Molding apparatus including a one-piece flexible mold having male and

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. The apparatus also includes a vacuum pot being of such size so as to receive said mold therein and forming a sealed generally annular chamber between the pot and the outer mold portion and means for drawing a vacuum in said chamber whereby the outer mold portion distends and expands into the vacuum chamber and the inner mold portion collapses to permit its withdrawal from the molded article. The apparatus further includes an upwardly extending mandrel fixed to the bottom wall of the pot for causing axial stretching of the inner mold portion when the vacuum is applied to cause it to contract in a uniform radial manner around the mandrel.