Field of the Invention The present invention relates to a wiring device.

Background of the Invention

There is conventionally available a wiring device including a pillar terminal designed to fasten an electric wire with a screw.

In the wiring device provided with the pillar terminal, a wire connecting work involves an increased amount of time and effort. In view of this, there has been developed a terminal unit (a so-called screw-less terminal unit) capable of making it easy to connect an electric wire to a wiring device and assuring reliable connection by maintaining consistency of connection (see, e.g., Japanese Patent Application Publication No. 2000-156259) . The screw- less terminal unit referred to above enables a user to perform the wire connection work without resort to a screw.

The screw-less terminal unit, sometimes called a quick-connection terminal unit, is held within a device casing of a wiring device and is connected to an electric wire extending into the device casing through a wire insertion hole defined in the device casing. The screw- less terminal unit includes a terminal plate for making contact with the electric wire extending into the device casing and a lock spring for gripping the electric wire between itself and the terminal plate to lock the electric wire against movement in a removal direction.

When one wishes to inspect the connection of the electric wire to the wiring device provided with the pillar terminal, a voltage checking task can be easily performed since the pillar terminal remains exposed to the outside. In case of the wiring device provided with the screw- less terminal unit, however, it is difficult to perform a voltage checking task because the screw- less terminal unit is stored within the wiring device.

In the wiring device provided with the screw- less terminal unit, e.g., in a socket device having plug insertion holes defined on the front surface thereof, a voltage checking task can be performed by inserting a detecting tool such as a voltage checking driver into one of the plug insertion holes. However, there is also available a socket device having opening/closing doors for keeping plug insertion holes closed when the plug insertion holes are not in use. In the socket device of this type, the opening/closing doors need to be opened in order to insert the voltage checking driver. This makes it difficult to perform the voltage checking task. Summary of the Invention

In view of the above, the present invention provides a wiring device capable of making it easy to perform a wire connecting work and making it possible to perform a voltage checking task with ease.

In accordance with the present invention, there is provided a wiring device including a device casing having a wire insertion hole defined on an outer surface thereof; and a terminal unit including a terminal plate for making contact with an electric wire inserted into the device casing through the wire insertion hole and a lock spring for gripping the electric wire between the lock spring and the terminal plate to prevent removal of the electric wire. The device casing further has a voltage checking hole through which the terminal plate or the lock spring is exposed.

Preferably, the terminal unit further includes a release lever having a push portion for pushing the lock spring and an operation portion extending from the push portion and exposed to the outside from the device casing, the release lever being configured such that, upon operating the operation portion, the push portion pushes the lock spring to release the removal prevention of the electric wire and such that, upon movement of the operation portion, at least a portion of the release lever is moved within the voltage checking hole. The terminal unit may be configured such that the terminal plate and the lock spring overlap with each other in an extent corresponding to the voltage checking hole .

Preferably, the terminal unit is arranged to allow the lock spring to be exposed through the voltage checking hole.

The terminal unit may is arranged to allow the terminal plate to be exposed through the voltage checking hole .

The present invention has an effect of providing a wiring device that makes it possible to perform a voltage checking task with ease .

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:

Fig. 1 is a perspective view showing a wiring device in accordance with a first embodiment of the present invention;

Fig. 2 is a front view of the wiring devices of the first embodiment installed on an installation surface;

Fig. 3 is a plan view of the wiring device of the first embodiment;

Fig. 4 is a section view showing some major parts of the wiring device of the first embodiment;

Fig. 5 is an exploded perspective view showing a terminal unit employed in the wiring device of the first embodiment ;

Fig. 6 is a section view of the terminal unit employed in the wiring device of the first embodiment;

Fig. 7 is a section view showing some major parts of the wiring device of the first embodiment, in which view an electric wire is connected to the wiring device;

Fig. 8 is a partially cut-away perspective view showing a wiring device in accordance with a second embodiment of the present invention;

Fig. 9 is a front view of the wiring devices of the second embodiment installed on an installation surface;

Fig. 10 is a perspective section view of the wiring device of the second embodiment;

Fig. 11 is a perspective view of the wiring device of the second embodiment;

Fig. 12 is a perspective view showing a terminal plate employed in the wiring device of the second embodiment; and Fig. 13 is a section view of the wiring device of the second embodiment .

