A FACE SHIELD FOR BEING ARRANGED IN FRONT OF A PORTION OF THE FACE OF A USER

Abstract

A face shield for being arranged in front of a portion of the face of a user, comprising: fastening means, a headgear, wherein the fastening means attach the upper portion of the face shield to the headgear, being characterized by: the face shield: being adaptable to a head shape of a user, the face shield provides a sealing contact with the temple areas and extending along a longitudinal z axis downward from the headgear, and being provided with a pre-shaped U-shape which will provide a pinching effect causing the face shield to connect in an air tight manner to the users temple areas and downwards due to local stress along the z axis in the shield, thus adapting to different head profiles along the z-axis when arranged over the face for providing a channel able to lead an airstream past the eyes, nose and mouth of the user.

Claims

1.-22. (canceled)

23. A face shield for being arranged in front of a portion of the face of a user, comprising: fastening means, a headgear, wherein the fastening means attach an upper portion of the face shield to the headgear, wherein the face shield: is adaptable to a head shape of a head of a user, the face shield providing a sealing contact with temple areas and extending along a longitudinal z axis downward from the headgear, and is provided with a pre-shaped U-shape to provide a side pinching effect causing the face shield to connect in an air tight manner to the temple areas and downwards due to local stress along the z axis in the face shield, thus adapting to different head profiles along the z axis when arranged over the face for providing a channel able to lead an airstream past eyes, a nose, and a mouth of the user, the face shield having a curved form shape around a longitudinal axis of the face shield, the curved form being maintained by the face shield having one or more longitudinally crease folds arranged to be in a lower portion of the face shield, such that a vertical sight field and a horizontal sight field through the face shield is not disturbed by any crease folds and thereby minimizing glare and increase the side pinching effect.

24. The face shield according to claim 23, wherein side portions of the face shield are substantially flat and parallel with a side of the head of the user from a temple and downwards, maintaining flexibility and adaptability to changing head shape along the z axis.

25. The face shield according to claim 23, the face shield having a form provided by one of a vacuum form process, a thermoforming process, or pre-molded in a form.

26. The face shield according to claim 23, wherein the face shield is made of one or more of: transparent material, semi-transparent material, polymer/plastic, pressure formed polymer/plastic, heat formed polymer/plastic, transparent or semi-transparent glass, transparent or semi-transparent fibers, or transparent or semi-transparent composites.

27. The face shield according to claim 23, wherein the headgear comprises an air supplying device and an air distribution device for channeling air from the air supplying device to a forehead area and wherein the air is channeled from the forehead area down past the face of the user when the air supplying device is activated.

28. The face shield according to claim 27, wherein the air supplying device comprises an air purifying device.

29. The face shield according to claim 27, wherein the face shield stretches downward past a cheek of the user, and one or more filter strips are attached on an inside of a bottom part of the face, and thus providing an effect of filtering away aerosols from exhaled air of the user.

30. The face shield according to claim 27, wherein a front outlet device is formed to distribute air from the air supplying device along a width of the forehead of the user and behind an upper portion of the face shield where the fastening means attach the face shield to the headgear, in a semi laminar manner, such that air with high carbon dioxide (CO2) content is displaced from area in front of the eyes, the nose and the mouth.

31. The face shield according to claim 30, wherein the front outlet device comprises an air laminating mesh spread along the front outlet device.

32. The face shield according to claim 30, wherein the front outlet device comprises a plurality of outlet nozzles/output orifices spread along the front outlet device.

33. The face shield according to claim 32, wherein the plurality of outlet nozzles/output orifices are distributed over an area extending sideways and outwards to increase an air exit area behind the upper portion of the face shield where the fastening means attach the face shield to the headgear.

34. The face shield according to claim 33, wherein the plurality of outlet nozzles/output orifices are distributed over an area extending outwards from an innermost position being a minimum distance from the forehead portion above the eyes to provide an airstream having less draft close to the eyes.

35. The face shield according to claim 23, wherein a frame is provided along portions of the face shield to enhance form fitting features pinching the face shield in a biased enclosing manner around the face area of the user.

