Liquid storage tank and filter cloth for liquid storage tank

Abstract

To provide a liquid storage tank equipped with a filter cloth which is made less likely to drop off from a header by adopting a structure other than that of fitting a filter cloth formed in a bag shape into a header, and the filter cloth. [Solution] A liquid storage tank having a tank 71 for storing liquid, a liquid discharge pipe 73, a head 76 for fixing the discharge pipe, and a cylindrical filter cloth 1 arranged to cover the discharge pipe, wherein the filter cloth has a first annular member 31 that is flexible and a second annular member 32 that is shape-retaining at its base end, one of the first annular member and the second annular member being shaped to be contained within the other, the tank having an opening 72 and an edge surrounding the opening and a wall portion rising from the edge, the base end of the filter cloth having the first annular member and the second annular member and shaped to protrude radially outward from the opening, and the part of the filter cloth protruding radially outward is fitted into a step formed by the edge and wall portion. A liquid storage tank.

Description

[Technical Field]

[0001] The present invention relates to a tank for storing liquid and a filter fabric for use in a tank for storing liquid. [Background technology]

[0002] Patent Document 1 below discloses a tank for diesel exhaust fluid (DEF). The tank has a header fixed to an opening of the tank by screws, a fluid outlet pipe fixed to the header, a tubular heater through which a heat transfer medium passes, and a bag filter covering the fluid outlet pipe and the heater. The bag filter is fitted onto the peripheral surface of the lower end of the header. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6560231 Summary of the Invention [Problem to be solved by the invention]

[0004] In the tank of Patent Document 1, the bag filter and the header are fixed by fitting the opening at the upper end of the bag filter into the lower end of the header. The bag filter is fixed to the tank by screwing the header to the edge of the opening of the tank.

[0005] In the structure of Patent Document 1, when hydraulic pressure acts on the bag filter, the bag filter may fall off from the header. To prevent this, strict dimensional control of the inner diameter of the opening of the bag filter and the outer diameter of the header is required. When a mounting bracket for the header is provided on the bag filter, the mounting bracket must be attached to the bag filter, and the mounting bracket for the bag filter must be aligned with the mounting portion at the bottom end of the header.

[0006] The present invention aims to provide a liquid storage tank equipped with a filter cloth that is less likely to fall off the bag-shaped filter cloth from the tank by adopting a structure other than that of fitting the bag-shaped filter cloth into the head, and the filter cloth. [Means for solving the problem]

[0007] The above-mentioned problem is solved by a liquid storage tank having a tank for storing liquid, a liquid discharge pipe, a head for fixing the discharge pipe, and a cylindrical filter cloth arranged to cover the discharge pipe, wherein the filter cloth has a first annular member that is flexible and a second annular member that is shape-retaining at its base end, one of the first annular member and the second annular member having a shape that is contained within the other of the first annular member and the second annular member, the tank has an opening, an edge portion that surrounds the opening, and a wall portion that rises from the edge portion, the base end of the filter cloth has the first annular member and the second annular member and is shaped to protrude radially outward from the opening, and the portion of the filter cloth that protrudes radially outward is fitted into a step formed by the edge portion and the wall portion.

[0008] The above-mentioned problems are solved by a filter cloth for a liquid storage tank, which has an opening at its base end that is large enough to accommodate a liquid discharge pipe, which is a component on the tank side, and is bag-shaped with a closed lower end, and the filter cloth has a first annular member that is flexible and a second annular member that has shape retention at its base end, one of the first annular member and the second annular member being shaped to be accommodated within the other of the first annular member and the second annular member, and the base end of the filter cloth has the first annular member and the second annular member, and is shaped to protrude radially outward from the opening.

[0009] In the liquid storage tank and the filter cloth for the liquid storage tank, the base end of the filter cloth, which includes a first annular member and a second annular member, can be fitted into the step formed by the edge and the wall, thereby fixing the bag-shaped filter cloth to the tank. The part of the filter cloth that protrudes radially outward is fitted into the step, and the base end of the filter cloth is fixed by the second annular member, which has shape retention, so the filter cloth is less likely to fall off the tank.

[0010] In the liquid storage tank and the filter cloth for the liquid storage tank, the first annular member can fill the gap between the base end of the filter cloth and the wall portion.

