Adolf Heil.

The manufacture of rubber goods : a practical handbook for the use of manufacturers, chemists, and others online

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In purchasing a wrapping-
machine it is of importance
to select one constructed on
such a system as permits of
the upper roller being auto-
matically lifted, by eccentric
action, whenever the wall of
the hose runs a little stouter.
Machines which are not pro-
vided with some such con-
trivance are of doubtful value,
since the variable pressure
which they exert tends to rub
through the hose. A very ser-
viceable and entirely new kind

of wrapping-machine is il-

V lust rated in fig. 52 ; this
machine has met with great
approval during the short

: time it has been working,

V and it embodies the sim-
^ plest of principles. • The

hose is driven by means of
a chain and chain wheel in
k connection with a variable-
1^ speed friction drive. The
elements of the latter can
be adjusted to run alter-




MANUFACTURE OF SOFT -RUBBER ARTICLES.



125



nately in either direction, and the output of the machine is exceeded
by no other make. In the case of hose up to 19 mm. in diameter,
made from suitable mixings, a single binder is sufficient, but when
this diameter is exceeded the hose is wrapped twice, up to a
diameter of 28 mm. Hose of greater dimensions still must be
wrapped three and often four times. If, however, it is found
necessary, in any given instance, to wrap a liose of normal dimen-
sions (say about 40 mm.) six .or eight times in order to produce
a perfect article, it is pretty certain that there is some great mis-
take in the composition of the rubber. At the same time, it may
be mentioned that liose with cloth insertion is also made with a
smooth surface, with false seam-markings running the length of
the hose, so-called " hose made by the English method." " This




Fig. 52.



kind of hose is not wrapped, but is cured in chalk in the open.
The proofed insertion cloth used in the manufacture of such hose
must have powerful adhesive properties. This class of hose also
can best be made on the hose machine nowadays, the separate
coats being run out from it, through a nozzle shaped so as to
form the imitation seams. In orcler to make the outside coating
of rubber adhere fiVmly and closely to the insertion, the tubular
mandrel as it comes through the machine is caused to travel a little
faster than tlie rubber emerges from the nozzle.

Anotlier article for which a great demand has arisen is the
so-called

(fj) High-pressure hose (hose with braided insertion of hemp, cotton,
or brass-wire). — High pressure, or, as it is briefly called, braided
hose, is the ideal hose for conveying water, and for conveying
purposes in general. Over ordinary canvas insertion hose it has
the great general advantage of being able to withstand enormously



126 RUBBER MANUFACTURE.

high pressures, and can therefore be used of a relatively thinner
substance than ordinary hose.

The process of manufacture of this high-pressure hose, the
demand for which is constantly on the increase, is the same in
principle as already described, with the exception that in place of
the ordinary cotton insertion, an insertion made on the braiding
machine is used. The method of procedure is as follows : — The
tubular mandrel, covered with the inner coating of rubber, on
leaving the hose machine, passes over a short conveyor belt, which
serves rather the purpose of pushing the mandrel along, into the
braiding machine (fig. 53). Tlie speed of this machine is regulated
in exact accordance with that of the hose machine behind it.




Fig. 53.

Between the hose machine and the braiding machine, and fitted on
to the latter, is a small apparatus for covering the rubber coating
on the mandrel with a rubber solution of medium thickness ; during
the braiding process which follows, this solution penetrates into the
fibre of the hemp or cotton yarn, and brings about a very intimate
union at every point. This small apparatus, as shown in fig. 54,
consists of a small storage vessel with an automatic stirrer to
prevent the solution from settling, and a mouthpiece connected with
the outflow, beneath which a sheet-iron tray is fixed in order to
catch any excess of solution. The mouthpiece or nozzle must be
one of an interchangeable series, and is varied according to the size
or outside diameter of the hose. Inside the nozzle is a jet for
the supply of solution, and in front of this a celluloid, spreading-
knife is fixed. When the insertion has been braided on to the hose
♦"•he mandrel passes through a larger solutioning apparatus, filled



MANUFACTURE OF SOFT-RUBBER ARTICLES. 1 27

with thicker solution, which is spread all round the insertion. In
order to dry this off rapidly, by evaporating the benzine, a cast-iron
heating jacket of about 100 mm. diameter is used, which can be
provided with suitable nozzles at each end. The drying-jacket is
heated to about 45° C. and the hose is driven through it — air being
blown through at the same time by a fan. On leaving the
drying cylinder the mandrel rests on tlie conveyor placed in front
of it, and is carried forward at the same speed as it travels
throuoh the two machines, until the whole leno-th of 40 metres has
been coated with the inner coating, covered with the braided insertion,
and spread with a coat of solution.

