Patent Publication Number: US-2013229010-A1

Title: Assembly with sealing gaskets having locking inserts

Description:
The present invention relates to a sealed and locked assembly, of the type comprising a spigot of a first pipe element, a socket of a second pipe element, and a composite sealing gasket for the sealed and locked assembly between the spigot and the socket, the sealing gasket comprising a ring made from an elastic material that extends along the central axis (X-X), and which has a body and an anchoring heel on the one hand, and at least one locking insert at least partially embedded in the anchoring heel on the other hand, 
     the socket comprising an annular anchoring groove, the anchoring groove being defined by an inclined surface positioned axially and radially between a bottom surface and an annular frontal surface, 
     the locking insert comprising,
         a head suitable for being inserted into the anchoring groove of the socket, and a foot,       

     the head including a radial projection, designed to press against the bottom surface of the anchoring groove of the socket and a first inclined projection, suitable for pressing against the inclined surface of the anchoring groove. 
     It in particular applies to sealed and locked assemblies for two cast-iron pipes. 
     Document EP-A-526 373 describes a sealing gasket comprising a sealing body and an anchoring heel made from an elastic material as well as a plurality of locking inserts made from a rigid material embedded in the anchoring heel. Each insert has an anchoring head designed to bear on the bottom of an anchoring groove formed in a socket, as well as catching teeth capable of engaging in the outer surface of a spigot so as to prevent axial movements that could separate the spigot from the socket under the action of the axial forces created by the pressure of the fluid circulating through the spigot and the socket. 
     The incline of each locking insert depends on the play between the outer diameter of the spigot and the inner diameter of the socket. The attachment of the insert on the spigot causes a reaction force whereof the incline angle on the median direction varies as a function of the play present between the assembled ends. 
     The higher this reaction angle, measured relative to the radial direction, the more the locking withstands the inner pressure of the fluid circulating through the assembly. Conversely, the attachment of the inserts in the outer surface of the spigot is better when the reaction angle is low. In fact, if the angle is too large, the teeth of the inserts risk not catching the spigot during pressurization, and sliding thereon, causing deficient locking. 
     The risk of poor resistance to pressure is critical toward the maximum plays where the reaction angle is naturally small, while the risk of having poor catching of the inserts is critical toward the minimal plays where that reaction angle is naturally large. 
     Consequently, the position of the locking insert relative to the spigot and the socket must be defined by any play allowed by manufacturing allowances between the anchoring groove and the spigot. However, the known locking junction limits the manufacturing allowances on the inserts and the anchoring groove of the socket. In fact, depending on the play present, the locking insert may assume a configuration in which it presses flat on the bottom surface of the anchoring groove or on the inclined surface connecting the bottom surface and the front surface. In the case where these surfaces include protrusions, the orientation of the insert relative to the socket is disrupted, leading to poor locking of the junction. Removing the protrusions is, however, costly. 
     One aim of the invention is therefore to design a locking insert and a corresponding junction that allow good catching over a wide range of plays, while having a low manufacturing cost. 
     Another aim of the invention is to optimize the compromise between the catching reliability of the insert on the spigot and the pressure resistance of the locking. 
     To that end, the invention relates to an assembly as indicated above, characterized in that the head comprises at least one frontal projection that is offset, radially, from the first inclined projection and designed to press against the annular frontal surface of the anchoring groove, the annular frontal surface and the inclined surface forming an angle smaller than 180° between them. 
