US2390985A

US2390985A - Burner control system

Info

Publication number: US2390985A
Authority: US
Publication date: 1945-12-18
Anticipated expiration: 1962-12-18

Description

Dec. 18, 1945. J. B. BOYER v BURNER CONTROL SYSTEM Filed Dec. 2, 1942 T7'0/7/VEY Patented Dec. 18, 1945 BURNER CONTROL SYSTEM James B. Boyer, Washington, D. 0., minor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application December 2, 1942, Serial No. 467,596

16 Clalms.

The present invention is concerned with a burner control system and more particularly with one employing an element whose magnetic properties vary with temperature.

It is conventional practice in the fuel burner art to provide some means for shutting oil the flow of fuel if the ignition means is not properly operating. Where a pilot burner is employed as an ignition means, some means responsive to the temperature 01' the pilot burner flame is usually employed for this purpose. It has been proposed to employ as a pilot burner flame responsive means a control device in which the position of the control device is determined by the temperature to which an element of Curie point metal is subjected. It is well known that certain metals, known as Curie point metals, possess the property of changing their magnetic characteristics at diiierent predetermined temperatures. In almost all cases, such metals become non-magnetic when heated above the Curie point temperature. These arrangements of the prior art employing a Curie point metal for controlling the flow of fuel to a burner have all employed this type of Curie point metal. Because of the fact that the Curie point metals which have been employed have become non-magnetic above a predetermined temperature rather than below a predetermined temperature, it has been necessary to devise various means to insure that these deprovide a control device having a magnetic holding means for holding a controlling element against its bias, this magnetic holding means comprising an element of Curie point material and being provided with an electromagnetic winding for controlling the operation of the holding means when the Curie point material is magnetic.

A still further object of the present invention is to provide such a burner control device in which the controlling element is a valve normally biased to a position preventing flow of fuel to vices move to a safe position upon a failure of the controlling mechanism. Such a safe position is a'position in which the operation of the burner is prevented. I have discovered that certain Curie point metalspossess the property of becoming magnetic when heated above a predetermined critlcal temperature and when used make it possible to simplify the control device and yet insure safe operation.

It is'an object of the present invention to provide an improved burner control device employing a positive Curie point metal; that is,v a metal which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature;

A further object of the present invention is to provide a burner control device which because 0! the employment of a positive Curie point'material is extremely simple in construction and has a minimum number oi parts.

A still further object of the invention is to provide a burner control device employing an element of Curie point material in which an electromagnetic winding is associated with one of the elements.

A further object of the present invention is to the burner and which is held against its bias-by the magnetic holding means in a position permitting such flow.

A still further object of the present invention is to provide an improved burner control system in which it is possible to control the flow of fuel to a main burner both in accordance with the value of a condition indicative of the demand for burner operation and also in accordance with a condition indicative of the proper operation of an ignition means for the burner.

Other objects of the invention will be apparent from a consideration of the accompanying specification, claims, and drawing, of which:

Figure 1 is a schematic view of my improved burner control system employing the novel burner control device of the present invention, and

Figure 2 is a modified form of burner control device.

Referring to the drawing for a more detailed understanding .of the invention, a main gas burner is indicated by the reference numeral II. This gas burner is supplied with gas by a gas p H which connects with a conventional mixin chamber l3. Leading into the mixing chamber I2 is a gas pipe it which communicates with the outlet side of my burner control device generally indicated by the reference numeral ll. Connected with the inlet side of the burner'control device I! is a gas supply pipe It leading from any suitable source of gas supply (not shown). Located adjacent to the main burner II 'is a pilot burner ll. This pilot burner is supplied with gas by a pipe it connected to pipe It. It will be obvious that pilot burner II is normally supplied constantly with gas from pipe It.

The control device It comprises a lower valve housing 20 and an upper housing II. The valve housing 20 is provided with the usual partition wall 22 which is apertured to provide a valve seat It. Cooperating with valve seat 23 is a valve disk 24 of conventional construction. A spring 2' is interposed between the valve disk and an is located series connected electromagnetic windlugs 82 and 88. The base of the U shaped core 8| is secured to a valve stem 88 which extends through the diaphragm 28 and is secured to valve disk 24. The valve stem is threaded and is clamped to the diaphragm 28 by nuts 88 or. other suitable fastening means.' The diaphragm 28 serves as'a gas tight seal between the housings 28 and 2|.

