Improvements in Block Systems for Electric Railways.
Year: 1895

page_text: Date of Application, 5th Nov., 1895
Complete Specification Left, 5th Sept., 1896-Accepted. 10th Oct. 1896
PROVISIONAL OPMOTEICATION.
Improvements in Block Systems for Electric Railways.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:-
My invention relates to block systems for electric railways and is applicable to
those railways wherein the conductor by which current is supplied to the car is
divided into insulated sections each section of the conductor serving a particular
section of the line.
The chief object of my invention is to provide means whereby when a car is
running or standing on one section of line, current is absolutely cut off from
the section of the line immediately in the rear of the first-named section. Other
objects attained by my invention will hereinafter be referred to.
In the following description I will confine myself to two consecutive sections of
the line, which I will refer to as section A and section B and I assume that the
cars move in the direction from B to A, that is section A is in front of section B.
In one method of carrying out my invention I arrange that the wire, hereinafter
called feed wire B, which conveys current from the main to the section of the
conductor which serves section B shall include an electromagnetic switch which is
controlled by the current flowing in the wire, hereinafter called feed wire A, which
conveys current from the main to the conductor section which serves section A, and
I provide that as long as a current is flowing in feed wire A the switch in feed
wire B shall be opened, hence when a car is upon section A no current can be
supplied through feed wire B and therefore no car can advance on section B. This
arrangement is especially applicable to those electric traction systems in which
current is supplied to the cars through exposed track terminals as described in
Specifications No. 14445 of 1894, and No. 3358 of 1895.
In another method of carrying out.my invention I provide a battery in circuit
with a relay which actuates a switch and I arrange that when a train is on section A
the relay circuit is closed thereby opening the switch in feed wire B. I prefer
however to modify this device by arranging that the switch B shall be opened
when current ceases to flow in the relay. The relay is in this case short-circuited
when a car is on section A. By this arrangement if the relay wire, one of the
rails, or any portion of the battery circuit be broken by mischance the switch in
feed wire B will not be closed as would be the case in the arrangement first
described.
I sometimes provide a second coil on the relay traversed by the current through
feed wire B, and adapted to oppose the action of the first coil and I so arrange
matters that when the first coil is excited and the switch in feed wire B is closed
the normal current in said feed wire shall be insufficient to open the said switch an
excessive current through the feed wire under these circumstances being required
for the purpose. If however the first coil be shortcircuited or no current flowing
through it then a current in feed wire B below the normal flowing through the
second coil will open the switch and the connection to the feed wire will be
broken.
These arrangements can be carried out in a variety of ways, for example I may
arrange that the current in the first coil of the relay shall attract a weight which
weight ordinarily assists the switch to open the circuit, an excessive current through
feed wire B will however open the circuit whether the weight be attracted by the
first coil of the relay or not.
In a modification I employ pneumatic devices for actuating the switches the air

page_text: .
supply to said devices being regulated by the relay so as to control the supply of
current through the feed wire in the manner above described. According to one
arrangement for example I provide an air valve which is capable of taking up
three stable positions. In the first position the air supply pipe is closed, the switch
being opened by a spring or otherwise. In the second position the air supply is
connected to a pneumatic switch in such a manner as to positively close the switch
and keep it closed, and in the third position of the valve the air supply is connected
to the switch in such a manner as to positively open the switch and keep it open.
I sometimes arrange this valve that when it has assumed the third position.no
change in the circuits will cause it to assume either the first or second positions.
To cause it to take either of these positions so as to allow a train to pass it requires
to be manually operated. As the operation of this valve against a large air
pressure requires considerable strength I preferably provide an auxiliary valve
which I attach to the main valve between the latter and the air supply. In the
normal position of the auxiliary valve the conditions of the air supply are not
changed. In its other position to which it may easily be moved by hand the air
supply is cut off from the main valve and at the same time communication is
opened between the upper and lower parts of the main valve cylinder the valve
being then in equilibrium returns to its first or normal position. At the same
time the position of the pneumatic switch is not altered. If the auxiliary valve
be wilfully secured in an abnormal position no harm can be done since the air
supply is cut off from the main valve and from the pneumatic switch.
provide that when the switch is opened an air blast is set up sufficient to blow out
any spark which may occur at the contacts, the blast being automatically shut off
again.
