Electrosurgical unit

An electrosurgical unit for use in tissue cutting or coagulation procedur A vacuum tube oscillator operating in push-pull relationship generates RF oscillations which are extracted across a balanced coil transformer, the secondary of which is ungrounded. Forceps are provided to be connected across the output of the transformer for producing an isolated voltage for use in sealing off bleeding blood vessels. A handpiece is also provided for connection across the transformer output for selectively producing a cutting voltage or a coagulation voltage. An intensity control circuit is capable of connection in the power supply to control the output voltage. A pulse modulation unit is capable of being connected at the input of the oscillator to control the "on" time of the oscillator. A switching circuit operates to interconnect the intensity control to the power supply when the cutting probe is being utilized for cutting procedures, and connects the pulse modulation unit to the oscillator when the coagulation signal is being provided across either the forceps or the handpiece. An indifferent plate, also known as a dispersion electrode, is utilized together with the handpiece for cutting procedures. The indifferent plate is completely isolated from ground to prevent shocks and burns occurring on the patient at inadvertent ground points.

BACKGROUND OF THE INVENTION 
This invention relates to electrosurgical devices and more particularly to 
an improved electrosurgical unit capable of providing an unmodulated 
signal for cutting tissue and a modulated signal for coagulation. 
High frequency oscillations have been utilized for various 
electrotherapeutic purposes. Some devices utilize the electrostatic field 
produced by a high frequency oscillator for surgery, coagulation, or 
sterilization of utensils. For example, U.S. Pat. No. 1,945,867 teaches 
the creation of such high frequency oscillatory electrostatic field which 
is utilized for electrotherapeutic purposes. More recently, use has been 
made of the high frequency electrical current produced. Electrosurgery has 
been carried out based upon the ability to localize and control the 
heating effect from such high frequency electrical current. Such electric 
current is localized at a sharp point, usually by means of a pointed 
electrode, to create a high current density which provides the intense 
localized power needed for tissue effect. A return electrode, usually a 
large plate positioned under the patient, returns the current back to the 
electrosurgical unit. By having a rather large return plate, the current 
density is dispersed, causing a low current density at the contact with 
the return plate. 
It has been found that tissue cutting can be produced by utilizing an 
undamped signal, while coagulation can be achieved by utilizing a damped 
frequency signal. Spark gap oscillators generally produce damped waveforms 
while vacuum tube oscillators produce undamped waveforms. As a result, 
many electrosurgical devices providing both tissue cutting and tissue 
coagulation outputs will utilize a spark gap generated waveform for 
coagulation, and a vacuum tube oscillator for tissue cutting. Typical of 
such unit is described in U.S. Pat. No. 3,058,470. Other electrosurgical 
units will rather utilize a single oscillator which alternates between 
damped and undamped signals. For example, U.S. Pat. No. 3,261,358 provides 
such alternating output. Also, U.S. Pat. No. 3,478,744 provides a 
modulated output which finds use for both cutting and coagulation. While 
vacuum tube oscillators are generally preferred, many units do not use 
them because they are usually bulky and heavy and require a long amount of 
warm up time during the turn-on periods. 
In general, all electrosurgical units provide a return electrode, 
frequently called the dispersion electrode, the indifferent plate, or the 
butt plate. Most such prior art units extract the oscillator output across 
an output transformer which has either one end, or a midpoint grounded, 
whereby the return plate operates as a ground plate. The use of this type 
of grounded output unit has created many surgical problems and numerous 
patient injuries. The main purpose of the return plate is to disperse the 
current and create a low current density contact between the patient and 
the return path. If the patient accidentally touches a piece of grounded 
metal, such as the operating table, there will occur a grounded return 
path at that point of contact. However, the contact point will be very 
small which will result in a high density current causing a burn at the 
contact point. Even if precautions are taken to prevent contact between 
the patient and the operating table, it is practically impossible to avoid 
complete contact, because of conductive paths provided by the spillage of 
blood, or saline solutions. Additionally, there generally exists 
capacitive paths between the patient and ground which can also cause 
return paths to ground with possible burns at the points of close contact 
between the patient and ground. In recent times where numerous monitoring 
units, such as EKGs, ECGs, etc., are connected to the patient during a 
surgical operation, the point of contact between such peripheral 
electrical equipment and the patient also causes the possibility of high 
current densities flowing at such points of contacts which may also cause 
burns as the current flows through the equipment to ground. A further 
hazard can result if the return cable to the electrosurgical unit breaks 
or if the return plate accidentally becomes disconnected. The current will 
then seek alternate ground paths through the patient. Such alternate 
contacts will frequently be over a very small area causing severe patient 
burns. 
