Improvements in Methods of Regulating Electrically Driven Mechanism and Apparatus for Putting the same Operation.
Year: 1892

page_text: Date of Application, 30th July, 1892-Accepted, 22nd Oct., 1892
COMPLETE SPECIFICATION.
Improvements in Methods of Regulating Electrically Driven
Mechanism and Apparatus for Putting the same
Operation.
into
We, WALTER H. KNIGHT, a citizen of the United States residing at
Newton, County of Middlesex, State of Massachusetts United States of America,
Electrician and WILLIAM B. POTTER a citizen of the United States residing at
Lynn, County of Essex, State of Massachusetts United States of America,
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 regulation of the power and speed of mechanism driven by electric motors
that are connected in circuit having a constant potential or pressure has always
been a source of much difficulty and loss. Under such circumstances it is necessary
for securing a rate of power and speed below the maximum, either, first, to reduce
the pressure delivered at the terminals of the motor by means of an artificial
resistance, or second, to diminish the effect of the pressure delivered at the
terminals of the motor by increasing the counter pressure which the motor would
naturally produce at such speed. Of these two methods the former is most
commonly employed, but it involves an extravagant loss due to the fact that the
current must pass through an artificial resistance before entering the motor, and
the heat which is generated in such a resistance is entirely lost, and this loss
becomes greater as the speed becomes less and the load increases. The second
method of regulation entails practically no loss of energy, but the limits within
which it may be applied are quite narrow, inasmuch as any given motor cannot
be made to produce a widely varying counter pressure without at the same time
changing its speed. In fact the only known method of varying the counter pressure
of a motor without change of speed is to vary the strength of its magnetic field, and
this method is applicable only within narrow limits if the motor is to operate without
injury.
In view, therefore, of the loss entailed by the first method, and the limited range
of the second method, it has been proposed to employ two separate motors for
driving the mechanism and thus secure the good results of the said second method
with at the same time a great increase of range, by placing the two motors in series
for slow speed and then changing them to multiple connection for higher speeds.
By doing this the two motors may be adapted to operate at a maximum speed when
in multiple, and then by changing them to series connection their counter pressure
for the same speed will be doubled, or what is the same thing, the counter pressure
remaining the same, the speed will be reduced one half without any loss occurring.
This method, known as the "series-multiple" method of regulation with its
inherent advantages has been proposed heretofore, and its characteristics have been
perfectly understood theoretically, but to our knowledge no one has succeeded in
carrying it into practice in a satisfactory manner. The principal difficulty in the
way of making a satisfactory application of this method appears to have been that
it is impossible to make the change of connection from series to multiple and
vice versa while the current is still passing through the motors without forming such
arcs at the contact points as would speedily disintegrate them and render the
apparatus unreliable and subject to rapid depreciation. For overcoming this
difficulty a number of plans have been suggested; for instance it has been proposed
that at the moment of making the change the circuit should be interrupted either
entirely or by the interposition of a considerable resistance, so that there should be
no current passing while the change was being made, and in consequence no arcs at

page_text: the contact points. It has also been proposed to effect the change by practically
killing the force of one motor by reducing the strength of its field magnetism until
it could be safely short-circuited and then placed in multiple with the other motor
with its magnetic strength restored to its normal point.
Such expedients, however, have not proved practical in view of the
complications thereby introduced, and also in view of the fact that while the
change was in progress there would be a break in the speed of the mechanism
occasioned by the withdrawal of all or at least one half of the motive power.
We have discovered after a long series of experiments that it is possible to short-
circuit one of the motors in series in a constant potential circuit without injury to
the motor even if the short circuit is maintained for a considerable length of time,
and also that such a short circuit could be interrupted without producing an arc
greater than can be easily dealt with. This may be explained on the theory that
although the motor may be short circuited and thereby has a tendency to become
a generator driven by the momentum of the mechanism and by the other motor,
and thus produce an excessive and injurious current within itself, yet such a
tendency is not permitted to take effect because it is necessary that there must first
be a reversal either of the armature or field magnet of the motor. As the arinature
connections are fixed, a reversal, if any takes place, must be in the field magnet
which involves the generation of such a current in the short circuit as will over-
power the magnetizing effect of the main current. Such a reversal cannot take
place until there has been a reversal of one of the parts of the motor.
The result
therefore is that the motor may be short-circuited with impunity and the short
circuit maintained during a practically indefinite period without any resulting
injury to the motor, and when such a short circuit is once established there
would be in it no such excessive current as would cause any serious are when it
is broken.
