JP2021023877A - Filter cloth - Google Patents

Abstract

To provide a filter cloth excellent in versatility and excellent in filtering performance.SOLUTION: A filter cloth has a sheet-like filter part composed of a woven fabric, and the woven fabric has elongation ratio of 10% or more and 35% or less when tension of 1 kgf is applied in a direction of 45 degrees to both of a warp and a weft.SELECTED DRAWING: Figure 1

Description

The present invention relates to a filter cloth for filtering a suspension.

Conventionally, a step of filtering a suspension discharged from a concrete placing site or a concrete product manufacturing site to remove solids such as cement contained in the suspension has been performed.
For example, in Patent Document 1 below, a non-woven fabric is formed into a bottomed cylindrical shape and used as a filter material, and a bottomed cylindrical frame material one size larger than the filter material is used as a holder for the filter material. It is described that the filter material is housed in the holder and used as a filter tank, and the suspension containing cement or the like is filtered using the filter tank.

JP-A-2002-28416

It cannot be said that the filter medium having a three-dimensional shape as described in Patent Document 1 is sufficiently versatile because it is difficult to attach it to a holder having a different shape.
Regarding such a problem in the conventional filtration tank, a filter cloth having a flat sheet-like filtration portion is used, and the filtration portion is held by a holder so as to have a downwardly recessed shape, and the filtration is performed. It is considered that if the suspension is poured into the recessed portion of the portion and filtered, the versatility of the filter cloth can be improved without any particular restriction on the shape of the holder.
However, if the filtration part is in the form of a flat sheet, it is difficult to form a recessed shape with sufficient depth as it is, and it is considered difficult to secure a wide effective area (area of the part that can be used for filtration) of the filtration part. ..

As described above, if a flat sheet-shaped filtration unit is provided in order to improve versatility, it becomes difficult to secure a wide filtration area, and it becomes difficult to exhibit good filtration performance.
Therefore, an object of the present invention is to solve such a problem, and an object of the present invention is to provide a filtration cloth having excellent versatility and excellent filtration performance.

In order to solve the above problems, the present invention
A filter cloth used as a component of a filter tank for filtering a suspension.
It has a sheet-like filtration unit composed of a woven fabric with warp and weft.
The filtration tank is provided with a holder for holding the filter so as to have a downwardly recessed shape, and the suspension is filtered by the filter while being held by the holder. Is composed of
The woven fabric constituting the filtration unit has an elongation rate of 10% or more and 35% or less when a tension of 1 kgf is applied in a direction of 45 degrees to both the warp and the weft. I will provide a.

Since the filtration cloth according to the present invention is made of a woven cloth in which the filtration part exhibits an appropriate elongation in an oblique direction, it is easy to form a deep recessed shape, and a wide area that can be effectively used for filtration is secured. be able to.
Further, in the present invention, the woven fabric constituting the filtration unit includes warp threads and weft threads.
The woven fabric exhibits an appropriate elongation in a direction oblique to the warp and weft (45 degree direction).
When this woven fabric is stretched in an oblique direction, it is possible to prevent the angle at which the warp and the weft intersect from being oblique and the opening from becoming excessively large.
Further, in the present invention, since the degree of elongation in the oblique direction is less than a certain level, it is possible to suppress the possibility that the yarn becomes thin and the opening becomes large due to excessive elongation.
That is, in the present invention, the possibility that solids such as cement are mixed in the filtered water can be suppressed.

For example, the woven fabric has an elongation rate when a tension of 1 kgf is applied in the direction of the warp threads and an elongation rate when a tension of 1 kgf is applied in the direction of the weft threads, both of which are less than 10%. May be good.

In such a filter cloth, since the elongation rate of the woven fabric in the warp and weft directions is less than a predetermined value, the warp and the weft become thin due to the elongation (the opening becomes large). Can be suppressed.

The filter cloth of the present invention is further provided with, for example, a fixing part for fixing the filter part to the holder, the woven cloth is rectangular, and four sides are parallel to the warp or the weft, respectively. , The fixing portion may be provided at the four corner portions of the woven fabric.