     According to particular embodiments, the assembly comprises one or more of the following features:
         the head comprises at least one second inclined projection, which is offset, in particular radially, from the first inclined projection and the frontal projection and designed to press against the inclined surface of the anchoring groove;   the first and second inclined projections are, in side view, connected by a concave or rectilinear profile;   the frontal projection and the inclined projection adjacent to the frontal projection are, in side view, connected by a concave or rectilinear profile;   in side view, the foot of the insert comprises at least one catching tooth adapted to catch on an outer surface of the spigot;   the frontal projection and the closest catching tooth are, in side view, made by a concave or rectilinear profile;   in side view, the head includes a catching nose, a first straight line extending from the radial projection toward the catching nose and a second straight line connecting the frontal projection to the first inclined projection, and the angle between said two straight lines is comprised between 60° and 120° and preferably smaller than 90°;   the head is a radially outer head, at least partially embedded in the anchoring heel and designed to press in the anchoring groove of the socket, and the foot is a radially inner foot, designed to press against the spigot;   the bottom surface that defines the annular anchoring groove is a cylindrical surface, in particular extending coaxially relative to the central axis (X-X), and the annular frontal surface is formed by an inlet flange of the socket, the annular frontal surface extending over an angle of at least 80° relative to the central axis (X-X); and   the inclined surface has an incline comprised between 30° and 60° relative to the central axis (X-X);   all of the projections are arranged such that for any diameter of the bottom surface of the socket and the outer surface of the spigot comprised in an allowance range and in a meridian cross-sectional view, the locking insert bears at the same time on at most three or two locations of the anchoring groove of the socket.       

    
    
     
       The invention will be better understood upon reading the following description, provided solely as an example and done in reference to the appended drawings, in which: 
         FIGS. 1 to 3  are meridian cross-sectional half-views of an assembly of two pipes and a composite sealing gasket inserted between them, respectively before, during and after production of the locked assembly according to the invention; 
         FIGS. 4 and 5  are enlarged meridian cross-sectional views of part of the assembly according to the invention during different assembly steps, the socket and the spigot defining a minimum play between them; 
         FIGS. 6 and 7  are enlarged meridian cross-sectional views of part of the assembly according to the invention in different assembly steps, the socket and the spigot defining a maximum play between them; 
         FIG. 8  is a meridian view of the locking insert of the assembly of  FIGS. 1 to 7 ; 
         FIGS. 9 and 10  are meridian cross-sectional half-views of an assembly of two pipes and a composite sealing gasket inserted between them after production of the locked assembly according to one alternative of the invention; and 
         FIG. 11  is a meridian view of a locking insert according to the alternative of the invention shown in  FIGS. 9 and 10 . 
     
    
    
       FIGS. 1 to 3  show a sealed and locked assembly according to the invention, designated by general reference  2 . 
     The sealed assembly  2  comprises a spigot  4  or male end secured to a first pipe  6 , a socket  8  or female end secured to a second pipe  10 , and a sealing gasket  12 . 
     The assembly  2  extends along a central axis X-X. Hereafter, the expressions “radially,” “axially,” “circumferentially” and “meridian” will be used relative to that axis. 
     The sealing gasket  12  includes, in meridian cross-section, an elastic ring  14  made from a flexible or resilient material, for example made from an elastomer, that extends along the central axis X-X, in which a plurality of locking inserts  20  are embedded. 
     The elastic ring  14  comprises an annular solid body  16  toward the bottom of the socket as well as, on the inlet side of the socket, an anchoring heel  18  protruding radially outward and a circular sealing lip  26  protruding radially inward. 
     The body  16  and the heel  18  are separated by a peripheral shoulder  22 . 
     The lip  26  extends substantially radially toward the axis X-X as far as the vicinity of the minimum inner diameter of the body  16 . The inserts  20  are regularly distributed over the entire perimeter of the ring  14 . Each locking insert  20  is made from a very hard material, for example a hard metal alloy or ceramic. 
     Each insert  20  comprises, in meridian view, a radially outer head  30  and a radially inner foot  32 . The head  30  extends substantially radially relative to the axis X-X, while the foot  32  is inclined relative to that axis, such that it converges toward the axis X-X in an insertion direction I of the spigot  4  into the socket  8 . The insert  20  thus has a curved profile. 
     Each insert  20  is partially embedded in the anchoring heel  18  of the gasket  12  and partially covered by the elastic material of the heel  18 . However, the heel  18  includes recesses  36  at the inserts  20 . The recesses  36  are radially outwardly open, such that the radially outer end of the head  30  is practically free from elastic. The recesses  36  are also axially open in the insertion direction I. 
     Likewise, the sealing gasket  12  comprises recesses  38 , open radially inwardly, and situated at the location of the inserts  20 , such that the radially inner end of the feet  32  is free from elastic material. 
