Leakage detecting device for electrical appliance

A leakage detecting device for electrical appliance is provided with electrodes (17) for detecting a state in which an electrical appliance such as a hair dryer is submerged in water. When the electrodes (17) are in a short-circuited state, relay means (3) is driven to open a contact (7). As a result, supply of the power supply voltage from a commercial power source (1) to the loads such as a motor (15), a heater (16) and the like is stopped so that an accident due to leakage can be prevented in such cases as a case in which the electrical appliance has been dropped into the water.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a leakage detecting device for electrical 
appliance. More particularly, the present invention relates to a leakage 
detecting device adapted to prevent a leakage accident such as injury to a 
human body by an electric shock and a damage to an electrical appliance 
such as a hair dryer or a hair iron when it has fallen into water or other 
liquid. 
2. Description of the Prior Art 
In a house of the latest design, a dressing table is often installed within 
a bath room. In such a case, if an electrical appliance such as a hair 
dryer or a hair iron with the power plug thereof being put into theplug 
receptacle has been dropped, by mistake, into the water of a bath tub or 
the like, there is a fear that an accident such as injury to a human body 
by an electric shock may occur. As the prior art for detecting leakage to 
prevent such an accident due to an electric shock, a technique as 
disclosed in British Patent Specification No. 1,408,316 or the Japenese 
Patent Publication Gazette No. 7885/1985 is known. A leakage detecting 
device indicated in the Japanese Patent Publication Gazette No. 7885/1985 
uses a zero-phase current transformer so that when a ground current flows 
from a load to the ground, a difference between the input and output 
currents flowing in the zero-phase current transformer is detected as an 
induced voltage for the zero-phase current transformer to cause the 
contact to be turned off. 
However, if an electrical appliance (a load) has been dropped in the water 
of a container such as a bath tub having a high insulation property, a 
leakage current flows in the water, and if a human in the water receives 
an electric shock, it is difficult for a zero-phase current transformer to 
detect the leakage current because a current equal to the leakage current 
returns to the power source, and the water and the power source also 
function as a part of the load. Furthermore, since a zero-phase current 
transformer detects generation of a minor leakage current, it is necessary 
to make it have a high sensitivity, which involves disadvantages in that 
the signal-to-noise ratio is not good and the zero-phase current 
transformer is liable to be affected by a magnetic noise from the 
exterior, causing erroneous operation. In addition, such a conventional 
device has a large number of components and is large-sized, and 
accordingly, the manufacturing cost thereof becomes high. 
SUMMARY OF THE INVENTION 
Therefore, a primary object of the present invention is to provide a 
leakage detecting device for electrical appliance, which can protect 
reliably a human body from electric shock and an electrical appliance from 
damage, and which can be manufactured at a low cost because the number of 
components in the device can be decreased. 
Briefly stated, the present invention is a leakage detecting device for an 
electrical appliance of a type in which the plug thereof is put in a plug 
receptacle so that power source voltage is supplied to a load. This 
leakage detecting device is structured so that, when a pair or pairs of 
electrodes are in the water and short-circuited, relay means is driven to 
stop the supply of the power source voltage from the plug to the load 
through the contact. 
Consequently, according to the present invention, if an electrical 
appliance is submerged under water or splashed with water, a conductive 
state is detected so that the relay means is operated immediately to stop 
the conduction to the electrical appliance. Thus, even if the electrical 
appliance is submerged in water, a human will never receive an electrical 
shock and deterioration of the performance of the electrical appliance due 
to the submersion can be avoided, and a firing or leakage accident due to 
conduction in a state in which water remains in some portions of the 
electrical appliance can be prevented. In addition, as compared with a 
conventional leakage breaker system, a device of the present invention has 
a simple structure and therefore the manufacturing cost can be remarkably 
decreased and the size of a device as a whole can be made small. 
