Patent GB-1473321-A (GB)
Title: Manufacture of a lens
IPC: B24B13/005
Filed: 1974-05-20
Abstract: 1473321 Grinding lenses DOLLOND & AITCHISON SERVICES Ltd 20 May 1974 [27 April 1973] 20081/73 Heading B3D A locator 1 for temporary attachment to a lens blank 30 whereby the blank can be located in a predetermined position in apparatus for operating on the blank, comprises a layer 2 of readily-deformable material which can assume a shape complementary to that of the blank, a central opening through which the blank can be viewed and formations 3 for co-operation with a complementary element 25 to locate the blank in a predetermined position relative to the element. The locator may have two layers, a layer 1 of solid neoprene rubber and a layer 2 which is more easily compressible, such as cellular plastics material, and which is coated with adhesive for temporary securing the locator to the lens. The locator is annular and the inner edge of at least the layer 1 is formed with indentations 3 which are engageable with projections 26 of an annular locating element 25 of a lens edging machine having driving or holding elements 27, 28 formed with rubber or like heads 29 for holding or rotating the lens during an edging-operation. The lens with the locator 1 attached can be removed from the edging machine for testing in the spectacle frame. An alternative locator consists of a single annular layer of ethylene vinyl acetate having adhesive on one surface 31, Fig. 6, for temporary attachment to the lens, and a chamfer 32 on its upper, inner edge to avoid contraction on to the locating element when the locator is attached to the curved surface of a lens. The inner surface has inwardly directed projections 34 for complementary engagement with the locating element and an external projection 36 to assist the operator in identifying the upper edge of the lens. The apparatus for applying the locator to the lens blank consists of a base 5 having a slot 6 for slidably receiving a bar 7 which is secured to a circular platform 8 guided for movement on the base by pins 9 engaging further slots in the base. One of the pins is connected by a link 14 to a lever 10 movable about a pivot 11 by a handle 13, to a position determined by a scale 12. An annular scale is marked on the periphery of platform 8 and a circular transparent cursor 15 is mounted over the platform. A transparent cover 16 is fixed to the platform over the cursor and has a base 17 projecting upwardly therefrom and rotatable relative to the bar 7, a handle 18 being provided to effect rotation of the base. A hollow cylindrical support 19 is vertically slidable on the boss, being biased upwardly against a stop by a spring, and has a rubber or like ring 20 for receiving the lens blank. A post 23 extends upwardly from the base and has sighting means 22 for viewing reference marks, e.g. marks indicating the optical centre and/or cylinder axis of the lens. Any offset of the optical centre and angle between the cylinder axis and a horizontal centre line of the lens is adjusted by movement of lever 10 and angular adjustment of the boss, the lens then being positioned on the ring by aligning the reference marks with the graticule of the sighting means. The lens is then pressed downwardly to engage the upper adhesive coated side of a locator placed in a locating element 21 supported on the boss 17.