An Improvement or Improvements in Globes or Bowls for Railway Carriage Roof Lamps and other Overhead Lamps, which Improvement or Improvements may also be Applied to Lamps Fixed to Walls or Vertical Surfaces.
Year: 1887

page_text: Date of Application, 26th Mar., 1887
Complete Left, 14th Dec., 1887
Complete Accepted, 20th Jan.. 1888
An Improvement or Improvements in Globes or Bowls for Railway
Carriage Roof Lamps and other Overhead Lamps, which
Improvement or Improvements may also be Applied to Lamps
Fixed to Walls or Vertical Surfaces.
We SAMUEL TELFORD DUTTON of Marl Bank in the City of Worcester Civil
Engineer and ALBERT CAY of Dartmouth Street Birmingham in the County of
Warwick Glass Manufacturer do bereby declare the nature of this Invention to be as
follows:-
Our invention is principally applicable to railway carriage roof lamps and we will
describe it in connection with a railway carriage roof lamp but our said invention is
also applicable to other roof lamps such for example as the roof lamps called sunlight
lamps as well as to lamps fixed against walls or other vertical surfaces or in angles
formed by two vertical walls or surfaces.
In order to facilitate the description of our invention we remark that a railway
carriage roof lamp as ordinarily constructed consists of a burner supported in a basin
like glass vessel having nearly the figure of a hollow hemisphere and commonly called
the globe. A concave reflector above the frame reflects downwards the light radiated
upwards from the flame but the light radiated from the flame horizontally is mostly
thrown on the sides and roof of the carriage all the parts of the carriage under the
lamp being very imperfectly illuminated. The object of our invention is more effectually
to illuminate the parts of the carriage under the lamp than is done by lamps of the
ordinary construction and we effect this in the following manner.
For convenience of application we make the glass vessel or globe of the lamp some-
what of the usual figure but instead of making the sides of the said globe parallel we
form on the outer surface of the globe a series of curved prisms or prismatic zones
concentric with the axis of the globe. The light radiated from the flame horizontally
or nearly horizontally talls upon the inner surface of the globe perpendicularly or
nearly so and suffers little or no refraction at that surface. On reaching the outer
surface of the globe the light passes from the glass into the air through the inclined
surfaces of the prismatic zones. At these surfaces it is refracted according to the well
known optical law called "Snell's law" or "law of sines" and is bent considerably
Q

page_text: downwards and most of the light which in ordinary lamps falls on the sides and upper
part of the compartment is refracted downwards and made to illuminate the body of
the carriage.
We prefer to make the bottom of the globe flat or concave externally which in the
case of the roof lamp forms a base on which the lamp may rest when out of its place
in the carriage roof.
In applying our invention to lamps fixed against walls or vertical surfaces or in
corners we employ lamp glasses or globes having the prismatic zones described but
consisting of only half globes or quarter globes or such other portions of globes as
will fit them for the particular situations in which they are to be used.
Member sixth day of March 1887.
W. T. WHITEMAN,
Agent for the Applicants.
An Improvement or Improvements in Globes or Bowls for Railway
other Overhead Lamps, which
Carriage Roof Lamps and
Improvement or Improvements may also be Applied to Lamps
Fixed to Walls or Vertical Surfaces.
We SAMUEL TELFORD DUTTON of Marl Bank in the City of Worcester, Civil
Engineer and ALBERT CAY of Dartmouth Street, Birmingham in the County of
Warwick, Glass Manufacturer do hereby declare the nature of our Invention and
in what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
Our invention is principally applicable to railway carriage roof lamps and we will
describe it in connection with a railway carriage roof lamp, but our said invention is
also applicable to other roof lamps such for example as the roof lamps called sunlight
lamps as well as to lamps fixed against walls or other vertical surfaces or in angles
formed by two vertical walls or surfaces.
In order to facilitate the description of our invention we remark that a railway carriage
roof lamp as ordinarily constructed consists of a burner supported in a basin like glass
vessel having nearly the figure of a hollow hemisphere and commonly called the globe.
A concave reflector above the flame reflects downwards the light radiated upwards from
the flame but the light radiated from the flame horizontally is mostly thrown on the
sides and roof of the carriage all the parts of the carriage under the lamp being very
imperfectly illuminated. The object of our invention is more effectually to illuminate

