DE102021001711A1 - protective mask - Google Patents

Abstract

1.1 The protective mask should reliably protect both the wearer and the environment from pollutants.1.2. The shape of the mask body 101 with the delimitation by the pressure difference-actuated valves 103, 104 and the design of the sealing lips significantly reduces the amount of CO2 that is inhaled again. The mask body 101 is made of elastic, gas-impermeable and largely transparent material. It connects to the nose and covers the mouth area up to the chin; a viewing window and a speech membrane 102 are optionally provided. The protective mask is equipped with one or two separate, replaceable filters 111, 112. The flow paths during inhalation and exhalation are completely separate. The inhalation filter can be slightly compressed by the negative pressure created when inhaling. The exhalation filter is designed in such a way that it can be slightly enlarged by the overpressure that occurs when exhaling (balloon effect). The filter materials do not have skin contact with the wearer.1.3 The mask can be configured either to protect the wearer, the environment or to protect the wearer and environment. This is helpful when used in clean rooms, dusty or aerosol-laden environments and to protect against pathogens.

Description

field of use

The invention relates to a protective mask according to the preamble of claim 1.

State of the art

• - Masken, die den Träger davor schützen, dass Verunreinigungen oder Krankheitserreger beim Atmen in seine Atemwege gelangen. Dieser Maskentyp wird oft als Atemschutzmaske bezeichnet
• - Masken, die andere Personen oder die Umgebung des Trägers vor Krankheitserregern oder Verunreinigungen schützt, welche der Maskenträger mit dem Atmen oder Sprechen ausscheidet. Dieser Maskentyp wird oft als Gesichtsmaske, chirurgische Maske oder Hygienemaske bezeichnet
• - Masken, die in beide Richtungen schützen und damit sowohl den Träger als auch die Umgebung schützen.

With protective masks, a distinction can be made between

• - Masks that protect the wearer from contaminants or pathogens entering their airways when they breathe. This type of mask is often referred to as a respirator
• - Masks that protect other people or the wearer's environment from pathogens or contamination that the mask wearer excretes through breathing or speaking. This type of mask is often referred to as a face mask, surgical mask or hygiene mask
• - Masks that protect in both directions, protecting both the wearer and the environment.

Respiratory protection masks usually have a shape that is intended to ensure a tight fit on the wearer's face. A distinction can be made between masks whose mask body consists primarily of porous filter material and those in which the mask body is gas-tight. The shape is designed in such a way that the mask body lies as close as possible to the face of the wearer due to the contact pressure of the harness. If necessary, supported by flexible sealing lips, which can adapt to the anatomy of the wearer. In addition to the mouth and nose, the protective mask sometimes also covers the eyes or is designed as a complete hood. In the case of masks with a gas-tight body, the filters are usually designed as cartridges and can be separated from the mask body. Solutions are known for both designs, which have been supplemented with an exhalation valve for easier exhalation and the associated lower physical stress on the wearer. This reduces the flow resistance for the exhaled air flow and thus increases the comfort for the wearer by reducing the physical strain.

A well-known example of a face mask to protect other people is the so-called surgical mask. This sits loosely in front of the wearer's mouth and nose. Due to the loose fit, such face masks are significantly more comfortable to wear than respirators. On both inhalation and exhalation, the loose fit allows for leakage at the edges of the mask. Loose-fitting masks usually do not have an exhalation valve, since the leakage keeps the flow resistance during exhalation low anyway.

Masks that protect in both directions are mostly tight-fitting masks that use the same filter for inhalation and exhalation. This very simple design has the disadvantage that some of the moisture in the exhaled air remains in the filter material and moistens it, which is disadvantageous both in terms of filtering capacity and wearing comfort. More complex versions are supplemented by an exhalation valve with a separate filter, shown for example in DE 699 21660 T2 (Japuntich et al)

Depending on the hazards (chemical substances, dust and particles, viruses and bacteria, etc.) against which the mask wearer is to be protected, different filter materials and combinations of filter materials are used. Respiratory protection filters against particles, viruses and bacteria are usually made up of several fleece layers made of polypropylene, which is woven or manufactured using the so-called melt-blown process. In most cases, these filter layers are embedded in a protective fabric, which protects against mechanical damage and holds back any loose fibers from the filter fleece. If the mask body consists of filter material, shape-stabilizing layers may also be necessary.

The filter effect of these filters depends - in addition to the properties of the medium to be filtered - on several factors of the filter material. These include the pore size, microstructure of the flow passages, adhesion and electrostatic forces, etc. Another very important factor for the effectiveness of the particle filtering mechanisms is the flow rate at which harmful particles are guided through the mask body. Basically it can be said that the permeability of a filter material for aerosols increases approximately quadratically with the flow rate (see e.g 10 in Tcharkhtchi et al. "An overview of filtration efficiency through the masks: Mechanisms of the aerosols penetration", Bioactive Materials Vol. 6, Issue 1, Jan. 2021, p. 106-122.)

Disadvantages of the Prior Art

The flow resistance of the filter medium causes a noticeably increased breathing resistance and therefore has an important influence on the wearing comfort and suitability of a mask for physically demanding activities. In practice, this means that the recommendations for wearing masks - depending on their filter performance - are sometimes limited to less than 2 hours.

