Suction strainer

Abstract

Air bubbles accumulated in this suction strainer provided along the horizontal direction with a filtration section can be discharged.　This suction strainer provided to a tank in which oil is stored is provided with: a cylindrical filtration section formed by folding a thin plate into a pleated shape; first and second end members for respectively covering both ends of the filtration section; and, a float provided to the first end member. The filtration section is provided along the horizontal direction. The first end member has: a plate-shaped first attachment section provided to a side surface of the tank; a second attachment section provided with the filtration section; a cylindrical section provided between the first attachment section and the second attachment section; and, a first hole for communicating a hollow section of the filtration section and the outside of the tank. The cylindrical section, the second attachment section, the filtration section, and the second end member are provided inside the tank. The cylindrical section is provided with an air vent hole that has one end open to the first hole and the other end open to the inside of the tank. The float is movably provided between a position for closing the air vent hole and a position for opening the air vent hole.

Description

Suction strainer

[0001] The present invention relates to a suction strainer.

[0002] Patent Document 1 discloses a suction filter in which a cover is provided on the upper end surface of a cylindrical first filtration section so as to cover the entire upper side of the first filtration section, and a valve is provided below the cover and in a hollow portion of the first filtration section. The valve has a first valve body movable along a rod-shaped member that can be switched between a closed state in which the hole in the cover is blocked and an open state in which the hole is not blocked.

[0003] Japanese Patent Application Laid-Open No. 2020-22924

[0004] However, the invention described in Patent Document 1 is applicable only when the axis of the cylindrical filtering section is aligned vertically and the cover is provided horizontally, and is not applicable when the cylindrical filtering section is provided horizontally.

[0005] The present invention has been made in consideration of these circumstances, and aims to provide a suction strainer that can discharge air bubbles that have accumulated inside when the filtration section is installed horizontally.

[0006] In order to solve the above problems, the suction strainer according to the present invention is a suction strainer provided in a tank for storing oil, for example, and includes a cylindrical filtering section formed by bending a thin plate into pleats, a first end member and a second end member covering both ends of the filtering section, respectively, and a float provided in the first end member, the filtering section being provided along a horizontal direction, and the first end member including a plate-shaped first mounting section provided on a side surface of the tank, a second mounting section on which the filtering section is provided, and a front The tank has a cylindrical portion provided between the first mounting portion and the second mounting portion, and a first hole connecting the hollow portion of the filtration portion with the outside of the tank, the cylindrical portion, the second mounting portion, the filtration portion, and the second end member are provided inside the tank, the cylindrical portion has an air vent hole whose one end opens to the first hole and whose other end opens to the inside of the tank, and the float is provided so as to be movable between a position that blocks the air vent hole and a position that opens the air vent hole.

[0007] According to the suction strainer of the present invention, a first end member covering one end of a cylindrical filtering section arranged along a horizontal direction has one end opening to a first hole connecting the hollow section of the filtering section to the outside of the tank and the other end opening to the inside of the tank. The first end member is provided with a float that is movable between a position that blocks the air vent hole and a position that opens the air vent hole. This allows air bubbles accumulated inside the suction strainer, whose filtering section is arranged along a horizontal direction, to be discharged. However, it is preferable that the air vent hole be provided at the vertical upper end of the cylindrical section.

[0008] The first end member may have a second hole connecting the hollow portion of the filtering portion to the air vent hole, thereby making it possible to efficiently discharge air bubbles that have accumulated in the hollow portion of the filtering portion.

[0009] The filtering section may have a cylindrical first filtering section and a cylindrical second filtering section provided inside the first filtering section, and the first end member may have a second hole connecting a hollow section of the second filtering section to the air vent hole, thereby enabling air bubbles accumulated in the hollow section of the second filtering section to be efficiently discharged.

[0010] The filtration section may have a cylindrical first filtration section and a cylindrical second filtration section provided inside the first filtration section, and the first end member may have a third hole connecting the space between the first filtration section and the second filtration section to the air vent hole. This allows air bubbles to accumulate between the first filtration section and the second filtration section and be discharged to the air vent hole via the third hole, thereby enabling the air bubbles to be efficiently discharged from the suction strainer.

[0011] The cylindrical portion may have an air vent hole at one end that does not open to the first hole and opens into the interior of the tank, and the first end member may have a fourth hole that connects the space between the first filtering portion and the second filtering portion to the air vent hole. This allows air bubbles to accumulate between the first filtering portion and the second filtering portion and be discharged to the air vent hole via the fourth hole, thereby efficiently discharging air bubbles from the suction strainer.

[0012] When the float blocks the air vent hole, the float and the upper end of the filtering section may be positioned at approximately the same height, or the float may be higher than the upper end of the filtering section, thereby allowing air accumulated inside to be effectively discharged to the outside of the suction strainer.

[0013] The first hole may have a through hole having a first end that is one end opening into an end of the first mounting part located on the tank side and a second end opposite the first end that opening into an end of the first mounting part on the filtration part side, and a recess provided vertically above the through hole, the through hole and the recess being integral, a third end that is one end of the recess opening into the air vent hole, and a fourth end opposite the third end that opening into an end of the first mounting part located outside the tank. This allows residual air accumulated in the recess to be discharged to the outside of the suction strainer through the air vent hole.

[0014] The recess may be bow-shaped, describing an arc that is convex vertically upward in a plane perpendicular to the central axis of the through hole, thereby narrowing the bottom surface (vertical upper end) of the recess, making it easier for residual air trapped in the recess to grow into large bubbles, and as a result, making it easier to release the residual air through the air vent hole.

[0015] According to the present invention, it is possible to discharge air bubbles that have accumulated inside a suction strainer in which a filtering portion is provided along a horizontal direction.

[0016] 1A is a diagram showing an outline of a hydraulic circuit 110 including a suction strainer 1 according to one embodiment of the present invention, and FIG. 1B is a diagram showing an outline of a tank 100 in which the suction strainer 1 is provided.

[0033] FIG. 1B is a diagram showing an outline of the suction strainer 1, where (A) is a perspective view and (B) is a cross-sectional view.

[0034] FIG. 1B is a diagram showing an outline of a plate 20 and a float 40, where (A) is a side view and (B) is a cross-sectional view taken along the line A-A of (A).

[0035] FIG. 1A and (B) are perspective views showing an outline of the plate 20 and the float 40.

[0036] FIG. 1B is a diagram showing an outline of the plate 20 and the float 40, where (A) is a front view, (B) is a left side view, (C) is a right side view, and (D) is a plan view.

[0037] FIG. 1C is a diagram showing an outline of the float 40.