[0011] In the liquid storage tank and the filter cloth for the liquid storage tank, the end of the first annular member may be shaped to protrude closer to the head than the end of the second annular member before the filter cloth is fitted into the step and the head is fixed. Furthermore, the first annular member may be crushed by the head when the head is fixed to the tank, increasing the radial thickness of the opening. This allows the thickness of the first annular member to expand radially to fill the gap between the base end of the filter cloth and the wall, thereby more reliably fixing the filter cloth to the tank.

[0012] In the liquid storage tank and the filter cloth for the liquid storage tank, the second annular member can be elastically deformed to switch between a first outer diameter and a second outer diameter. With the outer diameter of the second annular member reduced, the base end of the filter cloth is fitted into the step, and then the outer diameter of the second annular member is increased, thereby allowing the base end of the filter cloth to be fixed to the step in a simple procedure. [Effects of the Invention]

[0013] According to the present invention, by adopting a structure other than that of fitting a bag-shaped filter cloth into the head, it is possible to provide a liquid storage tank equipped with a filter cloth that makes it difficult for the bag-shaped filter cloth to fall off the tank, and the filter cloth. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 illustrates an example of a system for supplying diesel exhaust fluid to an exhaust pipe. [Figure 2] FIG. 10 is a perspective view showing the shape of the heating unit and the discharge pipe integrated by the head portion. [Figure 3] 2 is an enlarged view of the left side portion of the tank in FIG. 1, and is a cross-sectional view showing a state in which a filter cloth and a head portion to which a discharge pipe and a heating portion are fixed are attached to the tank. FIG. [Figure 4] 4 is an enlarged view of part A in FIG. 3, and is a cross-sectional view showing a state in which the head is separated from the tank. [Figure 5] 4 is an enlarged view of part A in FIG. 3, and is a cross-sectional view showing a state in which the head is attached to the tank. [Figure 6] FIG. 2 is a plan view showing an example of a first annular member and a second annular member. [Figure 7] 10 is a plan view showing another example of the first annular member and the second annular member. FIG. [Figure 8] FIG. 2 is a side view of a bag-shaped filter cloth. [Figure 9] FIG. 2 is a front view of a bag-shaped filter cloth. [Figure 10] FIG. 5 is a cross-sectional view corresponding to FIG. 4, showing another embodiment of the tank and the filter cloth. [Figure 11] FIG. 6 is a cross-sectional view corresponding to FIG. 5, showing another embodiment of the tank and the filter cloth. [Figure 12] 10 is a plan view showing another example of the first annular member and the second annular member. FIG. [Figure 13] FIG. 5 is a cross-sectional view corresponding to FIG. 4, showing another embodiment of the tank and the filter cloth. [Figure 14] FIG. 6 is a cross-sectional view corresponding to FIG. 5, showing another embodiment of the tank and the filter cloth. [Figure 15] 10 is a plan view showing another example of the first annular member and the second annular member. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes embodiments of the liquid storage tank and the filter cloth used therein of the present invention. The embodiments described below are merely limited examples of the present invention, and the technical scope of the present invention is not limited to the exemplified embodiments.

[0016] [First embodiment] One embodiment of a liquid storage tank 71 (hereinafter simply referred to as the tank) and a filter cloth 1 used therein are shown in Figures 1 to 6. The tank 71 has a liquid discharge pipe 73, a head portion 76 to which the discharge pipe 73 is fixed, and a tubular filter cloth 1 arranged to cover the discharge pipe 73. As shown in Figure 4, the filter cloth 1 has, at its base end, a flexible first annular member 31 and a shape-retaining second annular member 32, and one of the first annular member 31 and the second annular member 32 is shaped so as to be contained within the other of the first annular member 31 and the second annular member 32.

[0017] As shown in FIG. 4, the tank 71 has an opening 72, an edge 721 surrounding the opening 72, and a wall 722 rising from the edge 721. The wall 722 is a surface that forms a circular recess in a plan view. The base end of the filter cloth 1 includes the first annular member 31 and the second annular member 32. The base end of the filter cloth 1 is shaped to protrude radially outward from the opening 72, and the portion 17 of the filter cloth 1 that protrudes radially outward is fitted into a step 724 formed by the edge 721 and the wall 722. The edge 721 is shaped to have a support surface that extends in a direction intersecting the extension direction of the bag-shaped filter cloth 1. The base end of the filter cloth also has a shape that protrudes radially outward from the opening provided at the base end of the filter cloth.