A solution has been presented to provide an isolated output unit where the 
return plate is ungrounded and is in fact isolated from ground. In this 
way, the current will not seek ground contacts as return paths since the 
electrosurgical unit is isolated from ground. However, it has heretofore 
not been possible to obtain a very good isolated output and frequently, 
stray pathways to ground within the unit defeated the attempted isolation. 
Since the accidental disconnection of the return plate can cause burns in 
the patient as well as other hazardous conditions, many prior art units 
contain sensory warning devices to give an indication when such 
disconnection occurs or when the cable is broken. However, in most prior 
art units, even though the return plate is disconnected, the probe will 
still provide the high current density and continue cutting tissue, 
thereby continuing the possibility of burns. 
Prior art electrosurgical units have also presented other problems. In many 
cases it is desired to provide alternately either a coagulation signal or 
a cutting signal. Some units have provided two separate output probes, one 
for coagulation and one for cutting. However, frequently, both units are 
simultaneously activated so that while one of the probes is being used, 
someone may accidentally pick up the other probe and burn their hand. Some 
electrosurgical units only provide a single probe for alternately 
supplying a cutting or a coagulating output. With these units, however, 
when the surgeon is utilizing the single probe, it is not possible for an 
assistant to provide coagulation support to the surgeon. 
Another difficulty with prior art electrosurgical units is in connection 
with the magnitude of the coagulation or cutting output voltage. It is 
necessary to control the magnitude of these outputs depending upon the 
depth of cut, the impedance provided by the patient, and various other 
factors. Most units do provide some type of intensity control. However, 
the intensity control set for a cutting procedure may not be suitable for 
a coagulation procedure. As a result, it is necessary for the surgeon to 
reset the unit as he alternates between coagulating and cutting. 
Furthermore, in providing the modulated output for coagulation purposes, 
most electrosurgical units provide a single level of modulation, and 
usually use a standard 60 cycle per second output. However, it has been 
found that the patient acts as a rectifier for such 60 cycle modulation 
and muscle spasm will result during the coagulation procedure. 
Still a further problem with many eklectrosurgical units is that the 
switching between the coagulation and the cutting takes place at a high 
voltage. As a result, the possiblity of sparking exists and when using 
explosive chemicals there is the dangerous possiblity of an explosion 
occurring in the operating room. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide an 
electrosurgical unit which avoids the aforementioned problems of prior art 
devices. 
It is another object of the present invention to provide an electrosurgical 
unit with a highly isolated output. 
Yet a further object of the present invention is to provide an 
electrosurgical unit which utilizes two vacuum tubes in push-pull 
arrangement, in conjunction with a balanced transformer coil, to thereby 
produce a high isolated output. 
Still a further object of the present invention is to provide an electrical 
surgical unit which provides a forceps for sealing blood vessels and a 
handpiece for cutting. 
Another object of the present invention is to provide an electrosurgical 
unit which utilizes a handpiece to selectively provide either a 
coagulation or a cutting output voltage. 
Still another object of the present invention is to provide an 
electrosurgical unit which provides independent control for the level of 
the cutting voltage and the level of the coagulation voltage. 
A further object of the present invention is to provide an electrosurgical 
unit which includes a standby circuit for providing low standby power to 
heat the filaments of the oscillator vacuum tubes thereby minimizing the 
warm up period. 
Still another object of the present invention is to provide an 
electrosurgical unit which includes an interlock coupled to the return 
plate for stopping the cutting output and providing a warning signal when 
the return plate is disconnected. 
Still a further object of the present invention is to provide an 
electrosurgical unit which contains a standby switch and an operating 
switch and which includes a preventive circuit to prevent simultaneous 
activation of both these switches. 
Another object of the present invention is to provide an electrosurgical 
unit which contains output indicators for coagulation, cutting, standby, 
and operating conditions. 
Yet a further object of the present invention is to provide an 
electrosurgical unit which utilizes an improved transformer unit which 
prevents unbalance and reduces capacitive leakage to ground. 
Still another object of the present invention is to provide an 
electrosurgical unit which utilizes low voltage switching to prevent the 
possibility of explosions. 
