US635132A - Electric heater. - Google Patents

Description

N0. 635,|32. Patented Oct. I7, I899. E. E. GOLD.

ELECTRIC HEATER.

(Application filed May 18, 1898.) (No Model.)

FIG, 7.

WITNESSES; INVENTORZ 144 11 1 zwww AM By his Alzomeys,

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UN TED STATES PAIENT ELECTRlC HEATER.

SPECIFICATION forming part of Letters Patent No. 635,132, dated October 1'7, 1899.

Original application filed January 31,1898, Serial No. 668,528, Divided and this application filed May 18, 1898. Serial No. 681,012. (No model.)

To all whom, it may concern:

Be it known that I, EDWARD E. GOLD, a citi-- zen of the United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Electrio Heaters, of which the following is a specification.

This invention relates to electric heaters of that class in which the heat is generated by passing an electric current through a resistant wire which is exposed to the air and which are of that general construction in which such wire is wound first into a helix or coil, which helix is then wound'or coiled helically around a support to form a compound helix.

My invention relates to the means for supporting such compound resistant helix.

According to myinvention I provide a skeleton or open-work support in the general form of a tube and adapted to afford free circulation of air through the compound resistant helix, which is wound on such support in such manner that the latter is thoroughly ventilated and exposed as fully as possible to contact with the surrounding air, so as to be efficiently cooled thereby. Preferably this openwork support is made by coiling a wire or rod of sufficient strength into a helix with open convolutions spaced apart somewhat less than the diameter of the resistant helix, so that when the latter is coiled around the outside of said helical support it rests in the spaces between the convolutions thereof, so as to make exterior tangential contact therewith at two points in each loop or minor convolution of the resistant helix. The helical support ing-wire'is enameled or otherwise provided with heat-resisting insulation in order that the support shall insulate the successive convolutions of the compound resistant helix from one another.

My present application is a division of my application, Serial No. 668,528, filed January 31, 1898, that application having been in part divisional of my application, Serial No. 655,176, filed October 1 1-, 1897, in that claim 1 of the latter was transferred into it and is now by the filing of this application transferred from said application Serial No. 668,528 into my present application, being claim 1 herein.

My present application is in part specific to said application Serial No. 668,528.

Figure l of the accompanying drawings is a sectional elevation of a heater constructed according to my invention, being partly dissected away in vertical mid-section. Fig. 2 is a transverse section thereof. Fig. 3 is a sectional and partly-dissected elevation of a modified construction.

In the drawings let A designate a helix of resistant wire and let B designate the openwork support therefor, constructed preferably, as shown in Figs. 1, 2, and 3, of a stiff wire wound into a helix and enameled. The resistant wire A is first wound into ahelix in any usual manner as, for example, by winding it upon a mandrelthe helix thus formed being herein referred to as the minor helix. This minor helix is afterward coiled around the exterior of the helical support 13, the larger helix thus formed being herein referred to as a major helix. The wire thus coiled first into a minor helix and then into a major helix constitutes a compound helix. The supporting-wire B is of sufficient size to afford the requisite stiffness and is coiled into an open helix as by winding upon a mandrel of considerably larger diameter than that used in winding the minor helix. lts successive convolutions are spaced apart between centers somewhat wider than the exterior diameter ofthe minor helix A, to the end that when the resistant helix is wound around the support its successive major convolutions shall be spaced apart to afford ample insulation. At the same time the space between the convolutions of the helix B must be less than the exterior diameter of the minor helix A to prevent this helix falling into such space. The

' proportions shown are considered preferable,

since they afford ample support for the resistant helix and ample separation for the successive major convolutions thereof to atford the requisite insulation, while the convolutions of the supporting-helix are sufficiently separated to leave ample space between them for upward circulation of air in the manner indicated by the arrows. It will be seen that by this construction the resistant helix A is extended parallel with the supporting-wire B, so that the latter forms a continuous longitudinal support making contact with each successive convolution of the resistant helix. The resistant helix is at each convolution supported on two successive convolutions of the helix 13, so that it rests thereagainst at two points,thereby maltingits support firm and stiff. As these points of contact are formed by the exterior tangential contact of circles, they are, in fact, mere geometrical points disposed longitudinally of the supporting-wire B at a distance apart equal to the pitch of the minor helix A. It results from this that with the exception of these minute points the entire surface of the resistant wire of the helixA is out of contact with every other part and fully exposed to the air or other surrounding medium by which its generated heat can be rapidly conducted away, so that this form of heater at tains the ideal of free radiation, combined with a secure support for the resistant wire. The entire heater is, in fact, a skeleton having wide spaces through which the air may freely circulate, which spaces are crossed and subdivided at frequent intervals by the hot wires of the resistant helix, so that the air flowing through the heater is successively subdivided by these hot wires, and consequently is effectively heated. The support is also of such construction as to have the minimum of mass for a given degree of strength or rigidity, so that there is the least possible heat-absorptive property in the support consistent with its properly performing its supporting function. It results from this that the heater is highly efficient from the very instant when the electric current is turned on, since but a very small proportion of the heat is absorbed in heating up the support, and by reason of the support being so thoroughly subdivided into such slender elements as to expose a large radiating-surface it is capable of giving out the heat to the air almost as rapidly as of receiving it from the resistant wire, and hence it very quickly re ceives the maximum of heat which it is capable of retaining.