[0018] In the tank 71 and the filter cloth 1 of this embodiment, the heating unit 75 is contained inside the filter cloth 1, but the heating unit 75 may be omitted. Also, the heating unit may be separately disposed outside the filter cloth 1, or the tank 71 may be configured to be heated from the outside.

[0019] The tank 71 is, for example, a component of a system that sprays diesel exhaust fluid (DEF) onto exhaust gas. The diesel exhaust fluid contains a reducing agent containing nitrogen oxides, such as urea. FIG. 1 shows an example of a system that sprays a liquid reducing agent containing nitrogen oxides onto exhaust gas. The tank and filter cloth of the present invention can be suitably used in a diesel exhaust fluid spray system, but their use is not limited to diesel exhaust fluid supply systems.

[0020] The system in FIG. 1 includes a tank 71 that stores diesel exhaust fluid and an exhaust pipe 83 extending from a diesel engine 82. A nozzle 74 is disposed inside the exhaust pipe 83. The diesel exhaust fluid is supplied to the nozzle 74 via a discharge pipe 73 inserted into the tank or a supply path that communicates with the discharge pipe 73. By spraying the diesel exhaust fluid from the nozzle 74 onto the exhaust gas flowing inside the exhaust pipe 83, NOx contained in the exhaust gas is reduced and released into the environment. The discharge pipe 73 is provided with a pump 79 and a filter 78 for removing dust contained in the diesel exhaust fluid. The filter 78 is disposed upstream of the pump 79, and the diesel exhaust fluid from which dust has been removed by the filter 78 is supplied to the pump 79.

[0021] Tank 71 is provided with a heating unit 75. Heating unit 75 is composed of hollow tubes that circulate a heat exchange medium, such as a heated liquid, inside. A heat source 77 for the heat exchange medium is provided in the circulation path composed of the hollow tubes. A vehicle radiator, for example, can be used as heat source 77. Thermal energy generated by the engine is transferred to the heat exchange medium to heat the heat exchange medium. The hollow tubes that make up heating unit 75 are immersed in the diesel exhaust liquid stored inside tank 71, and transfer the thermal energy of the heated heat exchange medium to the diesel exhaust liquid, preventing the diesel exhaust liquid from freezing at low temperatures.

[0022] A float 731 is inserted into the discharge pipe 73. The float 731 rises and sinks in conjunction with the liquid level in the tank, detecting the liquid level in the tank and notifying the user via a display such as an indicator. When refilling the tank 71 with diesel exhaust liquid, the plug 81 fixed to the liquid filling opening 80 is removed, and the diesel exhaust liquid is poured in through the opening 80.

[0023] When diesel exhaust liquid is supplied to the exhaust pipe 83, the diesel exhaust liquid stored in the tank passes through the bag-shaped filter cloth 1, is sucked up by the discharge pipe 73, and is supplied to the exhaust pipe 83. Dust is filtered out by the filter cloth 1, reducing the amount of dust brought into the exhaust pipe 83. In addition, the amount of dust supplied to the filter 78 is reduced by the action of the filter cloth 1, so the frequency of replacing the filter 78 can be reduced.

[0024] Head 76, which is a part on the tank side, functions as a base that fixes discharge pipe 73 and heating unit 75 so that they do not move around inside tank 71, and also functions as a lid that closes opening 72 of tank 71. In the example of Figure 2, a configuration is illustrated in which discharge pipe 73 is fixed to head 76 by passing through head 76, but the structure for fixing discharge pipe 73 can be changed as appropriate. Similarly, in the example of Figure 2, a configuration is illustrated in which a hollow tube that constitutes heating unit 75 is fixed to head 76 by passing through head 76, but the structure for fixing heating unit 75 can be changed as appropriate.

[0025] For example, the heating unit may be configured by having a first hollow tube that constitutes the heating unit penetrate the head from the outside and reach the inside of the tank, and then having a second hollow tube that constitutes the heating unit connected to the end of the first hollow tube. The position at which the hollow tubes are connected may coincide with the position of the head, or may be either outside or inside the head. In this case, the first hollow tube and the second hollow tube may be connected to one end and the other end of a hollow tubular flow path provided in the head.

