Patent GB-921648-A (GB)
Title: Automatic grinding machine
IPC: G05B19/33
Filed: 1961-07-06
Abstract: 921,648. Numerical control of grinding machines. CINCINNATI MILLING MACHINE CO. July 6, 1961 [Sept. 1, 1960], No. 24454/61. Class 38 (6). [Also in Group XXIII] In a grinding machine, a work-table 12, Fig. 1, has a headstock 13 and a tailstock 15 with centres 16 adapted to receive a workpiece 17. The work-table is reciprocally movable along a base 92 by an hydraulic table motor TM, Fig. 2. A rotating grinding-wheel 18 is supported in a wheel-head 19 mounted for movement along an axis at right-angles to that of the workpiece. The wheel-head 19, Fig. 4, is advanced towards the workpiece by an hydraulic motor WM acting through a rapid advance hydraulic motor 104, comprising a piston movable over a curved path in a ring-shaped cylinder, and a rack-and-pinion 96, 94. Back-lash in the rack- and-pinion is prevented by an hydraulic ram 222, 226. The wheel 18 is trued by a diamond tool 22 carried on the tailstock 15. Wheel-head control system.-The wheel-head 19, Fig. 6, through a drive train 118 is driven by the hydraulic motor WM which is controlled by an electro-hydraulic servo-valve 112 actuated by an error signal from a synchro receiver 114 through an amplifier 116. The synchro receiver 114 is mechanically positioned by the motor WM through a gear train 115 and is electrically-responsive to the outputs of synchrotransmitters 138, 166, 120. Synchro-transmitter 120 is driven by a hand-wheel 124 or through direction-reversing clutches EC1, EC2 and a gear-train 126 by a two-phase wheel-head control motor WCM. The motor WCM is energized through relay contacts 68CR by an amplifier 127 responsive to signals from a rate control unit 136 and a feed-back tachogenerator 125. The hand wheel 124 is rotatable to a positive stop 128 to derive a reference position ; the stop being brought into operation by a solenoid, not shown. The synchro-transmitter 138 is positioned by a two-phase wheel-head position control motor WPCM controlled by an error amplifier 160 having rate feed-back from a tachogenerator 140. The input to the error amplifier is derived through a motor control circuit 152 from a two-channel signal amplifier 150 containing a synchronizing circuit which effects connection of one only of synchro elements 144, 146, 148 to the circuit 152 at a time. The circuit 152 includes an amplifier 154, a phase dntector 156 and a modulator 158. The synchro elements 144, 146, 148 are driven through gearing 143 by the motor WPCM and their outputs represent respectively coarse, medium and fine error in wheel-head position from the position stored in a position storage mechanism 162 responsive to an internal manually set dial and stepping switch system or to the output of a pecker contact tape reader 59 reading a punched tape 61. Table control system.-The table 12 through a gear train 34 is positioned by an hydraulic table motor TM controlled by an electro-mechanical valve 28 responsive through a micro-positioner 192 to the signal from an error amplifier 32 having an input from a synchro receiver 30 mechanically coupled to the table motor TM and electrically coupled to synchro-transmitters 36, 90. The synchro-transmitter 90 is directly positioned by a hand wheel 88 and the synchrotransmitter 36 is driven through a gearing 40 by a two-phase table control motor TCM. The motor TCM is controlled from an amplifier 44, having rate feed-back from a tacho-generator 42, and an input, through change-over contacts 17BCR of a relay, from an electronic unit 70 or from a switch unit 52, which through limit switches, a reversing switch on the table or stepping switches directs table movements during a manual or table dog controlled traverse grinding or truing operation. The electronic unit 70 is responsive to signals derived by a reader 59 from a punched tape 61 which through stepping switches 58, 60 and change-over contacts 54CR of a relay are applied to synchro resolvers 62, 64, 66 for deriving respectively, coarse, medium and fine table position error signals. The rotor windings of the resolvers are connected to an electronic synchronizing network 150 which connects the error signals in sequence to the electronic unit 70, comprising an amplifier 72, a phase detector 74 and a modulator 44, the maximum magnitude of the signal from which is determined by the setting of rate potentiometers in a bias circuit 78. The output from the electronic unit is fed through the contacts 17BCR to the error amplifier 44 of the table control motor TCM. The synchro resolvers are driven from the table motor through an electromagnetic clutch EC3 and a gear-train 65, the clutch being selectively disconnectable to allow movement of the table without altering the positions of the synchro resolvers.