MXPA96006715A - Justa threaded for metal tubes inter interpreting - Google Patents

Abstract

The present invention relates to a splined joint, characterized in that it comprises: an external surface, an internal surface, an annular end surface formed between the external surface and the internal surface, and having a surface abutment portion, and a sloping surface portion which extends along a generatrix from the abutment surface portion to the inner surface, and a protective layer covering at least a portion of the inner surface and the inclined surface portion, and a threaded connecting portion that is bolted with the threaded pipe, which has another inner surface an end connecting surface having a surface portion of opposed stop, and a connecting surface extending from the surface portion of the opposite stop to another inner surface, and another protective layer covering at least a portion of another internal surface and the connecting surface, wherein the portion n Opposite abutment surface of the threaded connection part limits in press-contact with the abutment surface portion of the threaded pipe, along a contact surface when the threaded pipe is screwed to the threaded connection part; angled inclination with respect to an extension of a contact line of the contact surface, when viewed in section by a plane passing through the axis of the threaded joint, to create an open area that opens progressively between the surface portion inclined and the connecting surface, the opening area is at least partially filled by the protective layer and the other protective layer, which are in press-contact with each other in the opening area at least for a predetermined length, beginning the predetermined length near a terminal point of the contact line, and that is not filled with additional material that is not part of the protective layer Tora, and yet another protective layer, the protective layer is of substantially uniform thickness on the inner surface, and which continues on the surface portion inclines

Description

THREADED GASKET FOR METAL TUBES WITH INTERIOR COATING Field of the invention The present invention relates in general to the use of layers or coatings applied on pipes and threaded joints for tubes, particularly to protect against corrosion or improve the conditions of fluid circulation inside them, and relates to pipes and threaded joints for metal tubes provided with such a coating or inner layer. Pipes of this kind and corresponding threaded joints are used for the exploitation of oil and gas deposits, in particular, for wells in which water injections are made. The invention particularly relates more generally to any tube and threaded joint with which it is associated, subject in fact to conditions of use in which severe corrosion occurs in contact with the circulating fluid. Such is in particular and in a non-limiting manner, the case of pipes and threaded joints used to circulate water, as for example in the case of oil wells REF: 23798 mentioned above or in wells for geothermal, by effect of the composition and the temperature of the water that is in contact with the tubes.

BACKGROUND OF THE INVENTION It is known and known to protect against corrosion the inner wall of the tube as well as the joint components associated with said tubes by means of a thin and adherent layer of a plastic coating, such as for example a resin, for example based on a polyepoxide. Such a coating has an excellent adhesion on steel and a very good resistance to corrosion. Regardless of these corrosion problems, each coating has also been applied to pipes and the joint components associated with said pipes to reduce the pressure losses and, in particular, to reduce the roughness of the surface of the inner wall of the pipes and of the pipes. the components of the joints, and to eliminate to the maximum the turbulence that can be produced on the inner walls of the pipes and joints due to the effect of the circulation of fluid.

But, at the level of a joint, between for example the annular surface of the male end of a section of pipe and an annular surface forming the support of the female component of the joint, it is observed at the time of tightening of the joint that the pressure Closing tends to cause a crack in the protective coating and its chipping in the immediate vicinity of the contact area. As a result there is a very important localized detachment and corrosion of the underlying metal that was thus stripped, or in the case where the coatings are used to improve the quality of the walls surfaces in contact with the circulating fluid, disturbances in the fluid outlet. Corrosion, even if it does not cause immediate leaks, prevents the new use without repair of joint components after disassembly. It can lead to the destruction of support and contact areas for sealing. Different solutions have been proposed to prevent this localized corrosion. They resort to the use of sealing rings made of elastomers or certain plastic materials.

