Abstract: The present invention relates to a method for taking out a molded product and an apparatus for the same. Use a chucking fixture (60) with claws (67a, 67b) which may clamp a upper extending portion (52A) of the molded product (52), is mounted on a robot arm (52a) of a taking out robot (55) and then said molded product (52) can be taken out by force produced by the molds (11) for separating the product (52) from the molds (11) through making chucking arms (66a-66d) with claws (67a, 67b) be in a state of moving along the horizontal direction without to bring load to between the product (52) and the upper extending portion (52A) thereof.

Abstract: Hollow articles of thermoplastic synthetic resin are produced by suction-blowing in an apparatus in which the shaping is decoupled from the extrusion. A preform handler, especially a six-axis robot, engages the preform at the extrusion or coextrusion head and carries it to the closed mold into which the preform is sucked by suction generated in the mold cavity. While shaping is effected in the mold, extrusion can continue at the head to form a further preform.

Abstract: A blow molding apparatus (10) including four molds (21, 22, 23, 24) that move into a common parison receiving position (26) from directions different from the directions that the molds move out of the parison receiving position (26). When in the parison receiving position (26), each mold receives, encloses and severs a length of parison then shapes the parison during blow molding. Two molds (21, 22) alternately move in respective first and second radial directions (36, 40) from the parison receiving position (26) to respective first and second outer positions (38, 39), to a common article take-out position (45) and then back to the parison receiving position (26) from a third radial direction (96). The third radial direction is angularly spaced between the first and second radial directions.

Abstract: At least one blow-molded plastic container and one compression molded lid are simultaneously produced in a blow mold. Preferably, the method and apparatus utilize a mold capable of simultaneously receiving a pair of extruded parisons. One of the parisons is utilized to produce a pair of aligned container bodies and the other of the parisons is utilized to form a pair of aligned closures. In this manner, a container and closure combination can be manufactured having perfect color matching and can be readily recycled in its entirety. In addition, the method and apparatus according to the present invention significantly reduces tooling costs and required machine capitol.

Abstract: The invention provides a blowing agent metering system and method for use in polymeric foam processing. The system may be used to control the rate of introduction of blowing agent into polymeric material in a processing apparatus to form a mixture having the desired blowing agent weight percentage. The metering system includes a restriction orifice which is positioned in a pathway between a blowing agent source and a blowing agent port within a foam processing apparatus. The metering system measures the pressure differential as blowing agent flows across the restriction orifice from the source to the port and may also measure the temperature of the blowing agent at one or more locations. Using a pre-determined relationship between the flow rate, the orifice dimensions (e.g., length, diameter) and the measured variables (e.g.

Abstract: A device for extruding and blow-molding thermoplastic tubular components with an extrusion head. The head has a central stem which is perforated in an axial direction. A distribution body lies radially around the stem so as to radially distribute the stream of thermoplastic material. An annular extrusion port is arranged downstream. The invention allows to avoid stagnations of material and to easily adapt the device to various types of thermoplastic material.

Abstract: A method for tracking multiple SKUs of ophthalmic devices in a manufacturing line, comprises the steps of: assembling first molding devices, at least one of the first molding devices having an identification device, such as, a bar-code or an inductive transmitting/receiving device; reading the identification device of the first molding devices; forming first molded parts using the first molding devices; providing a plurality of carriers, the carriers having carrier indicators; transferring the first molded parts to at least one of a plurality of carriers; reading the carrier indicator of the carrier carrying the first molded parts; and storing in machine-accessible memory the information associated with the identification device of the first molding devices and the information associated with the carrier indicator of the carrier carrying the first molded parts.

Abstract: A mold assembly for blow molding plastic articles is provided having an upper mold member, a lower mold member and a lower support member. The lower mold member is preferably a relatively lightweight plate having a generally centrally located molding cavity matingly matched with an upper molding cavity in the upper mold member. The lower mold member is moved horizontally and optionally vertically beneath an extrusion head as a molten parison is extruded. The lower mold member is then transported to, and positioned within, the lower support member. The upper mold member is then closed over the lower mold member and lower support to close the mold assembly. The molten parison is then expanded in the mold cavity. After the molding operation, the plastic part may be removed and the lower mold member may be cooled by immersion in a cooling fluid. The apparatus to move the lower mold member during extrusion of the parison and to the molding station may be a robotic arm.

