Electricity: circuit makers and breakers – Solid contact – Membrane type
Reexamination Certificate
2000-02-16
2001-12-25
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Membrane type
C200S275000, C200S406000, C200S512000
Reexamination Certificate
active
06333477
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a compact and thin-profile switch for use in various kinds of thin-thickness operation panels of electronic apparatus and other such application fields.
BACKGROUND OF THE INVENTION
There are two major categories in the structure of conventional switches used in operation panels.
The structure shown in
FIG. 12
, a cross sectional view, and
FIG. 13
, an exploded perspective view, belongs to category one. On an insulating substrate
1
of the switch, a pattern of fixed contact points
2
is formed, which consists of an outer contact point
2
A of ring shape and an inner contact point
2
B disposed in the center of the ring shape. The inner contact point
2
B is provided with a lead portion
2
C, which runs through a cut
2
D formed in the outer contact point
2
A. An insulation layer
3
is provided on the lead portion
2
C and the cut
2
D, and a movable contact point
4
of round dome shape made of an elastic thin metal sheet is placed on the outer contact point
2
A. A flexible insulating film
5
having an adhesive agent
5
A on the bottom surface is provided over the above described structure, and the movable contact point
4
and the insulating substrate
1
are fixed together thereby.
The structure of a category two switch is shown in
FIG. 14
, a cross sectional view, and
FIG. 15
, an exploded perspective view. The switch comprises an insulating substrate
6
, on which a pattern of fixed contact points
7
is formed. The pattern consists of an outer contact point
7
A of ring shape and an inner contact point
7
B disposed in the center of the ring shape. The inner contact point
7
B is provided with a through hole
7
C. The inner contact point
7
B is connected to the reverse surface of the insulating substrate
6
via the through hole
7
C provided at the center. A movable contact point
4
of round dome shape made of an elastic thin metal plate is placed on the outer contact point
7
A. A flexible insulating film
5
having an adhesive agent
5
A on the bottom surface is provided over the above described structure, and the movable contact point
4
and insulating substrate
6
are fixed together thereby.
In the switches of either category, a press given to the movable contact point
4
of round dome shape at the center causes an elastic inversion with the movable contact point
4
, which brings the bottom center into making contact with the inner contact point
2
B (or
7
B). The outer contact point
2
A and the inner contact point
2
B (or the outer contact point
7
A and the inner contact point
7
B) are thus short-circuited to generate an ON state in the switch.
Recently, along with the general trend of down-sizing among the electronic apparatus, it has been requested for the operation panels as well as the switches incorporated therein to have smaller dimensions. In order to down-size the switches of above described conventional structure, basically the dimensions have to be reduced with respect to each of the constituent parts and components. However, the range of dimensional dispersion that arises during processing of the constituent parts and components remains unchanged. Therefore, the size of inner contact point
2
B, or
7
B, on which the movable contact point
4
of round dome shape comes to make contact as a result of the elastic inversion, can not be reduced for a substantial extent; among those elements of fixed contact point
2
, or
7
, pattern-formed on the insulating substrate
1
, or
6
. This makes it difficult to form the outer contact point
2
A, or
7
A, around the inner contact point preserving a certain specific insulation gap in dimensions that can insure a stable contact. This is a limitation posed to the down-sizing effort.
Furthermore, the second category switches are costly because they need connection by wiring in the bottom surface of insulating substrate
6
. In addition, a subtle difference may arise with the category two switches in the quantity of switching stroke and the feeling of operation, depending on whether the center bottom of the inverted movable contact point
4
makes contact with the small-diameter fixed contact point
7
at a point precisely coincidental to the through hole
7
C, or not.
The present invention aims to offer a switch that provides a stable contact performance and a superior feeling of operation even in a down-sized configuration.
SUMMARY OF THE INVENTION
A switch in accordance with the present invention comprises an insulating substrate; a movable contact point disposed above the insulating substrate, which movable contact point being formed of a round dome section, a flat section disposed at a place outside the circumference of the round dome section and a connection section connecting the round dome section with the flat section; a first fixed contact point having a diameter smaller than that of the round dome section, disposed on the insulating substrate at a place underneath the round dome section; and a second fixed contact point disposed on the insulating substrate always keeping contact with the flat section.
In a switch of the above described structure, since the second fixed contact point, which always keeps contact with the movable contact point, can be disposed at a place off the round dome section of movable contact point, both the second fixed contact point and the first fixed contact point locating underneath the round dome section can be formed with the dimensions large enough to assure a stable contact. Thus the switch of the present invention offers both the stable contact performance and the superior feeling of operation.
It is preferred in a switch of the present invention that the flat section of movable contact point is provided with a protrusion that makes contact with the second fixed contact point disposed on insulating substrate. The protrusion makes sure of the contact between the flat section and the second fixed contact point.
A plurality of the movable contact points may be formed with a configuration where pluralities of the round dome sections share a flat section in common. By so doing, the number of constituent parts count may be reduced and the assembly operation will become easier. A switch block of matrix arrangement can be easily fabricated using a plurality of the movable contact points in which pluralities of the round dome sections are contained connected.
An insulation layer may be provided around, at least in part of, the first fixed contact point within a region that comes underneath the round dome section. By so doing, stroke quantity of the round dome section caused as a result of the elastic inversion can be increased for the thickness identical to that of the insulation layer, and a more stable operation and a better feeling of operation may be produced.
A flexible insulation film having an adhesive agent on the bottom surface may be further provided, that sticks on the insulating substrate covering the round dome section and the flat section. In this way, a switch of thin-profile and improved dust-free performance is implemented.
It is preferred that both the insulating substrate and the flat section are provided with a perforation for alignment to be used when combining the two items. A pin penetrating through the perforations in the two items insures a precise aligning accuracy with respect to the two items, and contributes to improving the efficiency of switch assembly.
The movable contact points may be provided easier by forming the round dome sections and the flat sections in an elastic thin metal sheet of belt shape, and then cutting the side alley that has been left in the side part of the elastic thin metal sheet as a result of formation of the above described sections therein. This contributes to offering a switch at a lower cost. More specifically, an operation switch panel having a plurality of individual switches disposed in matrix arrangement can be provided within smaller dimensions at a lower cost, by forming a plurality of round dome sections continually on an elastic thin metal sheet
Koyama Hiromichi
Sako Koji
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Scott J. R.
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