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Патент USA US2114704

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April'19,'1938.
'
1.. 1.. CUNNINGHAM ET AL
MULTIPLE ELECTRICAL PROPORTIONING
7
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Filed-July 25, 1935
'
2,114,704
SYSTEM
'
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2' Sheets-Sheet‘ l
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CZarerzce Wlléasall
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April 19, 1933-
v1.. L. CUNNINGHAM ET AL'
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2,114,704
MULTIPLE ELECTRICAL PROPORTIONING SYSTEM
Filed July 25, 1935
2 Sheets-Sheet 2
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C‘Zarerzce 771.7 lkfesselZ
‘2,114,704
Patented Apr. 19, 1938
mUNlTED ‘ STATES PATENT I OFF-ICE
2,114,704
' MULTIPLE ELECTRICAL PBOPOBTIONING
SYSTEM
'
LewisL. Cunningham, Minneapolis, Minn, and
- Clarence W. Nessell, Forest Park, Ill., assignors
to Minneapolis-Honeywell Regulator Company,
Minneapolis, Minn, a corporation of Delaware
Application July 25, 1935, Serial No. 33,070
14 Claims. (Cl. 172-239)
The present invention relates ‘to an electrical ‘is the provision of an electrically balanced or
electrically operated follow-up or proportioning
proportioning or follow-up system of the elec
trical follow-up type that is so arranged that a system which is so arranged that a number of ,
plurality of follow-up mechanisms or motor motor means may be simultaneusly and concur
rently controlled from a single controller, the 5
6 means may be concurrently controlled by a sin
electrical arrangement of'the system being such
gle controller, the arrangement being such that
each follow-up mechanism or motor means posi
tively moves to a position corresponding to the
that the various motor means cannot get "out
position oi.’ the controller, it being impossible for
for any length of time.
of-step” or at least cannot remain “out-of-step” .
,
More speci?cally, an object of the present in- 10
vention is the provision of an electrical follow-up
system or proportioning system in which each of
10 the follow-up mechanism or motor means to be
come “out-ot-step" for any length of time.
Electrical proportioning or follow-up systems
a plurality of follow-up mechanisms, each com
prising a balanced electromagnetic means, con
tact means, motor means and balancing react- l5
ance means, is electrically interconnected with
suitable impedance means in ‘such manner that
of this general character have been in use for a
period or time. In one such type, the motor
16 means is controlled by a pair of normally equally
energized electromagnetic _ coils,
or a center
tapped coil, which control suitable switching
its particular electromagnetic means can only be
balanced by the action 01 its own associated bal
ancing impedance means, even though a plural- 20
ity of such systems are directly connected to a
single controlling variable reactance means.
A further object of the invention is the pro
mechanism. The energizations of the electro
magnetic coils or o! the two portions of the cen
20 ter-tapped coil have been controlled by the con
joint operation of a controlling potentiometer
and a balancing potentiometer, the former being
operated in any desired manner, either auto
matically or manually, and the latter being op
vision of a multiple proportioning system in which
a single potentiometer controller directly controls 25
25 erated by the motor means. -
It is often desirable to control two or more
of such motor means or follow-up mechanisms
‘from a single controller or control potentiometer.
In the electrically balanced systems of the type
30 herein above described, it has been impossible to
have a single controller directly control two or
more such follow-up mechanisms since they
could get “out-of-step" so that the positionsyo!
the various follow-up m
or motor
35 means did not correspond to the podtion of the
controller.
a
-
In order to obtain a somewhat similar result,
has been usual practice to have one follow-‘up
mechanism or motor means operate a control
40 ling potentiometer tor a second motor means, as
well as operate its own balancing potentiometer.
In this manner, a number of follow-up mecha
nisms could be hooked up in tandem. This sys
tem, however, has its objection in that the move
45 ments 01 all the motor means is not simul
taneous, there being a considerable 'delay be
tween movement of the first and last i! any con
siderable number of motor means were so hooked
up in tandem.
50
‘
I
An object of the present invention, therefore,
a plurality of balanced relay means, the ener
glzations oi the balanced relay means being main
tained in balance by the action of associated
balancing potentiometers driven by motor means
controlled by the relay means, suitable imped- 30
ances being so associated with the individual re
lay means and balancing potentiometers as to
insure that each relay means will ‘only be re
balanced upon movement oi‘ the motor means,
which it controls, to the position demanded by 35
the controlling potentiometer.
The system of the present invention is, particu
larly adapted to temperature control systems, and
the like, and will be explained in detail in con
nection with such a system.
_
40
Further objects of the invention will be found
in the drawings, the claims and the detailed
description.
The term “impedance” as used in the speci?ca
tion and claims is intended to mean any device 45
or apparatus by which the flow of electrical cur
rent may be varied, and particularly resistance or
inductance.
For a more complete understanding of the
invention, reference may be had to the following 60
2
.
2,114,704
detailed description and accompanying drawings,
in which:
Fig. 1 is a digrammatic showing of the limi
tations of the type of system heretofore used.
Fig. 2 is a diagrammatic showing, similar to
Fig. 1, but disclosing the fundamentals oi’ the
system of the present invention, and
Fig. 3 is a diagrammatic showing of a complete
application of the present invention.
Referring ?rst to Fig. 1 of the drawings, there
10
is diagrammatically shown the fundamentals of
the manner in which a pair of electrical follow
up systems of the type now utilized in the art
would be connected in parallel to a single con
15 troller.
The single controller is, shown compris
ing a resistance I8 and a cooperating control con
tact II. The balancing mechanism of a ?rst
follow-up system is indicated by the ?rst balanc
ing resistance I2 and ?rst balancing contact ?n
ger I3. Associated with this balancing resistance
I2 is a pair of protective resistances I4 and I5.
Similarly, the balancing mechanism of the second
electrical follow-up mechanism is indicated by
a second balancing resistance I6 and a cooperat
25 ing balance contact I'I. Associated with the
balancing resistance I6 is a pair of protective re
sistances I8 and I 9. The ?rst electrically bal
anced follow-up system additionally includes a
pair of series connected electromagnetic coils 28
' and 2| whereas the second electrically balanced
2|, 22 and 28 are equally energized. Under these
conditions, as is well-known in the art, the motor
means which controls the balancing potentiom
eters in electrical follow-up systems of the type
referred to herein would be deenergized and the
balancing potentiometers would remain sta
tionary.
Now, if the control contact II were moved to
the dotted position wherein it engages the ex
treme right-hand end of control resistance I8, 10
electromagnetic coil 2| of the ?rst follow-up
mechanism would be completely short-circuited
except for the inclusion of protective resistance
I5. This partial short-circuit is as follows: from
the junction of electromagnetic coils 20 and 2 I ,wire
48, wire 41, wire 45, wire 43, control contact II,
wire 28, wire 3|, protective resistance I5, and wire
32 to the right hand end of electromagnetic coil
2|. Similarly, the electromagnetic coil 23 of the
second follow-up mechanism would be complete 20
ly short-circuited were it not for the protective
resistance I9. This substantial short~circuit is as
follows: from the junction of electromagnetic
coils 22 and 23, wire 41, wire 45, wire 43, control
contact | I, wire 28, wire 36, wire 39, protective re
sistance l9, and wire 40 to the right-hand end of
electromagnetic coil 23. The electromagnetic
coils 20 and 22 are therefore more highly ener
gized than electromagnetic coils 2| and 23'and
the two follow-up systems should be operated 30
follow-up system includes a pair of series con
so as to move their respective balancing contacts
nected electromagnetic coils 22 and 23.