Detailed Description of the Preferred Embodiments

Embodiments of the present invention will now be described with reference to the accompanying drawings which form a part hereof.

(First Embodiment)

A wiring device according to the first embodiment will be described with reference to Figs. 1 through 7. In the following description, the up-down direction and the left- right direction will be defined on the basis of Fig. 1. The direction orthogonal to the up-down direction and the left- right direction will be referred to as front-rear direction.

The wiring device of the present embodiment includes a device casing 106 and a terminal unit 40. The device casing

106 includes a generally rectangular hollow box-shaped body

107 with an open front side and a generally rectangular hollow box-shaped cover 108 with an open rear side, the cover 108 being arranged to cover the front side of the body 107. As shown in Fig. 2, the wiring device of the present embodiment is installed in an embedment hole (not shown) defined on an installation surface 50, with the front surface of the device casing 106 exposed to the outside. The embedment hole is closed by a cover plate 51 having a through-hole 51a through which the front surface of the device casing 106 is exposed. While the wiring device of the present embodiment is embedded in the installation surface 50, the manner of installation is not limited thereto. Alternatively, the wiring device may be installed so that it can be exposed from the installation surface 50 partially or in its entirety.

The body 107 includes engagement lugs 107a formed on the left and right surfaces thereof. The cover 108 includes engagement portions 108a formed on the left and right surfaces thereof. The cover 108 is. fixed to the body 107 by bringing the engagement portions 108a of the cover 108 into engagement with the engagement lugs 107a of the body 107.

Referring to Fig. 4, a partition wall 107d is formed within the body 107 to divide the internal space of the body 107 into two storage compartments 104 arranged one above the other (Only one of the storage compartments 104 is shown in Fig. 4) . A wire insertion hole 107b communicating with one of the storage compartments 104 is defined on the rear surface of the body 107. In addition, as shown in Fig. 3, voltage checking holes 107c communicating with the storage compartments 104 are defined side by side on the upper and lower surfaces of the body 107.

Plug insertion holes 108b are defined on the front surface of the cover 108. Opening/closing doors 109 for openably closing the plug insertion holes 108b are arranged inside the cover 108. The opening/closing doors 109 are opened as a plug is inserted into the plug insertion holes 108b but closed as the plug is removed from the plug insertion holes 108b. That is to say, the front surface of the cover 108 serves as a functional surface S. While the wiring device of the present embodiment is applied to a socket device having the plug insertion holes 108b defined on the functional surface S thereof (namely, on the front surface of the cover 108) , the kind of the wiring device is not limited thereto. The wiring device may be, e.g., a switch device having switches arranged on the functional surface thereof or a human detecting sensor.

The terminal unit 40 includes a terminal plate 24, a pair of lock springs 25 and a pair of release levers 26. The terminal unit 40 is often referred to as screw-less terminal unit or quick-connection terminal unit.

Referring to Fig. 5, the terminal plate 24 is made of an electrically conductive material and includes a generally H-shaped wire connection member 240 and a plug connection member 270. The wire connection member 240 includes a pair of strip-shaped base pieces 241 and 242 arranged one above the other and a connecting piece 243 for interconnecting the generally central portions of the base pieces 241 and 242.

Contact pieces 241a extending rearwards are formed in the upper left and right end portions of the base piece 241. Surrounding pieces 241b extending rearwards are formed in the lower left and right end portions of the base piece 241. Extension pieces 242a extending rearwards are formed at the lower left and right end portions of the base piece 242. A caulking hole 243a is defined in a generally central area of the connecting piece 243.

Surrounding pieces 241c of a generally triangular shape are formed at left and right sides of the base end portion of each contact piece 241a and extend downwards.

