U.S. patent number 5,904,184 [Application Number 08/836,407] was granted by the patent office on 1999-05-18 for reinforced flexible tube, in particular for use in oleodynamic circuits.
This patent grant is currently assigned to Manuli Rubber Industries, S.p.A. Zona Industriale Campolungo. Invention is credited to Ernesto Polini, Paolo Seghi.
United States Patent |
5,904,184 |
Polini , et al. |
May 18, 1999 |
Reinforced flexible tube, in particular for use in oleodynamic
circuits
Abstract
A flexible tube (10), in particular for use in oleodynamic
circuits, comprises a substrate shaped in the form of a tubular
core (12) around which at least one reinforcing layer (14) is
arranged. The substrate (12) comprises a radially internal layer of
elastomeric material extruded longitudinally (16) and a radially
external layer (20) obtained as a result of winding a strip of
rubber-coated fabric spirally around the internal layer (16).
Inventors: |
Polini; Ernesto (Ascoli Piceno,
IT), Seghi; Paolo (Milan, IT) |
Assignee: |
Manuli Rubber Industries, S.p.A.
Zona Industriale Campolungo (Ascoli Piceno, IT)
|
Family
ID: |
11412871 |
Appl.
No.: |
08/836,407 |
Filed: |
May 1, 1997 |
PCT
Filed: |
October 30, 1995 |
PCT No.: |
PCT/EP95/04261 |
371
Date: |
May 01, 1997 |
102(e)
Date: |
May 01, 1997 |
PCT
Pub. No.: |
WO96/14532 |
PCT
Pub. Date: |
May 17, 1996 |
Foreign Application Priority Data
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Nov 3, 1994 [IT] |
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T094A0877 |
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Current U.S.
Class: |
138/126; 138/124;
138/130; 138/137 |
Current CPC
Class: |
F16L
11/085 (20130101); F16L 11/081 (20130101) |
Current International
Class: |
F16L
11/08 (20060101); F16L 011/08 () |
Field of
Search: |
;138/126,123,129,139,124,127,137,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1007229 |
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Oct 1965 |
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GB |
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1400003 |
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Jul 1975 |
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GB |
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Primary Examiner: Brinson; Patrick F.
Attorney, Agent or Firm: Needle & Rosenberg, P.C.
Claims
We claim:
1. A flexible tube, in particular for use in oleodynamic circuits,
comprising a substrate shaped in the form of a tubular core around
which at least one reinforcing layer is arranged, said substrate
comprising a radially internal layer of elastomeric material
extruded longitudinally and a radially external layer obtained as a
result of winding a strip of rubber-coated fabric spirally around
the internal layer,
wherein the at least one reinforcing layer of said tube is produced
by braiding or coiling technology.
2. A flexible tube according to claim 1, wherein the strip of
rubber-coated fabric is wound in such a manner that its fabric
surface is remote from the radially internal layer of extruded
elastomeric material.
3. A flexible tube according to either of the preceding claims,
wherein the strip is wound round the radially internal layer,
overlapping adjacent turns to at least half of the width of the
strip.
4. A flexible tube according to claim 1, wherein the radially
external layer of the core is covered with an additional
elastomeric layer which promotes the adhesion of the reinforcing
layer to the core.
5. A flexible tube according to claim 1, wherein the substrate
shaped in the form of a tubular core has a thickness of between 0.5
and 6 mm.
6. A flexible tube according to claim 1, wherein the ratio between
the thicknesses of the radially internal and external layers is
between 0.1 and 10.
7. A flexible tube according to claim 2, wherein the radially
external layer of the core is covered with an additional
elastomeric layer which promotes the adhesion of the reinforcing
layer to the core.
8. A flexible tube according to claim 3, wherein the radially
external layer of the core is covered with an additional
elastomeric layer which promotes the adhesion of the reinforcing
layer to the core.
9. A flexible tube according to claim 2, wherein the substrate
shaped in the form of a tubular core has a thickness of between 0.5
and 6 mm.
10. A flexible tube according to claim 3, wherein the substrate
shaped in the form of a tubular core has a thickness of between 0.5
and 6 mm.
11. A flexible tube according to claim 4, wherein the substrate
shaped in the form of a tubular core has a thickness of between 0.5
and 6 mm.
12. A flexible tube according to claim 2, wherein the ratio between
the thicknesses of the radially internal and external layers is
between 0.1 and 10.
13. A flexible tube according to claim 3, wherein the ratio between
the thicknesses of the radially internal and external layers is
between 0.1 and 10.
14. A flexible tube according to claim 4, wherein the ratio between
the thicknesses of the radially internal and external layers is
between 0.1 and 10.
15. A flexible tube according to claim 5, wherein the ratio between
the thicknesses of the radially internal and external layers is
between 0.1 and 10.
Description
The present invention relates to a flexible tube, in particular for
use in oleodynamic circuits subjected to very high pressures,
comprising a substrate shaped in the form of a tubular core around
which at least one reinforcing layer is arranged.
The aim of the present invention is to provide a flexible tube
which has the properties necessary for the use indicated above,
with respect in particular to mechanical and chemical resistance,
and which at the same time has a simple structure compatible with
the usual techniques employed in the production of flexible
tubes.
This aim is achieved by means of a flexible tube of the type
indicated above which is characterised in that the substrate
comprises a radially internal layer of elastomeric material
extruded longitudinally and a radially external layer obtained as a
result of winding a strip of rubber-coated fabric spirally around
the internal layer.
