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Патент USA US2410524

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NW- 5, 1946.
Filed June 28, 1941
6 Sheets-Shoot 1
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Nov. 5, 1946.
Filéd June 28, 1941
6 Sheets-Sheet 2
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NW- 5, 1946.
Filed June 28, 1941.
6 Sheets-Sheet 3
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£110 1/- was!
NOV- 5, 1946-
Fil'ed June 28, 1941 _
s Sheets-Sheet 4
Nov. 5, 1946.
Filed June 28, 1941
6 Sheets-Sheet 5
Nov. 5, 1946.
Filed June 28, 1941
a Sheets-Slieet e
Patented Nov. 5, i946
Donald E. Richardson and Robert E. Yates, cm‘
111., assignors to. Drying Systems, Inc.,
' > ' Chicago, 111., a corporation of Illinois
' Application June 28, 1941, Serial No. v400,332 ,
(CI. 158-28) ’
16 Claims.
This invention relates to fuel burners and like
‘these the- electricalcurrent ?ow through the
heating devices and particularly to safety ‘con- '
?ame path is Produced by impressing a relatively
‘high voltage across the ?ame-sensing electrodes,
,trol apparatus‘ for use with such devices. _ '
Heating, baking and‘ drying systems embody- '
this'voltage being su?icient to set up a current '
ing fuel burners or the like are subject-to hazards ' 5 having a great enough magnitude-(provided a
that arise when‘ fuel‘ introduced into a burner
isnot properly ignited and is thereby enabled '
to accumulate in an unburned condition in the
?ame is present) to operate a relay Or the like.
_In the other form ofthis apparatus an alter
hating-current voltage is impressed upon the
system wherein the productsoi combustion from
flame-sensing circuit and an electron tube means
the burner'are normally utilized, thereby create 10 is arranged to be governed not only according to
ing a danger of explosion'or other serious dam-_
the magnitude of vthe current flow, through ‘the
age. It is therefore essential that systemsor _
installations of_ ‘the aforesaid character be
equipped with means for detecting ‘failure of '
combustion and which will respond automatically
in such a contingency to e?ect a control opera
tion, such as. shutting ed the supply'of' fuel to i
the burner or burners, and thus safeguard the
‘system against risk of. explosion or the like
?ame gap,- but also in response to the phase re
. lation of this current with respect to the im
vpressedfvoltage. An example of thellast-mene
tioned apparatus is disclosed in the, copendin'g
application of Robert
Yates; Serial No. 245,-‘
173, ?ied December 12, 1938, now Patent No.
2,282,551,- patented May 12, 1942, and one of its
. outstandingadvantages is that it operates to’
Numerous types of safety control means or ap—~ 20 detect not only ?ame failure but also an unsafe
' ' paratus of the aforesaid character have been
heretofore proposed. The earlier» forms of such
condition which may arise when the ?ame gap is
--accidentally._ short-circuited. :
apparatus entailed the .use of heat-sensitive de
Another-of the classes of ?ame detectors to
vices such "as thermostats.'thermocouples, pres-’- ‘ > whioh'reierenoe hasbeen made hereinabove en
,sure'ldiaphrasms and the like which were 'in
'25 tails anarrangement in which the conduction of
-_ directly responsive to thepresence or absence of
‘electrical current through the ?ame is made to
a ?ame in a burner for eifeotingwhatever con- ._~ depend not so much upon the conductivity of the
_ .troi operations were necessary-with respect'to
‘ ?ame itself as upon the electron-emitting prop
' ‘ the burner.‘ Such devices were generally unre
erties of an electrode which is arranged tobe
‘ liable because an appreciable time lag was en
.tailed in the operation thereof and such ‘devices
- were readily affected by disturbances such as
" external air draits?whiohhad no direct. relation
3° heated by the ?ame. Buch'?ame detectors tend
- to be unduly sensitiveand moreover are,unsatis
,faotorywhen used onv alternating-current be
_ cause of the fact that the ?ame itself has a cur
to combustion conditions in the burner. Later 1 rent-rectifying effect which tends to block the
‘forms of ?ame detectors have operated in de ‘a unidirectional now‘ of current set up by therm
pendence ‘;upon' the ?ow of ‘electrical current ‘ _ ionic -emissiOn,,.._1m1ess the‘ electrodes are so
" across a gap~between a pair of spaced electrodes ’ arranged that the emitter’ electrons travel from
I that are‘ arranged to be bridged by the ?ame of _
the hot-toof
cool‘ electrode
(that is, inaway
- the burner.’ - Usually one of these electrodes con-y
' stitutes what is known in the art as a ?ame rod 40 from the burner nozzle). It is disadvantageous
which is disposed in the ?ame zone of the burner -r 1 to arrange the‘electrodes in this manner, how
ever, because-the cool electrode must then be
present, while the other electrode may consist
‘ placed outside of, but very close to, the edge of
of another time rod similarly situated or it may
the ?ame and any fluctuations of the ?ame due
be afforded by a portion of the burner structure 45 to cross-drafts .or the like may produce corre
. itself. Flame detectors of this character may be ‘ fsponding ?uctuations in the'?ow of ‘electron
roughly divided into several classes. , a
current, with detrimental effects upon the ac
Oneclass'of such apparatus entails anarrange
curacy of operation.
so as to be contacted by a ?ame when one is
ment in which the value ofan ohmic resistanc
Still another, classof ?ame detecting safety
of the electrical path betweenf‘the electrodes is 50 devices is that wherein the arrangement makes
the determining factor in the operation of the ‘ use‘ of the substantially unilateral conductivity
apparatus, the magnitude of this resistance be
of a ?ame without relying upon any thermionic
ing governed by the presence or absence of ?ame ‘ emission characteristics of an electrode. Be
in‘ the burner. ‘This class in turn may be said
cause of the greater ease with which a current
to comprise at least two varieties. In one of pl’; of electrons or negative ions may ?ow in the
thereto, a substantially unidirectional ?ow of
insulation failure or carbonization of the electrode
in the region Of the ?ame itself. In these prior
devices an all-around leakage check of the flame
sensing circuit is made as a condition precedent
negative ions or electron current takes place be
tween the spaced electrodes in a direction away
from the burner nozzle when an alternating-cur
rent voltage is impressed across these electrodes.
This unidirectional or recti?ed current is uti
lized to charge a dielectric body such as a con
‘ denser to thereby control the potential applied to
the control element or grid of an electron tube
the normal flow of current through the ?ame,
whether this exists by reason of short-circuiting,
direction of ?ame propagation than contrary
to operation of the system. However, once the
. operation of the burners has been initiated, the
safety apparatus thereafter functions to detect
10’ only ?ame failure or the existence of a low
and thus regulate the amount of current ?ow in
an output circuit of the tube. If the ?ame is ex
tinguished or becomes too low,v the recti?ed cur
rent ?ow ceases and the condenser loses its
charge, the effect of this being to so condition
the electron tube circuit that a control opera
tion is effected or a warning signal given.
The present invention falls in the last men
resistance shunt pathbetween the ?ame elec
trodes, and it will’ not operate safely upon ?ame
failure if a leakage path having a resistance com
parable with that of a normal ?ame path is estab
lished between the ?ame electrodes in the region
of the ?ame while the burner is in operation.
Usually in such burner systems a safe reaction of
the control apparatus in response to the detection
of current leakage conditions in a burner does not
tioned class, but it affords several features which
are not realized in prior devices of this character, 20 occur until the system has been recycled, that is,
disabled due to the operation of some other means
and particularly it takes into consideration the
such as a room thermostat and then started up
possibility that the ?ame-sensing means itself.
again, and if such recycling does not occur soon
may become defective in several respects and
enough, a risk of explosion is created.
thereby cease to afford protection for the burner
system. For example, a ?ame-sensing rod or 25 ' Hence, a further object of our invention is to
enable the control apparatus to recognize all of
electrode may become softened due to the heat of
the unsafe conditions enumerated hereinabove.
‘the ?ame and may therefore so bend that it en
and particularly to ascertain whether the elec
gages a part of the burner. This is dangerous
because the ?ame'is short-circuited and is there
> trlcal path existing between the ?ame-sensing
fore no longer included in the input circuit of 30 electrodes while the burner is in operation is
afforded by the ?ame itself or whether the elec
the electron tube, so that the apparatus furnishes
trodes have been electrically connected in some
a false indication of the‘presence of ‘a ?ame
other manner, especially by a bilaterally con
unless it is adapted to function safely ‘upon the
ductive shunt or leakage path having an ohmic re
occurrence of such a contingency. Then again,
instead of there being a direct electrical contact 35 sistance of a value comparable with that of a
normal ?ame path.
‘of the ?ame rod with the burner there may be.
embody elec
an accumulation of ‘hygroscopic, carbonaceous or.
tron tubes, particularly those of the gas-?lled
other electrically conductive substance extending
type, it ‘is desirable to have the tube perform as
between the ?ame rod and the burner which has
little work as possible so as to prolong the lliev
a leakage or shunting effect that may simulate a
of the tube. Normally the control apparatus may
?ame even when there is no combustion. of the
well be in an idle condition and needbe called
fuel in the burner. It is likewise possible that
upon to function only on comparatively rare
su?icient leakage may take place through the,
occasions, as in the event of flame failure or upon
insulation surrounding the conductors in the
the occurrence of some other hazardous condi
?ame-sensing circuit to‘ produce a condition
tion against which the apparatus is designed to
simulating the presence of ?ame in the burner.
‘guard, and even then it need operate for only a
Prior safety control devices operating on the ?ame
short time. Hence, it is advantageous to so ar
rectification principle were unable to prevent
range the tubes that they remain nonconductive
misoperation of the system under at least some
while the burner system is in normal operation, or
of the circumstances enumerated above and
therefore an important object of the present in 50 in other words during the greater part of the
time, and become conductive only in an emer
vention is ‘to improve such safety apparatus in
gency requiring operation of the control appara
these respects.
. Heretofore it has been proposed to afford means
for checking leakage effects such as have just been
described in a number of ways, as by providing
one of the ?ame-sensing electrodes with a sleeve .
