Patent GB-681154-A (GB)
Title: Improvements in or relating to devices for holding gems or stones during grinding or polishing
Inventor: WEST CHARLES
IPC: B24B9/16
Filed: 1949-05-02
Abstract: 681,154. Dops. STONE, L., and OLIVER, H. March 3, 1950 [May 2, 1949], No. 11713/49. Class 60. A device for holding gems or stones comprises a holding member 24, Fig. 2, which is mounted in a head 20 so as to be rotatable and movable along the axis of rotation, means constrained against rotation about such axis to impart axial movement to the member for releasing the gem or stone, and indexing means 22 for retaining the holding member in any of a number of angular positions about its axis. The holding member 24 is in the form of a collet with a number of spring fingers which grip the stone to be treated when the flared end 25 of the collet is drawn against a correspondingly flared end on a sleeve 21 by the action of a spring 33 which is interposed between an abutment 32 in screw-threaded engagement with the upper part of the collet and the indexing member 22 which is secured to the sleeve 21. The latter is rotatably mounted in the head 20 which is provided with a slot to pivotally support a spring-loaded lever 44, Fig. 1, which co-operates with the toothed periphery of the indexing member. The collet is slidably keyed to the sleeve so that it turns with the latter to present successive facets of the stone to the polishing element and has a nut 34 in screw-threaded engagement with its upper portion to support a rod 38 which is adjusted to bear against the back of the stone. The nut 34 has a T-shaped slot to prevent it from moving freely on the collet. Axial displacement of the collet to release the stone is effected by pivotal movement of a lever 40 which is pivoted at 41 to an extension of the head 20. The latter is pivoted at 19 to a bracket plate 11 and bears against one side of an eccentric 13 the other side of which bears against a member 18 carried by the head. The spindle on which the eccentric is mounted is journalled in the plate 11 and carries a control knob provided with an indicator to co-operate with a scale on the back of the plate 11. A spindle 10 allows the plate to be secured to a tong. A stone which has been partly ground may be mounted for further treatment in the dop shown in Figs. 4 and 5. The ground portion of the stone is inserted in a cup 53 the interior of which is shaped to fit the stone. The cup is formed on a spindle 36 which is held in frictional engagement with a sleeve 56 by a spring. 67 interposed between a nut carried on the spindle and an indexing member 22 secured to the sleeve. The latter is mounted in a bifurcated head 20 for rotary and axial movement and is biassed by a spring 58. Axial movement of the sleeve is effected by rotation of a nut 65 which is in screw-threaded engagement with the head and has a conical face bearing against one end of a lever 62 the other end of which is provided with a pin 61 to engage an annular groove in the sleeve. The stone is held in the cup by an anvil 69 which is secured to the head by an adjustable clamping plate 78 so that it may be adjusted in the direction of the spindle axis. To insert a stone in the cup, the latter is withdrawn from the anvil by rotation of the nut 65. The indexing mechanism in both constructions may be arranged to rotate in consequence of the movement of the lever 44.