Field of the invention

The present invention concerns an active separation screen for providing highly efficient microbial and other protection of individuals in a variety of different environments and situations. More specifically, the present invention relates to a convenient air curtain device that can provide the user(s) with a high degree of protection from potentially harmful air-borne particles.

Background of the invention

Over the course of the last 70 years, there have been massive improvements in the treatment and prevention of infectious disease. This is a result of the development of highly effective and safe antibiotic and antiviral drug treatments, as well as of specific vaccines and other preventive means. However, in recent years, there have been many outbreaks of infectious disease caused by both bacteria (in particular, antibiotic-resistant strains) and viruses. The latter have become particularly prominent in the last decade, with increasing numbers of epidemics and pandemics caused by viral agents such as SARS, MERS, Ebola, and most recently the SARS-CoV-2 virus which is responsible for the COVID-19 pandemic.

One particularly problematic aspect of infectious agents affecting the upper and lower respiratory tracts is the fact that infection may easily occur by means of the person-to- person transmission of droplets and aerosols generated during coughing, sneezing and speech. While attempts have been made to use 'social distancing' as a means for reducing such transmission, effective compliance with such methods, especially over the long term, has been found to be very difficult to obtain. In addition, in some of the epidemics and pandemics of recent years, aerosol transmission has been observed over separation distances of less than the 2-meter separation aimed for in most social distancing strategies. The aforementioned problems related to aerosol transmission of infectious agents between individuals are seen in both social and work-related scenarios, in particular, in situations when subjects are seated around, or on opposite sides of, a table or desk.

There is thus an urgent need for effective, simple and convenient devices and methods which are able to reduce the interpersonal, air-borne transmission of infectious agents, such as viruses, over short distances.

The present invention meets this urgent need.

Summary of the invention

The present invention relates to a device which allows the user to create an air screen (also referred to herein as an air curtain or barrier) that can cause blocking, aspiration and sterilization of air containing aerosols, particles and droplets arising from breathing, speaking, shouting, coughing and the like, as well as blocking and aspirating any other air borne particles, and to sterilize the air going through and around it. It has also been found by the present inventors that unlike most prior art attempts, it is possible to construct a small, foldable, personal unit which may be carried from place to place and used to create an air barrier between two or more people on either side of said unit. In this way, 'safe spaces' may be created in any indoor space within a matter of a few minutes. Furthermore, the air barrier device of the present invention provides a high level of protection, at least as high as that afforded the industry standard N95 facepiece respirator mask.

In addition, the device of the present invention, it also comprises several other key advantages, including, but not limited to:

In some embodiments of the invention, the air that forms the barrier protecting the users is recycled. This design maximizes the removal of infective (or other injurious) particles from the air contained in the air barrier, since multiple passes through the sterilization unit (described hereinbelow) will incrementally decrease the number of such particles in the recycled air The present invention utilizes air outlets and air inlets that are situated opposite each other, such that the air barrier formed between said outlets and inlets may be likened to a 'waterfall of air', creating a barrier with a defined rectangular shape. In addition, this arrangement (i.e., air outlets directly opposite to aspiration inlets) also prevents both disturbances in air flow within the room air space due to the air curtain (e.g., by creating subflows or regions of turbulence) and disturbances of the air curtain itself by air currents within the room. As a result, this design is much more efficacious in distancing each user from potentially harmful airborne particles originating on the other side of the air barrier. The presence of the aspiration inlets, and their position opposite the airflow outlets has been found by the present inventors to be highly important for the generation of optimally effective air screens.

The present inventors have found that the vertical, downward air flow created by the device disclosed and claimed herein is highly effective with regard to blocking, aspirating and eliminating contaminants and other potentially harmful airborne particles, and is more effective than other configurations (such as upwardly directed airflow or horizontal airflow) which cause a much greater degree of disturbance to the airflow within the room, resulting in turbulent flow and a reduced barrier effect, and which in some cases may even increase the airborne transfer of aerosols and other particles between individuals.

Thus, the present invention primarily relates to a personal device for creating an active air barrier between two or more subjects comprising: a) an upper elongate horizontal member fitted with an array of downwardly pointing air outlets; b) a lower elongate horizontal member comprising an array of aspiration inlets; c) at least one elongate vertical member separating between said upper and said lower elongate members; d) one or more electrically powered fans configured such that they are capable of causing: i) air to flow downwards through said outlets; and ii) aspiration of air flowing from said air outlets into said aspiration inlets; e) means for sterilizing the air that has entered the device through said inlets; wherein said upper elongate horizontal member is disposed vertically above said lower elongate member and said array of air outlets is disposed vertically above and opposite said array of air inlets.

In one embodiment, the present invention is directed to a a personal device intended for creating an active air barrier between two or more subjects, comprising: a) a hollow upper elongate horizontal member having an array of downwardly pointing air outlets on its lower face, the lumen of said outlets being continuous with the lumen of said upper member; b) a hollow lower elongate horizontal member having an array of aspiration inlets, the lumen of said inlets being continuous with the lumen of said lower member; c) at least one hollow elongate vertical member separating between said upper and lower horizontal members, wherein said vertical member is connected to one end of each of said horizontal members; d) one or more electrically powered fans configured such that they are capable of causing: i) air to flow through the internal lumen of the upper horizontal elongate element and to exit said element through said air outlets; and ii) aspiration of air flowing from said air outlets into said aspiration inlets; e) means for sterilizing the air that has entered the device through said inlets; wherein the lower elongate horizontal member of said device is adapted to be placed on a flat surface such that said upper elongate horizontal member is disposed vertically above said lower elongate horizontal member and said array of air outlets is disposed vertically above and opposite said array of air inlets.

