US2776359A - Electrical water heater - Google Patents

Description

Jan. 1, 1957 Filed April 22, 1954 FIG! WATER SUPPLY H. F. BREMER ELECTRICAL WATER HEATER 4 She'ts-Sheet l a j. I

.INVEN TOR.

HERMANN F. BREMER ATTORNEYS Jan, 1, 1957 H. F. BREMER 2,776,359

ELECTRICAL WATER HEATER Filed April 22, 1954 4 Sheets-Sheet 2 Mb 53 r: y 4412+ 50 INVENTO.

HERMANN F. BREMER ATTORNEYS Jan. 1, 1957 H. F. BREMER ELECTRICAL WATER HEATER 4 Sheets-Shae;

Filed April 22. 1954 INVENTOR.

HERMANNE BREMER ATTORNEYS Jan. 1, 1957 BREMER 2,776,359

ELECTRICAL WATER HEATER Filed April 22, 1954 4 Sheets-Sheet 4 FIGS i Mi v ACTUATOR REsi x lvE 34 g 7 7 DEVICE 8&3 8(2 8! {/80 2 79/ TWO-PHASE 9 VOLTAGE SUPPLY IN V EN TOR.

HERMANN F. BREMER ATTORNEYS United States Patent ELECTRICAL warns. HEATER Hermann F. Brenner, Mayaguez, Puerto Rico, assignor, by mesne assignments, to Carbon Heater '(Jorporation, New York, N. Y., a corporation, of New Yer.

Application April 22, 1954, fierial No. 424,330

16 Claims; (Cl. 219-4tl) This invention relates generally to a method andapparatus for the heating of liquids and more particularly to improvements in electrical, water heaters.

Electrical water heaters are known wherein heating is effected by the conduction of electrical currents through the Water, the water acting as :a resistance. Heaters of this character usually make use of spaced carbon electrodes in opposing relation, between which the water circulates. It has been found-that waters at various localities, by reason of their mineral, content, possess different electrical resistance chanacteristics. Consequently, for a given voltage supply, different waters which are to be heated to approximately the same temperature entail different adjustments in the spacing or effective area between the electrodes. Such adjustments are difficult to make where the electrodes are fixedly mounted or where the electrode adjustment. means are disposed within the body of the heater.

Since the operation of electrical water heaters requires the connection of a voltagesource to the heater electrodes, in order to draw heated water from the device one must not only open the outlet valve or spigot but shortly thereafter it is also necessary to switch on the electrical current. in the event, however, the current is turned on before the outlet tapis opened to permit the continuous ilow of water through the heater, this may result in boiling of the water held in the heating chamber and give rise to a hazardous condition. Moreover where repeated use is made of the electrical heater, the need to first open the outlet tap and then to switch on the current constitutes a material inconvenience. It is. also important to bear in mind that the operation of water heaters involves extremely heavy current intensities, in the order of 90 to 120 amperes. Hence, an interruption in the flow of such currents by means of contact switches presents serious problems with respect to arcing and contact deterioration.

Another hazardous condition encountered with conventional heaters springs from the fact that water flowing through the heater and engaging the electrically-charged,

electrodes may convey an electrical charge and give an electrical shock to a consumer whose hands make contact with the water. This danger is particularly. troublesome when the heater outlet takes the form of an electrically non-conductive tube, such as a plastic hose, or an ungrounded metallic pipe.

Accordingly, it is the principal object of the invention to provide an improved method and apparatus for electrically heating a fluid wherein the above-described drawbacks are obviated.

More specifically, it is an object of the invention to provide an electric water heater wherein the available space between the electrodes through which the water to be heated passes may be readily adjusted, the adjusting means being accessible from the exterior of the heater. An advantage of apparatus in accordance with the invention lies in the fact that a wide range of adjustment is made possible to meet diverse water and temperature con.- ditions.