If a person breathes without a mask, a spatially limited jet of air forms when exhaling, which moves away from the mouth or nose at approx. 1m/s. A rebreathing of the exhaled volume is thus practically impossible. With the mask, the flow conditions change in such a way that the flow speed after passing through the mask is only approx. 0.01m/s. If the mask wearer does not move relative to the ambient air, the exhaled volume remains close to the mask (cf. Birgersson et.al, (2015) Reduction of Carbon Dioxide in Filtering Facepiece Respirators with an Active-Venting System: A Computational Study. PLoS ONE 10(6 ):e0130306.doi:10.1371/journal.pone.0130306)

In 1 a common mask type is shown schematically. A filter material formed into a cup 120 encloses the volume 123 between the cup and the wearer's face. A portion of the exhaled air just in front of the mask is rebreathed in the subsequent breath. In 2 this volume is denoted by 121 and bounded by the imaginary outer boundary 122 formed in front of the mask. An adult without physical exertion exhales about 500 cm ³ of gas with an exhalation of 140 (cf. Nishi (2004) Breathing of Humans and its Simulation. Dissertation LSTM-Erlangen). Depending on the design, about 150 cm ³ (corresponding to volume 141) remain within the mask. The volume portion 142 remains close to the filter surface, the volume portion 143 moves away depending on the flow rate when exhaling and the environmental influences, for example drafts or movement of the wearer. The following inhalation 144 consists of a volume 145 (remaining breathing air inside the shell), a volume of CO2-rich air (146) from the area in front of the mask and a volume of fresh air 147.

• - Die von den Probanden eingeatmete CO2-Konzentration liegt mit ca. 3% (vgl. Raymond J Roberge MD MPH, Aitor Coca PhD, W Jon Williams PhD, Jeffrey B Powell MSc, and Andrew J Palmiero: Physiological Impact of the N95 Filtering Facepiece Respirator on Healthcare Workers, RESPIRATORY CARE • MAY 2010 VOL 55 NO 5)
• - beim sechsfachen der gültigen Arbeitsplatzgrenzwerte nach TRGS900 (vgl. BArBl Heft 1/2006; Zuletzt geändert und ergänzt: GMBI 2020, S. 902 [Nr. 42] (v. 27.10.2020)) und
• - beim 15fachen der Empfehlung für die Raumluftkonzentration (vgl. Bundesgesundheitsbl - Gesundheitsforschung - Gesundheitsschutz 2008 • 51:1358-1369 DOI 10.1007/s00103-008-0707-2 © Springer Medizin Verlag 2008) .

The wearer must therefore breathe in more air than without a mask in order to achieve the same oxygen supply. The ratio of the gas volume of his breath to the volume 123 remaining in the mask plays a significant role here. With low physical exertion, eg in office and teaching activities, the proportion of rebreathed CO2 is significantly higher than the values of physically strenuous work. Smith et al. prove these relationships in a practical study and show the physical stress symptoms in connection with the proportion of rebreathed CO2, such as increased heart rate, dizziness, reduced vision, headaches, etc. (cf. Smith, CL, Whitelaw, JL & Davies, B. 2013 , 'Carbon dioxide rebreathing in respiratory protective devices: influence of speech and work rate in full-face masks', Ergonomics: an international journal of research and practice in human factors and ergonomics, vol. 56, no. 5, pp. 781- 790). Roberte et al. confirm the effects described in a further practical study and show that the physical reactions to the gas volume rebreathed from different masks are independent of whether they are equipped with an exhalation valve.

• - The CO2 concentration inhaled by the subjects is around 3% (see Raymond J Roberge MD MPH, Aitor Coca PhD, W Jon Williams PhD, Jeffrey B Powell MSc, and Andrew J Palmiero: Physiological Impact of the N95 Filtering Facepiece Respirator on Healthcare Workers, RESPIRATORY CARE • MAY 2010 VOL 55 NO 5)
• - at six times the applicable workplace limit values according to TRGS900 (cf. BArBl issue 1/2006; last changed and supplemented: GMBI 2020, p. 902 [no. 42] (of October 27th, 2020)) and
• - at 15 times the recommendation for the room air concentration (cf. Federal Health Gazette - Health Research - Health Protection 2008 • 51:1358-1369 DOI 10.1007/s00103-008-0707-2 © Springer Medizin Verlag 2008) .

The exhaled air also has a high moisture content and is around 37°C warm. As a result, condensation takes place on colder surfaces such as the filter fleece. The separated moisture soaks the mask and filter fleece over time. Depending on the design of the contact surfaces and the dimensional stability of the mask, it starts to stick when it comes into contact with the skin. This is perceived as uncomfortable by the wearer, and skin irritation can occur if the wearer wears it for a longer period of time. The press release of the Fraunhofer Institute ITWM from May 11, 2020
(https://www.itwm.fraunhofer.de/de/presse-publikationen/presseinformationen/ 2020/2020_05_11_tragedauer-schutzmasken-corona-kirche.html) explains how quickly the filter efficiency decreases with increasing moisture in the material and that with moisture penetration there is a risk of an infection bridge between the person carrying it and the environment.

Moisture and body heat also promote contamination on the side of the wearer and limit the useful life of a mask, regardless of specific filter tasks.

In addition to filter efficiency, leakage is particularly relevant for the protective effect of a mask. With high filter classes (FFP2 and higher), even a few percent of leakage between the mask and the face of the wearer ensures that the proportion of leakage in the respiratory volume determines the overall protective effect of the mask. leakage is either intentionally (in the case of surgical masks as a gain in comfort) or is determined by the design: in the case of FFP filter masks by the shape and the contact pressure generated by the straps. For masks with gas-tight mask bodies and full protective masks through elastic lips in the contact area. Especially in the case of masks without an exhalation valve, for example when sneezing, the internal pressure lifts the mask and a large part of the exhalation volume flow can escape past the mask.

