AU667950B2 - Apparatus for continuous extrusion of composite tubes reinforced by an insert - Google Patents

Description

OPI DATE 15/03/94 APPLN. ID 47130/93 AOJP DATE Q9/06/94 PCT NUMBER PCT/FR93/00805 AU9347130 DL (PCT) (51) Classification internationale des brevets 5 (11) Numero de publication internationale: WO 94/04338 B29C 47/02 Al (43) Date de publication internationale: 3 mars 1994 (03.03.94) (21) Numero de la demande internationale: PCT/FR93/00805 (81) Etats d6signes: AU, BR, CA, JP, NO, RU, US, VN, brevet europeen (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, (22) Date de dep6t international: 11 aofit 1993 (11.08.93) IT, LU, MC, NL, PT, SE).

Donnees relatives A la priorite: Publiie 92/10182 21 aoit 1992 (21.08,92) FR Avec rapport de recherche internationale.

(71) D6posant (pour tous les Etats designes sauf US): COFLEXIP [FR/FR]; 88 ter, avenue du Gn6ral-Leclerc, F-92100 Boulogne-Billancourt (FR).

(72) Inventeur; et Inventeur/Deposant (US seulement) DO, Anh, Tuan [FR/ FR]; 26, rue de Chatou, F-95240 Cormeilles-en-Parisis

(FR),

(74) Mandataire: LEVY, David; S.A. Fdit-Loriot et Autres, 38, avenue Hoche, F-75008 Paris (FR).

7 9 (54) Title: APPARATUS FOR CONTINUOUS EXTRUSION OF COMPOSITE TUBES REINFORCED BY AN INSERT (54) Titre: APPAREIL DE PRODUCTION, PAR EXTRUSION, EN CONTINU, DE TUBES COMPOSITES RENFORCES PAR UN INSERT (57) Abstract The apparatus comprises a frame an extrusion head a stationary support member an insert arranged about said support member according to a predetermined pitch, a rotary member and it is characterized in that it is provided with support and centring means (19) for the support member said means (19) comprise an assembly of radial elements which are angularly and longitudinaly offset about and along the axis so that the bearing surface of the radial elements on the support member determines a helical contact and the insert may thus be displaced without obstruction in said support and centring means Application particularly to the fabrication of flexible tubes used in the oil industry.

(57) Abreg6 Il est du type comprenant un bati une tete d'extrusion un organe support stationnaire un insert dispos6 autour dudit organe de support suivant un pas prd6etermine, un organe rotatif et il est caracteris6 en ce qu'il comporte des moyens de support et de centrage (19) de 'organe support qui comprennent un ensemble d'el6ments radiaux d6cales angulairement et longitudinalement autour et le long de I'axe de maniere que la surface d'appui des 616ments radiaux sur I'organe de support d6termine un contact suivant une helice et A permettre ainsi A l'insert de se d6placer sans obstacle dans lesdits moyens de support et de centrage. Application notamment A la fabrication de flexibles utilis6s dans une exploitation p6troliere.

APPARATUS FOR THE CONTINUOUS PRODUCTION BY EXTRUSION OF COMPOSITE MATERIAL TUBES REINFORCED BY AN INSERT The present invention concerns apparatus for the continuous manufacture by extrusion of a tube reinforced by an insert and which can be used as a component of a more complex hose for petroleum production applications adapted to withstand the high internal pressure generated when conveying a high-pressure fluid.

A tube reinforced by an insert is a composite material tube comprising a plastics material wall reinforced with a reinforcing member in the form of a relatively small pitch helical coil buried in said wall and formed from a profiled member such as a wire of constant cross-section and of relatively high hardness or strength.

For a long time attempts have been made to improve the mechanical properties of such tubes so that they can withstand both external and internal pressure causing outward deformation or swelling (expansion) of said tube.

The need for reinforcing the tubes was very soon realised.

A first attempt at a solution was to insert an armature in the form of a helically coiled wire between two layers of material.

Other proposals made before now entail embedding an armature or insert in a plastics material. The method most often used is extrusion of a reinforced tube.

Many publications cover continuous manufacture by extrusion of a reinforced tube. Reference may usefully be had to US patents 2 620 514, 2 730 761, 3 526 692, 3 725 178, 3 969 052 and 4 113 820, French patents 810 638, 1 546 655 and 2 506 661 and Swiss patent 279 391.

In this prior art helically wound insert is a placed around a mandrel and moved along the mandrel by mi i I~

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feed means to a confluence chamber in which it is embedded in plastics material leaving an extruder.

The various devices described in these patents differ in terms of the structure and/or the arrangement of the mandrel and the feed means.

In French patent 810 638, the device comprises an Archimedes screw whose pitch is substantially equal to that of the insert, said screw being attached to and rotated by a cylindrical envelope. A sleeve freely rotatable on the hub of the screw cooperates with part of the extrusion head to delimit an annular chamber receiving the plastics material and into which the insert is fed by said screw. Rotation of the sleeve is apparently Irevented by the viscosity of the plastics material. A drawback of a device of this kind is that it is not possible to use a long sleeve and a long mandrel and that the insert rubs constantly on said sleeve which wears very quickly, and the insert may even be broken because of this high friction. Moreover, reverse flow of the plastics material or flow of the material upstream of the extrusion head is not effectively prevented, especially after the sleeve has become worn.

The device described and shown in US patents 3 969 052 and 4 113 820 represents a major step forward.

In one specific embodiment the device comrlrises an extrusion head fed with plastics material, a fixed mandrel disposed inside a rotating envelope having a front (downstream) end facing the extrusion head and an upstream end fixed to a fixed support, s4ai, downstream end having screwthreads in which the insert is engaged and driven in translation on the fixed mandrel. However, as can be clearly seen from the drawings, the mandrel is cantilevered from the fixed support and is centread only in the region of the downstream end of the rotating 1 envelope. Even the smallest centring defect can lead to p~ i incorrect centring of the insert in the plastics material in which it is embedded and consequently a change to the mechanical properties of the reinforced tube such that it may have weakened areas.

The device described and shown in French patent 2 506 661 has plastics material inlets perpendicular to the confluence chamber and four rollers equi-angularly spaced around the mandrel which is fixed at one end to a frame; the rollers are offset axially or laterally by approximately one quarter of the diameter of the insert wire, which diameter corresponds to the minimum pitch of the helical insert when the turns are in contact. The rollers act on the helical wire in the region preceding its entry into the extrusion head in order to close up the turns of the helix before they enter the confluence chamber in which, after relaxing, they are embedded in the plastics material.

