US3905747A

US3905747A - Fuel control system and method of operating the same

Info

Publication number: US3905747A
Application number: US445258A
Authority: US
Inventors: Charles D Branson
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1974-02-25
Filing date: 1974-02-25
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16

Abstract

A fuel control system for a main burner having a pilot burner therefor and a thermostatically operated control device for directing fuel from a source to the pilot burner upon the demand of fuel for the main burner whereby a safety valve will direct fuel from the source to the main burner only upon the detection of a certain flame at the pilot burner. An electrical ignition unit is provided for igniting fuel issuing from the pilot burner. A condition responsive electrical switch is provided for rendering the ignition unit operable when fuel is directed to the pilot burner upon a demand for fuel for the main burner by the condition responsive switch being responsive to the fuel flow to the pilot burner. The condition responsive switch also renders the ignition unit inoperable when the safety valve is directing fuel from the source to the main burner upon a detection thereby of the certain flame at the pilot burner by the condition responsive switch being responsive to the fuel flow to the main burner.

Description

United States Patent Branson 51 Se t. :"16, 1975 [75] Inventor: Charles D. Branson, Greensburg,

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Feb. 25, 1974 [21] Appl. No.: 445,258

[52] US. Cl. 431/58; 236/15 A; 251/46; 431/61; 431/89 [51] lnt. Cl. F23Q 9/08 [58] Field of Search 431/44, 46, 72, 74, 58; 236/15 A; 251/46; 200/819 A [56] References Cited UNITED STATES PATENTS 2.625.216 l/1953 Strobel 431/44 2,652,110 9/1953 Main 431/46 3.575.542 4/1971 Branson et al 236/15 A Primary Examiner-William F. OlDea Assistant Examiner lames C. Yeung Attorney, Agent, or Firm-Candor, Candor & Tassone ABSTRACT A fuel control system for a main burner having a pilot burner therefor and a thermostatically operated control device for directing fuel from a source to the pilot burner upon the demand of fuel for the main burner whereby a safety valve will direct fuel from the source to the main burner only upon the detection of a certain flame at the pilot burner. An electrical ignition unit is provided for igniting fuel issuing from the pilot burner. A condition responsive electrical switch is provided for rendering the ignition unit operable when fuel is directed to the pilot burner upon a demand for fuel for the main burner by the condition responsive switch being responsive to the fuel flow to the pilot burner. The condition responsive switch also renders the ignition unit inoperable when the safety valve is directing fuel from the source to the main burner upon a detection thereby of the certain flame at the pilot burner by the condition responsive switch being responsive to the fuel flow to the main burner.

32 Claims, 2 Drawing Figures 78 L2- y W SHEET 2 OF 2 ATENTEU SEP 1 1975 FUEL CONTROL SYSTEM AND METHOD OF OPERATING THE SAME This invention relates to an improved fuel control system for a main burner of a cooking apparatus or the like as well as to an improved method of operating such a fuel control system or the like.

It is well known that fuel control systems for main burner means of cooking apparatus have been provided wherein each system has a pilot burner means for the main burner means and a thermostatically operated control device for directing fuel from a source thereof to the pilot burner means upon the demand of fuel for the main burner means whereby a safety valve will direct fuel from the source to the main burner means only upon the detection of a certain heater flame means at the pilot burner means. For example, such a system is illustrated and described in the US. patents to Tyler, US. Pat. No. 3,341,119, to Branson et al., US. Pat. No. 3,367,572 and to Rich] US Pat. No. 3,405,999.

However, it has been found that in such a fuel control system, the pilot burner means is constantly supplied a small standby flow of fuel from the fuel source manifold so that a constantly burning small standby flame exists at the pilot burner means which will either ignite the heater pilot fuel flow from the thermostatically operated control device or be expanded into such heater pilot flame means by having the heater pilot fuel flow added thereto as illustrated and described in the aforementioned U.S. patents whereby the ignition means for such a fuel control system constantly burns fuel at the pilot burner means for the main burner means even though the main burner means is not in use during large periods of time. Accordingly, it is believed that such constantly burning small standby flame during the nonuse of the main burner means constitutes an unnecessary loss of energy.

Therefore, it is a feature of this invention to provide a pilot burner ignition means for such a fuel control system wherein the pilot burner means is only rendered operable during a desired cycle of operation of the main burner means associated therewith.

In particular, one embodiment of this invention provides an electrical ignition means for igniting fuel issuing from a pilot burner means for a main burner means, the fuel issuing from the pilot burner means when a thermostatically operated control device directs fuel from a source thereof to the pilot burner means upon the sensing of the demand for fuel to issue from the main burner means. Thus, a safety valve will direct fuel from the fuel source to the main burner means only upon the detection of a certain heater flame means at the pilot burner means. A condition responsive electrical switch of this invention is provided for rendering the ignition means operable when fuel is directed to the pilot burner means upon a demand for fuel for the main burner means by the condition responsive electrical switch being responsive to the fuel flow to the pilot burner means. The condition responsive electrical switch renders the ignition means operable when the safety valve is directing fuel from the fuel source to the main burner means upon detection thereby of the certain heater flame means at the pilot burner means by the condition responsive electrical switch being responsive to the fuel flow to the main burner means.

