Abstract: A pipe connection for use in a ventilating duct system having ducts with circular cross-section is adapted to be inserted with a close fit into an outer pipe and be connected therewith. The pipe connection has a circumferential groove, in which a circumferential seal sealing against the inside of the outer pipe is arranged. A terminal edge portion of the pipe connection comprises an outer conical portion which has a diameter decreasing towards the end of the pipe connection, and a circumferential guide surface having such a diameter that said close fit is obtained. The axial length (L3) of the terminal edge portion constitutes about 1.5-5.5% of the diameter of the guide surface. The outer conical portion at its end has a diameter which constitutes about 97-99.9% of the diameter of the guide surface.

Abstract: A method for automatically generating and connecting a text string to an installation element in a representation of an installation system in a computer readable form, such as a CAD-drawing. The text string indicates the properties of said element in said installation system. The method comprises the steps of identifying the type of said installation element; reading for each element, from a database, predetermined rules and a text pattern corresponding to the type of said element. Further, the method comprises the steps of combining, from said representation of an installation system, the properties of said element, such as dimensions, with said text pattern to produce a text string for said element; and connecting said text string with said element in said representation.

Abstract: A method and apparatus for cutting spiral pipe is disclosed. The pipe cutting apparatus includes a driving mechanism that imparts rotation to a knife located inside the spiral pipe via a drive element, such as a drive shaft. The method includes forming a spiral pipe from a strip of material received at a forming head of a spiral pipe former, engaging a driving mechanism attached to a first knife positioned substantially inside the inner circumference of the pipe forming head to impart rotation to the first knife, and cutting the spiral pipe with the first knife by bringing a second knife positioned substantially outside the outer circumference of the forming head into overlapping contact with the first knife.

Abstract: A double-walled-structure, such as a silencer for use in a ventilation duct system, has a perforated inner tube, an outer casing which is arranged at a distance from the inner tube and encloses the same, and a tubular, sound-absorbing element which is arranged between the inner tube and the casing. The tubular element has an increasing density radially outwards from the center axis of the inner tube. The silencer is produced by the sound-absorbing element being arranged on the inner tube, and the inner tube with the sound-absorbing element arranged thereon being enclosed in the surrounding outer casing.

Abstract: An elongate supporting element has a cross section with a web (9) and two side flanges (10, 11) for the supporting of building panels or the like. The web (9) has an elongate, stress-equalising zone (4) which extends wholly or partly between the two outer ends (8a, 8b) of the supporting element and by means of which the supporting element (8) is reinforced.

Abstract: A method and apparatus for forming corrugated pipe is disclosed. The pipe forming apparatus includes a selectively operable corrugation module having an inner corrugation roller movably mounted relative to an outer corrugation roller via a cylinder assembly. The method includes forming a length of spiral pipe without corrugations, engaging a corrugation module to introduce a desired length of corrugated pipe, and retracting the corrugation unit to allow a second length of uncorrugated pipe to form. The uncorrugated portion of the pipe is then severed cleanly using overlapping inner and outer cutting knives.

Abstract: A tubular element has a sealing ring mounted at an end of the tubular element. The sealing ring has a base clamped against the outer surface of the tubular element. Further, the sealing ring has a sealing lip adapted to seal against an inner surface of an outer tube, in which the tubular element is inserted. The base is disposed in a groove that is formed in the wall of the tubular element. The sealing ring has a further lip that is positioned adjacent to the end of the tubular element and that is bent down and clamped against the base by means of the end portion, thereby providing secure fastening of the sealing ring. The sealing ring is fastened by a method involving bending of the end portion of the tubular element together with the further lip.

Abstract: A device for coupling two pipe sections comprises a clamping band of U-shaped cross-section with two inwardly directed flanges for encompassing end beads of the pipe sections which are to be coupled. The ends of the clamping band have cylindrical pockets each accommodating a cylindrical element which is rotatable about its own axis in the pocket. The clamping band is clamped by means of a threaded screw which is passed through an unthreaded hole in one cylindrical element and unthreaded holes in the ends of the clamping band, whereupon the screw is in threaded engagement with the other cylindrical element.

Abstract: A device for coupling together pipes, which at their end have an outwardly directed bead, comprises an annular clamping strap (1) and a clamping mechanism (4-6) arranged at the ends (2a, 2b) of the clamping strap. Between the ends (2a, 2b) of the clamping strap (1), a sealing element (7) is arranged for sealing the joint between the ends (2a, 2b).

Abstract: A double-walled structure in a ventilation duct system has an inner tube and an outer tube and, arranged therebetween, a sound-absorbing material. The inner tube is a helically-wound lock-seam tube formed from a sheet metal strip having parallel longitudinal areas of expanded metal.

Abstract: In a method of coupling a first pipe with a second pipe having a circumferential bead, use is made of an annular clamping band which is applied on the outside of the end beads and is tightened around the end beads when the pipes are placed end to end. The clamping band has on its inside a sealing ring, which is arranged against the end beads. A first recess of the sealing ring is formed on and held on the outside of the end bead of the first pipe in such a manner that a second recess of the sealing ring is arranged axially outside this end bead. The second recess of the sealing ring is then formed on the end bead of the second pipe, and finally the clamping band is tightened around the end beads with the sealing ring placed between the clamping band and the end beads.

Abstract: A pipe cutter having non-rotating, overlapping knives is provided. Also provided is a pipe cutter having non-rotatable overlapping knives wherein one of the knives is continuously reciprocated.

Abstract: In a method of producing a double-walled structure, such as a silencer for use in a ventilation duct system, use is made of an arrangement having a forming head for forming helically-wound lock-seam tubing. In the forming head, a perforated metal strip is helically wound together with an air-permeable cloth strip such that the tubing fed out of the forming head has an outer cover of said cloth. The tube assembly consisting of the perforated tube and the cloth cover is provided with an outer tubular layer of insulating material and then inserted in a casing which makes the silencer complete.

Abstract: In an apparatus for producing a double-walled structure, such as a silencer for use in a ventilation duct system, use is made of an arrangement having a forming head for forming helically-wound lock-seam tubing. In the forming head, a perforated metal strip is helically wound together with an air-permeable cloth strip such that the tubing fed out of the forming head has an outer cover of said cloth. The tube assembly consisting of the perforated tube and the cloth cover is provided with an outer tubular layer of insulating material and then inserted in a casing which makes the silencer complete.

Abstract: A pipe cutter having dual outer knives and a method of using the same is disclosed. The outer knives are mounted on knife positioners capable of swinging the outer knives into a pipe in an arc to overlap with a knife positioned inside the pipe. The method includes the step of simultaneously swinging the outer knives into a continuously rotating pipe in an arc having a rotational direction opposite the rotational direction of the pipe.