Patent GB-1054495-A (GB)
IPC: B24B9/14
Filed: 1964-12-15
Abstract: 1,054,495. Grinding. WILHELM LOH KOMM. GES. OPTIKMASCHINENFABRIK. Dec. 15, 1964 [Dec. 18, 1963], No. 51067/64. Heading B3D. Automatically operable loading mechanism for a centring machine for machining the edges of lenses comprises a lens receiving platform having a plurality of lens receiving stations, means for indexing the platform station by station past an unloading station, and lens transporting means movable between the unloading station and the spindles of the centring machine to deliver a lens between the spindles for grinding and for returning the lens when ground to the lens receiving station on the platform. The centring machine has two aligned centring spindles 2, 3, Fig. 1, each of which carries a centring tube 8 for engaging a lens 1 and aligning it with its optical axis coaxial with the axes of the spindles. The spindles are synchronously rotated by gearing 5, 6, 7 in bearings 4 in the machine, the upper spindle 2 being vertically movable for the insertion and removal of a lens by a gear 9 which engages a rack 10 on the spindle and is rockable by a link 12 connected by a rod 13 to a bell-crank lever movable about a pivot 14 against a spring 20 by a follower 17 in cooperation with a cam 18 on a spindle 19 driven by a motor. The lens receiving platform consists of a disc which is mounted on a rotatable shaft and is adapted to receive a magazine plate 29, Fig. 4, having a plurality of apertures each having a supporting bush 30, Fig. 5, for a lens 1 whose edge is to be ground. The lenses are carried to the centring spindles from the magazine plate by a suction chuck 34 having a conical nozzle 37 connected by a tube 36 to a source of vacuum. The chuck 34 is carried by a tube 33 on an arm 31, Fig. 4, mounted on the hub 42 of a pin 32, the arm being movable manually to a lower position, shown dotted, during mounting of a magazine plate on the disc and from the position shown solid, in which the chuck is aligned with a lens on the magazine plate, to an upper position, shown dotted, in which the chuck is aligned with the axes of the spindles 2, 3 of the centring machine by a cam 52, also mounted on the shaft 19, engaging a follower 51 on an arm 50 secured to the hub 42. The lower end of the pin 32 carries a roller 48, Fig. 6, which cooperates with four recesses 49a, 49b in a further cam 49 on the shaft 19 to effect raising and lowering of the chuck 35 into and out of engagement with a lens on the magazine plate 29 and for depositing a lens on and lifting it from the lower guide tube 8 on the spindle 3. A further cam 40 on the shaft 19 acts through a follower and bell-crank lever to control a valve controlling the source of vacuum. A final cam 53 on the shaft controls the indexing of the magazine plate 29 and co-operates with a follower 55, Fig. 8, on a lever 54, the other end of which is connected by a rod 56 to a bellcrank lever 52, 58 pivoted to the shaft 27 of the magazine plate. The arm 58 of the lever carries a pawl 59 for engaging a ratchet wheel 60 secured to the shaft 27. The cam 53 determines the end position of the pawl 59 but the initial position, and hence the angular movement imparted to the plate, is determined by a tubular cam 61 engaging the end of the arm 58. In operation, the arm 31 is initially swung manually to the lower dotted position shown in Fig. 4 for the mounting of a magazine plate 29 on the disc carried by shaft 27. The arm is then swung to the position shown solid and adjusted relative to pin 32 so that lens chuck 34 is above a lens on the magazine. In this position, the cam 18 is operative via lever 15, 16 to raise the spindle 2. Rotation of shaft 19 causes the pin 32 to drop in a recess 49a of cam 49 to lower the chuck 34 so that when cam 40 operates the valve controlling the source of vacuum, a lens is gripped by the chuck. Thereafter, the pin 32 leaves recess 49a to effect raising of the chuck and cam 52 permits a spring 71 to rock arm 31 to the upper position shown dotted in Fig. 4 in which the chuck is aligned with the spindles 2, 3 of the centring mechanism. The latter is enclosed in a housing having a transparent cover in which is a hinged window, the arm opening the window in its movement towards the spindles. When the chuck is aligned with the spindles, the cam 49 lowers the chuck and the cam 40 operates the valve to supply superatmospheric pressure to the chuck to remove the lens which is deposited on a resilient ring segment above the lower centring tube 8. The arm 31 is then raised and swung outwardly to its solid line position shown in Fig. 4, the window closing, and the spindle 2 is moved downwardly to engage the upper centring tube 8 with the lens which is thus held securely while it is rotated in contact with the grinding wheel during the grinding of its edge, the motor driving the spindle 19 being switched off. After grinding and bevelling the edge of the lens, the spindle 19 is again rotated to cause cam 18 to lift the spindle 2, an ejector pin in the spindle detaching the lens from the upper centring tube. The arm 31 then moves between the spindles 2. 3 and lowers the chuck into engagement with the lens. Vacuum is applied to the chuck which lifts the lens and the arm is raised, swung outwardly and lowered by cams 50 and 49 to position the lens above the bush from which it was taken, pressure then being applied to the chuck to drop the lens in the bushing and the arm being once again raised. The cam 53 then acts through levers 54, 57, 58 to move pawl 59 and index the magazine plate to position the next lens to be ground beneath the chuck 34. A gauge 65, Fig. 1, is mounted on the housing 25 and has a feeler pin which cooperates with indexes 66 to prevent a grinding operation if the lens to be ground is too thick or too thin.