Abstract: A reduced flash molding process and apparatus useful for a variety of parts, especially flat plastic panels, reduces trimming time, regrind waste, increases production speeds, reduces energy consumption, and reduces part weight. The reduction in flash is made possible by providing side members which close before molding material reaches them. Flash still occurs at the ends of the mold, but is eliminated from the sides. Because the parison can be more carefully managed during molding, the mold can be placed closer to the parison extrusion die, thereby reducing parison swell and sag and permitting more accurate filling of all areas within the mold geometry.

Abstract: A forced exhaust pipe is connected to an exhaust pipe connected with a cross head so that a negative pressure may be formed within an air passage so as to effect rapid control of air pressure (amount) within a parison, thereby stabilizing the air pressure within the parison. A parison stabilizing method and a system therefor for use in a hollow formation molding machine, according to the present invention, are so formed that a forced air-discharge is carried out through an exhaust pipe connected with the air passage formed within the cross head, so that a negative pressure is formed within the air passage. In this way, the above-mentioned system can effect quick control of an air pressure (amount) within the prison during a pre-blowing treatment, shorten a time period necessary for determining molding conditions, without having to increase the inner diameter of the air passage.

Abstract: A blow molding machine capable of relatively high production rates at relatively low cost is provided. The blow molding machine comprises a base, a reciprocating shuttle mechanism supported by the base, a single blow molding station supported by the base, and adapted to receive a parison for forming the hollow article at the blow molding station, a pair of cooling stations supported by the base on flanking sides of the blow molding station, a pair of blow pin carriages spaced from one another, each of which is connected to the shuttle mechanism and is indexable to the blow molding station and to one of the cooling stations. Each blow pin carriage can comprise one or more blow pin assemblies that are movable independent of the shuttle mechanism between a rest position and a blow position.

Abstract: A multi-layer thermoplastic packaging, the outer layer containing at least one filler having particles of different particle size and of a diameter ≧50 &mgr;m, to give a natural stone external appearance and a process for the preparation thereof which includes coextrusion and blowing of the inner and outer layers, to provide the packaging which can be in the form of a flask, bottle, pot or other desired shape.

Abstract: Machine for moulding containers (3a) made of plastic material, comprising an assembly (2) for extruding tubes (3) of plastic material, a blowing assembly (5), a mould for containing containers (3a), formed by two half-moulds (4a,4b) movable upon actuation of associated first means (100), in a longitudinal direction (X-X) and symmetrically with respect to a fixed axis (Z-Z) perpendicular to said longitudinal direction, the assembly formed by the mould (4) and the associated first actuating means (100) being movable, upon actuation of second actuating means (200), in a transverse direction (Y-Y) from a position corresponding to the extrusion assembly to a position corresponding to the blowing assembly and vice versa, wherein said first means for actuation in the longitudinal direction are of the electric type and means (110) for symmetrically adjusting the distance of the two half-moulds (4a,4b) from said fixed axis (Z-Z) are provided.

Abstract: In a conventional multilayer crosshead, only one pressure sensor is disposed in the inlet of the annular passage, preventing monitoring of membrane discontinuities; parison thickness is not constant; as the crosshead body is not cooled and parison temperature is high, a long time is required for cooling during blow molding, preventing the reduction of the molding cycle. A multilayer crosshead according to the present invention includes pressure sensors disposed in at least two positions of the annular passage so that the flow rate is controlled and monitored so as to eliminate the pressure difference between the pressure sensors, and parison temperature is lowered to a greater degree by a cooling jacket with a built-in heater disposed in the crosshead body so that a blow molding cycle is shortened.

Abstract: At least one blow-molded plastic container and one compression molded lid are simultaneously produced in a blow mold. Preferably, the method and apparatus utilize a mold capable of simultaneously receiving a pair of extruded parisons. One of the parisons is utilized to produce a pair of aligned container bodies and the other of the parisons is utilized to form a pair of aligned closures. In this manner, a container and closure combination can be manufactured having perfect color matching and can be readily recycled in its entirety. In addition, the method and apparatus according to the present invention significantly reduces tooling costs and required machine capitol.

