Improvements in or relating to Apparatus for Controlling and Governing Electric Motors.
Year: 1897

page_text: Date of Application, 23rd June, 1897
iComplete Specification Left, 16th Apr., 1898-Accepted, 28th May, 1
.1898
[Communicated from abroad by: HARRY G. DAVIS, of Pittsburg, in the State of
¡Pennsylvania, United States of America, Electrician.]
1
Improvements in or relating to Apparatus for Controlling and
Governing Electric Motors.
I, REGINALD BELFIELD, of '82, Victoria Street, in the County of London,
Electrician, hereby declare the nature of this invention to be as follows:-
The invention relates to apparatus for controlling and governing electric motors,
and is particularly applicable to devices for use with motors for operating elevators
and hoists.
An important teature of the invention consists in an improved construction of
starting, stopping, and reversing switch for use with compound and shunt wound
motors by means of which the direction of rotation of the motor can be reversed
without breaking the circuit including the shunt coil and armature of the motor.
Another feature of the invention consists in the construction of a resistance.switch
which is so arranged that when the circuit 'is made the resistance will be
automatically and gradually reduced until all the resistance has been cut out,
after which the device for operating the switch is itself cut out.
In order that the nature of the invention may be clearly understood I
will proceed to describe by way of example how it may be carried into practical
effect.
The improved starting, stopping, and reversing switch preferably takes the form
of a drum rotatably mounted in suitable bearings. Said drum is made of
insulating material and has secured to its periphery metallic strips which are
adapted to engage with fixed-contacts supported on the base piece of the switch,
the construction being similar to the well-known .controllers for electric motors.
The fixed contacts form the terminals to which the armature and starting
resistance, shunt, coil, and mains are connected. According to the present
invention, however, the movable contacts on the drum are so arranged and
connected that in every position of the drum, the terminals of the armature circuit
will be in electrical connection with the terminals of the shunt coil; at the same
time by rotating the drum in its bearings the current through the armature can be
reversed without reversing the current through the shunt 'coil, so that the
direction of rotation of the motor will be reversed. Means are preferably provided
whereby at the time of the reversal of the current through the armature
resistance is temporarily inserted in the armature circuit so that the passage of
excessive current through the shunt-coil is avoided.
1.
The improved construction of resistance switch for gradually diminishing the
starting resistance is as follows::-A series of resistances is provided and so
arranged in connection with the switch lever that the movement of said lever cuts
out or short-circuits. the resistances in succession. The said lever is adapted to
be maintained in its limiting position when all the resistances have been cut out by
means of an electromagnet included in the motor circuit. The means for operating

page_text: the switch lever to reduce the resistance preferably comprise a solenoid having
a core attached to a lever pivoted concentrically with the switch lever and so
located relatively thereto that when the core is drawn into the solenoid the switch
lever is rotated so as to reduce the resistance as herein before described. When
all the resistance has been cut out the solenoid itself is shortcircuited by reason
of a contact which is made by the said lever. The operating lever is then
restored to its initial position by means of a spring, the switch lever being
maintained in its limiting position by the magnet as hereinabove described.
Suitable means, such as a dash pot attached to the core of the solenoid, may
be provided for retarding the movement of the switch lever if desired.
It will be understood that the invention is not limited in its details to the
.construction hereinabove described since these may be varied to a considerable
extent without departing from the spirit and scope of the invention. The improved
construction of resistance switch is also applicable to any ordinary type of electric
motor.
Improvements in or relating to Apparatus for Controlling and
Governing Electric Motors.
I, REGINALD BELFIELD, of 32, Victoria Street, in the County of London, Electrician,
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:
The invention relates to apparatus for controlling and governing electric motors,
and is particularly applicable to devices for use with motors for operating
elevators and hoists.
An important feature of the invention consists in an improved construction of
starting, stopping, and reversing switch for use with compound and shunt wound
motors by means of which the direction of rotation of the motor can be reversed
without breaking the circuit including the shunt.coil and armature of the motor.
Another feature of the invention consists in the construction of a resistance switch
which is so arranged that when the circuit is made the resistance will be auto-
matically and gradually reduced until all the resistance has been cut out, after
which the devices for operating the switch is itself out out.
In the accompanying drawing :-
Figure 1 is a plan view of my improved stopping, starting and reversing
switch.
