Abstract: Molding apparatus for molding articles without a seam or parting line even though the articles may have severe backdraft portions. The apparatus includes a flexible mold of relatively thick and self-supporting wall construction which is deformable by the application of fluid pressure differential to thereby release the finished article from the mold. One modification of the mold also has a thick radially extending flange which forms a seal with a vacuum pot when the mold is simply set in the pot. One modification is directed to a male and female type mold in which the outer female mold is expanded to be withdrawn from the article and the inner mold portion collapses inwardly so as to be withdrawn from the article.

Abstract: Molding apparatus for molding articles without a seam or parting line even though the molded articles may have severe backdraft portions. The apparatus includes a one-piece flexible mold which is deformable subject to the application of fluid pressure, a vacuum pot large enough to accommodate the flexible mold therein and means for applying vacuum to the pot such that the mold may be expanded by the vacuum thereby releasing the molded article. The vacuum pot is provided with upwardly extending projections positioned in the bottom of the pot and the mold is provided with a restraining ring member for supporting the mold wall and for acting in conjunction with the upwardly extending projection to control the mode of expansion of the mold.

Abstract: A method of casting liquid compositions in elastomeric molds wherein the casting composition has a reaction temperature below about 235.degree. F comprising:A. introducing an organic solvent soluble polyol, a liquid polyisocyanate and a basic curing catalyst having a pK.sub.b value from between 7 and about 11 into an open elastomeric mold,B. controlling the ratio of polyol to polyisocyanate and the concentration of the curing catalyst and casting the resin such that the cured resin is: substantially free from entrapped air at the mold surface, free from foaming, has a cast time of generally less than about 15 minutes, has a tensile strength of at least about 2500 psi,C. removing the cast resin from the mold shortly after the composition is cast thereby providing unexpected prolonged mold life. The resin undergoes substantially no change in volume from the liquid to the cured state.

Abstract: Apparatus for molding, for example, a seamless brake drum female mold having a plurality of radially inwardly extending grooves and ridges. The apparatus includes a generally hollow one-piece distensible and flexible hollow male mold having an annular side wall having a plurality of radially extending projections and undercuts and includes an outer core box positioned around the flexible mold and defining an annular cavity with it. The apparatus further comprises a packing mandrel for supporting the hollow flexible mold while mold material is packed around it and a vacuum mandrel to be inserted within the flexible mold to cause the collapse of the flexible mold so that the molded article can be lifted off the flexible mold despite the radially extending projections.

Abstract: An apparatus for molding articles free of seams and parting lines including a one-piece flexible mold which is deformable and which includes a rigid core member, and a vacuum pot which is used to cause the mold to expand radially outwardly to allow the molded article to be released. The core member may comprise a rigid central mandrel which is rigidly embedded in the bottom wall of the mold and which is hollow and includes ports such that a pressurized catalytic gas may be injected into the mold material to cause a bonding agent to set.

Abstract: Molding apparatus for molding articles which are free of seams and parting lines even though the articles may have severe backdraft portions. The apparatus includes a one-piece distensible flexible mold of relatively thick and self-supporting wall construction which is deformable by fluid pressure in order to release the molded article. The flexible walls of the mold include internal slits extending from the mold cavity and partially through the walls for facilitating increased expansion of the mold. The ends of the slits include transversely extending slits in order to prevent tearing of the mold wall at the end of the slit and to further facilitate expansion of the mold.

Abstract: Molding apparatus for molding articles without a seam or parting line even though articles may have severe backdraft portions. The apparatus includes a one-piece flexible mold which is deformable by the application of a fluid pressure differential to thereby release the finished article from the mold. The mold has a self-supporting, radially extending annular flange which forms a seal with a vacuum pot when the mold is set in the pot and the flange has a downwardly extending annular projection or lip which fits freely over the outside diameter of the side wall of the pot. The downwardly extending projection is of sufficient inside diameter to allow the flange to be easily set upon or removed from the vacuum pot and the flange also has sufficiently close tolerances with respect to the outside diameter of the pot as to accurately align and center the mold in the pot.

Abstract: Molding apparatus for molding hollow articles without a seam or parting line even though the articles may have backdraft or undercut portions on both the inside and outside surfaces. The apparatus includes a generally one-piece flexible mold having a generally thick self-supporting wall construction which is deformable by the application of a fluid pressure differential. The mold includes a generally hollow outer portion and a generally hollow inner portion integrally formed with and extending upwardly from the bottom wall of the outer portion, said mold portions defining an upwardly opening generally annular cavity into which hardenable material is placed.