US2379872A - Electronic control apparatus - Google Patents

Description

ELECTRONIC CONTROL APPARATUS Filed Jan. 9, 1943 3 Sheets-Sheet 1 3nnentor WILL/5 l7. GIL/.5

Gttorneg y 1945. A w. H. GILLEI I 2,379,872

ELECTRONIC CONTROL APPARATUS Filed Jan. 9, 1943 3 Sheets-Sheet 2 Z. y mi g, m/ w mi 47 3/ Z5 I I H33 1 97 1/? A 5 i I Zhwentor WILL/5 H. G/LLE attorney July 10, 1945". H GILLE 2,37%892;

ELEC TRONI C CONTROL APPARATUS Filed Jan. 9, 1945 .v s Sheets-Sheet s Bnventot WILL/5 H GILLE Patented July 10,

reliable under certain c It is a general object to provide a control device of the ELECTRONIC OFF 1 CE Willis H. Gllle; St. Paul, Minn., assignor to Mlnpencils-Honeywell Regulator Company, vMinneapolis,

Minm, a corporation of Delaware Application January 9, 1943, Serial No. 471,833

with eleconditions.

of this present invention ype discussed ed with the arrangement disclosed in the aforesaidBeam application.

A still further object of the invention is to provide a burner control system -embodying the jects in which the means responsive tothe burner flame is rectifyingonly burner flame. 1

Other objects'of the invention will be apparent J from a consideration of when it is exposed'to a the accompanying speci flcation, claims, and drawings, of which:

Figurel is a schemati 0 view of the burnercon 66 by an electronic discharg' vice 38 trol system employing my novel control apparatus as a means of detecting a burner name.

Figure 2 is modified form of my control apparatus, a

Figure 3 is a still further control apparatus, and I Figure 4 is another modification of my control apparatus, this modification being shown in connection with a burner control system.

modified .form of my Disposed withinthe housing is a step-up, stepdown transformer l2 having a line voltage privoltage secondary windings II and and high voltage secondary windings I 6 and present invention is concerned, the transformer l2 constitutes the source of tion and claims, the expression "source of power source 01' power.

coil 26 being energized, switch blade 21 is moved engagement with switch conagainst its bias tact 28.

A condenser II is connected by conductors I2 shuntcondenser to eliminate any the current flowing through relay coil 28 is controlled device 80. This device comprises a conventional envelope II which encloses the various electrodes. The control'deis one which no mally comprises two into pulsations in coil 28.

The energization oi relay power and elsewhere in the speciflcatriodes. A double cathode 99 serves to form a cathode element for each of the two triodes. Associated with this cathode are a pair of heater elements 99 and 40 which are connected in parallel. The first triode comprises cathode element 99, a grid 4|, and a plate 42. A second triode is constituted by the cathode99, a grid 44, and a plate 45. Since the control apparatus of the present invention does not require the use of two triodes, the anode 45 is not employed. This anode is merely shown because in a conventional tube having two control grids such an anode would be present. The triode consisting of cathode 99, anode 42, and grid 4| is preferably of the type which is designed to operate with an anode voltage of such a magnitude that the triode conducts current whenever the grid potential is above a predetermined value negative with respect to the cathode. In other words, this triode is of the conventional y normally P- erated with a "negative cut of! poin The heater elements 99 and 40 are connected by conductors 49, 92, 41, 99 and 99 across the secondary [5. Secondary |5 thus serves to constantly energize the heater elements 99 and 40.

Resistors 49 and 49, and a condenser 59 form the elements of a filter network between the grid 4| and the cathode 99. as will be more fully explained later. A protective resistor 5| is con-' nected in series with grid 44. The numeral 52 is employed to designate a condenser which is employed to control the potential of grid 4|.

The secondary I6, a condenser 54, and a choke coil 55 constitute the elements of a phase shifting network. The condenser 54 and choke coil 55 are connected to secondary l9 by conductors 51, 59, 59, and 50. The voltage between the Junction of conductors 59 and 59 and the lower terminal of secondary l9 leads in phase the voltage between the upper and lower terminals of secondary l9 by 90.

The relay 25 is trolling an electrically operated gas valve 59. This gas valve is of the type which when energized permits a flow of gas and which upon deenergization interrupts such flow. The gas valve 99 controls the flow of gas through a pipe 94 to a main gas burner 99. Located adjacent to the main gas burner 95 is'a pilot burner 91, the flame of which is indicated by reference numeral 99. The pilot burner 91 is connected to ground as indicated at 99. The pilot burner is supplied with gas by a pipe 10 which is connected to the gas supply pipe 54 at a point on the upstream side of valve 99 so that the pilot burner 91 is normally constantly supplied with gas and hence normally constantly burning. A flame electrode 12 is located so as to extend into the path of pilot flame 59. This flame electrode is connected by conductors 19, terminal 14. and conductor I5 to the junction of conductors 59 and 59.

