DE102016009486B4 - Blower filter system and header monitor unit in such a blower filter system - Google Patents

Abstract

The invention is a blower filter system and a head piece monitoring unit (26) in such a blower filter system, the blower filter system comprising a head piece (10) and a blower filter device feeding the head piece (10) via a hose (16), with a differential pressure sensor assigned to the head piece (10) (22) to determine measured values for a differential pressure between an interior of the head piece (10) and the environment and a display element (24) in the head piece (10) that can be activated when there is a negative pressure in the interior of the head piece (10).

Description

The invention relates to a blower filter system with a blower filter device with a helmet or a hood, in particular according to DIN EN 12941 or with a blower filter device with a full mask, half mask or valve mask in particular after DIN EN 12942 . Helmet, hood, full face mask, half mask, valve mask and the like are collectively referred to below as the head piece of such a blower filter system. The invention also relates to a monitor unit in a head piece (head piece monitor unit) of such a blower filter system.

Blower filter systems of the type mentioned above are used for light and medium respiratory protection and support the user of respiratory protection filters by reducing the breathing resistance in contrast to conventional gas masks and thus making long and fatigue-free use possible. The main components of a blower filter system include, on the one hand, the blower filter device, which is usually worn on a belt, and, on the other hand, the head piece, which is designed, for example, as a hood or mask and sometimes also functions as head protection. These two components are usually connected to one another via a hose. Contaminated ambient air is sucked in through a filter by means of the blower filter device and thereby freed from harmful substances and then passed through the hose to the head piece and thus fed to the respirator.

In addition to the main function of air transport, the blower filter device also uses visual or acoustic signals to inform the wearer of the current operating status and any errors. The safe functioning of the blower filter system is of vital importance for the respirator. Therefore, the information about a malfunction of the blower filter device must reach the respirator safely. However, it has been found that, depending on the conditions of use, the respiratory protection wearer is often barely able to perceive visual signals from the blower filter system when worn on the back or acoustic signals in situations with a high level of noise pollution.

There is consequently the need to inform the respirator wearer, who is sometimes only referred to briefly below as the user, about the function of the blower filter system, in particular of the blower filter device it comprises.

A suitable alarm and information system is provided for this, which is connected to a blower filter device by cable or wirelessly. With this, status information of the blower filter device and any alarms can also be displayed in the head piece. This ensures that the respirator is informed about the vital condition of the blower filter device.

From the DE 101 47 045 A1 a data communication system for a protective headgear in the form of a mask or a helmet is known. The head protection there has a data display in which, depending on commands transmitted by voice input from the wearer of the respective head protection, measurement data from individual measuring devices are displayed on the data display.

The DE 20 2010 012 023 U1 In contrast, it does not aim to provide information to the respective emergency services, but rather to inform operations management personnel. There, an occupational health and safety system is described in which a body function sensor arrangement detects at least one monitoring variable related to a body function of a respective emergency worker and transmits it to a remote control device so that emergency control personnel can monitor the emergency worker. The body function sensor arrangement should be able to detect different body functions with a plurality of body function sensors. In this respect, a pulse detection, a body temperature detection, a respiration detection, a blood oxygen detection, a blood pressure detection and an arrangement for detecting a cardiac activity of the emergency worker are mentioned. Also addressed is an embodiment in which the work protection system comprises a breathing gas arrangement which supplies the emergency worker with inhaled gas and discharges exhaled gas, and also uses a respiration recording arrangement to record information about the respiratory tract of the emergency worker. With regard to the information recorded there, the breathing frequency, a tidal volume, a breathing gas consumption per unit of time and an exhaled gas composition are mentioned.

In the US 2005/022 817 A1 an approach is described in which, in a respiratory protective device, a switchover between a filter mode in which the ambient air is filtered and made available as breathing air and no air is taken from compressed air cylinders, and compressed air mode, in which the breathing air is taken from the compressed air cylinders should be possible. In this way, the possible duration of use for fire-fighting personnel, for example, should be able to be increased because breathing air is not taken from the compressed air cylinders carried along during the entire period of use.

The mere consideration of the pressure conditions inside a protective helmet is known in itself. For example, describes the U.S. 5,035,239 A the monitoring of the pressure inside a face mask using a differential pressure sensor. If the internal mask pressure falls below a predetermined threshold value, a display element is activated, which then emits a warning tone. When evaluating the differential pressure measured values, this disregards the problem that only interference-free components of the pressure signal can be meaningfully used for an evaluation and a reliable detection of a negative pressure situation is therefore not guaranteed.

