US2139344A - Gas control system - Google Patents

Gas control system Download PDF

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US2139344A
US2139344A US52009A US5200935A US2139344A US 2139344 A US2139344 A US 2139344A US 52009 A US52009 A US 52009A US 5200935 A US5200935 A US 5200935A US 2139344 A US2139344 A US 2139344A
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valve
burners
gas
pipe
diaphragm
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US52009A
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Christian S Andersen
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Pennsylvania Furnace & Iron Co
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Pennsylvania Furnace & Iron Co
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23NREGULATING OR CONTROLLING COMBUSTION
    • F23N1/00Regulating fuel supply

Description

Dec. 6,19%. c. s. ANDERSEN GAS CONTROL SYSTEM Filed Nqv. 29, 1955 2 Sheets-Sheet l INVENTOR CHRISTIAN S. ANDERSEN FIG-2 A TTORNEYJ C. S. ANDERSEN GAS CONTROL SYSTEM Dec. 6, 1938.
2 Sheets-Sheet 2 Filed Nov. 29, 1935 a w m 4 0 w 3 1 .w J a M 4 m 2 4, w w a 7 a r w m u G w. 6 I 4 .r v 0 n A. a M m m w J W a a i r J Q d a w a I Q LF w m 0M h v F 1 Q INVENTOR CHRISTIAN S..ANDER5EN FlG.-6
ATTORNEYS Patented Dec. 6, 1938 um'rso STATES PATENT OFFICE GAS CONL srs'ricu Application November 29, 1935, Serial No. 52,609
2 Claims.
This invention relates to the control of gaseous fuel supplied to gas burners, such as are used for heating domestic hot water heaters, or furnaces, boilers or other space heating equipment.
One object or" the invention is to provide a gas control system of the character described which is safeguarded from all standpoints, because all gas supply is out off to the main, pilot, and safety pilot burners in case of either intentional or accidental extinguishment of the flame, or of an abnormal drop in pressure of the gas supply, in any of which situations a manual operation is required in order to supply gas to the safety pilot, coupled with its ignition, before as can flow to the other control valves or burners.
Another object of the invention is to provide a gas control system of this character which operates by positive pressure of the gas preponiii an derating over atmospheric pressure, which simplifies the connections, the number of operating parts and their functional relationships to each other.
A further object of the invention is to provide llill ally or automatically, compels safe and proper operation of all other parts.
A. further object of the invention is to provide a simple gas control system which is readily controllable either manually when desired, or auto matically by the room temperature, or by any desired boiler or furnace function, such as boiler water level, steam pressure, water temperature or the like.
A further object is to provide a system of this character which provides convenient dual control of a Water boiler, a furnace or any heating equipment operated by the burners, with the burners arranged in two or more groups which are successively thrown into and out of operation at various temperatures as conditions vary, all for the purpose of avoidingthat undesirable low temperature of the space or device to be heated which occurs when the only regulation of the heating equipment is by simultaneously turning all burners on or oil with consequent hunting or unstable conditions.
Sill
a gas control system which dispenses with all leal;
(if/i. tid -1) Further objects of the invention are in part obvious and in part will appear more in detail hereinafter.
In the drawings, Fig. l is a'diagrammatic view illustrating one embodiment of the invention;
Fig. 2 is a detail sectional elevation of the master control valve and its diaphragm;
Fig. 3 is a detail sectional elevation oi the main valve and its diaphragm;
Fig. 4 is a detail section on the line l-- l, Fig. 1, illustrating a gas connection;
Fig. 5 is a detail sectional view illustrating a restricted orifice for controlling the gas supply;
Fig. 6 is a detail sectional elevation of a safety pilot burner and valve; and
Fig. 7 is a diagrammatic view, corresponding to Fig. l, and illustrating a modified arrangement of the parts.
in the drawings, for simplicity of illustration, no device to be heated is illustrated, the drawings showing only several burners together with the gas supply and control features therefor, but without such. illustration it is to be understood that the burners may be of any suitable form or character and arranged to heat any lrirld or character or device, such as the coil or heating unit of a domestic hot water heater, or said burners may be located in. the fire chamber of a hot air furnace or in the fire box of a vapor, steam or hot water boiler or the like. For example, the device to be heated may be a hot air furnace of the general type illustrated, described and claimed in a copencling application of Horace A. Crary for Furnaceconstruction, filed of even date herewith, Serial No. 51,988, to which reference may be had for a more complete descrip tion, if desirable or necessary.
