US2874904A - Modulating fuel control apparatus - Google Patents

Description

Feb. 24, 1959 J, c. 'scHwA-LBAcH 2,874,904

MODULAPING FUEL CONTROL APPARATUS Filed Debi 28, 1954 2 Sheets-Sheet 1 INVENTOR. Jbsepiq C Sc/m albach Y A. I

nited States Patent MODULATING FUEL CONTROL APPARATUS Joseph C. Schwalbach, Wauwatosa, Wis., assignor to Baso Inc., Milwaukee, Wis., a corporation of Wisconsin Application December 28, 1954, Serial No. 478,144

29 Claims. (Cl. 236-1) This inventionrelates to improvements in modulating fuel control apparatus and more particularly to apparatus affording modulating control of the flow of gaseous fuel.

Modulation of the fuel flow to the burner of a heater in accordance with the heat loss from the space heated is not only an efficient method of heating, but it also provides the greatest comfort for the occupants of the space by maintaining a substantially constant temperature. The provision of a modulating control for gaseous fuel burning apparatus is complicated by the fact that for every burner there is a safe minimum amount of fuel which is required forthe maintenance of a stable flame and below which the fuel flow cannot safely be modulated. 0n the otherhand, fuel in amounts substantially greater than the aforementioned safe minimum must be supplied to the burner for safe initial ignition of the fuel at said burner.

While continuous modulation of the fuel flow to a heater ordinarily affords the results desired as long as the temperature of the space being heated is within the modulating range of thefuel modulating apparatus, the operation of controlsheretofore available is not entirely satisfactory under all conditions, for example in heating up of cold rooms after a low temperature night setting.

In the latter instance prior modulating controls eifectively derate the heater by reducing its output as the temperature within the space rises, and a relatively long warm-up period is therefore required to bring the temperature of the space up to the desired level.

Still another undesirable feature of certain prior modulating controls is .the factthat once the fuel flow has been shut-off, for example in response to a rise in the temperature within the space beyond the modulating range, said temperature ,mustdrop substantially through the entire modulating range to the point where the demand for'heat is such that the control can supply sufficient fuel to the burner for safe ignition before such fuel is supplied to the burner. This, of course, subjects the space and its occupantsto undesirably large and uncomfortable temperature variations. i

. With the foregoing in mind, a general objective of the present, invention is the-provision of an improved modulating fuel control apparatus which, after shut off of the fuel, aflordssufficient fuel flow for safe, ignition at any time that the modulatingapparatus calls for heat, said apparatus, after the establishment of a stable flame at the burner, modulating the flow of said fuel in accordance with the temperature of the space being heated. Thus, safe ignition is insured regardless of what the temperature of the space may be when fuel flow is initiated, and the temperature of thespace is not required to cool to the lower end of the modulating range before safe ignition can be effected.

Another object of the invention is to provide an improved modulating fuel control, apparatus of the, character described which is provided with means affording quick warm-up after a low temperature night setting by permitting full burner capacity fuel flow during said,

2,874,904 Patented Feb. 24, 1959 "Ice warm-up period.

Another object of the invention is to provide an improved modulating fuel control apparatus of the class described wherein there is a modulator valve and an on-oifvalve, there being electroresponsive actuating means for said modulator valve biasing said valve to-,

ward a minimum flow-permitting position when said actuating means is energized and biasing said valve to .a.

full flow or ignition position when said actuating means is deenergized, said actuating means being connected in circuit with electrical source means effecting deenergization of said actuating means on closure of said onoif valve and continuing said deenergization for a predetermined period after said on-oif valve has, been opened, said period being suflicient to afford safe ignition of the fuel at the burner with a full or ignition flow of said fuel. 7

A more specific object of the invention is to provide an improved modulating fuel control apparatus of the character described wherein the actuating means for the modulator valve is connected in circuit with asource of electrical energy responsive to the heat of burning fuel at the burner, whereby on outage of said burner, said actuating means is deenergized and the modulator valve is moved to full flow or ignition position, said valve re maining in said position until subsequent establishment of a stable flame at said burner effects reenergization of said actuating means and biasing of said valve toward said minimum flow-permitting position. i

Another specific object of the invention is to provide.

animproved control apparatus of the class described wherein the delay in reenergization of the .actuating means for the modulator valve after opening of them:-

off valve is afforded by a time delay switchin circuit with an electrical energy source means and said actuating means, said switch being responsive to opening of the on-oif valve, and more specifically to the pressure of the fluid fuel flowing to the burner through said valve.

.Another object of the invention is to provide an improved modulating control apparatus of the class de to the burner on occurrence of an extreme in said condition, for example'a temperature above the modulating temperature range.

Another specific object of the invention is to provide, in control apparatus of the aforementioned character, electro-responsive latching means in circuit with the actuating means for the modulator valve for preventing movement of the on-otf valve from closed to openposi tion at any time that said actuating means is energized- This avoids any danger from downward adjustment'of the control point of the modulating mechanism effecting closure of the on-olf valve, followed immediately by upward readjustment of said control point tending to effect opening of said on-off valve before the modulator valve has been moved to its ignition position. i

Still another object of the invention is to provide an improved modulating fuel control apparatus of the character described having safety shut-off means operatively associated with the on-off valve for overcalling the modulating mechanism and effecting closure of said valve on means for the modulator valve, said contacts when latched preventing energization of said actuating means, there being reset means operatively associated wth the condition responsive modulating mechanism and said circuit controlling device, said reset means effecting movement of said contacts to latched position when the control point adjustment means of the modulating mechanism is turned to a low temperature night setting, there being releasable latching means for retaining said contacts in said latched position after readjustment of the control point of the modulating mechanism to a normal operating temperature setting and until said contacts are released by response of said circuit controlling device to a predetermined normal temperature setting, said contacts thereafter remaining unlatched until subsequently latched by readjustment of the control point of the modulating mechanism to a low temperature night setting. Still another object of the invention is to provide an improved modulating fuel control apparatus of the class described which may be entirely self-powered and therefore independent of any electrical utility in its operation.

Other objects and advantages of the invention will appearas the description proceeds, reference being had to the drawings accompanying and forming a part of this specification. In the drawings, which illustrate two forms of the invention, like characters of reference therein indicating the same parts in all of the views: 7

Figure 1 is a sectional view of an improved modulating fuel control device constructed in accordance with the invention, the associated fuel burning apparatus and electrical control circuit making up the remainder of the improved fuel control apparatus being shown semi-diagrammatically; r

Figure 2 is a fragmentary sectional view of the control device of Figure 1 illustrating the disposition of certain parts thereof during resetting of the safety shut-o mechanism;

Figure 3 is a fragmentary sectional view similar to Figure 2 and illustrating the disposition of the parts of the control device when the safety shut-off mechanism is in shut-off position;

Figure 4 is a fragmentary sectional view of the control device of Figure l and illustrates the resetting of the latchable contacts of the circuit controlling device on adjustment of the control point of the modulating mechanism to a low-temperature night setting; and

Figure 5 is a fragmentary semi-diagrammatic illustration of another form of the improved modulating fuel control apparatus.

Referring more particularly to Figure 1 of the drawing, the numeral indicates a modulating fuel flow controlling device for controlling the flow of gaseous fuel to a main burner 11 and to a pilot burner 12. The control device 10 comprises a sealed casing 13 having a removable cover 14 and having a transverse partition 15 separating said casing into a'fuel inlet chamber 16 and a fuel outlet chamber 17. i The partition 15. is provided with an aperture 18, and fuel flow through said aperture is controlled by a modulator valve 19 Which coacts with an annular seat 20 in the chamber 17 surrounding the margin of the aperture 18. Fuel flow from the chamber 17 to the burner 11 is permitted or prevented by an on-off valve 21 which coacts with an annular seat 22 sur- 4 rounding a fuel outlet passage 23 leading from the chamber 17.

