Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having electrostatic element
Reexamination Certificate
1998-09-01
2001-08-07
Kuntz, Curtis (Department: 2743)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having electrostatic element
C310S001000, C381S190000, C381S173000, C073S774000, C379S444000
Reexamination Certificate
active
06272228
ABSTRACT:
This invention relates to a sound transducer and more particularly to its process of manufacture and its integration into a card of narrow thickness able to produce acoustic signals.
Said card can be used to transfer confidential information in secure manner, towards a server for example, via a telephone line.
Acoustic signals are produced following the principle of data coding by a pair of frequencies of 697 to 1633 Hz and are better known by their English term Dual Tone Modulation Frequency (DTMF). In telephony these DTMF signals are used for numbering, code transmission etc.
Today it is known how to fabricate sound transducers in ceramic having a thickness of approximately 0.3 mm, for their insertion into cards of narrow thickness, that is to say approximately 0.8 mm thick. However, such transducers in ceramic are very expensive and considerably increase card cost price.
Other materials are therefore being researched with a view to producing low cost sound transducers. In particular, the use of a material in fluoride polyvinylidene (FPVD) has already been considered. FPVD is an advantageous material since it is cheap and also allows maintained amplitude differences existing between the two frequencies which determine DTMF signals.
However, up until now, it has proved impossible to produce a very thin FPVD transducer for its insertion into a card of conventional format, having a thickness of approximately 0.8 mm. The FPVD sound transducers currently produced all comprise two FPVD films that are electrically connected and placed under stress. These films are housed in a frame whose thickness lies between 0.8 and 1 mm. Each transducer thus formed forms a unit part which must then be fixed in a card, with contacts re-connected by means of conductor wires.
The assembly of such transducer in a card therefore requires meticulous care and is fastidious and time consuming. Also, the card is too thick, more than the normalized thickness for electronic cards since it is between 1.5 and 2 mm. Finally, the sound transducer is fragile since it cannot resist against stresses due to bending of the card in which it is inserted.
The present invention remedies all these drawbacks since it describes a process for manufacturing a sound transducer in FPVD and integrating the latter into a card of conventional format for electronic cards in accordance with standard ISO 78.16-12 and whose thickness is reduced to approximately 0.8 mm. This card can be used to produce acoustic signals transmittal by telephone route. On its rear surface it carries an interconnection array. The process of the invention is particularly characterized in that it consists of:
making dual surface metallization strips, forming electrodes, distributed over the entire width of a ribbon in FPVD of great length and of very narrow thickness,
cutting off each metallization strip to form unit films of great length,
fixing a portion of the film onto a predetermined site of the interconnection array on the rear surface of the card and cutting off excess film, and
placing the film portion under stress in such manner that it can emit acoustic signals when voltage is applied to it.
A further object of the invention concerns a sound transducer in FPVD integrated into a card producing acoustic signals transmittable by telephone route, whose rear surface carries an interconnection array, characterized in that it comprises:
grooves parallel to one another made on the rear surface of the card,
a portion of film in FPVD, of very narrow thickness, carrying two electrodes, one lower and one upper, connected to the interconnection array of the card, and
a stress part whose lower side comprises notches parallel to one another able to position themselves opposite the grooves and to press upon the portion of film so as to impart indentations upon it.
The sound transducer of the present invention is made within the card producing DTMF signals. Consequently, the transducer no longer has the appearance of a unit part inserted into the card but forms an integral part of the card. On this account, its mechanical resistance to stresses due to bending of the card for example is largely improved. Also, the integration of the transducer into the card is simple to perform by gluing.
REFERENCES:
patent: 4752678 (1988-06-01), Rikuna
patent: 4889980 (1989-12-01), Hara
patent: 5293035 (1994-03-01), Lyons
patent: 0209791 (1986-07-01), None
patent: 0664633 (1995-11-01), None
patent: 2263999 (1993-08-01), None
patent: WO 94/17562 (1994-08-01), None
Gemplus
Harvey Dionne
Kuntz Curtis
Plottel Roland
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