JOINT ARRANGEMENT FOR PIPE MEMBERS COMPRISING A SPIGOTEND AND A SOCKET END

Abstract: In a joint arrangement comprising two members to be joined, for example pipe members (1, 2) which comprise a spigot end (4) and a socket end (8) as well as a resilient gasket (3) serving to seal the joint arrangement by the squeezing thereof between the sealing surfaces (9 respectively 5, 10) of the members (1, 2), the sealing surfaces (9, 5) of the joint arrangement defining a first broader gap (12) holding a first gasket portion (7) which within certain deviations from concentricity constitute a main seal between the sealing surfaces (9, 5), and a narrower guiding gap (11) holding a second gasket portion (6) which absorbs transverse forces before the said deviations are exceeded, for thereby maintaining the main seal.

Description: 81/02 Joint arrangement for pipe members comprising a spigot end and a socket end The present invention relates to a joint arrangement comprising two members to be joined, for example pipe members comprising a spigot end and a socket end as well as a resilient gasket serving to seal the joint arrangement by the squeezing thereof between the sealing surfaces of the members. In connection with the laying of pipelines in trenches or the like, the joints between the pipe members consti¬ tuting the pipeline will in many cases be subjected to considerable transverse forces, which are due to the refilling of earth masses in the trenches or occasional loads from vehicles or similar. Besides, the joints must also allow a certain angular deviation from the straight line without thereby becoming untight. In connection with joint arrangements which for example comprise concrete pipes of the socket type, the gasket has to meet two requirements which in themselves are contra¬ dictory. Primarily, the gasket must provide a sealing against an inner or outer over pressure. Due to the irregularities of the surfaces of the pipes it is desired that the gasket is both soft and elastic. At the same time it is desired that the gasket has a relatively large width, so as to be adaptable to the tolerance deviations which may occure. In addition to meeting this primary requirement the gasket should offer such a large resistance against a further compression beyond what is necessary for absorbing the tolerance deviations, that it ensures such a concetric position for the pipes in the socket joint, that no direct contact between the concrete of the socket and the pipe will occur. This . is valid especially in the cases where the individual pipe members form an angle relative to each other. Such a contact between socket and pipe will entail a crushing of concrete and breakage of pipe or socket. The object of the present invention is to give instruc¬ tions for a joint arrangement which gives a solution to the two above mentioned contradictory. problems and in a joint arrangement of the type stated in the preamble, the solution is according to the invention characterized in that the sealing surfaces of the joint arrangement define a first broader gap holding a first gasket portion which within certain deviations from concentricity forms a main seal between the sealing surfaces, and a narrower guiding gap holding a second gasket portion which absorbs transverse forces before the said deviations are exceeded, for thereby maintaining the main seal. A prefered embodiment of the joint arrangement according to the invention is to the effect that the broader gap holding the main seal portion is at least 2.5 times larger than the narrower guiding gap, that the main seal portion is given such dimensions that it in a concentric assembly of the members to be joined is compressed approxi¬ mately 20 to 30 %, and that the guiding gap portion of the gasket fills the .guiding gap within a tolerance range which on the one hand fills the guiding gap with up to 10% compre- sion, and on the other hand allows for a play of about 30% of the width of the guiding gap. In such a joint arrangement the main seal portion will always fill the maximum gap which can be formed between the sealing surfaces of the members to be joined, and there can at the same time be used a gasket which is so soft that the expansion force which occure due to compression, will not be so large that the socket is broken, or that a too large force is required for putting the pipe members together. If the joint arrangement is influenced by a transverse force which gives rise to a displacement of the members consti¬ tuting the joint arrangement, both the main seal portion and the guiding gap portion will be compressed at the one side of the joint, whereas on the oposite side they will be relieved. The mutual dimensioning of the gaps and the two gasket portions will, however, give as a result that the OMPI //. IPO gasket portion being located in the narrower guiding gap, will take over the carrying function i.e. develop a counter pressure which is equal to or larger than the allowed trans¬ verse load for the pipes, before the decompression of the main seal portion has become so large that the main seal fails. If the transverse forces are large, it is not unusual that the gasket must be compressed down to 50% of its original thickness to achieve balance between the