It is to be understood, in the context of the present disclosure that the term "active air barrier" refers to the fact the barrier effect achieved by the present device is not the result of the presence of a static physical barrier (such as a wall or sheet of plastic or other material). Rather, the present invention relates to a moving "curtain" of air which is well defined in terms of its shape. Without wishing to be bound by theory, it is believed that the high efficacy achieved by the present invention is, at least in part, a consequence of the fact that the air curtain or barrier is both directed vertically downwards and aspirated at the lower margin of the curtain, in order to remove the potentially contaminated air from the room and to sterilize or decontaminate it, and to preserve uniform flow, with no undesired turbulent or sub-flow regions on either side of said curtain. Results will be presented hereinbelow demonstrating the superiority of the present invention, both in relation to static barriers (e.g., plastic sheets) and air flow devices lacking the lower aspiration inlets of the present invention.

The term "personal device", as used herein, refers to the fact that the device of the present invention is intended to provide protection for the people sitting (or standing) on either side thereof. This term is used in order to distinguish the present invention from prior art devices whose main function is to reduce the overall level of contamination in an entire room (e.g., produce a "clean room", as used in medicine, microchip manufacture, and so on).

The term "elongate member" as used herein refers to the fact that the main structural components of the present device are in the form or straight rods, bars or poles.

In a particularly preferred embodiment of the present invention, the two horizontal members are connected (and spaced apart) by means of only a single vertical member.

The term "array" of inlets or outlets, refers to the fact that said inlets or outlets are arranged along a straight line (preferably evenly spaced), and occupy most of the length of the lower and upper horizontal members, respectively. These arrays may consist either of discrete inlets/outlets (e.g., apertures or nozzles), or alternatively they may be formed as a continuous slit or groove. In some cases, the outlet or inlet array may comprise two or more parallel slits or series of apertures/nozzles. It is to be noted that the elongate members of the device, as disclosed above, are hollow, in order to permit the passage of air through the device to leave it via the outlets and enter it via the inlets. In some cases, the air passes through a simple internal chamber formed during manufacture of these members. In other cases, one or more pre-formed conduits or tubes are inserted within the hollow members, and the air passes through these instead.

In some preferred embodiments, the one or more fans, together with the sterilization means, are contained within a housing, wherein said housing is in fluid connection with the lumen of the lower elongate horizontal member by means of a first conduit, and wherein said housing is in fluid connection with the lumen of the elongate vertical member and the upper elongate horizontal member by means of a second conduit, and wherein said one or more fans are configured such that they are capable of aspirating air from the air inlets via said first conduit, and of recycling at least a portion of said air back to the air outlets via said second conduit. As will be explained in more detail hereinbelow, the housing also provides a UV-C shielding function (in the case that the sterilizing means are UV-C bulbs or other UV-emitting devices).

The term "fluid connection" is used herein to indicate a passage through which air is able to pass to move around the device (e.g., in a conduit or in the internal lumen of one of the elongate members).

In some embodiments having a fan and sterilization housing, as disclosed hereinabove, said housing contains only a single fan. In other embodiments, said housing contains two or more fans, preferably two fans.

As described above, in some embodiments, the housing is connected with the elongate members of the device via two conduits. In one preferred embodiment, both conduits may be contained within a single tube or hose. The first end of said tubing, tube or hose is connected to the inner cavity of the housing, while the second end thereof is connected to an internal recycling lumen in the lower elongate horizontal member, said lumen being continuous with the lumen of the elongate vertical member and the lumen of the upper elongate horizontal member. By means of this arrangement, the air that passes from the air outlets to the lower air inlets may be sterilized and then at least a portion of said sterilized air may be recycled to the outlets.

In some other preferred embodiment, the device may comprise two fans, wherein a first fan is contained in a housing, together with sterilizing means and wherein said housing is in fluid connection with the lumen of the lower elongate horizontal member by means of a conduit, and wherein a second fan is attached to the upper elongate horizontal member and is configured to cause air to flow downwards through the air outlets.

In some preferred embodiments, the upper horizontal elongate member may be fitted with two sets of air outlets: a downward-facing set (as in the other embodiments) and a second, upward-facing set. This arrangement may be used to alter and optimize the intake-output ratio for the device and thereby increase the barrier effect, as will be discussed in more detail hereinbelow.

Although the air outlets and inlets may take any convenient form, in some embodiments they are provided in a form selected from the group consisting of nozzles, apertures and slits.

The device of the present invention is intended for use as a portable device, rather than as a device which needs to be permanently fixed to a table or other structure. Thus, while it may be constructed with any desired dimensions, in a preferred embodiment (for the sake of portability and ease of storage), the vertical elongate element and both horizontal elongate members each have a length in the range of 50-130 cm.