[0038] FIG. 1D is a diagram showing an outline of the plate 20 and a float 40A according to a modified example. 1A and 1B are diagrams showing an outline of the suction strainer 2, where (A) is a front view, (B) is a cross-sectional view taken along line B-B of (A), and (C) is a plan view. 1B are diagrams showing an outline of the float 40B, where (A) is a plan view, and (B) is a cross-sectional view taken along line C-C of (A). 1C are cross-sectional views showing an outline of the suction strainer 3. 1C are diagrams showing an outline of the suction strainer 3, where (A) is a front view, (B) is a cross-sectional view taken along line D-D of (A), and (C) is a plan view. 1D are diagrams showing an outline of the suction strainer 4. 1D are cross-sectional views showing an outline of the suction strainer 5. 1D are diagrams showing an outline of the suction strainer 5, where (A) is a front view, and (B) is a plan view. 1E are cross-sectional views showing an outline of the suction strainer 6. 1E are diagrams showing an outline of the plate 20E, where (A) is a cross-sectional view, and (B) is a cross-sectional view taken along line E-E of (A).

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. <First embodiment> Fig. 1(A) is a diagram showing an outline of a hydraulic circuit 110 including a suction strainer 1 according to one embodiment of the present invention, and Fig. 1(B) is a diagram showing an outline of the suction strainer 1 and a tank 100. Hatching indicating a cross section is omitted in Fig. 1.

[0018] The tank 100 is installed in a work machine (for example, a hydraulic device) not shown, and is a tank for storing hydraulic oil provided in a hydraulic circuit 110 for supplying hydraulic oil to the hydraulic device. Note that the tank 100 is not limited to being installed in a hydraulic circuit, and the liquid stored in the tank 100 is not limited to hydraulic oil.

[0019] The tank 100 is, for example, box-shaped and hollow inside. Inside the tank 100, a suction strainer 1 and a return filter (not shown) are mainly provided.

[0020] In the hydraulic circuit 110, hydraulic oil is introduced into the tank 100 through a hydraulic device (not shown). The tank 100 is formed with an inlet (not shown) that allows the hydraulic oil to flow into the interior of the tank 100. The hydraulic oil that flows in from the inlet is guided to a return filter. The hydraulic oil is filtered by the return filter and stored in the tank 100.

[0021] An outlet 100c is formed near the lower end of the side surface 100b of the tank 100 (in this embodiment, at a position on the side surface of the tank 100 close to the bottom surface 100a) to allow the hydraulic oil in the tank 100 to flow out to a hydraulic pump (not shown). A suction strainer 1 is provided at the outlet 100c. The suction strainer 1 is cylindrical and is provided along the horizontal direction. Here, "along the horizontal direction" does not necessarily mean that the suction strainer is strictly along the horizontal direction, but also includes a case where the suction strainer is tilted by several degrees relative to the horizontal direction.

[0022] An elastic member 102 such as an O-ring is provided between the suction strainer 1 and the tank 100. Therefore, the hydraulic oil does not leak from between the suction strainer 1 and the tank 100.

[0023] The suction strainer 1 is provided with a suction pipe 101 that connects from the outside of the tank 100 to the suction port of a hydraulic pump 103. The hydraulic oil stored in the tank 100 is sucked into the hydraulic pump 103, flows out to the suction pipe 101 via the suction strainer 1, and is supplied again to the hydraulic device.

[0024] The outlet 100c and the suction strainer 1 only need to be provided on the side surface 100b of the tank 100, and the positions of the outlet 100c and the suction strainer 1 are not limited to the positions shown in FIG.

[0025] 2A and 2B are diagrams showing an outline of the suction strainer 1, with (A) being a perspective view and (B) being a cross-sectional view. Hereinafter, the extension direction of the suction strainer 1 (the extension direction of the central axis ax of the suction strainer 1) is defined as the x-direction, and the vertical direction is defined as the z-direction (vertically upward is the +z-direction). The direction perpendicular to the x-direction and z-direction is defined as the y-direction.

[0026] The suction strainer 1 mainly has a filtering section 10, a plate 20, F, and a float 40.

[0027] The filtration unit 10 mainly includes an inner tube 11 and a pleated filter medium 12. The inner tube 11 is a tubular (here, cylindrical) member with openings at both ends. The inner tube 11 is formed using a highly corrosion-resistant material (e.g., stainless steel). Holes through which hydraulic oil passes are formed over almost the entire inner tube 11. The diameter of the inner tube 11 is smaller than the diameter of the pleated filter medium 12, and the inner tube 11 is disposed inside the pleated filter medium 12.

[0028] The pleated filter medium 12 is a component for filtering hydraulic oil and is tubular (here, cylindrical). The height of the pleated filter medium 12 is approximately the same as the height of the inner cylinder 11. The pleated filter medium 12 is formed by pleating a sheet-like thin plate having holes formed over almost the entire area, connecting both ends of the pleated thin plate, and rolling it into a cylindrical shape. As a result, the pleated filter medium 12 is formed into an approximately cylindrical pleated shape. In this embodiment, the pleated filter medium 12 is formed from a metal (e.g., stainless steel) mesh with fine wires woven into a mesh, but filter paper made of synthetic resin, paper, etc. may also be used.

[0029] A plate 20 (corresponding to the first end member of the present invention) is provided at one end 10a of the filtration section 10 (the inner tube 11 and the pleated filter medium 12), and a plate 30 (corresponding to the second end member of the present invention) is provided at the other end 10b. The plates 20 and 30 are formed using a highly corrosion-resistant material (resin or metal). The plate 30 has a recess 30a into which the inner tube 11 and the pleated filter medium 12 are inserted, and when the recess 30a is provided in the filtration section 10, the plate 30 covers the end (opening) of the filtration section 10.

[0030] The plate 20 mainly has a plate-shaped mounting portion 21 provided on the tank 100 (see Figure 1), a mounting portion 22 to which the filtration portion 10 is attached, a cylindrical portion 23 provided between the mounting portions 21 and 22, a mounting pipe 24 to which the suction pipe 101 (see Figure 1) is attached, and a hole 25 (corresponding to the first hole of the present invention) that penetrates the mounting portion 21, the mounting portion 22, the cylindrical portion 23 and the mounting pipe 24.

[0031] The attachment pipe 24, attachment portion 21, tubular portion 23, and attachment portion 22 are aligned in this order along the x direction when the attachment portion 21 is installed in the tank 100. The hole 25 connects the hollow portion of the filtration section 10 with the outside of the tank 100 (here, the suction pipe 101). Note that, in the present embodiment, the hole 25 has a tapered shape in which the inner diameter becomes wider at each end, but the shape of the hole 25 is not limited to this. Also, in the present embodiment, the axis of the hole 25 coincides with the axis ax, but the axis of the hole 25 may be misaligned with the axis ax. Also, in the present embodiment, the hole 25 is aligned along the horizontal direction (here, the x direction) when the attachment portion 21 is installed in the tank 100, but may be inclined with respect to the horizontal direction.

