US3351725A

US3351725A - Combustion responsive device especially suitable for use in controlling the operation of a fuel burner

Info

Publication number: US3351725A
Application number: US535584A
Authority: US
Inventors: David F Gibson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1966-03-18
Filing date: 1966-03-18
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07
Also published as: GB1127873A; DE1551956A1; FR1514688A; NL6704038A

Description

3,351,725 R USE IN D F. GIBSON Nov. 7,1967

COMBUSTION RESPONSIVE DEVICE ESPECIALLY SUITABLE F0 CONTROLLING THE OPERATION OF A FUEL BURNER Filed March 18, 1966 3 Sheets-Sheet 1 INVENTOR. flaw'a/Fffiwsom Y Z.

Attorney- Nov. 7, 1967 3,351,725 R USE IN D. F. GIBSON COMBUSTION RESPONSIVE DEVICE ESPECIALLY SUITABLE F0 HE OPERATION OF A FUEL BURNER CONTROLLING T Filed March '18, 1966 3 Sheets-Sheet 2 Dav//FG/bs on,

NovQ7, 1967 I COMBUSTION RESPONSIVE D Filed March 18, 196

$71340) $747! NF!!! T/ON 4740.11157181! Stff 3,351,725 FOR USE IN OPERATION OF A FUEL BURNER 3 Sheets$heet 3 D. F. GIBSON EVICE ESPECIALLY SUITABLE CONTROLLING THE GAS FLOW /6;000BTU HP.

hi8. A/ex-zowga m s 10 2a 3s ans /-Pure4r;/6r0 #auex/aoa) fm enzors Dav/dFT'G/bson,

United States Patent l 3,351,725 COIWBUSTION RESPONSIVE DEVICE ESPECIALLY SUITABLE FOR USE IN CONTROLLING THE OPERATION OF A FUEL BURNER David F. Gibson, Sterling, Ill., assignor to General Electric Company, a corporation of New York Filed Mar. 18, 1966, Ser. No. 535,584 12 Claims. (Cl. 200137) ABSTRACT OF THE DISCLOSURE This invention relates to combustion responsive devices, and more particularly to an improved combustion responsive device especially suitable for use in controlling the operation of a fuel burner, such as a gas burner.

In the type of controls normally used for-operating fuel burners, as for example, a gas burner in a' clothes dryer, space heater and other gas fired equipment, it is customary to initiate combustion of fuel by an electric igniter having electrodes disposed near the burner outlet in proper location with respect to the fuel stream. The presence or absence of a burner flame at the burneroutlet is signaled to other components of the control device by a so-called thermally responsive flame detector assembly which has a temperature sensor deployed in proximity to and in heat exchange relation with the burner flame at the burner outlet. By way of illustration, in one kind of fuel burner control device, the'presence of a flame in the vicinity of the temperature sensor causes the assembly to actuate at least one combustion switch mounted at a location remote from the burner outlet. The switch in turn interruptscurrent to the electric ignitor to turn it off. The fuel burner controls disclosed in Patent 3,207,204 granted to P. W. Thompson on Sept. 21, 1965, and in Patent 3,155,144 granted to S. J. Budlane on Nov. 3, 1964, are representative of this general approach.

In the actual practice of such approach, there has been a practical difliculty or problem in providing an economical, yet rapidly responding and simply constructed flame detector assembly for utilization in the satisfactory control of fuel burner operation. In particular, in addition to the continuing problems associated with ,the attainment of low cost and simplification of construction, there is a need for a flame detector assembly which responds quickly and with minimum variation in connection with any number of different fuel-air flow input rates which, in turn, produce a multitude of diverse operatingcombustion conditions in the same burner and a wide variation in the operating temperature at the temperature sensor portion of the flame detector assembly. It is further desirable that the assembly be constructed such that it not only furnishes the above features, but also permits disposition of the temperature sensor in a lower temperature region of the fuel burner flame without appreciably interfering with the proper operation of the assembly. 7

Consequently, it is a primary object of the present invention to provide an improved combustion responsive device and in particular, a device especially suitable for utilization in controlling the operation of fuel burners.

