CH640776A5 - PROCESS AND DEVICE FOR THE MANUFACTURE OF BENT CONDUITS OF COMPOSITE MATERIAL. - Google Patents

Description

The present invention relates to a method for manufacturing curved pipes of composite material.

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The invention relates more particularly to a method and a device for the production by centrifugal molding of bent pipes made of composite material containing resin and filling materials, such as reinforcing materials and agglomerates, the pipe being bent or folded when it is still in an uncured state.

In recent years, considerable improvements have been made to the quality of pipes made of composite material. Improvements have also been made to improve the production efficiency of such pipes and to reduce manufacturing costs. Consequently, these pipes are today widely used in a plurality of possible arrangements. However, the manufacture of bent pipes encounters difficulties which do not otherwise allow the use of an efficient manufacturing process such as that which is used for the production of straight pipes. In the usual methods of manufacturing arched pipes, a template adapted to the shape of the arched pipe to be manufactured is used, a reinforcement material impregnated with resin being wound around the outer surface of the template or, alternatively, a mixture of resin and filling material, such as reinforcing material or the like, is introduced so as to fill the space between an interior mold and an exterior mold. The efficiency of such manufacturing processes is very poor, leading to high manufacturing costs.

Consequently, the object of the invention is to provide a method and a device for manufacturing, with high efficiency, curved pipes of composite material.

To achieve this goal, the method according to the invention is characterized in that it comprises the following steps:

- rotation around a rectilinear horizontal axis of rotation of a cylindrical molding tool, capable of being deformed from a configuration with a rectilinear axis to a configuration with a cambered axis;

- bringing the composite material into the tool;

Bending of the molding tool containing the pipe in the uncured state, the pipe being produced by centrifugal molding in the tool and formed from the composite material, and

- extraction of the pipe from the molding tool after hardening of the pipe.

The basic idea of the invention is to produce by centrifugal molding a straight pipe made of composite material and then to bend this pipe when it is not yet hardened. However, if the pipe produced by centrifugal molding were removed in the uncured state and then subjected to a bending operation, the shape of its section could practically not be maintained, which would make this pipe unusable.

On the other hand, according to the invention, by producing by centrifugal molding a straight pipe in a deformable molding tool and by bending or bending this tool when it contains the pipe in the uncured state, as indicated above, it is possible to fully retain the shape of the section of the pipe during the bending operation. In this way, pipes with precise tolerances can be efficiently produced by the centrifugal molding technique.

A device for implementing the method is also part of the invention, this device is characterized in that it comprises a molding tool of cylindrical shape, capable of being deformed from a configuration with a rectilinear axis to a configuration with a bent axis, axially rectilinear means for detachably holding the tool in position, rotation means for putting the tool, maintained in a rectilinear position, in rotation about a horizontal axis, and bending means for arching the tool when it is released from the means of rotation.

Said rotation means preferably comprise a cylindrical rotary frame, capable of being rotated about a horizontal axis, the internal surface of which serves as means for keeping the axis of the molding tool straight. As a variant, the rotary frame, arranged so as to surround or receive the molding tool, can be in the form of a bellows and means for limiting the movement of the bellows in the axial direction can be provided so as to be used as means for keep the axis of the molding tool straight.

In a preferred embodiment of the invention, a bag made of a sheet of flexible material is inserted into the molding line by centrifugal molding, and is inflated with air or gas under pressure, so as to press against the inside wall of the pipe before bending the tool, so that the surface of the inside wall of the pipe is erected and the shape of the section of the pipe is not deformed during the bending operation. A layer of absorbent material is preferably deposited on the outside surface of the bag to remove air or gas bubbles which may develop on the inside wall of the pipe.

In another embodiment of the invention, the molding tool is made of elastic material such as rubber and a hollow space is provided between the inner and outer walls of the tool, this space being filled with liquid during the centrifugal molding operation. Even if a deformation or an eccentricity is present in the tool or the frame, this arrangement makes it possible to give a perfectly cylindrical shape inside the tool during the centrifugal molding operation and thus to obtain pipes. with a uniform wall thickness. Another advantage of this arrangement is that, during the operation of extracting the pipe, it is possible to widen the internal diameter of the molding tool by evacuating the liquid contained in the hollow space mentioned using pressure imparted to the inside of the tool and then easily extract the line from the tool.