. that is intended to intercept any leakage current
passing between the electrodes by apath other
‘ than through the burner ?ame, and upon the oc
tus, and so to do is an object of a preferred form
of the present invention.
Electronic safety control apparatus of the char
acter in which an electron tube is adapted to be
rendered nonconductive when the presence of a
' ?ame in the burner is sensed may become sub
Ject to misoperation due to internal failure of
For example, the tube may become
nonconductive due to burning out of the file
ment or because of other circumstances tend
ing to decrease its-conductivity so that the tube
currence of excess leakage from anvelectrode to 60 the tube.
such a sleeve the apparatus is intended to react
as though there had been a ?ame failure. Such
an arrangement is unsatisfactory because ob
viously the sleeve cannot extend into the ?ame
none since it would then prevent the proper oper
atlon of the device, and hence it is ineffective to
detect leakage paths in this region.
Other *prior devices of the character which
tends to give a false indication that a ?ame is
present in the burner even though this may not
actually be the case. In the aforesaid copend
ing application, Serial No. 245,173, there is dis
closed means for causing the apparatus to react
function in dependence upon the ohmic resistance 70 safely in the event one or more electron tubes
become defective due to filament failure. How
ever, inasmuch as this is only one of the pos
sleeve on the ?ame-sensingelectrode, and it has
sible causes of tube failure, we have in the present
been intended in certairflinf .these devices that
instance provided means forautomatically check
they are to react safely whenever there is any
of the ?ame path have dispensed with the special
substantial leakage from an electrode other theta.” ing reaehelectron tube to determine whether or
not it is capable of operating ‘properly and to
detect failure of the tube due to any of a num
ber of causes. Preferably such checking of the
tubes should take place prior to the initiation of
operation of the heater system, and so to do con
stitutes another object of the invention.
“ A still further object is to adapt the safety
control apparatus for use in multiple burner sys
Referring first to Fig. 1,, wherein the basic
construction is shown, it will‘ be observed that
the apparatus is adapted to control the opera
tion of a burner generally designated I2 which is
supplied with fuel through 9. pipe I3 that is
grounded as indicated at H. A self-closing fuel
valve I5 having an operating solenoid i6 is em
bodied in the fuel supply pipe ii to prevent the
tems in a novel manner without unnecessary
supply of ?lel to the burner l2 when the solenoid
duplication of parts and at the same time to 10 i6 is in a deenergized condition. ‘The burner I2
a?ord the features and advantages described
is equipped with a ?ame-sensing rod or elec
trode II which is insulatedly mounted in such a
A specific object of a preferred form of the
manner as to extend into the ?ame F of the bum
present invention is to so arrange an electron
‘er when such a ?ame is present, the electrode
tube and a condenser in relation to an alter 15 I‘! being maintained in predetermined spaced re
nating current source and to the ?ame-sensing
lation with the tip or ‘nozzle of the burner l2.
electrodes that the substantially unilateral con
The electrode i1 is preferably made of a heat
ductivity of the electrical path through the ?ame
resisting, electrically conductive material hav
ing substantially no thermionic emissivity. In
normally enables the condenser to become uni
directionally charged during those half-cycles of 20 the present instance the burner i2, being
the alternating current in which the tube is
grounded, constitutes the other electrode; how
inoperative (that is, in the inverse half-cycles).
ever, it will be understood that a second rod such
An ancillary object is to so control the tube by .
as H positioned closer to the nozzle of the burner ,
the condenser that the tube remains continu
ouslyv nonconductive if and.when a. substantial
unidirectional charge exists on the condenser,
than the first rod i‘! may be employed equally
well for this purpose.
The control apparatus constituting the pre
whereby, if this charge is dissipatedv due to the
ferred form of the present invention includes an
establishment of a bilateral electrical connection
electron tube l8 which is diagrammatically rep
between the ?ame-sensing electrodes, such as
resented in Fig. 1 as being of the tetrode type,
may be caused by a short circuit ora. leakage 30 having a shield grid 65 connected directly to the
shunt, or if this charge leaks of! without be
cathode l9. Other types of tubes such as triodes
ing replenished because of flame failure, the tube
may be utilized in place of the tube 18, but for
becomes effective to conduct current during for
the purposes of the present invention a tetrode
ward half-cycles of the alternating current.
has been found to be the most satisfactory. We
‘ Other and further objects of the present in 35 prefer to employ a gas-filled electron tube III in
vention will be apparent from the following de
order to afford a trigger action, but here again
scription and claims and will be understood ‘by
it is to be understood that we do not limit our
reference to the accompanying drawings which,
selves to such a tube since a, vacuum tube may
by way of illustration, show preferred embodi
be utilized in lieu thereof if desired. The cathode
ments and the principle thereof and what we 40 l9 ofthe tube I8 is electrically-connected to a
now’ consider to be the best mode in which we
line wire Li which leads to. one pole of a suitable
‘ have contemplated applying that principle. 0th
source of alternating current. A line wire L2
er embodiments of the invention embodying the
leading from the other pole of said source of
same or equivalent principle may be used and
current is’ electrically connected to one end of'the
structural changes may be made as desired by 45 winding of a relay 20, the other end of this relay
those skilled in the art without departing from
winding being connected by a conductor 2| to
the present invention andzthe purview of the
the anode 22 of the tube ii. The heater ‘orfila
appended claims.
ment 23 of the tube I8 is electrically connected
to a suitable ?lament voltage supply source,
Fig. 1' is a diagrammatic view of the basic form 50
The relay 2|! has a contact 24 which is normally
of our invention;
closed when the relay is in a deenergized condi
Fig. 2 is a diagrammatic view similar to Fig. 1_
tion so as to establish an electrical connection‘
but illustrating one manner in which the inven- ,
from a conductor 25, which leads from one end
tion may be adapted for use in a, multiple burner
of the winding of the fuel valve solenoid IE, to
system; .
65 another conductor 26 that leads to one pole of a
Fig. 3 is a. schematic view of a master control
suitable source of voltage. The other pole of this
In the drawings,
unit embodyingvarlous improvements over the
apparatus shown in Fig. 1;.
conductor 21 to the other end of the winding of -
Fig. 4 is a. schematic view similar to Fig. 3
and showing another manner in which the ap
paratus may be incorporated in a multiple burner
- system;
Fig. 5 is a simpli?ed wiring diagram of the
apparatus illustrated in Figs. 3 and 4;
Fig. 6 is a diagrammatic view showing the
manner in which spare control units may be pro
tact 24 opens: upon energization of the relay 20,
the solenoid I6 is deenergized and the fuel valve
The voltage between the line wires LI and L2
Fig. '7 is a plan detail view of a tube socket as
Fig. 7A is a sectional detail view taken sub
stantially on the line ‘IA-‘IA on Fig. '7;
Fig. ‘7B is a partly sectional detail view of a
screw shown in Fig. 7A; and ,
Fig. 8 isa diagrammatic view of a modified form
of the invention.
the solenoid i6. Thus the solenoid i6 is main
tained energized so long as the relay contact 24
is closed, and while it is in this condition it holds
the fuel valve ii open to enable the supply of
fuel to the burner l2. However, if the relay con
Ii closes.
it is mounted in a control unit;
source of voltage is electrically connected by a
is of a sufficient value that it tends to cause the
tube i8 to fire and conduct current during those
70 half-cycles of the alternating current when the
anode 22 is positive with respect to the cathode
l9, thereby energizing the relay 2!! and breaking
the electrical connection between the conductors
25 and 26. However, as will be “seen presently,
the tube I8 is prevented from becoming conduc
tive under normal conditions when there is com
bustion of the fuel in the burner, so that the relay
20 remains deenergized and thereby enables the
‘fuel valve solenoid it to remain operative for
maintaining the fuel valve l5 open.
Since the tube I8 is to be responsive to com
bustion conditions in the burner l2, means have
F between the electrode I1 and the burner it.
As the apparatus is arranged in Fig. 1, the tube
It is conductive only during those half-cycles
of the alternating current in which the line-wire
L2 is positive with respect to the line wire Ll,
or in other words during the forward half-cycles.
Under these conditions the electrode I1 is nega
tive with respect to the burner 12 and therefore
the ?ame F is effective to block the flow of elec
of a ?ame as F in the burner, Thus, the control 10 tron current between the burner l2 and electrode
I1. 'During the inverse half-cycles, in which "
element or grid 28 of the tube It is connected
the polarities of the line wires Li and L2 are re
through the medium of a protective resistor 29 to
versed, the tube i8 is nonconductive but the flame
a conductor 30 which is electrically connected to
F then conducts current. Under the latter cir
the ?ame-sensing electrode l1. This conductor
30 is also electrically connected by a resistor Ii 1,5 cumstances, inasmuch as the line wire Ll is at
positive potential with respect to the line wire
to a conductor II which is connected by the ?la
LI, the condensers "and 31 are so charged that
ment of a lamp 3! to the wire 32 leading to the
the grid 28 of the tube I8 assumes a negative po
cathode i9 and line wire Ll, In order to prevent
tential with respect to the cathode la. The full
stray electrical disturbances from affecting the
tube II, the conductor 30, which in ordinary 20 charge on these condensers may be built up
throughout a series of inverse half-cycles, the
practice is apt to be of considerable length, is
length of time required to impart a substantially
enclosed in a metallic sheath II which is insu
steady charge to these condensers being deter
lated therefrom throughout its length, this
mined by the values of capacity and resistance
sheath 34 being electrically connected to the con
ductor ‘I. Usually the dielectric insulating me 25 in the circuit. Once the condensers ‘have as
sumed their full charge, the grid 28 is imparted
dium between the conductor 30 and the sheath
sufficient negative bias to prevent conduction
8‘ a?ords a slight amount of electrostatic capac
ity, which has been diagrammatically represented ’ of current through the tube l8.v The resistor Ii
has a high enough resistance so that the con
in Fig. 1 as being lumped in a single capacitance
30 denser charge is not appreciably diminished dur
8|. hereinafter referred to as a condenser.
ing the forward half-cycles so long as a flame P‘
- In order to complete the flame-sensing circuit
is maintained in the burner l2. Under these con
the line ‘wire L2 is grounded as indicated at It
ditions the relay 20 remains in a deenersized
so that whenever a flame F is present in the
state to thereby maintain an energizing circuit
burner I! an electrical circuit is established from
line wire L2 through the burner l2, flame F, elec 35 to the fuel valve solenoid l6, and hence fuel con
tinues to be supplied to the burner l2.
trode I ‘I, conductor Ill, and through the resistor
‘If for some reason the ?ame F should become
II and condenser 35 in parallel to the conductor
extinguished or unduly low, however, the above
ll, thence through the lamp 33 to the cathode
been provided to control the operation of this
tube in accordance with the presence or absence
described ?ame~sensing circuit is broken and
the line wire Ll. To augment the path afforded 40 the condensers l5 and I1 discharge through the
resistor 3|, causing the grid 28 to lose its nega
by the condenser 35 and resistor 8!, another con
tive bias‘, and thereupon the tube is is rendered
denser 81 may be electrically connected across
conductive during forward half-cycles of the
the conductors 30 and 4| in parallel with the
alternating current. Hence, a pulsating recti
resistor ll. Ordinarily the amount of current
flowing through this ?ame-sensing circuit is so 45 fled current passes through the winding of the
relay 20, causing this relay to energize and open
minute as to be incapable of lighting the lamp
its contact 24. Preferably the relay" is of the
ll, except when certain kinds of short-circuits‘
slow-to-release type so that it maintains its con
occur, as will be explained.