The plug connection member 270 includes a base plate

271 having a through-hole 217a defined in a generally central area thereof, a plug-pin rest portion 215 for a flat plug-pin extending forwards from the lower end of the base plate 271 and a pair of plug-pin rest portions 216 for a round plug-pin extending forwards from the left and right ends of the base plate 271.

The plug connection member 270 is combined with the wire connection member 240 by inserting a caulking member

272 through an insertion hole 271a of the base plate 271 and then caulking the caulking member 272 in the caulking hole 243a of the wire connection member 240.

Each lock spring 25 is formed into a generally C-like shape by bending an electrically conductive plate (e.g., a metal plate) with elasticity. Each lock spring 25 includes a central piece 251 facing the contact pieces 241a across a space for insertion of an electric wire 30, a lock piece 252 extending upwards from the rear end of the central piece 251 and a generally L-like abut piece 253 extending upwards from the front end of the central piece 251.

The lock piece 252 is inclined forwards as it extends upwards. The lock piece 252 makes contact with the contact piece 241a at its tip end. The abut piece 253 includes a base piece 253a and a bent piece 253b bent rearwards from the upper end of the base piece 253a to overlap with the upper surface of the corresponding contact piece 241a. The base piece 253a has a central-bent portion (a step portion 253c) so that an upper portion of the base piece 253a is located at the front side of the base piece 241 while a lower portion of the base piece 253a is located at the rear side of the base piece 241.

While the bent piece 253b of each of the lock springs 25 overlaps with the upper surface of the corresponding contact piece 241a in the present embodiment, the present invention is not limited thereto. It is only necessary that the bent piece 253b be exposed to the outside through at least one of the voltage checking holes 107c. In other words, a portion of the terminal plate 24 and the bent piece 253b of each of the lock springs 25 may be exposed to the outside through the corresponding voltage checking hole 107c The lower surface of the bent piece 253b makes contact with the upper surface of the corresponding contact piece 241a. The upper surface of the bent piece 253b is exposed to the outside through the corresponding voltage checking hole 107c of the body 107 (see Fig. 3) .

A connection portion 254 of the central piece 251 and the lock piece 252 is curved into an approximately semicircular arc shape. If a forwardly-acting force is applied to the lock piece 252, the curved connection portion 254 is reduced in diameter so that the lock piece 252 can be bent (or displaced) . The abut piece 253 extends forwards through one of cutouts 24a defined in the left and right edges of the connecting piece 243 of the terminal plate 24, extends around the base piece 241 and the rearwards. When the terminal plate 24 is held within one of the storage compartments 104 of the body 107, a portion of the abut piece 253 lying below the step portion 253c is supported by the base piece 242 of the terminal plate 24, since the step portion 253c extends through the corresponding cutout 24a (see Fig. 4) .

As shown in Fig. 4, the terminal plate 24 and the lock springs 25 configured as above are arranged within one of the storage compartments 104 of the body 107. If an electric wire 30 is inserted from the outside into one of the storage compartments 104 through one of the wire insertion holes 107b as illustrated in Fig. 7, the lock piece 252 is pushed by the tip end of the electric wire 30 and is bent away from the corresponding contact piece 241a (downwards) . Thus, the electric wire 30 is further inserted inwards. Once the electric wire 30 is inserted to a specified position, the tip end of the lock piece 252 makes contact with the electric wire 30, thereby preventing the electric wire 30 from being removed in the counter-insertion direction (rearwards) . By the restoring force (spring force) of the lock spring 25, the electric wire 30 is brought into resilient contact with the contact surface (lower surface) of the contact piece 241a. This makes it possible to provide electric connection between the electric wire 30 and the contact piece 241a.

In the terminal unit 40 of the present embodiment, if the electric wire 30 comes into contact with the lock piece 252 during the course of connecting the electric wire 30, the lock piece 252 is moved away from the contact pieces 241a (namely, in the clockwise direction in Fig. 7) using the connection portion 254 as a fulcrum. Accordingly, there is no possibility that the lock piece 252 is caught by the electric wire 30. This makes it possible to enhance the reliability of contact between the electric wire 30 and the terminal plate 24.

