The present invention regards a corrugated thermal-insulated tube.

Document WO 2014/134745 A1 discloses a tube according to the preamble of claim 1.

In such document, an outer surface of the tube is corrugated, that is to say it is provided with reliefs and depressions which - seen cross-sectionally - extend along arcs of a circle.

In the tube of document WO 2014/134745 A1 it is explained how the radius of the arc of the depressions must be greater than the radius of the arc of the reliefs, given that such condition allows to obtain a series of technical advantages, for example in terms of the thickness of the layer of outermost material, better tube folding, etc.

In the light of this prior art, the inventors of the present invention found that the prior art tube commented on herein is not satisfactory in terms of heat insulation.

More precisely, it was found that the greater depth of the depressions with respect to the reliefs locally reduces the thickness of the thermal-insulating material, hence the overall insulating thermal resistance deteriorates with respect to a smooth tube, and also with respect to a tube in which the radii of the reliefs and of the depressions are substantially identical.

Thus, the present invention falls within the previous context, by proposing to provide a thermal-insulated tube in which the amount of insulation is greater than the tubes of the prior art, without the need to renounce the surface corrugations which prove favourable when handling the tube.

As a matter of fact, in contrast to the enormous technical difficulty of providing the outer tubular body of the tube in a hollow space and with a small radius of curvature, the present inventors were able to provide an innovative thermal-insulated tube which is characterised by a greater radial amount of thermal barrier layer even at the depressions.

Such objective is achieved by means of a tube according to claim 1. The claims dependent on the latter show advantageous or preferred embodiments.

The object of the present invention will now be illustrated based on of the attached drawing, provided solely by way of non-limiting example. Figure 1 shows a schematic view of a longitudinal section of a tube portion, subject of the present invention, according to a possible embodiment.

It should be pointed out that the variant of figure 1 is only a schematisation, not to scale, hence the dimensional ratios of the layers and of the parts addressed hereinafter could be very different with respect to the shown variant.

With reference to the previous drawing, a thermal-insulated tube is marked - in its entirety - as 1.

According to an embodiment, the tube 1 is flexible, that is to say it is flexible enough to allow it to be wound on a storage reel. A possible use of such a tube is the transfer of an optionally heated fluid, for example for remote-heating systems, or the conveyance of gas or oil.

The thermal-insulated tube comprises at least one inner tubular body 2, a thermal barrier layer 6 and an outer tubular body 10.

It should be observed that, in the present description, the expressions "inner” and "outer” will be used with a merely relative connotation.

Thus, the so-called "outer” tubular body is located at the external of the so-called "inner” tubular body. It further ensues that the outer tubular body could be arranged inside a further layer or tubular body, arranged externally with respect to the outer tubular body.

The inner tubular body 2 extends around a longitudinal axis X to delimit a fluid through-flow conduit 4. Therefore, the through-flow conduit 4 is configured to receive a fluid, so as to convey it along the length thereof, advantageously without contaminating the fluid flowing through it, and without being contaminated by it.

According to an embodiment, the inner tubular body 2 at least partially (for example, completely) consists of a polymeric material.

According to different embodiments, the inner tubular body 2 could comprise a smooth tube (in which the wall 8 is externally and internally free of corrugations or knurlings) or at least one corrugated tube.

According to an embodiment, the tube 1 could comprise at least one pair of inner tubular bodies 2, arranged side by side to each other. In this case, the tube 1 according to such variant is a bi-lumen tube, or it could be a multi-lumen tube.

Optionally, if a plurality of inner tubular bodies is present, the latter could be smooth, corrugated, or at least one could be smooth and at least one could be corrugated.

It should be observed that, unless otherwise specified, the expressions "longitudinal”, "axial”, "radial”, or "transversal” will always be used to refer to the longitudinal extension axis X.

In the shown embodiment, such axis X is a substantially central axis, with respect to which the inner tubular body 2, the thermal barrier layer 6 and the outer tubular body 10 are arranged substantially coaxially.

