Improvements in Electric Heaters.
Year: 1892

page_text: Date of Application, 28th Sept., 1892-Accepted, 29th Oct., 1892
COMPLETE SPECIFICATION.
Improvements in Electric Heaters.
I, THOMAS AHEARN, of 70 Sparks Street, in the City of Ottawa, in the County
of Carleton, in the Province of Ontario, in the Dominion of Canada, Electriciau,
do hereby declare the nature of my invention for "IMPROVEMENTS IN ELECTRIC
HEATERS," and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
My invention, which will be hereinafter fully set forth and claimed, relates to
appliances for obtaining and utilizing heat from an electric current.
Fig. 1 is an elevation of my improved heater.
Fig. 2 is a horizontal section of the same on line a Fig. 1.
Fig. 3 is a vertical section of the same on line y y Fig. 2, showing the inner tube
in elevation, a part being broken out to show the section.
Fig. 4 is a top view of the same.
Fig. 5 shows a modification of the core.
Fig. 6 is a vertical section of a modification, having an additional inner and outer
casing.
Figs. 7 and 8 are top view and horizontal section of another modification having
additional radiating or air tubes, and
Fig. 9 is a vertical section of another modification.
A is a tube of a (preferably) good heat conducting material, such as iron, shown
of circular cross section in the drawing, but which may be square or polygonal,
plain or corrugated or of any other desired cross section. Upon the outer surface
of this are laid longitudinally and at short distances apart, strips of asbestos B and
upon these again strips of mica B'; these latter being so called non-combustible
materials and non-conductors of electricity. Upon these strips is wound a coil C of
wire or strips of refractory metal of low electric conductivity, such as iron, German
silver, and the like, the terminals of which are connected with leads c and c' and
each of these is passed through an insulator, C¹, which is afterwards secured in the
outer metallic casing. This resistance coil is preferably wound in opposite directions
to check induction. D is the outer casing consisting of a metallic tube having the
same length as the inner tube A and large enough to allow a clear annular space
between its inner surface and that of the cored coil and being of such a shape in
cross section as to correspond with the outline of the latter. The annular space thus
formed is packed with powdered fireclay, whiting or other powdered non-conducting
material, F. An asbestos packing ring E¹ is placed at each end, covering the space
so filled and the edges of the two tubes and these rings are held in place by a cover E
at each end, provided with lugs e through which pass bolts E". The lower cover
is provided with insulator feet G, so as to raise it sufficiently off the floor to allow
frec access to a current of air to enter into and pass through the inner tube.
This construction admits of numerous modifications of which a few are shown in
Figs. 5 6 7 8 and 9.
Instead of a metallic tube A, provided with insulating strips B and B¹, a non-
metallic non-combustible tube, such as fire proof tile pipe, A', Fig. 5, may be
employed. In these, a spiral groove a¹ is cut, to receive the resistance coil C, which
is wound direct upon the material in said groove and the groove afterwards filled
flush with non-combustible powdered or plastic material.
To condense and accelerate the air current passing through the inner tube A,
another light tube A', Fig. 6, closed at the bottom and allowing an annular space
between the two, may be inserted. An air current may also be caused to pass along
the surface of the outer tube D by enclosing it in another light casing All open at
the bottom. In this construction direct radiating will not be obtained.
11

page_text: The heating surface of the tubes A and D may be increased by corrugations and
projections and may also be augmented by additional radiating or air tubes A"",
inserted or formed between the inner and outer tubes A and D, open at top and
bottom, as shown in Figs. 7 and 8.
having a
In Fig. 9 one of the intermediate coils is provided with a lead
resistance coil c¹¹ inserted and connected with the main lead by a switch, c, so that
a portion of the coils may be "cut out" and the heating capacity thus reduced at
will. This may be done with a number of the coils.
In operation the electric current heats the coil C, which is insulated from the
metallic casings A and D by the asbestos and mica (or asbestos alone) on one side
and the powdered material F on the other, while the latter conducts the heat
generated to the encasing tubes, or principally to one or other of them if so desired.
whence it is taken up by the current of air by radiation.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is:
1. An electric heater composed of a core consisting of a coil of wire or strip of
refractory metal of low electric conducting power provided with leads and wound
upon an insulated tube, said core placed in another tube large enough to form an
annular space which is filled with powdered non-combustible non-electric conducting
material, substantially as set forth.
2. In an electric heater, the combination of a tube A, strips of asbestos B laid
upon said tube longitudinally, strips of mica B laid upon said asbestos strips, a coil
of wire or strip C of refractory metal of low electric conductive power wound upon
said strips and its terminals connected with leads, an outer tube D enclosing said
coil and leaving an annular space, a filling of powdered non-combustible non-electric
conducting material in said annular space, insulating packing rings E closing the
ends of said annular space, covers E having lugs e upon said packing rings and
bolts E passing through said lugs and holding said covers together, substantially as
set forth.
3. In an electric heater, the combination of a tube A, open at the ends, strips of
non-combustible non-electric conducting material laid longitudinally on said tube,
and a coil of wire or strip C of refractory metal of low electric conductive power,
substantially as set forth.
4. In an electric heater, the combination of a tubular core A insulated with strips
of asbestos B and mica B' carrying a coil C of wire or strip of refractory metal of
low electric conductive power, an outer tube D enclosing said core and forming an
annular space around said core and containing insulators through which pass the
leads connecting the terminals of said coil, a powdered non-electric conducting
material filling F in said annular space, insulated covers E closing said annular
space and held in place by bolts E", insulating feet G on one of said covers, an
inner tube A¹ closed at the bottom and a casing A" around the external tube D
open at the bottom and forming an annular space around the same, substantially as
set forth.
Dated this 16th day of September A.D. 1892.
THOMAS AHEARN,
Per A. Harvey,
His Attorney.