IMPROVEMENTS IN ELECTRIC BLOCK SIGNALS FOR RAILWAYS
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
ELECTRIC BLOCK SIGNALS FOR RAILWAYS" to be as follows:-
This Invention relates to a block system of railway signalling wherein an
automatic signal set by the passage of the train is employed; and the Invention
consists of an electric locking arrangement adapted for locking the signal board in
displayed position until the train that caused it to be set reaches the next signal
station, whereupon the signal board of the signal next in rear will be released,
indicating to the succeeding train that the line between it and the first signal
is clear.
The signal is raised or set by a train passing over a treadle lever alongside the
rail, and it is retained in its set position by an automatic time signal consisting of
clock work which engages with the signal and retards its descent for a definite
time after coming into action by means of a fan.
The electric locking appliance is applied to each signal except the last of the
series and consists of an electro-magnet whose armature is so arranged as to
intercept the revolution of the fan only when it is attracted by the passage of a
current through the magnet a spring withdrawing it when the electric current
ceases to flow through the magnet.
An electric switch or cut out is arranged to be opened and closed by the signal
board when it is raised and lowered.
The electrical connections in a system of several signals at suitable intervals
along the railway and which I will distinguish by numbers are as follows:-
All the electro-magnets in the system are in a closed battery circuit and their
armatures are constantly held in position to lock their respective time signals
except when cut out of circuit by means of a switch or cut out in connection with
each signal except the first which is opened and closed by the raising and lowering
of the signal. One post of each switch is connected to the main wire in rear of the
[Price 611

page_text: electro magnet of the same signal and the other post to the main wire in rear of
the electro magnet of the preceding signal, so that when the switch is closed by
the act of raising the signal the current will be switched off from the electro
magnet of the preceding signal thus permitting the release of its time signal
mechanism and allowing the signal to drop under its control. When the signal
has descended the switch will be again opened and the current will again pass
through the electro-magnet as before. Thus signal N° 1 will be set by the passing
train and locked until the train reaches N° 2 whereupon No 1 will be taken off
and No 2 will be set and locked until the train reaches N° 3 and so on in succession.
In case the electric system should get out of order the time signal remains,
which in itself is a good safeguard against collisions and which may be regulated
as to time by means of interchangeable fans.
It will be understood however that I do not confine myself to the use of the
time signal in connection with the electric systein as any other suitable automatic
signal might be used, but it is preferred to use this time signal, since by means of
the retarding mechanism, only a slight force applied to the fan is required to
effectually lock the signal board in displayed position.

page_text: I, ALEXANDER MELVILLE CLARK, of the firm of A. M., and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
ELECTRIC BLOCK SIGNALS FOR RAILWAYS" and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
This Invention relates to a block system of railway signalling wherein an
automatic signal set by the passage of the train is employed; and the Invention
consists of an electric locking arrangement adapted for locking the signal board in
displayed position until the train that caused it to be set reaches the next signal
station, whereupon the signal board of the signal next in rear will be released,
indicating to the succeeding train that the line between it and the first sigual
alead is clear,
Reference is to be had to the accompanying Drawings forming a part of this
Specification, in which :—
Figure 1 shows an automatic time signal having the electric locking attachment
of this Invention applied thereto. Figure 2 is a sectional elevation of the same,
taken on the line xx of Figure 1; and Figure 3 is a diagram view illustrating the
electric connections for several signals arranged in accordance with this Invention,
the signals being numbered.
The same letters of reference indicate similar parts in all the Figures.
In the present arrangement shown in the Drawings, the electrical locking
appliance A is contained within the signal housing B, so as to act in conjunction
with the fan C, acting as a lever to the retarding clock mechanism D, which
mechanism is adapted to clutch and retard the signal board E, when raised by a
train passing over the curved end of the bent lever F, the fan C revolving only
when the board E, descends.
The signal board E when elevated will be caught by the wheel m (of the clock
mechanism D) which gears with the rack m secured to the signal board and this
wheel is free to turn with its shaft in the direction of the arrow shown in
Figure 1; but by means of the ratchet k, secured to the shaft l, and the pawl l,
pivoted to the wheel m³, that is loose on the shaft, wheel m is prevented from
turning back, except as permitted by the clock mechanism, which is connected in
the ordinary way with the said wheel m³.
The electric locking appliance A consists of the electro-magnet a, lever b and
spring c attached to the lever b the said lever being so arranged as to intercept the
revolution of the fan C, only when the armature end of the lever is attracted by
the passage of a current of electricity through the magnet a, the spring c serving
to withdraw the lever from in front of the fan C, when the electric current ceases
to flow through the magnet.
G, is an electric switch or cut-out arranged to be opened and closed by the
stud d attached to the signal board E, when it is raised and lowered.
H represents the battery, one pole of which is grounded by the wire e the other
pole being connected with all of the electro-magnets a, in the signal system by the
wire f, which is grounded at next to the last signal on the line as shown at g, thus
making a closed circuit passing through the electro magnets a, which constantly
hold the levers b, in position for locking the fans C, when the signals are at rest.
The lower metallic post h of each switch G is connected by wire i to the main
wire f. The upper métallic post h¹ in signal Nº 2 is connected by wire j, to main