     As shown more precisely in  FIG. 6 , the head  30  comprises, at the radially outer end thereof, a profile forming a radial projection  40 . The head  30  also comprises a retaining nose  48  with a sharp edge oriented axially in the direction I. The nose  48  is practically free from elastic material owing to the recess  36 . 
     The head  30  also comprises an inclined projection  50 , extending obliquely relative to the central axis X-X. 
     In the case at hand, the two projections  40 ,  50  are formed by an arc-of-circle-shaped profile of the locking insert, in meridian view. 
     The head  30  also comprises a frontal projection  52  that is radially offset from the inclined projection  50  toward the axis X-X. 
     A substantially planar surface S 1  extends between the radial projection  40  and the retaining nose  48 , and a substantially planar surface S 2  extends between the two inclined  50  and frontal  52  projections. These surfaces S 1 , S 2  form an angle a smaller than 90° between them. 
     Furthermore, the foot  32  comprises, at the radially inner end thereof, three catching teeth  56 ,  58 ,  60  that are axially offset and that are designed to catch on the outer surface  70  of the spigot  4  (see below) and which, when the gasket is idle, extend outside the elastic ring  14 . In meridian view, the teeth  56 ,  58 ,  60  extend over a convex curve. Furthermore, the foot  32  includes, on the axial side opposite the head  30 , a catching stop  62  embedded in the body  16 . The catching stop  62  has, in meridian view, a profile that is rounded relative to the profile of the catching teeth  56 ,  58 ,  60 . 
     The stop  62 , the function of which is to limit the penetration of the insert  20  in the spigot  4  so as not to deteriorate the latter, preferably has a rounded or curved shape so as to favor the “flow” of the elastomer during fitting of the spigot  4 , so as to avoid stress concentrations that could cause tears in the elastomer. 
     In reference again to  FIG. 1 , it is shown that the spigot  4  comprises a cylindrical outer surface  70  with a diameter d provided with an inlet bevel  72 . The spigot  4  is manufactured with diametric allowances such that the actual diameter d can be situated between a maximum outer diameter d max  and a minimum outer diameter d min . The diameters d max  and d min  are indicated in mixed lines in  FIG. 1 . 
     The spigot  8  successively includes, axially from the inlet of the fitting toward the bottom, an inlet flange  80 , an annular anchoring groove  82  serving as a housing for the anchoring heel  18  of the gasket, a stepped part  84 , an inner bead  86 , and a receiving cavity  88 , designed to freely receive the end of the spigot  4 . 
     The inlet flange  80  defines an inlet surface  81 , which is a cylindrical surface with diameter DISE (cf.  FIG. 4 ). 
     The annular anchoring groove  82  is delimited by an annular frontal surface  90  of the inlet flange  80 , an inclined surface  91 , a cylindrical bottom surface  92  with a circular cross-section with axis X-X, and a frontal surface  94  of the stepped part  84 . 
     In general, the frontal surface  90  extends over an angle of at least 80° relative to the central axis X-X and has an axial component oriented in direction I. Preferably, the frontal surface  90  forms an angle of at least 85° with the axis X-X. The frontal surface  90  extends from the inlet surface  81  to the inclined surface  91 . 
     The inclined surface  91  extends over an angle comprised between 30° and 60° relative to the central axis X-X and has an axial component oriented in the direction I. The inclined surface  91  is therefore positioned radially and axially between the bottom surface  92  and the frontal surface  90 . 
     Furthermore, the annular frontal surface  90  connects directly to the inclined surface  91 , which in turn connects directly to the bottom surface  92 . In meridian view, the annular frontal surface  90  connects to the inclined surface  91  at the connecting point PR. This connecting point PR is situated at a distance DPRSE from the inlet surface  81 , that distance being comprised between 10% and 90% of the difference between the diameter of the inlet surface DISE and the diameter D of the bottom surface  92 . Preferably, the distance DPRSE is comprised between 40% and 60% of said difference or between 45% and 55% of said difference. 
     The angle y included by the frontal  90  and inclined  91  surfaces is smaller than 180°, and is in particular comprised between 110° and 160°. 
     For any play between the surfaces  70  and  92  comprised in the acceptable allowance range, the insert  20  presses both on the one hand against the bottom surface  92  and on the other hand against the inclined surface  91 , and/or against the frontal surface  90  when the pipes are subjected to the internal pressure of the fluid they convey. 
