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 method for continuously forming molded parts includes providing an extruder; directing a hollow column of plastic material from the extruder; providing a plurality of die blocks each including planar end segments having differing geometry and joined by the intermediate convoluted segments; continuously moving such die blocks for receiving and forming the hollow column into strut boots with planar end segments and intermediate convoluted segments and advancing the shaped column of plastic material from the continuously moving die blocks and providing a cutter synchronized to the movement of the shaped column for separating the planar end segments to form one or more parts having planar end segments of the same or differing geometry in each part or with differing geometry from part to part.

Abstract: In a process and an apparatus for making a plastic sleeve (56), plastic is fed into an extruder die (216). The plastic is extruded from the extruder die (216) as a molten plastic stream into a mold cavity (272) having an inner wall (270) with dimensions greater than the outside dimensions of the molten plastic stream. A first end (274) of the inner wall (270) includes a first projection (282) extending radially inward of the mold cavity (272) and circumferentially completely around the mold cavity (272). The molten plastic stream is vacuum expanded radially against the inner wall (270) and around the projection (282) to form a plastic sleeve (56) with a circumferential rib (74) and a aligned external first groove (92) at one end (60) of the sleeve (56).

Abstract: A method and apparatus for producing an extruded product includes a machine that cooperates with an extruder. The machine is commonly used as a corrugator and the extruded product is often corrugated piping. The machine has a frame supporting a trackway in a continuous path. A plurality of mold block assemblies travel about the continuous path to form a mold tunnel along a portion of the continuous path. The mold block assemblies include a carriage connected by at least one guide and linear bearings to a pair of mold holders. The mold holders are connected to at least one pair of opposing mold blocks. Guides and directors position the mold block pairs relative to one another while the assemblies travel along the continuous path. As the holders, and thus the mold block halves, are linearly displaceable from one another, the halves may meet to form the mold tunnel and separate to allow removal of the extruded product.

Abstract: A ribbed pipe molding apparatus has a die with a plastic flow passage which carries molten plastic from an extruder to a mold for making the ribbed pipe. The plastic flow passage has a downstream flow region which exits at an acute angle through the external surface of the die. The inner wall of the end region which locates downstream of the outer wall of the flow passage in the downstream flow region of the passage has a transition wall part which is also inclined relative to the exterior surface of the die but which is sloped at a angle less than the main part of the downstream flow region of the passage. The transition wall part of the inner wall shapes the mouth of the passage so as to produce a wedging of the plastic flowing through the passage into the mold for extremely efficient production of the ribs on the pipe.

Abstract: A sheet used as a spacer layer is made of photo-curing organic material and thermoplastic organic material, a stamper is pressed on the sheet, and light irradiating is performed after the stamper is stripped.

Abstract: Mold blocks and methods for thermoforming corrugated plastic pipe that provide a uniform vacuum on the internal lateral surface and optimize forced convective cooling on exterior surface is disclosed. Mating mold blocks have an interior surface with transverse corrugations and an exterior lateral surface having transverse channels containing radial slots that intersect circular slits formed in the interior mold surface. The channels are fitted with a dual cover arrangement that serves to provide (1) a low-resistance vacuum path to the slits located on the interior surface and (2) a forced convective heat transfer path to cool the mold blocks. The cover arrangement is removable, providing a convenient means of inspecting, maintaining and modifying the mold blocks.

Abstract: A molding apparatus which is used in a continuous molding operation includes an endless looped track, track carriers which are moved around the track to and from a product shaping mold region and a transfer system for replacement of mold block members used in the apparatus. The transfer system, which operates without interrupting the molding operation includes transfer carriers controlled to move synchronized with the track carriers at a transfer location remote from the mold region and actuators which slide the mold block members between the track carriers and the transfer carriers at the transfer location when the transfer carriers are synchronized with the track carriers.