The modulator valve 19 is provided with electroresponsive actuating means which may take the form of an electromagnetic operator 24 carried by a lug 24a projecting into the chamber 16 from a side wall of the casing 13 as shown. The operator 24 comprises an electromagnet 25 having an armature 26 movable to attracted and retracted positions wtih respect thereto and fixed to a pivotal armature arm 27. The operator, 25 also comprises a generally L-shaped valve arm 28 fixed at one end to a-resilient metal band hinge member 29, said arm carrying a valve stem 30, the outer end of which is threaded to receive a back-up nut 31, the modulator valve 19 and an internally threaded retaining sleeve 32 having an enlarged head at its outer end as shown. The position of the modulator valve 19 with respect to the stem 30 may be readily adjusted by adjustmentof the position of the nut 31 and sleeve 32 on said stem; The hinge member 29 normally. biases the modulator valve 19 away from the seat 20 toward a full flow-permitting orignition position (not shown). through a spaced member 33 is an energy storing leaf spring 34, and the free end of said leaf spring is connected to the armature arm 27 by a link'3 5. The arm 28 also carries an adjustable screw 36 having an end positioned for engagement by the leaf spring 34 during attractive movement of the'armature 26. In Figure 1 the armature is disposed'intermediate itsattracted and retracted positions, and the modulator valve is correspondingly disposedintermediate its minimum flow-permitting and full flow-permitting or ignition positions. 1

On energization of the operator 24 the armature 26 is attracted to the electromagnet 25, thereby pivoting the armature arm 27 and, through the link 35, defiecting the energy storing spring 34 tottoreenergy therein. This pulls the leaf 34 into engagement with the screw 36 to shorten the effective lengthfof said leaf and increase the spring rate thereof so that increasing amounts of energy are stored in the leaf 34w further attractive movement of the armature in the event that the energy stored in the leaf 34 plus the attractive force on the armature 26 at that point is insufiicient toovercorne the resistance of the modulator valve'19 to flow'restricting movement. In any event, however, except when prevented from so moving by mechanism to be hereinafter described, the modulator valve 19 is moved toward the seat2l) by energization of the operator 24. On deenergi- Zation of the operator 24, of course, the modulator valve 19 moves away from the seat 20 to a full flow-permitting or ignition position under the biasof the hinge spring 29.

A modulating mechanism indicated generally by the numeral 48 is provided for effecting'modulation of the modulator valve 19 in accordance with fluctuations in 'a condition, for exampletempera'ture, within a predetermined range. The aforementioned mechanism comprises a bracket 37 fixed to the casing 13, as by screws 38, said bracket beingformed with a circular aperture 39 to receive the externally threaded open end portion 40 of a tubular fitting 41. Thefittin'g 41 has a centrally apertured end wall 42, and has an external annular shoulder 43. in abutment with the inner surface of the bracket 37 at the margin of the aperture 39. ,"An annular spacer 44 surrounds the threaded portion 40-of the fitting 41 and abuts the outer surface of the bracket 37, said spacer having a radial slot 45 as shown. The. fitting 41 is held in position by a nut 46 which is threaded on the portion 40 and engages the spacer 44, clamping said spacer and. the bracket 37 between said nut and the shoulder 43. The threaded end portion 40 is ,providedwith a longitudinal slot 47, with which the slot 45 of the spacer 44 is in registry. p v

A condition responsive, for example temperature responsive, expansible .and contractible bellows assembly is positioned coaxially within the fitting and comprises a Fixed to the valve arm 28 external stem portion 55 which slidably projects through the aperture in the end wall 42 and through a bore 56 formed in the adjacent wall portion of the casing 13, terrninating in the chamber 17 of said casing. As shown,

the bore 56 extends through a bearing sleeve 57 formed integral with the casing 13. The stem 55 is preferably formed with peripheral grooves. to receive sealing rings 58 of rubber like material for preventing leakage of fuel from the chamber 17 along the stem 55. A coiled compression spring 59 surrounds the stem 55 within the fitting 41 and biases the bellows end fitting 50 toward the end fitting 51,, 3

Means are provided for adjusting the position of the bellows assembly 48 within the fitting 41 to thereby provide adjustment of the temperature control point of said assembly. More specifically, a manually engageable knob 59 is internally threaded on the portion 40 of the fitting 41, and a set screw 60 is coaxially threaded through the knob 59 and engages the bellows end fitting 51 as shown. The screw 60 may be locked in place relative to the knob 59 by a locking or jam nut 61.

A passage 62 in the end fitting 51 communicates with the bore of the guide sleeve 52, and a tube 63 affords communication between the passage 62 and a temperature sensing bulb 64. The inner end of the tube 63 is sealed within the passage 62 and 6 extends radially outwardly through the slots 47 and 45 as shown. The bulb 64 is preferably located at the comfort level in the space being heated, for example at the normal location for a room thermostat; With suitable adjustmennhowever, the bulb 64 may be mounted in other locations, for example in the cold air returnof the heating system. The bellows assembly 48 is commonly known as the solid-liquid fill type, and said bellows, tube 63 and bulb 64 are filled with a liquid having a high coefficient of expansion and having a boiling point at working pressure which is above the highest ambient temperature to which said fill might be exposed. The fill exists substantially entirely in the liquid phase, as differentiated from fills which existin the vapor phase as well as the liquid phase. A solid-liquid fill bellows provides actuating forces which result from thermal expansion of the liquid fill only, as distinguished from bellows utilizing a fill existing in both the liquid and vapor phasesythe latter providing actuating forces produced by vapor pressure. KChloroforrn is illustrative of a type of liquid well adapted for use as a fill in the bellows assembly 48.

Means is provided for effecting control of the modulator valve 19 and of the on-ofi valve 21 by the modulating mechanism 48 in accordance with the temperature sensed by the. bulb 64. For control of the modulator valve a lever 65 is pivoted intermediate its length, as on a pivot pin 66 carried by a boss 67 formed on the wall of the casing13 within the chamber 17.. The lever 65 has a bifurcated end 68 embracing the sleeve 32, preferably in spaced relation, and engageable with the enlarged head of said sleeve as shown. The opposite end 69 of the lever 65 is also bifurcated to embrace the stem 55, the bifurcated end portions thereof being slotted, as at 70, to receive a pin which extends diametrically through the stem 55.

Since the operator 24 has insufiicient power to over at any time that the operator 24 is deenergized, the modulator valve 19 is free to move under the bias of the hinge member 29 to its full flow-permitting or ignition position regardless of the position in which the lever is disposed by response of the modulating mechanism 48 to the ambient temperature sensed by the bulb 64. Whenever the operator 24 is energized, and the temperature sensed by the bulb 64 is within the modulating range, the modulating mechanism 48, by its action in restraining or limiting movement of the modulator valve 19 toward its seat under the bias of said operator, continually modulates said modulator valve in accordance with the temperature, between a minimum fiow-permittingposition wherein said valve is seated on the seat 20 and a full flow-permitting or ignition position.

The on-ofi valve 21 is carried by an L-shaped arm 72 pivotally mounted, as on a pin 73 carried by a boss 74 onthe interior of the casing 13. A coiled tension spring 75 has one end anchored to a lug 75a formed on the interior of the casing 13 and has its opposite end anchored to the arm 72 to bias the latter toward a stop lug 76 also formed on the interior of the casing 13 and defining the open or on position of the on-oif valve.

