Fabricating shaped laminated transparencies

A method of simultaneously shaping and laminating a lightweight laminated transparency comprising elements including a pair of outer relatively rigid plies of acrylic or polycarbonate plastic and a flexible interlayer composed of a material selected from the group consisting of polyurethane and plasticized polyvinyl butyral comprising assembling at least one layer of said interlayer material between said pair of relatively rigid plies to form an assembly to be simultaneously shaped and laminated, supporting said assembly to be shaped and laminated on a base of a flexible, non-porous cell larger in outline than said assembly in such a manner that the perimeter of said assembly to be simultaneously shaped and laminated is in spaced relation within a flexible wall of air impervious material enclosing said cell, bonding a first flexible diaphragm of air impervious material to the upper surface of said air impervious wall of said cell to form a roof for said cell, communicating said cell to a vacuum source to put said cell including the interfaces between the elements of said assembly within said cell under subatmospheric pressure, mounting said cell over a vacuum mold having an upward facing shaping surface of concave elevation conforming to the shape desired for said transparency including a vacuum opening so that said cell faces said vacuum opening, applying a second flexible diaphragm of air impervious material extending beyond said first flexible diaphragm over said first flexible diaphragm, adhering the portion of said second flexible diaphragm that extends beyond the first flexible diaphragm to the surface of said mold in spaced relation to the periphery of said cell to form a collapsible chamber surrounding said cell, heating said cell and said assembly while the latter are under vacuum to a deformation temperature of said assembly to sag said cell toward said upper shaping surface and applying vacuum through the vacuum opening of said mold while said cell is so heated and sealed to conform said cell to said shaping surface, the atmospheric pressure above said second diaphragm causing said layers of relatively rigid plastic to laminate to opposite sides of said interlayer while forcing said cell to conform to the shape of said shaping surface, and the layers of said assembly within said cell to laminate at a pressure not exceeding atmospheric pressure to convert said assembly to a bent laminated transparency, cooling said cell after it conforms to said shaping surface while maintaining said vacuum within said cell until said bent, laminated transparency within said cell retains its shape, separating said cell from said mold and separating said shaped, laminated transparency from said cell.