The energization of valve 99 is not only controlled by relay25 but also by a room thermostat 11. This room thermostat is of conventional construction and comprises a bimetallic element I9 to which is attached a contact arm 19. The contact arm 19 is adapted to be moved by the bimetallic'element 19 into and out of engagement with a contact 90. As indicated by the legends "C" and H. bimetallic element 19 is effective upon a drop in temperature to move the contact arm 19 to the left into engagement with contact 99. Upon a rise in temperature, it is adapted to move the contact arm 19 to the right out of v engagement with contact 90. A magnet 9| is illustratively shown as con- The following are values which can be em- 7 ployed in a specific embodiment of the invention: windings l9 and I1 may each be designed so that they produce voltages of approximately 300 volts. The secondary l5 can be designed to have a voltage output of approximately 12 volts. The winding i4 is preferably a 24-volt winding. In the same embodiment, the resistors 49 and 49 can be one and two megohm resistors respectively. The condensers 50 and 52 can be .02 microfarad condensers and the condenser 3| is preferably an 0.5 microfarad condenser. The resistor 5| may be a flve megohm resistor. The values of condenser 54 and choke coil 55 are so selected as to give substantially equal impedances'for current of the available frequency. It is to be understood that these values are merely illustrative values which can be varied over a wide range and that the invention is not in any way limited tov the use of elements having these values.

, Owns-nos or Fmimr: 1

When pilot burner is extinguished The various elements are shown in the position which they occupy when the pilot burner 51 is extinguished and when the temperature ad- Jacent room thermostat I1 is at or above the degirgd value so that the thermostat 11 is satise .5, charging circuit to condenser 52 is active: from the upper terminal of secondary l5 through conductors 92 and 99, condenser 52, conductors 94 and 99, resistor 5|, grid 44, cathode 99, and conductors 91, 59, 92 and 95 to the lower terminal of secondary l5. The flow of current through this circuit is only in the direction traced due to the rectifying action of the grid 44 and cathode 99. The effect of the current flow through condenser 52 in the direction traced is to cause a unidirectional voltage to be impressed across condenser 52. The polarity of this voltage is such that the right hand terminal of condenser 52 is negative and the left hand end positive. The right hand terminal of condenser 52 is connected by conductors 94, 99, resistors 49 and 49, and conductor 9| to grid 4|. The left hand end of condenser 52 is connected by conductors 99 and 92, the secondary l5, and conductors 99, 92, 99 and 91 to the cathode 99. In other words, the right hand terminal of condenser 52 is a grid terminal and the left hand end a cathode terminal. Since the right hand terminal of condenser 52 is a terminal which is negative, it will be obvious that the result of this unidirectional voltage across condenser 52 is to bias grid 4| negatively.

This action is aided by secondary Hi. It is to be noted that the upper terminal of secondary a is connected to the grid 4| through condenser cathode. The lower terminal is also connected by conductors 95, 99, and I00 to the upper terminal of secondary l1. The lower terminal of Under these conditions, the following' The lower terminal is connected to the previously traced due is 180' out of phase with respect to the anode voltage. Hence, the tendency of this voltage, to the extent'that it is applied to grid 4| the filter network,

result of the charge on condenser 82 an this out of phase voltage introduced by secondary I 8 is to bias the grid H below the cut off potential or at least sufliciently close to it that insufficient current flows through relay coil 26 to energize the relay efl'ectively. The charging of condenser 82 occurs not only through the circuit traced above but also through the following circuit: from the upper terminal of secondary I5 through conductors 82 and 8 8, condenser 52, conductors 84 and 88, resistors 48 and 49, conductor 8I, grld 4|, cathode 88,,and conductors 88, 92, and 98 back to the lower terminal of secondary I8. It will be noted that this circuit relies upon the rectifying effect of grid 4| and cathode 88. this circuit is somewhat less, however, than that 44 act as elements in rectifying circuits for charging condenser 82, the charging is accomplished principally through the first mentioned circuit including grid 44 and cathode 88.

As previously noted, the resistors 48 and 48 and condenser 88 function as elements of a fllter system. It is to be notedthat condenser 88 is connected by conductors 88 and 84 between the junction of resistors 48 and 48 connected to the grid 4| and conductor 81 leading to the cathode 88. It wilLbe readily apparent that condenser 88 functions in the usualmanner of a shunt condenser of a filter network to tend to filter out any alternating current voltage impulses that might otherwise be appliedtg grid 4 I.

It will be seen from the foregoing description that as long as a flame is absent, the grid 4| is biased negatively below the result of a charge impressed on condenser 82. As a result, the triode comprising cathode 88 and anode 42 is not conductive. As will presently be explained. this makes it impossible to cause en ergization of gas valve 88.

flame 88 is, present, a new charging circuit is established to condenser 82. This charging circuit is as follows: from the junction of conductors 88 and 88 of the, phase shifting network through conductor 18, terminal 14, conductor 18, flame electrode 12, flame 88, burner 81, ground connections 88 and 88, conductors 88 and 84, condenser 82, conductors 88 and 82,-secondary I8, and conductors 88, 82, and 88 to the lower end of the secondary I8 of the phase shifting bridge. It will be noted that the above circuit was traced through the flame in a direction opposite to Blame propagation. It has beenfound that the on flow through a flame is greatest' .in the direcion' of flame propagation. :onventional current flow through a flame is ireater in the direction opposite to flame proparation. Hence, while current may flow through lame 88 in both directions the current flow is much greater in the direction traced. As a re- The current ,flow through 011 s: fro to the presence of resistors I a as f ow m '48 and 48. Thus, while both the grids 4| and cut on" point as the that the last traced circuit was traced through condenser 82 in a direction opposite to that traced in connection with the first circuit. In other words, the effect of the current flow through the last traced circuit is to impress across condenser 82 a charge such as to make the right hand terminal of condenser 82 positive and the left hand terminal negative. As previously pointed out, the right hand terminal of condenser 82 is the grid terminal and the left hand end the cathode terminal. Thus, the throughthe last traced circuit including the flame is to raise the potential of the grid with respect to the cathode. The constants of the circuit are so selected that when a flame is present in the flame gap, this increase in the potential of the grid is sufiicient' to raise the grid potentialappreciably above the out 011- value sothat the triode including cathode 88 and plate 42 becomes conductive. when for a circuit to be established through relay coil the lower end of secondary I1 through conductor 81, relay coil 28, conductor 88, anode 42, cathode I1. The current flow through relay coil 28 as a result of the circuit just traced causes energization of relay coil 28 so as to move switch blade 21 into engagement possible the establishment of a circuit to gas valve 88 under thecontrol of room thermostat 11.

