US3419666A - Electric furnace - Google Patents

Description

Dec. 31, 1968 D. w. GRooM ELECTRIC FURNACE Sheet Filed Dec. 29, 1967 yen/on United States Patent 3,419,666 ELECTRIC FURNACE David W. Groom, 2262 E. Lake Sammamish Road SE., Issaquah, Wash. 98027 Continuation-impart of application Ser. No. 430,715, Mar. 15, 1965. This application Dec. 29, 1967, Ser. No. 694,528

13 Claims. (Cl. 13-20) ABSTRACT OF THE DISCLOSURE An electric furnace unit including a container, a heat sink mass of metal having a melting point below and a vaporizing point above the operating temperature of the furnace within the container, a vessel within the container and within said heat sink mass and adapted to receive material to be heated and an electric resistance heater element within the container and heat sink mass and engaged about the exterior of the vessel to heat the vessel and heat the heat sink mass to a temperature above its melting point whereby said mass is molten and such that upon heat transfer from said mass to the container convection currents are established in the mass whereby said molten mass scru-bs the exterior of the vessel for substantially total, uniform and continuous heat transfer between the mass and t-he vessel.

This is a continuation-in-part of my application Ser. No. 430,715, filed Mar. 15, 1965, for Electric Steam Generator, now Patent No. 3,338,299, issued on Aug. 29, 1967.

This invention has to do with an improved electric furnace and is more particularly concerned With a furnace for heating air or other gases and/or for generating steam, as desired, or as circumstances require.

The principal object and feature of this invention is to provide an electric furnace construction having novel heat conducting means for conducting heat generated by an electric resistance element to the medium to be heated and which includes a metal heat conducting medium, such as lead, which becomes molten or fluid within the operating temperature range of the furnace.

In ordinary or conventional electric furnaces, where electric resistance heater elements are provided, or employed, the elements are arranged in close proximity to a container or vessel which is preferably established of a suitable metal, or the like, which is a good heat conductor and in which the medium or material to be heated is arranged or through which said medium or material is circulated.

The heat generated by the heater elements serve to heat the adjacent parts and/or portions of the container or vessel by conduction where structural contact is established and by radiation where such contact is not established.

As a result of the above practice, a small part of the heat generated is transmitted directly to the container or vessel by conduction and that heat which is so conducted is not distributed uniformly throughout the surface of the container or vessel, but is applied in areas or zones, creating hot spots on and about the vessel or container.

The major part of the heat generated by the heater elements in structures of the character referred to is ice emitted therefrom in the form of radiant heat, a greater portion of which is directed away from the container or vessel and only a small portion of which can be recaptured and utilized as by means of reflectors and the like, which serve to bounce the heat back to the container or vessel.

Only a limited amount of that small portion of radiant heat generated by the heater elements and directed to the container or vessel, as well as a limited amount of the re-directed or bounced-back radiant heat directed to the container or vessel is absorbed by the container or vessel; the greater portion of such radiant heat being bounced back and away from the surface of the container or vessel.

As a result of the foregoing and in spite of extreme and costly efforts to insulate and retain as much heat as is possible for the work for which it is generated, electric furnaces have, prior to this invention, been extremely inefficient and ineffective.

The instant invention in its broadest sense involves an electric furnace including a vessel defining a chamber in or through which a material or medium to be heated is distributed or circulated, a container in which the vessel is freely arranged, an electric resistant heater element in the space ydefined by the container and vessel, and a fluid heat sink medium in said space dened by the container and vessel and about said element. The heat sink medium is preferably a metal, such as lead, the melting point of which is 620 F.

In operation, the heater element first raises the ternperature of the lead to its latent heat of fusion, or 620 F. and, subsequently, superheats the molten lead to a desired extent above 620 F. and short of its latent heat of vaporization. When the lead is thus heated and made molten or fluid, it establishes total and complete intimate contact with and about the exterior of the vessel and With and about the entire exterior of the resistance heater. In addition to the above, as the heat in the lead is conducted into and through the Wall of the vessel, convection currents are created in the molten lead which cause the heated lead to ow across and continuously scrub the exterior surface of the vessel so as to uniformly and continuously replenish and maintain the desired heat thereon.

