Field of the Invention
The present invention relates to a screw terminal for
supplying electric power from an electrical wire to a plug
in a state where round plug pins of the plug and the
electrical wire are connected to the screw terminal, and a
receptacle including the same.
Background of the Invention
As for a screw terminal, there has been known one
including a plug-pin receiving member for receiving plug
pins of a plug and a frame-shaped pillar member (electrical
wire connection unit) into which an electrical wire is
inserted. In such screw terminal, a screw member screwed
into the pillar member is firmly tightened, and the
electrical wire is firmly pressed against one end of the
pillar member (see, e.g., Japanese Patent Application
Publication No. 2000-243473) .
Specifically, as shown in Fig. 13A, a tapped hole 212
into which a screw member 220 is screwed is provided at a
surrounding wall 211 of a pillar member 210. A holding part
231 of a plug-pin receiving member 230 is inserted into the
surrounding wall 211 to face the tapped hole 212 in an up-
down direction Z.
By firmly tightening the screw member 220 in a state
where an electrical wire WR is inserted in the surrounding
wall 211 to pass therethrough in a front-rear direction X,
the electrical wire WR is held between an end portion 221 of
the screw member 220 and the holding part 231.
However, the screw terminal 200 including the pillar
member 210 and the plug-pin receiving member 230 is
disadvantageous in that the pillar member 210 and the plug-
pin receiving member 230 separately provided increase the
number of components and also increases the number of
assembly operations. To that end, it is considered to form
the pillar member 210 and the plug-pin receiving member 230
as one unit. For example, as shown in Fig. 13B, when the
pillar member 210 and the plug-pin receiving member 23 0 are
formed as one unit, the screw terminal 200 has a complicated
shape. Accordingly, a complicated bending process is
required, which makes it difficult to manufacture the screw
terminal 200. As a result, the costs for the screw terminal
and the receptacle including the same are increased.
Summary of the Invention
In view of the above, the present invention provides a
screw terminal having a plug-pin receiving member (plug-pin
receiver) and an electrical wire connection unit formed as
one unit with ease and a receptacle including the same.
In accordance with an aspect of the present invention,
there is provided a screw terminal including: an electrical
wire connecting portion to which an electrical wire is
connected by a screw member; and a plug-pin receiver for
gripping a plug pin of a plug. The electrical wire
connecting portion and the plug-pin receiver are made from a
single metal plate. The plug-pin receiver has a tubular
shape extending along an insertion direction of the plug pin,
and the electrical wire connecting portion is formed as a
frame body opened along the plug-pin insertion direction.
The screw terminal further includes a connecting
portion for connecting the plug-pin receiver and the frame
body, wherein the plug-pin receiver has a substantially
cylindrical shape, and the electrical wire is firmly pressed
against an inner peripheral surface of the frame body by
tightening the screw member into the frame body.
With such configuration, the plug-pin receiver and the
electrical wire connecting portion are made from a single
metal plate and thus can be formed as one unit. Further,
since the plug-pin receiver and the electrical wire
connecting portion are formed simply by bending, even if the
plug-pin receiver and the electrical wire connecting portion
are formed as one unit, the manufacturing process thereof
can be simplified.
The frame body may have a tapped hole into which the
screw terminal is screwed, and the tapped hole is formed by
burring.
With such configuration, the tapped hole is formed by
burring, so that the number of components of the screw
terminal can be reduced compared to a case where the tapped
hole is formed separately from the frame body. In addition,
the area of the inner surface of the tapped hole into which
the screw member is screwed can be increased compared to a
case where the tapped hole is formed in the frame body
within a thickness thereof.
The frame body may have a portion where side end
portions of the metal plate are overlapped, and a tapped
hole into which the screw member is screwed is formed at the
portion.
With such configuration, the tapped hole is formed at
the portion of the frame body where the side end portions of
the metal plate are overlapped. Therefore, even if the
burring for forming the tapped hole is omitted, it is
possible to ensure the area of the inner surface of the
tapped hole into which the screw member is screwed.
The plug-pin receiver may have a plug-pin holding part
which determine a minimum diameter of an inner diameter of
the plug-pin receiver and a tip end part which extend from
the plug-pin holding part along the plug-pin insertion
direction, the tip end part having a gradually increased
inner diameter.
With such configuration, the plug-pin receiver has the
tip end part, so that it is possible to suppress arc
generated between the plug pin and the" plug-pin receiver
from affecting other components of the receptacle compared
to a case of the plug-pin receiver without the tip end part.
The tip end part of the plug-pin receiver may have a
higher melting point than that of portions other than the
tip end part.
The tip end part of the plug-pin receivers receives
the arc, so that the tip end part is easily melted by the
arc compared to the other parts. In the present invention,
the tip end part of the plug-pin receiver has a higher
melting point compared to the other parts and thus can be
prevented from being melted by the arc.
The plug-pin receiver may have a plurality of gripping
pieces formed by slits extending along the plug-pin
insertion direction.
With such configuration, the plug-pin receiver is
easily elastically deformed compared to the plug-pin
receiver having no slits. Therefore, the elasticity of the
plug-pin receiver can be ensured.
The single metal plate may include a substantially
quadrangular portion forming the plug-pin receiver and
another substantially rectangular portion forming the frame
body, the plug-pin receiver and the frame body being formed
by bending the corresponding substantially quadrangular
portions, respectively.
The substantially quadrangular portion of the single
metal plate which forms the plug-pin receiver may have a
plurality of slits extending along the plug-pin insertion
direction.
In accordance with another aspect of the present
invention, there is provided a receptacle including the
screw terminal described above.
With such configuration, the plug-pin receiver of the
screw terminal is formed in the tubular shape and thus can
be scaled down compared to the conventional plug-pin
receiver. Hence, the receptacle can also be scaled down.
