Patent GB-638135-A (GB)
Title: Method and means for the mass production of multiple recesses or impressions in thin plates or strips of plastic material
IPC: B29C51/38
Filed: 1946-06-13
Abstract: 638,135. Moulding hollow articles from thermoplastic sheet material. NICOLLE, C. June 13, 1946, No. 17718. Convention date, Jan. 4, 1944. [Class 87 (ii)] [Also in Group XVII] Relates to the production of multiple recesses in thin sheets or strips of thermoplastic material such as cellulose acetate, particularly for the purpose 'of making containers for articles such as feeding-bottle caps, or lozenges. According to the invention, a cold sheet 3 of the material is fed into the machine, between a die 1 and counter-die 6 which, as well as plungers or "drawing pistons " movable through apertures 7, 2 in the counter-die and die are independently heated. " Heating pistons " 17 are also provided in the apertures 2. The sheet can thus be differentially heated when in the machine. In the apparatus shown, the plungers 9, located in apertures 7 of the counter-die 6, are secured to a plate 10, mounted on the slide 12 of a press, the plate supporting the counter-die 6 by spring-pressed rods 14. Beneath the fixed die 1 is a plate 19 which carries a series of " pistons " 17, arranged in the apertures 2 of the die 1, the plates 19, 10 being connected by rods 20 under the influence of springs 21, 25. The lower ends of the plungers 9 are shaped to produce the required recesses in the thermoplastic material, and the apertures 2, 7 are correspondingly shaped. The die and counter-die are independently and regularly heated, e.g. electrically, and the plungers 9 are similarly heated, indirectly through the plate 10. Heat is communicated to the parts 17 either independently or through the plate 19. Operation:-The heating circuits having been adjusted to provide for suitable heating of the different parts of the sheet which is to be recessed, the material is fed into position on the die 1, with the parts of the machine in the position shown in Fig. 4. The plate 10, together with the plungers 9 and the counter-die 6 descends, and when the counter-die first bears against the sheet 3 the ends of the plungers 9 are close to the sheet 3. There may be a momentary dwell at this point, to allow the necessary heating of the material to take place. Further downward movement causes the heating pistons 17 to recede, and they are followed by the plungers 9, which force the material through the apertures 2, forming the required recesses. Fig. 10 shows the position of the parts at the end of the downstroke, where there is another short dwell before the plate 10, with the plungers &c. rises. Cams 29 on a spindle 28 bear against the plate 19, following it by gravity as it descends and locking it in its lowermost position. When the plungers 9 have risen, the cams may be turned by a hand lever on the spindle 28, to allow the pistons 17 to rise and eject the moulded sheet; or the sheet may be removed by hand. The plungers 9 may be detachably connected to their operating plate ; alternatively, the head only of each plunger 9 may be detachably secured by a sunk screw to the plunger, to facilitate ready replacement by a plunger head of different form.