Abstract: Pipe molding apparatus having a molding mold tunnel includes an upstream (3) and at least one downstream mold block (7). Each mold block (3, 5, 7) comprises mold block sections which close with one another to form the pipe and which open relative to one another to release the pipe. The mold blocks (3, 5, 7) move downstream of the apparatus together with one another when forming the pipe and move upstream separately from one another when releasing the pipe which cools and shrinks in both diameter and length in the mold tunnel. Each mold block (3, 5, 7) has a hollow pipe forming region with the pipe forming region of the downstream mold block being decreased in both diameter and length relative to the pipe forming region of the upstream mold block (3) to compensate for the plastic shrinkage.

Abstract: The invention provides a molding apparatus and particularly a corrugator for manufacturing pipes, particularly corrugated pipes, having at least two series of circulation mold jaw parts, which form a molding channel in a predetermined area, and wherein the series are guided in respective circulation guides. The invention further provides that at least one exchangeable mold jaw parts or mold blocks is provided with another pipe molding wherein at least one exchange member is provided along at least one of the circulation guides of at least one of the mold jaw part series.

Abstract: An apparatus for the manufacture of corrugated plastic pipes comprises half shells. Each half shell has a base body which consists of a metal of a higher thermal conductivity and a lower specific gravity than steel and which holds a core. Provided in the core is a mold recess in which to form the corrugated pipes.

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: 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: The method and apparatus prevent the formation of pin-holes or other breakage during stretching of polymeric films, non-woven fibrous webs or laminates in the cross machine direction. Pin-holes and other breakage are prevented by creating slack areas along the length of the product where the edges of the non-woven strips meet with the polymer film, pressing the slack areas into the interdigital stretching rollers without stretching the slack areas, and stretching the remainder of the web in a typical manner. The slack regions are formed prior to interdigitation by, for example, formation of a furrow, a fold or a corrugation.

Abstract: A molding machine including a plurality of carriages for carrying mold blocks in an axial direction. The carriages each include wheels on opposite sides which follow a guide track along an endless path including a molding section extending in the axial direction. Two wings are secured to the carriages for pivoting about an axis extending in the axial direction whereby in one pivotal position the mold blocks are together in a molding position and in another pivotal position the mold blocks are separated in a releasing position. Each of the wings is adapted to carry one of the mold blocks and has a flat axially extending surface and guide wheels. A wing guide track engages the wing guide wheels and is adapted to place the wings in the molding position when the carriage is in the molding section. A first set of track rollers along the molding section engages the flat axially extending surface of one of the wings of carriages in the molding section along a first rolling plane extending in the axial direction.

Abstract: Described is an apparatus for the production of transversely ribbed tubes, having mold jaw halves which bear against each other along a common mold section and form a mold passage. Each mold jaw half has a cooling passage which is produced directly during the operation of casting the respective mold jaw half, for example by means of a so-called false casting core. The cooling passage extends in the corresponding mold jaw half from a first surface to a second surface so that said core can be easily removed from the casting of the mold jaw half. At the one surface, the cooling passage has a cooling agent feed means and, at a spacing therefrom, a cooling agent discharge means. The second surface which is at a distance therefrom is sealed off by means of a guide and slide element which is fixed to the corresponding mold jaw half.

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.

Abstract: Described is an apparatus for the production of transversely ribbed tubes, having mold jaw halves which bear against each other along a common mold section with front faces and form therebetween a mold passage. Each mold jaw half has vacuum passages which are in flow communication with the mold passage. Each mold jaw half also has a cooling passage (22). The front faces of the mold jaw halves are formed with vacuum communication channels which, along the common mold section, form vacuum communication passages. The vacuum communication passages are in flow communication with a stationary vacuum rail, along the common mold section of the apparatus. Along the common mold section, the cooling passages of the mold jaw halves are in fluid communication with a stationary cooling agent rail which has a cooling agent feed means and a cooling agent discharge means.

