Patent GB-1403348-A (GB)
Title: Machines for edge-trimming and bevelling spectacle lenses
IPC: C03B33/04
Filed: 1973-06-25
Abstract: 1403348 Grinding edges of lenses R R M ASSELIN and P H L ASSELIN 25 June 1973 [28 June 1972 9 May 1973] 29972/73 Heading B3D A machine for edge-trimming and bevelling spectacle lenses by grinding them to the shape of the bezels of the spectacle frame for which they are intended or a template comprises a frame or template support 1 rotatable relative to a feeler device 16 about an axis perpendicular to the mean plane of the frame bezel or template and synchronously with a likewise rotating lens support 120, and a transmission between the feeler device 16 and lens support 120 that controls grinding of the lens such that the grinding pressure is independent of the pressure between the feeler device and frame. In one embodiment, the machine is in two sections, a section A for determining the shape of the frame and a section B for grinding the lens according to the shape. Section A consists of a frame support 1 having a horizontal baseplate 3 on which the spectacle frame is clamped against a bar 52 movable along guides 53, 54 by a screw 55 by clamping means 56, 57. Each eyepiece of the frame is associated with a driving part 4, 5, the parts being adjustable relative to the platform by screws 45, 46 to positions determined by scales 49, 50. The parts 4, 5 can be selectively engaged by pins 7, Fig. 2, with a sleeve 6 rotatable in bearings 10, 11 in the end of an arm 8 mounted on a vertical pivot 12. The sleeve is formed with a gear 15 meshing with a gear 14 driven by a motor 13. The motor 13 is connected by means 44 for synchronous rotation with a motor 31 connected by gearing 32, 33 to the support 120 for the lens 26 to be ground by a wheel 28, the support holding the lens in a vertical plane and being rotatably carried on the end of an arm 29 movable about a horizontal pivot 30, a weight 34 determining the pressure between the lens and wheel. The feeler device consists of a feeler 16 on the end of a vertical rod 17 which extends through sleeve 6 and is carried by a horizontal rod 20 slidable through a support 21 by a hand lever 22 which controls the position of the feeler by abutment of an annular stop 23 against the support 21. The arm 9 is thereby positioned by a spring 24 engaging the spectacle frame with the feeler 16 which is adjustable by a micrometer screw 25. In use, when the stop 23 engages the support 21, a contact 40 is operated to energize motor 13 to rotate the frame and motor 31 to rotate the lens support. Movement ofthe arm 9 actuates a displacement detector 41 connected by a transmission 43 having an amplifier to drive means 38 for moving an arm 36 about a pivot 37 the arm having an adjustable abutment 35 for moving the arm 29 carrying the lens support about the pivot 30. The transmission 43 may consist of mechanical, hydraulic, optical, magnetic, electric or photo-electric means and may at the same time, drive a section B<SP>1</SP> identical to section B. After the lens for one eyepiece has been ground, the part 4 of the support is engaged with sleeve 6 for grinding of the lens for the second eyepiece. A second support 1 may be provided so that while one frame is being used in a first support, a second can be mounted in the second support. The information from the displacement detector may be stored on tape for controlling the lens supporting arm at a later stage. In other arrangements, the spectacle frame is replaced by a template which is abutted by a feeler head, or a sheet on which is inscribed the lens contour and the contour is sensed by a magnetic or optical detector. In the latter case, the arm 9 may remain stationary and the detector is movable, the movements being transmitted to the arm 29 carrying the lens support. In order to compensate for movement of the contact point 71, Fig. 7, from the line 72 joining the centres of the lens 74 and wheel 73, the feeler 16 may be mounted on an arm 78 to have a corresponding movement. In another embodiment, proximity detectors sense the position of the arm 58 to correct the position of arm 29. In a further embodiment, the feeler point 16 is flanked by auxiliary feelers 85, Fig. 13A, the movements of which are transmitted to a beam 92 movement of which varies the amount of light between a source and photoelectric cells, the outputs of which are connected in a differential configuration in order to effect movement of arm 78 and the feeler 16. Switchable resistors 111, Fig. 1, in the transmission between arms 9 and 29 determine the type of finish desired and potentiometer 112 provide continuous fine adjustment to compensate for wear of the grinding wheel.