Patent GB-752057-A (GB)
Title: Automatic anti-skid braking control and lockout control apparatus
IPC: B64C25/46
Filed: 1954-10-26
Abstract: 752,057. Hydraulic brakes. GOODYEAR TIRE & RUBBER CO. Oct. 26, 1954 [April 20, 1954], No. 30832/54. Class 103 (1). In the event of failure of an automatic antiskid brake control mechanism for hydraulicallyoperated brakes, provision is made for hydraulic operation of the brakes under the control of the master cylinder without loss of pedal pressure. In the general arrangement shown in Fig. 1, an aircraft wheel 1 is braked by means of an hydraulic disc brake apparatus 5, 6, 7 under the control of a master cylinder 8 via pipes 10 and 12 through an automatic lock-out and pressure control valve 11. An automatic anti-skid brake control mechanism 21, 13, 14, 11 acts to relieve hydraulic pressure from the brake cylinders 7 in the event of wheel locking. In operation, when the aircraft touches down and the weight on the telescopic undercarriage 3, 4 is such that the switch 21 is closed, the solenoid-operated spool valve 25 in the automatic lock-out and pressure control valve 11 ceases to become energised and is moved to the position illustrated in Fig. 3; the pin 50 of the piston 51, however, being raised out of the groove 52 by virtue of the high pressure fluid supply from the reservoir 18, pipe 37, port 57 to the underside of the piston 51. Pressure may then be supplied by operation of the master cylinder 8 via pipe 10, port 26 in valve body 23 of valve 11, annular groove 28 in spool valve 25, port 27, pipe 12 to the brake cylinders 7. Should wheel locking take place, the sharp drop in voltage supplied by generator 13, will cause a relay in the control mechanism 14 to close, energizing the solenoid 17 and moving the spool valve 25 to the left closing the communication between pipes 10 and 12 and allowing the high-pressure fluid, which is normally supplied via pipe 37 and port 38 to the right-hand end of cylinder 30 to keep the piston 33 at the left-hand end of the cylinder 30, to be exhausted to a sump 20 via ports 36, 47, 45, 44 and pipe 59; the check valve 40 closing to prevent further entry of high-pressure supply. The piston 33 is thus allowed to move to the right under the pressure in the pipe 12 and the brake cylinders 7 to form a relief reservoir; the fluid escaping into the enlarged storage chamber 29 and the wheel brakes becoming momentarily released. As soon as wheel locking ceases, the solenoid 17 is disengaged and the spool valve 25 returns to the position illustrated in Fig. 3. This cycling action continues until the aircraft is brought to rest. Should, however, the high pressure side cease to function, piston 51 will fall under the action of the spring 54 and the pin 50 will engage the groove 52 and retain the spool valve in the position illustrated in Fig. 3; the check valve 40 closing and the piston 33 being kept at the left-hand end of the cylinder 30 by the high-pressure fluid trapped in the right-hand end of the cylinder 30. The brakes may thus be applied at the control of the operator through the master cylinder system even though the automatic anti-skid brake control mechanism is inoperative.