I may
The air valve is actuated by a magnet or magnets energized by the currents in
the relay and in the feed wires in the manner following. When no current is
flowing in the magnet coil the valve is in its first position and the switch controlled
thereby is open. When current is flowing in the magnet coil the valve is actuated
and brought to its second position causing the pneumatic switch to close the feed
wire circuit of section B. The current flowing in the feed wire B flows through
this coil or another coil and if normal is not sufficiently strong to alter the
disposition of the valve controlling the pneumatic switch. If however, the current
through feed wire B. becomes excessive the air valve is quickly brought to its third
position in which air is supplied to the pneumatic switch in such a manner as to
quickly open the circuit of feed wire B. Instead of using a coil in the manner
above indicated I sometimes arrange that the current in the feed wire shall cause
a weight.to be applied to the main valve or admit air thereto in order to bring it to
the third position above mentioned. It is evident that apparatus of this description
is capable of very considerable variation in detail all of which variations are
included in my invention.
I sometimes arrange that the air valve is only capable of taking up two of the
positions hereinabove indicated in which case the opening of the circuit of feed
wire B when the current through such wire is excessive is not effected by the
operation of the valve.
In another method of carrying out my invention I arrange that the switch which
controls the current in the feed wire shall be altered in sensitiveness according as
the line is clear or not. For example the switch may be provided with two pivots
so adapted that when the relay coil is energized the switch turns on one pivot and
is more sensitive than when the relay coil is short-circuited by a train being on the
line in which case the switch turns on the other pivot. The alteration in the pivots
may be effected by other electrical means or pneumatically or mechanically if
desirable. Or I may provide a weight on the switch which weight is lifted either
pneumatically electrically or mechanically when the relay coil is energized or
de-energized, preferably the latter, and the switch can then operate very readily.
The switch is in general returned to its closed position by hand or otherwise
mechanically operated.

page_text: I sometimes arrange that the switch shall require current to be flowing in two
coils wound thereon before it is actuated to open with normal currents. One of
the coils is then energized when the section A is blocked by a train the other coil
being in feed wire B. In this case the switch is only actuated if a train on
section B attempts to take current through its feed wire when there is a train on
section A or if an excessive current be taken through the feed' wire B. Although
I have herein spoken of two sections only it is to be understood that the apparatus
is applied to every section on the line in a similar manner. Also instead of a train
on one section blocking the next preceding section only it may be easily arranged
in a similar manner to block the two or more sections next preceding if greater
safety is required:
In the above described methods 1 may arrange that the switches themselves, or
the pneumatic or electric actuating. and controlling devices shall be operated or
governed by the signal, the signal apparatus, or the signalman. Nor do I confine
myself to a pneumatic apparatus for actuating the switches and valves, as any suitable
fluid may be used instead of air. I may also arrange that the fluid pressure which
operates the switches shall also operate the signals and if desired be controlled by
the same valve.
Dated thin 5th 1.
SN100%
I, REGINALD BELFIELD, of 32, Victoria Street; in the City of Westminster,
Electrician, do hereby declare the nature of this invention, and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
My invention relates to block systems for electric railways, and is applicable to
those railways wherein the conductor, by which current is supplied to the car, is
divided into insulated parts, each part of the conductor serving one section of
track.
My invention also comprises an improved construction of electro-magnetic
switch for controlling an electric current, said switch being able to be readily
altered in sensitiveness by mechanical electro-magnetic or other means.
The chief object of my invention is to provide for railways such as above
mentioned a block system, so arranged that when a car is running or standing on
one section of track the current is absolutely cut off from the portion of the
conductor which serves the section of the track immediately in rear of the first
named section. Modifications of this arrangement will be also described, the
ultimate object in every case being to prevent collision between trains running in
the same direction on a single line of rails.
In order that my invention may be clearly understood I will now proceed to
describe with reference to the accompanying drawings various methods of carrying
the same into practice.
Figures 1 to 4 are diagrams illustrating various methods of carrying out my
invention.
Figure 5 is a sectional view of a pneumatic valve and switch constructed
according to my invention.
Figures 6 and 7 are similar views exhibiting different positions of the same.
Figure 8 is a diagrain illustrating a further modification in the wiring.
Figure 9 is an elevation partly sectional of an improved switch having variable
Bensitiveness.

page_text: Figure 10 is a similar view shewing the switch mechanism in another position.
Like letters of reference denote similar parts in all the drawings.