Such an arrangement of this invention can provide the aforementioned operation of the electrical ignition means each time the safety valve is cycled between its of and on" conditions to insure that the pilot burner means will be ignited when the fuel flow for creating the heater flame means is directed thereto by the thermostatically operated control device.

Another arrangement of this invention will provide for the aforementioned operation of the electrical ignition means only at the start of a particular cycle of operation of the main burner means whereby a small standby flame will be created at the pilot burner means after initial ignition thereof to provide for subsequent ignition of the heater pilot flow during the cyclic operation of the safety valve for the particular setting of the thermostatic control device.

Therefore, it is an object of this invention to provide an improved fuel control system having one or more of the novel'features set forth or hereinafter shown or described.

Another object of this invention is to provide an improved method of operating such a control system or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is a schematic view illustrating one embodiment of the improved fuel control system of this invention.

FIG. 2 is a view similar to FIG. 1 and illustrates another embodiment of this invention.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted for providing a fuel control system for a cooking apparatus, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide a fuel control system for other apparatus as desired.

Therefore, this invention is not to be limited to only the embodiments illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, one embodiment of the improved fuel control system of this invention is generally indicated by the reference numeral 10 and comprises a main burner means 11 for heating an over 12 of a suitable cooking apparatus 13 to tend to maintain the temperature of the oven 12 at the temperature setting of a selector means 14 of a thermostatically operated control device 15 in a manner hereinafter described.

The control device 15 comprises a housing means 16 having a chamber 17 therein and an inlet portion 18 leading to the chamber 17 and being disposed in fluid communio' ation with a fuel source manifold 19 as illustrated, thc inlet 18 having an on and of valve means 20 therein adapted to be opened and closed by the selector means 14. In particular, when the selector means 14 is moved to any onl condition thereof, the same not only opens the valve member 20 to interconnect the fuel supply manifold 19 with the chamber 17 of the control device 15, but also the selector l4 adjusts the fulcrum point of a pivotally mounted lever 21 disposed in the chamber 17 and carrying a valve member 22 on one end thereof for controlling a valve seat 23 and being responsive at the other end thereof to the expansion and contraction of a power element 24 having the interior chamber thereof interconnected by a capillary tube 25 to a temperature sensing bulb 26 disposed in the oven 12. When the selector 14 is moved to its off position, the same not only closes the valve 20 to disconnect the fuel supply manifold 19 from the chamber 17, but also the selector moves the lever 21 so that the valve member 22 fully closes the valve seat 23 regardless of the expanded or collapsed condition of the power element 24.

The valve seat 23 of the control device is interconnected by a conduit means 27 to a dual rate pilot burner means 28 by a branch conduit 29, the dual rate pilot burner means 28 being of a type similar to the pilot burner means described and illustrated in the aforementioned U.S. patent to Riehl, U.S. Pat. No. 3,405,999.

A bypass passage 30 is also provided in the housing means 16 of the control device 15 to supply a bypass flow of fluid from the chamber 17 of the control device 15 into the conduit 27 leading to the dual rate pilot burner means 28 for supplying a standby flow of fuel to the pilot burner means 28 when the valve member is in an open condition and the valve seat 23 is in a closed condition so that a small standby flame can exist at the pilot burner means 28 in an area not to be detected by a flame sensing bulb 31 of a safety valve 32 that has an outlet 33 thereof interconnected by a suitable orifice cup 34 to the interior of the burner means 11 and an outlet 35 interconnected by conduit means 36 to an outet 37 of the control device 15. A valve member 38 of the safety valve 32 is adapted to open and close a valve seat 39 separating the inlet 35 from the outlet 33 in a manner fully set forth in the aforementioned U.S. patents whereby when the bulb 31 detects a large heater flame at the end 40 of the dual rate pilot burner means 28 created in a manner hereinafter described, a power element 41 of the safety valve 32 will have expanded in such a manner that the same will operate a lever and spring arrangement 42 of the safety valve 32 to move the valve member 38 away from the valve seat 39 and hold the same in an open condition to interconnect the inlet 35 with the outlet 33 as long as the heater flame means exists at the end 40 of the dual rate pilot burner 28. Thus, fuel is adapted to flow from the chamber 17 of the control device 15 to the main burner means 11 to be ignited by the aforementioned small standby flame and/or the large heater flame at the end 40 of the dual rate pilot burner 28 so as to increase the temperature in the oven 12 as will be apparent hereinafter.

