Abstract: A pipe perforating apparatus has a spindle carrying a cutting tool and a drive for rotating the spindle about its own axis while revolving the spindle about the pipe. The cutter periodically engages and perforates the pipe. To provide for small, uniform sized holes in the pipe, the cutting tool is an end cutting punch and the spindle is rotated and revolved around the pipe to roll the punch into and out of the pipe without exerting a tangential force on the pipe.

Abstract: In an apparatus for producing multi-walled thermoplastic tubing in which the inner and outer tubing walls are continuously formed by extrusion one within the other, the inner tube being urged outwardly into pressing engagement with the outer tube, the mechanism for urging the inner tube outwardly into securement with the outer tube comprises a mandrel mounted coaxially with the die for extruding the inner tube and on the downstream side of it. The mandrel has an outer surface providing a tapered end portion positioned to receive the inner tube as it is extruded, and a generally cylindrical portion positioned to urge the inner tube into securement with the outer tube. To prevent sticking of the thermoplastic material to the mandrel, the outer surface of the mandrel is maintained at a temperature lower than the molding temperature and is transversely ribbed.

Abstract: A vertical format corrugator or the like tube producing apparatus has two sets of independent mold sections that circulate on respective paths. The mold sections co-operate to define a travelling mold cavity into which a thermoplastic tube may be extruded to be molded. Fixed tracks extend along the forward and return runs of the mold section paths and are engaged by track followers on the mold sections. The track followers support and guide the mold section, thus enabling the elimination of chains linking the mold sections. In preferred embodiments, transfer mechanisms are provided at the ends of the runs to transfer the mold sections individually from one run to the next. The mold sections may include removable mold blocks, means for automatically changing the configuration of the mold cavity and a system for internal cooling of the mold sections.

Abstract: In an apparatus for producing thermoplastic tubing, the apparatus being of the type comprising a pair of complementary mold assemblies providing recirculating mold units which cooperate in pairs along a forward run to define a mold cavity, each mold unit comprises a transversely displaceable die member providing a plurality of half molds which can be selectively displaced to an operative position. The apparatus includes selectively operable cam means positioned along the return runs of the mold units for selectively engaging the die members. The half molds in each die member are configured differently, there being at least one with a smooth inner surface and at least one with a corrugated inner surface.

Abstract: Apparatus for producing corrugated thermoplastic tubing of the type comprising a pair of complementary upper and lower mold assemblies each having an endless chain of articulately interconnected mold blocks which are driven along a forward run and back along a return run, the mold blocks cooperating in pairs along the forward run to form an axially extending tubular mold tunnel, within which the tubing is expanded by vacuum forming or blow molding. The mold blocks have mold-defining faces of corrugated form with alternating troughs and crests. Each mold block is formed with passages which extend between the bases of the troughs of the corrugations and the exterior of the mold block. These passages communicate with the base of each trough throughout its length, and serve to permit the escape of any atmospheric air which is trapped by the tubing in the troughs during expansion of the tubing.

Abstract: The invention provides a die assembly comprising a nozzle and at least one mandrel which defines with the nozzle an annular die orifice. The nozzle has a longitudinally extending stem terminating in the sleeve, the mandrel being located coaxially within the sleeve and coupled to the stem of the nozzle by an axially extending screw threaded coupling. The mandrel includes an internal flow passage having an inlet positioned to receive thermoplastic material from a supply passage extending along the nozzle and an outlet positioned to deliver the material to an annular distribution chamber defined by the opposing surfaces of the mandrel and the sleeve. The distribution chamber provides an uninterrupted annular flow path extending from the outlet to the die orifice, thereby avoiding the disadvantage of imperfect material distribution.

Abstract: A feed mechanism comprising a rotor and an endless flexible belt carried by the rotor. The rotor comprises a pair of cylindrical guide members arranged coaxially one within the other, the guide members being mounted for rotation in unison about a common axis. Each of the guide members provides a helical groove defining a respective feed channel, the grooves being of the same pitch and opposite hand, and the belt is constrained by the guide members to extend helically along the feed channels in sliding engagement with the guide members. The belt protrudes from one of the feed channels to engage a restraining surface which restrains the belt against rotation so that, in response to rotation of the rotor, the belt is continuously advanced along one of the feed channels and returned along the other, thereby providing a continuously advancing non-rotary bearing surface which bears against the restraining surface.

Abstract: An apparatus for producing multi-walled thermoplastic tubing having a corrugated wall and a substantially smooth inner wall secured to the corrugated wall, there is incorporated two sets of endless flexible belts each of which is entrained around rotatable end rolls, the outer runs of the belts of one of the sets thereof alternating with the outer runs of the other of the sets thereof, with these outer runs of the various belts serving to urge the inner wall against the corrugations of the corrugated wall while the thermoplastic material of the walls is soft thereby to secure the walls together, and with an electrically energizeable heating coil being provided for softening the thermoplastic material of the corrugated wall to ensure satisfactory securement between the walls.