The control system shown in the drawings is designed to control the supply of gas to a plurality, any suitable number, of groups of primary burners, the drawings showing for this purpose a group of two main burners l, and a group of secondary burners 2, only one of which is shown, although any number of burners may be used in either group and more than two groups may be employed. The gas supply comes from a supply main it through an ordinary pressure regulating diaphragm valve t, beyond which is a pipe 5 leading to a main supply valve 8 and by way of pipe 11 to a master control valve 8. From the main supply valve 6 the gas flows by way of the manifold 9 and standard gas cocks ID to the primary burners l of the first group, while beyond the master control valve 8 the gas flows by way of pipe II and cook l2 to the secondary ill burners 2 of the second group. For convenience and for the purpose of locating the connections to all burners in the same horizontal plane, the pipe passes directly through the manifold 8 but without communicating. with the passage therein, as shown in detail in Fig. 4.
Main supply valve 8 has the stem of its movable valve part connected to a daphragm i3 in a casing l4, the chamber l5 beneath said diaphragm communicating with a pipe IS. The movable part of the master control valve 8 likewise has its stem connected to a diaphragm l1 in a casing l8, the chamber l9 beneath which communicates with a pipe 20. The chambers above all diaphragms, including diaphragms l3 and H,- as well as the chamber above the diaphragm controlling the pressure regulating valve 4, all communicate freely with or are vented to atmosphere, preferably by way of branches from a pipe 2| communicating with the combustion chamber so as to charge into it and thence to the stack any gas which might accidentally escape as the result of a leaky diaphragm, or for any other reason.
The gas flowing through the master control valve 8 is utilized not only to supply the secondary burners 2, in case the latter are used, but also to supply gas for controlling purposes. That is to say, the chamber of valve 8, on the discharge side of said valve, communicates by way of a pipe 22 and stop cook 23 with a suitably restricted orifice 24 through which gas may fiow to pipe 28 and also by way of pipe 25 and its branches 25' to one or several, two being shown, of suitably located pilot burners 28, 26'. One of the branch pipes 25' communicates with a combined safety pilot burner and valve marked generally 21 in Fig. 1 and illustrated in detail in Fig. 6. This combined unit includes a casing 28 having a chamber 29 communicating. with pipe 25', said chamber containing a spring 38 effective to hold to its seat a valve 3| controlling one or a plurality of burner openings 32, said valve having a stem 33 extending to the outside of the casing and subject to the operating effect of a thermostatic element, such as the bimetallic strip 34, suitably located and arranged so as to be subject to the temperature at or near one of the pilot burners, such as the burner 28' to which it is shown attached. The bimetallic strip is so arranged that when it is heated either by a flame applied to it by hand or by heat communicated to it from the pilot burner, its free end flexes to the left in Fig. l and permits the valve 3| to close and cut oif the flow of gas from the pipe 25 to the burner ports 32. extinguishment of pilot flame, then the thermostatic element flexes to the right and opens the flow of gas to the burner ports-32, all subject to control of such fiow by other parts, as will appear.
The chamber on the discharge side of the master control valve 8 also communicates with a pipe 35 in which are located one or several control valves subject to such conditions as it is desired to utilize for control of the main burners For example, the pipe 35 may include an electrically operated valve 36 controlled by a thermostat in the room or space to be heated, a valve 31 sensitive to the temperature of water in the boiler, a valve 38 sensitive to level of water in the boiler or a valve 39 sensitive to the pressure of steam in the boiler, or any combination of such valves.
However, when the parts get cold bythe aforesaid pipe l6 leading to the chamber beneath the diaphragm l3 which controls the main supply valve 6.
. Pipe may also include an electrically operated valve 4| sensitive to the temperature in the 5 room or space to be heated, as will also more fully appear hereinafter.
Master control valve 8 is also provided with a manually operated lay-pass, including a pipe 42 communicating at its opposite ends with the chambers on opposite sides of the movable valve member, said pipe including a self closing valve 43 provided with an operating thumb button 44 which may be depressed to open the valve and hold it open so long as the thumb is held on the button.