Abstract: A method of extrusion blow molding is disclosed; the method allows the finished part to have consistent and even wall thickness within a broad range of local mold radii. This result is achieved without resorting to injection blow molding or other common techniques of deforming the parison.

Abstract: A molding system has a slide displaceable parallel to an axis through a relatively long stroke relative to a stationary overhead extruder head, a center support fixed on the slide, and a pair of end supports displaceable axially through relatively short strokes on the slide between inner and outer end positions. A pair of inner mold halves carried on the center support are directed axially oppositely therefrom toward the end supports. Respective outer mold halves carried on the end supports are axially engageable with the respective inner mold halves in the inner positions of the end supports. An end-support drive connected between the slide and the end supports moves the end supports between their end positions and a slide drive connected to the slide moves the slide axially relative to the head. Each of the end-support drives includes a respective motor mounted on the slide.

Abstract: A molding apparatus has a pair of mold halves having faces engageable together to form a nonstraight passage having an intake end and an output end, extruder means for forming a hollow plastic preform and feeding it to the intake end of the passage, pump means connected to the output end of the passage for drawing gas therefrom and thereby applying drawing the preform through the passage, and a seal carried on one of the faces, extending along the passage, and engaging the other of the faces for preventing gas flow between the faces into the passage when the mold halves are closed together.

Abstract: An apparatus for blow-molding a parison, the apparatus comprising a mold defining a cavity into which a parison may be introduced for blow-molding, a die for extruding the parison into said cavity, and means for blowing a gas around the outside of the parison in said cavity, the means for blowing a gas around the parison comprising (a) a distributor located at the entrance of the mold cavity for emitting gas around the circumference of the parison and (b) means for injecting gas directly into said distributor, wherein during use the die is separated from the distributor by unenclosed space.

Abstract: Depicted is an extruder (1), which converts preferably granular plastic material into the melted state and which comprises at least one

Abstract: An apparatus for the manufacture of profiled plastic pipes comprises a machine bed (1) that half shells (2, 2′) are guided on, forming a molding path (9). A driving pinion (17) is provided above the molding path (9). At least one lower driving pinion (41) is provided on the machine bed (1) along the molding path (9). A lower indentation (39, 39′) is formed in the area of the lower side (30, 30′) of the half shells (2, 2′), with the at least one lower driving pinion (41, 41′) engaging therewith.

Abstract: A plastic product, and method and device for producing such plastic products are disclosed. The present invention produces a plastic product having a completely sealed sidewall defining at least one cavity therein, or a plastic product filled with a filler, such as urethane foam, in the cavity, or a plastic product having both a sidewall with both open end portions and a filler contained in the cavity. The plastic forming process and device of this invention effectively produces a variety of plastic products, such as a variety of panels, pipes, channels, columns, boats, oil tanks, door panels, vehicle door panels, bumpers, vehicle hoods, and small-sized submarines, which are not produced by conventional plastic forming processes or devices.

Abstract: At least one blow-molded plastic container and one compression molded lid are simultaneously produced in a blow mold. Preferably, the method and apparatus utilize a mold capable of simultaneously receiving a pair of extruded parisons. One of the parisons is utilized to produce a pair of aligned container bodies and the other of the parisons is utilized to form a pair of aligned closures. In this manner, a container and closure combination can be manufactured having perfect color matching and can be readily recycled in its entirety. In addition, the method and apparatus according to the present invention significantly reduces tooling costs and required machine capitol.

Abstract: A one-piece self-draining container and method and apparatus for forming same. The container includes a body and a finish wall extending upwardly from a body opening. The finish wall surrounds a dispensing spout which extends above the top of the wall. A frustoconical web joins the finish wall and the dispensing spout to form a drain apron gutter channel having a relatively steeply inclined cone angle. A drain opening is defined adjacent the channel for draining fluid from the channel into the container body. A removable cap having a depending skirt defining a thread which mates with an internal thread on the container wall to thereby threadably engage and close the container. The method is performed on the type of extrusion-injection blow molding machine as generally disclosed in U.S. Pat. No. 2,804,654 as modified in accordance with the invention to form the web wall in situ with a frustoconical configuration of uniform cross sectional thickness.

