Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Multiple contact type
Reexamination Certificate
1999-11-02
2001-03-20
Scott, J. R. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Multiple contact type
Reexamination Certificate
active
06204742
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic switch for a starter, and relates in particular to a construction for reducing the size of a magnetic switch.
2. Description of the Related Art
A conventional magnetic switch for a starter may have a construction like that shown in
FIGS. 7 and 8
, for example.
FIG. 7
is an end elevation of a conventional magnetic switch for a starter, and
FIG. 8
is a cross-section taken through line VIII—VIII in FIG.
7
.
In
FIG. 8
, an electromagnetic coil
3
wound onto a coil winding frame
2
or a coil bobbin composed of an insulating body and from which lead wires
18
are drawn is housed in a generally cylindrical switch case
9
. A thin-walled cylindrical bush
12
is inserted inside the coil winding frame
2
and is secured by fitting into the switch case
9
. A cylindrical fixed core
1
composed of a magnetic body having a collar portion
1
a
on an end portion is disposed inside the bush
12
. Furthermore, a movable core
10
is disposed inside the bush
12
facing the fixed core
1
, and a return spring
11
which is a coil spring is compressed and disposed between the fixed core
1
and the movable core
10
.
The switch case
9
houses the electromagnetic coil
3
as well as the fixed core
1
, and also houses the movable core
10
so as to be able to slide freely on the inner circumferential surface of the bush
12
. An end portion of the hollow cylindrical portion of the switch case
9
is thin-walled and forms a thin-walled portion
9
a
for securing a molded cap
8
molded from resin by crimping. A crimped portion
9
b
is formed on the extreme end of the thin-walled portion
9
a
by roll crimping the thin-walled portion
9
a
of the switch case
9
over a stepped portion
8
b
disposed around the entire circumference of an end portion of the molded cap
8
.
A rod-shaped movable contact shaft
4
slidably supported by the fixed core
1
is disposed inside the fixed core
1
. Furthermore, a movable contact
5
which is a flat plate-shaped conductor is disposed on the movable contact shaft
4
, being held between insulating washers
6
and
13
composed of insulating material and kept electrically insulated from the movable contact shaft
4
. A pushing spring
15
which is a coil spring is compressed and disposed between the insulating washer
6
and a collar portion
4
a
of the movable contact shaft
4
. On the other hand, a retaining ring
14
is disposed in close proximity to the insulating washer
6
, being secured by insertion into a groove on the movable contact shaft
4
. Consequently, the movable contact
5
is slidably held on the collar portion
4
a
side of the movable contact shaft
4
.
In addition, a return spring
16
which is a coil spring is compressed and disposed between the molded cap
8
and the retaining ring
14
at the molded cap
8
end of the movable contact shaft
4
so as to cover the movable contact shaft
4
.
Two fixed contacts
7
comprising generally cylindrical fixed contacts
7
b
for contacting by the movable contact
5
, and fixed contact shafts
7
a
which are contact terminal conductors are disposed in positions on an inside portion of the molded cap
8
facing the movable contact
5
.
The fixed contacts
7
are inserted through the molded cap
8
and fastened. Sheet-shaped packing
19
is held between the fixed contacts
7
b
and the molded cap
8
to prevent moisture from seeping from outside the molded cap
8
around outer circumferential portions of the fixed contact shafts
7
a
into the inside of the molded cap
8
.
As shown in
FIG. 7
, on the outside of the molded cap
8
, the two fixed contacts
7
constitute an M terminal for electrical connection to a starter motor (not shown) and a B terminal for electric connection to a battery (not shown), respectively, and are disposed so as to have a distance L between B-M terminals which is the distance separating the axes of the two fixed contacts
7
. Furthermore, threads
7
c
are formed on the fixed contact shafts
7
a
of the fixed contacts
7
, and washers
17
forming terminal contact seats connected to the starter motor or the battery are disposed on the threads
7
c.
Furthermore, a partition portion
8
a is convexly disposed on the molded cap
8
between the two fixed contacts
7
to increase the insulation between the fixed contacts.
Furthermore, the pushing spring
15
and the return spring
16
keep the two fixed contacts
7
b
and the movable contact
5
in positions where they are separated from each other.
Next, the operation of the above will be explained.
When power is supplied to the electromagnetic coil
3
by means of the lead wires
18
so that the electromagnetic coil
3
is in an energized state, the movable core
10
is attracted towards the fixed core
1
and moves the movable contact shaft
4
towards the molded cap
8
. The fixed contacts are electrically connected to each other by the movable contact
5
contacting the two fixed contacts
7
b.
Now, when the movable contact contacts the fixed contacts
7
b,
the pushing spring
15
is compressed and the movable contact shaft
4
and the movable contact
5
are displaced relative to each other, and only the movable contact shaft
4
moves closer to the molded cap
8
.
Furthermore, when the electromagnetic coil
3
is no longer energized, the return spring
16
pushes the movable contact away from the fixed contacts
7
b
by elastic force.
In a conventional magnetic switch for a starter such as this, the joining of the molded cap
8
and the switch case
9
has involved forming the outside diameter of the molded cap
8
smaller than the outside diameter of the thin-walled portion
9
a
of the switch case
9
around its entire circumference, and roll crimping the molded cap
8
around its entire circumference with the thin-walled portion
9
a
of the switch case
9
covering the outer circumference of the molded cap
8
to crimp it.
However, when attempts were made to reduce the size of the magnetic switch by making the outside diameter of the switch case
9
smaller, because the thin-walled portion
9
a
of the switch case
9
covers the outer circumference of the molded cap
8
, it is necessary to make the outside diameter of the molded cap
8
smaller as well. For that reason, it is difficult to maintain the conventional distance L between B-M terminals.
That is to say, if one tries to keep the distance L between B-M terminals as large as possible, the walls of molded cap
8
become thin, leading to insufficient strength in the molded cap
8
and poor filling of the mold during the manufacture of the molded cap
8
.
On the other hand,
FIGS. 9 and 10
show the construction of a magnetic switch in a case where the magnetic switch is reduced in size by shortening the distance L between B-M terminals. Hereafter, parts or portions the same as or similar to those in
FIGS. 7 and 8
will be given the same numbering and duplicate explanations will be omitted.
FIGS. 9 and 10
differ from
FIGS. 7 and 8
in that the distance L between B-M terminals has been shortened. In this case, the conventional battery lead terminal for mounting on the B terminal and the motor lead terminal connected to the motor for mounting on the M terminal are obstructed by the partition portion
8
a
of the molded cap
8
and the lead terminals cannot be mounted.
Furthermore, it becomes difficult to maintain the insulating distance c between the fixed contacts
7
b
and the movable contact shaft
4
in the magnetic switch. In order to maintain sufficient insulating distance c, it is necessary to reduce the contact surface area between the fixed contacts
7
b
and the movable contact
5
, undesirably increasing the current density at the contact portion.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide a small, light-weight magnetic switch for a starter without reducing the distance between the axes of the fixed contacts.
In order to achieve the above object, ac
Hisamoto Motoi
Shiroyama Shigeru
Mitsubishi Denki & Kabushiki Kaisha
Scott J. R.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Magnetic switch for a starter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic switch for a starter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic switch for a starter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439882