Sieve for a particle monitoring system, sampling lid assembly for a particle monitoring system, particle monitoring system and air sampling method

Abstract

The present disclosure relates to a sieve for a particle monitoring system, a sampling lid assembly for a particle monitoring system, a particle monitoring system and an air sampling method.

Description

[0001] SIEVE FOR A PARTICLE MONITORING SYSTEM, SAMPLING LID ASSEMBLY FOR A PARTICLE MONITORING SYSTEM, PARTICLE MONITORING SYSTEM AND AIR SAMPLING METHOD

[0002] Technical Field

[0003] The present disclosure relates to a sieve for a particle monitoring system, a sampling lid assembly for a particle monitoring system, a particle monitoring system and an air sampling method.

[0004] Background

[0005] The active monitoring of sample fluids, either of liquids or more commonly of gases like air, is frequently performed for the purpose of evaluating contaminants, for classification and monitoring purposes, in a range of cleanroom and manufacturing environments requiring low levels of particles, such as cleanroom environments for electronics manufacturing or semiconductor manufacturing or measuring instruments manufacturing and aseptic environments for manufacturing pharmaceutical and biological products, such as sterile medicinal products.

[0006] For the purpose of monitoring fluid (air) in such a context, particle monitoring systems are known and comprise microbial or active gas (air) samplers and particle counters. Microbiological or active gas (air) samplers are beneficial because they allow a user to sample a quantitative amount of air and to determine the risk for contamination (microbial flora) to sterile products in a surrounding environment.

[0007] An example of a microbiological air sampler and method for sampling, detecting and / or characterizing particles, for example, via collection, growth, and analysis of viable biological particles such as microorganisms is disclosed in EP 0 964 240 Al. This device includes an integrated sampler and impact surface, such as the receiving surface of a growth media in a Petri-dish, for collecting biological particles. The collected particles are then typically incubated to grow living particles and are subsequently analysed by different techniques including naked eyes inspection, microscopy, fluorescence or auto-fluorescence, ATP detection or others. The present application pertains to particle monitoring systems where the sampling section for performing a sampling process on a sample fluid, preferably a gas, such as air, comprises a particle collector. The monitoring procedure and technology of the particle monitoring systems is as such unaffected by this invention and will not be described in detail.

[0008] US 2021 / 0214121 Al discloses an air sampler device for a particle monitoring system. The air sampler device includes a bottom plate on which a Petri dish is to be placed, and a top plate that is placed on the bottom plate to surround the Petri dish and that is an example of a sampling lid assembly. A vacuum tube is attached to an air port of the bottom plate. Air is then sucked into the sampler device through holes in the top plate, so that the air impinges on a test media contained in the Petri dish, which is accommodated inside the air sampler device between the top plate and the bottom plate. The air exits through the air port. At the end of the testing cycle, the top plate is taken off of the bottom plate, the Petri dish is removed, and the top plate is replaced. The Petri dish can then be analysed to determine the level of cleanliness of the surrounding environment.

[0009] The perforated sampling lids or top plates of air sampler devices for particle monitoring systems for environmental monitoring are exchanged from one testing environment or test run to another. The perforated component of the lids is generally termed a "sieve", and this component can be a replaceable entity as such or can be integrated in the lid with other functional features for the placement. In the context of the present disclosure the term "sieve" is used to refer to the functional entity that has the perforations or holes or openings through which the air is forced onto the test media, and the term "opening" or "air opening" will be used throughout.

[0010] There exist reusable perforated lids or sieves for air samplingthat are made from aluminum or stainless steel and there exist disposable single-use / daily-use perforated lids or sieves that are preferably made of polymer material, for example ABS. The present application pertains to both types of perforated lids or sieves.

[0011] Most of the current lids or sieves for environmental monitoring have air openings that have a straight cylindrical shape with an important ratio of length / diameter (see an illustration of a cross-section of one cylindrical air opening extending through the thickness of a sieve 6 in Figure 4). Generally, the dimensions of the air openings are between 0.5 mm and 1.0 mm for the diameter d, and around 3 mm for the axial length H in the direction of air flow through the opening which corresponds to the thickness of the sieve. The length / diameter ratio may therefore be calculated to be between around 6 and around 3. It has now been surprisingly discovered that this geometry generates significant pressure losses in each opening when an air sampling is performed. These significant pressure losses entail an increase in the power required on the side of a vacuum pump integrated in and / or connected to the air sampling device (particle monitoring system) for creating the suction force to force the air through the openings to perform the air sampling cycle. As a result, this increases the energy consumption of the air sampling devices which is not preferred from an environmental point of view, and reduces the operating time, in particular where the sampling devices, as is frequently the case, operate autonomously as a mobile device with a battery serving as the energy source. Such mobile device may then be placed at different locations in an environment that is to be tested.

[0012] The present application therefore aims at providing a sieve for a particle monitoring system, a sampling lid assembly for a particle monitoring system, a particle monitoring system and an air sampling method which are improved with respect to the energy consumption.