In another embodiment of the invention, an intermediate frame with multiple sections, or an intermediate frame in the form of a flexible bellows composed of flat metal parts wound in a spiral, is inserted between the rotary frame and the molding tool made of elastic material. This arrangement has the advantage of avoiding any deformation of the molding tool which may appear when the tool is extracted from the rotary frame. More particularly, in the case where an intermediate frame is used, it is possible to carry out the bending operation while the elastic tool is held in the intermediate frame, so that the shape of the section of the tool, and consequently that of the pipe, can be kept during the bending operation. During the extraction of the pipe, the stresses of the elastic tool can be easily eliminated by exerting a twist on the intermediate frame, in the direction opposite to that of the spiral winding of the flat strip, which allows d '' easily remove the pipe.

For the bending operation, any known method can be used, including that in which the pressure is exerted by a higher force and a lower force, or that in which the tool is. supported at both ends and in an intermediate position, the support points being modified according to the cambering requirements.

The invention will be described below, by way of example and with the aid of the drawing in which:

fig. 1 is a section in elevation of a centrifugal molding device;

fig. 2 shows an intermediate frame and a molding tool,

both extracted from a rotating frame and placed on a conveyor; fig. 3 is a section through the frame of FIG. 2;

fig. 4 is a side view of the molding tool delivered by the conveyor on bending means;

fig. 5 is an elevational view of the bending means, showing the molding tool held in position;

fig. 6 is an elevational view of the bending means showing the conditions after the bending operation;

fig. 7 is a section along the line VII-VII of FIG. 5;

fig. 8a-8d are sections showing different stages in the manufacture of the pipe during molding;

fig. 9 shows a bag;

fig. 10 shows an alternative embodiment of a bag;

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fig. 11 shows an elevational view of another embodiment of a centrifugal molding device;

fig. 12 shows an elevational view of a third embodiment of a centrifugal molding device;

fig. 13 is a section through the device of FIG. 12;

fig. 14 is an enlarged view of the part indicated by the arrow A in FIG. 12;

fig. 15 is a front view showing the intermediate frame and the molding tool in the arched state;

fig. 16 is an enlarged sectional view of the part indicated by the arrow B in FIG. 15;

fig. 17 is an enlarged sectional view of the part indicated by the arrow C in FIG. 15;

fig. 18 is a section through the means for inserting a bag, and FIG. 19 is a view showing the bag of FIG. 18 inserted.

The upper part of fig. 1, above the axis of rotation, shows the device with a pipe joint to be molded, and the part below the axis shows the device with a pipe to be molded.

Figs. 1 to 7 show a molding device according to a first embodiment of the invention.

In fig. 1, a rotary frame 2, capable of rotating about a horizontal axis 1, is formed of a cylindrical body 3 and comprises annular members 4 at its two ends. These annular members rest on rotary drive means 5 comprising a shaft 8 supported on a pair of supports 6 by bearings 7, wheels 9 mounted at the two ends of the shaft 8, a circular disc 10 fixed to each of the wheels 9, on one side thereof, and a drive mechanism (not shown) capable of transmitting power to the shaft 8. The wheels 9 have a convex peripheral surface 11. A contact surface 12 for the engagement with the wheels 9 is formed at the periphery of the annular members 4, and a circular groove 13 adapting to the discs 10 is provided on one of the sides of the contact surface 12. The annular member 4 also includes an interior surface convex 14, opposite the groove 13. The two annular members 4 each have an inner bearing 15. The cylindrical body 3 comprises at each of its ends rings 16 directed outwards. The rings 16 fit perfectly into the inner surfaces 15 and are fixed to the members 4 by fixing elements 17, at a plurality of places around their periphery. An intermediate frame 18 is supported and held in position by the cylindrical body 3. The frame 18 is divided into a plurality of separate parts (multiples of two) and is made, for example, of aluminum. The elastic molding tool 19 is supported and held in position by the intermediate frame 18. This tool 19 is made of elastic material, such as fluorine, silicone or urea-thanne rubber, and it includes collars 20 , 21 at both ends. The collar 20, on the side of the pipe joint, is engaged with a pressure ring 22 and the collar 21, on the side of the fixing end of the pipe to be molded, is engaged with a bearing surface of the intermediate frame 18. A l the fixing end of the intermediate frame 18 is mounted an end piece 23 adapted for passage through the body 3. At the end of the pipe joint is also an end piece 24 comprising a collar 24a, assembled to the ring 22 by a fixing member 25, and a tubular part 24b extending in the axial direction, at a certain distance from one side of the intermediate frame 18. The two parts 23, 24 are fixed by a plate 26 pressing one side on the parts 23, 24 and, on the other side, on the annular member 4, the plate 26, the member 4 and the ring 16 being assembled by fastening elements 27 in a plurality of places of the circumference. Tubular internal molding means 28 are inserted in the part 24 on the side of the pipe joint and are displaceable in the axial direction. These means are provided for molding the inside of the pipe joint when they are introduced into the molding tool 19. A ball 30, pushed radially in the direction of the axis by a spring 29, is provided in the tubular part 24b of the part 24. At the peripheral surface of the molding means 28 there are two housings 31, 32, at a certain distance from each other along the axis 1, these housings being designed to receive the ball 30 The position of the housings 31, 32 is calculated so that the ball 30 is inserted into the housing 31 when the inner end of the part 24 is aligned with the inner end of the molding means 28, and the ball 30 is inserted into the housing 32 when the means 28 cover the interior surface of the pipe joint. A control lever 33 is pivotally fixed to the support 6 by a horizontal pin 34. The upper end of the lever 33 is folded on one side and the lower part 35 of this end is of concave shape, so as to come in contact with the convex surface 14 of the annular member 4. The lower end of the lever 33 is bent on the opposite side. This end serves as attachment means 36 relative to the fixed support 6. A cylinder 37 for tilting the lever 33 is provided between the attachment means 36 and the support 6. A bag 80 consisting of a tubular film of a material resistant to solvents, such as silicone rubber with paraffin or fluorine rubber, is visible in the figure. The bag 80 is held at one of its ends by a clip 81, and at the other end is a coupling element 83 receiving air or gas under pressure through a stop valve 82. The element coupling 83 is capable of being coupled to another coupling element 84 adjacent to the rotary frame 2, this element communicating with a source of pressurized air (not shown). Means (not shown) are also provided for introducing the bag 80 into the molding tool after each molding operation cycle.

