Alarm in a device for dispensing volatile anesthetics

An alarm is associated with a device for dispensing volatile anesthetics. The alarm and device is designed such that an alarm is triggered whenever the operating voltage is interrupted and an assembly unit that determines the dispensing of at least one anesthetic is not in a prescribed state of operation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 of German Application DE 10 2004 046 644.0 filed Sep. 25, 2004, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to an alarm in a device for dispensing volatile anesthetics, which triggers an alarm when the dispensing device is not ready for dispensing without the presence of an intended operating voltage, i.e., when there is a risk for dispensing an insufficient quantity.

BACKGROUND OF THE INVENTION

The present invention can be used in an alarm control for an apparatus for dispensing volatile anesthetics, also called vapors, which said apparatus is controlled by means of a handwheel where dispensing, which cannot be guaranteed as a consequence of the lack of operating voltage, must be prevented from being set with the handwheel when the apparatus is switched off or in case of failure of the operating voltage.

Electricity, which is taken from a supply network, is usually necessary for the operation of an anesthetic dispensing apparatus. The dispensing proper is carried out by means of a mechanically adjustable assembly unit with variable flow cross section. The dispensing operation is controlled, monitored and secured by various electronic assembly units during normal operation. Critical states of operation are avoided or displayed by software-assisted warnings or alarm reports. Some of the functions intended for this are dispensable when the apparatus is put out of operation.

However, if the apparatus is not ready to operate, for example, because of the energy supply being interrupted or switched off, the user must be alerted about this at least when there is a risk for no dispensing or dispensing of an insufficient quantity of anesthetics. This function must not depend on the supply of the operating voltage via the supply network or the functioning of the software.

In case of conventional anesthetic dispensers with handwheel, securing against the incorrect dispensing or dispensing of an insufficient quantity of anesthetics is achieved by the handwheel for setting the dispensing concentration being locked in the zero position when the operating voltage from the supply network fails. It is thus impossible to set a dispensing concentration with the energy supply switched off when the handwheel was in the zero position at the time of interruption of the operating voltage.

However, this locking only becomes active in the zero position of the handwheel. However, if the energy supply fails at another concentration setting, an acoustic alarm of a limited duration in time is triggered, but the concentration setting continues to be able to be changed. The locking of the handwheel is subject, moreover, to mechanical wear and may be damaged by forcibly rotating the locking handwheel.

SUMMARY OF THE INVENTION

The object of the present invention is to provide security, in case of interruption of the operating voltage of a device for dispensing liquid anesthetics, against incorrect dispensing or dispensing of an insufficient quantity of anesthetics from the dispensing device, which functions independently from the state of operation of the dispensing device at the time of the interruption of the operating voltage and is subject to slight wear at best.

According to the invention, an alarm in a device for dispensing volatile anesthetics is provided. The alarm is designed such that an alarm is triggered whenever the operating voltage is interrupted and an assembly unit, that determines the dispensing of at least one anesthetic, is not in a prescribed state of operation.

The present invention is based on the fact that, in addition to the software-driven alarm control in a dispensing device for volatile anesthetics, an additional possibility of triggering an alarm is provided, which triggers an alarm independently from the functioning of the software or the provision of the operating voltage via the supply network as soon as there is a risk for incorrect dispensing or dispensing of an insufficient quantity of anesthetics. This alarm triggering advantageously takes place via the same acoustic signal transmitter as a software-controlled alarm triggering during normal operation.

The present invention comprises an alarm in a device for dispensing volatile anesthetics, which is designed such that an alarm is triggered whenever the operating voltage is interrupted and an assembly unit that determines the dispensing of at least one anesthetic is not in a prescribed state of operation.

It can be used especially when an assembly unit that determines the dispensing of at least one anesthetic comprises a mechanism with variable flow cross section, whose flow cross section can be set by means of a handwheel. This is the case, for example, with vapors.

The present invention can also be used advantageously when an assembly unit that determines the dispensing of at least one anesthetic comprises an electronically driven valve assembly unit. In an advantageous embodiment, at least one electronically driven valve assembly unit may be combined with a mechanism with variable flow cross section, whose flow cross section can be set by means of a handwheel.

