Abstract:
A pipe formed from a concrete cylinder has an end ring with a ferrule which can be snuggly mounted on one end of the pipe and a skirt axially adjacent to the ferrule for receiving a mail endpiece of another pipe. The ferrule is expanded as it is mounted on the cylinder and exerts a compressive force against the outer peripheral face of the cylinder for forming a secure seal. A rib may be disposed on an inner annular surface of the ferrule and an adhesive may be applied for enhancing the seal between the cylinder and the ferrule.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a pipe or the like, of the type comprising:
         a concrete cylinder possessing at least one annular end of determined longitudinal axis, defined in particular by a longitudinal outside peripheral face and by a transverse front face;   a female end ring coaxial with said end and secured thereto, the ring consisting in:
           firstly a longitudinal ferrule for securing to the cylinder, the ferrule being defined in particular by a longitudinal inside peripheral face fitting snugly against said outside peripheral face in the immediate vicinity of said front face; and   secondly a longitudinal skirt projecting longitudinally over said front face to engage coaxially on a male endpiece of another pipe or the like.   
               

   The term “the like” as used herein with respect to pipes means building elements and ducts that can be assembled by being engaged mutually, such as galleries, access holes, so-called “ovoid” interfittable ducting, ducts of the type sold under the registered trademark “MODULOVALE”, and shelter modules, with these examples not being limiting in any way, providing said outside peripheral face presents a cross-section that is curved and convex, either in usual manner or else following simple adaptation in order to implement the present invention. 
   Similarly, the term “concrete” should be understood herein in its most general sense, covering in particular both concrete based on resin and concretes based on a mineral binder. 
   In the present state of the art, the female end ring made of metal or of synthetic material is usually fastened to the cylinder by overmolding the cylinder directly onto the ferrule. By way of example, such a technique is described for a female end ring of synthetic material in British patent application No. 2 217 418, which also mentions the possibility of fixing the ring on the cylinder after the cylinder has been made, probably by using a cement given the complexity of some of the shapes described. 
   The fastening obtained in that way between the female end ring and the cylinder can be satisfactory providing the precaution is taken of shaping the ferrule in such a manner as to obtain mutual anchoring via complementary shapes, however whatever precautions are taken in this respect, sealing between the ferrule and the cylinder remains problematic, even if sealing is defined merely as an absence of any visible seepage of a liquid placed at a pressure close to ambient pressure going from one side to the other of the gasket between the ferrule and the cylinder. 
   Proposals have also been made, in U.S. Pat. No. 5,180,196, and specifically with reference to FIG. 6 of that document, to make a female endpiece on a longitudinal concrete cylinder by longitudinally engaging a ferrule-forming zone of a longitudinal female end ring on an outside peripheral face at one annular end of the cylinder under conditions such that another zone of the ring forms a skirt projecting longitudinally from the front face of the cylinder for receiving internally a pipe of different design. 
   Sealing between the ferrule of the female end ring and the outside peripheral face at the end of the cylinder is then provided by two transverse annular bands that are tightened by screws, locally surrounding the ferrule and locally pressing against the outside peripheral face at the end of the cylinder, thus also providing mutual fastening by friction between the cylinder and the female end ring. 
   The use of such bands can limit the applications of the pipe or the like made in that way in that the material from which the bands are made, which material is dictated by considerations of a mechanical nature, can be incompatible with certain installation conditions for the pipe or the like. Thus, as a general rule, bands are made of steels of a grade that is selected as a function of criteria concerning traction strength and modulus of elasticity, but such seals are generally vulnerable to corrosion and are consequently unusable whenever the pipes or the like are to be buried (unless they are subjected to additional anti-corrosion protection and/or treatment which is expensive and of short-term effectiveness). 
   In addition, the effectiveness of the sealing and the fastening between the ferrule of the female end ring and the outside peripheral face at the end of the cylinder then depends on the magnitude of the transverse pressure between them, which in turn depends on the value of the transverse pressure applied by the annular bands to the outside of the ferrule, and consequently to a circumferential tension given to the annular bands by screw-tightening. 
   Unfortunately, the pressure applied by the bands to the ferrule gives rise to transverse thrust pressure from the ferrule of the female endpiece on the outside peripheral face at the end of the cylinder only through the ferrule, making it necessary to ensure that the ferrule tends to shrink onto the outside peripheral face of the end of the cylinder from a rest condition in which it is engaged on said outside peripheral face. 
   The ferrule has a natural tendency to oppose such shrinkage from its rest condition so obtaining mutual transverse thrust pressure between the ferrule of the female end ring and the outside peripheral face of the cylinder with sufficient magnitude to ensure effective sealing between them and also to ensure that they are effectively fastened together requires a considerable amount of pressure to be developed between the bands and the ferrule by putting the bands under circumferential tension at the risk of causing irremediable damage to the ferrule. 
   In practice, the desire to avoid any risk of such damage leads to the magnitude of the circumferential tension in the bands and of the pressure they apply to the ferrule being limited, and the tendency of the ferrule to oppose shrinkage means that the magnitude of the transverse thrust pressure actually applied by the ferrule to the outside peripheral face of the cylinder is even smaller, i.e. not only is fastening between them ineffective, but also the resulting sealing is doubtful. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to remedy that drawback and to this end, the present invention provides a pipe or the like of the type specified in the introduction, characterized in that the ferrule is in a state of circumferential elastic tension providing sealing relative to said outside peripheral face by said inside peripheral face applying thereagainst transverse pressure which is circumferentially distributed in continuous manner. 
   Between the cylinder and the ferrule of the ring, and regardless of whether the ferrule is made of metal or of synthetic material, this transverse pressure creates contact that is much more intimate than in the prior art, with this intimate contact considerably improving mutual sealing. 
   Depending on the respective shapes of the inside peripheral face of the ferrule and of the outside peripheral face of the cylinder, and depending on the relative coefficient of friction between them, said circumferential elastic tension can also be such as to cause said inside peripheral face to be fastened at least in part to said outside peripheral face by the mutual friction effect that results from said transverse pressure, which effect can be reinforced by clamping the ferrule onto the outside peripheral face of the cylinder by means of at least one band surrounding the ferrule coaxially and placed under circumferential tension, supposing that such a band is technically feasible, in particular given the conditions under which the pipe or the like is to be installed. 
   Under such circumstances, and contrary to that which happens in the case of a female endpiece made in accordance with the teaching of U.S. Pat. No. 5,180,196, the band is merely optional and does no more than supplement, if necessary, a natural tendency of the ferrule that is placed in a state of circumferential elastic tension on the outside peripheral face of the cylinder to press elastically against said outside peripheral face, tending to establish mutual sealing and, where appropriate, mutual fastening. Thus, for a pipe or the like in accordance with the invention, instead of the ferrule and the band acting against each other in this respect, they become complementary, and the magnitude of the pressure which the band must apply to the ferrule in order to achieve a required magnitude of transverse contact pressure between the ferrule and the outside peripheral face of the end of the cylinder can remain considerably lower than with a pipe or the like in accordance with the teaching of the above-cited American patent. 
   Such a pipe of the invention can be made by a method including an initial step consisting in prefabricating a female end ring itself characteristic of the invention, presenting a longitudinal axis and constituting:
         firstly a longitudinal ferrule defined in particular by a longitudinal inside peripheral face; and   secondly a longitudinal skirt situated axially in line with the ferrule,       

   the ring being characterized in that the ferrule is elastically expandable circumferentially. 
   This method, likewise characteristic of the present invention, is itself characterized in that it comprises the following succession of steps: 
   a) prefabricating the cylinder independently of the ring, the ring being in accordance with the present invention and being dimensioned in such a manner that, at a determined longitudinal distance from the transition between the ferrule and the skirt, and in the absence of the ring being expanded circumferentially, said inside peripheral face presents transverse dimensions that are smaller than those presented by said outside peripheral face at the same longitudinal distance from said front face, but sufficiently close thereto to be capable of being increased to said dimensions by putting the ferrule under circumferential elastic tension; and 
   b) engaging the ferrule coaxially on the annular end of the cylinder to a determined relative position in which said transition coincides longitudinally with said front face, and fastening the ferrule to the cylinder in said determined relative position by placing said ferrule in a state of circumferential elastic tension providing sealing relative to said outside peripheral face by said inside peripheral face applying thereto transverse pressure that is distributed circumferentially in continuous manner. 
   When the above-specified conditions are satisfied for said circumferential elastic tension being such that said inside peripheral face is fastened to said outside peripheral face at least in part by a mutual friction effect resulting from said transverse pressure, then this effect can be reinforced by banding the ferrule in said determined relative position. 
   Step b) can be implemented by engaging the ring via its ferrule coaxially and by force on the annular end of the cylinder. This operation can be made easier if, respectively during the initial step and during step a), the ring and the cylinder are prefabricated in such a manner that said outside peripheral face and/or said inside peripheral face flare relative to their respective longitudinal axes in the longitudinal direction going away from said front face and relative to the transition between the ferrule and the skirt, respectively, preferably ensuring that the outside peripheral face is flared to a greater extent that said inside peripheral face relative to the respective longitudinal axes, thus enabling the engagement to be made progressive. It is also possible to facilitate such engagement by interposing a lubricant between said inside and outside peripheral faces in order to facilitate this operation. 
   The presence of such a lubricant nevertheless suffers from reducing the effect of mutual fastening by friction that can result from the circumferential elastic tension of the ferrule, and it is preferable to implement step b) in a manner that is characterized in that coaxial engagement of the ferrule on the annular end of the cylinder during step b) is facilitated by placing the ferrule in a state of circumferential expansion greater than that which corresponds to said state of circumferential elastic tension, until said relative position has been reached, and in that the ferrule is allowed to leave said state of circumferential expansion so as to allow said transverse pressure to be established once said relative position has been reached. 
   For example, the ferrule is placed in said state of circumferential expansion by means selected from the group comprising mechanical means and thermal means. 
   Various dispositions can be adopted to increase the mutual sealing effect, and where appropriate, the mutual fastening, that is obtained by applying the inside peripheral face of the ferrule under transverse pressure against the outside peripheral face of the cylinder. 
   In particular, provision can be made for said inside peripheral face to present at least one continuous annular portion in relief providing sealing relative to said outside peripheral face, being in a state of elastic and/or plastic transverse compression thereagainst, and formed integrally with the ferrule. 
   In particular, when said outside peripheral face and/or said inside peripheral face flare in the longitudinal direction going away from said front face and relative to the transition between the ferrule and the skirt, in particular for the purpose of making it easier to put the ferrule into place on the cylinder, at least one portion of said continuous annular relief can advantageously be provided to be present in the form of a rib. 
   The term “rib” is used herein to mean a portion in relief that is solid in shape when seen in section on a plane that contains the axis, and in particular a portion in relief formed by a step in the inside peripheral face of the ferrule and suitable for working essentially in compression against the outside peripheral face of the cylinder in order locally to increase the transverse mutual contact pressure between the inside peripheral face of the ferrule and the outside peripheral face of the cylinder around a continuous ring in order to improve relative sealing between them, and in opposition to a sealing lip which would operate for this purpose essentially in bending by having a long thin shape when seen in section on a plane containing the axis of the cylinder. 