As mentioned, the device is intended for personal use (i.e., to provide a barrier effect preventing the transfer of potentially contaminated air from person-to-person). The device also does not require to be permanently installed in the room, and thus may be readily transported and stored, when not in use. In order to assist with transport and storage, in one preferred embodiment, the first ends of the upper and lower elongate members (e.g., the left ends of each one) are connected to the upper and lower ends, respectively, of the vertical elongate member by means of foldable and lockable hinges, such that the device may be folded into a compact form for transportation and storage. Then, when required again for use, the members may be unfolded and locked into their working configuration. This embodiment will be described in more detail hereinbelow.

Any suitable means for sterilizing or decontamination the air may be used to work the present invention. However, preferably these comprise UV light-emitting devices (such as UV-C bulbs) and filters (e.g., HEPA filters) or combinations thereof.

In some embodiments, the device of the present invention may further comprise a transparent plastic sheet (e.g., made of an acrylic or other transparent polymeric material) attached along three sides of its perimeter to the two horizontal elongate members and the vertical member. Thus, in these embodiments, the device will comprise passive barrier means in addition to the active air barrier of the present invention.

In a yet further embodiment, the device comprises two fans, wherein a first fan is located adjacent to the lower elongate horizontal member, and in fluid connection therewith, and a second fan is attached to the upper elongate horizontal member and is configured to cause air to flow downwards through the air outlets. For the sake of convenience, the second fan may be a crossflow or other linear type of fan, having a length similar to that of the upper elongate horizontal member.

In yet a further embodiment, the present invention is directed to a personal device for creating an active air barrier between two or more subjects, comprising: a) an upper elongate horizontal member comprising an electrically powered crossflow fan, configured such that it is capable of pumping air from the room space in a downward direction; b) a hollow lower elongate horizontal member having an array of aspiration inlets, the lumen of said inlets being continuous with the lumen of said lower member; c) at least one hollow elongate vertical member separating between said upper and lower horizontal members, wherein said vertical member is connected to one end of each of said horizontal members; d) One or more additional electrically powered fans configured such that they are capable of causing the aspiration of air flowing from said crossflow fan fitted to the upper elongate horizontal member into said aspiration inlets; e) means for sterilizing the air that has entered the device through said inlets; wherein the lower elongate horizontal member of said device is adapted to be placed on a flat surface such that said upper elongate horizontal member is disposed vertically above said lower elongate horizontal member and said array of air outlets is disposed vertically above and opposite said array of air inlets.

It is to be noted that the crossflow fan (which may also be any other form of linear fan) preferably has approximately the same length as the upper elongate horizontal member, such that the airflow created thereby spreads along the whole length of said member, thereby creating an air curtain.

In another aspect, the present invention is directed to a method for preventing the transmission of respiratory passage-derived air, droplets and aerosols from one person to another, wherein said method comprises placing a personal active air barrier device on a surface located between said persons (e.g., such as a table-top, counter-top, work surface etc.), and operating said device such that a downwards-directed vertical air curtain is formed between said persons, wherein said air curtain is formed by air flowing downwards from air outlets in the upper part of the device and then being aspirated by air inlets in the lower part of the device, and wherein said aspirated air is then sterilized or decontaminated.

In one preferred embodiment, the personal air barrier device used in this method is the device as disclosed hereinabove and described in more detail hereinbelow. The present method, as disclosed above, is intended to protect one or more individuals from coming in contact with harmful or potentially harmful air, droplets, particles and/or aerosols that arise from, for example, speaking, shouting, singing, coughing and sneezing.

In one preferred embodiment of the method of the present invention, at least a portion of the sterilized or decontaminated air is recirculated to the air outlets.

It has been unexpectedly found by the present inventors that the optimum active barrier effect is obtained when the ratio of the volume flow rate of the air aspirated into the air inlets to the volume flow rate of the air leaving the air outlets is in the range of 3:1 to 10:1.

The above-disclosed method is intended to protect individuals by preventing person-to- person transmission of air and airborne particles and aerosols in many different places and settings, including (but not limited to) offices, shops, restaurants, other commercial premises, houses, apartments, public transportation and aircraft.

Further features and advantages of the present invention will become apparent as the description proceeds.

Brief description of the figures

Fig. l is a photograph showing two people located on either side of an air barrier device of the present invention, said device being place on a countertop.

Fig. 2 provides a perspective view of a typical embodiment of the air screen unit of the present invention.

Fig. 3 illustrates a first embodiment of the fan and sterilization unit of the present invention. Fig. 4 schematically illustrates the downward airflow within the confines of the air screen unit that creates the air barrier effect of the present invention.

Fig. 5 is a drawing that illustrates (at left) the air screen unit of the present invention when in its folded, storage and transport configuration; this drawing also shows (in the middle and right frames) the stages of opening the closed unit into its final working configuration. Fig. 6 schematically depicts a second embodiment of the present invention, in which a second fan is present in the lower fan and sterilization unit. Two different operational options are shown, both of which result in optimization of the air intake-to-outlet ratio.

Fig. 7 provides a close-up, cut-away perspective view of the two-fan lower unit shown in Fig. 6.

Fig. 8 schematically depicts a third embodiment of the device of the present invention, in which two fans are used: the first fan in the floor (fan and sterilization) unit, and the second fan fitted to the upper horizontal beam of the air screen unit.

Fig. 9 illustrates the flow of air into, and out of the lower fan unit in the embodiment shown in Fig. 8.

Fig. 10 schematically illustrates the air recirculation in the first embodiment of the present invention.

Fig. 11 schematically depicts a fourth embodiment of the device of the present invention, comprising two fans, one of which is fitted to the upper horizontal beam, while the second fan is located adjacent to the elongate base element of the air screen unit.