Despite of this, according to other embodiments (not shown), the longitudinal extension axis X could be offset in an eccentric position with respect to a symmetry axis of the outer tubular body 10. For example, should the tube 1 comprise more than one inner tubular body 2 (as discussed above for example).

According to an embodiment, the inner tubular body 2 has a substantially circular "cross-section” - that is orthogonal with respect to the axis X - advantageously constant along the longitudinal extension thereof. According to an embodiment, the outer tubular body 10 has a substantially circular cross-section, advantageously variable radially along the longitudinal extension thereof.

The thermal barrier layer 6 surrounds the at least one inner tubular body 2 in a prevailing or substantially complete manner to prevent or limit thermal dispersions through a tubular wall 8 of the latter;

In other words, the thermal barrier layer 6 encloses the inner tubular body 2 so that the heat of the conveyed fluid undergoes the least possible thermal dispersion.

Optionally, at least one end portion of the inner tubular body 2 could project axially beyond the thermal barrier layer 6.

As concerns the variants which provide for more than one inner tubular body 2, the thermal barrier layer 6 surrounds both of these bodies.

According to an advantageous variant, the thermal barrier layer 6 is interposed between at least one pair of inner tubular bodies 2. Therefore, according to such variant, the thermal barrier layer 6 advantageously occupies a space comprised between inner tubular bodies 2, for example arranged side by side to each other.

Optionally, the tube 1 could comprise at least one electrical conductor 30 arranged or embedded in the thermal barrier layer 6 and extending longitudinally. For example, such conductor could be part of a leak detection system.

According to an embodiment, the thermal barrier layer 6 is in direct contact with the inner tubular body 2. As a result, a radially inner surface 26 of the thermal barrier layer 6 (or better, of the material constituting such layer 6) adheres to a radially outer surface 28 of the inner tubular body 2.

According to an embodiment, the thermal barrier layer 6 could be in indirect contact with the inner tubular body 2, i.e. through one or more intermediate layers interposed between such layer 6 and such tubular body 2.

For example, the intermediate layer could have reinforcement properties (in particular, chemical, mechanical), for the barrier, for example with respect to gases, and/or adhesive properties.

According to an embodiment, the thermal barrier layer 6 comprises or consists of a solidified expanded polymeric foam. For example, it could be a polyurethane foam or a polyisocyanurate foam.

According to a variant, the thermal barrier layer 6 or the solidified expanded polymeric foam has a density comprised in the range from 45-80 kg/m ³ .

The outer tubular body 10 encloses the thermal barrier layer 6 and comprises - extending in a longitudinal direction - an alternation of crests 12 and depressions 14 connected to each other.

According to an advantageous variant, the crests and the depressions could be connected through substantially straight connecting portions.

According to an embodiment, the outer tubular body 10 at least partially (for example, completely) consists of a polymeric material, optionally irrespectively selected with respect to the polymeric material of the inner tubular body 2.

By way of example, the polymeric material that can be used for the tubular bodies of this invention could be irrespectively selected from among the group consisting of polyethylene (optionally high, medium or low density), polypropylene, polyvinyl chloride, polycarbonate, polyethylene terephthalate or combinations thereof.

According to an embodiment, the outer tubular body 10 and the thermal barrier layer 6 are in indirect contact, that is to say through one or more intermediate layers interposed between such body 10 and such layer 6.

For example, the intermediate layer could have reinforcement properties (in particular, chemical, mechanical), for the barrier, for example with respect to gases, and/or adhesive properties.

According to an embodiment, the outer tubular body 10 and the thermal barrier layer 6 are in direct contact with respect to each other.

According to a preferred variant, the outer tubular body 10 is obtained as a multi-layer.

More precisely, the outer tubular body 10 advantageously comprises a radially innermost layer obtained as a web or film loop-wound around the inner tubular body 2 and welded longitudinally, and a radially outermost layer at contact with the radially innermost layer.