[0013] US 2008 / 0070292 Al discloses a sieve for a bio-impactor comprising air passages from upstream to downstream of the sieve, the passages having a section that is progressively narrowed from an inlet opening towards an outlet opening.

[0014] EP 1 126 021 Al discloses a portable air-borne bacteria sampler with a specified nozzle to culture medium distance for high collection efficiency.

[0015] Summary

[0016] As described herein, this object is solved by providing a sieve for a particle monitoring system as defined by claim 1, a sampling lid assembly for a particle monitoring system as defined by claim 13, a particle monitoring system as defined by claim 14, and an air sampling method as defined by claim 15. Preferred embodiments are defined in the dependent claims.

[0017] The present application in particular provides a sieve for a particle monitoring system, preferably a mobile microbiological gas (air) sampler, the sieve configured to be removably mounted at a sampling section of the particle monitoring system to close an open side of a space above an impacting and collecting surface, preferably in a Petri-dish, the sieve provided with air openings arranged to direct, in operation of the particle monitoring system, air towards the impacting and collecting surface, preferably the Petri dish, placed on the sampling section. Some, preferably all, of the air openings of the sieve have a convex curved section narrowing a flow path cross-section at an inlet portion of the respective air opening in an axial direction from an upstream proximal side to a downstream distal side in the flow direction of the air through the air opening.

[0018] The present application improves the structure of the sieve by a special design of the air openings extending through the sieve for the purpose of reducing the pressure losses in each hole of an air sampling sieve when an air sampling is performed. The reduction of pressure loss is accompanied by a decrease in the energy consumption required to perform the air sampling cycle using this sieve. When the total pressure decreases, the air sampling device requires less energy to maintain the same airflow with the consequence that an operating time of a mobile air sampling device running on a battery (i.e. comprising a battery as the main or only power source) can be extended or that a mobile device can be equipped with a smaller battery to reduce the weight of the mobile device. It is noted that the present sieve is essentially a plate perforated with the air openings extending through the sieve, such air openings as defined herein.

[0019] Preferably, the openings of the sieve comprise a step-like recess, preferably with a rectangular or trapezoidal cross-section of the air opening, upstream of the convex curved section.

[0020] Preferably, an axial dimension of the step-like recess is less than half, preferably less than a third (i.e. 1 / 3) of an axial dimension of the convex curved section.

[0021] Preferably, an / the axial dimension of the curved convex section of the air opening in the flow direction of the air is from 0.1 mm to 0.5 mm.

[0022] Preferably, a curvature radius of the curved convex section of the air opening is from 0.1 mm to 1.0 mm, preferably from 0.1 mm to 0.5 mm.

[0023] Preferably, some, more preferably all, of the air openings have a truncated conical section downstream of the curved convex section in the flow direction of the air through the air opening, the truncated conical section narrowing the flow path cross-section from an upstream proximal side to a downstream distal side in the flow direction of the air. Preferably, the conical section has a lateral inclination in a cross-section from 0.5° to 5°, preferably from 1° to 3°, relative to a line parallel to an axial center line of the air opening.

[0024] Preferably, a transition between the truncated conical section and the conical convex section is smooth and continuous.

[0025] Preferably, a diameter of the air opening at the downstream distal end of the conical section is from 0.4 mm to 0.8 mm.

[0026] Preferably, the curved convex section and / or the conical section, if provided, is / are round- symmetrical.

[0027] Preferably, an axial dimension of the air opening from an upstream proximal end to a downstream distal end in the flow direction of the air is between 1.0 mm and 2.0 mm.

[0028] The sieve can be configured to be engaged with other identical sieves to form a self- supporting stack.

[0029] The present application also provides a sampling lid assembly for a particle monitoring system, preferably a mobile microbiological gas (air) sampler, comprising a support frame configured to be releasably attached to a sampling section of the particle monitoring system and to define a space surrounding an impacting and collecting surface, preferably a Petri dish, placed on the sampling section, and a sieve as described herein removably mounted at the support frame or integrated with the support frame to close an open side of the space above the impacting and collecting surface, preferably the Petri-dish, such that the fluid openings of the sieve are arranged to direct, in operation of the particle monitoring system, a gas towards the impacting and collecting surface, preferably the Petri dish, placed on the sampling section.

[0030] Moreover, the present application also provides a particle monitoring system, preferably a mobile microbiological gas (air) sampler or airborne particle counter, comprising a sampling section configured to removably receive an impacting and collecting surface, preferably a Petri dish, and a sampling lid assembly as defined herein removably attached to the sampling section so as to define a space surrounding the impacting and collecting surface, preferably the Petri dish. Finally, the present application provides a method of gas (air) sampling in a surrounding environment, the method comprising providing a particle monitoring system, preferably a mobile microbiological gas (air) sampler, as described herein in the surrounding environment, forcing the air to flow into the particle monitoring system and through the air openings in the sieve, so that the air strikes a test media contained on an impacting and collecting surface, preferably a Petri dish, in the particle monitoring system, and incubating particles collected on the test media to grow living particles and analysing by appropriate techniques including naked eyes inspection, microscopy, fluorescence or autofluorescence, ATP detection or others.