The operation of the device described above is explained below. When the molding means 28 are in a position outside the molding tool 19 and are held in this position by the ball 30 in the housing 31, as shown in fig. 1, in the part above the axis of rotation, the rotation drive means 5 are actuated to rotate the molding tool 19, as well as the rotary frame 2 around the axis 1. Then, through an opening at the ends of the parts 23 or 24, filling materials such as reinforcing fibers and sand are introduced into the molding tool 19, in the part of this tool corresponding to the pipe joint to be molded. A medium cure liquid resin comprising a resin mixture supplemented with a curing agent and a catalyst is also supplied. This allows the joint 38a of a pipe 38 to be molded as illustrated in FIG. 8a. The means 28 are then introduced inside. The position at which the means 28 are introduced is fixed by the ball 30 engaged in the housing 32. As before, filling materials are provided on the part 38a of the resin forming the pipe joint to be molded which is not open by the means 28, then a quick-hardening liquid resin, comprising a mixture of resin added with a hardening accelerator-coaccelerator and a catalyst, is delivered and a stepped part 38b of the pipe joint is molded by centrifugation, as illustrated in fig. 8b. Then, filling materials are delivered to the interior surface of the molding tool 19, between the stepped part 38b of the pipe joint and a point adjacent to the fixing end of the pipe, as well as a liquid resin. with a relatively low cure rate, comprising a mixture of resin added with an accelerator and an inhibiting catalyst, for molding the part 38c of the pipe body by centrifugation, as illustrated in FIG. 8c. Subsequently, filling materials and a quick-hardening liquid resin are delivered to the remaining part of the interior surface of the molding tool 19, as in the case of the molding of the stepped part 38b of the pipe joint, and the fixing end of the pipe 38d is produced by centrifugal molding, as illustrated in FIG. 8d. During these operations, it is expected that the seal 38a will harden with a normal cure rate, that the stepped portion 38b of the seal and the attachment portion 38d will cure soon after the materials are delivered and that the body 38c of the pipe hardens relatively slowly. Consequently, when the pipe is removed after the molding operation, the seal 38a, the stepped part 38b of this seal and the pipe fixing part 38d have hardened while the pipe body part 38c is still in shape. uncured condition. Arriving

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giant so that the resin-rich parts, such as the ends and the edges, harden quickly, it is possible to eliminate the possibility of cavities or voids due to the flow of the resin after the interruption of rotation . The subsequent bending of the pipe is carried out on the body 38c of the latter. If, above the liquid resin mentioned, there is resin for general applications, such as for example unsaturated polyester resin, products such as cobalt naphthenate and cobalt octoate are preferably used as accelerators , dimethylamiline as a co-accelerator, methyl ethyl ketone peroxide as a catalyst and hydroquinone as an inhibitor.

When the molding of the pipe is finished, the rotation of the frame 2 is stopped. Then, as shown in fig. 1, a bag 80 is introduced into the molded pipe 38, by suitable means, and is inflated by injection of pressurized air so that it exerts pressure against the interior wall of the pipe. Then, the stop valve 82 is closed and the coupling elements 83, 84 are separated from each other. The inner wall of the pipe is drawn up by the bag 80, which makes it possible to avoid any deformation of the section of the pipe which may occur during the following bending operation.

