US2974869A

US2974869A - Control apparatus

Info

Publication number: US2974869A
Application number: US547463A
Authority: US
Inventors: Charles E Hajny
Original assignee: Baso Inc
Current assignee: Baso Inc
Priority date: 1955-11-17
Filing date: 1955-11-17
Publication date: 1961-03-14
Anticipated expiration: 1978-03-14

Description

March 14, 1961 Q HAJNY I 2,974,869

CONTROL APPARATUS Filed Nov. 17. 1955 IN V EN TOR.

CZarZas 5' HQ '11 Unitedv States Patent CONTROL APPARATUS Charles E. Hajny, Milwaukee, Wis., assignor to Baso Inc., Milwaukee, Wis., a corporation of Wisconsin Filed Nov. 17, 1955, Ser. No. 547,463

Claims. c1. 236-1 This invention relates to improvements in modulating control apparatus, and more particularly to electroresponsive modulating fuel control devices.

In the control of fuel flow to gaseous fuel burners it is necessary to provide a relatively large amount of fuel fiow to safely ignite the burner, and once the burner is ignited a stable flame can be maintained at said burner even though the fuel flow is reduced to a substantially lesser amount. The minimum amount of fuel needed to maintain the flame is designated as a minimum safe flow and the amount of fuel necessary for safe ignition is designated as minimum safe ignition flow.

It is a general object of the present invention to provide a modulating fuel control device having fuel flow control means movable to said minimum safe flow and safe ignition positions, said control means being movable to said minimum safe flow position only after being in said safe ignition position.

Another object of the present invention is to provide a modulating device with first and second operator means operable when energized to actuate said fuel flow control means to a plurality of controlling positions, said operator means having interlock means preventing energization of one of said operator means when said flow control means is not in safe ignition position.

Another object of the present invention is to provide a device of the aforementioned characteristics with modulation flow control means, including an operator therefor, biased to an increased flow-permitting position and movable by its operator to a reduced flow-permitting position and an on-ofi flow control means, including an operator therefor, biased to a flow-preventing position and movable by its operator to a flow-permitting position, and interlock means permitting energization of said onoff operator when said modulating flow control means is in increased flow-permitting position only, to thereby assure safe ignition.

Another object of the present invention is to provide a device of the aforementioned characteristics with first and second operator means which are electroresponsive, both said operator means being connected in circuit with a single source of electrical energy for energization thereby, said circuit including interlock means which provides relatively long energization of alternatively only one of said operators and intermittent relatively short simultaneous energization of both said operators, said interlock means thereby affording that said single source of electrical energy may be of minimum size.

Another object of the present invention is to provide a device of the aforementioned characteristics with a modulating high-low flow control operator means having the characteristic of an inherent time lag between energization thereof and the etfectuation of movement of the modulating high-low flow control means, said time lag being at all times sufiicient to allow a substantial volume of fuel to flow to the main burner for safe ignition.

Another object of the present invention is to provide the aforementioned apparatus with a modulating high- 7 2,974,869 Patented Mar. 14, 1961 low fiow control operator means which is of the bellows type, having a heating element in heat conducting relation thereto and with a temperature sensitive fill therein, said fill having the characteristic of being a partial liquid below a predetermined temperature and of being entirely in a gaseous state above said temperature, energization of the heating element causing said fill to expand at a first expansion rate to thereby move an end wall of the bellows to in turn move a valve member, the heat input from said heating element after a predetermined interval being adapted to raise the temperature of said fill above said predetermined temperature whereupon the pressure rate of said fill upon said bellows is reduced to thereby prevent rupture of the latter.

Another object of the present invention is to provide an apparatus of the above characteristics with flow control means having high, low and off positions providing corresponding amounts of fuel flow to the main burner, 1

said apparatus having condition responsive circuit controlling means for controlling the operators which position the flow control means, said circuit controlling means having associated therewith anticipation means which is operable only when said flow control means is in said high position, said anticipation means not being necessary nor desirable when said flow control means is in low position because of the much smaller stored heat of the system.

Another object of the present invention is to provide an apparatus that is of a fail safe nature, in that failure of the modulating high-low flow control means and its operator means to operate properly as by failure of its heating element, rupture of the bellows, or by other mechanical or electrical failure, does not cause an unsafe ignition problem because the apparatus will continue to operate with full flow of fuel for ignition.

Another object of the present invention is to provide an apparatus of the foregoing type with a mechanical interlock between the on-oif valve and the modulating high-low flow control valve, said interlock preventing closure of said on-oif valve when said high-low valve is in low position thereby assuring safe ignition in normal operation, and in addition providing for opening of the on-off valve prior to movement of the high-low valve to its low position to thereby assure a large flow of fuel for safe ignition in the event of abnormal failure of the on-ofi operator.

