A SEAL RING FOR A SLEEVE JOINT

Abstract: This invention relates to a seal ring for a sleeve joint, which besides sealing also locks the sleeve (3) and an insert end (4) together in the longitudinal direction of the pipes. An axial locking is needed especially in connection with pressure pipes. The locking effect of the seal ring (6) can be improved by making the ring at least partially of a material (8) expanding when coming into contact with a liquid.

Description: A seal ring for a sleeve joint This invention relates to a seal ring for a sleeve joint, which seal ring is intended to be placed in a sealing groove of a sleeve between the sleeve and an insert end and which seal ring is of a flexible material and arranged to be pressed against the sleeve and the insert end to lock these together in the direction of their longitudinal axles. In water pipes and in some effluent pipes, such as pressure effluent pipes, the medium to be trans¬ ported is subjected to pressure. The pressurization is provided for instance by feeding the medium into a pipeline by means of pumps. Typical pressures are 3 to 8 bars. In certain situations, e.g. when the pumps are stopped, a considerable underpressure can also be created in the pipeline. At points of change of course and discontinuity of pressurized pipelines, such as bends, valves and branch connections, the pipes and interconnectors of the pipeline shall be locked together in order to keep the mutual location of the parts unchanged dur¬ ing a pressure load. Because the pipeline parts must not be displaced with respect to the surrounding earth either, parts shall be locked together along such a distance that the friction between the pipes and the earth is large enough to anchor the bend point in its place. Locking rims are generally used to lock the pipes together and to the interconnec- tors, which rims surround the joint and grip the in¬ sert end by means of teeth thrusting into its sur¬ face. The use of such a locking rim naturally causes costs, and because many plastic pipe materials, such as PVC, are sensitive to notch effect, the notches caused by the teeth weaken the pipe. The object of this invention is to provide a seal ring for a sleeve joint, creating between the sleeve and the insert end an interlocking so durable that locking rims can be omitted entirely. The seal ring according to the invention is characterized in that the seal ring is at least partially of a materi¬ al expanding when coming into contact with a liquid. The press force of the seal ring, directed to the sleeve and the insert end under the influence of the swelling, i.e. expanding, material included in the seal ring, increases when the pipeline is filled with water, the pipes being locked together in their longitudinal direction. Thanks to this, there is no need to use locking rims, due to which the pipeline costs are decreased and the installation time is shortened. According to an advantageous embodiment, a seal ring consists of three concentric layers, the inner- most and outermost layer of which are of a conven¬ tional material used for seal rings and the middle layer is of said expanding material. In a seal ring constructed in this manner, those surfaces which have a sealing and locking effect are of a conventional sealing material, which is most suitable for these purposes, while the middle part of the ring includes expanding material, the sealing effect of which is not always on the same level as that of a convention¬ al seal ring material, such as rubber. In order that a material expanding under the influence of humidity would expand as fast and much as possible when the pipeline is supplied with a liq¬ uid, it is advisable that the layer of the expanding material comprises recesses, such as holes, which open to the surface of the ring facing the interior of the pipe. Due to the recesses, the surface of the layer of the expanding material toward the interior of the pipe is larger than if the surface were even, thanks to which the advantages mentioned above are reached. The locking effect of the seal ring can be de¬ cisively improved by means of an embodiment of the invention, according to which the inner surface of the seal ring facing the insert end comprises a layer of a material increasing friction. The material in¬ creasing friction can be a grinding agent, such as corundum, and due to that the locking force between the seal ring and the insert end becomes greater than if the mere sealing material were pressed against the insert end. In general, relatively soft rubber qualities, 50 to 60 °IRH, are used as sealings. In these cases the sealings are dimensioned for great compressions (of ab. 30 %). This is usable at joints with small tolerances of sleeve and insert