BRICK-MAKING MACHINERY. Ma chines and structures employed to prepare, mold and dry plastic clay into rectangular blocks of various sizes. These blocks, after being hard ened by baking in ovens or kilns, are commer cially known as bricks and are extensively used for building and other purposes. For infor mation relative to the sizes, composition, qual ities and various uses of bricks, and the general history of brick manufacture, see BRICK. The types of brick-making machines are exceedingly numerous, but they may he conveniently divided into three classes — soft-clay process, stiff, tempered-clay process and dry-clay process. In the soft-clay process (Figs. 1 and 2), which is also known as sand-molding process, clay taken directly from the bank is pulverized, mixed with water and tempered in the machine and then pressed into sanded molds which are fed in beneath the press box. The molds thus filled under pressure are then moved forward to a delivery table, where they are emptied and then returned for refilling. This process makes bricks of a fine homogenous quality but is slow and the machines are, as a rule, used by the smaller manufacturers. Of late years improve ments have been made in machines for this process, raising the capacity to 5,000 bricks an hour for each machine, and may be capable of further development.
Die-working machines (stiff, tempered-clay proces —Figs. 3 and 4) are of two types— those in which the clay is moved out continu ously by means of a rotating auger and those in which the clay is pressed out in bars of specific lengths by the reciprocating motion of a plunger. In machinery for the stiff, tempered clay process of brick-making, the product of which is, perhaps, that most generally approved by brickmakers, builders, engineers and archi tects, the bar of clay is cut up into bricks of the required size by wires which, according to the mechanical contrivances adopted to operate them, give to these machines the additional designations end-cut and side-cut or, generally speaking, wire-cut. The machine for this proc ess is an expressing device for forcing the prepared material through a die (Fig. 6) and
forming it in a continuous column to the de sired size and shape. The latest types consist of a continuous screw in a case, of such diam eter and pitch as will give greatest efficiency, with suitable mechanism for driving the screw. The die is at the end of the screw and adja cent to it, and determines the size and shape of the column of clay which issues continu ously from it. In front of the die is located a cutting device (Fig. 5) carrying a series of wires so spaced as to cut up the column of clay into the desired sizes. The spacing of these wires determines the other dimension not de termined by the die, and provision is made for the cutting section to move with the bar of clay while in the apt of cutting and for its return to starting position after the cut has been made, these cycles being repeated auto matically as long as the column of clay is issuing from the die. Since, in accordance with the laws governing the movement of fluids under pressure, the clay as it moves through the die is retarded by friction at the corners and moves more freely at the centre, to obviate this a lubricant is applied to the column at the angles of the die to secure an uninterrupted and uniform flow throughout the cross-section of the bar of clay and ensuring square and well defined corners to the column.
Of the various devices employed to cut the clay bar, thus formed, into bricks the auto matic side-cut wire cutter is probably the best. (Fig. 5). It consists of a regulating frame or table on to which the bar of clay•is car ried from the die and by which the cut-off is controlled. The belt carrying the bar of clay runs around a measuring wheel which deter mines the exact thickness to be cut according to the desired size of bricks. The cut-off wires are strained on spring holders to a tension which, while sufficient to cut, yet yields readily to obstructions such as stones, either cutting around them or springing over them, and op crate automatically and without any trouble. A broken wire may be replaced at once, gen erally without stopping the machine.