Each of the contact pieces 241a is provided with a pair of surrounding pieces 241c. It is therefore possible for the surrounding pieces 241c to limit the transverse movement extent of the electric wire 30 if the latter is a solid wire. In case where the electric wire 30 is a twisted wire, it is possible for the surrounding pieces 241c to limit the untwisting extent of individual strands of the twisted wire. This provides an advantage in that the reliability of contact between the electric wire 30 and the terminal plate 24 is further enhanced. In the present embodiment, the tip end portions of the pair of surrounding pieces 241c are shaped to protrude toward the corresponding surrounding piece 241b. This makes it possible to reliably limit the movement extent or the untwisting extent of the electric wire 30. In addition, the provision of the surrounding pieces 241b in the terminal plate 24 makes it possible to restrain the electric wire 30 from moving away from each of the contact pieces 241a.

In the terminal unit 40 of the present embodiment, the contact piece 241a of the terminal plate 24 is flexible in a direction in which the contact piece 241a makes contact with the electric wire 30 (namely, in the up-down direction) . Accordingly, even when the electric wire 30 is inclined with respect to the corresponding wire insertion hole 107b, the contact pieces 241a can adapt itself to the movement of the electric wire 30. This makes it possible to assure stable contact at all times. Moreover, even if the electric wire 30 composed of a twisted wire is untwisted or even if the electric wire 30 is formed of a small-diameter (thin) wire, the contact piece 241a and the lock piece 252 can resiliently grip the electric wire 30, thereby stabilizing the contact state between the terminal plate 24 and the lock springs 25. Since the bending extent of the contact piece 241a is limited by the inner wall surface of the storage compartment 104 of the body 107, it is possible to prevent the contact piece 241a from undergoing plastic deformation even when the electric wire 30 is inclined.

Next, description will be given on each release lever

26. The release lever 26 is molded from a synthetic resin and is formed into a generally C-like shape as a whole. The release lever 26 includes a pair of semicircular disc-shaped support portions 261, a rectangular plate-shaped operation portion 262 and a pair of generally triangular plate-shaped connecting portions 263 for interconnecting the support portions 261 and the operation portion 262, respectively.

Push portions 264 protrude from the respective connecting portions 263. Each of the push portions 264 is formed into a generally flat triangular prism shape. A slant surface of each of the push portions 264 facing the lock piece 252 makes contact with lock piece 252 in a separable manner. An apex portion of each of the push portions 264 existing at the opposite side of the slant surface makes contact with the contact piece 241a. The operation portion 262 of the release lever 26 is exposed to the outside through the voltage checking hole 107c of the body 107 and is movably arranged within the voltage checking hole 107c. The release lever 26 is positioned within the corresponding storage compartment 104 of the body 107 with the contact piece 241a and the lock spring 25 arranged between the connecting portions 263. A bearing stand 105 having a semicircular arc-shaped sliding surface is provided within each of the storage compartments 104 (see Fig. 7) . The support portion 261 of the release lever 26 positioned within the storage compartment 104 is mounted on the bearing stand 105. Thus, each of the release levers 26 is rotatably supported on the body 107 using the support portion 261 as a fulcrum.

In order to remove the electric wire 30 connected to the terminal unit 40, a finger may be inserted into each of the voltage checking holes 107c and then the operation portion 262 exposed toward the upper surface of the body 107 may be pulled upwards as shown in Fig. 7. More specifically, if the operation portion 262 is pulled upwards within each of the voltage checking holes 107c, each of the release levers 26 is rotated clockwise about the support portions 261. The upper apex portions of the push portions 264 begin to displace the tip end portion of the contact piece 241a away from the electric wire 30 (upwards) . If each of the release levers 26 is further rotated clockwise, then the push portions 264 press the lock piece 252 downwards, thereby causing the lock piece 252 remaining in contact with the electric wire 30 to move away from the electric wire 30. Accordingly, the electric wire 30 can be removed from the terminal unit 40.

