A PLASTIC PIPE COMPRISING AN OUTER CORRUGATED PIPE AND A SMOOTH INNER WALL, AND A METHOD OF REPAIRING OR RENOVATING A SEWAGE PIPE

Abstract: A plastic pipe l consisting of an outer corrugated plastic pipe 2 and an inner smooth wall 4 consisting of a wear resistant elastomer, particularly a thermoplastic rubber fixed in the inner bottoms wave valleys 8a to said outer corrugated pipe 2. The inner wall 4 consists of a pipe which has been coextruded with the outer corrugated pipe 2 so that the inner and outer pipe are heat welded to each other l0a. The cavities 9 between the inner pipe l0 and the corrugations 3 may be filled with a foam plastic 7. This plastic pipe l is used for repairing or renewing a sewage pipe l2 by installing such a pipe l from a vertical shaft ll of the sewage system into the sewage pipes l2. The interstices l6 between the outer side of the corrugations 3 and the inner side of the sewage pipe l2 may be filled with a mortar l7.

Description: The invention relates to a plastic pipe comprising an outer pipe with rigid external corrugations being at least covered on their inner side by sealing surfaces made of deformable material to form an essentially smooth inner wall. A plastic pipe of this type is known from German Auslegeschrift 2.4l3.878. If the sealing surfaces of such a pipe consist of a plastic film of plasticised polyvinyl chloride having a thickness of 0.05 mm, said pipe is readily deformable and can easily be installed at the correct required place from many different positions. A drawback of said pipe is, however, the poor resistance to wear, so that only liquids can be transported through the pipe. If liquids containing solid substances are transported, a plastic film of this type forming the inner wall of the pipe, is very rapidly damaged, resulting in an unusable pipe. An object of the invention is therefore to provide a plastic pipe of the abovementioned type which does not present these disadvantages. This objective is achieved according to the invention in that the sealing surfaces consist of a material possessing elastic properties. A plastic pipe of this type is deformable in a similar manner to a plastic pipe without sealing surfaces, but offers the great advantage that the inner side is very resistant to wear and is therefore suitable for transporting media containing solid particles or for passing through cables and the like. More particularly, a plastic pipe of this type lends itself for use in a method for the repair or renewal of a sewage pipe system by installing a plastic pipe in an existing concrete sewage pipe from an essentially vertical access to a sewage pipe system. A method of this type for the repair or renewal of a sewage pipe system by pulling a plastic sleeve into such sewage pipes is generally known since the sewage pipe systems made of concrete pipes and dating in many cases from the last century or from the beginning of this century are, in particular, now exhibiting the drawback of leakage at various points, so that the waste water transported through sewage pipe systems of this type has a strongly contaminating effect on the soil or groundwater surrounding the sewage pipe systems. In view of the considerable damages to road or street covering during the breaking up and replacement of said sewage pipe systems by new plastic pipes or concrete pipes, this method can often not be applied in practice. Nor does lining of the sewage pipe systems with plastic sheets always provide a solution since this method can only be applied if the sewage pipes have such dimensions that they are accessible for people, which is usually not the case. Although it has been proposed to wind a wound pipe from a plastic strip in the existing concrete sewage pipes, difficulties often occur in welding the edges of the plastic profiled strip to each other and on account of the equipment to be used in forming this connection. The invention therefore also relates to a method of repairing or renewing a sewage pipe system by installing a plastic pipe in an existing concrete sewage particularly pipe from an essentially vertical access to a sewage pipe system, said method being characterized in that the plastic pipe comprises an outer pipe with rigid external corrugations which are at least covered on their innner side, by particularly wear-resistant, sealing surfaces of a material possessing elastic properties to form a substantially smooth inner wall. Advantageously the sealing surfaces are formed from an elastomer, more particularly, a thermoplastic elastomer, while the outer pipe consists of a polyolefin or substantially of a polyvinylchloride. An outer pipe consisting substantially of polyvinylchloride means that said PVC pipe may contain substances improving the impact strength or components improving other properties of said pipe. Expediently the sealing surfaces are attached to the outside pipe chemically, physicochemically and/or mechanically, particularly by welding. Very preferably the assembly of outer corrugated pipe and inner pipe of material possessing elastic properties are formed by coextrusion. During coextrusion an outer smooth extruded pipe is corrugated and the inner pipe is simultaneously fixed to the inner side of the wave valleys of the outer pipe. This can be achieved particularly with an olefin based thermoplastic elastomer such as an ethylene based and/or propylene based thermoplastic elastomer and an outer pipe consisting of a polyolefin such as polyethylene or polypropylene weldably joined thereto. Said pipes are very wear-resistant in an aqueous medium. The invention will now be explained with reference to an embodiment by means of the drawing in which Fig. l shows a plastic pipe according to the invention; Fig. 2 shows a variant of a plastic pipe of this type; Fig. 3 shows yet another variant; Fig. 4 shows yet another variant; and Fig. 5 a diagram illustrating the method according to the invention for repairing sewage pipes. In Fig. l a section is shown of a plastic pipe l which may be used for the repair or renewal of a sewage pipe system. Said plastic pipe l consists of an outer pipe 2 with rigid external corrugations 3 which are covered on their inner side by sufficiently wear-resistant sealing surfaces 4, made of a material possessing elastic properties, to form an essentially smooth inner wall 5. The sealing surfaces are 0.5 mm thick, but it will be obvious that said thickness may be greater. The sealing surfaces 4 may, for example, be attached by adhesive bonding or by welding between the walls which define the open sides of the cavity 9 formed by the rigid external corrugations 3. In Fig. 2 another embodiment is shown in which the sealing surfaces 4 are joined to each other to form an inner pipe l0 with a smooth inner wall. Said inner pipe l0 consists of a thermoplastic elastomer, while the outer pipe 2 consists of polypropylene. The assembly of inner pipe and outer pipe has been formed by coextrusion. Fig. 3 shows an embodiment in which the rigid external corrugations 3 of the outer pipe together form a corrugated pipe 8 with wave valleys 8a. The inner pipe comprising the sealing surfaces 4 consist of a thermoplastic elastomer. By suitable choice of the plastic of the corrugated pipe 8, for example a polyethylene or a polypropylene plastic pipe, and of an inner pipe made of a ethylene or propylene based thermoplastic elastomer, the inner pipe providing the sealing surfaces 4 is attached by welding such as during coextrusion,in the wave valleys 8a to the corrugated pipe, in which process welded joints l0a are produced. Preferably these pipes have been manufactured by coextrusion automatically. Finally, Fig. 4 shows yet another embodiment in which the cavities 9 of the external corrugations 3 of the outer pipe are filled with a compressible foam 7 made of a thermoplastic plastic. This compressible foam may consist of, for example a polyolefin foam, a polyurethanfoam, or for example, foam of an elastomer, in particular a thermoplastic elastomer. Suitable materials for the sealing surfaces 4 of the inner pipe are thermoplastic Santoprene rubber, Kraton thermoplastic rubber and Keltan thermoplastic rubber. These provide very wear-reistant surfaces in an aqueous medium of a thickness of at least 0.5 mm, for example l mm or more, is used. Finally, Fig. 5 shows a concrete sewage pipe l2 provided with an access leading to the surface of the road covering l5 in the form of a shaft ll. When a sewage pipe system with a concrete sewage pipe l2 of this type has to be repaired or renewed a plastic pipe l consisting of an outer pipe 2 with rigid external corrugations 3 which are covered on their inner side to form an essentially smooth inner wall 5 by sealing surfaces 4 made of a material possessing elastic properties and having a thickness of l mm, is guided into the shaft and bent over at the junction l4 between the access shaft ll and a concrete sewage pipe l2 at an angle of virtually 90°C and guided into the concrete sewage pipe, consecutively the plastic pipe is pulled through the concrete sewage pipe l2 by means of the pulling element l3. Evidently by a suitable choice of the diameter of the outer pipe with rigid external corrugations 3 the outer side of the outer tube 2 and the inner side of the concrete sewage pipe will tightly engage each other. The interstices l6 between the outer side of the corrugations 3 and the inner side of the concrete pipe l2 may expediently be filled with a curable material l7, for example a curable mortar.