36. The face shield according to claim 28, wherein the air purifying device comprises: a motor, a power source, an impeller being rotated by the motor, and a rotating filter being rotationally connected to the impeller.

37. The face shield according to claim 36, wherein the rotating filter comprises a pleated filter.

38. The face shield according to claim 36, wherein the impeller comprises a plurality of fan blades arranged radially extending from a center cone, the center cone having a tapering form towards a first air intake side, and the fan blades being formed to provide an axial fan at the air intake side, such that air is set in motion with a rotational flow pattern, the fan blades being formed to provide a radial fan towards the circumferential outlet side of the impeller, such that air is pushed towards the rotationally connected filter with a substantially uniform distribution over the inlet channels of the filter in a z direction.

39. The face shield according to claim 36, wherein the air distribution device is formed in an enclosing manner around the circumferential outlet of the impeller and the filter and further comprising a conduit forming a channel for the air flow from the enclosure around the impeller and filter towards and through the front outlet device and to the forehead area of a user.

40. The face shield according to claim 37, wherein the air filters have a cylindrical form, wherein the face shield is configured according to the relation Gu=fh*pr/(2*ro*ε{circumflex over ( )}¼)>0.8, wherein Gu number correlates to a function of the commercial usefulness based on, and accounting for, needs of the user, such as CADR, dB, product size, functioning and cost, wherein pr=/pleat spacing, and pleat spacing is the distance between two adjacent pleat tops on the inner radius, and ε is the ASHRAE efficiency.

41. The face shield according to claim 40, wherein the air filters have a height between 10 and 30 mm, and an outer diameter between 65 and 105 mm.

42. The face shield according to claim 41, wherein the air filters have a height of 25 mm, and an outer diameter of 85 mm.

43. The face shield according to claim 23, wherein the fastening means comprise an lock/unlock feature enabling the face shield to attach and to detach from the headgear and thereby providing an replaceable face shield function.

44. The face shield according to claim 41, wherein the air filters have a height between 15 and 25 mm, and an outer diameter between 75 and 95 mm.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0042] The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.

[0043] FIG. 1A shows a side perspective of the face shield mounted to a head gear worn by a user according to an embodiment of the present disclosure.

[0044] FIGS. 1B and 1C shows variations of the face shield mounted with an arched and a more flat front connection to the headgear, translated to different angle and glare of front and side portions, and the latter biased abilities.

[0045] FIG. 1D shows a side view of a further embodiment of the invention according to present disclosure.

[0046] FIG. 1E shows an oblique view from below of the embodiment of FIG. 1D.

[0047] FIG. 1F and FIG. 1G show prototypes of the embodiment of FIG. 1D.

[0048] FIG. 1H shows a face shield of FIG. 1D comprising air permeable sponge for chin and jaw region support.

[0049] FIG. 1I shows a face shield of FIG. 1D seen from inside and below.

[0050] FIG. 2 shows a side perspective of the headgear and inside arranged air purifying device according to an embodiment of the present disclosure.

[0051] FIG. 3A shows a front view of the face shield mounted to a head gear according to an embodiment of the present disclosure.

[0052] FIGS. 3B and 3C shows a second embodiment of the face shield seen from front and above respectively.

[0053] FIG. 4 shows a side perspective of the face shield with exhale filters mounted to a head gear according to an embodiment of the present disclosure.

[0054] FIG. 5 shows a bottom up perspective of the face shield mounted to a head gear according to an embodiment of the present disclosure.

[0055] FIG. 6 shows an oblique bottom up perspective of the face shield mounted to a head gear according to an embodiment of the present disclosure.

[0056] FIG. 7 shows an oblique side cross section perspective of the head gear according to an embodiment of the present disclosure.

[0057] FIG. 8 shows a side cross section perspective of a portion of the head gear holding the impeller, filter and motor according to an embodiment of the present disclosure.

[0058] FIG. 9 shows an oblique top cross section perspective of a portion of the head gear holding the impeller, filter and motor with focus on the pleated filter configuration according to an embodiment of the present disclosure.