For example, the radially outermost layer could comprise an extruded (and solidified) material on the outer surface of the radially innermost layer.

According to such variant, the thermal barrier layer 6 advantageously occupies an interspace between the radially outer surface 28 of the inner tubular body 2 and the inner surface of the radially innermost layer of the outer tubular body 10.

According to an embodiment, the radially innermost layer and the radially outermost layer are made of the same polymeric material, or they consist of different polymeric materials which are mutually compatible.

In the present description, the expression "compatible” is used to indicate materials suitable for joining or welding together, without the use of adhesive substances or adhesion promoters, for example when one of them in molten form is placed in contact with the other.

The crests 12 have a radius of curvature Rc, and the depressions 14 have a radius of curvature R _A and penetrate into the thickness of the thermal barrier layer 6.

In other words, an outer surface 20 of the thermal barrier layer 6 delimits a plurality of recesses 22 (in particular with annular-shaped cross-section) in which the material of the depressions 14 is at least partially received.

According to a variant embodiment, the outer surface 20 of the thermal barrier layer 6 has a substantially complementary shape with respect to an inner surface 24 of the outer tubular body 10.

According to the invention, the R _A /R _C ratio is smaller than 1, hence the radius of curvature R _A of the depressions is smaller than the radius of curvature Rc of the crests 12.

According to an advantageous variant, the R _A /R _C ratio is smaller than 0,8, optionally comprised in the range 0,1 -0,7, for example comprised in the range from 0,2-0, 5.

With reference to the variant shown in the drawing, it can be observed that the thermal barrier layer 6 undergoes a radial thinning 16 on the depressions 14, and on the contrary, a radial thickening 18 on the crests 12.

According to an advantageous variant, the overall longitudinal extension of the radial thinnings 16 along the outer tubular body 10 - that is, the sum of the thinned longitudinal portions - is smaller than the overall longitudinal extension of the radial thickenings 18 - that is, the sum of the thickened longitudinal portions. Thus, the average thickness of the thermal barrier layer 6 increases with respect to the prior art, hence the insulating thermal resistance also increases correspondingly.

Just for the sake of completeness, it should actually be observed the insulating thermal resistance is proportional to the average thickness of the thermal barrier layer 6, and it is inversely proportional to the coefficient of thermal exchange l of the material.

In other words, the thermal barrier toward the external can be increased by raising the average thickness of the layer 6 (as in the present case), or by selecting a more performing insulating material, with a lower coefficient l.

According to an embodiment, the crests 12 and the depressions 14 create slight undulations of the outer tubular body 10, that is to say equal to or smaller than 4,0 millimetres in the radial direction.

According to a further embodiment, the difference between a diameter Dc of the outer tubular body 10 on the crests 12 and a diameter D _A of the outer tubular body 10 on the depressions 14 is equal to or smaller than 8,0 millimetres.

Advantageously, the difference D _C -D _A is equal to or smaller than 8,0 millimetres for diameters of the tube 1 comprised in the range 63-202 millimetres, for example 120-202 millimetres, optionally in the ranges 63-90 millimetres and/or 90-202 millimetres.

In other words, according to such variant, the slight undulation or the difference DC-DA remains unvaried irrespective of the outer diameter of the thermal-insulated tube 1.

According to an advantageous embodiment, the aforementioned undulation or the aforementioned difference DC-DA is in the range 3, 0-7, 8 millimetres.

As far as the distance between the depressions is concerned, a variant provides that the pitch P between successive depressions 14 (that is, arranged on both sides of a given crest 12) is comprised in the range 25-50, optionally in the range 35-40 millimetres.

For example, pitch P could be substantially 37,5 millimetres.

