IMPROVEMENTS IN RAILWAYS . CONTACT BOXES ON ELECTRIC
Year: 1883

page_text: LETTERS PATENT to William Edward Ayrton, professor of Technical Physics,
Fellow of the Royal Society, and John Perry, Professor of Mechanical
Engineering and Applied Mathematics in the City and Guilds of London,
Technical College Finsbury in the County of Middlesex for an Invention of
LUDRAWBRAYOG
PROVISIONAL SPECIFICATION left by the said William Edward Ayrton and
John Perry at the Office of the Commissioners of Patents on the 11th May
1883.
WILLIAM EDWARD AYRTON, professor of Technical Physics, Fellow of the Royal
Society, and JOHN PERRY professor of Mechanical Engineering and applied
Mathematics in the City & Guilds of London Technical College Finsbury in the
County of Middlesex IMPROVEMENTS IN
RAILWAYS
.
CONTACT BOXES ON ELECTRIC
In our patent specification N° 783 of 1881 for "Improvements in Electrical
Conductors applicable to Electric Railways and to Electrical Signalling and in
apparatus connected therewith " we stated line 7 page 15 ;—
"
<<
"
"
Instead of the mechanical plungers shown in sheet 2 for automatically
connecting the main cable with the section just entered by the train and for
automatically disconnecting the main cable from the section the train is leaving,
we may use electric means for this purpose based on the wheels, rollers, or
"brushes on one side of a carriage completing an electric circuit through, the
wheels, rollers, or brushes on the other side, or based on the wheels rollers or
"brushes in the front of a carriage or train being in connection with the insulated
"section just entered on while the wheels, rollers or brushes in the rear of a
carriage or train are in contact with the insulated section being left and so
connecting for a short time the two insulated sections electrically together, or we
may employ a magnetic arrangement depending for its action not on the weight
of the train but on its magnetic mass'
"
We now propose to describe the various contrivances we have since designed for
carrying out the idea of dispensing with the blow given by the passing train, for
the working of the contact boxes, and which contrivances are some of them suitable
for the series system and some of them for the parallel system of the electric
transport of goods and passengers. The arrow-heads on the figures show the
direction of the train in every case.
First let us consider the series system. Let B₁ C, C D be contact rails or ropes

page_text: used in the series system to convey the current. Then when no train is in the
neighbourhood of B¹ C and C¹ D, in order to keep up electrical continuity, a
current must pass from B C to C¹ D across the break C C by a contact-maker
at C C; while, on the other hand, when the train is partly on C₁ D and partly
on B¹ C the contact at C C³ must be opened so that the electricity may pass
through the electro-motor attached to the train, which bridges over the gap C C'.
In working this series system it has hitherto been our custom to allow a cam on
the front of the train to strike a lever and thus break the electrical contact between
the two sections, another cam on the rear of the train establishing the junction
again. The simplest of our electrical methods for producing this automatic opening
and closing is as follows;-
By means of the electro magnet M figure 3, through the coils of which the main
current usually passes the arm p q is attracted down against the action of the
spring & so as to come in contact with the stud t. When the train passes over the
break the electro-magnet M is short circuited by the front wheel of the first carriage
touching C and C simultaneously, or by two brushes on the front carriage, one in
the front of the carriage and the other in the rear, which short circuit M through
the body of the carriage: M being short circuited the spring 8 forces up the
lever pg and so opens the circuit and allows the electricity to pass through the
train and propel it. In order to pull down p. q and restore contact on the train
quitting the section C D one or other of two devices may be adopted; the one the
insertion of a high resistance between q and t less than infinity, so that in fact
when c c¹ is short-circuited the circuit Cpqt C¹ is not entirely broken but its
resistance is very great, consequently when the train has passed entirely beyond CC¹
the potential difference between C and C¹ will be very much increased, and this
will be especially the case if a constant-current dynamo be used with this electric
railway, hence the current which will flow through M for the moment may be
very great, even although there is this resistance between q and t. The result will
then be that the arm p q will be powerfully pulled down and again make contact
with t so that the contact C C¹ is now again closed. Another plan for restoring
contact after the passage of the train is to have wound round the electro-magnet a
fine wire coil of high resistance which acts as a shunt to C C¹ figure 4. In this
case, of course, there is no resistance put in between q and t. The arangement fig 3
is superior to figure 4 in that the induced current produced when the lever p q
leaves the contact t will tend to urge on the train which is partly on section B¹ C
and partly on section C¹ D, whereas in figure 4 portions of this induced current will
simply be shunted through the fine wire resistance coil.
In figure 1 the strong lines B' C, C' D & are the insulated conductor. When
no train is in the neighbourhood the current crosses from the section D C¹ to the
section CB¹ by the path tp sq, s being the attracted pole piece of the electro-
magnet M through which the current passes, and being such that when no current
passes it springs up and breaks contact with p. Besides being wound with a coil
for the direct current, the electro-magnet M is also wound with a shunt circuit
from the two sides of the juncaion BB. Now when the front wheels of a train
come to the junction C C₁ it is arranged that they short-circuit that junction so
that only a comparatively small current continues to flow through the electro-
magnet M, insufficient to attract the armature s which breaks contact with p and
remains broken until, when the front of the train opens the contact B B¹ in the
same manner, the magnet M is worked by the shunt circuit from B B and establishes
connection at CC¹ again.
Another method which we adopt is to insert a short piece c figure 12 between
the two ends of the conductor CC which have to be connected and disconnected
at the contact box. The insulated piece c is connected with C' by means of wire
of not very great resistance coiled round the Electro-magnet M, and the contact
maker & which is on the armature of this electro-magnet is connected with C¹ by a
second coil which is the coil spoken of in the previous cases. The arrow shows the
direction of motion of the train. Usually the current passes through CM 8t and

page_text: when the front wheel of the train reaches c the current passes from c to C¹ and
then from C¹ through 8 t, but either in short circuiting C and c or when it has
passed beyond C no current passes through M, and 8 springs up breaking contact,
and this broken contact is maintained until the hind wheel makes it again. When
the hind wheel reaches c current passes from C¹ to c through the magnet M and
establishes a connection. The magnetisation is greater when the wheels short
circuit c and C and is maintained after the hind wheel passes C. Contact is
therefore broken by the front wheel and made by the hind wheel automatically.
The objection to all of these methods is that at every contact box, even when
the circuit is closed, there is in the main circuit a resistance of the thick wire coil
on the magnet M. We have therefore devised a plan in which there is usually no
resistance at any contact box, and in which the resistance of the Electro-magnet M
is only introduced at the one contact box which, at any moment is next in front of
the coming train. This is seen in figure 2 where B B¹ C C¹ D D' are, as before,
the places where contact is to be broken or made between the sections. As before
let us consider the place CC¹. When no train is near there is immediate contact
through tp.sfq s being, as before, the armature of the electro magnet M which is
always tending, because of a spring, to break contact with p, and f being the
armature of the electro magnet mf being always acted on by a spring which
enables it to press 8 down on its contact p if there is no magnetic action. The
electro-magnet M is wound with a coil of wire passing from a to s and with a
shunt coil from the two sides of the junction BB'. The electro-magnet m is
wound with a shunt coil from the rear side of the junction D D' to the forward
side of the junction C C¹, so that it will become magnetic if either or both of the
junctions CC and D D¹ are opened. Let us suppose that a train coming in the
direction of the arrow opens D D¹ then at C C¹ m will attract f and contact at C C¹
is partly broken, but the current still continues to pass through t p 8 q, the contact
between 8 and t being maintained by the attraction of the Electro-magnet M.
When the front wheels of the train short circuit CC as in the previous cases only
a small current passes through the Electro-magnet M, the contact s p is broken so
that contact at CC is now completely broken and the current passes through the
train. As the train advances, contact at B B' is broken likewise and the shunt
circuit of the magnet M which comes from the two sides of BB¹ causes M to
attracts and establish a connection at CC¹. If D D¹ is now closed it is arranged
that m shall cease acting on f and the spring on ƒ causes it to maintain direct
contact between fs and p as it was before the train came into the neighbourhood.
Care is taken that when f breaks its contact with 8 this contact is broken before a
break occurs between 8 and p
Another method of effecting the same object is shown in figure 5 where at the
place C C¹ the contact is usually made through tsp q, the soft iron pieces being
on the end of a flexible arm which a spring tends to keep in contact with p. If
now the front of the train comes to C C¹, a magnet on the train attracts & and
breaks contact between p and 8 which is prevented from making contact again by
the catch f so that CC¹ remains open until the second next contact A A' is
opened by the train in the same way, and then the shunt circuit from A. A¹ causes
the Electro-magnet m to attract the catch f which allows s to fall under the action
of a spring thus closing contact at the place CC again. In figure 6 we show how
to effect the lifting of the soft iron pieces of figure 5 without the agency of a
magnet carried by the train. In this case some means is employed for allowing
the train to connect the end of one section C with e which is one end of the
wire of an Electro-magnet M whose other end e¹ is to earth. When the train
effects this connection, which may be done in many ways, M attracts & breaking
contact between 8 and p and afterwards the action of the apparatus is as in the
description of figure 5. The objection to this method is in the train putting the
line to earth at every junction box so that there is a permanent danger of
leakage. Various methods may however be suggested for disconnecting e¹ from
the earth except at the time when the train is approaching. Thus for example

