GB1269632A - Improvements in or relating to units comprising metallic sheets joined to cellular cores - Google Patents

Abstract

1,269,632. Welding by pressure; brazing. BURNLEY ENG. PRODUCTS Ltd. 14 April, 1969 [6 May, 1968; 16 May, 1968 (2); 17 July, 1968], Nos. 21441/68, 23207/68, 23208/68 and 34136/68. Heading B3R. In a unit comprising a first metal sheet 11, a second metal sheet 14 and a cellular metal core 12 between the sheets, the first sheet 11 is welded to attachment elements 15 formed on the core and the second sheet 14 is brazed to the core, the brazing material extending into the corners of the cells of the core but not reaching the first sheet. The unit may form an acoustic panel for silencing a gas turbine engine or a heat resistant tubular element for use in association with the hot end equipment for exhaust gases of such an engine. Metal strips are spot welded together to form the cellular core 12, the strips being plain as shown or corrugated or fluted, and having discontinuous flanges 15 on one edge interrupted by cut-outs 16. The flanges are spot welded to the metal sheet 11, which may be formed of metal mesh filled with metal fibrous material, brazing alloy is applied to the junction of the strips at the corners of the cells 13 at positions remote from the flanges 15 and a thin dispersion of brazing alloy is also applied to the face of the metal sheet 14, the sheet 14 is optionally locally welded to projections 19 formed on the core 12 and the assembly is heated in a furnace to braze the sheet 14 to the core 12. During heating brazing alloy flows along the edges of the strips remote from the flanges 15 and along the corners of the cells towards the cut-outs 16 but without contacting the sheet 11. The ends of the strips forming the core, remote from sheet 11, may also be formed with flanges to facilitate brazing. Corrugations in the strips forming the core permit bending of the strips when a curved panel is formed. In a curved panel a continuous metal ribbon may be brazed to the sheet 14 between cells which may become separated or mismatched. Although the cells may be of equilateral diamond shape they may be formed by abutting antiphase sinusoidal strips or the strips may provide circular cells. Instead of flanges 15 to permit spot welding projecting teeth may be provided to facilitate welding to sheet 11. Instead of providing cut-outs 16 the comers of the cells may be stopped off by surface treatment to prevent brazing material flowing on to the sheet 11.