Control circuit for electrosurgical units

• US 3,913,583 A
• Filed: 06/03/1974
• Issued: 10/21/1975
• Est. Priority Date: 06/03/1974
• Status: Expired due to Term

• Current Assignee: Castle, Inc.
• Original Assignee: William T. Bross
• Inventors: Bross, William T.
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Cohen, Lee S.
• Application Number:
  US05/475,668
• Time in Patent Office: 505 Days
• Field of Search: 128/303.14,303.13,303.17 330/8 336/155 323/56,6
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: Y10S 323/911 Medical electronics

Abstract

A control circuit for electrosurgical units which controls power levels to patient electrode in response to load conditions thereof. A saturable reactor is connected in series between the output of the electrosurgical unit and the patient electrodes. The saturable reactor is biased by a control coil activated by a rectified current corresponding to the alternating current flowing between the patient electrodes which is an indication of the area of contact between the patient and one of the electrodes.

Claims

1. In combination with an electrosurgical unit having an oscillator applying variable high frequency current to a plurality of patient electrodes, a control circuit comprising:

a saturable reactor connected between said oscillator and at least one of said patient electrodes; and

bias means responsive to current flow through said patient electrodes for biasing said saturable reactor to control the impedance thereof, whereby for a first range of current flow through said patient electrodes said saturable reactor represents an inductive reactance to said oscillator and during a second range of current flow through said patient electrodes substantially greater than said first current flow said reactor represents a lower inductive reactance to said oscillator.

2. A control circuit as defined in claim 1, wherein said saturable reactor includes:

a ferromagnetic core;

a plurality of variable reactances windings, and a control winding.

3. A control circuit as defined in claim 2, wherein said bias means includes:

a diode rectifying bridge connected between one of said patient electrodes and said control winding, said bridge having a DC current output corresponding to the amplitude of AC current flow, said DC output being applied to said control winding for biasing said saturable reactor.

4. A control circuit as defined in claim 3 which further includes an indicator means connected across said bias means so as to be indicative of said bias current and load conditions across said patient electrodes.

5. A control circuit as defined in claim 2, wherein said variable reactance windings are interconnected so as to nullify any induced voltage in said control winding.

6. A control circuit as defined in claim 5, which further includes an electrostatic shield means interposed between said variable reactance windings and said control windings.

7. A control circuit defined in claim 1, wherein said saturable reactor is comprised of:

two cup cores;

at least one variable reactance winding wound about each of said cup cores; and

at least one DC control bias winding wound about each of said cup cores, whereas said variable reactance windings are connected in series so as to nullify the effect on said DC control coils winding.