In the wiring device of the present embodiment configured as above, the terminal unit 40 (the bent piece 253b of each of the lock springs 25) is partially exposed to the outside through the upper surface of the body 107. As stated above, the terminal plate 24 and the lock springs 25 are made of an electrically conductive material. Therefore, a voltage checking task for the terminal plate 24 can be performed through each of the lock springs 25 by inserting a voltage checking driver into each of the voltage checking holes 107c and bringing the voltage checking driver into contact with each of the bent piece 253b.

With the wiring device of the present embodiment, it is possible to easily perform the wire connecting work and the voltage checking task.

Since each of the voltage checking holes 107c serves as a space through which a portion of the connecting portions 263 of each of the release levers 26 can move, there is no need to additionally provide a space for movement of the connecting portions 263. This helps simplify the structure of the wiring device.

Further, the bent piece 253b of each of the lock springs 25 and each of the contact pieces 241a of the terminal plate 24 are arranged to overlap with each other in the penetration direction of each of the voltage checking holes 107c (in the up-down direction) , it is possible to increase the strength of the portion of the terminal unit 40 with which the voltage checking driver comes into contact.

Owing to the fact that the bent piece 253b of each of the lock springs 25 is arranged nearer to each of the voltage checking holes 107c than each of the contact pieces 241a of the terminal plate 24 is, there is no possibility that the voltage checking driver makes direct contact with each of the contact pieces 241a of the terminal plate 24. This makes it possible to prevent the terminal plate 24 from being damaged.

(Second Embodiment)

A wiring device according to the second embodiment will be described with reference to Figs. 8 through 13. Referring to Fig. 8, the wiring device of the present embodiment includes a device casing 10 and terminal units 20 arranged within the device casing 10. As shown in Fig. 9, the wiring device of the present embodiment is installed in an embedment hole (not shown) defined on an installation surface 50, with the front surface of the device casing 10 exposed to the outside. The embedment hole is closed by a cover plate 51 having a through-hole 51a through which the front surface of the device casing 10 is exposed. While the wiring device of the present embodiment is embedded in the installation surface 50, the manner of installation is not limited thereto. Alternatively, the wiring device may be installed so that it can be exposed from the installation surface 50 partially or in its entirety. In the following description, the up-down direction and the left-right direction will be defined on the basis of Fig. 8. The direction orthogonal to the up-down direction and the left- right direction will be referred to as front-rear direction.

The device casing 10 includes a generally rectangular box-shaped body 101 made of a synthetic resin and provided with an open front side, and a generally rectangular box- shaped cover 102 made of a synthetic resin and provided with an open rear side, the cover 102 being combined with the body 101 to cover the front side opening of the body 101.

As shown in Fig. 10, the body 101 is formed into a generally rectangular box shape and is provided with an open front side. A partition wall 101a bisecting the internal space of the body 101 in the up-down direction is formed substantially at the vertical center of the body 101. Two storage compartments 104 are defined in the body 101 with the partition wall 101a interposed therebetween. Terminal units 20 are held within the respective storage compartments 104.

As illustrated in Fig. 11, a pair of wire insertion holes 101b is defined side by side along the left-right direction in the area of the rear surface of the body 101 corresponding to each of the storage compartments 104. The wire insertion holes 101b communicate with the corresponding storage compartment 104 into which electric wires 30 are inserted from the outside through the wire insertion holes 101b. In other words, at most four electric wires including outgoing wires can be connected to the wiring device of the present embodiment .

As shown in Figs. 8 and 11, a pair of voltage checking holes lOld is defined side by side along the left-right direction on the upper surface (upper side surface) of the body 101. The voltage checking holes lOld are defined in alignment with contact point portions 213 to be set forth later.

A pair of plug insertion holes (functional portions) 102a is defined along the up-down direction on the front surface of the cover 102. Opening/closing doors 109 for openably closing the plug insertion holes 102a are arranged inside the cover 102. The opening/closing doors 109 are opened as a plug is inserted into the plug insertion holes 102a but closed as the plug is removed from the plug insertion holes 102a. That is to say, the front surface of the cover 102 serves as a functional surface S. A partition wall lOld for bisecting the internal space of the cover 102 in the up-down direction is formed substantially at the center of the front surface of the cover 102. The partition wall 102d makes contact with the partition wall 101a of the body 101 at the tip end thereof and vertically bisects the internal space of the device casing 10 in cooperation with the partition wall 101a of the body 101. While the wiring device of the present embodiment is applied to a socket device having the plug insertion holes 102a defined on the functional surface S thereof, the kind of the wiring device is not limited thereto. The wiring device may be, e.g., a switch device having switches arranged on the functional surface thereof or a human detecting sensor.

