| 摘要 |
1,023,054. Hump yard control systems. AMERICAN BRAKE SHOE CO. Oct. 3, 1963 [Oct. 3, 1962], No. 38970/63. Heading . B7N. [Also in Divisions G1 and H3] A railway car retarder comprising at least one pair of brake shoes 13 (Fig. 1) is operated by an electrical control system 18 which receives from a vibration-sensitive transducer 17A or 17B attached to the rail a signal whose frequency depends upon the speed with which a car wheel travels over a series of equally spaced discontinuities 16, such as notches, ridges or grooves in .the rail surface. An automatic switch circuit 21 selects the transducer giving the higher amplitude output and applies this to a compressor amplifier and clipper 22, 23 which supply to an adjustable filter 24 a varying frequency signal of substantially constant amplitude. The filter 24 may be set to have a frequency cut-off corresponding to any desired speed (e.g. 4 m.p.h.) and if the car is travelling faster than this the filter gives no brake inhibiting output to a driver amplifier 25. At the same time the output from the compressor amplifier also flows via the low and high-pass filters 28, 29 whose cut-off frequencies respectively determine the maximum and minimum car speeds to which the noise amplifier 31 will respond. An associated noise relay consequently operates the signal relay and control 26 and hence the brake relay 27 provided that a car is approaching within the limits of these speeds, e.g. 3 to 15 m.p.h. When the car is retarded to the required speed of, say, 4 m.p.h., the filter 24 provides a significant drive signal to the signal relay 26 and de-energizes the brake relay to allow the car to continue at that speed. The high pass filter 29 serves to remove the effect of extraneous low frequency signals arising for example from wheel flat spots, the car travelling over points &c. The low pass filter removes undesirable harmonics in the transducer signal, which could operate the brake with no car approaching, but it is shorted out by the signal relay 26, when this operates, in order to increase the holding signal supplied to the noise relay and thus to avoid relay chatter should the signal level momentarily drop. The automatic level' switch 21 also provides a safety output (91, Fig. 2, not shown) which operates the brake if a car travelling faster than 15 m.p.h., the limit of the low pass filter 28, should approach. In the slightly modified system of Fig. 6 (not shown), the adjustable filter 24 serves also as the low pass filter in the noise channel, and filter 28, Fig. 1, is dispensed with, the operation of this layout being otherwise substantially as above. |