In a preferred embodiment of the present invention, relay means is 
contained in a plug and a pair or pairs of electrodes are contained in an 
electrical appliance. The relay means comprises: a core; a primary coil 
and a secondary coil wound around this core; a movable core; a fixed 
contact connected to a terminal of a plug; and a movable contact coupled 
to the movable core. Normally, the relay means supplies power source 
voltage to the primary coil to generate a magnetic flux in the core, so 
that the movable core is opened and the movable contact is in contact with 
the fixed contact, whereby the power source voltage is applied to the 
load. When the pair of electrodes detects a leakage, a magnetic flux is 
generated from the secondary coil and, as a result, the movable core is 
closed and the movable contact is detached from the fixed contact, whereby 
the power source voltage supplied to the load is stopped. 
Thus, in this preferred embodiment of the present invention, the relay 
means is provided within the plug and a pair or pairs of electrodes need 
only to be provided within the body of the electrical appliance. 
Accordingly, without a complicated structure, supply of the power source 
voltage to the load can be stopped when leakage occurs. 
In a further preferred embodiment of the present invention, a trip switch 
is used as the pair of electrodes. The trip switch includes a contact 
which is closed by reaction with water as a result of wetting of the 
electrical appliance. When this contact is closed, the relay means is 
operated so that supply of the power source voltage to the load is 
stopped. 
In a further preferred embodiment of the present invention, a manual switch 
is provided in parallel with the pair of electrodes and, when this manual 
switch is turned off, the relay means is operated so that supply of the 
power source voltage to the load is stopped. 
Accordingly, in this preferred embodiment of the present invention, if an 
electrical appliance is submerged in water with the power plug being 
connected to the plug receptacle, an electric shock to a human body can be 
prevented reliably because no electric power is supplied to the load of 
the electrical appliance. 
Furthermore, in a preferred embodiment of the present invention, the 
present invention is applied to a hair dryer as an electrical appliance. 
These objects and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an essential portion sectional view showing a structure of a hair 
dryer in which an embodiment of the present invention is applied; FIG. 2 
is a cross sectional view taken along the line II--II in FIG. 1; FIG. 3 is 
an electrical circuit diagram of this embodiment of the present invention; 
and FIGS. 4A and 4B are views showing a structure of a transfer relay used 
in this embodiment of the present invention. 
First, referring to FIGS. 1 through 4B, a structure of the above stated 
embodiment of the present invention will be described. In the following 
description of the embodiment, the present invention is applied to a hair 
dryer as an example of an electrical appliance which is of a transportable 
type and is used in contact with a human body in a state in which the plug 
is put in a plug receptacle to supply power source voltage to the load. 
The power plug 2 is put in a plug receptacle of a commercial power source 
1. The power plug 2 contains a transfer relay 3 as the relay means. In a 
housing 11a of a hair dryer body 11, a cold and warm wind outlet 11b is 
formed. This housing 11a contains a manual switch 12 and a load circuit 
comprising a motor 15 and a heater 16. A fan 15a is coupled to the motor 
15. The heater 16 is surrounded by a frame 11c. Electrodes 17 are provided 
in association with the frame 11c. The electrodes 17 are formed as a pair 
of electrode pieces 18 and 19 and serve to detect a leakage when the 
resistance of the pair of electrode pieces 18 and 19 is lowered if the 
hair dryer body 11 is submerged in water. The power plug 2 and the body 11 
are connected by a power cable 8. This power cable 8 contains detecting 
lines 9 and 10. The manual switch 12 includes a contact 13 for operating 
the motor 15 and a contact 14 for operating the heater 16 as shown in FIG. 
3. 
Next, referring to FIGS. 4A and 4B, the structure of the transfer relay 3 
will be described. The transfer relay 3 comprises a core 5, a primary coil 
4, a secondary coil 6, a movable core 20 and a contact 7. The core 5 
comprises a first core portion 51, a second core portion 52, a third core 
portion 53 projecting from one end of the second core portion 52, and a 
fourth core portion 54 projecting from the other end of the second core 
portion 52. The primary coil 4 is wound around the first core portion 51 
and this primary coil 4 is connected to a terminal of the plug 2. The 
secondary coil 6 is wound around the second core portion 52 and this 
secondary coil 6 is connected to the electrodes 17 contained in the body 
11 through the detecting lines 9 and 10. 
