GB483467A - Improvements in brake control mechanism for aircraft - Google Patents

Abstract

483,467. Aircraft wheel brakes; hydraulic accumulators; valves. BENDIX AVIATION CORPORATION. Sept. 17, 1936, No. 25322. Convention date, Oct. 16, 1935. [Class 4] [Also in Group XXIX] A hydraulic braking system for aeroplanes comprises a pair of master cylinders each connected separately with a wheel brake cylinder, means for operating the master cylinders independently or concurrently to apply and relieve pressure in the brake cylinders and means for maintaining a predetermined pressure in the wheel cylinders which is independent of the position of the pistons in the master cylinders and of effects of temperature change. The system comprises master cylinders 426, 428, Fig. 2, each associated with a rudder pedal and having pistons 430, 432, respectively. The cylinders are connected to a reservoir 450 through ports 454 uncovered at the bottom of the stroke and through non-return valves 446 in the cylinder heads and are also connected with brake cylinders 440, 442 respectively through a valve member 438. Valve member 438 comprises two parallel cylinders to one of which, 468, are connected conduits 434, 436 connected to the master cylinders and conduits 441, 443 leading to the brake cylinders. Between the associated pairs of conduits are arranged check valves 470, 472 which in the position of Fig. 2 permit fluid to pass from the master cylinders to the brakes, but not to return but may be held off their seats as shown in Fig. 3 by rotation of a cam 478 bearing on pistons 480, 482 which in turn contact with the stems of the check valves to permit free flow in either direction. The second cylinder 469 is connected by conduits 512, 514 to a pressure reservoir 510 and by conduits 490, 492 to conduits 441, 433. A pair of check valves 494, 496 controlled by a cam 508 are arranged either to place the reservoir in free communication with the brake cylinders, Fig. 2, or to isolate it from the system, Fig. 3. The cams 478, 508 are arranged on a common manually-rotatable shaft. The arrangement is such that when the cam shaft is in the position of Fig. 3 the brakes may be independently or conjointly operated whilst in the position shown in Fig. 2 operation of the pistons in the master cylinders causes the brakes to be applied and to be maintained applied under a fluid pressure determined by the pre-setting of the spring of pressure reservoir 510 until such time as the valve control is moved. The master cylinder are pivotally carried by brackets welded to a cross shaft 458, Fig. 5, to which are welded brackets carrying swinging rudder stirrups and are operated by piston rods connected to levers formed on pedals pivotally mounted on the lower transverse member of the stirrup. The pressure accumulator 510 may be of the spring-loaded piston type shown diagrammatically in Fig. 2 or as shown in Fig. 7 comprise a piston 632 loaded by a piston 642 working in a cylinder 638 charged with air under pressure. In this form piston rod 644 bears on the top of the piston 632 and the travel of the latter is limited by a stop formed on its bottom surface. The reservoir 450, Fig. 11, is provided with a vented cover 552 having ports 554 and an annular sealing ring 556. A spring snap disc 558 formed with a central opening 560 is arranged to seal the cover when the aircraft is inverted and to snap back to the position shown when fluid is withdrawn from the reservoir.