U.S. patent application number 10/569304 was filed with the patent office on 2008-10-02 for hot air heater.
This patent application is currently assigned to BAN-YU CO., LTD. Invention is credited to Takeshi Hirohata, Yoshio Ono.
Application Number | 20080240690 10/569304 |
Document ID | / |
Family ID | 36059979 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080240690 |
Kind Code |
A1 |
Ono; Yoshio ; et
al. |
October 2, 2008 |
Hot Air Heater
Abstract
A hot air heater includes heating wires (3a, 3b) wound around an
insulating fire-resistant support in such a way that currents flow
reversely through the heating wires (3a, 3b) in order to compensate
electromagnetic waves generated from the heating wires (3a, 3b),
thus reducing electromagnetic waves.
Inventors: |
Ono; Yoshio; (Osaka, JP)
; Hirohata; Takeshi; (Osaka, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
BAN-YU CO., LTD
Osaka-shi, Osaka
JP
OSAKA PREFECTURAL GOVERNMENT
Osaka-shi, Osaka
JP
|
Family ID: |
36059979 |
Appl. No.: |
10/569304 |
Filed: |
September 12, 2005 |
PCT Filed: |
September 12, 2005 |
PCT NO: |
PCT/JP2005/016715 |
371 Date: |
June 12, 2008 |
Current U.S.
Class: |
392/384 |
Current CPC
Class: |
A45D 20/10 20130101;
H05B 3/16 20130101; A45D 20/30 20130101; F24H 3/0423 20130101 |
Class at
Publication: |
392/384 |
International
Class: |
F24H 3/04 20060101
F24H003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2004 |
JP |
2004-267008 |
Apr 28, 2005 |
JP |
2005-130877 |
Claims
1. A hot air heater comprising heating wires wound around an
insulating fire-resistant substrate, wherein a plurality of heating
wires that are connected in parallel or series between an input
line and an output line of an electric power supply line are wound
around the insulating fire-resistant substrate in such a manner
that current runs in opposite directions through the heating wires
so as to cancel out electromagnetic waves generated from the
heating wires.
2. The hot air heater according to claim 1, wherein a first heating
wire and a second heating wire are connected in parallel between an
input line and an output line of an electric power supply line and
are alternatively wound around the insulating fire-resistant
substrate in the same direction such that current runs in opposite
directions through the first and second heating wires so as to
cancel out electromagnetic waves generated from the heating wires,
and adjacent loops of the first and second heating wires have the
same or substantially similar winding diameters.
3. The hot air heater according to claim 1, wherein a ceramic
honeycomb structure is disposed downstream of air heated by the
heating wires.
4. The hot air heater according to claim 3, wherein the ceramic
honeycomb structure is furnished with a coating containing carbon
powder, and the coated ceramic honeycomb structure has an
emissivity of 0.8 or greater over the entire infrared wavelength
region.
5. The hot air heater according to claim 4, wherein the coated
ceramic honeycomb structure has an emissivity of 0.9 or greater
over the entire infrared wavelength region.
6. The hot air heater according to claim 4, wherein the coating
containing carbon powder is created by impregnation.
7. The hot air heater according to claim 3, wherein the ceramic
honeycomb structure is disposed in the vicinity of the heating
wires.
8. The hot air heater according to claim 3, wherein the ceramic
honeycomb structure is coated with glassy carbon, and the glassy
carbon coating is formed by impregnating the ceramic honeycomb
structure with resin containing glassy carbon and calcining the
impregnated ceramic honeycomb structure in a non-oxidizing
atmosphere.
9. The hot air heater according to claim 2, wherein a ceramic
honeycomb structure is disposed downstream of air heated by the
heating wires.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to hot air heaters, such as
hair driers, desktop hot air heaters, etc.
BACKGROUND OF THE INVENTION
[0002] Hot air heaters having a heating element such as nichrome
wire, wound around an insulating, fire-resistant substrate such as
a mica plate, are generally known.