One end of the movable core 20 is rotatably supported by the third core 
portion 53 and this movable core 20 is normally opened by the elastic 
force of a coil spring 21. The contact 7 includes fixed contact segments 
71 and movable contact segments 72. The fixed contact segments 71 are 
connected to the terminal of the plug 2 and the ends of the movable 
contact segments 72 on one side are connected to one end of the third core 
portion 20 by means of terminal portions 8a. The terminal portions 8a are 
connected with one end of the power cable 8 and the other end of the power 
cable 8 is connected to the body 11. 
Now, the operation of the transfer relay 3 will be described. When the 
electrodes 17 contained in the body 11 are opened, that is, when a state 
of leakage is not detected, power source voltage from the commercial power 
source 1 is supplied to the primary coil 4 so that a magnetic flux 22 is 
generated in the first core portion 51 and the second core portion 52 as 
shown in FIG. 4A. By this magnetic flux 22, a low voltage is induced in 
the secondary coil 6. In this state, the magnetic flux does not flow in 
the movable core 20 and the free end of the movable core 20 is kept 
separated from the fourth core portion 54 by the elastic force of the coil 
spring 21. At this time, the movable contact segments 72 coupled to the 
movable core 20 contact the fixed contact segments 71 and the power source 
voltage from the commercial power source 1 is supplied to the body 11 
through the power plug 2, the fixed contact segments 71, the movable 
contact segments 72 and the power cable 8. The core 20 and the movable 
contact segments 72 are, needless to say, insulated from each other. 
Then, when the electrodes 17 of the body 11 are in a short-circuited state 
as a result of submersion of the body 11 in water, a state as shown in 
FIG. 4B is brought about. More specifically, the resistance value between 
the pair of electrode pieces 18 and 19 becomes small so that the secondary 
coil 6 is short-circuited. Since the secondary coil 6 is wound to generate 
a magnetic flux opposite to the magnetic flux generated by the primary 
coil 4, it becomes difficult for the magnetic flux to pass through the 
second core portion 52 within the secondary coil 6. As a result, the 
magnetic flux 22 generated through the primary coil 4 flows from the first 
core portion 51 through the third core portion 53, the movable core 20 and 
the fourth core portion 54. On this occasion, energy is stored in a gap 
between the movable core 20 and the fourth core portion 54 and the movable 
core 20 moves in opposition to the elastic force of the coil spring 21, 
whereby the free end of the movable core 20 is attracted toward the fourth 
core portion 54 and is in contact therewith. In this state, the movable 
contact segments 72 coupled to the movable core 20 are separated from the 
fixed contact segments 71. Since the contact 7 is a contact of a type 
cutting off both ends of a load, supply of the power source voltage to the 
load circuit of the dryer body 11 is stopped. 
Next, referring to FIGS. 1 through 4B, the operation of the whole of the 
above described embodiment of the present invention will be described. In 
the normal state, the resistance value between the pair of electrode 
pieces 18 and 19 of the electrodes 17 is high and the electrodes 17 are in 
the OFF state. Accordingly, the transfer relay 3 is as shown in FIG. 4A, 
namely, the free end of the movable core 20 is separated from the fourth 
core portion 54 and the movable contact segments 72 are in contact with 
the fixed contact segments 71. In consequence, power source voltage is 
supplied from the commercial power source 1 to the dryer body 11 through 
the power plug 2, the fixed contact segments 71, the movable contact 
segments 72 and the power cable 8. 
When the contact 13 of the switch 12 of the dryer body 11 is turned on, 
power source voltage is supplied to the motor 15 so that the motor 15 
rotates. According to the rotation of the motor 15, a cold wind is made to 
blow by the fan 15a. Then, when the contact 14 of the manual switch 12 is 
turned on, power source voltage is also supplied to the heater 16 so that 
the air is heated and a warm wind blows. When the contacts 13 and 14 of 
the manual switch 12 are both turned off, the dryer stops blowing the 
wind. 