[0059] FIG. 10A illustrates a cylindrical formed pleated filter seen at an oblique angle

[0060] FIG. 10 B is the filter in FIG. 10A seen from above with a section of the pleats enlarged

[0061] FIG. 11A describes the pressure graph over the axial to radial impeller and filter

[0062] FIG. 11B illustrates the value of a filters' Gu-number according to the present invention

[0063] FIG. 11C is a concrete case study of performance CADR/L at 35 dB with various Gu for present invention v.s. typical prior art

[0064] FIG. 11D is a concrete case study of performance CADR/Volume of filter cylinder at 35 dB with various Gu for present invention v.s. typical prior art

[0065] FIG. 12 shows corridor and column effects through pleated filter

[0066] FIG. 13 illustrates pleats in cylindrical filter in—air passage

DETAILED DESCRIPTION

[0067] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

[0068] FIG. 1A shows the face shield mounted to a head gear worn by a user according to an embodiment of the present disclosure

[0069] The first aspect of this disclosure shows a face shield 1 for being arranged in front of a portion of the face of a user 30, comprising: fastening means, a headgear 2, wherein the fastening means 3 attach the upper portion of the face shield 1 to the headgear 2, being characterized by: the face shield 1: being adaptable to a head shape of a user 30, the face shield 1 provides a sealing contact with the temple areas and extending along a longitudinal z axis 40 downward from the headgear 2, and being provided with a pre-shaped U-shape which will provide a pinching effect causing the face shield to connect in an air tight manner to the users temple areas and downwards due to local stress along the z axis 40 in the shield 1, thus adapting to different head profiles along the z-axis 40 when arranged over the face for providing a channel able to lead an airstream 25 past the eyes, nose and mouth of the user.

[0070] The inward pointing force by which the side portions are biased due to the pre formed U shape may vary, but need not be strong, since the main purpose is to provide a conduit for air flowing from the headgear over the eyes, nose and mouth of user, and when this flow is provided, the natural way to flow is down wards and out at the lower end of the face shield. Super pressure will inhibit inflow along the side portions of the face shield, even if the side portions at small sections in the z axis does not completely contact the side of the head.

[0071] FIG. 1B shows an arched 55 connection of the face shield to the head gear, and the arc radius may be varied to compensate for glare if desired. As shown in FIG. 1C the arc 65 connecting form is almost flat, and glare will be more or less fully compensated. The design of the face shield may be adapted to those environmental conditions that is prioritized. The arc design of the face shield will also impact on the fold angle α′, α″ of the side portions, and thus will impact on the biased force of the side portions. This again is an important element when selecting face shield form to be usable and able to maintain a leakage free space in front of a user's face for the clean air to be flowing.

[0072] As glare may distort the view for the user, and specifically glare that occurs inside transparent shield elements being arranged with sharp angles between them. A further advantageous embodiment of present invention is illustrated in FIG. 1D, FIG. 1E, FIG. 1F, FIG. 1G, and FIG. 1H to mitigate such glare effects.

[0073] It was surprisingly experienced that when the face shield 1 was formed with a continuous arc form over the upper portion 16 in front of the eyes, and the longitudinally crease folds 6″ was only arranged to be in the lower portion 16′ of the face shield 1, then the side pressure on the sides of the face shield 1 could be maintained over the whole face shield height, but almost all glare disappeared. Thus the face shield in front of the vertical β and horizontal β′ sight field is provided with an evenly arched form 55′ stretching from outer distal left side to the outer distal right side in the upper portion 16 of the face shield 1. The view from the eyes of the user thereby has an unobstructed view considering any longitudinally crease folds 6″.