end, i.e. when the clearance is small, so that the pressure does not press the sealing out of the sleeve. Now it has been observed unexpectedly that by using relatively hard rubber qualities together with an expanding material at a seal ring the advantage is reached that the ring endures, except strain by compression, also tension strain without being pushed out of the sleeve. This need appears with emphasis when a joint allowing an¬ gular variations is constructed, which makes large joint clearances necessary. When a hard sealing is used, there is a risk that the joint leaks on the groove side. Such leakages can be prevented in such a manner that the rubber ring has a zone of a softer rubber quality on the back side of the ring as well as on the insert end side of the ring. The seal ring according to the invention is described in the following in greater detail with reference to the enclosed drawing, in which Figure 1 shows a sleeve joint using a seal ring according to the invention, in partial longitudinal section, Figure 2 shows a detail of the joint on a larger scale, the seal ring differing to some extent from the one shown in Figure 1, and Figure 3 shows a third embodiment of the seal ring. Figure 1 shows a sleeve joint between two pipes 1 and 2. At the end of the pipe 1 there is a sleeve 3 surrounding an insert end 4 of the pipe 2. The sleeve 3 is provided with a sealing groove 5 opening inwards and having a seal ring 6. The seal ring is made of a flexible material and it is dimensioned in a usual manner with a cross- section so great that it is pressed against the sleeve 3 and the insert end 4, to seal the slot be¬ tween these parts and to lock them together in the longitudinal direction of the pipeline. According to the invention, the seal ring 6 consists partly of a conventional seal ring material 7 and partly of a material 8 expanding when coming into contact with a liquid. In the embodiment of Figure 1, the seal ring surfaces positioned against the sleeve 3 and the in¬ sert end 4 consist of the seal ring material 7 and between them, in the middle part of the ring cross- section, there is a layer of the expanding material 8. This layer extends up to the ring surface on that side of the ring which faces the interior of the pipeline, due to which the liquid in the pipeline comes into contact with the material 8. The material 7 preferably consists of a hard rubber, the °IRH of which is at least 70. It can, if necessary, be coated with a layer of a softer rubber, which layer faces the sealing groove 5 of the sleeve and the insert end 2. Figure 1 shows also a mounting socket 9 surrounding the insert end, which socket can be used to facilitate the positioning of the seal ring. The seal ring according to the invention func- tions in the following manner. The seal ring 6 is brought to the mounting place in an airtight packing in order that the humidity of air would not cause an expansion of the material 8, which can be for in¬ stance hydrophile rubber. The seal ring is taken out of the packing and arranged in the sealing groove 5 of the sleeve, after which the mounting socket 9 is pushed so far into the sleeve that it covers the in¬ ner surface of the seal ring. After this the insert end 4 is pushed into the mounting socket and the socket is drawn out of the slot between the sleeve and the insert end. The invention is intended to be used primarily in connection with pressure pipes, which are disin¬ fected before use and tested as to pressure-tight- ness. In connection with these measures, the pipe is filled with a liquid seeking its way from the interi¬ or of the pipe through the slot between the insert end and the sleeve to the seal ring. The hydrophile material 8 begins to swell when being contacted by the liquid, due to which the outer and inner surfaces of the seal ring are pressed with great force against the sleeve and the insert end locking them in place in the longitudinal direction of the pipe. Figure 2 shows a seal ring, the structure of which somewhat differs from the ring shown in Figure 1. In this case, the layer 8 of the expanding materi¬ al extends across the seal ring from edge to edge and said layer has recesses 10 adjacent to each other, one of which is shown in broken lines in Figure 2. The recesses in the embodiment of Figure 2 are holes having a bottom and opening to that surface of the ring facing the interior of the pipe, so that liquid can come into the holes when the pipe is filled with water. The object of the holes is to extend the sur- face of the layer 8 to improve the expanding effect of the material. The embodiment of Figure 2 differs from the em¬ bodiment described earlier also in the respect that the inner surface of the seal ring 6 facing the in- sert