Patent GB-1358767-A (GB)
IPC: B24B49/10
Filed: 1971-09-20
Abstract: 1358767 Grinding LITTON INDUSTRIES Inc 20 Sept 1971 [21 Sept 1970] 43668/71 Heading B3D [Also in Divisions H3 and G4] In a machine tool positioning system, pulses supplied to a motor 27 (Fig. 1A) to drive the movable member are also counted in a counter 105-109 (Fig. 1B) including a non-volatile memory 146-150 so that in the event of power failure or shut off the position of the member remains stored. At a start signal 50 a sequence control counter 48 enables a controller 34 to advance the wheel support 12 for a grinding wheel 13 rapidly until a bracket 41 on the support engages a switch 43 to step the counter 48. The counter then gives a signal on lead 69 so that pulses from an oscillator 61 are fed via a binary rate multiplier 58, controlled by manually operated rate switches 63, to a counter 32 controlling via decoder drive circuitry, the electrohydraulic pulse motor 27 which moves the wheel support 12 until the count in counter 105-109, also receiving the output of the multiplier 58, equals the count set up by an operator on switches 85-89 (representing a desired end point). When comparator 95-99 detects equality the counter 48 is again stepped to establish an output signal on lead 68. This results in a binary rate multiplier delivering a somewhat lower rate output. When a transducer 52 provides a signal indicating that the grinding wheel 13 has contacted a surface of the workpiece W the counter 48 is again stepped to provide a signal on lead 67. (If transducer 52 fails to respond counter 48 is stepped when the state of operator controlled switches 113-117 coincide with the count in counter 105-109). The new output signal from counter 48 controls multiplier 58 to establish a slower feed rate and enables switches 118-122 so that at equality of the counter 105-109 and switches 118-122 the counter 48 is again stepped resulting in the motor 27 stopping. A first dwell enable signal is then established on lead 78 and comparator 54 supplies a counter advance signal upon the lapse of a dwell period established by the setting of switches 76. During this period a caliper 45 is moved so that a probe 46 engages the workpiece. At the end of the first dwell enable signal a second enable signal on lead 66 results in motor 27 again being enabled to advance the grinding wheel. The grinding wheel continues to advance until the caliper senses that a portion of the workpiece has reached a predetermined diameter when a second dwell enable signal occurs. During this signal the grinding wheel continues to rotate without advancing to round out the ground portion of the workpiece. At the end of the signal the counter 48 is stepped to establish a signal on lead 65 resulting in a fine feed rate for the grinding wheel until the caliper signals that the final required diameter has been reached. The grinding wheel then rotates again without advancing for a third dwell period to remove any remaining irregularities. If the signal received from caliper 45 indicates that the diameter is correct the counter 48 advances to establish a retracted signal on lead 40 so that the grinding wheel is moved away from the workpiece. Otherwise the fine grinding process is repeated. The count in counter 105- 109 which represents the position of the grinding wheel may be used to display the dimension of the workpiece. The counter 32 and counter 105-109 which are binary coded decimal counters include for each decade an adder/subtractor and for each binary bit a non-volatile store including a core. The core (200, Fig. 2, not shown) has two write wires (201, 202) connected to the collectors of transistors (203, 206). A read wire (208) is connected via a transistor (211) to a bi-stable (214) receiving at its other input read pulses. In the event of power failure at the restoration of the power the first read pulse results in the state of the core being read out.