Filter and method for manufacturing this filter

Abstract

Provided is a filter having a high classification characteristic and a method for manufacturing the filter. This filter comprises a mesh-like sieve part 10 which is woven using a wire material 20A formed of a predetermined resin so that wire materials 20A, 20B three-dimensionally cross from at least two mutually different directions (X, Y), the filter classifying desired granular or powder-like objects to be sieved from an opening section 10A of the sieve part 10, wherein the wire materials 20A, 20B have recesses and protrusions formed, through a sandblast treatment using a predetermined water-soluble blast material, by processing an upper surface U of the opening section 10A through which the object to be sieved pass, and side surfaces S3, S4 that form a gap between the upper surface U and a lower surface D.

Description

Technical Field

[0001] The present invention relates to a sieve for sorting granular materials for food by dropping them through a number of apertures according to the size of the granule shape, and particularly to a filter with a high classification function (sorting function) capable of efficiently sorting the powder particle shape of the granular material without causing clogging, and a method for manufacturing this filter.

Background Art

[0002] Conventionally, like filter media used for filtering fluids such as air filters and oil filters, and "sieve meshes" used for sieving granular materials and separating aggregated particles (secondary particles) into individual particles (primary particles), a network filter has been proposed for passing and sorting specific substances from mixtures of solids and fluids or mixtures of solids (these may be referred to as "processed materials" to distinguish them from the "classified materials" for food or pharmaceuticals in the present invention) according to powder particle size and other physical properties (see, for example, Patent Document 1).

[0003] Regarding the network filter described in this Patent Document 1, it is configured with wire materials that make point contact with the granular processed material mixed in the processed material to be sieved, or a predetermined surface treatment is performed to enable uniform processing, or a granular material smaller than the mesh opening is used as an ejectant (which may be referred to as an "ejected granular material"), and this ejected granular material is sprayed onto the wire material to perform surface treatment. As a result, Patent Document 1 discloses that various effects can be expected by performing these treatments.

[0004] Particularly, in the case of a network filter using a metallic wire material, by generating plastic deformation on the wire surface due to the collision with the ejected granular material during processing, it is possible to increase the hardness of the wire surface and suppress the occurrence of wear on the wire surface, or effects such as imparting compressive residual stress and improving durability over a long period, and preventing clogging are described.

[0005] In addition to the metal filter described in Patent Document 1 above, other proposed products include, for example, "resin sieves" used to screen (or classify) materials to be processed such as powders and granular substances, "resin filters" used for filtering materials to be processed such as fluids, "mesh elements" used in these "sieves" and "filters," and "resin wires" used in these "mesh elements" (see, for example, Patent Document 2).

[0006] In the resin wire described in Patent Document 2, by forming fine scratches on the contact surface of the resin mesh element used in the part that comes into contact with the workpiece using a fine shot blasting process, and by setting the arithmetic mean roughness (Ra: see the embodiment described later for the definition) of the contact surface to 0.3 to 1.2 μm, the following effects are disclosed.

[0007] In other words, with the aforementioned resin wire, when performing predetermined treatments such as sieving powdered or granular materials or filtering liquids, the adhesion of the material to be treated to the resin mesh element (sieve screen or filter screen) can be suppressed relatively easily and at low cost. This is said to suppress clogging of the sieve mesh (screen, mesh, filter). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-170408 [Patent Document 2] Japanese Patent Publication No. 2020-972 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, in all of the patent documents described, the processing of the wires constituting the filter was limited to the front part of the filter that is sieved, in other words, the part corresponding to the top surface of the wires when the material to be processed falls, and processing of other surfaces was neglected.

[0010] In view of the above circumstances, the present invention aims to provide a filter with high classification characteristics and a method for manufacturing this filter. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides a filter having a mesh-like sieve section formed by weaving wires made of a predetermined resin so that the wires intersect three-dimensionally from at least two different directions, wherein the wires facing the opening through which the material to be classified passes are made of a predetermined substance and are water-soluble and can be removed by washing. of The surface is characterized by being processed and having irregularities formed on at least the upper surface and the side surface between the upper and lower surfaces through sandblasting using a blasting material. ru.

[0012] The wire material is the sand The average distance S between adjacent protrusions, which form local peaks in the uneven areas created by blasting, is equal to the diameter (D) of the granular material being classified. 50 It is formed to be smaller than the opening, and is configured to contact only the local peak of the wire when the object to be classified passes through the opening. ru.

[0014] The wire is characterized by being formed from one of the following resin materials: nylon, polyester, polypropylene, fluororesin, polyether ether ketone, polyamide 66, polyamide 6, polyimide, or polyethylene. ru.

[0015] The sieving section is characterized in that the opening width of the opening is at least 1 μm to 5 mm at maximum. ru.

[0016] The average interval S between adjacent convex portions that become local peaks of the uneven portions of the wire rod is 0.93 to 1.36 μm on the upper surface and 0.927 to 1.42 μm on the side surface in the case of a low mesh having an opening width of 1000 μm, and ,before The arithmetic mean roughness Ra of the uneven portions is 0.225 to 0.406 μm on the upper surface and 0.205 to 0.365 μm on the side surface in the case of a low mesh having an opening width of 1000 μm, which is characterized. ru.

[0017] The classified material is characterized in that it is a powder or granule for food or pharmaceuticals. ru.

[0018] front Note The processed surface of the wire rod whose surface is processed and unevenness is formed by sandblasting treatment includes, in addition to the upper surface of the wire rod facing the opening through which the classified material passes in the sieving section and the side surface of the wire rod forming the space between the upper and lower surfaces of the wire rod, the lower surface of the wire rod opposite to the upper surface of the wire rod, which is characterized. ru.

[0019] Further, the manufacturing method of the filter of the present invention uses a wire rod formed of a predetermined resin, and includes a mesh-like sieving section woven so that the wire rods intersect three-dimensionally from at least two different directions, and classifies a desired powdery or granular classified material from the opening portion which is the gap between the wire rods in the sieving section. It is a manufacturing method of a filter, wherein the wire rods are woven into a mesh shape to form a sieving section, and a sandblasting treatment is performed to spray a predetermined water-soluble blasting material onto at least the surface portion of the upper surface and the surface portion of the side surface between the upper and lower surfaces of the wire rod facing the opening of the sieving section through which the classified material passes, and unevenness is formed on at least the surface portion of the upper surface and the surface portion of the side surface of the wire rod facing the opening of the sieving section, which is characterized. ru.

[0021] the The specified resin is any one of nylon, polyester, polypropylene, fluororesin, polyether ether ketone, polyamide 66, polyamide 6, polyimide, polyethylene ru.

[0022] The blasting material uses any one of silica (silicate compound), sodium chloride (NaCl), sodium hydrogen carbonate, citric acid, magnesium chloride, oxalic acid, calcium stearate, sodium phosphate, calcium carbonate, potassium aluminum sulfate (alum). ru.

[0023] before Note The processed surface of the wire rod whose surface is processed by end-blasting to form unevenness includes, in addition to the upper surface of the wire rod facing the opening through which the classified material passes in the screening section and the side surface of the wire rod forming between the upper surface and the lower surface, the lower surface of the wire rod opposite to the upper surface. ru.

