IMPROVEMENTS IN THE MANUFACTURE OF INDIA-RUBBER TUBES OR PIPES
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Louis Victor Lerenard at the Office
of the Commissioners of Patents on the 29th September 1879.
LOUIS VICTOR LERENARD, of the Societé Lerenard fils et Benjamins, of Paris,
Manufacturers. "IMPROVEMENTS IN THE MANUFACTURE OF INDIA-RUBBER TUBES
OR PIPES."
This Invention relates to the manufacture of those flexible india-rubber tubes
which are provided with metallic strengthening or supporting spirals or coils in
their interior, and consists in substituting hardened india-rubber strengthening
spirals for the metallic spirals at present in use.
The employment in a large number of industrial applications for the transference
of wines and other liquids, acids, and other corrosive fluids, of tubes or pipes
having interior spirals of iron or other metal offers various inconveniences which
are obviated by the use of hardened india-rubber spirals in the interior of the
tubes, these latter spirals possessing the requisite unchangeable and resisting
properties.
According to this Invention the tube is composed, firstly, of a spiral or coil of
hardened india-rubber, and may have any desired section; this spiral forms the
interior wall or lining of the flexible india-rubber tube, or it may be placed
between two thicknesses of flexible india-rubber tubing. The sectional dimensions
of the spiral are established according to the resistance of the tubes to the action of
suction and forcing. The spirals themselves may be straight, bent, or any other
shape that may be taken by the tubes to which they are adapted, and by
vulcanizing they receive a certain elasticity and hardness sufficient to form
a spring.
It is essential that the india-rubber spirals be not too rigid, as if a tube
sustained a blow outside or is crushed-in, the thread of the coil inside would be
broken, and the tube would no longer be maintained.
I have discovered a composition for the thread of the coil or spiral having such a
resistance that it may be twisted 15 or 20 times before its breaking.
The mixture with which this thread of a coil is formed is composed of pure
caoutchouc "para," with a proportion of flowers of sulphur determined according
to the vulcanization of the hardened india-rubber thread.
The vulcanization to which the india-rubber thread of the coil is subjected is such
that after submitting a tube made with the said thread to a pressure causing the

page_text: two interior walls to touch each other the thread remains unbroken, and the tube
resumes its original shape, and without any injury.
Thus resistance to suction and perfect solidity are obtained, and the flexibility
and lightness is one third greater than an ordinary tube or pipe of the same
thickness of walls, and of equal diameters.
The threads employed to form the interior coils or spirals of hardened india-
rubber may have a circular section, and be drawn through the machine or draw
plates; but sometimes grains of sulphur are contained in the thread, and its
manufacture is somewhat difficult, and after numerous experiments I have adopted
a square section, the thread of the coil being composed of a very homogeneous
compound or mixture, and presenting an equal resistance over the whole of its
length.
A square threaded coil has the great advantage over the round threaded coil, it
being easier to place in position, and is not liable to be displaced when the tube
or pipe is being used, its resistance or strength also boing much greater.
These square section threads are made in the following manner:-
A sheet or layer of caoutchouc is wound round a mandril or lathe "chuck," and
the solid cylinder thus formed is cut perpendicularly to its axis during its rotation
in such a manner as to forın rings or discs of caoutchouc, the size of which is equal
to the thickness of the sheet or layer of caoutchouc employed. Threads of square
section are thus formed which are used in the manufacture of these tubes with
inoxydizable strengthening spirals.