page_text: the contact between .e' and the earth may be always broken except when an
armature of a magnet, whose coil shunts the two sides of a back contact box on the
line, such as D D is attracted, or again it is easy to arrange that the opening of
a back contact D D' shall connect e¹ with the earth permanently and that the
opening of a forward box such as A. A¹ shall disconnect e¹ from the earth.
8
In figure 7 another method is adopted. When no train is in the neighbourhood
contact is made at the junction C C through tp sq, the armature 8 of the Electro
magnet M is pressed away from the magnet by a spring and keeps making contact
with P. Now the catch fis on the armature of the magnet m which is doubly
wound as a shunt of E E and A A'. If either E E' or A A¹ is opened therefore,
the catch will be pulled forward and forces s to make contact between 8 and p;
holding it in position. When the magnet m ceases to act the catch f allows 8 to
make contact with p or not to make that contact according as the magnet M is
not acting or is acting. When the front of a train therefore comes to E E' and '
opens that contact the magnet m attracts the catch f and maintains good contact
between 8 and p, when the train now opens the box D D¹. As the magnet M is
doubly wound with coils which shunt the place D D¹ and the place C. C' so that
it acts if either D D' or C C₁ is opened; when the box D D¹ is opened the
magnet M attracts the armature 8 but cannot produce a break of contact with p
until the box E E¹ is closed. When this happens the catch f allows 8 to be
attracted and the contact is broken with p. Contact at C C' being broken the
magnet M continues to attracts even if the box DD' should close and this continues
until the train opens the box A A' when the magnet m immediately acts and the
catch fcloses the contact at CƠ¹
In figure 8 the Electro-magnet M is wound with three coils one of which
shunts C C another is a shunt to D D¹ and another to B B¹ so that when either
of these boxes is opened the magnet M. will attract its armature which is on the
lever so that contact at p will be broken. If, however, neither of these
places is open rx is forced downwards so as to make contact with p by means of
a spring. But there is a second way in which the two sides of the box C C¹ may
be connected viz through the contact piece re which makes contact with P which
is immediately connected to C¹. If either of the two contacts x or e is made there
is a good contact between C and C. Now the Electro-magnet k is wound with
two coils one of which always shunts the box D D¹, the other always shunts the
box C C¹ so that if either box is opened k is magnetic and tends to attract the
armature of re. The Electro-magnet m is wound with a coil which shunts the
box E E' so that if this box is opened m. becomes magnetic and helps a spring to
tend to close the contact e. The series of operations at the contact box C C¹ is as
follows. When the contact box E E¹ is opened x is closed and e is closed; but
when D D¹ is opened a opens whereas e remains closed the action of the magnet m
and the spring preponderating; but now if the box E E¹ is closed the contact e
opens and as a is already opened, the box C C¹ is opened. If now the contact
box D D is closed and if B B' is opened we still see that both contacts x and e
remain open, but if now the hind wheels of the train short circuit the box C C¹
although the contact a remains open e is closed; when in the same manner the
box B B¹ is closed x also closes and the box C C is completely closed.
. Although in special cases it is sometimes possible to use one of the Electro-
magnets described above for working the block, we prefer that our blocking
arrangements shall be just as independent of the above described parts of our
contact boxes as if the above operations were performed by the train striking a
lever, that is if we wish an opened box to keep a backward box closed. In the
backward box there is a contact piece on the armature of an Electromagnet and
this contact piece is of itself sufficient to short-circuit the box so long as it is
attracted, springing out of contact when it is not attracted, its magnet being wound
by a shunt circuit from two sides of the forward box whose being open creates
a block.
The previous methods are especially suitable to the series system. of working

page_text: railways. In our parallel system of working railways as described in our Patent
N° 783 of 1881 we divide the rubbed rail, which immediately supplies the train
with electricity into a number of sections, each of which is fairly well insulated
from the next and from the earth, and we arrange that the train when on any
section, automatically makes contact between that section of the rubbed rail and
the well insulated conductor which conveys the main current. We have arranged
plans for doing this electrically somewhat on the same principle as our methods
above described for the series system, but there is this objection to them when
applied to railways running on the ground; that it is in the power of anybody by
short circuiting, by means of a crowbar for example, either the insulated rail and
the earth rail in the one case, or one insulated rail and another insulated rail in
another case, to imitate the action of the train, and so to put electricity on to a
section where no train is and thus to increase the leakage of the line - Of course
this objection exists to a much greater degree in any of the ordinary systems of
parallel working where our plan is not employed of dividing up the rubbed rail
into sections each fairly well insulated from the earth and from its neighbour,
because the placing of a crowbar across the two rails, in ordinary electric railways
or so as to make contact between the third insulated rail (if there be one)
supplying the electricity, and the earth sends all the electric current to the earth.
and so stops the whole traffic on the line. For this reason, we prefer, for railways
on the ground, not to replace our automatic mechanical contact-makers by electrical
contact-makers operated by the mere short-circuiting action of the wheels or
brushes on a train, but instead to employ a current which the Motor is itself able
to produce by running on as a Dynamo Machine with its own momentum, when
a train enters a new section not yet supplied by electricity or to use the
accumulators or a battery, or small magneto or dynamo machine on the train to
operate the contact-maker, or lastly to arrange that the short-circuiting of two
things at any contact box can only put current on to a section, if the current has
already been supplied to the previous section, that is to say-although the
successive short-circuiting action produced by the train at each contact box will
in succession connect the next section with the main supply cable and disconnect
the last section, the 'short-circuiting of certain things at any one contact-box at
random will produce no effect whatever.
To illustrate this more clearly we will first describe one of the contact-boxes we
have devised for the parallel system and which operates by the mere short-circuiting
action of a passing train. In figure 13 AB, CD are the insulated rubbed rails
EK and LF the return earth rail and GH the supply cable. J is a short
insulated piece in the earth rail. As the train comes along in the direction of the
arrow a short circuit is made between J and K or between J and L through the
wheels and framework on one side of the train, or on one side of one or more
carriages, or through the collecting brushes at the front and back of one side of
the train, or at the front and back of one side of one or more of the carriages.
On J being put to earth a current flows from the main supply cable G H through
a fine wire coil uw J wound on the electro magnet M and in consequence pulls
down the lever p q against the springs and so brings p q into contact with the
stud u.
This completes the circuit up qx and thus brings the insulated, rubbed
rail C D into contact with G. H. A current then flows through the thick wire
coil on the Electro-magnet M and continues to flow through it thereby holding
down the lever p q as long as the train is on the section C D and is being supplied
with electricity. As soon, however, as the train leaves this section, the current
ceases, the lever p q is forced up by the spring and the section C D becomes again
insulated from the main supply cable G. H.
A modification of this is shown in figure 11 where the piece J is in line with,
but electrically disconnected from, the insulated rubbed rail instead of being, as in
figure 13, in line with the uninsulated rubbed rail. The necessary motion of the
contact lever is performed in this case by a portion of the train receiving
electricity from the section A B when on A B, while another portion of the train,

