US3386656A

US3386656A - Two burner oven systems and controls

Info

Publication number: US3386656A
Application number: US621016A
Authority: US
Inventors: Frank H Bergquist
Original assignee: Harper Wyman Co
Current assignee: Harper Wyman Co
Priority date: 1967-03-06
Filing date: 1967-03-06
Publication date: 1968-06-04
Anticipated expiration: 1985-06-04
Also published as: GB1167700A

Description

June 4, 1968 F. BERGQUIST 3,386,656

TWO BURNER OVEN SYSTEMS AND CONTROLS Filed March 6, 1967 4 Sheets-Sheet 1 INVENTOR FRANK If. BERGQU/ST ByW/m, 9661mm, IQdMaM. 3 21744 Attorneys June 4, 1968 F. H. BERGQUIST TWO BURNER OVEN SYSTEMS AND CONTROLS 4 Sheets-Sheet 2 Filed March 6, 1967 H0 FIG. 4 32 W Ew mmw MB V WW Attorneys June 4, 1968 BERGQUIST 3,386,656

TWO BURNER OVEN SYSTEMS AND CONTROLS Filed March 6, 1967 4 Sheets-Sheet 3 FIG 6 64 IN-VENTOR.

FRANK H BERGOUIST By%zaa4, f obwamfizmm J ;4

Attorneys June 1968 F. H. BERGQUIST 3,386,656

TWO BURNER OVEN SYSTEMS AND CONTROLS IN VENTOR.

FRANK H. BERGOU/ST By%am, 32],.

Attorneys United States Patent ABSTRACT OF THE DISCLOSURE A gas oven includes bake and broil burners each having a control pilot, and a sensor for each pilot. A safety valve for each burner admits gas to the burner when a flame indication is sensed at the corresponding pilot. An additional valve controlled by the bake pilot sensor prevents gas from flowing to the broil burner when a flame indication is sensed at the bake pilot. An oven control provides bake operation wherein the bake burner cycles at a high rate; broil operation wherein the broil burner operates continuously at a high rate; and low broil or rotisserie operation wherein the broil burner operates continuously at a low rate.

The present invention relates to gas ovens and particularly to improved control systems and valves for two burner ovens. Primary objects of the invention are to provide an improved two burner oven system, an improved control valve for such systems, and an improved safety arrangement for preventing simultaneous gas flow to both oven burners.

Two burner gas ovens include a bake burner usually positioned at the bottom of the oven and a broil burner located in the upper region of the oven. The bake burner is used for heating the oven for baking operation, while the broil burner is used for high temperature broiling operation. In addition the broil burner may be used for reduced temperature, or rotisserie operation.

Typical two burner oven systems can include a control pilot for each burner, and a pilot responsive safety valve or automatic valve controlling the admission of gas to each burner. In one type of system, a combined shut-off and thermostatic valve is used to supply a main flow of gas for the burners, and a selector valve is provided for channeling the main flow of gas either to the bake burner or the broil burner, simultaneously providing gas to the corresponding control pilot. Such systems may include separate knobs for controlling the combined valve and the selector valve, but in view of the objections to separate knobs, single knob systems have been devised wherein a mechanical or other linkage allows simultaneous control of the combined valve and the selector valve.

In order to overcome the necessity for using an expensive and complicated selector or Y valve for channeling the main gas flow either to the bake or broil burner, systems have been devised wherein the main gas flow is continuously available to both the bake safety valve and the broil safety valve, the selection being accomplished by providing a flame indication at the control pilot of the selected burner. In such systems, a single control has been used for providing on-off control, for providing thermostatic regulation of the gas flow, and for selecting either the bake control pilot or the broil control pilot. However, such controls developed heretofore have been complicated, expensive, and otherwise unsatisfactory.

In some installations it is desirable to operate the broil burner at a low oven temperature to accomplish rotisserie operation. In known two burner oven systems, a separate control has been required to operate the broil burner in this manner.

ice

A disadvantage of two burner oven systems arises because the main gas flow is available simultaneously to the bake burner safety valve and to the broil burner safety valve. With this arrangement, if the bake burner heats the oven to a high temperature, the broil burner safety valve may open even though there is no flame indication at the broil heater pilot. This gives rise to a dangerous condition because should the broil burner ignition means not be operating, unignited gas flows from the broil burner into the oven.

Another difficulty arises because of a thermal lag in the operation of pilot responsive safety valves or automatic valves. For example, at the end of a baking operation, the flow to the bake control pilot is discontinued. After a time lag, due to the thermal delay in the cooling of the sensing element, the bake safety valve closes. If the oven control is changed from bake to broil, it is possible for the broil safety valve to open before the bake safety valve closes. As a result, gas may be admitted simultaneously to the bake and broil burners, and if the ignition means for a burner is not operating unignited gas escapes into the oven.

In accordance with the present invention, there is provided a simplified and reliable control for controlling the normal bake and broil operations of a two burner oven. In addition, the control of the present invention is capable of providing in a simple manner a continuous low rate flow of gas to the broil burner for rotisserie operation. There is also provided a novel valve arrangement for automatically preventing simultaneous flow to both burners of the oven.

