IE78622B1 - Locked pipe fitting with composite seal assembly - Google Patents

Abstract

The head (24) of each insert (18) for locking the seal has, on the body side, a sharp-edged snout (30) delimited by two disengaged surfaces (29, 31), the arrangement being such that when the seal is in place in the housing (socket) (3) and the male end (1) is forcefully inserted into the latter, thereby radially compressing the body of the seal, the two disengaged surfaces (29,31) form between them, in the vicinity of the sharp edge (30), an angle projecting towards the bottom of the housing (socket), and this is the case at least for large diameters of the male end. Application to locking pressurised pipelines made of spheroidal graphite cast iron. <IMAGE>

Description

The present invention relates to locked assemblies between a male end of a pipe and a socket of another pipe. It deals more particularly with a locked assembly between a first pipe with a male end and a second pipe with a socket with the interposition of an ? annular seal between the two pipes, the said seal exhibiting an axis which is coincident with the axis of the , assembly and comprising: a body made of elastic material, compressed radially between the socket and the male end; an anchoring heel made of elastic material, housed in an anchoring groove of the socket delimited by a bottom bordered by two stop walls, namely a rear wall situated on the entry side of the socket and a more or less radial front wall situated facing the previous one; and several locking inserts made of a rigid material embedded in the heel and located generally along generatrices of a cone having the same axis as the seal and which converge in the direction of the body, each insert projecting out of the seal towards the axis of the latter, the head or radially outer part of each insert exhibiting, on the same side as the body, a hook for holding the insert while the male end is being pushed into the socket, this hook having a sharp edge and being delimited by two undercut surfaces .

In assemblies between pipes using such seals, as is known, for example, from DE-A-2,226,151, each locking insert, made of a hard material, is braced up between the socket and the male end, with a certain inclination. Such locking prevents the axial movements of one pipe with respect to the other which could compromise the good sealing of the joint and even completely detach the initially assembled pipes under the action of the axial separation forces generated by the pressure of the fluid contained within the pipes.

This type of locking advantageously replaces a costly system of fastening a run of pipe to foundations anchored in the ground, as well as the devices with bolted flange and mating flange.

However, such locking is fully effective only if it can guarantee a maximum distance by which the male end can move backwards when the fluid pressure is established. For this to be the case, it is necessary to be sure that the forcible insertion of the male end into the socket is not going to extrude the inserts or the entire seal towards the bottom of the socket into the annular space between the latter and the male end.

The object of the invention is to provide a simple solution to this problem, which can he applied directly to existing pipes.

To this end, the subject of the invention is an assembly of the aforementioned type, characterized in that the sharp edge is immediately followed by a radially inner part with a deeply concave rounded portion which allows the insert, when the male end is forcibly introduced into the socket, radially compressing the body of the seal and bringing the sharp edge into contact with the front wall with which it forms a connection, to pivot about this connection while maintaining it, the said connection forming a distinct stop which prevents the insert from being extruded out of the groove of the socket.

According to other variations: the two undercut surfaces form an angle projecting towards the bottom of the socket for any diameter of the male end lying within its tolerance band and for any position of insertion of the male end into the socket; the said angle is markedly less than 90°; the said angle is slightly greater than 90°; each insert exhibits several teeth for catching on the male end, these teeth being offset from one another axially and radially; the head of each insert exhibits, on the opposite side from the hook, a surface which is inclined radially towards the inside and axially towards the outside of the socket, this surface preferably ending in rounded portions the seal includes a substantially radial inner sealing lip on the entry side of the socket. Another subject of the invention is a locked assembly with a male end and a socket comprising a seal as defined hereinabove, the body of the seal being compressed radially between the socket and the male end, its heel being housed in an anchoring groove of the socket delimited by a bottom bordered by two stop walls, including a more or less radial front wall, the radially inner part of each insert is designed to come into locking engagement with the periphery of the male end with its head bearing against the bottom of the groove and possibly on its stop wall situated on the entry side of the socket.

In the case, already mentioned, in which the head of each insert exhibits, on the opposite side from the hook, a surface which is inclined radially towards the inside and axially towards the outside of the socket, this surface preferably ending in rounded portions, the stop wall of the socket situated on its entry side advantageously exhibits a frustoconical radially outer part so that the head of the inserts bears more or less on the join between this part and the bottom of the groove for large diameters of the male end whereas it bears on this bottom and on the same inclined part for small diameters of the male end.

According to another variation of the assembly, the angle that the outer undercut surface forms with the said front wall is less than the angle that the other undercut surface forms with this front wall.