In such a filter cloth, by supplying a suspension to a filter portion having a recessed shape, tension is applied to the woven fabric constituting the filter portion by utilizing the weight of the suspension. Moreover, it is easy to apply the tension in the direction from the central portion of the woven fabric to the corner portion where the fixed portion is formed.
That is, in the filter cloth having such a structure, when the suspension is filtered, the woven cloth tends to be stretched in an oblique direction, and the filtration area tends to expand.

In the filter cloth of the present invention, for example, the fixing portion may be further provided at the central portion of the four sides.
In such a filter cloth, it is possible to prevent an excessive tension from being applied in an oblique direction when the suspension is supplied to the recessed filter section.

As described above, in the present invention, a filtration cloth having excellent versatility and excellent filtration performance can be provided.

It is a figure for demonstrating the use state (filter tank) of the filter cloth which concerns on this embodiment. It is a front view of the filter cloth which concerns on this embodiment. It is a back view of the filter cloth which concerns on this embodiment. It is a top view of the filter cloth which concerns on this embodiment. It is a right side view of the filter cloth which concerns on this embodiment. In FIG. 6, (a) is an enlarged view of a corner portion on the front side of the filter cloth, and (b) is an enlarged view of a corner portion on the back side of the filter cloth. It is sectional drawing of the filter cloth which concerns on the same embodiment, and is sectional drawing at the position of line VII-VII in FIG. 6 (b). In FIG. 8, (a) is an enlarged view of the front side of the straight portion of the filter cloth, and (b) is an enlarged view of the back side of the straight portion of the filter cloth. It is sectional drawing of the filter cloth which concerns on this embodiment, and is sectional drawing at the position of IX-IX line in FIG. 8B. It is the figure which showed the state of the yarn by enlarging a part of the woven cloth which constitutes a filter cloth. It is a figure which showed a part of the woven cloth further enlarged than FIG. It is a front view of the filtration cloth used for the filtration method which concerns on this embodiment. It is a figure for demonstrating the method of measuring the elongation rate of a woven cloth.

Hereinafter, the filter cloth according to the embodiment of the present invention will be described with reference to the drawings.

The cleaning drainage after cleaning the pumps and pipes of concrete pump trucks that have finished discharging concrete is in a suspended state containing granular substances such as concrete.
As shown in FIG. 1, the filter cloth according to the present embodiment is used to filter the suspension S such as the washing wastewater to separate the solid content S1 such as the concrete component and the water content S2. To.
That is, the filtration cloth 1 according to the present embodiment is used as a constituent member of the filtration tank 100 for filtering the suspension S.

The filtration tank 100 of the present embodiment includes the filtration cloth 1 having a flat sheet shape in a natural state, and a holder T for holding the filtration cloth 1 so as to have a concave shape downward. It has.
The filtration cloth 1 of the present embodiment is provided with a filtration unit 2 as an area for carrying out the filtration.
The filtration unit 2 of the present embodiment has an edge portion 21 provided along the outer peripheral edge and a main body portion 22 surrounded by the edge portion 21.
In the filtration tank 100 of the present embodiment, the filtration cloth 1 is held by the holder T so that the recessed portion 210 having a shape recessed downward is formed in the main body portion 22.

As shown in FIG. 1, the filtration tank 100 of the present embodiment is configured to filter the suspension S at the recessed portion 210.
That is, in the filtration tank 100 of the present embodiment, the recessed portion 210 formed in the filtration portion 2 by recessing a part thereof downward is used as an accommodation space 101 in which the suspension S is accommodated. Utilized, the suspension S contained in the recess 210 is filtered by the action of gravity, and the water content S2 of the suspension S is passed from the upper surface side to the lower surface side of the filtration cloth 1 and the suspension is passed. S1 is configured to be able to be deposited on the upper surface side of the filtration cloth 1.

In the filtration tank 100 of the present embodiment, a drain port for draining the water S2, which is a filtrate that permeates the filter cloth 1, is provided on the bottom surface portion T1 of the holder T, and the holder T On the lower side, a water receiving portion P for receiving the water S2 obtained by filtration is provided.
In the filtration tank 100 of the present embodiment, the water receiving portion P is configured by a water receiving pit whose shape in top view is one size larger than that of the holder T and whose height in side view is lower than that of the holder T. ing.

