Abstract: An apparatus for making smooth walled tube (20) in a travelling mold tunnel (26) includes corrugations (32) for traction of tube being molded. An extrusion nozzle (16) having an exit angle of 45.degree. or more may provide additional advantage.

Abstract: An improved manifold assembly which can be used in conjunction with a die head in the extrusion of a plastic with the manifold assembly having a water inlet tube, a tube through which a vacuum is pulled, a water return tube, a calibration finger first section, and a calibration finger second section.

Abstract: An improved manifold assembly which can be used in the extrusion of a plastic with the manifold assembly having a die having a first end and a second end, with the die having a die head sectored at the second end, sets of a plurality of tubes located centrally of one another, each set positioned longitudinally within a respective die manifold tube with the outermost surface of each set of tubes spaced a first distance from the die manifold tube, each of the die manifold tubes extending through the die, at least two calibration fingers secured to the die, each of the calibration fingers having a proximal portion adjacent the die head, the proximal portion of each calibration finger being spaced a second distance from the die head, with the manifold assembly being vented to atmosphere by a venting channel, the venting channel extending from between the proximal tip and the die head to the first end of the die head with a portion of the venting channel being between the die manifold tube and the otuermost surfac

Abstract: An apparatus for the manufacturing of plastic pipes has half shells of which two at a time combine as a pair to form a mold. It is provided with a temperature-regulating bell. Supply lines are formed as flexible supply hoses of temperature-resistant plastic material. A line conduit accommodating them is provided with a protecting tube, which accommodates the supply hoses and which is provided with a heat insulation towards an injection head.

Abstract: A prosthetic casting machine receives an amputated stump while a patient is standing so that a hard socket can be made based upon the shape of the stump when it is under load. The machine includes a brim for accommodating an above-the-knee stump or a retaining disc for below-the-knee stumps. A telescoping leg enables precise adjustment of the height of the machine to accommodate patients of differing heights. The patient's stump is inserted into a liner and the liner is coated with plaster before the stump is inserted into the machine. After insertion, while the patient is standing, compressed air is introduced into a space between a transparent flexible bladder and a transparent rigid cylinder so that a uniform pressure is applied to the plaster by the bladder. The transparent parts enable a prosthetist to observe the results of the pressurization so that corrective steps may be taken if the plaster is not evenly compressed.

Abstract: An apparatus for curing a tapered airsleeve has a bladder curing chamber into which a rigid tapered sleeve cartridge is inserted to form the airsleeve thereon. The bladder curing chamber is formed by a rigid bladder support tube positioned between upper and lower plates and joined by strain rods. A straight cylindrical bladder is positioned within the bladder support tube and the ends are sealed by flipping them from the inside of the bladder support tube 180.degree. over each end of the tube for sealing the curing chamber. The hollow tapered sleeve mold or cartridge is inserted into the bladder curing chamber and will be dimensionally similar to the airsleeve to be molded therein. A preshaped uncured green sleeve is positioned over the tapered sleeve cartridge before inserting it into the curing chamber. The straight cylindrical bladder is inflated and expands radially outwardly causing the uncured sleeve to conform against the tapered sleeve cartridge.

Abstract: An improved pipe production line is provided having an improved manifold assembly component and an improved former component.

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: A method and an apparatus for orienting amorphous plastic material causes the material to be displaced through a gap with a smallest gap width less than the material thickness of the plastic material. During such displacement, the material is oriented, under the formation of a transition zone (18) between as yet unoriented (thicker) material (16b) and oriented (thinner) material (16a). The material is displaced at a speed entailing that crystallization energy released on orientation reaches the defining surfaces (14, 17) of the plastic material at a point in time when the material has already assumed its reduced thickness. The apparatus includes a drawing ring (50) and a mandrel (60), between which the gap is formed. When the plastic material enters into the gap, the gap is of a width which substantially corresponds to the material thickness of the amorphous material.

