ZA200600402B - Anti-extrusion pressure seal for pipes - Google Patents

Description

ANTI-EXTRUSION PRESSURE SEAL FOR PIPES s TECHNICAL FIELD:

Thiss invention relates to composite pipe seals comprising an elastomer and plasstics for sealing a pipe connection comprising a spigot within a socket, at least the socket being formed with an internall groove and the seal being possitioned within the groove. The invention is ¢ oncerned primarily, though not exclusively, with seals for relatively ‘large diameter pipes of plasstics, fibre reinforced compounds and metanl.

BA CKGROUND ART:

The groove in the socket usually has a generally rounded triangular profile that, with the spigot, has a smaller angle in the direction towards the end of the socket than towards the body of the pipe. The elastomer, usually rubber, is profiled with leading and trailing lips to facilitate insertion of the spigot into the socket and to expand aand lock to the spigot and socket when subjected to a pressure fluid in the= pipe. The hardness of the rubober clearly has an effect on the function off the seal. Softer rubber is dessired for effective sealing of pipes that may have bumps and anomalies, such as thin walled pipes and pipes that are not axially aligned. However, such softer rubbers can extrude through the gap between socket and spigot under high pressure and are known to fall out oft the grooves in the sockets du ring transport and handling. Thus several designs of composite seals of elastomer and plastics or metal have been propoosed. Such composite seals ha ve the sealing benefits of soft rubbers and simultaneously the an-ti-extrusion and locking in the socket groove properties of hard rubbers.

Ar example of a composite seal is that made by Trelleborg Forsheda and sold ure der the code Forsheda 576 with the trade name Anger-Lock™". This se al comprises a plastics tip bonded to or co-e=xtruded with a soft rubber se al. This seal is superficially similar to the commposite mould and sealing rimg of US 4,818,209 to Forsheda AB, the purposes and functions of the two se als being different, however. US 4,666,165 aulso to Forsheda AB discloses a «composite seal comprising a rubber body ard a separate longitudinally spe lit locking ring that seats in a groove in the- rubber body. All of these

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SE ; 1055, 00402 exarnples have longitudinally extending slots or slits to permit flexing of the golastics in order to fit the sealing ring into a socket.

This invention seeks to provide a composite seal that is easy and relatively inexpensive to manufacture or that cam be made using standard manufacturing technology without co-injection or other special techniques or technologies or that does not require bonding or that facilitates variations of shape and hardness of the elastomer or that can be bent without fracturing in order to fit it into a pipe socket or that provides reactive forces against extrusion of the sealing ring at high pressures.

DIS«CLOSURE OF THE INVENTION:

The invention provides a composite pipe seal comprising an elastomeric sealling body and a retaining ring of a suitalble material, the retaining ring and sealing body being connectable to each other by inter-engaging forrmations.

Preferably the retaining ring has a V-shape with a hollow core that can receive a portion of the sealing body.

Preferably at least one, and optimally both, of the free ends of the

V-shape has an inwardly directed lip that engag es a shoulder in the sealing body to inhibit disengagement of the retaining ring and body.

Pre ferably the retaining ring has a thin walled construction, with the wa lls being flexible in order to facilitate bending for fitting the sealing ring to a pipe.

Pre=ferably the retaining ring and sealing body~ are shaped such that the retaining ring fits substantially into the triangular shape formed between a peipe spigot and groove in a pipe socket in use.

Further features, variants and/or advantages of the invention will emerge fro m the following non-limiting description of a n example of the invention 3s made with reference to the accompanying schermatic drawings and from the cla ims, which are to be regarded as an integral part of this description.

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BRIEF DE SCRIPTION OF THE DRAWINGS:

Figure 1 shows a section through the end regions of two pipes joined by a socket and spigot connection, the connection being sealed by a composite pipe seal of the invention; s Figure 2 shows a sectioned detail of a portion of Fig ure 1, illustrating the composite pipe seal of the invention, the seal being shown in its natural shape in dashed lines and in-Lase shape in solid lines; and

Figure 3 shows a sectioned detail of the composite= pipe seal of the invention.

DESCRIP*TION OF ILLUSTRATED EMBODIMENTS:

Figure 1 shows the end regions of two connected pipes 1 O. Each pipe has a plain, spigot end 12 and an enlarged diameter socket end 14. The socket, in a direction towards the end, has an enlarged diameter region 16 and an internal, triangular shaped groove 18. A pipe seal 2 O is seated in the groove. The gap or difference in diameter between the owutside of the spigot and the i nside of the socket is designed to be about 2 nnm, but in practice it may bes as large as 4 mm or may be 4 mm or larger with pipes that are not axially al igned. The gap permits an elastomeric sealing ring to be extruded out of the pipe connection at high pressure.