Briefly, an embodiment of the present invention may include a lower bake burner, an upper broil burner, a control pilot for each burner and a pilot responsive safety or automatic valve for each burner serving to admit gas to the burner only in response to heat sensed adjacent the corresponding control pilot. In accordance with an important feature of the present invention, there is provided an additional valve controlled in accordance with the presence or absence of a flame indication at the bake control pilot for preventing gas from flowing to the broil burner when a flame indication is sensed at the bake control pilot. Thus, under no circumstances may gas flow simultaneously to the bake burner and to the broil burner.

In accordance with another feature of the invention, there is provided a simplified control for controlling the bake and broil operations. The control includes a housing within which is a chamber, and a first valve controls the admission of gas into the chamber. A control knob is movable between off, bake and broil positions, and in both the bake and broil positions a substantially unrestricted fiow of gas is admitted by the first valve to the chamber. in the bake position gas flows from the chamber through a bake pilot valve to the bake control pilot, and through a main gas outlet to the bake safety valve. When the control knob is moved to the broil position, the brake pilot valve is securely closed preventing gas from flowing to the bake control pilot, and gas flows from the first valve through a passageway to the broil control pilot. Oven temperature responsive means cycles the bake pilot valve in bake operation to maintain a selected bake temperature by cycling operation of the bake burner. In broil, a continuous flow to the broil burner is thermostatically throttled at a predetermined high broil temperature.

In accordance with another feature, the control includes means for producing continuous low rate broil or rotisserie operation. When the control knob is turned to a low broil position, gas is supplied from the first valve to the broil control pilot, and additionally a continuous low rate flow is provided into the chamber and C!) from the chamber via the broil safety valve to the broil burner.

Other objects and advantages of the invention will appear from the following description of illustrative embodiments, in the course of which reference is had to the accompanying drawings, in which:

FIG. 1 is a largely schematic illustration of a two burner oven system embodying features of the present invention, in which an oven control and a safety valve assembly are illustrated in diagrammatic form;

FIG. 2 is a perspective view, partly broken away, of the safety valve assembly of FIG. 1;

FIG. 3 is an elevational view of the assembly of FIG. 2 with the cover removed more clearly to illustrate the interior;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3 assuming FIG. 3 to show the complete assembly;

FIG. 5 is a fragmentary diagrammatic illustration somewhat similar to part of FIG. 1 and illustrating an alternative embodiment of the invention;

FIG. 6 is a sectional view of the control valve of FIG. 1, taken along the line 66 of FIG. 7, and assuming FIG. 7 to show the complete control;

FIG. 7 is an elevational view, on a reduced scale, of the valve body taken from the line 7-7 of FIG. 6;

FIG. 8 is an elevational view of the other side of the valve body taken from the line 88 of FIG. 6;

FIG. 9 is a fragmentary sectional view, on an enlarged scale, taken along the line 9-9 of FIG. 7;

FIG. 10 is an enlarged sectional view taken along the line 1010 of FIG. 8;

FIG. 11 is a composite view of the control knob and portions of the control valve shown in a sectional view taken along the line 1111 of FIG. 6, illustrating the off position; and

FIGS. 12-14 are views similar to FIG. 11 illustrating the bake, low broil and broil positions respectively.

Referring now to the drawings, and initially to FIG. 1, there is illustrated a two burner oven system embodying features of the present invention and designated as a whole by the reference numeral 10. The system is associated with an oven 12 illustrated in broken lines within which are secured a lower bake burner 14 and an upper broil burner 16. Gas is supplied to the system 10 from a gas manifold 18 and is supplied to the

burners

14 and 16 from a novel oven control generally designated as 20 and a novel safety valve assembly generally designated as 22.

Located adjacent the bake burner 14 are a bake control or heater pilot 24, a continuously burning igniter pilot 26 supplied from the manifold 13 by a conduit 28, and a flame sensing bulb 30 communicating by means of a capillary tube 32 with the safety valve assembly 22. When it is desired to operate the bake burner 14, a control knob 34 of the control 26 is turned to a bake position, and gas is supplied through a conduit 36 to the bake control pilot 24 and through a conduit 38 to the safety valve assembly 22. Gas flowing from the bake control pilot 24 is ignited by the continuous pilot 26 thus providing a flame indication heating the flame sensing bulb 30. When the flame sensing bulb is heated the safety valve 22 allows gas to flow through a conduit 39 to the bake burner 14 where it is ignited by the continuous pilot 26.

The arrangement for lighting the broil burner 16 is similar and a broil control or heater pilot 40, a continuously burning pilot 42 supplied by a conduit 44, and a flame sensing bulb 46 communicating with a capillary tube 48 are located adjacent the broil burner 16. When it is desired to operate the broil burner, the control knob 34 is turned to a broil position and gas is supplied through a conduit 50 to the broil control pilot 4t) and through the conduit 38 to the safety valve assembly 22. Gas flowing from the broil control pilot is ignited by the continuous pilot 42 and heats the flame sensing bulb 46,

whereupon gas flows from the safety valve assembly 22 through a conduit 51 to the burner 16 for ignition by the continuous pilot 42. The continuous pilot 42 may be an aerated type disclosed and claimed in the co-pending application of Charles C. Lamar, Ser. No. 462,334.

Although the ignition means for the burners have been illustrated as

continuous pilots

26 and 42, any other type of ignition such as an electrical glow coil system or a spark ignition system may be used. The separate control and continuous pilots for one or both of the

main burners

14 and 16 may be replaced with a dual rate pilot. In this case the flame indication sensed by the flame sensing bulb would be an increased flame size rather than the presence of a flame. Although flame sensing bulbs have been illustrated, any type of flame sensing device may be used to control the operation of the safety valve assembly 22.

