Digital position-indicating units adapted for use in apparatus for detecting and setting the position of a movable object, such as a rotatable shaft; and such apparatus

摘要

942,684. Electric selective signalling systems. CRYSTAL STRUCTURES Ltd., and A.M.WOOSTER. March 15,1962 [March 17,1961], No.9935/61. Heading G4H. A shaft is positioned in accordance with a number set up on a switch by circuitry shown in Fig. 2. The number is set on the a and b sides of switches 27, 28, and 29 which each select one of ten square waves provided by generator 26. The ten square waves are progressively phase displaced from each other so that a selected square wave represents a particular digit by its phase relative to the square wave representing digit "0". The ten square waves connected to the a sides of the switches are in antiphase to those connected to the b sides, and the six selected waves pass to switches 31, 32, which lead to a comparator comprising units 33-38. The shaft 24 to be positioned is driven by a motor 25 which also drives, by means of a Geneva gear, a device comprising three banks 11, 12, 13, one of which is illustrated in Fig. 1. A bank consists of a metal segment 18 which is rotated over a set of ten segments 15 connected to the generator 26. There is capaci- .tative coupling between adjacent segments 18 and 15 so that the three outputs from the banks 11, 12, 13, are each a train of alternate positive and negative spikes, their phase depending upon the present position of the shaft 24. These wave trains are fed as a third input to the comparator, via switch 30. The comparator detects the phases of its three inputs, using first the waveforms representing the most significant digit (in Fig. 2 this is "6") and controls relays to connect motor 25 for rotation either forwards or backwards or to disconnect the motor. Dependent, then, on the comparator output the motor drives shaft 24 until bank 13 reaches position "6", whereupon the motor stops and switches 30, 31, 32 are stepped to transmit the next significant digit and the comparison cycle repeats. Various modifications in the construction of the banks 11, 12, 13 are described. It is stated that the comparator need have only one square wave input, instead of the two indicated above. Position can be indicated by amplitude or frequency instead of phase significance of the waveforms.