The interior of the casing 13 is formed with annular shoulder means 77 affording support-for a snap disc 78 having the normal unstressed configurationshown. The lever 72 is provided with a projection 79 positioned adjacent the concave surface of the snap disc 78 as shown. A circular dished member 80 is fixed to the end of the stem 55, as by a pin '81, and is positioned for engagement with the convex surface of the snap disc 78 as shown. As long as the temperature sensed by the bulb 64 is within the modulating range for which the modulating mechanism 48 is set, the dished member 80 moves axially with the stem 55 in accordance withfluctuations in the temperature without actuating the snap disc 78. However, when the temperature sensed bythe bulb 64 goes beyond the modulating range for which the modulating mechanism is set, expansion of the bellows fill forces the member 80 against the snap disc 78 with sufficient force to snap said disc. to thedot and dash line overcenter position shown in Figure. 1. As the snap disc snaps to the overcenter position it engages the projection 79 on the arm 72 and pivots said arm and the valve 21 to the dot and dash line closed or .oif position shown in Figure 1, thereby shutting off all fuel flow to the burner 11.

In order to provide for energization of the operator 24 one end of the energizing coil of the electromagnet 25 is connected in circuit with a terminal member 82 insulatablyextending through the cover 14 and exposed within an internally threaded external socket 83 formed on said cover. Suitable means, for example, the conductor 84 connects the terminal member 82 with one terminal of an electrical energy source responsive to the heat of fuel burned at the main burner 11. In the embodiment of the invention illustrated in Figure 1, said source takes the form of a thermoelectric generator 85 positioned to be subject to the heat of fuel burned at said main burner. The other terminal of the generator 85 is preferably grounded as shown.

Means is provided for affording quick warm-up of the space being heated after the control knob 59 is adjusted from a low temperature night setting to a higher temperature normal daytime operating setting, said means avoiding derating of the heating system characteristic of modulating controls. To this end a condition responsive, for example temperature responsive, circuit controlling device 86 is provided, saiddevicei comprising a hermetically sealed bellows 91 having amovablel wall and a wall 89 fixed, as by screws 88, to a flange 87 formed on the fitting 41. The fixed wall 89 is apertured t of said stern terminating in a portion of enlarged diameter.

and a spherical contact tip 94. At its outer end the contact stem 93 is provided with an insulatably mounted terminal member 95 for connection with an electrical conductor 96. Mounted on the contact stem 93 between the contact tip 94 and the glass seal 92 is a generally spherical insulating member 99 having a diameter larger than the diameter of the contact tip 94 as shown.

The conductor% is connected in circuit with a terminal member 97 insulatably extending through a wall portion of the casing 13 and in turn connected in circuit with the other end of the energizing coil of the'electromagnet 24 within the chamber 16. The 'movable wall 90 of the bellows 91 carries a movable contact member 98 of generally U-shaped conformation and having a pair of resilient jaws for frictionally engaging the contact tip 94 as shown, to elfect a low resistance electrical connection therewith." The contact 98 is, of course, grounded to the casing 13 through the bellows -91, fitting 41 and bracket 37. I

v The fixed wall 89 of the bellows 91 is bored to sealingly receive a capillary tube 100 alfording communica- 'tion between the interiorof said bellows and a bulb 101 which may be mounted adjacent the bulb 64. The bellows 91, tube 100 and bulb 101 all contain a common sub-atmospheric volatile fluid fill whose vapor pressure increases and decreases in response to increases and decreases in temperature. The fill is also of a type'which will not react with the contacts 94 and 98 to form films thereon or in any way increase the contact resistance. While the fills used in difierent applications may vary in accordance with the temperature encountered in said 1 application, satisfactory fills for space heating applications are ether and isopentane, both of which provide a sub-atmospheric fill at operating temperatures. Thus, in the event of a leak anywhere in the fluid system, i. e., in either the bellows, tube 100 or bulb 101, atmospheric pressure enters this system and tends to expand the bellows to separate the contacts therein.

Means is provided for compressing the bellows 91 to move the frictional contact 98 into clamping engagement with the insulating ball 99 as shown in Figure 4 and to thereby interrupt the circuit between the contacts 94 and 98. For convenience, the disposition of the contacts shown in Figure 4 will be termed a reset position, and the operation of moving the parts of the device 86 from the position of Figure 1 to the position of Figure 4 will be termed a resetting operation. The aforementioned resetting operation is accomplished. by mechanism including a lever 102 mounted for pivotal movement ona pivot pin 103 carried by the annular shoulder 43 within a radial slot formed therein, as. shown most clearly in Figure 4. The bracket 37 is formed with an integral bearing sleeve 104 on which a pin 105' is axially slidable. The pin 105 has a rounded head 105a for coaction with the lever 102, and the opposite end of said pin projects from the sleeve 104 for coaction with the inner surface of the knob 59 as shown.

When the parts are disposed as shown in Figure l, the knob .59 is set so that the temperature control point of the modulating mechanism 48 is at a normal daytime operating temperature setting, and the inherent bias .of the bellows 91, and the vapor pressure of the fill therein, act through the lever 102 to bias the stem 105 into engagementwith the inner surface of the knob 59, while at the same time biasing the jaws of the contact 98 into engagement with the contact tip 94. When, however, the knob 59 is turned inwardly to adjust the temperature control point of the modulating mechanism 48 to a low temperature nightjsetting, said inward movement is imparted to the slidable pin 105 to effect pivoting of the lever 102 to the position of Figure 4 and cause thelatter to compress the bellows 91, thereby sliding the jaws of the contact 98 into clamping engagement with the insulating ball 99 and out of electrical contactwith thecontact tip 94. This interrupts the power circuit to setting, the sliding pin and lever 102 do not follow such outward movement, since'as long as the room, temperature is below a predetermined control point or release value to which the device '86 is responsive, for example 70 F, the clamping engagement of the jaws of the contact 93 withthe insulating ball 99 is sufficient to overcome the inherent bias of the bellows 91 and the vapor pressure of the fill within the bellows tending to. As a result, the electrical circuit'to expand thelatter. the operator 24 remains interrupted, after upward readjustment of the knob 59 from a night turndown setting, and therefore the modulator valve 19 remains in full.

open or ignition position, affording maximum output of the heater continuously until the temperature, of the space as sensed by the bulb. 101 is raised to the predetermined control point of the circuit controlling device 86, for example the 70 P. value mentioned hereinbefore.

pansion afforded by the clamping engagement of the jaws of the-contact 98 with the ball 99, and the bellows expands to the position of Figure 1. In this position the contact 99 efiects a low resistance electrical connection with the contact tip 94 to complete the low resistance power circuit for the electromagnet 25 for energization.

thereof by current from the source 85. It is apparent; therefore, that the circuit controlling device 86 provides fast warm-up after night turndown by preventing modulation of the fuel flow by the modulator'valve until 'the space has been heated to near the temperature control point for which the modulating mechanism has been set.

Interlock means is provided for insuring against the unsafe condition which would result if the on-offvalve 21 were closed to shut off all main burner fuel flow, and

then allowed to reopen before the generator 85 has had time to cool and deenergize the operator 24 for movement of the modulator valve 19 to its full open or ignition position.- In the absence of the aforementioned interlock means, such a situation could be brought about by turning the knob 59 inwardly sufficiently to effect snapping of the disc 78 and closure of the on-ofi valve 21, and then immediately turning said knob outwardly to permit the snap disc to return to 'its normal position. Without the means to be described hereinafter, the on-ofii valve member 21 would move to open position as the snap disc 78 returns to its normal position. Since the generator 35 has not had time to cool sufficiently todeenergize the operator 24, said operator continues to hold the modulator valve 19 in a reduced flow-permitting position thus creating a dangerous situation by supplying insufficient fuel to the burner 11 for safe ignition.