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flange at. The spring a transformerandhasaline voltageprimary which isconnectedtolinewirunandll leadingto any suitable source of power (not shown).

' Operation of Figure 1 species The elements of the system are shown in the position which they occupy when the thermostat Cooperating with the electromagnet core 8| is a plate 88 of Curie point material. This plate 88 forms the upper closure for housing 2|. The plate 88 projects substantially beyond the housing 2| so as to project into the path of the flame of pilot burner II. If desired, the plate 88 can terminate adjacent th housing 2| and suitable means can be provided for conducting the heat from the pilot flame to the plate. The plate 88 isof that form of Curie point material which 48 is calling for heat and when the pilot burner i1 is properly ignited. Under these conditions, the plate 88 of Curie point material is heated by the flame of pilot burner above its Curie point and is consequently magnetic. The electromagnetic windings 82 and 88 are also energized through the following circuit: from the right hand terminal of transformer 88 through conductor 88, bimetallic element 48, contact blade 41, contact 48, conductor 8|, switch 82. conductor 82, windings Hand 82, and conductor 88 to the left hand terminal of transformer 88. Since the windings 82 and 88 are energized, flux flows through the magnetic circuit consisting of core 8| and armature 88 so thatthe core 8| of the electromagnet is held in engagement with the plate 88 and thus serves to hold valve disk 24 in open position against the biasing action of spring 28. Gas is thus able to flow through the valve casing to burner I8 where it is burned.

Under normal circumstances, the burner will continue in operation until the thermostat 48 becomes magnetic when heated above a certain temperature. One type of material which has this property is cobalt and certain cobalt steels likewise have this p p rty. the Curie point depending upon the amount of cobalt present in the alloy. In my device, a cobalt steel which has a Curie point substantially above a normal bumer chamber temperature but less than the pilot burner flame temperature is employed.

The energization of the electromagnetic windings 82 and 88 is controlled by a room thermostat or by a switch responsive to a condition indicative of the demand for heat. For example, this switch may be a conventional room thermostat indicated in the drawing by the reference numeral 48. This thermostat comprises a bimetallic element 48 to which is secured a contact arm 41. The contact arm 41 is movable into and out of engagement with a fixed contact 48. As indicated by the legends C and H, thecontact arm 41 is moved by the bimetallic element towards the left into engagement with contact 48 upon a drop in temperature and towards the right out of engagement with contact 48 upon a rise in temperature. -A magnet 48 is associated with the contact blade 41 and serves to impart a snap action to the contact blade.

The energization of windings 82 and 88 is also controlled by'a limit switch 88. This limit switch is of conventional construction comprising a bimetallic element II which I is operatively connected to a mercury switch 82. The bimetallic element is located so as to be responsive to the furnace temperature. For example, the bimetallic element may be located within the bonnet of becomes satisfied or the temperature adjacent the bimetallic element 8| of limit switch 88 reaches the setting of the limit switch. In either case, the circuit traced to electromagnetic windings 82 and 88 is interrupted with the result that the windings 82 and 88 are deenergized. Consequently, no flux is produced and there ceases to be any attraction between core 8| and plate 88. The biasing spring 28 is able to move valve disk 24 into engagement with the valve seat 28, this movement being aided by the effect of gravity. Movement of valve disk24 into engagement with valve seat 28 interrupts the flow of gas to main burner l8 and causes the extlnguishment of the main burner. Upon both thermostat 48 and limit switch 88 again being reclosed, the circuit to windings 82 and 88 is reestablished so that core II is again moved upwardly to reopen the valve.

It will thus be seen that during normal operation, the valve disk is moved away from its seat by the cooperatin action of the core 8|, the windings 82 and 88, and the plate 88.

If at any time the pilot burner I1 is extingulshed, it is desirable that the flow of gas to the main burner be interrupted. Whenever such an extinguishment of the flanie of pilot burner l1 occurs, plate 88 is no longer heated. As a result, the plate 88 cools below its critical temperature with the result that it becomes substantially non-magnetic. The effect of this is that there is no longer an attraction between core 8| and plate 28 with the result that despite the energization of windings 82 and 88, the spring 28 is capable of moving the valve disk' to closed position, The valve will r'emain'in this position until such time as pilot burner I1 is relishted and the pilot burner is effective to reheat plate 88.

It will be seen that by the use of a Curie point material which becomes magnetic when heated above a certain temperature rather than one which becomes magnetic when its temperature is below a certain value, it is possible to have a much simpler and more direct acting device. With the arrangement of my control device, the valve is biased to closed position which is the safe position. If anything at all goes wrong with the operatin mechanism, the biasing is effective to move the valve to the safe position.