In order to compensate for these disadvantages, there are isolated solutions with active fans in the area of full protective masks and in some cases also in the area of respiratory masks. The disadvantages of this are the increased costs, the additional weight including energy supply and the resulting noise level.

In general, protective masks cover a large part of the wearer's face. As a result, a large part of the non-verbal communication cannot be perceived by the other person. Since the facial expressions remain hidden, expressing and reading emotions is difficult or even impossible. This makes working for therapists and speech therapists, for example, difficult or even impossible. For the same reason, people with hearing impairments no longer use lip reading as a communication-supporting technique. The same applies to communication in environments with loud background noise.

Another disadvantage is that the voice quality suffers when speaking through masks of any type. On the one hand, the reduction of the sound pressure leads to reduced volume, on the other hand, the damping via the mask body and filter material leads to changes in the frequency response. Anyone who speaks through a protective mask is therefore more difficult to understand. The change in frequency response can lead to modern hearing aids completely blocking out the speaker.

• - das Volumen innerhalb der Maske ist im Vergleich zum Volumen eines Atemzugs groß
• - die CO2-Anreicherung in der Atemluft beim Einatmen hat nachteilige Effekte auf Komfort und Leistungsfähigkeit des Trägers und ist bei entsprechenden Risikofaktoren ggf. gesundheitsschädlich
• - die Filterfläche für Einatmung ist klein. Dies führt zu einem hohen Druckverlust und damit zu einem hohen Atemwiederstand bei gleichzeitig großen Strömungsgeschwindigkeiten durch das Filtermaterial
• - Die bei der Ausatmung durchströmte Filterfläche außerhalb des Ausatmungsventils ist noch kleiner als die Einatemfilterfläche. Ein zur Entlastung des Trägers niedriger Ausatemwiederstand lässt sich nur über eine erheblich reduzierte Filterwirkung erreichen, der Schutz für die Umgebung wird schlechter
• - die Innen- und/oder Außenseite der Maske wird bei der Verwendung kontaminiert (z.B. mit Viren), damit ist das Absetzen und wieder Aufsetzen mit Übertragungsrisiken für den Träger verbunden.
• - die Masken ist für den Einmalgebrauch vorgesehen. Selbst ohne Kontamination wird der häufige Austausch der kompletten Maske erforderlich, weil sich in durchfeuchteten Filter Bakterien und Keime vermehren können. Der massenhafte Einsatz solcher Masken zum Bevölkerungsschutz während einer Pandemie erzeugt eine immense Menge an Müll und entsprechenden Entsorgungsaufwänden.
• - Die Maske feuchtet bei längerem Tragen durch und verliert ihre Filtereffizienz. Dieser Effekt ist umso stärker, je kälter die Umgebung ist in der die Maske getragen wird.

In the following, reference is primarily made to masks that protect both the wearer and the environment, such as are required in large numbers during a pandemic triggered by a respiratory disease. Such an example in EP1100592 (Japuntich et al.) has several disadvantages,

• - the volume inside the mask is large compared to the volume of one breath
• - the accumulation of CO2 in the breathing air when inhaled has adverse effects on the comfort and performance of the wearer and may be harmful to health if the risk factors are appropriate
• - the filter surface for inhalation is small. This leads to a high pressure loss and thus to a high breathing resistance with high flow speeds through the filter material at the same time
• - The filter surface outside of the exhalation valve through which air flows during exhalation is even smaller than the inhalation filter surface. A low exhalation resistance to relieve the wearer can only be achieved with a significantly reduced filter effect, the protection for the environment becomes worse
• - the inside and/or outside of the mask becomes contaminated during use (e.g. with viruses), so taking it off and putting it on again is associated with transmission risks for the wearer.
• - the masks are intended for single use. Even without contamination, the entire mask has to be replaced frequently because bacteria and germs can multiply in a damp filter. The massive use of such masks for civil protection during a pandemic generates an immense amount of waste and the corresponding disposal costs.
• - The mask becomes wet when worn for a long time and loses its filter efficiency. This effect is stronger the colder the environment in which the mask is worn.

object of the invention

• • sowohl den Maskenträger als auch seine Umwelt vor Schadstoffen wie Stäuben, Aerosolen, Krankheitserregern etc. zu schützen
• • die zusätzlichen körperlichen Belastungen für den Maskenträger durch erhöhte Ein- und Ausatemwiederstände sowie durch die Menge an rückgeatmeten CO2 zu minimieren
• • den Tragekomfort so weit zu verbessern, so dass der Träger seine Atemschutzmaske auch über einen Zeitraum von mehreren Stunden im Alltagsbetrieb nutzen kann
• • das Durchfeuchten des Einatemfilters effektiv zu verhindern
• • die akustische Sprachqualität beim Tragen von Masken zu verbessern
• • das Lippenlesen auch beim Tragen einer Maske zu ermöglichen
• • die Müllmenge zu reduzieren
• • den Kostenaufwand für die Träger zu reduzieren
• • den Komfort und die Filtereffizienz beim Tragen in kälteren Umgebungen zu verbessern

