BE535811A - - Google Patents

Description

       

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   This invention relates to a new and improved design process and apparatus for the manufacture of tubes, pipes or other articles from a plastic or other material.



   It also relates to an improved method and apparatus for friction welding of plastics or the like.



   The invention also relates to a process as well as to an improved apparatus for the manufacture of reinforced materials such as plastics reinforced or reinforced with stronger materials, or more generally any weaker reinforced material. or armed with a stronger or more resistant material.



   The use in industry of tubes, pipes, or other articles made of plastics is constantly increasing as a result of the many advantages offered by tubes, pipes and other articles of plastic over tubes, pipes or tubes. other articles consisting, for example, of metals.



   The main drawback of plastic tubes or pipes has heretofore been their insufficient strength in comparison with that of metal tubes and pipes, and also the tendency of many plastics to deform or suffer. cold creep under the action of a load, so that it has not been possible, for example, to use plastic tubes or pipes to convey fluids under high pressures or even under high pressure. medium pressures.



   In addition, ordinary processes and apparatus of common construction used in the manufacture of tubes, pipes and other articles from plastics more generally require treatment of the bulk material, so that differences arise. processing and, consequently, divergences in the properties of the elements of the material at different places on the wall of such a pipe or other object.



   An object of the present invention is to provide a method and to provide an apparatus for obtaining a much greater uniformity of the strength properties of the material throughout its extent, in order to eliminate spots. weak points which occur with conventional methods, these weak points reducing, as one can imagine, the total resistance of the whole of the object in question.



   Another object of the invention is to be able to strengthen practically all the elements of the material thanks to the use of the intrinsic properties of the latter (especially in the case of numerous plastics), instead of leaving them not used, as in conventional processes.



   Yet another object of the invention is to ensure the orientation of the elements of the material (radii of curvature or the like), instead of leaving the elements unoriented as is the case with conventional methods.



   Another object of the invention is to allow the realization of an integral joining of the elements of the material with each adjacent element, thus eliminating the weak points due to this cause in the conventional processes.



   'Yet another object of the invention is to be sure that each element of the material will contribute to withstanding the load weighing on the whole, that is to say to prevent certain elements from being char - aged while others are not, as results from the causes mentioned above in conventional processes, that is to say in which the

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 Elements that contribute to resistance also do not have uniform resistance, but have weak points.



     Yet another object of the invention is to create a method and to allow the production of an apparatus making it possible to reinforce or arm a tube, pipe or other object beyond the maximum strength which can be obtained by treating the material itself thanks to the combination of this material with materials having greater mechanical resistance.



   With a view to obtaining the above-mentioned objects, the invention provides a method and an apparatus for manufacturing tubes, pipes or other objects from plastics or other materials according to the principle of differentiation and integration. , this process consisting in differentiating certain elements from the mass of material used, in working this mass in a differentiated form (in the form of elements) under pressure, and in integrating the elements thus worked in a substantially similar orientation (radii of curvature) while continuing to work the material.



   This can imply, according to the invention that: 1) Each element (layer or part of a strip or a wire) of the material is worked individually and more or less uniformly.



   2) Each element (layer or part of strip or wire) is stretched under pressure in a substantially uniform manner (the word "stretching" being used here in its general sense as encompassing the various reinforcing operations, such as stretching. properly speaking, elongation, winding, calendering and similar operations, considered in whole or in part,) the same conditions prevailing all around the periphery of the element.



   3) The elements are oriented substantially uniformly (radii of curvature and the like) under substantially equal tension and pressure conditions.



   4) Each element is fully combined (joined or welded) to all adjacent layers, on all side surfaces and under pressure.



   As a result, each element of the material which has been treated according to the above-described process can be used to participate in the resistance to the load applied to the tube, pipe or other object produced, the drawbacks resulting from conventional processes which have been produced. been recalled in the foregoing being here deleted.



   Such being these aims, the invention also pursues other results, taking into account the following facts:
In the manufacture of tubes, pipes and other articles from various materials, and in particular in certain plastics manners, no advantage is taken of the fact that these materials are considerably improved from the point of view of their tensile strength. , by operations such as stretching, stretching, calendering, or the like (hereinafter encompassed in the sense of the general word "stretching"), a phenomenon which can be explained on the basis of the hypothesis of the extension and orientation of macro-molecules.



   Another object of the invention is to take advantage of this property to reinforce tubes, pipes or other objects, either for any type of load, or in one direction or in particular directions against a dominant force, such for example as the circular force due to the internal pressure which prevails in a tube or pipe.

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   Another object of the invention is to use the aforementioned phenomenon to ensure the reduction or elimination of considerable cold tracking or flow, that is to say of the elongation under a constant load. to which many plastics are subject.



   Yet another object of the invention is to create a process and to allow the production of an apparatus for the manufacture of tubes, pipes and similar objects constituted by a material homogenized and reinforced unidirectionally or multidirectionally, from a material. unreinforced bulk material, for example using a new device of the so-called "screw" type.



   Yet another object of the invention is to create a method and to allow the production of an apparatus for the manufacture of tubes, pipes and other objects constituted by a material homogenized and reinforced unidirectionally or multidirectionally from strips of material. reinforced previously conformed.



   This improved method and apparatus allows the production of tubes, pipes and other articles having much greater strengths (in the transverse direction and (or) in the longitudinal direction) as compared to a tube or a pipe having the same dimensions (even wall thickness and same diameter) produced using the same material by conventional methods, in order to open up new fields of application for the materials in question when conventional manufacturing methods gave rise to too few parts resistant, particularly in the technique of manufacturing pipes for conveying fluids under pressure.



   The method and apparatus which are the subject of the invention make it possible to manufacture the reinforced tubes or pipes in question according to any diameter, that is to say to obtain results which do not include the imposed dimensions. in this field by the conventional methods, this method and this apparatus allowing the manufacture of the tubes and pipes in question 'in continuous and in great lengths, the speed of manufacture of these tubes and pipes being notably increased in comparison with that than allow the conventional methods, the apparatus also allowing the production on the site of large lengths of pipes that can be made mobile, for example for their mounting on a tractor.



   Yet another object of the invention is to create a method and to allow the production of an apparatus which can be used for carrying out welding.
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 by friction in; ' c0ntf: t: lU (i -,
The method which is the object of the invention consists in working individually under pressure elements such as layers or parts of strips or filaments of the plastic or other material in question, and in combining said elements under pressure according to patterns. substantially similar orientations, at least part of said operations being carried out between an internal member and an external member which surrounds at least part of said internal member,

   at least one of said members being subjected to continuous rotation and at least one of the members having a shape such that a plane enclosing the axis of the internal member intersects its working surface along a line which represents at least partly a curve.



   The elements in question can be subjected to stretching under pressure (the word "stretching" being taken here in its general sense, as has already been said) and, by combining said worked elements, the latter can be brought together (if their treatment separated to implied their separation).

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  This approximation and staking may involve pressure welding, friction welding or the like process occurring under pressure.



   The apparatus which forms the subject of the invention and which allows the implementation of the method which has just been indicated comprises at least two members, an internal member (for example a mandrel) and an external member (for example. example a sleeve or sheath) surrounding, at least in part, said internal member, at least one of said members being driven in a continuous rotation and at least one of these members having a shape such that a plane enclosing the axis of this member intersects its working surface along a line partially representing a curve.



   Said members can, still according to the invention be constituted respectively by a mandrel and a sleeve, one of them being driven in a continuous rotation and having on its working surface a rib or a helical thread, at least one of the characteristics of which (radial depth, pitch, diameter of its original circumference and shape of the profile) varies over at least part of its length.



   Such being the aims which the invention aims (creation of the method and of the apparatus which has just been mentioned), several possible embodiments will be described below.
The first embodiment is embodied in a method of continuously manufacturing tubes, pipes and other objects from a plastic or other material which is in the plastic state, this method comprising detaching layers of a material thereof. bulk, in individually working, kneading and stretching said layers under pressure, then in combining these layers of material in substantially similar orientations, then in kneading them again under pressure, by carrying out the work between a mandrel and a sleeve forming an envelope,

   at least one of the components in question being driven in a continuous rotation and having on its working surface a rib or a helical thread, at least part of which has the characteristics (radial depth, pitch, diameter of the pitch circle and shape in profile) varies over at least part of its length.



   The rib or the helical thread may extend over at least two zones, the radial depth of this thread varying progressively in the second zone in the direction opposite to that of the progressive change of this radial depth in the first zone.



   More specifically, in the first zone just mentioned, the radial depth of the helical thread can increase from zero at the entry end up to a maximum radial depth, at the right of which the radial distance between said mandrel and said wrapping sleeve is reduced to zero (contact in principle between the deepest thread and the adjacent surface of the other member) and, in the second zone the radial depth of the thread is reduced from this maximum value to zero at the output end of the device.



   During operation, the apparatus loosens thin layers of the bulk material introduced at the inlet end, folds them individually into the grooves of increasing depth between the threads during working (kneading, stretching). under pressure, the intensity of this pressure in the axial direction and in the radial direction as well as the other operative features being regulated by a suitably chosen variation of the radial depth and of the other characteristics of the thread, including the length zones, etc ...

   This operation of detaching the thin layers of material, that is to say all in all, of differentiating the conditioning of the material, continues until the net

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 of maximum depth which is in contact with the adjacent surface of the other member, to prevent any layer from passing through it in the axial direction and therefore has the consequence of detaching the last layers of the material introduced, so that the totality of the bulk material is differentiated into elements (layers) which are individually worked under pressure and oriented to some extent helically. In the net reduction area, the layers of material are then unwound and integrated to be converted into a bulk material
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 fully worked andGtu.i,

  ennëintenov.z soïmae'.â un.'lva7.aaa.s -pressure and oriented. In this way, the material is significantly strengthened and made uniform in strength, removing weak points which otherwise limit the total strength of the tube or pipe.