We make use of this discovery in our process of regulation which has proved
effective in practice and is now being utilized commercially. This method in
general consists in regulating the power and speed of mechanism driven by two
electric motors by placing the two motors in series for slow speed and changing
them to multiple connection for higher speed by first short-circuiting one motor
while its field magnet is still energized, and then disconnecting one terminal of
such motor and reconnecting it to the corresponding terminal of the other motor,
whereby the two motors will be in multiple with each other. We accomplish this
without the use of external means such as a circuit breaker or resistance to
interrupt or substantially reduce the current while the change is being made.
The method also involves the securing of additional rates of speed, first by a
comparatively small resistance only to be used at the instant of starting or when
the very slowest speed is required, and second by a modification of the field maguet
strength for the last or very highest rate of speed.
To carry out this method we make use of certain novel apparatus. This
apparatus is illustrated in the accompanying drawings in which
Figures 1 to 9 show in diagram the different connections made by the successive
steps in the regulation.
Figure 10 is a transverse section of the switch taken through one pair of contact
plates.
Figure 11 is a diagram of the switch connections.
Figure 12 is a plan of the switch.
Figure 13 is a longitudinal section on the line ay in Figure 10.
Figures 14, 15 and 16 show in detail the cam cylinder.
Figure 17 is a plan of the switch with the cover removed.
Figures 18 to 25 show in detail the connections for cach step in the regulation.
Figure 26 shows in diagram the method of applying the apparatus to an electric
street car.
Referring to Figures 1 to 9 it will appear that in the first position, with the
motors out of action, there would be two breaks in the circuit one between the

page_text: trolley T and resistance R, and the other between the armature Aa of the motor A
and the field Bf of the motor B. In the second step, Figure 2, the latter break
will be closed, there remaining only the break between the trolley and resistance.
In the second step the two combinations shown in Figures 2 and 3 will be produced,
the two breaks in the circuit being closed in succession and the motors being left in
series with each other and the resistance. In the third step the resistance is short-
circuited and the motors are in series as shown in Figure 4.
At the fourth step
the two combinations shown in Figures 5 and 6 are produced. At the fifth step
the combinations shown in Figures 7 and 8 are produced; and lastly at the sixth
step the combination shown in Figure 9 is effected. It will be apparent that with
these different combinations there will be five rates of speed, which is sufficient for
all practical purposes.
Turning now to the switch mechanism for producing these successive com-
binations, it will be found to consist first, of an enclosing metallic box or casing C
in which are placed a series of contact levers with their operating cam and the
blow-out magnets, and secondly a cover D for the case upon which are placed a
series of contact plates and circuit wires leading therefrom, with which plates the
levers are adapted to make connection. The contact plates on the cover are
arranged in pairs as shown in Figure 12. the pairs being marked 1 2,3 4,5 6, 78,
9 10, 11 12, 13, the last plate of the last pair being divided into two insulated
parts for a purpose hereinafter explained. The construction of these plates is
shown best in Figures 10 and 12, from which it will appear that they are placed
along opposite sides of a series of openings in the cover D and are provided with
small spring buffers E, the two buffers of each pair of contact plates normally
resting opposite each other but out of contact, and adapted to be forced apart by
the tip on the vertically moving rod V, the said tip being so shaped that when
the rod V is forced up by the pressure of the lever H it will be pressed between the
two buffers E spreading them apart and establishing a good electrical connection
between them. The upper surfaces of the contact plates 1 2, 34, etc. are ribbed
as shown in Figure 12, there being one longitudinal and two transverse ribs on
each. Of the transverse ribs one is midway between the two ends, and the other
is at the extreme end, forming a pointed tip as shown in Figure 12. The object of
this formation will be explained hereafter. The levers H, six in number (one for
each pair of contact plates,) are placed side by side as shown in Figure 17, and
have a common horizontal pivotal rod Q. To the end of each lever H is pivoted
a wooden rod V, adapted to move vertically in guides J, and each rod V carries a
tip which as has already been explained, is adapted to establish a connection
between one pair of contact plates. Each of the levers N is provided with two
short arms on opposite sides of the pivotal rods I, and embracing the cam
cylinder L. This cam cylinder is shown in detail in Figure 14 from which it will
be seen that the cams on the cylinder are arranged in a certain predetermined
order, and are adapted to engage with the arms K and thereby actuate the levers H
positively in each direction. The arms K have small friction rolls against which
the cams bear. It will also be noted in Figure 14 that the cams are 12 in number
two being provided for each lever H, one for each of the arms K respectively. It
will be apparent from the description thus far given that by turning the cam
cylinder L the rods V will be thrown up in a predetermined order remaining each
a predetermined length of time and being positively withdrawn at a predetermined
instant. The blow-out magnet M for interrupting any arc which may be formed
between a pair of contact plates is best illustrated in Figures 10 to 17. It con-
sists of two iron rods N extending through the box on opposite sides of the upright
pieces upon which are wound a series of spools O, the winding in any two
successive spoels being reversed so as to produce a consequent pole between them.
