Improvements in Electric Heaters.
Year: 1897

page_text: Date of Application, 11th Sept., 1897
Complete Specification Left, 11th June, 1898-Accepted, 30th July, 1898
Improvements in Electric Heaters.
I, EDWARD ETHEL GOLD, of Number 64, West Seventy-seventh Street,
in the City of New York, United States of America, Manufacturer, do hereby
declare the nature of the said invention to be as follows:-
This invention relates to means for utilizing the heat generated by the passage
of a current of electricity over a poor or resistant conductor. I employ a resis-
tant wire coiled into a helix or otherwise suitably arranged, and either naked or
having only a thin and readily heat-conducting covering, in order that the heat
contained in the wire may be readily given off to air, water or other fluid surround-
ing it, such fluid being kept in motion, so that by its circulation it may be effective
in conducting away the heat from the wire.
According to one form of my invention, I wind a resistant wire around a mandrel
to form it into a helix, the convolutions of which are slightly separated in order
to avoid contact and consequent shortcircuiting of the current; and I then coil
the helix thus formed (which I will distinguish as the minor helix) into a spiral
or larger helix (which I will distinguish as the major helix). The compound
helix thus formed I enclose in a tube so shaped or adapted as to retain it in shape
and support it exteriorly, while holding its convolutions out of contact, and leav
ing a free space between them for circulation through and around the convolutions
of the fluid to be heated. For heating air, the compound helix is enclosed in a
perforated tube, so that the air may freely circulate through the perforations.
The enclosing tube is insulated from the coils or helices of wire, either by coating
the wire with an insulating material so thin as to not materially resist the con-
duction of heat, or preferably by coating the tube interiorly with insulating
material unaffected by heat, such as vitreous enamel. That the tube may properly
support the convolutions of the compound helix, it is formed internally with spiral
The helix is wound openly,
grooves or corrugations into which the helix enters.
so that its convolutions tend to spring apart, thereby giving the compound helix
an expansive tendency which holds it firmly in place in the said grooves. The
enclosing tube or casing may contain blocks of insulating material in which are
formed grooves for supporting the helix, and between which is a space or flue
for circulation of air. Preferably, however, the enclosing tube is spirally corru-
gated and internally enamelled. The tube may be of sheet metal, drawn or rolled,
and afterward corrugated, or it may be of cast metal. In the latter case I prefer
to divide it diametrically into two parts, which are afterward fastened together
by screws or otherwise.
A heater for liquids may be thus constructed of a compound helix by making
the enclosing tube imperforate.
According to the second part of my invention, I wind the resistant wire into
a coil or helix (the same as the minor helix before referred to), and I mount this
helix upon a support consisting of a bar or rod of wire or other material extending
parallel with it and preferably inside of it, although it may be exterior to it.

page_text: The supporting rod or wire is of suitable stiffness, and is extended in any direction
that it is desired the supported resistant helix shall take, either in a flat back
and forth or zigzag coil, or in a flat spiral, or in a helical spiral. In the latter
case the resistant helix becomes a compound helix, differing from that provided
by the first part of my invention only in the means for supporting it. The sup-
porting wire is a helix extending parallel with the major helix, and either passing
through it or extending parallel thereto exteriorly of it or interiorly of it. The
resistant wire and the supporting wire are insulated from one another by coating
either with insulating material which should be resistant to heat; preferably it
is the supporting wire that is thus coated, and preferably the insulating material
is a coating of vitreous enamel. I employ this insulated supporting wire also as
a conducting wire for leading the electric current to one end of the resistant coil,
so that the connectors or binding posts may be arranged both at one end of the
heater.
According to a further feature of my invention, I employ such supporting wire
as a part of the heat generator, by making it small enough to be electrically
resistant to the requisite degree, and I afford it mechanical supports at intervals.
Thus heat is given out both by the supporting wire and the resistant helix. In
this manner I may build up a heater composed of a succession of compound helices
wound one around another, being alternately insulated and naked, each major
convolution being supported by the one within it and supporting the one exterior
to it, thus concentrating in a small space a great length of resistant wire.