   It should be understood that depending on the properties of the material and the condition of the material at the time it enters the apparatus, and following analogous factors, the characteristics of the net and of the working surface of the machine. other organ (which does not need to be cylindrical) are studied in such a way as to obtain the results indicated above.



  Thus, for example, for a material which requires high compression, the diameter of the pitch circle of the thread can vary continuously under conditions such as to reduce the specific volume of this material and likewise the pitch can be continuously reduced. and the profile may change to cope with the properties in question.



   Means allowing the escape of the air or more generally of the gases which are released during the process are provided if necessary.



  There is also provided an interesting heating either the mandrel or the sleeve, or these two members at the same time.



   However, in a preferred embodiment no heating means is provided, the only heat which is applied comes from the mechanical work being performed. In addition to the simplification and the fact that the heating will be integral and uniform since all the layers of the material are individually and substantially uniformly processed, this allows the apparatus to be made self-regulating. .



   The reason for the above is that obtaining a certain consistency of the material (and melting in the extreme hypothesis) is felt in the torque resistance of the screw and in the fluctuation of speed resulting from this change in torque. This can be used to adjust the running of the machine to ensure uniform high quality throughput.



   The apparatus generally described can be used for the production of tubes or pipes directly from the outlet end, with a minimum of extrusion. It can also be used as an extrusion screw having markedly better properties of homogenization at the same time as of reinforcement, the extrusion head being mounted after exiting the apparatus and ensuring the extrusion of rods and according to n ' any required sections.



   The embodiment which has just been reduced may be suitable for the introduction of a reinforcing frame in the form of a metal wire, a textile thread, or in a similar form within the tube or pipe in process. If such an adaptation is provided, the net does not need to enter directly into the tube or pipe.
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 in a plastic way. has already been zonf o'rmêt. be (until 1 to the tprdfolïàetir (or jus4u'aug deep1iÍi-s ') to. lkùèllé (from to which)' the Benforoément must be provided, an enmidage mechanism: -4 being coordinated with the ^ fillet at the depth required to introduce the

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 necessarily with the necessary helical shape.

   The reduction net then serves to bring the plastic material back by kneading onto the reinforcement frame, which ensures a good junction while reinforcing the layers of material being treated.



   A second embodiment of the object of the invention concerns the continuous manufacturing process of a tube, pipe or similar object in plastic or other material in the plastic state in the form of a preformed strip, this process consisting in working parts of this strip under pressure, in combining these parts in a substantially helical form and in joining them under pressure, said operations being carried out between an internal member and an external member of the apparatus provided for by the invention said external member at least partially surrounding said internal member, at least one of the aforementioned members being driven in continuous rotation,

   and at least one of them having a shape such that a plane containing the axis of the member in question intersects the working surface of the latter along a line representing at least in part a curve.



   The method in question may include the operation of joining said portions of the strips on the field, under pressure applied over their entire circumference, between a mandrel and an outer wrapping sleeve of the apparatus as provided. the invention, at least one of the aforementioned organs lending itself to a continuous rotational movement, this rotary member being provided on its working surface with a rib or a helical thread, at least one of which characteristics (radial depth, pitch, diameter of the pitch circle and shape of the profile) change over at least part of the length of the member in question to produce a radial and axial pressure on the material,

   the joining taking place continuously around the circumference from a zero angular value up to an angular value equal to 2 #, and the radial depth of which varies continuously from the zero value to the total radial depth of the tube or pipe wall (differentiation-integration).



   Further, the method may include friction welding of the portions of the bands subjected to radial and axial pressure.



   The method which is the subject of the invention may also consist, after the production of a constituent layer of a tube or pipe from a strip obtained by the process in question, in helically winding another layer of the strip. pre-shaped on the aforementioned first layer now forming a mandrel, said parts of this second strip being joined together as described, as well as to the layer formed by the first strip.



  According to this process, the second layer, or the subsequent layers envided or wound on a first layer, can have a different helical arrangement (different pitches, different number of origins, opposite direction of rotation, for example), so that the tube or pipe can withstand different forces. In addition, the different layers may be made up of different plastics or other materials, whatever their state of plasticity, which may or may not be welded together and which may furthermore be provided for obtaining a result other than 'reinforcement, in particular thermal insulation.



   Still according to the method provided for by the invention, a constituent layer of a tube or pipe made from a strip of preformed material can be wound on a layer of this tube or pipe established by the first embodiment of the invention or by other methods.



   In addition, according to the invention, the shapes in cross section of the preformed material strip can be established so as to facilitate the joining of the helically wound parts of the strips, this

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 straight section recalling for example the shape of a Z, a rhombus or a U shape, this @ @ nière being particularly indicated for the establishment of tubes or pipes formed of two layers in the case where the sections in U can be arranged so as to interlock with one another and to be already entangled in the unjoined state.



  This embodiment may also be suitable for the manufacture of a reinforced tube or pipe by winding a reinforcement in the form of a wire or a strip between the strips of plastic material. which, in this case, are preformed so as to leave a space for the reinforcement. The operation described serves to produce not only the welding and possibly the heat treatment, but to ensure a satisfactory junction between the reinforcement and the material constituted. - tutive of the tube or pipe.



   An apparatus constituting an embodiment of the invention with a view to the manufacture of a tube, pipe or the like starting from a plastic material, or more generally from a material endowed with plasticity exhibiting in the form of a preformed strip, comprises at least two members among which an external member surrounds, at least in part, an internal member while leaving a certain clearance between them, a device winding the tape helically in space included between said organs, and another device transported:

   the. band through said members, at least one of these two members being driven in continuous rotation, the working surface of at least one of these members being shaped so that the radial clearance between them changes on at least part of the length of the apparatus in order to join the helically wound parts of the strips under radial and axial pressure.



   The internal and external members can be constituted respectively by a mandrel and by an external enveloping sleeve, this sleeve being driven in a continuous rotation and having on its working surface a helical thread of which at least one of the characteristics ( radial depth, pitch, pitch circle diameter and profile shape) changes over at least part of its length, in order to join the helically wound parts of the bands under radial and axial pressure and to convey said band and tube or pipe formed therefrom along the mandrel.



   The apparatus may comprise a backing plate subjected to the load of a spring and placed in the vicinity of the winding mechanism in order to exert a relay pressure on the strip subjected to the winding in the space between the mandrel and sleeve, and a device for adjusting the spring load weighing on the backing plate.



   This apparatus may further comprise a device for friction welding of the helically wound portions of the strips, under axial and radial pressure. This friction welding device may include members generating a relative movement between the surfaces of the strips being welded and (or) a relative movement between the surfaces of the strips of material to be welded and metallic or other members which are brought into frictional contact with said surfaces, or else which are inserted between the surfaces of adjacent bands which are to be welded.

   The relative frictional motion in question, which is intended to produce or prepare for friction welding, may be of any suitable kind, for example rectilinear, curved, rotary, alternating or combined motion, such as that is to say, participating in the various movements indicated above.



   The friction members as provided for by the invention are characterized in that they consist of a thin sheet oompor-

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 both an edge or which may have any suitable shape tapering off to form an edge, and further in that they are so constructed and arranged that when the relative frictional motion occurs, the edge in question deviates from the space between the adjacent faces of the strips to be welded, which then meet immediately under the effect of this pressure without allowing air to penetrate between the surfaces to be welded , so that effective friction welding occurs.

   These friction members can be discs rotating at any required speed suitable for ensuring rapid heating and effective welding of the surfaces of the strips between which they are interposed, they can also affect the shape of blades or sheets moving relatively to the bands between which they are ', interposed.

   These friction members can have varied surface states, in particular a certain roughness, or else a particular smoothness, depending on the properties of the material to be welded, or they can be provided with little cavities or dimples. deep called to be filled by an initial layer of the material to be welded and thus to produce a frictional contact of the material where the need arises. As an alternative, these friction members can be provided with slots which may have different shapes or inclinations, depending on the relative friction speed, or cavities and (or) slits opening towards the edge, etc. In addition, the surface conditions may change, for example to become smoother or to on the contrary, rougher towards the edges.

   Either the members can be coated or coated with materials with beneficial properties to facilitate friction, or the friction welding process.



   The apparatus just mentioned for friction welding can therefore include a constituent rotary member provided on its working surface with a helical thread (single or multiple), at least one of the characteristics of which (radial depth, pitch, diameter of the pitch circle and shape in profile) changes over at least part of the length of this organ, in order to exert radial and axial pressures on the helically wound parts of the bands, the thread in question being combined with one or more sheets of a metallic material or other interposed between the edges of the adjacent parts of the strips of material and cooperating under pressure with them by exerting friction along these edges in order to produce local heating allowing friction welding,

   said sheets being provided with tapered edges and decreasing in thickness after a required frictional contact distance with said strips, in order to allow gradual release out of the space between said portions of the strips which are joined by radial pressure and axial by the thread during the welding operation without allowing the access of air, this welding taking place gradually from zero to the full depth of the thread (differentiation-integration).



   Downstream of the friction welding equipment which has just been described, a rotary annular tool can be provided, this tool comprising a thread, at least one of the characteristics of which (radial depth, pitch diameter of the pitch circle and shape in profile) varies so as to produce, if necessary, an additional work of the material by imposing a considerable pressure across the welded part, in order to reduce or cancel the resulting torque on the tube or pipe produced by the 'welding crew, in order to obviate the frictional resistance interfering with the advancing movement of the mandrel or, alternatively, and if the circumstances so require, to exert a back pressure on the tube or pipe in order to maintain axial pressure on the output end of the welding crew.

