disadvantage of not being homogenous enough and too porus, which will prevent
the easy erasing or wiping away of the writing.
We have made it our object to produce dulled or glossless surfaces of the hardest
possible enamel, provided with indelible ruling.
After much trouble and numerous experiments we have succeeded in producing
indelible colored lines upon dim enameled surfaces of metal plates, without having
to subject them to a second glowing heat.
To carry our invention into practice we provide a suitable plate or piece of sheet
iron, prepared for enameling in the usual and well known manner, with a good,
rather hard flowing enamel, burn it in, and subsequently deaden or dim the glossy
surface by any of the well known processes, such as for instance by means of a sand
blast or by the application of fluoric acid etc. With a suitable ruling machine,
provided with elastic pens or styles of a material not attacked by or protected
against acids we rule the plates thus enameled and prepared with saturated mineral
acid, such as for instance sulphuric or muriatic acid.
The lines drawn with these acids are visible but for most purposes too pale.
In order to obtain lines of a deeper color we therefore dissolve metallic salts, by
preference cobaltic oxide or ferric oxide in the ascids by preference in sulphuric or
muriatic ascid, which after entering into the enamel produce durable and sharply
defined lines. There is no particular proportion necessary for the metallic salt and
acid as long as the solution is of a suitable consistency for flowing freely and
properly from the pens or styles.
By ruling the tablets in the manner described we obtain the great advantage
that this ruling does not require a glowing heat for burning it in but that a
moderate heat will suffice to fix the lines. In this way the enamel is prevented
from melting again, and the dim surface is thereby preserved.
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.
Metal writing tablets with a dimmed enamel or glass flux covering, and ruled
with mineral ascids in which by preference metallic salts are dissolved which may
be burnt in at a heat less than that required for melting the enamel or flux
employed substantially as described.
Dated this 12th day of February 1892