Certain sealing rings, such as those made of polytetrafluoroethylene have the combined advantages of good mechanical adhesion, excellent resistance to corrosion and good compatibility with plastic coatings, used for metal pipes and their mounting means. The rings used can be reinforced with glass or carbon fibers. Numerous examples describe the use of such rings. Thus, US Pat. No. 3,100,656 describes an integral type assembly in which the threaded male end of a tube section is fixed by screwing it into a female housing of another section. The inner walls of the tubes and the joint components are coated with a layer of a phenolic resin, such as, for example, phenol formaldehyde and a thickness of 0.05 to 0.15 mm. A sealing ring made of polytetrafluoroethylene is placed partly inside an annular housing of the female wall and rests against a step thereof. This ring has a section in the form of WI ", so that its outer elongated area makes contact with the housing, while the end of the male element at the end of the screwing closes a lateral edge of the ring against the step. US Pat. No. 4,875,713 discloses another way of assembling the tube sections, using a sleeve that allows the assembly of one of the male ends of two tube sections one after the other. The internal wall of the tube is protected from corrosion by means of a plastic coating consisting of a layer of phenolic or epoxyphenolic resin or even epoxypolyamides.The ring is mounted here by means of a sleeve in a double throat. polytetrafluoroethylene reinforced with 5% glass fibers and 5% carbon fibers; It has an inverted WU shape whose two arms are placed inside two parallel grooves The two front ends of the male elements partially cover the apex of each arm, thus blocking the joint inside its housing. of the cuff control the degree of tightening of each element.

In the North American Patent No. 5,236,230 an assembly analogous to that of the aforementioned patent is described. However, a polytetrafluoroethylene ring is used whose section is substantially rectangular and whose radial height is approximately one and a half times the width measured parallel to the axis. Such co can be seen in Figures 4A and 4B, when the facing male front ends are pressed against the ring, its initially rectangular section is reformed to become a "T" and its inner surface defines a passage section equal to the section of passage of the tubes, which avoids any disturbance in the circulation of the fluid. The tightening is controlled by stop steps. There is no indication of the risk of cracking of the coating at right angles, or almost straight angles, represented in Figure 4B. Although these different corrosion protection methods of the joint joining zone offer certain advantages, they all have the drawback of using elastomer rings or plastomers which themselves have real drawbacks. These rings must, in general, be accurately positioned so that they rest properly against the sealing surfaces; after each loosening and tightening they must be carefully controlled, and, in most cases, replaced by causes of aging or plastic deformation. In the case of tively rigid rings such as the two polytetrafluoroethylene rings, they can be cut if they are misplaced and can eventually cause cracking of too soft a plastic coating. The rings can also be expelled from their housing and be found inside the tube or even be dragged or damaged during the internal control of the tubes. It should also be noted that, in the place of use, these rings require supplementary manipulations that must be executed with precision.

