Patent GB-808329-A (GB)
Title: Improvements in and relating to an edge grinding machine
Inventor: WYLDE STEPHEN JACK
IPC: B24B9/14
Filed: 1957-02-08
Abstract: 808,329. Edge grinding lenses. TAYLOR (HOLDINGS) Ltd., J. & H. Feb. 8, 1957, No. 4467/57. Class 60. A lens-grinding machine has rough and fine grinding wheels 6, 7, Fig. 2, a rotatable lensholding means 40, 41 on a carriage 35 which is shiftably supported so as to be capable of movement to bring a lens blank L into engagement with one or other of the grinding wheels, and means for controlling the grinding operation including a cam element C mounted for rotation on the carriage co-axial with the lensholding means and form shoes 66, 67 for cooperating with the cam element to limit the movement of the carriage during grinding. The grinding wheels are disposed in a chamber 10 formed by a bracket 8 on a base-plate 1, and are driven from a motor 5 by belt-driven pulleys 22, 28, 26, 30. The fine grinding wheel 7 may be grooved in order to grind a bevel edge on the lens blank. The carriage 35 is mounted for swinging movement about a hollow shaft 34, Fig. 3, disposed centrally between the two grinding wheels 6, 7. The lens blank is held on the carriage between rotatable shafts 40, 41, the former being axially-slidable and spring-urged towards the latter, and a pivotted lever 50 co-acting with a link 57 being provided for axially displacing the shaft 41 to insert the lens blank between the shafts ; a suction cap may be located on the end of the shaft 40 to retain the blank in position, locating pins and holes being provided in the end of the shaft and cap. The shafts 40, 41 are driven by chains 82, 82<SP>1</SP> from sprockets 83 mounted in a shaft 84 which is disposed within the hollow shaft 34 and rotated by a motor 80, Fig. 2. The cam element C is located on the end of the shaft 41 by pins 60, Fig. 1, for co-operation with either of two form shoes 66, 67 which are located for vertical adjustment by threaded portions 68 on a pivotted switch-bar 69 carried by a plate 71 slidably mounted in a bracket 73 secured to the base-plate 1. A portion 69<SP>1</SP>, Fig. 8, of the bar 69 extends downwardly between opposed switches 127, 127<SP>1</SP> so that, as the operative form shoe is actuated by the cam element, the bar 69 pivots to close one or other of the switches 127, 127<SP>1</SP> and so actuate a relay to control the operation of the motor 80. The motor 80 is also controlled by (a) a micro-switch 115 actuated by an arm M, Fig. 1, which has, at one end a counterweight 117, and, at the other end, a roller 119 which co-operates with the carriage 35 when in the fine grinding position, and (b) a micro-switch actuated by a button 112, Fig. 2, which co-operates with a pivotted lever 109 spring-urged away from the button 112 into contact with a counterweight 123 carried at the end of a rod 120 secured to a block 121 on the end of a horizontal shaft 15. Lift-fingers 14 are secured to the shaft 15 and co-operate with the carriage to disengage the lens blank from the grinding wheels. In operation, a lens blank is gripped between the shafts 40, 41 and the carriage placed in the left-hand position for the rough-grinding operation ; in this position, the roller 119 is not engaged with the carriage and the arm M closes the switch 115. Depression of a handle 122 on the block 121 then disengages the lift-finger 14 from the carriage 35 to permit the lens blank to engage the wheel 6 and cause the counterweight 123 to rock the arm 109 which actuates the micro-switch to start the motor 80 and light an indicator lamp; a projection on the counterweight also engages the arm 109 to retain the finger 14 out of engagement with the carriage. When the lens blank reaches the finished rough-grinding size, the cam-element C contacts the form shoe 66 and the switch bar 69 is rocked to actuate the micro-switch 127<SP>1</SP>. An electronic timer is provided to prevent the motor 80 stopping until the cam has remained in contact with the shoe and the switch 127<SP>1</SP> remained closed for one further complete revolution, whereupon the motor is stopped, a different indicator lamp lit, and a solenoid operated to disengage the arm 109 from the counterweight 123, the fingers 14 thus lifting the lens blank from engagement with the wheel 6. The carriage is then swung by the operator into the right-hand position where it contacts the roller 119 and lifts the arm M. from the microswitch 115. The handle 122 is depressed as before, but the motor 80 operates so that the lens is rotated only in steps, each of these occuring when the cam element rocks the switchbar 69 to actuate switch 127 to start the motor and rotate the lens a few degrees until an unground portion again lifts the cam from the switch-bar. This stepped operation continues until, when the cam has maintained contact with the shoe for a complete revolution, the electronic timer is actuated as before to provide one further complete revolution. The shaft 251 of the grinding wheel 7 is axially floating to permit the wheel to follow the contour of the lens blank during bevel grinding. An adjustable radial arm secured to a collar on the shaft 251 has two rollers, Fig. 5 (not shown) which engage one on either side of an extension disposed parallel to the axis of the shaft 251 and secured to a bracket on a shaft 25. Alternatively, the collar may be secured to the shaft 25 and the bracket to the shaft 25<SP>1</SP>. The shaft 251 may be axially spring-urged by a collar 101 which engages a flange on an extension 100 of the shaft 25<SP>1</SP> to provide an offset bevel. The grinding wheel 6 is axially adjustable by means of a handle 90 to compensate for uneven wear. The grinding chamber 10 may be partly by a shroud plate to minimise the spray from the coolant water which is fed to each grinding wheel.