This is accomplished, moreover. without the use I of any shunting members whatsoever.

The use of a positive Curie point material, moreover, has the further advantage that it makes possible the use of an electromagnet which is controlled in the normal manner by switches which close upon a demand for heat.- In this way it is possible to dispense with a eparate electromag'netically positioned shut-oi! valve. It will be noted that my control device functions both as a thermostatically controlled shut-oil valve and also as a means for interrupting gas flow upon pilot extinguishment.

Species of Figure 2 In Figure 2, I have shown a modiflcation of my burner control devices In this species, the electromagnet is stationary and the only element that is movable 'is an armature member. In order to facilitate a comparison of the two figures, identical reference numerals havebeen applied to elements of Figure 2 which correspond identically with elements of Figure 1. It will be noted that as in Figure 1 the control device comprises a lower valve housing and a valve disk 24 biased to closed position by a spring 25. There is also an upper valve housing II and a diaphragm 28 disposed between the two housings. In this species, the stem is connected to an armature member 80 which cooperates with a pair of magnetic core members 81 and I! which are secured to a plate 00 of Curie point material correspondin to plate It. Disposed on the core members 81 and 88 are a pair of windings II and 81 corresponding to windings I2 and 33 of the species of Figure 1. The plate I! is adapted to be exposed to the flame of pilot burner II in the same manner as is plate 39. Like plate a, it becomes magnetic when heated above a predeter: mined critical temperature. I

In this form, the magnetic circuit of the holding means consists of core member l1. plate '0, core member 88, and armature l6. Flux flows through this magnetic circuit whenever plate 8! is heated and windings 90 and ii are energized. Upon either plate I! beingunheaied so as to be substantially non-magnetic or upon windings O0 and 9! being deenergized, the armature I! separates from core members 81 and II and spring 25 is effective to move valve 2 to closed-position.

It will be readily apparent that the various advantages outlined vfor the device of Figure 1 apply equally well to the species of Figure 2. The species of Figure 2 has the advantage that the only element which is movable is the armature I! which can be made relatively light, if necesy.

With either species, control in accordance with both the demand for burner operation and the condition of the pilot flame i obtainedwith a minimum of apparatus.

While I have shown certain speciflc embodiments ofmy invention, it is to be understood that this is for purposes of illustration only and that my invention is to be limited solely by the scope of .the appended claims.

I claim as my invention: 1. A safety mechanism for a fuel burner comprising a control device biased to-a fuel feed preventing position, and holding means for retaining the control device in a fuel feed permitting position against its bias, j'isaid holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being adapted to be heated by a burner flame and being of a material which is normally substantially non-magnetic but which becomes magnetic when heated by said flame above a predetermined temperature.

2. A valve mechanism comprising a valve biased to a first position, and holding means for retaining the valve in a second position against its bias, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being adapted to be heated by a burner flame and being of a material which is normally substantially nonmagnetic but which becomes magnetic when heated by said flame above a predetermined temperature.

3. A safety mechanism for a fuel burner comprising a control device biased to a fuel feed preventing position, holding means for retaining the control device in a fuel feed permitting position against its bias, said holding means comprising a magnet and an armature cooperating to form a magnetic circuit, and a connection between said armature and said control device, a portion of said magnet being adapted to be heated by a burner flame and being of a material which is normally substantially non-magnetic but which becomes magnetic when heated by said flame above a predetermined temperature.

4. A safety mechanism for a' fuel burner comprising a control device biased to a fuel feed preventing position, holding meansfor retaining the control device in a fuel feed permitting position against its bias, said holding means comprising a plurality of elements of magnetic material coopcrating to form a magnetic circuit, one of said elements being adapted to be heated by a burner flame and being of a material which is normally 40 substantially non-magnetic but which becomes magnetic when heated by said flame above a predetermined temperature, and an electromagnetic winding on another of said elements.

5. A safety mechanism for a fuel burner comprising a control device biased to a-fuel feed preventing position, holding means for retaining the control device in a fuel feed permitting position against its bias, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being adapted to be heated by a burner flame and being of a material which is normally substantially non-magnetic but which becomes magnetic when heated by said flame above apredetermined temperature, an electromagnetic winding on another of said elements, and thermostatically controlled means for controlling the energization of said winding.

