US2939524A

US2939524A - Control system for gas burners

Info

Publication number: US2939524A
Application number: US681111A
Authority: US
Inventors: John B Mathis; Earl D Hillebrand
Original assignee: Geo D Roper Corp
Current assignee: Geo D Roper Corp
Priority date: 1957-08-29
Filing date: 1957-08-29
Publication date: 1960-06-07
Anticipated expiration: 1977-06-07

Description

June 7, 1960 Filed Aug. 29, 1957 .1. B. MATHIS ET AL 2,939,524

vCONTROL SYSTEM FOR GAS BURNERS 3 Sheets-Sheet l jzza/erizsa s 908a? 3111a??? 60x6 D /zfzfebrozai.

June 7, 1960 J. B. MATHIS ET AL 2,939,524

CONTROL SYSTEM FOR GAS BURNEIRS Filed Aug. 29, 1957 3 Sheets-Sheet 2 June 7, 196 0 J. B. MATHIS ETAL 2,939,524

CONTROL SYSTEM FOR GAS BURNERS Filed Aug. 29, 1957 3 Sheets-Sheet 3 M5 y Mart/zw fi aeeeabrmd CONTROL SYSTEM FOR GAS BURNERS John B. Mathis and Earl D. Hillebrand, Chicago, -Ill., assignors to Geo. D. Roper Corporation Filed Aug. 29, 1957, Ser. No. 681,111

1 Claim. 01. 158-141) The invention relates to the control of the fuel supply for gas burners and it is more particularly concerned with fuel supply systems in which burner operation is auto- .matically regulated to maintain the space or object heated by the burner at predetermined temperature levels.

Systems of the above general character conventionally employ temperature responsive means for regulating the amount of gas supplied to the burner to vary its heat output in accordance with the temperature of the space or object being heated. In order to provide the required accuracy of control, such devices are usually arranged to regulate the fuel supply by a gradual throttling or modulating action. y

Most gas burners in general use are capable of maintaining combustion, that is, of sustaining a flame, with the gas supply throttled down to approximately to of the rated capacity of the burner. Upon further throttling or reduction of the gas supply, the flame becomes extinguished and, of course, the unburned gas is discharged through theburner ports. When it is considered that a burner used for gas heating may have a capacity of 200,000 B.t.u. per hour and that an average gas range top burner may have a capacity of 12,000 B.t.u. per hour, it will be evident that a very dangerous condition may develop when such throttling controls are employed with gas burners operating indoors.

One object of the present invention is to provide controls which eifectively eliminate the above mentioned objectionable and dangerous conditions in the operation 'of thermostatically regulated gas burners.

A more specific object is to provide an improved safety shut-01f valve for use with burners supplied with gas under thermostatic control which automatically terminates all gas flow to the main burner when the available supply is reduced below the level required to sustain a flame at the burner.

Another object is'to provide a safety shut-off valve for thermostatically controlled gas burners which snaps into full open position substantially instantaneously when sufficient gas is available for safe operation of the burner and which returns to closed position with equal promptness .when the gas supply falls below the safe operating level.

Another object is to provide novel control means for shutting ofi a main burner when the gas supply is reduced to a predetermined level and for thereafter providing modulated control of a simmer burner whereby to extend the range of modulating control.

A further object is to provide a safety shut-off valve of the above general character embodying novel means for adjusting the shut-0E point of the valve.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred form and modifications illustrated in the accompanying drawings, in which: Figure 1 is adiagrammatic view of a thermostatically regulated gas burner'installation equipped with a safety Patented June 7 1960 shut-off valve embodying the features of the invention, the control valve of the system being shown in the o position.

Fig. 2 is a view similar to Fig. 1 showing the control valve open for delivering a maximum supply of gas to .of the invention, the valves and burner being shown in high flame position.

Fig. 5 is a view of the burner installation shown in Fig. 4 with the thermostatically controlled valve set to throttle the gas supply below the level required to sustain a flame at the main burner.

Fig. 6 is a diagrammatic view of a thermostatically controlled gas burner installation equipped with another modified form of safety shut-off valve embodying the features of the invention, the valves and burner-being shown in the high" flame position. i

Fig. 7 is a diagrammatic view of the burner installation shown in Fig. 6 with the thermostatically controlled valve set to throttle the gas supply below the level required to sustain a flame at the main burner.