In accordance with an important feature of the invention, the valve assembly 22 not only performs the function of a safety valve or automatic valve for each of the

burners

14 and 16, but also serves automatically and positively to prevent gas from flowing simultaneously to both the lower bake burner 14 and the upper broil burner 16. The valve 22 includes a bake safety valve or automatic valve generally designated as 52 allowing gas to flow to the bake burner 14 only when the flame sensing bulb 30 is heated by a flame indication at the bake control pilot 2.4. The valve 22 also includes a broil safety valve or automatic valve generally designated as 56 allowing gas to flow to the broil burner 16 only when the flame sensing bulb 46 is heated as by a flame indication at the broil control pilot 40.

In known systems of the type using pilot responsive safety valves, it is possible for a dangerous condition to arise since gas may be admitted simultaneously to both burners. To overcome this disadvantage, the assembly 22 includes a valve generally designated as 60 for preventing the simultaneous flow of gas to both the bake burner 14 and the broil burner 16. The valve 60 functions independently of the broil safety valve 56 as it is controlled in accordance with the presence or absence of a flame indication at the bake burner pilot 24. The valve 60 allows gas to flow to the broil burner only when no flame indication exists at the bake control pilot 24, and prevents 'gas from flowing to the broil burner 16 when a flame indication exists at the bake control pilot 24. The arrangement is such that whenever the bake safety valve 52 is closed the valve 60 is open, and vice versa. Thus it is not possible for gas to flow simultaneously both to the bake burner 14 and the broil burner 16.

In accordance with another feature of the present invention, the control 20 controls the bake and broil operations of the system 10 in a novel and simple manner. The control 10 is a single knob control in that all functions of the system are controlled by manipulation of the single knob 34. In both the bake and broil operations a substantially unrestricted flow of gas is introduced into a chamber 62 of the control 20, and is channeled to the safety valve assembly 22 via the conduit 38. In bake operation a flame indication is provided at the bake heater pilot 24 by gas flowing through the conduit 36, and in broil operation a flame is produced at the broil control pilot 46 by gas flowing through the conduit 50.

Gas is introduced into the valve body 64 of the control 29 by a conduit 66 extending from the manifold 18, and flows through an inlet passage 68 in the valve body to a valving surface 64a: on the valve body. In the off position of the control knob 34, gas does not enter the chamber 62, but if the control knob 34 is turned to a bake or broil position, a recess in a valve rotor 70 allows gas to flow freely from the passage 68 through a passage '72 and into the chamber 62. When the control knob is moved to a selected bake position corresponding to a desired oven 'emperature, an adjustable pivot block 74 moves a pair of

control levers

76 and 78 to open a bake pilot valve generally designated as 80, thereby allowing gas to flow through a passage 82 in the valve body 64, through a passage 84 in the valve housing member 86 and through the conduit 36 to the bake control pilot 24.

Upon ignition of the bake burner 14, the oven temperature begins to rise, this temperature being sensed by a temperature sensing bulb 88 communicating via a capillary tube 90 with an expansible diaphragm 92 within the chamber 62. When the selected bake temperature is reached, or slightly exceeded, the bake pilot valve 80 closes and the oven temperature begins to fall until the bake pilot valve 80 reopens, and a cycling operation ensues to maintain the selected bake temperature. During bake operation, gas is available at a substantially unrestricted flow rate to the safety valve 22.

In broil operation the control knob 34 is turned to a broil position, and the pivot block 74 is moved to a position where the control levers 76 and '78 maintain the bake pilot valve closed continuously at all oven temperatures. The recess in the rotor 76) establishes communication between the inlet passage 68 and the passage 72, and also allows gas to flow through a broil pilot passage 94, through a passage 96 in the housing 86, and through conduit St) to the broil control pilot 40. Thus the broil safety valve 56 is continuously open and the broil burner 16 perates continuously rather than cycling as is the case with the bake burner 14.

In broil operation the flow of gas from the chamber 62 through the conduit 38 is throttled by means of a high broil temperature valve generally designated as $8. This valve is coupled directly to the expansible diaphragm 92 and throttles the gas flow when the oven temperature approaches a predetermined high broil temperature such as 625. The valve 98 also throttles gas flow should a runaway condition occur during bake operation, such as might be caused by the bake pilot valve becoming stuck in an open position.

In two burner oven systems it is desirable to provide for rotisserie operation of the broil burner wherein the broil burner operates to produce a low oven temperature rather than the usual high broil temperature. In known two burner oven systems this type of operation is achieved by operating the broil burner in the same way that the bake burner is operated at low oven temperatures. This may be accomplished by including an additional rotisserie selector valve for channeling flow intended for the bake control pilot to the broil control pilot. This has the disadvantage that the low temperature broil burner operation is cycling rather than continuous, whereas continuous low rate operation is more desirable especially when the broil burner is an infra-red burner.

In accordance with the present invention, the control 20- includes a simple arrangement for providing a continuous low rate broil or rotisserie operation. Vfhen the control knob 34 is turned to a low broil position, communication between the inlet passage 68 and the passage 72 is closed. The recess in the rotor 7 1) establishes communication between the passage 68 and the broil pilot passage 94 thereby providing a dame indication at the broil control pilot 49 for opening the broil safety valve 56. Simultaneously, gas flows through a small area, low rate flow passage 1% from the valving surface 64a to the chamber 62, and only a low rate gas flow reaches the broil burner 16.