From the US 2010/0 083 967 A1 an approach is known in which an overpressure in a face mask is also to be ensured as a function of the breathing activity of the respiratory protection wearer. To do this, the position of an exhalation valve is monitored and, if necessary, a warning lamp is activated. The advantage of the present invention over this prior art is that the monitoring can take place independently of a detection of valve positions, for example a valve position of an exhalation valve, and accordingly a corresponding sensor system and signal lines are not required.

Approaches to the computational determination of the beginning of an inhalation and an end of an exhalation are from the WO 2013/082 649 A1 known.

From the EP 0 241 188 A1 a blower filter device with a head piece is known. A differential pressure sensor for determining a differential pressure between an interior of the headpiece and the surroundings is assigned to the head piece. A negative pressure detected by means of the differential pressure sensor in the interior of the head piece is signaled to the user in an acoustic manner by a display element as an audible hissing sound. In addition, the measured pressure values recorded by the differential pressure sensor serve as the basis for a controlled supply of air from an air supply. The air supply is designed, for example, as a compressed gas or compressed air cylinder.

From the US 2003/0 062 046 A1 an arrangement of a physiological sensor, for example designed as a CO ₂ sensor, in the exhalation line of a breathing apparatus operated with compressed air is known. This sensor is used to measure the amount of exhaled carbon dioxide. The measured values can be presented to the user for information by means of a display unit arranged in the mask.

The invention is thus based on the problem of informing the respirator wearer even better and more directly about possible faults in the blower filter system.

The invention solves this problem with a blower filter system having the features of claim 1.

For this purpose, in a blower filter system of the type mentioned, which comprises a head piece for supplying a respirator wearer with breathing air and a blower filter device that feeds the head piece via a hose, a differential pressure sensor assigned to the head piece for determining measured values for a differential pressure between an interior of the head piece ( Breathing space) and the environment, a display element in the headpiece that can be activated when there is a negative pressure in the interior of the headpiece, as well as a unit with a logic and decision-making logic as well as means for respiratory phase detection and means for respiratory frequency range monitoring in a signal path from the differential pressure sensor to the display element.

The unit with the linking and decision logic ensures, by means of the means for respiratory phase recognition and respiratory frequency range monitoring, that only interference-free pressure signals are evaluated and that interfered signals are discarded.

The device (s) for monitoring the respiratory frequency range is or are briefly referred to below as respiratory frequency range monitoring and the function carried out is also referred to as respiratory frequency range monitoring. The respiratory frequency range monitoring checks the signals of the differential pressure sensor for a physiologically meaningful frequency range. At rest, this frequency range extends from around 12 to 32 breaths per minute with high physical exertion. If this range is left, it can be assumed that the pressure signal is disturbed and the signal is classified as disturbed. In addition, the breathing rate does not change suddenly or erratically. If the breathing rate changes by more than 25% between two breathing phases, an overlay with an interference signal can also be assumed.

The device (s) for respiratory phase detection is or are briefly referred to below as respiratory phase detector and the function performed as respiratory phase detection and the respiratory phase detector, for example, only evaluates signals that have been assessed as physiologically meaningful by respiratory rate range monitoring. As a result, the breathing phase detector is able to robustly detect the breathing phases of the respirator wearer from the measured values from the differential pressure sensor, ie phases of the To distinguish inhalation (inspiration) from phases of exhalation (expiration). A reverse sequence is also conceivable, in such a way that the respiratory phase detector uses the measured values from the differential pressure sensor to detect inhalation pauses of a user of the blower filter system, i.e. times of maximum inhalation, and then, by means of the respiratory rate range monitoring, a plausibility of a recognized inhalation pause is determined on the basis of anatomically possible occurrence probabilities. The following description is continued on this basis - but without renouncing any further general applicability. Both of the sequences outlined above are always to be read along with this and are to be regarded as being included in the description provided.

The combination and decision logic evaluates the results of the respiratory phase detection and the respiratory frequency range monitoring in such a way that only interference-free parts of the pressure signal are used for further evaluation and processing and thus, when a negative pressure is repeatedly reached, a signal is generated by means of the display element, which then the respiratory protection wearer or a person charged with monitoring the negative pressure situation warns of an unsafe state of respiratory protection.

A head piece with a mask that fits tightly is also advantageous for the detection of negative pressure situations proposed here, in particular during special breathing phases, in particular breathing pauses. In the case of head pieces without a seal on the face (similar to those of protective visors for welders or painters), where the supply air supplied by the blower only flows down from above - mostly from the forehead area - actual air movements often cause disturbances in the pressure signals. Such air movements result, for example, from head movements, cross winds or the like. Such disturbances can make breathing phase detection more difficult.

The use of a differential pressure sensor assigned to the head piece takes into account the knowledge that it is crucial for respiratory protection to exclude negative pressure in the head piece during the inhalation phase. Only then can it be assumed that the inhaled air comes exclusively from the air supply through the blower filter device and has not penetrated into the interior of the headpiece from the possibly contaminated environment and via possible leaks in the headpiece.