Abstract: A blow molding machine comprising an extruding device 2, one pair of mold-clamping devices 3, 3′, and hammering devices 4, 4′ for hammering blow pins 40, 40′ respectively into molds 30, 30′ in the one pair of mold-clamping devices 3, 3′, for blowing, a parison P extruded from the extruding device 2 being clamped by alternately switching the mold-clamping devices 3, 3′ and then, the blow pins 40, 40′ being hammered into the molds 30, 30′ by the hammering devices 4, 4′, respectively, wherein the one pair of mold-clamping devices 3, 3′ are linearly arranged in the same direction as an opening- and-closing direction of the molds 30, 30′ in the mold-clamping devices 3, 3′.

Abstract: A hollow article is manufactured to have a configuration in which the wall thickness of each of both end portions changes multidirectionally with extremely high accuracy.

Abstract: A process for producing a plastic blow-molded part. A plastically deformable plastic parison with a first subregion and an opposite second subregion is placed between a molding element having a projecting region and a mold interacting with the molding element. A positive pressure is generated between the molding element and the first subregion and within the parison, to keep the first subregion at a distance from the molding element and to keep the first and second subregions at a distance from each other. A stretching region of the first subregion is preformed by moving the molding element in relation to an edge region in the direction of the mold and by generating a negative pressure between the projecting region and the stretching region of the first subregion. The subregions are deformed for generating a positive pressure within the parison.

Abstract: A microcellular injection blow molding system and method, and microcellular blow molded articles produced thereby, are described. The system is equipped to extrude microcellular material that changes in thickness, material density, or both in the machine direction while maintaining a constant pressure drop rate during nucleation just prior to extrusion, providing the ability to produce consistent uniform microcellular material independent of material thickness. The systems and methods are particularly useful in production of strong, thin-walled, non-liquid-permeable, opaque containers that do not contain reinforcing agent, chromophore, or residue of chemical blowing agent or chemical blowing agent by-product.

Abstract: A blow pin assembly for a mold of a rotary blow molding machine includes a base, a carriage supported by and movable relative to the base, a sub-base supported by and movable relative to the carriage, and a blow pin mounted to the sub-base for movement between a home position and a mold-engaging position. The blow pin is constructed with a low profile to clear an extruder head above the mold. This permits a method of forming a blow molded product to be used wherein the blow pin is inserted into the mold (and a parison in the mold), while the mold is at the extrusion workstation of the blow molding machine or very nearly so.

Abstract: The present invention provides an apparatus for manufacturing bellows which contributes to expand the life of the resin bellows to be used for vehicles and to improve the quality of the same.

Abstract: Shuttle blow molding apparatus having an extruder or a blow head for substantially continuously emitting a thermoplastic material in tubular or parison form at a moldable temperature downwardly along a vertical axis. A finite length of the thermoplastic material is grasped by a first mold set, which then moves downwardly with respect to the extruder or blow head to provide clearance for a second mold set to move to a position to grasp a second finite length of the emitted thermoplastic. The first mold set is then moved horizontally away to permit the emitted thermoplastic length therein to be blown into a hollow article, and thereafter removed from the first mold set that is permitted to return and engage an other finite length of the thermoplastic material. The second mold set follows the first mold set in a path of travel traced by the first mold set.

Abstract: In blow molding, each mold has two or more cavities, each respectively fed by two or more parisons. Each cavity fed by a separate parison may itself include two or more article cavities aligned with its parison.

Abstract: A method and an apparatus for the manufacture of pipes of thermoplastics with transverse profile features comprises mold segment halves which are circulated by twos on a molding path. A conveying device of the type of a gantry crane is provided for recirculation of the mold segment halves. On a conveying bridge that bridges the molding path, provision is made for two conveying carriages, which are movable in opposite directions and crosswise of the direction of production and which have mounted on them a downward conveying arm with a holding device for a respective mold segment half. Provided downstream of the downstream end of the molding path are parking positions for additional mold segment halves, those of which that are closest to the molding path being carriages which are movable out of the path of displacement of the conveying arms.

Abstract: The invention provides blow molding methods and systems for polymer processing. The methods involve blow molding a parison of polymeric material using a variable blow pressure. The pressure is varied to produce high quality blow molded articles which may be formed of solid polymer or polymeric foam including microcellular material. In particular, foam articles can be produced at relatively low densities and/or with good definition. The blow molding systems and methods may be used to produce a variety of different types of articles including bottles, containers, cases, automotive parts, toys and panels.