page_text: which has advanced on to the section J still continues to receive electricity from
the section A B through the coil of the Electro-magnet M. And this arrangement
would be suitable where there are two or more carriages in the train each.fitted
with Electro-motors. The two halves of the lever p q are electrically insulated
from one another and are connected respectively with the two ends of the thick
wire coil of the electro-magnet M which with this arrangement requires no fine
wire coil.
Now let a carriage with a. Motor be partly on J and partly on CD while a rear
carriage, also furnished with a Motor, is wholly on the section AB, then electricity
to feed the Motor on the advanced carriage will pass by the circuit Bt p through
the coil of the magnet M to .q and J. The lever p q will. therefore be attracted
down and the circuit up M q v C, closed, so that the main supply cable G H is
now connected with CD and will remain connected as long as the train is on C D
drawing electricity from that section. While on the train passing off the
section C D the magnet M ceases to be magnetised and the lever p q is pushed by
the spring into its original position, thus cutting off the connection between the
section CD and the main supply cable.
It will be observed that to operate this lever two conditions are necessary, first,
that electricity should be already being supplied to the section A B from a train
being on that section, secondly, that a metallic connection must be made between J
and E F. The latter operation alone being performed by a passer-by cannot
affect the lever or produce any waste. of electricity; while on the other if a train
has entered the section A B and the passer by now maintains a metallic connection
between J and E F with say a crowbar, there will undoubtedly be a waste of
electricity but the waste will tend to pull up the train on A B and prevent it
running into the obstruction.
The plan shown in figure 11 is superior to that shown in figure 13 in that no
mere short-circuiting of two things by a passer-by can produce any effect unless a
train is immediately in the rear, when the waste of electricity is advantageous in
tending to prevent the train running into the obstruction placed on the rails, but
both plans have the disadvantage that if the electric circuit through a train which
has passed entirely on to the section CD, fails from any cause the lever p q
immediately returns to its original position, cutting off the supply of electricity
from C D, and which the train has no means of turning on again. This would
not be a serious disadvantage when the driver of a train stopped it intentionally,
since he could do this by shunting the current through a resistance on the train
instead of through the Motor, but it would be serious if the current were
interrupted accidentally, and further, it would prevent our automatic block system
being employed, since if a train ran into a blocked section, that is one in which the
running of the train on to the section could not automatically make electric
'connection between the supply cable G H and the rubbed rail, there would be no
means of making such connection when the block was removed by the train of the
section in advance passing out of that section.
To overcome the various difficulties we have devised the following methods.
Let A B, C D figure 9 be two sections of our insulated rubbed rail on the parallel
system, and E F a portion of the earth rail by which the current returns to the
Dynamo, and let the train be passing from the section A B to the section C D.
Then we wish the train to automatically perform the operation of cutting off the
connection between the well insulated conductor G H and the section A. B and
make connection between G H and the section CD. This is effected as follows;-
The Electro-magnet M has the two ends of its coil attached respectively to the
well insulated rubbed rail CD and the lever p q. A spring 8 pushes the
armature p q against the stud t which is in contact with the earth rail E. F so that,
in the present circumstances, the coil of the Electro-magnet M is joined to the
insulated rail C D. and the earth rail E F, & the train entering the section C D,
which at present is not supplied with electricity, makes temporary contact, through
the wheels on one side of it, between the section A B just left, and the section CD

page_text: just entered on, and so sends a temporary current from the main supply cable G H
through A B to CD and thence through the Electro-magnet M to the earth
rail E F, or if it be arranged that no such electric connection is made between B
and C as the train passes from B to C, then the Motor on the train which has run
on to a section not supplied with electricity is changed so as to act temporarily
as a Dynamo Machine by the method fully described in our patent for Haulage
No 3380 of 1882, and the temporary current which it produces passes through the
electro-magnet M, or such a current is sent by an accumulator, or battery, or by a
hand magneto or dynamo machine carried on the train. The current so sent-
magnetises the electro-magnet M and consequently attracts down the lever p q
which now makes contact with the well insulated stud u which is joined to the.
main supply cable G H. The effect is now that the current from the main supply.
cable G H, flows through up q, the coil of the electro-magnet M to the insulated
rubbed rail C D and supplies the train with electricity, and by doing so continues
to hold the lever p q in contact with the stud u. On the train leaving the
section CD the current no longer passes through the electro-magnet M, the
lever p q is therefore forced up by the spring and breaks the contact between p
and u, making contact between p and t. Should the train have its current cut off
anywhere in section CD for the purpose of stopping it, the electro-magnet M will
cease to be magnetised and the lever p q will rise, cutting off the connection
between the rubbed rail CD and the main supply cable GH so that not only.
will no section on which there is no train be connected with the supply cable or
introduce leakage, but the section on which the train is at rest, and therefore not
requiring current, will be disconnected with the main supply cable. When the
train is to be restarted it must, of course, receive a current through the electro-
magnet M. To do this as it is started from rest there must be a few accumulators
(which are charged when the train is receiving energy, and which will also be very
convenient for continuously lighting the train when on a block section) or there
must be a small battery, or hand dynamo or magneto machine carried by the
train.
In this case it is probable that the very short thick wire that will be put on
the electro-magnet to hold down the armature p q when the main current is passing
through M to drive the train when it is on the section C D, would not have
sufficient convolutions to enable the weaker current produced by the accumulators
or battery on the train to pull down the armature p q, but this is easily got over
by the following arrangement. Instead of joining the stud t figure 10 directly to
the earth rail E F, t is joined to the fine wire coil which passes round the magnet,
so that when p q is in contact with t the circuit is from. CD through the thick
coil of M through q p to t and then through the fine wire coil on M to the earth
rail E F so that the lever-p q is pulled down by the action of the two coils com-
bined, but is kept down by the action of the thick one only. It is to be observed
that although a train which has been at rest in any section can, by one application
of the battery it carries, cause, at will, the main supply cable to become connected
with that section, and as it proceeds along can, without any further application of
this battery, connect the supply cable with every section in succession, disconnecting
it in succession from each section left, no mere random short-circuiting of the end
and beginning of the insulated rails of any two sections, or of the insulated and
earth rail of any one section, by means of a crowbar for example, can produce any
effect at all.
As the mechanisms above described are for the purpose of effecting by electricity
the motion of a lever or other arrangement in our contact boxes, previously effected
mechanically by the passing train, any of the systems of blocking described in our
original patent specification N° 783 of 1881 can be employed with any of the
contact boxes here shown excepting those illustrated in figures 11 and 13.
,
But since, to effect this blocking, one wire must pass from the blocking contact box
to the one blocked in the rear this wire may be used not merely to block but also to
take off the current from the section the train has just left, and the battery or hand

page_text: machine on the train may be dispensed with for restarting the train should it stop
intentionally or stop because the current is cut-off either from the train having run
on to a blocked section, or because the current has momentarily failed from some
irregularity in the brushes or commutators of the Motor &c.
Figure 14 shows one of the arrangements we have devised for utilising the
blocking wire so as to act as the releasing agent in a contact box worked wholly by
electricity. When the wheels or brushes on one side of the train which is entering
on the section C D connects electrically B and C temporarily together a current
passes from B to C thence through the left hand side p of the lever p q, which
left-hand side is insulated from q, the right hand side, and thence through the coil
of the electro-magnet M to the earth rail. The lever p q is thus pulled down into
contact with u and, since there is not, as in the previous arrangements, any spring
to pull it back, p remains in contact with u even although the motion of the lever
breaks the contact between t and p and so stops the current flowing round the
electro-magnet M. p coming into contact with u connects the main supply cable
GH with the section C D through the lever r and the contact the supply
current used to propel the train not, as in the previous arrangements, passing
through the magnet M.
.
On the train arriving at the next contact box in advance the corresponding lever
is pulled down, and which performs for that box the same operation as is performed
at the contact box in the figure by the depression of the lever p q, but the
depression of the lever in the box in advance of C D in addition sends back a
current along the insulated wire J to the contact box in the figure and this current
flows round the thick wire coiled on M' through the right hand end g of the
lever p q to w, with which q is now in contact, and thence to the earth rail E F.
M' is therefore magnetised and the lever p q is pulled up, the contact between q
and wis therefore broken and the current through M is interrupted, so that on a
train leaving the section C D it takes off the electric supply from C D. The
current through M¹ is, as explained, only momentary, and consequently, if required,
may be a very strong current without producing any sensible waste of energy But
after the current coming along the wire J is prevented from flowing through the
coil of the electromagnet M' a weak current continues to flow through the fine
wire coil of the electro-magnet M. & this current continues to flow as long as the
train is on the section in advance of CD Now this current which continues to
flow through m blocks the section C D, since by magnetising the magnet m it pulls
the lever away from the contact v and so interrupts the connection between u
and the supply cable G. H. If then a train now enters on C D the lever p q will
be attracted down in the manner already explained, and will remain in contact
with u until the train in question passes out of this section C D. But such a train
will receive no supply of electricity as long as r is also attracted away from v that
is as long as there is a train on the section in advance of C D.
With the above variations then we perform, for a train running in one direction,
all the various operations described in our previous specification, but we do it
without any blow of any kind being given by the passing train and with only one
wire between each two contact boxes.
To avoid complication in the symbolical diagram figure 14 the insulated spring
on the lever p q by means of which the motion of this lever sends to the contact.
box in the rear a releasing and blocking current is not shown, nor in any of the
figures have we shown the springs we sometimes attach to the levers to prolong
the electric action connected with their movement, nor have we shown the shunt
coils we sometimes attach to some of the electro-magnets to allow the induced
currents to circulate on interrupting the main current, and by which contrivance,
as is well known, the action of an electro-magnet can be prolonged after the
cessation of the main current

