Filtration circulation system

Abstract

This filtration circulation system for filtering and circulating a polluted fluid, which is a fluid mixed with solid foreign matter during use in a metal processing machine, comprises: a filtration device for filtering the polluted fluid; a drain box 3 for housing the fluid discharged during backwashing of the filtration device; and a backwashing liquid outflow pipe L5 connected to the lower surface of the drain box 3, and through which the fluid flows out from the drain box 3. A bottom plate 32 of the drain box 3 is provided with an outflow port 33a which brings the internal space of the drain box 3 and the backwashing liquid outflow pipe L5 into communication with each other, and the opening area of the outflow port 33a is smaller than the cross-sectional area of the flow passage of the backwashing liquid outflow pipe L5.

Description

Filtration Circulation System

[0001] The present invention relates to a filtration and circulation system for filtering and circulating coolant liquid used in metalworking machines and the like.

[0002] Conventionally, metalworking machines use fluids such as cutting oil, grinding oil, and coolant (collectively referred to as "coolant") for cooling, lubrication, cleaning, and other purposes. Therefore, used coolant is contaminated with particulate solid matter such as cutting chips and grinding chips (hereinafter referred to as "sludge"). Generally, this coolant is reused repeatedly through a circulation system. However, since using coolant containing sludge can affect cutting and other processes, it is necessary to remove the sludge from used coolant.

[0003] Various filtration devices have been proposed for removing sludge from coolant. For example, the filtration device disclosed in Patent Document 1 includes a substantially cylindrical filter and an outer shell surrounding the filter. As the sludge-containing coolant passes through the filter, the sludge is filtered. The filtered sludge adheres to the filter or settles at the bottom of the outer shell. As the amount of sludge increases, the filtration performance deteriorates. Therefore, backwashing is required to remove the sludge that has adhered to the filter or settled at the bottom of the outer shell.

[0004] In Patent Document 1, during backwashing, a valve in a backwash liquid discharge pipe connected to the bottom of the outer shell is opened and air is allowed to flow in from the top of the filter, thereby discharging sludge from the filtering device to the outside.

[0005] The coolant discharged by backwashing naturally contains sludge, and the sludge must be removed before the coolant can be reused. Patent Document 1 uses a magnetic separator for this purpose (see FIG. 5 of Patent Document 1). Specifically, an auxiliary tank is provided below the filtration device, and the auxiliary tank and the magnetic separator are connected via piping. Therefore, the coolant used for backwashing falls into the auxiliary tank together with the sludge, and is reused after the sludge is removed by the magnetic separator.

[0006] Japanese Patent Application Laid-Open No. 2007-038205

[0007] When an auxiliary tank (corresponding to the drain box in the present invention) such as that shown in the embodiment of FIG. 5 of Patent Document 1 is used, the coolant is temporarily stored in the auxiliary tank before flowing into the magnetic separator. This allows the magnetic separator to be reduced in capacity and the coolant flows more slowly into the magnetic separator. However, this configuration can lead to sludge accumulation on the inner walls of the piping connecting the auxiliary tank and the magnetic separator. Furthermore, during backwashing, sludge adhering to the filter can fall into the auxiliary tank in clumps, potentially clogging the opening connecting the auxiliary tank's interior to the piping. In either case, the coolant may be blocked from flowing out of the auxiliary tank, potentially causing the coolant to overflow.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a filtration circulation system and a drain box in which the flow of fluid used for backwashing is less likely to be obstructed.

[0009] In order to solve the above problems, the present invention provides a filtration circulation system for filtering and circulating a contaminated fluid, which is a fluid that has become contaminated with solid foreign matter due to use in a metal processing machine. The filtration circulation system includes a filtration device for filtering the contaminated fluid, a drain box for storing the fluid discharged during backwashing of the filtration device, and a backwash liquid outlet pipe connected to the underside of the drain box and for discharging the fluid in the drain box. The bottom plate of the drain box is formed with an outlet that connects the internal space of the drain box with the backwash liquid outlet pipe, and the opening area of ​​the outlet is smaller than the flow path cross-sectional area of ​​the backwash liquid outlet pipe.

