Improvements in Safety Appliances for Electric Cars.
Year: 1895

page_text: Date of Application, 1st Aug., 1895-Accepted, 23rd Nov., 1895
COMPLETE SPECIFICATION.
Improvements in Safety Appliances for Electric Cars.
I, JOSEPH (RAWHALL CHAPMAN, Chartered Patent Agent, of 70, Chancery
Lane. in the County of London, (a communication to me from abroad from
William B. Potter, of Schenectady, in the County of Schenectady, State of
New York, United States of America, Electrical Engineer,) 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:-
My invention relates to safety appliances for electric cars; and has for its object
to provide a controller equipped with a reversing switch having a certain additional
series of contacts therein by which I am enabled to stop the car within a very
short space when any emergency demands that such a stop shall be made.
As ordinarily constructed, reversing switches provide only for reversing the
motion of the motors by means of the power of the trolley current; that is to say,
the switch has two positions, in the forward position the motor acting to propel the
car in one direction, and in its backward position to propel it in the other. It has
also been proposed to equip cars with electric brakes of one type or another, and to
provide these brakes with stops of greater or less efficiency; but many forms of
controller now upon the market are incapable of conversion economically into
controllers equipped with electric braking appliances, and in other cases it is
impracticable commercially to equip the cars with electric brakes on account of the
cost. It is for such cases that I have designed my improved emergency stop.
It is to be applied to the reversing cylinder, and con-ists in two sets of contacts
adapted to short-circuit the motors without resistance. I accomplish this by
short-circuiting each motor upon itself independently; where this precaution is not
taken, it is impossible to apply the stop which I have devised to a car when running
backward or when one of the motors is cut out; as if the motors be (as it is
commonly called) "bucked" one against the other, one acts as a generator to drive
the other, and if one be open-circuited, there is no braking action; while if both
be rotated backwards, there is no resistance to the motion. This latter objection
becomes of great importance in cases where a car is running up hill and the power
suddenly fails or the brake gives out, or for any other reason the car runs away
backwards. Under such circumstances, if my improved emergency stop be on the
controller (it being entirely independent of the trolley circuit), the car may be
brought immediately to a standstill without the destructive racking which it must
receive when such a stop is applied while the vehicle is running at the speed which
it would attain while the motorman was going to the other end of the car to apply
the stop on the brake there. It is of course not designed to utilize the emergency
stop as an electric brake in any sense, as the current generated is altogether too
high for safety to the motors; but it is to be applied at times when the most
important consideration is the stoppage of the car, irrespective of any destructive
results that may occur from the stopping, as when there is danger to life, either from
persons on the track or from collision.
The accompanying drawings show embodiments of iny invention. Therein
Fig. 1 is a front elevation of a controller equipped with my improved stop, with
the cover partly broken away;
Fig. 2 is a plan showing the handle and the detent therefor ;
Fig. 3 is a side elevation, partly in section, of the parts shown in Fig. 2 ;
Fig. 4 illustrates the interlock between the controlling and the reversing

