Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1997-11-21
1999-06-29
Horabik, Michael
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
707400, 341 20, 341 21, 341 22, 341 33, 341 34, 310366, 310340, 310363, 200 5A, 200512, 178 18, 345173, 307400, G11C 1302
Patent
active
059174374
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a keyboard which comprises one or more keys and their corresponding electromechanical converting means, and in particular, the present invention is related to a keyboard in which said electromechanical converting means are realized using a polymer film.
Piezoelectric films can be manufactured from certain polymer materials by means of a manufacturing process whereby said material is polarized by changing the orientation of crystals contained in said material by using both a mechanical procedure and a strong electric field. The best known film used in keyboards is polyvinylidene film, or PVDF, which is commercially available under several brand names. A PVDF switch element can be produced, for example, by silk-screening electrodes onto both charged surfaces of the film and connecting to said electrodes circuitry which conducts current produced in said film when a key is pressed to a control unit which detects said key. Keyboards based on the use of PVDF are presented in publications EP-A2 203 261 and GB-B 2 222 014, of which the first deals especially with wiring methods which improve noise resistance and the second with realization of converting elements.
One film which functions as an electromechanical converting means is an electret film with a bubble construction which is known as electromechanical film, or EMF. This Finnish invention and its variations and methods of manufacture is presented in patent publications FI 71267 and FI 76225 and patent application FI 913741. The film material is an insulator, such as polypropene, which contains gas-filled cells produced by means of a special method and a permanent electric charge is injected in the surface of said cells. A change in the thickness of the film, such as is caused by pressure, creates a current pulse which can be detected via electrodes attached to the surface of said film.
The idea of applying EMF to keyboards is rather obvious to a person skilled in the art, and said idea is referred to, for example, in the patent publication FI 71267 mentioned above. EMF is less costly to produce than PVDF and, in principle, a corresponding noise resistant converting element can be produced with EMF as with PVDF. For example, polypropene-based EMF is characterized in that it is very flexible and naturally lightweight due to its bubble construction. The sensitivity of EMF as an electromechanical converting means is also good. Also, very thin structures can be realized with EMF. The film can be as thin as 40 .mu.m, for example. The disadvantage of said polypropene-based EMF is its poor mechanical durability. To our knowledge, this apparently is the reason why EMF has not been used in keyboard applications.
In studying possibilities of using flexible, lightweight and thin EMF in keyboard realizations, we came upon a surprising discovery that, with certain applications in mind, an extremely advantageous solution is obtained by combining said flexible, lightweight and thin EMF construction with a relatively stiff and massive cover plate.
A keyboard according to the invention, including a solid, stiff cover plate, keys, each of which is formed by an area on a first side of the cover plate, and electromechanical converting means corresponding to each key area, is characterized in that electromechanical converting means for the key areas are formed by one common film construction attached on the second side, opposite to the first side, of the cover plate and including an electret film with a bubble construction known as EMF, and circuit pattern on said EMF film for forming electrodes for each converting means.
The EMF construction may be directly or via a thin intermediate layer against a base.
In one advantageous embodiment of the keyboard according to the invention the cover plate also forms a frame of said keyboard. The base may be a plastic layer cast on the cover plate which together with said cover plate tightly surrounds the EMF construction.
In another advantageous embodiment the base also forms a frame of said keyboard.
Th
REFERENCES:
patent: 3925610 (1975-12-01), French
patent: 4057660 (1977-11-01), Yoshida
patent: 4633123 (1986-12-01), Radice
patent: 4654546 (1987-03-01), Kirjavainen
patent: 4857887 (1989-08-01), Iten
patent: 4975616 (1990-12-01), Park
Ojala Jukka
Raisanen Lasse
Horabik Michael
Screentec Ky
Wong Albert K.
LandOfFree
Keyboard does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Keyboard, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Keyboard will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1379203