The holder T in the present embodiment is, for example, a basket-shaped member having an opening that opens upward so that the central portion of the filter cloth 1 can be recessed downward and held. ..
The holder T of the present embodiment includes a bottom surface portion T1 and a side surface portion T2 rising from the outer peripheral edge of the bottom surface portion T1, and the opening is defined by the upper end edge of the side surface portion T2.
The holder T of the present embodiment is a basket-shaped member having a rectangular parallelepiped shape of a space formed inside the bottom surface portion T1 and the side surface portion T2.
That is, the holder T in the present embodiment is formed so that the shape in the top view is rectangular.

In the holder T of the present embodiment, the height of the upper end edge of the side surface portion T2 that defines the opening is common to the entire circumference around the opening.
On the outside of the side surface portion T2 of the holder T of the present embodiment, a locking portion Ta in which the filter cloth 1 is locked is formed below the upper end edge of the side surface portion T2.
The locking portion Ta of the present embodiment is configured by a hook (not shown).
The locking portions Ta are provided at a plurality of locations at intervals in a direction in which they orbit around the side surface portion T2.
The locking portions Ta are provided at eight locations, four rectangular corner portions and four side center portions, which are the shapes of the holder T in a top view.

The filtration cloth 1 of the present embodiment has a larger area than the opening of the holder T, and the recessed portion 210 can be formed inside the side wall portion of the holder T, and the outer peripheral portion of the holder T can be formed. It has a size that allows it to be wrapped outward beyond the upper edge of the side wall.

FIG. 2 is a front view of the filter cloth 1, and FIG. 3 is a rear view showing a state in which the filter cloth 1 is viewed from the side opposite to that of FIG.
The front view (FIG. 2) and the rear view (FIG. 3) are shown symmetrically in the vertical direction.
That is, the upper end in FIG. 2 is the lower end in FIG.

FIG. 4 is a plan view of the filter cloth 1, and is a view of the filter cloth 1 of FIG. 2 as viewed from below.
The right side view of the filter cloth 1 (the view of the filter cloth 1 of FIG. 2 viewed from the right side) is shown in FIG. 5, but the left side view of the filter cloth 1 (the filter cloth 1 of FIG. 2 is on the left). The view from the side) has a shape symmetrical to that of the filter cloth 1 shown in FIG.

The filtration cloth 1 of the present embodiment is attached to the holder T so that the first surface 11 which is the front surface in FIG. 2 is the upper surface and the second surface 12 which is the front surface in FIG. 3 is the lower surface. It is used for filtration of suspension S.
In the filtration cloth 1 of the present embodiment, the filtration unit 2 has a horizontally long rectangular shape as described above, and for example, the long side dimension of the filtration unit 2 is 150 to 200 cm and the short side dimension is 100 to 150 cm. Can be the size of.

In the filter cloth 1 of the present embodiment, the filter portion 2 is made of a woven cloth, and the outer peripheral portion of the woven cloth constituting the main body portion 22 is folded back to form the end edge portion 21.
The edge portion 21 may be reinforced by sandwiching a band-shaped member different from the woven fabric.
As shown in FIGS. 2 and 3, the edge portion 21 includes a horizontal end edge portion 21a extending in the lateral direction and a vertical end edge portion 21b extending in the vertical direction.

As shown in FIGS. 1 to 3, the filter cloth 1 has a fixing portion 3 for fixing to the holder T and a connecting means 4 for connecting the fixing portion 3 to the filtering portion 2 (see FIGS. 6 and 8). ) And.

As shown in FIGS. 2 and 3, the fixing portion 3 for fixing the filtration portion 2 to the holder T is formed in a band shape having a longitudinal direction and a lateral direction orthogonal to the longitudinal direction. One end in the longitudinal direction is connected to the end edge 21 of the filtration section 2.
The fixing portion 3 of the present embodiment is configured by superimposing flat strings.
A plurality of the fixing portions 3 are attached to the filtering portion 2.
In the present embodiment, the fixing portion 3 is attached to the corner portion 200 and the straight portion 201 of the filtration portion 2.
The fixing portion 3 attached to the straight portion 201 is attached to the central portion of the straight portion 201.
More specifically, the fixing portion 3 is provided at each of the four corners of the rectangular woven fabric constituting the filtration portion 2 and at the center of the four sides of the rectangular woven fabric. ing.
That is, the fixing portion 3 of the present embodiment includes a central portion of the horizontal end edge portion 21a, a central portion of the vertical end edge portion 21b, and a connection portion between the horizontal end edge portion 21a and the vertical end edge portion 21b. It is connected to eight places with the corners, and eight are attached to one filtration part 2.