Current blower filter systems ensure through a significant excess of air in the interior of the head piece that the inhaled air comes exclusively from the air supply through the blower filter device. Excess air flows continuously through the exhalation valve into the environment. In addition, the supplied air is used to flush the exhaled air enriched with carbon dioxide (CO ₂ ) from the headpiece. However, a particular enrichment of the exhaled air with carbon dioxide only becomes apparent when the person wearing the respirator begins to tire or hypoxia occurs.

A negative pressure situation can arise due to leakages, which in turn can result from the wearing situation of the head piece or possible damage to the head piece.

The differential pressure sensor assigned to the headpiece enables negative pressure situations in the headpiece to be recognized and, based on this, information can be provided to the respiratory protection wearer with a corresponding activation of the display element also provided in the headpiece. The differential pressure sensor measures the differential pressure between the interior of the head piece and the environment and outputs a corresponding measured value. The display element is then activated on the basis of the respective measured value or a processed form of the measured value. In any case, in the case of a blower filter system that includes a differential pressure sensor assigned to the head piece, the respirator wearer can be informed immediately of a possible negative pressure situation in the head piece by a display element controlled on the basis of the measured value supplied by the differential pressure sensor.

A special feature of the blower filter system proposed here is that the measured values from the differential pressure sensor are evaluated in relation to a possible negative pressure situation during the inhalation pauses (times of maximum inhalation) of the respirator wearer, i.e. the user of the blower filter system. For this purpose, the blower filter system comprises, as a means for breathing phase recognition, a breathing phase detector for recognizing pauses in breathing of the respirator wearer. Because the pressure conditions in the interior of the headpiece inevitably change when the person wearing the respirator inhales and exhales, the pressure conditions during the breathing pauses and especially during the inhalation pauses are particularly characteristic for a detection of a possible negative pressure situation. The blower filter system therefore delivers particularly reliable results when signaling a negative pressure situation due to the detection of breathing phases and due to an evaluation of the measured values of the differential pressure sensor precisely during an inhalation pause that is automatically recognized and avoids disruptive and above all unsettling false alarms for the respirator.

An analysis of the differential pressure signal is carried out by means of the breathing phase detector to detect a pause in inhalation. From a recognized inhalation pause, i.e. a recognized phase of maximum inhalation (local minimum in the differential pressure signal), a time value is obtained in relation to the differential pressure signal. With such a time value, the differential pressure signal can be checked at a point determined by the time value with regard to the presence of a possible negative pressure situation, for example by comparing the amplitude of the differential pressure signal at the respective time value with a predefined or predefinable threshold value and, if the value falls below the threshold value, to the actual presence of a negative pressure situation is concluded. A signal for controlling the respective display element or a plurality of display elements is then generated.

Another special feature of the fan filter system proposed here is that it includes a device or software functionality or a combination of software functionality with associated device elements (µP, µC, PLC) in the signal path from the differential pressure sensor to the display element. This is determined for the plausibility check of a recognized breathing pause on the basis of anatomically possible occurrence probabilities of inhalation and / or exhalation pauses. The inhalation pauses result, for example, as the locations of the minima between two adjacent zero crossings in the differential pressure signal. For the plausibility check, it can be taken into account whether the determined location of the breathing pause is sufficiently in the middle between the two zero crossings. If this is not the case, it is more likely to be assumed that the differential pressure signal is partially incorrect or that, for example, only a local extreme value was recognized. An alternative or additional possibility for a plausibility check is to take into account a duration during which the differential pressure signal remains at the level of the determined extreme value, with a duration that is too short, i.e. a duration below a specified or specifiable time limit value, due to an incorrect evaluation or suggests that the differential pressure signal is incorrect. Other statistical or other criteria are also conceivable, for example a sufficient steepness of the profile of the differential pressure signal before the extreme value determined as the inhalation pause, etc. By using such a breathing frequency range monitoring, it is possible to further reduce incorrect evaluations.

