Improvements in and connected with Electric Brakes for Electrically Propelled Vehicles.
Year: 1896

page_text: Date of Application, 19th May, 1896-Accepted, 29th Aug., 1896
COMPLETE SPECIFICATION.
Improvements in and connected with Electric Brakes for
Electrically Propelled Vehicles.
I, JAMES DEVONSHIRE, Secretary of the British Thomson-Houston, Limited, of
38 Parliament Street, Westminster, London, do hereby declare the nature of this
invention (a communication to me from abroad by William B. Potter, Electrical
Engineer, of Schenectady, in the State of New York, United States of America,)
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 electric brakes, and more particularly to the now known
emergency brakes or stops, such as that defined in my British Patent No. 14,639
dated Aug. 1st, 1895, in which motors operated by the momentum of a moving
vehicle or load are short-circuited while operating as generators, and bring the
vehicle to an abrupt stop. These contrivances are designel to be used in case of
emergency, and not to take the place of an ordinary electric brake or other braking
appliance; they are however extremely severe upon the truck and motors, as well
as upon passengers, and their appliance is to be avoided if possible, although they
afford a useful safety appliance.
To obviate the disadvantages and discomforts attending these devices when used
as electric brakes, is the object of my present invention, which consists briefly in an
improved combination of reversing switch and electric braking mechanism, which
may be applied to present standard equipments, and may operate if necessary with
great energy, but which may be also regulated so that the inconveniences just
referred to will be obviated.
For this purpose I prefer to employ a series-parallel controller, such as that
described in my British Patent No. 6049 dated March 18, 1896. In this the
combinations are from series, with and without resistance, into multiple with and
without resistance, the progression being effected by shunting one of the motors
before going into the multiple position, and increased speeds in the two positions
being obtained by shunting the field-magnets and thus reducing the strength of the
motor field. This method of regulation is effective and useful.
To accomplish the purpose of my invention I combine with the ordinary reversing
switch illustrated and described in Patent No. 6048 of 1896, a second set of contacts
upon each side, so that there are in reality four sets of contacts (although some of
the first two series are extended so as to unite with the latter, and thus apparently
there are only two sets, as will be more fully explained hereinafter); two of these
sets of contacts act in the ordinary manner to determine the direction of rotation
of the motors, while the other two serve to disconnect the trolley circuit and to
close the circuit of the motors upon themselves, the circuit, however, being still
open at the controller. When this latter circuit is closed the apparatus acts as an
electric brake, and the usual combinations of the motors in series and parallel with
and without resistances and with and without the fields shunted, are effected for the
purpose of regulating the motors while acting as generators. It is of course under-
stood that the auxiliary switch to which I have referred acts not only to cut off
the trolley and close the circuit of the motors, but also to reverse the rotation of
armature and field, so that they act as generators.
The accompanying drawings show diagrammatic embodiments of my invention,
Fig. 1 showing the controlling switch and auxiliary switch developed, and with
the circuits and motors connected therewith.