   A person skilled in the art will readily understand that the presence of at least one continuous annular sealing portion in relief on the inside peripheral face of the ferrule can also increase the effect whereby the ferrule is fastened to the cylinder, when the above-specified conditions are satisfied for ensuring that the inside peripheral face of the ferrule is fastened to the outside peripheral face of the cylinder, at least in part, by a mutual friction effect. 
   Nevertheless, whether as a supplement or as a replacement, and if the transverse pressure between the inside peripheral face of the ferrule and the outside peripheral face of the cylinder is insufficient on its own to guarantee mutual fastening, provision can be made for said inside peripheral face to be fastened to said outside peripheral face by annular adhesive between them, in particular continuously annular adhesive, thus also improving mutual sealing. 
   A preferred implementation of the method of the invention for this purpose is characterized in that between steps a) and b), a ring of adhesive, in particular a continuous ring, is deposited on a localized zone of said outside peripheral face and/or of said inside peripheral face selected in such a manner that when implementing step b) and thereafter said zone constitutes a zone of mutual contact via said adhesive and of application of said transverse pressure. 
   To further improve the sealing, it is also possible to provide that the pipe or the like of the invention has at least one continuous ring of a plastic sealing material interposed between said inside peripheral face and said outside peripheral face. 
   A preferred implementation of the method of the invention for this purpose is characterized in that between steps a) and b), at least one continuous ring of plastic sealing material is placed on said outside peripheral face and/or said inside peripheral face, and in that during step b), said plastic sealing material between said inside peripheral face and said outside peripheral face is caused to be flattened and/or to creep. 
   For these same purposes of improving sealing, it is also possible to provide for the pipe or the like of the invention to include an annular sealing gasket of elastically compressible material interposed in elastic transverse compression stress between said inside peripheral face and said outside peripheral face, at least in the immediate vicinity of said front face. 
   A preferred implementation of the method of the invention, for this purpose, is characterized in that between steps a) and b), a sealing gasket of elastically compressible material is put into place on said outside peripheral face at least in the immediate vicinity of said front face, and in that during step b), said gasket is put into elastic transverse compression stress between said inside peripheral face and said outside peripheral face. 
   Preferably, said outside peripheral face presents an annular setback occupying at least the immediate vicinity of said front face, and said gasket is received over a fraction of its transverse dimension in said setback. 
   This makes it possible to provide effective retention of the sealing gasket on the outside peripheral face of the cylinder, in particular before and during installation of the ferrule thereon, and for the sealing gasket to benefit from greater thickness, thereby increasing its mechanical strength particularly in shear between the outside peripheral face of the cylinder and the inside peripheral face of the ferrule, and leaving room for a greater elastic compression stroke which is favorable to matching the sealing gasket specifically to the surface state of the outside peripheral face of the cylinder, thereby improving sealing. The localized setback in the outside peripheral face of the annular end of the cylinder is advantageously made during prefabrication thereof, in step a) of the method of the invention, and said gasket is put into place between steps a) and b), being received over a fraction of its transverse dimension in said setback. 
   Nevertheless, said gasket can advantageously be in the form of a film, and in particular a film which extends from said front face over a longitudinal dimension that is less than the longitudinal dimension respectively of said outside peripheral face and of said inside peripheral face. 
   To increase the mutual fastening between the ferrule and the cylinder, the inside peripheral face of the ferrule can be fastened to the film constituting the sealing gasket by means of annular adhesive between them, in particular adhesive occupying a continuous annulus, thus also improving relative sealing. To this end, between steps a) and b) of the method of the invention, and after said film has been put into place, a ring of adhesive, in particular a continuous ring, is deposited on a localized zone of said film and/or of said inside peripheral face which is selected in such a manner that when implementing step b) and thereafter said zone constitutes a zone of mutual contact through said adhesive, and of application of said transverse pressure. 
   Advantageously, if the ferrule of the ring is put into place on the cylinder by progressive forced coaxial engagement of the ferrule on the annular end of said cylinder, the adhesive used for fastening the inside peripheral face of the ferrule with the above-mentioned film and/or for fastening the inside peripheral face of the ferrule with the outside peripheral face of the cylinder is advantageously selected in such a manner that, when in the fresh state, it constitutes a lubricant making said progressive forced engagement easier, while nevertheless being suitable subsequently for providing the desired mutual fastening. 
   The above-cited film for constituting a sealing gasket between the outside peripheral face of the cylinder and the inside peripheral face of the ferrule can be placed in such a manner that its thickness at rest is substantially constant, or else in such a manner that it presents at least one continuous annular bulge spaced longitudinally from said front face by a distance that is less than the longitudinal dimension respectively of said outside peripheral face and said inside peripheral face, and leading to a longitudinally localized increase in said tension and in said pressure. 
   This continuous annular bulge can advantageously correspond to a continuous annular groove in the inside peripheral face of the ferrule, and in particular the hardness and the dimensions of said continuous annular bulge can be selected and step b) can be implemented in such a manner that in the determined relative position said continuous annular bulge causes said corresponding continuous annular groove to be formed in the inside peripheral face of the ferrule, in particular by localized plastic deformation thereof. In particular, under such circumstances, step b) is implemented by placing the ferrule in a state of excess circumferential expansion so as to make it easier to engage coaxially on the annular end of the cylinder until their final determined relative position is reached, in which position the ferrule is allowed to leave this state of excess circumferential expansion and establish the transverse pressure that provides relative sealing as described above, and it is during this reduction in the circumferential expansion of the ferrule that, by pressing its inside peripheral face against the bulge of the film forming the sealing gasket that the ferrule is subjected, on coming into contact with said bulge, to localized plastic deformation which gives rise to a continuous annular groove in correspondence with said bulge. 
   Preferably, in order to facilitate stopping coaxial engagement of the ferrule on the annular end of the cylinder during step b) in the determined relative position, the ring presents internal longitudinal stop means for engaging said front face at the transition between the ferrule and the skirt, said means projecting transversely relative to said inside peripheral face. Under such circumstances, during step b), coaxial engagement of the ferrule on the annular end of the cylinder is stopped when the longitudinal stop means come into abutment against said front face in register with which the stop means remain positioned once the pipe has been completed. The same stop means can be used as a longitudinal abutment for the male endpiece providing they also project transversely relative to a longitudinal inside peripheral face of the skirt. 
   The stop means can present a variety of shapes, and in particular they can consist in localized projections regularly distributed angularly around the axis, however in a preferred embodiment these stop means comprise a circumferentially continuous transverse annulus of uniform longitudinal dimension. Such an annulus stiffens the ring locally against any increase in its radial and circumferential dimensions, thus contributing to maintaining the circumferential elastic tension state of the ferrule and the transverse pressure between the inside peripheral face of the ferrule and the outside peripheral face of the annular end of the cylinder once the pipe has been made, i.e. to maintaining the mutual sealing effect and, where applicable, the mutual fastening effect, while also providing at least approximate control over the transverse dimension of the skirt, i.e. control within tolerance limits that are acceptable. 
   The abutment means can be used to retain the film forming the sealing gasket if, between steps a) and b), a transverse annular rim of said film is formed on said front face of the annular end of the cylinder, in which case, during step b), coaxial engagement of the ferrule of the ring on the annular end of the cylinder is stopped when the longitudinal stop means come into abutment against said front face via said rim, which retains this function as an intermediary through which pressure is applied once the pipe has been completed. 
   Naturally, when assembling a plurality of pipes or the like in accordance with the invention by engaging a male endpiece of one coaxially in the skirt of the female end ring of another, it is necessary for said ring to be placed in sealing relationship not only with the pipe or the like of which it forms a part, but also with the male endpiece of the other pipe or the like. 
   To this end, provision can be made to mount a sealing gasket on the male endpiece prior to engaging it in the female endpiece, however it is preferable for the ring to be made in such a manner that its skirt is shaped on the inside specifically to receive and to retain at least one transverse annular gasket providing sealing relative to the male endpiece, and during step a) on manufacture of the ring, or subsequent to step b), e.g. on the site where pipes or the like are being installed, at least one transverse annular gasket is secured to the skirt on the inside thereof to provide sealing relative to the male endpiece. 
   When it is feared that mutual fastening between the ferrule of the ring and the annular end of the cylinder by a mutual friction effect resulting from the inside peripheral face of the ferrule pressing transversely on the outside peripheral face of the annular end and/or from adhesive between the inside peripheral face of the ferrule and the outside peripheral face of the annular end and/or from a sealing film between said faces and/or from locking a continuous annular groove in the inside peripheral face of the ferrule onto a continuous annular bulge of said film will not be sufficient, then those various means of providing mutual fastening can be supplemented or replaced by other means. 
   One such means consist in transverse pins regularly distributed circumferentially for fastening the ferrule to the cylinder after step b), and another consists in mutual snap-fastening. 
   To this end, the female end ring is made in such a form that the ferrule presents at least one catch projecting transversely relative to the inside peripheral face of the ferrule in the immediate vicinity of said edge, e.g. a plurality of such catches that are circumferentially localized and regularly distributed circumferentially, all occupying the same longitudinal position. Then, during step a), the cylinder is prefabricated in such a manner as to present at least one depression in said outside peripheral face for receiving said catch at a longitudinal distance from said front face that corresponds to the longitudinal distance between said catch and the transition between the ferrule and the skirt, there being at least one such catch, and step b) of progressively coaxially engaging the ferrule by force on the annular end of the cylinder is implemented by pressing said at least one catch on said outside peripheral face, thereby elastically deforming the ring increasingly, and then enabling the catch(es) to engage in said at least one depression by elastic return once said determined relative position has been reached so as to retain the ferrule longitudinally on the cylinder in said determined relative position after the pipe has been completed. Preferably, during step a), said depression is made in the form of a transverse annular groove in the outside peripheral face of the cylinder, so that the relative angular orientation of the ring and the cylinder about their common axis is immaterial while they are being engaged coaxially in step b), however it would also be possible to provide for each catch to be associated with a respective localized depression. 
   Given that making a pipe of the invention, in particular using the method of the invention, makes use of a female end ring of special design, the present invention also extends to such a female end ring, presenting a longitudinal axis and constituting:
         firstly a longitudinal ferrule defined in particular by a longitudinal inside peripheral face; and   secondly a longitudinal skirt situated axially in line with the ferrule,   the ring being characterized in that the ferrule is elastically expandable circumferentially.       

   The ring can also present the preferred characteristics mentioned above with respect to the pipe or the like or the method of manufacturing it; 
   In addition, the ferrule and the skirt are preferably of respective shapes and transverse dimensions suitable for enabling a plurality of rings to be releasably nested coaxially one in another by mutual coaxial engagement of the ferrule of one ring with the skirt of another. This makes it possible to store female end rings in a minimum amount of space while waiting for assembly to concrete cylinders, in order to make pipes or the like in accordance with the invention. 

   
     DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages of the various aspects of the invention appear in the following description relating to a few non-limiting implementations, and also from the accompanying drawings which form an integral portion of the description. 
       FIG. 1  is an axial view of a female end ring of the invention as seen by its ferrule in a direction referenced by an arrow I in FIG.  2 . 