In fig. 1, a chamber 85 for a mold lubricant is delimited by the interior surface of the tubular part 24b of the end piece 24, and seals 86a, 86b are provided on either side of this chamber. This protects the internal molding means 28 against any deterioration due to the resin. The internal surfaces 87, 88 of the two end pieces 23 and of the means 28 are conical, their diameter widening towards the outside, so that any fragment of material falling on these surfaces is evacuated towards the outside by force centrifugal. In addition, the part 23 and the molding means 28 have flanges 89, 90, at their ends facing the molding tool 19, which are turned towards this tool so as to avoid the formation of burrs at the ends of the conduct.

Means for removing the intermediate frame 18 and the molding tool 19 from the rotary frame 2 are described in relation to FIGS. 2 and 4. Extraction means 39 are used to extract the intermediate frame 18 from the rotary frame 2, by gripping the end piece 24 coupled to the frame 18. The means 39 comprise a piston cylinder 40 situated in the extension of axis 1, a plate 42 fixed to the front end of a piston rod 41 of the cylinder 40, a pair of rocking arms 44a, 44b mounted on the plate 42 by pins 43a, 43b, claws 45a, 45b formed by folded parts of the tilting arms, and means 46 for actuating the arms 44a, 44b to lower and raise the latter. A conveyor 47 is provided, between the rotary frame 2 and the extraction means 39, to receive the intermediate frame 18 when the latter is removed from the frame 2 by the extraction means 39. The conveyor 47 comprises a pair of rotary shafts 49, 50 mounted on a support 48 and arranged at a certain distance from each other in the direction of extraction, a pair of chain wheels 51, 52 mounted on each of the shafts 49, 50, a pair roller chains 53 driven by the wheels 51, 52, rails 55 mounted on the support 48 to guide the rollers 54 of the chain 53, and receiving plates 56 of concave shape mounted on either side, in opposition , along the path of movement of the chains 53 on the rails 55, the reception plates 56 being arranged regularly along the path of movement of the chains 53. Each reception plate 56 comprises at its upper part, and on each side, a pivoting lock 62. The support 48 comprises on one side of its base a tilting shaft 57 passing through the support 48 parallel to the axis of rotation of the frame 2, the shaft 57 being rotatably supported by brackets 59 fixed to the ground 58. A cylinder 60 for tilting the support 48 is provided between the other side of the latter and the ground 58. A stop 61 is also provided to stop the support 48. Cambering means 63 are provided for receiving the molding tool taken out of the device.

The operation of the extraction means 39 is explained below. When the rotation of the rotary frame 2 is stopped during molding of the pipe 38 by the centrifugal molding device, the fixing member 27 is released and the plate 26 is moved away, so that the intermediate frame 18 can be taken out. The cylinder 40 then advances the rod 41 with the rocking arms 44a and 44b separated, and these come in front of the end piece 24. In this position, the arms 44a and 44b are moved one against the other under the action of the means 46, so that the claws 45a and 45b of these arms engage in the part 24. The withdrawal of the rod 41 then allows the intermediate frame 18 to come out of the rotary frame 2 through the piece end 24, the molding tool 19 and the pipe 38 being removed at the same time. The intermediate frame 18 is received by the receiving plates 56 on the conveyor 47. The force required to remove the intermediate frame 18 can be used to set the conveyor 47 in motion or, otherwise, the conveyor can be moved by a separate drive. As shown in fig. 2, the intermediate frame 18 taken out of the rotary frame 2 is entirely received by the conveyor 47. Next, the means 46 are actuated to separate the arms 44a, 44b from one another, as indicated in dotted lines in FIG. 2. The upper half of the intermediate frame 18 is then removed, as shown in dotted lines in the figure, using lifting means (not shown) while the lower half is retained by the latches 62. The conveyor 47 is then tilted around the shaft 57, as shown in fig. 4, so that the molding tool 19 and the molding line 38 which it contains are supplied to the cambering means 63, as shown in dashed lines in the figure.

