| 摘要 |
1,148,138. Grinding. TEXTRON Inc. 9 Nov., 1967 [6 Dec., 1966], No. 51091/67. Heading B3D. A lens block for mounting a lens blank comprises a curved surface 4 to which a correspondingly curved surface 5 of a lens blank is adapted to be secured, a central opening 6 opening at one end on the curved surface 4, and a plug 8 sealingly and removably mounted in the opening to shield the surface of the lens blank secured to the block. Removal of the plug permits the power of the lens to be checked during the generating of the lens without necessitating removal of the lens blank from the block. The block may be of a low-melting point metal comprising a mixture of lead, bismuth, tin, indium and cadmium moulded to the surface of the lens which may be coated with plastic material or tape, the lens being of either glass or plastic material. The block has a cylindrical portion 2, on which is a flat acting as a horizontal reference surface, and a conical portion 3 formed with two dome-shaped holes 7 for engagement by a chuck of the optical surface generating machine. The block is moulded around the plug 8 which thereby forms the centre hole for permitting checking of the optical surface when the plug is removed. The plugs may be cylindrical or conical and be of plastic material and on its outer surface is formed with a ring or helical projection to provide an interlock with the hole. A protruding. part provides a finger grip for removing the plug from the hole. In a further embodiment, the plug is of metal or hard thermosetting plastic and is sealed in the opening by a soft rubber 0-ring. The lens block may be moulded in two portions, the inner portion having a lower melting point than the outer. |