The prescribed state of operation, in which no alarm is triggered in case of interruption of the operating voltage from the supply network, may be the closed state of the mechanism with variable flow cross section, in which the handwheel is in a zero position.

As an alternative, the prescribed state of operation, in which no alarm is triggered in case of interruption of the operating voltage from the supply network, may be a state of the mechanism with variable flow cross section in which the flow cross section is below a threshold value.

The position of the handwheel can be evaluated as the indicator of the state of operation of the mechanical assembly unit in both cases. In case of failure of the operating voltage from the supply network, the energy for the alarm that may become necessary is taken from a buffer source, preferably a rechargeable battery.

This can be advantageously embodied when at least one switch is contained, which is actuated by the handwheel and is in the open state when the handwheel is in a position in which no alarm is to be triggered, and which is in the closed state when the handwheel is in a position in which an alarm is to be triggered, and which is integrated in a current path that connects the alarm-triggering component with the output voltage of a buffer source only when the operating voltage from the supply network is interrupted. Such a current path may lead, for example, via at least one semiconductor element that is not conductive when the operating voltage is present. The output voltage of the buffer source can be present at the alarm-triggering component only when the semiconductor component becomes conductive and when the switch at the handwheel is additionally closed. An alarm can thus be triggered independently from the software. Furthermore, it is advantageous if no current is taken from the buffer source when the anesthetic dispenser is switched off and the handwheel is in the zero position.

An additional locking may be dispensed with due to the software-independent alarm control, because the user is alerted by an acoustic alarm, whose duration in time is limited only by the capacity of the buffer source, when the handwheel is opened that the apparatus for dispensing anesthetics is not ready to operate. Moreover, the same behavior is always obtained regardless of the concentration that was set on the handwheel at the time of the interruption of the operating voltage from the supply network.

In case of failure of the energy supply during the dispensing, the user is prompted by the permanent alarm to turn the handwheel into the zero position, which is necessary for the proper restart of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, a printed circuit board1is arranged under the handwheel20for setting the dispensing concentration and carries two Reed switches S1and S2. These are opened below a minimum concentration setting and are otherwise closed. The minimum concentration setting may also be a possibly mechanically supported zero position22. The switching states are evaluated during normal operation by the software of a microcontroller2. A switching circuit or switch debouncer3(that monitors switches and provides a switch change-of-state output, simplifying microprocessor (μP) or the microcontroller2polling and interrupts, for example, a MAX6818 is provided for processing the signals. S1and S2are advantageously designed as a redundant pair of switches.

A rechargeable battery BT1is charged as needed during the normal operation by a charging circuit4. Furthermore, an acoustic signal transmitter LS1is present, which is controlled by the microcontroller2during the normal operation. The above-mentioned elements are connected with one another by a circuit5, which ensures that only output signals of the microcontroller2can lead to triggering of the acoustic signal transmitter LS1in the presence of the prescribed operating voltage from the supply network, whereas a closed switch S1always leads to the triggering of an alarm due to the triggering of the acoustic signal transmitter LS1in case of interruption of the operating voltage.

The mode of operation of the circuit in the presence and interruption of the operating voltage from the supply network will be explained below.

The operating voltage +5 VD from the supply network is present during normal operation. This is in a voltage range from +4.75 V to +5.5 V, and the microcontroller2is active. No software-independent alarm must be triggered on opening the handwheel. This is ensured as follows: Current is flowing into the resistor R3via the two diodes D4and D5. As a result, a voltage of about 3.6 V becomes established at the gate G6of the N-channel MOSFET Q6, and the drain-source section of Q6becomes conductive. As a result, a voltage of approx. 0 V becomes established at the gate G4of the N-channel MOSFET Q4, so that the drain-source section thereof is blocked.

The gates of the two MOSFETs Q2and Q3are maintained at a voltage of 0 V via the resistor R2with the handwheel switch S1opened, so that Q2and Q3are blocked as well.

If the handwheel switch S1closes, the voltage increases at the gates of Q2and Q3and both MOSFETs become conductive. Q3passes on the switching state of S1to the debouncer circuit3. No current can flow over the drain-source section of Q2, because Q4is blocked. Thus, no current is flowing over the resistor R1, either, the gate-source voltage of the P-channel MOSFET Q1is zero, and Q1is blocked.