page_text: the parts of the carriage under the lamp than is done by lamps of the ordinary
construction and we effect this in the following manner :-
For convenience of application we make the glass vessel or globe of the lamp some-
what of the usual figure but instead of making the sides of the said globe parallel wo
form on the outer surface of the globe a series of curved prisms or prismatic zones
concentric with the axis of the globe. The light radiated from the flame horizontally
or nearly horizontally falls upon the inner surface of the globe perpendicularly or
nearly so and suffers little or no refraction at that surface. On reaching the outer
surface of the globe the light passes from the glass into the air through the inclined
surfaces of the prismatic zones. At these surfaces it is refracted according to the well
known optical law called "Snell's law" or "law of sines" and is bent considerably
downwards and most of the light which in ordinary lamps falls on the sides and upper
part of the compartiment is refracted downwards and made to illuminate the body of
the carriage.
We prefer to make the bottom of the globe flat or concave externally which in the
case of the roof lamp forms a'base on which the lamp may rest when out of its place
in the carriage roof.
In applying our invention to lamps fixed against walls or vertical surfaces or in
corners we employ lamp glasses or globes having the prismatic zones described but
consisting of only half globes or quarter globes or such other portions of globes as will
fit them for the particular situations in which they are to be used.
Figures and 2 of the accompanying Drawings represent respectively a vertical
section and a half external elevation of the globe or bowl of a railway carriage roof
lamp constructed according to our invention and Figure 3 represents drawn to a small
scale a cross section of a railway carriage with one of our improved lamp globes or
bowls applied to the roof lamp of the same, the dotted lines in the said Figure 3
indicating the principal rays of light spread by the action of the glass globe or bowl
over the lower part of the carriage.
bis the glass globe or bowl of the roof lamp in which the burner is supported the
outer surface of the said globe or bowl being made into a series of curved prisms or
prismatic zones concentric with the axis of the globe according to our invention. The
curved prisms or prismatic zones are preferably graduated as represented in the
drawing but we do not limit ourselves thereto as the prismatic zones may be of the same
size throughout. The bottom of the globe or bowl 6 is concave externally or it may
be made convex externally as in the globe represented in Figures 4 and 5. The bottom
may however be made flat or provided with a hole as represented in Figures 10
and 11.
The letter a indicates the centre of the light a the paths of the principal rays of
light after refraction through the curved prisms or prismatic zones of the globe or
bowl b; subordinate rays pass obliquely through the bases of the prisms at various
angles which it is unnecessary here to describe or follow; a are the radial points from:
which the convex zones of the globe or bowl b are drawn. The radial points a³ are
obtained by tracing the rays of light through the prismatic zones in accordance with
the law of sines.
The dotted lines and f' indicate the range of the reflected rays in the globe or
bowl.
The wick tube c, oil cistern d and reflector e are shown in position but these parts
may be of any desired construction.
Figures 4 and 5 represent respectively a vertical section and an external elevation
of a glass globe or bowl constructed according to our invention suitable for a sun or
ceiling light with the reflector e in position, the parts being marked with the same
letters of reference as corresponding parts in Figures 1. 2 and 3. The bottom of this
globe or bowl may be concave or flat or provided with a hole.
Figures 6 and 7 represent respectively an external elevation and a plan of a semi
circular glass globe or bowl constructed according to our invention suitable for fixing
against a wall.

page_text: Figures 8 and 9 are similar views of a globe of a quadrant or sector like shape
constructed according to our invention suitable for fixing in an angle or corner.
Figures 10 and 11 represent respectively a vertical section and a plan of a glass
globe or bowl refracting the light less downwards such as would be suitable for a
pendant lamp, the said globe or bowl being open at bottom.
Where it is wished to refract the light downwards without concentrating it the outer
faces of the prismatic zones are made rectilinear in cross section but when it is wished
not only to refract the light downwards but also to concentrate it the outer faces of
the zones are made convex.
For convenience in manufacture the globes shown in Figures 4, 5, 10 and 11 may
be made in parts and mounted in a frame.
Having now particularly described and ascertained the nature of our invention
and the manner in which the same is to be performed we declare that we claim as our
invention of An improvement or improvements in globes or bowls for railway
carriage roof lamps and other overhead lamps and lamps fixed to walls or vertical
surfaces;-
Forming on the outside surface of the glass globes or bowls of the said lamps a
series of curved prisms or prismatic zones preferably graduated and so formed as to
refract or refract and concentrate downwards those rays of light which are radiated
from the flame of the lamp upwards and horizontally and thereby to illuminate
those parts of a carriage or place situated underneath or at a lower level than the
lamp substantially as herein before described and illustrated in the accompanying
Drawings.