Improvements in the System of Circuit Control for Electric Machines.
Year: 1894

page_text: Date of Application, 9th May, 1894-Accepted, 7th July, 1894
Improvements in the System of Circuit Control for Electric
Machines.
I, CHARLES ERVIN DAVIS, of Corner 39th Street and Stewart Avenue
Chicago, County of Cook, State of Illinois, United States of America, Gentleman,
do hereby declare the nature of the said invention and in what manner the same
is operated, to be particularly described and ascertained in and by the following
statement:-
My invention relates to electric starting devices for an electric motor or motors,
and consists in combining therewith mechanism whereby said starting device may
be also used to govern or control the current entering the motor at the same
time being combined with devices which automatically turn the motors, or one of
them, into a generator whereby current is produced at the expense of mechanical
energy which, being consumed, causes retardation and final stopping of the motor
or motors and connected machinery. It also consists of sundry details which
render the construction of the apparatus more effective and economical. These
are described in the following Specification and particularly pointed out in the
claims, being at the same time illustrated in the accompanying drawings, in
which:
Fig. 1 represents a diagramatic view of the starting device in its simpler form,
showing also automatic catch;
Fig. 2 shows a section of the roller or drum;
Fig. 3 shows a plan of same, also illustrating the retarding device;
Fig. 3 represents a detail of plunger with dash pot shown in Fig. 3;
Fig. 4 represents a diagramatic view of the controller and its connections to the
motor;
Fig. 5 shows a front elevation of a varied form of the controller, involving a
separate rheostat drum with a handle standing in one-quarter position;
Fig. 6 is a side elevation of same, showing handle in a central or off position;
Figs. 7 and 8 show diagramatic views of the connections of the controller when
two motors are used;
Figs. 9, 10 and 11 show diagramatic views of the temporary, short-circuiting
device for the motors, or one of them, and its relative location upon same.
Similar letters of reference indicate like parts throughout the several views.
Let A represent the ordinary controlling handle which in its off position stands
as is shown in Figs. 3 and 2. Let A' be the box or case in which the drum a
is located and journaled by the shaft A". Secured to the drum a are the circular
contacts B operating in conjunction with the stationary contacts C, the circuit
connection being established by auxiliary contacts C₁, these contacts being con-
nected by springs C" which in turn are mounted on stationary portions C3 of the
framework of the box, the object being to allow of a very large circular movement
involving nearly the entire circumference of the circle. The middle or off
position is shown by A in Fig. 2; thence in either direction, one direction being
to supply current from an extraneous source, such as the trolley wire, to the
motor or motors; the other direction being to so change the connections and
possibly eliminate the supply connection that the motors, or one of them, will
be transformed into a generator thereby abstracting power from the connected
machinery. To facilitate the holding of the drum a in its middle position, and
also to facilitate the accurate placing of same and keeping it from going too
far in either direction I provide a mechanical stop which, though stopping the
rum in exactly the center of its revolution, does not prevent it from being

page_text: moved from that position in either direction. Any of the well known devices
may be used for this purpose; I prefer the one shown in diagram in this figure
(Fig. 2) consisting in the notch d, roller d' and spring d".
When turning in one direction, preferably the one in which the motors are made
to generate current, it is not well to have the movement of the drum too free for
fear of over-application of the electric brake, allowing the generator to produce too
much current, tending to over-heat same. This prevent by placing a device
which will retard the action of the drum a when in its brake region, shown by a
dash pot D provided with plunger D' and lever D₁ to which the plunger is
attached, same being fulcrumed at d and also provided with a toothed segment d'
co-operating with a corresponding toothed segment secured to the drum. Fig. 3ª
illustrates the construction of the plunger D' showing a valve D³ by means of
which the plunger may be made to move one way with freedom.
