US2164694A - Thermoelectrically controlled device - Google Patents

Description

July 4, 1939. P. L. BETZ ET AL THERMOELECTRICALLY CONTROLLED DEVICE Filed Oct. 16, 1954 Patented July 4, 1939 PATENT OFFICE THERMOEIECTRIOALLY CONTROLLED DEVICE Paul L. Bets, Baltimore, MIL, and Sebastian Karrer, Washington, D. C.

, asliznors to Consolidated Gas Electric Light and Power Company of Baltimore, Baltimore, MIL, a corporation of Maryland Application October 16, 1934, Serial No. 748,516

2 Claims. (Cl. 137 -139) This invention relates to thermoelectrically operated devices, and as respects certain features thereof it has particular reference to safety devices for gas burners whereby a valve in the gas 5 line will be closed automatically whenever a flame to which it is subjected, as a pilot flame, goes out, while as respects other features thereof it has reference to means whereby a thermoelectric couple may be automatically shunted whenever a predetermined condition arises so that the device controlled by the thermoelectric current, whether gas valve or other device, may be actuated independently of the thermoelectric couple.

In the patent of Sebastian Karrer, No. 2,097,838, granted November 2, 1937, for Safety device for gas burners, a safety device for gas burners has been disclosed which-permits theuse of a relatively small valve that can be opened wide, thereby avoiding the use of valve members with only a relatively small lift with respect to their seat and the consequent need for a relatively large valve port in order that the desired flow gas therethrough can be maintained, which may be removed from the burner to any suitable extent and disposed either above or below as well as in the plane of the burner without interfering with its sensitivity or reliability, and which uses the principle of a thermoelectric couple and an electromagnet energized by said couple to hold the valve in open position as long as the fiame to which the couple is subjected is maintained but efl'ecting a prompt closure of the valve when the flame goes out. A device embodying these principles but of improved construction is disclosed in the later application of Paul L. Betz and Sebastian Karrer, Serial No. 699,590, filed November 24, 1983, for Safety device for gas burners.

It is an object of this invention to provide means, in combination with a device of any suitable character which is controlled by a thermoelectric couple, for deenergizing the electromagnet or other means in circuit with said couple when an undesirable or dangerous or other predetermined condition arises but without altering the constants of the thermocouple circuit or affecting its subsequent operation in any way.

Another object of this invention is to provide means in association with a device of the type above characterized for deenergizing the electromagnetic means and effecting the closure of the gas valve in the event that the temperature or pressure in the device rises to a degree that is considered undesirable or dangerous.

Another object of this invention is to provide a safety device for gas burners wherein all movable parts, except the valve member and its stem, are removed from the passages through which the gas flows.

Another object of this invention is to provide an improved safety device for gas burners, wherein the various parts composing the electromagnet, its armature, its operating mechanism, etc., may be constructed of simple elements that may be readily standardized and are inexpensive to manufacture and assemble.

Other objects will appear as the description of the invention proceeds.

The invention is capable of receiving a variety oi mechanical expressions, one of which is shown on the accompanying drawing, but it is to be expressly understood that the drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that purpose.

Rei'erring in detail to the drawing, wherein the same reference characters are employed to designate corresponding parts in the several figures,

Fig. 1 is a plan-view of mechanism embodying the present invention;

Fig. 2 is an axial section through the valve mechanism of Fig. 1 and associated parts;

Fig. 3 is an enlarged detail view of a part of the device; and

Fig. 4 is a perspective view of a thermocouple element.

The invention in so far as it relates to means for deenergizing a thermoelectrically controlled device can be embodied in a wide variety of constructions for use with a wide variety of devices employing thermoelectric couples, but for purposes of illustration the invention has been shown as embodied in a safety device for automatically closing a valve in a gas line whenever a flame is extinguished, which safety device embodies other features of the invention.

As here shown a main burner 01 a heater is indlcated at 8 and may be of any suitable construction. Said burner is supplied with gas through pipe 8 and the gas supply line may be provided, as is more or less common, with a valve under the control of a thermostat of any suitable construction (not shown), in order that said valve may be actuated and gas supplied to or shut off from said burner as required to maintain the temperature of the water between predetermined limits. Also associated with said burner 8 is a pilot ll) of any suitable construction and supplied with gas through pipe II, which communicates with the main gas conduit on the inlet side 01' and ahead of the conventional thermostatically operated valve (not'shown) ,although it is to be understood that the safety device to be described may be used with any other suitable formof gas burner, with or without a pilot.