According to a further feature of my invention, I construct the enclosing
casing for an air heater of a helical coil of wire the convolutions of which are
spaced apart sufficiently to admit of free circulation of air between them. This
wire I preferably coat with insulating enamel, and if desired it may serve as an
additional heating coil for use for example in an emergency requiring a maximum
heat generating capacity, by making it of wire small enough to be electro resistant,
and providing a switch for throwing it in or out of circuit. In addition, I pro-
vide longitudinal rods either within or exterior to the enclosing coil, and in close
contact with it to maintain its convolutions in place and prevent sagging thereof,
and hence to maintain the casing centrally around the heating coil. The opposite
ends of the enclosing coil and of the casing, are connected to end disks or heads,
and these are held at fixed distances by the said rods. A heater thus constructed
may be arranged vertically by mounting it on suitable legs at one end, or it may
be arranged horizontally by hanging it for example beneath the seat of a railway
carriage.
Improvements in Electric Heaters.
I, EDWARD ETHEL GOLD, of Number 64 West Seventy-seventh Street,
Borough of Manhattan, in the City of New York, United States of America,
Manufacturer, do hereby declare the nature of the said invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:—
This invention relates to means for utilizing the heat generated by the passage
of a current of electricity over a poor or resistant conductor. I employ a resistant
wire coiled into a helix, or other equivalent arrangement, and either naked or

page_text: having only a thin and readily heat-conducting covering, in order that the heat
contained in the wire may be readily given off to air, water or other fluid surround-
ing it, such fluid being kept in motion, so that by its circulation it may be effective
in conducting away the heat from the wire.
According to one form of my invention, I wind a resistant wire around a
mandrel to form it into a helix, the convolutions of which are slightly separated in
order to avoid contact and consequent short-circuiting of the current; and I then
coil the helix thus formed (which I will distinguish as the minor helix) into a
spiral or larger helix (which I will distinguish as the major helix). The com-
pound helix thus formed I enclose in a tube so shaped or adapted as to retain it
in shape and support it exteriorly, while holding its convolutions out of contact,
and leaving a free space between them for circulation through and around the
convolutions of the fluid to be heated. For heating air, the compound helix is
enclosed in a perforated tube, so that the air may freely circulate through the
perforations. The enclosing tube is insulated from the coils or helices of wire,
either by coating the wire with an insulating material so thin as to not materially
resist the conduction of heat, or preferably by coating the tube interiorly with
insulating material unaffected by heat, such as vitreous enamel. That the tube
may properly support the convolutions of the compound helix, it is formed inter-
nally with spiral grooves or corrugations into which the helix enters. The helix
is wound openly, so that its convolutions tend to spring apart, thereby giving
the compound helix an expansive tendency which holds it firmly in place in the
said grooves. The enclosing tube or casing may contain blocks of insulating
material in which are formed grooves for supporting the helix, and between which
is a space or flue for circulation of air. Preferably, however, the enclosing tube
is-spirally corrugated and internally enamelled. The tube may be of sheet metal,
drawn or rolled, and afterward corrugated, or it may be of cast metal. In the
latter case I prefer to divide it diametrically into two parts, which are afterward
fastened together by screws or otherwise.
A heater for liquids may be thus constructed of a compound helix by making
the enclosing tube imperforate.
According to the second part of my invention, I wind the resistant wire into
a coil or helix (the same as the minor helix before referred to), and I mount this
helix upon a support consisting of a bar or rod of wire or other material extending
parallel with it and preferably inside of it, although it may be exterior to it.
The supporting rod or wire is of suitable stiffness, and is extended in any direction
that it is desired the supported resistant helix shall take, either in a flat back and
forth or zigzag coil, or in a flat spiral, or in a helical spiral. In the latter case
the resistant helix becomes a compound helix, differing from that provided by the
first part of my invention only in the means for supporting it. The supporting
wire is a helix extending parallel with the major helix, and either passing through
it or extending parallel thereto exteriorly of it or interiorly of it. The resistant
wire and the supporting wire are insulated from one another by coating either
with insulating material which should be resistant to heat; preferably it
is the supporting wire that is thus coated, and preferably the insulating material
is a coating of vitreous enamel. I employ this insulated supporting wire also as
a conducting wire for leading the electric current to one end of the resistant coil,
so that the connectors or binding posts may be arranged both at one end of the
heater.