[0032] The mounting portion 21 is plate-shaped and is provided on the outside of the tank 100. The cylindrical portion 23 and the mounting pipe 24 are provided on the mounting portion 21. When the mounting portion 21 is provided on the tank 100, the mounting portion 22 and the cylindrical portion 23 are disposed inside the tank 100, and the mounting pipe 24 is disposed outside the tank 100. The mounting portion 22 is plate-shaped and is provided to cover the end 10a. By providing the filtration portion 10 on the mounting portion 22, the filtration portion 10 is extended along the horizontal direction. The cylindrical portion 23 has a smaller diameter than the mounting portion 22.

[0033] Fig. 3 is a diagram showing an outline of the plate 20 and the float 40, where (A) is a side view and (B) is a cross-sectional view taken along line A-A of (A). Figs. 4(A) and (B) are perspective views showing an outline of the plate 20 and the float 40. Fig. 5 is a diagram showing an outline of the plate 20 and the float 40, where (A) is a front view, (B) is a left side view, (C) is a right side view, and (D) is a plan view. The front view and the rear view are symmetrical.

[0034] The mounting portion 21 has a recess 21a into which the elastic member 102 is inserted, and holes 21b into which bolts or the like are inserted to mount the mounting portion 21 to the tank 100. Note that the positions and sizes of the holes 21b are not limited to this. For example, to make it easier to distinguish between the up and down directions, the positions of the upper two holes 21b in the y direction may be different from the positions of the lower two holes 21b in the y direction. Furthermore, to make it easier to distinguish between the up and down directions, letters such as "UP" may be displayed on the surface of the mounting portion 21 by casting or the like.

[0035] The mounting portion 22 has a recess 22a into which the end 10a (see FIG. 2) is inserted. A hole 25 opens in the end face of the mounting portion 22. The hole 25 also opens into the mounting tube 24.

[0036] The plate 20 is provided with two protrusions 23a and two protrusions 23b adjacent to the outer peripheral surface of the cylindrical portion 23. In the present embodiment, portions of the protrusions 23a and 23b abut against the outer peripheral surface of the cylindrical portion 23, but portions of the protrusions 23a and 23b do not have to abut against the outer peripheral surface of the cylindrical portion 23. Whether portions of the protrusions 23a and 23b abut against the outer peripheral surface of the cylindrical portion 23 or not, the fact remains that the protrusions 23a and 23b are adjacent to the outer peripheral surface of the cylindrical portion 23.

[0037] The pair of protrusions 23a is provided on the mounting portion 21, and the pair of protrusions 23b is provided on the mounting portion 22. The protrusions 23a and 23b face each other. Since the protrusions 23a and 23b have the same shape, the following description of the protrusions 23a and 23b will be limited to the protrusion 23a.

[0038] The pair of protrusions 23a are provided opposite each other across the cylindrical portion 23. The two protrusions 23a are positioned at the same position in the z direction. The protrusions 23a are generally U-shaped or U-shaped and have a groove 23d therein. The groove 23d extends along the z direction, and its upper end is covered by the protrusions 23a. A protrusion 44 (described in detail later) of the float 40 is inserted into the groove 23d, and the float 40 moves in the z direction as the protrusion 44 moves along the groove 23d.

[0039] An air vent hole 23c is provided in the cylindrical portion 23. The axis of the cylindrical portion 23 is aligned horizontally, and the air vent hole 23c is provided at the vertical upper end of the cylindrical portion 23. One end of the air vent hole 23c opens to the hole 25, and the other end opens to the interior of the tank 100. Therefore, air accumulated near the upper end of the hole 25 can be discharged to the outside of the suction strainer 1 via the air vent hole 23c.

[0040] The protrusions 23a and 23b are provided with a float 40. The float 40 has a substantially U-shape when viewed along the axis ax (the axis of the cylindrical portion 23).

[0041] 6 is a diagram showing an outline of the float 40. The float 40 has a main body 41, legs 42, an insertion portion 43, and a protrusion 44. A rod-shaped insertion portion 43 is provided on the -z side surface of the main body 41. When the main body 41 covers the air vent hole 23c, the insertion portion 43 is inserted into the air vent hole 23c. Two legs 42 are provided on each end of the main body 41. A protrusion 44 is provided at the tip of each leg 42.

[0042] Returning to the explanation of Figures 3 to 5, protrusions 44 are provided on protrusions 23a and 23b and slide along groove 23d. As a result, as shown in Figure 3(B), float 40 can move in the vertical direction (z direction) between a position where main body 41 blocks air vent hole 23c (see dotted line in Figure 3(B)) and a position where air vent hole 23c is open (see solid line in Figure 3(B)).

[0043] Next, a description will be given of the function of the suction strainer 1 configured as above. As shown in Fig. 1, the suction strainer 1 is attached horizontally to a tank 100, and the tank 100 stores hydraulic oil.

[0044] Since a plate 20 is provided at end 10a of the filtration section 10 and a plate 30 is provided at end 10b, when the hydraulic oil stored in the tank 100 is sucked into the hydraulic pump (not shown), as shown by the solid arrow in Figure 1, it is sucked from the outside of the filtration section 10 through the pleated filter material 12 and inner tube 11 into the inside of the filtration section 10 and flows out into the suction pipe 101 through the hole 25.

[0045] Furthermore, as hydraulic oil is sucked by the hydraulic pump, the float 40 is pulled in the −z direction together with the hydraulic oil, causing the float 40 to abut against the cylindrical portion 23, and the main body portion 41 to block the air vent hole 23c. This prevents hydraulic oil from flowing into the suction strainer 1 from any source other than the filtering portion 10.

[0046] When hydraulic oil is sucked into the filter section 10, air bubbles contained in the hydraulic oil are also sucked into the filter section 10. The air bubbles solidify inside the filter section 10 and the holes 25 and grow into larger bubbles. The grown air bubbles push the float 40 upward in the +z direction, opening the air vent hole 23c. As a result, the air bubbles are discharged from the suction strainer 1 through the air vent hole 23c, as shown by the two-dot chain arrow in Figure 1.

[0047] According to this embodiment, when the suction strainer 1 is installed horizontally, air bubbles accumulated inside the suction strainer 1 can be discharged from the suction strainer 1 through the air vent hole 23c. As a result, it is possible to prevent problems caused by air bubbles accumulating in the suction pipe 101 and air being sucked into the pump. It is also possible to prevent damage to parts caused by temporary extreme increases in the temperature and pressure of the hydraulic oil due to air bubbles bursting in the hydraulic circuit.

[0048] Furthermore, according to this embodiment, since the float 40 is provided on the outside of the cylindrical portion 23, the flow of hydraulic oil through the hole 25 is not obstructed.

[0049] In this embodiment, the float 40 is generally U-shaped, but the shape of the float is not limited to this. Fig. 7 is a diagram showing an outline of the plate 20 and a float 40A according to a modified example. In Fig. 7, hatching indicating a cross section is omitted.

