489. Clark, W., [a communication]. Feb. 19.
Delivering molten metal; drawing; obtaining metal; pressing; rolling; shaping; cutting glass. Relates to the manufacture of window glass in continuous sheets. The metal is melted in platinum or clay crucibles b, c, d, b1, c1, d1, Fig. 1, arranged in steps one above the other. The crucibles are of the form shown in section in Fig. 7, and are filled with raw materials, and recharged as fusion continues, so that all are full after complete fusion. New matter is then introduced into the upper crucibles b, c, b1, c1, and as fusion continues the molten metal overflows to the lower crucibles d, d1, through the channels G and a, and finally through gutters e, e1, into a receiving trough H, Figs. l and 4. The glass is purer through, being drawn off from below the surface. The glass then passes through openings in the lower part of the trough H into a platinum &c. cell o, which forms a bottomless case within the trough H. The cell o may be furnished with a bottom having a single opening, if desired, so that the two lots of glass supplied from the two sets of crucibles may meet at the opening and so be thoroughly mixed. The trough H is situated in a narrow gallery or furnace L, which is heated from the melting furnace. When the trough H and cell o are quite full, the formation of the sheet of glass S is commenced. Two iron hooks l, Fig. 4, are lowered into the molten glass, so that they become red hot and adhere to the glass. These hooks can be adjusted laterally and vertically by screws p and q, Fig.1. They prevent lateral contraction of the sheet of glass during its formation. A bar of iron C, Fig. 4, is made red hot at its lower edge, and lowered into the cell o, and is then gently removed with the glass adhering to it, the hooks l being raised with it by means of the vertical screws for about an inch and a half as the glass is drawn up. The hooks then stop, and the bar C is carried upwards. Instead of using the hooks described, the glass may be prevented from shrinking by means of two tubes r, Fig. 8, through which water is caused to circulate. The tubes are arranged by means of balance weights u to lightly touch the edges of the sheet, which are thereby cooled and enabled to retain their proper form. The glass is next drawn up through a series of wood or india-rubber rollers z, Fig. 4, mounted on shafts x, x1, and driven by bevel gearing from a belt-pulley. These rollers are adapted to open to allow the passage of the bar C, and may be fixed in any position on the shafts by means of clutches X. They are caused to exert a pressure on the glass by means of weights Y, Fig. 6. When all the rollers have come into operation, the bar C is removed from the glass by means of a cutting diamond, and the glass is carried upwards by the rollers alone to a cutting frame, Fig. 9, which may be moved out of the way by a lever so as to allow the bar C to pass. When the glass has reached the required height, the clamping screws g of the cutting frame are tightened by means of a crank i so as to grip the sheet, which is cut off by running a diamond point along the straight edge j. The frame is hinged at f, and may be lowered into a horizontal position during the removal of the sheet of glass. The thickness of the glass depends upon the rate at which it is withdrawn from the cell o.
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