I3 and I‘! along their balancing resistances I2
Electrical power is shown as being furnished and I6 towards their left-hand ends to cause re
by a step-down transformer 24, having a high balancing of the energizations of the two sets of
,
.
35 voltage primary 25 and a low-voltage secondary electromagnetic coils.
35
26. It will be noted that the control resistance
However, assume that for some reason the
I8 and the ?rst balancing resistance I2 are com
balancing contact I ‘I of the second follow-up
nected in parallel with each other by wires 21 and mechanism did not operate or remained sta
28 and are connected in parallel with the series
tionary, and that the balancing contact I3 of the
40 connected electromagnetic coils 28 and 2|, first follow-up mechanism was moved to the 40
through protective resistances I4 and I5, by wires dotted position shown wherein it engages the ex
29, 38, 3| and 32. Wires 33 and 34 connect the treme left-hand end of its associated balancing
secondary 26 to the wires 38 and 32 so that the resistance l2. Under these conditions, electro
electromagneticcoils 28 and 2|, in series, are con
magnetic coil 28 is substantially short-circuited,
nected
across the secondary 26 and the control complete short-circuiting being prevented by
45
45
resistance I8, as well as the ?rst balancing re
reason of the inclusion of protective resistance
sistance I2, are connected across the secondary I 4, This partial short-circuit is as follows: from
26 through the protective resistances I4 and I5. the junction of electromagnetic coils 28 and 2|,
In "a similar manner, the control resistance I8 '
‘ is connected in parallel with the second balanc
50
ing resistance I6 by means of wires 21, 28, 35 and
36. Also, this control resistance I8 and the second
balancing resistance I6 are connected in parallel
with the series-connected electromagnetic coils
55 22 and 23, through protective resistances I8 and
I3, by wires 31, 38, 39 and 48. Wires 33 and 34,
and wires 4| and 42 connect the series-connected
electromagnetic coils
22 ’ and
23 across the
secondary 26 and also connect the controlre
wires 48, 41, wire 45, wire 44,‘ balancing con
tact I3, wire 23, protective resistance I4, and
wire 38 to the left-hand end of electromagnetic
coil 28. Likewise, the electromagnetic coil 22 is
substantially completely short-circuited, com
plete short~circuiting being prevented by reason
of the inclusion of protective resistance I8. ,‘I'his
partial short-circuit is as follows: from the junc
tion of electromagnetic coils 22 and 23, wire 41:,
wire 45, wire 44, balancing contact I3, wire 36,
wire 31, protective resistance I8, and wire 38 to
sistance I8 and second balancing resistance I6, [the left hand end of electromagnetic coil 22.
through the protective resistances I8 and I3, Electromagnetic coils 28 and 2|, and electromag
across the source 01’ power 26.,
The control contact II, the ?rst balancing con
tact I8, the second balancing contact II, the'
junction of electromagnetic coils 22 and 23, and
the Junction of electromagnetic coils 28 and 2|
are all interconnected by means of wires 43, 44,
46, 46, 41 and 48.
With the parts in the full line position wherein
the control contact I I, the ?rst balancing contact
70 I3 ‘and the second balancing contact H are re
spectively engaged with the mid-portions of con
trol resistance I8, the ?rst balancing resistance
I2 and the second balancing resistance l6, ltwill
be evident that all or the electromagnetic coils 28,
76
netic coils 22 and 23 are now equally energized,
and will be equally energized with control con
tact II and balancing contact I3 in the dotted
positions shown irrespective of the position of
balancing contact II. It is therefore obvious that
the energizations, oi’ the two sets of electromag- .
netic coils can be balanced out where two of the
present type of electrically balanced follow-up
systems are connected in parallel with a single
controller, even though only one balancing po
tentiometer has been operated to the proper
position. In fact, upon inspection of the system
of Fig. 1, it will be seen that the electromagnetic '
coils will beequally energized whenever any one
3
2,114,704
of the contacts ll, l8 and I1 is in one extreme
position and any other of these remaining con
tacts is in the opposite extreme position. There
fore, it will be seen that there is no manner of
positively providing that the two or more elec
trically balanced follow-up systems will remain in
proper step or proper relation to the position
of the control contact ll.
Turning now to Fig. 2, there is a diagrammatic
10 showing of the fundamentals of the system of the
present invention. In the showing of Fig. 2, a
single controller is indicated by the control re
sistance 55 and the cooperating control contact
5|. A first balancing mechanism is indicated by
the balancing resistance 52 and the associated
balancing contact 53. The ?rst balancing fol
low-up system further includes a pair of series
connected electromagnetic coils 54 and 55. A
second balancing mechanism is indicated by a
20 resistance 55 and a cooperating balancing con
tact 51. Associated with the balancing resist
ance 55 and balancing contact 51 is a pair of
series-connected electro-magnetic coils 58 and 59.
A source of power is indicated by the step-down
25 transformer 55‘ which is provided with a high
voltage primary GI and low voltage secondary
52. The control resistance 55 and-the two sets
of series connected electro-magnetic coils 54 and
55 and 55 and 59 are all connected in parallel
with each other and across the secondary 52 by
wires 53, 54, 55, 55, 51 and 55. The balancing
resistance 52 is connected in parallel with its
associated series-connected electromagnetic coils
54 and 55, through protective resistances 59 and
35 15, by wires 1|, 12, 13 and 14.
Similarly, the balancing resistance 55 is con
nected in parallel with its associated series-con
nected electromagnetic coils 55 and 59, through
protective resistances 15 and 15, by wires 55, 11,
40 15, 58, 19 and 55. The junction of electromaga
netic coils 54 and 55 is connected to the associ
ated balancing contact 53 by a wire 5| and is
also connected to the control contact 5|, through
a resistance 52, by wires 83 and 54.
In a like
manner, the junction of electromagnetic coils 58
and 59 is connected to the balancing contact 51
by a wire 55, and is connected to the control con
tact 5|, through a protective resistance 55, by
means of wires 51 and 85.
