Field of the Invention
The present invention relates to a plug which is
adapted to be connected to a direct current (DC) outlet.
Background of the Invention
Conventionally, there are known a DC outlet for
supplying a DC power to a DC device, e.g., a radio, a
television set or the like, having a DC power supply as a
driving power supply, and a plug which is detachably
connected to the DC outlet (see, e.g., Japanese Patent
Application Publication No. H7-15835 (paragraphs [0021] to
?0023], and Fig. 1) (JP7-15835A).
The DC outlet of JP07-015835A includes a main body
chat is accommodated in a switch box provided inside a wall;
and a converter provided inside the main body to convert an
AC power to a DC power. Further, the DC outlet includes an
AC connection terminal provided on a rear side of the main
body which faces the switch box; and an outlet part provided
on a front side of the main body which faces an inside of a
room. A power line of an AC power source installed inside
the wall is connected to the AC connection terminal, and a
plug of an electric device is detachably connected to the
outlet part. Accordingly, when the. power line of the AC
power source is connected to the AC connection terminal of
the DC outlet, an AC power is converted to a DC power by the
converter, so that the DC power can be supplied to the
electric device having the plug that is connected to the
outlet part thereof.
In the meantime, when a plug is connected to and
disconnected from a DC outlet, an arc may be generated.
Especially, in the case of the DC outlet for supplying a DC
power, the generated arc may be maintained as compared with
an AC outlet and, thus, the DC outlet needs an' arc
protecting unit. However, the DC outlet of JP07-015835A has
an outlet part of a pin-jack type terminal and the plug is
formed as a pin-jack type plug to be connected to the pin-
jack type terminal. Thus, no member for surrounding plug
pins of a plug. Accordingly, the generated arc may be seen
from the outside.
As an example of a DC outlet and a DC plug including
an arc protecting unit, there has been disclosed a plug and
a socket of a safety extra low voltage (SELV) voltage
standardized by the IEC standard (CEI/IEC 60906-3). Figs.
15C and 15D show a plug 110 standardized by the IEC standard.
Two plug pins 112 are arranged inside a cylindrical portion
111 provided at a front end portion of the-plug 110.
Meanwhile, as shown in Figs. 37A and 37B, a socket 100
includes a circular opening 101 tKrough which the
cylindrical portion ill of the plug liO is inserted; a
cylindrical protruding portion 102 which protrudes from the
circular opening 101 to be inserted into the cylindrical
portion 111; pin-inserting holes 103 which are opened to an
front end surface of the protruding portion 102; and pin-
receiving pieces 104 provided inside the protruding portion
102 to communicate with the pin-inserting holes 103. When
the plug 110 is connected to the socket 100, the plug pins
112 which are Inserted into the protruding portion 102
through the pin-inserting holes 103 are respectively engaged
with the pin-receiving pieces 104, so that a power is
supplied from the socket 100 to the plug 110.
As shown in Figs. 15A to 15D, in the socket 100
standardized by the IEC standard, the two pin-inserting
holes 103 are opened on a line L1 extending through the
center o£ the protruding portion 102 and at two symmetric
positions with regard to the center of the protruding
portion 102 and the two plug pins 112 are disposed on a line
L2 extending through the center of the cylindrical portion
111 and at,two symmetric positions with regard to the center
of the cylindrical portion 102. For that reason, a keyway
105 is formed on a peripheral surface of the protruding
portion 102 and a rib 113 is formed on an inner peripheral
surface of the cylindrical portion 111 such that the plug
pins 112 would not be inserted into the pin-inserting holes
103 in a state that their polarities are misaligned.
Further, the plug 110 and the socket 100 standardised
by the IEC standard correspond to four kinds of supply
volr.agPs. To identify the kinds of supply voltages, the
socket 100 and the plug 110 respectively include a voltage-
identifying groove 106 formed on the peripheral surface of
the protruding portion 102 at a predetermined angle with
regard to the keyway 105; and a voltage-identifying rib 114
protrudently formed on the inner peripheral surface of the
cylindrical unit 111 of the plug 110 at a predetermined
angle with regard to the rib 113.
Then, the plug no is prevented from being inserted
into the socket 100 reversely or wrongly with their
polarities misaligned by engaging the keyway 105 and the
voltage-identifying groove 106 with the rib 113 and the
voltage-identifying rib 114, respectively. When, however,
the cylindrical portion 111 is inserted into the circular
opening ioi, it is required to find positions at which the
ribs 113 and 114 of the cylindrical portion 111 are
respectively engaged with the keyway 105 and the groove 106
of the socket 100 while rotating the plug 110. Accordingly,
it becomes inconvenient to use the socket 100 and the plug
110.
In the socket 100 and the plug 110 described above, in
order to prevent the plug 110 from being reversely inserted
into the socket 100 without using the keyway 105 and the rib
113, it is considered to arrange the two pin-inserting holes
103 at a side below or above the line L1 (e.g., at a side •
below the line L1) while arranging the plug pins 112 at a
side below or above the line L2 (e.g., at a side below the
line L2) as shown in Figs. 15A and 15C by the dotted lines).
Since, however, the cylindrical portion 111 hac the
cylindrical shape, the distance between the plug pins 112
becomes closer when the plug pins 112 are arranged at a side
below or above line L2. Accordingly, the plug 110 becomes
scaled up in order to obtain an insulating distance.
Summary of the Invention
In view of the above, the present invention provides a
plug capable of preventing its reverse insertion into a DC
outlet without being scaled up and being easily aligned with ,
the DC outlet when the plug is connected thereto.
In accordance with an aspect of the present invention,
there is provided a plug which is adapted to be connected to
a direct current (DC) outlet for supplying a DC power
thereto, the DC outlet having an insertion groove formed
around a plurality of pin insertion holes opened at a front
side and having therein pin-receiving pieces corresponding
to the pin insertion holes, the plug including: a plurality
of round bar-shaped plug pins which protrudes from a front
surface of a plug main body, the plug pins being adapted to
be connected the pin-receiving pieces through the pin
insertion holes of the DC outlet and to be supplied with
power from the DC outlet; and a surrounding wall which
protrudes from the front surface of the plug main body to
surround the plug pins, the surrounding wall being adapted
to be inserted into the insertion groove of the DC outlet,
wherein the surrounding wall is formed in a substantially
quadrangular shape, viewed from a front side thereof, and
the plug pins are arranged along a •• reference surface
corresponding to one inner surface of the surrounding wall
and offset closer to the reference surface than to an inner
surface opposite to the reference surface.
The shape of the surrounding wall, viewed from the
front side thereof, may be partially changed depending on
the kinds of a supply voltage, a supply current or a power
supply circuit.