Briefly, the invention provides an electrosurgical unit which includes a 
vacuum tube oscillator means for providing an ungrounded output of a given 
frequency. A power supply means supplies the oscillator with a voltage. A 
coagulation output means is available for coupling to the oscillator means 
and providing a coagulation voltage for use in coagulation procedures. A 
cutting output means is also available for coupling to the oscillator 
means and providing a cutting voltage for use in cutting procedures. A 
switching circuit means can selectively connect the coagulation output 
means or the cutting output means to the oscillator means. An intensity 
control means is also available for coupling to the power supply and 
varying the voltage provided to the oscillator means. A modulation means 
is also available for coupling to the oscillator means and providing 
intermittent operation of the oscillator means. The switching means 
interconnects the intensity control means to the power supply means only 
when the cutting output means is connected to the oscillator means, and 
interconnects the modulation means to the oscillator means only when the 
coagulation output means is connected to the oscillator means. 
The cutting output means further includes a handpiece unit for applying the 
cutting voltage as a high density RF voltage and a return plate for 
returning the current to the oscillator means. Neither the handpiece unit 
nor the return plate are grounded, and both are highly isolated from 
ground.

In the various figures of the drawings, like reference characters designate 
like parts. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Electrosurgical units generally contain an RF oscillator which provides a 
high frequency output electrical current which is extracted across an 
output transformer. The current is applied to the patient from an 
electrode in a handpice unit and returns from a wide area return plate, 
hereinafter referred to as the indifferent plate. 
Referring now to FIGS. 1 and 2 there will be compared the non-isolated or 
grounded output unit, shown in FIG. 1, with the isolated output unit, 
shown in FIG. 2. In FIG. 1, the electrosurgical unit, shown generally at 
10 indicates an output transformer 12 having one end thereof grounded at 
14. The high frequency output current is applied by means of a handpiece 
electrode 16 to the patient 18. The current path returns through the 
indifferent plate 20, generally placed under a wide area of the patient 
such as the buttocks. It will therefore be appreciated that the return 
plate is in fact grounded. The indifferent plate is generally made large 
to permit a broad area of contact with the patient thereby providing a low 
current density path for the return current. In fact, the only difference 
between the handpiece 16 and the plate 20 is that the handpiece provides a 
high density current which thereby causes the burning or cutting of the 
tissue, while the low density plate 20 will not cause any such burning or 
cutting. 
Frequently there are connected additional peripheral electrical equipment 
21 such as monitoring units, EKG units, etc. These equipment units are 
grounded and are connected to the patient by means of contacts, for 
example, contacts 22. As a result these contacts also provide a path 
leading to ground. Additionally, there exists capacitive paths, shown by 
the dotted lines 24, between the patient and ground. As a result, the main 
current path from the electrosurgical unit will pass through the probe 16 
and return through the indifferent plate 20, as shown by path 26. However, 
additional current paths 28 will also exist through the contacts 22 to the 
peripheral equipment 21, as well as current paths 30 through the 
capacitive coupling to ground. At any of these additional current paths a 
burn could result if there is a small enough area of contact. Such small 
are of contact would duplicate the probe electrode 16 and cause a high 
density RF current to flow which will burn, and may cut the tissue. 
An even more serious problem can occur if the return cable 32 were to be 
severed, as for example at point 34. In this case there no longer exists 
the wide area of the indifferent plate to provide a low density return 
path. The current will therefore seek the alternate paths to return to 
ground and will cause severe burns, as shown at contact 36. 
In the isolated system, shown in FIG. 2, the output transformer 12 is not 
grounded and is therefore isolated from ground. As a result, neither the 
handpiece 16 nor the indifferent plate 20 is grounded and there only 
exists the single current path 26 flowing from the handpiece, througe the 
patient, the back to the electrosurgical unit through the indifferent 
plate 20. While the electrosurgical unit itself may be grounded at 14, the 
output transformer is isolated from ground and prevents any current flow 
path to ground. As a result, even though peripheral equipment 21 may be 
connected to the patient through contacts 22, and although capacitive 
paths 24 may exist to ground, these do not provide any current flow path 
back to the electrosurgical unit. Furthermore, even if the return cable 32 
should be severed at 34, no burns would occur at any of the contacts 22, 
and in fact, no further current would flow from the electrosurgical unit 
10 to the handpiece 16. 
While in theory the isolated output units provide beneficial results, in 
practice it has heretofore not been possible to achieve such perfect 
isolation and even isolated output units have caused burns, and other 
problems to both patients and peripheral equipment. 