X is the positive main which is connected through the supply wires to the
various sections of the conductor which convey the current to the car, said sections
being denoted by the letters A, B, C... In the drawings the conductor sections
are illustrated as being long plates or wires with a small distance between successive
sections. It will be obvious, however, that my invention equally applies to
railways wherein the conductor sections take the form of conducting blocks or
studs, as is the case in some railway systems. Y is the negative main which is,
connected to a continuous conductor Y₁ which is joined to the car motor through
the wheels or a contact carried by the car or by any other well-known means.
If
'desired the negative conductor Y¹ may also be split up into sections in a similar
manner to the positive conductors A, B, C. . . and connected to the negative main
in the same way.
The sections of the track which are served by the conductor sections will, for
the sake of brevity be hereafter referred to as sections A, B, C, of the track,
meaning the section of track supplied by conductor section A, B, C
.
In the description of the first four figures I will confine myself to two con-
secutive sections of track A and B, and I will assuine that the cars are moving in
the direction from B to A as shewn by the arrows in said figures.
Referring now to Figure 1 the supply wires marked a, b which connect the
sections A, B to the positive main are each provided with an electro-magnetic
switch as at a², 61, so arranged that the current flowing in one supply wire shall
through the medium of an electro-magnet operate the switch in the section to the
rear so as to open the circuit in the supply wire and prevent current being supplied
to said section in the rear. For example, if a car be receiving current from
conductor section A through supply wire a the current flowing in the electro-
magnet a² will operate the switch and thus break the circuit of supply wire b
which connects the conductor section B to the main. It will, therefore, be seen
that the presence of a car receiving current from section A. of the track will
absolutely prevent the supply of current to the section B of the track immediately
in rear.
Instead of operating the switch in the supply wire by an electro-magnet included
in the supply wire of the section in front. I sometimes arrange that said switch
shall be operated by the signal guarding the section in front, so that when said
signal is lowered the switch of the supply wire is closed, being opened when the
signal is raised.
In another method of carrying out my invention, I divide the rails into insulated
sections corresponding with the conductor sections, and I connect each pair of rails
to a relay circuit comprising a battery and an electro-magnet adapted to act when
the relay circuit is closed upon the switch in the supply wire of the section next in
rear so as to open said switch and prevent current being supplied to a car on said
section. This method is illustrated in Figure 2 wherein the relay circuit is
marked a³, the electro-magnet a² and the battery at. Instead of causing the switch
in the supply wire b for example, to be opened when a current flows in the relay
circuit a³ I may modify the arrangements by providing that the switch b₁ shall be
opened, when no current flows in the electro-magnet a³. In this case the connec-
tions are arranged as shewn in Figure 3, so that when a car is running or standing
on the rails A' A' for example, the relay magnet a² is short-circuited and permits
switch to open. Such opening can be accomplished by weighting the switch or
providing same with a spring. By this arrangement if the relay wire, one
of the rails, or any portion of the battery circuit be broken by mischance the
switch in the supply wire through which current is supplied to the section in the
rear will not be closed, whereas in the arrangement illustrated in Figure 2 such
an accident would at once close the switch iu the supply wire.
1 sometimes provide a second coil in the electro-magnetic switch in each supply.
wire, which coil is traversed by the current through said supply wire, and is

page_text: adapted to oppose the action of the coil in the relay circuit of the section in front,
for example as shewn in Figure 4 is a coil adapted to act on switch b' in
opposition to the coil a'.
I so arrange matters that when the coil a² is excited and
the switch bis closed the normal current in coil 6 shall be insufficient to open the
switch against the pull of the coil a². If, however, an excessive current is taken
from the conductor section B, and a large current thereby passes through supply
wire b and coil 6, the action of the coil a' is overcome, and the switch 6' opened so
as to cut off the conductor section B from the main. Also if the coil a' be short-
circuited by a car being on the rails A1 A. or if no current be flowing in coil a
through any mischance, a current in the wire below the normal flowing through
the coil will open the switch 6'. It will be understood that all the sections of
the line are fitted as hereinabove described for the sections A and B.
Instead of using the ordinary car rails to form part of the circuit containing the
relay coil a supplementary insulated rails may be provided for this purpose which
are connected to the car as long as a train is on the section.
Arrangements similar to those above described can be carried out in a variety of
ways. For example, I may arrange that the current in the relay coil a' ahall
attract a weight which weight ordinarily assists the switch to open the circuit.
