pump

Abstract

To provide a pump capable of preventing foreign matter such as string-like, fibrous-like or cloth-like foreign matter from blocking an impeller.SOLUTION: A pump comprises an impeller 1 and an impeller casing 5 housing the impeller 1. The impeller 1 has a hub 13, a single sweptback blade 2 connected to the hub 13, and a shroud 25 to which the hub 13 and the swept blade 2 are connected.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pump for transporting a liquid, and more particularly to a pump for transporting a liquid containing string-like, fibrous, cloth-like or other foreign matter. [Background technology]

[0002] Centrifugal pumps have been used to transport liquids such as wastewater flowing through sewer pipes. Such wastewater may contain long, thin foreign objects such as strings, fibers, and cloth. These long, thin foreign objects tend to get caught in the impeller and impede the rotation of the impeller. Therefore, swept-back blades that are less likely to clog the impeller have been adopted to remove the foreign objects caught in the impeller (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-186284 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because conventional impellers have two or more swept-back blades, the impeller itself is small in a small sewage pump, and the distance between the blades (hereinafter referred to as the passage diameter) is also small. As a result, it is not possible to ensure a passage diameter large enough to allow foreign matter to pass through in a sewage pump, and the impeller may become clogged with foreign matter.

[0005] Therefore, the present invention provides a pump that can prevent string-like, fibrous, cloth-like, or other foreign matter from clogging the impeller. [Means for solving the problem]

[0006] In one aspect, a pump for transporting a liquid containing foreign matter is provided, comprising an impeller and an impeller casing that houses the impeller, the impeller having a hub, a single swept-back blade connected to the hub, and a shroud connecting the hub and the swept-back blade.

[0007] In one embodiment, the swept-back vane has a leading edge extending radially outward from the hub and a trailing edge extending spirally from the leading edge in a direction opposite to the rotational direction of the impeller, and the wrap angle of the swept-back vane from the center of the leading edge to the center of the aft end of the trailing edge is within a range of 320 to 410 degrees. In one aspect, the inner end of the leading edge extends in a tangential direction to the outer circumferential surface of the hub. In one embodiment, the impeller further comprises a balance weight. [Effects of the Invention]

[0008] The impeller has a single swept-back blade, which allows for a large passage diameter within the impeller, allowing foreign matter contained in the liquid to pass through the impeller without clogging it. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of a pump. [Figure 2] FIG. 2 is a front view of the impeller as seen from the direction indicated by arrow A in FIG. [Figure 3] FIG. [Figure 4] FIG. 1 is a front view of a conventional impeller having two swept-back blades. [Figure 5] FIG. 3 is a diagram illustrating the wrap angle of the swept-back blade of the impeller shown in FIG. 2. [Figure 6] 1 is a graph showing an example of the relationship between the wrap angle of a swept-back blade and impeller efficiency. [Figure 7] FIG. 3 is a meridional cross-sectional view of the impeller shown in FIG. 2. [Figure 8] FIG. 3 is a rear view of the impeller shown in FIG. 2. [Figure 9] FIG. 3 is a side view of the impeller shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing one embodiment of a pump. The pump shown in Fig. 1 is a centrifugal pump used to transport liquids containing string-like, fibrous, or cloth-like foreign matter (e.g., sewage flowing through sewer pipes).

[0011] As shown in Figure 1, the pump has a rotating shaft 11, an impeller 1 fixed to the rotating shaft 11, and an impeller casing 5 that houses the impeller 1. The rotating shaft 11 is connected to a motor 12. The impeller 1 rotates integrally with the rotating shaft 11 within the impeller casing 5 by the motor 12. A mechanical seal 15 is disposed between the motor 12 and the impeller 1. This mechanical seal 15 prevents liquid from entering the motor 12.

[0012] The impeller casing 5 has a casing body 6 arranged around the impeller 1, and a casing liner 8 connected to the casing body 6. The impeller casing 5 has an inlet 3 and a discharge port 4. More specifically, the casing liner 8 has a cylindrical inlet 3, and the casing body 6 has a discharge port 4. The impeller casing 5 has a volute chamber 7 formed inside the casing body 6, and the impeller 1 is disposed within the volute chamber 7. The volute chamber 7 has a shape that surrounds the periphery of the impeller 1. The inlet 3 and the discharge port 4 are in communication with the volute chamber 7.

