GB819474A - Contact lenses - Google Patents

Abstract

819,474. Moulding contact lenses. RIDLEY, F. T. Aug. 3, 1956 [May 13, 1955], No. 13863/55. Class 87(2). A method of making a contact lens from plastic matreial, e.g. methyl methacrylate, comprises heating the material in a moulding tool, placing a plaster mould in the tool, placing the tool in a moulding press to mould the material into a lens on the plaster mould and applying cooling means to the tool as soon as the lens is moulded. The press comprises platens 2, 38 with heating and cooling means and connections 48, 39 to sources of compressed air and vacuum respectively. The moulding tool comprises members 4, 26 clamped together by clips 28, having coaxial bores 6, 32 the member 4 having a projecting ring 8 and spring loaded annulus 10. In operation a sheet of plastic material 20 is located in the moulding tool by ridges 18, Fig. 2 (not shown), on the member 4, the tool is closed by the clips 28 causing the annulus 10 to clamp the sheet in position against the member 26 and the tool and contents is then heated, e.g. in an oven. A plaster mould 40 and a packing piece 44 are then placed in the bore 32 above the plastic sheet 20, the tool is placed in the heated press, the press closed, vacuum applied through the connection 39 to draw the sheet 20 against the mould 40 and compressed air is then admitted through the connection 48 to fully mould the lens. After moulding the press is cooled and when the moulding tool is cool it is removed from the press, the ring 8 removed and replaced by a longer shearing ring, the packing piece 44 is removed and the moulding tool replaced in the press which, on closing, causes the shearing ring to shear the moulded lens from the sheet 20 and to lift the lens and mould into the bore 32. A method of making the mould 40 is described.