Filtration and circulation system

Abstract

The present invention provides a filtration and circulation system and a drain box that minimize obstruction to the fluid flow used in backwashing. [Solution] A filtration and circulation system for filtering and circulating contaminated fluid, which is a fluid contaminated with solid foreign matter due to use in metalworking machinery, comprises a filtration device for filtering the contaminated fluid, a drain box 3 for containing the fluid discharged during backwashing of the filtration device, and a backwash fluid outlet pipe L5 connected to the bottom surface of the drain box 3 for draining the fluid inside the drain box 3. An outlet 33a is formed in the bottom plate 32 of the drain box 3, connecting the internal space of the drain box 3 to the backwash fluid outlet pipe L5, and the opening area of ​​the outlet 33a is smaller than the cross-sectional area of ​​the flow path of the backwash fluid outlet pipe L5.

Description

Technical Field

[0001] The present invention relates to a filtration and circulation system for filtering and circulating a coolant liquid used in a metal processing machine or the like, and a drain box used in the filtration and circulation system.

Background Art

[0002] Conventionally, in metal processing machines, fluids such as cutting oil, grinding oil, and coolant liquid (hereinafter collectively referred to as coolant liquid) are used for purposes such as cooling, lubrication, and cleaning. Therefore, particulate solid foreign matter such as cutting chips and grinding chips (hereinafter referred to as sludge) is mixed in the used coolant liquid. Generally, this coolant liquid is repeatedly used through a circulation device, but since using the coolant liquid mixed with sludge affects processing such as cutting, it is necessary to remove the sludge from the once-used coolant liquid.

[0003] Various filtration devices have been proposed for removing sludge from coolant liquid. For example, the filtration device of Patent Document 1 includes a substantially cylindrical filter and an outer shell surrounding the filter, and sludge is filtered when the coolant liquid containing sludge passes through the filter. The filtered sludge adheres to the filter or precipitates at the bottom of the outer shell. When such sludge increases, it causes a decrease in filtration performance, so it is necessary to perform backwashing to discharge the sludge adhering to the filter or precipitating at the bottom of the outer shell to the outside.

[0004] In Patent Document 1, during backwashing, the valve of the reverse washing liquid discharge pipe connected to the bottom of the outer shell is opened and air is allowed to flow in from the upper part of the filter. Thereby, the sludge in the filtration device is discharged to the outside.

[0005] Since the coolant fluid discharged by backwashing naturally contains sludge, it is necessary to remove the sludge in order to reuse this coolant fluid. Patent Document 1 uses a magnetic separator for this purpose (see Figure 5 of Patent Document 1). Specifically, an auxiliary tank is provided below the filtration device, and this auxiliary tank and the magnetic separator are connected via piping. Therefore, the coolant fluid used for backwashing falls into the auxiliary tank along with the sludge, and after the sludge is removed by the magnetic separator, it is reused. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2007-038205 [Overview of the project] [Problems that the invention aims to solve]

[0007] If an auxiliary tank (corresponding to the drain box in this invention) as shown in the embodiment of Figure 5 of Patent Document 1 is used, the coolant liquid is temporarily stored in the auxiliary tank before flowing out to the magnetic separator. This allows for a smaller capacity for the magnetic separator and a gentler flow of coolant liquid into the magnetic separator. However, in such a configuration, sludge may accumulate on the inner wall of the piping connecting the auxiliary tank and the magnetic separator. Furthermore, during backwashing, sludge adhering to the filter may fall into the auxiliary tank in clumps, potentially blocking the opening that connects the internal space of the auxiliary tank to the piping. In either case, the outflow of coolant liquid from the auxiliary tank may be obstructed, potentially causing the coolant liquid to overflow from the auxiliary tank.

[0008] The present invention has been made in view of the above problems, and its purpose is to provide a filtration circulation system and a drain box that do not easily obstruct the flow of the fluid used for backwashing. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides a filtration and circulation system for filtering and circulating a contaminated fluid, which is a fluid contaminated with solid foreign matter due to use in metalworking machinery, comprising: a filtration device for filtering the contaminated fluid; a drain box for containing the fluid discharged during backwashing of the filtration device; and a backwash liquid outlet pipe connected to the bottom surface of the drain box for discharging the fluid from the drain box. The bottom plate of the drain box has an outlet that connects the internal space of the drain box to the backwash liquid outlet pipe, and the opening area of ​​the outlet is smaller than the cross-sectional area of ​​the flow path of the backwash liquid outlet pipe.

