Patent Publication Number: US-2021190344-A1

Title: A diffuser head and an air cleaning apparatus comprising same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of PCT/DK2019/050120 filed Apr. 15, 2019, which claims priority to Denmark Patent Application PA201870242, filed Apr. 24, 2018, the entire content of both are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a diffuser head adapted for local application of air to a target, which diffuser head has a main body with an air inlet surface that has a first area, towards an air outlet surface, that has a second area that is greater than the first area. 
     BACKGROUND OF THE INVENTION 
     Many people suffer from respiratory conditions, such as asthma, allergies, Pneumonia, Chronic Obstructive Pulmonary Disease (COPD), chronic bronchitis, emphysema, lung cancer, cystic fibrosis, pulmonary hypertension, and bronchiectasis. Some are more unpleasant and dangerous than other and many people need medications to alleviate symptoms such as cough, wheezing, chest tightness and shortness of breath, etc. Asthma and chronic obstructive pulmonary disease (COPD) are significant public health burdens, and so are allergies, the most common being allergies to dust, mold, animal danders and other indoor allergens. 
     An air filter or room air cleaner may help an individual to breath better and reduce symptoms. In particular at places where smoking takes place. Secondhand smoke worsens respiratory conditions such as asthma symptoms and nasal congestion for small children. Almost all room air cleaners efficiently remove smoke from the room (as long as the air filter is large enough, the fan turned on, and the air filter is maintained). This also applies to places exposed to other pollution sources, such as traffic pollution and during the pollen season. 
     Room air cleaners only work in the room in which they are placed, so persons having the respiratory condition may need a separate room air cleaner for each of the rooms he/she stays in. Room air cleaners include ozone generators, whole-house air cleaners, and high-efficiency, particulate air (HEPA) filters. 
     The ozone generator is very expensive and ozone concentration difficult to control. Moreover ozone causes bronchospasm in people with asthma, even in low concentrations. 
     Whole-house air cleaners are installed in the heating or air-conditioning system of the house, which is a complicated and expensive task. Whole-house air cleaner, HVAC, system includes air filters designed to reduce the accumulation of dust and dirt in the ducts and coils of the system but can only remove large particles, not the small particles in the house that are inhaled into the lungs. 
     Known mechanical high-efficiency particulate air (HEPA) filter, as we known from vacuum cleaners, use a noisy fan that typically is installed at the ceiling or at the floor, to force air through a special screen that traps particles such as smoke, pollens, and other airborne allergens. However the fan cannot be directed at carpets, drapes or clothes, since this is likely to raise dust around the individual, so instead of helping the individual, he/she is exposed to more dust than before the fan was actuated. 
     The HEPA filters are however beneficial for e.g. asthma and allergy sufferers, because the HEPA filter traps very fine airborne particles, such as pollen and dust mite feces, which is the most frequent cause of allergy and asthma symptoms. 
     US patent application no. 2006252364 relates to an air supply device for obtaining zones of clean air in premises. The air supply device is connected to an air supply tube located at the ceiling and ends in an air permeable body with an inner part facing the air intake and an outer part facing the target. The inner part is of porous filtering material that offers resistance when air flows therethrough as waved partial air streams. The outer part is non-porous and have passages or channels which are rectilinear and of uniform thickness, and which extend in parallel relative to each other to generate a rectilinear partial air stream at the mouth of a passage and also farther away therefrom. US patent application no. 2006252364 specifically teaches that non-parallel partial air streams involves turbulence and are unfit for use, or at least cannot be used to deliver a well-defined, targeted local application of air. 
     German patent application no. DE2608792 relates to a nozzle for producing a radial displacement air flow to rooms. A spherical structure has a nozzle structure of stacked layers provided along an outer periphery. The nozzle structure inside the spherical structure extends a short distance from the outer periphery of the spherical structure towards the center of the spherical structure leaving a large free space above a combined air inlet surface of the air ducts of the stacked layer of the nozzle structure. The layered nozzle structure is composed of an outmost wire mesh layer closest to the outer periphery of the spherical structure, a multi-cellular type dust filter layer second from the outmost wire mesh layer, thus closer inside the spherical structure, and a textile layer third from the outmost wire mesh layer and closest inside the spherical structure. 
     Both the air supply device described in relation to US patent application no. 2006252364 and the air supply device of German patent application no. DE2608792 has a very large air empty space above the air inlet surface to the nozzles, thus at the location where the air to be diffused enters the air ducts. So air from the surrounding environment is drawn into and must pass this large space before the air reach the air duct inlets to be expelled through at the exit of the short nozzle layer, which constructions induce substantial turbulence and little control of the shape of the “clean zone”. 
     SUMMARY OF THE INVENTION 
     The present invention provides a solution to the above-mentioned disadvantages and problems. 