[0074] It is further advantageous to provide a side portion 5, 5′ of the face shield 1 to have a face shield width 17 long enough to reach pass the jawline/ear in backward direction of the user. When the longitudinally crease folds 6″ of the lower portion 16′ of the face shield 1 is provided, the effect will be that the face shield 1 will on the sides be angled towards the jaw, cheek, and temple and provide a light pressure towards these portions of the face. When the upper portion 16 of the face shield 1 is not provided with longitudinally crease folds 6″, the side portions 5, 5′ of the face shield 1 will take on an outward curving 19 form, such that pressure against jaw, cheek and temple is maintained. At the same time, the rear portion of the side portions 5, 5′ of the face shield 1 will tend to bend away from the side of the head of the user. Thus, the face shield 1 upholds a firm contact with the side of the head, but no sharp edges touches the head. Only the inside of the outward arcing side portion 5, 5′ of the face shield 1 makes contact with the side of the head.

[0075] It is an advantage when the arc of the upper portion 16 of the face shield 1 is as wide as possible, and the straighter the front portion is then even less glare is maintained. Thus the a cross section 16″ of the upper portion of the face shield may be provided in an elliptic form in the eye sight field β, β′.

[0076] An air permeable sponge/cushion 13′ arranged horizontally in the height of the underside of the users chin and jaw, as seen in FIG. 1H, provides a filter and anti-throwback of air. If this air permeable sponge/cushion 13′ is correctly mounted by the user this permeable sponge/cushion 13′ will ensure that the environment behind the face shield 1 has a slight overpressure compared to the ambient air outside the face shield 1. Thus, no air will enter the breading space from below.

[0077] The width of the longitudinally crease folded 6″ face shield portion 16′ may taper Ω towards the lower end of the face shield. This is exemplified in FIG. 1I and the tapering angle of the longitudinally crease fold 6″ ensures that the side portions of the face shield will curve outwards and maintain a pressure along the whole side of the head.

[0078] The length of the face shield may vary, and good protective effect of the eyes, nose and mouth by the air flow may be achieved even if the face shield does not stretch far below pass the eye-nose height of the user. Best effect will be achieved by a face shield stretching in the z direction below the cheek height.

[0079] Best contact with the side of the head is achieved if the side portions 1′,1″ of the face shield are substantially flat and parallel with the side of the head of a user 30 from the temple and downwards, maintaining flexibility and adaptability to changing head shape along the z-axis.

[0080] As seen in the figures the face shield 1 is provided with a curved form shape around its longitudinal axis 40, wherein the curved form being maintained by the face shield having one or more longitudinally crease folds 6,6′ running upwards from the bottom portion of the face shield 1. The one or more longitudinally crease folds 6,6′ may or may not run along the complete longitudinal length of the face shield. A biased force holding the side portions of the face shields to the temple area of the users head may for example be sufficiently provided by the folds 6, 6′ being formed for example only on the lower ½ or ⅓ of the face shield.

[0081] Fold angle α′, α″ and sharpness of the fold may be varied individually in thickness, crease width, and pre-strain orientation which again may customize the variations in the biased force along the z axis of the face shield. Fold sharpness can be maximized by minimizing crease width and thickness.

[0082] Although the figures show a face shield being pre-formed by longitudinal crease folds 6, 6′ it is within the scope of the present invention to provide the face shield 1 having a form provided by one of a vacuum form process, thermoforming process, or a pre-molded form. This means that the face shield may be adapted to individual head shapes, or individual needed inward pointing bias along the side portions 5, 5′ in the z-axis may be provided. One such shape may be a U shape with a half circular center portion and straight or slightly narrowing side portions such as illustrated in FIG. 3B. A cross section of this version of the face shield is illustrated in FIG. 3B.

[0083] The face shield 1 of present invention is typically used for protecting persons and workers, and it is foreseen that most embodiments will be provided with a clear fully transparent material. However, it shall be considered to be within the inventive concept to provide a semi-transparent face shield for use for example in certain industry or military applications where for example dampening of light may be advantageous. The face shield therefore may be provided as one or more of: [0084] transparent material [0085] semi-transparent material [0086] polymer/plastic [0087] pressure formed polymer/plastic [0088] heat formed polymer/plastic [0089] transparent or semi-transparent glass [0090] transparent or semi-transparent fibers [0091] transparent or semi-transparent composites

[0092] According to a preferred embodiment of the invention the face shield is provided connected to a headgear 2, an air supplying device, and an air distribution device 10 for channeling air from the air supplying device to the forehead area and the air is channeled 25 from the forehead area down pass the face of a user 30 when the air supplying device is activated. The figures illustrate the air supplying device implemented in the head gear, but it is foreseen that an air supply module may be separately or partially separately arranged and connected to the head gear and air supplying device for example via an air supply channel (not shown), or powered by power line to a separately arranged power source.

