Long tubular pipe comprising a separating member and methods for mounting and bending such a pipe

The invention relates to a long tubular pipe comprising an outer tube, an inner fluid-transporting tube mounted in the outer tube, and a separating member designed to transmit bending efforts between said outer tube and said inner tube when said outer tube is bent, the separating member comprising means for the longitudinal passage of fluid between the inner tube and the outer tube, the separating member comprising a first edge and a second edge together defining an assembly slot, the first edge and the second edge respectively comprising a first connecting element and a second connecting element designed to cooperate mechanically on the outer periphery of the inner tube.

TECHNICAL FIELD

The present invention relates to the field of pipes for the transport of a fluid and, more particularly, the transport of fluid in an aircraft.

In a known manner, a “double skin” or “lined” pipe which comprises an outer tube wherein is mounted an inner fluid transporting tube is known in the prior art. The inner tube makes it possible, for example, to conduct a flow of fuel whereas the outer tube forms a protective envelope which makes it possible, on the one hand, to protect the inner tube in the event of impact and, on the other hand, to collect fuel in the outer tube in the event of leakage of the inner tube. This type of pipe also contributes to the confinement of fuel vapours.

The manufacture of such a tubular pipe is complex given that it is necessary that the inner tube is positioned coaxially with the outer tube. Furthermore, it is necessary to avoid that the tubes enter into contact during manufacture in order to create zones of weakness or obstruction to the passage of fuel. Important difficulties arise for the manufacture of a pipe of curved shape.

Conventionally, to obtain a curved pipe, a step of bending a longitudinal pipe is carried out wherein a separating member has been introduced beforehand between the inner surface of the outer tube and the outer surface of the inner tube. The separating member fulfils a function of interface between the inner tube and the outer tube during bending and makes it possible to avoid any contact between said tubes.

With reference toFIGS. 1 and 2, a tubular pipe101comprising an outer tube102wherein is mounted an inner tube104, a longitudinal separating member103is positioned between said outer tube102and said inner tube104prior to the bending of the tubular pipe101is known from the U.S. Pat. No. 5,497,809. The separating member103comprises passage means130configured to enable a longitudinal circulation of fluid between the inner tube104and the outer tube102. According to an embodiment of the U.S. Pat. No. 5,497,809, with reference toFIG. 2, the separating member103comprises a first longitudinal edge131aand a second longitudinal edge131bdelimiting between them a longitudinal slot F in order to facilitate the mounting of the separating member103at the periphery of the inner tube104. Due to the longitudinal slot F, the inner diameter of the separating member103is larger than the outer diameter of the inner tube104, which can lead to a displacement of the separating member103during the mounting of the outer tube102. Also, during bending, there exists a risk that the separating member103is not correctly positioned, which may lead to bending defects (folds, ovalisation, etc.). Moreover, the separating member103is liable to be displaced in the pipe101during the manipulation of said pipe101, which can affect the positioning of the inner tube104in the outer tube102and create weak zones. The separating member103may be maintained in position on the inner tube104manually by an operator but this manipulation is not very practical. Also, to maintain the separating member103in position, an added tightening element is positioned at the periphery of the separating member103. Such a tightening element increases the time for putting in place the separating member103and has an influence during bending.

In addition, such a separating member103has limitations for the bending of a pipe101made of double skin plastic material, that is to say, comprising an inner tube104made of plastic material and an outer tube102made of plastic material. Indeed, to enable optimal bending of a pipe made of double skin plastic material101, it is known to heat the portion to bend beforehand. The use of a separating member103such as described by the U.S. Pat. No. 5,497,809 may disrupt the heating and thus prevent that the inner tube104is sufficiently heated. Indeed, the heating of the inner tube104at the level of the mounting slot F may not be sufficient. Also, during bending, the inner tube104may be deformed in an undesired manner and cause bending defects (folds, ovalisation, etc.).

The aim of the invention is thus to overcome these drawbacks by proposing a novel type of double skin pipe which can be bent with a reduced risk of defects, which is simple to assemble and practical to bend.

Although the invention was originally conceived for a pipe made of plastic material, it also applies to a metal pipe, in particular, made of aluminium.