Master control valve 8 not only is subject to automatic diaphragm control, as will appear, but is also capable of manual control to either turn it off or to release it so that it may be controlled automatically. For this purpose the easing of its diaphragm supports a rod 45 urged downwardly by a spring 46 to a position in which it holds the movable member or valve 8 to its seat and prevents it from opening, but which rod 45 may be elevated by operation of a cam 41 provided with an operating handle 48, in the usual manner. When the handle. is thrown to the ofi position valve 8 is closed and all gas flow to all valves and burners is cut off, whereas when the handle is thrown to on" position, valve 8 may open under certain conditions and permit gas flow, as will appear.
The operation is as follows: i
Secondary burners 2, together with the pipe and electrically operated valve 4| controlling them, are not essential and may be omitted, as in cases where satisfactory results may be secured by simultaneous operation of all burners, all of which are then included in the group of primary burners I.
Assuming such an arrangement, let us further assume that all parts are cold and that the space or device to be heated is demanding heat. In
that case the thermostatically controlled valve or valves, such as either or both of 38 and 31, are open. It must further be assumed that valve 39 sensitive to steam pressure and valve 38 sensitive to water level, or either of said valves utilized, are open. 50
To provide heat to supply the demand it is necessary to turn on the gas, ignite it and keep it burning. This is accomplished by moving lever 48 to the on position and pressing with the thumb on the button 44 to open the by-pass 42 around valve 8. Gas thereupon flows from the pipe I through valve 8 to pipe 22. Stop cook 23 is manually opened and is permitted to remain open. Gas then flows through the orifice 24 to each of pipes 20 and 25 and thence to the cham- 0 her beneath diaphragm l1 and to the two pilot burners 28, 26' and to the safety pilot 21. All three pilot burners are open and the gas is ignited at these burners. Restricted orifice 24 is of such size as to be incapable of supplying sufficient gas to simultaneously provide full flow through the safety pilot 21 and pilots 26 and 28 and at the same time build up pressure by way of pipe 20 in the chamber I9. As a consequence, the diaphragm H at first does not rise. However, ignition of the safety pilot burner 21 heats the bimetallic strip 34, which ultimately moves over and permits valve 3| to move to its seat, thus but no gas ilows through said valve.
till
26', are open and burning and the additional back pressure through the restricted orifice 24 now available becomes effective through pipe 20 in the diaphragm chamber l9, elevates diaphragm I1 and opens the valve 8. It being assumed that pilot burners 26 and 26' have been ignited, the thermostatic strip 34 will remain flexed, diaphragm I! will remain elevated, and valve 8 will remain open with free flow of gas therethrough. Push button 44 is now released.
Gas will now flow through the valve 8 and by way of pipe and through the open valves 36, 3i, 38 and 39, or such of them as are employed, to the escapement pilot burner and also by way of pipe iii to the chamber i5 beneath diaphragm l3, elevating the latter and opening and holding open the main valve ii. As a consequence, gas now flows to the burners l which are ignited by the pilot burners and continue to burn a full now of gas.
if at any time the pressure in the lines or passing through valve l drops so that the pressure beyond said valve is abnormally low, then said pressure becomes ineffective to support master control valve diaphragm ll, which drops and cuts oil the flow through valve t. Thereupon the gas supplied to each of pipes 22 and 3% is cut oil and pressure is evacuated from the main valve diaphragm chamber ill, so that the main valve it also closes. Gas remaining in the pipes beyond valves ii and t is evacuated through the main burners B, through the escapement burner and through the pilot burners. All burners, both main and pilot, including the safety pilot, go out and ultimately the thermostatic strip moves over and opens the safety pilot valve, It is then necessary, upon a demand for heat, to restart the entire system in the manner before described.
Likewise, if any one of the valves 335, ill, Jill or closes, such as occurs upon termination of the demand of the room thermostat for heat, upon an abnormal rise in steam pressure, upon an abnormal drop in water level, or upon an abnormal rise in water temperature, or any of them, the flow of gas through pipe Lid is out off. Thereupon the pressure in chamber lti beneath the main valve diaphragm is evacuated and main valve ii closes, remaining closed until the valve or valves which caused its closing operation is again opened to cause a'free flow of pressure through pipe 35.