Finally, a special feature of the blower filter system is that it includes the logic and decision-making logic in the signal path from the differential pressure sensor to the or each display element. This is intended on the one hand to link a recognized breathing pause of the respirator wearer with a measured value obtained from the differential pressure sensor and on the other hand to decide whether a negative pressure situation is present in the head piece on the basis of the measured value. The recognized inhalation pause of the respiratory protection wearer, that is to say a recognized phase of maximum inhalation, specifies a point in time relevant for the evaluation of the differential pressure signal. The value of the differential pressure signal at this point in time is evaluated in order to make a decision with regard to the presence of a negative pressure situation in the head piece. A negative pressure situation is present when the associated differential pressure value determined is below a predetermined or predeterminable threshold value. Optionally, it can be provided that a decision is made as to the existence of a negative pressure situation only if the determined differential pressure value is below the predetermined or specifiable threshold value for at least a specified or specifiable period of time. Taking into account the duration of the undershooting of the threshold value and without taking into account such a duration, this can optionally be expanded to the extent that a decision is made as to the existence of a negative pressure situation only if the undershooting of the threshold value occurs during a predetermined or predeterminable plurality of recognized inhalation pauses, for example during four , five or eight consecutive inhalation pauses. This is effective for further reducing possible incorrect evaluations. If, by means of the unit with linking and decision-making logic, a negative pressure situation is detected during an inhalation pause that is recognized as plausible, the unit with linking and decision-making logic generates the alarm signal for controlling the display element.

An optical and / or an acoustic display element can be considered as the display element. In the case of an optical display element, this can, for example, trigger different optical stimuli (color, brightness, flashing interval, etc.). The same applies in principle to an acoustic display element and the acoustic stimuli that can be triggered with it (pitch, volume, tone sequence, etc.). Depending on the measured value supplied by the differential pressure sensor, specific control of the display element can take place, which informs the respiratory protection wearer about the extent of the negative pressure situation recognized and, for example, in the case of only a slight negative pressure situation, to control the display element to emit an optical signal with a first color and in a serious negative pressure situation leads to a control of the display element to output an optical signal with a second color. The specific response to the degree of each The detected negative pressure can also be made more finely granular, so that, for example, with increasing severity of the detected negative pressure situation, a combination of different optical stimuli is displayed by the display element (for example color and brightness or color and blinking). Furthermore, the color and the flashing frequency can then also change with the severity of the detected negative pressure situation, so that the respiratory protection wearer is very precisely oriented about the function and possibly a residual function of the blower filter system.

The optical signals described are only examples and acoustic signals or a combination of optical and acoustic signals and a combination of corresponding display elements can also be considered. Additionally or alternatively, a display of a possible negative pressure situation by means of tactilely perceptible signals can also be considered. The activatable display element then leads, for example, to a vibration of the head piece or of a part of the head piece, which is easily perceptible to the respiratory protection wearer. Here, too, it is possible to adapt the display to the severity of the respective negative pressure situation, in that a frequency and / or an amplitude or a frequency sequence of the vibration is or is adapted to the severity of the negative pressure situation.

Advantageous embodiments of the invention are the subject of the subclaims. References used here indicate the further development of the subject matter of the main claim through the features of the respective subclaim. They are not to be understood as a waiver of the achievement of an independent, objective protection for the combinations of features of the related dependent claims. Furthermore, with regard to an interpretation of the claims in a more detailed specification of a feature in a subordinate claim, it can be assumed that such a restriction does not exist in the respective preceding claims.

In one embodiment of the blower filter system, the head piece is a mask, in particular a mask that fits tightly on the face of a user / respirator wearer, for use in environments with concentrations of gases (chemical, biochemical, biological, smoke gases) or vapors ( Propellants, aerosols, solvents) and the like. Such a mask has a mostly passive exhalation valve, in particular in one embodiment as a non-return valve, through which the user exhales used exhaled air to the environment.

In one embodiment of the blower filter system, a low-pass filter is provided in a signal path from the differential pressure sensor to the display element. In this way, irrelevant aspects of the differential pressure signal, that is to say of a time profile of the measured values supplied by the differential pressure sensor, can be masked out. This is particularly relevant for a possible digital processing of the differential pressure signal, because then the necessary sampling rate can be reduced and this is accompanied by a reduction in the computing power required for processing the differential pressure signal. Such irrelevant aspects of the differential pressure signal are referred to below as transient movement artifacts and result, for example, from movements or actions of the respiratory protection wearer and associated pressure changes.

To analyze the differential pressure signal to detect pauses in breathing by the user, it is provided that the breathing phase detector can be used to determine a minimum between two adjacent zero crossings in the differential pressure signal, i.e. in a measured value curve obtainable from the differential pressure sensor. A breathing phase detector can in particular be implemented as part of a software functionality for processing the differential pressure signal. The device processes a digitized form of the differential pressure signal and is able, for example, to recognize individual zero crossings based on a change in sign of adjacent measured values within the differential pressure signal. Between two adjacent zero crossings, the minimum of the measured values included between the zero crossings is then determined in a manner known per se and as soon as the lowest measured value representing the minimum has been determined within this section of the differential pressure signal, a time value describing an inhalation pause of the respiratory protection wearer is therefore in relation to the differential pressure signal in front.

The consideration of the minima and not also the maxima has the advantage that only inhalation pauses are recognized as breathing pauses, because at the end of the inhalation the relatively lowest pressure in the interior of the head piece can be expected and the corresponding negative pressure situations are then particularly easy to recognize.