According to a further feature of my invention, I may employ such supporting
wire as a part of the heat generator, by making it small enough to be electrically
resistant to the requisite degree, and I afford it mechanical supports at intervals.
Thus heat is given out both by the supporting wire and the resistant helix. In
this manner I may build up a heater composed of a succession of compound helices
wound one around another, being alternately insulated and naked, each major
convolution being supported by the one within it and supporting the one exterior
to it, thus concentrating in a small space a great length of resistant wire.

page_text: According to a further feature of my invention, I construct the enclosing casing
for an air heater of a helical coil of wire the convolutions of which are spaced
apart sufficiently to admit of free circulation of air between them. This wire I
preferably coat with insulating enamel, and if desired it may serve as an additional
heating coil for use for example in an emergency requiring a maximum heat
generating capacity, by making it of wire small enough to be electro resistant,
and providing a switch for throwing it in or out of circuit. In addition, I provide
longitudinal rods either within or exterior to the enclosing coil, and in close
contact with it to maintain its convolutions in place and prevent sagging thereof,
and hence to maintain the casing centrally around the heating coil. The opposite
ends of the enclosing coil or casing, are connected to end disks or heads, and these
are held at fixed distances by the said rods. A heater thus constructed may be
arranged vertically by mounting it on suitable legs at one end, or it may be
arranged horizontally by hanging it for example beneath the seat of a railway
carriage.
Having now indicated the nature of my invention, I will now proceed to more
fully describe the same with reference to the accompanying drawings.
The first part of my invention is illustrated in Sheets 1 and 2 of said drawings,
wherein,
Fig. 1 is a sectional side view of one construction of heater, Figs. 2 and 3 being
transverse sections thereof in spiral planes denoted by the lines 2-2 and 3-3
respectively in Fig. 1. Fig. 4 is a plan view thereof. Figs. 5 and 6 are a vertical
longitudinal section and a transverse section respectively of a modified construc-
tion. Fig. 7 is a plan partly in horizontal section and partly dissected showing
another construction, of which Fig. 8 is a transverse section on the line 8-8,
and Fig. 9 is a side elevation partly dissected away. Fig. 10 is a sectional and
dissected elevation of a further modification, and Fig. 10 is an elevation of a
modification of Fig. 10. Fig. 11 is a sectional elevation of a further modification.
Let A designate the resistant wire, which is first wound into a minor helix,
and this helix is then coiled into a major helix. Let B designate the enclosing
tube or support, which is so shaped as to retain the compound coil in shape and
support it while holding its convolutions out of contact. For heating air the tube
is perforated, as shown in Figs. 1 to 10, either with prolonged slots 66 or holes cc,
so that the air may freely circulate through the perforations. For heating liquid,
the enclosing tube is made imperforate, as shown in Fig. 10, so that liquid
which is caused to flow through the tube will pass in contact with the resistant
wire and be heated thereby. The enclosing tube is insulated from the resistant.
wire, either by coating the wire with an insulation so thin as to not materially
resist the conduction of heat, or preferably by coating the tubular support with
insulating material, as shown at a a in Figs. 1 to 3. The insulating material
must be unaffected by the heat, a vitreous enamel being preferable. That the
tube B may properly support the convolutions of the compound helix, it is
formed internally with spiral grooves or corrugations ff. The helix is wound
openly, giving it an expansive tendency which holds it firmly in said grooves.
These grooves are preferably formed by corrugating the tube. The tube may be of
sheet metal drawn or rolled and afterward corrugated, as shown in Figs. 5 and 6.
Or it may be of cast metal, as shown in Figs. 1 to 4. In the latter case I prefer
to divide it diametrically into two parts, as shown, which are afterward fastened
together by screws or bolts e e passing through ears dd. Instead of forming
the tube itself with internal grooves, it may contain blocks of insulating material,
as shown at C C in Figs. 7, 8 and 9, in which blocks are formed segmental
grooves f¹ for supporting the helix, and between which is a space or flue g for
circulation of air. In Fig. 10 the tube B instead of being of metal coated with
insulation, is made itself of insulating material such as earthenware, having
perforations at intervals, and formed interiorly with spiral grooves for holding.
the compound helix in place.