Further, the shape of the surrounding wall viewed from
the front side may be changed such that an area of a portion
surrounded by the surrounding wall is decreased compared to
a case that the surrounding wall has the substantially
quadrangular shape viewed from the front side. In this case,
the shape of the surrounding wall viewed from the front side
may be partially changed by cutting at least one corner of
the substantially quadrangular shape of the surrounding wall
depending on the kinds of the supply voltage, supply current
or power supply circuit.
Preferably, a portion of the surrounding wall whose
shape is changed depending on the kinds of the supply
voltage, supply current or power supply circuit is closer to
the inner surface opposite to the reference surface than the
reference surface.
Alternatively, the shape of the surrounding wall
viewed from the front side may be changed such that an area
of a portion surrounded by the surrounding wall is increased
as compared with a case that the surrounding wall has the
substantially quadrangular shape viewed from the front side.
Further, the shape of the surrounding wall viewed from
the front side may be partially changed by forming an
extended portion protruding from a surface of the
surrounding wall. In this case, the extended portion
extends inward from an inner surface the surrounding wall.
Preferably, the extended portion is disposed closer to a
surface opposite to the reference surface of the surrounding
wall. Alternatively, the extended portion may extend
outward from an outer surface of the surrounding wall.
Further, the shape of the surrounding wail viewed from
the front side may be partially changed drily when the power
supply circuit is a safety extra low voltage (SELV) circuit.
In addition, the plug pins of the plug may include a
ground pin. In this case, the ground pin may be provided
offset closer to the inner surface opposite to the reference
surface.
Furthermore, the plug main body may include: a box-
shaped front case having an open rear portion, the
surrounding wall being provided on a front surface of the
front case; and a box-shaped rear case having an open front
portion, the rear case being fixed to the front case so as
to block the rear opening of the front case, wherein the
plug pins are received in the front and the rear case.
Alternatively, the plug main body may include: a
fixing portion for fixing the plug pins; and a housing
formed at an outer side of the fixing portion by a secondary
molding, the housing being made of synthetic resin, wherein
the surrounding wall is formed as a unit with the housing.
In accordance with the present invention described
above, the plug pins to which power is supplied are arranged
along the reference surface corresponding to one inner
surface of the substantially quadrangular-shaped surrounding
wall and offset closer to the reference surface than to the
inner surface opposite to the reference surface. Thus, it
is possible to easily recognize the orientation of the plug
to be inserted into the DC outlet. Further, the
substantially quadrangular-shaped surrounding wall is
inserted"into the insertion groove of the DC outlet, so that
the orientation of the plug to be inserted into the DC
outlet is limited. This allows the easy position alignment
of the plug and enables realization of the plug which is
convenient in use and has a configuration of preventing
reverse insertion. Even if the plug pins are arranged
offset closer to the reference surface, the gap between the
plug pins does not decrease due to the substantially
quadrangular shape of the surrounding wall. Hence, it is
unnecessary to scale up the plug to ensure an insulation
distance.
Further, since the shape of the surrounding wall
viewed from the front side is partially changed by cutting
at least one of the corners of the surrounding wall
depending on the kinds of supply voltage, supply current or
power supply circuit, a user can easily identify the kinds
of the supply voltage, supply current or power supply
circuit from the shape of the surrounding; wall and recognize
the orientation of the plug to be inserted into the DC
outlet. Accordingly, the position alignment of the plug and
the DC outlet can be easily carried out.
In addition, the shape of the surrounding wall viewed
from the front side is partially changed by cutting the
corner(s) near the surface opposite to the reference surface
of the surrounding wall, so that it is possible to obtain a
sufficient distance between the plug pins and the
surrounding wall compared to the case of cutting the
corner(s) near the reference surface. This enables easy
fabrication of the plug.
Moreover, the kinds of supply voltage, supply current
or power supply circuit can be identified by the extended
portion protruding from the surface of the surrounding wall.
The extended portion extends from the surface of the
surrounding wall, so that the extended portion has a
sufficient strength compared to a case that it is formed
separately from the surrounding wall.
Besides,, by forming the extended portion at the inner -
surface, scaling up of the plug can be prevented compared to
a case that the extended portion is formed at the outer
surface of the surrounding wall.
Further, by forming the extended portion at the inner
surface of the surrounding wall close to the surface
opposite to the reference surface of the surrounding wall,
it is possible to obtain a sufficient distance between the
plug pins and the surrounding wall including the extended
portion compared to a case that the extended portion is
formed close to the reference surface. This enables easy
fabrication of the plug.
Brief Description of the Drawings
The other objects and features of the present
invention will become apparent from the following
description of embodiments, given in conjunction with the
accompanying drawings, in which:
Figs. 1A and 1B depict a plug in accordance with a
first embodiment of the present invention, wherein Pig. 1A
is a perspective view seen from the front, and Fig. 1B is a
perspective view seen from the rear which depicts a state
before the plug is connected to a DC outlet;
Figs. 2A to 2C illustrate a DC outlet to which the
plug is connected, wherein Fig. 2A is a top view, Fig. 2B is
a right side view and Fig. 2C is a partial bottom section
view;
Figs. 3A to 3E show front views of a plug in
accordance with a second embodiment of the presenc
invention;
Figs. 4A to 4c show a modification of the plug in
accordance with the second embodiment of the present
invention,
Figs. 5A to 5D present front views of a plug in
accordance with a third embodiment of the present invention;
Figs. SA to 6E represent front views of another
example of the plug;
Fig. 7 depicts a configuration of a DC power
distribution system using the plug;
Figs. 8A and 8B shows a plug in accordance with a
fourth embodiment of the present invention, wherein Fig. 8A
is a perspective view seen from the front, and Fig. 8B is a
perspective view seen from the rear which depicts a state
before the plug is connected to a DC outlet;
Figs. 9A to 9C are a front view, a right side view and
a bottom view of the plug of the fourth embodiment;
Fig. 10 is an exploded perspective view of the plug of
the fourth embodiment;
Figs. llA and 11C show a contactor block of the plug
of the fourth embodiment, wherein Pig. 11A is a perspective
view seen from the front. Fig. 11B is a perspective view
seen from the rear and Fig. 11C is an exploded perspective •
vies seen from the rear;
Figs. 12A and 12B shows a plug in accordance with a
fifth embodiment of the present invention, wherein Fig. 8A
is a perspective view seen from the front, and Fig. 8B is a
perspective view seen from the rear which depicts a state
before an outer case is formed by a secondary molding;
Fig. 13 is a perspective view of the plug of the fifth
embodiment having a ground pin,
Figs. 14A to 14D explain a case where plug pine of a
plug have a flat-blade shape; and
Figs. 15A to 15D illustrate a plug and a socket for an
SELV circuit standardized by IEC standard, wherein Figs. 9A
and 9C are respectively front views of the socket and the
plug, and Pigs. 9B and 9D are respectively cross sectional
views of the socket and the plug.
