Earth unit

Abstract

To provide an earth unit capable of effectively preventing erroneous connection of an earth wire.SOLUTION: Each earth terminal unit 2 is provided with two wire insertion holes 25A, 25B into which load-side earth wires 51 can be inserted, and a switching lever 8 capable of sliding back and forth. By operating the switching lever 8, only one of the two wire insertion holes 25A, 25B can be opened, while closing the other. In other words, by operating the switching lever 8, the wire insertion hole that does not correspond to a bar fitting that needs to be wired, and further to an earth bar, can be blocked, therefore, there is no risk of erroneous connection of the load-side earth wire 51 to an earth bar different from an earth bar that should be connected, therefore, it can efficiently prevent erroneous connection of the earth wire of the load-side earth wire 51.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an earth unit that is installed in, for example, a distribution board to ground a load device. [Background technology]

[0002] Conventionally, an earth unit installed in, for example, a distribution board has multiple electrically independent earth bars. For example, the earth unit described in Patent Document 1 has a first earth bar for grounding load equipment that is not connected to an electric circuit protected by an earth leakage breaker, and a second earth bar for grounding load equipment that is connected to an electric circuit protected by an earth leakage breaker. The earth unit is configured so that when a load-side earth wire is inserted into the first wire insertion hole, the load-side earth wire is connected to the first earth bar, and when a load-side earth wire is inserted into the second wire insertion hole, the load-side earth wire is connected to the second earth bar. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-103317 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the earth unit described in Patent Document 1, the load side earth wire can always be inserted into either the first wire insertion hole or the second wire insertion hole, which means that there is a risk that the load side earth wire will be mistakenly connected to a different earth bar than the one to which it should be connected.

[0005] SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems, and aims to provide a grounding unit that can effectively prevent incorrect connection of a grounding wire. [Means for solving the problem]

[0006] In order to achieve the above object, the invention described in claim 1 of the present invention is an earth unit having at least two electrically independent earth bars built in and an earth wire connection part having wire insertion holes for connecting earth wires to the earth bars, each of which is provided corresponding to the earth bars, wherein the earth wire connection part is provided with a switching means for opening only one of the wire insertion holes and closing the others, so that the one wire insertion hole to be opened can be switched by a predetermined operation. The invention described in claim 2 is characterized in that, in the invention described in claim 1, a plurality of the earth wire connection parts are provided, and for each of the earth wire connection parts, the earth bar to which the earth wire is connected can be selected by operating the switching means. [Effects of the Invention]

[0007] According to the present invention, the earth wire connection section is provided with a switching means for opening only one of the wire insertion holes and closing the others, which is capable of switching which one of the wire insertion holes to open by a predetermined operation. That is, the switching means closes the wire insertion hole that does not correspond to the earth bar to which the earth wire is to be connected, so there is no risk of erroneously connecting the earth wire to an earth bar other than the earth bar to which it should be connected, and erroneous connection of the earth wire can be effectively prevented. Furthermore, according to the invention described in claim 2, in an apparatus having a plurality of earth wire connection parts, the earth bar to which the earth wire is connected can be selected by operating the switching means for each earth wire connection part, thereby making it possible to extremely effectively prevent incorrect connection of the earth wire. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective explanatory view showing an earth unit to which a ground-side earth wire and a load-side earth wire are connected; FIG. [Figure 2]FIG. 10 is an explanatory perspective view showing the earth unit disassembled into a plurality of terminal units and a terminal base unit. [Figure 3] FIG. 2 is a perspective explanatory view showing the terminal unit in an exploded state. [Figure 4] FIG. 10 is a perspective explanatory view showing the terminal base unit in an exploded state. [Figure 5] 10 is an explanatory diagram showing a horizontal cross section of the leftmost terminal base unit and the second terminal units from the left in the earth unit. FIG. [Figure 6] 10 is an explanatory diagram showing a vertical cross section of a state in which a first wire insertion hole is opened by a switching lever and a load-side earth wire is inserted through the first wire insertion hole. FIG. [Figure 7] 10 is an explanatory diagram showing a vertical cross section of a state in which a second wire insertion hole is opened by a switching lever and a load-side earth wire is inserted through the second wire insertion hole. FIG. [Figure 8] 8 is an explanatory diagram showing a state in which the switching lever is being operated to remove the load-side earth wire from the state shown in FIG. 7.