     According to an aspect of the present invention is provided a diffuser head of the kind mentioned in the opening paragraph, which can provide for local and controlled supply of purified air to a target. 
     According to yet an aspect of the present invention is provided a diffuser head of the kind mentioned in the opening paragraph, by means of which is established a defined shape of expelled air around a target. 
     According to an aspect of the present invention is provided a diffuser head having improved directional effect on through-going air and diffusing of air to a target, e.g. cleaned air, 
     According to an aspect of the present invention is provided an air cleaning apparatus comprising the diffuser head, which air cleaning apparatus can be set up on demand, instantaneously and at any desired location. 
     According to an aspect of the present invention is provided an air cleaning apparatus including a diffuser head that is smaller in size than the known air cleaning device described in e.g. German patent application no. DE2608792 and US patent application no. 2006252364 but able to provide similar or larger “clean zones”. 
     The novel unique whereby these and other aspects are achieved according to the present invention consists in that the main body has a plurality of continuous expanding air ducts extending lengthwise between the air inlet surface and the air outlet surface, wherein an air duct has a third cross-sectional area that increases continuously from an air duct inlet at said air inlet surface towards an air duct outlet at said air outlet surface. 
     Within the context of the present invention the term “air inlet surface” means the surface at the location where the air to be diffused enters the plurality of continuous expanding air ducts. 
     Within the context of the present invention the term “air outlet surface” means the surface at the location where the air leaves the plurality of continuous expanding air ducts. 
     Within the context of the present invention the term “zone” means the three-dimensional shape of the air flow when expelled by the diffuser head, where “clean zone” refers to a zone of clean air. The zone is typically cone-shaped due to the expanding air ducts. 
     The plurality of continuous expanding air ducts guides the diffused air towards the target as a laminar flow of air expelled via the air duct outlets. Because the air ducts diverge towards the respective air duct outlets at said air outlet surface the velocity of the air drops from the air duct inlet to the air duct outlet, whereby the exit pressure of air has been reduced to a level that does not raise dust around the target, such as an allergic person. Instead the individual is subjected to a gentle, unnoticeable volumetric flow of air, that, due to the plurality of diverging air ducts, creates a well-defined zone of air around him/her. When using the diffuser head of the present invention the individual can be in his/her individual comfortable zone of air in a room next to individuals being outside said zone. There is no visible demarcation line around the zone, just a local environment of air. Instead of centrally diffusing, optionally also cleaning, all air in a room the diffuser head diffuses, optionally cleans, just a small amount of the air in the room, and applies air locally to the person (s) in need of such. 
     The “main body” is delimited by an exterior circumferential wall that surrounds the most exterior air ducts of the plurality of air ducts. The main body has an upper surface/upper plane and a lower surface. The lower surface includes the air outlet surface. The air inlet surface may be the same as the upper surface if the air inlet surface is planar, or be slightly below such an upper plane, thereby leaving a very small head space above the air inlet surface. Within the context of the present invention the term “head space” refers exclusively to the space or volume between the upper plane, typically a plane that traverses the diffuser head below the tubular extension, and the air inlet surface. Said head space has a volume of maximum 10% of the total volume delimited circumferentially by the most exterior air ducts of the plurality of air ducts, the upper plane and the air outlet surface. 
     In a preferred embodiment at least the main body of the diffuser head is solid and the plurality of continuous expanding air ducts are bores or channels in the solid main body. 
     In another preferred embodiment at least the main body of the diffuser head is assembled of sub-components joined so that an air duct is generated by adjacent walls of the sub-components. A sub-component can e.g. be a panel. 
     Within the context of the present invention “cleaning of air” means the process of removing unwanted substances, such as dirt, infectious agents, and other impurities, from air taken into the diffuser head from an environment outside the infuser head. Within the context of the present invention the terms “purification of air” and “cleaning of air” are used interchangingly. “Purification of air” may however refer to a specific kind of cleaning of air, e.g. selectively removal of a certain impurity, or to a higher degree of cleaning air than the term “cleaning of air”, e.g. a higher percentage of removal or removal of more impurities. 
     To obtain a homogenous spreading of air onto a target the air ducts may advantageously extend divergingly from each other from the air inlet surface towards the air outlet surface, whereby the out-going air may assume a cone-shaped clean zone. 
     Turbulence in the marginal zone of the clean zone may be experiences as draft. To further reduce the risk of that the air that flows into the diffuser head may also pass through a turbulence reducing member, such as a porous member. The porous member may e.g. be a filter means upstream or downstream a pump means that supplies air from the surroundings to the diffuser head. 
     The interior surface of an air duct may preferably be without substantial irregularities, such as being smooth to further eliminate any turbulence-inducing factors. 