If a signal that can be generated to activate a display element or several display elements in the headpiece when a negative pressure situation is detected can also be transmitted to the blower filter device, the negative pressure situation can also be signaled there, for example, optically and / or acoustically, so that, for example, other emergency services can assist the respiratory protection wearer can come.

If a carbon dioxide sensor is provided in the head piece and the blower filter system, in particular an evaluation unit in the head piece of the blower filter system, comprises means for activating a display element in the head piece as a function of a measured value obtainable from the carbon dioxide sensor, the respirator can also easily perceive a critical carbon dioxide concentration be brought to the attention.

A display device functioning as a headpiece monitor unit comes into consideration as a location for attaching the or each display element in the head piece of the blower filter system. A combined attachment of a possible plurality of display elements has the advantage that these are usually perceived simultaneously by the respiratory protection wearer if the display device is attached in a suitable location. Such a combined attachment also has the advantage that a state of the display device can easily be monitored and a separate display element can be provided for visualizing this state. In the case of purely optical display elements, the respiratory protection wearer would, for example, be signaled by a green display element that the display device is in the correct state. In the event of a fault, at least one further display element signals a negative pressure situation. On the basis of the green illuminated display element, the respirator recognizes that the absence of an optical signal from the at least one other display element cannot result from failure of the display element or the display device and that the blower filter system is accordingly working properly. The display device can also be used to display alarms from the blower filter device.

The above problem is also solved with a method for operating the blower filter system as described here and in the following. The differential pressure sensor is used to determine measured values for a differential pressure between the interior of the headpiece and the environment, and if there is a vacuum in the interior of the headpiece, the display element in the headpiece or one of the display elements in the headpiece is activated in order to make the respirator aware of the vacuum situation .

A special feature of the method is that pauses in breathing of the respiratory protection wearer are determined, with a test for a possible negative pressure in the headpiece taking place during such pauses in breathing. The determination of the breathing pauses allows the check for a possible negative pressure at particularly suitable times and thus helps to avoid incorrect evaluations. A particularly efficient possibility for determining breathing pauses is that a minimum between two adjacent zero crossings is determined in a measured value curve (differential pressure signal) obtainable from the differential pressure sensor.

Another special feature of the method is that a recognized negative pressure situation or a recognized breathing pause is checked for plausibility by means of the respiratory frequency range monitoring on the basis of anatomically possible occurrence probabilities. In this way, the risk of incorrect evaluations can be reduced even further. Suitable criteria that describe the plausibility of a breathing pause can be particularly easily coded in software, for example a check as to whether a point in time determined as a breathing pause is sufficiently in the middle between two adjacent zero crossings, and so on. The respiratory rate range monitoring is implemented, for example, in the form of software with programmed step and branch sequences.

Finally, a special feature of the method is that the combination and decision logic is used to link a plausible inhalation pause of the respirator wearer - a detected phase of maximum inhalation - with a measured value obtained from the differential pressure sensor. The time of the inhalation pause specifies the measured value to be observed or the value of the differential pressure signal to be observed. To make a decision with regard to the presence of a negative pressure situation in the head piece, this is compared with a threshold value. If the threshold value is not reached, a negative pressure situation is recognized. The duration of a shortfall can also be taken into account, so that the shortfall must exist at least for a predetermined period of time in order to avoid short-term pressure changes being unnecessarily signaled as potentially dangerous negative pressure situations. In addition, a certain number of successive inhalation pauses with falling below a threshold value can be used as a criterion for the detection of potentially dangerous negative pressure situations. This is particularly useful for suppressing false positives.

Embodiments of the method are characterized in that the measured values obtainable from the differential pressure sensor are digitized and a resulting differential pressure signal is filtered with a low-pass filter. The low-pass filtering is effective, for example, to eliminate or at least reduce transient movement artifacts.

An exemplary embodiment of the invention is described in greater detail below with reference to the drawings explained. Objects or elements that correspond to one another are provided with the same reference symbols in all figures.

The or each embodiment is not to be understood as a limitation of the invention. Rather, changes and modifications are possible within the scope of the present disclosure, in particular those variants and combinations which, for example, by combining or modifying individual features or features described in the general or special part of the description and contained in the claims and / or the drawing. Elements or process steps can be inferred by the person skilled in the art with a view to solving the problem on which this invention is based and, through combinable features, lead to a new object or to new process steps or process step sequences, also insofar as they relate to testing and working processes.