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Edward Ayrton and John Perry-in the Great Seal Patent
Office on the 10th November 1883.
WILLIAM EDWARD AYRTON, Professor of Technical Physics, Fellow of the
Royal Society, and JOHN PERRY Professor of Mechanical Engineering and
Applied Mathematics in the City and Guilds of London Technical College
Finsbury in the County of Middlesex IMPROVEMENTS IN CONTACT BOXES ON
ELECTRIC RAILWAYS.
"
In our English patent specification No 783 of 1881 for improvements in
Electrical conductors applicable to Electric Railways and to Electric Signalling
and apparatus connected therewith we stated line 7 page 15 :-"Instead of the
"mechanical plungers shown on sheet for automatically connecting the main
"cable with the section just entered by the train & for automatically disconnecting
"the main cable from the section the train is leaving, we may use electric means,
"based on the wheels rollers or brushes, on one side of a carriage completing an
"Electric circuit through the wheels rollers or brushes on the other side, or based
on the wheels rollers or brushes in the front of a carriage or tram being in
"connection with the insulated section just entered on, while the wheels rollers or
"brushes in the rear of a carriage or train are in contact with the insulated section
being left, and so connecting for a short time the two insulated sections electrically
" together, or we may employ a magnetic arrangement depending for its action
"not on the weight of the train but on its magnetic mass." We now propose to
describe the various contrivances we have since designed for carrying out the idea
of dispensing with the blow given by the passing train for the working of the
contact boxes, and which contrivances are some of them suitable for the series
system and some of them for the parallel system of the electric transport of goods
and passengers. The arrow heads on the figures show the direction of motion of
the train in every case. First let us consider the series system. The strong
lines A¹ B-B¹ C-C' D in the figures 1 to 14 are the insulated rails or ropes used
in the series system to convey the current, and such rails or ropes may or may not
be the rails or ropes on which the trains run. Wheels rollers or brushes on the
train collect the current from one rail and return it to.another. When no train is
in the neighbourhood of B' C and C¹ D in order to keep up electrical continuity a
current must pass from B¹ C to CD across the break CC by a contact maker
at C C. While on the other hand when the train is partly on C¹ D and partly
on B¹ C the contact at C C¹ must be opened so that the Electricity may pass
through the Electric motor attached to the train which bridges over the gap C C',
In working this series system it has hitherto been our custom to allow a cam on
the front of the train to strike a lever and thus break the electrical contact between
the two sections, another cam on the rear of the train establishing the junction
again The simplest of our electrical methods for producing the automatic opening
and closing is as follows:-By means of the Electro-magnet M figure 1 through
the coils of which the main current usually passes, the arm p q is attracted down
against the action of the spring S, so as to come in contact with the stud t-When
the train passes over the break C C¹ the Electro-magnet M is short circuited by the
front wheels of the first carriage touching C and C¹ simultaneously or by two brushes
on the front carriage, one in the front of the carriage and the other in the rear, which
short circuit M through the body of the carriage where it is of metal, or through a
conductor of low resistance-M being short circuited the spring S forces up the
lever Pq and so opens
the circuit and allows the Electricity to pass through the train

page_text: and propel it-In order to pull down pq and restore the contact on the train quitting
the section CD one or other of two devices may be adopted, the one the insertion
of a resistance r between 9 and t less than infinity so that in fact when C C¹ is short
circuited the circuit Cpqt C' is not entirely broken but its resistance being great,
compared with the resistance of the motor on the train, the current passing along
the coil is not sufficiently strong to excite the magnet while the train is bridging the
gap CC, but when the train has passed entirely beyond CC the potential
difference C and C¹ will be very much increased, and this will especially be the
case if a constant current dynamo is used with this Electric railway, hence the
current flowing through M for the moment will be very much increased, so that
the arm p q will be powerfully pulled down and again make contact with t so that
the contact between C C is again closed and the main current flowing through M
will keep it closed. Another plan for restoring contact after the passage of a train
is to have wound round the electro-magnet a fine wire coil of high resistance as
shown in figure 2 through which a small current only passes when the train is
bridging the gap C C¹ but a considerable current when the train leaves the section
C¹ D so as to excite the magnet and cause it to attract the lever p. q. The resistance
R in figure 1 not being wound round the magnet there is a shunt circuit to the
magnet coil when the front of the train bridges the gap C C¹ which prevents
sparking between t and p q. In figure 3 we show how to effect the closing of the
boxes without introducing into the main circuit either the resistance R of figure 1
or the resistance of the fine coil of the magnet in figure 2. The lever p q as before
is pressed against the stud t by the attraction of the electro-magnet, through the
thick coil of which passes the main current when the box is closed, and the box is
opened by the front wheels' of the train short circuiting this coil; contact between
Pq and t being broken by the spring S. The fine coil of the Electro-magnet shunts
the gap B B¹ in advance of C C₁ and being of a resistance not very great compared
with that of the motor, sufficient current passes along it when the box B B¹ is open,
to excite the electro-magnet in C C' and close the contact between pq and t before
the hind wheel of the train leaves the section CD. In some cases we find it
convenient to insert short insulated pieces c d figures 4 to 7 between the two ends
of the conductor which have to be connected and disconnected at the contact boxes.
In figure 4 as in figure 1 the box is kept closed by the main current passing round
the thick coil of the electro-magnet M and opened by the short circuiting of this
thick coil by the front wheels of the train. The short piece c is connected to C¹D
by a coil of not very great resistance wound round the electro-magnet M. When
the hind wheel of the train reaches c current passes from C¹ to c through the
magnet M and re-establishes the contact, so that when the hind wheel reaches C
the current passes as before through the thick coil. Contact is therefore broken
by the front wheels and made by the hind wheels automatically. As the contact
boxes illustrated in figures 1 to 4 open when the current ceases to pass along the
line, in some cases we find it advisable to wind another coil round each magnet so
that the coils being connected by a separate conductor, a current may be sent
through them and the boxes closed-An objection that might be urged against any
of these methods is that at every contact box, even when the circuit is closed, there
is in the main circuit the resistance of the thick coil on the magnet M. We have
therefore devised plans in which there is no resistance in the contact boxes or a
resistance is only introduced for a short time. In figure 5 the short insulated piece c
is connected to each of the adjacent sections B¹ C and C' D through coils wound
round the electro-magnets M, M³. The lever p q connected to the section B' C is
kept pressed down against the stud t connected to the section CD by the spring S,
so that the current ordinarily passes along the circuit C¹t qp C-Suppose a train
proceeding in the direction of the arrow to approach the box C C¹ the box D D'
being open; When the front wheel or brush is on c the current passing through
the motor reaches B¹C partly through the coil on magnet M and partly the
circuit c t q p.
The lever p q is attracted by both magnets and the contact t is
broken. The main current then flows through the coil M, a derived current in the

page_text: direction opposite to that of the first current passing through the coil M¹. When the
front wheel momentarily connects C and c the magnet M is short circuited, but the
magnet M continues to attract p q, and does so until the hind wheels or brushes which
must be arranged to connect C and C¹ electrically, short circuit both magnets and
allow the spring s to close the box-Both coils may be wound on one magnet if the
coil M is of thicker wire than M' so that owing to its low coefficient of self
induction M will act very quickly and so instantly break the contact t, when both
coils assist one another. In figure 6 the lever p q in each contact box is kept
against t by a spring and drawn away from it by the magnet M-A catch k
engages the lever p q and keeps it away from t. The magnet M is wound with a
coil connecting CD with the short section e through the coil in the box E E¹ not
shown in the figure-The magnet m of the contact box D D¹ is wound with a
coil connecting the short section d with B¹ C through the magnet M in box C C¹.
When the hind wheels of the train connect d to D¹ E a current flows along the
coils m in box D D' and M in C C-The magnet m attracts the catch k in D D¹
and the spring S draws p q against t thus connecting CD to D¹ E. The magnet M
in CC attracts p q away from t until it is engaged by the catch k so that the
connection between B C and CD is broken and the current must pass through
the motor on the train-When, as is most usual, the locomotive in front of the
train has two wheels or brushes electrically connected which can connect the short
section c to C the method of figure 7 which also shows one of our methods of
blocking may be Employed. The box D D¹ being open and there being a difference
of potentials between the points D and D¹ when c is connected by the train with
C or C¹ a current flows round the magnet M in the box C C₁ and m in the
box D D¹. As in fig 6 M attracts p q and opens the box C C¹ while m closes the
box D D. In order to prevent p q leaving the stud t before the front of the train
has reached B¹ C in which case the main current would be altogether broken M
must be a slowly acting magnet, or the motion of p q may be checked by a dash
pot or other mechanical means-Or the insulated piece c may be placed out of the
line of the main conductor, and connected electrically with B¹ C or C D after the
front part of the train has reached B' C. When the lever p is engaged by the
catch it is contact with another stud u which is connected by a wire of low
resistance J to the section D' E so that as long as the box C C¹ is open, even if a
train coming up behind does open the box D D¹ it receives no current as it is
short circuited by the blocking wire J and remains short circuited until the
box C C is closed. That is the simplest case in which the blocking wire is carried
back to the next section; we prefer however to carry it back to the next section
but one, or to the next but two-in which cases two or 3 blocking wires are
required and in general if we desire to have a minimum interval of n sections
between two trains each blocking wire must be carried back to the nth box and
there must be a blocking wires-This method of blocking is also applicable to the
systems herein before described and illustrated in figures 1. 2. 3. 4. 5 and 6 and to
those hereinafter described and illustrated in figures 10. 11. 12. Where we wish
to block a considerable number of sections back and it is not desirable to have a
number of blocking wires we employ the method illustrated in figure 8. In this
case there are blocking boxes placed at intervals along the line, the intermediate
boxes being simple boxes, that is without any blocking arrangement; worked on
any of the bereinbefore described methods-for example that of figure 3. The
blocking boxes one of which is supposed to be placed at the gap C C and another
at F F, while the boxes at D D' and E E' are simple boxes, are connected by a
single blocking wire which extends from the stud u in C C¹ round the coil M³ in
the box F F to the lever p q which is connected to the section F' G. On the end
of the lever p is a catch k which engages the lever and prevents it making
contact with u-When as herein before described the front wheels of the train
short circuit the magnet M in C C' the spring S draws down the lever p q and the
catch being drawn up, the lever which is connected with the section C¹ D is
released and drawn by its spring against the stud u. The box D.D' being open