An electrical ignition unit 43 is disposed adjacent the pilot burner means 28 for igniting fuel issuing therefrom when the unit 43 is energized, the unit 43 being any desired electrically operated ignition means, such as a conventional electrical ignition coil or the like.

In any event, the electrically operated ignition unit 43 has opposed

sides

44 and 45 thereof respectively interconnected by

leads

46 and 47 to oppose

sides

48 and 49 of a secondary winding 50 of an electrical transformer 51 having a primary winding 52. The primary winding 52 of the transformer 51 has opposed

sides

53 and 54 respectively interconnected to leads 55 and 56.

The lead 55 is interconnected to a power source lead Ll while the other lead 56 is adapted to be interconnected by a condition responsive electrical switch construction of this invention, that is generally indicated by the reference numeral 57, to a lead 58 that is interconnected to another power source lead L2 so that when the electrical switch construction 57 is in a closed condition thereof as illustrated in FIG. 1, electrical current is adapted to flow from the power source leads L1 and L2 through the primary winding 52 of the transformer 51 and thereby induce a current flow in the secondary winding 50 which will electrically operate the ignition unit 43 for igniting any fuel that is issuing from the pilot burner means 28 in a manner hereinafter described. When the electrical switch construction 57 is in an open condition, no current flow can be induced in the ignition means 43 whereby the open electrical switch construction 57 renders the ignition unit 43 inoperable for a purpose hereinafter described.

The electrical switch construction 57 of this invention comprises a housing means 59 carrying a pair of

flexible diaphragms

60 and 61 that divide the housing means 59 into three

separate chambers

62, 63 and 64, the chamber 62 being interconnected by a conduit means 65 to the branch conduit means 29 that leads to the pilot burner means 28, the chamber 63 being interconnected by a conduit means 66 to the fuel supply manifold 19 and the chamber 64 being interconnected by a conduit 67 to the outlet 33 of the safety valve 32 downstream from the valve seat 39 thereof for a purpose hereinafter described.

An electrical switch 68 is disposed in the chamber 63 of the switch construction 57 and comprises a fixed terminal 69 having a contact 70 thereon and a pair of projecting out through an insulating part 71 of the housing means 59 to be interconnected to the lead 58. A movable spring switch blade 72 carried by another terminal 73 of the construction 57 that has a pair thereof projecting out through another insulating part 74 of the housing 59 to be interconnected to the lead 56, the switch blade 72 carrying a contact 75 adapted to cooperate with the contact 70 and having a natural bias toward the contact 70 for closing the electrical switch 68. However, the switch blade 72 is interconnected to a projection 76 on the diaphragm 60 so that movement of the diaphragm 60 to the right in FIG. 1 in a manner hereinafter described will cause movement of the switch blade 72 to the' right to open the contact 75 away from the contact 70 and thereby terminate current flow through the switch 68 for a purpose hereinafter described.

The diaphragm 61 carries a projection 77 which is not interconnected with the switch blade 72 but is adapted to engage against the same and move the switch blade 72 to the right to open the switch 68 when the diaphragm 61 is moved to the right in a manner hereinafter described, the diaphragm 61 being normally biased to the right by a compression spring 78 disposed in the chamber 64.

The conduit 29 that leads to the dual rate pilot burner 28 has a restriction 79 therein for a purpose hereinafter described and the

conduits

65 and 67 can respectively have restriction means 80 and 81 therein adjacent the respective chambers 62 and 64 of the construction 57 so that should leaks occur through either or both

diaphragms

60 and 61, the restriction means 80 and 81 will prevent any adverse amount of gas to escape from the chamber 63 to the atmosphere through the

conduits

65 and 67.

Also, an indicator light 82 can have opposed

sides

83 and 84 thereof interconnected respectively by leads 85 and 86 to the leads 56 and 55 so that the indicator light 82 will indicate to the operator when current is flowing through the transformer 51 and, thus, is operating the igniting unit 43 for a purpose hereinafter described.

The operation of the control system will now be described.

When the control system 10 is disposed in an of condition by the selector 14 being disposed in its off position, the valve 20 in the control device 15 is disposed in a closed position so that no fuel can flow through the control device 15 to the safety valve means 32 and pilot burner means 28 whereby the chambers 62 and 64 of the electrically operated switch construction 57 are at atmospheric conditions. Thus, since the chamber 63 of the device 57 is interconnected to the fuel source manifold 19, the fuel pressure in the chamber 63 acts respectively on the

diaphragms

61 and 60 to move the same respectively to the left and to the right in FIG. 1 in such a manner that the diaphragm 61 compresses the spring 78 so that the bumper 77 thereof is out of contact with the switch blade 72. The diaphragm 60 is moved to the right in such a manner that the natural bias of the switch blade 72 is overcome by the diaphragm 60 being moved to the right so that the switch blade 72 is held out of contact with the fixed contact 70 so that no electrical current can flow through the device 57 to cause operation of the ignition means 43.