The receptacle may further include a peripheral wall
insertion groove formed into a substantially quadrangular
shape when viewed from the plug-pin insertion direction, a
peripheral wall of the plug surrounding the plug pin being
adapted to be inserted into the peripheral wall insertion
groove; and a plug receiving part surrounded by the
peripheral wall insertion groove and formed into a
substantially quadrangular shape when viewed from the plug-
pin insertion direction. The plug receiving part is
provided with a plurality of plug-pin insertion holes
disposed along a reference side that is one side of- an outer
periphery of the plug receiving part, each of the plug-pin
insertion holes having a circular shape. The plug-pin
insertion holes are disposed closer to the reference side
than to an opposite side of the outer periphery of the plug
receiving part in a direction perpendicular to the reference
side.
With such configuration, the peripheral wall insertion
groove has a substantially quadrangular shape, so that the
insertion orientation of the peripheral wall of the plug is
restricted compared to a case where the peripheral wall
insertion groove has a round shape. Accordingly, an
operator can easily recognize the plug insertion orientation,
which is convenient in use. Further, the plug-pin insertion
holes are arranged offset closer to the reference side than
to the opposite side. Therefore, the reverse insertion of
the plug into the receptacle can be prevented without
forming a separate structure for preventing the reverse
insertion at the peripheral wall insertion groove and the
peripheral wall of the plug. Hence, the scaling up of the
receptacle can be suppressed compared to a receptacle having
a separate structure for preventing the reverse insertion.
In accordance with the present invention, it is
possible to provide a screw terminal having a plug-pin
receiver and an electrical wire connecting portion formed as
one unit with ease and a receptacle including the screw
terminal.
Brief Description of the Drawings
The 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 to 1C show a receptacle in accordance with an
embodiment of the present invention, wherein Fig. 1A is a
perspective view showing a perspective structure of the
receptacle, Fig. 1B is a plan view showing a plan structure
of the receptacle seen from the front, and Fig. XC is a plan
view showing a plan structure of the receptacle seen from
the rear;
Fig 2 is a perspective view showing an exploded
perspective structure of the receptacle;
Figs. 3A to 3D show a screw terminal, wherein Fig. 3A
is a perspective view showing an exploded perspective view
of the screw terminal, Fig. 3B is a plan view showing a plan
structure of the screw terminal seen from the rear. Fig. 3C
is a plan view showing a plan structure of the screw
terminal seen from the front, and Fig, 3D is a cross
sectional view showing a cross sectional structure of the
plug-pin receiver;
Figs. 4A to 4D are schematic perspective views showing
processes of manufacturing a screw terminal by using a metal
plate,-
Fig. 5 is a cross sectional view showing a cross
sectional structure of the receptacle;
Figs. 6A and 6B show a plug inserted into the
receptacle, wherein Fig. 6A is a perspective view showing a
perspective structure of the plug, and Fig. 6B is a plan
view showing a front structure of the plug;
Figs. 7A and 7B show the receptacle and the plug,
wherein Fig. 7A is a perspective view showing the insertion
of the plug into the receptacle, and Fig. 7B is a plan view
showing a plan structure of the receptacle and the
positional relationship between plug-pin insertion holes and
plug pins in case of reversely inserting the plug into the
receptacle,-
Figs. 8A to 8C show a plug-pin receiving member and
plug pins, wherein Fig. 8A is a cross sectional view showing
a cross sectional structure in a state where the plug pins
are inserted into the plug-pin receiver, Fig. 8B is a plan
view showing a plan structure of the plug-pin receiver in a
state where the plug pins are inserted into the plug-pin
receiver, and Fig. 8C is a cross sectional view showing a
cross sectional structure of the plug-pin receiver in a
state where the plug pins are disconnected from the plug-pin
receiver;
Figs. 9A and 9B are plan views showing a front
structure of the receptacle installed on a wall surface;
Fig. 10 is a perspective view showing a perspective
structure of a receptacle in accordance with another
embodiment of the present invention;
Figs. 11A and 11B are perspective views showing an
exploded perspective structure of a pillar member of the
receptacle in accordance with another embodiment of the
present invention;
Figs. 12A to 12D are plan views showing a plan
structure of a receptacle as a comparative example; and
Fig. 13 shows a conventional screw terminal, wherein
Pig. 13A is a perspective view showing an exploded
perspective structure of the screw terminal, and Fig. 13B is
a perspective view showing another perspective structure of
the screw terminal.
Detailed Description of the Embodiment
A receptacle in accordance with an embodiment of the
present invention will be described in detail with reference
to Figs. 1A to 9B, in which the receptacle is exemplified as-
a wall-embedded DC receptacle.
A configuration of the receptacle 10 will be described
with reference to Figs. 1A to 5. Hereafter, a long side
direction of the receptacle 10 is defined as "a left-right
direction Y", and a short side direction thereof is defined
as "an up-down direction 2." A direction perpendicular to
both the left-right direction Y and the up-down direction Z
is defined as "a front-rear direction X." In this
embodiment, the front-rear direction X corresponds to the
plug-pin insertion direction in which plug pins 44 (see Fig.
6) are inserted into the receptacle 10.
As shown in Fig. 1A, a body 11 and a cover 12, which
are made of a synthetic resin by injection molding,. are
fixed with each other by a pair of metal assembly frames 13
to thereby form a body of the receptacle 10 with a
substantially rectangular parallelepiped shape.
The receptacle 10 is designed to have a size
conforming to Japanese Industrial Standards (see JIS C 8303) .
Namely, the receptacle 10 is formed to have a size of one
module dimensions (hereinafter, referred to as "a single
module dimensions"), in which three receptacles .with the
single module dimensions can be accommodated in a mounting
frame of a large rectangular string wiring accessory (see
JIS C 8375) . Further, a front surface 12a of the cover 12
is formed to have a width HI in the left-right direction Y
approximately the same as a width of the mounting frame with
a rectangular shape in the left-right direction Y.
As shown in Fig. IB, the front surface 12a of the
cover 12 includes: a peripheral wall insertion groove 14
recessed backwardly from the front surface 12a; and a plug
receiving part 15 surrounded by the peripheral wall
insertion groove 14. The peripheral wall insertion groove
14 is formed to have a substantially quadrangular shape
whose two lower corners are cut away viewed from its front
side. A front surface 15e of the plug receiving part is
formed flush with the front surface 12a of the cover 12.