[0031] Brief description of the drawings

[0032] The present application is now described in detail on the basis of preferred embodiments by reference to the following exemplary schematic drawings:

[0033] Figures la, lb, and lc show an example of a prior art sampling lid assembly with separate sieve and support sections in a perspective view (Figure la), in a perspective cross-sectional view (Figure lb), and in a sectional elevation view (Figure lc), each in conjunction with a sampling section of a particle monitoring system.

[0034] Figures 2a, 2b, and 2c show an example of a prior art sampling lid assembly with integral sieve and support sections in a perspective view (Figure 2a), in a perspective cross-sectional view (Figure 2b), and in a sectional elevation view (Figure 2c), each in conjunction with a sampling section of a particle monitoring system.

[0035] Figure 3 shows a perspective view of another variant of a prior art sampling lid assembly with a sieve separated from a support frame.

[0036] Figure 4 shows a magnified cross-sectional side view of a prior art sieve through a single air opening.

[0037] Figure 5 shows a magnified cross-sectional side view of a sieve through a single air opening according to an exemplary embodiment.

[0038] In the Figures similar reference numerals are used to indicate similar elements. For reasons of clarity, when referring to Figures 2a to 2c an apostrophe is added to the respective reference numeral. Detailed description

[0039] For the purposes of the present application, terms such as "horizontal", "vertical", "perpendicular", "parallel", and similar terms are - if not already explicitly indicated - considered to be "essentially horizontal", "essentially vertical", "essentially perpendicular", "essentially parallel", provided that this does not negatively affect functionality. Preferably, the term "essentially" is to denote a deviation of at most 10°, more preferably of at most 5°, even more preferably of at most 4° or 3°, still even more preferably of at most 2° or 1° from being horizontal, vertical, perpendicular, and parallel, respectively.

[0040] For the purposes of the present application, the terms "fluid" or "gas" may be used interchangeably, with air being a preferred gas.

[0041] Although the Figures la, lb, lc, 2a, 2b, and 2c show examples of prior art sampling lid assemblies 1,1' in conjunction with a sampling section 3,3' of a particle monitoring system (the further details of which are not shown), these examples are used to explain the basic functions and optional aspects that can be used in conjunction with a sieve as defined herein (and that will be described by specific reference to Figure 5 below).

[0042] It is remarked that the sampling section 3,3' is not part of the invention but is a component of particle monitoring systems known per se. The sampling lid assembly 1,1' is in any case designed to be compatible with a respective sampling section 3,3' to provide the below described functionalities.

[0043] Turning to the example of a prior art sampling lid assembly with separate sieve and support sections as shown in Figures la to lc, the sampling lid assembly 1 for a particle monitoring system comprises a support frame 2 configured to be releasably attached and fixed to the sampling section 3 of the particle monitoring system and to define a space 5 surrounding an impacting and collecting surface, such as a Petri dish 4, placed on a base 3a of the sampling section 3 (as described above in conjunction with the prior art).

[0044] Though generally throughout this application the present sampling lid assembly is described with a Petri dish with respective culture (or growth) medium, such as a nutrient agar-based test media, on an impacting and collecting surface, it is to be understood that instead of a Petri dish any impacting and collecting surface may be used. It is also noted that a Petri dish generally comprises a bottom and a lid, with the bottom preferably comprising the culture medium.

[0045] The sampling lid assembly 1 also comprises a sieve 6 formed as a component separate and distinct from the support frame 2 and configured to be removably mounted at the support frame 2 to close an open side of the space 5 above the Petri-dish 4. The sieve 6 is provided with an array of air openings 7 arranged to direct, in operation of the particle monitoring system, air that is sucked in by means of a vacuum pump of the particle monitoring system (not shown) and that may contain and suspend bacteria contaminants and project the air with particles towards and onto the surface of the growth or test media (e.g. an agar-based test media) accommodated within the Petri-dish 4 by the kinetic energy. The air, after having impinged on the media in the Petri-dish 4, is guided towards the periphery of the sieve 6 and from there through a gap 16 between the support frame and the Petri-dish to an outlet port 3b of the sampling section (the entire flow of the air is forced by a reduced pressure created by the vacuum pump downstream of the outlet port 3b). The particles, on the other hand, are captured and remain on the surface of the test media.

[0046] In the prior art the support frame and the sieve are either integrally formed, or the support frame 2 and the sieve 6 are separate components with the consequence that the support frame 2 and the sieve 6 may be made from different materials. In particular, the support frame 2 may be a reusable component and may be made from a material capable of withstanding autoclaving for sterilisation, preferably may be made from a metal material, preferably from stainless steel or aluminum.

