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Nov. 5, 1946.
M. K. PARKHURST
2,410,677
AUTOMATI C CHANGE- OVER RELAY
Filed Feb. 1, 1945
2 Sheds-Sheet l
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COHAVNEGR SRMYELATYE
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SIGNAL
PISLWOTCH
INVENTOR
MAIN
MALCOLM K. PARKHURST
INVE
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ATTORNEYS
Nov. 5, 1946.
M_ K_ PARKHURST
2,41\o,677
AUTOMATIC CHANGE-OVER RELAY
Filed Feb. 1, 1945
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INVENTOR
MALCOLM K. PARKHU as?
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‘ATTORNEYS
Patented Nov. .5, 1946
2,410,677
UNITED STATES PATENT OFFICE
2,410,677
‘
AUTOMATIC CHANGE-OVER RELAY
Malcolm K. Parkhurst, New York, N. Y., assignor
to The Wilcolator Company, Elizabeth, N. J., a
corporation of Delaware
Application February 1, 1945, Serial No. 575,663
5 Claims.
1
This invention relates to an improved change
over relay and more particularly to an automatic
relay adapted to quickly change from a main
source of power to a spare source of power.
Certain heavy aircraft are equipped with a
main inverter and a spare inverter for produc
ing alternating current for electrical circuits par
(Cl. 171-97).
2
delay relay, means for supplying direct current
through the D. C. relay for starting the main
inverter, means for supplying direct current to
the time delay relay, means for supplying altemat
ing current from the started inverter to energize
the A. C. relay to thereby form the normally
closed contact, means for energizing the D. C.
ticularly connected with the control of super
relay from the time delay relay, and means for
chargers for the aircraft engines. Certain of
passing direct ‘current through the energized D. C.
these circuits at the present time require the use 10 relay for initiating the operation of the spare
of 115 volt, 400 cycle alternating current. The
inverter when the A. C. relay is .deenergized upon
inverter used to produce this current is a motor
the failure of the main inverter.
generator set comprising a 26 volt direct current
Another important feature of the invention
motor coupled to a 115 volt, 400 cycle alternating
associated with the system described above, com
current generator. The main inverter or gen 15 prises the use of a heater-operated time delay
erator provides the power for the alternating cur
relay, means for maintaining the D. C. relay en
rent control circuits, except in the case of its
ergized independent of the time delay relay, and
failure. It is extremely important in the case of
for deenergizing the heater-operated relay upon
such failure to immediately start the spare in
the initial energization of the D. C. relay. This
verter so that the ‘115 volt current is continued
feature avoids the necessity of keeping the heater
with as little interruption as possible.
of the heater-operated relay in continuous use,
Attempts have been made to provide change
and therefore promotes the long life of the change
over relay systems to cut in the spare inverter
‘ over system.
upon the failure of the main inverter, but they
Still another important feature of the present
have not been entirely successful because no pro 25 invention is the correlation of the operation of
vision has been made for avoiding the use of the
the relays described above. D. C. current is ini
spare inverter when the aircraft is started up
tially supplied through a closed contact of the
after the main switch has been turned off. For
D. C. relay for starting the main inverter, and
example, in some systems, it has been found that
D. C. current is simultaneously supplied through
when the pilot turns off the main switch after 30 a closed contact to the heater ,of the time-delay
the aircraft lands, this action operates the relay
relay which is timed at approximately six seconds.
system in the same manner as if the main .in
This relay eventually energizes the D. C. relay
verter had failed, so that, when the main switch
and changes the contacts, but prior to this, alter
is again turned on, the spare inverter is cut into
nating current is supplied from the main in
the circuit.
35 verter to the A. C. relay which controls a switch
The primary object, therefore, of the present
for normally supplying direct current for main
taining the operation of the main inverter. As
long as alternating current ?ows from the main
verter or generator is constantly maintained in
inverter through the A. C. relay, a circuit is
service, except upon its failure.
.
40 closed from the D. C. source to keep the main
Another object of the invention is to provide
inverter in operation. At the instant of the fail
improved automatic change-over relay system
we of the main inverter, the A. C. relay is de
adapted to effectively and immediately cut in a
energized and the switch closes a contact directing
spare source of power upon the failure of a main
direct current through a closed contact of the
source of power.
