Note: Descriptions are shown in the official language in which they were submitted.
1.
HOSE MANUFACT~RE
This invention relates to a method of rnanuEacture of
hose and in particular, though not exclusively, to a
method su~table for the continuous manufacture of long
length hose. Conventionally, long length hose is manuf~ct-
ured by ex~ruding inner lining layer of elastomeric material
onto a mandrel, applying a braided wire or cord, or
helically wound strip, reinforcement layer by means of a
braiding machine or strip winding machine, applying an
outer ~overing layer of elastomeric material and vulcanis-
ing the assembly. Long lengths of such hose are made on
a flexible mandrel, for example a nylon rod, and in this
case the assembled hose is covered by a sheath oflead,
which is applied by a lead press or lead extruder, to
protect the outer cover from marking by steam during
vulcanisation and damage by handling. ~he assembly is
then coiled up and placed in a curing oven in this
coiled state, After curing, the lead sheath is slit
and remo~ed whereupon the lead may be re-used.
Whilst produclng good quality hose, the lead sheath
method has the di~advantage of requiring the provision of
expensive lead coa~ing apparatus7
Surface marking by ~team and damage by handling can
to a certain extent be avoided by providing the hose with
a temporary wrapping shaath of, for example, helically
wound nylon strip material during vulcanisation. This
does, however, leave a helically extending imprint on the
outer hose ~urface where the hose has been contacted
2.
directly by edges of the nylon ~trip. This imprint is not
cor.sidered by customers to be indicative oE a high quality
product and it i5 highly desirable to avoid the formation
of such markings.
Damage by handl.ing can alternatively be avoided by
use of a catenary me~hod o manufacture in whlch following
the formation of a cover layer over a reinforcement structure
the resulting hose assembly, supported internal.ly by a
mandrel, is fed continuousl~ to a steam heating chamber
where it is suspended out of contact with the structure of
the chamber. The cover and other curable layers of the
hose stxucture are cured sufficiently before the hose leaves
the chamber so that no surface damage results from contact
of the hose with seals at the exit of the ch~mber. This
method is cheap to use and also convenient since steam
supplies are commonly availabla in factories especially
those making use of vulcanisation equipment. In practlae,
however, ik has been found that at ~he required vuloani~-
ation temperaturQ~ the pres~ure which can be u~ed i5
insuflcient to effectively bond the layers toyether and
hoses manufactured by this rnethod have tended to fail by
bursting or separation of cvver and reinforcement layers
sooner than equivalent hoses made by the lead ~heath method.
According to one asp~ct of the present invention,
we provide a method of continuous hose manuacture comprising
continuously feeding a long leng$h flexible mandrel supporting
a~ ,f~u~ hose assembly comprising an inner liner of
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~ uncured polymeric material and a reinforcement structure to
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3.
an extruder and extru~iny an ou-ter cover of curable polymeric
material around said reinforcement structure and continuously
fe~ding said mandrel and covered hose assembly through a
curing unit in which said covered hose assemhly is surrounded
by and in contact with heating fluid at a pressure in the
range from lO0 to 500 p.s.i. and a temperatu~ suffic~ent to
effect curing of sai~ lin~r and cover materials, said curing
temperature being substantially independent of the curing
pressure and subsequently removing said flexible mandrel~
By the use of a pressure greater than lO0 p.s.i., it
has been found that the resulting hose has a resistance to
failure very similar to that of hose manufactured by the lead
sheath method. Whilst it is ~ecessary to provide a suitable
curing unit and:means for the supply of heating fluid at a
high pressure, this will in general be less costly than the
provision of lead sheathing and stripping equipment.
Preferably the pre~sure of the heating fluid is greater than
: 250 p.s.i. and more preferably is of the order oE 400 p,~.1.,
though even higher pressures may be used. The use of very high
pressures leads to difficulty in ensuxiny~an adequate heatiny
1uid seal be~wee~ the curing unit and hose passing therefrom,
and does not result in any improvement in hose quality. Thus
the use of pressures greater than in the order of 500 p.s.i.
is not genexally envisaged.
Preferably the heating fluid is a compound having
a liquid form at vulcanisation temperatures of the order of
170-200C and the vulcanisation temperature is substantially
independent of changes in pressure. Consequently, for a
vulcanisation temperature of the order of 170-200C
.; the pressure of the heating fluid can be
',~
,: ,
~lAh~ 3
selected ~or example in the range ~rom 100 to 500 p.~,i , 50
that the layers of the hose are sufficiently bonded to one
another. ~n this way a hose of similar ~uality to that obtained
by the lead sheath process may be obtained without the above-
mentioned problems and disadvantages of the lead sheath process.
