Circuit protecting device for an automotive wiring harness

A circuit protecting device for an automotive wiring harness designed to make the dimensions of wires downstream from fuses smaller and minimize the number of circuits which will be brought into an inoperative state upon blowout of a fuse resulting from a short circuit which occurs in a wire by supplying protecting circuits for supplying power from a power source to loads with fuses provided in the circuits connected in one-to-one relationship with the loads so that, upon blowout of one fuse, only a power supply to the load connected with this fuse is cut off. The fuses are formed by a flat fuse 20 including a plurality of conductive fusible elements 21 arranged at specified intervals on the surface of an insulating plate 22.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a circuit protecting device for an 
automotive wiring harness. 
2. Description of the Prior Art 
In a prior art circuit protecting device for an automotive wiring harness, 
a fuse is provided between a power source and loads so that, upon a flow 
of an overcurrent, it blows out to protect circuits. Fuses used in the 
prior art devices includes blade fuses and minifuses. These fuses are 
connected with only a single circuit or a plurality of circuits connected 
in parallel. Further, the dimensions of these fuses are relatively large: 
20.times.18.times.5 mm (blade fuses) and 16.times.11.times.4 mm 
(minifuses). Accordingly, in particular if the space taken by a terminal 
to be connected with the fuse is taken into account, a considerably large 
space is required for the arrangement of one fuse. In view of this, one 
circuit connected with the fuse is divided into a plurality of branch 
circuits, which are to be connected with the respective loads. In other 
words, a plurality of loads are connected in parallel with one fuse to 
protect circuits. 
Specifically, the prior art device is constructed as shown in FIG. 8. A 
wire W1 connected with a power source BA is connected with a circuit 3A 
formed by busbars or the like accommodated in a junction box 2. A fuse 4 
mounted in a fuse receptacle is connected with the circuit 3A. A circuit 
3B connected with a downstream end of the fuse 4 is divided into a 
plurality of branch circuits or subcircuits 5A to 5C which are connected 
with loads 6A to 6C via wires W2 to W4. The above connection enables power 
to be supplied to the respective loads 6A to 6C. 
In the case that a plurality of loads 6A to 6C are connected with one fuse 
4 as described above, if the current carrying capacities of electric 
devices as the loads 6A to 6C are 3 ampere (A), 5 A, and 2 A, 
respectively, the total current carrying capacity of the loads 6A to 6C is 
10 A. The current carrying capacity of the fuse 4 connected with the loads 
6A to 6C needs to be 10/0.7=14.3 A because a current carrying capacity 
ratio of the fuse to the loads is set to be about 70% in a vehicle 
compartment. Thus, a fuse having a current carrying capacity of at least 
about 15 A needs to be used as the fuse 4, e.g. in the case of an 
application in the field of automotive vehicles. 
The relationship between the fuse 4 and the dimensions of the wires W2 to 
W4 to be connected with the downstream end of the fuse 4 is determined as 
follows. When the wire downstream from the fuse experiences a short 
circuit or like problem, the fuse needs to blow out before the wire 
experiences smoking or the circuit is damaged in order to protect the wire 
and circuits. Accordingly, there is used a wire having a large current 
carrying capacity compared with an actually flowing current, i.e. a wire 
having a large core cross section of 0.5 mm.sup.2 and a heavy weight. The 
relationship between the current carrying capacity of the fuse and the 
dimensions of the wire connected with the downstream end of the fuse is as 
defined in TABLE-1. 
TABLE 1 
__________________________________________________________________________ 
Vehicle Compartment 
Engine Compartment 
__________________________________________________________________________ 
Wire Dimensions (Core 
0.3 
0.5 
0.85 
1.25 
2 0.3 
0.5 
0.85 
1.25 
2 
Cross Section (mm.sup.2)) 
Current Carrying 
7A 
11A 
15A 
19A 
25A 
4A 
6A 
8A 10A 
19A 
Capacity (A) of Wire 
Current 
7.5A .smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
Carrying 
10A .smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
Capacity 
15A x .smallcircle. 