[0093] When a person stays in a contaminated/polluted environment, the ambient air may contain virus, pollen or allergens, industrial pollution, or other, and in such environments the air supplying device in present invention may be provided as an air purifying device 50, as illustrated in various embodiments in FIGS. 2, 7, 8, and 9. The air purifying device 50 may comprising a motor 9, and an impeller 7,7′. The impeller 7, 7′ being rotated by the motor 9, and the air purifying device may further comprising a rotating filter 8 being rotationally connected to the impeller 7,7′ and/or the motor 9. The motor 9 may have an integrated power source, such as a rechargeable or changeable battery. In case a rechargeable battery is used, a connector for plugging in a charging device may be provided (not shown). Battery, rechargeable or disposable/changeable, may alternatively be arranged inside the headgear (not shown), in a carry on shoulder bag or the like (not shown), or other.

[0094] The face shield 1 of present invention may be provided in variations of embodiments, and one that is used as example embodiment in FIG. 4 stretches downward past the cheek of a user 30, wherein one or more filter strips 13 may be attached on the inside of the bottom part of the face shield, and thus providing the effect of filtering away aerosols from a user's 30 exhaled air.

[0095] It is within the inventive concept of present invention to provide a face shield of varying length in the z-direction, wherein the aim is to provide a continuous flow of clean air supply form the forehead area of the user and down over the eyes, nose and mouth. With a sufficient volume of air being supplied, for example 1-3 liter/sec. it is assumed that a user may avoid or reduce allergy ailments even if the face shield is only covering portions of the face, for example from the head gear and as far down as below the eyes of the user.

[0096] It is further an option to provide the present invention with an exchangeable face shield, such that face shields of various length, form and material may be used and adapted to specific needs of the user.

[0097] In one embodiment of present invention a front outlet device 4 is formed to distribute the air from the air supplying device/air purifying device 50 along the width of the forehead of a user 30 and behind the upper portion of the face shield where the fastening means attach the face shield to the headgear, in an air flow flowing in a semi laminar manner, such that air with high CO2 content is displaced from area in front of eyes, nose and mouth by the fresh air flow from the outlet device 4.

[0098] The front outlet device 4 may be provided in a variation of forms and design, and in one embodiment the front outlet device comprising multiple outlet nozzles/output orifices spread along the front outlet device. The design/form of the outlet nozzles/output orifices may be such that the air flow 25 may be directed, for example outwards or sideways to avoid draft, or for boosting the airflow in specific areas or flow lines pass the face of the user.

[0099] In the present invention it is a task to maximize the area of the airstream over the cross sectional area between the inside of the face shield 1 and the face of the user, and thereby providing a large air flow that is not felt as a draft, or a blowing wind, as this may lead to uncomfortable feeling of the user, and inconveniences such as running eyes. One effect that is provided to achieve such flow patterns is to provide the outlet nozzles/output orifices distributed over an area extending sideways and outwards to increase air exit area behind the upper portion of the face shield where the fastening means attach the face shield to the headgear.

[0100] In an even further embodiment the outlet nozzles/output orifices are distributed over an area extending outwards from an innermost position being a minimum distance d from the forehead portion above the eyes to provide an airstream having less draft close to the eyes.

[0101] Even if the self-sustained biased form of the face shield is provided by the biased formatting of the face shield, it is also within the inventive concept of present invention to provide a frame (not shown) arranged along perimetrically portions of the face shield to enhance the form fitting features pinching the face shield in a biased enclosing manner around the face area of a user. One could also use such a frame for embodiments intended to be used in harsh environments, for example outdoor extreme weather scenarios, firefighters, riot control personnel or other.

