The present invention, relates to a type of gasket which is adapted for sealing the gap between two approximately parallel sealing surfaces which during the assembly are dis¬ placed axially relative to each other, whereby the gasket is compressed therebetween, for example a pipe with an associ¬ ated socket, as well as a method for manufacturing the pipes in which the gasket is included as a part thereof.

There exists a great number of known types of gaskets which are to be used for this purpose, also including the group to which the present gasket can be said to be related, in which the gasket profile substantially consists of two main parts which are tied together through a connection piece of narrower width.

The first main body of the gasket profile designated "the attachment part", is mounted undisplaceable on the one sealing' surface, whereas the other, designated "the sliding part", which is disposed outside the first one, is provided with more or less marked sealing lips which point in both directions relative to the axis of the gasket.

The distance between the main bodies is smallest at the insertion side of the gasket. The purpose thereof is that the gasket will have such a large opening that a pipe can be pushed thereinto, whereafter the pipe will abut against the concave surface of the sliding part, and because this is connected to the first stationary attachment part with the thin intermediate piece, the sliding part will pivot about the intermediate piece so that both sides of the concave sliding surface with the sealing lips will abut against the pipe pushed thereinto, and a sealing is thereby established in both directions. Among other known gaskets having aproxi- mately similar function are those mentioned in Norwegian Patent Specification 137400 - US Patent Specification 2809853 - 3158376 and British Patent Specification 154.409.

"BUREA

OMPI

Gaskets in accordance with the above-mentioned patent specifications and also others of the same group, function largely satisfactorily, if the gasket in one or another manner is very well attached to one of the sealing surfaces, for example by having an especially broad abutment surface or by mounting the gasket in a relatively deep groove adapted therefor. If this attachment does not function satisfactorily, the gasket profile will, even if it is supplied with a lubri¬ cant on the surface, due to the friction existing between the pipe and the gasket, still be apt to pivot about its own axis, so that the assembly becomes unsuccessful. One may seek to counteract this by connecting the gasket parts more or less offset relative to the axis of the gasket or the profile, but none of these known provisions function satisfactorily in this respect.

However, experiments have shown that this problem can be solved in a satisfactory manner, and this invention which in the following is to be further described with reference to the drawings, is intended to give instructions for a gasket profile in which the above-mentioned disadvantages are elimi¬ nated, a larger part of the gasket volume being actively engaged in the sealing efficiency.

Fig. 1 is a section through a first embodiment of the gasket profile. This can be said to be constructed from three main elements. The attachment part (1), the sliding part (2) and an inclined connection part (3) therebetween.

The attachment part 1 can have a special shape, so that it matches a groove or similar, adapted thereto, but generally it will have a width which is substantially larger than the height, it will preferably have a concave abutment side and end surfaces 7 and 8 with abrupt corners.

The sliding part 2 shall have a concave surface 4. The surface can be evenly curved or for example consist of several inclined surfaces. The end surfaces 5 and 6 should preferably define acute angles together with the surface 4 so as to provide outwardly protruding sealing lips. To facilitate the insertion of one of the sealing surfaces into the other,

the sliding part 2 has an inclined position relative to the attachment part 1 , so that the gasket height C is substantially less than the gasket height d.

The connection part 3 is attached to the sliding part 2 at the front edge of the gasket, in the proximity of the point of attack A and extends therefrom obliquely downwards towards the inner surface 7 of the attachment part 1 under an angle of 45° or less. The twisting force which influences the gasket in the direction of the arrow in the proximity of A, will then via the connection part 3 be directed towards the supporting surface and the limiting surface 7 of the attachment part 1 , so that the gasket will be given a pivot point close to B, and the connection part 3 which has a greater length than the pivot radius, will act as a thrust bar and prevent rotation of the profile.

Fig. 2 illustrates a cutting out of a gasket mounted on the spigot end of a pipe 9. For the fixing of the gasket on the pipe this can be provided with a step 10. Onto the pipe there is pushed another pipe 11 having a socket 12. The socket 12 has a somewhat larger diameter D than the diameter d of the gasket and is additionally provided with a radius of entrance 13.

As the socket 12 is pushed onto the sliding part 2 of the gasket it will hit the inclined concave sliding surface

4 thereof. Because the connection part 3 has less sectional area than the attachment and sliding part 1 and 2, respec¬ tively, the sliding part 2 will pivot thereabout close to the attachment point B, and since this point is at a maximum distance from the point of attack A, the efficiency of the pivot movement which renders an increased thickness, will be at a maximum at the point of attack A. The sealing lips

5 and 6 will thereby obtain a sufficient sealing pressure even if the gap between the pipe 9 and the socket 12 should be substantially larger than the nominal dimension thereof, as this is illustrated in Fig. 3.

Due to its structure the gasket can also be used, even if the gap between the sealing surfaces should be substantially

narrower than predicted. The approximate Z-shape of the profile will then, as it is illustrated in Fig. 4, be converted to a flat compressed Z-shape, substantially by bending the material, and the sealing pressure will therefore not increase above acceptable values.