Effect of the Invention

[0024] Due to the configuration of the filter of the present invention described above, the wire rod in a mesh state after weaving the wire rods constituting the filter is surface-treated by sandblasting using a predetermined water-soluble blasting material, and the surface is processed to have unevenness provided at an interval smaller than at least the outer dimension of the classified material on the upper surface of the opening through which the screened material passes and on the side surface forming between this upper surface and the lower surface. Therefore, when classifying the screened material, the screened material not only makes point contact with the convex portion on the upper surface, but also makes point contact with the convex portion on the side surface when passing through the opening portion, thereby increasing the slipperiness of the screened material contacting on this side surface. As a result, the screening effect (in other words, the sieving effect) when passing through the opening portion is improved.

[0025] Furthermore, with the filter manufacturing method of the present invention, by performing sandblasting (spraying) on ​​the wires in the mesh state after weaving the wires that constitute the filter using a predetermined water-soluble blasting material, it becomes possible to easily make the roughness of the uneven surface formed on the wires on the upper side of the opening different from the roughness of the uneven surface formed on the wires on the side of the opening, thereby simplifying the manufacture of the filter.

[0026] Furthermore, according to the filter manufacturing method of the present invention, a water-soluble blast is used as the sandblasting material (hereinafter referred to as "blast material"), and the blast material is washed away with washing water after manufacturing, so that the blast material does not remain on the mesh surface. In addition, even if some blast material remains, if it is mixed with food or pharmaceuticals, which are the materials to be sieved, and ingested into the body, it can be excreted from the body relatively easily. [Brief explanation of the drawing]

[0027] [Figure 1] This is a plan view showing an enlarged view of a part of the sieve (mesh) of a filter according to the first embodiment of the present invention. [Figure 2] (A) is a cross-sectional view taken along the line II-II in Figure 1, and (B) is an enlarged view of the α portion in (A). [Figure 3(A)] This is an enlarged explanatory diagram showing an image of the blast material impacting the wire material that constitutes the sieve (mesh) according to this embodiment, when irregularities are formed mainly on the top and side surfaces of the wire material by sandblasting. [Figure 3(B)] This is an enlarged explanatory diagram showing the trajectories of some of the blast material when it collides with the top and side surfaces of the wire in Figure 3(A). [Figure 4] This is a flowchart illustrating a method for manufacturing a filter according to a second embodiment of the present invention. [Figure 5(A)] This is an exploded perspective view of a framed filter in a method for manufacturing a filter according to a modified example of the second embodiment of the present invention. [Figure 5(B)]This is a partial cross-sectional view showing the assembled state of a framed filter in the method for manufacturing a filter according to a second embodiment of the present invention. [Figure 6] Figure 5 shows a cross-sectional view of the main part of the filter when the sieve (mesh) shown is attached to the cylindrical body to complete the filter as a product. [Figure 7] (A) is an explanatory diagram illustrating the state when the deviation from the mean line to the measurement curve is magnified, by extracting a reference length l from the roughness curve in the direction of the mean line in order to explain the arithmetic mean roughness Ra of the irregularities formed on a wire by sandblasting the filter of the present invention, and (B) is an explanatory diagram similar to (A) that specifically shows the average interval S of the local peaks. [Modes for carrying out the invention]

[0028] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings illustrating this embodiment, the X and Y directions indicate the vertical and horizontal arrangement directions of the openings 10A, which are the mesh of the filter 1 described later. The Z direction is perpendicular to the arrangement plane of the openings 10A of the filter 1 when classifying the material to be sieved (hereinafter referred to as "the material to be classified"), and also indicates the direction in which gravity acts. Furthermore, the directions of these mutually orthogonal three-dimensional Cartesian coordinates X, Y, and Z are shown in a right-handed system.

[0029] The present invention will be described in the following order. 1. A first embodiment describing the structure, operation, and effects of the filter according to the present invention. 2. A second embodiment describing a method for manufacturing a filter according to the present invention, 3. A modified example of the second embodiment describing a modified example of the method for manufacturing a filter according to the present invention, 4. An experimental example of the sieving effect, etc., using the filter, etc., of the first embodiment of the present invention (referred to as "Experimental Example 1"), 5. Reference Example 1 shows surface processing data, etc., when sandblasting is performed using a filter formed from a different material (from the first embodiment) according to the present invention. 6. An experimental example (referred to as "Experimental Example 2") of the sieving effect, etc., using a filter formed from a different material than that of the first embodiment of the present invention. 7. Reference Example 2, showing surface processing data, etc., when sandblasting is performed using a filter formed from a different material (from the first embodiment) according to the present invention. 8. An example of an additional experiment that explains the evaluation when an additional experiment was conducted according to the present invention.

[0030] <1. First Embodiment> (composition) Figure 1 shows a mesh-like sieve section 10 (hereinafter sometimes referred to as "mesh 10") of a filter according to the present invention. This mesh 10 is designed to classify a desired granular material through the mesh openings 10A. It is constructed in a mesh-like manner by using wires 20A and 20B made of a predetermined resin as the warp elements (hereinafter sometimes referred to as "warp threads") and weft elements (hereinafter sometimes referred to as "weft threads"), respectively, and weaving the wires 20A and 20B to intersect alternately in three dimensions from at least two directions (X, Y).

[0031] The wires 20A and 20B that make up the warp and weft threads, which are the elements of the mesh 10 in this embodiment, are formed by melting pellet-like material made of a suitable resin in a furnace and stretching it into a thread-like shape from a die, thereby forming wires with a roughly circular cross-section. However, the cross-sectional shape does not have to be this specific. In other words, the cross-sectional shape does not have to be particularly limited, as long as it is a flattened shape, an elliptical shape, or any other shape that has a significant effect on classification performance.

[0032] Furthermore, regarding the outer diameter of the wires 20A and 20B, although it depends on the weaving method, in the case of plain weave (ASTM, XXX, HC&P) or XX weave as shown in Figure 1, for example, both the warp and weft threads are of the same diameter. Note that the outer diameter of one of them may be made thicker (or thinner).

[0033] Regarding the specific outer diameters of the wires 20A and 20B in this embodiment, for example, in Experimental Example 1 described later, wires with outer diameters of 750 μm and 515 μm were used, and in Experimental Example 2, wires with outer diameters of 122 μm, 81.5 μm, 77 μm, and 62 μm were used, but the invention is not limited to these outer diameters.

[0034] The resin component of the wires 20A and 20B in this embodiment is preferably nylon, polyester, polypropylene, fluororesin, polyetheretherketone, polyamide 66, polyamide 6, polyimide, polyethylene, or the like. Considering affinity with the material to be classified during classification, stretchability, elasticity, ease of processing, and other factors, nylon and polyester are preferred, but nylon is particularly optimal from the viewpoint of versatility, processability with the water-soluble abrasive B (hereinafter referred to as "blasting material B") described later, cost, and other factors.

[0035] Furthermore, the opening 10A has a distance of a μm between warp threads and a distance of b μm between weft threads (where a ≠ b), but both the distance between warp threads and the distance between weft threads may be the same, meaning that the opening shape of the opening 10A is geometrically square (a = b) or approximately square (a ≈ b).

