Abstrict
An electric heater with a sensor for preventing no-water heating
includes a heating plate and/or a metal plate fixed on the heating
plate, a heating film electro-plated on a lower surface of the heating
plate, and a water level probe, or a sensing electrode, or a water
level sensor and a temperature fuse fixed with the heating plate.
The water level probe, the sensing electrode or the water level
sensor produces alteration of electric potential in case of the
water level becoming very low, triggering a switch of an A/D amplifying
circuit automatically cutting off power of the heating film.
Claims
What is claimed is:
1. An electric heater with a sensor for preventing no-water heating
comprising: a heating plate provided with a vertical hole, having
a heating film electroplated on a lower surface and two silver terminals
fixed with said heating film for connecting with wires; a water
level probe fixed in said vertical hole of said heating plate for
detecting water level of the water stored in a water tank on said
heating plate, producing alteration of electric potential in case
of sensing a very low water level, wherein said alteration of electric
potential is fed to a control circuit, said control circuit then
operates to automatically cut power off said electric heating film.
2. The electric heater with a sensor for preventing no-water heating
as claimed in claim 1, wherein a metal plate is additionally provided
on said heating plate.
3. An electric heater with a sensor for preventing no-water heating
comprising: a heating plate having a heating film electro-plated
on a lower surface thereof and two silver terminals fixed with said
heating film for connecting with wires; a sensing electrode is provided
on the lower surface of said heating plate for sensing water level
of the water stored in a water tank on said heating plate, producing
alteration of electric potential in case of sensing a very low water
level wherein, said alteration of electric potential is fed to a
control circuit, said control circuit then operates to automatically
cut power off said electric heating film.
4. The electric heater with a sensor for preventing no-water heating
as claimed in claim 3, wherein a metal plate is additionally provided
on said heating plate.
5. An electric heater with a sensor for preventing no-water heating
comprising: a heating plate having a heating film electro-plated
on a lower surface thereof and two silver terminals fixed with said
heating film for connecting with wires, wherein the heating plate
has a recess on the lower surface; a water level sensor with and
a temperature fuse provided in the recess on the lower surface of
said heating plate for sensing water level of the water stored in
a water tank on said heating plate, producing alteration of electric
potential in case of sensing a very low water level, wherein said
alteration of electric potential is fed to a control circuit, said
control circuit then operates to automatically cut power off said
electric, heating film.
6. The electric heater with a sensor for preventing no-water heating
as claimed in claim 5, wherein a metal plate is additionally provided
on said heating plate.
7. The electric heater with a sensor for preventing no-water heating
as claimed in claim 1, wherein said heating plate is cylindrical.
8. The electric heater with a sensor for preventing no-water heating
as claimed in claim 1, wherein said heating plate has a recess.
9. The electric heater with a sensor for preventing no-water heating
as claimed in claim 1, said heating plate has a projection.
10. The electric heater with a sensor for preventing no-water heating
as claimed in claim 1, wherein said control circuit includes an
A/D amplifying circuit, which magnifies signals coming from said
water level probe; and then sends the magnified signals to a switch,
said switch automatically cuts off the power of said heating film
when receiving the magnified signals.
Description FIELD OF THE INVENTION
This invention relates to an electric heater with a sensor for
preventing no-water heating, particularly to one provided with a
water level probe, a sensing electrode for detecting the water level
stored in a water tank on a heater so as to automatically cut off
power of an electric heating film, enhancing safety in use of an
electric heating appliance.
BACKGROUND OF THE INVENTION
An electric oven disclosed in a Taiwan patent application of publication
number 301523 includes a heater made of micro-crystal plane glass
coated with a heating film on a lower surface of the glass for producing
heat. But it has a drawback of possible cracking by external force,
leading to water or electricity leakage and subsequent danger to
the user.
Another Taiwan patent application of publication number 319373
entitled "Water heater provided with a heating film" includes
a heating chamber made of insulating material, and a heating film
provided in the heating chamber, and the insulating material is
made of micro-crystal glass, which has the same problem and drawback
as the case of No. 301523.
Another Taiwan patent application of publication number 509453
entitled "Electric heating disc" includes a heat-transmitting
disc, a heating film member, heat-insulating cotton, and a frame
plate. The heating film member produces heat to be transmitted to
the heat-transmitting disc, and is made of an electric heating tube
or piece, with the heat-transmitting disc indirectly heated up,
this kind of heating disc has inferior heat efficiency.
Another Taiwan patent application of publication number 427500
entitled "Heating plate of an electric heater" includes
a heating plate made of porcelain, glass and steel and coated with
enamel, and a tubular or plate heater is placed in the heating plate,
which has the problem of inferior heat efficiency.
SUMMARY OF THE INVENTION
The objective of the invention is to offer an electric heater with
a sensor for preventing no-water heating, by means of automatic
cutting off power of the electric heating film with provision of
a water level sensor, so as to enhance the safety in using an electric
heating appliance.
The invention has the following features.
1. An electric heater with a sensor for preventing no-water heating
has a heating plate with its lower surface electro-plated with an
electric heating film for producing heat electrically, and the heat
is transmitted to and by the heating plate to obtain high heating
efficiency.
2. An electric heater with a sensor for preventing no-water heating
has a metal plate fixed on the heating plate for strengthening the
upper surface of the heating plate.
3. An electric heater with sensor for preventing no-water heating
has a water-level probe or a sensing electrode provided on a proper
location of the heating plate and extending upward or downward the
heating plate to directly detect the water level in a water tank.
An electric heater with a sensor for preventing no-water heating
has a temperature sensor and a temperature fuse to perform detection
of the water level and controlling of the temperature.
