Patent GB-582083-A (GB)
Title: Improvements in and relating to the steering devices of air or water craft, torpedoes and the like
IPC: F42B19/01
Filed: 1941-07-23
Abstract: 582,083. Fluid-pressure servomotor-control systems. WILSON, W.G. July 23, 1941, No. 6641. [Class 135] An automatic servomotor mechanism for checking and rectifying the deviation off course of a craft, has a mechanical follow-up mechanism interposed between a power device operating a rudder and the controlling device, said mechanism comprising a damping element and/or an inertia element coupled through resilient or yielding means with the rest of the follow-up train. As shown in Fig. 1, the tiller lever 39 is actuated by a pair of bellows 38, 38a connected by pipes 37, 37a with nozzles 35, 35a supplied with compressed air delivered through nozzles 34, 34a under the control of a partcylindrical or part-spherical intercepting baffle 33. This baffle is carried by a lever 20 pivoted at 30 and provided with a forked end engaging a pin 32 stabilized in space by a gyroscope 31. A followback train of links and levers and delay action devices x, xl, x<2> connect the pivot 30 with an arm 41 on the tiller lever. The device x comprises a segmental plate 79 pivoted at 80 provided with a segmental rack 81 meshing with a pinion 82 turning on a fixed axis and connected with a dashpot or a damping device consisting of a drum 83a partly filled with liquid and provided with internal radial baffles and external air-brake vanes. A lever 106 mounted on a pivot 107 is coupled to the plate 79 by springs 109, 109a and to the tiller arm 41 by a link 75, bell-crank 74 and link 72. The device x<1> comprises a segmental plate 91 pivoted at 92 and connected by a link 90 with the plate 79. A lever 93 mounted on the pivot 92 is connected by a link 94, bellcrank 76 and link 78 with the fulcrum 30 of the lever 20. A pinion 82 carried by the lever 93 engages a segmental rack 81 on the plate 91 and is connected to a damping device 84 similar to the device 83a. The device x<2> forms a centring device and comprises a pair of pivoted arms 95, 95a connected by a spring 99 and embracing a fixed stop and a projection 98 on the link 94. If'the craft has a drifting movement to starboard in the direction of the arrow 100, the baffle 33 is moved clockwise, admitting air to the bellows 38a to turn the rudder to port. At the same time the arm 41 imparts a movement of the link 101 towards the left which tensions the spring 109a, which tension causes the plate 79 to rotate slowly in an anticlockwise direction under the control of the damping device. The movement of the plate 79 causes the link 90 to move to the left rotating the plate 91 in an anticlockwise direction, this movement stresses the spring 99 and is transmitted without any time lag to the fulcrum 30. This movement of the 'fulcrum moves the baffle in an anticlockwise direction, stopping the passage of further air to the bellows. This movement is, however, slowed down by the rotation of the damping device 84 under the action of the spring 99. The action of the device x<1> is slow compared with that of the device x. This action is repeated until the craft is brought back to its course although it may not be on the same line. In a modification of the device x<1>, the pinion 82 is integral with a large pinion engaging a small pinion integral with the damping device. In a modification, a device y, Fig. 6, which replaces the device x, comprises an inverted T-shaped lever 106 pivoted at 107 to a segmental plate 79 pivoted at 80. The shorter arms of the lever 106 are connected by springs 109, 109a to the plate 79, while the longer arm is connected to the rods 75, 90. A segmental rack on the plate 79 engages a pinion 82 on the damping device 84. The pivot 108 may be moved into one of a series of holes or adjusted in a slot 101 in the lever. The device y<1> is similar to the device y except that it has a different period of oscillation. A . single device may replace these two devices. The device y<2> comprises a secondary relay whereby the movement of the rod 90a is transmitted substantially without lag, this being followed by a relatively slow reverse movement so that the interceptor valve is first closed and then opened slowly and possibly with a continuing movement to give a permanent helm of a constant or variable degree. The rod 90a is pivoted to a segmental plate 112 pivoted at 114 to bell-crank lever 113, 115 pivoted at 116. The arm 113 is connected to the gyroscopecontrolled interceptor baffle while the other arm is bent at right angles to form an interceptor baffle co-operating with a pair of nozzles 124. When the baffle is displaced, a rotary impeller drum 119 is rotated in one direction or the other, thereby rotating a pinion 120 engaging a toothed segment on the plate 112. In a modification, an epicyclic gear is interposed between the impeller drum and the segment 112 and the annulus is fitted with a damping device and is connected to the impeller drum by a torsional spring. In another arrangement, two rotary impeller devices z, z<1>, Fig. 8, replace the device y<2>. The device z is controlled in a similar manner to the device y<2>, while the baffle of the device z<1> is actuated by a toothed segment 137 engaging a pinion 120 rotated by the impeller of the device z. This not only keeps the craft on course, but restores it to its original line. The invention may be applied to the pitching movement of a projectile, in which case an additional set of bellows and associated mechanism is fitted. Additional controls may be provided by radio transmission or by the slipstream. According to the Provisional Specification, a damped pendulum is used to maintain the craft on an even keel. This pendulum actuates an interrupter valve controlling another set of bellows having a follow-back connection to the interrupter valve similar to that described above. The movement of these bellows may be combined with that of the bellows operating the rudder or elevator so that complete control may be obtained from one set of control surfaces. The pendulum weight is supported at two points, one just above its centre of mass, the other on a link which is of the same length as the pendulum. The weight preferably comprises a mass of liquid housed in a tube divided into a number of cells varying in length and having restricted communication with one another. The cells are each approximately three-quarters the length of the pendulum and the tube is filled to above two-thirds its capacity with a suitable liquid. The splashing of the liquid makes a considerable damping- force without introducing a zero error. Specifications 579,807, [Group XXI], and 579,816 are referred to in the Provisional and Complete Specifications respectively.