US2673920A - Electric heater for water or the like - Google Patents

Description

March 30, 1954 w. J. DONOVAN ETAL ELECTRIC HEATER FOR WATER. OR THE LIKE 4 Sheet s-S'heet 1 Filed July 20, 1950 DRINK OON OENTRATES ENTORS Donguan. ,BOZLIZ THERMOSTATIO CONTROL William CecLl Mr ATT March so, 1954 W. J. DONOVAN ET AL ELECTRICHEATER FOR WATER OR THE LIKE Filed July 20', 1950 4 Sheets-Sheet 2 w. J. DONOVAN ETAL ELECTRIC HEATER FOR WATER OR THE LIKE 511 a July 20, 1950' Much 30, .1954

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) EN'roRs onoydn Cecil Boll/n7 ATTOR s W.J. DONOVAN ETAL. 2,673,920 ELECTRIC HEATER FOR WATER OR THE LIKE k March 30, 1954 Filed July 20, 1950.

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Patented Mar. 30, 1954 ELECTRIC HEATER FOR WATER OR THE LIKE William J. Donovan, Mamaroneck, and Cecil Boling, Brewster, N. Y., assignors to The Heat- X-Changer Co., Inc., Brewster, N. Y., a corporation of New York Application July 20, 1950, Serial No. 174,956

7 Claims. (Cl. 219-39) This invention relates to fluid heating, and more in particular to electric heating of water in hot-drink dispensing machines.

An object of this invention is to provide an improved water heater construction which is ef ficient and dependable in use", inexpensive to manufacture and maintain, compact and lightweight in construction, and thoroughly satisfactory in every respect for commercial use. A further object is to provide an arrangement for preparing hot beverages; for example, for immediate use or sale. A further object is to provide apparatus of the abovecharacter which is free of objectionable characteristics of similar prior apparatus; such, for example, as the objection that some apparatus is unsanitary because it tends to collect sediment and impurities. A further object is to provide a simplified construction of the above character which is adaptable to many different conditions of operation. These and other objects will be in part obvious and in part pointed out below. i

The invention accordingly consists in the features of construction, combinationsof elements, and arrangements of parts as will be exemplified in th structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In the drawings:

Figure 1 is a partially schematic view of one embodiment of the invention;

Figure 2 is a side elevation of the water heater of Figure l, with the centerbroken away and parts in section;

Figure 3 is a phantom view showing the electric coils and the water tubes of the water heater of Figures 1 and 2; and,

Figure '4 is a sectional view of a portion of the water heater.

In the past various arrangements have been provided for heating 'water or similar fluids with electricity but each of these prior arrangements has characteristics or features which are objectionable and which have caused difiiculty in use.

Some such arrangements are inefficient while others do not meet the strict standards of such agencies as the Underwriters Laboratories and local health agencies, and they do not satisfy the various safety codes. Particular difiiculty has been encountered where attempts have been made to heat water or the like when serving beverages to the public.

In accordance with the present invention an arrangementis provided for heating water or the like in atube where the rate or water flow may be quite rapid and either constant or intermittent. In the illustrative embodiment of the present invention water is heated and mixed with constituents to form hot drinks, such as cofiee, tea or the like; and the hot drinks are dispensed automatically under the control of a coin-actuated or coin-control mechanism. The heater unit of the illustrative embodiment is particularly suited for the specific use shown and has special advantages when so used. However, the same or similar heater units may be used in other types of apparatus and for other purposes, and yet certain of the advantages of the present invention will be obtained.

Referring particularly to Figure 1 of the drawings, a hot-drink dispensing machine 2 includes a coin control mechanism 4 into which a proper coin is deposited by a patron to operate the machine; the machine then mixes and dispenses a selected hot drink such as coiTee, tea, or the like. The depositing of the coin causes the machine to dispense a predetermined quantity of a drink concentrate together with a quantity of hot water into a heat-resistant container or cup 6. The drink concentrate is dispensed, from the particular tank l0 containing the selected drink concentrate, through a metering valve 8 which also meters the hot water; in this embodiment, tap water is heated as it is dispensed in a water heater [2.

