Improved Means for Supplying and Controlling the Supply of Power to Electric Motors.
Year: 1898

page_text: Date of Application, 30th Nov., 1898-Accepted, 4th Mar., 1899
COMPLETE SPECIFICATION.
Improved Means for Supplying and Controlling the Supply of
Power to Electric Motors.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by Andrew L. Riker, of the City, County and State
of New York, United States of America, Electrical Engineer,) and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement:-
In the operation of electric motors it is frequently found necessary or desirable
to quickly stop the motor or the mechanism driven thereby, or both, by the appli-
cation of suitable brake devices. At such times the source of power should be
cut off from the motor immediately, but through the carelessness or excitement
of the operator this is liable to be omitted with resultant damage to the motor
and the driven mechanism. In a like manner great damage is liable to result
from overloading the motor, as, for example, when the wheels of a motor-cycle
become stuck in the mud or when a serious obstruction is encountered by any of
the moving parts.
In case the power has through any agency been cut off from the motor, con-
siderations of safety for the operator and the machinery render it imperative that
when the power is again admitted to the motor it should not be at its full,
maximum strength, but should be gradually increased from the zero or minimum
point until any desired rate of speed for the motor is secured.
One object of this invention is to avoid the difficulties due to overloading of
the motor, or the failure of the operator to cut off motive power from the motor
on the application of the brakes; and a further object is to render it impossible
when power has been cut off, to resupply the motor with power except by com-
mencing at the zero or minimum point and increasing until the desired motive
power has been reached.
With these objects in view the invention consists in providing means whereby
power will be automatically cut off from the motor when the brake is applied or
the motor is overloaded, and in combining with the said automatically operated
cut-off means whereby power may be restored to the motor only by commencing
at the zero or minimum point and increasing to the extent desired.
Figures 1 and 2 of the accompanying drawings are diagrammatic views shewing
the parts of the controlling mechanism in different positions which they may
assume.
Figure 3 is a side elevation of the controller and cut-off switch with the con-
troller in position to close the switch and at the same time cut off the current;
Figure 4 shews the switch closed and the controller in position to turn on the
current; and
Figure 5 shews the switch open and the controller in position to leave the
current on.
Referring to Figures 1 and 2, A indicates an electric motor, B a source of

page_text: electricity, as a battery, for supplying power to the motor, C is a controller for
regulating the supply of current to the motor, C is the controller lever, and D) is
a switch in the circuit F, the said switch having the stationary jaw or member d
and the pivoted or otherwise movable member . The switch is held closed
against the tension of the spring r by a latch G engaging the latch pin g on
the pivoted member d¹. S is a solenoid, the heavy wire of the main circuit F
making a limited number of turns around the core w thereof, and thence to the
battery B. The course of this main circuit is from the battery B, the motor A,
the switch D, the controller C around the solenoid S, to the battery.
Connected to the movable member of the switch D is a fine wire f which
passes with a large number of coils around the solenoid core w and thence to a
contact point e, and from a second contact e¹ to the battery.
E is a pivoted brake-lever having connected thereto, but insulated therefrom,
a metallic contact plate E¹ wiping across the two contact points e e¹ when the
brake lever is in position to apply a brake (see Figure 2) but normally occupying
a position in contact with but one of the said points as shewn in Figure 1. H is
a lug or arm on the controller C, and d² is a cam projection on the movable
part of the switch 1), the relative positions and proportions of the arm and
cam being such that the arm H by impinging on the cam d² when the controller is
rotated, closes the switch against the spring r and permits the catch G to drop
over the latch pin g.
In the position of the parts shewn in Figure 1, the switch D is closed so that
current may pass therethrough to the line F but the parts are so arranged that
when the arm H wipes the cam d² as in Figures 1 and 3 the controller C occupies
a position which completely shuts off current, that is, it is at the zero point. In
the position of the parts shewn in Figure 2 the controller is in position to allow
a strong current to pass therethrough but the switch D is open. In neither case
can power reach the motor.
Referring now to Figures 3, 4 and 5 it will be seen that in the position shewn
in Figure 3 the switch is closed but the controller is at the zero position. In
Figure 4 the controller has been turned from the zero position, and the switch D
being closed, the circuit through the main line F is complete from the battery to
the motor. The core of the solenoid is so weighted that the normal current
passing over the line F and around the solenoid just serves to balance the core.
If now the motor should be overloaded from any cause, the consequent excess of
current from the battery passing over the main line F would advance the core w
of the solenoid and lift the latch G, as shewn in dotted lines in Figure 5, per-
mitting the switch arm to fly open under the stress of the spring whereupon,
the circuit being opened, the solenoid w and the latch G would drop back to the
position shewn in full lines in Figure 5. In this position of the parts the con-
troller C is in position to permit current to pass to the motor if the switch 1) were
closed, but to close the switch D the controller must be turned to the position
shewn in Figure 3, that is to the zero point, and after the switch is closed the
controller may. then be returned to admit current to the motor, as shewn in
Figure 4. It will thus be seen that if the switch D is open it is necessary, before
it can be closed, to turn the controller to the zero position, so that when the
switch is closed again no current can reach the motor till the controller is operated
for that purpose.
Assuming that the switch D is closed and the controller in position to admit
current to the motor as in Figure 4, and the brake E be in the position shewn in.
Figure 1, the current passing in the main line F to operate the motor would
hold the core w of the solenoid balanced, and no current passes over the fine wire f.
If now this brake lever E be moved from the position shewn in Figure 1 to
that of Figure 2 the contact plate E¹ wipes over both contact points e e¹ and a
portion of the current on the main wire F will pass to the battery through the
fine wire f. But this current by reason of the fact that the fine wire has many
more coils around the solenoid than the wire F, will act to advance the core wand

