GB632313A

GB632313A -

Info

Publication number: GB632313A
Authority: GB

Abstract

632,313. Torsional vibration-dampers. DE HAVILLAND AIRCRAFT CO., Ltd., and HADWIN, R. N. Jan. 31, 1947, No. 3091. Class 108 (iii)] [Also in Group XXXIII] A vibration damper or absorber for attachment to a rotating shaft, comprises a casing containing a mass consisting of a pre-determined quantity of a mobile non-viscous or low-viscous liquid such as mercury, and so dimensioned internally as to permit the volume of liquid to change its shape under the vibrationproducing force, with consequent movement of its centre of mass in a pendulous manner at a frequency bearing a constant ratio to the rotational speed of the shaft. The liquid may be mercury or alternatively some other mobile non-viscous liquid such as acetylene tetrabromide or Clerici, or a combination of mercury and one of the latter liquids. For use at high temperatures a fusible metal such as Wood's metal may be employed in a stainless steel casing. As shown in Fig. 5, applied to the damping of an airscrew shaft, the casing 3 is tapered externally to fit a recess 8 in the blade root. The casing is sealed by a closure plate 4 which may be removable or (as shown) may be welded, or otherwise secured in position, and fitted with a closable inlet passage axially arranged in a stem portion 5 for the introduction of the mercury 1. Balancing washers 7 may be mounted on the stem 5 and retained by a nut 6. In a similar construction (Fig. 1, not shown) the plate 4 is externally screw-threaded for engagement with the casing, the internal shape of which is part-spherical. In another construction (Fig. 4, not shown), the internal shape is of part-conical formation while in a further construction (Fig. 3, not shown), the casing is of cylindrical shape and is screw-threaded externally, the cavity being of annular formation. A number of the dampers may'be embodied in the airscrew, shaft, &c. each being tuned to deal with vibrations of a respective order. Specifications 7035/40 (as open to inspection under Sect. 91), 600,498 and 604,528 are referred to.