     More specifically, for a given position, when the play between the surfaces  70  and  92  is in a first play range delimited by the minimum play J 1  ( FIGS. 4 and 5 ) and an intermediate play, the locking insert  20  presses against the bottom surface  92  and the inclined surface  91  when the pressure is established, but does not press against the frontal surface  90 . 
     When the play between the surfaces  70  and  92  is situated in a second play range, delimited by the maximum play J 2  ( FIGS. 6 and 7 ) and the intermediate play, the locking insert  20  presses against the bottom surface  92  and the frontal surface  90  when the pressure is established, but not against the inclined surface  91 . It should be noted in this case that, when the pressure is established and before reaching the said final bearing configuration, the insert  20  first goes through a configuration in which it presses against the bottom surface  92  and the inclined surface  91 , then through an intermediate configuration in which it presses simultaneously against the bottom surface  92 , the inclined surface  91  and the frontal surface  90 . 
     The frontal surface  94  is oriented toward the inlet flange  80 , against the direction I. 
     As indicated in  FIG. 3 , the bottom surface  92  is also subject to manufacturing allowances, such that its actual diameter D can vary between a maximum diameter D max  and a minimum diameter D min . 
     It should be noted that the maximum diameter d max  of the surface  70  is smaller than the diameter DISE of the surface  81 . 
     The assembly according to the invention is assembled as follows. 
     The sealing gasket  12  is first inserted into the socket  8 , the body  16  pressing against the stepped part  84  and the anchoring heel  18  being placed in the annular anchoring groove  82 , such that the axis of the gasket  12  is combined with that of the socket. 
     Then, the spigot  4  is aligned with the socket and is inserted through the gasket  12  in the direction I while first folding the lip  26 , which presses with some pressure against the outer surface  70 . When the spigot  4  crosses the threshold of the inserts  20 , the latter parts become inclined through regular travel against the body  16 . The insertion of the spigot  4  continues until its bevel  72  arrives near the bottom of the cavity  88 . 
     The spigot  4  is then axially brought backwards so as to brush the inserts  20  back up. The inserts  20  modify their incline relative to the axis X-X through an inverse travel opposite the preceding travel and with a small amplitude. During this brushing up, at least one of the teeth  56 ,  58 ,  60  catches on the outer surface  70  of the spigot  4  and then offers significant resistance to the continuation of the axial removal movement of the spigot  4 . The assembly is thus locked. 
     Subsequently, in reference to  FIGS. 4 to 7 , the operation of the sealing gasket according to the invention will be described as a function of the diametric allowances on the diameters d and D under the action of pressurized fluid. In these Figures, the ring  14  has been omitted for better clarity of the drawing. 
     After the aforementioned angular travel of the inserts  20  during the assembly of the pipes  6  and  10 , each insert  20  assumes an inclined position that varies as a function of the play present between the diameters d and D. 
       FIG. 4  shows the position of an insert  20  during catching on the spigot  4  during pressurization in the case where the play between the pipes is a minimum play J 1 . To that end, the socket  8  comprises an anchoring groove  82  whereof the diameter D corresponds to the minimum diameter D min , while the spigot  4  has a surface  70  whereof the outer diameter corresponds to the maximum diameter d max . The two diameters D min  and d max  thus define a minimum play J 1  between the two surfaces  92  and  70 . 
     One can see that, during catching on the spigot  4 , the insert  20  presses against the groove  82  in two places, on the one hand with its radial projection  40  against the bottom surface  92  and on the other hand with its inclined projection  50  against the inclined surface  91 . Furthermore, only the catching tooth  56  closest to the fitting inlet presses against the outer surface  70  of the spigot. 
     The insert  20  is inclined by a reaction angle that is defined as follows. In meridian view, the two lines L 1 , L 2  that extend perpendicular to the surfaces  92 ,  91  at the respective projections  40 ,  50  for pressing the insert  20  against the groove  82  intersect at a point P. The pressing point of the tooth  56  on the surface  70  defines, with the point P, a third line L 3  serving as a support for the reaction force of the insert  20 . The angle β 1  measured between said line L 3  and a plane perpendicular to the axis X-X is called the catching “reaction angle.” 