It is to be understood that reference to lead is herein made as an example of one suitable heat sink medium that can be advantageously employed in carrying out my invention. In practice, any suitable mineral, metal or alloy having a relatively low or desired melting point and a relatively high vaporizing point can be employed without departing from the spirit of this invention. For example, tin which has a melting point of 446 F., bismuth which has a melting point of 500 F., zinc with a melting point of 785 F., or tellurium with a melting point of 840 F. could be used, if desired or as required.

Another object and feature of this invention is to provide a furnace construction of the general character referred to wherein the container can be opened or hermetically sealed with and about the vessel as circumstances require or as desired.

Yet another object of the present invention is to provide a furnace of the general character referred to Wherein the vessel can be in the nature of an open pot or kettle, or, if desired, can be in the nature of a closed ask With suitable inlet and outlet fittings related to it.

It is another object of my invention to provide a furnace of the character referred to vincluding a plurality of interconnected and interrelated furnace units, each of which includes a vessel, a container, one or more electric heater elements and a heat sink medium, such as lead as set forth above and wherein the several units cooperate successively to heat the material or medium to be heated.

It is an object of this invention to provide a furnace of the general character referred to above wherein the several heater units can be connected one to the other in series or wherein certain of the units can be connected together in parallel with each other and in series with certain of the other units.

A further object of this invention is to provide an electric furnace which is easy and economical to manufacture, operate and maintain and a furnace which is materially more eiiicient and effective than electric furnaces provided by the prior art.

The foregoing and other objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of my invention, throughout which description reference is made to the accompanying drawings, in which:

FIG. l is an isometric view of one form of my invention, with portions broken away to better illustrate details of the construction;

FIG. 2 is a sectional view of another form of my invention;

FIG. 3 is a detailed sectional view of another and preferred form of my invention;

FIG. 4 is a plan sectional view of a preferred embodiment of my invention;

FIG. 5 is a sectional view taken substantially as indicated by line 5-5 on FIG. 4; and,

FIG. 6 is a diagrammatic view of a modified form of the invention.

In its simplest form and as illustrated in FIG. l of the drawings, the instant invention involves a heater unit comprising a vessel V to receive a medium or material to be heated, a container C in which the vessel V is freely positioned to define an annular space between the container and the vessel, and, if desired, between the bottom of the vessel and the container, an electric resistance heater element H about the exterior of the vessel V and within the space and a fluid, heat conducting heat sink material S within said space about the vessel V and the heater element H.

In the first form of the invention, now under consideration, the vessel is a simple, upwardly opening metal pot-like vessel having a cylindrical side wall 10, a spherical bottom 11 and a radially outwardly projecting rim tlange 12 about the upper end of the side wall. The rim flange 12 is shown provided with a downwardly projecting skirt 13 of limited vertical extent, about its outer perimeter.

The container C is a simple, upwardly opening metal cam-like metal container having a vertical cylindrical side wall 14 with a at, upper end or rim 15 and a flat bottom (not shown).

The container C is greater in vertical extent than the vessel and is greater in diametric extent than the vessel, but is less in diametric extent than the outside diameter of the rim flange of the vessel.

With the above relationship of parts, when the vessel V is engaged in the container C, centrally thereof, the rim flange 12 engages and seats on the rim 15 of the container and supports the main portion of the vessel V centrally in the container, in spaced relationship from the side wall 14 and bottom thereof.

The skirt 13 lits loosely about the exterior of the container and serves as a centering means to maintain the vessel substantially central in the container.

Suitable hold-down means D is provided to hold and maintain the vessel V down in the container and against upward flotation in the heat sink medium S. The means D is shown as including circumferentially spaced clamp bolts 16 carried by the skirt 13 and engaging the exterior of the container.

