IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC RAILWAYS WHICH IMPROVEMENTS ARE IN PART TO
Year: 1882

page_text: LETTERS PATENT to John Hopkinson of Westminster Chambers in the
County of Middlesex F.R.S. for an Invention of "IMPROVEMENTS IN AND
CONNECTED WITH ELECTRIC RAILWAYS WHICH IMPROVEMENTS ARE IN PART
PROVISIONAL SPECIFICATION left by the said John Hopkinson at the Office
of the Commissioners of Patents on the 4th October, 1882.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC RAILWAYS WHICH IMPROVE-
MENTS ARE IN PART APPLICABLE TO OTHER ELECTRICAL PURPOSES"
My Invention has for its principal object to provide means in connection with
electric Railways whereby leakage of the electric current is prevented or greatly
diminished.
According to my said Invention I divide the rail (either one or both of a pair)
into sections or lengths insulated from each other. I carry the Conductor along
the track preferably completely insulating the said Conductor and I lead froin it
branches to each section or length of rail. In each of these branches I provide a
switch by which communication with the Conductor is maintained whilst sufficient
current flows by an electro-magnet through the coils of which the current passes.
Connection may be started mechanically but I prefer to make use of the rise of
potential caused by the running Car coming on the section. This is done by con-
necting the two rails of the pair through a high resistance electro-magnet which
serves to make the contact for the main circuit which contact is then maintained
by the current which flows from the main. It will be well to provide that when
the current from the main conductor flows it shall by means of a third electro-
magnet break the circuit of the high resistance electro-magnet When the car
leaves the section of rail the current fails and the section of rail becomes discon-
nected from the main conductor subsequently the high resistance circuit is made
where it was broken when the current began to flow ready for the next Car which
may come upon the section.

page_text: The functions of the three electro magnets may be accomplished by a singlo
electro-magnet wound with two coils one of low resistance for the current from the
main to the section of rail and the other of high resistance from one rail to the
other of the pair I prefer to provide this electro-magnet with a single armature
which is attracted first as the Car comes on to the section by the current passing
through the fine wire coil of the magnet so that it first completes the circuit for the
main current and thereafter breaks the fine wire circuit maintaining the main
circuit whilst the Car passes from the section of rail to the next and when the Car
leaves tho section the main current being discontinued through the electro-magnet
the armature drops and makes contact with the fine wire circuit for the repetition
of the making and breaking of the contacts by the next car. A convenient arrango-
inent for the contact piece of the fine wire circuit is to carry it upon a aleove
through which a spindle from the armature passes the said spindle having a
projection at its end which projection when the armature is attracted and hus
completed the main circuit lifts the sleeve piece and the contact maker to break
the fine wire circuit. When the main current ceases through the section of rail
the armature drops and the fine wire circuit is completed by the descent of the
contact piece on the sleeve.
The current when the Car is stopped is not discontinued wholly in order to
enable it to be started again. The necessary continuance of current for this purpose
may be through a resistance on the Car switched in when the Car is about to stop.
An alternative is to place a small secondary battery on the Car which serves to
operate the switch through the fine wire coil..
"
The arrangement. hereinbefore described will be applied to onch section of the
mail. One or both of the pair of rails may be in insulated sections and in this
latter case the switch Apparatus herein before described may be cominon to the
sections of both rails.
The switch Apparatus hereinbefore described may be applied to the regulation or
control of currents for other purposes than that described for example it inay bo
used with dynamo machines arranged in parallel series to enable any machine to be
thrown out as required