[0003] Also known are hot air heaters in which a carbon molding is
additionally attached to the hot air nozzle to thereby add
far-infrared ray effects produced by the carbon molding (e.g.,
Japanese Utility Model Registration Publication No. 3011964).
[0004] Electromagnetic waves are generally classified into radio
waves, infrared rays, visible light, ultraviolet rays, X-rays and
.gamma. rays, in order from the longest wavelength to the shortest
(i.e., from the lowest frequency to the highest), and the shorter
the wavelength, the larger the photon energy. When visible light or
ultraviolet rays strike a substance, such electromagnetic waves
cause a chemical reaction and deteriorate the substance. Intense
ultraviolet rays, X-rays and .gamma.-rays adversely affect the
living body. Electromagnetic waves with wavelengths longer than
infrared rays generally do not cause chemical reactions, but at
high intensities, they heat substances. It has not been clarified
whether electromagnetic waves with longer wavelengths than infrared
rays (radio waves) influence the human body, but studies have been
made recently in many countries on the effects of some types of
radio waves on the human body. Some countries, for example, Sweden,
restrict electric fields to a maximum of 0.025 kV/m and magnetic
fields to a maximum of 2.5 mG in the case of radio waves with
wavelengths of 2 to 2000 Hz and at a distance of 50 cm from the
human body (SWEDISH BOARD FOR TECHNICAL ACCREDITATION GUIDELINE:
MPR2). Conventional hair driers are said to generate a magnetic
field of about 70 mG at a distance of 50 cm. Further, it has been
reported that electromagnetic waves have caused malfunctions in
electronic devices such as semiconductors, pacemakers, etc.
[0005] Hot air heaters having a carbon molding attached to the hot
air nozzle are disadvantageous in that carbon moldings are
expensive and increase the price of the heaters.
DISCLOSURE OF THE INVENTION
[0006] An object of the invention is to provide a hot air heater
capable of reducing the emission of a certain type of
electromagnetic wave.
[0007] Another object of the invention is to provide a hot air
heater with enhanced infrared radiation efficiency at low cost.
[0008] To achieve the first object, the hot air heater of the
invention comprises an insulating fire-resistant substrate and
heating wires wound therearound, wherein a plurality of wires that
are connected in parallel or series between an input line and an
output line of an electric power supply line are wound around the
insulating fire-resistant substrate in such a manner that the
current runs in opposite directions through the heating wires so
that the electromagnetic waves generated from the heating wires
cancel each other out.
[0009] The hot air heater of the invention may be configured in
such a manner that a first heating wire and a second heating wire
are connected in parallel between the input line and the output
line of the electric power supply line and are alternatively wound
around the insulating fire-resistant substrate in the same
direction and wherein the adjacent loops of first and second
heating wires have the same or substantially similar winding
diameters, in such a manner that the current runs in opposite
directions through the first and second heating wires so that the
electromagnetic waves generated from the heating wires cancel each
other out.
[0010] To achieve the second object, the hot air heater of the
invention is characterized by comprising a ceramic honeycomb
structure disposed downstream of the heating wire.
[0011] Preferably, the ceramic honeycomb structure has a coating
containing carbon powder and the coated ceramic honeycomb structure
has an emissivity of 0.8 or more over the entire infrared
wavelength region.
[0012] More preferably, the coated ceramic honeycomb structure has
an emissivity of 0.9 or more over the entire infrared wavelength
region.
[0013] Preferably, the coating containing carbon powder is an
impregnation coating.
[0014] Preferably, the ceramic honeycomb structure is disposed in
the vicinity of the heating wire.
[0015] Preferably, the ceramic honeycomb structure is coated with a
glassy carbon. The glassy carbon coating is preferably formed by
impregnating a ceramic honeycomb structure with a glassy carbon
precursor resin, followed by calcination under a non-oxidizing
atmosphere.
[0016] According to the hot air heater of the invention,
electromagnetic waves are weakened by causing the current to run in
opposite directions through adjacent heating wires.
