Patent GB-1389967-A (GB)
Title: Brazing method and apparatus
IPC: B21D53/40
Filed: 1973-10-24
Abstract: 1389967 Soldering TAMIC INTERNATIONAL PTY Ltd 24 Oct 1973 [26 Oct 1972] 49528/73 Heading B3R In a method of brazing together two metal workpiece elements, particularly, and as shown, a leaf 52 and a cylindrical boss 48 of a hinge member, wherein the elements are supported in mutual abutment, flux and heat fusible brazing material are applied to the abutment region, and said brazing material is melted by applied heat and allowed to cool, some of the applied heat is directed on to a part of the elements (generally that of the greater heat capacity) at a position spaced from the abutment region so that heat is conducted to the abutment region and the brazing material through said one element and some of the heat is applied directly to the abutment region and the brazing material. As shown, an apparatus for carrying out the above method includes a horizontal slat conveyer 12 having upper and return lower runs 13, 14 and comprising flat plates 15 hinged at their leading ends to conveyer chains 16 which slide on upper rails 28. The plates have rollers 29 which co-operate with lower rails 32 to hold the plates horizontal on the return run. At opposite ends of the conveyer, the chains are taken round idler sprockets (18) and drive sprockets (17), the latter being driven by a motor (26) via a gearbox (24) and chain drive (23, 22, 21). Each plate 15 has bolted thereto, at 38, a standard 33 which comprises two posts 34 and top and bottom plates 36, 37 and supports a pair of hinge component holders 39. Each holder 39 comprises a mounting plate 41 from which extends, perpendicularly, four hinge support and four hinge locating flanges 42, 43 to carry two hinge leaf and boss combinations. The flanges 42 have projections 49, 51 and hook ends 47 to support the hinge leaves and bosses in mutual abutment. The flanges 43 retain the leaves and bosses longitudinally. Half of the bosses 48 have pins 54, as shown, and the other half have complementary sockets, and each holder 39 may carry two leaf and boss combinations for a complete hinge assembly. The holders 39 are retained on the standards 33 by engagement of standard pins 58 in holder holes 57 and standard turn button tubes 59 with holder ramps 62. The apparatus also comprises successively operative first and second heating stages 63, 64. The stage 63 comprises two rows of gas burners each constituted by successively operative relatively low and high heat burners 67, 68 having gas slots aligned to provide continuous gas curtains upwardly and inclinably arranged to impinge on the workpiece hinge bosses. The stage 64 comprises two rows of gas burners 76 having gas jets downwardly arranged to impinge on the workpiece abutment region. Gas and air mixture is fed from a main manifold 71 to the burners 67, 68, via individual control valves 73, and to the burners 76 via control valves 79 and manifolds 77. Heat loss is minimized by radiant and gas deflecting elements (e.g. fire bricks) 74, 80 respectively above the burners 67, 68 and below the burners 76. In operation, the hinge leaves and bosses may be fed into the holders 39 by hand. Brazing rods 66 and flux are placed in the channels formed between the leaves and bosses before the latter reach the first heating stage 63. As the leaf and boss combinations are conveyed along the stage 63 the temperature of the bosses is raised gradually and heat is conducted to the abutment regions, and as they are conveyed along the second heating stage 64, the abutment region temperature is raised to melt the rods 66. The molten brazing material then seeps downwardly under gravity and capillary action to join the hinges and leaves together. Such seepage may result in a lower fillet 81 in addition to an upper fillet 82. After leaving the second heating stage 64 the joined leaf and boss combinations cool and are tipped from the holders 39 on to a further conveyer (83) as the conveyer plates 15 pass round the drive sprockets (17). The burners of the heating stages are adjustable so that 2/3 of the heat input to the abutment region is indirect from the first stage 63 and the remainder of the heat input is direct from the second stage 64. The final few of the second stage burners smooth out the joint top surface. The heat fusible brazing material may be, as shown, rod with a melting temperature of 1000-1800‹ F. or, e.g., for fire door hinges, a powder with a brazing temperature of 1800‹ F. in which latter case the abutment region may be preheated slightly before the addition of the powder.