Improvements in Railway Electrical Signalling Apparatus.
Year: 1888

page_text: PROVISIONAL SPECIFICATION.
Improvements in Railway Electrical Signalling Apparatus.
I, EDWARD DUNN of 21 Ingestre Road, Farebridge, Stafford, Telegraph Inspector
of The London and North Western Railway Company do hereby declare the nature
of my invention for THE ELECTRICAL SIGNALLING OF TRAINS ETC. UPON RAILWAYS
to be as follows:-
--
Hitherto two systems of Railway Electrical Block Signalling of trains upon
Railways have been in use. One a system of permanent current Signals whereby
one wire is required for each class of Instrument viz. :-one wire each for the Up
and "Down "Signal Indicators or Needles, and one wire for the Bell communication―
The other a system of momentary current Signals whereby one wire only is required
for the whole system of "Up" and "Down "Signal Indicators and bell: the Signal
Indicators or needles being moved or deflected by an electric current but retained in
position by permanent magnetism and not by the electric current as in the other
system. This latter system of momentary currents and permanent magnetisms has
the great disadvantage of its Signal Indicators, or needles, being easily deranged by
atmospheric or earth currents, and therefore unreliable.
Now my invention has for its object to so simplify & improve the apparatus now
in use that the permanent current Signalling can be performed upon two wires
instead of three-For this purpose I employ an improved form of Instrument, or
pair of Instruments, each of which contains two single needle coils & dials for "Up'
and "Down" Signal Indicators, a bell, and two commutators, one of which is con-
nected with a plunger and has a movement longitudinally as well as a turning or
side movement-The two wires I employ to form two distinct circuits, each of which
comprises, one commutator and one coil & dial of the one Instrument, together with
one commutator one coil & dial and the bell of the other Instrument, each circuit
thus forming a complete system of Signal Indicators and bell for Up" or "Down"
line working.
**
The Signal Indicators or needles I deflect and retain in position in the usual manner
by electric currents and the bell in each Instrument I so regulate that a stronger

page_text: current (in either direction) than what is used to deflect the needles or Indicators, is
necessary to attract the bell armature; and this stronger, or increase of, current I
apply by means of an improved commutator and plunger. This commutator I also
have so arranged that no movement or deflection of the Indicators or needles can be
made without at the same time ringing the bell and thus calling attention to the
change made in the Signal indication.
When either pair of needles or Indicators forming together part of one circuit are
at the normal or perpendicular position, the respective coils are cut out by the action
of the commutators leaving the circuit complete for the bell communication.
Dated this 9th day of March 1888.

page_text: COMPLETE SPECIFICATION.
Improvements in Railway Electrical Signalling Apparatus.
1, EDWARD DUNN of 21 Ingestre Road, Farebridge, Stafford Telegraph Inspector
of The London and North Western Railway Company do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
--
My invention consists of improved. means and apparatus for the electrical
Signalling of trains upon Railways.
Hitherto two systems of Railway electrical Block Signalling of trains upon
Railways have been in use. One, a system of permanent current Signals whereby
one wire is required for each class of instrument, viz.-one wire each for the "Up"
and "Down" Signal indicators or needles, and one wire for the bell communication.
The other, a system of momentary current Signals whereby one wire only is required
for the whole system of "Up" and "Down" Signal indicators, and bell; the Signal
indicators, or needles being moved or deflected by the electric current, but retained in.
position by permanent magnetism, and not by the electric current as in the other
system.
This latter system of momentary currents and permanent magnetism has the
great disadvantage of its Signal indicators or needles, being easily deranged by
atmospheric or earth currents, and therefore unreliable.
Now my invention has for its object to so simplify and improve the apparatus now
in use, that the permanent current Signalling can be performed upon two wires instead
of three. For this purpose I employ an improved form of instrument, or pair of
instruments, each of which contains, two single needlo coils and dials for "Up" and
"Down" Signal indicators, a bell with relay, and, two commutators one of which is
connected with a plunger and has a movement longitudinally as well as a turning or
side movement. The two wires I employ to form two distinct circuits, each of which
comprises; the commutator with the plunger, and one needle coil and dial of the one
instrument together with the commutator without a plunger, one needle coil and dial,
and the bell of the other instrument; each circuit thus forming a complete system of
Signal indicators and bell for "Up" or "Down" line Signalling. The Signal
indicators, or needles, I deflect and retain in position in the usual manner by electric
currents, and the bell in each instrument I so regulate that a stronger current than
what is used to deflect the needles, or indicators, is necessary to attract the bell
armature, and this stronger, or increase of, current I apply by means of an improved
commutator and plunger. This commutator I also so arrange that no movement or
deflection of the needles or indicators can be made without at the same time ringing
the bell at the other or distant end of the circuit, and thus calling attention to the
change made in the indication. When either pair of the needles or indicators forming
together part of one circuit, are at the normal or perpendicular position the respective.
coils are cut out, or shunted, by the action of the commutators, leaving the circuit
complete for the bell communication.