@ ~
tact 2| open so long as pulsating current is de
For the purpose of further protecting the de
return wire 32 which is electrically connected to ,
vice from stray electrical disturbances as well as 50 livered to this relay winding by the tube ll.
The energizing circuit for the fuel valve solenoid
to prevent accidental injury by electrical shock
It is thereby broken; causing the fuel valve II to
to persons working with the apparatus, the cable
close and prevent any further supply of fuel to
comprising the conductor 30 andsheath 84 may
the burner it.
be passed through a conduit 38 which is grounded
as indicated at 38, the sheath ll being suitably 58 For the purpose of initiating operation of the
burner- ‘after it has been disabled by the safety
insulated from this conduit. The presence of the
apparatus a normally open starting switch ll
sheath 3| intermediate the conductor I0 and
may be connected in parallel with the relay con
' . grounded conduit 38 has a tendency to prevent
tact 24 in the fuel valve energizing circuit. This
excessive leakage through the insulation sur
rounding the conductor 10, inasmuch as this 00 switch is momentarily closed 'by the operator to
sheath lslmaintained at substantially the same
energize the solenoid l6 independently of the
potential as the line wire Li and therefore tends
'relay 20 to enable fuel to be supplied to the burn
to divert any leakage current proceeding from the '
er II. The fuel is ignited by suitable ignition
line wire L2 by way of ground away from the con
means (not shown) which is temporarily’ren
doctor I0.
dered operative for the purpose of starting the
It has been explained herelnabove that a flame burner in operation, such ignition means pref
as F in a fuel burner as It has the property of
rectifying alternating current; that is, during
erably being under the control of the starting
switch 40. When the operatorascertains that
those half-cycles in which the burner I2 is nega
tive with respect to the electrode I'I, electrons or 70 the fuel has been properly ignited he releases
the switch 40 and thereafter the valve energizing
negative ions may ?ow from the burner I! to the
circuit is maintained closed through the contact
electrode I‘! in the direction of ?ame propaga
24 of the. relay Ill (the tube I! having been ren
tion, provided a ?ame as F is present. However,
during the intervening half-cycles substantially
dered nonconductive upon the establishment of a
no current flow can take place through the flame 15 name F in the burner it‘) unless and until a
hazardous condition again arises requiring a
the condensers 35 and 31. and the relay 20 is
thereupon energized to shut off the fuel supply.
vshut-down of the system.
There are occasions in practice when the safety
control apparatus is rendered partially defective
by unwanted leakage or short-circuit conditions
in the ?ame-sensing circuit. For example, the
It has been stated hereinabove that the pres
ent invention may be readily adapted for use in
multiple burner systems, and one such arrange
ment for achieving this object is diagrammatical
electrode ll may accidentally come into contact
with the burner l2 or to some other grounded
part of the structure, or there may be a leakage
ly illustrated in Fig. 2.v Thus, there is provided a
master control unit designated MU which is sub
stantially identical with the device shown in Fig.
10 l, and which is operatively associated with one
path existing between the electrode I‘! and burn
er l2 due to accumulation of carbon deposits or‘
the like. Such a‘, condition is undesirable because
then current ?ow can take place between the
electrode l1 and burner I2 independently of
whether or not the ?ame as F is present. In
of the fuel burners l2 included in a bank of bum
ers that are supplied with fuel by a single pipe I3
having the necessary branch connections to the
various burners.
the apparatus shown in Fig. 1, however, .the
by like reference characters and it will be un
derstood that the operation of the master control
unit MU is substantially the same as that of the
safety control apparatus will respond in a safe
manner under such circumstances. Thus, if
there is a short circuit between the electrode l1
apparatus shown in Fig. l.
and the burner 12, the potential of the grid 23 20
becomes substantially the same as that of the
I line wire L2 so that the tube I3 is rendered con
ductive during forward half-cycles.
Corresponding parts of the
'- structure shown in Figs. 1 and 2 are designated
‘ '
In addition to the master control unit MU there
are provided a plurality of secondary control
units designated SU which are respectively asso
ciated with the other burners I2’ 01' the system
in much the same manner as the master unit MU if there is a leakage path between the electrode
i1 and burner |2,‘then because of the non-recti 25 is associated with the burner l2. Thus, each
burner I2’ has an electrode I1’ which is connected
fying or bilateral character ‘of this leakage .path
by a shielded conductor 30" to the control grid
the condensers as 35 and 31 do not assume any
28' of the electron tube ill’ in the respective sec
appreciable unidirectional charge. Any charge
ondary unit SU. The shielded conductors 30 and
which the condenser receives during the inverse
half -cycle is generally lost during the succeeding 30 30' may be passed through individua1 grounded
conduits such as 38, Fig. 1, or it may be pre
ferred to run these conductors through a common
forward half-cycle so that the grid ‘23 has no
opportunity to retain its negative bias and there
fore the tube I8 is rendered conductive to inter
rupt operation of the burner I2.
It should be noted in this connection that safe
operation of the apparatus is insured even though
‘the leakage resistance in the ?ame gap is of a
value approximately equal to the ohmic resistance
of a ?ame as F, and this is true even though the
false ?ame resistance comes into being while the
burner is in‘ operation. In most instances where
bilateral conduction through a leakage path oc
curs, the response of the apparatus is practically
instantaneous. In other instances, where the
leakage resistance is of a critical value, the ap
paratus may wait until there'is an actual ?ame
failure (if and when this occurs) before operat
ing to shut off the fuel supply to the burner. ‘In
any event, however, the emission of unburned
fuel is prevented, and it is not necessary as in
the case of prior types of control apparatus to
go through the process of recycling the system
(that is, effecting a shutdown by other means and
then starting the system inoperation again) in
order to so condition the apparatus that it will
disable the fuel supply means upon detecting
current leakage in the ?ame path.
Y conduit for at least a portion of their respective
lengths._ The secondary units are substantially
Another undesirable condition may exist when
there is excessive leakage or a direct short-cir-'
35 identical in construction with the master unit
MU except that they do not include any relays.
as 20, and hence corresponding parts of the mas
ter' and secondary control units bear similar ref
erence characters which differ only in the prime
40 sumxes. The anodes 22' of the tubes l3’in the
several secondary units SU are respectively con
nected by conductors 2|’ to a common conductor
45 which is electrically connected to the anode 22
of the tube l8 in the master control unit MU.
45 In like manner the cathode IQ of the tube in and
> the cathodes I!’ of the tubes III’ are all electrical
ly connected by wires 32 and 32', respectively, to
a common conductor 46 leading to the line wire
Ll. Hence, the electron tubes [8 and I8’ in the
60 various control‘ units are all connected in par
allel and the combined anode current of these
tubes passes through the winding of the relay 20.
The conductors 30' are connected through the
medium of resistors 30’ and condensers 31' to con- _
ductors 4|’, which are also connected to the
sheaths 34', and from the conductors 4|’ electri- ’
cal connections with the respective cathode re
turn wires 32' are established through the ?la
. ments of lamps 33’ embodied in the units SU.
It will be recalled that when a ?ame as F is
cuit between the conductor 30' and the sheath“, 60
present in a burner as I2 the associated tube as
such as may be caused by a failure of the insu
I8 is rendered nonconductive at all times. Simi
lation. In this case the amount of resistance in
when the ?ames are present in all of the
parallel with the condensers 35 and 31 is greatly
other burners l2’ the corresponding tubes I8’ are
reduced so that these condensers discharge prac 65 all nonconductive, and under these circumstances
tically instantaneously during forward 'half
the relay 20 remains deenergized. However, if
cycles of the alternating current, thereby render;
a ?ame in any one of the burners becomes ex
ing the tube _I8 conductive ‘with the effect afore
.tinguished, or too low, the tube associated with
said. There is also a possibility that the sheath
such burner is rendered conductive so that cur
34 may become grounded, causing the filament 70 rent ?ow takes place in the common anode cir
of the warning lamp 33 to be connected directly
cuit including the windings of the relay 20, which
across the line wires LI and L2. This produces a
relay thereupon energizes and opens its contact i
relatively heavy flow of current through this fila
24. The fuel supply pipe I 3 has a valve l5 con
ment, causing the lamp 33 to light. The tube l3
trolled by the solenoid I6 which receives its ener
also becomes conductive due to the shunting of 75 sizing current through the relay contact 24. but
when the relay 2!! is energized to open the con
tact 24 the solenoid 1-6 deenergizes and enables
the fuel valve It to close and thereby interrupt
the supply of fuel to all of the burners in the
system. One of the advantages of arranging the
electron tubes to be nonconductive under normal
combustion conditions is that the relay 2') need
merely be sensitive to any substantial current
respectively.- The pilot burner 50 is so positioned
with respect to the main burner 5| that a pilot
flame originating in the burner 50 may ignite fuel
issuing from the nozzle of the main burner 5|.