The peripheral wall insertion groove 14 includes: a
pair of first insertion grooves 14a extending along the up-
down direction Z; a pair of second insertion grooves 14b
extending along the left-right direction Y; and a pair of
inclination grooves 14c connecting the respective first
insertion grooves 14a to the lower second insertion groove
14b located. The inclination grooves 14c are provided below
the center line Ll of the plug receiving part 15 in the up-
down direction Z (at the middle of the plug receiving part
15 in the up-down direction Z) . Further, at a center
portion of the lower second insertion groove 14b in the
left-right direction Y, there is provided an extension
groove I4d extending upwardly from the lower second
insertion groove 14b.
The plug receiving part 15 has first sides 15a
corresponding to the first insertion grooves 14a; second
sides 15b corresponding to the second insertion grooves 14b;
inclination sides 15c corresponding to the inclination
grooves 14c; and a recessed side 15d corresponding to the
extension groove 14d. Each of the inclination side 15c is
formed to extend in parallel to an opposite side 14e facing
to the inclination side 15c, which constitutes a part of the
inclination groove 14c.
Above the center position L1 of the plug receiving
part 15, a pair of plug-pin insertion holes 16 with a
circular shape viewed from its front side is provided, which
are extended through the plug receiving part in the front-
rear direction X. Namely, supposed that the upper second
side 15b is defined as a reference side KL, the plug-pin
insertion holes 16 are disposed closer to the reference side
KL than the lower second side 15b.
Meanwhile, the peripheral wall insertion groove 14 is
formed to have different shapes depending on a type of a
power supply circuit (not shown) serving as a power supply
source. The power supply circuit is interposed between a DC
power supplying section and the receptacle 10, and, for
example, installed in a power distribution panel (not shown).
The above power supply circuit has at least two kinds
of circuits such as an ELV circuit (Extra-Low Voltage
circuit) and a SELV circuit (Safety Extra-Low Voltage
circuit) . The ELV and the SELV circuit are specified as
IEC60950-1 and IEC60335-1 by IEC standards, respectively.
Electrical appliances, such as information equipment
and lighting apparatuses, have different internal insulation
structures depending on the ELV or the SELV circuit. In
other words, an electrical appliance based on the ELV
circuit requires a strict insulation structure, that is,
adopts a double insulation structure or a reinforced
insulation structure. On the other hand, an electrical
appliance based on the SELV circuit may not adopt the double
insulation structure or the reinforced insulation structure,
thereby requiring more simplified insulation structures as
compared with the electrical appliance according to the ELV
circuit.
In the case where the electrical appliance based on
the ELV circuit is connected to the receptacle 10 for the
SELV circuit, there is no problem because the electrical
appliance has the strict insulation structure. On the other
hand, in the case where the electrical appliance based on
the SELV circuit is connected to the receptacle for the ELV
circuit, there is a problem such that the electrical
appliance may be destroyed when a hazardous voltage is
applied thereto because the electrical appliance has the
simplified insulation structure. Accordingly, the
receptacles 10 and the plugs 30 (see Fig. 6), for the ELV
circuit and for the SELV circuit, need to be distinguished
from each other. Particularly, it is required to prevent
the electrical appliance based on the SELV circuit from
being connected to the receptacle for the ELV circuit by
mistake.
Accordingly, in the present embodiment, as the cover
12 for the SELV circuit, the extension groove 14d is
provided in the peripheral wall insertion groove 14. On the
other hand, as a cover for the ELV circuit, the extension
groove 14d is not provided in a peripheral wall insertion
groove. Further, a plug 40 of the electrical appliance for
the SELV circuit has a rib 45a in its peripheral wall 45.
On the other hand, a plug of the electrical appliance for
the ELV circuit has no rib 45a described above. Accordingly,
the plug for the ELV circuit can be inserted into the
peripheral wall insertion groove 14 for the SELV circuit,
whereas the plug for the SELV circuit can not be inserted
into the peripheral wall insertion groove for the ELV
circuit. Accordingly, it can be prevented that the
electrical appliance based on the SELV circuit is connected
to the receptacle for the ELV circuit by mistake.
As shown in Fig. 1C, two electrical wire insertion
holes 11b through which an electrical wire (not shown)
inserted are formed through a bottom wall 11a of the body 11
in the up-down direction Z. Moreover, a portion of the
bottom wall 11a where the electrical wire insertion holes
11b are formed protrudes rearward from the bottom wall 11a.
As shown in Fig. 2, two screw terminals 17 are
accommodated in the inner space defined by the body 11 and
the cover 12. Specifically, the body 11 has two terminal
seat portions 11c adjacent to each other in the left-right
direction Y. The terminal seat portions 11c penetrate a
sidewall 11d of the body 11 in the up-down direction Z and
are opened at the front side. The screw terminals 17 are
received in the terminal seat portions 11c.
The structure and the manufacturing process of the
screw terminal 17 will be described with reference to Figs.
3A to 4D. In Figs. 3B and 3C, a screw member 22 is omitted.
As shown in Fig. 3A, the screw terminal 17 includes a
pillar member (electrical wire connection unit) 20 for
connecting an electrical wire, a plug-pin receiver 21 for
gripping the plug pin 34 of the plug 30, and the screw
member 22 screwed into the pillar member 20. A single
connecting portion 28 for connecting the pillar member 20
and the plug-pin receiver 21 is provided between the pillar
member 20 and the plug-pin receiver 21. The screw terminal
17 of the present embodiment is formed by pressing a single
copper plate having a thickness which ensures the elasticity
of the plug-pin receiver 21.
The plug-pin receiver 21 has a substantially
cylindrical part 21a extending from the front end portion of
the connecting portion 28 in the front-rear direction X.
The cylindrical part 21a is provided with three slits 23
extending in the front-rear direction X, so that the
cylindrical part 21a is configured to have four gripping
pieces 24. Specifically, when viewed from the front, the
cylindrical part 21a has a substantially circular shape
formed by combining the four arch-shaped gripping pieces 24
(see Fig. 3C).