Figs. 12, 13 and 14 provide pictorial representations of the results of a CFD study of the barrier effect provided by a device of the present invention following simulated loud talking at (respectively) 0.6, 1.3 and 1.7 seconds after time zero.

Fig. 15 provides a pictorial representation of the results of the same CFD study that yielded the results shown in Figs. 12-14. In this figure, however, the position and velocity of the airflow is also shown.

Fig. 16 are photographs showing the results of a separation efficiency test of the device of the present invention (lower frame) compared with two plastic sheets (upper and middle frames). The white cloud seen in these figures represents the aerosol spray generated by loud talking.

Fig. 17 graphically depicts the results for aerosol cloud spread and density of the three barriers compared in the same separation efficiency test reported in Fig. 16; A = device of the present invention; B = 150x150 cm plastic sheet; C = 60x60 cm plastic sheet.

Fig. 18 schematically represents the key dimensions used to define and determine the volume of the moving air barrier generated by the air screen unit of the present invention. Fig. 19 compares a CFD simulation between the airflow provided by a device of the present invention fitted with both air inlets and outlets (right pane) and that provided by a device that has air outlets only, and therefore makes no provision for aspiration at the bottom of the airflow (left pane).

Detailed description of the preferred embodiments

The device of the present invention is suitable for use in the office, home, clinic or any other daily environment in which two or more people are located within possible contagion distance of each other, as shown in Fig. 1. Typically, the device is small enough, and of sufficiently light weight to allow it to be carried by a single person and moved from place to place, as required. The height and the width of the air screen created by the device are determined by the length of the upper and horizontal elements of the device, and are each typically within the range of 50-130 cm. These dimensions are, however, not to be understood as limiting the size of the presently disclosed device, which may be either smaller or larger in height and/or width than indicated by this range.

In its most general form, the device of the present invention comprises two sub-systems:

1. Air Screen Unit- this unit shapes the air screen within its borders.

2. Fan and Sterilization Unit - this unit circulates and sterilize the air in the system.

In some embodiments, however, the device may comprise more than one fan, while in other embodiments, at least one fan be incorporated into the air screen unit (rather than being in the form of a separate unit or subsystem).

The device of the present invention, comprising the two subsystems defined above, may function as an independent system. Flowever, in certain embodiments, two or more such devices may be connected, thereby creating a chain of air screens. The various elements contained within the device of the present invention will now be described with reference to Figs. 2-11.

Thus, in most embodiments of the device of the present invention, as shown in Fig. 2, the air screen unit of the device comprises the following three elongate elements: a horizontally disposed base element 1 (also referred to herein as a lower elongate horizontal member) having a first end and a second end, wherein said first end, during use, is connected to the lower end of a vertical post 2 (also referred to herein as an elongate vertical member), the upper end of which is connected to the first end of an upper horizontal beam 3 (also referred to herein as an upper elongate horizontal member). While the second end of said upper horizontal beam 3 may be connected to the second end base element 1 by an additional vertically disposed elongate post, in most embodiments (such as the one shown in Fig. 2) there is no such connection.

It is to be noted that each of the three elongate elements described above and depicted in Fig. 2 are hollow, being fitted with one or more internal lumens or cavities, and disposed such that the lumen of the base element 1 is continuous with one lumen of air tube 7. The internal lumen(s) of vertical post 2 is continuous with the corresponding lumen of upper horizontal beam 3. Typically, the air tube contains one or more internal lumens, and is used for the transfer of air from the air inlets and base element (i.e., the lower horizontal beam) 1 into the fan and sterilization unit, as well as the transfer of sterilized air from said fan and sterilization unit to the internal lumen of vertical post 2 and therefrom to the lumen of upper horizontal beam 3 and the air outlets on the lower surface thereof. In a particularly preferred embodiment, air tube 7 is a dual-lumen tube.

Fig. 3 depicts a first embodiment of the fan and sterilization unit of the present invention. In this embodiment, said unit comprises a case 4 which functions both as container for the other components of this unit, and as an acoustic body in order to reduce the transmission of noise and vibration into the air surrounding the device. In addition, the housing also acts as a UV-C blocker, preventing transmission of UV-C radiation from the UV sterilization bulb (when used) to the external environment. Optionally, the housing may contain a brushed aluminum (or similar) coating on its internal wall to maximize internal UV-C reflection. A rotating fan 5 is mounted on a spindle in the lower part of the unit. Preferably, the dimensions and speed of the fan are selected such that it is capable of producing a flow of air through the air screen unit, without being so powerful that it generates excessive noise or vibration or is overly large. The unit also comprises one or more means for sterilizing the air that enters the unit via an internal lumen of air pipe 7, including a removable (and therefore replaceable) UV bulb 6, and/or a filter, such as a high-efficiency particulate air (HEPA) filter.

The fan and sterilization unit of the device of the present invention may be powered by mains electricity from the electricity network. Alternatively, in other embodiments, the device may be configured as a rechargeable or battery-powered device.