The substrate has, overall, a thickness which is preferably between
0.5 and 6 mm, and the ratio between the thicknesses of the radially
internal and external layers is preferably between 0.1 and 10.
Each of the two layers forming the core of the tube of the
invention confers on the tube some of the properties necessary to
satisfy requirements in use.
To be more specific, the extruded internal layer ensures complete
impermeability to the fluid flowing inside.
This impermeability could not be reliably ensured by a wound
internal layer because of the possibility of errors occurring
during its manufacturing process. This process provides that a
strip of material is wound spirally around a central spindle,
partially overlapping adjacent turns in the direction of the width
of the strip. If, however, the overlapping is not carried out
correctly, leaving a gap between adjacent turns, the fluid flowing
in the tube may pass through the gap and damage the structure of
the tube irreparably.
The fact that the external layer of rubber-coated fabric is wound
clearly does not jeopardise the impermeability of the tube but,
rather, confers an advantageous firmness to its structure owing
both to the possibility of using elastomeric materials that differ
from those of the internal layer and therefore have the necessary
mechanical characteristics, and to the presence of the reinforcing
fabric associated with the rubber.
This structure of the external layer is thus capable of
withstanding satisfactorily the stresses which are transmitted to
it both during the vulcanisation phase and during use, especially
when high-performance steels capable of withstanding extremely high
loads are used in the reinforcing layer(s).
More generally, the external layer of the core confers on the tube
according to the invention excellent properties of mechanical
strength while the internal layer confers on it excellent sealing
and chemical resistance properties.
This functional separation can advantageously be optimised by using
different materials for the compositions employed in the
manufacture of these two layers.
For example, it is possible to use for the internal extruded layer
compositions having excellent resistance to oils of vegetable
origin, the use of which is becoming ever more widespread, even if
these compositions have a reduced mechanical strength, because this
latter property is conferred to a sufficient degree by the external
wound layer.
The double-layered structure of the substrate, shaped in the form
of a tubular core, of the tube according to the invention also
constitutes intrinsic security against possible defects in one of
the two layers, by guaranteeing that the tube performs its function
even if there are such defects.
One or more reinforcing layers which are preferably produced by
coiling and/or braiding technology are arranged coaxially around
the substrate of the tube of the invention.
In this last case in particular high-pressure tubes are obtained
which are capable of withstanding high torsional and bending
stresses, with the external layer of the core, which layer acts as
a support for the braided reinforcing layer lying over it and which
restricts the swelling of the extruded layer beneath it, exercising
overall an anti-burst barrier action.
The overall thickness of the substrate of the tube of the invention
may be less than that which would be necessary if this substrate
were made entirely of extruded elastomeric material or of wound
rubber-coated fabric. This therefore increases the mechanical
efficiency of the braided reinforcing layer which may be arranged
in accordance with a greater curvature.
Other advantages and characteristics of the present invention will
become clear from the following detailed description which is given
with reference to the appended drawing which is provided purely by
way of non-limiting example and in which:
the single FIGURE is a partially sectional side view of a piece of
tube according to the invention fitted on a spindle.
A flexible tube 10, in particular for use in oleodynamic circuits,
comprises a substrate shaped in the form of a tubular core 12
around which is arranged a reinforcing layer 14 which is produced
by braiding or coiling technology.
The core 12 is formed by a radially internal layer 16 of
elastomeric material extruded longitudinally around a spindle 18
and by a radially external layer 20 obtained as a result of winding
a strip of rubber-coated fabric spirally around the internal layer
16.
The winding operation, and also the extruding operation, are
carried out using techniques and machinery customarily employed in
the production of flexible tubes.
The strip is wound in such a manner that its fabric surface 22 is
remote from the radially internal layer 16 of extruded elastomeric
material and in such a manner that adjacent turns overlap to half
of the width of the strip.
An external layer 20 of which the thickness is double than that of
the strip is thus obtained. It is of course possible to overlap
adjacent turns to a greater extent, thus producing a corresponding
increase in the thickness of the wound external layer 20.
The latter layer may be covered with an additional elastomeric
layer 24 which may, for example, be wound spirally in the
longitudinal direction and which promotes the adhesion of the
reinforcing layer 14 to the core 12.
Alternatively, this adhesive elastomeric layer may be integrated in
the strip of rubber-coated fabric which would then be composed of
the fabric contained between two layers of rubber. The entire
sandwich can be obtained by means of the same calendering
process.
The resulting structure thus has an elastomeric covering layer 26
and the tube 10 thus produced is subjected to vulcanisation.
The composite structure of the core 12 of the tube 10 makes it
possible to obtain all the advantages associated with the
technologies of extrusion and winding used for the manufacture of
the internal layer 16 and the external layer 20, respectively.
The extruded internal layer 16 ensures impermeability and can be
produced using materials which exhibit a high degree of chemical
resistance to the fluid which flows inside the tube 10, even if
those materials have a reduced mechanical strength, this strength
in any case being guaranteed by the wound external layer 20.
Naturally, it will be appreciated that, the principle of the
invention remaining the same, the details of construction and forms
of embodiment may vary widely with respect to those described and
illustrated in the drawing, without thereby departing from the
scope of the present invention.
For example, in embodiments not illustrated of the tube of the
invention, it is possible to arrange coaxially around the core more
reinforcing layers produced by braiding and/or coiling technologies
and/or simply to arrange the turns of the wound external layer of
the core close together without causing any overlapping between
them.
* * * * *