   To this end, this rotary annular tool can be designed so as to turn in the opposite direction to the direction of rotation of the probing tool.

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 in principle drives at a different speed of rotation.



   However, since in general the friction welding tool can be driven with a certain rotational speed corresponding to the requirements of the winding mechanism, the production speed of the equipment and to d Other factors, the relative friction rate between the bands and the frictional component of the welding tool is limited. However, it is advantageous, and even necessary in some cases, for the friction heating to occur after a short time, in order to heat and melt the top layers only, without allowing the heating to occur. be felt within the band, which would adversely affect some of the specified advantages of the process.

   In addition, the material of the strip may prevent it from taking the curvature of the mandrel from the straight strand at the required speed, so that some gradual bending is then necessary.



   For the reasons in question, it is necessary or advantageous to provide an apparatus for the preliminary heating of the edges of the strip of material which must be joined by welding, to a temperature substantially equal to that at which the upper layers melt. , causing little friction on the part of the friction tool and performing the function which may be required in addition to gradually bend the web of material.



   The invention therefore provides for an apparatus for pre-heating the edges of the previously shaped strip which must be welded, this apparatus comprising rotating members assembled with friction disks and a device for passing the strip of material between the disks beneath. the pressure exerted by them.



   The disks in question can be axially movable on said member and can be brought together by springs, means being provided to adjust the load exerted by the latter.



   In addition, these discs can rotate with the shaft on which they are mounted, in order to be axially movable under the load exerted by their springs.



   The preheater may, in addition to the discs arranged to rotate with the shaft on which they are axially movable under the load exerted by their springs, comprise a sheet of metal or other material endowed with elasticity and helically wound, this sheet being able to exert a friction and being mounted on said shaft between the discs and in contact with them, said helically wound sheet being able to rotate with said shaft and being movable axially to it, means being provided for engaging the strip of material previously shaped on said shaft along the helical path formed by the wound strip and by the discs,

  as well as means for rotating the shaft and this helically wound sheet in order to produce the required relative friction speed between the edge of the strip and said walls.
Since the speed of the web itself is represented by the translational speed determined by the winding mechanism of the welding apparatus, the shaft preferably rotates in the opposite direction to that of the web movement, in order to generate a relative friction speed which is the sum of the translation speed v1 of the strip and the circumferential speed v2 of the rotating sheet, that is to say a relative friction speed represented by (v1 + v2).



    The preheating equipment is designed to allow the gradual bending of stiffer strips of material since the rotating shaft has a section which gradually decreases from a relatively large diameter at the inlet end to a diameter of smaller at the output end. As an alternative, a number of preheating crews can be mounted one after the other for this result.

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   Due to the fact that the material constituting the strip is worked under pressure, this preheating unit achieves considerable stretching and consequently reinforcement of the strip under pressure,
The pressure is adjustable using the members forming springs; it is increased by the dynamic effects and in particular by the acceleration of Coriolis due to the change in direction of the strip.



   The invention also encompasses an apparatus for the manufacture of tubes or pipes using two or more layers each of which is formed of a strip, this apparatus comprising a device for establishing a layer of the material. constituting the pipe from a strip as described above then, downstream of this device, a second device similar to the first and serving to wind the second layer of strips on the first layer forming a mandrel, this second dispositiff which may or may not include prior heating depending on the requirements.



   The only difference between, on the one hand, the second device and the other devices corresponding to the subsequent layers and, on the other hand, the first device corresponding to the first layer, it is, in the case where it is provided a friction welding in the apparatus that the friction sheet not only extends redially between the adjacent strips, but that the first turn of that friction strip is folded back to have a cylindrical shape and extend between the first layer and the first layer. -second layer '-wound on it,

   in order to behave also in the manner of a friction sheet between the two layers o This friction sheet can also gradually decrease in section to form an edge after a sufficient length to heat the material up to a proper temperature welding, this being carried out under the effect of the pressure which is generated by the contraction thread of the annular tool which rotates
According to the invention, combinations of preheating and welding equipment can also be studied with a view to establishing plates or panels starting from a strip of previously formed material, several of these crews producing plates formed from multiple layers,

   the bands being arranged in different directions according to the preferred embodiments.



   The invention also encompasses a device for stretching or elongating a constituent layer of a tube or pipe in the circumferential direction as well as, where appropriate, in the axial direction, this device comprising a mandrel with expandable diameter, a sleeve of 'wrapping surrounding this chuck, at least one of the components in question being mounted so as to be able to turn and comprising on its working surface a rib or a helical thread, one of which takes care of the characteristics (radial depth , pitch, diameter of the pitch circle and shape of the profile) varies in the direction of the length of said element in order to axially displace the constituent layer of the tube or pipe longitudinally to the expansion space between the mandrel and the sleeve, and also for produce if necessary,

   the expansion of this layer of material in the axial direction in addition to its elongation in the circumferential direction.



   This equipment can be used in combination with any of the devices forming part of the apparatus for the manufacture of tubes or pipes, as described, and more generally with any apparatus of the conventional type.
The invention is described below, by way of example and in certain details, with reference to the appended schematic drawings:
Figure 1 is a longitudinal sectional view of the upper half

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 of an apparatus constituting a first embodiment of the invention, this apparatus being designed with a view to performing a differentiating action on the bulk material, a working and an integrating action in one and only one. same device.



   FIG. 2 is a view similar to FIG. 1, showing a variant of the mandrel that the apparatus comprises.



   Figure 3 is a fragmentary cross-sectional view taken through line 3-3 in Figure 1.



   Figure 4 is a cross-sectional view of the mandrel visible in Figure 1.



   Figure 5 is a sectional view drawn on a larger scale of a portion of the rib of the helical thread which runs on the surface of the mandrel.



   Figure 6 is a sectional view similar to Figure 1 showing a variant of the mandrel having a substantially uniform average diameter and usable in the apparatus constituting the first embodiment.



   Figure 7 is a fragmentary longitudinal sectional view of a second embodiment of the device for making a preformed and drawn strip, and for converting this strip of material into a tube or pipe, the work comprising a differentiation and integration.



   Figures 8 and 9 are sectional views of a previously shaped strip of material having a cross section different from that shown in Figure 7.



   Figures 10 and 11 are respectively a sectional view and a side elevational view of a third embodiment of the apparatus provided for by the invention, these views showing a device for working, preparing and soldering by welding. friction a strip of preformed material and to manufacture a tube or pipe using this strip drawn and subjected to friction welding.



   Figures 12 and 13 are respectively a sectional view and a side elevational view of a variant embodiment of this third apparatus as provided for by the invention, this variant being designed with a view to the friction welding of layers of bands preformed one above the other.



   Figure 14 is a sectional view of another device for working and stretching a layer of material.



   Figures 15 and 16 are respectively a sectional view and a side elevational view of another alternative embodiment, the construction being similar in principle to the first, but with a modification allowing the integration of a reinforcing bar. the constituent material of the tube or pipe;
Fig. 17 is a fragmentary longitudinal sectional view of the second embodiment shown in Fig. 7, but designed for the introduction of a reinforcing bar, the tube or pipe being established from a preformed material strip.



   FIG. 18 is a sectional view of a strip of preformed material, but within which is embedded a reinforcement, this strip of material being usable in the version of the apparatus shown in FIG. 7.



   In Figures 1 to 5, are shown, embodiments

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 of the object of the invention which are directly applicable to the production of tubes or pipes and are in the form of extrusion screws, this embodiment involving the general process of differentiation, work and integration, as it is described below.



   In the apparatus shown in Figures 1 to 5, 10 denotes a mandrel which is driven in rotation about its axis under the action of any device, in a fixed cylindrical enveloping sleeve 11.



  This mandrel 10 has an average diameter which varies gradually; its smallest diameter is at its inlet end 14, that is to say at the place where the plastic material 12 is sent into the annular space between the mandrel 10 and the sleeve 11. The plastic material is driven and worked by a rib or a helical thread 13 integral with the surface of the mandrel 10.

   This thread is a thread with four origins, having a variable radial depth, a variable pitch circle diameter, a variable pitch and a shape of profile also variable; starts at zero depth at its inlet end 14 from the cylindrical surface of the first part of the mandrel 10, and increases in radial depth as well as in mean diameter throughout the range. the expansion section 15, up to a maximum where the deepest part of this thread 13 has a diameter substantially equal to the internal diameter of the enveloping sleeve 11.



   The depth of the thread 13 is then gradually reduced throughout the extent of the reduction section 16, the average diameter remaining substantially constant or increasing only at a lower rate than in the expansion section, until that the ± thread depth reaches zero at the outlet end 17 where the thread insensibly connects with a smooth cylindrical part of the mandrel 100
Internal longitudinal ribs 18 of relatively short axial length are provided on the internal face of the enveloping sleeve.
11 (as shown in Figures 1 and 3), in order to prevent the material from rotating with the mandrel 10 at the output end 17.



   Channels can be made in the wrapping sleeve
11 or in the mandrel 10, or in these two elements at the same time, in order to ensure the circulation of steam oa. another heating fluid. The mandrel which is shown in FIG. 2 is hollow at the location indicated by 19 in order to allow the circulation of such a fluid. Alternatively, the wrapping sleeve 11 or both can be heated electrically.



   A ventilation system allowing the escape of air or other gases which are released during the work can be provided in one or more suitable places of the enveloping sleeve 11.



