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Description  |
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This invention relates to an electrosurgical device. The device of this
invention represents an improvement in the type of device shown in my U.S.
Pat. No. 3,870,047 issued Mar. 11, 1975.
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.
A secondary winding 146 of the transformer 130 supplied a voltage of
approximately 2000 volts AC across leads 150 and 151. The lead 150 is
connected to ground as is a cathode 152 of 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 section 146A of the second secondary winding 146 of the transformer 130
is connected in parallel with a capacitor 146B to form a tuned 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 other 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 swithc 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
resistors 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.
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