It is another object of the present invention to provide an improved flame detector assembly which furnishes the desirable features and overcomes the problems mentioned heretofore.

It is still another object of the present invention to provide an improved flame detector assembly which permits economy and simplification in its manufacture and con struction, is easy to install, is versatile in application, and responds rapidly and with minimum variation to a number of diverse operating combustion conditions.

It is a further object of the present invention to provide an improved flame detector assembly of the type operating on a differential temperature-expansion principle and which includes a novel temperature sensorwhich achieves greater temperature differential at various operating combustion conditions than was possible with previous temperature sensors.

It is a final object of this invention to provide a fuel burner unit utilizing the flame detector assembly of the instant invention.

In carrying out the invention in one form, I provide an improved combustion responsive device especially suitable for use in the control of a gas burner of the type normally used in clothes dryers or the like. The combustion responsive device includes a flame detector assembly having a temperature sensor in the form of an elongate body member of non-circular cross section and formed from a single flat sheet of metallic material characterized by relatively low thermal conductivity, together with a mechanical lever suitably mounted in the body member for switch actuation upon difierential expansion of the body member. The temperature sensor, in this one illustrated exemplification of the invention, is of generally triangular cross section, including a base wall section mounted so as to present a temperature sensitive region to a burner flame, a pair of converging side wall sections including generally parallel free edge portions, and outwardly diverging cooling fins on the free edge portions of the wall sections disposed in opposed relation to the temperature sensitive region. The cooling fins are normally located in a portion of the heating chamber in which the burner outlet and flame detector assembly are mounted which receives cooling air due primarily to a secondary air flow therethrough. as well as convection air currents caused by the burning ,gases. Thus, such cooling fins eliminate the necessity for an elaborate and expensive flame shield generally required by prior art devices in order to achieve the necesfied form of the triangular body member with cooling fins,

will adequately function when located in a relatively cool part of the burner flame, and thus will have an extended useful life. Further, cost reduction is effected as the sensor may be'quickly and inexpensively fabricated of flat sheet stock material rather than the round or tubular stock used in the prior art sensors, and also may be more readily assembled.

The body member is supported at one end on a'stationany support, the other end of the member being free, in a cantilevered fashion. The. aforementioned mechanical lever comprises a switch actuator arm which is fixedly mounted at the free end. of the body member, the arm extending through the body member and past the supported end thereof and including suitable switch actuating means at the free end thereof. The switchestare located in a control section of the combustion responsive device,

readily appreciated, they could also be normally open. The detector assembly operates on a principle of differential temperature expansion, wherein when the temperature sensitive region of the sensor or body member is exposed to the burner flame, it will be rapidly heated thereby and hence expand, while the opposed portion of the body member, by virtue of various factors to be explained more fully below, will be heated more slowly and hence expand at a relatively slower rate. This uneven expansion of the body member will cause deflection thereof, which, although very slight is greatly magnified by the switch actuator arm in order to actuate the aforementioned switches in the control portion of the device.

Further aspects of the invention will become apparent from the more detailed description of the invention which follows. It will be understood that the specification concludes with claims which particularly point out and distinctly claim the subject matter which I regard as my invention. The invention, however, both as to organization and method of operation, may be best understood with reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a perspective view of a burner mounted combustion responsive control unit embodying one form of my invention;

FIGURE 2 is a perspective view similar to that of FIG- URE 1 illustrating the control unit as well as a flame pattern for one condition of combustion emanating from the burner;

FIGURE 3 is a horizontal sectional view taken substantially on the plane of the line 3-3 of FIGURE 1;

FIGURE 4 is an exploded perspective view of the various components of the combustion responsive unit comprising one form of my invention;

FIGURES 5 and 6 are graphic representations of various operating characteristics of the flame detector assembly illustrated in FIGURES 1-4 above, the sensor member being of a specified size, as compared to a prior art flame detector assembly having a sensor member of comparable size, illustrating the favorable manner of operation of my invention; and

FIGURE 7 is an enlarged vertical sectional view taken substantially on the plane of the line 7-7 of FIGURE 3.

