Abstract: An elongated product is formed such that first a core is formed, the outer surface of the core being made of plastic. Thereafter, a tubular metal layer is extruded such that the layer is seamless. When the metal layer is extruded, a clearance is allowed between the metal layer and the core. After the metal layer has cooled, the diameter of the metal layer is reduced such that the metal layer contacts the plastic core. Thereafter, the metal is annealed such that the flexibility of the metal layer increases.

Abstract: An elongated product is formed such that first a core is formed, the outer surface of the core being made of plastic. Thereafter, a tubular metal layer is extruded such that the layer is seamless. When the metal layer is extruded, a clearance (16) is allowed between the metal layer and the core. After the metal layer has cooled, the outer surface of the core is arranged against the inner surface of the metal layer. An adhesive action is arranged between the core and the metal layer and a permanent compressive force is arranged, which compressive force compresses the core and the metal layer together.

Abstract: An elongated product is formed such that first a core is formed, the outer surface of the core being made of plastic. Thereafter, a tubular metal layer is extruded such that the layer is seamless. When the metal layer is extruded, a clearance is allowed between the metal layer and the core. After the metal layer has cooled, the diameter of the metal layer is reduced such that the metal layer contacts the plastic core. Thereafter, the metal is annealed such that the flexibility of the metal layer increases.

Abstract: An elongated product is formed such that first a core is formed, the outer surface of the core being made of plastic. Thereafter, a tubular metal layer is extruded such that the layer is seamless. When the metal layer is extruded, a clearance (16) is allowed between the metal layer and the core.

Abstract: A tubular product has a tubular base layer, a tubular innermost layer made of plastic by continuous extrusion, and a tubular tie layer of foamed plastic between and adhered to the base layer and the innermost layer. The tie layer is made of melt processable adhesion plastic, is extruded simultaneously with the innermost layer against the base layer, and has better adhesions to the base and innermost layers than the base and innermost layers have to each other.

Abstract: The invention relates to a branch piece for a pipework, comprising a body (1) including at least one branch fitting (2). A connecting piece (3) is arrangeable in the branch fitting (2). The branch piece includes a locking means made up of one or more parts for locking the connecting piece (3) in place.

Abstract: A multilayer pipe which comprises at least an inner layer and an outer layer. The inner layer is made of extrudable plastic, such as polyethylene PE, cross-linked polyethylene PEX or polypropylene PP. The outer layer forms a fire-protecting layer and the matrix plastic of the outer layer is also made of extrudable plastic. A foaming agent, which does not react during the manufacture of the pipe, is mixed with the matrix. Further, the outer layer contains at least one additive in such a manner that the outer layer has a pipe-reinforcing component and a fire-retardant component. Most preferably, at least the outer layer is extruded by an extruder having a screw length ratio of less than 10 to its biggest diameter.

Abstract: An apparatus for manufacturing an extruded plastic product, the apparatus including at least one rotor and at least one stator defining a clearance having a feed gap between them, the rotor and stator collectively including a groove for moving material to be extruded from a feed zone of the apparatus to a shear zone of the apparatus upon rotation of the rotor and a countergroove for facilitating the extrusion of the material, the groove and countergroove being disposed on opposite sides of the feed gap, the countergroove having a thread that is opposite in direction to a thread of the groove, the groove having a cross-section that is substantially unchanging, the countergroove being disposed substantially along an entire length of the shear zone, the groove, countergroove and clearance forming a processing cavity having a volume that is the volumes of grooves, countergrooves and the clearance, the processing cavity having a cross-sectional area that decreases continuously along at least a part of an axis of t

Abstract: A branched pipe (5) is manufactured by continuous extrusion in such a manner that a manifold (5a) of a branched pipe (5) is manufactured by extruding plastic material into the space defined by moving chill moulds (1, 2) and a mandrel (10) arranged therein with an extruder (4). The manifold (5a) is provided with branch pipes (5b) simultaneously with the extrusion thereof.

Abstract: The invention relates to a method and apparatus for using recycled plastic material, and to a plastic product produced by an extruder. In the invention, crosslinked polyethylene is ground to powder form and mixed with e.g. polyethylene so that the proportion of the crosslinked polyethylene in the mixture is less than 30%. The mixture is supplied through an extruder (2) for making an extruded plastic product. In this way, crosslinked polyethylene can be recycled in a cost-effective and simple manner, while producing a plastic product that contains recycled crosslinked polyethylene.