When a sufficient electric current is passed through the wire to heat it, the heat

page_text: is imparted to the air in the perforated tube or casing, which is set into circula-
tion so that a constant rising current of air is maintained, as indicated by the
arrows in Fig. 2. If employed to heat liquid, the tube being made imperforate
as in Fig. 10, the liquid is forced to travel longitudinally through the tube, and
abstracts the heat from the wire. If a non-conducting liquid such as oil is used,
the wire may be naked, but if employed for heating water, it is preferable to
insulate the wire with a thin coating of enamel.
The form or construction of the tubular support B may be greatly varied, it
being only essential that it shall be adapted to support and enclose the coil or helix,
and that means be provided to prevent contact between the successive major con-
volutions of the latter.
According to a modification of my invention, the compound helix of resistant
wire is wound around the outside of the perforated tubular support instead of
being wound inside of it, this construction being shown in Fig. 1. In this case
the perforated tube if not itself of insulating material, requires to be coated with
insulation upon the exterior instead of the interior. Also in order that the com-
pound wire helix may press into firm contact with the supporting tube, it is
necessary that the wire be wound with a contractile tendency instead of with an
expansive tendency. Hence instead of winding the wire originally into an open
helix which is partially pressed together in inserting it within a tubular support,
the wire is wound originally in a close helix, which is partially pulled open or
distended in winding it around the tubular support. This modification retains
the same advantages of efficient circulation of air into and through all portions of
the compound helix as in the constructions first described.
My invention possesses important practical advantages over that construction
of electric heater heretofore used wherein a helix of resistant wire is wound
spirally around the exterior of a solid cylinder of earthenware having a spiral
groove for holding the convolutions of the compound helix in place. In such
construction the access of air to the interior of the major helix is precluded by
the presence of the solid cylinder, which also obstructs the flow of air above it,
with the result that the wire is unequally cooled, those portions in contact with
the cylinder having less access of air than the outer portions, and the convolution's
along the top of the cylinder resting in comparatively dead air, and becoming
so overheated that they gradually relax their tension and open out, thereby per-
mitting the convolutions on the lower side of the support to draw closer together,
so that in time some of the lower convolutions are liable to come into contact and
are short-circuited, thereby lowering the resistance of the heater. My invention
provides such thorough ventilation and such free circulation of air in the interior
of the major helix, that all portions of the wire are efficiently cooled and no
overheating or unequal heating occurs, so that no distortion of the wire and no
consequent short circuiting can take place.
The second part of my invention is illustrated in Sheets 3, 4 and 5 of the accom-
panying drawings, wherein,
Fig. 1 is a transverse section of a railway car or carriage showing my heater
hung beneath a seat, Fig. 2 being an end view of the seat and heater. Fig. 3 is
a side elevation of the heater partly dissected away in vertical section, and Fig. 4
is a transverse section thereof. Fig. 5 is a side elevation of another form of
heater partly dissected away, and Fig. 6a transverse section thereof. Fig. 7 is a
sectional or dissected side elevation of still another form of heater, of which Fig. 8
is a transverse section. Fig. 9 is a dissected sectional elevation of a complete
heater and casing for heating air. Fig. 10 is a dissected elevation of a heater and
enclosing tube for heating liquid. Fig. 11 is a plan of a flat spiral heater. Fig. 12
is a cross-section of the resistant helix showing two supports within it. Fig. 13
shows a flat zig-zag heater.
In Sheet 5, Fig. 14 is a dissected side elevation of a duplex coil heater, of which
Fig. 15 is a transverse section. Figs. 16 and 17 are dissected side elevations of two

page_text: other forms of heaters. Figs. 17 and 17" show details of Fig. 17. Fig. 18 is a
transverse section of one minor convolution and its supports.