[0023] FIG. [Figure 9] FIG. 4 is an explanatory diagram showing a vertical cross section of the terminal base unit. [Figure 10] 10A and 10B are explanatory diagrams showing modified examples of the earth unit. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ground unit according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0010] FIG. 1 is an explanatory perspective view showing an earthing unit 1 to which ground-side earth wires 50, 50 and load-side earth wires 51, 51·· are connected. FIG. 2 is an explanatory perspective view showing the earthing unit 1 disassembled into multiple terminal units 2, 2·· and terminal base units 3, 3. FIG. 3 is an explanatory perspective view showing the terminal unit 2 in the disassembled state. FIG. 4 is an explanatory perspective view showing the terminal base unit 3 in the disassembled state. FIG. 5 is an explanatory view showing a horizontal cross section of the leftmost terminal base unit 3 and the second-to-left terminal units 2, 2 in the earthing unit 1. FIG. 6 is an explanatory view showing a vertical cross section in which the first wire insertion hole 25A is opened by the switching lever 8 and the load-side earth wire 51 is inserted through the first wire insertion hole 25A. FIG. 7 is an explanatory view showing a vertical cross section in which the second wire insertion hole 25B is opened by the switching lever 8 and the load-side earth wire 51 is inserted through the second wire insertion hole 25B. Fig. 8 is an explanatory diagram showing a state in which the switching lever 8 is being operated to remove the load-side earth wire 51 from the state shown in Fig. 7. Fig. 9 is an explanatory diagram showing a vertical cross section of the terminal base unit 3.

[0011] The earthing unit 1 is used to ground a load device (not shown) and comprises a terminal unit assembly in which a plurality of terminal units 2, 2... are connected in a row as described below, and terminal base units 3, 3 connected to both ends of the terminal unit assembly. This earthing unit 1 is installed, for example, in a distribution board, and enables grounding of the load device by connecting load-side earth wires 51, 51... extending from the load device side to the terminal units 2, 2... and ground-side earth wires 50, 50 extending to the ground side to the terminal base unit 3, respectively.

[0012] First, the terminal unit 2 will be described. The terminal unit 2 comprises a base 6, bar fittings 7A, 7B and a switching lever 8 mounted within the base 6, and a cover body 9 attached to cover the top surface of the base 6. The base 6 is a block body made of synthetic resin molded into a roughly cubic shape, with a first accommodating recess 10A for accommodating the bar fitting 7A provided at the front of the base 6 and a second accommodating recess 10B for accommodating the bar fitting 7B provided at the rear of the base 6. The first accommodating recess 10A and the second accommodating recess 10B open to the top surface of the base 6 and are separated into the front and rear of the base 6 by an insulating wall 13. Furthermore, two front and rear notches 11A and 11B are provided on the left side surface of base 6, cutting downward from the upper edge to approximately the same depth as both accommodating recesses 10A and 10B, with front notch 11A communicating with first accommodating recess 10A and rear notch 11B communicating with second accommodating recess 10B. Meanwhile, two front and rear sockets 12A and 12B are provided on the right side surface of base 6, with front socket 12A communicating with the internal space of first accommodating recess 10A and rear socket 12B communicating with the internal space of second accommodating recess 10B. The distance between sockets 12A and 12B in the front-to-rear direction is the same as the distance between notches 11A and 11B in the front-to-rear direction. In addition, screw holes 14 for fastening the cover body 9 with fixing screws 26 are drilled in the upper surface of the base 6, particularly in the upper surface of the insulating wall 13 portion.

