GB752943A - Method and apparatus for making closure seals including shaping of web, curing and cutting pads for application to shells - Google Patents

Abstract

752,943. Moulding sealing pads for crown caps &c. CONTINENTAL CAN CO., Inc. May 17, 1954, No. 14337/54. Classes 70 and 87(2) [Also in Group XVII] A method of making closure seals each embodying an elastic cushion pad in a cap comprises (i) forming a curable elastic composition into a sheet (ii) shaping the sheet into spaced cushion pad configurations each with an annular thick ring and thin central web, those parts of the sheet between the pads constituting their connecting webs of scrap stock, (iii) curing the composition as a shaped sheet, (iv) punching cured cushion pads from the sheet and introducing each of them in a cap. The material 10 is first formed into a sheet between rollers 11 and 12. The material may be rubber compositions, comprising creper ubber worked in a mill with the addition of a plasticizer, anti-oxidant, pigments and fillers, lubricant waxy material and a vulcanizing agent; or it may be a composition comprising a vinyl resin, plasticizers, inert fillers and a lubricant. The sheeted material passes between rollers 12, 14 which may be adjusted to give it a thickness of from .008 to .015 inches, round a roller 15 and then into contact with a steel belt 17 which extends from a roller 14a round a curing roller 15a and thence round a roller 16 and back round rollers 18. The rollers 14a, 15a are hollow and steam is admitted to them and to a jacket 19 to cure the composition. Any of the.rollers 14, 14a, 15a may be configured to produce rings 80 in the sheet, Fig. 4, joined by thin central webs 81. If the composition requires further curing this may be done in an oven 22. The underside of the sheet is sprayed with adhesive from a nozzle 26, pumped from aa reservoir 28, of a type which becomes adhesive when heated, e.g. plasticized vinyl resin, isobutylene polymer or a rubber cement. The sheet passes through an oven 27 to dry the adhesive and then to the punching mechanism, which comprises a pair of feed rollers 40, 41, the roller 40 being engraved to grip the material and intermittently driven; a punch 43, driven 50. The crown shells into which the pads are to be placed are carried in pockets 88 of links 89 of a chain 60, driven by a sprocket 65<1> in time with the reciprocation of the punch 43 through the action of, a link 62 which operates a pawl 64 co-operating with a ratchet 65 forming part of the sprocket. A heated blast from a nozzle 92 warms the crown shell 87 so that the adhesive on the punched out closure seal causes it to stick in the shell. In addition to, or instead of, the adhesive already sprayed on the sheet, adhesive may be applied directly to each crown shell by a pump 73, operated by a shaft 70 driven from the shaft 62<1> and therefore in synchronism, which draws the correct quantity at each stroke from the reservoir 28 and delivers it through a pipe 75. With certain rubber compositions, e.g. where sulphur is present in a combined form as used for sealing food containers, no separate adhesive is required if the shell is heated to a sufficient temperature and is pressed in contact with the pad for a short time. In a modification, the configurations of the pads are impressed on the sheet.as it is calendered and it is then conveyed by a moving belt through a curing oven. The perforated scrap sheet 51 is drawn off as a roll 52 which is discarded. The punching and seal-applying assembly, Fig. 1A, may be located at a bottling works and the prepared sheet shipped in rolls and fed to the rollers 40, 41. A suitable curable elastic composition comprises, in proportions by weight: crepe rubber 88, semi-solid isobutylene polymer 12, hydrated precipitated calcium silicate 63, clay 65, zinc oxide 5, stearic acid 2, heptylated diphenylamine 1, dipentamethylene thiuram tetrasulphide 1, tetramethyl thiuram monosulphide 1¢.