U.S. patent number 3,905,373 [Application Number 05/461,983] was granted by the patent office on 1975-09-16 for electrosurgical device.
This patent grant is currently assigned to Dentsply Research & Development Corporation. Invention is credited to Donald I. Gonser.
United States Patent |
3,905,373 |
Gonser |
September 16, 1975 |
Electrosurgical device
Abstract
A radiofrequency electrosurgical device which includes an active
electrode means and a passive electrode coupled to a chassis ground
of a radiofrequency generator of the device. If the passive
electrode is disconnected from the chassis ground, a potential
develops between the chassis ground and a system ground. This
potential is used to actuate a relay to disable the radiofrequency
generator if the passive electrode becomes disconnected.
Inventors: |
Gonser; Donald I. (Forest Park,
OH) |
Assignee: |
Dentsply Research & Development
Corporation (Milford, DE)
|
Family
ID: |
23834748 |
Appl.
No.: |
05/461,983 |
Filed: |
April 18, 1974 |
Current U.S.
Class: |
606/35; 361/160;
361/42; 606/37 |
Current CPC
Class: |
A61B
18/16 (20130101) |
Current International
Class: |
A61B
18/16 (20060101); A61B 18/14 (20060101); A61B
017/36 (); A61N 003/02 () |
Field of
Search: |
;128/303.14,303.13,303.17,303.18,2.1P ;317/18B |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
855,459 |
|
Nov 1960 |
|
GB |
|
1,139,927 |
|
Nov 1962 |
|
DT |
|
Other References
Wald et al., "Accidental Burns", JAMA, Aug. 16, 1971, Vol. 217, No.
7, pp. 916-921..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Cohen; Lee S.
Attorney, Agent or Firm: Pearce; James W. Schaeperklaus; Roy
F. Berkstresser; J. William
Claims
Having described my invention, what I claim as new and desire to
secure by letters patent is:
1. A radio-frequency electrosurgical device which comprises a
radio-frequency generator having a chassis ground, an active
electrode means connected to the radio-frequency generator, the
generator being constructed to power the active electrode means, a
passive electrode coupled to the chassis ground, a system ground, a
transformer, means including a primary winding of the transformer
for connecting the system ground to the chassis ground, a relay
connected to a secondary winding of the transformer to be actuated
when there is a predetermined radio-frequency potential across said
connecting means, and means actuated by the relay for disabling the
generator from powering the active electrode when the potential
across the connecting means exceeds the predetermined value.
2. A radio-frequency electrosurgical device in accordance with
claim 1 wherein the means for coupling the passive electrode to the
chassis ground includes capacitor means in series between the
passive electrode and the chassis ground.
3. A radio-frequency electrosurgical device as in claim 1 which
includes a variable resistance connected in parallel with the relay
for determining the predetermined value of the potential across the
connecting means at which the relay is actuated.
4. A radio-frequency electrosurgical device as in claim 1 wherein
there is means actuated by the relay for producing an audible
warning signal when the relay is actuated.
5. In combination with a radio-frequency electrosurgical device
which includes a radio-frequency generator, power source means for
supplying power to the radio-frequency generator, circuit means
connected to the radio-frequency generator for performing
electrosurgery on a patient, said circuit means establishing a
first current return path from the patient to the radio-frequency
generator when connected to the patient, means for establishing an
alternate current return path for at least part of said first
current return path from the patient to the radio-frequency
generator, a monitoring system means connected to the alternate
current return path for sensing radio-frequency current passing in
said alternate current return path, and means connected to the
monitoring system means for disabling the power source means from
powering the radio-frequency generator when the radio-frequency
current level in the alternate current return path exceeds a
predetermined radio-frequency current level.
6. A combination as in claim 5 wherein the alternate current return
path is between a system ground and a chassis ground.
Description
This invention relates to an electrosurgical device. The device of
the invention represents an improvement in the type of device shown
in my co-pending application Ser. No. 414,646 filed Nov. 12,
1973.
