Note: Descriptions are shown in the official language in which they were submitted.
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W O 97/03815 PCTtG B96/01733
IMPROVEMENTS IN AND RELATING TO REINFORCED HOSE
This invention relates to a method for the manufacture of flexible
reinforced hose and to flexible reinforced hose which may be made by the
method of the invention.
The invention relates in particular, though not exclusively, to so-called
industrial type hose having a bore size typically of at least 10 mm, for
example in the range 10 mm to 100 mm, and able to transport fluid under
pressure.
The invention relates also, but not exclusively, to a hose and method
of manufacture of a hose of a rubber/plastics type for example having a
spiralled plastics strip liner or cover.
The invention further relates to a hose and method of manufacture of
hose which may be of a kind for use as delivery hose or for suction and
discharge .
An object of the present invention is to provide a method of hose
manufacture which may be undertaken using substantially conventional
manufacturing equipment and which is economical to perform.
Another object of the present invention is to provide an improved
reinforced hose and an improved method of manufacture of reinforced hose.
According to one aspect of the present invention a method of
manufacture of flexible reinforced hose comprises providing a support
mandrel, applying about the mandrel at least one layer of plastics material
and at least one layer of reinforcement material and then subjecting the
assembly so formed to a hot moulding process to increase the temperature
of the plastics material whereby in the finished product a bond is achieved
between component layers in consequence of said hot moulding process.
The invention envisages that preferably the materials for forming the
hose are applied about the support mandrel without the use of solvents and
without the use of applied heat.
Optionally the assembly formed about the mandrel may remain
supported by the mandrel during the hot moulding process. In an alternative
the reinforcement and plastics material are drawn or otherwise removed
W O 97/03815 ~ ~ n ~ 7 ~ ~ PCT/GB96/01733
from the mandrel, which may be a short length mandrel ~e.g. Iength less
than 2 metres, and optionally less than 0.5 metres), before being subjected
to the hot moulding process.
The layer of plastics material typically may be a layer of
thermoplastics material.
The invention teaches that all components of the hose may be applied
cold, by which is meant a temperature below 50 C, optionally below 30 C.
The layer of plastics material is applied in accordance with the
invention without any requirement that it should be pre-heated. Typically
it may be applied at ambient temperature, or at least at a temperature below
50 C. In the case of a plastics layer of thermoplastics typically it is applied
at a temperature below that at which it is mobile. An elevated temperature
which significantly reduces the handleability of the material, e g when in
strip or sheet form, preferably is avoided.
A suitable plastics material is a thermoplastic plastics material such
as polyvinylchloride. Other suitable materials include, for example,
polythene, ultra high molecular weight polyethylene, cross-linked
polyethylene, and low density polyethylene.
The plastics material may be applied in strip form, either helically,
with or without an overlap, or longitudinally and again with or without an
overlap.
A carrier of strip material may rotate about a non-rotating mandrel,
or a mandrel may rotate and strip material may be supplied from a non-
rotating carrier or feed. Similarly, a carrier or feed of strip material may
move axially along the length of a mandrel or a carrier or feed for strip
material may be fixed axially against movement in the direction of the length
of the mandrel and a mandrel may be caused to move axially past said
carrier or feed.
Two or more layers of plastics strip material may be provided. One
layer may extend helically in a first sense and another may extend helically
in an o,oposite sense. A combination of helically and longitudinally
extending strips may be provided.
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WO 97/03815 PCT/GB96/01733
The reinforcement layer may be formed from reinforcing elements of
textile or metallic material which may be applied or arranged to lie helically.
Reinforcing elements may be braided, knitted or spirally applied and may be
overlapped. The reinforcing elements may each be of a mono filament type
or comprise a plurality of filaments such as in a yarn or wire. Suitable
reinforcing materials include, for example, cotton, nylon, polyester, and
aramid, rayon and metallic materials such as brass-coated steel. Reinforcing
elements alternatively may be in the form of a woven fabric such as tyre
cord fabric.
The reinforcement layer need not comprise discrete reinforcing
elements. It may be formed by a tape or tube of a suitable material such as
nylon, e g extruded nylon, or of ultra high molecular weight polyethylene.
The reinforcement layer may be formed concurrent with the layer of
plastics material, for example by the use of a strip of plastics material
having reinforcing elements secured relative thereto, e g extending
longitudinally relative to the length of the strip. Reinforcing elements may
be secured relative to a strip of plastics by the use of an adhesive or by
embedding the elements in the plastics, e g during extrusion or calendering
of plastics to form the strip or soon after extrusion whilst the plastics strip
material is still hot and sufficiently soft to allow embedding of the elements.
A composite strip of plastics and reinforcing elements may be formed from
an assembly of two superimposed layers of strip material having reinforcing
elements sandwiched therebetween.
To assist in stabilizing the relative positions of neighbouring elements
of reinforcing material, especially discrete non-woven elements such as
yarns, the reinforcing elements may be interconnected by a flexible
polymeric membrane which in effect may form a web between neighbouring
reinforcing elements. The membrane may be employed to stabilise the
reinforcing elements either during application about a mandrel and/or in the
assembled arrangement prior to the hot moulding process. The membrane
may be of rubber or plastics. It may have a thickness less than 1.0 mm,
e.g. Iess than 0.4 mm.
WO 97/03815 ~ 7 ~ ~ ~ 3 ~ PCT/GB96/01733
The method may comprise forming a lining layer about the mandrel
prior to forming the layers of plastics and reinforcement materials.
The lining layer may be of a vulcanisable material such as rubber or
a cross linkable plastic at least in part vulcanised by the hot moulding
process step of the invention. Optionally layers of pre-cross linked
thermoplastic material may be incorporated in the hose.