In practice, if desired, the vessel V could be slightly greater in vertical extent than the container and the rim flange 12 and skirt 13 could be dispensed with so that the vessel, when engaged in the container, will simply seat and rest on the bottom of the container. In such a case, suitable centering and hold-down means, other than the centering means and hold-down means D referred to above, would be required.

In light of the above, it will be apparent that the particular centering means and hold-down means D are only illustrative of one carrying out of the invention and can be varied widely without departing from the spirit of this invention.

The heater element H is a conventional, elongate, industrial type, metal jacketed, hermetically sealed resistance heating element and has terminal posts 17 at its opposite ends to connect with suitable power lines (not shown).

In the case illustrated, the central portion of the elongate heater element is formed in a substantial W shape, with the several leg portions joined by rounded connecting portions and -is bent or formed in a circular form to engage about and embrace the exterior of the vessel. The terminal end portions of the element, continuing from the upper ends 4of the end legs of the W formed central portion are turned to extend horizontally and radially outward from the vessel and container and so that the terminal posts 17 are accessible at the exterior of the construction.

In practice, the upper edge 15 and skirt 13 can be suitably notched to accommodate the end portions of the element H.

The heat sink medium in the space deiined by the container and vessel is a body or mass of lead poured into said space, to a suitable level, below the upper edge or rim 15 of the container.

In the form of the invention illustrated and described above, the rirn flange 12 and skirt 13 are provided, pri marily, to cover the open top of the container C and prevent foreign matter, such as water, from dropping into the molten lead and to prevent excessive spillage of the molten lead, as might occur if the structure is shaken, when in use.

This form of the invention is suitable for use as a Sauna bath heater, vaporizer for medicinal or therapeutic use, or can be used as a simple, effective humidifier or steam generator, as desired or as circumstances require.

In the form of the invention illustrated in FIG. 2 of the drawings, the container C', heater element H and heat sink S are essentially the same as those same elements or components in the first form of the invention, except that the end portions of the heater extend upwardly, rather than radially outward.

The vessel V in this second form of the invention is a metal cylinder or flask having cylindrical side walls 10', a spherical lbottom 11', a spherical top or upper end 18 a`nd an upwardly projecting, externally threaded central neck 19.

The neck 19 is closed by a suitable cap 20 having a lateral outlet port 21, above the upper end of the neck and in which a discharge line 22 is engaged and a central vertical opening 23 in and thro-ugh which an elongate vertical injector tube 24 is engaged. The injector tube 24 depends centrally into the vessel V', with its lower open end disposed towards and spaced above the center of the concavo inside bottom surface of the vessel. The upper end of the tube 24 terminates above the cap and is connected with a liquid supply line L 4by means of a suitable fitting 25.

The tube depends freely through and in spaced relationship from the interior side walls or surfaces of the neck and cap.

In operation, liquid to vbe heated and vaporized is introduced into the tube 24 under suitable head and is discharged into the flask lor vessel to'impinge upon the center of the inner concaved surface of the bottom thereof and so it is deflected and distributed substantially uniformly radially on said bottom surface. The curvature of the inner bottom surface of the vessel directs the liquid upwardly along or across the inner surface of the side wall of the vessel and in such a manner thatv most effective and efiicient heat transfer and vaporization of liquid is effected.

The vaporized material then flows up through the neck 19, about the tube 24, into the cap 20 and, thence, out through the discharge line 22. l,

In all other respects, the structure in this second form of the invention functions the same as the first form of the invention.

In FIG. 3 of the drawings, I have shown another preferred form of the invention. In this third form of the invention, the vessel Va is the same as the vessel V in the second form of the invention and is characterized by a cylinder side wall a, spherical top and bottom ends 11a and 18E, and a neck 19a. As in the second form of the invention, a cap 20a with a port 21a and opening 23a with a discharge line 22a and injector tube 24a is provided with or for the vessel.