Abstract: A plastic pipe provided with a socket and a method of providing a plastic pipe with a socket, whereby the socket comprises at least two layers. The orientation of at least one socket layer is different from the orientation of another layer and the orientation of at least one layer is different from the orientation of a body portion of the plastic pipe. The socket is made for instance from a plastic pipe comprising at least two layers. The orientation temperatures of at least two different layers are different. The plastic pipe is heated to a temperature at which the material of at least one layer is oriented during expansion and the material of at least one layer is substantially not oriented during expansion. The end of the plastic pipe is expanded at said temperature so as to provide it with a socket.

Abstract: The invention relates to a method and an arrangement for cooling an extruded hollow product. According to the invention, the extruder (1) is provided with means for sucking air through the pipe (2). The air to be sucked is thus in contact with the inner surface of the pipe (2), cooling the pipe from the inside. Therefore the cooling of the pipe (2) can be realized in an efficient and simple manner. By arranging the sucking to occur from the middle of the conical extruder (1), no weld line will be formed in the extruded product, and the extruder (1) can be cooled effectively from the inside. According to the invention, the heat contained by the air that has been sucked through the pipe (2) can also be utilized.

Abstract: An extruded multilayer plastic pipe is provided. The pipe comprises an inner layer, an outer layer and an intermediate layer. Each of the inner and outer layers is comprised of a thermoplastic material. The intermediate layer consists essentially of a lower density material than said inner and outer layers, and the intermediate layer is situated between and abuts both the inner layer and the outer layer. At least one of the inner, outer and intermediate layers consists of reinforced solid or foamed reprocessed plastic.

Abstract: An apparatus for molding plastic including: (a) an injection space; (b) forming apparatus for supplying plastic material to the injection space, the forming apparatus having at least an inner conical stator and an outer conical stator and at least one rotatable rotor disposed outside of the inner conical stator; and (c) a piston for compressing the plastic material supplied to the injection space into a mold to form the plastic material into a shape determined by the mold.

Abstract: A branched pipe (5) is manufactured by continuous extrusion in such a manner that a manifold (5a) of a branched pipe (5) is manufactured by extruding plastic material into the space defined by moving chill molds (1, 2) and a mandrel (10) arranged therein with an extruder (4). The manifold (5a) is provided with branch pipes (5b) simultaneously with the extrusion thereof.

Abstract: A method for manufacturing an extrudable product including the steps of (a) providing an apparatus including an extruder having at least one rotor with first grooves, at least one stator with second grooves and a clearance between the rotor and the stator, the first grooves, second grooves and clearance forming a processing cavity having a volume that is equal to the volumes of the first grooves, the second grooves and the clearance, the processing cavity having a cross-sectional area that decreases continuously along at least a part of an axis of the extruder, the extruder further having a supply for feeding a material to be extruded into the processing cavity; b) feeding the material to be extruded in a powder, pellet or granuate form into the processing cavity through the supply and causing rotation of the rotor relative to the stator such that the material is forced to proceed along an x-axis in a shear zone of the extruder where the material is subjected to a shear which causes a fictional heat that melt

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 lest 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 the 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: A method for extruding an extrudable material to form an extruded product, the method including the steps of (a) providing an extruder having a periphery and at least a first stator, an outer rotor and an inner rotor, the first stator being disposed between the outer rotor and the inner rotor to define at least two annular feed gaps disposed one within the other in a radial direction within the periphery of the extruder, a first of the at least two annular feed gaps being defined by the outer rotor and the first stator and being disposed outside of the first stator between the first stator and the outer rotor with the outer rotor being closer to the periphery than the first stator, the first feed gap being the outermost feed gap in the extruder, the extruder including a supply conduit for supplying the material to the first feed gap through the first stator; and (b) supplying the material to the at least two annular feed gaps, with at least a part of the material being supplied through the first stator to the

Abstract: An extruder having at least one conical stator and at least one rotatable conical rotor. The rotor is mounted from its widest point with first and second bearings in such a way that the first bearing receives the forces acting in one axial direction of the rotor and the second bearing receives the forces acting in an opposite axial direction of the rotor. A method for using the extruder involves feeding a material to the extruder between the rotor and stator and rotating the rotor to cause the extruder to extrude the material.

Abstract: The present invention relates to an apparatus for producing pipes of a moldable material, preferably plastic, comprising an extruder, a cylindrical mold comprising chill molds (4, 5), a mandrel (8) inside the extruder and a kernel (9) as an extension of the mandrel. The mandrel is attached at its front end to the extruder. The mandrel (8) and the kernel (9) can be kept concentric with the extruder and the mold if the mandrel and the kernel are joined to each other in such a manner that the angle between their center lines is adjustable.