Description of the invention It is generally sought to improve the adhesion of the layers in coatings applied on the inner walls of tubes at the level of the union of tubes without resorting to the use of rings, that these layers have been used to protect against corrosion or reduce the loss of load in the tubes or in any other use. A general means is sought to avoid the use of sealing rings made of elastomers or plastics such as polytetrafluoroethylene. It also seeks the possibility of carrying out a significant number of loosening and tightening of joints of tubes or sections of metal tubes coated with a plastic layer, and that are not provided with rings, without causing the ase of this layer in the tight joint area established between the end of a tube and another joint component, said detachment being coupled with rapid corrosion of the underlying metal. It is also sought to suppress the sealing rings both in the case of an established connection between male ends of two sections of tubes established by means of a sleeve comprising two female housings, as in the case of a direct connection, called "integral" connection. , between the male end of a tube section and the female end of the next tube. The gasket for metal tubes according to the invention allows the assembly, protected against corrosion, of two tubes assembled with a threaded connection. This joint comprises two tubular components, each of which is provided with a thread that allows the assembly, these components being made on the ends of tubes or sections of tubes that must be assembled. The assembly of two components is performed by screwing and tightening at least one component comprising a male thread on a corresponding female threaded housing. Each component comprises an internal tubular zone corresponding to the inner wall of the component in question in the vicinity of the joint zone. The diameter of this internal tubular zone will be equal to the inner diameter of a current part of the tube on the end of which the component is madeor it will be slightly different from said diameter in the case where the end of the tube has been preformed, for example, by imparting a degree of conicity, before the component is made. This internal tubular zone is prolonged at the level of the joint by an annular surface of generally radial orientation with respect to the internal tubular zone. The annular surfaces of the components are designed so that, during the assembly of the joint, they are in common support contact on a part of their surface located towards the exterior of the component. This common support contact is translated by a common contact generatrix, in a cutting plane passing through the joint axis, over a fraction of the total radial extension of said annular surfaces. This common contact generatrix advantageously constituted by a straight line segment that can either be in perpendicular relation with the axis of the joint, or be inclined with respect to said axis of the joint. It can also be constituted by any constant or variable curve curve segment. The internal tubular zone of each component is covered by a layer intended to protect the metal against corrosion due to the fluid circulating inside the component, or for any other use, such as, for example, the reduction of head losses. This protective layer is prolonged from the internal tubular zone, for each of the components, by at least a fraction of the radial extension of the annular surface defined above. On the fraction of the radial extension of the annular surfaces located next to the internal tubular zone where these surfaces are no longer in contact in the tightened state, to each of the generatrixes defining each of the annular surfaces, and located in a plane of cut that passes through the axis of the joint, is given a form such that, in the state of tight, the generatrices form from a common initial point of contact a progressive opening, the axial distance between the two generatrices increases progressively as it moves away from the initial point towards the axis of the joint, the two generatrices come back together with the internal tubular zone of their respective component. This progressive opening is produced as it moves away from the natural geometrical prolongation, towards the interior of the component, of the common contact generatrix by at least one of the annular surfaces. The layer will extend, before the first tightening, on a more or less important fraction of the annular surfaces. It can, for example, cover a part of the support zones of each component beyond the initial point, or it can end up in the vicinity of the starting point. The opening can, for example and in a non-limiting manner, take the form of an MV "corresponding the sides of the opening to a conical surface centered on the axis of the joint.The opening is dimensioned so that when the joint is assembled, being the annular surfaces in abutment contact, the opening is at least partially filled by the protective layers that are in contact with the two components.The opening characterized by its opening angle at the initial point and its length will be advantageously determined in such a way that the contact pressures present between the two layers of coatings progressively decrease from the initial point of the end of the opening, the layers remain in contact with at least a part of the length of the opening. initial point, on the one hand a contact generatrix of sufficient length to absorb, in the presence of conditions, is preserved good, the tightening and / or compression efforts occurring in the service and, on the other hand, the pressures produced by the contacting of the support surfaces in the coating layer are distributed in such a way that a progressive decompression has place in the opening, the layer retains, in the opening due to the shape of the opening, a sufficient overall cohesion so that no part of the metal is devoid of its protective layer. In a very advantageous manner, the opening will be dimensioned so as to extend substantially to the point where the two layers stop being in contact with each other, thus avoiding creating, in the passage of the fluid circulating through the tube, a corner or a diameter discontinuity capable of causing turbulence or the accumulation of circulating fluid. The opening angle will depend on the radial length of generatrix available from the starting point. In practice, by way of example and without limitation, this angle can have, for example, a value of 5 ° to 15 °, and preferably should not be greater than 30 °, to obtain the progressive decompression of the layers of coating as explained above. If, by way of example, the shape of a "V" is imparted to the opening, it can be seen that if "L" is designated the wall length necessary for the decompression of the coating layers, for a layer of thickness "e" "and a total angle of" X ", we obtain L = e / sin X / 2. If for example "e" = 0.1 mm and X = 10 ° is L = 1.15 mm. This zone of fixation of the layer that plays an important role can be realized by increasing the value of the length "L" thus found. The angle of the opening between the generatrices of the opening zone of the components can be divided so as to have, for example, a symmetrical arrangement. It is also possible that the angle is made on a single component. Beyond this opening zone, the coated wall is connected to the internal tubular area of the corresponding component.

In this splice zone, it is equally important to minimize the stresses due more particularly to the geometric and temperature variations, and preferably the angles forms are to be avoided. When this splicing area forms an angle of, for example, 90 ° with the generatrix of the internal tubular zone, preferably chamfer, for example approximately 45 °, possibly joined by rounded portions or chamfered angles, obtained for example by means of the application of sandblasting, or resorting to any other general progressive form. The tests carried out have shown the possibility of thus constructing joints according to the invention between two components which, in their internal tubular area, are coated with an epoxy layer, capable of supporting approximately ten loosening and tightening operations after a first initial tightening. , without any noticeable deterioration and even without any deterioration of the entire coating layer. In particular, it remains everywhere except for the contact area of support of the annular surfaces where the layer wears, an adherent film in contact with the metal and sufficient to protect the metal, and the contact contact area of the surfaces Annular as for itself is protected by the layers that fill the opening. The boards according to the inventive can be made in terms of their basic structure, in many different ways of which we will offer below, without having a limiting character, two modes of realization. In a first embodiment of the joint, the two tubular components are two male elements and each one carries an external thread in the vicinity of its end. Each of the components bears close to its end an internal tubular zone, which extends at the end of the component by a frontal annular surface of generally radial orientation. Each of these two components is placed inside a housing having a female thread corresponding to the male thread of the component with which it is to be coupled, the two housings being made at both ends of a coupling sleeve, being a sleeve whose length and shape are such as to allow the annular surfaces of the two components to be placed in abutting contact on a part of their surface, part located next to the outer diameter of said components, during the assembly of the joint by means of of tightening and axial closure. The area located inside the sleeve, between the two female threaded housings, allows the passage of the ends of male components of the seal and can be designed so as to also ensure different functions. In this way, it is possible to provide on this internal area forms that allow sealing to be established by establishing metal-to-metal sealing contacts between each component of the joint and the sleeve, these contact areas being able to comprise conical surfaces of relatively slight taper, for example the order of 2 ° to 30 ° with respect to the joint axis. It is also possible to provide, both on the sleeve and on the male component or the various such components, support steps which, while at the same time ensuring the tightening and closing of the seal, obtain exact centering of the two components inside the sleeve.