.smallcircle. 
.smallcircle. 
.smallcircle. 
x x .smallcircle. 
.smallcircle. 
.smallcircle. 
of Fuse 
20A x x .smallcircle. 
.smallcircle. 
.smallcircle. 
x x x .smallcircle. 
.smallcircle. 
(A) 25A x x x .smallcircle. 
.smallcircle. 
x x x x .smallcircle. 
30A x x x x .smallcircle. 
x x x x .smallcircle. 
__________________________________________________________________________ 
(.smallcircle.: wire can be used, x: wire cannot be used) 
As can be seen from TABLE-1, if a plurality of loads are connected e.g. in 
parallel with one fuse, the dimensions of the wires for connecting the 
fuse and the respective loads need to be large, leading to a considerable 
increase in the weight of the wiring harness. This in turn requires 
accessories for the wiring harness such as clips for engaging the wiring 
harness with a vehicle body and a protector to be enlarged and 
strengthened, and leads to an increased cost and size for the wires. Thus, 
the above connection results in an increased production cost of the wiring 
harness. 
Particularly, in automotive vehicles, about 70% of all wires (circuits) are 
connected with the loads having a current carrying capacity of 1 A or 
lower to transmit signals. The wires suitable for the above connection are 
too thick for the wires for signal circuits. 
Further, in FIG. 8, if the fuse 4 blows out upon occurrence of a short 
circuit in point A of the wire W2 connecting the load 6A and the fuse 4, 
power is not supplied to the wires W3, W4 having experienced no short 
circuit. Thus, the loads 6B and 6C disadvantageously stop operating. 
Furthermore, when a plurality of loads 6A-6C are connected in parallel with 
one single fuse 4, as can be seen in FIG. 8, the current carrying capacity 
of the fuse 4 has to be set higher than the sum of all currents actually 
flowing in the loads 6A-6C. Therefore the actual current at which the fuse 
4 will blow in case of a short circuit is raised, thus enlarging the 
danger for each load 6A-6C (e.g. an electronic circuit) of being damaged. 
Furthermore when the fuse 4 is blown it is difficult to discriminate which 
of the loads 6A-6C has caused an increased current to flow. 
In view of the above problems, an object of the invention is to provide an 
improved circuit protecting device allowing for a better protection of the 
connected loads and having a reduced size. 
SUMMARY OF THE INVENTION 
According to the invention there is provided, a circuit protecting device 
for an automotive wiring harness, comprising at least one primary side 
connecting portion, at least two secondary side connecting portions and at 
least two fusible elements. 
According to a preferred embodiment of the invention, each secondary side 
connecting portion is connected with the at least one primary connecting 
portion via at least one fusible element. 
Preferably, there is provided an equal number of secondary side connecting 
portions and primary connecting portions and wherein each secondary side 
connecting portion is connected with a corresponding primary side 
connecting portion via a fusible element. 
Further preferably, the at least one primary side connecting portion, the 
at least two secondary side connecting portions and the at least two 
fusible elements are arranged in and/or on a body, wherein the body is 
preferably formed by one or more covers and/or casted as a single molded 
body. 
According to a further embodiment, the each fusible element comprises at 
least one wire having a predetermined or predeterminable current carrying 
capacity, preferably wherein the wires each have an individually 
predetermined or predeterminable current carrying capacity, wherein 
further preferably the wires have a core cross section in the range of 
about 0.05 mm.sup.2 to about 0.3 mm.sup.2. 
According to a further preferred embodiment, the fusible elements are 
arranged at specified intervals on the surface of an insulating plate. 
Preferably, the at least one primary side connecting portion, the at least 
two secondary side connecting portions and the at least two fusible 
elements are arrangeable in a single socket means. 
Further preferably, at least fusible parts of the fusible elements are 
visible from the outside, such that a burned fusible element is easily 
recognizable. 