The present invention is of the isolated type system, heretofore described, 
but is capable of providing an exceedingly high isolation from ground due 
to the use of an improved RF generating circuit in conjunction with low 
capacitance interconnecting cables and an improved design for the output 
coil. Although prior art electrosurgical units have utilized vacuum tubes, 
the trend has been to eliminate such use because of the bulky size 
involved as well as the long delays which occur during warm-up of the 
filaments when the vacuum tubes are turned on. These problems have been 
avoided in the present invention by the unique design of the 
electrosurgical unit to be described in conjunction with FIG. 3. 
The RF electrical current is provided by means of the oscillator 40 which 
includes two vacuum tubes 42, 44 connected in push-pull relationship. The 
cathodes 46, 48 of the tubes are interconnected along line 50. A first 
control grid 52, 54 of each tube are interconnected through respective 
resistors 56, 58 to opposite ends G, G' of the grid coil 60 of the 
transformer to be hereinafter described. The centerpoint Gc of the grid 
coil is connected through resistor 62 to ground 64. The second grid 66, 68 
of each tube are interconnected along line 70 and coupled through resistor 
72 to the power supply 74 to be hereinafter described. Capacitor 76 
connected to ground, filters the high voltage supplied to the tubes. 
A third control grid 78, 80 of each tube, is respectively connected to the 
filaments 46, 48 of the tubes through the capacitors 82, 84. The plates of 
the tube 86, 88 are interconnected to the end points P, P' of the plate 
coil 90 of the transformer. The centerpoint Pc of the plate coil is also 
connected to the main power supply 74. 
The output coil 92 of the transformer has its ends 0, 0' connected across a 
tuning capacitor 94 and connects to the centerpoints of switches 96, 98 of 
the switching circuit 100. Switches 96, 98 are normally in their cutting 
position a which respectfully interconnects to the cutter handpiece shown 
generally at 102, and the indifferent plate or dispersion electrode shown 
generally at 104. When the switches 96, 98 are connected to their 
positions b, they interconnect to the coagulation forceps, shown generally 
at 106. 
The forceps 106 provide the means for sealing blood vessels and includes 
the two arms 108, 110 connected to the main unit by means of a plug and 
jack 112. The outer shield 114 of the forceps is also connected through 
the plug and jack to a ground through line 116. When the two ends of the 
forceps are brought together, an integral switch 118 is closed contacting 
onto point 120 which is connected to ground 116 through resistor 122. 
Closing of the switch 118, energizes the relay coil 124 whose other end is 
connected to the +V supply, which is a low voltage supply. 
The cutter handpiece 102 includes an electrode 126 coupled through the plug 
and jack arrangement 128 to the position a of switch 98. The shield 130 of 
the probe electrode is coupled to the shield 132 of the indifferent plate 
134. A coag/cut switch 136 is contained on the probe so that the user can 
provide both a cutting signal and a coagulation signal by using the same 
probe. When placed on its coag position, it interconnects point 138 with 
point 140. Switch 142 is available to connect ground 144 to point 138 or 
point 140. When switch 136 is placed in its cut position, it connects 
point 138 to point 146. 
A foot pedal, shown generally at 150, operates in parallel with the switch 
136 whereby the user can either manipulate the hand switch 136 to obtain 
the coag or cutting signal from the handpiece 102 or can utilize the foot 
pedal to obtain the same results. The foot pedal includes two separate 
switches 152 and 154. When desiring a coagulation output, switch 152 is 
moved from its normal position C to position d which interconnects point 
138 with point 140, similar to the action of switch 136. When a cutting 
signal is desired, switch 154 is moved from its normal position f to 
position e which interconnects point 138 to point 146, similar to the 
action of switch 136. The foot pedal 150 is connected to the main unit 
through the plug and jack arrangement 156. If both foot pedal switches are 
inadvertently activated at the same time, only the coagulate function is 
provided. 
The indifferent plate 134 is connected through a plug and jack arrangement 
158 to position a of switch 96. An interlock circuit 160 is also connected 
to the plug and jack to provide a visual indication when the plug and jack 
arrangement 158 has been opened. A low voltage supply +V passes through 
resistor 162 and is normally shorted to ground 166 though the shorting 
wire 164 on the plug side of the plug and jack arrangement 158. However, 
when the plug has been displaced from the jack, the current will pass 
through the light emitting diode 168 to provide a visual indication of the 
disconnection. At the same time, when the indifferent plate 134 has been 
removed from the circuit, no voltage will pass through the probe unit 102 
since both the probe and the indifferent plate are connected to opposite 
ends of the output coil 92 and no return path to the unit will be then 
provided. 