Referring now to FIGS. 2-4 as well as FIG. 1, the construction of the safety valve assembly 22 will be described. The assembly 22 includes a body 102 closed by a pair of cover plates 104 and 1% held in place by suitable fasteners. An inlet port 198 receives the main gas flow from the control 20 and a bake outlet port 110 and a broil outlet port 112 supply fuel to the bake and

broil burners

14 and 16 respectively, either by conduits as illustrated in PEG. 1 or directly into the burner miring tubes if desired. If the gas is discharged directly into the tral longitudinal wall 114 and there is continuous com munication through the wall 114 via a passageway 116 beneath the cover plate 104. The regions beneath the cover plate 106 and and the regions beneath the cover plate 104 are separated by a solid portion of the body 102 and communicate with one another by way of a pair of internally threaded

bores

118 and 120, one located on either side of the central wall 114. A pair of threaded

valve seat members

122 and 124 received in the bore 118 (best shown in FIG. 4) divide the region at one side of the central wall 114 into a bake outlet chamber 126, an inlet chamber 128 communicating with the inlet 1% via a passageway 13%, and a lower region communicating with the passageway 116. A threaded valve seat member 132 in the bore divides the region on the other side of the wall 114 into a broil outlet chamber 134 and a lower region communicating with the passageway 116.

The bake safety valve 52 controls the flow of gas from the inlet chamber 128 to the bake outlet chamber 126 and comprises the valve seat member 122 and a valve member 136 normally biased against the valve seat memher 122 by a spring 138, Flow from the inlet chamber 128 to the passage 116 and then to the broil burner is controlled by the valve 60 comprising the seat member 124 and the valve member 1%.

Movement of the valve member 136 between its alternate positions against the

seat members

122 and 124 is guided by a slip fit connection with a guide pin 140. The valve member 136 includes a rigid central member bounded on both sides by discs of resilient material such as rubber engageable with the

valve seat members

122 and 124 respectively. The assembly is held together by means of a friction element 142, and an operating post 144 extends upwardly from the valve member into the bake outlet chamber 126.

The position of the valve member 136 is controlled by a closed fluid system including the flame sensing bulb 30, the conduit 32 and an expansible diaphragm 146. The diaphragm 146 is coupled to the valve operating post 144 by means of a lever 148 mounted on a bracket 150 by a pivot pin 152.

When a flame indication is sensed at the bake control pilot, the diaphragm 146 expands rapidly, after a period of thermal delay, thus pivoting the lever 148 and forcing the operating post 144 downwardly. This moves the valve member 136 away from the seat member 122 and against the seat member 124 thereby opening the bake safety valve 52 and closing the additional valve 60 and establishes communication between the inlet port 108 and the bake outlet port 110 while simultaneously preventing the flow between the inlet port 108 and the broil safety valve 56. Overtravel of the operating post 144 with respect to the valve member 136 is permitted by means of it; overtravel assembly generally designated as 154 (FIG.

Flow between the passageway 116 and the broil outlet chamber is controlled by the broil safety valve 56 comprising the valve seat member 132 and a valve member 156 normally biased against the seat member 132 by a spring 158. Movement of the valve member 156 is guided by a slip fit connection with a guide pin 160, and the valve member including a rigid portion and a resilient wafer is held assembled by a friction element 162. An operating post 164 extends upwardly from the valve member 156 and is engaged by a lever 166 supported by a pivot pin 163 and a bracket 170. When a flame indication is sensed by the flame sensing bulb 46, an expansible diaphragm 1'71. moves the valve member 156 away from the seat member 132, thus opening the broil safety valve 56. Opening of the valve 56 establishes communication between the passage 116 and the broil outlet port 110.

The broil safety valve 56 opens to establish communication between the passage 116 and broil outlet chamber 134 only when the flame sensing bulb 46 is heated as by a flame indication at the broil control pilot 46. However, in accordance with the present invention fuel is not permitted to flow to the broil burner when the additional valve 60 is closed, even if the broil safety valve 56 is open. The valve 60 operates independently of the broil safety valve 56, and is controlled in accordance with the presence or absence of a flame indication at the bake control pilot 24 to shut off flow to the broil burner whenever the bake safety valve 52 is open, and vice versa, thereby positively and automatically preventing simultaneous flow of gas to the bake and broil burners.

It is not necessary for the broil safety valve 56 to be in the same housing as the bake safety valve 52 and the valve 6t). PEG. is a diagrammatic illustration of portions of a two burner oven control system similar to the system shown in FIG. 1, except that the safety valve assembly is in separate housings. In order to divide the valve 22 into separate housings, the central wall 114 may be divided into separate walls 114a and 114b, and the passage 116 replaced with a conduit 116. The operation of the system of FIG. 5 is identical with the operation of the system of FIG. 1.

Having reference now to FIGS. 6-14 as well as FIG. 1, the construction of the control 20 will be described. The body 64 and the housing 86 and a face plate 174 of the control 26 are held together by suitable bolts, and the chamber 62 is defined between the housing 86 and the body 64. Gas is introduced into the control 20 through an inlet port 76 communicating with the inlet passage 68 (FIG. 10), and the main gas flow is deiivered from the chamber 62 through an outlet port 178 (FIG. 6).