The water heater I2 is shown in Figures 2 to 4 and comprises a sheet metal casing I4 (see Figure 2) within which is mounted the heater unit 16. The heater unit I 6 is mounted on a sheet metal cylinder [3 which rests upon an annular plate or ring of insulating material l5 which rests in turn upon the bottom wall of casing M. The heater unit is clamped in place by stud bolt H, the head of which is held by a bracket l 9 and the end of which is threaded into a recess in the bottom of the heater unit. The head of stud bolt I! is insulated from bracket [9 by an insulating washer 2|. An annular ring 23 is positioned around the heater unit near its top and helps support the heater unit in the position shown. Thus, the heater unit is spaced a substantial distance from all of the walls of the casin and the space between the heater unit and the casing is filled with fiber glass which is an excellent insulating material.

The heater unit I6 is a cylindrical block of cast aluminum l8 in which are embedded electric heating elements in the form of two heater coils 20 (see Figure 3) and a water tube assembly in the form of a double helical copper tube 22. The

heater coils 20 are of the Calrod" type with each comprising a resistance wire embedded in electrical-insulating and heat-conducting material and enclosed within a metal tube. The heater coils are wound together into a double helix with each element extending substantially three complete turns and with the ends of the elements projecting from the top of easing hi and having integral terminals 2 2. The water tube is formed by an inner coil 26, from which the water inlet end 28 of the tube extends, and an outer coil 30 from which the water outlet end 32 of the tube extends; the outer and inner coils are connected at the bottom of the unit. The inner coil has twelve turns and is positioned inside the heater coils 2G while the outer coil has eight turns and is positioned outside the heater coils.

As shown best in Figure 4, the water coils and the heater coils are spaced from each other, and the adjacent turns of each individual 0011 are spaced from each other. The relationship is such that heat passes eiiiciently from the entire surfaces of both of the heater coils into the aluminum block l8 and then passes from the block in an efficient manner through the entire surface of the water tube 22. Thus, as heat is produced in the heater coils it is carried from them and they are not subjected to excessive heating. Furthermore, the water in tube 22 absorbs the heat readily because of the extremely eflicient heat-transfer relationship from the aluminum block through the tube walls and to the water.

The heater coilsare controlled by a thermostatic control unit 34 (see Figure 1) having a bulb 36 positioned in a well 38 formed by a copper tube positioned at the side or the water inlet end 28 of the water tube. This copper tube has its end embedded in the aluminum block and therefore it is held rigidly against the tube. During use, the flow of water through tube 22 results in the cold water passing in heat exhange relationship with bulb 36 and, therefore, the bulb is cooled and the control unit turns on the electric current to the heater coils.

The positioning of the thermostat bulb is such that it is also responsive to the temperature of block l8; thus, when water is not liowing, the block ismaintained at an elevated temperature and the tube is filled with hot water. Withthe aluminum block thus heated, the cold water en- :25: tering the tube is heated immediately by heat from the block so that the block in a sense acts as a holdover. Also, as indicated, the flow of cold water into the tube turns on the electric current to the heater coils so that the heater 5,."-

coils start to heat the block again. This action is rapid and efficient and the water is heated to the desired temperature as it flows from the water outlet 32. The electric current to the heater coils is turned off instantly whenever the temperature of the bulb rises; this occurs when the flow of cold water has stopped and the block temperature has been raised to the desired value. It is thus seen that the heating is controlled in accordance with the water flow and .1;

also in accordance with the residual heat stored up in the holdover block Hi. In actual use the outlet water temperature is maintained very constant even under intermittent flow conditions. Well 38 extends into block it and bulb 38 is positioned as shown with itscenter at substan- 4 ature of the block, while it moved toward the top of the well it is more responsive to the temperature of the water tube 22. When the bulb is positioned near the bottom of the well it is relatively unresponsive to the starting of water flow through tube 22 and, therefore, the heater coils may not be turned on immediately when flow starts.