In this first embodiment, shown in Figs. 2 and 3, the device functions as follows: fan 5 in the fan and sterilization Unit circulates the air to the air screen unit through a forward-flow conduit located within air pipe 7. The air is directed inside the inner cavity of vertical post 2 to the upper horizontal beam 3, following which the air is ejected through a plurality of specially designed outlet nozzles 43, thereby creating a series of downwardly moving focused, high speed air jets 42, as shown in Fig. 4, thereby producing a powerful and uniformly rectangular air barrier between the two opposite sides of the vertically downward airflow thus produced. The air is then aspirated into the one or more inlet apertures 45 formed in the upper surface of the base element 1. The design of the air inlet(s) and the air pressure parameters create an area of low pressure (i.e., a vacuum) that captures and retains the flow of air from upper beam 3 and ensures that it aspirates said air back into the system through said inlet apertures 45 into the base unit, thereby reducing or preventing the formation areas of sub-flow or turbulence (both within the confines of the air curtain, and also in the surrounding air in the room). Air is then directed back to the fan and sterilization Unit via a separate return flow lumen located within air pipe 7, to be fully sterilized by UV light bulb 6 (and/or a filter) and then recirculated to the air screen unit, to repeat the same process. In this manner, the volume of air that forms the vertically downward air barrier or curtain is constantly re-sterilized and recycled. The vertically directed air screen barrier thus formed eliminates, or at least significantly reduces, the exchange of air-borne particles and aerosols between people located on opposite sides of said barrier, by means of directing a strong and uniform flow of air from top to bottom without affecting the native air circulation in the room.

Fig. 6 depicts a second embodiment of the device of the present invention. In this embodiment, the fan and sterilization unit comprises two separate electric fans. The reason for the use of the additional lower fan is to increase the intake-to-outlet flow ratio, such that said ratio is in the range of between 3 and 10. Preliminary studies performed by the present inventors (data not shown) indicate that an optimum barrier effect is obtained using intake-to-outlet flow ratios within this range. Thus, as schematically shown in Fig. 6, the intake flow 64 (i.e., the volume flow of air entering the inlet nozzles or apertures in the base element) is greater than the outflow of air 62 that exits the nozzles or apertures in the upper horizontal element of the air screen unit.

These preferred intake-to-outlet flow ratios may be obtained in two different way. Firstly, as indicated by the letter Ά' in Fig. 6, the second fan in the lower unit may be used to vent a portion of the sterilized air into the general air space in the room, thereby reducing the airflow that is returned to the outlet nozzles in the upper horizontal beam. This version is shown in the close-up cut-away view of the fan and sterilization unit shown in Fig. 7, in which the two fans, an upper fan 71 and a lower fan 72, can be seen within the cavity of said unit. The set of arrows indicated by the letter Ά' show the portion of the air that evicted by lower fan 72 to the volume of air in the room.

In a second version, indicated by the letter 'B' in Fig. 6, the required flow ratio is achieved by having two sets of outlet nozzles (or apertures) in the upper horizontal beam: the first set (as in the previous embodiments) is directed downwards, and is used to create the air barrier effect. The second set of outlets is directed upwards. In this way, a portion of the air entering the upper horizontal beam does not pass downwards into the air barrier region, but rather is vented to the general room air space, via the upwardly pointing nozzles. Fig. 8 depicts a third embodiment of the device of the invention, in which two fans are used to create the airflow needed for the barrier effect. However, unlike in the previous embodiments, in addition to the single fan in the fan and sterilization unit (i.e., the lower or floor unit), a second fan is housed within the upper horizontal beam of the air screen unit. As shown in Fig. 8, this second fan is a linear or crossflow fan 82 that is incorporated within the upper horizontal beam. This fan pumps air from the room space through the outlet nozzles, thereby producing the air barrier effect indicated by the vertically downward arrows in Fig. 8. The air entering the base element through the inlet nozzles is then passed through a lumen in the air pipe (not shown) into the inner cavity of the fan and sterilization unit (generally situated on the floor). This unit is shown in more detail in Fig. 9, in which the air stream 92 originating in the air barrier and passing through the inlet nozzles enters the internal cavity of the fan and sterilization unit housing through the air pipe. A centrifugal pump 94 is then used to generate an output stream 96 (consisting of all of the input air) which passes through apertures in said housing to the air in the room space. It may be appreciated that this embodiment differs from those described hereinabove, which either recirculate a portion of the air (as shown in Figs. 6 and 7) or all of the air, as in the first embodiment, the airflow path of which is shown in Fig. 10. In contradistinction to these embodiments, the third embodiment (Figs. 8 and 9) does not recirculate the sterilized air, and this version is thus technically simpler to construct.

Fig. 11 depicts a fourth embodiment, which while functionally similar to the third embodiment described hereinabove (i.e., the air is not recirculated), the implementation with regard to the fan location is different. Thus, in this embodiment, both fans are located within, or in close proximity to, the air screen unit (i.e., the upper or table-top unit). This is seen in the device of Fig. 11, which has an upper, crossflow fan 112 housed within the upper horizontal beam, which, as in the third embodiment is used to pump air derived from the room space through the outlet nozzles, thereby creating the downwardly moving air barrier. However, in this embodiment (unlike the previous one), the air that passes through the lower inlet nozzles and then passes through the inner lumen of the base element is vented to the room air space by means of a second, centrifugal, fan 114 which is located adjacent to (and preferably connected to) the table-top air screen unit.