[0050] The float 40A is generally U-shaped and primarily comprises a plate-shaped main body 41A, legs 42A, an insertion portion 43, and a protrusion 44. A rod-shaped insertion portion 43 is provided on the -z side surface of the main body 41A. When the main body 41A covers the air vent hole 23c, the insertion portion 43 is inserted into the air vent hole 23c. Two legs 42A are provided on each end of the main body 41A. A protrusion 44 is provided at the tip of each leg 42A. The protrusions 44 are provided on the protrusions 23a and 23b and slide along the groove 23d. As a result, the float 40A can move in the z direction between a position where the main body 41A blocks the air vent hole 23c (see dotted line in FIG. 7 ) and a position where the air vent hole 23c is open (see solid line in FIG. 7 ).

[0051] <Second embodiment> In the first embodiment of the present invention, the diameter of the cylindrical portion 23 is smaller than the diameter of the mounting portion 22, and the float 40 is located lower than the upper end of the pleated filter medium 12, but the position of the float is not limited to this.

[0052] In the second embodiment of the present invention, the height of the upper end of the float and the height of the upper end of the pleated filter medium are approximately the same. The suction strainer 2 according to the second embodiment will be described below. Note that the same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0053] 8A and 8B are diagrams showing an outline of the suction strainer 2, with (A) being a front view (upper half shown in cross section), (B) being a cross-sectional view taken along line B-B of (A), and (C) being a plan view (only essential parts are shown). In (A) of FIG. 8, the upper half is shown in cross section. Also, hatching indicating cross sections is omitted in FIG. 8.

[0054] The suction strainer 2 mainly includes a filtering section 10, plates 20A and 30, and a float 40B.

[0055] Plate 20A (corresponding to the first end member of the present invention) mainly has an attachment portion 21, an attachment portion 22, a cylindrical portion 23A provided between attachment portions 21 and 22, an attachment tube 24, a hole 25, and a recess 26.

[0056] The cylindrical portion 23A has a cylindrical portion 23h whose diameter is smaller than that of the mounting portion 22, and a protrusion 23e that protrudes upward (in the +z direction) from the cylindrical portion 23h. An air vent hole 23f is provided in the cylindrical portion 23h and the protrusion 23e. The air vent hole 23f is provided at the vertical upper end of the cylindrical portion 23A, with one end opening to the hole 25 and the other end opening into the interior of the tank 100. Therefore, air accumulated near the upper end of the hole 25 can be discharged to the outside of the suction strainer 2 via the air vent hole 23f.

[0057] The hole 25 is also provided with a recess 26 that communicates with the hollow portion of the filtering section 10. The recess 26 makes it easier for air that has accumulated in the hollow portion of the filtering section 10 to be guided to the air vent hole 23f.

[0058] The plate 20A has a pair of protrusions 23g provided adjacent to the outer circumferential surface of the cylindrical portion 23h. A float 40B is provided on the protrusions 23g. The float 40B is generally U-shaped.

[0059] 9A and 9B are diagrams showing an outline of the float 40B, with (A) being a plan view and (B) being a cross-sectional view taken along the line CC of (A). The float 40B has a main body 41B, legs 42B, and an insertion portion 43B. The rod-shaped insertion portion 43B is provided on the -z side surface of the main body 41B. Two legs 42B are provided on each end of the main body 41B.

[0060] Returning to the explanation of Figure 8, the leg portion 42B is provided on the protrusion 23g, and the leg portion 42B is movable in the z direction along the protrusion 23g. As a result, the float 40B is movable in the vertical direction (z direction) between a position where the main body portion 41B blocks the air vent hole 23f and a position where the air vent hole 23f is open. When the main body portion 41B blocks the air vent hole 23f, the insertion portion 43B is inserted into the air vent hole 23f.

[0061] While hydraulic oil is being sucked by the hydraulic pump, the float 40B is pulled in the −z direction together with the hydraulic oil, and the float 40B comes into contact with the cylindrical portion 23A, causing the main body portion 41B to close the air vent hole 23f. This prevents hydraulic oil from flowing into the suction strainer 2 from any source other than the filtering portion 10.

[0062] When hydraulic oil is sucked into the filter section 10, air bubbles contained in the hydraulic oil are also sucked into the filter section 10 along with the hydraulic oil. The air bubbles solidify inside the filter section 10 and the holes 25 and grow into larger bubbles. The grown air bubbles push the float 40B up in the +z direction, opening the air vent hole 23f. As a result, the air bubbles are discharged to the outside of the suction strainer 2 through the air vent hole 23f.

[0063] According to this embodiment, when the suction strainer 2 is installed horizontally, air bubbles accumulated inside the suction strainer 2 can be discharged from the suction strainer 2 through the air vent hole 23f. In particular, when the float 40B blocks the air vent hole 23f, the upper ends of the float 40B and the filtration section 10 (pleated filter medium 12) are positioned at approximately the same height, so air accumulated inside the filtration section 10 and holes 25 can be effectively discharged to the outside of the suction strainer 2.

[0064] In the present embodiment, the float 40B is formed into a generally U-shape by extending the legs 42B in the z direction, but the shape of the float 40B is not limited to this. For example, the float may be plate-shaped (the legs 42B are not extended in the z direction).

[0065] In addition, in this embodiment, when the float 40B blocks the air vent hole 23f, the float 40B and the upper end of the pleated filter medium 12 are positioned at approximately the same height, but the float 40B may be higher than the upper end of the pleated filter medium 12. Even in this case, air accumulated inside the filtration section 10 and the holes 25 can be effectively discharged to the outside of the suction strainer 2.

[0066] <Third embodiment> In the first and second embodiments of the present invention, the floats 40, 40A, 40B are provided on the outside of the cylindrical portions 23, 23A, but the configuration of the floats is not limited to this. In the third embodiment of the present invention, the floats are inserted into the air vent holes. A suction strainer 3 according to the third embodiment will be described below. Note that the same parts as those in the first embodiment are designated by the same reference numerals, and description thereof will be omitted.

[0067] Figure 10 is a cross-sectional view showing an outline of the suction strainer 3. Figure 11 is a view showing an outline of the suction strainer 3, with (A) being a front view (upper half shown in cross section), (B) being a cross-sectional view taken along line D-D of (A), and (C) being a plan view (only essential parts shown). In Figure 11 (A), the upper half is shown in cross section. Furthermore, hatching indicating a cross section is omitted in Figure 11.

[0068] The suction strainer 3 mainly includes a filtering section 10, plates 20B and 30, and a float 40C.

[0069] Plate 20B (corresponding to the first end member of the present invention) mainly has an attachment portion 21, an attachment portion 22, a cylindrical portion 23B provided between attachment portions 21 and 22, an attachment tube 24, a hole 25, and a hole 27.

[0070] The cylindrical portion 23B has a cylindrical portion 23h whose diameter is smaller than that of the mounting portion 22, and a protrusion 23i that protrudes upward (in the +z direction) from the cylindrical portion 23h. An air vent hole 23j is provided in the cylindrical portion 23h and the protrusion 23i. The air vent hole 23j is provided at the vertical upper end of the cylindrical portion 23B, with one end opening to the hole 25 and the other end opening to the interior of the tank 100.

