Method and Apparatus for the Manufacture of Asbestos Articles suitable for Insulating Purposes.
Year: 1898

page_text: Date of Application, 29th Nov., 1898-Accepted, 11th Mar., 1899
COMPLETE SPECIFICATION.
Method and Apparatus for the Manufacture of Asbestos Articles
suitable for Insulating Purposes.
I, LUDWIG GROTE, of 84B, East India Dock Road, Poplar, E., in the County
of London, Manufacturer, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
This invention relates to a process by means of which asbestos paper, asbestos
cardboard or asbestos cloth which have been previously impregnated and pre-
pared in a certain suitable manner, is made use of as material for accumulator
casings or other insulating receptacles for electrical or chemical purposes and from
which insulating strips, boards, covers and similar articles may also be manu-
factured.
The receptacles thus made, are capable of acting as insulators; they are
waterproof and acid proof and impervious to caustic fluids. On the other hand,
the insulating strips, boards and covers are respectively either waterproof and
acid-proof or only heat-resisting according to the mode of treating them and
the purposes they are intended for.
The articles made by this process not only possess all the good qualities of
similar articles made of vulcanite for the same purpose, but they are considerably
lighter and are almost unbreakable.
The invention mainly consists in first impregnating the asbestos material to
be worked; then of the different processes for forming (lapping and glueing)
the articles, and finally in the further suitable treatment of same, namely an
impregnation with resins, wax or paraffin.
The various appliances which are made use of are represented in the accom-
panying drawings including an apparatus for forming the articles used in the
manufacture of casings for accumulators;
Figs. 1 and 2 represent a front and side view of the apparatus when closed;
Figs. 3 and 4 this apparatus partly opened;
Figs. 5 and 6 are longitudinal sections of the apparatus;
Fig. 7 shows a sheet of asbestos paper or cardboard specially cut ready for
lapping in the form of a casing;
Figs. 8 to 10 represent the apparatus with the asbestos cardboard partially
apped and particularly shows how the bottom of the casing is formed.
On Sheet 2 is shown the arrangement for the manufacture of insulating strips
or similar articles and the like;
Fig. 11 shows a mould, into which the asbestos cardboard previously prepared
s laid and shaped;
Fig. 12 the same mould, the filling material being placed in position and
epresenting the method of fastening used;
Fig. 13 is a cross section of the finished insulating strip or board, with its cover

page_text: put on, the latter being made of stronger asbestos cardboard and shaped to
increase its stability;
Fig. 14 is a moulding iron provided with a handle and shaped in order to
enable the operator to give the desired profile to the insulating board to be shaped.
The method of making the casing is as follows:-
Cardboard made of asbestos fibres possesses the disadvantages of cardboard
in general inasmuch as it is brittle and cannot be bent at acute angles. In order
to render asbestos cardboard suitable for lapping, it must be dipped into a
solution of potassium-or sodium water glass of specific gravity of 1,100 equal
to 12 degrees Beaumé, by which means it becomes so sort, that the cardboard
may be lapped without breaking.
In case the cardboard is cut in any special shape-as shown in Fig. 7-and
sufficiently saturated by the said solution, it will be advisable to pass it through
two parallel rollers in order to make it uniform in thickness and more compact,
Afterwards this
and then to let it dry until the cardboard feels merely moist.
cardboard having now again attained a certain degree of resistance is laid round
a lapping apparatus, which will be more particularly described below.
This lapping of the asbestos cardboard is done in such a manner that the parts
numbered 1 to 4 (Fig. 7) come in contact with the four sides of the apparatus
(Figs. 8 to 10). The remaining portion (5 to 8) of the asbestos cardboard is
then coated by any suitable heat resisting adhesive substance, such as water glass
and is lapped upon the apparatus in the same way as No. 1 to 4, so that the
parts 1 to 4 are fully covered by the parts 5 to 8, thus by the aid of the adhesive
coating, forming a solid whole, that is to say, the walls of the casing.