page_text: In order to more fully explain my invention I have appended three sheets of
drawings, of which Sheet I represents the electrical diagram of one instrument.
The commutator Cis of cylindrical construction, with the metal pieces 1. 1. and 2. 2.
on the one side or half of the cylinder, in electrical connection with the end metal
_pieces 1. and 2. respectively.
<:
The metal piece M is an insulated plate (on the reverse side or half of the cylinder)
with which the springs on that side make contact only when the cylinder or com-
mutator stands in the position necessary to produce the indication or Signal "Line
closed." When the indicating plate " exhibits the words "Line closed the com-
mutator stands in a position so that the contact points of the springs on both sides
of the cylinder touch it on the lines A. B. and the needles, or indicators stand vertical
indicating Line closed." When the plate 1" is turned to exhibit Line clear the
springs touch the commutator on the line C. D. and the needles are deflected to
indicate Line clear." When turned to exhibit Train on line" the springs touch
the commutator on the line E. F. and the needles are deflected to indicate "Train on
line;
and the bell at the other or distant end of the section or circuit is rung once
each time the commutator is turned from one position to another. When the
commutator stands in either of these three positions, the hell can be rung for calling
attention, or other purposes, by pressing in the plunger G; this longitudinal or inward
movement of the commutator having the effect of ringing the bell without altering
the position or indication of the needles.
The other commutator C is also cylindrical and carries the insulated metal plate K,
by means of which and the springs, as shewn, the needle or indicator coils are shunted
into or out of the circuit, of which they together form part.
This commutator C with its indicating plate P is intended to be moved with a
turning or side movement and to produce the two effects as above. When the plate P
exhibits the words "Line closed" the springs touch the metal plate K on the line A. B.
and the needle or indicator coils V are then shunted or cut out of the circuit. When
the plate Pexhibits "Line open" (or other convenient words) the springs touch the
commutator on the line C. D. and the needle or indicator coils V are then in, and
form part of, the circuit and will indicate by deflection of the needle N the signals or
indications produced by the different positions of the commutator Cat the other or
distant end of the circuit.
The incoming current, or current from the Instrument at the other or distant end
of the circuit, enters at the point L", and from there passes by means of the springs of
the commutator through the needle coils V, and the coils of the relay R to
Earth The needle N is deflected in accordance with the polarity of the current and
the armature of the relay R is attracted, or drawn, into contact with point. U, thus
closing the short, or local, circuit through the bell coils-When this local circuit is
closed the battery which is inserted between the points C and Z causes the bell
armature X to be attracted, & thus, by means of the hammer Y, to sound the bell
or gong Q.
The battery to be inserted between the points C and Z, may be, and is, the same
battery (in whole or in part) that is used for producing the bell signals by means of
the commutator C¹.
Referring to Sheet 1: The operation of the commutator is as follows.-
When the indicating plate exhibits Line closed" and the springs touch the
cylinder on the lines A B, the bell of the other or distant instrument is sounded by
pressing in the plunger G. This causes the cylinder to move longitudinally or in the
direction of its axis, and when thus pressed in, the two springs a' (which is a
terminal of the larger battery) and 6, come into contact with each other through the
metal plate M, thus putting the larger battery to the line thro L', and so by L"
(where the current enters) through the relay of the other or distant instrument to
earth. This current from the large battery attracts the armature of the relay R,
which by closing the local circuit through the bell coils, attracts the bell armature
and sounds the bell.
When the cylinder c¹ is turned by means of the handle If, into the next position