page_text: and there consequently being a difference of potentials between C¹ D and F¹Ga
current passes along the circuit C¹ plu M¹ F¹ exciting the magnet M¹ in the
box F F. This causes the lever to be attracted and to be Engaged by the
catch k, and the block at some box in the rear of F F¹ to be removed. As long
as the lever is pressed against u in the box C C¹ there is a low resistance circuit
connecting CD and F G so that even if a train should follow too closely and open
the box F F¹ before C C is closed it will receive comparatively little current and
will consequently have its speed greatly reduced-In some of our methods the
box D D is closed and CC is opened simultaneously. In this case, and where
the resistance of the main conductor is small, compared with the resistance of the
blocking circuit, instead of winding the main blocking wire round the magnet M' in
box F F¹ we wind this magnet with a fine wire coil shunting the box C C₁ so that
when that box is opened the blocking contact in box F F' is broken and the block
is thereby taken off the sections behind. In this arrangement which is shown in
figure 9 only one additional wire K besides the blocking wire J is necessary to
remove the block.
When the box C C¹ is open the lever is in contact with u
so that there is a shunt circuit to C C along the path C¹plu J round the
Magnet M in the box F F¹ and to B¹ C along the wire K. In figure 10 a
resistance is introduced in the main circuit in each contact box only when a train
has opened the next contact box in the rear. When no train is near the place CC¹
there is immediate contact through C¹fqp C the lever of f being pressed against
the lever pq by the spring S¹ and preventing the spring S breaking the contact.
The coil of the electro-magnet m shunts the gap C C' and D D' so that when either
box is open the lever f is attracted and breaks contact with p q. The main
current now passes from C¹ to C round the thick coil of the magnet M maintaining
the contact until the front wheels of the train bridge the gap C C¹ and short-
circuit the thick coil of the magnet M. The box is now open and remains open
until the box in advance B B₁ is opened, A current then passes along the fine
coil of the magnet M which shunts the gap B B' and the armature p q is attracted,
closing the contact t, D D¹ being already closed. The magnet m ceases to act and
the spring S¹ draws the leverf down on the lever p q thus completely closing the
box. Another method of effecting the same object is shown in figure 11 where
at the place CC¹ the contact is usually made through pqt the lever p q which has
a soft iron piece on it being pressed against t by the spring S. When the front of
the train reaches C C¹ a magnet on it is arranged to attract the lever p q so as to
break contact with t. The catch on the lever f engages p q and prevents it from
making contact with t again until the box B B¹ is opened in the same way.
shunt circuit from B B¹ then causes the electromagnet m to attract the lever f
which allows p q to fall under the action of the spring S thus closing the box C C¹.
In figure 12 we show how to effect the lifting of the lever p q without the agency
of a magnet carried by the train. In this case some means is employed for
allowing the train to connect the end of one section C¹ with e which is one end of
the coil of an electro-magnet M whose other end e¹ is to earth. When the train
effects this connection which may be done in many ways M attracts p q and the
box is opened. The closing of the box is effected as in figure 11. The objection
to this method is in the train putting the line to earth at every contact box so
that there is a permanent danger of leakage. Various methods may however be
suggested for disconnecting e¹ from the earth except at the time when the train is
approaching. Thus for example the contact between e¹ and the earth may be
always broken except when an armature of a magnet whose coil shunts
the two sides of a back contact box such as D D is attracted, or again
it is easy to arrange that the opening of a back contact D D' shall connect e¹
with the earth permanently until the opening of a forward box such as A A¹
disconnects it. In figures 13 and 14 are shown methods by using which
several disadvantages are avoided. Current has not to pass through coils in each
box when no train is near the box there are no short insulated sections, and the
train has not to carry a magnet or put the line to earth as in figure 12. In
A

page_text: figure 13 when no train is in the neighbourhood contact is made at the
junction D D¹ through t p q. The armature p q of the electro magnet M is pressed
away from the magnet by a spring s¹ against the stud t. The catch K is on the
armature of the magnet m which is doubly wound as a shunt to B B¹ and F F¹:
If either of these boxes are open the catch K is pulled forward and engages p q
When the magnet m ceases to act the catch k is drawn away from p q by the
spring S. The magnet M is doubly wound as a shunt of D D and E E. In this
case the train is long enough to reach the section C¹D before its hind wheels
short-circuit the gap F F'. When this takes place the box F F¹ is closed by the
spring S¹ and the magnet m in D D¹ ceases to be excited. The spring S therefore
draws back the catch k and the lever p q is attracted by M, and the box D D' is
opened and remains open until the hind wheels of the train short circuit the .
magnet M in D D'. When the box B B¹ is opened the catch k is again attracted
and prevents the box D D₁ being opened, thus blocking the following train. In
figure 14 there are two contact-makers p q and l. The magnet M is wound with
three coils which shunt the boxes B B¹ C C₁E E' so that if any one or more of
these boxes are open the contact between p q, and t which is ordinarily kept closed
by a spring, is broken, the lever is pressed against u by a spring S and the
magnet m whose coil shunts E E. The magnet M¹ which is doubly wound as a
shunt of C C and D D¹ tends to attract and breaks its contact with u. It will
be seen that the train which must be longer than two sections opens the contact t
when it reaches the box E E', but the magnet m will keep the contact u closed
until the section E¹ F is left so that the box C C is not completely opened until
the front wheels are on the section B¹ C. The box remains open until the hind
wheels of the train short circuit the coil of the magnet M' which shunts C C¹.
The contact u is then closed and small t is closed when the same operation is
performed at B B¹. By winding the magnet m with a coil which shunts a box in
advance such as A A¹ we may block a following train but we prefer that our
blocking arrangement shall be just as independent of the other parts of our contact
boxes as if the opening and closing of the boxes were performed by a train striking
a lever, that is, if we wish an open box to keep a backward box closed. Such a
system of blocking is shown in figure 15 where the electro-magnet M² in C C¹
attracts the lever In when A. A¹ is open thus connecting C with C¹ by the circuit
Clnu RC. The method of opening and closing the contact t is the same as in
figure 3, the box being opened by the short circuiting of the thick coil on M.
through which the current usually passes, and closed by the opening of the
box B B'. The resistance R is introduced to prevent the blocking circuit short-
circuiting the thick coil of M. It will thus be seen that a train may open the
contact by short-circuiting the thick coil of M, but if the box A A¹ is open the
train will receive very little current and will consequently be blocked until
the box A. A¹ is closed, when the blocking contact will be opened by the spring S¹
The blocking wires J K may be carried further forward than A A' if we wish to
have a longer interval between two trains. This method of blocking may also be
employed in connection with any of the methods shown in figures 1. 2. 10. 11. 12
and 16-In figure 16 the contact box C C is closed by the train leaving the
section C¹ D a current being sent along the high resistance circuit through the
electro-magnet M' in C C¹ and M in B B¹ the box in advance. When M becomes
magnetic the lever p q is attracted and engaged by the catch k which is on the
armature of the magnet M¹. The contact t is thus broken and remains broken
until the train leaves the section C¹D when the lever lk is attracted and p q being
liberated the spring S draws it into contact with t. A momentary current thus
closes one box and opens the next in advance. The advantage of this method over
those of figures 1 and 2 is that the boxes remain closed even after the current
ceases to pass along the line, so that it is not necessary to have a high electro-
motive force or a separate coil wound on each magnet to close them. In order to
avoid excessive sparking in the methods of figs 1. 2. 16 the train may have a
second wheel or brush behind the brush. usually at the End of the train and

