GB698170A - Improvements in or relating to edge grinding particularly for forming bevelled edgeson articles such as ophthalmic lenses - Google Patents

Abstract

698,170. Edge grinding lenses. ABBEY, A. (American Optical Co.). July 7, 1952, No. 17081/52. Class 60. A tool for edge grinding lenses comprises an abrading wheel 16, Fig. 8, having a peripherally disposed V-groove shaped abrading surface 27 having both its opposed wall surfaces offset other than normal with respect to the axis of the wheel, and wherein lines drawn through the apex of the groove to divide it into substantially equal angles will define a cone having its apex substantially on the axis of the wheel. The wheel is clamped by a nut 25 and washer 24 against a collar 22 on a shaft 21 which is rotated by a shaft 17 and belt 18, Fig. 1. The lens 73 is clamped between two pads mounted on rotatable spindles 55, 58, Fig. 3, one of which is adapted to be axially displaced against spring pressure by a manually-operated helical cam device to allow insertion or removal of a lens. The spindles are carried by arms 41 pivotally connected by screws 43, Fig. 5, to a yoke 38 mounted on a vertical pivot 33. Movement about the latter pivot to maintain the curved edge of the lens in register with the groove in the tool is effected by a cam surface 90 and an adjustably positioned pin 91, relative movement between these last two members taking place in consequence of the movement of the lens towards and away from the tool. This movement is controlled by a template 75 mounted on the spindle 55 and adapted to co-operate with a shoe 78 which makes an electric contact 83, 84 when depressed. As grinding proceeds, the template descends with the lens until the shoe 78 is engaged and depressed whereupon an electric motor 54 is energized to rotate the lens through a shaft 53 and gears 52, 69 until the engagement of an unground portion of the lens with the tool lifts the template clear of the shoe. Alternatively, the lens may be rotated continuously. Adjustment of the pin 91 by means of a screw 96 enables the position of the bevel apex to be varied in relation to the front and rear surfaces of the lens. An adjustable weight 44 partly balances the weight of the arms 41 and the lens-holding assembly. A coolant or lubricant is directed on to the lens by a nozzle 101 supplied from a tank 99. Trueing.-To provide access to the wheel, the arms 41 are displaced about their pivots to a position to one side of the machine where they are supported by a bracket 125 which is raised to a vertical position about a pivot 126. A V- shaped trueing diamond 120, Fig. 13, supported by a rod 104 connected by a universal joint at one end to the base of the machine, is then lifted into engagement with the groove in the wheel and the rod 104 is moved to follow the contour of a template (not shown). The diamond is mounted in a slide 115 urged by a spring 117 into engagement with a calibrated screw cap 121 by means of which it may be adjusted in relation to the rod 104. Coolant is supplied through a bore 122 and passages 123 by transferring the connection from the nozzle 101.