Window Prism Lights having the Sides of their Prisms Connected by Short Slightly Curved Prisms.
Year: 1897

page_text: Date of Application, 13th July, 1897-Accepted, 28th Aug., 1897
COMPLETE SPECIFICATION.
Window Prism Lights having the Sides of their Prisms Connected by
Short Slightly Curved Prisms.
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 prismatic glass for windows, or the like, and has for its
object to provide a new and improved form of glass for this purpose, of which the
following is a description, reference being 'had to the accompanying drawings,
wherein
Figure 1 is a face view of a section of prismatic glass embodying my
invention;
Figure 2 is an edge view of the same;
Figures 3 and 4 are edge views of sections of glass provided with projecting
ribs or prisms, the angles of which are different from those shown in Figure 1.
Like letters refer to like parts throughout the several figures.
In the construction of prismatic glass for windows, it is found that the angular
relation of the faces of the prisms depends upon the conditions to be met and
hence are not the same for all windows. One of the objects of my invention is
to provide a form of glass whereby these prisms or projecting ribs may be formed
with the faces of any desired angular relation, and still have the width of the
prisms at the base and the length of the prisms substantially the same in all cases.
In Figures 1 and 2 I have shown a section of glass A provided with the projecting
ribs B, the outer edge of the ribs being curved at C, instead of being brought to a
sharp edge. This allows the surfaces D and D of the prisms to be made of any
desired angular relation without materially changing the length of the ribs or
their thickness at the base. I have found that the best general form of this glass
is that having the upper surface D of the ribs formed at an angle of approximately
75 degrees. In Figures 1 and 2 I have shown a section of glass in which the
upper surface D is formed at an angle of 75 degrees while the lower surface D¹
is 65 degrees. In Figure 3, the upper surface D is 75 degrees and the lower
surface D¹, 70 degrees. In Figure 4 both the upper and lower surfaces are formed
at angle of 75 degrees.
6
The device I prefer to call a prism light" as previously suggested. When
these lights are made thin and of brilliant or clear glass and when they are
mounted in thin or net-like frames slight irregularities or departures from
uniformity become greatly magnified and detract from the value of the product.
These prism lights are being put into the most expensive windows in elegant
stores on first-class street and hence the necessity of meeting the requirements of
the public by attending to even comparatively unimportant defects.
I find that in such prism lights, it is highly desirable, first, to preserve a practi-
cally uniform thickness of the glass of the entire prism plate into which these

page_text: prism lights are worked-that is, a practically uniform distance from the plane
surface of the plate to the extremity of the prism on the opposite side throughout
the several prism lights on the plate. I also find to get the desired result, it is
necessary to preserve a substantially uniform width of the prism at its base, so that
in every part of the complete plate there shall be exactly the same number of
prisms to the inch, and the various lines of the prisms, particularly as seen from
the outside, will run entirely across the plate in straight lines.
The importance of these features will be all the more evident when it is realized
that in mounting these prisms lights in prism plates, the prisms with surfaces of
different angles are used on various parts of the plate. It is, however, probably
best to have in any such plate the upper angle of the prism substantially the
· same, the variation being made in the lower angle.
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
clain is:
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Dated this 13th day of July 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.