GB841540A - Improvements in method of moulding articles - Google Patents

Abstract

841,540. Moulding articles having concave paroboloidal surfaces. UNITED STATES RUBBER CO. July 31, 1957 [Oct. 19, 1956], No. 24238/57. Class 87(2). In a method of moulding a boot or shoe having a sole with a concave paraboloidal inner surface, a mould holding a solidifiable and gellable liquid is rotated about an axis inclined to the vertical during gelation of part of the liquid to form the upper portion of the boot or shoe, and, during gelation of the remainder of the liquid, is rotated about a vertical axis at such a speed that the inner surface of the sole portion assumes the desired paraboidal shape is formed by filling a mould 14, Figs. 4 and 5, with a plastisol, e.g. of polyvinyl chloride and dioctyl phthalate, and pouring out the plastisol to leave sufficient for forming the boot. The mould 14, which has a paraboloidal inner surface at the sole portion, is then clamped to a turntable 20 so as to be rotatable about the axis of the paraboloid by a variable speed motor carried by a platform 21. The latter is first tilted about a hinge 22 so that the axis of rotation of the mould is inclined at about 30 degrees to the horizontal, and the mould is rotated at about 30 r.p.m. whilst the upper portion of the mould is heated to gel some of the plastisol or to form the upper, whilst the remainder of the plastisol drains to the bottom of the mould. After an appropriate period the turntable 20 is made horizontal the rotation is stopped, and the mould 14 tilted so that the remaining liquid plastisol flows into the sole cavity. The mould 14 is then rotated about a vertical axis whilst the sole portion is heated to gel the plastisol. The rotation is then stopped and the heel cavity of the mould filled with plastisol which is gelled by heat to form the heel. Finally the whole mould is heated to fuse the plastisol, cooled, and the finished boot removed. Specification 726,784 is referred to.