Patent GB-643855-A (GB)
Title: Method and apparatus for molding articles from plastic materials
IPC: B29C43/22
Filed: 1947-01-09
Abstract: 643,855. Moulding articles from plastic strip material. GORA-LEE CORPORATION. Jan. 9, 1947, No. 792. Convention date, Jan. 19, 1946. [Class 87 (ii)] [Also in Group XVII] Articles such as buttons, grommets and packing discs for bottle caps and jar lids are made by a continuous process from material which can be moulded and cured, e.g. rubber, the articles being first blanked out and moulded from a coutinuously formed strip of the material and subsequently vulcanized or cured on a conveyer passing through an oven heated, e.g. by infra-red lamps. The moulding machine comprises a pair of mill rollers 34, 35 heated by fluid circulating internally, the roller 34 rotating faster than and being hotter than the other so that a sheet is built up on it from the bank of material 50 in the nip of the rollers. The roller spacing is adjustable by the usual adjusting screws. Near one end of roller 34 a pair of spaced adjustably-mounted knives 51b cut off a strip 51 which is led over a driven roller 51a, through a tapering guide 51d between a pair of rotating drums 30, 31 carrying co-operating dies 52, 53 which blank out and mould pieces from the strip 51 leaving a web 78 which is led over idle rollers 79b, c, and a driven roller 79 to the bank 50 for re-use. The web 79 and any replenishing material is fed to the-bank 50 at the ends of the rollers away-from the end from which the strip 51 is taken. The articles (which adhere to the drum 31 which is hotter than the drum 30) are ejected by plungers 67 operated by a fixed cam 72 and fall on to a shoot 100 from which they may fall on to a conveyer passing through the curing oven. The dies are lubricated by nozzles 101 as they approach the moulding station 32. The drums and hence the dies are heated by fluid circulating in annular passages 47 in the drums and fed thereto through pipes 48 and the hollow axles 26, 27 of the drums. The mill rollers, drums 30 and 31 and roller 79 are driven from a common motor through gears and belts. The drums 30, 31 accommodate two sets of dies in their width and, as shown for making buttons and grommets, the dies 52 (Figs. 3 and 5) are part cylindrical, mounted in complementary housings in the drum 30 and capable of slight rotation in the housings to enable them to engage fully the fixed dies 53 over a short region at the moulding station. The dies 52 are secured to the drum 30 by wire strapping 63. The dies 53 are bolted to the drum 31 and have thin edges to cut the strip 51. As shown, the plungers 67 which are spring-urged against the cam 72 have core extensions to form a central passage in the button being moulded, the extensions being forced to the bottoms of the cavities in the dies 52 at the moulding station by cam rollers 72a eccentrically mounted for adjustment on the cam 72. To avoid all dimensions being held to close tolerances the cam 72 has a slight clearance about the shaft 27 and is spring-urged to the right by means not shown (see Fig. 26, not shown). The cam 72 also has a slight angular adjustment. The cam 72 effects ejection of the articles and stripping from the core extensions of the plungers 67 in two stages by means of two noses connected by a flat 75. The chambers in which the plungers 67 work communicate with the outside of the drum by passages 31c to permit moulding material finding its way past the plungers from the dies to escape. When moulding solid articles the cam 72 is dispensed with, the ejecting plungers being operated by suitably positioned cam rollers. Metal inserts to be moulded into the article may be inserted into the dies by hand or other means as they approach the moulding station. For moulding articles with undercut recesses such as grommets for leading wires through metal panels, slides 110, Fig. 9, are mounted on the drum 31 and are pushed inwards at the moulding station by cam tracks 116, the inner ends of the slides being appropriately shaped to form the required recess. The slides are retracted immediately beyond the moulding station. To form the central hole in the grommet the ejecting plungers 94 have core extensions as before. Cam rollers for projecting the cores at the moulding station and for ejecting the articles are provided at appropriate places. For making packing discs for crown bottle caps, both dies are fixed in their respective drums (Fig. 17), one die 126 adjustably mounted in the drum 121 having a part spherical surface and the cooperating surface of the die 127 on the drum 122 has a surface convex in a section in the plane of the drum and concave in a section at right angles, the die 126 rolling over the die 127. The cut and shaped discs are not ejected but carried round on the drum 31 to a station where they are pressed into the crown caps (see Group XVII). Linings for caps or lids of smooth contour may be made and pressed directly into the cap or lid (Fig. 25) the caps or lids 173 forming liners for the female dies 182 and the male dies in this case having convex surfaces. Ejecting plungers 188 are provided.