For purposes of illustration the invention has been shown as incorporated in the fuel supply system for a main gas burner =10 and a simmer burner 11 which system includes a manually settable thermostatically actuated modulating type control valve Va The small simmer burner 11 is a small, auxiliary burner supported in proximity to the main burner. A constantly burning pilot light 12 serves to ignite both burners when the gas is turned on. r

Theburner 10 may be of any preferred construction, that shown being a conventional top burner of the type used in kitchen ranges. It has an elongated mixing chamber 13 with a gas and air inlet opening 14 at one end. The mixing chamber opens into a central distributing chamber 15 having a series of portsat which the issuing gas, and air mixture burns. 'Usually such burners are supported on the stove structure below a grate ortthe like provided for supporting a utensil 16for other object Thus, while the burner 10 may be designed for a heat output of 12,000 B.t.u. per hour, the burner 11 will generally be designed for a heat output of not more than 1,000 B.t.u. per hour since its primary function is to maintain the temperature of a utensil and its contents initially heated to a desired temperature by the main burner. Pilot light 12 as shown comprises a single small orifice at the end of a supply tube for maintaining an open flame in the vicinity of the

burners

10 and 11. It will be appreciated that other arrangements for lighting the burner may be employed.

Gas is supplied to the main burner 10 and the simmer burner 11 from a gas line or manifold 17 under control Octo'ber 25, 1954, now Patent No. 2,862,667, andas- "signed to the assignee of the instant application.

temperature sensing element.

ber is rotated to different positions. A knob or handle 23 is provided on the valve member for manual rotatable setting of the same.

' From the valve chamber 21, gas is discharged through a port 24 into a secondary valve chamber 25 from which it' passes by way of an outlet conduit 26 to the gas burners'with which the valve V is associated. Flow of gas through the port 24 is controlled by a valve member 27 movable toward or from the port by temperature re sponsive means positioned to react to the temperature of the utensil or space being heated by the burner. It will be understood, of course, that when used with burners designed for heating ovens or for other space heating purposes the temperature responsive means will be positioned to react to the temperature of the heated space.

The temperature responsive means may be of any preferred type, that shown comprising a liquid or gas filled expansible element or bellows 28 connected by a tube 29 with a temperature sensing bulb 30. In the particular installation illustrated, the bulb 30 is mounted in a position to establish contact with the bottom of the utensil supported in position to be heated by the burner 10 but shielded from the direct influence of the burner flame.

Provision is made for variably setting the temperature responsive means or the valve member actuated by it so that the valve member 27 is automatically positioned to throttle the gas flow through the valve port 24 as required to maintain a predetermined temperature at the In other words, the valve mechanism is adjusted so that the gas issuing from the port 24 is regulated in accordance with the heat output required from the burner to maintain the utensil and its contents at a selected temperature The regulation thus attained is progressive or modulated, that is, the gas flow is throttled down to a greater or less extent as required, although seldom completely interrupted under normal operating conditions. When a relatively small amount of heat suifices to maintain the desired temperature, the throttling action may reduce the gas supply below the level required to sustain a flame at the burner. This is particularly likely to occur in case the water or other liquid in the utensil boils ofi, leaving only the pan and solid contents to absorb the heat producedby the burner.

In accordance with the invention safety shut-ft means is provided for automatically interrupting all delivery of gas to the main burner when for any reason the amount supplied from the control valve is reduced below the level required to sustain a flame at the burner. This means, as shown, comprises a valve V1 adapted to be interposed between the control valve V and the burner and operative to open or close in accordance with the volume of gas supplied from the control valve. More particularly, the shut-off valve is constructed and arranged so that it opens and remains open when the volume of gas supplied is suflicient for the burner to operate but automatically closes and remains closed when the volume ,of gas supplied is reduced below the flame sustaining level. V

.body 35 formed with an outwardly turned flange 36 around its open upper end. A partition 37 divides the valve body into two

chambers

38 and 39. In the exemplaryvalvegchamber 38 is the inlet chamber and has an opening for connecting with the conduit 26 through which gas is supplied from the control valve V. Chamber 39 is the outlet chamber and has an outlet opening through a conduit 40. Conduit 40 extends to the mixing tube 13 of the burner 10 and has a restricted discharge orifice 41 operative to meter the flow of gas to the burner and to direct it in the form of a jet into the open end of the burner mixing tube.