[0013] When the impeller 1 is rotated, liquid is sucked in through the suction port 3. The liquid that flows in through the suction port 3 is discharged circumferentially into the volute chamber 7 as the impeller 1 rotates. The rotation of the impeller 1 imparts velocity energy to the liquid, and as the liquid passes through the volute chamber 7, this velocity energy is converted into pressure, increasing the pressure of the liquid. The pressurized liquid is discharged from the discharge port 4. The blades 2 of the impeller 1 face the inner surface 8a of the casing liner 8 of the impeller casing 5 with a small gap between them. This gap is, for example, in the range of 0.3 mm to 0.7 mm.

[0014] Fig. 2 is a front view of the impeller 1 as viewed from the direction indicated by arrow A in Fig. 1, and Fig. 3 is a perspective view of the impeller 1. The impeller 1 has a single swept-back vane 2, a cylindrical hub 13, and a shroud 25 to which the swept-back vane 2 and hub 13 are connected. The hub 13 has a through-hole 13a into which the end of the rotating shaft 11 shown in Fig. 1 is inserted, and the hub 13 is fixed to the end of the rotating shaft 11 by a fixture (not shown). The impeller 1 is rotated in the direction of the arrow by a motor 12.

[0015] The swept-back vane 2 has a leading edge 21 extending radially outward from the hub 13, and a trailing edge 22 extending spirally from the leading edge 21. The trailing edge 22 has a spiral shape extending from an outer end 21b of the leading edge 21 in a direction opposite to the rotation direction of the impeller 1. A rear end 22a of the trailing edge 22 is located on the outer periphery of the shroud 25 and is connected to the shroud 25. As shown in FIG. 3 , the entire swept-back vane 2 is inclined with respect to the axis CL of the impeller 1.

[0016] 1, the leading edge portion 21 is located within the suction port 3 of the impeller casing 5 and is exposed within the suction port 3. On the other hand, the trailing edge portion 22 faces the inner surface of the impeller casing 5 (more specifically, the inner surface 8a of the casing liner 8). A small gap is formed between the trailing edge portion 22 and the inner surface 8a of the casing liner 8.

[0017] 2 and 3, the shroud 25 is integral with the hub 13. The swept back wings 2 are connected to the upper side of the shroud 25, and the swept back wings 2, the hub 13, and the shroud 25 rotate together.

[0018] The leading edge portion 21 extends in an arc shape radially outward from the hub 13. More specifically, the leading edge portion 21 curves from the hub 13 in a direction opposite to the rotation direction of the impeller 1. Therefore, the outer end 21b of the leading edge portion 21 is positioned rearward of the inner end 21a of the leading edge portion 21 in the rotation direction of the rotary shaft 11. The trailing edge portion 22 extends in a spiral shape from the outer end 21b of the leading edge portion 21.

[0019] An inner end 21a of the leading edge 21 extends in a tangential direction to the outer peripheral surface of the hub 13 and is smoothly connected to the outer peripheral surface of the hub 13. It has been confirmed through actual operation of the pump that this shape allows foreign matter in the liquid to move smoothly over the leading edge 21 as the impeller 1 rotates, making it less likely to clog the impeller 1.

[0020] In Figure 2, symbol D1 represents the diameter through which string-like, fibrous, cloth-like, or other foreign matter contained in the liquid can pass. In other words, if the size of the foreign matter is equal to or smaller than the diameter D1, it is expected that the foreign matter will be able to pass through the impeller 1 together with the liquid without clogging the impeller 1.

[0021] FIG. 4 is a front view of a conventional impeller having two swept-back vanes 100. In FIG. 4, symbol D2 represents the passage diameter through which string-like, fibrous, or cloth-like foreign matter contained in the liquid can pass. As can be seen from a comparison between FIG. 2 and FIG. 4, the impeller 1 of this embodiment has a single swept-back vane 2, so the passage diameter D1 within the impeller 1 is larger than the passage diameter D2 within a conventional two-blade impeller. Therefore, according to this embodiment, foreign matter contained in the liquid can pass through the impeller 1 without clogging it.