' In the device shown the flow of gas to the main burner 8 is to be automatically and promptly stopped bythe closure of a suitable valve whenever the pilot flame goes out, and as illustrated, a valve casing I2, of any suitable size, constniction and material, and which may be a brass or aluminum casting. is mounted in the main gas line, said casing having an outlet nipple I31 with which the pipe 9 leading to the main burner 8 is coupled in any suitable way, as by a Y screw threaded coupling. .The -casing is also provided with an inlet connection I4 that is threaded or otherwise suitably formed for connection with a gas inlet pipe (not shown).

The valve casing I2 is provided with a valve port I! which may have a yieldable seat and with .which cooperates a coned valve member I8 with the operating mechanism is restricted in order to prevent the accumulation of dirt, oil, or other foreign substance which might cause sticking of the armature or otherwise interfere with its intended operation. As illustrated a partition in the form of a plate I8 of any suitable material, which may be resilient or flexible but is not necessarily so, is clamped between the valve casing I 2 and a flange I9 formed on a housing member 20. The valve stem IT at its lower end is enlarged in diameter at 2| and the partition I8 is provided at its center with an opening which permits free movement of the enlarged head 2i of the valve stem therethrough. The length of the head 2I is such that when the valve is in the open position shown in the drawing, the enlarged head extends slightly above the upper or rear surface of the partition I8. Surrounding the valve stem I! at the upper side of the partition I8 is a flat washer 22 which can move freely with respect to the valve stem I1 and which rests by gravity on the enlarged head 2I. With this construction, the passage of gas from the valve casing to the upper side of the partition I8 is impeded by the restricted path due to the small spacing between the back face of the coned valve member I8 and the partition I8 and also to the small spacing between the flat washer 22 and said partition. When the partition I8 is resilient or flexible, the lift of the valve I6 may be such as to bring the rear face of the valve into contact therewith and the washer 22 may be omitted. Any other suitable means for restricting or preventing flow of gas through the valve stem opening to the outer side of the partition I8 may be employed if preferred.

Supported by the housing member is an electromagnet formed of inner and outer tubular members 23 and 24 made of a material suitable for a magnetic circuit and preferably of high permeability. Extending between said tubular members, at the outer ends thereof, is an annular member which is also of suitable magnetic material and which closes the magnetic gap between the tubular'members 23 and 24. This annular member 25 may if desired be formed integrally with one of the tubular members 23 or 24 or it maybe suitably attached to either or both of said tubular members. At the opposite ends of said tubularmembers is a second annular member 28 which may be suitably formed on or attached to the inner tubular member 23 and which is also formed of the same or similar magnetic material as the tubular members 23 and 24. The annular member 26, however, does not extend completely from the inner tubular member 28 to the outer tubular member 24, but leaves an annular space forming a gap in the magnetic circuit which may be closed if desired by a ring 21 of suitable non-magnetic material.

The tubular members 23 and 24 and the annular members 25 and 28 enclose an electromagnet coil 28 which is energized as hereinafter described and acts to maintain the valve member I6 in the open position shown in the drawing. The valve stem I1 is tubular and extends freely within the tubular member 23, Within the tubular valve stem is a tubular plug or sleeve 29 against which bears one end of a coil spring 30, the other end of said spring engaging the lower end of a plug 3| that is inserted within the inner tubular member 28. Spring 30 therefore urges the valve member l8 toward closed position, but the valve is maintained in open position as long as the electromagnet is energized by virtue of a disk-like armature 32 mounted on and suitably secured to the tubular valve stem l1 and of a suflicient diameter to bridge the gap in the magnetic circuit at the ring 21. The construction istherefore such as to provide a large surface of engagement between the relatively adjacent pole faces of the electromagnet and the armature 32, assuring against accidental dislodgment of the armature under the shocks and jars to which the device may be subjected under the normal conditions of its service. The outer walls of the electromagnet and the member 28 form a gas tight enclosure for the electromagnet and its armature to prevent escape of such gas as may pass the aperture in the partition I8, or if preferred a separate gas tight housing may surround the electromagnet.

Extending through a bore in the center of the threaded plug 8! and also through the spring 30 and into the tubular valve stem I! is a slidable wire or rod 88. At its outer end, the rod 33 is suitably formed at '84 to provide a hand grip, and at its inner end said rod is provided with an enlarged head 35 which is of sufilclent diameter to engage the inner end of the plug 29 within the valve stem when the rod is lifted. The valve It can thus be opened manually by pulling on therod 33, the head engaging the plug 29 and lifting the valve I8 and valve stem I 1 against the tension of the spring 30 until the armature 32 comes into contact with the poles of the electromagnet. If the electromagnet is energized, the valve will be maintained in this open position and the rod 33 may then be returned to the position shown in the drawing in order not to interfere with free movement of the valve to its closed position. This is made possible by the space provided between the end of the valve stem and the plug 29. If the electromagnet is not energized, however, the valve will be returned to closed position by the spring-30 as soon as the rod 33 is released.