Of course the gasket can also be used having the attach¬ ment part fixedly connected to a socket 14, as this is illu¬ strated in Fig. 6, in which the spigot end 15 is pushed into the gasket.

An embodiment of this method of jointing, which is of special interest, involves a system for manufacturing the socket of the pipe, in which the gasket, as illustrated in Fig. 5, is mounted and compressed on a construction mandrel 16 with its gliding part 2 in contact therewith, on the outside of which mandrel the socket 14 of the pipe thereafter is constructed. After cooling or curing the mandrel 16 is pulled out of the socket, whereby the gasket is released and takes the shape as illustrated in Fig. 6, the pipe then being ready for use.

However, if the gasket is to be used in such a sealing system, the gasket must be prevented from being stretched when being mounted outside the construction mandrel 16. The gasket must therefore be provided with a non-stretchable reinforcement 7. If this has a diameter which is adapted to the circumstances, the gasket will take a prestressed and compressed position as illustrated in Fig. 5. As previously described the gasket will then regain its original shape as soon as the construction mandrel 16 is removed.

In addition to its primary function (to compress the profile), the external reinforcement ring 17 also constitutes a substantial expedient for improving the pipe structure. Because the reinforcement is designed to absorb the maximum gasket pressure which can develop, the designer of the pipe needs no longer to take into consideration the uncertainty associated with which load this will give on the socket.

It is reason to believe that he is therefore able to reduce the dimensions of the materials considerably when

he only needs to give due consideration to the transverse forces and similar, which influence the socket.

The embodiment including an external reinforcement ring for gaskets which in a precompressed state are built into the socket, during the manufacturing of a pipe, can of course be used for other compression gaskets, for example of that type which is illustrated in Fig. 7 and consequently is not bound to the first described embodiment.

When in use the gaskets of the type illustrated in Fig. 1 must be provided with an appropriate lubricant on the surface 4 before the assembly. For the elimination thereof the gaskets can be provided with a closed sliding jacket of the type described in US Patent Specification (4.299.399), in which the jacket 18 in Fig. 7 during the assembly slides across the sliding surface 4 - 19a of the gasket body and forms a double supporting layer 20 i continuation of the gasket. Especially in connection with the application of the gasket when this is mounted on a construction mandrel it may be unfavourable that it in this case must be compressed too strongly, primarily because this may make it difficult for the mounting thereof on the construction mandrel. In such a case it would be more convenient if the gasket could have its thickness of material increased, and thereby its compression during the assembly of the pipes.

If a relatively long assembly movement can be accepted and if there at the same time is enough gap space inside the body of the gasket, such a gasket thickness can be achieved by increasing the thickness of the sliding gasket 18 towards its connection 21 to the gasket body 19.

The long sockets which will be necessary for achieving anything essential by this approach, are however frequently not desired, and a substantially larger increase of thickness can be achieved by another and newly developed embodiment of the above closed sliding jacket. This embodiment will be further described in the following, reference being had to Fig. 8.

The sliding jacket 22 which in this embodiment is provided with an increasing thickness, is at its thickest end attached to the front side of the body 5-19c in the same manner as in Fig. 7, whereas the other end of the jacket 22c, which preferably is given a bulge 25, is attached to the point of attack A of the gasket body in such a manner that the bulge 25 obtains a diameter 26 which is less than the diameter 27 of the gasket body. The largest width of the sliding jacket extends forwardly and outwards towards the socket opening 28. The inner surfaces of the sliding jacket which may be supplied with locking ribs 29, is in known manner provided with a suitable lubricant.

When the pipe 9 is pushed into the socket 1 , it will hit the double sliding jacket 22 at the bulge 25 thereof, and this will follow the movement of the pipe inwardly along the gasket body 2-19, whereas the lubricated inner surfaces 29 will slide relative to each other, the jacket at the same time rolling across the gasket body and forming a double layer thereover. The thickness of the material and the com¬ pression will then increase corresponding to two jacket thick¬ ness dimensions in the sealing gap.

By adapting the width of the sliding jacket and the length of the assembly movement it is also by this embodiment possible to achieve a supporting layer 30-31, which may extend beyond the sealing width 32 in one or both directions. Besides, this embodiment can give the jacket 22 such a width that it by being inserted by the pipe 9 only will give a double jacket layer 20 across the sealing width 32, so that the gasket also can be used even if no gap is available inside the sealing gap, as this is illustrated in Fig. 9 and 10.

From the description it will appear that this embodiment of a closed double sliding jacket is especially favourable in the described example, but the invention is not limited thereby, but can be used in connection with any other appropri¬ ate gasket structure.

For example, there can also be used a closed double sliding jacket in connection with that type of lamellae gasket

IfURE _/

illustrated in Fig. 7, the sliding jacket being attached only to one point of the gasket body, for example in the area 17. During assembly the inner jacket surfaces will then slide relative to each other, the portion of the gasket surface resting against the gasket body, i.e. the inner portion, being relatively stationary in relation to the gasket body, whereas the outer portion will slide along the inner.