transverse forces and the carrying ability of the gasket, and a special feature of the invention is thus to the effect that the guiding gap portion of the gasket has such a large width that 50% compression develops a counter pres¬ sure which is equal to or larger than the allowed transverse load of the pipes. Preferably, there may be used a gasket of the type involving a sliding jacket, the guiding gap portion of the gasket then having the shape of a sliding gasket which is entrained by the sealing surface of the one member to be joined when the two members are assembled into each other, so that the guiding gap portion in the finished mounted position is constituted by a double sliding jacket. In the following the invention will be further described, reference being had to the drawing which illu¬ strates an embodiment of the joint arrangement according to the invention. Fig. 1 is a diagrammatic view of a joint arrangement according to the invention. Fig. 2 is on a larger scale a section through a fraction of the joint arrangement when the joint members are assembled. The joint arrangement illustrated in fig. 1 comprises two pipe members 1 and 2 to be joined, the pipe member 1 comprising a spigot end 4 and the pipe member 2 comprising a socket end 8". At the tip of the spigot end 4 there is on a step 5 mounted a gasket 3, for example a gasket having a sliding jacket of the type which is further described in Norwegian patent application No. 78 3644, and which has a OMPI «/-_. WIPO -i larger thickness than the distance between the sealing surfaces of the members in mounted position of the joint arrangement. During assembly the pipe member 1 is pushed into the pipe member 2, so that the gasket 3 which is mounted on the spigot end 4 of the pipe member 1, slides into the socket end 4 of the pipe member 2, for thereby being squeezed between the sealing surfaces of the pipe members. In fig. 2 which shows a section through the finished assembled joint arrangement, the jacket 6 of the gasket 3 has been pulled along the main seal portion or the main gasket body 7 itself, by friction between the jacket 6 and the socket end 8 of the pipe member 2 when the members 1, 2 are pushed together during the assembly. After the assembly the jacket 6 will have a folded position between the sealing surface 9 of the socket end 8 and a carrying surface 10 on the spigot end 4 of the pipe member 1, the surfaces 9 and 10 defining a relatively narrow guiding gap 11 between the spigot and socket end. The gasket body 7 must have such a large thickness that it together with the jacket 6 can always fill the largest gap 12 which is formed between the step 5 on the spigot end 4 and the sealing surface 9 of the socket end 8. At the same time the gasket body 7 must be so soft that the expansion force which develops due to the compression during the assembly, will not be so large that the socket end 8 is cracked or that too large a force is required to push the pipe members into each other. If the pipe member 2 is influenced by a transverse force P which is larger than or oppositely directed to the transverse forces influencing the pipe member 1, the sealing surface 9 of the socket end will compress the gasket 3 until a balance is achieved between the transverse force and the carrying ability of the gasket. If the transverse forces are large it is usual that the gasket must be com¬ pressed to approximately 50% of its original thickness to achieve such a relation. OMPI For a normal rolling gasket joint for a pipe accor¬ ding to for example NS 3028, this will for example mean that a gasket which originally has a thickness of 15 mm will be compressed to 7.5 mm. When the gasket then in a con- sentric assembly of the pipe members is given a preco pres- sion of 25%, the eccentricity will become 3.75 mm, which involves that the gasket on the diametrical opposite side of the pipe will be without compression and accordingly not exercise a satisfactory gasket pressure. In connection with some new pipe types, for example PR-3-S, there has in order to cope with the mentioned conditions involving reduced compression defect when eccentricity occures, been manufactured pipes having fine tolerances and a narrow guiding gap similar to the gap 11 discussed above. When transverse loads occur, the pipe ends will then have concrete contact in the narrow gap before the gasket on the opposite side of the pipe will be relieved of its compression so much that leackage will occure. Due to the point loading involved in connection with concrete contact, only small directional deviations can be allowed and the pipes must be manufactured more sturdy than corre¬ sponding pipes of another type. When using a joint arrangement according to the invention, for example of the embodiment discussed above, the joint arrangement will, when influenced by transverse forces, function in the following way: If the larger gap 12 between the step 5 on the spigot end 4 and the sealing surface 9 of the socket end, has a dimension a of for example 11.25 mm and the guiding gap 11 between the sealing surface 9 of the socket end 8 and the supporting surface 10 of the spigot end 4 has a dimension b of 3 mm, the thickness of the gasket 3 prior to compres¬ sion being 15 mm and the thickness