[0036] In this embodiment, the opening 10A has openings of 2000 μm and 1000 μm in the vertical and horizontal directions in Experimental Example 1, and 200 μm and 100 μm in the vertical and horizontal directions in Experimental Example 2, but it is of course not limited to these. For example, this opening width may range from a minimum of 1 μm to a maximum of about 5 mm, or it may extend to a wider area.

[0037] Furthermore, in this invention, although the detailed method will be described later, sandblasting is performed on the wires 20A and 20B of the sieve section 10 in a woven state (not as individual wires) using blast material B, which constitutes a water-soluble abrasive. As a result, not only are fine irregularities created on the upper surface U of the wires 20A and 20B of the sieve section 10, but fine irregularities are also created on their side surfaces L in particular.

[0038] Furthermore, in wires 20A and 20B, the blast material B also wraps around to the bottom surface D, which is the opposite side from the top surface U, and is subjected to fine surface processing. Although the proportion of surface irregularities formed on the bottom surface D is smaller than on the top surface U and side surface L, the probability of the granular material being classified wrapping around to the bottom surface D of the wire is not very high during actual classification. However, for granular material that has wrapped around to the bottom surface D, which is the back surface of the wire, the contact area with the granular material is reduced even at the surface irregularities on the bottom surface D, thus reducing both the frictional resistance to the granular material on the bottom surface D and the amount of adhesion.

[0039] (The wire material is nylon mesh) The fine irregularities on the wires 20A and 20B are, for example, in the case of a nylon mesh woven from nylon material, for example, as described in [Table 1] below, for example, the arithmetic mean roughness (Ra) is, if the opening 10A is 1000 μm × 1000 μm, the diameter (D 50 When processing using a 10μm blast material, the top surface is 0.225~0.406μm and the sides are 0.205~0.365μm. Note that D 50 This represents the cumulative average diameter, which is the particle size at which the number or mass of particles larger than a certain particle size accounts for 50% of the total powder particles.

[0040] On the other hand, the surface roughness of the wire without sandblasting (no treatment) was 0.103 to 0.132 μm on the top surface and 0.06 to 0.162 μm on the sides. Here, the arithmetic mean roughness (Ra; JIS B 0601:1994, unit μm) is defined by the following equation (1) (see Figure 7(A)).

[0041]

number

[0042] Therefore, as will be explained in detail later, considering the contact of the material to be classified with the protrusions during classification and the movement of the material to be classified into the recesses between the protrusions, filter 1, which has undergone sandblasting treatment, has a greater surface roughness on its top and sides compared to the filter that has not undergone sandblasting treatment. Consequently, it becomes more difficult for the material to be classified to reach the deepest part of the recesses, thus minimizing the risk of the material penetrating deep into the recesses and becoming trapped there. In other words, depending on the particle size of the material to be classified, the greater the difference in surface roughness, the less likely the material is to penetrate deep into the recesses. As a result, the occurrence of problems such as the material to be classified becoming trapped deep in the recesses and causing clogging can be greatly reduced. Of course, this also reduces the contact area with the material to be classified.

[0043] Furthermore, the fine irregularities on the wires 20A and 20B are, for example, in the case of a nylon mesh woven from nylon, as shown in [Table 1], the average distance S(μm) between local peaks on the surface of the wires 20A and 20B (hereinafter referred to as "average interval" S(μm)) is such that the opening 10A is 1000μm × 1000μm, and the diameter (D 50When processing using 10 μm blast material, the top surface was 0.93 to 1.36 μm and the side surface was 0.927 to 1.42 μm. On the other hand, when no sandblasting treatment was performed (no treatment), the average spacing S (μm) of local peaks of the wire was, for example, 1.21 to 1.49 μm on the top surface and 1.14 to 1.60 μm on the side surface. Here, the average spacing of peaks (local peaks) (S; JIS B 0601:1994, unit μm) is defined by the following equation (2) (see Figure 7(B)).

[0044]

number

[0045] Therefore, as will be described in detail later, in particular, in the filter 1 that has undergone sandblasting, the average spacing S of local peaks on the side portions of wires 20A and 20B is considerably shorter compared to the untreated one. In particular, in this embodiment, the average spacing (S) between adjacent peaks (tops) of convex parts of wires 20A and 20B formed by blasting is the diameter (D) of the object to be classified during classification. 50 It is formed to be smaller than granular material.

[0046] [Effect] Therefore, when classifying the material to be classified using the actual filter 1, the material can pass through the opening 10A while only contacting the peak portion. Furthermore, when the material to be classified comes into contact with the wires 20A and 20B during classification, the frequency of contact at the side peak portions of the wires 20A and 20B increases. As a result, point contact at the peak portions of the convexity on the upper surface U and side surface L of the wires 20A and 20B, and the scraping force on the material to be classified due to elastic vibration increase, and a smooth sieving effect from the opening 10A can be expected. At the same time, since the material to be classified makes point contact rather than surface contact with the peaks of the convexity on the wires 20A and 20B, the frictional force between the material and the wires 20A and 20B decreases, further improving the classification performance.

[0047] By the way, in this embodiment, qualitative and quantitative explanations are omitted, but at the grid point C (see Figures 1 and 2) of the woven mesh, many irregularities are formed, as shown in Figure 2(B). That is, in the wires 20A and 20B in the vicinity of the grid point C (indicated as "A1" in Figure 1), when the object to be classified falls onto the upper surface U portion of the wires 20A and 20B, when the colliding upper surface U region is viewed from above, the colliding area per unit area (referred to as the "collision probability area") is almost doubled compared to the upper surface U region (indicated as "A2" in Figure 1) where only either the warp or weft threads away from the grid point C exist (however, this may vary depending on the size of the set area).

[0048] Furthermore, as shown in Figure 3(B), for example, if the blasting material B collides with a protrusion on the upper surface U at an opening 10A near a grid point C of the warp thread wire 20A (or weft thread wire 20B), it is possible, though very rare, that the blasting material B will bounce off the upper surface U of that warp thread (or weft thread) and collide again with the side surface L (or upper surface U) of either the nearby warp or weft thread. In such cases, the collision frequency is expected to be significantly higher probabilistically in region "A1" compared to the case where the blasting material B bounces off region "A2" and collides again with another thread, due to the larger collision probability area.

[0049] Furthermore, for example, at grid point C shown in Figure 2(B), as will be explained in detail in the second embodiment described later, at grid point C and the neighboring region "A1", the warp wire 20A is located above the weft wire 20B. Therefore, it is possible that the material to be classified, falling from above, will first collide with the warp wire and then fall onto the weft wire located below it (colliding multiple times). Consequently, from this point of view as well, the number of collisions is statistically higher at grid point C and the neighboring region "A1" compared to the collision of blast material in region "A2" which consists of only one of the warp or weft threads (of course, the same phenomenon occurs with the opposite warp or weft thread at the adjacent grid point).

[0050] For these reasons, the region "A1" near grid point C tends to have a higher number of processing steps per unit surface area for creating irregularities compared to the region "A2" which consists only of warp and weft threads. Consequently, the absolute number of irregularities formed at and near grid point C is also greater.