45 energized D. C. relay to start the spare inverter
An important feature of the present invention
which is immediately put in operation to supply ,
is the provision of a novel automatic change
alternating current to the desired aircraft cir
over relay system by which a spare inverter may ' cults.
be quickly put into service upon the failure of a
These and other features, objects and advan
main inverter, the system including an alternat 50 tages of the present invention will be better un
ing current relay with a normally closed and a
derstood by reference to the following detailed
normally open contact, a direct current relay with
description thereof, taken in conjunction with
the combination of a normally open and normally
the accompanying drawings illustrating. one form
closed contact, and a separate normally closed
of the new change-over relay. In the drawings:
‘and a separate normally open contact, a. time 55
Fig. 1 is a. schematic wiring diagram illustrat
invention is to provide an improved automatic
change-over relay system by which the main in;
2,410,077
3
-
4
rect current to relay IS without having to pass
through the relay 40, so that the relay 40 can
now be changed without affecting the supply of
ing the preferred arrangement of the elements
oi! the automatic change-over relay system and
its associated main and spare inverters for sup
plying alternating current.
P18. 2 is a plan view showing a compact assem
bly of the elements of the change-over relay of
the present invention.
Fig. 3 is a vertical elevational view of the
change-over relay as shown in Fig. 2.
Referring to Fig. 1 of the drawings, the auto 10
direct current to the relay i5 which supplies cur
rent to and from the main inverter 14. Further
more, as long as alternating current is supplied
from the inverter [4 through the lead 54, the
relay 5! will maintain the bypass circuit through
the lead 52, but if for any reason the inverter
matic change-over relay system of the present
14 should‘fail, the relay 58 will be deenergized
and the switch 50 will automatically close the
invention is shown primarily in a rectangular en
upper contact.
The time delay relay 50 is timed at approxi
closure IO. The apparatus shown in this figure
mately six seconds, so as to give ample time for
of the drawings also includes a direct current
feeder bar l2, a main inverter or motor genera 15 the'relay 58 to be energized, after which the
tor l4, a relay ii of conventional design for in
relay 50 moves a contact 54 to establish a circuit
verter I4, a spare inverter ill, a relay 2!! like the
from the terminal 34 through a lead 56 and a
relay l8 for the spare inverter, an inverter-fail
coil 68 of relay 40, the coil 88 being connected
ure-indicating signal 22, and a relay 23 therefor.
by a lead 69 to terminal 52 and grounded. The
The elements of the automatic change-over relay 20 energizing of coil 58 of relay in disconnects the
system it are shown in Figs. 2 and 3, and may
contacts 38 and 48 and establishes a circuit from
be assembled as a compact unit which is pref
the terminal 34, lead 35, through a contact 10 and
erably connected into the apparatus shown in
the coil 58. This circuit maintains the relay 4.
Fig. 1 by means of binding posts shown as cir
in energized condition so that it does not depend
cles in the connecting lead wires.
25 upon the maintenance of a circuit through the
In general, the direct current for operating the
relay 50 and the lead 65.
inverters and the alternating current generated
By energizing the relay 40 a second contact 12
thereby, are supplied through separate relays
in the relay 40 is closed to establish a potential
which are operated from the automatic change
circuit from the terminal 34, switch 50, a lead
over relay system of the present invention. For 30 14, a terminal '15 and a lead ‘ll, for supplying cur
example. 26 volt direct current is supplied from
rent to the coils of the relay 20. It will be un
a battery or other source to the feeder bar l2
derstood that while contact 12 is now maintained
through leads 24 through the relays l6 and 2D
in closed position, there will be no current ?ow
to the inverters l4 and II. The 115 volt, 400
ing to the relay 20 except upon the failure of the
cycle alternating current generated by the in 3 inverter 14 and the deenergizing of the relay
verters l4 and II is conducted through feeder
58. As soon as the relay 58 is deenergized, the
lines 26, and 26 volt or 115 volt current is con
current through the terminal 44 to the relay I‘
ducted through parallel feeder lines 28. Respec
will cut off, and current will be supplied from
tive contacts in the relays I6 and 20 are nor
the terminal 34 through the switch 60, the lead
mally open, but are bridged when the relays are 4 O 14, contact 12, terminal 16 and lead ‘ll, to the
energized, so that D. C. current will be supplied
coil of the relay 20, and then to ground, so that
to the respective inverter through a line 24, and
the spare inverter l8 will be cut in and will supply
the generated alternating current will be con
alternating current to the feeder lines 25 and 2|.
ducted into the main A. C. feeder lines 25 and 28.
It will be noted that the inverter-failure-indi
Direct current is fed to the change-over relay 45 cating signal relay 23 is directly supplied with
system through a lead 30 containing a main or
pilot switch 32 and which is connected to a ter
mine] 24. The closing of the switch 32 estab
lishes a 26 volt direct current circuit from the
direct current from feeder l2 and also with alter
nating current from feeder 25, and that it is con
shown. As soon as the inverter 14 is placed in
relay 40 also prepares a circuit to the relay 20,
nected to ground. When the alternating current
in the lead 26 is interrupted by the failure of the
feeder l2 through the terminal 34, then through 50 inverter I 4, the relay 23 is deenergized to inter
a line 35, a normally closed contact 38 on a
rupt the supply of direct current to the signal 22
D. C. relay 4', out through a. line 42, terminal
which is grounded, as shown. These features re‘
44, through the coils of the relay l6, and then to
lating to the signal 22 and relay 23 constitute no
ground. This circuit through the relay 40 and
part of the present invention.
