US2748250A

US2748250A - Thermoelectric protective unit

Info

Publication number: US2748250A
Application number: US377515A
Authority: US
Inventors: Orrin E Andrus
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1953-08-31
Filing date: 1953-08-31
Publication date: 1956-05-29
Anticipated expiration: 1973-05-29

Description

y 9, 1956 o. E. ANDRUS THERMOELECTRIC PROTECTIVE UNIT Filed Aug. 31, 1955 INVENTOR Orrm E.Anclrus ATTORNEYS.

United States harem THERMOELECTRIC PRQTECTWE Orrin E. Andrus, Milwaukee, Wis, assignor to A;. 0. Smith Corporation, Milwaukee, Wis, a corporation of New York Application August 31, 1953, Serial No. 377,515

11 Claims. (Ci. 219-48) This invention relates to a thermoelectric device in combination with the controls of a liquid heating mechanism for the purpose of insuring the adequate cathodic protection of the metallic surfaces in contact with the liquid being heated or stored. This invention is particularly adapted for protection of a domestic hot water heater and the like.

An object of the invention is toprovide an automatic shutoif of the main burner heating the liquid should the cathodic protection become inadequate to prevent corrosion of the metal surfaces.

Another object of the invention is to provide a thermoelectric generator having the dual function of serving as a source of current for cathodic protection and also serving as a source of current for an electrical safety mechanism with which to control the heat source for the liquid.

Another object of the invention is to provide a thermoelectric generator unit wherein the casing for the unit may be utilized as one of the thermoelectric elements.

Another object of the invention is toprovide a cathodic protection device which shuts olf the main burner should component parts of the device fail.

A further object of the invention is to provide a simply constructed and low cost unit for insuring cathodic protection of a hot fluid storage tank.

in general, the protective unit comprises a thermoelectric generator utilized in combination with an anode for cathodic protection of a fluid container and in combination with an electrical device capable of discontinuing the heat supply to the fluid stored in the container for purposes of warning of inadequacy of cathodic protection and of minimizing corrosion. For purposes. of illustration, the adaption of this device to a domestic hot water heater is described. The thermoelectric generator, housed in a casing, is heated by such means as a gas flame, a pilot burner, or an electric heating element. It. the source of heat is reduced for any reason so that the thermoelectric generator is not generating a suflicient current for effective or desired cathodic protection, the current generated and carried to the safety device hecomes inadequate to energize the electrical device and as a result the heat supply to the water is automatically discontinued. If used with a pilot burner in conjunction with a combustion-type heater, the electrical device may also shut off the gas supply to the pilot burner to insure maximum. safety. The inability to draw hot. water from the container serves to indicate the probable necessity of repair and relighting of the pilot burner.

Water heater corrosion during a period of shut off of cathodic protection is substantially arrested by reason of the discontinuance of heat input. Water is far less corrosive when cold than when hot. Furthermore, dissolved air and carbon dioxide which are necessary to support water corrosion are excluded from further entrance into the container if water is not withdrawn by reason of the lack of heated water.

Zfidhfiih Patented May 239, 1956 ice In the drawing:

Figure l is a cross-sectional view of the thermoelectric generator unit attached tov the wall of a container and connected. in circuit with an anode and a safety shut oif device;

Fig. 2 is a cross-sectional view of another embodiment of the thermoelectric generator unit;

Pig. 3 isa cross-sectional view of another embodiment of the thermoelectric generator unit;

Fig. 4 is-a cross-sectional view of a fourth embodiment of. the invention.

Referring particularly to Figure l, the thermoelectric generator. unit comprises a generally cylindrical casing 1 which is formed from a heat-resistant metal or other suitable material. The casing 1 is formed by deep drawing a blank to provide a one-piece housing having a generally curved outer end 2. The construction of casing 1 is one piece so that no welding of the curved outer end 2 need be resorted to in order to close the outer end of the casing. If welds are employed in the construction of casing 1, it is so positioned that the Welds are removed from the location where heat is applied, as subsequently described.