In US patent 3 526 692 two concentric layers are extruded in two successive operations with a helically coiled wire between them and flexible and elastic fingers centre the tube in a second extrusion head. In this case the inner part of the tube is centred during a second step of extruding the plastics material.

For extruding short reinforced tubes the mandrel or fixed member can be of the cantilever type, being short and supported at only one end. If the mandrel is longer, however, any ralial deformation of the mandrel can modify the structure of the reinforced tube and consequently its mechanical properties, which is not acceptable in the continuous manufacture of long lengths of tube.

The need has therefore arisen for a device in which the relatively moving parts are centred and supported so that they do not have any influence on the structure of the reinforced tube or on the various conmponents of said reinforced tube, for example the pitch and/or the i ra~ iA..

IC-~CI mY 4 concentricity of the insert or the thickness of the plastics material in which said insert is embedded.

To manufacture long tubes by continuous extrusion over many consecutive hours or days a long mandrel is required. However, a mandrel of this kind is not rigid enough to be supported either cantilever fashion at one end or by the extrusion head.

It would be desirable to provide an apparatus in which a long mandrel is supported and centred despite the presence of the insert along said mandrel.

It would also be desirable to provide an apparatus in which the mandrel floats and is not necessarily fixed at either end.

It would be desirable to provide means for preventing rotation of the mandrel which also constitute axial abutment means which can further constitute additional mandrel support and centring means.

*o o o•It would further be desirable to achieve a correct geometrical configuration 15 of the finished reinforced tube on leaving the extruder, the tube being then cooled to assume its final mechanical strength and so that it can be coiled onto a storage •spool.

According to the present invention, there is provided an apparatus for the continuous production by extrusion of tubes reinforced by an insert, of the type 20 including: a frame including an extruder head in which are formed an annular 0 confluence chamber and a plurality of passages discharging into said annular confluence chamber and through which at least one extrudable material is injected; 25 a stationary support member disposed partly in said extrusion head the

*OSS

outer surface of which has a general shape that is rotational about a longitudinal axis; an insert disposed around and along said support member with a predetermined pitch; a feed member driven in rotation and mounted in the frame, said feed member having an end disposed in said extruder head and provided with at least one helical groove adapted to receive at least one turn of said insert and to move r IFC-~-qp~-~rrC i 4A the latter in translation, wherein it further includes first means for supporting and centring the support member disposed inside and attached to said feed member, said first centring and support means including a set of radial members equiangularly spaced around the stationary support member and offset longitudinally in the direction of movement in translation of said insert parallel to said longitudinal axis of the stationary support member so that the surface at which said radial members bear on said stationary support member determines contact along a helix and so enables the insert to move freely in said support and centring means.

Other features and advantages of this invention will emerge from a reading of the description of a preferred embodiment of the invention and from the appended drawings in which: Figure 1 is a partial sectional view of a preferred apparatus in accordance with the invention including an extrusion head of an extruder.

15 Figures 2 and 2a are diagrammatic partial representations of means for preventing rotation of the rotary member in a second embodiment of the invention.

Figure 3 is a partial diagrammatic representation of means for immobilising the support member in a third 0 e o c o* 0.

*0000.

Q a embodiment of the invention.

Figure 4 is a diagrammatic representation of the means for admitting a fluid into the support member.

Figure 5 is a diagrammatic representation of two solenoids associated with a device for conforming the composite material tube produced by the apparatus of the invention.

Figure is a diagrammatic sectional view of another embodiment of the cooling means.

Figure 7 is a diagrammatic sectional view of another embodiment of the immobilising means.

Figure 1 shows apparatus for continuous production by extrusion of composite material tubes reinforced by an insert.

The apparatus is mounted on a frame 1 and comprises a right-angle extruder head 2 attached to the frame i.

The extruder head 2 comprises passages 3 which are preferably radial and which discharge into a confluence chamber 4.

Any extrudable material can be used, such as a thermoplastic polymer or an elastomer polymer, or a mixture of such materials, or a mixture loaded with fibres or microspheres, for example.

A mandrel 5 is mounted in the frame and the extruder head 2. Its outside surface is a body of revolution about a longitudinal axis A. An annular depression 6 on the outside surface of the mandrel facing the passages 3 cooperates with the inside wall 2L of the extruder head 2 to define the confluence chamber 4. The mandrel 5 extends a long distance in the frame i, on the upstream side of the confluence chamber 4, i.e.

towards the right in figure 1. In accordance with the invention, the mandrel can advantageously be in the form of an isolated part having some stiffness and preferably made of metal; it is not supported directly, for example 6 by enclosing its end in a fixed chassis fastened to the frame i, but is instead supported, centred and immobilised entirely by specific means to be described below. As an alternative to this, the mandrel 5 can be supported at the end opposite the extruder head by a fixed chassis, the specific means described below providing additional support so that there is no risk of the mandrel suffering excessive deformation, despite its great length.

An insert 7 in the form of a profiled member or wire of constant, for example circular, cross-section and of great length is coiled helically with a predetermined or nominal pitch P and a constant mean diameter. It is introduced from the riglithand end of the frame (as seen in figure 1) so that it is disposed around the mandrel and moves towards the extruder head. Known methods can be used to form the insert 7 simultaneously with its insertion. into the apparatus of the invention and extrusion of the tube, by continuous coiling of the wire, the resulting insert being immobile in rotation about its longitudinal axis. As an alternative to this the insert can be made separately, in a preliminary operation, and then stored before it is used to manufacture the composite material tube.

The insert can be made from any appropriate material, such as steel, and its diameter and other dimensional characteristics and its plrsical and mechanical properties are appropriate to its use as a reinforcing member in a composite material tube, depending on the intended applications of the continuously extruded composite material tube of the invention.

