Improvements in Electric Brakes.
Year: 1896

page_text: Date of Application, 22nd Sept., 1896-Accepted, 28th Nov., 1896
Improvements in Electric Brakes.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 38, Parliament
Street, Westminster, in the County of London, Electrical Engineers, do hereby
declare the nature of this invention (which has been communicated to us from
abroad by Alexander F. Macdonald, of Schenectady, County of Schenectady,
State of New York, United States of America), and the manner in which the same
s to be performed to be particularly described and ascertained in and by the
following statement :-
The present invention relates to electric brakes, more particularly when applied
to electric locomotives having four or more motors used for propelling and braking
purposes, but it is also applicable to vehicles having only two motors. Motors used
both for propelling and braking a vehicle are more subject to heating than those
used only for propelling, for the reason that they are in constant or practically
constant use, and where the motors would have a chance to cool when the power
was off and mechanical brakes applied, they now have work to perform in
transforming mechanical energy due to the momentum of the vehicle into electrical
energy.
One object of this invention is to lessen the amount of heating in the motors by
giving them a chance to run idle at certain times on the brake side of the system.
To attain this end the motors, in a four-motor equipment, are arranged to operate
in pairs, one of a pair on each truck for the purpose of distributing the active
motors in such a manner as to obtain the greatest tractive effect; the advantages
of which are well known. In a two-motor equipment, a motor would be mounted
on each axle, in the ordinary mauner.
A suitable controlling mechanism is provided which is adapted to vary the circuit
relations of the motors when propelling the vehicle, and to vary the resistance of
the brake circuit when the motors are converted into generators and used for
braking.
In controllers of existing types used for regulating the power of electric brakes,
it is necessary to provide extra resistance on the brake side of the system, in order
to cut down the current of the generators. The current produced by the motors
of a vehicle when operated as generators is much greater than is needed for braking
purposes; instead of inserting extra resistance in the brake side of the system, we
prefer to cut a part of the motors out of the brake circuit and use the same or less
resistance than that in the power side. This permits the motor or motors cut out
of circuit to cool, and by the use of automatic means first one pair of motors and
then another is used, or where only two motors are used, one motor is used for
braking and then the other; this alternation in either case may be effected each
time the vehicle is to be stopped, or after a number of such stops.
It is preferable to have the switching done automatically each time the vehicle
is to be stopped, but it is within the scope of the invention to have this switching
done by hand, and at whatever interval may be desired; the particular time at
which the switching is doue, either automatically or by hand, is immaterial.
The invention further relates to the distribution of the electric brakes and
motors with respect to one another. Preferably the motors one and three, which
form a pair, are mounted on separate trucks, and when used for braking are in
circuit with the brakes mounted on the axles carrying motors two and four; this
distributes the braking effect over the entire vehicle, the generators acting as
brakes on one pair of axles, and the brake magnets on the other.

page_text: If at any time the braking effect of the two motors and the two brakes is not
enough, a switch is provided, operated by the motorman, to throw more of
the brakes into circuit; ordinarily, however, the, extra brakes would not be
necessary.
In the accompanying drawings,
Fig. 1 is a diagrammatic view of a controller embodying the invention;
Fig. 2 is a detail view of the automatic switch, and
Figs. 3 to 8 are diagrams of connections.
Two sets of contacts A and B are provided.; these.may be carried by a single
cylinder and operated by one handle, or separate cylinders and operating, handles
may be provided; in the present instance two separate cylinders are shown.
C is the automatic switch, the operation of which will be hereinafter describeil."
Two sets of brushes are shown; those numbered 1 to 17 are adapted to engage
with the contacts on cylinder A to vary the speed of the motors M1, M2, M3, M,
when used for propelling the vehicle, and the brushes 3 to 17' inclusive and 20 are
adapted to engage with the contacts on cylinder 13 to vary the resistance of the
brake circuit.
It is assumed that the locomotive is provided with two trucks, and a motor
mounted on each axle, the motors mounted on axles 1" and 3" forming one pair,
and those on axles 2" and 4" forming a second pair. The brake magnets E, E, E³, E,
are arranged in like manner; brakes E and E3 form a pair and are mounted on
the axles with motors M and M3; brakes E and E also form a pair and are
mounted on the axles with motors M and M. A switch D is provided to connect
the brake magnets in pairs or in series.
