Improvements in Signals for Railway and other Purposes.
Year: 1888

page_text: Date of Application, 5th June, 1888
Specification Accepted, 6th July, 1888
Improvements in Signals for Railway and other Purposes.
1 JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this Invention which has been com-
municated to me from abroad by Charles Herschel Koyt of Swarthmore in the
State of Pennsylvania in the United States of America and in what manner the
samo is to be performed to be particularly described and ascertained in and by
the following statement
It is mainly the object of this Invention to provide a night signal to be used in
conjunction with the semaphore now extensively used on railroads for day signalling
purposes.
The night signals commonly employed for this purpose consist of various coloured
lights the use of which is on many accounts objectionable as is well known. It is
the object of this Invention to provide for this purpose an elongated beam of light of
well defined dimensions the position of which like that of the ordinary semaphore
arm, can be shifted from the vertical to the horizontal position (as distinguished from
a series of separate lights obtained from a series of detached deflecting surfaces set at
an angle to the light)
According to this invention the reflecting surface is made of the contour of the
longitudinal section of a paraboloid or approximately so; and this section is mounted
or pivoted in such a manner that it is capable of rotating about an axis corresponding
to the axis of the paraboloid, and the light is fixed or placed at a point corresponding
to the focus of the paraboloid.
A reflecting surface of the form specified has the property of making parallel all
rays reflected by it, the consequence being that there is obtained by this means a
continuous band or beam of light of definite dimensions. In practice in view of the
fact that this band or beam should be of such dimensions that at the conventional
distance at which the signal comes under the observation of the engineer, it shall be
wide enough to extend across the track to which it is appropriated and deep or broad

page_text: enough to about cover the observation portion of the cab of the engine it will be
found desirable to slightly modify both the longitudinal and transverse curvature of
the paraboloidal section which forms the reflecting surface so that at such distance
there will be sufficient divergence of the rays to produce a beam of the dimensions
indicated To accomplish this result however the modification in form of the reflector
need be very slight, and it remains to all intents and purposes of the contour of the
section of a paraboloid
By mounting or pivoting this reflector so that it will be rotatable about an axis
corresponding to the axis of the paraboloid and by placing the lamp or light at the
focus of the paraboloid an arrangement of parts is obtained by wluch the continuous
band or elongated beam of light is produced in any position to which the reflector
may be moved.
For railroad signalling it will be found convenient and desirable to mount the
reflector on, or in, the pivoted semaphore arm; and it is in this connection that the
improvement is illustrated in the accompanying drawings to which I will now proceed
to refer in order that the manner in which this invention is or may be carried into
offect may be better understood.
Figure 1 is a side elevation of so much of a semaphore as is needed to illustrate
the invention.
Figure 2 is a plan of the same.
Figure 3 is a section on line 3-3 figure 1.
Figure 4 is a diagram illustrative of the theoretical considerations which are
involved in the invention.
A is the post or standard and-B is the semaphore arm, which is pivoted to the said
post and is operated by the usual means which latter are not shown inasmuch as they
are well known and form no part of this invention.
The reflector which is employed is represented at C. It is mounted in, or on, the
pivoted semaphore arm B as indicated and moves with it.
The reflector proper is made of silvered glass, burnished metal or other proper
reflecting material, the shape of which approximates closely to, and is practically
the same as that of the section of a paraboloid, the concave face of which is the
reflecting surface.
In the diagram Figure 4, a is a portion of a parabolic curve of which 61 is the
axis, and c the focus. Divergent rays of light from a lamp or other light placed at
the focus c will be reflected from the parabolic surface as rays parallel with one
another So that from a section of the paraboloid (or approximately so) will be
obtained a band or elongated beam of light of definite dimensions which can be made
to assume a vertical or horizontal or any intermediate position by shifting corre-
spondingly the position of the section about an axis corresponding to the axis of the
paraboloid.
To this end, in the signalling device shown in Figures 1 and 2, inasmuch as the
reflector C is mounted on and moves with the pivoted semaphore arm B, the axis b¹
of motion of the latter is so situated with reference to the reflector that it will
correspond to or coincide with the axis of the paraboloid of which the reflector is a
section and the lamp D, or other source of light is fixed or attached to the standard A
in such position that it will be situated at the focus of the paraboloid of which C is a
section, and ₁ is the axis.
The reflecting surface can be held in any suitable frame m of wood or other material
and the said frame may if desired be fitted with a slide n for the purpose of covering
the reflector during the day which slide is of course to be withdrawn from over the
reflector whenever the latter is required for use.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. In a signalling apparatus the combination with a support or standard of a
reflector having the shape or approximately the shape of the section of a paraboloid

page_text: as described, and mounted on or pivoted to the said support so as to be rotateable
about an axis corresponding to or coincident with the axis of the paraboloid of
which the said reflector is a section substantially as and for the purposes hereinbefore
set forth.
2. The combination in a signalling apparatus of a support or standard, a reflector
having the shape or approximately the shape, of the section of a paraboloid as
described, and mounted on or pivotted to the said support so as to be rotatable about
an axis coincident with the axis of the paraboloid of which the said reflector is a
section, and a lamp or other source of light situated on said support, at the focal
point of the said paraboloidal reflecting section substantially as and for the purposes
herein before set forth.
1
1
0 T
1000
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C.,
Agents.