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

page_text: Date of Application, 26th May, 1896-Accepted, 5th Sept., 1896
COMPLETE SPECIFICATION.
Improvements in and connected with Electric Brakes for Electrically
Propelled Vehicles.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 38, Parliament
Street, Westminster, London, Electrical Engineers, do hereby declare the nature
of this invention which has been communicated to us 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 :-
Our invention relates to electric brakes; and has for its object to provide a
braking apparatus which shall be operative in whichever direction the car may be,
moving, and which shall also have an interlock so arranged as to prevent its
improper manipulation.
To the ends pointed out we arrange our controller for the improved braking
apparatus with three cylinders, one for the ordinary control of the motors in.
propelling the car, the other the usual reversing switch, and the third a switch for
converting the motors into generators, and utilizing the current in braking magnets
or otherwise to arrest the motion of the car. This latter switch is of peculiar
construction and the interlock adapted to it is also a peculiar one. The switch has
two directions of rotation from its off position, these two directions corresponding
to the two positions of the reversing switch. When the reversing switch is in the
forward position or that corresponding to the position in which the motors propel
the car forward, one set of contacts upon the braking switch are utilized to arrest
the motion of the car, and the position of the interlock is such that the braking
switch handle can be rotated only in the direction rendering this set of contacts
operative; when the reversing switch however is in the backward position, then
the other set of contacts upon the braking switch is to be brought into play, and the
interlock is arranged so that the handle of the braking switch may be operated: to
bring this set of contacts into operation.
The accompanying drawings show an embodiment of our invention,
Fig. 1 being a plan view of the controller with the cover removed, showing the
arrangement of the interlocking mechanism;
Fig. 2 being a front elevation partly in section, also illustrating the interlock;
Figs. 3 and 4 are details more fully described hereinafter, and
Fig. 5 is a diagram of the circuits (which are cylindrical) developed in plane.
In Figs. 1 and 2, A is the back of the controller and B is the cover. In suitable
bearings are mounted the three switching cylinders D, E, F, operated respectively
by the handles C, C1, C2, these parts being of the usual type. These cylinders
are provided with step-by-step devices consisting of ratchets, or, as they are now
called in the art, "star wheels," D, E, F, having notches in which fit pawls L, G,
H, I, I, provided with the usual cam rollers, and held in place against the star
wheels by springs N, N¹. Upon the cylinder D is a collar P. provided with a
slot P with which the pawls G, H may register: Another collar O is provided
upon the reversing switch shaft, having two notches 0, 0, in which the pawls I, P
may respectively be inserted. The detail of this collar.is best seen in Fig. 3. The
star wheel Fupon the braking cylinder is illustrated in Fig. 4. It consists of two
parts in different planes, the upper one adapted to operate the pawl I, and the
lower one operating the pawl I; the latter construction.being best seen in Eig..2.
The two pawls I, 1' have their bearing in a suitable lugs depending from the top
of the apparatus. The pawl H is carried upon two links K, K, journalled in