Three hands are, as a rule, sufficient for the whole of this piece
of work : one to look after the hose machine, a girl to look to the




Fig. 54.

braiding macliine, and the third to superintend the working of the
whole plant.

This hose is generally made with two layers of braided inser-
tion, often with several layers, the method of procedure being the
same as above described, except that the hose machine runs empty
in the intermediate stages. The outer coating of the hose is also
run from the machine, and, as a rule, a slightly higher speed is
given to the conveyor, so as to cause the layer of rubber to adliere
firmly to the braiding. The braiding machines are mounted on
movable trolleys which can be run along rails lying transversely
in front of the hose machine, so that for the different sizes of hose,
different braiding machines can be used in conjunction with a single
hose machine. For diameters of from 10 to 28 mm, a 48-bobbin
machine will do ; for larger sizes, on the other hand, a machine with
sixty bobbins should be used. It is not advisable to use the same
braiding machine for all sizes, or the braiding will be in some cases



128 RUBBER MANUFACTURE.

too close- or too wide-meshed, and too long in spite of the adjust-
able transport. On the other hand, if some of the bobbins be left
out, the mesh becomes too open.

It is possible to make hose which will withstand a pressure of
200 atmospheres : in attempting this the number of ply of insertion
must be correctly selected with reference to the internal diameter.
For specially high pressure work it is advisable to carry out the
penultimate braiding with brass wire, which is followed by a final
braiding of hemp, this being in turn secured by a spiral wire.

(c) Manufacture of "Spiral" Hose. — The process is, in this case,
the same as for ordinary hose, except that in arranging the spiral
wire one must be guided by the purpose for which the hose is to
be used, whether for suction or for high internal pressures, or
whether it is to be adapted for both purposes, and the spiral wire
must be arranged according to requirements.

In the case of hose up to 30 mm, in diameter, the inside coating
is run directly on to the metal mandrel from the hose machine ; in
the case of the larger sizes, on the other hand, it is usual to proceed
according to the older method, by laying the sheet round the
mandrel, cutting down from end to end, pressing the seams well
together, and covering them, as a safeguard, with a narrow strip of
the same quality rubber, so that one may be doubly sure of the
seams holding. If the hose is to be used as a suction hose, the
spiral wire must be inserted immediately round the inside coating.
On the other hand, when it is to be used as pressure hose it is an
advantage to first of all roll the insertion down on to the inside
coating, and then to slip the spiral on. The spiral is generally
made of hard galvanised iron wire. Whereas the spiral used
formerly to be run on to the hose by hand, special machines have
come into use more recently, which coil the wire into suitable
spirals. The size of the spiral is regulated by the adjustment of
the matrices, so that it is only necessary to slip the ready-made
spiral over the inner coating. This method is a far more rational
as well as a more certain one than the old method. If the spiral is
wound on to the inside coat the latter gets greatly twisted, and
often torn, by the coiling on and expanding of the spiral. The
ends of the spiral are soldered and held in position by a strip of
unvulcanised rubber. On the top of the spiral there is always
placed a coat of rubber, and over this the insertion. On the other
hand, in the case of smooth-surface spiral hose, the interspaces
between successive coils of the wire are filled up with strips of
rubber, and then covered over. The making up is carried out in



MANUFACTURE OF SOFT-RUBBER ARTICLES. 1 29

the way previously described, according to the number of ply of
insertion, and finally the hose is surrounded with the cover. In
wrapping spiral tubing great care must be taken to see that all the
parts are perfectly tightly pressed together, so that no blisters can
be formed during vulcanisation. For this purpose a specially
constructed machine is employed, the principle of which may be
briefly explained. When the hose has been wrapped, it must be
well corded with strong hempen cord. In a slide in front of the
bench runs a winder, 2 metres long, with three cylinders, over
which the cord runs with one turn round each, and is thereby
braked. Above this the cord passes through a guide on to the
hose, and, the mandrel having been set in motion, is allowed to run
on to it under tension from the cylinders; thus directed by the
guide it is laid tight in the interspaces between the successive turns
of the spiral. As soon as the cord has reached the end of the
winder this is moved forward along the slide according to the
length of the hose, and there fixed, so that the cord can be wound
round still further along. This operation can be performed with a
good deal more power than by the workman passing the cord round
his own body and exerting the braking force by leaning on it.