Referring to Fig. 2, the operating mechanism for the automatic switch C will be
described. Mounted on a disc carried by the cylinder B is an arm F adapted th
be held in the position shown by means of a spring F1 the end of the arm engaging.
with the teeth of the star-wheel J. To regulate the step-by-step movement of the
star-wheel, a pawl and spring H' are used, and secured to the back of the
controller in any desired manner. The brake cylinder B is shown in its off
position; to operate it the handle (not shown) would be thrown to the left, and
the cylinder would move in the direction indicated by the arrow. This would
cause the arm F to rotate the star wheel J and the switch C attached thereto,
through a certain number of degrees; as soon as it had rotated far enough for the
roller carried by the pawl H to pass the point of a tooth, the switch would be
snapped into place, and a continued movement of the cylinder B would have no
effect on it. The switch cylinder C is provided with contacts and insulation
which alternate with each other in such a manner that in one position of
the switch the brake circuit is closed through one motor or group of motors, and
when moved ahead the circuit is closed through another motor or group of motors.
The switches are so arranged that the cylinder C establishes its connections before
the cylinder B closes the connections through the brakes.
The moving of the handle back to the original position does not change the
position of the switch C, for the reason that the arm F is free to move in a
direction away from the pin F which formis a stop when it moves in the opposite
direction. A second movement of the handle in the direction of the arrow would,
however, cause the cylinder C to rotate and establish new circuit relations. If it
is desired to leave the switch C in one position or control it by hand, the arm Fis
thrown into the position shown in dotted lines, and the spring F1 serves to hold it
in place.
For the purpose of operating the switch by hand, a-handle I is secured to the
operating shaft and is preferably outside of the controller case; one motor 'or a
group of motors can now be used as long as desired. If for any reason one motor
or a pair of motors was disabled; it would be necessary to have this switcli
remain in one position, otherwise the brake circuit would be thrown upon the
inoperative motor or motors.
Referring to Fig. 1, the connections for the circuits will be described. Assume

page_text: 2:
the brushes to, be in their.. first position on the cylinder. The current enters by
the trolley T, to brush: 1, to the cylinder A, to brush, 2, through all the
resistance R to brush 5, cross-connected, to brush 6, by cylinder A to, brush 7, to.
wire 7; here the circuit, divides, one circuit, being to the arinature of motor M',
thence by wire 8 to brush. 8, by cylinder. A to brush 9, by wire to the field of
the motor M', to wire 12. Going back to the circuit from the brush 7 and
wire, 7; the second: circuit, is formed through the armature of motor M³, to
wire 10 to brush 10, by cylinder, A to brush 11, by wire 11 to the field of
motor M³, to wire 1211; here it unites with the circuit from motor M', passing to
brush 12, by, the cylinder A, to brush. 13, to wire 13. It divides again at this
point, one path being by, way of, wire 13, armature of, motor, M, wire 14,
brush 14, cylinder A to, brush 15, wire, 151, to the field of motor M to ground.
Going back to the, wire 13" where the circuit divided, the other path is through
the armature of motor M, wire 16", brush 16, by cylinder A. to brush 17, wire 17,
to the field, of motor M', to ground. The motors are now connected as shown
in Fig. 3, with full resistance in circuit.
A continued rotation of the cylinder A would simply cut the resistance out of
circuit and the motors would be connected as shown in Fig. 4. It is to be under-
stood of course that any desired connection of the motors could be used, as for
instance, a series-parallel arrangement.
If it were desired to brake the vehicle, the cylinder B would be thrown into
engagement with its vertical line of brushes, and assuming that motors M and M*
are to be, used for. braking purposes, the, switch C being so situated as to close the
circuits of these motors, then with the brushes in the first position on the brake
cylinder, the circuit would be as follows: The current emanating from the armatures
of motors M2 and M, passes by wires 14 and 16" to brushes 14 and 16, to the
cylinder, B, thence by cross connections to brushes 15 and 171, by wires 15 and 1711
to the fields of motors M2 and M, to ground G, thence to ground G through the
brake, shoes, E, E, to the switch D, by wire 21, through the contact plate on
switch, C, to brush 20, cylinder B, by cross-connection to brush 6', cross-connected
to brush, througli two sections of resistance R to brush 3', to cylinder B, by
cross-connection to brush 13, through the contact plate on switch C to wire 13,
to, the negative sides of the armatures of motors M and M'. The motors are now
connected with the brake magnets, as shown in Fig. 5.
A continued movement of the cylinder B would cut out more and more resistance
until finally the circuit relations will be those shown in Fig. 6.
