Improvements in Controlling Switches and Apparatus for Electric Motors.
Year: 1899

page_text: Date of Application, 20th Mar., 1899-Accepted, 23rd Sept., 1899
COMPLETE SPECIFICATION.
Improvements in Controlling Switches and Apparatus for Electric
Motors.
I, REESE HUTCHISON, Electrical Engineer, of 65, North Commerce Street,
Mobile, Mobile County, Alabama, 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:-
My invention is especially useful in the electric propulsion of wheeled vehicles,
such as street cars and auto-mobile road vehicles as well as in the operation of
stationary motors.
The object of my invention is to automatically control the switch employed to
vary the strength of current in the motor circuit and to prevent a careless or
ignorant operator from injuring the motor by introducing excessive strengths
of current or abruptly varying the current.
My improvement differs from any automatic controlling or locking device for
similar purposes heretofore known or described in that it normally holds the
switch locked so that it cannot be changed from one contact position to another
unless the predetermined safe strength of current is present; I thus obviate the
possibility of turning the switch to any desired point by the expedient of first
opening the circuit at a separated point, then moving the controlling switch and
then closing the circuit at such separated point as has sometimes been done in
the attempt to evade the control of such automatic apparatus.
I provide a toothed ratchet fixed on the movable portion of the switch and a
pivoted dog normally engaging the ratchet, an electro-magnet controls the dog;
this magnet is in a normally open circuit; the circuit has two break points, one
operated by a relay adjusted to respond to a predetermined strength of current,
located in the main circuit, the second break point is closed by the movable
member of the motor-switch during a part of its excursion and while it is desirable
to maintain automatic control. This last named break point may, however, if
preferred, be done away with and the circuit maintained permanently closed at
the described point. I provide hand operated switches for use in emergencies, as.
for instance, when necessary to feed current to a car to avoid collision or to pull
another car on the track. Each such switch has a severable seal to operate as
a "tell-tale " in case such switch has been used; I also provide for mechanically
and forcibly disengaging the dog from the toothed ratchet, this apparatus con-
sists of a cam-shaped lever in position to engage the surface of the dog and force
it away from engagement with the ratchet.
The accompanying drawings illustrate my invention.
Fig. 1 is a diagrammatic representation of the apparatus and circuits as applied
to a vehicle traveling upon rails. Fig. 2 shows essential parts of the well-known
series multiple motor-controller with the cam-shaped lever and its operating
handle to force the dog out of engagement with the ratchet.
S is a supply circuit connected with a source of electricity; T is a trolley or
collecting device connecting the motor circuit on the moving vehicle with the

page_text: supply circuit S; M is an electric motor and W a car wheel, propelled by the
motor, through which wheel the return circuit is completed. It is to be under-
stood that the source of electricity may be stationary with respect to the motor
and controller and that these moving connections may then be dispensed with.
E is a multiple-contact motor controlling switch of which the well-known series
multiple car controller is a type; it employs a series of sections of artificial resis-
tance a, b, c, connected, respectively, to a series of fixed contacts 2, 3, 4, and 5;
while 1 is a dead or open contact. The movable contact of the switch is repre-
sented by the radial arm A, operating to make contact successively with the
fixed contacts 1 to 5. Circuit normally passes from S, via T, 21, 22, 23, to the
motor M, 24, and W, to the return circuit. The strength of current in the
motor is determined by the amount of artificial resistance in circuit, and the
counter electro-motive force of the motor which varies with its speed of rotation,
as is well known.
I provide an automatic locking device, normally locking and holding the
switch at rest during intervals of no current and of excess of current, the switch
being freed by a controlling electro-magnet during the establishment of a pre-
determined intermediate safe strength of current only. In this locking device,
w is a toothed ratchet wheel fixed to the movable contact A of the switch E.
A dog 8 is pivoted at 6; a spring s holds the dog 8 normally in contact by engage-
ment with a tooth of the ratchet w. n is an electro-magnetic device in the form
of a solenoid with its core pivoted to dog 8 at 7; when magnet n is energized
dog 8 is drawn out of engagement with wheel w. The coils of magnet n are in
a local circuit like 30, 31, 32, in which circuit are two separate break points con-
trolled by the movable contact A of switch E and by an electro-magnet m. On
switch E there is a fixed contact B, arc-shaped, and in extent equal to that of
the points 2, 3, and 4, of the switch; this limits the unlocking operation of the
device to the conditions existing when the switch is in danger of being operated
to the detriment of the motor; for no harm can be done to the motor while
contact A is on point 1, and circuit is open; or when contact A is on point 5, and
the only possible change of the switch would result in a reduction of current
strength in the motor circuit. The coils of magnet m are in the motor circuit;
the core or armature of m is retracted by a spring u having its force regulated
by the adjusting screw v, so as to close the contact points 19, 20, during the
existence of a predetermined safe strength of current, but to be overcome and
permit of opening said contact points during any excess of current beyond the
predetermined amount. It will thus be seen that with an interval of no current
magnet n is, of course, de-energized, and dog 8 locks the ratchet w; with an
excess of current the circuit of magnet n is opened at 19, 20; and with a pre-
current the circuit of magnet n is opened at 19, 20; and with a predetermined
intermediate strength of current magnet m permits the spring u to close points 19,
20, while current is present and available to operate magnet n.
The operation is as follows; Switch arm A is, as shown, upon point 1, no
current flows in the motor circuit to operate magnet m or n, although points 19,20
are closed by spring u; the dog 8 engages the surface of the wheel w; arm A
is now moved to point 2; dog 8 locks it against further movement by engaging
with the first tooth of wheel w; an excess of current is flowing in the motor
circuit, and magnet m quickly draws in its core, the points 19, 20, are separated.
magnet n can get no current although the circuit 30 is connected to the circuit 21
by the arm A resting on B. As motor M speeds up, its counter electro-motive
force decreases the current in the motor circuit to the predetermined safe point
and the spring u closes points 19, 20, against the force of magnet m, the circuit 30,
31, 32, is closed at both points, magnet n draws in its core and separates dog 8
from wheel w. Arm A is now free to be moved to point 3 where the same action
last described takes place, provided the load on the motor is so great as to prevent
the motor from speeding up sufficiently to take the next two points in succession
without excess of current. The controller is not necessarily locked on each

