Patent GB-447610-A (GB)
Title: Improvements in or relating to retractable undercarriages for aircraft
IPC: B64C25/10
Filed: 1934-10-18
Abstract: 447,610. Retractable undercarriages for aircraft. FAIREY AVIATION CO., Ltd., Cranford Lane, Hayes, and ORDIDGE, F. H., Soircroft, Croft Gardens, Ruislip, both in Middlesex. Oct. 18, 1934, Nos. 29839/34 and 9031/35. [Class 4] In retractable undercarriages for aircraft of the kind in which a landing wheel is carried by a leg and a strut or radius rod, one of these members being pivoted on a fixed part of the aircraft and the other being pivotally attached to a block movably secured on a guide, and so arranged as to be substantially perpendicular to the guide when the undercarriage is fully extended, the guide is constituted by a rack and the block is provided with a pawl co-operating with the rack in such manner that on lowering of the undercarriage the pawl rides freely over the rack whilst reverse movement is normally prevented by the engagement of the pawl with the teeth of the rack, means being provided for disengaging the pawl from the rack and moving the block over the guide to retract the undercarriage. In one form, Figs. 1A, 1B, 1D, a wheel 1 is mounted between two shockabsorbing legs of which cylinders 3, 3<1> are cross-braced and pivoted on a fixed part of the aircraft structure. On each cylinder is pivoted one end of a strut 10 or 10<1> the other ends of which are pivoted on blocks 11 slidable upon a pair of parallel guides 13 each provided with a rack 22. Each block 11 is provided with a pawl 23 spring urged to engage rack 22. Retraction is effected by a cable 24 connected with a lever 25 attached to pawl 23 and adapted when pulled, first to disengage the pawl and then to slide block 11 up the guide. The undercarriage may be lowered by gravity or by a second cable 26. Figs. 2A, 2B, show a leg 2 comprising a single cylinder 3 stayed against transverse loads by struts 8, 9 pivotally attached at their upper ends to a member 4 secured between upper and lower booms 5, 6 of a wing spar. A strut 10 pivotally attached to cylinder 3 is secured at its upper end to a cross-head 11, Fig. 2D, mounted upon wheels or rollers 12 movable in a guide comprising two parallel rods 13 and secured between spar boom 5 and a rigid bracket 28. Crosshead 11 is moved on guide rods 13 by two hydraulic cylinders 14 movable over fixed pistons 15 of which the piston rods are arranged parallel to guides 13. Alternatively the cylinders may be pivotally attached to a fixed part of the wing structure and the piston rods pivoted on crosshead 11 or the wheel may be retracted in a clockwise direction, the strut 10 in this case being forward of the leg and guide 13 extending upwardly and rearwardly. Figs. 4A, 4B show a modification in which the struts 8, 9, 10 of Figs. 2A, 2B are replaced by two rearwardly extending divergent struts 10, 10<1> each pivoted at its upper end to a block 11, or 11<1> slidably mounted on a single guide rod 13 or 13<1>. The guides may be inclined inwardly or outwardly as well as upwardly as indicated in dotted lines in Fig. 4B. Alternatively curved guides may be employed in which case the struts 10 are arranged to be substantially perpendicular to the tangent to the guide at the point of attachment of the guide block when in the lowered position. Figs. 5A and 5B show such an arrangement, a curved guide 13 which may be tilted as indicated at 13<1> being employed. In a further form the cylinder 3 of an oleo strut is pivotally attached to a block movable along a fixed guide and the wheel-carrying axle is pivotally attached to a fixed part of the aircraft. In a further modification, Fig. 7B, cylinder 3 of leg 2 is pivoted on the wing structure about a transverse axis as also are a pair of lateral bracing struts 8, 9 and is retracted by a strut 10 pivotally attached at its lower end to a collar 20 freely rotatable on the bottom of cylinder 3 and pin jointed at its upper end to a block 11 movable along a fixed transverse guide 13. The invention may be applied to an undercarriage swingable about a fore-and-aft axis as shown in Fig. 9A. When the wheel-carrying leg is pivoted about a transverse axis means may be provided for causing the wheel to turn into a horizontal position during retraction. Such means may be of the kind described in Specification 420,120, or as shown in Fig. 10B, in which a cylinder 3 is pivoted to the wing structure in such manner as to be rotatable about its own axis, the inner member of the leg being splined to the cylinder, and in which the retracting strut 10 is pivoted at its lower end to cylinder 3 and pin jointed at its upper end to a block 11 moving on a horizontal transverse guide. A lateral bracing strut 8 is pivotally attached at its lower end to a collar 21 freely rotatable on cylinder 3. The means employed for moving the guide along the block in any form of the invention may comprise cables, chains, an electric motor, a hydraulic or a pneumatic ram and where a ram is used this may serve as a dashpot to control the speed of lowering. The invention may be applied to float undercarriages and to tail wheels.