Still further preferably, the fusible elements are connectable to loads 
having a small current carrying capacity, in particular of 2 A or smaller 
in a one-to-one relationship. 
According to a further preferred embodiment, a multitude of fusible 
elements, which are connectable with neighboring loads are accommodated as 
a single unit in a fuse receptacle, in particular being located in an 
electrical connection box or in a fuse box which are dispersedly 
disposable in an automotive vehicle, in particular so as to shorten the 
length of wires connecting the corresponding fuses and loads. 
Preferably, thin wires having a core cross section of about 0.05 mm.sup.2 
to about 0.3 mm.sup.2 are usable as connecting wires for connecting the 
fusible elements and the loads, while wires having a core cross section of 
about 0.5 mm.sup.2 or larger are usable as power source side wires and are 
disposed on the power source side of the fusible elements, wherein further 
preferably the usable power source side wires each have one end connected 
with a power source and the other end branched to be connected with one or 
more fusible elements. 
According to a preferred embodiment, there is provided a circuit protecting 
device for an automotive wiring harness, comprising a fuse mounted in each 
circuit for supplying power from a power source to a corresponding load, 
wherein one fuse is connected only with one load so that, upon blowout of 
the fuse, only a power supply to the load connected with the blown fuse is 
cut off. 
In other words, a single fuse is provided in a circuit for connecting a 
power source and a load so that the fuse blows out upon a short circuit of 
a wire to prevent a wire from getting burnt. Especially, only a power 
supply to a circuit having experienced a short circuit is cut, thereby 
eliminating an influence on other circuits and shortening a total length 
of the wires used to connect the fuses and the loads. 
In other words, a fuse is provided in a circuit for connecting a power 
source and a load so that the fuse blows upon a short circuit of a wire to 
prevent a wire from getting burned. Especially, only a power supply to a 
circuit having experienced a short circuit is cut, thereby eliminating an 
influence on other circuits. 
Thus there is provided a way to provide a lighter wiring harness by making 
the dimensions of wires to be connected with loads at downstream sides of 
fuses and to ensure a secure power supply to loads connected with wires 
having experienced no short circuit. 
In the above circuit protecting device, the fuses and the loads are 
connected in one-to-one relationship and, accordingly, the current 
carrying capacity of each fuse can be made smaller. Thus, the dimensions 
of the wires for connecting the fuses and the loads can be made smaller, 
which contributes to lightening the wiring harness. Further, since the 
circuits are individually protected, upon blowout of a fuse, only a power 
supply to a load connected with this fuse is cut off. Thus, the loads 
connected with the wires having experienced no short circuit are not 
influenced. 
As is clear from the above, since the loads and fuses are mounted in 
one-to-one relationship, the current carrying capacity of each fuse can be 
made smaller. As a result, thin wires having a core diameter of 0.3 
mm.sup.2 to 0.05 mm.sup.2 can be used as wires for connecting the fuses 
and the loads. Particularly, in the case that the load is a signal device 
having a current carrying capacity of 1 A or smaller, the fuse is allowed 
to have a capacity of 2 A or smaller and the wire for connecting the fuse 
and the signal device is allowed to have a very small core cross section 
of 0.14 mm.sup.2. Since about 70% of all circuits are signal circuits, the 
total weight of the wires constituting the wiring harness can be 
remarkably reduced. At the same time, the wiring harness can be 
manufactured at a reduced size because of the use of thin wires. 
Further, a circuit protection can be individually realized for the loads. 
Accordingly, when the wire experiences a short circuit, only the fuse 
connected with this wire blows out. Since only the circuit connected with 
the wire having experienced a short circuit is brought into an inoperative 
state, the number of inoperative circuits can be minimized. 
Furthermore, if the fuses connected with the respective loads are formed by 
an integrated flat fuse including a plurality of small size and small 
capacity electrodes, an increase in the number of fuses to be mounted 
neither requires a large mounting space nor makes the junction box larger 
and heavier. 