To avoid the aforementioned dangerous condition, an electromagnet 106 is fixedly mounted within the chamber 17 adjacent the valve arm 72 and has an energizing coil 107, one end of which is grounded to the casing 13,: and the other end of which is connected in circuit with the terminal member 82 by a conductor 108 which ex tends through an aperture 109 in the partition 15 as shown. The valve arm 72 carries a magnetically permeable armature 110 for coaction with the electromagnet' 106. The electromagnet 106 is thereby connected in parallel circuit relation with respect to the operator 24 and is energized by electrical energy from the source 85 at any time that the operator 24 is energized. Thus, at

any time that the operator Z4 is energized to hold the modulator'valve in a reduced flow-permitting positionand the'on-off valve 21 is moved to closed position, the

simultaneously energized electromagnet106 magnetically When this predetermined temperature is reached, the inherent bias of the bellows and the vapor pressure within said bellows overcome resistance to bellows ex-' latches the armature 110 thereto and prevents opening of the on-otf valve member 21. The on-ofi valve cannot be opened under the bias of the spring 75 until the electromagnet 106 is deenergized, and such deenerglzation can occur only simultaneously with 'deenergization of the operator 24, so that when the on-ofi valveis opened, the modulator valve 19 is certain to be in its full flow or ignition position, Safe ignition of-the fuel at the burner 11 is thereby insured at any time that the on-olf valve 21 is moved from closed to open position.

Means is provided for overcalling the modulating mechanism and for providing 100 percent shut-off of the fuel to the main and pilot burners in the, event of outage of the flame of the pilot burner 12. The aforementioned means comprises a manuallyresettable electromagnetic safety shut-off mechanism indicated generally by the numeral 111 and includes a generally cylindrical hood or casing 112 which is axially slidable within a cylindrical guide-way 113 formed in the chamber .17 of the casing 13. Fixed Within the hood 112 is an electromagnet 114 having an energizing coil, one end of which is grounded to said hood, and the other end of which is provided with a suitable flexible lead which extends to a terminal member 115 insulatably extending through the cover 14 and exposed within an internally threaded external, socket 116 formed on said cover.

An armature 119 is cooperable with the electromagnet 114 and is carried by an axially slidable stem 120 which projects through a suitable bearing in an end wall of the hood 112 and is fixed, as by a pin 121, to a generally cup-shaped member 122 having a nose 123 engageable with the valve arm 72. A coiled compression spring 124 surrounds the stem 120 between the hood 112 and the member 122 and biases the armature 119 away from the electromagnet 114,simultaneously biasing the member 122, away from the hood 112. The guideway-113 is formed with a longitudinal groove 125 in which a leaf type positioning spring 126 is mounted as shown, said spring having a curved end portion 127 for coaction with an indentation 128 formed in the adjacent wall portion of the hood 112, for a purpose to be hereinafter set forth. Electricalsource means, for example a thermoelectric generator, responsive to the heat of fuel burned at the pilot burner 12 is connected in circuit with the electromagnet 114 by having one terminal thereof connected in, circuit with the terminal member 115, as by the conductor 118 shown diagrammatically. The other terminal of the generator is grounded in the usual manner. I

The cover 14 is formed with an outwardlypro ectmg externally threaded socket 129 and with a coaxial inwardly projecting externally threaded socket 130. The socket 130 is counterbored to afford an annular pilot fuel valve seat 131, there being a pilot fuel outlet passage 132 affording communication between said bore and an internally threaded socket 134 which is adapted to receive a pilot fuel supply pipe indicated diagrammatically at 1 12, the hood 112 of the safety shut-off mechanism 111" is provided with an integral stem 140 which projects through the bore of the socket and through a coaxial bore 141in the cover 14, into the bore of the socket 129. The stem carries a pilot fuel valve 142 which is cooperable with the annular valve seat 131 to control pilot fuel flow. An internally threaded cup-shaped cap 143 is threaded on the socket 130 and is bored to slidably receive the stem 140. If desired, the bore of the member 143 may be grooved to receive a resilient sealing ring 144 of rubber-like material.

An internally threaded cup-shaped retaining nut 145 is threaded on the socket 129 and is formed with an aperture 146 having adiameter smaller than the bore of' said socket, so that said nut has an annular flange portion 150 in which the outer end of the received.

pair of diametrically opposed longitudinal. slots 151 for stem 140 is slidably "receiving the opposite ends of a pin 152 ,which extends diametrically through the adjacent end portion of the stem 140. A coiled compression spring 148 surrounds the stem 140, having one end surrounding the tubular portion 150 and in engagement with the reset button 147, and the opposite end in engagement with suitable sealing material 149 surrounding the stem 140 at the base of. the bore of socket 129. Thus, thespring 148 biases the reset button 147 outwardly to the position shown in Figure l, and simultaneously biases the material 149 into sealing engagement with the stern 140.

Whenever the electromagnet 114 is deenergized, the parts of the safety shut-off mechanism 111 are disposed as shown in Figure 3. When the parts are so disposed, the spring 124 biases the nose into engagement with the valve arm 72 and holdsthe on-oif valve 21 closed against the bias of the spring 75. At the same time, the spring 124 biases the hood 112 in the opposite direction, and through the stem 140,

provided.

135. A pilot fuel inlet passage l33.affords communica tion between the counterbore of the socket 130 and an.

have a lock nut 139, is threaded into the cover 14 as shown and controls the amount of fuel which, can flow through the by-pass 137, said screw being so set that at least sufficient, fuel can flow through the by-pass to By having thepilot fuel inlet passage 133 communicate with fuel inlet chamber 16 through the passage 136, the

, provide the minimum safe flame at the main burner ,11 when the modulator valve 19 is seated on the seat 20.

fuel flow to the pilot burner is not subject to the pressure fluctuations to which it would be subjected if said passage led from the chamber 17. 1 i

To afford control of the fuel flow to the pilotburner In order to set the improved modulatingfuel control apparatus into operation, the safety shut-01f mechanism 111 must first be reset and the pilot burner 12 ignited. To reset the safety shut-off mechanism 111 and establish fuel flow to the pilot burner 12, the reset button 147is depressed as shown in Figure 2, thereby moving the stem 140, pilot valve 142 and hood 112 toward the right as viewed in Figure 2. Unseating the pilot valve member 142 establishes, fuel flow from the pilot fuel inlet passage 133 through the pilot fuel outlet passage 132, and thence to the pilot burner 12 through the supply pipe 13$,for ignition at the pilot burner. ment of pilot fuel flow, depression of the: reset button 147 and corresponding movement of the hood 112 simultaneously compresses the spring 124 and moves the electromagnet 114 into engagement with the armature 119.

At the same time, the on-olf valve is being held closed by coaction of the nose 123 of the member 122 with the valve arm 72, and flow interruption is thereby provided to prevent How of any fuel to the main burner during the resetting operation. 1

The reset button 147 is held depressedfor a period suflicient to' allow the ignited pilot burner to heat the generator 117 and energize the electromagnet 114 to effect magnetic latching of the armature 119 thereto.

On release of the reset button, the spring 148, which has.

been compressed by depression oftsaid button, biasesthe. latter to its outermost position shown in Figures 1 and 3..

