Patent GB-1207315-A (GB)
Title: Faceting gem stones
Inventor: LEIBOWITZ ALEC
IPC: B24B9/16
Filed: 1966-12-20
Abstract: 1,207,315. Faceting gems. SPECTRUM DIAMONDS (PTY) Ltd. 10 Nov., 1967 [20 Dec., 1966], No. 56978/66. Heading B3D. Apparatus for automatically developing a plurality of facets on a gem stone comprises: (i) a tang; (ii) a chuck mounted on the tang adapted to carry a gem stone or a gem stone in a holder with the stone axis inclined to the tang, the chuck being capable of rotational motion about the stone axis and orbital motion about another axis substantially perpendicular to the tang; (iii) means for lowering the tang towards a polishing surface; (iv) means for lifting the tang away from the polishing surface; (v) first indexing means for rotating the chuck in faceting steps about the stone axis; (vi) second indexing means independent of the first indexing means for orbiting the chuck about said another axis to alter the polishing direction; and (vii) automatic control means for repeatedly operating the lifting and lowering means and the first and second indexing means to successively develop a plurality of facets on the stone, the control means including: (a) means for automatically operating the tang lifting means when each facet has been polished to the same predetermined depth; (b) means for automatically operating the first indexing means between each successive faceting operation; and (c) means for automatically operating the second indexing means between at least some successive faceting operations. A tang comprises a metal bar 2 having at one end a claw 3 engaging over a bar 4 on a carriage 5 having rollers 13 guided in tracks 14 on a base 12; the carriage is reciprocated by an automatically reversing double-acting hydraulic piston and cylinder 15. The tang is raised between faceting operations by a single-acting pneumatic piston and cylinder 16, and its descent is controlled by a dashpot 18. The free end of the bar 2 carries a chuck 7, the inclination of which to the surface of a polishing wheel 9 is adjustable by a pivoted bracket II. The chuck is rotatable by a motor 20 about an axis passing through the centre of a gem held by a holder in the chuck and is movable by a motor 8 about an axis defined by a pivot 6 perpendicular to the bar. A suitable polishing direction for the first facet is established manually and the orbital position of the chuck manually set accordingly; control section D activates reciprocation of the bar 2. Control sections A, B, C are then actuated. Polishing of the first facet continues until the gem holder contacts the polishing wheel, thus making a circuit through connections a, b, whereupon control section A activates the piston and cylinder 16 to raise the bar 2. When the bar is up, control section B activates the motor 20 for a set time to index the chuck for the next facet; the motor 8 may be activated for a set time to index the chuck about pivot 6 to establish the correct polishing direction for this next facet as determined by the programming of section B. At the completion of indexing, control section C activates the piston and cylinder 16 to lower the bar. The cycle is automatically repeated until all the facets have been formed. A counting mechanism may then stop the machine or give a visible or audible signal.