SUMMARY

To this end, the invention relates to a longitudinal tubular pipe comprising a fluid transporting outer tube having an outer bent portion, a fluid transporting inner tube, mounted in the outer tube, having an inner bent portion substantially coaxial to the outer bent portion and a separating member, comprising a flexible longitudinal body, which is positioned between the inner bent portion and the outer bent portion and which extends coaxially to said bent portions, the separating member being configured to transmit bending forces between said outer tube and said inner tube when said outer tube is bent, the separating member comprising longitudinal fluid passage means between the inner tube and the outer tube, the separating member comprising a first edge and a second edge delimiting between them a mounting slot.

The pipe is remarkable in that the first edge and the second edge respectively comprise at least one first connecting element and at least one second connecting element configured to cooperate mechanically together at the outer periphery of the inner tube.

Thanks to the invention, the separating member may be locked in a practical manner at the outer periphery of the inner tube. It is advantageously not necessary to resort to an added tightening element as in the prior art. The use of such a separating member makes it possible to avoid any undesirable displacement liable to bring about bending defects. Finally, during heating, the edges are continuous, which makes it possible to achieve homogenous heating, guaranteeing optimal bending conditions. The separating member makes it possible to ensure homogenous thermal conduction between the outer tube and the inner tube without requiring particular heating means. The separating member may be, on the one hand, positioned in a practical manner thanks to the mounting slot in unlocked position. On the other hand, the separating member is advantageously continuous at the outer surface of the inner tube in locked position. Thus, the separating member has the advantages of a tubular peripheral separating member while having the advantages of a separating member having a slot to facilitate its mounting.

Preferably, the thickness of the separating member is constant at the periphery of the inner tube. The heating is thus homogenous at the periphery of the inner tube.

According to a preferred aspect, the inner tube and the outer tube each have a circular section.

Preferably, the inner tube and the outer tube are made of plastic material. The use of such a separating member is advantageous for tubes made of plastic material given that the risk of bending defect is higher. Since the heating is homogenous and regular at the periphery of the inner tube due to the thermal conduction of the separating member, bending is optimal.

Preferably, the separating member comprising an inner face and an outer face opposite to the inner face, the first connecting element and the second connecting element are formed on opposite faces.

According to a preferred aspect, the first connecting element comprises a first hollow part and a first projecting part whereas the second connecting element comprises a second hollow part and a second projecting part which are suited to cooperate respectively with the first projecting part and the first hollow part of the first connecting element. Such connecting elements make it possible to achieve peripheral retention by simple mechanical cooperation. Advantageously, the connecting elements have complementary shapes so that the separating member has a constant thickness at the periphery of the inner tube. Advantageously, each connecting element is in the form of a tongue.

Preferably, the projecting parts of each connecting element extend respectively to the free ends of the edges. Thus, they may be retained one with the other during the locking of the separating member without creating over-thickness.

Preferably, the first connecting element extends over the entire length of the first edge. Also preferably, the second connecting element extends over the entire length of the second edge which makes it possible to achieve a continuous closing of the mounting slot.

Alternatively, the first edge and the second edge respectively comprise a plurality of first connecting elements and a plurality of second connecting elements configured to cooperate mechanically together at the outer periphery of the inner tube. Preferably, the first connecting elements and the second connecting elements cooperate together by fitting of the male/female type. Preferably, the first connecting elements are distributed over the length of the first edge so as to form a plurality of elementary connection points. Further preferably, the separating member has a constant thickness.

Preferably, the edges are longitudinal, preferably, rectilinear. Such longitudinal edges make it possible to define a mounting slot that is longitudinal, which facilitates the putting in place of the separating member on a portion to bend of the inner tube.

Preferably, the fluid passage means are in the form of longitudinal orifices. Thus, the fluid is guided inside the separating member in the event of leakage, which does not affect the separation with an inner tube or an outer tube. According to a preferred aspect, the fluid passage means are distributed equally at the outer periphery of the inner tube.

The invention also relates to a method for mounting a longitudinal tubular pipe as described previously, the method comprising:a step of positioning a separating member on a portion to bend of the inner tube, the separating member being in the unlocked state,a step of cooperation of the first connecting element with the second connecting element so as to lock the separating member on the inner tube anda step of inserting the inner tube associated with the separating member into the outer tube.

