Patent GB-1498660-A (GB)
Title: Corrugating apparatus
IPC: B29C48/13
Filed: 1975-11-03
Abstract: 1498660 Corrugating extruded tube G P H LUPKE 3 Nov 1975 45670/75 Heading B5A [Also in Division F2] A thermoplastics tube 41, Fig. 4, having annular corrugations, is continuously made by extruding an annular tube from an orifice defined between the die and mandrel of a die head 29 and delivering separate supplies of inflating and cooling air through the die head 29 to respectively sequentially inflate the tube 41 into, and cool it internally within a corrugating cavity defined, along a path extending axially of the die head 29, by the co-operation of mould halves 16 of an opposed pair of continuously moving upper and lower endless chains 14, 15, of the mould halves. An extension tube from the (die 29) mandrel carries seals 42 to define with the tube 41 an upstream space 43 into which the inflating air is admitted through the mandrel, and also carries a seal 44 which defines with the tube 41 and the seals 42, a downstream space 45 into which the cooling air is admitted, at openings 50 of the extension tube, to flow around heat exchanger coils 51 which are carried by the extension tube and through which cooling fluid is circulated from the die head 29 by passages 52, 53 through the extension tube. The extension tube is supported at its downstream end by an enlargement 40 bearing against the corrugated surface of the tube 41. The die orifice from which the thermoplastic tube is extruded may be a conical passage defined between inner and outer members, Fig. 6 (not shown), screw threaded on to the die head 29 for relative axial adjustment to vary the thickness of the extruded tube. The endless chains 14, 15, are mounted on a wheeled carriage which is displaceable along tracks into the moulding position with the extrusion die head 29, and is provided with mechanical jacks for upward displacement of the upper chain 14 for cleaning purposes. Each chain, Fig. 10, comprises a pair of spaced apart chains extending around driving sprockets, and along guide rails, and between which the mould halves are each articulated at leading and trailing pivots 34, 35, and 36, 37, with the leading pivot 34 of the upper chain and the trailing pivot 37 of the lower chain having vertical lost motion, so that the halves separate at the end of the moulding path in parallel alignment to avoid pinching of the moulded tube. The corrugating surfaces of the mould halves of each chain are cooled by air delivered from blowers, via a distributing duct extending along the return run of each chain, and are also each cooled by passage around a tank through which cooling water is circulated, and which may be provided with an electrical immersion heater for heating to the required water temperature at the commencement of extrusion. The mould halves 16, Fig. 8, are provided along their abutting horizontal surfaces with grooves 33 for the escape of air trapped between the extruded tube and mould halves. Alignment between the upper and lower mould halves along the moulding path is ensured by a pair of pins 30 on the lower mould halves engaging corresponding sockets on the upper mould halves, and alignment between adjacent mould halves in each chain may be ensured by pins 31 and sockets at opposite ends of the mould halves, with the pins 31 being loaded by springs to a retracted position to permit disengagement of the mould halves at the end of the moulding path, and being displaced to a socket engaging position by cams which engage the guide rails. Adjacent moulds of each train abut at a location corresponding to an external valley of the corrugations at which the tube wall, inflated from a uniform thickness tube, will be thicker and thereby minimize any misalignment effect between the mould halves. The mould chains are driven by chain and sprocket drives and, to ensure alignment between the chains, they are coupled together by a pair of spur gears, which are respectively fixedly and angularly adjustably coupled to the drive shafts of the upper and lower mould chains. For its adjustable coupling, the lower spur gear 69, Figs. 11 and 12, is carried by a plate 80 which is adjustably coupled to a plate 70 fixed to the drive shaft of the lower train, the adjustable coupling comprising a threaded block 74 mounted to the plate 80 and threadedly engaged for the adjustment by a rotatable shaft 71 extending between bearings 72, 73, carried by the plate 70. The adjusted position of spur gear 69 is locked by a device 81.