Abstract: A method and an apparatus for the orientation of a plastic pipe, wherein a pipe blank (2) is produced with an extruder and fed into a pipe forming apparatus provided with movable moulds (3), such as a corrugator, the pipe being conveyed forward in the corrugator with said moulds over a mandrel (4), along which the pipe is further conveyed out from the corrugator. In accordance with the invention, the plastic pipe (7) is oriented radially immediately after the corrugator by means of a conically widening mandrel (5) forming an extension of said corrugator. The invention also relates to an oriented ribbed plastic pipe produced by the method.

Abstract: An apparatus for manufacturing from a mouldable material a pipe having ribs on its outer surface and a smooth inner surface has a core including a shaft, a conically widening mandrel located downstream of the shaft in a direction of production and a kernel having an initial zone and an end zone respectively of substantially uniform diameters successively disposed downstream of the mandrel. An extrusion sleeve surrounds the core and forms with the core a nozzle for the material. The extrusion sleeve has a first end face located upstream of the kernel. Moulds encase the extrusion sleeve and the core, the moulds being movable along endless paths and having grooves on inner surfaces for forming the ribs on the pipe. A heater heats the initial zone of the kernel, the initial zone of the kernel being cylindrical. A first cooler cools the end zone of the kernel.

Abstract: A production line for manufacturing corrugated pipe also has a calibrating basin for manufacturing smooth-walled pipe arranged between form paths of the corrugator when the paths have been separated. An extruder that normally feeds a molten plastic pipe blank to the corrugator for making corrugated pipe then feeds the pipe blank to the calibrating basin for making smooth-walled pipe, and other down-the-production-line equipment can be the same, too.

Abstract: Pipe for relining underground pipelines, which is of the composite type having an annularly rigid corrugated outside wall (10) of polymer material, which is connected to the outside surface of a smooth inside wall (11) which consists of a thermoplastic elastomer so that it can be stretched and compressed. According to the invention there is provided on the inside of the smooth inside wall (11) a thin layer (13) of the thermoplastic having a lower frictional coefficient and/or greater wear-resistance than the material of the inside wall.

Abstract: The invention relates to a method and apparatus for manufacturing ribbed piping, wherein a formable mass in a plastic state is extruded into a substantially cylindrical forming space of a corrugator, the forming space being delimited by forming molds movable in the production direction of the apparatus and having grooves on the inner surface thereof for forming rib flanges. A stationary kernel portion of a mandrel cools the interior surface of the piping and extends beyond the forming space constituted by the forming molds of the corrugator.

Abstract: A method of joining tubes (A and B) having a corrugated wall (10) of fusible plastic material and terminating at a cut through a corrugation rib, comprises the following steps. An annular body (14) expanding when energy is supplied to it, is positioned in an annular space (13) formed by the corrugation ribs at the end of one tube (A) and an inner boundary which can be formed by an inner wall (11) of fusible plastic material, integral with the corrugated wall of said one tube, or by a sleeve inserted into the adjacent ends of the tubes, also of fusible material. The tube ends are put together to close said space by the end of the other tube (13), and a radial and axial support (19) for the corrugation ribs is arranged on the outside of the tubes. Then, the annular body is expanded by heating to fuse said body to the walls of the tubes and the sleeve, respectively.

Abstract: This invention relates to a device for the production of grate constructions. In general, such constructions are manufactured manually by connecting transverse ribs to elongated supporting means by welding. Grate constructions can be manufactured automatically at a single step by means of an extruder known from pipe manufacturing techniques. Chill moulds moving in the production direction are thereby modified in such a manner that the chill moulds comprise at least two moulding spaces communicating with each other by means of conduits.

Abstract: This invention relates to a method and an apparatus for the production of ribbed pipes. According to the method a plastic material is fed through an extruder into a pipe molding space (12) defined by an extrusion sleeve (4), a mandrel (9) and chill molds (1, 2) moving in the direction of the central axis of the mandrel. When the pressure of the molding space (12) deviates from a desired value, a gap is formed between the chill molds (1,2), and plastic material is squeezed into the gap, or grooves (13) of the chill molds are filled up incompletely. In order to restore the pressure to the proper value, the pressure of the material contained in the molding space is directly measured by means of a pressure sensor (14) which adjusts the speed of the extruder or the chill molds.

Abstract: A method and apparatus for producing a pipe transports first and second sets of chill moulds respectively along first and second endless paths, the chill moulds of each set being so transported one after another, and the endless paths being positioned such that junction faces of the respective chill moulds of the respective sets are positioned against each other in a pipe moulding zone of the endless paths. So positioning the respective chill moulds of the respective sets also defines outer surfaces thereof that are opposite the junction faces and outer surfaces that extend along edges of the junction faces at least generally in the direction of the transporting of the chill moulds.

Abstract: This invention relates to an apparatus and a method for the production of outwardly ribbed, plastic pipes. The apparatus includes a core around which a plasticized material is pressed from a nozzle. A kernel having an essentially constant diameter is positioned at the terminal end of the core for a smooth inner face of the pipe. The outer face of the pipe is ribbed by grooves of axially displaceable chill moulds. The end zone of the kernel is provided for the cooling of the inner face of the pipe. In known apparatuses the grooves of the chill moulds are often filled incompletely and the inner face of the pipe becomes uneven on account of air bubbles, for instance. These disadvantages are avoided by heating an initial zone of the kernel for heating the inner face of the pipe and by shaping the surface of the initial zone to slightly expand conicallly in the production direction.

Abstract: The invention relates to a method and an apparatus for the extrusion of plastic pipes. Today, plastic pipes are provided with a sleeve in such a manner that the end of the pipe is heated, whereafter the end is expanded by means of a mandrel or a pressure medium. This step requires a separate sleeve machine, and it also takes plenty of time and consumes thermal energy. According to the invention a sleeve (22) is formed in connection with the extrusion of a pipe in an apparatus in which a mandrel (8) is surrounded by chill moulds (1, 2) moving in the axial direction of the apparatus. The sleeve is formed by providing some of the chill moulds with a recess (16) the shape of which corresponds to that of the sleeve (22) and by pressing a plasticized plastic hose (11) extruded through a nozzle (10) against the walls of the recess in the area thereof by means of pressure air.

Abstract: This invention relates to a method and an apparatus for the production of ribbed pipes. The apparatus comprises a core which together with an extrusion sleeve forms a nozzle through which a plastic material is fed into a moulding space defined between a conically-enlarging mandrel and chill moulds moveable with respect to the mandrel. The volume of a moulding space defined between a plane at an end face of the extrusion sleeve, a surface of the mandrel, and a cylindrical plane projection from the surface of a kernel on the mandrel equals the combined volume of the grooves positioned at the mandrel at the mandrel at each particular moment. The method feeds a volume of the plastic material per unit time equal to volume of the pipe wall and ribs produced in that unit time.

Abstract: This invention relates to a plastic pipe. The wall thickness of this kind of pipes is very small and, consequently, the impact strength is poor. The impact strength of pipes made of polyvinyl chloride can be improved by adding an admixture to the raw material, which, however, increases costs. According to the invention the impact strength can be improved by a ring-shaped elevation formed at the foot of the ribs on both sides thereof, which elevation joins the side wall of the rib over a sharp transitional juncture.