[0047] As defined herein, the sieve 6 is either a reusable component or a disposable component. For being reusable, the sieve 6 is preferably made from a material that can easily be sterilized, such as aluminum or stainless steel.

[0048] For being disposable, the sieve 6 is generally made from a disposable material, preferably from a polymer material. The choice of polymer material is not particularly limited. A suitable polymer material may, for example, be selected from the list consisting of acrylonitrile butadiene styrene (ABS); polypropylene (PP), such as propylene homopolymer, propylene random copolymer, or heterophasic propylene block copolymer; polycarbonate (PC); polystyrene (PS), such as high-impact polystyrene (HIPS); polyamides (PA); and polyesters. The concept of separating the support frame 3 and the sieve 6 is, however, applicable to a concept where the sieve, too, is reusable and in this case may be made from a material capable of withstanding autoclaving for sterilisation. In any case, the separation of these two components reduces the volume of the part of the sampling lid assembly 1 (i.e. the sieve) that is disposable while a significant part (i.e. the support frame) is reusable.

[0049] The support frame 2 and the sieve 6 are configured to be releasably engaged with each other, preferably but not necessarily in a form-locking engagement.

[0050] The support frame 2 and the sieve 6 are configured to be engaged by a movement along an axial direction of the support frame 2 and / or by a lateral movement along a radial direction of the support frame 2. In the example the sieve 6 is provided with an annular ridge 8 protruding downward from a downward-facing side and formed to engage with a mating circular groove 9 recessed in an upper surface of the support frame 2.

[0051] The support frame 2 and the sieve 6 may also be provided with mating centering features for defining a mounted position, preferably mating conical surfaces and / or one or more mating protrusions and recesses. As the sieve is pulled / pushed towards the support frame by the flow of air in use, a particularly tight connection or engagement is not necessary but may be implemented depending on the situation.

[0052] The sieve 6 may also be provided with an extension of an inner wall 10 that extends downward so as to shield substantially the entire inner peripheral wall of the support frame 2 facing towards the space 5. Such an extension (not shown) may be formed of a relatively thin, sheet-like strip of material integrally formed with the sieve and reduces or avoids the exposure of the inner peripheral wall of the support frame to contaminants in the fluid.

[0053] The number and arrangement / distribution of the openings 7 on the sieve 6 is not particularly limited as long as it fulfils the function of directing a desired flow of fluid towards the media in the Petri-dish 4. In the example, the openings 7 are shown to be in the form of radial, elongated narrow slits directed towards a center of the sieve. However, the form of the openings 7 is the subject of the present application as will be described below in connection with Figure 5.

[0054] The surface where the openings are formed may be in the form of a recessed, trough-like portion 11 surrounded by an elevated peripheral rim 12. The lower side of the peripheral rim 12 may accommodate and form an annular channel 13 for directing the fluid through the gap between the support frame 2 and the Petri-dish 4 to the outlet port 3b.

[0055] As shown in Figures la and lb, the elevated peripheral rim 12 of the sieve 6 may be provided with a number of radial ribs 14 on its upper side, distributed about the circumference, to enhance, in addition to the effect of the elevated peripheral rim 12, the rigidity of the sieve against bending deformation while allowing the material thickness of the walls as such to be reduced. This allows for the sieve to be gripped and handled by a gripper implement of a robot.

[0056] The support frame 2 may be specifically designed to have a relatively simple geometrical shape with mainly flat and preferably uninterrupted continuous smooth surfaces and only a minimum of recesses or sharp edges. Thus, it can be easily cleaned even without special autoclaving equipment to remove contaminants potentially adhering thereto, whereas the more complex structure of the sieve 6 with slits, openings, ribs etc. does not allow cleaning with such simple equipment and calls for autoclaving if reuse is desired.

[0057] In the example the support frame 2 is a ring-like body, preferably with one or more small lateral protrusions and / or recesses, preferably in the form of a peripheral shoulder or shallow groove 15 to avoid that the support frame slides through a gripper of a robot or gloves in case of a manual handling. For ease of implementation, the support frame 2 preferably has a sufficiently wide essentially vertical surface along the outer perimeter, to allow easy and reliable gripping. The support frame 2 is designed to be fixed to the base 3a of the sampling section 3. This can be realized in that the support frame 2 and the base 3a are provided with mating centering and engaging features for defining a releasable mounted position. As compared to the releasable connection between the sieve and the support frame, the releasable connection between the base 3a and the support frame 2 should be more rigid if the support frame 2 is to remain in place for several cycles of exchange of the sieve 6 as the reusable support ring 2 does not need to be cleaned between each sampling cycle.

[0058] In a variant of an exemplary sieve and lid assembly including the sieve of the invention as shown in Figure 3 the support frame 2 and the sieve 6 may be provided with mating centering features for defining a mounted position, in this case with mating conical surfaces 18. In the example of Figure 3 the reusable support frame 2 and the disposable sieve 6 are each designed with a conical shape at the mating contact surfaces in order to facilitate the positioning of the disposable sieve on the support frame 2 even in case of automated handling.