   During operation, the mass 12 of the plastic material which may, depending on the nature of this material and the working conditions it is called upon to undergo, be in various states of plasticity, from a state close to the state liquid to a state close to the solid state, is detached in the form of extremely thin layers (see the 4µ F cut zones drawn in dotted lines in figure 4) due to the fact that the thread increases in depth radial in the expansion section 15, until;

   for a maximum depth of the thread, all of the mass of plastic material has been differentiated into these thin layers.The latter are worked under a compression, considerably increased in all directions, then folded back into the grooves between the threaded and drawn, in substantially helical directions under these pressures to give more strength and uniformity to the plastic, as more fully described below.

   In

 <Desc / Clms Page number 13>

   @ the reduction section 16 of the mandrel 10, these layers are gradually integrated while still being worked under pressure to form a homogenized and considerably reinforced bulk material, within which a certain degree of orientation of the elements in helical directions, following the general shape of the net, was obtained.

   Therefore, the way of differentiating matter into elements (thin layers) and then working these elements individually under pressure and re-integrating these same elements with orientation while continuing to work is carried out as it has just been said in the apparatus object of the invention
The homogenized and reinforced material can be used directly to form a tube or pipe or, if the apparatus is part of an extrusion machine, it can also be used for the shaping of other extruded parts, to be then brought to the extrusion head after the process as provided for by the invention has been carried out, as indicated above.



   The operation of the apparatus will be understood with greater precision by reference to Figures 4 and 5 which illustrate it in greater detail. The indentation of the spiral thread in section 15 within the material plastic deepens radially at a rate represented by the formula # R # dt, in which denotes the angular speed of the screw and2 ## R the increase in external diameter per turn.



   This produces, by a kind of tightening phenomenon of the expansion net towards the surface of the enveloping sleeve, an increase equal to # p1, towards the plastic material at the place designated by 22 in figure 5, in the direction radial. At the same time, thin layers having in a straight section the surface # F (see figure 4) are detached at the places designated by 23 and acquire the axial speed vt of the thread which, since the speed of advance of the mass of plastic material is smaller, results in another clamping action in the axial direction, which results in an increase in pressure # P2 in the axial direction at the point designated by 23 (see double arrows for pressure increases.)

   
As a result, the thin film detached as said is worked under increased compression (p + # p1) in the radial direction and (p + # p2) in the axial direction, both increases in question being considerable. , because the bottom of the groove 24 moves radially outwards, a clamping phenomenon occurs which results in an increase in the pressure # p3. In addition to the fact that the rear part of the net denoted by 25 moves away from the mass of the plastic which moves more slowly, there is a suction effect, which itself results in a reduction in the mass. pressure equal to p as indicated o These effects produce,

   in addition to a helical movement of the plastic in the thread groove with a velocity vector vs, as shown, during which the plastic is subjected to helical stretching under pressure, a slow rotation (circ- ulation) around the axis of this vector and inside each groove, as shown in figure 50 If it is almost solid plastics, then a slow rotation of the layers occurs material in the groove, which has a very useful effect in gradually replacing fully worked layers with less worked layers.



   As this rotation takes place around the axis of the vector v which itself rotates around the geometric axis of the shaft of the apparatus, gyroscopic and pseudo-gyroscopic effects, such as those which have been

 <Desc / Clms Page number 14>

 described in a technical report by the author in an English-language publication entitled Oscillatory Occurences a Ball Bearings ", published in the" Journal of the Royal Aeronautical Society "(issue of December 1952), occurring causing other rotational movements and increasing compression.



   Thus, the thin layers of the plastic material are gradually loosened, worked and helically stretched under a continuously increasing pressure and they are forced to pass through grooves of various shapes while being subjected to stress. rotational movements in these same grooves. These layers of material are therefore worked and compressed by many different forces which change both in intensity and in direction following the successive variations in the shapes of the grooves which are designed to meet the requirements imposed by the material in question in order to obtain the best strength and uniformity required for the material.



   In the expansion section 15 of the embodiment of the net shown in figure 6 and which differs from that shown in figures 1 and 2 in that the average diameter increases only very slightly, the work is increased. produced under analogous conditions except that, as the bottoms of the grooves 24 (Figure 5) approach the center line, a phenomenon of suction also occurs which contributes to the circulation.



   In the two examples in question, the processes are reversed to some extent in the reduction section 16 located downstream of the maximum diameter thread, which is substantially in contact with the wall to prevent any amount of the plastic material from being caught. leaving the device without having been worked o The elementary layers of the material are now unwound by the helical threads which gradually decrease in depth, an increase in pressure being caused by the clamping effect exerted by the bottoms of the grooves, which approach the wall of the enveloping sleeve 11.



   The helical speed components, which are canceled out by the axial ribs 18, also serve to increase compression as the inner layers of material come into contact with those outer layers which are not rotating. In addition, each thin layer is, during its unwinding, further stretched due to its cohesion with the material which is still in the groove. Thus, in the reduction section 16, all the layers of the material which have been loosened and which have been individually worked under pressure in the expansion section 15 are unwound (integrated) and stretched further, and then also oriented. in this reduction section 16.

   In this way, the illustrated embodiments act to greatly increase the strength of the plastic material as a result of working (stretching and orientation) by increasing the uniformity of this material, and eliminating the weak spots. - wounds which otherwise adversely affect the strength of the whole product.



   It is understood that the optimum effect of all the factors listed depends on the relations of the characteristic properties of the thread, and the changes in these characteristics (radial depth, pitch, diameter of the pitch circle, profile shape, length of the expansion and reduction sections possible change in the diameter of the enveloping sleeve, etc.) must be determined mathematically according to the properties of the materials and also according to the particular results which are intended and other similar considerations.



   From the point of view of the application of heat, these embodiments

 <Desc / Clms Page number 15>

   These systems have great advantages in that they offer very large heat transfer surfaces between a metal and the plastic material and that, thanks to them, each layer of material comes into contact with the rotating wall.



   However, according to the preferred embodiments of the object of the invention, no heating device is provided in the mandrel or the enveloping sleeve. It is in fact preferable that the required heat result from simple mechanical work. In this respect, the construction
 EMI15.1
 represented presents particular advantages' 'being' do = 9-qm the total11é 'of ititli1a # re s -'t..1.13.' 'f eie3eri = t'.atieéla, e'.t' state of threadJ.10E ; S (úÚv ".06. J ',' \. IJ .. a '- gi: 1 ... Lt:

  U! Ûxlt the advantage of allowing a self-regulation of the working process which takes place in the apparatus since the obtaining of a certain consistency of the material (which can go in the extreme hypothesis until it melts) acts on the mechanical torque that is required to advance the screw and on the speed fluctuation resulting from this change in torque. This factor can be used to adjust the rate of the apparatus to ensure uniformity of flow of higher quality material.



   In Figure 7 is shown another embodiment of the object of the invention allowing the manufacture of tubes 1, or pipes starting from a pre-formed and stretched strip of plastic or other material located at the plastic state, ensuring the process of differentiation, work and integration of the elements as described below,
In this FIG. 7, 30 designates a fixed cylindrical mandrel provided with channels 31 traversed by a heating fluid or serving to house an electric heating element. An outer ring 22 rotates around the mandrel under the action of some suitable system such as the gear designated by 33; it is also provided with channels 31 or else electric elements used for heating.



   The bore of the ring 32 gradually decreases in section and it is provided with a shallow thread 34 which decreases in radial depth towards the end of the bore which has the smallest diameter, by connecting with a smooth cylindrical surface. A preformed strip
 EMI15.2
 and stretched plastic material is wound helically on the mandrel
30 under the effect of ur winding mechanism which may or may not be part of the rotating ring at its entrance. This pre-formed and stretched strip of plastic material has a straight section suitable for facilitating welding under the pressure exerted by the rotary annular tool, for example a straight section resembling the shape of a Z, which is indicated for the strip 35.



   The rotatable annular member 32 forces the web of material axially along the surface of the mandrel 30. Following a construction to be preferably adopted, a backing plate subjected to the load of a spring such as that which is shown in connection with the construction shown in figure 10 is intended to withstand the axial compression exerted from the inlet, and at the same time the annular member compresses the strip both radially and axially, This is due to the that the thread is designed with such variations in radial depth, pitch, pitch circle diameter and profile shape, that pressure forces are produced with the intensities and directions necessary in the radial directions,

   axial and circumferential
The web of material is heated as a result of its contact with the mandrel 30 and with the annular member. As it passes between them, it undergoes to some extent stretching under compression, while

 <Desc / Clms Page number 16>

 that the edges of the adjacent sections of the strip weld together under this compression during the work, so that it is a complete tube or pipe which comes out of the slender end of the apparatus.
The edges in contact with the strip of material can be realistically worked before this strip is wound up on the mandrel, in order to facilitate their joining by welding.

   Thus, for example, the strip can pass through toothed rollers which hollow out and soften its edges, or between preheating elements, as described in the following, using friction heating.



   In figures 8 and 9 are shown in cross section variants of a preformed and stretched strip usable in the apparatus shown in figure 70
This example represents an embodiment of the method and of the general apparatus as provided for by the invention, as indicated below.



   A) As the strips of material enter the rotating annular tool 32, they are subjected to differential work and integrated, the members having a radial depth denoted by A R, as shown in Fig. 7. At the start. when at the entry into the annular tool a radial pressure is applied to the strip by the thread, the distribution of the pressures in depth is quite similar to what is indicated by the small graph which constitutes figure 70 falls from a maximum value p on the external surface, as a result of the effect of elastic compression combined with a certain displacement, which manifests itself on elements having a depth R each of which can be ;:

     considered as an elementary spring subjected to friction on the neighboring edges of the adjacent bands.



