Patent GB-755432-A (GB)
Title: Improvements in hydraulic servo-controls for manual and automatic piloting of aircraft
IPC: F15B11/08
Filed: 1954-02-04
Abstract: 755,432. Fluid-pressure servomotor-control systems. SOC D'APPLICATIONS DES MACHINES MOTRICES. Feb. 4, 1954 [March 30, 1953], No. 3349/54. Class 135. In a hydraulic servo system for the hand control and the automatic piloting of aircraft in which the control surface is operated by a single jack the distributer of which is controlled directly and selectively by the automatic control and the manual control, means are provided, when one of the controls is effective, for making the other control take up or position corresponding to the position of the control surface effected by the effective control. In Figs. 1, 1<SP>1</SP>, the jack piston is operative in a body 1 under the control of a rotary cylindrical or other suitable distributer 8 and has a piston rod 2 linked at one end to a floating lever 4 to which the hand control is applied and at the other end to a floating lever 6 to which the electric motor 30 of the automatic pilot is connected through gearing 29 and a link 28. The control surface is coupled to the pivot 3 or if it is desired to give the pilot a sense of " feel " of the control to a pivot 7. The arm 9 of the distributer 8 is linked to a lever 19 the ends of which are connected to further levers 21, 25 in turn connected by links 22, 26 to the floating levers 4, 6, respectively. The levers 21, 25 have re-entrant or cup-shaped parts 31, 35 engaged by the ends of spring- loaded pistons 32, 36 to lock the levers 21, 25 against rotation. If the manual control is effective the lever 25 is locked and if the automatic pilot is effective the lever 21 is locked. The pistons 32, 36 are held out of locking engagement by oil under pressure supplied through pipes 15, 16 controlled by a twoposition electromagrietically-operated distributer 14 so that normally one pipe is connected to a pressure pipe 12 and the other is connected to an exhaust pipe 17. The pipe 12 itself may be connected with a pressure supply pipe 10 or with exhaust under the control of an electromagnetically operated valve 11. As shown, the hand control is effective and the lever 25 is locked. During this time the motor 30 is passive but still follows the movements of the rod 2 and therefore those of the control surface. If the pressure supply fails or the pipe 12 is connected to exhaust, both levers 21, 25 are locked but direct manual actuation by the lever 4 is possible provided the jack is fitted with a suitable by-pass valve. The piston rod 2 and its pivot 3 may be fixed and the jack body coupled to the control surface. In this case the motor 30 and its transmission follows the movements of the jack body. The mechanical linkage between the piston rod 2, the lever 25, and the motor 30 may be replaced by electrical means. Thus the piston rod 2 and the lever 25 may operate potentiometer sliders the signals of which are fed to the automatic pilot for controlling the motor 30. In another arrangement, the piston rod is geared to a selsyn to register the output movement which is compared with the input movement registered by another selsyn in the automatic pilot and any difference is applied to a differential selsyn controlling the motor 30. Specification 731,881 is referred to.