Communication between the inlet chamber 38 and the outlet chamber 39 is by way of a port or passage 42 opening upwardly through the partition 37. Preferably the port is encircled by an upstanding wall 43 which may be formed integrally with the partition. Gas flow through the passage is controlled by a valve member in the form of a flexible diaphragm 45 supported in overlying relation to the passage. The diaphragm, which may be of rubber or other suitable flexible material, is clamped in place between the flange 36 on the valve body and a complemental "flange formed on a cup-shaped cap 46 rigidly secured to the valve body in any preferred manner. The

cap is conveniently vented as at 46 to prevent entrapped air from interferring with the movements of the diaphragm.

To insure tight seating of the diaphragm against the wall 43 and thus complete closure of the passage 42, the upper edge of the wall is beveled to present a sharp edge for engagement by the diaphragm. Additionally, a weight 47 is secured to the diaphragm above the passage. Preferably the weight is shaped, dimensioned and positioned on the diaphragm so that it extends over the edge of the wall 43 to press the diaphragm tight against the wall when the pressure in the chamber 38 allows the valve to close It will be understood that the weight 47 is selected to provide for the closing of the passage 42 upon apredetermined reduction of the pressure in the chambers 38 and 39due to reduced supply from the controlvalve V.

With the construction shown, only the limited area of the diaphragm 45 directly overlying the passage 42 'is exposed to the pressure obtaining in the chamber 38 the chamber 39 drops rapidly due to the continuous discharge through the orifice 41 to the burner. Accordingly, the total force acting on the diaphragm is quickly reduced, allowing the valve to close with a snap action.

To render the valve V1 responsive to the rate at which gas is supplied from the control valve, provision is made 'for continuously bleeding ofi gas from the inlet chamher 38 at a rate substantially equal to that at which the shut-01f or closing of the valve is desired. Thus, pressure build-up in the chamber 38 is avoided even though gas continues to flow through the control valve at the reduced rate called for by the temperature sensing means.

In the exemplary valve the chamber 38 has a bleed port 48 opening to a conduit 49 which conveys the gas to a suitable discharge point. In the particular installation shown, the conduit 49 discharges the gas to the simmer burner 11 which .thus remains in operation after the main burner 10 is shut .oif. An orifice 50 at the discharge end of the conduit 49 restricts flow of gas to a desired rate and assists in maintaining proper distribution'of gas to both burners when both are in operation.

The operation of the burner controls will be readily apparent .from the foregoing. Both burners may be shut ofi by turning the valvem'ember 22 to the closed ber 21.

assess;

position shown in Fig. 1. Under such conditions the valve V1 closes while the thermostatically controlled valve member 27 is shifted to the full open position by the cooling of the temperature sensing element 30.

Assuming that the utensil 16 and its contents are to be rapidly heated to a predetermined temperature and then maintained at that temperature for an extended period, the desired temperature is selected by screwing the valve member 27 toward or from its actuating element .28. Such adjustment is made by manual rotation of a stem 27' which extends through the knob 23 for that purpose.

With the utensil supported above the burner in contact with the temperature sensing element 30, control valve member 22 is turned to the open position thereby initiating flow of gas from the line 17 to the valve cham- The valve member 27 .being in open position, gas passes through the port 24, chamber 25 and conduit 26 to inlet chamber 28 of shut-off valve V1. A portion .of this gas. is diver-ted through the bleed port 48 and conduit 49 to the simmer burner which is lighted by the continuously burning pilot light 12.

Orifice 50 in the conduit 49 limits the flow of gas through the bleed port to the rated capacity of the simmer burner. -Since gas is supplied from the control valve V at a rate corresponding to the rated capacity of both burners, the pressure in the chamber 38 will rise quickly until the diaphragm'45 is lifted from the wall 43. Gas then enters the chamber 39 through the passage 42 and quickly lifts the diaphragm to the full open position shown in .Fig. 2, allowing gas to flow to the burner 10 at the maximum rate permitted by the orifice 41. The burner 10 is lighted'by the pilot light 12 or the simmer burner 11 and heating of the utensil 16 begins.