According to a preferred embodiment, the fuses connected in one-to-one 
relationship with the loads are formed by an integrated flat fuse 
comprising a plurality of conductive fusible elements arranged at 
specified intervals on the surface of an insulating plate, and that a 
plurality of flat fuses are accommodated in fuse receptacles formed on a 
junction box. 
A flat fuse which the present applicant proposed in Japanese Unexamined 
Patent Applications Nos. 7-91698 and 7-91699 may be suitably used for the 
above flat fuse. This flat fuse is such that fusible elements made of 
metal wire or flat metal tape are adhered to the surface of an insulating 
plate at specified intervals. 
The number of fuses increases because the fuses are mounted in one-to-one 
relationship with the loads. By using a flat fuse, a plurality of fuses 
can be integrated on one insulating plate. The multielectrode fuse 
necessitates no large fuse mounting space, and enables the fuses to be 
smaller and lighter. 
Preferably, the loads connected in one-to-one relationship with the fuses 
have a small current carrying capacity of 2 A or smaller, and wherein the 
loads are connected with the fuses having a small current carrying 
capacity of 3 A via thin wires having a core cross section of 0.3 mm.sup.2 
to 0.05 mm.sup.2, preferably 0.14 mm.sup.2. 
If the loads connected in one-to-one relationship with the fuses are signal 
devices having a current carrying capacity of 2 A, mostly of 1 A or 
smaller, thin wires having a core cross section of 0.3 mm.sup.2 to 0.05 
mm.sup.2, preferably 0.14 mm.sup.2 can be used as wires for the signal 
circuits. Then, since about 70% of all circuits are signal circuits, the 
total weight of the wiring harness can be remarkably reduced. 
A preferred embodiment of the invention provides a circuit protecting 
device for an automotive wiring harness, wherein in circuits connected 
with loads mounted in an automotive vehicle, fuses are connected in 
one-to-one relationship with the loads and that a multitude of fuses 
connected with neighboring loads are accommodated as a single unit in a 
fuse receptacle of one of the electrical connection boxes or in one of the 
fuse boxes which are dispersedly disposed in the vehicle so as to shorten 
the length of wires connecting the corresponding fuses and loads. 
In the above circuit protecting device, since the fuses are connected in 
one-to-one relationship with the corresponding loads, the current carrying 
capacity thereof can be made smaller. Accordingly, the wires connecting 
the fuses and loads are allowed to have a smaller core cross section, 
thereby making the wiring harness lighter. Further, upon blowout of one 
fuse due to a short circuit in one wire, a power supply to one load 
connected with the blown fuse is cut off. Thus, the circuits are 
individually protected and the loads connected with the wires having 
experienced no short circuit are not affected. 
Further, the fuses connected in one-to-one relationship with the 
neighboring loads are combined and accommodated in the branch connection 
box or fuse box which is located near the neighboring loads. Accordingly, 
the length of the wires connecting the corresponding fuses and loads can 
be shortened. This prevents a total length of the wires from getting 
excessively long even if one fuse is provided for each load. 
It is preferable to form the fuses by flat fuses having a plurality of 
electrodes in which conductive fusible elements are arranged at specified 
intervals on the surface of an insulating plate, and to accommodate the 
flat fuses in the fuse receptacles of the electrical connection boxes 
and/or in the fuse boxes which are dispersedly disposed in the vehicle. 
Although the number of the fuses increases because they are provided in 
one-to-one relationship with the loads, if the flat fuse is as above, a 
multitude of fuses can be arranged on a single insulating plate. By using 
the flat fuses, no extra space is required to dispose the fuses and the 
fuses can be made smaller and lighter. 
It is also preferable to use thin wires having a core cross section of 0.05 
mm.sup.2 to 0.3 mm.sup.2 as the wires for connecting the fusible elements 
of the flat fuse and the loads, and to use wires having a core cross 
section of 0.5 mm.sup.2 or larger as the wires each having one end 
connected with a power source and the other end branched to be connected 
with a plurality of fusible elements. 