A multivibrator unit, shown generally at 170 is adapted to be coupled to 
the input of the oscillator unit 40 to effectively pulse modulate the 
operation of the oscillator. The multivibrator 170 includes transistors 
172 and 174 whose emitters are coupled together along line 176 and whose 
collectors are respectively connected to resistors 178 and 180. The base 
of transistor 172 is interconnected to the collector of transistor 174 
through capacitor 182 while the base of transistor 174 is connected to the 
collector of transistor 172 through capacitor 184. The bases of the two 
transistors are interconnected through the fixed base resistors 186 and 
188 and through the variable resistor 190 which is controlled by means of 
the variable control 192 connected at the end of resistors 178 and 180 
which is also connected to the +V supply. 
By means of the variable control 192, it is possible to control the duty 
cycle of the multivibrator and thereby control the pulse width of the 
output pulses produced. 
One of the output pulses of the multivibrator 170 is applied to the 
amplifier switch circuit 194. This circuit includes a first transistor 196 
having its emitter coupled to the +V supply and its collector coupled 
through a voltage divider comprising resistors 198, 200 to the base of a 
grounded emitter transistor 202. A diode 204 is connected across the 
collector-emitter path of transistor 196. The base of transistor 196 is 
connected through the resistor 206 to one of the outputs of the 
multivibrator 170 and specifically to the collector of transistor 172. It 
is also coupled to point 146 and also connected through capacitor 208 to 
ground. The collector of transistor 202 is connected to line 50 of the 
oscillator unit and the emitter of transistor 202 is grounded. 
When the multivibrator 170 is operating, one polarity of the output pulses 
will be applied through the transistor 196 and inverted by the transistor 
202 to control the oscillator 40. Each time that pulse appears, the 
oscillator will be operative. By means of the coag level control 192, the 
on time of the oscillator can be controlled. At the same time, when the 
point 146 is grounded by placing the switch 136 or the foot pedal 150 in 
the cut position, the transistor 196 will cause the oscillator to be 
continuously operative. 
Power is supplied to the unit through the main power supply 74 which is 
interconnected to an AC source 208. The current passes through a circuit 
breaker 210 and through the series of cross connected switches 212 to the 
transformer 214. The output of transformer 214 is rectified by means of 
the rectifier 216 and filtered by the filter 218 to provide a high voltage 
output at line 220. This high voltage output is fed through the switch 
222, which is normally in its open position g. When the operating switch 
224 is moved upward to its run position, switch 222 is caused to move to 
position h which interconnects the high voltage to the point Pc of the 
plate transformer coil 90, as well as to the screen grids 66 and 68 of the 
tubes 42 and 44 of the oscillator. 
The primary of the transformer 214 is connected to a variac coil 226. The 
variac can be controlled by means of the control arm 228. The variac is 
interconnected to the primary by means of the switch 230 being in position 
i. When moved to position j, the variac is removed from the circuit. In 
position j, the maximum output voltage is provided from the power supply, 
while in position i, the control arm 228 can vary the output from a low 
value up to its maximum value. 
An auxillary and filament supply circuit 232 is provided for forming the 
filament current to heat the vacuum tubes as well as to provide the low 
voltage supply for operating the tubes and transistors. The auxillary and 
filament supply 232 is connected to the main power lines by means of the 
transformer 234. One end of the secondary of the transformer 234 is 
connected to point 236 and the other end is connected to point 238. The 
center tap is connected to point 240. A standby indicator bulb 242 has one 
end connected to resistor 246, and its other end connected to point 248. A 
run indicator bulb 244 is connected between resistor 246 and point 250. 
Switches 252 and 254 are operated by means of the standby switch 256. The 
filament output is taken across the end of switch 252 on the one hand, and 
the point 236 on the other hand. 
When the switch 256 is upward in its standby position, point 236 will be 
connected to one end of the transformer 234 and, with switch 252 in its 
upward position on point 240, the other end of the filament output will be 
connected to the mid point of the transformer 234. In this way, only half 
of the output of the transformer 234 will be applied to the filament. At 
the same time, switch 254 will be upward on position 248 which 
interconnects the standby bulb 242 directly across the entire output of 
the transformer 234 so that the entire output voltage will be available to 
energize the standby bulb 242. 