[0071] The plate 20B has a hole 27 (corresponding to a second hole of the present invention) extending parallel to the axis ax. The hole 27 connects the internal space of the filtration section 10 with the air vent hole 23j. This allows air bubbles that have accumulated near the upper end of the hollow section of the filtration section 10 to flow out through the hole 27 to the air vent hole 23j.

[0072] The cylindrical portion 23B is provided with a plate-like member 23o that covers the air vent hole 23j. The plate-like member 23o is provided with a hole 23p. In a plan view, the air vent hole 23j and the hole 23p overlap. Therefore, air that has accumulated near the upper end of the hole 25 can be discharged to the outside of the suction strainer 3 via the air vent hole 23j and the hole 23p (corresponding to the air vent hole of the present invention).

[0073] A float 40C is provided in the air vent hole 23j and hole 23p. The float 40C has a main body 41C and legs 42C. The legs 42C are provided on the -z side surface of the main body 41C. A claw 43C is provided at the tip of the leg 42C. The leg 42C and the claw 43C are inserted into the air vent hole 23j and hole 23p.

[0074] In plan view (as viewed from the z direction), the diameter of hole 23p is smaller than the diameter of air vent hole 23j, and the diameter of main body 41C is larger than the diameter of hole 23p. Also, in plan view, the distance between the outer sides of two legs 42C is smaller than the diameter of hole 23p, and the distance between two claws 43C is larger than the diameter of hole 23p. Because legs 42C are easily deformed, legs 42C are deformed to insert claws 43C into holes 23p, thereby attaching float 40C to plate-like member 23o, and plate-like member 23o and float 40C are attached to protrusion 23i.

[0075] As the legs 42C and the claws 43C move in the z direction along the air vent hole 23j, the float 40C can move in the z direction between a position where the main body 41C blocks the hole 23p and the air vent hole 23j and a position where the hole 23p and the air vent hole 23j are open.

[0076] While hydraulic oil is being sucked by the hydraulic pump, the float 40C is pulled in the −z direction together with the hydraulic oil, and the float 40C blocks the hole 23p and the air vent hole 23j. This prevents hydraulic oil from flowing into the suction strainer 3 from any place other than the filtering section 10.

[0077] Air bubbles sucked into the filter section 10 together with the hydraulic oil solidify inside the filter section 10 and hole 25, growing into larger bubbles that then flow into the air vent hole 23j. Air bubbles that grow near the upper end of the hollow section of the filter section 10 flow into the air vent hole 23j via hole 27. The air bubbles that accumulate inside the air vent hole 23j push the float 40C up in the +z direction, opening hole 23p and air vent hole 23j. As a result, the air bubbles are discharged to the outside of the suction strainer 3 through the air vent hole 23j and hole 23p.

[0078] According to this embodiment, when the suction strainer 3 is installed horizontally, air bubbles accumulated inside the suction strainer 3 can be discharged from the suction strainer 3 through the holes 23p and the air vent holes 23j. Furthermore, by providing the holes 27, air bubbles accumulated near the upper end of the hollow part of the filtering section 10 can be discharged from the holes 27 to the air vent holes 23j, thereby efficiently discharging the air bubbles from the suction strainer 3. Furthermore, when the float 40C blocks the holes 23p and the air vent holes 23j, the float 40C is higher than the upper end of the filtering section 10, so that air can be effectively discharged to the outside of the suction strainer 3.

[0079] In this embodiment, the holes 27 are circular holes provided along the x direction (parallel to the axis ax), but the shape and position of the holes 27 are not limited to this. For example, the holes 27 may be inclined with respect to the x direction.

[0080] <Fourth embodiment> In the first and second embodiments of the present invention, the filtration section 10 has one pleated filter medium 12, but the number of pleated filter mediums is not limited to this. In the fourth embodiment of the present invention, the filtration section has a plurality of pleated filter mediums. Below, a suction strainer 4 according to the third embodiment will be described. Note that the same parts as those in the first embodiment are given the same reference numerals, and description thereof will be omitted.

[0081] Fig. 12 is a front view showing a schematic of the suction strainer 4. In Fig. 12, the upper half is shown in cross section, and hatching indicating the cross section is omitted. The suction strainer 4 mainly has a filtering section 10A, plates 20C and 30A, and a float 40B.

[0082] The filtration section 10A mainly includes inner cylinders 11 and 13 and pleated filter media 12 and 14. The pleated filter media 14 (corresponding to the second filtration section of the present invention) is formed by pleating a sheet-like thin plate with holes formed over almost the entire area, connecting both ends of the pleated thin plate, and rolling it into a cylindrical shape, similar to the pleated filter media 12 (corresponding to the first filtration section of the present invention). In this embodiment, the pleated filter media 14 is formed from a metal (e.g., stainless steel) mesh with fine wires woven into a mesh, but filter paper made of synthetic resin, paper, etc. may also be used.

[0083] The height of the pleated filter medium 14 is approximately the same as the height of the inner cylinder 11 and the pleated filter medium 12. The diameter of the pleated filter medium 14 is smaller than the diameter of the pleated filter medium 12, and the pleated filter medium 14 is provided inside the pleated filter medium 12.

[0084] The inner cylinder 13, like the inner cylinder 11, is a tubular (here, cylindrical) member with openings at both ends and is made of a highly corrosion-resistant material (e.g., stainless steel). Holes through which hydraulic oil passes are formed over almost the entire inner cylinder 13. The diameter of the inner cylinder 13 is smaller than the diameter of the pleated filter medium 14, and the inner cylinder 13 is disposed inside the pleated filter medium 14.

[0085] Plate 20C (corresponding to the first end member of the present invention) mainly has an attachment portion 21, an attachment portion 22A, a cylindrical portion 23C provided between attachment portions 21 and 22A, an attachment tube 24, a hole 25A (corresponding to the first hole of the present invention), and a hole 27A (corresponding to the third hole of the present invention).

[0086] The mounting portion 22A has a recess 22a into which the inner tube 11 and the end 10a of the pleated filter medium 12 are inserted, and a recess 22b into which the inner tube 13 and the end 10c of the pleated filter medium 14 are inserted. A hole 25A opens in the end face of the mounting portion 22A. The hole 25A also opens into the mounting pipe 24. This allows the hole 25A to communicate between the hollow portion of the filtration portion 10A and the outside of the tank 100. A float 40B is provided in the cylindrical portion 23C.

[0087] The plate 20C has a hole 27A extending parallel to the axis ax. The hole 27A connects the air vent hole 23f with the space inside the inner tube 11 and pleated filter medium 12 and the space outside the inner tube 13 and pleated filter medium 14. As with the hole 27, the shape and position of the hole 27A are not limited to those shown.

[0088] Plate 30A (corresponding to the second end member of the present invention) is formed using a highly corrosion-resistant material (resin or metal) similar to plate 30. Plate 30A has recesses 30b into which end 10b of inner tube 11 and pleated filter medium 12 and end 10d of inner tube 13 and pleated filter medium 14 are inserted. Plate 30A is provided so as to cover the end (opening) of filtration section 10A.

