Process for producing a cylindrical unit

Abstract

 Process for producing and treating a cylindrical unit, in which process a hose is made from flexible threads around a tube, upon which the hose is subjected to thermal treatment and is molded to form a cylinder around the tube, wherein the hose is made from threads con­taining fibrous material and a thermoplastic or thermosetting polymer which are braided or knitted together.
A cylindrical unit according to this invention can be used for replacing cylindrical units made of other materials, and espe­cially in those cases in which a low weight and a high torsional and flexural resistance are deemed to be important.

Description

[0001] The invention relates to a process for producing and treating a cylindrical unit, in which process a hose is made from flexible threads around a tube, upon which the hose is subjected to thermal treatment and is molded to form a cylinder around the tube.

[0002] Such a process is known from US-A-4202718. In this process a cylindrical unit is formed by winding threads spirally around a mandrel into a cylindrical reinforcing layer, after which the layer is incorporated in a tubular product by impregnating it with a resinous material and thermoforming it. It is described that a second set of threads can be wound spirally in the other direction to bind the first threads. Further longitudinal strands are added. In a modification of the process tapes of resinous material can be wound around the reinforcing layer before thermoforming it.

[0003] The disadvantage of this product is that the wounded rein­forcing layers have no coherend structure of themselves. In case of disrupture of the cylindrical unit, the reinforcing layers will dela­minate.

[0004] The object of the invention is to provide a process of the above-mentioned kind, in which process a product is formed which does not have said disadvantage.

[0005] This object is achieved according to the invention in that the hose is made from threads containing fibrous material and a ther­moplastic or thermosetting polymer which are braided or knitted together.

[0006] As the fibres are thus already mixed with the material suited for the impregnation, the impregnating step customary in the state of the art can be omitted. Also, the good homogeneous distribution of the material suited for the impregnation and of the fibres is safe­guarded.

[0007] A process for producing a braided or knitted hose for impregnating use is known from NL-A-8502880.

[0008] In this process the hose is produced by means of a so-called circular braiding machine on a support tube and is subsequently rolled on a reel. After that this hose is drawn over another support tube and impregnated.

[0009] The disadvantage of this process is that, after the braiding and before the further treatment, the hose must first be impregnated with a material suited for that purpose. Owing to this on-line impregnation, the hose is relatively hard to process, because it will stick to the equipment and because in all treatments which the hose is subjected to it must be supported in the process on the inside by a support tube. So as not to let the support tube move along with the hose, this tube must, according to the state of the art, be supported and fixed by rolls, which also take care of the movement of the hose, which press against the tube right through the hose material. This may cause inhomogeneity of the hose material and interfere with the move­ment of the hose. Further, the impregnation with liquid resins is problematical from an environmental point of view.

[0010] Another disadvantage of the process according to NL-A-8502880 is that the process is not continuous. When a reel is empty, the pro­cess is stopped and a next one is connected. This makes the process quite laborious.

[0011] In the process according to the invention, the support tube need no longer be fixed with rolls pressing through the hose material, but this is effected via the piece of tube passing through the heart of the circular braiding machine, round which the hose is produced. When the bobbins of braiding thread of one machine are empty, the next circular braiding machine may be connected in a continuous process, so that in principle an endlessly long hose can be obtained.

[0012] It is possible to vary the pitch of the braiding hanks and by doing so to determine the angle at which they cross each other.

[0013] It is also possible to apply various layers of braided fabric with or without difference in pitch and of different materials one on top of the other, and it is possible to apply additional lengthwise threads, knitted fabrics, woven fabrics and/or flat braids either con­tinuously or not.

[0014] It is possible to produce a hose filled with a core of, for instance, foamed material by allowing this endlessly or not endlessly long core in the treatment of the hose to move along with the hose through, in this case, the hollow tube, in which process the sup­porting function of the tube is taken over, after the end of said tube, by the core material.

[0015] Thanks to this on-line arrangement of one or more circular braiding machines and further processing equipment, the product can be adjusted, locally if so desired, to highly specific requirements in a continuous process.

[0016] In an embodiment according to the invention the hose is built up, at least in part, of threads consisting, on the one side, of fibres not meltable in the subsequent melting and moulding step and, on the other side, of thermoplastic or thermosetting fibres of a material suited for the impregnation.

[0017] In an embodiment deviating herefrom the hose is built up at least in part of fibres coated with a material suited for the impregnation.

[0018] In yet other variants of this process a powdery material suited for the impregnation is incorporated in at least a part of the fibres from which the hose is produced.

[0019] Other characteristics and advantages will be clear from the description following hereinafter, in which description reference will be made to the attached drawing.

[0020] In it a diagrammatic representation is given of a device for carrying out the process according to the invention.