page_text: lugs K', K' upon the back of the apparatus. The link K has a fork upon its end
which embraces both of the pawls I, I', so that, whichever one of these pawls is
operated, the pawl H will also be actuated thereby, and whichever one of the
pawls 1, is not operated by the proper portion of the star wheel F will remain at
rest, the fork being free to move over it.
The operation of the device thus described is as follows: The controlling
cylinder D is illustrated in its off position, the reversing switch cylinder E in its
forward position. In this position the notch or slot P in the collar P is in
aligument with the two pawls G, H. The braking switch eylinder F being also at
its off position, any one, of the three handles may now be operated. If the reversing
switch handle C' be operated, it will be brought first to its middle position, and in
this case the portion of the controller O intermediate between the notches O', 0
would be brought opposite the two pawls I, I', and the motion of the braking
switch would be prevented, inasmuch as these pawls would lock its star wheels in
place. In this position all of the cylinders would be locked against motion,
inasmuch as the pawl G would also be inserted in the slot P'; locking the controlling
cylinder. The further rotation of the reversing switch handle would release the
other two cylinders as soon as the cam roller upon the pawl G fell either into the
forward or back notch of the star wheel E. But assuming the reversing switch
handle to remain in its illustrated position, the controlling cylinder D may be
rotated as desired. Allowing it to remain in its illustrated position, if it be
attempted to rotate the brake cylinder F, it may only be rotated clock-wise, the
handle C moving toward the operator, inasmuch as (see also Figs. 3 and 4), the
lower part of the cam wheel Foperates the pawl I, which is free to move in and
out of the notch O' of the collar O, the upper part of the wheel not operating the
pawl I. This brings into operation the proper set of contacts upon the braking
cylinder, having reference to the connections between that and the reversing
cylinder, which will presently be described.
With the reversing switch handle thrown to the backward position, the operation
of the braking switch would however be reversed; as in this case the notch O
would no longer be in alignment with the pawl I', the motion of the braking switch
handle C' must be reversed, as that pawl would then strike against the collar O
and prevent its operation in the former direction; the pawl I however being free
to move in and out of the notch O'.
Referring now to Fig. 5, we illustrate the circuits of the apparatus; the necessity
for the characteristic interlocking arrangement will be apparent from this figure.
The cylinders are lettered as in Figs. 1 and 2, the contacts being developed in
plane and being numbered upon the controlling switch 1 to 8, upon the reversing
switch 9 10 14, and upon the braking switch 15 to 24 and 15 to 24. The motor
armature is lettered MA, the motor field M F, the trolley T, and the, brake
shoe BS. The small circles represent the fixed contacts for the various cylinders.
The controlling switch D is one adapted for the ordinary resistance control with a
single motor. We may however employ a series-parallel or any other form of
controller, inasmuch as this forms no part of my invention. It will be understood
readily that the different contacts of the controller short-circuit different parts of
the resistance R until it is entirely cut out. In its first position the circuit would
.be as follows:
From the trolley T to contact 1, to contact 2 of the controller, thence to contact 9
upon the reversing switch, to contact 9, to contact 26 upon the braking switch, to
contact 26, through the motor armature, to contact 25, to contact 25, to contact 10
upon the reversing switch, to contact 10, through the motor field M F through
the resistance to contact 7 upon the controller, to contact 8 and out at ground.
With the controller at the off position, and the braking switch and reversing
switch in their illustrated position, the circuit is open; but upon operating the
brake switch to bring the fixed contacts upon the set of contacts 15", &c., the
'circuit is closed through the brake shoe B S and resistance R, as follows:
Starting from the plus brush of the motor armature, the current passes to

page_text: contact 26, thence to contact plate 22", to contact plate 23, through the brake
shoe to 24 to contact plate 21, contact 25", to contact 10, 10° upon the reversing
switch, through the motor field and resistance, contact 19ª upon the braking switch,.
to 20, contact 25, and back to the minus brush of the motor.
The further manipulation of the brake switch serves to cut out sections of the
resistance, permitting the generation of more and more current and a greater and
greater magnetization of the brake shoe, until the car is finally brought to a stop..
When however the reversing switch is upon the contacts 11 to 14 or in its backward
position, the contacts 15 to 24 of the braking switch are utilized; the circuit would
theu be as follows: The relation of armature and field being reversed relatively to
their former connection, the current leaves the minus brush of the motor thus
passing through the field in the proper direction, for well known reasons:
From the minus brush of the motor armature M A, to contact 25, to contact--
plate 20, to contact-plate 23, through the brake shoe to contact-plate 24, to
contact-plate 22, to contact 26", to contact 9" upon the reversing switch, to contact 12,.
to contact 14, to contact 10", through the motor field and resistance, to contact
plate 19 upon the braking switch, to contact-plate 21, to contact 26, and to the plus-
brush of the motor armature.
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 us.
from abroad, we declare that what we claim is:
1. In an electric braking apparatus, the combination of a controlling switch, a
reversing switch, and a braking switch having two sets of contacts corresponding
respectively to the forward and backward running positions of the reversing switch,
and means for locking the switches so that only one of the switches may be
operated at one time, the interlocking means being so arranged that the braking
switch may be operated only in a direction corresponding to the proper position of
the reversing switch.
2. In an electric brake, the combination of a controlling switch, a reversing
switch, and a braking switch provided with two sets of contacts corresponding to
the forward and backward running positions of the reversing switch, and an interlock
between the reversing switch, controller and braking switch; the interlock arranged
to permit the operation of the braking switch in one direction when the reversing
switch is set forward, and in the other direction when the reversing switch is set
back.
3. In an electric brake, the combination of a controlling switch, a reversing
switch, and a braking switch having two sets of contacts corresponding respectively
to the forward and backward positions of the reversing switch, a pawl operated by
a cam upon the reversing switch to lock the controlling switch, a second paw!
operated by the braking switch and locking the controller, a pair of pawls operated
by corresponding star-wheels or cams upon the braking switch, one of said pawls
locking the reversing switch in its forward position, the other in its backward
position, and one being operated by the rotation of the braking switch in one-
direction, the other by its rotation in the opposite direction.
Dated this 26th day of May 1896.
For the Applica
US,
J. C. CHAPMAN,
70 Chancery Lane, London, W.C., Chartered Patent Agent.