Filter for circulation tank and purification system

Abstract

To provide a filter for a circulation tank which can remove dirt of a filter medium efficiently without installing a special vibration generator separately, and to provide a purification system.SOLUTION: In a purification system provided with a backwash function, a filter 30 for a circulation tank includes: a filter medium 41 forming a bag-like shape; and a core material 51 supporting the filter medium 41 from the inner surface side. The core material 51 includes first core bars 52 and second core bars 53 along the inner surface of the filter medium 41 at intervals in a circumferential direction. Each second core bar 53 has an outer diameter smaller than that of the first core bar 52 and has strength lower than that of the first core bar 52. Since the second core bars 53 having the relatively low strength easily vibrate by water flow during backwashing, the vibration is transmitted to the filter medium 41 and efficiently removes dirt adhering to the filter medium 41. Meanwhile, the first core bars 52 having relatively high strength inhibit crushing of the entire core material 51 by the water flow.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a filter for a circulation tank and a purification system.

Background Art

[0002] In a water tank (circulation tank) such as a bathtub or a pool, there may be provided a purification system that removes dirt from a liquid such as water or hot water (hereinafter referred to as "circulating water") collected from a circulation layer by a filter and returns it to the circulation tank.

[0003] Among purification systems, there has also been proposed a system that removes dirt adhering to a filter by backwashing, which imparts a flow in a direction opposite to the circulation direction of the circulating water to the filter (see Patent Documents 1 and 2). As the filter, the present inventor has proposed a filter using a non-woven fabric so that only the filter medium can be replaced (see Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a filter using a non-woven fabric as a filter medium, a mandrel is provided to support the non-woven fabric wound in a cylindrical shape from the inner peripheral side. In this case, in order to prevent the mandrel from bending due to the water flow, a mandrel with high strength is used.

[0006] The inventors of the present invention have recognized that the problem of how to improve the efficiency of removing dirt from nonwoven fabrics by backwashing is a problem and have come up with the idea of ​​applying vibration to the filter. However, if a dedicated vibration generator is installed to apply vibration to the filter, installation costs and maintenance costs for the vibration generator are also required.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a filter for a circulation tank and a purification system that can efficiently remove dirt from the filter material without the need to separately install a dedicated vibration generating device. [Means for solving the problem]

[0008] In order to achieve the above object, the filter for a circulating tank of the present invention comprises: A filter for a circulation tank comprising a filter material and a core material supporting the filter material, The filter medium includes a cylindrical portion, The core material supports the cylindrical portion from an inner peripheral surface side thereof, The core material includes a plurality of core rods spaced apart from one another in the circumferential direction along the inner circumferential surface, The plurality of core rods include at least a first core rod and a second core rod having a strength lower than that of the first core rod.

[0009] In addition, the purification system of the present invention includes: A filtration tank having the circulation tank filter attached thereto, The filtration tank includes: an introduction section that introduces the liquid recovered from the circulation tank into the filtration tank; a discharge portion that discharges the liquid filtered by the outer peripheral surface of the filter from an inner peripheral side of the filter; Equipped with a backwash mechanism for introducing liquid from the outlet portion to an inner peripheral side of the filter for the circulation tank to remove dirt adhering to an outer peripheral surface of the filter for the circulation tank; Equipped with.

[0010] According to the above-described filter for the circulation tank and the purification system, the second mandrel with relatively low strength is likely to vibrate due to the water flow during backwashing. Since the vibration of the second mandrel reaches the filter medium and the filter medium also vibrates, the dirt adhering to the filter medium can be efficiently removed without separately providing a vibration imparting mechanism. On the other hand, the collapse of the entire core material due to the water flow is suppressed by the first mandrel with relatively high strength. Thus, by using a core material including the first mandrel and the second mandrel with different strengths, it is possible to achieve both efficient dirt removal by backwashing and protection from damage.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a purification system according to an embodiment embodying the present invention and a filter for a circulation tank used therein will be described with reference to the drawings. The purification system is installed to purify a liquid such as water or hot water (hereinafter referred to as "circulating water") recovered from a circulation tank such as a bathtub or a pool and return it to the circulation tank.