The object of the invention is

• • to protect both the mask wearer and their environment from pollutants such as dust, aerosols, pathogens, etc
• • to minimize the additional physical strain on the mask wearer due to increased inhalation and exhalation resistance and the amount of rebreathed CO2
• • to improve the wearing comfort to such an extent that the wearer can also use his respirator mask over a period of several hours in everyday operation
• • to effectively prevent the inhalation filter from becoming wet
• • to improve the acoustic speech quality when wearing masks
• • enable lip reading even when wearing a mask
• • reduce the amount of waste
• • to reduce the costs for the carriers
• • Improve comfort and filter efficiency when worn in colder environments

solution of the task

• • Durch die ausgeführte Gestaltung des Maskenkörpers und seine Begrenzung durch Ventile in Richtung der Filter wird das beim Einatmen zurückgeatmeten Volumen erheblich verringert. Während Schutzmasken ähnlich EP 1100 592 B1ein Rückatemvolumen in der Größenordnung 150 ml aufweisen, kann mit dem beschriebenen Ansatz dieses auf weniger als 55 ml, im besten Fall sogar auf weniger als 40 ml reduziert werden. Die Menge an wieder eingeatmetem CO2 reduziert sich um etwa 64 bis 74 %.
• • Der Maskenkörper ist aus elastischem, gasundurchlässigem Material aufgebaut. Seine Formgebung weist eine spezielle Dichtlippenkontur auf, welche zum einen das zuvor angesprochene Restvolumen begrenzt und andererseits Leckage verhindert. Die Schutzwirkung der Maske wird damit alleine durch die Filtereffizienz bestimmt.
• • Der Maskenkörper ist weitgehend aus transparentem Material hergestellt. Dies ermöglicht eine gute Belichtung der Mundpartie des Maskenträgers und ermöglicht vorteilhaft das Lippenlesen durch den volltransparenten Bereich vor dem Mund.
• • Der Maskenkörper kann auf einfache weise gereinigt und desinfiziert werden. Vorgesehen ist eine Reinigung durch Seifenlauge oder handelsübliche Flächendesinfektionsmittel auf Alkoholbasis. Der Maskenkörper kann vollständig wiederverwendet und dauerhaft eingesetzt werden.
• • Der Maskenkörper schließt an die Nase an und bedeckt die Mundpartie bis zum Kinn. Die insgesamt abgedeckte Gesichtsfläche ist klein. Der Maskenkörper ist elastisch ausgeführt und kann den Gesichtsbewegungen insbesondere beim Reden folgen.
• • Je ein durch Druckdifferenz betätigtes Ventil trennt den Maskenkörper vom Ein- und vom Ausatemkanal. Dadurch entstehen vollständig voneinander getrennte Strömungswege für das Ein- und Ausatmen. Die Ventile sind so ausgeführt, dass durch ihre Formgebung die Geräuschentwicklung beim Betätigen auf ein Minimum reduziert wird. Die Ventile sind Bestandteil des Maskenkörpers und werden mit diesem zusammen gereinigt und desinfiziert.
• • Der Maskenkörper trägt optional ein Sichtfenster, eine Sprechmembran oder beide Elemente. Dieses Bauteil besteht aus einer vorzugsweise vollständig transparenten, vorgespannten Kunststoffmembran auf einem mit dem Maskenkörper auf einfache Art verbindbaren Rahmen. Die Sprechmembran ist unter akustischen Gesichtspunkten so ausgelegt, dass sie Resonanzfrequenzen wirkungsvoll in einen Frequenzbereich oberhalb 2500 Hz verschiebt und einen Sprachübertragungsindex gem. IEC 60268-16 über 0,6 aufweist
• • Das Beschlagen des Sichtfensters bzw. der Spechmembran wird wirksam vermieden, dadurch dass der Einatemfilter trocken bleibt und es zu keiner Anfeuchtung der Frischluft kommt. Zusätzlich ist durch das geringe Volumen im Maskenkörper der absolute Wasseranteil gering und der Frischluftanteil beim Einatmen hoch, so dass Niederschlag an der Innenseite des Sichtfensters bzw. der Sprechmembran effektiv und schnell abtrocknet.
• • Am Maskenkörper befinden sich die Befestigungen für die Bebänderung der Schutzmaske. Vorzugsweise wird die Maske mit zwei Haltebändern über den Hinterkopf des Trägers befestigt. Diese Bänder sind elastisch und können in der Länge verstellt werden. Die Bänder sind mit einem Verschluss ausgeführt, welcher ein leichtes Öffnen und Schließen ermöglicht, beispielsweise mit einem magnetischen oder einem Druckknopf. Die Bebänderung ist ebenfalls waschbar.
• • Die Schutzmaske ist ausgestattet mit einem oder zwei voneinander getrennten, auswechselbaren Filtern. Damit kann wahlweise eine Konfiguration zum Schutz des Trägers, zum Schutz der Umgebung oder zum Schutz von Träger und Umgebung aufgebaut werden. Die Filter sind durch einen trennbaren Verschluss mit dem Maskenkörper verbunden und können bei Bedarf ausgetauscht werden. Ein- und Ausatemfilter können situationsbedingt unterschiedliche Filtereffizienzen bzw. Filtergrade aufweisen.
• • Die Filter sind seitlich am Kopf des Trägers positioniert und werden durch die Bebänderung gehalten. Das erlaubt zum einen ein uneingeschränktes Sichtfeld für den Träger. Weiter ist es von Vorteil, dass der Gesamtschwerpunkt nach hinten verlagert wird, was die nötige Spannung in den Haltebändern reduziert und den Tragekomfort verbessert. Eine Kollision mit einer Brille oder einem Gesichtsschild kann so wirksam verhindert werden. Die seitliche Position erlaubt die Verwendung von im Verhältnis zu bekannten Maskentypen Filtereinheiten mit großen Wirkflächen. Bei Bedarf kann die Filterfläche durch Falten und Plissieren weiter erhöht werden. Die große Filterfläche führt zu geringen Durchströmungs- bzw. Atemwiederständen und geringen Strömungsgeschwindigkeiten im Filter mit entsprechend positiven Auswirkungen auf die körperliche Belastung des Trägers, den Tragekomfort und die Filtereffizienz.
• • Die Gasvolumen in den Filtern sind durch die eingesetzten Ventile nicht Teil des rückgeatmeten Restvolumens
• • Durch die vollständig getrennten Strömungswege beim Ein- und Ausatmen wird der Einatemfilter zu keinem Zeitpunkt von feuchter Ausatem-Luft durchströmt, eine Durchnässung mit den aufgezeigten Nachteilen für den Träger wird vermieden.
• • Ein und Ausatemfilter können bedarfsgerecht zu unterschiedlichen Zeitpunkten getauscht werden.
• • Der Einatemfilter ist so aufgebaut, dass er durch den beim Einatmen entstehenden Unterdruck leicht komprimiert werden kann. Nur ein Teil des Einatemvolumens wird mit dem Atemzug durch die Filtermembran gezogen. Nach dem Ende des Einatemzugs sorgt die mechanische Struktur des Filters dafür, dass dieser sich in die Ausgangslage und -größe zurückbewegt. Dadurch wird ein Teil des für den nächsten Einatemzugs notwendigen Volumens bereits zum Zeitpunkt des Ausatmens ohne Muskelarbeit des Trägers gefiltert und bereitgestellt.
• • Der Ausatemfilter ist so aufgebaut, dass er durch den beim Ausatmen entstehenden Überdruck leicht vergrößert werden kann (Balloneffekt). Nur ein Teil des Ausatemvolumens wird mit dem Atemzug durch die Filtermembran gedrückt. Nach dem Ende des Ausatemzugs sorgt die mechanische Struktur des Filters dafür, dass dieser sich in die Ausgangslage und -größe zurückbewegt. Dadurch wird ein Teil des Ausatemvolumens noch zum Zeitpunkt des Einatmens ohne Muskelarbeit des Trägers gefiltert und an die Umgebung abgegeben.
• • Die Filtermaterialien haben keinen Hautkontakt mit dem Träger
• • Die Schutzmaske wird durch einen im Ausatemkanal befindlichen Lüfter auch nach dem Ende des Ausatmens weiter aktiv belüftet. Dabei wirkt das Lüfterrad beim Ausatmen als Turbine und treibt ein mechanisch verbundenes Schwungrad an. Dessen gespeicherte Energie treibt für einen Zeitraum nach dem Ausatmen weiterhin das Lüfterrad an, welches nun als aktives Gebläse verbrauchte Atemluft aus dem Maskenkörper in Richtung Ausatemfilter fördert und frische Luft durch den Einatemfilter nachzieht. Damit kann der CO2-Gehalt vor Beginn des Einatmens reduziert werden.