An excessive current through the supply wire b, will, however, open the circuit to
conductor section B whether the weight be attracted or not. I shall hereinafter
describe a special form of switch which will serve this purpose.
Figures 5 to 7 illustrate one form of accessory apparatus for use with the system
shewn in Figure 4 and designed to ensure the positive and certain operation of the
switch in a supply wire by employing compressed air or other fluid as a means for
actuating said switch. D is a casing in which a piston valve D' is adapted to move
up and down under the control of a spiral spring D'. Below said casing is
provided an electro-magnet having a core E of suitable shape, and a coil E¹
connected to the rails through the wires a which coil E corresponds to the coil a²
shewn in Figures 3 and 4. The armature E' of said electro-magnet is loosely
mounted on a stalk Ds attached to the piston D' which however is provided with a
collar D so that when said armature is attracted upwards it engages with said
collar and causes stalk and valve D' to rise up a distance equal to that passed
through by the armature when attracted. Attached to the bottom of the stalk D³
is a weight F which forms the plunger of a coil G included in the circuit of the
supply wire, said coil G corresponds to the coil 6 hereinabove described with
reference to Figure 4. The switch in the supply wire is provided with two contact
pieces G¹ G, preferably of carbon, and the bridge piece G³ of said switch is
attached to a rod G carrying a piston H, moving in a pneumatic cylinder H¹.
Said piston is forced upwards by a spring H2 and is adapted to slide on two or
more bolts H to the lower ends of which is attached a ring H*.
I is a tube opening into the cylinder H₁ at its lower part, the entrance to said
tube being at such a distance above the bottom of the cylinder that when the
ring His at the bottom of the cylinder as shewn in Figure 6 the entrance to the
tube I is open. When, however, the piston H¹ rises to the top, and the ring H* is
lifted, as shewn in Figure 5, the entrance to the tube is closed. Communicating
with the cylinder H is a cylinder J having a piston J¹ therein pressed down-
wards by means of a spring. J. The communicating channel between the two
cylinders enters the cylinder H' at the top, and the cylinder J at the bottom. The
piston rod J³ of the piston J' is connected by suitable mechanism to a signal arm,
so that when the piston J' is at the bottom of its cylinder the signal arm is at
danger." When, however, the piston rises to the top of the cylinder the arm is
depressed shewing "line clear." The top of the cylinder His connected by a
channel with the top of the cylinder D. The cylinder D is also connected at a
point somewhere about half-way up through a channel to the interior of the
cylinder Hat a point a little distance above the bottom. The cylinder D is
also provided with ports d, d', d³, d³, dª, and d³ for_purposes hereinafter described.
The piston D is provided with orifices de, d', d³. Dis a pin moving in a socket E
66

page_text: in the electro-magnet core E which prevents the valve D¹ from rotating in the
cylinder. The supply pipe for compressed air is shewn at K, and a cock is
provided in said pipe, having a solid portion K' with perforations K² K³ as shewn.
By means of the weighted handle K the valve K' can be rotated in its seating to
cut off the supply of air from the cylinder D as hereinafter described..
I will now describe the operation of the apparatus, and for the sake of simplicity
will consider the coil. E as being included in the relay circuit as attached to
section A of the track and the coil G in the supply wire b of the section B of the
track. In the first place if no car is in section A the coil E' is energized, and
the electro-magnet attracts the armature E³, thus raising the valve D' through the
mcdium of collar D and stalk D³ to the second position as shewn in Figure 6.
In this position of the valve the port d is closed. The channel is connected
through the recess d to the port d¹ consequently the space below the piston Hin
the cylinder H³ is connected with the outside air. The space above piston. H in
the cylinder H is connected through channel h, channel and. port d to the air
supply; port is closed and the bottom of cylinder D is connected through
channel d and port to the air supply. Consequently the full air pressure is
exerted on the top of piston H, which descends compressing, the spring. Hand
bridging the switch contacts G G through the bar G. Also the air pressure
below the piston Jin the cylinder J causes said piston to rise compressing, the
spring and operating the signal arm and placing it in the position of "line
clear," this signal is at the entrance of section A or at. the end of section B, and
shews that the section A is clear.. At the same time the switch in supply wire b
having been closed a train on section B. will be able to obtain current and advance
through said section. The piston D¹ is in equilibrium as far as the air pressure is
concerned, since the space both above and below is open to the air pressure, the
spring D is, however, compressed but does not exert sufficient. force to overcome
the upward pressure due to the attraction of the electro-magnet core E on.its
armature E..
