Patent GB-1236680-A (GB)
Title: Method of forming separable moulded articles
IPC: B29C45/16
Filed: 1969-08-04
Abstract: 1,236,680. Moulding container closures. CONTINENTAL CAN CO. Inc. 4 Aug., 1969 [5 Aug., 1968], No. 38967/69. Heading B5A. [Also in Division B8] The container closure of Specification 1,234,488, comprising a surrounding plastics panel part internally whereof is located, at a weakening line, an internal manually separable tear part, is formed by moulding one of the parts, at the weakening line, to the other part, both parts being formed by injection, transfer, compression, or impulse moulding, the temperature and pressure of the moulded plastics, and the mould temperature and moulding time, being suitably controlled to ensure that the weakening line preserves its preformed configuration around or within the preformed part and an unbreakable seal thereat is not formed. The parts may comprise polyethylene, polypropylene, a filled phenolic, or rubber, and both parts may comprise the same material, e.g. polypropylene, which may be of different properties for each part, or different materials, e.g. one part of polypropylene and the other of polyethylene. In the preferred embodiment, the internal and surrounding parts of the closure 10 are sequentially injection moulded respectively within a plurality of lower and upper cavities 38, 39 of a stationary mould part 32, which are closed by an indexing mould part 33 which carries the mouldings on linear retraction from the part 32, when an indexing head part 53 thereof also simultaneously rotates through 180 degrees and ejects the moulded closures 10 and aligns the moulded inner parts with the cavities 39, into which they are located for moulding therearound of the surrounding panel part upon linear return movement of the mould part 33. The cavities 38, 39 are provided with openings 40, 46 respectively to mould and to retain an upstanding post portion of the closure inner part. Injection into the cavities 38 is effected through a sprue opening 44 and runners 43, 42 in the mould part 32, and into the cavities 39 through a sprue 51 and runners 49,48 defined between the stationary and indexing mould parts 32, 33. The indexing mould part 33 comprises a non- rotary housing 52 to which is mounted a shaft 66 guided, during opening and closing movement of the part 33, through a bearing 67 in a support assembly 57. An indexing head 53 is turnable within the housing 52 and comprises a face-plate 72, which coacts with and closes the cavities 38, 39, and a rear plate 54 to which is fixed an index shaft 56 which is slidable through the support assembly 57, and carries a spring-biased pin 58 which co-operates with axially and helically extending grooves in the shaft 56, to effect the 180 degrees rotation of the indexing head 53 upon retraction of the indexing part 33 and the linear return movement thereof. The retention of the moulded parts to the retracting indexing mould part 33 is ensured by openings 79, in cavity closing parts 73, 74 of the face-plate 72, into which the injected plastics flows. Each part 73 and 74 is provided with an ejector assembly 82 comprising a support plate 83, and the lower whereof is displaceable, upon retraction and 180 degrees rotation of the head 53, by an actuating pin 89 fixed to the support 57 so that ejecting pins 84, 85 pass through the openings 79 in the lower cavity closing part, 73 or 74, to eject the moulded closure and runner assembly, the sprue from opening 44 simultaneously being separated therefrom by an ejector rod 94, a base 92 of which abuts shoulders on both plates 83 for alternate actuation by one thereof. The stationary and indexing mould parts 32, 33 are aligned, via dowels and openings 96, 97 and are cooled by fluid admitted internally at 98, 99.