In some embodiments of the present invention, the air screen unit may further comprise a transparent sheet (e.g., of an acrylic or acetate material) which is adhered or otherwise fastened (e.g., by bolts or screws) to the margins of said unit (i.e., to one side of the upper horizontal beam, vertical post and base element). It is to be emphasized that in embodiments of this type, the largest portion of the barrier effect is provided by the air curtain generated by the moving air, and that the presence of the additional acetate barrier provides a relatively small effect. It may, however, be useful, for example, as a backup measure in the event of unexpected shut-down of the device fan(s), for example during an electric power outage. Thus, any of the four basic embodiments of the present invention may be modified by including the above-described acetate or acrylic sheet (or other transparent physical barrier) attached to the air screen unit.

In order to improve this barrier effect still further, the fan and sterilization unit may, in some embodiments, be fitted with a cooling unit to cool the air leaving the outlet and passing downwards towards the air inlet.

In some embodiments, the device may optionally further comprise additional means for sterilizing the air, such as heating the air, diffusion of air through detergent ora HEPA filter. Such means may either be located within the fan and sterilization unit, or at other locations within the present device.

The various embodiments of the device of the present invention may be used in the following manner: the user locates the air screen unit between himself and other person (e.g., on the top of a table or desk, with each person on either side of the device) in such a way that the eye contact passes through the area defined by the outer borders of the Air Screen Unit. Once the user activates the device the air separation screen (or "air curtain" or "air barrier") is created. The user and other person(s) are protected from airborne particles and aerosols produced by person sitting or standing opposition them during speech (and/or as a result of coughing or sneezing). The device also affords similar protection to other people who may incidentally be sitting, standing or passing close to the intended users.

When desired, most embodiments of the air screen unit may be folded into a compact conformation of small size (e.g., height H of 5-15 cm and length L 50-130 cm, as shown in Fig. 5), in order to facilitate transport and easy storage thereof. The largest dimension of the device in its folded conformation is thus the length of base element 51. Fig. 5 also illustrates the manner in which the folded device is opened prior to use. Thus, firstly the vertical post 52, which was previously contained with a recessed portion of base element 51 is moved out of said recessed portion into an upright position. Said post is maintained in this position by means of a simple mechanical locking element located within the hinge that is positioned between said post and base element 51. Then in a second stage, the upper horizontal beam 53 Is moved out of its storage position, within a recess in vertical post 52, and then locked into its horizontal working position.

The UV light bulb 6 (shown in Fig. 3) and/or air filter may be readily replaced by the user as needed.

Referring to Figs. 2 and 3, the first embodiment of the device described hereinabove is assembled in the following manner:

Base element 1 is connected to vertical post 2 using a lockable hinge. Similarly, vertical post 2 is connected to upper horizontal beam 3 with a lockable hinge. One end of air pipe or tube 7 is glued into and aperture formed in the end of base element 1 to which vertical post 2 is connected. The second end of said air pipe is glued into place in an aperture formed in the wall of the casing 4 of the fan and sterilization unit. The fan 5 is fixed in place within the cavity of casing 4. Finally, the UV sterilization lamp 6 is screwed into place in a threaded housing within the cavity of casing 4. The base element, vertical post and upper horizontal beam may be manufactured from either plastic materials (such as polyamides) or metals (such as aluminum) using standard techniques well known to the skilled artisan in the field, including additive manufacturing (i.e., 3-D printing), injection molding, machining and so on.

The air outlets and inlets may either be simple apertures formed within the body of the base element and upper horizontal beam, or may be formed from specially constructed (e.g., molded) nozzles inserted and fixed into such apertures. The base element and upper horizontal beam may contain any suitable number of, respectively, inlet apertures (or nozzles) and outlet apertures (or nozzles). In one embodiment, the outlets and/or inlets are formed within an elongated slit which occupies most or all of the length of the base element and upper horizontal beam. In some embodiments, said slit itself forms a single, continuous air outlet or inlet. In still other embodiments, the air inlet comprises two parallel slits separated by a small distance (e.g., 1-10 cm, and, in one particular embodiment, preferably in the order of 5 cm) formed along the upper face of the base element, said slits having a length the same as, or slightly less than, the length of said base element. As explained above, in some cases, each of said slits can themselves act as a continuous inlet, while in other cases, individual apertures and/or nozzles may be present within each slit, along its length. It is to be noted that one of the advantages of using parallel inlet slits (or parallel rows of inlet nozzles) is the fact that some cases there is a broadening of the air screen (or "air curtain") from top to bottom. In such situations it is therefore necessary to provide a correspondingly larger inlet area.

The casing of the fan and sterilization unit may be manufactured from either a metal, such as aluminum, or from any suitable polymer, such as (but not limited to) polyamide.

The air pipe (or tube) may be manufactured from any suitable polymeric material, including but not limited to a silicone material. In some preferred embodiments, the air pipe will contain two separate internal lumens that pass along its length, in order to permit the recirculation of air (e.g., the collection of air from the lower inlets in one lumen, and the transfer of that air -following UV light sterilization within the housing cavity -in the second lumen back to the air outlets in the upper horizontal beam).

In some embodiments of the invention (e.g., the sole fan in the first embodiment described hereinabove, and the lower fan in other embodiments in which two fans are used) the fan used to generate the airflow will be a centrifugal fan. Generally, in this type of fan (which is well known to skilled artisans in this technical field), a series of rotor blades are contained within a circular housing which is driven by an electrically powered motor to rotate at the desired speed. One example of such a fan is the centrifugal fan, model no. PB3N190B2E72T-00 provided by PBM Motor and Fan (Suzhou) Co., Ltd., China. This fan, which has a cylindrical outer form (190 mm outer diameter and 88 mm length), is fitted with seven impeller blades (made of polypropylene reinforced with glass-fiber).