In radio-frequency electrosurgical devices, a passive electrode
having a broad face engaging a patient is used to link the patient
to a chassis ground connection. It is essential that the
connections linking the passive electrode to the chassis ground be
unbroken to avoid danger to the patient by inadvertent alternate
radio-frequency return paths from the patient. Such inadvertent
alternate radio-frequency return paths can cause radio-frequency
skin burns on the patient. Various systems have been devised to
monitor the integrity of a passive electrode radio-frequency return
path grounding system using direct or low frequency interrogation
currents which can conduct through the patient under some
circumstances. However, such currents can be dangerous to the
patient, and an object of this invention is to provide a monitoring
system which does not require an unsafe interrogation monitoring
current which, when present, may pass through the patient.
It has been determined that, if a passive electrode is not properly
linked to chassis ground in such a device, a radio-frequency
potential is set up between the chassis ground and system ground if
a small inductance is placed between the system ground and the
chassis ground, and a further object of this invention is to
provide a monitoring system which uses this potential to signal a
passive electrode ground failure.
A further object of this invention is to provide such a monitoring
system which shuts off the electrosurgical device if a
predetermined radio-frequency potential is set up between chassis
ground and system ground.
Briefly, this invention provides a radio-frequency electrosurgical
generator device which includes a transformer which has a primary
winding in a line which connects system ground to chassis ground. A
secondary winding of this transformer operates a relay having
contacts which disconnect a power lead to a driver oscillator of
the device and actuate a buzzer horn when the predetermined
radio-frequency potential is set up. Other contacts of the relay
actuate an electrical hold-in circuit which prevents re-energizing
of the radio-frequency active output lead until the generator
device has been turned off.
The above and other objects and features of the invention will be
apparent to those skilled in the art to which this invention
pertains from the following detailed description and the drawing
which:
The drawing is a schematic circuit diagram of a radio-frequency
electrosurgical device constructed in accordance with an embodiment
of this invention.
In the following detailed description and the drawing, like
reference characters indicate like parts.
In the drawing is shown schematically the wiring diagram of a
radio-frequency electrosurgical device constructed in accordance
with an embodiment of this invention. Alternating current power is
supplied by power leads 11 and 12. A grounding line 13 is connected
to an appropriate system ground such as a water pipe 14 and/or to
an appropriate operating room grounding system. The grounding line
13 is connected to one side of a primary winding 16 of a
transformer 17. The other side of the primary winding 16 is
connected to a chassis ground. In the drawing, a ground symbol
indicates chassis ground. When a radio-frequency potential is set
up between the system ground 14 and the chassis ground, a potential
is set up by a transformer secondary 18 between leads 23 and 24. A
power line fuse 118 is provided in the lead 11. An interlock switch
119 is closed during operation of the device but can be arranged to
open when a casing of the device (not shown) is opened.
Leads 121 and 122 are connected to poles 123 and 124, respectively,
of a triple pole double throw on-off switch 126. When the on-off
switch 126 is in the position shown (off position), the leads 121
and 122 are connected to power a primary winding 127 of a
transformer 128 to impress a low voltage such as 4 volts on a
secondary winding 129 thereof. When the on-off switch 126 is in its
other position (on position), the leads 121 and 122 are connected
to a primary winding 1291 of a transformer 130 to power the
transformer. A panel light 131 is connected in parallel with the
primary winding 1291 to indicate that the primary winding 1291 is
powered. A thermally activated circuit breaker 1292 in series with
the primary winding 1291 protects the transformer 130. A third pole
132 of the switch 126, when in the on position, connects leads 133
and 134 to connect one side of a heater electrode 135 of a tetrode
main power amplifier tube 136 to one side of a first secondary
winding 137 of the transformer 130, which can be constructed to
produce approximately 6 volts AC to the heater electrode 135. A
capacitor 2135 is connected between the line 133 and ground to
shunt any radio-frequency current from the heater electrode 135.
