GB611749A - Improvements in or relating to electronic commutators or the like - Google Patents

Abstract

611,749. Thermionic distributers. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 2, 1946, No. 10169. Convention date, April 10, 1945. [Class 40 (iii)] [Also in Group XL (c)] A hard valve commutator comprises a chain of trigger stages S1 ... 3, each consisting of a pair of valves 68a, b, cross-connected to have two stable states, one valve 68b in each stage being connected also to the previous stage in such a manner that sequential reversal occurs with successive impulses applied simultaneously to all the stages. The valves 68a, b are coupled by a common cathode resistance 69 and also by cross-connection to two potentiometers comprising resistances 62a, 63a, 64a and 62b, &c., respectively. A stage in the OFF condition has the valve 68a conductive, rendering the potential of the corresponding point 67b low and the valve 68b non-conductive. Switching impulses are obtained by differentiation in the network 5, 6 of a square waveform generated by the multivibrator 1. Positive-going components in the differentiated train are suppressed by a valve 3 with grid-current bias, while the negative-going components cause positive-going pulses to appear in the anode circuit and on the line 54. An impulse on the line 54 will switch to ON any stage in which the suppressor-grid potential of the valve 68b is high. The valve 68b then becomes conductive, reducing the potential of the corresponding point 67a and rendering the valve 68a non- conductive. The potential of the point 67b rises and maintains the valve 68b conductive, and also applies a high potential to the corresponding line 10 which conditions the valve 68b in the subsequent stage for switching to ON. Successive impulses thus switch the stages S1 . . . 3 sequentially to ON. A phasereversing valve 78 is interposed in the line 11 whereby the stage S1 is conditioned for switching to OFF by a reduction in the potential of the line 11 when the stage S3 is switched to ON. Further impulses then switch the stages S1 ... 3 successively OFF, each conditioning the next by a reduction in the potential of the corresponding line 10. With the switching OFF of the stage S3 the cycle is complete and the stage S1 conditioned for a further cycle by reason of an increase in the potential of the line 11. The reversal of each stage is assisted by condensers 65a, b which cause the changes of potential of the points 66a, b respectively to produce corresponding impulsive changes at the points 67a, b respectively. A further condenser 71 connected across each line 9 ensures that the subsequent stage is not conditioned for switching before the termination of the pulse which switches the prior stage. Specification 593,577 is referred to.