page_text: connected to it by a resistance so that the main current is never Entirely stopped.
The previous methods are Especially suitable to the series system of working
railways. In our parallel system of working railways as described in our patent
No 783 of 1881 we divide the rubbed rail, which immediately supplies the train with
electricity, into a number of sections each of which is fairly well insulated from the
next and from the earth, and we arrange that the train when on any section
automatically makes contact between that section of the rubbed rail and the well
insulated conductor which conveys the main current. We have arranged plans for
doing this electrically, somewhat on the same principle as our methods above
described for the series. system, but there is this objection to them when applied
to railways running on the ground, that it is in the power of any body by short
circuiting, by means of a crowbar for example, either the insulated rail and the
earth rail in the one case, or one insulated rail and another insulated rail in another
case, to imitate the action of the train, and secondly to put electricity on to a
section where no train is and thus to increase the leakage of the line-Of course
the objection exists to a much greater degree in any of the ordinary well known
systems of working electric railways when our plan is not Employed of dividing
up the rubbed rail into sections, each fairly well insulated from the earth and from
its neighbours, because in an ordinary electric. railway the placing of a crowbar
across the two rails, or so as to make contact between the third insulated rail if
there be one supplying the electricity, and the earth sends all the electric current
to the earth and so stops the whole traffic on the line. For this reason we prefer
for railways on the ground not to replace our automatic mechanical contact makers
by electric contact makers operated by the mere short circuiting action of the
wheels or brushes on a train, but instead to employ a current which the motor is
itself able to produce by running on as a Dynamo-machine with its own momentum
when a train enters a new section not yet supplied by electricity, or to use the
accumulators or a battery, a small magneto or Dynamo machine for the train to
operate the contact maker, or lastly to arrange that the short circuiting of two things
at any contact box can put current on a section only if the current had already
been supplied to the previous section that is to say although the successive short
circuiting action produced by the train at each contact box will in succession
connect the next section with the main supply cable and disconnect the last section,
the short circuiting of certain things at any one contact box at random will produce
no effect whatever. To illustrate this more clearly we will first describe one of the
contact boxes we have devised for the parallel system and which operates by the
mere short circuiting action of a passing train. In figure 17 A B, C D are the
insulated rubbed rails, E K and L F the return earth rail and G H the supply cable;
J is a short insulated piece on the earth rail-As the train comes along in the
direction of the arrow a short circuit is made between J and K or between J and L
through the wheels on one side of a train and framework, or on one side of one or
more carriages, or through the collecting brush at the front and back of one side of
the train, or at the front and back of one side of one or more of the carriages.
On J being put to earth a current flows from the main supply cable G H through
a fine wire coil u w J wound on the electro-magnet M. and in Consequence pulis
down the lever pq against the spring 'S and so brings p q into contact with the
stud u.
This completes the circuit upq x C and brings the insulated rubbed
rail CD into contact with G H. A current then flows through the thick wire
coil on the electro-magnet M and continues to flow through it thereby holding
down the lever p q as long as the train is on the section C D and so being supplied
with electricity. As soon however as the train leaves this section the current
ceases, the lever p q therefore is forced up by the spring and the section C D becomes
again insulated from the main supply cable G H. A modification of this is shown
in figure 18 where the piece J is in line with but electrically disconnected from the
insulated rubbed rail instead of being as in figure 17 in line with the uninsulated
rubbed rail. The lever p q which has its two Ends insulated from one another is
kept pressed by the spring S so as to have one end in contact with t and the other

page_text: end electrically in contact with J-It will thus be seen that when J is connected
with the earth rail by a conductor having a moderate resistance such as that of a
motor a current will pass along the circuit Bt p Mq J exciting the magnet M.
The lever p q is consequently attracted and C D is connected to the main con-
ductor G H through the coil of the magnet M and remains connected to it as long
as the train is on CD receiving current from C D.
In order to ensure the working of the box it is advisable to have two motors on
the train, one being fed by brushes which can be on J and C D while the other is
fed direct from A B or a brush which reaches from B to C. The back motor thus
keeps the box through which A. B is receiving current closed until after the box
at C D is closed on the train passing off the section C D the magnet M ceases to
be magnetised and the lever p q is pushed by the spring into its original position,
thus cutting off the connection between the section CD and the main supply cable:
It will be observed that to operate this lever two conditions are necessary, first,
that Electricity should be already being supplied to the section A B from a train
being on that section; secondly that a metallic connection must be made between
J and E F. The half operation alone being performed by a passer by cannot effect
the lever or produce any waste of electricity, while on the other hand if a train has
entered the section A B and a passer by now maintains a metallic connection
between J and E F with, say a Crowbar, there will immediately be a waste of
electricity, but the waste will tend to pull up the train on A B and prevent it
running into the obstruction-The plan shown in figure 18 is superior to that
shown in figure 17 in that no mere short circuiting of two things by a passer by
can produce any effect, unless a train is immediately in the rear, when the waste of
electricity is advantageous in tending to prevent the train running into the
obstruction placed on the rails, but both plans have the disadvantage that if the
electric circuit through a train which has passed Entirely into the section C D
fails from any cause the lever p q immediately returns to its original position
cutting off the supply of electricity from C D and which the train has no means of
turning on again This would not be a serious disadvantage when the driver of a
train stopped it intentionally, since he could do this by shunting the current
through a resistance on the train, instead of through the motor, but it would be
serious if the current were interrupted accidently and further it would prevent an
automatic block system being employed, since if a train ran into a blocked section,
that is one in which the running of the train into the section could not
automatically make electric connection between the supply cable G H and the
rubbed rail, there would be no means of making such connection, when the block
was removed by the train of the section in advance passing out of that section―
To overcome the various difficulties we have devised the following methods.
Let AB, CD in figure 19 be two sections of our insulated rubbed rail on the
parallel system and EF a position of the earth rail, by which the current returns
to the Dynamo and let the train be passing from the section AB to the
section CD-Then we wish the train to automatically perform the operation of
cutting off the connection between the well insulated conductor G H and the
section AB and make connection between G H and the section CD-This is
effected as follows:-The electro-magnet M has the two ends of its coil attached
respectively to the insulated rubbed rail CD and the lever p q. A spring S
pushes the armature p q against the stud t which is in contact with the earth
rail EF so that in the present circumstances the coil of the electro-magnet M is
joined to the insulated rail CD and the earth rail EF, and the train entering the
section C D which at present is not supplied with electricity, makes temporary
contact through the wheels on one side of it between the section A B just loft, and
the section CD just Entered on and so sends a temporary current from the
main supply cable GH through AB and CD and thence through the electro-
magnet M to the earth rail E F, or if it be arranged that no such electric
connection is made between B and C as the train passes from B and C then the
motor on the train, which has run into a section not supplied with electricity, is

page_text: changed so as to act temporarily as a Dynamo-machine by the method fully
described in our English patent for Haulage N° 3380-1882, and the temporary
current which it produces, passes through the Electro-magnet M or such a current
is sent by an accumulator or battery or by a hand magneto Dynamo carried on the
train through the electro magnet M and consequently attracts down the lever p q
which now makes contact with the well insulated stud U which is joined to the
main supply cable G E-The effect is now that the current from the main
supply cable G H flows through upq the coil of the electro-magnet M to the
insulated rubbed rail CD and supplies the train with electricity and by doing so
continues to hold the lever p q in contact with the stud U. On the train leaving
the section C D the current no longer passes through the electro-magnet M, the
lever pq is therefore forced by the spring and breaks the contact between p
and u. Should the train have its current cut off anywhere in section C D for
the purpose of stopping it, the electro-magnet M will cease to be magnetised, and
the lever pq will rise, cutting off the connection between the rubbed rail C D
and the main supply cable G H, so that not only will no section on which there is
no train be connected with the supply cable or introduce leakage, but the section
on which the train is at rest, and therefore not receiving current, will be
disconnected with the main supply cable-When the train is to be restarted
it must of course receive a current through the electro-magnet M. To do this
as it is started from rest there must be a few accumulators (which are charged
when the train is receiving energy, and which will also be very convenient for
continuously lighting the train when on a blocked section) or there must be
a small battery or hand Dynamo or magneto carried by the train-In this case
it is probable that the very short thick wire that will be wound on the electro-
magnet M to hold down the armature pq when the main current is passing
through M to drive the train when it is on the section C D would not have
sufficient convolutions to enable the weaker current produced by the accumulators
or battery on the train to pull down the armature p q, but this is easily got over
by the following arrangement-Instead of joining the stud t in figure 20 directly
to the earth rail E Ft is joined to the fine wire coil which passes round the
magnet, so that when p q is in contact with t, the circuit is from C D through the
thick wire coil of M through qp to t and then through the fine wire coil on M to
the earth rail E F so that the lever p q is pulled down by the action of the two
coils combined, but is kept down by the action of the thick one only. It is to be
observed that although a train which has been at rest in any section, can by one
application of the battery it carries, cause at will the main supply cable to become
connected with that section as it proceeds along can without any further application
of this battery, connect the supply cable with every section in succession dis-
connecting it in succession from each section left, no mere random short circuiting
of the end, and beginning of the insulated rails of any two sections or of the
insulated rails of any two sections, or of the insulated and earth rail any one
section by means of a crow bar for example, can produce any Effect at all. As the
mechanisms above described are for the purpose of Effecting by Electricity the
motion of a lever or other arrangements in our contact boxes previously Effected
mechanically by the passing train, any of the systems of blocking described in our
original patent specification N° 783 of 1881 can be Employed with any of the
contact boxes here shown excepting those illustrated in figures 17 and 18. But
since to Effect this blocking one wire must pass from the blocking contact box D
to the one blocked in the rear, this wire may be used not merely to block, but
also to take off the current from the section the train has just left, and we shall
see that the battery or hand machine on the train may be dispensed with for
restarting the train should it stop intentionally or stop because the current is cut off
either from the train having run into a blocked section, or because the current bas
momentarily failed from some irregularity in the brushes or commutator of the motor,
Current then flows through the thick wire coil on the electro-magnet M and
continues.to flow through the thick wire coil x. Figure 21 shows an arrangement