A rotary or rotation drive member 8 whose interior is hollow and at least whose inside surface is preferably a body of revolution about the lorqitudinal axis A of the '3

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1 _m mandrel is disposed in the frame 1 and receives within its interior 9 the mandrel 5 and the insert 7, the latter being accommodated between the rotary member 8 and the mandrel 5. The downstream end 10 of the rotary member 8 includes feed means for imparting translatory movement to the insert 7. In the example shown in figure 1 these translatory feed means comprise a helical groove 11 in the cylindrical inside wall of the downstream part or head 10 of the rotary member 8. The downstream part thus constitutes a kind of nut with a pitch which is preferably equal to or less than the nominal pitch P of the insert 7, this nominal pitch P being defined as the pitch of the helix formed by the insert when no gravity force or other external force is applied to it. The helical groove 11 preferably has a square cross-section over a length sufficient for inserting at least one turn 12 of the insert 7. The head 10 of the rotary member 8 is at an appropriate distance from the confluence chamber 4 to delimit a space 13 in which several turns of the insert are preferably free to move relative to each other and in particular to move closer together, in the direction of compression, to constitute a seal preventing material fed into the confluence chamber 4 from flowing in the upstream direction. The number of turns 12 of the insert in the head 10 is preferably two or three.

The translatory feed means for the insert 7 can be of any known type such as that descrioed in French patent 2 506 661 (rotating disks) or that described in US patent 2 730 761 (disks or endless belts) The rotary member 8 is rotated by an appropriate transmission system (not shown) of which only a toothed ring 14 is shown in figure 1. The toothed ring meshes with any means coupled to a motor (also not shown). The rotation speed co of the rotary member 8 is determined, in accordance with the nominal pitch P of the insert 7, to

V'

I i 8 obtain the required value of the speed v of translatory movement of the insert 7 parallel to the axis A, these three values being related by the equation: vcm min Crpm Pcm turn The speed v of translatory movement of the insert 7 is normally equal to the speed V 0 at which the composite material tube leaves the extruder, this speed V 0 being determined by traction means (not shown) such as triple caterpillar tracks which act on the composite material tube downstream of the extruder head and the cooling device. If the angular speed c is different from the synchronous speed (00 determined by the equation 0 0 VO/P, in the finished composite material tube the insert 7 has a pitch different from its nominal value P, and this can be defect of greater or lesser significance.

The rotary member 8 is centred and supported by two bearings which in this example are rollers 15 rotating on shafts 16 attached to the frame 1. It is prevented from movement in longitudinal translation by an axial abutment, for example a double series of rollers 17 whose shafts 18 are also attached to the frame 1, the rollers 17 rolling on the flanks of the toothed ring 14.

The apparatus of the invention includes at least one device for supporting and centring the mandrel constituted by radial support members 19 19. and 19b) facing the mandrel and attached to and disposed inside the rotary member 8 so that their inner end bears on the outside surface 5a of the mandrel 5. The inner ends 20 of the radial members 19a, 19h can in this way constitute at least three bearing surfaces equiangularly distributed around the circumference uf the external surface of the mandrei, each bearing surface having a circumferential length which can be relatively 9 small or virtually zero. The bearing surfaces are regularly offset relative to each other in the direction of the axis A, the distances between two consecutive bearing surfaces parallel to the axis A being equal and such that, given the angular offset around the axis A, the set of bearing surfaces traces a helix on the surface of the mandrel whose pitch is advantageously equal to the nominal pitch P of the insert.

As an alternative to this, the first support and centring means can include cont'inuous radial support members similar to the screwthreads of a nut and the inner ends 20 of the radial members can constitute a continuous bearing surface which also defines a helix at the surface of the mandrel, preferably with a pitch equal to the pitch P.

In the direction perpendicular to the helical line formed by the bearing surfaces, the thickness of the radial members is sufficiently small for them to be housed in the free space between two contiguous turns of the insert if the latter has a pitch equal to the pitch of said helical line of bearing surfaces.

The radial members 19a, 19b constituting the support and centring means are rotated about the axis A at the same angular speed O as the rotary member 8 and the insert 7 accommodated in the helical path so constituted can move in translation across the support and centring means which accordingly, via the obstacle constituted by the insert, position the mandrel so that it is coaxial with the rotary member.

In the embodiment shown in figure 1 the first mandrel support and centring means 5 comprise at least three radial pins 19, of which only pins 19a and 19b are shown, preferably four such pins, equi-angularly spaced around the mandrel. 5 and offset longitudinally relative to each other in the direction of translatory movement of the insert 7, parallel to the axis A, by a sub-multiple of the nominal pitch of the insert so that they define a helical path whose pitch is preferably equal to the nominal pitch P. If four pins are used, as in the preferred embodiment of the invention, they are offset laterally relative to each other by one quarter-pitch.

Figure 1 shows diagramatically a top pin 19b offset longitudinally from a bottom pin 19.. The pins 19A, 19b are attached to the rotary member 8 so that the mandrel is supported and centred by said rotary member. Facing the inner end 20 of the pins 19_q, 19b, the mandrel 5 has an annular track 21 on its outside surface 5. The pins 19a, 19b rub on said track 21 which is surface-hardened where it is in contact with the pins by appropriate surface treatment such as, for example, hard chromium plating, sulfinisation or stellite surfacing. The track 21 can also, if required, be covered with a material with a low coefficient of friction such as '?TFE.

The offsetting in the longitudinal direction (the direction of translatory movement of the insert) of the pins which rotate with the rotary member 8, in the manner indicated, allows the insert 7 to move in translation on the mandrel 5 without said pins impeding displacement of said insert 7.

If the mandrel 5 is entirely isolated, supported by the rotary member 8 and the pins 19., 19h, rather than being supported directly by a frame fixed to its end opposite the extruder head, the mandrel 5 is immobilised in translation by axial abutment means.

In the advantageous embodiment of the invention shown in figure 1 the stop and abutment means comprise at least one disk 22, preferably two such disks, rotating on shafts 22a fastened to the rotary member 8, said shafts 22a being preferably at a small or zero angle to the axis A.

*i 11 In figure 1 the disks 22 are disposed between the two series of rollers The disks 22 are diametrally opposed around the mandrel and offset longitudinally or in the direction of the axis A by a distance which is preferably equal to half the nominal pitch P. The disks 22 roll in an annular groove 23 in the mandrel 5, the side walls of said groove 23 being hardened or coated with a material having a very low coefficient of friction, as already explained with reference to the track 21.

The axial abutment device can comprise a second assembly (not shown) of at least one disk, preferably two such disks, implemented in a similar mannier to the assembly of the first two disks 22, but offset in the longitudinal direction of the axis A and offset at 900 to the disks 22 so that their rotation axes lie in a diametral plane orthogonal to the plane defined by the shafts 22a of the disks 22. The edges of the disks of the second set roll in a groove similar to but separate from the groove 23.