Figure 2 is a transverse section on line x, x, of Figure 1.
Figure 3 is a diagram of the controller switches and circuits.
Figure 4 is a plan view of the variable resistance and the controlling mechanism
therefor, the flange at the front side of the top of the frame being broken away in
order to more clearly disclose the operative parts of the device.
Figure 5 is a front elevation of the resistance and the controlling switch therefor.
Figure 6 is a vertical section taken on line y, y, of Figure 5.
Figure 7 is a similar view to Figure 2 illustrating a modified constraction.
Referring now particularly to Figures 1, 2, and 3- of the drawings, 1 is a base
provided with bearings 2 in which is mounted a shaft 3. This shaft has rigidly

page_text: mounted upon it a drum 4 provided with contact strips, 5, 5ª, 6, 6, 7 and 7
The contact strips 6 and 7 are electrically connected as are also the strips 6ª and
7, and the strips 5 and 5* extend completely around the drum. Suitable stationary
contacts 8 engage the contact strips above referred to. The spaces between the
strips 6 and 7 and between the strips 6 and are of such a width that they are
bridged by. the corresponding stationary contacts 8, as the drum. is rotated. Upon
the drum near the respective ends thereof, are mounted contact pieces or arms 9
and 9 which project some little distance thorefrom: These engage. respectively
with stationary contacts 10 and 10": Each of the contacts 10 and 10° is partially
surrounded by the pole pieces 11 of an electromagnet, the coil 12 of which is
included in the main circuit. The object of these magnets is to rupture any arcs
which may be formed when the circuit is interrupted by the separation of the
contacts 9 and 10 and 9 and 10%. Said magnets may, however, be dispensed with
if desired.
The operation of this switch will be hereinafter more fully described in connection
with that of the other controlling devices.
-
Referring now to Figures 4, 5, and 6 in connection with Figure 3, 13 is a
resistance column monnted in a frame 14 and comprising six elements or parts
a, b, c, d, e, and the ends of which are connected to two sets of stationary
contacts 15, 16; 17 and 18, and 19, 20, 21, and 22, arranged in the arc of a circle
on the frame 14. 28 is a bell crank lever, pivotally mounted upon a bearing stud
or post 24, projecting from the frame 14. The free end of the short arm of
lever 23 is provided with an armature 28 and the free end of its long arm is pro-
vided with a long contact brush 25 which is of sufficient length to constitute a
conducting bridge between two stationary contacts which are not in the same set
and which are separated by two or more intervening contacts. An auxiliary
contact brush 26 is mounted upon lover 23 and is electrically and mechanically
joined to the brush 25. The brush 26 is so.located with reference to the brush 25
that it will make contact with a stationary contact piece 27, when the resistances
are all shortcircuited. A second bell crank lever 29 is pivotally mounted upon the
stud 24, independently of the lever 28.
The inside of the long arm of the lever 23 is provided with a lug 23, and the
adjacent side of the corresponding arm of the lever 29 is provided with a
corresponding lug 29* located behind the former. The long arm of the lever 23
is connected to the frame 14 by a coil spring 30, and the corresponding arm of
lever 29 is connected to the frame by a similar spring 30º. A stop lug or post 31
projects from the frame 14 in position to be engaged by the lever 29 when it is
retracted by its spring.
A solenoid 82 is mounted upon the frame 14 and, as shewn in the present
instance, a portion of its casing forms an integral part of such frame. A small
magnet 33 is mounted above the solenoid 32 in position to attract and hold the
armature 28 when the latter is brought within its magnetic field. The core 34
of the solenoid 32 is loosely attached at its upper end to the free end of the adjacent
arm of lever 29 by a slot and pin connection. The rod 24", constituting a con-
tinuation of core 34, extends through and is fastened to a dash pot plunger 35,
which is provided with passages 35. A thin metal disc 35b, having one or more
small holes 35° is loosely mounted upon a bushing 35d which surrounds the lower
end of rod 84*. The dash pot cylinder 36 contains a suitable liquid for retarding
the movement of the core by the solenoid:32.
