Improvements in Electric Brakes.
Year: 1895

page_text: Date of Application, 29th Oct., 1895-Accepted, 14th Dec., 1895
Improvements in Electric Brakes.
I, JAMES DEVONSHIRE, Secretary of the British Thomson Houston Limited
of No. 38 Parliament Street, Westminster, London (a communication to me from
abroad by Frank E. Case, Electrical Engineer, of Schenectady, in the State of
New York, United States of America) 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 :-
car.
My invention relates to electric brakes, and has for its object to provide means,
including suitable apparatus, for utilizing the wasted force in a motor driving a
tram-car or other vehicle and generating electro-motive force by its momentum
after the current is cut off from it. Ordinarily this electro-motive force is either
wasted or has to be overcome by the friction of the brake shoe, thus increasing the
difficulty of stopping the car. By my invention, however, I am enabled to utilize
this force in applying the brake shoe to the wheel and thus assist in stopping the
At the same time I provide a means of regulating the amount of force applied
to the brake, which means is put within the control of the driver of the vehicle and
in the special apparatus in which I have embodied my invention the brake is
controlled by a single handle in its application, while the degree of force with
which it is applied is regulated by the handle of the motor controller, and the
motorman has thus only the two handles to engage his attention. It is of course
designed to add the ordinary hand braking apparatus to provide for emergency in
case the magnetic brake should fail to act, from imperfection in its construction or
from accident; but ordinarily this apparatus will not be employed by the motorman
and it will be unnecessary to make further reference thereto.
To effect the objects of my invention, I therefore provide a controlling apparatus
which is adapted to regulate the speed of the motors in either direction; and
I provide in the same case with this controller a second switch, preferably cylindrical,
which acts to change the circuit connections so that the motors are brought into
local circuit acting either directly or through suitable gearing upon the brake
shoes. This local circuit is completed through a controlling apparatus, and this
apparatus therefore regulates the electro-motive force of the motors by cutting in
or out resistance either in series with the motor or in shunt to the fields in ordinary
ways. In this construction, which is the preferred one, the entire office of the
brake or auxiliary handle is to throw the brake into operative condition and its
entire movement is controlled by the handle of the motor regulator, as pointed out
above.
The accompanying drawings show an embodiment of my invention. Therein
Fig. 1 is a front elevation of my improved braking apparatus showing the
connection with a controller of the type described, the cover being removed to
show the apparatus.
Fig. 2 is a view of the interlocking mechanism which I use.
Fig. 3 is a diagram showing a modification of the circuit connections, to be more
fully described hereafter.
Fig. 4 is a view of an electric car equipped with my improved brake.
Fig. 5 is a diagram showing the wiring of such a car with the controllers at each
end of the braking switch shown in their prover relations ;

page_text: Fig. is a mustrative diagram showing the method of operation in a simple
manner,
and
Fig. 7 is a diagram showing the combination of Fig. 3 with the apparatus as illus-
trated in Fig. 5, except that only one motor is shown, for clearness of illustration.
Referring now to Fig. 1, A is the case of the controller, to which the switches
are secured; B is the controlling switch provided with contacts B¹, B², B³, and
brushes C, C, C; D is the blow-out magnet; is the shaft upon which the
switch is mounted; E is the handle of the controller switch.
All of these parts
3
are of con mon construction, and form no part of my invention except in combina-
tion with other features presently to be referred to. F is a cylindrical switch
provided with suitable contacts and with a handle F. The connections and
method of operation will be more fully described in connection with other figures.