Now, assuming that the dryer body 11 is submerged in water, water 
penetrates between the pair of electrode pieces 18 and 19 of the 
electrodes 17 and the resistance value between the pair of electrode 
pieces 18 and 19 is rapidly lowered, whereby the secondary coil 6 of the 
transfer relay 3 is short-circuited. As a result, as described previously, 
electric current flows in the secondary coil 6 and a magnetic flux is 
generated in a manner opposing the magnetic flux 22 generated by the 
primary coil 5 so that the movable core 20 moves and the free end of the 
movable core 20 contacts the fourth core portion 54. Consequently, the 
movable contact segments 72 are moved away from the fixed contact segments 
71 and power source voltage is not supplied to the load circuit of the 
dryer body 11. 
Since the secondary coil 6 of the transfer relay 3 is supplied with a low 
voltage and is isolated from the commercial power source 1, it is a safe 
coil and serves to prevent a human from receiving an electric shock. 
FIG. 5 is an electrical circuit diagram of another embodiment of the 
present invention. In the embodiment shown in FIG. 5, a contact 23 is 
provided in the manual switch 12 and is connected in parallel with the 
electrodes 17 instead of the contact 13 shown in FIG. 3. The other 
structure of this embodiment in FIG. 5 is the same as the embodiment in 
FIG. 3. By the connection of the contact 23 in parallel with the 
electrodes 17, the contact 23 is turned on to short-circuit the secondary 
coil 6 of the transfer relay 3 when the switch 12 is turned off (the dryer 
is in the stop state). More specifically, when the manual switch 12 is 
turned off, a state equal to the state in which the electrodes 17 are 
short-circuited is established and the contact 7 of the transfer relay 3 
is turned off so that power source voltage is not supplied to the load 
circuit of the dryer body 11 to bring the dryer into the OFF state. 
When the manual switch 12 is turned on, the contact 23 is turned off and 
the contact 7 of the transfer relay 3 is turned on so that power source 
voltage is supplied to the motor 15 to send a cold wind. When the contact 
14 is turned on in that state, power source voltage is also supplied to 
the heater 16 so that a warm wind blows. The other operation is performed 
in the same manner as in the above described embodiment. 
In the embodiment shown in FIG. 5, the load circuit of the dryer body 11 is 
not supplied with any power source voltage even if the power plug 2 is 
connected to the commercial power source 1. Consequently, if the dryer 
body 11 is submerged in water in that state (this will be most likely to 
occur), an accident involving an electric shock can be prevented reliably. 
FIG. 6 is an electrical circuit diagram of a further embodiment of the 
present invention; FIG. 7 is an essential portion sectional view showing a 
structure of a hair dryer in which this embodiment of the present 
invention is applied; and FIG. 8 is a cross sectional view taken along the 
line VIII--VIII in FIG. 7. 
Referring to FIGS. 6 to 8, this embodiment of the present invention will be 
described. In this embodiment, a trip switch 31 is provided in parallel 
with the electrodes 17 and a frame 11c of the heater 16 is utilized also 
as one electrode piece 19 of the electrodes 17. The other structure of the 
embodiment is the same as the above described embodiment shown in FIGS. 1 
to 3. 
The trip switch 31 is provided near a component whose performance is 
degraded once it is submerged in water, for example, the motor 15, and the 
trip switch 31 continues to cut off the circuit to prevent secondary 
failure after the body 11 of the hair dryer has been taken out from the 
water. More specifically, when the trip switch 31 is submerged in water, 
the contact 32 is turned on by chemical reaction or the like and this 
state is maintained after the dryer body 11 has been taken out of the 
water, whereby supply of electric power to the load circuit of the body 11 
is kept stopped. 