Let it now be assumed that the room thermostat 11 calls for burner operation; that is, that contact arm 18- is moved into engagement'with contact 88. when this happens, the following circuit is established to gas valve 88; from the upper terminal of secondary I4, through conductor I8I, terminal I82, conductor I88, bimetallic element 18, contact blade 18, contact 88, conductor I84, terminal I88, conductor I88, terminal I81, conductor I88, gas valve 88, conductor I 88, terminal H8, conductor III, switch blade 2-1, contact 28, and conductor II2, to the other terminal of secondary I4. The energizatioh of gas valve 8 causesit to move to,open position permitting gas to ilow through pipe 84 to the main burner 88. Since it has'already been assured that the pilot burner 81 is burning, it is certain that main burner 88 will be properly ignited. I v

Normally the burner 88 will remain ignited until the thermostat 11 becomes satisfied. When this happens,"the contact arm 18 separates from contact 88 thus interrupting the energizing circuit to valve 88 and causing valve 88 to close.

If at any time during the operation of the system, the pilot burner 81 is extinguished, the control device of the present invention is effective to cause almost immediate closure of main gas: valve-88. 'As soon as the pilot flame 88 is interrupted, current can no longer flow through the last traced charging circuit for condenser 82. Asa result, the only charging circuit for ult', there is a definite direct current component i condenser 82 is the one first traced. It will be recalled that the efl'ect of this charging circuit is to produce a charge across condenser 82 which biases the grid 4I- below the, effective cut of! potential. The time required for charging this condenser is extremely small. Thus, almost immediately after the pilot flame 88 is extinguished, the potential of grid 4I is lowered to a value such that the burner relay 251s denergized. This causes an interruption of the circuit to main gas valve 88 so as to terminate the flow of gas to the main burner 88.

tendency of the current flow this happens, it is possible 88, and conductors 81, 88, t 82, 88. and I88 to the upper terminal of secondary v with contact 28." This makes When flame gap is bridved by high resistance impedance It occasionally may happen that the flame gap becomes bridged accidentally. One difflculty which is occasionally encountered is that carbon builds up on the flame electrode 68 to the point where the carbon either-engages the burner 61 or is separated from burner so slightly that the impedance betweenthe flame electrode and the burner is substantially below the open circuit impedance and may even be very close to the flame impedance. It is obvious that the flame responsive apparatus should not respond to, the presence of such an impedance in the same manner as it does to a flame. My present apparatus is particularly designed to distinguish between such a high resistance impedance and a flame.

It will be recalled that the charging of condenser 52 in the direction opposite to that in which it is charged by the biasing circuits depended upon the rectifying effect of flame 68. Any normal impedance bridging the flame gap is not rectifying in effect. Under such'circumstances, accordingly, the current flow through the condenser 52 as a result or .thelast traced circuit is the same in both directions so that the only voltage impressed upon condenser 52 as a result of such current flow is an alternating voltage. Such an alternating voltage in no way affects the direct current potential. Furthermore, this alternating voltage has such a phase relation with respect to the voltage applied to the anode circuit that it tends to further lower the potential of grid 4|, as will be pointed out presently. This later effect is more pronounced when the 1mpedancebetween flame gap I2 and burner 61 is relatively low in magnitude.

When substantial short circuit exists across flame yap Under certain circumstances, a substantial short circuit condition can exist between the flame gap and the burner 61. A typical condition is that which occurs when the flame electrode becomes unduly heated and softens so as to bend down and touch the burner 61; Under these conditions, the impedance between the electrode 12 and the burner 61 is relatively small. When this happens, the current flow through condenser 52 as a result of the circuit to the flame gap becomes very substantial. Or, viewed in another light, the impedance between the grid terminal of condenser 52 and the junction of conductors 58' and 59 becomes relatively low. The effect of this is to cause grid 4| to tend to assume the potential of the junction of conductors 58 and 59. Several other factors must be considered, however, in determining the potential which is applied to grid 4| under these circumstances. It is to be noted. that the junction of conductors 84 and 85 towhich grid 4| is connected is also the junction of a connection involving condenser 52 and the impedance between flame gap 12 and burner 61. In other words, the grid is connected to the junction of two conductive legs one or which contains the capacity of impedance of condenser 52 and the other of which contains the resistive impedance of the flame gap. The condenser and the impedance of the flame gap constitute, in effect, a phase shifting bridge. As long as the value of the impedance between flame electrode and. burner 61 is comparatively high, the effect of this phase shifting action is not serious. vAsit becomes lower, however, a more pronounced phase shifting action takes place. If the grid were connected directly to the upper end of secondary I8 and ii the condenser 52 were not present, the grid would be at a potential 180 displaced from the potential of anode 42. This would be desirable but is not possible in view of condenser 52. Due to the presence of condenser 52 and the resultant phase shifting action, the grid 4| would no longer be at a potential 180 displaced from that of the anode unless-a phase shifting bridge was provided. The-phase shifting bridge including condenser 54and choke coil 55 operates to cause the voltage between the junction of conductors 58 and 59 and the lower end of secondary I6 to lead that between the upper and lower terminals of secondary Hi. This lead in" the voltage compensates for the lag in the voltage introduced by the presence of condenser The result is that the two phase shifting actions cancel each other so that grid 4| tends to be maintained at a potential substantially 180 displaced from the anode potential. Thus, as the impedance between flame electrode 12 and burner 61 decreases, the potential of grid 4| is lowered as a resultof the out of phase alternating voltage applied to the grid by the connection through the flame gap to the phase shifting bridge.