[0017] Further, the infrared radiation efficiency can be enhanced
by disposing a ceramic honeycomb structure downstream of the
heating wire.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a cut-away view of a first embodiment of the hot
air heater of the invention.
[0019] FIG. 2 is a conceptual diagram illustrating a method of
winding the heating wires according to the first embodiment.
[0020] FIG. 3 is a conceptual diagram illustrating a method of
winding the heating wires according to the second embodiment.
[0021] FIG. 4 is a partial broken isometric projection illustrating
a method of winding the heating wire according to the third
embodiment.
[0022] FIG. 5 is a schematic diagram illustrating a modification of
the third embodiment.
[0023] FIG. 6 is a schematic diagram illustrating a method of
winding the heating wire according to the forth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Embodiments of a hot air heater according to the invention
are described below with reference to FIG. 1 to FIG. 6. The
embodiments described below illustrate examples of hair driers.
Like numerals represent like elements throughout the drawings.
[0025] A first embodiment of a hot air dryer according to the
invention is described first. As shown in FIG. 1, the hot air dryer
1 comprises an insulating fire-resistant supporter 2 that is wound
with heating wires 3. The heating wires 3 are wound to form a coil
along the direction in which hot air flows from the hot air dryer 1
or in the opposite direction.
[0026] The insulating fire-resistant supporter 2 may be made of a
mica plate, a ceramic plate, or the like. The insulating
fire-resistant supporter 2 shown in FIG. 1 is made of a
crisscrossed plate-like body. The heating wires 3 may be composed
of a coiled nichrome wire or the like. In FIG. 1, the numeral 4
represents a fan motor, and the numeral 5 represents a fan.
[0027] The heating wires 3 comprise, as schematically shown in FIG.
2, two wires, a first heating wire 3a and a second heating wire 3b
which are connected in parallel between an input line 6 and an
output line 7 of a power supply line. Note that the heating wire is
shown rather than in a coil shape but by a mere solid line for the
sake of convenience.
[0028] The first heating wire 3a has its input line 6 side wound
from the rear end of the insulating fire-resistant supporter 2
toward the front end thereof, and connected to the output line 7 at
the front end of the insulating fire-resistant supporter.
[0029] In contrast, the second heating wire 3b is connected with
the input line at the front end of the insulating fire-resistant
supporter, wound from the front end toward the rear end, and
connected to the output line 7 at the rear end of the insulating
fire-resistant supporter 2.
[0030] The first heating wire 3a and the second heating wire 3b are
wound at a desired interval so that they are alternately arranged.
Both the heating wires 3a, 3b are wound in the same direction. In
addition, as shown in FIG. 1, the adjacent first heating wire 3a
and the second heating wire 3b are wound around the insulating
fire-resistant supporter 2 with the same diameter.
[0031] Current flowing in the adjacent first heating wire 3a and
the second heating wire 3b as described above is in opposite
directions to each other. Note that the power supply of the hot air
heater is generally an alternating-current power supply. In this
case, the current flowing in adjacent heating wires has opposite
phases, and the current flowing in a given period of time is in
opposite directions.
[0032] When the current flowing in the adjacent first heating wire
3a is in the opposite direction to that of the second heating wire
3b, magnetic lines of force and electric lines of force are
cancelled out. This phenomenon is caused by phase inversion of the
electric and magnetic fields.
[0033] Next, the hot air heater according to the second embodiment
of the invention is explained with reference to the schematic
diagram shown in FIG. 3.
[0034] As in the first embodiment, the hot air heater of the second
embodiment comprises a first heating wire 3a and a second electric
heating wire 3b connected in parallel between an input line 6 and
an output line 7.
[0035] According to the second embodiment, the first heating wire
3a and the second heating wire 3b are both wound around insulating
fire-resistant substrates (not shown), the second heating wire 3b
being wound within the windings of the first heating wire 3a. The
first heating wire 3a and the second heating wire 3b are wound in
opposite directions. The first heating wire 3a and the second
heating wire 3b are wound parallel to each other along the hot air
stream direction, forming a concentric circle when viewed from the
front.