     Within the scope of the present invention the term “porous” or “porous material” means that the material has many small holes, so that air slowly can pass through. Thus a porous material distributes the air evenly above the diffuser head, which results in one or more of reducing air velocity, very even distribution of the air to and from the diffuser head, and reduction in the turbulence. 
     Purification of a flow of air from the surrounding environment may take place upon passage of a filter means selected to remove particles and/or chemicals present in said flow of air. Diffusion, cleaning and/or purification can stop at any time and the diffuser head be moved around to be arranged where need emerges. The shape of the diffuser head, the shape of the air ducts, the velocity and the pressure of the diffused air through the air ducts are some of the structures and feature responsible for the shape of the zone, and in some application of a reduced level of noise compared to air cleaners without local diffuser heads. 
     The diffuser head can be used to distribute already purified air or gases to a target, e.g. be used in operating rooms at hospitals, at maternity wards, at neo-natal wards, in relation to patients with burns, in relation to delivering certain gases locally at green houses, in cowsheds, stables, hen houses, pigsties, in drug production and food production, in air plains, busses, trains and cars, etc. This list is not exhaustive in that the diffuser head of the present invention can be used with and in relation to any target what so ever. 
     Furthermore, a diffuser head without filter means can be used to deliver already purified air. 
     Within the context of the present invention the term “velocity” means the speed of the air along an air duct. 
     It may be preferred that the plurality of continuous expanding air ducts is arranged about a longitudinal axis of the diffuser head in a uniform pattern, so that the individual within the zone can easily adopt an impression of the border of the clean zone to keep at least his/her airways inside said zone, such as a “clean zone” in case the diffuser head is used with a filter means, thereby breathing air of own choice. A uniform pattern may provide a concentric expansion of air, such as cleaned air from the surrounding environment, gasses or pre-cleaned air. 
     A longitudinal axis of an air duct may, at least for m, jority of the plurality of continuous expanding air ducts of a diffuser head, intersect its respective air duct outlet perpendicularly to its air duct outlet surface. So the longitudinal axis of an air duct may in a preferred embodiment be normal to the surface of the air duct outlet. 
     It should however be noted that the pattern of air ducts need not be uniform. As an example a not-uniform pattern may be preferred in some embodiments to customize and tailor a specific shape of the zone, in particular of a “clean zone” of cleaned or specific air around the target. 
     The third cross-sectional area of an air duct can have many different geometries. The third cross-sectional area of an air duct can for example be polygonal or follow a smooth, closed curve, e.g. be circular or oval. A diffuser head wherein the third cross-sectional area of an air duct is hexagonal, preferably regular hexagonal, utilizes the third cross-sectional area and axial length at its optimum. In this embodiment each air duct is a hexagonal frustum extending along the length of the diffuser head, and at least the majority of the plurality of continuous expanding air ducts may diverge from the longitudinal axis of the diffuser head by being closer to said longitudinal axis of the diffuser head, and having the smallest third cross-sectional area, at the air duct inlet, and spreading apart the closer the air ducts get to their respective air duct outlet, where the air duct has its largest third cross-sectional area. 
     It is to be understood that “a regular hexagon” is a hexagon that is both equilateral and equiangular. However alternatives are within the scope of the present invention. For example can the outline of all of the plurality of continuous expanding air ducts in a plane perpendicular to the longitudinal axis of the diffuser head have a substantially circular, elliptic or hexagonal third cross-sectional area. 
     All of the plurality of air ducts can have same third cross-sectional area, but different third cross-sectional areas are within the scope of the present invention. Further options include but are not limited to provide air ducts having one or more of different third cross-sectional areas, different outlines, and mixtures thereof to provide a diffuser head able of supplying different concentrations of clean air to selected localities within the zone, including within a “clean zone” in case the embodiment includes a filter means. Yet an option is to arrange the plurality of air ducts in concentric rings around the longitudinal axis of the diffuser head, or in any desired arbitrary pattern. Thus any pattern and third cross-sectional area of air ducts are within the scope of the present invention. It is however essential that an air duct extends the whole length from the air inlet surface and the air outlet surface and that air taken from the surrounding environment to be diffused and/or cleaned has no large space to fill up before it enters the plurality of air duct inlets at the air inlet surface, which space causes turbulence of air and little guiding of the air along an air duct. So a head space above the air inlet surface should be preferably be very little, whereby the length of an air duct gets long, so that the air flowing through the air duct is guided and can exit the diffuser head at minimum turbulence, preferably as a laminar flow, or at least a substantially laminar flow, of air to the target, and where the shape of the zone is well-defined. 
     In a preferred embodiment the air outlet surface can be planar, concave or convex, and/or the air inlet surface can be planar, concave or convex in order to further design the shape of the zone. 
