Surgery – Truss – Pad
Patent
1987-06-24
1988-12-27
Freeh, William L.
Surgery
Truss
Pad
12830314, A61B 1739
Patent
active
047933453
ABSTRACT:
A phacoemulsification probe for ultrasound removal of an eye lens (for example a lens having a cataract) is provided with a safety circuit for prevention of shock to the patient. The probe includes a piezoelectric sound transducer electrically powered with over 200 volts (RMS) at 50 kHz. This voltage, if improperly grounded, can be life threatening when the probe is used in the vicinity of the optic nerve. According to the improvement, the probe is provided with at least two discrete grounded paths. The power supply to the probe is enabled by a comparator testing a small current to ground through at least one and preferably both ground wires. When the existence of at least one ground path is verified and power to the probe is thus enabled, ground return from the probe flows through the paired grounded wires. This flow to ground is compared for precisely equal flows. Where non-equal flow of current to ground occurs, power to the probe is immediately interrupted. Detection of the non-equality of current flow to ground preferably occurs through a conventional toroidal current sensor electromagnetically induced by cancelling current paths within the toroid core. Where one of the paths to ground includes more than nominal resistance, as by a ground conductor being stressed, power supply trip immediately occurs. Thus, any irregularity in the required dual safety path to ground deactivates the probe and requires repair. The loss of one ground conductor terminates the application of power to the probe while still maintaining a safe ground connection through the remaining ground conductor.
REFERENCES:
patent: 3699968 (1972-10-01), Bolduc
patent: 3895635 (1975-07-01), Justus
patent: 4122854 (1978-10-01), Blackett
patent: 4437464 (1984-03-01), Crow
1984 Linear Supplement Databook, National Semiconductor Corporation, National Semiconductor LM 1851 Ground Fault Interrupter, pp. S10-8-S10-14.
Freeh William L.
Olds Ted
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