The operation of the control 20 and the two burner oven system is controlled with the single knob 34 which is connected to a valve stem 180 journaled in a cap portion of the face plate 17 (FIG. 6). Rotation of the control knob 34 and valve stem 180 serves to control the mode of operation of the oven system by rotating the rotor 70, and also serves to adjust the thermostatic control so that the selected oven temperature is maintained during bake operation.

In order to accomplish these functions, the stem 180 is secured to rotate with a rotor drive yoke 182 and a shaft driving member 184. The rotor 7t) includes a valve face 70a held against the valving surface 64a of the valve body by means of a spring 186 held in compression between a spring plate 188 and the shaft driving member 184. The valving surface 64a and the valve face 70a comprise flat lapped surfaces in sealing engagement with one another (FIG. 6).

Rotation of the valve stem 180 serves to cause rotation of the rotor by virtue of a drive finger 182a of the rotor drive yoke 182 received in a slot 190 in the rotor 70. The yoke also includes a stop member 18212 receivable in a recess 174a in the face plate for locking the valve in the off position illustrated in FIG. 6, so that the control cannot be turned on or between broil and bake accidentally. In order to move the control knob 34 from or through the off position, it is necessary to depress the knob to release the member 182b from the recess 174a.

Rotation of the valve stem 180 is imparted to an operating shaft 192 by a pin and slot connection between the shaft driving member 184 and shaft 192. The operating shaft 192 includes a threaded portion 192a received in a threaded opening 194 in the valve body 64 to the end that rotation of the shaft 192 is translated to axial movement of the shaft.

Referring now particularly to FIG. 8, the valving surface 64a of the valve body 64 includes an inlet recess 68a communicating with the inlet passage 68 as well as an arcuate outlet recess 72a communicating with the passage 72, these recesses being separated by a land portion of the valving surface 6%. In the locked, off position of b the control knob 34 illustrated in FIGS. 6 and 11, the valve face 76a covers the recess 72a and other recesses described hereinafter, so that no gas flows into the system 10 through the control 20.

If the control knob 34 is depressed and turned in a counter clockwise direction to select a desired baking temperature as illustrated in FIG. 12, the inlet recess 68a and the outlet recess 72:: are brought into communication by means of a control recess 196 in the rotor thereby channelling a substantially unrestricted flow of gas to the chamber 62.

Rotation of the control knob 34 to the selected baking temperature also causes axial movement of the operating shaft 192 in an upward direction as viewed in FIG. 6. The pivot block 74 is held in position along the shaft by means of an overtravel spring 198 held between the pivot block and a washer 200. As the shaft is moved to the point corresponding to the selected bake temperature, the

levers

76 and 78 also move and open the bake pilot valve 86.

The bake pilot valve 80 comprises a small valve seat 262 (FIG. 7) engageable by a valve member 204, the valve member 264- being supported in the closed position by the valve seat 262 and by a support abutment 206. A spring 2 38 urges the valve member 264 away from the seat 202, and the spring may be arranged to tend to tilt the valve member 264 upwardly in the region over the valve seat 262 to effect a clam shell opening and closing action.

After the control 20 has been set for bake operation at 425, for eXample, as illustrated in FIG. 12, the gas entering the chamber 62 flows through the intially opened bake pilot valve 86. After opening of the bake safety valve 52,, gas also flows from the chamber 62 through the outlet port 178 and to the bake burner 14.

The diaphragm 92 is supported in a recess 210 on the inner face of the valve body 64 (FIG. 7), and a shoulder 2.11 above the diaphragm )2 engages one end of the lever 76 for thermostatically controlling the valve 80 by pivoting the lever 76 around the pivot block 74. When the oven temperature reaches or slightly exceeds the selected bake temperature, the valve 36 closes, closing the bake safety valve 52 and terminating flow through the chamber 62 and outlet 178. Subsequent cooling of the oven results in reopening of the bake pilot valve 80 and a cycling operation of the bake burner takes place for maintaining the selected bake oven temperature.

When the control knob 34 is turned to a broil position, the bake pilot valve 8% is ositively and securely held in an off condition. The knob is arranged so that the bake position is reached by turning the knob in a counter clockwise direction from the off position, and the broil position is reached by turning the knob in a clockwise direction from the position. A suitable abutment (not shown) is engageable with the locking abutment 1821) and prevents the knob from being turned from bake to broil or broil to bake without going through the off position. When the knob 34 is turned to the broil position (or to the low broil position) the shaft 192 is moved down as shown in FIG. 6 and the pivot block 74 is forced down wardly by the compressed over-travel spring 198. This arrangement assures that the bake pilot valve is never opened during broil (or low broil) operation at any oven temperature.

In the broil position of the control 26 (FIG. 14), gas passes through a broil pilot recess 94a through a broil pilot passage 94, the passage 96 in the housing 86, and the conduit 56 to the broil control pilot 40, and the broil safety valve 56 is opened. The valve 60 being open, gas passes through the passage 72, the chamber 62, and the outlet 178 to the broil burner 16. Since the flow of gas to the broil control pilot 40 is continuous, the broil burner operates continuously.

In the illustrated embodiment of the invention, the flow of gas to the broil burner is throttled by the valve 98 when the predetermined high broil temperature, such as 625", is reached. Valve 98 includes a valve member 212, supported on a shaft 214 extending upwardly from the expansible diaphragm 92, co-operable with the wall of the housing 86 to throttle gas flowing from the chamber 62 through the outlet 178.