Another object of'the present invention is to provide a control device wherein the high-low and on-olf valves are in a back to back relationship for inexpensive casting, manufacture and assembly, said arrangement also permitting the manufacture and sale of a control device without the modulating subassembly which may be easily incorporated in the field at a later time.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation together with additional objects and advantages thereof will best be understood by the following description of the specific embodiment when read in connection with the accompanying drawing, in which:

The sole figure is a sectional view of a modulating fuel control device constructed in accordance with the invention and operatively associated with the fuel burning apparatus, the electrical circuit of said device and parts of said apparatus being shown semi-diagrammatically.

Referring to the drawing, the improved modulating fuel control apparatus comprises a fuel control device indicated generally by the numeral 10 and hasayalye body 7 provided with an inlet chamber 20, an outlet chamber 26 and an intermediate chamber 22. The control device is interposed in the fuel supply line 19 to a fluid fuel burner 16 and controls the flow of gaseous fuel to said burner by means of an on-oif valve member 48 and a high-low modulating valve member 54 serially arranged in the fuel stream, there being a solenoid type electroresponsive operator 46 for the on-off valve member 48 and an electroresponsive bellows type operator 56 forthe high-low valve member 54.

The two operators are disposed on opposite sides of a partition 8 having a bore 23 formed therein affording communication between the chambers 22 and 26, there being an annular valve seat 49 surrounding said bore within the chamber 22 and with which the on-ofi valve member 48 coacts, and an annular valve seat 55 surrounding said bore within the chamber 26 and with which the high-low valve member 54 coacts. The valve member 54 when open affords a high fuel flow and a by-pass passageway 30 leading from the bore 23 to the outlet chamber 26 forms a passageway for a low or minimum safe fuel flow when the valve 54 is closed. A metering screw 32 is disposed within the by-pass passageway 30 for controlling the amount of fuel flow therethrough and is adjusted to provide a stable flame at the burner 16. The solenoid operator 46 actuates valve member 48 in the normal manner, i.e. opens the valve when energized and closes the valve under the bias of spring 52 when deenergized whereas the modulating high-low operator 56 operates valve member 54 in the reverse manner, i.e. closes valve member 54 when energized and opens valve member 54 when deenergized. I

The entire high-low modulating flow control means and its operator 56 may be a separated subassembly unit made up for attachment to the underside of the valve body 7 as shown and comprises three major parts namely an operator assembly 56, an electrical interlock assembly 59 which controls the on-off valve circuit, and a valve assembly 54a, all of which are concentrically disposed surrounding a long valve stem 57. The operator assembly 56 which imparts the movement to the stem 57 comprises an outer cup-shaped housing member 63 disposed without the valve body 7 and having a flared upper lip portion 64 which extends radially outwardly for cooperation with the interlock assembly 59 and an inner flange portions 65 which extends radially inwardly a short distance from the side walls 63a. An annular cup-shaped expansible and contractible bellows 66 is attached to flange 65 as by solder or other suitable sealing connection means and is disposed within the cupshaped housing 63 to form therewith the generally U-shaped in cross section annular hermetically sealed enclosure 69. The bellows 66 end wall 67 forms the movable wall of the expansible and contractible enclosure 69 and has centrally attached thereto for movement therewith an annular cup-shaped receptacle 68 for the. lower end of'valve stem 57 which is disposed in bearing engagement therein. Enclosure 69 is adapted to be filled 'witha temperature sensitive fill which is responsive to a heater coil 53 which may, if preferred,

be disposed surroundingly to the housing member 63 to heat the fill to thereby cause expansion of the enclosure 69 to close valve member 54. 7 An annular cover plate 70 caps the housing 63, it being mounted upon the radial housing flange 64 and formed with a central bore 75 which is adapted to receive and mount an axially elongated bearing sleeve 71 which guides the stem 57 which projects therethrough. A biasing spring 72. is interposed between the underside of the cover plate 70 and an annular cup-shaped collar 73 attached to the stem 57 as by an E-ring 74, for biasing the stem 57 toward engagement with the cup-shaped receptacle 68 and also for providing a spring pressure bias for the bellows 66.