Next, description will be given on how to combine the body 101 and the cover 102 into the device casing 10. In the present embodiment, the body 101 and the cover 102 are combined into the device casing 10 by fitting each of interlock members 103 to corresponding engagement prongs lOle and 102f formed in the body 101 and the cover 102, respectively.

As shown in Fig. 8, each of the terminal units 20 includes a terminal plate 21, a pair of lock springs 22 for bringing an electric wire 30 inserted through the corresponding wire insertion hole 101b into contact with the terminal plate 21 in the radial direction of the electric wire 30 and for preventing removal of the electric wire 30, and a release lever 23 for releasing the electric wire 30 out of the connection state.

Referring to Fig. 12, the terminal plate 21 is made of a metal and includes a generally rectangular plate-shaped base plate 211, a pair of opposing walls 212 extending vertically upwards from the left and right ends of the base plate 211, a pair of contact point portions 213 formed by bending the tip end portions of the opposing walls 212 outwardly in the left-right direction, and a pair of plug- pin rest portions 214.

The plug-pin rest portions 214 includes a plug-pin rest portion 215 for a flat plug blade extending from the front end of the base plate 211 and a pair of plug-pin rest portions 216 for a round plug-pin extending from the front ends of the opposing walls 212. As shown in Fig. 13, the terminal plate 21 is arranged in each of the storage compartments 104 with the base plate 211 kept in contact with the partition wall 101a and the contact point portions 213 kept in contact with one of the side surfaces of the body 101. In this connection, the contact point portions 213 of the terminal plate 21 arranged in the upper storage compartment 104 make contact with the upper side surface of the body 101, and the contact point portions 213 of the terminal plate 21 arranged in the lower storage compartment 104 come into contact with the lower side surface of the body 101.

The contact point portions 213 of the terminal plate 21 arranged in each of the storage compartments 104 as mentioned above are exposed to the outside through the voltage checking holes lOld defined on the upper surface of the body 101.

Referring again to Fig. 8, the lock springs 22 are formed by bending an electrically conductive plate (e.g., a metal plate) with elasticity and are arranged in an opposing relationship with the opposing walls 212 and the contact point portions 213 of the terminal plate 21. That is to say, two lock springs 22 are provided with respect to one terminal plate 21.

Each of the lock springs 22 includes a resilient push portion 221 formed into a generally S-like cross-sectional shape and designed to push the corresponding contact point portion 213 of the terminal plate 21 at one end thereof, a lock portion 222 positioned at the rear side of the push portion 221 to make contact with the contact point portion 213 at one end thereof, and a corresponding connecting portion 223 for interconnecting the other ends of the push portion 221 and the lock portion 222.

The lock portion 222 is integrally formed with the connecting portion 223 and has a generally V-like cross- sectional shape. The lock portion 222 is resilient and is inclined toward the corresponding contact point portion 213 as it extends in the insertion direction of the electric wire 30. The lock portion 222 pushes the electric wire 30 against the corresponding contact point portion 213 and cuts into the electric wire 30, thereby preventing removal of the electric wire 30.

One end of the push portion 221 makes contact with the lower surface of the corresponding contact point portion 213 and faces each of the voltage checking holes lOld across the corresponding contact point portion 213. In other words, the push portion 221 is kept in contact with the lower surface of the corresponding contact point portion 213, and the upper surface of the corresponding contact point portion 213 is exposed to the outside through the corresponding voltage checking hole lOld. While the contact point portions 213 of the terminal plate 21 are exposed to the outside through the voltage checking holes lOld in the present embodiment, the present invention is not limited thereto. The lock springs 22 may be partially exposed to the outside through the voltage checking holes lOld.

