Prismatic Pavement, Ceiling and Vault Lights.
Year: 1897

page_text: Prismatic Pavement, Ceiling and Vault Lights.
I, JOHN MEIGGS EWEN, 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 light diffusing devices and has for its object to provide
a new and improved light diffusing device, of which the following is a description,
reference being had to the accompanying drawings, wherein
Figure 1 is a section through a vault light embodying my invention;
Figure 2 is a plan view of a ceiling light embodying my invention;
Figure 3 is a section through the same;
Figure 4 is a section through a ceiling light showing the prismatic ribs having
curved surfaces;
Figure 5 is an edge view of a prismatic window glass showing a modified form
of my invention.
Like letters refer to like parts throughout the several figures.
My present invention is applicable to prismatic glass of any description. In
the prismatic glass as ordinarily constructed the prisms of whatsoever form are
provided with a reflecting surface which is shaped so as to receive the light coming
from some particular direction and project it toward some given point.
In Figure I have shown a vault light having projecting ribs or prisms A,
each prism being provided with the reflecting surface B. In the vault light shown
in this figure, the reflecting surface B is shaped so as to receive the rays of light C
and project them toward some given point. As ordinarily constructed only a
portion of this reflecting surface is effective, the light striking the remaining
portion of such surface being changed in direction so that it strikes the prism in
front and is thereby practically lost. This effect will be readily seen by referring
to the ray of light C shown in the figure by dotted line.
One of the objects of my invention is to form this surface so as to avoid this
result. I divide the surface B into two surfaces at an angle to each other, the
surface B being at such an angle that when the rays of light, for which the
surface B is formed, strike the surface 131, they are refracted instead of being
reflected and hence are changed in direction so as not to be interfered with by
any of the prisms. When the angle between the surfaces A and B is small, the
risms when made in the ordinary manner must be placed very close together or
must be made of an extreme length. The distance between the inner ends of
he prisms being very small as indicated at B. When these prisms are placed
close together, only a small portion of the surface B is utilized, the most of the

page_text: light from said surface being obstructed by the prism in front. By the use of my
construction I am enabled to separate these prisms so as to decrease the amount of
light obstructed by the prisms in front, and at the same time obtain the additional
beneficial result due to the refracted rays of light which strike the surface B¹,
and which but for such surface would be lost under any condition. When the
prisms are made in the ordinary manner with the surface B continued until it
meets the surface A", another evil result from the narrow space between the prisms
at their inner ends. This narrow space makes it necessary to use thin tools in
the construction of the prisms and the excessive heat to which these tools or
moulds are subjected when in this narrow space soon destroys them. When my
form of prism is used, this evil is also obviated.
In Figures 2 and 3 I have shown my invention in connection with a ceiling
light to be placed in the ceiling of a room so as to thrown the light downwardly,
the prisms being formed so as to give a substantially equal distribution of the
light over the floor.
In Figure 4, I have shown a section through a ceiling light in which the
surfaces B and B are curved. It is of course evident that one of these surfaces
may be straight and the other curved, if desired.
In Figure 5 I have shown a window glass in which the surface A¹ is broken
into two surfaces at an angle to each other or in other words where the surface B¹
is associated with the surface A¹ instead of with the surface B.
It will be noticed that the opposed surfaces of any given prisms are joined
by a third surface at an angle to both of said opposed surfaces. The constructions
shown in Figures 3 and 5 might be used together, that is, both the opposed
surfaces of the prisms might be at an angle to each other.
It is of course evident, that other constructions than those herein shown may
be used and that the angles of the several surfaces may be changed at will without
departing from the spirit of my invention.
I have used the word prism light" in connection with this invention to
indicate generally a body of glass on one side of which are the prisms having the
peculiar characteristics above set out. The mass of glass is substantially flat and
preferably with a plane surface on the back or receiving side, substantially as
described.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is:.
1. As a new article of manufacture, a prism light consisting of a substantially
flat body of glass with a series of prisms systemmatically arranged on one side
thereof to produce an increased illuminating effect in the apartment, each prism
having two faces, one of said faces being divided into two surfaces at such an
angle to each other that the light falling upon the receiving side of such prism
plate from a given direction will pass into the plate and be part of it reflected by
one of said surfaces and part of it refracted by the other.
2. As a new article of manufacture, a prism light consisting of a substantially
flat body of glass having a plane receiving surface on one side and with a series
of prisms systemmatically arranged on one side thereof to produce an increased
illuminating effect in the apartment, each prism having two faces, one of said
faces being divided into two surfaces at such an angle to each other that the light
falling upon the receiving side of such prism plate from a given direction will
pass into the plate and be part of it reflected by one of said surfaces and part of
it refracted by the other.
3. As a new article of manufacture, a prism light consisting of a substantially
flat body of glass with a receiving surface on one side and a series of prisms
systemmatically arranged on the other side so as to produce an increased illuminat-
ing effect in the apartment, one face of each of said prisms divided into two parts

page_text: which intersect each other at an obtuse angle, one of said two surfaces joining the
single surface of the next succeeding prism at an acute angle.
Dated this 13th day of July 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.