The cambering means 63 are described below with the aid of FIGS. 5 to 7. These means, in the form of a carriage, comprise a base plate 64 provided at its lower side with a plurality of wheels 65. On the base plate 64 is mounted a pair of supports 66a, 66b. Between the upper ends of these supports 66a, 66b is disposed a horizontal camshaft 68 in bearings 67a, 67b. The camshaft 68 is coupled by an endless transmission mechanism to a motor 69 fixed to the base plate 64. The latter also comprises a pair of vertical side plates 71a, 71b, arranged parallel to the axis of the molding tool 19. A support block 72a of concave shape supports the end of the workpiece 24. Similarly, a support block 72b of concave shape supports the workpiece 23. The blocks 72a and 72b have engagement members intended to prevent the movement of the end pieces 23, 24 in the axial direction. The concave-shaped support blocks 72c, 72d, 72e and 72f support the molding tool 19 in different places along the axis of the latter. The support blocks 72a-72f are individually fixed to the base plates 73a-73f assembled, interchangeably, to the door structures 74a-74f by fixing elements (bolts and nuts). The side plates of the door structures 74a-74f are in contact with the outer surface of the side plates 71a, 71b so that the door structures 74a-74f cannot rotate when they are moved up and down and forward backward. Under the front plates of the door structures 74a-74f are mounted individual operating blocks 76a-76f comprising cam grooves 77a-77f. A plurality of cam discs 78a-78f are engaged in the grooves 77a-77f and are mounted on the camshaft 68. These discs are capable of moving the operating units up and down by tilting them.

The cambering means 63, as described above, receive the molding tool 19 when all the support blocks 72a-72f are held horizontally in position by the engagement of the cam discs 78a-78f with the operating blocks 76a- 76f. The molding tool 19 is received so that it is supported by the concave surface of the support blocks 72c-72f, the end pieces 24 and 23 being supported by the concave surfaces of the support blocks 72a, 72b when the engagement members 72a ', 72b' of the blocks 72a, 72b are engaged with the end pieces 24, 23. At this stage, the motor 69 is started to rotate the cam disks 78a-78f using the shaft 68. The cam disks 78a-78f act by their particular configuration in the grooves 77a-77f , so that the support blocks 72a-72f are moved by the operating blocks 76a-76f, the door structures 74a-74f and the base plates 73a-73f, which ef5

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bends the pipe 38 at the same time as that of the molding tool 19, as illustrated in fig. 6. After the bending operation, the molding tool 19 can be delivered to the next stage for hardening the pipe, after which the latter is removed from the molding tool 19.

The bag 80, shown in fig. 1, and described as being composed of a tubular film only, is preferably made as indicated in FIG. 9. In this figure, the bag comprises an absorbent tubular layer 91 formed from corrosion-resistant fiber, such as cotton or polyester, or from a flexible, porous and corrosion-resistant material. Layer 91 surrounds the outer surface of bag 80 and a porous film 92 of solvent resistant material, such as polyethylene, polyester and nylon, is deposited on layer 91. The reason for making such a bag is that the inside the molded pipe 38, in the uncured state, is often subject to the presence of air bubbles, in particular in the case of a pipe made of composite material containing reinforcing fibers, these bubbles being produced by the recovery of these fibers when stopping the rotation of the frame 2, which requires eliminating these bubbles, that is to say a de-aeration. If a bag formed only from a tubular film is inflated in one operation, an air layer may form between the interior surface of the pipe and the bag, so that air can enter the wall of the pipe. On the contrary, if an absorbent layer 91 is provided, as indicated in FIG. 9, when the bag 80 is inflated and pressed against the inside wall of the pipe 38, the compressed air against the inside wall of the pipe can pass through the porous film 92 in the absorbent layer 91, so that the inside wall of the pipe 38 has no air bubbles.

The embodiment of the bag according to FIGS. 1 and 9 is not limiting. Another embodiment is indicated in fig. 10. In this, a pipe 93 for pressurized air is provided to be introduced into the molding tool 19, along the axis 1 of the rotary frame 2, one of its ends being stopped by a stop 94 and the other end communicating with a source of pressurized air (not shown). A bag 95 is mounted around the pipe 93, the two ends of this bag being fixed in an airtight manner to the pipe 93 comprising a plurality of openings 96 along its axis. On the outer surface of the bag 95 are arranged an absorbent layer 97 and a porous film 98, both similar to those of FIG. 9. The insertion of the type of bag in fig. 10 in the molding tool 19 can be made by the pipe 93. If the angle of camber of the pipe to be molded 38 is large, it is necessary that the pipe 93 adequately supports the bag 95 and that it has good flexibility.

