Strainer cover, suction strainer, and tank device

Abstract

To provide a strainer cover, a suction strainer and a tank device where bubbles are hardly suctioned in a hydraulic pump.SOLUTION: A strainer cover is disposed so as to surround a suction strainer at the inside of a tank storing a liquid. An inflow part becoming the flow passage of the liquid is disposed in the vicinity of the bottom surface of the tank.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a strainer cover, a suction strainer, and a tank device.

Background Art

[0002] Patent Document 1 discloses a suction strainer in which an air vent hole is formed in an upper plate that covers the entire upper surface of a substantially cylindrical filtering portion formed by bending a thin plate into a pleated shape.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, when the suction strainer is installed inside the tank, if air (initial air) inside the suction strainer or bubbles sucked into the suction strainer together with the hydraulic oil grow and accumulate on the lower side of the upper plate, this accumulated air can be discharged from the inside of the suction strainer to the tank. However, in the invention described in Patent Document 1, there is a risk that small bubbles sucked into the suction strainer together with the hydraulic oil are not discharged from the air vent hole but are sucked by the hydraulic pump.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide a strainer cover, a suction strainer, and a tank device in which it is difficult for bubbles to be sucked by a hydraulic pump.

Means for Solving the Problems

[0006] To solve the above problems, the strainer cover according to the present invention is, for example, a strainer cover provided inside a tank for storing liquid so as to surround a suction strainer, characterized in that an inlet portion which serves as a flow path for the liquid is provided near the bottom surface of the tank.

[0007] Furthermore, another embodiment of the present invention provides a tank device comprising, for example, a tank for storing hydraulic fluid, a suction strainer and a return filter provided inside the tank, and a strainer cover, wherein the height of the strainer cover is higher than the height of the hydraulic fluid level.

[0008] Furthermore, a suction strainer according to another aspect of the present invention is, for example, a suction strainer provided inside a tank for storing liquid, comprising a cylindrical filtration section and a plate provided in the filtration section, wherein the plate has a plate-like portion that covers the upper end surface of the filtration section and a cylindrical outer cylinder that surrounds the side surface of the filtration section, and the upper end of the outer cylinder is provided in the plate-like portion.

[0009] Furthermore, another embodiment of the present invention provides a tank device comprising, for example, a tank for storing hydraulic fluid, a return filter provided inside the tank, and a suction strainer, wherein the filtration section and the outer cylinder are provided so that their central axes are aligned vertically, and the height of the lower end of the outer cylinder is lower than the height of the lower end of the filtration section.

[0010] In any of the above embodiments of the present invention, the strainer cover surrounds the suction strainer or the outer cylinder surrounds the filtration section, so that the strainer cover or outer cylinder blocks air bubbles and makes it difficult for air bubbles to be drawn into the hydraulic pump.

[0011] The strainer cover may be cylindrical and surround the entire side surface of the suction strainer. Furthermore, the length of the outer cylinder along its centerline may be longer than the length along the central axis of the filtration section. This makes it more difficult for air bubbles to enter the strainer cover or the outer cylinder, effectively preventing air bubbles from being drawn into the hydraulic pump.

[0012] The inlet has one or more openings, and at least one of the openings may be composed of multiple micropores. Furthermore, the opening is a hole located adjacent to the bottom surface of the tank, and a mesh member may be provided in the hole. This effectively prevents bubbles from entering from the inlet.

[0013] The strainer cover may be provided with a float located inside, and the float may be configured to float on the hydraulic fluid. This suppresses the generation of bubbles caused by foaming of the oil surface inside the strainer cover.

[0014] A partition plate may be provided between the return filter and the strainer cover. Alternatively, a partition plate may be provided between the return filter and the suction strainer. This prevents the hydraulic fluid flowing out of the return filter from directly entering the inside of the strainer cover or outer cylinder, making it less likely for air bubbles to be drawn into the strainer, i.e., the hydraulic pump.

[0015] The height of the hole may be lower than the lower position of the suction strainer. This prevents the suction strainer from directly sucking in the hydraulic fluid that has flowed into the inside of the strainer cover, thereby suppressing the suction of air bubbles into the suction strainer.

[0016] The side of the tank may constitute a part of the side of the strainer cover. This allows the tank device to have a simple shape.

[0017] The outer cylinder may have holes in positions that do not overlap with the filtration section. This allows the hydraulic fluid to flow easily into the inside of the outer cylinder. It also prevents the hydraulic fluid (including air bubbles) that flows in through the holes from being directly sucked into the filtration section.

[0018] There may be a gap between the lower end of the outer cylinder and the bottom surface of the tank, and this gap may be an inflow portion for allowing the liquid to flow into the interior of the outer cylinder. Thereby, the inflow portion can be arranged at a position lower than the lower end of the filtration portion. Therefore, even if air bubbles flow into the interior of the outer cylinder from the inflow portion, the filtration portion is prevented from directly sucking in the air bubbles.

Effect of the Invention

[0019] According to the present invention, it is difficult for air bubbles to be sucked into the hydraulic pump.