Abstract: A travelling mold tunnel for forming double walled corrugated tube has a first portion for forming corrugated tube and a second belled portion for forming a cuff portion suitable for coupling with another tube. At the upstream end of the belled portion, radial small diameter passages are provided so that a pressure differential may be set up between the inside and the outside of a first parison within the belled portion. Thus, vacuum may be applied through the radial passages to allow an inner parison to laminate with the first parison over its inner surface in the belled portion. The first parison is drawn into the passages in protruding balloons. These may be ruptured. Alternatively, positive pressure may be used. In this case, the balloons may be ruptured inwardly.

Abstract: A reusable laminate mandrel which is unaffected by extreme temperature changes. The flexible laminate mandrel is comprised of sheets stacked to produce the required configuration, a cover wrap that applies pressure to the mandrel laminate, maintaining the stack cross-section. Then after use, the mandrels can be removed, disassembled, and reused. In the method of extracting the flexible mandrel from one end of a composite stiffener, individual ones of the laminae of the flexible mandrel or all are extracted at the same time, depending on severity of the contour.

Abstract: A mandrel for making a rigid tubular article that has integrally-formed straight and arcuate portions. The mandrel has a plurality of shape-providing elements slidably disposed on interconnected straight and arcuate rods. After a rigid tubular article has been formed about the mandrel, the shape-providing elements can be slid off the straight and arcuate rods so that the mandrel can be removed from the rigid tubular article's interior. This provides for easy separation of the mandrel from the tubular article.

Abstract: A method for temperature conditioning a blank of plastic material in which a conditioning mandrel is placed within the blank and thereafter expanded into reliable abutment against the inner surface of the blank. The mandrel is thereafter returned to its initial position. The outer surface of the mandrel is adjusted to and maintained at a certain temperature, whereby, during the abutment, an energy exchange takes place between the blank and the mandrel for adjusting the temperature of the blank. At high temperatures of the mandrel, the mandrel is displaced out of the blank after such short time that the plastic material in the region of the abutment surface never passes the critical temperature of tackiness of the plastic material and/or thermal crystallization of the plastic material. As a rule, the expansion and contraction of the mandrel is repeated one or more times.

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: For the continuous manufacture of a compound pipe with a pipe socket including a smooth internal tube and an external tube provided with transverse grooves and welded together with the latter, an external tube and an internal tube are extruded, the latter into the external tube. While the normal compound pipe is manufactured, gas is blown at a slight overpressure into the space beteen the external tube and the internal tube. When the pipe socket is produced, this space is vented so that a full-surface bearing of the internal tube against the external tube is achieved, to which end the internal tube is acted upon from its inside by gas under pressure.

Abstract: Vulcanizing apparatus including a sealable vulcanizing vessel having an access cover on the top thereof, and a mold to be inserted in the vulcanizing vessel. The length of a rubber sleeve provided to cover the unvulcanized rubber belt molding A formed over the external circumference of the mold is sized a little longer than the height of the mold so that both ends of the rubber sleeve when placed in covering position protrude slightly from both the top and bottom ends of the mold. A holding seat is provided in the lower part of the vulcanizing vessel, and a pressing seat corresponding to the holding seat is provided on the access cover via a cylinder unit so that the pressing seat can be extended and retracted as required. The inner structures of both the pressing seat and holding seat include cooling jackets.

Abstract: An apparatus for shaping, and/or directing the flow of deformable materials, wherein the apparatus includes a novel vibrating wall assembly having at least one surface which defines a specific geometric shape over which the deformable material will pass. The novel vibrating wall assembly of this present invention includes the following components: (a) a plurality of pulsating, polygonally-shaped surface elements which are movable between a resting position and an energized position; (b) an energizing device for moving at least one of the plurality of pulsating surface elements from its resting position to its energized position, to form an energized surface element; (c) a biasing device for moving the energized surface element from its energized position back to its resting position; and (d) a linking device for interconnecting the plurality of pulsating surface elements, wherein the linking device allows for the limited pulsating movement of the plurality of pulsating surface elements.