As shown in Fig. 3B, the pillar member 20 is formed by
a surrounding wall having a rectangular shape whose long
side is extended in the left-right direction Y when viewed
from the rear. A screw fixing portion 25 into which the
screw member 22 is screwed is formed at an upper wall 20a of
the pillar member 20 by burring. The screw fixing portion
25 has a substantially cylindrical shape extending downward
from the upper wall 20a. Further, a female thread is formed
at the screw fixing portion 25 by screw processing.
As shown in Fig. 3C, the plug-pin receiver 21 and the
pillar member 20 are overlapped with each other in the up-
down direction Z. In other words, the plug-pin receiver 21
is received in the pillar member 20 in the up-down direction
Z. Accordingly, the screw terminal 17 can be scaled down
compared to a case where the plug-pin receiver and the
pillar member are offset when viewed in the. up-down
direction Z.
As shown in Fig. 3D, the front side of the plug-pin
receiver 21 is provided with a plug-pin holding part 24a
adapted to make contact with and hold the plug pin 34 (see
Fig. 6) and an arc receiving part 24b extending forwardly
from the plug-pin holding parts 24a. The plug-pin holding
part 24a determines a minimum diameter Dmin of an inner
diameter D of the plug-pin receiver 21. The arc receiving
part 24b has an inclined surface 24c with a larger inner
diameter as it goes forward. When the plug pin 34 is
inserted into the plug-pin receiver 24, the plug pin 34 is
guided to the plug-pin holding part 24a by the inclined
surface 24c. Accordingly, the plug pin 34 can be easily
inserted into the plug-pin receiver 21. Besides, due to the
contact between the inclined surface 24c and the plug pin 34,
the gripping pieces 24 can be easily elastically deformed
away from each other.
Here, the arc receiving part 24b is formed to have a
higher melting point than that of the other parts of the
plug-pin holding part 24a. Specifically, the arc receiving
parts 24b are plated with nickel tungsten.
Fig. 4A shows a sheet of metal plate M. The sheet is
punched to form a developed shape of the pillar member 20,
the plug-pin receiver 21 and the connecting portion 28 (see
Fig. 4B) . Further, the pillar member 20 is provided with
the screw fixing portion 25, and the plug-pin receiver 21 is
provided with the slits 23 and the gripping pieces 24. As
shown in Fig. 4C, each of the gripping pieces 24 is bent
into an arch shape by bending work, and opposite side ends
26 of the plug-pin receiver 21 (cylindrical part 21a) are
bent into a circle shape around the connecting portion 28 as
indicated by arrows Rl. As a result, the plug-pin receiver
21 is made into a substantially cylindrical shape as shown
in Fig. 4D. In the same manner, opposite side end portions
27 of the pillar member 20 are bent by bending work around
the connecting portion 28 as indicated by arrows Rl. As a
consequence, a frame body having a shape of a rectangular
surrounding wall is formed. Here, the opposite side ends 26
of the plug-pin receiver 21 are separated from each other by
a gap. Furthermore, the opposite side end portions 27 of
the pillar member 20 are separated from each other by a gap
while facing each other.
Position of the screw terminal 17 in the receptacle 10
will be described with reference to Fig. 5.
The pillar member 20 is received in the body 11 and is
positioned below the cover 12. In other words, the pillar
member 20 is located below the peripheral wall insertion
groove 14.
Further, the plug-pin receiver 21 has a portion
protruding frontward beyond the body 11 to be received in
the cover 12. The plug-pin receiver 21 is received within
an area surrounded by the peripheral wall insertion groove
14 (namely, the area corresponding to the plug receiving
part 15 in the up-down direction Z and the left-right
direction Y) and is partially overlapped with the peripheral
wall insertion groove 14 in the front-rear direction X.
Hereinafter, connection and disconnection of the
electrical wire to and from the receptacle 10 will be
described.
When the electrical wire is connected to the
receptacle 10, the electrical wire is inserted into the
electrical wire insertion hole 11b of the body 11 and then
into the pillar member 20. In such state, the screw member
22 is firmly tightened, so that the electrical wire is
clamped between a lower end surface 22a of the screw member
22 and an inner peripheral surface 20c of a lower wall 20b
(see Figs. 3A and 3B) . As a consequence, the electrical
wire is connected to the screw terminal 17, and the
connection of the receptacle 10 and the electrical wire is
completed. On the other hand, when the electrical wire is
disconnected from the receptacle 10, the force to clamp the
electrical wire is reduced by loosening the screw member 22.
Then, the electrical wire is pulled out rearward and
disconnected from the receptacle 10.
Hereinafter, with reference to Figs. 6A to 7B, a
configuration of the plug 30 will be described, and
connection and disconnection structures of the plug 30 to
and from the receptacle 10 will be described with reference
to Figs. 8A to 8C.
As shown in Fig. 6A, the plug 30 includes a cable 32,
and a plug main body 31 connected to the cable 32. .The plug
main body 31 includes a surface 33 adapted to be opposite to
the plug receiving part 15 (see Figs. 7A and 7B) in the
front-rear direction X; two round plug pins 34 extending
backwardly from the surface 33; and a peripheral wall 35
surrounding the plug pins 34 from outside. The peripheral
wall 3 5 has the same shape as the peripheral wall insertion
groove 14 (see Figs. 7A and 7B) . Further, rear ends of the
plug pins 34 are located slightly forward of a rear end
surface of the peripheral wall 35.
As shown in Fig. 6B, the plug pins 34 are positioned
above a center line L2 in the up-down direction Z of the
peripheral wall 35. Moreover, the plug pins 34 are arranged
along the left-right direction Y. The plug pins 34 include
a positive plug pin (e.g., left-hand side in Fig. 6B) and a
negative plug pin (e.g., right-hand side in Fig. 6B).
As shown in Fig. 7A, at the time when the plug 3 0 is
inserted into the receptacle 10, the peripheral wall 35 is
inserted into the peripheral wall insertion groove 14. Then,
the plug pins 34 are inserted into the plug-pin insertion
holes 16. The plug-pin insertion holes 16 include a
positive plug-pin insertion hole for inserting the positive
plug pin 34 and a negative plug-pin insertion hole for
inserting the negative plug pin 34.
As shown in Fig. 7B, when the plug 30 would be
reversely inserted into the receptacle 10, the plug pins 34
are positioned below the center line L1 of the plug
receiving part 15.