However, once the operator turns the selector means 14 to a desired on" condition thereof, such as-a 350 F setting for the oven 12, such movement of the selector means 14 to such on condition not only opens the valve means to interconnect the fuel supply manifold 19 to the chamber 17 of the control device 15, but

also the selector means 14 sets the fulcrum point for the lever 21 so that the valve member 22 is moved immediately to its fully open condition relative to the valve seat 23 as the bulb 26 is at room temperature and thereby causing the power element 24 to be in its completely collapsed condition and thereby demanding full heat from the burner means 11. Thus, a large amount of fuel from the chamber 17 passes through the fully opened valve seat 23 to the dual rate pilot burner means 28. However, because of the restriction 79 in the conduit 29 upstream from the dual rate pilot burner 28, sufficient back pressure of fuel is created in the conduit 65 and the chamber 62 of the device 57 so that the same acting on the right side of the diaphragm 60 in combination with the natural force of the spring blade 72 overcomes the force of the fluid in the chamber 63 acting on the left side of the diaphragm 60 and moves the switch blade 72 into contact with the fixed contact 70 and thereby operates the transformer 51 so that the electrically operated ignition unit 43 is likewise operated to ignite fuel now issuing from the pilot burner means 28.

Since the fuel now issuing from the pilot burner means 28 is the large flow provided by the fully opened valve seat 23, a large heater flame is created at the pilot burner means 28 which is detected by the bulb 31 which causes the safety valve 32 to open its valve member 38 away from the valve seat 39 and interconnect the flow of fuel into the chamber 17 of the control de vice 15 to the main burner means 11 so that the same can issue from the main burner means 11 and be ignited by the pilot burner means 28.

When the valve member 38 of the safety valve means 32 opens to direct fuel to the main burner means 11,

such flow of fuel through the open valve seat 39 of the safety valve means 32 is transmitted by the conduit 67 to the chamber 64 of the electrical switch construction 57 and the same in combination with the force of the compression spring 78 acts on the diaphragm 61 to move the diaphragm to the right and, through the bumper means 77 thereof moves the switch blade 72 and diaphragm 60 to the right so that the switch blade 72 is out of contact with the contact 70. Thus, the electrical switch construction 57 now has its switch 68 disposed in an open condition whereby the ignition unit 43 is rendered inoperative during the flow of fuel through the opened safety valve 32.

In this manner, the burner means 11 continue to operate as set forth above until the temperature sensing bulb 26 senses that the temperature in the oven 12 is now at or slightly above the desired temperature setting of the selector means 14, which, in the above example, is 350 F. At this time the power element 24 has so expanded that the same has caused the valve member 22 to close against the valve seat 23 and thereby terminate the large flow of fuel to the pilot burner means 28 whereby the large heater flame at the end 40 of the pilot burner means 28 now ceases to exist even though the bypass passage 30 is still directing a sufficient bypass fuel flow into the conduit 27 to support a small standby flame at the pilot burner means 28 which will not be detected by the bulb 31. Thus, since the bulb 31 now detects that no larger heater flame exist at end 40 of the pilot burner means 28, the safety valve 32 closes its valve member 38 against the valve seat 39 to terminate the flow of fuel to the main burner means 11.

At this time, the chambers 62 and 64 of the switch construction 57 bleed down to substantially atmospheric condition, but the switch 68 remains open as the fuel pressure in the chamber 63 holds the diaphragm to the right so that the switch blade 72 cannot contact the contact 70 as the small standby flow of fuel through the bypass passage 30 is not sufficient to build up sufficient pressure in the chamber 62 to overcome the pressure in chamber 63.

Subsequently, when the temperature in the oven 12 falls slightly below the selected temperature of 350 F, the power element 24 has collapsed only slightly so that the valve member 22 only is moved a slight distance away from the valve seat 23 so that a relatively small flow of additional fuel now passes through the open valve seat 23 in comparison with the amount when the oven 12 was at a temperature greatly below the temperature setting of the selector means 14, as upon the initial operation of the control device 15, so that while the flow of fuel that is now permitted to pass through the open valve seat 23 is sufficient to create a large heater flame means at the end 40 of the pilot burner means 28 to be detected by the detector 31, such flow of fuel is not sufficiently great to cause a build up of pressure in the chamber 62 to overcome the force of the pressure in the chamber 63 that tends to hold the diaphragm 60 and switch blade 72 to the right. Thus, the switch 68 remains in an open condition so that upon this opening of the valve member 22 away from the valve seat 23 of the control device 15, the electrical operated ignition unit 43 is not operated and the increased flow of fuel to the pilot burner means 28 through the open valve seat 23 is caused to burn by the previously described standby flame at the pilot burner means 28 so that the safety valve 32 can be opened in the manner previously described to direct fuel to the main burner means 11 to be ignited by the dual rate pilot burner means 28 to tend to heat up the oven 12 to the selected temperature.