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Still another object of the invention is to provide an electrical water heater in conjunction with an electrical switching device wherein the current flow through the heater is distributed among a plurality of electrode sections, each co-operating with an independent contact switch to minimize arcing phenomena.

It is yet another object of the invention to provide an electrical switching device of the above-described type including a flow-responsive actuator common to the plurality of contact switching units whereby the current is automatically switched on and off as the outlet valve of the heater is opened and closed. A significant feature of the invention resides in the fact that the flow-responsive switching device acts to disconnect the electrical lead to one of the electrodes before it disconnects the lead to the opposing electrode, thereby further minimizing arcing.

Also an object of the invention is to provide an electrical heater wherein the water emerging from the heater is maintained at ground potential, thereby eliminating all danger of electrical shock.

t is also an object of the invention to provide a sturdy and compact electrical water heater of highly efficient construction and one which may be inexpensively manufactored.

For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed description to be read in connection with the annexed drawings wherein corresponding components in the several views are identified by like reference numerals.

in the drawings which show for purposes of illustration one form of apparatus embodying and capable of use according to the invention:

Fig. l is a vertical section of an electrical heating apparatus made in accordance with the present invention taken in the plane 1, l of Fig. 3, showingthe flow, responsive switch in the position it assumes when water is flowmg.

Fig. 2 is a similar section taken in the planes 2, 2 of Fig. 3, showing the flow-responsive switch in the position it assumes when no water is flowing.

Fig. 3 is a top plan view of the apparatus.

Fig. 4 is a horizontal section in the plane 4, 4- of Fig. 1.

Fig. 5 is a bottom plan view of the apparatus.

Fig. 6 is a schematic diagram of the electrical circuit connections for the apparatus.

Referring now to the drawings and more particularly to Figs. 1 and 2, the electrical heating apparatus in accordance with the invention is generally constituted by a heater assembly in and a flow-responsive electrical switching device 11 associated therewith. These elements will be separately described in the order named.

The electrical heater assembly The heater assembly 19 comprises a water-heating chamber formed by an open-ended outer casing 12 made of a suitable metal such as copper and a cylindrical in- As best seen in Fig. 4, concentrically disposed within the heater chamber is an electrode structure constituted by a unitary rotor electrode element 18 and a segmental stator electrode defined by stator sections 19, 20, 21 and 22. The rotor electrode element 18 is preferably machined from a cylindrical block of solid carbon or graphite, longitudinal. channels being cut therein to pro-" The duce four symmetrically-arranged pole pieces 23, 24, and 26. The stator sections 19, 2t), 21 and 22, which complement said pole pieces, are arranged circumferentially at equi-spaced positions about rotor electrode element 18 and are spaced therefrom to define an annular water passage 27. The stator sections are formed of carbon or graphite strips and, as is evident from Fig. 4, have an arcuate cross-section whose curvature corresponds to that of the faces of the pole pieces. The extremities of stator sections 19, 20, 21 and 22 are secured within circular slots 28 and 29 in discs Li and 15, respectively. Thus, rotation of rotor element 18 will vary the angular position of the pole pieces 23 to 26 with respect to stator sections 19 to 22 from a point at which they are exactly in register to a point at which they are altogether out of register.

Discs 14 and 15 are centrally provided with bores 30 and 31, respectively, disposed in axial alignment, bore 31 serving as the inlet to the heating chamber. The rotor electrode element 18 is rotatably mounted on metal shaft 32. The shaft passes through bore 30 in disc 13 and projects without the heater assembly to terminate in an adjusting screw head 33, which head facilitates the use of a screw driver to adjust the angular position of the rotor element. The lower end of rotor element 18 rests upon the upper face of boss 14%.