Thanks to the mounting method according to the invention, the separating member is positioned in a rapid and precise manner by an operator on a portion to bend, the risk of defective positioning is thus limited.

The invention further relates to a method for bending a longitudinal tubular pipe as described previously, the longitudinal tubular pipe comprising a portion to bend wherein is positioned a separating member between the inner tube and the outer tube, the method comprising:a step of heating the portion to bend of the tubular pipe anda step of deforming the portion to bend in order to bend the longitudinal tubular pipe into a curve, the separating member transmitting bending forces between said outer tube and said inner tube when said outer tube is bent.

Once locked, the separating member has a continuous surface at the periphery of the inner tube. During heating of the tubular pipe, the outer tube is heated. By thermal conduction, the separating member is heated and heats, by thermal conduction, the inner tube. The absence of mounting slot, that is to say of discontinuity, makes it possible to achieve homogenous thermal conduction during heating.

It should be noted that the figures set out the invention in a detailed manner to implement the invention, said figures obviously being able to serve to better define the invention if need be.

DETAILED DESCRIPTION

The invention will now be described for a longitudinal tubular pipe1comprising at least one bent portion10, as illustrated inFIG. 3.

The tubular pipe1comprises a fluid transporting outer tube2having an outer bent portion20, a fluid transporting inner tube4, mounted in the outer tube2, having an inner bent portion40substantially coaxial to the outer bent portion20and a separating member3which is positioned between the inner bent portion40and the outer bent portion20and extending coaxially to said bent portions20,40.

Preferably, the tubular pipe1is made of plastic material, that is to say, the outer tube2and the inner tube4are made of plastic material, which makes it possible to limit the weight of the tubular pipe1. However, it goes without saying that the invention also applies to a tubular pipe1made of metal material.

In this example, with reference toFIG. 4representing the tubular pipe1prior to its bending, the tubular pipe1extends longitudinally along an axis X and comprises an outer longitudinal tube2and an inner longitudinal tube4mounted in said outer longitudinal tube2. In condition of use, the tubes2,4extend coaxially and are separated from each other by a running clearance. Preferably, each tube2,4has a circular section. As an example, with reference toFIG. 9, the outer tube2has a thickness of the order of 1 mm and an inner diameter D2of the order of 19 mm whereas the inner tube4has a thickness of the order of 1 mm and an outer diameter D4of the order of 13 mm so as to define a running clearance less than 6 mm. In practice, the outer tube2is shorter than the inner tube4in order that the inner tube4extends projecting from each end of the outer tube2, as illustrated inFIG. 4.

According to the invention, with reference toFIG. 4, the separating member3is positioned between the outer tube2and the inner tube4and is configured to transmit bending forces between said outer tube2and said inner tube4when said outer tube2is bent. Thus, as illustrated inFIG. 3, after bending, the separating member3is positioned between the inner bent portion40and the outer bent portion20and extending coaxially to said bent portions20,40. In the example ofFIG. 4, the tubular pipe1comprises three separating members3,3′,3″ in order to form three portions to bend10,10′,10″.

As illustrated inFIG. 4, the separating member3comprises a longitudinal body of which the length is defined along the direction X. The separating member3has a body made of flexible material so as to be able to be wound at the outer periphery of the inner tube4. Preferably, the separating member3extends flatly, as illustrated inFIG. 5, and is wound during its use. Advantageously, the separating member3is simple to form by cutting out of a roll of flexible material. In this example, the separating member3has a thickness comprised between 3.1 mm and 3.3 mm. The separating member3is made of elastomer, preferably, silicone, fluorosilicone, fluorinated elastomer, perfluorinated elastomer. The use of an elastomer is advantageous given that such a material benefits from an elongation at break at least two times greater than that of Teflon. In other words, the separating member3makes it possible to carry out important bendings in a practical manner. Moreover, it makes it possible to hug the shape of the inner tube4to be in permanent contact with the latter to heat it efficiently and to protect it during bending.