Therefore, it can be seen that on subsequent openings and closings of the valve member 22 to cause subsequent on-off operation of the main burner means 11 to tend to maintain the temperature in the oven at selected temperature, the flow of fuel through the heater pilot valve seat 23 is not sufficient to cause the electrically operated switch construction 57 to have the switch 68 thereof closed as when the same was closed by the initial opening of the valve seat 23 upon the start ,of the operation of the control system in the manner previously described.

When it is desired to terminate the previously described operation of the oven 12, the operator turns the selector means 14 to the of condition thereof whereby the valve member 20 is moved to a closed position and the valve member 22 is moved to a closed position. Since a heater flame can no longer exist at the pilot burner means 28, the safety valve 32 closes and since no fuel can flow into the chamber 17 of the control device 15, the standby pilot flow of fuel through the bypass passage 30 is terminated so that no flame will exist at the pilot burner means 28. Also, the chambers 62 and 64 of the electrical switch construction 57 return to atmospheric condition so that the pressure in the chamber 63 in the manifold 19 moves the

diaphragms

61 and 60 in the manner previously described so that the switch 68 is held in an open condition during the entire time that the control system 10 is in the off condition.

Thus, it can be seen that the control system 10 of this invention prevents any standing pilot flame to exit at the pilot burner means 28 during the nonuse of the oven 12 and when it is desired to utilize the oven 12, the electrically operated ignition unit 43 is only operated at the start of the cycle of operation of the oven 12 as a standby pilot flame is created at the pilot burner means 28 for permitting cylical operation of the safety valve means 32 and, thus, the burner means 11 during the operation of the oven 12 in the manner previously described.

However, it may be desired to have electrically operated ignition unit 43 be operated each time the safety valve means 32 is cycled between its closed and open position and therefore another control system of this invention can be utilized and is generally indicated by the reference numeral 10A in FIG. 2 where parts ofthe system 10A substantially identical to parts of the system 10 previously described are indicated by like reference numerals followed by the reference letter As illustrated in'FIG. 2, the main burner means 11A, pilot burner means 28A, safety valve means 32A and control device A are substantially identical to like parts of the system 10 previously described but a different electrical switch construction is provided which is generally indicated by the reference numeral 57A in FIG. 2, and comprises only one diaphragm 61A for separating the housing means 59A into two

chambers

64A and 87. Further, the electrically operated ignition unit 43A for the pilot burner means 28A has the opposed sides 44A and 45A thereof respectively interconnected to leads 88 and 89 with the lead 88 being directly interconnected to the power source lead L2 while the lead 89 is adapted to be interconnected through the electrical switch construction 57A to a lead 90 that is interconnected to a power source lead L1.

The electrical switch 68A that is disposed in the chamber 87 of the switch construction 57A has the blade 72A thereof provided with a normal bias in a direction to close the same against the fixed contact 7 0A. However, the compression spring 78A disposed in the chamber 64A and acting on the diaphragm 61A normally tends to move the bumper 77A of the diaphragm 61A upwardly to hold the switch blade 72A in the open condition illustrated in FIG. 2.

If desired, the indicator light 82A can have the

leads

85A and 86A thereof respectively interconnected to the

leads

88 and 89 so that the light 82A will turn on whenever the switch 68A is closed to indicate that the electrical ignition unit 43A is being operated.

The operation of the control system 10A will now be described.

When the selector means 14A of the control device 15A is in the of position so that the valve means 20A and 22A are closed, the

chambers

87 and 64A of the electrical construction 57A are at atmospheric conditions so that the force of the compression spring 78A has moved the diaphragm 61A upwardly as illustrated in FIG. 2 to hold the switch 68A in the open condition illustrated whereby the ignition means 43A cannot be operated and no fuel is permitted to pass from the chamber 17A of the control device 15A to the pilot burner means 28A so that no flame exists at the pilot burner means 28A.

However, when the operator turns the selector means 14A to a desired temperature setting for the oven 12A, such on position of the selector means 14A not only opens the valve means 20A, but also the selector means 14A moves the fulcrum point for the lever 21A to the selected temperature setting position thereof and since the oven 12A is in a cold condition, the valve member 22A is moved fully away from the valve seat 23A in the manner illustrated in FIG. 2 so that fuel is now adapted to flow to the pilot burner means 28A as well as to the chamber 87 of the electrical switch construction 57A. The presssure of the full fuel flow in the chamber 87 acts on the diaphragm 61A and overcomes the force of the compression spring 78A to move the diaphragm 61A downwardly in FIG. 2 whereby the switch blade 72A is adapted to follow such downward movement through the natural resiliency thereof to close the switch 68A and thereby interconnect the ignition unit 43A across the power source leads L1 and L2 so that the unit 43A can ignite the fuel now issuing from the pilot burner means 28A. Thus, a large heater flame now exists at the end 40A of the pilot burner means 28A to be detected by the detector 31A so that the safety valve means 32A can be moved to an open condition thereof.