[0013] The bar fitting 7A is formed by integrating an electric wire clamping fitting 15, which is formed by bending a strip-shaped metal plate into a roughly U-shape in side view, and an earth bar fitting 16, which is a metal plate whose thickness is in the front-to-rear direction and is arranged so as to penetrate the electric wire clamping fitting 15 in the left-to-right direction. Both longitudinal ends of the electric wire clamping fittings 15, which face each other from the front to the rear, are provided with portions bent in directions that bring them closer to each other, and these bent portions function as electric wire clamping portions 17 that clamp, from the front and rear, the load-side earth wire 51 inserted into the electric wire clamping fitting 15 from above. Meanwhile, the end of the earth bar fitting 16 protruding to the right from the electric wire clamping fitting 15 is formed in a bifurcated shape, and this bifurcated portion serves as a blade receiving spring portion 18 that has a function similar to that of a blade receiving spring that clamps the plug blades of a plug in an outlet device. Furthermore, the portion of the earth bar fitting 16 that protrudes leftward from the wire clamping fitting 15 protrudes leftward beyond the base 6 via the cutout portion 11A when housed in the first housing recess 10A of the bar fitting 7A, and serves as a blade portion 19 that has the same function as the blades of a plug. Note that, like the bar fitting 7A, the bar fitting 7B is formed by integrating the wire clamping fitting 15 having the wire clamping portion 17 with the earth bar fitting 16 having the blade receiving spring portion 18 and the blade portion 19.

[0014] The switching lever 8 comprises a strip-shaped cover portion 20 extending in the front-to-rear direction and a knob portion 21 protruding upward from the top surface of the cover portion 20, and the cover portion 20 is arranged to be slidable in the front-to-rear direction on the base 6, and in particular to be slidable in the front-to-rear direction on the electric wire clamping portions 17 of the bar fittings 7A, 7B arranged in both accommodating recesses 10A, 10B. In addition, the cover portion 20 is provided at both the front and rear ends with claw portions 22 protruding downward and notches 23 for avoiding interference with the load-side earth wire 51 inserted into the accommodating recesses 10A, 10B.

[0015] Meanwhile, cover body 9 is provided with an operation hole 24 through which knob 21 can pass and which guides the movement of knob 21 as switching lever 8 moves forward and backward. A first wire insertion hole 25A is provided in front of operation hole 24 for inserting load-side earth wire 51 into first accommodating recess 10A. A second wire insertion hole 25B is provided behind operation hole 24 for inserting load-side earth wire 51 into second accommodating recess 10B. In addition, fixing holes 47 are drilled at locations corresponding to screw holes 14 for fastening cover body 9 to the top surface of base 6 with fixing screws 26.

[0016] The terminal unit 2 as described above is assembled by accommodating the bar fittings 7A, 7B in both accommodating recesses 10A, 10B of the base 6, then arranging the switching lever 8 in a position on the top surface of the base 6 above the wire clamping portions 17, 17, and finally screwing the cover body 9 to the top surface of the base 6 while causing the knob portion 21 of the switching lever 8 to protrude upward through the operation hole 24. In this assembled state, the blade portions 19, 19 of the bar fittings 7A, 7B protrude leftward beyond the base 6 through the notches 11A, 11B. Furthermore, the blade receiving spring portions 18, 18 of the bar fittings 7A, 7B are located to the left of the insertion port 12A in the first accommodating recess 10A and to the left of the insertion port 12B in the second accommodating recess 10B. Therefore, when the two terminal units 2, 2 are lined up side by side and the blade portions 19, 19 of the right terminal unit 2 are inserted into both accommodating recesses 10A, 10B through the insertion openings 12A, 12B of the left terminal unit 2, the blade portions 19, 19 of the right terminal unit 2 are clamped by the blade receiving spring portions 18, 18 of the left terminal unit 2, and electrical continuity is established between the bar fittings 7A of the right terminal unit 2 and the bar fittings 7A of the left terminal unit 2, and between the bar fittings 7B of the right terminal unit 2 and the bar fittings 7B of the left terminal unit 2. Note that the bar fittings 7A and 7B are insulated from each other.