Assuming that the switch, C is now rotated by means of the arm Fin the
manner described above, the motors M and M3 would he placed in circuit, and.
the connections would be as follows: The current emanating from the armatures af
motors M and M³, would pass by wires 8 and 10" to brushes 8 and 101, by
cross-connection to. brushes 91 and 11', by wires 9 and 11 to the fields of
motors M and M³, thence by wire 12 to brush 12', cylinder B, to ground C F on
the controller frame, thence by ground G2 to the left-hand side of switch D to
brake-shoes E and E', to switch D, to wire 22, through the contact plate on
switch C, to brush 20, to cylinder B, by cross-connection to brush. 61, cross-
connected to 5', through two sections of resistance R to brush 3, cylinder B,
cross-connected to brush 7', through the contact on switch C, to the wire 7", to
the negative side of the arinatures of motors M and M³. The circuit through
the motors is now the same as that shown in Fig. 5, except that motors M' and M³
Dare used instead of M and M. A continued movement of the cylinder B would
cut out the resistance R and the circuit would be as shown in Fig. 6.
If at any time the braking effect of either the brakes E', E3 or E², Et is not
enough, the switch D is thrown to the left; this connects all four brakes in circuit,
as shown in Fig. 7. The circuit, assuming motors M and M³ to be in circuit,
would be from the ground C F on the controller frame, to ground G', (ground.G2
being, open circuited) through brake magnets E', E2, E3, E, to the switch D and
through wire 22 to the contact plate on switch C, the balance of the circuit being

page_text: the same as before. The right-hand blade of the switch D is made of sufficient
width to cover two contacts; this is to complete the circuit through the switch C
in case the end of either wire 21 or 22 is on insulation.
Fig. 8 shows the same condition of circuits, except that the resistance R is cut
out. The circuits through the motors are the same as before, so that further
description is unnecessary.
When a two motor equipinent is used, the motors are alternated with each other
for braking purposes, and they are treated in the same manner as the groups of
motors explained above.
The invention has been described in connection with a system in which brake
magnets have been employed, this being a common arrangement at the present
time, but we do not limit ourselves to this; the invention applies equally well to
systems where the retarding effect of the generators is alone used for braking
purposes. We claim broadly an electric brake system in which the generator or
generators used for braking purposes are shifted each time a stop is male, or after
a number of stops; the particular way in which the shifting is done, or the number
of stops before such change is made, is immaterial.
Having now particularly described and ascertained the nature of our said inven-
tion as communicated to us from abroad by our foreign correspondent and in what
manner the same is to be performed, we declare that what we claim is :-
1. In an electric brake system, a switch for shifting the dynamo electric
machine or machines employed for braking purposes each time the brake circuit is
closed.
2. In an electric brake system, an automatic switch for changing the dynamo
electric machine or machines employed for braking purposes, at predetermined
intervals, the switch being controlled by the operation of the brake circuit closing
Bwitch.
3. In an electric brake system, an automatic switch for changing the dynamo
electric machine or machines employed for braking purposes, the switch operating
nt the interval between the closing of the brake circuit for one stop and the closing
of the brake circuit for another stop.
4. In an electric brake system, the combination of a plurality of dynamo electric
machines for propelling and braking a vehicle, circuits for the machines, and means
for shifting the connection of the brake magnets from one to another of the dynamo
electric machines.
5. In an electric brake system, a plurality of dynamo electric machines adapted
to propel or brake a vehicle, in combination with means for alternately connecting
'a part of them to the brake circuit.
6. In an electric brake system, the combination of a plurality of dynamo electric
machines for propelling and braking a vehicle, brake magnets and ineans for
alternately connecting the brake magnets to the dynamo electric machines.
7. In an electric brake system, the combination of plurality of dynamo electric
machines for propelling and braking a vehicle, brake magnets, means for closing
the circuit between the magnets, and a dynamo electric machine for one stop or
a given number of stops, and means for closing the circuits of the magnets with
another dynamo electric machine for a second stop or number of stops.
8. In an electric brake system, the combination of a plurality of dynamo electric
machines adapted to propel or brake a vehicle, means for dividing the dynamo
electric machines into groups, and means for alternately connecting the groups
to the brake magnets.
9. In an electric brake system, the combination of a plurality of motors for
propelling and braking a vehicle, a brake circuit, a switch for closing the brake
circuit through less than the total number of motors, and means for determining
which of the motors shall be in the brake circuit.