The electromagnet is energized by current from a thermocouple subjected to the pilot flame of pilot burner I0, so that as long as the pilot is burning, current will flow through the electromagnet coil to maintain the valve 16 in open position, but when the pilot flame is extinguished, the current flow through the electromagnet will decrease and the spring 30 will be efiective to close the valve I6. In the form shown, suitable leads 36 and 31 are connected to the opposite ends of the coil of the electromagnet and to a pair of conducting arms 38 and 39 which extend toward the pilot Ill. Suitably attached to the ends of said arms are the two members 40 and 4| of the thermoelectric couple, said two members preferably having a suitable flame resistant extension 42 of any suitable metal. Said' thermoelectric couple may be formed a of any suitable material, such as chromel-constantan. The arms 38 and 39 are of such length and extend in such a direction as to dispose the extension 42 in the flame of the pilot Ill. The members 40 and 4| may have any suitable length to maintain the proper temperature differential between the junction of these members at 42 and the opposite ends of said members, in order to obtain the desired thermoelectric current, but as the material of the members 40 and 4| is ordinarily expensive, these members are preferably made as short as is consistent with the maintenance of aproper difierence in temperature between the opposite ends thereof. Convection and radiation as well as conduction along arms 38 and 39 are relied on for maintaining the proper temperature at the junctions between the members 40 and 4| and the arms 38 and 39, which junctions will be also hot but are cooler than the junction at 42 and from the standpoint of the thermoelectric couple are cold junctions. Any suitable means may be provided for cooling these junctions if desired in order to increase the temperature differtial of the coupling.

If preferred, one of the junctions between the members 46 and 4| and arms 38 and 39 may be made closer to the junction 42 than the other, or the junctions may be so constructed that one tends to retain its temperature longer than the other, so that when the pilot flame goes out one junction will cool before the other and thereby a reversal of the thermoelectric current will be obtained through the coil of the electromagnet to the end that the latter may be completely demagnetized. For example, when a chromel-constantan thermocouple is used, with members 38 and 39 of copper, a reversal of current is obtained when junction 42 is allowed to cool and the temperature is maintained in either or both of the junctions between members til and 4t and arms 38 and Either or both of these junctions may be covered with thermal insulation to give the desired cooling rate. With other materials than chromel and constantan for members 46 and 4| it may be desirable to cause one junction to cool more rapidly than the other, as by providing one of the junctions with a radiating fin 39'. Reversal of current through the electromagnet, however, is not necessary, particularly where a spring is used to initiate movement of the armature and valve member.

The means for deenergizing the electromagnet and thereby permitting closure of the valve l6 by the spring 39 in case a dangerous condition, such as an excessive pressure or temperature existing in the water heater 1 or other device to which the burner is applied, is shown in Fig. 2. Although a means of this kind is disclosed herein only in association with the particular safety device described above, it may be associated with equal facility with any other thermoelectrically operated safety device, as for example the device shown in the aforesaid prior patent of Sebastian Karrer, No. 2,097,838, granted November 2, 1937, or the device disclosed in the aforesaid prior application of Paul L. Beta and Sebastian Karrer, Serial No. 699,590, filed November 24, 1933, or other similar devices, and as heretofore pointed out it may be also used in conjunction with any other suitable device controlled by a thermoelectric couple when it is desired to short circuit the couple upon the arising of some predetermined condition.

Broadly considered, this means as shown comprises a device responsive to changes either in pressure or temperature, as desired, and efiective on increase of pressure or temperature to alter the electric circuit of the electromagnet in such a way that it becomes deenergized and the valve I6 closes. Although in some instances this may be accomplished by operating a make and break contact device in the circuit of the magnet from the pressure responsive or temperature responsive means, it is preferable where the electromagnet is energized by a current from a thermoelectric couple to short circuit the electromagnet thereby avoiding the interposition of make and break contacts in the circuit through which the thermoelectric current flows.

For purposes of exemplification, a temperature responsive means is shown which comprises a circuit shunted across the leads 36 and 31, said shunt circuit containing a contact adapted to be closed by a suitable thermostatic device herein shown as a bellows thermostat subjected to the temperature within the water heater. A casing 43 extends through a suitable opening in the wall of the water heater 1 and into heat conducting relation with the water in the heater, said casing 43 being composed of suitable electrically conductive material. The head or end wall 44 of said casing is electrically connected by means of a lead 45 with one of the leads 3! to the electromagnet. Suitably mounted within the casing 43 is a thermostat 46 of any suitable construction, which is also composed of electrically conductive material and has the form of a bellows which may be charged with a suitable liquid, gas-or vaporizable liquid, so as to effect a predetermined expansion of said thermostat when the temperature of the water in the heater has reached a predetermined degree. It Wil be seen that the bellows is responsive to increases of pressure of the contained medium, which is also sensitive to temperature changes, and the same operation would be ob- '4. If desired, thermostatic means other than such pressure-actuated devices can be employed. Mounted in the outer Wall or head 44 of the casing and suitably insulated therefrom as by insulating sleeves or Washers 4'! is a contact member 48 in line with and adapted to be engaged by a contact member 49 on the end of the thermostat. The contact 48 is suitably connected as by means of a lead 50 with the other lead 36 to the magnet.