       FIG. 2  is a view of the ring in section on a plane containing its axis, such as the plane referenced II—II in FIG.  1 . 
       FIG. 3  shows a detail of the skirt referenced III in FIG.  2  and on a much larger scale than that of FIG.  2 . 
       FIG. 4  shows mutual coaxial nesting of a plurality of female end rings of the invention waiting to be mounted on a concrete cylinder for the purpose of making a pipe or the like in accordance with the invention, the rings being shown in section on a plane that contains their axis which is then common. 
       FIGS. 5  to  8  show respectively the state of a female end ring and the annular end of the tube immediately prior to their being assembled together, their assembled state, their state after a sealing gasket has been placed inside the skirt of the female end ring facing a male endpiece, and their state after such a male endpiece has been inserted in the female endpiece constituted by the skirt of the female end ring, all shown in section on a common plane containing the then common axis of the female end ring, of the annular end of the cylinder, and in  FIG. 8 , of the male endpiece. 
       FIGS. 9 and 10  show two variant ways of assembling the ferrule of the female end ring with the annular end of the cylinder, in views corresponding to that of  FIG. 5  except that they have added thereto in part and in chain-dotted lines a representation of the ferrule in a state corresponding to that of FIG.  6 . 
       FIG. 11  shows another variant assembly of the ferrule with the annular end of the cylinder, in a view analogous to that of  FIG. 7  except that the male endpiece is represented diagrammatically in a position corresponding to that of FIG.  8 . 
       FIGS. 12  to  17  are perspective views showing various stages in assembling the female end ring with the help of means for temporarily holding its ferrule with excessive circumferential expansion on the annular end of the cylinder, the assembly thus achieved between the female end ring and the cylinder, and the subsequent assembly performed on a male endpiece. 
       FIGS. 18 and 19  are views corresponding respectively to those of  FIGS. 5 and 8  showing a variant embodiment of the ferrule of the female end ring and a variant implementation of the sealing between the female end ring and the annular end of the cylinder. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   These figures show the invention implemented by making a female endpiece for a pipe in order to provide a leakproof assembly with a male endpiece of another pipe, however a person skilled in the art will readily understand that the present invention can be applied whenever it is necessary mutually to engage in leakproof manner two ducts or other building elements analogous to pipes, in particular those listed in the introduction by way of non-limiting example. 
   In addition, although the present invention is described below for pipes and female end rings that are both bodies of revolution about a common axis, the invention can also be applied when the pipes or the like present shapes other than being bodies of revolution about their axes, and it comes within the normal aptitudes of a person skilled in the art to adapt the dispositions described below in any manner necessary wherever appropriate. 
   Insofar as the various implementations of the invention shown in the figures are very analogous to one another, the same numerical references are used to designate elements which correspond from one embodiment to another, specifically: 1 designates the pipe of the invention, 2 its cylinder of tubular shape, in this case a rectilinear cylinder, 3 an annular end thereof, 4 a female end ring of the invention integral with a ferrule  5  for leakproof connection to the annular end  3  of the cylinder  2  and with a skirt  6  forming a female endpiece for the pipe  1 ,  7  a male endpiece of another pipe  8 , which male endpiece  7  is engaged in leakproof manner in the skirt  6  forming the female endpiece of the pipe  1 , and  9  a longitudinal axis about which the cylinder  2 , in particular its annular end  3 , the ring  4 , in particular its ferrule  5  and its skirt  6 , and the pipe  8 , in particular its male endpiece  7  are respective bodies of revolution. In the description below, this axis  9  constitutes the reference for concepts of “axial” or “longitudinal” direction, of “radial” or “transverse” direction, and of “circumferential” direction, and also as a reference for any derived concepts. Similarly, it is considered that an “inside” periphery covers any face looking towards the axis  9 , an “outside” periphery covers any face looking away from the axis, while the term “frontal” designates any transverse face, whether it is a face of the cylinder  2 , of the pipe  1 , of its female end ring  4 , or of the pipe  8 . 
   In accordance with one of the aspects of the present invention, the ring  4  and the cylinder  2  are prefabricated separately by molding the cylinder  2  out of concrete and by molding the female end ring  4  as a single piece of synthetic material, e.g. polypropylene, or as a single piece of metal, e.g. stainless steel, or indeed by making it as an assembly of a plurality of pieces of metal, these examples of materials and methods of manufacture not being limiting in any way. 
   As manufactured and as it remains without modification after being assembled with the ferrule  5 , the cylinder  2  is defined over its entire longitudinal dimension, and in particular at its annular end  3 , by a circularly cylindrical inside peripheral face  10 . At the annular end  3 , this inside peripheral face  10  connects with a circularly annular front face  11  that is plane and perpendicular to the axis  9 , connecting the inside peripheral face  10  in a direction going away from said axis  9  to an outside peripheral face  12  which is circularly frustoconical, flaring in longitudinal direction  13  away form the front face  11 , forming an angle relative to the axis  9 , which angle is not referenced but is of the order of a few degrees, e.g. 3.5°, this figure nevertheless merely constituting a non-limiting example. In the direction  13 , the face  12  is connected to a main outside peripheral face  15  of the cylinder  2  by a plane transverse annular shoulder  14  facing in the direction opposite to the direction  13 , which peripheral face  15  is circularly cylindrical and extends in the direction  13  for example as far as a male endpiece of the pipe  1 , which male endpiece is not shown but can be identical to the male endpiece  7  of the pipe  8 . 
   Preferably, as shown, the face  12  connects to the face  11  via a circularly annular chamfer  16 . In addition, in the immediate vicinity of its connection with the front face  11 , i.e. at the chamfer  16  and over a portion of its longitudinal extent going away from the connection, i.e. from the chamfer  16 , e.g. over about half its longitudinal dimension between the front face  11  and the shoulder  14 , the face  12  preferably presents an annular setback  17  preferably made during prefabrication of the cylinder  2  and designed to receive a sealing gasket  18  between the annular end  3  of the cylinder  2  and the ferrule  5  of the ring  4 . In the example shown in  FIGS. 5  to  7 , this sealing gasket  18  implemented in the form of a film of elastically compressible sealing material. e.g. a synthetic rubber having hardness of about 60 DIDC, this material and this hardness being given purely by way of non-limiting example, having a thickness or about 1.7 millimeters (mm) in the absence of compression, this figure likewise being given purely by way of non-limiting example, and the setback  17  is defined by a wall  19  having the same cone angle as the face  12  and set back from it by about half the above specified thickness of the gasket or film  18  relative to a geometrical extension  20  of the face  12  from the chamfer  16  to a transverse annular shoulder  21  connecting with the remainder of the face  12 , which shoulder  21  is plane, perpendicular to the axis  9 , and faces in the direction opposite to the direction  13 . Opposite said shoulder  21 , i.e. going away from it in the direction opposite to the direction  13 , the wall  19  of the setback  17  connects directly with the chamfer  16 ; correspondingly, and preferably, the film constituting the gasket  18  is dimensioned in such a manner that once it has been put into place on, the wall  19  of the setback  17  so that it is in a state of circumferential elastic extension, it extends in the direction opposite from the direction  13  from the shoulder  21  to the chamfer  16  and goes round the chamfer so as to form a transverse annular rim on the front face  11  over at least a fraction of the radial extent thereof from the chamfer  16  and going no further than the connection between said front face  11  and the face  10 , the gasket fitting closely to the wall  19  of the setback  17 , to the chamfer  16 , and to the corresponding portion of the front face  11 , and projecting by about half its thickness relative to the geometrical extension  20  of the face  12  between the shoulder  21  and the chamfer  16  in the absence of any elastic compression being applied to said gasket or film  18 . 
   The sealing film or gasket  18  is thus put into place on the annular end  3  of the cylinder  2  prior to putting the ring  4  into place via its ferrule  5  on said annular end  3 . 
   The female end ring  4  is prefabricated in a shape that can be seen in  FIGS. 1  to  5  and which is described below. This shape is that in which the ring  4  is in its rest state, i.e. before it has been subjected to any stress extending it radially and circumferentially, it being understood that securing it to the annular end  3  of the cylinder  2  causes its ferrule  5  to pass to a state in which it is elastically extended circumferentially and radially while the skirt  6  retains at least approximately its rest shape and dimensions. Nevertheless, the ferrule  5  and the skirt  6  are oriented longitudinally and are situated at least approximately longitudinally in line with each other in both states, and they are cantilevered respectively in the direction  13  and in the direction opposite to the direction  13  from a transition  22  between them, which transition forms a circular annulus. 
   Going from the transition  22 , the ferrule  5  is defined by inside and outside peripheral faces respectively  23  and  24  which are connected to each other in the direction  13 , i.e. longitudinally going away from the transition  22  along a free edge  25  that constitutes a circular annulus. Similarly, going away from the transition  22 , the skirt  6  is defined by inside and outside peripheral faces  26  and  27  which extend in the direction opposite to the direction  13  away from the transition  22  to a free edge  28  that is a circular annulus and that is thus longitudinally opposite from the transition  22 . 
   Considering the ferrule  5  in the rest state, as shown in  FIG. 5 , its outside peripheral face  24  is substantially a circular-cylinder, it being understood that it could present a small amount of circular conicity converging in the direction  13  so as to make unmolding easier if the ring  4  is made as a one-piece molding. Likewise with the ferrule  5  in the rest state, the inside peripheral face  23  is in the form of a circular truncated cone which diverges in the direction  13  so as to form an angle (not referenced) relative to the axis  9  which is smaller than the angle formed by the outside peripheral face  12  of the annular end  3  of the cylinder  2  relative to the same axis  9 , being, for example, about 2.5° when the other angle is about 3.5°, these figures being given purely as non-limiting examples. In addition, the ferrule  5  is dimensioned in such a manner that in the rest state, at a longitudinal distance determined by the transition  22 , its inside peripheral face  23  presents transverse dimensions that are smaller than those presented by the outside peripheral face  12  of the annular end  3  of the cylinder at the same longitudinal distance from the front face  11 , but sufficiently close thereto to allow them to be expanded to match, and preferably even further, by putting the ferrule  5  under circumferential elastic tension; when the face  12  presents a setback  17 , the dimensions to be taken into consideration for the above relationship between the dimensions of the inside peripheral face  23  and the dimensions of the outside peripheral face  12  are the dimensions of the geometrical extension  20  of the face  12  where it overlies the setback  17 ; in addition, in the presence of a rim of the sealing film or gasket  18  on the front face  11  of the annular end  3  of the cylinder  2 , the longitudinal distance that should be taken into account concerning the face  12  needs to include the thickness of the rim in question, i.e. this distance should be measured not from the front face  11  itself, but from the front end of the film or gasket  18  in the direction opposite from the direction  13 ; naturally, it is generally possible to ignore this thickness of the rim of the film or gasket  18  because this thickness is relatively small and because of the conical shape of the faces  12  and  23 , with the longitudinal distance in question being measured from the front face  11  in the direction  13 . 