Abstract: The invention concerns a cooling plug for sizing the interior surface of thermoplastic extruded pipe. Vacuum and/or pneumatic pressure is applied at the surface of the plug. The pneumatic pressure may cause the inner wall to balloon outwardly to form bells within a mold or within an outer wall, to fit into corrugations of an outer corrugated tube, etc. The vacuum may be used to pull the inner wall back to the surface of the plug after application of pneumatic pressure.

Abstract: A forming assembly comprises two presser members (22,24) each having a corrugated surface for receiving a workpiece made up of generally diamond-shaped pockets (10). Each presser member is made up of sections (22a,22b; 24a, 24b) mounted on slide rods (38) for movement between a spaced-apart position, in which a workpiece can be located therebetween, and a closed position, movement into which, while the workpiece is held between the presser members, is effective to compress the workpiece laterally. For holding the pockets in their diamond shape formers (20) are inserted therein. A flange (18) is formed at one end of the workpiece and integral therewith by pressing outwardly folded material against a lateral end face of the presser members (22,24) using a presser plate (52). This forming method is especially suitable for forming self-supporting filter units.

Abstract: A mandrel for manufacturing a hollow composite material body. The mandrel is formed by a homogeneous graphite felt block whose fibers are embedded in a pyrolysis carbon matrix. The densification of the arrangement of fibers forming the hollow body is carried out in a neutral atmosphere.

Abstract: A method of the device for producing a hollow columnar piece whereby a blend of essentially thermoplastic particles is melted into a billet, introduced into a mold, looped into layers inside the mold, and transformed into a piece, subsequent to which the piece is solidified by cooling and removed. The billet (3) is rotated around its axis and concentric with its face as it is introduced into a mold (4), the mold accommodates a core (20), space is left between the core and the inner surface (6) of the mold, the billet is laid along the circumference of the space, and the billet continues to be introduced into the space until the mold's inner surface and core are uniformly and continuously wet with constituents of the billet.

Abstract: A process for manufacturing porous tubes made from carbon-carbon composite material by winding over a mandrel a non-woven sheet, made from a carbon fiber precursor, followed by compression and hot stabilisation of the assembly, with impregnation of the compressed sheet by a resin, followed by a thermal carbonisation treatment of the resin. Tubes are obtained having high permeability, small pore diameter and an inner surface of low rugosity. The tubes produced ar particularly suitable for the manufacture of filtration elements and of filtering membrane supports.

Abstract: A continuous, non-hesitant apparatus and process for producing a molded body of plastics material and for simultaneously securing the molded body to a tubular body by means of a plurality of heading units mounted in series on a continuous conveyor, each heading unit having a mold cavity associated with the mold arm slidably positionable with respect to a mandrel arm having a mandrel, press rod and mold core secured thereto, the mold core and press rod in coaxial alignment with the mold cavity, each of which responsive to a camming surface, the tubular body positioned on the mandrel and brought in registration with a continuous web of hot plastics material which is positioned at one end of the tubular body, the tubular body and mold core then positioned within the mold cavity responsive to the camming surfaces for a time sufficient to form the molded body and secure the molded body to the tubular body, the molded body and tubular body then released from the heading unit, the heading unit recirculating to obtai

Abstract: A process for the manufacture of a thin-walled tube of fluorinated resin, particularly polytetrafluoroethylene, in which a ribbon of fluorinated resin obtained by lubricated extrusion and calendaring, is wound into a tube on a mandrel, the winding of the ribbon being performed in a plurality of layers, and the thus-wound ribbon on the mandrel being brought to a temperature above the sintering temperature of the fluorinated resin for sufficient time to produce sintering. The wound tube and the mandrel are cooled; while on the mandrel the thin-walled tube is rolled to elongate the tube, to reduce the thickness of the tube, and to increase the inside diameter of the tube; and then the mandrel within the tube is extracted.

Abstract: A helical tooling process for economical production of high quality, high temperature thermoplastic composite tubes uses a mandrel or external cylinder to resist a force applied from a helical member for consolidation pressure, compaction, and part removal. The helical too long process facilitates the prescription of a desired consolidation pressure and diameter, independent of temperature. The advantages of the disclosed process include improved produced part quality, increased process flexibility, and enhanced economic efficiency. These advantages stem from the device being easily controlled and fabricated and having a low thermal mass.