One embodiment of the invention will now be described with regard to the appended drawings in which: - Figure 1 is a half-view in axial section of a socket equipped with a seal according to the invention and of a male end ready to be inserted into this socket; Figure 2 is a similar view showing the resulting locked assembly; - Figures 3 and 4 illustrate on a larger scale, also in axial half-section, the behaviour of the inserts of the seal upon insertion of the male end, respectively for a maximum diameter and for a minimum diameter of this male end, the elastic part of the seal having been omitted for reasons of clarity of the drawing; and - Figures 5 to 8 illustrate in a similar manner the locking of the assembly for decreasing diameters of the male end.

Figure 1 represents the male end 1 of a first pipe 2 and the socket 3 of the second pipe 4, this socket being equipped with a seal 5. The three elements 1, 3 and 5 are substantially of revolution about one and the same axis X-X assumed to be horizontal. The two pipes are made of spheroidal graphite cast iron for example.

The male end 1 exhibits a cylindrical outer surface, externally chamfered at 6 at its end.

The socket 3 includes an entry collar 7 then, in succession, from the rear forwards, that is to say going from this collar towards the bottom of the socket: a relatively deep anchoring groove 8, a shallower sealing cavity 9, an internal projection 10 axially limiting this cavity 9, and a front cavity 11 which is shallower than the cavity 9 and freely accommodates the end of the male end 1. For a given entry diameter of the socket, the manufacturing tolerances on the male end and the errors in positioning it (misalignment of the axes, and angular deflection) have the result that in each axial sectioning half-plane, the outer generatrix of the male end may be situated in a whole range of positions between a position corresponding to practically no radial clearance with respect to the collar 7 and a maximum amount of radial clearance with respect to this same collar. This is equivalent to a range of outside diameters of the male end which lies between a maximum value and a minimum value with a perfectly centred position of the male end, and, in the rest of the description, reference will only be made to such a range of diameters.

As better seen in Figure 3, the groove 8 of the socket is delimited towards the rear by a radially inner wall 12 which is slightly inclined to the vertical, and by a radially outer wall 13 which is markedly more inclined, at more or less 45° in the example represented. The wall 13 connects the cylindrical bottom 14 of the groove 8, which bottom in turn connects to a more or less radial front wall 15 of this groove. As far as the cavity 9 is concerned, it includes a cylindrical bottom 16 connected to the wall 15 and a [lacuna] or less radial front end shoulder 17.

The seal 5 (Figure 1) is a moulded component made of flexible or resilient material, for example of elastomer, in which a series of locking inserts 18 are embedded. At the front it comprises a solid body 19, and at the rear it comprises an anchoring heel 20 projecting radially towards the outside and a lip 21 projecting radially towards the inside.

At rest, the rear and radially outer profiles of the seal are substantially the same as the profiles of the surfaces 12 to 16 of the socket 3. More specifically, the seal is housed in the socket without appreciable deformation, and clearance therefore remains between it and the surfaces 12 to 14 of the socket, whereas it is pressed against the surfaces 15 and 16. A gap therefore remains between the front end 22, of concave shape, of the body 19, and the surface 17.

In addition: - the inside surface 23 of the body 19 converges towards the front in a substantially conical manner from a diameter close to the inside diameter of the collar 7 to a diameter which is smaller than the smallest possible outside diameter of the male end 1, in the sense indicated earlier; - the lip 21 points substantially radially and extends more or less between the same diameters as the inside surface 23, extending the rear end surface of the body 19.

Each insert 18 (Figures 1, 3 and 4) is contained within a radial plane, has the general shape of an L and includes a radially outer head 24 embedded in the heel 2 0 and a radially inner tail 25 which converges towards the front until it projects slightly from the surface 23 of the body of the seal, more or less mid-way along it.

The head 24 (Figures 3 and 4) exhibits a rectangular overall shape, with: - at the rear, a side 26 which, at rest, is more or less parallel to the surface 13 of the socket; - radially on the outside, a side 27 which is more or less perpendicular to the previous side and is connected to the latter by a rounded portion 28; and - at the front, a side in the form of a hook, made in two parts: a radially outer part 29 forming an obtuse angle, of the order of 135° in this example, with the side 27 and extending as far as a sharp edge 30; and a radially inner part 31 with a deeply concave rounded portion subtending an angle of approximately 90°. The tangent to this rounded portion at the sharp edge 30 forms an angle slightly greater than 90° with the part 29 of the hook. As an alternative, this angle could be markedly less than 90°.