Means is provided to prevent energization of the on-olf operator 46 when valve member 54 is restricting the fuel flow below the flow necessary for safe ignition, i.e. closed position. This means, called the interlock assembly 59, is preferably disposed between the sealing plate 95 for the valve and the cover plate 70 for the operator assembly 56 and comprises a switch in the on-oif operator circuit which is actuated by the stem 57. The interlock comprises a pair of contacts 84 and 85 disposed between the two plates 95 and 70 which form the end walls of a contact enclosure 76, the side walls thereof being comprised of a pair of annular side wall members and 90 which are preferably composed of a suitable dielectric material such as a phenolic plastic. The lower annular insulating side wall member 80 is formed with a bore 79 and a counterbore 81which define a shoulder 78, said bore 79 being adapted to receive the housing member 63 which is snugly disposed therein with the shoulder 78 abutting and seating the underside of the flanged lip 64 of housing member. A series of grooves 77 and 58 are formed on opposite sides of the member 80, both on the exterior surface thereof and within the bore 81, for receiving and insulating a pair of somewhat U-shaped'opposing terminal conductor strips 82 and 92 which may be fixedly attached in said grooves 77 and 58 by suitable terminal screws 87 for the circuit to the onoff operator 46. The upper annular insulating sidewall member 9iiis formed with a 'main body 90a and a radially extending annular flange 90b, the former telescopically fits within the bore 81 to snugly hold the conducting strips 82 and 92in their respective grooves.

The circuit to operator 46 is controlled by a flexible spring contact carrying strip 83 which is attached to the inner end of conducting strip 92 and which carries a movable contact 84 formed at the free end thereof for coaction with the fixed contact 85 which is fixed to the inner end of conductor strip 82. The contact strip 83 biases contact 84 into engagement with contact 85 and may be formed with a bore 83a which is larger than the reduced portion 83a of an annular stem collar 88 which said strip surrounds. Collar 88 is fixed to stem 57 and is preferably composed of dielectric material. The collar 88 has an enlarged extent 88b which together with the reduced portion 88a forms the shoulder 880 which upon outward movement of the stem 57 will engage the strip 83 to separate contacts 84 and 85 and thus deenergize operator 46. If desired, the upper surface of the plate 70 and the lower surface of plate 95 may be covered with a suitable dielectric material 96 such as treated paper or the like so that the entire contact enclosure 76 is electrically insulated.

The entire modulating flow control subassembly is fixedly and sealingly attached to the valve 7 by fastening means, such as the bolts 11, which extend through the annular insulating members 80 and and cover plate 95, the seal being provided by the attachment of cover plate and the peripheral gasket of a diaphragm 102 to the outer end surface of a bore 100 and counterbore 98 which are formed in the outer wall of the valve 7 concentric to fuel passage bore 23. Thestem 57 sealingly extends into outer fuel chamber 26 of the valve body through an aperture 104 in cover plate 95 for movement of the valve member 54 between its open and closed positions. A flexible fluid seal preventing escape of fuel through the aperture 104 is provided by the diaphragm 102 which includes the peripheral gasket aforementioned and a central washer 101, the latter surrounds and sealingly abuts upon a shoulder 103 of the stem 57 as shown Within outlet chamber 26 and intermediate the stem end 61 and shoulder 103 is the high-low valve member 54 which may be a generally cup-shaped stamping formed with a central aperture 54b which slidingly fits on said stem and abuts against stop means such as E-ring which is clampingly fixed to a groove 111 in said stem. The disposition of the groove 111, and thus the valve member 54, from the end 61 of the stem 57 is such that when the valve 54 seats on seat 55,'the end 61 positions tacts 113-114 are closed.

valve 48 a substantial distance away from seat 49. Bias ing means, here indicated by a spring 106, is interposed between the underside of the cup-shaped valve member 54 and a pressure collar 108 to thereby provide a lost motion connection between the stem and the valve member 54, so as to permit continued movement of the valve stem 57 through the aperture 5411 upon seating of the valve member 54 upon the valve seat 55.

Condition responsive, for example temperature responsive, circuit controlling means such as the thermostat 60 is provided to control the energization of the operators or actuators 46 and 56, and hence the operation of valve members 48 and 54. In the illustrated embodiment of the invention, the electrical energy for powering the electroresponsive actuators 46 and 56 is derived from a transformer here indicated by the numeral 50, it being understood, of course, that the currents supplied to the actuators 46 and 56 may be of any suitable or desired magnitude. One terminal 46a of the electroresponsive actuator 46 is connected in circuit with the transformer 50 by a conductor 52. The other terminal 46b of operator 46 is connected to the transformer 50 through the temperature responsive circuit controlling means 60 and the relatively

movable contacts

115 and 116 therein, and also through the electrical interlock means 59 comprising contacts 84 and 85 via the conductor 51 as shown.

The thermostat 60 is'preferably of the plural stage type and in the accompanying embodiment is schematically shown as comprising a temperature sensitive bellows 118 which expands upon heating and contracts upon cooling, a conducting strip 112 being pivotally mounted on the bellows stem 125 and carrying at the extremities thereof

movable contacts

113 and 116 which coact with their respective

fixed contacts

114 and 115. Magnetic means such as

magnets

119 and 120 are provided to impart a snap action to the contact movement. Stop means 121 is provided to keep contact pressure on contacts 115-116 when contacts 113114 snap open.

