Patent GB-792630-A (GB)
Abstract: 792,630. Gyroscopic apparatus. BOEING AIRPLANE CO. Dec. 12, 1955 [Dec. 13, 1954], No. 35644/55. Class 97(3) [Also in Group XXXVIII] In a rate-of-turn gyro, a mass of liquid is channelled in a casing mounted on the base in a continuous path about an axis parallel to the gimbal axis, and is coupled to the gimbal assembly, in such a manner that the inertial torque of the liquid mass acts compensatively against the inertia torque of the gimbal assembly, when the instrument is accelerated about the gimbal axis, by members attached to the gimbal assembly and moving in passages formed in the casing and forming part of the liquid path so as to force liquid round the path by precessional deflection of the gimbal. The 'principles are illustrated in Fig. 1, where the gyroscope rotor 12a is mounted in a gimbal 12b carried in journal blocks 10a, 10b on the base 10. When the base 10 turns about its axis Ar, the rotor, which spins about axis As, precesses about its axis Ag against action of a spring 14. The deflection, which is a measure of the rate of turn of base 10, may be translated into an electrical signal as by a potentiometer 16a and its associated electrical circuit. A cylinder 24 is journalled in an extension of block 10b for rotation about its axis Ac which is parallel to, or co-incident with. the axis Ag, and is connected to the gimbal shaft 12c by gears 26, 28. If the moments of inertia of the cylinder and gimbal (including parts rotating therewith) are in the same ratio as the diameters of the gears 26, 28, the effect of angular acceleration about the axis Ag on the gimbal will be compensated by the effect on the cylinder 24. The effect of the cylinder on the natural frequency of the gimbal system depends on tne square of the gear ratio, and it is thus possible to choose a moment of inertia for the cylinder 24, and a ratio for the gears 26, 28, which results in a chosen natural frequency and at the same time gives compensation for the effect of angular acceler-' ation about the axis Ag. According to the invention compensation is effected by means of a mass of liquid, instead of a solid mass, as shown in Fig. 2. The gimbal assembly consists of a hollow cylinder 28a, enclosing the gyro rotor 30 and pivoted in a casing cylinder 28a is kept in central position by preferably pre-loaded tension springs 34. The liquid mass news in a path 36 having upper and lower branches 36a, 36b and chambers 36c into which project vanes 32 on the cylinder 28. As shown, the upper and lower branches cross so that movement of the liquid opposes that of cylinder 28, when subjected to angular accelerating about axis Ag. Precessional movement of the rotor causes cylinder 28 to move, and so causes a flow of liquid in path 36. This movement moves a float 38 in a tube 36b<SP>1</SP>. The float is non-magnet and is centred by springs 46. It carries a ferromagnetic sleeve 40 moving within coils 42, 44 by which an electrical signal, which measures the rate of turn, can be derived. The float may be by-passed by a pipe 36b<SP>11</SP>, flow through which is varied by means of a throttle valve 48 to vary the natural frequency of the gimbal system. Alternatively the diameter of the pipe is chosen for a desired frequency. or the float 38 is made of such diameter that sufficient liquid flows past it to give the same effect as a by-pass pipe..