of jacket 6 being 1.5 mm, the following condition will develop when the joint arrange¬ ment is subjected to transverse forces. During assembly the gasket is compressed approximately 25% corresponding to 3.75 mm by squeezing between the step 5 and the sealing surface 9, the jacket 6 being entrained by the sealing surface 9 inwardly along the supporting surface 10 to end up in a folded condition between the said surfaces for thus filling the guiding gap 11 to a larger or lesser degree. For the double jacket 6 to balance any trans¬ verse forces, the two layers which together constitute 3 mm must be compressed approximately 50% corresponding to 1.5 mm of the double jacket in the area where the transverse forces come into action. The influence of the transverse forces give rise to an eccentricity which entailes that the gasket on the diametrically opposite side of the pipe is subjected to a release of compression from 25% corresponding to 3.75 mm to 15% corresponding to 3.75 mml.5 = 2.25 mm, which is sufficient for a satisfactory sealing. Due to the resilient properties of the rubber there will not develop a concentrated point load at any place in the joint arrangement, and the above mentioned guiding gap is nevertheless so large that the joint arrangement can absorb normal directional deviations without difficulties. Appropriately, the sliding jacket 6 and the main seal portion 7 can have surfaces including sawtoothed ribs 13 which slide along each other during assembly, but which in mounted position are locked in each other for thereby affixing the joint arrangement in axial direction. Although the joint arrangement according the invention can be realized most appropriately by means of a sliding jacket of the type discussed above, the invention is not bound to such a gasket structure. All gaskets comprising a sealing portion having a relatively large thickness which is compresssed relatively much during the assembly, and also comprising a thinner portion which will take a postion between the guiding surfaces and under the influence of only a relatively small eccentricity of the pipe members offer a per cent large compression, meet the preconditions of the invention.

Claims: P a t e n t c l a i m s: 1. Joint arrangement comprising two members to be joined for example pipe members (1, 2) comprising a spigot end (4) and a socket end (8) as well as a resilient gasket (3) serving to seal the joint arrangement by the squeezing thereof between the seling surfaces (9 respectively 5, 10) of the members (1, 2), c h a r a c t e r i z e d i n that the sealing surfaces (9, 5) of the joint arrangement define a first broader gap (12) holding a first gasket portion (7) which within certain deviations from concentri¬ city forms a main seal between the sealing surfaces (9, 5) , and a narrower guiding gap (11) holding a second gasket portion (6) which absorbs transverse forces before the said deviations are exceeded, for thereby maintaining the main seal. 2. Arrangement as claimed in claim 1, c h a r a c t e ¬ r i z e d i n that the broader gap (12) holding the main seal portion (7) is at least 2.5 times as large as the narrower guiding gap (11) , that the main seal portion (7) is so di entioned that it in a concentric assembly of the joint members (1, 2) will be compressed approximately 20- 30 %, and that the guiding gap (6) of the gasket fills the guiding gap (11) within a tolerance range which on the one hand fills the guiding gap (11) with up tc 10% compression and on the other hand allows for a play of about 30% of the width (b) of the guiding gap (11) . 3. Arrangement as claimed in claim 1, c h a r a c t e ¬ r i z e d i n that the guiding gap (11) and the guiding gap portion (6) of the gasket (3) is so dimensioned relative to each other that approximately 50% of the guiding gap portion (6) renders a counter pressure which is at least equal to the allowed transverse load of the pipes. 4. Arrangement as claimed in claim 1, 2 or 3, c h a r a c t e r i z e d i n that the guiding gap (11) and the gasket portion (6) contained therein is so dimensio¬ ned relative to the larger main seal gap (12) that the OMPI longitudinal axis of the pipe members can be deflected so much relative to each other as stated in the standards of interest pertaining to the joint members in question without giving rise to the occurrence of concrete contact between pipe and socket or a reduction of the effect of the main seal. 5. Arrangement as stated in any of the preceding claims: c h a r a c t e r i z e d i n that the gasket (3) is of a sliding jacket type, the jacket (6) following the move¬ ment of the socket sealing surface (9) inwardly along the spigot end (4) , so that the guiding gap portion (6) of the gasket is constituted by a double sliding jacket. 6. Arrangement as claimed in claim 5, c h a r a c t e ¬ r i z e d i n that the sliding jacket (6) and the main seal portion (7) have surfaces including sawtoothed ribs (13) which during assembly slide along each other, but which in mounted position are locked in each other for thereby axially affixing the joint arrangement. OMPI

Inventors: HAALAND P
Applicants: ALFANOR AS, HAALAND P, NORSKE REMFABRIK AS
Application year: 1981
Main classification: F16L21
IPC codes: F16L21, F16L27