Referring now more specifically to the drawings, and particularly to FIGURES 14, reference numeral 10 generally denotes a combustion responsive control unit for a gas burner 12. The unit 10 includes a control generally denoted by reference numeral 14 of the general type set forth in the aforementioned Thompson Patent No. 3,207,- 204, an igniter 16 of the general type illustrated in Patent No. 3,147,401 granted to G. H. Wotring on Sept. 1, 1964, and a combustion of flame detector assembly 18 of the general type as shown in the aforementioned Budlane Patent No. 3,155,144.

The control unit 10 has a basic bracket support 19 upon which the various operating components are mounted, the bracket support 19 having suitable means 20 thereon for enabling the unit 10 to be mounted on the burner 12 adjacent tthe burner outlet port 22. The burner 12 of the exemplification is generally conventional in construction, comprising an elongated and rigid tubular casing 24 forming a burner chamber 26 therein terminating in outlet port 22. A suitable baflie 28 is mounted over the outlet port 22 in order to provide a desired flame pattern, the flame pattern being best illustrated in FIGURES 2 and 3 and denoted by reference numeral 30. It will be understood that the illustrated burner is used by way of example only, and that the exemplified control unit may be used with various other burner embodiments, such as for example a horizontal type of burner having a plurality of ports therein for directing jet flame upwardly therefrom.

Reference may be made to the aforementioned Thompson patent for a description of the specific operation of the control 14. However, for purposes of explaining this invention it will be seen that the control 14 includes a U-shaped supporting bracket 32 which is mounted on the bracket support 19 by suitable mounting means, the supporting bracket 32 including a pair of parallel supporting

legs

34 and 36. It will be understood that the control 14 includes a cover which has been left oif so as to better illustrate the operating components thereof. The control 14 includes one or more combustion switches 38, only one of which is schematically illustrated in FIGURE 3. The switch 38 includes a pair of supporting

arms

37 and 39, carried in a supporting stack 41, one of the arms being normally flexible. In this instance, arm 37 is flexible so as to be responsive to applied force thereon. Each

arm

37 and 39 carries a contact button 40 at the outermost or distal end thereof. The switch 38 is provided to control the operation of a lookout device (not illustrated) in accordance with the preferred operation of the Thompson patent, No. 3,207,204. Further, the switch 38, when actuated, interrupts current to igniter 16 to turn it off.

The igniter 16 is disclosed in the aforementioned Wotring patent and specifically described therein. For purposes of explaining this invention, it will be seen that the igniter 16 includes a pair of electrodes, a stationary electrode 42 and a movable electrode 44. The

electrodes

42 and 44 are disposed in the general area forward of burner outlet port 22 as the igniter 16 is supported in depending relation from bracket support 19, in order to provide ignition means for the burner. The

electrodes

42 and 44, respectively, include

electrode contacts

46 and 48 mounted on the forward ends thereof. Thus, when the electrode 44 is moved away from electrode 42 in accordance with the operation of the igniter 16, an arc will be formed between the

contacts

46 and 48 to ignite the gases from burner 12.

The flame detector assembly 18 is provided in the control unit 10 in order to indicate the presence or absence of flame at the burner outlet port 22. The flame detector assembly 18 is responsive to the flame condition of the burner 12 for operating the switches 38 in control 14, so that the control may automatically regulate the igniter 16 as well as automatically control the supply of gases to burner 12. The assembly 18 comprises a combustion responsive sensor element generally denoted by reference numeral 52, which in this exemplification of the invention is in the form of an elongate longitudinally extending differential temperature expansion body member of non-circular cross section. The body or sensor member 52 includes a base wall section 54 and a pair of generally non-parallel or converging

side wall sections

56 and 58. The member 52 is formed from a sing-1e piece of sheet metal material, such as stainless steel or the like so as to have a low thermal conductivity. It will be understood, of course, that the member 52 may be formed from any suitable material characterized by low thermal conductivity. One such suitable metal is stainless steel which has a thermal conductivity of 12.8 B.t.u./sq. ft./hr./ F./ ft. (932 F.).