   The inside peripheral face  23  can be smooth, but to improve a subsequent effect of the ferrule  5  anchoring on the face  12 , and where appropriate on the sealing film or gasket  18 , it is preferable for it to have the shape shown in  FIG. 3  whereby said face  23  presents at least one and preferably a plurality of continuous annular portions in relief  29  that are elastically and/or plastically compressible in a transverse direction, and that are integrally formed with the ferrule  5 , e.g. being present in the form of ribs. 
   Each of these ribs, defined as specified in the introduction and thus forming a localized projection towards the axis  9  from a geometrical extension  30  of the face  23  in the vicinity thereof, is defined, for example, by a transverse annular shoulder  31  facing in the direction  13  and connected to the remainder of the face  23  going away from the axis  9  by a circularly cylindrical annular flank  32 , or for unmolding purposes if the ring  4  is made by molding, circularly frustoconical, forming relative to the axis  9  an angle that is smaller than the angle of the remainder of the face  23 , said flank  32  connecting the shoulder  31  in its zone closest to the axis  9  to the remainder of the face  23  in the direction opposite to the direction  13 . When such ribs or other continuous annular portions in relief  29  are provided in this way, the dimensions to be taken into account for the inside peripheral face  23  when performing the above comparison with the dimensions of the outside peripheral face  12  of the annular end  3  of the cylinder  2  or of the geometrical extension  20  of said face  12  are the dimensions of the face  23  ignoring the ribs or other portions in relief  29 , and of the geometrical extension  30  of said face  23  where the ribs or other portions in relief  29  are located. 
   Going away from the transition  22 , the inside peripheral face  23  and the outside peripheral face  24  extend over a longitudinal dimension that is not greater than and that is preferably less than the dimension of the face  12  measured between the shoulder  14  and the front face  11 , or where appropriate the limit in the direction opposite to the direction  13  of the rim of the sealing gasket or film  18 , but greater than the longitudinal distance between the shoulder  21  of the face  11  or the above-specified limit of the rim of the sealing gasket or film  18 . At the free edge  25 , the inside and outside endpiece faces  23  and  24  are connected together by a circularly annular chamfer  33  presenting longitudinal dimensions that are negligible compared with the longitudinal dimensions of the faces  23 ,  24 , and  12 . 
   At the transition  22  between the ferrule  5  and the skirt  6 , the corresponding outside peripheral faces  24  and  27  connect together directly, whereas the corresponding inside peripheral faces  23  and  26  preferably connect together as shown via a circularly transverse annulus  34  that is circumferentially continuous, presenting a longitudinal dimension or thickness that is uniform and that projects towards the axis  9  from the two inside peripheral faces  23  and  26 . 
   More precisely, the annulus  34  is defined both in the direction  13  and in the opposite direction by respective plane circular annular front faces  35  and  36  perpendicular to the axis  9  and connected respectively to the inside peripheral face  23  and to the inside peripheral face  26  going away from said axis  9 . Going towards the axis, these faces  35  and  36  are connected together via an inside end face  37  which could be circularly cylindrical about the axis  9  but which, for unmolding purposes if the ring is made by molding, is in the form of a truncated circular cone about said axis, e.g. converging in the direction  13 ; nevertheless, the minimum diameter of this end face  37  is greater than the diameter of the inside peripheral face  10  of the cylinder  2 , and is preferably approximately identical to the minimum diameter of the rim of the sealing gasket or film  18  formed on the front face  11  at the end  3  of the cylinder  2  when such a rim is provided. 
   As explained below, the face  35  of the annulus  34  serves as an abutment for the ring  4  in the direction  13  against the front face  11  of the cylinder  2 , where appropriate via the rim of the film or gasket  18  on said front face  11 , and serves via its face  36  as an abutment against the male endpiece  7  of the other pipe  8  in the direction  13  relative to the ring  4 . It could be replaced for these two purposes by internal portions in relief circumferentially localized and distributed around the ring  4  but circumferentially spaced apart, however implementing the abutment means in the form of a continuous annulus is advantageous in stiffening the skirt  6 , i.e. in opposing deformation thereof when the ferrule  5  is subjected to circumferential radial expansion, as described below, in order to mount it on the annular end  3  of the cylinder  2 . away from the transition with the skirt  6 , the skirt is of substantially constant radial thickness substantially identical to and locally greater than the maximum thickness of the ferrule  5 , i.e. the thickness presented by the ferrule in the immediate vicinity of the transition  22 . 
   Starting from the transition  22 , i.e. the face  36  of the annulus  34 , and going in the direction opposite to the direction  13 , the inside peripheral face  26  of the skirt  6  presents a plurality of approximately circularly cylindrical segments  38 ,  39 , and  42 , ignoring the slight conical shape converging in the direction  13  for unmolding purposes if the ring  4  is made by molding. 
   The first segment  38  which connects to the base  36  in the direction  13  has a maximum diameter at its end opposite from said connection which is less than the diameter presented by the outside peripheral face  24  of the ferrule  5  at its free edge  25 , but greater than the minimum diameter of the inside peripheral face  23 , i.e. the diameter it presents where it connects with the face  35  of the annulus  34 . Longitudinally opposite from its connection with the face  36 , the segment  38  connects with a second one of the above-mentioned segments  39  via a plane annular shoulder  40  extending perpendicularly to the axis  9  and facing in the direction opposite to the direction  13 . Where it connects with said shoulder  40 , the minimum diameter of the segment  39  is greater than the diameter presented by the outside peripheral face  24  of the ferrule  5  where it connects with the free edge  25 , and longitudinally opposite from its connection with the shoulder  40 , the segment  39  connects via a circularly annular chamfer  41  to a third one of the segments  42 , which segment has a minimum diameter where it connects with the chamfer  41  that is slightly greater than the diameter presented by the outside peripheral face  24  of the ferrule  5  at a longitudinal distance from the free edge  25  that is equal to the longitudinal distance between the shoulder  40  and the chamfer  41 . Longitudinally opposite from its connection with the chamfer  41 , the segment  42  connects, via a chamfer  43  that is likewise circularly annular, to a front face  44  of the skirt  6 , which front face is a plane circular annulus extending perpendicularly to the axis  9  and facing in the direction opposite to the direction  13 , and it defines the free edge  28 . 
   Given the above-specified dimensions for the segments  38 ,  38 , and  42  of the inside endpiece face  26  of the skirt  6 , compared with the dimensions of the outside peripheral face  24  of the ferrule  5 , prefabricated rings  4  waiting to be mounted on respective cylinders can be stored in a coaxially nested state as shown in FIG.  4 . In this nested state, the ferrule  5  of one ring  4  is engaged in the direction  13  inside the skirt  6  of another ring  4  that is identical and that follows it in the direction  13 , and this takes place under conditions such that the free edge  25  of the first ring  4  bears in the direction  13  against the shoulder  40  of the second ring  4  and the segment  42  of the inside peripheral face  26  thereof by forming a transverse abutment for the outside peripheral face  24  of the ferrule  5  engaged in this way prevents the rings  4  from becoming mutually misaligned. Storage can be performed with the coinciding axes  9  either horizontal or vertical, e.g. by stacking nested rings  4 , with the bottom ring  4  resting on the ground or on a pallet via the face  44  of its free edge  28 . 
   It will be observed that because of the simplicity of the shapes of the inside peripheral face  26  of the skirt  6 , the undercut formed by the chamfer  41  between the segments  39  and  42  does not impede manufacture by molding using techniques well known to molders, it being understood that it could also be obtained by machining to finish off the ring  4  as a final manufacturing step. 
   Going radially away from the axis  9 , the front face  44  connects the chamfer  43  to the outside peripheral face  27  of the skirt  6 , which outside peripheral face  27  presents, like the inside peripheral face  26 , three approximately circular cylindrical segments about the axis  9 , but if it is manufactured by molding these segments taper slightly, converging in the direction  13 , these three segments being referenced  46 ,  47 ,  48  and following one another in the direction  13  going away from the face  44 , and corresponding essentially in a radial direction respectively to the segment  42 , to the segment  39 , and to the segment  38 . 
   At the transition  22 , the minimum diameter of the segment  48  is greater than the maximum diameter presented by the outside peripheral face  24  of the ferrule  5  at said transition  22 , and it connects to the outside peripheral face  24  of the ferrule  5  via a circularly frustoconical chamfer  49  converging in the direction  13 . The slope of the segment  48  relative to the axis  9  is substantially identical to that of the segment  38  such that the thickness of the skirt  6  between the segments  38  and  48  is approximately constant, and the same applies to the segments  47  and  39 . The minimum diameter of the segment  47  is at its junction with the segment  48  in the direction  13 , and these two segments  47  and  48  are connected together via a circularly frustoconical chamfer  50  which corresponds to the shoulder  40  and which is located relative thereto in such a manner as to maintain substantially constant thickness for the skirt  6 . 
   In contrast, in the immediate vicinity of the free edge  28  of the skirt  6 , the segment  46  and the segment  42  form extra thickness increasing the second moment of area of the skirt  6  for opposing radial and circumferential elastic expansion thereof, and for this purpose the segment  46  presents a minimum diameter where it connects with the segment  47  that is greater than the maximum diameter presented by the segment  47  where it connects with the segment  46 , and these two segment  47  and  46  are connected together via a plane circularly annular shoulder  51  extending perpendicularly to the axis  9  and facing in the direction  13 . 
   Once the cylinder  2  and the ring  4  presenting the above characteristics have been manufactured, and where appropriate after the sealing gasket or film  18  has been put into place on the cylinder  2  in the manner described above, manufacture of the pipe  1  is terminated by engaging the ferrule  5  of the ring  4  coaxially onto the annular end  3  of the cylinder  2  in the direction  13  up to a determined relative position as shown in  FIG. 6  where the transition  22  between the ferrule  5  and the skirt  6  coincides longitudinally with the front face  11 , and more precisely where the face  35  of the annulus  34  comes into abutment in the direction  13  against said face  11 , where appropriate via the rim of the film or gasket  18  on said face  11 . 
   Given the dimensional characteristics of the inside peripheral face  23  of the ferrule  5  relative to those of the outside peripheral face  12  of the annular end  3  of the cylinder  2 , including the sealing gasket or film  18 , if any, this coaxial engagement can be achieved by forcing the inside peripheral face  23  of the ferrule  5  against the outside peripheral face  12  of the annular end  3  of the cylinder  2 , optionally carrying the sealing gasket or film  18 , thereby progressively putting the ferrule  5  into a state of circumferential elastic tension which reaches its maximum when, relative to the cylinder  2 , it reaches the determined position in which the face  35  of the annulus  34  bears in the direction  13  against the front face  11 , possibly via the rim of the sealing gasket or film  18 . Once this determined relative position has been reached, the circumferential elastic tension in the ferrule  5  is such that via its inside peripheral face  23  it applies transverse pressure that is continuously distributed circumferentially over the face  12  alone, in the absence of the setback  17  and the sealing gasket or film  18 , or if such a sealing gasket or film  18  is present, firstly against said sealing gasket or film  18  thereby compressing it transversely, and secondly against the face  12  beyond the shoulder  21  in the direction  13 , with this transverse pressure establishing leaktightness between them, which leaktightness is increased if there are any ribs or other portions in relief  29  present, since they create additional transverse pressure around respective continuous transverse rings. 