Positioned within a recess in disc 15 is a circular grounding-plate 34 having a central opening 35 in axial alignment with bore 31 in disc 15. Grounding-plate 34 is held in place by means of a single screw 36 received in an internally-threaded sleeve 37, the sleeve fitting snugly into a suitable aperture extending through disc 15. Similarly positioned within a recess in disc 14 is a circular grounding plate 38 having a central opening to accommodate boss 14. Plate 38 is held in place by a single screw 39 received in an internally-threaded metal sleeve 40 inserted in a suitable aperture in disc 14. Grounding-plates 34- and 38 are both fabricated of the same material as that of the electrode structure.

The upper end of tie-rod 17 is electrically connected to grounding-plate 34 with the aid of a fiat metal link 41, the link being secured and electrically connected to the upper end of sleeve 37 by means of a bolt 42. In a similar manner the lower end of tie-rod 17 is electrically connected to grounding-plate 38 via a flat metal link 43, the link being secured to the lower end of sleeve 40 by means of a bolt 44. The upper end of tie-rod 17 is employed as a terminal for connection to a point of ground potential, the connecting lead being attached or soldered to the nut 17*, whereby the grounding- plates 34 and 38 may both be held at ground potential. Electrical connection to the rotor electrode element 18 is effected via a metallic brush having a pair of parallel resilient extensions 46 and 47 which frictionally engage opposing surfaces on shaft 32. Brush 45 is secured and electrically connected to the lower end of tierod 16 by means of a nut 48.

An outlet pipe 49 is provided for the heater chamber, the pipe extending through an opening in disc 14 and being secured thereto by a nut 50. Pipe 49 is internally threaded for coupling with the aid of a suitable hose 51 to a conventional water valve or spigot 52. To permit passage of the heated water from the heating chamber into outlet pipe 49, the inner wall of disc 14 is provided with a notch 14 affording clearance between the edge of plate 38 and the inner wall of disc 14.

To render the water-heating chamber fluid-tight, 0 rings formed of elastic material such as rubber are provided, the rings being placed within suitable circumferential channels formed in the associated elements. Thus, disc 14 is provided with an O ring 53 etfecting a water seal between disc 14 and outer casing 12, and disc 15 is provided with a ring 54 effecting a similar seal. A water seal between shaft 32 and disc 14 is obtained by means of an 0 ring 55. Tie-rod 16 is pro- 4 vided at either end thereof with 0 rings 56 and 57, and tie-rod 17 is likewise provided with rings 58 and 59. Sleeves 37 and 40 are furnished with 0 rings 60 and 61, respectively. A water-tight heating chamber is thereby ensured.

Thus, water entering the heating chamber via inlet bore 31 in disc 15 will first pass through the central opening in grounding-plate 35 and then flow down the annular passage 27 between the rotor element 18 and the stator sections 19 to 22, the water thereupon making contact with grounding-plate 38 before passing through notch 14 into the outlet pipe 49 for discharge under the control of spigot 52.

The flow-responsive switch The flow-responsive electrical switching device 11 is mounted above disc 15 on the heating assembly 10 and generally comprises a flow chamber 61 formed by a hollow, metal cylinder, an insulating collar 62 surrounding said cylinder and adapted to support a plurality of electrical switching units, and a common actuator for said units constituted by an insulating cap 63 slidably mounted on the upper end of chamber 61 and coupled to a plunger 64 slidably disposed within the flow chamber. Axial displacement of the flow chamber 61 relative to the collar 62 is prevented by means of a split ring 65 fitting into a circular groove adjacent the lower end of the chamber.

The interior of flow chamber 61 is stepped in diameter to define an upper section 66 of relatively small diameter, an intermediate section 67 and a lower section 68 of larger diameter, a bevelled shoulder 67 being formed between bore sections 66 and 67, and a shoulder 68 being formed between bore sections 67 and 68. Plunger 64 is preferably machined from a single piece of metal, such as brass, having a circular cross-section to form at one end a disc-shaped head 69 whose upper face is bevelled. The diameter of head 69 is slightly smaller than that of intermediate section 67 to provide a clearance thercbetween in the order, for example, of .002 inch, whereby the head is slidable within section 67 to an extent limited in the upward direction by shoulder 67 The other end of plunger 64 is shaped to define a mounting post 70 upon which the actuator cap 63 is supported, the cap resting on an enlarged portion 71 of the plunger whose diameter corresponds substantially to the diameter of section 66 of the chamber. The cap 63 is secured to post 70 by means of a removable wire clasp 72.