Accordingly, the plug pins 34 are brought into contact
with the front surface 15e of the plug receiving part 15,
thereby preventing the insertion of the plug 30 into the
receptacle 10.
The expression "reverse insertion" indicates a state
where the positive plug pin is inserted into the negative
plug-pin insertion hole and the negative plug pin is
inserted into the positive plug-pin insertion hole. When
the plug is reversely inserted, an inappropriate voltage is
applied to the plug pins 34, which may result in damage of
an electric appliance connected to the plug pins 34.
Even if the reverse insertion of the plug pins 34 into
the plug-pin insertion holes 16 is attempted, the reverse
insertion can be reliably prevented because the plug-pin
insertion holes 16 and the plug pins 34 are separated from
each other in the up-down direction Z.
As shown in Fig. 8A, when the plug pin 34 is inserted
into the plug-pin receiver 21, the plug-pin receivers 21 are
elastically deformed away from each other as indicated by
arrows Yl as a tip end part 34a of the plug pin 34 is moved
from the arc receiving parts 24 to the plug-pin holding part
24a. Specifically, the gripping pieces 24 opposed to each
other through the plug pins 34 in a diametric direction are
elastically deformed away from each other as shown in Fig.
8A. Then, the plug pins 34 are held by a recovery force of
the plug-pin receiver 21 (the recovery force of each
gripping piece 24) . Moreover, the plug pins 34 are held by
being in line contact with the four gripping pieces along
the circumferential direction thereof.
On the other hand, as shown in Fig. 8C, when the plug
30 is disconnected from the receptacle 10, the gripping
pieces 24 of the plug-pin receiver 21 are deformed to come
closer to each other by their recovery forces as indicated
by arrow Y2 as the tip end part 34a of the plug pin 34 is
moved from the plug-pin holding part 24a to the arc
receiving part 24b.
Further, when the plug pin 34 are pulled out from the
plug-pin receivers 21, the plug-pin receivers 21 return to
its initial state before the insertion of the plug pin 34.
When the plug pins 34 are moved from the plug-pin
holding part 24a to the arc receiving parts 24b, arc may
occur between the plug pins 34 and the plug-pin receivers 21.
The arc is received by the arc receiving parts 24b.
The variation in the arrangement of the receptacle 10
will be described with reference to Figs. 9A and 9B.
As shown in Fig. 9A, one receptacle 10 is installed at
a mounting frame, and a decorative plate 40 is installed to
the mounting frame from its front side. The decorative
plate 40 has an opening hole 41 with the single module
dimensions formed to expose the front surface 12a of the
cover 12.
As shown in Fig. 9B, since the receptacle 10 is
designed to have the single module dimensions, another
receptacle 10 or other wiring accessories, which have the
single module dimensions or double module dimensions
standardized by Japanese Industrial Standards (e.g., an
outlet 43 for coaxial cables and a modular jack 44 for
telephone lines), can be installed at the mounting frame.
In other words, the receptacle 10 and the above wiring
accessories can be attached to the common mounting frame.
Note that the decorative plate 40 is provided with the
opening hole 42 having three-piece module dimensions.
Besides, note that the above wiring accessories are not
1imited to the outlet 43 and the modular j ack 44, other
wiring accessories such as an AC receptacle and a modular
jack for LAN cables may be employed.
In accordance with the screw terminal 17 and the
receptacle 10 including the screw terminal 17 of the present
embodiment, the following effects can be obtained.
(1) In accordance with the present embodiment, the
pillar members 20 and the plug-pin receivers 21 are made
from a single metal plate M. Therefore, the number of
components of the terminal can be reduced compared to when
the terminal and the plug-pin receivers are formed as
separate members.
(2) In accordance with the present embodiment, the
plug-pin receivers 21 are formed in a substantially
cylindrical shape. Hence, the plug-pin receivers 21 can be
scaled down in the up-down direction Z compared to the
conventional plug-pin receiving member 230 shown in Fig. 13B.
As a result, the receptacle 10 can be scaled down in the up-
down direction Z.
Further, when the plug-pin receiving members 230 of
Fig. 13B are scaled down in the up-down direction Z in order
to scale down the receptacle in the up-down direction Z, the
area of the holding surface 231 of the plug-pin receiving
member 230 is reduced. Hence, the electrical resistance of
the holding surface 231 is increased, and the amount of heat
generated by electrical connection of the plug pin and the
holding surface 231 is increased. Since, however, the plug-
pin receiver 21 has a substantially cylindrical shape in the
present embodiment, the reduction in the area for holding
the plug pin 34 can be suppressed. - Accordingly, the
increase in the electrical resistance can be suppressed
compared to the case of scaling down the conventional plug-
pin receiving member 230 of Pig. 13B.
In the conventional plug-pin receiving member 230, the
plug pin is held at two contact points and thus cannot be
stably supported. To that end, in the present embodiment,
the plug-pin receiver 21 is formed in a substantially
cylindrical shape, so that the plug pin 34 can contact with
the plug-pin receivers 21 along the circumferential
direction thereof. Accordingly, the plug pin 34 can be
stably held by the plug-pin receiver 21.
Especially, in the present embodiment, the receptacle
10 has the single module dimension, and the peripheral wall
insertion groove 14 is formed at the cover 12. Therefore, a
pair of plug-pin receivers 21 needs to be accommodated in an
area surrounded by the peripheral wall insertion groove 14.
However, the conventional plug-pin receiving member 230 has
a large size in the up-down direction Z and thus cannot be
accommodated in the area surrounded by the peripheral wall
insertion groove 14. In the present embodiment, the plug-
pin receiver 21 has a substantially cylindrical shape and is
scaled down in the up-down direction Z, so that it is easy
to accommodate the plug-pin receivers 21 in the area
surrounded by the peripheral wall insertion groove 14.
Besides, the pillar members 20 are arranged at positions
lower than the peripheral wall insertion groove 14. Hence,
even if the pillar members 20 are provided outside the
peripheral wall insertion groove 14, the scaling up of the
receptacle 10 can be suppressed.