Thecasing 1 not only houses the thermoelectric elements, but also supports an anode 3 protruding from the casing and extending into the structure to be protected as disclosed in my copending application entitled Thermopile-Anode Structure, Serial No. 365,798, filed July .3, 1953. For purposes of illustration, the casing is secured within an opening in the structure to be protected with the open end of the casing extending a suitable distance within the structure. Alhough the casing 1 is shown secured to wall 4 by a circumferential weld 5, it may be otherwise secured thereto as by threads.

The open end of easing 1 supports the anode 3 projecting within liquid in the structure. The anode 3 is supported in the casing l as by swaging or clamping'the casing 1 about the anode. To insure a physically strong attachment to the casing i, the anode 3 is annularly recessed, as at 6. A tubular member 7 of neoprene rubber or other suitable insulating and sealing material is disposed between anode 3 and the casing 1. The tubular member 7 is folded back over. the end of the casing to minimize the current flow between the anode and the casing 1.

The container Wall is coated with. an insulating lining 8 of vitreous enamel or other suitable material.

The embodiment of the thermoelectric generator unit illustrated in Figure l is composed of a thermopile h and --resist'ant insulating material is placed between the closed end 2 of the casing 1 and the hot junctions of the thermopile 9. Similarly, a suitable insulating material 12 is disposed between the anode 3 and the cold junctions of the thermopile 9.

In accordance with this invention it is immaterial how thethermopile is constructed. it will sufi ice to state that the thermopile is suitably insulated from the casing or any other metal members with which it might come into contact to thereby prevent electrical shorts.

The positive terminal of thermopile 9 is connected to the anode 3 and the negative terminal is connected to the casing 1. When the hot junctions of the thermopile are heated, a currentv is generated by the thermopile which flows to the anode, through the liquid within the structure, to the wall of the structure, and back to the thermopile.

The thermocouple 10 is formed with a conductor 13 and the casing 1 as the thermoelectric elements. The conductor 13 is welded to the casing 1 generally centrally on the inner surface of the curved end 2 thereof to form the hot junction of the thermocouple. Conductor 13 extends through an aperture 14 in casing 1 and is connected to one side of the relay winding 15 of electromagnetic relay 16. The casing 1 is connected to the other side of winding 15 by a conductor 17. When the hot junction of the thermocouple is heated, the relay winding 15 is energized and holds a contact 18, carried on an armature 19, in a closed position with a contact 20.

The aperture 14 in the casing is hermetically sealed about the conductor 13 in order to prevent the approach of any injurious foreign matter from the surrounding atmosphere to the thermopile 9. The sealing of aperture 14 in the casing is accomplished by brazing or otherwise securing a metallic tube 21 to the wall of the aperture. The conductor 13 passes through the tube 21 and disposed therebetween is powdered magnesium oxide 22 or other suitable insulating material. The end of the tube 21 is sealed by a member 23 of plastic or other suitably pliable material held under compressive forces within the end of the tube 21 about the conductor 13. The member 23 is held in the tube 21 by crimping the end of tube 21 inwardly as at 24 over a fiber washer 25 or the like disposed between the member 23 and the inwardly crimped portion of the tube. This form of seal is disclosed in my copending application entitled, Sealed Thermopiles, filed April 20, 1953, Serial No. 349,696.

Armature 19 and the

contacts

18 and 20 are connected in series in the power supply circuit of a solenoid operated valve 26. The valve 26 is inserted in the fuel line 27 such that fuel may flow to the main burner, not shown, only when the solenoid 28 is energized.

In addition to the normal function of igniting the main burner, a pilot burner 29 simultaneously heats the thermopile 9 and the thermocouple 1t and thereby creates a flow of current in each when the pilot burner is lighted. Although the pilot burner 29 is connected, as diagrammatically illustrated, to the fuel supply line following the valve 26, it may be connected to the fuel line preceding the valve 26. If the pilot burner is connected before the solenoid valve 26, it continues to operate after the main burner is extinguished whereas if connected after the valve 26, it is extinguished when the valve closes and the pilot burner unit must then be manually re-started.