The member 52 is fixedly mounted in a generally triangular-shaped aperture 60 in the leg 34 of supporting bracket 32, the aperture being best illustrated in FIG- URE 4. It will be seen that the aperture 60 includes an additional projection portion 62 for a purpose to be more fully discussed below. The particular configuration of the body member 52 allows it to be quite rigidly supported in the leg 34 even though the member is supported in canti lever fashion. Each wall section of the body member is supported against one edge of the aperture, and the member 52 is secured firmly in place by spot welds or other suitable securement means. Thus, member 52 is supported at each face or surface adjacent one end thereof.

The illustrated configuration of the body member 52 provides optimum operating results due to the relatively thin material used for the construction thereof. Thus, the thin-walled construction of the body member allows optimum response to differential temperatures, and the minimum mass thereof provides low thermal conductivity.

However, in spite of the use of this thin material and also the cantilevered support of member 52, an unusually rigid member is provided by this construction. 7 It will be observed that, as ilhrstrated, the bodymember 52 is preferably stamped from a single piece of

portions

64 and 66 of the

side wall sections

56 and 58, {5

respectively are flattened out or bent so as to be pgall in order to provide fastening ears for an @ngate switch actuating arm 68.

The actuating arm 68 is an elfigate arm preferably 52, with the side wall sections converging inwardly away from the flame for burner 12, will prevent the flame from enveloping the member. Thus, while the flame may impinge directly on the base wall section, and specifically on the temperature sensitive region 94, the tendency to goaround the corners 59 and 61 is reduced and the flames impingement directly :upon the

sidewall sections

56 and 58 is reduced (see FIGURE 2 for example). This construction, along with the low thermal conductivity ofthe tion of the assembly 18. Furthe actuating arm 68 is constructed, in tlyxe iication of the invention, of material ha ing r'elatively greater thermal mass than the ernbfi 52, and since the arm is fixed directly to the base wall section 54 by a weld, which affords a ready heat flow path, the arm 68 will act as a heat sink and will conduct heat away from the

side wall sections

56 and 58.

Referring again to FIGURES 3 and 4 as well as to 0 material of which member 52 is composed will create necessary temperature gradient in the me ior operaformed of a metallic material having suitable thermal 0 FIGURE 7, it ill b ob r d that a pair of cooling conductive qualities as well as rigidity or strength, the arm including a flat fastening tab portion having a projecting nose 72 thereon and a longitudinally extending strengthening rib 74 therein. Referring to FIGURE 3

fins

82 and 84 are integrally formed at the unsecured longitudinal edges of the converging

side wall sections

56 and 58 intermediate the secured and free ends of member 52. The cooling fins are provided to augment the in Particular, it Will be Observed that the fastening tab above mentioned features of, the inventionfor maintainportion 70 is disposed in the free end 71 of the sensor or body member 52, this free end being opposite the end supported in leg 34. The nose 72 abuts the base wall section 54 and the

fastening ears

64 and 66 sandwich the sides of the tab 70. The arm 68 is thus spot welded or otherwise suitably mounted in this position with

ears

64 and 66 being spot welded. to the tab 70 and the base wall 54 spot welded tovnose portion 72.-The arm is thereby rigidly mounted at one end in the body or sensor member 52.