[0059] In the example shown in Figure 3 the sieve 6 is preferably provided with one or more lateral protrusions 19, preferably in the form of one or more lugs (only one being shown), allowing gripping of the sieve 6 for the purpose of positioning it at the support frame 2 without touching the recessed portion where the openings 7 are provided and without introducing a bending force on the sieve as such.

[0060] Alternatively to a sampling lid assembly with separate sieve section and support frame (or section), a sampling assembly may also be formed as a single piece, i.e. integrally with sieve and support sections as is shown in Figures 2a to 2c. The sampling lid 1' for a particle monitoring system comprises a support section 2' configured to be releasably attached and fixed to the sampling section 3' of the particle monitoring system and to define a space 5' surrounding an impacting and collecting surface, such as a petri dish 4', placed on a base 3a' of the sampling section 3'.

[0061] The sampling lid 1' also comprises a sieve section 6' integrally formed with the support section 2' and configured to close an open side of the space 5' above the petri-dish 4'. The sieve section 6' is provided with an array of fluid openings 7' (which may in this application also be referred to as "holes") arranged to direct, in operation of the particle monitoring system, a fluid that may support bacteria contaminants towards a growth or test media accommodated within the petri-dish 4' placed on the sampling section 3'. For clarification it is noted that in operation of the particle monitoring system the lid of the petri dish 4' is removed. The fluid, after having impinged on the media in the petri-dish 4', is guided towards the periphery of the sieve section 6' and from there through a gap 16' between the support section 2' and the petri-dish 4' to an outlet port 3b' of the sampling section (the flow of the fluid is forced by a reduced pressure created by a vacuum pump downstream of the outlet port 3b').

[0062] The support section 2' and the sieve section 6' of the sampling lid 1' are integrally formed, preferably are integrally molded, preferably by injection molding. Thus, the sampling lid 1' is preferably a disposable solution composed of a single-use disposable plastic part compatible with an environmental monitoring air sampler in order to avoid the need for autoclaving. The choice of plastics material is not particularly limited. A suitable plastics material may, for example, be selected from the list consisting of acrylonitrile butadiene styrene (ABS); polypropylene (PP), such as propylene homopolymer, propylene random copolymer, or heterophasic propylene block copolymer; polycarbonate (PC); polystyrene (PS), such as high-impact polystyrene (HIPS); polyamides (PA); and polyesters.

[0063] The form, number and arrangement of the openings 7' on the upper side of the sieve section 6' is not particularly limited as long as it fulfils the function of directing a desired flow of fluid towards the media in the petri-dish 4'. In the embodiment the openings 7' are in the form of radially aligned rows of small holes directed towards a center of the sieve section. The surface where the openings 7' are formed is in the form of a recessed, troughlike portion 11' surrounded by an elevated peripheral rim 12'. The lower side of the peripheral rim 12' accommodates and forms an annular channel 13' for directing the fluid through a gap 16' between the sampling lid 1' and the petri-dish 4' to the outlet port 3b'.

[0064] The sieve section 6' is peripherally surrounded by the raised peripheral rim 12' of the support section 2' and preferably is axially recessed from a top surface 12a' of the peripheral rim 12' of the support section 2' towards the impacting and collecting surface, preferably the petri dish 4' to form the trough-like portion 11'. Further, as shown in Figure 2c, the peripheral rim 12' of the support section 2', on a side facing the sampling section 3' of the particle monitoring system, is formed so as to surround, in the mounted state on the sampling section 3', a raised outer peripheral wall 4a' of the impacting and collecting surface, preferably the petri dish 4', creating an inverted U- or V-shaped gap 16' through which a fluid can pass from a central region 5a' of the space 5' above the impacting and collecting surface and below the sieve section 6' to an outer peripheral region 5b' of the space 5' surrounding the impacting and collecting surface, preferably the petri dish 4'.

[0065] As shown in Figures 2a and 2b, the support section 2' is provided with a plurality of radial ribs and / or recesses 17' between the ribs (or, not shown, recessed in a smooth outer wall surface) distributed about the outer periphery thereof in equal intervals to allow or at least facilitate gripping of the support section 2' by a gripper implement of a robot for the purpose of positioning it on the sampling section 3' and / or to increase the rigidity against deformation.

[0066] Although not shown, the elevated peripheral rim 12' surrounding the sieve section 6' may also be provided with a number of radial ribs on its upper side, distributed about the circumference, to enhance, in addition to the effect of the elevated peripheral rim 12' and the radial ribs or protrusions 17', the rigidity of the sampling lid 1' against bending deformation while allowing the material thickness of the walls as such to be reduced. This allows that the sampling lid 1' can be gripped and handled by a gripper implement of a robot or by a hand of a user.

