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271,854 · Ingalls · "Illuminating Roofs, &c." · Page 2 Home  > Prism Glass  > Patent Index  > Page 2

271,854: 2 of 5

The surplus is then removed and the surface rubbed over with a piece of wood, which imparts a high degree of polish. Thus it will be seen that by my method the lens is molded with its reflecting-surface a-- the only surface requiring a polish-- uppermost and out of contact with the mold. If a plunger be employed, this is the surface that will be in contact therewith; but the plunger is not apt to chill and deaden the glass. The mold may be made in sections, as usual, for convenience in removing the lens. The other forms of lenses shown will all be made in this way, in each case the surface a forming the open top of the mold.     The lens A' (shown in Figs. 4 and 5) is designed to be set in a horizontal or substantially horizontal plate, the same as that shown in Fig. 1, but to direct the light to a different angle, as indicated by the dotted lines marked "Light" in Fig. 4. This lens consists of a section of a cylinder, the cylinder from which it is cut being indicated by the dotted lines a a. Its reflecting-surface a extends quite to its top surface, d, which it meets at an angle of about seventy-five degrees, while the axis of the cylinder is inclined to the top surface at an angle of about fifty-two and a half degrees in the opposite direction.     Figs. 6 to 10 show a lens, A², set in a vertical plate, as the riser of a step and to direct the light, as shown in Fig. 9. It is a section of the half of a cylinder, the outlines of the entire cylinder being denoted by dotted lines c c in Fig. 9. Its bottom side is flat and stands horizontally, forming the reflecting-surface a. The front or outside surface, d, forms a right angle with the surface a, and the axis of the cylinder is inclined to it at an angle of forty-five degrees. The front of the lens is in outline approximately a half-circle or half-ellipse. The socket in the plate B' is flat on its bottom, and curved above to conform to the lens and to keep the latter in place when set. It has or may have a toe or projection, e, cast on it, which extends backward or inside the building, and on which the bottom surface, a, of the lens rests, as on a bracket. The lens has usually but three projections, b b, as shown in dotted lines in Fig. 7, all being arranged on the upper side of the lens.     The lens A³ (shown in Figs. 11 to 13) is also a section of a half-cylinder, as denoted in Fig. 13, and is also shown set in a vertical plate, B', as illustrated in Figs. 11 and 12. It is like the lens A², except that the axis of the cylinder is inclined to the front surface, d, at an angle of about thirty-five degrees, and the reflecting-surface a forms an angle of about one hundred and five degrees with the front surface. This obtuse angle causes the light to be directed at a lower angle, as denoted in Fig. 13. Both of these lenses A² and A³ are designed to collect the nearly vertical rays of light striking the plate B' at an angle diverging but slightly from it, and to throw them back into the building in the same manner and for the same purpose

as the lens A. They are chiefly useful where it is necessary to set the plates nearly vertical and it is desirable to reflect the light in a nearly horizontal direction. Either of my lenses may be used in a more or less inclined plate, in which case the direction in which the light is sent will be correspondingly changed. By choosing among these four lenses, any inclination ordinarily adopted may be so fitted with lenses as to direct the greater portion of the light to any desired part of the room. I have shown and described these lenses as being sections of cylinders; but they may instead be sections of square or polygonal prisms, if preferred; but I prefer the cylindrical form, because it gives a more compact form to the lens and does not weaken the socket-plate as much as other forms.     I will now describe the applications of my lenses to the various forms of roofs, &c.     Fig. 14 shows the back part of a basement having a convex or curved "basement extension-roof" or "lean-to," C, which is supposed to be set with my lenses. The lenses are so chosen and set at such angles that the parallel rays of light descending at the rear of the building are refracted and reflected into the basement, and are caused to cross each other at a common focal level or line, D, within the building, and at a short distance below the ceiling-- say, for instance, one foot below. After crossing at this common point on line the rays separate, and most of them strike the ceiling toward the center and darker portion of the basement at different angles, and are thence reflected downward to various parts of the room. By thus arranging a focal line and causing the rays of light to cross it the greatest practical advantage of the illumination is secured. In Fig. 15 the same arrangement is shown as applied to the front of a basement where the light passes through illuminating steps and risers. Here the lenses are shown or indicated on a small scale.     It will be understood that in referring in this specification to the rays of light passing through and directed by the lenses I refer to the principal portion of the light, that which is actually reflected as described, and not that smaller portion which passes through without reflection or is otherwise diffused or scattered. Fig. 16 shows more in detail how the several sets of lenses are to be arranged to accomplish this result. The upper portion of the lean-to roof, where it is nearly horizontal, is set with lenses A A. As the inclination becomes gradually steeper the axes of these lenses are gradually more inclined, thereby reflecting the light up at successively higher angles until a point is reached where the surface a is presented so abruptly to the rays of light that it no longer reflects them, but permits them to pass through. At that point, or just before that point is reached, the lenses A' A' are substituted, or else the curved roof is broken up in partial steps, so that the lenses