The hose assembly may comprise outwards of layers of plastics
material and reinforcing material a constraining layer which co-operates with
the support mandrel to cause consolidation of the underlying layers during
said hot moulding process. The constraining layer may be a temporary layer
which is removed after the hot moulding process or it may remain as a part
of the finished hose; it may serve as an outer cover layer. The constraining
layer may be of a type which shrinks with increase of temperature. It is
taught that preferably the increase of temperature will reduce the viscosity
of the plastics material.
The invention teaches that bonding together of layers of non-
vulcanising material may be achieved by use of a hot moulding process
which is performed after assembly of components, preferably all
components, of a hose in a non-bonded condition around a mandrel.
The time duration and temperature of the hot moulding process is
selected to be sufficient to soften the plastics material to achieve a bond
between component layers in the finished hose. It may achieve a bond
between all of the component layers. The time duration and temperature
preferably is such that plastics material does not extrude through any
surrounding layers such as a constraining layer.
The hot moulding process may comprise application of heat, and
optionally also external pressure, to the external surface of the assembly of
layers for forming the finished hose. Heating may be provided by the use
of external heaters, such as radiant heaters, or an autoclave.
The invention envisages that in one embodiment optionally the
method may comprise forming about the mandrel a lining layer of extruded
material which is still warm from an extruder, and the thermal energy of that
WO 97/03815 ~ 7 3 ~ PCT/GB96/01733
layer may be utilised in part to perform the hot moulding process.
The method may use a solid or tubular mandrel. It may be of a metal
such as steel, or of plastics. The mandrel may be of a long length type
having a length of at least three (3) metres, typically a length of at least
forty (40) metres. Alternatively it may be of a short length as
aforedescribed .
The invention also provides a hose made by the method of the
invention.
The invention further provides a reinforced hose for use as a suction
hose and comprising a layer of plastics material, such as a thermoplastic
plastics material having embedded therein a helically extending metallic
reinforcing structure. The reinforcing structure may be of a steel wire and
be relatively stiff as compared with the body of the hose whereby it
provides the hose with resistance to collapse when the pressure external of
the hose exceeds that in the bore of the hose.
A suitable plastics material is polyvinylchloride (pvc).
Said suction hose may be manufactured by the method of the present
invention .
The suction hose alternatively may have embedded in the plastics
layer a metallic reinforcement, which may be a woven wire reinforcement,
to provide resistance to pressure arising in the bore of the hose, and a helix
of plastics material, such as pvc to provide resistance to collapse.
Embodiments of the present invention will now be described, by way
of example only, with reference to the accompanying diagrammatic
drawings in which:-
Figure 1 is a transverse section of a composite plastics andreinforcement strip for use in manufacture of a hose;
Figure 2 shows in perspective a part-formed hose assembly at a
first stage;
Figure 3 is a perspective view showing a part-formed hose
assembly at a second stage;
Figure 4 is a perspective of part of a part-formed hose at a third
W O 97/03815 ~ PCTIGB96/01733
stage of manufacture, and
Figure 5 is a side view of part of a suction hose, half in
longitudinal section, in accordance with another
embodiment of the invention.
A delivery type industrial hose having a one inch bore is
manufactured by extruding a rubber lining layer 11 about a mandrel 10.
Two composite hose body/reinforcement layers 12,13 are then formed
around the lining layer 11 by the helical winding of strip material 14 as
shown in transverse section in Figure 1. The strip material comprises a
layer 15 of pvc to one surface of which a plurality of rayon reinforcing cords
16 have been applied, to extend longitudinally in the direction of the length
of the strip. The rayon cords have been caused to embed in the plastics
material 15 by passing the cords and strip between a pair of rollers that
apply a light consolidating pressure to embed the cords into the plastics
before it has cooled.
Particularly to assist handleability no measures are taken to retain any
component in a warm condition prior to subsequent manufacture of the
hose. Thus, utilising the composite strips 14 of plastics material and
reinforcing elements at ambient temperature, one hose layer 12 is formed
by helically winding a first strip in a first sense (see Figure 3), and that is
then surrounded by a second layer 13 formed by winding a second strip 14
in an opposite sense, as shown in Figure 4.
The hose assembly so formed is then surrounded by a helically wound
woven nylon wrapping tape which serves as a constraining layer.
Subsequently the hose assembly so formed and supported by the mandrel
10 is placed in an autoclave and subjected to a temperature of
approximately 150 C for 35 minutes.
The temperature and duration of time in the autoclave are selected
such that the components of the hose become bonded together in
consequence of softening of the plastics material, but without the plastics
material softening such that the integrity and dimensional stability of the
structure is adversely affected.
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Subsequently the heated hose assembly is allowed to cool and the
constraining wrapper is removed.
For the manufacture of a suction/delivery hose having a four inch
bore a lining (21 ) (see Figure 5) is formed by spirally applying a strip of pvconto a hollow steel support mandrel.
A layer of reinforcement strip (22) comprising polyester yarns
longitudinally embedded in pvc, is spirally applied over the hose lining.
A steel wire (23) of a relatively stiff type known per se for use in the
manufacture of suction type hose, is then applied to form a helix over the
first reinforcement layer.
A second reinforcement layer (24) of material the same as first layer
(22) is spirally applied over the wire helix. A hose outer cover (25) of pvc
in strip form is applied spirally.
The hose assembly so formed is then surrounded by a helically wound
nylon wrapping strip to serve as a constraining layer.
Subsequently the hose assembly so formed and supported is
subjected in a steam autoclave to heating for 35 minutes at approximately
150 C.
Subsequently the heat-moulded hose assembly is allowed to cool, the
constraining wrapper is removed and the hose is then removed from the
mandrel .
The hose may have an outer shape which is corrugated or which is
smooth.
