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Reverberatory Furnace

Democritus is supposed to have invented the reverberatory furnace long before the birth of Christ. These furnaces are constructed so that the materials to be treated are operated upon by the heat of the flame without their coming into direct contact with the fuel. The reverberatory furnace is commonly employed for metallurgic purposes, and is especially advantageous for extracting metals from their ores, and for the numerous processes connected with the manufacture of malleable iron, steel, melting cast-iron, brass, etc.

The furnace consists usually of a rectangular fire-brick construction about twelve feet long, six feet wide, and from five to six feet in height, contained within iron plates which are bound together by an arrangement of buckstays and bolts. The fireplace at one end is separated from the bed proper by a fire-bridge, and an arched roof is made to dip towards the chimney at the opposite end of the furnace; by this means the flame is caused to play with considerable force over the fire-bridge and against the roof, to be again reflected or reverberated downwards upon whatever has been placed upon the bed behind the bridge. A charging-hole is provided on the side opposite to the fireplace for fuel, and a larger one for charging the materials to be operated upon is also provided convenient to the bed, some distance from its bottom. The latter hole is opened and closed by a vertically sliding door, the inner side of which is lined with fire-bricks, and is controlled by means of a lever; but the hole at the fireplace is simply stopped with coal. A hole at the bottom of the chimney allows the cinder produced during the puddling process to escape as it flows down from the bed over a bridge built in the flue. Other smaller holes are provided to permit a free use of iron bars for polling, etc., during the operations. Except in a few minor particulars, the air or reverberatory furnace for melting metals answers to the above description. See PUDDLING-FURNACE; MALLEABLE IRON; POLLING. Reverse-mould is sometimes termed a dummy-block, and consists of forming in loam or sand, by means of the spindle-centre or otherwise, any model, the impression of which it is desired to copy in the cope or other containing part of the mould. This means is employed when it is desired to obtain a casting such as a bevel or spur-wheel, etc., without incurring the expense of supplying a whole pattern.

For example, if it was required to mould a bevel-wheel after this manner, the first operation would be to strike a reverse-mould or "dummy" answering to the permanent joint at the points of the teeth, and from thence over the entire back of the wheel exact to the wheel's form and dimensions on that side. This would give a true model of the back, the impression of which being obtained in the cope, it only remains to first destroy the "dummy" and then sweep out the lower surface direct, commencing at the points of the teeth again, as for the cope impression. After the teeth are rammed from the segment supplied, and the arm-cores have been placed, the cope, as previously obtained from the reverse-mould, is returned.

The joint is the original one from which the cope impression was taken; if tops of teeth and arm-cores are made to correspond with the original model obtained, the mould will close as accurately as when a full pattern is employed. A thicknessed pan-core serves as a reverse-mould for the cope. See DUMMY-BLOCK; KETTLE; BACKING-OUT.