[0026] For example, a first hollow pipe constituting the discharge pipe may penetrate the head from the outside and reach the inside of the tank, and a second hollow pipe constituting the discharge pipe may be joined to the end of the first hollow pipe, thereby fixing the second hollow pipe constituting the discharge pipe. The joining position of the hollow pipe may coincide with the head, or may be upstream or downstream of the head. In this case, the first hollow pipe and the second hollow pipe may be connected to one end and the other end of a hollow flow path provided in the head.

[0027] 4 and other figures, the base end of the filter cloth 1 includes the first annular member 31 and the second annular member 32, and has a shape that protrudes radially outward from the opening 72. To fix the filter cloth 1 to the tank 71, the portion 17 at the base end of the filter cloth 1 that protrudes radially outward is placed on a step 724 formed by an edge 721 and a wall 722 of the opening 72 of the tank 71.

[0028] As shown in FIG. 4 and other figures, the filter fabric 1 includes a flexible first annular member 31 and a shape-retaining second annular member 32 at its base end. In the example of FIG. 4, the flexible first annular member 31 is configured to enclose the shape-retaining second annular member 32. The first annular member 31 and the second annular member 32 are secured to the filter fabric 1 by placing the first annular member 31 on the outside and the second annular member 32 on the inside of a bag-shaped fabric, and sewing the fabric to a second tubular portion 12 (described later). The bag is annular and forms an opening for the filter fabric 1. The second annular member 32 is shape-retaining, allowing the filter fabric 1 to maintain a shape that protrudes radially outward from the opening 72. In the example of this embodiment, the bag-shaped fabric is made of woven fabric. The dashed lines in FIG. 4 indicate stitches (the same applies to FIGS. 3, 5, 10, 11, 13, and 14).

[0029] In the filter fabric 1 of this embodiment, as shown by the dashed line in FIG. 6 , the second annular member 32 can be elastically deformed to switch between a first outer diameter and a second outer diameter. In FIG. 6 , the dashed line indicates a state in which the outer diameter is reduced. The first outer diameter is larger than the second outer diameter. The second annular member 32 may be any member capable of elastically deforming to switch between the first and second outer diameters. Examples include a metal ring, an elastomer ring, an annular member with a partially open annular portion as shown in FIG. 7 , or a snap ring. The second annular member 32d in FIG. 7 is partially open, but this specification also includes a partially open annular shape. The outer diameter of the second annular member 32d in FIG. 7 can be changed by deforming it in the direction of the arrow in FIG. 7 so that the spacing between the open annular portions decreases. The first annular member 31d in FIG. 7 is in a closed state, but it may also be partially open.

[0030] When fixing the filter cloth 1 to the tank 71, as shown in FIG. 6 , the shape-retaining second annular member 32 is deformed to reduce the outer diameter of the opening of the filter cloth incorporating the first and second annular members 31 and 32, and the filter cloth 1 is then fitted into the opening 72 of the tank 71. When the external force applied to the second annular member 32 is removed and the outer diameter of the second annular member 32 is restored to its original state, the restoring force of the second annular member 32 presses the flexible first annular member 31 and the filter cloth 1 against the wall portion 722, as indicated by the arrows in FIG. 5 . This fills the gap between the opening 72 of the tank 71 and the base end of the filter cloth 1, suppressing rattle of the filter cloth 1 and reliably fixing the filter cloth 1 to the opening of the tank 71. As shown in FIG. 4 , the head portion 76 is placed on the second edge portion 721 of the tank 71 while aligning the filter cloth 1 so that the heating unit 75 and the discharge pipe 73 are contained within the opening. The head 76 and the tank 71 are fixed together by screws 762 via a diaphragm 761. The diaphragm 761 is made of an elastic material and provides sealing properties. In Figure 4 and other figures, the shape of the screws is omitted. Known bolts, nuts, etc. can be used as the screws.

[0031] The flexible first annular member 31 fills the gap between the wall portion 722 and the filter cloth 1, which allows for looser dimensional control of the base end of the filter cloth incorporating the first annular member 31 and the second annular member 32 and the tank 71. This allows for improved yield of the filter cloth during manufacturing.