     The overall figure of the plurality of air ducts may have 3D shape-similarity with the figure of a single air duct, whereby the interior space of the diffuser head can be fully occupied and utilized at its optimum. The number of air ducts of the plurality of continuous expanding air ducts can be optimized and the amount of goods between said air ducts be kept minimum, which reduces material cost of the diffuser head. This design also provides the user with a visual perception of the figure of the potential zone, but this design is not mandatory. The diffuser head may further be provided with a surrounding jacket or mantel that delimits a gap for accommodating the components needed to drive the diffuser head, including electronic components and optionally a motor. 
     As in the prior art the air outlet surface can be spherical or domed but the plurality of air ducts is much longer in running the whole length from the air inlet surface and the air outlet surface, which air inlet surface is located where the cross-section of the diffuser head at the air intake side of the diffuser head is smaller than the air inlet surface. 
     In contrast to the prior art air cleaning devices the main body that delimits and/or accommodates the diffuser head of the present invention leaves no or only little free space above the air inlet surface. 
     The size and shape of the air inlet surface may in one embodiment of the present invention almost correspond to the cross-section of the intake of air from the surrounding environment to the diffuser head. The intake of air may however be larger than the air inlet surface, e.g. to accommodate a wider filter means or turbulence reducing member. 
     Said intake of air may e.g. take place through a tubular extension facing away from the air inlet surface, which tubular extension may be wider than the air inlet surface and even expand away from the air inlet surface. The tubular extension is not part of the main body. 
     An optimum efficiency of a diffuser head of the present invention may have a plurality of continuous expanding air ducts having lengths that are equal to or longer than the smallest widths or diameters of the air duct inlets. In such an embodiment of a diffuser head the distribution of air is even and draft is avoided. Preferably the ratio between a length of an air duct and its smallest width or diameter of is at least 1.5. 
     At such ratios between length and width/diameter of an air duct the direction of the outlet air can be kept under control and turbulence be avoided. 
     Within the scope of the present invention the “length” of an air duct is the distance between the respective air duct inlet and air duct outlet taken at the longitudinal central axis of an air duct. The smallest width or diameter is at the air inlet surface. 
     The best results have been obtained when the air velocity of air entering the air duct inlets from the surroundings and passing along the air duct and out of the air duct outlets is at maximum 0.15 m/s at a distance of between 35-60 cm from the air outlet surfaces of the air duct outlets. Optionally said air velocity is as gentle as at maximum of 0.10 m/s at a distance of between 35-60 cm from the air outlet surfaces of the air duct outlets. 
     The present invention further relates to an air cleaning apparatus comprising the diffuser head described above. The air cleaning apparatus further comprises a pump means, such as a fan, that drives air from the surrounding environment. 
     Optionally air is driven by the pump means towards the diffuser head via a turbulence reducing member, which turbulence reducing member can be provided upstream or downstream the pump means. A suitable turbulence reducing member can be any porous member, including be a filter means, e.g. a HERA filter. A filter means can also be used in combination with another turbulence reducing member, such as a porous member, be arranged adjacent the other turbulence reducing member, spaced apart from the other turbulence reducing member, and be on an opposite side of the pump means than the other turbulence reducing member. The pump means air drives air from the surrounding into the plurality of air duct inlets at the air inlet surface, along the lengths of the plurality of air ducts, and out of the plurality of air duct outlets at the air outlet surface towards the target thereby creating a clean zone for the target. 
     The present invention is however not limited to filter means in form of HERA filters or carbon filters, or to use filter means at all, in that a diffuser head can be used to diffuse any kind of air or gas, whether it is pre-cleaned, pre-purified, already clean, already pure, or not cleaned at all. 
     Any filter means that can clean or purify a flow of air of airborne particles, and optionally of chemicals, are comprised within the scope of the present invention. One alternative filter means can e.g. be an activated carbon filter. 
     The pump means may be e.g. a fan. Various locations of pump means and turbulence reducing member are possible within the scope of the present invention. The turbulence reducing member can e.g. be arranged at a location selected from the group of locations including: between the air inlet surface and the pump means, on the side of the pump means opposite the side of the pump means facing the air inlet surface, or in an air intake tube or hose remote from the diffuser head. Optionally also the pump means can be provided remote from the turbulence reducing member means can differ between embodiments. 
     The turbulence reducing member may advantageously be inserted between the pump means and the diffuser head, or the turbulence reducing member can be provided on the side of the pump means opposite the diffuser head. Preferably the turbulence reducing member and the pump means can be inserted in a pipe piece in extension of the air inlet surface of the main body of the diffuser head. 
     The air cleaning apparatus may further comprise a tubing adapted for intake of air, e.g. by being coupled to pipe piece in extension of the air inlet surface of the main body of the diffuser head, to be diffused, optionally, cleaned and delivered to the target via the diffuser head. 