Although a flame of a pilot burner is illustrated for the operation of the thermoelectric generator, it is possible to employ a flame other than that of the pilot burner.

The fuel safety shutoff system, as shown, is for purposes of illustration only and may be replaced by any other suitable electrically controlled system; for example, 1) an electromagnetic relay switch to shut oif an electric heating element such as is used in conjunction with electric water heaters, (2) an electromagnetic relay to operate a small gas valve which in turn opens and closes the fuel line, or (3) a vacuum tube relay to control the heat source.

The operation of the embodiment of the invention as illustrated in Figure 1 is described as follows:

The pilot burner 29 heats the hot junctions of the thermopile 9 and the thermocouple and thereby generates a current flow in each of them.

The current from the thermopile 9 is employed to cathodically protect the wall of the structure from corrosion.

The current from the thermocouple 1t energizes the relay winding and holds contact 18 engaged with contact 211 in order to close the energization circuit for solenoid 28. When energized, the solenoid 28 opens the valve 26 and allows fuel to flow to the main burner.

When the flame of pilot burner 29 is extinguished or appreciably diminished in intensity, the current generated by the thermopile 9 is inadequate to effectively cathodically protect the structure from corrosion. If the latter of one end of the casing to one side of the relay 41.

occurs, the current generated by the thermocouple 10 is reduced and the relay winding 15 is de-energized and consequently contact 18 is disengaged from contact 20. The energization circuit for solenoid 28 is then open and the valve 26 closes the fuel line 27 with a consequent discontinuance of the heating of the liquid within the structure.

The operation of the invention, in general, and the advantages thereof have been previously described and no further explanation is deemed necessary.

Fig. 2 illustrates a construction of a thermoelectric generator unit which does not physically support the anode.

The anode 34) is separately secured to the structure to be protected of which only the wall 31, corresponding to the wall 4 of Figure 1, is shown and insulated therefrom in any suitable manner, such as illustrated and described in my copending application entitled, Self-Sealing Anode Structure, Serial No. 365,797, filed July 3, 1953. A plug 32 is threaded in the wall 31 with anode 30 extending from the plug into the liquid within the structure. The anode 30 is insulated from the plug 32 by suitable insulating material 33 disposed therebetween. An electrical conductor 34 extends from anode 30 through the plug 32. A pliable sealing and insulating material 35' held under compressive forces about the conductor 34 seals the unit against leakage.

A thermopile 36 is housed in a hermetically sealed casing 37 with the cold junctions 33 at both ends and hot junctions 39 at the center as set forth in my copending application entitled, Sealed Thermopiles, Serial No. 349,696, filed April 20, 1953.

The positive lead 41) of the thermopile extends out The negative lead 42 of the thermopile is connected to the casing 37 as by weld 43 and the casing 37 is connected to the wall 31 as by conductor 44-. The relay 41 is connected to the anode 311 by conductor 45 to complete a series circuit which for purposes of illsutration is shown as follows: Starting with thermopile 36 the current flows through the relay 41, the anode 36, the fluid in the structure, and the wall 31 of the structure back to thremopile 36.

The relay 41 is connected in a safety circuit, as shown and described in Figure 1, or in any other suitable safety circuit.

The operation of the embodiment of the invention, as shown in Fig. 2, is the same a described with Figure 1 With the additional safety feature that if practically any component part of the system fails the heating mechanism is shut off.

The embodiment of the invention illustrated in Fig. 3 utilizes a thermopile with the anode and an electromagnetic winding connected in parallel thereto.

The thermopile 46 is constructed as previously described for Fig. 2. A conductor 47 is connected to one of the cold junctions of the thremopile to carry a current therefrom to the relay winding 43 of an electromagnetic gas valve 49. The other side of the relay winding 48 is connected to the casing as by conductor 50. The condoctor 47 is connected to the thermopile 46 at any desired junction to carry a suitable current to the relay winding. 48.

