US2448497A - Flame electrode control device - Google Patents

Description

Aug. 31, 1948.

J. O. ROSCHE FLAME ELECTRODE CONTROL DEVICE Filed April 18, 1945 INVENTUI? Jon 0105015 flfrfllflvf) Patented Aug. 31, 1948 FLAME ELECTRODE coN'rnoL DEVICE JohnO. Rosche, Minneapolis, Minn asslgnor to Minn 'eapolis-Honeywell' Regulator Company,

Minneapolis, Minn., a corporation ofDelaware Application April 18, 1945, Serial No. 588,960

My invention is generally related to a combustion control device. One particular use of the arrangement is'in conjunction with 'a flame detecting mechanism used in an electrically operated combustion system and comprising a flam detecting electrode. g

Flame detecting mechanisms are well known and their function is un rstood by persons skilled in the art. In brief, devices of this particular nature are positioned in the combustion area of a furnace or the like so that a flame may impinge upon a portion of the device. The electron conducting property of the flame is utilized to complete an electric circuit which will include the detecting mechanism and generally the burner from which the flame is issuing. The relatively small current so conducted is then greatly amplified and utilized as a control impulse for operating mechanisms associated with the proper operation of the furnace or the like.

' The previously known devices generally consisted of a metal rod which served as an electrode and was insulatingly mounted in the side of a furnace with the rod extending to a point adjacent the burner. After a period of use, and particularly when the device is used in conjunction with an oil burning furnace, a deposit of the products of combustion will. form on the rod and its supporting structure in such a manner as to provide a conduction path between the electrode and its supporting structure or the body of the furnace, both of which are usually connected through ground to the burner.

In certain flame detecting apparatus of this general nature, a continuous deposit of the prod- .ucts of combustion between the electrode and other flame detecting apparatus is designed to distinguish between a flame and a short circuit;

in this case the short circuit usually causes the flame detecting, apparatus to'be maintained in a condition normally assumed when there is no flame even though a flame be actually present thereby causing a less dangerous but troublesome culty in either type of apparatus, it was customary to mount the electrode in a long pipe or tube to impede the deposition of these combustion 5Claims. (01.158 28) products-between the electrode and the supporting member. However, when the deposition was the result-of a minor explosion or blow-back it ternal surfaces of the tube in such a manner as to form a -conduction path between the eleca functioning of the furnace. To off-set this diffitrode and the support and thereby defeat the purpose of the tube.

To completely overcome this difllculty, the present device is constructed with a protector which is mounted in relation to the insulator and the electrode to prevent the formationof I such a continuous layer of the products of combusiion which may result as either a gradual accumulation or a rapid deposition which might result from a blow-back. The protector is constructed in the form of a cup-shaped baflle whichis mounted on the insulator and in electrical contact with the electrode, but positioned so that theclosed end of the cup-shaped protector extends in the direction of the combustion area, while the open end of the cup-shaped protector surrounds the insulator for a substantial distance in such a manner that it is neither in contact with 'the insulator nor the supporting structure. Thus it will prevent -a direct deposition of the products of combustion over the entire length. of the insulator and it also provides. an enclosed air pocket about the insulator which forms a compressible air cushion to prevent the products of combustion from entering the enclosed portion between the protector and the insulator.

The principal object of the invention is to provide an arrangement for mounting a flame detecting electrode in a supporting structure in such a manner as to prevent the deposition of a. continuous layer of the products of combustion having conducting properties from forming between the electrode and the supportingmember.

Another object isto provide means for mounting an electrode within a furnace with a protector that forms a compressible air. cushion around a portion of the electrode supporting structures, so as to prevent the formation of a short circuiting, layer of substances resulting from combustion within the furnace.

Other and further objects may become apparent from the following description and claims and in the appended drawing in which the single figure is a cross-sectional view of the assembly with certain parts broken.

' Referring now to the drawing, the device consists of a metallic electrode H! which is mounted within a casing member indicated by the general refe'rencenumeral H. The casing II is adapted to be threadedly disposed on a nipple l2 which is suitably fastened as by welding in the wall of ,a furnace, indicated by the reference numeral IS, in such a manner that a flame |4 issuing from a burner pipe l5 will impinge on a portion of the electrode Ill.

The casing II has a tubular shank portion l6 which is provided with an inwardly disposed threaded portion ll, adapted to cooperate with the threads on the nipple l2. At its other end, the shank portion I6 is provided with a flange |8, in which are'disposed a number of screws I!) for supporting a cup-shaped -member 20 against the flange It! by a plurality of key hole slots, not shown. One or more apertures 2| are provided in the cup-shaped member 20 to provide for the passage of conductors to the electrode. A cap member 22 is provided to be frictionally engaged on the open end of th cup-shaped member 20 to enclose the same.

A spacing adapter 23 is threadedly disposed within the flanged portion of the shank I6 to support an assembly of parts. A ceramic tube 25, preferably formed of Pyrex, is positioned within the adapter and sealed thereto by a cement ring 24 which is introduced in a fluid form' between asbestos washers 24a, 24b and permitted to solidify as a sealing means. A metallic tube 26 is located within the Pyrex insulator 25 in such a manner that it engages and supports the electrode ill. The metallic tube 26 is fastened to the insulator 25 by a soft washer 21, a metallic washer 28, and a nut 29, which is threaded on the outer periphery of the tube 26. A connecting adapter 30 having an internal thread and provided with a compressible washer 3| surrounds both the electrode l and the tube 26 in such a manner that when it is turned on the threaded portion of the tube 26, the adapter will firmly engage the electrode [0 within the assembly. By loosening adapter 30 on tube 26, the electrode Ill which is held in place by pressure on the soft washer 3|, may be readily removed through the rear of the adapter without removing the casing II from the furnace wall.