As an alternative to this the circular edges of the disks 22 can bear on the bottom of the groove 23 which is also hardened or coated with a low-friction material. In this case the disks also constitute second support and centring means for the mandrel In another variant a set of at least three rotating disks attached to the rotary member, similar to the disks 22, can constitute the first support and centring means for the mandrel 5, instead of the radial pins 19 shown in figure i. In this case said rotating disks have a diameter such that they bear radially on an annular track on the outside surface of the mandrel. The rotation axes of the rotating disks which in this way locate the mandrel in the radial direction can advantageously be at an angle to the longitudinal axis A of the mandrel whose value is complementary to the "reinforcement angle" of the helix formed by the insert 7, so that at the point at which they may come into contact with the insert the lateral surfaces of the disks are approximately parallel to the generatrices of the profiled member constituting the insert. The reinforcement angle is the angle between the axis A and the helical wire constituting the insert and is in the order of 750 to 90°, for example.

The axial abutment means can equally be constituted by at least one pin, preferably a pair of diametrally opposed radial pins preferably offset in the direction of the axis A by half the pitch P, attached to the rotary member 8 and similar to the pins 19s., 19h except that their inner end is housed in an annular groove in the outside surface of the mandrel 5, translatory movement of the mandrel being prevented by contact along a radial line between the axial abutment pins and the lateral flanks of the groove. It is preferable to use one groove for each group of pins.

In another variant (not shown) the support and centring means and/or the axial abutment means for the mandrel can be a member forming a nut attached to and inside the rotary member 8 with a helical radial member defining a helical groove adapted to receive a section of the insert 7.

If this nut member constitutes mandrel support and centring means, the inner end of the helical radial member constitutes a helical bearing surface in contact with an ann.ilar track on the surface of the mandrel.

In accordance with another important feature of the invention the apparatus further comprises means for preventing rotation of the mandrel 5 if the latter is an isolated member supported by the rotary member 8.

In the first embodiment of the invention shown in figure 1 the means for preventing rotation of the mandrel /i 13 comprise a solenoid 27 attached to the frame 1 and cooperating with a bar magnet 28 inset radially into the mandrel 5. The lines of force of the resulting magnetic field generate a return torque in response to the slightest rotation of the mandrel 5, which is thus prevented from rotating.

In the advantageous embodiment of the invention shown in figure 1 a short section 24 of the rotary member 8 has a helical groove 25 receiving at least one turn of the insert 7. This section 24 is shaped to stretch the insert and has a pitch greater than the nominal pitch of said insert 7. If this section 24 accommodates two turns, the distance between two turns must be greater than the nominal pitch of the insert. The outside diameter of the mandrel 5 can be reduced slightly in line with the section 24 to enable slight constriction of the turn of the insert concerned.

The outside of the rotary member 8 in the portion incorporating the screwthreaded section 24 includes a groove 26 adapted to house the poles of the solenoid 27 whose width is such that they can be placed in the empty space between two consecutive turns of the part of the insert positioned by the groove This arrangement increases the effectiveness of the magnetic immobiliser device by reducing the size of the air gap between the magnetic poles of the solenoid and the bar magnet.

In a second embodiment of the invention the means for immobilising the mandrel 5 against rotation, shown in figure 2, comprises a set of cooperating toothed wheels.

A toothed wheel 29 rotates freely on a shaft 30 attached to the frame i, on the upstream side of the ring 14 driving the rotary member 8, in the part of the apparatus in which no member attached to th3 rotary member has any part in the annular space between the frame 1 and the -r insert 7 around the mandrel The teeth 31 of the toothed wheel 29 have a profile through which the insert 7 can pass, so that the toothed wheel 29 meshes with the insert 7 in the manner of a rack and pinion, but possibly with play. Another toothed wheel 32 with lateral parts similarly meshing with the insert 7 and cooperating with the toothed wheel 29 rotates freely on a shaft 33 and is fastened to the rmandrel 5. The toothed wheel 32 projects partly above the mandrel 5 and is thicker than the toothed wheel 29.

The toothed wheel 32 has a groove 34 in it in which the ends of the teeth 31 of the toothed wheel 29 engage to prevent rotation of the mandrel In another embodiment of the invention shown diagrammatically in figure 3 the means for immobilising the mandrel 5 against rotation are on the downstream side of the drive ring 14 and include a fixed toothed ring attached to the frame 1. Another toothed ring 36 is mounted on the mandrel 5 in a space 37 provided for this purpose. The number of teeth on the toothed ring 36 is equal to the number of teeth on the fixed toothed ring A shaft 38 passing radially through the rotary member 8 and journalled in a bearing 39 attached to the rotary member has a bevel gear 40, 41 at each end. The gear 40 meshes with the fixed toothed ring 35 and the gear 41 meshes with the toothed ring 36. As the bevel gears 40 and 41 have the same number of teeth, it follows that the set of rings and gears as described prevents any rotation of the mandrel 5. The same result can be obtained with different numbers of teeth on the two rings and 36 and on the two bevel gears 40, 41. In this case, if the gear ratio k is defined as the ratio k N/n where N is the number of teeth on a ring 35 (or 36) and a is the number of teeth on the corresponding gear 40 (or 41), the mandrel is immobilised against rotation if the •i values ke and ki of the gear ratios of the external gears 35-40 and the internal gears 36-41, respectively, are equal.

It is sometimes necessary to cool the molten material constituting the wall of the composite material tube on the downstream side of the confluence chamber 4.

In the manufacture of a tube with an insert, as in the case of the present invention, the presence of the insert constitutes an obstacle to passing a cooling liquid through the composite tube because the insert moves continuously from the upstream end to said confluence chamber 4 in which it is embedded in the plastics material injected into the confluence chamber 4 via the passages 3.

In accordance with another feature of the invention, this problem is solved in that the apparatus can include a section in which the pitch of the insert is increased over the nominal pitch on either side of said section and in the finished tube.

The short-section 24 as described previously can be modified in the manner shown in figures 1 and 4 to enable the provision of at least one radial fluid passage device.

The rotary member 8 includes a cylindrical bearing surface 42 facing an inside surface 43 of the frame 1, a seal being provided by 0-rings 44. An annular chamber is preferably formed in the bearing surface 42 between the O-rings 44.