However, because of the lost motion provided by coaction annular lip within 129 cooperable with the nut 145 to limit axial outward movement of said button. The reset button 147 is formed Witha coaxial tubular portion The tubular portion 150 is formed with a 123 of the member122 In addition to the establish of the pin 152 with the slots 151in the tubular portion 150 of the reset button, the stem 140 and hood 112 are not moved outwardly far enough to seat the pilot fuel valve 142, but rather, they are moved only far enough for the curved end portion 127 of the positioning spring 126 to seat in the hood depression 128 and thereby define the operative position of the hood 112 and valve 142 shown in Figure 1. Pilot fuel,'therefore, continues to flow to the pilot burner 12.

As the hood 112 is moved outwardly with the stem 140 in the manner described, the magnetic latching of the armature 119 to the electromagnet 114 maintains the spring 124 compressed and moves the member 122 with said hood to the position shown in Figure 1, thereby freeing the on-off valve 21 for movement from its closed position to its full'op'en position shown in Figure 1.

Theparts of the safety shut-off mechanism 111 remain in the position shown in Figure 1 as long as the generator 117 continues to be heated by the flame of the pilot burner 12. However, on outage of the pilot burner 12, the generator 117 cools, the electromagnet 114 becomes deenergized, and the spring 124'thereupon pulls the armature 119 away from the electromagnet 114 and disposes the-parts as shown in Figure 3 to provide 100 percent shut-ofi of the fuel.

Assume that the bulb 64 is subjected to a temperature above the modulating range and expansion of the fill in bellows 49 has moved the stem 55 toward the snap disc 78 to actuate the latter to its overcenter position and to also rotate the lever 65 clockwise to the position where it permits the modulator valve 19 to be seated on the seat 20 on energization of the electromagnetic operator 24. Closure of the 011-011? valve 21 on snapping of the disc 78, extinguishes the main burner 11, and the generator 85 cools to deenergize the operator 24 and move the modulator valve 19 to its full flow-permitting or ignition position.

As the room cools below the upper end of the modulating range, contraction of the fill within the bellows 49 withdraws the stem 55 and permits the snap disc 78 to return to its normal position shown in Figure 1, where-p upon the valve lever 72 and the on-olf valve 21 move under the bias of the spring 75, to their solid line open position shown in Figure 1. This, of course, permits a full flow of fuel to the main burnerll for safe ignition. This'full flow of fuel continues until the burning of fuel I modulating mechanism, via the lever 65, permits. The

flow of fuel to the burner 11 is thereafter modulated in accordance with the temperature sensed by the bulb 64 of the modulating mechanism. As the temperature approaches the upper end of thernodulating range the fuel flow may be modulated down to the point where the modulator'valve 19 is seated, at which point a minimum safe flow of fuel can still flow to the burner 11 through the by-pass 137.

It will be observed that with the improvedmodulating fuel'control apparatus the temperature of the space being heated does not have to drop through the entire modulating range before the main burner can be reignited, since at any time the on-ofi valve.21 is moved from closed to open position, the modulator valve 19 is at the same time disposed in full open or ignition position to insure safe ignition of the main'burner 11. Whenever the electro- 'magnetic operator 24 is energized, it biases the modulator valve 19 toward its seat 20, but, as described hereinbeforc, the actual modulated position of said valve is determined by the response of the modulating mechanism 48 to the temperature sensed by its bulb 64. As the fill in the bellows 49 expands in response-to increased temperature sensed the bulb 64, the stem moves downwardly, as viewed in Figure l, and the lever 65rotates clockwise 12 to permit the energized operator 24 to pull the modulator valve 19 closer toward the seat 20, thereby reducing the amount of fuel flowing to the burner 11 and thereby the amount of heat generated thereat. Conversely, contraction of the fill in the modulating mechanism in response to a drop in temperature sensed by the bulb 64, withdraws the stem 55 upwardly, as viewed in Figure 1, and pivots the lever 65 in a counterclockwise direction, thereby pulling the modulator valve 19 away from its seat 20 to an increased flow-permitting position to thereby increase the amount of fuel flowing to the burner 11 and correspondingly increase the heat generated at said burner.

The snap disc 78 operates as a high temperature limit device, since the parts are so arranged that said snap disc is not snapped to overcenter position until after the temperature sensed by the bulb 64 has reached the upper end of the modulating rangeand the modulator valve 19 has been seated on its seat to thereby throttle the fuel flow to the main burner 11 to the safe minimum amount. Any further rise in temperature sensed by the bulb 64 moves the stem 55 downwardly beyond the position thereof permitting seating of the valve 19, and the snap disc is thereby snapped to its overcenter position, effecting closure of the on-ofi valve.

Closure of the on-off valve 21, of course, shuts 011 the flow of fuel to the main burner 11, and the generator thereupon cools to elfect dcenergization of the operator 24 and of the electromagnet 106. As the operator 24 is deenergized, the modulator valve 19 drops to the full open or ignition position to afford safe ignition of the fuel at the main burner on subsequent opening of the on-otf valve as the modulating mechanism 48 responds to a drop in temperature sensed by the bulb 64.

In Figure 5 another form of the invention is illustrated, and all of the parts in Figure 5 indicated by primed reference character s maybe identical with the parts in Figure 1 indicated by the same reference characters unprimed. The modulating control device 10' may be identical with the control device 10 illustrated in Figure 1, parts of the device 10' being illustrated diagrammatically only in Figure 5. In the form of the invention shown in Figure 5, the time delay between opening of the on-ofi valve 21 and movement of the modulator valve of the device 10 to a reduced flow-permitting position is provided by a fluid pressure responsive time delay switch 153 located in the fuel supply line 154 to the main burner 11. The normally open low resistance contacts of the switch 153 are connected in circuit with heat source means, for example a thermoelectric generator 117, subject to the heat of the pilot burner 12. The switch 153 controls the flow of energizing current from said generator to the electromagnetic operator 24 and to the electromagnet 106', said operator and magnet being connected in parallel circuit relation, and said operator being connected in series 4 -circuit relation with the circuit controlling device 86 corresponding to the circuit controlling device 86 of the modulating control device 10 as shown in Figure 1. It will be noted that the safety shutofi mechanism electromagnet 114' is also connected in circuit with the generator 117', wherefore said generator affords the sole source ofelectrical energy for the apparatus illustrated in Figure 5. r

In the form of the invention illustrated in Figure 5,

when the modulator mechanismthereof calls forheat and efiects opening of the on-off valve -21 in the manner described in connection with the form of theinvention shown in Figure 1, the pressure of the fuel flowing through the supply pipe 154 to the burner 11 actuates the fluid pressure responsive switch 153, which, after a predeterminedtime delay,'closes the contacts thereof and completes the electrical circuit between the generator 117', operator 24' and electromagnet 106.. The time delay afforded by the switch 153 allows a full flow of fuel to flow to the main burner 11' for a period 'sufiicient to insure safe ignition'of said fuel at the main burner before the contacts ofutheswitch 153 are closed to ener- 154, thereby immediately deenergizing the operator 245.

and causing the modulator valve of the device to move to full open or ignition position. Where the response of the switch 153 to a pressure drop in the supply line 154 is substantially instantaneous, the interlock af forded by the electromagnet106' and armature 110 may not be required and therefore may be eliminated. Except for the different means for providing the desired time delay, i. e., by the switch 153, and for the fact that the apparatus in Figure 5 is powered from a single generator 117 as distinguished from the powering of the apparatus of Figure l by the generators 85 and 117, the operation of the apparatus shown in Figure 5 is substantially identical with that of the apparatus shown in Figure 1.