[0036] The first heating wire 3a and the second heating wire 3b are
each wound around an insulating fire-resistant substrate (not
shown) at regular intervals, preferably, as close as possible to
one another.
[0037] In the second embodiment, the first heating wire 3a and the
second heating wire 3b may be connected to the input line 6 (or
output line 7) either at the front-end or at the rear-end of the
insulating fire-resistant substrates.
[0038] In the second embodiment having the above structure, as in
the first embodiment, the directions of the current running through
the first heating wire 3a and the second heating wire 3b are
opposite each other, thus enabling reduction of the electromagnetic
waves.
[0039] Although the second embodiment has been described as using
two heating wires, one skilled in the art will understand that four
or more even-numbered heating wires may be employed instead. The
number of heating wires can also be three or more odd numbers, and
in such a case, by applying resistance to designated heating wires
and thereby limiting the amount of current, or by other means, the
electromagnetic waves generated from the heating wires can be made
to cancel each other out.
[0040] FIG. 4 is a partially broken perspective view illustrating a
third embodiment. In the third embodiment, a single heating wire 3
is connected in series between an input line 6 and an output line
7. The heating wire 3 is wound into a concentric cylinder-like
form. The heating wire 3 is wound around the inner insulating
fire-resistant substrate 2a, folded back at the end, and then wound
in the opposite direction around the outer insulating
fire-resistant substrate 2b.
[0041] As schematically shown in FIG. 5, a heating wire 3 on the
inner and outer sides may be cross-wound to provide parallel
connections, using the insulating fire-resistant substrate 2b as an
insulating layer. Therefore, the condition that "the current runs
in opposite directions" herein does not necessarily mean that all
of the directional components of the current are opposed each
other, but means only that some of them are opposite. For example,
in FIG. 5, the directional components (3ax, 3ay) of the current in
the inner heating wire 3a and the directional components (3bx, 3by)
of the current in the outer heating wire 3b have opposite
components 3ay and 3by, whereby a weakening of the electromagnetic
waves is achievable.
[0042] FIG. 6 is a schematic diagram illustrating the fourth
embodiment. In the fourth embodiment, a heating wire 3a wound in
the first winding direction and a heating wire 3b wound in the
second winding direction, which is opposite to the first winding
direction, are positioned adjacently and supported by an insulating
fire-resistant substrate 2. In the illustrated example, the heating
wire 3a and the heating wire 3b are composed of one heating wire
and connected in series between an input line 6 and an output line
7, and the winding direction of such a heating wire is reversed
between the heating wire 3a and the heating wire 3b. Although not
illustrated, the heating wires 3a and 3b may be connected in
parallel.
[0043] Further, as shown in FIG. 1, the hot-air heater of the
present invention may have a cylindrical ceramic honeycomb
structure mounted in a casing 10. The ceramic honeycomb structure 9
is disposed downstream of hot air stream from the heating wires 3
and has a multiplicity of hexagonal apertures formed along the
direction of the air stream.
[0044] The ceramic honeycomb structure 9 can be made of SiC,
SiO.sub.2, B.sub.4C, AlN, Al.sub.2O.sub.3, MgO and like known
ceramic materials; in light of the production costs, cordilite can
be advantageously used.
[0045] It is generally known that heated materials emit radiant
energy proportional to the fourth root of the absolute temperature.
In such a case, the radiant energy varies according to surface
state. The higher the emissivity, the greater the radiant energy
will be. The radiant energy approaches a maximum the closer the
emissivity of a heating element is to 1, because an ideal blackbody
has an emissivity of 1.
[0046] The ceramic honeycomb structure 9, thus constructed with
such an above material, usually has an infrared radiation
emissivity of 0.8 to 0.98. This, however, may be reduced to 0.7 or
lower depending of the wavelength of infrared radiation.
[0047] Carbon powder has a high emissivity over the entire
wavelength range. Taking advantage of this property, a coating
containing carbon powder can be applied to the ceramic honeycomb
structure 9 to give an emissivity of preferably 0.8 or higher, and
more preferably 0.9 or higher, over the entire infrared wavelength
range.