It is of course essential to insulate the re sistant wire A. from the supportingwlire B. This might be done by coating either wire with insulating material; but since to coat the wire A would obstruct the radiation of heat therefrom it is preferable to apply the insulation to the supporting-wire B. This insulation must be of such character as to be unaffected by the heat which is generated, and for this reason it is preferable to employ a vitreous enamel. This is found highly successful in practice, it being only necessary to employ an iron wire of sufficient diameter, wind it into the helix desired, then dip it into enamel, and fire this enamel on. he ends of the wire, however, are preferably left uncoated in order that they may be screw-threaded for attaching the supporting-helix in the heater. The enamel coating is lettered a a.

It is essential that the minor helix A shall be wound upon the helical support with a contractile tension in order that this tension shall cause it to draw itself constantly into close and firm contact with the supportingwire. To this end the resistant wire is wound closely upon its mandrel, and in then winding it into a major helix around the support B it is stretched as it is wound on, thereby opening or pulling apart its minor convolutions. The tension should be sufficient to maintain the resistant wire firmly against the support notwithstanding its tendency to expand when heated by the current and notwithstanding the extent to which its tension will be weakened by such heat. No considerable degree of tension need be allowed for, however, in view of these considerations, since in my heater, owing tothe perfect ventilation, the wires are never permitted to become highly heated.

For supporting the helical support B, I have shown in Figs. 1 and 3 a head or disk 0, preferably of porcelain, at each end of the heater, the two heads being held rigidly apart either by means of an exterior casing G, as shown in Fig. 1, or by a tie-rod D, as shown in 3, which rod may pass centrally through the heater within the axis of the helix B, its ends being screw threaded and having nuts cl screwed thereon to clamp the heads tightly upon the .rod. If the casing G is used, as shown in Fig. 1, it may be held by its ends, slipping over bosses 0, formed on the heads 0 (land entering its ends. The opposite ends of the helix l3 are inserted through suitable holes in these heads and, being screw-threaded, have nuts 0 screwed thereon, whereby to draw them firmly against the heads to take up any looseness or slack and also preferably to slightly stretch the helix B to impart firmness and rigidity to its convolutions and in Fig. l to press the heads firmly against the ends of the casing G. The ends of the helix A are secured by being fastened to binding posts or bolts E, of which one is shown, which pass through holes in the heads, being secured by screwing a nut e on the outer end, to which post the circuit wire it may be clamped by the same nut or by an outer nut c.

I prefer to construct the heater with the outer casing G, which incloses the compound coil, as shown. This casing is made of enameled metal, preferably in the form of a foraminous or open-work tube, so as to admit free passage of air; but any skeleton form of suitable strength will answer. It is arranged substantially concentric with the compound coil which it incloses and is but slightly larger than the diameter of this coil in order that if the resistant wire should break, so as to release it from restraint, the consequent expansion or unwinding of the minor helix in its endeavor to straighten out into its original form will almost instantly be restrained by the casing, so that the severed wires can do no harm. "With existing heaters when the formation of short circuits.

It will be understood that my invention provides a novel support for the compound helix consisting of a hollowopen-work body in the general form of a hollow cylinder or tube, which permit-s free circulation of air through the central space inclosed within the major helix, so that air may circulate freely through and across the convolutions of the resistant wire. By this means the convolutions of wire extending along the top of the support do not become overheated, as in the case of a solid cylindrical support.

The open-work or skeleton tubular support may be constructed otherwise than by coiling a supporting-wire into a helix. One suitable modification thereof consists in making it of a foraminous tube, as shown in my said application, Serial No. 655,176, filed October 1 L, 1807. It made of metal, it should be coated with insulating enamel.

I claim as my invention the tollowing defined novel features, substantially as hereinbefore specified, namely:

1. An electric heater comprising a skeleton or open-work support in the general form of a tube, and a helix of resistant wire wound helically around said support, whereby air may circulate between the meshes of said helix and through the openings into and out of the interior of said support, and into con tact with all portions of the heated resistant wire.

2. An electric heater comprising a skeleton support in the general form of a tube, consisting of a supporting-wire coiled into an open helix, and a helix of resistant wire coiled into a'compound helix around the outside of said supporting-helix and resting in the spaces between the convolutions thereof so as to make tangential contact therewith at two points in each minor convolution.

An electric heater comprising a supporting-helix B with open convolutions, and a re= sistant helix A wound distensively into a compound helix around the outside of said helix B, so that it rests in the spaces between adjacent convolutions thereof, and has a contractile tension drawing it into firm tangen tial contact therewith.

at. An electric heater comprising a compound helix of resistant wire, an internal support around which said, helix is wound, and an outer inclosing casing G consisting of an open-work tube of enameled metal, whereby in case of breakage of the resistant wire the unwinding thereof would be restrained by the casing, and short-circuiting and arcing prevented.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

EDXVARD E. GOLD.

Vitnesses:

FRED WHITE, THOMAS F. WALLAOE.

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