It will be seen that I have provided a control mechanism which operates under all circum- 1 stances to distinguish between a rectifying and non-rectifying impedance without the use of a second triode. In the above operation, the anode 45 playsno part whatsoever and could be omitted in a tube especially designed for applicants control mechanism.

Srncms or Fromm 2 The species of Figure 2 is similar to that of Figure 1 with the exception of the type of phase shifting bridge that is employed. Since the gas valve 63, the gas burner 66, and the thermostat 11- are all identically the same in structure and in the manner in which they cooperate with the control apparatus, these elements have not been shown in Figure 2. To further enable a more ready comparison of the arrangements of 2 and Figure 1, identicalreference characters have been applied in the two figures to corresponding elements. Those elements which correspond to elements 01 Figure 1 and whose function is readily apparent from the foregoing description of Figure 1 are not described again 1 connection with Figure 2.

In the present species, the transformer I2 not only comprises the secondaries I4, I5, and I1, but also a center tapped secondary IIBwhich takes 1 the place of secondary I6 in the species of Figure junction ot conductors I23 and I24. The voltage existing between the junction of conductors I28 and I24 and the center tap H8 is displaced in phase from the potential between the upper and lower terminals of secondary IIS, the potential difference across the Junctions of the phase shifting bridge leading the potential difference between the terminals or secondary I I6. In other and I26 back to the 95, conductors 65 asvaera species of Figure 1. The essential difference between the two phase shifting bridges is that in the species of Figure 1, a condenser and inductance combination is employed. while in that of Figure 2 a condenser-resistor combination is employed. While the condenser-inductance combination gives a greater phase shift, the phase shift resulting from the phase shifting network of Figure-1 is only 90 because of the fact that a center tapped secondary is not employed.

Referring again to Figure 2, the lower terminal of secondary I is connected'by conductors I26, I21 and I26 to conductor 66 which, as previously noted, is connected to the cathode 26. The upper terminal of secondary I5 is connected through conductors 62 and 63 with condenser 52.

It is believed that the operation of the species of Figure 2 will be the foregoing description. When there is no flame, a charging circuit is established through condenser 52 as follows: from the upper terminal of secondary I5 through conductors 62 and 62,

condenser 52, conductors 64 and 66, resistor 5| readily apparent in view of grid 44, cathode l5, and conductors 51, I6, I26, I 21,

other terminal of secondary I5. Due to the rectifying action of grid 44 and cathode 26, the current flow takes placethrough condenser 52 only in the direction traced so th'at a direct current potential is impressed across con: denser-52, the polarity of this potential being such that the right hand end of condenser 52 is nega tive and the left hand end positiv Since condenser 52 is connected to grid H in the same manner as in Figure 1, it will be obvious that the tendency of this charge is to impress a negative voltage on grid M. This voltage is furthermore aided by the alternating potential across secondary I5;

- It is to be noted that, as in Figure 1, th'e voltage phase of this voltage with respect to the cathode 36 is displaced 180 from the voltage applied to the anode bysecondary I1. Thus, in the absence oi. a flame, the grid is biased negatively below the cut 011 point so that insuflicient current can flow through the relay coil 26 to cause energization of the same. 1

Upon flame being established, an energizing circuit is established from th'e Junction of conductors I23 and I24 through conductor 15, terminal 14, conductor 13, burner electrode 12, bumer flame 66, burner 61, ground connections 66 and and 64, condenser 52, conductors 83 and 82, secondary I5, and conductors I26,

I21, I28, and 89 to the center tap II6 of the secondary H6. The output voltage of the phase shifting bridge is thus applied to the flame electhe rectifying action of the flame, a direct current voltage is applied to the condenser 52, which voltage is opposite to th'e voltage produced by the previously traced charging circuit. Thus, the potential of grid 4I is raised sufliciently to cause energization of relay coil 26 so as to permit the establishment of an energizing circuit to gas valve 63.

Inthe event of the flame gap being short circuited, the operation is again substantially the same as in Figure 1. In the first place, the impedance bridging the flame gap has no rectifying effect so that there is no tendency for condenser 52 to be charged in a direction opposite to which tential 180 out of phase with ary windings I4 and it is charmed by the biasing circuits. In the second place, the establishment of a non-rectifying. impedance connection across the flame gap tends to cause the grid II to assume an alternating pcthe anode potential. species of Figure 1, the phase shitting of condenser 52 and the impedance flame gap is compensated for by the phase shifting effect of the phaseshifting bridge including condenser I20 and resistor I2I.