[0051] [effect] Therefore, according to the filter 1 of this embodiment, by performing sandblasting on the sieve portion (mesh) 10 of the woven filter 1, it is expected that the sieving effect at and near the grid point C will be significantly larger than in other areas when classifying the material to be classified with this filter 1. In other words, when classifying using the sieve portion (mesh) 10 of the woven filter 1, when the material to be classified (powder or granules) collides with the peaks of the protrusions near grid point C of the wires 20A and 20B, the powder or granules will more often change their orientation toward the opening 10A and pass through the sieve due to the physical and mechanical scraping action.

[0052] Furthermore, in addition to these physical and mechanical effects, particularly at the tops of the irregularities formed at a higher density (than other areas) at lattice point C and its vicinity, electrostatic forces (Coulomb forces) based on Coulomb's law, generated by electrostatic action, may also act from an electromagnetic perspective. That is, an electrostatic repulsive force is generated between the tops of the convex parts of the wire and the object being classified, which may cause the object to change its direction of travel and move towards the opening 10A. In this way, according to this embodiment, the classification effect on the object being classified (in other words, the scraping effect on the object being classified) can be greatly exerted.

[0053] Furthermore, of the wires 20A and 20B that make up filter 1, the wire positioned on the upper side at grid point C bulges upward (in the -Z direction) compared to the parts other than grid point C. Therefore, in terms of potential energy, it is located higher (at the very top) in the +Z direction where gravitational acceleration (g) acts. Consequently, the object to be classified falling from above will collide with filter 1 first at grid point C. As a result, the classification process first takes place centered at grid point C, and then spreads to the classification process at the wires 20A and 20B, which are individual threads in the vertical and horizontal directions. This prevents the generation of localized classification functions that are biased in a particular region, and allows for a nearly uniform classification function across the entire surface of the filter.

[0054] In this embodiment, sandblasting was performed on the upper surface U and side surface L of the wires 20A and 20B to exclusively create a textured surface on the upper surface U and side surface L. However, separately from this processing, for example, the filter 1 may be inverted so that the part that was the lower surface D faces upward, and sandblasting may be performed again to create a textured surface on the lower surface D in the same way as the upper surface U.

[0055] <2. Second Embodiment> Next, a second embodiment of the present invention will be described with reference to the drawings. Figure 4 shows a method for manufacturing a filter 1 according to a second embodiment of the present invention, which consists of a first step S1 to a fifth step S5.

[0056] [Filter Manufacturing Method] Step 1 S1 involves preparing the required wires 20A and 20B to be used as weft and warp threads of a certain length, and weaving them into a mesh net 1 using a required loom (not shown) in an appropriate weaving manner. 0The wires are woven together. In this case, for example in Experimental Example 1 described later, the wires 20A and 20B used as the warp and weft threads are made of resin, for example, nylon with an outer diameter of 515 μm or 750 μm. These wires 20A and 20B are then woven together, for example, in plain weave (ASTM 18-1000 or ASTM 10-2000), to form a square mesh 10 (sieve section) with openings 10A (width and height opening dimensions a and b) of 1000 μm or 2000 μm, that is, opening dimensions of 1 mm or 2 mm in both the width and height.

[0057] In the second step S2, as will be described in detail later, the already woven wires 20A and 20B (which constitute the mesh 10) are subjected to a predetermined sandblasting process to create fine irregularities on their upper surface U and side surface L while maintaining a constant tension using a predetermined jig or the like. Although less frequently than on other surfaces, this sandblasting process also causes some of the blast material to wrap around to the lower surface D of the wires 20A and 20B, creating fine irregularities (see Figure 3).

[0058] In this embodiment, the method for processing fine irregularities is as shown in Figure 3. For example, a sieve section 10 is placed horizontally parallel to the XY plane. Using a suitable spraying device (blasting device), a sprayer 100 is used to traverse along the X direction (or Y direction) and spray a blasting material B made of a water-soluble abrasive onto the sieve section 10 from directly above the sieve 10 in the +Z direction, thereby performing sandblasting.

[0059] In this case, the injection direction is configured to be directed vertically (+Z), but the blast material B immediately after being ejected from the nozzle 100A diffuses in a fan shape (or cone shape) with a constant spread at an angle θ (for example, about 14 degrees), so the surface of the side L of the wires 20A and 20B is also processed relatively effectively to create an uneven texture.

[0060] As described above, a water-soluble abrasive is used as blasting material B as a means of impacting the wires 20A and 20B to form fine irregularities on their surfaces. That is, considering that this filter 1 is intended for the classification of powders and granules for food or pharmaceutical use, the blasting material B used is, for example, a water-soluble silica (silicic acid compound) or sodium chloride with a particle size of 10 μm or 100 μm. However, the blasting material of the present invention is not limited to this particle size as long as a similar effect can be obtained. For example, the minimum particle size may be 1 μm or less and the maximum particle size may be 1000 μm (= 1 mm). Furthermore, water-soluble powders and granules used as food additives can be used as blasting material B. For example, in addition to the above, sodium bicarbonate (baking soda or also known as sodium bicarbonate), citric acid, magnesium chloride, oxalic acid, calcium stearate, sodium phosphate, calcium carbonate, and potassium aluminum sulfate (alum) can be used.

[0061] On the other hand, the wires 20A and 20B use one of the following materials that exhibit high effectiveness and efficiency with respect to the material being classified: nylon, polyester (e.g., PET: polyethylene terephthalate), polypropylene, fluororesin (Teflon (a registered trademark of DuPont), polyvinylidene fluoride, polyetheretherketone, polyethylene, etc.), but nylon and polyester are particularly preferred. Furthermore, for these wires 20A and 20B, for example, those with fine openings of 100 μm and 200 μm have outer diameters of 77 μm and 122 μm, respectively, while those with coarse openings of 1000 μm and 2000 μm have outer diameters of 515 μm and 750 μm, respectively. Furthermore, regarding the necessary requirements for the resin material constituting the wire of the present invention, from a physical property standpoint, it is preferable that the resin material is flexible, has low vibration damping properties, or has excellent physical properties in terms of at least one of the following: vibration resistance, viscoelasticity, etc.

[0062] As explained with reference to Figure 3, the blast material B is injected together with compressed gas towards the wires 20A and 20B of the woven net 10 using the injector 100 of an appropriate injection device (blasting device). The processing conditions at this time are, for example, in the range of injection pressure 0.1 MPa to 0.6 MPa, preferably 0.2 MPa to 0.5 MPa, but are not limited to this range.

[0063] In the third step S3, there is a possibility that the blast material B may remain trapped in the grid points of the warp and weft threads of the mesh 10 formed in the second step S2, or may remain in the depressions of the surface irregularities of the wires 20A and 20B, which are made up of wires 20A and 20B that have been sandblasted. Therefore, in order to remove this, the mesh may be washed with a predetermined washing water, such as high-pressure washing, ultrasonic washing, or purified water, or it may be washed with alcohol. Furthermore, in order to perform an efficient heat-sealing operation when assembling the mesh 10 to the frame by heat-sealing in the next step, in this third step S3, as a preparatory step, the mesh 10 is dried by appropriate means and any remaining washing water is removed.

