GB856186A - Improvements in rotational casting - Google Patents

Abstract

856,186. Centrifugal moulding. SUN RUBBER CO. July 21, 1958 [July 26, 1957], No. 23830/57. Class 87(2). Hollow articles are cast from synthetic resin, e.g. vinyl resin, plastisols by charging a cool mould or series of moulds with a predetermined amount of plastisol and then subjecting them to strong rotative forces on a first axis while heating to the gelling temperature of the plastisol followed by simultaneously applied weaker rotative forces about the first axis and a second divergent axis while heating to the fusion temperature. The moulds are rotated at a slow rate about the first axis before the application of heat to distribute the plastisol and uniformly heat the moulds and following the application of heat, the temperature of the moulds is reduced while rotating them at a slow rate about the first axis. In the spparatus described the mould carrying arm 35 comprises an outer shaft 37 coaxially rotatable upon an inner shaft 36, the outer end of the latter carrying a T-shaped transmission block 38 in which a cross-shaft 39 is rotatably journalled transversely of the shaft 36. At one end the crossshaft has a mitre gear 40 meshing with a gear 41 on the outer shaft 37 so that rotation of this shaft causes the mould carriers 22 mounted on the cross-shaft to rotate on a transverse axis (the " first " axis) while rotation of shaft 36 causes rotation about a longitudinal axis (the " second " axis). The rotation of these two shafts 36, 37 is brought about by the apparatus shown which has a vertical post 30 on which is mounted a hub block 50, shaft 36 being journalled in this hub block which has a gear 51 carrying a friction clutch cone 52 journalled on the shaft 36. Gear 51 is driven by a gear 153 carried by a sleeve 154 rotatably mounted on the upper end of the post 30 and the lower end of this sleeve carries a large gear 155. The inner end of the inner shaft axis 37 is journalled around a bearing sleeve 54 carried on the shaft 36. A gear 55 carrying a friction clutch is journalled on the shaft 37 and driven by a gear 157 having a hub portion 158 carrying a large gear 159. Gears 158, 159 are driven by electric motors 166, 164 respectively. Electric motor 84 drives the moulds about the transverse axis at a high speed (50-150 R.P.M. compared with 2-30 R.P.M. for the other rotations) by means of a gear and chain mechanism when the clutch means referred to above have disengaged motors 164, 166. In one form of the machine, the hub block 50 carries three mould carrying arms 35 and is mounted in a turret 31. An indexing device is used to rotate the turret by means of a rack and pinion device 73, 74 so as to move the arms successively from a stripping and loading station to a curing oven 24 and thence to a cooling station.