As best seen in Fig. 1, an inlet to the flow chamber 61 is provided by means of an internally-threaded bore 73 opening into chamber section 66 and communicating with a water inlet pipe 74 via a notch 75 cut into collar 62. The lower section 68 of flow chamber 61 is coupled to inlet bore 31 of the heating chamber via a coupling member 76 inserted therein and having a flanged portion 76a which is received within section 68 and is provided with an 0 ring 77, effecting a water seal therebetween. Coupling member 76 is secured to disc 15 by means of a nut 78.

As will be evident from Fig. 3, circumferentially-arranged and supported on collar 62 are a plurality of individual contact switching units 79, 80, 81, 82 and 33. The angular positions of units 79 to 82 correspond to that of the stator electrode sections 20, 21, 22 and 19, respectively, while the angular position of unit 83 corresponds to that of tie-rod 16. Switching units 79 to 82 are of identical construction. As best observed in Fig. 2 with respect to unit 81, each of these units comprises an L-shaped metal strip 84 supporting a contact 85, and a flat spring finger 86 bearing a contact 87 in co-acting relation with contact 85. The contacts are preferably made of silver. The upper portion of finger 86 is bent to afford a V-shaped projection 86a whose apex faces the outer wall of actuator cap 63.

Contact 85 functions as the stationary contact of the switching unit and is connected via strip 34 to the associated stator. This is accomplished by means of an internally-threaded metal sleeve 88 inserted in a suitable aperture in disc 15, a screw 89 afiixing the foot of strip 84 to the upper end of sleeve Sit and passing therethrough threadably to engage stator section 22. The other stator sections are connected to the respective stationary contacts of switching units 79, St) and 82 in a similar manner.

Contact 87, which co-acts with contact 85, functions as the movable contact of the switching unit. All movable contacts in units 79 to 82 are electrically interconnected by means of an arcuate metal strap 9d, bridging the spring fingers 86 of these units. Thus, by means of a lead 91 extending from terminal A of a voltage source to strap 9t}, a connection is completed via the individual switching units 79, 8t 81, 82 to stator electrode sections 20, 21, 22 and 19, respectively.

The remaining switching unit $3 serves to effect a connection from another terminal B of the voltage supply to the rotor electrode element 18. Switching unit 83, as best seen in Fig. 1, includes an L-shaped strip 92 bearing a stationary contact 93 which is connected serially via tie-rod 16, brush 45 and shaft 32 to rotor electrode element 18. tion with contact 93, is borne by a flat spring finger 96 bent at its upper end to define a V-shaped projection 96:: whose apex also faces the outer wall of actuator cap 63. Thus, by extending a lead 97 from terminal B to spring finger 96, a connection is completed via switching unit 83 to rotor electrode 18.

All of the spring fingers in switching units 79 to 83 are biased to urge the related movable contacts into engagement with the fixed contacts. it is important to note that projections 86a in switches 79 to 82 are at the same elevational position, whereas the projection 96:! of switch 33 is at a slightly greater height. The makeand-break operation of the switching units is governed by the position of actuator cap 63, the cap having a rest position, as shown in Fig. 1, and a raised position, as shown in Fig. 2.