The injector tube 24a is the same as the tube 24 in the second form of the invention and is connected with a supply line La by means of a fitting 25a.

The heater element I-I2L is the same as the element H in the second form of the invention.

The container Ca in this third form of the invention differs from the container C and C' in the first two forms of the invention in that the bottom thereof is spherical and occurs in uniform spaced relationship from the spherical bottom 11a of the vessel Va and the upper end of the container is closed by a cover plate 31, which plate is provided with openings to cooperatively receive the cap 20a and upper end parts of the heater element and which is hermetically sealed with the container and said cap and end portions of the element as by welding, as clearly illustrated in the drawings. The container Ca is filled with the heat sink medium Sa to -a level spaced below the cover plate 31. The space between the cover plate and level of the heat sink is suflicient to allow for expansion and contraction of the heat sink Sa and, if desired, can be filled with argon or other suitable inert gas to inhibit any oxidation of the heat sink medium.

With the structure provided in the third form of the invention, the heat sink medium cannot escape or spill from the container, even if the structure is tipped or turned upside down when in operation.

Further, in this third form of the invention, during operation and as heat is exchanged between the vessel walls and the heat sink, the relationship of the bottoms 11a and 30 of the vessel and container as such as to allow for free and extensive convection currents in the heat sink medium and about the vessel, as indicated by the arrows in FIG. 3 of the drawings.

The first, second and third forms of my invention, described above, are furnace units and are such that they can be employed by themselves to heat and/or vaporize gases or liquids.

The second and third forms of the invention described above are particularly adapted 'for use in combination with other like furnace units in the establishment of special high efficiency furnace constructions.

In FIGS. 4 and 5 of the drawings, I have illustrated a special high efficiency, high output electric furnace F which includes a plurality of parallel -and series-connected furnace units U, each of which is that form of unit illustrated in FIG. 3 of the drawings, but which could, if desired, include that form of unit shown in FIG. 2 of the drawings.

The furnace F includes an elongate cylindrical insulated case A having a vertical cylindrical side wall 40, a fiat ybottom wall 41 and a flat top wall or closure 42. The Walls 40, 41 and 42 are characterized by or include a sheet metal or asbestos outer skin O, an inner skin I of low heat conducting material such as asbestos, and a core G of heat conducting material such as fiber glass.

Arranged in spaced relationship from the inner surface of the inner skins of the several Walls of the case I provide side, bottom and top panels of highly polished, preferably corrugated aluminum foil defining reflective insulating panels 43, 44 and 45.

Since aluminum is a good heat conductor, to obtain desired insulating effect of aluminum foil, it must not be in contact with another heat conducting material.

In the structure that I provide, minimum heat conduction contact is established between the corrugated foil panels and the inner skins I of the case A and the inner skins I of the case are established of heat insulating or non-heat conductive material. Accordingly, the curtains 43, 44 and 45 are extremely efficient heat insulators.

The combined insulating effect of the case A and the panels 431, 44 and 45 result in an extremely effective and ecient insulated structure in which the units U can be housed.

In the invention now under consideration, I provide six circumfercntially spaced primary furnace units U and a single, central secondary unit U. The several units are arranged within the case, spaced from the side and top panels 43 and 45 and resting or seated on the bottom panels 44.

An elongate pre-heater tube 46 extending from a suitable supply of liquid to be vaporized (not sho-wn) enters the side of the case A and is formed and arranged therein to extend helically upwardly about the interior of the case and about the exterior of the group or cluster of runits U and U'.

The upper inner end of the pre-heater tube 46 is connected with an annular manifold ring 47 arranged in the upper end of the case about the primary units U. The manifold ring 47 is provided with a plurality of circumferentially spaced, laterally extending 'branches or supply lines L', each of which is connected `with the injector tube 24a of a related primary unit U, -by means of a fitting 25a.