I will now consider the case wherein a train is on section A. so that the coil E
is short-circuited or when through one of the rails A' A' being broken or by any
other mischance current is cut off from coil E. Under these circumstances the
armature E being no longer attracted is allowed to drop, and the piston D¹ is
pressed down under the influence of spring D to the bottom of the cylinder D.
This position of the apparatus is shewn in Figure 5.. The bottom of cylinder D
communicates with the outside through the port d: and, is cut off from the air
supply port d which is closed. The bottom of the cylinder H' is still connected
through channel and port d to the outside. The port d' is closed and the top of
the cylinder D, the top of the cylinder H', and the bottom of the cylinder Jare
all connected through channel ds, port and channel d to the outside.. Under
these conditions then the piston His in equilibrium as far as the air supply is
concerned, and is therefore pressed upwards by the spring H. The bar G³ is
raised and breaks the circuit in the feed wire b. Also the piston J' is pressed
down by the spring J' and puts the signal to "danger.' Hence if section A is
occupied by a train, or some accident has happened. in said section, the signal is.
placed at "danger," and the current cut off from conductor section B.owing to the
circuit through supply wire b being broken. It will be observed that when the
valve D changes from the second position shewn in Figure 6 to the first position
shewn in Figure 5 no current will in general be flowing in the supply wire b,
because this change in the position of the valve is due to a train entering section A,
consequently no spark will in general, occur when the bar G is raised from the
contacts G G. Also said bar is raised very quickly and to a considerable distance
above the contacts..
"
The third position of the piston D! and the state of the signal when such
position is assumed is shown in Figure 7. If when the piston D¹ is in the second
position the switch in wire b being closed an excessive current be caused to flow
through said wire.b owing to a short-circuit occurring in the car motor or from an

page_text: accidental short-circuit of the track sections or from any other cause; the plunger F
will be attracted into the coil G and will through the medium of the stalk D³:
raise the piston D¹ to the top of the cylinder D compressing the spring D³ to its
smallest extent, The armature E being loose on the stalk D permits the latter
to rise as hereinabove described. In this position port d is closed and channel h¹
and the bottom of the cylinder D are connected through channel d' and port d
with the air supply pipe. The top of the cylinder H and the bottom of the
cylinder J are connected through channel h to the top of the cylinder D and through
channel de port d' and port d with the outside. The piston H rises very rapidly in
its cylinder under the combined influence of the spring H' and the large air pressure
on its underside thus breaking the circuit of feed wire b. As the piston rises the
pipe 1 is opened to the cylinder H' and the compressed air escapes through the
same blowing out the spark at the switch contacts G1 G. As soon as the piston H
reaches the top of the cylinder the bolts H³ raise the ring H from the bottom of
the cylinder and close the entrance to the pipe I so that the compressed air is cut
off from said pipe. The piston J₁ having only atmospheric pressure below it is
pressed down by the spring J and places the signal at "danger."
It will be observed under these conditions that the conductor section B is cut off
from the main, consequently o train can advance on section B also the signal at
the beginning of section A is put to "danger."
It will be clear that no change in the conditions of the circuit can cause the
piston D¹ to move down since for this to occur it is necessary to establish equilibrium
of pressure between the top and bottom of the valve. This is effected by lifting
the weighted arm K₁ to the position shewn, in dotted lines in Figure 7 so as to
rotate the plug K' this shuts off the air supply from the pipe K and puts-the port d
in connection with port d' through the channel K' the bottom of the cylinder D is.
thereby opened to the atmospheric air and the piston D' descends under the influence
of the spring D' to its first position as shewn in Figure 5. The position of the
pistons H and J' will not however be altered. This manual operation of the
lever K is desirable inasmuch as the valve D'only assumes the third position under
abnormal conditions as above stated consequently the attention of the engine driver
or signalman is at once drawn to the state of affairs since no change in the position
of the valve can be effected without manually operating the lever..
Furthermore if any accident occur or if for any reasou it is necessary to block
the line this can readily be done by operating the arm K' as above mentioned since
Euch operation causes the signal to be put to " danger," moreover as long as the
arm K is in its raised position the air supply is cut off and no operation either of
signal or switch can take place.
