GB782432A - Apparatus for fully automatic control of the tool feed in grinding machines, e.g. internal grinding machines - Google Patents

Abstract

782,432. Photo-electric control systems. MULLER, W. Nov. 29, 1954 [Nov. 27, 1953], No. 34535/54. Class 40 (3). [Also in Groups XXIII, XXIX and XXXV] A grinding-machine, e.g. an internal grinding- machine, has automatic control of the feed of the grinding wheel such that the rapid approach movement changes, on contact of the wheel with the work, to a grinding feed, and thereafter if the feed is too rapid it is discontinued until conditions return to normal. The control is effected in accordance with either changes in the current consumption of the wheel-driving motor or changes in the speed of the wheel. A slide 4 carries a grinding-wheel 1 and a motor 5 driving the wheel either through a belt or directly; mechanism for feeding the slide 4 is operated alternatively by a vane motor 9 or by pawl-and-ratchet mechanism 7, 8. An ammeter 10 is connected in the circuit of motor 5, its needle co-operating with adjustable contacts 11, 12. The operating cycle is as follows:- 1. The grinding-wheel 1 being out of contact with the work, the current consumption of motor 5 is low; the needle of ammeter 10 touches contact 11, thus energizing solenoid 16 to close switch 17 to energize electromagnet 20 which moves valve 24 downwardly from its normal central position. Oil is supplied through pipe 25 to the vane 9 which rotates clockwise, giving rapid feed to approach the grinding- wheel towards the work. 2. When the grinding-wheel 1 touches the work, the current consumption of motor 5 increases; the needle of ammeter 10 moves away from contact 11, thus de-energizing solenoid 16 to open switch 17 to de-energize electromagnet 20, a spring 26 then returning valve 24 to its normal central position. The supply of oil to the vane 9 is cut off, so stopping the rapid feed, and oil is supplied to a circuit containing valves 30, 32, 39 whereby a piston 45 is reciprocated to actuate the pawl and ratchet grinding feed. 3. If the current consumption of the motor 5 increases to such an extent that the needle of the ammeter 10 touches contact 12, a solenoid 54 is energized to close switch 55 to energize electromagnet 57 which moves valve 24 upwardly from its normal central position; the supply of oil to the circuit for reciprocating the piston 45 is cut off, so that the pawl and ratchet grinding feed is rendered inoperative until the current consumption of the motor 5 decreases. 4. Shortly before the finished size is reached, a truing stroke for the grinding-wheel is interposed; pressure oil supplied through duct 59 moves the valve 28 into its lower position, in which the duct 29 is disconnected from duct 27 and is connected to the pressure duct 22 through a throttle valve 62. Feed of the grinding-wheel then takes place at a slower rate. When the finished size is reached, oil is supplied to the duct 60 to move valve 28 into its upper position and to the duct 64 to move valve 65 to the right against spring pressure ; the piston 45 is moved to the left so that the pawl 7 is disengaged from the ratchet wheel 8, and the vane 9 is returned to its starting position. In a modification, Fig. 2, the ammeter is replaced by a tachometer D. The end of the grinding-wheel spindle 2 carries a black-andwhite disc 71 which is in the line of sight of telescope 72 with photo-cell and is illuminated by a spot-light 73 disposed therein.