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
+
the said John Hopkinson in the Great Seal Patent Office on the 4th April
1883.
JOHN. HOPKINSON of Westminster, Chambers in the County of Middlesex F.R.S.
" IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC RAILWAYS WHICH IMPROVE-
MENTS ARE IN PART APPLICABLE TO OTHER ELECTRICAL PURPOSES."
"
My Invention has for its principal object to provide means in connection with
electric railways whereby leakage of the electric current is prevented or greatly
diminished.
According to my said Invention I divide the rail (either one or both of a pair)
into sections or lengths insulated from each other. I carry the conductor along the
track insulating the said conductor and I lend from it branches to each section or
length of rail. In each of these branches I provide a switch by which communi-
cation with the conductor is maintained (whilst sufficient current flows) by an
electro-magnet through the coils of which the current passes.
Connection is started by making use of the rise of potential caused by the
running car coming on the section. This is done by connecting the two rails of
the pair through a high resistance. electro-magnet which serves to make the contact
for the main circuit which contact is then maintained by the current which flows.
from the main. It will be well to provide that when the current from the main
conductor flows it shall by means of a third electro-magnet break the circuit of the
high resistance electro-magnet. When the car leaves the section of rail the current
fails and the section of rail becomes disconnected from the main conductor.subse-
quently the high resistance circuit made where it was broken when the current
began to flow ready for the next car which may come upon the section.
The functions of the three electro magnets may be accomplished by a single
electro magnet wound with two coils one of low resistance for the current from the
main to the section of rail and the other of high resistance from one rail to the
other of the pair. I prefer to provide this electro-magnet with a single armature
which is attracted first as the car comes onto the section by the current passing
through the fine wire coil of the magnet so that it first completes the circuit for
the main current and thereafter breaks the fine wire circuit maintaining the main
circuit whilst the car passes from the section of rail to the next and when the car
leaves the section the main current being discontinued through the electro-magnet
the armature drops and makes contact with the fine wire circuit for the repetition
of the making and breaking of the contacts by the next car. A convenient
arrangement for the contact piece of the fine wire circuit is to carry it upon a
sleeve through which a spindle from the armature passes the said spindle having a
projection at its end which projection when the armature is attracted and has
completed the main circuit lifts the sleeve piece and the contact maker to break
the fine wire circuit. When the main current ceases through the section of rail the
armature drops and the fine wire circuit is completed by the descent of the contact
piece on the sleeve.
The current when the car is stopped is not discontinued wholly in order to
enable the car to be started again. The necessary continuance of current for this
purpose may be through a resistance on the car switched in when the car is about
to stop. An alternative is to place a small secondary battery on the car which
serves to operate the switch through the fine wire coil.
The arrangement herein before described will be applied to each section of the
rail. One or both of the pair of rails may be in insulated sections and in this latter

page_text: case the switch apparatus hereinbefore described may be common to the sections of
both rails.
The switch apparatus hereinbefore described may be applied to the regulation or
control of currents for other purposes than that described for example it may be
used with dynamo machines arranged in parallel series to enable any machine to
be thrown out as required.
And in Order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
tho several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
Figure 1 represents diagrammatically a pair of rails A. B. of an electrical railway
and a conductor C for convoying the electric current, with connections leading
through electro-magnetic switches D one of which is shewn drawn to an enlarged
scale in figure 2. The rail B. is insulated and divided into sections. b b which are
insulated from one another as at b*
"
Each of the said sections, has a branch leading to the insulated conductor C and
in oach of these branches is placed the electro-magnetic switch D. the function of
which is first to put its section of niil into electrical communication with the
conductor C when the car comes on the section and then to leave it' disconnected
after the car has left the said section so that leakage may be reduced as much'as
possible.
11
Then supposing the conductor O to be in communication with the positive pole
of the source of electricity and the rail A with the negative pole, the direction of
the current when a car is travelling over a section b will be from the conductor C.
through the electro-magnetic switch D. to the section b and then through the pair of
wheels of the car and its dynamo machine and back by the other pair of wheels to
the rail A and to the negative pole of the generator.
The arrangement for causing the switch D to automatically make and break the
main circuit at the required time consists as follows. A shunt circuit of fine
wire E, E, which extends from a section of the rail B to the rail A and is wound
round the core of an electro magnet F around which is also wound a coil of thick
wire which forms the main circuit (between the conductor C and the insulated
section b.
"
The function of the shunt circuit E is to close the main circuit G by causing a
current to flow round the electro-magnet so as to make it actuate an armature
which shall by its motion, mechanically first complete the main circuit and thereaftor
break the shunt circuit.
The current which produces this change is started in the shunt circuit, by the
difference of potential, which is set up between the two rails, ie the rail A and n
section b of the rail B. when the car comes onto that section,
1
*The wheels of the running car are sufficient to form a momentary contact between
the new section b and the one before it, (which is in electrical connection with the
conductor C) so as to place the new section at the required potential in order to
send a current through the shunt circuit. Indeed the reveise electro-motive
force of the dynamo on the car would be in general sufficient to effect the required
change.
.
Figure 2 shows the details of the electro-magnetic switch and also diagram-
matically the connections with the rails A. B. and the Conductor C.
11t
Tho switch consists of an electro-magnet F with two cores F F each wound
with a coil of the thick wire G of low resistanco forming the main circuit between'
the rail B. and the conductor C. and also with two thin wire coils E of high
resistance, forming a shunt circuit between the rail A and any section b'of the
rail B. The armature fixed to a spindle is partly supported by a spring i
and is capable of being attracted upwards by the electro-magnet F. The contact
maker is fixod to the spindle for making connection across the terminals k
through the springs . A sleeve piece or sliding contact breaker m is mounted
upon the spindle so as to be capable of moving up and down thereon between
い?