Referring to Fig. 13, the release lever 23 is made of a synthetic resin to have a generally rectangular solid shape and is arranged in a state that the rear surface of the release lever 23 makes contact with a rear surface of inside of the body 101. A protrusion 231 is formed on the rear surface of the release lever 23 to protrude into a through-hole 101c defined on the rear surface of the body 101 (see Fig. 13) . A pair of push lugs 232 is formed on the front surface of the release lever 23 along the left-right direction. The push lugs 232 make contact with the corresponding lock portion 222 of the lock spring 22 at the rear side thereof.

Forward movements of the terminal plate 21 and the lock springs 22 of the terminal units 20 are respectively restrained by ribs 102b and 102c protruding rearwards from the front surface of the cover 102.

Next, description will be made on how to connect the electric wire 30 to the terminal plate 21. First, a wire core 30a exposed by removing the coating of the tip end portion of the electric wire 30 is inserted into the device casing 10 through one of the wire insertion holes 101b. At this time, the tip end portion of the wire core 30a pushes the lock portion 222 of the lock spring 22. Thus, the lock portion 222 is bent toward the connecting portion 223, allowing the wire core 30a to be further inserted in the insertion direction. If the wire core 30a is further inserted, the tip end portion of the wire core 30a pushes the push portion 221 of the lock spring 22. As a result, the push portion 221 is bent toward the connecting portion 223 and the wire core 30a is gripped between the push portion 221 of the lock spring 22 and the corresponding contact point portion 213 of the terminal plate 21. Consequently, the electric wire 30 is mechanically and electrically connected to the terminal plate 21.

Due to the resilience of the push portion 221, a restoring force acts to bias the push portion 221 toward the corresponding contact point portion 213. By the pushing force of the push portion 221, the wire core 30a is brought into contact with the corresponding contact point portion 213 under a specified pressure. If one attempts to draw out the wire core 30a, the lock portion 222 cuts into the wire core 30a, thereby preventing removal of the wire core 30a. Therefore, it is not easy to release the electric wire 30 from the terminal plate 21.

In order to release the electric wire 30 from the terminal plate 21, the protrusion 231 of the release lever 23 is pushed by, e.g., a pin through the through-hole 101c of the device casing 10. Thus, the release lever 23 is moved forwards and the push lugs 232 of the release lever 23 cause the lock portion 222 of the lock spring 22 to be bent toward the connecting portion 223. As a result, the lock of the electric wire 30 is released, making it possible to draw out the electric wire 30 from the device casing 10 with ease.

In the wiring device of the present embodiment configured as above, each terminal plate 21 of the terminal units 20 held within the device casing 10 is exposed to the outside through the corresponding voltage checking hole lOld defined in the device casing 10 (the body 101) . Accordingly, a voltage checking task can be readily carried out by inserting a voltage checking tool such as a voltage checking driver into each of the voltage checking holes lOld. While the voltage checking holes lOld are defined on the side surface of the device casing 10 (the upper surface of the device casing 10 in Fig. 8) in the present embodiment, the position of the voltage checking holes lOld is not limited thereto. Alternatively, the voltage checking holes lOld may be defined on other surfaces of the device casing 10 (e.g., on the front surface or the rear surface of the device casing 10) . It is preferred that the voltage checking holes lOld be defined on the rear surface of the device casing 10.

While the voltage checking holes lOld are defined only on the upper surface of the body 101 in the present embodiment, they may be defined on both the upper surface and the lower surface of the body 101.

With the wiring device of the present embodiment, it is possible to easily perform the wire connecting work and the voltage checking task.

In the present embodiment, the push portion 221 of the lock spring 22 makes contact with the lower surface of the corresponding contact point portion 213, and the upper surface of the corresponding contact point portion 213 is exposed to the outside through the corresponding voltage checking hole lOld. This enables the voltage checking driver to make direct contact with the electrically conductive terminal plate 21 (the contact point portions 213) , making it possible to perform the voltage checking task with increased accuracy.

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.