Brief Description of the Drawings

[0020] [Figure 1] It is a view showing an outline of the strainer cover 1 and the tank device 2, and is a cross-sectional view of the strainer cover 1 and the tank device 2 as seen from the front. [Figure 2] It is a cross-sectional view taken along the line A-A of FIG. 1. [Figure 3] It is a plan view showing an outline of the strainer cover 1 and the tank device 2. [Figure 4] It is a perspective view showing an outline of the strainer cover 1. [Figure 5] It is a view showing an outline of the strainer cover 1, where (A) is a front view, (B) is a side view, and (C) is a plan view. [Figure 6] It is a view showing an outline of the strainer cover 1A according to a modified example, where (A) is a front view and (B) is a side view. [Figure 7] It is a cross-sectional view showing an outline of the tank device 2A having a float 26. [Figure 8] It is a view showing an outline of the strainer cover 1B and the tank device 2B, where (A) is a cross-sectional view as seen from the front, (B) is a cross-sectional view taken along the line B-B of (A), and (C) is a plan view. [Figure 9] It is a view showing an outline of the strainer cover 1C and the tank device 2C, where (A) is a cross-sectional view as seen from the front, (B) is a cross-sectional view taken along the line C-C of (A), and (C) is a plan view. [Figure 10]This diagram shows a schematic representation of the strainer cover 1D and the tank device 2D, where (A) is a cross-sectional view from the front, (B) is a cross-sectional view of (A) DD, and (C) is a plan view. [Figure 11] (A) to (D) are plan views showing schematics of strainer covers 1E to 1H related to modified examples. [Figure 12] This diagram shows a schematic of the suction strainer 20A and tank device 2E, where (A) is a cross-sectional view from the front, (B) is a cross-sectional view of (A) at EE, and (C) is a plan view. [Figure 13] This diagram shows a schematic representation of the suction strainer 20A, where (A) is a side view, (B) is a front view, and (C) is a perspective view of the main part as seen from the +z direction. [Figure 14] This figure shows a schematic of the modified suction strainer 20B, where (A) is a side view, (B) is a front view, and (C) is a perspective view of the main part as seen from the +z direction. [Figure 15] This diagram shows a schematic representation of the strainer cover 1I and the tank device 2F, where (A) is a cross-sectional view from the front, (B) is an FF cross-sectional view of (A), and (C) is a plan view. [Figure 16] This is a perspective view (perspective view of the main part) showing a schematic of the modified tank device 2G. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described in detail below with reference to the drawings. <First Embodiment> Figure 1 is a schematic diagram of a strainer cover 1 and tank device 2, which is one embodiment of the present invention, and is a cross-sectional view of the strainer cover 1 and tank device 2 viewed from the front. Figure 2 is a cross-sectional view AA of Figure 1. Figure 3 is a schematic plan view (viewed from above in the vertical direction) of the strainer cover 1 and tank device 2. The strainer cover 1 is installed inside the tank device 2. In Figures 1 and 2, some hatching indicating the cross-section has been omitted.

[0022] Hereinafter, the vertical direction will be defined as the z direction, and the horizontal direction will be defined as the x and y directions. In this embodiment, the tank device 2 is mounted on a surface aligned with the horizontal direction, but the tank device 2 may also be mounted on a surface inclined with respect to the horizontal direction.

[0023] The tank device 2 mainly comprises a strainer cover 1, a tank 10, a suction strainer 20, and a return filter 30. The tank 10 is installed in a working machine (e.g., a hydraulic system) not shown, and is located within the hydraulic circuit that supplies hydraulic fluid to the hydraulic system, storing the hydraulic fluid. In the hydraulic circuit, the hydraulic fluid is introduced into the tank 10 through the hydraulic system. The tank 10 is hollow inside and is equipped with a suction strainer 20, a return filter 30, etc.

[0024] An inlet (not shown) is provided on the side of the tank 10. The hydraulic fluid flowing in through the inlet is guided to the return filter 30. The hydraulic fluid is filtered by the return filter 30 and stored in the tank 10.

[0025] A lid 11 is provided to cover the opening at the top of the tank 10. The lid 11 has an opening 11a which is used for maintenance of the return filter 30, etc. A cover body 12 is attached to the opening 11a. The cover body 12 is provided on the lid 11.

[0026] A mounting member 13 is provided near the lower end of the tank 10 (in this embodiment, near the bottom surface 10a of the side of the tank 10). The hollow portion of the mounting member 13 forms an outlet 13a that allows the hydraulic fluid inside the tank 10 to flow out to a hydraulic pump (not shown). A pipe (not shown) is provided on the mounting member 13 that connects from the outside of the tank 10 to the suction port of the hydraulic pump.

[0027] Furthermore, a suction pipe 14 is provided on the mounting member 13 from the inside of the tank 10. A suction strainer 20 is provided at the upper end of the suction pipe 14 (inside the tank 10) to prevent foreign matter from entering the suction pipe 14. The hydraulic fluid stored in the tank 10 is sucked into a hydraulic pump (not shown), flows out through the suction strainer 20 into the suction pipe 14, and is supplied back to the hydraulic system.

[0028] Note that the outlet 13a is not limited to the position shown in Figures 1 and 2, as long as it is near the lower end of the tank 10. For example, the outlet 13a may be formed on the bottom surface 10a of the tank 10.

