Patent GB-1438613-A (GB)
Title: Electrical control device for controlling the operation of  vehicle brakes
IPC: B60T13/66
Filed: 1974-02-08
Abstract: 1438613 Electrical control of fluid pressure braking systems KNORR-BREMSE GmbH 8 Feb 1974 [10 Feb 1973] 05973/74 Heading F2F The (pneumatic or hydraulic) braking pressure in a brake cylinder 33 on a rail vehicle is controlled by means of a normally closed solenoid valve 31 and a normally open solenoid valve 34 connected respectively to an electrical brake apply line 28 and an electrical brake release line 29 to be responsive to control signals thereon: the control signals are derived from an electrical control device comprising a voltage divider 4 operable by a manual lever 10 and connected by a line 12 to one input I of a voltage comparison device 15 whose other input II is connected to a circuit comprising a capacitor 17 with an adjustable charging resistor 16 and an adjustable discharging resistor 21, whereby comparison of the signals at the inputs I, II produces a signal on a line 22 to control the activations of lines 28, 29. As shown, the line 22 is connected to switch amplifiers 7, 8 which respectively connect with output lines 24, 23. The output line 23 leads to a switch contact 3 and to the excitation coil of a relay 20 and the output line 24 leads to the excitation coil of a relay 6. The relay 6 on excitation closes switch contacts 5, 25 and the relay 20 on excitation closes a switch contact 19 and opens a contact 26. The contact 25 is connected between a voltage source 27 and the apply line 28 while the contact 26 is connected between source 27 and the release line 29. To obtain brake release, the brake lever 10 is in the release position L and the switch contact 3 is closed by a coupling 11 and the top 9 of the divider 4 as well as line 12 and input I are at earth potential. The switch contact 19 is closed and the switch contact 26 is opened by excitation of relay 20 consequent upon the closure of switch contact 3 and earth potential prevails on both sides of capacitor 17. On both inputs I, II there is earth potential, the line 22 conducts no signal and output lines 23, 24 are held disconnected from a line 2 connected to a voltage relay source 1. Relay 6 is not excited, contacts 5, 25 are thus open and with both contacts 25, 26 open lines 28, 29 are dead, valve 34 is open to connect cylinder 33 to atmosphere via a nozzle 35 and valve 31 is closed. To carry out braking the lever 10 is moved in the range B whereby contact 3 is opened to de-energize relay 20 to open contact 19 and close contact 26. Release line 29 is connected to source 27 to energize valve 34 to separate brake cylinder 33 from atmosphere. The now displaced top 9 causes a more negative potential on input I input II being instantaneously at earth potential whereby a negative output signal on line 22 closes switch amplifier 7. Hence relay 6 is energized to close contacts 5, 25 and apply line 28 is energized to open valve 31 whereby compressed air flows from a storage vessel 30 via a nozzle 32 to cylinder 33 to actuate the brakes, the nozzle 32 determining the period of pressure rise in cylinder 33. During this period the capacitor 17 is charged up through contact 5 and resistor 16 from source 1 whereby the potential on II becomes more negative and by an appropriate setting of resistor 16 at the point of time at which the pressure level in cylinder 33 conforms to the position of lever 10 the potential at II becomes equal to the potential at I, and the device 15 interrupts signal transmission to line 22 and contacts 5, 25 are opened to de-energize the apply line 28. For increasing brake actuation the lever 10 is moved away from L to increase the negative voltage at input I. For decreasing brake actuation the lever 10 is moved towards L to decrease the negative voltage at I which causes device 15 to direct a positive signal to line 22. This actuates amplifier 1 to excite relay 20 to close switch 19, open switch 26 and de-energize line 29 whereby valve 34 is opened. Capacitor 17 discharges through resistor 21 and switch contact 19 until the potentials at I, II again become equal. The device 15 may be a comparator or a polarized relay, and a polarized relay may also replace the switch amplifiers 7, 8. By exchanging the switch amplifiers 7, 8 the polarity of source 1 may be reversed.