AN IMPROVEMENT IN APPARATUS FOR ELECTRICALLY CONTROLLING RAILWAY. SIGNALS
Year: 1884

page_text: I, CHARLES HODGSON of Canterbury Road Kilburn in the County of Middlesex,
Mechanical Engineer do hereby declare the nature of my said Invention for
"AN IMPROVEMENT IN APPARATUS FOR ELECTRICALLY CONTROLLING RAILWAY.
SIGNALS" to be as follows :——
In the Specification to Letters Patent granted to me on the 6th June 1883
No 2817, I described means of controlling the working of a railway signal at one
station by electric communication from a distant station, using, for the purpose of
communicating, the ordinary block telegraph instruments with certain modifications.
I also described a modification of signalling apparatus electrically controlled, so that
a free signal cannot be displayed unless one or several signalmen at different
stations, or signalmen in conjunction with the action of passing trains have put
the electrical connections in such a condition. that the signal may be displayed
with safety. My present Invention relates to a modification of, and addition to
the electrical connections employed in such cases as are above referred to, whereby
I provide against possible dangers that might.result from negligence or inattention
of the operators. In order that my Invention may be understood, I will suppose
that there is a section of railway worked on the block system extending between
two stations occupied by signalman A and B. A, working his telegraph instrument,
communicates electrically with B, shewing on B's instrument, usually by the
movement of a miniature semaphore therein, the condition of the line as being
"clear" or "blocked." When the "line clear" signal is transmitted from A to B,
the electrical impulse, besides moving B's miniature semaphore, also moves a
contact key which brings a local battery at B's station into circuit with the -
electrical signal apparatus there, whereby that apparatus is kept in such a condition
that a free signal can be displayed by B allowing the passage of a train. This
local circuit may then be opened by a third signalman at some part of the line,
or by the passage of a train over a contact treadle or trigger, and thereupon
B should be rendered powerless to again display the signal until he has received
a subsequent "line clear" signal from A. But it might happen that A, through
inattention, had left his electrical connection with B complete, and consequently.
B's local circuit would still be effective on the sigual controlling apparatus at his
station, and B could therefore display a signal when he should not be able to do so.

page_text: To provide against this risk, I introduce in the conducting line from A to B an
electro magnet provided with an armature which works a contact key in B's local
circuit, and I connect this armature with the electrically controlled. signalling
apparatus worked by B-and acted upon by the other circuit opening apparatus
worked by the passing train or otherwise, so that, when the local circuit is opened,
the armature is moved up to the poles of the electro-magnet, the key worked by it
when it is in that position opening the local circuit. Now if A's electrical
connection with B happened to be maintained, the electro-magnet would continue
to hold its armature in position, thereby keeping B's local circuit open and
rendering it impossible for B to free his signal. If, on the other hand, A had
properly broken electrical connection with B, then the electro magnet, being inert,
would cease to hold its armature, and B's circuit would then be so far closed that B
could operate by it for freeing his signal, provided the circuit were also closed at
its other point by a "line clear" signal from A.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.

