US2726315A

US2726315A - Corrosion resistant immersion heater

Info

Publication number: US2726315A
Application number: US339413A
Authority: US
Inventors: Bruce A Fleming
Original assignee: Edwin L Wiegand Co
Current assignee: Edwin L Wiegand Co
Priority date: 1953-02-27
Filing date: 1953-02-27
Publication date: 1955-12-06
Anticipated expiration: 1972-12-06

Description

Bec. 63, 1955 A FLEMING l CORROSION RESISTANT IMMERSION HEATER Filed Feb. 27, 1953 I N VEN TOR.

United States Patent CORROSION RESISTANT IMMERSION HEATER Bruce A. Fleming, Pittsburgh, Pa., assigner to Edwin L'.` Wiegand Company, Pittsburgh, Pa., a corporation Pennsylvania Application February 27, 1953, Serial No. 339,413

7 Claims. (Cl. 219-38) My invention relates to means for protecting an electric immersion heater against corrosive galvanic action and the principal object of my invention is to provide new and improved means of the character described.

For some time, electric water heaters or tanks have been provided with a protective magnesium rod which is adapted to be immersed in the water in the interior of the tank. This magnesium rod is installed to protect the interior wall of the tank against the formation of rust in the event the protective lining of the tank is faulty. The magnesium rod accomplishes the foregoing by setting .up galvanic currents between itself and the unprotected portion of the tank wall which causes magnesium from the rod to become deposited upon such unprotected portion. This plating action thus protects the interior of the tank against rust and corrosion.

in using magnesium rods in water heaters having conventional electric immersion heating elements, it was found that the magnesium rod was rapidly being consumed because of the galvanic action set up between the rod and the heating element. This galvanic action alected transference of magnesium from the rod to the heating element and, since the bare metallic sheath of the heating element presented a considerable area, the magnesium rod was rapidly dissipated.

ln order to protect the magnesium rod from too rapid dissipation with consequent loss of protection to the tank relatively early in its useful life, it was proposed that the heating element be electrically insulated from the tank wall to thereby break the galvanic circuit between the magnesium rod and the heating element.

insulating the heating element from the tank wall proved satisfactory from the standpoint of magnesium rod life; however, a more serious problem developed. A certain amount of galvanic current flow still occurred between the magnesium rod and the heating element, the current completing the circuit between the heating element and the tank Wall by passing through the water. This resulted in serious corrosion of the sheath of the heating element and consequent early failure of the element when the corrosion reached the interior of the sheath.

My invention solves the corrosion problem that exists in electric water heaters using prior art immersion heating elements. This and other advantages will become apparent from a study of the following description and of the drawing appended hereto.

in the drawing accompanying this specication and forming a part of this application there is shown, for purpose of illustration, an embodiment which my invention may assume, and in this drawing:

Figure 1 is a perspective View of an electric immersion heater constructed in accordance with my invention,

Figure 2 is an enlarged, fragmentary sectional view generally corresponding to the line 2 2 of Figure l, and

Figure 3 is an interior view of a water heater embodyying my improved immersion heater.

rice

As shown in the drawing and particularly in Figure 3, the embodiment of the invention herein disclosed corn prises a U-shaped sheathed electric resistance heating element 10 disposed interiorly of a water heater 11. The wall of the water heater 11 is apertured at 12 to permit insertion of the heating element 10, and the conventional lange member 13 is secured to the inner wall of the heater adjacent the aperture 12 to strengthen the wall at this point.

Although the presently disclosed embodiment of the invention is a flange-mounted element, it will be understood that the element may be secured to the wall of the water heater by any other suitable means.

As illustrated, the heating element 1) comprises a sheathed electric resistance element formed to a generally U-shape to provide spaced-apart leg portions 14. The leg portions 14 extend through respective apertures formed in a gasket plate 15 and each of the legs 14 is secured to the gasket plate by welding, soldering, or other suitable means. The terminal portions of the legs 14 extend beyond the plate 15 as shown, and it is to be understood that the welding or soldering operation forms a water-tight joint between each of the legs 14 and the plate 15 for a purpose that will later be clear.

As best shown in Figure 2, a sleeve 14a is disposed over each leg 14 before securing the gasket plate 15 in position. After the gasket plate 15 has been secured to the legs 1li in the manner heretofore described, each of the sleeves 14a may be secured to the plate 15 by welding, soldering or the like as indicated at 14h. Thus, the legs 11i, sleeves 14a and the gasket plate 15 form an integral unit electrically connected together for a purpose to be shown.

A flange plate 16 is adapted to overlie the gasket plate 15, each of the legs 14 extending through a respective aperture 17 provided in the flange plate. A dielectric sleeve 18 is interposed between the ange plate 16 and the sheath 19 of each of the legs 14 as shown, and a dielectric gasket 2t) is interposed between adjoining faces of the two plates. The plate 16 is recessed at 21 to provide clearance over lips 22 extending laterally of the gasket plate 15, 'and it will be clear that the plate 15 and the legs 111i are thus electrically insulated from the flange plate 16.

As illustrated, conventional terminal pins 23 extend from the ends of each of the legs 14 and the pins are spective ends of the legs 14 for a purpose to be shown.