page_text: we have devised for utilising the blocking wire to act as the releasing agent in a
contact box worked wholly by Electricity. When the wheels or brushes on one
side of a train which is Entering on the section CD connect electrically B and C
temporarily together, a current passes from B to C round the fine coil of the
nagnet M to earth-The lever r is consequently drawn down against the stud t
and there being no spring to act upon it, remains in contact with t until it is
attracted by the magnet M¹-The lever p q is a double lever with its two Ends
insulated from one another and ordinarily is kept pressed by a spring as shown in
the figure, one End being in contact with the stud u and the other in contact with
the stud w-When q is pressed against w and r is in contact with t the rubbed
rail C D is in direct connection with the insulated conductor G H and the train
can receive current. The train on reaching the next section in advance connects
it with C D and the operations just described are repeated. The blocking wire J
is thus connected to the main conductor as long as the lever r in the box in
advance is in contact with t-A current therefore flows along J to earth partly
through the low resistance coil of M¹ and partly through the high resistance coil
of m.
M consequently acts quickly owing to its low Coefficient of self induction
and attracts the lever r drawing it away from t, before the magnet m has
attracted its armature and broken the contact up. The lever lr remains away
from t, as may be easily arranged mechanically and the block is thus taken off the
section in the rear-The contact u being broken no current flows round M' so that
an advancing train may close the contact t in the manner described above; and
that contact will remain closed, but the contact w being broken the rail C D is not.
.connected to the insulated conductor G H, so that the train will be brought to rest
by its motor receiving no current. When however the train in front in the same
manner disconnects the blocking wire from the main conductor by, causing M¹ to
attract in the box in advance, m in the box in the figure ceases to be excited
and the spring S forces the lever p q into contact with u and w so that if through
.the presence of a train at the contact box which is shown in the figure, the lever / r
is in contact with t, the rubbed rail is now connected with the main conductor, and
the blocked train is started automatically. It will moreover be observed that a
train running on to a blocked section draws over the lever lr and connects the
blocking wire to the main conductor and thus blocks a train in the rear as long as
it is on that section whether it be itself blocked or not. Instead of making the
lever remain in Either of two positions we sometimes cause a spring to press it
against the stud t.
When the magnet M' attracts it it is engaged by a catch which
is on the armature of the magnet M so that when M is magnetic the lever ris
released and makes contact with t-A contact box on this principle is hereinafter
described and illustrated in figures 29. 30. 31. 32. In any of the hereinbefore
described contact boxes instead of using springs to work the various levers we may
make them fall by their own weight which has the advantage of being constant
throughout the whole range of the motion whereas the pull of a spring varies with
the Extension. Hence the pull of a spring is in many cases strongest where for
Electrical reasons we may wish it to be weakest and weakest where we may wish
it to be strongest-We sometimes attach springs to the levers to prolong the electric
action connected with their movement, and sometimes shunt coils to the electro-
magnets to allow the induced current to circulate, on interrupting the main current
a contrivance, as is well known, by which the action of an Electro-magnet can be
prolonged after the cessation of the main current. Having described and illustrated
diagrammatically our various systems of automatically actuating the contact boxes,
we now propose to describe the various forms of apparatus which we have designed
to carry out these systems-In figure 23 A. is a metal box closed by a cover B
bolted to it, the joint being made perfectly watertight by india rubber or other
packing introduced between the flange of the box and the cover. The lower part
of the box has a socket into which is cemented an insulator I which may have a
receptacle for paraffin oil in order to prevent surface leakage, as is well known to elec-
tricians, and which supports the box. A block of wood or other insulating material C is

page_text: fastened in the upper part of the box and supports the magnet M. This magnēt con-
sists of a hollow core partly of iron D. and D' and partly of brass or other non magnetic
substance E-Iron plates F are screwed or fixed on the ends of the core forming a
reel or bobbin on which the wire is coiled-The whole bobbin is then covered by
an iron shell G. In bushes at the Ends of the magnet slides a hollow plunger
partly of iron H and partly of brass J. A spring S is fastened to the boss on a
contact piece P screwed to the lower part of the tube, and passing up through the
tube is fastened to the bolt which passes through a square hole in the insulating
piece so that it cannot turn but can move longitudinally-The spring is adjusted
by means of the nut so as to draw P up against the metal of the magnet and the
position of the plunger itself can be adjusted by screwing round the plate P.
A dome of metal is screwed down over the nut so as to exclude moisture.
Immediately beneath the magnet is fastened and insulated from the box a plate of
copper O-Two studs of copper Q Q' are supported on steel springs R R¹ fastened
to blocks of wood fixed in the box. The studs are kept from touching P and O
and each other by the springs R R¹, but when the plunger is drawn down P makes
contact with both the studs and presses them down on the plate O-Strips of
copper T T¹ bent zig-zag so as not to interfere with the action of the springs R R'
are fastened to the studs and connect them with the wires, which are covered with
india rubber and cemented into the tubulars V V₁. In some cases a third wire
passes out through the tubular U-This box may be used in any of the systems
illustrated in figures 1. 2. 3. 4 and 17-If used as in figure 2 for example the
I bobbin is wound with a thick coil whose Ends are connected one to the side which
passes through the tubular V to the section C D of figure 2 and the other to the
copper strip fastened to the stud Q. The stud Q₁ is connected to the section B¹ C
by a wire passing through V₁. A coil of fine wire is also wound round the magnet,
the two coils filling the whole of the space; the ends of the fine wire coil are
connected with the wires which pass through V and V-On a difference of
potentials being established between C and C¹ of fig 2 the magnet is excited by the
current passing through the fine coil and the ends or edges of the iron tubes D D¹
become opposite magnetic poles. There is thus a strong magnetic field between D
and D' and the iron of the plunger is attracted down into this field-It is arranged
that the studs Q Q are being pressed down on the plate O just as the Edge of the
iron tube is opposite the edge of the lower core tube, this being the position of
maximum magnetic attraction-The studs QQ being electrically connected the
main current passes from C to C¹ of fig 2 round the thick coil of the magnet and
thus continues to force the plunger down on the studs QQ-When the front
wheels or brushes of the train, as herein before described connect C and C
electrically, very little current passes round the thick coil of the magnet so that
the magnetic field is greatly weakened, and the spring S draws up the plunger.
The springs on which the studs Q Q¹ are fixed cause them to follow and remain in
contact with P after they have ceased to be in contact with O. The slight
spark which occurs when the circuit joining C and C¹ is broken therefore occurs
between Q and P or between Q' and P, but there is no spark between Q and O or
Q' and O. These lower contacts which are the important ones are consequently
always clean. In figure 24 the disc of wood-C is fastened to the metal base A to
which may be cemented as before an insulator I. The magnet M is of the same
construction as in figure 23 and is supported by the brass frame L which connects
it electrically to the plate O. The plunger which is electrically connected to the
magnet by the copper strip K falls by its own weight and makes contact with the
stud pressing it on to the plate O. When a current is passing round a coil on
the magnet, the plunger P is drawn up and presses the contact maker Q¹ which
has three or more copper studs on it, against the frame L. If the box is used as in
figure 3Q is represented by t in that figure and is connected to one section of the
line. Qis the stud u of figures 8 and 9 and is connected to the blocking wire.
Three or more tubulars V in the base A allow the wires to pass out and being
filled with insulating cement prevent the entrance of moisture. A dome of metal B