Fig. 11 shows another embodiment of a centrifugal molding device in which a rotary frame 102 is supported by a plurality of rollers 103 for its rotation around a horizontal axis of rotation 101. An intermediate frame 104 with divisions multiple circumferentials is fitted into the rotary frame 102. The device also comprises an elastic molding tool 105, for example made of fluorine, silicone or urethane rubber or similar material, fitted into the intermediate frame 104, the tool 105 comprising collars 106,107 at its two ends. Pressure rings 108, 109 are placed at the two ends of the rotary frame 102, between the latter and the collars 106, 107. End pieces 110, 111 are fixed to the ends of the rotary frame 102 by annular fixing members 112, the end pieces comprising flanges 110a, 11a fixed to the pressure rings 108,109 and tubular parts 110b, 11 lb , each of these being partially inserted into the molding tool 105. Auxiliary molding means 113 for molding the interior of the pipe joint are mounted at the end of the part 111 opposite the corresponding end of the tool 105. The means 113 are movable between an advanced position in the direction of the region 105 of the pipe joint and a withdrawal position in the part 111. They are made of the same elastic material as the molding tool 105 The auxiliary molding means 113 are normally positioned so as to be able to withdraw into the part 111 by their own elasticity. The operative surface 113a of the means 113 has a projection 114. An operative tubular element 115 is fixed in the tubular part 11 lb of the part 111, and it is movable in the axial direction of the axis 1. This element is liable to push the auxiliary means 113 opposite the zone 105a for molding the pipe joint when they are introduced into the molding tool 105. Pushing means 116, abutting against one end of the element 115, comprise a cylinder piston 117 and a floating roller 118 in a piston rod of cylinder 117. The interior of the body of the molding tool 105 is formed so as to include a housing 119 for liquids 120 such as fluorine oil and added oil of a suitable powder material to give it a density greater than that of the resin. The housing 119 is such that there is no leakage of liquid. The housing 119 being angular in shape, the inner tubular part of the elastic molding tool can be coupled by coupling means 121 suitable for the other tubular parts, or the housing 119 can be formed of open cell material so that the inner part of the tube does not deform by gravity. A reservoir 122 of liquid is provided in the tubular part 110b of the part 110, this reservoir communicating with the housing 119 by a plurality of passages 123. The reservoir comprises a liquid inlet 124.

The stages of centrifugal molding of the pipe to be molded by the device of FIG. 11 and the subsequent bending operation of this pipe are substantially the same as those described in the first embodiment. The protrusions 114 of the auxiliary molding means 113 are intended to produce peripheral grooves on the inner surface of the seal 125a of the pipe 125 to be molded, these grooves being provided for receiving sealing rings. If, during the centrifugal molding operation, deformations due to errors or eccentricity occur in the frame 102, the intermediate frame 104 and / or the molding tool 105, the cylindricity can be preserved from satisfactorily by the action of the liquid introduced from the reservoir 122 into the housing 119 through the passages 123. In addition, the extraction of the pipe to be molded and bent can be easily carried out by evacuating the liquid 120 from the chamber 119 in the reservoir 122 through the passage 123. To evacuate this liquid, it is possible, for example, to put the interior of the molding tool 105 under air pressure.

Figs. 12 to 17 illustrate another embodiment of the device according to the invention.

Fig. 12 shows a rotary frame 202 with multiple circumferential divisions supported and rotated about a horizontal axis by a plurality of rollers 203. An intermediate frame 204 is mounted inside the rotary frame 202. As shown in FIGS. 12 to 14, the body of the frame 204 is formed of bands 205 wound in a spiral, the opposite lateral ends of the spiral being held by adaptation parts 206 which can be moved, between certain limits, parallel to the axis of rotation 201. A lateral sides of the strips 205 is folded in an inner hook 207 curved outward, and the other side is folded in an outer hook 208 curved inward. These hooks engage one in the other and, in their state of engagement, they are movable between certain limits. A molding tool 210 made of elastic material is introduced inside the intermediate frame 204. A housing, in the lower part of the tool 210, is filled with a liquid 211. The tool 210 does not have any part of pipe joint formation, but it can also be provided with such a part, in a similar manner to that of the previous embodiments. Collars 212a, 212b are provided on the outer periphery of the molding tool 210, at each of its ends. Pressure rings 213a, 213b, in contact with the collars 212a, 212b, are fixed to the two ends of the rotary frame 202. End pieces 214a, 214b are mounted on the frame 202, at the two ends of the latter. The parts 214a, 214b include tubular parts 215a, 215b, one end of each of which can be introduced into the molding tool 210, and collars 216a, 216b in contact with one or the other of the ends of the frame 202 and fixed to the sealing rings 213a, 213b by fastening elements 217a,

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217b. The end pieces have internal conical parts 218a, 218b and projections 219a, 219b. A coupling element 220 is provided in the housing of the tool 210.