According to this second part of my invention, the wire is first wound into a
minor helix A as before described, and this helix is then mounted upon a support B
consisting of a bar or rod of wire or other material of suitable stiffness to support
the helix. This supporting rod or wire is extended in any direction that it is
desired the supported resistant helix shall take, either in a straight direction back
and forth, in a flat zigzag as shown in Fig. 13, or in a flat spiral as in Fig. 11
or in a helical spiral as in Figs. 3 to 10 or 14 to 17. In the latter case the sup-
porting wire is a helix extending parallel with the major resistant helix A, and
either passing through it (as in Figs. 3, 4, 7, 8, 9, 10, 11, 12 and 13) or extending
parallel thereto exteriorly of it (as shown in Figs. 5 and 6 and in Fig. 17) or
interiorly of it (as shown in Fig. 16).
In any case the resistant wire A and the supporting wire B are insulated from
one another by coating either with heat-resisting insulating material. I prefer to
thus coat the supporting wire, in order that the resistant wire may be left naked
and so as to most freely radiate its heat. I prefer to use vitreous enamel as the
insulating material, this insulation being shown at a a¹ in the drawings.
The supporting wire or rod should be no larger than is necessary to give the
requisite stiffness for supporting the resistant helix. Hence if it is arranged within
the resistant helix, it is much smaller than the interior thereof so as to make
contact therewith tangentially at only one point in each minor convolution,
leaving the interior of the helix otherwise free and open for unobstructed circula-
tion of air within it, as shown in Figs. 3, 7, 9 and 10. The supporting wire may
be extended in any direction that it is desired the supported resistant helix shall
take. The curving of the supporting wire into either a flat spiral (Fig. 11) or a
helix (Figs. 3, 7, 9 and 10) causes the resistant wire when passed thereover to
press by reason of its elasticity against the supporting wire, thereby ensuring its
tangential contact therewith at one point only in each minor convolution. In
Figs. 9, 10 and 11 the resistant helix is shown pressing outwardly against the
supporting wire by reason of the helix having been wound originally on a straight
mandrel, so that its tendency to restraighten itself causes it to expand against the
support. In Figs. 3 and 7, the resistant helix is shown as pressing inwardly
against the supporting wire, a result which may be attained by winding it
originally in a close helix and distending it into an open helix on the supporting
wire.
When the supporting wire is coiled into a helix and extends within the resistant
helix, its convolutions must be wound sufficiently open to hold the successive
major convolutions of the compound resistant helix sufficiently apart so as to
prevent any possibility of their touching each other and thereby short-circuiting
à portion of the resistant wire. They are shown suitably spaced open in Figs. 3,
7, 9 and 10.
Instead of a single supporting wire extending within the resistant helix, the
support may be duplicated as shown in Figs. 12 and 13.
When the supporting wire is arranged exterior to the minor helix of resistant
wire, it is necessary to provide two points of support for the latter, as shown
diagrammatically in Fig. 18, where the resistant helix A rests on two supporting
wires (or convolutions of wire) 1 B. This is best provided by coiling the sup-
porting wire into a helix, so that the resistant helix by being coiled into a major
helix parallel with it, may have each minor convolution supported at two points
on two successive convolutions of the supporting wire. One suitable arrangement
is shown in Fig. 16, where the enamelled supporting helix B has the resistant
helix A carried around its exterior. Another suitable arrangement is shown in
Figs. 5 and 17, where the resistant helix A is wound inside of the supporting
helix B. In either case the resistant helix (which in all cases is of resilient wire)
is so wound as to press firmly into contact with the supporting helix so as to
crowd itself partly into the space between two adjoining convolutions thereof, as

page_text: I may employ the supporting wire B as a part of the heat generator, by making
it small enough to be electrically resistant to the requisite degree, but as this
reduces its stiffness and weakens it, it becomes, necessary to provide mechanical
supports at intervals; which may be done, as shown in Figs. 5 and 6, by arranging
the longitudinal rods E E in close contact with the supporting helix B.