page_text: has its flange fastened to the base by screws and covers the magnet and the
contact pieces, this arrangement allowing easy access to the interior for the purpose
of examining the contacts. It will be seen that, as before, a clean contact is
effectually obtained by the arrangement of double contacts as the springs which
carry the studs Q and Q¹ cause them to leave the lower plate O and the upper
plate F before they leave the contact piece P. If any spark occurs it will therefore
be between the studs Q Q¹ and P and the rubbing which takes place between Q Q!
and P will remove the metallic oxides formed and keep these contacts clean. The
magnet may be wound with a thick coil one of whose ends passes out at a
tubular V and is connected to one section of the line, the other end being connected
through the copper strip T to the stud Q. A fine coil may also be wound on the
magnet with one end connected to one end of the thick coil, the other end being
brought through a tubular V and attached to a telegraph wire which connects it to
the section in advance. The box will then be worked nearly on the same principle
as described under figure 3, being opened by the short-circuiting of the thick coil
by the front wheels of the train and closed by the train opening the box in
advance. The blocked wire connected to the stud Q may be carried back as many
sections as we please. This box may also be used in working the methods of
figures 19 and 20 on the parallel system. A simpler form of box is shown in
figure 25 the shell G of the magnet being extended to cover the working parts.
The iron core tubes D D' are dispensed with and replaced by one brass tube E to
which are screwed the iron end plates F F¹. The iron part H of the plunger is
lengthened so as to nearly touch the upper plate F when the contact piece P
is making firm contact with the stud Q. In this way we get the same advantages
as before, of long range and considerable pressure, with simplicity of construction.
A metal cap is screwed on to the top of the tube to exclude moisture and an eye
bolt I is screwed into it by which the box may be hung from the insulated rail;
the box itself and the plunger being thus connected electrically to one section of
the rail. The lower part of the box is closed by a block of insulating material
through which the wires pass. Figure 26 shows a catch which we sometimes.
place in the cap of the box to engage the plunger when it is drawn up. The
plunger J has its end turned, as shown, to fit the catch on the armature A of
the electro-magnet M M' which in this case is shown of the ordinary form, and
whose coils may be connected as shown in any of the figures 6.7 11 or 12-A
spring S forces the armature away from the inagnet and causes the catch to engage
the plunger. We can easily arrange that the spring draws the catch away from
the plunger while the magnet causes it to engage it, in which case the system
shown in figure 13 may be used. Two studs Q and Q₁ are shewn in figure 25
either of which may be connected to the adjacent section of the line or to the
blocking wire as convenient, and the magnet may be arranged to draw the plunger
down as in figure 23, or up as in figure 24. The form of magnet in figures 23, 24 and
25 is one which is particularly applicable to cases in which it is desired to have a
long range of pull, as in the ordinary form of solenoid with an iron plunger, and
also considerable pressure at the end of the stroke as is the case with the ordinary
form of electro-magnet shown in figure 26. It consists essentially of an iron core,
and a hollow iron shell connected by circular plates of iron. The space between
the core and the shell is completely filled with one or more coils of wire whose
ends are brought out through holes in the end plates or slots in the shell. Part of
the iron is removed and replaced by brass or other non-magnetic substance so that
when a current is passed round the coils, a strong magnetic field lies between the
edges of the iron. In figures 23 and 24 and figure 27a the core is hollow and
partly of iron, the centre being a tube of brass. In figure 25 and figure 27e the
whole of the iron core is removed and a corresponding addition is made to the
iron of the plunger. In b figure 27 the iron is removed from one end of the
hollow core.
In c and d parts of the shell are cut away, in which case we use an
iron tube enclosing the shell as an armature. We prefer to use a circular horse
shoe magnet of this kind in our contact boxes, but we may use any ordinary form

page_text: of magnet. The magnet shown in figure 28 has the same advantages as the
circular horse shoe magnet, it consists of a sole plate of iron S to which is fastened
.the iron core C and the bobbin or solenoid B. On the end of the iron core is pivotted
a lever L which has a plunger P working on it. When a current is passed round
the wire on the bobbin, the plunger is sucked in, and if now a current passes round
either of the coils it is attracted to the iron sole plate with considerable pressure.
In figure 22 is shown an actual contact box used in the parallel system of Electric
Railways as described in our English Patent N° 783 of 1881. The wheel of the
train W depresses the trigger T which works on a pin attached to the rail R and
pushes back the spring S which is fastened to the outside of the box B. The
catch K is then released mechanically and the section which the train is entering
is connected with the main cable. We can however dispense with the blow given
by the train and draw back the spring by means of an electromagnet actuated by
the presence of the train. This magnet is placed preferably inside the box.
Figures 29 and 31 are sectional elevations and figure 30 a plan of our mechanical
contact box. Figure 32 shows the addition we make to figure 29 in order to
work the box in nearly the same manner as is illustrated diagrammatically in
figure 21. In figures 29 and 30 the connection to the main cable C passes in
through a tube t₁ and is fastened to the lever ₁ which works on a metal cap
cemented to the insulator I which preferably has a receptacle for paraffin oil to
prevent surface leakage. The catch K and the lever ₁ are drawn up by the
springs, so as to press the contact piece p, against the lever and force its contact
piece pe against the angle piece D, which is bolted to, but insulated from the box.
An iron plunger P, sliding in the tube of the solenoid M, draws down the-lever l
when a current passes round the wire of M₁ the catch K is then engaged by the
spring S, and as the lever ₁, is prevented from falling on p₁ by the stop N the
contact between p₁ and 7, and between ₁ and D, is broken. In figure 31, which
shows the contact box inverted, the lever l, is drawn up by the spring 8, and down
by the plunger P₂ of the solenoid M₂. The lever is raised by the contact piece
on and has its contact piece p, pressed against D, which is insulated from the
box. When l is drawn down 7, follows it for a short distance until it is caught
by the stop F. A wire connects D₁ and p₁, and p₁ and P. Another wire
connects p, and D₂ to the section of the rubbed rail. It will thus be seen that
when both levers are up this rail is connected with the main conductor through C
and a train on the section will receive current, a wire extends from the box in
advance round the coil M₁ to p, which when the lever l, is up is pressed against
the stud in the spring s, and so put to earth. Another wire extends from Pi
round the corresponding coils of the box in the rear. The different wires are
brought through the tube to which is then filled up with cement. Normally l, is
up and l is down so that the main cable is insulated from the section of the
rubbed rail. On a train approaching, the trigger Tis pressed down, or the
magnet m figure 32 is excited and its armature is attracted. In either case the
catch K is released and the spring s₁ draws up the lever le so that p, presses Ps
against D, and the main conductor is connected with the contact piece p. If now
a train is on the section in front a current passes back along the blocking wire
round the fine coil M, whose end is always to earth. The plunger P2 is therefore
drawn down and consequently Ps P. and D₂ are not in contact, so that the rubbed
rail is not connected with the main conductor. As soon however as the train in
front leaves the section in advance, the box in advance is opened and the current
ceases to pass along the blocking wire round M₂. The spring s₂ can therefore
draw up the lever l, so as to bring p, into contact. with p, and D. The rubbed
rail is now connected with the main conductor and the train receives current.
When the train as it proceeds closes the box in advance a current passes back
along the blocking wire to earth exciting the coils M, and M. The levers l₂
and are both drawn down, l, having its catch K engaged by the spring S and 5
therefore being kept down until another train closes the box in the same manner.
When l is down p, is disconnected from p, and the current no longer passes

page_text: round M. The coil M, however continues to be excited and keeps p₁₂ away
from p, as long as the train is on the section in front. The electrical connections
are explained diagrammatically in figure 21 which shows clearly a method of
exciting the magnet m of figure 32. D Hopkinson in his English patent No 4718
of 1882 has described an electro-magnetic switch, which he has designed for
automatically connecting and disconnecting the sections of an electric railway to
and from the main conductor when worked on the parallel system and which has
certain resemblances to one of our methods. His method of actuating the box is
that previously suggested by us in our original patent No 783 of 1881 page 15
lines 12 to 16, and used by us in the method illustrated in figure 20 of this
specification. .Our contact box described in detail in this specification has however
the advantage over that of Dr Hopkinson that the wire or cable from the main
conductor to the contact box is not wound round an electro-magnet in which case
there is danger of permanent leakage, but is brought direct to a stud or lever
which can be well insulated in the manner shown in figures 29 and 30. We alsɔ
pass the current round both the coils of the electro-magnet in order to close the
box, and are therefore Enabled to use a smaller magnet. Having now described
the nature of our invention and the method of carrying it out, we would have it
understood that we claim (1) The use of electro-magnetic contact boxes actuated
Electrically by the presence of a train on one or more sections of the line or by a
train Entering or leaving a section of the line in electric railways on the series
system substantially as herein before described and illustrated in figures 1. 2. 3. 4. 5.
6. 7. 10. 11. 13. 14. 16. (2) The use of the arrangement of Electro-magnetic
contact boxes actuated Electrically by the presence of a train on one or more
sections of the line, or by a train Entering or leaving a section of the line, shown
in figures 17. 18. 19. 20 and 21 in electric railways on the parallel system
substantially as hereinbefore described. (3) The use of a contact box actuated by
a temporary current flowing to earth, when the train connects an insulated section
with a fixed brush or collector as described and illustrated in figure 12-(4) The
method of blocking for the series system in which a section of the line is connected
Electrically through a contact box with a section in the rear, thus short circuiting
an advancing train as described and illustrated in figures 7. 8 and 9-(5) The use
of short insulated sections between two sections of the rubbed rail, or in the earth
rail of the parallel system of electric railways connected with other sections through
magnets in contact boxes as described and illustrated in figures 4. 5. 6. 7. 17
and 18. (6) The method of blocking for the parallel system described and
illustrated in figure 21-(7) The forms of contact box apparatus illustrated in
figures 23. 24. 25. 26. 27. 28. 29. 30. 31 and 32. In Witness whereof, I, the said
William Edward Ayrton, have hereunto on my own behalf-and on behalf of
John Perry, set my hand and seal this Tenth day of November, in the year of
our Lord One thousand eight hundred and eighty three.
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VIDLA AL
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AYRTON
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(LAD.)