Electricity: circuit makers and breakers – Liquid contact – Time delay
Patent
1986-08-08
1988-12-27
Recla, Henry J.
Electricity: circuit makers and breakers
Liquid contact
Time delay
200305, 200 5A, 2003022, H01L 1302
Patent
active
047942150
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a push switch which is widely used in keyboards and other inputting manipulation means such as those in video tape recorders, particularly of the type having a mount base made of a heat resisting and insulating material and having a recess in the top surface thereof, the recess receiving a plurality of contact terminals disposed such that contact portions constituting at least a pair of conductor circuits are arranged in the recess, a curved push spring having an inverting function and disposed in the recess, and an operating portion through which the push spring is operated.
PRIOR ART
FIG. 1 shows the construction of a known push switch of the type mentioned above.
Referring to this Figure, a mount base 1 has a circular recess 1a formed in the top side thereof. Contact terminals 2a, 3a constituting a conductive circuit are fixed by insertion molding such that the contact portions of these contact terminals are disposed on the bottom surface of the recess. These contact terminals 2a and 3a are extended to the outside of the mount base 1, so as to form external terminals 2b, 3b. A reference numeral 4 denotes a disc-shaped push spring having an inverting function and curved to convex upwardly. The push spring 4 is so shaped that it always contacts with the contact terminals 2a but is normally kept away from the contact terminal 3a. A reference numeral 5 designates a circular push plate which has a projection 5a projecting from the central portion of the lower surface thereof, so as to lightly press the upper surface of the push spring thereby preventing any play of the push spring 4. On the other hand, a projection 5b is formed on the upper side of the push plate so as to be depressed by a finger when the switch is operated. The push plate 5 is received in the recess 1a in the mount base 1 with a slight play so that it can be moved downward against the force of the push spring 4 when pushed. The push plate 5 is held by a cover plate 6 fixed to the mount base by means of caulking tabs 1b provided on the mount base 1. In the normal state of the switch, the push spring contacts only the contact terminals 2a so that the switch is in OFF state. As the push plate 5 is pressed against the biasing force of the push spring 4, the push spring contacts also the contact terminal 3a, whereby the switch is turned on. However, the switch is turned off again as the push plate 5 is released from the pressing force.
In loading this switch on a printed circuit board by soldering, it is necessary to dip the terminals 2b and 3b in a soldering flux solution. It is often experienced that, when the height of the push switch is small, the flux comes into the switch through a minute gap between the cover plate 6 and the push plate 5, partly because of a capillary action and partly because of flying of the flux particles. It is also experienced that the dust and other foreign matters, as well as the chips of the ground push plate 5, come into the switch so as to cause a bad contact in the switch.
On the other hand, there is an increasing demand for a reduction in the size and thickness of the switch, which in turn has given rise to the demand for development of a new push switch which can be loaded by re-flow soldering or solder dipping. The conventional push switch, however, cannot meet such a demand.
SUMMARY OF THE INVENTION
According to the invention, there is provided a push switch having a mount base made of a heat resisting and insulating material and having a recess in the top surface thereof, the recess receiving a plurality of contact terminals disposed such that contact portions constituting at least a pair of conductor circuits are arranged in the recess, a curved push spring having an inverting function and disposed in the recess, and an operating portion through which the push spring is operated so as to turn the switch on and off, the operating portion being constituted by a flexible heat resistant film attached to the mount base in a manner such as to cover the ent
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Matsui Futoshi
Onda Katsuyoshi
Sawada Masaki
Cusick Ernest G.
Matsushita Electric - Industrial Co., Ltd.
Recla Henry J.
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