According to a second embodiment, the gasket comprises a male component provided with an external thread, which component in the vicinity of its end is provided with an internal tubular area, which at the end of said component is extended by an annular surface front of generally radial orientation. The other component is a female component provided with an internal thread that forms a housing in the vicinity of its end. Beyond the inner end of the thread, this component comprises an internal tubular area which at its threaded end is extended by an annular surface of generally radial orientation. The threaded female housing in which the male component is screwed consists of the same female component, component whose dimensions, shape and threading are to correspond in every way with the male component and allow, during assembly by means of tightening and closing, the putting in partial support contact, next to the outer diameter of the tubes, the annular surface of the male component with the annular surface of the female component.

Between the annular surface and the threading of each component, the shapes of the two components can make it possible to ensure different functionalities, such as, for example, a sealing by metal contact zones with the metal according to principles and known embodiments. In the second embodiment of the base structure of the gasket that is being described, the female component can be made at the end of a long tube. In this case, a so-called integral joint is made, which directly connects two tubes together. In order to dispose of the desired metal thicknesses, it will be advantageous to carry out in advance, according to techniques known per se, a diametric expansion of the female component and a diametral contraction of the male component. As a variant of the second embodiment, the female component can be constituted by the end of a coupling sleeve that also forms a housing for the male component, the second end of the sleeve allowing the housing of another tube provided by a threaded end male, the joint functioning in the same conditions at the two ends of the sleeve, the two housings being separated by a bead whose inner wall constitutes the internal tubular area of the female component. Of course in all the embodiments of the base structure of the gasket described above, the internal tubular zones and the annular surfaces extending them are coated with a layer as already described, for example up to the vicinity of the initial point . These layers, which may be intended to protect against corrosion or ensure other functions, may be made of any known material and used to deposit thin layers on metals. In order to ensure the desired function, and the layers can be deposited according to any known technique. Thus, it is possible to use non-limiting layers made of a plastic material, such as, for example, a polyepoxide, often referred to as epoxy layers. These layers may also contain, to increase their resistance to wear, non-metallic particles such as, for example, glass, carbon or ceramic particles carried by a plastic binder which allows them to be deposited in good conditions. Of course, such a layer will also be deposited over the entire interior of the tubes assembled by the gasket according to the invention. When the annular surface of the second component is a surface forming part of a female housing, in which the threaded male end of the first component whose annular surface partially rests against this surface is screwed, it is possible, in a known manner, to complete the device according to the invention, establishing a metal-to-metal contact sealing between a surface, for example, of a conical conical trunk type, arranged in the immediate vicinity of the leading end of the male component on its outer wall, and a surface, for example of corresponding conical trunk type, made on the wall of the female housing, the inclination of the generatrices substantially parallel of these two surfaces with respect to the axis of the joint, having for example a value of approximately 2 ° to 30 °.

This arrangement guarantees an excellent tightness to withstand the internal and external overpressures to which the gasket according to the invention is subjected. The layer deposited before the first screwing can cover all of the annular surfaces. This layer, on the part of the annular surfaces that will be in contact of support, will show a tendency to be deteriorated by the contact pressure. However, this does not prevent, due to the effect of the controlled opening created between the annular surfaces in the tightened state, ensuring the coherence of the protective layer on the parts of the components subjected to corrosion.

