Patent GB-415097-A (GB)
Title: Improvements in or relating to brakes for aircraft-wheels
IPC: B64C25/48
Filed: 1933-02-15
Abstract: 415,097. Aircraft wheel - brakes. INDIA RUBBER, GUTTA PERCHA, & TELEGRAPH WORKS CO., Ltd., Aldwych House, Aldwych, and TARRIS, F. J., c/o India Rubber, Gutta Percha, & Telegraph Works, Silvertown, both in London. Feb. 15, 1933, Nos. 4692, 10785, and 29486. [Class 4.] In an aircraft which may be steered on the ground by differential braking of the wheelbrakes, a main control device is operated by the pilot to admit pressure to a pair of auxiliary controls on each brake set, each control having an operative connection with the rudder bar in the form of an extensible coupling member adapted to establish or disestablish the connection at will. Each auxiliary device is connected to serve only one brake set and comprises means to release the braking pressure in that brake set substantially without increasing the pressure in the opposite brake set, the actuating element for the releasing means operatively connecting or being capable of operatively connecting the auxiliary device with the rudder bar. As shown in Fig. 1, a main control valve 8 having a locking device 9 is operated by the pilot to admit fluid pressure from a reservoir 106 to auxiliary control devices 11, 12, by means of pipes 10, 13, 14 and at the same time admit pressure to the two brake sets through pipes 15, 16. The auxiliary devices 11, 12 are adapted to be operated directly by the rudder bar to release the pressure in one of the brakes. Should the rudder bar be out of its neutral position in landing, an equal initial application of the brakes is assured since the actuator piston 41, Fig. 4, of the auxiliary control is unable to attain a fully extended position to operate the auxiliary control valve 72. The main and auxiliary controls may be combined in one casting, the main control being operated by a Bowden wire 22, Fig. 3, connected to a stirrup lever 24 which operates sleeve 25 to compress spring 27 and close piston 28 on its seat 30 and by a projection 32 open valve 21 to admit pressure from a pipe 20 to ducts 34, 35, 36, the latter being shown in Fig. 4. Pressure in duct 36 passes to the actuator 41 of the auxiliary control and directly to the brake pipe 48 through a normally open valve 46. The actuator 41 is attached to a rubber sleeve 43 secured at the open end by a flange 42 and a piston 49 controlling the pressure fluid to one set of brakes houses a valve 72 compressed by a spring 47 which is regulated by the pressure of a spring 409 surrounding the piston 49. The valve 72 is similar to the valve 28, Fig. 3, and in its normal position to the right maintains the valve 46 open. A pivoted link 50 is connected at one end to piston 49 and at the other by a toggle 53, 54 to the actuator 41. The toggle link 54 is provided with a buffer 60 adapted to contact with a buffer 58 on a pivoted member 56 operated by the rudder bar. A similar buffer is adapted to contact with a buffer on the other auxiliary brake cylinder. In the position shown in Fig. 3, the spring 27 is compressed by the sleeve 25 and the valve 29 closed, the extension 31 contacting with extension 32 to open valve 21 and admit fluid pressure to conduits 34, 35, 36. The actuator 41, Fig. 4, is forced outwardly and piston 49 remains unaffected and maintains valve 46 open to admit pressure to the brakes through pipe 48. When the rudder is turned buffers 58, 60 contact and toggle 54, 53 maintained in alignment whereby actuator 41 is forced inwardly and piston 49 drawn outwardly. This releases the pressure on spring 47 and allows valve 72 to move outwardly and permit valve 46 to close. Air pressure from the brakes then leaks off through flutes 61 in valve 72 to exhaust through orifices 62. If the rudder bar is out of its central position when landing both brakes are equally applied, the differential action being applied after the rudder has been centralized. The pistons 41 may be urged by a spring to collapse the toggle, the spring being opposed by air pressure applied by operation of the main control so that the collapsed position is assumed as soon as the brakes are released. In a modification the main control supplies pressure to the actuator 41 and the toggle is repaced by a link which acts on lever 50 to withdraw the plunger 49, a separate pressure connection to the brakes being opened by movement of the valve 72 against the pressure of spring 47. In this case spring 409 is dispensed with and the valve 46 is maintained closed by reservoir pressure. When the main control moves actuator 41 outwardly the spring 47 is compressed, thereby closing valve 72 and opening valve 46 to admit pressure to the brakes until the pressure in the brake system is sufficient to act on the face of valve 72 to dislodge it from its seat so that air escapes at 62. In this manner the brake pressure is balanced against the compression of the spring 47. The second Provisional Specification describes differential braking by liquid or mechanical means in apparatus similar to that described in Specification 397,497, whereby the operation of one or the other of the auxiliary control devices releases the braking pressure on one side without substantial increase on the opposite side.