The invention has the following advantages over the prior art:

• • Due to the design of the mask body and its limitation by valves in the direction of the filters, the rebreathed volume during inhalation is significantly reduced. While protective masks similar EP 1100 592 B1 have a rebreathing volume of the order of 150 ml, this can be reduced to less than 55 ml, in the best case even to less than 40 ml, using the approach described. The amount of rebreathed CO2 is reduced by about 64 to 74%.
• • The mask body is made of elastic, gas-impermeable material. Its shape has a special sealing lip contour, which on the one hand limits the residual volume mentioned above and on the other hand prevents leakage. The protective effect of the mask is therefore determined solely by the filter efficiency.
• • The mask body is largely made of transparent material. This enables good exposure of the mouth area of the mask wearer and advantageously enables lip reading through the fully transparent area in front of the mouth.
• • The mask body can be easily cleaned and disinfected. Cleaning with soapy water or standard alcohol-based surface disinfectants is planned. The mask body can be completely reused and used permanently.
• • The mask body connects to the nose and covers the mouth area up to the chin. The total facial area covered is small. The mask body is elastic and can follow facial movements, especially when speaking.
• • A valve actuated by the pressure difference separates the mask body from the inhalation and exhalation channels. This creates completely separate flow paths for inhalation and exhalation. The valves are designed in such a way that the noise generated when they are actuated is reduced to a minimum due to their shape. The valves are part of the mask body and are cleaned and disinfected together with it.
• • The mask body optionally carries a viewing window, a speech membrane or both elements. This component consists of a preferably completely transparent, prestressed plastic membrane on a frame that can be easily connected to the mask body. From an acoustic point of view, the speech membrane is designed in such a way that it effectively shifts resonance frequencies to a frequency range above 2500 Hz and has a speech transmission index of over 0.6 in accordance with IEC 60268-16
• • The fogging up of the viewing window or the speech membrane is effectively avoided because the inhalation filter remains dry and the fresh air is not humidified. In addition, due to the small volume in the mask body, the absolute water content is low and the fresh air content when inhaling is high, so that precipitation on the inside of the viewing window or speech membrane dries effectively and quickly.
• • The fastenings for the straps of the protective mask are located on the mask body. The mask is preferably fastened with two straps over the back of the wearer's head. These straps are elastic and can be adjusted in length. The straps are designed with a closure that allows easy opening and closing, for example with a magnetic or snap button. The harness is also washable.
• • The protective mask is equipped with one or two separate, replaceable filters. This allows a configuration to be set up to protect the wearer, to protect the environment, or to protect the wearer and the environment. The filters are connected to the mask body by a separable fastener and can be replaced if necessary. Inhalation and exhalation filters can have different filter efficiencies or filter grades depending on the situation.
• • The filters are positioned on the side of the wearer's head and are held in place by the harness. On the one hand, this allows an unrestricted field of vision for the wearer. It is also an advantage that the overall center of gravity is shifted backwards, which reduces the necessary tension in the straps and improves wearing comfort. A collision with glasses or a face shield can thus be effectively prevented. The lateral position allows the use of in relation to well-known mask types filter units with large effective areas. If necessary, the filter surface can be further increased by folding and pleating. The large filter surface leads to low flow and breathing resistance and low flow velocities in the filter with correspondingly positive effects on the physical strain on the wearer, the wearing comfort and the filter efficiency.
• • The gas volumes in the filters are not part of the rebreathed residual volume due to the valves used
• • Due to the completely separate flow paths during inhalation and exhalation, the inhalation filter is never flowed through by moist exhaled air, soaking with the disadvantages for the wearer shown is avoided.
• • Inhalation and exhalation filters can be exchanged at different times as required.
• • The inhalation filter is constructed in such a way that it can be slightly compressed by the negative pressure that occurs when you inhale. Only part of the inhaled volume is drawn through the filter membrane with the breath. After the end of the inhalation, the mechanical structure of the filter ensures that it returns to its original position and size. As a result, part of the volume required for the next inhalation is already filtered and made available at the time of exhalation without any muscle work on the part of the wearer.
• • The exhalation filter is constructed in such a way that it can be slightly enlarged by the excess pressure that occurs when exhaling (balloon effect). Only part of the exhaled volume is pushed through the filter membrane with the breath. After the end of the exhalation, the mechanical structure of the filter ensures that it returns to its original position and size. As a result, part of the exhaled volume is filtered and released into the environment at the time of inhalation without the wearer having to do any muscle work.
• • The filter materials have no skin contact with the wearer
• • The protective mask continues to be actively ventilated by a fan located in the exhalation channel even after exhalation has ended. The fan wheel acts as a turbine when you exhale and drives a mechanically connected flywheel. Its stored energy continues to drive the fan wheel for a period of time after exhalation, which now acts as an active blower and pumps used breathing air out of the mask body in the direction of the exhalation filter and draws fresh air through the inhalation filter. This allows the CO2 content to be reduced before inhalation begins.

