Appeal No. 1995-5010
Application 08/116,261
piezoelectric crystal transducer in a surgical handpiece and
the feedback piezoelectric crystal provides a feedback signal
which is a function of the actual frequency of vibration of
the ultrasonic piezoelectric crystal transducer in a surgical
handpiece and which phase comparator compares the phase of the
feedback signal of the feedback piezoelectric crystal and of a
driving signal and provides a control signal which maintains
the driving signal at the resonant frequency of the ultrasonic
piezoelectric crystal transducer in a surgical handpiece,
wherein said amplifier is a sinusoidally oscillating voltage
source amplifier, the sinusoidally oscillating voltage source
amplifier in parallel with a tuning inductor and having an
output which is connected to the ultrasonic piezoelectric
crystal transducer in a surgical handpiece and to provide the
driving signal, includes a second control loop comprising:
a means for sensing the amplitude of vibration of the
ultrasonic piezoelectric crystal transducer in a surgical
handpiece and providing an amplitude signal in proportion
thereto, means for comparing the amplitude signal with a
command signal adjustable by an operator and generating an
error signal in proportion to the difference between the
amplitude signal and the command signal, the error signal of
the second control loop changing the amplitude of vibration to
a desired level with the second control loop as an automatic
gain control loop, the amplitude signal in proportion with the
command signal under varying loads and in which the automatic
gain control loop including a limiter so the maximum error
signal output of the loop may be adjusted and limited by an
operator to achieve tissue selectivity, and
a switching unit connected to provide a feedback command
signal as input to the second control loop, the switching unit
connects to limit selectivity with the operator amplitude set
point or a low reference point according to second output
signal.
The Examiner relies on the following references:
Takahashi et al. (Takahashi) 4,888,514 Dec. 19, 1989
Sakurai 4,965,532 Oct. 23, 1990
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