GB839915A - Labyrinth seals - Google Patents

Abstract

839,915. Stuffing-box substitutes. ROLLSROYCE Ltd. Jan. 20, 1959 [Jan. 20, 1958], No. 1937/58. Class 122 (5). Also in Group XXII] A labyrinth seal comprises a sealing member 11 formed by a number of metal strip annuli 19, adjacent annuli being axially spaced apart at their peripheral sealing edges 19b, and cooperating with at least one rib 10b which cuts its own path in the annuli if rubbing therebetween occurs. The annuli may be either initially separate and mounted as a stack or in the form of a continuous helix. The invention is shown in Fig. 1 applied to sealing gas turbine blades 10, ribs 10b on the blade shrouds 10a co-operating with spaced sealing members 11 in a ring 12 secured to the turbine stator 14 and cooled by cooling air circulated through a chamber 16. Preferably the metal of the annuli 19 is softer or has a lower melting point than that of the projections 10b. In the embodiment shown in Fig. 2 each annulus has an outer enlarged V-section portion 19a received in the corresponding portion of the adjacent annulus and a thin sealing portion 19b of, for example <6>/1000 inch thickness. The annuli are clamped between a shoulder 12c on the ring 12 and a ring 13. In a modification, the annuli are of constant thickness metal and have circumferential corrugations at their outer peripheries engaging corresponding corrugations on adjacent annuli. In another modification, Fig. 5, the annuli are spaced by dimples 23, 24 formed on alternate annuli and spot-welded at their troughs to adjacent non-dimpled annuli. In a further modification, Fig. 6, each annulus is formed with dimples 25, the dimples on alternate annuli being circumferentially staggered with respect to those on adjacent annuli. The portions of flanges 26 in the region of the dimples are bent radially outwards to form tangs 27 protruding through slots 28 in a ring 29, the tangs 27, the flanges 26 and also end plates 30, 31 being welded to the ring 29. In yet another modification, the annuli are spaced by dimples formed on one side only of each annulus. The annuli may be made by forming a continuous strip of the metal to the desired cross-section by drawing, rolling or extruding and then winding the formed strip around a mandrel to provide a helically coiled strip from which separate annuli may be cut.