Srncms or FIGURE 3 The species of Figure 3 Figure 1 as far as the phase shifting" bridge is concerned. However, in this species, instead of employing the rectifying eflect of the grid and cathode of a second triode, a tube having an auxiliaryanode, commonly referred to as a diode, is employed. A second condenser connected in series with this diode and the cathode is ch'anged through the rectifyingaction of the diode and cathode andiurnishes a constant source of biasing potential.

The transformer I2 in this case comprises the primary winding It and the low voltage second- I5 as in the case of Figure 1. It also comprises high voltage windings I 6 and I 1. In addition. a low voltage winding I40 is provided for the purpose of energizing the cathode heater.

As in Figure l, the secondary I6 is employed as the, power supply of a phase shifting bridge. Connected across the terminals of this bridgein series with each other are a condenser 54 and a choke coil 56.

The electronic amplifier in the present species is designated by the reference numeral I45. This amplifier comprises an envelope I46, an anode I41, a grid I46, a cathode I46, and a diode I56. Associated with the cathode I46 is a cathode heater I52 which is connected by conductors I54 and I65 with the terminals of secondary I46.

In addition to the condenser 52 of the species previously described, there is also provided in this species a further condenser I56.

The condenser I56 is charged as a result of the following charging circuit: from the lower terminal of secondary l5 through conductor I56,

. diode I5Il,- cathode I49, conductors 6'1, 86, and

i tifying action of I59, condenser I56, and conductor 62 back to the upper terminal of secondary I5. Due to the recthe diode and cathode, the current now through this circuit takes place oniy in terminal is connected throughconductor 66, condenser 62, conductors 64 and 66, resistors 46 and establishment of flame. a charging circuit through condenser 52 is established. This charging circuit is from the junction of conducis similar to that of tors 58 and 59 through conductor 15, terminal 14, conductor 13, flame electrode 12, flame 68, burner 81, ground connections 69 and 95, conductors 85 and 84, condenser 52, conductor 88, condenser I56, conductor I59, and conductor 89, to the lower terminal of secondary I of the phase shifting bridge. As was explained in connection with the previous species, due to the rectifying action of the flame, the current flowthrough the circuit just traced takes place to a greater extent in the direction traced than in the opposite direction. The result of this current flow is that the condenser 52 becomes charged with a voltage of such polarity that the right hand terminal of condenser 52 is positive with respect to the left hand terminal. Furthermore, this positive charge on condenser 52 is suflicient in magnitude to overcome the voltage across condenser I56 sumciently to raise the potential of grid I48 substantially above the cut off point. As a result, the relay coil 26 is energized through the following circuit: from the lower terminal of secondary I1 through conductor 91, relay coil 26, conductor 98, anode I41, cathode I49, and conductors 81, 88, I59, and I69, to the other terminal of secondary I1.

The action of the phase shifting bridge is substantially'the same as with the previous species. Were conductor 15 connected directly to the upper terminal of secondary I8, 9. definite phase shifting action would exist whenever a non-rectifying impedance were connected in the flame gap. It is to be noted that the grid I48 is connected to the junction of conductors 84 and 85. Conductor 84 is connected through condensers 52 and I56 in series to the lower terminal of secondary I6. Conductor 85 is, on the other hand, connected through ground connections 95 and 69 and through the impedance of the flame gap to the conductor 15. Were conductor 15 connected to the upper end of the secondary I6, the'result would be that there would be a phase shifting bridge with the resistive impedance of the flame gap in one leg and the capacitive impedance of condensers 52 and I56 in the other leg. This phase shifting eflfect becomes particularly marked whenever the flame gap is bridged by a non-rectifying impedance, particularly one with a relatively low impedance value. By interposing the phase shifting bridge consisting of condenser 54 and choke 55, however, this phase shifting action I4, a center tapped high v'oltage'winding I19, and

a low voltage filament secondary I14. Th secondary I19 is provided with a center tap HI and a tap I12 displaced slightly from the center tap. A condenser I15 and a resistor I15 are connected between opposite terminals of the secondary I18 by conductors I11, I18, I19, and I88.

The electronic amplifier in this species is designated by thereference numeral I84. This amplifler is a conventional type of triode amplifier having an anode I86, a grid I 81, and an indirectly heated cathode I88. The heater I89 of the cathode is connected by conductors I 90 and I9I to the secondar I14.

A charge is normally maintained on condenser 52, this charge being of such a polarity that the grid I81 is maintained at a potential close to or below the cut of! potential. This charge is established by the following circuit: from the tap I12 through conductor I95, condenser 52, conductor I95, resistor I91, conductor I98, grid I81, cathode I68, and conductor I99, to the center tap I1I of secondary I19. Due to the rectifying action of the grid and cathode, the flow of current through the circuit just traced takes place only in the direction traced. This direction is such that the right hand end of condenser 52 becomes charged negatively and the left hand end positively. The

result is that the potential of grid I81 with respect to cathode I88 is lowered to a value close to or the opposite side of tap Hi from the lower terof condenser I56 and the impedance of the flame gap is counter-acted so that the tendency of the connections including the conductor 15 and the flame gap is to maintain the grid at a potential 180 displaced in phase with respect to the anode potential. In this way, it is assured that whenever the flame gap is bridged by a non-rectifying impedance, the potential of grid I48 will be lowered sufiiciently that the relay coil 26 will'not be energized.