The power for energization of the high-low actuator 56 may be from a separate or from the same power source as on-oif operator 46 such as the transformer 50. The particular electrical system shown in the accompanying illustration is especially desirable in that the transformer 50 supplying power to both operators may be of a minimum size. This obtains because the interlock contacts 84-85 provide that in normal operation only one of the two operators 46 and 56 are energized over long periods of time, as will be apparent from the operation of the device. Thus, even though electrical power is supplied to both operators simultaneously, it is only at the intermittent short periods of going from one to another of controlling stages and therefor a transformer of minimum size may be utilized. The circuit for actuator 56 comprises a parallel circuit with the on-oif actuator 46 as by conductor 51a which is connected through heater element 53 which may, if preferred, surround housing member 63 in a heat conducting relationship. The actuator 56 is connected through the thermostat 60, the relatively movable contacts 113-114 controlling its energization. Means is provided for anticipating the stored heat of the burner mass to prevent over-shoot of heat into the area to be controlled, said means comprising the heating element 117 which is disposed in a heat conducting relationship to bellows 118, closure of contacts 113-114 providing a shunt circuit around the anticipation means 117 to deenergize same, said means being energized and thrown into the highlow circuit whenever contacts 113114 are open and contacts 115-J16 are closed.

The thermostat 60 preferably has first, second and third controlling positions, for example, in the first controlling position wherein the bellows 118 has expanded to the extent that contacts 115-116 are open and con- In the second controlling position the bellows 118 has contracted sufiiciently to disengage the conducting strip 112 from magnet 120, but not from the magnet 119 such that both sets of contacts, 113-414 and 115-116, are closed, while in the third stage the bellows 118 has contracted still further to disengage the strip 112 from magnet 119 such that contacts 113-114 are open and contacts 115-116 are closed. Contacts 115-116 make or close when the control point temperature is reached, i.e. the temperature at which the bellows 118 contracts sutficiently to disengage strip 112 from magnet 120 and move contacts 116 into engagement with contact 115. During subsequent expansion of the bellows 118 the strip 112 is first drawn into engagement with the magnet 119 to efiect closure of contacts 113-114. Upon further expansion of the bellows 118 the strip 112 is moved into engagement with the magnet 120 to cause opening of contacts 115-116. It will be apparent that once the contacts 115-116 are made, they do not break or open until a predetermined higher temperature (high limit) is sensed by the bellows 118. Thus, there is a temperature difierential between making and breaking of the contacts 115--116.

Contacts 113114 make at the control point temperature, the identical temperature at which contacts 115 116 make. However, in contradistinction to contacts 115116, they break at a predetermined tempearture lower than the control point temperature (low limit). Thus, there is also temperature difierential between making and breaking of the contacts 113-114.

Therefore, at any one given temperature between the high and low limit temperatures, there are more than one controlling positions which the contacts may assume. For example, if the temperature is 71 F. and has risen from below a low limit temperature of F. and is approaching a control point temperature of 72 F., the contacts are in the third controlling position, i.e. contacts 113--114 are open and contacts 116 are closed. On the other hand, if the temperature is 71 F. and has dropped from above the control point temperature (72 F.) and is approaching the low limit temperature (70 F.), the contacts are in the second controlling position, i.e. both sets of contacts are closed.

If preferred, a flame failure electromagnetic safety shut-off system responsive to outage of the pilot burner 42 may be disposed within the valve body with the valve member '35 upstream of the on-off valve 48. An electromagnetic safety shut-otf operator 34 powered by a thermocouple 31 associated with a pilot burner 42 holds the valve member 35 away from a valve seat 18 when said burner is ignited. A reset mechanism 36 is provided to cook the operator 34 and position a flow interruption disc 37 so that it coacts with seat 17 and allows flow of fuel through pilot pipe 43 to burner 42 and prevents flow to the main burner 16 during the reset operation for safe ignition of the pilot burner as is well known and understood in the art. The shut-off valve 35 and its electromagnetic operator means 34 may be of the form shown and described, for example in Oscar I. Leins, Patent No. 2,126,564, issued August 9, 1938. The reset button 36 and flow interruption disc 37 and their operation may be of the form shown and described, for example in Charles V. Hildebrecht, Patent No. 2,114,446, issued April 19, 1938.