It will be understood from this construction that when the circuit through the
controller is closed the solenoid core will be attracted and therefore moved down-
ward. The rapid movement of the solenoid core which would otherwise result is
prevented by the dash pot, the disc 35 being moved upward by the liquid in
cylinder 36 to close the passages 35 when the solenoid core is moved downward,
and thus preventing the passage of the retarding liquid, except through the small
openings 35. As the lug 29 on the lever 29 is behind the corresponding lug 23 on
the lever 23, the former will engage the latter and gradually move the brush 25

page_text: over the stationary contacts 15-22. When the limit of the stroke is nearly
reached, the armature 28 will be within the field of the magnet #83. The further
*movement of the lever 23' which serves to bring the auxiliary brush. 26 into engage-
ment with the stationary contact 27, will therefore be effected by the magnet 33.
The solenoid 32 being shortoircuited by means of the brush 26 and the contact
27, the core 84 will be released and the retracting spring 30 will draw the lever 29
and the core 34 back to their original positions, the movement: being comparatively
rapid on account of tlie opening of the passages 85 by the depression of the
disc 35. As the magnet -33 remains in circuit, it will hold the brushes in the
position to which they were moved by the solenoid 32 until the main circuit is
interrupted.
The operation of the entire apparatus is as follows:-Assuming that the parts
of both switches are in the positions indicated diagrammatically in Figure 3 of the
drawings, and the motor, to be controlled and its load therefore at rest, if the
shaft 3 be turned by any convenient means, so that the contact strips 6 and 6* are
brought into engagement with the corresponding stationary contacts 8 and the
contact arms 9 and 9 into engagement with the respective stationary
contacts 10 and 10", as indicated in Figures 1 and 2 the circuit through the motor
will be closed and the course of the current will be as follows:-Through the
conductor 37, the coils 12 of the.-arc-rupturing.magnets:the stationary contact 10°,
the contact arm 9, the contact strips.7 and 6, the stationary contact 8 in (engage-
ment with the latter, the motor armature 38, the magnet 33, the solenoid 32, the
stationary contact 22 of the resistance switch, all of the resistance 13, the stationary
contact 18, back to the contact strip 6 through the corresponding stationary
contact 8 across to the contact strip 7 and thence through the contact:arm 9, the
stationary contact 10, and out through the series winding 39 of the motor field
*magnet.
Where a motor having a compound wound fleld magnet is employed, as indi-
cated in the drawings, the shunted current passes from the contract strip 9 to
the strip 5º, thence to the corresponding stationary contact.18, 'through the shunt
winding 40 of the motor, to the strip 5 and tlience out through the contacts.9 and
10 and the series winding.39.
By reason of the construction of the reversing switch herein before described,
whereby the middle contact fingers 8 are always in contact with either the strips
6 and 16 or the strips 7 and 7, the circuit which includes the shunt winding 40,
the armature 38 and the resistance switch is maintained permanently closed, all
danger of breaking down the insulation of the shunt winding being thus sub-
stantially avoided. This is an important feature since the opening of the shunt
oircuits of compound and shunt wound motors by the switches heretofore employed
bas frequently been productive of material injuries to insulation. It will be ob-
served however that in one position of the drum the strips 7, 6 and 7,6ª are
directly connected through the brushes 8 being wide enough to bridge the insula-
tion between the ends of the strips that is to say the motor armature will be
short circuited through the shunt coil if the resistance 13 has not been re-in-
serted. To avoid such an occurrence and consequent injury to the insulation of
the shunt winding the brushes 8 may be made in two parts as shewn at 48, 49
Figure 7 separated far enough to bridge the gap between the contact strips on the
drum the two parts of the brush are connected through a resistance.50 which takes
the armature discharge at the time of reversal.
As soon as the current has started through the course above indicated, the
solenoid 32 will obviously draw down its core against the action of the retracting
spring and the dash pot, and by reason of the inpinging of the lug 29 on the lever
29 against the corresponding lug 23, on the lever 23, the contact brush will be
.moved over the stationary contacts in such order that in its second position it will
bridge the contacts 16 and 19. When in this position, the current will pass
through the resistances fe, and d, the stationary contacts 19, the ibrush, the

page_text: resistances b and a, and thence to the stationary contact 8 in engagement with the
strip 6, and so on as above indicated, the resistance c being short-circuited.