For purposes of illustration, a standard electromagnetic gas .valve 49 is shown as an alternative safety mechanism for the relay 16 and solenoid valve 26 of Fig. 1.

The gas valve 49 comprises a chamber 51 with a diaphragm 52 separating the chamber into two compartments.

The relay winding 48 is housed within the upper compartment (in the drawing) and is connected to the thermopile as previously described. The armature-53 of relay winding 48 is pivotally supported from the upper wall of the chamber 51.

Positioned to the left of the armature 53 (in the drawarenas-o ing) is an exhaust nozzle 4 terior of the chamber '51.

Positioned to the right of the armature 53 (in the drawing) is a gas inlet nozzle 55 which extends from the chamber 51 and communicates'with the gas line 56 from the main supply, not shown.

The nozzles 5 and 55 are so positioned with" respect to the armature 53 that when the relay winding 48 is energized the gas nozzle 55 is closed; whereas, when the relay winding 48 is de-energized the exhaust nozzle 54 is closed. When the one nozzle is closed, the other nozzle is open.

he lower side of the diaphragm 52- carries a valve closure member 57 which opens and closes the gas line 56 extending Within the lower compartment in chamber 51. An outlet pipe 58 carries the gas from the lower chamber to the main burner, not shown, when the gas line 56 is open.

The operation of the valve is described as follows: The current from the thermopile as energizes the relay winding 43 which closes the gas nozzle 55 and opens the exhaust nozzle 5d. The gas flows from the gas line 56 forcing the valve member 5'7 up and thereby permits the flow of gas to the main burner. If the current from the thermopile d6 discontinues or is sufiiciently reduced, the armature 53 is released and the gas nozzle 55 opens while the exhaust nozzle 5 closes. Gas then passes through the nozzle 55 and forces the valve member 57 against the valve seat of the gas line 56 and shuts oif the flow of gas to the main burner.

The positive terminal 59 of the thermopile is connected to the anode 60 to carry a current thereto. The anode is secured to and insulated from the structure Wall 61, as described with respect to Fig. 2. The wall of the structure is connected to the thermopile housing 62 as shown by conductor 63.

The embodiments of the invention illustrated in Fig ures l and 3 function in the same manner except that the embodiment in Fig. 3 also discontinues the heating of the liquid if the thermopile structure breaks down.

Other than for the above noted changes, the embodimerit of the invention described in Fig. 3 is the same as Fig. 2.

Fig. 4 illustrates an embodiment of the invention suitable for use with an electrically heated water heater. This embodiment employs an electrical heating element to heat the thermoelectric generator.

The thermopile 64 is constructed as previously described with respect to Figs. 2 and 3. The positive terminal 65 is connected to the anode 66' and thenegative terminal is connected to the casing 67 whichis in turn connected to the structure wall 68.

A thermocouple s9 is housed within the casing 67 and is heated by an electric heating element 7% which is connected to a suitable source of heat. The thermocouple 69 is electrically insulated from the thermopile 64 and the casing 67.

Thermocouple 69 is connected across the relay winding 71. The relay winding 71 opens and closes the contacts '72 which are connected to a suitable electric safety system, not shown, to shut off the flow of electricity to an electric heating element, not shown, for heating the liquid in the tank. Contacts 72 may, if desired, be so constructed as to require manual resetting. following the opening of these contacts as a result of insufiicient heat applied to the thermocouple 69.

Other than for the above noted changes, the embodiment of the invention illustrated in Fig. 4 is the same as Fig. 2.

The thermocouple 6d may be replaced by a suitable thermopile within the scope of the invention.

The embodiment of the invention in Fig. 4 operates to protect the structure against corrosion in the same manner as previously described with respect to Figure 1.