With the arrangement described, it is clear that not only is the main supply valve it sensi tive to the operation of any one or more of the valves lit, 31", fit! and till, for automatic control of the gas burners, but also said valve is subject to the operation of the master control valve ll, which in turn is sensitive to manual control and, thermostatically, to automatic control by the safety pilot, and in case all flames are extinguished either intentionally or accidentally, the supply of gas is cut on not only to the main burners but also to all pilot burners, including the safety pilot, and to all valves and diaphragms.
In case dual control is desirable, the group of secondary burners 2, together with the supply pipe l l and controlling valve ti for such group, may be employed. Here temperature sensitive valves 36 and M are made sensitive, separately, to two thermostats in the room or space to be heated, or to two sets of contacts controlled by the same thermostatic element, or by any other suitable control system so that upon a light demand for heat the secondary burners 2 are first thrown into operation and may continue in oper-' ation for a relatively long period, while the primary burners l are thrown into operation only intermittently and upon a greater demand for heat.
The drawings show conventionally a room thermostatic element operating two sets of contacts 5|, 52. Contacts 5! are electrically connected with the coil of the secondary control valve 4|, while contacts 52 are electrically connected with the coil of the primary control valve 36. The two sets of contacts are so set or adjusted that as the temperature drops first to one value, say 70 F., the contacts 5| are closed, thereby opening valve ti and permitting the secondary burners 2 to ignite. Under mild weather conditions continued operation of these secondary burners, say one or two burners in a bank of nine in all, may sufiice to keep the room nearly at an average temperature of 70. However, if the temperature falls still farther, say to 68, the thermostatic element moves over still farther and finally closes contacts '52, so as to energize the coil and operate valve thereby fully opening pipe 35, permitting pressure to flow to the diaphragm ill, which opens main valve ti and permits the main burners i to ignite.
Therefore, with abnormal drop in temperature all burners are finally turned on and continue to operate until the room temperature rises.
Upon rise in room temperature the reverse operations take place, contacts lit first opening and causing the flow of gas to the primary burners l to be.cut oil, and finally contacts til are opened and the secondary burners 2 are cut oil.
This system avoids overheating during relatively mild weather, such as during the spring and fall, prevents hunting or unstable temperature conditions and reduces the number of operations of the main thermostat and controls which would be necessary if all burners were simultaneously operated. The ultimate efiect is to level out high and low temperature peaks and maintain more nearly uniform the desirable temperature.
Various modifications of the invention will be apparent to those skilled in the art, the invention not being limited to the form shown in the drawings and including all structures within the scope of the claims appended hereto. For example, in the arrangement shown in Fig. l, the master control valve ii and main valve ii are in parallel, as it were, neither of said valves directly supply ing gas to the other. Fig. '2 illustrates a modified arrangement in which the same two valves are in series, the master control valve supplying and controlling the supply of gas to the main valve. Most of the parts illustrated in this view are of the same form as those described in connection with Fig. i, as a result of which they have been given the same reference numbers with the addl-- tion of letter a, so that detailed description of the various parts will be unnecessary.
Referring to Fig. 7, the arrangement illustrated includes two primary burners id and a single secondary burner lla. The gaseous fuel is supplied by way of a main supplypipe to to a standard pressure regulator valve ta from which it flows by pipe to to the master control valve to, beyond which is the main valve to communicating with a manifold to which supplies the primary burners la by gas cocks llla as before. Master control valve 86: and main valve 6a are diaphragm valves of the same form shown in Figs. 2 and 3 respectively, being actuated. by diaphragms in the casings Ma and l8a respectively. 43a is the Gil push button starting valve for the master control valve. It is in a line 42a by-passing valve 8a, beyond which is a pipe 6| communicating by way of the restricted orifice 2441 with a pipe 20a communicating witn the chamber beneath the diaphragm in casing 18a and by way of a pipe a with one or more pilot burners 26a, and with a thermostatic pilot 21a. The chamber beneath the diaphragm in casing Ha communicates by way of a pipe lie with an escapement pilot burner 40a, and with an electrically operated valve 360. which is thermostatically controlled by room temperature or the like in the same manner as the valve 16, the gas supply connection for the valve 360. being by way of pipe 22a communicating with the pipe 60 which connects valves 8a and 8a. The secondary burner 20. is supplied by way of a pipe Ila which also communicates with the pipe 60 and includes an electrically operated valve Ma which is thermostatically controlled by room temperature in the same manner as the valve ll before referred to. The upper chambers of the three diaphragm casings all communicate with the same vent pipe 2la, as before.