,A protector in the shape ofv a cup-shaped baille 35 surrounds a portion of the insulator 25 within the shank 6 so as to form a partially enclosed air layer about the insulator 25. The protector 35 is fastened to the tube 26 by spinning or swaging and is separated from the insulator 25 by a soft insulating washer 36. This bailie or protector 35 constitutes a vital part of the device and is constructed to prevent the formation of a continuous layer of soot between theelectrode l0 and any of-the metallic parts of the casing indicated by the general reference numeral H in such a manner that current conducted by the electrode could be short circuited to the casing. Current is conducted from the amplifier 40 through conductor 4| to the adapter 30, whence it travels through the electrode It). In the event the flame I4 is existent, current will be conducted through it to the burner whence it returns to the amplifier through conductor 42. The flame i4 and burner l5 are shown merely'as an example to illustrate the electrical path and in actual use may be either an oil burner or a gas pilot. In actual use, the electrode l0, which is shown as being broken, may extend into theifurnace for a sufficient distance to beadjacent the combustion area.

When in operation, the combustion process within the furnace will produce waste products which are normally of a gaseous nature and whose escape is provided for by the exhaust flue. When oil is used as a fuel it frequently happens that through incomplete combustion a portion of the hydrocarbons are not completely consumed and the gases become ladened with a carbonaceous soot. Not all of the soot will escape through the flue and this portion will tend to settle on the surrounding walls and portions of the furnace. The flame detecting mechanism which is normally positioned in a side wall of the furnace is equally subject to the deposition of. soot along with other interior parts of the furnace. However, if' a continuous layer of soot forms on the electrode and its supporting structure this will result in th undesirable short circuit previously mentioned. Under normal operation, only a relatively small amount of the soot ladened gases will enter the device and this soot will principally deposit on the exterior of the bailie. However, at times, and due to delayed ignition, aminor explosion may occur forming gases which contain a relatively large amount of soot. These gases expand rapidly and will force themselves in all directions. Under these conditions, the gases entering the device are initially retarded by the fact that the enclosure is sealed, but the soot will nevertheless be deposited on the interior walls of shank IS, the exterior of battle 35, and to a structur I From the foregoing,-it should be evident that I have, by this arrangement, mounted a conducting electrode within a combustion furnace in such a manner that it may be readily removed for replacement, and a particular featureof the device is that the products of combustion cannot deposit themselves between the electrode and its supporting structure in such a continuous manner as to provide a short circuit for the current conducted by the electrode. As my invention may assume different shapes and proportions, I do not wish to be limited by the single disclosure, but rather by the terms of the appended claims.

I claim as my invention:

1. In a combustion indicating device, in combination, an electrode for conducting current in a circuit which includes a flame, means for insulatingly supporting a portion of said electrode adiacent a combustion area, and means for preventing formation of a continuous conducting deposit of the products of combustion between said electrode and said supporting means, said means including a hollow cylindrical member surrounding said supporting means in spaced relation and sealed thereto at the end nearer the combustion area to form a. static air pocket in cooperation with said supporting means.

2. In a device or the class described, a housing structure adapted to be mounted in communitubular protecting baffle surrounding said insulator in'spaced relation thereto and formed at one end to engage said insulator to form a sealed junction with said insulator with the sealed end extending in the direction of the combustion area, said baille cooperating with said insulator to form a static air pocket to prevent deposition of residual combustion products on the surface of said insulator enclosed by said baffle.

3. In a device of the class described, a housing structure adapted to be mounted in communication with the combustion area of a furnace, a conducting electrode adapted to be mounted within said housing and extending into the combustion area of said furnace, an insulator supportingly surrounding a portion of said electrode to electrically isolate's'aid electrode from said housing, and a hollow cylindrical baflle surrounding a portion of said insulator in spaced relation and sealed thereto at the end adjacent the combustion area of said furnace, said baflle cooperating with said insulator to form a static air pocket operable to prevent the deposition of the residual products of combustion upon the entirety of said insulator exposed to the combustion in said furnace.

4. In a device of the class described, a housing structure adapted to be mounted in communication with the combustion area of a furnace, a current conducting electrode, an insulator, said insulator surrounding an end portion of said electrode and insulatingly supporting the end portion of said electrode within said housing, and a, hollow cylindrical member having an inner diameter larger than the outer diameter of said insulator ber and said insulator forming a static air pocket to prevent the deposition of the conducting ressymmetrically spaced about said insulator and 35 sealed thereto at the end of said member facing the combustion area of said furnace, said memidueof combustion products upon a portion of said insulator.

5. In combination, a hollow housing structure adapted to be mounted in-communication with the combustion area of a furnace, a current conducting electrode, coupling means, an insulator, said insulator being mounted within said housing, having an outside'diameter less than the inside diameter of said housing, surrounding an end portion of said electrode, and sealed at one end of said housing by said coupling means to form a, forwardly facing static air pocket, a hollow cylindrical member having a mean diameter less than the inside diameter of said housing but greater than the outside diameter of said insulator and sealed to said insulator at the end of said member closest to the combustion area of the furnace, said member and said insulator comprising a rearwardly facing static air pocket within said forwardly facing pocket to prevent the deposition of residual combustion products on the surface of said insulator within said rearwardly facing pocket.

' JOHN O. ROSCHE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Yates May 12, 1942

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