With the above structure, it will be apparent that liquid introduced into the structure through the line 46 is preheated as it is conducted into the manifold ring 47 and thence through the lines L and into the units U. It is effectively vaporized in the units U and is directed or conducted out of and away from the units U through the discharge lines 22a thereof.

In the form of the invention illustrated in FIGS. 4 and 5 of the drawings, the six units U are divided into three adjacent pairs of units, each of which pairs of units are connected in parallel by a common inter-connecting or bridging discharge line 22a.

Each of the three discharge lines 222l is provided with a central substantially radially inwardly projecting branch line 50, each of which lbranch lines connects with a cornmon central manifold block 51 connected with and carried by the upper end of the injector tube 2.4@L of the central, secondary unit U', as clearly illustrated in the drawings.

The discharge line 22b of the central, secondary unit U is preferably larger than the lines 22a of the primary units U and extends laterally and outwardly through the case A to a suitable place for discharge and use of the vaporized material.

In the case illustrated, the lines P and 22b extend through a suitable insulating grommet 55 engaged in a suitable opening 56 provided in the case A.

The terminals 17 of the heater elements H of the several units U and U are connected with power lines 57 branching from a suitable loom 58, which loom extends through an insulating grommet 59 engaged in an opening 60 in the case, as clearly illustrated in the drawings.

The top wall 42 of the case is preferably removable to provide access to the structure within the case.

In the forms of the invention thus far considered, I have shown a single heater element H related to each unit. In practice, if desired and as shown in FIG. 6 of the drawings, more than one such element can be provided in each unit. In FIG. 6 of the drawings I have shown a unit Ua with three heater elements Ha, which units are connected in three phase, making the unit particularly suitable for heavy duty or industrial use.

Having described only typical preferred forms and applications of my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any modifications and/ or variations which may appear to those skilled in the art and which fall within the scope of the following claims.

Having described my invention, I claim:

1. An electric furnace unit comprising a container, a heat sink mass of metal within the container having a melting point below and a vaporizing point above the operating temperature of the furnace, a vessel mounted within the container and within said heat sink mass and adapted to receive material to be heated and an electric resistance heater element supported within the container and in the heat sink mass and engaged about the exterior of the vessel to heat the -vessel and to heat the heat sink mass to a temperature above its melting point where-by said mass is molten and such that upon heat transfer from said mass to the container convection currents are established in the mass whereby said molten mass scrubs the exterior of the vessel for substatially total, uniform and continuous heat transfer between the mass and the vessel.

2. A structure as set forth in claim 1 wherein said container and vessel have spaced cylindrical side walls defining an annular space in which said heat sink mass and heater element are deposited and arranged.

3. A structure as set forth in claim 1 wherein said container and vessel open upwardly and have spaced cylindrical side walls defining an annulus in which said mass is deposited and said element is arranged, said element ybeing an elongate insulated resistance heater element formed to extend longitudinally and circumferentially about the vessel and having terminal end portions extending from within the container and accessible at the exterior thereof.

4. A structure as set forth in claim 1 wherein said vessel is a iiask having a cylindrical side wall, top and bottom ends and a neck projecting from its top end, said structure further including a cap engaged on and closing the neck of the flask and having an opening and a port above the neck, an elongate injector tube with inner and outer open ends engaged through the opening and extending centrally and freely through the neck and into the vessel to terminate in spaced relationship from the bottom of the vessel with its inner end directed towards said bottom means at the outer end of the injector tube to connect with a liquid supply and a discharge line connected with said port.

5. A structure as set forth in claim 1 wherein said vessel is a ask having a cylindrical side wall, top and bottom ends and a neck projecting from its top end, said structure further including a cup engaged on and closing the neck of the flask and having an opening and a port above the neck, an elongate injector tube with inner and outer open ends engaged through the opening and extending centrally and freely through the neck and into the vessel to terminate in spaced relationship from the bottom of the vessel with its inner end directed towards said bottom means at the outer end of the injector tube to connect with a liquid supply and a discharge line connected with said port, the inner surface of the lbottom end of the vessel being concaved whereby liquid issuing from the inner end of the injector tube and impinging on the bottom end of the vessel is directed uniformly radially outwardly and, thence, upwardly in the vessel longitudinally of the side wall thereof.