Even with the retarding device just described it is found that sometimes it is
possible to over-apply the brake, in which case I provide a device shown at the
bottom of Fig. 1 whereby such over-application is rendered in. possible, consisting
in the magnet E with the armature E' and provided with a stop E" and retracting
spring E. The opposite end of the armature E' is beveled and forms a dog which
co-operates with the teeth E4, which teeth are located on a portion only of the
circumference of the drum a, being in such a position that when such drum is in its
brake region, as shown in the figure, the teeth are in proximity to the dog and
upon an over-charge of current through the magnet E the same will retract its
armature and entirely prevent farther rotation of the drum until the current
intensity has sufficiently subsided to allow the retracting spring E³ to withdraw it
from engagement with the teeth E. As indicated in Fig. 4 when compelling the
drum a to operate in both directions it is found necessary to duplicate the portion
which gradually removes the resistance indicated in this figure as a', together with
all the co-operating contacts indicated at c c, etc., the resistance in the circuit being
represented by R. To obviate the necessity of this duplication I have devised
means shown in Figs. 5 and 6 whereby the handle A and shaft All are provided
with two drums, the drum a below being rigid upon the shaft and the larger
drum a above being loose upon the shaft A", and provided at its lower extremity
with a bevel pinion f co-operating with a bevel rack mounted on a lever F and
and pivoted at the lower part of the case A' upon the shaft f" journaled in ears
shown at f3f3f3, the shaft A" stopping above the shaft f as shown in Fig. 6.
The shaft A is provided with a crank or cam co-operating with a long pin f
protruding from the lateral face of the lever F. This pin is locked by the
universal joint or block g' so that the motion of the cam or crank pin g is imparted
to the said block g' and in turn imparts its motion, swinging about the center of the
shaft to the pin f' as it moves in either direction from its middle position shown
in Fig. 6, the block at the same time sliding back and forth from about the center
of the pin, being shown in this position in Fig. 6 and in its extreme position in one
direction in Fig. 5, in which position it will be readily understood to have moved
the lever F to its central or upright position and therefore to have revolved the
drum a through one quarter more or less of its total movement in one direction,
being in fact the direction in which the above drum moves during application of
current from the extraneous source to the machine when used as a motor.
Referring now to the mechanism shown in Figs. 9, 10, and 11, it will readily be
understood that when the circuits of the motor are so changed that its rotation
will produce a current the relative connections of its armature and field and the
direction of the passage of current therethrough will have been changed or
reversed. I utilize this fact or law to operate a device which temporarily short-
circuits the motor after it has been converted into a generator to aid in the
quicker building up of its field. I have found that this action is almost instan-
taneous when so short-circuited, but when a large amount of resistance is in the
circuit the building up of the field is very much slower, and in some instances
too slow to derive the benefit in its operation. The alternate use of the machine

page_text: as a generator and motor is contemplated in the action of this device. In Fig. 9
let and indicate two compound-wound electro-magnets or solenoids, one of the
circuits being that of the field F of the motor, the other being the circuit of
the armature X. The connections are such that when the machine is used as a
motor the direction of the current is shown by the arrows in full lines, and when
the machine is used as a generator the direction of the current is indicated by
the dotted arrows, a suitable reversing switch being shown in the figure. In the
former instance it will be seen that the direction of the currents is opposite in
the windings of solenoid i, and hence neutralize each other, leaving this solenoid
inactive. The currents in the solenoid are all alike, rendering it active,
drawing down its core i¹ against its lifting spring and attached lever i³,
fulcrumed as shown, from the stop it, and by means of a flexible cord 1³, preferably
of insulating material, also withdrawing the lever i, swinging on its fulcrum
against its retractile spring 8, into the relative position shown in Fig. 10, in which
the hooks shown at interlock, being held in their interlocked position by the
retractile spring shown in both figures. It will now be readily understood that
when the current ceases to flow in the motor the said spring will again lift its
lever into its former position against the stop , in which position electrical contact
or communication will be established between the two levers 13 and 1 by means of
the split contacts indicated at 10. In this position they remain at rest until the
current again circulates through the machine. Let us suppose that in this instance
the current circulates through the machine "motor-wise," the two levers 3 and i
will now again assume the position shown in Fig. 10 and upon the current again
ceasing, electrical contact between these levers will be re-established. Let us now
suppose that the current circulates through the machine, which is at the time a
generator, in this instance the current will traverse the armature as indicated by
the dotted arrows in which case the magnet or solenoid will become inactive, and
the magnet or solenoid i will become active, drawing against its spring until the
hook has disengaged itself from the lever leaving same free to fly quickly
upward under the tension of the spring until stopped as by the flexible con-
nection, thus breaking the electrical connection between the two levers. One of
these levers is connected with auxiliary contacts k and k¹ upon the drum a and is
always open while the machine is used as a motor, being closed again at the instant
the machine is rendered a generator, so that the closure of the electrical contact
between the levers 3 and is of no avail and inactive until the drum a is turned in
the direction in which the machine becomes a generator, whereupon the circuit is
closed between k and k¹ which allows the machine to generate a current upon a
short circuit through the magnets i and ", levers and i, contacts k and k¹ and
connecting wires, and upon the increase of current up to a predetermined point this
circuit is automatically broken, the current continuing to flow out through the
controlling resistance, other devices, motor if there be one, etc., as will be herein-
after specified. The preferred location of the device in respect to the motor is
shown in Fig. 11, the location being such that the lines of force from a magnet, for
instance the magnet N of the motor or dynamo, will tend to rupture the arc formed
between the contact 10 and the lever iº.