[0029] A partition plate 15 is provided in the tank 10. The partition plate 15 is located between the return filter 30 and the strainer cover 1, dividing the space where the suction strainer 20 is located from the space where the return filter 30 is located. Note that the partition plate 15 is not mandatory.

[0030] The suction strainer 20 mainly comprises a strainer section 21 and a rod 22 connected to the strainer section 21.

[0031] The strainer section 21 is a cylindrical member. The strainer section 21 mainly consists of a filtration section 23 and plates 24 and 25.

[0032] The filtration section 23 is formed by folding a sheet-like thin plate, which has holes formed almost entirely over its surface, into a pleated shape, and then connecting both ends of the folded thin plate to roll it into a cylindrical shape. The filtration section is formed from a fine mesh of metal (e.g., stainless steel) with fine wires woven into a mesh, but filter paper made of synthetic resin or paper may also be used. The filtration section is for filtering hydraulic fluid.

[0033] The plate 24 is provided on the upper end surface of the filtration section 23. The plate 24 has a plate-like portion 24c that covers the upper end surface of the filtration section 23, and the plate-like portion 24c is provided with an air vent portion 24a that discharges air accumulated inside the strainer section 21 from the strainer section 21. The plate 24 also has a cylindrical portion 24b that surrounds the side surface of the filtration section 23. Note that the cylindrical portion 24b only needs to surround the area of ​​the side surface of the filtration section 23 that is adjacent to the upper end surface of the filtration section 23.

[0034] The plate 25 covers the lower end surface of the filtration section 23. A suction pipe 14 is provided on the plate 25.

[0035] The rod 22 is positioned to extend upward from the strainer section 21, with one end attached to the strainer section 21 and the other end attached to the lid 11. By removing the lid 11 from the tank 10 and pulling the upper end of the rod 22, the suction strainer 20 can be pulled out from the tank 10 for maintenance purposes.

[0036] The strainer cover 1 is cylindrical and is installed to surround the suction strainer 20. The strainer cover 1 is also installed on the bottom surface 10a of the tank 10. The position of the suction strainer 20 (position in the x, y, and z directions) is arbitrary.

[0037] The strainer cover 1 has an inlet 52 located near the bottom surface 10a of the tank 10. The inlet 52 is a passage for hydraulic fluid, guiding the hydraulic fluid into the interior of the strainer cover 1. The inlet 52 has a plurality of openings. In this embodiment, the openings are holes 52a, 52b, 52c, and 52d.

[0038] Figure 4 is a schematic perspective view of the strainer cover 1. Figure 5 is a schematic diagram of the strainer cover 1, where (A) is a front view, (B) is a side view, and (C) is a top view. In this embodiment, the strainer cover 1 has four sides 51a, 51b, 51c, and 51d. Holes 52a, 52b, 52c, and 52d are formed in the sides 51a, 51b, 51c, and 51d, respectively.

[0039] The positions and shapes of holes 52a, 52b, 52c, and 52d are not limited to those shown. Furthermore, holes 52a, 52b, 52c, and 52d are not mandatory; the inlet 52 only needs to have at least one of holes 52a, 52b, 52c, or 52d.

[0040] Returning to the explanation of Figures 1-3, the height of the inlet 52, i.e., the holes 52a, 52b, 52c, and 52d, is lower than the lower position of the suction strainer 20. Also, the holes 52a, 52b, 52c, and 52d are provided so as to be in contact with the bottom surface 10a of the tank 10. However, the holes 52a, 52b, 52c, and 52d only need to be provided in a position adjacent to the bottom surface 10a, and the inlet 52 may be provided a little distance (for example, a few mm) away from the bottom surface 10a.

[0041] The height of the strainer cover 1 is higher than the oil level S of the hydraulic fluid stored in the tank 10. Therefore, hydraulic fluid does not flow into the inside of the strainer cover 1 from anywhere other than the inlet 51. Also, even if the hydraulic fluid foams up due to fluctuations in the oil level S, these bubbles do not flow into the inside of the strainer cover 1.

[0042] The partition plate 15 is provided adjacent to the strainer cover 1. The height of the partition plate 15 is lower than the height of the strainer cover 1 and also lower than the height of the oil level S. Furthermore, the height of the partition plate 15 is higher than the height of the outlet section 31, which is the outlet for the hydraulic fluid from the return filter 30. The partition plate 15 and the bottom surface 10a may be in contact, or a gap may be formed between the partition plate 15 and the bottom surface 10a.

[0043] Next, the functions of the strainer cover 1 and tank device 2 configured in this way will be explained.

[0044] The hydraulic fluid that flows into the tank device 2 is filtered by the return filter 30 and flows out from the outlet 31, where it is stored inside the tank 10. The hydraulic fluid flowing out from the outlet 31 contains air bubbles. Because a partition plate 15 is provided, the hydraulic fluid does not flow directly toward the strainer cover 1, and an upward flow is formed. Therefore, the air bubbles contained in the hydraulic fluid also flow upward and accumulate near the oil level S.

[0045] When the hydraulic fluid stored in tank 10 is drawn into a hydraulic pump (not shown), it flows into the inside of strainer cover 1 from the inlet 52, is filtered by suction strainer 20, and flows out from suction pipe 14.