[0064] In the fourth step S4, the woven mesh 10, which has undergone a predetermined sandblasting treatment, is attached to a pre-formed frame (made of wood or resin, not shown) using adhesive. Fixed via The mesh is assembled to the frame by (especially in the case of resin, heat fusion is also acceptable). The shape of this frame can, of course, vary, and various shapes such as square, circular, and cylindrical are applicable. Furthermore, regarding the method of fixing the mesh 10 to the frame, in this embodiment, since nylon, a thermoplastic resin, is used, it is also possible to form the filter (sieve) 1 by heating the mesh 10 to an appropriate temperature considering its melting point using an appropriate heating means and fusing and fixing it to the frame. If it is desired to assemble the mesh 10 to the frame under tension, it is necessary to hold the outer circumference (end) side of the mesh 10 under a predetermined high tension using a jig or the like (not shown).

[0065] Next, in the fifth step S5, the filter 1 formed in this manner is finally fixed into a main body having a flat, short cylindrical or ring-shaped frame, such as the inner frame 30 and outer frame 40 in Figure 5, or a long cylindrical frame not shown. This completes the filter (filter device) as a product.

[0066] In this embodiment, the frame used is made of wood or resin, but it can also be made of metal, or even ceramic if possible.

[0067] Therefore, according to this embodiment, the third step S3 is performed by washing with washing water. As a result, even if any blasting material B remains attached to the mesh 10 after sandblasting, it can be removed by washing with washing water. Therefore, even when used for classifying powders and granules for food or pharmaceuticals, for example, a filter (filter device) with ensured safety can be provided.

[0068] [Effect] Next, the operation of this embodiment, particularly the sandblasting process in the second step S2 to create uneven surfaces, will be explained in detail with reference to Figures 2 and 3, which schematically depict enlarged views of the wires 20A and 20B. For example, in the second step S2, if a predetermined jig (not shown) is used to firmly maintain a constant tensile strength while a fine textured surface is applied to the upper surface U and side surface L by a predetermined sandblasting process, as shown in Figure 3, the wires 20A and 20B, which are the warp and weft threads, are mostly sprayed onto the upper surface by the sprayer 100, resulting in a fine textured surface. If maintaining a tensile state is not particularly necessary, this tensile state is not required during the blasting process.

[0069] As a result, while there is a high probability that the blast material B raining down from vertically above (Z direction) will directly collide with the upper surface U of each wire 20A, 20B, the blast material B is also emitted from the nozzle 100A of the injector 100 not only vertically (Z) upwards and vertically downwards, but also spreads outwards. For example, the blast material B is ejected in a conical shape at an angle θ (e.g., 14°). Consequently, even around the upper surface U, that is, on the side L, collision events with the blast material B occur, albeit with less probability than on the upper surface U, but from an oblique direction relative to the vertical (Z) direction.

[0070] Furthermore, at this time, as shown in Figure 3(B), for example, a portion of the blast material B that has fallen vertically (g) onto the upper surface U of an adjacent wire (wire 20A on the right in the figure) may be specularly reflected off the surface of the upper surface U (however, for the sake of clarity, the surface of wire 20A at this point of impact is approximately assumed to be a smooth curved surface without irregularities), and may collide with the side surface L of the wire 20A to its left. Such phenomena can occur (although they may be infrequent).

[0071] In this way, in terms of the frequency of formation of irregularities, the top surface U, followed by the side surface L, is subjected to sandblasting, which creates a large number of irregularities. Furthermore, in this sandblasting process, in addition to the top surface U and side surface L of the wires 20A and 20B, some of the blast material B may also wrap around to the bottom surface (back surface) D of the wires 20A and 20B, creating fine irregularities (although this is not very frequent).

[0072] In this embodiment, the sandblasting process is configured in the second step S2 shown in Figure 4 to create irregularities by blasting blast material B onto the warp and weft threads 20A and 20B that make up the net 10 immediately after weaving, causing them to collide with the surface. However, the surface processing is not limited to this step.

[0073] For example, the filter (sieve) 1 may be configured to perform surface treatment on the warp and weft threads with a blasting material immediately after the entire product is completed. In that case, after this surface treatment, a washing process should be carried out to remove any remaining blasting material.

[0074] Furthermore, if a similar effect can be obtained, the blasting process may be performed on the individual wires 20A and 20B before weaving. However, when blasting is performed on the individual wires before weaving, for example, if the same uneven processing is applied to the entire 360-degree surface, when these wires are combined as warp and weft threads to weave the sieve (mesh) 10, at the lattice points C where the warp and weft threads overlap, the overlapping surfaces where the warp and weft threads come into contact with each other are also subjected to the same uneven processing as the other surfaces.

[0075] Furthermore, since slack in the sieve (mesh) 10 woven as warp and weft threads would reduce the classification effect, it is necessary to continuously maintain a state of being pulled with a predetermined tension. Therefore, at the overlapping portions of the warp and weft threads that form lattice points C, the uneven surfaces of the warp and weft threads interact with each other and are prone to damage. Considering these circumstances, it is preferable to perform the sandblasting process at least after weaving.

[0076] In this embodiment, as mentioned above, the wires 20A and 20B used are made from one of the following materials, which exhibit high effectiveness and efficiency with respect to the material being classified: nylon, polyester (e.g., PET: polyethylene terephthalate), polypropylene, fluororesin (e.g., Teflon®, polyvinylidene fluoride), polyetheretherketone, polyamide 66, polyamide 6, polyimide, polyethylene, etc.

[0077] Furthermore, considering that the blasting material B, which is used to create fine depressions on the surface of wires 20A and 20B by impacting them, is intended as a filter for classifying powders and granules for food or pharmaceutical use, water-soluble materials such as silica (silicic acid compound) and sodium chloride (NaCl) are used. Since there is a risk of blasting material residue remaining after the surface treatment, it is washed with a specified washing water.

[0078] [effect] Therefore, according to this embodiment, the third step S3 is performed by washing with washing water. As a result, even if any blasting material B remains attached to the mesh 10 after sandblasting, it can be removed by washing with washing water. Therefore, even when used for classifying powders and granules for food or pharmaceuticals, for example, a filter (filter device) with ensured safety can be provided.

[0079] Thus, according to this embodiment, even if blasting material remains on the surface of the wires 20A and 20B, safety can be ensured by removing it with cleaning water. In addition to the above, other blasting materials that can be used include sodium bicarbonate (baking soda or also known as sodium bicarbonate), citric acid, magnesium chloride, oxalic acid, calcium stearate, sodium phosphate, calcium carbonate, and potassium aluminum sulfate (alum).

[0080] Furthermore, if any residual blasting material remains after being washed with this water, and is subsequently filtered through filter 1 to classify the material, even if it is mixed in with the material, there is no significant safety concern since the blasting material used is the aforementioned silica or sodium chloride. As mentioned above, the blasting material used can be water-soluble or granular material used as a food additive.