Detailed Description of the Embodiment
Embodiments of the present invention will now be
described with reference to the accompanying drawings which
form a part hereof.
(First Embodiment)
A first embodiment of the present invention will be
described with reference to Figs. 1A to 2C. A plug 1 in
accordance with this embodiment is, e.g., detachably
connected to a DC outlet 2 buried in a construction surface
such as a wall. As shown in Fig. 1B, a plug connector for a
DC power is constituted by the plug 1 and the DC outlet 2
which is connected to the plug 1 to supply a DC power
thereto. Unless otherwise described, upward, downward, left
and right directions of the plug 1 are defined based on Fig.
1A. The paper surface in Fig. 1A indicates the front side
of the plug 1.
As illustrated in Figs. 1A and 1B, the plug 1 includes
a plug main body 11 having a horizontally elongated
rectangular parallelepiped shape and a size which can be
gripped by a user, the plug main body 11 being made of
thermoplastic synthetic resin. Two round bar-shaped plug
pins 12 to which power from the DC outlet 2 is supplied are
protruded from a front surface of the plug main body 11 (the
surface facing the DC outlet 2) . A surrounding wall 13 is
formed as a unit with the plug main body 11 and is protruded
therefrom to surround the two plug pins 12. Further, an
electric wire 14 of a load device extends from a rear
surface of the plug main body 11. Hence, when the plug 1 is
connected to the DC outlet 2, the DC power is supplied to
the load device through the electric wire 14.
The surrounding wall 13 protruding from the front
surface of the plug main body 11 is formed in a
substantially quadrangular shape as viewed in a plug
insertion direction (from the front side). The two plug
pins 12 are arrange along a reference surface corresponding
to one inner surface (e.g., upper inner surface) of the
surrounding wall 13 and offset closer to the reference
surface than to an inner surface (lower inner surface)
opposite to the reference surface. Moreover, in this
embodiment, a distance between the plug pins 12 and the
upper inner surface of the surrounding wall 13 is 1/2 or
less of a distance between the plug pins 12 and the lower
inner surface of the surrounding wall 13, so that the plug
pins 12 which are offset closer to the upper side can be
easily recognized. In addition, a distance between the
front surface of the plug main body 11 and the leading end
of the surrounding wall 13 is set to be slightly larger than
a distance between the front surface of Che plug main body
11 and leading ends of the plug pins 12.
Meanwhile, as shown in Figs. 1B and 2, the DC outlet 2
to which the plug 1 is detachably connected includes a
outlet main body 20 made of synthetic resin and buried in a
construction surface. The outlet main body 20 has a
substantially box-shaped body 21 having an open front
portion and made of synthetic resin and a substantially box-
shaped cover 22 having an open rear portion and made of
synthetic resin. The body 21 and the cover 22 can be
assembled to each other by assembly frames 23 made of a
metal.
The outlet main body 20 has a size conforming to
Japanese Industrial Standard (see JIS C 8303). The outlet
main bodies 20 has one module dimension, and three outlet
main bodies can be attached side by side to a mounting frame
for interchanging wring devices of large square boss type
(see JIS C 8375) .
Although an outlet fixed to a fixture is described as
an example of the DC outlet 2 connected to the plug 1, the
plug l may be connected to an outlet fixed to an electric
device, a cord connector body used for extension connection
of a cord without being fixed, a unfixed multi-outlet power
strip and the like.
On a front surface of the cover 22, a boss 22a is
forwardly protruded therefrom as a single unit to be fixed
in an opening of a mounting frame (not shown) . A central
portion of the substantially U-shaped assembling frame 13 is
mounted in each of shoulders 22b provided at opposite end
sides of the boss 22a. Opposite end sides of the assembling
frame 23 are respectively inserted into' engaging recesses
22c and 21a formed at side surfaces of the cover 22 and the
body 21, and substantially V-shaped engaging claws 23c
provided at leading end portions of the opposite end sides
of the assembling frame 23 are respectively expanded to be
engaged with the opposite end portions of the engaging
recess 21a. Accordingly, the body 21 and the cover 22 are
combined by the assembling frame 23.
Protrudently provided at an outer peripheral portion
of a central portion of the assembling frame 23 is a pair of .
engaging claws 23a capable of being engaged with engaging
openings provided on the mounting frame made of a synthetic
resin material. Further, engaging openings 23b are provided
at a protruding portion forwardly protruding from an inner
peripheral portion of the central portion of the assembling
frame 23 to be engaged with engaging claws of a mounting
frame (not shown) made of a metal material when being
installed in the mounting frame.
Provided on a front surface of the boss 22a is an
outlet unit 24 to which the plug 1 is detachably connected.
Specifically, the outlet unit 24 is provided at a central
portion of the front surface of the boss 22a. The outlet
unit 24 has a substantially quadrangular shape viewed from
the front thereof and includes a plug-receiving portion 25
in which two circular pin-inserting holes 26 are formed; an
insertion groove 27 formed to surround the plug-receiving
portion 25 so as to receive a surrounding wall 13 of the
plug l; and two pin-receiving pieces 28 for being
respectively engaged with plug pins 12 of the plug 1
inserted into the outlet main body 20 through the pin-
inserting holes 26.
Specifically, the two pin-inserting holes 26 are
provided to correspond to the two (positive and negative)
pin-receiving pieces 28 for supplying a DC power. The pin-
inserting holes 26 are arranged along a side, e.g., an upper
side, in the present embodiment, serving a reference side KL,
of the plug-receiving portion 25 and closer to the upper
side (the reference side KL) of the plug-receiving portion
25 than a lower side thereof opposite to the reference side
KL.
Received into the outlet main body 20 are connection
terminals (not shown) of so-called quick connection terminal
structure to be respectively electrically connected to the
pin-receiving pieces 28. A power supply line (not shown) of
a DC power supply is inserted through a line-inserting hole
opened at a rear side of the body 21 to be connected to the
connection terminal. Further, the conventional quick
connection terminal disclosed in the Japanese Patent
Application Publication No. H10-144424, for example, may be
employed as the connection terminals (not shown) of quick
connection terminal structure, and the description and
illustration thereof will be omitted.
When the plug 1 is connected to the DC outlet 2, the
plug 1 first approaches the DC outlet 2 such that the plug
pins 12 are aligned with the pin-inserting holes 26. Then,
the surrounding wall 13 of the plug 1 is inserted into the
insertion groove 27 of the DC outlet 2, and the plug pins 12
are fitted into the pin-inserting holes 2V6. Thereafter, the
plug l continuously reaches a predetermined position to
thereby engage the plug pins 12 with the pin-receiving
pieces 28 electrically and mechanically. '" In addition, when
the'plug pins 12 are engaged to pin-receiving pieces 28, the
front end portion of the surrounding wall 13 has been
inserted into the insertion groove 27. Accordingly, even
when an arc is generated during the engagement of the plug
pins 12, the generated arc is not seen from the outside.