Having thus described two specific embodiments of the present invention, it is to be understood that these forms have been selected to facilitate the disclosure rather than to limit the number of forms which the invention may assume. Various modifications, adaptations and alterations may be applied to the specific forms shown to meet the requirements of practice, without in any manner departing from thespirit or scope of the present invention, and all of such modifications, adaptations and alterations are contemplated as may come within the scope of the appended claims.

Whatis claimed as the invention is: 1. Apparatus for controlling the flow of fuel to a fluid fuel burner comprising, a first control member having an ignition position and a lesser flow-permitting po sition, a second control member having fuel flow-permitting and fuel flow-preventing positions, and electro:

responsive actuating means for biasing said first control member toward said lesser flow-permitting position when energized and toward said ignition position when deenergized, and time delay means in circuit with said actuating means, for preventing energization of the latter and movement of said first control member toward said lesser flow-permitting position for a predetermined period after movement of said second control member to flow-permitting position, said period being of sufiicient duration for safe ignition of the fuel at said burner.

2. Apparatus for controlling the flow of fuel to a fluid fuel burner comprising, a first control member having an ignition position and a lesser fiow-permittingposition, a second control member having fuel flow-perfor safe ignition of the fuel at said burner, said time delay means comprising electric energy source means responsive to the heat of fuel burned at said burner for energizing said first actuating means.

3. Apparatus for controlling the flow of fuel to a fluid fuel burner comprising, a first control member having an ignition position and a lesser flow-permitting position, a second control member having fuel flow-permitting and fuel flow-preventing positions, an electroresponsive actuating means for biasing said first control member toward said lesser flow-permitting position when energized and toward said ignition position when deenergized, and time delay means in circuit with said first 14 actuating means for preventing energizatlon of. the lat ter and movement of said first control member toward said lesser flow-permitting position for a predetermined period aftermovement of said secondcontrol member' to flow-permitting position, said period being of sufficient duration for safe ignition of the fuel at said burner, said time delay means comprising means including a thermoelectric generator subject to the heat of fuel burned at said burner for energizing said first actuating means.

4. Apparatus for controlling the flow of fuel to a fluid fuel burner comprising, a first control member having an ignition position and a lesser flow-permitting position, a second control member having fuel flow-permitting and fuel flow-preventing positions, an electroresponsive actuating means for biasing said first control member toward said lesser flow-permitting position when energized and toward said ignition position when deener gized, and time delay means in circuit with said first actuating means for preventing energization of the latter and movement of said first control member toward said lesser flow-permitting position for a predetermined period after movement. of said second control member to flow-permitting position, said period being 0f sufficient duration for safe ignition of the fuel at said burner,

.said time delay means comprising time delay switch means in circuit with a source of electric energy and with said first actuating means, said switch means being responsive to movement of said second control member toward flowpermitting position. i i

5. Fuel flow control apparatus, comprising enclosure means having fuel flow passage means therein, first and second flow control members for controlling fuel flow through said passagemeans and each movable to first and second controlling positions with respect to said passage means, first condition responsive actuating means for said first control member operable to bias the latter toward its first controlling position in response to a first condition, and second actuating means operatively related to said first control member for restraining the movement of the latter towardits first controlling position under the influence of said first actuating means, the restraint afforded by said second actuating means being variable in accordance with normal fluctuations in a second condition, said second actuating means also being operatively related to said second control member for actuation of the latter toward its second controlling position in response to an extreme in said second condi: tion.

6. Fuel control apparatus, comprising enclosure means having fuel flow passage means therein, first and second flow control members forcontrolling fuel flow through said passage means and each movable to first and second controlling positions with respect to said passage means, first condition responsive actuating means for said first control member operable to bias the latter toward its first controlling position in response to a first condition, second its second controlling position in response to an extreme in said second condition, and condition responsive safety shut-01f means operatively-related to said second control member for insuring disposition of said second control member in its second controlling position in response to a third condition.

7. Fuel control apparatus, comprising enclosure means having fuel flow passage means therein, first and second control members for controlling fuel flow through said passage means and each movable to first and second controlling positions with respectto said passage means, first condition responsive actuating means for said first control member operable to biasthe latter toward its first controlling position in response to a first condition, second actuating means also operatively related to said first control member for restraining the movement of the latter toward its first controlling position under the influence of said first actuating means, the restraint afforded by said second actuating means being variable in accordance with normal fluctuations in a second condition, said second actuating means also being operatively related to said second control member to bias the latter toward its first position during said normal fluctuations in said second condition and to actuate said control member toward its second controlling position in response to an extreme in said second condition, and condition responsive safety shut-off means operatively related to said second control member for overcalling said second actuating means and insuring disposition of said second control member in its second controlling position in response to a third condition irrespective of the response of said second actuating means to said second condition.

8. In combination with a burnenapparatus for controlling the flow of-fuel to said burner comprising, enclosure means having flow passage means therein for the flowv of fuel therethrough to said burner, first and second flow control members each movable to first and second flow controlling positions with respect to said passage means, first actuatingmeans for said first control member responsive to the heat of fuel burned at said burner for biasing said control member toward its first controlling position on burner outage and biasing said control member toward its second controlling position when fuel is burned at said burner, and second condi under the influence of said'first actuating means to thereby variably position said first flow control member in accordance with normal fluctuations in a second condition, said restraint being afiorded only when fuel is burned '40 at said burner, said secondactuating means also being operatively related to v said second control member for actuation of the latter toward its second controlling position in response to an extreme in said second condition.

9. In combination with aburner, apparatus for controlling the flow of fuel to said burner comprising a control body having flow passage means therein for the flow of fuel therethrough to said burner, first and second control members each movable to first and second controlling positions for control of the flow of fuel through said control body, electroresponsive first actuating means for said first control member biasing said control member toward its first controlling position when deenergized' and biasing said controlmember toward its second controlling position when energizedmeans in circuit with-said actuating means for energizing said actuating means in response to burning of said fuel at said burner and for deenergizing said actuatingmeans in response to outage ofsaid burner, whereby said first control member is biased toward its first controlling position on burner outage and is biased toward its second controlling position in response. to burning of fuel at said burner, and second condition responsive actuating means operativelyrelated to said first control member to variably restrain movement of said first control member toward its second controlling position under the influence of said first actuating means, the restraint afforded by said second actuating means positioning'said first control member in various positions in accordance with normal fluctuations in a second con-dition, said second actuating means also being operatively related to said secondcontrol member for actuation of the latter to its second controlling position in response to an extreme in said second condition irrespective of the position of said firstcontrol' member.

10. Modulating fuel control apparatus comprising, enclosure meanshaving fuel flow passage means therein, a

modulating fuel control valve member in said passage means biased toward a full flow-permitting position and movable toward a reduced flow-permitting position with respect to fuel flow through said passage means, an on-ofi fuel control valve in said passage means biased to an on position and movable to an off position with respect to fuel flow through said passage means, first condition responsive actuating means operatively related to said modulating valve member and tending to move the latter toward said reduced flow-permitting position against said bias in response to a first condition, arid second actuating means operatively related to said modulating valve member for restraining the movement of the latter under the influence of said first actuating means, the restraint afforded by said'second actuating means being variable in accordance with normal fluctuations in a second condition to afford modulation of the fuel in accordance with said fluctuations, said second actuating means also being operatively related to said on-off valve for actuation of the latter to said off position in response to an extreme in said condition.