With reference toFIG. 5, the separating member3comprises fluid passage means30between the inner tube4and the outer tube2along the longitudinal direction. Thus, in the event of leakage of the fluid transported by the inner tube4, the fluid is conducted in a confined manner in the longitudinal pipe1between the inner tube4and the outer tube2. In this example, the fluid passage means30are in the form of through orifices but it goes without saying that other embodiments could be suitable, notably, inner serrations formed facing the inner tube4, outer serrations formed facing the outer tube2, cannula and others.

As illustrated inFIGS. 5 and 6, the separating member3comprises a first longitudinal edge3aand a second longitudinal edge3bdelimiting between them a longitudinal mounting slot make it possible to facilitate the winding of the separating member3around the inner tube4. In an analogous manner to the prior art, such a longitudinal mounting slot makes it possible to put in place the separating member3in a precise manner on a portion to bend40of the inner tube4.

In this example, the mounting slot is longitudinal but it goes without saying that it could be inclined, elliptical, etc, the important thing being that the mounting slot makes it possible to offer a radial clearance for the mounting of the separating member3on the inner tube4. The separating member3thus does not necessarily need to be slid along the inner tube4during mounting.

According to the invention, with reference toFIGS. 5 to 7, the first longitudinal edge3aand the second longitudinal edge3brespectively comprise a first connecting element31aand a second connecting element31bconfigured to cooperate mechanically together at the outer periphery of the inner tube4. In other words, the separating member3evolves between an unlocked state, in which the connecting elements31a,31bdo not cooperate and the edges3a,3bare moved apart to arrange a mounting slot, and a locked state, wherein the connecting elements31a,31bcooperate and the edges3a,3bare in contact so as to prohibit any displacement on the separating member3on the inner tube4. Moreover, the separating member3extends continuously at the periphery of the inner tube4, which makes it possible to improve thermal transfer, as will be described hereafter.

As illustrated inFIGS. 5 and 6, the connecting elements31a,31bare configured to cooperate mechanically by fitting, in particular, by complementarity of shapes. In locked position, the connecting elements31a,31bare aligned radially.

Advantageously, as illustrated inFIG. 5, the separating member3is symmetrical to be mounted on an inner tube4without taking account of the orientation of the separating member3. Such a characteristic makes it possible, on the one hand, to accelerate the mounting of the separating member3and, on the other hand, to avoid an incorrect mounting which would impose unnecessary manipulations of the inner tube4, thus increasing the risk of damage. With reference toFIG. 5, the first connecting element31ais formed at the left end of the upper face whereas the second connecting element31bis formed at the right end of the lower face.

Each connecting element31a,31bis, in this example, in the form of a tongue but it goes without saying that other shapes could be suitable to arrange a mounting slot. With reference toFIG. 5, the first connecting element31acomprises a first hollow part311aand a first projecting part312awhereas the second connecting element31bcomprises a second hollow part311band a second projecting part312bwhich are suited to cooperate respectively with the first projecting part312aand the first hollow part311aof the first connecting element31a. The projecting part312a,312bof each connecting element31a,31bextends to a free end so as to enable retention. Each connecting element31a,31bextends over the entire length of the edge3a,3bso as to enable continuous closing of the mounting slot.

As an example, with reference toFIG. 6, each hollow part311a,311bhas a thickness E1comprised between 1 mm and 1.6 mm a width L1comprised between 2 mm and 3 mm. In an analogous manner, each projecting part312a,312bhas a thickness E2comprised between 1.5 mm and 2.3 mm and a width L2comprised between 2 mm and 3 mm. The thickness E2is greater than the thickness E1. For a connecting element31a,31b, its hollow part311a,311bis adjacent to its projecting part312a,312b. Preferably, the widths L1, L2are equal and the sum of the thicknesses E1and E2is equal to the total thickness E, here comprised between 3.1 mm and 3.3 mm, so that the separating member3has a continuous and constant thickness at the periphery of the inner tube4in locked position. In other words, in locked position, the section of the separating member3is in the form of a ring, as illustrated inFIG. 8.