Further, since about 70% of the loads connected in one-to-one relationship 
with the fuses are signal devices having a current carrying capacity of 2 
A or lower, mostly 1 A or lower, thin wires having a core cross section of 
0.05 mm.sup.2 to 0.3 mm.sup.2, practically 0.14 mm.sup.2 can be used as 
wires for signal circuits having a current carrying capacity of 1 A or 
lower. Thus, the total weight of the wiring harness can be remarkably 
reduced. 
As is clear from the above description, in the above circuit protecting 
device for an automotive wiring harness, since the loads and fuses are 
connected in one-to-one relationship, the current carrying capacity of the 
fuses can be made smaller. As a result, thin wires having a core cross 
section of 0.05 mm.sup.2 to 0.3 mm.sup.2 can be used as wires connecting 
the corresponding fuses and loads. Particularly, when the load is a signal 
device having a current carrying capacity of 1 A or lower, the fuse is 
allowed to have a current carrying capacity of 2 A or lower, and the wire 
connecting these fuse and load is allowed to have a core cross section of 
as small as 0.14 mm.sup.2. Further, since about 70% of all circuits are 
signal circuits, a total weight of the wires forming the wiring harnesses 
can be remarkably reduced. At the same time, the use of thin wires leads 
to a reduction in a production cost. 
Further, a circuit protection can be individually realized for the loads. 
Accordingly, when the wire experiences a short circuit, only the fuse 
connected with this wire blows out. Since only the circuit connected with 
the wire having experienced a short circuit is brought into an inoperative 
state, the number of inoperative circuits can be minimized. 
Further, the fuse boxes are dispersedly disposed in the automotive vehicle, 
in positions near many neighboring loads. These loads are connected with 
the fuses accommodated in the fuse boxes. Accordingly, despite the 
provision of the fuses in one-to-one relationship with the loads, the 
total length of the wires can be shortened. 
Although the number of the fuses increases because they are connected in 
one-to-one relationship with a multitude of loads, no problem arises if 
small size and small capacity flat fuses having a multitude of integrated 
electrodes are used. In other words, a large number of fuses does not lead 
to a larger space, or a larger size or a heavier weight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 1(A), loads 10A to 10J are connected, via wires or cables 
11A to 11J and connecting portions or connectors 17A-17J, with downstream 
ends of fuses 14A to 14J accommodated in fuse receptacles 13A, 13B formed 
on a junction box 12. In other words, unlike the prior art shown in FIG. 3 
wherein a plurality of loads are connected with one fuse, one fuse is 
connected with one load via one wire. 
Upstream ends of the fuses 14A to 14E connected with a battery BA are 
connected with one circuit 15A via connecting portions or connectors 
16A-16E, whereas upstream ends of the fuses 14G to 14J are connected with 
one circuit 15B via connecting portions or connectors 16G-16J. The 
circuits 15A and 15B are joined and connected with the battery BA. 
In this embodiment, the loads 10A to 10J connected with the fuses 14A to 
14J in one-to-one relationship include signal devices have a current 
carrying capacity or nominal current value or nominal power value of 1 A 
or smaller. Accordingly, the current carrying capacity of the fuses 14A to 
14J connected with these loads 10A to 10J via the wires 11A to 11J is set 
e.g. at 2 A. The wires 11A to 11J are thin wires having a core cross 
section of 0.14 mm.sup.2 and having a current carrying capacity of 5 A. 
The wires are lightweight with a mass of 2.4 g/m, and an outer diameter of 
the final wire covered with insulation coating of 1.0 mm. 
In the case of the use in the vehicle compartment, a current carrying 
capacity ratio of the fuse to the load is set at about 70% as described 
above. For example, if a load has a current carrying capacity of 5 A, a 
fuse having a current carrying capacity of about 7 A is used. In this 
case, a wire connecting a downstream end of the fuse and the load is a 
thin wire suitable for an actual current flow. For example, a wire having 
a core cross section of 0.3 mm.sup.2 and a current carrying capacity of 8 
A is used. 