6. A valve mechanism comprising a valve biased to a flow preventing position, a housing for said valve, holding means for retaining the control .device in a flow permitting position against its bias, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, and a second housing for said holding means, a flexible wall between said first and second housings, one of said elements of said magnetic circuit being movable and secured to said valve through said flexible wall, and another of said elements being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature.

7. A control mechanism comprising a control device biased to a first safe position, magnetic holding means for retaining the device in a second active position, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, and a housing for said control device and holding means, one of the elements of said magnetic circuit extending beyond said housing so as to be adapted tobe heated by a flame, said element being of a material which is normally substantially nonmagnetic but which becomes magnetic when heated by said flame above a predetermined temperature.

8. A control mechanism comprising a control device biased to a first position, magnetic holding means for retaining the device in a second position, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, a housing for said control device and holding means, one of the elements of said magnetic circuit extending beyond said housing so as to be adapted to be heated by a flame, said element being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature, and an electromagnetic windingon another of said elements.

9. A control mechanism comprising a valve device biased to a closed position, magnetic holding means for detaining said valve in open position,

said holdingmeans comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, and a housing for said control device and holding means, one of the elements of said magnetic circuit extending beyond said housing so as to be adapted to be heated by a flame, said element being of a material which is normally substantially non-magnetic but which becomes magnetic when heated by said flame above a predetermined temperature.

10. A control mechanism comprising a control device biased to a first safe position, magnetic material cooperating to form a magnetic circuit. one ofrsaid elements being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature, said element being exposed to the heat of the pilot burner flame.

13. In a burner system, a burner, ignition means therefor, a control device for said burner biased to a position preventing bumer operation, holding means for retaining said control device in a second position permitting burner operation, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being of a material which is normally substantially nonmagnetic but which becomes magnetic when heated above a predetermined temperature, said element being exposed to the heat of the ignition means, an electromagnetic winding on another of said elements, and means responsive to a condition indicative of the demand for heat for controlling the energization of said winding.

14. In a fluid fuel burner system, a burner, ignition means therefor, a valve controlling the flow of fuel tosaid burner and biased to a position preventing the flow of fuel to said burner, holding means for retaining said valve in a second position permitting a flow of fuel to said burner, said holding means comprising a plurality of,e'lements of magnetic material cooperating to form a mag netic circuit, one of said elements being of a material which is normally substantially nonmagnetic but which becomes magnetic when heated above a predetermined temperature, said element being exposed to the heat of the ignition means, an electromagnetic winding on another of said elements, and means responsive to a condition indicative of the demand for heat for controlling the energization of said windingl 15. In a fluid fuel burner system, a main burner, a pilot burner therefor, a valve controlholding means for retaining the device in a seccircuit, a housing for said control device and.

holding means, said electromagnet being movably mounted within said housing and connected to said control device, and said stationary element extending beyond said housing so as to be adapted to be heated by a flame, said stationary element being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature.

11. In a burner .system, a burner, ignition means therefor, a control device for said burner biased to a position preventing burner operation, and holding means for retaining said control device in a second position permitting burner operation, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature, said element being exposed to the heat of the ignition means.

12. In afuel burner system, a main burner, a pilot burner therefor, a control device for said main burner biased to a position preventing burner operation, and holding means for retaining said control device in a second position permitting burner operation, said holding means comprising a plurality of elements of magnetic ling the flow of fuel to said main burner and biased to a position preventing the flow of fuel to said main burner, holding means for retaining said valve in a second position permitting a flow of fuel to" said burner, said holding means comprising a plurality of elements of magnetic materlal cooperating to form a magnetic circuit, one of said elements being of a material which is normally substantially non-magnetic but which becomes magnetic when heated above a predetermined temperature, said element'being exposed to the heat of said pilot burner, an electromagnetic winding on another of said elements, and means responsive to a condition indicative of the demand for heat for controlling the energization of said windings a 16. In a burner control system, burner means,

'a control device for said burner means biased to a position limiting burner operation, holding means for retaining said control device in a second position permitting full burner operation, said holding means comprising a plurality of elements of magnetic material cooperating to form a magnetic circuit, one of said elements being of a Curie point material which is appreciably magnetic only within a predetermined temperature range, means for controlling the temperature of said one element in accordance with a first normaloperative condition of said burner means, an electromagnetic winding on another of said elements, and means responsive to a second condition indicative of the demand for heat for controlling the energization of said winding.

JAMES B. BOYER.