When it is desired to concentrate in a small space a great length of resistant
wire, I may build up a heater composed of a succession of compound helices
wound one around another, these helices if of naked wire being alternated with
insulated wire supports, an example of which is shown in Figs. 14 and 15. In
these figures the supporting helix B of enamelled wire carries two compound
resistant helices, one of which, A, is wound outside the support with a contractile
tension, while the other, A', is wound inside the support with an expansive
tension. The current enters by binding post E, traverses the outer coil A, the left
hand end of which is connected to the inner coil, and passes back through the
latter to the binding post E¹.
I may construct the enclosing casing for an air heater of a helical coil of wire,
as shown at D in Figs. 3 and 4, or as shown at G in Figs. 14 and 15. This wire
I preferably coat with insulating enamel, as shown at a in Fig. 14. If desired it
may serve as an additional heating coil for use in an emergency requiring a
maximum heat generating capacity, by making it of wire small enough to be
electro-resistant, as shown for example in Figs. 3 and 4, and providing a switch
for throwing it in or out of circuit. To maintain the convolutions
of this helical casing in place and prevent sagging thereof, and to
hold the casing centrally around the heating coil, I provide longitudinal
rods in close contact with it. For this purpose I may use the rods E E,
arranged as shown in Figs. 3 and 4, (these same rods being shown in
Figs. 14 and 15 lettered D D), or I may arrange rods within the casing as shown
in dotted lines at bb in Fig. 4.
A heater constructed according to this part of my invention may be arranged
vertically, by providing it with suitable legs at one end, as shown at i in Fig. 1,
on which it may stand, or it may be arranged horizontally by hanging it for
example beneath the seat of a railway carriage, as shown in Figs. 1 and 2,
where hh designate hangers.
The horizontal arrangement of the heater is preferable because it exposes the
resistant wires more fully and equally to circulation of air. Thus arranged, the
helical supporting wire B serves as an open grating or skeleton through which
the air can flow into the interior of the compound helix, escaping upwardly there-
from by again flowing through the spaces between the wires; while at the same
time the air by flowing into the resistant helix and across the heated wires thereof,
is repeatedly subdivided by hot wires and effectually heated.
I make no claim to a construction of electric heater in which a supporting
helix of enamelled wire is arranged on a vertical axis with both ends of the wire
carried to the upper end of the helix and there supported in a casing consisting
of an upright cylindrical tube enclosing the supporting helix and forming a flue
or chimney, and with a fine resistant wire wound closely and tightly upon the
enamelled wire, as on a core, so that the resistant wire forms a helix which is entirely
filled by the supporting enamelled wire, so as to prevent all circulation of air
within the resistant helix. That form of my invention in which the enamelled
supporting wire passes through the resistant helix, is distinguished from the con-
struction just described by the supporting wire being proportionately smaller in
diameter so as to occupy only a small portion of the area of the interior of the
minor convolutions of the resistant helix, and so as to make contact therewith
My invention
tangentially at one point only in the circumference thereof.
permits the use of a smaller and lighter wire for the supporting helix, since the
latter is supported at opposite ends, which permits of putting the supporting helix
under tension by drawing these ends apart (by screwing up the nuts on the
threaded ends of the wire shown in Fig. 9 and Figs. 14 to 17) whereby a much

page_text: clearly shown. In the construction of Fig. 16, this is accomplished by winding
the resistant wire rigidly in a close helix and stretching it open as this helix is
wound around the support. With the construction shown in Figs. 5 and 17,
this is accomplished by winding the resistant wire originally in an open helix, and
compressing it so as to close its convolutions together when placing it inside the
support. Hence in the former case the resistant helix tends to contract upon the
support, and in the latter case it tends to expand within it. The supporting helix
must be wound with its convolutions further apart between centers than the outside
diameter of the minor helix, in order that the major convolutions of the compound
helix shall be held out of contact with each other to prevent short-circuiting.
The space between the convolutions of the supporting helix must be sufficiently
less than the outside diameter of the helix A to adequately support the latter.
The proportions shown in Figs. 16 and 17 are suitable.