• 1 einen Atemschutzträger mit einem Gebläsefiltersystem,
• 2 eine Atemschutzmaske als mögliches Kopfstück eines Gebläsefiltersystems und in dem Kopfstück angebrachte Anzeigeelemente zur Information des Atemschutzträgers sowie
• 3 ein Blockschaltbild eines Verfahrens zum Betrieb eines Gebläsefiltersystems und zur Auswertung eines Differenzdrucksignals sowie zur Generierung von Statusinformationen.

Show it:

• 1 a respirator with a blower filter system,
• 2 a respirator mask as a possible head piece of a blower filter system and display elements attached in the head piece to inform the respirator wearer and
• 3 a block diagram of a method for operating a blower filter system and for evaluating a differential pressure signal and for generating status information.

1 shows a user wearing protective headgear in the form of a respiratory protection hood. This acts as a head piece 10 a blower filter system 12th , to the one next to the head piece 10 another blower filter device 14th and a blower filter device 14th and the headpiece 10 connecting hose 16 belong. On the blower filter device 14th is a filter 18th attached to the sucked in and over the hose 16 to the head piece 10 Guided breathing air filters. The blower filter device 14th is by means of a shoulder strap 20th carried.

2 Figure 11 shows an alternate embodiment of one having a blower filter system 12th ( 1 ) usable head piece 10 in the form of a respirator. The blower filter device 14th ( 1 ) is not shown. The one for the head piece is also shown 10 leading hose 16 . As part of the head piece 10 is a differential pressure sensor 22nd shown. Depending on the differential pressure sensor 22nd At least one display element is activated when the measured values delivered are supplied 24 inside the head piece 10 , so that the user through the status of one or more display elements 24 (on, off, color change, flashing etc.) about the status of the blower filter system 12th is informed. A configuration is shown in which several display elements 24 in one in the head piece 10 and there in the field of vision of the user attached headpiece monitor unit 26th are summarized.

The differential pressure sensor 22nd measures the differential pressure between the interior of the head piece 10 and the environment. This can lead to dangerous phases in which there is negative pressure in the head piece 10 prevails, to be recognized. The differential pressure sensor 22nd is in one of the blower filter device 14th Integrated remote alarm and information system that connects to the blower filter device by cable or radio 14th connected is. In the case of a radio link, the alarm and information system also includes a voltage source in the form of a battery or the like. Otherwise the voltage supply can be via the blower filter device 14th respectively. A processing functionality in the form of or in the manner of a microprocessor or the like for processing the measured values of the differential pressure sensor 22nd and to control one or more display elements 24 depending on the differential pressure sensor 22nd The measured values obtained can either be this alarm and information system or the blower filter device 14th be assigned.

3 shows a block diagram of a method for evaluating the differential pressure sensor 22nd obtained measured values. The method is implemented in software, for example, so that the representation also shows a corresponding evaluation algorithm in a schematically simplified form. In principle, implementation in hardware or partly in hardware and partly in software is also possible. The function blocks shown represent appropriate hardware units for such a situation.

The block diagram in 3 includes a low pass filter 30th , a band pass filter 32 , one as a breathing phase detector 34 functioning functional unit for respiratory phase recognition (medium 34 for respiratory phase detection), a functional unit for respiratory rate range monitoring (means 36 for respiratory rate range monitoring; Respiratory rate range monitoring 36 ) and a linkage and decision logic 38 . The entirety of the in 3 Functional units shown, but at least the logic and decision-making logic 38 together with the breathing phase detector 34 and respiratory rate range monitoring 36 , are as a unit with linkage and decision logic 38 designated. This is preferably designed as a programmable controller (processor, µC, µP, DSP, PLC) or as another programmable component with an associated memory (RAM, ROM). The means 34 , 36 for respiratory phase detection and respiratory rate range monitoring and possibly also the band pass filter 32 are preferably in or on the unit with linkage and decision logic 38 arranged or as software functionalities with the unit with linkage and decision logic 38 combined.

The low-pass filter on the input side 30th is used as a differential pressure signal 40 a sequence of measured values (p (t)) of the differential pressure sensor 22nd fed. One of the unity with linkage and decision logic 38 generated alarm signal 42 is used directly or indirectly to control one or more display elements 24 used. The alarm signal 42 can be a digital alarm signal 42 and indicates a possibly existing negative pressure situation by its level. The alarm signal 42 however, it can also be an analog alarm signal 42 be, the respective amplitude of which encodes a severity of a possibly existing negative pressure situation. Furthermore, the alarm signal 42 can also be output in the form of a plurality of digital signals, the severity of a possibly present negative pressure situation being coded by a number of the respectively activated digital signals. The block diagram in 3 shows a possible signal path from the differential pressure signal 40 to the alarm signal 42 because the alarm signal 42 is based on the differential pressure signal 40 . One way of generating an alarm signal 42 based on the differential pressure signal 40 is described below.

