Prism Plates for Windows having Prisms of Varying Angular Arrangement.
Year: 1897

page_text: Date of Application, 13th July, 1897-Accepted, 28th Aug., 1897
COMPLETE SPECIFICATION.
Prism Plates for Windows having Prisms of Varying Angular
Arrangement.
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 invention relates to the production of prism plates for windows or openings
where it is desired to usefully direct an increased amount of light into and about
the apartment to be illuminated.
Prismatic lights are made up into large prismatic plates, the several lights
being united together in various ways. The preferred form of the light is that
in which it has one plane surface and a series of parallel prisms on the opposite
surface, and the preferred form of prism plate is that in which a series of such
prism lights is mounted together by a suitable grid, net or frame so as to present
a substantially plane exterior surface. Now, under the various conditions to
which such prism lights are subjected, conditions which vary with the width of
the street or opening opposite the window, the height of the buildings or obstruc-
tions opposite, the position of such obstructions, the direction toward which such
opening looks, it is evident to any one who is familiar with the principle on which
such prism lights operate, that there must be in many such complete prism
plates a variety of prisms, that is to say, prisms of different angular arrangement.
Such prism plates are in demand for very valuable properties, and are used in
high class stores and building fronts and upon popular thoroughfares, so that
it has become necessary to furnish not merely the increased effect desired, but also
a highly finished, ornamental and beautiful window plate which shall not offend
the laws of good taste.
To get the best results, it is found that the exterior of the plate should be uniform
and regular, but irregularities on the inside of the plate, or rather on the prism
side, are of less consequence, because it is from that side that the light, as these
plates are ordinarily, used, proceeds. The prism side is therefore luminous to such
a degree and in such a manner that slight irregularities there will be of little con-
sequence. These prism plates are manufactured and shipped all complete and
ready for insertion in the window or other openings, and to make them safe and
suitable for shipping, handling and selling in the market, they must be practi-
cally of uniform thickness. Moreover, if, when the plates are put in position,
there are any prisms which project or any sets of prisms which extend out into
the room further than the others, it is quite evident that all such prisms will
become convenient resting places for dust, dirt, and the like, whereby the
efficiency and beauty of the prism plate will be rapidly deteriorated. Constructors
have been at great expense and trouble to render such work sufficiently smooth,
uniform, regular and free from dirt and the like. Uniform thickness is highly

page_text: desirable, that is to say, each prism wherever located on the finished plate should
be shaped so that its outer extremity will be the same distance from the surface
of the plane side of the prism as the outer extremity of each other prism.
To give the finished plate a uniformi, regular and harmonious appearance when
viewed from the plane side, there should be the same number of prisms to each
unit of length in every part of the prism plate. It is also desirable that every
prism should have the same width at its base. These three features are preferably
embraced in one and the same prism plate, and to do so the side surfaces of the
prisms preferably should be joined by a curved surface at the outer extremity of
such prism, where otherwise the prism would project too far inwardly.
My invention is illustrated in the accompanying drawings, wherein
Figure 1 is an elevation of a prism plate looking toward the prism side.
Figure 2 is a section on the line 2-2 of Figure 1.
It will be evident that many other forms and combinations of prisms will occur
in practice and that the prisms of different angles will be distributed differently
over the plate. I have simply shown one arrangement, diagrammatically as it
were, for in a plate having but nine prism lights there would ordinarily be little
occasion for any great difference in angles or prisms.
In this form which I have shown, at the top of the plato are prisms having
the upper interior angle about 75° and the lower interior angle about 50°. This
is the prism, which, with a given base, will have its outer edge the least removed
from the plane surface of the prism plate when compared with other prism lights
in the plate. It is therefore taken as a standard for that particular plate and
fixes the thickness of the plate and prisms. Farther down along the plate are
prisms having an upper interior angle about 60° and other prisms having upper
interior angles of 750 and lower interior angles of 70°. Obviously, such prisms
in order to have the same elevation as the first-mentioned prism, must either have
narrow bases or their outer projecting parts must be removed, and if removed,
the two side surfaces of the prism should be connected by a curved surface.
In these two sets of prisms, I have shown in dotted lines the distance to which
they would project with their sides not connected by curved surfaces, and I have
also shown by dotted lines their narrow bases, were they to be constructed so as
to have the same elevation as the upper prisms and yet have the same number to
each unit of distance measured up the plate.
Like parts are indicated by the same letter in all the figures.
A is the surrounding frame, B, B1, B2 are the prism lights set in a grid composed
of the warps C and the short ties D, the lights are preferably electro-glazed into a
net or frame. Each prism light preferably has the plane receiving surface E.
The prism light B has the prisms F, the prism lights B' the prisms G, and the
prism light B and the prisms H. These several prisms having the angular
arrangement above referred to, and the dotted lines indicate what has already
been described.
Of course, so far as the appearance of the light from the exterior is concerned,
it is not essential that the prisms should all have an equal elevation, but it is
important that there should be an equal number of prisms for each unit of distance
up the plate. As previously explained, it is absolutely necessary that there should
be prisms of different angles in many such plates in order to adapt them for the
conditions under which they are to be used.
Having now particularly described and ascertained the nature of the said in-
vention, and in what manner the same is to be performed, I declare that what
I claim is:
1. A substantially flat prism plate consisting of a body of glass, either made
of one piece or of a series of sections, and provided with a receiving surface on
one side and a series of prisms running across the plate on the opposite side, such
prisms systematically arranged to produce an increased illuminating effect in.

page_text: the apartment and having cross-sections varying in their angular conformation
systematically and regularly from one portion of the plate to another to give
an increased refraction of light from one portion of the plate to another.
2. A substantially flat prism plate consisting of a body of glass, either made
of one piece or of a series of sections, and provided with a receiving surface on
one side and a series of prisms running across the plate on the opposite side, such
prisms systematically arranged to produce an increased illuminating effect in
the apartment and having cross-sections varying in their angular conformation
systematically and regularly from one portion of the plate to another to give
an increased refraction of light from one portion of the plate to another, and such
prisms arranged so as to have equal bases and so that there will be an equal
number of such prisms for each unit of length measured transversely to the prisms.
3. A prism plate composed of a series of prism lights having the peculiarities
illustrated in Figures 1 and 2 and substantially as described.
4. A prism plate comprising a series of prism lights secured together in a
suitable frame so as to form such plate, each prism light having uniform prisms
but the prisms of different lights varying in angular arrangement.
5. A prism plate comprising a series of prism lights joined together to form
such prism plate, the prisms of the plate having different angles, such prisms
arranged so that there are uniform numbers of prisms for equal distances measured
transversely to such prisms, and all the prisms of an equal elevation measured
from the plane side of the prism plate and all the prisms having equal widths
at their bases.
Dated this 13th day of July, 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.