The other side of the first secondary winding 137 is connected to
ground as is the opposite side of the heater electrode 135. A fan
motor 1371 is also connected in parallel with the primary winding
1291 to drive a fan 1372 which blows air on the tetrode 136 and
other components to cool the tetrode and other components. When the
on-off switch 126 is swung to its off position, the pole 132
connects the lead 133 to the secondary winding 129 of the
transformer 128 so that the heater electrode 135 is heated not only
when the on-off switch 126 is in the on position but also when the
on-off switch 126 is in the off position. As already pointed out,
the secondary winding 129 of the transformer 128 can be arranged to
deliver about four volts so that the heater electrode 135 is heated
but at a lower temperature when the switch 126 is in the off
position but is maintained at a sufficient temperature that the
device will operate at once when the switch 126 is turned on.
A secondary winding 146 of the transformer 130 supplies a voltage
of approximately 2000 volts AC across leads 147 and 148 to a full
wave bridge rectifier 149 which supplies 2000 volts direct current
across leads 150 and 151. The lead 150 is connected to ground as is
a cathode 152 of the tetrode 136. The lead 151 is connected through
a plate choke 153 and a parasitic suppressor network 154 to a plate
156 of the tetrode 136 so that 2000 volts DC is impressed between
the cathode 152 and the plate 156 of the tetrode 136. A filter
condenser 157 smooths out wave form ripple from the rectifier 149.
A tapped resistor 159 and a fixed resistor 159A are connected in
series across the leads 150 and 151. A lead 158 connected to the
tap of the tapped resistor 159 supplies a positive potential
through a resistor 161 and a lead 162 to a screen grid 1620 of the
tetrode 136. A voltage of approximately 380 volts can be taken off
at the tap which is maintained on the screen grid An appropriate
resistance 164 bleeds off screen grid current to chassis ground. A
capacitor 166 connected between the screen grid lead 162 and ground
removes or shunts out radio frequency from the screen grid. Zener
diodes 3000 and 3001 connected in series suppress voltage
transients and regulate the maximum steady state voltage on the
screen grid 1620.
A second 146A of the second secondary winding 146 of the
transformer 130 is connected in parallel with a capacitor 146B to
form a circuit tuned to a line input frequency, which can be 60
Hertz, to stabilize the secondary winding voltages to a variation
of approximately .+-.1% with a change in input voltage of .+-.10%
impressed on the primary winding 1291. Thus, the transformer 130 is
a substantially constant voltage transformer stabilizing all the
circuitry of the device.
A bias voltage for a control grid 168 of the tetrode 136 is
supplied by a third secondary winding 169 of the transformer 130. A
first lead 171 from the winding 169 is connected to chassis ground
and a second lead 172 from the winding 169 is connected to a
rectifier 173. The rectifier 173 supplies a negative potential
through a resistance 1741 and an inductance 1742 to a lead 174,
which is connected to one end of a first series winding 176 of a
transformer 1761. The other end of the winding 176 is connected
through a second series winding 1762 of the transformer 1761 to a
lead 179 connected to the control grid 168 of the tetrode 136. A
condenser 181 which is connected between chassis ground and a
junction 1743 smooths out the wave form of the potential from the
rectifier 173. A resistance 183 connected in parallel with the
condenser 181 serves to discharge the condenser 181 when the device
is turned off. The bias voltage can be approximately -120
volts.
Oscillator circuits 184 and 186 for the device are powered from a
fourth secondary winding 187 of the transformer 130. Leads 188, 189
and 190 from the winding 187 are connected through a single pole
double throw switch 191 to a full wave bridge rectifier 192 which
supplies a DC voltage across leads 193 and 194. When the switch 191
is in the position shown, a voltage of approximately 16 volts is
supplied across the leads 193 and 194. When the switch 191 is in
its other position, a voltage of approximately 25 volts is supplied
across the leads 193 and 194. A condenser 195 connected across
leads 193 and 194 smooths ripple voltage. A resistance 1961
connected across the leads 193 and 194 discharges the condenser 195
when the device is turned off. The lead 193 is connected to chassis
ground. The lead 194 is a main power lead and normally is connected
through normally closed contacts 311 and 312 of a relay 31 and a
lead 321 to the pole of a single pole double throw switch 196. When
the switch 196 is in the position shown, the lead 321 is connected
through a short lead 197 to the pole of a single pole double throw
switch 198. The switches 196 and 198 can be foot operated switches.