[0032] The first annular member 31 is made of a flexible annular member. The first annular member 31 may have a partially open shape and may not be a complete annular member. The first annular member 31 may be made of, for example, a nonwoven fabric, a woven Edited The first annular member 31 can be made of a cloth or an elastic material such as rubber, etc. In this embodiment, the first annular member 31 is made of a nonwoven fabric whose thickness is easily adjusted.

[0033] The first annular member 31 and the second annular member 32 are preferably formed as annular plates, which allows a protrusion with a certain width to be formed at the base end of the filter cloth 1.

[0034] 8 and 9, the filter cloth 1 includes a first cylindrical portion 11 made of a bag-shaped fabric that houses a first annular member 31 and a second annular member 32, and a second cylindrical portion 12 that is connected to the first cylindrical portion 11 and covers the tip of the discharge pipe 73. The first cylindrical portion 11 is made of a fabric that is thinner than the fabric that makes up the second cylindrical portion 12. Because of this configuration, when the discharge pipe 73 and the heating unit 75 are inserted into the bag-shaped filter cloth 1, the first cylindrical portion 11 can easily deform to fit the shapes of the discharge pipe 73 and the heating unit 75, making it easier to attach the filter cloth 1, the discharge pipe 73, and the heating unit 75.

[0035] In this embodiment, as shown in FIG. 3 , the heating section 75 has a shape in which the tip of the heating section 75 extends in a second direction intersecting the first direction in which the base of the heating section 75 extends. The base and tip are continuous at a curved portion 751. When attaching the filter cloth 1 to a head section 76 having a heating section 73 of this shape, the filter cloth 1 is raised toward the head section 76 so that the opening of the filter cloth 1 is aligned with the heating section 75. When performing this operation, the first cylindrical section 11 is configured to be more easily deformed than the second cylindrical section 16, making it easier to attach the filter cloth 1 to the head section 76 so that it encloses the heating section 75. Note that, although the heating section has a curved shape in this embodiment, the discharge pipe may also have a curved shape. In such a case, a curved bag-shaped filter cloth can also be used.

[0036] In this embodiment, as shown in FIG. 8, the filter cloth 1 has a first portion 15 that covers the base end of the discharge pipe 73 and a second portion 16 that covers the tip end of the discharge pipe. The first portion 15 is tubular and extends along the first direction. The second portion 16 is tubular and extends along the second direction, and has a bag-like shape with a closed tip. The tip end of the first portion 15 and the base end of the second portion 16 are connected. The filter cloth 1 has a shape that allows the filter cloth 1 to bend at a bending portion 14. The shape of the filter cloth can be changed to match the shape of the discharge pipe or other parts on the tank side, and may, for example, be a cylindrical shape that extends linearly as a whole.

[0037] The thickness of the first cylindrical portion 11 can be, for example, 10 to 50% of the thickness of the second cylindrical portion 12. The first cylindrical portion 11 can be suitably made of woven or knitted fabric to reduce its thickness. The second cylindrical portion 12 can be suitably made of nonwoven fabric to increase its thickness. By increasing the thickness of the second cylindrical portion 12, it becomes less likely to deform due to the pressure applied when sucking the diesel exhaust liquid, and the filter cloth 1 can be less likely to interfere with the discharge pipe 73 or the heating portion 75.

[0038] The second cylindrical portion 12 is made of a fabric having higher breathability than the first cylindrical portion 11. The filter cloth 1 can prevent the flow rate of the diesel exhaust liquid from being excessively reduced when it is sucked out of the discharge pipe 73. Also, the resistance when sucking into the discharge pipe 73 can be prevented from being excessively increased. The breathability of the second cylindrical portion 12 is, for example, 12 to 25 cm 3 / cm 2 The air permeability of the first cylindrical portion 11 can be set to, for example, 3 to 10 cm / sec. 3 / cm 2 / seconds.

[0039] The above air permeability is determined in accordance with JIS L 1096, Method A (Fragile method). There is a correlation between air permeability and water permeability in filter fabrics; the higher the air permeability, the higher the water permeability. Note that water permeability does not only refer to water, but also to the ability to pass aqueous solutions such as diesel exhaust fluid.