[0010] The inventors of the present invention (hereinafter referred to as "the inventors") have found that when backwash liquid in the internal space of a drain box flows out to the backwash liquid outlet pipe via the outlet, if the flow resistance of the backwash liquid outlet pipe is high, solid foreign matter tends to accumulate in the flow path (inner wall) of the backwash liquid outlet pipe. Based on this finding, the inventors have come up with a configuration in which the opening area of ​​the outlet formed in the bottom plate of the drain box is made smaller than the flow path cross-sectional area of ​​the backwash liquid outlet pipe in order to reduce the flow resistance of the backwash liquid outlet pipe. As a result, the accumulation of solid foreign matter in the flow path of the backwash liquid outlet pipe can be suppressed, and the outflow of backwash liquid from the drain box is less likely to be obstructed.

[0011] Furthermore, the present invention also extends to a drain box used in a filtration circulation system equipped with a filtration device for filtering contaminated fluid, which is a fluid contaminated with solid foreign matter due to use in metalworking machinery. Such a drain box contains the fluid discharged during backwashing of the filtration device, and an outlet is formed in the bottom plate of the drain box, connecting the internal space of the drain box to the backwash fluid outlet pipe. The opening area of ​​the outlet is smaller than the cross-sectional area of ​​the flow path of the backwash fluid outlet pipe, which is connected to the lower surface of the drain box and discharges the fluid from inside the drain box.

[0012] A drain box with this configuration produces the same effects as the filtration and circulation system described above.

[0013] It has been found that the accumulation of solid foreign matter in the flow path of the backwash fluid outlet pipe is not the only thing that obstructs the outflow of backwash fluid from the drain box. For example, lumpy (plate-shaped) solid foreign matter may be mixed into the backwash fluid, and if such solid foreign matter rests on the outlet, it may obstruct the outflow of backwash fluid from the drain box. In response to this problem, the inventors, through ingenuity and effort, have found that if the shape of the outlet is polygonal (excluding regular polygons), plate-shaped solid foreign matter becomes easier to break down.

[0014] Therefore, in one preferred embodiment of the drain box according to the present invention, the plan view shape of the outlet is polygonal (excluding regular polygons).

[0015] In this configuration, even if a plate-shaped solid foreign object rests 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 break down. The broken-down solid foreign object then flows out more easily along with the fluid. This makes it less likely for the flow of backwash liquid from the drain box to be obstructed. [Brief explanation of the drawing]

[0016] [Figure 1] This is a block diagram of the filtration and circulation system. [Figure 2] This is a cross-sectional view of a filtration device. [Figure 3] (a) is a perspective view of the drain box, (b) is a cross-sectional view of the drain box along line B-B', and (c) is a cross-sectional view of the drain box along line C-C'. [Modes for carrying out the invention]

[0017] An embodiment of the filtration and circulation system according to the present invention will be described below with reference to the drawings. Figure 1 is a block diagram of the filtration and circulation system A in this embodiment. The filtration and circulation system A circulates coolant liquid (an example of a fluid in the present invention) used for cleaning, cooling, and lubrication in a metalworking machine B, and comprises a dirty tank 1, a filtration device 2, a drain box 3, and a magnetic separator 4. Furthermore, the piping L, which is equipped with a flow path for the coolant liquid, includes a dirty liquid first piping L1 for flowing coolant liquid containing sludge (an example of solid foreign matter in this invention) (dirty liquid, an example of contaminated fluid in this invention) from the metalworking machine B to the dirty tank 1, a dirty liquid second 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 clean fluid in this invention) from which the sludge has been filtered in the filtration device 2 to the metalworking machine B, a backwash liquid first piping L4 for flowing the coolant liquid used for backwashing (hereinafter referred to as backwash liquid) from the filtration device 2 to the drain box 3, a backwash liquid second piping L5 (an example of a backwash liquid outlet pipe in this 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 the sludge has been removed in the magnetic separator 4 to the dirty tank 1. Furthermore, the system includes valves V that control the opening and closing of the flow paths in piping L, specifically a clean liquid piping valve V1 that controls the opening and closing of the clean liquid piping L3, and a backwash liquid piping valve V2 that controls the opening and closing of the backwash liquid piping first L4. Note that in Figure 1, some of the piping L, valves V, and the pump for circulating the coolant liquid are omitted.

