Patent GB-688021-A (GB)
Title: Improvements in or relating to methods for manufacturing hollow and solid articles from thermoplastic materials
IPC: B29C48/06
Filed: 1948-08-10
Abstract: 688,021. Moulding thermoplastic articles. LORENIAN, Z. Aug. 10, 1948 [Aug. 14, 1946], No. 21101/48. Class 87 (ii). [Also in Group XVII] Hollow or solid articles are made by introducing thermoplastic material in warm mouldable condition from a core C into a mould 15. The core C is initially disposed at a distance from the top of the mould (so as to form a space D, Fig. 1) and when a hollow article is being made, e.g. a toothpaste tube, this distance corresponds to the thickness of the top of the article. When the space D has been filled with material, the core is withdrawn from the mould, as shown in Fig. 2, and as it is withdrawn the material issues from one or more channels 25 in the core and forms a lining on the inside of the mould, this lining being the body portion of the article. While space D is being filled, air escapes therefrom through valve 16, and while the mould is being withdrawn cooling or vacuum-preventing means is introduced into the article through pipe 20, one or more passages 11 and valve 12 in the core. The construction shown is for making a hollow article having a closed top. To make a hollow article having an open top, cooling or vacuum-preventing means is introduced into space D at the same time as the thermoplastic material is introduced, the relative quantities being controlled. When a solid article is being made, thermoplastic material is introduced through channel 25 and also through passage 11. The articles are removed from the (split) mould, and when they are hollow the lower ends are closed by pressing the walls together. The cooling &c. means introduced through the passage 11 may be the material for which the hollow article serves as a container, or may be air, water, oil, &c. A vacuum may be produced in the mould before introduction of thermoplastic material there into. The valve 16 may be omitted, the outlet being closed by escaping thermoplastic material. In a modification, Figs. 4 and 5 (not shown), the mould 15 is replaced by a part-mould extending only a little way towards the base 1 of the core. The core comprises a base 1 having a channel 23<SP>1</SP> through which the plastic material 23 is forced into the mould by a piston or screw. The core comprises several concentric pipes, viz. (proceeding from the outside inwardly) 3, 6, 5, 10 and 8. The plastic material travels from channel 23' through the space between pipes 5 and 10 and emerges at an annular space 24 formed between the mould and the head 14 of the core. This head 14 is screwed on the upper end of pipe 10. Spacers 28, 29 on pipes 5 and 10 correctly centre these pipes. Between pipes 5 and 6 is formed a space for heating or cooling fluid which is introduced by pipe 19 and carried off by pipe 19a. Pipe 3 is a sleeve which is slidable on the outside of pipe 6, and may be raised or lowered to vary the size of the space 24 and hence the rate of feed of plastic material into the mould. Pipe 3 is raised or lowered by means of a piston 4 with which it is rigid, the piston being operated by compressed air pipes 21, 22.