In the third position the brush will bridge the contacts 16 and 20, and the
resistances c and d will be shortcircuited. In the fourth position, the brush will
bridge the contacts 17 and 20 and resistances b, c and d will be shortcircuited. In
the fifth position, the contacts 17 and 21 will be bridged and the resistances b, c, d
and e will be shortcircuited. In the sixth position, the contacts 18 and 21 will be
bridged, and the resistances a, b, c, d and e, will be shortcircuited, and in the
seventh and final position the contacts 18 and 22 will be bridged and all of the
resistances will be shortcircuited, the current passing directly through the brush.
When the brush has reached this position, the auxiliary contact brush 26 will
engage with the stationary contact 27, and the current, which has previously
passed through the large solenoid, will shortcircuit this coil and pass from the
auxiliary stationary contact. 27 through the two brushes to contact 18 and out.
When the brushes have been moved to their final positions, the armature 28 will
rest upon the top of the smaller coil 33 and will be held in that position by said
coil, but the larger coil being shortcircuited, the core 34 will be released and its
lever 29 will be retracted to its original position by means of the retracting
spring 30, the brushes being retained in position for shortcircuiting the resistances
by means of the small coil 83.
If it be now desired to either stop the motor or to reverse its movement, the
dram 4 will be rotated in the reverse direction to that above specified. The main
current will thus be interrupted by the separation of the contacts 9; 9, and 10, 10³.
The lever 23 and its brushes being released, they will be quickly returned to their
initial position by the action of the retracting spring.
If it is desired to reverse the direction of rotation of the motor, the drum will be
rotated still further in the direction last indicated until the contact strips 7 and 7ª,
and the arms 9, 9 are brought into contact with the corresponding stationary
contacts and 10 and 10, when the current will pass through the arc-rupturing
magnets the contacts 10 and 9ª, the strip 7", the corresponding stationary contact.8,
the contact 18 of the resistance switch all of the resistances beginning with the
resistance a and ending with the resistance f, to the stationary contact 22, through
the solenoid 32, the coil 33 and through the armature in the reverse direction to
that before described, thence to the strip 7, the arm 9, stationary contact 10 and
out through the series winding 39 of the field magnet. The course of the current
and the operation of the resistance switch will thereafter be the same as before
described, except that, the current will be at all times in the reverse direction
through the solenoids and the armature of the motor..
It will be seen from the construction and operation of the apparatus described
that the maximum amount of resistance is in oircuit with the motor at the start, as is
necessary in the starting of electric motors undor load; that such resistance is
slowly and automatically reduced until the maximum speed is attained, and that
the slowly moving means for securing this automatic reduction of the amount of
resistance in circuit is then retracted out of the way of the arm of the switch, so
that the latter may quickly return to its initial position when the circuit is
interrupted. Another advantage incident to the construction described is that the
large, switch-actuating solenoid which is included in series in the circuit, during
the reduction of the resistance, is shortcircuited when the resistance has been all
removed and consequently the resistance of its many turns of fine wire is removed
from the circuit and the amount of effective current for use in operating the motor
is thus materially increased beyond what it would be if this coil remained in
oironit.
While I have shown and described a specific construction of apparatus, I desire
to be understood that variations in the form of the same and in the details of
construction of the various parts may be made without departing from the spirit
and scope of the invention.

page_text: It will also be understood that the invention is not limited to the control of
motors having compound wound field magnets.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is:-
1. For compound or shunt wound electric motors, a switch by means of which
the direction of rotation of the motor can be reversed without breaking the circuit
consisting of the armature and shunt magnet coil.
2. For use with electric motors a starting resistance, which is automatically and
gradually reduced by means of a magnetically operated switch, the operating
magnet being itself shortoircuited as soon as the resistance attains its minimum
value.
3. For use with electric motors a starting, stopping and reversing switch
constructed and operating substantially as described with reference to Figures 1, 2
and 3 of the accompanying drawings
4. The modification of the starting, stopping and reversing switch, wherein the
brushes for the armature contacts are each made in two parts connected by a
resistance substantially as and for the purpose specified.
5. A starting resistance constructed and operating substantially as described
with reference to Figures 4, 5 and 6 of the accompanying drawings.
Dated this 16th day of April 1898.
W. P. THOMPSON & Co.,
Of. London, Liverpool, Manchester, and Birmingham,
Patent Agents for the Applicant.