[0102] The pleated filter may be substituted or added with a carbon filter (not shown) to stop unwanted gasses and volatile organic compounds (VOCs).

[0103] In an advantageous embodiment of the invention the rotating filter 8 is a pleated filter.

[0104] The present invention thereby provides an important filter effect influencing the power consumption coming from the propelling of both dust particles and air into a rotating pleated filter. Compared to an air supply system where a fan works in combination with a static filter, the turbulent hydrodynamic energy loss or the fan loss, is almost eliminated. As a result the power consumption is significantly reduced. Compared to products with similar function and size, power consumption is reduced with 40-90%.

[0105] The following description describes in more detail the effects of how the spinning pleated filter enhances the transport of air molecules through the filter, and which is illustrated by the details in FIG. 10A-13.

[0106] In FIG. 11A, a cross section half of the spinning filter and axial to radial impeller blade is illustrated with the air flow 2010 building up radial pressure p as it passes through the impeller. Ideally in accordance with: p=0.5*.sub.ρ*.sub.ω.sup.2*(r.sub.o.sup.2−r.sub.a.sup.2). Where r.sub.i is the inner radius of the pleated filter. r.sub.a is a characteristic radius depending upon incoming radius for each streamline and more specifically where the morphed impeller cause more radial than axial pressure build up. ρ is the air density, ω the angular frequency. The radiuses r.sub.o and r.sub.a are defined in FIG. 11A. However the actual pressure field is much more complex and it is difficult to express useful relationships by simple analytic expressions.

[0107] The pressure zone can simplified be divided in the following sections: [0108] 1) The axial to radial pressure build up zone. [0109] 2) The radial spin pressure. [0110] 3) The pressure distribution in the filter. [0111] 4) The pressure in the rotational exit air.

[0112] A phenomenological representation of how the tangentially averaged pressure is distributed radially is shown in the bottom of FIG. 11A. The actual pressure however varies a lot depending upon how both blades and pleats in the filter accelerates and decelerates both around the rotational axis 41 and in radial direction. The shaping of the impeller blades are done to evenly distribute in both z direction and around the circumference of the rotational axis 41. The figure illustrates how the exit velocity and spin field represents a suction effect on the air molecules exiting the pleated filter.

[0113] In FIG. 12 we see exaggerated examples of streamlines through the pleated filter under static and rotational conditions, and how slow air molecule build-up in static filters increase pressure drop relative to a spinning filter wherein: [0114] I. Corridor effect (Discovered): Air molecules entering the exit channel normal to exit channel are partly accelerated by the high speed core flow (B) which in turn, in the static case, are accelerated by a high pressure in the bottom of the exit channels. The resulting increased pressure, compared to that of a parallel flow situation, may thus be postulated as the Corridor effect. When spinning a pleated filter, centrifugal forces pull/accelerate the newly fed air molecules together with the column and core, hence the speed of the core can be lower in order to exit the same amount of air. Corridor effect is then reduced and a more uniform velocity profile occurs at the outlet, reducing the pressure drop in the exit channel. Efficiency is increased with less viscous loss and loss of kinetic energy in the exit jet (A). With narrow exit channels and high media velocities the corridor effects become more important. [0115] II. Column effect (Discovered) while spinning: Centrifugal forces help pull the entire column so the actual pressure build-up along the exit channel decreases. Given the right pleat geometry a spinning pleated filter enables more even pressure which promotes more flow through the innermost portion of the exit channel relative to a static pleated filter situation. More even flow is the result and this reduces the differential pressure over the filter media. Pressure drop in the inlet channel is not discussed, but this is important to understand the whole picture. [0116] III. Result of column effect and reduction of corridor effect while spinning: More flow can enter at low radius at bottom of exit channel A′. Filter usage is more even B′ hence media pressure difference is reduced. Core velocity in exit channel are reduced hence less pressure is needed to accelerate the core C′. This reduces the pressure deep in the exit channel and promote flow through filter media at low R. Dynamic losses in exit channel are reduced as air exit with lower speed.