The relationship between the current carrying capacity (A) and the wire 
dimensions is as shown in TABLE-2. Accordingly, the loads are connected in 
one-to-one relationship with the fuses having specified current carrying 
capacities corresponding to the current carrying capacities of the 
respective loads via the wires of specified dimensions having current 
carrying capacities corresponding to the current carrying capacities of 
the respective fuses. Thus, if the current carrying capacities of the 
loads differ, e.g. 3 A, 5 A and 2 A as in the prior art shown in FIG. 8, 
thin wires of different dimensions may be used for connection. 
Alternatively, in accordance with the maximum current carrying capacity of 
the load, i.e. 5 A, all wires may have a core cross section of 0.3 
mm.sup.2. 
TABLE 2 
______________________________________ 
Core Cross 
Current Carrying 
Mass Final Outer 
Section (mm.sup.2) 
Capacity (A) (g/m) Diameter (mm) 
______________________________________ 
0.14 5 2.4 1.0 
0.2 6 3.2 1.2 
0.3 8 5 1.4 
0.5 11 7 1.6 
______________________________________ 
As described above, by connecting the loads having a small current carrying 
capacity and mainly including signal devices in one-to-one relationship 
with the fuses, thin wires can be used downstream from the fuses, thereby 
remarkably reducing the weight of the wires. In the case that a short 
circuit occurs in point P of the wire 11A between the load 10A and the 
fuse 14A, the fuse 14A blows out before the wire 11A experiences smoking, 
thereby protecting the load 10A. Further, since the loads 10B to 10E 
connected with the other wires 11B to 11E which have not experienced any 
short circuit are not influenced, power can be supplied to them. 
A further preferred embodiment of the invention is shown in FIG. 1(B). The 
embodiment shown in FIG. 1(B) differs from the embodiment shown in FIG. 
1(A) in that the two fusible elements or fuses 14A and 14B are connected 
with the circuit 15A via one single connector or connecting portion 16AB' 
which may be a wire and/or solder connecting two wires and/or a metal 
plate or the like. 
The fuses 14A to 14E, 14F to 14J of a small current carrying capacity to be 
connected in one-to-one relationship with the loads 10A to 10E, 10F to 10J 
are formed by flat fuses 20 having five electrodes as shown in FIGS. 2(A) 
and 2(B). The fuses 20 are to be accommodated in the fuse receptacles 13A, 
13B formed on the junction box 12 and connected with circuits formed by 
busbars (not shown) accommodated in the junction box 12. 
Each fuse 20 with five electrodes includes five fusible elements (fuse main 
body) 21 made of metal flat tape and an insulating plate 22 formed at its 
upper end with a window 22a. The five fusible elements 21 are arranged at 
specified intervals and bent such that they hold the insulating plate 22 
from opposite sides and their bent portions are located in the window 22a. 
After being fitted with covers 23 or after being integrally casted in a 
molded body, being preferably transparent, the flat fuses 20 are inserted 
into the fuse receptacles 13A, 13B formed on the junction box 12. In the 
respective fuse receptacles 13A, 13B, the insulating plate 22 is placed on 
an insulating base plate 24, bringing five pairs of terminal electrodes 
25', 25" projecting from the opposite surfaces of the base plate 24 into 
contact with the five fusible elements 21 via connecting portions or 
connectors 26', 26" being arranged on the opposite surfaces of the 
insulating plate 22 of the flat fuse 20, in particular in a parallel 
manner. The connectors 26, 26" interact with the electrodes 25', 25" on 
the base plate 24 thereby deflecting these and insuring a good and 
reliable electric connection. Two or more of the connectors 26' or 26" may 
be formed of a single metal piece or be electrically connected so as to 
form a single electrode. The electrodes 26', 26" may be deflectable, in 
particular in a direction normal to the insulating plate 22, in order to 
insure easy placement of the flat fuse 20 inside the fuse receptacle 
13(A), 13(B). If a transparent body or cover 23 is used, it can be easily 
discriminated which of the fusible elements 21 has burned thus allowing a 
possibility of discriminating which load has drawn an increased current. 