. As the temperature of. the utensil and its contents :approaches the value for which the thermostatically controlled valve has been set, the valve member 27 is shifted toward the closed position to gradually throttle down the gas supply and reduce the heat output of the burner 10. Gas pressure in the shut-ofi valve decreases proportionately. If the heat demand on the burner, that is, the heat required to maintain the utensil and its contents at the selected temperature, is suflicient to require more than the minimum amount of gas at the burner 10 the shut-off valve remains open and the burner continues in operation. However, if the heat demand on the burner falls below the level at which the amount of gas supplied is insufficient to sustain a flame at the burner, the diaphragm 45 snaps into closed position and positively shuts off gas flow to the main burner. All of the gas supplied through the control valve is then directed to the simmer burner which continues in operation at a rate determined by the position of the thermostatically controlled valve.

As the simmer burner is quite small as compared to the main burner, the gas supply will seldom if ever be throttled down below the flame sustaining level. If that should occur due to some abnormal condition such as the utensil boiling dry, unburned gas may be discharged from the burner but in an amount too small to be objectionable or dangerous.

Figs. 4 and show a modified form of safety shut-off valve V1,, operating in the same manner as the valve V1 to shut off gas flow to the main burner when the supply available is insufiicient to sustain a flame at that burner. This shut-off valve is adapted to be interposed between the control valve V and the burner in precisely the same manner as the valve V1 previously described. As shown, the valve V1 comprises a casing 35,, divided by a partition 37, into an inlet chamber 38,, and an outlet chamber 39,. Inlet chamber 38,, is connected to receive gas from the valve V by way of the conduit 26 and outlet chamber 39,, is connected to discharge gas through the conduit 40 to the mixing chamber 13 of the main burner. Inlet chamber 38,, also has a 6 r V a bleed port 48,, adapted to bypass a predetermined amount of gas from the inlet chamber to the simmer burner 11 by way of the conduit 49.

A passage 42,, in the partition 37,, affords communication between the inlet and outlet chambers of the safety valve. Flow of gas through this passage is con-trolled by a valve member 45,, herein shown as a thin flat plate or disc of substantially greater area than the passage 42 and disposed in overlying relation to the passage. Provision is made for supporting the valve member for movement toward and from the partition with a snap action to open or close the passage. A spring 47,, biases the valve member toward the closed position.

To enable the valve member to respond quickly to pressure changes in the valve casing, the member has its outer face fixed to the forward end of a cup-shaped bellows element 46,, supported in the outlet chamber as by a perforated partitioning plate or spider 49,,. The bellows is preferably vented to the atmosphere as shown (50,,) and the spring 47,, is just strong enough to close the valve member 45 under zero or low flow conditions.

Consequently, spring 47,, will act to hold the valve member in closed position until the pressure of the gas in the inlet chamber 38,, increases to a value sutficient to overcome the force of the spring and thus move the valve member toward open position. Upon such initial opening of the passage 42,, pressure in the outlet chamber 39,, builds up above atmospheric. This pressure, being greater than the pressure inside the bellows, causes the latter to be compressed, thereby rapidly retracting the valve member to the-fully open position.

When the volume of gas delivered from the control valve V decreases to the extent that it is insufficient to maintain a flame at the main burner, .the pressure in the outlet chamber decreases, thus allowing the bellows to expand. This, with the help of the spring 47 causes the valve member 45, to return to closed position, thus completely and positively interrupting all gas flow to the burner 10. As long as the gas flow to the safety valve continues at the reduced level, sufficient gas is bled 01? or bypassed to the simmer burner to prevent a pressure rise in the inlet chamber of the safety valve and the shut-01f valve remains closed. An increase of gas flow above the minimum flamevsustaining limit reopens the valve passage 42 and restores the main burner to operation.