page_text: wire f, in rear of the electro-magnets in signal N° 1. Each upper post h in all of
the other signals throughout the system is connected by a wire ¹, to the lower
post of the signal next in rear, so that when the spring 12, of the switch is forced
against the upper post by the button d, the electric current will be switched off
from the electro-magnets of the signal next in rear, thus permitting spring c to 5
withdraw the end of the lever b of such signal out of the way of the fan C, and
thus permit the signal board E of such signal to drop within its housing B.
When all the signal boards in the system are down, the electric current, as above
intimated, will pass along the main wire f, and through all of the magnets in the
system. When one of the signal boards is raised, say that of signal N° 2, the 1
current will pass through wire j, upper post, spring h², over post h, and wire i,
again into main wire f, thus cutting out of the circuit the magnets a in signal N° 1.
When the signal board in signal N° 2 drops into its housing, the switch G being
thus opened, the current will follow its original course through the main wire f
except as next described.
Now the action of this system is as follows:-
It will be understood that the signals will be placed at suitable intervals along
the line of the railroad. All the signal boards along the line being down within
their housings, a train starting along the line, in passing signal N° 1 will elevate
and display the signal board E thereof which will be locked in elevated position by
the retarding mechanism D, lever b, and fan C, and held until the train reaches
signal N° 2. In passing signal N° 2, the train will elevate the signal board E of
such signal, which in like manner will be locked and held in displayed position,
and the raising of this signal board in signal N° 2 will also close the switch G,
which will take the electric current from the magnets a of signal N° 1, which will
cause lever b to release fan C, thus permitting the signal board in N° 1 to descend
within its housing indicating-to-the-next_oncoming train that the preceding train
has passed signal N° 2. The first train in passing signal No 3 will in like manner-
cause that signal board to be displayed and close its switch G whereupon the
electric current will pass from the switch G in signal N° 2 over wire ³, thence
through the switch G, of signal N° 3 and wire i¹, again into the main wire f. This
will cut the current from the magnets in signal N° 2, and thus cause its signal
board to recede into its housing which will open the switch G, of such signal N° 2
and thus cause the current to again pass through its magnets a and the magnet of
signal No 1, putting these signals in readiness for subsequent action. As soon as
the reaction of the signal board of signal N° 2, opens the switch G thereof, the
current will pass directly over the main wire f, as in starting, until the signal.
board of signal N° 4 is set, which will switch the current from the magnets in
signal N° 3, and release its signal board, and the whole operation just described
will be repeated with every set of four or any number of signals throughout
the line.
In this manner it will be seen that the system is perfectly automatic and that
the system is a perfect block signal system..
In case the electric system should get out of order, the time signal remains,
which in itself, is a good safeguard against collisions and which may be regulated
as to time by means of interchangeable fans.
It will be understood however that I do not confine myself to the use of the time
signal in connection with the electric system as any other suitable automatic signal
might be used, but it is preferred to use this time signal, since by means of the
retarding mechanism D, only a slight force applied to the fan C is required to
effectually lock the signal board in displayed position.
4
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 The signal board E adapted to be automatically elevated by the passage of a
Lian mashaniam D and the fan C or its equivalent. in

page_text: combination with the magnets a, lever b, spring c, and switch G connected as
described and adapted to be opened and closed by the signal board E, substantially
as specified.
2nd In a signalling system the switches G, connected to the main wire f, by
wires, and and adapted to be opened and closed by the signal board E, in
combination with the magnets a and the locking mechanism, whereby the setting
of one signal will release the other, substantially as described.
Date
C