US2747143A - Catalytic fuel igniters - Google Patents

Description

M y 22, 1956 w. J. KUCZYNSKI ET AL CATALYTIC FUEL IGNITERS Filed Nov. 22, 1950 IN VEN TOR.

WALTER J. KUCZYNSKI GEORGE J. LEHMANN United States Patent CATALYTIC FUEL IGNITERS Walter J. Kuezynski, Newark, and George J. Lehmann, Arlington, N. J., assignors to Baker & Co., Inc., Newark, N. J., a corporation of New Jersey Application November 22, 1950, Serial No. 197,164

11 Claims. (Cl. 317-83) This invention relates to catalytic igniters for gas burners, and is concerned in particular with maintaining such igniters in a highly active state.

During the past few years hot wire igniters have been used more and more to replace the common pilot flames in the ignition systems for domestic gas stoves and furnaces and for many industrial applications. Of the known hot wire igniters there are those that require resistance heating by a relatively high electric current before they may reach a temperature high enough to ignite a gaseous or atomized fuel. If such igniters, when installed for operation, are maintained at all times at fuel ignition temperatures, which should be done to insure ignition under all conditions, such as when a burner flame becomes extinguished though the fuel continues to flow, then it is found that they deteriorate rapidly, whereby ther useful life is substantially reduced, requiring replacement and involving expense and inconvenience.

More recently catalytic fuel igniters especially those embodying a heterophase arrangement have been employed in gas burner ignition systems. Such heterophase type igniters need not be maintained at a temperature high enough to combust a fuel, but may be kept at a much lower temperature and still function properly. Besides having a heterophase configuration, igniters of this type are preferably formed of metals of the platinum group of alloys thereof or sintered agglomerates of such metals or metal compositions.

Some fuels are, of course, more easily ignited than are others. In particular, manufactured gas, i. e. city gas, for example, will ignite more readily than will natural gas.

It has now been found that when catalytic igniters are maintained in a heated condition below a certain temperature, more fully explained hereinafter, they become less active and may, in some cases even within a few hours of disuse, lose their ignition efiiciency or even become unable to ignite catalytically some of the more diflicultly ignitable fuels. This loss in activity with respect to the more difficultly ignitable fuels is gradual and is dependent on several factors among which are the temperature to which the igniter is heated, the nature of the flame to be produced, i. e. aerated or non-aerated, and the velocity at which the gas impinges on the igniter filament.

it is accordingly, an object of the invention to provide for maintaining a catalytic igniter in an active state with respect to fuels which are particularly difficult to ignite. More specifically, it is an object of the invention to provide means and method for maintaining a catalytic igniter in an active state when employed in a flash-back system for gas burners, and yet not cause it to deteriorate and impair its usefulness over long periods of operation. Further objects and various advantages of the invention will become apparent from the following detailed description thereof, and from the accompanying drawing, the single figure of which is a wiring diagram showing an electric circuit for an igniter filament, and constructed according to the invention.

The present invention deals with the ignition of combustible gases by means of a catalytic igniter coil which is energized by a two stage application of electrical energy, whereby the first stage comprises the passing of electrical energy through said coil at a value sufficient to heat the coil to a stand-by temperature below the ignition temperature of the gas. The second stage comprises the momentary elevation of said first stage energy at spaced intervals to occasionally or periodically raise the temperature of the igniter coil above the stand-by temperature, thereby periodically reactivating the igniter coil to maintain it in a stimulated and catalytically active state.

This repetitive periodically spaced flash activation is applied during prolonged stand-by periods during which otherwise there occurs a lowering of ignition efliciency or other deactivation of the catalytic igniter coil.

In order to overcome the decrease in the ignition efiiciency the igniter coil is, in accordance with the invention subjected at spaced intervals of time to an instantaneous flash of high heat i. e. a temporary heating to a higher temperature than the stand-by temperature. This periodically spaced flash-heating i. e. higher heating stimulates or rejuvenates the catalytic activity of the coil. The duration of this flashing (i. e. heating) operation may be of the order of a second or less. Longer flashing or heating is not necessary and may be detrimental to the igniter filament, especially where very fine filaments are involved. Where thicker filaments are used the high heating may last even longer than one second. The exact temperature required for reactivation is not accurately known, but as a general rule, it is essential that a regular operating temperature be maintained below the ignition point of the gas and that the stand-by temperature be increased at appropriate intervals; which may be accomplished by energizing the circuit into which the igniter is inserted or the filament may be energized for a second or so with a voltage of about 50% to 60% higher than the normal operating voltage. Under normal conditions of heat loss, since voltage is directly proportional to power input and since the current remains approximately the same, then by energizing the filament with about a 50% increase in voltage an approximate increase in temperature of about 50% is obtained. It necessarily follows therefore that any external means may be used to raise the temperature about 50% higher than normal operating temperatures in order to perform the method step of reactivating the igniter coil, and although the following description refers to intermittent heating by electrical means, which would appear to be the most obvious means, the method of my invention is not necessarily limited to the use of such means, but rather such structure is in the nature of a preferred embodiment. The time interval between the heat flashes or intermittent catalyst rejuvenating heating may be of the order of six hours or more.