page_text: I, CHARLES HODGSON of Canterbury Road, Kilburn, in the County of Middlesex,
Mechanical Engineer do hereby declare the nature of my Invention for "AN
IMPROVEMENT IN APPARATUS FOR ELECTRICALLY CONTROLLING RAILWAY SIGNALS "
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement:―
5
In the Specification to Letters Patent granted to me on the 6th June 1883
N° 2817 I described means of controlling the working of a railway signal at one
station by electric communication from a distant station, using, for the purpose of
communicating, the ordinary block telegraph instruments with certain modifications.
I also described a modification of signalling apparatus electrically controlled, so
that a free signal cannot be displayed unless one or several signalmen at different
stations, or signalmen in conjunction with passing trains, have put the electrical
connections in such a condition that the signal may be displayed with safety
My present Invention relates to a modification of, and addition to the electrical
connections employed in such cases as are above referred to, whereby I provide
against possible dangers that might result from negligence on inattention of the
operators. In order that my Invention may be understood, I will suppose that
there is a section of railway worked on the block system extending between two
stations occupied by signalmen A and B. A working his telegraph instrument,
communicates electrically with B, shewing on B's instrument, usually by the
movement of a miniature semaphore therein, the condition of the line, as being
"clear" or "blocked." When the "line clear" signal is transmitted from A to B,
the electrical impulse, besides moving B's miniature semaphore, also movės a
contact key, which brings a local battery at B's. station into circuit with the
electrical signal apparatus there, whereby that apparatus is kept in such a condition
that a free signal can be displayed by B allowing the passage of a train. This
local circuit may then be opened by a third signalman at some part of the line
or by the passage of a train over a contact treadle or trigger, and thereupon
B should be rendered powerless to again display the signal until he has received
a subsequent "line clear" signal from A. But it might happen that A, through
inattention, had left his electrical connection with B complete, and consequently
B's local circuit would still be effective on the signal controlling apparatus at his
station, and B could therefore display a signal when he should not be able to do so.
To provide against this risk,. I introduce in the conducting line from A to B an
electro-magnet provided with an armature which works the contact key in B's
local circuit, and I connect this armature with the electrically controlled signalling
apparatus worked by B and acted upon by the other circuit opening apparatus
worked by the passing train or otherwise, so that when the local circuit is opened
the armature is moved up to the poles of the electromagnet, the key worked by.it,
when it is in that position, opening the local circuit.
Now, if A's electrical connection with B happened to be maintained, the electro-
magnet would continue to hold its armature in position, thereby keeping B's local
circuit open and rendering it impossible for B to free his sigual. If, on the other
hand, A had properly broken electrical connection with B, then the electromagnet,
being inert, would cease to hold its armature, and B's circuit would then be so far
closed that B could operate by it for freeing his signal, provided the circuit were
also closed at its other point by a "line clear" signal from A.
Figs. 1 and 2 shew the lever apparatus of the kind described in my Specification,
No 2817 of 1883 above referred to, with the addition thereto, according to my

page_text: present Invention, of the means for keeping open the local circuit under the
conditions above mentioned. Fig. 1 shews the apparatus in such a condition that
the local circuit is, or can be closed. Fig. 2 shews the condition under which the
local circuit cannot be closed so long as the electrical current from a distance
is maintained acting on the block telegraph instrument. In these Figures L L' are
parts of the conducting wires of the local circuit, terminating in springs e e¹, which
while they are pressed by a plate P close that portion of the circuit. The plate P
is fixed on a loaded lever carrying the armature A of an electro-magnet M which
has its coil in circuit with the block telegraph instrument operated by the current
from a distance. While the magnet M remains unexcited, and the armature A is
away from the poles of M, the local circuit of which L L' form part, can, so far
as this contact affects it, be closed, and the lever B of the apparatus can be raised,
lowering the signal, without affecting the contacts e e¹ because the end b, in
descending, passes the loaded pawl C, merely lifting its counterweight. But, when
the lever B has once been raised lowering the signal, then during the descent of B
restoring the signal to its " danger" position, the end b, in rising, raises C and
with it the rod D, and brings the armature lever of M into the position shewn in
Fig. 2.
'
'
If it happens that M is excited, it retains the armature A attracted to it, and
the plate P being thus held away from the springs e e', the local circuit cannot
be closed. When the current in the coil of M ceases, the armature A is drawn
away by the weight on its lever, and the plate P is again pressed against the
springs e e as shewn in Fig. 1 so that the local circuit can be again closed.
The coil of M may obviously be in circuit with a local battery brought into
action by a relay operated by the current that acts on the block telegraph
instrument.
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 claim is
1. In combination with electrically controlled signal lever apparatus, a contact
key, which if the lever apparatus has been once used for lowering the signal and
if the key is held by the maintenance of a current from a distance, prevents the
electrical control of the lever apparatus from so operating, as to permit the signal
to be again lowered, until the current from a distance ceases.
2. In combination with signal lever apparatus of the kind described in the
Specification N° 2817 of 1883, the electromagnet M, the contacts Pl, the rod D
and the weighted pawl C acted on by the lever B, substantially as and for the
purposes herein set forth.
Doted this ord
1004
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