The operation of the modulation apparatus is as folopen and

contacts

113 and 114 are closed; the on-oft operator 46 and the high-low operator 56 both being deenergizedso that valve member 43 is seated against seat 49 under the'bias of spring 52 and valve member 54'being spaced away from valve seat 55 due to the expansion of modulating flow control bellows 66 and the bias of spring '72-, and stem 57 and collar 88 being in the position shown allowing closure of contacts =84 and 85. The apparatus is thus in off or flow-preventing condition, all fuel being prevented from flowing to the main burner 16 by on-off valve member 48.

As the area surrounding the thermostat 60 cools, the bellows 118 therein contracts and upon reaching the control point of the thermostat, contacts 115116 close thereby supplying electrical energy to the on-otf operator 46, which immediately opens valve member 48 and allows a full capacity fuel flow to the burner 16 for ignition. Inasmuch as the temperature is above the low limit, contacts 113-114 are closed, and electrical energy is, therefore, simultaneously supplied to heater coil 53 surrounding the housing 63 of the on-ofl? operator 56 which heats up the temperature sensitive fill within the enclosure 69'. After a predetermined interval, the fill expands moving end wall 67 of the bellows 66 upwardly as viewed in the drawing and thus valve stem 57 toward valve seat 55 to thereby seat valve member 54 on said seat. As valve stem 57 seats high-low valve member 54 upon seat 55, the fuel-way is restricted to the by-pass passageway 30, and thus a reduced flow or low amount of fuel is supplied to the main burner 16 which may be just sufficient to maintain a stable flame. As the valve stem 57 is moved upwardly as viewed in the drawing through bore 23 upon expansion of the fill within the enclosure 69 and prior to seating of the high-low valve member 54 upon valve seat 55, the shoulder 880 of the dielectric collar 88 within contact enclosure 76 engages the underside of the conducting spring 83 which lifts movable contact 84 away from contact '85 thereby deenergizing the circuit to the on-ofi operator 46 which thereupon relinquishes its control over on-ofi valve member 48. The on-oif valve mem ber 48 under the bias of spring 52 then engages the protruding tip 61 of the stem 57 which mechanically prevents said on-oif valve member 48 from engaging seat 49 and spacing is therefrom a distance that allows full flow of fuel through bore 23. Thus, the on-off valve member .48 is under the control of the modulating operator 56 through stem 57 and remains under its control until valve stem 57 retracts sufficiently to allow contacts 84 and 85 to reengage when

contacts

115 and 116 are closed.

The effects of the minimum safe reduced flow or low amount of fuel in terms of heat output of the main burner 16 upon the thermostat 60 may be measured in terms of the escape losses of the ambient heat in the area to be controlled, the three general situations being that the heat input is (1) approximately equivalent to, (2) larger than or (3) smaller than the amount of escape losses. Under the first situation, the thermostat contacts are in their econd controlling position, i.e. both sets of contacts are made, minor temperature fluctuations of the ambient temperature between the high and low limits of thermostat 64) in the area to be controlled, for example such as losses caused by opening and closing doors, clouds covering the sun, etc., are compensated for by the low heat output of the burner 16, the low heat input to the control area continuing until either the high or low limit temperatures of the thermostat are reached.

and shut-off all flow of fuel to the main burner 16 until the thermostat again 'calls for heat.

Under the third general situation where the escape losses are higher than the burner heat output at the reduced fuel flow, the area'being controlled cools until the low limit temperature of thermostat 6.6 .is reached, the thermostat 60 thereupon assumes its third controlling position, i.e. bellows 118 is then contracted to the extent that contacts 113-114 move from closed to opened position, contacts 115116 remaining closed. The shunt circuit around the anticipator means 117 is thus opened and the anticipation means 117 thereupon becomes energized. When the anticipation means 117 is put in circuit with the heater coil 53, the heat output of the latter is effectively reduced inasmuch as the anticipation means 117 has a much higher resistance than the heater coil 53. Thus, energization of the anticipation means 117 serves to effectively deenergize operator 56, and the fill within enclosure 69 cools causing the valve stem 57 to recede allowing contacts 84 and to make. The on-olf operator 46 is thereupon energized and holds the on-otf valve member 48 in the on position allowing an increased or full fuel flow to the burner which increases the heat input to the controlled area.