In the above described structure, power source voltage is not supplied if 
the performance of the hair dryer body 11 is worsened or the hair dryer is 
in trouble as a result of submersion of the body 11 in water, and 
accordingly, an accident such as firing or leakage caused by supply of 
power source voltage can be prevented. The hair dryer body thus submerged 
can be repaired by exchanging the trip switch 31 for a new one after 
inspection of the components. 
FIGS. 9A and 9B are views for explaining a structure and operation of a 
trip switch mechanism. 
Referring to FIG. 9A, the trip switch 31 comprises a contact segment 32, a 
water soluble material 33 and a contact segment 34. The contact segment 32 
is formed of an elastic material which can be inherently in contact with 
the contact segment 34, and the water soluble material 33 of such as 
crystal of sodium chloride is placed so as to push the contact segment 32 
upward. The contact segment 32 is connected with one detecting line 9 and 
the contact segment 34 is connected with the other detecting line 10. If 
the trip switch 31 is submerged in water, the water soluble material 33 
begins to be dissolved in water and the volume thereof decreases. As shown 
in FIG. 9B, the contact segment 32 is made in contact with the contact 
segment 34 by the elastic force of the contact segment 32 so that the 
contact of the trip switch 31 is closed and this closed state is 
maintained. Thus, using the trip switch 31, the contact can be closed as a 
result of a leakage when it is submerged in water. 
FIGS. 10A through 14B are views for explaining structures and operation of 
other examples of a trip switch. 
The example shown in FIGS. 10A and 10B uses a material 35 such as bridge 
structure of sodium polyacrylate, which is excellent in water absorption 
and water retentivity and swells hygroscopically. In other words, the 
contact segment 32 has such elastic force as to be opened normally. The 
hygroscopically swelling material 35 covered with a permeable elastic film 
is disposed above the contact segment 32 as shown in FIG. 10A. When the 
material 35 is submerged in water, the material 35 contains water and 
swells so that the contact segment 32 is in contact with the contact 
segment 34 as shown in FIG. 10B. Even after the material 35 has been taken 
out of the water, the closed state of the contact is maintained since the 
material 35 has water retentivity. 
In the example shown in FIG. 11A, detecting lines 9 and 10 are connected to 
a reed switch 36 and a guard 37 is provided near the reed switch 36, a 
magnet 38 and a hygroscopically swelling material 39 covered with a 
permeable elastic film being contained in the guard 37. Normally, the 
material 39 is not swollen and accordingly the magnet 38 is at a position 
distant from the reed switch 36, which is turned off. When the switch 
mechanism in this state is submerged in water, the material 39 swells with 
water and the magnet 38 is pushed by the material 39 and is moved in the 
guard 37 as shown in FIG. 11B. When the magnet 38 approaches the reed 
switch 36, the reed switch 36 is turned on. Even after the switch 
mechanism has been taken out of the water, the contact of the reed switch 
36 is kept closed because the swollen state of the material 39 is 
maintained. 
The trip switches shown in FIGS. 12A, 12B, 13A and 13B are examples using a 
pyrogenic material such as sulfate which produces heat by reaction with 
water. More specifically, the example shown in FIG. 12A uses an 
irreversible shape memory alloy 40 as the contact segment 32 shown in FIG. 
9A. A pyrogenic material 41 such as sulfate is disposed near the shape 
memory alloy 40. When the pyrogenic material 41 is submerged in water, it 
produces heat by reaction with water and by this heat, the shape memory 
alloy 40 is transformed as shown in FIG. 12B so that the contact segment 
32 is closed and this closed state is maintained. 
The example shown in FIG. 13A uses an elastic material as the contact 
segment 32, which inherently tends to be in contact with the contact 
segment 34 but is fixed to be opened from the contact segment 34 by means 
of a thermal fuse 42 such as solder. The pyrogenic material 41 is disposed 
around the thermal fuse 42. When the pyrogenic material 41 is submerged in 
water, the pyrogenic material 41 reacts with water to generate heat so 
that the thermal fuse 42 is melted. As a result, as shown in FIG. 13B, the 
contact segment 32 is in contact with the contact segment 34 by the 
elastic force of the contact segment 32 so that the contact is closed. 