     The pump means may be the means that that drives air from the surroundings into the plurality of air duct inlets at the air inlet surface, in which embodiment the pump means, e.g. a fan, can be selected to provide the air velocity of maximum 0.15 m/s at a distance of between 35-60 cm from the air outlet surfaces of the air duct outlets, optionally an air velocity of maximum 0.10 m/s at a distance of between 35-60 cm from the air outlet surfaces of the air duct outlets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described below in further details by way of exemplary embodiments with reference to the accompanying drawing in which 
         FIG. 1 a    is a perspective view seen from the air inlet surface of a first embodiment of a diffuser head according to the present invention; 
         FIG. 1 b    is a sectional view taken along line  1   b - 1   b  in  FIG. 1   a;    
         FIG. 1 c    shows the diffuser head seen in  FIG. 1 a    from the air inlet surface; 
         FIG. 1 d    shows the diffuser head seen in  FIG. 1 a    from the air outlet surface; 
         FIG. 1 e    shows the diffuser head seen in  FIG. 1 a    from the side; 
         FIG. 2 a    is a perspective view seen from the air inlet surface of a second embodiment of a diffuser head according to the present invention; 
         FIG. 2 b    is a sectional view taken along line  1   ib - 1   ib  in  FIG. 2   a;    
         FIG. 2 c    shows the diffuser head seen in  FIG. 2 a    from the air inlet surface; 
         FIG. 2 d    shows the diffuser head seen in  FIG. 2 a    from the air outlet surface; 
         FIG. 2 e    shows the diffuser head seen in  FIG. 2 a    from the side; 
         FIG. 3 a    is a perspective view seen from the air inlet surface of a third embodiment of a diffuser head according to the present invention; 
         FIG. 3 b    is a sectional view taken along line IIIb-IIIb in  FIG. 3   a;    
         FIG. 3 c    shows the diffuser head seen in  FIG. 3 a    from the air inlet surface; 
         FIG. 3 d    shows the diffuser head seen in  FIG. 3 a    from the air outlet surface; 
         FIG. 3 e    shows the diffuser head seen in  FIG. 3 a    from the side; 
         FIG. 4 a    is a perspective view seen from the air inlet surface of a fourth embodiment of a diffuser head according to the present invention; 
         FIG. 4 b    is a sectional view taken along line IVb-IVb in  FIG. 4   a;    
         FIG. 4 c    shows the diffuser head seen in  FIG. 4 a    from the air inlet surface; 
         FIG. 4 d    shows the diffuser head seen in  FIG. 4 a    from the air outlet surface; 
         FIG. 4 e    shows the diffuser head seen in  FIG. 4 a    from the side; 
         FIG. 5 a    is a perspective view seen from the air inlet surface of a fifth embodiment of a diffuser head according to the present invention; 
         FIG. 5 b    is a sectional view taken along line Vb-Vb in  FIG. 5   a;    
         FIG. 5 c    shows the diffuser head seen in  FIG. 5 a    from the air inlet surface; 
         FIG. 5 d    shows the diffuser head seen in  FIG. 5 a    from the air outlet surface; 
         FIG. 5 e    shows the diffuser head seen in  FIG. 5 a    from the side; 
         FIG. 6  is an exploded perspective view of an air cleaning apparatus comprising the fourth embodiment of a diffuser head; 
         FIG. 7  shows the same in assembled state oblique from above; 
         FIG. 8  shows the same from above; 
         FIG. 9  is a perspective view of the air cleaning apparatus seen in  FIG. 6  in operative state in relation to a target; 
         FIG. 10  is an exploded perspective view of a modification of the air cleaning apparatus seen in  FIG. 6 ; 
         FIG. 11  shows in exploded perspective a sixth embodiment of a diffuser head according to the present invention, 
         FIG. 12  shows the headspace above the air inlet surface illustrated on the first embodiment; 
         FIG. 13  shows the cleaning efficiency of the air cleaning apparatus shown in  FIGS. 6-9 ; and 
         FIG. 14  shows the air velocity at difference distances from a longitudinal axis of a diffuser head situated about 35 cm from the target. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The first embodiment of a diffuser head  1  seen in figs,  1   a - 1   e  is cone-shaped. A plurality of air ducts  2 , all having regular hexagonal cross-sections, extends divergingly from each other from an air inlet surface  3 , with a first area A 1  towards an air outlet surface  4  with a second area A 2 . As illustrated best in  FIGS. 1 c  and 1 d    the third cross-sectional area A of an air duct inlet  5  at the air inlet surface  3  is much smaller than the third cross-sectional area A of an air duct outlet  6  of said air duct  2  at the air outlet surface  4  due to the air ducts  2  expanding the whole of its length from said air inlet surface  3  to said air outlet surface  4 , as seen in  FIG. 1 b   . At the air inlet surface  3  the diffuser head  1  is provided with a short tubular extension  7  for one or more of accommodating e.g. an optional filter means (not shown) coupling to a supply tube for supplying air from the surrounding environment, coupling to a pipe piece for accommodating a pump means, as will be described later in relation to yet an embodiment of a diffuser head. The short tubular extension  7  extends towards the air inlet surface  3  into the conical main body  8  of the diffuser head  1 , which conical main body  8  has an exterior circumferential wall  9  around the plurality of air ducts  2 , an upper plane PI and a lower surface SI. The upper plane PI is the same as the air inlet surface  3 , so there is no head space between the tubular extension  7 , which is not part of the main body  7 , and the air inlet surface  3 , as seen best in  FIG. 1 b   . The lower surface SI is the same as air outlet surface  4 . For the first embodiment of a diffuser head  1  of the present invention the air inlet surface  3  and the air outlet surface  4  are planar and parallel. The partition walls  10  between the adjacent air ducts  2  of the plurality extend the whole length from the air inlet surface  3  to the air outlet surface  4  and the most exterior air ducts of the plurality of air ducts terminate in the circumferential wall  9 . 