   This radial pressure applied by the inside endpiece face  23  of the ferrule  5  against the outside peripheral face  12  of the annular end  3  of the cylinder  2  which fits closely thereagainst, and where present, the sealing gasket or film  18  against which the face  23  also fits closely and which in turn fits closely over the wall  19  of the setback  17 , can be sufficient to provide by mutual friction all or part of the fastening between the ferrule  5 , i.e. the ring  4 , and the cylinder  2 , depending on the friction coefficients relating to the various materials thus put into mutual contact, on the slopes of the faces  12  and  23  relative to the axis  9 , and on the areas of mutual contact. 
   Such conditions can be satisfied particularly when there is no need to apply lubricant between the inside peripheral face  23  and the outside peripheral face  12  and the sealing gasket or film  18  for the purpose of putting the ring  4  via its ferrule  5  into place on the end  3  of the cylinder, i.e.:
         either because mounting is performed by forced engagement in the absence of a setback  17  and a sealing gasket or film  18 ; or else   in the presence or absence of the setback  17  and the sealing gasket or film  18 , when the ring  4  is mounted using a method that is described below with reference to  FIGS. 12  to  17 .       

   When such conditions are satisfied, the effect of mutual fastening by friction between the inside peripheral face  23  of the ferrule  5  and the outside peripheral face  12  of the annular end  3  of the cylinder  2  can be reinforced by banding the ferrule  5  after it has reached the determined relative position shown in  FIG. 6 , using at least one band  91  placed coaxially around the outside peripheral face  24  of the ferrule  5 , preferably in the immediate vicinity of its free end  25 , as shown in chain-dotted lines in  FIG. 6 , and after it has been put under circumferential tension using means known to the person skilled in the art so as to increase the pressure applied via the ferrule  5  between the inside peripheral face  23  and the outside peripheral face  12 . It will be observed that this banding also has the effect of increasing leaktightness between these faces  12  and  23 . 
   In contrast, if mounting is performed by forced engagement under conditions that require lubricant to be present between the inside peripheral face  23  of the ferrule  5  and the outside peripheral face  12  of the annular end  3  of the cylinder  2  and optionally the sealing gasket or film  18 , then the fastening obtained in this way by friction can be insufficient, specifically because the lubricant continues to be present, in which case it must be complemented by suitable means, an example being described below with reference to  FIGS. 5 and 6  and other examples being described for variant embodiments of the invention with reference to  FIGS. 9 and 11 . 
   The means shown in  FIGS. 5 and 6  consist, prior to forced engagement of the ferrule  5  on the annular end  3  of the cylinder  2 , and then while said engagement is taking place, in creating a film of adhesive which, while fresh, acts as lubricant to facilitate longitudinal sliding of the face  23  over the sealing gasket or film  18 , if any, and over the outside peripheral face  12  of the annular end  3  of the cylinder  2 , and subsequently, once the limit position has been reached in which the face  35  of the annulus  34  bears in the direction  13  against the front face  11 , optionally via the rim of the sealing gasket or film  18 , the adhesive sets between the inside peripheral face  23  of the ferrule  5  and the outside peripheral face  12  of the annular end  3  of the cylinder  2  and the sealing gasket or film  18 , if any, thereby fastening the ferrule  5  with the ring  4  to the cylinder  2  and the gasket or film  18 , if any, by adhesion in the zone where they are mutually in contact. 
   So long as care is taken to ensure that such mutual adhesion takes place around a circumferentially continuous ring, it also serves to improve leaktightness. 
   In particularly advantageous manner, as shown in  FIG. 5 , the adhesive is applied prior to the ferrule  5  being engaged on the annular end  3  of the cylinder  2  in the form of a continuous ring  52  over a zone of the outside peripheral face  12  that is selected in such a manner that during forced engagement it constitutes a zone of contact with the inside peripheral face  23  of the ferrule  5 , e.g. in the immediate vicinity of the shoulder  21  when a setback  17  and a sealing gasket or film  18  are provided, or indeed in the immediate vicinity of the chamfer  16  in the absence of such a setback  17  and such a sealing gasket or film  18 . When such a sealing gasket or film  18  is provided, another continuous ring of adhesive  53  can be placed thereon in the immediate vicinity of the transition between the setback  17  and the chamfer  16 . Thus, as forced engagement progresses, the face  23  entrains the adhesive of the ring  53  and the adhesive of the ring  52  in succession so as to spread said adhesive over the sealing gasket or film  18  and over the face  12 , respectively, in the mutual contact zone while conserving the circumferential continuity of each ring of adhesive that is spread in this way. 
   In a variant, and in a manner that is not illustrated, the adhesive could also be deposited as a plurality of rings, in particular continuous rings, over the sealing gasket or film  18 , if any, and/or over the outside peripheral face  12  of the annular end  3  of the cylinder  2 , or indeed as one or more continuous annular rings on the inside peripheral face  23  of the ferrule  5  in zones suitably selected to constitute zones of mutual contact during the process of forced engagement and at the end of said process, with this preferably being done from the beginning of the process. 
   Also in non-illustrated manner, but in a manner that will easily be understood from that described above for improving leaktightness between the faces  12  and  23  by means of at least one continuous ring  52  of adhesive, said leaktightness could be improved or indeed established, e.g. in the absence of the sealing film  18 , by replacing adhesive in the provision of said ring with a plastic sealing material, commonly referred to as “compound”, which is caused to be flattened out and/or to creep between the faces  12  and  23  as the above-mentioned engagement process is taking place so that by the end of said process at least one continuous sealing ring has been formed between said faces  12  and  23 . Like the above-described adhesive, the plastic sealing material could also be disposed in at least one continuous ring on the inside peripheral face  23  of the ferrule in at least one zone selected to constitute a contact zone with the outside peripheral face  12  of the cylinder  2  during the process of forced engagement and at the end thereof. The sealing provided by the plastic sealing material can replace the sealing provided by the gasket  18  or can be additional thereto in a zone in which said gasket  18  is not interposed between the faces  12  and  23 . 
   At the end of engagement, i.e. when the annulus  34  comes into abutment via its face  35  in the direction  13  against the front face  11  at the annular end  3  of the cylinder  2 , possibly via the rim of the gasket or film  18  as shown in  FIG. 6 , the skirt  6  projects longitudinally from the front face  11  in the direction opposite to the direction  13 , thereby constituting a female endpiece  54  for the pipe  1  in line with the annular end  3  of the cylinder  2  to which the skirt  6  is fastened by means of the ferrule  5 . 
   This female endpiece  54  is intended to receive the male endpiece  7  of the pipe  8  by longitudinal engagement in the direction  13 , and as shown in FIG.  8 . 
   To this end, and relative to the shape of the skirt  6 , the male endpiece  7  presents the known shape for a male endpiece given the shape of the female endpiece in which it is to engage. It can thus present any known design. 
   In the example shown, the male endpiece  7  is integrally molded as a single piece of concrete with a cylinder  55  of the pipe  8 , which cylinder is entirely analogous to the cylinder  2  of the pipe  1  (which in turn can also present a male endpiece identical to the male endpiece  7 ), and it is located at its end longitudinally opposite from its annular end  3  having the ring  4  fitted thereon, and in like manner the cylinder  55  of the pipe  8  can be provided with a ring analogous to the ring  4  at its end longitudinally opposite from its male endpiece  7 . 
   In the example shown, and if the male endpiece  7  is assumed to be occupying a finally engaged position inside the female endpiece  54  constituted by the skirt  6 , as shown in  FIG. 8 , then the male endpiece  7  is defined towards the axis  9  by an inside peripheral face  56  common to the entire cylinder  55  and constituting a circular cylinder having the same diameter as the face  10  which is extended longitudinally in the direction opposite to the direction  13  by said face  56 . In the direction  13 , the face  56  connects to a front face  57  of the cylinder  55 , which face is a plane circular annulus perpendicular to the axis  9  and faces in the direction  13 . Radially opposite from its connection with the face  56 , the face  57  presents a maximum diameter which is intermediate between the minimum diameter of the face  36  of the annulus  34  of the ring  4 , i.e. the minimum diameter of the end face  37  of said annulus  34 , and the minimum diameter of the segment  28  of the inside peripheral face  26  of the skirt  6  of the ring  4 , so that the cylinder  55  of the pipe  8  bears flat in the direction  13  via its face  57  against the face  37  of the annulus  34 , and via said annulus and the rim of the sealing gasket or film  18 , if any, against the front face  11  of the annular end  3  of the cylinder  2  of the pipe  1 . 
   Via its greatest diameter as defined in this way, the front face  57  connects via a circularly frustoconical chamfer  58  that converges in the direction  13  to an outside peripheral face  59  of the male endpiece  7 , which face is likewise circularly frustoconical, converging in the direction  13  and forming an angle relative to the axis  9  that is of substantially the same size as the angle formed relative to said axis by the outside peripheral face  12  of the annular end  3  of the cylinder  2 . At a longitudinal distance from the front face  57  that is greater than the longitudinal distance between the front face  44  of the skirt  6  of the ring  4  and the face  36  of its annulus  34 , the outside peripheral face  59  connects via a chamfer (not referenced) to a circularly annular shoulder  60  that is plane and perpendicular to the axis  9 , facing in the direction  13 , thereby connecting the outside peripheral face  59  to a main outside peripheral face  61  of the cylinder  55  which is advantageously circularly cylindrical, having a diameter that is identical to that of the main outside peripheral face  15  of the cylinder  2  of the pipe  1 , it being possible for the two pipes  1  and  8  to be identical. 
   Various means can be provided for providing leaktightness between the male endpiece  7  and the female endpiece  54  constituted by the skirt  6 , and in particular, and in conventional manner, this can be done by mounting an annular sealing gasket on the outside peripheral face  59  of the male endpiece  7 . Under such circumstances, the segment  38  of the inside peripheral face  26  of the skirt  6  of the ring  4  can extend without discontinuity in the longitudinal direction from the face  36  of the annulus  34  to the front face  44  of the skirt  6 , and likewise the segment  48  of the outside peripheral face  27  of this skirt  6  can extend without discontinuity from the chamfer  49  to said front face  44 , the setbacks constituted by the shoulder  40  and the chamfer  41  in the face  26  being omitted as is the projection formed on the face  27  by the chamfers  50  and  51  and by the segments  46  and  47  of the outside peripheral face. 
   Such an embodiment is not shown and comes within the normal competence of a person skilled in the art concerning the above modification in the shape of the skirt  6  of the ring  4 . 
   To provide leaktightness, it is also possible for the inside of the skirt  6  to be fastened prior to longitudinal engagement on the male endpiece  7  to at least one transverse annular sealing gasket facing the male endpiece  7 . 
   Such a transverse sealing gasket can be mounted when the ring  4  is prefabricated, or as shown in  FIG. 7 , it can be mounted after the ring  4  has been fastened via its ferrule  5  on the annular end  3  of the cylinder  2  as shown in FIG.  6  and before the male endpiece  7  of the pipe  8  is engaged as shown in FIG.  8 . 