[0081] Furthermore, in this embodiment, the blast material B has a particle size of 10 μm or 100 μm. For example, when using a particle size of 10 μm, it is possible to achieve a fine, microscopic uneven surface. When using a particle size of 100 μm, it is possible to achieve a slightly coarser uneven surface. As mentioned above, the particle size to be processed may be, for example, a minimum particle size of 1 μm or less to a maximum particle size of 1000 μm (= 1 mm), and similar effects can be expected.

[0082] Furthermore, in this embodiment, although the details of the opening 10A will be described later, for example, when the opening 10A is fine-mesh, such as 100 μm or 200 μm, a significantly greater classification effect can be obtained compared to those without microfabrication on the wire surface. Also, when the opening 10A is coarse-mesh, such as 1000 μm or 2000 μm, the opening is too large and not very effective for sieving food. However, for example, filter 1 with an opening 10A of 1000 μm can obtain a better classification effect for oily foods such as pancake mix compared to filters with a finer opening 10A of 100 μm or 200 μm.

[0083] <3. Modified form of the second embodiment> Furthermore, in the second embodiment, since the mesh 10 is made of resin, the mesh was attached to the frame by heat fusion. However, other than this, for example as shown in Figure 5, the mesh may be assembled integrally by sandwiching it between a flat cylindrical or ring-shaped inner frame 30 and an outer frame 40 with an O-ring 50 interposed between them (for example, in the case of a metal outer frame, clamping or crimping may be performed).

[0084] In this case as well, when assembling the mesh 10 to the inner frame 30 and outer frame 40, it is necessary to hold the outer circumference (end) of the mesh 10 under a predetermined high tension using a jig or the like (not shown). Furthermore, when assembling the mesh 10 to this frame, for example, if the inner frame 30, outer frame 40 and O-ring 50 are made of suitable resin, the resin mesh 10 and the resin inner frame 30, outer frame 40 and O-ring 50 may be fixed together as a single unit by heat fusion.

[0085] Furthermore, after attaching the mesh 10 to the inner frame 30 and outer frame 40, the excess portion of the mesh 10 that protrudes to the outside is cut off using an appropriate cutting means to form a framed mesh (sometimes called a "framed filter 60"). Then, this framed filter 60 is attached and fixed to the inner surface of a pre-formed cylindrical body 80 using a ring-shaped fastener 70. Figure 6 shows the cross-sectional state when assembled in this way.

[0086] The framed filter 60 formed in this manner is fixed to the inner circumference of a cylindrical body 80 formed in a roughly cylindrical shape from an appropriate material, and then assembled and fixed as a single unit by clamping it with a fastener 70 fitted over it.

[0087] The framed filter 60 in this embodiment has a structure as shown in Figures 5(A) and (B), for example, but this is merely one embodiment and is not limited to this structure; any structure can be applied as appropriate. Furthermore, the mounting state of the framed filter 60 to the cylindrical body 80 in this embodiment is not limited to the configuration shown in Figure 6.

[0088] For example, if the framed filter is to be replaced as needed with various types that differ in wire diameter, opening size, or weaving method, or if the wire of the framed filter needs to be replaced with a new one as needed when it deteriorates, but frequent replacement is required, the framed filter may be configured to be detachable.

[0089] <4. Experimental Example 1> Next, for wires 20A and 20B having various openings, weaving patterns, and outer diameter dimensions that constitute the warp and weft threads of the filter 1 according to the present invention, a sieving experiment was conducted to evaluate the arithmetic mean roughness Ra of the uneven portions formed when sandblasted, the average spacing S of the local peaks, the weight of the sieved granular material, the classification ratio (percentage of material that was not sieved), and the rate of increase in classification compared to the unsandblasted material (UP rate), as well as the sieving test (Experimental Example 1). The experimental data obtained at that time is shown in [Table 1].

[0090] The sieving apparatus used in this powder sieving experiment was a Meiji Junior Sifter 200. The powder material used was strong flour, specifically pancake mix powder (NIPPN S600). The experimental conditions involved adding 900g of the powder material per minute five times (total input amount 4500g), and measuring the weight of the sieved powder after 5 minutes. However, the sandblasting conditions used here were as follows. • Equipment used: SG-11B (conveyor type) (manufactured by Fuji Seisakusho Co., Ltd.) • Injection pressure: 0.5 MPa • Nozzle diameter: φ9 • Spray time: 35 min (both sides) • Propellant: Sodium chloride (average particle size 10 μm) • Mesh used: Resin mesh (Nylon (13XXX-100: (SEFER (Switzerland) nylon mesh NYTAL)) • Work size: 570mm x 500mm (length x width dimensions of the sieve in the powder sieving experiment apparatus)

[0091] [Table 1] (Note 1) The wire is made from nylon. (Note 2) In the evaluation, ◎ indicates good, ○ indicates good, and × indicates poor. (Note 3) ASTM18-1000 has an aperture of 1000 μm, and ASTM10-2000 has an aperture of 2000 μm.

[0092] According to the measurement results in this experimental example 1, as shown in [Table 1] above, it was confirmed that by applying sandblasting treatment to the mesh 10, the surface roughness (arithmetic mean roughness Ra in [Table 1]) of the upper and side surfaces of the wires 20A and 20B, which are the warp and weft threads constituting the mesh 10, and the average spacing S of the local peaks could be changed compared to wires that were not sandblasted. In particular, the change in surface irregularities in the arithmetic mean roughness Ra could be greatly increased.

[0093] Furthermore, regarding the classification effect of a mesh using wire material with fine surface irregularities formed in this manner, as shown in [Table 1] above, when classifying pancake mix powder (NIPPN S600) using a Meiji Junior Sifter, it was confirmed that the classification effect increased by 14-16% for meshes with an opening of 1000 μm compared to meshes that were not sandblasted. However, no significant difference was observed in classification performance (evaluation) due to differences in the particle size of the blasting material.

[0094] For meshes with an aperture of 1000 μm, the arithmetic mean roughness Ra of the top and side surfaces of the meshes using wires with these surface micro-irregularities was 0.229–0.286 μm for the top surface and 0.205–0.248 μm for the side surfaces for those with a good evaluation (◎). For those with a good evaluation (〇), the values ​​were 0.225–0.406 μm for the top surface and 0.263–0.365 μm for the side surfaces.

[0095] On the other hand, in the case of a mesh with an opening of 2000 μm, no difference in effect could be found between the pancake mix powder that was sandblasted and the powder that was not sandblasted, possibly because the opening was too large. This suggests that the opening was too large, resulting in too much material being filtered through the sieve.

[0096] <5. Reference example 1> In Experimental Example 1 described above, the wires 20A and 20B according to the present invention were formed using nylon as the raw material for the experiment. On the other hand, in Reference Example 1, instead of nylon, wires formed using polyester, one of the resin materials according to the present invention, were used, and the same sandblasting treatment was performed. However, the openings formed by the gaps between adjacent wires in the sieve section of the filter used here were 1000 μm in diameter.