The opening of the safety valve 32A to interconnect the fuel from the chamber 17A of the control device 15A to the main burner means 11A also interconnects fuel through the conduit 67A to the chamber 64A of the switch construction 57A whereby even though the fuel pressure differential across the diaphragm 61A is now equal, the force of the compression spring 78A is greater than the natural resiliency of the spring blade 72A so that the diaphragm 61A is moved upwardly in the manner illustrated in FIG. 2 to open the switch 68A and terminate the operation of the unit 43A.

The safety valve 32A continues to supply fuel to the burner means 11A as long as the valve member 22A is in an open condition. However, when the bulb 26A senses that the temperature of the oven 12A is at or slightly above the temperature setting of the selector means 14A, the power element 24A has expanded to such an extent that the same closes the valve member 22A against the valve seat 23A and the flow of fuel to the pilot burner means 28A is now terminated through the valve seat 23A whereby if the bypass 30A is provided in the control device 15A, only a small standby flame will exist at the pilot burner means 28A.

Subsequently, should the temperature of the oven fall I below the selected temperature, the valve member 22A is again moved away from the valve seat 23A and sufficient fuel now entersthe chamber 87 of the electrical switch construction 57A to combine with the force of the spring blade 72A to overcome the force of the compression spring 78A and move the switch blade 72A to a closed position so that the ignitor 43A will again be operated to ignite the fuel issuing from the pilot burner means 28A at the end 40A thereof if the standing pilot flame thereof ceases to exist or does not exist through elimination of the bypass passage 30A as the case may be.

Thus, it can be seen that each time the heater pilot 28A is cycled on, the ignition unit 43A will be operated by the switch means 57A to insure ignition thereof so that the valve means 32A can be moved to its open condition to supply the fuel to the burner means 11A.

Of course, the

springs

72A and 78A and the diaphragm 61A can be so sized that the diaphragm 71A will not be moved downwardly in FIG. 2 to close the switch 68A when the valve member 22A is only moved partially away from the valve seat 23A after the temperature of the oven has come to near the selected temperature as in the system 10 previously described whereby the switch construction 57A will only cause the ignition unit 43A to be operated at the start of a particular cycle of operation of the oven 12A in the manner provided by the system 10 previously described.

In any event, it can be seen that this invention provides an improved fuel control system having ignition means that will only be rendered operative during a selected use of the control system so that no standing pilot flame is required for the system during nonuse of the system as in the control systems set forth in the aforementioned U.S. patents.

Thus, this invention not only provides an improved fuel control system but also this invention provides an improved method of operating such a control system or having a pilot burner means therefor and a thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means, the improvement wherein electrical ignition means is provided for igniting fuel issuing from said pilot burner means, and a condition responsive device is provided for rendering said ignition means operable when fuel is directed to said pilot burner means upon a demand for fuel for said main burner means'by said condition responsive device being responsive to said fuel flow to said pilot burner means and for rendering said ignition means inoperable when said safety valve is directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means by said condition responsive device being responsive to said fuel flow to said main burner means.

2. In a fuel control system as set forth in claim l,said condition responsive device rendering said ignition means so operable and then inoperable each time said fuel is directed to said pilot burner means by said control device upon said demand for fuel for said main burner means.

3. In a fuel control system as set forth in claim 1, said condition responsive device rendering said ignition means so operable-and then inoperable substantially only at the start of a cycle of operation of said main burner means as set by said control device.

4. In a fuel control system as set forth in claim 1, said pilot burner means being a dual rate pilot burner means whereby said system has means for directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by said safety valve means.

5. In a fuel control system as set forth in claim 4, said control device having means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an of condition thereof.

6. In a fuel control system as set forth in claim 1, said condition responsive device comprising a diaphragm operated electrical switch construction for interconnecting an electrical power source to said ignition means when an electrical switch of said construction is closed.

7. In a fuel control system as set forth in claim 6, said diaphragm switch construction having a single diaphragm operatively controlling said switch, said construction having means for imposing pilot burner means fuel flow pressure on one side of said diaphragm to tend to close said switch and having means for imposing main burner means fuel flow pressure on the other side of said diaphragm to tend to open said switch.

8. In a fuel control system as set forth in claim 7, said switch construction having biasing means operatively acting on said switch in a direction to normally maintain said switch in an open condition thereof.

9. In a fuel control system as set forth in claim 6, said diaphragm switch construction having a pair of diaphragms operatively controlling said switch, said construction having means for imposing pilot burner means fuel flow pressure on one side of one of said diaphragm to tend to close said switch and having means for imposing main burner means fuel flow pressure on one side of the other of said diaphragms to tend to open said switch.

10. In a fuel control system as set forth in claim 9, said diaphragm switch construction having means for directing source fuel pressure between said diaphragms to respectively act on the other sides thereof to tend to maintain said switch in the open conditions thereof.

