Improvements in or relating to Electric Braking Apparatus adapted especially for use in Electric Tramways.
Year: 1898

page_text: Date of Application, 20th Sept., 1898-Accepted, 12th Nov.,
1898
COMPLETE SPECIFICATION.
Improvements in or relating to Electric Braking Apparatus adapted
especially for use in Electric Tramways.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of
this invention (which has been communicated to us from abroad by John B. Linn,
residing at Schenectady, in the County of Schenectady, State of New York,
United States of America, Electrical Engineer), and in what manner the same is
to be performed to be particularly described and ascertained in and by the
following statement:―
The present invention relates to electric braking apparatus; and has for its
object to provide a system of connections which will obviate to some extent one
of the difficulties attendant upon the operation of those devices that is, the slipping.
of the wheels which sometimes occurs when the brake is applied with too much
force.
This is done by connecting the armature of each motor to the field of the other,
in a two-motor equipment; or in equipments where more than that number of
motors is used, the same systems of connections could of course be applied by
connecting the field of each motor to the armature of some other motor. By
this arrangement, when the brake-shoe upon any axle checks the rotation of the
latter too much, the motor upon the sticking axle ceases to generate current and
the field of the other motor is killed, the shoe is released and the axles begin again
to revolve.
The invention also comprises a controlling device having contacts and con-
nections to effect this object. It is manifest that this may be greatly varied, and
that it is possible to so describe the contacts and system of wiring as to include
all the variations. The broadest aspect of the present invention therefore includes
an electric braking apparatus in which the field of one motor is connected to the
armature of another, the brake-shoes upon the same axle as the respective arma-
tures being still kept in circuit with them.
The accompanying drawings show the invention applied to a controller, Fig. 1
being a development of a controlling device for operating motors both as motors
and generators. with the invention applied thereto; Fig. 2 shows the first brake
combination, Fig. 3 the first position of the motors when driving the ears.
connections will be traced only so far as is necessary for the comprehension of
the invention.
The
The combination shown in Fig. 3 may be traced as follows: the current enters
from the trolley to contact 1, thence by the various cross-connections to contact 6ª.
then to the brush 6. to the resistance R. to the brush 23 contact 23, by cross-
connection to contact 20%, to brush 20. through the armature A1, to brush 22.
thence to contact 18, through the field F1, thence passing to the right to the
contact 26 by the cross connections to contact 9% to the brush 9 thence to
brush 19, through the armature A contact 21. to contact 17. through the field F2.
contact 15 and thence to contact 14. to the common terminal X of the brake shoes.