50
Again, with the parts in the position shown
in Fig. 2, it will be evident that the energize.
tions of the electromagnetic coils 54 and 55 and
,58 and 59 are equal. If the control contact 5|
.is moved to the dotted position shown wherein
65 it engages the extreme right hand end of con
trol resistance 55, electromagnetic coil 55 will be
substantially completely short-circuited, com
. plete short-circuiting being prevented by the re
sistance 52. This partial short-circuit is as fol
00 lows: from the junction of electromagnetic coils
54 and 55, wire 53, resistance 52, wire 54, con
trol contact 5|, wire 51 and wire 58 to the right
hand end of electromagnetic coil 55. In a simi
lar manner, electromagnetic coil 59 will be sub
65
stantially completely short-circuited, complete
short-circuiting being prevented by reason of
the resistance 55. Thispartial short-circuit is
as follows: from the junction of electromagnetic
coils 55 and 59, wire 51, resistance 85, wire 85,
70 control contact 5|, and wire 51, to the right-hand
end of electromagnetic coil 59.
Now assuming that the balancing contact 53
moves to the dotted position wherein it is en
gaging the extreme left-hand end of its associ
75 ated balancing resistance 52 and that the bal
ancing contact 51 remains stationary, electro
magnetic coil 54 will be substantially completely
short-circuited, complete short-circuiting being
prevented by reason of the protective resistance
59. This partial short-circuit is as follows: from
the junction of electromagnetic coils 54 and 55,
wire 5|, balancing contact 53, wire 12, protective
resistance 59, and wire 1| to the left-hand end
of electromagnetic coil 54. By properly propor
tioning the protective resistance 59 and the re
10
sistance 52, the electromagnetic coils 54 and 55
will now be equally energized.
Because of cer
tain other circuits involved, this equal energiza
tion of electromagnetic coils 54 and 55 is not ob
tained by having the resistances 59 and 52 of 15
equal value.
While the energization of electromagnetic coil
58 is changed upon movement of the control con
tact 5| to the dotted position and movement of
the balancing contact 53 to the dotted position, 20
the energizations of electromagnetic coils 55 and
59 are not made equal. For instance, in trying
to trace a shunt circuit for electromagnetic coil
55 through its associated protective resistance
15, it will be seen that this shunt circuit is as 25
follows: from the junction of electromagnetic
coils 55 and 59, wire 85, balancing contact 51, the
left-hand portion of balancing resistance 55, wire
15, protective resistance 15, wire 11, and wire 55
to the left-hand end of electromagnetic coil 55. 30
It will be seen that this shunt circuit not only
includes the protective resistance 15 but also in
cludes half of the balancing resistance 55. There
fore, if the protective resistance 15 and the re
sistance 85 are properly proportioned equal ener 35
gizations of electromagnetic coils 58 and 59 can
only result provided the balancing contact 51
moves to the extreme left-hand end of balancing
resistance 55.
In this manner, by segregating the connections 40
between the control contact 5| and the junctions
of the sets of electromagnetic coils 54 and 55
and 55 and 59, through the interposition of re
sistances such as resistances 52 and 55, it has
been found impossible to rebalance the ener 45
gizations of each of the sets of electromagnetic
coils 54 and 55 and 58 and 59 unless their re
spectively associated balancing contacts 53 and
51 move to positions along their balancing re
sistances 52 and 55 in conformity with the posi
tion which the control contact 5| has assumed
upon controlvresistance 55.
In this manner, it
is positively assured that the various follow-up
mechanisms will keep in proper step with the
movements of the control contact 5|.
While it would probably be possible to give a
number of very detailed and highly complicated
electrical theoretical explanations as to why exact
positioning of the balancing contacts 53 and 51
must be had in order to equalize the energizations 60
of the respective sets of electromagnetic coils 54
and 55 and 55 and 59, it is thought that the above
comparison of the conditions that may arise in
the system of Fig. 1 and are prevented by the
system of Fig. 2 will su?ice to show the under
lying principle of the present invention.
Referring now to Fig. 3, a complete diagram
matic showing of the control of a pair of electri
cally balanced follow-up systems by a single con
troller is disclosed. The single controller is 70
shown as a control potentiometer, generally in
dicated at I55, which comprises a control resist
ance NH and a cooperating control contact or
movable member N12. The control contact I02
may be positioned manually or automatically in 75
4
2,114,704
any desired manner and is herein shown as con
trolled by temperature changes, the control ele
ment being indicated at I03 and being illus
trated as a bimetallic element.
The ?rst electrically balanced follow-up mech
anism includes a 'pair of series-connected sole
noid coils I04 and I05 that conjointly control
the position of a single plunger or armature I06.
The armature I06 controls a double-circuit
10 switching mechanism comprised by a switch arm
I01 and a pair of cooperating contacts I08 and
I09. The arrangement is such that switch arm
I101 may be disposed between contacts I08 and.
I09 and not engaging either of them or may be
15 selectively moved into engagement with either
of them.
This switch arm I01 is connected to
or armature I44. The plunger I44'controls a
double-circuit open contact switching mechanism
that includes a switch arm I45 and cooperating
contacts I46 and I41. Here again, the arrange
ment is such that the switch arm I45 may be dis
posed intermediate contacts I46 and I41 so that
it engages neither of them or may be selectively
moved into engagement with either of them. The
plunger I44 is connected to the switch arm I46
by a non-magnetic connection I40.
10
The switching mechanism I45-—I46--I41 se
lectively controls the energization of a pair of
high voltage ?eld windings I49 and I 50. These
?eld windings I49 and I50 respectively cooper
ate with motor rotors I5I and I52 which are se
cured to a common rotor shaft I53. It will be
plunger I06 by a nonmagnetic connection IIO.
evident that the two ?eld windings and two mo
This switching mechanism I01—I08—I09 con
trols a balanced relay that includes a pair of
tor rotors comprise a reversible motor means
20 series-connected relay windings III and
H2.
‘These relay windings III and H2 cooperate in
the control of a single plunger or armature H3.
The plunger I I3 controls a double-circuit switch
ing mechcanism comprising a switch arm H4
25 and a pair of spaced cooperating contacts I I 5 and
H6. The arrangement is such that switch arm
II4 may be disposed between the contacts II 5
and H6 so that it engages neither of them or it
may be selectively moved into engagement with
30 either of them. This switch arm I I4 is connected
and it is to be understood that any other suitable
type of reversible motor means could be utilized. 20
The rotor shaft I53 is coupled to a main op_
erating shaft I54 through reduction gearing in
dicated generally at I55. This main operating
shaft I54 may be utilized to position any desired
device and is herein shown as controlling a valve
I56. The valve I56 is provided with the usual
stem I51 to which a rack I58 is secured. A pin
ion I59 cooperates with the rack I58 and is se
cured to the main operating shaft I54. The
main operating shaft I54 also controls a balanc 30
to the plunger II3 by a non-magnetic connec
ing potentiometer which comprises a balancing
tion II1.
resistance I60 and a cooperating balancing con
tact I 6| which is secured to or operated by the
.
The switching mechanism II4—II5-—II6 se
lectively controls the energization of a pair of
35 high voltage ?eld windings H8 and H9 which
form a part of a reversible electric motor means.
main operating shaft I54.
I
will be evident that any other suitable type of
Low voltage electrical power is supplied to the
controller I00 and to the two electrically bal
anced follow-up mechanisms by means of a step
down transformer I10 that is provided with a high
voltage primary HI and a low voltage secondary
I12. Wires I13 and I14 are connected to the
opposite sides of low voltage secondary I12 and
may be utilized to supply energy to similar fur
reversible electric motor means could be utilized.