[0022] As described above, a single swept-back vane 2 can prevent clogging of the impeller 1 by foreign matter, but the impeller efficiency is likely to decrease compared to an impeller with multiple swept-back vanes. Therefore, to improve the impeller efficiency, as shown in FIG. 5 , the wrap angle θ of the swept-back vane 2 in this embodiment is set to a range of 320 to 410 degrees, more preferably a range of 330 to 390 degrees. The wrap angle θ of the swept-back vane 2 is the angle from the start point to the end point of the camber line D of the swept-back vane 2. In other words, it is the angle from the center of the leading edge 21 to the center of the aft end 22a of the trailing edge 22. More specifically, the wrap angle θ of the swept-back vane 2 is the angle between a line L1 extending from the center of the impeller 1 to the center of the leading edge 21 and a line L2 extending from the center of the impeller 1 to the center of the aft end 22a of the trailing edge 22.

[0023] FIG. 6 is a graph showing an example of the relationship between the wrap angle θ of the swept-back vane 2 and impeller efficiency. As shown in FIG. 6, as the wrap angle θ of the swept-back vane 2 increases, the impeller efficiency tends to improve. On the other hand, if the wrap angle θ of the swept-back vane 2 is too large, the impeller efficiency actually decreases. In addition, if the wrap angle θ of the swept-back vane 2 is too large (especially if the wrap angle of the swept-back vane 2 exceeds 410 degrees), the passage diameter D1 described with reference to FIG. 2 becomes small. From these points of view, the wrap angle θ of the swept-back vane 2 is within a range of 320 to 410 degrees, and more preferably within a range of 330 to 390 degrees.

[0024] An impeller 1 having one swept blade 2 and a wrap angle θ within the above-mentioned range can achieve high impeller efficiency while preventing clogging of the impeller 1 by foreign matter.

[0025] Fig. 7 is a meridional cross section of the impeller 1 shown in Fig. 2, and Fig. 8 is a rear view of the impeller 1 shown in Fig. 2. The impeller 1 of this embodiment has one swept-back blade 2, and therefore has a balance weight 30 to balance the rotation of the impeller 1. This balance weight 30 is provided on the rear side of the shroud 25. The balance weight 30 may be integral with the shroud 25.

[0026] The balance weight 30 prevents vibration when the impeller 1 rotates at high speed, and can prevent the impeller 1 from contacting the impeller casing 5.

[0027] Fig. 9 is a side view of the impeller 1 shown in Fig. 2. As shown in Fig. 9, the rear end 22a of the trailing edge portion 22 is connected obliquely to the shroud 25. That is, when viewed from a direction perpendicular to the axis CL of the impeller 1, the rear end 22a of the trailing edge portion 22 is inclined with respect to the axis CL of the impeller 1. The connection angle α between the rear end 22a of the trailing edge portion 22 and the shroud 25 is greater than 90°. That is, the connection angle α satisfies 90°<α<180°.

[0028] The rear end 22a of the trailing edge portion 22 corresponds to the outlet of the swept-back blade 2. The oblique shape of the rear end 22a of the trailing edge portion 22 can reduce the radial load that the rotating impeller 1 receives from the liquid. As a result, the rotation of the impeller 1 becomes stable.

[0029] In one embodiment, the angle of connection α between the aft end 22a of the trailing edge 22 and the shroud 25 may be 90° or less than 90°, i.e., the angle of connection α is 0°<α≦90°.

[0030] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0031] 1 impeller 2 swept wings 3 Intake port 4 outlet 5 Impeller casing 6 Casing body 7 Volute chamber 8 Casing liner 11 Rotation axis 12 motors 13. Hub 15 Mechanical seal 21 leading edge 21a Inner end of leading edge 21b Outer edge of leading edge 22 Trailing edge 22a Rear end of trailing edge 25 Shroud 30 balance weight

Claims

1. A pump for transporting a liquid containing foreign matter, An impeller and an impeller casing that houses the impeller; The impeller is Hub and a single swept wing connected to the hub; a shroud connecting the hub and the swept-back wing; The swept-back blade has a leading edge portion extending radially outward from the hub and a trailing edge portion extending spirally from the leading edge portion in a direction opposite to the rotation direction of the impeller, When a wrap angle of the swept-back vane is defined as the angle between a line extending from the center of the impeller to the center of the leading edge and a line extending from the center of the impeller to the center of the aft end of the trailing edge, the wrap angle is within a range of 320 to 410 degrees.

2. The pump of claim 1 , wherein an inner end of the leading edge extends tangentially to an outer peripheral surface of the hub.

3. The pump of claim 1 , wherein the impeller further comprises a balance weight.

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