It will thus be seen that my invention as applied to a compound helix of
resistant wire, affords an open-work or skeleton support therefor affording the
most complete ventilation, so that the circulation of air through the heater may
effectively cool all portions of the resistant wire. The prevention of overheating
or unequal heating of the wire, avoids distortion thereof and consequent short-
circuiting, and increases the life of the heater. The support is effected by mere
tangential contact with the resistant wire at minute points, so that practically all
portions of the wire are exposed to the air. The support is of such small mass that
no considerable portion of the heat is stored up in the support itself; hence the
heater is immediately effective for radiating heat to its full capacity. With these
advantages the resistant wire is firmly held in place, its support is not affected by
expansion or contraction as it heats or cools, and while it is not restrained against
vibration (in the case of heaters carried on moving vehicles) no such vibration can
disarrange or injure it.
My preferred construction wherein the supporting wire extends through the
minor resistant helix (Figs. 3, and 9 to 13) has the further and novel advantages
that the resistant helix cannot possibly escape or become displaced; even in the
event of the breakage or cutting of the wire, the resistant helix could not fly out
of place or straighten out, but would be restrained by its support from any serious
displacement. This construction also has the advantage that the heater can be
made in any desired shape, not being limited to the form of a compound helix,
since the supporting wire can be extended in any direction that it is desired that
the resistant helix shall take.
I sometimes employ the insulated supporting wire B also as a conducting wire
for leading the electric current to one end of the resistant coil, so that the con-
nectors or binding posts may be arranged both at one end of the heater. This
is shown for example in Fig. 3, where the circuit connections are made with
binding posts, the former of which connects with one end of the resistant
wire A, the opposite end of which connects at d with a metal stripe connecting
with one end of the supporting wire B, the opposite end of which connects with
the second binding post . In other cases I may arrange a separate binding
post at each end of the heater, this being the construction shown in
Fig. 9 (where the binding post at one end is shown at () and in
Figs. 16 and 17 (where the binding post at one end is shown at E, the circuit wire
being connected between nuts e e¹). In Fig. 17 a bracket F is interposed between
the binding post E and the end of the helix A, to receive the end thrust of the
latter.
The supporting wire is itself suitably supported at opposite ends by disks or
heads CC, which are preferably held apart by any suitable means, as by longi-
tudinal rods lettered E E in Figs. 3 to 8, (or by rods lettered D 1) in Figs. 14
to 17, fastened to the heads by nuts dd), or by a perforated tube as shown at D
in Fig. 9, which also serves as an enclosing casing. The ends of the supporting
wire may be screwthreaded and fastened by a nut b (Figs. 14 to 17) or f in
Fio 9

page_text: 9. An electric heater comprising an open resilient helix of resistant wire, and
a support therefor consisting of a helix of stiff wire making only tangential contact
therewith, essentially as described.
10. An electric heater comprising a compound helix of resistant wire, and a
support therefor consisting of a helical wire extended inside the minor helix, the
resistant wire being under tension pressing into tangential contact with said sup-
porting wire, essentially as described with reference to Figs. 3, 4, 7, 8, 9 and 10 of
Sheets 3 and 4.
.
11. An electric heater comprising a supporting wire wound into an open helix,
and a helix of resistant wire wound into a compound helix around said helical
support under distensive tension so as to press partly into the space between suc-
cessive convolutions, essentially as described with reference to Figs. 14, 15 and 16
of Sheet 5.
:
12. An electric heater comprising a supporting wire wound into an open helix,
and an open helix of resistant wire wound into a compound helix within said
helical support under compressive tension so that it expands into the space between
successive convolutions of the support, essentially as described with reference to
Figs. 5 and 6 of Sheet 3, and Figs. 14, 15 and 17 of Sheet 5.
13. An electric heater comprising a supporting helix carrying two compound
helices of resistant wire wound the one exteriorly and the other interiorly of the
support, essentially as described with reference to Figs. 14 and 15 of Sheet 5.
14. An electric heater comprising a supporting helix arranged on a horizontal
axis, and supported at its opposite ends between heads, with a compound helix of
resistant wire supported thereon, the space between said heads being open for
free circulation of air upward across and through said helical support, whereby.
the air is divided thereby and comes into contact with all portions of the resistant
wire, essentially as described with reference to Figs. 3 to 9 and 14 to 17 of
Sheets 3, 4 and 5.