the relay ii bridges all of the contacts in the 55
The energizing of the D. C. relay 40 not only
relay l5, and therefore supplies 26 volt direct
provides a new circuit for maintaining it in en
current through one line 24 to the inverter I4
ergized condition, but also opens the circuit to
which is immediately put in operation. The
the time-delay relay 50 through contact 46, and
current through the terminal 34 is also supplied
thereby eliminates the heater and the wasting of
through the lead” and a second normally closed 60 current. The original circuit from terminal 34
contact 46 of the relay 4|), through a lead 48 to
through lead 35 and contact 38, is opened, thus
a time delay heater-operated relay 5'], and ?nally
permitting the relay ii to open upon the failure
into a terminal 52 which leads to ground, as
of the main inverter l4. The energizing of the
operating condition and the 115 volt, 400 cycle 65 so that when the main inverter l4 fails and opens
alternating current builds up in the line 20, this
the A. C. relay 58, the relay 20 immediately closes
current will be conducted through a connecting
and the spare inverter i8 is started. ‘It will be
lead 54, a terminal 56, through the coil of an
apparent from the foregoing description that it
A. C. relay 58, and then to ground through a
the main inverter I4 should be inoperative at the
lead 50 and terminal 52. When the relay 5! is 70 time the pilot switch 32 is closed, the relay 2.
energized, a switch BI is changed to establish a
bypass circuit for direct current from terminal
34 through leads SI and 82 and a portion of lead
42 and terminal 44 to relay it. This change ef
fected by the relay 58 insures the supply of. di
will be energized as soon as the heater relay ll
goes through its cycle to energize the relay 44
and close the contact ‘I2.
Figs. 2 and 3 show in substantial detail the
75 structure and arrangement of a suitable embodi
2,410,677
5
ment of apparatus elements shown diagrammat
ically in the enclosure in of Fig. 1. In these ?g
ures, the same reference numerals used in Fig.
1 apply to the same parts of the apparatus. It
will be noted that the three relays 40, 50 and 58 5
are mounted on a mounting plate 80 of insulating
for starting the main inverter for generating al
ternating current, means for simultaneously es
tablishing a direct current circuit through the
heater-operated relay, means for establishing an
alternating current circuit from the current out
put of the main inverter through the alternating
material, by means of suitable screws and bolts,
current relay-for operating the switch associated
as indicated. All of the wiring of Fig. 1 is not
therewith to change it from its normally closed
shown in Figs. 2 and 3, but in general, the wires
contact, means whereby said heater-operated re
from the different relays are passed downward 10 lay establishes a circuit for energizing the D. C.
through holes in the plate 80, such as 8|, along
relay to open said closed contacts and close the
under the plate, and up through holes along the
two normally open contacts one of which estab
upper edge of the plate, to be connected to the
lishes an independentcircuit through said D. C.
terminals 84, 44, 52, 56 and 16. The relay 40
vrelay to maintain it in energized condition and
comprises a pivoted plate 82 which is operated 15 the other of which establishes a potential circuit
by the solenoid coil 68 to close the contacts 10
from the direct current source to means for start
and ‘I2 in the manner indicated in Fig. -1, by the
ing the spare inverter, the energizing of said D. C.
moving of spring members 83. The solenoid coil
relay also opening the circuit through the heater
58 of the A. C. relay, operates a pivoted plate 84
generated time-delay relay.
and an arm 85 to move the switch member 60 20
2. An automatic electrical change-over relay
from its normal engagement with the contact of
system for quickly supplying alternating current
the lead ‘H to engage the contact of the lead ~82.
from a spare inverter upon the failure of a main
The heater-operated switch or relay 50 com
inverter for producing alternating current, com
prises a three-legged bracket member 86, the free
prising an alternating current relay having a nor
ends of the legs of which are rigidly attached to 25 mally closed and a normally open contact, a di
an upright metal bar 88 with the middle leg on
rect current relay having two normally open con
the opposite side of the bar to that of the upper
tacts and two normally closed contacts, a time
and lower legs of the bracket. The middle leg
delay relay for closing a switch which is normally
of the bracket 88 is covered with a piece of re
open, a source of direct current for said relay sys
refactory insulation and a resistance heating ele 80 tem, means for establishing a direct current cir
ment 98 wound around it to provide a heater for
cuit through one of the closed contacts of said
the middle leg of the bracket. The resistance
D. C. relay to means for starting the main in
wire 90 is connected to upper and lower termi
verter for generating alternating current, means
nals, respectively, mounted on a vertically-ar
for simultaneously establishing a direct current
ranged piece of insulating material 92, spaced 85 circuit through the time-delay relay, means for
from the vertical bar 88. It will be apparent that
establishing an alternating current circuit from
when the heating resistance element 90 is ener
the current output of the main inverter through
gized, it will heat and expand the middle leg of
the alternating current relay for operating the
the bracket 86 and cause the bracket to bend so
switch associated therewith to change it from its
that the contact 84 is moved into engagement 40 normally closed contact, means whereby said
with the contact of the lead 68. The closing of
time-delay relay establishes a circuit for energiz
this switch, as pointed out above, energizes the
ing the D. C. relay to open said closed contacts
relay ‘8.