[0017] 6, when the knob 21 is positioned toward the rear end within the operation hole 24, the cover 20 closes the wire insertion hole 25B, leaving only the wire insertion hole 25A open, allowing only the load ground wire 51 to be inserted into the first accommodating recess 10A. Conversely, when the knob 21 is positioned toward the front end within the operation hole 24, the cover 20 closes the wire insertion hole 25A, leaving only the wire insertion hole 25B open, allowing only the load ground wire 51 to be inserted into the second accommodating recess 10B. When the load ground wire 51 is inserted into the first accommodating recess 10A through the wire insertion hole 25A, the load ground wire 51 is clamped by the wire clamping portion 17 of the bar fitting 7A, establishing electrical continuity between the load ground wire 51 and the bar fitting 7A. Furthermore, when the load side earth wire 51 is inserted into the second accommodating recess 10B through the wire insertion hole 25B, the load side earth wire 51 is clamped by the wire clamping portion 17 of the bar fitting 7B, and the load side earth wire 51 and the bar fitting 7B are brought into an electrically conductive state.

[0018] When removing the load-side earth wire 51, the switch lever 8 is operated in a direction away from the load-side earth wire 51 (toward the edge nearest the operation hole 24). For example, when the load-side earth wire 51 is inserted in the second accommodating recess 10B as shown in Fig. 7, the switch lever 8 is operated forward. Then, as shown in Fig. 8, the rear claws 22 interfere with the wire clamping portions 17 of the bar fitting 7B, pushing the wire clamping portions 17 apart, making it possible to remove the load-side earth wire 51 from the second accommodating recess 10B.

[0019] Next, the terminal base unit 3 will be described. The terminal base unit 3 includes a base 27, nuts 28A, 28B and terminal seat fittings 29A, 29B attached to the base 27, and terminal screws 30A, 30B for electrically connecting ground wires 50, 50 to the terminal seat fittings 29A, 29B. The base 27 is a block body made of synthetic resin and molded into a substantially rectangular parallelepiped shape that is long in the front-to-rear direction, with a first terminal base mounting portion 31A provided at the front of the base 27 and a second terminal base mounting portion 31B provided at the rear of the base 27. The terminal base mounting portions 31A, 31B are separated into front and rear portions by an insulating wall 32 that stands upright in the center of the top surface of the base 27 in the front-to-rear direction. Furthermore, each terminal base mounting portion 31A, 31B has flat portions 33A, 33B that become approximately flat when nuts 28A, 28B are fitted into them, and metal fitting accommodating recesses 34A, 34B that are recessed downward from the surfaces of flat portions 33A, 33B at the edge of insulating wall 32 and can accommodate part of terminal metal fittings 29A, 29B. Reference numeral 44 denotes an attachment hole for fastening terminal metal fittings 29A, 29B to terminal base mounting portions 31A, 31B with attachment screws 43.

[0020] Two front and rear connecting pieces 35, 35 protruding leftward are provided on the left side surface of the base 27. Each connecting piece 35 is shaped similarly to the blade portions 19 of the terminal unit 2, and the distance between the two connecting pieces 35 in the front-to-rear direction is the same as the distance between the blade portions 19 of the terminal unit 2 in the front-to-rear direction. Furthermore, two front and rear sockets 36A, 36B are provided on the right side surface of the base 27, with the front socket 36A communicating with the internal space of the front metal fitting accommodating recess 34A and the rear socket 36B communicating with the internal space of the rear metal fitting accommodating recess 34B. The distance between the sockets 36A and 36B in the front-to-rear direction is the same as the distance between the blade portions 19 of the terminal unit 2 in the front-to-rear direction. In addition, installation pieces 37, 37 having installation holes for installing the terminal base unit 3, and therefore the earth unit 1, in a distribution board or the like are provided on the bottom of the base 27 and protrude in the left and right directions.