The following Figures describe, in a non-limiting manner, embodiments of the joint according to the invention.

Figure 1 schematically shows a sectional view of the central part of a joint according to the invention in the case of the sleeve assembly of two male components adapted to come into abutting contact during tightening.

Figure 2 also shows a sectional view of the ends of two male components of Figure 1 in abutment contact.

Figure 3 is a sectional view of a variant embodiment of the joint of Figures 1 and 2 shown at levels of the annular zones.

Figure 4 schematically shows the sectional view of a gasket according to the invention in the case where the male component is screwed into a female housing provided in a sleeve.

Figure 1 shows in its central part and at a greatly increased scale the areas of unthreaded ends 1 and 2 of two male components 3 and 4 of the joint 5 represented according to an axial section view, showing only the part of the section located above of the Xl-Xl axis of the joint, these components 3 and 4 being made on the ends of tubes that must be assembled and that are not shown in the Figure. As can be seen in the Figure, these two male components 3 and 4 are assembled by means of a sleeve 6. This sleeve has at each end a respective housing and 8, whose threading 9 and 10 corresponds to the threads respectively 11 and 12 of each one of the male components 3 and 4. The thread not shown in detail, comprises in this case a conical thread, whose load flank will advantageously be a negative inclination flank. In its central area 13, the sleeve 6 has a cylindrical shape of revolution, which allows the ends 1 and 2, also cylindrical and belonging to the male components, to be screwed on each end of the sleeve. Each male component 3 and 4 has in its respective end 1 and 2 respective internal tubular zone 14 and 15, which corresponds to the inner wall of the tube constituting the omponent. Each internal tubular zone is extended by means of a respective annular surface 16 and 17, of generally radial orientation and arranged frontally at each of the ends 1 and 2.

This annular surface comprises in its fraction located at the outer end of the component a respective flat surface 16.1 and 17.1 generated by a generatrix constituted by a straight line segment perpendicular to the axis Xl-Xl. Figure 2 represents the joint of Figure 1 in the tight and closed condition. Surfaces 16.1 and 17.1 are now in support contact, which may be more or less tight. For the purpose of perfectly centering the gasket in the sleeve and at each end of the cylindrical central part and in front of the beginning of the threaded area, a respective centering step 18 and 19 is provided, which is complemented by a corresponding step 20 and 21 provided on each of the male components, said steps being designed so that when the annular surfaces 16.1 and 17.1 are brought into abutment contact at least one of the steps 20 and 21 of the male components ceases to be in contact with the steps 18 and 19 corresponding to the sleeve 6. Here only the centering steps 19, 21 are in abutment contact.

The annular surfaces 16 and 17 present from the respective points 16.2 and 17.2 an inclination with respect to the natural geometric extension of the generatrix of the bearing surfaces 16.1 and 17.1, before meeting their respective internal tubular zone 14 and 15. In this manner, the surfaces 16.3 and 17.3 have here a generally conical shape of axis Xl-Xl prolonged by a rounded portion 16.4 and 17.4. The generatrices of surfaces 16.3. Y 17. 3 they form with the common plane perpendicular to the axis Xl-Xl respectively al and a2, both angles being equal. A respective epoxy layer of 22 and 23 is before the first pressing of the gasket deposited on the inner surface of each male component 3 and 4., and covers it in the desired way to protect it against corrosion. This layer extends over the internal tubular zones 14 and 15 and extends outside the points 16.2 and 17.2 defined above by a part of the stop abutment surfaces 16.1 and 17.1. It should be understood that the layer is not represented to scale in the Figure to better emphasize the description of this point.

In Figure 2 it can be seen that the progressive opening zone 24 formed by the conical surfaces 16.3 and 17.3 during the tightening and closing of the joint is at least partially filled by the protective layers 22 and 23, which are crushed against each other. in the upper part of the WV form "of the opening before recovering its original structure in the lower part of said opening Layer 22 and 23 has also been flattened in the stop abutment area 16.1 and 17.1 and has been driven partly within the "V" shaped opening For example, the layer may have a thickness of the order of 0.15 mm in its current part, if at the angles a and a2 a value of 10 ° is assigned, the total angle X4 of the aperture measured from the initial points 16.2 and 17.2 now has a value of 20. That assigns L, length over which the layers of the two components will be in contact or in compression and will fill the aperture 24, a minimum value of 0.15 mm (it is pesor) divided by 0.174 (sine of 10 °), that is 0.86 mm.