From these consequent polar points extend arched polar extensions P, having a
form indicated in Figure 10. These polar extensions reach through the cover D
of the casing to a point somewhat higher than the contact plates, and are faced
with thin strips of fibre Q, Figures 12 and 13. It is now possible to describe the

page_text: above mentioned formation of the contact plates. Referring to Figure 10, in
which the tip shown as establishing electrical connection between the two
buffers E of the contact plates 1 and 2, it will be evident that if a strong current
is passing between the two plates by means of the connection established by the
tip F, there would be an arc formed between the two buffers in the event of the tip
being withdrawn from its indicated position between them. As the blow-out
magnet is always energized so long as there is any current in the apparatus, the
two polar extensions P, each adjacent to the space between the two buffers,
instantly cause the arc to be forced upward and outward along the central ribs on
the upper surface of the contact plates until, if the arc is powerful, it will reach the
two extremities of the contact plates and there be extinguished by the continued
action of the magnet. If however, the arc is not a powerful one it will be broken
by the time it reaches the intermediate transverse ribs. Of course in action the
interruption of the arc takes place instantly and any burning or fusing takes place
on the ribs of the contact plates where it can have no bad effect. It has proved
in practice that there is practically no fusing even of the ribs and that the rupture
of the arc is so sudden and complete that the fibre plates Q are not even
blackened.
For operating the switch a shaft is provided forming an extension of the
cylinder L and is connected thereto by an insulating coupling S shown in
Figures 12 and 13. Electrical connection with the contact plates is made in any
desired manner, the connections being as indicated in diagram in Figure 11, while
in Figure 12 the actual connections to the contact plates are shown, there being
eight wires extending from the switch box.
The arrangement of cams on the cylinder L is such that during one complete
revolution the rods V are thrown upward in the order indicated by the series of
diagrams in Figures 18 to 25. In these figures the six pairs of contact plates
are numbered 12, 34, etc. while the circuit shown by the dotted lines is the one
including the coils. In the various figures the different pairs which are con-
nected by the tips Fare indicated. Thus in Figure 18 there are no connections
and the circuit is open. In Figure 19, 9 and 10 are connected. In Figure 20
1 and 2 and 9 and 10 are connected. In Figure 21, 1 and 2, 3 and 4, and 9
and 10 are connected. In Figure 22, 1 and 2, 5 and 6, and 9 and 10 are con-
nected. In Figure 23 1 and 2, 3 and 4, and 5 and 6 are connected. In Figure 24,
1 and 2, 3 and 4, 5 and 6, and 7 and 8 are connected. In Figure 25, 1 and 2,
3 and 4, 5 and 6, 7 and 8, and 11, 12, 13 are connected. These different figures
show the combinations made at each step in the regulation. Thus, referring again
to the figures, in Figure 18 the circuit is open at two points; in Figure 19 the
circuit is open between 1 and 2 and closed between 9 and 10; in Figure 20 the
circuit is as follows:-From trolley T to plates 1 and 2, to resistance R to
field Af, to armature Aa, to blow-out magnet, to plates and 10, to field Bf, to
armature Ba, to ground G, giving the combination indicated in Figure 3. In
Figure 21 the circuit is from the trolley T to plates 1 and 2, to plates 4 and 3, to
field Af, to armature Aa, to blow-out magnet, to plates 9 and 10, to field Bf, to
armature Ba, to ground G giving the combination indicated in Figure 4.