[0046] Since the height of the strainer cover 1 is higher than the oil level S, air bubbles that accumulate near the oil level S do not flow into the interior of the strainer cover 1. In addition, the flow of hydraulic fluid is blocked by the partition plate 15, so it does not flow directly toward the strainer cover 1, preventing air bubbles from flowing into the interior of the strainer cover 1.

[0047] Since the height of the inlet 52 is lower than the lower position of the suction strainer 20, even if air bubbles flow into the inside of the strainer cover 1 from the inlet 52, the suction strainer 20 is prevented from directly sucking in the air bubbles.

[0048] Furthermore, because the height of the inlet 52 is lower than the lower position of the suction strainer 20, the hydraulic fluid flows upward inside the strainer cover 1. Therefore, even if air bubbles enter the strainer cover 1 along with the hydraulic fluid, the air bubbles rise to the oil level S through the space between the suction strainer 20 and the strainer cover 1, preventing them from being sucked into the suction strainer 20.

[0049] According to this embodiment, by providing a strainer cover 1 so as to surround the entire side surface of the suction strainer 20, it is difficult for air bubbles to flow into the inside of the strainer cover 1, and as a result, it is difficult for air bubbles to be sucked into the hydraulic pump via the suction strainer 20. In particular, by making the strainer cover 1 higher than the oil level S, air bubbles near the oil level S are prevented from flowing in, thereby enhancing the effect of preventing air bubbles from being sucked into the hydraulic pump.

[0050] In this embodiment, the inlet 52 has multiple openings, but it may have only one opening. For example, the opening may be only hole 52a.

[0051] Furthermore, in this embodiment, the inlet 52 consists of openings (holes 52a, 52b, 52c, 52d), but the shape of the inlet is not limited to this. Figure 6 is a schematic diagram of a modified strainer cover 1A, where (A) is a front view and (B) is a side view. A mesh member 53 is provided in at least one of the openings, holes 52a, 52b, 52c, and 52d, in this case holes 52a, 52c, and 52d. The mesh member 53 is, for example, wire mesh. By providing the mesh member 53 in holes 52a, 52c, and 52d, the opening is composed of multiple micro-holes. As a result, air bubbles are blocked by the mesh member 53, and it is possible to more effectively prevent air bubbles from flowing into the inside of the strainer cover 1.

[0052] In the strainer cover 1A shown in Figure 6, the suction pipe 14 passes through the hole 52b furthest from the outlet 31, so a mesh member 53 is not provided in hole 52b. However, a mesh member 53 may be provided in hole 52b. Also, since air bubbles are less likely to flow into hole 52a adjacent to the partition plate 15, a mesh member 53 may not be provided in that hole.

[0053] Furthermore, in the strainer cover 1A, the inlet 52A is constructed with multiple micro-holes by providing a mesh member 53 in holes 52a, 52c, and 52d, but the configuration of the inlet with multiple micro-holes is not limited to this. For example, perforated metal, a resin mesh, etc., may be provided in holes 52a, 52b, 52c, and 52d. When perforated metal is provided in holes 52a, 52b, 52c, and 52d, the diameter of the holes in the perforated metal can be made small, for example, 1 mm or less, to construct the inlet with multiple micro-holes.

[0054] In this embodiment, a strainer cover 1 is provided to surround the suction strainer 20, but a float may be provided inside the strainer cover 1. Figure 7 is a schematic cross-sectional view of a tank device 2A having a float 26. Since the float 26 is configured to float on the hydraulic fluid, the float 26 floats on the oil surface S inside the strainer cover 1. Therefore, even if the oil surface S is disturbed by vibrations, etc., the generation of air bubbles inside the strainer cover 1 can be suppressed. In Figure 7, the shape of the strainer cover 1 and the shape of the float 26 are substantially the same in plan view, but the shape of the float is arbitrary; for example, it may be disc-shaped or rectangular.

[0055] Furthermore, the shape of the strainer cover 1 in plan view (the cross-sectional shape when cut by a plane along a direction substantially perpendicular to the longitudinal direction) is not limited to the illustrated form. For example, the shape of the strainer cover in plan view may be circular, elliptical, or rectangular. Also, slits or the like may be formed on the side surface of the strainer cover 1. In this case as well, it is included in the cylindrical shape of the present invention.

[0056] <Second Embodiment> In the first embodiment, the strainer cover 1 was configured in a cylindrical shape with four sides 51a, 51b, 51c, and 51d, but the side of the tank may constitute part of the side of the strainer cover.

[0057] A second embodiment of the present invention is a configuration in which the side surface of the tank constitutes one side surface of the strainer cover. The strainer cover 1B and tank device 2B according to the second embodiment will be described below. Parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0058] Figure 8 is a schematic diagram of the strainer cover 1B and tank device 2B according to the second embodiment, where (A) is a cross-sectional view from the front, (B) is a cross-sectional view of (A) BB, and (C) is a plan view. In Figure 8, hatching indicating cross-sections is omitted. The tank device 2B mainly comprises a strainer cover 1B, a tank 10, a suction strainer 20, and a return filter 30. The strainer cover 1B is cylindrical and is provided so as to surround the entire side surface of the suction strainer 20. The height of the strainer cover 1B is higher than the height of the oil level S of the hydraulic fluid stored in the tank 10.