Meanwhile, the anticipation means 117 starts to supply a false response in terms of heat to the bellows 118 to cause contacts 113-114 to close, thereby reducing the flow of fuel to the main burner prior to the ambient temperature in the control area attaining the control point temperature. The anticipation means 117 prevents an over-shoot of heat input into the area to be controlled, said over-shoot being caused by the stored heat in the thermal mass of the burner and environs. Without the anticipation means in this apparatus, the practical effect would be to eliminate the low or reduced fuel flow input to the burner 16 upon a heat up of the control area where the thermostat is calling for a lot of heat, i.e. the device would provide fuel flow from a full on status to completely off status :because if the stored heat in the thermal .mass of the burner is not anticipated, it could cause a very rapid rise (overshoot) in the ambient temperature of the control area, the stored heat rapidly sending the ambient temperature from the control point above the high limit point of the thermostat 60, thus effectively eliminating the throttled down heat input on fast Warm .up. On the other hand, anticipation means is not needed .or desired in the apparatus when the fuel flow goes from low or minimum safe reduced flow to 01f when the high limit temperature of the thermostat is reached, be-

cause the storedheat of the thermal mass of the burner 16 and environs is considerably lower due to the reduced input and thus does not adversely effect the control area. Further, anticipation under low fiow conditions could cause short-cycling of the apparatus.

The modulating apparatus always provides for safe ignition of burner 16 inasmuch as it is impossible for the on-off valve to go to off and back to on position when the high-low valve is in minimum safe flow (low) position, because the protruding tip 61 of stem 57 provides a mechanical interlock preventing such movement. A further safe ignition feature is the electrical interlock provided by the contacts 84 and 85 which prevent energization of the on-ofi operator 46 unless the modulating flow control operator 54 is in its high, i.e.

of such a duration to have a full fuel flow to aid in establishing a heat stack and to supply an excess of heat for initial heating of the mass of the burner unit. In normal applications this period of time, approximately two minutes, is considerably longer than the time that is normally required to assure a sufiicient fuel flow for safe ignition purposes (which is approximately five seconds of full flow).

The apparatus has several fail safe features, such as assuring safe ignition under abnormal conditions where fuel may flow to the main burner 16. For example, failure of

contacts

113 and 114 or conductors 53 in the high-low circuit transforms the apparatus into a thermostatic on-off fuel flow system that is safe in that full flow for ignition is provided, the system cycling on the high limit of the thermostat, the modulating flow control member 54 remaining in the deenergized open position spaced away from the valve seat 55. On the other hand, failure of contacts 115-416 is of a safe nature because such failure shuts down the system completely for lack of power. Safe ignition of the main burner is also provided in the abnormal event of failure of contacts 84 and 85, or any part of the electric circuitry for the electroresponsive operator 46, in that the protruding stem tip 61 opens on-olf valve member 48 prior to the seating of high-low valve member 54. The opening of on-off valve member 48 by short distance, for example a few thousandths of an inch, allows substantially a full flow of gas through the bore 23, and thus a full flow of gas will be available for ignition of the main burner 16 prior to the seating of the high-low valve member.

In order that the device is fail safe even in the event of abnormal failure of the circuitry of on-oif operator 46, it is preferable that the time lag interval between the lifting of the valve 48 away from its seat sufficient for full fuel flow by the engagement of the protruding stem tip 61, and the seating of valve member 54 upon its seat, should be suflicient for safe ignition. This interval plus a safety factor, under normal conditions does not exceed approximately 15 seconds.

The desired time lag of operator 56 behind operator 46 for both safe ignition and initial heating is provided by the bellows 66 and is a function of the amount of heat supplied thereto by heater 53, of its thermal mass, of the amount of energy required to balance the spring forces upon the bellows, of the area of the bellows 66 and of the temperature pressure characteristics of the fill therein. The relationship should be such that on a time vs. movement curve of the bellows, starting with energization of the heater element 53, suificient time (normally 15 seconds) should be expended in the movement of stem, to thereby allow sufficient fuel flow for safe ignition in event of inoperativeness of the on-off operator 46.

The temperature sensitive fill within the bellows 66 is preferably at a pressure greater than atmospheric so that rupture of the bellows 66 causes end wall 67 to move away from valve seat 55 allowing the system to operate as an on-ofi system. Another preferred characteristic of the fill is that it have a fadeaway temperature pressurerelation so that there is a reduction in pressure rate per increment of heat above a predetermined temperature pressure point. For example, the fill may be butane or propane under a pressure whereby prior to the valve stem being stopped from outward movement, the fill changes from a vapor to a gaseous state. Thus when there is continued heat input to enclosure 69 from the heater element 53, and just prior valve stem 57 being stopped from outward movement by end surface 88d of the dielectric collar 88 abutting on cover plate 95, the pressure within the bellows increases at a reduced rate, which aids in the prevention of rupture of the bellows 66.

Although there has been shown and described certain specific embodiments of the invention, it is with full awareness that many modifications thereof were possible.

. 1O v The invention, therefore, is not to be restricted except insofar as is necessitated by the spirit of the appended claims.

