Patent GB-191208527-A (GB)
Title: Improvements relating to the Balancing of Rotating Masses.
IPC: F16F15/36
Filed: 1912-04-10
Granted: 1913-04-10
Abstract: 8527. Soc. Anon. pour I'Exploitation des ProcÚdÚs Westinghouse-Leblanc. July 27, 1911, [Convention date]. Balancing moving parts. -An automatic balancing-device for a high-speed shaft carrying rotating masses and mounted so as to be free to select its own axis of rotation, which naturally tends to be one of the principal axes of inertia passing through the centre of gravity, comprises two or more circular channels arranged on either side of the rotating masses concentrically with the geometrical axis and partly filled with mercury, the disposition of which under centrifugal action tends to cause the principal axis of inertia about which the shaft is rotating to coincide with the geometrical axis. The device is applicable to driving apparatus such as a turbine &c. preferably combined with driven-apparatus such as a rotary compressor &c., both mounted on the same shaft and rotating at the same speed. The shaft &c. to be balanced is mounted in suitable bearings to allow the necessary freedom of movement and may be connected to a rigid shaft mounted in fixed bearings by means of a flexible coupling which may, for example, comprise a rubber tube protected by vegetable fibres. The circular channels may be formed by grooved rings I, Fig. 2, shrunk upon a small fly-wheel or other part J carried by the shaft, being partly filled with mercury through holes K which are afterwards plugged. Several such rings may be shrunk upon one another. The outer wall P, Fig. 3, of any channel being concentric with the geometrical axis O of the rotary masses. Upon the shaft commencing to rotate about a principal axis of inertia of the rotating masses (not including the mercury) such as G, centrifugal force causes the mercury to collect in the now eccentric channel P in such a manner as to alter the centre of gravity and to bring the resultant principal axis of inertia such as L nearer to the geometrical axis O. The varia-. tions in the centrifugal force in relation to the displacement and the relative proportions of the requisite balancing-devices for a predetermined maximum displacement of the axis are calculated in the Specification. Where several wheels &c. are carried by the shaft, balancing- devices are preferably attached to each wheel. The mercury containers may be formed by flat annular tubes of thin steel similar to Bourdongauge tubes but with their ends soldered together to form hollow rings. Such rings may be sprung into recesses or otherwise attached in the vicinity of the blades to each wheel of a steam turbine, and may be arranged to maintain a balance even when. blades are stripped. In cases where the balancers cannot be mounted along the shaft, they may be arranged at opposite ends as at S' in Fig. 7. To limit the displacement of the shaft in the event of an accident, two or more fixed guard-rings T<1>, T<2>, Fig. 7, with the requisite clearance may be provided. A form of bearing allowing the shaft to select its own axis of rotation is shown in Fig. 1. A bush A is free to move within a ring B, rotation of both members being prevented by a tube C which admits oil under pressure to lubricate the journal and also to flow between the bush and the ring. To effectively damp the movements of the bush, a spiral coil or one or several very thin concentric rings a of aluminium, celluloid, &c. are arranged between the bush and the ring. The ring B is supported by three struts E, which are arranged to fuse when the strain exceeds a certain limit, the ring B then becoming movable. This arrangement used in combination with the guard rings shown in Fig. 7, prevents contact between the shaft and the guard-rings during normal running, but collapses under excessive strain, whereupon the shaft rolls within the guard-rings. The Specification as open to inspection under Section 91 (3) (a) describes also the use of steel balls or metallic filings as balancing masses instead of mercury; this subject-matter does not appear in the Specification as accepted.