[0059] The strainer cover 1B is provided on the bottom surface 10a and the front (-y side) side surface 10b of the tank 10. The strainer cover 1B has three sides 51e, 51f, and 51g, and the three sides 51e, 51f, and 51g are formed in a U-shape when viewed from above (from the +z direction). Sides 51e and 51f are attached to side surface 10b. Sides 51e, 51f, 51g and side surface 10b form a cylindrical shape for the strainer cover 1B.

[0060] Holes 52e, 52f, and 52g are formed on the sides 51e, 51f, and 51g, respectively. Holes 52e, 52f, and 52g are located adjacent to the bottom surface 10a of the tank 10. Holes 52e, 52f, and 52g are passages for the hydraulic fluid and are openings for the inlet 52B that guide the hydraulic fluid into the interior of the strainer cover 1B. The height of holes 52e, 52f, and 52g is lower than the lower position of the suction strainer 20.

[0061] In this embodiment, since a strainer cover 1B is provided, bubbles generated from the outlet 31 and bubbles generated by fluctuations in the oil level S are less likely to flow into the inside of the strainer cover 1B, and bubbles are less likely to be sucked into the hydraulic pump via the suction strainer 20.

[0062] Furthermore, in this embodiment, since the side surface 10b of the tank 10 constitutes a part of the side surface of the strainer cover 1B, the strainer cover 1B and the tank device 2B can be made into a simple shape.

[0063] In this case, one side 10b of the tank 10 constitutes one side of the strainer cover 1B, but multiple sides of the tank may constitute multiple sides of the strainer cover.

[0064] Figure 9 is a schematic diagram of a modified strainer cover 1C and tank device 2C, where (A) is a front cross-sectional view, (B) is a cross-sectional view of (A) at CC, and (C) is a plan view. In Figure 9, hatching indicating cross-sections is omitted. The tank device 2C mainly comprises a strainer cover 1C, a tank 10, a suction strainer 20, and a return filter 30. The strainer cover 1C is cylindrical and is provided to surround the suction strainer 20. The height of the strainer cover 1C is higher than the height of the hydraulic fluid level S stored in the tank 10.

[0065] The strainer cover 1C is provided on the bottom surface 10a of the tank 10, the front (-y side) side 10b, and the left (-x side) side 10c. The strainer cover 1C has two sides 51e and 51h, which are formed in an L-shape in plan view. Holes 52e and 52h, which serve as openings for the inlet, are provided on sides 51e and 51h. Side 51e is attached to side 10b, and side 51h is attached to side 10c. Sides 51e, 51h and sides 10b and 10c form a cylindrical shape for the strainer cover 1C. This allows the strainer cover 1C and the tank device 2C to have a simpler shape.

[0066] In this embodiment and its modifications, the inlet has multiple openings, but it may have only one opening. For example, the -z-side end faces of the strainer covers 1B and 1C may be separated from the bottom surface 10a, and the -z-side end faces of the strainer covers 1B and 1C may be used as the openings for the inlet sections 52B and 52C. In this case, there may be no holes as openings.

[0067] <Third Embodiment> In the first embodiment, the strainer cover 1 is configured in a cylindrical shape with four sides 51a, 51b, 51c, and 51d, and surrounds the entire side of the suction strainer 20, but the strainer cover does not have to be cylindrical.

[0068] A third embodiment of the present invention is a configuration in which a portion of the side surface of the tank is omitted. The strainer cover 1D and tank device 2D according to the third embodiment will be described below. Parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0069] Figure 10 is a schematic diagram of the strainer cover 1D and tank device 2D according to the third embodiment, where (A) is a cross-sectional view from the front, (B) is a DD cross-sectional view of (A), and (C) is a plan view. In Figure 10, hatching indicating cross-sections is omitted. The tank device 2D mainly comprises a strainer cover 1D, a tank 10, a suction strainer 20, and a return filter 30. The strainer cover 1D is provided so as to surround the suction strainer 20. The height of the strainer cover 1D is higher than the height of the oil level S of the hydraulic oil stored in the tank 10.

[0070] The strainer cover 1D is provided on the bottom surface 10a of the tank 10. The strainer cover 1D has three sides 51g, 51i, and 51j, and the three sides 51g, 51i, and 51j are formed in a U-shape when viewed from above.

[0071] According to this embodiment, since the strainer cover 1D surrounds the suction strainer 20, the inflow of air bubbles into the suction strainer 20 is prevented. Furthermore, since the opening surface of the strainer cover 1D (the surface other than the sides 51g, 51i, and 51j) is located furthest from the return filter 30, it is difficult for air bubbles to flow into the interior of the strainer cover 1D, and it is difficult for air bubbles to be drawn into the hydraulic pump via the suction strainer 20.

[0072] In this embodiment, the strainer cover 1D has openings 52g and 52j, but since hydraulic fluid can flow in from the opening surface of the strainer cover 1D, the openings are not essential.

[0073] Furthermore, in this embodiment, the strainer cover 1D had a U-shape in plan view, but the form of the strainer cover is not limited to this. Figures 11(A) to (D) are plan views showing schematics of strainer covers 1E to 1H according to modified examples.