When the standby position is lowered, during full operation of the unit, 
switch 252 will be in its lower position contacting 238 whereby the entire 
output voltage of the transformer 234 will be available to heat the 
filament. This voltage will be twice as much as the standby voltage and 
will be sufficient to fully operate the vacuum tubes of the oscillator. At 
the same time, switch 254 will also be in its lower position contacting 
point 250 which will place the entire output voltage of the transformer 
234 across the run bulb 244 to energize it. 
In the above described manner, during standby operation, a low voltage will 
be supplied to the filament to permit it to remain in a slightly heated 
position so that when full operation of the unit is desired, a reduced 
amount of time will be needed to fully heat up the unit. 
Rectifier 257 is connected across the filament output, and filter 258 
filters the output from the rectifier. The filtered output provides the 
low voltage supply +V which is utilized to energize the transistors and 
relay coils of the circuit. 
Standby switch 256 and operating switch 224 can both be activated 
independently. Since no mechanical lockout is provided between the two 
switches, the circuit 212 is arranged to prevent simultaneous operation of 
both these switches. The circuit includes switches 260 and 260' on the one 
hand, which operate in opposition to switches 262 and 262' on the other 
hand. The wires interconnecting switches 260 and 262, as well as the wires 
interconnecting 260' and 262' are crossed. In this manner, current will be 
provided to the transformers 214 and 234 only when the standby switch 256 
and the operating switch 224 are opposite to each other. Specifically, if 
the standby switch is in its upward position, indicating a standby 
condition, the operating switch 224 must be in its lower position in order 
for current to be supplied. At the same time, when the operating switch 
224 is placed upward, indicating a run position, the standby switch 256 
must be in its lower position in order for current to flow. 
An indicating circuit 264 is available for indicating whether the circuit 
is operting to supply a coagulation output or a cutting output. The 
indicating circuit is connected through a diode 266 to the line 50 of the 
oscillator unit, and includes a light emitting diode 268 for indicating 
when the cutting output is being supplied, and a light emitting diode 270 
to indicate when the coagulation output is being supplied. The two light 
emitting diodes are connected to ground on the one hand through resistor 
272 and on the other hand to opposite contacts of a switch 274. The switch 
274 is connected through resistor 276 to the low voltage supply +V. 
The switch 274 is operated by means of the relay coil 280 connected in the 
collector circuit of the transistor 278 whose emitter is connected to the 
low voltage supply +V. The base of transistor 278 is connected through the 
base resistor 282 and a choke 284 to the position 140. The capacitor 285 
filters the base of transistor 278 to ground. 
The operation of the circuit shown in FIG. 3 is as follows. The indifferent 
plate 134 is placed in contact with the patient and the unit is placed in 
its standby position. The standby switch 256 is moved upward and the 
operation switch 224 is moved downward. The standby bulb 242 will be 
illuminated and reduced standby voltage will be applied to the filaments 
of the vacuum tubes of the oscillator. 
When the unit is to be operated, the standby switch 256 is placed in its 
lower position and the operating switch 224 is placed in its upward 
position, thereby providing the full filament voltage and producing the 
full +V voltage. Moving switch 224 upward also connects the high voltage 
to the output coil. To operate the forceps 106, the arms 108 and 110 are 
clamped onto a bleeding vessel. Continuing pressure on the forceps 
automatically closes the switch 118 thereby energizing the coil 124 by 
completing its circuit to ground 116. Coupled to the coil 124 are switches 
96, 98 and 142. Switches 96 and 98 move to their b position which sends 
current passing through the arms of the forceps 108, 110. This current 
passes through the capacitors 281, 287 which allow actual shorting of the 
forceps together without stopping the system. 
Switch 142 is moved onto position 140 which is now grounded through the 
switch to point 144. Grounding of this point turns on the transistors 278 
which causes the coil 280 to become energized. This coil causes the switch 
274 to move on its lower position thereby turning on the light emitting 
diode 270 indicating that the coagulation procedure is being utilized. 
Switch 230 also moves to its lower position j which cuts out the variac 
control 228 and provides the maximum output voltage from the transformer 
214. 
When switch 142 operates to ground position 140, it also turns on the 
multivibrator 170 and permits pulse modulation control of the oscillator 
through the amplifier switch 194. By adjusting the coagulation level 
control switch 192, the system can produce high peak power with a low 
average power by virtue of its operation at a short duty cycle. The 
coagulation level control is set at the desired power level required for 
coagulation procedures on a given patient. 