3 Referring again to FIGURE 3, it will be observed that the actuator arm 68 extends through the member 52 and through the aperture 60 into the control 14. Of course, it will be appreciated that the majority of the control elements orcomponents have been left out of FIGURE 3 for purposes of illustrating the movement of the free endof arm 68. It will be seen that the arm 68 extends past the switch supporting stack 41 and that the arm includes a generally L-shaped bracket 80 on the free end thereof. The bracket 80 has a threaded actuating screw 78 adjustably mounted therein, the screw 78. extending into control 14 so as to engage the switch button 40 upon actuation of the detector assembly 18. The switch 38 includes

switch contacts

79 and 81 respectively carried on rigid and

flexible arms

39, 37. The contacts in this instance are normally. closed so as to maintain the switch 38 closed. The actuating screw 78 is adapted to abut theswitch button 40 so as to bend apart the

arms

37 and 39 and open the contacts 79, 81and hence switch 38 in response to flame detection, and is threaded so as to, be adjustable in the initial position thereof in bracket 80.

In accordance with the operating principles of my invention, a diiferential temperature occurs in the sensor member 52 between a temperature sensitive region or zone 94 of the base wall section 54 and a region or zone 60 on the opposite side of'the member SZremote from the region 94. This differential temperature will causedifferential expansion in the member and thus deflection at the free end 71 about the mounting leg 34. The actuator arm 68 is provided to greatly magnify'this slight deflection at the free end 71 of member 52, the arm being mounted at this end and extending into control 14 and carrying the actuating screw 78 at the free end thereof. Since'it is necessary to achieve temperature dilferential in the sensor member 52, the temperature sensitive region must be thermally isolated from the opposed side of the member. This isolation is achieved in several ways in accordance with the novel aspects of my invention. By referring to FIGURES 2 and 3 in particular, it Will be observed that the particular construction of the member 75 ing a temperature gradient in the body member 52 during operation. The

arms

82 and 84 diverging outwardly, as is best illustrated in FIGURE 7, in order to provide the maximum accessibility to air flow thereover for purposes of 'cooling'The particular surface area of the fins will depend, of course, upon the particular application to be made of the member 52.

By referring again to FIGURE 3 in particular, it will be understood that the sensor member 52 may be dis- 5 posed in a heating chamber adjacent the burner outlet port 22. While the chamber'is not fully illustrated,'a portion thereof in the form of wall 86 of a cylinder or other suitable means is shown for purposes of explanation. Thus, only the free end 71 of the member 52 will be subjected to the flame from the burner 12, it being'desirable to isolate the other operating elements of the control unit 10 from the flame-In this regard, a'bafile 88 in the form of a generally L-shaped member is mounted on the sensor member to control the flame pattern 30. One leg 90 of the baifle is attached to the base wall section 54 as best illustrated in FIGURE 3, and the other leg 92 thereof is disposed substantially adjacent the outlet port 22 to direct the flame pattern 30 in the manner illustrated in FIGURE 3. The bafl le 88 is mounted transversely across the base wall section 54 in order to concentrate the flame from burner 12 near the free end 71 of member 52, and to isolate the flame from control 14. The baffle 88 acts to create turbulence adjacent the temperature sensitive region 94 of base wall section 54 so as to pull the flame onto the wall 54 and hence the baflle produces impingement of the flame on the sensor element 52.

A number of flame detector assemblies have been built in accordance with the illustrated exemplification of my invention. The body member was constructed of 0.015 inch thick stainless steel, the member being approximately 3.5 inches in length and the'arm 68 being approximately 5.5 inches in length (nominal dimensions);

. It has been found during testing of these assemblies that a' 'steady state difierential temperature of 200 -300 65 Fahrenheitis possible under certain operating conditions,

and that this temperature'dilferential or gradientreadily provides for operation of the device in the manner intended. a

