Electricity: circuit makers and breakers – Solid contact – Push button operated
Reexamination Certificate
2000-08-16
2001-12-04
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Push button operated
C200S531000, C200S341000
Reexamination Certificate
active
06326570
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a switch used for controlling switching-on and-off of a stop lamp that is turned on and off in operable connection with a brake pedal in an automobile.
2. Description of Related Art
There are two types of stop lamp switch of an automobile: One is a large-current type, wherein a stop lamp circuit connected to a power source is directly opened and closed with a switch, and the other is a small-current type, wherein such stop lamp circuit is indirectly opened and closed by the control of a microprocessor in an electronic circuit through relays or the like. With the progress of overall electronic control of automobiles in recent years, the latter has found more applications.
One of the conventional switches will be described below with reference to
FIGS. 11
to
14
.
FIG. 11
is a cross sectional view of a conventional switch and
FIG. 12
is an exploded perspective of the same. The switch
10
comprises a cylindrical case
1
made of insulating resin having an inner bottom surface
1
A and an upper open end. A pair of stationary contacts
2
consisting of a conductive metal plate is embedded in the inner wall
1
B of the case
1
. The distal ends of this pair of stationary contacts
2
make connection parts
2
A and protrude through apertures in the bottom of the case
1
, these being connected to an electronic circuit of the automobile through a connector (not shown).
Reference numeral
3
denotes a contact piece that is made of a conductive thin metal plate having resiliency, and numeral
4
denotes an operation shaft that is accommodated within the case
1
such as to be displaceable in an upward and a downward directions. One end of the contact piece
3
is fixed to one side (right hand side in the drawing) of a support portion
4
A at the lower end of the operation shaft
4
with a rivet
5
, while the other end, which makes a pair of movable contacts
3
A, is resiliently pressed against the stationary contacts
2
. The contact piece
3
has two arms
3
B connecting the movable contacts
3
A with the base end of the contact piece, and these are slightly deformed when the movable contacts
3
A are in contact with the stationary contacts
2
. A coil spring
6
is inserted in a compressed state in a cavity
4
B formed on the underside of the operation shaft
4
and pressed against the inner bottom surface
1
A of the case
1
so that it gives the operation shaft
4
an upward biasing force.
The upper open end of the case
1
is covered by a cover
7
, which has a through-hole
7
A in the center thereof. A cylindrical bearing
8
having threads on the outer periphery thereof is fixed on the through-hole
7
A, so that the operation shaft
4
extends through the through-hole
7
A of the cover
7
and the hole
8
A bored in the bearing
8
.
The switch
10
constructed as described above is mounted to an automobile and operates as described below.
FIG. 13
is a side view showing a state wherein the switch
10
is mounted on an automobile. Reference numeral
11
denotes a brake pedal, which is integrally formed with an angle
11
A. The upper end of the angle
11
A is supported around a support
11
B such as to be rockable in relation to the automobile body. The switch
10
is mounted to the automobile body with nuts
12
which engage the threads on the bearing
8
in a state wherein the operation shaft
4
is pressed by the angle
11
A.
As previously mentioned, a connector
13
is attached to the switch
10
, so that one of the pair of stationary contacts
2
is directly connected to an electronic circuit
15
of the automobile, while the other stationary contact
2
is connected to the electronic circuit
15
through a power source
14
. The electronic circuit
15
comprises microprocessors for controlling a stop lamp circuit, anti-lock brake system, traction control device, and others.
While the operation shaft
4
of the switch is pressed by the angle
11
A, the movable contacts
3
A of the contact piece
3
are resiliently pressed against the inner wall
1
B of the case
1
at a point that is away from the stationary contacts
2
, as shown in FIG.
14
A. When the brake pedal
11
is depressed, as indicated by broken lines in
FIG. 13
, the angle
11
A rocks around the support
11
B as the fulcrum. When the angle
11
A departs from the operation shaft
4
of the switch
10
, the operation shaft
4
returns to the state shown in
FIG. 11
by the force of the coil spring
6
, whereupon the movable contacts
3
A of the contact piece
3
slide against the inner wall
1
B of the case
1
as being resiliently pressed thereto, and contact the pair of stationary contacts
2
as shown in FIG.
14
B. The two stationary contacts
2
are thus connected to each other through the contact piece
3
, thereby turning on the stop lamp.
In such switch as described above, because the movable contacts
3
A of the contact piece
3
make point contact with the stationary contacts
2
and they slide against the stationary contacts
2
and the inner wall
1
B of the case
1
always at the same point, when foreign substances exist between the contacting parts, they cannot establish reliable contact with each other. Particularly, it is often the case that foreign substances, such as galls of the insulating resin of the case
1
or carbides due to the arcs generated when the contact piece
3
contacts with and separates from the stationary contacts
2
, are deposited on the stationary contacts
2
.
Moreover, the contact piece
3
is held on one side of the support part
4
A at the lower end of the operation shaft
4
, and the movable contacts
3
A of the contact piece
3
are pressed against the stationary contacts
2
through the arms
3
B that are slightly deformed. A certain load is thus exerted to the operation shaft
4
on one side, whereby the operation shaft
4
is accommodated in a slightly tilted manner within the case
1
and the bearing
8
, within a range determined by the gaps present between the operation shaft
4
and the hole
8
A of the bearing
8
. Consequently, when mounted on the automobile, as the brake pedal
11
is depressed and the angle
11
A departs from the operation shaft
4
, whereby the operation shaft
4
is released from the pressing force from the angle
11
A and restores to its initial position by means of the coil spring
6
, the switch
10
may sometimes produce noises, as the tilted operation shaft
4
collides against the case
1
or the bearing
8
.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a switch for turning on and off the brake lamp of an automobile, whereby stable contact at the contacting portions can be achieved and noises in operation can be eliminated.
To accomplish the above object, a switch according to the present invention comprises:
a cylindrical case made of insulating resin having an upper open end;
a pair of opposite spaced stationary contacts arranged on an inner wall of the case, each of said pair of stationary contacts having a contact part that extends vertically within the case in a position spaced away from the inner wall of the case, with a lower end thereof being bent outwards;
an operation shaft that is supported within the case such as to be displaceable with respect to the case in an upward and a downward directions;
a coil spring provided within the case for biasing the operation shaft upwards;
a cover for closing the upper open end of the cylindrical case, said cover having a central through-hole through which the operation shaft passes;
a bearing connected to the upper open end of the cylindrical case for uprightly supporting the operation shaft; and
a contact piece inserted between a bottom end of the operation shaft and the coil spring, said contact piece comprising a middle part at which it is connected to the bottom end of the operation shaft, a pair of arms that extend obliquely downward from opposite edges of said middle part in an outwardly spreading manner, and a pair of movabl
Fujii Takeshi
Ishihara Shoichi
Matsushita Teruhisa
Nishimura Yusaku
Friedhofer Michael
Jordan and Hamburg LLP
Matsushita Electric - Industrial Co., Ltd.
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