Abstract: A molding machine including a plurality of carriages for carrying mold blocks in an axial direction and a track for the carriages including a molding section, the track including spaced apart channels receiving the carriage wheels for guiding the carriages along the track. The carriages each include wheels on opposite sides of the carriage, a first set of oppositely facing and axially extending flat surfaces on one side of the carriage, a second set of oppositely facing and axially extending flat surfaces on the other side of the carriage, and centering rollers having facing rolling surfaces spaced apart a distance X. The track includes first and second sets of track rollers associated with one of the channels, the first and second track roller sets defining a first pair of axially extending, parallel facing rolling planes whereby the first and second roller sets engage the first set of flat surfaces of carriages in the molding section.

Abstract: A pipe molding apparatus for forming double walled plastic pipe comprises an extruder which feeds first and second parisons of flowing plastic material to a moving mold tunnel to make respectively the outer and inner walls of the pipe. The moving mold tunnel includes a cooling plug over which the second parison moves to form the inner pipe wall while the outer wall of the pipe is formed against the interior surface of the mold tunnel. An air assist is provided internally of and helps to move the inner parison onto the cooling plug.

Abstract: Described is an apparatus for the production of transversely ribbed tubes, having mold jaw halves which bear against each other along a common mold section with front faces, and form a mold passage. Each mold jaw half is connected at a surface to a support element. The support elements are guided along a first linear guide device. A guide and slide element is fixed to a second surface of each mold jaw half. The guide and slide elements are guided along a second linear guide device. The support elements and the guide and slide elements comprise the same material. The mold jaw halves comprise a material of relatively low specific weight and a coefficient of thermal expansion (.alpha..sub.B) which is high in comparison with the coefficient of thermal expansion (.alpha..sub.A) of the material for the support elements and the guide and slide elements.

Abstract: A process for the production of pile-up lids, each of which comprises an upper wall (1) and an element (2) arranged around the perimeter of said upper wall (1) and which forms a lip (3) protruding above said upper wall (1), and skirt (4) extending below said upper wall (1); the process includes the steps of bringing together in a synchronous manner external sector elements (9) and internal sector elements (10) in radially opposite directions so that, owing to the forced approach of the contact surfaces of the external and internal sector elements (9, 10) with said upper lip (3) of said lid interposed between them, a reeding pressure-molding is obtained on both the inner and the outer surfaces of said upper lip (3), giving said lip (3) an outline to allow piling up on other similar lids.

Abstract: A mold block which is used in a moving mold tunnel comprises first and second mold block sections which meet at their parting faces to close the mold block. Each mold block section has a product shaping interior surface and an air movement passage having an entrance at the base of each mold block section, a first opening to the interior surface and a second opening to the parting face of each mold block section. An air flow controller is provided between the parting face opening and the interior surface opening of the passage in the first mold block section and an air flow controller is provided between the entrance and the interior surface opening in the passage in the second mold block section.

Abstract: An apparatus for the production of plastic compound pipes has a pipe head and half shells completing each other in pairs to form a mold. The pipe head has a supporting ring, which is joined to a connecting piece of an extruder by a first adjusting device. Hereby the width of an injection channel can be modified over its circumference. Between the supporting ring and an external nozzle jacket, a second adjusting device is provided, by which the width of an external channel is adjustable over its circumference.

Abstract: In an apparatus for the production of corrugated plastic tubes an extrusion device passes plastic material into a perpendicularly arranged injection head for injecting the plastic material into a perpendicularly arranged mold section comprising at least two pairs of movable mold jaws arranged in axially mutually superposed relationship. A drive device is associated with each pair of mold jaws for displacement thereof in the radial and axial directions.