[0067] The support section 2' may be specifically designed to have a relatively simple geometrical shape with mainly flat and preferably uninterrupted continuous smooth surfaces (except for the above-mentioned ribs 17') and only a minimum of recesses or sharp edges. Thus, it can be easily formed by injection molding.

[0068] In the embodiment the support section 2' is a ring-like body that comprises a lower skirt portion 2a' and an upper skirt portion 2b', the lower skirt portion 2a' having a slightly larger diameter than the upper skirt portion 2b' such that there is a step-like transition portion 2c' between the two. The stepped structure enhances the rigidity of the sampling lid against distortion, in particular when the lid is handled by the gripper implement, yet allows for a reduction of the material thickness.

[0069] In the embodiment the outer ribs or protrusions 17' are formed as extensions of the lower skirt portion 2a' extending onto the upper skirt portion 2b' beyond the step-like transition portion 2c'. Further, the lower skirt portion 2a' is formed to surround and preferably releasably engage with a peripheral edge 3c' of the sampling section 3' to create a sealing contact. The sealing contact may, however, be also formed by flat mating surfaces that are pressed against each other upon application of the vacuum described later.

[0070] The lateral ribs or protrusions 17' and / or recesses help avoiding that the sampling lid slides through the gripper implement of a robot or gloves in case of manual handling. For ease of implementation, the support section 2' preferably has a sufficiently wide essentially vertical surface along the outer perimeter, to allow easy and reliable gripping.

[0071] The support section 2' is designed to be fixed to the base 3a' of the sampling section 3'. This can be realized in that the support section 2' and the base 3a' are provided with mating centering and engaging features for defining a releasable mounted position. The releasable connection between the base 3a' and the support section 2' should be more rigid if the sampling lid 1' is to remain in place for several sampling cycles.

[0072] The present application now is specifically directed to improving the structure of the sieve 6,6' to be used as separate component with a support frame 2,2' in a lid assembly as described above or to be used as an integral part with a support frame. More specifically, the present application is concerned with a special design of the air openings extending though the sieve for the purpose of reducing the pressure losses in each hole of an air sampling sieve when an air sampling is performed. The significant reduction of pressure losses is accompanied by a decrease in the energy consumption required to perform the air sampling cycle. When the total pressure decreases, the device requires less energy to maintain the same airflow and thus extends the operating time of a mobile air sampling device running on a battery or allows a mobile device to be equipped with a smaller battery to reduce the weight of the mobile device.

[0073] This specific shape of the air openings 7,7' in the sieve 6,6' according to an exemplary embodiment is exemplified in Figure 5 which shows a magnified cross-sectional side view of the sieve 6,6' through a single air opening 7,7'.

[0074] As a primary measure to reduce the pressure drop some, preferably all of the air openings 7,7' of the sieve 6,6' have a convex curved section 20 narrowing a flow path cross-section from an inlet 25 of the respective air opening 7,7' in an axial direction from an upstream proximal side (the upper side in Figure 5) to a downstream distal side in the flow direction of the air through the air opening 7,7' (the lower side in Figure 5). The air openings at the inlet section are thus expanded flaring outward towards the air stream sucked towards the sieve like a horn or funnel.

[0075] Optionally, all or some of the air openings 7,7' of the sieve 6,6' may further comprise an optional step-like recess 21, preferably with a rectangular or trapezoidal cross-section, upstream of the convex curved section 20. Thus, the lateral peripheral wall of the recess 21 may be perpendicular to the upper plane of the sieve or may be slightly inclined inward towards the curved section 20 like a phase (not shown). An axial dimension S of the steplike recess 21 may be less than half, preferably less than a third of an axial dimension C of the convex curved section 20. The recess 21 facilitates manufacturing of the opening because the rounded transition does not have to be perfectly flush with the upper surface of the sieve and assists the flow of air into the opening.

[0076] The axial dimension C of the curved convex section 20 of the air opening 7,7' (in the flow direction of the air, i.e. perpendicular to the upper plane of the sieve) is preferably from 0.1 mm to 0.5 mm. A curvature radius R of the curved convex section 20 of the air opening 7,7' is from 0.1 mm to 1.0 mm, preferably from 0.1 mm to 0.5 mm. The curved contour that smoothly narrows the cross-section of the flow channel of the opening allows the flow of airto be directed and straightened, corresponding to a transition from turbulent to laminar flow, through the opening with less effort needed.

[0077] Preferably, some, more preferably all of the air openings 7,7' have a truncated conical section 22 downstream of the curved convex section 20 in the flow direction of the air through the air opening 7. The truncated conical section 22 in continuation of the curved convex section 20 further narrows the flow path cross-section from an upstream proximal side to a downstream distal side in the flow direction of the air but with a reduced progression and over a longer distance.