One end of the fixed portion 3 in the longitudinal direction is a fixed end attached to the filtration portion 2, and the other end is a free end.

In the present embodiment, the connecting means 4, which is a means for connecting the fixing portion 3 to the filtering portion 2, is a sewing thread and forms a seam portion 40.
Specifically, the fixing portion 3 is sewn to the end edge portion 21 of the filtering portion 2 using a sewing thread.

As shown in FIGS. 6 to 9, the seam portions 40 are formed so as to intersect the fixing portions 3 in the longitudinal direction.
The seam portion 40 has a pair of first seam portions 41 separated from each other in the longitudinal direction of the fixing portion 3, and a second seam portion 42 formed so as to connect the pair of first seam portions 41. ..
The pair of first seam portions 41 extend in a direction substantially orthogonal to the longitudinal direction of the fixing portion 3. The second seam portion 42 extends so as to connect one end of one of the first seam portions 41 of the pair of first seam portions 41 and the other end of the other first seam portion 41. ..
That is, the seam portion 40 of the present embodiment is formed in a Z shape.

The filter cloth 1 of the present embodiment has a holder in which one end in the longitudinal direction is connected to the end edge 21 by the connecting means 4 and the other end of the fixing portion 3 is locked to a predetermined position of the holder T. The position with respect to T is fixed.
When the filter cloth 1 of the present embodiment is set on the holder T, each of the eight fixing portions 3 is attached to the locking portions Ta provided at eight locations outside the side surface portion of the holder T. Is configured to be able to lock.

In the filtration tank 100 of the present embodiment, for example, a plurality of filtration cloths 1 as shown in FIG. 2 are provided, and the suspension S is filtered using a laminate 10 in which the plurality of filtration cloths 1 are laminated. Will be done.
In the laminated body 10 in the present embodiment, the lower surface of the lowermost filtration cloth 1 does not simultaneously contact the entire upper surface of the bottom surface portion T1 of the holder T in the state before being used for filtering the suspension S. It is set in the holder T so as to be.

The laminated body 10 of the present embodiment is configured by stacking a plurality of filter cloths 1 having the same shape so that the outer peripheral edge and the fixed portion of the filter unit 2 are aligned in the vertical direction. A plurality of filter cloths 1 are superposed on the filter cloth 1.

As will be described in more detail later, the filter cloth 1 of the present embodiment has a sheet-like filter unit 2 composed of a woven fabric including warp threads and weft threads, and the filtration unit 2 has a suspension S. It is configured so that filtration can be performed.
Therefore, the laminated body 10 is configured so that the direction of the warp and the direction of the weft are common between the vertically overlapping filter cloths 1.

In the following, the length direction of the warp threads is referred to as a woven fabric or the longitudinal direction, and the length direction of the weft threads is referred to as a lateral direction of the woven fabric.
In the filter cloth 1 of the present embodiment, the woven cloth has a rectangular shape, and more specifically, the woven cloth has a shape of a horizontally long rectangular shape when viewed from the front.
In the woven fabric of the present embodiment, the direction along the short side of the rectangle is the direction of the warp (longitudinal direction), and the direction along the long side of the rectangle is the direction of the weft (horizontal direction).
In the present embodiment, the vertical direction and the horizontal direction of the filter cloth 1 and the laminated body 10 are common to the vertical direction and the horizontal direction of the woven cloth, respectively.

The woven fabric constituting the filtering unit 2 may be a plain weave woven fabric, a twill woven woven fabric, or a red woven woven fabric.

