Patent GB-1493021-A (GB)
Title: Oven for re-heating preforms for a blow moulding apparatu
IPC: B29C49/68
Filed: 1975-03-11
Abstract: 1493021 Oven for plastic preforms MONSANTO CO 11 March 1975 [11 March 1974] 10040/75 Heading F4B Apparatus for heating plastic pre-forms for stretch blow moulding comprises a continuous motion preform conveyer with loading and discharging stations, the pre-forms being carried longitudinally through the oven being continuously rotated meanwhile and, after, treatment, being discharged over the stretch pins 16 of a stretch blow moulding apparatus 13 to be blown into bottles. The pins 16 are mounted on a chain 17 passing round sprockets on a discharge turret 12 and on the moulding machine 13. A carrier member 15 on the turret carries a series of funnels 14 adapted to receive treated pre-forms discharged from the heating apparatus and to guide them on to the pins 16. The conveyer consists of end sprockets and three chains 98. Each chain carries a series of oppositely projecting brackets 108, Fig. 15 each adapted to carry a magnetic sleeve 111 and running on a rail 125. The pre-forms may be inserted in the sleeves through funnels 138, Fig. 1A, a shoulder on the neck end of the preform being received in an enlarged bore in the sleeve, and preventing the pre-form passing right through the sleeve. The sleeve is rotatably retained in its bracket 108 and during movement through the oven the sleeve is acted upon by a magnetic arm 151 of a magnet 150 and thereby caused to rotate to ensure that the preform carried in it is evenly heated. The preforms inserted through the funnel 138 are carried clockwise round the idler sprocket 91 being retained in their sleeves by arcuate guides 141 which engage the necks of the preforms. At the lowermost point the preforms 10 engage flat rails over which they slide until they enter the oven 240. During their movement through the oven the preforms slide over cooling pipes 158, Fig. 15 which keep the neck parts cool. The oven consists of seven heater units 299, Fig. 47, slightly staggered in vertical position, providing six tunnels 327 through which the pre-forms pass. The heater units each consist of a series of heater rods 308, Fig. 45 separated by deflectors 306 with offset side edges. A baffle 309 prevents the escape of heat at the bottom of the unit. The heater frame is releasably secured in the oven hood. The whole oven is mounted by chains 271, Fig. 35 so that if a jam occurs the oven can be raised to avoid overheating the preforms. The chains are wrapped round side sprockets 270 on shafts at each side of the oven, the shafts being connected by a chain and sprockets and rotatable by an air cylinder through another chain and sprocket. In the raised position the oven may be moved sideways on rollers 264 running on the supporting girders 119. This movement may be manual or by air cylinder after passing between the heater frames of the oven, the pre-forms pass between cooling plates 390 Fig. 42 having serpentine channels formed in them for cooling water supplied through pipes 396, 397. There is also a heater 409 for maintaining the temperature of the neck part of the pre-forms. If the moulding apparatus 13 breaks down, the oven can be put into a "dump" operation. For this purpose the gaps through which the preforms fall at the end of the guide rails 158, 160, Fig. 6, is closed by movable guide rails 161 which move to the right so that the preforms, instead of falling down on to the stretch blow pins 16 are carried on over fixed guide rails 169 to be taken to a dump station. The movable guide rails 161 are carried on a cross member 162, which is mounted by arms 163 to sliders 165. If a jam occurs the downward pressure on the guide rail 161 will cause the cross member 162 to pivot and operate a switch. Any pre-form not passing through the discharge opening is detected by a photoswitch 173 which co-operates with a reflector 174 on the opposite side of the conveyer. A flipper gate is provided at the discharge point (Figs. 48-50, not shown) to hold the pre-forms straight until they have dropped off the discharte shelf. Instead of being fed in as shown in Fig. 1A through a funnel 138, the pre-forms may be fed upwardly into the sleeves just after they have entered the heating part of the oven (Fig. 24, not shown).