     The catching of the insert  20  is better when this reaction angle is low. Owing to the presence of the radial projection  40  and the inclined surface  91 , the point P is located in a position that is axially relatively close to the tooth  56 , such that the angle β 1  is small for the given play J 1 , which favors catching of the locking insert  20  on the surface  70 . 
       FIG. 5  shows the part of the assembly of  FIG. 4  when the pressure is established. 
     One can see that, after catching of the insert  20 , the latter has tilted in the clockwise position relative to  FIG. 4 , and the three catching teeth  56 ,  58 ,  60  now penetrate the material of the spigot  4 . 
     As before, the locking insert  20  presses, by its radial projection  40 , against the bottom surface  92 , and by its projection  50  against the inclined surface  91 . 
     The point P is once again the point of intersection of the lines L 1 , L 2  of the normals to the surfaces  92 ,  91  at the projections  40 ,  50 . Conversely, the assembly defines a line L 3 , which extends between the point P and a point M situated substantially axially midway between the catching teeth  56  and  60 . 
     The line L 3  defines, with a plane perpendicular to the axis X-X, a reaction angle β 1  under established pressure that is thus relatively large for the given play J 1 , which leads to good pressure resistance of the locked assembly. 
     It should be noted that, during tilting of the insert  20  when the pressure is being established, the maintenance of contact at the radial projection  40  as well as the catching of axially offset teeth in the direction I of the tooth  56  closest to the fitting inlet makes it possible to increase the reaction angle and, inter alia, to thereby offset the decreased reaction angle resulting from the tilting of the insert in the clockwise direction; this thereby results in a large enough angle β 2  to guarantee good pressure resistance. 
     In the case of minimum play J 1 , the front projection  52  is out of contact with the front surface  90  both during the insertion of the spigot  4  into the socket  8  and during and after the establishment of pressure. 
     The explanations relative to  FIGS. 4 and 5  are valid for any play comprised in the first play range. 
       FIG. 6  shows an assembly similar to that of  FIG. 4 , with the following differences. 
     The surface  92  has a diameter D max , while the surface  70  has a diameter d min , such that these two surfaces define a play J 2  between them that is larger than the play J 1 . This play J 2  is the maximum acceptable play for the manufacturing allowances of the spigot  4  and the socket  8 . 
     One can see that, upon catching on the spigot  4 , during the pressurization, the insert  20  presses against the groove  82  in two places, on the one hand with its radial projection  40  against the bottom surface  92  and on the other hand with its inclined projection  50  against the inclined surface  91 . The frontal projection  52  is out of contact with the frontal surface  90 . Furthermore, only the catching tooth  60  furthest from the fitting inlet presses against the outer surface  70  of the spigot. 
     The catching reaction angle β 3  obtained is measured between the radial direction and a line passing through the point P, substantially identical to that of the assembly of  FIG. 5 , and by the point of contact between the surface  70  and the tooth  60 . This angle β 3  is small and therefore compatible with good catching of the insert  20 . 
       FIG. 7  shows the assembly of  FIG. 6  once the pressure is established, therefore after catching of the insert  20  and after tilting thereof in the clockwise direction in the Figures. 
     At the end of that tilting, the insert  20  presses only with its radial projection  40  against the bottom surface  92  and only with its frontal projection  52  against the frontal surface  90 , while the other projection  50  is out of contact with the surface  91 . Furthermore, only the intermediate teeth  58  and the tooth  60  furthest from the fitting inlet catch in the surface  70  of the spigot  4 . 
     With maximum play J 2 , the contact at the frontal projection  52  increases the reaction angle and offsets the reaction angle resulting from the tilting of the insert in the clockwise direction during pressurization. This thus makes it possible to obtain, owing to this projection  52  that generates a point P situated near the axis X-X, a final established pressure reaction angle β 4  that is large enough to guarantee good pressure resistance of the locked assembly. 
     The explanations in reference to  FIGS. 6 and 7  are valid for any play comprised in the second play range. 
     For all acceptable plays between the surfaces  70  and  92 , the insert  20  presses, in meridian view, against the bottom surface  92 , the inclined surface  91  and/or the front surface  90  in each contact location, according to a periodic and nonlinear contact. Thus, the manufacturing allowances of the insert and the surfaces  90 ,  91 ,  92  may be significant. 