The valve 98 has substantially no effect upon the flow of gas to the bake burner 14 during normal baking operation because the oven temperature does not approach the predetermined high broil temperature at which the valve 98 begins to throttle. However, in the event of a runaway condition wherein the bake burner 14 operates continuously, the valve 98 functions to prevent the oven temperature from exceeding a predetermined high broil temperature. Such a runaway condition might occur if the bake burner safety valve 62 or the bake pilot valve 80 jams in the open position.

If desired the valve 98 may be omitted, and the maximum rate of gas flow to the bake burner 14 and the broil burner 16 may be limited by the size of the adjustable burner orifices, as is well known to those skilled in the art.

If it is desired to operate the broil burner 16 in a low flow rate or rotisserie mode, control knob 34 is turned to the low broil position illustrated in FIG. 13. In this position the valve face 70a of the rotor closes the outlet recess 72a in the valving surface 64a so that there is no unrestricted flow of gas into the chamber 62. Rather the control recess 196 in the rotor communicates the inlet passage 68 with the broil pilot recess 94a and with a low rate recess 100a in the valving face 64a. The low rate passage 100 through the valve body extends between the low rate recess 100a and an opening 100i; (FIG. 7) in the region beneath the diaphragm 92 in the chamber 62.

In low broil operation the broil control pilot 49 operates continuously to maintain the broil safety valve 56 continuously open. At the same time, a low rate fiow of gas is supplied by the low rate passageway 101) to the chamber 62, which flow passes through the outlet 178 to the broil burner. The valve 98 does not affect this How since the oven temperature is low.

Having reference now to FIG. 9, a variable orifice adjustment assembly 218 is provided to adjust the rate of flow to the broil control pilot 40. Similar adjustment assemblies 22$) and 222 (FIG. 8) are provided for adjusting the flow rate to the bake control pilot 24 and the fiow rate through the low rate passageway 100. The flow through the low rate passageway 100 may be adjusted to the minimum flow for satisfactory ignition and combustion characteristics with the type of broil burner and fuel used.

In the broil position of the control knob 34 as illustrated in FIG. 14, the low rate passageway ltiti is parallel with the substantially unrestricted passage 72, and has no effect in broil operation. If rotisserie operation is not de sired, the adjustment assembly 222 in the low rate passageway ltit) may be closed. In this situation, the control 20 functions as a compact and simple control for the bake and broil operations as described above.

Operation of the two burner oven system including the safety valve 22 and the control will be apparent to those skilled in the art from the preceeding detailed description. Briefly, in the off position gas is supplied only to the

continuous pilots

26 and 42. In this position the control knob 34 is locked and gas does not flow to the safety valve or to the

control pilots

24 and 40.

In bake operation, the knob 34 is depressed and turned in a counter clockwise direction to select a desired baking temperature. Gas is admitted through the passageway '72 into the chamber 62 and the bake pilot valve 8t} is opened. Gas flows to the bake control pilot 24 heating the flame sensing bulb 3t and opening the bake safety valve 52. Simultaneously the additional valve 6t) is closed to assure that no gas is admitted to the broil burner 16 1Q even if the oven temperature rises enough to open the broil safety valve 56. The thermostatic arrangement including the diaphragm 92 opens and closes the bake pilot valve to cycle the bake safety valve 52 and maintain the selected temperature.

For broil operation the control valve is rotated in a clockwise direction to the broil position, whereupon gas is admitted to the chamber 62 through the passage '72. The operating shaft 192 is moved by clockwise rotation of the knob so that the bake pilot valve 80 is positively closed. Gas is supplied to the broil control pilot 4% heating the flame sensing bulb 46 and opening the broil safety valve 56. Valve 6t) is opened in the absence of a flame indication at the bake control pilot 24 and gas flows continuously from the chamber 62 to the broil burner 58. Oven temperature is maintained below a predetermined high limit by the throttling valve $8, or alternatively by the inlet orifice at the broil burner 16.

In the low broil position of the knob 34, the bake pilot valve 363' is again positively held in the otf position, and the unrestricted passage '72 to the chamber 62 is closed. Gas is supplied to the chamber 62 only at a low fiow rate by way of the low rate passageway 1&6, and gas is also supplied to the broil control pilot 4G to hold the safety valve 56 continuously open.

While the present invention has been described in connection with the details of illustrative embodiments thereof, it should be understood that these details are not intended to limit the invention except insofar as set forth in the accompanying claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A control system for an oven having a bake burner and a broil burner, comprising bake and broil pilots, a pilot responsive bake valve having an inlet and having an outlet connected to the bake burner, a bake sensor adjacent said bake pilot and operably connected to the bake valve for admitting gas to the bake burner only in response to heat sensed adjacent the bake pilot, a pilot responsive broil valve having an inlet and having an outlet connected to the broil burner, a broil sensor adjacent said broil pilot and operably connected to the broil valve for admitting gas to the broil burner only in response to heat sensed adjacent the broil pilot, a single control knob movable to bake and broil positions, a control valve connected to said pilots and to said bake valve inlet and controlled by said control knob for supplying gas at high flow rates to said bake valve inlet in both the bake and broil positions of the control knob, said control valve including means for supplying gas to produce flame indications at the bake and broil pilots respectively in the bake and broil positions of the control knob, and an additional valve connected between said bake valve inlet and said broil valve inlet and operably connected to said bake sensor for admitting gas to the broil valve inlet only in the absence of a flame indication at the bake pilot.