The pipe molding process using the device of FIG. 12 is substantially the same as that of the first embodiment, except that the operation of molding the pipe joint does not exist. After the molding of the pipe is finished, the parts of the rotary frame 202 are separated and the intermediate frame 204, the molding tool 210 and the molding pipe 221 are removed. The parts 214a, 214b are also removed during the same operation. The whole is then subjected to the cambering operation as indicated in fig. 15. As shown in fig. 17, the movement between the limits 209 of the hooks 207, 208 takes place at the outer periphery, so that the object to be arched is elongated on the side of this outer periphery. Its internal periphery is maintained between the limits 209. It follows that the bending of the pipe is carried out by elongation of its external periphery, but without contraction of its internal periphery. When the pipe in the tool 210 is bent and hardened, the end pieces 214a, 214b are removed. The intermediate frame 204 is subjected to a torsion in the opposite direction to that of the spiral, so as to enlarge its diameter, and the molding tool is removed. The pipe is then removed from the tool 210. During the tool removal operation, the liquid 211 is poured out. The adjustment of the diameter of the molding tool is effected by the quantity introduced of this liquid.

Finally, an example relating to the means for inserting the bag is described in relation to FIGS. 18 and 19. In these figures, the rotary frame and the molding tool 301 are shown diagrammatically and the molding tool is shown as being of rotary type with circumferential divisions. The tool 301 rotates about a horizontal axis 304 and it is driven by a plurality of rollers 303. A bag delivery pipe 305 is movable along the axis 304. This pipe 305, supported by a plurality of rollers 306, can insert a bag into the rotary tool and remove it from it by the normal or reverse movement of a drive roller 307. A bag 80, in the non-inflated state, is visible in the pipe 305.

The pipe 305 comprises, at its end facing the molding tool 301, a flaring 308 at the end of which is attached a piece of rubber 309. An annular air reservoir 310 is formed in the flaring 308 and a nozzle 311 communicating with the reservoir 310 opens into the pipe 305, in the direction of the opposite end of the latter. The nozzle 311 can be of porous or slotted type. The air tank 310 communicates with the other end s of the pipe 305 by an air passage 312 in the form of a pipe. This communicates with an air source via a pipe 314 comprising a valve 313.

As shown in fig. 18, when the molding line 302 is molded inside the molding tool 301, the rotation of the latter is stopped and the drive roller 307 is started. As indicated in dotted lines, the pipe 305 is introduced and positioned in the tool 301, and a coupling element 83 is connected to another coupling element 84. Next, the valves 82 and 313 are green on to supply air and the rotation of the roller 307 is reversed to gradually withdraw the line 305. During this operation, a bag 80 is delivered by the line 305 in the molding line 302, this bag is inflated by the air supplied by the valve 82 and, as shown in fig. 19, it is pressed against the internal wall of the pipe 302. The surface pressed by the bag increases gradually. from one end of the pipe 302 to the other by the withdrawal of the pipe 305, so that an air cushion cannot form between the bag and the molding pipe 302. It also occurs a pinching effect, which makes it possible to deaerate the interior of the line to be molded. During this operation, it is possible that the air introduced into the bag swells the part of the latter which is still in the pipe 305, which produces a resistance preventing the exit of this bag or damaging the latter. However, in the device described, the air is supplied between the interior of the pipe 305 and the bag 80 by the nozzle 311. The pressure of the air supplied is greater than that prevailing inside the bag 80 Consequently, an air cushion is formed between the interior of the pipe 305 and the bag 80, which allows the gradual exit of the bag, without pressure resistance. Part of the air supplied by the nozzle 311 could also return back, but this is avoided by the fact that the rubber seal 309 abuts against the bag 80. When the bag 80 is completely out of the line 305 and that it is pressed over its entire length against the internal wall of the molding pipe 302, the valves are closed and the coupling elements 83, 84 are disassembled.

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13 sheets of drawings

Claims (20)