page_text: the stops ¹³ which are fixed to the said spindle. The spring n prevents the
said sleeve piece m from rising, until the stop h reaches it and forcibly lifts it,
thereupon breaking the circuit across the terminals p p. and liberating the two
spring contacts. 9.9. are metal strips, which serve to connect the terminals
with the spring contacts ll and q² are similar metal strips for connecting the
spring contacts qq with the terminals pp. It will be seen from figure 2, that the
armature His capable of assuming two different positions. First. That which is
shewn in full lines which is its normal position e. when no current passes through
the coils G or E so that no magnetic force is acting upon it, and secondly, that
which is shown in dotted lines, and which represents the position when a current
is flowing through the coils G and the armature H is attracted by the electro
magnet F., When the armature is in its normal position the part m on the
'sleeve m makes contact across pp by the springs q and strips q so that the shunt
circuit remains closed but when the armature His attracted the main circuit is
closed across by the contact maker j springs and strips 12 and immediately
after the shunt circuit is broken across p p by the part m² on the sleeve pieco m
being raised by the stop h³. Supposing then the switch to be inserted in the main
circuit between the conductor,c and any section 6 of the rail B, as shown in
figure 1, the following will be the cycle of operations produced by a car coming on
the section. A current will be sent through the shunt circuit as previously.
explained, this will cause the armature to be attracted, which will first close the
main circuit and then break the shunt circuit, the current continuing to flow
through the main circuit and keeping the armature attracted. Later on when the
car leaves the section the current will cease to flow through the main circuit to that
section, the armature will be released and will fall, first breaking the main circuit
and subsequently closing the shunt circuit leaving it closed for a repetition of the
same change by the next car.
"
By extending, the spindle h and introducing a second contact maker similar to
that at jit is practicable to make and break the connection of the second rail A
with the return main conductor. In this case the said rail A would be divided
into sections, corresponding with those of the rail B. As already explained it is
necessary to provide means for maintaining or renewing connection between the
rail and the main conductor when the car stops on the road this may be effected
as follows. The connection between the rails may be maintained through a
suitable resistance which may be switched in when the car is about to stop and is
opened as soon as the current passes through the dynamo. or a small secondary
battery may be placed upon the car, of sufficient electro-motive force to send a
sufficient current through the thin coils E and so make contact in the same way as
when the running car enters upon the section.
.
In figure 2 I have indicated the course of the current through the main circuit
by single headed arrows and that through the shunt circuit by double headed
AITOWS.
I have described the best method with which I am acquainted for carrying my
Invention into effect but I wish it to be understood, that I do not confine myself
to the precise details herein before described and illustrated in the accompanying
drawing as the same may be varied without departing from the nature of my said
Invention for example instead of using the rails as the conductor, it may be more
convenient to use a separate conductor, on which slide contact pieces connected to
the car, this conductor being divided into insulated sections each section to be
connected through an electro-magnetic switch with a main conductor which be
thoroughly insulated.
may
Again the single electro-magnet, shown in figure 2 may be replaced by a set of
three electro-magnets which together effect the series of changes of connections as
has been hereinbefore described.
Having now described and particularly ascertained the nature of my said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original

page_text: and therefore claim as the Invention secured to me by the herein before in part
recited Lotters Patent is.
First In electrical railways having a rail or rails or other conductor divided
into insulated sections or lengths and an insulated main conductor from which
branches lead to each section or length of rail or other conductor the employment.
in combination therewith of electro magnetic switches for initiating maintaining
and breaking communication between the said sections or lengths of mail or other
conductor and the main conductor.substantially as herein before described.
Secondly The switch apparatus for regulating or controlling electrical currents
for electrical railways or for other purposes the said apparatus being constructed
or arranged substantially as hereinbefore described and illustrated in Figure 2 of
the accompanying drawings.
In witness whereof I tho said John Hopkinson have to this my Specification
set my hand and seal the fourth day of April One thousand eight 'hundred
and eighty three.
JOHN HOPKINSON (LS)