     A second embodiment of a diffuser head  11  is seen in  FIGS. 2 a -2 e   . The second embodiment of a diffuser head  11  differs from the first embodiment of a diffuser head  1  mainly in having a main body  12  that has an exterior circumferential wall  13  that is trumpet-shaped or flared instead of conical, and in the air outlet surface  16  being concave, when seen from below the diffuser head  11 . The second embodiment of a diffuser head  11  has an upper plane P 2  and a lower surface SI. The upper plane P 2  is the same as the air inlet surface  15 , so there is no head space between the tubular extension  7 , which is not part of the main body  12 , and the air inlet surface  15 , as seen best in  FIG. 2 b   . The lower surface S 2  is the same as the air outlet surface  16 . A plurality of air ducts  14 , all being regular or close to regular hexagonal, has third cross-sectional areas A at the air inlet surface  15  but irregular hexagonal third cross-sectional areas A 1  at the air outlet surface  16  due to the trumpet- or flared shape of the main body  12 . The plurality of air ducts  14  extends divergingly from each other from the air inlet surface  15  towards the air outlet surface  16 . The air ducts  14  closest to the exterior circumferential wall  13  having the most irregular hexagonal third cross-sectional areas A 1 , and the air ducts  14  closest to the center longitudinal axis of the diffuser head  11  having the most regular hexagonal third cross-sectional areas A. The air ducts  14  expand the whole of their length, as seen in  FIG. 2 b   . At the air inlet surface  15  the diffuser head  11  is provided with a short tubular extension  7  to be used as described for the first embodiment of a diffuser head  1 , The partition walls  17  between the adjacent air ducts  14  of the plurality extend the whole length from the substantially planar air inlet surface  15  to the substantially planar air outlet surface  16 . The most exterior air ducts of the plurality of air ducts terminate in the circumferential wall  13 , which has an increased thickness at the upper plane due to the trumpet- or flared shape of the main body  12 . 
     A third embodiment of a diffuser head  18  is seen  FIGS. 3 a -3 e   . The third embodiment of a diffuser head  18  is a modification of the first embodiment of a diffuser head  1  and differs from said first embodiment of a diffuser head  1  mainly in that the air outlet surface  19  is convex, when seen from below the diffuser head  18  opposite the air inlet surface  3 , and in being less conical. However for the third embodiment of a diffuser head  18  the main body  20  is also conical, and the main body of the diffuser head  18  also has a tubular extension  7 ′, but then tubular extension ‘I’ is longer than the tubular extension  7  of the first embodiment of a diffuser head  1 . The convex curvature of said air outlet surface  19  compensates for the small conicity of the exterior circumferential wall  21  of the main body  20  to still offer a large air outlet surface  19 . The third embodiment of a diffuser head  18  has an upper plane P 3  and a lower surface S 3 . The upper plane P 3  is the same as the air inlet surface  3 , so there is no head space between the tubular extension  7 ′, which is not part of the main body  20 , and the air inlet surface  3 , as seen best in  FIG. 3 b   . The lower surface S 3  is the same as air outlet surface  19 . The air ducts  22  expand the whole of their length, as seen in  FIG. 3 b    and has third cross-sectional areas A that are regular hexagonal except from the parts protruding beyond the exterior circumferential wall  21 . At the outlet surface  19  the air duct outlets  22  thus curve in accordance with the convex curvature of said outlet surface  19 . 