The rotor shaft I22 is connected to a main op
as will be apparent from an inspection of the
Associated-with the respective ?eld windings I I8
and H9 are motor rotors I20 and I2I which
are secured toga common rotor shaft I22. While
40 the reversible electric motor means has been
herein shown as a pair of induction motors, it
erating shaft I23 through suitable reduction gear
ing indicated at I24. The main operating shaft
I 23 may be utilized to position any desired mem~
bar and is herein shown as positioning a valve I25
which has a rack I26 connected to its stem I21.
A pinion I28 cooperates with the rack I26 and
is secured to the main operating shaft I23. The
main operating shaft I23 also controls a balanc
ing potentiometer comprising a balancing re
sistance I29 and a cooperating balancing con
55 tact I30 which is secured to or operated by the
main operating shaft I23.
The second electrically balanced follow-up
system. includes a pair of ‘series-connected sole
noid coils I35 and I36 which conjointly con
trol an associated plunger or armature I31.
This plunger I31 controls a double-circuit open
contact switching mechanism that includes a
switch arm I38 and a pair of cooperating con
tacts I39 and I40. The arrangement is such
65 that the switch arm I38 may be disposed inter
mediate the two contacts I39 and I40 so as to
engage neither of ‘them or may be selectively
moved into engagement with either of them.
The switch arm I38 is connected to plunger I31
by a non-magnetic connection MI.
The switching mechanism I38—I39-I40 con—
trols a balanced relay that includes relay wind
ings I 42 and I 43 which are connected in series.
These series connected relay windings I42 and
75 I43 conjointly control the position of a plunger
ther electrically balanced follow-up mechanisms
drawings.
The control resistance IOI has its opposite ends
45
connected to wires I13 and I14, respectively, by
wires I15 and I16. The series-connected solenoid
-coils I04 and I 05 are also connected to the wires
I13 and I14 by wires I11 and I18. The balancing 50
resistance I29 has its ends connected to wires
I 11 and I18 through protective resistances I19
and I80 by wires I8I, I82, I83 and I84. A wire
I85 is connected to the bimetallic element I03 and
therefore to the control contact I02. The junc 55
tion of solenoid coils I04 and I05 is connected
to this wire I85, through a resistance I86, by
wires I81 and I88. The junction of solenoid coils
I04 and I05 is further connected to the balanc
ing contact I30 by wires I89 and I90.
The relay windings I II and I I2, in series, are
connected to the wires I14 and I13 by wires I9I,
I92, I93 and I94. The junction of relay windings
III and II 2 is connected to the switch arm I01,
through a resistance I95, and to the junction of 65
solenoid coils I04 and I05, through a resistance
I96, by wires I91, I98, I99, 200 and I89. The
contact I08 is connected to the junction of wires
I9I and I92 by a wire 20I and the contact I09 is
connected to the junction of wires I93 and I 94 70
by a wire 202.
The solenoid coils I35 and I36, the relay wind
ings I42 and I43, and all the other associated
parts of the second electrically balanced follow
up mechanism are inter-connected and con- 1'
8,212,704
5
nected to wires I12, I14 and I22 in a manner
moves to the left and brings switch arm I21 into
similar to that just described in connection with
the first electrically balanced follow-up mecha
nism. In other words, the series-connected sole
of arm I21 with contact I22 places the resistance
noid coils I25 and I22 are connected to the wires
engagement with contact I22. Such engagement
I22 in parallel with the relay winding III and the
‘full ?ow of current through relay winding III
and resistance I22, in parallel, traverses the relay
I12 and I14 bywires 2" and 2H. Thebalancing
resistance I22 has its opposite ends connected to winding II2. This circuit vis as follows: second
ary I12, wire I12, wire I24, wire- I22 and relay
wires 2" and 2“, through protective
2I2 and M2, by wires 2“, 2I2, 2I2 and ill. The ’ winding H2, at which point the circuit splits,
iunction of‘solenoid coils I22-and I22 is connected I part going by way of relay winding III, wire "I, 10
wire I22, and wire I12 to the other side of
to wire I22, through a resistance 2“, by wires
2I2 and 222. This Junction of solenoid coils I22
and I22 is also connected to the balancing con
tact IN by wires HI and 222.'
The relay windings I42 and I42, in series. are
15
connected to the wires I14 and I12 by wires 222,
224, 222 and 228. The Junction of relay wind
ings I42 and I42 is connected to switch arm I22,
through a resistance 221, and to the junction of
solenoid coils I25 and I22, through a resistance
222, by wires 222. 222, 227i, 222, and 22I. Con
tact I22 is connected to wires 222 and 224 by a
wire 222 and contact I42 is connected to ‘wires
225 and 222 by a wire 224.
25
-
Operation of the system of Pia. 3
Referring to Fig. 3 of the drawings, it will be
noted that the two sets of series-connected sole
noid coils I24 and I22 and I22 and I22 and the
30 control resistance I 2| are all connected across
the source of‘ power or‘ secondary I12 and are all
in parallel with each other. The balancing re
sistance I28 is in parallel with the series [con
nected solenoid coils I24 and I22 but the pro
tective resistances I18 and I22 are interposed in
this circuit. Similarly, the balancing resistance
secondary I12, whereas the other portion‘goes by
way of wire I21, resistance I22, wire I22, switch
arm‘ I21, contact I22, wire 22I, and wire I22 to
wire I12 and the same side of secondary I12. 15
Engagement of switch arm I21 with contact I22
also sets up an auxiliary flow of. current through
solenoid coil I24 and resistance I28 by a circuit
which is‘ as follows: secondary I12, wire I12,
wire I11, solenoid coil I24, wire I28, wire 222, 20
resistance I22, wire I82, wire I88, switch arm I2'I,.
contact I22, wire "I, wire. I92, and wire I14 to
the other side 02 secondary I12. This auxiliary
flow of current through the solenoid coil I24 in
creases the pull on plunger I28 so that switch 25
~arm I21 is held in ?rm engagement with con
tact I22.
