Keyboard switch by Hiroshi Hasegawa
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| Country | US |
|---|---|
| Patent number | 4482932 |
| Issued on | 13 November 1984 |
| Inventor | Hiroshi Hasegawa |
| Assignee | Topre Corporation |
| Reference | US4482932 |
Keyboard switch by Hiroshi Hasegawa is a linear operational with constant hysteresis capacitive keyboard switch. Its patent was filed on 1981 and granted on 1984. The assignee was Topre Corporation. [1]
Contents
Description
Keyboard switch
- Inventor: Hiroshi Hasegawa
- Filing date: 19 October 1981
- Issue date: 13 November 1984
Background
The three main concerns outlined by Hiroshi Hasegawa were as follow:
(1) If the capacitance is higher than a given value the switch is capacitive-coupled to allow a high frecuency of AC current flow. If lower than the given value, the switch is no longer capacitive-coupled so it is turned off.
(2) Figure 1 shows the changing rate of prior art capacitance when depth of depression is narrow, and increases when depth of depression exceeds a given value.
(3) For example, if an operating value is set according to depth of depression, then hysteresis is low. Something that must be avoided.
Invention
- A switch with constant hysteresis regardless of the operational value that is set.
- Electrodes in an insulating substrate with a dielectric in between.
- Linear change of the area by which electrodes face one another, so the electrodes are capacitive coupled when the operational value that was set is exceeded.
Detailed description
Figure 3 shows electrodes (32) (36) and a dielectric (34), where d is the distance between electrodes (32) (36) and S is the area that electrodes (32) (36) face one another. Now let ϵ be the constant of the dielectric, the capacitance C that is obtained as a result, depends entirely on the facing portions of the area of electrodes (32) (36), since it varies substantially after depressing the button (24) as shown in Figure 4.
C = ϵ ( S / d )
Based on that, the operational values for the switch must be adjusted accordingly. So the switch may be turned on with half full depth of depression of the button let C have an adjusted value of 12 (pF) , and the capacitance value for the off position is set to 8 (pF) which is 4 (pF) lower than the value for the operation when the switch is turned on. [1]
Claims of the invention
The claims of the invention are as follow:
- (1) A keyboard switch comprising an insulating substrate in which:
- (a) an electrode is fixed to the substrate and a second electrode is fixed to the said substrate, apart from the other.
- (b) A dielectric between the electrodes.
- (c) An auxiliary electrode on a cross-sectional circular conical coil spring which has a large diameter as the base portion and small diameter in the other end, in contact with the dielectric.
- (c) A button mounted on the smaller diameter of the auxiliary switch.
- (2) The keyboard switch according to claim (1) wherein the auxiliary electrode - by overspread action of first and second electrodes on the dielectric - becomes flat after depressing the aforementioned button from claim (1).
- (3) A keyboard switch according to claim (2) where the auxiliary electrode has an end portion greater than the combination of the first and second electrodes.
- (4) A keyboard switch according to claim (1) (2) (3) in which said auxiliary electrode has a circular section.
- (5) A keyboard switch according to claim (4) in which a dielectric is attached to the auxiliary electrode.
- (6) A keyboard switch according to claim (4) in which the dielectric is attached to the surfaces of first and second electrodes.
- (7) A keyboard swich according to claims (1) (2) (3) in which the auxiliary electrode has a rectangular section with its base facing the insulating substrate
- (8) A keyboard switch according to claim (7) in which the dielectric is attached to the auxiliary electrode.
- (9) A keyboard switch according to claim (8) in which the dielectric is attached to first and second electrodes.
Patents cited
- US patent 1740159, William Dttbilieb, "Variable condenses", issued 17 December 1929
- US patent 3653038, Richard C. Webb, "Capacitive electric signal device and keyboard using said signal", issued 8 March 1972
- US patent 3693059, Richard H. Harris, "Capacitive coupling switch and actuator background", issued 1972
- US patent, Edward H. Lau, "Capacitive switch", issued 6 September 1977, assigned to Burroughs Corporation
- US patent 4288836, David D. Thornburg, "Capacitance controlled keyswitch", issued 8 September 1981, assigned to Xerox Corporation
Referenced by
- US patent 4584444, Takao Nagashima, "Keyboard switch", issued 22 April 1986, assigned to Topre Corporation
- US patent 4851626, Takao Nagashima, "Keyswitch device", issued 25 July 1989, assigned to Topre Corporation
- US patent 7579569, Hans-Jürgen Romanowski, "Capacitive proximity and/or touch-sensitive switch", issued 25 August 2009, assigned to Bsh Bosch und Siemens Hausgeraete GmbH
Images
References
- ↑ 1.0 1.1 US patent 4482932, Hiroshi Hasegawa, "Keyboard switch", issued 13 November 1984, assigned to Topre Corporation