In the case of natural gas and for coils formed of a platinum metal or of platinum metal alloys, the tem perature threshold above which catalytic activity remains unaltered is about 800 C. Such coils lose their relative activity upon standing at temperatures below about 800 0; however, when formed to a heterophase configuration, they could function advantageously in the usual flash-back systems, at low temperatures, e. g. about 700 C. and even less, if their catalytic activity is not reduced upon standing. It is desirable, of course, to keep the standby temperature for the coil as low as possible, since deterioration of the coil occurs at high temperatures but is practically negligible at low temperatures of the order of 700 C. and less.

Since, an igniter is kept idle at standby temperature for frequent indefinite periods of time, it is good practice to provide an automatic time switch device in connection with the intermittent heating means for supplying flashes of heat to the igniter coil at regular intervals, i. e., for example, every 6, 12 or 24 hours, depending upon the characteristics of the ignition system and other factors that influence the speed of ignition in a given installation.

teferring now to the drawing showing a preferred apparatus for performing the standby operation, there is shown a catalytic fuel igniter filament l, in the form of a coiled coil, connected into an electric circuit for maintaining the coil at a low standby temperature and for automatically and periodically subjecting the coil to an instantaneous heat flash. The coiled coil configuration of the filament it is a preferred embodiment of the heterophase principle mentioned herein above.

The source of current, indicated by the reference numeral 2, may be that the ordinary electric circuit found in homes and in industrial plants. From this conventional electric supply, current is carried by the conductors 3 and 4 to the primary coil 5 of a transformer 6. The secondary coil 7 of the transformer 6 is connected at one end to the wire 8 which in turn is connccted to one end of the filament l. The other ends of the secondary coil and the filament are joined to the wires 9 and 14) respectively, which close the circuit of the secondary side of the transformer by being joined through an automatic time switch mechanism 11. A lead-off conductor 12 from between the ends of the secondary coil 7 is also connected to the switch mechanism ill, the point of contact of the conductor 12 with the coil 7 being spaced from that end of the coil which is joined to the wire 3, by a distance of about two thirds the length of the coil.

The specific construction or" the automatic time switch 11 is well known in the art and does not, per se, constitute part of the invention. Accordingly, a detailed description thereof is not necessary for the purpose of this specification. it is sutficient state that the mechanism 11 contains a switch 13 which is operable between the contacts 14 and for alternately closing the circuit having tr e lead-off conductor 12 and the circuit having wire 9. The mechanism 11 may be energized through the conductors 16.

Under standby conditions the switch is closed against the contact 14- whercby an electrical potential of e. g., about two volts may be impressed across the filament i from the transformer 6. After a predetermined time interval, depending on the setting of the timing mechanism ii, the switch .13 will be flipped to the contact 15 and then bacl; to the contact 14. When this occurs the filament 1 becomes momentarily connected into a circuit having a potential of, for example, about three volts, whereby the filament will be heated substantially above its standby temperature and will thus be reactivated.

It will, of course, be understood that the ignition system of this invention could be provided with a manually operated switch in place of the automatic switch 11, a manually operated switch can be used whenever reactivation of the igniter filament is required.

From the above description, it will be seen that the invent 1 provides a simple means and a method of maintaining an igniter rent at a standby temperature below that which would cause objectionable deterioration of the filament over a long period of time, and enables reactivation of the filament when necessary, turning any prolonged standby period.

The foregoing disclosure is to be regarded as descriptive and illustrative only, and not as restrictive or limita tive of the invention of which obviously an embodiment may be constructed including modifications without departing from the general scope herein indicated and denoted in the appended claims.