A ?ame-sensing electrode I1 is mounted in asso
ciation with these burners in such a manner that
it extends into the region of the pilot ?ame, and
if gaseous fuel is being utilized in the main
burner the electrode I] may also pass through the
flow whatsoever in the common anode circuit.
On the other hand, if the tubes were arranged 10 main burner ?ame zone.
However, if atomized
liquid or pulverized solid fuel is being used in the
to be conductive when ?ames were present in
main burner it may be preferable to arrange the
their corresponding burners, and nonconductive
electrode l1 so that it barely skirts the fringe
in the absence of flame, the relay 20 would be
of the main ?ame as it enters the pilot ?ame
required to detect a proportional decrease in
total anode currentlfor each tube rendered non 15 zone, thus minimizing the possibility of fuel
gathering on the electrode and forming carbon
conductive. In a multiple burner system having,
accumulations thereon, while at the same time
say, sixteen burners and associated ?ame-detect
insuring that the pilot ?ame must be at least
ing tubes, the operation of the relay 20 might
high enough to ignite the atomized or pulverized
become quite critical and on that account easily
in?uenced by external factors such as ?uctuating 20 fuel in order that it may contact the electrode.
The pilot and main burner fuel supply pipes H
line voltages having no relation to the combustion
and 53 are respectively provided with fuel valves
conditions in the burners. Hence, we prefer that
54 and I! which are operated by solenoids I8 and
the electron tubes should be adapted to pass cur- ’
51, respectively. When these solenoids are in a
rent only under abnormal conditions.
The other safety features described herein 25 deenergized condition the fuel valves 54 and II
are closed so that fuel is not supplied to the
above in connection with the circuit of Fig. 1 are
burners 50 and ii.
also afforded in the case of each and every con~
The application of the control apparatus
trol unit in the multiple system as shown in Fig.
shown in Fig. 3 to a burner system having a plu
2. Thus, if there is a shunting of the ?ame gap
in any particular burner due to grounding out of 30 rality of main burners and pilot burners will be
explained subsequently in connection with Figs. 4
the ?ame-sensing electrode or the building up of
and 5, and for ‘the present it will be assumed that
a non-rectifying resistance path across the ?ame
the control apparatus comprises merely a master
gap as a result of carbonization and the like, the
unit MU controlling a single main burner 5i and
electron tube in the control unit associated with
that burner is rendered conductive to shut off 35 associated pilot burner 50. Electrical current is
supplied to the apparatus by a suitable source of
the supply of fuel. The same is true if there is
alternating-current voltage whenever the double
an insulation failure which causes excessive leak
pole switch S is closed. One of the poles of the
age in the cable including a conductor 30 or 30'
switch 8 is connected directly by a wire L0 to a
leading to the ?ame electrode of a particular
burner. Hence, a dependable safety control ap-, 40 terminal 58 on the control unit MU. The other
vparatus for a multiple burner system is afforded
pole of the switch 8 is connected to a wire L!
which serves as one of the line wires for the
with a minimum duplication of parts, it being
electrical system when the switch S is closed.
noted that only one relay 20 and fuel valve l5
The pole of the switch S to which the wire Ll is
need be employed. The other portions of the
apparatus such as electron tubes, resistors and 45 connected is likewise electrically connected to
another line wire Ll through the medium of a
condensers are relatively inexpensive so that the
preliminary control apparatus indicated by the
construction is quite economical in addition to
rectangle designated 59, Fig. 3. Such preliminary
being reliable.
control apparatus may comprise several forms
It has been mentioned that another object of
the present invention is to provide means for 50 of contact-making devices such as ?ow switches,
time delay devices and the like which all serve
automatically checking the conductivity of the
the function of insuring that the heater in which
electron tube or tubes embodied in the safety
the products of combustion from the burner 5|
control apparatus as a condition precedent to
are to be utilized is first thoroughly scavenged
initiating operation of the fuel burner system,
and otherwise conditioned for operation before
and to thereby insure that if any tube is defec
any combustion can take place. After the ap~
tive so that it is unable to give an indication of
?ame failure, the system will be prevented from ' paratus' 59 has performed this function it causes
an electrical connection to be established between
operating until a good tube has been substituted
the line wire LI and the switch pole connecting
for the defective one. It is also desired to insure
that the system will not function unless tubes 60 with the source of electrical current.
The line wires Li’ and L2 are respectively con
which are especially adapted to be used in a
nected to terminals 60 and 61 on the control unit
safety control apparatus of this character are
MU, and conductors G2 and 53 lead from these
utilized in making tube replacements. A fur
terminals to the primary winding of a trans
ther object is to adapt the control apparatus for
former 64 included in the unit MU. The second
governing the operation of a burner system hav
ary of the transformer 6i supplies voltage to a
ing both pilot burners and main burners. For
filament 23 of the tube l8, this tube being similar
the purpose of attaining these and other objects
to and performing the same function as the tube
the type of apparatus illustrated in Figs. 3, 4
I8, Fig. l. The tube 18 is provided with a shield
and 5 may be conveniently employed.
Referring ?rst to Fig. 3, the control apparatus 70 grid 85 that is directly connected to the cathode
IQ of the tube, and the cathode is is also elec
is there represented as comprising a master unit
trically connected to the center tap on the second
MU which is operatively associated with a burner
ary of the transformer 64.
system including a pilot burner 50 and a main
An electron tube such as [8 of the character
fuel burner 5|, these burners being supplied with
which we contemplate utilizing in the circuit of
fuel through separate supply pipes 52 and 53.
Fig. 3 is customarily provided with eight prongs
tube as I 8 shown in Fig. 3. This arrangement
insures that the heater of the thermal switch
‘II will not be energized unless a tube particu
larly adapted for use in the control unit MU is
in its base, these prongs being adapted to be re~
ceived in correspondingly positioned contacts afi
forded in a tube ‘socket as 9, Figs.‘ 7 and 7A. The
various elements. of the tube are internally con
nected to respective prongs, and electrical con
employed. It should also‘be noted that the line
wire LI, which is not grounded, normally has
nection between these tube elements and the por- '
a direct electrical v‘connection with the contact 4
tions of the circuits external of the tube are es
of the tube I8 and thence through the jumper
tablished through the prongs of the tube and
66 to contact I, but if the jumper 66 is‘ missing
the contacts of the tube socket in which these 10 there is no electrical connection of 'the line wire
prongs are received, the various external circuit
LI with the contact I. Under the latter condi
conductors being soldered or otherwise suitably
tions the contact I is at substantially the same
secured to the aforesaid contacts. In Fig. 3 the
potential as the line wire L2, which is grounded
various tube socket contacts are diagrammatically
as indicated at 86. (It will be understood, of
represented as though viewed from the bottom 15 course,
thatv the wire L2 itself need not be ground
' and are designated I to 8, respectively. Ordinar
ed if they pole of the source of electrical cur
ily contact I‘ is not used except when the tube is
rent to which-this wire is connected by the switch
provided with an integral shield, in which event
S is grounded.) Hence, if an operator should
the shield is connected to the prong that ?ts into
carelessly insert into the tube socket a tube hav
contact I, which is in turn grounded. However, 20 ing a shield electrically connected to the prong
in the present instance the electron tubes which
which ?tsinto the No. 1 contact, but not being
are to be employed in the apparatus are not
provided with a jumper 86, there is no danger
shielded, or if they are shielded the shields are
he will receive a shock, since the potential
connected to ground in some manner other than '
of the ungrounded or‘ “hot” line wire LI is not through the No. I contact in the tube socket. 25 applied to the shield of the tube.
The ?lament 23 is'connected to the prongs that
_ The purpose of the thermal switch ‘I3 is to
are received in contacts 2 and ‘I, across which
afford a preliminary warming-up period for the
the secondary of the ?lament transformer 81 is
?lament 23 of the tube It before any anode volt
connected. The contacts numbered I, 5 and 8
age is supplied to the tube, this being a precau
are respectively adapted to receive the prongs 30 tionary measure toprevent damage to‘ the tube.
that are connected, to the anode 22, contjrollgrid The heater ‘II of the switch ‘I! starts to warm
28 and screen grid 65 of the tube I8.
up concurrently with the ?lament 23, and after
For the purpose which will appear presently,
.ample time has ‘elapsed for the ?lament 23 to
we prefer to provide each tube I8 with a special
Jumper 66 which electrically interconnects the
prongs of the tube I8 that are'adapted to be re
ceived in the contacts land 4 of the tube socket.
If convenient, this jumper may be incorporated
in the tube base in the course of manufacture
‘thereof so that the two prongs to which the ends
of the jumper are connected will be electrically
in permanent connection with each other. The
attain operating temperature, the bimetallic strip
35 80 ,ofthe switch It ?exes and closes the switch
to establish an electrical connection ‘between the a
_ aforesaid conductor ‘I2 and another conductor ll
contact 4 of the tube socket is connected by a
conductor 61 to the conductor 62 leading to the
line terminal 60 of the control unit, while con
tact I is connected by a conductor 68 to a ter
minal 89 on the control unit MU. In the present ‘
I instance, where ‘only'a single control unit is being
that leads to one end of the winding of the relay '
18,-the other end of this relay winding being
40 ' connected
by the conductor 82 to the conductor
‘I9 leading to the line wire L2. Closure of the
switch‘I3 therefore causes relay It to energize,
and-in so doing the relay movesv its contact blade
‘I5 away from the contact 15a and Into engage
ment with a contact 15b. The heater ‘I! of the
switch" is thereupon deenergized and the bi
metallic strip III thereafter cools off and sepa
rates the contacts of the switch ‘II. The contact
employed, the terminal 69 is connected by a
15b of the relay ‘I6 is connected to the conductor
Jumper 10 to a similar terminal ‘II from which 50 8|
which leads to the winding of this relay, so
a conductor ‘I2 leads to one contact of a thermal
that immediately upon energizatlon of relay 18
switch generally designated ‘I3. A branch con
a holding circuit is established from‘the con
ductor ‘I4 electrically connects the conductor 12
to a movable contact blade 15 of a relay ‘I6 in- '
cluded in the control unit MU. When the relay
‘I8 is in a deenergized condition the blade ‘I5
engages a stationary contact 15a from which a
conductor 11 leads to one end of the winding ‘I8
ductor ‘I2 through conductor ‘Hand contact 15b
to the relay winding; hence opening of the switch
‘II does not deenergize the relay ‘I6, which re
mainsiocked up through the just described hold
ing circuit. Thus the thermal switch ‘I3 merely
performs the function of initially energizing the
of-a heating element embodied in the thermal
relay ‘I6 and is not called upon to operate con
switch ‘I3, the other end of this heater winding 60 tinuously
for holding the relay energized. .