Advantageously, the pitch P between successive depressions 14 is comprised in the range 25-50 millimetres, optionally in the range 35-40 millimetres, for example it is substantially 37,5 millimetres for diameters of the tube 1 comprised in the range 63-202 millimetres, for example 120-202 millimetres, optionally in the ranges 63-90 millimetres and/or 90-202 millimetres.

In other words, according to such variant, the pitch P remains unvaried irrespective of the outer diameter of the thermal-insulated tube 1. As concerns the method for manufacturing the thermal-insulated tube of the present invention, reference shall be made to the prior art, for example to the description of WO 2014/134745 A1.

Obviously, the provision of the tube subject of the present invention requires particular solutions to allow the material of the outer tubular body 10 to fully penetrate into the depressions.

For example, the extrusion nozzles of the radially outermost layer could be oriented from 30° to 70° with respect to the conveyance direction of the tube being manufactured.

By way of a further example, the pressure of the extruded material for obtaining the radially outermost layer could be increased so that a jet of such material can completely occupy the space of the depression. Innovatively, the present invention is capable of overcoming the drawbacks linked to the prior art.

More precisely, in the present tube the presence of a corrugation in which the depressions have smaller radii of curvature than the crests allows to position - as a whole - a greater amount of thermal barrier, hence the performance of the present tube is improved considerably.

Advantageously, the thermal capacity of the present tube is further improved by selecting a "slight” undulation of the surface, given that in this way the thermal barrier layer is not thinned excessively.

Nevertheless, according to a further advantageous aspect, the smaller undulation depth does not imply an operational deterioration in the handling or installation of the tube.

Advantageously, the tube according to the present invention has a greater average thickness of the thermal barrier layer as compared to the prior art.

Advantageously, the tube subject of the present invention has a pitch of the undulation selected specifically to allow to optimise the logistics and use thereof.

Advantageously, in the tube subject of the present invention the standardisation of the undulation depth and/or of the pitch allows to obtain very advantageous productive economies.

Advantageously, a greater quantity of material of the outer tubular body at the depression allows to obtain a favourable resistance, in particular in terms of bending, to the tearing of such body.

Advantageously, the crests of the present tube have a wide radius, thereby providing a greater outer friction surface.

As a result, with respect to the prior art, despite the frictions being higher, they are nevertheless better supported by the tube by virtue of the increased contact surface.

According to a further advantageous aspect, in the present tube the amount of material of the outer tubular body which can deposit in the depressions is smaller with respect to the prior art.

Thus, since a large amount of material in the depressions has no particular utility, in the present invention such amount of material can only be small by virtue of the little radius used.

Furthermore, it should also be pointed out that, during the formation of the outer tubular body, the material forming said body tends to flow into the depressions so that, as discussed, the extent of such redistribution of material in the depressions can only be limited. Advantageously, the flexibility of the tube according to the present invention is not compromised with respect to the corresponding tubes of the prior art and such tube, considering the same bending characteristics, has greater insulation capacity in any case.

Advantageously, the pitch of the crests and depressions according to the present invention was designed to favourably influence the overall flexibility of the tube.

With respect to the embodiments of the aforementioned tube, the man skilled in the art may replace or modify the described characteristics according to the contingencies. These variants are also to be considered included in the scope of protection as outlined in the claims that follow.

Furthermore, it should be observed that any embodiment may be implemented independently with respect to the other embodiments described.

LIST OF REFERENCE NUMBERS

1 thermal-insulated tube

2 inner tubular body

4 through-flow conduit

6 thermal barrier layer

8 tubular wall of the inner tubular body

10 outer tubular body

12 crest

14 depression

16 radial thinning

18 radial thickening

20 outer surface of the thermal barrier layer

22 recess

24 inner surface of the outer tubular body

26 radially inner surface of the thermal barrier layer

28 radially outer surface of the inner tubular body

30 electrical conductor

X longitudinal extension axis

Dc diameter of the tubular body external to the crests

DA diameter of the tubular body external to the depressions

Rc radius of curvature of the crests

RA radius of curvature of the depressions