[0010] The inventor of the present invention (hereinafter referred to as the "inventor") discovered that when backwash liquid in the internal space of a drain box flows out through an outlet into a backwash liquid outlet pipe, if the flow resistance of the backwash liquid outlet pipe is high, solid foreign matter is likely to accumulate in the flow path (inner wall) of the backwash liquid outlet pipe. Based on this discovery, the inventor came up with a configuration in which the opening area of ​​the outlet formed in the bottom plate of the drain box is smaller than the flow cross-sectional area of ​​the backwash liquid outlet pipe in order to reduce the flow resistance of the backwash liquid outlet pipe. This prevents solid foreign matter from accumulating in the flow path of the backwash liquid outlet pipe, making it less likely that the backwash liquid will be obstructed from flowing out of the drain box.

[0011] It has been found that the outflow of backwash liquid from the drain box is hindered not only by the accumulation of solid foreign matter in the flow path of the backwash liquid outflow pipe. For example, clumped (plate-shaped) solid foreign matter may be mixed into the backwash liquid, and if such solid foreign matter sits on the outlet, it may hinder the outflow of backwash liquid from the drain box. In response to this problem, the inventors have found, through ingenuity, that if the outlet is shaped like a polygon (excluding regular polygons), plate-shaped solid foreign matter will be more likely to break down.

[0012] Therefore, in one preferred embodiment of the filtration circulation system according to the present invention, the shape of the outlet in a plan view is a polygon (excluding a regular polygon).

[0013] In this configuration, even if a plate-shaped solid foreign object is placed on the outlet, the force of the liquid trying to flow out of the outlet acts unevenly on the solid foreign object, making it more likely to crumble and flow out with the fluid. This makes it less likely that the flow of backwash liquid from the drain box will be obstructed.

[0014] 1 is a block diagram of a filtration circulation system, and is a cross-sectional view of a filtration device, (a) a perspective view of a drain box, (b) a BB' cross-sectional view of the drain box, and (c) a CC' cross-sectional view of the drain box.

[0015] An embodiment of a filtration circulation system according to the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram of a filtration circulation system A according to this embodiment. The filtration circulation system A circulates a coolant (an example of a fluid in the present invention) used for cleaning, cooling, and lubrication in a metalworking machine B, and includes a dirty tank 1, a filtration device 2, a drain box 3, and a magnetic separator 4. The piping L having a flow path for flowing the coolant liquid includes a first dirty liquid piping L1 for flowing coolant liquid (dirty liquid, an example of a contaminated fluid in the present invention) containing sludge (an example of a solid foreign matter in the present invention) from the metal processing machine B to the dirty tank 1, a second dirty liquid piping L2 for flowing the dirty liquid from the dirty tank 1 to the filtration device 2, a clean liquid piping L3 for flowing coolant liquid (clean liquid, an example of a clean fluid in the present invention) from which sludge has been filtered in the filtration device 2 to the metal processing machine B, a first backwash liquid piping L4 for flowing coolant liquid used for backwashing (hereinafter referred to as backwash liquid) from the filtration device 2 to the drain box 3, a second backwash liquid piping L5 (an example of a backwash liquid outlet pipe in the present invention) for flowing the backwash liquid from the drain box 3 to the magnetic separator 4, and a return piping L6 for flowing the coolant liquid from which sludge has been removed in the magnetic separator 4 to the dirty tank 1. Furthermore, as valves V for controlling the opening and closing of the flow paths of the pipes L, a clean liquid piping valve V1 for controlling the opening and closing of the flow path of the clean liquid pipe L3 and a backwash liquid piping valve V2 for controlling the opening and closing of the flow path of the first backwash liquid pipe L4 are provided. Note that in Fig. 1, the pipes L and some of the valves V, as well as a pump for circulating the coolant liquid, etc. are omitted.

[0016] Next, a brief description will be given of the flow of coolant in the filtration circulation system A. First, the flow during normal circulation and filtration will be described. At this time, the clean liquid piping valve V1 is "open" and the backwash liquid piping valve V2 is "closed." Coolant (dirty liquid) used in the metalworking machine B and containing sludge flows into the dirty tank 1 through the first dirty liquid piping L1. A pump (not shown) supplies the dirty liquid in the dirty tank 1 through the second dirty liquid piping L2 to the filtration device 2. As will be described in detail later, the filtration device 2 is equipped with a filter that filters sludge from the dirty liquid. The coolant (clean liquid) from which the sludge has been removed is supplied again to the metalworking machine B through the clean liquid piping L3 and used.