Abstract: A corrugator and mold management apparatus and methods for continuously forming transverse corrugations and other shapes in a tubular polymer melt parison formed by an extrusion die employs a plurality of molds that interlock when mated. Each mold has common outside dimensions and a pair of open linear bearings that provide the mold axis and maintain alignment of the molds parallel to and in the same horizontal plane as the axis of the extrusion die. The molds are moved axially along supported rails by bi-directional linear actuating modules and between the pairs of supported rails by lateral transport units. Inner supported rails define the mold tunnel and outer supported rails provide an outer path to move molds upstream back toward the extrusion die. The lateral transport units include extensible rails that facilitate the transfer of molds to and from the mold tunnel and the outer return paths. Delivery units remove from and introduce molds from a plurality of parking stations.

Abstract: Shuttle blow molding apparatus having an extruder for substantially continuously extruding a thermoplastic material in tubular form at a moldable temperature downwardly along a vertical axis. A first finite length of the thermoplastic material is grasped by a first mold set, which then moves outwardly and downwardly with respect to the extruder to provide clearance for a second mold set to move to a position to grasp a second finite length of the extruded thermoplastic tube. The first mold set is then moved horizontally away to permit the finite length of thermoplastic tube therein to be blown into a hollow article, and thereafter removed from the first mold set at a second position of the first mold set.

Abstract: The invention concerns a method whereby in an installation (1, 2, 3) for making containers (200, 300) by blowing blanks (400), for example thermoplastic preforms, the high pressure fluid derived from degassing a container is re-used and injected (14) into a container previously degassed, for example for cooling it or for thoroughly spraying the inside thereof to solidify the material.

Abstract: A blow molding machine for producing three-dimensional low-waste articles including at least one horizontally separated blow mold formed of upper and lower half-molds, a device for vertically displacing at least one of the upper and lower half-molds between an open mold position in which the upper half-mold is spaced from the lower half-mold, and a closed mold position in which the upper and lower half-molds engage each other, a device for locking the upper and lower half-molds in the closed position, and a device for pivoting the upper half-mold in the open mold position about a horizontal axis by substantially 90° and/or displacing the upper half mold in a horizontal plane.

Abstract: A multi-station rotary blow molding machine suitable for molding hollow articles from a thermoplastic parison is described. Plural, indexable dials present blow mold assemblies for parison insertion at a common, shared parison insertion station. The parisons can be extruded parisons or injection molded preforms.

Abstract: This invention relates to a method and a device for producing blow-molded plastic hollow bodies. The device is of an enhanced design which avoids the shortcomings of traditional blow-molding technology. The extrusion die according to this invention is adjustable for different settings to produce different, partly overlapping wall thicknesses of the parison blank in order to compensate for the insufficiencies inherent in blow-molding and to obtain a finished blow-molded product with as consistent and uniform a wall thickness as possible, with an overlay, for instance in vertical wall sections, of evenly spaced longitudinal ribs. A technical concept is introduced whereby, as a novel process, the two conventional measures used to achieve a uniform wall thickness in the finished blow-molded hollow body are complemented by an additional, third step which makes it possible to produce containers whose hollow bodies are provided with targeted, intentional and reproducible irregular wall-thickness patterns.

Abstract: An apparatus for extrusion molding that includes an extruding die that permits extrusion of a material into a hollow tubular molding, a molding die, first and second clamping devices and a device for releasing compressed air. The first and second clamping devices are positioned along opposite end portions of the molding die and configured to clamp the molding independently from one another to form an air-tight space therebetween. The molding die includes two die cavity halves and is arranged to close around the air-tight space and compress the molding to conform the same to a final product configuration. The device for releasing compressed air is arranged to release compressed air before the die cavity halves are separated.

Abstract: A synchronous moving and sealing apparatus for a blow-molded product is disclosed. It mainly comprises a vertical moving mechanism and a sealing mechanism. The sealing mechanism has a clamping gear activator and two pulling rod activators with two pulling rods. The sealing mechanism and the plastic material will move down. The pulling rods and two clamping rods makes this edge closed approximately as a straight line and will seal the edge of the plastic material synchronously. So, a higher quality of the final blow-molded product is obtained and the safety of the operator is enhanced.