[0021] As shown in the figure, a hose is formed by means of circular braiding machines 10, two such machines being shown in the figure, but it is clear that such a hose can be realized also with one or with more than two circular braiding machines. The circular braiding machine 10 forms the hose round tube 7 (dotted), which is secured on the one side by a frame on which also the circular braiding machines 10 have been mounted, and which, on the other side, projects through the central openings in the circular braiding machines 10, all of it as customary in this art. For more information about the winding round a tube reference may be made, for instance, to the German Offenle­gungsschrift 3245705. It is clear that within the scope of the inven­tion other types of circular braiding machines can be used without problem. An important element is always that a hose will be formed by the machine round a tube. The braiding or knitting according to the invention has major advantages over DE-3.245.705. When the product of the winding process is twisted, there will be a risk of delamination. In the process according to the invention all threads bind in turns, so that a better distribution is obtained, with the product having strong resistance against torsion without delamination. Moreover, the process of DE-3.245.705 is only possible with a rubbery hose-pipe as the mandrel.

[0022] For the purpose of this invention it is further necessary that the tube should extend through the arrangement in so far as the hose must be supported on the inside, except where such support is taken over by a core as described above.

[0023] After the formed hose over tube 7 has left the last circular braiding machine, it may optionally yet be provided with an extra layer of material suited for the impregnation. This material may be unrolled, for instance, from rolls 8 placed on either side of the tube in the embodiment shown, but it is clear that more than two rolls may be present also and optionally only one roll may be present, too. As the fibres themselves contain material suited for impregnation, such a step can mostly be omitted.

[0024] Subsequently the hose, still moving over tube 7, enters an oven 2. In it the hose is heated to a temperature at which the material suited for impregnation becomes soft. The chosen temperature, of course, depends on the composition of the material suited for impregnation.

[0025] Materials suited for the matrix include all thermoplastics such as, for instance, polyethylene, polypropylene, acrylonitril-­butadiene-styrene graft copolymer (ABS), various grades of polyamides, polyesters, etc., or thermosetting resins such as, for instance, epoxy resin, unsaturated polyester resin, polyurethane resin, acrylate resin, phenolformaldehyde resin, melamineformaldehyde resin, etc.

[0026] For the fibre, too, all known materials available as fibres can be incorporated such as, for instance, glass, carbon, aramide, nylon-6, nylon-6,6, nylon-12,nylon-4,6, acrylonitrile, etc. The melting temperature of the fibre must, of course, be significantly higher than the curing or melting temperature of the material suited for impregnation.

[0027] After having left oven 2 the hose enters a mould or shaping device 3. The hose then still moves over the tube and is thus, on the inside, kept in the shape of it. The outer shape of the tube can be chosen in such a form as is required for the cylindrical unit which is to be produced. At the same time the outside is brought into the correct shape. In shaping device 3 the hose is cooled to a temperature below the softening temperature, in which process a cylinder is obtained. If thermosetting material is used, the heating and moulding steps will both take place in oven (2), upon which the cylinder can be cooled at (3) if so desired. The shape of this cylinder may be round, but may also be oblong, or the cylinder may be of any other shape. In mould or shaping section 3 the cylinder leaves tube 7 and is sub­sequently subjected to further treatment in a cooling tunnel 4, where the cylinder is cooled further. Finally, the cylinder passes through a drawing unit 5 and is moved on to a sawing unit 6, where the cylinder is cut to the correct length to form a cylindrical unit. At this moment the hose is a completely solid and hard cylindrical unit. It is clear that the hose or cylinder is moved forward by means of drawing unit 5, so that a process is created called pultrusion. Within the scope of the invention numerous other variants are, of course, possible.

[0028] A cylindrical unit according to this invention can be used for replacing cylindrical units made of other materials, and espe­cially in those cases in which a low weight and a high torsional and flexural resistance are deemed to be important.

[0029] If a thermoplastic polymer is used as matrix material, the cylindrical unit may yet be thermically shaped later on. With a ther­mosetting matrix material the shaping must take place during the curing.

Claims

1. Process for producing and treating a cylindrical unit, in which process a hose is made from flexible threads around a tube, upon which the hose is subjected to thermal treatment and is molded to form a cylinder around the tube, the process being characterized in that the hose is made from threads containing fibrous material and a thermoplastic or thermosetting polymer which are braided or knitted together.

2. Process according to claim 1, characterized in that the hose is built up at least in part from threads consisting on the one side of fibres that do not melt during subsequent treatment and on the other side fibres from a material suited for impregnation that do melt.

3. Process according to any one of claims 1-2, characterized in that the hose is built up at least in part from fibres coated with a material suited for impregnation.

4. Process according to any one of claims 1-3, characterized in that in at least a part of the threads from which the hose is built up particles of a material suited for impregnation are incorporated.

5. Process according to any one of claims 1-4, characterized in that the pitch of the braiding hanks is varied.

6. Process according to any one of claims 1-5, characterized in that lengthwise threads, knitted fabrics, woven fabrics and/or flat braids are added to the braided fabric.

7. Process according to any one of claims 1-6, characterized in that various layers of braided fabric and/or other fibrous material are laid one on top of the other.

8. Process according to any one of claims 1-7, characterized in that the hose is coated after the braiding with an extra layer of material suited for impregnation.

9. Process according to any one of claims 1-8, characterized in that the hose is moved through the various stages of treatment by means of pultrusion.

10. Cylindrical unit obtained while applying the process according to any one of claims 1-9.

Drawing