The switches 196 and 198 are shown in their normal positions. When
the switch 196 is turned to its outer position, the main power lead
194 is connected to a lead 199. When the switch 198 is turned to
its other position, while the switch 196 remains in the position
shown, the main power lead 194 is connected to a lead 200. If the
switches 196 and 198 are both turned to their other position, the
lead 194 is connected to the lead 199, and it is impossible to
connect both the leads 199 and 200 to the lead 194 at the same
time. The lead 199 is connected to one side of a potentiometer 201.
The other side of the potentiometer 201 is connected to chassis
ground through an adjustable resistor 202. In a similar manner, the
lead 200 is connected to one side of a potentiometer 203. The other
side of the potentiometer 203 is connected to chassis ground
through an adjustable resistor 204. Thus, when the switch 196 is
advanced to its other position, a selected DC voltage is impressed
across the potentiometer 201 and when the switch 198 is advanced to
its other position while the switch 196 remains in the position
shown, a selected DC voltage is impressed across the potentiometer
203.
A voltage between zero and the selected voltage is impressed upon a
lead 206 connected to the tap of the potentiometer 203 when the
switch 198 is in its other position and the switch 196 is in the
position shown. The lead 206 is connected through an inductance or
choke 207 to the collector of a transistor 208, which is a part of
the oscillator circuit 186. The emitter of the transistor 208 is
connected to chassis ground. The lead 206 is also connected through
resistors 209 and 211 and a rectifier 212 to one side of a tickler
coil 213. The rectifier 212 functions to reverse bias the base of
the transistor 208 and is connected to one side of the tickler coil
213, which is excited by a tank circuit consisting of an inductance
214 and a condenser 216 coupled to the transistor 208 in which
continuous oscillation is set up by the tank circuit. The other
side of the tickler coil 213 is connected to the base of the
transistor 208. The rectifier 212 establishes the reverse bias
required by the base of the transistor 208 and is also connected to
chassis ground through a condenser 217 which establishes the bias
network circuitry. A bias rectifier 2171 is connected between
chassis ground and a junction between the resistors 209 and 211.
The tank circuit is connected with the collector of the transistor
208 through a coupling condenser 218. A condenser 219 is connected
between the emitter and the collector of the transistor 208 to
shunt out radio frequency potentials. A capacitor 777 acts to
provide a bypass to ground shunt for attenuating radio frequency
feed-back into the line 206 when the oscillating circuit 186 is in
operation. The tank circuit can be tuned to oscillate at a rate of
approximately 1.8 megaHertz. The oscillation is picked up by the
transformer winding 1762 and the voltage thereof is multiplied by
the transformer winding and impressed by way of the lead 179 on the
control grid 168 of the tetrode 136 to provide an amplified output
by the tetrode 136 of that frequency. The output of the tetrode 136
is impressed by way of a lead 220 on an output circuit which is
coupled through condenser 221 to a tuned pie network which includes
condensers 222 and 225 and inductances 223 and 226. Right-hand ends
of the inductances 223 and 226 are connected to chassis ground so
that, if there should be failure of the condensers 221 and 222, the
direct current output of the tetrode 136 would be drained off to
chassis ground without danger to the patient. A take-off lead 224
which is connected between the condenser 222 and the inductance 223
extends to one side of the condenser 225. The other side of the
condenser 225 is connected to a central lead 63 of a coaxial cable
18 and through a cable end assembly 53 to one end of a driver coil
28. The other end of the driver coil 28 is connected through a
condenser 49 to chassis ground. An annular conductor 68 of the
coaxial cable 18 is connected to chassis ground. A passive
electrode 22 is connected by a lead 422 to one side of a condenser
227. The other side of the condenser 227 is connected to chassis
ground. Thus, a continuous radio-frequency oscillating potential is
set up in a driver coil 26 and in an electrode 19 and an
electrosurgical operation can be performed when the electrode 19 is
advanced to a patient 70 mounted on a treatment table 71 with the
passive electrode 22 engaging the patient.