In other embodiments, the device may comprise one (and in some cases, two) crossflow fans, or other similar fans that have an elongated, linear form (e.g., tubular axial fans or tangential fans). Such fans are typically used when it is required that one or both of the fans are mounted adjacent (or integral) to the upper horizontal beam and/or base element of the air screen unit (e.g., in some of the embodiments described hereinabove).

For the purposes of disinfecting the air that passed downwards within the confines of the air screen unit, any suitably sized replaceable UV-C bulb may be mounted in a threaded or bayonet-type socket fitted within the inner cavity of the fan and sterilization unit housing. Said bulb receives its power supply from the general supply (mains or battery) used to provide power to the fan(s). One non-limiting example of a UV-C bulb suitable for use in the present invention is a 16mm germicidal 16W lamp (model TUV TL Mini TUV 16W FAM) supplied by the Philips company.

A range of different operating fan speeds may be used to implement the invention and provide an acceptable air barrier. It is to be appreciated that there needs to be a trade-off between efficacy of air barrier function and potentially undesirable effects such as fan and air-flow noise, as well as excessive vibration, both of which can occur when the fans are rotating at an unnecessarily high speed, and which can interfere with the ability of the users to easily speak and be heard across the air barrier without the need to raise their voices. Of course, the volume flow of air (measured, for example in cubic feet per minute (CFM)), is dependent on both the air inlet velocity (i.e., a function of fan speed) and the linear dimensions of the air screen unit (table-top device). Thus, Fig. 18 schematically represents the key dimensions that determine the volume of the moving air barrier generated by the air screen unit of the present invention. In one typical example of the device, the values of these dimensions are as follows:

• B = C = 2 [cm]

• E = 70 [cm]

• D = 5 [cm]

Thus, for a device having these dimensions, it was found that an optimum air barrier effect (i.e. acceptable efficacy combined with mimization of noise and vibration and undesirable regions of sub-flow and turbulence) was obtained using an inlet air velocity of 2 meters/second, which yielded a volume flow rate of approximately 50 CFM. In some preferred embodiments, the device of the present inveniton may be operated such that the volume flow rate is in the range of 25-50 CFM, while in other embodiments the volume flow rate is 50-200 CFM. In one preferred embodiment, the volume flow rate is 50 CFM.

Some of the key features of the present invention will now be described in more detail in the following non-limiting examples. Examples Example 1

Computational fluid dynamics (CFD) study of the protection provided by the device of the present invention

In this study, CFD analysis was used to study the dynamics of aerosol cloud spread from the mouth and nose of the person speaking or shouting (or as a result of sneezing or coughing) and its elimination by the device of the present invention.

The CFD simulations used in this study were performed using the scFLOW-Cradle software package (supplied by MSC Software of Irvine, California, USA). This is a widely-used package, based on a polyhedral mesher, which solves Navia stokes set of partial differential equations which are used to model the movement of fluids. The dimensions and airflow speeds of the device of the present invention used in the modeling are the same as described hereinabove, with reference to Fig. 18.

The results of this analysis are shown in Figs. 12-14. Each figure provides a representation of the path followed by aerosols and airborne particles produced during loud speaking by a subject situated on one side of the air barrier device of the present invention, at various time periods beginning with the initiation of the test speaking and shouting.

Thus, Fig. 12 shows both the posititon of the emitted particles (small and large droplets) at -0.6 seconds following time zero. At this stage, none of the varioius-sized particles have reached the vertical midline of the air screen unit of the present invention (represented by an imaginary line connecting the upper horizontal beam 122 and base element 124). The larger and heavier air droplets are seen to fall downwards to the ground (or table surface), while the amaller and lighter-than-air particles float straight forward in the direction of the air curtain and the person who would be sitting on the far side thereof.

Fig. 13 represents the situation at 1.3 seconds after speech initiation. It will be noted that larger, heavier than air droplets fall to the ground at a substantial distance from the air screen, while smaller and lighter than air droplets float straight forward, the most advanced of them reaching the position of the air barrier.

Fig. 14 shows the position of the emitted particles 1.7 seconds after time zero. It may be seen from this picture that the larger particles are still in the same position as in the previous stage (i.e., still falling to the ground or table-top at a safe distance from the distance). The small droplets (aerosols), however, are now being fully blocked by the vertical air curtain and are drawn into the air inlets in base unit, and thereby removed from the immediate environment. It is also to be noted that no particles (either large or small) are seen on the other side of the barrier from the speaker.

Fig. 15 shows both the position of the particles emitted by the loud-speaking person, and the position and velocity of the airflow. It will be noted that the air curtain (or barrier) produced by the device is narrower in its upper portion (i.e., where the airflow leaves the air outlets), and broadens as it approaches the air inlets at the bottom of the device.

The results from this study show that the device of the present invention is highly effective in blocking the transfer of airborne particles arising from a person speaking with a loud voice, such that none of said particles would be able to pass to the other side of the air screen, thereby providing total protection for a second person located on that side.