6. A structure as set forth in claim 1 wherein said vessel is a liask having a cylindrical side wall, top and bottom ends and a neck projecting from its top end, said structure further including a cup engaged on and closing the neck of the ask and having an opening and a port above the neck, an elongate injector tube with inner and outer open ends engaged through the opening and extending centrally and freely through the neck and into the vessel to terminate in spaced relationship from the bottom of the vessel with its inner end directed towards said bottom means at the outer end of the injector tube to connect with a liquid supply and a discharge line connected with said port, and closure means related to the elements, vessel and the container to seal the space defined thereby and in which said mass is arranged, the volume of said mass being less than the volume of the space to allow for expansion of said mass when said mass is heated.

7. A furnace including a heat insulated case, a plural` ity of primary furnace units and at least one secondary furnace unit within the case, each furnace unit comprising a container, a vessel arranged in the container with a neck extending therefrom, a heat sink mass of metal having a melting point below and a vaporizing point above the operating temperature range of the furnace in the container and about the vessel and an electric resistance element arranged in the container and heat sink mass and about the vessel, a cap with an opening and a port engaged on the neck of each vessel, an elongate injector tube with open inner and outer ends engaged through the opening of each cap and extending freely through the neck and terminating in spaced relationship from the bottom end of its related vessel, a dis charge line connected With the port in each cap, a liquid supply line extending from a liquid supply remote from the furnace and entering the case, manifold means connecting the supply line with the outer ends of the injector tubes of the primary furnace units, a manifold block on the outer end of the injector tube of the secondary furnace unit and connected With the discharge lines of the primary furnace units, the discharge line of the secondary unit extending outwardly through the case to a delivery point and an electric loom extending from a suitable power source remote from the furnace, through and into the case and connected with the resistance elements of the several furnace units.

8. A structure as set forth in claim 7 wherein said primary furnace units are divided into pairs and the discharge lines of the furnace units of each pair of units connect with a common discharge branch line connected with the manifold block.

9. A structure as set forth in claim 7 wherein said supply line extends helically within the case and about the several furnace units Within the case where-by liquid flowing through said supply line is pre-heated before being introduced into the vessels of the several furnace units.

10. A structure as set forth in claim 7 wherein said case has top, bottom and side walls with inner and outer skins and cores of heat insulating material, said inner skins established of non-heat conducting material and heat insulating partitions of polished metal within the case in substantially spaced relationship from the inner skins thereof.

11. A structure as set forth in claim 7 wherein said primary furnace units are divided into pairs and the discharge lines of the furnace units of each pair of units connect with a common discharge `branch line connected with the manifold block, said supply linev extending helically within the case and about the several furnace units within the case whereby liquid iiowing through said supply line is pre-heated before being introduced into the vessels of the several furnace units.

12. A structure as set forth in claim 7 wherein said primary furnace units are divided into pairs and the discharge lines of the furnace units of each pair of units 'connect with a common discharge branch line connected with the manifold block, said case having top, bottom and side walls with inner and outer skins and cores of heat insulating material, said inner skins established of non-heat conducting material and heat insulating partitions of polished metal within the case in substantially spaced relationship from the inner skins thereof.

13. A structure as set forth in claim 7 wherein said supply line extends helically within the case and about the several furnace units Within the case whereby liquid flowing through said supply line is pre-heated `before being introduced into the vessels of the several furnace units, said case having top, bottom and side walls with inner and outer skins and cores of heat insulating material, said inner skins established of non-heat conducting material and heat insulating partitions of polished metal within the case in substantially spaced relationship from the inner skins thereof.

References Cited UNITED STATES PATENTS BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

U.S. Cl. X.R. 13-31

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