[0013] As shown in FIG. 1, the purification system 10 of the present embodiment includes a hair catcher 12, a pressure pump 13, a filtration tank 14, and a boiler 15, which are connected by pipes 16 and 17. The pipes 16 and 17 include a forward pipe 16 for sending the circulating water recovered from the circulation tank 11 to the boiler 15, and a return pipe 17 for returning the circulating water from the boiler 15 to the circulation tank 11. Among the forward pipes 16, the part from the circulation tank 11 to the filtration tank 14 provided between the circulation tank 11 and the boiler 15 is defined as the first forward pipe 16a, and the part from the filtration tank 14 to the boiler 15 is defined as the second forward pipe 16b.

[0014] One end of the first forward pipe 16a is connected to the drain port 11a of the circulation tank 11, and the other end is connected to the inlet 14a of the filtration tank 14. The inlet 14a corresponds to the introduction part of the filtration tank 14. In the first forward pipe 16a, between the circulation tank 11 and the filtration tank 14, a hair catcher 12, a pressure pump 13, and a first switching valve 21 are provided in order from the circulation tank 11 side (upstream side). In FIG. 1, the flow of the circulating water is indicated by a solid arrow.

[0015] The hair catcher 12 is a device for removing foreign matters such as hair and gravel contained in the circulating water recovered from the circulation tank 11. The pressure pump 13 is provided on the downstream side of the hair catcher 12 and pumps the circulating water from which foreign matters have been removed by the hair catcher 12 to its downstream side. Due to the suction force generated by the pressure pumping of the circulating water by the pressure pump 13, the circulating water is sucked from the drain port 11a of the circulation tank 11.

[0016] The first switching valve 21 is a four-way valve provided on the downstream side of the pressure pump 13, and the flow of the circulating water can be switched by switching the communication destinations of the four ports (the first port 21a to the fourth port 21d). When the circulating water flows in the circulating direction, the first port 21a and the second port 21b are communicated, and the circulating water pumped from the pressure pump 13 is supplied to the filtration tank 14 through the first switching valve 21.

[0017] In the filtration tank 14, a plurality or a large number of filters 30 for the circulation tank (hereinafter simply referred to as "filter 30") are provided inside. Each filter 30 is the same and is detachably attached to a filter attachment portion 14b provided inside the filtration tank 14. When the circulating water introduced into the filtration tank 14 passes through the filter 30 from the outside to the inside, dirt such as scale contained therein is removed. The filter attachment portion 14b is provided with a purified water outlet portion 14c through which the circulating water filtered by the filter 30 is led out. The purified circulating water led out from the purified water outlet portion 14c as an outlet is discharged from the discharge port 14d.

[0018] One end of the second forward pipe 16b is connected to the discharge port 14d of the filtration tank 14, and the other end is connected to the boiler 15. In the second forward pipe 16b, a second switching valve 22 is provided between the filtration tank 14 and the boiler 15. The second switching valve 22 is a three-way valve provided on the downstream side of the pressure pump 13, and the flow of the circulating water is switched by switching the communication destinations of the three ports (the first port 22a to the third port 22c). When the circulating water is made to flow in the circulating direction, the first port 22a and the second port 22b are communicated, and the circulating water discharged from the filtration tank 14 is supplied to the boiler 15 through the second switching valve 22.

[0019] The boiler 15 is a device that heats the introduced circulating water to a preset temperature. The circulating water introduced into the boiler 15 is heated to the set temperature and then discharged, and is returned to the circulation tank 11 through the return pipe 17.

[0020] In addition, the purification system 10 of the present embodiment also has a function of removing dirt adhering to the filter 30 in the filtration tank 14 by backwashing, which imparts a flow in a direction opposite to the circulation direction of the circulating water. Therefore, the purification system 10 has a backwash pipe 18 connecting the first switching valve 21 and the second switching valve 22, and a drain pipe 19. The backwash mechanism section is configured to include these first switching valve 21, second switching valve 22, backwash pipe 18, and drain pipe 19. In FIG. 1, the flow of the circulating water when backwashing the filter 30 is indicated by a dotted arrow.

