Patent GB-997281-A (GB)
Title: Improvements in undercarriage assemblies for aircraft or for other vehicles
Inventor: DOWTY GEORGE HERBERT
IPC: B64C25/50
Filed: 1960-09-17
Abstract: 997,281. Fluid-pressure servomotor systems. DOWTY TECHNICAL DEVELOPMENTS Ltd. Sept.15, 1961 [Sept. 17,1960; Oct. 1,1960; Dec. 24, 1960], Nos. 32066/60, 33781/60 and 44368/60. Heading G3P. [Also in Division B7] A steerable wheel mounting for an aircraft or a road vehicle comprises a rotary "actuator", having a vane or vanes movable by fluid pressure about an axis, which is secured coaxially with a suspension device incorporating resilient support means interposed between the ground wheels and the vehicle or aircraft. As shown in Fig. 1, a retractable tubular member 2 is pivoted at 3 to an aircraft and has rotatably mounted therein a member 4 pivoted at 6 to a lever 7 by which the ground wheels are supported at 8, a liquid spring device being connected to the lever 7 at 10 and to the member 4 at 11. The member 4 is rotatable in bearings 52 and 51 (Fig. 2) and a thrust bearing 26 is provided. A spindle 19 is fixed to the member 2 and extends through the rotary actuator 15 which comprises a thick walled cylinder 16 to which is secured a pair of vanes 17 and 18 in sealing contact with the spindle 19 from which extend vanes 21 and 22 making sealing contact with the cylinder 16 whereby four working spaces are defined to which pressure liquid may be supplied or exahusted in opposite pairs for steering purposes through the passages 48 and 49, Fig. 3, extending through the spindle 19. The rotary actuator 15 is attached to a member 27 incorporating cylinders 33 housing pistons 32, pressure fluid being applicable to either end of which to move the pistons against which bear pins 28 which, in the retracted position, allow free castoring movement of the ground wheels and which, in the protracted position, extend into apertures 29 in a plate 31 secured to the member 4 whereby a steering movement may be transmitted to the wheels. A pair of coaxial tubes 43 and 44 are connected to the members 27 and 31 respectively and to a pair of position responsive devices 45 and 46 which control a valve, not shown, admitting pressure fluid through the passages 48 and 49 so that when it is required to steer the groundwheels relative movement between the members 37 and 21 is produced to bring the holes 29 into register with the pins 28. As the pins enter the holes 29 they encounter and move the ends of bell crank levers 37 pivoted to the plate 21 and connected at their other ends to a spindle 29 which extends through the tubes 43 and 44 and is connected through a lever 41 to a switch 42 which is actuated to bring the fluid control valve into a steering position. In a modification, Fig.4, of the embodiment of Fig. 1, the rotary activator 88 is interposed between the spindle member 19 and a cylindrical member 83, the suspension unit being carried by a rotary member 82 rotatable in bearing sleeves 86, a thrust race 87 being provided, relative rotation between the members 82 and 83 providing a castering action for ground manoeuvering and the relative rotation being prevented to allow controlled steering by the insertion of plungers 98 carried by the member 82 into holes 102 in a flange 102 at the lower end of member 83, the plungers being urged into their engaged position by springs 99 and being withdrawn therefrom and held in a disengaged position by tool 108 manipulated by a member of the ground crew. The steering control includes a three way valve for supplying fluid to one or other of the pairs of working spaces in the actuator or for cutting off the supply and is actuated in response to the differential mechanical input movement in the pilot's cabin supplied to a differential gear and a mechanical drive from the casing 83. The first Provisional Specification describes an actuator having a single vane. Specification 935,769 is referred to.