The flame detector assembly18 is readily mounted in 94 7 place in the unit 10 with the sensor or body member 52 fixedly mounted at one end to the leg 34 with the other end 71 being free in cantilevered fashion. The actuator arm 68 is fixedly mounted in the free end 71 extending completely through the member and aperture to a position'within the control 14. The sensor member 52 is positioned to present the temperature sensitive region 94 of base wall section 54 to the flame from the burner 12, it being illustrated in FIGURE 2, for example, that the flame pattern 30, will strike the temperature sensitive region 94, but will not impinge on the

side wall sections

56 and 58. The member 52 was placed in the actual assemblies in the path of the flame pattern to be sensed so that the temperature sensitive region 94 was at approximately a 45 degree angle to the direction of the flames impingement. Thus, the member 52 was not placed in the hottest part .of the flame as it will readily function while supported in a cooler portion of the flame, for example, in a portion ranging from 092 135? Fahrenheit. This will obviously increase the useful lifeof the detector assembly. As mentioned above, the temperature dilferential or gradient between the temperature sensitive region 94 and the opposed side of the sensor member 52 was in the range of approximately 200-300 Fahrenheit at steady state, this being sufficient to cause unequal expansion in the member 52 and hence deflection about the leg 34.

The temperature differential or gradient occurs in the member 52 for several reasons: First the particular configuration of the

side wall sections

54 and 58 will prevent direct impingement of the flame thereon. Second, the cooling

fins

82 and 84 will be primarily cooled by a secondary air flow through the heating chamber as well as by aspirated air. Third, the body member is composed of material which has low thermal conductivity, and hence the heat applied to region 94 will not be readily conducted through the member. Fourth, the actuating arm 6% acts as a heat sink to conduct heat away from the

side wall sections

56 and 58.

The movement of the free end of actuator arm 68 in control 14 in this exemplification of the invention may be best appreciated by referring to FIGURE 3 wherein it is shown that the right end of the arm 68, the end at which the adjustable actuating screw 78 is supported, will move upwardly a good deal further than the movement at free end '71 of member 52, the arm 68 acting to multiply the motion at end 71, thus moving the contact button 82 from the position illustrated by lines in full to the position illustrated by lines in ghosts in order to open the switch contacts 79 and 31. Such movement of arm 68 is facilitated by the projecting portion 62 of aperture 60 referred to supra. In the constructed assemblies, the movement at screw 78 was .025 inch minimum, which will cause the switch contacts '79 and 81 to open inasmuch as the contacts will open upon relative movement therebetween of .008.0l6 inch.

With the above discussion of my instant invention in mind, reference is now made to FIGURES 5 and 6 wherein the advantageous operating characteristics of my sensor are graphically illustrated. Referring first to FIGURE 5, the full line curves are representative of the deflection of a number of tests made on my actual sensor members, of the type described above, under various combustion conditions in relation to time. The broken line curves indicate the characteristics of a prior art sensor of the tubular type and the same general size as my sensor, the prior art sensor also including a complex flame shield for cooling purposes. It was determined that it is most desirable to obtain maximum deflection in the shortest amount of time, with the primary objective being to obtain an average deflection of .018 inch in as short a time as possible under a variety of different combustion heating condi tions. As illustrated in FIGURE 5, upon actual testing of the prior art sensor and my sensor taken under the same general conditions and used with the same type control units, it will be noted that there is less response variation in my sensor member 52 under a number of diverse operating combustion heating conditions than in the prior art sensor for the same conditions. It will also become apparent from FIGURE 5 that my sensor member normally reaches .018 inch deflection sooner than the prior art sensor, and thus has more desirable operating characteristics and less variation or deviation than this prior art device.

As stated above, it is desirable to reach .018 inch deflection at the screw 78 as soon as possible. However, while such deflection will usually open the

switch contacts

79 and 81, a significant reduction in temperature gradient in the member 52 may cause enough reverse movement of the actuator arm to allow the contacts to close. However, it is desirable to reach steady state conditions as soon as possible, under which conditions the deflection at the screw 78 will be greater than .018 inch, and thus prevent such problems of recycling. Accordingly, reference is now made to FIGURE 6, wherein there is illustrated the deflection of the two above referred to sensor members plotted against a steady state gas input rate, my sensor member 52 again being represented by the lines in full and the prior art sensor represented by the broken lines. The steady state gas inputrate may be as low as 6,000 B.t.u. per hour for some applications, and with my sensor, superior results will be noted at these low input heating conditions, where satisfactory results are quite diflicult to obtain. Thus, it will be readily apparent from FIGURE 6 that at the low end of the heating cycle especially, my sensor member achieves consistently better results than the prior art device.