‘
Since relay winding “2 is now more highly
energized than relay winding III, plunger II2
moves to the right and switch arm II4 engages 30
contact II2 whereupon the ?eld winding H2 is
energized. The circuit for ?eld winding II! in
cludes a limit switch diagrammatically indicated
at 242 which may be operated in any of the
usual manners by the main operating shaft I22 35
so as to limit the movement of shaft I22 in
I22 is connected in parallel with the series-con
counterclockwise direction as. viewed from the
shown wherein the control contact I22 is en
I2l in counter-clockwise direction, as viewed from
the left, whereupon main operating shaft I22 is
nected solenoid coils I25 and I28 except that the left. The circuit for the ?eld winding H8 is as‘
protective resistances 2I2 and 2I2 are included .follows: line wire 2“, switch arm II4, contact
II8, wire 242, limit switch 242, wire 242 and ?eld 40
40 in the circuit. The analogy between these parts
and the diagrammatic showing of'li‘lg. 2 should winding II2 to line wire 244. Energization of
now be apparent. With the parts in the position ?eld winding II2 causes rotation of’ motor rotor
gaging the middle of control
"I and
45 the two balancing contacts I22 and "I are en
gaging the middle of balancingrresistance I22
and I82, it will be apparent that solenoid coils
I24 and, I25 are equally energized and solenoid
coils I25 and I28 are equally energized. The
50 switch arms I21 and I22 are therefore disposed
intermediate their cooperating contacts I22 and
I29 and I28 and I42. The relay windings III
and I I2 are therefore equally energized since they
are connected in series across the secondary I12
' and the relay coils I42 and I42 are equally ener
also rotated in counter-clockwise direction as 45
viewed from the left. Balancing contact I32
therefore moves downwardly along balancing
resistance I22 towards its lower end and the rack
I22 is moved downwardly to vclose valve I25. This '
movement of balancing contact I22 along balanc 60
ing resistance I22 will continue until the balanc~
ing contact I22 engages the extreme lower end of
balancing resistance I 28 and is directly connected
to the wire I22. When this occurs, the solenoid
coil I24 is substantially short circuited, complete
55
gized for the same reason. The switch arms [I4 short circuiting being prevented by protective
and I45 are therefore disposed intermediate their - resistance I12. This partial short circuit is as
cooperating contacts H5, H8 and I48 and I41.
As a. result, none of the ?eld windings, H2, H8,
I49 or I52 is energized and the two main oper
ating shafts I22 and I54 are stationary. The
valves I25 and I58 are in half open position.
Now assume that the temperature to which bi
metallic element I22 responds should suddenly
rise to a point wherein the control contact I22 is
moved instantaneously to the extreme right-hand
end of control resistance I2I. Solenoid coil I28
is thereupon substantially short circulted,- com
plete short circuiting being prevented by the
resistance I88. This partial short circuit is as
follows: from the junction of solenoid coils I24
and I28,‘ wire I21, resistance I22, wire I22, wire
I25, bi-metallic element I22, control contact I22;
wire I18, wire I14, and wire I12 to the right-hand
end of solenoid coil I25. Plunger I22 therefore
follows: from the junction of solenoid coils I24
and I22, wire I22, wire I22, balancing contact I22,
wire I22, protective resistance I19, and wire I8I 60
to the left-hand end of solenoid coil I24. The
solenoid coils I24 and I25 are now substantially
equally energizedagain and the plunger I28 moves
iar enough tothe right to disengage switch arm
I21 from I22. Whenthis occurs, the resistance 65
I82 is disconnected from its parallel relationship
with relay winding III whereupon relay windings
III and H2 are again connected in series across
the secondary I12 and plunger H2 returns to its
central position.- Switch arm II4, therefore, dis 70
engages contact H8 and ?eld winding H8 is de
energlzed. This movement of main operating
shaft I22 has completely closed valve I28.
Engagement of control contact I22 with the
extreme right-hand end of control resistance I2I 75
2,114,704
/ also substantially short-circuits the solenoid coil
I36, complete short circuiting being prevented by
reason of the inclusion of resistance 2I8. This
partial short circuit is as follows: from the junc
tion of. solenoid coils I35 and I33, wire 2| 9, re
sistance 2I8, wire 228, wire I85, bi-metallic ele
ment I83, control contact I82, wire I13, wire I14,
and wire 2“ to the right-hand end’ of solenoid
coil I33. Plunger I31 thereupon moves to the
10 left and switch arm I38 moves into engagement
with contact I39. Engagement of switch arm I38
with contact I39 places the resistance 221 in
parallel with relay winding I42 so that the cur
rent ?ow through both the relay winding I42 and
15 the resistance 221 traverses the relay winding I43.
This circuit is as follows: secondary I12, wire I13,
wire 223, wire 225 and relay winding I43, at which
point the circuit branches, part going by way of
relay winding I42, wire 223, wire 224 and wire
20 I14 to'the other side of secondary I12 whereas
the other portion goes by way of wire 229, re
sistance 221, wire 238, switch arm I38, contact
I39, wire 233 and wire 224 to wire I14 and the'
same side of secondary I12. Plunger I44 there
25 fore moves to the right and switch arm I45 is
moved into engagement with'contact I 41.
'
Engagement of switch arm- I38 with contact
I39 also sets up an auxiliary circuit through sole
noid coil I35 and resistance 223 which is as fol
30 lows: secondary I12, wire I13, wire 2I8, solenoid
coil I35, wire 22I, wire 232,_resistance 228, wire
23I, wire 238, switch arm I38, contact I39, wire
233, wire 224 and wire I 14 to the other side of
secondary I12. This auxiliary circuit for sole
35 noid coil I35 increases the pull on armature or
plunger I31 so‘ as to maintain switch arm I 38 in
?rm engagement with contact I39. Field wind
ing I58 is energized, upon engagement of switch
arm I45 and contact I 41,‘ through a limit switch
40 245, by a circuit which is as follows: line wire 243,
switch arm I45, contact I41, wire 241, limit
switch 245, wire 248 and field winding I58 to line
wire 249. Rotor I52 is therefore rotated in a
counter-clockwise direction as viewed from the
45 left and main operating shaft I54 is operated
in the same direction. Valve I53 is therefore
moved towards closed position and balancing con
tact I3I moves downwardly along balancing re
sistance I38. When balancing contact I3I
50 reaches the extreme lower end of balancing re
sistance I38, the solenoid coil I35 is substantially
completely short-c'ircuited, complete short-cir
cuiting being‘prevented by reason of the protec
tive resistance 2I2. This partial short-circuit is
55 as follows: from the junction of solenoid coils
is directly connected to wire I13, then the op
posite action takes place. ‘ Under these condi
tions, solenoid coil I84 is'substantially complete
ly short-circuited, complete short-circuiting
again being prevented by inclusion of resistance
I83.
This partial I short-circuit is as follows:
from the Junction of solenoid coils I 84 and I83,
wire I81, resistance I83, wire I88, wire I83, bi
metallic element .I83,'.contro1 contact I82, wire
I13, wire I13 and wire I11 to the left-hand end 10
of solenoid coil I84.
Solenoid coil I83 is now
more highly energized than solenoid coil I84 and
plunger I83 moves to the right and brings switch
arm I 81 into engagement with contact I89. The
resistance I93 is now placed in parallel with re
16
lay winding II2 and the circuits for relay wind
ings III and H2 and resistance I93 are as fol
lows: secondary I12, wire I14, wire I92, wire "I
and relay winding I II, at which point the circuit
splits, part going by way of relay winding II2, 20
wire I93, wire I94 and wire I13 to the other side
of secondary I12, whereas the other portion goes
by way of wire I91, resistance I93, wire I99,
switch arm I81, contact I89, wire 282, and wire
I94 to wire I13 and the same side of secondary 23
I12._ Relay winding III is therefore more highly
energized than relay winding H2 and switch arm
H4 is moved into engagement with contact III.
