Abstract: A process for the manufacture of a flat-shaped hollow body through the use of a forming die, wherein mold segment halves move continuously along a forming die and which, upon entering the forming die, are moved in an operating direction facing each other in pairs in a closed mold in tight proximity to each other. The mold is injected with warm thermoplastic hose stock which is shaped under vacuum action in the mold. In order to produce flat-shaped hollow bodies on a continuous basis the hose stock is subjected to vacuum action over at least a portion of its cross section even before mold segment halves are brought together and is pressed together accompanied by the formation of welds and the creation of hollow spaces over a portion of its cross section.

Abstract: In the manufacture of double-wall plastic tubing in which the outer wall has transverse corrugations and the inner wall is smooth, in the case of annular transverse corrugations the air pressure between the two walls cannot be balanced with the external air pressure, resulting in deformations of the inner tube. To permit an equilibrium of pressure before the inner wall hardens, openings are pierced in the outer wall or openings are produced between the two walls for communication between the inner chambers of the transverse corrugations. After the hardening of the inner tube, these openings are reclosed by fusion.

Abstract: An apparatus for the manufacture of transversely contoured tubing from thermoplastic material. The tube emerges in the plastic state from an extrusion nozzle and is guided into a mold composed of a plurality of mold sections in series, with inner side working surfaces forming the transverse contours. Each of the mold sections is composed of two mold halves which are arrayed along a straight molding run in two confronting rows and which are circulated. In the circulation, the first two mold halves are moved apart and out of the molding run at the end of the molding run and are guided to a return run on which they are separately returned to the beginning of the molding run where they are rejoined to the preceding mold half. The mold halves are guided on the return run in a continuous, accelerated and then decelerated movement by a transfer mechanism which couples and uncouples from the mold halves as actuated by pneumatic cylinders under the control of limit switches.

Abstract: A synthetic plastic drain pipe comprising a continuous pipe of plastic material having transverse, angular or helical corrugations, said pipe having openings for the entry of water, said openings being disposed in said pipe at regular repeating intervals between corrugated lengths of pipe at least at every 20 cm, preferably 30-50 cm, said pipe being free of any opening between said intervals; an apparatus for producing such a synthetic drain pipe, particularly a pipe having distinct portions of general cross section wherein on said portions there are longitudinally running grooves through which there are disposed openings, said apparatus comprising an extruder having an extrusion head, said extrusion head having a generally annular opening defined by a generally circular die disposed about a generally circular mandrel, said apparatus having in general axial alignment with said opening a pair of endless traveling means in the form of a mold train, each of which traveling means carries cooperating mold halves w

Abstract: An apparatus for cutting openings at arbitrarily selectable intervals into a pipe which has a smooth inside or outside surface or a transversely corrugated inside or outside surface comprising a knife disposed inside or outside said pipe, and a movable element whose movement is responsive to a signal to move the knife and pipe wall into mutual contact so that the knife cuts into the pipe wall. Disclosed herein is an apparatus which cuts an opening through the surface of a smooth inner pipe disposed within an outer pipe having transverse corrugations. Also disclosed is an apparatus whose knife is disposed exteriorly and is employed to cut openings into the exteriorly disposed transversely corrugated pipe. The application further discloses an apparatus comprising a pipe forming machine, an apparatus which cuts a hole in a pipe from within the pipe and an apparatus which cuts a hole in a pipe from outside the pipe.

Abstract: In the manufacture of double-wall plastic tubing in which the outer wall has transverse corrugations and the inner wall is smooth, in the case of annular transverse corrugations the air pressure between the two walls cannot be balanced with the external air pressure, resulting in deformations of the inner tube. To permit an equilibrium of pressure before the inner wall hardens, openings are pierced in the outer wall or openings are produced between the two walls for communication between the inner chambers of the transverse corrugations. After the hardening of the inner tube, these openings are reclosed by fusion.

Abstract: A synthetic plastic drain pipe comprising a continuous pipe of plastic material having transverse, angular or helical corrugations, said pipe having openings for the entry of water, said openings being disposed in said pipe at regular repeating intervals between corrugated lengths of pipe at least at every 20 cm, preferably 30-50 cm, said pipe being free of any opening between said intervals; an apparatus for producing such a synthetic drain pipe, particularly a pipe having distinct portions of general cross section wherein on said portions there are longitudinally running grooves through which there are disposed openings, said apparatus comprising an extruder having an extrusion head, said extrusion head having a generally annular opening defined by a generally circular die disposed about a generally circular mandrel, said apparatus having in general axial alignment with said opening a pair of endless traveling means in the form of a mold train, each of which traveling means carries cooperating mold halves w

Abstract: An improvement in the process of producing a double-walled synthetic plastic tube having a concentric outer tube and an inner tube wherein an outer tube of molten synthetic plastic is extruded from an annular die and passing to a mold cavity formed by a divided mold having two cooperating endless recirculating trains of mold halves which close to complete the mold cavity and an inner tube of molten synthetic plastic is extruded from a die orifice located in the interior of said mold which improvement comprises introducing a first gas into the space between said inner tube and said outer tube before said synthetic plastic has fully hardened, said gas being at a pressure above atmospheric and at a temperature at or above the softening point of said synthetic plastic and permitting said outer inner tubes to cool; an apparatus for carrying out the process comprising an extruder having a first die disposed over a first mandrel to define a first annular space through which molten synthetic plastic can flow en route

Abstract: An improvement in an extruder head for extruding an outer tubular extrusion or sheath about an inner tube or cable which extrusion head has a means for passing an inner tube or cable through the extruder head which extruder head also terminates in a generally annular passage disposed about said inner tube or cable, the improvement residing in means for feeding molten material through an introducing passage at an angle to said extruder head and then into said annular passage, dividing means in said introducing passage for dividing said molten material into a stream of U-shaped cross-section, said dividing means including a leading parting edge; a method of producing a carrier ring which carries the dividing means by passing a machining tool into the introducing passage and passing the tool along paths having progressively larger U-shaped loops.

Abstract: An improvement in an apparatus for forming an outer corrugated tube wherein the corrugations of said tube abut an inner tube within said corrugated tube, said apparatus comprising means for forming an outer corrugated tube about a dye, means for forming said inner tube about a central mandrel within said corrugated tube, the improvement comprising means for urging an inner tube against the corrugations of said outer corrugated tube, said means comprising a presser floating mounted within said inner tube in facing relationship to said inner tube and bearing outward towards said inner tube.