       FIG. 8  shows the insert  20  on a larger scale. 
     The following explanations refer to the meridian, therefore side, view of the locking insert  20 . 
     The locking insert  20  includes an arc-of-circle-shaped rounded profile  100 , which forms the projections  40  and  50 . This rounded profile  100  extends over an angular range greater than 90°. 
     A rectilinear profile  102  extends between the rounded profile  100  and the catching nose  48 . This profile  102  connects tangentially to the profile  100  and forms the surface S 1 . 
     Between the rounded profile  100 , or the inclined projection  50 , and the frontal projection  52 , another rectilinear profile  104  extends. This profile  104  is tangentially connected to the profile  100  and forms the surface S 2 . 
     The frontal projection  52  is formed by a rounded profile, preferably in an arc-of-circle shape, extending over an angular range greater than 90°. 
     The frontal projection  52  and the catching tooth  56  are connected by a concave profile  106 . This concave profile  106  constitutes the passage for the tooth  56  and comprises a rectilinear partial profile  108  that extends from the frontal projection  52 . 
       FIGS. 9 to 11  show one alternative of the invention, which differs from the embodiment above only as follows. Similar elements bear identical references. 
       FIG. 9  shows the assembly with average play. 
       FIG. 10  shows the assembly with maximum play J 2 . 
     The locking insert  20  includes a second inclined projection  54 , radially offset from the first inclined projection  50 . This inclined projection  54  is designed to press against the inclined surface  91  of the anchoring groove. 
     In meridian view, therefore in side view, a rectilinear profile  104  extends between the frontal projection  52  and the second inclined projection  54 , while the second inclined projection  54  and the first inclined projection  50  are separated by a concave profile  110 . The straight line that connects the two inclined projections  50 ,  54  forms, with the rectilinear profile, an angle δ that is different from the angle y between the two frontal  90  and inclined  91  surfaces, and preferably smaller than that angle. Thus, the number and expanse of the contact locations between the locking insert  20  and the surfaces  90 ,  91  are small. 
     The angle δ is smaller than 180°. 
     Furthermore, the concave profile  110  helps minimize the contact locations between the locking insert  20  and the inclined surface  91 . 
     In an alternative not shown, the two inclined projections  50 ,  54  are separated by a rectilinear profile. 
     Also in an alternative not shown, the frontal projection  52  and the inclined projection adjacent to the frontal projection, which is the projection  54  in  FIG. 11 , are connected by a concave profile. 
     Owing to the geometric characteristics of the inserts  20  and the surfaces  90 ,  91 , the sealing gasket leads to a good compromise between the catching of the inserts on the spigot and pressure resistance, independently of the actual play existing between the surfaces  70  and  92 . 
     Furthermore, the recesses  36  make the bearing of the inserts  20  toward the minimum plays more reliable, by reducing the fitting force of the spigot  4  and avoiding compression stresses in the elastomer that can cause poor positioning of the inserts  20  by tilting in a direction tending to increase the reaction angle (and therefore harm the proper catching of the inserts  20  with minimal play). Furthermore, the recesses  36  facilitate the overall deformation of the ring  14  during its placement of the gasket in the socket. 
     The invention may also include the following features:
         The foot  32  includes a catching stop  62  that is embedded in the body  16  and that is positioned on the side axially opposite the head  30 .   The catching stop  62 , in meridian cross-section along the central axis X-X, has a more rounded profile than the profile of the catching teeth  56 ,  58 ,  60 .   The ring  14  comprises at least one recess  36  at a locking insert  20 , and the recess  36  is radially outwardly open such that a radial end of the head  30  is practically free from elastic.   The catching teeth extend outside the ring  14 .   The head  30  of each locking insert  20  comprises a retaining nose  48  oriented axially opposite the first inclined projection  50 , and the recess  36  is axially open such that the retaining nose  48  is practically free from elastic material.   The anchoring heel  18  and the body  16  are separated by at least one hollow, in particular a peripheral groove or recesses circumferentially aligned with the inserts  20 .   The frontal surface  90  is on the inlet side of the socket.