As long as the passive electrode 22 is coupled to chassis ground
through the lead 422 and the condenser 227, a return path is
provided for radio-frequency current, and, when the electrode 19 is
brought close to or into engagement with the patient 70, an
electrosurgical operation can be performed safely. However, if this
coupling is broken as by electrical failure of the lead 422, the
low impedance return path to chassis ground through the passive
electrode is broken. As indicated by the dashed line 72, the
surgical table can be at system ground, and other items which can
be connected to the patient can be at system ground providing
unwanted alternate return paths to system ground. A radio-frequency
potential is developed between the system ground 14 and the chassis
ground causing a radio-frequency potential to be set up in the
transformer 17 between the leads 23 and 24. This potential is
rectified by a rectifier 74 to provide a direct current potential
across the coil of the relay 31 to energize the relay 31. A
condenser 76 mounted in parallel with the relay coil 31 smooths out
the current to the relay coil 31. An adjustable resistor 77, which
is connected in parallel with the relay coil 31, can be adjusted to
determine the voltage at which the relay 31 is energized. When the
relay 31 is energized, normally closed contacts 311 and 312 open
and normally open contacts 312-313 close to disconnect the main low
voltage direct current power lead 194 from the lead 321 to
de-energize the switch 196 and to connect the main low voltage
direct current power lead 194 to the coil of the relay 31 to
maintain the relay 31 energized through a resistor 431 to chassis
ground. At the same time, normally open relay contacts 316-317
close to connect a buzzer horn 81 across the transformer leads 188
and 190 to cause the horn 81 to sound. The relay 31 is reset
automatically when the main on-off switch 126 is turned to the off
position.
When the on-off switch 126 is in its other or on position, the
switch 198 is moved to its other position and the switch 196
remains in the position shown and a single pole double throw blend
switch 2341 is in the off position shown, a continuous oscillation
is impressed on the driver coil 28. When the switch 196 is moved to
its other position and while the single pole double throw blend
switch 2341 is in the off position shown, the oscillating circuit
184 is energized to produce an interrupted oscillation in the
driver coil 28. The oscillating circuit 184 is generally similar to
the circuit 186 already described and includes a transistor 237, a
tank circuit inductance 238, a tank circuit capacitor 239, and a
tickler coil 240 and associated elements. A lead 241, which is
connected to the tap of the potentiometer 201, is connected through
a choke 242 to the collector of the transistor 237. Moving of the
switch 196 to its other position impresses a selected DC voltage
across the potentiometer 201 and a DC voltage between zero and the
selected voltage is impressed upon the lead 241. The emitter of the
transistor 237 is connected to chassis ground. The oscillating
circuit 184 is set in operation to deliver an oscillator frequency
of approximately 1.8 megaHertz on the control grid of the tetrode
136. The lead 199, which is connected to the high side of the
potentiometer 201, is also connected through the pole of the blend
switch 2341 to a lead 245, which is connected to base leads of
transistors 244 and 246, which form a multivibrator circuit,
through resistors 247 and 248, respectively. The collector lead of
the transistor 244 is coupled through a condenser 249 to the base
of the transistor 246 and the collector of the transistor 246 is
coupled through a condenser 251 to the base of the transistor 244.