[0018] Next, we will briefly explain the flow of coolant in the filtration circulation system A. First, we will explain the flow during normal circulation and filtration, in which case the valve V1 for the clean liquid piping is "open" and the valve V2 for the backwash liquid piping is "closed". The coolant liquid (dirty liquid) used in the metalworking machine B and containing sludge flows into the dirty tank 1 through the dirty liquid first piping L1. A pump (not shown) supplies the dirty liquid in the dirty tank 1 to the filtration device 2 through the dirty liquid second piping L2. As will be explained in detail later, the filtration device 2 is equipped with a filter, which filters the sludge from the dirty liquid. The coolant liquid (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.

[0019] If this process continues, sludge will adhere to the filter of filtration device 2 or settle at the bottom of filtration device 2. This will lead to a decrease in the filtration performance of filtration device 2, so it is necessary to perform backwashing periodically 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 there are multiple filtration devices 2 and the timing of their backwashing is staggered so that filtration is always being performed by one of the filtration devices 2, the clean liquid piping valve V1 remains "open".

[0020] As will be explained in more detail later, the first backwash fluid pipe L4 is connected to the lower end of the filtration device 2 and extends straight downwards. The flow path of the first backwash fluid pipe L4 has a relatively large diameter. Therefore, when the valve V2 for the backwash fluid pipe is controlled to "open", the coolant liquid in the filtration device 2 flows out forcefully. At this time, sludge that is attached to the filter of the filtration device 2 or has settled at the bottom of the filtration device 2 flows out into the drain box 3 along with the backwash fluid through the first backwash fluid pipe L4.

[0021] The reverse cleaning liquid flows into the drain box 3 and then outflows to the magnetic separator 4 through the reverse cleaning liquid second pipe L5. In the magnetic separator 4, magnetic sludge in the reverse cleaning liquid is removed. The reverse cleaning liquid from which the magnetic sludge has been removed is returned to the dirty tank 1 through the return pipe L6.

[0022] Figure 2 is a cross-sectional view of the filtration device 2 in this embodiment. The filtration device 2 has a substantially cylindrical shape and includes a casing composed of an upper casing 21 having a ceiling and opening downward, and a substantially funnel-shaped lower casing 22 opening upward. Spaces are formed inside the upper casing 21 and the lower casing 22, which are referred to as an upper space 21a and a lower space 22a, respectively. By tightly fastening the lower end of the upper casing 21 and the upper end of the lower casing 22 watertightly using screws or the like, the upper casing 21 and the lower casing 22 are connected and fixed to form the casing. At this time, they are fixed so that the respective openings coincide, and the lower space 22a and the upper space 21a communicate with each other.

[0023] An inlet through which dirty liquid flows in is formed in the lower casing 22, and a dirty liquid second pipe L2 is connected to the inlet. On the other hand, an outlet through which clean liquid flows out is formed in the upper casing 21, and a clean liquid pipe L3 is connected to the outlet. Further, an outlet opening downward is formed at the lower end of the lower casing 22, and a reverse cleaning liquid first pipe L4 is connected to the outlet.

[0024] Further, a filter section for filtering sludge from the dirty liquid is provided inside the upper casing 21. The filter section includes a support 23 and a filter body (not shown) enclosed in the support 23. The support 23 is a substantially cylindrical body, the upper part of which is closed by a top plate, while the lower part is open to form an inlet. A plurality of leakage holes are formed in the wall surface of the support 23. The diameter of this leakage hole is larger than the particle diameter of the sludge, but there is no particular limitation. If the diameter of the leakage hole is too small, it is not preferable because it hinders the outflow of the coolant liquid.

[0025] The support body 23 is positioned so that its inlet coincides with the opening of the upper casing 21 and the opening of the lower casing 22. Therefore, dirty liquid flows from the lower space 22a to the upper space 21a, and more specifically, into the internal space 23a of the support body 23, through this inlet. Also, as shown in Figure 2, a gap is formed between the outer surface of the support body 23 and the inner surface of the upper casing 21, which serves as a flow path for filtered coolant liquid (clean liquid).

[0026] 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 a mesh finer than the particle size of the material to be filtered. As the filter body, a single-layer or multi-layered nonwoven fabric made of synthetic fibers or plastic fiber cloth can be used.

[0027] As such a filtration device 2, for example, the filtration device disclosed in Japanese Patent Application Publication No. 2023-025359 can be used.

[0028] Next, using Figure 2, we will explain the process of filtering the dirty liquid using the filtration device 2. The arrows in the figure indicate the flow of the coolant liquid.