[0021] One end of the backwash pipe 18 is connected to the third port 21c of the first switching valve 21, and the other end is connected to the third port 22c of the second switching valve 22. One end of the drain pipe 19 is connected to the fourth port 21d of the first switching valve 21, and the other end serves as a drain port 19a. An on-off valve 23 is provided in the drain pipe 19 and is held in a closed state when the circulating water flows in the circulation direction. During backwashing, in the first switching valve 21, the first port 21a and the third port 21c are communicated, and the second port 21b and the fourth port 21d are communicated. In the second switching valve 22, the first port 22a and the third port 22c are connected. Also, the on-off valve 23 is switched to an open state.

[0022] During backwashing, the circulating water pumped from the pressure pump 13 flows from the first switching valve 21 through the backwash pipe 18 to the second switching valve 22, flows in the direction opposite to the circulation direction through the second forward pipe 16b, and is introduced into the filtration tank 14 from its discharge port 14d. The circulating water introduced from the discharge port 14d is introduced into the interior of the filter 30 from the purified water outlet section 14c, passes through the filter 30 from the inner side to the outer side in the direction opposite to that during circulation, and is discharged from the inlet 14a of the filtration tank 14. When the circulating water passes through the filter 30 in the direction opposite to that during circulation, the dirt adhering to the outer peripheral surface of the filter 30 is removed. Therefore, the circulating water reaching the inlet 14a of the filtration tank 14 contains the dirt that had adhered to the filter 30. Such circulating water containing dirt is discharged from the inlet 14a of the filtration tank 14, then flows to the drain pipe 19 at the first switching valve 21, passes through the open on-off valve 23, and is discharged from the drain outlet 19a of the drain pipe 19. Thereby, the dirt adhering to the outer peripheral surface of the filter 30 can be removed, and the filter 30 can be regenerated.

[0023] Note that the purification system 10 is provided with a control unit (not shown) for controlling the flow of the circulating water in the circulation direction and the backwashing of the filter 30. The pressure pump 13, the boiler 15, each of the switching valves 21, 22, and the on-off valve 23 are electrically connected to the control unit (not shown). The operations of the pressure pump 13 and the boiler 15, the switching operations of the flow paths at the respective switching valves 21, 22, and the opening and closing operations of the on-off valve 23 are controlled by the control unit (not shown).

[0024] The basic configuration of the purification system 10 of the present embodiment and the explanations of the flow of the circulating water during circulation and backwashing are as described above. On top of that, the purification system 10 of the present embodiment is characterized by the configuration of the filter 30 provided in the filtration tank 14, and has a function of efficiently removing dirt without separately installing a dedicated vibration generating device during backwashing. Hereinafter, the configuration of the filter 30 and its effects will be described.

[0025] As shown in FIGS. 2 and 3, the filter 30 has a base material 31, a filter medium 41, and a core material 51.

[0026] The base material 31 is a filter mounting member for being mounted on a filter mounting portion 14b provided on the filtration tank 14. Referring also to FIG. 4, the base material 31 has a base plate portion 32 having a disk shape, and has a flat surface portion 33 and a screw portion 34 provided on the opposite side thereof. The flat surface portion 33 is orthogonal to the axial direction in which the screw portion 34 extends. The screw portion 34 is screwed into a mounting hole (not shown) provided in the filter mounting portion 14b, whereby the filter 30 is mounted on the filter mounting portion 14b. A communication passage 35 is provided in the base material 31 along the axial direction of the screw portion 34. The communication passage 35 penetrates the base material 31 along the axial direction of the screw portion 34, and opening portions 36 are provided at the flat surface portion 33 and the end portion of the screw portion 34. The communication passage 35 communicates with the purified water derivation portion 14c of the filter mounting portion 14b.