10. In an electric brake system, the combination of a plurality of motors for
propelling and braking a vehicle, power and brake circuits for the motors, and an

page_text: automatic Switching device for shifting the connections of the Drake magnets
from one or more dynamo electric machines to a similar machine or machines.
11. In an electric brake system, the combination of dynamo electric machines.
used for braking purposes, means for closing the brake circuit through less thau
the total number of machines, and means for changing the machines which are
used for braking purposes.
12. In an electric brake system, the combination of dynamo electric machines
used for propelling and braking a vehicle, a switch for closing the brake circuit
through less than the total number of machines, and an automatic switch for
changing the machines used for braking purposes.
13. In an electric brake system, the combination of a plurality of dynamo
electric machines adapted to propel a vehicle, and means for closing the circuit
between less than the total number of dynamo electric machines and the
brake magnets, the magnets thus included in circuit being on axles carrying the
idle machines.
14. In an electric brake system, the combination of a plurality of dynamo
electric machines adapted to propel or brake a vehicle, and automatic means. for
alternately closing the circuit between groups of the dynamo electric machines and
the brake magnets, the machines and brake magnets thus included in circuit being
situated on different axles.
15. In an electric brake system, the combination of a plurality of dynamo
electric machines arranged in groups and adapted to propel or brake a vehicle, an
automatic switching device for alternately closing the groups of machines on
the brake circuit, and a switch for including extra brake magnets in circuit with
the machines.
16. In an electric brake system, the combination of a plurality of dynaino
electric machines supported by separate axles, the machines being divided
electrically into groups, brake magnets supported by the axles, and means for
alternately closing the circuit between certain of the dynamo electric machines and
the brake magnets.
17. In an electric brake system, the combination of dynamo-electric machines
divided into pairs of groups, the machines of each pair or group being mounte.
on different axles, brake magnets also mounted on the axles, and means for including
the brake magnets which are mounted on axles provided with idle motors, in circuit
with a pair of group of dynamo electric machines,
18. In an electric brake system, the combination of a cylinder provided with
suitable contacts for regulating the energy supplied to the brakes, and a switch
controlled by the brake cylinder for cutting a machine or group of machines out
of circuit.
19. In a controller for an electric brake system, the combination of motors
electrically connected in pairs, a brake cylinder provided with suitable contacts
for varying the connections of the motors when the brake circuit is closed, and a
switching mechanism controlled by the operating mechanism for opening the circuit
of one pair of motors when on the brake side.
20. In a controller for electric brakes, the combination of contacts for varying
the resistance of the motor circuit, contacts for varying the energy supplied to
the brake magnets, and means controlled by the operating handle for alternately
including the dynamo electric machines in circuit with the brake magnets.
21. In a controller for electric brakes, the combination of a contact cylinder
for regulating the motor circuit, a contact cylinder for regulating the amount of
energy supplied to the brake magnets, and an automatic switching device controlled
by the brake cylinder, for alternately including the dynamo electric machines in
circuit with the brake magnets.
22. In a controller for an electric brake system, the combination of power and
brake cylinders, a plurality of circuits therefor, and a rotary switch operated by
the brake cylinder, for determining which dynamo electric machine shall be in
circuit with the brakes.

page_text: 23. In a controller. for electric brakes, the combination of power and brake
cylinders, and a switch actuated in the interval between the time the power circuit.
is broken and the brake circuit established, for determining which dynamo electric
machine shall be in circuit with the brakes.
24. In a controller for electric brakes, the combination of a contact cylinder
for regulating the motor circuit, a contact cylinder for varying the energy supplied
tasthe brake magnets, an automatic switch for including one or another group
of dynamo electric machines with the brake magnets, and a switch for varying the
number of magnets in circuit.
25. In an electric brake system, the combination of a dynamo electric machine
far. propelling and braking purposes, a resistance adapted to be included in both
power and brake circuits, contacts mounted on a cylinder for including the total
resistance in circuit with the machine at the time the circuit is completed on the
power side of the system, and contacts mounted on a cylinder for closing the
circuit through less than the total amount of the resistance at the time the brake
circuit is closed.
26. In an electric brake system, the combination of a plurality of dynamo
electric machines for propelling and braking a vehicle, a resistance divided into
sections and adapted to be included in both power and brake circuits, contacts
mounted on a cylinder for including the total resistance in circuit with the
machines at the time the circuit is completed on the power side of the system,
and contacts mounted on a cylinder for closing the circuit between the brake
magnets and the machines through less than the total amount of resistance at the
time the circuit is completed.