11. In combination with a burner, modulating fuel control apparatus for controlling the flow of fuel to said burner comprising a valve body having flow passage means therein for the flow of fuel therethrough to said burner, a modulating fuel control valve member in said valve body biased toward a full flow-permitting position and movable toward a reduced flow-permitting position with respect to fuel flow through said passage means, an on-ofi' fuel control valve in said passage means biased to an on position and .movable to an off position with respect to fuel flow through said passage means, said on-ofi valve when in said off position preventing all fuel flow through said passage means to said burner, first condition responsive actuating means tending to move said modulating valve member toward said reduced flow-pennittingposition against said bias in response to the heat of fuel burned at said burner, said bias returning said valve member to full flow-permitting position on burner outage, and second condition responsive actuating means operatively related to said modulating valve member for restraining movement of the latter under the influence of said first actuating means, the restraint afforded by said second actuating means being variable in accordance with normal fluctuations in a second condition to afford modulation of the fuel in accordance with said fluctuations, said second actuating means also being operatively related to said on-off valve for actuation of the latter to its said off position shutting off all fuel flow to said burner in response to an extreme in said second condition, whereupon said modulating valve member moves toward its full flow-permitting position-in response to burner outage.

'12. Fluid fuel flow control apparatus comprising first and second flow control members movable between first and second controlling positions with respect to the'fuel flow, first actuating means for biasing said first control member toward its second controlling position, condition responsive second actuating means operable to actuate said second control member between its controlling positions and including manually operable control point adjustrnent means, resettable condition responsive control means operatively related to said first actuating means and including a pair of relatively movable latchable members having a released position and movable toward a reset position preventing said first actuating means from positioning said first control memberin its second position, means latching said latchable members in said reset position when moved thereto, said latching means being releasable by said control means in response to a predetermined condition, and resetting means operatively associated with said control means and said control point adjustment means for effecting resetting of said latchable members upon an adjustment of said control point setting means to' a first predetermined setting, said latching 17 sition after a readjustment of said control point setting means to a second predetermined setting at which said resetting means is inoperative for resetting purposes for disposition of said first flow control member in its first controlling position until said latchable members are released by response of said control means to said predetermined condition. r

13. Fluid fuel flow control apparatus comprising first and second flow control members biased toward first and movable toward second controlling positions with respect to the fuel flow, first electroresponsive actuating means tending when energized to move said first fiow control member against its bias toward its second controlling position, condition responsive second actuating means operable to actuate said second flow control member between its controlling positions and including manually operable control point adjustment means, resettable temperature responsive circuit controlling means in .circuit with said first actuating means and a source of electric energy, said control means including a pair of relatively movable latchable contacts having a reset positionpreventing energization of said first actuating means and thus preventing the latter from moving said first control member toward its second position, said contacts having a released position permitting energization of said first actuating means by electric energy from said source, means latching said contacts in said reset position when moved thereto, said latching means being releasable by said circuit controlling means in response to a predetermined temperature, and resetting means operatively associated with said circuit controlling means and said control point adjustment means for effecting resetting of said contacts upon an adjustment of said control point setting means to a first. predetermined setting, said latching means retaining said contacts in said reset position after a readjustment of said control point setting means to a second predetermined setting at which said resetting means is inoperative for resetting purposes to maintain said first actuating means deenergized for disposition of said first flow control member in its first controlling position until said contacts are released by response of said circuit controlling means to said predetermined tempera ture. i

14. A control device for controlling the flow of fuel to a fluid fuel burner, comprising a first valve disposed in the path of fluid fuel to said burner and having an ignition and a lesser flow-permitting position, a second valve also disposed in the path of fluid fuel to said burner and having open and closed positions, first means for actuating said first valve to its ignition position in response to a predetermined condition, second actuating means operable to move said second valve from its closed to open position, and interlock means operatively associated with both of said actuating means and operable to overcall said second actuating means and prevent movement of said second valve from its closed to open position except when said predetermined condition prefvails, thereby insuring safe ignition, of said burner.

15. A control device for controlling the flow of fuel to a fluid fuel burner and tending to insure safe ignition thereof, comprising a modulator valve disposed in the path of fluid fuel to said burner and having an ignition and a lesser flow-permitting position, an on-oif valve also disposed in the path of fluid fuel to said burnerand having open and closed positions, actuating means normally operable to move said second valve from its closed toward its open position, and latching means for said on-ott valve operatively related to said modulator valve in a manner to be rendered operative when said modulator valve is in said lesser flow-permitting position and inoperative when said modulator valve is in said ignition position, said latching means when operative latching said on-oif valve in closed position when moved thereto and thereafter retaining said on-oft' valve in said closed also disposed in the path of fluid fuel to said burner and having open and closed positions, first electroresponsive actuating means for biasing said modulator valve toward its ignition position when deenergized and biasing said valve toward said lesser flow-permitting position when energized, second actuating means for said on-oif valve, and electroresponsive latching means operatively asso- ,ciated with said on-off valve and operable when energized to prevent movement of said on-olf valve from closed to open position, said latching means being connected in circuit with said first actuating means to be energizable and deenergizable simultaneously therewith, wherefore said on-oif valve is prevented from moving from closed toward open position whenever said modulator valve is biased toward said lesser flow-permitting position by said first actuating means.

17. A fuel flow control device for main and pilot burners comprising relatively movable first and second flow control members serially arranged :in the path of fluid fuel to said main burner and a third control member in the path of fluid fuel to said pilot burner, said first flow control member being biased to an increased flow-permitting position and movable toward a reduced flow-permitting position, said second flow control member being movable between flow-permitting and flow-preventing positions, said third control member being movable between flowpreventing and flow-permitting; positions, second operator means operatively related to said second flow control member for moving the latter between its flowpreventing and flow-permitting positions, first operator means responsive to heat of burning fuel at said main burner for moving said first flow control member from increased flow-permitting toward reduced flow-permitting position only after ignition of fuel. at said main burner, and condition responsive safety shut-off means operatively related to said second and third flow control members for overcalling said second operator means to position said second flow control member in its flowpreventing position and to simultaneously position said third flow controlmember in its flow-preventing position in response to a predetermined condition. 18. A control device for controlling the flow of fuel to a fluid fuel burner, comprising condition responsive first fuel control means for said burner having a safe initial ignition flow-permitting position in which it is disposed in response to a predetermined condition and having a lesser than safe initial ignition flow-permitting position, second fuel control means for said burner having first and second controlling positions, and interlock means operatively associated with said first and second fuel control means and operable to prevent movement of said second flow control means from its first toward its second position except when said predetermined condition prevails.

19. A control device for controlling the flow of fuel to a fluid fuel burner, comprising condition responsive first valve means for said burner having a safe initial ignition flow-permitting position in which it is disposed in responsive to a first condition and having a lesser than safe initial ignition flow-permitting position in which it is disposed in response to a second condition induced by the burning of fuel at said burner, second valve means for said burner having first and second position against any tendency of the actuating means 15 controlling positions, actuating means ope-rableto move i9 said second valve-means from its first to second position, and interlock means operatively associated with said actuating-means and said firstvalve means and operable to overcall said actuating means and prevent movement of said second valve means from its first to second position except when said first condition prevails.

20. A control device for controlling the flow of fuel to a fluid fuel burner and tending to insure safe ignition thereof, comprising first flow-control means having an ignition and a lesser than safe initial ignition flow-permitting position, second flow-control means for said burner and having first and second controlling positions, actuating means normally operable tomove said second flow-control means from its first toward its second controlling position, and latching means for said second flow-control means operatively related to said first flowcontrol means in a manner to be rendered operative when said first flow-control means is in said lesser than safe initial ignition flow-permitting position and inoperative when said first flow-control means is in said ignition position, said latching means when operative latching said second flow-control means in said second position when moved thereto and thereafter retaining said second flow-control means in said second position against any tendency' of the actuating means therefor to move said second flow-control means toward its first position until said latching means is rendered inoperative with subsequent movement of said first flow-control means to said ignition position, whereupon said second flowcontrol means is released by said latching means.