The state of the signals on a track equipped at all its sections in the maouer
hereinabove described may be briefly summarised as follows:-Assuming that the
line is in its normal state as regards insulation I will consider the effect of a single
train stationary or running on one section, the remaining sections of the line being
completely clear of trains. Under these circumstances if the train be at section A
the relay inagnet coil a' will be short-circuited and the signal at the end of section B.
or beginning of section A will be set to "danger," current being cut off from
section B. All the remaining signals on the track will be at "line clear" and the
conductor sections will all be connected to the main.
In a modification of the system shewn in Figure 4 the magnet coil which when
energised closes the switch in the supply wire is wound with two circuits as shown
in Figure 8 one of said circuits being the relay circuit a*, for example of one section,.
and the other circuit being that of the relay of the section immediately
following the first named section. It is understood in this case that the switch
controls the supply current of the second section through supply wire b. The two
magnet coils are furthermore arranged to
Under these.
each other.
oppose
conditions it is evident that if section A and section B are both clear of trains the
magnet coils will both be active and the switch be opened thus cutting off the
current from track section B and putting the signal at the end of that section or

page_text: beginning of section A at danger. If however there be a train on section A or on
section B the corresponding relay coil will be short circuited and the switch will be
closed so that current is supplied to section B and the signal at the end of section B
or beginning of section A will be put to "line clear." It will be seen therefore
that the fact of a train being on one section supposing all the other sections are
clear of trains causes the signal guarding the entrance to the section in front to be
Bet "line clear" and also the signal guarding the section upon which the train is to
be set "line clear." Furthermore, the conductor section serving the train will be
connected to the main and the conductor section behind the train will also be
connected to the main. All the other signals on the line will be at "danger" and
the conductor sections cut off from the main. If by any unforeseen circumstance
a train should enter section B for example when there is a train already on
section A in front, the entrance of such train on section B will short-circuit the
coil the current in which opposes the attraction due to the current in coil a² where-
upon the piston valve will assume its first position and the signal guarding the
entrance to section A be brought to "danger" section B being also cut off from
the line. Such an event is, however, very unlikely to happen since the sections in
rear of section B will not be affected by a train standing on section A and will have
their signals at danger and their conductors cut off from the main.
It is evident that the apparatus above described can be varied very considerably
in detail, all of which variations are included within the scope of my invention.
I sometimes arrange that the piston valve shall only be capable of taking up two
of the three positions hereinabove described, in which case the opening of the circuit
of the supply wire when the current through such wire is excessive is not effected
by the operation of the valve.
Also may arrange that the signal shall be operated by the piston H and
dispense with the cylinder J.
Figures 9 and 10 are elevations of an improved switch which is capable of
varying in sensitiveness under different conditions. This switch, although peculiarly
adapted for use in electric block systems such as herein described, can also be
employed for many other purposes, and my invention is not confined to the use of
the switch in railway systems.
The parts of said switch will now be described :- L is the base to which are
secured the terminals M N of the switch. On the base is also secured an arm L'
having downwardly extending parts L' at the lower extremity of which is pivoted
the arm O. At the end of the arm L¹ is secured a solenoid P the core P¹ of which
is secured to the end of the pivoted arm O, a stop P' is provided which prevents
the arm from moving too far away from the coil. The bridge piece Q of the
switch is pivoted at Q to the terminal M and is adapted to make contact with a
Euitable contact piece N attached to the terminal N. A latch R pivoted at R¹ to
the base is adapted to engage with the free end of the bridge piece Q as shewn.
Said latch is loosely connected by the adjustable screw R* to one end of a lever S
which is provided with two pivots or knife edges one near the middle and the other
at the end. The centre pivot L is fixed to the arms L' and the end pivot O' is
attached to the arm O. The lever S has secured to it near the pivot LB a weight S¹
and at the end, above the screw R', the armature T of a magnet, the coil of which
as shewn at T is mounted on the base L.
The action of the switch is as follows:-
If the coil P is energised it attracts the core P¹ as shewn in Figure 9 and raises
the arm to its highest position, the lever S will then be pivoted on the end
pivot O¹ and be weighted with the weight S' consequently it will be necessary
to pass a very large current through the coil T¹ before said coil can raise the
arniature T and lever S so as to lift the latch R and release the arm Q. Under
these conditions the switch is unsensitive. If, however, the coil P is not energized
the plunger P¹ and arm O drop to their lowest position as shewn in Figure 10.