[0017] If this process continues, sludge will adhere to the filters of the filtration device 2 or settle at the bottom of the filtration device 2. This will reduce the filtration performance of the filtration device 2, so it is necessary to periodically perform backwashing to remove this sludge. During backwashing, the clean liquid piping valve V1 is "closed" and the backwash liquid piping valve V2 is "open." However, as shown in Figure 3, if multiple filtration devices 2 are provided and the timing of each backwash is staggered so that any one of the filtration devices 2 can always perform filtration, the clean liquid piping valve V1 will remain "open."

[0018] As will be described in detail later, the first backwash liquid pipe L4 is connected to the lower end of the filtration device 2 and extends straight down. The flow path of the first backwash liquid pipe L4 has a relatively large diameter. Therefore, when the backwash liquid pipe valve V2 is controlled to be "open," the coolant liquid in the filtration device 2 flows out with force. At this time, sludge adhering to the filter of the filtration device 2 or settling at the bottom of the filtration device 2 flows out together with the backwash liquid through the first backwash liquid pipe L4 into the drain box 3.

[0019] The backwash liquid flows into the drain box 3, then passes through the second backwash liquid pipe L5, and flows out to the magnetic separator 4. The magnetic separator 4 removes magnetic sludge from the backwash liquid. The backwash liquid from which the magnetic sludge has been removed is returned to the dirty tank 1 through the return pipe L6.

[0020] 2 is a cross-sectional view of the filtration device 2 according to this embodiment. The filtration device 2 includes a casing consisting of an upper casing 21 that is generally cylindrical, has a ceiling, and opens downward, and a generally funnel-shaped lower casing 22 that opens upward. Spaces are formed inside the upper casing 21 and the lower casing 22, referred to as the upper space 21a and the lower space 22a, respectively. The upper casing 21 and the lower casing 22 are connected and fixed together to form a casing by fastening the lower end of the upper casing 21 and the upper end of the lower casing 22 together in a watertight manner using screws or the like. The casings are fixed so that their openings are aligned, and the lower space 22a and the upper space 21a are in communication with each other.

[0021] The lower casing 22 is formed with an inlet through which the contaminated fluid flows in, and a second contaminated fluid pipe L2 is connected to the inlet. Meanwhile, the upper casing 21 is formed with an outlet through which the clean fluid flows out, and a clean fluid pipe L3 is connected to the outlet. In addition, a discharge port that opens downward is formed at the bottom end of the lower casing 22, and a first backwash fluid pipe L4 is connected to the discharge port.

[0022] The upper casing 21 also includes a filter section for filtering sludge from the contaminated coolant. The filter section includes a support 23 and a filter body (not shown) housed within the support 23. The support 23 is generally cylindrical, with the upper end closed by a top plate and the lower end open to form an inlet. Multiple leakage holes are formed in the wall of the support 23. The diameter of these leakage holes is larger than the particle size of the sludge, but is not particularly limited. It is not desirable for the diameter of the leakage holes to be too small, as this will hinder the outflow of the coolant.

[0023] The support body 23 is positioned so that its inlet is aligned with the opening of the upper casing 21 and the opening of the lower casing 22. Therefore, contaminated coolant flows from the lower space 22a to the upper space 21a, more specifically, into the internal space 23a of the support body 23, via this inlet. In addition, as shown in Figure 2, a gap is formed between the outer peripheral surface of the support body 23 and the inner peripheral surface of the upper casing 21, which serves as a flow path for filtered coolant (clean liquid).

[0024] The filter body is used to filter the coolant liquid containing sludge and remove the sludge from the coolant liquid, and is made of a filter cloth or the like with meshes finer than the particle size of the particles to be filtered. The filter body can be made of a single layer or multiple layers of synthetic fiber nonwoven fabric or plastic fiber fabric.

[0025] As such a filtering device 2, for example, the filtering device disclosed in Japanese Patent Application Laid-Open No. 2023-025359 can be used.

[0026] Next, the process of filtering the contaminated coolant by the filter device 2 will be described with reference to Figure 2. The arrows in the figure indicate the flow of the coolant.

