Patent GB-238088-A (GB)
Title: Improvements in lens edging machines
IPC: B24B9/14
Filed: 1924-09-29
Abstract: 238,088. Long, E. M. Sept. 29, 1924. Lenses, grinding and polishing; bevelling.-In a lens edging machine of the type in which the rotary lens holder is disposed diagonally of the plane of rotation of a rotary grinder to bring the edge of the lens in contact with opposed faces of the grinder for bevelling both corners of the edge of the lens at the same time and is free to move axially and radially by contact of different portions of the edge of the lens with the opposed grinding faces, means are provided for moving the grinding-mechanism towards the lensholder a predetermined distance for a given rotational movement of the lens-holder. The rotary grindstone 14 of the V-shaped groove type is carried by a shaft 12 journaled in bearings 13 on arms 9 of a supplemental frame 8 which is pivotally mounted on the main driving shaft 5. The grindstone 14 is rotated by a belt 18 from a shaft 5, the lensholder being driven from the shaft 5 by a worm 21 mounted on a shaft 23 through a coaxial worm 22 and gears 27. The lens-holder is in two parts 35, 36, the latter being mounted on pivots 38 within part 35 which is supported on trunnions 37 in a carriage 25 adjustable vertically on vertical rods 24, 24<1> supported in cross-bars 3, 3<1> on the main frame 1. The lower end of the shaft 23 is provided with an eccentric pin 51 adapted to engage one arm of a bell-crank lever 52 pivoted to the bar 3' at 53 and passing through the frame 54, its outer end being pivoted to a forwardlyextending spring-controlled pawl 55, which engages the teeth of a ratchet wheel 57 secured to a shaft 58 carried by bearings in the carriage 8. Secured to the intermediate portion of the shaft 58 is a spiral cam 59 adapted to ride against a hardened bearing 60, Fig. 6, secured to the frame 1 so that during one revolution of the shaft 58 the carriage 8 will be raised a distance equal to the throw of the cam. Mounted on the hub 62 of the ratchet wheel 56 is a pawl-tripping plate 61 provided with a peripheral flange 63 extending across the teeth of the ratchet and adapted at the end of each revolution of the cam to engage and trip the pawl. the length of the flange 63 being equal to cr slightly greater than the maximum lengthwise travel of the pawl, the pawl sliding backward and forward on the plate 63 when the lowest point of the cam engages the bearing 60. To permit of an angular adjustment of the plate 61 by hand so as to shift the plate 63 forward and allow the pawl to engage the ratchet wheel, a slot 64 on the plate 61 concentric with the shaft 58 is provided for the reception of a stud 65 on the ratchet wheel, the plate when released being automatically retracted by a spring 66 connecting the stud on a shoulder 67 on the plate 61. When, therefore, the maximum throw of the eccentric 51 is imparted to the lever 52, the pawl will be moved a distance substantially equal to a certain number, e.g. three, of teeth of the wheel 57 which, with its shaft 58, will be moved angularly through that distance, thus operating the cam 59 and moving the carriage 8 and the grindstone 14 towards the lens-holder a predetermined amount for each revolution of the lens-holder, the driving connection between the shaft 23 and the lens-holder and between the shaft 23 and the shaft 58 being adjusted to establish a definite minimum ratio of rotation between the lens-holder and the shaft 58, e.g. forty revolutions of the lens-holder to one revolution of the cam shaft. To vary the speed ratio by varying the travel of the pawl 55, a shaft 68 is provided with an eccentric pin 71 extending into, and engaging, a slot 72 in the pawl 55, the pin being operated by a handle 70. In order to lift the lens-holder 40 away from the grindstone 14 when the highest point of the cam 59 engages the bearing 60 a notch 74 on a disc 73 carried by the shaft 52 is adapted to be engaged by the notched end of a bar 75 pivoted to a crank 76 on a shaft 77 mounted in bearings on the carriage 8 and provided with a crank arm 78 pivotally connected to link 79 connected to a crank 80 carried by a vertical shaft 81 mounted at its lower end in a bearing 82 and at its upper end in a bearing 83 in the carriage 35. The upper end of the shaft 81 is provided with a crank 84 which is adapted to engage the rear end of a spring-controlled pawl 85, pivoted at 86 to the underside of the frame 36, when the notch 74 is engaged by the lever 75 and so bring the pawl 85 into the path of, and into engagement with, arms 88 carried by a cam 87 on the rotary shaft 46 and so raise the pawl 85 on the carriage 36 into the vertical position, thereby breaking connection between the gears on the shaft 44<1>, 46 and stopping the rotation of the lens-holder. The pawl 85 is normally held out of the path of the rotary members 88 by a spring 91. When the shaft 58 rotates further, and the bearing 60 engages the lowest point of the cam 59, the notched end of the lever 75 will be forced out of the notch 74 and the pawl 85 will be drawn from engagement with the member 88 by the spring 91, allowing the lens-holder to be restored to its grinding position, the plate 61 being retracted by the spring 66 to allow the pawl to re-engage the ratchet wheel and start the cycle of operations again.