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[Co., Ltd.] Stretching device for diaphragm ◎ Japanese Patent Application No. 45-65317 @
Application A. 45 (1970) Jul. 24 @ Inventor Toko Koto, Yokohama, Kohoku Kita-Kanbeshima 880
Matsushita Communication Industrial Co., Ltd. 0 Applicant Matsushita Electric Co., Ltd. Industry
Co., Ltd. Kadoma City Oji Kadoma 1006 [phase] Agent patent attorney Toshio Nakao 1 person
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an essential part of an
embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining its
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for
raising a diaphragm such as a capacitor type microphone or speaker to a predetermined tension.
Conventionally, the tension of the vibrating membrane as described above is made constant by
raising it beyond the elastic limit of the vibrating membrane, or the one and the resonance
frequency are measured to adjust the tension constant by cut and try. Such methods are taken.
However, in the former method, tension can only be raised by one fixed value, and in particular,
making tension constant in such a manner is the maximum value that tension can always take, In
other words, the sensitivity is always at the minimum. Also, the latter method has a disadvantage
that it can be set to an arbitrary value but it is extremely inefficient. The present invention
provides an apparatus which can be constantly and easily adjusted to any tension except for the
above drawbacks. Hereinafter, an embodiment of the present invention will be described with
reference to the drawings. Reference numeral 1 denotes a load electrode of a capacitor type
microphone or a speaker, and 2 denotes a conductive vibrating film to be raised by the load
electrode 2 through an insulator 3, and the outer periphery thereof is supported by a fixing
member. [11111114 is a motor, 5 is a motor shaft of the motor, 6 is a hollow rotary shaft having
an outer peripheral portion screwed, and a screw portion 7 of the outer periphery is screwed into
a screw hole of the fixed bearing 8. Numeral 9 is an insulator attached to the tip of the rotary
shaft 6, and the tip surface of the insulator 9 is in electrical contact with the back of the load
electrode 1 and conductive contact for pressing it. Horny 10 is attached. The motor shaft 5 of the
motor 4 is movably inserted into the hollow hole at the other end of the rotary shaft 6, and a
motor shaft 5Vc is provided in the elongated hole 11 provided in the longitudinal direction of the
rotary shaft 6. A pin 12 projecting in the perpendicular direction is inserted and engaged.
Therefore, when the motor shaft 5 rotates, the rotating shaft 6 also rotates, and the rotating shaft
6 is rotated by the screw 7 and the fixed bearing 8 provided on the outer periphery thereof
according to the rotation direction of the motor ← shaft 5. Can move forward or backward. 13 is
a high frequency oscillation circuit, 14 is a DC polarization voltage supply circuit, 15 is a high
frequency amplifier, 16 is an FM detector, 17 is a low frequency amplifier, and 18 is a frequency
valve ff1J! , 19 is a DC amplifier, 20 is a rotating direction switching polarized relay switched by
the DC amplifier 19, 21 is a motor drive power source, 22 is a main power switch, 23 is a choke
coil, 24 is one end is the high frequency oscillation 25. A DC blocking capacitor connected to the
oscillation coil of the circuit 13 and to the connection point A, the other end of which is
connected to the contact 10, one end of the choke coil 23, and one end of the DC polarization
voltage supply circuit 14; Is a high frequency transformer for supplying the output of the high
frequency oscillation circuit 13 to the human power of the high frequency amplifier 15 and the
frequency discriminator 18.
The operation of this apparatus will now be described. First, assuming that the vibrating
membrane 2 is vibrated by some method, the electrostatic capacitance formed between the
vibrating membrane 2 and the charge electrode 1 changes due to the vibration displacement,
whereby the oscillation frequency of the high frequency oscillating circuit 13 changes. That is,
the high frequency oscillation circuit 13 receives frequency [111111] EndPage: number
modulation due to the vibration of the vibrating membrane 2. The frequency modulation wave is
amplified by the high frequency amplifier 15 through the high frequency transformer 25 and
further subjected to the FM detection by the FM detector 16 so that a voltage proportional to the
vibration displacement of the vibrating membrane 2 is taken out. Then, this voltage is amplified
by the low frequency amplifier 17, and the diaphragm 2 is driven together with the polarized DC
voltage from the DC polarized voltage supply circuit 14 through the choke coil 23. As a result, a
feedback loop is formed, and the oscillation characteristic of the diaphragm 2 is oscillated at the
resonance frequency. When the oscillation frequency is discriminated by the frequency
discriminator 18 which is partially set to a predetermined center frequency, the output passes
through the DC amplifier 19 to drive the polarized relay 20 to switch the contacts. As a result,
the motor 4 is rotated forward, stopped or reversely, and the rotation shaft 6. The back electrode
1 is moved forward, stopped or retracted via the insulator 9 and the contactor 10. Therefore, if
the vibrating membrane 2 is weaker than a predetermined tension, it is made strong by the
advance of the contact 10 and hence the back electrode 1, and conversely if it is stronger than
the predetermined tension, it is weakened by the retraction of the contact 10 and hence the back
electrode 1, and the frequency discriminator 18 It is held at a predetermined tension set at. This
relationship is shown in FIG. In FIG. 2, the resonance frequency decreases as the solid curve 26
shows, the output of the [111111] number discriminator decreases. When the preset resonance
frequency fo is reached, the output of the frequency discriminator 18 enters the stop region from
the forward rotation region, and reverses if it exceeds this. Thus, the tension cuff 5 is dynamically
set to a constant value so that the resonance frequency of the vibrating membrane 2 becomes a
constant value. In the above example, the tension is automatically set to a constant value, but if
necessary, a human monitors the frequency discriminator output instead of the polarized relay
20 and manually operates the motor. By controlling the rotation, it is possible to set the tension
manually. As described above, according to the present invention, it is possible to obtain a very
excellent effect that the tension of the vibrating membrane can be adjusted arbitrarily and always
to be constant while the structure is relatively simple.
(1) Claim 1 Means for detecting the displacement of the diaphragm and obtaining an electrical
signal according to the displacement, a feedback oscillation circuit for driving the diaphragm
with the signal from the means, and oscillation of the feedback oscillation circuit A vibrating film
lifting apparatus comprising: means for discriminating frequency; and mechanical tension
adjusting means driven by an output from the discriminating means to make the tension of the
vibrating membrane equal to a predetermined value. [111111]EndPage: 2