Abstract: The invention concerns an apparatus and process particularly for molding profile thermoplastic tubing and process. The apparatus includes the travelling mold type for molding profile tubing, e.g. corrugated or ribbed, including double walled tubing of various types. A sizing plug for the internal diameter of the pipe is provided with suction applying device which applies suction of diminishing strength in the upstream direction of the plug to the inside diameter of the pipe to provide a smooth inside wall of the pipe and allowing faster pipe formation. Suitably, the plug is a cooling plug and provision may be made for communicating the suction to cooling liquid to draw it to the surface of the plug to provide lubrication for a faster pipe forming process.

Abstract: A multi-luminal catheter is characterized in that the cross-sectional shape of each lumen at a connection portion for an extension tube is molded in accordance with the outer shape of the extension tube to be connected. Accordingly, smooth and hermetic connection between a catheter body and the extension tube, that has not been accomplished in the past, can be obtained, and the formation of steps of the lumen which increases fluid resistance can be prevented. This mult-luminal catheter can be produced by pressing a core metal having substantially the same shape as that of the outer shape of the extension tube into each lumen of the catheter body at the connection portion for the extension tube and inserting the connection portion for the extension tube into a molding die while heating it.

Abstract: A device for forming a rolled rim at the unrimmed mouth of the body of a container having a body which is fabricated from a sheet of an expanded thermoplastic material, the device including a first member with a first annular rim-forming surface, and a second member which is reciprocable relative to the first member. The second member has a second annular rim-forming surface which forms a generally closed rim-forming chamber with the first annular rim-forming surface when the second member is in a first position relative to the first member, the second member being reciprocable to a second position in which the first annular surface and the second annular surface are separated to permit the withdrawal of a container with a rolled rim at the mouth from the first member.

Abstract: A method for regenerating a used mandrel made of a fluororesin, includes the steps of heating the mandrel under substantially unloaded conditions to a temperature above the temperature at which the fluororesin is crystallized and gradually cooling the mandrel to a temperature below the temperature at which the fluororesin is crystallized.

Abstract: An apparatus for continuous manufacture of bent rods having a shaped cross section from a reinforced stabilizing material, produced inside a supporting mold wound on a mandrel and containing reinforcing elements impregnated with stabilizable material. The material is stabilized over at least a portion of a length of the mandrel, with the bent rods being adapted to be used in reinforcements for flexible tubing.

Abstract: A method for temperature conditioning a blank of plastic material in which a conditioning mandrel is placed within the blank and thereafter expanded into reliable abutment against the inner surface of the blank. The mandrel is thereafter returned to its initial position. The outer surface of the mandrel is adjusted to and maintained at a certain temperature, whereby, during the abutment, an energy exchange takes place between the blank and the mandrel for adjusting the temperature of the blank. At high temperatures of the mandrel, the mandrel is displaced out of the blank after such short time that the plastic material in the region of the abutment surface never passes the critical temperature of tackiness of the plastic material and/or thermal crystallization of the plastic material. As a rule, the expansion and contraction of the mandrel is repeated one or more times.

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 corrugated elastomeric tube having a smooth interior surface (28) generally free from nipples is produced. A first step in the process is carried out by positioning an unvulcanized elastomeric tubing (14) over a mandrel (12) having a corrugated outer surface (13). The mandrel (12) has an exterior surface (30) which is free from holes. Next, each end of the tubing (14) is clamped to the mandrel (12). The tubing (14) and the mandrel (12) are heated to soften and vulcanizing the tubing (14). Also, pressure is provided to cause the tubing (14) to conform with the corrugated outer surface (13) of the mandrel (12). The vulcanized corrugated tube is then removed from the mandrel (12).