being connected by a conductor ‘I9 tothe conduc
‘I6 has another contact “which is
tor 63 which leads to the terminal BI on the con
normally open when this relay is in a deenergized
trol unit MU.
condition, but when the relay ‘I8 is energized in
When the line wires LI and L2 are potential
the manner just described the contact 84 closes
' ized a predetermined time following closure of the
and electrically connects a‘ conductor 83 with
switch S, a circuit is completed from wire LI
another conductor 85 that is tapped onto the
through the conductors 62 and 61, jumper 86
cathode return wire 32. The conductor 83 is
in the base of the tube l8, conductor 68, jumper
‘electrically connected by the conductors 61. and
‘III, conductors 12 and ‘H, relay contact 15a and
62 to the terminal 80 to which the line wire LI
conductor 11 to the heater winding ‘I8 and thence 70 is connected. Hence, so long as relay ‘I6 is main
by conductors ‘I9 and 63 back to the terminal 6|
tained energized, the cathode return .wire 32 is
which is connected to the line wire L2. It is to
potentialized by the line wire LI through the
be noted, however, that this circuit could not ' medium of the closed relay contact 84.
be established if a tube which was not equipped
When the switch S is ?rst closed, a circuit is
with a jumper as 66 had been used in lieu of a 75
completed through the wire L0 to the terminal
50, thence through a conductor 90 to a stationary
contact 96a, of the relay ‘I6, thence through a
contact blade 86. which is normally engaged with
the contact 80a, and a conductor 81 to a terminal
83 on the control unit MU. An alarm 99, which
may be of either the visible or audible type, is
connected on one side to the terminal 08 and on
the other side to the line wire-L2, and hence
when the switch S is first closed the alarm 89
22 and cathode I9 and thus produces a flow of cur
rent through the tube I9. This current flows only
during forward half-cycles of the alternating
current, that is half-cycles in which the line wire
L2 is positive with respect to the line wire LI, so
that a pulsating direct current is passed by the
tube I8. The relay I09 is a slow-to-release relay
which energizes when such a pulsating current
is sent through its winding and assumes a con
tinuously operative condition so long as such cur
is energized from the wire L0 to thereby indicate
that the preliminary scavenging operations re
ferred to hereinabove have commenced. When
the relay ‘I6 is energized in the manner just de
scribed, however, there is a momentary interrup
tion in the operation of the alarm 89‘ while the 15
contact blade 90 of the relay moves out of engage
ment with the contact 09a and into engagement
with the contact 09b. A conductor 9I connects
the contact 96b to a contact 92a of another relay
93. A contact blade 92 is normally engaged with 20
the contact 92a when the relay 93 is deenerglzed,
and this blade 92 is connected by a conductor 95
to the cathode return wire 22 leading to the cath
ode l9 of the tube I9. Inasmuch as the wire 32
is potentializ‘ed by the line wire LI upon ener
gization oi’ the relay 19, as just explained. the
alarm 09 is maintained energized from this
rent flow continues.
The relay I09 has a pair of movable contact
blades H2 and H3 which are normally engaged
with contacts IIZa and I'l3a when the relay
is deenergized, but upon energization of the re
lay these blades become separated from the con
tacts I I2a and I I3a and engage the contacts I I2!)
and II3b. The blade H3 is connected ‘by. a con
ductor Ill to the cathode return wire 32 and the
contact II3b is connected by a conductor H5 to
a terminal IIS on the control unit MU. For sin
gle-burner operation the terminal H9 is con
nected by a jumper ill to a terminal II! on the
control unit MU, which latter terminal is con
nected by a conductor II9 to‘another conductor
I20 interiorly of the unit MU. The conductor
I20 leads'to one of a pair of spaced contacts I2I
which are adapted to be bridged by the plunger
source until such time as the relay 93 becomes
of a push-button switch I22, the other of this
energized in a manner to be described. ‘
pair of contacts I2 I being connected to a conductor
The control grid 28 01 the tube It is connected 80 I23.’ Normally the plunger of the switch I22 is
through a protective re'sistor29 and a conductor
retracted into engagement with a pair of spaced
I00 to a terminal "II on the master unit MU, to
contacts I24, one of which is connected to the
which terminal the conductor 30 leading from the
conductor I23 and the other to a conductor I25,
?ame-sensing electrode I1 is connected exteriorly
the conductors I23 and I25 being connected to
of the control unit. The sheath 34 enclosing the
terminals I29 and I21, respectively, on the control
conductor 30 is electrically connected by a con
unit MU.
ductor II to a terminal I02 on the control unit
MU, while the resistor 3| and condenser 91 (which
perform functions analogous to those of the like
numbered parts in Fig. 1) are connected in par
allel between the terminals I02 and IN. The
terminal I02 is connected by the ?lament of a
lamp 2! to a. terminal I03, and in the present
Assuming that the preliminary scavenging and
like operations have been duly performed and
that the tube I9 has become conductive to ener
gize the relay I09, the operator manually depresses
the push button I22 to thereby electrically con
nect the spaced contacts I2I. Thereupon a cir
cuit is completed from the cathode return wire
instance where there is but a single burner to be ‘5 32 (which is connected to the line wire LI)
controlled. a Jumper I09 interconnects the ter
through conductor I“, contact I I36 of relay I09,
minal I03 with another terminal I05 to which
conductor II5, jumper II'I, conductor H9, con
the cathode return wire 32 is connected. The
tacts I2! and conductor I23 to the winding 01'
pilot burner fuel pipe 52 is grounded as indicated
relay 93, thence through this relay winding and
at I09 so that an electrical connection between 50 conductors I28 and II I to the line wire L2. Re
the grounded line wire L2 and the electrode I1
lay 93 is thus energized and closes a normally open
is a?orded through the medium of a ?ame from
contact I29 thereof, at the same time disengag
the pilot burner 90 whenever such a ?ame is
ing the contact blade 92 from the contact 92a
and engaging this blade with the contact 92b
During the preliminary operations which have 55 that is connected to the aforesaid conductor I20.
been described thus far, the fuel valves 94 and 59
Disengagernent of the blade 92 and contact 92a
remain closed and no ?ame exists in either the
breaks ‘the circuit‘to the alarm 09 and causes
pilot burner 50 or the main burner 5i; hence no
this alarm to cease operating.
current ?ow can take place through the ?ame
Engagement of the blade 92 of the relay 93
sensing circuit including as
I1 and
charge ‘exists
on ‘o with the contact 92b thereof closes a circuit from
conductor 30. Inasmuch
the cathode return wire 32 through conductor 95,
contacts 92 and 92b, conductor I20, contacts HI
“the condenser 31 under these conditions, the con
trol grid 28 of the tube I9 is at substantially the
0! the switch I22 (provided the plunger of this '
same potential as the cathode I9. Anode voltage
switch is maintained depressed by i the opera
is supplied to the tube I9 through a path compris
tor) and conductor I23 to terminal I29 and thence
ing a conductor I09 which leads from the
exteriorly of the control unit ‘MU through a con
or anode contact in the socket of the tube I0 to
ductor I30 to the winding of the solenoid 56 which
one side of the winding of a relay I09, this wind
operates the pilot fuel valve 54, this solenoid
ing being connected on its other side by con
being connected on its other side to the line wire
ductors H0 and III to the conductor 93 leading
L2 to complete the circuit. A parallel circuit is
to the terminal 0| to which the line wire L2
likewise established under control of the switch
connected. It has been previously explained
I22, this circuit extending from the conductor I23
that the cathode I9 and its return wire 32 are
through a conductor I3I connected therewith,
connected to the line wire LI when the relay 16
contact blade H2 and contact II2b of relay I09
is energized; hence energization of this relay 75 (this relay still being in an energized condition)
causes a voltage to be impressed across the anode
2,410,594 '
29 of the tube I9 appreciably negative with re
and a conductor I92 to a terminal I99 on the con
trol unit MU. and thence the circuit continues
exteriorly of the unit MU through a conductor
III to the primary of an ignition transformer
I95 and. from this primary winding back to the
line wire L2. Thus the pilot fuel valve solenoidv
99 and theignition transformer I95v are concur
rently energized when the push button I22 is de
Pressed. The pilot burner 50 is equipped with a
spark, plug I96, the terminal of which is connected 10
spect to that of the cathode I9, and whatever
charge leaks off of the condenser 91 during such
forward half-cycles is regained during the suc»
ceeding inverse half-cycles. Hence, the tube It
is prevented from conducting current so that
current ?ow ceases in the anode circuit includ
ing the winding of the relay I09. The relay I09
therefore deenergizes, causing its contact blades
-I I2 and III to separate from the contacts “2?;
and II2b and‘ reengage the contacts H21; and
I Ila, respectively, one of the results of this being
this secondary, being grounded. High potential / that the circuit to the primary of the ignition
transformer I95 is broken and the spark plug
is thus applied to the spark plug as the pilot fuel
—' wvalve v“opens so that the fuel issuing from the 15 I99 is deenergized. Also, the electrical connec
tion between the conductors H4 and H5 is bro
~ pilot b""urner*l0'ma'"ybe ignited.
ken so that the contact I2I of the switch I22'
' 'Upon the establishment of a pilot ?ame in the '
whichis connected to the conductor I20 is no
burner "electrical current commences to ?ow
longer connected to the cathode return wire 92‘
through the ?ame-sensingcircuit', but due to the
by a conductor I31 'to one end of the secondary
winding of the transformer III, the other end of
rectifying property of the pilot ?ame such cur
rent will ?ow‘between the electrodes I1 and the
burner 99 ‘only when the electrode I1 is positive
energized in the manner hereinabove explained,
with respect to ground potential. In other words,.
a circuit was closed from the wire 92 through _
‘ current flow through the pilot ?ame takes place
only during those half-cycles when the line wire
LI is positive with respect to the line wire'L2.
