Improvements in the Manufacture of Hollow India-rubber Balls.
Year: 1888

page_text: Improvements in the Manufacture of Hollow India-rubber Balls.
We, EDGAR HERBST, of Breitensee, near Vienna, Factory Manager, SALOMON
KOHNBERGER and ARNOLD MANDL, both of 23, Schottenring, Vienna, Manufacturers,
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:-
The process hitherto usually employed in the manufacture from india-rubber of
hollow playing balls consists in first forming four segments of a hollow sphere,
composed of the usual mixture of caoutchouc and sulphur, cementing these together
and at the same time introducing into the ball thus formed a small quantity of water,
alcohol, ether or solid carbonate of ammonia; the ball being finally vulcanized in a
bi-part mould consisting of two hollow hemispheres, which when fitted together form
a spherical cavity.
Upon the temperature being raised to the degree requisite for the process of
vulcanization, the liquid is evaporated or the carbonate of ammonia is decomposed,
and the vapour or gas evolved within the ball presses the sides thereof against the hot
sides of the mould and ensures the vulcanization of the caoutchouc.
When the process of vulcanization is completed, the mould is allowed to cool and
the ball is removed. The vapour on cooling condenses; or, when carbonate of
ammonia is used, the same partly resumes its solid condition, with the result that the
ball comes out of the mould in a slack state, unfit for playing purposes.
In order to reinflate the ball and render it fit for use, it is perforated by means of
a hollow needle at a part where its side is thickened by an internal rubber disc; the
said hollow needle serving as a filling pipe, through which the ball is inflated with
compressed air. Finally, the puncture made by the hollow needle is closed with
rubber cement.
The liquid or salt introduced into the ball before the latter is vulcanized serves
solely by its expansion to press the sides of the ball against the sides of the mould
during the process of vulcanization; the vapour evolved not being intended to inflate
the ball to the extent necessary to adapt it for use.

page_text: Our invention has for its object the vulcanization and inflation of the ball at one
and the same operation. The materials above referred to as being commonly
introduced into hollow rubber balls are inappropriate for the purpose of our
invention.
In carrying out our improved process of manufacture, we employ nitrites of the
alkalis, and, by preference, as this has proved most suitable, a mixture of equivalent
quantities of nitrite of soda and of ammonium chloride; the interior of each ball
being charged with a definite quantity of the said mixture according to the size of
the ball. The precise quantity appropriate for each size may be best determined by
experiment, inasmuch as the quantity will vary to some extent with the quality of the
india-rubber employed. Where, for example, the india-rubber is hard and resisting,
a greater quantity of the mixture will be required than in those cases where the
material is soft and elastic. In the manufacture of a ball not exceeding 80 millimeters
in diameter from india-rubber of average elasticity, we use about half a gramme of
the mixture of nitrite of soda and ammonium chloride to each 100 cubic centimeters
of the ball's volume. For balls exceeding 80 millimeters in diameter, we find two-
fifths of a gramme of the mixture for each 100 cubic centimeters of the ball's volume
appropriate. The temperature required for the vulcanization of the rubber suffices
to produce the decomposition of the mixture, the salts thereof recombining according
to the following equation
-
Na NO2 + NH, Cl = Na Cl + 2 H₂ O + 2 N.
-
-2
The nitrogen evolved not only effects the dilatation of the ball, but maintains it in
an inflated state after the mould has cooled.
By these means, the supplementary process of perforation, inflation and re-sealing
is dispensed with, and the employment of the rubber thickening disc avoidedⓇ;
security against subsequent slackening being at the same time afforded.
Having thus particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we claim :-
1st: The improved process of manufacturing hollow india-rubber balls sub-
stantially as herein described whereby vulcanization and inflation are effected at a
single operation.
2ndly-In the process of manufacturing hollow india-rubber balls, introducing to
the interior of each ball previously to vulcanization a suitable quantity of a mixture of
a nitrite of an alkali with ammonium chloride, substantially as and for the purposes
set forth.
Dated this 21st day of November 1888.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C.,
Agent for the Applicants.