Improvements in Prismatic Pavement Lights.
Year: 1897

page_text: Improvements in Prismatic Pavement Lights.
I, FRANK CLEMENT SOPER, 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 per-
formed to be particularly described and ascertained in and by the following
statement:-
My invention relates to devices for distributing light and has for its object
to provide a new and improved device for this purpose.
My invention is illustrated in the accompanying drawings, wherein
Figure 1 is a side view of a vault light embodying my invention;
Figure 2 is a plan view of the same;
Figure 3 is a section on Line 3-3 Figure 1;
Like letters refer to like parts throughout the several figures.
It has been the custom heretofore in constructing vault lights and the like to
consider simply the rays of light which fall substantially perpendicularly upon the
receiving surface. The object of my invention is to provide a vault or other light
or similar device so constructed as to utilize the rays of light which strike the
receiving surface at an angle, such rays being lost when the ordinary vault light
is used.
I have illustrated in the drawings, a vault light provided with a body
portion A, having a receiving surface A¹ and having the projecting parts or
prisms B. I have constructed this vault light so as to embody my invention
and although I have shown a peculiar kind of vault light, to illustrate my inven-
tion, it is of course evident that I may use my invention in connection with any
light diffusing device to which it can be applied. Each of the projecting prisms B
is provided with the reflecting surface B and the refracting surface B and is
provided with the inclined edges C, the prisms shown being made so that they
are wider at the bottom than at the top. I have shown these edges in the
drawings, as broken up into a series of ribs having substantially parallel surfaces,
but I do not wish to be understood as limiting myself in any particular to this
construction as these faces or edges may simply consist of an inclined surface or
they may be of any other suitable shape or form, the only condition being that
they will reflect the oblique rays of light. Neither do I limit myself to the
embodiment of my invention in a vault light as it may be used in connection

page_text: with other light diffusing devices. I have indicated in Figures 2 and 3 some
of the rays of light which strike the receiving surfaces at an angle and which are
then reflected and refracted by the prisms so as to be projected toward the point
where the light is desired.
The use and operation of my invention are as follows:-
When the rays of light that strike the receiving surface of the vault light are
substantially perpendicular to such surface they are reflected by the reflecting
surface and refracted in the ordinary manner. When the oblique rays of light E,
for example, strike the receiving, surface of the vault light they are refracted and
then strike the surface C and are then reflected, the line of direction being
changed so that they will strike the reflecting surface B¹ in a more nearly vertical
direction. The rays of light are then reflected and pass out through the refract-
ing surface B and are hence directed toward the point where the light is to be
utilized. In the vault light as ordinarily constructed these rays of light pass
through the surface C or are reflected in a direction not desired and are thereby
lost. When my construction is used these rays instead of being lost are pro-
jected toward the point where the light is desired, and a much better illumination
is obtained. The inclination of the edges of the prism B is intended first to
receive the light and reflect it downwardly as indicated in the drawings; and
in the second place, when these edge surfaces are themselves prismed or ribbed,
to permit the light reflected from the upper prism surface to pass downwardly
without striking the next prism, which would occur if such prisms were arranged
on a vertical surface; and in the third place, the reason for these side edges is to
give a larger area at the bottom to reflect the light, an area approximately equal
to the exterior surface length. These ribs or prisms on the edges of the principal
prism I have called the secondary prisms.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, 1 declare that what I
claim is :-
1. A prism light for vaults having the converging sides substantially as shown
and for the purpose specified.
2. A prism light for vaults having the prism sides or edges substantially as
shown and described.
3. A prism light for vaults having the converging sides with prisms thereon
substantially as shown and specified.
Dated this 13th day of July 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.