Abstract: A method and apparatus are disclosed for calibrating the individual amounts of each of several different reactive components separately recirculated in a closed loop system wherein separate portions of such components are periodically withdrawn from the system and intermixed in a mixing head of a reaction injection molding machine for delivery in homogeneously mixed condition to a closed mold under pressure. Calibrating means is provided to enable accurate monitoring and correction of the relative proportions of the reactive components delivered to the chamber of the mixing head, under actual operating pressure conditions prevailing during an actual injection molding operation, without substantially interrupting the molding process or requiring any dismantling of the apparatus to gain access to the individual component streams.

Abstract: An improved molding apparatus is described for use with relatively light weight molds, particularly molds for articles having a plurality of voids therein. A light weight two-piece mold, one-half being substantially rigid and the other relatively flexible, is disposed in a jig. The two halves of the mold are held in sealing relationship by inserting a hollow inflatable bag between the exterior of the relatively flexible mold piece and the interior wall of the adjacent jig member and inflating said bag to a pressure superior to that exerted by the expanding foam mix in the mold.The use of the improved apparatus obviates the need for molds of high structural strength (and hence excessive weight) and gives molded articles, particularly those of complex configuration, which are free from flashing.