page_text: :
"line clear," the spring a (which is also a terminal of the large battery) first comes
into contact with the metal piece 1, thus sending a strong current by way of the
needle coils V' (the needle N of which is deflected to indicate Line clear")
by L where the current passes through the needle coils V (deflecting the
needle N), and thence through the coils of the relay to earth causing the
bell to be sounded as before.
The cylinder e comes to rest, for the position Line clear, with the springs
touching it on the line CD and then the terminal spring d', of the large battery,
touches the insulation only and is disconnected, while the terminal spring e of
the small battery remains in contact with the metal piece & by means of the
weaker current from the small battery retains the needles of both instruments in
the position indicating "Line clear."
Now while the cylinder c¹ is in this position, the bell is rung by pressing in
the plunger G this causes the terminal spring e' of the small battery to be dis-
connected from, and the terminal spring of the large battery to be brought
into contact with, the line wire, which will ring the bell as before. By turning
the cylinder into the next position "Train on line" the same operations produce
the same results.
Fig. 2. Sheet 2. represents an end view of the commutator C, to shew the
manner and position in which the springs are placed to the cylinders.
Fig. 1. Sheet 2. represents the front of the lower part of one instrument case
and shows the indicating plates P1 and P with the manner of exhibiting the
different indications through the small openings O.
Fig. 1 Sheet 3 represents a sectional plan of the improved mechanical arrange-
ment of, plunger & handle, and handle, by means of which the commutators are
operated.
The plunger G is of square section between the points A and B. and circular,
or round in the other parts. Upon this square part the barrel D which is provided
with an inner collar C. C. is fitted, so that when the handle H, which is rigidly
connected to the barrel D, is turned to the right or to the left, the plunger (and
therefore the commutator which is attached to and forms part of the plunger)
also turns. This barrel D is provided with a pin E which seats, by the action of
the spiral spring S, in the plaie F.
To turn the commutator from one position to another, the pin E must be withdrawn
from its socket or seat in plate by means of the handle H, and the handle turned
slightly in the direction required; then if the withdrawing action is released and the
turning action continued, the pin E will reseat itself in the plate F immediately on
the arrival of the commutator in the proper position, and lock the commutator and
its attachments in that position until again released by withdrawal.
A modification of this locking arrangement, by the pin and socket being made
conical, permits of the handle being turned without having to previously withdraw
the pin. This however is but partial locking although preferable under some
circumstances.
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
(First) The mode of signalling and arrangements of circuits and apparatus
constituting a two wire system of permanent current block signalling telegraphy, as
herein described.
(Secondly) The application to a block signalling instrument, or pair of instruments,
in general construction similar to that described in this specification, of two
commutators, as herein described, for the purpose of adapting such instruments to
the system. of block signalling by means of two wires (instead of three) claimed as
part of this invention.
(Thirdly) The method as described of obtaining an electric bell signal upon a
wire, (when the said wire is already occupied by an indicating or deflecting

page_text: current) by the substitution of a stronger current of similar polarity, substantially
as described.
(Fourthly) The particular form of handle & locking, also of handle and plunger
and locking arrangement substantially as described.
(Fifthly) The application to any form of block signalling instrument of the
particular form of handle & locking, and handle and plunger and locking, hercin
described.
(Sixthly) In a permanent current block signalling instrument, the particular
combination of parts constituting the commutator, plate with indications and handle
and plunger with locking substantially as described.
Dated this 2nd day of Danamba 1000
EDWARD DUNN.