[0074] Strainer cover 1E has sides 51g, 51h, 51j, 51k, and 51l. Sides 51k and 51l are located on the same plane, and strainer cover 1E is cut in a strip between 51k and 51l. Strainer cover 1F has sides 51g, 51j, 51h, and 51m. Strainer cover 1F is cut in a strip between side 51m and side 51h. Strainer cover 1G is substantially cylindrical, and a portion of side 51n is cut in a strip.

[0075] The strainer cover 1H has sides 51g and 51j, and the two sides 51g and 51j are formed in an L-shape in plan view. Gaps are formed between side 51j and side 10b (see Figure 9) and between side 51g and side 10c (see Figure 9). Even with these modified forms, the strainer covers 1E to 1H surround the suction strainer 20 and block air bubbles, making it difficult for air bubbles to be drawn into the hydraulic pump.

[0076] <Fourth Embodiment> In the first embodiment, a cylindrical strainer cover 1 is provided so as to surround the suction strainer 20, making it difficult for the suction strainer 20 to suck in air bubbles. However, the method for making it difficult for the strainer to suck in air bubbles is not limited to this.

[0077] A fourth embodiment of the present invention is a suction strainer having an outer cylinder. The suction strainer 20A and tank device 2E according to the fourth embodiment will be described below. Parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0078] Figure 12 is a schematic diagram of the suction strainer 20A and the tank device 2E, where (A) is a cross-sectional view from the front, (B) is an EE cross-sectional view of (A), and (C) is a plan view. In Figure 12, hatching indicating cross-sections is omitted. The tank device 2E mainly comprises a tank 10, a suction strainer 20A, and a return filter 30. The suction strainer 20A mainly comprises a strainer section 21A and a rod 22 connected to the strainer section 21A.

[0079] The strainer section 21A is a cylindrical member. The strainer section 21 mainly consists of a cylindrical filtration section 23 and plates 24A and 25.

[0080] The plate 24A is provided in the filtration section 23 and has a plate-shaped portion 24c that covers the upper end surface of the filtration section 23 and a cylindrical outer cylinder 24d that surrounds the side surface of the filtration section 23. The outer cylinder 24d is cylindrical and its upper end is provided on the plate-shaped portion 24c.

[0081] In this embodiment, the strainer section 21A, the filtration section 23, and the outer cylinder 24d are cylindrical in shape, but are not limited to a cylindrical shape; for example, they may be polygonal or elliptical. Furthermore, the cylindrical shape of the present invention also includes cases where a part of the outer cylinder 24d is separated by slits or the like.

[0082] The length of the outer cylinder 24d along its central axis ax is longer than the length of the filtration section 23 along its central axis ax. Inside the tank 10, the filtration section 23 and the outer cylinder 24d are positioned so that their central axis ax is aligned with the vertical direction (z direction). Therefore, the height of the lower end of the outer cylinder 24d is lower than the height of the lower end of the filtration section 23, and the lower end of the outer cylinder 24d is closer to the bottom surface 10a than the lower end of the filtration section 23.

[0083] In Figure 12, the flow of hydraulic fluid is indicated by arrows. There is a gap between the lower end of the outer cylinder 24d and the bottom surface 10a of the tank 10, and this gap is the inlet through which hydraulic fluid flows into the interior of the outer cylinder 24d. From the viewpoint of preventing the inflow of air bubbles, it is desirable that the lower end of the outer cylinder 24d be as close as possible to the bottom surface 10a.

[0084] Figure 13 is a schematic diagram of the suction strainer 20A, where (A) is a side view, (B) is a front view, and (C) is a perspective view of the main part as seen from the +z direction. A gap G through which hydraulic fluid flows is formed between the outer flow surface of the filter section 23 and the inner circumferential surface of the outer cylinder 24d. If the outer flow surface of the filter section 23 and the inner circumferential surface of the outer cylinder 24d come into contact, or if the distance between the outer flow surface of the filter section 23 and the inner circumferential surface of the outer cylinder 24d is too small, hydraulic fluid will not flow into the filter section 23. Therefore, it is desirable to set the distance d between the outer flow surface of the filter section 23 and the inner circumferential surface of the outer cylinder 24d to 1 mm to 2 mm or more. The optimal size of the gap G (distance d) varies depending on the negative pressure of the hydraulic pump, the size of the filter section 23, the passage resistance of the filter section 23, the viscosity of the oil, etc.

[0085] The outer cylinder 24d is provided with holes 24e to avoid obstacles such as the suction pipe 14. The holes 24e are notches formed along the lower end of the outer cylinder 24d. However, the holes 24e are not essential.

[0086] Returning to the explanation of Figure 12, the hydraulic fluid that flows into the tank device 2E is filtered by the return filter 30, as indicated by the arrow, and flows out from the outlet 31, where it is stored inside the tank 10. When the hydraulic fluid stored in the tank 10 is drawn into the hydraulic pump (not shown), it flows into the inside of the outer cylinder 24d from the inlet 52, is filtered by the suction strainer 20A, and flows out from the suction pipe 14.

[0087] Since a partition plate 15 is provided between the return filter 30 and the suction strainer 20A, the hydraulic fluid containing air bubbles flowing out from the outlet 31 does not flow directly toward the suction strainer 20A, thus preventing air bubbles from entering the inside of the outer cylinder 24d.