   However, during the progression of the material in the helicoid, the maximum pressure becomes that at which the welding will occur, and it will then successively penetrate all the layers, up to the heart of the thickness of the wall of the tube or pipe. and up to the mandrel, minus a reduction due to friction. In this way, the apparatus represented produces a differentiation in elements of thickness # R, it works these elements individually under pressure and integrates them by successive welding on the neighboring edges of the elements adjacent to the strip, until all elements forming the entire thickness of the wall are welded (integrated).



   B) According to an alternative examination of the operation of the apparatus according to this embodiment of the invention, this apparatus divides one or more bands having an indefinite length into elements having a unit length represented by 2. #. R, by winding them on the mandrel (R denoting the average radius of the strip when it is wound). These elements are stretched helically and worked by compression by the tightening thread of the annular tool, which rotates while being helically oriented, then they are finally integrated as a result of pressure welding which transforms them into tubes or pipes, the welding evolving by elements R. dt, according to the method and the apparatus as provided for by the invention.



   As opposed to a plastics extrusion machine, the present apparatus can operate at very high speeds for the production of tubes or pipes and, owing to its simplicity and lightness, it can be operated at very high speeds. can be mounted on a tractor, for example to produce on-site continuous (i.e. one-piece) tubes or pipes from a pre-formed and drawn strip of material supplied *, by drums , coils or similar power sources.

 <Desc / Clms Page number 17>

 



   Because the preformed strip of material has been subjected to stretching operations which can bring its tensile strength to the maximum attainable by stretching and orientation of the macro-molecules, which is a multiple of its strength in the unstretched state, especially for certain plastics, this apparatus allows the manufacture of a tube or pipe having a resistance to internal pressures exceeding that of an ordinary extruded tube or pipe at least in the intake between the re- tensile strengths of stretched tape and unstretched tape, while being much less prone to cold creep than them. This is an extremely important consideration in tubes or pipes called upon to withstand very high internal pressures.

   Thus, the present process for producing tubes or pipes as provided for by the invention opens up an enormous field of application to the technique of manufacturing conduits made up of certain plastics which, when they were produced by the processes. conventional, were too weak to be able to withstand the pressures in question. Indeed, the present process allows the manufacture of much stronger tubes or pipes, although they do not have a greater wall thickness, and this using the same materials.



  As an alternative, the process allows significant savings to be made in terms of the materials employed and a reduction in other manufacturing costs by making it possible to reduce the consumption of material compared to that imposed by the manufacturing processes. conventional, while allowing satisfactory resistance to be obtained at higher pressures.



   It will be understood that the apparatus forming the embodiment which is represented by FIG. 7 is applied to a certain range of materials, but that it may require preheating of the edges of the material which are to be welded, or even an advantageous heating. the thickness of the material strip.



   If the heating system shown is provided and if the net is capable of exerting the very high pressures which are required in various directions, the apparatus can be designed so as to heat treat the plastic material at the same time as the tube or pipe. is manufactured by the process in question. the application of heat either from the elements themselves, or from mechanical work, or from sources of radiant heating, or from several of these factors acting in various combinations.



   In Figures 10 and 11 is shown another embodiment of the object of the invention which makes it possible to manufacture a double pipe starting from a preformed and stretched strip of a plastic material or of another material presented in the plastic state, by friction welding the strips of material, this embodiment of the invention allowing the accomplishment of the process of differentiation of work and integration of the elements which is described below.



   As shown in Figure 10,40 denotes a fixed mandrel on which the strip of preformed material is stretched 41 is wound by an annular tool 42 which rotates under the action of a source of covenable force constituted for example by a gear 43. This annular tool 42 is provided internally with a shallow thread 44, having a radial depth which decreases as well as a decreasing pitch circle diameter, not to mention its other properties which are described below. In this tool 42 is further mounted a helical friction member 45 in the form of a helical knife penetrating into the spaces between the adjacent bands.

   On the entry side, a backing plate 16, subjected to the load of an adjustable spring 47 is provided for applying to the strip of material a predetermined axial pressure. This serves to

 <Desc / Clms Page number 18>

 maintain the axial pressure on the strip notwithstanding the small variations in width which may appear in the precast plastic strip.
As shown, the friction members 45 act first of all by crossing the entire thickness of the plastic strip, for:

  , terminate in slots of mandrel 40, and continue in this manner for the time required to produce a sufficient degree of heating of the edges to be friction welded, the selection being made in consideration of the speed of rotation, the pressure between the edges of the strip and the friction member (which in turn depends on the contour of the thread), and also the friction properties of the plastic material and the friction member, When the welding conditions have been fulfilled with regard to the edges of the material strip, the friction members gradually decrease in depth, which produces a gradual withdrawal of the knife, while at the same time the thread is modified so as to push back the edges and bring them together under the welding pressure,

   which takes place just below the cutting edges of the knife, without allowing the access of air which would interfere with the progress of the welding. This reduction of the friction members continues until they are finally erased in the external annular tool, the welding then affecting the entire thickness of the wall.



   In this example it is preva. (as shown) downstream of the friction welding member, a separate ring tool 48, rotatably driven by a suitable gear 49. This additional ring tool may be required (depending on the welding properties). by friction and the other properties of the material used) in view of the additional working of the material, in order to give the welding its full resistance if this is not already the case due to the treatment by the tool friction welding.



   Alternatively, or in addition, the additional annular tool may be required to advance the tube or pipe shaped on the mandrel, or to exert some resistance in order to maintain axial back pressure on the welding tool. by friction, In view of these results, this additional annular tool is provided with an internal thread 50 which is designed with a view to one and (or) of the other of the above-mentioned results.



   In fact, there may be advantage, both from the point of view of exerting additional pressure across the welds and from the point of view of the working of the material and the point of view of neutralization of the material. torque exerted by the friction welding tool on the pipe itself, to rotate this additional tool in the opposite direction of the direction of rotation of the friction welding tool
Due to the fact that the speed of friction between the friction members 45 and the edges of the strip of material 41 is necessarily limited by the speed of the winding mechanism of this strip, which speed may be insufficient with certain materials for produce the heat which is necessary for - 'friction welding,

   or may require too great a length from the annular tool 42 to achieve this result, which would imply too long a lapse of time for the uncertain penetration of heat into the strip, it is a working and preheating band for the band is provided, as shown in FIGS. 10 and 11. This set comprises a shaft 52 mounted to rotate at 53 and on which the band 41 passes between the end pieces 54 with axial mobility, which are subjected to the adjustable spring load 55.



   On the shaft 52 is mounted, between the end pieces just mentioned, a helical sheet 56 of metal or other suitable material, under conditions such that this sheet can rotate.

 <Desc / Clms Page number 19>

 with the shaft but is movable axially with respect to it, which has the effect of separating the edges which must be welded from the strip 41.



   Since the frictional effect increases with the relative frictional speed and with the pressure (which in this case includes the dynamic pressure due to the Coriolis acceleration), the preheating crew is preferably driven by a rotation in the direction opposite to that of the movement of the strip in the annular friction welding tool. If under these conditions v1 denotes the average circumferential speed of the movement of the strip, and v2 that of the rotating walls, the friction speed relative is represented by the formula (v1 + v2), and if v2 is not limited by any of the factors which limit the value of v1, this speed can be made very high in order to ensure preheating. from the edges of the strip to be welded to a stage close to that at which it begins to melt,

   the process going very quickly. When the preheating has reached this stage, the annular friction welding tool can complete the welding operation very quickly and therefore can have a shorter length to a corresponding extent. The pressure, which is the other factor important, can be adjusted by the spring to aid rapid preheating.



   The preheating apparatus shown further provides a certain degree of stretching and elongation of the web itself, since it rotates in the opposite direction to the movement of the web, and it can do this work very efficiently since 'he acts under pressure.



   In addition, depending on the properties of the material used, and which can sometimes not be very easily pliable, this pre-heating equipment can fulfill the very important function of imparting to the strip of material the curvature required for the get into the heater by friction. For this purpose, the shaft 52 may have a cross section gradually decreasing, its largest diameter corresponding to the inlet end of the strip and its smallest diameter to its outlet end. With a view to the same result, several preheating devices can also be provided.



   The preheated strip is guided to the welding device in channel 58, the walls of which can be thermally insulated or even heated to maintain the temperature produced in the edges of the strip which are to be welded.



   The construction of the preheater shown is intended for a material requiring relatively high high speed friction to ensure effective preheating. In many cases, however, a very simplified device consisting essentially of two friction discs subjected to the spring load and driven in rotation at high speed, between which the strip of material passes, would be sufficient.



  This simplified embodiment is described in what follows with regard to the example of an apparatus for friction welding.



   This example represents an embodiment of the method and of the apparatus as provided for by the invention, but is presented in different ways, namely:
A) In the friction welding device, the strips of material are worked and integrated differentially with respect to strip elements of thickness 4 R (see elements # R1, # R2, # R3 shown schematically as d 'examples) since, as a result of the gradual withdrawal of the friction members 45, the working and welding of the material occurs on these elementary bands having a thickness # R with the integration.

   This is completed by a more accentuated work, if cella

 <Desc / Clms Page number 20>

 is necessary, in the device placed downstream and comprising the rotary annular tool 49.



   B) Considering from another aspect the work carried out by the apparatus, it divides the strip or strips of material having originally an indefinite length into elements having a unit length 2 # R by winding them on the mandrel (R being the average radius of the strip of material when it is wound). These elements are helically drawn and worked by compression by the tightening thread of the rotary annular tool, while having been and still being helically oriented and they are finally integrated by welding into the tube or pipe below. pressure according to the method and apparatus provided for by the invention.



