Patent GB-720178-A (GB)
Title: Improvements in or relating to fluid pressure control devices
IPC: B64C25/48
Filed: 1951-09-25
Abstract: 720,178. Braking aircraft. DUNLOP RUBBER CO., Ltd., and TREVASKIS, H. W. Aug. 21, 1952, [Sept. 25, 1951], No. 22359/51. Class 4. [Also in Groups XXIX, XXXI and XXXIV] A fluid pressure control device for controlling the braking of aircraft wheels and also the steering of aircraft on the ground by the differential braking of such wheels comprises a housing 1 containing two valve units, each comprising an operating chamber 3 connected to a brake operating mechanism, an exhaust chamber 2, inlet and exhaust valves 17, 27, spring means 24 to maintain the inlet valve closed against fluid pressure, and a plunger 28 movable in one direction to close the exhaust valve and then open the inlet valve and movable in the other direction by fluid pressure in the operating chamber 3 to close the inlet valve. Each plunger 28 is operated by one of pair of centrally pivoted levers 33, each bearing at one end on the plunger and at the other on one of a pair of operating cams 44, 45 angularly movable by lever arms 50 to which a braking load is applied through pairs of links 52, 53, the braking load exerted by each lever arm being varied differentially by the engagement with the links 53 of triangular members 62 movable differentially by a rocker shaft 70 rotated by a lever arm 71 linked to the rudder bar (not shown). The valve units are similar to those described in Specification 687,358, [Group XXIX]. The operating chambers 3 have outlets 5, and the exhaust chambers 2 connect with a common outlet 4. A single inlet 6 supplies pressure fluid to a filter chamber 13. From the latter two tubular inlet connections 7 project through holes 8 into the respective operating chambers 3. Each inlet connection 7 has a blind bore 14 with radial holes 16 opening into the filter chamber 13, and a radial hole 15 with which the inlet valve comprising a ball 17 co-operates. The ball 17 is retained in a cup-shaped member 18 carried in a cradle 19 which straddles the inlet connection 7 and is urged by a spring 24 against a tubular member 21 slidable in a wall 9. The member 21 is sealed by a ring 22 and is formed with a seat 23 for the exhaust valve 27. The cams 44, 45 are mounted in a cam holder 43 movable about a pivot 47 by the lever arm 50, which is loaded by a compression spring 54. The lever 33 normally rests on a peg 32. A fulcrum 34 engaging with a knife edge bearing 35 on a fulcrum beam 36 bears on the upper face of the lever 33. The fulcrum is held in position by a plate spring 37. The beam 36 bears on its upper face against an adjustable bearing 40 at one end and against an adjustable wedge 41 at the other end. The cams 44, 45 roll on convex surfaces at their adjacent ends and have knife edges at their remote ends, these engaging the lever 33 and a notch 48 in a support plate 49 respectively. The lever arms 50 are connected for simultaneous operation to a cable 57 by mechanism such as is described in Specification 507,162, such mechanism including the links 52 pivoted to the arms 50 and to elbow-shaped links 53, the shorter arms 55 of which have a common pivot on a slidable member 56 to which the cable 57 is attached. The longer arms 58 of the links 53 carry rollers 59 (Fig. 4) engaging inclined surfaces 61 in the triangular members 62 pivoted by trunnions 64 in bushes 65. Each triangular member also carries a roller 67 engaged by one of a pair of rocker arms 68, 69 on the shaft 70, so that as the arm 71 is turned from its central position the operative relation of the cable 57 to each of the lever arms 50 is changed and a different braking pressure in each of the two brake operating mechanisms results.