Abstract: An apparatus for the production of pile-up lids, each of which comprises an upper wall (1) and an element (2) arranged around the perimeter of said upper wall (1) and which forms a lip (3) protruding above said upper wall (1), and skirt (4) extending below said upper wall (1). The apparatus is used for carrying out a process which includes bringing together in a synchronous manner external sector elements (9) and internal sector elements (10) in radially opposite directions so that, owing to the forced approach of the contact surfaces of the external and internal sector elements (9, 10) with said upper lip (3) of said lid interposed between them, a reeding pressure-moulding is obtained on both the inner and the outer surfaces of said upper lip (3), giving said lip (3) an outline to allow piling up on other similar lids.

Abstract: An apparatus for forming grooves in the cylindrical surfaces of tubes or rods has a passage through the apparatus with a grooving roller mounted adjacent the passage. The roller has a helically extending ridge formed on its circumference, with the ridge extending into the passage and the roller being mounted for rotation about an axis inclined to the axis of the passage. The angle of inclination of the axis is such that the ridge, where it extends into the passage, runs at right angles to the axis of the passage. The roller is made to rotate about the tube or rod as the tube passes through the apparatus.

Abstract: The invention consists of a machine for continuously reprofiling a corrugated material comprising:support bars (7) for the corrugated material, driven in translation and perpendicular to their direction of displacement,reprofiling bars (2) fixed to an endless chain (11) rotatably driven and movable in translation with respect to said chain (11),counter-forming bars (6) fixed to another endless chain (16), also rotatably driven, and movable in translation with respect to said chain (16),the profile of the counter-forming bars being complementary to that of the reprofiling bars, the reprofiling bars (2) and counter-forming bars (6) being positioned on either side of the plane of the support bars (7) in such a way that parts of said bars are opposite one another and the translation movements of the reprofiling and counter-forming bars opposite one another are made approximately perpendicular to the plane of the support bars.

Abstract: Convoluted tubing of thermoplastic resin is made by extruding the resin as a molten tubular extrudate, feeding said extrudate into the interior of a rotating tubular member which has a helical thread in the interior of said member, the spiral thread having a deformation zone receiving the extrudate and a cooling zone downstream from the deformation zone. A vacuum can be used to force the extrudate against the spiral thread in the deformation zone to spirally convolute the extrudate. The rotation of the tubular member causes the resultant convoluted tubing to engage the spiral thread in the cooling zone for conveyance through such zone. Apparatus comprising the rotating tubular member with the interior thread for forming the convoluted tubing is provided.

Abstract: A plastic part forming apparatus includes a mold tunnel into which molten plastic is fed to form the plastic part. The mold tunnel is made from thermally conductive material and has a part shaping interior face which is non-reflective such that the interior surface has high capacity to absorb heat energy from the plastic fed into the mold tunnel. The thermally conductive material then dissipates the heat energy from the mold tunnel.

Abstract: This invention pertains to a method and apparatus for wrapping an article, wherein a metal foil is pleated and then formed in to a dished shape such that the pleats unfold, and then an article is placed within this dished shape.

Abstract: A method of forming a two-layer plastic pipe (4;8) to be laid in the ground for conducting material therethrough forms a core pipe (2) consisting essentially of a first plastic material and forms a detachable outer hose (3;7) of a second plastic material around said core pipe (2) by a suitable coating method, including in said second plastic material an amount of additives effective to protect said core pipe with said outer hose from stresses and loads of laying said core pipe and outer hose and usage thereof in ground.

Abstract: An apparatus for forming a thermoplastic pipe having a profiled surface includes a nozzle having an extrusion orifice feeding extrudate in a downstream direction to a mold path which extends from the nozzle and along which are provided a first mold block and a second mold block downstream of the first mold block. The mold blocks are closable around the extrudate to form the pipe and are openable to release the pipe. The mold blocks are moved together with one another and with the pipe in the downstream direction when the mold blocks are closed and are opened and sequentially moved in an upstream direction along an axis contiguous with the axis of the mold path while the extrudate continues to move in the downstream direction. The first mold block is moved in the upstream direction before the second mold block such that the mold blocks never pass one another on the mold path.