On the other hand, when the bulb is positioned near the, top of the well it is cooled when the water flow first starts and is therefore immediately responsive to even momentary water flow. With the position of the bulb adjusted, an appropriate adjustment is made in the thermostatic control unit 34 so that the heater units are turned on and off at the desired range of temperatures. Thus, a ready adjustment is provided whereby a relatively wide range in the mode of operation is provided.

It has been pointed out above that the aluminum block is extremely eificient in transmitting the heat from the heater coils to the water tube. This efiiciency depends upon carefully controlled spacing of the coil turns, and also upon maintaining the proper relationship between the volumes and shapes of the portions of the block and the sizes thereof relative to the sizes of the coils. Thus, during manufacture the molten aluminum flows in and around the individual turns of the coilsand when it is cooled the aluminum shrinks more than do the coils. This causes the aluminum to become stressed with hoop tension so that each tube portion of tube 22, as well as each tube portion of the tubes forming the sheaths for the heater coils, is surrounded by a solid wall of aluminum having an opening through which the tube portion extends, the normal size of which is smaller than the normal size of that tube portion. Therefore, each tube portion is resiliently compressed by its surrounding wall and this maintains a very excellent heattransfer relationship between the aluminum block and the tube wall.

The web of aluminum between the coils and also between the turns of each coil is sufficiently strong to hold the hoop tension forces which are involved. However, during the castingoperation there is a tendency for the metal forming tube 22 to become melted or dissolved into the aluminum. In fact, when the casting temperatures are too high the tube walls are apt to become punctured by such melting or dissolving of the copper, and the danger of this is greater when the volume of molten aluminum is increased in proportion to the volume of metal forming the tube. It has been found that the proportions of the parts shown in the drawings gives very satisfactory service in actual use. The construction is simple and it is highly einclent both in use of tially the top surface of the block-,and when so positioned the results just described are obtained.

However, when the bulb is moved further intothe" well it becomes more responsive to the temper the materials and in heating the water.

Furthermore, the unit is free of difficulties requiring maintenance because the heater or water coils are not subjected to abuse, such as excessive heating or rapid cooling, and the water flowing through the tube does not tend to leave behind any sediment or other accumulation. That is,- there is no stationary body of water as there is when water is heated by immersing a heating coil in a pressure tank. Furthermore, by embedding the heating coils in the block of alurnia num the difiiculties are avoided which are encountered when the heater coils are immersed in the water to be heated. The size and weig'htf of the heater unit is minimum and this has great-advantage in certain uses where weight :and space features. areimportant.

It should be noted also that while the heater unit is rigidly 'held in place, still the heater unit 16 is electrically and thermally insulated from casing fl. That is, it is completely surrounded by the fibre glassto a thickness of substantially one and one-half inches at the side and along the bottom and top; and, the insulating rings l5 and 23 and washer 2| are all of material which is good electrical and heat insulation. The top wall of casing I4 is provided with an opening through which the ends of the heater units project, and two openings through which the ends of pipe 22 and well 38 project and, therefore, these elements do not transmit heat to the casing. Thus, while the heater unit 16 is maintained in heated condition, there is no appreciable tendency for the casing to become heated. With this arrangement, extremely eflicient operation is obtained because there is no heat loss. Furthermore, the fact that there is no danger of the casing becoming excessively heated makes it practical to position other parts or elements of the apparatus adjacent the casing without fear of the other apparatus becoming overheated. The feature of electrically insulating the heater unit is also important because it renders the unit thoroughly safe from an electrical standpoint, whereas with some similar equipment it is necessary to provide expensive and bulky accessories to satisfy even the minimum safety requirements.

