GB950983A - Damping vibrations in chimneys, towers, or masts - Google Patents

Abstract

950,983. Frictional vibration-dampers. SULZER FRERES S.A. April 20, 1961 (May 6, 1960], No. 14378/61. Heading F2S. [Also in Division F4] In order to prevent the growth of oscillations at the natural frequency of tall sheet metal structures such as chimneys, towers, masts, &c., due e.g. to eddy concavitations produced by winds a frictional dynamic-oscillation damper is fitted to the top of the structure. As shown in Fig. 1 a vibration damper 2, secured to the top of a chimney 1 having a heat insulation layer 12 located between an outer skin 10 and a lining 11, comprises an annular base plate 14 which is secured to the skin 10 by brackets 13 and freely supports an inertia ring 16. The latter, which is sub-divided into several segments 24 interconnected by pins 26 engaging loosely within apertures 25 to ensure uniform distribution of the friction forces, carries spring-loaded buffers 17, 18 which prevent it from colliding against the skin 10 and a cylindrical outer cover 15. Small gaps 29 between the edges of the base plate 14 and the members 10, 15 provide an escape for abraded particles. The damper has a top cover 22. The buffers 17, 18 may be replaced by spring strips 27, Fig. 3. In a modification, Fig. 5 (not shown), the inertia mass consists of a number of segmental U-shaped damping elements which loosely straddle a fixed rigid ring the base plate being in the form of a grating, and corrugated steel buffer strips being connected around the skin 10 and the cylindrical wall 15. In a combined liquid and friction damping arrangement, Fig. 7, a casing 40, wholly or partly filled with liquid e.g. oil, contains an I-section damping mass. A liquid friction damper is described which comprises a fluid-tight annular vessel having perforated upright and radially-extending plates the sectors between which are filled e.g. with steel swarf. The liquid can be loaded with suspensible particles. Sand, metal scraps, &c., and the other non-suspensible particles can also be added to the liquid in which case the loose fill can be omitted. In a further modification, Fig. 9, sheet metal rings 61 welded to the skin 10 support rings 62 spaced from the chimney lining 11 which is loaded by the insulation layer 12. In a variant of this arrangement brackets on the lining 11 support a stack of rings 71, 72, Fig. 10. The damper may be in the form of a number of circumferentially-spaced radially-extending hydraulic piston and cylinder units with, or without, conventional valve systems. The piston in each cylinder may be replaced by a ball.