Further, the plug-pin insertion holes 16 are
positioned above the center line L1 of the plug receiving
part 15. In case of using the conventional plug-pin
receiving member 230 shown in Fig. 13B, the plug-pin
receiving member 230 needs to be accommodated in the area
surrounded by the peripheral wall insertion groove, so that
only the upper end portions of the plug-pin receiving member
230 are overlapped with the plug-pin insertion holes in the
front-rear direction X. Accordingly, the plug pins are held
only by the upper end portions of the plug-pin receiving
member 230, which makes it difficult to stably support the
plug pins 230 by the conventional plug-pin receiving member
230. On the other hand, in the pre sent embodiment, the
plug-pin receivers 21 having a substantially cylindrical
shape extending in the front-rear direction X are formed at
positions corresponding to the positions of the plug-pin
insertion holes 16 and, hence, the plug pins 34 can be
stably held.
(3) In accordance with the present embodiment, the
screw fixing portion 25 is formed at the pillar member 20 by
burring. As a consequence, the screw member 22 can be
screwed into the pillar member 20.
In a general screw terminal having a pillar member, it
is known that the pillar member and the plug-pin receiver
are made from separate metal plates. This is because the
pillar member requires a thick thickness to form a through
hole at the pillar member and a female thread at the inner
peripheral surface of the through hole. On the other hand,
the plug-pin receiver requires an extremely thin thickness
to ensure elasticity. For such reasons, the pillar member
and the plug-pin receiver are separately provided. However,
the pillar member and the plug-pin receiver provided as
separate members result in the increase in the number of the
components.
In this regard, in the present embodiment, the pillar
member 20 and the plug-pin receiver 21 are made from a
single metal plate M and, also, the screw fixing portion 25
is formed at the pillar member 20 by burring. Hence, even
if the pillar member is made from a metal plate M having a
thickness which ensures the elasticity of the plug-pin
receiver 21, the screw member 22 can be screwed thereinto.
To be specific, the screw fixing portion 25 is formed as a
substantially cylindrical tapped hole, so that it is
possible to ensure the area where the female thread is
formed. Accordingly, the screw member 22 can be screwed
into the screw fixing portion 25.
(4) In accordance with the present embodiment, the
plug-pin receiver 21 is formed by bending. Thus, the
elasticity of the plug-pin receivers 21 can be ensured
compared to that formed by cutting. Moreover, the plug-pin
receiver 21 can be easily formed compared to that formed by
drawing.
(5) In accordance with the present embodiment, the
plug-pin receiver 21 is provided with the slits 23.
Therefore, the elasticity of the plug-pin receivers 21 is
improved compared to that having no slits. Resultantly, the
plug pins 34 can be stably held by the plug-pin receiver 21.
In addition, the contact area is increased compared to
the conventional plug-pin receiving member 230 shown in Fig,
13B. Hence, the electrical connection of the plug-pin
receivers 21 and the plug pins 34 can be ensured.
(6) in accordance with the present embodiment, the
plug-pin receiver 21 has the arc receiving part 24b.
Therefore, it is possible to reduce the effects of the arc
on other components of the receptacle 10 such as the cover
12 and the like compared to the case of using the plug-pin
receiver having no arc receiving part 24b.
Especially, in the present embodiment, the receptacle
10 is a DC receptacle, so that the arc is generated for a
longer period of time compared to an AC receptacle and
affects the plug-pin receiver 21, the cover 12 and the like.
Since, however, the arc is received by the arc receiving
part 24b, the effects of the arc on the other components can
be reduced, which is preferable for a DC receptacle.
(7) In accordance with the present embodiment, the arc
receiving part 24b has a higher melting point compared to
the other parts of the plug-pin receiver 21. Hence, it is
possible to prevent the arc receiving part 24b from being
melted by the arc.
(8) In accordance with the present embodiment, the
peripheral wall insertion groove 14 has a substantially
quadrangular shape whose two lower corners are cut away.
Therefore, the insertion orientation of the peripheral wall
35 into the plug 30 is restricted compared to the case of
using the receptacle standardized by IEC standard which has
the round peripheral wall insertion groove 111 shown in Figs.
12A and 12B. Accordingly, an operator can easily recognize
the insertion orientation of the plug 30 into the receptacle
10, which is convenient in use. Resultantly, the operator
can easily insert the plug 30 into the receptacle 10 while
avoiding the reverse insertion.
Further, the plug-pin insertion holes 16 are
positioned above the center line L1 in the outer periphery
of the plug receiving part 15. Therefore, the reverse
insertion of the plug 30 into the receptacle 10 can be
prevented without providing a separate structure for
preventing the reverse insertion to the peripheral wall
insertion groove 14 and the peripheral wall 35. Accordingly,
the scaling up of the receptacle 10 can be suppressed
compared to the receptacle having the separate structure for
preventing the reverse insertion.
Meanwhile, if the peripheral wall insertion groove 111
has an annular shape as shown in Fig. 12B, the following
problem will be caused. That is, when the plug-pin
insertion holes 112 are disposed on the upper half side in
the circle, the distance between the plug-pin insertion
holes 112 is reduced to decrease their dielectric strength.
Further, when the peripheral wall insertion groove 111 of
the receptacle 100 has a quadrangular shape and the plug-pin
insertion holes 112 has a rectangular shape whose long side
extends in the up-down direction Z as shown in Fig. 12C, it
is necessary to scale up the receptacle 100 as shown in Fig.
12D in order to locate the plug-pin insertion holes 112 on
the upper half side in the quadrangle.
In this regard, in the present embodiment, the plug-
pin insertion holes 16 are formed in a circular shape while
the peripheral wall insertion groove 14 is formed to have a
quadrangular shape. Therefore, even if the plug-pin
insertion holes 16 are positioned above the center line L1,
the distance between the plug-pin insertion holes 16 is not
reduced. Accordingly, the dielectric strength is improved
compared to the receptacle 100 shown in Fig. 12B, and the
scaling up of the receptacle 10 is not required unlike the
receptacle 100 of Fig. 12B. Resultantly, the receptacle 10
can have the module dimension.
