Patent GB-581898-A (GB)
Title: Improvements in or relating to brazing, soldering or the like processes
IPC: B23K1/00
Filed: 1943-04-06
Abstract: 581,898. Soldering engine cylinders. BRISTOL AEROPLANE CO., Ltd., and LEE, G. H. April 6, 1943, No. 5510. [Classes 83 (i), 83 (ii), 83 (iii) and 83 (iv)] Chucks; casting composite cylinders.-In a centrifugal brazing or soldering process the parts to be united are rotated together at a variable speed whilst they are being heated to maintain the brazing &c. material in a molten condition so that the material is caused to ebb and flow over the parts. In securing together the parts of a junk-head of a sleeve-valve internal combustion engine comprising a copper or like base plate 14, provided with adapters 20 for securing sparking-plugs, cooling fins 17 and a cast-iron carrier ring 41 for forming a seal between the head and the sleeve valve, and a steel sleeve 12 secured to the cylinder by studs passing through the flange 13, the fins which are preformed enough to make a loose fit with the inclined wall of the dish-shaped face 15 of the base-plate, are secured to a tray 18 lying transversely of the fins. The tray has a central opening 19 and the ends of the fins in its vicinity terminate at its edge so that the plugs may pass therethrough into the head. The adapters are coated with flux and then screwed into the base-plate. The face 15 is brushed with a flux solution and the face of the spigot joint 21 between the base and the sleeve is also brushed With flux solution. Previously, the sleeve has been fluxed and dipped in a brazing bath with its outside protected by cement so as to coat the inner surface and lower edge with brazing material, excess thereof being removed. The pack of fins is then placed on the base plate 14 and the sleeve then spigoted on the base plate. A band 42 is then placed in position to encircle the parts to the height of the fins to prevent leakage of solder through the joint 21 under centrifugal force. The assembly is then placed on a platform 24 which may be rotated on a vertical or other axis by a variable speed electric motor and belt 27 on a pedestal bearing 23 over a ring gas burner 28. The assembly is clamped on the platform by bolts 36 passing through a spider 32 connected by arms 33 to lugs 34 of the platform support 35, the pack of fins being pressed into contact with the face 15 by a turn bolt 37 threaded through the spider and engaging a stirrup 38 resting on a ring 39 which lies on the upper edge of the fin pack. Flux solution is then poured into the assembly, a cylindrical shield 30 protecting the operator from splashes of hot material. The platform is rotated and the assembly is heated to brazing temperature in about 10 minutes. -Rotation is effected at various speeds so that the flux washes all over the surfaces to be brazed. The rotation is then stopped and molten brazing material poured in from a iron pot 40. The motor is again started and in two minutes the assembly is twice speeded up to 350 r.p.m. so that the molten brazing material reaches the top of the fins and ebbs and flows over the parts. The speed is then reduced to 150 r.p.m. and the burner extinguished. The speed is maintained until the temperature falls well below 630‹ C. so that the distribution of brazing material is controlled during solidification so that a predetermined depth of brazing material is provided over the surfaces 15 and 16 and complete contact is ensured between the fins 17 and face 15. After slow cooling the inside of the head is cleaned, and excess flux removed by washing with nitric acid followed by water. Stresses may then be relieved by heat treatment at 450‹ C. for one hour. The carrier 41 is, previous to assembly of the parts, shrunk on the plate 14 or shrunk and brazed thereon. In the latter -case the carrier before applying to the plate 14 is coated with brazing material on its inner surface, is then washed with flux, heated and then shrunk on to the plate 14. Holes 43 in the plate communicate with the recess which receives the carrier 41.