     The third embodiment of a diffuser head  18  can e.g. be made by  2 K molding. The diffuser head  18  can thus be made as a rigid component of a thermosetting plastic polymer or of a thermoplastic polymer and the tubular extension ‘I’ be made in same molding operation of an elastomeric polymer, thereby providing a diffuser head  18  with the ability to be elastically fitted on a coupling piece of a supply tube for supplying the air from the surrounding environment to be diffused and/or cleaned. 
     An elastic tubular extension can be provided on any of the embodiments of a diffuser head within the scope of the present invention. Such a diffuser head can be mounted on coupling pieces with diameters with mounting tolerance and mounting can be done without tools, and in different installations. 
     A fourth embodiment of a diffuser head  23  is seen  FIGS. 4 a -4 e   . The fourth embodiment of a diffuser head  23  differs from the first embodiment of a diffuser head  1 , the second embodiment of a diffuser head  11  and the third embodiment of a diffuser head  18  in that the main body  24  is hemispherical and delimited by a hemispherical exterior circumferential wall  25 , thus the air outlet surface  26  is convex as for the third embodiment of a diffuser head  18 . The air ducts  27  are separated by partition walls  17 ′ and expand the whole of their length from the air inlet surface  28  to the air outlet surface  26 , as seen in  FIG. 4 b   , and has third cross-sectional areas A that are regular hexagonal. The fourth embodiment of a diffuser head  23  also differs from the previously discussed embodiments in that the tubular extension  29  has locking webs  30   a ,  30  that protrude radially, inwards to mate below corresponding locking webs of another component to assemble the diffuser head. The fourth embodiment of a diffuser head  23  has an upper plane P 4  and a semi-hemispherical lower surface S 4  that includes the air outlet surface  26  defined by the plurality of air duct outlets. The upper plane P 4  is the same as the air inlet surface  28 , so there is no head space between the tubular extension  29 , which is not part of the main body  24 , and the air inlet surface  28 , as seen best in  FIG. 4   b.    
     An alternative configuration of a tubular extension that can lock with other components may in the alternative have an internal or external screw thread or snap-fitting means. 
     A fifth embodiment of a diffuser head  31  is seen  FIGS. 5 a -5 e   . The fifth embodiment of a diffuser head  31  differs from the fourth embodiment of a diffuser head  23  in the tubular extension being the tubular extension  7  of the first embodiment of a diffuser head  1 , and in that the air ducts  32 , that are separated by partitions walls  17 ′ expand the whole of their length from the air inlet surface  33  to the air outlet surface  34 , has third cross-sectional areas A that are circular. The fifth embodiment of a diffuser head  31  has an upper plane P 5  and a semi-hemispherical lower surface S 4  that includes the air outlet surface  34  defined by the plurality of air duct outlets. The upper plane P 5  is the same as the air inlet surface  33 , so there is no head space between the tubular extension  7 , which is not part of the main body  24 , and the air inlet surface  28 , as seen best in  FIG. 4   b.    
     The wall thickness of the partition walls is kept as little as possible to obtain the largest possible number of air ducts within the main body, and still preserve the dimensional configuration and structural stability of the diffuser head. 
       FIGS. 6, 7 and 8  illustrate an air cleaning apparatus  35  comprising, as an example, the fourth embodiment of a diffuser head  23 , a filter means  36 , such as e.g. a HEPA filter, a pump means  37  in form of a fan, and a connection piece  38  that also may serve as a housing for the filter means  36  and the pump means  37 . The connection piece  38  is then connected to an air supply tube or hose (not shown). The pump means may be driven by an electric motor (not shown) also stored in the connection piece  38 . Alternatively, the pump means may be located remote from the diffuser head  23 , e.g. in the air supply tube (not shown). 
       FIG. 9  is a perspective view of the air cleaning apparatus  35  seen in  FIG. 7  in operative state in relation to a target  39 , which target in the present example, is a baby. The air cleaning apparatus  35  spreads the flow of purified air produced by the diffuser head  23  into a cone-shaped clean zone  40 . 
       FIG. 10  is an exploded perspective view of a modification  41  of the air cleaning apparatus seen in  FIG. 6 . The air cleaning apparatus  41  differs from the air cleaning apparatus  35  in that the axial order of the filter means  36  and the pump means  37  has been reversed, and in that a counter-rotation device  42  has been inserted between the pump means  37  and the diffuser head  23  to compensate for potential turbulence induced by the pump means  37  to thereby supply a substantially balanced flow of air into the air ducts to further ensure that the flow of diffused air out of the plurality of air ducts is as close to laminar as possible. In  FIG. 10  the connection piece  38  is illustrated transparent to show that the filter means  36  may be positioned inside it. 
     It is emphasised that any of the components above the air inlet surface may be wider than the air inlet surface e.g. by virtue of extending radially into the aforementioned surrounding jacket, or due to the tubular extension expanding away from the air inlet surface, or due to the exterior wall at the air inlet surface enlarges the exterior perimeter of the diffuser head at the location of the air inlet surface. 