Engagement of switch arm I 81 and contact I89
also sets up an auxiliary circuit through solenoid 30
coil I83 and resistance I93 which is as follows:
secondary I12, wire I14, wire I18, solenoid coil '
I83, wire I89, wire 288, resistance I93, wire I99.
wire I98, switch arm I81, contact I89, wire 282,
wire I94 and wire I13 to the secondary I12. Field 35
winding H8 is energized by engagement of switch
arm H4 and contact II3, through a limit switch
258, by the following circuit: line wire 2“, switch
arm II4, contact II3, wire 25I, limit switch 238,
wire 232, and field winding II8 to line wire 244. 40
Rotor I28 is therefore rotated in a clockwise di
rection as viewed from the left and main oper
ating shaft I23 rotates in the same direction.
This causes upward movement of rack I23 and
consequent opening movement of valve I23. 45
Such movement of main operating shaft I23 also
causes movement of balancing contact I38 up
wardly along balancing resistance I29.
When the balancing contact I38 has complete
ly traversed balancing resistance I29, then sole
noid coil I83 is substantially completely short
50
circuited by a circuit as follows: from the Junc
tion of solenoid coils I84 and I83, wire I89, wire
I98, balancing contact I38, wire I94, protective
resistance I88 and wire I83, to the right hand end 55
of solenoid coil I83. Solenoid coils I84 and I83
are thereupon again substantially equally ener
wire 2“ to the left hand end of solenoid coil,
I35. Theenergizations of solenoid coils I33 and gized and plunger I83 moves to' the left so as to
move switch arm I81 from engagement with
60 I33 are therefore substantially equal and plunger
contact
I 89. Resistance I95 is thereupon re
I31 moves far enough to the right to disengage
switch arm I38 from contact I39. The resistance moved from its parallel relationshipwith relay
winding H2, and switch arm II4 disengages con
221 is therefore removed from its parallel rela
tionship with relay winding I42 and relay wind,‘ tact I I3 thereby deenergizing ?eld winding III.
This separation of switch arm I81-from contact
65 ings I42 and I43 are again equally energized.’
I89 also interrupts the auxiliary circuit through 65
Plunger I44 therefore moves to its central posi
solenoid
coil I83 and resistance I93. Valve I23
tion and switch arm I45 disengages contact I41 is now completely
opened.
>
whereupon field winding I58 is deenergized. The
Such engagement of control contact I82 with
valve I53 has now been moved to fully closed
the extreme left-hand end of control resistance
position.
I8I operates upon the second follow-up mecha
If, on the other hand, the temperature to nism in the manner Just described for the ?rst 70'
which bimetallic element I83 responds should follow-up mechanism. In other words, solenoid
instantaneously fall to such an extent that con
coil I33 is substantially short-circuited by the
trol contact I82 moves to the extreme left end of following circuit: from the junction of solenoid
75 control resistance I8I, so that control contact I82 coils I33 and I33, wire 2I9, resistance 2I8, wire 75
I35 and I33, wire 22I, wire 222, balancing con
tact I3I, wire 2I5, protective resistance 2I2 and
2,114,704
7
226, wire I66, bimetallic element I62, control con
tact I02, wire I16, wire I12, and wire 2" to the
as the bimetallic element I02, the movements of
control contact I62 along control resistance III
left hand end of solenoid coil I26. Plunler I21
thereupon moves to the right and switch arm I26
engages contact I40. Resistance 221 is there
of control contact I62 in respect to control resist
ance III has been sui'?ciently great to unbalance
the voltage drops across solenoid coils I04 and
I66 suihciently to lightly engage switch arm I61
with either of contacts I06 or I06, a follow-up
action will take place. The reason for the auxil
iary current ?ows described in connection with 10
solenoid coils I04 and I05 is to immediately in
upon placed in parallel with relay winding I42
and the circuit for relay windings I42 and I42
and nsistance 221 is as follows: secondary I12,
wire I14, wire 224, wire 222 and relay winding I42,
10 at which point the circuit splits, one portion
going by way of relay winding I42, wire 226, wire
226 and wire I12 to the opposite side of secondary
I12 whereas the other portion goes by way of wire
226, resistance 221, wire 220, switch arm I26, con
15 tact I40, wire 234 and wire 226 to wire I12 and
the same side of secondary I12. Relay winding
I42 is therefore more highly energized than relay
winding I43 and plunger I44 moves to the left
bringing switch arm I46 into engagement with
contact I46. Engagement of switch arm I26 with
contact I40 also sets up an auxiliary circuit
through solenoid coil I26 and resistance 226
which is as follows: secondary I12, wire I14, wire
2I I, solenoid coil I26, wire 22I, wire 222, resist
ance 226, wire 23I, wire 220, switch arm I26, con
tact I40, wire 224, wire 226 and wire I12 to the
opposite side of secondary I12. This auxiliary
current ?ow through solenoid coil I26 causes
switch arm I26 to be held ?rmly in engagement
with contact I40.
Engagement of switch arm I46 with contact I46
causes energization of ?eld winding I46 through
a limit switch 252 by a circuit which is as fol
lows: line wire 246, switch arm I46, contact I46,
wire 264, limit switch 262, wire 266 and ?eld wind
ing I49 to line wire 246. Rotor III is therefore
rotated in a clockwise direction as viewed from
the left and main operating shaft I64 is rotated
in a similar direction. Rack I66 moves upwardly
and valve I56 is moved towards open position.
Such movement of main operating shaft I64 also
moves balancing contact I6I upwardly along bal
ancing resistance I60.
when balancing contact I6I has completely
traversed balancing resistance I60,‘solenoid coil
I26 is substantially short-circuited as follows:
from the junction of solenoid coils I26 and I26,
wire 22I, wire 222, balancing contact I6I, wire
2", protective resistance 2I2 and wire 2" to the
right-hand end of solenoid coil I26. Solenoid
coils I26 and I26 are thereupon substantially
equally energized and plunger I21 moves towards
the left su?lciently to disengage switch arm I36
from contact I40. The resistance 221 is therefore
removed from its parallel relationship with relay
winding I42 whereupon relay windings I42 and
I42 are again connected in series across the sec
ondary I12 and are equally energized. Plunger
I44 therefore returns to its central position
wherein switch arm I46 is disengaged from con
tact I45. Field winding I46 is thereupon de
energized. Disengagement of switch arm I26
from contact I40 also interrupts the auxiliary
?ow of current through solenoid coil I26 and
resistance 226 whereupon solenoid coils I26 and
I26 are again equally energized. Valve I66 is now
in its full open position.
.