Figure 22, the circuit is from the trolley T to plates 1 and 2, to resistance K to
the field Af, to the armature Aa, to blow out magnet, to plates 5 and 6, to
field Bf, to armature Ba, to ground G, giving the combination shown in Figure 6
with the motor A, short-circuited by a connection through plates 9 and 10 to
ground G. In Figure 23, the circuit is from the trolley T to plates 1 and 2, to
plates 4 and 3, to field Af, to armature Aa, to blow-out magnet, to plates 5 and 6
to ground G giving the combination shown in Figure 7. In Figure 24 the circuit
is from trolley T to plates 1 and 2, where it divides, one branch going by plates 4
and 3 to field Af to armature Aa to blow out magnet, to plates 5 and 6, to
ground G, while the other branch goes by plates 8 and 7 to field Bf, to
armature Ba and to ground G, giving the combination shown in Figure 8. In
Figure 25 the circuit is from trolley T to plates 1 and 2, then dividing and one
In

page_text: branch going by plates 4 and 3 to field Af, to armature Aa, to blow-out magnet
to plates 5 and 6, to ground G with a sub branch going from plate 4 to plates 8
aud 7, to plates 11 and 12 to armature Aa and thence to ground as before,
establishing thus a shunt around the field magnet Af, containing resistance Y.
The other branch goes from plate 4 to plates 8 and 7, to field Bf to armature Ba,
and to ground at G, with a sub branch from plate 7 to plates 11 and 13, and by a
resistance to arinature Ba, to ground G, thus shunting the field Bf.
This gives
the last combination indicated in Figure 9. In Figures 18 to 25 we have shown only
the connections that are used at each step, but the connections as permanently
made are indicated in diagram in Figure 11, which it will not be necessary to
describe further.
In Figure 26 one of the convenient locations on a street car for a switch box
such as ours is indicated. The switch is operated by means of a shaft extending
in opposite directions from the cam cylinder L, and connected thereto by means of
insulated joints S. This shaft W extends longitudinally along the car and
terminates at each end in a bevel pinion. One of these pinions engages directly
with a similar pinion on the lower end of a spindle on the platform, while the other
pinion engages in a similar manner with a corresponding spindle on the other
platform by the intervention of a transverse shaft X.
It will be apparent that many forms of switching apparatus may be designed
for carrying the method which we have described above into effect, and while
we consider the apparatus described to be especially well adapted for the purpose,
yet we do not limit ourselves to this form as the only one capable of use in
carrying out our plan.
By
It will thus be seen that in the various combinations that we have brought about
by the successive connections established by the switch, we have first placed the
motors in series for slow speed as in Figure 4, and then short-circuited one motor
as in Figure 6, then disconnected the inner terminal of the short-circuited motor,
as shown in Figure 7, and finally reconnected the said terminal to the corre-
sponding terminal of the other motor, as in Figure 8 so that the two have
gradually been shifted from series to multiple connection. In addition we have
modified the action of the two motors while in their respective connections by
means of resistance R when they were in series, and by shunting their field
magnets when in multiple and thereby secured additional rates of speed.
this plan we only use a resistance when the current is at a minimum, the motors
being in series, but when a greater amount of current is required by the motors
in multiple we do not use a resistance but rely upon a change in their field
magnet strength to attain the last degree of regulation, thereby avoiding loss in
resistance. It must also be noted that the combinations shown in Figures 5 and 6
are effected almost simultaneously the object of reinserting the resistance being
to have it take the place for a short period of the short circuited motor, and
preserve the other motor from being injured by a sudden excess of current, and
it is not intended and does not in effect act to cause a material decrease of the
current so that the change of connections shall take place while the circuit is
substantially opened.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is: :-
1. The method of regulating the power and speed of mechanism driven by two
electric motors, which consists in placing the two motors in series for slow speeds
and changing them to multiple connection for higher speeds by the method
described by first completing a circuit around one motor while its field magnet is
still energized, and then shifting the connections, as set forth.
2. The method of regulating the power and speed of mechanism driven by two
electric motors, which consists in placing the two motors in series for slow speed
and changing them to multiple connection for higher speed, and securing additional

page_text: rates of speed by modifying the action of the motors both before and after the
changes in connection, substantially as described.
3. The apparatus for regulating the power and speed of mechanism driven by
two electric motors, consisting of a series of contact plates and connections there-
from to the motors, with means for establishing and interrupting the electrical
connection therewith, so as to change the motors from series to multiple arc, and
means for establishing a magnetic field adjacent to the contact plates, so as to
interrupt any are that may be formed on the rupture of the circuit.
4. The apparatus substantially as herein described consisting of a series of
switch levers, and a cylinder having a series of cams arranged to operate the
switching levers in a predetermined order, the said apparatus being so connected in
the circuit of two electric motors as to successively change them from series to
multiple arc connection.
Dated this 30th day of July 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W C., Agents for the Applicants.