The safety shut-off valve V1, shown in Figs. 6 and 7 of the drawings, utilizes the same partitioned casing 35 and diaphragm 45 as the valve V1 previously described. In this case, however, the weight 47,, secured to the diaphragm 45 is made of magnetic material. Supported below the weight within the passage 42 is a permanent magnet 43,, positioned to exert an attracting force on the weight 47,, in a direction to urge the diaphragm into closed position.

Magnet 43, is conveniently supported on a threaded stem 44,, received in a threaded socket 46 A knob 47 provided on the lower end of the stem is readily accessible for manual manipulation whereby the magnet may be shifted toward or from the weight to vary its biasing effectiveness. Thus, a simple easily operated adjusting mechanism is provided for regulating the shutoff point of the valve, that is, the pressure level at which the diaphragm 45 is effective to close the passage 42. Since the attractive force exerted by the magnet varies inversely with its distance from the weight, the snap ac- '7 down to its lower operating limitof approximately 1700 B;t.u. per hour. Withthe novel arrangement for controlling the gas supply whom the main burnerand an adjacent simmer burner having a rated capacity of from 1000 to 1200 B.t.u. per hour, reliable modulating control is extended close to the lower operating limit of the smaller burner, as, for example, to approximately 350 B.t.u. per hour or less. This permits accurate'regulation of utensil temperatures down to about 160 F. and elimination of the danger of burning or scorching of cooking food left unattended on. the burners.

The above embodiments, in addition to their safety feature, afford greater economy plus a wider modulating range than conventional controls. In conventional thermostatic gas controls, after the flow'has been modulated down to, say, 1000 B.t.u. per hour, the flow of gas goes on and leakage of unburned gasoccurs until such time as more heat is called for; Withcontrols provided by the instant invention," modulation continues down to a flow of approximately 350 B.t.u. per hour or even lower, i.e., below the cooking level. "The controls may be used, of course, with a' main control valve of the type having a fixed'by-pass insuring at least a minimum supply of gas to the simmer burner below modulating levels in which case the'fiame never goes out. in any case, however, no gas is'discharged tothe atmosphere until it has been usefully burned.

While the invention has been described in connection with a main and simmer burner organization in which the inlet chamber is vented through the simmer burner, it will be apparent from the above teachings that it may be employed in its broader aspects 'in burner organization in which the chamber is vented to an auxiliary burner or vent remote from the main burner. 3

Also, changes may be madein'the main or control valve without departing from the invention; for example, such valve may be constructed to provide manual throttling from the manifold to the inlet chamber without any thermostatic control. Alternatively, the main valve may be entirely thermostatic in action without any manual control, provision being made elsewhere in the system for shutting off the gas supply when necessary. The important thing is the novel provision for positive shut-off of the main burner under low flow conditions.

It will be apparent from the foregoing that the invention provides controls of novel and advantageous char- 8 acter which efliectively eliminate .the possibility of discharge'of unburned gases from 'a. thermostatically "regulated burner when the gas supply is throttled down below the level required to sustain a flame. jThe controls are simple,'yetefl"1cient,' and efiectively eliminate one of the major objections J heretofore urged against the application of thermostatic controls to gas burners.

We claim as our'invention:

In a gas stove, the combination comprising a source of gas, a main burner and a simmer burner, means defining a. gas pressure chamber, means including an automatic control valve interposed between said gas source and said chamber for throttling admission of gas to the chamber -modulated in accordance with the temperature of. acooking utensil .positionedj'to be heated by said burners,'a safety shut-off valve interposed between said pressure chamber and said main burner, said shut-off valve being constructed and'arranged to open fully when the pressure in the chamber rises to a predetermined value.and to close completelywhen the pressure in the chamber drops to'a predetermined lower value whereby. to shut off'flow of gasto the main burner under .low demand conditions, said simmer burner being'connejcted'to said chamber and continuing to operate at a modulated rate under low demand conditions when said'auxiliary valve is closed thereby preventing build-up of pressure in'the chamber during continuanee of the low demand conditions, said main burner being sufficiently close to said simmer burner to insure positive reignition upon opening of said auxiliary valve incident to a major increase in demand.

References Cited in the file of this patent UNITED STATES PATENTS 960,057

Great Britain Nov. 21, 1956