US2912664A - Electric heater element - Google Patents

Description

Nov. 10, 1959 T. s. KINNEY 2,912,654

ELECTRIC HEATER ELEMENT Filed Nov. 9, 1956 INVENTOR. 4 THEODO E s. KINNEY ELECTRIC HEATER ELEMENT Theodore S. Kinney, Bellevue, Wash.

Application November 9, 1956, Serial No. 621,260

El Claim. (Cl. 338-229) This invention relates to improvements in an electric heater element for liquid tanks, and more particularly, relates to a heater element of high wattage, compact design for installation in a tubular heater housing.

Among the more-important objects of this invention are the provision of an electric heater element which has a maximum of heat generating ability in a minimum of mass, which is adaptable to and may be installed in existing tubular housing without requiring alteration of such housing and without the likelihood of damage to such housing, and which is simple to construct and easy of installation.

These and other objects of this invention will be apparent during the course of the following description. I set forth herein a preferred embodiment of my invention. Such changes and modifications as will occur to those skilled in this art and which are the fair equivalents of this invention are contemplated a part of this invention and to be covered by the subjoined claim.

In the drawings:

Figure 1 is a fragmentary elevation view of a fluid tank containing my heater element;

Figure 2 is an enlarged cross-section view taken on line 22 of Figure 1;

Figure 3 is an enlarged elevation view of my heater element with portions broken away and shown in section;

Figure4 is a schematic diagram of the coiled-wire element of my heater;

Figure 5 is a face view of an insulator body of my heater; and

Figure 6 is a face view of a junction block used in my heater.

Referring to Figure 1, within tank 10 is installed the tubular heater housing 12 having its inner end closed by cap 14 and its outer end secured in the threaded and flanged bushing 16. Tank 10 has a threaded fitting 18 attached thereto into which bushing 16 is threadedly engaged. Tank 10 is typified by any conventional hotwater heater tank. The tubular housing 12 is typical of many hundreds of thousands that have been installed over the years. Cap 14 is normally brazed into the end of tube 12. Tube 12 is normally hard soldered into bushing 16. It is imperative, when a low-wattage element as normally supplied with housing 14 is replaced by a high wattage element, that these brazed and soldered water-tight joints not be subjected to heat concentrations operable to destroy the bonds. It has been an object of this invention to provide a heater element which meets this requirement.

The heater element, designated as a whole in Figure 1 by the numeral 20, is cylindrical and closely fits within housing 12 being inserted longitudinally through bushing 16.

As may be seen in Figure 3, the element comprises the inner spacer body 22, the intermediate radiator bodies 24, and outer terminal body 26. Bodies 22, 24 and 26 are formed of high temperature ceramic materials and have identical cross-sections most clearly illustrated in Figure 5. Each body is cylindrical and has a plurality of United States Patent 0 grooves 30 symmetrically arranged in a radial manner relative the longitudinal axis of the body. Each groove 30 has a restricted mouth 32 formed by the closing together of the outer portions of the material forming the walls of the grooves 30. On opposite sides of the body axis is a pair of smaller passages 34, 34. It will be noted that there is an even number of grooves 30 in this preferred form of body. To aid in comprehension of this structure I prefer that such ceramic body be approximately one and eleven-thirty-seconds inches in diameter and that the width of grooves 30 be one-quarter inch with a mouth of approximately one-eighth inch. The length of bodies 22, 24 and 26 varies from one-half inch for body 22, to about two inches with bodies 24, and body 26 is about one and one-half inches long. These dimensions are typical in a water heater in which the overall length of element 20 would be about sixteen inches. Naturally these dimensions would be varied for heaters of greater or lesser capacity yet without departing from the inventive principles involved here. For example, greater diameters and greater lengths may be employed and the heaters may be used in oil tanks and the like.

In Figure 4 I schematically show in plan the arrange ment of the coiled wire resistance element which is threaded into blocks 24 and 26 shown in elevation in Figure 3. From connector lug 36 terminal lead 38 is straight for a distance slightly less than the length of body 26 and is then coiled in sinuous runs 40 as is conventional with electric resistance elements. Runs 40 are physically par: allel to each other and, by means of bends 42 are shown here in series arrangement electrically. The other terminal lead 44 ends at lug 46. It will be apparent that an electrically parallel arrangement is also operable in this apparatus. Deleterious effects on the element wires of juxtaposed elements are avoided by interposing, throughout the full length of the heater, a ceramic wall between each pair of element runs 40. This ceramic wall is constituted by the ceramic material between any pair of grooves 30.

