GB776060A - Indexing devices - Google Patents

Abstract

776,060. Grinding impellers &c. THOMPSON PRODUCTS, Inc. Dec. 14, 1953, No. 34798/53. Class 60 [Also in Group XXII] An indexing device for a machine tool comprises a mechanism 16, 18 for approximately indexing the work 2 relatively to the tool 12, a feeler 22 to engage a reference surface on the work, and a mechanism for completing the indexing step in response to deflection of the feeler 22. As applied to indexing an impeller one surface of each of the blades of which has already been finished and is to serve as the reference surface for the other surface, the impeller is mounted on a shaft 4 rotated by a continuously-acting, constanttorque, irreversible electric-motor 14 through a worm gear and approximately indexed by a pawl 16 engaging a ratchet 18 on the shaft when the milling cutter 12 has been withdrawn from the impeller. The tool-slide 8, Fig. 1, supports a valverod 32 in a friction bush 34, the rod operating a valve 30 to admit compressed air to a jack 28 for projecting the feeler into the path of the blades of the rotating impeller A bracket 24 pivotally-supports the feeler 22 and is carried on a shaft 26 which supports a lever 42 operating between a pair of switches 44, 46 controlling lamps which, when extinguished during an indexing step, indicate that the impeller is correctly indexed, the lever 42 being initially turned by a balance weight 40 to close the switch 44. The pawl 16 is pivoted eccentrically on a pin 70 adjustable by a lever 72 under hydraulic control to allow the small movements of the ratchet effected by the motor 14 in finishing the indexing step. The lever 72 is turned clockwise by a jack 64 to which fluid is fed through a valve 60 and a non-return valve 68 when a solenoid 48 is energized, to re-set the valve 60, by a circuit through the switch 44 and a switch 38 above an adjustable stop 36 on the bracket 24 and closed by contact with the feeler 22. A further solenoid, in circuit with the switches 38, 44, arrests advance of the toolslide . until the impeller is correctly indexed. Upon withdrawal of the tool-slide 8 after the machining operation, the jack 28 operates to withdraw the feeler, 'a hydraulic jack 20, Fig. 3, also controlled from the slide, withdraws the pawl 16 and a switch 56 is closed to energize a solenoid 58-which opens a stop-valve 66 to allow anti-clockwise rotation of the lever 72 and return of 'the pawl-pivot 70 to its advanced position.