Although the flat fuse shown in FIGS. 2(A), 2(B) has five electrodes, there 
can be provided a flat fuse having a desired number of electrodes only by 
increasing the number of fusible elements arranged on the insulating 
plate. However some electrodes or connecting portions, in particular on 
the current input side or primary side, may be joined in one or more 
single electrodes. The use of the integrated flat fuse 20 including a 
plurality of small size and small capacity electrodes compensates for an 
increase in the number of fuses due to the one-to-one arrangement of loads 
and fuses, thereby preventing the protecting device from getting larger 
and heavier. 
As shown in FIG. 3, according to this embodiment, junction boxes A, B are 
disposed on the opposite sides of an instrument panel, i.e. of a front 
portion of a vehicle compartment, and fuse boxes C, D are disposed in an 
engine compartment and a trunk compartment, respectively. A flat fuse 
having a multitude of integrated electrodes is accommodated in each of the 
boxes A to D. 
A circuit for connecting a power source or battery BA with the flat fuses 
accommodated in the boxes A to D is constructed as shown in FIG. 4. 
Specifically, the power source BA is connected with the junction boxes A 
and B via branch wires W20 and W10, respectively. In the junction box A, a 
power source side circuit is branched and connected with fuses H1 to H3 
connected with loads E1 to E3 via thin wires W30, and through circuits or 
connections T1 and T2 connected with the fuse boxes C and D via wires W40, 
W50, respectively are provided. On the other hand, in the junction box B, 
the power source side circuit is branched and connected with fuses H4 to 
H8 connected with loads E4 to E8 via thin wires W30. 
In the fuse box C connected with the through circuit T1 of the junction box 
A via the wire W40, the wire W40 is branched and connected with fuses H9 
to H11 connected with loads E9 to 11 via thin wires W30, respectively. 
Likewise, in the fuse box D connected with the through circuit T2 of the 
junction box A via the wire W50, the wire W50 is branched and connected 
with fuses H12 to H16 connected with loads E12 to E16 via thin wires W30, 
respectively. 
The loads E1 to E16 connected in one-to-one relationship with the fuses 
accommodated in the boxes A to D are disposed in the vicinity of the 
corresponding fuses. In other words, the fuses connected with the 
neighboring loads are combined and accommodated in a neighboring one of 
the junction boxes or fuses boxes which are dispersedly disposed in the 
automotive vehicle. 
In this embodiment, the loads E1 to E16 connected in one-to-one 
relationship with the fuses H1 to H16 include signal devices having a 
current carrying capacity of 1 A and, accordingly, the current carrying 
capacity of the fuses H1 to H16 connected with the loads E1 to E16 via the 
wires W30 are set to about 2 A. Further, wires having a current carrying 
capacity of 5 A and a small core cross section of 0.14 mm.sup.2 are used 
as wires W30. The wire having a core cross section of 0.14 mm.sup.2 is 
lightweight with a mass of 2.4 g/m, and an outer diameter of the final 
wire covered with insulation coating of 1.0 mm. 
As described above, by connecting the loads having a small current carrying 
capacity and mainly including signal devices in one-to-one relationship 
with the fuses, thin wires can be used downstream from the fuses, thereby 
remarkably reducing the weight of the wires. In the case that a short 
circuit occurs in point P of the wire W30 between the load E1 and the fuse 
H1, the fuse H1 blows out before the wire W30 experiences smoking, thereby 
protecting the load E1. Further, since the loads E2 to E16 connected with 
the other wires W30 which have not experienced any short circuit are not 
affected, power can be supplied to them. 