The lever S will therefore be pivoted on the pivot L' and, since the weight S
is near to said pivot, will be very readily moved by the force exerted on the

page_text: armature T when a small current passes through the coil T¹. In this position,
therefore, the switch is sensitive.
It will be readily seen that the essential feature of the switch is that the centre
of rotation of one of the moving parts is altered without altering either the number
or weight of the parts of the switch.
In using this switch in a block system such as described with reference to
Figure 4, the coil P is joined in the relay circuit, and the coil T' is joined in the
feed wire circuit, that is to say, the coil P takes the place of the coil a³ and T¹
takes the place of coil 6. Under these circumstances it will be seen that when a
train is on section A. coil P is short-circuited and the switch is in the position shewn
in Figure 10 in which position even a small current taken through the supply
wire 6 by a train entering section B will cause the circuit to be broken by the
release of the arm Q which must be manually operated by the engine driver or
signalman before current can he obtained on section B through the supply wire.
When section A is clear the coil P is energized and the apparatus takes the position
shewn in Figure 9 in which case a norinal current through supply wire b and coil T¹
will not be sufficient to raise the lever S and release the arm Q. If, however, a
short circuit occur either in the motor or on the track or if from any cause an
excessive current be taken through the supply wire, the lever S will be raised and
the switch arm Q allowed to drop thus breaking the circuit in the supply wire.
The systems hereinabove described are arranged so that a train on one section
blocks the next preceding section only. My invention, however, includes such
modifications as will cause a train on one section to block the two or more next
preceding sections if greater safety be desired. These modifications are very
simple, and I have already described one in which all the sections except the one
immediately in the rear of the train are blocked in the manner above mentioned.
Furthermore my invention also includes arrangements in which the switches them-
selves or the pneumatic or electric actuating and controlling devices are operated
or governed by a signal, a signal apparatus, or the signalman, the modifications in
the apparatus required to attain these ends being readily made by a person skilled
in the art. Moreover I do not confine myself to a pneumatic apparatus for actuating
the switches and valves since any suitable fluid may be used instead of air.
I am aware that cut outs have been made in which an adjustable weight is
provided which weight can be altered in order to provide for a circuit being broken
when the cut out reaches a certain intensity also fuse blocks are sometimes arranged
so that different sizes of fuses may be plugged in at will, these devices are however
essentially different from my improved automatic switches inasmuch as an alteration
of the parts of the switch requires to be made, whereas in switches constructed
according to my invention the position of the centre of rotation of the moving part
of the switch only is altered in order to vary the sensitiveness.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. In electric railway systems wherein the track is divided into sections each said
section having one or more separate supply wires supplying current to the car or
train on the section, the provision of means whereby when a car or train is on the
section the supply of current to a train on the section next or next but one in the
rear is automatically interrupted, for the purpose specified.
2. In electric railway systems wherein the track is divided into sections each said
section having one or more separate supply wires supplying current to the car or
train on the section, means whereby the signal guarding a section and the switch
governing the supply of current to the train on a rear section are simultaneously
operated from one source.
3. For electric railways a block system in which the presence of a train on a
section short-circuits an electro-magnet coil which operates a switch in the supply
wire of the preceding section or sections, substantially as described.
.

page_text: .4. The various block systems arranged substantially as described with reference
to Figures 1 to 4 or to Figure 8 of the accompanying drawings and operating
as specified.
5. The valve for controlling the operation of a switch by compressed air or
other fluid either with or without the devices for operating the signal arm, and
arranged to assume either three or only two positions, constructed and operating
substantially as described with reference to Figure 5 of the accompanying
drawings.
6. An automatic electric switch in which the sensitiveness can be varied by
altering the position of the centre of rotation of the moving part.
7. An automatic electric switch having a releasing arm provided with two or
more pivots for the purpose of imparting a variable sensitiveness to the switch,
substantially as described.
8. An automatic electric switch constructed substantially as described with
reference to the accompanying drawing.
.9. An automatic electric switch the sensitiveness of which varies according.
the current flowing in an electric circuit which does not include said switch.
.to
10. In a block system the employment of switches having varying sensitiveness
and constructed substantially as described with reference to Figures 9 and 10 of
the accompanying drawings.
Dated this: Fourth day of September 1896.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.