Actuator cap 63 is shaped to define a crown portion @311 of reduced diameter, a tapering intermediate portion 63b, and a brim portion 630 of relatively large diameter. As will be explained hereinafter, by reason of the movement of plunger at the cap assumes the rest position when spigot 52 is opened and is forced upwardly by plunger 64 to the raised position when spigot 52 is closed. in the rest position of the cap, the apexes of the finger projections 86a and 96a of the several switching units lie adjacent but not abutting the crown 63a of actuator cap 63. Hence, in this situation, all of the switching units occupy their make position. When, however, the actuator cap 63 is raised upwardly, the spring finger projections 36a and 96a are engaged by the enlarged brim 630 of the cap, thereby forcing the spring fingers outwardly and breaking the switch contacts. inasmuch as the projection 96a of unit 83 is at a greater height than the projections 86a of the other units, it is the last to be engaged by the upward movement of cap 63. Consequently, the switching units 79 to $2 first break simultaneously, which operation is then followed by breaking of switching unit 33.

The electrical circuit The external voltage supply may be connected to the heating apparatus in various ways, depending upon the nature of the available current; i. e., whether it is direct, single-phase or two-phase alternating current.

In the equivalent schematic diagram shown in 6, it will be assumed that the voltage supply is a two-phase source having a terminal A yielding voltage of one phase and a terminal B yielding a voltage in phase opposition thereto, the center or common terminal C being grounded.

It will be seen that voltage from terminal A will be A movable contact 95, in co-acting rela-,

supplied via switching units 79 to 82 to stator electrode sections 20, 21, 22 and 19, respectively, and that rotor electrode element 18 is separately supplied a voltage via switch 33 connected to terminal B, terminal C of the voltage supply as well as grounding plates 35 and 38 being grounded.

' When spigot 52 is opened, the actuator cap 63 is caused to assume its rest position, in which event all of switching units 79 to 83 occupy their make position, to establish an electric field between the rotor electrode 18 and each of the stator electrode sections 19 to 22. This will, of course, produce an electric-current flow in the water passing between the electrodes, and thereby heat the water to an extent depending on the magnitude of the voltage and the spacing and effective area of the opposing electrodes. This current flow is evenly distributed in parallel relation among the stator electrodes 19 to 22; hence, assuming a total current intensity of amperes, each of the associated switching units will carry only 25 amperes. Thus, the tendency to produce an are upon interruption of the current flow is reduced. It is to be understood thatwhile only four stator sections have been illustrated, a greater or smaller number may be successfully employed in conjunction with a rotor possessing an equal number of poles.

When the spigot 52 is closed, the resultant pressure in flow chamber 61 elevates the actuator cap 63, whereby the coacting contacts of switches '79 to 82 are first disengaged and shortly thereafter the contacts of switching unit 83. Thus, interruption in current flow from terminal A to the stator sections precedes that from terminal B to the rotor electrode, and a further reduction in arcing is obtained. The grounding- plates 35 and 38 maintain the water both at the inlet and the outlet of the heating assembly at ground potential. Water discharging from the spigot will, therefore, be at ground potential, eliminating all danger of shock to the consumer.

It is to be noted that while the circuit has been described as it operates with a two-phase alternating current source, a single-phase or a direct current supply may be connected in lieu thereof at terminals A and B, the behavior of the circuit otherwise being the same as described hereinabove.

General operation When spigot 52 is open, water supplied through inlet pipe 74- enters flow chamber 61 and passes via coupling member '75 into heating assembly 10 where it flows into channel 27 between rotor electrode 18 and the stator electrode sections 19 to 22 to be heated by electrical conduction. The heated water is then discharged through outlet pipe 51.