A ring 46 disposed in a housing 47 provided for this purpose in the mandrel 5 at a location corresponding to that of the cylindrical bearing surface 42 is sleeved, for example force-fitted, into the inside surface 49 of the rotary member 8, the ring rotating in the housing 47 about the axis A of the inandrel 5. A helical passage with a square cross-secion, for example, can be formed in the ring 46 with a helix diameter and cross-section width and depth such that it can accommodate one or two turns of the insert 7. In the advantageous embodiment of the invention shown in figure 4 the pitch of the helix formed by the passage 50 is determined as in the embodiment previously described in order to increase the pitch of the turns of the insert 7. This increase in the pitch of thle turns is exploited to enable the accommodation of a hollow radial member such as a nozzle 51 which is, for example, screwed into the rotary member 8 and into the ring 46, the fixing of said nozzle being sealed by well-known means.

The outer end of the nozzle 51 discharges into the annular chamber 45. The inner end of the nozzle 51 discharges into an annular chamber 52 delimited by a groove or two facing grooves in the ring 46 and/or the mandrel 5. A seal is provided between the ring 46 and the mandrel 5 on either side of the annular chamber 52 by seals such as O-rings 53. The annular chamber 52 is connected to an internal passage 54 which extends inside the mandrel 5 as far as the downstream end 55 of the latter (figure The cooling fluid is fed into the annular chamber 45 via a conventional fluid inlet 56 mounted on the frame 1 and connected to a cooling fluid supply (not shown). Exactly as previously, the insert 7 moves with the increased pitch in the helical passage of the ring 46 with sufficient radial clearing to enable constriction of the helix. After cooling the confluence chamber 4 or any other component to be cooled, the cooling fluid leaves the mandrel 5 for the frame 1 and is taken off via a fluid outlet 57 by means of another rotary coupling device similar to the first device used to supply this fluid.

It is obviously possible to provide a single rotary coupling device with two passages (inlet/outlet) in the i increased pitch section, as shown in figure 1.

Another embodiment of the invention, for locally increasing the pitch of the helix of a section of the insert, can be as follows.

Two devices for setting the pitch of the insert, each fastened to and inside the rotary member 8, are disposed at a distance from each other in the longitudinal direction of the axis A so as to lie one on each side of the section of the insert whose pitch is to be increased. Each of these two devices includes radial members which trace a helix on the cylindrical surface containing the longitudinal axis of the insert 7. The helix formed in each of these two devices has a pitch which can be equal to the nominal pitch P of the insert 7, for example, and a length corresponding to at least approximately one complete turn. The helical radial members thus delimit a hollow helical path whose width and depth are such that a section of the insert corresponding to at least about one turn can be accommodated therein and caused to move parallel to the axis A at a speed corresponding to the speed V 0 imposed on the composite tube with no unwanted rotation about the axis A. The thickness of a radial member between its lateral surfaces separating two segments of the hollow helical passage is sufficiently small that, combined with the necessary width of the latter, the resulting total length is equal to the required helix pitch.

In this way it is possible, in a precise and stable manner, i.e. with no variation in time as the insert moves in translation and the composite tube is formed, to bring about a localised increase in the pitch of the insert, by virtue of the positioning of two short sections in the two pitch setting devices. To this end, the number of turns corresponding to the pitch of the insert in the free s. ace between the two pitch setting devices is reduced compared to the number of turns that would correspond to the nominal pitch P, which number is equal to the axial length of the aforementioned free distance divided by the pitch P. For example, if the free distance between the two pitch setting devices is equal to 6P, the pitch over the intermediate length of the insert has a mean value equal to twice or three times the nominal pitch P, for example, the apparatus being set up so that the number of turns of the interleaved insert is equal to two or three, rather than six. The helix can be locally stretched without any particular problem because its axial stiffness in the direction of the axis A is relatively low, causing it to behave like a coil spring.

A radial passage member can be placed in the space between the two pitch setting devices, attached to the rotary member and with an outside diameter such that it can be housed in the locally enlarged space between two contiguous turns of the insert. In a similar manner to the nozzle 51 of the embodiment shown in figure 4, the radial passage member is connected and sealed at its outside and inside ends, respectively, to a passage 56 in the frame 1 and to a passage 54 in the mandrel 5, by two rotary coupling type members, one on the outside and the other on the inside, each having an annular chamber analogous to the respective chamber 45 and 52, together with respective corresponding O-rings 44 and 53. A device of this kind can be used equally well to convey a fluid or to transmit an electrical current.

Figure 7 shows a variant of the pitch setting devices. Each device 119 and 1191 includes four radial pins 119A through 119f, 119'a through 119'A of which only pins 119a and 119h, 19'a and 119.'h are shown.

The pins are fixed to the rotary feed member 8 and can be cylindrical rods oriented towards the mandrel

?O

19 in directions perpendicular to the axis A, for example.

In the case shown here in which the function of the pins is limited to setting the pitch of the insert, the inner end of tht. pins has some radial clearance relative to the outside surface of the mandrel 5, although the length of the pins is sufficient for them to bear laterally on the insert 7. Alternatively, the inner end of the pins 119 and/or 119' can bear on the outside surface of the mandrel 5; the pins 119 and/or 119' of the pitch setting devices then constitute additional or possibly the first support and centring means for the mandrel 5. As an alternative to this, the outside surface of each pin can be in- the flrm of a cylindrical sleeve rotating freely on the central part of the pin, like a fixed bearing.

The four pins of the first pitch setting device 119 are regularly disposed around the mandrel 5, the radial axes of the pins 119g, 119b and 119d being at angles of respectively 900, 1800 and 2700 to the pin 119a. In the longitudinal direction of the axis A the four pins 119 are inscribed in diametral planes which are also regularly spaced, in the same order, from the pin 119a to the pin 119d, the distance between two consecutive planes being advantageously equal to P/4. Considering the cylindrical surface along the axis A on which is inscribed the longitudinal axis of the profiled member coiled helically to constitute the insert 7, the trace on said cylindrical surface of the radial axes of the four pins 119A, 119c, 119b and 119d defines a helical line with axis A whose pitch is advantageously equal to the nominal pitch P of the insert 7.

The four pins 119 being attached to the rotary member 8, each turns about the. axis A at the angular speed 0, which enables them to i ove within the free space between two contiguous turns of the insert 7 without impeding movement of the latter in translation parallel to the axis A.

Similarly, the four pins 119'g, 119'.Q, 119'h and 119' constituting the second pitch setting device are also regularly staggered, i.e. equi-angularly in the circumferential direction around the axis A and longitudinally in the direction of the axis A, so that they define a helical passage whose pitch is advantageously equal to P and which turns about the axis A at the angular speed CO and in which the insert 7 can move freely.