2. A control system for an oven having first and second main burners comprising:

a pilot burner;

a burner selector control in communication with said pilot burner and inciuding means for providing a flame indication at the pilot burner only when it is desired to operate said first burner;

sensing means disposed adjacent said pilot burner for detecting a flame indication at said pilot burner;

means for supplying a flow of gas for said first and second burners;

a first valve connected in flow controlling relation between said supplying means and the first burner;

a second valve connected in flow controlling relation between said supplying means and the second burner;

and valve closure means engageable with said first and second second valves and operably connected to said sensing means for closing said first valve in the ab sence of a flame indication at said pilot burner and closing said second valve when a flame indication is detected at said pilot burner.

35. The control system of claim 2, said first and second valves comprising a single housing having a common inlet and having first and second outlets, a valve seat surrounding each outlet, said seats being substantially parallel to one another and spaced apart in a direction normal to said seats, and a pair of oppositely facing valve sealing surfaces mounted for simultaneous movement between said seats for closing one or the other of said seats.

4. A control valve for use with a gas oven system of the type having a broil burner and a bake burner, a control pilot associated with each burner, and normally closed safety valve means for each burner operable to permit gas to flow to the burner in response to a flame indication at the corresponding control pilot, said control valve comprising:

a housing defining a chamber;

a first valve for controlling the admission of gas from a gas supply to the chamber;

manually opera le means comprising a knob rotatable in one direction from an off position to a broil position and in the other direction from off to a bake position and connected to said first valve for admitting a substantially unrestricted flow of gas to said chamber in the bake and broil positions;

a main gas outlet from said chamber for supplying gas to the burners via the safety valve means;

a broil pilot passageway extending from said first valve for supplying gas to produce a flame indication at the broil control pilot;

means associated with said first valve for opening said broil pilot passageway in the broil position of the manually operable means;

a bake pilot outlet from said chamber for supplying gas to produce a flame indication at the bake control pilot;

bake pilot valve means for controlling flow through said bake pilot outlet and including a valve seat adjacent said bake pilot outlet and a valve member cooperating with said seat to open and close the bake pilot valve means;

and control means associated with said manually operble means for opening said bake pilot valve means in the bake position and for closing said bake pilot valve means in the broil position;

said control means including lever means connected to said valve member for moving said valve member away from said seat as said knob is rotated toward bake position and for moving said valve member against said seat as the knob is rotated toward broil position.

5. A control valve as claimed in claim 4, further comprising means releasably locking the knob in the off position.

6. The control valve of claim 4, oven temperature responsive means connected to move said lever means to cycle said bake pilot valve means during bake operation; and overtravel means disposed between said lever means and said knob for holding said bake pilot valve means in a closed position at all temperatures during broil operation.

'7. The control valve of claim 4, further comprising an additional passageway extending from said first valve to said chamber and having a small cross sectional area for supplying a low rate gas flow;

said manually operable means being movable to a low broil position;

and means associated with said first valve for opening said additional passageway and said broil pilot passageway and for blocking said substantially unrestricted flow in the low broil position.

8. The control valve of claim '7,

thermostatic means responsive to oven temperature;

means connected between said thermostatic means and 12 said bake pilot valve for cycling said bake pilot valve to maintain a bake temperature by cycling operation of the bake burner during bake operation; and

an additional valve controlling the flow of gas through said main gas outlet and controlled by said thermostatic means to throttle the gas flow when the oven temperature approaches a predetermined high broil temperature.

9. A control valve for use with an oven system of the type having an upper broil burner and a lower bake burner, a control pilot associated with each burner, and normally closed safety valve means for each burner operable to permit gas to flow to the burner in response to a flame indication at the corresponding control pilot, said control valve comprising:

a valve body having a valving surface;

a gas inlet passageway extending to said valving surface;

a main gas outlet passageway extending from said valving surface for supplying gas to the bake and broil burners via the safety valve means;

a valve member having a valve face sealingly and movably engaged with said valving surface;

manually operable means connected to said valve member for moving said valve member between off, bake, broil and low broil positions;

said valve face closing said main gas outlet passageway in the olf and low broil positions of the valve memher;

a recess in said valve face communicating with said inlet passageway in the bake, broil and low broil positions of the valve member and communicating with said main gas outlet passageway in the bake and broil positions of the valve member;

a broil pilot passageway extending from said valving surface for supplying gas to produce a flame indication at the broil control pilot;

said recess communicating with said broil pilot passageway in the broil and low broil positions of the valve member;

and a low broil passageway extending from said valving surface and communicating with said main gas outlet passageway and having a small cross sectional area for delivering a low rate gas flow;

said recess communicating with said low broil recess in the low broil position of the valve member.

10. The control valve of claim 9, further comprising an outlet chamber receiving the gas flow from said main gas outlet passageway and from said low broil passageway;

an outlet port extending from said outlet chamber for supplying gas to the burners via the safety valve means;

a bake pilot passageway extending from said outlet chamber for supplying gas to produce a flame indication at the bake control pilot;

a bake pilot valve controlling the flow of gas through said bake pilot passageway;

and means connected between said manually operable means and said bake pilot valve for closing said bake pilot valve in the broil and low broil positions of said valve member.