[0021] The terminal washer 29A is formed by bending downward the rear portion of a strip-shaped metal plate extending in the front-to-rear direction. The strip-shaped portion extending in the front-to-rear direction forms a connection portion 38 to which the ground wire 50 is connected, and the portion extending downward forms a fixing portion 39 to which a blade receiving spring fitting 40 is fixed. The blade receiving spring fitting 40 functions similarly to the blade receiving spring portion 18 of the terminal unit 2 and is fixed to the front surface of the fixing portion 39 in a position that allows connection to the blade 19 of the terminal unit 2 from the right side. The fixing portion 39 and the blade receiving spring fitting 40 can be accommodated within the fitting accommodating recess 34A. When the fixing portion 39 and the blade receiving spring fitting 40 are accommodated within the fitting accommodating recess 34A, the connection portion 38 rests on the flat portion 33A. A terminal hole 41 is provided at the location corresponding to the nut 28A for threading the terminal screw 30A into the base 27 via the nut 28A. Furthermore, the connection portion 38 is provided with a round hole 42 for fastening the terminal washer 29A to the terminal seat mounting portion 31A with a mounting screw 43. The terminal washer 29B is formed by bending downward the front portion of a strip-shaped metal plate extending in the front-to-rear direction, and like the terminal washer 29A, the strip-shaped portion extending in the front-to-rear direction is the connection portion 38, and the portion extending downward is the fixing portion 39. A blade receiving spring fitting 40 is fixed to the rear surface of the fixing portion 39 in a position that allows connection to the blade portion 19 of the terminal unit 2 from the right side.

[0022] When assembling the terminal base unit 3 described above, first, nuts 28A, 28B are fitted into terminal base mounting portions 31A, 31B, respectively, to form flat portions 33A, 33B, and then, as shown in Fig. 9, the fixing portion 39 and blade receiving spring fitting 40 of terminal washer 29A are accommodated in fitting accommodating recess 34A, and the fixing portion 39 and blade receiving spring fitting 40 of terminal washer 29B are accommodated in fitting accommodating recess 34B, respectively, and connecting portions 38, 38 are placed on flat portions 33A, 33B. Next, mounting screws 43, 43 are screwed in to attach terminal washer 29A, 29B to terminal base mounting portions 31A, 31B, and assembly of terminal base unit 3 is completed. In the terminal base unit 3 assembled in this manner, the blade receiving spring fittings 40 of the terminal seat fittings 29A, 29B are located to the left of the insertion opening 36A in the fitting accommodating recess 34A and to the left of the insertion opening 36B in the fitting accommodating recess 34B. When the terminal unit 2 is placed on the right side of the terminal base unit 3 and the blade portions 19 of the terminal unit 2 are inserted into the fitting accommodating recesses 34A, 34B through the insertion openings 36A, 36B of the terminal base unit 3, the blade portions 19 are clamped between the blade receiving spring fittings 40, establishing electrical continuity between the bar fitting 7A of the terminal unit 2 and the terminal seat fitting 29A of the terminal base unit 3, and between the bar fitting 7B of the terminal unit 2 and the terminal seat fitting 29B of the terminal base unit 3. Furthermore, when the ground-side earth wire 50 is screwed to the connection portion 38 of the terminal seat metal 29A using the terminal screw 30A, the ground-side earth wire 50 is connected to the terminal seat metal 29A, and when the ground-side earth wire 50 is screwed to the connection portion 38 of the terminal seat metal 29B using the terminal screw 30B, the ground-side earth wire 50 is connected to the terminal seat metal 29B. The terminal seat metal 29A and the terminal seat metal 29B are insulated from each other.