In each of the pitch setting devices 119 and 119' the pins 119a and 119'a are those nearest the otbor device, respectively 119' and 119, the axial distince between them parallel to the axis A determining the distance over which the pitch of the insert- can be increased to the required value. The free distance L can thus be defined as equal to the distance between the two radial planes in which lie the axes of the two parts of the insert 7 respectively bearing on the pins 119 and I19'a.

In the example shown the free distance L corresponds to an integer number of turns of the insert when the latter is wound at a nominal pitch, with L 9P.

However, the insert has only three turns rather than nine turns between the pins 119 and 119'1a, i.e. in this free space the insert has a locally increased pitch P 1 which is three times the nominal pitch P.

Although in theory a single pin is sufficient for each of the two pitch setting devices. 119 and 119', the number of pins per device is preferably equal to at least three and is advantageously equal to four, as shown in figure 7, so that the pins define a helical passage able to accommodate at least one turn of the insert 7.

As an alternative to this, the pitch setting devices 119 and 119' can include rotating disks rather than pins, preferably at least three such disks for each of the two devices. The rotation axes of the disks can be parallel to the axis A. The axes of the disks are advantageously in planes parallel to the axis A and at a relatively small angle to the latter, whose value is complementary to the angle of the helix traced by the insert 7.

As an alternative to this, instead of being separate from each other the radial members constituting each of the two pitch setting devices can form a continuous geometrical surface like the helical groove in a nut, with cross-section dimensions accommodating one turn of the insert 7, for example.

The figure shows a radial fluid passage device with a double coupling seal similar to the figure 4 embodiment installed in the space between the two pitch setting devices.

The radial passage device includes a ring 146 in an annular housing 147 on the outside surface of the mandrel rotating freely on the mandrel 5 and fastened to the rotary member by a radial spacer The radial spacer (ER) is disposed radially in the annular space between the rotary member 8 and the mandrel 5 occupied by the insert 7 and has a cross-section which can be small in size.

In the area of the radial spacer (ER) the rotary member 8 and the frame 1 have f acing bearing surfaces with a small clearance between them, provided in the embodiment shown by an upstanding annular part 142 on the outside of the rotary member 8 or alternatively by an upstanding annular part on the ins_ .e of the frame 1.

The radial fluid passage device includes a sealed hollow radial passage member such as a nozzle 151 disposed inside the rotary member 8 and the radial spacer (ER) and discharging at the outer end into an annular groove 145 on the outside surface of the rotary member 8, in the upstanding part 3.42, for example, ?and/or onto the inside surface of the frame 1. The inner end of the nozzle 151 discharges into an annular groove 152 on the inside surface of the ring 146 attached to the rotary member 8 and/or onto the surface of the housing 147 in the mandrel A passage 156 connected to external circuits via the frame 1 discharges into the outer annular groove 145.

A passage 154 inside the mandrel discharges into the inner annular groove 152.

The two concentric rotary couplings obtained in this way are sealed by two O-rings 144 and by two further O-rings 153 respectively surrounding the 'rooves 145 and 152 to provide a sealed radial fluid passage between the passages 156 and 154.

The width of thA annular ring 146 in the direction of the axis A is advantageously greater than the dimension of the radial spacer (ER) in the direction of the axis A. This reduces the overall size of the radial spacer between the turns of the insert 7 and enlarges the space that can be used to accommodate the groove 152 and the 0-rings 153. In this case the rincr 146 has a cylindrical outside surface extending the outside surface of the mandrel 5, except for where it is joined to the radial spacer (ER).

However, the ring 146 and the radial spacer (ER) can equally well have the same dimension in the direction of the axis A. In particular, the width of the ring 146 can be reduced by providing O-rings 143 in the mandrel on the radial lateral surfaces of the annular housing 147.

In some cases, depending in particular on the diameter of the insert and on the nominal pitch P, it is possible to install a radial fluid passage device with double rotary coupling, as described above, without it being necessary to increase the pitch of the insert or to dispose the fluid passage device between two insert pitch setting devices.

In the continuous manufacture of a tube reinforced by an insert the tube must be as regular and as homogeneous as possible to maintain the physical characteristics of the tube constant along all of its length. This is all the more important when the tube is to be manufactured in long continuous lengths, for example several hundred metres or even several kilometres. Such tubes are frequently used in petroleum production.

To obtain a regular and homogeneous tube it is necessary to maintain the regularity of the pitch and the concentricity of the insert at the outleL from the extruder head and a correct conformation of the tubular wall constituted by the extruded plastics material as it solidifies.

To this end the apparatus of the invention includes a magnetic device 58, referred to hereinafter as a magnetic nut, formed by solenoid'A whose successive poles are disposed in a helix as close as possible to the turns of the insert 7. The pitrh of the helix traced by the solenoid poles is equal to the nominal pitch P of the turns of the insert 7.

The pitch and concentricity of the insert 7 are stabilised immediately on leaving the extruder head 2 before entering the area in which the extruded plastics material cools and solidifies. The operation is controlled by means of equi-angularly spaced proximity sensors relatively near the turns of the insert 7.

The proximity sensors, which can be of the variable capacitance or inductance type, allow correct control of the intensity of the forces applied to the insert 7 by the solenoids. The insert 7 must obviously include a ferromagnetic material such as carbon steel for the turns of the insert to be centred and for the pitch of said turns to be corrected.

The magnetic nut 58 is preferably rotated at the same angular speed CO as the rotary member 8 by appropriate (mechanical or other) means.

As an alternative to this, the magnetic nut can be stationary. In this case the angular speed c of the rotary member 8 is copied by electrical means such as a Selsyn pole-switching system defining an instantaneous helix of pitch P reating about the axis A at the required angular speed.

The magnetic nut as described in the above two variants is associated with an external conforming device 59 which comprises a thin cylindrical sleeve 60 made from a metal which is a particularly good conductor of heat and which extends continuously from the extruder head 2, which it prolongs, to cooling means such as a finned heatsink 61 which is strongly cooled (shown in the lower half of figure 1) or an annular chamber 70 in which a cooling fluid such as water is circulated (shown in the upper half of figure 1).

The external conforming device 59 can include two aligned sections of thin cylindrical sleeves 71 and 72, both made from a metal that is an excellent conductor, between which is inserted an insulative material rng 73.