BRIEF DESCRIPTION OF DRAWINGS
This invention will be better understood by referring to the accompanying
drawings, wherein:
FIG. 1 is a cross-sectional view of a first embodiment of an electric
heater in the present invention;
FIG. 2 is a cross-sectional view of a second embodiment of an electric
heater in the present invention;
FIG. 3 is a cross-sectional view of a third embodiment of an electric
heater in the present invention;
FIG. 4 is a cross-sectional view of a fourth embodiment of an electric
heater in the present invention;
FIG. 5 is a cross-sectional view of a fifth embodiment of an electric
heater in the present invention;
FIG. 6 is a cross-sectional view of a sixth embodiment of an electric
heater in the present invention;
FIG. 7 is a cross-sectional view of an electric heater fixed in
one way in the present invention;
FIG. 8 is a cross-sectional view of an electric heater fixed in
another way in the present invention;
FIG. 9 is a cross-sectional view of a seventh embodiment of an
electric heater in the present invention; and,
FIG. 10 is a diagram of a control circuit of the electric heater
in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of an electric heater with a sensor for preventing
no-water heating, as shown in FIG. 1, includes a heating plate 1,
an electric heating film 2, and a water level probe 3.
The heating plate 1 is preferably made of micro-crystal plane glass,
porcelain, quartz, or other electrically insulating material, having
a vertical hole 10, and the electric heating film 2 is electroplated
on a lower surface of the heating plate 1, which has at last two
silver terminals 20 to connect with wires 21. Then, the electric
heating film 2 produces heat by electricity, and the heat generated
is transmitted to the heating plate 1, so the electric heater can
be applied to various heating devices, such as coffee pots, a drinking
water dispenser, an electric water heater, etc. Further the water
level probe 3 is fitted in the vertical hole 10, or more than one
probes 3 may be used if needed. The function of the water level
probe 3 is to produce alternation of electric potential to send
a signal of that condition to an A/D amplifying circuit 5 as shown
in FIG. 10, when the water level in a water tank 7 moves slowly
down from the line A (showing a safe water level and the sensing
electrode still no triggering alteration of electric potential)
in FIG. 8 and reaches the line B, that is the level of little or
almost no water, with the water level probe 3 affected by the highly
heated heating plate 1, as shown in FIGS. 8, 9 and 10. Then the
A/D amplifying circuit sends a signal to a switch 6 to cut off the
power of electric heating film 2 automatically, thus preventing
no-water heating of the heating film 2, and enhancing safety in
using the heater.
Next. FIG. 2 shows a second embodiment of an electric heater with
a sensor for preventing no-water heating in the present invention,
only differing from the first embodiment in that a metal plate 4
is additionally provided on the heating plate 1. The metal plate
4 is made of steel, iron, aluminum, aluminum alloy, or stainless
steel, etc. having high heat transmitting coefficient. Preferably,
metal plate 4 is made of steel which also has good shock-enduring
feature.
Further, FIG. 3 shows a third embodiment of the invention, different
from the first embodiment in that a sensing electrode 3A is attached
on a lower surface of the heating plate 1. As shown in FIGS. 8,
9 and 10, when the water level is at the line A, a normal water
level, the sensing electrode 3A does not trigger to send an output
of alteration of electric potential. But when the water level moves
down to the line B, an abnormal water level of little water, the
sensing electrode 3A may sense alteration of electric potential
to feed a signal to the control A/D amplifying circuit 5, which
then sends a signal to the switch 6, which then cuts off the power
of heating film 2 automatically, preventing the heating film 2 from
heating under no-water condition, and enhancing safety of the heater.
Further, FIG. 4 shows a fourth embodiment of the invention, modified
from the third embodiment, only differing from the third one in
that a metal plate 4 is additionally provided on the heating plate
1. Metal plate 4 is made of steel, iron, aluminum, aluminum alloy,
or stainless steel of high heat transmitting coefficient. Preferably,
metal plate 4 is made of steel which also has shock-endurance.
FIG. 5 shows a fifth embodiment of the invention, having the same
structure as the first one except that the heating plate 1 has a
projection or a recess 10A, where a water level sensor 3C and a
temperature fuse 3B are received, functioning as the same as the
sensing electrode 3A to detect the water level, to let the heating
film 2 automatically cut off power.
Further, FIG. 6 shows a sixth embodiment of the invention, modified
from the fifth embodiment, and differing in that a metal plat 4
is additionally provided on the heating plate 1, which is made of
steel, iron, aluminum, aluminum alloy, or stainless steel of high
heat transmitting coefficient. Preferably, metal plate 4 is made
of steel which also has shock-endurance.
FIG. 9 shows a seventh embodiment of the invention, possible to
be applied to all the embodiments described above. The seventh one
includes a heating cylinder 1A, and a heating film 2 electroplated
on an intermediate portion of the heating cylinder 1A, two silver
terminals 2 attached with the heating film 2 to be connected with
wires 21, and a water level probe 3 or an sensing electrode 3A is
fixed with the heating cylinder 1A to detect the water level to
let the heating film 2 automatically cut off power in case of little
or no water remained in a water tank on the heating plate, so as
to enhance the safety in using the heater.
In short, the electric heater with a sensor for preventing no-water
heating according to the invention has a heating film directly provided
on the heating plate to increase heating efficiency, and a water
level probe, a sensing electrode or a water level sensor with a
temperature fuse to let the heating film automatically cut off power
in case of little or no water remained in a water tank on the heating
plate, preventing the heater from danger of no-water heating, and
enhancing safety.
While the preferred embodiments of the invention have been described
above, it will be recognized and understood that various modifications
may be made therein and the appended claims are intended to cover
all such modifications that may fall within the spirit and scope
of the invention.
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