Referring now to Fig 2, I show a plan view of the interlocking mechanism
employed between the two cylinders or switches, a side elevation of which is
shown in the upper portion of the case in Fig. 1. Therein G is a star wheel
with notches 93, indicating the running positions of the controller; a pawl G¹
provided with a friction roller 92 and a spring y' engages with these notches
successively. The notches on opposite sides of the wheel are identical in position,
inasmuch as I employ in this construction controlling switches adapted to run the
motors in either direction from a central position, moving the handle in one
direction running the car forward, and moving the handle in the other direction
running it back; although I may employ switches of other forms. H is a lever
having a projecting end engaging with a notch or stop g on a disc or collar
surmounting the star wheel G. At 1 is shown a second star wheel or cam provided
with notches i, i, and a pawl K with a friction roller k, the purpose of these parts
being identical with that of the first star wheel G and its pawl, and adjuncts. The
lever His pivoted at / to the pawl K. The operation of these parts is as follows:
When the controller cylinder B is in the "off" position, and the circuit is broken,
the switch lever F may be thrown to rotate the braking switch cylinder F. The
cam I attached to this cylinder would then be rotated to its central position, braking
the connections as hereinafter described, and at the same time throwing the pawi K
further from the centre of the cylinder F forcing the end of the lever H into the
notch g and holding the cylinder in its "off" position. The object of this is to
prevent the cylinder B from being rotated to turn on current, while the connections
of the brake are still broken or in process of being changed, thus preventing sparking
and the destruction of the contacts on the braking switch cylinder.
When,
however, the cam I is rotated so that the pawl K engages with either its upper or
lower notch, as shown in the figure, the cylinder B will be free to move and current
may be turned in to operate either the braking magnet or the motors.
Referring now to Fig. 5, I illustrate the connectious which are employed. In
that figure the parts at the left and right respectively of the contacts are develop
ments of the controller cylinder and the braking switch cylinder. Upon the
controller cylinder the contact plates 5, 6, 7, 8, 9, 10 and 11 show the means of
cutting in or out the several sections o, o, of the resistance O, while those
marked 1, 2, 3, 4, are the contacts of the motors adapted to reverse them in
accordance with the direction of motion of the controlling handle.
Referring now to Fig. 6, I show in simple diagram the principle of the apparatus
which will be more fully described by further reference to Fig. 5. In this
Figure (6) M is the motor, I) the blow-out magnet, F is the double pole switch,
N is the braking magnet and N' is its core. I do not illustrate any special form
of braking levers or shoes, as these may be of any form known in the art and
form no essential part of my invention. At S is the trolley. Following the
circuit from the trolley, the current enters and passing through the switch Fin
its illustrated position, goes around the blow-out magnet D, through the motor M
and resistance O, back to the switch by its other blade and out at the ground.
When the switch is in its dotted position however, no current enters from the
trolley, but the motor is on a local circuit, which may be traced from M to the

page_text: switch, through the braking magnet, by the other blade of the switch, through
the blow-out magnet and back to the motor, passing on its way through the
resistance in series with the motor and through the reversing switch S', which, as
illustrated, affects only the armature circuit. When short-circuited upon itself in
this way, the motor acts to generate current, and the magnet core N' is strongly
attracted, thus putting on the brake by any suitable connections.
art.
Referring again to Fig. 5, the operation thus briefly indicated is carried out by
means of the cylindrical switches shown, the parts being diagrammatically indicated
without regard to their relative position, which is well known to those skilled in the
The current entering from the trolley S passes to the contact on the right
of the figure to the plate l, thence to the contact v, around the blow-out magnet D,
by the lead to the contact I, to contact plate 1b, cross connected to the plate 2b,
thence to contact 2, then by the lead to the motor armatures M, M', returning
through the motors' armatures to the contact 3, thence to contact plate 3b, by cross-
connection to contact plate 4", thence to contact 4, then through the motor-
fields L, L, through the resistance O, to contact 5, then to contact plate 5,
thence to contact plate 11, then to contact 11, then by the lead to the contact Y,
thence to contact plate m upon the braking switch cylinder, thence to contact
and out at ground. In this position it will be seen that the braking magnet N
takes no current, its terminals w, being open-circuited; and it will also be
observed that further rotation of the cylinder B will cut out successive sections of
resistance in the ordinary way and regulate the speed of the motors without
actuating the braking magnet. Also by reference to Fig. 2, the position of the
interlocking mechanism will be seen to correspond with the positions of the
cylinders as shown in Fig. 5.