   C) If we consider the preheating device and the welding device in combination for implementing the method provided for by the invention, we see that this preheating device already differentiates the strip of originally indefinite length into elements. having a unit length equal to 2 #. R and works them individually under compression.

   This function is particularly important if, in the case of a strip of material having a certain stiffness., The bending must be carried out gradually by winding the strip on a preheating device shaft, the cross section of which is gradually decreases from a rather large diameter to the required diameter o The bands are then individually worked under pressure, thick oriented and finally integrated by friction welding into the welding device, by the process and apparatus here planned, the integration also proceeding by elements designated by R. d #.



   The embodiment of the invention including friction welding can, under certain circumstances, have considerable advantages over other embodiments. In fact, in friction welding, only the effective edges to be welded are heated, it follows that the production speed is not limited by other factors; such as delays occurring in cooling or solidification, and factors such as possible shrinkage, distortion and the like with temperature change need not be taken into account.



   In addition, with the method of manufacturing tubes or pipes from a strip of material, there is no limitation on the diameter of the. tube or pipe, the rotating tool being capable of being established in several sections, or, alternatively, not needing to be constituted by a complete ring in order to be an external member capable of filling the required functions of the friction heater.



   If the process is applied to the production of tubes or pipes formed from several layers of material starting from a strip, each layer then being produced individually and being wound in such a way as to resist the forces which occur in one or more directions. In particular, pipes with a very high resistance to the amount of material employed can be produced by the method and apparatus provided for by the invention.



   In Figures 12 and 13, there is shown another embodiment of the apparatus shown in Figures 10 and 11, but which is designed for the manufacture of tubes or pipes formed of two layers constituted by a preformed strip of material according to the invention. The apparatus of the present example can be designed, of course, to produce any desired number of layers from the web of material, with different helical orientations of the web.

 <Desc / Clms Page number 21>

 stretched, in order to withstand most effectively the various combinations of forces which occur, or to form assemblies which are resistant to fluctuations in the load in the case of various types of loads.



   In Figures 12 and 13, the pre-formed and drawn strip of material 61 is wound onto the mandrel 60 by the annular tool 63 which is. mounted and actuated by a suitable device 64 in the form of a gear. The backing plate 65 subjected to the load of an adjustable spring 66 exerts an axial pressure on the strip as it enters the annular tool.



   The friction members 67, metallic or otherwise, are placed in the net 68, substantially as described in connection with the previous example, except that, in this case, the net has two origins and that it is by therefore provided a helical friction member also having two origins. In this case, the thread is designed so that its radial depth, its pitch, the diameter of its pitch circle and its profile shape vary in the length direction of the ring tool according to the properties. the plastic material and various other factors, the friction knives being gradually released.



   Downstream of the annular welding tool is mounted an annular transport tool 69 also participating in the work, which is rotatably mounted on an axis 70 and which is driven by a suitable device such as the gear 71. Its thread 72, of which one or more of the characteristics of radial pitch depth, diameter, pitch circle and profile shape vary along its length, is designed to fulfill either of the combinations required for the results indicated below.



   (a) To work the material, especially through welds if this is necessary to bring them to their full strength and if, due to the nature of the plastic material and the process, this has not been obtained by the previous annular tool.



   (b) To assist in routing layer 74 of the tube or pipe formed in the apparatus to the greatest extent possible despite the frictional resistance of the mandrel.



   (c) If necessary, to generate an axial back pressure capable of maintaining the pressure in the ring weld tool 63.



   (d) To neutralize the torque exerted on the pipe by the effect of the rotary welding tool 63.



   -To allow the accomplishment of one or the other or more of the functions which have just been indicated, this annular tool can turn in the opposite direction to the direction of rotation of the annular welding tool and it can have a helical thread at an angle with the helical thread of the ring tool.



   Downstream of this device is a corresponding coiling and friction welding tool for applying a second layer to the first layer which now acts as a mandrel. The annular tool is substantially similar to the first device. The same reference numbers therefore designate the same members. It can be followed by a similar working and transport tool, which is not shown here.



  The differences with the first welding device lie in the design of the thread which in most cases will produce a different helical strip in the second layer and which can wind the strip of material in the opposite direction to resist some kind of pressure. different effort. According to a structural difference with respect to the first element, the first helical turn

 <Desc / Clms Page number 22>

 The blade of the friction-acting strip is folded back in the axial direction forming a friction sheet 73 which produces friction between the two layers (coming into contact with them) under the pressure produced by the contour of the thread of the screw and -which gradually decreases in section to form a ridge after a sufficient length of rubbing surface has brought the edges to a condition suitable for efficient welding.

   



   It will be appreciated that by virtue of this particular construction, the preheating and pre-working device shown by the example shown in Figures 10 and 11 can be used in general. If the material requires less preheating, an enhanced version of a preheating device essentially comprises two friction discs subjected to the load of springs and driven in a rotation at high speed, these discs being mounted directly on the canceling tool so that the strip of material passes between them a little before winding up on the mandrel, which is sufficient. This crew is represented by 76 in Figure 13.



   The partially cut away section of the tube or pipe wall shown in Figure 12 shows the bands 74 and 75 forming the respective inner and outer layers oriented at an angle to each other, the helicoids then being in opposite directions of rotation.

   With regard to the friction welding of the strip belonging to the outer layer to the inner layer, it can be seen that the inner surface of the outer layer is subjected to preliminary heating by the preheating device shown in FIG. 10 by as a result of its contact with the rotary shaft of this device, this preliminary heating being just equal to that which is imparted to the lateral edges given that the relative speed of friction is high and that the radial pressure between the strip and the arb e is important in all cases because of the great tension Se # #. . The outer surface of the inner layer is of course fully preheated as a result of the work performed by the support tool.
 EMI22.1
 dageTBt 'the tool placed downstream.



   In this way, in such a tube or pipe formed of two layers or of a greater number of layers and produced by the apparatus as provided for by the invention:
1) Not only the side edges of the bands, but also the inner and outer edges of these bands 'are friction welded' - to their adjacent bandero
2) A more important factor from the point of view of the cohesion between the two layers of material, is obtained by the tension by winding the bands under a total tension S. e / u (# 1 + # 2), S denoting the tension initial, # 1 the total angle of passage through the preheater and 02 the total contact angle of the web in the welding tool.

   It is-. git @ the sum (integral) of the continuous differential increases in voltage (and therefore radial pressure) S.e / u d during the entire passage of the web through the preheater and the welding tool. This provides a pre-tension load which acts on the outer layer, and a pre-compressive load which acts on the inner layer, the radial pressure corresponding to this relative tension.



   This results in a considerable increase in the mutual adhesion between the two layers of material and also between the side edges of the adjacent layers beyond that produced by the soldering.

 <Desc / Clms Page number 23>

 



   3) Since the bands which are in adjacent layers cross at an angle (between 0 and 180), a further increase in cohesion in all directions is obtained (both in the axial direction than in the radial direction) beyond the increase in cohesion which is described under point (2) above.



   4) The factors described in the three points indicated above result in a considerable increase in the resistance of the tube or pipe vis-à-vis the loads which weigh on it and, due to the different orientations of the reinforced bands helically wound that are in the different layers, this resistance is manifested in all directions.



   This shows the considerable advantages of a tube or pipe formed of at least two layers of material, as described above, compared to a pipe or pipe having the same wall thickness but formed of only one layer of material. strip having the same thickness as the two layers of the first tube or pipe, without counting of course the improvement represented by the tube or pipe formed from a single layer of material but consisting of the strip of material in question by comparison with a tube or pipe manufactured by conventional methods.



   In FIG. 14 is shown an exemplary embodiment of the apparatus as provided for by the invention, serving to stretch under pressure circumferentially (and also axially if necessary) a layer entering into the constitution of a tube or pipe.



   In this figure 14, the mandrel 80 is provided with an expansion section or part 82 terminating in a stronger cylindrical section.
83, the latter being surrounded by a sleeve 64 rotatably mounted at 85 and driven by a gear 86, this sleeve internally having a slightly pronounced helical rib 87 starting from a shallow radial depth and increasing to the point of view of the diameter of its pitch circle as well as from the point of view of its pitch in the direction of its length, in order to transport the layer of material 88 through the apparatus, to work and to lengthen this layer of material circumferentially (and as a result of the increase in pitch axially) under pressure, these elongations being integrals of continuously produced differential elongations.



   The apparatus thus constituted can be combined with any of the devices described or with a conventional device in order to reinforce tubes or pipes or layers of material entering into their constitution, especially when it comes to the manufacture of tubescou pipes formed of multiple layers.



   In Figures 15 and 16 is shown an apparatus according to the invention for reinforcing a tube or pipe of a plastic or other material in the plastic state by means of a more resistant material. in the form of a strip, of a wire, of a cord or in a similar form. This apparatus is an adaptation of the apparatus constituting the first embodiment of the invention which has been described with reference to the figures 1 to 6; it differs from it in that the thread is in the rotating outer sleeve, while the mandrel does not turn, and furthermore in that in its deepest section the thread does not penetrate the wall of the tube outpauiujusor mandrel, but only to a depth at which the reinforcement should be placed.



   The apparatus can be used independently or in the form of a mechanical accessory mounted on the machines for manufacturing tubes or pipes, for example according to the first embodiment, or else

 <Desc / Clms Page number 24>

 also in the form of an accessory adaptable to any apparatus for manufacturing tubes or pipes, for example in the form of an extrusion device.