Abstract: Corrugated tubing is advanced along its axial path by rotatably driven lead screw members the screw threading of which is in meshing engagement with the corrugations of the tubing, the lead screw members being in pairs with the screw threading of the members of each pair being of opposite hand and the lead screw members each pair being rotated in opposite directions. The lead screw members of each pair present outwardly directed cutters which are synchronized substantially simultaneously to intersect the tubing thereby, in perforating the tubing, to restrain the tubing against rotation thereof about the axial path.

Abstract: In apparatus for producing corrugated thermoplastic tubing and which comprises a pair of complementary upper and lower mold assemblies each having an endless array of articulately interconnected mold blocks which are driven along a forward run and back along a return run, the mold blocks co-operatively interengaging in pairs along said forward run to form an axially extending tubular mold tunnel, there is disposed at the entrance to the tunnel an extrusion head having an inner core member and an outer member which surrounds the core member and is spaced therefrom to define therebetween an annular passage terminating in an annular orifice and through which the tubing of thermoplastic material is extruded for expansion by blow molding within the tubular mold tunnel, the annular orifice having portions of increased width in axial alignment with the locations of interengagement between the mold blocks of the mold assemblies in the forward runs thereof, thereby to provide the tubing with thickened portions at thes

Abstract: Corrugated tubing is advanced along its axial path by rotatably driven lead screw members the screw threading of which is in meshing engagement with the corrugations of the tubing, the lead screw members being in pairs with the screw threading of the members of each pair being of opposite hand and the lead screw members of each pair being rotated in opposite directions. The lead screw members of each pair present outwardly directed cutters which are synchronized substantially simultaneously to intersect the tubing thereby, in perforating the tubing, to restrain the tubing against rotation thereof about the axial path. There is also disclosed a method of producing the lead screw members with the outwardly projecting cutters mounted thereon.

Abstract: In order, in the molding of corrugated thermoplastic tubing, to overcome the disadvantage that pressurized air which is supplied to a zone within the tube of thermoplastic material as it is extruded from an extrusion head into the entrance of a tubular mold tunnel may tend to cause rupturing of the tube at the area immediately adjacent to the extrusion head where the tube is unsupported by the wall of the tubular mold tunnel the pressurized gas is supplied at a low pressure to a first zone within the tube of thermoplastic material to support the tube against the wall of the tunnel, and pressurized gas at different, successively higher pressures is supplied to second and third zones within the tube to urge the tube outwardly into the corrugations of the tubular mold tunnel. A gas leakage path between the second and third zones permits leakage from the third to the second zone, the pressure in the second zone being controlled by venting gas therefrom at a controlled rate.

Abstract: Pipe sections are coupled end to end by shrinking a heat shrinkable sleeve in frictional engagement with the end portions of the pipe sections. In a preferred application of the invention, the pipe sections are corrugated and the sleeve conforms to the corrugated surfaces thereof providing a sound mechanical interlock.

Abstract: In order, in the molding of corrugated thermoplastic tubing, to overcome the disadvantage that pressurized air which is supplied to a zone within the tube of thermoplastic material as it is extruded from an extrusion head into the entrance of a tubular mold tunnel may tend to cause rupturing of the tube at the area immediately adjacent to the extrusion head where the tube is unsupported by the wall of the tubular mold tunnel the pressurized gas is supplied at a low pressure to a first zone within the tube of thermoplastic material to support the tube against the wall of the tunnel, and pressurized gas at a higher pressure is supplied to a second zone within the tube to urge the tube outwardly into the corrugations of the tubular mold tunnel. A first sealing arrangement separates the first zone from the second zone which is disposed downstream of the first zone, and a second sealing arrangement defines the downstream end of the second zone.

Abstract: A high speed corrugator for producing corrugated thermoplastic tubing comprises a pair of complementary upper and lower mold assemblies each comprising an endless chain of articulately interconnected mold blocks and means for guiding the mold blocks along an endless track having a forward run and a return run, each mold block being complimentary to a respective mold block of the other assembly, the mold blocks co-operating in pairs along said forward run to form an axially extending tunnel defining a tubular mold having a corrugated wall. The mold assemblies are positioned so as to locate the extrusion head at the entrance to the tunnel coaxially therewith, and extruded thermoplastic material is expanded by blow molding to conform to the interior surface of the mold. Cooling air is fed along an air distributor duct extending along the tunnel for cooling the molded thermoplastic, the cooling air being divided from the blow molding air by a baffle.