The low-pass filter on the input side 30th first effects a filtering of the differential pressure signal 40 and eliminates disturbances and details of the differential pressure signal that are irrelevant for the subsequent evaluation 40 . The low pass filter 30th can be an analog low-pass filter 30th or a digital low pass filter 30th be. With a digital low-pass filter 30th there is an analog / digital conversion of the differential pressure signal on the input side, not shown here but known per se 40 . With an analog low-pass filter 30th can in the further course of the signal processing, for example before the breathing phase detector 34 , such an analog / digital conversion (also not shown) happen.

The cutoff frequency of the low pass filter 30th is above, in particular just above, the usual breathing frequencies of a user of the blower filter system 12th and also breathing frequencies such as those that arise in operational situations, i.e. under physical strain. Empirical values are available for such respiratory frequencies, so that the setting of the cut-off frequency of the low-pass filter 30th is easily possible. The low-pass filtering eliminates influences on the differential pressure signal 40 that do not affect the function of the blower filter system 12th or the breathing of the respirator. These are, for example, effects that arise when the respirator wearer moves and the head piece moves as a result 10 on the head of the respirator. These effects are therefore referred to here and in the following as transient movement artifacts and the otherwise optional low-pass filter 30th is effective for preventing such movement artifacts in the differential pressure signal 40 to eliminate or at least reduce.

The low-pass filtering also brings about, in a manner known per se, a restriction of the filtered differential pressure signal on the output side 40 to comparatively low frequencies, so that a sampling rate can be minimized. On the one hand, this reduces the storage space required for the further processing of the differential pressure signal 40 and also the computing power required for this.

Because in the differential pressure signal 40 furthermore with the breathing phase detector 34 Breathing pauses are determined, namely extreme values in the differential pressure signal 40 are sought that indicate such breathing pauses in the form of inhalation and exhalation pauses, comes on the input side of the breathing phase detector 34 a fundamentally optional bandpass filtering of the differential pressure signal 40 with the band pass filter 32 into consideration. The band pass filter 32 eliminated in the differential pressure signal 40 now also low frequencies that are below the breathing frequencies normally expected by the respirator.

The respiratory phase detector 34 supplied, filtered form of the differential pressure signal 40 is shown in 3 inside of the breathing phase detector 34 symbolizing function blocks shown in idealized form as a sinusoidal signal. The falling edges of such a signal correspond to the inhalation process of the respirator. The lower peaks of the signal correspond to an inhalation pause during the breathing process of the respirator. This moment represents the moment of the strongest inhalation by the respirator and is also referred to below as maximum inhalation. An area around the lower apex represents a phase of maximum inhalation. The rising flanks correspond to an exhalation process and the upper apexes of the signal result from an exhalation pause of the respirator before a subsequent inhalation process.

The breathing phase detector 34 detects adjacent zero crossings in the signal fed to it and then the minimum between each two adjacent zero crossings. The location of a minimum determined in this way corresponds to the time of maximum inhalation. In the representation in 3 is inside the the breathing phase detector 34 symbolizing function block denotes such a recognized minimum with an upward pointing arrow.

The or each minimum determined in this way is a candidate for periods of least pressure in the head piece 10 . Using the respiratory rate range monitoring 36 the points in time correlated with the minima are checked for plausibility by comparing them with anatomically possible probabilities of occurrence. Once the most plausible minimum candidates have been determined, the linking and decision logic 38 the differential pressure values for these times are determined and a decision is made as to whether and for how long a negative pressure in the head piece 10 prevailed. Depending on this, the alarm signal 42 generated.

A blower filter system 12th of the type described here protects the respirator from contaminated ambient air by removing the interior of the headpiece 10 (Breathing space) is kept at least slightly overpressure and negative pressure is avoided in any case. In addition, however, the exhaled carbon dioxide must also be evacuated from the breathing space so that the person wearing the respirator does not inhale it again if possible. Such an evacuation of the exhaled carbon dioxide is called a flushing of the breathing space. In general, there is no direct connection between the pressure in the breathing space and the freedom of the inhaled air from carbon dioxide. Rather, the flushing depends on the flow guidance. However, some of the exhaled air generally remains in the headpiece 10 . In addition to the differential pressure sensor 22nd ( 2 ) a carbon dioxide sensor (CO ₂ sensor; not shown) can be installed in the head piece as a further part of the alarm and information system 10 to get integrated. The carbon dioxide sensor can continuously monitor the carbon dioxide concentration in the head piece 10 Existing breathing air checked and if a limit value is exceeded by activating a display element 24 ( 2 ) an alarm can be generated. To do this, the carbon dioxide sensor must be close to the mouth and nose area of the headpiece 10 be placed and be able to detect changes in concentration sufficiently quickly. It is also possible to control the concentration of harmful gases such as hydrogen sulfide (H ₂ S) or the like, despite the overpressure and the flushing of the head piece 10 get into its interior, to be determined by suitable sensors and also to generate an alarm if limit values are exceeded.