Description of exemplary embodiments

In 3 the invention is shown schematically. The entire volume of the mask 113 is limited by the wearer's face, the airtight shell 101 and the viewing window or speech membrane 102 and proportionately by the channels 105 and 106 up to the check valves 103 and 104 . This volume is preferably kept below 55 cm ³ , more preferably below 40 cm ³ .

When the wearer inhales, a negative pressure is created in the volume 113, the pressure difference to the environment closes the exhalation valve 104 and opens the inhalation valve 103. Air is drawn from the volume 107 into the volume 113 and flows through the filter 111.

When the wearer exhales, overpressure is created in volume 113, inhalation valve 103 remains closed, exhalation valve 104 opens and air flows through volume 108 and on through filter 112.

In particular, if only an inhalation filter or an exhalation filter is used, it is necessary for the valves to close automatically. This can be achieved, for example, by the spring force or elasticity of the component.

Filter 111 is spatially remote from filter 112 . This ensures that no exhaled air is breathed in again from outside the protective mask.

Aerosols and pathogens that the wearer breathes out are caught by the filter 112 and thus do not get into the wearer's environment. Aerosols and pollutants from the environment are caught by the filter 111 and do not enter the wearer's respiratory tract.

The shell 101 of the mask body is preferably made of an elastic, transparent and gas-tight material, for example a skin-friendly silicone material. For the optical design of the mask, the shell can be colored in whole or in part. The viewing window 102 or, in a functionally expanded design, the speech membrane 102 is preferably made of a clear, fully transparent material, for example a PEEK, PET or PTFE film. Optionally, this window or the Speech membrane can be supplemented with an anti-fog coating.

In 4 the volume ratios during inhalation and exhalation are shown qualitatively. During inhalation 134 , the inhaled volume is made up of a volume fraction of previously exhaled air 135 , corresponding to volume 113 , and a volume fraction of fresh air 136 . During exhalation 130, a residual volume of exhaled air 131 remains in volume 113 within the mask, and volume portion 132 is conveyed through valve 104 into volume 108 and from there into the environment.

In 5 the basic structure of the two filters with variable volume is shown. The memory 109 is large when depressurized. The rigidity and elasticity of the structure are adjusted in such a way that when you breathe in, the walls contract even at low negative pressure. When the inhalation is complete, the valve 103 closes, the elastic structure expands again and increases the volume, as a result of which more air is drawn in through the filter 111 into the volume 107 independently of the wearer. This reduces the inhalation resistance, which increases wearing comfort, and reduces the flow rate through the filter, which increases filter effectiveness.

When exhaling, the reservoir 110 is small when there is no pressure. The rigidity and elasticity of the structure are adjusted in such a way that the walls expand when the patient breathes out, even at low overpressure. When the exhalation is complete, the valve 104 closes, the elastic structure contracts and reduces the volume, whereby used air is released through the filter 112 to the environment independently of the wearer. This reduces the resistance to exhalation, which increases wearing comfort, and reduces the flow rate through the filter, thereby increasing filter effectiveness.

In 6 the spatial arrangement of the entry and exit openings of the protective mask with filters is illustrated. The angle 117 between the main directions for inflow 116 and outflow 115 is preferably 90° to 180°. The minimum distance 118 between the entry window and the exit window should preferably be at least 50 mm.