In the foregoing description, two extreme posi
tions of control contact I02 have been described
70
so that the description of Fig. 3 is in conformity
with the illustrations already set out in connec
15
tion with Fig. 1 and Fig. 2. In actual practice,
if the control contact I02 is controlled auto
matically by a condition responsive member such
will be relatively slow. As soon as this movement
crease the contact pressure between the switch
arm I01 and either of the contacts I06 or I66
upon the very light engagement between these
parts. This insures a good ?rm contact. Plunger 15
I I2 is thereupon operated as previously described
to energize one or the other of ?eld windings H6
or II9 to drive balancing resistance I20 in the
proper direction to rebalance the voltage drops
across solenoid coils I04 and I05 suiiiciently to 20
barely separate switch arm I01 from the particu
lar contact I06 or I09 with which it is in engage
ment. Immediately this separation takes place,
as brought out in the above description, the auxil
iary current ?ow through solenoid coil I04 or coil
I05 is interrupted whereupon the separation be
tween switch arm I01 and either of the contacts
I66 or I66 is substantially increased so that fur
ther movement of the main operating shaft I22
cannot take place until there is a reasonable
movement of control contact I02 in respect to
control resistance IOI. As indicated above, the
limit switches 240 and 250 are operated in the
usual well-known manner to limit the extreme
movements of main operating shaft I22. While 35
for the sake of clearness the extreme positions
have been shown as being reached by a balancing
out process wherein the balancing contact I20
moves to the extreme end of balancing resistance
I26, in actual practice the balancing out of the 40
voltage drops across solenoid coils I04 and I05 is
not relied upon for the extreme positions but the
limit switches 240 and 250 are utilized to obtain
exact stopping of the main operating shaft I22
when the desired extreme position is reached.
The above comments are all equally applicable
to the second follow-up system which includes
the solenoid coils I25 and I26 and the associated
control apparatus.
For a more complete understanding of the
manner in which these follow-up systems operate
generally, reference may be had to the copending
application of Lewis L. Cunningham, S. N.
673,236, which was ?led May 27, 1933.
In this system of Fig. 3, the two follow-up sys 55
tems will stay in exact step in relation to the
position of control contact I02 for the same rea
son as set forth in connection with Fig. 2.
In
other words, the junctions of the two sets of 60
solenoid coils I04 and I05 and I25 and I36 are
individually connected to the control contact I02
through individual resistances I66 and 2 I6 so that
even though control contact I02 goes to an ex
treme position and one of the balancing contacts
I26 or I6I goes to an opposite extreme position,
still only that set of solenoid coils which is di
rectly associated with the particular balancing
contact is rebalanced and the other set of solenoid
coils is not balanced untilits own associated bal 10.
ancing contact resumes the proper position. It
will therefore be evident that our invention pro
vides a novel manner of connecting a plurality of
follow-up systems in parallel with a single vari
able eontroiler and in such a manner that each 75
8
2,114,704
particular follow-up system must assume the
position demanded by the position of the con
troller. In addition, the system of the present
invention includes the highly desirable com
mercial feature of increasing the contact pressure
of that switching mechanism which is operated
in a marginal manner rather than an on and off
manner.
As far as the switching mechanisms
II|—II5-—II6 and l45'—I46-I4'I are concerned,
10 these are in the nature of on and of! apparatus
rather than marginal controls so that increasing
the contact pressure therebetween is unnecessary.
In the event that motor ?eld windings I I8 and
H9 and I49 and I50 are low voltage windings,
15 then the intermediate relay may be eliminated
and the relay windings may become the motor
?eld windings. It should also be noted that the
individual follow-up systems utilized in this in
vention are entirely capable of being controlled by
20 individual controllers so that the follow-up mech
anisms of the present invention may be utilized
either individually or in a multiple system.
As an example of the values of the various
resistances and impedances used in an operable
set-up of the system of Fig. 3, the secondary I12
produces 20 volts, the control resistance I I'll is
100 ohms, the balancing resistances I29 and IE0
are each 135 ohms, the protective resistances
I19, I80, 2I2 and 2I3 are 35 ohmseach, the
30 resistances I86 and 2I8 are 50 ohms each, the
resistances I96 and 228 are each 2400 ohms, the
resistances I95 and 221 are each 35 ohms and
the impedance of each set of series connected
solenoid and relay coils I04 and I05, III and
35 H2, I35 and I36, and I42 and I43 is 120 ohms.
It will be evident that a number of changes
may be made in the details of the present in
vention, and particularly the values given above,
without departing from the scope of the inven
40 tion and we are therefore to be limited only in
accordance with the appended claims.
We claim:
1. In a temperature control system, in com
bination, a single variable impedance controller,
45 a pair of electrical follow-up systems concur
rently controlled thereby, a temperature con
trolling device controlled by each of said follow
up systems, and a single source of electrical
power connected to said controller and each of
50 said follow-up systems, each follow-up system
comprising a pair of normally electrically bal
anced electromagnetic coils, balancing impedance
means therefor, motor means in control of the
balancing impedance means, and impedance
means associated with the electromagnetic
means and balancing impedance means in a
manner to cause each motor means to position
cause each motor means to move to a position
corresponding to the condition of said controller
in order to eilfect a rebalancing of the energlza
tion of its particular relay means.
,
3. The combination with a plurality of elec
trically balanced proportioning control systems
each of which comprises relay means normally
energized in a certain manner, motor mea'_s op
erated thereby upon a disturbance of such ener
gization and balancing impedance means oper
10
ated by the motor means to restore such ener
gization, of a single impedance controller, means
electrically connecting said relays in parallel to
said controller so as to cause the latter to be
operable to vary the energization to each of said 15
relay means, and impedance means connected to
each of said relay means and its associated bal
ancing impedance means in a manner to prevent
restoration of such energization of the relay
means. until the associated motor means reaches 20
a position corresponding to the condition of said
controller whereby all of said control systems
are maintained in ‘proper step.
4. In a multiple electrical follow-up system;
in combination; a plurality of electrical follow 25
up systems each comprising a pair of normally
equally energized electromagnetic coils, switch
ing means controlled thereby, motor means con
trolled by the switching means and a balancing
potentiometer controlled by the motor means and 30
operative to maintain the energizations of said
coils equal; a single control potentiometer con
nected to each of said pairs of coils and opera
tive to unequalize the energizations thereof, and
resistance means associated with each of said 35
pairs of coils and its associated balancing poten
tiometer operative to permit equalization of the
energizations of each pair of coils only when
such associated balancing potentiometer has been
operated to the position it would have to assume 40
if only one follow-up system were being con—
trolled by said control potentiometer whereby a
plurality of such follow-up systems may be oper
ated from a single controller and maintained in
proper step.