It will be seen thatthe species of Figure 3 is substantially the same in principle as that of Figure 1 but eliminates the need of a second triode. Furthermore, by reason of the relatively large current capacity oi. the diode-cathode rectifying path, it is assured that a relatively constant source of biasing potential is available.

Srncras or FIGURE 4 The species of Figure 4 differs from that of Figures 1 and 3 in that it employs merely a single triode and depends upon the rectifying effect of the grid and cathode of this single triode to provide the biasing potential.

minal of secondary I18 to which anode I86 is connected. Thus, when anode I86 is positive with respect to cathode I88, the tap I12 is negative with respect to the cathode I 88. The condenser 52 and resistor I91 thus connect the grid I81 with a point of such voltage phase that when the anode is positive with respect to the cathode, this connection tends to render the grid negative. Viewed in either light, the result is that the grid is sufiiciently negative with respect to the cathode under no flame conditions so that insufficient current flows through relay coil 28.

Upon the occurrence of a flame, a conductive path is established through condenser 52 as follows: from the Junction of conductors I18 and I19 through conductor 15, terminal 14, conductor.

18, flame electrode 12, burner flame 68, burner 81, ground connections 69 and 95, conductor I98, condenser 52, and conductor I95 to terminal I 12 of secondary I19. Due to the rectifying action of the flame, a greater current flow through condenser 52 takes place in the direction traced so that there tends to be impressed across condenser 62 a voltage of such polarity that the right hand terminal of condenser 52 is positive and the left hand terminal, negative. This positive voltage is in effect connected in series with the alternating potential of that portion of the secondary I18 between taps I11 and 112. The magnitude of the positive voltage across condenser 52 due to flame rectification is large enough to cause the potential of grid I81 to be raisedsufllciently above the out ofl point. As a result, current flows from the lower end of secondary I16 through conductor 91, relay coil 26, conductor 88, anode I86, cathode I88, and conductor I99 back to the center tap I1I of secondary I18.

The condenser I15 and resistor I18 cooperate with secondary I19 to provide a corrective phase which said amplifier fier is effectively conducting.

shifting action as in the previous species. Were conductor 19 connected to the upper terminal of I secondary I10, the grid I81 would be connected to the junction of two legs of shifting bridge consisting of secondary I'll), condenser of approximately .02 microiarad capacity is employed for condenser 52. In the same embodiment, tap H2 is spaced by a voltage of 24 volts from the voltage of center tap I'll.

Conctusron It will be seen that I mechanism two triodes. Furthermore, by shifting network, I am able to involve the use of the use of a phase obtain a controlled corrective does not vary erratically depending upon certain operating conditions, which have no relation to the amount of phase shift necessary.

Although in the illustrated embodiments of my invention, I have shown the rectifying impedance to be a burner flame, it is to be understood that other rectifying impedances may be employed even where the mechanism is controlled as a burner controltdevice. For example, a flame gap may be replaced by a photoelectric cell exposed to the burner flame. Such a photoelectric cell permits current flow in only one direction and allows such current HOW to take place only when the photoelectric cell has been exposed to a source of illumination. Accordingly, where the expression "means responsive to a burner flame is employed in the claims, it'is to be understood that this expression is sufliciently broad to cover either a flame gap or a photoelectric cell.

In general, while I have shown certain specific embodiments of my invention, it is to be understood that this is for purposes of illustration and that my invention is to be limited solely by the scop of the appended claims.

I claim as my invention:

1. In combination, a phase shifting network including a, source of alternating power, an electronic discharge amplifier having an anode, a cathode, and a control electrode, a connection between said control electrode and said phase shifting network, the potentia1 of the point oi! connection with said phase shifting network being such that said connection tends to cause said control electrode to be maintained at a value at is eflectively non-conductive, said connection having a gap therein adapted to impedance, and means associated with said connection and responsive to the direct current flowing across the terminals of said gap when said gap is bridged by a rectifying impedance to cause the potential of the control electrode to assume a value at which said ampliphase shift which associated with said connection 2. In combination, a phase shifting network including a source of alternating power, an electronic discharge amplifier having an anode, a

value at which said is effectively conducting. 3. In combination, a phase shifting network comprising an anode, a. cathode, and a control of propagation of said flame; reactance means when said gap is so tion tending whenever the gap is bridged by a non-rectifying impedance to cause said control condenser,-the potential of said junction beingsuch that said connection tends to cause said control electrode to be maintained at a value at which said amplifier is eflectivelynon-conductive, said connection having a gap therein adapted to be bridged by an impedance; and means associated with said connection and responsive to the direct current flowing across the terminals of said gap when said gap is bridged by a rectifying impedance to cause the potential of the control electrode to assume a value at which said amplifier is effectively conducting. v

7. In combination; a phase shifting bridge including a center tapped source of alternating power, a capacitive reactance, and an inductive reactance; an electronic discharge amplifier having an anode, a, cathode, and a control electrode; a connection between the center tap of said source of power and said cathode; a connection bgtween said control electrode and the junction said two reactances of said phase shitting bridge, the potentialof said junction with respect to that of saidjanode being such that said last named connection tends to cause said control electrode to be maintained at a value at which said amplifier is effectively non-conducpower, each of which tends to cause said control electrode to assume a potential at which said amplifier is efiectively non-conducting; a first of said connections comprising a reactance; a second of said connections having a gap adapted to be bridged by an impedance; said reactance being tions between said control electrode and said tive, said last named connection having a gap therein adapted to be bridged by an impedance; and means associated with said last named connection and responsive to the direct current flowing across the terminals of said gap when said gap is bridged by a rectifying impedance to cause the potential of the control electrode to assume a value at which said amplifier is effectively conducting.