end is provided with a layer of a material in¬ creasing friction, for instance a grinding agent, such as corundum. This layer is indicated by the ref¬ erence numeral 11. In addition to the grinding agent, the layer includes a binding agent binding the grind- ing agent to the surface of the seal ring. Especially in this embodiment, it is recommendable to use a mounting socket 9, because the grinding agent makes it heavy to push the insert end into the sleeve otherwise. The seal ring has a lip 12 arranged to be pushed into a non-shown groove parallel to the peri¬ phery and located in the outer surface of the insert end. In the embodiment of Figure 3, the seal ring 6 has two layers, the outer layer 7 of which consists of a conventional seal ring material and the inner layer 8 of a hydrophile rubber or the like. The inner surface of the ring comprises a layer 11 of a materi¬ al increasing friction. The inner and outer surface of the sealing additionally have zones 13 consisting of a seal ring material being softer than the materi¬ al of the layer 7. The zones prevent leakages when the layer 7 consists of a hard material. According to Figure 3, the inner surface of the groove 5 and the outer surface of the seal ring facing the sleeve are formed to a circular segment. This is to an advantage when the pipes are placed in an angle with each other, and additionally, it helps to provide a locking of the insert end, because the sealing can turn in the groove when swelling and can thus be adjusted to a possible angular variation of the joint. Further, in a ready-mounted pipeline the sealing can freely follow possible angular varia¬ tions. Differing from the above, the inner surface of the seal ring according to Figure 1 can also be pro¬ vided with a layer increasing friction or the surface can be handled in some other way so that it engages well in the insert end. So, a split ring made of metal and having teeth on its inner surface can be placed on the inner surface of the seal ring. The expanding layer 8 extends most preferably along the whole length of the seal ring as a continu¬ ous layer. Alternatively, the expanding layer can be a ring, which is loose with respect to a ring of a conventional seal ring material and can be located outside or inside the lastmentioned ring or within it. The expanding material can also form the whole seal ring.

Claims: Claims: 1. A seal ring for a sleeve joint, which seal ring is intended to be placed in a sealing groove of a sleeve between the sleeve and an insert end and which seal ring (6) is of a flexible material and arranged to be pressed against the sleeve (3) and the insert end (4) to lock these together in the direc¬ tion of their longitudinal axles, c h a r a c - t e r i z e d in that the seal ring (6) is at least partially of a material (8) expanding when coming into contact with a liquid. 2. A seal ring according to claim 1, c h a r ¬ a c t e r i z e d in that the seal ring consists of three concentric layers, the innermost and outermost layer (7) being of a conventional material used for seal rings and the middle ring (8) being of said ex¬ panding material. 3. A seal ring according to claim 1, c h a r - a c t e r i z e d in that the expanding material forms a layer (8) on the inner surface of the ring. 4. A seal ring according to claim 2 or 3, c h a r a c t e r i z e d in that the layer of the expanding material has recesses, such as holes (10), opening to the side of the ring facing the interior of the pipe. 5. A seal ring according to claim 1, c h a r ¬ a c t e r i z e d in that said expanding material (8) is hydrophile rubber. 6. A seal ring according to claim 1, c h a r ¬ a c t e r i z e d in that the inner surface of the seal ring against the insert end (4) has a layer (11) of a material increasing friction, which material is a grinding agent, such as corundum. 7. A seal ring according to claim 1, c h a r - a c t e r i z e d in that the seal ring has a lip (12) arranged to be pushed into the groove on the outer surface of the insert end. 8. A sleeve joint according to claim 1, c h a r a c t e r i z e d in that the material (7) surrounding the expanding material is hard rubber, the °IRH of which is at least 70. 9. A sleeve joint according to claim 8, c h a r a c t e r i z e d in that the hard rubber is on the outer and inner surface of the seal ring (6) coated with a layer of a softer rubber. 10. A sleeve joint according one of the preced¬ ing claims, c h a r a c t e r i z e d in that the surface of the seal ring (6) facing the sleeve has a cross-section in the form of a circular segment.

Inventors: JAERVENKYLAE JYRI, JAERVENKYLAE, JYRI
Applicants: UPONOR NV, UPONOR N.V.
Application year: 1990
Main classification: F16L21
IPC codes: F16L17, F16L21