It will be understood that when the connections are made as herein described,
and after the connections of both motors are altered so that they will both tend to
generate a current, it is difficult to know which will preponderate the other in
electro-motive-fr.ce and the constant opposition of the starting electro-motive-
forces retards the general action. The device located upon one of the motors
localizes the generation as between the two and eliminates almost entirely the time
element, its action being almost instantaneous. This latter feature is also true
when only one motor or electric machine is used. It being one of the primary
objects of the invention to transform or convert the electrical machinery which is
connected to the circuit controller from a motor, with its connections to the source
of supply, into a generator with or without such connection by the simple turning

page_text: of a handle in either direction from a central or middle position of rest, it will
readily be understood that the particular connections which obtain as between
such circuit controller and the motor or motors are material to the invention,
especially the particular circuit connections which obtain when circuit connections
are complete and connected to the source of electrical supply. For instance,
when acting as motors the machinery or motors which the electrical controller
supplies may be either coupled in series or in multiple, or successively in
both relations, or the machinery may consist in one motor with two armatures
or a single armature with two windings which are respectively coupled in
series or in multiple, it simply being important to the present invention that
by the moving or turning of the handle the circuit relations are such that
they are respectively transformed from motors into generators, or at least one
of such machines (provided there are more than one) be so transformed,
and the currents so generated are led through a controlling resistance, together
with other devices, which is preferably handled by the same handle, so that starting
with the middle position the farther such handle is turned the more of such
resistance is cut in or out, preferably the latter. In this regard it may be pointed
out that it is not necessary that the controlling handle above referred to should be
connected with a rotating shaft, but the electrical contacts may be placed upon a
sliding block or a swinging arm and the handle may simply vibrate back and forth
in either direction from its central position or region of movement.
The contacts operating upon the drum a" will be readily understood by former
reference to the upper half of the diagram in Fig. 4. The circuit connections will
now be more fully described, when either one or two motors are employed, and
may be pointed out as follows. Referring to Fig. 4 let X represent the armature
and F the field. Suppose now the drum be turned in the direction applying
current from an extraneous source to the motor and the direction indicated by the
arrows, the current would flow from the trolley partially through the contact c
and a and partially through resistance R to the right hand brush, through the
armature, out of the left hand brush to contact c¹ into contact plate b to contact b¹
by internal connection, then to contact " by wire to reversing switch, thence
through field F in the direction of the arrow, returning to the reversing switch
and to contact c³, to the plates 61 and 63, to contact c¹ and to the ground G. The
direction traversed by the current through the field will be determined by the
position of the reversing switch as will be readily understood. For convenience
the reversing switch and resistance R are duplicated in the drawing but in practice
this is not found necessary. Let us suppose now that the drum is turned in the
opposite direction. Here we will see that the trolley contacts and a¹ to the left
are inactive. Supposing now that the machine generates and that the current
flows through the field in the same direction as before, by following the arrows it
will be seen to pass through the reversing switch, thence through the magnet E
for the purpose above referred to, thence into the left hand brush through the
armature, out of the right hand brush through the resistance or contact a', thence
by contacts cc, etc., and plates bl¹, etc., to contact c8, thence by reversing switch
to the field F by the connections indicated, current flowing also in the direction
indicated by the arrows. In this instance the current will be seen to have travelled
in opposite direction through the armature the wires passing to the left from both
armature and field, being open-circuited and inactive. The connections of the
drum a in Figs. 5 and 6 are represented in Figs. 7 and 8, the opportunity being
taken to illustrate the connections where two motors are used, it being readily
understood that in this case both may be treated as a single motor in exactly the
same manner as last above described, but it is preferred that one of the motors act
as a generator and the current so generated be conducted through the other motor
which at the same time is so changed as to circuit relations that it will tend to
oppose the motion of its armature or other moving part thereby utilizing the
currents flowing through the system in a two-fold mauner, and at the same time

page_text: require but a very small resistance at R. Fig. 7 is an ultra-diagramatic view for
the purpose of rendering the circuits more easily traceable. Suppose now the
handle A. being turned to the left, shown in its position in Fig. 5, the connections
are supposed to be as indicated in full lines in Fig. 7 wherein the current will flow
from the trolley through the resistance where it will divide, passing through each
of the motors as indicated by the arrows in full lines, whereupon if the handle A
be turned to the right the connections will be indicated by the switch arms in their
positions shown in dotted lines, in which case the motors are coupled in series.