[0078] The truncated conical section 22 has a lateral inclination in a cross-section from 0.5° to 5°, preferably from 1° to 3°, relative to a line parallel to an axial center line of the air opening 7,7', wherein the side walls in the cross-section are straight lines. For reasons of clarity it is noted that the truncated conical section 22 is laterally inclined such that its diameter at the exit 24 is smaller than its diameter in proximity to inlet 25. A transition 23 between the truncated conical section 22 and the conical convex section 20 is smooth and continuous to avoid forming vortices. The conical shape has a significant impact on the reduction of pressure losses.

[0079] A diameter d of the air opening 7,7' at the downstream distal end of the conical section 22 and thus at the exit 24 from the opening is from 0.4 mm to 0.8 mm in order to guarantee flow rate, flow speed and d50 values in accordance with the collection efficiency required for validation of microbial air samplers by standard EN 17141 (The d50 value indicates the particle size at which 50% of the airborne particles are impacted onto the agar surface by the microbial air sampler. The biological efficiency is the ability of the air sampler to safely capture organisms from the air).

[0080] The downstream distal end of the conical section 22 may be flush with the lower surface of the sieve and correspond to the exit 24 from the opening. It is possible, however, that a section with constant diameter is connected between the downstream distal end of the conical section 22 and the lower surface of the sieve without changing the flow path crosssection (not shown).

[0081] An axial dimension H of the air opening 7,7' from an upstream proximal end at the upper surface of the sieve to a downstream distal end (in the flow direction of the air) at the lower surface of the sieve is preferably between 1.0 mm and 2.0 mm. Thus, the dimension K of the conical section 22 (and possibly a cylindrical section) in the axial direction can be determined as (H minus C).

[0082] In the embodiment the entire opening 7,7' including the curved convex section 20, the conical section 22 and the step-like recess 21, if provided, is round-symmetrical. This in particular is a result where the air sampling sieve with this new shape of the opening is produced by machining (drilling, grinding) using a customized rotary tool that reproduces the shape of the hole (for reusable variants of the sieve made from aluminum or stainless steel).

[0083] However, the air sampling sieve with this new shape of the opening can be produced by a plastic (injection) moulding process or by additive manufacturing or by ablating technologies.

[0084] In order to confirm the improvement of air sampling with the sieve 6,6' as defined herein a numerical simulation study was conducted. The study evaluates the difference of pressure lost between an air sampling cycle conducted using a sieve (A) with cylindrical holes as shown in Figure 4 and an air sampling cycle conducted using a sieve (B) with the optimized shape of the openings as described herein and as shown in Figure 5.

[0085] The result shows that the total pressure aspiration is reduced by around 35% when the air sampling is conducted using the sieve (B) compared to the air sampling cycle conducted using the sieve (A). The decrease in total pressure is accompanied by a reduction in the energy consumption of the air sampler as the device then requires less energy to maintain the same airflow. To confirm this, some energy consumption tests were conducted and showed that an increase of the number of air sampling cycles possible with a full battery load in the range of about 20% could be achieved when using a sieve (or lid) with the optimized shape of the openings.

[0086] A sequence of characteristic stages of an air monitoring process using the sampling lid assembly with a sieve as defined herein in conjunction with the sampling section of a particle monitoring system comprises the following steps:

[0087] To start an air monitoring process, the Petri-dish 4,4' (with the growth or test media, for example agar media) is placed on the base 3a, 3a' of the sampling section 3,3' of the particle monitoring system (for example an air sampling system). This stage is as such known in the art. The Petri-dish 4,4' can be positioned indifferently manually or automatically with a robot.

[0088] Then, the reusable support frame 2 is positioned on the base 3a of the sampling section 3, too, so as to surround the Petri-dish 4 with a gap 16. The support frame 2 can be positioned indifferently manually or automatically with a robot.

[0089] In the next step, the disposable sieve 6 is positioned on the reusable support frame 2. The disposable sieve 6 can be positioned indifferently manually or automatically with a robot. The rigidity of the disposable sieve 6 and, if necessary, the use of a rigid packaging (not shown) as primary packaging of the disposable sieve 6 will permit the automation and robotic use of the proposed solution by using the gripper. The primary packaging can be a unit packaging or a packaging of several sieves 6. In the second case, the design of the sieve will preferably allow them to be easily stacked and taken up one-by-one by the gripper implement.

[0090] Once the sieve 6 is placed on top of the support frame 2, the fluid sampling system is ready to start, and a vacuum pump (not shown) is started to suck air through the holes 7 of the sieve 6 and the contaminated particles entrained in the stream of air are projected onto the surface of the media within the Petri-dish 4 by the kinetic energy and remain on the media surface. The sucked air is forced outward and upward at the peripheral wall of the Petri-dish 4 and is further guided and turned downward by the annular channel 13 of the sieve 6 and is directed through the gap 16 between the inner peripheral wall of the support frame 3 and the Petri-dish 4 to the outlet port 3b to finally exit through the port 3b of the air sampling system (see also Figure 3).

