Abstract:
A supplementary acoustic warning signal is provided for a high-frequency electrosurgical unit which sounds only after the lapse of an interval set by a first delay circuit shows that one of the high-frequency generators in the unit remains active longer than what, on the average, is normal. A second delay circuit is provided to assure shut-off of the high-frequency generators if at least one of the high-frequency generators remains active without interruption longer by an interval set by a second delay circuit beyond the lapse of an interval of the interval set by the first delay circuit. The supplementary acoustic signal thus sounds before the second delay circuit shuts off the high-frequency generators. The intervals determined by each of the delay circuits are adjustable. The output signal of the second delay circuit which activates the shut-off relays is maintained until a switch is operated to reset the system, so that the malfunction which has led to shut-down will be dealt with before the unit is used again.

Description:
This application is a continuation of application Ser. No. 514,473, filed July 18, 1983, now abandoned. 
    
    
     This invention concerns a high-frequency electrosurgical unit for cutting and coagulating biological tissues in which one or more high-frequency generators are controllable by finger switches, foot switches or automatic switch systems and when there are two or more of them, can be controlled simultaneously or independently from each other, and particularly units of that type containing means for producing visible and audible signals while one or more of the high-frequency generators are in operation. 
     The high-frequency generators of high-frequency electrosurgical units already known can be activated simultaneously or independently of each other for any length of interval and as often as desired by finger switches, of which switches are automatic switching devices. 
     The high frequency electrosurgical units are dangerous in activated condition, since each contact of the patient or of operating personnel with the active electrode can produce burns and this holds, for example, even for the neutral electrode in the case of apparatus with floating output. Finger switches or foot switches which activate the high-frequency generators only while the surgeon or his assistant presses the corresponding switch and immediately switch off the high-frequency generators when the switch is no longer pressed are used in high-frequency electrosurgical units now in use on account of the danger just mentioned. In addition, known high-frequency electrosurgical units are equipped with optical and acoustic signal devices which are activated at the same time as the high-frequency generators. By this means the surgeon and other personnel present are intended to be made aware of the danger even during intended activation of the high-frequency generators. 
     It has been found in practical application of the known high-frequency electrosurgical units that the optical and acoustical signals do not provide sufficient safety against burns or injuries to patients or personnel. The optical signal devices of known high-frequency electrosurgical units are always disposed on the front panel of the units, which as a rule cannot continuously be observed either by the surgeon or by other attending personnel during an operation. The high-frequency electrosurgical unit is often placed as far as possible from the operating table, since freedom of movement must be assured for the surgeon. The acoustic signal that is activated simultaneously with the high-frequency generators is regarded as disturbing by many surgeons, because it distracts them from their concentration, so that this signal is either set very low or completely shut off. On the other hand there are surgeons who become so used to the acoustic signal that they lose all awareness of it. A clearly significant signal would be particularly important when the high-frequency generators of the high-frequency electrosurgical units are unintentionally activated. Unintentional activation of the high-frequency generators can result from unintentional actuation of the finger switch or foot switch, or of its circuit by failures in the switches or in the cables or plug connectors thereof. Failures in the electronics within the high-frequency electrosurgical units can also activate the high-frequency generator. This holds also for automatic switch-on equipment. 
     Accidents have also come to light in which electrically conducting liquids, such as blood, physiological salt solutions, urine or fruit juice for example, have flowed into the finger switches set in hand controls, as a result of which the high-frequency generators have been unintentionally activated. 
     In the case of unintentional activation of the high-frequency generators, particularly as the result of technical errors or failures, the presence of the known optical and acoustical signals alone is not sufficient, in some cases, for the resulting danger to be recognized in time, and, in particular, to be reacted to sufficiently fast and correctly. This applies, for example, to endoscopic operations. If a high-frequency electrosurgical unit is unintentionally activated as the result of a technical failure during a transurethral resection, the resection loop used in such an operation could cut right through the urinary bladder before the surgeon recognizes the danger and has made the correct reaction thereto. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a high-frequency electrosurgical unit in which unintended activation resulting from causes like those mentioned above do not lead to any threat to the safety of the patient or the user, or at least greatly reduce the danger. 
     Briefly, a supplementary signal system is provided which is triggered by a first delay circuit only when a high-frequency generator has remained activated for more than a predetermined time interval and a second delay circuit is provided for switching off the high-frequency generators by a cut-off relay when a high-frequency generator has remained activated longer than the delay period of the first delay circuit, so that the supplementary acoustic signal is provided as a warning before the second delay circuit shuts off the high-frequency generator. The additional acoustic signal provided by the present invention which is distinct from the known acoustic signals activated simultaneously with the high-frequency generator and appears only after at least one of the usually more than one high-frequency generators of a high-frequency electrosurgical unit has remained in operation longer than what is on the average usual, is produced by means of a delay circuit that is definitively adjustable to an appropriate setting. Furthermore, the high frequency electrosurgical unit according to the invention is equipped with a shut-off relay that is activated by another adjustable delay circuit which assures the automatic shutting off of the high-frequency generators after the lapse of the sum of the two delay intervals and also keeps them shut off thereafter until a reset switch is actuated on the high-frequency electrosurgical unit and thereby releases the shut-off relay and enables the reactivation of the high-frequency generator. 