The ?ame-sensing circuit is traced from the line
wire LI to the cathode return wire 92 in the man- ' I
ner described hereinabove, thence, through the
jumper I04, lamp 92, resistor 9| and, condenser, 30
91 in parallel (as well as through the dielectric
insulating medium between the sheath I9 and
conductor 90), ?ame-sensing electrode I1, and
thence through the pilot name to the pilot burner
90. which is electrically at the same potential as
the line wire L2. However, during the half-cycle
through the path including the conductors -I It,
II! and Ill. However, when the relay 99 was
conductor 95, contacts 92 ‘and 92b of the relay
99, and conductor I20 to the lust-described con
tact I2I of the switch I22. Hence, so long as
the relay 93 remains energized the energizing
circuit to the pilot fuel valve solenoid .06 con
tinues, providing the push button I22 is held
The relay 99 may be maintained energized
through two possible holding circuits, one ‘of
these being traced from the cathode return wire
92 through the aforesaid contacts 92 and 92b of
35 the relay 99, conductor I20, contacts I2I of the
switch I22 and conductor I29 .to the winding of '
in which such current ?ow may take place
through the ?ame-sensing circuit the tube I9 is e
the relay 93. The other holding circuit is estab
‘ lished when the contact blade H9 of the relay
connected to the wire 92 is then positive with
I09 engages the contact Illa upon deenergiza
tion of this relay, this circuit being traced from
respect to the anode 22, which is connected
through the winding of the relay I09 to the con
ductor III leading to the line wire L2. That
is to say, the current ?ow through the flame
tor ' I4, con'acts III and “la, a conductor “0,
contact I29 of the relay 93 (this contact being
closed so long as the relay 9! is energized, con
> inoperative inasmuch as the cathode I9 which is
takes place only during the inverse, half-cycles
of the alternating current, and therefore a recti
?ed current flows through the condenser 91, as
well ‘as through the capacitance between the
sheath 34 and‘ conductor 90, the direction of this
current v?ow being such as to cause the terminal
, I92 of the control unit MU to assume a potential
which is positive with respect to that of the ter
minal IN. Terminal I02 is connected through
the lamp 99, Jumper I04 ‘and wire 92 to the cath
ode I9_of the tube I9, while the terminal IOI
is connected through the conductor I00 and pro
tective resistor 29 to the control grid 29 of this
tube; therefore, the grid 29 becomes negative
~\with respect to the cathode I9 due to the uni-v
the cathode return wire 92 through the conduc
ductor I29. winding of relay 99 and conductors
' I29 and III to the line wire L2.
The relay 9!
remains locked up through this latter holding
circuit so long as relay I09 remains deenergized.
During the interim while the blade III of the
relay I09 is traversing the gap, between the
spacedv contacts H911 and Ilia upon deenergiza
tion of the relay I09, the relay 93 is held ener-'
gized solely through the ?rst-mentioned holding
circuit including the contacts 92 and 92b of the
relay 99 and the contacts I2I of the push-but
ton switch I22, and hence there is no interrup
tion ofthe circuit through which the pilot fuel
valve solenoid -59 is held energized. The same re
sult could- be obtained without the use of this
directional charge which accumulates on the 60 manually controlled holding circuit by arrang
ing the contacts “9:1 and H911 of the relay I09
in a r'nake-before-break manner so that the blade
The charge on the condenser 91 (which will
II! engages the contact II9a prior to disengag
hereinafter be assumed to include the capacity
ing the contact I I9b. However, in the present
' of the insulation between the conductor 90 and
instance it is preferred not to employ make-be
sheath 94) may continue to build up throughout
fore-break relay contacts but instead to utilize '
a plurality of inverse half-cycles until a sub
condenser 31.
stantially steady-state condition is attained so
‘the manually controlled holding circuit for the
long as a ?ame is present in the burner 90; Dur
aforesaid purpose.
To summarize the foregoing operations, the
ing ‘forward half-cycles of the alternating cur-.
rent, when the relativepolarities of the line wires 70 establishment of a pilot ?ame in the burner 90
causes the tube I 9 to cease conducting current
. LI and L2 are such that the anode 22 of the
and brings about deenergization of the relay I09,
tube I9 is positive with respect to "the cathode .
as an incident to which a holding circuit is estab
I9, the charge on the condenser 31 is slightly
lished for maintaining the relay 93 energized so
diminished but remains at a suiliciently high
level to maintain the potential of the control grid 75 long as relay I09 remains deenergized. As can
be seen from Fig. 3, the establishment of this
enabling the relay 93 and pilot valve solenoid 56
holding circuit also serves to maintain the con
ductor I23 at the same potential as the cathode
return wire 32 which is electrically connected to
the line wire LI, so that the pilot fuel valve sole
hold 56 is held energized. As the relay I09 de
as well as the ignition transformer I25 to become
energizes and closes its contact II2a, a circuit is
completed from conductor I23 through conductor
solenoid 51 to become energized when the push
energized when the push button I22 is depressed,
after which the tube |8 becomes nonconductive
upon the establishment of a pilot flame and de
energizes the relay 1 I09 to‘ enable the main valve
‘button I22 is released. Thus, if there is an in
ternal failure of the tube l8 which causes this
HI and the contact‘ “M to the conductor |4| ,
leading to a lamp I42 and thence through the 10 tube to be permanently nonconductive or sub
stantially so, the pilot fuel valve 54 is prevented
?lament of this lamp and conductors I43 and I II
from opening. On the other hand if the tube I3
to the line wire L2. The lamp I42 thereupon
fails in such a manner that it is permanently con
‘ lights to indicate that a holding circuit has been
ductive, it ‘will be possible to open the pilot fuel
valve 54 but the main fuel valve 55 will be prevent
ed from opening because of the fact that the relay
I09 cannot be deenergized. In either event the
operator is duly apprised of the situation from
upon restored to break the electrical connection
an observation of either the burners themselves
between the contacts |2I and reestablish the con
nection between the contacts I24. This results 20 or the indicating lamps I42 and I46, and he may
then shut down the system entirely by opening
in automatically closing a circuit from the con
the switch S to enable a. check to be made.
ductor I23 through the contacts I24 and conduc
As in the case of the previously described em
tor I25 to the terminal I21 and thence through
bodiments of the invention, it is desirable to
the conductor I45 and the winding of the solenoid
check the system for abnormal conditions other
51, which controls the main fuel valve 55, back
than failure of combustion which may be a source
to the line wire L2. The solenoid 51 energizes
of danger, and particularly to automatically de
and opens the valve 55 to admit fuel to the main
tect any defective conditions in the ?ame-sensing
burner 5 I, and as the fuel issues from the burner
circuit. Thus, for example, the electrode I1 may
5| it is ignited by the pilot ?ame from the burner
50 and thus the operation of the heater is initi 30 become deformed so that it engages the burner
50 or 5| and is thus connected directly to ground,
ated. As an incident to this a lamp I46, which
that is to say, to the line wire L2. This causes
is connected across the conductors I25 and III,
the grid 26 to be positive with respect to the
lights to thereby indicate that the main burner
cathode I 8 during forward half-cycles, and hence
5| is in operation.
the tube passes current to energize the relay I09
If for any reason there should be a failure of
.and thereby interrupt operation of the burners
the pilot ?ame, or if this ?ame becomes too low
50 and 5| in the manner hereinabove explained.
or is otherwise rendered ineffective to ignite the
Similarly, if a non-rectifying or bilateral leakage
fuel discharged from the nozzle of the main
resistance is established between the electrode l1
burner 5|, so that there is an interruption of the
or conductor 30 and ground, such as may be
electrical connection through the ?ame between‘
caused by carbonization of the electrode I1 or
the electrode I1 and the pilot burner 50, rectified
failure of the insulation around the conductor
current ceases to flow in the ?ame-sensing circuit
30, this nulli?es the current-rectifying action of
and the condenser 31 thereupon loses its charge.
the ?ame and causes an alternating current to
The potential of the control grid 28 of the tube
pass through the condenser 31. On alternating
I8 is thus brought to approximately the same
current the condenser 31 acts more or less as a
level as that of the cathode I9, and the tube IB
shunt and is not likely to build up any appreci
is thereupon rendered effective to pass current
ably steady charge; or in other words, any charge
during the forward half-cycles. This results in
which is imparted to this condenser during an
energization of the relay I09, as an incident to
which the lamp I42 is extinguished and the hold 50 inverse half-cycle may be lost during the suc
ceeding forward half-cycle. This results in ren
ing circuit for the relay 93 is broken, causing this
. dering the system inoperative in the same man
relay to release and also bringing about the de
ner as though there had been a ?ame failure or
energization of the pilot valve solenoid 55, main
ground-out condition, the fuel supply either be
valve solenoid 51 and lamp I46. As the relay 83
is deenergized, the blade 92 thereof engages the 55 ing interrupted immediately or being prepared
for interruption in the event of a ?ame failure,
contact 92a and thereby closes circuit to the alarm
depending upon the value of the leakage resist
89, whereupon the alarm operates to give warning
ance. Likewise, failure of the insulation between
of what has happened.
the conductor 30 and the sheath 34 so as to
The valves 54 and 55 close when the solenoids
56 and 51 are deenergized to thereby interrupt
establish a low-resistance leakage path in shunt
the admission of fuel to the burners 50 and 5|. 60 with the condenser 31 renders this condenser in
eifective to bias the control grid 28, with the
In order to start the burners in operation again,
above described results.
it is necessary to repeat the above described steps
If more than one set of pilot and main burners
commencing with actuation of the starting switch
I22 and culminating in the opening of the main 65 is included in the burner system it is advanta
geous to have the fuel supply to all of the burnfuel valve 55. If combustion conditions in the
as controlled by a single master unit MU, the
heater are favorable so that the fuel issuing from
operation of which is in turn partially controlled
the ‘burners 50 and 5| is properly ignited, the
system operates automatically to continue the
by one or more secondary units SU, Fig. 4, the
supply of fuel to these burners unless and until 70 master unit MU being allocated to one of the
another abnormal condition arises.
main burners 5| and its associated pilot burner
50 and each secondary unit SU being likewise
It is to be noted from the foregoing that in the
process of initiating operation of the main burner _ allocated to a respective main burner 5|’ and
5| the tube I8 must initially be in a conductive
pilot burner 50’. The secondary units SU are of
condition for energizing the relay I09 and thereby
identical construction with respect to each other
established by the relay I09 for the relay 93 and
the pilot fuel valve solenoid 56. Upon observing
this indication the operator releases the push
button I22, and the plunger of the switch is there
but are greatly simplified as compared with the
master unit MU. Thus, referring to Fig. 4, each
secondary unit SU includes a tube I8’ which is
identical with the tube I8 of the master unit
MU, Fig. 3, and which functions in a correspond
ing manner.