page_text: At this point the current divides, going through the shunting resistance R³ to
ground, and passing also in multiple through the brake shoes B1, B2 to con-
tacts 12 and 13 respectively, which are connected with contact 11 and thus to
the ground wire.
The object of the resistance R2 is to momentarily pass the trolley current, or a
small portion of it, through the brake shoes, to demagnetize them, and cause
their immediate release when the motor current is turned on. This, however,
forms no part of the present invention. The other steps of the controller on
the motor side first cut out the resistance until the two motors are left in series,
the brake shoes and shunting resistance being of course out of circuit. At the
transition point where the contacts upon the right of the controller marked 10b
and 11° come into circuit, the motors are thrown in multiple, one of them being
first shunted to ground; this being now a well-known form of series-parallel
controller, which is also no part of the present invention.
When, however, the controlling device is rotated in the other direction from
the off position (this being the position in which it is represented), the contacts
on the left of Fig. 1 are brought into operation, and here the combination of
Fig. 2 is affected. This figure illustrates the essence of the invention, as in it
the armature and brake shoe upon one axle are connected to the field of the
motor upon the other axle, for the reasons already pointed out. In tracing the
connections, it will be found simplest to start from the terminal O of the resist-
ance. Here the path of the current is to the brush 23. and thence by the con-
tacts 23b, etc., to the brushes 21 and 22. The path divides at this point, and the
two armatures A1, A2 will be found in multiple. Passing through the brush 22,
the circuit is through the armature A¹, to brush 20, and thence by the contacts 20b
and 17b to brush 17, through the field F2 of the second motor to the brush 15, by
contacts 15 and 12 to brush 12, thence through the brake shoe B¹ to the common
terminal X. Returning to the contact 21, the path is through the armature A2
to brush 19, by contacts 19b and 18b to brush 18, thence through the field F¹ of
the first motor, to contact 16, and by 16 and 13b to brush 13, through the brake
shoe B2 to the common terminal X; thence to the brush 14, and by 14 and 11b
to the brush 11, to the ground wire, thence to brush 7, and by the cross-connec-
tions to the contact 5. This, it will be observed, is extended to the other side
of the controller, and here the brush 24 touches the contact 4" which is connected
to 5, and thus the circuit is completed to the other terminal of the resistance R,
the resistance R2 being thus short-circuited. Although the ground wire is thus
used and the ground circuit is maintained, the latter plays no part in the con-
nections, the ground wire being used for convenience only.
It is shown in Fig. 2 in the dotted lines that the brake shoes may be well
connected between the armatures and fields as between the fields and ground wire.
It is manifest that the operation of these connections will be substantially identical
with those shown.
It is not considered necessary to show the particular changes in the controller,
as they would be apparent to an engineer.
The operation electrically of the device indicated is as follows: if the arma-
ture A3, for instance, should cease to rotate by the application of the shoe B³ upon
the same axle, the field F¹ of the motor A¹ would not only get no current from
the armature A8, but such current as would reach it from its own armature would
be in a reverse direction; that is, if the armature A¹ should for a moment con-
tinue to generate, it would send current through the field F3 or the other motor,
through its own brake shoe B¹ and in a reverse direction through the shoe B
and the field F¹ to the armature Aª, tending to drive the latter as a motor. The
consequence is that the shoe B³ would be demagnetized and the armature A¹
would have its field practically killed. As soon, however as the shoe B³ was
released, both the armatures would be driven by the momentum of the car in the
usual way, and the shoes would be at once again applied. In practice this effect

page_text: is produced as the current alternates between the two motors, without the actual
release of the different brake shoes, but their attractive effect is slightly weakened
so that the sticking armature begins to revolve.
Having now particularly described and ascertained the nature of our said inven-
tion, (as communicated to us from abroad) and in what manner the same is to
be performed, we declare that what we claim is :-
1-In an electric braking apparatus, the combination, with a number of
dynamo-electric armatures and brake mechanism upon common axles, of means
for passing the current from one armature through the field of another of the
dynamo-electric machines.
2-In an electric braking apparatus, the combination with a number of dynamo
electric machines, each provided with a magnetic brake shoe controlling the axle
connected to its armature, of means for passing through the field of any given
dynamo the current from the armature and brake circuit of another axle.
3-In an electric braking apparatus, the combination, with dynamo electric
machines, each having a magnetic brake shoe controlling the axle connected
to its armature, of a controlling device provided with contacts and connections
for regulating the dynamo electric-machines as motors from rest to full speed.
and with braking contacts for cross connecting the field of one machine to the
armature of another while still passing the same current through the brake-shoe
of the armature so connected.
4 In an electric braking apparatus, the combination with two dynamo electric
machines having magnetic brake shoes controlling the axles to which the respec-
tive armatures are connected, of a controller having contacts and connections
for regulating the speed and torque of dynamos as motors, and having also con-
tacts and connections for connecting the field of each dynamo when used as a
braking generator in circuit with the armature and brake shoe of the other
dynamo, as described, for the purpose set forth.
Dated this 20th day of September 1898.
THE BRITISH THOMSON-HOUSTON CO., LTD.,
A. R. MONKS,
Director,
ALFRED CLEMENTS,
Assistant Secretary.