[0029] In metalworking machine B, the coolant liquid (dirty liquid) contaminated with sludge flows into the lower space 22a of the lower casing 22 from the dirty liquid second pipe L2. At this time, the backwash liquid piping valve V2 is closed, and the dirty liquid does not flow out from the backwash liquid first pipe L4. Therefore, as the inflow of dirty liquid continues, the water level of the dirty liquid in the lower space 22a rises. When the water level exceeds the upper end of the lower space 22a, the dirty liquid flows into the upper space 21a, i.e., the internal space 23a of the support 23, through the inlet. The dirty liquid that has flowed into the internal space 23a of the support 23 is subjected to downward pressure due to the further inflow of dirty liquid, and when the internal space 23a of the support 23 is filled with dirty liquid, this pressure acts as a force that causes the dirty liquid in the internal space 23a of the support 23 to flow out of the support 23. At this time, since the upper part of the support 23 is closed, the dirty liquid in the internal space 23a of the support 23 can only flow out radially outward. In this case, sludge with a relatively high specific gravity settles, but sludge with a low specific gravity floats inside. Pressure acts radially outward on this sludge. As described above, since 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 liquid flows out to the outside of the filter body.

[0030] In this way, the coolant liquid (clean liquid) filtered by the filter body flows out of the support 23 through the leakage hole in the support 23 to the outside of the support 23. The coolant liquid that has flowed out to the outside of the support 23 flows through the channel formed between the support 23 and the upper casing 21 to the clean liquid piping L3. The clean liquid is then used again in the metalworking machine B.

[0031] In such a 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. As the amount of sludge inside the filtration device 2 increases, the filtration performance decreases, so it is necessary to periodically remove it, a process known as backwashing. When backwashing is performed, the valve V2 for the backwash fluid piping is opened. This causes the coolant liquid accumulated inside the filtration device 2, along with the sludge that has settled at the bottom or adhered to the inner surface of the filter body, to be discharged through the first backwash fluid pipe L4. Hereinafter, the coolant liquid discharged through the first backwash fluid pipe L4 will be referred to as the backwash fluid.

[0032] As described above, in the filtration circulation system A of the present invention, a 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 into the magnetic separator 4 through the second backwash liquid pipe L5. The coolant liquid from which magnetic sludge has been removed by the magnetic separator 4 then flows back to the dirty tank 2 through the return pipe L6.

[0033] By providing a drain box 3 between the filtration device 2 and the magnetic separator 4, the capacity of the magnetic separator 4 can be reduced. Furthermore, if the backwash liquid that flows out forcefully from the first backwash liquid pipe L4 is allowed to flow directly into the magnetic separator 4, undesirable phenomena such as foaming may occur. However, by using the drain box 3, the occurrence of such undesirable phenomena can be suppressed.

[0034] However, it has been found that sludge contained in the backwash fluid tends to accumulate on the inner wall of the second backwash fluid pipe L5 due to pipe resistance. In the drain box 3 according to the present invention, the pipe resistance of the second backwash fluid pipe L5 is reduced by the following configuration, thereby suppressing sludge accumulation.

[0035] Figure 3(a) is a perspective view of the drain box 3 in this embodiment, Figure 3(b) is a cross-sectional view taken along line B-B', and Figure 3(c) is a cross-sectional view taken along line C-C'. Note that the top plate 31 is not shown in Figure 3(c). The drain box 3 is a hollow, roughly rectangular parallelepiped, and is installed at an angle such that the left side in Figure 3(a) (the side where the outlet 33a is formed) is slightly downward. The first backwash liquid pipe L4 is connected to the top plate 31. In this embodiment, since there are two filtration devices 2, two first backwash liquid pipes L4 are connected to the drain box 3. By providing multiple filtration devices 2 in this way and staggering the timing of backwashing each filtration device 2, backwashing can be performed without stopping the circulation filtration process in the entire filtration circulation system A.

[0036] As shown in Figure 3(c), an opening 32a is formed in the bottom plate 32 of the drain box 3, and the backwash fluid second pipe L5 and the internal space of the drain box 3 are in communication through the opening 32a. In this embodiment, the shape of the opening 32a and the cross-sectional shape of the flow path of the backwash fluid second pipe L5 are congruent, and their areas are the same, however the cross-sectional area of ​​the flow path of the backwash fluid second 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.