[0027] Coolant (contaminated liquid) used in the metalworking machine B and containing sludge flows from the second contaminated liquid pipe L2 into the lower space 22a of the lower casing 22. At this time, the backwash liquid piping valve V2 is closed, and the contaminated liquid does not flow out from the first backwash liquid pipe L4. Therefore, as the inflow of contaminated liquid continues, the level of the contaminated liquid in the lower space 22a rises. When the water level exceeds the upper end of the lower space 22a, the contaminated liquid flows into the upper space 21a, i.e., the internal space 23a of the support body 23, through the inlet. The contaminated liquid that has flowed into the internal space 23a of the support body 23 is subjected to pressure from below due to the inflow of further contaminated liquid. When the internal space 23a of the support body 23 is filled with contaminated liquid, this pressure acts as a force to cause the contaminated liquid in the internal space 23a of the support body 23 to flow out of the support body 23. At this time, because the top of the support 23 is closed, the contaminated coolant in the internal space 23a of the support 23 can only flow out radially outward from the support 23. At this time, sludge with a relatively high specific gravity settles, while sludge with a low specific gravity floats inside. This sludge is subjected to radially outward pressure. As mentioned above, because the mesh of the filter body is finer than the particle size of the sludge, this radially outward pressure causes the sludge to adhere to the inner surface of the filter body, and only the coolant flows out of the filter body.

[0028] In this way, the coolant liquid (clean liquid) filtered by the filter body flows out of the support body 23 through the leakage hole in the support body 23. The coolant liquid that has flowed out of the support body 23 passes through a flow path formed between the support body 23 and the upper casing 21 and flows into the clean liquid pipe L3. The clean liquid is then reused in the metalworking machine B.

[0029] In this type of filtration device 2, as described above, sludge adheres to the inner surface of the filter body or settles at the bottom of the lower casing 22. If such sludge accumulates inside the filtration device 2, the filtration performance will decrease, so it is necessary to periodically remove this sludge, which is called backwashing. To perform backwashing, the backwash liquid piping valve V2 is opened. Then, the sludge that has settled to the bottom or adhered to the inner surface of the filter body is discharged together with the coolant liquid that has accumulated inside the filtration device 2 via the first backwash liquid piping L4. Hereinafter, the coolant liquid discharged via the first backwash liquid piping L4 will be referred to as the backwash liquid.

[0030] As described above, in the filtration circulation system A of the present invention, the drain box 3 is provided below the first backwash liquid pipe L4, so the backwash liquid flows into the drain box 3. The backwash liquid that flows into the drain box 3 flows through the second backwash liquid pipe L5 into the magnetic separator 4. Then, the coolant liquid from which the magnetic sludge has been removed by the magnetic separator 4 flows back to the dirty tank 2 through the return pipe L6.

[0031] By providing the drain box 3 between the filtration device 2 and the magnetic separator 4, it is possible to reduce the capacity of the magnetic separator 4. Furthermore, if the backwash liquid that flows out vigorously from the first backwash liquid pipe L4 is allowed to flow directly into the magnetic separator 4, undesirable phenomena such as foaming may occur, but by passing the backwash liquid through the drain box 3, it is possible to prevent such undesirable phenomena from occurring.

[0032] However, it has been found that sludge contained in the backwash liquid is likely to accumulate on the inner wall of the second backwash liquid pipe L5 due to piping resistance. The drain box 3 according to the present invention has the following configuration to reduce the piping resistance of the second backwash liquid pipe L5 and suppress the accumulation of sludge.

[0033] FIG. 3(a) is a perspective view of the drain box 3 in this embodiment, FIG. 3(b) is a cross-sectional view taken along line B-B', and FIG. 3(c) is a cross-sectional view taken along line C-C'. The top plate 31 is not shown in FIG. 3(c). The drain box 3 is hollow and approximately rectangular, and is installed at a slight angle so that the left side (the side where the outlet 33a is formed) in FIG. 3(a) is slightly downward. A first backwash liquid pipe L4 is connected to the top plate 31. In this embodiment, two filtration devices 2 are provided, and therefore two first backwash liquid pipes L4 are connected to the drain box 3. By providing multiple filtration devices 2 and staggering the timing of backwashing for each filtration device 2, backwashing can be performed without stopping the circulation and filtration process in the entire filtration circulation system A.

[0034] 3(c), an opening 32a is formed in the bottom plate 32 of the drain box 3, and the second backwash liquid pipe L5 communicates with the internal space of the drain box 3 through the opening 32a. In this embodiment, the shape of the opening 32a and the cross-sectional shape of the flow path of the second backwash liquid pipe L5 are congruent and their areas are the same, but the cross-sectional area of ​​the flow path of the second backwash liquid pipe L5 may be larger than the opening area of ​​the opening 32a. Note that the cross-sectional area of ​​the flow path is the cross-sectional area in a plane perpendicular to the flow direction of the flow path.