7 clarifies the requirements for good washability and disinfectability of the mask body. It is assumed that the mask body is placed on a horizontal plane. The cavities before and after the valves need a sufficient gradient in the direction away from the valves for drainage, ie the design of the angles 152 and 153 must be greater than 90°. Correspondingly, 154 and 155 are designed as angles of less than 90°. The sealing lip 159 must also have a slope, either inwards or outwards. Angles 156 and 157 must be greater than 90°.

In 8th Convenient placement areas for the filters are shown as the envelope of volume 162 . The volume shown ensures a good field of vision, for example for reading with glasses or varifocals or for wearing a visor. Furthermore, head tilts forward or to the side are not affected by annoying filter volumes in the chin area.

The preferred embodiment 162 can be easily combined by means of retaining straps 114 both behind the head and neck and alternatively behind the ears. Even with a limited outer area, by pleating the filter material within the volume 162 shown, a sufficiently large effective area of the filter, preferably 250 cm ² , more preferably 500 cm ² , can be achieved. Depending on the nonwoven or filter material used, the change in volume of the filter is achieved by a suitable design of the pleating and/or an additional spring function.

9 shows the geometric details of the check valves. An elastic tongue 180 automatically contacts the frame 181 in the event of a pressure difference in the blocking direction 183 . The valve separates the gas volumes on the front and back. A pressure difference against the blocking direction 183 opens the valve. A spring effect can support the function, for example through elastic pretensioning of the tongue, to support the closing process. To reduce impact noise, the shape in the area of the contact surface between frame 181 and tongue 180 can be designed in such a way that when the two elements first come into contact, only a partial surface touches and only with increasing pressure in the blocking direction does the tongue come into full contact. This shape can be implemented as a corrugated contour 182, for example.

10 shows details of the implementation of an optimized sealing lip arrangement of the mask body. For this purpose, the mask body is provided with a sealing lip 159 running inwards. The mask body itself is double-walled, with the inner mask body 170 with the inner sealing lip 171 terminating towards the wearer's face in such a way that the volume 172 does not participate in the gas exchange during inhalation and exhalation. In a further preferred embodiment form the Sealing lip 159 and the inner sealing lip 171 a closed hollow body.

11 shows the installation position of the flywheel fan between exhalation valve 104 and filter 112. The protective mask continues to be actively ventilated by a fan 184 located in the exhalation channel even after exhalation has ended. The fan wheel acts as a turbine during exhalation and drives a mechanically linked flywheel 185 . Its stored energy continues to drive the fan wheel for a period of time after exhalation, which now, as an active blower, conveys used respiratory air in volume 113 out of the mask body in the direction of exhalation filter 112 and draws fresh air through inhalation filter 111 . This allows the CO2 content to be reduced before inhalation begins.

Reference List

101

Mask body, not permeable to air

102

Viewing window, speech membrane

103

inhalation valve

104

exhalation valve

105,106

channel

107, 108

Volume between valve and filter

109

Storage volume inhalation, unpressurized large

110

Storage volume exhalation, pressureless small

111, 112

Changeable filters

113

Volume limited by face, skirt and valves

114

retaining straps

115

Main direction, outflow opening

116

Main direction, inflow opening

117

Angles between principal directions

118

Minimum distance between inflow and outflow opening

120

Mask body made of filter material

121

Volume of exhaled air that remains near the mask and is drawn back through the filter back into the mask on the next inhalation

122

Fictitious boundary between exhaled air and ambient air

123

Volume limited by mask body and face

124, 125

Separation point of mask and filter element

130

total exhalation volume

131

Percentage of volume that remains in front of the wearer's mouth and nose when exhaling within the mask volume limited by valves

132

Volume fraction that is not inhaled again after exhalation

134

total volume inhaled

135

Volume fraction of remaining, exhaled air that remains before inhalation within the mask volume limited by valves in front of the wearer's mouth/nose

136

Volume fraction of fresh air that is inhaled through the valve

140

total exhalation volume

141

Percentage of volume that remains inside the mask during exhalation

142

Volume of exhaled air that is drawn back through the filter and back into the mask the next time you breathe in

143

Volume fraction that is not inhaled again after exhalation

144

total volume inhaled

145

Volume fraction of residual exhaled air that remains inside the filter after exhalation

146

Percentage of volume outside the filter that is rebreathed

147

Volume fraction of fresh air that is inhaled

151

direction of gravity

152

Location of the valve (exhalation side)

153

Location of the valve (inhalation side)

154

Drainage Angle Flow Channel (Exhalation Side)

155

Drainage Angle Flow Channel (Inhalation Side)

156

Angle to the sealing lip in the mask body area

157

Angle to the sealing lip in the lower mask body area

158

horizontal

159

sealing lip

162

Desired installation space for filter units

170

Inner skirt

171

Inner sealing lip

172

Volume with minimized air exchange

180

Tongue

181

Conventional valve seat

182

Wavy sealing edge

183

blocking direction

184

fan wheel

185

flywheel

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 69921660 T2 [0005]
• EP 1100592 [0018, 0020]

Claims (36)