Abstract: An apparatus for the manufacture of pipes of thermoplastic plastics having transverse profile features comprises mold segment halves guided by twos to circulate on a molding path. A conveying device is provided for the recirculation of the mold segment halves, working in the way of a gantry crane. On a conveying bridge overlapping the molding path, two conveying carriages are provided, which are displaceable in directions opposite to each other and at right angles to the direction of production and to each of which is attached a conveying arm directed downwards and having a holding device for a mold segment half.

Abstract: A container of beverage sealed under pressure is provided with a secondary chamber in the form of a hollow insert adapted to provide a flow of gas through an orifice into the beverage when the container is opened. The insert is in the form of an elongate tubular member whose axis extends around an axis corresponding generally to the axis of the container.

Abstract: A machine for making plastic tubing including a plurality of separate carriages for carrying mold blocks about the continuous path. First and second wheel pairs on opposite sides of each carriage ride on first and second tracks respectively through a molding section of the path. An offset wheel is disposed between the wheels of each pair and rides on guide tracks associated with and facing oppositely to the first and second tracks respectively through the molding section. Each mold block is a plurality of sub-blocks secured end to end, with each sub-block having an arcuate face and corrugated with not more than one complete wavelength. Vacuum channels about sub-block end surfaces connect the block face to a vacuum port.

Abstract: A travelling mold has mold blocks formed by opposing mold block sections which open and close relative to one another. The mold sections travel horizontally around a continuous track which is fitted with a plurality of side-by-side mold block carriers on which the mold block sections are releasably supported. The mold block carriers are provided with carrier gears which engage with the main drive gear of the mold so that the mold is driven by engagement of the drive gear with the carriers and not the mold block sections.

Abstract: An apparatus with pivoting blades and closable surfaces for forming a sheet of material into a flower pot or flower pot cover having fins. In an embodiment for forming outwardly extending fins, the apparatus includes a male mold and a plurality of plates arranged in pairs to define a forming opening. The male mold has a plurality of fingers which are laterally extendable from the outer periphery of the male mold. A pneumatic or hydraulic piston and cylinder is provided to move the male mold between a storage position spaced from the forming opening and a forming position within the forming opening. Each pair of plates is movable between an open position and a closed position. In operation, the fingers are extended to push folded portions of a sheet of material between the pairs of plates, which are closed to press the folded portions into fins. In an alternate embodiment for forming outwardly extending fins, pairs of movable plates are positioned between stationary segments.

Abstract: A mold apparatus has a plurality of sets of mold block parts which move to and from a product forming mold tunnel along the apparatus. Each set of mold block parts has at least one liquid receiving channel and a liquid supply is provided for supplying cooling liquid to the channel. The ends of the channel are open for feeding the cooling liquid into one end and draining the cooling liquid from the other end of the channel when the set of mold block parts is in the mold tunnel and seals are provided to prevent leakage of any cooling liquid trapped in the channel when the mold block parts are away from the mold tunnel.

Abstract: An apparatus for the manufacture of corrugated pipes of thermoplastic plastics, which has circulating mold segment halves disposed in two opposite rows subsequent to an injection head, includes a wedge element for separating the mold segment halves. This wedge element is displaceable parallel to the direction of production. Further, grab equipments are provided to be displaceable,counter to the direction of production, by which one additional mold segment half at a time can be moved to the downstream end of a molding path, removed from the latter in the direction of production and moved into a parking position.

Abstract: A travelling mold has mold block sections which are driven around an endless track. The mold has a drive system including a first drive component which drives the mold block sections in abutting positions with one another to a second component in the drive system which accelerates and separates the mold block sections and which then decelerates and regroups the mold block sections in their abutting positions before the mold block sections are returned to the first drive component. This separation and regrouping of the mold block sections eliminates the necessity of having a complete chain of abutting mold block sections completely around the mold.

