Patent GB-978479-A (GB)
Title: Improvements in systems for the automatic electrical control of the machining of mechanical parts
IPC: B23Q15/00
Filed: 1962-10-26
Abstract: 978,479. Electric selective signalling. COMPAGNIE GENERALE D'AUTOMATISME. Oct. 26,1962 [Oct. 27,1961], No. 40683/62. Heading G4H. The invention relates to an automatic machine for truing mechanical parts. A part to be balanced with respect to a given rotation axis is rotated in a test unit, the unbalance resulting in vibrations which are picked up electromagnetically to give two sinusoidal voltages u 1 , u 2  the amplitude and phases of which give the magnitudes and directions of two vectors specifying the unbalance, an alternator connected to the rotating part furnishing a 3- phase A. C. reference voltage of the same frequency. Since machining is not generally convenient at the sites on the part where measurements of unbalance took place, the voltages u 1  and u 2  are applied to a weighted summation network e.g. to the primaries of transformers T 1 , T 2  each of which has two secondaries of suitable turns ratios linked together as shown (Fig. 5) or that the voltages V 1 , V 2 , appearing across output terminals 23 1 , 24 1  and 23 2 , 24 2  represent the equivalent unbalance at the two intended machining sites. From each voltage V 1 , V 2  is now derived two voltages, X 1 , y 1  and x 2 , y 2  respectively, the amplitude of each of which represents the quantity of material to be machined off in one of two perpendicular directions at one of the two sites. This is done for v 1  in "dashed box" H 1  (Fig. 5), similar arrangements being provided for v 2 . A D.C. voltage of amplitude proportional to that of v 1  is produced across a capacitor 25 by a bridge rectifier Rd 1  and used in a balanced modulator Md 1 , also fed with 50 c/s A.C., to produce a 50 c/s A.C. voltage of proportionate amplitude. This A.C. voltage is fed to the rotor of a resolver R 1  whose two stator windings provide the voltages x 1 , y 1  provided the rotor is in the correct angular position. This is achieved by feeding the reference A.C. A. C. produced by the test unit to the stator windings of a phase variometer VP the rotor of which is on the same shaft A 3  as the resolver rotor. The phases of voltage v 1  and that across the variometer rotor are compared in a modulator Md 3  the D.C. output of which feeds a servomechanism S (details in Fig. 6, not shown) controlling the angular position of shaft A 3 . Since the voltages x 1 , y 1 , x 2 , y 2  may have phases demanding the addition of material to the part to be trued, which is impossible, further voltages X 1 , Y 1 , X 2 , Y 2 , X 0 , Y 0  are derived representing equivalent (positive) quantities to be machined off at three sites. The quadrang in which the phases of voltages x 1 , y 1  lie are indicated by photo-electric currents obtained with the aid of a slotted disc D 1  on the shaft A 3  of resolver R 1 . Similar arrangements exist for discovering the phase quadrants of X 2 , y 2 . These photo-electric currents (each zero or a positive value) are used to control the linear combination of X 1 , X 2  to give X 1 , X 2 , X 0  and of y 1 , y 2  to give Y 1 , Y 2 , Y 0 , as follows. Two photocurrents indicating the phase quadrants of X 1  and x 2 , and their inverses, are fed to the inputs of four D.C. transistorised amplifiers through individual resistors, the amplifier receiving respectively (a) the two photocurrents, (b) the two inverses, (c) photocurrent 1 and inverse 2, (d) photocurrent 2 and inverse 1. The output of each amplifier is connected to a respective relay in a relay box Brl 1  (Fig. 7) and produces a current sufficient to energize the relay only if the voltages fed to it are both zero. Thus only one of the four relays is energized. The voltages x 1 , X 2  are applied to the primaries of transformers T 3 , T 4  (Fig. 7), secondaries of which are so connected together and to the relays as to provide the voltages X 1 , X 2 , X 0  appropriate to the phases of x 1 , X 2 . Voltages Y 1 , Y 2 , Y 0  are produced similarly. Each voltage X 1 , Y 1  &c., is next converted into the angular position of a shaft A 4  (Fig. 9, not shown) by means of a servomechanism (details in Fig. 9, not shown). The angular position of shaft A 4  is converted non-linearly into the angular position of a second shaft by known means (e.g. cams) to convert magnitudes representing quantities of material to be removed to magnitudes representing lengths of machining tool infeeding. The position of the second shaft is coded in pure binary form photo-electrically using a slotted disc on the shaft. Alternatively the non-linear transformation and the coding can both be done by a slotted disc alone, the lengths of the slots depending on their angular positions on the disc. The six sets of digital data, representing X 1 , Y 1 , X 2 , Y 2 , X 0 , Y 0 , are fed to the six channels of a multi-channel shift register. Each part to be machined passes through machining and storage stations alternately, there being three of each, followed by a final checking station. Two machining operations are carried out at each machining station, e.g. X 1 , Y 1  at the first, and machining data not yet used occupy a stage of the shift register corresponding to the station occupied by the part. A motor advancing each machining tool also rotates a holed disc which produces photo-electric current pulses from a photo-cell which are allowed to enter a counter as soon as a relay is actuated by contact being made between the tool and the part. Machining is stopped when the number of photo-current pulses passed to the counter equals the value of the corresponding machining datum: a comparator may be used to compare the datum in the register with the counter reading or a counter alone may be used. A number of parts may occupy the chain of stations at a time, the parts being transferred from station to station, and the data moved from stage to stage in the register, automatically on completion of machining at all machining stations. Other modification: The coder could be of the translational type or involve sliding contacts.