IMPROVEMENTS IN LENSES FOR SIGNAL LIGHTS OR LANTERNS ON RAILWAYS AND ELSEWHERE, MORE ESPECIALLY WHERE LIGHT HAS TO BE PROJECTED TO A GREAT DISTANCE
Year: 1877

page_text: LETTERS PATENT to William Phillips Thompson, of 6, Lord Street, Liverpool,
in the County of Lancaster, British and International Patent Agent and Con-
sulting Engineer, for the Invention of "IMPROVEMENTS IN LENSES FOR
SIGNAL LIGHTS OR LANTERNS ON RAILWAYS AND ELSEWHERE, MORE ESPECIALLY
WHERE LIGHT HAS TO BE PROJECTED TO A GREAT DISTANCE." A communication
from abroad by Charles Frederic Haughton, of Corning, in the County of
Steuben, and State of New York.
PROVISIONAL SPECIFICATION left by the said William Phillips Thompson
at the Office of the Commissioners of Patents on the 24th December 1877.
WILLIAM PHILLIPS THOMPSON, of 6, Lord Street, Liverpool, in the County of
Lancaster, British and International Patent Agent and Consulting Engineer. "IM-
PROVEMENTS IN LENSES FOR SIGNAL LIGHTS OR LANTERNS ON RAILWAYS AND
ELSEWHERE, MORE ESPECIALLY WHERE LIGHT HAS TO BE PROJECTED TO A GREAT
DISTANCE" A communication from abroad by Charles Frederic Haughton, of
Corning, in the County of Steuben, and State of New York.
This Invention, which is specially adapted to signal lights or lanterns used upon
railways, but will also be found useful in all cases where light is to be projected to
a great distance, has for its object to produce a lens possessing a sufficient degree of
elasticity in all directions to avoid rupture by expansion from the heat of the illu-
minating flame, and also to secure the projection of a portion of the rays to a long
distance, with sufficient dispersion of the others over a larger near field. I propose
to effect this by forming on either or both of the surfaces or faces of a meniscus
lens, being the segment of either a sphere or spheroid, a series of concentric zones
of Iternate elevat ions and depressions.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Phillips Thompson in the Great Seal Patent Office on the
14th May 1878.
WILLIAM PHILLIPS THOMPSON, of 6, Lord Street, Liverpool, in the County of
Lancaster, British and International Patent Agent and Consulting Engineer.
"IM-
PROVEMENTS IN LENSES FOR SIGNAL LIGHTS OR LANTERNS ON RAILWAYS AND
ELSEWHERE, MORE ESPECIALLY WHERE LIGHT HAS TO BE PROJECTED TO A GREAT
DISTANCE" A communication from abroad by Charles Frederic Haughton, of
Corning, in the County of Steuben, and State of New York.
My Invention relates to lenses which are employed in giving signals used upon
railway lamps or lanterns where light is to be projected to a great distance, and
has for its object the production of a more durable and cheaper lens, adapted to
the illumination of a greater surface, and giving a broader field of illumination than
is possible in lenses as now constructed.
The Invention consists in a lens, meniscal in form, and the segment of either a
sphere or spheroid, having upon either or both of its surfaces or faces a series of
concentric zones, thus producing a lens possessing a sufficient degree of elasticity
in all directions to avoid rupture by reason of local expansion from the heat
incident to the illuminating flame, as will be herein-after more fully set forth.
For full comprehension thereof reference must be had to the annexed Drawings, in
which,
.
Fig. 1 is a front elevation of a lens embodying my Invention, which is in the
form of a segment of a sphere.
Figs. 2 and 3 are vertical central sectional views showing the lens respectively,
with the concentric zones on the outer and inner faces.
Similar letters of reference indicate like parts.
In manufacturing my Invention I employ a solid piece of glass, which I mould
into a meniscal form, giving it the general configuration of a segment of a sphere,
or a segment of a spheroid, as shown respectively at A and A'in the Drawings.
Upon either the convex or concave faces of these said lenses A and A¹, I form by
means of suitable moulds a series of concentric zones or alternate elevations and
dopressions, as shown plainly at a, b, and a¹, b1, respectively, in Figures 2 and 3;
or, when it is so desired, both the convex and concave faces of said lenses are given
a series of concentric zones.
By means of my lens A or A³, mensical in form, and the segment of either a sphere
or spheroid, and having upon either or both of its faces a series of concentric zones,
I am enabled to produce a refracting surface for illumination, and to secure the pro-
jection of a portion of the rays to a long distance, attended with a sufficient dis-
persion of other rays to render the light easily visible over a larger near field, and
at also a greater distance than in lenses as ordinarily constructed.
By employing the form described I also obtain a lens which, from its concave
shape internally, does not come so near the illuminating flame as those of hollow,
cylindric, or prismatic form heretofore used, and will thus measurably avoid the
heating of the central part of the lens, and also by reason of the curvature in all
directions introduce an element of elasticity not found in prismatic, cylindric, or
plano-convex lenses.
My lenses, it is evident, are therefore especially adapted to be employed
in all cases where a semaphore lens is required, and in all signal lanterns and
railway lights.
Having now described the construction and operation of my Invention, I beg to
state that what I claim is as follows:-A semaphore lens of meniscal form, having
one surface, a portion of sphere or spheroid, and the other composed of zones of a
parabolic or hyperbolic form, with two surfaces, one adapted to project a portion of

page_text: the rays to a long distance, and another at the same time, by dispersing another
portion of the rays to illuminate a field near the lens, substantially as set forth.
In witness whereof, I, the said William Phillips Thompson, have hereunto
set my hand and seal, this Tenth day of April, in the year of our Lord One
thousand eight hundred and seventy-eight.
Witness,
JOHN O. O'BRIEN,
Clerk to the said
William Phillips Thompson.
WILLIAM P. THOMPSON. (LS)