Claims: 1. A plastic pipe (l) comprising an outer pipe (2) with rigid external corrugations (3) being at least covered on their inner side by sealing surfaces (4) made of deformable material to form an essentially smooth inner wall, characterized in that the sealing surfaces (4) consist of a material possessing elastic properties. 2. A plastic pipe according to claim l, characterized in that the sealing surfaces (4) are formed from a wear resistant elastomer, preferably a thermoplastic elastomer. 3. A plastic pipe according to claim l-2, characterized in that the sealing surfaces (4) have a wall thickness of at least 0.5 mm. 4. A plastic pipe according to claims l to 3, characterized in that the outer pipe is formed from a polyolefin or substantially from a polyvinylchloride. 5. A plastic pipe according to claims l to 4, characterized in that the sealing surfaces (4) are attached to the outer pipe (2) chemically, physicochemically, or mechanically, particularly by coextrusion or by welding. 6. Plastic pipe according to claims l to 5, characterized in that the cavity (9) between the sealing surfaces (4) and the inner side of the external corrugations (3) is filled with a compressible foam (7) made of thermoplastic plastic material. 7. Plastic pipe according to claims l to 6, characterized in that the sealing surfaces 64) are joined to each other into an integral inner pipe (l0) and/or the external corrugations (3) adjoin each other to form a corrugated pipe (8). 8. Plastic pipe according to claims l-7, characterized in that the outer pipe consists of a polyolefinic material and the sealing surfaces (4) joined to each other to form an inner pipe consist of an olefin based thermoplastic elastomer being joined to the polyolefin of the outer pipe, in particular by coextrusion or welding. 9. Method of repairing or renewing a sewage pipe system by installing a plastic pipe in an existing concrete sewage pipe, particularly from an essentially vertical access to a sewage pipe system, characterized in that a plastic pipe according to any one of the precending claims is used. l0. Method according to claim 9 characterized in that the interstices (l6) between the outer side of the corrugations of the plastic pipe and the inner side of the concrete pipe (l2) are filled with a curable material (l7).

Inventors: DE PUTTER, WARNER JAN
Applicants: WAVIN B.V.
Application year: 1986
Main classification: F16L9
IPC codes: F16L1, F16L11, F16L9, F16L55