The filtration unit 2 in the present embodiment is composed of a satin weave woven fabric as shown in FIGS. 10 and 11.
Therefore, as shown in the figure, on the first surface 11 of the filtration unit 2, the ratio of the area of the portion where the warp yarn 24 extending in the vertical direction appears is the area of the exposed portion of the weft yarn 25 extending in the horizontal direction. It is smaller than the ratio of.
Specifically, on the first surface 11 of the filtration unit 2, the warp threads 24 are exposed at a rate of once with respect to the five weft threads 25.
Although not shown in the figure, the ratio of the area of the exposed portion of the warp 24 on the second surface 12 of the filtration unit 2 opposite to the first surface 11 is the expression of the weft 25. It is larger than the ratio of the area of the part.
Specifically, on the second surface 12 of the filtration unit 2, the weft thread 25 is exposed once for every five warp threads 24.

The warp threads 24 and the weft threads 25 of the present embodiment may be made of the same material or different materials, and examples of the materials of these threads include polypropylene, polyethylene, and polyester (polyethylene terephthalate, polybutylene terephthalate, etc.). Polyester polymer), synthetic resin fibers such as polyamide (aliphatic polyamide, aromatic polyamide) and the like can be mentioned.
These yarns may be composed of natural fibers such as cotton, linen, bamboo, wool, silk and rock wool.
The fibers constituting the yarn may be recycled fibers such as cupra and rayon, or semi-synthetic fibers such as acetate.
The fiber may be a metal fiber such as steel wool.

The warp 24 and the weft 25 in the present embodiment are preferably made of either polyester or polyamide, and more preferably made of polyester.
Among them, the warp threads 24 and the weft threads 25 are preferably made of polyester other than polyester elastomer, and are preferably made of polyethylene terephthalate or polybutylene terephthalate.

The warp yarn 24 and the weft yarn 25 of the present embodiment may be spun yarn or filament yarn.
When the warp yarn 24 and the weft yarn 25 of the present embodiment are the filament yarns, these yarns may be monofilament yarns or multifilament yarns.
When the warp yarns 24 and the weft yarns 25 of the present embodiment are multifilament yarns, these yarns may be pull-aligned yarns in which filaments are simply aligned, or twisted yarns in which twists are added.

When the warp yarns 24 and the weft yarns 25 of the present embodiment are twisted yarns, these yarns have a number of twists of 500 times / m or more and less than 1000 times / m even if the number of twists is less than 500 times / m. It may be medium-twisted yarn.
These yarns may be strong twisted yarns having a number of reliance of 1000 times / m or more and less than 2500 times / m, or super strong twisted yarns having a number of reliance of 2500 times / m or more.

In the woven fabric of the present embodiment, at least one of the warp yarn 24 and the weft yarn 25 is preferably a multifilament yarn, and more preferably both are multifilament yarns.
In the woven fabric of the present embodiment, both the warp yarn 24 and the weft yarn 25 are multifilament yarns.

The warp threads 24 and the weft threads 25 may have the same or different thicknesses themselves, filaments, and the like.
The filaments constituting the warp threads 24 and the weft threads 25 may have a thickness of, for example, 0.5 dtex or more and 30 dtex or less.
The warp threads 24 and the weft threads 25 may have a total fineness of 100 dtex or more and 2000 dtex or less, for example.

In the woven fabric of the present embodiment, at least one of the warp 24 and the weft 25 is preferably the sweet twisted yarn or the medium twisted yarn, and both are the sweet twisted yarn or the medium twisted yarn. preferable.
In the woven fabric of the present embodiment, both the warp yarn 24 and the weft yarn 25 are the sweet twisted yarn or the middle twisted yarn.

When filtering the suspension S, the water content S2 usually passes through a gap formed between two adjacent warp threads 24 and a gap formed between two adjacent weft threads 25. To do.
Since the warp threads 24 and the weft threads 25 are multifilament threads, the moisture S2 can pass between the filaments constituting the threads and pass through the filtering unit 2.

In the woven fabric, as shown in FIG. 11, one of the two adjacent weft threads 25 (25a) passes under the warp thread 24, and the other weft thread 25 (25b) passes over the upper side of the warp thread 24. At the passing portion, a relatively large gap Z is likely to be formed next to the warp thread 24 according to the thickness of the warp thread 24.
That is, at a position where two adjacent weft threads 25 sandwich the warp threads 24 from above and below, as shown in FIG. 11, the side edge portion of the warp threads 24 and the upper edge portion of the lower weft threads 25a A triangular gap Z surrounded by the lower edge of the upper weft 25b is likely to be formed.
A gap Z may be formed on the side of the weft 25 as well.
That is, even in a place where one of the two adjacent warp threads 24 passes under the weft thread 25 and the other warp thread 24 passes above the weft thread 25, the thickness of the weft thread 25 is adjacent to the weft thread 25. A triangular gap Z can be formed accordingly.