     The filter means may be arranged spaced from the air inlet surface, or simply rest on the air inlet surface. 
     It should be noted that the air outlet surface is at least double as large than the air inlet surface. 
     In the first embodiment of a diffuser head  1 , seen in figs,  1   a - 1   e , the air outlet surface is about 7 times larger than the air inlet surface. In the second embodiment of a diffuser head  11  seen in  FIG. 2  the air outlet surface is about 5 times larger than the air inlet surface. In the third embodiment of a diffuser head  18  seen in  FIGS. 3 a -3 e   , the fourth embodiment of a diffuser head  23  seen in  FIGS. 4 a -4 e   , and in the fifth embodiment of a diffuser head  31  seen in  FIGS. 5 a -5 c    the air outlet surface is about 2.5-3 times larger than the air inlet surface. 
       FIG. 11  shows a sixth embodiment of a diffuser head  43 . The sixth embodiment of a diffuser head  43  is a modification of the fourth embodiment of a diffuser head  23  seen in  FIGS. 4 a -4 e   . in that the overall shape is oblong. The diffuser head  23  has been divided into diffuser head parts  23   a ,  23   b  along a plane taken along the longitudinal axis of the diffuser head  23 . A longitudinal diffuser element  44  having same or different air ducts have been interposed between the diffuser head parts  23   a ,  23   b.    
     None of the embodiments of a diffuser head of the present invention has air ducts that extend perpendicular to the longitudinal axis A of the respective diffuser head, as illustrated to the left in  FIG. 11 . All air ducts may preferably extend at an angle a less than 90° from the longitudinal axis A of a diffuser head, e.g. less than 85°, less than 80°, less than 75°, less than 75° less than 60°, less than 55°, less than 50°; less than 45°, less than 40°; less than 35°, less than 30°; less than 25°; less than 20°; less than 15°, less than 10°; or less than 5°. 
     The diffuser head of the present invention can have various 3D configurations. E.g. the air inlet surface and/or the air outlet surface can be oblong, such as elliptic, or just elongate, as in  FIG. 11 . Furthermore, several diffuser heads can be coupled to an air intake manifold, or to individual air intake tubes or hoses. 
     As seen in  FIG. 12  of a first embodiment of a diffuser head  1  the headspace H above the air inlet surface  6  and below the upper surface or upper plane PT is substantially smaller than the total volume of the main body  9  of the first embodiment of a diffuser head  1 . The same applies for all embodiments of the present invention, wherein said head space always is below 10% of the total volume delimited circumferentially by the most exterior air ducts of the plurality of air ducts; the upper plane and the air outlet surface. 
     Example 
     The cleaning apparatus shown in  FIGS. 6-9  was tested with the diffuser head at a distance of 35 cm from a 32° C. warm target simulating the baby seen in  FIG. 9 . 
     The diffuser head had a diameter of 132 mm at the air inlet surface and a diameter of 168 at the air outlet surface had 313 air ducts of hexagonal cross-section. The smallest width of a hexagonal air duct is between parallel sides of the hexagon. The smallest width is at the first area A 1  and is 6 mm. The third cross-sectional area A increases so that a larger outlet width is at the second area A 2 , which outlet width is 7.2 mm for the shortest air duct that has a length of 20 mm, and which outlet width is 8.9 mm for the longest air duct that has a length of 32 mm. As common for all embodiment of diffuser head of the present invention the length of an air duct becomes shorts the closer to the most exterior air ducts, typically gradually shorter due to lack of head space. The headspace was zero in that the air inlet surface was plane and straight. 
     The tubular extension had a length of 20 cm. 
     The pump means was a 100×25 mm centrifugal air pump bringing an air flow from the surroundings to the diffuser head at an average velocity of 0.25-0.30 m/s via a 136×32 mm HEPA filter having a pressure drop of 18 Pa. 
     The particle count for particles sized 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 mpi was measured both in the surrounding air as reference, and in treated air emitted by the diffuser head using an optical particle counter of type Lasair 3, 310B from Particle Measuring Systems. The results for particles sized 0.3 mpi are shown in  FIG. 13 . 
       FIG. 14  shows the air velocity at difference distances from a center axis of a diffuser head situated about 35 cm from the target. The farther away from the center axis the lower the velocity. The distance 0 corresponds to about 5 cm above the center of the target. 
     It can be concluded that the diffuser head of the present invention provides a clean zone without turbulence and where draft at the “border” of the clean zone is inferior. Thus the clean zone will not be noticed by the target at all. Furthermore the particle count reduction is substantial and up to at least 70% just above the target. Similar test has shown particle count reduction of 80%, and even further reduction might be possible, e.g. by change of filter means.