ULTRASONIC SURGICAL APPARATUS WITH POWER REDUCTION
An ultrasonic surgical includes a probe with an operative edge or surface at a distal end, an electromechanical transducer connected to the probe, and an activation circuit connected to the transducer for supplying thereto an electrical waveform having an ultrasonic frequency and an amplitude. The activation circuit includes a signal generator and further includes a power reduction circuit operatively connected to the signal generator for inducing the signal generator to automatically reduce the amplitude of the waveform upon a sensing by the power reduction circuit of reduced load on the probe.
1 . An ultrasonic surgical apparatus comprising: a probe including an operative edge or surface at a distal end; an electromechanical transducer connected to said probe; and an activation circuit operatively connected to said transducer for supplying thereto an electrical waveform having an ultrasonic frequency and an amplitude, said activation circuit including a signal generator and further including a power reduction circuit operatively connected to said signal generator for inducing said signal generator to automatically reduce the amplitude of said waveform upon a sensing by said power reduction circuit of reduced load on said probe.
2 . The apparatus defined in claim 1 wherein said power reduction circuit includes a load detector.
3 . The apparatus defined in claim 2 wherein said load detector includes a current sensor.
4 . The apparatus defined in claim 3 wherein said load detector further includes a comparator operatively connected to said current sensor for comparing an output of said sensor with a pre-established reference value.
5 . The apparatus defined in claim 4 wherein said activation circuit includes a manually actuatable power switch and wherein said power reduction circuit further includes a switching circuit operatively connected at inputs to said power switch and said comparator and at an output to said signal generator.
6 . The apparatus defined in claim 1 wherein said power reduction circuit includes a current sensor, said sensor being operatively connected to a lead extending from said signal generator to said transducer.
7 . The apparatus defined in claim 1 wherein said load power reduction circuit includes a comparator configured to compare a sensed load parameter with a pre-established reference value.
8 . The apparatus defined in claim 1 wherein said activation circuit includes a manually actuatable power switch and wherein said power reduction circuit further includes a switching circuit operatively connected at an input to said power switch and at an output to said signal generator.
9 . A surgical method comprising: operating an ultrasonic cutting tool to cut through bone of a patient; during the operating of said cutting tool, operating a sensor to automatically monitor load on said cutting tool; during the operating of said cutting tool, automatically detecting a change in output of said sensor indicative of a reduced load on said cutting tool owing to a passing of said cutting tool at least partially through the bone; and automatically reducing power to said cutting tool upon the detecting of reduced load on said cutting tool.
10 . The method defined in claim 9 wherein the detecting of a change in output of said sensor includes comparing output of said sensor with a preselected reference value.
11 . The method defined in claim 9 wherein the reducing of power to said cutting tool includes reducing amplitude of an ultrasonic electrical waveform fed to an electromechanical transducer.
12 . The method defined in claim 9 wherein the operating of said sensor includes detecting current flow to an electromechanical transducer connected to said tool.