[0040] The first and second cylindrical portions and the base end of the filter cloth can be made of any material. In the filter cloth of this embodiment, the first and second cylindrical portions are both made of polypropylene fibers. The first and second cylindrical portions and the base end of the filter cloth can be made of known materials such as polyester, polypropylene, nylon, etc. Polypropylene has high resistance to diesel exhaust fluid and is therefore suitable for use when the temperature inside the tank is high. Polyester and nylon can be used when the temperature inside the tank is low.

[0041] The first cylindrical portion 11 is preferably shaped so that the lower end of the first cylindrical portion 11 is positioned higher than the maximum liquid level set in the tank 71. In this way, the diesel exhaust liquid can be filtered by the second cylindrical portion 12.

[0042] [Second embodiment] The filter cloth 1b of this embodiment differs from the filter cloth 1 of the first embodiment in the configuration of the base end of the filter cloth. As shown in FIG. 10, the base end of the filter cloth 1b is shaped so that the end of the first annular member 31b protrudes closer to the head than the end of the second annular member 32b before the filter cloth 1 is fitted into the step portion 724 and the head portion 76 is fixed. As shown in FIG. 10, the end of the first annular member 31b reaches a position higher than the second edge portion 725 of the tank 71. The amount by which the first annular member 31b protrudes from the second end portion 725 of the tank is not particularly limited, but can be approximately 5 to 15 mm. The base end of the filter cloth 1b has a portion 17b protruding radially outward from the opening 72 of the tank 71. To fix the filter cloth 1b to the tank 71, the portion 17b protruding radially outward at the base end of the filter cloth 1b is placed on a step 724 formed by the edge 721 and wall 722 of the opening 72 of the tank 71.

[0043] The filter fabric 1b has a flexible first annular member 31b disposed radially outward, and a shape-retaining second annular member 32b disposed inside the first annular member 31b. When the head 76 is fixed to the tank 71, the first annular member 31b is pressed and compressed by the head 76, increasing the width of the first annular member 31b radially outward. Because the shape-retaining second annular member 32b is disposed inside the first annular member 31b, the first annular member 31b is compressed to expand primarily outward, and the compressed first annular member 31b and the filter fabric 1b are pressed against the wall portion 722. This fills the gap between the opening 72 of the tank 71 and the base end of the filter fabric 1b, suppressing rattle of the filter fabric 1b and ensuring that the filter fabric 1b is securely fixed to the opening of the tank 71.

[0044] The flexible first annular member 31b fills the gap between the wall portion 722 and the filter cloth 1b, which allows for looser dimensional control of the tank and the base end of the filter cloth incorporating the first annular member 31b and the second annular member 32b, thereby improving the yield of the filter cloth during manufacturing.

[0045] The first annular member 31b and the second annular member 32b may be made of the same materials as those in the above embodiment. The second annular member 32b may be made of a material that is less prone to elastic deformation, as shown in FIG.

[0046] [Third embodiment] The filter cloth 1c of this embodiment differs from the filter cloth 1 of the above embodiment in the configuration of the base end of the filter cloth. As shown in Fig. 13, in the filter cloth 1c, the end of the first annular member 31c is shaped to protrude toward the head 76 more than the end of the second annular member 32c before the filter cloth 1c is fitted into the step portion 724 and the head 76 is fixed. As shown in Fig. 13, the end of the first annular member 31c reaches a position higher than the second edge 725 of the tank 71.

[0047] The base end of the filter fabric 1c has a portion 17c that protrudes radially outward from the opening 72 of the tank 71. To fix the filter fabric 1c to the tank 71, the portion 17c that protrudes radially outward at the base end of the filter fabric 1c is placed on a step 724 formed by an edge 721 and a wall 722 of the opening 72 of the tank 71.

[0048] The filter fabric 1c has a flexible first annular member 31c disposed radially inside, and a shape-retaining second annular member 32c positioned outside the first annular member 31c. When the head 76 is fixed to the tank 71, the first annular member 31c is pressed and compressed by the head 76, increasing the width of the first annular member 31c in the radial direction of the opening. Because the shape-retaining second annular member 32c is disposed outside the first annular member 31c, the compressed first annular member 31c presses the second annular member 32c and the filter fabric 1c against the wall portion 722. This fills the gap between the opening 72 of the tank 71 and the base end of the filter fabric 1b, suppressing rattle of the filter fabric 1b and ensuring that the filter fabric 1b is securely fixed to the opening 72 of the tank 71.