   In the example shown, only one annular sealing gasket  62  is provided inside the skirt  6 , and this annular sealing gasket  62  is fixed and held on the segment  39  of the inside peripheral face  26 , e.g. by adhesive, between the shoulder  40  and the chamfer  41  which contributes to preventing it from sliding longitudinally relative to the skirt  6  during engagement of the annular sealing gasket  62  in a circularly annular groove  63  defined as a recess in the inside peripheral face  26  by the shoulder  40 , the chamfer  41 , and the segment  39 . 
   More precisely, the sealing gasket  62  which is made of an elastically compressible sealing material such as a synthetic rubber presents a longitudinal and circularly annular sleeve  64  complementary in shape to the groove  63  so as to engage therein, and so as to enable it to be fixed to the skirt  6  of the ring  4 , e.g. by being stuck to the segment  39  of the inside peripheral face  26 , together with an annular transverse sealing portion in relief  65  projecting radially towards the axis  9  from the sleeve  64  and geometrically extending the segment  38  of the inside peripheral face  36  of the skirt  6  of the ring  4 . When the sealing gasket  62  is at rest, i.e. when it is not subjected to any stress as is the case prior to the male endpiece  7  of the pipe  8  being longitudinally engaged in the female endpiece  54  defined by the skirt  6 , this projection is of radial dimension such that during said engagement the portion in relief  65  comes into contact under pressure against the outside peripheral face  59  of said male endpiece  7 , thereby pushing back said portion in relief  65  in the direction  13  (which is the engagement direction) and compressing the portion in relief  65  against the sleeve  64 , which itself can optionally be compressed going away from the axis  9  against the segment  39  of the inside peripheral face  26  of the skirt  6  of the ring  4  so as to provide leaktightness between said skirt  4  and the male endpiece  7 . 
   The way in which the portion in relief  65  is shaped and dimensioned for this purpose is readily determined by a person skilled in the art. As a non-limiting example, the portion in relief  65  is defined in the example shown and when in the rest state as shown in  FIG. 7  by a circularly frustoconical upstream flank  66  converging in the direction  13  and forming an angle of about 45° relative to the axis  9 , and by a circularly annular downstream flank  67  which is plane and perpendicular to the axis  9 , where the concept of upstream and downstream are relative to the direction  13 . The portion in relief  65  is located approximately in the upstream half of the gasket  62  whose downstream portion is defined by the sleeve  64  which then presents an inside peripheral face  68  constituting a circular cylinder. Once the male endpiece  7  of the pipe  8  has been engaged fully in the female endpiece  54  defined by the skirt  6  of the ring  4 , i.e. once the front face  57  comes to bear flat in the direction  13  against the face  36  of the annulus  34 , as shown in  FIG. 8 , the portion in relief  65  is folded downstream against the sleeve  64  under conditions such that its face  67  is snug against the face  68 , with the assembly constituted by the portion in relief  65  and the sleeve  64  being compressed away from the axis  9  against the segment  39  of the inside peripheral face  26  of the skirt  6  of the ring  4  so as to provide leaktight sealing. Naturally, the sleeve  64  and the portion  65  of the sealing gasket  62  are circumferentially continuous for this purpose. 
   The description above with reference to  FIGS. 5  to  8  describes how the ferrule  5  of the ring  4  can be fastened to the annular end  3  of the cylinder  2  either by friction or by adhesive. 
     FIG. 9  shows a technique relying on snap-fastening, which can be in addition to or instead of the above two fastening techniques. 
   In  FIG. 9 , the various portions of the cylinder  2  and of the ring  4  as described above with reference to  FIGS. 5 and 8  are shown again identically and using the same numerical references, with the  FIG. 9  variant differing from that described with reference to  FIGS. 5  to  8  only in the additional characteristics that are described below. 
   One of these characteristics consists in the ferrule of the ring  4 , as prefabricated, presenting at least one fastening catch in relief  69  in the immediate vicinity of its free edge  25  and projecting from its inside peripheral face  23 , the catch  69  being designed to engage the outside peripheral face  12  of the annular end  3  of the cylinder  2 , and preferably being provided in the form of a plurality of catches each localized circumferentially and together distributed regularly around the circumference, and all occupying the same longitudinal position. The person skilled in the art can easily determine the number of catches  69  needed to achieve the mechanical strength required to prevent the ferrule  5  becoming detached longitudinally from the annular end  3  of the cylinder  2 . 
   In the example shown, each of these catches  69  presents on its upstream side relative to the direction  13 , a flank  70  that is plane and perpendicular to the axis  9 , and on its downstream side, a convex flank  71  presenting a section in a plane that includes the axis  9  which is curved, e.g. circularly arcuate, similar to the chamfer  33 , so that the flank  70  connects to the outside peripheral face  24  of the ferrule  5 . 
   The cylinder  2  is prefabricated in such a manner as to present a continuous transverse annular groove  72  in its outside peripheral face  12  in which the catches  69  can engage, as represented by chain-dotted lines in  FIG. 9 , once the ring  4 , on being engaged longitudinally on the cylinder  2 , reaches the determined limit position in which it comes into abutment via the face  35  of the annulus  34  against the front face  11  of the annular end  3  of the cylinder  2 , and via the rim of the sealing gasket or film  18 , if any. 
   To this end, the groove  72  is defined on the upstream side relative to the direction  13  by an annular flank  73  that is plane, extending transversely perpendicularly to the axis  9  and facing in the direction  13 , said flank  73  being situated at a longitudinal distance from the front face  11  or from the upstream limit of the sealing gasket or film  18 , if any, on said front face  11  that is substantially equal to the longitudinal distance between each of the upstream facing flanks  70  of the catches  69  and the face  35  of the annulus  34 . In addition, the groove  72  is defined by a downstream flank  74  that is likewise plane, annular, and perpendicular to the axis  8 , but faces in the direction opposite to the direction  13 , said flank  74  being spaced apart longitudinally from the flank  73  by a distance that is not less than the distance between each flank  70  and the free edge  25  of the ferrule  5  of the ring  4 , and by a circularly frustoconical bottom wall  75  having a cone angle identical to that of the outside peripheral face  12 , with said bottom wall  75  being set back therefrom by a depth that is not less than the transverse dimension of each flank  70 . 
   The ring  4  is thus mounted on the cylinder  2  by progressive forced coaxial engagement of the ferrule  5  in the direction  13  onto the annular end  3  of the cylinder  2 , possibly using a lubricant as described above, with the catches  69  pressing via their flanks  71  against the outside peripheral face  12 , and against the sealing gasket or film  18 , if any, and with the ring  4  progressing in the direction  13  relative to the cylinder  2 , thereby causing the ferrule to be increasingly deformed elastically in a radially outward direction and in a circumferential direction until the face  35  of the annulus  34  comes into abutment against the front face  11 , via the rim of the gasket or film  18 , if any. The flank  70  of each catch  69  then coincides with the flank  73  of the groove  72  and the natural tendency of the ferrule  5  to return elastically to its original shape causes the catches  69  to engage in the groove  72  until they occupy a position in which their flanks  70  bear against the flanks  73  of the groove in the direction opposite to the direction  13 , thus fastening the ferrule  5 , i.e. the ring  4 , to the cylinder  2  against separation in the longitudinal direction. 
   The person skilled in the art will readily understand that the groove  72  could be replaced by as many depressions in the outside peripheral face  12  as there are catches  69  without that going beyond the ambit of the present invention. 
   In another variant, shown in  FIG. 11 , it is also possible to fasten the ferrule  5 , i.e. the ring  4 , to the annular end  3  of the cylinder  2  by transverse pins that are regularly distributed circumferentially, e.g. by means of radial rivets  76  passing through the ferrule  5  in a zone situated beyond, in the direction  13 , the setback  17  for receiving the sealing gasket  18 , and anchored in respective blind holes pierced in the outside peripheral face  12  of the annular end  3  of the cylinder  2 . These rivets could be replaced by screws, or by any other mechanical means for directly fastening the ferrule  5  to the annular end  3  of the cylinder  2  without that going beyond the ambit of the present invention. The number of pins required for providing the required degree of fastening can readily be determined by the person skilled in the art. 
     FIG. 11  also shows a setback  17  of a shape that is different from that described with reference to  FIGS. 5  to  8 , together with an associated different shape for the sealing gasket  18  which is held in radial sealing compression against the inside peripheral face  23  of the ferrule  5  and which does not have a rim extending over the front face  11  of the annular end  3  of the cylinder  2 . Nevertheless, it should be understood that regardless of the way in which the ferrule  5  is fastened to said annular end  3 , sealing between them can be provided by any of the means described with reference to  FIGS. 3 ,  5  to  9 , and  11 , with any compatible combination between the various dispositions described and shown in the present specification being considered as coming within the ambit thereof. 
   Thus,  FIGS. 18 and 19  show a variant implementation of the present invention combining various dispositions that are described above. 
   Thus, the variant shown in  FIGS. 18 and 19  is similar to the variant shown in  FIG. 11  in that it uses a sealing gasket  18  which does not have a rim on the front face  11  of the annular end  3  of the cylinder  2 . 
   In this variant, the setback  17  is narrowly located at the junction between the front face  11  and the outside peripheral face  12  of the annular end  3  of the cylinder  2  in that its bottom wall  19  is of much smaller longitudinal size, compared with the longitudinal size of the outside peripheral face  12  than is the case in the variants described with reference to  FIGS. 5  to  10 . In contrast, the shoulder  21  which defines the setback  17  in the direction  13  presents a radial dimension greater than that which is presented in the above-mentioned variants, relative to the radial dimension (not referenced) between the outside peripheral face  12  (e.g. where it joins the shoulder  21 ) and the inside peripheral face  10  of the cylinder  2 . In the example shown, the bottom wall  19  and the shoulder  21  defining the setback  17  are both circularly frustoconical about the axis  9  (not shown in  FIGS. 18 and 19 ) and they flare in the direction  13  with the shoulder  21  flaring more than the bottom wall  19 , and the transition between the shoulder  21  and the outside peripheral face  12  of the annular end  3  of the cylinder  2  presents a diameter of substantially the same size as that of the free edge  25  of the ferrule  5  of the ring  4  when said ferrule  5  is in the rest state as shown in FIG.  18 . 
   In association with a setback  17  of this shape, the sealing gasket  18  has a “drop” shape which, when seen in section on an axial plane as is the case in  FIGS. 18 and 19 , comprises a flat zone  91  and an enlarged zone  92  respectively constituting a downstream zone and an upstream zone relative to the direction  13 . 
   The sealing gasket  18  is shaped and dimensioned in such a manner as to be mounted on the end  3  of the cylinder  2  in a state of circumferential elastic extension, and in a position in which:
         the flat zone  91  fits snugly against the marginal portion of the outside peripheral face  12  immediately adjacent to the shoulder  21 , from which said zone  19  extends in the direction  13  over a longitudinal distance that is much shorter than the longitudinal distance between the shoulders  14  and  21 , being for example about one-third of said longitudinal distance; and   the zone  92  bent towards the axis  9  relative to the zone  91  fits snugly against the shoulder  21  and at least a portion of the bottom wall  19  immediately adjacent to said shoulder  21 , thereby contributing to holding the gasket  18  against being moved in the direction  13  over the annular end  3  of the cylinder  2  while the female end ring  4  is being put into place on said end  3  under conditions that are described below, and forms an axial projection in the direction opposite to the direction  13  relative to a coplanar geometrical extension (not shown) of the front face  11  of the end  3  of the cylinder  2  when, as shown in  FIG. 18 , the female end ring  4  is not yet in place on the annular end  3  of the cylinder  2 .       