8. In combination; a, phase shifting network including a center tapped source of alternating power, a capacitive reactance, and an inductive 'reactance; an electronic discharge amplifier having an anode, a, cathode, and a control electrode; a first connection between the center tap of said source of power and said cathode; a second connection between one terminal of said source of power and said anode; a thirdconnection between said control electrode and the junction of said two reactances of said phase shifting bridge, the potential of said junction with respect to the terminal to which said anode is connected being such. that said third connection tends to cause saidcontrol electrode to be maintained at a value at which said amplifier is effectively non -conductive, said third connection having a gap therein adapted to be bridged by an impedance; and means associated with said last named connection and responsive to the direct current flowing across the terminals of said gap when said gap is bridged by a rectifying impedance to cause the potential of the control electrode to assume a value at which said amplifier is effectively conducting.

9. In combination; an electronic amplifier having an anode, a cathode, and a control electrode; a source of alternating power; two connections between said control electrode and said source of source of power, each oi" which tends to cause said control electrode to assume a potential at which said amplifier is effectively non-conducting; a first of said connections comprising a reactance; a second of said connections having a gap adapted to be bridged by an impedance; said reactance being effective when said impedance is rectifying in the direction of the control electrode to cause the potential of said control electrode to assume a value at which said amplifier is conductive despite both of said connections; and a phase shifting network in said second connection compensating. for the phase shifting efiect of said impedance and said reactance.

'11. In combination; an electronic amplifier having an anode, a cathode, and a, control electrode; a source of alternating power; two connections between said control electrode and said source of power, each of which tends to cause said control electrode to assume a potential at which said amplifier is eflectively non-conducting; a first of said connections comprising a condenser; a second of said connections having a gap adapted to be bridged by an impedance; said condenser being effective when said impedance is rectifying in the direction or thecontrolelectrode to become charged in such a manner as to cause the potential of said control electrode to assume a value at which said amplifier is conductive despite both of said connections; and a phase shifting network in said second connection compensating for the phase shifting effect of said impedance and said condenser.

12. In combination; an electrically operated control device whose energizationis to be controlled in accordance with the presence or absence of a burner flame; an electronic amplifier controlling the energization of said control device, said amplifier having an anode, a cathode, and a control electrode; a source of alternating power; two connections between said control electrode and said source of power, each of which tends to cause said control electrode to assume a potential at which said amplifier is eflectively non-conducting; a first of said connections comprising a condenser; a second of said connections having a gap adapted to be-bridged by means responsive to a flame and acting as a rectifying impedance when exposed to a flame; said condenser being effective when said flame responsive means is exposed to a flame and is rectifying in the direction of the control electrode to becomecharged in such a manner as to cause the potential of said control electrode to assume a value at which said amplifier is conductive despite both of said connections; and a phase shifting network in said second connection compensating for the phase shifting effect of said impedance and said condenser.

13. In combination; an electrically operated control device whose energization is to be controlled in accordance with the presence or absence of a burner flame; an electronic amplifier controlling the energization of said control device, said amplifier having an anode, a cathode, and a control electrode; a source of alternating power; two connections between said control electrode and said source of power, each of which tends to cause said control electrode to assume a potential at which said amplifier is effectively non-conducting; a first of said connections comprising a condenser; a second of said connections having a gap adapted to be bridged by a burner fiame with the conductive path to said control electrode being opposite to the direction of flame propagation; said condenser being effective when said gap is so bridged by a burner fiame to become charged in such a manner as to cause the potential of said control electrode to assume a value at which said amplifier is conductive despite vboth of said connections; and a phase shifting network in said second connection compensating for the phase shifting effect of said impedance and said condenser.

14. In combination; an electronic discharge amplifier comprising an anode, a cathode, and a control electrode; a source of alternating power; a reactance element connected to said control electrode to affect the potential applied thereto;

first and second circuits for causing a unidirectional voltage drop across said reactance; said first circuit including a rectifier so disposed as to cause a voltage drop across said reactance element of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively nonconducting; said second circuit including a gap adapted to be bridged by a rectifying impedance having an efiect opposite to that of said previously named rectifier, so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal of said reactance and a phase shifting network having a phase shifting effect which compensates for the phase shifting efiect present by reason of said reactance when said gap is bridged by a non rectifying impedance, said connection being effective when said gap is bridged by a nonrectifying impedance to maintain said control electrode at a polarity at'which said amplifier is non-conductive.

15. In combination; an electronic discharge amplifier comprising an anode, a cathode, and a control electrode; a, source of alternating power; a condenser connected to said control electrode to aifect the potential applied thereto; first and second circuits for charging said condenser; said first circuit including a rectifier so disposed as to cause a charge across said condenser of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively non-conducting; said second circuit including a gap adapted to be bridged by a rectifying impedance having an effect opposite to that of said previously named rectifier, so that when said gap is so bridged, the amplifier. is rendered conductive; said gap being interposed in a connection between the control electrode terminal of said condenser and a phase shifting network having a phase shifting effect which compensates for the tional voltage drop across said reactance; said electrode at a polarity at which said amplifier is V non-conductive.