Protective mask, characterized in that the breathing volume flow is directed through the mask via the mouth and nose both when breathing in and when breathing out device after claim 1 , characterized in that the mask covers part of the face, preferably the mouth area and at least part of the nose area Device according to at least one of the preceding claims, characterized in that more than 1 flow path is available for the respiratory volume flow, preferably a separate flow path for inhalation and a separate flow path for exhalation Device according to at least one of the preceding claims, characterized in that the flow paths are separated by 2 valves, preferably actuated by the pressure differences occurring when breathing through the mask Device according to at least one of the preceding claims, characterized in that at least one flow path to the environment is closed off by a filtering element which can be separated from the mask and replaced Device according to at least one of the preceding claims, characterized in that the possibility of air flows past this filtering element is prevented or at least minimized by the shape and design of the mask Device according to at least one of the preceding claims, characterized in that the design of the gas-tight mask body and the valve arrangement are designed in such a way that the volume of used air remaining between the mask and the face after exhalation is as small as possible, preferably below 55 ml, still more preferably below 40 ml. Device according to at least one of the preceding claims, characterized in that the design of the sealing lips between the mask body and the carrier is designed in such a way that the outer sealing lip points towards the inside of the mask and together with an inner sealing lip a part of the volume between the mask body and carrier from the gas exchange during Excludes inhaling and exhaling. Device according to at least one of the preceding claims, characterized in that the outer sealing lip and the inner sealing lip form a closed hollow body. Device according to at least one of the preceding claims, characterized in that the combination of a material elasticity below 40° Shore A and the geometric shape ensures an elastic deformation of at least 10 mm, so that the mask body follows movements of the face, in particular the chin movement, without leakage can. Device according to at least one of the preceding claims, characterized in that the facial area covered by the mask body is as small as possible, preferably with an area of less than 50 cm ² , more preferably with an area of less than 35 cm ² . Device according to at least one of the preceding claims, characterized in that the mask body forms a sealing surface with the nose in the area of the nostrils. Device according to at least one of the preceding claims, characterized in that the mask body consists at least partially of a transparent, elastic, skin-friendly material, preferably a silicone material. Device according to at least one of the preceding claims, characterized in that the mask body is designed such that when stored on level 158, measured vertically downwards in the direction of gravity 151, sufficiently large angles to the outflow directions can be displayed, for example the angle to the outflow direction is 152 and 153 preferably at least 95°, and the angle to the outflow direction 154 and 155 preferably at most 85°. Device according to at least one of the preceding claims, characterized in that the mask body has a transparent viewing window in front of the wearer's mouth area Device according to at least one of the preceding claims, characterized in that the mask body has a speech membrane in front of the wearer's mouth area. Device according to at least one of the preceding claims, characterized in that the speech membrane is transparent and at the same time serves as a viewing window. Device according to at least one of the preceding claims, characterized in that the speech membrane consists of a prestressed plastic film and a stabilizing frame Device according to at least one of the preceding claims, characterized in that the speech membrane film is between 0.01 mm and 0.05 mm thick. Device according to at least one of the preceding claims, characterized in that the speech membrane has a resonant frequency above 1800 Hz, preferably a resonant frequency above 2500 Hz and even more preferably above 3000 Hz. Device according to at least one of the preceding claims, characterized in that the mask is equipped with at least one removable filter insert. Device according to at least one of the preceding claims, characterized in that the filter insert enables elastic deformation and volume change when the pressure difference between the internal pressure in the filter and the ambient pressure outside the mask changes, preferably a volume change greater than 125 cm ³ , more preferably a volume change greater than 250 cm ³ and automatically returns to its original shape when the pressure difference decreases. Device according to at least one of the preceding claims, characterized in that at least part of the filter element is located to the side of the head. Device according to at least one of the preceding claims, characterized in that the filter element forms a unit with the harness. Device according to at least one of the preceding claims, in which the flow paths for inhalation and exhalation volume flow are designed such that the entry window into the flow channel for inhalation is spatially separated from the exit window of the flow channel for exhalation, preferably at a distance of at least 50 mm. Device according to at least one of the preceding claims, characterized in that the shape and position of the flow channels and filtering elements form a sufficiently large angle between the main flow directions for inhalation and exhalation, preferably between 90° and 180°. Device according to at least one of the preceding claims, in which the entrance to the flow channel for inhalation and the exit of the flow channel for exhalation are on different sides of the head, preferably on the right and left. Device according to at least one of the preceding claims, characterized in that the flow through the filter element only takes place in one defined direction. Device according to at least one of the preceding claims, characterized in that when stored on level 158, measured vertically downwards in the direction of gravity 151, the angles 156 and 157 are preferably at least 95°, more preferably at least 110°, taking into account the mask's own weight without filter arrangements. Device according to at least one of the preceding claims, characterized in that when stored on level 158, measured vertically downwards in the direction of gravity 151, the inner sealing lip 171 slopes in the outflow direction. Device according to at least one of the preceding claims, characterized in that the filtering element can be disinfected, either by heating above 60°C, by steam or by UV-C light. Device according to at least one of the preceding claims, characterized in that the filtering element is washable with a liquid solution, either with a soap solution or with an alcohol-based disinfectant. Device according to at least one of the preceding claims, characterized in that the effective area of the filter units is preferably larger than 250 cm ² , even more preferably larger than 500 cm ² . Device according to at least one of the preceding claims, characterized in that the mask can be configured, depending on the number and arrangement of the filter elements, either as a respiratory protection mask, as a face mask or as a mask which protects both the wearer and the environment. Device according to at least one of the preceding claims, characterized in that the shape of the valve seat 181 in the area of the contact surface ensures that in the initial contact of the two elements initially only one Touches part of the surface and only applies the tongue completely with increasing pressure in the blocking direction, preferably by a contour with 1 or more waves 182 and an amplitude between 0.1 mm and 2 mm. Device according to at least one of the preceding claims, characterized in that an energy store charged by the exhalation volume flow drives a ventilation element which replaces the used air remaining in the mask body after the end of exhalation with fresh air, preferably by a fan wheel connected to a flywheel.

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