In a preferred embodiment of the invention the apparatus includes an internal conforming device referred to hereinafter as a "fluid conforming device" comprising a piston 62 provided with one or more fluid-tight scraper segments 63. In the lower half of figure 1 the piston 62 is shown resting on a seat 64 consisting of the end 55 of the mandrel 5, this position corresponding to the start of extrusion of the tube. Shortly after extrusion is started, the pressure of the fluid on the piston 62 pushes the latter towards the position shown in the top half of figure i. The fluid is admitted from the feed passage 56, for example by the rotary coupling device described previously, into a central passage 65 attached to the mandrel 5 made from a material that is a poor conductor of heat. The fluid leaves the passage 65 via radial orifices 66 attached to the piston 62 and fills an annular chamber 67 closed off at the front (the downstream side) in a fluid-tight manner by the piston 62 with the scraper segment 63 and closed off laterally by the inside wall of the composite tube and by the outside surface of a sliding hollow rod attached to the piston 62. The hollow rod is freely moveable in translation in the direction of the axis A, fitting around and sliding on the central passage for example.

The flow of the fluid is shown by the arrow 68 in figure 1. Lapping the inside wall of the composite tube leaving the confluence chamber 4, the fluid both supports and cools said tube.

When it reaches the upstream end of the annular chamber 67, limited in this example by the seat 64 constituting the downstream end 55 of the mandrel 5, the fluid flows into the annular space between the mandrel and the hollow rod and then into the annular space between the passage 65 and the mandrel 5 until, via passages in the mandrel 5, it reaches a second rotary coupling radial passage device whence it is evacuated via the passage 57.

Alternatively, the internal conforming device can comprise a liner 80 having a cylindrical or slightly conical outside surface 81, made of metal, for example, and possibly covered with PTFE, on which the inside wall of the composite tube 83 slides, the interior of this liner constituting an annular chamber 82 in which the cooling fluid 84 flows. The fluid can flow in an open circuit with just a fluid inlet 56 or in a closed circuit with additionally a fluid outlet 57 (figure 6).

Alternatively, in another embodiment of the invention, the internal conforming device can include a plurality of elongate endless belts in the direction of the generatrices of the composite tube pressed together contiguously or with a slight overlap so that the geometrical surface enveloped by the outside surface of each outside half-strip corresponds to the required cylindrical shape of the inside wall of the composite tube. The strips are made from a material having some longitudinal elasticity. The strips are wound at each end around a spindle supported by a rigid cylindrical sleeve which constitutes an extension of the mandrel beyond the extruder head. Each strip therefore passes from the inside to the outside of the sleeve at one end and vice versa at the other end; the radial run is taken through a mortice or beyond said sleeve, as appropriate.

The set of external half-strips supported by the strong interior sleeve constitute a cylindrical conformation surface of the required diameter on which the composite tube bears as it moves in translation but without movement relative to the strips. Endless belt internal conforming devices are described in German patent 2 338 948 and French patent 2 239 638, for example.

Figure 5 shows a device for improved friction-free sliding of the composite tube on the surfaces of internal and/or external conforming devices. The solenoid 27 from figure 1 carried by the frame 1 is replaced by two solenoids 74 and 75 whose respective North and South poles are close together but -slightly offset in the circumferential direction about the axis A so that the two North/South axes are at a small angle to each other, 27 which angle can be adjusted. The two solenoids are energised alternately, turn and turn about, for example by a rectifier bridge, one solenoid being energised when the other is not, and so create an oscillating force field which causes the bar magnet 76 to vibrate at a particular frequency, for example a frequency related to that of the mains electrical power supply.

The foregoing description refers to a horizontal longitudinal axis A. The longitudinal axis A of the apparatus can be vertical, however. In this case the insert 7 can be fed from the top of the frame 1, the composite tube being extracted from below the extruder head. An arrangement of this kind can enhance the concentricity of the insert in the wall of the composite tube.

Whichever embodiment of the invention is used, the pitch of the turns of the insert 7 is corrected by adjusting various operating parameters, in particular: the traction applied to the composite r-ube by the traction member when it has acquired sufficient mechanical strength on cooling, this traction being adjusted in correlation with the speed at which the insert is formed upstream of the apparatus (when the insert is coiled simultaneously with extrusion of the composite material tube), the angular speed C of the rotary member 8, and the rate at which the plastics material is extruded by the extruder, these parameters being adjusted in accordance with the nominal pitch P of the insert and their action possibly being complemented by the regulatory effect of the magnetic nut 58.

The insert 7 can comprise two profile memb .rs coiled in a helix (same wire diameter, same pitch, same 235 mean helix diameter) offset by half a pitch. In this case, the head 10 (nut) has two identical helical grooves 11 offset by half a pitch.

In a preferred embodiment of the invention the insert 7 is manufactured :ontinuously from a continuous wire by a known type coiling machine and the insert 7 does not rotate. Coiling machines are described in US patents 3 725 178, 3 885 605, 4 799 373 and 5 014 533, for example. The speed of fabrication corresponds to the traction speed. The winding diameter and nominal pitch P of the insert 7 are therefore predetermined. In the manufacture of a reinforced composite material tube in accordance with the present invention, which can have a length of several kilometres, it is imperative not to interrupt extrision for any reason whatsoever. It is therefore essential to provide between the means for simultaneous coiling of the insert (or the storage means) at the extruder head 2 a sufficient length for welding a new length of insert produced Ly the coiling machine to the length of insert already in use.

The insert 7 is fitted around the upstream end of the mandrel 5 and is fed through the devices of the apparatus as described above until it enters the extruder head 2. In the initial phase of loading and adjusting the apparatus, the rotary device is driven progressively to facilitate the progress of the insert 7 into the apparatus.

When the insert 7 reaches the confluence chamber it is embedded in the extruded material fed in through the passages 3. The parameters defined above are adjusted, i.e. the rotary member 8 is driven at the speed W and the material flowrate is adjusted until the composite material tube travels at the speed x with an insert having a nominal pitch P.