When the plug l is disconnected from the DC outlet 2,
the plug l is first gripped and pulled out. Then, the plug
pins 12 are disengaged from the pin-receiving pieces 28 and
the pin-inserting holes 26. Thereafter, the surrounding
wall 13 of the plug l is separated out from the insertion
groove 27, to thereby disconnect the plug 1 from the DC
outlet 2 easily. In addition, when the plug pins 12 are
disengaged from the pin-receiving pieces 28, the leading end
of the surrounding wall 13 has still been inserted into the
insertion groove 27. Accordingly, even when an arc is •
generated during the disengagement of the plug pins 12, the
generated arc is not seen from the outside.
In the plug l of this embodiment, the surrounding wall
13 has a substantially quadrangular shape viewed from the
front side (in the plug insertion direction) , and the two
plug pins 13 are arranged along a reference surface
corresponding to one inner surface (upper inner surface) of
the surrounding wall 13 and offset closer to the reference
surface than to the inner surface (lower inner surface)
opposite to the reference surface. Hence, the orientation
of the plug 1 to be inserted into the DC outlet 2 can be
easily recognized.
Since the substantially quadrangular-shaped
surrounding wall 13 is inserted into the insertion groove 27
formed around the quadrilateral plug receiving portion 25,
the orientation of the plug 1 to be inserted into the DC
outlet 2 is limited. This allows the position of the plug l
and that of the DC outlet 2 to be easily aligned.
Accordingly, the plug 1 which is convenient in use and has a
configuration that prevents reverse insertion can be
realized.
Unlike the aforementioned plug used for an SELV
circuit specified in IEC standard which is provided with
reverse insertion preventing ribs, the plug main body 11 has
on the front surface thereof the surrounding wall 13 formed
around the plug pins 12. Therefore, the plug l can have a
simple shape, and it is unnecessary to scale up the plug 1
to ensure strength.
When the surrounding wall 13 has a cylindrical shape
viewed in the plug insertion direction (from the front side),
if the two plug pins 12 are arranged offset closer to one
side of the surrounding wall 13, the gap between the two
plug pins 12 decreases. However, in this embodiment, the .
surrounding wall 13 has a substantially quadrangular shape
viewed in the plug insertion direction. Therefore, even if
a plurality of (e.g., two in this embodiment) plug pins 12
is arranged offset closer to the reference surface, the gap
between the plug pins 12 is not decreased. As a consequence,
it is unnecessary to scale up the plug for socket 1 to
ensure an insulation distance.
In the above-described plug connector, the plug 1 may
be provided with flat plug blades instead of the round bar-
shaped plug pins 12, and the plug receiving portion 25 may
be provided with rectangular pin insertion holes. In that
case, a vertical size of the flat plug blades becomes
greater than that of the round bar-shaped plug pins 12 in
order to have the same cross sectional area. As a
consequence, a vertical size of pin insertion holes 26'
formed at the plug receiving portion 2 5 is greater than that
of the round pin insertion holes 26, as can be seen from Fig.
8A. when the outlet main body 20 has a size of one module
dimension, a difference between the vertical sizes of the *
pin insertion holes 26' and the plug receiving portion 25 is
small. Hence, even if the pin insertion holes 26' are
arranged offset closer to the upper side with respect to the
center of the plug receiving portion 25; the offset amount
of the pin insertion holes 26' does not increase. This
makes it difficult to discriminate whether the pin insertion
holes 26' are arranged offset closer to the upper side or
the lower side. As for the plug 1 as well, it is difficult
to determine whether the flat plug blades are offset closer
to the upper side or the lower side. Moreover, the vertical
size of the pin insertion holes 26' is greater than that of
the flat plug blades. Therefore, if the vertical offset
amount of the pin insertion holes 26' is small, the ends of
the flat plug blades may be inserted into the pin insertion .
holes 26' when the plug 1 is connected in a reverse
orientation. To that end, it is required to increase the
vertical offset amount of the opening positions of the pin
insertion holes 26' as shown in Fig. 14B. In the plug 1 as
well, the vertical size of the plug main body 11 and the
vertical offset amount of the flat plug blades need to be
increased, which leads to scaling up of the outlet main body
2 0 or the plug 1. Therefore, in this embodiment, the plug
pins 12 are formed in a round bar shape, and the pin
insertion holes 26 are formed in a roundt hole shape. This
can increase the vertical offset amount or the plug pins 12
compared to the case that the plug pins are formed in a
flat-blade shape, so that it ie possible to eacily recognise
whether the plug pins 12 are offset closer to the upper side
or the lower side. As a result, incorrect (reverse)
insertion of the plug 1 into the pin insertion holes 26 can
be prevented.
Meanwhile, the DC outlet 2 of the present embodiment
is employed in a DC power distribution system shown in Fig.
7. Fig. 7 shows an example in which the DC power
distribution system is applied to a .detached house H-
Alternatively, the DC power distribution system may be
applied to a multi-family attached house or a building such
as a tenant building.
In the house H, a DC power supply unit 52 for
outputting a DC power; the DC outlets 2, ' provided at
necessary positions, to which a DC power is supplied through
DC supply lines Wdc; and a plurality of electric devices
(e.g., a refrigerator 60a, a TV 60b, and a phone 60c) that
are operated by the DC power are installed. The DC power is
supplied to the electric devices 60a to 60c by connecting
outlet plugs of the electric devices 60a to 60c to the DC
outlets 2. Further, DC breakers 53 are respectively *
provided between the DC power supply unit 52 and the DC
outlets 2 in order to monitor currents flowing .through the
DC supply lines Wdc and restrict or interrupt the power
supply from the DC power supply unit 52 to the DC outlets 2
through the DC supply lines Wdc when detecting an
abnormality.
The DC power supply unit 52 typically converts into a
DC power an AC power supplied from an AC power" source AC,
e.g., a commercial power source, outside the house H. In
Fig. 7, the DC power supply unit 52 includes an AC/DC
converter 54 and a control unit 55, and the AC power is
inputted to the AC/DC converter 54 including a switching
power source through a master breaker 51 provided in a power
distributor 50. The converted DC power is inputted to the
respective DC breakers 53 through the control unit 55.
The DC power supply unit 52 further includes a
secondary battery 57 to prepare for a time during which no
power ie supplied from fche AC power source AC (e.g., the
blackout of the AC power source AC) . A fuel battery 58 .
and/or a solar battery 56 for generating a DC power may be
employed together in addition to the secondary battery 57.