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawing, is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. In heating apparatus of the character described, the combination of, a tube adapted to have water or the like flow therethrough to be heated and being in the form of a coil having concentrically positioned inner and outer helical portions, a resistance heater element which is a rod-like member formed into a coil positioned between said helical portions of said tube producing heat at a rapid rate when electricity flows therethrough, and a block of aluminum which has been cast around said tube and said heater element and forming webs of suflicient cross section around the embedded portions to form a good heat transfer relationship therewith whereby the heat is carried away from said heater element at such a rate that the temperature does not rise excessively and whereby the heat is transferred to the tube at a rapid rate.

2. Apparatus as described in claim 1 which includes means forming a control well having a portion thereof embedded in the block and a portion thereof in heat transfer relationship with the end of the tube into which water or the like flows to be heated whereby the position of a control element may be regulated to be selectively responsive to the temperature of the block and the incoming water or the like.

3. In electrical heating apparatus for supplying a stream of water at a predetermined temperature, the combination of, a double coil of tubing for the flow of a stream of water there through comprising two concentrically positioned coils of difierent diameters which are in terconnected at one axial extent thereof and which have inlet and outlet connections atlthe other axial extent, said coils being of sufiiciently different diameters to provide a substantial annular zone therebetween, a heating unit comprising electric resistor means enclosed within a metal tube and formed into a coil of a diameter intermediate the-diameter of the first-mentioned coils and positioned concentrically therebetween, a cast aluminum block enclosing said double coil of tubing and said heating means with the aluminum having been cast around the coils so that during the casting operation the tube walls are substantially compressed by the shrinkage of the aluminum and an intimate heat exchange relationship is provided between the heating means and the aluminum block and also between the aluminum block and liquid within said double coil tubing, means forming a thermostat well in said block adjacent said inlet connection for the tubing, a casing surrounding said block and providing a substantial heat insulating zone between the outer surface of the bolck and the casing, and means anchoring said block within said casing.

4. A unit as described in claim 3 wherein said casing comprises a cylindrical member and a pair of end plates respectively closing the ends of the cylindrical member, a collar positioned between the inner surface of said cylindrical member and the outer surface of said block, and wherein said anchor means comprises a collar and a stud bolt holding said block against said collar.

5. In electrical heating apparatus for supplying a stream of water at a predetermined temperature, the combination of, a double coil of tubing for the iiow of a stream of water therethrough comprising two concentrically positioned coils of different diameters which are interconnected at one axial extent thereof and which have inlet and outlet connections at the other axial extent, said coils being of suiiiciently different diameters and spacings to provide substantial spacing therebetween, a heating unit comprising a rod-like electric resistor means formed into a coil, a cast aluminum block enclosing said double coil of tubing and said heating means with the aluminum having been cast around the coils so that during the casting operation the tube walls are substantially compressed by the shrinkage of the aluminum and an intimate heat exchange relationship is provided between the heating means and the aluminum block and also between the aluminum block and liquid within said double coil of tubing, and means forming a heat-insulating enclosure surrounding said block and providing a substantial heat insulating zone around the outer surface of the block.

6. Apparatus as described in claim 5, wherein said heat insulating enclosure includes a metal casing and spacer means, positioning said block within said casing, an anchor comprising an inverted U-bracket fixed to said casing and defining a recess within said casing, and a stud bolt having its head positioned within said recess and its remote end threaded into said block.

7. Apparatus as described in claim 6, which includes a water inlet tube extending into said casing, and connected to said double coil, and a thermostat tube extending parallel to and adjacent said water inlet tube and anchored into said block.

WILLIAM J. DONOVAN. CECIL BOLING.

(References on following page) References "(litedtinathe file of this patent UNITED STATES PATENTS Number Name Date Hynes Jan. 6, 1929 Notar et a1 Dec. 3, 1935 Clinefelter July 21, 1936 Beyrodt Nov. 2, 1937 Beyrodt Jan. ,31, 1939 :Number Number 8 :Name Date McIIrath ;Ju1y11, 1941 FOREIGN PATENTS Country Date Great Britain Jan. 4, 1932 France Oct. v23, 1920

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