[0027] The filter medium 41 is formed in a bottomed cylindrical shape (bag shape) by a non-woven fabric and has a cylindrical portion 42. The filter medium 41 is fixed to the base material 31. The filter medium 41 is put on the base material 31 so as to cover the flat surface portion 33 of the base plate portion 32. A binding band B is provided outside the opening side of the filter medium 41, and the opening of the filter medium 41 is closed by tightening the binding band B against the side portion of the base plate portion 32. The filter medium 41 is replaceable. At the time of replacement, the binding band B is cut off, and a new filter medium 41 is put on the base material 31 and re-fixed with the binding band B.

[0028] The core material 51 is provided on the flat surface portion 33 of the base plate portion 32 of the base material 31, on the side opposite to the side where the screw portion 34 is provided. The core material 51 supports the cylindrical portion 42 of the bag-shaped filter medium 41 from the inner peripheral surface side. The core material 51 is configured to include a plurality of at least three or more core rods 52 and 53. In the present embodiment, two core rods 52 and 53 of two different outer diameters are provided two by two, and a total of four core rods 52 and 53 are provided. Hereinafter, when distinguishing between the two types of core rods 52 and 53, the thicker one in diameter is referred to as the first core rod 52, and the thinner one in diameter is referred to as the second core rod 53. Each of the core rods 52 and 53 is formed of the same material among metals such as stainless steel and aluminum, and is a round bar having a circular cross section.

[0029] Each mandrel 52, 53 has one end attached to the flat surface 33 of the base plate portion 32, and extends from there along the inner peripheral surface of the cylindrical portion 42 of the filter medium 41 from the opening side to the bottom side of the cylindrical portion 42. Then, at the bottom side of the filter medium 41, it is folded back to the side opposite to the inner peripheral surface of the cylindrical portion 42, extends again from the bottom side to the opening side, and the other end is attached to the flat surface 33 of the base plate portion 32. Both ends of the mandrels 52, 53 are attached to the flat surface 33 of the base plate portion 32, and the mandrels 52, 53 are provided so as to protrude from the flat surface 33 while following the inner peripheral surface of the filter medium 41. The protruding ends of each mandrel 52, 53 are formed in a convex curved shape and intersect each other in a non-connected state. Each mandrel 52, 53 shown in FIGS. 2 and 3 has two first mandrels 52 intersecting, and two second mandrels 53 intersecting on the base end side (the side of the base material 31) rather than that.

[0030] As shown in FIG. 4, each mandrel 52, 53 is provided at intervals in the circumferential direction on the flat surface 33 of the base plate portion 32. When viewed from the protruding direction of the core material 51, each mandrel 52, 53 is provided so that the angle with the adjacent mandrel 52, 53 in the circumferential direction is the same and forms an equidistant radial shape. Therefore, as shown in FIGS. 2 and 3, when the mandrels 52, 53 are viewed from the side, the first mandrel 52 and the second mandrel 53 are alternately provided along the circumferential direction.

[0031] Since the filter 30 having the above configuration is provided, during circulation, when the circulating water introduced into the filtration tank 14 passes from the outside to the inside of the filter medium 41, the dirt contained in the circulating water is filtered and purified. At this time, the first mandrel 52 having relatively higher strength than the second mandrel 53 suppresses the crushing of the entire core material 51 by the water flow from the outside to the inside of the filter medium 41. The purified circulating water flowing inside the filter medium 41 passes through the communication passage 35 provided in the base material 31 and the purified water outlet portion 14c of the filter attachment portion 14b, and is discharged from the discharge port 14d of the filtration tank 14 to the second forward pipe 16b.

[0032] During backwashing, water is introduced into the inside of the filter medium 41 from the purified water outlet 14c and the communication passage 35, contrary to this flow. When the circulating water passes from the inside to the outside of the filter medium 41, the dirt adhering to the filter medium 41 is removed from the filter medium 41 by the water flow. At this time, the second mandrel 53, which has relatively lower strength than the first mandrel 52, is more likely to vibrate due to the water flow during backwashing. Therefore, the vibration of the second mandrel 53 reaches the filter medium 41 in contact with the second mandrel 53 on the inner peripheral side, causing the filter medium 41 to vibrate as well. Due to the vibration of the filter medium 41, the dirt adhering to the filter medium 41 is efficiently removed.