[0117] In FIG. 13 it is shown how the cylindrical shape of the pleated filter facilitates wider exit channels than input channels, which is the result when bending a pleated filter in a curve and to a cylindrical shape. The present invention postulates that because the pressure drop in the exit pleat channel is larger than a same sized inlet pleat channel it is beneficial to reverse the direction of flow of cylindrical filters from how they typically are used today where the air goes through the filter from the outside of the filter to the inside of the filter. When additionally the other positive discovered effects that are present in a rotating pleated filter are added, the advantages of a rotating filter become very significant. [0118] IV. Cylindrical shape: Widening exit channel reduces exit velocity. Pressure build up and corridor effects are reduced further. [0119] V. Spin outside exit channels promotes suction/pull and reduces final exit velocities and hence energy loss. This increases the efficiency of the system.

[0120] Some or all features discussed in relation to FIG. 11-13 is independent on which embodiment configuration the pleated filter is implemented in.

[0121] Reference is made to FIG. 10A and FIG. 10B, which shows a pleated filter having a cylindrical shape.

[0122] The filters of present invention provide a certain ratio between the inner radius r.sub.i and the outer radius r.sub.o of the filter, and between the inner radius r.sub.i and the length f.sub.h along the rotational axis 41 of the filter. If the inner radius r.sub.i is to large, and the RPM too high, the entering air would hit the pleats too hard, and energy is spoiled in turbulence and noise instead of building up pressure. In such a case, in order to obtain sufficient centrifugal driving pressure overcoming the pressure drop of the filter, the outer radius r.sub.o could be chosen larger, however since the tangential exit velocity scales with r, this results in too much energy input to the spinning exiting air. On the other hand, too small inner radius r.sub.i of the pleated filter results in small entrance area into the channels in the pleated filter that result in high air inflow velocity that makes it hard to feed the filter portion close to the entrance, resulting in uneven filter use. The same negative effect from high air inflow velocity can be seen when air is fed from just one of the filter openings. Further negative effects with one opening is that it requires greater motor torque to maintain the performance which in turn requires a larger and more expensive motor.

[0123] The usefulness of different embodiments of rotating pleated filters depend upon a series of measures or parameters that might be weighted differently for the different embodiments. The product size is of importance when available space is very limited as in the present head gear. Other vital parameters, are the noise and clean air delivery rate (CADR). After studying the range of available prior art air purifiers thoroughly, as well as the intricate physics holding the key to the potential of the rotating pleated filter, it has been discovered that it is possible to define a new relation that surprisingly well describes the usefulness of the rotating pleated filter of present invention.

[0124] For appropriate operation without other functioning pressure improving parts attached, the relationships between r.sub.i, r.sub.o, pleat spacing p.sub.s, filter efficiency ε and height f.sub.h of the spinning pleated filter can be expressed by the dimensionless number which hereby has been denoted as the Gu number. The number applies also for rotating pleated filters used in ventilation systems.

[0125] The relation is phenomenological and empirical based and derived through CFD (Computational Fluid Dynamics) simulations, 3D printing and measurements on numerous models as well as testing different filters. The Gu number is defined as:

Gu number≡f*p.sub.r/(2*r.sub.o*ε.sup.1/4)

[0126] Where r.sub.o may represent the outer pressure generating radius spanning over an optional additional filter, such as for example a carbon filter. p.sub.r is defined by: (r.sub.o−r.sub.i)/p.sub.s, where p.sub.s is the pleat spacing. The precision of the Gu number is more accurate in the growth interval of the usefulness level, however as system scales the boundary layer need to be accounted more properly for better precision. These considerations will be investigated as the present invention is further developed. It is assumed that smaller systems than tested will underperform. In practice also the larger will underperform since it is not expedient to spin very thick filters. As the Gu number gets higher, passing 10, it will be more difficult to interpret usefulness depending on which parameter is altered, and how the resulting effect from these alterations are regarded by the observer. Such variations may be in relation to how the observers regard product size, and how they perceive different levels of noise. Also the pollution level and type in the environment of use will contribute, typically from 2 to 4 or higher.

