Patent GB-903748-A (GB)
Abstract: 903,748. Drilling-machines. AVERY Ltd., W. & T. Nov. 4, 1958 [Nov. 7, 1957], No. 35315/58. Class 83 (3). [Also in Groups XXIV and XXXVIII] Apparatus for measuring and removing rotary unbalance in a disc-shaped rotor which is to be modified by subsequent drilling or by the addition of further masses comprises means for measuring the magnitude and position of the unbalance of the unfinished rotor, and automatically positioning the machining tool so that the original unbalance is neutralized by that introduced by the subsequent machining. As shown (Fig. 3) an unfinished disc rotor 31 is rotated by a vertical shaft 30a simultaneously with a reference generator 456 supplying two quadrature voltages, and having a displaceable stator 456a. The unbalance is measured by a moving coil pickup 403, whose signal, after modification by rheostat 403a (Fig. 4) in accordance with the unbalance to be subsequently introduced, is fed to two wattmeter-type instruments 401, 402, together with the sine and cosine voltages respectively from generator 456, whereby the pointers 401c, 402c of the meters are deflected. Pointer 402c via contact 402e or 402f and switch 407c of an impulse transmitter 407 driven by a continuously running motor 407a, intermittently energizes relay 406 and motor 404 which rotates the stator 456a of generator 456 until the pointer 402c is restored to its undeflected position, the angular position of the stator then corresponding to the angular position of the unbalance of rotor 31, and wattmeter 401 indicating its magnitude. Its pointer 401c is locked in this position by a solenoid 401b energized via pointer 402c and centre contact 402m, and via a preset time delay switch, the speed of rotation of the rotor shaft 30a is reduced. Located at the lower end of reference generator 456 are contacts 456d carried by the stator 456a, and a cam 456c which close contacts 456d in the correct angular position, whereby, through a centrifugal switch 456e, a solenoid 435 is energized to attract a lever 35a (Fig. 3) and raise a sleeve 30i to locate a series of pegs 30g carried on a disc 30k attached to the shaft 30a in corresponding holes 30h, and the shaft is brought to rest at an angular position corresponding to the unbalance in the rotor 31. When the pointer 401c is locked in position it contacts one contact 401x of a bank of contacts, each individually connected by a group of leads 405y to corresponding contacts on a stepping switch 405, whose arm 405a hunts for the marked contact 405x corresponding to contact 401x, when it stops the stepping motion by energization of switch 405f. The motor 37c is now energized via switch 413a and moves the machining device 37 (Fig. 3) until switch 409 is operated by arm 405c, when the drills 37g are correctly located in accordance with the magnitude of the resultant unbalance measured on wattmeter 401. In another embodiment (Figs. 5, 6), the unbalance of the unfinished rotor 51 is measured by pick-up 603 and its two components determined by wattmeters 601 1 , 601 2  and reference generator 656. The rotor 51 is then clamped in a fixed angular position by means of pegs 50g and holes 50h, and the readings of the wattmeters transferred by stepping mechanisms 605 1 , 605 2  to position the drill support 57 by means of motors 56c 1 , 57c 2  which move the support in the co-ordinate directions in accordance with the magnitudes of the unbalance components. Allowance for the unbalance introduced by the subsequent machining is effected by rheostat 603a. Further allowances for the vibration of the bearing support and errors in the accuracy of the clamping mechanism are introduced by a further vibration pick-up 673 mounted on arm 673a. Specifications 744,295, 744,662 and 889,877 are referred to.