[0023] On the other hand, when the terminal base unit 3 is disposed on the right side of the terminal unit 2 and the connecting pieces 35, 35 of the terminal base unit 3 are inserted into the accommodating recesses 10A, 10B through the insertion openings 12A, 12B of the terminal unit 2, the connecting pieces 35, 35 are clamped by the blade receiving spring portions 18, 18, connecting the terminal unit 2 and the terminal base unit 3. In this connected state, the bar fittings 7A, 7B inside the terminal unit 2 are not electrically connected to the terminal base unit 3, so there is no need to attach nuts 28A, 28B, terminal seat fittings 29A, 29B, terminal screws 30A, 30B, etc. to the terminal base unit 3 connected in this way.

[0024] Here, a description will be given of how to use the earth unit 1 formed by connecting the terminal unit 2 and the terminal base unit 3. First, a desired number of terminal units 2, 2... are connected together by inserting blades 19, 19 into sockets 12A, 12B to form a terminal unit assembly. In this usage mode, the blades 19, 19 at the left end of the terminal unit assembly are inserted into sockets 36A, 36B from the right side of terminal base unit 3, which has terminal seats 29A, 29B attached. Meanwhile, the connecting pieces 35, 35 of terminal base unit 3, which does not have terminal seats 29A, 29B attached, are inserted into sockets 12A, 12B from the right side of the terminal unit assembly to form grounding unit 1. The grounding unit is then installed in a distribution board or the like by fastening the installation pieces 37, 37 with screws. Ground wires 50 are then connected to terminal seats 29A, 29B of the leftmost terminal base unit 3, respectively. This results in two electrically independent grounding bars at the front and rear of grounding unit 1. That is, a first earth bar is formed from the terminal seat metal fitting 29A and the bar metal fittings 7A, 7A··, and a second earth bar is formed from the terminal seat metal fitting 29B and the bar metal fittings 7B, 7B··.

[0025] Therefore, in this usage mode, the first earth bar is used as an earth bar for type D grounding of load equipment not connected to an electric circuit protected by an earth leakage breaker, and the second earth bar is used as an earth bar for grounding of load equipment connected to an electric circuit protected by an earth leakage breaker, i.e., so-called ELB grounding. That is, when performing type D grounding of the load equipment, the switch lever 8 is slid rearward and the load-side earth wire 51 is inserted into the base 6 through the wire insertion hole 25A, so that the load-side earth wire 51 is connected to the first earth bar. On the other hand, when performing ELB grounding of the load equipment, the switch lever 8 is slid forward and the load-side earth wire 51 is inserted into the base 6 through the wire insertion hole 25B, so that the load-side earth wire 51 is connected to the second earth bar. Therefore, the switching lever 8 can be operated depending on the type of load equipment to which the load side earth wire 51 is connected to the terminal unit 2, and the appropriate earth bar to which it is connected can be selected.In the example shown in Figure 1, the load side earth wires 51 connected to the third and fourth terminal units 2 from the left are connected to the first earth bar, and the load side earth wires 51 connected to the first, second, and fifth terminal units 2 from the left are connected to the second earth bar.

[0026] Furthermore, when the number of load devices to be grounded increases, simply remove the right-most terminal base unit 3, add the required number of terminal units 2 to the terminal unit assembly, and then reconnect the terminal base unit 3 to the right end. Increasing the number of terminal units 2 in this way results in a longer overall length of the earth bar. Conversely, when the number of load devices to be grounded decreases, simply reduce the number of terminal units 2 in the terminal unit assembly. That is, simply remove the terminal units 2 that are no longer needed. Reducing the number of terminal units 2 in this way results in a shorter overall length of the earth bar. It is possible to reverse the installation orientation of the earth unit 1 in a distribution board, etc., so that the terminal base metal fittings 29A, 29B, etc. appear to be attached to the right-most terminal base unit 3. Furthermore, if a large number of terminal units 2 are required and the earth unit 1, especially the terminal unit assembly, becomes too long, there is no problem with installing multiple earth units 1 in a single distribution board.

