Vulcanized sheet comprising annular rubber articles, a method of and an apparatus for separating the articles from the vulcanized sheet

A method of separating annular rubber articles from a vulcanized sheet, the method comprising the steps of:

• providing the vulcanized sheet which comprises:
• the annular rubber articles separable from the sheet and distributed over a plane body of the sheet;
• an outer waste formed around each article;
• an inner waste formed inside the article;
• an outer breakable boundary between the outer waste and an outer periphery of the article;
• the outer waste consisting of:
• an external flash surrounding the outer boundary;
• a thin annular zone intervening between the external flash and the body and being of such a thickness as preventing a vulcanization pressure from escaping;
• and thick external bridges formed integral with the body and the flash and disposed in and along the annular zone at regular angular intervals;
• an inner breakable boundary between the inner waste and an inner periphery of the article;
• and a recess formed centrally of the inner waste and engageable with a positioning means;
• then removing the inner waste out of each annular article, by placing on a first die each of portions where the annular articles are formed in the vulcanized sheet, the first die having formed therein a bore, subsequently fitting a guide lug as the positioning means in the recess of each annular article so as to position the portion correctly relative to the first die, before gripping the portion with and between the first die and a first thruster, and thereafter causing a first punch to force the inner waste into the bore so that the inner waste is torn off the article at the inner breakable boundary, wherein the first punch having an outer diameter substantially corresponding to but slightly smaller than an inner diameter of the article;
• and
• finally separating each annular article out of the vulcanized sheet, by placing on a second die each of the portions where the annular articles having their inner wastes removed are arranged in the vulcanized sheet, the second die having formed therein a further bore whose diameter substantially corresponds to but is slightly smaller than an outer diameter of the article, subsequently fitting a further guide lug in a space from which the inner waste has been removed so as to position the portion correctly relative to the second die, before gripping the external flash with and between the second die and a second thruster, and thereafter causing a second punch to force the annular article into the further bore so that the annular article is torn off the vulcanized sheet at the outer breakable boundary.