It is within the scope of the invention to make the groove 11 with a non-constant pitch, which pitch can be substantially equal to the nominal pitch P for the first turn on the upstream side and have a smaller value for the last turn on the downstream side immediately prior to the space 13.

ii s-

Claims (23)

1. Apparatus for the continuous production by extrusion of tubes reinforced by an insert, of the type includinr" a frame including an extruder head in which are formed an annular confluence chamber and a plurality of passages discharging into said annular confluence chamber and through which at least one extrudable material is injected; a stationary support member disposed partly in said extrusion head the outer surface of which has a general shape that is rotational about a longitudinal axis; San insert disposed around and along said support member with a 0**e l.,e predetermined pitch; 0* Og a feed member driven in rotation and mounted in the frame, said feed 15 member having an end disposed in said extruder head and provided with at least *0 one helical groove adapted to receive at least one turn of said insert and to move @SO@ the latter in translation, wherein it further includes first means for supporting and centring the support member disposed inside and attached to said feed member, said first centring and support means including a set of radial members equi- 20 angularly spaced around the stationary support member and offset longitudinally oo', in the direction of movement in translation of said insert parallel to said 9• longitudinal axis of the stationary support member so that the surface at which go o° said radial members bear on said stationary support member determines contact along a helix and so enables the insert to move freely in said support and centring 25 means. 0055 S 0*59@S

2. Apparatus according to claim 1 wherein the first support and centring means include at least three radial support members equi-angularly spaced around the stationary support member, the distances between two consecutive members being the same. r t: -4PI~ W 31

3. Apparatus according to claim 2 wherein the radial support members include pins.

4. Apparatus according to claim 3 wherein it includes four radial pins offset in the direction of movement in translation by one quarter of the pitch of the insert. Apparatus according to claim 2 wherein the radial members include at least three discs.

6. Apparatus according to any one of claims 2 to 5 wherein the stationary support member includes a contact track on which bear inner ends of said radial members.

7. Apparatus according to claim 6 wherein the outside surface of the contact 15 track is surface hardened by surface treatment.

8. Apparatus according to claim 6 wherein the outside surface of the contact track is covered with a material having a relatively low coefficient of friction. 20 9. Apparatus according to claim 1 wherein the stationary support member is immobilised against movement in translation by axial abutment means including at least one radial abutment member cooperating with at least one annular groove in the stationary support member. 25 10. Apparatus according to claim 9 wherein the axial abutment means include boo ,,oose two radial abutment means which are diametrally opposed and offset in the direction of movement in translation of the insert.

11. Apparatus according to claim 10 wherein the side walls of said annular groove are hardened by surface treatment. k I-

12. Apparatus according to claim 9 wherein the side walls of said annular groove are covered with a material having a relatively low coefficient of friction.

13. Apparatus according to any one of claims 9 to 12 wherein the axial abutment means also constitute second support and centring means for the stationary support member.

14. Apparatus according to claim 1 wherein it further includes means for preventing rotation of the stationary support member. Apparatus according to claim 14 wherein the rotation prevention means include first magnetic means attached to the stationary support member and m second magnetic means attached to the frame, said first and second magnetic O• means each having poles diametrally opposed relative to said longitudinal axis of Q 0 15 the stationary support member.

16. Apparatus according to claim 15 wherein the rotation prevention means include a section in the rotary member having a helical groove whose pitch is greater than the nominal pitch of the insert and in which part of the insert is 20 accommodated and an annular groove in the outside surface of the rotary member and in which the poles of the second magnetic means are accommodated. 9 4 •Ca 17 Apparatus according to claim 14 wherein the means for preventing rotation 25 of the stationary support member include two toothed wheels cooperating with .,i S each other, one wheel being fastened to the frame and the other wheel being fastened to the stationary support member.

18. Apparatus according to claim 14 wherein the means for preventing rotation of the stationary support member include a shaft mounted radially in the feed member and including a bevel gear at each end, one gear meshing with a first fixed toothed ring attached to the frame and the other gear meshing with a second toothed ring mounted on the stationary support member.

19. Apparatus according to claim 1 wherein it further includes means for feeding fluid to the interior of the stationary support member and including at least one radial passage attached to the rotary member and discharging at each end into annular chambers to constitute two concentric rotating couplings. Apparatus according to claim 19 wherein the fluid feed means further include a ring attached to the rotary member, a helical passage whose pitch is greater than the nominal pitch of the insert io formed in said ring and part of the insert is accommodated in said passage,

21. Apparatus according to claim 1 wherein it includes two means for setting the pitch of the insert disposed at a distance from each other in the longitudinal direction of the stationary support member, the number of turns of said insert io, 15 between the two setting means being less than the number of turns sIe corresponding to the nominal pitch of said insert.

22. Apparatus according to claims 19 and 21 wherein the fluid feed means are disposed between the setting means and include a ring turning inside a housing 20 in the stationary support member and connected to the rotary member by a radial spacer in which the radial passage is accommodated.

23. Apparatus according to claim 1 wherein it further includes a magnetic device mounted on the downstream side of the extruder head and whose successive poles are disposed in a helix as close as possible to the turns of the ,oo insert and the pitch of said helix is equal to the nominal or predetermined pitch of 0 the turns of said insert.

24. Apparatus according to claim 23 wherein it includes proximity sensors for appropriately adjusting the intensity of the forces applied by the magnetic device to the insert. 34 Apparatus according to claim 1 wherein it further includes an external conforming device on the downstream side of the extruder head.

26. Apparatus according to claim 25 wherein the conforming device includes an annular chamber in which a cooling fluid flows.

27. Apparatus according to claim 25 wherein the conforming device has two thin cylindrical sections between which is an insulative material ring.

28. Apparatus according to claim I wherein it includes an internal conforming device having a piston fastened to a hollow road sliding relative to a passage fastened to the stationary support member and said piston moves from a first position bearing on a seat at the end of the stationary support member to a second position at which it delimits an annular chamber fed with fluid via radial 15 orifices in the piston. C O a

29. Apparatus according to claim 1 wherein it further includes two solenoids which are slightly offset in the circumferential direction around the axis of the fixed support member and are energised alternately to create an oscillating force field.

30. Apparatus substantially as herein described with reference to any one of the embodiments illustrated in the accompanying drawings. V* 09* DATED: 13 July, 1995 25 PHILLIPS ORMONDE FITZPATRICK *oooQ• Attorneys for: COFLEXIP r-C" ABS TRAC T Apparatus for continuous manufacture by extrusion of composite material tubes reinforced by an insert. Lt is of the type comprising a frame an extruder head a stationary support member an insert disposed around said support member with a predetermined pitch and a rotary member and is characterised in that it includes means (19) for supporting and centring the support member which comprise a set of radial members offset angularly and longitudinally around and along the axis so that the bearing surface of the radial members on the suppor member defines contact along a helix and so enables the insert to move freely in said support and centring means. Applications include the manufacture of hoses used in the petroleum production. Figure 1.