| 摘要 |
In the production of kiln fired bricks and hollow structural tiles a substantial loss (about 3.5%-7%) occurs during drying and firing, principally in the bottom layers adjacent the kiln car deck. This can be minimized by reducing the size of the core holes in the bottom rows of bricks, large holes being maintained in the upper layers to reduce the load on the bottom bricks, economising in fuel and clay. The method and apparatus involve use of a longitudinally movable core plug for each hole produced the downstream end portion of which produces small holes while an upstream portion produces large holes, the shape being such that in cooperation with the extrusion nozzle uniform flow and compression are maintained to equalise final column swell sizes as much as possible for both large and small core hole brick preforms. The pressure of the clay flow can move the plug to the position for the production of large core holes, while an automatic controlled motor means move the core plugs to the position for the production of small core holes, the core plug can be moved to the position in which the smaller core hole size becomes zero for the production of solid "paver" bricks.
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