Although the gap Z serves as a passage for the water content S2, it can also serve as a passage for a solid content S1 having a relatively small size (floating solid matter or the like).
That is, the gap Z can also be a factor that lowers the water quality of the filtrate.

When the filtering portion 2 is made of a plain weave woven fabric, the warp threads 24 and the weft threads 25 appear alternately in the vertical direction and the horizontal direction, respectively, and the gap Z can be formed in many places. In the present embodiment, since the woven fabric is a satin weave, the number of places where such a gap Z can be formed is smaller than that in the case of a plain weave woven fabric.

In the satin weave fabric, usually, two warp threads 24 adjacent to each other and two weft threads 25 adjacent to each other are vertically overlapped to form a grid-like portion.
In the satin weave fabric, a rectangular gap may be formed at a position where the threads are arranged in a grid pattern in addition to the triangular gap Z.
When a woven fabric woven with monofilament yarn, strong twisted yarn, or the like is used as the woven fabric constituting the filtration unit 2, the warp yarn and the weft yarn are unlikely to have a flat shape in the thickness direction, and the rectangular gap and the above-mentioned The area of the triangular gap can be large.
However, in the present embodiment, since the warp 24 and the weft 25 are sweet-twisted yarns or medium-twisted yarns, the warp yarns 24 and the weft yarns 25 are easily deformed into a flat shape, and the area of these gaps can be reduced.

In order to improve the water quality of the filtrate, the area of the gap is ^{preferably 1500 μm 2} or less, ^{more preferably 1000 μm 2} or less, and 800 μm ² or less, even if it is the maximum. Is even more preferable.
^{The area of the maximum gap is preferably 100 μm 2} or more, more preferably 150 μm ² or more, and ^{further preferably 200 μm 2} or more in order to secure a constant filtration speed.

The maximum clearance area of the woven fabric in the present embodiment is, for example, the gap of the woven fabric when the woven fabric is arranged on a horizontally arranged glass plate and the woven fabric is viewed from the upper surface side. It can be obtained by observing with a microscope a point (bright point) that looks brighter than the surroundings due to the light transmitted from the lower surface side.
For the largest gap, select some of the bright spots to be observed, take a magnified photograph with a microscope, analyze the obtained photograph, and calculate the area of each. Can be identified.
Further, the area at that time can be the area of the largest gap.
In selecting the bright point to be measured, for example, from the first direction in which the elevation angle from the observation point of the woven fabric is 45 degrees and parallel to the warp, and from the observation point of the woven fabric. The bright point may be observed in the direction in which the elevation angle is 45 degrees and in the second direction parallel to the weft.
Further, the area of the largest gap can also be obtained by observing in the direction of 45 degrees.

Not only is the area of the gap preferably constant or less, but the width is also preferably constant or less.
The gap has the maximum width in order to improve the water quality of the filtrate, and the width is preferably 35 μm or less, more preferably 30 μm or less, and more preferably 25 μm or less. Is even more preferable.

The maximum width of the gap can be obtained in the same manner as the maximum area of the gap, and is obtained by observing a plurality of bright points from an angle of 45 degrees with a microscope and measuring the width of each bright point. be able to.

The filtration cloth 1 in the present embodiment filters the suspension S in a state of being held by the holder T so that the filtration unit 2 is recessed downward as described above. ..
That is, the filter cloth 1 of the present embodiment is held by the holder T in a state where the recessed portion 210 is formed in the central portion of the rectangular filtration portion 2 when the suspension S is filtered.
In the filtration cloth 1 of the present embodiment, the four corner regions (hereinafter, also referred to as “corner region X”) divided by the virtual line XL in FIG. 12 are inflated outward by the weight of the suspension S, and the suspension is suspended. In order to expand the area that can be effectively used for filtering S, the filtration section 2 is formed by using a woven cloth that exhibits a certain degree of elongation in the oblique direction.

