Patent GB-730783-A (GB)
Title: Improvements in or relating to rate-of-turn-responsive apparatus
Inventor: MORROW CHARLES TABOR
IPC: G01C19/42
Filed: 1952-08-08
Abstract: 730,783. Turn-sensitive vibrating masses. SPERRY CORPORATION. Aug. 8, 1952, No. 20080/52. Class 97 (3). [Also in Group XXXVIII] Apparatus responsive to the rate of turn of a support'about an axis comprises a tuning fork 11 mounted on the support 19 by torsionallyresilient means permitting small angular movements of the tuning fork about its axis of symmetry YY<SP>1</SP> lying in the plane of symmetry YY<SP>1</SP>, ZZ<SP>1</SP> normal to which the fork vibrates, means for maintaining the fork in vibration, means for detecting torsional oscillations of the fork about its axis YY<SP>1</SP> set up as a result of the . turning of the support 19 about axis YY<SP>1</SP>, and a mechanical vibration filtering arrangement forming part of the mounting for reducing or preventing the transmission to the detector of unwanted modes of vibration of the tuning fork other than symmetrically opposite lateral vibrations of the tines normal to the plane of symmetry. As shown, the heel 16 of the fork is mounted on a torsion structure 17 connected by a thin cylindrical torsion spring 18 to the support 19. The fork is driven by electromagnetic coils 20, 21 from a drive and reference amplifier 24, to which the signal from a pick-up 23 is fed. When the support 19 rotates about axis YY<SP>1</SP> a torsional vibration of the fork is set up about axis YY<SP>1</SP>. By means of pick-ups 30, 31 an electrical signal corresponding to the torsional vibration is produced, the amplitude and phase sense of which are a measure of the magnitude and direction respectively of the rate of turn of support 19. This signal is fed through an amplifier 37 to a phase-sensitive detector 38, which also receives part of the output of amplifier 24. The output from detector 38 is applied to a meter 39 calibrated to indicate the rate of turn. If the tines of the fork are not accurately balanced, spurious vibrations may be set up, which together with vibrations originating outside the apparatus, must be prevented from affecting pick-ups 30, 31 if accurate readings are to be obtained. Axial vibrations are prevented from being transmitted along structure 17 by forming therein two pairs of slots 40, 41, the thin webs between the pairs being at right-angles. Reedlike vibrations of the structure 17 and fork 11 are prevented by providing supports 43, 44 at antinodal points. Support 43 comprises a cartwheel-like structure having a rim 45 fixed to rigid walls of the apparatus and spokes 46, 47 attached to a hub 48. Structure 17 has prongs 17<SP>1</SP> between which fork 11 is mounted and on which hub 48 is mounted. Support 44 is similar with a rim 48<SP>1</SP> and spokes 49, 50 attached to the structure 17. The pick-ups 30, 31 comprise armatures 32, 33 extending between coils 33<SP>1</SP>, 34, 35, 36 from a part 110 embracing the lower end of structure 17. Means are described for adjusting the positions of the coils, so that compensation may be made for residual spurious vibrations. Means are also described for adjusting the positions of the driving coils 20, 21 so that the tines may be driven as nearly as possible in their natural plane of vibration. Damping means are provided to stop the torsional vibration quickly on completion of an applied rate of turn, and comprise a metal core 100 fixed to support 19 and almost filling the inside of cylindrical spring 18. Rods 101 extend from the top of core 100 into holes 102 in the lower part of structure 17 with close clearance, and the space between the core and structure 17 and spring 18 is filled with viscous liquid, e.g. a low viscosity silicone oil. Specification 618,328 is referred to.