In this case, with respect to a major power source including
the AC/DC converter 54 for generating a DC power by using an
AC power supplied from the AC power source AC, the solar
battery 56, the secondary battery 57 and/or the fuel battery
5 8 serve as decentralized power sources. In addition, each
of the solar battery 56, the secondary battery 57 and the
fuel battery 58 includes a circuit unit "for controlling an
output, voltage. Further, the secondary battery 57 includes
a circuit unit for controlling a charging as well as the
circuit unit for controlling an output voltage.
The electric devices 60a to 60c need a plurality of
kinds of voltages depending on device types. For that
reason, the control unit 55 preferably includes a DC/DC
converter for converting a specific voltage supplied from
the major and the decentralized power sources into necessary
voltages to respectively supply the converted voltage to
corresponding DC outlets 2. The supply voltages of the DC
power may adequately be determined depending on the electric
devices and/or the use environment of a building. Here, a
power supply circuit of the power supply source for
supplying a DC power to the DC outlet 2 is provided between
the AC power supply source AC and the DC outlet 2, e.g.,
inside the power distributor 50.
(Second Embodiment)
A second embodiment of the present invention will be
described with reference to Figs. 3A to 3F. The plug 1 of
this embodiment is used for a plurality of supply voltages,
and a shape of the surrounding wall 13 is partially changed
depending on the kinds of supply voltages. The second
embodiment is the same as the first embodiment except for
the shape of the surrounding wall 13. Therefore, like parts .
are designated by like reference numerals, and redundant
description thereof will be omitted.
The plug 1 of this embodiment is used for four DC
supply voltages (e.g., about 6V, 12V, 24V and 48V). Thus,
the shape of the surrounding wall 13 is partially changed
depending on the kinds of the supply voltages.
Figs. 3A to 3D provide front views of the plugs 1 used
for 6V, 12V, 24V and 48V, respectively. " In the plug 1 for
24V, the surrounding wall 13 has - a substantially
quadrangular shape viewed in the plug insertion direction
(from the front side) . In the plugs 1 for 6V, 12V and 48V,
the shape of the surrounding wall 13 as viewed from the
front side of the plug main body 11 is partially changed by
cutting at least one corner of the surrounding wall 13
depending on the kinds of supply voltages. For example, in
the plug 1 for 6V, an inclined portion 13a is formed by
slantingly cutting the right lower corner of the surrounding
wall 13. In the plug 1 for 12V, an inclined portion 13a is
formed by slantingly cutting the left lower corner of the •
surrounding wall 13. in the plug 1 for 48V, inclined
portions 13a are formed by slantingly cutting the right and
the left lower corners of the surrounding wall 13. As the
shape of the surrounding wall 13 of the plug 1 is changed,
the shape of the insertion groove 27 of the DC outlet 2 is
also changed depending on the kinds of supply voltages.
Among the plugs l for four voltages, the plug 1 for
24V has the surrounding wall 13 formed in a substantially
quadrangular shape as viewed from the front side. In the
plugs l for 6V, 12V and 48V, the shape of the surrounding
wall 13 as viewed from the front side of the plug main body
11 is partially changed by cutting at least one corner of
the surrounding wall 13. For that reason, a user can easily
recognize the kinds of supply voltages from the shape of the .
surrounding wall 13 viewed from the front side. Further,
the difference between the shapes of the surrounding wall 13
and the insertion groove 27 can be easily recognized, so
chat the position alignment of the plug 1 and the DC outlet
2 can be carried out. Since the shapes of the surrounding
wall 13 of the plug 1 and the insertion groove 27 are
partially changed depending on the kinds of supply voltages,
the plug 1 can be prevented from being incorrectly connected
to the DC outlet 2 for a different supply voltage.
Accordingly, it is possible to prevent a DC voltage
different from a rated voltage from being supplied to a load
device.
in this embodiment, when the shape of the surrounding
wall 13 is changed depending on the kinds of supply voltages,
at least one corner of the substantially quadrangular shape
is cut so as to reduce an area surrounded by the surrounding
wall 13. This prevents outward extension of the surrounding
wall 13 and, thus, scaling up of the plug 1 can be avoided.
Although the corner of the surrounding wall 13 is slantingly .
cut in this embodiment, the corner may be cut in any shape.
For example, an angular recess 13b may be formed by cutting
the corner at a substantially right angle, as shown in Fig.
3E.
Further, when the corner of the substantially
quadrangular shape is cut depending on the kinds of supply
voltages, the lower corner(s) of the surrounding wall 13 is
cut. Therefore, it is possible to obtain a sufficient
distance between the plug pins 12 and the surrounding wall
13 compared with the case of cutting the upper corner near
the reference surface (upper inner surface) close to the
plug pins 12, and this enables easy fabrication of the plug
1. However, the corner near the reference surface of the
surrounding wall 13 may be cut. Further;- both of the upper
corner (near the reference surface) and the lower corner
(near the opposite surface to the reference surface) may be
cut, as can be seen from Fig. 3F.
When the shape of the corner of the surrounding wall
13 is changed depending on the kinds of supply voltages, the
position and the number of corners to be changed and the
shape of changed portions can vary without being limited to
those described in the above embodiment as long as the kinds
of supply voltages can be identified.
, _ Further, in addition to or independently from the
shape- change of the surrounding wall 13 of the plug 1
depending on the kinds of supply voltages, the chape of the
surrounding wall 13 of the plug 1 may be changed depending
on the kinds of supply current, as shown in Figs. 4A to 4C.
Referring to Figs. 4A to 4C, the plug 1 for the supply
voltage of 48V will be described as an example.
There is a plurality of electronic devices requiring
supply currents, e.g., 6, 12, 16 A. Here, the shape of the
surrounding wall 17 as viewed from the front thereof is •
changed by forming a r1B or ribs on the inner surface
thereof, to thereby make the plug l distinguishable
depending on the kinds of the supplied current. In other
words, based on the plug 1 for the supply: current of 6 A as
shown in Fig. 4A, the rib(s) is provided to the plug 1 of
the supply current of 12 and 16 A.
Specifically, in the plug 1 for 12 A as shown in Fig.
4B, a triangularly shaped r1B 13a' is provided at an upper
portion of the inclined portion 13a by partially protruding
the inclined portion 13a inwardly. Moreover, in the plug 1
for 16 A as shown in Fig. 4C, the ribs 13a' are provided at
both of the upper portions of the inclined portions 13a.
Meanwhile, in case the inclined portion 13a is not provided
to the surrounding wall 13, the rib(s) may be formed to have
the substantially quadrangular shape as viewed from the
front thereof.
(Third Embodiment)
A third embodiment of the present invention will be
described with reference to Figs. 5A to 6E. In the second
embodiment, the shape of the corner of the surrounding wall
li is changed depending on the kinds of supply voltages.