Assuming now that the brake is to be actuated, the controller handle will be
brought so that the contacts are "off" as in Fig. 2 and in Fig. 5. The handle F
(see Fig. 1) will then be thrown so that the cam I (Fig. 2) is rotated until the
pawl K comes into the lower notch i, the intermediate notch i locking the controller
cylinder B until the switch F is entirely thrown. But when the lower notch i is
reached, the rod H is withdrawn and the controller cylinder becomes free to move.
Now referring again to Fig. 5, when the locking mechanism is in the new position
just described, the contact plates n, n' upon the switch F will connect the
terminals v,,, y respectively, and the trolley contact U and the ground contact z
will be cut out, thus throwing the motors M, M' into local circuit with the
braking magnet N.
Assuming that the positive brushes of the motors M, M' are those marked with
a plus sign, the electro-motive force generated in their armatures will send the
current from these positive brushes connected in multiple to the contact 2, thence
to contact plate 2ª, (on the development of the switch B shown on the left of the
contacts) thence by cross connection to contact plate 4", thence to contact 4, thence
through the motor-fields L, L', thence through the resistance to contact 5, then
to contact plate 5*, thence to contact plate 11*, thence to contact 11, theuce by the
lead to contact y, to contact plate, thence to contact, thence through the
braking magnet N, thence to contact w, thence to contact plate n, thence to
contact v, around the blow-out magnet D to contact 1, to contact plate 1ª by cross
connection to contact plate 3º to contact 3. thence to the lead from contact 3 to
the minus brush of the motors, passing, as will be seen, in the reverse direction
from that in which it flowed when controlled by the contacts shown in the
development of the right hand half of the cylinder B. This current energizes the
braking coil N and draws up the core N, thus drawing up the lever and
applying the brake shoe Q' to the wheels. As already pointed out, any form of
interposed gear may be employed to increase the leverage or all such gear may be
dispensed with, as the engineer may elect. It is unnecessary to further trace the
circuits in Fig. 5, inasmuch as the rotation of the cylinder B from this point on
effects the regulation of the braking power by cutting in or out sections of the
resistance O, as already pointed out. After the car has come to a stop, the

page_text: switch B will be brought to the off position, and the switch F then thrown to make
the connection again with the trolley.
The apparatus illustrated on the left in Fig. 5-is-the counterpart of that shown
in the right hand part of the figure, and is operated-in précisély the same way from
the other end of the car. In order, however, to prevent manipulation of the
controller at the opposite end of the car from that where the motorman is
stationed, I provide upon the underside of the handle F¹ a lug y' moving under a
'circular segment, which prevents the handle F from being removed except when
it is in its central position, in which the middle notch i upon the cam I engages
with the pawl K and locks the controller cylinder in position. It is thus
impossible for unauthorized persons to, tamper with the controller at one end of the
'car while the motorman is at the other end.
Referring to Figs. 3 and 7, I illustrate the application of my method of control
to the combination of a motor field-magnet shanted through a variable resistance
so that the current may be varied by varying the resistance and therefore the
strength of the generated current may be also changed and the effect of the brake-
magnet graduated. In Fig. 3 I do not illustrate the entire combination with the
line circuit, this being a diagram only so as to show the motor and its shunted
field in the simplest possible relation. I also en ploy in these figures only one
motor (although it is manifest that two may be employed, and in ordinary practice
would be so employed), so as to exemplify the method of control in the simplest
manner possible. Further referring to Fig. 3, after the line current has been cut
off and the motor reversed so as to send current through its field L in the same
direction as the line current which formerly passed through the field, I may rotate
the switch B to cut in a greater or less amount of resistance.