Abstract: Apparatus for inserting a generally U-shaped liner into a pipe and reforming the U-shaped liner into a generally cylindrical cross-section to line the pipe includes winches for pulling the U-shaped liner through the pipe, pigs for cleaning the pipe, manifolds to connection at opposite ends of the pipe and wedge-shaped expansion members for initially mechanically reforming the ends of the liner projecting from the pipe. The wedge-shaped members include bores for communicating fluid at elevated temperature and pressure within the liner for setting the liner in generally cylindrical configuration against the pipe wall. A flaring tool is used to flare the opposite ends of the liner.

Abstract: In accordance with the present invention, there is provided a process for producing polytetrafluoroethylene (PTFE) resin molded articles, wherein an unsintered PTFE resin paste extrusion molded article as extruded from an extrusion machine and inserted into a sintering mold having an inside diameter slightly larger than an outside diameter of said unsintered PTFE resin molded article is sintered at a temperature higher than a melting point of the PTFE resin. In another aspect of the invention, PTFE resin molded articles are produced by a process wherein an unsintered PTFE resin paste extrusion molded article immediately after being extruded from an extrusion machine is sized by means of a sizing die, and the unsintered PTFE molded article thus sized is inserted into a sintering mold having an inside diameter slightly larger than an outside diameter of said unsintered molded article, followed by sintering at a temperature higher than a melting point of the PTFE resin.

Abstract: A method for forming an inflatable catheter balloon from an initial length of tubing includes longitudinally stretching a first end segment of the tubing element and longitudinally stretching a second end segment of the tubing element. The longitudinally stretched tubing is then heated, blow-molded to radially stretch it and define a desired inflatable portion for the balloon, and cooled.

Abstract: An apparatus for molding hollow composite articles having a plurality of internal webs. A mandrel assembly apparatus includes slidable sidewall members, an inflatable pressure membrane surrounding the length of the slidable sidewall members and actuator means mounted on the interior of the sidewall members for lateral displacement thereof together with the inflatable membrane. Adjacent mandrel assemblies accurately position the internal webs of the composite article mechanically, while the inflatable membranes serve to compact the web laminates. The expandable sidewall members also prevent bridging or tearing of the pressure membrane associated with the formation of inner corner radii.

Abstract: A heat exchanger, especially a heat exchanger in the form of a comfort heat exchanger, includes two manifold elements adapted to receive and discharge fluid, and a plurality of tube units transversely located between the manifolds, each tube unit being integrally connected to substantially rigid end elements that fit into the manifolds. The tubes are preferably oriented and expanded to about their original diameter. The heat exchanger is intended to be fabricated from polymer, especially polyamide compositions. The tube units are intended to be manufactured using injection moulding techniques, and then subjected to orientation and expansion steps. Parts fabricated during manufacture of the heat exchangers are also included. The heat exchangers are particularly intended for use as comfort heat exchangers in automobiles.

Abstract: An improvement is provided in a jacket used in the formation/curing of transmission belts. Such a jacket typically has a substantially cylindrical surface which is engaged with assembled belt components during a curing process therefor. The improvement resides in the provision of vent structure for allowing air to escape from between the cylindrical surface on the belt forming jacket and assembled belt components during a curing process.

Abstract: Apparatus for shaping a tubular preform into a hollow body in which an axially directed wall of the preform primarily comprises oriented and/or crystallized plastic material. The tubular preform (10d) is fixed in a circumferential region (13d) in the vicinity of the mouth edge (14d) of the preform between mechanical forming devices (30,40), after which the devices, during continued clamping of the circumferential region, are displaced in the axial direction of the preform relative to a mandrel (50). Thus, the mandrel is displaced into the preform during simultaneous expansion thereof and the material is oriented and/or crystallized. In a preferred embodiment, there is compensation of the stretching forces, which arise in the material when inserting the mandrel, by applying a force to the bottom of the preform by a bottom support (75).

Abstract: Forming process, during vulcanization on a mandrel, of the end portions of rubber tubes, using a tool having a radially deformable skirt in the form of a corolla, made of vulcanized rubber which encloses the end portions of rubber tubes using solely the action of the circumferential elasticity of its corolla. The disengagement of the part after vulcanization is accomplished by a simple axial thrust on the corolla. An upturned position of the radially deformable skirt makes possible the installation of the rubber tubes and other preparation operations.

