Year: 1897

page_text: Date of Application (in United Kingdom), 13th July, 1897
Complete Specification Left, 13th July, 1897-Accepted, 13th July, 1898
I, WILLIAM STORES MACHARG, of No. 1129, The Rookery, Chicago, County of
Cook, State of Illinois, United States of America, Mechanical Engineer, do hereby
declare the nature of my invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following.
statement:-
My invention relates to prism lights for windows, such as are commonly
described under the title of prismatic lights. The object of such glass is to receive
the light and distribute it in the apartment to be illuminated in a manner different
from that in which it would ordinarily be distributed where the ordinary glass
is used or where there is no window glass. The effect of window glass or windows
having the ordinary glass on the reception and distribution of light in the apart-
ment to be illuminated is considerably varied, owing to the shape and position of
the shaft, alley or street from which the light is received. For example, if the
window is in a building rising free from all surrounding obstructions, or in other
words, a considerable distance from other buildings, it is plain that the angle
of reception of light will be very large, for example, approximately ninety degrees,
that is to say, that some of the rays of light passing through that
window and tending to illuminate the apartment will be derived from
all parts of the angle of ninety degrees, the greater number of
such rays of course being derived from perhaps the middle half of
such ninety degrees. This is so because the rays which fall approximating
the vertical are reflected away by the window glass in large numbers, whereas there
is a comparatively small number of rays of light travelling horizontally to their
surface. Now, if on the opposite side of a comparatively wide street, a series of
high buildings be erected, it is evident that the greater portion of this angle
of reception of light or angle of supply of light has been cut off, and it is clear that
as the buildings on the opposite side of the street are increased
in height, or as the street is diminished in width, the angle through
which the light is received will be diminished until finally, under
certain conditions, as for example, in very narrow streets or alleys or courts or
air shafts, and particularly where high buildings are on the opposite sides of such
spaces, the light received against the glass will be almost wholly re-
flected
away from it, and
the only light of any consequence passing
through the window will be the light generally diffused through the atmosphere
outside of the window and thus passing through the glass. Now, in the use of
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page_text: prismatic lights, it is found impracticable to make very excessively deep or heavy
prisms from various difficulties, which will readily occur to any one familiar with
this subject, and moreover in the practical use, supply and sale of such devices, it
is desirable of course to have uniform sizes and thicknesses and so far as may be
possible uniform shapes of all the prisms. In the conditions above referred to,
however, it is desirable that the prismatic glass should be so arranged as to
introduce the greatest amount of light, or in other words, so as to reflect away
from the exterior of the glass the least amount of light possible under practical
conditions. These conditions vary of course, though ordinarily within certain
reasonable and well defined limits, and the particular configuration of the receiving
surfaces and the prisms proper must vary, but a few general types must answer
practically for all ordinary conditions. In my drawing, therefore, I do not
pretend to more than, as it were, diagrammatically suggest or illustrate the idea
without attempting to give all the forms or indeed any necessary form of the
glass. I have, however, desired to illustrate my invention in connection with
prismatic glass, such as is now in more or less extended use.
Figure 1 shows a cross-section through a prismatic glass or tile, such as can
be used to make up a window glass having a flat or plain exterior surface.
Figure 2 shows a similar glass with a series of receiving surfaces on the formerly
flat surface opposite each prism.
Figure 3 shows longer receiving surfaces;
Figure 4 shows shorter receiving surfaces;
Figure 5 is a diagrammatic illustration of an alley or shaft with a window at
the bottom equipped with my improved light, and dotted lines showing the course
of the light, and also showing the construction of the glass, if my improvement
were omitted, the difference in the reflecting power of such glass being illustrated
by the dotted lines running off to the ground. The same thing is shown on a
larger scale in Figure 3.
No attempt has been made to adhere to the absolutely correct angles of the glass
surfaces or angles of reflection, but as previously suggested, I am simply trying
to illustrate the idea.
Referring to the figures, like parts are indicated by the same letter in all the
figures. A is the body of the glass, having in Figure 1 the smooth surface B; in
Figure 2, the receiving surface C; in Figure 3, the receiving surface D; in
Figure 4, the receiving surface E. F is a building, G a building on the opposite
side of the alley or court H; and J the receiving surfaces of the window A at
the bottom of such shaft or court. K are the prisms, which in this case act as
refracting prisms.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
As a new article of manufacture, a prism light for windows, comprising a sub-
stantially flat glass body with prisms systematically arranged to produce an
increased illuminating effect in the apartment on both sides of the glass body and
extending across the same substantially parallel to each other.
Dated this 13th day of July 1897
Dated this 13th day of July 1897
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.