Electricity: electrical systems and devices – Igniting systems
Reexamination Certificate
2000-02-07
2002-07-09
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Igniting systems
C361S104000, C337S168000, C337S170000, C337S186000, C337S414000
Reexamination Certificate
active
06418005
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power circuit breaker to cut off instantaneously a power circuit with a gas pressure generated by an igniter unit to release a fuse element from a pair of interconnection terminals.
2. Related Art
FIG. 3
shows a conventional fuse
61
for cutting off a large power circuit. The fuse
61
has a synthetic resin main housing
62
, a conductive metal fuse element
63
received in the main housing, and a synthetic resin cover
64
for covering an upper opening of the main housing
62
.
The fuse element
63
has a generally U-shaped base plate
65
, two terminals
66
each unitarily formed with the base plate
65
at one end thereof, a tin piece
67
disposed on the base plate
65
for thermal accumulation. Each terminal
66
is opposed to a resilient contact strip
68
formed separately from the fuse element
63
. The terminal
66
and resilient contact strip
68
can contact a pin terminal of a fuse box (not shown) or the like. The pin terminal is inserted from a lower opening
69
of the main housing
62
.
The base plate
65
is formed with a locking piece
70
extending diagonally outward. The locking piece
70
abuts against an inner shoulder of the main housing
62
to prevent the fuse element
63
from being released from the main housing
62
. The base plate
65
is fused by an overcurrent to cut off an associated power circuit.
FIG. 4
is a graph showing a time required for fusing of the fuse
61
. The time is a function of applied current. This fuse characteristic is obtained by a measurement devise shown in FIG.
5
.
In
FIG. 5
, denoted
61
is a fuse,
71
a busbar connected to the fuse
61
, and
72
an electrical wire connected to the busbar
71
for power supply. Two busbars
71
are fixed on a base
73
made of an insulation material. Each busbar
71
has an upward extending male terminal
74
which can be connected to the terminal
66
(
FIG. 3
) of the fuse
61
.
As illustrated in
FIG. 4
, the fusing time T of the fuse
61
(
FIG. 5
) decreases like a quadratic curve as current I increases. Particularly, where the applied current I is comparatively small, the fusing time T increases significantly, which is shown in a zone surrounded by a phantom line A. The vertical scale for the fusing time T is logarithmic.
The conventional fuse
61
, as shown in
FIG. 4
, requires a significantly long fusing time when the overcurrent is within a smaller range. Thus, it is difficult to cut off instantaneously an associated circuit against a smaller overcurrent. This happens also in case of an intermittent short circuit or a rare short circuit current. In addition, even in an abnormal vehicle state like a collision accident, a power circuit is not cut off when no sufficient excessive current is supplied. The conventional fuse has the disadvantages.
To solve these problems, there is proposed a power circuit breaker
76
shown in
FIGS. 6 and 7
.
Referring to
FIG. 6
, the power circuit breaker
76
has a pair of terminals
77
,
78
, two multi-contact-point elastic plates
80
(
FIG. 7
) each connected to one of the terminals
77
,
78
, an electrically conductive shaft
79
slidably contacting with the plates
80
, and an igniter unit
81
disposed in one side of the shaft
79
.
The shaft
79
is joined to a drive shaft
82
at the other end thereof. The drive shaft
82
is mounted with a torsion spring
83
. The igniter unit
81
has a gas-blasting agent and a heater therein. The heater is connected to a pair of lead wires
84
. The shaft
79
and the drive shaft
82
are slidably received in a housing
85
of the power circuit breaker
76
.
In
FIG. 6
, the terminals
77
,
78
each are connected to the shaft
79
by way of one of the plates
80
. An overcurrent flown between the terminals
77
,
78
is detected by a sensor. Successively, a current is applied to the lead wires
84
, so that the heater heats up the gas blasting agent. The blasting gas pressure moves the shaft
79
in its disconnecting direction, This cuts off electrical connection between the terminals
77
,
78
. The torsion spring
83
urges the stopper
86
outward so that the stopper
86
abuts against the housing
85
, preventing a return movement of the shaft
79
.
However, the power circuit breaker
76
has disadvantages described in the following. That is, the power circuit breaker
76
has the expensive multi-contact-point elastic plates
80
connected to the terminals
77
,
78
for allowing a decreased friction force. Furthermore, the power circuit breaker
76
requires parts increased in number and in cost and is complicated in configuration, because the torsion spring
83
and the stopper
86
are applied for stopping the shaft
79
. In addition, the multi-contact-point elastic plates
80
make the terminals
77
,
78
and the shaft
79
larger for reducing an electrical resistance between the plates
80
and the shaft
79
, which tends to enlarge related parts of the power circuit breaker
76
, resulted in an enlarged breaker in overall size.
Japanese Patent Application H. 10-241524 discloses a power circuit breaker (not shown) in which a gas bursting force breaks a connection substrate to cut off a power circuit. Because of this configuration, the power circuit breaker is not reusable and is not commonly applied to various uses. Moreover, the power circuit breaker has another disadvantage that its main housing including an igniter unit requires an additional fitting work to secure it by bolting.
SUMMARY OF THE INVENTION
In view of the disadvantages of the aforementioned fuse and breakers, an object of the invention is to provide a power circuit breaker which can positively cut off a power circuit even at a smaller overcurrent. The breaker also allows a reliable cut-off of the power circuit when a sensor detects an abnormal state like an unintentional heat generation state or on a vehicle collision accident. In addition, the breaker has a simplified configuration consisting of parts reduced in number. The breaker is not expensive in cost, compact, easy in assembling, reusable, and suitable for a general-purpose.
For achieving the object, a power circuit breaker according to a first aspect of the present invention includes a main housing, an igniter unit disposed in a cylindrical wall formed in the main housing, a holder disposed in the cylindrical wall so as to oppose to the igniter unit, a boss of the holder engaging with the cylindrical wall, a fuse element held by the holder, and a pair of interconnection terminals disposed in the main housing. Each end of the fuse element is electrically connected to one of the interconnection terminals.
In a second additional aspect of the present invention, the holder is locked by a locking lance formed in the main housing when each end of the fuse element has engaged with one of the interconnection terminals.
In a third additional aspect of the present invention, an activating pressure force generated by the igniter unit is larger than the sum of the stopping force of the locking lance and the friction force of the interconnection terminals to the fuse element.
In a fourth additional aspect of the present invention, the holder rests on the locking lance when the fuse element has been released from the interconnection terminals after activation of the igniter unit.
In a fifth additional aspect of the present invention, the fuse element is engaged with and stopped by an insertion hole of the holder.
In a sixth additional aspect of the present invention, the igniter unit is pressed into to be mounted in the cylindrical wall.
In a seventh additional aspect of the present invention, the interconnection terminals each are locked in the main housing with a locking piece.
In an eighth additional aspect of the present invention, the interconnection terminals each are a receptacle type terminal having two resilient contact strip portions one of which is connected to one end of the fuse element and the other of which is connected to an opposing terminal of a power circuit.
In the
Endo Takayoshi
Matsumura Norio
Nakamura Goro
Armstrong Westerman & Hattori, LLP.
Leja Ronald W.
Yazaki -Corporation
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