   In Figures 15 and 16, 93 denotes a cylindrical mandrel on which moves a tube or pipe blank 92 from an extrusion device 91; 94 designates an annular rotary tool in which the helical thread 98 with four origins starts without a projection from the cylindrical surface 97 'formed at the entry, gradually increasing in radial depth in the section of expansion "A", on both sides of the original cylindrical surface, in order to shape by kneading the grooves 98 which go gradually deepening into the still plastic pipe blank 92, and to push the plastic material back displaced, layer by layer in the helical ridges of increasing depth 100 which separate the grooves 99.

   During this operation, the material is detached by successive thin layers and stacked layer by layer to form the ribs or ridges, while being heated (if necessary) by the heating device ± -109 while being worked under forces of increased compression which vary in direction and intensity according to the different shapes of the helical threads through which the plastic material passes, as has already been explained with regard to Figures 6.



  At the height of the deepest indentation 101, the reinforcement 102, which is only drawn schematically, is introduced through a channel 104 under uniform tension and according to the precise position which is imposed by the configuration of the reinforcement by. guidance equipment 105-106.



   In section B of the tool which follows on from the previous one, the helical thread 98 exhibits a gradual feathering from both sides to the cylindrical end surface 97. As a result, the material which, in section A, has been peeled away layer by layer to form the grooves 99, has been stacked to form the ridges 100, and has undergone compression work, is unwound layer by layer and under increasing pressure and temperature in section B, in order to ensure a uniform satisfactory bond with the reinforcement 102 and to achieve a perfect seal above the reinforcement, the gasket being constituted by a plastic material homogenized and reinforced as has already been described in connection with the figures. 1 to 6, weakening points,

   which would otherwise adversely affect the overall strength of the tube or pipe, having been removed from the plastic subjected to treatment.



   In Figure 17 is shown an apparatus also in accordance with the invention and allowing the manufacture of a tube or reinforced pipe in plastic material, or more generally in any material in the plastic state in the form of a preformed strip combined with a reinforcement wound with this tape, this apparatus being an adaptation of the second embodiment of the object of the invention which has already been described with reference to FIGS. 7, 8 and 9. The construction and the operation of the device is understood by referring to the description of Figure 7. Like reference numerals denote like members.

   The difference here resides in the introduction by the winding mechanism of the reinforcement 111 at the same time as the re-shaped strip of material is wound up, this strip being shaped, for example along the straight section recalling the shape. of a Z which is shown, so as to receive the reinforcement in a cavity formed between the adjacent strips.



   In figure 18 is shown another example of a strip of preformed material in which the reinforcement is already located, which has been introduced into this strip by a process similar to that used for the manufacture of sheathed cables, and which is then trans-

 <Desc / Clms Page number 25>

 formed to give rise to the reinforced tube or pipe starting from a helical strip at one or more origins.



   It is understood that tubes or pipes comprising several layers formed of helicoids with different orientations so as to withstand different types of forces can be manufactured according to the invention by providing a number of elements equal to that of the layers of material in order to wind additional layers over the previous layers, acting as a mandrel. It is also possible to manufacture tubes or pipes formed of layers of material: some of which are reinforced while others are layers made more resistant by the apparatus provided in Examples 7 to 14.



   It should be understood that the foregoing description has been given only by way of example and that numerous other exemplary embodiments are suitable without departing from the invention, the details of operation being capable of being modified. in the field of technical equivalences.



   CLAIMS
1. Method of manufacturing tubes, pipes and other objects starting from a plastic material or another material in the plastic state according to the principle of differentiation and integration consisting in differentiating elements of the mass of the material, to work said mass in the differentiated form (elements) under pressure, and to integrate the elements thus worked according to the required orientation while continuing to work the material.



   2. Process for the continuous manufacture of tubes, pipes or other articles from a plastics material or other material in the plastic state, consisting in working individually under pressure elements such as layers or parts of bands or threads or cords of said material, and to combine said elements under pressure in substantially similar orientations.


    

Claims (1)