There is no significant difference between the conventional filter cloth and the filter cloth 1 of the present embodiment in terms of filtration in the central cross region (hereinafter, also referred to as “cross region Y”) excluding the corner region X.
In the filtration cloth 1 of the present embodiment, the corner region X exhibits an excellent function for filtering the suspension S, particularly in the latter half of the filtration.
To explain this point concretely, since the filtration unit 2 is not clogged in the initial stage of filtration, the water content S2 contained in the suspension S is contained in the recessed portion 210 formed in the filtration unit 2. Quickly passes through the woven fabric, and the retention of the suspension S becomes small.
On the other hand, in the latter half of the filtration, since the solid content S1 is deposited inside the recessed portion 210, the permeation speed of the water content S2 is reduced and the retention amount of the suspension S is increased.
Then, when the retention of the suspension S increases, in addition to the weight of the accumulated solid content S1, the weight of the suspension S acts as an outward force on the recessed portion 210.
At this time, in the filter cloth 1 of the present embodiment, the woven cloth stretches in the oblique direction, so that the corner region X can be stretched and the filtration area can be expanded.

In order to exert the above functions, in the present embodiment, the elongation rate when a tension of 1 kgf is applied in the direction of 45 degrees to both the warp threads 24 and the weft threads 25 is 10% or more. The filtration unit 2 is composed of the woven cloth.
In order to more reliably exert the function, the elongation rate is preferably 12% or more, more preferably 14% or more, and further preferably 16% or more.
However, excessive elongation may allow the permeation of the solid content S1 to cause deterioration of the water quality of the filtrate. Therefore, the filtration unit 2 of the present embodiment is made of a woven fabric having an elongation rate of 35% or less. Has been done.
In order to keep the water quality of the filtrate in a good state, the elongation rate is preferably 33% or less, more preferably 31% or less, and further preferably 29% or less.

When the woven fabric is stretched in an oblique direction, the warp threads 24 and the weft threads 25 are diagonally intersected at the stretched portion.
Therefore, the rectangular gap formed at the position where the two warp threads 24 and the weft threads 25 are vertically overlapped to form a grid shape has a parallelogram shape and a narrow area.
Further, the area of the triangular gap Z that can be formed on both sides of the warp 24 as shown in FIG. 11 is narrowed because the warp 24 is slanted to close a part of the gap Z.
For this reason, the filter cloth 1 of the present embodiment can suppress a decrease in the filtration speed in the latter stage of filtration and can also suppress a decrease in the water quality of the filtrate.

It is preferable that the woven fabric of the present embodiment exhibits an appropriate elongation in an oblique direction, but does not exhibit much elongation in a direction (longitudinal direction or horizontal direction) along the warp threads 24 and the weft threads 25.
That is, it is preferable that the elongation of the woven fabric in the longitudinal direction and the elongation in the lateral direction is less than the elongation in the oblique direction (the direction in which the warp and weft are 45 degrees).
Specifically, the woven fabric has an elongation rate when a tension of 1 kgf is applied in the direction of the warp thread 24 and an elongation rate when a tension of 1 kgf is applied in the direction of the weft thread 25. It is preferably less than%.
The elongation rate in the vertical direction and the horizontal direction is more preferably less than 8%, and further preferably less than 6%.

The elongation of the woven fabric in the diagonal direction and the vertical and horizontal directions is measured using a square sample having a side length of 20 cm collected from the woven fabric.
The method of measuring the elongation rate will be described with reference to FIG. 13 which schematically shows the state of measuring the elongation rate in the diagonal direction of the woven fabric. First, when measuring the elongation rate in the diagonal direction, weaving The cloth is cut along the warp and weft directions to cut out a square sample SP having a side length of 20 cm.
By setting a distance of 15 cm on this sample SP, drawing two marked lines A, and measuring how much the distance between the marked lines (15 cm with no load) extends when a tension of 1 kgf is applied. Find the growth rate.
At this time, the marked line A is provided so as to be separated by 15 cm along the diagonal line AL so that the intermediate point thereof is the center of the diagonal line AL as much as possible.
In order to provide such a marked line A, the length of the diagonal line of a square having a side of 20 cm is about 28.3 cm (20 × 2 ^1/2 ), so from each of the two diagonal corners of the sample SP. Marking lines A may be drawn at positions approximately 6.6 cm inward along the diagonal line AL.
In the measurement of the elongation rate, next, a hole HH through which the hook is passed is provided at a point moved 4 cm outward from the marked line A toward each corner.
Here, the distance (D0) between the marked lines is accurately measured with a caliper or the like while the sample SP maintains a square shape.
Next, the sample SP is hung using one of the holes HH provided earlier, the sample SP is pulled downward so that a force of 1 kgf is applied to the hook through the hook through the other hole, and the marked line is again in this state. The distance between them (D1) is measured.