In the position
shown, practically the entire resistance will be cut out when the line of
contacts 1, 2, 3, &c., touches the contact plates 9, 10, &c., and in this position the
path of the current will be from the upper brush of the motor through the braking
magnet N to the contact 8, thence to the contact plate 16, by cross-connection to
the contact plate 15, to the contact 7, by the lead to the contact 6, by cross-
connection to the contact 1, to the other brush of the motor; the second path
being from the contact 7 through the field L to the contact 1, to the other brush
of the motor; and still a third path being from the contact 7 through the
steps o, o', of the resistance O', to the contact 1, to the other brush. In this
way the field is shunted by a connection of practically no resistance and also
through the resistance O. The field-magnet being thus practically unexcited
save for the small amount of residual magnetism remaining in it, very little
current is generated by the rotation of the armature of the motor. The further
rotation of the switch B acts to cut in more and more of the resistance as the
contacts 6, 5, 4, and so on, pass off from the contact plates 14, 18, 12, aud so ou,
until finally the resistance contacts are all cut out and the shunt connection
around the field L is entirely through the resistance O' which by this time has
become of such an amount as practically to pass the entire current generated in
the motor armature through its field; the potential and volume of current
therefore, run up rapidly, and the action of the braking magnet upon its core N¹
becomes exceedingly strong.
In Fig. 71 illustrate, as already pointed out, the combination of Fig. 3 with the
other parts of my apparatus, the illustration being merely diagrammatic. In this
figure the paths of the current are as follows: The current, entering from the
trolley S, passes to the contact U, to the contact-plate 1, thence to the contact v,
around the blow-out magnet D to the contact 1, to the contact-plate 16, by cross-
connection to the contact-plate 2b, to the contact 2, through the motor-armature M,
to the contact 3, to the contact-plate 3b, by cross-connection to contact-plate 4b,
through the motor-field L. to contact z, to contact-plate m, to contact z', to contact 10,
through the resistance to contact 5, to contact-plate 5, by cross-connection to
contact-plate 11°, to contact 11 and to ground at G; the further rotation of the
right hand part of the switch acting, as before described with reference to Fig. 5,

page_text: و2
merely to cut out sections of the resistance until it is entirely short-circuited.
When, however, the right hand switch carrying the contact-plates l, m, n, n' is
thrown, the contacts 1, 2, 3, &c. being then in the off position, the current takes a
different path. In that case the trolley contacts. u, v, are disconnected as they pass
off the contact-plate 7 and the series regulating resistance O is also disconnected as
its contacts zt
pass from the contact-plate m; the contact-plates n, n¹ in this
position complete the circuits throwing the armature M and brake-magnet N.in
series with the field L and resistance O, these latter two being in multiple with
each other, as shown diagrammatically in Fig. 3. The path of the current in this case
is as follows, assuming that it passes from the brush marked + of the motor-armature
to that marked to the contact 2, to the contact-plate 2*, by cross-connection to
the contact-plate 4ª, to the contact 4, through the motor field L to the contact z, to
the contact-plate n!, thence to .contact upon the same contact-plate n', then
through the brake-magnet N to the contact to, to the contact-plate n, to contact v,
around the blow-out magnet D, to the contact I, to the contact-plate 1°, by cross-
connection to the contact-plate 3, to contact 3, and back to the minus brush. At
the point q a shunt circuit through the resistance O' starts, coming to contact 16,
and passing in accordance with the position of the switch B. through different
sections of the resistance O', its first path being when the contacts 13, 14, &c. just
touch the contact-plates-13*, &c., in which case it passes from contact 16 to contact-
plate 16, by cross-connection to contact-plate 12, then to contact 12, to contact y,
to contact-platen, to contact z, there joining the lead to the field L. In this
position of the switch Ba the resistance and the field are entirely shunted, and very
little current will flow in the field, while, as the resistance is progressively cut in,
the field will become more and more strongly magnetized.