3. Process for the continuous manufacture of tubes, pipes and other articles from a plastic material or other material present in the plastic state according to claim 2, characterized in that a part at least one of the operations is carried out between an internal member and an external member which surrounds, at least in part, said internal member at least one of said members being driven in continuous rotation, and at least one of these members having a shape such that a plane containing the axis of said member intersects its working surface along a line formed, at least in part, by a curve. 4. A method of continuous manufacture of tubes, pipes and other objects using a plastic or other material according to any one of the preceding claims, characterized in that said elements formed by this material are subjected to drawing under pressure. . 5. A method of continuously manufacturing casings, pipes and other articles using a plastic or other material in the plastic state according to any one of the preceding claims, characterized in that said elements sant united under pressure. 6. A method of continuous manufacture of tubes, pipes and other objects using a plastic or other material according to any one of the preceding claims, characterized in that said elements are welded under pressure. 7. A process for the continuous manufacture of tubes, pipes and other articles using plastics or other material in the plastic state. <Desc / Clms Page number 26> tick consisting in detaching thin layers from the bulk material, in working, kneading and stretching individually said layers under pressure and in combining said layers in substantially similar orientations, then in kneading them further under pressure between a man- drin and an enveloping sleeve, at least one of said members being driven in a continuous rotation and having on its working surface a rib or a helical thread, at least one of the characteristics of which (radial depth, pitch, diameter pitch circle and profile shape) varies over at least part of its length., 8. A method of continuously manufacturing a tube, pipe or other article from a plastics material or other material in a plastic state according to claim 7, characterized in that the rib or the helical thread extends through two zones in the second of which the change of at least one of the aforementioned characteristics takes place in the opposite direction to the change of said characteristic in the first zone. 9. A method of continuously manufacturing a tube, pipe or other object using a plastic or other material in the plastic state according to claim 8, characterized in that the radial depth of the net varies progressively from zero to a maximum value, and then gradually decreases to zero in the length of said organ. 10. A method of continuously manufacturing a tube, pipe or other object using a plastics material or other material in the plastic state according to claim 9, characterized in that the edge free of the thread having a maximum radial depth touches or very closely approaches the working surface of the other component. 11. A method of continuously manufacturing a tube, pipe or other object according to any one of claims 7 to 10, characterized in that the rib or the helical thread is on the surface of the mandrel which gradually decreases in diameter. and the smallest diameter of which is at the end where the plastic material enters between the mandrel and the enveloping sleeve. 12. A method according to any one of claims 1 to 6 for the continuous manufacture of a tube, pipe or other object of plastic or other material in the plastic state in the form of a preformed strip. consisting in working parts of this strip (elements) individually under pressure, in combining the elements in a substantially helical formation and in joining said elements under pressure between an internal member and an external member, which surrounds at least in part said internal member, at least one of said continuously rotating members and at least one of these members having a shape such that a plar containing the axis of this member intersects its working surface along a line which represents at less in part a curve. 13. A method of continuously manufacturing a tube, pipe or other object using a plastics material or other material in the plastic state according to claim 12, characterized in that said parts bands (elements) are joined under pressure by their edges, all around their circumference, between a mandrel and an external enveloping sleeve, at least one of these members rotating continuously, the rotating member being provided on its working surface a rib or a helical thread of which at least one of the characteristics (radial depth, pitch, diameter of the pitch circle and profile shape) changes over at least part of the length of this member in order to subject said material to radial and axial pressure. <Desc / Clms Page number 27> 14. A method of continuously manufacturing a tube, pipe or other object using a plastics material or other material in the plastic state in the form of a preformed strip according to claim. 13, characterized in that said parts of the strips (elements) are joined under pressure by their edges, this joining taking place continuously all around the circumference from a zero angle up to an angle shown. by 2 #, and in radial depth continuously from zero to a total radial depth corresponding to the wall of the tube or pipe (differential-integral). 15. A process for the continuous manufacture of a tube, pipe or other object using a plastics material or other material in the plastic state in the form of a pre-formed strip according to the any of claims 13 and 14, characterized in that said parts of the bands (elements) are joined by friction welding. 16. A method of continuously manufacturing a tube, pipe or other object using a plastic or other material in the plastic state in the form of a preformed strip characterized in that ' after establishing a wall layer of the tube or pipe from a tape according to any one of claims 12 to 15 a further layer of the tape is helically wound over the first layer {now as a mandrel) said portions of the bands (forming this second layer) being joined under pressure according to any one of claims 12 to 15. 17. A process for the continuous manufacture of a tube, pipe or other object using a plastics material or other material in the plastic state in the form of a pre-formed strip according to Claim 16, characterized in that, in the different layers, the bands are presented in equally different helical formations. 18. A method of manufacturing a tube, pipe or other object using a plastic or other material in the plastic state in the form of a pre-formed strip according to any preceding claim. , characterized in that this strip is subjected to stretching. 19. Apparatus for manufacturing a tube, pipe or other object from a plastic or other material in the plastic state characterized in that it comprises at least two members among which an external member. surrounds at least in part an internal member, in order to work individually under pressure elements, such as layers or parts of strips or threads of said material and to combine said elements in substantially similar orientations, one to the other. less of said continuously rotating members, and at least one of these members having a shape such that a plane containing the axis of said member intersects its working surface along a line forming, at least in part, a curve. 20. Apparatus for manufacturing a tube, pipe or other object using a plastic or other material in the plastic state according to claim 19, characterized in that it comprises a mandrel, a enveloping sleeve surrounding this mandrel, and a device for rotating at least one of these members, the rotating member having on its working surface a rib or a helical thread of which at least one of the characteristics (depth radial pitch, pitch circle diameter and profile shape) varies over at least part of its length. 21. Apparatus for manufacturing a tube, pipe or other object using a plastic material or other material in the plastic state according to claim 20, characterized in that the rib or the helical thread s 'extends over two zones in the second of which the change <Desc / Clms Page number 28> of at least one of the characteristics operates in the opposite direction to the change of said characteristic in the first zone. 22. Apparatus for making a tube, pipe or other object by means of a plastics material or the like according to claim 21, characterized in that it comprises a mandrel, a surrounding sleeve. this mandrel and a device for rotating either the sleeve, the wrapping or the mandrel, the rotating member having on its working surface a rib or a helical thread the radial depth of which continuously increases from zero at one end to to a maximum (integration of differentials), then continuously decreases to return to zero. 23. Apparatus according to claim 22, characterized in that the free edge of the thread at its point of maximum radial depth, touches or approaches very close to the work surface of the other member. 24. Apparatus according to any one of claims 20 to 23 characterized in that the helical thread has several origins. 25. Apparatus according to any one of claims 20 to 24, characterized in that the inner wall of the enveloping sleeve is cylindrical, the mandrel being rotated and having a diameter which gradually decreases between two cylindrical parts. spaced apart, at least a part of the length of the rib or of the helical thread being integral with the part of the mandrel whose section gradually decreases. 26. Apparatus according to any one of claims 20 to 24, characterized in that the internal wall of the enveloping sleeve is cylindrical, the rib or the helical thread etanr integral with the mandrel, the mean diameter of which is substantially uniform. 27. Apparatus according to any one of claims 20 to 22 or claims 24 to 26, characterized by a device for introducing and winding a reinforcement in the form of a metal wire, a strip or a wire. or bead in rib or helical thread, to required radial depth. 28. Apparatus for manufacturing a tube, pipe or other object from a plastics material or other material in the plastics state in the form of a preformed strip according to claim 19, characterized in that it comprises at least two members, the outer member of which at least partially surrounds the inner member while leaving a certain clearance between the two members, a device winding the parts of said strip (elements) helically in space included between said members, a device transforming the strip of material through said members, and a device imparting a continuous rotation to at least one of said organs, the working surface of at least one of these organs being shaped so that the radial space between these two components changes over at least part of the: length of the apparatus in order to unite said elements (parts of the bands) under radial and axial pressure. 29. Apparatus for manufacturing a tube, pipe or other object. with the aid of a plastics material or other material in the plastics state in the form of a preformed strip according to claim 28, characterized in that it comprises at least one mandrel and one sleeve of 'wrapping located at some distance from this mandrel a device winding parts of- said strip (elements) -in the space between the mandrel and the sleeve, at least one of the aforementioned members being able to turn and having a helical thread on its work surface, at least one of the characteristics of which (radial depth, pitch, pitch circle diameter and profile shape) changes over at least part of the length of this <Desc / Clms Page number 29> member for joining said parts of the strip (elements) by their edges under radial and axial pressure and for conveying said strip and the tube or pipes which are formed therefrom along the mandrel. 30. Apparatus for manufacturing a tube or pipe or other object using a plastics or other material in the plastic state in the form of a preformed strip according to any one of the claims. 28 and 29, characterized in that it comprises at least one backing plate subjected to the load of a spring and adjacent to the winding device in order to exert an axial pressure on the strip of material being wound up - ment in the space between the mandrel and the sleeve, and a device making it possible to adjust the load exerted by the spring on the loading plate. 31. Apparatus for manufacturing a tube, pipe or other object according to any one of claims 28 to 31. characterized in that it comprises a device for friction welding of said parts of the strips (elements) under pressure. radial and axial between the two organs in question. 32. Apparatus for manufacturing a tube, pipe or other object according to any one of claims 28 to 31, characterized in that said rotary member has on its working surface a helical thread of which the at least one of the characteristics (radial depth, pitch, diameter of the pitch circle and profile shape) changes over at least part of the length of this member in order to exert a radial and axial pressure on said parts of the bands, this thread receiving a or several metal or other sheets extending between the edges of the adjacent parts of the strips of material and being in contact with them so as to generate friction along said edges and to generate therein a local heating specific to friction welding, said sheets being provided with sharp edges and gradually decreasing from a maximum depth to a zero depth in order to gradually free themselves from the space between said parts of the strip which are joined by radial and axial pressure exerted by said thread during the friction welding operation without permitting air penetration. said welding taking place gradually from zero depth to maximum web depth (differential-integral). 33. Apparatus for manufacturing a tube, pipe or other object according to any one of claims 28 to 32, characterized in that the device providing friction welding comprises at least one liquid mounted on or in one. said members, this disc being rotatable and extending between the edges of the adjacent parts (elements) with which it is in frictional contact, in order to produce or contribute to the production of a friction welding of said adjacent edges of said sections. parts of the band. 34. Apparatus for manufacturing a tube, pipe or other object according to any one of claims 28 to 33, characterized in that it comprises a device for preheating the edges to be welded of the parts of the preformed strip. 35. Apparatus for manufacturing a tube, pipe or other object according to claim 34, characterized in that this device for pre-heating the edges to be welded of said parts of the preformed strip (elements) comprises a rotating member as well as friction discs , and equipment passing said strip between these discs under the pressure exerted by the latter. 36.Apparatus for making a tube, pipe or other object <Desc / Clms Page number 30> according to claim 35, characterized in that the discs are axially movable on the rotary member and are subjected to the load of a spring which is exerted from both sides and which brings them together, the equipment being studied in such a way to allow adjustment of the spring load. 37. Apparatus for manufacturing a tube, pipe or other object according to claim 36, characterized in that the discs rotate with a shaft on which they are mounted so as to be axially movable under the load of their springs. 38. Apparatus for manufacturing a tube, pipe or other object according to claim 37, characterized in that a helical elastic friction sheet is mounted on said shaft between and in contact with the disks. so as to rotate with and shaft and to be axially movable with respect to it, a device being provided for engaging the pre-formed strip on said shaft and in the helical path of length n2. # formed by said helical sheet and the disks in question, the equipment being designed so as to rotate this shaft and the helical sheet in order to produce the required relative speed between the edges of the strip and said walls, under the required pressure. 39. Apparatus for manufacturing a tube, pipe or other object according to any one of claims 28 to 38, characterized in that it comprises a rotary annular tool according to a joining assembly and mounted on an extension of the mandrel. , a device rotating the annular tool, the latter comprising on its working face a helical thread of which at least one of the characteristics (radial depth, pitch, diameter of the pitch circle and shape in profile) varies over a part at least of its length, in order to ensure subsequent work of the material constituting the tube or pipe. 40. Apparatus for manufacturing a tube, pipe or other object using a plastic or other material in the plastic state in the form of a pre-formed strip forming at least two layers, character- terized in that it comprises a device as specified in claims 28 to 39, for forming a layer of the wall of the tube or pipe from the preformed strip, and a second device which is one of which - Conch of claims 28 to 39, this second device being adjacent to the first for winding the strip forming the second layer on the first layer acting as a mandrel and for shaping this second layer from said strip. 41. Apparatus for manufacturing a tube, pipe or other object according to claim 40, characterized in that the second device is designed so as to force the bands of the second layer to cross the bands of the first. layer at an angle of value between 0 and 180. 42. Apparatus for manufacturing a tube, pipe or other object reinforced with a plastics material or other material in a plastics state in the form of a preformed strip according to any one of claims 28 to 41, characterized in that it comprises a device simultaneously winding with said preformed strip a reinforcement in the form of a metal wire, a strip or a wire or bead interposed between the strips of plastic material, the latter having a shape such in cross section that they leave a cavity forming the housing of said reinforcement. 43. Apparatus for manufacturing a tube, pipe or other reinforced article according to any one of claims 28 to 41, characterized in that said preformed strip receives said reinforcement during its production. <Desc / Clms Page number 31> 44. Apparatus for manufacturing a tube, pipe or other object of reinforced plastic material according to claim 19, characterized in that it comprises a heated fixed cylindrical mandrel and a heated annular organer capable of rotating around said mandrel while leaving between them an annular space providing passage for a strip of plastic material and a metal wire or equivalent forming a reinforcement) wound helically on the mandrel at one end, the bore of this annular member gradually decreasing by section and having a shallow helical thread which advances the strip of material along the mandrel and includes it radially and axially. 45. Apparatus for preheating by friction of a preformed strip characterized in that it comprises a rotating shaft, at least two disks movable axially relative to this shaft and mounted on the latter to rotate with it, a device subjecting the two -discs loaded by a spring to bring them closer to one another, the member which exerts the load being adjustable, a sheet * helical elastic friction mounted on this shaft between the disks and in contact with them in order to rotate with the shaft and to be axially movable with respect to it, a device for engaging said strip along a helical path having a length represented by n. 2. #, a carrying device; said strip, and a device rotating the shaft with said helical sheet in order to angle a required relative friction speed between the edges of the strip and said walls over a length ranging from 0 to the value of n. 2. # (integration of differentials). 46. Apparatus for working a tube or pipe or a layer of material forming part of a tube or pipe according to claim 19, characterized in that it comprises a mandrel comprising, between two cylindrical parts, an expansion section, a casing sleeve surrounding at least this expansion section of the mandrel, but leaving a radial space between said members, a device rotating at least one of said members, this member rotary comprising on its grid surface * a rib or a helical thread of which at least one of the characteristics (radial depth, pitch, diameter of the pitch circle and profile shape) varies over at least part of the length of this member to displace the tube or pipe or the layer of material entering into its constitution axially. through the expansion space between the mandrel and the enveloping sleeve, with elongation in the circumferential direction of the tube or pipe or of the aforementioned layer of material, the resulting expansion being an integration of differential expansions produced continuously. 47. Apparatus according to claim 46, characterized in that at least the pitch of the thread provided in the rotary member is continuously increasing in the length of this member in order to produce, in addition to the circumferential expansion, an elongation. axially, as an integration of continuously produced differential axial elongations;