Patent GB-1293762-A (GB)
Title: Extrusion of corrugated material
Inventor: HEMINSLEY JAMES EDWIN
IPC: B29C48/09
Filed: 1968-11-23
Abstract: 1293762 Corrugating extruded material DUNLOP HOLDINGS Ltd 19 Nov 1969 [23 Nov 1968] 55653/68 Heading B5A [Also in Division F2] Corrugations are formed in an extruded tube or sheet of rubber, plastics, or metal, by intermittently urging the extrudate and support into frictional engagement or into increased frictional engagement to intermittently restrict the passage of the extrudate over a support In the Fig. 5 embodiment, an internally directed corrugation is produced in the extruded tube 35 by intermittently restricting the passage thereof, over a reduced diameter mandrel extension 20, by intermittently supplied pressure air directed externally from an annular jet 50 as the formation of a corrugation is assisted by pressure air directed internally from circumferentially spaced jets 47. In the Fig. 6 embodiment, the tube is extruded at a diameter approximating that of the maximum of the corrugations and is compressed on to a reduced size mandrel extension 20 by surrounding rings of pressure air jets 54, located on either side of an annular mandrel groove 55 from which pressure air issues to form the corrugations 57. The tube may be supported against the jets 54, and the passage of the tube over the mandrel facilitated, by pressure air fed to circumferential mandrel recesses 58 and, in the Fig. 4 embodiment (not shown), a similar single surrounding ring of air jets (42) and supporting pressure air mandrel recess (44) are employed to restrict the passage of the extruded tube over a mandrel extension of the extrusion orifice diameter, as the formation of an externally directed corrugation (36) is assisted by a similar preceding circumferential mandrel groove (26), which may be connected to atmosphere or may alternatively supply pressure air. In the Fig. 7 embodiment, the passage of the extruded tube is restricted by an external split ring the parts whereof are radially reciprocated by pneumatic rams or cams to clamp the tube against a mandrel extension, as an externally directed corrugation 75 is formed by pressure air directed outwardly from a mandrel groove 71, the mandrel 62 being axially reciprocated by a pneumatic ram to displace a restriction 66 away from the die 64 to increase the extrusion flow therethrough during formation of the corrugation. In the Fig. 2 embodiment (not shown), a similar external split ring clamp 31 is employed with a similar mandrel groove connected to atmosphere, the mandrel being non-reciprocatory. In the Fig. 1 embodiment (not shown), the mandrel extension is provided with a cylindrical diaphragm (27) which is intermittently deflected by suction, and then expanded by pressure air to restrict passage of the extruded tube thereover as the extruded tube builds up to form a corrugation, the formation whereof is facilitated by a circumferential mandrel groove (26) connected to atmospheric pressure. The circumferential mandrel recesses supplied with pressure air, of the Fig. 6 embodiment, may also be employed in the Fig. 2 embodiment, and in the Fig. 1 embodiment on either or both sides of the cylindrical diaphragm. The diaphragm of the Fig. 1 embodiment may also be employed in conjunction with the split ring of the Fig. 7 embodiment. In the production of a corrugated tube, a passage preferably extends through to the mandrel end through which pressure air is blown, preferably including chalk to prevent the tube walls sticking together. The mandrel may also be coated with P.T.F.E. at locations other than where the passage of the tube is restricted.