The collectors of the transistors 244 and 246 are connected to the
lead 245 through resistors 2511 and 2512, respectively. Emitters of
the transistors 244 and 246 are connected to chassis ground. The
multivibrator circuit can be arranged to oscillate at a rate of
approximately 7000 Hertz. A lead 252 from the collector of the
transistor 244 is connected through a coupling condenser 253 and a
rectifier 2531, and a resistor 2532 connected in parallel with the
rectifier 2531, to the base of the transistor 237 so that the
operation of the oscillating circuit 184 is interrupted at a rate
of 7000 Hertz to put an interrupted oscillating potential on the
control grid of the tetrode 136 and to supply an interrupted
radio-frequency oscillating potential at the electrode 19. The
rectifier 2531 and the resistor 2532 connected in parallel with the
rectifier 2531 forms a network which preserves the wave form
generated by the multivibrator circuit as it is transmitted to the
oscillator circuit 184.
An adjustable capacitor 1765 is connected between the lead 179 and
chassis ground and can be adjusted so that it tunes with the
transformer secondary coils 176 and 1762 and with the capacitor
2172 so that the grid input is tuned with the plate series tuned
circuit 222, 223, 225, and 226. Both of these circuits are tuned
with the driver input oscillating circuits 184 and 186 at
approximately 1.8 megaHertz.
When the blend switch 2341 is disposed in its other or "on"
position, moving of the switch 198 to its other position while the
switch 196 is in the position shown energizes both of the
oscillating circuits 184 and 186. The oscillating circuit 186 is
energized in the same manner as already described. The lead 200,
which is connected to the switch 198, is connected through a lead
256, a rectifier 257, the blend switch 2341, the lead 245, and an
adjustable resistor 2572 to the lead 199, which is connected to the
right hand end of the potentiometer 201. The rectifier 257 prevents
unwanted cross feed between the leads 199 and 200. A rectifier 2570
provides full direct current voltage to the multivibrator circuit
associated with the transistors 244 and 246 when the direct current
voltage dropping resistor 2572 is switched into the circuit, blend
position, to maintain a constant voltage on the multivibrator
circuit to insure stable operation. Both the oscillating circuit
184 and the oscillating circuit 186 are set in operation and an
output is provided from the tetrode 136 for energizing the
electrode 19 which combines the interrupted oscillation of the
circuit 184 with the uninterrupted oscillation of the circuit
186.
The lead 245 of the multivibrator circuit is also connected to a
sonic signalling device 271, which is constructed to produce a
sound signal of a selected frequency, which can be 2900 Hz. The
sonic signalling device 271 is connected to chassis ground through
a pole 2721 of an on-off switch 272 and a resistor 273. Similarly,
the lead 200, which is connected to the high side of the
potentiometer 203, is also connected to a second sonic signalling
device 274, which is constructed to produce a sound signal of a
second selected frequency, which can be 4500 Hz. The sonic
signalling device 274 is connected to ground through a pole 2722 of
the on-off switch 272 and a resistor 276. The sonic signalling
device 271 sounds when the potentiometer 201 is energized to
energize the oscillating circuit 184 to produce a sound signal
which indicates to the user of the device that the oscillating
circuit 184 is operating. The sonic signalling device 274 similarly
produces a sound signal when the oscillating circuit 186 is
energized to indicate that the oscillating circuit 186 is
operating. When both the oscillating circuits 184 and 186 are
operating, i.e., when a blended current is being produced, a sound
signal is produced which is a blend of the selected frequencies.
The rectifier 2570 insures a direct current voltage on the sonic
signalling device 271 when the switch 2341 is in the blend (other
or on) position. If the user does not want sound signals, the
on-off switch 272 can be opened. The resistance values of the
resistor 273 and 276 determines the loudness of the sound
signals.
The condenser 227, through which the passive electrode 22 is
coupled to chassis ground, permits passage of radiofrequency
current to permit electrosurgical action but limits passage of
lower frequency current which might shock the patient. The
condenser 49, through which the driver coil 28 is coupled to
chassis ground, similarly permits passage of radiofrequency current
but prevents passage of lower frequency current generated as a
sub-harmonic of the radiofrequency current to isolate the coils 28
and 26 from such lower frequency current to eliminate the so-called
"faradic" effect or involuntary muscle contraction effect.
The electrosurgical device described above and illustrated in the
drawings is subject to structural modification without departing
from the spirit and scope of the appended claims.
* * * * *