    
    
      THE DRAWINGS 
     The invention is further described by way of illustrative example with reference to the annexed drawings, in which: 
     FIG. 1 is a block circuit diagram of a high-frequency electrosurgical unit according to the invention, and 
     FIG. 2 is a circuit diagram of the two delay circuits of the embodiment shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The high-frequency electrosurgical unit of FIG. 1 contains two high-frequency generators 1 and 6. A power amplifier 2 is coupled by a transformer 3 to the oscillator of the high-frequency generator 1. The output of the power amplifier 2 can be adjusted in level over a wide range (e.g. from 2 watts to 400 watts). Another transformer 4 is connected to the output of the power amplifier 2 which provides the potential isolation necessary for high-frequency electrosurgical unit between the low-frequency supply voltage U 1  and the circuit that passes through the patient. The first high-frequency generator 1 is a conventional high-frequency oscillator, with its frequency controlled by an external circuit or a stabilizing element such as a quartz crystal. 
     An active electrode AE and a neutral electrode NE are shown in FIG. 1 connected to the secondary winding 5 of the transformer 4, these electrodes representing any of the well-known electrode arrangements used with high-frequency surgical apparatus. 
     The second high-frequency generator 6 shown in FIG. 1 is a self-excited HF generator including its own output adjustment by which its output power can be set at any value within a wide range, (e.g. from 2 to 50 watts). The output of the high-frequency generator 6, like that of the power amplifier 2 of the high-frequency generator 1 is equipped with an output transformer 7. The secondary winding of this transformer 7 is designed, for example, for bipolar coagulation electrodes designated BIP. 
     Windings 9 and 10 are respectively coupled to the high-frequency transformers 3 and 7 and have high-frequency voltages induced therein if and so long as the respective high-frequency generators 1 and 6 are active. These high-frequency alternating voltages are rectified in rectifiers 11 and 12 respectively by diodes D 1  and D 3  and filtered (smoothed) by capacitors C 1 , C 2 , C 3  and C 4  and inductances L 1  and L 2  as shown in FIG. 1. 
     The capacitors C 1  to C 4  and the inductances L 1  and L 2  have sufficiently great electrical values of capacitance and inductance respectively while filtering out not only the high H frequency but any lower modulation frequency, such as are used in high-frequency electrosurgical unit for producing coagulation (e.g. 20 kHz). The outputs of the two rectifiers 11 and 12 are brought together into a common circuit through the respective diodes D 2  and D 4 . A voltage-limiting diode D4A is connected so as to limit the output voltage of the rectifier 12. At the output of the rectifiers 11 and/or 12 a d.c. voltage level is produced so long as the respective high-frequency generators 1 and/or 6 is or are activated and that d.c. level produced by rectification is then supplied to a delay circuit 13. Resistances R 2  and R 3  are designed to discharge the respective capacitor pairs C 1 , C 2  and C 3 , C 4  sufficiently fast as the respective high-frequency generators are shut off. 
     As soon as one of the two high-frequency generators 1 and 6 is switched on, there arises, with neglibible delay from the time constants of the components of the rectifiers 11 and 12, at the instant t 1  a d.c. voltage u 1  at the input of the delay circuit 13 which dies away again as soon as the respective high-frequency generators are shut off. The shut-off instant is designated t 2  in this context. The instant t 1  is thus the instant at which at least one of the high-frequency generators is switched on. The instant t 2  is the instant at which the last of all of the high-frequency generators that may have been operating is shut off. As soon as a voltage u 1  arises at the input of the delay circuit 13 at the instant t 1 , the delay element (as shown in FIG. 2 and described below) in the delay circuit 13 becomes effective and after the delay interval t 13  =t 3  -t 1  which has been set, for example, at 3 seconds, delivers a voltage u 2  at the instant t 3  to the output of the delay circuit 13. The duration of the delay interval t 13  is adjustable. The output voltage u 2  is maintained until all high-frequency generators are shut off, which happens at the instant t 2 . The delay interval t 13  =t 3  -t 1  can be set as required, so that according to the intended application of the high-frequency electrosurgical unit this delay interval t 13  will be greater than the normal switch-on duration of the high-frequency generators. Thus, at the output of the delay circuit 3 no voltage u 2  arises in normal operation and all following stages remain out of operation. If, however, as the result of operator error or a failure in the switch-on electronics or in the finger-operated or foot-operated switch, at least one of the high-frequency generators is activated longer than t 13  =t 3  -t 1 , an output voltage u 2  arises at the instant t 3  at the output of the delay circuit 13, causing an acoustic signal to be emitted at once by triggering a signal device 14, making the surgeon aware of the fact that the normal switch-on interval has been exceeded. If the acoustics warning signal sounds even though the surgeon has already turned off the high-frequency generators, the surgeon or other attending personnel know at once that the high-frequency electrosurgical unit has malfunctioned and can deal with it correspondingly, for example turning off the supply of power to the equipment from the electrical supply lines. If this acoustic warning signal is disregarded or if no action is taken for reliably shutting down the high-frequency generator, a second delay circuit 15 becomes effective which will assure the shut-off of all high-frequency generators by their shut-off relays 16 and 17 after the further adjustable delay interval t 15  =t 4  -t 3 . 