[0097] Furthermore, it was found that the polyester wire used in this Reference Example 1 has the following physical properties. Regarding the average distance (S) between local peaks: The average distance (S) between adjacent local peaks of uneven areas on the wire surface showed almost no difference between the top and side surfaces of nylon compared to untreated materials, and the same was true for polyester compared to untreated materials. • About arithmetic mean roughness (Ra): In Experimental Example 1, when nylon was used, with an opening of 1000 μm, the arithmetic mean roughness (Ra) was approximately 2.18 to 3.07 times higher on the top surface and 1.53 to 2.25 times higher on the sides compared to the untreated material. In contrast, when polyester was used in Reference Example 1, the arithmetic mean roughness (Ra) was approximately 3.5 to 7.48 times higher on the top surface and approximately 2.38 to 3.58 times higher on the sides compared to the untreated material (all comparisons are between maximum values). This suggests that polyester has a rougher surface, which is easily understood given that nylon has higher flexibility as a physical property.

[0098] Although the size of the opening differs from that used in this reference experiment 1, the following findings have been obtained from similar experiments using a filter with wires having the same physical properties, i.e., a sieve section with an opening of 2000 μm between the wires. Specifically, the arithmetic mean roughness (Ra) of the nylon material was approximately 2.3 to 4.1 times higher on the top surface and 1.7 to 1.8 times higher on the sides compared to the untreated material, while the arithmetic mean roughness of the polyester material was approximately 2.5 to 6.37 times higher on the top surface and 1.86 to 5.4 times higher on the sides compared to the untreated material (all comparisons are between maximum values). Furthermore, regarding the average spacing of local peaks (S), there was almost no difference between the top and sides of the nylon material compared to the untreated material. On the other hand, there was also almost no difference between the top and sides of the polyester material compared to the untreated material. Thus, even with sieves that have a wide opening, polyester has a greater surface roughness (difference in unevenness), but this can be easily understood because nylon is more flexible.

[0099] We conducted an experiment similar to Experiment 1 (hereinafter referred to as "Reference Experiment 1") on a filter using a sieve section formed by weaving together wire materials having the aforementioned uneven surface configuration. The experimental results were as follows (referred to as [Table 2]).

[0100] [Table 2] (Note) The wire material is made from polyester.

[0101] Therefore, when the same blasting material was used to create a textured surface on wires made of nylon and polyester, it was found that the polyester wire could form a larger textured surface than the nylon wire. This is easily predictable because nylon has higher flexibility in terms of its physical properties.

[0102] Furthermore, in the experiment in Reference Example 1, i.e., Reference Experiment 1, as shown in "Table 2," pancake mix powder was used as the material to be classified, and the experimental data regarding the sieving rate showed almost no difference compared to those who did not undergo sandblasting. This suggests that, similar to the case with nylon materials, the opening was too large, resulting in excessive sieving.

[0103] <6. Experimental Example 2> Next, for nylon wires 20A and 20B, which constitute the warp and weft threads of the filter 1 according to the present invention, and have various openings, weaving methods, and outer diameter dimensions, a sieving experiment was similarly conducted (Experimental Example 2) to evaluate the arithmetic mean roughness (Ra) of the uneven surface formed when sandblasting was performed on a finer mesh sieve, i.e., a screen, compared to Experimental Example 1. This experiment measured the weight of the granular material that passed through the sieve, the classification ratio (percentage of material that passed through the sieve), and the rate of increase in classification compared to untreated material (UP rate). The experimental data obtained are shown in [Table 3].

[0104] The sieving apparatus used in this experiment was the same Meiji Junior Sifter 200 as in the previous experiment. The powder material used was cake flour (American soft white wheat). The experimental conditions involved adding 900g of the powder material at a rate of 5 times (total amount added: 4500g), and the weight of the sieved powder was measured after 5 minutes.

[0105] [Table 3] (Note 1) The wire is made from nylon. (Note 2) In the evaluation, ◎ indicates good, ○ indicates good, and × indicates poor. (Note 3) Weaving method XX: Normal Quality, XXX: Heavy fabrics (plain weave, large yarn diameter)

[0106] According to the measurement results in this experimental example 2, as shown in Table 3 above, by applying sandblasting treatment to the mesh 10, a significant classification effect was observed in the surface roughness of the top and side surfaces of the wires 20A and 20B, which are the warp and weft threads constituting the mesh 10, for both 100 μm and 200 μm openings, compared to wires that were not sandblasted. From this, it can be inferred that these top and side surfaces were subjected to fine uneven processing by the blasting material.

[0107] Furthermore, regarding the classification performance of meshes using wire materials with fine surface irregularities formed in this manner, as shown in [Table 3], when classifying cake flour using a Meiji Junior Sifter, it was confirmed that the classification performance increased by 1.26 to 17 times or more when the opening was 200 μm in both the vertical and horizontal directions. In particular, there was a significant difference in the effect depending on the weaving method, and it was found that the effect of sandblasting on classification performance was greater for XXX weave (plain weave) than for XX weave. On the other hand, a similar effect was observed in the case of meshes with an opening of 100 μm, but the effect of sandblasting on classification performance due to the difference in weaving method was not as significant as that for meshes with an opening of 200 μm.

[0108] Therefore, according to this experimental example 2, as can be easily understood from [Table 3], the classification performance of filters with finer mesh differs significantly depending on whether or not blast treatment is performed, compared to those with coarser mesh (wider openings) in [Table 1]. In particular, although the reason is unclear, it was found that the effect of sandblasting on classification performance differs greatly depending on the weave. Specifically, according to this experimental example 2, it was confirmed that the XXX weave (plain weave) showed 13.6 times (for an opening of 200 μm) and 4.69 times (for an opening of 100 μm) higher classification performance than the XX weave.

[0109] <7. Reference example 2> In Experimental Example 2 described above, the wires 20A and 20B according to the present invention were formed using nylon as the raw material for the experiment. On the other hand, in Reference Example 2, instead of nylon, wires formed using polyester, one of the resin materials according to the present invention, were used, and the same sandblasting treatment was performed. However, for the openings formed by the gaps between adjacent wires in the sieve section of the filter used here, 100 μm (PET105) and 200 μm (PET200) were used.

[0110] In this Reference Example 2, we conducted an experiment on the sieving effect similar to that of Example 2 (hereinafter referred to as "Reference Experiment 2"), and obtained the results shown in [Table 4] below.

[0111] [Table 4]

[0112] According to this reference experiment 2, as shown in [Table 4], although the effect is not as significant as that obtained in the powder sieving experiment in Experiment Example 2 using nylon, as shown in [Table 3], it was confirmed that a certain degree of sieving effect is produced.

[0113] <8. Additional experimental examples> In the experiments using the meshes described above in Experimental Examples 1 and 2, and Reference Examples 1 and 2, when the wire material was sandblasted, the sandblasting was performed not only on the surface and sides of the wire material, but also on a portion of the underside. However, separate from the sandblasted meshes used in these Experimental Examples and Reference Examples, the inventors also conducted a similar experiment (hereinafter referred to as the "additional experiment") on a mesh in which the underside of the wire material used for the mesh was not sandblasted, i.e., the back surface opposite to the top surface where the material to be classified falls through the sieve falls, meaning that no irregularities were formed. The results shown in Table 5 below were obtained.

[0114] [Table 5] (Note 1) The wire is made from nylon. (Note 2) In the evaluation, △ indicates slightly good. (Note 3) Weaving method XX: Normal Quality,

[0115] This additional experiment confirmed that, as shown in [Table 5], even a mesh made with wire treated with sandblasting on only one side showed a slight improvement in classification performance, similar to the case of double-sided treatment.