The trip switch shown in FIGS. 14A and 14B uses a humidity sensor such as a 
sensor of TiO-SiO.sub.2 ceramic. More specifically, the humidity sensor 43 
is provided between the detecting lines 9 and 10 and a water retentive 
material 44 having good water absorptivity is provided around the humidity 
sensor 43. The humidity sensor 43 has a high resistance value before it is 
submerged in water. When the humidity sensor 43 is submerged in water, 
water is absorbed in the water retentive material 44 and this water causes 
the humidity sensor 43 to have a low resistance value so that the trip 
switch is turned on. After the switch has been taken out from the water, 
the ON state is maintained because the water retentive material 44 
continues to keep water. 
In the trip switch 31 structured as described above, it does not matter if 
the reaction speed is a little decreased. When the dryer body 11 is 
submerged in water, the electrodes 17 react immediately to interrupt the 
transfer relay 3 and, therefore, the trip switch 31 has only to react to 
be turned on till the dryer body 11 is taken out from the water. If the 
dryer body 11 has been submerged in water for a long period, the ON 
resistance between the pair of electrode pieces 18 and 19 of the 
electrodes 17 becomes high due to electrolysis of water or the like and it 
becomes easier for the trip switch 31 to be maintained in the ON state, 
and thus safety can be assured with higher reliability. 
FIGS. 15A and 15B are views showing a structure of another example of a 
transfer relay. Referring to FIG. 15A, a fifth core portion 55 and a sixth 
core portion 56 are provided in the core 5 in addition to the first core 
portion 51 and the second core portion 52. The fifth core portion 55 
extends from one end of the second core portion 52 and the sixth core 
portion 56 extends from the other end of the second core portion 52, the 
outer side surface of the fifth core portion 55 and the inner side surface 
of the sixth core portion 56 being formed on the same plane. The end 
surfaces of the fifth core portion 55 support rotatably a movable core 20 
with the central portion of the movable core 20 being regarded as a 
fulcrum 30. One end of a coil spring 21 is coupled to one end of the 
movable core 20 and a coil spring 23 is provided between the other end of 
the movable core 20 and the second core portion 52. Accordingly, the 
movable core 20 is normally rotated clockwise by the coil springs 21 and 
23, one end of the movable core 20 being separated from the outer side 
surface of the fifth core portion 55 and the other end thereof being 
separated from the inner side surface of the sixth core portion 56. 
Movable contact segments 72 are formed at one end of the movable core 20 
and the movable contact segments 72 are in contact with fixed contact 
segments 71. 
When the electrodes 17 are turned off in the transfer relay constructed as 
described above, the movable core 20 is distant from the fifth core 
portion 55 and distant from the sixth core portion 56 by the elastic 
forces of the coil springs 21 and 23, respectively, and the movable 
contact segments 72 are in contact with the fixed contact segments 71, as 
shown in FIG. 15A. 
If the electrodes 17 are turned on as a result of submersion in water, 
magnetic flux hardly flows in the secondary coil 6 and the movable core 20 
rotates anticlockwise in opposition to the elastic forces of the coil 
springs 21 and 23, whereby one end of the movable core 20 is attracted to 
the fifth core portion 55 and the other end thereof is attracted to the 
sixth core portion 56 as shown in FIG. 15B. As a result, the movable 
contact segments 72 are separated from the fixed contact segments 71 so 
that the contact 7 is turned off. 
The transfer relay shown in FIGS. 15A and 15B has an advantage that 
erroneous operation will hardly be caused by a linear shock because the 
movable core 20 is balanced on the fulcrum point 30. 
FIGS. 16, 17A and 17B are views showing various examples of the electrodes 
provided in a hair dryer body. 
Referring now to FIGS. 16 through 17B, the electrodes 17 will be described. 