Each unit SU may include an in
maintaining the alarm 89 energized so long as
the relay 93 remains deenergized.
Each secondary unit SU has a relay I58, the
winding of which is connected on one side by a
conductor I59 to the No. 3 or anode contact of the
tube I8’ in said unit, Fig. 4, and on its other side
by a conductor I60 to the terminal BI’ which is
dividual ?lament transformer 64', the primary
electrically connected to the line wire L2, Thus,
of which is connected across the line wires LI
the relay I58 is included in the anode circuit of
and L2, but it is to be understood that a single
transformer 64, Fig. 3, may be utilized to supply 10 the tube I8’ to be energized whenever the tube I8’
is rendered conductive. Terminals I05’ of all the
current for heating all of the tube ?laments.
secondary units SU are electrically connected to
Each tube I8’ is provided with a jumper 66' which
the cathode return wires 32' of their tubes I8’
is electrically connected to the prongs that are
and are electrically connected exteriorly of the ‘
received in the tube socket contacts I and 4 as
15 secondary units SU to a common conductor I65
in the case of the tube I 8, Fig. 3.
which leads back to the terminal I05 of the mas
When the master unit MU is to be operated in
conjunction with one or more secondary units
ter unit MU, Fig. 3. Thus, referring to Fig. 5, the
SU the jumper ‘I0 between the terminals 69 and
‘II, Fig. 3, is omitted‘and a conductor I50, Fig. 4,
leads from the terminal ‘II of the master unit
'MU to the terminal 68' on the last secondary unit
SU in the series. A conductor I5I connects the
terminal 68 of the master unit MU to the termi
nal ‘II’ of the ?rst secondary unit SU in the
cathodes of the tubes I8 and I8’ are simultane
ously potentialized when the relay device I55 con
nects the cathode return wire 32 of the master
unit MU with the line wire LI .
The control grids 28’ of the tubes I8’ in the
various secondary control units SU, Fig. 4, are
respectively connected to the ?ame-sensing elec
series. Interiorly of this secondary ‘unit a con 25 trodes I'I’ associated with the pilot burners 50’
to which the units SU are respectively allocated.
ductor I52 leads to the No. 4 tube socket con
When a pilot ?ame is present in a particular
tact, and if a tube I8’ properly equipped with a
burner 50’ a circuit is established from the line
jumper 66' is received in the tube socket the
wire L2, Fig. 5, through said burner 50’ and the
circuit continues from the conductor I52 and the
No. 4 contact through this jumper 66’ to the No. 30 path afforded by the pilot ?ame to the associated
electrode I‘I’, thence through the conductors 30’
I contact and thence through a conductor I53
to the terminal 69’ on the secondary unit SU.
and I00’ and the resistor3l’, condenser 31’ and
lamp 33', Figs. 4 and 5, included in that particular
A conductor I54 then leads from this terminal
69’ to the terminal ‘I I ' on the next secondary unit
control unit SU to the cathode return wire 32',
SU in the series or if there is only one other sec 35 from which point the circuit is completed through
ondary unit SU, this conductor I54 is connected
the common conductor I65 and wire 32 in the
to the terminal ‘II’ of such unit. If there are
master unit MU to the line wire LI. Recti?ed
more than two secondary units SU the terminal
current ?owing through such circuit builds up a
69' of each such unit is connected by a con
charge on the condenser 31' included therein so
‘ ductor as I54 to the terminal ‘II’ on the next 40 that the associated tube I8’ is biased to the point
unit, except for the last unit SU in the series,
where it is‘ nonconductive. However, when a
the terminal 69' of which is connected to the
flame is absent in the particular pilot burner 50’
conductor I50 leading back to the terminal ‘II,
the tube I8’ is rendered conductive and passes
Figs. 3 and 4, .of the master unit MU. As a re
current through its anode circuit to energize the
sult of these connections, if the proper type of 46 relay I58.
tube I8’ has been installed in each secondary unit
Referring again to Figs. 3 and 4, the relay I09
SU, a series circuit is established through the
in the anode circuit of the tube I8 in the master
jumpers 66 ‘and 66’ of the tubes I8 and I8’
unit MU has a contact “31) which is connected
in the master and secondary units, as can be seen
to a terminal II6 on the master unit MU. For
by reference to the simplified circuit diagram in
multiple burner operation the jumper I [1, Fig. 3,
‘ Fig. 5. This series circuit connects the line wire
is omitted and a conductor I56, Fig. 4, is em
LI with the conductor ‘I2 leading to the time
ployed to connect this terminal I IE to a terminal
' delay device generally designated I55 in Fig. 5,
IS‘! on the ?rst of the secondary units SU in the
this device I55 comprising the thermal switch ‘I3
series. The relay I58 in this secondary unit has a
and relay ‘I6, Fig. 3, which are wired up in the 55 contact I6l which is normally open when the re
lay is deenergized but which closes when the relay
manner shown in the latter view. The circuit
is energized, in a manner presently to be ex
then continues through the heater element and
plained, to electrically connect the terminal I51
I vrelay winding of the device I55 and through a
on the secondary unit SU to a terminal I62 on
conductor ‘I9 back to the line wire L2.
When the conductors LI and L2 are potential 60 said unit. The terminal IE2 is connected by a
conductor I63 to the terminal as IE1 of the next
ized, assuming that the aforesaid series circuit
secondary unit SU, and the terminal as I62 of
has been established, the ?laments of the tubes ' this unit is in turn connected by another con
I8 and I8’ immediately commence to heat up
ductor I63 to the terminal as I51 of the next suc
during the time delay interval which is afforded 65 ceeding secondary unit as SU, and so on until the
by the action of the device I55, Fig. 5. At the
last of the secondary units SU in the series is
expiration of this interval the device I55 closes
reached. The terminal I62 of this last unit is '
its contact 84, thereby connecting the cathode
connected by a conductor I66 to the terminal I I8
return wire 32 to the conductor 61 which is con
of the master unit MU, Figs. 3 and 4, Thus, re
nected to the line wire LI, and thus applying the 70 ferring to Fig. 5, all of the relays I 09 and I58 in
potential of the line wire LI to the cathode return
the various control units must be energized in
wire 32. The device I55 likewise shifts its contact
_ order to establish an electrical connection be
tween the conductors H4 and H9, Figs. 3 and 5.
blade 86 into engagement with the contact 86b
to thereby close a, circuit from the wire 32
Before operation of any of the burners can be
through the alarm 89 to the line wire L2 for 75 initiated the tubes I8 and I8’ must all be ren
ing condition they will automatically become
conductive as soon as the cathode return wires
82 and I2’ are potentialized inasmuch as there is
no substantial bias on the control grids of these
tubes in the absence of flames in the associated
?ames in the burners 50' has come into existence,
the jumper IIM between the terminals I03 and
III! of the master unit MU, Fig. 3, is omitted and
the terminal I03 is connected by a conductor I'I‘I
dered conductive, and if the tubes are all in work
‘ to a terminal Ill! in the first of the series of sec
ondary units EU. The terminal ill on this unit
BU is electrically connected by a contact I19 of
burners. Assuming that all of the tubes are in
the relay I58 to another terminal III on this
good condition so that the relays I" and Ill in
unit whenever the relay I58 is in a deenergized
their anode circuits become energized, a series
circuit is completed from the cathode return wire 10 condition, but when the relay is energized this
connection is broken. >The terminal I" of the
82 of the master unit MU. Fig. 3, through the con
secondary unit BU is connected by a conductor
ductor Ill and the contact Illb of the relay I"
Ill to the terminal I18 on the next secondary
and thence through the contacts Iii of the re
unit EU in the series until the last of the sec
lays I" to the conductor I", Figs. 4 and 5,1ead
in: back to the conductor I It, Figs. 3 and 5, which 15 ondary units SU is reached. The terminal I" of
this last unit is connected by a Jumper I82 to the
is connected to the conductor I20 leading to a
terminal ID!’ to which the common conductor III
contact III of the switch m, The system is
is connected.
thereupon conditioned to become operative when
Thus,’referring to Fig. 5, an electrical connec
the button of the switch I2! is pushed.