[0116] In other words, to explain this in detail, in a mesh (7XX-200S) using wire that had been sandblasted on only one side (top side), the classification rate was confirmed to be about 6% higher than that of a mesh using wire that had not been sandblasted at all (sometimes called a "mesh using untreated wire"), but it was found that the effect of the sandblasting was not very significant. On the other hand, in the case of a mesh (7XX-200D) using wire that had been sandblasted on both sides, the classification rate was confirmed to be slightly higher, about 3%, than that of a mesh using untreated wire.

[0117] In other words, for wires that were sandblasted all the way to the bottom, it was initially expected that the contact area with the powder and granules would be reduced even in the uneven areas of the bottom surface D, thus reducing frictional resistance to the powder and granules on the bottom surface D, as well as reducing the amount of adhesion, and theoretically increasing the classification rate (sieving rate). However, in this additional experiment, the classification rate of the mesh using wires that had been sandblasted on both sides was slightly lower than that of the mesh using wires that had been sandblasted on only one side. In other words, it was confirmed that sandblasting on one side could achieve the same effect as sandblasting on both sides. From this, it can be inferred that, in the case of wires used in meshes that are double-sided, even though the lower side of the wire is formed with double-sided processing, the classification action on the material to be classified on the lower side, that is, the reduction in frictional resistance force (amount) due to the reduction in contact area with the material to be classified due to the formation of irregularities on the lower side of the wire, is less significant than the fact that some of the material to be classified gets stuck in the recesses of the irregularities and remains there, preventing the sieving action from being removed, thus reducing the sieving rate.

[0118] Furthermore, in this additional experiment, the sandblasting effect on the wire rod was lower than in the previous Experimental Examples 1 and 2, regardless of whether the sandblasting was done on one side or both sides. One possible reason for this is that the powder material used for classification was weak flour. In other words, even with the mesh using wire rods that had not been sandblasted, 89% of the material was able to pass through the sieve, suggesting that it was a relatively easy powder to sieve through. Another possible reason for the low effectiveness of the sandblasting is that this additional experiment was conducted in mid-summer (August 21st) under high humidity (85%), and the high humidity may have had some effect on the powder material, leading to an increase in the sieve rate on the mesh that had not been sandblasted.

[0119] Thus, in these additional experimental examples, no significant differences in classification effectiveness were observed whether the wire used was blast-treated on only one side, on both sides, or on a mesh made with wire that was not blast-treated.

[0120] Finally, the above-described embodiments are merely examples of the present invention, and the present invention is not limited to the embodiments described above. Therefore, it goes without saying that various modifications are possible even in embodiments other than those described above, as long as they do not depart from the technical spirit of the present invention. Furthermore, various resin materials such as nylon, polyester, polypropylene, fluororesins, polyetheretherketone, polyamide 66, polyamide 6, polyimide, and polyethylene can be widely applied as wire materials for use in the present invention. [Explanation of symbols]

[0121] 1 filter 10 Phloem (net) 10A opening 20A wire (warp thread) 20B wire (weft thread) 30 Inner frame 40 Outer frame 50 O-rings 60 framed filters 70 fasteners 80 Cylindrical body 100 injectors 100A nozzle 200 Powder sieving experimental apparatus (Meiji Junior Sifter) A1 Grid point and surrounding region A2 Region of individual warp and weft threads B. Blast material (water-soluble abrasive) C Grid points where warp and weft threads (wires) intersect. D The underside (back side) of the warp and weft threads (wires) L Side of the vertical and horizontal threads (wires) Ra: Arithmetic mean roughness S: Average distance between local mountain peaks U The top surface (front) of the vertical and horizontal threads (wires) W1, W2 warp threads W3, W4 weft threads XX type of weave (Normal Quality) XXX A type of weaving (plain weave) Z: Vertical (gravitational acceleration) direction a. Distance between warp threads b Distance between weft threads

Claims

1. A filter having a mesh-like sieve portion woven using wires formed from a predetermined resin, such that the wires intersect three-dimensionally from at least two different directions, The wire facing the opening through which the material to be classified passes in the sieve is made of a predetermined material, and its surface is processed by sandblasting using a water-soluble blasting material that can be removed by washing, so that at least the upper surface and the side surface between the upper and lower surfaces have irregularities formed on them. A filter characterized by the following features.

2. The wire rod has an average distance S between adjacent protrusions that form local peaks in the uneven portion formed by the sandblasting process, where S is the diameter (D) of the powder or granular material being classified. ５０ It is formed to be smaller than ) The object to be classified is configured to contact only the local peak of the wire when it passes through the opening. The filter according to feature 1.

3. The filter according to claim 2, characterized in that the sieve portion has an opening width of at least 1 μm to a maximum of 5 mm.

4. The average spacing S between adjacent protrusions that form local peaks in the uneven portion of the wire is 0.93 to 1.36 μm on the top surface and 0.927 to 1.42 μm on the side surface in the case of a low mesh having an opening width of 1000 μm, The arithmetic mean roughness Ra of the aforementioned uneven portion is 0.225 to 0.406 μm on the top surface and 0.205 to 0.365 μm on the side surface in the case of a low mesh with an opening width of 1000 μm. The filter according to claim 3.

5. The filter according to claim 1 or 2, characterized in that the material to be classified is a powder or granular material for food or pharmaceutical use.

6. The processed surface of the wire, which has been processed and given an uneven surface by the sandblasting process, includes not only the upper surface of the wire facing the opening of the sieve through which the material to be classified passes, and the side surface of the wire between the upper and lower surfaces of the wire, but also the lower surface of the wire opposite to the upper surface of the wire. The filter according to any one of claims 1 to 5, characterized by the features described herein.

7. A method for manufacturing a filter comprising a mesh-like sieve section formed by weaving wires made of a predetermined resin so that the wires intersect three-dimensionally from at least two different directions, wherein the sieve section is used to classify a desired powder-like material to be classified through openings that are gaps between the wires, The aforementioned wire material is woven into a mesh to form a sieve. A sandblasting process is performed on at least the upper surface portion and the side surface portion between the upper and lower surfaces of the wire facing the opening of the sieve through which the material to be classified passes, by spraying a predetermined water-soluble blasting material onto them. The wire material facing the opening of the sieve portion has irregularities formed on at least the upper surface portion and the side surface portion. A method for manufacturing a filter characterized by the following:

8. The method for manufacturing a filter according to claim 7, characterized in that the blasting material is one of the following: silica (silicic acid compound), sodium chloride (NaCl), sodium bicarbonate, citric acid, magnesium chloride, oxalic acid, calcium stearate, sodium phosphate, calcium carbonate, or potassium aluminum sulfate (alum).

9. The processed surface of the wire, which is processed by the sandblasting process and has irregularities formed on its surface, includes not only the upper surface of the wire facing the opening of the sieve through which the material to be classified passes, and the side surface of the wire between the upper and lower surfaces, but also the lower surface of the wire opposite to the upper surface. A method for manufacturing a filter according to claim 7 or 8, characterized in that it is a method for manufacturing a filter.

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