Abstract: The Assembly has a circular platform, which is threaded about its periphery, and has an upstanding stub about which to set a sleeve-type or cylindrical seal, as well as an arcuately cross-sectioned groove in circumscription of the base of the stub. A cup-shaped closure, having a circular wall, and threaded on the inner wall surface, threadedly engages the threaded periphery of the platform. Upon the platform and closure being threadedly engaged, the closure forces the seal along the stub until an inner end of the seal enters the groove and takes on a proper flare. The closure protects the seal from shipping damage.

Abstract: An apparatus and method for the manufacture of plastic couplings for joining together two lengths of plastic pipe. The couplings are manufactured from blanks of plastic material, such as polyvinyl chloride, which are heated to the thermoplastic state. The blanks are expanded between two mandrels which come together inside the ends of the blank. The mandrels have an outer member with a thin walled section and a nosepiece inside of that section which collapses at the end of the inward stroke of the mandrels so that the center shoulder of the coupling is not as wide as that of the prior art coupling. This results in a coupling which is shorter and lighter than the prior art coupling and yet is the full equivalent of the prior art coupling.

Abstract: Low cost medical micro pipette tips for difficult to reach places, and related methods. The leading or distal portion of the micro pipette tips are materially elongated and ultra thin. This accommodates placement of the distal influent port, for receiving expensive biological extracts, in hard to reach places.

Abstract: A device for forming a rolled rim at the unrimmed mouth of the body of a container having a body which is fabricated from a sheet of an expanded thermoplastic material, the device including a first member with a first annular rim-forming surface, and a second member which is reciprocable relative to the first member. The second member has a second annular rim-forming surface which forms a generally closed rim-forming chamber with the first annular rim-forming surface when the second member is in a first position relative to the first member, the second member being reciprocable to a second position in which the first annular surface and the second annular surface are separated to permit the withdrawal of a container with a rolled rim at the mouth from the first member.

Abstract: Apparatus for applying gasket material to the skirt of a gasket for the mounting cup of an aerosol container, wherein the gasket material is mechanically applied to the mounting cup through the use of a novel mandrel and cutting arrangement. A mounting cup, having a uniquely placed gasket, said gasket extending from the skirt into the channel of the mounting cup.

Abstract: The invention concerns apparatus for molding thermoplastic tubing having solid annular ribs. The apparatus is of the type where a tubular mold is defined by cooperatively interengaged mold block of a pair of mold assemblies. An annular extrusion orifice for the tube extends into the mold tunnel and tubing is extruded about a mandrel. The invention provides an accumulator chamber in the region of the extrusion nozzle to provide for pressure differences which build up at that point. Thus, the effective volume of the accumulator chamber can compensate for the varying requirement for the thermoplastic material resulting from the varying radial wall thickness.

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 of making annular polymeric articles in which a workpiece is placed on a cylindrical shaping surface and is divided about the perimeter into alternating first and second portions. Moulding is done in two stages, the first stage including moulding the first portions, and the second stage including moulding the second portions interposed between the first portions at the same time maintaining the pressure exerted on the first portion, after which the workpiece is vulcanized. The mould includes a cylindrical core (1) having a shaped surface, mounted on a base and serving to accommodate the workpiece thereon, and elements (5, 6) for squeezing the workpiece arranged around the cylindrical core (1) alternately, the first elements (5) having each side surfaces (7) parallel with the axis of symmetry of this element (5), whereas the second elements (6) having each side surfaces (7) of the neighboring first elements (5) arranged at an angle (.alpha.

Abstract: In the production of plastic tubes or pipes which are internally smooth-walled but have peripheral ribs externally, in particular from extrudable, more especially thermoplastic plastic such as PVC, a good filling of the cavities in the moving mold which are provided to form the ribs, is achieved in that said cavities are filled with the molten plastic first at a distance from the separating plane of the moving mold and last in the region of said separating plane.