As shown in Figure 3 leads 38 and 44 are passed into the arms of lugs 36 and 46 respectively and are then reversed and the free ends are twisted about the standing part as at 48.

The terminal block 50 formed of similar ceramic material is essentially T-shaped in cross-section and comprises leg 52 and cross arms 54, 54. It supports a pair of bolts 56, 58 outstanding one on each side of leg 52 from the underside of an arm 54. Each arm 54 is also posted to form a passage 60 through which the terminal leads 38 or 44 are passed.

In the assembly of Figure 3, a run 40 of the coiledwire resistance element passes through aligned grooves 30 of a series of bodies 24. At each end of an adjacent pair of runs a bend 42 straddles the wall material separating adjacent grooves. This may be seen in Figure 3. The resistance is sinuously arranged in the grooves 30 in the arrangement depicted in Figure 4. Leads 38, 44 outstanding from the outer end of the series of bodies 24 are passed into and through mating grooves 30 in body 26, thence through one of the passages 60 whereupon the lug 36 or 46 is attached and same secured to a bolt 56 or 58 I by a nut 62.

By arranging that all the holes 34 of bodies 22, 24 and 26 are aligned with a similarly spaced pair of holes 64, 64 through block 50, a wire bent U-shaped to provide strands 66, 66 may be inserted from the outer end inward. The inner ends of wires 66, 66 pass through the spacer body 22 and twist 68 secures them together and retains the bodies and element in assembled relation.

This electric heater element may be installed in the tubular housing 12 by longitudinal insertion. The terminal block 50 bears on and abuts the outer face of bushing 16. Supply conductor wires 70, 70 are then connected to bolts 56 and 58 and the heater will operate.

By means of the construction described and shown, when the heater is activated and the coils 40 are radiant the heat generated passes outward of grooves 30 through throats 32 and directly to the inner surface of tube 12 to heat the same. By this means I insure that the maximum amount of heat from the element to the heat/transfer surface be by direct radiation and not only by conduction through the ceramic bodies. This arrangement eliminates any possibility of a serious accumulation of heat within the ceramic bodies, especially along their axis, which would tend to destroy them. Since no elementruns are located within the symmetric arrangement here there is likewise avoided any possible damage to the element from over-heating. U a

The use of spacer body 22 separates the brazed in place cap 14 from the heat sufliciently to. avoid heat-destruction of the brazing. Likewise terminal body 26 spaces the radiant heater element away from the soldered junction between tube 12 and bushing 16'to avoid its injury or destruction.

It will be seen from the foregoing that this apparatus effectively accomplishes the stated and other apparent objectives with simplicity and certainty.

Having thus described my invention, I claim: An electric heater element for installation in a tubular ,metallic heater housing, comprising: an inner spacer body, an intermediate radiator body, and an outer terholes aligned; said intermediate radiator body being cylindrical and having a plurality of grooves radially disposed longitudinally along its outer surface, each said groove being inwardly enlarged relative the mouth of the groove for the reception of a coiled resistance element larger in cross-section than said groove mouth; a coiled wire resistance element, sinuously laced into said grooves in continuous manner from a first terminal end to a second terminal end, said terminal ends both being located at the outer end of said radiator body, and said terminal body having'a pair of passages each to receive a terminal end for external connection to a power source and a U-shaped,

straight strand, wire loop inserted into said aligned holes from the outer end inward andhaving the inner strand ends joined together to secure said bodies against endwise movement relative each other and providing an extension protruding longitudinally from said spacer body to abut the inner face of the tubular housing and separate the inner spacer body therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,320,890' Moffat Nov. 4, 1919 1,394,518 Abbott Oct. 25,1921 7 1,715,287 Head May 28, 1929 2,666,838 Krah et a1. Jan. 19, 1954 FOREIGN PATENTS 105,946 Great Britain Apr. 30, 1917 5,323 Australia Dec. 24. 1926

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