Patent GB-455923-A (GB)
Title: Improvements in or relating to the manufacture of metal-walled vacuum chambers
IPC: A47J41/02
Filed: 1935-04-27
Abstract: 455,923. Vacuum - jacketed vessels. JACKSON, L. MELLERSH-, 28, Southampton Buildings, Chancery Lane, London.-(Shellwood-Johnson Co. ; 6, Wood Street, Paterson, New Jersey, U.S.A.) April 27, 1935, No. 12697. [Class 29] [See also Groups II, XXII, XXVIII, XXXVI, and XL] The sheet-metal walls of a vacuum chamber or container are rendered impermeable to air or gas by applying sealing metal of lower melting point than that of the metal of the walls and having an alloying attraction therewith, and heating said walls assembled in the form of a chamber in a reducing atmosphere to a temperature above the melting point of the sealing metal but below that of the wall metal, to cause the sealing metal to flow over the wall surfaces and permeate the pores and passages therein and to flow into and seal the crevices between the wall parts and braze the joints. The sealing metal may be applied to the inside surface or the outside surface or both. The vacuum chamber may form a panel or enclosure for restricting heat transfer in refrigerators, cookers, basins or other vessels or may form a double walled tube to insulate flow passages. In the case of a chamber having iron walls, the sealing metal, copper, may be mixed with pyroxylin and applied as a paste or wash, or the metal may be sprayed directly on the walls, mechanically rubbed on or plated chemically or electrically : the assembled chambers are then carried slowly through a hydrogen furnace passing thence into a cooling chamber. Alternatively, the sealing metal may be silver or aluminium. A vacuum chamber, Fig. 4, comprises inner and outer cylindrical walls 14, 22, bottom discs 16, 26 and closing top ring 30 : the disc 26 and ring 30 have flanges 28, 32. A port for exhausting the chamber comprises a central passage 42 in a port piece 38 sealed in a circular flange in the disc 26 ; threads 40 are provided on the outer surface of the piece 38 and a plug is used to stop the passage 42. The sealing metal, copper is applied to the outer sides of the walls. A chromium plating or nickel layer may be applied over the copper to provide a bright surface for heat reflection. The walls may be assembled by pressure fit, gas or electric welding, seams or crimping. The chamber may be completed as a vacuum flask, Fig. 1, in which an outer shell 48 of low conductive material such as that known under the Registered Trade Mark " Bakelite " is provided. The wall 22 has a flange 68 at its upper end, and the inner wall 14 may be tapered near the ring 30. A cap 54 overlies the container walls, such cap having threads 58 engaging threads in a ring 70 cemented to shell 48 ; the cap also has inner threads to rceive a stopper 74. In a modification, Fig. 2, the flange 68 is continued upwardly and provided with threads 64. An evacuated metal ring 76 is held between the cap 54 and a resilient washer 72. Threads 86 at the bottom of the shell 48 serve for attaching a similar container by means of the threads of another ring 70. The space 24 may be filled, before exhaustion, with a mass of hard granules, some or all of which are of activated carbon.