15. An electric heater comprising a horizontally-arranged supporting helix with
opposite end heads connected together at a fixed distance apart in such manner
as to admit of stiffening said helix by putting it under strain between said heads,
and a compound resistant helix carried on said helical support, substantially as
described with reference to Figs. 3 to 9 and Figs. 14 to 17 of Sheets 3, 4 and 5.
16. An enclosing casing. for an electric heater, comprising an open helix of wire
extended between opposite end heads, with or without longitudinal rods extending.
between said heads in tangential contact with said helical casing.
17. An electric heater comprising an open resilient helix of resistant wire, and
a supporting wire extending through it, bent into a flat spiral coil or back and
forth into a zigzag coil, as shown respectively in Figs. 11 and 13 of Sheet 4.
Dated this 11th day of June 1898
J. C. MEWBURN & ELLIS,:
55 and 56, Chancery Lane, London, Chartered Patent Agents.

page_text: smaller and lighter wire is given the requisite stiffness and strength. The
supporting wire by touching the resistant wire at only one point, absorbs less
heat from it, and by being of smaller diameter has less heat absorptive capacity.
In the vertical arrangement referred to, the air entering at bottom is first heated
by the lower major convolutions of resistant wire, and ascending encounters suc-
cessively other convolutions thereof by which it is continually raised in tempera-
ture, until at the top of the heater the air is highly heated and has become
ineffective to cool the uppermost convolutions of resistant wire, so that the latter
are liable to become overheated and burn out. This difficulty is overcome in my
horizontal arrangement of heater wherein the supporting helix becomes a skeleton
frame through which each portion of air in circulating comes in contact with only
two convolutions of heated wire, so that a large volume of air is moderately heated
while effectively cooling the wires, instead of a small volume of air being so highly
heated as to become ineffective for cooling the wires.
A heater for liquids may be constructed of a compound helix according to the
second part of my invention, by enclosing it in an imperforate tube F, as shown
in Fig. 10, the tube being internally coated with enamel or other insulating
material, as shown at j.
In Fig. 18 the helix A may be held against the supporting wires B¹ by a third
insulated wire B².
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. An electric heater comprising a compound helix of resistant wire having an
openwork or skeleton support admitting circulation of air to and from the interior
of the major helix, essentially as described.
2. An electric heater comprising a compound helix of resistant wire having
u support of an, openwork or foraminous tube, formed with grooves or corrugations
for holding the successive convolutions of said helix, essentially as described with
reference to Figs. 1 to 11 of Sheets 1 and 2.
3. An electric heater comprising a compound helix of resistant wire having, an
openwork or skeleton support, and the helix adapted thereto under tension so as
to press into firm contact therewith, essentially as described.
4. An electric heater comprising a compound helix of resistant wire combined
with a support, the helix being compressed against said support so that it exerts
an expansive tendency, essentially as described.
5. An electric heater comprising a compound helix of resistant wire combined
with a tubular insulating casing, said helix enclosed in and supported by said
casing, essentially as described with reference to Figs. 1 to 10 of Sheets 1 and 2.
6. An electric heater comprising an open resilient helix of resistant wire, and
a support therefor consisting of a stiff wire or rod (one or more) extended parallel
therewith and making only tangential contact with the successive convolutions
thereof, whereby the helix is almost wholly exposed to circulation of air within
and around it, essentially as described with reference to Figs. 1 to 18 of Sheets 3,
4 and 5.
7. An electric heater comprising an open resilient helix of resistant wire, and
a support therefor consisting of a stiff wire or rod (one or more) extended within
said helix, of materially smaller diameter than the interior thereof, so as to leave
it internally open for free circulation of air within it, and supporting it by
tangential contact at only a single point in its circumference, essentially as
described with reference to Figs. 3, 7, 9, 10, 11, 12 and 13 of Sheets 3, and 4.
8. An electric heater comprising an open resilient helix of resistant wire, and
a support therefor consisting of a stiff wire or rod extended within said helix,
and said helix confined on said support under tension in such manner that its
5 convolutions are pressed elastically into tangential contact therewith, essentially as
described.