(9) In accordance with the present embodiment, the
cylindrical part 21a and the pillar member 20 are bent with
respect to the connecting portion 28 in the same directions
indicated by arrows Rl and R2 (see Fig. 4C) . Hence, the
cylindrical part 21a, the pillar member 20 and the
connecting portion 28 can be easily formed compared to the
case of bending the cylindrical part and the pillar member
in, e.g., opposite directions. As a result, the screw
terminal 17 can be easily manufactured.
(10) In accordance with the present embodiment, the
ends 26 of the cylindrical part 21a are separated from each
other. Thus, the elasticity of two gripping pieces 24
having the ends 26 separated from each other can be improved
compared to the case where the ends 26 are connected to each
other. As a consequence, the elasticity of the plug-pin
receiver 21 can be ensured.
(11) In accordance with the present embodiment, the
plug-pin receiver 21 is provided forwardly of the pillar
member 20 and is provided at the same position as the pillar
member 20 in the up-down direction Z and the left-right
direction Y. Hence, the screw terminal 17 can be scaled
down in the up-down direction 2 compared to the conventional
screw terminal 200 shown in Fig. 13B.
(12) In accordance with the present embodiment, the
screw terminal 17 has one connecting portion 28 for
connecting the plug-pin receiver 21 and the pillar member 20.
Therefore, the bending of the plug-pin receiver 21, the
pillar member 20 and the connecting portion 28 can be easily
performed compared to the screw terminal having a plurality
of connecting portions 28.
(13) In accordance with the present embodiment, the
receptacle 10 has a size of the single module dimensions
based on Japanese Industrial Standards, in which three
receptacles with the single module dimensions can be
accommodated in a mounting frame of a large rectangular
string wiring accessory. Therefore, the receptacle 10 can
be attached to a mounting frame of the other wiring
accessories standardized by the same standards. Accordingly,
there is no necessary to manufacture a dedicated mounting
frame for the receptacle 10 independently, and the mounting
frame can be used commonly. Consequently, the receptacle 10
can be attached to the mounting frame together with the
other wiring accessories having the single module dimensions
or the two-piece module dimensions, thereby improving its
operability.
(14) In accordance with the present embodiment, the
front surface 12a of the cover 12 and the front surface 15e
of the plug receiving unit 15 are formed flush with each
other in the front-rear direction X, and the plug pins 34
are configured to be located slightly forward of the rear
end portion of the peripheral wall 35. With such
configuration, when the plug 30 is reversely inserted into
the receptacle 10, the plug pins 34 come into contact with
the plug receiving part 15 before the peripheral wall 35 is
excessively inserted into the peripheral wall insertion
groove 14. Thus, an operator can easily recognize the
reverse insertion, and the state in which the plug 30 is
reversely inserted in the receptacle 10 cannot be maintained.
Hence, the reverse insertion state cannot be maintained.
(Other embodiments)
The receptacle 10 of the present invention is not
limited to the above embodiment and can be modified as will
be described below. Moreover, following modifications may be
applied to the aforementioned embodiment, and the
combination of the different modifications may also be
possible.
In the above-described embodiment, a DC receptacle is
employed as the receptacle 10. However, an AC receptacle to
which an AC receptacle is supplied may be employed as the
receptacle 10.
Although the plug-pin insertion holes 16 are
positioned above the center line L1 in the above-described
embodiment, the plug-pin insertion holes 16 may be
positioned at the same level as the center line L1 or below
the center line L1.
In the above-described embodiment, two inclined
grooves 14c and one extension groove 14d are provided at the
peripheral wall insertion groove 14. However, the shape of
the peripheral wall insertion groove 14 is not limited to
the above. For example, as shown in Fig. 10, the peripheral
wall insertion groove 14 may have a substantially
quadrangular shape in which the inclined grooves 14c and the
extension groove 14d are omitted. In other words, the
peripheral wall insertion groove 14 may have a quadrangular
shape viewed from the front. In that case, the plug
receiving part 15 is also formed in a substantially
quadrangular shape viewed from the front. With such
configuration, the aforementioned effect (8) can also be
achieved.
Further, depending on the shape of the peripheral wall
insertion groove 14, a type of supply voltage suitable for
the receptacle 10 can be changed. Specifically, the shape
of the peripheral wall insertion groove 14 shown in Fig. 10
may be suitable for the receptacle 10 of a supply voltage
24V, whereas the shape of the peripheral wall insertion
groove 14 with a quadrangular shape whose both lower corners
are cut away to provide the inc 1 ined grooves 14 c may be
suitable for the receptacle 10 of a supply voltage 48V.
Further, the peripheral wall insertion groove 14 may have a
quadrangular shape whose one lower corner is cut away to
provide the inclined grooves 14c. This may be suitable for
a receptacle of a supply voltage 12V or 6V, for example.
The peripheral wall insertion groove 14 and the plug
receiving part 15 are not necessarily formed in a
substantially quadrangular shape, and may be formed in a
round shape. With such configuration, the aforementioned
effect (1) can also be obtained.
Although the peripheral wall insertion groove 14 is
provided at the cover 12 of the receptacle 10 in the above-
described embodiment, the peripheral wall insertion groove
14 may be omitted. Hence, the peripheral wall 35 of the
plug 30 which is inserted into the receptacle 10 is also
omitted.
In the above-described embodiment, only the power
plug-pin insertion holes 16 are formed in the plug receiving
part 15. However, as shown in Fig. 10, a ground pin
insertion hole 16a may also be formed in addition to the
power plug-pin insertion holes 16. In that case, the ground
pin insertion hole 16a is positioned below the center line
LI and at the center in the left-right direction Y. In such
configuration, there are provided three screw terminals 17
corresponding to the two plug-pin insertion holes 16 and the
single ground insertion hole 16a, respectively.
In the above-described embodiment, the arc receiving
part 24b is plated with nickel tungsten to have a higher
melting point compared to the other parts of the plug-pin
receiver 21. However, the configuration in which the arc
receiving parts 24b have a higher melting point is not
limited thereto. For example, by using clad material which
is a metal plate of composite material, the arc receiving
part 24b may be formed of a material having a higher melting
point compared to the other parts. Specifically, for
example, the arc receiving part 24b are made of tungsten and
the other parts are made of copper.