However, in the third embodiment, the "shape of the
surrounding wall 13 1A partially changed by forming an
extended portion protruding from the surface of the
surrounding wall 13 depending on the kinds of power supply
circuits serving as power supply sources. The third
embodiment is the same as the second embodiment except for
the shape of the surrounding wall 13. Hence, like parts are
designated by like reference numerals, and description
thereof will be omitted.
The power supply circuits serving as power supply
sources, e.g., an SELV circuit, an ELV circuit, an FELV
circuit and the like, are standardized in IEC standard. In .
a plug l used for an SELV circuit, an extended portion 15
protrudes inward from a lower central part of the
surrounding wall 13, as illustrated in Figs. 5A to 5D. Figs.
5A to 5D show plugs for a socket 1 which handle 6V, 12V, 24V
and 48V, respectively. As in the first embodiment, the
shape of the surrounding wall 13 viewed from the front side
of the plug main body 11 is partially changed by cutting at
least one corner of the surrounding wall 13. In the power
distribution system of Fig. 7, the power supply circuit
serving as a power supply source is provided between the AC
power supply and the DC outlet 2, e.g., inside the power
distributor 50'.
The plug 1 used for an ELV circuit is not provided
with the extended portion 15, as shown in Figs. 3A to 3D.
Thus, the kinds of the power supply circuits can be easily
recognized in accordance with existence/non-existence of the
extended portion 15.
in the DC outlet 2 used for an SELV circuit, an
identifying groove is formed to extend from the insertion
groove 27 into the plug-receiving portion 25, the extended
portion 15 being adapted to be fitted in the identifying
groove However, the DC outlet 2 used for an ELV circuit
has on identifying groove. Therefore, the plug 1 used for
an ELV circuit can be connected to both of the DC outlet 2
used for an ELV circuit and the DC outlet 2 used for an SELV
circuit, whereas the plug l used for an SELV circuit 1 can
be connected only to the DC outlet 2 used for an SELV
circuit.
An insulation class of the SELV circuit is higher than
that of the ELV circuit, so that a load device used in the
SELV circuit (hereinafter, referred to as "SELV device")
does not require high insulation performance compared to a
load device used in the ELV circuit (hereinafter, referred
to as "ELV device") . Since the insulation performance of
the SELV device is lower than that of the ELV device, when
the SELV device having insufficient insulation performance
compared to the ELV device is used in the ELV circuit whose
insulation class is lower than that of the SELV circuit,
breakdown caused by electric leakage or the like may occur.
However, in this embodiment, the SELV device cannot be used
in the ELV circuit. This is because the plug 1 used for an
SELV circuit cannot be connected to the DC outlet 2 used for
an ELV circuit and can be connected only to the DC outlet 2
used for an SELV circuit. Meanwhile, the ELV device can be
connected to the DC outlet 2 used for an SELV circuit. When
the ELV device is used in the SELV circuit, the above-
described problem is not generated. This is because the ELV
device has insulation performance higher than that of the •
SELV device and the insulation class of the SELV circuit is
higher than that of the ELV circuit.
In the plug 1 of this embodiment, the extended portion
15 for identifying the kinds of power supply circuits •
protrudes from the surface of the surrounding wall 13, so
that the strength of the extended portion . 15 can be
maintained compared to when the extended portion 15 is
formed separately from the surrounding wall 1.
Moreover, the extended portion 15 protrudes inward
from the inner surface of the surrounding wall 13. Thus,
the plug 1 is not scaled up compared to when the extended
portion 15 is formed at an outer portion of the surrounding
wall 13.
Furthermore, the extended portion 15 formed at the
inner surface of the surrounding wall 13 is disposed at the
surface opposite to the reference surface (inner surface of
upper wall) of the surrounding wall 13. Therefore, the
distance between the extended portion 15 and the plug pins
12 can increase compared to when the extended portion 15 is
disposed at the reference surface, and this enables easy
fabrication of the plug 1. The position, the shape and the
number of the extended portion are not limited to those of
the above, embodiment, and can be changed as long as the
kinds of power supply circuits as power supply sources can
be identified.
In the plug 1 depicted in Figs. 5A to 5D, the shape of
the surrounding wall 13 is partially changed by forming the
extended portion 15 protruding inward from the inner surface
of the surrounding wall 13 depending on the kinds of power
supply circuits. However, the shape of the surrounding wall
13 can be partially changed by forming an extended portion
16 protruding outward from the outer surface of the
surrounding wall 13, as shown in Fig. 6A. Fig. 6A shows a
front view of the plug 1 used for an SELV circuit. The
extended portion 16 shown in Fig. 6A protrudes outward from
a lower left portion of the surrounding wall 13.
In the DC outlet 2 used for an SELV circuit which •
corresponds to this plug l, an identifying groove (not
shown) extends outward from the insertion groove.27, and the
extended portion 16 is adapted to be fitted in the
identifying groove. Meanwhile, the plug 1 used for an ELV
circuit is not provided with the extended portion 16, and
the DC outlet 2 used for an ELV circuit also has no
identifying groove.
Therefore, the plug 1 used for an ELV circuit can be
connected to both of the DC outlet 2 used for an ELV circuit
and the DC outlet 2 used for an SELV circuit, whereas the
plug 1 used for an SELV circuit can be connected only to the
DC outlet 2 used for an SELV circuit. When the extended
portion 16 protrudes outward from the outer surface of the
surrounding wall 13, a apace between the plug pins 12 and
the surrounding wall 13 does not decrease, which enables
easy fabrication of the plug 1.
The position, the shape and the number of the extended
portion 16 are not limited to those in the above-described
embodiment. The extended portion 16 may protrude outward
from the lower portion of the left surface of the
surrounding wall 13 as shown in Fig. 6B, or from the right
portion of the lower surface of the surrounding wall 13 as
shown in Fig. 6C or, the extended portion 16 may protrude
outward from the lower portion of the right surface of the
surrounding wall 13 as depicted in Fig. €D.
In addition, the shape of the surrounding wall 13 may-
be changed so as to increase an area surrounded by the
surrounding wall 13 by forming an enlarged portion 17,
instead of the extended portion 15 or 16, at a part of the
surrounding wall 13, as can be seen from Fig. 6E. In that
case, the space between the plug pins 12 and the surrounding
wall 13 does hot decrease, which enables easy fabrication of
the plug 1.
The shapes of the plug receiving portion 25 and the
insertion groove 27 of the DC outlet 2 are also changed in
accordance with the shape of the surrounding wall 13 of the
plug l of this embodiment. The shapes of the plug receiving
portion 25 and the insertion groove 27 of the socket 2 are
described in PCT Application No. PCT/IB2010/001892 filed by
the present Applicant, the contents of which are
incorporated herein by reference.