[0033] According to the purification system 10 of the present embodiment described above, the following operational effects can be obtained.

[0034] (1) In the filter 30, the second mandrel 53 with relatively lower strength is more likely to vibrate due to the water flow during backwashing, and the vibration of the second mandrel 53 reaches the filter medium 41, causing the filter medium 41 to vibrate as well. Therefore, even without providing a separate vibration applying mechanism, the dirt adhering to the filter medium 41 can be efficiently removed. On the other hand, since the first mandrel 52 with relatively higher strength is also provided, the collapse of the entire core material 51 due to the water flow during circulation is suppressed by the first mandrel 52. In this way, by using the core material 51 including the first mandrel 52 and the second mandrel 53 with different strengths, it is possible to achieve both efficient dirt removal by backwashing and protection from damage.

[0035] (2) The first mandrel 52 and the second mandrel 53 are alternately arranged in the circumferential direction when viewed from the direction in which the core material 51 protrudes from the flat surface portion 33 of the base plate portion 32. Therefore, while the strength of the entire core material 51 can be maintained by the first mandrels 52 on both sides of the second mandrel 53, during backwashing, the entire filter medium 41 between the adjacent first mandrels 52 can be vibrated by the second mandrels 53 on both sides of the first mandrel 52. As a result, the bias in the vibrating portions where the vibration of the second mandrel 53 is transmitted is eliminated, and the dirt on the entire filter medium 41 can be removed.

[0036] (3) The portion on the protruding end side of the core material 51 where the plurality of mandrels 52 and 53 are folded back is formed in a convex curved shape. As in the filter 80 shown in FIG. 7, when the protruding end sides of the mandrels 81 and 82 are bent at a right angle or the like, it becomes difficult to vibrate the mandrels 81 and 82. However, since it is formed in a curved shape, the second mandrel 53 is likely to vibrate. In addition, there is no risk that the filter medium 41 hits the corners of the bent mandrels 81 and 82 and the filter medium 41 is damaged. Moreover, the fact that the plurality of mandrels 52 and 53 are round bars also leads to preventing the filter medium 41 from being damaged.

[0037] The embodiment of the present invention is not limited to the filter 30 of the above embodiment, and may be in the following forms, for example.

[0038] (a) In the filter 30 of the above embodiment, two types of mandrels 52 and 53 with different strengths are arranged alternately, but three or more types of mandrels may be used. For example, as shown in FIG. 5, when the outer diameters are sequentially made thinner to make the strengths different, and the first mandrel 61, the second mandrel 62, and the third mandrel 63 are set in order from the stronger one (the thicker outer diameter), they are arranged in the order of the first mandrel 61, the second mandrel 62, and the third mandrel 63 along the circumferential direction. Next, they are again arranged in the order of the first mandrel 61, the second mandrel 62, and the third mandrel 63. Even with such a configuration, the third mandrel 63 with the relatively weakest strength vibrates the most by the water flow during backwashing, and the second mandrel 62 with intermediate strength vibrates weaker than that by the water flow during backwashing, and the plurality of vibrations are amplified to more efficiently remove the dirt attached to the filter medium 41.

[0039] (b) Instead of the plurality of mandrels 52 and 53 in which the protruding end side of the core material 51 is formed into a curved shape that becomes convex by being folded back, as shown in FIG. 6, a filter 70 having a core material 73 composed of a plurality of mandrels 71 and 72 formed linearly may be used. In this case, a base material 31 is provided on one end side of the plurality of mandrels 71 and 72, a disc plate 74 is provided on the other end side, and the respective end portions of the mandrels 71 and 72 are attached to the flat portion 33 of the base material 31 and the flat portion 75 of the disc plate 74. And the filter medium 76 to be used is, unlike the bag shape, a cylindrical portion 77 having both ends open. One open side is fixed to the side portion of the base material 31, and the other open side is fixed to the side portion of the disc plate 74 by a fixing member such as a binding band B, etc., and both ends of the filter medium 76 are blocked.