     The aggregate delay t a  =t 4  -t 1  can be so set by suitable selection of the individual delay t 13  =t 3  -t 1  and t 15  =t 4  -t 3  that damage in case of error can be limited to a minimum. 
     A Zener diode is provided in the rectifier 12 which limits the output voltage u 1 . This is necessary because the input coupling coil 10 of the rectifier 12 is coupled to the output transformer 7 of the high-frequency generator 6, where the voltage induced in the coil 10 depends both on the power adjustment of the high-frequency generator 6 and the loading of the coil 8. Limiting of the output voltage u 1  is not necessary in the rectifier 11, because the coupling coil 9 is coupled to the transformer 3, so that the voltage induced in the coil 9 is independent of the output power of the power amplifier 2 and of the loading of the secondary coil 5. 
     FIG. 2 shows an illustrative embodiment of both of the delay circuits 13 and 15. The input voltage u 1  is inverted in inverters IC 1  and IC 2 , the input signal U 4  of IC 2  Δ being delayed by the time constant of a combination of an adjustable resistor R 5  and a capacitor C 5  for a time lapse Δt 13  =t 3  -t 1 . In contrast thereto the inverted output signal u 5  produced by IC 1  appears undelayed at the inverter output. If u 1  is switched off at the instant t 2 , then IC 5  immediately discharges via the diode D 5  and the resistances R 2  and R 3  (in FIG. 1), as the result of which the switch-off instant t 2  appears practically undelayed at the output of IC 2 . A diode D 6  is provided to limit negative input voltage of IC 2 . 
     The respective output voltages u 5  and u 6  of the inverters IC 1  and IC 2  are supplied to a NOR logic element IC 3  at the output of which the voltage u 2  appears only when t 2  takes longer to appear than t 3 , at which time both input voltages u 5  =u 6  =0. 
     The high-frequency generator can be activated as often as desired without appearance of the output voltage u 2  at the output of IC 3 . If the high-frequency generators are not activated without interruption for a duration longer than Δt 13  =t 3  -t 1 , that is, so long as t 2  -t 1  &lt;t 3  -t 1 . If the high-frequency generators are activated for longer than t 13 , u 2  appears and immediately switches on the acoustic signal device 14. 
     IC 5  and IC 6  in the delay circuit 15, each being shown in FIG. 2 as a NAND gate, are connected together to form an RS flipflop, of which the output voltage u 3  is set at zero or &#34;low&#34; when the supply voltage U 3  and the supply voltage U 4  are turned on. 
     If and when the voltage u 2  appears at the input of the delay circuit 15, it is supplied to the input of an inverter IC 4  over an adjustable resistance R 6  where it becomes effective subject to the time constant of the combination of the resistor R 6  and a capacitor C 6  to produce a delay of Δt 15  =t 4  -t 3 . A diode D 7  is provided for discharging by H capacitor C 6  practically without delay by H resistance R 11  as soon as the voltage u 2  drops to zero. A diode D 8  is provided to limit negative input voltages for IC 4 . The output voltage u 8  of IC 4  is differentiated by a capacitor C 8  and the differentiated pulse u 9  =f(t) is applied to the input of IC 6 , as the result of which the RS flipflop consisting of IC 5  and IC 6  switches over and delivers the voltage u 3  at the output of the flipflop. The voltage u 3  switches off the supply current U 1  for the high-frequency generator 1 and U 2  for the high-frequency generator 6 by means of the relay 16 and 17 (in FIG. 1) practically without delay. The voltage u 3  is maintained until the RS flipflop is reset by a brief interruption of the supply voltage U 3 , for example by briefly switching off the energizing AC supply line by the power switch 23 (FIG. 1) of the apparatus and then right away switching it on again, or by brief depression of a reset button or key 22. 
     A diode D 11  limits inverse input voltages at IC 5 . C 7  and R 7  delay the input voltage for IC 5  when the high-frequency surgery apparatus is turned on, so that the RS flipflop is definitely set. C 7  is quickly discharged over D 10  and R 8  when the operating voltage U 3  is interrupted. 
     Although the invention has been described with reference to a particular illustrative example, it will be understood that modifications and variations are possible within the inventive concept.