A partic~llarly suitable heating fluid is a salt, such asa eutectic mixure of sodium and potassium nitrates, or a nitrate
such as that identified by the trade mark Cassell TR155 ex I.C.I.
which has a liquid form at temperatures of the order of 170C.
The reinforcement structure may be formed from a layer o~
lapped, s~iralled, or braided reinforcement of metal wire or
filaments, strands or yarns made of plastics material or other
suitable material for example nylon or an aromatic polyamide
such as that identified by the trade mark Kevlar (poly (p-phenylene
terephthalamide) ) ex Du Pont.
The invention also provides hose manufactured by method
in accordanae wlth the present invention.
One embodiment of the invention will now be described by way
of example, with reference to the accompanyiny diagrammatic dr~wing
showiny apparatus for the application of a cover layer to a part
formed hose assembly and curing of the covered hose assembly.
The apparatus comprises a tubular curing unit 10 curved
along its length so as to conform substantially to the catenary
curve shape as adopted by the hose being passed through the unit
25 on a flexible mandrel supported only
, .i,.
s.
at the end~ of the unit. One end o~ the curing unit surround~
the ou~let of an. extruder 11 provided ~or application o~ a
cover layer lS to a part formed ho~e as3emb1y 14, and at the
other end o~ the curing unit a water seal 12 is provided to
5 seal again~t the outer ~urface of substantially cured ho~e
and re3trict lo~ o~ heating fluid from the curing unit~
The curing unit i~ provided with an inlet 13 in the region
of the water qeal for the ~upply of pressurised heatiny
fluid to the curing unit, and an outlet 16, for the heat-
ing Eluid i~ provided on an upper part of the curing unitclose to the extruder 11. Haul-off means (not shown) i~
provided to draw cured hose from the curing unit.
In use of the apparatus a part fDrmed hose assembly
14 compr~ing a neoprene lining layer and a wire braided
reinforaement layer surrounding the li~ing layer and
~upported on an inner flexible nylon mandrel 17 i9 Eed
; to the extruder 11 ~or application oE a rubber covex
~ layer 15 over the braided reinEorcemen.t. On leaving
: the extruder the covered ho~e as~emhly immediataly
enter~ the tubular curiny unit 10 and pa~es along the
length o~ the curing unit to emerge through the water end
seal 12 in a substantially cured condition~ Whil~t
pa~ing through tho curing unit the covered ho3e a~3embly
15 i8 ~ubjected to heating from a salt mixture of sodium
nitrite and 30dium nitrate supplled to the curing unit
at a pre3sure in the order of 400 p.s.i~ and temperature
of 200C. Subsequent to pa~age through the curing
unit the mandrel 17 i~ removed from the covered ho~e
6.
as~embly.
Typically the flexible nylon mandrel has a length
in the ord~r of SOO ~eet. Preferably to facilitate
ease of continuous operation and to avoid the need for
re-threading of the mandrel and covered hose assembly
through the water end seal 12, two or ~-ore long
length mandrels may be joined together for consecutive
passage through the extruder and curing unit and
subsequently separated to facilitate mandrel removal
and coiling of the manufactured hose.
Whilst in the above-described embodiment reference
is made to the use of a nylon mandrel, other materials
such as steel may be used, and the mandrel may be of
tubular or rod construction. An appropriate selection
of the form of the mandxel enables the effect of
buoyancy of the heating fluid on hose a3semblies of
different diameter and density to be counteracked
and thereby ensure that ~or a given haul-of~ ten~ion,
the uncured ho~e material lS remain~ out o~ contact
with the inner wall o~ ~he curing tube 10. Alternatively,
similar mandrel~ may be used for a range of hose
thicknesses and material~, and the variation of
buoyancy counteracted by suitable adjustment of t~e
haul-off tension.
The use of a catenary shaped curing tube is not
sssential, and in an alternative apparatus the curing
unit may be arranged ~o that the hose passee ~er~ically
therethrough. Such an alternative doe3, however,
7.
requirs the provisiozl of a suitably tall building and thus
the substantially horizontal catenary process i3
preferrsd as ~eing more .readily per~ormed in conventional
factory ~pace.