Upon release of the arms 108 and 110, the coils 124 and 280 are both 
deenergized and all of the switches return back to their initial 
positions. In these initial positions, switches 96 and 98 are connected to 
their a point, which activates the cutter handpiece 102 and provides for a 
cutting procedure. However, the cutter handpiece will not be supplied with 
current until the switch 136 is actually placed onto its cut position. In 
so doing, point 146 is then grounded which turns on the amplifier switch 
194 to keep the oscillator operating constantly. At the same time, with 
the relay 280 deactivated, the switch 274 activates the diode 268 
providing a visual indication that a cutting output is being supplied. 
Switch 230 will also be in position i thereby including the variac control 
By manipulating the arm 228 on the variac control, the output voltage 
provided to the oscillator can be varied thereby controlling the intensity 
for the cutting procedure. 
The cutter probe can also be used for coagulation purposes by operating 
switch 136 to its coagulation position, thereby grounding point 140. This 
serves to turn on the multivibrator and at the same time energize the 
relay 280 which cuts out the intensity control circuit and switches the 
indicating circuit to provide visual indication that the coagulation 
procedure is being utilized. The foot pedal 150 can operate in identical 
manner to the switch 136 and produce the same results. 
It is noted from FIG. 3 that the indifferent plate 134 is not grounded, and 
the output is taken directly across the opposite ends of the output coil 
92. The output is highly isolated from ground because the output voltage 
and current appears only across the two ends of the output coil rather 
than from either end to ground. In addition, the high degree of isolation 
is achieved by utilizing a unique design for the transformer coils which 
provides a completely balanced coil with a minimum of capacitive effect 
between the coils. 
Referring now to FIGS. 4 through 8 there will be described the unique 
arrangement of the coil assembly. The coil assembly includes three 
sections of tubing 284, 286 and 288 which are each of cylindrical shape 
and precisely the same length. All three tubes contain alignment mounting 
holes 290 and 292 on opposite ends thereof. The largest tube 284 is used 
for winding of the output coil; the middle tube 286 is utilized for 
winding of the plate coil, and the smallest tube 288 is utilized for 
winding of the grid coil. Tube 288 contains three holes herein 294, 
through which the wires 296, 298 and 300 can pass, interconnecting to the 
point G, G', and Gc. The winding area for the tube 288 is precisely 
centered between the outermost holes. 
The inner tube 286 also contains three holes 302, which permit the passage 
therein of the three wires 304, 306 and 308 respectively connecting to the 
end points P and P' and the mid point Pc. The winding area is precisely 
centered between the two outermost holes. 
The upper most tube 284 contains two openings 310 through which terminals 
312 can protrude, for connection thereto of the opposite ends of the coil 
0 and 0'. Eyelet holes 314 are located in the outer edges of the tube 284 
to permit the eyelet termnals 316 to pass therein and to which are 
connected the wires from the plate coil and the grid coil, as shown in 
FIG. 6. 
The three coils are nested together and are assembled by means of the 
mounting screws 318 and 320 which respectively extend through the mounting 
holes 290 and 292. By utilizing the arrangement as shown, the winding can 
be located on precise centers of the three tubes without causing any 
unbalance between the tubes, thereby eliminating any capacitive effect 
between them. Although there may exist very small capacitive effects 
between the tubes and ground, such minute capacitive effects can be 
neglected because of their exceedingly small values. Additionally, by 
operating at a relatively low frequency, these capacitive effects are 
further diminished. Also, the coil can be isolated from the rest of the 
system to thereby additionally prevent the effects of such capacitive 
leakage paths to ground. Isolation is further enhanced by confining the 
output pickup coil to the center region of the plate coil so that coupling 
is predominantly magnetic with a minimum of capactive coupling from the 
ends of the plate coil. 
By way of example, the tubing can be made of high pressure laminated 
material. The length of each tubing can be approximately 33/8 inches with 
the winding area of the output coil being approximately one inch, the 
winding area of the plate coil being approximately 21/8 inches, and the 
winding area of the grid coil being approximately 3/4 inch. The output 
coil would have approximately 20 coil turns with a 20 turns per inch 
winding density; the plate coil would have 76 coil turns with a density 
winding of 36 turns per inch, and the grid coil would have 34 coil turns 
with a winding density of 45 turns per inch. The outside diameter of the 
largest tube would be 11/8 inches; the outside diameter of the center tube 
would be 7/8 inches and the outside diameter of the innermost tube would 
be 11/16 inches. 