If the temperature within the water heater rises to a predetermined degree, which for example may be chosen below the temperature at which undesirable or dangerous conditions may exist if the heat continues, the thermostat 46 will by expansion close the shunt circuit by engaging the contact 49 with the contact 48. The thermoelectric current, instead of flowing through the electromagnet only, will be divided, one part flowing through the electromagnet and the other part flowing through one of the leads 45 (or 50) and through the casing 43, thermostat 46 and L contacts 49 and 48 to the other lead 50 (or 45).

The electromagnet thus has its current reduced and is thereby sufllciently deenergized to release armature 32 under the action of spring 30, thereby closing the valve iii. The operation is the same if the bellows 46 is responsive tolpressure conditions within the water heater rather than temperature conditions, or if said bellows be replaced by any other suitable type of temperature or pressure responsive device. As will now be apparent, such automatic means for deenergizing an electromagnet or other suitable means in circuit with a thermoelectric couple may also be employed in other devices than safety devices for gas valves, and in fact wherever it is desired to discontinue the active control of such a couple upon the occurrence of predetermined conditions.

In the form shown the safety device responsive to temperature or pressure conditions in the water heater insures automatic closing of the valve in case dangerous conditions exist therein, and this is accomplished in the form shown without in any way interfering with the constants of the thermoelectric circuit in normal operation. The safety device may also be positioned at any desired point with respect to the burner and may be located as remote from the heat of the burner as desired, so that the parts may be effectively insulated from the heat generated by the burner and may be composed of materials which might be injured if subjected to the heat of the burner. The electromagnet and its armature as well as all of the movable and operating parts except the valve and the valve stem are positioned exteriorly of the gas passages, and all of the parts are simple in construction, inexpensive to manufacture and easy to assemble, whereby they may be standardized for production in large quantities and at small expense by the use of the relatively unskilled labor. At the same time the device is certain in operation; the cooperation between the armature and the electromagnet poles is such as to assure against accidental and improper disengagement of the armature; and the fact that the armature and electromagnet poles are removed from the path of the gas assures that de posits of dirt, oil, etc., corrosion or other action arising from contact with the gas will not inter fere with the proper and desired operation of the device.

While one embodiment of the invention has been illustrated and described with considerable particularity, it is to be expressly understood that the invention is not to be restricted thereto as the same is capable of receiving a variety of mechanical expressions, some of which will now readily suggest themselves to those skilled in the art,

- while changes may be made in the details of conout other features, without departing from the spirit of the invention. Moreover, while the invention has been illustrated and described as employed in conjunction, with a pilot light, it will be apparent that the invention can also be used as a safety device in connection with other sources of heat to prevent the occurrences of dangerous conditions. It is also to be expressly understood that the means for short circuiting the thermoelectric couple may be combined with a wide variety of other electrically operated devices, and that any suitable temperature responsive or pressure responsive device and any suitable switch device as well as other suitable means for actuating the same upon the occurrence of predetermined conditions may be substituted for the forms illustrated. Reference is therefore to be had to the claims appended hereto for a definition of the limits of the invention.

What is claimed is:

1; In a safety device for gas burners, a safety valve for controlling the flow of gas, an electromagnet for maintaining said valve normally in open position, said electromagnet having a bore and said valve having a tubular valve stem extending into said bore at one end thereof, means forming a shoulder within said tubular valve stem, a spring interposed between said electromagnet and shoulder, and a rod extending through said bore and into said valve stem past said shoulder, said rod having an enlarged head at its end within the valve stem adapted to engage said shoulder whereby the valve can be opened manually.

2. In a safety device for gas burners, a safety valve for controlling the flow of gas, an electromagnet formaintaining said valve normally in open position, said electromagnet having a bore and said valve having a tubular valve stem extending into said bore at one end thereof, means forming a shoulder within said tubular valve stem, a spring interposed between said electromagnet and shoulder, and a rod extending through said bore and into said valve stem past said shoulder, said rod having an enlarge head at its end within the valve stem adapted to engage said shoulder whereby the valve can be opened manually, said shoulder being spaced from the valve end of the valve stem by a distance not less than the movement of the valve from open to closed position.

PAUL L. BETZ. SEBASTIAN KARRER.

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