16. In combination; an electronic discharge amplifier comprising an anode, a cathode, and i a control electrode; a. source of alternating power; a reactance element connected to said control electrode to affect the potential applied thereto; first and second circuits for causing a unidirectional voltage drop across said reactance; saidfirst circuit including a further control electrode and cathode acting as a rectifier and so connected as to cause a voltage drop across said reactance element of a, polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively non-conducting; said second circuit including a gap adapted to be bridged by a rectifying impedance having an effect opposite to that of said further control electrode and cathode, so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal of said reactance and a phase shifting network having a phase shifting eflect which compensates for the phase shifting eflect present by reason of said reactance when said gap is bridged by a non-rectifying impedance, said connection being efiective when said gap is bridged by a non-rectifying impedance to maintain said control electrode at a polarity at which said amplifier is non-conductive.

17. In combination; an electronic discharge amplifier comprising an anode, a cathode, and a control electrode; a source of alternating power; a reactance element connected to said control electrode to affect the potential applied thereto; first and second circuits for causing a unidirecfirst circuit including a diode and said cathode acting as a rectifier and so connected as to cause a voltage drop across said reactance element of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is efiectively non-conducting; said second circuit including a gap adapted to be bridged by a rectifying impedance having an effect opposite to that of said diode and cathode, so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal of said reactance and a phase shifting network having a phase shifting eflect which compensates for the phase shifting eifect present by reason of said reactance when said 7 amplifier comprising an anode, a cathode, and a control electrode; a source of alternating power; a first condenser connected between said control electrode and cathode and acting as a filter; a second condenser connected between said control electrode and said source of power to affect the potential applied thereto; first and second circuits for charging said second condenser; said first circuit including a rectifier so disposed as to cause oi. a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively non-conducting; said second circuit including a gap adapted to be bridged by a rectifying impedance having an effect opposite to that of said previously named rectifier, so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal or said second condenser and a phase shifting bridge having a phase shifting effect which compensates for the phase shifting effect present by reason of said second condenser when said gap is bridged by a non-rectifying impedance, said connection being efiective when said gap is bridged by a nonrectifying impedance to maintain said control electrode at a olarity at which said amplifier is non-conductive.

19. A control device of the electronic type having only one electronic discharge device, said device comprising only one anode, a cathode, and a single control electrode; a source of alternating power; a reactance element connected to said control electrode to afi'ect the potential applied thereto; first and second circuits for causing a unidirectional voltage drop across said reactance; said first circuit consisting entirely of said control electrode, said cathode, resistance connections, and a portion of said source of power of such voltage phase as to cause a voltage drop across said reactance element of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively non-conducting; said second circuit including a gap adapted to be bridged by a rectitying impedance having an eflect opposite to that or said control electrode and cathode; so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal or said reactance and a phase shifting bridge having a phase shifting eflect which compensateg for the phase shifting eflect present by reason of said reactance when said gap is bridged by a non-rectifying impedance, said connection being effective when said gap is bridged by a nonrectii'ying impedance to maintain said control electrode at a polarity at which said amplifier is non-conductive.

20. A control device of the electronic type having only one electronic discharge device, said device comprising only one anode, a cathode, and a single control electrode; a source of alternating power; a first connection between said anode and said source of power; a second connection between said cathode and aid source of power; a condenser; source of power, said condenser,

a third connection between said and said control a charge across said second condenserplifier is non-conductive.

electrode to cause said condenser to affect the potential applied to said control electrode: first and second circuits for causing a unidirectional voltage drop across said condenser; said first circuit consisting entirely of said control electrode, said cathode, said second and third connections, and a portion of said Source of power of such voltage phase as to cause a charge across said condenser of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is efiectively non-conducting; said second circuit including a gap adapted-to be bridged by a rectifying impedance having an effect opposite to that of said control electrode and cathode, so that when said gap is so bridged, the amplifier is rendered conductive; said gap being interposed in a connection between the control electrode terminal of said condenser and a phase shifting bridge having a phase shifting effect which compensates for the phase shifting efiect present by reason of said condenser when said gap is bridged by a non-rectifying impedance, said connection being effective when said gap is bridged by a non-rectifying impedance to maintain said control electrode at a polarity at which said amplifier is non-conductive.

21. In combination, an electrically operated control device; an electronic discharge amplifier controlling the energization of said control device, said amplifier comprising an anode, a cathode, and a control electrode; a source or alternating power; a reactance element connected to said control electrode to afiect the potential applied thereto; first and second circuits for causing a unidirectional voltage drop across said reactance; said first circuit including a rectifier so disposed as to cause a voltage drop across said reactance element of a polarity such that the resulting potential applied to the control electrode assumes a value at which the amplifier is effectively non-conducting; said second circuit including a fiame gap adapted to be bridged by a flame in such a direction that the rectifying effect of the flame has an effect opposite to that of said previously named rectifier, so that when said fiame gap is so bridged, the amplifier is rendered conductive; said flame gap being interposed in a connecti n between the control electrode terrpinal of id reactance and a phase shifting dge having a phase shifting effect which corn nsates for the phase shifting effect present by reason: of said reactance when said flame gap is accidentally bridged by a non-rectifying impedance, said connection being efleq tive when said gap is accidentally bridged by a non-rectifying impedance to maintain said control electrode at a polarity at which said am- WIILIS H. GILLE.

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