Although the arc receiving part 24b is provided at the
front side of the plug-pin holding part 24a in the above
embodiment, the arc receiving part 24b may be omitted. For
example, the front end portion of the plug-pin receiver 21
may have a higher melting point compared to the other
portions.
In the above-described embodiment, the peripheral wall
insertion groove 14 has a substantially rectangular shape
whose long side extending in the left-right direction Y and
short side extending in the up-down direction Z. However,
the shape of the peripheral wall insertion groove 14 is not
limited thereto.
The peripheral wall insertion groove 14 may be formed
in a square shape having the same length in the left-right
direction Y and the up-down direction Z.
Although the opposite side end portions 27 of the
pillar member 20 are separated from each other in the above-
described embodiment, the shape of the pillar member 20 is
not limited thereto. As shown in Fig. 11A, the portion of
the surrounding wall (lower wall 20b), which is opposite to
the screw member 22 in the up-down direction Z, may be
formed by overlapping the side end portions 27 of the pillar
member 20 with each other in the up-down direction Z.
Accordingly, the lower wall 20b can be prevented from being
deformed by the screw member 22 pressing the electrical wire
against the lower wall 20b. Further, as shown in Fig. 11B,
the screw fixing portion 25 may be formed after the opposite
side end portions 27 of the pillar member 20 are overlapped
with each other. In other words, the screw fixing portion
25 is provided at the portion of the pillar member 20 where
side end portions of the metal plate M are overlapped.
Accordingly, the burring work for forming the screw fixing
portion 25 can be omitted.
In the above-described embodiment, the plug-pin
insertion holes 16 have a round shape. However, the shape
of the plug-pin insertion holes 16 is not limited thereto.
For example, the plug-pin insertion holes 16 may be formed
in a rectangular shape whose long side extends in the up-
down direction Z and short side extends in the left-right
direction Y. With such configuration, the aforementioned
effect (1) can also be achieved.
In the above-described embodiment, the plug-pin
receiver 21 has the cylindrical part 21a. However, the the
plug-pin receiver 21 may have other tubular shapes than the
cylindrical shape. For example, the plug-pin receiver may
have a substantially square column shape viewed from the
front. With such configuration, the aforementioned effect
(2) can also be obtained.
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.
What is claimed is:
1. A screw terminal comprising:
an electrical wire connecting portion to which an
electrical wire is connected by a screw member; and
a plug-pin receiver for gripping a plug pin of a plug,
wherein the electrical wire connecting portion and the
plug-pin receiver are made from a single metal plate; the
plug-pin receiver has a tubular shape extending along an
insertion direction of the plug pin; and the electrical wire
connecting portion is formed as a frame body opened along
the plug-pin insertion direction.
2. The screw terminal of claim 1, further comprising a
connecting portion for connecting the plug-pin receiver and
the frame body, wherein the plug-pin receiver has a
substantially cylindrical shape extending along the plug-pin
insertion direction, and the electrical wire is firmly
pressed against an inner peripheral surface of the frame
body by tightening the screw member into the frame body.
3. The screw terminal of claim 2, wherein the frame body
has a tapped hole into which the screw terminal is screwed,
and the tapped hole is formed by burring.
4. The screw terminal of claim 2, wherein the frame body
has a portion where side end portions of the metal plate are
overlapped, and a tapped hole into which the screw member is
screwed is formed at the portion.
5. The screw terminal of any one of claims 2 to 4,
wherein the plug-pin receiver has a plug-pin holding part
which determine a minimum diameter of an inner diameter of
the plug-pin receiver and a tip end part which extend from
the plug-pin holding part along the plug-pin insertion
direction, the tip end part having a gradually increased
inner diameter.
6. The screw terminal of any one of claims 2 to 4,
wherein the tip end part of the plug-pin receiver has a
higher melting point than that of portions other than the
tip end part.
7. The screw terminal of any one of claims 2 to 4,
wherein the plug-pin receiver has a plurality of gripping
pieces formed by slits extending along the plug-pin
insertion direction.
8. The screw terminal of any one of claims 2 to 4,
wherein the single metal plate includes a substantially
quadrangular portion forming the plug-pin receiver and
another substantially rectangular portion forming the frame
body, the plug-pin receiver and the frame body being formed
by bending the corresponding substantially quadrangular
portions, respectively.
9. The screw terminal of claim 8, wherein the
substantially quadrangular portion of the single metal plate
which forms the plug-pin receiver has a plurality of slits
extending along the plug-pin insertion direction.
10. A receptacle comprising the screw terminal described
in any one of claims 2 to 4.
11. The receptacle of claim 10, further comprising:
a peripheral wall insertion groove formed into a
substantially quadrangular shape when viewed from the plug-
pin insertion direction, a peripheral wall of the plug
surrounding the plug pin being adapted to be inserted into
the peripheral wall insertion groove; and
a plug receiving part surrounded by the peripheral
wall insertion groove and formed into a substantially
quadrangular shape when viewed from the plug-pin insertion
direction,
wherein the plug receiving part is provided with a
plurality of plug-pin insertion holes disposed along a
reference side that is one side of an outer periphery of the
plug receiving part, each of the plug-pin insertion holes
having a circular shape, and
wherein the plug-pin insertion holes are disposed
closer to the reference side than to an opposite side of the
outer periphery of the plug receiving part in a direction
perpendicular to the reference side.

ABSTRACT

A screw terminal includes an electrical
wire connecting portion to which an electrical wire is
connected by a screw member, and a plug-pin receiver
for gripping a plug pin of a plug. The electrical wire
connecting portion and the plug-pin receiver are made
from a single metal plate. The plug-pin receiver has a
tubular shape extending along an insertion direction of
the plug pin and the electrical wire connecting portion is
formed as a frame body opened along the plug-pin insertion
direction. A connecting portion connects the plugpin
receiver to the frame body. The plug- pin receiver
has a substantially cylindrical shape, and the electrical
wire is firmly pressed against an inner peripheral surface
of the frame body by tightening the screw member into
the frame body.