page_text: Fig. 5 is a diagram showing the cylinder or the reversing Swit
plane;
Fig. 6 is a diagram illustrating the motor conditions.
Referring by letter, A is the controller, C is the main controlling cylinder, B is
the handle thereof, D is the reversing switch, and E is its handle. The
peculiarity of the reversing switch, which is the only feature of novelty herein
In Fig. 2, E is
shown, is more fully illustrated in the drawings following Fig. 1.
the handle; E' is the segment over which the handle moves, provided with the
notch in its central position, which is the only one in which the handle may be
removed; this is an old device commonly practised. As my improved reversing
switch has, however, four positions, I provide two additional lugs upon the segment
marked E2, E. As will be observed, these lugs are bevelled upon one side only,
and have a radial surface upon the other. The object of this will be apparent from
an inspection of Fig. 3. The ordinary lug projecting from the reversing switch
handle E is in this figure replaced by a latch e working about a pivot and provided
with a spring el. From a comparison of the two figures, it will be seen that the
latch is free to pass the lugs E2, E2, but cannot return unless the motorman presses
The object
up the part against which the spring e¹ bears, so as to release it.
of this provision is to prevent the lunge of the car throwing the motorman against
the handle E with such force as to throw off the emergency stop. Ordmarily it is
applied by drawing the handle toward the motorman, as in the act of reversing the
car. This will permit the latch, as just pointed out, to pass the lug E², nearest to
the motorman, but when, as the car stops (which it does with great suddenness), the
operator is driven against the handle, yet the brake will not be thrown off until he
is ready to permit it.
Referring to Fig. 4, I illustrate the details of the interlock between the
controlling cylinder and ny improved reversing switch. The cam G co-operates
with the pawl F, provided with the bolt F' registering with the notch fin a disc
or collar Fupon the shaft of the controller cylinder. The cam is provided with
notches 9 to 1. When the cam roller upon the pawl F2 rests in either one of the
notches g¹, g³, in other words, in either the forwaid or the backward position, then
the controller cylinder may be rotated by the handle B, but when it rests in
either of the other notches, that is, in the position corresponding to the notch d³
upon the segment E', or when the han lle is so that the latch his passed either
of the lugs E, then the bolt F1 register with the notch and the controller
cylinder is locked against movement, thus preventing the accidental application of
the power.
Referring now to Fig. 5, I illustrate the contacts and circuits of my improved
safety appliance. 1 have lettered the fixed contacts or brushes 1 to 9, and the
movable o rotating contacts 10 to 33. The contacts 15 to 26 inclusive are those
ordinarily found upon the reversing switch cylinder of a two-motor controller, and
therefore will not be further described. The armatures of the motors are
lettered A', A2, and the fields MF, MF'. At CFI have indicated diagram-
matically the connections to the controller frame, S', S' are the cut-out switches
for the respective motors. In ordinary use, with the brushes upon the series of
contacts 15 to 18, the current would enter by the leads to the brushes 4 and 8, to
the contacts 16 and 18 respectively, thence through the motor armatures to the
contacts 15 and 17 respectively, and out through the fields, going in one case to
the controller frame which is grounded, and in the other case (depending upon the
connections from the controller) either directly to ground or passing through the
other motor. But when my improved stop is thrown on, the current passes, in
motor No. 1, from the armature to the brush 2, contact 10, then to brush 1, to the
switch S', the motor field MF' and to the controller frame, entering from the
In
controller frame to the contact 11, to brush 3 and back to the armature.
motor No. 2 it passes from the armature A² to the brush 6, contact 12. to brush 5,
through the motor field MF, switch S2, brush 9, contact 14, cross-connected to
The motors are thus
contact 13, thence to brush 7, and back to the armature.

page_text: each upon independent short-circuit, as shown in Fig. 6. With the car running in
the other direction, however, the series of contact-plates 27 to 33 is brought into
operation, and the circuit is, starting from the armature A³, to brush 3, contact 29,
cross-connected to contact 27, switch S¹, motor field MF', controller frame,
from the controller frame to contact 28, to brush 2 and back to armature.
motor No. 2, from armature A' to brush 7, contact 32, cross-connected to
contact 30, brush 5, motor field MF, switch S³, brush 9, contact 33. cross-
connected to contact 31, brush 6, and back to the armature.
In
It will be seen that this arrangement brings the current through the motor fields
in the same direction in every case, this being a necessary feature, as the reversal
of current in the field would demagnetize it and the motor would not act as a
generator in the short circuit.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
: -
1. In an electrically propelled vehicle, a controller, and a cylindrical switch
therein provided with four series of contacts, two of such series designed for
the normal operation of the motors in running forward or backward, and the
other two series arranged respectively to connect the motors each in an independent
short circuit, the oue series when running forward, the other when running
backward.
2. In an electrically propelled vehicle, a controller, one or more motors operating
the vehicle, and a cylindrical switch in the controller provided with contacts and
cross-connections adapted to reverse the relation of armature and field in the motor
or motors, and to throw the motors upon short-circuit without resistance in
whichever direction the vehicle may be moving.
3. In an electrically propelled vehicle, a controller, one or more motors operating
the vehicle, a switch co-operating with the controllers and adapted in its normal
positions to determine the direction of motion of the vehicle, contacts upon the
Switch arranged to connect the motors each in an independent short-circuit, the
contacts being arranged in two series, one designed to operate in the forward
motion of the car, the other in its backward motion; and interlocking means
between the controller and the switch, whereby the controller is free to move when
the switch is in one or the other of its normal positions, and is locked against
motion in its other positions.
4. In an electrically propelled vehicle, an auxiliary switch designed to act as a
reversing switch in its normal operation, two series of contacts other than the
reversing switch contacts carried thereon, such contacts adapted to short-circuit
the motors upon a local circuit to act as an emergency stop, a handle for the
auxiliary switch, and locking means for the handle so arranged that the handle
may be thrown to the end of its stroke in either direction, but will be locked
against accidental displacement after being thrown.
Dated this 1st day of August 1895.
J. C. CHAPMAN.