For the electrodes 17, it is necessary to make the area of the electrodes 
as large as possible and the distance between the electrodes as short as 
possible so that the transfer relay 3 is operated even by water of high 
resistance. Therefore, in the example shown in FIG. 16, electrode pieces 
18 and 19 are formed by two sheets of metallic plates of stainless steel 
or the like having high resistance to corrosion, these electrode pieces 18 
and 19 being opposed to each other. Spacers 24 serving as insulators for 
maintaining a certain distance between the electrodes are disposed at the 
four corners between the electrode pieces 18 and 19, the spacers 24 being 
fixed to the respective electrode pieces 18 and 19 by an adhesive agent. 
The electrodes 17 shown in FIG. 17A are formed in the following manner. 
Electrode pieces 18 and 19 each shaped like comb-teeth are formed close to 
each other on one base plate 27 by applying etching or the like to copper 
foil on the base plate 27, and two spacers 24a and 24b formed of an 
insulating material and two metallic spacers 25 and 26 are fixed at the 
four corners of the base plate 27, respectively. In the same manner as for 
the base plate 27, electrode pieces 18 and 19 shaped like comb-tooth are 
formed on the other base plate 28 so that the electrode pieces 18 and 19 
on the base plate 27 are opposed to the electrode pieces 18 and 19 on the 
base plate 28, respectively. The base plates 27 and 28 are faced toward 
each other with the spacers 24a and 24b being interposed therebetween, so 
that the portions contacting the metallic spacer 25 have one polarity 
equal to that of the portions contacting the spacer 24a and the portions 
contacting the metallic spacer 26 have the other polarity equal to that of 
the portions contacting the spacer 24b. Detecting lines 9 and 10 are 
connected to the metallic spacers 25 and 26, respectively. The spacers 24a 
and 24b are fixed to the base plate 28 by an adhesive agent and the 
metallic spacers 25 and 26 are electrically connected to the base plate 28 
by soldering. 
In the above described embodiment shown in FIGS. 16, 17A and 17B, four 
openings as air exits are formed by thus providing the spacers 24 at the 
four corners of the base plates, and in consequence, irrespective of the 
direction and the speed of penetration of water into the electrodes 17, 
air will never remain within the electrodes 17 and a low resistance value 
as desired can be obtained. The copper foil patterns of the electrode 
pieces 18 and 19 are preferably plated with a material such as nickel 
having good anti-corrosive property so that corrosion on the surfaces of 
the electrodes can be prevented. 
Although, in the above described embodiments, the electrodes 17 are 
provided near the outlet opening 11b of the hair dryer body 11, the 
electrodes 17 may be provided in various portions depending on situations 
in which water enters; for example, they may be provided in the vicinity 
of an inlet opening of the body 11, the manual switch 12 or the outlet of 
the power cable 8. 
In the above described embodiments, the distance between the electrode 
pieces 18 and 19 is made short and, consequently, it takes much time to 
remove the water from the space between the electrode pieces 18 and 19 
once the dryer body 11 has been submerged in water. Furthermore, in a 
transfer relay system, once the contact has been turned on, the resistance 
between the electrode pieces 18 and 19 for turning off the contact is 
required to be higher than the resistance in the ON state of the contact 
because of hysteresis. Accordingly, the time required for turning off the 
contact is further increased. Thus, once the dryer body 11 has been 
submerged in water, the OFF state can be maintained for a long period and, 
therefore, the device can be set so that it may be automatically returned 
to the initial state after having been turned off only for a period 
sufficient to enable the water in the electrical appliance to be removed 
therefrom. 
In addition, although the present invention is applied to a hair dryer in 
the above described embodiments, the present invention is not limited 
thereto. The present invention is applicable to any electrical appliance 
as far as such electrical appliance is transportable and used in contact 
with a human body in a state in which power source voltage is supplied to 
the load by putting the plug into a plug receptacle. 
Although the present invention has been described and illustrated in 
detail, it is clearly understood that the same is by way of illustration 
and example only and is not to be taken by way of limitation, the spirit 
and scope of the present invention being limited only by the terms of the 
appended claims.