   When in the rest state as shown in  FIG. 18 , the female end ring  4  is of the shape described with reference to  FIGS. 1  to  5  except that instead of being smooth or instead of having a plurality of longitudinally distributed continuous annular portions in relief as shown in  FIG. 3 , e.g. constituted by ribs that are elastically and/or plastically compressible transversely, the inside peripheral face  23  of the ferrule  5  has only one such continuous annular portion in relief  29  that is elastically and/or plastically compressible transversely, that is integrally formed with the ferrule  5  and that is situated at a longitudinal distance from the face  35  of the annulus  34  that is greater than the longitudinal distance between the front face  11  and the downstream limit of the gasket  18  relative to the direction  13 , although shorter than the longitudinal distance between the free edge  25  of the ferrule  5  and the face  35  of the annulus  34 . More precisely, the portion in relief  29  is substantially closer, longitudinally, to the free edge  25  than to the face  35 . 
   In the example shown, this portion in relief  29  is defined by a shoulder facing in the direction  13  and interconnecting two zones that are not referenced but both belonging to the inside peripheral face  23  and that has substantially the same cone angle when the ferrule  5  is in the rest state, as shown in FIG.  18 . 
   The skirt  6  of the ring  4  is of a shape that is completely identical to that described above, and in particular it is suitable for receiving internally and retaining a gasket  62  that is identical to that described with reference to  FIGS. 7 and 8  and suitable for providing leakproofing relative to a male endpiece  7  of a cylinder  55  of a pipe  8 , e.g. one identical to the pipe  1 , under the same conditions as those described with reference to  FIGS. 7 and 8 , and as shown in FIG.  19 . 
   The ring  4  designed in this way is mounted and fastened to the end zone  3  of the cylinder  2  under conditions that are identical to those described above with reference to  FIGS. 5 and 6 , either before or after the gasket  62  has been put into place in the skirt  6 . 
   In particular, prior to engaging the female end ring in the direction  13  by force on the end zone  3  of the cylinder  2  provided with the sealing gasket  18 , respective continuous annular beads of adhesive  53  and  54  that are circular about the axis  9  are placed on an annular location of the zone  92  having a diameter approximately identical to that of the free edge  25  of the ferrule  5 , i.e. where initial contact is made between the ferrule  5  and the gasket  18  when the ferrule of the ring  4  is engaged coaxially by force on the end  3 , in the direction  13 , and at the downstream limit of said gasket  18  relative to the direction  13 , i.e. more precisely at the transition between the zone  91  of said gasket and the outside peripheral face  12  of the end zone  3  of the cylinder  2 . Thus, as the ferrule  5  of the ring  4  is progressively forced onto the end  3  in the direction  13 , the inside peripheral face  23  of the ferrule  5  entrains in succession the adhesive of the bead  53  and then the adhesive of the bead  54  and it spreads said adhesive over the zone  91  of the gasket  18  and over the portion of the outside peripheral face  12  of the end zone  3  that is progressively covered by the inside peripheral face  23  of the ferrule  5 . 
   The presence of the annular portion in relief  29  makes such spreading of the adhesive in the bead  53  and then in the bead  54  easier, making it possible initially to create a thin film of still-fresh adhesive that is continuous both in the circumferential direction and in the longitudinal direction between the inside peripheral face  23  and both the sealing gasket  18  and the outside peripheral face  12 , thereby easing relative longitudinal sliding, and then, as this adhesive sets, creating fastening that is likewise as continuous as possible both in the circumferential direction and in the longitudinal direction between the inside peripheral face  23  and both the sealing gasket  18  via its zone  91  and the outside peripheral face  12 . 
   This engagement movement of the ferrule  5  of the female end ring  4  under force over the end zone  3  of the cylinder  2  causes the zone  91  of the gasket  18  to be compressed progressively in the radial direction between the inside peripheral face  23  of the ferrule  5  which is progressively being extended elastically in the circumferential direction and the outside peripheral face  12  of the annular end  3  of the cylinder  2 , thereby providing effective sealing at the gasket, and then causes the zone  92  to be elastically compressed in the longitudinal direction between the face  35  and the shoulder  21  and the bottom wall  19  of the setback  17 , thereby also establishing sealing at this location when the face  35  of the annulus  34  of the ring  4  comes into abutment in the direction  13  against the front face  11  of the annular end  3  of the cylinder  2 , thus defining the final relative position of the ring  4  relative to the cylinder  2 , as shown in FIG.  19 . 
   In this position, the inside peripheral face  23  of the ferrule  5 , which is in a state of elastic circumferential extension, presses elastically against the outside peripheral face of the annular end  3  of the cylinder  2  in two zones, namely:
         indirectly via the zone  91  of the gasket  18  in the portion of the face  12  covered by said zone  91 ; and   directly via the annular portion in relief  29 ; and possibly also in a third zone, i.e. directly at the free edge  25 .       

   This provides particularly effective sealing between the ferrule  5  and the annular end  3  of the cylinder  2 , with this sealing being further increased by the face  35  of the annulus  34  pressing against the zone  92  of the gasket  18 . 
   The ring  4  is thus likewise fastened in particularly effective manner via its ferrule  5  to the annular end  3  of the cylinder  2 , both because of the presence of the adhesive and because of the mutual compression in a direction that is approximately radial relative to the axis  9 . 
   The person skilled in the art will readily understand that other variations in implementation and relative positioning of the female end ring  4 , of the sealing gasket  18 , and of the annular end of the cylinder  2 , are all possible without thereby going beyond the ambit of the present invention, in particular by combining various ones of the dispositions described and shown above. 
   Thus, although the ferrule  5  is described with reference to  FIGS. 5  to  9 ,  11 ,  18 , and  19  as being mounted on the annular end  3  of the cylinder  2  by progressive forced engagement, generally with an interposed lubricant which can advantageously be constituted by an adhesive that subsequently contributes to mutual fastening and leakproofing, it is also possible for the ferrule  5  of the ring  4  to be subjected temporarily to radial and circumferential elastic expansion while it is being engaged coaxially on the annular end  3  by using means other than pressing against the outside peripheral face  12  of said annular end  3  and of the sealing gasket or film  18 , if any, for the purpose of making such forced engagement easier or even for replacing it with mere mutual engagement without compression and consequently without friction between the inside peripheral face  23  of the ferrule  5  of the ring  4  and the outside peripheral face  12  of the annular end  3  of the cylinder  2 , and of the sealing gasket or film  18 , if any, with the ferrule  5  subsequently being allowed to return to a state in which it applies such mutual compression only after it has reached the limit position in which the face  35  of the annulus  34  bears flat in the direction  13  against the front face  11  of the annular end  3  of the cylinder  2 , and via the rim of the sealing gasket or film  18 , if any. 
   Such an implementation presents the advantage of making it possible to omit any lubricant between the inside peripheral face  23  of the ferrule  5  of the ring  4  and the outside peripheral face  12  of the annular end  3  of the cylinder  2 , and the sealing gasket or film  18 , if any, consequently encouraging mutual fastening by friction, possibly without adding any additional fastening means. 
   To this end, it is possible to heat the ring  4  so as to cause it to expand thermally on a temporary basis, and to remove heating once the ring has reached its limit position for longitudinal engagement on the annular end  3  of the cylinder  2 , and this can be sufficient when the outside peripheral face  12  of the annular end  3  of the cylinder  2  and of the sealing gasket or film  18 , if any, and when the ferrule  5  of the ring  4  have the shape described with reference to  FIGS. 3 ,  5  to  8 , or  9 , and concerning the sealing gasket  18 , the shape described with reference to FIG.  11 . It is also possible to use mechanical means for this purpose, using a method which is described with reference to  FIGS. 12  to  17 , both with shapes as described with reference to  FIGS. 3 ,  5  to  9 , and  11 , and more particularly with a shape that is described below with reference to FIG.  10 . 
   In this figure, there can be seen the cylinder  2 , the ring  4 , and the sealing gasket or film  18  identical to those described with reference to  FIGS. 5  to  8 , and having the same numerical references for their various components, with the exception of the differences described below. 
   At rest, i.e. before being put into place on the cylinder  2 , the ring  4  is completely identical to that described with reference to  FIGS. 1  to  5 . In contrast, although the sealing gasket or film  18  remains uniform where it has a rim over the front face  11  of the annular end  3  of the cylinder  2 , over the chamfer  16  thereof, and over the most part of its longitudinal extent going away from the chamfer  16  to the vicinity of the shoulder  21  of the setback  17 , in the immediate vicinity of said shoulder  21  it presents a continuous annular bulge  77  forming a ring which is circular in section on any section plane containing the axis  9 , the sealing gasket or film  18  being described prior to the ring  4  having its ferrule  5  put into place on the annular end  3  of the cylinder  2 . To receive a corresponding portion of the bulge  77 , the bottom wall  19  of the setback  17  is locally indented in the immediate vicinity of the shoulder  21  to form a continuous annular groove  78  whose section is that of a circular arc on any plane that contains the axis  9  so as to be able to receive this portion of the bulge  77 , whereas the remainder thereof projects radially away from the axis  9  from the outside peripheral face  12  of the annular end  3  of the cylinder  2  and also from the portion of the sealing gasket or film  18  which lies on the bottom wall  19  of the setback  17 . 
   The person skilled in the art will readily understand that when the ferrule  5  presses its inside peripheral face  23  against the outside peripheral face  12  of the annular end  3  of the cylinder  2  and against the sealing gasket or film  18  on respective opposite sides of the bulge  77 , this bulge  77  gives rise to a longitudinally localized increase in the circumferential tension of the ferrule  5  and in the contact pressure against the inside peripheral face  23  thereof. 
   Preferably, as shown in  FIG. 10 , where chain-dotted lines represent the position of the ferrule  5  when the ring  4  is pressed via the face  35  of the annulus  34  against the front face  11  of the annular end  3  of the cylinder  2  through the rim of the sealing gasket or film  18 , the hardness and the dimensions of the bulge  77  are selected and the ring  4  is put into place via its ferrule  5  on the annular end  3  of the cylinder  2  and on the sealing gasket or film  18  in such a manner that, in this limit position, the bulge  77  causes a corresponding continuous annular groove  79  to be formed in the inside peripheral face  23  of the ferrule  5  having a shape that is exactly complementary to the portion of the bulge  77  that projects from the outside peripheral face  12  of the annular end  3  of the cylinder  2  and from the portion of the sealing gasket or film  18  that corresponds to the bottom wall  19  of the setback  17 , and does so in particular by giving rise to localized plastic deformation of the ferrule  5 . 