What is claimed as the invention is: 1. In an apparatus for the control of fluid fuel, a modulation flow control member biased to an increased flowpermitting position and movable to a reduced flow-permitting position, an on-ofi" flow control member biased to flow-preventing position and movable to a flow-permit. ting position, first operator means operable to move said modulation flow control member from an increased flowpermitting to a reduced flow-permitting position and to insure disposition of said on-ofi flow control member in its flow-permitting position when said modulation flow control member is in its reduced flow-permitting position,

and second operator means operable to actuate said onofi flow control member to its'flow-permitting position only when said modulating flow control member is in its increased flow-permitting position.

2. In apparatus for controlling the flow of fluid fuel, a flow controlling member in the path of the fluid flow having an electroresponsive actuator operable in a plurality of levels of energization to position said flow controlling member in a plurality of controlling positions, temperature responsive circuit controlling means in circuit with a source of electrical energy and with said electroresponsive actuator means, electroresponsive temperature anticipating means for said circuit controlling means in circuit with said circuit controlling means and said actuating means, said circuit controlling means having a first position at a predetermined temperature wherein it connects said actuating means in circuit with said source directly to afford one level of energization of said actuating means, said circuit controlling means having a second position at a second predetermined temperature lower than said first temperature wherein said actuating means is connected in circuit with said source through said anticipation means to thereby simultaneously afford energization of said anticipation means and energization of said actuating means at a second level, and said circuit controlling means also having a third position at a third predetermined temperature higher than said first temperature wherein the circuit between said source and said actuator means is open to thereby deenergize said actuator means.

3. Apparatus for controlling the flow of fluid fuel comprising: A first flow controlling member biased toward a first position and movable to a second position, a second flow controlling member in series with said first flow controlling member in the path of the fluid fuel, said second flow controlling member being biased toward flow-preventing position and movable to a flow-permitting position, first electroresponsive actuating means operable when energized to move the first flow controlling member toward its second position, second electroresponsive actuating means operable when energized to move the second fiow controlling member toward flow-permitting position, and circuit controlling means including electrical resistance means in circuit with said first and second actuating means and with a source of electrical energy, said circuit controlling means having a first position in which the circuit between said source and said first and second actuating means is open, a second position in which the first and second actuating means are connected directly to said source for energization thereby, and a third position in which the first actuating means is connected to said source through said resistance means and said second actuating means is connected to said source directly for energization thereby, said first actuating means being substantially deenergized when said circuit controlling means is in its third position.

4. Apparatus for controlling the flow of fluid fuel comprising: A first fluid flow controlling member biased toward a first position and movable to a second position, a second fluid flow controlling member in series with said first flow controlling member in the path of the fluid fuel,

1 1 said second flow controlling member being biased, toward flow-preventing position and movable to a flow-permitting position, first electroresponsive actuating means operable when energized to movethe first flow controlling member toward its second position, second electroresponsive actuating means operable when energized to move the second flow controlling member toward flow-permitting position, and circuit controlling means including electrical resistance means in circuit with said first and second actuating means and with a source of electrical energy, said circuit controlling means having a first position in which the circuit between said source and first and second actuating means is open, a second position in which the first and second actuating means are connected directly to said source for .energization thereby, and a third position in which the first actuating means is connected to said source through said resistance means and said second actuating means is connected to said source directly for energization thereby, said first actuating means being substantially deenergized when said circuit controlling means is in its third position, and a switch in circuit with said second actuating means and operatively related to said first flow :controlling member whereby movement of the latter to its second position opens the circuit to said second actuating means and deenergizes the latter. 7 5. Apparatus for controlling the flow of fluid fuel comprising: A first flow controlling member biased toward a first position and movable to a second position, a second flow controlling member in series with said first flow controlling member in the path of the fluid fuel, said second flow controlling member beingrbiased toward flow-preventing position and movable to a flowpermitting position, rst electroresponsive actuating means having first, second and deenergized energy levels for controlling the position of said first flow controlling member, said first actuating means when at said second energy level tending to position said first flow controlling means insaid second position, and when at said first and third energy levels tending to allow said bias to position the latter in said first position, said second electroresponsive actuating means being operable when energized to move the second flow controlling member toward flow-permitting position, and condition responsive circuit controlling means including electrical resistance means in circuit with said first and second actuating means and with a source of electrical energy, said circuit'controlling means having a first position in which the circuit between said source and said first and second actuating means is open to thereby afiord said first actuating means said deenergizedenergy level, said circuit controlling means having a second position in which the first and second actuating means are connected directly to said source for energization thereby, to thereby afford said first actuating means said second energy level, and said circuit controlling means also having a third position in which said second actuating means is con-' nected to said source directly for energization thereby and the first actuating means is connected to said source through said resistance means to thereby afford said first energy level. V

