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288,572 · Hyatt · "Vault-Covering or Illuminating-Grating and Surface Made Therefrom" · Page 2
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fastened to the face of the building for the area-covering to rest upon at that side, and I indicates the support of the area-covering at its front edge.
    K indicates perforated metal plates made to imitate in size and shape ornamental slates, and fastened to purlins.
    K' indicates the same after having been set with glasses, and thus made ready for the ornamental facing.
    m indicates the facing material.
    K² indicates finished plates.
    K³ indicates composite ornamental roofing plates or tiles, each plate representing a number of tiles.
    o indicates curved fillets cast on the face of the plates.
    M indicates rafters or purlins.
    N indicates guttered or drainage roofing-plates; m, the gutters or drainage-surface; Q, weather-surface made of glass plates; r, dripping-points of the glass plates; p, under lip of plate, and cemented joint at abutting scalloped edges of plates N M.
    The bar-gratings, for convenience of being cut to lengths, are preferably made of wrought iron. The purpose of the web-and-flange form of grating is to be able to make illuminating constructions in themselves self-supporting, and thus adapted to any span; but self-supporting cast-iron gratings, or gratings cast with supporting-bars upon them, if made in panel or tile shape, cannot be made to be good for anything. If the tile is properly made to give light, the mass of iron in the supports will, in the cooling of the casting, tear the life out of the grating. Experimenters are all the time trying this impossible feat and patenting it; but the law of cast-iron, like the eternal law of gravitation, won't be fooled with, and the strength of these "self-supporting gratings" is a sham. Here is the explanation of it: The form of grating-- that is, panel form-- means width, and the supports for a wide casting must be strong, and therefore heavy or massive, because width of tile supposes load-carrying capacity in the tile. To be able to cast such wide gratings with supports adapted to them requires that the light-holes of the grating should be less in number and wider apart, so as to create more weight of metal in the panel, to balance the mass of metal in the supports, to make all the parts of the casting cool equally at the same time, and thus prevent unequal shrinkage and cracking or straining; but to place the light-holes of the grating wider apart is to this extent to destroy the function of the grating for transmitting light; hence the proposition to cast supports upon illuminating-gratings made in panel or tile shape is an absurdity; but when the gratings are cast with only a double row of holes-one on each side of the supporting bar or web-- especially if such holes are half-holes, or made with an open side, it can be readily seen that there need be no difficulty whatever in casting such self-supporting gratings.
Gratings so narrow as bar-gratings need comparatively little metal in the supporting-blades; but these blades, being, on account of the narrowness of the grating, near together, make a strong construction, even though light, just as a number of light beams placed close to each other make a stiffer and better floor than heavier timbers at great distances apart.
    I do not limit my invention of bar light-gratings to the T and L form of bars, but propose to employ others, especially the U or "channel-iron" form of bar.
    When for any reason it becomes desirable to make self-supporting gratings in tile or panel shape, my method of procedure is to galvanize or tin the separate bars, and then make them up mechanically by riveting or soldering them together, or both rivet and solder. Figs. 2 and 6 represent panels so made. Figs. 7, 8, arid 9 represent constructions made of bar-gratings not previously made into panels. The manner in which I make constructions of the kind represented by Figs. 7 and 8 is to build up the structure on the ground before applying the glasses, this mode of construction being made necessary by the open-side light-hole feature of the gratings.
    In ordinary patent light constructions the seams between the parts composing the roof or foot surface are straight seams; but where the edges or borders of the gratings are cut out or scalloped with open-side light-holes, the seams are largely made up of the light-holes themselves, so that the joint-glasses, under these circumstances, become, in combination with the waterproofing-cement, a portion of the closure material employed to make good the joint between the gratings, as indicated by e' in Figs. 7 and 8.
    The fifth novel feature of the invention relates to ornamental illuminating slate roofs or imitation slate. I construct these roofs (by the method illustrated on Sheet 3, Fig. 10) of metal perforated plates in size and shape made to resemble ornamental slates, and having first cemented the glasses in the light-holes, I then put on the facing. If the facing be natural slate, I make light-holes in it to match those of the metal back, and cement it fast, the glasses, which stand above the face of the metal, entering the light-holes of the slate, where they are again encircled with additional cement; but if the facing be hydraulic cement put on in plastic form, I place the metal tile in a mold, after having first fixed the glasses, and then lay on the facing. When the plastic facing has become hard, the tile is ready for use. The half-holes in the sides of the tiles are set with glasses only after the tiles are in position and fixed to the purlins of the roof. In some cases I make the roof by first fastening the metal plates all in position thereon, the whole holes of the plates having been previously set with glasses, and the half-holes after being completed, and their put on the plastic ornamental facing by the employment of suitable molds for the purpose. By the