The above described invention provides a compact which extends to the ex- G thermoelectric apparatus for insuring adequate cathodic protection of a metallic surface in contact with acorosive liquid.

Various modes of carrying out the invention are corrtemplated as within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

Various embodiments of the invention may be employed within the scope of the following claims.

I claim:

l. A thermoelectric protective apparatus for insuring cathodic protection of a metallic structure in contact with a heated liquid, which comprises an anode supported in contactwith said liquid, a thermoelectric generator having a. positive terminal connected to said anode and having a negative terminal connected to said structure, electrical insulation disposed between said anode and said structure to permit maintenance of a potential difference therebetw'een by said thermoelectric generator, a separate source of relatively low heat for energization of the thermoelectric generator, an electrical heat control device connected to the heat source for said liquid, and said thermoelectric generator being electrically connected to said heat control device to discontinue the heating of said liquid if the current from said thermoelectric generator falls below a predetermined value.

2. A thermoelectric protective apparatus for insuring cathodic protection of a container for storing a heated liquid, which comprises an anode in contact with the liquid in the container, electrical insulating material disposed between said anode and said container to permit maintenance of a potential difference therebetweeu, thermoelectric means electrically connected between said anode and said container, an electrical heat-control circuit to govern the heating of said liquid, said thermoelectric means connected in the circuit of said electrical heat-control circuit to control the current flow therein, a hermetically sealed casing enclosing said thermoelectric means, and a source of heat independent of the main source of heat for the liquid and being disposed adjacent said thermoelectric means to cause a generation of current by said thermoelectric means, said construction operating to discontinue the heating of the fluid within the container when said thermoelectric means fails to provide a predetermined current flow for cathodic protection.

3'. In a thermoelectric protective device for cathodically protecting a vitreous enamel lined container for storing a heated liquid, an anode supported from the wall of the tank and in contact with said liquid, electrical insulation disposed between said anode and said tank to permit maintenance of a potential therebetween, a thermoelectric generator connected between said anode and said container to cause current flow from said anode to said container through said liquid, an electric circuit to govern the heating of said liquid, said thermoelectric generator connected in saidelectric circuit to control the circuit, and an independent source of heat positioned adiacent said thermoelectric generator to create current flow in said thermoelectric generator normally suilicicnt to cathodically protect the container against corrosion, said construction operating to discontinue the heating of the liquid when insuiiicient current flows between said anode and said container through said liquid to effect adequate cathodic protection of said container.

4. A thermoelectric protective device for cathodically protecting the inner Wall of a structure for holding a heated liquid, comprising an anode supported within the tank, means to electrically insulate the anode from the tank to limit current flow therebetween to that through the liquid in the tank, thermoelectric means electrically connected to the anode to carry a current thereto, a source of heat adjacent said thermoelectric means for raising the temperature of the hot junctions there of, and control means for controlling the heating of said liquid by the thermoelectric means, said control means connected in series circuit with said thermoelectric means and said anode to discontinue the heating of said liquid in the event the current generated by said thermoelectric means is reduced to a predetermined value.

5. A protective device for protecting a metallic tank against the corrosive etiects or" a heated liquid within the metallic tank, which comprises an anode supported from the wall of said tank and extending within the tank, means to insulate said anode from said tank to confine current flow from the anode to the tank to the flow through the liquid in the tank, a thermopile electrically connected between the anode and the tank to provide a current flow from said anode to said tank, a metallic casing hermetically housing said thermopile, a conductor electrically connected to said casing adjacent the hot junctions of the thermopile, said conductor and casing being of dissimilar metals to form a thermocouple, a source of heat positioned adjacent the hot junctions of said thermopile and said thermocouple, an electric control device operable to discontinue the heating of the liquid, and electrical circuit connections between said thermocouple and said electric control to limit the heating of said liquid in response to a predetermined current generated by said thermocouple.

