Patent GB-666179-A (GB)
Title: Improvements in or relating to devices for blocking lenses, discs, and like articles
IPC: B24B13/005
Filed: 1949-05-31
Abstract: 666,179. Grinding lenses &c. ABBEY, A. (American Optical Co.). May 31, 1949, No. 14608/49. Class 60. [Also in Group XI] A device for mounting a lens or like blank 50, Fig. 2, upon a block to permit the grinding of the blank comprises a member 90 for supporting the adhesive-coated block, a member 55 mounted in substantially axial alignment with this member for holding the blank, means for supporting the blank between these members and for adjusting it to a pre-determined planal and axial relation to said members, and a movable heating element 122, Fig. 3, adapted to be moved into position between the members 55, 90 for heating the adjacent surface of the blank and the adhesive on the block, one of the two members 55, 90 being movable towards the other so as to bring the blank into engagement with the adhesive on the block. In operation, the lens blank 50 is first correctly positioned on a table 8 and then gripped by fingers 63 on the member 55. A lens block 92, Fig. 7, having an adhesive layer 101 thereon is then positioned on an adaptor 91 which is inserted over the member 90, and the heater 122 is swung into position, the table 8 having previously been withdrawn; the table 8, Figs. 2 and 3, which is supported on extensions 2, 3 of a hollow base 1, can be swung about a vertical axis by the provision at one corner of a depending shaft 15 which is rotatably and vertically movable in the extension 3, the vertical movement being effected by a rotatable cam shaft 19. Coacting metal pads 9, 10 are provided on the opposed faces of the table and extensions 2, 3, and locking pins serve to locate the table in operative position; in addition, the rear of the table has an adjustable positioning stop 153, Fig. 2. Located on the table over an opening 31 therein is a disc 28 which is rotatable within a ring 36 and carries a central translucent panel 30. A ring 38 mounted on the disc has an annular series of openings for the reception of removable upstanding pins 43 for supporting the blank 50. The pins 43, which are of varying heights according to the desired characteristics of the finished lens, are secured in position by a spring ring 45, Fig. 9, engaging a circumferential groove 39 in the ring 38. The upper end of each pin may have a ball-shaped tip or an upstanding extension at the apex of a conical portion. If desired, a ring of holes may be provided in the disc 28 for receiving supporting pins in the form of balls, 155, Fig. 11, with extensions 156. A body member 55 is movable vertically in a housing 58 by means of a handoperated pinion 81 engaging a rack 79 and is fitted with a sighting tube 68 provided at opposite ends with an apertured washer 70 and translucent disc 76; the tube 68 is fixed in adjusted position by screws 74 engaging a tapered face on an apertured cap 69. Pins 51 for contacting the upper face of the blank are mounted in the member 55, being urged downwardly relatively to the latter by springs 52. A plurality of spring fingers 63 having cushioned gripping portions 65 depends from a ring 64 on the member 55 for gripping the edge of a blank under the control of a handle on a casing 67. The blank 50 is correctly located on the pins 43 after viewing through the sighting tube, the member 55 is then lowered, and the pins 51 and grips 65 are engaged with the blank. The member 55, with the blank, is then raised by the rack 79, the table 8 is raised and swung outwardly and the apparatus is ready for applying the blanks to the lens block 92, Fig. 7. This block is prepared with an adhesive layer 101 which is in the form of a preformed disc of pitch or other thermo-plastic material having a backing of coarse reinforcement, the adhesive layer being united to the holder under heat in an electric furnace (see Group XI). The block so prepared is secured to the upper end of a tapered and hollow adaptor 91, Fig. 7, which is fitted on to the similarly tapered and hollow support 90, Fig. 2, arranged on the hollow base 1 in alignment with the sighting tube 68. At this stage, an electric heater 122, Fig. 3, carried by a pivoted bracket 121 is swung from its normal position in a housing 126 into position between the raised blank 50 and lens holder 92. When the heater reaches this position, a stud carried by the hinge pin 111 of the bracket operates a switch to energize the heater, and a spring-pressed locking latch 39 engages a notch in the rear of the bracket. After a pre-determined time, controlled by an adjustable electronic circuit (Fig. 16, not shown), a solenoid 138 is energised to withdraw the latch 139 and permit the heater to swing back under the action of a spring into its housing. As the heater reaches its housed position, it operates a further switch so as to energize a solenoid 144, Fig. 2, the armature 146 of which then forces downwardly the rack 79 and housing 55 and the heated lens blank is pressed on to the softened adhesive on the block 92; a dash-pot 147 damps this downward movement. A lamp 33 in the hollow base 1 provides illumination for the viewing operation. In a modification, the table 8, instead of being hinged, has a tapered portion adapted to fit over the tapered upright 90. Specification 633,666 is referred to.