11. In a fuel control system for a main burner means having a pilot burner means therefor and a manually settable thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means so that said safety valve will be cycled on and of to tend to maintain the output temperature effect of said main burner means at the particular setting of said control device, the improvement wherein an electrical ignition means is provided for igniting fuel issuing from said pilot burner means, and for rendering said ignition means operable substantially only when fuel is initially directed to said pilot burner means upon a demand for fuel for said main burner means caused by an initial setting of said control from an of condition thereof to a desired on" condition thereof and for thereafter rendering said ignition means inoperable for that particular setting of said control device when said safety valve is initially directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means even though said safety valve is subsequently cycled on" and of during that particular setting of said control devicev 12. In a fuel control system as set forth in claim 11, said pilot burner means being a dual rate pilot burner means whereby said system has means for directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by said safety valve means.

13. In a fuel control system as set forth in claim 12, said control device having means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an off" condition thereof.

14. In a fuel control system as set forth in claim 1, said means for operating said ignition means comprising a diaphragm operated electrical switch construction for interconnecting an electrical power source to said ignition means when an electrical switch of said construction is closed.

15. In a fuel control system as set forth in claim 14, said diaphragm switch construction having a pair of diaphragms operatively controlling said switch, said construction having means for imposing pilot burner means fuel flow pressure on one side of one of said diaphragms to tend to close said switch and having means for imposing main burner means fuel flow pressure on one side of the other of said diaphragms to tend to open said switch.

16. In a fuel control system as set forth in claim 15, said diaphragm switch construction having means for directing source fuel pressure between said diaphragms to respectively act on the other sides thereof to tend to maintain said switch in the open condition thereof.

17. In a method of operating a fuel control system for a main burner means having a pilot burner means therefor and a thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means, the improvement comprising the steps of providing an electrical ignition means for igniting fuel issuing from said pilot burner means, providing a condition responsive device, rendering said ignition means operable with said condition responsive device when fuel is directed to said pilot burner means upon a demand for fuel for said main burner means by causing said condition responsive device to be responsive to said fuel flow to said pilot burner means, and rendering said ignition means inoperable with said condition responsive device when said safety valve is directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means by causing said condition responsive device to be responsive to said fuel flow to said main burner means.

18. In a method as set forth in claim 17, the additional step of causing said condition responsive device to render said ignition means so operable and then inoperable each time said fuel is directed to said pilot burner means by said control device upon said demand for fuel for said main burner means.

19. In a method as set forth in claim 17, the additional step of causing said condition responsive device to render said ignition means so operable and then inoperable substantially only at the start of a cycle of operation of said main burner means as set by said control device.

20. In a method as set forth in claim 17, the additional step of forming said pilot burner means from a dual rate pilot burner means, and directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by said safety valve means.

21. In a method as set forth in claim 20, the additional step of forming said control device with means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an of condition thereof.

22. In a method as set forth in claim 17, the additional step of forming said condition responsive device from a diaphragm operated electrical switch construction for interconnecting an electrical power source to said ignition means when an electrical switch of said construction is closed.

23. In a method as set forth in claim 22, the additional steps of forming said diaphragm switch construction with a single diaphragm operatively controlling said switch, imposing pilot burner means fuel flow pressure on one side of said diaphragm to tend to close said switch, and imposing main burner means fuel flow pressure on the other side of said diaphragm to tend to open said switch.

24. In a method as set forth in claim 23, the additional step of forming said switch construction with biasing means for operatively acting on said switch in a direction to normally maintain said switch in an open condition thereof.

25. In a method as set forth in claim 22, the additional steps of forming said diaphragm switch construction with a pair of diaphragms operatively controlling said switch, imposing pilot burner means fuel flow pressure on one side of one of said diaphragms to tend to close said switch, and imposing main burner means fuel flow pressure on one side of the other of said diaphragms to tend to open said switch.

26. In a method as set forth in claim 25, the additional step of directing source fuel pressure between said diaphragms to respectively act on the other sides thereof to tend to maintain said switch in the open condition thereof.

27. In a method for operating a fuel control system for a main burner means having a pilot burner means therefor and a manuallly settable thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means so that said safety valve will by cycled on and of to tend to maintain the output temperature effect of said main burner means at the particular setting of said control device, the improvement comprising the steps of providing an electrical ignition means for igniting fueliiissuring from said pilot burner means, rendering said ignition means operable substantially only when fuel is initially directed to said pilot burner means upon a demand for fuel for said main burner means caused by an initial setting of said control from an of condition thereof to a desired on condition thereof and thereafter rendering said ignition means inoperabale for that particular setting of said control device when said safety valve is initially directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means even though said safety valve is subsequently cycled on" and off" during that particular setting of said control device.

28. In a method as set forth in claim 27, the additional steps of forming said pilot burner means from a dual rate pilot burner means, and directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by saidsafety valve means.