21. Fuel control apparatus comprising, a burner, first control means for controlling the flow of fuel to said burner and having a safe ignition position and a lesser than safe ignition flow-permitting position, second control means having fuel flow-permitting and fuel flow-preventing positions with respect to said burner, and actuating means for said first control means operable to actuate said first control means from said ignition position toward said lesser flow-permitting position but only when fuel is burning at said burner, whereby to insure that upon movement of said second control means from flowpreventing to flow-permitting position a safe ignition flow of fuel is supplied to said burner at least until said fuel is ignited at said burner.

22. Fuel control apparatus comprising, a burner, first control means for controlling the flow of fuel to said burner biased toward a safe ignition position and having a lesser than safe ignition flow-permitting position,

second control means serially arranged with respect to said first control means and having fuel flow-permitting and fuel flow-preventing positions with respect to said burner, actuating means operable to move said second control means between flow-permitting and flow-preventing positions, and actuating means for said first control means operable to actuate said first control means toward said lesser flow-permitting position against said bias but only when fuel is burning at said burner, whereby to insure that upon movement of said second control means from flow-preventing to flow-permitting position byiits actuating means a safe ignition flow of fuel. is supplied to said burner at least until said fuel is ignited at said burner. .23. Fuel control apparatus, comprising enclosure means, first and second control means for controlling fuel flow through said enclosure means and each movable to first and second controlling positions with respect to the fuel flow therethrough, first actuating means for said first control means operable to bias the latter toward its first controlling position, and second actuating means operatively related to said first control means for restraining the movement of the latter toward its first controlling position under the influence of said first actuating means, the restraint afforded by said second actuating means being variable in accordance with note spect to the fuel flow therethrough, first actuating means for said first control means operable to bias the lattertoward its first controlling position, second actuating means also operatively related to said firstvcontrol means. for restraining the movement of the latter toward its first controlling'position under the influence of said first actuating means, the restraint afforded by said second actuatingmeans being variable in accordance, with normal fluctuations in a condition, said second actuating means also being operatively related to said second control means for actuation of the latter toward its second controlling position in response to an extreme in said condition, and condition responsive safety shut-01f means operatively related to said second control means for. insuring disposition of said second control means in its. second controlling position in response to another cone dition.

25. A control device for controlling the, fiow of fuel to a fluid fuel burner and tending to insure safe ignition thereof comprising first control means disposed to control the flow of fluid fuel to said burner and having an ignition and a lesser than safe initial ignition flowpermitting position, second control means also disposed to control the flow of 'fiuid fuel to said burnerand having first and second positions with. respect to the fuel flow, first electroresponsive actuating means for biasing said first'control means toward its ignition-position when deenergized and biasing said valve toward said lesser than safe initial ignition flow-permitting posi-' tion when energized, second actuating means for said second control means, and electroresponsive latching means operatively associated with said second control means and operable when energized to prevent movement of said second control means from its second to its first position, said latching means being connected in circuit with said first actuating means to be energizable and deenergizable simultaneously therewith, wherefore said second control means is prevented from moving from its second toward its first position whenever said first control meansis biased toward said lesser than safe initial ignition flow-permitting position by said first actuating means.

26. A fuel flow control device for main and pilot burners comprising relatively movable first and second flow control means disposed to control the flow of fluid fuelto said main burner and a third control means disposed to control the fiow of fiuid fuel to said pilot burner, said first flow control means having an increased flow: permitting position and being movable toward a reduced flow-permitting position, said second flow control means being movable between first and second controlling positions, said third control member being movable between first and second controlling positions, second operator means operatively related to said second flow control means for moving the latter between its first and second controlling positions, first operator means responsive to a predetermined condition for moving said first flow control means from increased flow-permitting toward reduced flow-permitting position only upon occurrence of said predetermined condition, and condition responsive safety shut-off means operatively related to said second and third fiow control means for overcalling said second operator means to position said second flow control means in its second position and to simultaneously position said third. flow control member in its secondposis tion in response to a different predetermined condition.

27. Modulating condition controlling apparatus, comprising means for varying a condition of a medium operable at a rate variable in accordance With corresponding changes in a condition of a given controlling fluid, flow controlling means for effecting changes in said condition 'of the controlling fluid, actuating means for said flow controlling means responsive to variations in the condition of said medium and operable to modulate the flow of said controlling fluid in a flow restricting manner and thereby to derate said condition varying means in response to a change in the condition of said medium in one sense and to modulate the flow of said controlling fluid in a flow increasing manner and thereby to increase the rate of said condition varying means in response to a change in the condition of said medium in the opposite sense, control point adjustment means for said actuating means, and means for insuring a rapid change in the condition of said medium in response to a predetermined adjustment of the setting of said control point adjustment means calling for operation of said condition varying means, said insuring means including condition responsive means operatively associated with said control point adjustment means and with said actuating means and operable, following said adjustment, to prevent restriction of flow of said controlling fluid and derating of said condition varying means until the condition of said medium reaches a predeter mined value.

28. Modulating condition controlling apparatus, comprising means including a burner for varying a condition of a medium operable at a rate variable in accordance with corresponding changes in the rate of fuel flow to said burner, flow controlling means for effecting changes in the rate of said fuel flow, actuating means for said flow controlling means responsive to variations in the condition of said medium and operable to modulate the fuel flow in a flow restricting manner and thereby to derate said condition varying means in response to a change in the condition of said medium in one sense and to modulate the fuel flow in a flow increasing manner and thereby to increase the rate of said condition varying means in response to a change in the condition of said medium in the opposite sense, control point adjustment means for said actuating means, and means for insuring a rapid change in the condition of said medium in response to a predetermined adjustment of the setting of said control point adjustment 22 means calling for operation of said condition varying means, said insuring means including condition responsive means operatively associated with said control point adjustment means and with said actuating means and operable, following said adjustment, to prevent restriction of said fuel flow and derating of said condition varying means until the condition of said medium reaches a predetermined value.

29. Modulating condition controlling apparatus, comprising a heater including a burner for heating a medium operable at a rate variable in accordance with corresponding changes in the rate of fuel flow to said burner, flow controlling means for effecting changes in the rate of said fuel flow, actuating means for said flow controlling means responsive to variations in the temperature of said medium and operable to modulate said fuel flow in a flow restricting manner and thereby to derate said heater in response to arise in the temperature of said medium and to modulate said fuel flow in a flow increasing manner and thereby to increase the rate of said heater in response to a drop in the temperature of said medium, control point adjustment means for said actuating means, and means for insuring a rapid rise in the temperature of said medium in response to a predetermined adjustment of the setting of said control point adjustment means calling for operation of said heater, said insuring means including temperature responsive means operatively associated with said control point adjustment means and with said actuating means and operable, following said adjustment, to prevent restriction of said fuel flow and derating of said heater until the temperature of said medium reaches a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,319,708 Smith et al May 18, 1943 2,389,111 Dillman Nov. 13, 1945 2,526,069 Douglas Oct. 17, 1950 2,683,565 Johnson July 13, 1954 OTHER REFERENCES Catalog No. 51 of General Controls Company, published 1941, front cover, and pages 11 and 17 relied on (copy in Div. 30), 236-75.

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