List of reference symbols

10

Headjoint

12

Blower filter system

14th

Blower filter device

16

tube

18th

filter

20th

Carrying strap

22nd

Differential pressure sensor

24

Display element

26th

Headpiece monitor unit

28

---

30th

Low pass filter

32

Band pass filter

34

Means for respiratory phase detection, respiratory phase detector

36

Means for breathing rate range monitoring, breathing rate range monitoring

38

Linkage and decision logic

40

Differential pressure signal

42

Alarm signal

Claims (11)

Blower filter system (12) with a head piece (10) and a blower filter device (14) feeding the head piece (10) via a hose (16), with a differential pressure sensor (22) assigned to the head piece (10) for determining measured values for a differential pressure between a Interior of the head piece (10) and the surroundings and with a display element (24) in the head piece (10) that can be activated on the basis of an alarm signal (42) when there is a negative pressure in the interior of the head piece (10), characterized by a unit with a logic and decision-making logic ( 38) as well as with means (34) for respiratory phase detection and means (36) for respiratory frequency range monitoring in a signal path from the differential pressure sensor (22) to the display element (24), wherein the means (34) for respiratory phase detection based on the measured values from the differential pressure sensor (22) pauses inhalation Users of the blower filter system (12), that is to say times of maximum inhalation, are recognizable, with the means (36) for breathing frequencyb Area monitoring, a plausibility of a recognized inhalation pause can be determined on the basis of anatomically possible occurrence probabilities, with a measured value of the differential pressure sensor (22), which belongs to an inhalation pause of the user recognized as plausible, for the decision with regard to the presence by means of the linking and decision logic (38) a negative pressure situation in the head piece (10) can be evaluated and the alarm signal (42) can be generated in the event of a negative pressure situation being detected. Blower filter system (12) Claim 1 , with a low-pass filter (30) in the signal path from the differential pressure sensor (22) to the display element (24). Blower filter system (12) Claim 1 or 2 , with the means (34) for respiratory phase recognition for recognizing pauses in breathing by the user being able to determine a minimum between two adjacent zero crossings in a measured value curve obtainable from the differential pressure sensor (22). Blower filter system (12) according to one of the preceding claims, wherein by means of the combination and decision logic (38) for the detection of a negative pressure situation and the generation of the alarm signal (42) a duration of the stay of the measured value associated with an inhalation pause recognized as plausible can be evaluated below a threshold value . Blower filter system (12) according to one of the preceding claims, wherein by means of the linking and decision logic (38) during a predetermined or predeterminable plurality of recognized inhalation pauses of the user, a respective measured value from the differential pressure sensor (22) for the recognition of a negative pressure situation and the generation of the alarm signal ( 42) can be evaluated. Blower filter system (12) according to one of the preceding claims, wherein the alarm signal (42) that can be generated to activate the display element (24) can also be transmitted to the blower filter device (14). Blower filter system (12) according to one of the preceding claims, with a carbon dioxide sensor in the head piece (10) and means for activating a display element (24) in the head piece (10) as a function of a measured value obtainable from the carbon dioxide sensor. Blower filter system (12) according to one of the preceding claims, with a display device in the head piece (10) of the blower filter system (12) comprising the or each display element (24) and functioning as a head piece monitor unit (26). Method for operating a blower filter system (12) according to one of the preceding claims, wherein measured values for a differential pressure between the interior of the head piece (10) and the environment are determined by means of the differential pressure sensor (22), the display element (24) located in the headpiece (10) being activated in the event of a negative pressure in the interior of the head piece (10), with the means (34) for respiratory phase detection on the basis of the measured values from the differential pressure sensor (22) identifying pauses for inhalation of a user of the blower filter system (12), i.e. times of maximum inhalation, with the means (36) for monitoring the respiratory rate range, a plausibility of a recognized inhalation pause is determined on the basis of anatomically possible occurrence probabilities, whereby by means of the linking and decision logic (38) a measured value of the differential pressure sensor (22), which belongs to an inhalation pause of the user recognized as plausible, is evaluated for the decision with regard to the presence of a negative pressure situation in the head piece (10) and in the case of a detected negative pressure situation the alarm signal (42) is generated. Procedure according to Claim 9 to operate a blower filter system (12) Claim 2 , the measured values obtainable from the differential pressure sensor (22) being digitized and filtered with a low-pass filter (30). Procedure according to Claim 10 , the inhalation and exhalation pauses being determined by determining a minimum between two adjacent zero crossings in a measured value curve obtainable from the differential pressure sensor (22).

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