[0040] The plurality of mandrels 71 and 72 have a first mandrel 71 and a second mandrel 72 whose strengths are relatively different due to the difference in outer diameter. Both mandrels 71 and 72 are provided along the inner peripheral surface of the cylindrical portion 77 of the filter medium 76 and are alternately provided along the circumferential direction. In the filter 70 having such a configuration, during circulation, the circulating water flows from the outer peripheral side to the inner peripheral side of the cylindrical portion 77 of the filter medium 76 and is purified. During backwashing, the circulating water flows from the inner peripheral side to the outer peripheral side, and the dirt of the filter medium 76 is removed. Even with such a configuration, by using the core material 73 including the first mandrel 71 and the second mandrel 72 having different strengths from each other, it is possible to achieve both efficient dirt removal by backwashing and protection from breakage.

[0041] However, in the filter 30 of the above embodiment, the plurality of mandrels 52 and 53 serving as the core material 51 extend from the flat portion 33 of the base plate portion 32 along the inner peripheral surface of the cylindrical portion 42 from the opening side to the bottom side, and then are folded back at the bottom side and reach the opening side again, and both ends are attached to the flat portion 33 of the base plate portion 32. By using the core material 51 with the mandrels 52 and 53 folded back on the protruding side in this way, the member (base material 31) for attaching the mandrels 52 and 53 only needs to be on one side in the protruding direction of the mandrels 52 and 53, and the disc plate 74 provided on the protruding side becomes unnecessary. Also, unlike the filter 70 of the above-mentioned alternative example in which the linearly shaped mandrels 71 and 72 are fixed at both ends in the length direction, the second mandrel 53 becomes more likely to vibrate.

[0042] Further, in the filter 30 of the above embodiment, the filter medium 41 used is formed in a bag shape, one end side of the cylindrical portion 42 is closed, and the other end side is open. Therefore, unlike the filter 70 of another form shown in FIG. 6 where the disc plate 74 is provided on the other end side, the protruding end side of the core material 51 can also be utilized as the filter medium 41. As a result, compared with the filter medium 76 shown in FIG. 6 with both ends open, the effective area of the filter medium 41 can be increased, and accordingly, the height of the filter 30 can be reduced. As a result, it can also contribute to the miniaturization of the filtration tank 14. The filter 30 of the above embodiment has various advantages as described above compared with the filter 70 of another form shown in FIG. 6.

[0043] (c) As a configuration for relatively changing the strengths of the plurality of mandrels 52 and 53, in addition to making the outer diameters different as in the above embodiment, it may be realized by using materials with different strengths, such as making the stronger one made of stainless steel and the weaker one made of aluminum. Further, it may be realized by making the cross-sectional shapes different, such as making the stronger one a square bar and the weaker one a round bar. As an example of making the cross-sectional shapes different, while using round bars of the same diameter, the cross-section of the weaker one may be formed in a D-shaped cross-section and provided in a state where the flat portion faces inward. According to this configuration, since the curved portion faces outward, the strength can be made weaker than that of a round bar without damaging the filter medium 41. Furthermore, not only by making the materials and cross-sectional shapes different, but also by making the partial structures different, such as making the diameter thinner and the strength weaker at the base end sides of the mandrels 52 and 53 on the side of the base material 31 while being made of the same stainless steel and having the same outer diameter, the strength can be made to have strong and weak portions.

[0044] (d) Instead of the mandrels 52 and 53 made of round bars, the mandrels 81 and 82 may be made of square bars (illustrated as square cross-sections) with a polygonal cross-section (not necessarily a square cross-section. For example, it may be a rectangular shape with a thinner inner and outer direction). Even when the mandrels 81 and 82 are made of such square bars, like the mandrels 52 and 53 in the filter 30 of the above embodiment, the folded-back portion may be formed in a curved shape that protrudes convexly in the protruding direction. Also, like the filter medium 83 shown in FIG. 7, the shape of the bag-shaped filter medium can be arbitrary, such as a square bag shape with a flat bottom 64.