[0027] According to the earth unit 1 having the above-described configuration, each terminal unit 2 is provided with two wire insertion holes 25A, 25B into which the load side earth wire 51 can be inserted, and is also provided with a switch lever 8 that can slide back and forth, and by operating the switch lever 8, it is possible to open only one of the two wire insertion holes 25A, 25B and close the other wire insertion holes. In other words, by operating the switch lever 8, it is possible to close the wire insertion holes that do not correspond to the bar fitting to be wired, and therefore to the earth bar, so there is no risk of erroneously connecting the load side earth wire 51 to an earth bar other than the earth bar to which it should be connected, and erroneous connection of the load side earth wire 51 can be effectively prevented.

[0028] Furthermore, in a configuration in which multiple terminal units 2, 2... are connected, the earth bar to which the load side earth wire 51 is connected can be selected by operating the switching lever 8 for each terminal unit 2, thereby making it possible to extremely effectively prevent incorrect wiring of the load side earth wire 51.

[0029] Furthermore, in each terminal unit 2, the bar fittings 7A, 7B are each provided with an earth bar fitting 16 having blades 19 protruding in a predetermined direction from the base 6 and blade receiving springs 18 capable of clamping the blades 19, and insertion openings 12A, 12B into which the blades 19 can be inserted are provided at locations on the base 6 corresponding to the blade receiving springs 18. The blades 19 of one terminal unit 2 are inserted into the base 6 through the insertion openings 12A, 12B of the other terminal unit 2 and clamped between the blade receiving springs 18, thereby connecting the two terminal units 2 with the bar fittings 7A, 7A and the bar fittings 7B, 7B conducting to each other, and the overall length of the earth bar can be adjusted by changing the number of connected terminal units 2, 2... Therefore, an increase or decrease in the number of load devices can be flexibly accommodated simply by increasing or decreasing the number of terminal units 2, 2, etc., and even if the number of load devices increases significantly, the earth unit 1 does not require work such as re-installing the earth bar.

[0030] The earthing unit of the present invention is not limited to the above-described embodiment, and the overall configuration of the terminal unit and terminal base unit can be appropriately modified as needed within the scope of the present invention.

[0031] For example, in the above embodiment, a terminal unit assembly is formed by connecting multiple terminal units, but it is also possible to use a single terminal unit 72 as shown in Figure 10 instead of such a terminal unit assembly.

[0032] Here, a ground unit 71 employing a terminal unit 72 according to a modification of the present invention will be described with reference to FIG. The earthing unit 71 includes a terminal unit 72 to which the load-side earth wires 51, 51... are connected, and a terminal base unit 73 to which the ground-side earth wires 50, 50 are connected. The terminal unit 72 includes a base 74 having two earth bars (not shown) installed therein, and a cover body 75 attached to the top surface of the base 74. The first earth bar is installed in the front of the base 74 and extends in the left-right direction, while the second earth bar is installed in the rear of the base 74 and extends in the left-right direction, with both earth bars being insulated by an insulating wall (not shown). The terminal unit 72 is connected to a terminal base unit 73 having a first terminal seat 76A and a second terminal seat 76B installed therein. In this connected state, the terminal seat 76A is electrically connected to the first earth bar, and the terminal seat 76B is electrically connected to the second earth bar. Furthermore, the ground-side earth wire 50 is connected to the terminal seat metal fitting 76A by a terminal screw 77A, and the ground-side earth wire 50 is connected to the terminal seat metal fitting 76B by a terminal screw 77B.