If the water entering the apparatus is, for example, at a pressure of 50 pounds and spigot 52. is closed, all parts of the heater assembly It) and the flow chamber 61 will contain water in. a stationary condition at a static pressure of 50 pounds. Under these conditions, the pressure imposed on both sides of plunger head 69 is equal since there is a clearance of about .002 inch between the head and the wall of section 67. However, the pressure exerted on the upper face of the head 69 affects only an annulus region. The pressure operating upon the under face of head 13 affects the entire disc-shaped area, including the central portion thereof. Under these conditions, plunger 64 and the actuator cap 63 are raised upwardly so that it assumes the position shown in Fig. 2, the reason, of course, being that the pressure of 50 pounds per square inch on the central area is greater than the outside atmospheric pressure on the end of the plunger. When spigot 52 is open and water begins to flow, the pressure in flow chamber 61 falls. Consequently, the SO-pound pressure on the upper face of the head 69 pushes plunger 64 downwardly until there is a clearance between shoulder 68:: and head 69 sufiicient to allow full flow of water at that point. When spigot is again closed with the plunger in the position of Fig. 1, pressure equalizes on both sides of the piston headand, once again, the 50-pound pressure on the central area of the under face of the head operating against outside atmospheric pressure forces the plunger back to the position of Fig. 2.

From the foregoing description, it will be seen that when one opens the spigot, the voltage supply will automatically be connected to the heater electrodes so that the water discharged from the spigot is heated. And when one closes the spigot, the operating voltage is automatically shut off. This feature is a particular convenience where frequent and repeated use is made of the water heater.

To adopt the heater apparatus in accordance with the invention to installations in regions where the water sup ply differs materially in salt content and hence in resistivity, one has merely to adjust by means of a screwdriver the angular position of the rotor electrode element 18 relative to the stator sections. Adjustment may also be made to obtain a desired water temperature.

The method hereinafter claimed is not dependent upon the use of a particular apparatus. The apparatus herein shown and described is suitable for use in carrying out the method. it is to be understood that while a preferred embodiment of the invention has been disclosed, many changes and modifications may be made therein without departing from the essential spirit of the invention, as set forth in the following claims.

What is claimed is:

1. Apparatus for heating fluid by electrical conduction comprising spaced electrodes forming a fluid passage, circuit means including an electrical switch to establish a potential difference between said electrodes to produce a heating current in fluid flowing through said passage, and means responsive to said fluid flow to actuate said switch to disconnect said electrodes upon cessation of said fluid flow.

2. Flow-responsive apparatus for heating a fluid by electrical conduction comprising a heating chamber, spaced electrodes disposed within said heating chamber to form a fluid passage therebetween, a flow-responsive device including a flow chamber, means transmitting a fluid to be heated through said flow chamber and into said heating chamber, circuit means including an electrical switch connecting said spaced electrodes to a volttagc supply, and means coupled to said device for actuating said switch to disconnect said electrodes from said supply when the fluid in said flow chamber is stationary.

3. Apparatus for heating water by electrical conduction comprising a heating chamber having an inlet and an outlet, spaced electrodes disposed within said heating chamber to form a water passage extending between said inlet and said outlet, a flow-responsive device including a flow chamber, means for transmitting water to the heater via said flow chamber into said inlet, means including an electrical switch connecting said spaced electrodes to a voltage supply, and an actuator operatively coupling said device to said switch to disconnect said electrodes from said supply when the water in said flow chamber is stationary and to re-malte said connection when said water is flowing.

4. Apparatus for heating water by electrical conduction comprising a heating chamber having an inlet and an outlet, spaced electrodes disposed within said heating chamber to form a water passage extending between said inlet and said outlet, at flow-responsive device including a flow chamber, means for transmitting water to the heater via said flow chamber into said inlet, means including an electrical switch connecting said spaced electrodes to a voltage supply, an actuator operatively coupling said device to said switch to disconnect said electrodes from said supply when the water in said flow chamber is stationary and to remake said connection when said water is flowing, a grounding-plate disposed within said heating chamber adjacent said outlet, and

' means connecting said plate to a point of ground potential.

5. A flow-responsive electrical water-heating apparatus comprising a water-heater assembly including an inlet, an outlet adapted to be coupled to a tap and spaced electrodes forming a water passage between said inlet and outlet; a flow-responsive device including a fluid chamber having an inlet adapted to be coupled to a water supply and an outlet, the outlet of said flow chamber being coupled to the inlet of said assembly, and a plunger slidable Within said fluid chamber to occupy as a function of the water pressure therein a first position in the condition when said tap is opened and a second position when said tap is closed; circuit means including an electrical switch connecting said electrodes to a voltage supply; and an actuator supported on said plunger for movement therewith and operatively coupled to said switch to effect a make action in said first position and a break action in said second position.

