Pressure-determined shaping system for each of multiple, commonly

Abstract

Pressure is controlled in plural stages of a shaping system for a green tire in a curing press, so that each successive shaping stage is completed when a target pressure for that stage is reached. A radial tire is preferably shaped in three stages in the first of which a first target pressure in the range from 2 psig to 5 psig is the desired shaping pressure; in the second stage, a second target pressure in the range from 7-10 psig is desired; in the third stage, a third target pressure in the range from 10-15 psig is desired. A pressure transducer (PT) senses the pressure in a bladder, one PT for each bladder. A programmable controller (PC) which controls operation of the press, stores and executes a sequence of instructions which determine the optimum desired shaping pressure for each stage, computed from the type and size of the tire to be cured, the period of time the press is down before it is loaded, and the number of heats on each bladder. The automatic computation of optimum desired pressure for each shaping stage avoids having an operator set a mean pressure for each stage by trial and error, making such adjustments for change of bladder, and unduly long press down time which in his judgment appear to be reasonably likely to produce a defect-free cured tire.