Abstract: A machine for making plastic tubing including a plurality of separate carriages for carrying mold blocks about the continuous path. First and second wheel pairs on opposite sides of each carriage ride on first and second tracks respectively through a molding section of the path. An offset wheel is disposed between the wheels of each pair and rides on guide tracks associated with and facing oppositely to the first and second tracks respectively through the molding section. Each mold block is a plurality of sub-blocks secured end to end, with each sub-block having an arcuate face and corrugated with not more than one complete wavelength. Vacuum channels about sub-block end surfaces connect the block face to a vacuum port. Cooling water channels about sub-block end surfaces connect to water inlet and discharge ports for selectively circulating cooling water through the blocks.

Abstract: In a method of forming a hollow product in a molding apparatus having an upstream and a downsteam end a parison of thermoplastic material is extruded in a molten state from a heated extruder at the upstream end and moved through a product shaping region towards the downstream end of the apparatus. The material is cooled by passing a cooling medium internally of the product from the downstream end towards the upstream end of the apparatus.

Abstract: An apparatus for the production of corrugated tubing from thermoplastic synthetic resin including a shaping path following an extrusion head of an extruder and composed of a guide which is arranged in a frame and on which mold halves, fitted together in a pair at an inlet to define annular molds in a compact train as a travelling mold moving with the tube are advanced by at least one drive pinion arranged at an initial part of the shaping path, the pinion being in mesh with racks on the fitted together mold halves. At an exit point following the shaping path, the mold halves are separated from one another and are gripped by gripping arms provided with coupling devices and area shunted back to the inlet of the shaping path. The gripping arms are bearinged by drives in a movable fashion on carriages. The carriages are able to be reciprocated by drives on guides on return paths parallel to the shaping path.

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 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 method and apparatus for production of smooth or corrugated small and large diameter thermoplastic tubing and composite tubular structures. The apparatus includes a supporting framework, a plurality of mold carriages mounted on said framework for reciprocal linear travel therealong, at least one mold block mounted on each of said mold carriages, each said mold block comprising a pair of opposed semi-cylindrical segments mounted on a carriage for transverse linear reciprocal travel therealong for closing and opening of said mold block, an actuating mechanism for moving said opposed mold segments towards and away from each other, and a single actuating mechanism for selectively moving said carriages.

Abstract: Provided is an improved corrugated containerboard that includes a corrugated medium sandwiched between and secured to a top liner and a bottom liner. The corrugated medium, top liner, and bottom liner each include fibers that are oriented in a machine direction, and the corrugated medium defines a plurality of flutes that are oriented in the machine direction. The improved corrugated containerboard is constructed from conventional paperboard which is drawn through a corrugation system in the machine direction. A first piece of paperboard is drawn between a pair of dies to form the corrugated medium with flutes oriented in the machine direction. A second and third piece of paperboard are glued to either side of the corrugated medium to form the corrugated containerboard. Each die includes an engaging surface with ridges thereon, and the engaging surfaces are opposed and define a forming zone therebetween which the first piece of paperboard is drawn through.

Abstract: A machine for making plastic tubing including a plurality of separate carriages for carrying mold blocks about the continuous path. A mold train drive engages a selected number of carriages at the beginning of the mold tunnel to continuously drive the carriages along the mold tunnel. A shuttle drive follows the continuous path through a shuttle area and spaced from the path along a substantial portion of the mold tunnel, and includes first and second carriage engaging sections at substantially opposite points along the drive so that a carriage at the end of the mold tunnel becomes engaged by one shuttle drive engaging section while the other shuttle drive engaging section engages a carriage at the beginning of the mold tunnel.

Abstract: A machine for making plastic tubing including a plurality of separate carriages for carrying mold blocks about the continuous path. First and second wheel pairs on opposite sides of each carriage ride on first and second tracks respectively through a molding section of the path. An offset wheel is disposed between the wheels of each pair and rides on guide tracks associated with and facing oppositely to the first and second tracks respectively through the molding section.