[0048] Such a coating containing carbon powder can be prepared by
mixing and dispersing carbon powder in a resin binder, applying the
obtained mixture to the ceramic honeycomb structure 9 using a
sprayer, brush, etc., or by impregnating the structure with the
mixture as in a dipping method, etc., and by subsequently drying
the structure with the applied mixture coated thereon. Usable
carbon powders include noncrystalline substances such as glassy
carbon in addition to crystalline substances such as black-lead.
The coating can also be applied to only one side, e.g. the hot air
outlet side, of the ceramic honeycomb structure 9.
[0049] Stated more specifically, the coating can be prepared by,
for example, mixing with stirring 5 to 30 parts by weight of carbon
powder and 100 parts by weight of a room temperature-setting
inorganic/organic hybrid binder (e.g. a phosphate- and
polyhydroxybenzene-based binder: EMULSION TECHNOLOGY CO., LTD.),
applying the obtained mixture to the structure or dipping the
structure in the mixture, and air drying.
[0050] The average particle diameter of the carbon powder is
preferably approximately 1 to 50 .mu.m, more preferably
approximately 1 to 30 .mu.m, and most preferably 1 to 5 .mu.m. The
smaller are the particles, the more homogeneously the coating can
be applied to or impregnated on the ceramic surface.
[0051] Alternatively, the infrared radiant efficiency can be
enhanced without using carbon powder in the coating. A glassy
carbon coating can be formed by, for example, impregnating the
ceramic honeycomb structure with a glassy carbon precursor resin,
followed by calcining under a non-oxidizing atmosphere at a
predetermined temperature (approximately 800.degree. C. to
approximately 2000.degree. C.) for a certain necessary period of
time. A glassy carbon coating may have a thickness of 5 to 100
.mu.m.
[0052] The glassy carbon coating, when carbonized, will have an
enhanced infrared radiation efficiency, and should exhibit an
average emissivity of 0.95 or higher over the entire infrared
wavelength range. For example, such a glassy carbon coating has a
radiant emittance of 1.227 kW/m.sup.2 at .epsilon.=0.95 at
120.degree. C. at the hot air outlet of the hot air heater (1.292
kW/m.sup.2 for a blackbody of .epsilon.=1 over the entire infrared
wavelength range beyond a wavelength of 0.7 .mu.m).
[0053] Preferable examples of such a ceramic honeycomb structure 9
are those made of porous materials for better impregnation. Pore
diameters are preferably approximately 1 to 50 .mu.m. When the pore
diameter of the porous material is smaller than 1 .mu.m, carbon
powder tend to be lumpy. When the pore diameter is greater than 50
.mu.m, inhomogeneous coating tends to result.
[0054] The ceramic honeycomb structure 9 is positioned downstream
of the heating wire 3. In view of an infrared radiant efficiency,
it is preferably disposed in the vicinity of the heating wire 3,
e.g. preferably about 0 to 2 cm from the heating wire 3. When the
heating wire 3 is disposed to wind, for example, cylindrically, the
ceramic honeycomb structure 9 can be disposed in the cylindrical
space formed by the wound heating wire 3.
[0055] Measurements were made of the electromagnetic waves of a hot
air dryer having the heating wire configuration shown in FIG. 6
(Example 1) and of a commercially available conventional hot air
dryer wherein all the heating wires are coiled in the same
direction and all electric current flows in the same direction
(Comparative Example 1). The results are shown in Table 1.
[0056] The test conditions were as follows:
Heating wire: 0.3 mm .phi., nichrome wire Power consumption: 1200 W
Power supply: AC 100 V, 60 Hz Measuring instrument:
[0057] Electric field: ME3 electromagnetic wave measuring
instrument produced by Marburg Technic (Germany)
[0058] Magnetic field: EMS tester TES1390 produced by TES
Electrical Electronic Corp.