To make it possible to transmit the switching state of S1to the debouncer circuit3, it is necessary for the signal HRS1B to carry a voltage that is sufficient for the energizing of Q3. This voltage is provided either from the rechargeable battery BT1via the diode D3or from the +5 VD operating voltage via D1.

The signal line LS+ always carries a voltage of about +4.3 V during normal operation. This is the positive supply voltage for the signal transmitter LS1. The microcontroller2controls the alarm via the digital signal, which is provided via D_Out and is present above the resistor R6at the gate of the N-channel MOSFET Q7.

If this signal has a high level, i.e., about +5 V, then Q7is conductive and Q5is blocked, because its gate G5is grounded. As a result, no current can flow through the signal transmitter LS1.

If D_Out carries a low level, i.e., about 0 V, then Q7is blocked and Q5is conductive. The signal transmitter LS1is energized and an acoustic alarm is triggered.

In the switched-off state or with the operating voltage from the supply network interrupted, the voltage on +5 VD is about 0 V. The microcontroller is not operating and the control output D_Out has high ohmic resistance. The gate of Q7is maintained at a low level in a defined manner via the resistor R6, so that Q7is blocked.

The HRS1B signal is set at a voltage of about 6 V via the diode D3, which approximately corresponds to the output voltage of the rechargeable battery BT1. At the same time, D1prevents current from being able to flow from the battery into +5 VD and to put the electronic control unit into operation.

The gate G6of Q6is maintained at 0 V in a defined manner via R3. Thus, Q6remains blocked and Q4is energized via R4. The gate of Q2(HRS1A signal) is maintained at 0 V in a defined manner via R2when the handwheel switch S1is opened, i.e., when the handwheel is in the zero position, so that Q2is blocked. Thus, no current is flowing over the resistor R1, the gate source voltage of Q1is zero, and Q1is blocked as well. The voltage on the signal LS+is approx. 0 V.

Since MOSFETs do not take up any control current in case of static triggering, no appreciable current is taken from the battery with the handwheel switch opened.

If the handwheel switch S1is closed, the voltage on the HRS1A signal increases to approx. 6 V. As a result, the two MOSFETs Q2and Q3are energized.

Due to its electric insulation between the gate and the drain-source section, Q3prevents current from being able to flow into the input of the debouncer circuit3.

Due to Q2being energized, current flows through R1, as a result of which a voltage drops over R1, and this voltage will now also cause the P-channel MOSFET Q1to become conductive. Its gate-source voltage is approx. −6 V in this state. Current flows via Q3and Q1from the rechargeable battery BT1to the signal transmitter LS1. The LS+signal now carries a voltage of approx. 6 V. Since Q7is blocked, Q5is energized via the resistor R5and current is sent to the signal transmitter LS1. Thus, an acoustic alarm is always triggered in the absence of an operating voltage from the supply network if the switch S1is closed. It can thus be guaranteed by a corresponding linking of the switch S1with the handwheel that the alarm will always be triggered when the handwheel is outside the zero position or outside a set range of positions.

FIG. 2shows an assembly unit18with an actuation element or handwheel20for changing a setting. The setting of the assembly unit18determines the dispensing of at least one anesthetic. According to the invention, the actuation element or handwheel20has a prescribed state of operation or operation position in which no alarm is triggered, which in the example is a zero position22. The assembly unit18, that determines the dispensing of at least one anesthetic, may comprise an electronically driven valve assembly unit24. Unit24may be a variable flow cross section portion, whose flow cross section can be set by means of the handwheel20. In this case the prescribed state of operation, in which no alarm is triggered in case of interruption of the operating voltage, is the closed state of the mechanism with variable cross section. In this case the handwheel20is in the zero position22. However, the prescribed state of operation, in which no alarm is triggered in case of interruption of the operating voltage, may be the state of the mechanism with variable flow cross section, in which the flow cross section is below a threshold value. The switches S1and S2are connected to the handwheel20as noted above. The switch (S1and/or S2) is actuated by the actuation element or handwheel20. The switch (S1and/or S2) is in an open state when the actuation element or handwheel20is in a position in which no alarm is to be triggered (zero position22or below the threshold), and the switch (S1and/or S2) is in a closed state when said actuation element or handwheel20is in a position in which an alarm is to be triggered.