[0035] In this embodiment, an elastic plate 33 having an outlet 33a formed therein is provided above the opening 32a. The elastic plate 33 is slightly larger than the opening 32a and is positioned to cover the entire opening 32a, with its periphery pressed and fixed by a retaining plate 34. The opening area of ​​the outlet 33a is smaller than the flow path cross-sectional area of ​​the second backwash liquid pipe L5, and the outlet 33a is positioned so that the entire outlet 33a fits within the inner circumference of the second backwash liquid pipe L5. This reduces the piping resistance of the second backwash liquid pipe L5 and suppresses sludge accumulation. In this embodiment, the outlet 33a is shaped like a home plate, a pentagon with two right-angled corners.

[0036] The backwash liquid flowing out from the filtration device 2 may contain not only sludge that has settled at the bottom of the filtration device 2, but also sludge that has adhered to the filter body. In particular, in the case of a filtration device 2 having a support such as that disclosed in Figures 6 and 7 of JP 2023-025359 A, sludge may adhere to the filter body in a plate-like form, and this plate-like sludge may flow into the drain box 3 due to backwashing. Such plate-like sludge may clog the outlet 33a and hinder the backwash liquid from flowing out from the second backwash liquid piping L5.

[0037] After much ingenuity, the inventors of the present invention discovered that if the shape of the outlet 33a is polygonal (excluding regular polygons), plate-like sludge placed on the outlet 33a tends to break down. This is thought to be because, when the shape of the outlet 33a is polygonal (excluding regular polygons), the force of the backwash liquid trying to flow out of the outlet 33a acts unevenly on the plate-like sludge, making the plate-like sludge tend to break down. The inventors also discovered that, among polygons, pentagons and hexagons are more preferable.

[0038] In this way, in the circulation filtration system A and drain box 3 according to the present invention, the opening area of ​​the outlet 33a formed in the bottom plate 33 of the drain box 3 is made smaller than the flow cross-sectional area of ​​the second backwash liquid pipe L5, thereby reducing the flow resistance of the flow path of the second backwash liquid pipe L5. This makes it possible to prevent sludge from accumulating in the flow path of the second backwash liquid pipe L5. Furthermore, by making the shape of the outlet 33a polygonal (excluding a regular polygon), plate-shaped or other clumps of sludge that sit above the outlet 33a are easily broken down, preventing the sludge from clogging the outlet 33a.

[0039] (1) In the above-described embodiment, the drain box 3 is provided with the elastic plate 33 having the outlet 33a, but the elastic plate 33 may be omitted. In this case, the opening 32a serves as the outlet, and the opening 32a is formed so that its opening area is smaller than the cross-sectional area of ​​the second backwash liquid pipe L5.

[0040] (2) In the above embodiment, the opening shape of the outlet 33a and the cross-sectional shape of the second backwash liquid pipe L5 are neither congruent nor similar, but they may be similar. Even in this case, the opening area of ​​the outlet may be smaller than the cross-sectional area of ​​the second backwash liquid pipe L5. For example, both may be circular, and the diameter of the opening shape of the outlet 33a may be smaller than the diameter of the cross-sectional shape of the second backwash liquid pipe L5.

[0041] The present invention can be used in a filtration circulation system that filters and circulates fluids containing solid foreign matter, including coolant liquids used in metalworking machines, and in drain boxes used in such filtration circulation systems.

[0042] A: Filtration circulation system B: Metal processing machine L5: Second backwash liquid piping (backwash liquid outflow pipe) 1: Dirty tank 2: Filtration device 3: Drain box 33a: Outlet 4: Magnetic separator

Claims

1. A filtration circulation system for filtering and circulating a polluted fluid, which is a fluid that has become contaminated with solid foreign matter due to use in a metalworking machine, comprising: a filtration device for filtering the polluted fluid; a drain box for storing the fluid discharged during backwashing of the filtration device; and a backwash liquid outlet pipe connected to the underside of the drain box and for discharging the fluid within the drain box, wherein an outlet is formed in the bottom plate of the drain box to communicate the internal space of the drain box with the backwash liquid outlet pipe, and the opening area of ​​the outlet is smaller than the flow path cross-sectional area of ​​the backwash liquid outlet pipe.

2. The filtration circulation system according to claim 1, wherein the shape of said outlet in plan view is a polygon (excluding a regular polygon).

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