6. Apparatus for heating water by electrical conduction comprising a heater chamber, an inner electrode disposed within said heating chamber, a plurality of outer electrode sections disposed about said inner elec- ,trode and spaced therefrom to form a water passage, 2. flow-responsive device having a flow chamber, conduit means to feed water to the heater via said flow chamber into said heating chamber, a voltage supply provided with first and second terminals, means connecting said inner electrode to said first terminal, means including an individual switching unit connecting each of said electrode sections to said second terminal, and means coupled to said device for actuating said switching units simultaneously to disconnect said sections from said second terminal when the fluid in said flow chamber is stationary.

7. Apparatus for heating water by electrical conduction comprising a heater chamber, an inner electrode disposed within said heating chamber, a plurality of outer electrode sections disposed about said unit electrode and spaced therefrom to form a water passage, a flowresponsive device having a flow chamber, conduit means to feed water to the heater via said flow chamber into said heating chamber, a voltage supply provided with first and second terminals, means including a switching element to connect said inner electrode to said first terminal, means including an individual switching unit connecting each of said electrode sections to said second terminal, and means coupled to said device and operative when the fluid in said flow chamber is stationary for first actuating said switching units simultaneously to disconnect said sections from said second terminal, and thereafter actuating said switching element to disconnect said inner electrode from said first terminal.

8. In an electric water heating apparatus a heating chamber, a cylindrical rotor electrode disposed within said chamber and provided with a plurality of symmetrically arranged pole pieces, a shaft supporting said rotor electrode and extending without said chamber to facilitate adjustment of said electrode, a like plurality of complementary stator sections disposed within said chamber and circumferentially arranged about said rotor electrode in spaced relation therewith, and a groundingplate disposed adjacent either end of said rotor electrode.

9. In an electrical water heating apparatus, a heater assembly comprising an open-ended cylindrical outer casing, an inner shell disposed Within said casing, first and second insulating discs enclosing the ends of said casing to define a heating chamber, an electrode structure disposed Within said chamber and including a cylindrical rotor electrode provided with a plurality of symmetrically-arranged pole pieces, a like plurality of complementary stator sections circumferentially arranged about said rotor electrode in spaced relation therewith to form an annular water passage, a shaft supporting said rotor electrode and projecting through one of said discs to the exterior of said chamber to facilitate adjustment of said pole pieces relative to said stator sections, an outlet extending through said one of said discs, an inlet extending through the other of said discs, a groundingplate within said chamber disposed adjacent to said inlet, and a second grounding-plate within said chamber disposed adjacent said outlet; said rotor electrodes, said stator sections, said shell and said plates being formed of carbon.

10. In an electrical water heating apparatus, a heater assembly comprising an open-ended cylindrical outer casing, an inner shell disposed within said casing, first and second insulating discs enclosing the ends of said casing to define a heating chamber, an electrode structure disposed within said chamber and including a cylindrical rotor electrode provided with a plurality of symmetrically-arranged pole pieces, a like plurality of complementary stator sections circumferentially arranged about said rotor electrode in spaced relation therewith to form an annular water passage, a shaft supporting said rotor electrode and projecting through one of said discs to the exterior of said chamber to facilitate adjustment of said pole pieces relative to said stator sections, an outlet extending through said one of said discs, an inlet extending through the other of said discs, a grounding-plate within said chamber disposed adjacent to said inlet, a second grounding-plate within said chamber disposed adjacent said outlet; said rotor electrodes, said stator sections, said shell and said plates being formed of carbon, a flowresponsive device mounted upon the other of said discs and including a flow chamber communicating with the inlet to said heating chamber, inlet means to couple a water supply to said flow chamber, aplunger slidable within said flow chamber and adapted to occupy a longitudinal position therein depending on water flow, switching means to connect said electrodes to a voltage supply to establish a potential difference between said rotor electrode and said stator sections, and an actuator coupled to said plunger and movable therewith, said actuator being operatively coupled to said switching means to disconnect said electrodes when the water in said flow chamber is stationary.