Utilizing such arrangement described and with a high output voltage of 
approximately 530 volts, there can be achieved a peak to peak voltage 
across the ends of the output coil of 1500 volts. Since the impedance 
ratio is the inverse of the turns ratio squared, there results a very low 
source impedance which provides a constant output power regardless of the 
loading on the system. Typically, the oscillator produces a frequency of 
800 Kcs and the multivibrator produces a modulation frequency of 1 Kc. 
Utilizing the standby current to heat the filament of the tubes provides a 
warm-up time after the system is put in its run position of approximately 
5-6 seconds to achieve full power. The low voltage applied to the control 
circuitry can typically be +8 volts. 
Referring now to FIG. 9 it will be noted that the main body of the 
electrosurgical unit can be placed in a housing 322 which can be supported 
on a stand 324. The external equipment can be interconnected to the main 
unit by means of the plug and jack arrangements. The handpiece unit 102 
can be interconnected to the jack 128; the forceps unit 106 can be 
interconnected to the jack 112; the indifferent plate unit 104 can be 
interconnected to the jack 158, and the foot pedal unit 150 can be 
interconnected to the jack 156. The switch 118 is shown locatd directly on 
the forceps. However, it can be inherently included within the arms of the 
forceps so that as the arms are brought together the switch is 
automatically closed, as is shown in FIG. 10. In this embodiment, the arms 
108 and 110 are bowed outwardly with the switch contacts 118 and 120 
positioned on the inner sides of the arms. As the arms 108 and 110 are 
brought together, the switches 118 and 120 contact each other to complete 
the circuit and energize the relay coil 124. The coagulation current is 
sent to the arms 108 and 110 through the capacitors 280 and 282. The arms 
108 and 110 are insulated by the polyvinyl chloride encapsulation 326. The 
arms are also separated by the insulation block 328. 
The switch 136 is shown located on the handpiece unit, however, it is also 
possible to include this switch directly on the main housing unit 322. The 
main housing unit includes the standby switch 256, the operating switch 
224 and a main power switch which can be connected in series with the main 
source of energy. A dial switch 327 is connected to give an indication of 
the coagulation level and would be coupled to the variable control 192 of 
the multivibrator. A further dial 328 is provided to give an indication of 
the control of the variac arm 228 which controls the cut intensity. Five 
indicating bulbs are provided: the standby bulb 242, the operating bulb 
244, the coagulation indicator 270, the cutting indicator 268, and the 
interlock warning indicator 168. 
With the foregoing described arrangement it will be noted that the present 
invention provides an improved electrosurgical unit with a highly isolated 
output by using two vacuum tubes in push-pull arrangement for generating 
the RF signal. Furthermore, the isolation is achieved by utilizing low 
capacitance output cable and a uniquely arranged coil assembly which is 
completely balanced end to end. The output voltage and current appears 
only across the two ends of the output coil without having any part 
thereof grounded. Separate circuits are provided to control the output 
intensity of the cutting signal, by utilizing a variac in parallel with 
the main power supply transformer, and a separate control is provided for 
the coagulation intensity by controlling the duty cycle of the 
multivibrator which in turn pulse modulates the operation of the 
oscillator. While both a forceps for coagulation and a handpiece for 
cutting are provided, the cutting handpiece can also be utilized for 
coagulation. However, when either the forceps or the cutting probe are 
utilized, the other is prevented from being operational thereby preventing 
the possibility of causing burns to someone who may accidentally grab the 
unused instrument. An interlock is provided to warn when the indifferent 
plate has been disconnected. Additionally, upon disconnection of the 
indifferent plate, no current will be provided to the cutting handpiece. 
While a very high voltage is provided for the cutting and coagulating 
procedures, a low voltage is also provided for operating the transistors 
and the switches thereby avoiding the possibility of causing an explosion 
due to sparking at the switches. A standby low voltage filament supply is 
also included to provide for standby heating of the filament thereby 
reducing the warmup time when the system is turned on. Also, a preventive 
circuit is included to avoid the possiblity of having both the standby and 
the operating switches both being operated. Furthermore, the forceps are 
made such that they can be shorted together without necessarily 
disconnecting the operation of the entire system. 
Numerous alterations of the structure herein disclosed will suggest 
themselves to those skilled in the art. However, it is to be understood 
that the present disclosure relates to a preferred embodiment of the 
invention which is for purposes of illustration only and is not to be 
construed as a limitation of the invention.