| 摘要 |
<p>940,232. Electric selective signalling systems. NATIONAL-STANDARD CO. Feb. 7, 1961 [March 9, 1960], No. 4576/61. Heading G4H. In an electro-mechanical transmission system, the drive ratio between a reference member 17 and a driven member 27 may be varied by adjusting the maximum count of a counter 22 which is supplied with an electrical pulse for each given increment of rotation of member 17, counter 22 supplying a command pulse to a stepping unit 25 each time its maximum count is reached, and unit 25 producing a predetermined increment of rotation of member 27 for each command pulse received. The system shown in Fig. 3 is designed for rapidly positioning member 27 in one of a range of positions which may be represented by an 8-digit number and which differ only in the two least significant digits. The mechanical drive through shafts 60, 62, 58 to differential gear 57 is sufficiently accurate to position member 27 to within 6 significant figures, and counter 22 is preset manually to determine the two least significant digits, the maximum count preset in counter 22 depending on the initial rotation of member 17 which it is desired to transmit, and the number of pulses produced by magnetic tachometer transducer 20 for a given rotation of member 17. In the system of Fig. 4 three control channels are used, each having a variable drive ratio, channel 85 determining the first three significant figures, channel 77 the next three and channel 70 the last two. Stepper 25 may comprise a uniselector type switch which pulses the input leads to a step-bystep motor in succession. In this system, if member 17 is rotated a constant amount to produce a constant number of pulses the position assumed by member 27 is determined solely by the drive ratios selected for the different channels. As shown in Fig. 4 the outputs of the three channels are coupled through differential gears 74, 82 and the output shaft 86 is coupled to member 27 through a further gear train 32, pulse producer 34 and stepping unit 25. The transmission system may be used for the control of machine tools and for winding coils or control grids for electron discharge tubes.</p> |
