Abstract: An extruder according to the invention comprises at least two annular conical feed gaps (9) one within the other, formed between a rotatable rotor (1) and a stator (4, 5). At least some of the material to be extruded is subjected in the different feed gaps (9) of the extruder alternately to a higher pressure and then to a lower pressure. The rotor (1) or stator (4, 5) between the feed gaps (9) can then be balanced such that the pressure effect provides a hydrodynamic bearing, whereby, when the extruder is used, even at worst a very small force is exerted on die other bearings of the rotor (1) or stator (4, 5). By the method of the invention, a product can also be produced which contains cross-linked and at least partly oriented polyethylene.

Abstract: An extrusion apparatus including at least one conical stator, and at least one conical rotor. The rotor is adapted for defibering or orienting a plastic material. The apparatus has an opening for receiving an elongate product or mandrel. The product or mandrel may be disposed in the apparatus such that, with the product or mandrel received in the opening, an extrusion conduit is defined in the opening between the product or mandrel and the rotor and stator. The rotor and stator are disposed with respect to one another to form a supply opening wherein the plastic material flows between the stator and rotor and is pressed into the extrusion conduit.

Abstract: A method for making a product to be extruded and an extruder. The extruder has at least two conical stators and at least one conical rotor placed rotatably between the stators. The extruder further has supply conduits for feeding the material to be extruded separately into the exterior and interior of the rotor. Each supply conduit is provided with a separately adjustable feeding device by means of which the amount of material flow to be supplied can be adjusted. The degree to which the space between the rotor and the stator is filled and the amount of the heat generated by friction can be regulated. Further, the ratio of the material flows in the different supply conduits determines the ratio of the thickness of the layers obtained. The method and extruder according to the invention make it possible to regulate the properties of a final product easily and in several different ways.

Abstract: A method for joining a first tubular member to a second tubular member. The method provides a stretchable and compressible welding ring having a flexible inner ring, a resistance coil wound around the inner ring and at least one layer of plastic coating the resistance coil. The method includes the step of arranging the first and second tubular members in overlapping relation with an end of the first tubular member inserted into an end of the second tubular member and with the welding ring encircling the first tubular member and compressed between the first and second tubular members. The method also includes the step of applying electric energy to the resistance coil to melt the at least one layer of plastic so that, upon cooling, the respective ends of the first and second tubular members are welded to the welding ring.

Abstract: The invention relates to a process for heating polymer material, including irradiation of said polymer material with infrared radiation. In accordance with the process according to the invention the infrared radiation has wave lengths which substantially are not equal to the absorption peaks of the polymer material in respect of infrared radiation.

Abstract: An extruder including: (a) at least two concentric stators including (i) an inner stator having at least an outer surface that is at least mostly conical and (ii) an outer stator having at least an inner surface that is at least mostly conical; (b) at least one rotatable rotor that is at least mostly conical; and (c) a supply conduit for supplying material into a space between the stators. The at least one rotatable rotor being disposed in the space between the inner stator and the outer stator. The at least one rotor includes a plurality of ducts that define passages through which material can flow from the space to an interior of the rotor. Each of the plurality of ducts defines an opening or groove that opens into the space. The supply conduit has a conduit end defining an orifice.

Abstract: A method for producing a homogeneous material with an extruder is provided. The extruder has at least two annular conical feed gaps situated between a rotatable rotor and a stator so that the material to be extruded is supplied between the rotor and the stator. Between the delivery point of the material to be extruded and the nozzle of the extruder in the direction of travel of the material the at least one rotor or stator of the extruder is provided with openings passing therethrough so that at least some of the material to be extruded is made to flow through the openings from one annular conical feed gap to another annular conical feed gap. The invention also relates to an extruder and to a multilayer plastic pipe.

Abstract: A sizing sleeve for controlling the diameter of plastic tube includes pressurized sizing sleeve portions in which fluid is injected under pressure about the tube circumference to form a lubricating layer. Drainage zones axially separate and isolate adjacent pressurized portions to allow independent temperature and pressure control. Each pressurized portion has flow stabilizer reducing variations in flow responsive to changes in the lubricating layer pressure. The flow stabilizer may comprise a high pressure fluid source and high pressure drop constrictor comprising fine apertures, which may be formed as grooves milled into end surface of abutting sizing sleeve segments.

Abstract: The invention relates to a method for manufacturing a multi-layer corrugated pipe and to a corrugated pipe manufactured by the method and comprising an inner tube (2), a corrugated outer tube (5) and a plastic layer therebetween. Separate layers (3,6) of plastic are formed on the outer surface of the inner tube (2) and the inner surface of the outer tube (5), said separate layers of plastic being affixed to one another at least at the web portions (5a) of the corrugations of the outer tube (5) when the inner tube and outer tube are connected.

Abstract: The present invention relates to a branch pipe connection for connecting a branch pipe to a lightly constructed underground sewage and drainage pipe. The connection includes a locking ring and a sleeve that are arranged against one another and can be tightened in their axial direction. The connection further includes a support flange. The locking ring has a slit by means of which the locking ring can be placed inside the underground sewage and drainage pipe through a hole made for the branch pipe from outside the underground sewage and drainage pipe. The pipe connection also comprises a sealing that is arranged to extend from the inner surface of the underground sewage and drainage pipe as far as the sleeve. A compact, dismountable connection for improving the ring stiffness of the underground sewage and drainage pipe is produced in this way.

Abstract: A method of socketing a pipe of oriented plastic having an annular groove inside the socket. An end portion (15) of the pipe is pushed onto a cylindrical mandrel element (11) and the region (l.sub.1) of the end portion at the opening thereof where the groove is to be located is heated to a temperature above the glass transition temperature of amorphous plastic and the crystalline melting point of crystalline plastic, respectively. The rest of the end portion is maintained at a temperature below the glass transition temperature or the crystalline melting point, respectively. The end portion (15) when said region is at a temperature above the glass transition temperature or the crystalline melting point, respectively, is pushed onto a second mandrel element (13) axially aligned with the first mandrel element the bottom portion of the socket being formed by said second mandrel element (13). The rest of the end portion is expanded to form the bottom portion of the socket.

Abstract: A method of forming a two-layer plastic pipe (4;8) to be laid in the ground for conducting material therethrough forms a core pipe (2) consisting essentially of a first plastic material and forms a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method, including in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground.

Abstract: The invention relates to a socket joint for plastic pipes, whereupon a spigot end (1a) of one (1) of the pipes to be connected is inserted in an expanded section (2a) of a socket (2), and an intermediate space (3) situated between the spigot end and the expanded section comprises a housing sealing unit (4) that extends along a considerable part of the length of said intermediate space and that comprises several circular flexible lip seals (6) on its outer and inner circumference. The outer and inner circumference of the sealing unit (4) also comprise several circular support seals (7) which have a substantially smaller compressibility especially in the radial direction than the lip seals (6).

Abstract: The invention relates to a method and an apparatus for forming ribs with sideward projections in a plastic pipe. The projections are formed by means of elongated rolls (10) each moving around the pipe and rotating about its central axis, the rolls being in an inclined position and at an oblique angle with respect to the central axis of the pipe.

Abstract: A circumferentially or biaxially oriented plastics pipe comprising a body with an integral socket at one end thereof The socket has a wall of lesser axial draw than the body of the pipe.

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: 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: 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.