29. In a method as set forth in claim 28, the additional step of forming said control device with means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an off" condition thereof.

30. [n a method as set forth in claim 27, the additional step of providing means for operating said ignition means from a diaphragm operated electrical switch construction for interconnecting an electrical power source to said ignition means when an electrical switch of said construction is closed.

31. In a fuel control system as set forth in claim 30, the additional steps of forming said diaphragm switch construction with a pair of diaphragms operatively controlling said switch, imposing pilot burner means fuel flow pressure on one side of one of said diaphragms to tend to close said switch, and imposing main burner means fuel flow pressure on one side of the other of said diaphragms to tend to open said switch.

32. In a method as set forth in claim 31, the additional step of directing source fuel pressure between said diaphragms to respectively act on the other sides thereof to tend to maintain said switch in the open con dition thereof.

Claims

1. In a fuel control system for a main burner means having a pilot burner means therefor and a thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means, the improvement wherein electrical ignition means is provided for igniting fuel issuing from said pilot burner means, and a condition responsive device is provided for rendering said ignition means operable when fuel is directed to said pilot burner means upon a demand for fuel for said main burner means by said condition responsive device being responsive to said fuel flow to said pilot burner means and for rendering said ignition means inoperable when said safety valve is directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means by said condition responsive device being responsive to said fuel flow to said main burner means.

2. In a fuel control system as set forth in claim 1, said condition responsive device rendering said ignition means so operable and then inoperable each time said fuel is directed to said pilot burner means by said control device upon said demand for fuel for said main burner means.

3. In a fuel control system as set forth in claim 1, said condition responsive device rendering said ignition means so operable and then inoperable substantially only at the start of a cycle of operation of said main burner means as set by said control device.

5. In a fuel control system as set forth in claim 4, said control device having means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an ''''off'''' condition thereof.

11. In a fuel control system for a main burner means having a pilot burner means therefor and a manually settable thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means so that said safety valve will be cycled ''''on'''' and ''''off'''' to tend to maintain the output temperature effect of said main burner means at the particular setting of said control device, the improvement wherein an electrical ignition means is provided for igniting fuel issuing from said pilot burner means, and for rendering said ignition means operable substantially only when fuel is initially directed to said pilot burner means upon a demand for fuel for said main burner means caused by an initial setting of said control from an ''''off'''' condition thereof to a desired ''''on'''' condition thereof and for thereafter rendering said ignition means inoperable for that particular setting of said control device when said safety valve is initially directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means even though said safety valve is subsequently cycled ''''on'''' and ''''off'''' during that particular setting of said control device.

12. In a fuel control system as set forth in claim 11, said pilot burner means being a dual rate pilot burner means whereby said system has means for directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by said safety valve means.

13. In a fuel control system as set forth in claim 12, said control device having means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an ''''off'''' condition thereof.

21. In a method as set forth in claim 20, the additional step of forming said control device with means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an ''''off'''' condition thereof.

27. In a method for operating a fuel control system for a main burner means having a pilot burner means therefor and a manuallly settable thermostatically operated control device for directing fuel from a source thereof to said pilot burner means upon the demand of fuel for said main burner means whereby a safety valve will direct fuel from said source to said main burner means only upon the detection of a certain flame means at said pilot burner means so that said safety valve will by cycled ''''on'''' and ''''off'''' to tend to maintain the output temperature effect of said main burner means at the particular setting of said control device, the improvement comprising the steps of providing an electrical ignition means for igniting fuel issuring from said pilot burner means, rendering said ignition means operable substantiallY only when fuel is initially directed to said pilot burner means upon a demand for fuel for said main burner means caused by an initial setting of said control from an ''''off'''' condition thereof to a desired ''''on'''' condition thereof and thereafter rendering said ignition means inoperabale for that particular setting of said control device when said safety valve is initially directing fuel from said source to said main burner means upon a detection thereby of said certain flame means at said pilot burner means even though said safety valve is subsequently cycled ''''on'''' and ''''off'''' during that particular setting of said control device.

28. In a method as set forth in claim 27, the additional steps of forming said pilot burner means from a dual rate pilot burner means, and directing a standby flow of fuel from said source to said pilot burner means to produce a standby flame means at said pilot burner means that is not detected by said safety valve means.

29. In a method as set forth in claim 28, the additional step of forming said control device with means for terminating said flow of fuel to said pilot burner means when said control device is disposed in an ''''off'''' condition thereof.

30. In a method as set forth in claim 27, the additional step of providing means for operating said ignition means from a diaphragm operated electrical switch construction for interconnecting an electrical power source to said ignition means when an electrical switch of said construction is closed.

32. In a method as set forth in claim 31, the additional step of directing source fuel pressure between said diaphragms to respectively act on the other sides thereof to tend to maintain said switch in the open condition thereof.