(Fourth Embodiment)
A fourth embodiment of the present invention will be
descxibed with reference to rigs. 5 to 8. In the
description of the fourth embodiment, like reference
numerals will be used for the same components as those of
the above-described embodiments, and redundant description .
thereof will be omitted.
As shown in Figs. 8 to 11, a plug main body 11 of a
plug l of this embodiment is partitioned into two parts in
the front-rear direction. The plug main body 11 has a size
that can be gripped by a hand and includes: a box-shaped
front case 30 made of synthetic resin and having an open
rear portion; and a box-shaped rear case 31 made of
synthetic reein and having an open front portion, which, is
fixed by screws 32 to the front case 30 so as to block the
rear opening of the front case 30. The plug main body 11
accommodates therein a contactor block 34. In the contactor
block 34, an electrode block 36 having a terminal plate 37
and two round bar-shaped plug pins 12 to which power from
the DC outlet 2 is supplied is supported by an inner case 35
made of synthetic resin.
The two plug pins 12 protrude frontward from the front
surface of the plug main body 11, i.e., the front surface of
the front case 30 (the surface facing the DC outlet 2). The
surrounding wall 13 is formed as a unit with the front case '
30 so as to protrude therefrom and surround the two plug
pins 12.
The surrounding wall 13 of the front case 30 has a
substantially quadrangular shape viewed in the plug
insertion direction (from the front side), and the central
portion of the front surface of the inner case 35 is exposed
through the inner portion of the surrounding wall 13. The
two plug pins 12 are arranged along the reference surface
corresponding to one inner surface (e.g, the upper inner
surface) of the surrounding wall 13 and offset closer to the
reference surface than to the inner surface (the lower inner
surface) opposite to the reference surface. "Moreover, in
this embodiment, a distance between the plug pins 12 and the
upper inner surface of the surrounding wall 13 is 1/2 or .
less of a distance between the plug pins 12 and the lower
inner surface of the surrounding wall 13, so that the plug
pins 12 offset close to the upper side can be easily
recognized. Further, a distance between the front surface
of the plug main body 11 and the leading end of the
surrounding wall 13 is set to be slightly larger than a
distance between the front surface of the plug main body 11
and the leading ends of the plug pins 12.
The inner case 35 has a substantially box shape having
an open rear surface and is partitioned into a plurality of
compartments 35a by a partition wall. The electrode block
36 is attached to each of the compartments 35a. A
protruding table 35b is formed as a unit with the inner case
35 and protrudes frontward from the center of the front
surface of the inner case 3 5 to be inserted into the
surrounding wall 13 of the front case 30. The protruding
table 35b has insertion through holes 35c opened
correspondingly to the compartments 35a, so that the leading
ends of the plug pins 12 protrude frontward through the
insertion through holes 35c.
The terminal plate 37 of the electrode block 36
includes: a fixing piece 37a having an opening for fixing an
axial portion 12a formed at the rear end portion of the plug
pin 12,- and a terminal piece 37b extending rearward from one
side of the fixing piece 37a, the fixing piece 37a and the
terminal piece 37b being formed as a unit. A core of the
electric wire 14 from the load device is clamped and fixed
between a terminal screw 38 and the terminal piece 37b. The
axial portions 12a of the plug pins 12 are fixed to the
openings of the fixing pieces 37a and, then, the plug pins
12 are inserted into the insertion through holes 35c from
the rear portions of the compartments 35a of the inner case
35. Next, fixing screws 39, e.g., tapping screws, are .
inserted into insertion through holes 37c and coupled to
fixing holes 35d of the inner case 35. As a consequence.
the electrode block 36 is fixed to the inner case 35. When
the electrode block 36 is fixed to the inner case 35, the
leading end portions of the plug pins 12 protrude frontward
through the insertion through holes 35c of the inner case 35.
In addition, an electric wire insertion through hole
31A is opened at the rear surface of the,plug main body 11,
i.e., the rear case 31, and the electric wire 14 of the load
device which is inserted through the electric wire insertion
through hole 31a is fixed by screws to the terminal plate 37
of the electrode block 36. When the contactor block 34 is
accommodated in the front case 30, the rear case 31 is
attached to the rear surface of the front case 30. By
coupling the front case 30 and the rear case 31 by screws 32,
the plug main body 11 is formed. When the assembly is
completed, the plug pins 12 are positioned at the inner
portion of the surrounding wall 13. Besides, an electric
wire holding plate 40 for holding the electric wire 14 is
fixed by screws 41 to the rear portion of the rear case 31
and reduces tension applied to the connection portion
between the electric wire 14 and the terminal plate 37.
When the plug 1 is connected to the DC outlet 2, the DC
power is supplied to the load device v1A the electrode block
36 and the electric wire 14.
In case the plug main body 11 is partitioned into two
parts horizontally or vertically, the surrounding wall 13 is
not formed as a unit therewith and this decreases strength
of the surrounding wall 13. Thus, when the plug main body
11 is attached to or detached from the DC outlet 2, the
"surrounding wall 13 may be broken. However, in this
embodiment, the plug main body 11 is formed by coupling the

front case 30 having the surrounding wall 13 and the rear
case 31. Hence, the surrounding wall 13 can be formed as a
unit with the plug main body 11, which increases the
strength of the surrounding wall 13.
(Fifth Embodiment)
A fifth embodiment of the present invention will be
described with reference to Figs. 12A and 12B. In the
description of the fifth embodiment, like reference numerals
will be used for the same components as those of the above-
described embodiment, and redundant description thereof will
be omitted.
As illustrated in Figs. 12A and 12B, the plug main
body 11 includes: an inner case 11a (fixing portion) for
fixing the two plug pins 12; and an outer case l1B (housing)
formed at an outer side of the inner case 11a by a secondary
molding and having a surrounding wall 13 formed as a unit
therewith, the outer case l1B being made of synthetic resin.
Terminals 112a electrically connected to the plug pins 12
protrude outward from the rear portion of the inner case 11a,
and the core of the electric wire 13 is caulk-fixed to the
terminals 112a. The terminals 112a are covered by resin
when the outer case l1B is formed by the secondary molding,
so that a charging portion is not exposed. The plug main
body 11 can be simply assembled by forming the outer case
l1B having the surrounding wall 13 at an outer portion of
the inner case 11a for fixing the plug pins 12. Further, the
inner case lla fixes a plurality of (two in this embodiment)
plug pins 12 spaced from each -other at a predetermined
interval while maintaining insulation property. In this
embodiment, the plug pins 12 are supported by the inner ease
11a made of synthetic resin. However, the inner case 11a
may not be made of synthetic resin as long as the plug pins
12 are insulated from each other.