As has been described hereinabove, the switch‘ 20 tion between the terminals Ill and III! of the
master unit MU, Fig. 3, is not established until all
III is manually actuated tosenergize the pilot
of the relays III in the secondary units BU, F18. 4,
fuel valve solenoid It and, the-ignition means.
have been deenergized to close their'contacts Ill;
that is tosay, the ?ame-sensing circuit of the
In the present instance, where a plurality of pilot
burners are to be ignited, it is advantageous to
employ a distributor Ill, Fig. 5, having a num 25 master unit MU does not become effective until
?ames have been established in all of the pilot
ber of contact segments I'll, each of which is
burners ISO’ to render all the tubes II’ in the
connected by a conductor ill to a spark plug
secondary. units 8U nonconductive. Thereupon
I" on a pilot burner It or II’. The distributor
the ?ame-sensing circuit of the master unit MU
III has a wiper I‘Il insulatedly mounted on the
shaft I" of a motor Ill. The motor I'll is con 30 is rendered effective, and if a flame is present in
the pilot burner 50 the tube ll becomes non
nected in parallel with the primary of the igni
conductive to deenergize the relay I". The re
tion transformer I", while the high potential
lay I" closes its contact Ilia and thereby es
terminal of the transformer secondary is electri
fuel valve N. As the wiper I'll successively en
gages the contacts "I, the spark plugs I" are
tablishes “a holding circuit for the relay II and
the pilot fuel valve solenoid 58, at the same time
opening its contact I Ilb to disable the ignition
means including the transformer I 35 and motor
Ill. The lamp I42 ?ashes on as the relay I09
closes its contact I‘I2a to indicate that the push
button I22 may be released to initiate operation
thereby causing the relay in in the anode circuit
this system. If the abnormal condition should
of such tube to deenergize.
arise at the burner with which the master unit
cally connected by a conductor I10 to the wiper
I'll of the distributor Ill, The motor "I is en
ergized and commences rotating the wiper I'll
simultaneously with the energisation of the igni
tion transformer I" and the opening of the pilot
of the main burners BI and ‘I’ in the manner
energized in rapid succession for igniting the fuel
previously explained.
in the various pilot burners I0 and 50', By em
If an abnormal condition should arise at any
ploying such a distributor arrangement, it is pos
of the burners with which the secondary units
sible to utilize a single ignition transformer which
need only be capable of energizing a single spark 45 8U, Fig. 4, are associated, such as a failure ‘of
combustion in such burner, the-tube II’ in the sec
plug at a time, and on the whole a more satisfac
ondary unit SU becomes conductive and energizes
tory and economical operation is insured than
its relay I58. As this relay energizes it opens its
would be the case if a separate ignition trans
contact I19 and thereby breaks the ?ame-sensing
former were provided for each burner or if a
single transformer were arranged to supply po 50 circuit for the master unit MU. This causes the
tube I! in the master unit MU to pass current and
tential to a number of spark plugs in parallel.
thereby energize the relay I08, causing the relay
As each pilot burner 50’ is ignited a rectified
contact Illa to open and break the holding cir
current flow is established in the flame-sensing
cuit for the relay 93, which in turn results in de
circuit associated with such pilot burner, and in
the manner explained hereinabove, this causes the 55, energizing the fuel valve solenoids 58 and 51, thus
interrupting operation of all of the burners in
corresponding tube I8’ to become nonconductive,
In the present in
MU is associated, then the tube I8 is immediately
stance, however, it is desirable that the relay I08,
Figs. 3 and 5, in the anode circuit of the tube II 60 rendered conductive with the effect just described.
It is manifest that the apparatus will function in
of the master unit MU remain energized at least
a safe manner for any of the abnormal conditions
‘until all of the tubes I8’ in the secondary units
referred to hereinabove, such as ground-out or
leakage effects, as well as for a failure of com~
sponding burners 50', regardless of whether the 65 bustion. It should also be noted that if any of
the cable sheaths 34 or 34’ becomes grounded, the
flame in the pilot burner 50 associated with the
associated warning lamp 33 or 33' lights to indi
master unit MU has been established, for so to
cate the location of the fault.
do insures that the holding circuit for the relay
While the master unit MU and secondary units
ll and pilot valve solenoid 56 will not be estab—
lished, nor will the ignition transformer I35 and
SU have been described hereinabove as constitut
BU have been rendered operative in response to
the establishment of pilot flames in their corre
motor I" be deenergized, at least until ?ames
are present in all of the pilot burners M’.
For the purpose of delaying the response of the
master unit MU to the establishment of a pilot
?ame in the burner 50 until the last of the Pilot 75
ing separate control units which may be mounted
in individual cabinets that are wired together by
external connectiom and independently located
with respect to each other, it is to be understood
that these various control units may be embodied
ghp geries circuit extéhkiipg through the jumpers.
alarm‘89 back ‘to the line ‘wire L2. Operation
trically connected to the cathode return wire 32 i
of the‘ alarm 99 thus signi?es that the neces
by way or a series circuit extending through the
contacts I19 of the relays I58 in the secondary
units SU, whereas the condensers 91’ and re
sistors II’ of the secondary units SU are con-''
nected directly to their cathode return wires 92'.
There may be instances in which it is desired
sary preliminary operations have been performed
and that the heater system is ready for oper
atlon. ‘
' As the line wire LI becomes potentialized the
voltage existing between the wires LI and L2
is impressed across the cathodes I91 and anodes
I99 of the various tubes I92. The control grids
.205 of the tubes I92 are respectively connected
to have the flame-sensing circuits of all the
control units arranged in an identical manner
and yet insure that the main fuel valve’ 59 is
not opened untillpilot ?ames have been estabé
lished in all of the" pilot burners in the system.
To this end, and for the purpose of e?ecting
various other improvements, the modi?cation
shown in Fig. 8 may be conveniently utilized.
The control apparatus shown'in Fig. 8 com
byv conductors 209 to terminals 201 on the con
trol units U.'irom which terminals the conductors
90 lead to therespective ?ame-sensing electrodes
I1 associated with the pilot burners 50. The
sheaths 94 o! the conductors 30 are respectively.
connected toterminals 299 which are electrically
. prises a relay unit BU which containscertain of
connected through theTiillments of lamps 209 to
burner 00 in the system. The controlLunits ‘U
out?ts-‘including the ‘electrodes I1, conductors
‘90,.conde'nsers N2I0and~ resistors 2“ prior to the
‘establishment orpuot '?ames‘in the burners 90.
the relays and associated devices for controlling " the terminals I99 on the units U. Each con
trol unit U has a condenser 2I9 and a resistor 2I I
operation or the fuel supply and ignition means.‘
Operation 01 this relay unit RU is] in turn gov 20 which are electrically connected in parallel across
erned by the flame-detecting units 0‘; volie‘oi'y the terminals 201 vand‘ 208. Since there is no
which is operatively associatedwi?ij each pilot" 1 J. current? ?ow‘ through the various ‘ name-sensing
are 01 unii'orm construction and each includes 7
an electron tube I92 and new; III-havingits
there is"initlelly no'substantial negative bias on
the control grids 209 so that the tubes I92 are
tube. The ?laments oi the tubes'yl‘ll are ‘pret
erably supplied with current by individual illa-v ; able "to'conduct' current as soon as the line wire
LI is potentialized. ,1! each tube is in good con
ment transformers ‘I94 having their primaries,
connected across terminals I99 ‘and. llllwhich 30 dition'so that itpasses currentjthroush its anode
winding connected in the anode circuit" or said
~ are respec vely connected to the line‘wires L2
and L0.
e cathodes I91 01 "the tubes I92 are
circult,;thena11‘oi the relays-I99 in the various
controlunitsJU become energized. but it, any
tube is defective so that it is permanently non
connected to terminals I99 which are electrically
conductive, its'relay I99 remains in a deenexgized
connected to the line wire LI. The anode I99
‘Y ‘W P
of each tube‘ I92 is connected by a conductor 200 as condition.
Energizatlonoi the relays I99 serves to es
to one end of the-winding 01 the relay I99, the
tablishaseiies ‘circuit through ‘the contacts 2I2
other end of thia'..wlnding being connected by
the conductor 29!" to the terminal I95. It will ‘ of these relays for the purpose of conditioning
be understood that although the relay unit EU ‘0 the relay unit RU to initiate operation of the
and ?ame-detecting units U are represented in 40 pilot burners 90. Each relay contact 2I2 is ar
rranged-to'bridge a pair of terminals 2I3 and 2“
Fig. 8 as constituting separate units, they may
on its controlunit U when the relay I93 isyener
be conveniently incorporated in the same cabinet
gized. The terminal 2“ of the last control unit
to afford a single control unit for the‘ entire
U in the series is connected to the line wire LI,
burner system.
It will be recalled that the line wire LI ls'not 45 while the terminal 2“ oi each of the other units
U is connected by a conductor ‘M5 to the terminal
immediately potentialized upon closure of the
2I3 of the next succeeding unit U in the series.
switch S but must await the establishment of
A conductor 2“; leads from the terminal 2|! 0!
an electrical connection with the wire L0 through '
the ?rst unit U to a contact 2031) 01 the relay
the medium of the preliminary control apparatus
99. Hence, while closure of the switch S im 50 204 in the unit RU, Irom which relay contact
the blade 203 is normally disengaged when the
mediately potentializes the wires L0 and. L2 for
relay 204 is deenergized. A push button 2I1 is
thereby energizing the ?lament transformers I94
arranged to bridge a pair of spaced contacts 2I9,
and initiating heating of the cathodes I91, the.
one of which is ‘connected to the conductor 2“
line potential is not impressed upon the anode
circuits of the tubes I92 until the scavenging ‘and 55 and the other to a conductor 2I9 leading to the
winding of the pilot fuel valve solenoid 59. 'As
other preliminary operations have been per
suming that all of the tubes I92 areconducting
formed under control of the ‘apparatus. 59. Or
current so that all of the relays I99 are ener
dlnarily this a?ordssu?lcient time for the tubes
gized to maintain their contacts 2I2 closed, an
I92 to be conditionedior operation, but if a longer,
delay period is desired this can be afforded by 60 electrical path is established from the line wire
LI through the relay contacts 2I2 in series to
an arrangement such "as that comprising the
the conductor 2 I6. However, if any of the tubes
thermal switch 19 and relay‘ 19, Fig. 3. It is
I92 is defective so that its relay I93 remains
likewise apparent that the series circuit arrange
deenergized, the conductor 2IB remains discon
ment oi’ Jumpers 99 and 69', Figs. 4 and 5, may
be employed to insure that the control apparatus 65 nected from the line wire LI.
Assuming that all of the tubes I92 are con
is not conditioned ‘,for operation unless tubes of
ducting current, operation of the pilot burners
the proper type are installed in all of the active
‘50 is initiated by manually closing the switch 2I1
control units U. At the completion of the afore
whereby a. circuit is completed through the wind
said scavenging cycle the line wire LI assumes
the same potential as the line wire L0, whereupon 70 ing of the solenoid 59 for energizing this solenoid
and opening. the pilot fuel valve‘ 54. Closure of
a circuit is established from wire LI through a
the switch 2I1 also causes a circuit to be ex
conductor 202, a_contact blade 203 of a relay
tended through the conductor 2I9, a blade 220
204 included in the relay unit RU, a contact 203a
of a relay 2-2I included in the unit RU, a contact
with which the blade» 203 cooperates when the
220a which the blade 220 normally engages and
relay 2“ is deenergized, and thence through. an
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