Incidentally, it should be understood that, while specific reference has been made to the heating cycle of the burner and the attendant operation of my sensor, my sensor achieves similar advantageous operations during the cooling cycle. Further, it will be readily apparent that the detector assembly responds in a substantially similar, but reverse manner during the cooling cycle.

It will be apparent from the foregoing that my flame detector assembly makes it possible to achieve rapid and uniform response to a member of diverse operating combustion conditions for controlling a gas burner. Further, my detector may be economically constructed from a wide range of readily available materials and easily assembled and mounted for use in a control unit. Still further, the advantages attained by my invention are available, while the total cost thereof is lower than the cost of flame detection devices generally used in the prior art.

While the present invention has been described by reference to the particular embodiment thereof, it is to be understood that many modifications may be made to the improved flame detector assembly by those skilled in the art without actually departing from my invention. It is, therefore, intended in the following claims to cover all such equivalent variations as fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A flame detector assembly for detecting the presence of a flame at a burner outlet of 'a fuel burner unit and for transmitting the detection to a switch means for controlling the fuel =burner unit; said assembly com-prising, an elongate longitudinally extending temperature differential expansion member having a base wall section, said base wall section joined to a pair of generally nonparallel side wall sections, one end of said member being fixedly attached to a stationary support, the other end of said member being free and formed by at least a portion of said sections with a part of the base wall section providing a temperature sensitive region adapted to be disposed in the vicinity of the burner outlet, an elongate switch actuator arm having one end secured to said free end of said member and having a free end projecting beyond said one end of said member, actuator means carried substantially adjacent said free end of said actuator arm for actuating the switch means in response to movement of said actuator arm, and cooling means associated with said member in opposed relation to said temperature sensitive region for maintaining a preselected region of said member spaced from the temperature sensitive region at a relatively lower temperature than said temperature sensitive region whereby said member will readily respond to application of heat from the burner flame.

2. The flame detector assembly of claim 1 wherein said side wall sections generally converge and include generally parallel spaced apart edge portions opposite their juncture to said base Wall section, said cooling means comprising a pair of cooling fins, each of said cooling fins integrally formed with one of said side wall sections and extending outwardly from said edge portions.

3. The assembly of claim 2 wherein said cooling fins are attached at said edge portions and diverge outwardly from the side Wall sections.

4. The assembly of claim 1 wherein said member is formed of sheet material characterized by low thermal conductivity.

5. The assembly of claim 1 wherein said member is formed from a single piece of said sheet material, and mem-ber being generally triangular in cross section, said actuator arm having a major portion of its length contained within the confines of said member and a minor portion of its length without the confines of said member, said actuator means on said minor portion.

6. The assembly of claim 5 wherein said converging side wall sections include generally parallel spaced apart edge portions opposite their juncture with said base wall section, said cooling means comprising at least one cooling fin, said cooling fin integrally formed with one of said side wall sections and extending outwardly from said edge portion.

7. In a fuel burner unit having a fuel burner outlet port means, means for controlling the fuel supply to the unit, and means for initiating combustion of the fuel to produce a burner flame; a temperature responsive device comprising, an elongate temperature differential expansion member having a non-circular cross section and being formed from a single piece of sheet material of relatively low thermal conductivity, said member including a base wall section adapted to be disposed in the vicinity of the burner outlet port means wherein the burner flame will impinge upon the base wall section and a pair of side wall sections each having one longitudinal edge integrally joined to said base wall section, said member supported at one end and free at the other end, a switch actuator arm, said arm rigidly attached at one end to the free end of said member and the other end of said arm extending through said member beyond the supported end thereof, and switch actuating means on said other end of said arm.