Example 2

Separation efficiency test: comparison of a device of the present invention with plastic sheets

The goal of this study was to study the ability of a device of the present invention to prevent the transfer of an aerosol cloud from a speaker to a position on the far side of the air screen produced by said device (i.e., the position where an additional person would normally be seated). In addition, this study compared the blocking ability of the present device with that of two different-sized plastic screens (as are commonly used to provide a barrier to prevent viral transmission between individuals).

Method:

Following the initiation of loud speaking and using a vaporizer in order to produce a simulated aerosol cloud, a photograph of the subject, the barrier and the area on the far side of said barrier was taken from a lateral view every 2.5 seconds. This was performed for each of the three barriers tested:

1. Standard size plastic screen 60X60 cm.

2. Very large size plastic screen 150X150 cm.

3. A device of the present invention having the same dimensions as that used in Example 1.

The pictures were then analyzed for "simulated aerosol cloud" (SAC) propagation, which was measured using two different parameters: spread and density, defined as follows:

A grid consisting of 6X4 squares is added to each photograph picture on each side of the screen, each square measuring ~ lOXIOcm.

The spread of the aerosol cloud was measured by counting the number of squares in the photograph in which the aerosol cloud could be seen.

The density of the aerosol cloud was determining using the following semi-quantitative scale which is based on how white each square in the grid appears:

0 No aerosol particles

1 25% density

2 50% density

3 75% density

4 100% density Results:

Fig. 16 presents three photographs, obtained as described above, with the subject located on the left of each photograph, and with the 6x4 grid superimposed on the picture. The aerosol produced by the subject as a result of loud talking is seen as a white cloud in these pictures, with the barrier (device of the present invention or plastic sheet shown as a vertical white line or stripe to the right of the centre of the photograph.

The upper frame of Fig. 16 shows the pattern of aerosol spread seen using a 60x60 cm plastic screen as the barrier. It may be seen that the 60x60cm plastic sheet does not block the aerosol cloud, and that there is significant transfer of the aerosol cloud around and above the plastic screen to the other side thereof. The significance of this is that a plastic screen of these dimensions would not be able to protect a subject from contact with salivary droplets emanating from a person on the other side of the screen.

The middle frame of Fig. 16 shows the pattern of aerosol spread seen using a 150x150cm plastic sheet as the barrier. It may be seen that while the larger screen does prevent spread of the aerosol cloud to the other side, there is, however, an area of stagnation on the same side of the screen. This means that an aerosol cloud of high density would remain (unseen) close to the large plastic screen for a long period of time, acting as a potential source of infective material for whoever approaches the screen at a later time. In addition, the aerosol cloud would not be eliminated from the room space, and thus could travel to other areas within the room at a later time.

The lower frame of Fig. 16 shows the pattern of aerosol spread using a device of the present invention as the barrier. It may be seen from this frame that the present invention completely blocks transfer of the aerosol cloud from one side to the other of the air screen. Furthermore, the device also creates an airflow pattern that significantly reduces both spread and density of the aerosol cloud on the same side (by means of removal of the particles by the moving air cloud), thereby preventing the stagnation problems seen with the large plastic sheet. Fig. 17 is a graphical plot of the change in aerosol spread with time following initiation of the aerosol (loud speaking) for the three types of barrier (the data plotted on this graph were taken from the same experiments that yielded the photographs in Fig. 16.) It may be seen from this graph that only the device of the present invention (line A) actually reduced the aerosol spread over the course of the ten second period recorded. Also, the maximum spread seen (at 5 seconds) was less than half of the maximum achieved with the 150x150cm plastic screen (line B) and less than one quarter of the maximum spread achieved with the 60x60m screen (line C). The density values at 10 seconds are also indicated on each of the lines in this graph, and it is clear from these results that the present invention (A) was the most effective at reducing density (value of 1.0), while both plastic sheets yielded much higher density values - in particular the very large sheet (B; value of 1.8) which is an additional indication of the stagnation zone that forms next to this type of barrier.

The results of this study demonstrate that the air barrier device of the present invention is significantly more effective than either of the two plastic sheets tested with regard to providing an active barrier to airborne contaminants, and for removal of said contaminants from the room space.

Example 3

Computational fluid dynamics (CFD) comparison of the air barrier produced by the device of the present invention with a device lacking aspiration inlets

A further CFD study using the same methods as described in Example 1, above, was performed, in order to compare the flow characteristics of the air barrier produced by a device of the present invention with the airflow produced by a device in which there are no aspiration inlets.

The parameters and conditions used in this study (e.g., flow velocity, size, room space etc.) were identical for the two types of device that were modelled. Thus, the only difference between the two devices modelled is the absence of inlet aspiration in one of them. The results of this comparison are shown in Fig. 19. It may be clearly seen from this figure that the device of the present invention (right pane), fitted with both air outlets 192 and air inlets 194 generates a uniform air screen with minimal or no leakage or flow of air to the sides of said screen. However, in the absence of a lower aspiration inlet (left pane), strong horizontal air flow to both sides of the screen is generated, thereby creating undesirable uncontrolled airflow in all directions, together with areas of turbulence 196. These effects would clearly increase the ability of the aerosol cloud to float to the opposite sides of the screen, as well as increasing distance and time in which the airborne particles are present on both sides of the screen within the air space of the room.

We therefore conclude that the presence of the aspiration inlets in the present invention is essential for the generation of a uniform, narrow air curtain with minimal leakage and turbulence, and therefore for achieving maximum barrier effectiveness.