11. The control valve of claim 10, further comprising thermostatic means responsive to oven temperature for cycling said bake pilot valve between open and closed positions to produce a cycling flame indication at the bake control pilot during bake operation, thereby effecting cycling operation of the safety valve means for maintaining a predetermined bake oven temperature.

12. The control valve of claim 11, further comprising means coupled between said manually operated means and said bake pilot valve for adjusting the predetermined oven temperature for bake operation.

[3. The control valve of claim 12, further comprising an outlet valve controlling the flow from said outlet chamber through said outlet port, and means coupled between said outlet valve and said thermostatic means for thermostatically throttling the flow through said outlet port when the oven temperaure approaches a predetermined broil temperature, thereby preventing the oven temperature from exceeding the predetermined broil temperature under any condition.

14,. A gas oven system comprising:

a first burner and a second burner;

a first pilot and a second pilot;

control means having a main gas outlet and including means for controlling gas flow through said outlet for the first and second burners, said control means being in communication with said first and second pilots and including means for producing a flame indication at the first pilot when it is desired to operate the first burner and for producing a flame indication at the second pilot when it is desired to operate the second burner;

normally closed first safety valve means connected between said outlet and said first burner for controlling the admission of gas to the first burner;

first heat sensing means responsive to heat near said first pilot for opening said first safety valve means in response to a flame indication at the first pilot;

normally closed second safety valve means connected between said outlet and said second burner for controlling the admission of gas to the second burner;

second heat sensing means responsive to heat near the second pilot for opening said second safety valve means in response to a flame indication at the second pilot;

and an improvement for preventing the simultaneous admission of gas to the first and second burners, said improvement comprising:

an additional valve connected in series flow relationship with said second safety valve means for controlling the gas flow to the second burner;

and means including said first heat sensing means for maintaining said additional valve closed when a flame indication is sensed at the first pilot.

15. The system of claim 14, further comprising a housing having two spaced valve seats, said first safety valve means comprising one of the seats and said additional valve comprising the other of the seats, and valve closure means controlled by said first heat sensing means and movable with respect to the two seats alternately to close one or the other of said first safety valve means and said additional valve.

16. Safety valve apparatus for use with a gas oven of the type having first and second main burners, a pilot for each burner, a sensor for each pilot and a control system for providing a main gas flow for the burners and for producing a flame indication at the first pilot in order to operate the corresponding burner, said apparatus comprising:

a valve body having an inlet for receiving the main gas flow from the control system;

first and second valve seats in said valve body;

a first outlet for supplying gas to the first burner and communicating with said inlet via said first valve seat;

a second outlet for supplying gas to the second burner and communicating with said inlet via said second valve seat;

valve closure means alternatively engageable with said first and second valve seats and controlled by the first pilot sensor for closing said first outlet and open ing said second outlet in the absence of a flame indication at the first pilot; and

said valve closure means being operable to close said second outlet and open said first outlet when a flame indication is sensed at the first pilot.

17. The apparatus of claim 16, further comprising means for producing a flame indication at the second pilot in order to operate the second burner, and an additional, normally closed valve for controlling the flow from said second outlet to the second burner, and. means for opening said normally closed valve when a flame indication is sensed at the second pilot.

1%. A safety valve for use in a heating system including two burners and a pilot burner, said valve comprising:

a housing having an internal cavity;

an inlet in said housing in continuous communication with said cavity and adapted to be communicated with a supply of fuel;

a pair of outlets in said housing adapted to communicate with said burners;

a heat sensing means adapted to be disposed in heat sensing relation to said pilot burner;

a power element mounted on said housing and communicated with said heat sensing means for movement between first and second positions in response to heating and cooling of said heat sensing means;

a first valve controlling flow through one of said outlets and a second valve controlling flow through the other of said outlets;

and valve operating means coupled between said power element and said first and second valves for opening only one of said valves in each position of said power element.

1.9. The valve of claim 18, said valves each including a valve seat surrounding one of said outlets, said valve seats being substantially parallel to one another and being spaced apart in a direction normal to said valve seats; and a pair of valve closing surfaces fixed together for simultaneous movement between first and second positions for engaging said first and second valve seats respectively.

26'. The valve of claim 19, said valve operating means comprising a lever pivotally mounted within said housing and extending from said power element to a region adjacent said valve seats.

21. Safety valve apparatus for preventing gas from flowing simultaneously to first and second burners in a heating system of the type in which a flame indication is produced at a corresponding pilot burner only when it is desired to operate the first burner, said safety valve apparatus comprising:

a housing means having an inlet adapted to be communicated with a supply of gas;

first and second outlets for supplying gas to the first and second burners;

fiame detecting means for detecting the presence and absence of a flame indication at the pilot;

a first valve communicated between said inlet and said first outlet and a second valve communicated between said inlet and said second outlet;

and valve operating means coupled between said fiame detecting means and said first and second valves and controlled by said flame detecting means for (a) opening said first valve and closing said second valve in response to the presence of a flame indication at the pilot and (b) closing said first valve and opening said second valve in response to the absence of a flame indication at the pilot.

References Cited UNITED STATES PATENTS 3,232,534 2/1966 Branson 236-15 3,236,448 2/1966 Willson 236-45 3,312,396 4/1967 Willson 236---15 ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner.