Prismatic Window Lights with one Surface of Each Prism Curved.
Year: 1897

page_text: Date of Application, 13th July, 1897-Accepted, 21st Aug.,
1897
COMPLETE SPECIFICATION.
Prismatic Window Lights with one Surface of Each Prism Curved.
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
performed, to be particularly described and ascertained in and by the following
statement:
My inventions relates to prismatic glass and particularly to such as is designed
for use in windows and the like. Generally speaking it consists of a plate of glass
with a series of prismatic ribs an one side thereof, the same having in many
instances one face somewhat nearly parallel to the horizontal, another set at a
sharp incline to the first, and wholly or partially curved. I have illustrated my
invention and improvement in the accompanying drawing, wherein
Figure 1 shows an old form of glass, the lines showing approximately the action
of some of the rays of light which pass therethrough;
Figure 2 is another like form with my improvement applied showing in like
manner the passage of the rays of light.
Figure 3 is a preferred modification.
Like parts are indicated by the same letter in all the figures.
A is the body or the plate of glass, B a series of prisms thereon having each a
face C and an inclined face D. As shown in Figure 1 these faces are all plain.
F is a ray of light bent in the body of glass as indicated at G and again bent as
indicated at H, this latter bend occuring as it issues from the inclined face. Of
course, the faces C C may be more or less inclined. J indicates a ray of light
which is received on the face C and is reflected away. K indicates a part of the
prism which may be removed for certain purposes, thus giving more or less of the
incline to upper face of the prisms. In Figures 2 and 3, the action of the curved
surface is such that a large number of rays, as indicated, are directed into lines
not greatly departing from the horizontal and are thus in the first instance pre-
vented from being received upon and reflected away by the surface C, even when
that surface is elevated above the line of parallelism with the course of light
through the glass and in the second instance the action of the curve is such as to
distribute the light so as to cause equal quantities of light so to speak to fall upon
equal surface area at different distances from the window along a horizontal line
as indicated by the diagram lines L, L', L³, L3, L4, L5 and L. This curve can
of course be varied and must be varied to suit different requirements. By varying
the curve somewhat, the light can be directed so that equal quantities of light will
fall upon equal horizontal areas at different distances from the window instead
of equal areas as indicated by the diagram of Figure 3. Moreover, the curves
should vary perhaps according to the directions from which the greater quantity
of light to be transmitted is received. Under the conditions assumed in Figure 3,
the light to be received along the lines parallel with the ray F and it being
intended to deliver substantially equal quantites of light over equal areas at
different distances from the window, the curve should be substantially as shown.

page_text: If the light is to be thrown into more nearly horizontal lines the surface C may
be less inclined than indicated in Figure 3 and may even be substantially hori-
zontal as indicated in Figure 2, but of course for most practical purposes the
light should be distributed somewhat below the horizontal lines and in such cases
with this improvement it might be desirable to have the upper surface C very
materially inclined with reference to the horizontal: The curvature of the surface
of the prism must be such that it will produce the desired result and to produce
such result, this curvature must be other than the are of a circle, as shown in the
drawing.
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:
As a new article of manufacture, a prism light comprising a substantially flat
body of glass with a receiving surface on one side and a series of prisms on the
opposite side, extending substantially across the body and systematically arranged 1
to produce an increased illuminating effect in the apartment, each prism having
two faces, one a plane face and the other a curved face, the curvature being other
than the arc of a circle and such, substantially as shown and described, that all
the rays of light falling from a predetermined direction upon the receiving surface
pass into the body and are thence transmitted in such manner that equal quantites 2
of such light fall on equal areas taken at different distances from the prism light
along a horizontal line, such areas perpendicular to the direction of the ray of such
light derived from the prism light.
Dated this 15th day of July 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.