With this arrangement the operation is quite like that of the form first described.
Assuming all parts cold and with full demand for heat from both room temperature thermostatic circuits, the master control valve handle 48a is thrown to the on position, as before, manual push button starting valve 43a is pressed to open it, and gas flows to the pilots 26a and to the thermostatic pilot 2111, all of which are lighted. As soon as the thermostatic element at the thermostatic pilot heats up, the thermostatic pilot valve closes and pressure thereupon builds up beneath the diaphragm in casing l8a to open and hold open the master control valve 8a, as before. The push button can then be released. Gas now flows from valve 8a to valve 6a by way of pipe 60. Assuming that both of Valves 36a and a are open, due to heat demand, the operation of said two valves is as follows: Gas flows by way of pipes 22a and lSa to the chamber beneath the diaphragm in casing Ha, raises said diaphragm and opens the main valve 60, so that gas flows to the main burners Ia. Likewise, valve a. being open, gas flows by way of pipe Ila to the secondary burner 2a. Both the primary and secondary burners are ignited and the furnace continues in operation until the temperature rises, whereupon first valve 360 closes and shuts off the supply to the primary burners, following which valve 4 la closes and shuts off the supply to the secondary burners 2a. The operation of the two sets of burners is in sequence and at various temperatures in the manner before described. 11.
the temperature falls, reverse operations take place, the secondary burners 2a being first thrown in and finally the primary burners la being thrown in if the demand for heat becomes greater than can be supplied by the secondary burners 7 alone.
If the thermostatic element at the thermostatic pilot for any reason becomes cold, such as by an emergency failure of gas supply or because the pilots are blown out, then thesafety pilot valve 21!: opens and robs the diaphragm chamber of the master control valve of the pressure being supplied to it, so that the diaphragm falls and valve 8a closes. This operation cuts off the supply to the chamber of the diaphragm for the main valve, which also closes. As a result, all gas supply is shut off not only to the primary and secondary burners, but also to all pilot burners. Upon resumption of the gas supply or detection of the emergency condition, it is necessary to now start the system by operations beginning with actuation of the push button valve 43a, as before.
In both forms described, full automatic control of all parts offers complete protection against any accidents resulting from escaping gas. If the fire is extinguished by draft or for any other reason the automatic controls completely shut off all gas, regardless of all other conditions, and it is impossible to again turn on the gas to the pilots and burners until the safety pilot has first been manually lighted by the use of the push button and the thermostatic element 34 has been heated sufficiently to maintain open the master control valve 8.
Further advantages of the invention will be apparent to those skilled in the art.
What I claim is:
1. Apparatus of the character described, comprising a primary gas burner, a secondary gas burner, master control valve mechanism which supplies the secondary burner and controls the supply to the primary burner, and two thermostatically operated controlling devices sensitive to the temperature in a space to be heated and located in said space adjacent to each other but remote from both burners, one thereof being effective at one temperature and arranged to control the primary burner, and the other thereof being effective at another temperature and arranged to control the secondary burner.
2. Apparatus of the character described, comprising a primary gas burner, a secondary gas burner, main valve mechanism which supplies the primary burner, master control valve mechanism which supplies the secondary burner and controls the main valve mechanism, and two thermostatically operated controlling devices sensitive to the temperature in a space to be heated and located in said space adjacent to each other but remote from both burners, one thereof being effective at one temperature and arranged to control the main valve mechanism, and the other thereof being effective at another temperature and arranged to control the secondary burner.
CHRISTIAN S. ANDERSEN.
