US2155239A - Electric heater - Google Patents

Description

Ap 1939- c. P. RANDOLPH ELECTRIC I HEATER Filed May 15, 1936 Inventor: Chow-\es F? F? ndol'ph, y WMZ ILJML is Attorneu.

Patented Apr. 18, 1939 UNITED STATES 2,155,239 ELECTRIC HEATER 7 Charles P. Randolph, Oak Park, 111., assignor to Edison General Electric Appliance Company, Incorporated, Chicago, 111., a corporation of New York Application May :15, 193 Serial ,No. 79,887 1 Claim. (01. 201-6 1) This invention relatesto electric heaters, more particularly to electric heaters of the metallically sheathed type, and it has forits object the provision of an improved terminal structure for heaters of this character which is electrically and mechanically strong and which is impervious to moisture and dirt. n 7

Although this invention has other applications, it is particularly useful in connection with electric immersion heaters of the type having an encased or sheathed heating unit in which an insulated resistance conductor is enclosed in; an outer metallic protective casing. One immersion heater of this type is described and claimed in the United States Patent to C. C. Abbott, No. 1,322,992, dated January 13, 1925. 1

.As there described, the heater is formed into the shape of a hair pin so thatits terminal ends are adjacent each other. ,Some difllculty has been experienced with heaters of this type due to electrical break-down of the terminals during severe electrical storms, such as occur, for example, in thesouthern states of the United States. 1 g

It is an object-of thisinvention to increase materially the electrical strength of the terminals of electrical heaters, especially those ,of the immersion type referred to above. ,At' the same time, this invention contemplates a mechanically strong terminal construction, and one that is moisture and dirt proof.

In accordance with this invention, the ends of the sheath and the terminals projecting therefrom are embedded in a substantially homogeneous mass of electrically insulating and sealing material. It is contemplated that this mass of material have a high electrical resistance and also a relatively great mechanical strength.

For a more complete understanding of this invention, reference should be had to the accompanying drawing in which Fig. 1 is a fragmentary elevation of an electric heater embodying this invention, portions being broken away and portions shown in section so as to illustrate certain details of construction; and Fig. 2 is an end elevation of the electric heater of Fig. 1.

Referring to the drawing, I have shown my invention in one form in connection with an electric immersion heater of the type described and claimed in the above-mentioned Abbott patent. This heater is provided with a pair of sheathed heating units Ill mounted in a suitable supporting member II. The heating units Ill have substantially the same construction, and each heater, as shown, is of the helical coil sheathed type,

, ly insulating disc-shaped mass of sealing material described and claimed in the United States Patent to C. C. Abbott No. 1,367,341, dated February 1, 1921. Briefly, eachheater comprises an outer metallic sheath I2 in which a helical, electrical resistance conductor i3 is embedded'ina com- I pacted mass of powdered heat refractory, electrically insulating material it, such as magnesium oxide. ,The resistance conductor I3 has its ends secured in any suitable manner to electrical terminals I5 which project from'the ends of the sheath and which have theirinner ends, as shown, embedded in the insulating mass M. Such units can be bent easily into any desired shape. In the immersion heater shown, each heating unit is bent substantially in the form 15 of a hairpin. Clearly, various other arrangements and configurations of the heating unit may be used.

The ends of each hairpin heating unit ID, as shown, are directed through suitable spaced apertures l6 provided for them in the metallic supporting member it so to pass through irom one side to the other of the supporting 18. This mass of material i8 preferably will be formed of a suitable phenol condensation product.

Preferably, the bushings il will be so proportioned that their outer faces will not extend to the outer face of the support i l, but will fall short thereof so as to provide shallow recesses 19. These recesses will be filled with the insulating sealing material I8. These recesses assist in anchoring the insulating mass.

Also, it is preferable that the mass of powdered insulating material 14 in the sheath come substantially close to the ends of the sheath, but not quite to these ends, so that relatively shallow cup-shaped recesses 20 are provided in the ends. These recesses also are filled with the insulating sealing material so that the ex- Hosed portions of the insulating material 14 at the sheath ends are completely covered by the rial I4, and thereby increases the electrical strength of the heater.

Secured to the outer ends of the terminals ll are terminal connection members 2l= shown to be in the form of nuts threaded to the terminals. The lower ends of these members 2|, as shown, are knurled and these knurled portions are'embedded in the insulating mass ll so as to secure the members 2| rigidly to the terminals, and so as to insulate them from each other.

In making the electric heater thus far described, it will be understood thabthe heating units l0 will be constructed in the form of hairpins, and their ends will be projected through the apertures It provided for them in the support II and secured to the support by means oi the bushings ll. Previous to this the ends of the sheath will be reamed out to provide the recesses 2!. Then the terminal members 2| will be threaded on the terminals. After this, the mass of insulating material I8 will be applied. This insulating material may be applied in any suitable fashion, but preferably will be applied autosmall nuts 25 secure the jumpers to the opposite pair of terminals.

It will be observed that the mass of insulating and sealing material l8 projects for a material distance from the metallic plate II. Thus, it forms a sealing mass embedding the ends of the sheath and the terminals to remove the terminals electrically from the sheath l2 and the supporting plate I I, as well as from each other.

Moreover, it will be observed that the insulating mass 18 covering the exposed ends of the insulating material i4, and embedding the ends of the sheath and the terminal portions which project from the sheath completely seals the heating unit against the admission of moisture and dirt.

It is also to be noted that the insulating mass [8 is anchored solely by the support II, the projecting ends of the sheath, the terminals and terminal connector members 2|, the adherence of the insulating mass to these members constituing the sole supporting means for the mass.

The connector members 2| are rigidly sec by the insulating mass. This arrangement with the rigid structure eiiected by the Jumpers at the terminal ends makes a very strong terminal structure.

Ithasbeeniound thatmyterminalsealis superior mechanically and also electrically to those in-use heretofore. The electrical superiority is particularly noticeable in those sections of the country where severe electrical storms occur. Previous to this invention, diiiiculty was experienced by electrical break-down oi the terminals. This invention has obviated this diiiiculty.

While I have shown a particular embodiment of my invention, it will be understood, 0! course, that I do not wish to belimited thereto since many modifications may be made, and I, therefore, contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent 0! the United States, is:

An electric heater comprising a resistance conductor, a metallic sheath encasing said conductor having its ends adjacent each other, terminals within the end portions of said sheath connected with said resistance conductor and projecting from said ends, a mass of ctrically-insulating, heat-conducting material bedding said resistance conductor and the inner ends of said terminals, said mass extending not quite to the ends or said sheath so as to leave shallow cup-shaped recesses in said ends, a metallic support having spaced apertures extending through it through which the ends of said sheath are passed from one side to the other of said support so as to project beyond the latter side of said support, a single, substantially homogeneous disc-like mass of electricallyulatigg sealing material molded on said side a d projfiting therefrom to embed the projecting ends of said sheath and the terminals projecting from said ends and so as to fill said recesses in said sheath, and terminal members having exterior knurled portions secured to said terminals spaced from the ends of said sheath and having said knurled portions embedded in said molded mass of insulating sealing material, the sides and outer surfaces of said mass 0! insulating material being exposed and the adherence of said mass to said side of said support, and the portions of said sheath, terminals and terminal members embedded thereby constituting the sole supporting means for said mass.

CHARLES P. RANDOLPH.

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