What we claim is:

1. In the operation of a catalytic iguiter coil in a gas burner, the method including electrically heating said coil to an elevated temperature below that temperature at which the gas to be burned will ignite, supplying electrical energy to said coil at a constant level so as to maintain said coil at the elevated temperature and obtain standby operation, and temporarily applying heat to said coil to increase said elevated temperature at spaced intervals to a value sufficient to stimulate the activity of said coil while maintaining the atmosphere surrounding said coil free from any ignitable gases.

2. In the operation of a catalytic igniter coil having a heterophase configuration in use in a gas burner, the method of standby operation including heating said coil by the passage of electric energy there-through to an elevated temperature below that temperature at which the gas to be burned will ignite, said aforementioned temperature being the stand-by temperature, supplying electrical energy to said coil at a constant level to maintain said coil at the stand-by temperature, and temporarily and periodically increasing the said electrical energy level to raise the temperature of said filament coil to a value sufficient to reactivate said coil while maintaining the atmosphere surrounding said coil free from any ignitable gases.

3. In the operation of a catalytic igniter coil having a heterophase configuration in use in a gas burner, the method of standby operation including passing electrical energy through said coil of a value sufiicient to heat said coil to a. standby temperature below the ignition temperature of said gas, supplying electrical energy to said coil at the aforementioned value to maintain said coil at the stand-by temperature, and temporarily and at spaced intervals discontinuing the passage of electrical energy through said coil at said first value and simul taneously passing another higher value of electrical energy through said coil while maintaining the atmosphere surrounding said coil free from any ignitable gases, said second higher value being of an amount sutlicient to intermittently reactivate said filament during its standby operation.

4. The method of claim 2 wherein the said electric energy level passed through said coil is of a value sufficient to maintain the coil temperature in the range of about 600 C. to about 800 C. and the step of increas ing the said electrical energy level consists in increasing the energy level by an amount suificient to raise the filament temperature above 800 C.

5. The method of claim 4 wherein the voltage of the said energy level is increased by about one and one-half times its initial value.

6. The method of claim 3 wherein said first value of electrical energy is of a value sutficicnt to attain a coil temperature in the range of about 600 C. to about 800 C. and the second value of electrical energy is of a value sutficient to raise the coil temperature above 809 C.

7. The method of claim 6 wherein the voltage of said second energy level is about one and one half times the voltage of said first energy level.

8. In a gas burner having a flash-back ignition means, a catalytic igniter filament having a heterophase configuration, an electrical circuit including a source of current and said filament, a first branched closed path and a second branched closed path in said circuit having said filament as a common element therein, said first branched closed path being adapted to carry a lesser voltage than said second branched closed path, and means for normal- 1y keeping said second path open and for temporarily closing said second path at spaced intervals for supplying a surge of voltage through said filament.

9. In a gas burner having a flash back ignition means, a catalytic igniter filament having a heterophase configuration, an electrical circuit including a source of current, a transformer having a secondary coil and said filament, a first branched closed path and a second branched closed path in said circuit including as common elements a portion of s rid secondary coil and said filament, said first branched path being adapted to carry a lesser voltage than said second branched path, and switch means in said circuit biased to normally keep said second branched path open and for periodically and temporarily closing said second path to instantaneously increase the energy that passes through said filament.

10. The flashback system adapted for stand-by operation of claim 9 wherein one end of said secondary coil is connected to one end of said filament, a switch means including at least two spaced apart contact eleinents and a contact lever, said lever being normally closed against one of said contact elements, the other end of said filament being electrically connected to said contact lever, said one contact element being connected to said secondary coil between the ends thereof to complete said first branched path which is adapted to provide a continuous supply of electric energy to said filament for heating it to an elevated temperature below that temperature at which the gas to be burned will ignite, the other of said switch contact elements being connected to the other end of said secondary coil to complete said second branched path, said switch contact lever being adapted to be periodically and temporarily closed to said other contact element whereby the passage of electrical energy through said filament is energized with an increased voltage and the activity of said filament is stimuiated.

11. The flash-back system of claim 10 wherein said switch means includes an automatic time switching mechanism which is adapted to periodically and temporarily move said contact lever from said one contact element to said other contact element.

References Cited in the file of this patent UNITED STATES PATENTS 1,118,943 Lyon Dec. 1, 1914 2,192,631 Beam Mar. 5, 1940 2,360,608 Kauffman Oct. 17, 1944 2,487,752 Cohn Nov. 8, 1949 2,487,753 Cohn Nov. 8, 1949 2,487,754 Cohn Nov. 8, 1949 2,530,827 Lakota et a1. Nov. 21, 1950

Images