[0088] Furthermore, the partition plate 15 creates an upward flow of the hydraulic fluid. Consequently, air bubbles contained in the hydraulic fluid also flow upward and accumulate near the oil level S. By covering the upper end of the suction strainer 20A with the plate-shaped portion 24c, and by making the space between the lower end of the outer cylinder 24d and the bottom surface 10a an inlet, the air bubbles accumulated near the oil level S do not flow into the interior of the suction strainer 20A.

[0089] Since the inlet is located lower than the lower end of the filtration section 23, even if air bubbles were to flow into the suction strainer 20A from the inlet, the filtration section 23 would be prevented from directly sucking in the air bubbles.

[0090] According to this embodiment, by providing an outer cylinder 24d that surrounds the entire side surface of the filtration section 23, it is difficult for air bubbles to flow into the inside of the outer cylinder 24d, and as a result, it is difficult for air bubbles to be sucked into the hydraulic pump via the suction strainer 20A.

[0091] In this embodiment, the inlet (lower end of the outer cylinder 24d) is adjacent to the bottom surface 10a, but the position of the lower end of the outer cylinder 24d is not limited to this. In this embodiment, since a partition plate 15 is provided between the return filter 30 and the suction strainer 20A, the outer cylinder 24d may be shorter than the configuration shown in Figure 13, and by making the lower end of the outer cylinder 24d (height of the inlet) lower than the lower end of the filtration section 23, it is possible to prevent air bubbles from flowing into the inside of the outer cylinder 24d.

[0092] Furthermore, in this embodiment, an air vent 24a is provided on the plate-shaped portion 24c, but other air vents besides the air vent 24a may be provided on the plate 24A. For example, an air vent 24a for discharging air accumulated inside the filtration portion 23 and an air vent 24h (see dotted line in Figure 13) for discharging air accumulated between the filtration portion 23 and the outer cylinder 24d may be provided on the plate. These air vents 24a and 24h may be various types of valves, such as check valves that push up valve bodies such as floats with air pressure, or they may be simple holes.

[0093] Furthermore, in this embodiment, the gap between the lower end of the outer cylinder 24d and the bottom surface 10a of the tank 10 served as an inlet for hydraulic fluid to flow into the interior of the outer cylinder 24d, but the form of the inlet is not limited to this. For example, the outer cylinder may have a hole.

[0094] Figure 14 is a schematic diagram of a modified suction strainer 20B, where (A) is a side view, (B) is a front view, and (C) is a perspective view of the main part as seen from the +z direction. The suction strainer 20B mainly comprises a strainer section 21B and a rod 22 connected to the strainer section 21B. The strainer section 21B mainly comprises a cylindrical (here, cylindrical) filtration section 23 and plates 24B and 25.

[0095] Plate 24B is provided in the filtration section 23 and has a plate-like portion 24c that covers the upper end surface of the filtration section 23 and a cylindrical outer cylinder 24g that surrounds the side surface of the filtration section 23. The difference between the outer cylinder 24d and the outer cylinder 24g is the presence or absence of holes.

[0096] The outer cylinder 24g has holes 24e and 24f in positions that do not overlap with the filtration section 23. The gap between the lower end of the outer cylinder 24g and the bottom surface 10a (see Figure 13, etc.) and the hole 24f are inlets for the hydraulic fluid to flow into the inside of the outer cylinder 24g. By providing the hole 24f, the hydraulic fluid can flow more easily into the inside of the outer cylinder 24g, and the gap between the lower end of the outer cylinder 24g and the bottom surface 10a can be narrowed. In addition, by providing the holes 24e and 24f in positions that do not overlap with the filtration section 23, the hydraulic fluid and air bubbles that flow in through the holes 24e and 24f are prevented from being directly sucked into the filtration section 23.

[0097] In this embodiment, the holes 24e and 24f are notches formed along the lower end of the outer cylinder 24g, but the position and shape of the holes 24e and 24f are not limited to this. For example, round holes, elliptical holes, or polygonal holes may be provided near the lower end of the outer cylinder 24g. Furthermore, the position of the holes provided in the outer cylinder 24g is not limited to the lower end, but can be any position that does not overlap with the filtration section 23. Moreover, the number of holes provided in the outer cylinder 24g is not limited to the illustrated configuration.

[0098] <Fifth Embodiment> In the first embodiment, the suction strainer 20 was positioned vertically (with its central axis aligned in the z-direction), but the arrangement of the suction strainer is not limited to this.

[0099] A fifth embodiment of the present invention is a configuration in which the suction strainer is placed horizontally. The strainer cover 1I and tank device 2F according to the fifth embodiment will be described below. Parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0100] Figure 15 is a schematic diagram of the strainer cover 1I and the tank device 2F, where (A) is a cross-sectional view from the front, (B) is an FF cross-sectional view of (A), and (C) is a plan view. In Figure 15, hatching indicating the cross-section is omitted. The tank device 2F mainly consists of the strainer cover 1I, the tank 10, the suction strainer 20C, and the return filter 30.

[0101] The strainer cover 1I is cylindrical and is installed to surround the suction strainer 20C. The height of the strainer cover 1I is higher than the height of the hydraulic fluid level S stored in the tank 10.