Figure 2 shows that the groove 18 has a generally mounded triangular profile with a leading slope 18.1 that has a smaller imcluded angle with the spigot than a trailing end 18.2. This is conventional and is designed to provide an abutment for the seal during insertion of a spigot into the socket a nd a ramp or wedge for compressing the seal when under pressure.

The seal ing ring 20 is a composite of a suitable rubber sealing body 22 and a flexibl e plastics anti-extrusion tip 24. The sealing body 22 is broadly triangular with a leading end 26, an outer edge 28 withh three sealing ribs 28.1, a trailing end 30 with pressure deformable sealing lips 30.1 and 30.2, ard an inner edge 32 with a trailing end directead sealing lip 32.1.

The leading end 26 is substantially triangular and pa rtially separated or distinguished from the major portion of body by a groove= forming a shoulder 34 and =an annular slot 36. In use the sealing body is ceompressed between the spigot and socket as shown, with the sealing ribs and lips ensuring a seal eveen when the pipe is not pressured.

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The tip 24 has aa V-shape with an insertion chamfer 38 at its leading edge, arms 40 and 42, and inwardly turned locating lips 40.1 and 42.1 respectively, at the free ends of the arms. The inside of the V-shape substantially matches the shape of the leading end 26 of the sealing body.

The lips 40.1 amd 42.1, respectively, engage the slot 36 and shoulder 34.

The tip has a thin wall construction so that it can bend and flex without breaking.

In use, the seali ng body 22 and tip are manufactured separately, each being made of materi als with optimum properties for its intended purpose. Thus, the sealing bodily may have any desired shape and hardness for its sealing function and an y of such sealing body variants may be used with a common tip 24. The co mposite seal is assembled by simply insesrting the tip over the leading ed ge of the sealing body until the locating lips engage the 1s shoulder and slot. Co-extrusion, bonding, welding amd the like joining techniques are2 no longer required. The assembled se al is then bent or folded so that Tt can be inserted into a pipe socket groove. Once inserted the tip 24 is stiff enough to ensure that, in combination with the forces generated by t he sealing body 22, the seal remains in the groove during transport and handling. When an assembled pipe is pressurised, the pressure acts to urge the seal towards the free end of the socket; this urges the tip into the tapered gap between spigot and socket where it locks because it is not compressible or extrudable. At the same time, this movement causes the arms of the tip to clamp the lead ing end of sealing body and hold the tip and sealing body in engagement. Also, the leading end is compr essed into the tip and forces the arms of the tip apart, further ensurimng the tip cannot be pushed through thes gap.

The inventions is not limited to the precise details described above and shown in the drawings. Modifications may be made and other embodiments developed without departing from the spirit of the invertion. For example, the tip may bee provided with an annular serrated finger formation that engages in ar annular slot in the leading end of the sealing body.

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Claims (7)

CLAIMS:

1. A composite pipe seal comprising an elastomeric sealing body and a retaining ring of a suitable material, the retaining ring and sealing body being connectable to each other by inter-engaging formations.

2. The composite pipe seal of claim 1, wherein the retaining ring has a V-shape with a hollow core that can receive a portion of the sealing body.

3. The composite pipe seal of claim 2, wherein at least one of the free ends of the V-shape has an inwardly directed lip that engages a shoulder in the sealing body to inhibit disengagement of the retaining ring and body.

4. The composite pipe seal of claim 3, wherein both of the free ends of the V-shape have an inwardly directed lip that engages a shoulder in the sealing body.

5S. The composite pipe seal of any one of claims 1 to 4, wherein the retaining ring has a thin walled construction, with the walls being sufficiently flexible to facilitate bermding for fitting the sealing ring to a pipe.

6. The composite pipe seal of any one of claims 1 to 5, wherein the retaining ring and sealing body are shaped such that the retaining ring fits substantially into the triangular shape formed between a pipe spigot and groove in a pipe socket in use.

7. A composite pipe seal substantially as herein described with reference to and as illustrated in the drawings. / DATE 04 January 2006 0 Hh RE 4 HH 0 LES fis HER & CO. Applicant's Agents C2445EPNS 03.01.2008 page 6 A