The plug 1 descried in the aforementioned embodiments
has no ground electrode pin. However, as shown in Fig. 13,
a ground electrode pin 19 may be provided in addition to the
plug pins 12. Although Fig. 13 shows that the ground
electrode pin is provided at the plug 1 of the fifth .
embodiment, the ground electrode pin 19 may be provided at
the plug 1 of the other embodiments. In the plug 1 of Pig.
13, the ground electrode pin 19 is positioned at the apex of
an isosceles triangle having the base connecting the two
plug pins 12 serving as voltage electrodes. However, the
position of the ground electrode pin 19 is not limited to
that shown in Fig. 13.
While the invention has been shown and described with
respect to the embodiments, it will be understood by those
skilled in the art that various changes and modification may
be made without departing from the scope of the invention as
defined in the following claims.
We Claim:
1. A plug which is adapted to be connected to a direct
current (DC) outlet for supplying a DC power thereto, the DC
outlet having an insertion groove formed around a plurality
of pin insertion holes opened at a front side and having
therein pin-receiving pieces corresponding to the pin
insertion holes, the plug comprising:
a plurality of round bar-shaped plug pins which
protrudes from a front surface of a plug main body, the plug
pins being adapted to be connected the pin-receiving pieces •
through the pin insertion holes of the DC outlet and to be
supplied with power from the DC outlet; and
a surrounding wall which protrudes from the front
surface of the plug main body to surround the plug pins, the
surrounding wall being adapted to be inserted into the
insertion groove of the DC outlet,
wherein the surrounding wall is formed in a
substantially quadrangular shape, viewed from a front side
thereof, and the plug pins are arranged along a reference
surface corresponding to one inner surface of the
surrounding wall and offset closer to the reference surface
than to an inner surface opposite to the reference surface.
2. The plug of claim 1, wherein the shape of the
surrounding wall, viewed from the front side, is partially
changed depending on the kinds of a supply voltage or a
supply current.
3. The plug of claim 2, wherein the shape of the
surrounding wall viewed from the front side is changed such
that an area of a portion surrounded by the surrounding wall
compared to a case that the surrounding wall has the
substantially quadrangular shape viewed from the front side.
4. The plug of claim 3, wherein the shape of the
surrounding wall viewed from the front side is partially
changed by cutting at least one corner of the substantially
quadrangular shape of the surrounding wall depending on the
kinds of the supply voltage or supply current.
5. The plug of claim 2, wherein a portion of the
surrounding wall whose shape is changed depending on the
kinds of the supply voltage or supply current is closer to .
the inner surface opposite to the reference surface than the
reference surface.
6. The plug of claim 2, wherein the shape of the
currounding wall viewed from the front aide is changed cuch
that an area of a portion surrounded by the surrounding wall
is increased as compared with a case that the surrounding
wall has the substantially quadrangular shape viewed from
the front side.
7. The plug of claim 2 or 4, wherein the shape of the
surrounding wall viewed from the front side is partially
changed by forming an extended portion protruding from a
surface of the surrounding wall.
8. The plug; of claim 7, wherein the extended portion
extends inward from an inner surface the surrounding wa11.
9. The plug of claim 7, wherein the extended portion is
disposed closer to a surface opposite to the reference
surface of the surrounding wall.
10. The plug of claim 7, wherein the extended portion
extends outward from an outer surface of the surrounding
wall.
11. The plug of claim 1, wherein the shape of the
surrounding wall, viewed from the front side, is partially
changed depending on the kinds of a power supply circuit
serving as a power supply source.
12. The plug of claim 11, wherein the shape of the
surrounding wall viewed from the front side is changed such
that an area of a portion surrounded by the surrounding wall
compared to a case that the surrounding wall has the
substantially quadrangular shape viewed from the front side.
13. The plug of claim 12, wherein the shape of the
surrounding wall viewed from the front side is partially
changed by cutting at least one corner of the substantially
quadrangular shape of the surrounding wall depending on the
kinds of the power supply circuit.
14. The plug of claim 11, wherein a portion of the
surrounding wall whose shape is changed depending on the
kinds of the power supply circuit is closer to the inner
surface opposite to the reference surface than the reference
surface.
15. The plug of claim 11, wherein the shape of the
surrounding wall viewed from the front side is changed such
that an area of a portion surrounded by the surrounding wall
is increased as compared with a case that the surrounding
wall has the substantially quadrangular shape viewed from
the front side.
16. The plug of claim 11 or 13, wherein the shape of the
surrounding wall viewed from the front side is partially
changed by forming an extended portion protruding from a
surface of the surrounding wall.
17. The plug of claim 16, wherein the extended portion
extends inward from an inner surface the surrounding wall.
18. The plug of claim 7, wherein the extended portion is
disposed closer to a surface opposite to the reference .
surface of the surrounding wall.
19. The plug of claim 7, wherein the extended portion
extends outward from an outer surface of the surrounding
wall.
20. The plug of claim 11, wherein the shape of the
surrounding wall viewed from the front side is partially
changed only when the power supply circuit is a safety extra
low voltage (SELV) circuit.
21. The plug of claim 1, wherein the plug pins of the plug
include a ground pin.
22. The plug of claim 21, wherein the ground pin is
provided offset closer to the inner surface opposite to the
reference surface.
23. The plug of any one of claims 1, 2, 11 and 21, wherein
the plug main body indludes: a box-ehaped front case having
an open rear portion, the surrounding wall being provided on
a front surface of the front case; and a box-shaped rear
case having an open front portion, the rear case being fixed
to the front case so as to block the rear opening of the
front case, and wherein the plug pins are received in the
front and the rear case.
24. The plug of any one of claims 1, 2, 11 and 21, wherein
the plug main body includes: a fixing portion for fixing the
plug pins; and a housing formed at an outer side of the
fixing portion by a secondary molding, the housing being
made of synthetic resin, and wherein the surrounding wall is
formed as a unit with the housing.

ABSTRACT

A plug is adapted to be.
connected to a DC outlet to supply a DC
power to the plug. The plug includes
plug pins and a substantially quadrangular
- shaped surrounding wall for surrounding
the plug pins. The DC outle
includes: an outlet main body having an
outlet unit to which the plug is adapted
to be connected. The outlet unit includes
a plug- receiving portion having
pin- inserting holes into which the plug
pins are inserted; an insertion groove
formed to surround a periphery of the
plug-receiving portion, the insertion
groove being adapted to receive the surrounding
wall; and pin- receiving pieces
for being connected with the plug pins
that are respectively inserted through the
pin- receiving holes. Two pin-receiving
boles corresponding to the pin-receiving
pieces are arranged along a reference
side of the plug- receiving portion and
offset closer to the reference side than
an opposite side to the reference side,