45
5. In a multiple electrical follow-up system;
in combination; a plurality of electrical follow
-up mechanisms each comprising a pair of series
connected electromagnetic coils, switching means
controlled thereby, motor means, controlled by 50
the switching means and a balancing potentiom
eter controlled by the motor‘means and includ
ing a balancing resistance and a. balancing con
tact; a single source of ‘power; a single control
potentiometer including a control resistance con 55
nected across said source of power and a con
trol contact; a plurality, of resistances; connec
tions connecting said control contact to the junc
tion of each pair of coils through a separate one
its temperature controlling device in accordance
with the position of said controller, at least one
60 of the coils of each of said systems being con
N of said resistances; connections connecting the
nected together and to said controller.
junction of each pair of coils to its associated
2. In a multiple electrical follow-up system, balancing contact; connections connecting each
the combination with a plurality of electrical pair of series connected coils across said source
follow-up mechanisms each comprising a nor
65 mally electrically balanced relay means, motor of power; and connections connecting each bal
ancing resistance in parallel with its associated 65
means controlled by the relay means, and bal series connected coils.
ancing impedance means controlled by the‘motor
6. In a multiple electrical follow-up system;
‘ means operative to maintain the relay means in combination; a plurality of electrical follow
electrically balanced, of a single variable imped
up mechanisms each comprising a pair of series
70 ance controller for unbalancing the energiza
connected electromagnetic coils, switching means 70
tions of the relays, means electrically connect
controlled thereby, motor means controlled by
ing the relays of both of said mechanismsto
the switching means and a balancing potentiom
gether and to said controller, and impedance eter controlled by the motor means and includ
means associated with both said relay means
75 and both said balancing impedance means to ing a balancing resistance and a balancing con
tact; a single source of power; a single control 75
2,114,704
potentiometer including a control resistance con
nected across said source of power and a con
trol contact; a plurality oi’ resistances; connec
tions connecting said control contact to the Junc~
tion of each pair of coils through a separate one
of said resistances; connections connecting the
Junction 01' each pair of coils to its associated
balancing contact; connections connecting each
pair oi’ series connected coils across said source
10 of power; connections connecting each balanc
ing resistance in parallel with its associated series
connected coils; and resistance means associated
with each pair of coils and its associated bal
ancing potentiometer operative to prevent com
15 plete short circuiting of either coil by its balancing potentiometer.
.
7. In a multiple graduated control system; in
combination; a source 01' power; a plurality of in
dividual follow-up systems each comprising a pair
20 of electromagnetic coils connected in series across
said source of power, an open contact switch con
trolled thereby, motor means controlled by said
switch, means including connections and im
pedance means controlled by said switch for
25 changing the energizations of said coils upon
closure of said switch in a manner to increase the
pressure of closing of said switch and impedance
means controlled by said motor means and opera
tive to equalize the energizations of said coils to
30 cause opening of said switch; a single control im
pedance connected to each pair of coils and opera
tive to change the energizations of the same; and
impedance means associated with each pair of
coils and said control impedance operative to
keep each follow-up system in proper step with
said control impedance.
-
8. The combination with a plurality of elec
trically balanced proportioning control systems
each of which comprises electrical relay means
40 normally energized in a. certain manner, electrical
motor means operated thereby upon a disturbance
of such energization and balancing resistance
means operated by the motor means to restore
such energization, of variable control resistance
means electrically connected to each of said re
lay means and operable to vary the energization of
each of said relay means, and resistance means
connected to each of said relay means and its
associated balancing resistance means in a, man
50 ner to prevent restoration of such energization
of the relay means until the associated motor
means moves to a position corresponding to the
condition of the variable control resistance means
whereby all of said control systems are main
55 tained in .proper step.
9. The combination with a plurality of elec
trlcally balanced proportioning control systems
each of which comprises plural coil electromag
netic means, an armature controlled thereby,
9
tion of any of said motor means unless the motor
means assumes a position corresponding to the
condition of said control resistance means where
by all of said control systems are maintained in
proper step.
10. In a temperature control system, in com
bination, a single variable impedance controller,
a pair of electrical follow-up systems connected
to and concurrently controlled thereby, a tem
perature controlling device controlled by each oi 10
said follow-up systems and positioned thereby, a
single alternating current source of electrical
power for said controller and follow-up systems,
and impedance means in the connections between
‘ said controller and said follow-up systems effec
15
tive to cause each of said devices to move to the
position corresponding to the position of the con
troller.
11. In a multiple electrical follow-up system,
in combination, a plurality oi’ electrical follow-up
systems each comprising electrical relay means
normally energized in a certain manner, elec
trical motor means operated thereby upon a dis
turbance of such energization and balancing im
pedance means operated by the motor means to 25
‘restore such energization, variable impedance
control means, means connecting the relay means
of each of said systems together and to said con
trol ' means to render said variable impedance
control means operable to vary the energization
of each of said relay means, and impedance means
operative to permit restoration of the original
energization of each relay means only when the
associated balancing impedance means has been
moved to the position it would have to assume if 35
only one follow-up system were being controlled
by said control potentiometer whereby a plurality
of such follow-up systems may be operated from
a single controller and maintained in proper step.
12. In a multiple electrical follow-up system, 40
in combination, a plurality of electrical follow-up
systems each comprising electrical relay means
normally energized in a certain manner, elec
trical motor means operated thereby upon a dis
turbance of such energization and balancing im 45
pedance means operated by the motor means to
restore such energization, variable impedance
control means, means connecting the relay means
of each of said systems together; and to said con
trol means to render said variable impedance. 50
control means operable to vary the energization of
each of said relay means and impedance means
between said control means and each of said relay
means operative to permit restoration of the
original energization of each relay means only 55
when the associated balancing impedance means
has been moved to'the position it would have to
assume if only one follow-up system were being
controlled by said control potentiometer where
00 switching means controlled by the armature,
by a plurality of such follow-up systems may be 60
operated from a single controller and maintained
in proper step.
13. In a multiple electrical follow-up system,
means and operated by the motor means in a , in combination, a. plurality of electrical follow-up
65 manner to cause deenergization of the motor
mechanisms each comprising a pair of series con 65
means whenever the motor means is energized, of nected electromagnetic coils, motor means con
means including control resistance, means, and trolled in accordance with the energization of said
connections between said last-named means and coils, and a balancing potentiometer controlled
at least one oi! the coils of each of said electro
by the motor means and including a balancing
70 magnetic means electrically connecting said coils resistance and a balancing contact, a single source 70
together and to said control resistance means and of power, a single control potentiometer includ
operable to vary the relative energizations of said ing a control resistance connected across said
electromagnetic means upon variation of said source of power and a control contact, a plu
control resistance means to cause operation of rality of resistances, connections connecting said
motor means controlled by the switching means,
and balancing resistance means connected to at
least one of the coils of said electromagnetic
75 aid switching means and to prevent deenergiza
control contact to the junction of each pair of 75
1O
2,114,704
coils through a. separate one of said resistances, low-up systems comprising a motor and a device
connections connecting the junction of each pair ' variably positioned thereby, a single alternating
oi’ coils to its associated balancing contact. con
current source of electrical power for said con
nections connecting each pair of series connected troller and follow-up systems, and impedance
coils across said source of power and connections
connecting each balancing resistance in parallel
with its associated series connected coils.
14. In a. motor control system, in combination,
a single variable impedance controller, a plurality
10 of electrical follow-up systems connected to and
concurrently controlled thereby, each of said lol
means in the connections between said controller
and said follow-up systems effective to cause each
of said devices to move to the position correspond
ing to the position of the controller.
LEWIS L. CUNNINGHAM.
CLARENCE W. NESSELL.
10
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