The tail 25 is laterally delimited by two more or less parallel sides: a rear side 32 connected to the side 2 6 by a rounded portion 33, and a front side 34 connected tangentially to the rounded portion 31. The tail 25 ends in four projections 35 which are offset from one another axially and radially. As will be explained in detail later, the three projections 35 situated towards the rear constitute teeth for catching on the male end, whereas the fourth projection 35, situated towards the front, that is to say towards the bottom of the socket, constitutes an anti-penetration heel limiting the penetration of the teeth into the male end.

When the male end 1 is inserted into the socket 3, it folds back the lip 21 then pushes the body 19 forwards, compressing it radially. The whole seal therefore tends to move forwards. This brings the sharp edge 30 of the inserts 18 into contact with the surface 15 of Ί the socket (Figures 3 and 4) and the arrangement is such that regardless of the outside diameter of the male end, as the latter is being inserted, this edge 3 0 always projects forwards over the head of the inserts and is always opposite the surface 15.

This distinct stop 30-15 prevents the inserts from slipping radially towards the inside of the socket, out of the chamber, and hence from being extruded. As Figures 3 and 4 indicate, this manner of proceeding could continue as far as the imaginary position, that is to say beyond the normal range of operation, indicated in chain line, thus affording a large safety margin.

Furthermore, for the normal ranges of operation, that is to say for the band of diameters of the male end and for the fitting-together positions envisaged, and even beyond, the pair 30-15 behave like a unidirectional system further increasing the reliability of the whole. This is because the angle of incidence a between the surfaces 29 and 15 remains less than the angle β between the surfaces 31 and 15 (Figures 3 and 4) so that the insert can easily penetrate the chamber 8 (towards the surface 14 of the socket) when subjected to radial forces in this direction, whereas it is blocked if the direction of the radial forces is reversed.

It should be noted that the width of the tail 25 is less than the radial clearance between the surface 16 and the male end, to prevent any risk of the joint becoming jammed. Moreover, it will be understood that the stop 30-15 is important mainly for large outside diameters of the male end, for which the risk of driving the seal along is high (Figure 3).

Upon completion of the insertion of the male end and when the run of pipe is pressurized, the male ends are generally urged backwards. The inserts 18 limit this backwards travel in the following manner, illustrated in Figures 5 to 8.

When the outside diameter of the male end is at a maximum (no radial clearance between the male end and the collar 7 of the socket), its moving back brings the rounded portion 28 of each insert more or less into the angle formed by the surfaces 13 and 14 of the socket, and the second tooth 35 from the rear comes into engagement with the male end. This defines a bracing force 36 and a centre of rotation 37 of the insert. The arrangement is such that the inclination of the force 36 in the radial direction lies between a lower limit for which there is a risk of the tooth perforating the male end, and an upper limit for which there would be a risk of the tooth slipping on the male end.

For outside diameters of the male end which decrease from the maximum diameter (Figure 6), the head of the inserts bears on the socket in the same way as before, but the two intermediate teeth 35, then just the third tooth, come into engagement with the male end, which has the effect of keeping the inclination of the bracing force 36 within the aforementioned limits despite the greater inclination of the tail of the inserts.

As the outside diameter of the male end continues to decrease, the tilting of the inserts continues until the side 26 presses on the surface 13 of the socket (Figure 7). The centre of rotation of the inserts then switches from the point 37 to another point 38 situated closer to the axis X-X and further to the rear, allowing the bracing force to remain within the desired limits even though it would come outside of these limits for the same diameter of male end without this principle.

Finally, in the lower end of the range of outside diameters of the male end (Figure 8), the third tooth 35 is still in engagement with the male end, and the head of the inserts presses at two points into the groove 8: via the rounded portion 28 onto the bottom 14, and via the rounded portion 33 onto.the surface 13. Once again, the centre of rotation 3 8 is sited so as to guarantee an appropriate inclination of the force 36.

This maintaining of the inclination of the force 36 by virtue of the double pressing of the head of the inserts has the advantageous consequence of increasing the permissible internal pressure for the run of pipe, this pressure being substantially proportional to the angle that the bracing force makes with the radial direction. It should be noted that this is obtained without calling upon additional teeth for the inserts, which makes it possible to make savings in material, size and in the manufacture of the inserts.

In all cases, the bearing of the edge 30 on the surface 15 during fitting-together limits the maximum possible extent to which the male end can move backwards when the run of pipe is commissioned.