[0089] When the hydraulic oil stored in the tank 100 is sucked into the hydraulic pump (not shown), it is sucked from the outside of the filtration section 10A through the inner tube 11 and pleated filter material 12, and then through the inner tube 13 and pleated filter material 14, and then into the inside of the filtration section 10A, and flows out into the suction pipe 101 through the hole 25.

[0090] When hydraulic oil is sucked into the inside of the filtration unit 10A, air bubbles contained in the hydraulic oil are also sucked into the inside of the filtration unit 10A along with the hydraulic oil. Because the pleated filter media 12, 14 are double-layered, air bubbles tend to accumulate between the pleated filter media 12 and 14. Air bubbles that accumulate between the pleated filter media 12 and 14 flow out to the air vent hole 23f through the hole 27. Air bubbles that pass through the inner tube 13 and the pleated filter media 14 flow out of the filtration unit 10A through the hole 25A and into the air vent hole 23f.

[0091] The bubbles that flow into the air vent hole 23f solidify inside and grow into large bubbles, which push the float 40B up in the +z direction and open the air vent hole 23f, causing the bubbles to be discharged to the outside of the suction strainer 4 through the air vent hole 23f.

[0092] According to this embodiment, when the suction strainer 4 is installed horizontally, air bubbles accumulated inside the suction strainer 4 can be discharged from the suction strainer 4 through the air vent hole 23f. Furthermore, by doubling the pleated filter media 12, 14 and accumulating air bubbles between the pleated filter media 12 and 14 and discharging the air bubbles through the hole 27 to the air vent hole 23f, air bubbles can be efficiently discharged from the suction strainer 4. Furthermore, because air bubbles accumulate between the pleated filter media 12 and 14, making it difficult for the air bubbles to flow into the hole 25, it is possible to prevent air bubbles from accumulating in the suction pipe 101 and problems caused by the pump sucking air.

[0093] In this embodiment, the suction strainer 4 has the float 40B, but it may have a float 40C instead of the float 40B.

[0094] <Fifth embodiment> Although the fourth embodiment of the present invention has one float 40, the number of floats is not limited to this. The fifth embodiment of the present invention has a configuration having a plurality of floats. A suction strainer 5 according to the fifth embodiment will be described below. Note that the same parts as those in the first embodiment are designated by the same reference numerals, and description thereof will be omitted.

[0095] Figure 13 is a cross-sectional view showing an outline of the suction strainer 5. Figure 14 is a diagram showing an outline of the suction strainer 5, with (A) being a front view and (B) being a plan view. In Figure 14(A), the upper half is shown in cross section, and the hatching indicating the cross section is omitted. The suction strainer 5 mainly has a filtration section 10A, plates 20D and 30A, and a float 40C.

[0096] Plate 20D (corresponding to the first end member of the present invention) mainly has an attachment portion 21, an attachment portion 22A, a cylindrical portion 23D provided between attachment portion 21 and attachment portion 22A, an attachment tube 24, a hole 25B, and a hole 27B.

[0097] Cylindrical portion 23D has a cylindrical portion 23k whose diameter is smaller than that of mounting portion 22, and a protrusion 23l that protrudes upward (in the +z direction) from cylindrical portion 23k. Air vent holes 23m and 23n are provided in cylindrical portion 23k and protrusion 23l. Air vent holes 23m and 23n are provided at the vertical upper end of cylindrical portion 23D.

[0098] Plate 20D has holes 27B extending parallel to axis ax. Hole 27B includes hole 27a (corresponding to the second hole of the present invention) that connects the space inside inner tube 13 and pleated filter medium 14 with air vent hole 23m, and hole 27b (corresponding to the third hole of the present invention) that connects the space inside inner tube 11 and pleated filter medium 12 and outside inner tube 13 and pleated filter medium 14 with air vent hole 23n. However, hole 27a is not essential.

[0099] One end of air vent hole 23m opens to hole 25B, and the other end opens to the interior of tank 100. Therefore, air bubbles that have accumulated inside hole 25B flow out to air vent hole 23m. Also, air bubbles that have accumulated near the upper end of the space inside inner tube 13 and pleated filter medium 14 flow out to air vent hole 23m via hole 27a.

[0100] One end of air vent hole 23n opens to the inside of tank 100, but does not open to hole 25B. Air bubbles that have accumulated near the upper end of the space inside inner tube 11 and pleated filter medium 12 and outside inner tube 13 and pleated filter medium 14 flow out to air vent hole 23n through hole 27b.

[0101] Cylindrical portion 23D has plate-like member 23q arranged to cover air vent hole 23m and air vent hole 23n. Plate-like member 23q has two holes 23p. A float 40C is inserted into each of the two holes 23p, and plate-like member 23q and float 40C are attached to cylindrical portion 23k. As a result, float 40C is inserted into air vent hole 23m and hole 23p (corresponding to the air vent hole in the present invention), and air vent hole 23n and hole 23p (corresponding to the air vent hole in the present invention).

[0102] As the legs 42C and the claws 43C move in the z direction along the air vent holes 23m and 23n, the float 40C can move in the z direction between a position where the main body 41C blocks the air vent holes 23m, 23n and 23p, and a position where the air vent holes 23m, 23n and 23p are open.

[0103] While hydraulic oil is being sucked by the hydraulic pump, the float 40C is pulled in the −z direction together with the hydraulic oil, and the float 40C blocks the air vent holes 23m, 23n, and 23p. This prevents hydraulic oil from flowing into the suction strainer 5 from any source other than the filtration section 10.

[0104] The air bubbles sucked into the filter section 10 together with the hydraulic oil solidify inside the filter section 10A and the hole 25B and grow into large bubbles. The air bubbles that flow out from the hole 25B and the hole 27a to the air vent hole 23m push the float 40B up in the +z direction, opening the hole 23p and the air vent hole 23m. As a result, the air bubbles are discharged to the outside of the suction strainer 5 from the hole 23p and the air vent hole 23m.

[0105] Air bubbles trapped between the pleated filter medium 12 and the pleated filter medium 14 flow out through the holes 27b to the air vent hole 23n, pushing the float 40B upward in the +z direction and opening the holes 23p and the air vent hole 23n. As a result, the air bubbles are expelled from the suction strainer 5 through the holes 23p and the air vent hole 23n.

[0106] According to this embodiment, when the suction strainer 5 is installed horizontally, air bubbles accumulated inside the suction strainer 5 can be discharged from the suction strainer 5 through the air vent holes 23m, 23n, and 23p. Furthermore, when the float 40C blocks the holes 23p, 23m, and 23n, the float 40C is higher than the upper end of the filtering section 10A, so that air can be effectively discharged to the outside of the suction strainer 5.

