Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With fusible – combustible or explosive material
Reexamination Certificate
1999-11-15
2001-08-28
Picard, Leo P. (Department: 2832)
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With fusible, combustible or explosive material
C337S405000, C337S182000, C337S185000, C361S011000
Reexamination Certificate
active
06281782
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a circuit breaker, and more particularly to a circuit breaker for cutting off an electric circuit in a short time.
In an electric equipment system installed in a vehicle, if any abnormality should occur due to load of power window or the like, or if any abnormality should occur in the wire harness or the like composed of plural wires connecting the battery and each load, a large-current fuse interposed between the battery and the wire harness is melted to cut off between the battery and the wire harness, thereby preventing the loads and wire harness from burning down.
In the electric equipment system using such large-current fuse, however, if any abnormality should occur in the load such as power window, or if abnormality should occur in the wire harness of the like connecting the battery and each load, it is set so as not to melt down unless a current large than the preset allowable value flows in the large-current fuse.
Recently, various protective devices have been developed for cutting off between the battery and wire harness by detecting when a large current close to the allowable value is flowing continuously.
SUMMARY OF THE INVENTION
According to the investigation by the present inventors, a protective device as shown in
FIG. 10
is considered.
FIG. 10
is a sectional view showing an example of protective device using a bimetal.
Such protective device comprises a housing
103
made of an insulating resin or the like, and forming a fuse compartment
102
at the upper side, a lid
113
for opening and closing the fuse compartment
102
of the housing
103
, a power source terminal
105
disposed at the lower side of the housing
103
so that its upper end portion projects into the fuse compartment
102
, and the lower end exposed outside, with the portion exposed outside connected to a positive terminal of a battery
104
, and a load terminal
109
disposed at the lower side of the housing so that its upper end portion projects into the fuse compartment
102
, and the lower end exposed outside, with the portion exposed outside connected to a load
108
through a wire
107
for composing a wire harness
106
.
Such protective device further comprises a fusible element
110
made of a low melting point metal disposed in the fuse compartment
102
, with one end connected to the upper end of the power source terminal
105
, and other end connected to the upper end of the load terminal
109
, an intermediate terminal
111
disposed at an intermediate position of the power source terminal
105
and load terminal
109
, with the lower end disposed at the lower side of the housing
103
so as to be exposed outside, and the portion exposed outside connected to a negative terminal of the battery
104
, and a bimetal
112
made of two long plate members of different metals glued together, with the lower end side connected to the upper end of the intermediate terminal
111
and the upper end side being bent in an L-shape and disposed oppositely to the fusible element
110
.
In such constitution, by manipulation of an ignition switch or the like of the vehicle, while a current is flowing in a route of positive terminal of battery
104
, power source terminal
105
, fusible element
110
, load terminal
109
, wire
107
of wire harness
106
, load
108
, and negative terminal of battery
104
, if any abnormality should occur in the load
108
or the wire harness
106
connecting the load
108
and the protective device
101
, and a current exceeding the allowable value should flow in the fusible element
110
, it is heated and melted down.
As a result, the circuit is cut off, and the load
108
and wire harness
106
are protected.
Or when a large current flows in the fusible element
110
due to some abnormality occurring in the load
108
or the wire harness
106
connecting the load
108
and protective device
101
, if it does not exceed the allowable value, the fusible element
110
is heated by the current flowing in the fusible element
110
, and the bimetal
112
begins to deform. In a specified time after a large current begins to flow in the fusible element
110
, the leading end of the bimetal
112
contacts with the fusible element
110
, and a large short-circuit current flows in the fusible element
110
in a route composed of positive terminal of battery
104
, power source terminal
105
, fusible element
110
, intermediate terminal
111
and negative terminal of battery
104
, so that it is melted down.
As a result, if lower than the allowable value, when a certain current flows longer than a preset time, the circuit is cut off, and the wire harness
106
and load
108
are protected.
Aside from such protective device
101
, a protective device
121
shown in
FIG. 11
is also devised by the present inventor.
The protective device
121
shown in
FIG. 11
comprises a housing
122
made of insulating resin or the like, a power source terminal
124
buried at one side of the housing
122
, with the lower end portion connected to a positive terminal of a battery
123
, and a load terminal
128
buried at other side of the housing
122
, with the lower end portion connected to a load
127
through a wire
126
composing a wire harness
125
.
Moreover, one end of a wire
131
composed of a fusible conductor
129
made of a low melting point metal or the like formed in a U-shape and a heat resistant covering
130
formed to cover the fusible conductor
129
is connected to the upper end of the power source terminal
124
, and other end is connected to the upper end of the load terminal
128
. This wire
131
has a coil
132
made of a shape memory alloy, showing a shape being wound around the wire
131
as shown in
FIG. 9
when it is in martensite phase, and returning to the mother phase in a shape of tightening the wire
131
when heated to temperature of 120° C. to 170° C.
Further, outside of the housing
122
, there is an external terminal
133
with the upper end connected to one end of the coil
132
and lower end connected to a negative terminal of the battery
123
.
In such constitution, by manipulation of an ignition switch or the like of the vehicle, while a current is flowing in a route of positive terminal of battery
123
, power source terminal
124
, fusible element
129
of wire
131
, load terminal
128
, wire
126
of wire harness
124
, load
127
, and negative terminal of battery
123
, if any abnormality should occur in the load
127
or the wire harness
125
connecting the load
127
and the protective device
121
, and a current exceeding the allowable value should flow in the fusible element
129
, it is heated and melted down.
As a result, the circuit is cut off, and the load
127
and wire harness
125
are protected.
Or when a large current flows in the fusible conductor
129
due to some abnormality occurring in the load
127
or the wire harness
125
connecting the load
127
and protective device
121
, if it does not exceed the allowable value, the fusible conductor
129
is heated by the current flowing in the fusible conductor
129
, and the temperature of the coil
132
climbs up. In a specified time after a large current begins to flow in the fusible conductor
129
, when the temperature of the coil
132
reaches 120° C. to 170° C., the coil
132
is shifted from the martensite phase to the mother phase, and bites into the heat resistant covering
130
softened by heat, an contacts with the fusible conductor
129
, and a large short-circuit current flows in the fusible conductor
129
in a route composed of positive terminal of battery
123
, power source terminal
124
, fusible conductor
129
, coil
132
, external terminal
133
and negative terminal of battery
123
, so that it is melted down.
As a result, if lower than the allowable value, when a certain current flows longer than a preset time, the circuit is cut off, and the wire harness
125
and load
127
are protected.
In these protective devices
101
and
121
, however, the following problems have been disclosed.
Firs
Morimoto Mitsuaki
Yamaguchi Noboru
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Picard Leo P.
Vortman Anatoly
Yazaki -Corporation
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