IMPROVEMENTS IN ELECTRICAL SIGNALLING APPARATUS FOR USE ON RAILWAYS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Walter Walker at the Office of the
Commissioners of Patents on the 18th January 1883. Communicated to him
from abroad by Charles D, Tisdale of Boston, Massachusetts, United States of
America
WALTER WALKER of the City and State of New York, United States of
America, now of, 8 Southampton Buildings, London, "IMPROVEMENTS IN
ELECTRICAL SIGNALLING APPARATUS FOR USE ON RAILWAYS" [Communicated to
him from abroad by Charles D, Tisdale of Boston, Massachusetts, United States of
America]
This invention relates to electrical signalling apparatus for use on railways.
Apparatus of this kind has been heretofore constructed wherein one or more
signals are controlled by electro-magnets in a circuit that is normally closed, but
is momentarily broken, as a train passes a given point, so as to demagnetize the
magnets, release the armatures, and permit the position of the signals to be changed.
When thus released, the armature is retracted so far from the poles of the magnet
as to be substantially unaffected thereby, so that, upon the subsequent closing of
the circuit, it is not again attracted to the poles, and the signal remains in the
position assumed upon the breaking of the circuit until the armature is moved up
to the poles of its magnet by means of mechanism actuated by the passing train.
By this arrangement it is possible to cause the armature to move away from the
poles of the magnet by a circuit-breaker operated at any point to which the circuit
can be extended; but it is not practicable to extend the mechanical connections to
any considerable distance, so that the armature can be moved up to the poles of
the magnet only when the train passes the point at which the said magnet and
signal are located. In the said apparatus, moreover, the signal is in the position
indicating "danger" when the armature is attracted, and indicating "safety"
when the armature is removed from the poles of its magnet, the train, when
passing a signal-post, mechanically setting the signal at "danger" by moving the
armature up to the poles of its magnet, where it is retained by the attraction
thereof while the train is passing over the block-section, at the end of which it
breaks the circuit and permits the signal to return to the "safety" position, where
it remains till operated by another train, the circuit-breaker being closed imme-
diately after the train has passed, so that the signal will be held at "danger" when
set by the next train.
"

page_text: It is desirable that the signal should indicate "danger" when the armature is
retracted, and "safety" when it is held by the magnet, as any failure or breakage
in any part of the apparatus will thus be indicated at once; to accomplish this,
desired
and to enable the proper moveinents of the signal to be controlled from any
point aro the objects of the present invention, which consists mainly in employing!
any auxiliary magnet and circuit properly arranged to draw the armature into the
range of its main controlling-magnet, instead of employing mechanical means to
effect this operation.
In apparatus constructed according to the present invention, the auxiliary
circuit containing the auxiliary magnets is normally open, but can be closed
momentarily at any desired point to set the signal to "safety," where it is retained
by the main magnet after the auxiliary circuit is restored to its normal or open
condition. The said auxiliary circuit is, in some cases, an open branch of the main
circuit, provided with circuit-closers placed at the points from which it is desired
to operate the signals, so that, when closed, a portion of the current of the main
battery will pass through the auxiliary magnet and cause it to draw the armature
up to the poles of the said magnet, and thus restore the signal to its "safoty"
position, where it is held by the main magnet until the main circuit is broken.
"
The magnets are sometimes arranged to act upon a lever at different distances
from its fulcrum, the main magnet being remote from the fulcrum where the
movement is large, and the auxiliary magnet being near the fulcrum where the
.movement is small, so that the armature does not pass beyond the range of its
effective attractive influence. By this arrangement a current of given strength
divided between the two magnets will have a greater effect upon the lever when
retracted than if the current is confined to the main magnet, and the various parts
may be properly adjusted.
The apparatus is mounted upon a signal-post, provided with a head or case of
suitable form to enclose the operating parts and provided with an opening, behind
which the signal is placed when desired to indicate "danger," and from which it
is removed when desired to indicate "safety."
The signal consists of a disc of any desired color, usually red, mounted at the
end of a lever, pivotted at one end and connected by a link with the vibrating end
of an armature-lever which is pivotted at its other end.
The said armature-lever may be made of iron, or provided with armatures
properly arranged to be controlled by the main and auxiliary electro-magnets, the
former being placed remote from the pivot of the said lever where its movement is
great, and the latter being placed near its pivotal point where its movement is
very slight. By this arrangement the lever is retracted by the weight of the
signal (when the main magnet in a normally-closed circuit is momentarily
demagnetized) to a position so remote from the poles of the said magnet that the
latter is not able to draw it up thereto when subsequently magnetized, although
the said magnet is amply strong to retain the lever when moved up thereto
The auxiliary-maguet (which may be made more powerful than the main
magnet, and which does all the work of operating the signal,) owing to the smaller
movement of the lever from its poles, is able to affect the said lever, and when its
circuit, which is normally open, is momentarily closed, it draws the lever up to the
proper position, where it is held by the main magnet, the circuit of which is at
this time closed.
The main circuit (including the main battery which may be located at any
desired point therein) contains circuit-breakers which are normally closed, but are
adapted to be opened by the train in passing. The said circuit includes the coils
of the main signal-magucts of as many siguals as it is desired to operate simul-
taneously in the circuit, all the said magnets being demagnetized by the operation
of any of the said circuit-breakers, and permitting the signals to drop to indicate
danger," and carry the armature-lever beyond the effective influence of the said
magnet.
"
The auxiliary circuit sometimes consists of a wire branching from the main
.:

page_text: circuit on one side of the battery and a wire branching from it at the other side.
This auxiliary circuit, including the coils of the auxiliary magnets, has terminals
or electrodes properly located to be connected by a circuit-closer at any desired
point, the said terminals being carried in some cases to the remote end of the
section, and connected with opposite rails, so that the wheels and axles of the
train, as it passes, will close the said branch circuit and cause a portion of the
current of the battery to pass through the auxiliary magnet and magnetize it, and
cause it to draw the lever up to the poles of the main magnet to set the signal to
safety" again. In other cases it is necessary to close the branch circuit at either
end of the section, and each wire, extended throughout the section, has at each end
thereof branches or electrodes connected with the opposite rails.
"
If desired, the auxiliary magnets, may be operated by an independent circuit;
or, if the divided curront of the battery, in acting upon both the magnets, is not
of sufficient power to draw up the armature-lever and set the signal to "safety,"
an auxiliary battery, located, in the auxiliary branch circuit, may be employed, its
current being confined to the auxiliary magnet.
Circuit-breakers are located at any point in the main circuit to set the signals
to "danger," or the said signals are set by cutting the wire circuit in case of
emergency.
In order to set the signals to "safety " it is necessary, in addition to again
closing the main circuit, to operate the auxiliary maguet, as, for example, by
forming a connection between the branch wires to close its circuit. A device for
accomplishing this consists of an electric switch or key pivotted at one end, in
connection with one portion of the main circuit, and resting on an anvil or button
to complete the main circuit when in one position. When in another position the
main circuit is broken, the said switch being properly connected with the apparatus
employed to move the rails or draw-bridge bolt to assume this position when the
rails are separated. The wires have anvils or buttons placed in such position
relatively to the button in tho main circuit that while the said switch is being
returned from one position to the other it is in contact with all the buttons
simultaneously, so that it connects the wires to bring the auxiliary magnet in
circuit, causing the armature-lever to be drawn up, as abovo described, and before
it has disconnected the said wires it has completed the main circuit to return the
said armature up to the poles of its magnet.
Circuit-controllers of this description may be placed in suitable boxes upon the
telegraph-poles by which the circuit wires are carried, so that the signals may be
operated by hand from those points, as is sometimes desired by the workmen on
railways.
A form of circuit-breaker that I sometimes employ with good results is
mounted upon a sleeper or the like, properly chambered to receive it, tho said
sleeper being cut away beneath the rail to permit a downward movement of the
said rail relatively to the sleeper as the train passes over it. The circuit-breaking
lever is pivotted at one end and its other end extends beneath the flange of the
rail. The said lever, which is of metal, and is connected with one of the wires
of the circuit to be broken, is normally held, by a link or bolt, in contact with its
anvil-piece, which is connected with the other wire of the circuit, and consists of
a netal plate fixed relatively to the sleeper, the said link being insulated from
the anvil and provided with a spring, of india-rubber, for example, to forcibly press
the two terminals of the circuit together. When a train passes, it depresses the
rail which engages the end of the lever and disconnects it from the anvil, thereby
breaking the circuit.
In some cases, when it is desired to set the signal only when the train enters
the section, in order to guard its rear while in the said section, the circuit of
the main magnet need not extend beyond the signal-post, or it may extend
as far as a given break in the rails the condition of which is to be indicated by
the signal.
The terms "main" and "auxiliary" are merely used for the sake of distinction,

page_text: the former being the one that is in effective operation the greater portion of the
time; but the auxiliary magnet may be much larger and stronger than the main
magnet, and be operated by a larger battery,
According to a modification of the present invention the auxiliary circuit is
normally closed, as well as the main circuit, the auxiliary magnet being placed
opposite to the main magnet, and acting in opposition thereto. In this arrangement
either magnet is able to draw the armature lever across the spaco between it and
the opposite magnet, when unopposed by the said opposite magnet, and when both
magnets are magnetized the lever will remain in contact with the one which is
nearest thereto, the other, on account of its greater distance, being unable to
withdraw it. Thus, the signal being in its normal or "safety "position, and the
lever nearest the main magnet, and both magnets being magnetized, if the main
circuit is momentarily broken, the auxiliary magnet will be unopposed and will
attract the lever, causing the signal to indicate "danger," and it will retain it in
this "danger" position after the main circuit has again been closed until the
auxiliary circuit is broken, as, for example, by the train arriving at the opposite
end of the section, when the reverse operation will take place, the armaturo being
attracted by the unopposed main magnet, and then held thoroby after the secondary
circuit is closed and its magnet opposed to the main magnet The circuit-controllers,
which govern the action of the auxiliary magnets, are sometimes placed outside
of the controllers governing the main circuit, so that, when a train enters the
section from either end, it operates the main circuit-controllers last, and leaves
the signal in the corresponding position until the train passes off the section, when
it operates the auxiliary controller last, leaving the signal in the corresponding
position, as desired.