and close the two normally open contacts one of
The speci?c apparatus elements shown in Figs.
which establishes an independent circuit through
2 and 3 are merely illustrative of switches and ' said D. C. relay to maintain it in energized con
relays which are adapted to carry out the func
dition and the other of which establishes a po
tions and operations described above in connec
tential circuit from the direct current source to
tion with the diagrammatic showing in Fig. 1 of
means for starting the spare inverter, the ener
the drawings. It will be apparent that different
gizing of said D. C. relay also opening the cir
relays, and that a different arrangement, may be 50‘ cuit through the time-delay relay.
used. The heater-operated time-delay switch or
3. An automatic electrical change-over relay
relay is merely one example of a time-delay relay
system for quickly supplying alternating cur
which could be used to retard the energizing of
rent from a spare inverter upon the failure ,of
the D. C. relay 40 until after the A. C. relay 58
a main inverter for producing alternating cur
had been energized by .the alternating current 55 rent, comprising an alternating current relay
built up from the main inverter I4. Various
having a normally closed and a normally open
other modi?cations may be made in the appa
contact, a direct current relay having two nor
ratus and at the same time carry out essentially
mally open contacts and two normally closed
the same functions and operations, without de
contacts, a time-delay relay for closing a switch
parting from the spirit and scope of the present 60 which is normally open, a source of direct cur
invention, as de?ned by the claims.
rent for said relay system, means for establish
What I claim is:
ing a direct current circuit through one of ‘the
1. An automatic electrical change-over relay
closed contacts of said D. C. relay to means for
system for quickly supplying alternating current
starting the main inverter for generating alter
from a spare inverter upon the failure of a main 65 nating current, means for simultaneously estab
inverter for producing alternating‘ current, com
lishing a direct current circuit through the time
prising an alternating current relay having a
delay relay, means for establishing an alternat
normally closed and a normally open contact, a
ing current circuit from the current output of
direct current relay having two normally open
the main inverter through the alternating cur
contacts and two normally closed contacts, a 0 rent relay for operating the switch associated
time-delay heater-operated relay for closing a
therewith to change it from its normally closed
switch which is normally open,’ a source of di
contact to its other contact, means including the
rect current for said relay system, means for es
switch of the time-delay relay for establishing a
tablishing a direct current circuit through one
circuit for energizing the D. C. relay to open
of the closed contacts of said D. C. relay to means 75 said closed contacts and close the two normally
2,410,877
7
ing the switch in said potential circuit whereby
open contacts one of which establishes an inde
pendent circuit through said D. C. relay to main
the spare inverter is started.
tain it in energized condition and the other of
5. In a change-over relay system for automat
which establishes a potential circuit from the
ically supplying current from a spare current
direct current source to means for starting the
source upon the failure of current supply from
spare inverter.
a main source of current, a relay, a current oper
4. In a change-over relay system for automat
ated time delay switch operable after a pre
ically supplying current from a spare inverter
determined period 01 time to close the switch,
upon the failure of a main inverter normally
means for energizing said relay by the closing of
supplying current, a relay, a heat-responsive 10 said switch after said period of time and Ior
thereby establishing a potential circuit through
switch provided with an electric heater operable
the relay to the spare current source, a switch
by current flow therethrough to cause the oper
in said potential circuit, means responsive to the
ation of said switch alter a lapse of a predeter
initial flow of current from said main source of
mined period of time, means for energizing said
current for opening said switch in said poten
relay through said switch after said period of
tial circuit, means for simultaneously supplying
time and for establishing a potential circuit
current to said time delay switch and through
through the relay for starting the spare inverter,
said relay to initiate the supply of current from
a switch in said potential circuit, means respon
said main source of current, and means respon
sive to the initiation of the operation of the main 20 sive to a failure of current supply from said main
inverter for opening the switch in said potential
source of current for closing said switch in said
circuit. means for simultaneously supplying cur
potential circuit to thereby establish a. circuit
rent to said electric heater and through said re
for the supply of current from said spare cur
lay to start the main inverter, and means respon
rent source.
sive to the failure of the main inverter for clos
MALCOLM K. PARKHURST.
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