GB295955A - Improvements relating to the heat treatment of ceramic articles - Google Patents

Abstract

295,955. McDougal, T. G. Feb. 21, 1927. Tunnel kilns; charges, conveying.-In a tunnel kiln for firing ceramic ware such as sparking-plug porcelain, insulators, &c., the ware is carried by a conveyer mechanism located mainly outside the heating chamber and having article-supporting ends which project into the heating chamber through a narrow slot, the ends being of not greater width than the slot, so that the parts of the articles adjacent thereto are not shielded from heat radiated from the walls. The conveying device shown in Fig. 9 comprises refractory members 30 having upwardly-extending projections 32 terminating in pins 33 upon which the porcelains 34 are mounted. The sides of the member 30 are irregularly shaped to fit the corresponding configuration of the walls of the slot, and the ends may be similarly formed to prevent direct passage of radiant heat to the conveyer chain 40. The lower ends of the members 30 may be shod with metal and may slide directly on a rail or on rollers, or may be provided with wheels. The kiln comprises a preheating zone, a firing zone, and a cooling zone in three sections, the first or second with indirect air and water cooling respectively, and the third with direct air cooling. The firing and cooling zones are separated by a transverse wall having an opening closely conforming to the shape of the ware. In the firing zone, Fig. 4, the tunnel is somewhat enlarged, and the slot may have an upwardly-diverging mouth 46. A combustible mixture is supplied through passages 20. In a modification, Fig. 10, the lower parts of the walls are made of parabolic form to focus the rays, of heat upon the ware. The joints 54 between the top and bottom sections of the tunnel are offset to prevent movement of the upper block. In another construction, Fig. 11, having three conveyer mechanisms for the one heating chamber. the intermediate portions 60 of the floor are supported by beams 72 on rollers 70 mounted on the shafts 62 which carry the rollers 64 of the refractory members 30. Stops are provided for preventing endwise movement of the floor portions 60.