Then, the elongation rate (E (%)) can be obtained by calculating the following formula.

E = (D1-D0) / D0 × 100 (%)

The elongation rate is usually calculated for a plurality of (for example, 5) samples and can be obtained as an arithmetic mean value thereof.
The elongation ratios in the vertical direction and the horizontal direction can also be obtained in the same manner as described above by using a sample cut so that the tensile directions are the respective directions.

In the filter cloth 1 of the present embodiment, the fixing portion 3 is provided at a corner portion of the woven cloth, and since the fixing portion is locked to the holder T, the filtering cloth 1 is oblique to the four corners of the filtering portion 2 during filtration. Tension in the direction can be automatically generated, and the fixing portion 3 is also provided at the center of the side of the woven fabric, and the fixing portion 3 is locked to the holder T. It is configured so that the tension in the diagonal direction does not act excessively.

In the filtration tank 100 of the present embodiment, since filtration is performed using the filtration cloth 1 provided with the above-mentioned woven cloth, the decrease in the filtration speed in the latter stage of the filtration can be suppressed, but finally the filtration cloth 1 The solid content S1 deposited on the top makes it difficult to continue the filtration.
In that case, the filtration performance can be restored by removing the uppermost filtration cloth 1a constituting the laminated body 10.
At this time, a new filter cloth may be added to the laminate instead of the filter cloth 1a to be removed.
The new filter cloth can be added, for example, to the lower side of the lowermost filter cloth 1b of the laminate 10.

By using the filter cloth in the present embodiment as described above, the work efficiency of filtration can be greatly improved as compared with the conventional case.
Further, the filter cloth of the present embodiment is excellent in versatility because the form of the holder T to be mounted is not particularly restricted, and the above-mentioned improvement in work efficiency can be exhibited in various situations.
The configuration and usage state of the filter cloth in the present embodiment are not limited to the above embodiment, and various changes can be made.
That is, the present invention is not limited to the above examples.

1 ... Filtration cloth, 2 ... Filtration part, 21 ... Edge part, 21a ... Horizontal end edge part, 21b ... Vertical end edge part, 22 ... Main body part, 24 ... Warp, 25 ... Weft, 200 ... Corner part, 201 ... Straight part, 3 ... Fixed part, 4 ... Connection means, 40 ... Seam part, 10 ... Laminated body, 100 ... Filtration tank, P ... Water receiving part, S ... Suspension, S1 ... Solid content, S2 ... Moisture, T ... holder, Z ... gap

Claims (4)

A filter cloth used as a component of a filter tank for filtering a suspension.
It has a sheet-like filtration unit composed of a woven fabric with warp and weft.
The filtration tank is provided with a holder for holding the filter so as to have a downwardly recessed shape, and the suspension is filtered by the filter while being held by the holder. Is composed of
The woven fabric constituting the filtration unit is a filtration fabric having an elongation rate of 10% or more and 35% or less when a tension of 1 kgf is applied in a direction of 45 degrees to both the warp and the weft. Claim 1 that the woven fabric has an elongation rate when a tension of 1 kgf is applied in the direction of the warp threads and an elongation rate when a tension of 1 kgf is applied in the direction of the weft threads, both of which are less than 10%. The filter cloth described. A fixing portion for fixing the filtration portion to the holder is further provided.
The woven fabric has a rectangular shape, and the four sides are parallel to the warp or the weft, respectively.
The filter cloth according to claim 1 or 2, wherein the fixing part is provided at four corners of the woven cloth. The filtration cloth according to claim 3, wherein the fixing portion is further provided at the central portion of the four sides.