page_text: Fig. 2 is an interlocking mechanism which may be employed;'
Figs. 3 and 4 show respectively the operation of the controller in its first position
when regulating the motors, and when operated as a brake, and
Fig. 5 embraces a series of diagrams showing the braking combinations.
Referring first to Fig. 2, I is a star wheel operating a pawl K with a friction
roller K. L is a disc provided with a recess K' into which the pawl K is inserted
by the revolution of the star wheel or cam I. The notches of the star wheel_are
upon the same radius, excepting the notch I'. When in this position the disc L is
locked, the roller K' being in the notch I' and thrusting the pawl K into the
notch K. The star wheel I is mounted upon the shaft of the cylindrical switch M,
and the disc L upon the shaft of the controlling switch N. The switch M has
four operating positions defined by the four notches upon the radius of the cam [ ;
but in the central position of the switch the mechanism is locked and its circuit is
open. This interlocking mechanism is explained only for clearness of illustration
ard is not claimed herein, inasmuch as similar devices are described and claimed in
my Patent No. 14,639 of 1895 above referred to, and they, in combination with the
present illustration, will render the application of the interlock evident to those
skilled in the art.
Referring now to Fig. 1, the brushes or fixed contacts of the switch M are
numbered 1 to 10, and those of the controller N 11 to 20. The positions of the
controller are indicated by the letters a to 1, and the motor combinations effected
by it are shown in the diagrams of Fig. 5 by corresponding letters. It is to be
understood that when the trolley current is on, the motors are combined in the
position shown in Fig. 3 and other combinations, as illustrated in my patent first
referred to above, which are not therefore further explained herein.
The positions of the switch M are shown by the lines to respectively. The
lower two contact plates form a connection from the trolley T. Auxiliary contact
plates m, n are connected to the ground wire at G1, G2. The motor armatures are
lettered respectively A1, A2, and the fields B1, B2. Resistances R, R1, R2 are also
provided. The first combination of the controller when the electric machines are
operating as motors, is shown in Fig. 3, the row of contacts upon the switch M
standing upon the line w, and those upon the controller N standing upon the line a;
its circuit being as follows:
From the trolley T current passes to contact 10, by cross-connection to contact 9,.
to contact 11 upon the controller, by cross-connection to contact 12, through the
resistance R to the lead 15, and by that lead to the lead 8, to contact 8 upon the
switch M, to contact 7, by the lead 7 to the plus brush of the armature A',.through
the armature to the lead 6, to contact 6, to contact 5, by the lead 5 through the
field B', to lead 18, to contact 18 upon the controller, to contact 16 by the cross-
connection, by the lead 4 to contact 4 upon the switch M, to contact 3, by the
lead 3 to the plus brush of the armature A³, through that armature to the lead 2,
to contact 2, to contact 1, through the field B2 and out at ground; giving the
combination shown in Fig. 3. The other combinations made as the controller is
rotated are described in my Patent No. 6048 of 1896.
When, however, it is desired to use the motors as an electric braking appliance,
the switch M is turned so that the brushes rest upon the line 2, including the
auxiliary contact n, opening the trolley circuits, and closing the circuit of the
motors through the ground wire, but still leaving the local circuit open at the con-
troller; the relation of armature and field in the motors has of course been reversed,
as will be evident from the cross-connection of the movable contacts upon the
right of switch M. It will be observed that the reversing of the motors is
accomplished by the same act as when they are to be reversed in their direction of
rotation; this being so arranged because the instinctive act of the motorman in
checking the car is to throw back the handle of the reversing switch. In this
combination the circuit is as follows:
Starting from the contact plate m, it passes to the contact 11 upon the controller,
to contact 12 by the lead 12, through the resistance R, to lead, 15, by that lead

page_text: and lead 8 to contact 8, by the cross-connection to contact 6, by the leal 6 to the
armature A¹, entering at its minus side, thence by the lead 7 to the contact 7, by
cross-connection to contact 5, by lead 5 through the field B₁ in the same direction
as before (the rotation of armature and field being reversed, as will be observed),
to the lead 18, to the controller at contact 18, to contact 16, by lead 4 to contact 4,
by cross-connection to contact 2, by lead 2 to the minus brush of the armature A',
through the armature to the lead, to contact 3, by cross-connection to contact 1,
through the field B2, to ground at G, completing the local circuit at G' to the
contact plate n; giving the combination of motors and resistances, the motors
operating as generators, as shown in Fig. 4.
The other combinations of the controller are illustrated in detail in Fig. 5, the
diagrams a to being the various combinations of motors and resistances produced
by the rotation of the controller N to the positions indicated respectively by those
letters. They are self evident, and the circuits will not be traced in detail,
inasınuch as they are simply the same combinations reversed as those described in
my Patent No. 6048 of 1896 already referred to. Briefly, the first position a is in
series with a resistance; the second, third and fourth, lettered b, c, d respectively,
are also resistance steps, the last one being with the two machines in series and the
resistance cut out. The next step e shows the field shunted. is the same as
position b. In position a shunt is thrown around one of the machines. In the
shunt is open, as also in h', which is meant to indicate that this being a transition
step, the contacts are somewhat extended, so that it may not be passed over too
abruptly. At the machines are in multiple. At j an additional portion of
resistance is cut out. At k all of the resistance is cut out. At the fields are
shunted.
Practically all of the steps after that shown at d might be omitted, as it is not
desired or interded that the apparatus as designed shall be used for making ordinary
service stops, it being an intermediate device between the emergency stop (the
limits of which have been defined in my statement of invention), and a properly
designed electric braking apparatus, which may be continuously used. It is
designed to combine with the power of the emergency stop a few gradations which
will prevent its being so extremely severe, although in case of accident it may still
be employed, the motorman rapidly passing through all of the steps necessary to
bring the car to a stop, and by a single movement of the hand short circuit the
motors. The most effective position for stopping the apparatus is that shown at k
in which the two motors are in multiple.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me
from abroad, I declare that what I claim is:
The combination of a controlling switch arranged to connect a plurality of
motors in series or in parallel with and without resistance, and an emergency switch
in the controller provided with contacts and connections arranged to open the
trolley circuit, and to close a local circuit through the motors, the local circuit being
left open at the controller; by which the controller may be used as power apparatus
in one position of the auxiliary switch, but in other positions will combine the
motors as generators in steps in series and parallel with and without resistance.
Dated this 19th day of Mar 1896.
J. C. CHAPMAN,
70 Chancery Lane, London, W.C., Chartered Patent Agent.