The bottom of the casing is made of the portions 1' 21 31 and 4' by first fastening
the part 2 to the front of the lapping apparatus. Hereupon the parts 11 and 34
are coated with adhesive substance and folded over part 2 in such a manner,
that they come together at the centre (Fig. 10); and finally part 4' after having
also been coated with the same substance, is folded over parts 1 and 31. This
arrangement results in the formation of a staunch bottom, because the layers
forming this bottom are alternate, whereby all the joints are closed.
After having lapped the casing in the way described upon the apparatus, the
screw of the latter must be loosened, whereby the lateral dimensions of the
apparatus are reduced and the finished casing may be easily withdrawn.
The casing is then dried in the atmospheric air for 6 to 12 hours according to
the thickness of its walls, the drying being finally completed by 2 to 3 hours
exposure in a room or chamber heated up to 100 deg. Reaumur.
The casing still in a hot state is then placed in a bath of molten resins, paraffin
or the like having a temperature of 160 deg. Reaumur.
In this bath, the casing remains for 2 to 8 hours, according to the thickness
of its walls, and after it has been sufficiently saturated with the said resins or
the like, the casing is placed in another receptacle which is also heated to a high
temperature thus giving the superfluous resins an opportunity to drain or to
sweat away.
After this process the casing is perfectly dry and has become so solid, that it
can be treated by planing, grinding, sawing and so on, just as if it were made
of horn, ivory or vulcanite.
In point of solidity, this casing is not in any way inferior to a casing of
vulcanite, but it is much more easily worked, and notwithstanding its hardness
the material, is not so brittle as vulcanite.
The impregnating of the asbestos cardboard with a solution of exactly 12 deg.
potassium or sodium water glass is necessary on account of the fact that the
stronger solution which would render the casing hard and steadfast against pres-
sure, would not comply with the second purpose in view, viz. to make it water-
proof and acid proof; because stronger solutions of water glass than 12 deg. do
not permit the absorption of resins by the asbestos and would consequently be
re-dissolved in any other liquid.

page_text: Moreover, a weaker solution than 12 deg. potassium-or sodium water glass
is inapplicable for saturating the cardboard because it leaves the resulting casing
too soft and in a condition unsuitable for being worked in the manner described
above.
The adhesive substance used for the manufacture of the casing must in the
first place be heat-resisting, because otherwise it would melt in
the drying
process to which the casing is submitted, and this latter would become unlapped.
Secondly, it must be waterproof and nevertheless capable of absorbing liquid
resins or of combining with them, whereby the said substance remains insoluble
in acids and other liquids. If the adhesive substance has not all the qualities
required, it renders the casing defective and therefore worthless.
The lapping apparatus above mentioned, serving for the manufacture of this
casing, and being an essential advantage for this manufacture, is made in such
a form, that two obliquely running cheeks a and b one opposite to the other are
capable of being moved backwards and forwards upon two inclined planes of a
centre piece c guided for the time being in dove-tailed recesses. This movement
is effected by means of a screw e held by a nut d and guided in a stationary
piece . By turning the handle f of the screw e to the left side, the centre
piece c is caused to move backward out of the two cheeks a and b (Fig. 3) and as
the faces of the centre piece care tapered towards the front, the lapping apparatus
will become much narrower laterally, than it really is (see the dotted lines in
Figs. 3 & 5) by reason of which diminution, the casing lapped on the apparatus
may be easily withdrawn.
By turning the handle f to the right, the apparatus is brought back to its
original position necessary to give the required dimensions to the casing to be
manufactured.
For making the insulating strips, boards and other similar articles waterproof and
acid proof, I treat them exactly in the same manner as the casings. These articles
are intended to be made use of, in wet or damp localities.
If however, the insulating boards, strips and the like are to be heat-resisting,
in order to prevent them from melting in case the electric current is short-cir
cuited, they are only treated with solutions of sodium--or potassium water glass
of 1,100 spec. gravity, equal to 12 deg. B., and, when finished, they are dried, and
coated with a suitable adhesive substance, as described before, in referring to the
accumulator casings.