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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2453382A (en) * 1942-05-12 1948-11-09 Dravo Corp Heating and ventilating apparatus
US2470996A (en) * 1942-10-26 1949-05-24 Honeywell Regulator Co Burner control system
US2494737A (en) * 1946-12-30 1950-01-17 Simon V Borst Heat controlling system
US2549952A (en) * 1947-07-10 1951-04-24 Carlton M Wheelock Heating device and automatic control means therefor
US2625992A (en) * 1949-06-30 1953-01-20 Vernon S Beck Multiple group gas burners with independent fuel and secondary air supplies
US3494552A (en) * 1968-04-03 1970-02-10 Ray B Fannin Orchard heating system
US3951336A (en) * 1974-08-28 1976-04-20 Miller And Sons Structures, Inc. Ventilation system for livestock housing
US5470018A (en) * 1993-08-24 1995-11-28 Desa International, Inc. Thermostatically controlled gas heater
US20040025861A1 (en) * 2002-08-08 2004-02-12 W. C. Bradley Company Combination barbecue grill and cooker
US20100001087A1 (en) * 2008-07-03 2010-01-07 Mike Gum Variable output heating control system
US20100015559A1 (en) * 2008-07-18 2010-01-21 Invensys Controls Australia Pty Ltd. Micro-Pilot For Gas Appliance
US9585400B2 (en) 2004-03-23 2017-03-07 The Middleby Corporation Conveyor oven apparatus and method
US9585401B2 (en) 2004-03-23 2017-03-07 The Middleby Corporation Conveyor oven apparatus and method
US9609981B2 (en) 2009-08-28 2017-04-04 The Middleby Corporation Apparatus and method for controlling a conveyor oven
US10024548B2 (en) 2003-02-21 2018-07-17 The Middleby Corporation Self-cleaning oven
US10920980B2 (en) 2016-06-14 2021-02-16 The Middleby Corporation Convection conveyor oven manifold and damper system

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2453382A (en) * 1942-05-12 1948-11-09 Dravo Corp Heating and ventilating apparatus
US2470996A (en) * 1942-10-26 1949-05-24 Honeywell Regulator Co Burner control system
US2494737A (en) * 1946-12-30 1950-01-17 Simon V Borst Heat controlling system
US2549952A (en) * 1947-07-10 1951-04-24 Carlton M Wheelock Heating device and automatic control means therefor
US2625992A (en) * 1949-06-30 1953-01-20 Vernon S Beck Multiple group gas burners with independent fuel and secondary air supplies
US3494552A (en) * 1968-04-03 1970-02-10 Ray B Fannin Orchard heating system
US3951336A (en) * 1974-08-28 1976-04-20 Miller And Sons Structures, Inc. Ventilation system for livestock housing
US5470018A (en) * 1993-08-24 1995-11-28 Desa International, Inc. Thermostatically controlled gas heater
US20040025861A1 (en) * 2002-08-08 2004-02-12 W. C. Bradley Company Combination barbecue grill and cooker
US10036558B2 (en) 2003-02-21 2018-07-31 The Middleby Corporation Self-cleaning oven
US10024548B2 (en) 2003-02-21 2018-07-17 The Middleby Corporation Self-cleaning oven
US10039289B2 (en) 2004-03-23 2018-08-07 The Middleby Corporation Conveyor oven apparatus and method
US9585400B2 (en) 2004-03-23 2017-03-07 The Middleby Corporation Conveyor oven apparatus and method
US9585401B2 (en) 2004-03-23 2017-03-07 The Middleby Corporation Conveyor oven apparatus and method
US10842156B2 (en) 2004-03-23 2020-11-24 The Middleby Corporation Conveyor oven apparatus and method
US9317046B2 (en) * 2008-07-03 2016-04-19 Mike Gum Variable output heating control system
US20160195285A1 (en) * 2008-07-03 2016-07-07 Mike Gum Variable Output Heating Control System
US20100001087A1 (en) * 2008-07-03 2010-01-07 Mike Gum Variable output heating control system
US8454352B2 (en) * 2008-07-18 2013-06-04 Invensys Controls Australia Pty Ltd. Micro-pilot for gas appliance
US20100015559A1 (en) * 2008-07-18 2010-01-21 Invensys Controls Australia Pty Ltd. Micro-Pilot For Gas Appliance
US10362898B2 (en) 2009-08-28 2019-07-30 The Middleby Corporation Apparatus and method for controlling a conveyor oven
US9609981B2 (en) 2009-08-28 2017-04-04 The Middleby Corporation Apparatus and method for controlling a conveyor oven
US10920980B2 (en) 2016-06-14 2021-02-16 The Middleby Corporation Convection conveyor oven manifold and damper system

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