Abstract: A molding apparatus has a pair of mold halves having faces engageable together to form a nonstraight passage having an intake end and an output end, extruder means for forming a hollow plastic preform and feeding it to the intake end of the passage, pump means connected to the output end of the passage for drawing gas therefrom and thereby applying drawing the preform through the passage, and a seal carried on one of the faces, extending along the passage, and engaging the other of the faces for preventing gas flow between the faces into the passage when the mold halves are closed together.

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 refers to a pallet container (10) including a bottom pallet (12), a plastic receptacle (14) arranged thereon and a support jacket (16) closely surrounding the plastic receptacle (14) and fixedly connected (but detachably) on the bottom side with the bottom pallet (12). Conventionally, the thickened pinch-off seam produced in the lower receptacle plate (and also in the upper receptacle plate (22)) through pinching off the tubular parison interferes with a flow of the residual liquid to the bottom-side discharge valve (28). Thus, in accordance with the invention, the inner plastic receptacle (14) is provided with welded pinch-off seams (30) on two diametrically opposing side walls, preferably with one seam ending directly in the integral discharge valve (28). The discharge valve (28) thus lies in the middle of the side walls with the joining weld for the first time entirely in the tube pinch-off area around the blow mandrel within the tube.

Abstract: An extrusion head for blow molding extruded plastic containers, with a ring gap nozzle having a mandrel and a ring-shaped nozzle body having an elastically deformable sleeve, and setting devices for radially deforming the elastic sleeve. The sleeve defines a nozzle gap, the width of which is variable by axially movement of the mandrel and/or of the nozzle body. The geometry of the gap can be changed by deforming the sleeve in the course of extrusion of a hose-like, pre-shaped blank. The sleeve is axially supported in the nozzle body, and/or on the mandrel only on segment-like surfaces.

Abstract: A blow molding machine comprising a base, a wheel mounted rotationally on the base, a controller to control operation of a pin within a die, and a position detector for detecting a short run mold on the wheel wherein the wheel comprises a plurality of identical molds and the short run mold which differs in size and/or shape from each of the plurality of identical molds. The position detector, upon detecting the short run mold, switches a relay to switch from a first pin control program causing the extrusion of a parison having appropriate parameters for the plurality of identical molds, to a second pin control program causing the extrusion of a parison having appropriate parameters for the short run mold.

Abstract: A method and apparatus for manufacturing a hollow plastic product is provided. In accordance with one aspect, into a mold half having a tubular groove portion and a projecting groove portion which projects outwardly from the tubular groove section is supplied a parison into the tubular groove portion and a clump of molding material into the projecting groove portion, and when blow molding is carried out by introducing a pressurized gas into the parison, the clump becomes integrated with the parison thereby providing a plastic product of unitary structure. In accordance with another aspect of the present invention, a parison extrusion nozzle is provided with at least two passages each of which is connected, preferably through a valve, to a corresponding dispensing unit for dispensing a desired molding material. A control unit is provided as connected to each of the dispensing units to control the supply of molding material so that there is obtained a parison having regions of different molding materials.

Abstract: An extrusion molding process including the steps of: i) extruding a material through an extruding die into a tubular molding. ii) driving two clamping devices to clamp the tubular molding at different elevations, causing an air-tight space to be formed within the tubular. iii) closing two symmetrical halves of a molding die on the molding between the clamping devices and simultaneously lowering one clamping device to stretch the molding downwards, causing the molding to be compressed in a die cavity between the two symmetrical halves of the molding die and molded into the desired finished product: and iv) opening the molding die from the finished product and returning the clamping devices to their former positions.

Abstract: A molding system has an extruder for concentrically extruding an outer tubular strand having an inner diameter and an inner tubular strand having an outer diameter from respective annular nozzle openings defined between respective inner and outer nozzle walls. The outer strand at least is are of a resin that swells transversely as it issue from the respective nozzle opening. The nozzle walls are positioned such that the outer diameter of the inner strand is substantially smaller than the inner diameter of the outer strand and the inner strand is separated by a space from the outer strand as the strands issue from the respective nozzle openings. An outer wall of the inner strand engages an inner wall of the outer strand at a spacing from the nozzle openings after substantially all swelling of the strands has taken place. A closeable mold has a passage for drawing the strands through the passage by applying suction to a downstream end of the passage.