11. Apparatus, as set forth in claim 10, wherein said flow chamber is constituted by a cylinder having an internal bore stepped in diameter to form a first section of relatively small diameter and a second section of larger diameter, said inlet means for said flow chamber communicating with said first section, said second section communicating with the inlet of said heating chamber, and wherein said plunger slidable within said flow chamber is provided with a disc-shaped head portion whose diameter is greater than the diameter of said first section and slightly smaller than that of said second section whereby said head is adapted to reciprocate within said second section, the movement of said plunger being governed by the water pressure difference above and below said head.

12. A flow-controlled automatic electric water heating apparatus comprising a water heating assembly including a heating chamber having an inlet and an outlet, said outlet being adapted for coupling to a spigot, and an electrode structure within said heating chamber provided with a primary electrode and a plurality of secondary electrodes surrounding said primary electrode and spaced therefrom to form an annular passage extending between said inlet and said outlet; a flow-responsive device including a cylindrical flow chamber and a plunger slidable therein, said flow chamber being interposed in a water supply feeding into said heating chamber whereby the axial position occupied by said plunger depends on whether said spigot is open or closed; an actuator cap supported at one end of said plunger and slidably received on the corresponding end of said cylindrical flow chamber; circuit means including a plurality of switching units to connect said electrodes to a voltage supply to establish a potential difference between said primary and said secondary electrodes, said actuator cap being disposed in operative relation to said units to break said switching units when said spigot is closed in a sequence wherein said units connecting said secondary electrodes to the supply are actuated before the unit connecting the primary electrode to the supply.

13. Apparatus, as set forth in claim 12, wherein said switching units are each constituted by a strip bearing a stationary contact and a spring finger bearing a movable contact in cooperative relation with said stationary contact, said fingers being biased to maintain said contacts in engagement, an insulating collar surrounding said cylindrical flow chamber for supporting said units at spaced circumferential positions thereabout, said spring fingers being provided with projections disposed in operative relation to said actuator cap whereby when said cap occupies a position resulting from closing of said spigot, said fingers are flexed outwardly to break said contacts.

14. Apparatus, as set forth in claim 13, wherein said actuator cap has a crown portion of relatively small diameter and a brim portion of larger diameter, said spring finger projections being disposed adjacent the crown portion when said cap is in the position resulting upon opening said spigot and is engaged by said brim portion when said cap is in the position resulting upon closing said spigot, whereby said fingers are flexed outwardly to break said contacts.

15. Apparatus, as set forth in claim 14, wherein the projection on the spring finger of the switching unit connected to said primary electrode is at a difierent elevation than the projections on the remaining fingers whereby actuation of said unit occurs at a different point in time.

16. The method of heating fluid by electrical conduction comprising the steps of supplying voltages to a primary electrode and a secondary electrode which forms with the primary electrode a passage for the flow of fluid, said voltages establishing a potential difierence between said primary and secondary electrodes to effect heating of said fluid, interrupting the supply of voltage to said secondary electrode in response to a change in the flow of said fluid, and thereafter interrupting the supply of voltage to said primary electrode in response to said change.

References Cited in the file of this patent UNITED STATES PATENTS 1,999,962 Des Rosiers Apr. 30, 1935 2,258,744 Des Rosiers Oct. 14, 1941 2,355,687 Van Hise Aug. 15, 1944 2,588,314 Wicks Mar. 4, 1952 2,599,806 Benchemoul June 10, 1952

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