Indeed, having a part of the protective layer been compressed inside the opening 34, the value of L will be in practice higher than 0. 86 mm and can reach, for example, the value of 1 mm. It is also possible to assign the thickness Hl between the internal tubular zones 14 and 15 and the inflection points 16.2 and 17.2 of the surfaces 16 and 17 a value of the order of 1.5 mm, which makes it possible to ensure a union of the tubular areas 14 and 15 in good condition and in practice maintain a thickness H2 for the abutment abutment surfaces 16.1 and 17.1 sufficient to ensure a satisfactory operation of the joint without during the tightening the plasticization of the abutment surfaces occurs. It was found that a joint of such structure can be screwed and unscrewed a certain number of times ensuring at all times good conditions for protection against corrosion. The protective layer 22 and 23 deposited before the first tightening may not cover all of the conical surfaces 18.3 and 17.3 not extend beyond points 16.2 and 17.2 as described above. The important thing is that the protective layers 22 and 23 are brought into contact, preferably in compression contact, in the opening area 24 during tightening, so that the metal is not devoid of protection and subjected to corrosion caused by the circulating fluid. Of course, the angled surfaces at the junction of the conical surfaces 16.3 and 17.3 with the internal tubular areas 14 and 15 may be avoided, and such angled surfaces may cause the protective layers 22 and 23 to break. A rounded portion such as that shown in FIG. Figures 1 and 2 in 16.4 and 17.4, or chamfers such as those indicated at 44 and 45, whose joint angles have been lowered by sandblasting operations, as shown in Figure 4, can for example be used. Figure 3 shows a variant of Figures 1 and 2. The gasket shown in the central part of this Figure 3 has the same base structure of the gasket of Figure 1, but in this case the progressive opening zone 24 is not symmetric Instead of dividing the opening in the form of "V" on the two ends of the male components 1 and 2, this opening has been in this case, made only on a single end, in this case the end I, assigned to the corresponding surface 16. 3 an angle a3 with the plane perpendicular to the axis Xl-Xl, angle whose value is substantially equal to the sum of al and a2. The annular surface 17 of the end 2 is in this case flat and perpendicular to the axis Xl-Xl.

Naturally, care will be taken to control the joining areas of the annular surfaces 16 and 17 with the internal tubular areas 14 and 15, in order to avoid sharp angles. An embodiment such as that shown in Figure 3 offers the advantage of simplifying the manufacture of one of the components of the joint, in this case the component 4, which is not modified in relation to its usual shape. Such an arrangement is particularly interesting when the slope of the annular surface of the stop contact area 16.1 is conical and has an angle such as that shown in FIG.

Figure 4 for the male component. Figure 4 is a greatly enlarged representation of an embodiment of a joint 30, shown in the assembled condition comprising a male component 31 screwed in a female housing 32 constituted by the female component 33, complementing the male thread 34 and the female thread 35, and only the part representing the assembly of two components has been represented in section by the upper part of the axis X2-X2 of the joint. The base structure of the joint 30 corresponds, for example, to a seal such as that described in European Patent 0488 912 B2, without this precision being in any way limiting. This Figure 4 can be applied in the case where the female component 33 represents with the housing 32 one end of a bead sleeve and of which only one end is shown, and the end not shown is to the right of the Figure . It can also be applied in the case where the joint is of the integral type, a situation in which the component 33 is the female component made at the end of the tube, generally of great length, not shown and located to the right of the figure. As shown in Figure 4 schematically, the annular surfaces 36 and 37 which extend to the internal tubular zones 38 and 39 are again found here, with respective protective layers 40 and 41 deposited as described with reference to the Figures 1 to 3. The end of the male component 31 comprises a male abutment surface 36.1 tightened by screwing against a corresponding female stop surface 37.1 of the female housing 32 of an assembly sleeve, or a female end housing of a length of tube. These two stop surfaces have a contact generatrix X3-X3 which has an inclination of an angle of approximately 5o to 35 ° with respect to a plane perpendicular to the axis of the joint. The opening area 42 comprises a total opening angle of a4 of a value of approximately 10 °, and the protective layers 40 and 41 have a thickness such that in the tightening state the "V" shaped opening has its greater part fills up to the reference point 43 by the layers that are partly compressed. Under these conditions, the height H3 has a value of, for example, of the order of 2.5 mm, taking into account the thickness necessary to ensure the union of the zones 38 and 39. As in the case of the pertinent examples, the profile of the The union of the annular surfaces 36 and 37 with the internal tubular zones 38 and 39 is obtained by means of curves of sufficient radius as advantageously represented by chamfers of approximately 45 °. Under these conditions an excellent adhesion of the protective layer is verified even after numerous screwing and unscrewing operations. In particular, it is found that, in the opening zone 42, an adherent layer is maintained on the metal, just as in the vicinity of the abutting contact surfaces 36.1 and 37.1, notwithstanding the ejection of a part of this layer subjected to crushing effect effected by the metal walls of the opening area. It will be appreciated that in these different embodiments of the joint according to the invention, the base combination of a protective layer with a progressive opening zone adjacent to the stop contact area prevents the passage of corrosive fluids in the direction of the underlying metal and maintains the integrity of the protective layer. Numerous variations can be made in relation to the indicated examples and the description, being variants that fit within the protected domain of the invention. In particular, all types of known threads can be used in the production of threaded joints, such as, for example, single, multi-part, conical or cylindrical threads. It is noted that in relation to this date, the best method known by the applicant to carry out the present invention, is the conventional one for the manufacture of the objects to which it refers. Having described the present invention as above, the content of the following is claimed as property:

Claims (15)

1. A threaded joint for tubes comprises two tubular components, each component being provided with a thread, and comprising an internal tubular area prolonged by an annular surface, a layer coats the inner tubular area of each component and at least a fraction of the radial extent of the annular surface, the assembly of two components being made by the screwing of at least one threaded male component in a female threaded housing, characterized in that in the state of screwing the two annular surfaces are in abutment contact according to a generatrix common on an outer part of its surface, the generatrices of the annular surfaces form, towards the interior of the joint from a starting point, a progressive opening which then meets the internal tubular zone of its respective component, the opening being filled at least in part by the protective layers that are in contact with the two components.

2. The gasket according to claim 1, characterized in that in the opening zone the axial distance between the two generatrices increases progressively from the initial point, and the generatrix of at least one component deviates from the natural geometric prolongation in the common generatrix.

3. The gasket according to any of the preceding claims, characterized in that the protective layer covers a part of the stop contact zones of each component outside the initial point before the first screwing.

4. The gasket according to any of claims 1 to 2, characterized in that the protective layer covers before the first screwing a zone ending in the vicinity of the initial point.

5. The gasket according to any of the preceding claims, characterized in that the opening has an angle of a value comprised between 5 ° and 30 ° at the initial point.

6. The gasket according to any of the preceding claims, characterized in that the opening has the shape of "V", the opening angle which is divided into equal or unequal parts between the two-component generators.

7. The gasket according to any of the preceding claims, characterized in that the protective layer is a plastic layer based on polyepoxide.

8. The gasket according to any of the preceding claims, characterized in that the two components are male components, provided with external threads, which are threaded into housings provided with female threads corresponding to the external threads, the housings being made in two. ends of a coupling sleeve that allows in the state of screwing that the annular surfaces are put in abutment contact on a part of their surface.

9. The gasket according to any of claims 1 to 7, characterized in that it comprises a male component provided with an external thread and a female component provided with an internal thread corresponding to the external thread, serving the female housing component of assembly, the annular surfaces entering in abutment contact on a part of their surface inside the female component.

10. The gasket according to claim 9, characterized in that it is an integral gasket, the female component being made at the end of a tube of running length.

11. The gasket according to claim 9, characterized in that the female component forming the housing is made at one end of a coupling sleeve whose second end is provided with a housing identical to the housing of the first end and which allows the assembly of another tube provided at its end with a component identical to the male component, the two housings being separated by a bead whose inner wall constitutes the internal tubular zone.

12. The gasket according to any of claims 8 to 11, characterized in that it comprises at least one sealing area of metal-to-metal contact between the male component and the female housing.

13. The gasket according to any of the preceding claims, characterized in that the opening zone is joined to the internal tubular zone of each component by means of a chamfer or a rounded portion.

14. The gasket according to the preceding claims, characterized in that the layer is a layer intended to protect the gasket against corrosion.

15. The gasket according to any of claims 1 to 13, characterized in that the layer is a layer intended to reduce the pressure losses of the fluid in circulation.