The fuses H1 to H16 of a small current carrying capacity to be connected in 
one-to-one relationship with the loads E1 to E16 are formed by flat fuses 
20 having a plurality of electrodes as shown in FIGS. 2(A) and 2(B). 
The flat fuse to be accommodated in the junction box A has at least 3 
electrodes; the flat fuse to be accommodated in the junction box B is the 
one having at least 5 electrodes as shown in FIGS. 2(A) and 2(B); the flat 
fuse to be accommodated in the fuse box C has at least 3 electrodes; and 
the flat fuse to be accommodated in the fuse box D has at least 5 
electrodes. 
The flat fuse to be accommodated in the junction box A or B is similarly 
constructed to the flat fuse described in reference to FIGS. 2(A) and 
2(B). 
The fuse box D is constructed as shown in FIGS. 5(A) to 5(D), and a flat 
fuse 20 is accommodated in a housing 30. Similar to the flat fuse shown in 
FIGS. 2(A) and 2(b), the flat fuse 20 is such that five fusible elements 
21 are bent over the opposite surfaces of an upright insulating plate 22 
and terminal fittings 31, 32 connected with the wires W40 and W30 are 
pressingly connected with the opposite sides of the fusible elements 21. 
The housing 30 is provided with a lid 35. The housing 30 is closed by the 
lid 35 after the flat fuse 20 is accommodated therein. 
The terminal fitting 31 connected with the wires W40 at the power supply 
side includes two terminal fittings 31A, 31B. The terminal fitting 31A is 
formed with two contact portions 31a, 31b connectable with two fusible 
elements 21 at its upper portion, and a connection portion 31c at its 
lower portion. A wire mount portion 31d is formed at the bottom of one 
lateral side of the connection portion 31c. The terminal fitting 31A is 
connected with the wire W40 via the wire mount portion 31d. The terminal 
fitting 31B is similarly shaped to the terminal fitting 31A, and has three 
contact portions connectable with three fusible elements 21 at its upper 
portion. 
Each of the terminal fittings 32 connected with the loads E12 to E16 via 
the wires W30 is formed with a contact portion 32a to be brought into 
pressing contact with one fusible element 21 at its upper portion, a wire 
mount portion 32b to be connected with one wire W30 at its lower end. The 
terminal fitting 32 is connected with the wire W30 via the wire mount 
portion 32b. 
Since the fuse box C is similarly constructed to the fuse box D, no 
description is given thereto. 
As described above, by bringing the terminal fittings 31, 32 connected with 
the respective wires into pressing contact with the opposite sides of the 
fusible elements 21 bent over the opposite surfaces of the insulating 
plate 22, each load is connected with one fuse (fusible element 21). 
The construction of the fuse boxes C and D is not limited to the one shown 
in FIGS. 5(A) to 5(D). They may be constructed as shown in FIGS. 6(A) and 
6(B). Specifically, at the power source side of the fuse box, there is 
disposed a busbar 36 connected with the power source via the wire W40 or 
W50 and a connector (not shown). The busbar 36 is formed with five tabs 
36a projecting in parallel. Intermediate terminal fittings 37 are fitted 
on the tabs 36a, and contact portions 37a thereof are pressingly connected 
with the fusible elements 21. Since the load side of the fuse box has the 
same construction as a corresponding side of the fuse box shown in FIGS. 
5(A) to 5(D), no description is given thereto. 
If the fuse boxes C, D are dispersedly disposed in positions close to a 
multitude of neighboring loads to be connected with the fuses, the length 
of the wires connecting the loads and the fuses can be shortened as 
compared to a case where the fuses are accommodated only in the junction 
boxes A and B and connected with the respective loads as shown in FIG. 7. 
Therefore, a total length of the wires forming wiring harnesses to be 
arranged in a vehicle can be shortened. 
Further, as described above, since thin wires can be used to connect the 
fuses and the loads in one-to-one relationship, the total weight of wiring 
harnesses to be mounted in the vehicle can be remarkably reduced.