Claims

Claims1. A sieve (6,6') for a particle monitoring system, preferably a mobile microbiological gas (air) sampler, the sieve (6,6') configured to be removably mounted at a sampling section (3.3') of the particle monitoring system to close an open side of a space (5,5') above an impacting and collecting surface, preferably a Petri-dish (4,4'), the sieve (6,6') provided with air openings (7,7') arranged to direct, in operation of the particle monitoring system, air towards the impacting and collecting surface, preferably the Petri dish (4,4'), placed on the sampling section (3,3'), wherein some, preferably all, of the air openings (7,7') of the sieve (6,6') have a convex curved section (20) narrowing a flow path cross-section at an inlet portion of the respective air opening (7,7') in an axial direction from an upstream proximal side to a downstream distal side in the flow direction of the air through the air opening (7,7').

2. The sieve (6,6') according to claim 1, comprising a step-like recess (21), preferably with a rectangular or trapezoidal cross-section of the air opening (7,7'), upstream of the convex curved section (20).

3. The sieve (6,6') according to claim 2, wherein an axial dimension (S) of the step-like recess (21) is less than half, preferably less than a third of an axial dimension (C) of the convex curved section (20).

4. The sieve (6,6') according to any one of claims 1 to 3, wherein an / the axial dimension (C) of the curved convex section (20) of the air opening (7,7') (in the flow direction of the air) is from 0.1 mm to 0.5 mm.

5. The sieve (6,6') according to any one of claims 1 to 4, wherein a curvature radius (R) of the curved convex section (20) of the air opening (7,7') is from 0.1 mm to 1.0 mm, preferably from 0.1 mm to 0.5 mm.

6. The sieve (6,6') according to any one of claims 1 to 5, wherein some, preferably all of the air openings (7,7') have a truncated conical section (22) downstream of the curved convex section (20), in the flow direction of the air through the air opening (7,7'), the truncated conical section (22) narrowing the flow path cross-section from an upstream proximal side to a downstream distal side in the flow direction of the air.

7. The sieve (6,6') according to claim 6, wherein the conical section (22) has a lateral inclination in a cross-section from 0.5° to 5°, preferably from 1° to 3°, relative to a line parallel to an axial center line of the air opening (7,7').

8. The sieve (6,6') according to claim 6 or claim 7, wherein a transition (23) between the truncated conical section (22) and the conical convex section (20) is smooth and continuous.

9. The sieve (6,6') according to any one of claims 6, 7 and 8, wherein a diameter (d) of the air opening (7,7') at the downstream distal end of the conical section (22) is from 0.4 mm to 0.8 mm.

10. The sieve (6,6') according to any one of claims 1 to 9, wherein the curved convex section (20) and / or the conical section (22), if provided, is / are round-symmetrical.

11. The sieve (6,6') according to any one of claims 1 to 10, wherein an axial dimension (H) of the air opening (7,7') from an upstream proximal end to a downstream distal end (in the flow direction of the air) is between 1.0 mm and 2.0 mm.

12. The sieve (6,6') according to any one of claims 1 to 11, wherein the sieve (6,6') is configured to be engaged with other identical sieves (6,6') to form a self-supporting stack.

13. A sampling lid assembly (1,1') for a particle monitoring system, preferably a mobile microbiological gas (air) sampler, comprising a support frame (2,2') configured to be releasably attached to a sampling section (3,3') of the particle monitoring system and to define a space (5,5') surrounding an impacting and collecting surface, preferably a Petri dish (4,4'), placed on the sampling section (3,3'); and a sieve (6,6') according to any one of claims 1 to 12 removably mounted at the support frame (2,2') or integrated with the support frame (2,2') to close an open side of the space (5) above the impacting and collecting surface, preferably the Petri-dish (4,4'), such that the fluid openings (7,7') of the sieve (6,6') are arranged to direct, in operation of the particle monitoring system, a gas towards the impacting and collecting surface, preferably the Petri dish (4,4'), placed on the sampling section (3,3').

14. A particle monitoring system, preferably a mobile microbiological gas (air) sampler or airborne particle counter, comprising a sampling section (3,3') configured to removably receive an impacting and collecting surface, preferably a Petri dish (4,4'); and a sampling lid assembly according to claim 13 removably attached to the sampling section (3,3') so as to define a space (5,5') surrounding the impacting and collecting surface, preferably the Petri dish (4,4').

15. A method of sampling a quantitative amount of air and determining the risk for contamination in a surrounding environment, the method comprising: providing a particle monitoring system, preferably a mobile microbiological gas (air) sampler, according to claim 14 in the surrounding environment; forcing the air to flow into the particle monitoring system and through the air openings (7,7') in the sieve (6,6'), so that the air strikes a test media contained on an impacting and collecting surface, preferably a Petri dish (4,4') in the particle monitoring system; and incubating particles collected on the test media to grow living particles and analysing by appropriate techniques including naked eyes inspection, microscopy, fluorescence or auto-fluorescence, ATP detection or others.

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