6. A corrosion-protective apparatus to insure protection of a metallic structure from corrosive eflects of a heated liquid contained therein, which comprises an anode supported within the structure and insulated therefrom in order to limit current flow from said anode to said structure to that through the liquid, a thermopile with its positive terminal connected to the anode and its negative terminal connected to the structure, electromagnetic means connected to automatically interrupt the heating of the fluid, conductors connecting said electromagnetic means to said thermopile in parallel with said anode, and a small source of heat adjacent said thermopile for raising the temperature of the hot junctions of said thermopile independently of the heating of the liquid.

7. A protective unit for insuring adequate cathodic protection of a tank containing a heated liquid, which comprises an anode supported within the tank, electrical insulation disposed between said anode and said tank to limit current flow therebetween to current flowing through the liquid, a thermopile having a positive terminal connected to said anode and having a negative terminal connected to said tank for the cathodic protection of the tank, a thermocouple with its hot junctions adjacent those of said thermopile, a source of heat for simultaneous heating of the hot junctions of said thermopile and said thermocouple, an electric control circuit to automatically interrupt the heating of the fluid in the tank, said thermocouple connected to open said electric control circuit and discontinue the heating of the fluid in said tank when the source of heat is sufliciently reduced, and a casing hermetically enclosing said thermopile and said thermocouple.

8. A protective device to prevent corrosion of a tank containing a heated liquid which comprises an anode supported within the tank, means to electrically insulate the anode from the tank in order to confine current flow from said anode to said tank to that passing through the liquid, a thermopile electrically connected between the anode and the tank wall to provide a potential difference between said anode and said tank wall, a source of heat for raising the temperature of the hot junctions of said thermopile, a thermocouple positioned adjacent to and insulated from said first named thermopile to be heated by said source of heat, and an electrically controlled device connected to a heat supply for said liquid to govern heating of said liquid, said thermocouple being electrically connected to said device to control operation of the latter.

9. A protective device to prevent corrosion by a heated liquid in a metallic tank having a pilot burner and a main burner for heating the liquid in the tank, which comprises an anode supported within the tank, means to electrically insulate the anode from the tank to confine current flow therebetween to current flow through the liquid, 3. thermoelectric generator electrically connected between the anode and the tank to provide a current from the anode to the tank, electromagnetic means operably connected with the main burner to automatically interrupt the operation of the main burner, said thermoelectric generator being electrically connected to said electromagnetic means to energize the latter, and said thermoelectric generator positioned adjacent the pilot burner to be heated thereby.

10. A protective apparatus for the prevention of corrosion by a heated liquid in a metallic tank having an electric element for heating the liquid in the tank, which comprises an anode supported within the tank, means to electrically insulate said anode from the tank whereby electrical conduction from said anode to said tank is limited to that flowing through the liquid, a thermoelectric generator electrically connected between said anode and said tank to provide a current flow from the anode to the tank through the liquid, electric control means operably connected to the electric heating element for heating said liquid in the tank to control the heating of the liquid, said thermoelectric generator being connected in circuit with said electric control means to govern the operation of the latter, and separate electric heating means to raise the temperature of the hot junctions of the thermoelectric generator.

11. In a protective system for the prevention of corrosion by a heated liquid in a metallic tank, an anode supported within the tank and electrically insulated therefrom to restrict a current flow from the anode to the tank to that flowing through the liquid, a hermetically encased thermopile electrically connected between said anode and said tank to provide a current flow from the anode to the tank, electric control means connected to govern a source of heat for said liquid, circuit means connecting said thermopile in circuit with said control means, and a separate source of heat for the thermopile providing predetermined flow of cathodic protection current, said construction operating to discontinue the source of heat for said liquid when said thermopile fails to provide the predetermined current flow.

References Cited in the file of this patent UNITED STATES PATENTS 88,285 Farmer Mar. 30, 1869 2,362,259 Findley Nov. 7, 1944 2,443,641 Ray June 22, 1948 2,459,123 Bates et al. Jan. 11, 1949 2,649,532 Woodman Aug. 18, 1953