[0049] In the filter cloth 1c of this embodiment, the flexible first annular member 31c also fills the gap between the wall portion 722 and the filter cloth 1c, so that the dimensional control of the base end of the filter cloth incorporating the first annular member 31c and the second annular member 32c and the tank can be relaxed, thereby improving the yield of the filter cloth during manufacturing.

[0050] The first annular member 31c and the second annular member 32c can be made of the same materials as those in the above embodiment. [Explanation of symbols]

[0051] 71 Tank 73 Discharge pipe 75 Heating section 76 Head 72 Opening 721 Edge 722 Wall 1 filter cloth 1b Filter cloth 1c filter cloth 11 First cylindrical portion 12 Second cylindrical portion 31 First annular member 31b First annular member 31c First annular member 32 Second annular member 32b Second annular member 32c Second annular member 17 Protruding Parts 17b Protruding part 17c Protruding part

Claims

1. A liquid storage tank including a tank for storing a liquid, a liquid discharge pipe, a head portion for fixing the discharge pipe, and a cylindrical filter cloth arranged to cover the discharge pipe, the filter cloth having an opening at a base end and a closed tip end, The filter cloth has a first annular member having flexibility and a second annular member having shape retention at a base end thereof, one of the first annular member and the second annular member has a shape that is contained within the other of the first annular member and the second annular member, The tank has an opening, an edge surrounding the opening, and a wall extending from the edge; A bag-shaped fabric containing the first annular member and the second annular member is sewn to the filter cloth to form a base end of the filter cloth, the first annular member having flexibility is disposed on the radially outer side, and the second annular member having shape retention is disposed on the inner side of the first annular member; The base end of the filter cloth is maintained in a shape protruding radially outward from the opening by the second annular member having shape retention, The portion of the filter cloth protruding outward in the radial direction is fitted into a step formed by the edge portion and the wall portion, The end of the first annular member is shaped to protrude closer to the head than the end of the second annular member before the filter cloth is fitted into the step portion and the head is fixed to the tank. Liquid storage tank.

2. The liquid storage tank according to claim 1 , wherein the first annular member fills a gap between a base end of the filter cloth and the wall portion.

3. 3. The liquid storage tank according to claim 1, wherein the first annular member is crushed by the head when the head is fixed to the tank, thereby increasing the thickness of the opening in the radial direction.

4. The liquid storage tank according to claim 1 or 2, wherein the second annular member is capable of switching between a first outer diameter and a second outer diameter by elastic deformation.

5. A filter cloth for a tank that stores liquid. The filter cloth has an opening at its base end that is large enough to accommodate the liquid discharge pipe, which is a member on the tank side, and is cylindrical with a closed tip end, The filter cloth has a first annular member having flexibility and a second annular member having shape retention at a base end thereof, one of the first annular member and the second annular member has a shape that is contained within the other of the first annular member and the second annular member, A bag-shaped fabric containing the first annular member and the second annular member is sewn to the filter cloth to form a base end of the filter cloth, the first annular member having flexibility is disposed on the radially outer side, and the second annular member having shape retention is disposed on the inner side of the first annular member; The base end of the filter cloth is maintained in a shape protruding radially outward from the opening by the second annular member having shape retention, The tank has an opening, an edge portion surrounding the opening, and a wall portion rising from the edge portion, and a portion of the filter cloth protruding radially outward is fitted into a step formed by the edge portion and the wall portion, A filter cloth for a liquid storage tank, in which the end of the first annular member is shaped to protrude closer to the head than the end of the second annular member before the filter cloth is fitted into the step portion and the head is fixed to the tank.

6. 6. The filter cloth for a liquid storage tank according to claim 5, wherein the length of the first annular member in the extension direction of the filter cloth is longer than the length of the second annular member in the extension direction of the filter cloth.

7. 7. The filter fabric for a liquid storage tank according to claim 5, wherein the second annular member is capable of switching between a first outer diameter and a second outer diameter by elastic deformation.

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