   To this end, and in order to enable the ferrule  5  to go past the bulge  77  of the sealing gasket or film  18  while it is being put into place thereon and on the outside peripheral face  12  of the annular end  3  of the cylinder  2  without difficulty and without giving rise to damage, it is preferable for this installation to be performed by the method described below with reference to  FIGS. 12  to  17 , it being understood that in certain conditions it would still be possible to put the ferrule in place as a force-fit as described with reference to  FIGS. 1 and 9  to  11 , or by temporary thermal expansion of the ring  4 , and in particular of its ferrule  5 , even when the sealing gasket or film  18  presents a bulge  77  as described with reference to FIG.  10 . 
   For mounting the ring  4  via its ferrule  5  on the annular end  3  of the cylinder  2 ,  FIGS. 12  to  17  show the use of a method which consists in causing the ferrule  5  temporarily to take up a state of circumferential expansion that is greater than the circumferential expansion it will occupy once it is resting against the outside peripheral face  12  of the annular end  3  of the cylinder  2  and on the sealing gasket or film  18  generating its own pressure for sealing purposes. This enlarged state is maintained temporarily, i.e. for the time required to move the ring  4  in longitudinal translation relative to the annular end  3  of the cylinder  2  until the face  35  of the annulus  34  comes to bear flat against the front face  11  of the annular end  3  of the cylinder  2 , via the rim of the sealing gasket or film  18 , if any. The ferrule  5  is then allowed to leave this circumferentially extended state so that the elasticity of the ferrule  5  establishes the required transverse pressure once the said relative position has been reached. 
   Instead of using thermal means for temporarily expanding the ring  4 , and in particular its ferrule  5 , it is possible to cause such temporary expansion by mechanical means in this version of the method as shown in  FIGS. 12  to  17 . 
     FIG. 12  shows the ring  4  in the rest state and, on the same axis as the ring  4  and longitudinally facing the free edge  25  of the ferrule  5 , there can also be seen an annular tool  80  for expanding the ferrule  5  circumferentially and radially. 
   This tool  80  is essentially constituted by a semi-rigid hoop  81  which is described in this position of axial alignment with the ring  4 . 
   In the rest state shown in  FIG. 12 , the hoop  81  is defined towards the axis  9  and going away from the axis  9  by an inside peripheral face  82  and by an outside peripheral face  83 , respectively, both being circular cylinders about the axis  9 , and between these faces  82  and  83  the thickness of the hoop  81  is as small as possible while nevertheless being sufficient to ensure that it has mechanical strength suitable for the use described below. In the direction  13  and in the direction opposite to the direction  13 , the faces  82  and  83  are connected together respectively by a downstream front face  84  and by an upstream front face  85 , both of which are circular annuluses about the axis  9 , plane, and perpendicular to the axis. Between the two front faces  84  and  85 , the hoop  81  presents a longitudinal size or length that is no longer than that of the face  23  between the face  35  of the annulus  34  and the free edge  25 , and that is preferably no greater than or approximately equal to the difference between said longitudinal side of the face  23  and the longitudinal distance between the bulge  77  of the sealing gasket or film  18  and the front face  11  of the annular end  3  of the cylinder  2  or the extreme limit of the rim of the sealing gasket or film  18 , if any, on said front face  11 . The inside peripheral face  82  has a diameter greater than the maximum diameter of the bulge  77  and greater than the diameter presented by the face  12  at a longitudinal distance from the free edge  25  of the ferrule  5  when it bears flat via the face  35  of the annulus  34  against the front face  11  of the annular end  3  of the cylinder  2 , via the rim, if any, of the sealing gasket or film  18  on said front face  11 , which distance corresponds to the longitudinal size of the hoop  81  between its front faces  84  and  85 . 
   On its downstream front face  84  the hoop  81  carries a plurality of rigid tabs  86  that are uniformly distributed angularly around the axis  9  (apart from two of them which are adjacent to each other), the tabs projecting radially from the outside peripheral face  83 , i.e. away from the axis  9 , without projecting radially from the inside peripheral face  82 , i.e. towards the axis  9 . By way of non-limiting example, two of these tabs  86  are shown as being in diametrically opposite positions, a third tab  86  on a diameter perpendicular to the diameter between the above-mentioned two tabs  86 , and two more tabs  86  are adjacent to each other and placed symmetrically about a position that is diametrically opposite to the above-mentioned third tab  86 . 
   Between these two adjacent tabs  86 , the hoop  81  is split obliquely, i.e. on a plane that is not referenced and that is oblique relative to the axis  9  so as to define two plane end faces  87  perpendicular to the inside and outside peripheral faces  82  and  83  but oblique, e.g. at 45°, relative to the front faces  84  and  85 . When the hoop  81  is in the rest state, as shown in  FIG. 12 , these two end faces  87  press against each other in the circumferential direction so as to cause the hoop  81 , its peripheral faces  82  and  83 , and its front faces  84  and  85  to appear to be continuous. 
   Nevertheless, starting from this rest state and as shown in  FIG. 13 , it is possible to offset one of the end faces  87  relative to the other so that they slide longitudinally over each other in a direction compatible with the oblique section, where necessary after putting the hoop  81  under stress, thus enabling the diameter of the inside and outside peripheral faces  82  and  83  thereof to be reduced, and in particular reducing the diameter of the outside peripheral face  83  to a value which is smaller than the diameter of the inside peripheral face  23  of the ferrule  5  in the vicinity of its edge  25 . The hoop  81  can thus be inserted in the direction opposite to the direction  13  into the ferrule  5  so that its outside peripheral face  83  comes against the inside peripheral face  23  of the ferrule until the tab  86  closest to the end face  87  which is offset upstream relative to the direction  13  relative to the other end face  87  comes to bear in the direction opposite to the direction  13  against the free edge  25 , with at least one other tab close to the same side of the split in the hoop  81  coming to bear thereagainst while the other tabs  86 , although offset downstream from the free edge  25 , are distant therefrom by distances which are less than the longitudinal dimension of the hoop  81  between its front faces  84  and  85  such that the outside peripheral face  83  of the hoop  81  is engaged in full or in part, depending on the zone thereof under consideration, against the entire circumferential dimension of the inside of the ferrule  5  against the face  23  thereof. With the hoop  81  in this state of radial contraction as shown in  FIG. 13 , the ring  4  is still in its rest state. 
   Then, as shown in  FIG. 13 , a mandrel  81  is forced longitudinally in the direction opposite to the direction  13  into the hoop  81  as engaged in the ferrule  5  of the ring  4 . The mandrel  88  is defined going away from the axis  9  by an outside peripheral face  89  that is circularly frustoconical about said axis and that converges in the direction opposite to the direction  13  between a minimum diameter that is smaller than the diameter then presented by the inside peripheral face  82  of the hoop  81 , which diameter can easily be deduced by the person skilled in the art from the diameter of the inside peripheral face  23  of the ferrule  5  given the thickness of the hoop  81  between its inside and outside peripheral faces  82  and  83 , and a maximum diameter that is not less than the diameter presented by the inside peripheral face  82  of the hoop  81  when in the rest state. 
   The person skilled in the art will readily understand that this coaxial insertion of the mandrel  88  into the hoop  81  and thus into the ferrule  5  of the ring  4  causes the diameter of the inside peripheral face  82  of the hoop  81  to expand progressively, consequently causing the diameter both of its outside peripheral face  83  and of the inside peripheral face  23  of the ferrule  5  to expand, thus expanding the ferrule both radially and circumferentially. 
   The mandrel  88  continues to be inserted coaxially in the direction opposite to the direction  13  into the hoop  81  while it is itself received inside the ferrule  5  until the inside and outside peripheral faces  82  and  83  have returned to the diameter they present when at rest, and this is accompanied by the end faces  87  sliding over each other until they are again pressed flat one against the other, and the hoop  81  as a whole has returned to its rest configuration. At this point, all of the tabs  86  are pressed in the direction opposite to the direction  13  against the free edge  25  of the ferrule  5 , as shown in  FIG. 14 , and the ring  4  and the tool  80  as inserted in this ferrule  5  temporarily constitute an assembly  90  which is stabilized by the end faces  87  bearing against each other circumferentially under the effect of the radial pressure applied by the ferrule  5  to the hoop  81 , it then being possible to extract the mandrel  88  in the direction  13 . 
   Given the diameter then presented by the inside peripheral face  82  of the hoop  81 , the assembly  90  can be engaged in the direction  13  on the annular end  3  of the cylinder  2  and on the sealing gasket or film  18 , including its bulge  77 , quite freely until the limit position is reached in which the annulus  34  bears via its face  35  in the direction  13  against the front face  11  of the annular end  3  of the cylinder  2 , via the rim, if any, of the sealing gasket or film  18 , which corresponds to the state shown in FIG.  15 . 
   Then, by applying thrust or shocks in the direction  13  to the tabs  86  (which tabs extend radially far enough to project from the outside peripheral face  24  of the ferrule  5 ) it is possible to extract the hoop  81  from the free edge  25  while keeping the ring in the above-mentioned limit position insofar as the annulus  34  is kept bearing via its face  35  against the front face  11 , via the rim, if any, of the sealing gasket or film  18  so as to prevent the ring  4  from moving together with the tool  80  relative to the cylinder  2 . 
   As soon as the upstream front face  85  of the hoop  81  escapes from the ferrule  5 , the ferrule contracts elastically to press its inside peripheral face  23  against the outside peripheral face  12  of the annular end  3  of the cylinder  2  and against the sealing gasket or film  18  whose bulge  77  gives rise to a localized increase in pressure in a continuous ring causing the groove  79  to be formed in the inside peripheral face  23  of the ferrule  5 , preferably by plastic deformation of the ferrule  5 . 
   In order to make it easier to extract the tool  80  from the ferrule  5 , the longitudinal distance between the shoulder  14  of the cylinder  2  and its front face  11 , or the upstream limit of the rim, if any, of the sealing gasket or film  18  on said front face  11  is greater than the longitudinal distance between the free edge  25  of the ferrule  5  and the face  35  of the annulus  34  by an amount greater than the longitudinal dimension of the hoop  81  between its upstream front face  85  and the downstream limit of the tabs  86  fixed to its downstream front face  84  so that during extraction the tool  80  does not come into abutment the shoulder  14  before it has been fully disengaged from the ferrule  5 . 
   Thereafter, the hoop  81  can be opened by applying traction in a circumferential direction on opposite sides of its split between the faces  87  so as to open up the split and enable the tool  80  to be removed either by sliding it in the direction  13  over the outside peripheral face  15  of the cylinder  2  or in the direction opposite to the direction  13  over the ring  4 . 
   The pipe  1  is then terminated, as shown in  FIG. 16 , and the skirt  6  of the ring  4  constitutes its female endpiece  54  into which it is possible subsequently to mount (if this has not already been done) a sealing gasket, e.g.  62  of the type described with reference to  FIGS. 7 and 8 , and then subsequently insert coaxially the male endpiece  7  of the other pipe  8 , as shown in FIG.  17 . 
   Transposing this method of mounting the ring  4  on the cylinder  2  in the absence of a sealing gasket or film  18 , possibly replacing it with at least one sealing ring of plastic material, or in the case of a different shape for the sealing gasket  18 , comes within the normal competence of a person skilled in the art. 
   In general, such a person skilled in the art will understand that the present invention can be implemented in a wide variety of ways differing from those described above, in particular by combining the variants described insofar as they are mutually compatible, without that going beyond the ambit of the invention.