According to another embodiment, with reference toFIG. 11, the first edge3aand the second edge3brespectively comprise a plurality of first connecting elements31aand a plurality of second connecting elements31bconfigured to cooperate mechanically together at the outer periphery of the inner tube104. The first connecting elements31aand the second connecting elements31bcooperate together by fitting of the male/female type. Further preferably, the separating member3has a constant thickness, the connecting elements31a,31bbeing produced by cutting of a body of constant thickness, which reduces the cost and facilitates the manufacture. As illustrated inFIG. 11, each first connecting element31ais in the form of a tongue, here in dovetail shape, which cooperates with each second connecting element31bbeing in the form of a notch of complementary shape to the tongue. In other words, each first connecting element31ais connected to a second connecting element31bin a manner analogous to a puzzle.

Preferably, the first connecting elements31aare distributed over the length of the first edge3a. The same applies to the second connecting elements31bdistributed over the length of the first edge3a. Thus, closing is achieved by a plurality of elementary connection points. Such a closing is simple to be carried out by an operator during the mounting of a separating member3on the inner tube4.

An exemplary embodiment of the invention will now be described with reference toFIGS. 7 to 10for the bending of a tubular pipe1made of plastic material.

As illustrated inFIG. 7, each separating member3is in the form of a flat strip which is curved around the outer surface of the inner tube4in order to make the connecting elements31a,31bcooperate and to lock them together. The second hollow part311band the second projecting part312bof the second connecting member31bcooperate respectively with the first projecting part312aand the first hollow part311aof the first connecting element31ato enable retention. The cooperation is radial between the connecting members31a,31b, as illustrated inFIGS. 8 to 10. The separating member3is in intimate contact with the outer surface of the inner tube4, which guarantees optimal thermal conduction during heating and optimal transmission of forces during bending.

Advantageously, the positioning of the separating member3on the portion to bend40is precise and does not lead to forces on the separating member3or the inner tube4, which limits the risk of damage. This is advantageous and practical by comparison with a mounting of a tubular separating member that would be slid along the inner tube4.

Following the cooperation, as illustrated inFIG. 8, the separating member3has a continuous thickness at the periphery of the inner tube4in locked position. Thus, the inner tube4is protected uniformly with a view to bending it.

Preferably, several separating members3are positioned at different longitudinal positions of the inner tube4in order to correspond to the longitudinal portions to bend. Preferably, the longitudinal length of each separating member3is chosen as a function of the bending to carry out for a determined longitudinal portion. In this example, with reference toFIG. 4, the tubular pipe1comprises three separating members3,3′,3″ in order to form three portions to bend10,10′,10″.

With reference toFIG. 9, the inner tube4on which are mounted the separating members3,3′,3″ is introduced into the inner cavity of the outer tube2so that each separating member3,3′,3″ extends between the inner tube4and the outer tube2. To facilitate mounting, the inner tube4associated with the separating members3,3′,3″ may be cooled to a temperature below −10° C. in order to facilitate its mounting with the outer tube2which remains at ambient temperature. Thus, as illustrated inFIG. 9, the inner tube4, the outer tube2and the separating member3are coaxial.

Prior to the step of mechanical deformation of the tubular pipe1, each portion to bend10,10′,10″ is heated so as to facilitate its deformation. Preferably, heating means5, notably by infrared, heat in a peripheral and external manner the portion to bend10as illustrated inFIG. 10. In practice, the heating means5emit infrared radiation which does not make it possible to heat imposing thicknesses of pipe to high temperatures. Also, it is important to benefit from good thermal conduction to make it possible to heat the inner tube4. Optimal thermal conduction is furthermore desired for any type of heating.

Thus, the temperature of the outer tube2increases progressively, which heats, by thermal conduction, the separating member3. Since the separating member3has a continuous thickness at the periphery of the inner tube4, the thermal conduction by the separating member3is homogenous, which makes it possible to heat in a homogenous manner the inner tube4. In other words, thanks to the invention, the inner tube4is heated in an optimal manner using conventional heating means5.

The portion to bend10of the tubular pipe1may next be bent by a conventional bending machine (not represented) in order to deform mechanically the inner tube and the outer tube2of the tubular pipe1. In a known manner, a mandrel is introduced into the inner cavity of the inner tube4during bending. Advantageously, the separating member3makes it possible to transmit bending forces between the outer tube2and the inner tube4, which limits the appearance of bending defects (folds, ovalisation, etc.). Thanks to the invention, the separating member3is not displaced during the step of deformation, which ensures a controlled and precise deformation, limiting the risk of defects.