In Fig. 4 I design to illustrate the application of my improved braking system to
an electric car in a diagrammatic manner, controllers A, A, being represented upon
each end of the car P, which is of any ordinary type. It will be seen that the
method of operation which is outlined above is in brief to disconnect the trolley
from the car apparatus, close the motors in a local circuit with the brake magnet
and by preference with the blow-out magnets, inasmuch as it is desirable to keep
these always energized so that sparks may not destroy the commutating switch
contacts, and then to move the controller ordinarily employed to regulate the speed
of the motors as a means of reversing the motors and then regulating their electro-
motive force. It is important that the motors be reversed when they are place
upon local circuit, which, however, is not a closed circuit until the controller handle
is moved; that is to say, the switch F breaks the trolley circuit, and closes, with
the exception of one break, the local circuit through the motors and the braking
magnet; but this brake is not closed until the rotation of the controller handle is
begun, the first step of this rotation determining the direction of the current,
and the second and further steps controlling the amount of resistance in circuit.
The object of reversing the motors (by which expression I mean such a reversal
of the relation of armature and field as would act, if the line. current were still on,
to rotate the armature in the opposite direction if they were free to move in that
direction, and would act, first to stop the car and then to force it in the other
direction) is to cause the current from the armature to pass through the field in such
a direction as to build up its magnetism; that is to say, to cause the electro-motive
force generated in the motor-armature to send the current through the fields in the
same direction in which it would pass when driven by the impressed electro-motive
force of the line current; if the direction of current through the motor as a whole
he reversed, the motor will, of course, while still continuing to run in the same
direction, beat down or demagnetize its own field, and will then cease to operate
as a-generator.
The order of steps which I have pointed out as one embodying my invention
presents great advantages because of the absence of sparking in the braking switch
contacts and their consequent destruction, the circuit being always broken..at the
motor controller before the switch controlling the braking action.is thrown. The

page_text: blow-out magnet of the main controller serves to prevent sparking in the same
manner when used on the trolley circuit and when used on the local circuit with the
motors and the braking magnet, so that no harmful effect is experienced.
It is manifest that in addition to the mechanical friction of the brake shoe, the
magnetic drag of the revolving motor armature must be overcome by the momentum
of the car, and the combined effects of the two act to bring the car quickly to a
stand still.
Having now particularly described and 'ascertained the nature of the said inven-
tion and in what manner the sanie to be performed as communicated to me
from abroad I declare that what I claim is :-
1. The method of operating an electric brake actuated by the current derived
from, the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field-magnets of the motors, reversing the
motors, and including them in a local circuit, substantially as described.
2. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field-magnets of the motors through a
resistance, reversing the motors, and including them in a local circuit.
3. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field-magnets of the motors through an
adjustable resistance, reversing the motors, including them in a local circuit and
varying the resistance in the shunt, substantially as described.
4. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors, and
shunting their field-magnets, and including them in a local circuit.
5. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field magnets through a resistance, and including them in a local
circuit.
6. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field-magnets through a variable resistance, including the motors in
a local circuit, and then varying the resistance.
7. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field-magnets of the motors, reversing the
motors and including them in a local circuit with a brake magnet.
8. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field magnets of the motors through a
resistance, and including them in a local circuit containing a brake magnet.
9. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, shunting the field-magnets of the motors through an
adjustable resistance, reversing the motors, including them in a local circuit
containing a brake magnet, and varying the resistance in the shunt.
10. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field-magnets, and then including them in a local circuit containing
a brake magnet.
11. The method of operating an electric brake actuated by the current derived

page_text: from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field-magnets through a resistance, and then connecting the motors
in a local circuit containing a brake magnet.
12. The method of operating an electric brake actuated by the current derived:
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field-magnets through a variable resistance, including the motors in
a local circuit containing a brake magnet, and varying the resistance.
13. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
opening the line circuit, simultaneously or successively reversing the motors and
shunting their field-magnets through a variable resistance, including the motors in
a local circuit containing a brake magnet, and varying the resistance.
14. In an electric brake and in combination, a line circuit, motors operating an
electrically propelled apparatus, mechanism adapted to open the line circuit, t
shunt the field-magnets of the motors, to reverse the motors, and to include them,
&c., substantially as described.
15. In an electric brake and in combination, a line circuit, motors actuating an
electrically driven apparatus, a resistance, mechanism adapted to open the line
circuit, to reverse the motors, to include them, &c., and to shunt the field-magnets
of the motors through the resistance.
16. In an electric brake and in combination, a line circuit, an adjustable
resistance, motors operating an electrically-driven apparatus, and mechanism
adapted to open the line circuit, to reverse the motors, to include them, &c., to
shunt the field-inagnets of the motors through the resistance, and to vary the
resistance in the shunt.
17. In an electric brake and in combination, a line circuit, motors actuating an
electrically driven apparatus, a local circuit including a brake magnet, mechanisin
adapted to open the line circuit, to shunt the field-maguets of the motors, and to
reverse the motors through the local circuit.
a
18. In an electric brake and in combination, a line circuit, motors operating an
electrically-driven apparatus, a local circuit including a brake magnet,
resistance, and mechanism adapted to open the line circuit, to shunt the field-
magnets of the motors through the resistance, and reverse the motors through
the local circuit.
19. In an electric brake and in combination, a line circuit, motors operating an
electrically driven apparatus, a local circuit including a brake magnet, an
adjustable resistance, and mechanism adapted to open the line circuit, to shunt the
field-magnets of the motor through the adjustable resistance, to reverse the motors
in the local circuit, and to vary the resistance in the shunt.
20. The method of operating an electric brake actuated by the current derived
from the motor or motors of an electrically propelled apparatus, which consists in
cutting out the external source of current at the motor-controller, then disconnecting
the motor from the external circuit by means independent of such controller, ther
including the motor or motors in a local circuit with a brake magnet, then closing
the local circuit at the motor-controller through a resistance and reversing the
direction of the current in the motor-armature, and finally varying the resistance to
vary the action of the motor and the braking magnet, as set forth.
21. In an electric brake, a motor or motors driving an apparatus, a controller
for such motor or motors adapted to break the external circuit, to reverse the
current in the motor, to regulate its speed, a switch adapted to disconnect the
motor from the external source of current and to put it in an open local circuit
including the controller and a resistance operated thereby, and a brake magnet
in the local circuit; whereby the switch effects the changes in the relation of the
motors, the external circuit, and the brake magnet, while the circuit is open, and

page_text: the controller closes the circuit to reverse the motors and regulate the braking
action after the switch is operated, substantially as described.
22. In an electric brake, a motor or motors driving an apparatus, a controller
for the motor or motors including a cut out, a resistance, and a reversing switch, a
second switch adapted to break the external circuit and put the motor or motors on
local circuit with a brake magnet, and interlocking mechanism between the
controller and the switch; whereby either the switch or controller may be operated
only when the other is in proper position, substantially as described.
23. In an electric brake, motors driving an electric car or apparatus, a controller
for such motors comprising a resistance and a switch adapted to cut in or out
successive sections of resistance, to reverse the motors, and to cut off the current, a
second switch adapted to disconnect the external circuit and put the motors in a
local circuit including the motor-controller, a brake-magnet in such circuit, and
interlocking mechanism between the switch and the controller, consisting of a stop
upon the controller and a lever upon the switch, such mechanism adapted to
prevent the motion of the controller while the switch is being thrown, and to
prevent the motion of the switch while the current is on.
Dated this 29th day of October 1895
PPC
J. C. CHAPMAN,
70, Chancery Lane, London, W.C., Chartered Patent Agent.