The manufacture of the insulating strips or boards is carried out in the
following manner:
I place the asbestos cardboard or paper which has previously been suitably cut
and impregnated with a solution of potassium-or sodium water glass, into a
shaped mould g of any required length and suitable for the purpose, and then I
work it with a moulding iron F which is shaped in the reversed way to the
mould g and provided with a handle, by rolling the said iron to and fro inside
the mould g in such a manner, that the still soft and smooth asbestos cardboard
or paper (as shown in Figs. 11 and 12) takes the shape of the profile of the said
mould. I then fill up the spaces either with asbestos or (for the sake of
economy) with wood or any other suitable material h¹ which must previously be
made heat resisting, in any suitable way. Now I coat its uppermost face with
any suitable. adhesive substance, and place upon it an asbestos layer (Fig. 12).
The two free ends and 7 of the asbestos cardboard now adhere when bent one
after the other upon the layer i in such a manner, that when the product is taken
out of the mould g, an insulating board or strip L of the desired length and
shaped as shown in cross section in Fig. 13 is obtained.
The cover m consisting of a somewhat thicker asbestos cardboard is also
saturated in a suitable manner and according to the purpose for which it is
intended the requisite stability being imparted to the cover by shaping it in a
mould and by using the moulding iron.

page_text: 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 method of manufacturing water-proof and acid proof insulating casing
for accumulators, receptacles or vessels, insulating strips or boards and similar
articles of asbestos paper, cardboard or cloth, substantially as set forth.
2. In manufacturing waterproof and acid proof insulating casings for accumu-
lators, receptacles, insulating strips or boards and similar articles of asbestos
paper, cardboard or cloth, according to the first claim, the employment of a
solution of potassium or sodium water glass of 1,100 spec. gravity, for the
impregnation of asbestos material, substantially as set forth.
3. In manufacturing water proof and acid proof insulating casings for accumu-
lators, receptacles, and other articles, of asbestos paper, cardboard or cloth,
according to the first claim, the employment of a lapping apparatus in such a
manner, that the sides of the accumulator casing or other articles composed of
two layers, and the bottom boards are composed of three layers of asbestos card-
board, substantially as set forth and shown in the drawings.
4. In manufacturing waterproof and acid proof insulating casings for accumu-
lators, receptacles vessels and the like, of asbestos paper, cardboard or cloth,
according to the first claim, the submitting the said casing to a second process
of impregnation with resins wax or paraffin, substantially as set forth.
5. In manufacturing waterproof and acid proof insulating casings for accumu-
lators, receptacles and other articles, of asbestos paper, cardboard or cloth, accord-
ing to the first claim, the employment of a lapping apparatus consisting of two
obliquely running cheeks one opposite to the other and of a centre piece movable
in a dove-tailed guide, substantially as set forth and shown in the drawings.
6. In manufacturing waterproof and acid proof insulating strips or boards or
other articles of asbestos paper, cardboard or cloth, the employment of moulds
of any desired profile, and of moulding irons having the corresponding reversed
profile of the said mould, and the filling up of the spaces between the various
profiles with asbestos or with other material previously made heat-resisting by
coating it in a suitable way, substantially as set forth and shown in the drawings.
7. In manufacturing waterproof and acid proof covers and other articles, of
asbestos paper, cardboard or cloth, according to the first claim, the employment
of somewhat thicker asbestos cardboard-saturated in a suitable manner and
according to the purpose for which it is intended-providing the said covers with
a profile by means of a mould and a moulding iron, substantially as set forth
and shown in the drawings.
8. In manufacturing waterproof and acid proof insulating casings for accumu-
lators, receptacles, insulating strips or other articles of asbestos paper, cardboard
or cloth, according to the first claim, the employment of a bath of molten resins,
wax, paraffin or other suitable material, and having a constant temperature of
160 deg. Reaumur, wherein the casing remains for a period of from 2 to 8 hours:
and the further employment of a receptacle for drying the articles, substantially
as set forth.