The smallest end projection 35 situated on the entry side of the socket is a safety feature intended for cases in which the inserts have been poorly positioned with respect to their normal position. The end projection 35 situated towards the bottom of the socket is an antipenetration heel which makes it possible to limit the contact pressure between the neighbouring intermediate tooth and male ends exhibiting the smallest diameters, and thus makes it possible to increase the maximum threshold of permissible pressure.

The lip 21 provides sealing against the external elements, that is to say makes it possible to avoid harmful or corrosive external elements being introduced into the locked zone. By virtue of its radial orientation, there is no risk of it becoming positioned under the inserts during fitting-together.

If desired, the inserts may be coated with an electrically insulating material, for example with a ceramic .

Claims (11)

1. Locked assembly between a first pipe (2) with a male end (1) and a second pipe (4) with a socket (3) with the interposition of an annular seal (5) between the two pipes, the said seal (5) exhibiting an axis (X-X) which is coincident with the axis of the assembly and comprising: a body (19) made of elastic material, compressed radially between the socket (3) and the male end (1); an anchoring heel (20) made of elastic material, housed in an anchoring groove (8) of the socket delimited by a bottom (14) bordered by two stop walls (12-13, 15), namely a rear wall (12-13) situated on the entry side of the socket (3) and a more or less radial front wall (15) situated facing the previous one; and several locking inserts (18) made of a rigid material embedded in the heel (20) and located generally along generatrices of a cone having the same axis (X-X) as the seal and which converge in the direction of the body (19) , each insert projecting out of the seal (5) towards the axis of the latter, the head (24) or radially outer part of each insert (18) exhibiting, on the same side as the body (19) , a hook for holding the insert while the male end is being pushed into the socket, this hook having a sharp edge (3 0) and being delimited by two undercut surfaces (29, 31) , characterized in that the sharp edge (30) is immediately followed by a radially inner part (31) with a deeply concave rounded portion which allows the insert (18) , when the male end (1) is forcibly introduced into the socket (3) , radially compressing the body of the seal (5) and bringing the sharp edge (30) into contact with the front wall (15) with which it forms a connection (30; 15) , to pivot about this connection (30; 15) while maintaining it, the said connection (30; 15) forming a distinct stop which prevents the insert (18) from being extruded out of the groove (8) of the socket.

2. Assembly according to Claim 1, characterized in that the two undercut surfaces (2 9, 31) form a projecting angle directed towards the front wall (15) for any diameter of the male end (1) lying within its tolerance band and for any position of insertion of the male end into the socket.

3. Assembly according to Claim 1 or 2, characterized in that the said angle is markedly less than 90°.

4. Assembly according to Claim 1 or 2, characterized in that the said angle is slightly greater than 90°.

5. Assembly according to any one of Claims 1 to 4, characterized in that, for any diameter of the male end (1) lying within its tolerance band and for any position of insertion of the male end into the socket, the angle (a) that the outer undercut surface (29) forms with the said front wall (15) is less than the angle (β) that the other undercut surface (31) forms with this front wall.

6. Assembly according to any one of Claims 1 to 5, characterized in that the head (24) of . each insert (18) exhibits, on the opposite side from the hook (29 to 31), a surface (26) which is inclined radially towards the inside and axially towards the outside of the socket, this surface preferably ending in rounded portions (28, 33) .

7. Assembly according to any one of Claims 1 to 6, characterized in that the radially inner part (25) of each insert (18) is designed to come into locking engagement with the periphery of the male end with its head (24) bearing against the bottom (14) of the groove (8) and possibly on its stop wall (12-13) situated on the entry side of the socket.

8. Assembly according to Claim 7, characterized in that the seal (5) complies with Claim 6, and the stop wall (12-13) of the socket (3) situated on its entry side exhibits a frustoconical radially outer part (13) so that the head (24) of the inserts (18) bears more or less on the join between this part (13) and the bottom (14) of the groove (8) for large diameters of the male end (1) whereas it bears on this bottom (14) and on the same inclined part (13) for small diameters of the male end.

9. Assembly according to any one of Claims 1 to 8, 5 characterized in that each insert (18) exhibits several teeth (35) for catching on the male end (1), these teeth being offset from one another axially and radially.

10. Assembly according to any one of Claims 1 to 9, characterized in that the seal (5) includes a subs tan10 tially radial inner sealing lip (21) on the entry side of the socket (3).

11. Assembly substantially as herein described with reference to and as illustrated in the accompanying drawings .