6. in apparatus for controlling the flow of fluid fuel, a flow controlling member'in the path of the fiuid flow having an eiectroresponsive actuator operable at a pluraiity of levels or" energization to position said flow controlling member in a plurality of controlling positions, condition responsive circuit controlling means in circuit with a source of electrical energy and with said electroresponsive actuator means, electroresponsive condition anticipating means for said circuit controlling means in circuit with said circuit controlling means and said actuating means, said circuit controlling means having a first position in response to afirst predetermined condition wherein it affords one level of energization of said actuating means, said circuit controlling means having a second position in response to a predetermined condi- 12 tion change in one sense from said first condition wherein it simultaneously afiords energization of said anticipation means and energiz'ation of said actuating means at a second level, and said circuit controlling means also having a third position in response to a predetermined condition change in the opposite sense from said first condition wherein the circuit between said source and said actuator means is open to thereby deenergize said actuator means.

7. A control device for fluid fuel burning apparatus having a burner, comprising fuel flow control means having a flow-preventing and movable to full flow and reduced flow positions with respect to the fuel flow to said burner, safety means for safe ignition of the burner requiring movement of said flow control means to said full flow position prior to movement to said reduced flow position when moved from said flow-preventing positioning comprising first and second operator means for moving said flow control means between said controlling positions, said second operator means being normally operable to first move said flow control means from said flow-preventing to said full flow position and said first operator means including time delay means so as to lag said second operator means whereby said first operator means is normally operable after said second operator means to move said flow control means from said full flow to said reduced flow position, said first operator means also including means operable in the event of failure of said second operator means for moving said flow control means from said flow-preventing to said full flow position prior to its movement of said flow control means from said full HOW to said reduced flow position thereby insuring safe ignition of said fuel at said burner whether or not said second operating means is operative.

8. A control device for fluid fuel burning apparatus having a burner, comprising fuel flow control means having a flow-preventing and movable to full flow and reduced flow positions with respect to the fuel flow, safety means for safe ignition of the burner requiring movement of said flow control means to said full flow position prior to movement to said reduced flow position when moved from said flow-preventing position comprising first and second electroresponsive operator means operable upon energization and deenergization for moving said flow control means between said flow controlling positions, said first operator means including time delay means for providing predetermined lag thereto, circuit controlling means in circuit with a source of electrical energy and said first and second operator means to control the state of energization of said operator means, said circuit controlling means having a first position in which the circuit between said source and the first and second operator means is open to effect said flow-preventing position, positioning of said flow control means in said circuit controlling means having a second position in which the first and second operator means are connected directly to said source to simultaneously energize both said first and second operator means whereby said second operator means immediately moves said flow control means from said flow-preventing to said full flow-permitting position and said first operator means after a predetermined time eriod moves said flow control means from saidfull fiow to said reduced flow position, said first operator means including means operable, in the event of failure of the energizing circuit of said second operator means, for moving said flow control means from said flow-preventing to said full flow position prior to its movement of said flow control means from said full flow to said reduced flow position thereby insuring safe ignition of said fuel at said burner whether or not said circuit to said second operating means is operative.

9. A control device for fluid fuel burning apparatus comprising, first flow control means having -a first and movable to a second position, second 'flow control means having a first and movable to a second position and operatively related to said first flow control means to insure disposition of the latter in its second position when said second flow control means is in its second position, first electroresponsive actuating means connected in circuit with a source of electrical energy and operable when energized to move said first flow control means from its first to its second position, second electroresponsive actuating means also connected in circuit to said source and operable when energized to move said second flow control means from its first to its second position, and interlock means operatively associated with said second actuating means and in circuit with said first actuating means for preventing energization of the latter after said second flow control means is actuated a predetermined distance from its first toward its second position by said second actuating means, said first flow control means during disposition of said second flow control means at or beyond said predetermined distance being held in its second position by its operative relation to said second flow control means wherefore simultaneous energization of both said actuating means is required for only relatively short period and said source of electrical energy may therefore be of minimum size.

10. A control device for fluid fuel burning apparatus having a burner, comprising fuel flow control means having flow preventing, full flow and reduced flow positions with respect to the fuel flow, safety means for safe ignition of the burner requiring movement of said flow control means to said full flow position prior to movement to said reduced flow position when moved from said flow preventing position comprising first and second operator means for moving said fioW control means between said controlling positions, said second operator means being normally operable to first move said flow control means from said flow preventing to said full flow position and said first operator normally being operable thereafter to move said flow control means from said full flow to said reduced fiow position, said first operator including means operable in the event of failure of said second operator means for moving said flow control means from said fiow preventing to said full flow position prior to its movement of said flow control means from said full flow to said reduced flow position, thereby insuring safe ignition of said fuel at said burner Whether or not said second operating means is operative.

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