[0107] Furthermore, according to this embodiment, the pleated filter media 12, 14 are doubled, air bubbles are trapped between the pleated filter media 12 and 14, and the air bubbles are then discharged through the hole 27b to the air vent hole 23n, thereby enabling the air bubbles to be efficiently discharged from the suction strainer 5. Furthermore, by providing the hole 27a, even if air bubbles accumulate near the upper end of the space inside the inner tube 13 and the pleated filter media 14, the air bubbles can be efficiently discharged from the suction strainer 5.

[0108] <Sixth embodiment> In the third embodiment of the present invention, the float 40C is inserted into the air vent hole 23j, but the configuration of the air vent hole 23j and the hole 25 is not limited to this. In the sixth embodiment of the present invention, a recess is provided integrally with the hole 25. A suction strainer 6 according to the sixth embodiment will be described below. Note that the same parts as those in the first and third embodiments are designated by the same reference numerals, and description thereof will be omitted.

[0109] Fig. 15 is a cross-sectional view showing an outline of the suction strainer 6. In Fig. 15, the upper half is shown in cross section.

[0110] The suction strainer 6 mainly includes a filtering section 10, plates 20E and 30, and a float 40C.

[0111] Plate 20E (corresponding to the first end member of the present invention) mainly has an attachment portion 21, an attachment portion 22, a cylindrical portion 23E provided between attachment portions 21 and 22, an attachment tube 24, and a hole 25C.

[0112] An air vent hole 23r is provided in the cylindrical portion 23E. The air vent hole 23r is provided at the vertical upper end of the cylindrical portion 23E, with one end opening to the hole 25C and the other end opening to the inside of the tank 100. A float 40C is provided in the air vent hole 23r.

[0113] The hole 25C is provided along the horizontal direction and connects the hollow portion of the filtration unit 10 to the outside of the tank 100 (here, the suction pipe 101).

[0114] Next, the holes 25C and the air vent holes 23r will be described with reference to Fig. 16. Fig. 16 is a diagram showing an outline of the plate 20E, where (A) is a cross-sectional view and (B) is a cross-sectional view taken along the line E-E of (A).

[0115] The air vent hole 23r mainly includes holes 23s, 23t, and a hole 23u. The hole 23u is provided between the holes 23s and 23t, and the diameter of the hole 23u is smaller than the diameters of both the holes 23s and 23t.

[0116] The maximum horizontal dimension of the main body 42C of the float 40C is smaller than the diameter of the hole 23u, and the maximum horizontal dimension between the two claws 43C is larger than the diameter of the hole 23u (see FIG. 15). Therefore, the float 40C can move in the z direction between a position where the main body 41C (see FIG. 15) abuts against the bottom surface of the hole 23s to block the air vent hole 23r, and a position where the claws 43C (see FIG. 15) abut against the bottom surface of the hole 23t to open the air vent hole 23r.

[0117] Hole 25C mainly has a through hole 25a and a recess 25b. Through hole 25a and recess 25b are integral. In Figure 16, the boundary between through hole 25a and recess 25b is shown by a dotted line. In this embodiment, the axis of hole 25C coincides with axis ax, but the axis of hole 25C may be misaligned with axis ax.

[0118] 16(A), one end (-y side) of through-hole 25a (corresponding to a first end of the present invention) opens to end 20a of plate 20E located outside tank 100, and the opposite end (+y side) (corresponding to a second end of the present invention) opens to end 20b of plate 20E on the side where filtration section 10 is provided. Through-hole 25a has a tapered shape in which the inner diameter becomes wider at both ends, but the shape of through-hole 25a is not limited to this.

[0119] The recess 25b is provided downstream of the air vent hole 23r (on the suction pipe 101 side). One end 25c (corresponding to the third end of the present invention) of the recess 25b is located inside the air vent hole 23r, and the other end 25d (corresponding to the third end of the present invention) of the recess 25b opens to the end 20a.

[0120] The recess 25b is provided by cutting out a portion of the upper circumferential surface of the through-hole 25a in the vertical direction, and increases the opening area of ​​the hole 25C in a plane perpendicular to the axis ax. The recess 25b is also provided substantially parallel to the central axis of the through-hole 25a (here, the axis ax).

[0121] The recess 25b does not have to be substantially parallel to the axis ax. For example, the recess 25b may be inclined with respect to the axis ax so that the upper end of the recess 25b moves toward the +z side as it approaches the air vent hole 23r (as it moves toward the +y side).

[0122] As shown in FIG. 16B , the recess 25b is arch-shaped in a plane perpendicular to the axis ax. The recess 25b is curved so that the arc is convex upward in the vertical direction. Although the recess 25b may be curved in a shape convex upward in the vertical direction or rectangular, the recess 25b in this embodiment is described as having a partial circular shape. The radius r1 of the arch forming the recess 25b is smaller than the radius r2 of the through hole 25a. Furthermore, the circle C2 including the recess 25b overlaps with the circle C1 including the through hole 25a. In other words, the through hole 25a and the recess 25b are integrated. As a result, the recess 25b widens the cross-sectional area of ​​the hole 25C in a plane perpendicular to the axis ax.

[0123] The through hole 25a has a tapered shape with an inner diameter that becomes wider at each end, and the radius of the circle C1 varies depending on the position, but the circles C1 and C2 overlap regardless of the position of the cross section, and the radius of the circle C2 is smaller than the radius of the circle C1.

[0124] In Figure 15, solid arrows indicate the flow of hydraulic oil, and dashed arrows indicate the flow of air. Air bubbles sucked into the filter section 10 along with the hydraulic oil flow from the end 20b into the through-hole 25a and then into the air vent hole 23r. The air bubbles that accumulate inside the air vent hole 23r push the float 40C upward in the +z direction, opening the air vent hole 23r. As a result, the air bubbles are discharged from the air vent hole 23r to the outside of the suction strainer 6.

[0125] However, some of the air bubbles that flow into air vent hole 23r do not completely escape through air vent hole 23r and remain in hole 25C and suction pipe 101. Hereinafter, the remaining air bubbles will be referred to as "residual air." Because recess 25b is provided vertically above through-hole 25a, the residual air in hole 25C accumulates in recess 25b.

[0126] When the work machine is operating or stopped, the float 40C is lowered in the -z direction and the air vent hole 23r is closed. However, when refueling (for example, when refueling a new tank 100 with hydraulic oil or replacing the hydraulic oil in the tank 100), the air in the pipe 101 is replaced with hydraulic oil, and the air pushes up the float 40C, causing the float 40C to move in the +z direction and opening the air vent hole 23r.

[0127] When the air vent hole 23r opens during fuel supply, the residual air accumulated in the recess 25b flows into the air vent hole 23r and is discharged from the air vent hole 23r to the outside of the suction strainer 6. Furthermore, when the air vent hole 23r opens during fuel supply, the residual air accumulated in the suction pipe 101 also flows into the recess 25b and is then discharged to the outside of the suction strainer 6 via the air vent hole 23r.