[0045] (e) In the filter 30 of the above embodiment, the opening of the filter medium 41 is closed with the binding band B and fixed to the base material 31. However, it is not necessary that the binding band B be used to fix it to the base material 31. Various fixing members can be used as long as they can make the filter medium 41 detachable, such as a metal hose band. Also, the fixing position of the filter medium 41 using a fixing member such as the binding band B is arbitrary. For example, it may be between the base plate portion 32 and the screw portion 34 of the base material 31, and may be fixed at a small-diameter portion with a smaller diameter than the base plate portion 32. When the filter medium 41 is fixed to the base material 31 at this small-diameter portion, it is possible to prevent the base material 31 from coming out of the opening of the filter medium 41 due to the water flow generated during backwashing.

[0046] (f) In the filter 30 of the above-described embodiment, as shown in FIGS. 2 and 3, on the protruding end side of the core material 51, two first core bars 52 intersect, and on the base end side (the side of the base material 31) rather than that, two second core bars 53 intersect. The configuration in which the core bars 52 and 53 having different strengths intersect at the folded-back portion on the protruding end side of the core material 51 may be such that, for example, the two second core bars 53 intersect on the protruding end side rather than the two first core bars 52, or the first core bars 52 and the second core bars 53 may intersect in an alternating manner. This also holds true even when the types of the core bars 52 and 53 increase. By providing a core bar that vibrates due to the water flow during backwashing, such as the second core bar 53 in the filter 30 of the above-described embodiment, at the outermost protruding end side, the vibration of the core bar existing inside can be transmitted even at the bottom side of the filter medium 41, and the entire filter medium 41 can be vibrated.

Explanation of Reference Numerals

[0047] 10... Purification system, 14... Filtration tank, 14a... Inlet (introduction part), 14c... Downwardly drooping outlet (derivation part), 18... Backwash pipe (backwash mechanism part), 19... Drain pipe (backwash mechanism part), 21... First switching valve (backwash mechanism part), 22... Second switching valve (backwash mechanism part), 30... Filter (filter for circulation tank), 31... Base material, 35... Communication path, 41... Filter medium, 42... Cylindrical part, 51... Core material, 52... First core bar, 53... Second core bar.

Claims

1. A filter for a circulation tank comprising a filter material and a core material supporting the filter material, The filter medium includes a cylindrical portion, The core material supports the cylindrical portion from an inner peripheral surface side thereof, The core material includes a plurality of core rods spaced apart from one another in the circumferential direction along the inner circumferential surface, The filter for a circulation tank, wherein the plurality of core rods include at least a first core rod and a second core rod having a strength lower than that of the first core rod.

2. 2. The filter for a circulating tank according to claim 1, wherein the first core rods and the second core rods are arranged alternately in the circumferential direction.

3. A base material to which the ends of the plurality of core rods are attached is provided, The filter medium is removably fixed to the base material, 3. The filter for a circulating tank according to claim 1, wherein the base material has a communication passage formed therein that communicates with an inner periphery of the filter medium.

4. The plurality of core rods extend from the base material along the inner circumferential surface of the cylindrical portion from one end side to the other end side, The other end is folded back toward the opposing side of the inner circumferential surface and extends from the other end to the one end, The filter for a circulating tank according to claim 3 , wherein both ends of the plurality of core rods are attached to the base material.

5. 5. The filter for a circulation tank according to claim 4, wherein the filter material is formed in a bag shape such that the other end side of the cylindrical portion is closed and the one end side of the cylindrical portion is open.

6. The filter for a circulation tank according to claim 4 , wherein the folded-back portions of the plurality of core rods are formed in a curved shape that is convex toward the other end side.

7. A filtration tank having the circulating tank filter according to claim 1 attached thereto, The filtration tank includes: an introduction section that introduces the liquid recovered from the circulation tank into the filtration tank; a discharge portion that discharges the liquid filtered by the outer peripheral surface of the filter from an inner peripheral side of the filter; Equipped with a backwash mechanism for introducing liquid from the outlet portion to an inner peripheral side of the filter for the circulation tank to remove dirt adhering to an outer peripheral surface of the filter for the circulation tank; A purification system comprising:

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