Patent GB-560318-A (GB)
Title: Improvements in or relating to means for operating aircraft control surfaces and thelike
IPC: B64C25/22
Filed: 1942-05-22
Abstract: 560,318. Controlling aircraft. LING, E. M. May 22, 1942, No. 6977. [Class 4] Control apparatus for operating aircraft elevators, rudders, ailerons, retractable undercarriages or landing flaps through hydraulic servomotors comprises a lever, movable in two planes at right angles and rotatable about its longitudinal axis, mounted in a frame or casing, the lever being connected to three shafts for controlling three different elements by connections each comprising a universal joint situated in or at the control lever. The frame comprises longitudinal and cross members 22, 24, 26, 27 and 28 a vertical shaft 30 being journalled in .a bearing in the cross.-piece 28 and connected to a forked member 32. A member 37 has upturned lugs 38, 39, the lugs 39 being connected by normally longitudinal pivots to the upper end of the forked member 32, and the lugs 38 supporting a pillar 36 upon a normally transverse pivot. The pillar 36 carries a control lever 34 fitted with a transverse handle 90. A transverse shaft 45 supported in brackets 48, 50 has arms 82 connected to the pillar 36 by a ballended rod 84. The joint at the pillar can be tightened by a screw 89 within the lever 34. A longitudinal shaft 46, journalled in brackets 52, 54, has an arm 62 connected by a ball-ended rod 64 to a member 66 carried by the member 37 and normally in alignment with the pillar 36. Levers 56, 60, 44 mounted respectively on the shafts 45, 46 and the member 32, may be connected to the elevator, ailerons and rudder, but when used with the power mechanism described they are not so connected. The whole of the mechanism except the levers 56 and 60 and the ends of the lever 44 may be enclosed in a casing 29. Hydraulic power mechanism used to actuate the control elements, comprises selector units, for distributing the pressure fluid to double acting jacks, mounted on the assembly and actuated from the three control shafts 30, 45, 46, the connection for actuating the elevator being shown in Fig. 1. For this purpose the arms 82 on the shaft 45 are connected by a link 200 to a lever 202 on a shaft 206, a second lever 204 being connected by a link 212 to a rocking lever 214 carrying rollers 220, 222 co-operating with heads 126, 130 on rods 132, 136 forming part of the valve mechanism shown in Fig. 3. The rods 132, 136 are connected to balanced piston valves 148, 160 working in chambers connected by the ports shown to a central chamber 122, and to two parallel passages 104, 106 connected at the left of the apparatus to opposite ends of the jack cylinder, not shown. Another piston valve 154 works in the chamber 122 and is connected to a rod having a head 128 engaging behind the heads 126, 130 so as to be moved inwards when either of the two outer valves are moved inwards. Normally the valve 154 places a port 180, connected to the delivery side of a pump, 'into communication with a port 184 connected to the intake side of the pump or to the pump reservoir so as to permit free circulation. Upon depression of either rod 132, 136 one or other of the passages 104, 103 is put into communication with the port 180 and, on account of the simultaneous displacement of the valve 154, the other passage is put into communication with a port 186, in the central chamber, which is connected to the pump intake or reservoir. Two non-return valves 262, 264 are provided in the passages leading to the jack so as to form a hydraulic lock for the .control surface, and to permit the flow of pressure fluid to and from the jack during its actuation, the valve on the exhaust side is opened by one of two rods 272, 274 movable by cams 246, 248 connected to a piston 244 in a transverse passage connecting the two main passages 104, 106. The piston 244 is normally centred by springs 254, 256 but is displaced by the pressure fluid in the appropriate direction. The supply of pressure fluid is cut off and the passage 104 or 106 connected to the pump reservoir at any desired point in the movement of the control lever 34 by a separate cut-off valve interposed between the pump and the port 180 and actuated by a flexible connection from a thumb-lever on the control lever 34. As applied to a landing flap a pressure relief valve 296 in a passage to one side of but communicating with the passages 104 and 106 enables the landing flap to yield under excessive load in one direction but when the device is applied to the elevator, aileron or rudder this valve is rendered inoperative by screwing down a plug 302 connected to a cylindrical plug 300 to compress the valve spring. Two oppositely; directed relief valves 280, 282 prevent damage to the apparatus due to excessive pressure in either passage 104 or 106.