The present invention concerns a cylin- drically shaped flat-ring gasket of elastomeric material and its use for sealing propulsion-type pipes, having a spigot provided at the pipe end along with a connect- ing sleeve enclosing the gasket.

During laying of so-called spigot-ended pipes, i.e. pipes provided with the end section of an outer diameter smaller than that of the pipe, the pipes are joined by means of connecting sleeves enclosing the spigots. As a rule, a so-called slip-ring gasket is installed between the connecting sleeve and the spigot on the pipe end or in the groove of the spigot, as described, for example, by D. Stein et al in Pipes and Pipelines International, July/August 1983, pp. 7 to 13. Providing a groove for the slip-ring gasket on the spigot ends of the pipes, of necessity, results in weakening of the pipe wall so that in difficult conditions of propulsion, damages to the pipe in the area of connection are repeatedly observed

causing, in the long-term, undesirable leakages. With¬ out the groove the sealing capacity of a simple slip-ring gasket is frequently inadequate.

From DE-OS 1,475,807, a connecting and sealing element is known for service pipes in which two pipe ends, are joined together tightly and tensionally by means of a pipe sleeve extending over these latter. The sealing element, on each end on the internal and external periphery thereof, is provided with a bulge ^' comprising a narrow neck and laminations which protrude on the upright fins both internal and external peri¬ phery, and which are higher than the bulges. These laminations engage circumferentially provided grooves of the connecting sleeve and, in the mounted state they are under pressure. The bulges engage corres¬ ponding grooves provided in the connecting sleeve and in the outside of the wall pipe thereby providing a safe fit of the sealing element.

However, this type of gasket is not suitable for use with so-called propulsive pipes due to the necessary grooves in the connecting sleeve and in the pipe ends, because in propulsion technology, cylin- drically-shaped connecting sleeves are employed with relatively low wall diameters in which grooves could only be made at a high cost.

The present invention provides a speci¬ fically flat ring-gasket for use with propulsion- -type, spigot-ended pipes which can be easily mounted on the pipe spigot and whose sealing capacity is superior to that of conventional slip-ring gaskets.

Deficiencies of known gaskets are overcome by the use of annular, cylindrically-shaped flat-ring gaskets of elastomeric material, comprising a plurality of spaced- -apart circumferenti l bulges of semi-circular cross- -section that are disposed on the continuous flat-ring gasket and are directed outwardly, with the lateral outer bulges terminating flatly toward the ends of the gasket as gaskets for propulsion-type pipes having spigots at the pipe ends the outer diameters of which are smaller than the pipe diameter. The gasket is placed on the smooth spigot and, under pressure, is enclosed by the sleeve of the matching pipe.

Preferably, the basic body of the cylin- drically-shaped flat-ring gasket, in cross-section, is of a spherical configuration. In one form of embodi¬ ment, on the inner side of the cyclindrically-shaped body facing the pipe spigot, a circumferential rack- -type profile is formed to assure a better fit of the gasket under pressure on the outer pipe wall.

Preferably, the gaskets are secured to the spigots of the propulsion pipes by means of an adhesive.

If the connecting sleeve of a pipe is secured to the spigot by applying adhesive or by shrinkage, it is necessary only to provide a gasket on the spigot of the pipe to be inserted into the connecting sleeve.

However, it is also possible to provide at both abutting ends of the pipes respectively one of the gaskets of this invention which pipe ends are then jointly enclosed by a connecting sleeve extending over the full length of the pipe spigots. This connecting sleeve has an

external diameter corresponding to the external diameter of the propulsion pipes, with the internal diameter being such that pressure is exerted on the gasket.

To facilitate insertion of a spigot provided with a gasket into the pipe end of another pipe fur¬ nished with a connecting sleeve, the cross-section of the cylindrically-shaped basic body of the flat-ring gasket is slightly spherical in configuration. For an improved fit on the pipe wall it is advantageous ^" for the gasket to have, circumferentially, a rack-type profile on the inner side facing the pipe spigot. Such a profile, at the same time, facilitates the anchoring operation, improving adherence of the gasket to the pipe spigot. Such anchoring can be effected by an adhesive or a fast-curing molding material. It is preferred, especially with propulsive pipes made of glass fiber-reinforced plastic material to use dual-component adhesives such as epoxy resin adhesives.

Materials used for gaskets include synthetic elastomers, chloroprene rubber, other natural and synthetic rubbers, fluoropolymers of adequate durability and flexibility so as to deform under pressure the con¬ necting sleeve so that the necessary sealing effect is achieved.

The specifically formed flat-ring gaskets of the present invention comprise a cylindrically- -shaped basic body having a width of between 40 and 140 mm, preferably between 60 and 110 mm. The thickness in the area of the bulges provided on the outer surface and being semi-circular in cross-section, is between

2.5 and 20 mm, and the groove depth between the bulges is between 1 and 16 mm, preferably, between 1 and 8 nun.

The inside diameter of the cylindrically- -shaped basic body depends on the outer diameter of the pipe spigot of the propulsion pipe which, 'in respect of sewage pipes, can be between 340 and 1730 ram, depending on ^' the nominal diameter of the pipe. The space between two of the bulges on the gasket, i.e. the groove width, corresponds to twice the radius of the bulges plus 3 mm. The number of round profiles or bulges on the cylindrically-shaped basic body is between 5 and 12/ preferably 6 to 8, with the circumferential round profiles being arranged at the distance referred to above. The round profiles or bulges disposed on the two lateral ends externally extend flatly toward the gasket ends.

The figure 1 illustrates a sectional view of the arrangement of the gasket on spigot 2 of a spigot- -ended pipe 3. The end of the one pipe provided with the spigot 1 is inserted into the connecting sleeve 4 of the connecting pipe 5. The connecting sleeve 4 is secured to the spigot end of the spigot-ended pipe by means of adhesive or by shrinkage thereby eliminat- ing the need for a seal between the connecting sleeve and the external wall of the pipe. Gasket 1 is under pressure from the connecting sleeve 4 so that the elasticity of the gasket material produces a top-sided flattening and a lateral expansion of the bulges. In the example of the embodiment, gasket 1 is secured to spigot 2 of the pipe by means of an adhesive.

The figure 2 illustrates a sectional view of the embodiment of the gasket 1 with the plurality of spaced-apart, out¬ wardly directed circumferential bulges 7 of semi-circular cross-section disposed on the continuous cylindrical flat- ring gasket, with the lateral external bulges extending flatly toward the gasket end and with a circumferential rack-type profile 6 on the internal side of the flat-ring gasket facing the spigot on the propulsive pipe later on.

The above-described special flat-ring gaskets are particularly suitable for propulsive pipes of glass fiber-reinforced plastic material. However, basically, these gaskets can also be employed for propulsive! pipes made of other materials such as cement. ^•

A special advantage involved therewith resides in that the specifically formed flat-ring gaskets do not require any specifically shaped spigots on the pipe ends or specifically shaped connecting sleeves. They can be easily pushed over the spigots of the pipe and, optionally, be secured by an adhesive.