Editing Keyboard switch by Hiroshi Hasegawa

{{infobox patent
| image     = [[file:keyswitch.png|frameless]]
| country   = US
| number    = 4482932
| inventor  = Hiroshi Hasegawa
| issued    = 13 November 1984
| assignee  = [[Topre Corporation]]
| reference = {{cite patent|number=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]]. <ref name=topre> {{ cite patent | country = US | number = 4482932 | status = patent | title = Keyboard switch | pubdate =  | gdate = 13 November 1984 | fdate = 19 October 1981 | pridate =  | inventor = Hiroshi Hasegawa | invent1 =  | invent2 =  | assign1 = Topre Corporation | assign2 =  | class = }} </ref>

==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) [[Keyboard switch by Hiroshi Hasegawa#Images|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==

[[#Images|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 '''&#1013;''' 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 [[#Images|Figure 4]].

''C'' = &#1013; ( ''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. <ref name=topre/>

==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==

*{{ cite patent | country = US | number = 1740159 | status = patent | title = Variable condenses | pubdate =  | gdate = 17 December 1929 | fdate = 16 January 1924 | pridate =  | inventor = William Dttbilieb | invent1 =  | invent2 =  | assign1 =  | assign2 =  | class = }} 
*{{ cite patent | country = US | number = 3653038 | status = patent | title = Capacitive electric signal device and keyboard using said signal | pubdate =  | gdate = 8 March 1972 | fdate = 20 February 1970 | pridate =  | inventor = Richard C. Webb | invent1 =  | invent2 =  | assign1 =  | assign2 =  | class = }}
*{{ cite patent | country = US | number = 3693059 | status = patent | title = Capacitive coupling switch and actuator background | pubdate =  | gdate = 1972 | fdate = 17 June 1971 | pridate =  | inventor = Richard H. Harris | invent1 =  | invent2 =  | assign1 =  | assign2 =  | class = }}
*{{ cite patent | country = US | number =  | status = patent | title = Capacitive switch | pubdate =  | gdate = 6 September 1977 | fdate = 12 April 1976 | pridate =  | inventor = Edward H. Lau | invent1 =  | invent2 =  | assign1 = Burroughs Corporation | assign2 =  | class = }}
*{{ cite patent | country = US | number = 4288836 | status = patent | title = Capacitance controlled keyswitch | pubdate =  | gdate = 8 September 1981 | fdate = 29 May 1979 | pridate =  | inventor = David D. Thornburg | invent1 =  | invent2 =  | assign1 = Xerox Corporation | assign2 =  | class = }}

==Referenced by==

*{{ cite patent | country = US | number = 4584444 | status = patent | title = Keyboard switch | pubdate =  | gdate = 22 April 1986 | fdate = 21 September 1984 | pridate =  | inventor = Takao Nagashima | invent1 =  | invent2 =  | assign1 = Topre Corporation | assign2 =  | class = }}
*{{ cite patent | country = US | number = 4851626 | status = patent | title = Keyswitch device | pubdate =  | gdate = 25 July 1989 | fdate = 24 June 1988 | pridate =  | inventor = Takao Nagashima | invent1 =  | invent2 =  | assign1 = Topre Corporation | assign2 =  | class = }}
*{{ cite patent | country = US | number = 7579569 | status = patent | title = Capacitive proximity and/or touch-sensitive switch | pubdate =  | gdate = 25 August 2009 | fdate = 23 September 2005 | pridate =  | inventor = Hans-Jürgen Romanowski | invent1 =  | invent2 =  | assign1 = Bsh Bosch und Siemens Hausgeraete GmbH | assign2 =  | class = }}

==Images==

<gallery widths=170 heights=250>
File:Fig1,5.png
File:Keyswitch.png
File:Keyswitch-1.png
File:Keyswitch-2.png
File:Keyswitch-3.png
File:Keyswitch-4.png
File:Keyswitch-5.png
File:Keyswitch-6.png
File:Keyswitch-7.png
File:Keyswitch-8.png
</gallery>

==References==
<references/>

[[Category:Patents]]