[0102] The strainer cover 1I is provided on the bottom surface 10a and the sides 10b and 10c of the tank 10. The strainer cover 1C has two sides 51o and 51p, which are formed in an L-shape in plan view. Holes 52o and 52p are provided in the sides 51o and 51p, which serve as openings for the inlet. By attaching side 51o to side 10b and side 51p to side 10c, the strainer cover 1I is formed in a cylindrical shape by sides 51o and 51p and sides 10b and 10c.

[0103] The suction strainer 20C mainly consists of a cylindrical filter section 23A and plates 24B and 25A. The filter section 23A differs from the filter section 23 only in size. Plate 24B is provided on the filter section 23A and the side surface 10c. Plate 25A covers one end of the filter section 23A.

[0104] According to this embodiment, since the strainer cover 1I surrounds the suction strainer 20C, the inflow of air bubbles into the suction strainer 20C is suppressed.

[0105] In Figure 15, the inlet (holes 52o, 52p) is positioned higher than the lower end of the filter section 23A, but 52o and 52p may be positioned lower than the lower end of the filter section 23A.

[0106] In the above embodiment, the tank 10 was a rectangular box shape, but the shape of the tank is not limited to a rectangular box. Similarly, the shape of the return filter is not limited to a rectangular box. For example, a tank device 2G having a tank 10A, a partition plate 15A, a suction strainer 20, and a return filter 30A, as shown in Figure 16, may be used. In the above embodiment, the strainer covers 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H and the outer cylinders 24d, 24g were made longer (higher) than the filtration section 23 to surround the entire filtration section 23. However, even if the strainer cover or outer cylinder surrounds only a part of the filtration section 23, the effect of blocking air bubbles can still be obtained. However, in order to prevent air bubbles from being drawn into the hydraulic pump, it is desirable to make the length (height) of the strainer cover or outer cylinder longer (higher) than the length (height) of the filtration section.

[0107] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are also included within the scope of the gist of this invention. For example, the above embodiments are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace some of the configurations of an embodiment with those of another embodiment, and it is also possible to add, delete, or replace other configurations in an embodiment.

[0108] Furthermore, in this invention, "approximately" is a concept that includes not only cases where the two are strictly identical, but also errors or modifications that do not result in a loss of identity. For example, "approximately orthogonal" is a concept that includes errors of, for example, a few degrees, and is not limited to cases where the two are strictly orthogonal. Also, for example, when simply using terms such as orthogonal, parallel, or coincident, it includes not only cases where the two are strictly orthogonal, parallel, or coincident, but also cases where they are approximately parallel, approximately orthogonal, or approximately coincident.

[0109] Furthermore, in this invention, "neighborhood" means a region that includes a certain range (which can be arbitrarily defined) near a reference position. For example, when we say "neighborhood of an edge," it refers to a region that is near an edge, and may or may not include the edge. [Explanation of symbols]

[0110] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I: Strainer cover 2, 2A, 2B, 2C, 2D, 2E, 2F, 2G: Tank equipment 10, 10A, 10B: Tanks 10a: Base 10b, 10c: Side 11: Lid 11a: Opening 12: Lid 13: Mounting components 13a: Outlet 14: Suction pipe 15: Partition plate 20, 20A, 20B, 20C: Suction Strainer 21: Strainer Department 21a: Plate 21b: Air vent 22: Rod 23, 23A: Filtration section 24, 24A, 24B: Plate 24a, 24h: Air vent section 24b: Cylindrical part 24c: Plate-like part 24d, 24g: Outer tube 24e, 24f: hole 25, 25A: Plate 26: Float 30: Return Filter 31: Outlet 51 :Inflow part 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h, 51i, 51j, 51k, 51l: Side 52, 52A, 52B, 52C: Inflow section 52a, 52b, 52c, 52d, 52e, 52f, 52g: Hole 53: Mesh member

Claims

1. A strainer cover is provided inside a tank for storing liquid, so as to surround the suction strainer, An inlet is provided near the bottom of the tank, which serves as a flow path for the liquid. The strainer cover is characterized in that its height is higher than the liquid level of the liquid.

2. The strainer cover according to claim 1, characterized in that the strainer cover is cylindrical and surrounds the entire side surface of the suction strainer.

3. The inlet has one or more openings, The strainer cover according to claim 1 or 2, characterized in that at least one of the openings is composed of a plurality of micropores.

4. The strainer cover according to claim 3, characterized in that the opening is a hole provided adjacent to the bottom surface of the tank, and a mesh member is provided in the hole.

5. A tank for storing hydraulic fluid, A suction strainer and a return filter are provided inside the tank, A strainer cover according to any one of claims 1 to 4, A tank device equipped with the following features.

6. The strainer cover is equipped with a float located inside it. The tank device according to claim 5, characterized in that the float is configured to float on the hydraulic fluid.

7. The tank apparatus according to claim 5 or 6, further characterized by comprising a partition plate provided between the return filter and the strainer cover.

8. The strainer cover according to claim 4, characterized in that the height of the hole is lower than the lower position of the suction strainer.

9. The strainer cover according to claim 8, characterized in that the side surface of the tank constitutes a part of the side surface of the strainer cover.

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