Vulcanisation follows the cording process, and is carried out in a
long pipe, as in the case of all other hose. In conclusion, it is worth
mentioning that after the hose has been vulcanised and unwrapped,
it is best drawn off the mandrel by blowing compressed air between
the mandrel and the hose throuo^h a conical nozzle. A few twists
of the hose are sufficient to start it, and to enable it to be drawn off
the mandrel. In dealing with strong spiral hose of large dimensions
it is, however, necessary to make use of a forcing apparatus ; this
is brought into contact with one end of the hose, which it pushes
along slightly towards the other end, at the same time giving it a
twist against the tension of the spring. In this way hose up to
500 mm. in diameter, can be easily drawn off. For large-size hose
it is advisable to use as mandrels sheet-iron tubes, which can be
allowed to spring, or be drawn inwards. The most suitable mandrels
for hose manufacture are smooth-drawn steel tubes the ends of
which are united by screw couplings. These tubes last much longer
than brass mandrels, and on account of their absolutely smooth
surface make the inner surface of the tube as smooth as glass.
Steel tubes have yet another advantage over other metal mandrels,
in that the rubber does not adhere so firmly to them.

(d) Canvas Hose with Rubber Lining — Although the manufac-
ture of canvas hose really constitutes an industry in itself, it

9



I30



RUBBER MANUFACTURE.



often happens that the proofing is carried out as a speciality in
rubber-works. The manufacture may therefore be briefly dealt
with so that the reader may acquire some slight acquaintance with
the weaving of canvas hose. Power-driven iron looms have been
in use now for about fifteen years for making canvas hose ; the old
wooden hand-looms, which were formerly to be found in every
Thuringian peasant's dwelling, forming one branch of the cottage
industry, have entirely disappeared. The manufacture is now
carried out in factories only. Flax, cotton, or hemp yarn, spun in
different ways according to the size of the hose to be woven, is
used. Just as in the case of all other fabrics, a distinction is made in
canvas hose between the warp and the weft threads. The former,
which are twice as many as are required for the width of the hose,




Fig. 55.

are beamed by means of a beaming machine (figs. 55 and 55a) on
the warp beam. The mounting with the hcddles, through which
the separate threads are run, is also arranged exactly as in other
looms ; only the way in which the individual mountings move is
different, the warp first separating into upper and under warp, the
mountings then setting the upper warp so that the shuttle carries
the thread through on the lathe, whereupon the under warp lifts
and the weft thread is shot through in the same way. In this way
the seamless hose fabric is produced. The finished tube is rolled
up on a reel. About 300 metres can be made with one warp. The
rough hose, if it is to be rubber-lined, is finished oft' in the following
way: —

The hose is opened out by a machine (figs. 56 and 56a), and the
tape necessary for pulling the rubber lining through is then drawn
through it. The rubber lining, made on the tube machine, is partly
cured for thirty minutes, then covered with solution, and drawn



MANUFACTURE OF SOFT-RUBBER ARTICLES. I3I

through the hose by means of the tape already mentioned. The hose




Fig. 55a.



is then fixed on to a vulcanising cone, and firmly clamped on the
tube. The lower end is connected to the condensed steam pipe, and




Fig. 56.



the final vulcanisation can then be begun. It is advisable to subject
the hose to a steam pressure of about four to five atmospheres.

By the high pressure the hose-lining is forced firmly on to the



132



RUBBER MANUFACTURE.



walls of the canvas hose, the solution penetrating the interstices,
and the fabric and th§ rubber lining are thus intimately united.
After lowering the steam pressure the hose is tested with a water
pressure of 20 atmospheres, and hot air is then blown through it
to thoroughly dry it. This method of lining hose with rubber is,
however, being displaced by a new system which has important
advantages over the old well-known method, in that there is no
possibility of the hose-lining developing leaks. It is not always
possible to avoid the formation of thin places in the walls of the




Fig. 56a.

rubber lining when drawn into the hose by the old method, and
sometimes little grains or nibs of one or other of the ingredients,
which "iiave been introduced into the rubber in the course of mixing,
get shot out of their places, leaving holes in the rubber where
leakage may afterwards occur. In the new method the canvas hose
(figs. 57 and 58) is stretched out in a heating chamber 30 metres long,
arranged so as to be used in three sections. The fastening is by
means of plates screwed on to the foundation plate by six screws.
These plates are fixed to a movable frame, provided with a groove,
which can be so adjusted by turning the screws that the hose
inside the chamber is tightly stretched. The wires, to which are
attached the rubber brushes, the object of which is to draw the



MANUFACTURE OF SOFT-RUBBER ARTICLES.



^33



solution evenly along the tube, are run through the hose, and pass
over rollers at either end of the apparatus. These rollers can be




OrusfieT^ ^fl"^^-^^^ of insulating materia]




Fig. 57.



mechanically driven in either direction. Between the rollers and
the chamber is introduced a piece of apparatus which is connected



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Online LibraryAdolf HeilThe manufacture of rubber goods : a practical handbook for the use of manufacturers, chemists, and others → online text (page 12 of 21)