[0128] According to this embodiment, when the suction strainer 6 is installed horizontally, air bubbles accumulated inside the suction strainer 6 can be discharged from the suction strainer 6 through the air vent hole 23r. Furthermore, because the recess 25b is provided vertically above the through-hole 25a, residual air accumulated in the recess 25b during fueling can be discharged from the suction strainer 6 through the air vent hole 23r. Therefore, air can be effectively discharged to the outside of the suction strainer 6.

[0129] In this embodiment, the recess 25b is bow-shaped, describing an arc that convexes vertically upward in the plane perpendicular to the axis ax, but the shape and position of the hole 27 are not limited to this. For example, the recess 25b may be rectangular in the plane perpendicular to the axis ax. Essentially, it is sufficient that the through-hole 25a and the recess 25b are integral and the recess 25b is provided vertically above the through-hole 25a. However, by making the recess 25b bow-shaped in the plane perpendicular to the axis ax, making the radius of the bow smaller than the radius of the through-hole 25a, and making the arc shape of the bow convex vertically upward, air bubbles tend to collect near the upper peripheral surface (vertical upper end) of the recess 25b, and the air accumulated in the recess 25b tends to flow into the air vent hole 23r. Furthermore, by making the radius of the arch of the recess 25b smaller than the radius of the through-hole 25a, the upper peripheral surface of the recess 25b is narrowed, and air bubbles accumulated in the recess 25b tend to gather together and grow into larger bubbles.

[0130] In addition, in this embodiment, the recess 25b is added to the suction strainer 3, but it is also possible to add the recess 25b to the suction strainers 1, 2, 4, and 5.

[0131] In the first to fifth embodiments, the air vent holes and air vent holes are round holes provided near the top end of the cylindrical portion, but the shape and location of the air vent holes and air vent holes are not limited to this. The air vent holes and air vent holes may be provided at any position on the cylindrical portion. For example, the air vent holes and air vent holes may be provided at the +y or -y end of the cylindrical portion along the horizontal direction. However, because air bubbles rise inside the hydraulic oil, it is desirable to provide the air vent holes and air vent holes near the top end of the cylindrical portion.

[0132] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to these embodiments, and design modifications within the scope of the gist of the present invention are also included. For example, the above examples have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add, delete, or replace other configurations to the configuration of one embodiment.

[0133] In the present invention, the term "substantially" does not only mean strictly identical, but also includes errors or deformations to the extent that identity is not lost. For example, "substantially perpendicular" is not limited to strictly perpendicular, but includes an error of, for example, several degrees. Furthermore, for example, when expressing orthogonal, parallel, coincident, etc., it includes not only strictly perpendicular, parallel, coincident, etc., but also substantially parallel, substantially perpendicular, substantially coincident, etc.

[0134] In addition, in the present invention, "vicinity" means including a certain range (which can be determined arbitrarily) near a reference position. For example, "near an end" is a concept indicating a certain range near the end, which may or may not include the end.

[0135] 1, 2, 3, 4, 5, 6: Suction strainer 10, 10A: Filtration section 10a, 10b, 10c, 10d: End 11, 13: Inner cylinder 12, 14: Pleated filter material 20, 20A, 20B, 20C, 20D, 20E: Plate 20a, 20b: End 21: Mounting section 21a: Recess 21b: Hole 22, 22A: Mounting section 22a, 22b: Recess 23, 23A, 23B, 23C, 23D, 23E: Cylindrical section 23a, 23b: Protrusion 23c, 23f, 23j, 23m, 23r: Air vent hole 23d: Groove 23e, 23i, 23l: Protrusion 23g: Protrusion 23h, 23k: Cylindrical section 23n, 23q: Air vent hole 23o: Plate-like member 23p, 23u: Hole 23s, 23t: Hole 24: Mounting tube 25, 25A, 25B, 25C: Hole 25a: Through hole 25b: Recess 25c, 25d: End 26: Recess 27, 27A, 27B, 27a, 27b: Hole 30, 30A: Plate 30a, 30b: Recess 40, 40A, 40B, 40C: Float 41, 41A, 41B, 41C: Main body 42, 42A, 42B, 42C: Leg 43, 43B: Insertion part 43C: Claw 44: Protrusion 100: Tank 100a: Bottom surface 100b: Side surface 100c : Outlet port 101 : Suction pipe 102 : Elastic member 103 : Hydraulic pump 110 : Hydraulic circuit

Claims

1. A suction strainer provided in a tank in which oil is stored, a cylindrical filtering portion formed by folding a thin plate into a pleated shape; a first end member and a second end member covering both ends of the filtration unit, respectively; a float provided on the first end member; Equipped with The filtering section is provided along a horizontal direction, the first end member has a plate-like first mounting portion provided on a side surface of the tank, a second mounting portion provided with the filtration portion, a cylindrical portion provided between the first mounting portion and the second mounting portion, and a first hole communicating a hollow portion of the filtration portion with the outside of the tank, the cylindrical portion, the second mounting portion, the filtering portion, and the second end member are provided inside the tank, the cylindrical portion is provided with an air vent hole, one end of which opens to the first hole and the other end of which opens to the inside of the tank, The float is provided so as to be movable between a position where the float closes the air vent hole and a position where the float opens the air vent hole. A suction strainer characterized by:

2. The first end member has a second hole that connects the hollow portion of the filtering portion and the air vent hole.

2. The suction strainer according to claim 1 .

3. The filtration unit includes a cylindrical first filtration unit and a cylindrical second filtration unit provided inside the first filtration unit, The first end member has a second hole that connects the hollow portion of the second filtering portion and the air vent hole.

2. The suction strainer according to claim 1 .

4. The filtration unit includes a cylindrical first filtration unit and a cylindrical second filtration unit provided inside the first filtration unit, The first end member has a third hole that connects the space between the first filtering section and the second filtering section to the air vent hole.

2. The suction strainer according to claim 1 .

5. the cylindrical portion has an air vent hole that does not open to the first hole and has one end that opens to the inside of the tank, The first end member has a fourth hole that connects the space between the first filtering section and the second filtering section to the air vent hole.

4. The suction strainer according to claim 3.

6. When the float blocks the air vent hole, the float and the upper end of the filtering section are positioned at approximately the same height, or the float is higher than the upper end of the filtering section.

6. A suction strainer according to any one of claims 1 to 5.

7. The first hole is a through hole having a first end that is one end and opens at an end of the first mounting portion disposed on the tank side, and a second end opposite to the first end and opening at an end of the first mounting portion on the filtration portion side; a recess provided vertically above the through hole, the through hole and the recess are integral with each other, A third end, which is one end of the recess, opens to the air vent hole, and a fourth end opposite to the third end opens to an end of the first mounting portion disposed outside the tank.

6. A suction strainer according to any one of claims 1 to 5.

8. The recess is arch-shaped, drawing an arc that is convex upward in the vertical direction on a plane perpendicular to the central axis of the through hole.

8. The suction strainer according to claim 7.