Measurement positions: (A)-(C)
[0059] (A): about 5 cm in the blowing direction from the hot air
outlet
[0060] (B) about 5 cm from the casing surface over the position of
the heating wire
[0061] (C) about 5 cm from the casing surface over the position of
the fan motor
TABLE-US-00001 TABLE 1 Comparative Example 1 Example 1 Magnetic
field 1.5 mG 22.0 mG (measurement position: A) Electric field 30
V/m 90 V/m (measurement position: A) Magnetic field 4.0 mG 30 mG
(measurement position: B) Electric field 80 V/m 100 V/m
(measurement position: B) Magnetic field 60.0 mG 60 mG (measurement
position: C) Electric field 100 V/m 110 V/m (measurement position:
C)
[0062] The results in Table 1 show that in Example 1, the magnetic
field and electric field decreased sharply at the measurement
position (A).
[0063] Since, in a hair dryer or the like, the hot air outlet is
closest to the human body, it is important that the electromagnetic
waves at the measurement position (A) be small. Although the
measurements in Table 1 were carried out without grounding, the
electric field will be further decreased if measurements are
carried out with the hot air heater grounded.
[0064] Next, comparative experiments with ceramic honeycomb
structures were conducted to compare those having a carbon powder
coating with those having no carbon powder coating in terms of
infrared emissivity.
EXAMPLE A OF A CERAMIC HONEYCOMB STRUCTURE
[0065] Graphite powder (1 g) (average particle diameter: 12 .mu.m)
was mixed into a resol-type type phenol resin methanol solution (10
g) (resin content: 50 wt %). A ceramic honeycomb structure
(diameter: 3 cm) comprising cordierite was coated with this mixture
by impregnation and dried. The resulting product had an infrared
emissivity of 0.96.
EXAMPLE B OF A CERAMIC HONEYCOMB STRUCTURE
[0066] A solution of a resol-type phenol resin in methanol was
adjusted to a resin solid content of 30 wt %, giving a glassy
carbon precursor resin. A mullite honeycomb structure was
impregnated with the glassy carbon precursor resin, dried, and then
cured at 150.degree. C. After this was calcined in nitrogen gas
from room temperature to 1000.degree. C. over 12 hours, the
temperature was lowered to room temperature over 8 hours, thereby
coating the mullite honeycomb structure with glassy carbon. The
resulting mullite honeycomb structure coated with glassy carbon had
an infrared emissivity of 0.95.
EXAMPLE C OF A CERAMIC HONEYCOMB STRUCTURE
[0067] A solution of resorcin (1 mol), terephthalaldehyde (1.5
mol), and curing accelerator (p-toluenesulfonic acid) (0.01 mol) in
ethanol was adjusted to a resin solid content of 30 wt %, giving a
glassy carbon precursor resin. A mullite honeycomb structure was
impregnated with the glassy carbon precursor resin, dried, and then
left at room temperature for 5 hours to be cured. After this was
calcined in nitrogen gas from room temperature to 1000.degree. C.
over 12 hours, the temperature was lowered to room temperature over
8 hours, thereby coating the mullite honeycomb structure with
glassy carbon. The resulting mullite honeycomb structure coated
with glassy carbon had an infrared emissivity of 0.95.
[0068] In contrast, uncoated ceramic honeycomb structures as
comparative examples of ceramic honeycomb structures had an
infrared emissivity of 0.87 to 0.89.
[0069] The measurements of infrared emissivity were carried out
using an IT-54ON radiation thermometer (product of Horiba, Ltd.) in
the following manner: (1) A black body spray was applied to part of
the object to be measured, and the object was then heated. (2) The
part to which the black body spray had been applied was subjected
to measurement using an IT-54ON radiation thermometer with the
emissivity of the black body spray being the emissivity set value.
(3) A part to which the black body spray had not been applied was
subjected to measurement, adjusting the emissivity set value such
that the measurement value was equal to the already measured
temperature of the part to which the black body spray had been
applied. (4) The emissivity obtained by adjustment was taken as the
emissivity of the object.
* * * * *