Patent GB-475222-A (GB)
Title: Improvement in landing gear for aircraft
IPC: B64C25/20
Filed: 1936-11-23
Abstract: 475,222. Retractable undercarriages for aircraft. SAULNIER, R. Nov. 23, 1936, No. 31997. Convention date, Nov. 23, 1935. Addition to 456,632. [Class 4] The retractable undercarriage described in Specification 456,632 is provided with means for ensuring extension of the gear in the event of failure of the fluid pressure system, with means for locking the folding strut in its extended position, and with a single manual control for effecting locking, unlocking, extension and retraction. The means for ensuring extension may comprise elastic cables 8, 9 fixed to the jack head at 10, 11 respectively at their inner ends and to fixed points on the halves of the folding strut at their outer ends. The lines of action of the cables are prevented from passing through points of articulation O when the strut is folded by the presence of bracings 14, 15. In another form, Fig. 3, a spring compression strut 17, 18 pivoted at one end on a fixed part of the aircraft 19 acts at its other end on the upper half of the folding leg. The locking device comprises in one form, Fig. 5, an element 21 formed with jaws adapted in the extended position of the strut to embrace lugs 22 on the half struts. Element 21 is slidably mounted along the axis of the jack and is urged to locking position by spring 23. The outer sides of the jaws are bevelled in such manner that as the strut straightens out the lugs 22 on striking the element 21 will force it outwardly against the pressure of spring 23, thus ensuring automatic locking. Unlocking is effected by a fluid pressure servomotor comprising a cylinder 24 and a piston 25 of which the rod engages one arm of a bell-crank lever 28, the other arm of which acts through a link 29 on element 21. In a modification, the servo cylinder is formed in the end of the jack, Fig. 9, and contains a piston 34 acting directly on element 21 through a key 32. In this form an external spring 23<1> is fitted, but an internal spring may be used compressed between the cylinder head and the outer face of the piston 34. The control device comprises a handle 37, Fig. 10, movable in a gate 39 about axes X<1>, X<2>. Movement about axis X2 is communicated by a link 40 to a piston valve 42 controlling the supply of pressure fluid to the retracting jack. Movement about axis X<1> is transmitted through link 41 and lever 47 to plunger 48 of a valve 43 controlling supply of pressure fluid to the servo cylinder actuating the locking element 21. The arrangement of the gate is such that before movement of lever 37 about axis X<2> for retracting or extending the landing gear, valve 43 is actuated to produce outward movement of locking element 21. Completion of movement of lever 37 in either direction brings valve 43 back into " locking " position. A gate such as shown in Fig. 15 may be used providing an intermediate position in which the piston of valve 42 is in the position of Fig. 12 in which fluid flow to or from either end of the jack cylinder is prevented. The knob of lever 37 is in the form of a wheel in order to identify the lever as that controlling the undercarriage.