A dielectric block 25 is adapted to overlie apertures 17 of the flange plate 16, the block 25 being apertured at 26 to pass respective terminal pins 23 and recessed at 27 to provide clearance over the apertures 17 and over the ends of the legs 14 that protrude beyond the flange plate 16. The space defined by the aperture 26 and the recess 27 of the block 25 and the interior of the sheath 19 and the end of the refractory material 24, is adapted to be filled with a semiplastic non-hardening electric insulating putty-like material 28 that serves to seal the open ends of the legs 14 and protects the refractory material 24 against moisture.

The block 25 is adapted to be held in position against the plate 16 in the following manner to thereby lock the foregoing parts together. The block 25 is recessed adjacent each of the apertures 26 to receive one leg of a terminal clip 29 to which a power lead may be attached and each terminal clip is adapted to be spot welded to a respective terminal pin 23 at 30.

As previously mentioned and as shown in Figure 3, the

heating element is adapted to be inserted through the aperture 1'2 in the wall of the water heater 11 and secured in position by cap screws that pass through apertures 31 in the tiange plate and

apertures

32, 33 formed in the gasket 2t) and the gasket plate 15 respectively and that are threaded into apertures provided in the wall of the water heater. It is to be noted that apertures 33 in the gasket plate 15 are enlarged to insure that the fastening cap screws do not engage the plate 15. A dielectric gasket 34 (shown by dot-dash lines in Figures 1 and 2) is adapted to be interposed between adjoining surfaces of the gasket plate 15 and the outer wall of the water heater 11 for sealing purposes.

As shown in Figure 3, a galvanic current 35 will ow between the magnesium rod 36 and the immersion heating element and the circuit will be completed by current passing from the element 10 through the Water and to the wall of the water heater as indicated at 37. However, since the sleeves 14a surround the legs 14 adjacent the wall of the water heater and since the sleeves are electrically connected to the sheath 19 of the legs 14, it will be clear that corrosive galvanic action will attack the sleeves 14a and not the sheath of the heating element.

In view of the foregoing it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

I claim:

l. For use with a vessel containing uid to be heated, an immersion heater comprising a sheathed electric heating element disposed interiorly of said vessel and in electrically insulated relation with respect thereto, and an electrically conductive, sacrificial sleeve surrounding said heater and electrically connected thereto for diverting corrosive galvanic action therefrom.

2. In a liquid heater construction, a metallic tank for the liquid to be heated, said tank having an opening in its defining wall, an immersion heater having a sheathed portion extending through said tank opening and into engagement with the liquid in said tank, and shield means interposed between a part of said tank wall adjacent to said opening and that part only of said sheath which is adjacent to said tank wall part, said means being positioned for attack by corrosive galvanic action, thereby protecting said sheath part from such action.

3. In a liquid heater construction, a metallic tank for the liquid to be heated, said tank having an opening in its dening wall, an immersion heater having a sheathed portion extending through said tank opening and into engagement with the liquid in said tank, and currentconductive shield means electrically connected to said heater sheath and interposed in the path of galvanic current flow between said sheath and said tank to conduct that galvanic current flow from the liquid to the tank which normally would tlow through said sheath.

4. An immersion heater for heating liquid in a container, comprising arigid body having a surface adapted to over-lie the opening into the container, sheathed electric heating means carried by said body and adapted to extend through the container, and a metallic sleeve surrounding said sheath in the vicinity adjacent to the container opening and interposed in the path of any galvanic current flow between said sheath and the container to be subjected to corrosive action which may be induced by said galvanic current flow and thus protect said sheath from such action.

5. In a liquid heater construction, a metallic tank for the liquid to be heated, said tank having an opening in its deiining wall, an immersion heater comprising a supporting body connected to said tank and sheathed heating means within said tank and in engagement with the liquid therein, means electrically insulating said immersion heater from said tank, and current-conductive shield means electrically connected to said heater and interposed in the path of galvanic current flow between said heater and said tank.

6. An immersion heater for heating liquid in a container, comprising a body having a surface adapted to overlie the opening into the container, sheathed electric heating means carried by said body and adapted to extend through the container opening and into the container, a gasket plate adapted to be interposed between said body surface and the adjacent surface of the container margining the container opening to prevent exposure of said body surface to substance within said container, and shield means adapted to be interposed between the sheath of said electric heating means and the adjacent part of said container to conduct any galvanic current ow from the liquid in said container to said container and thus relieve said sheath of such conducting action.

7. An immersion heater for heating liquid in a container, comprising a ferrous body having a surface adapted to overlie the opening into the container, sheathed electric heating means carried by said body and adapted to extend through the container opening and into engagement with the liquid within said container, a non-ferrous gasket plate adapted to be interposed between said body surface and the adjacent surface of the container margining the container opening to prevent exposure of said body surface to substance within said container, and a metallic sleeve electrically connected to said gasket plate and adapted to be interposed in the path of galvanic current iiow between said heater sheath and said tank to conduct that galvanic current flow from the liquid to the tank which normally would tiow through said sheath.

References Cited in the iile of this patent UNITED STATES PATENTS 2,459,123 Bates et al. Ian. ll, 1949 2,560,960 Klumb July 17, 1951 2,617,009 Hasley Nov. 4, 1952 2,649,532 Woodman Aug. 18, 1953