including the controlling resistance R, the connections to the extraneous source of
supply being broken and the current will flow in the same direction as before
through the armature X', as indicated by the full arrows at this point; thence to
contact plate and resistance R, right hand brush of armature X through the
armature in opposite direction to the current heretofore as indicated by the dotted
arrows, thence to the field F which was the starting point. These connections are
also shown in Fig. 8 in their true relation to the drum a with the addition of the
complete connection of the temporary short-circuiting device described and shown.
in Figs. 9 and 10, the circuits being easily traced as last above described by the
direction of the arrows. The addition of the controlling resistance K to the
device described whereby the full control of the application of the brake is
permitted while employing only one of the motors as a generator is one of especial
value and utility.
It will readily be understood that the windings on the coils i and iª may be
coupled in shunt of the armature and field circuit as well as in series, or these wires
may constitute a combination of series and multiple of each branch and yet fulfil
the functions above referred to, or each magnet such as i¹ might be replaced by
two separate magnets pulling at the opposite ends of the core or the opposite ends
of the walking beam or lever, constituting thereby a system of magnets repre-
senting the two windings and ultimate effect of which would be the same as of
those herein described. I do not therefore care to limit myself to the particular
coupling herein shown.
The use and operation of my devices have been pointed out in the description,
and require therefore no separate treatment.
It will be observed that certain devices such as switches, connections, etc., have
been omittted from the circuit at various places for the sake of simplicity and
clearness their use being generally understood by those versed in the art to which
this invention appertains.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
1 claim is ;-
-
1. The method of variably retarding or checking the motion of motors normally
coupled to the feed circuit in pairs, together with a variable resistance for the
operation of such motors, consisting in breaking the supply circuit, connecting the
motors in series on a local circuit including said variable resistance, and then
causing said resistance to be regulated to suit the requirements in regulating or
varying said retardation, as herein shown and described.
2. The method of variably checking the motion of motors normally coupled to
the feed circuit in pairs, together with a variable resistance for the operation of
such motors, consisting in breaking the supply circuit, connecting the motors in
series on a local circuit, the coupling being such that the electro-motive force of
the two motors acting through said variable resistance though unequal are
normally opposed to each other, said local circuit including said variable resistance
and regulating such resistance to vary the said checking of the motion, as herein
shown and described.
3. The method of arresting or checking the motion of motors normally coupled
to the feed circuit in pairs, consisting in breaking the supply circuit, connecting the
motors in series with each other, closing a short circuit upon one of the motors,

page_text: and causing the said short circuit to be automatically opened by an electric current,
as herein shown and described.
4. The method of variably retarding or checking the motion of motors as herein
shown and described.
5. A circuit controlling device substantially as described and shown in Figs. 5, 6,
and 8.
6. The combination with a system of electric control herein shown and described,
of the device shown and described with relation to Figs. 9, 10, and 11.
7. The herein described apparatus for controlling electric motors for the purpose
and in the manner set forth.
Dated this 9th day of May 1894.
DAY, DAVIES & HUNT,
321, High Holborn, London, W.C., Agents for the Applicant.