8. The temperature responsive device of claim 7 wherein at least a portion of said sidewall sections converge inwardly from .said longitudinal edges, and another portion of said side wall sections adjacent the free end of said member being generally parallel and supporting a portion of said arm.

9. The temperature responsive device of claim 8 wherein said inwardly converging side wall sections terminate in unsecured longitudinal edges, and cooling means integrally joined to at least one of said unsecured longitudinal edges for maintaining said unsecured longitudinal edge at a relatively lower temperature than said base wall section.

10. The temperature responsive device of claim 9 wherein said cooling means comprises a cooling fin extending outwardly from said unsecured longitudinal edge, said cooling fin being substantially planar in shape and adapted to be disposed in a cooling air stream for cooling thereof.

11. A temperature difierential responsive device comprising. a sensing element; means for supporting said element at one end only; said sensing element formed from a single piece of sheet material characterized by relatively low thermal conductivity; said sensing element including, a base wall section having a temperature sensitive region adapted to be disposed in the vicinity of a source of heat, and a pair of converging side wall sections intermediate the end-s of said sensing element, one longitudinal edge of each side wall section integrally joined to said base wall section, said side wall sections terminating in parallel unsecured longitudinal edges; switch actuating arm means having a first end attached to said base wall section and to a portion of at least one of said side wall sections at the end of said element remote from said supported end, said arm extending through said sensing element and having a second free end; switch actuating means on said second free end for actuating switches in response to deflection of said sensing element about the supported end thereof.

12. The temperature responsive device of claim 11 including at least one cooling means integrally joined to one of said side wall sections at the unsecured longitudinal edge thereof, said cooling means being substantially shorter than said unsecured edge and extending lateral-1y outwardly therefrom and adapted to be disposed in a cooling air stream for cooling thereof.

References Cited UNITED STATES PATENTS 2,266,721 12/ 1941 Christiansen 200-137 2,392,065 l/ 1946 Rodgers 200-137 2,494,660 1/1950 Kathe 158-127 2,721,915 10/1955 Huntley 200-137 3,132,805 5/ 1964- I T-ramontini et al. 236-102 3,155,144 11/1964 Budlane 158-123 2,185,436 1/1940 Gordon 158-117.1 3,207,204 9/1965 Thompson 158-128 BERNARD A. GILHEANY, Primary Examiner.

H. A. LEWITTER, Assistant Examiner.

Claims

7. IN A FUEL BURNER UNIT HAVING A FUEL BURNER OUTLET PORT MEANS, MEANS FOR CONTROLLING THE FUEL SUPPLY TO THE UNIT, AND MEANS FOR INITIATING COMBUSTION OF THE FUEL TO PRODUCE A BURNER FLAME; A TEMPERATURE RESPONSIVE DEVICE COMPRISING, AN ELONGATE TEMPERATURE DIFFERNENTIAL EXPANSION MEMBER HAVING A NON-CIRCULAR CROSS SECTION AND BEING FORMED FROM A SINGLE PIECE OF SHEET MATERIAL OF RELATIVELY LOW THERMAL CONDUCTIVITY, SAID MEMBER INCLUDING A BASE WALL SECTION ADAPTED TO BE DISPOSED IN THE VICINITY OF THE BURNER OUTLET PORT MEANS WHEREIN THE BURNER FLAME WILL IMPINGE UPON THE BASE WALL SECTION AND A PAIR OF SIDE WALL SECTIONS EACH HAVING ONE LONGITUDINAL EDGE INTEGRALLY JOINED TO SAID BASE WALL SECTION, SAID MEMBER SUPPORTED AT ONE END AND FREE AT THE OTHER END, A SWITCH ACTUATOR ARM, SAID ARM RIGIDLY ATTACHED AT ONE END OF THE FREE END OF SAID MEMBER AND THE OTHER END OF SAID ARM EXTENDING THROUGH SAID MEMBER BEYOND THE SUPPORTED END THEREOF, AND SWITCH ACTUATING MEANS ON SAID OTHER END OF SAID ARM.