[0127] The Gu number take into account the fluid dynamics in every involved parameter, but it's not trivial in any way to isolate or address why and how these parameters contribute isolated and hence apply. By best effort it is concluded or stated that every parameter contributes well, over a relatively wide range. The relation applies for filter efficiencies from 20% to well above 90%.

[0128] In order to be able to prove the unique positive effects of the rotating pleated filters it has been necessary to do experiments within the interval shown in FIG. 11B. Outside this interval at Gu≤0.8 it is not possible to explore the benefits due to high noise per CADR. In prior art the above discussed and postulated effects have not been recognized, and they have been running at Gu numbers below 0.8. Additionally prior art embodiments have been running at too high RPM without reflecting on the above discussed relationships, or even discussing any such, manufacturers has put their minds and development in other directions, and the hidden potential has remained undiscovered.

[0129] Present invention claim the following interval:

Gu>0.8

[0130] Thus an embodiment of present invention is provided wherein the air filters having a cylindrical form, and is further designed according to the relation Gu=fh*pr/(2*ro*ε{circumflex over ( )}¼)>0.8, wherein Gu number correlates to a function of the commercial usefulness based on, and accounting for, the main customer's needs, such as CADR, dB, product size, functioning and cost, wherein pr=ro−ri/pleat spacing ps, and pleat spacing ps is the distance between two adjacent pleat tops on the inner radius ri, and ε is the ASHRAE efficiency.

[0131] In another embodiment of the present invention the filter 42 is provided with a Gu>1.2.

[0132] In another embodiment of the present invention the filter 42 is provided with Gu>1.5.

[0133] The impeller 7,7′ may comprise a plurality of fan blades arranged radially extending from a center cone 12, the center cone 12 having a tapering form towards the a first air intake 20 side, and the fan blades being formed to provide an axial fan 7′ at the air intake side. The air is thus set in motion 21 with a rotational flow pattern, and the fan blades being formed to provide a radial fan 7″ towards the circumferential outlet side of the impeller, such that air is pushed 21,22 towards the rotationally connected filter 8, 42 with a close to uniform distribution over the inlet channels of the filter in the z direction. The center cone 12 ensures that the air is distributed evenly out along the height h of the rotating filter.

[0134] A further feature of the present invention is the air distribution device 10 that is formed in an enclosing manner 11 around the circumferential outlet of the impeller 7,7′ and filter 8 and further comprising a conduit 14,10 forming a channel for the air flow from the enclosure around the impeller 7,7′ and filter 8, 42 towards and through 23, 24 the front outlet device 4 and to 25 the forehead area of a user 30. This way all the exiting air 23 from the spinning filter is collected and led towards 24 the front outlet device 4.

[0135] In one embodiment, as illustrated in FIG. 2, of the present invention it is provided an air laminating mesh 70 spread along the impeller side of the front outlet device 4, in order to facilitate a better distribution of the air flow over the front outlet device 4. The air laminating mesh 70 may be a fine course metal alloy, cloth, filter material or other, including a mesh which is integrated with/in the front outlet device 4. The air laminating mesh may further improve the air flow and dampen turbulent flow currents in the air flow.

[0136] In a typical embodiment of present invention the air filters having a height between 15 and 35 mm, and an outer diameter between 65 and 105 mm, and more advantageously a height between 20 and 30 mm, and an outer diameter between 75 and 95 mm. In a most advantageous format the filter dimension of 25 mm height and 85 mm outer diameter is used, which would have optimal performance at an acceptable form factor to be carried inside a head gear. These ranges and combinations of sizes are merely exemplary, and the inventive concept may have other sizes where external factors enable or limit such other sizes.

[0137] As briefly discussed above the fastening means 3 comprising an lock/unlock feature (not shown) enabling to attach and detach the face shield 1 from the headgear and thus providing an replaceable face shield 1 function.

[0138] The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. For example, Placing the motor, impeller and filter remote of the headgear, using a connector (not shown) and cabling to an electrical power source carried on the side, Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.