page_text: lift the latch G, as shewn in dotted lines Figure 5, and permit the switch D to
open. The parts would then occupy the position shewn in Figure 2, it being under-
stood of course that the exact position of the controller is immaterial, except that
it is turned to admit current to the motor.
If now the brake lever E and the contact plate E¹ be permitted to return to
the position shewn in Figure 1, the other parts will remain as in Figure 2 with
the switch 1 open and the controller in position to permit current to pass. Before,
however, the switch D can be closed it is necessary to turn the controller C
back to the zero position, upon which the arm H strikes the cam d² and closes
the switch as shewn in Figure 1.
It will thus be seen that upon the imposition of an overload or the throwing
of a brake lever the switch D is opened, cutting off the current from the motor,
and that in either case, the controller must be returned to the zero position in
resetting or closing the switch D, thereby rendering it impossible to so close the
switch as to suddenly readmit a heavy current to the motor, with its attendant
ill effects.
The cut-off which acts upon the imposition of an overload or the throw of the
brake-lever, is shewn as the switch D), but manifestly the form of cut-off may
vary with the form of motor employed. The controller is also indicated by the
star C, it is however wholly immaterial what form the controller may assume,
the essential feature being that some form of cut-off operates with some form of
controller, the two being so arranged with relation to each other that the cut-off is
restored to its operative position only by throwing the controller to the zero or
minimum power supply position.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I claim
is:
1. The combination with an electric motor, and means for supplying current
thereto, of an automatic cut-off device rendered operative upon the application of a
brake, substantially as hereinbefore described.
2. The combination with an electric motor, and means for supplying current
thereto, of an automatic cut off device rendered operative upon the application
of an overload, substantially as herein before described.
3. The combination of an electric motor, a current supply therefor, and auto-
matic means for opening the circuit upon the application of an overload, sub-
stantially as herein before described.
4. The combination of an elèctric motor, a current supply therefor, and auto-
matic means for opening the circuit upon the application of a brake, substantially
as hereinbefore described.
5. The combination of an electric motor, a current supply therefor, a switch in
the supply circuit, means tending to open said switch restraining devices normally
holding the switch closed, and means releasing the said switch and permitting it
to open upon the imposition of an overload, substantially as herein before described.
6. The combination of an electric motor, a current supply therefor, a switch in
the supply circuit, means tending to open the said switch, restraining devices
normally holding the switch closed, and means releasing the said switch and
permitting it to open upon the application of a brake, substantially as herein-
before described.
7. The combination of an electric motor, a current supply therefor, a switch in
the supply circuit, a spring tending to open the switch, a latch holding the switch
normally closed, and automatic trip mechanism operative upon the imposition of
an overload, substantially as herein before described.
8. The combination of an electric motor, a current supply therefor, a switch in
the supply circuit normally held closed against spring tension by a latch, a
solenoid having coils forming a part of the supply circuit, a core in the solenoid in
proximity to said latch, the said core being balanced by the passage of the normal

page_text: working current but advancing to lift the said latch upon the passage of an
increased current, substantially as hereinbefore described.
9. The combination of an electric motor, a current supply, a controller therefor,
a normally closed switch in the supply circuit, automatic means for opening the
said switch, and means automatically operated solely by the controller to close the
said switch, substantially as described.
10. The combination of an electric motor, a current supply, a controller therefor,
a normally closed switch in the supply circuit, automatic means for opening the
said switch and means automatically operated by the controller to close the said
switch only when the former is in the position of zero or minimum current supply,
substantially as hereinbefore described.
11. The combination of an electric motor, a current supply, a controller therefor,
a switch in the supply circuit normally held closed against spring tension by a
latch, a solenoid with coils forming a part of the current supply circuit, a core in
the solenoid and in proximity to the switch latch, the said core being weighted so
as to be balanced by the normal working current, a light wire connected to one
member of the switch and passing in coils around the solenoid and thence to the
latter, a break in the said fine wire, and a switch closing the said break upon the
turn of the brake lever, substantially as herein before described.
12. The combination of an electric motor, a main circuit therefor, an automatic
electro-magnetically controlled switch in the said circuit, the said switch operating
to open the circuit upon the application of a brake or overload, a controller in
the said circuit connected with the said switch and operating to close the same
only when the controller is in the zero or normal position, substantially as herein-
before described.
Dated this 30th day of November 1898
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C.,
Agents.