page_text: point, the locking depends entirely upon the load upon the motor; thus, an un-
loaded car can be safely fed much faster than when heavily loaded. A device.
to hold the controller for a given length of time upon each point is useless when
the load is variable. This device acts in accordance with the load upon the
motor. A motor-man used to feeding current to his car at approximately the same
rate when heavily loaded as when light does the damage when the car is heavily
loaded or slow to pick up speed. Points 3 and 4 are caught if the current is in
excess at these points. If a car is up to speed and the current shut off by rapidly
moving controller to the "off" position, current can be rapidly fed again by the
controller, the arm not being locked until possibly at a point in the last part of
the rotation the current may become excessive, due to probable loss of speed
during the interval of time when current is shut off and then fed again. Thus
a motor-man shutting off current temporarily at a crossing, can quickly bring his
handle around to full speed position without interference from the locking device.
Hence no headway is lost by an unnecessary detention of the handle. When the
arm A is moved to point 5 circuit of magnet n is broken between A and B and the
unlocking device is out of action; the dog 8 rides on the periphery of wheel w.
On the reverse movement of arm A current is constantly decreased.
In time of emergency, as when necessary to pull another car on the track or
avoid collision, it is desirable to feed current to the motor more rapidly than the
locking device would permit. So to cut the action of said device out when neces-
sary, I provide a pivoted hand switch 50 in position to connect the wires 30 and 31
across the break points 19, 20; this switch is normally held open by a severable
seal 51, consisting of a short section of soft metal, connecting a fixed point with
the switch arm; when the switch is operated the seal is broken and an account
thereof given to the manager or employer. For the same purpose, a switch may
be located, as shown at 52, in position to connect the conductors 22 and 23 so that
the coils of the magnet m may be completely cut out of circuit; this switch is
similar to that last described and has a similar severable seal 53. In other words,
switch 50 may be arranged as shown at 53 and do the same as when at 50. I
have shown an arrangement in Fig. 2 for mechanically cutting the locking device
out by forcibly removing the dog from contact range with the teeth of the
ratchet. The magnet n is shown, its armature connected with the dog 8 in
position to engage the ratchet wheel w. The cam lever L is fixed to a vertical
spindle journaled in a bearing in the case of the controlling switch. The
spindle has an operating handle H and there is a severable seal 60, such as
a length of soft copper wire, which is passed through registering holes in the
spindle and in the bearing therefor b and sealed; when the handle H is turned,
the wire is cut and the lower surface of the cam lever L engages the upper surface
of the dog 8 and forces the point thereof out of engagement with the teeth of the
ratchet w. Either of these emergency devices may be used, as only one is
necessary.
"
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The arrangement of an electric motor, an electric circuit, a motor switch for
varying the current strength in said circuit and means for normally locking and
automatically controlling the movement of said switch.
2. The arrangement of an electric motor, a suitable circuit, a switch for vary-
ing the strength of current in the motor coils, an automatic lock for said switch
and an electro-magnetic device to control said lock, said electro-magnetic device
being connected with the motor circuit and so adjusted that upon the establish-
ment of a predetermined strength of current the switch is released, substantially
as described.
3. The arrangement of an electric motor, a suitable circuit therefor, a multiple
contact motor switch for varying the strength of current in the motor coils, an

page_text: automatic lock, normally holding the switch at rest, and an electro-magnetic
device connected with the motor circuit operating to release the switch upon the
establishment of a predetermined strength of current only.
4. The arrangement of an electric motor, a circuit therefor, a multiple contact
switch to vary the strength of current in the motor, a lock to normally hold the
switch in any contact position, with magnets and circuits to operate said lock,
substantially as described.
5. The arrangement of an electric motor, a motor circuit therefor, means for
varying the effective strength of current in said circuit, including a multiple
contact switch, an automatic electro-magnetic locking device for holding said
switch in any contact position and means for disengaging said locking device by
directly and mechanically displacing the movable member thereof, substantially
as described.
6. The arrangement of the motor, a controlling switch, a lock normally engag-
ing and holding the switch and electro-magnetic devices to release the switch as
shown and described.
7. The arrangement of an electric motor, a circuit therefor, a multiple contact
switch to vary the strength of current, a lock in position to normally hold the
switch; magnets and circuits to operate said lock and hand switches arranged,
substantially as described.
Dated the 20th day of March 1899.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.