[0037] In this embodiment, an elastic plate 33 is provided with an outlet 33a formed 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 backwash fluid second pipe L5, and the entire outlet 33a is positioned to fit inside the inner circumference of the backwash fluid second pipe L5. This reduces the piping resistance of the backwash fluid second pipe L5 and suppresses the accumulation of sludge. In this embodiment, the outlet 33a is a so-called home plate shape, a pentagon with two right angles.

[0038] The backwash fluid discharged from the filtration device 2 may contain not only sludge that had settled at the bottom of the filtration device 2, but also sludge that had adhered to the filter body. In particular, in the case of a filtration device 2 having a support as disclosed in Figures 6 and 7 of Japanese Patent Application Publication No. 2023-025359, sludge may adhere to the filter body in a plate-like manner, and this plate-like sludge may flow into the drain box 3 during backwashing. Such plate-like sludge may block the outlet 33a and obstruct the outflow of backwash fluid from the second backwash fluid pipe L5.

[0039] The inventors of this invention, through ingenuity and effort, have found that if the shape of the outlet 33a is polygonal (excluding regular polygons), the plate-like sludge resting on the outlet 33a becomes more easily broken 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 it more easily broken down. Furthermore, the inventors have also found that pentagons and hexagons are even more preferable among the polygonal shapes.

[0040] In the circulating filtration system A and drain box 3 according to the present invention, the flow resistance of the flow path of the backwash liquid second pipe L5 is reduced by making the opening area of ​​the outlet 33a formed in the bottom plate 33 of the drain box 3 smaller than the flow path cross-sectional area of ​​the backwash liquid second pipe L5. This makes it possible to suppress the accumulation of sludge in the flow path of the backwash liquid second pipe L5. In addition, by making the shape of the outlet 33a polygonal (excluding regular polygons), plate-like or clumpy sludge that rests on top of the outlet 33a is made easier to break down, preventing sludge from blocking the outlet 33a.

[0041] [Another embodiment] (1) In the above embodiment, the drain box 3 is provided with an elastic plate 33 having an outlet 33a, but it is also possible to have a configuration without an elastic plate 33. In this case, the opening 32a is used as the outlet, and the opening 32a should be formed such that its opening area is smaller than the flow path cross-sectional area of ​​the backwash liquid second pipe L5.

[0042] (2) In the above embodiment, the opening shape of the outlet 33a and the flow path cross-sectional shape of the backwash fluid second pipe L5 were neither congruent nor similar, but they may be similar in shape. In this case as well, the opening area of ​​the outlet should be smaller than the flow path cross-sectional area of ​​the backwash fluid second pipe L5. For example, both can be made circular, and the diameter of the opening shape of the outlet 33a can be made smaller than the diameter of the flow path cross-sectional shape of the backwash fluid second pipe L5. [Industrial applicability]

[0043] This invention can be used in filtration and circulation systems that filter and circulate fluids containing solid foreign matter, such as coolant used in metalworking machines, and in drain boxes used in such filtration and circulation systems. [Explanation of Symbols]

[0044] A: Filtration and circulation system B: Metal processing machinery L5: Backwash liquid second pipe (backwash liquid outflow pipe) 1: Dirty Tank 2:Filtration device 3: Drain box 33a: Outlet 4: Magnetic separator

Claims

1. A filtration and circulation system for filtering and circulating contaminated fluid, which is a fluid contaminated with solid foreign matter due to use in metalworking machinery, A filtration device for filtering the contaminated fluid, A drain box for containing the fluid discharged during backwashing of the filtration device, The drain box is connected to the lower surface of the drain box and includes a backwash liquid outlet pipe that discharges the fluid inside the drain box, An outlet is formed in the bottom plate of the drain box, which connects the internal space of the drain box with the backwash liquid outlet pipe. A filtration and circulation system in which the opening area of ​​the outlet is smaller than the cross-sectional area of ​​the flow path of the backwash liquid outlet pipe.

2. A drain box used in a filtration and circulation system equipped with a filtration device for filtering contaminated fluid, which is a fluid containing solid foreign matter due to use in metalworking machinery, The drain box contains the fluid discharged during the backwashing of the filtration device. An outlet is formed in the bottom plate of the drain box, which connects the internal space of the drain box with the backwash liquid outlet pipe. A drain box in which the opening area of ​​the outlet is smaller than the cross-sectional area of ​​the flow path of a backwash liquid outlet pipe connected to the lower surface of the drain box and which discharges the fluid inside the drain box.

3. The drain box according to claim 2, wherein the plan view shape of the outlet is a polygon (excluding regular polygons).

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