Patent GB-531331-A (GB)
Title: Improvements in or relating to lens edging machines
IPC: B24B9/14
Filed: 1939-07-18
Abstract: 531,331. Grinding lenses. STEVENS, A. H. (Shuron Optical Co., Inc.). July 18, 1939, No. 20857. [Class 60] In a machine for grinding the edges of circular or other concave-convex or flat lenses comprising a pair of co-axial lens-engaging means rotated with the edge of the lens in contact with the periphery of a rotating abrasive wheel, one of the lens-engaging means is mounted so that it may be swung out of co-axial alignment with the other so that a lens may be accurately positioned thereon. The grinding wheel 5 is rotated by a belt in bearings in a cradle 10 which is pivoted at 12 and adjustable by a bolt 14 to compensate for wear. The lens holder comprises a pair of rubber or leatherfaced heads 17 17<SP>1</SP>, removably mounted on rotary spindles 18, 18<SP>1</SP> in a carriage 20 which is pivoted at 21 in a frame 22, oscillatable about pivots 23, 23<SP>1</SP> arranged in a plane normal to the axis of the wheel and spindles in that the lens may be moved across the face of the grinding wheel with the angular position thereof constantly changing as shown in Fig. 16. The lens L is pressed against the wheel by a weight 108, Fig. 15, adjustable on the arm of a bracket 111 which is pivoted at 112 and is connected by links 113, 114 to an arm 101 projecting from a handle 100 carried by the carriage 20. The carriage may be held in raised position when required by a pivoted slotted latch member 103 engaging a pin 105 on the frame 22 and released by a finger piece 103<SP>1</SP>. The spindle 18 is mounted in the carriage 20 in a T-shaped member 28, so that it may be turned by a handle 97 about the lateral part 29 thereof so as to arrange the spindle 18 in a vertical position for applying the lens L to the head 17. The head 17 is provided with crossed lines 26, 26<SP>1</SP> co-operating with dots or marks on the lens to facilitate positioning of the lens thereon, the position of which is observed through an apperture 180 in an arm 181 mounted on the carriage 20. When the lens is in position it is temporarily secured on the head by a spring clamp A and the member 28 is then swung back so that the head 17 is co-axial with the head 17<SP>1</SP>, the member 28 is locked in either position by a spring-fixture pin 32 engaging holes 33 with part 29. The part 29 is provided with a screw 30 moving in a slot 31 in the carriage and engaging an adjustable screw 51 so as to correct the alignment of the heads. The head 17<SP>1</SP> is moved towards and from the head 17 and the pin 32 withdrawn by a handle 50 on a control shaft 40. The part 44 of the shaft 40 is eccentric and engages a recess 45 in a pivoted arm 46 operatively connected to a collar 48 on the spindle 18<SP>1</SP> so as to move the head 17<SP>1</SP> against the head 17, whereupon the clamp A is removed. When it is desired to free the locking pin 32, further rotation of the shaft 40 causes a pin 38 thereon to engage on arm 37 on a stud 36 so as to operate an arm 35 passing through a slot 321 in the locking pin. Stop pins 43, prevent the pin 38 from moving beyond the arm 37. The spindle 18 is rotated from the grinding wheel shaft by worm gear 70, 71, 75, Fig. 4, shaft 76 with diametrically slotted head 77, shaft 79, universal joint 83 and bevel wheel 85 on shaft 84. The bevel wheel 85 engages a bevel wheel 86 loosely mounted on a shaft 55, which is geared with spindle 18 by spiral gear 59 and bevel gear 63, 64. The wheel 86 is clutched to the shaft 55 by a finger knob 88 having a screw 89 engaging a longitudinal recess 90 in the shaft and provided with longitudinal pins 91 engaging holes in the gear 86. The pins 91 also pass through holes in the hub 57 of a spur wheel 58, which is geared to the spur wheel 67 on the spindle 18<SP>1</SP> through an idle wheel 66. By pulling back the knob 88 the spindles 18, 18<SP>1</SP> may be rotated by hand. A spring-pressed adjustable brake mounted in the handle 97 is applied to the spindle 18 to compensate for back-lash in the drive. The frame 22 is oscillated by an eccentric 117, Fig. 4, on the shaft 26 operating a piston 118 engaging by a screw 120 and spring plunger 119 a spherical end 121<SP>1</SP> on a vertical shaft 121 on the frame 22 at one side of the pivots 23, 23<SP>1</SP>. The path of travel of the frame may be varied during oscillation to suit lenses of various crosssectional contours or curvatures by arranging the spherical end 121<SP>1</SP> eccentrically and rotating it by a cross-handle so as to vary the effective length of the pitman. The cross-handle is arranged in a frame containing a lens from the spherical end through the axis of the shaft 121 and one end is tapered so as to indicate in which direction adjustment is to be made. The initial grinding operation is effected with the pattern 130 which is removably mounted on the end of the spindle 18, out of action. Subsequently the pattern engages a shoe 145, Fig. 10, on a back rest 133, which is pivoted at 134 on a bracket 135 adjustable by a screw 137 in the frame 22. A spring allows a limited movement of the rest 133 about its pivot. The position of the back rest is adjusted to suit the size of the pattern by a screw-threaded graduated index wheel 140, the graduations moving against an index lens 143 in the frame. The lens may be ground slightly larger or smaller than the pattern by a slight adjustment of the index wheel. The back rest has a rubber tipped pin 149 which closes a switch 151 in an electric circuit containing a signalling lamp when the back rest is pressed back by the pattern. Such lamp lights up intermittently until the whole edge of the lens is ground to the pattern, when it remains alight continuously. Water is supplied to the grinding wheel from a pipe 160, Fig. 2, connected by a valve 159 with a receptacle 156 in the frame. The top of the grinding wheel is kept clear of dust and water,by a sponge 164 in a case 161.