[0033] In addition, a total of five earth wire connection portions 78, 78·· are provided in the left-right direction on the terminal unit 72. The earth wire connection portion 78 includes a first wire insertion hole 79A into which the load side earth wire 51 can be inserted to connect it to the first earth bar, a second wire insertion hole 79B into which the load side earth wire 51 can be inserted to connect it to the second earth bar, a switching lever 80 that can be slid forward and backward, and two wire clamping portions (not shown) that are built into the base 74 and are used to connect the load side earth wire 51 inserted from each of the wire insertion holes 79A, 79B to the corresponding earth bar. The switching lever 80 and the wire clamping portion are configured in the same manner as the switching lever 8 and the wire clamping portion 17 of the above embodiment, and by sliding the switching lever 80 back and forth, one of the two wire insertion holes 79A, 79B is opened and the other is closed, allowing the load side earth wire 51 to be inserted only into the wire insertion hole that is open.

[0034] In the above-described grounding unit 71, each ground wire connection portion 78 is provided with two wire insertion holes 79A, 79B into which the load-side ground wire 51 can be inserted, and is also provided with a switch lever 80 that can slide back and forth. By operating the switch lever 80, only one of the two wire insertion holes 79A, 79B can be opened and the other wire insertion holes can be closed. That is, by operating the switch lever 80, the wire insertion hole that does not correspond to the desired earth bar can be closed, eliminating the risk of incorrectly connecting the load-side ground wire 51 to an earth bar other than the one to which it should be connected, and effectively preventing incorrect connection of the load-side ground wire 51. Furthermore, in a unit with multiple ground wire connection portions 78, 78..., the earth bar to which the load-side ground wire 51 is connected can be selected by operating the switch lever 80 for each earth wire connection portion 78, thereby extremely effectively preventing incorrect connection of the load-side ground wire 51.

[0035] Further, other modified examples may be considered in which the specific structure of the switching means is changed. That is, in the above-described embodiments and modified examples, a switching lever that slides in the forward and backward direction is used as the switching means, but it is also possible to provide a switching means that switches the wire insertion hole that is opened by rotating it about an axis in the up and down direction, or a switching means that switches the wire insertion hole that is opened by tilting it in the forward and backward direction about an axis in the left and right direction, and the specific structure of the switching means can be designed and modified as appropriate.

[0036] Furthermore, the present invention can be suitably employed in an earth unit that has only one earth wire connection portion, such as an earth unit that uses only one terminal unit in the above embodiment. In addition, with regard to the configuration of connecting multiple terminal units, the specific connecting structure to be adopted can be modified in design, and instead of the structure in the above embodiment in which connections are made by inserting a plug into an outlet, there is no problem in adopting a structure in which the bases are connected to each other so that the bar fittings are connected to each other in a conductive state. [Explanation of symbols]

[0037] 1· Earth unit, 2· Terminal unit, 3· Terminal base unit, 6· Base, 7A, 7B· Bar fitting (earth bar), 8· Switching lever (switching means), 9· Cover body, 12A, 12B· Socket, 15· Wire clamping fitting (earth wire connection portion), 16· Earth bar fitting (earth bar), 17· Wire clamping portion, 18· Blade holder spring portion, 19· Plug blade portion, 20· Cover portion, 21· Knob portion, 24· Operation hole, 25A, 25B· Wire insertion hole (earth wire connection portion), 71· Earth unit, 72· Terminal unit, 73· Terminal base unit, 74· Base, 78· Earth wire connection portion, 79A, 79B· Wire insertion hole, 80· Switching lever (switching means).

Claims

1. An earth unit having at least two electrically independent earth bars built in and an earth wire connection section in which wire insertion holes for connecting earth wires to the earth bars are provided corresponding to the earth bars, An earth unit characterized in that the earth wire connection portion is provided with a switching means that opens only one of the wire insertion holes and closes the other wire insertion holes, and is capable of switching which of the wire insertion holes is opened by a predetermined operation.

2. A plurality of the earth wire connection portions are provided, 2. The earth unit according to claim 1, wherein the earth bar to which the earth wire is connected can be selected for each of the earth wire connection portions by operating the switching means.

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