640,776 1. Method for manufacturing curved pipes made of composite material, characterized in that it comprises the following stages: - Rotation around a horizontal recti-line axis of rotation of a cylindrical molding tool, capable of being deformed from a configuration with a rectilinear axis to a configuration with a cambered axis; - bringing the composite material into the tool; Bending of the molding tool containing the pipe in the uncured state, the pipe being produced by centrifugal molding in the tool and formed from the composite material, and - extraction of the pipe from the molding tool after hardening of the pipe. 2. Method according to claim 1, characterized in that a bag of flexible material is introduced into the pipe and inflated, the bag exerting pressure against the internal wall of the pipe during the bending operation. 2 3. Method according to claim 2, characterized in that bubbles of air or gas liable to develop on the surface of the internal wall of the pipe are eliminated by a layer of absorbent material on the external surface of the bag. 4. Method according to one of claims 1 or 2, characterized in that the molding tool is held in a rectilinear manner in a rotating rotary frame and is removed therefrom when the rotation of said frame is stopped, the tool then subjected to the bending operation. 5. Method according to claim 4, characterized in that it uses a molding tool made of elastic material and of cylindrical shape, the tool comprising a hollow space, between its internal and external walls, which is filled with liquid during l centrifugal molding operation of the pipe. 6. Method according to claim 4, characterized in that it uses a molding tool of elastic material held in position in an intermediate frame with circumferential divisions during the centrifugal molding operation, and in that, at the end of the centrifugal molding operation, the intermediate frame and the molding tool which it contains are removed, that the tool is released from the frame and subjected to the bending operation. 7. Method according to claim 4, characterized in that it uses a molding tool made of elastic material held in position in a flexible intermediate frame formed by bands wound in a spiral, the adjacent ends of the bands being capable of sliding one relative to each other in the axial direction, the flexible intermediate frame being introduced into the rotary frame during the centrifugal molding operation, and by the fact that, at the end of the centrifugal molding operation, the flexible frame and the 'elastic tool it contains are removed and the intermediate frame is subjected to the bending operation. 8. Device for implementing the method according to claim 1, characterized in that it comprises a molding tool (19, 105, 210) of cylindrical shape capable of being deformed from a configuration with a rectilinear axis at a configuration with cambered axis, axially rectilinear means (18,104,204) for detachably holding the tool in position, rotation means (9,4, 103,203) for putting the tool, maintained in rectilinear position, in rotation around a horizontal axis, and cambering means (63) for cambering the tool when it is released from the rotation means. 9. Device according to claim 8, characterized in that the rotation means comprise a rotary frame (2,102,202) capable of being rotated, the internal surface of the rotary frame now rectilinear the axis of the molding tool. 10. Device according to claim 9, characterized in that the molding tool (105) is made of elastic material and comprises a hollow space (119) between its internal and external walls, this space being filled with liquid (120). 11. Device according to claim 10, characterized in that the rotary frame (102) comprises a liquid reservoir (122) at one of its ends, the reservoir communicating with the hollow space (119). 12. Device according to one of claims 9 or 10, characterized in that the molding tool (105) is made of elastic material, and in that the device comprises an intermediate frame (104) with multiple circumferential divisions, the intermediate frame. being capable of adapting to the external periphery of the elastic molding tool to surround and hold in position the molding tool, the intermediate frame being included in the rotary frame. 13. Device according to claim 10, characterized in that the molding tool (105) comprises at least at one of its ends a collar (106,107) at its outer periphery, the collar being clamped between the workpiece end (110,111) and a pressure ring (108,109), the end piece comprising interior molding means (113) for molding the interior of an end portion of the pipe, the means being movable in the axial direction of driving. 14. Device according to claim 9, characterized in that the molding tool (210) is made of elastic material, and in that the device comprises a flexible intermediate frame (204) capable of adapting to the external periphery of the molding tool to surround and hold in position the molding tool, the flexible intermediate frame being formed of flat bands (205) wound in a spiral, the adjacent ends of the bands being capable of sliding one relative to the other in the axial direction, the flexible intermediate frame being included in the rotary frame (202). 15. Device according to claim 9, characterized in that an end piece (214a, 214b) is mounted against each of the two ends of the molding tool, the end pieces being supported by the rotary frame ( 202). 16. Device according to claim 15, characterized in that the end piece (214a, 214b) comprises a projection (219a, 219b), on its internal surface, penetrating into the molding tool (210). 17. Device according to claim 9, characterized in that it comprises at one end of the rotary frame extraction means (39) for extracting the molding tool, the extraction means comprising means (40, 41 , 44a, 44b, 46) movable in the axial direction of the rotary frame and capable of engaging with the end piece. 18. Device according to claim 8, characterized in that it comprises a bag (80) formed of a sheet of flexible material into which air or gas under pressure can be injected, the bag being capable of be introduced into said molding tool. 19. Device according to claim 18, characterized in that the bag (80) comprises a tubular absorbent layer (91) formed at the external periphery of the bag and a layer of a porous film (98) on the absorbent layer. 20. Device according to claim 8, characterized in that said cambering means (63) comprise support blocks (72a-72f) for supporting the molding tool in several places, operative blocks (76a-76f) fixed individually respectively to one of the support blocks and each comprising a cam groove (77a-77f), a cam shaft (68) on which cam discs (78a-78f) are mounted facing the operating blocks, and rotation means (69, 70) for rotating the camshaft, the operating units being controlled in an upward and downward movement by the cam discs by performing a tilting movement.