pump

Abstract

A pump casing is provided that can prevent blockage of the pump by foreign matter. [Solution] The pump 1 comprises an impeller 4 and a pump casing 5 that houses the impeller 4. The pump casing 5 is equipped with a cutter 30 facing the front edge 20 of the impeller 4. The cutter 30 has a front side surface 36 that constitutes the front side of the cutter 30 in the direction of rotation of the impeller 4. When viewed from the direction of the rotation axis CL of the impeller 4, the angle between the front side surface 36 and the front edge 20 as the impeller 4 rotates gradually decreases, and the maximum value of the angle is less than 90 degrees.

Description

Technical Field

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[0001] The present invention relates to a pump for transferring a liquid.

Background Art

[0002] A pump (particularly, a centrifugal pump) is used to transfer a liquid such as sewage flowing through a sewer pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such sewage may contain foreign substances such as fibrous substances and solid substances. If such foreign substances adhere to and accumulate on the blades of the impeller, the pump may be blocked by the foreign substances.

[0005] Therefore, an object of the present invention is to provide a pump capable of preventing the pump from being blocked by foreign substances.

Means for Solving the Problems

[0006] In one aspect, a pump is provided that includes an impeller and a pump casing that houses the impeller. The pump casing includes a cutter that faces the leading edge of the impeller. The cutter has a front side surface that constitutes the front side of the cutter in the rotational direction of the impeller. When viewed from the axial direction of the rotation axis of the impeller, the angle formed between the front side surface of the cutter and the leading edge of the impeller as the impeller rotates gradually decreases as the impeller rotates, and the maximum value of the angle is less than 90 degrees. In one embodiment, the front side surface of the cutter has a curved shape when viewed from the direction of the rotation axis. In one embodiment, the cutter has an upper surface facing the leading edge of the impeller, and the angle between the upper surface of the cutter and the front side surface is acute. In one embodiment, the leading edge of the impeller has a front corner located on the front side of the leading edge in the rotational direction of the impeller, and the front corner has an acute cross-section.

[0007] In one embodiment, at least a portion of the front side surface of the cutter has a serrated shape. In one embodiment, the leading edge of the impeller has a front corner located on the front side of the leading edge in the rotational direction of the impeller, and at least a portion of the front corner has a serrated shape. In one embodiment, the pump casing has a groove formed on its inner surface, the groove being located adjacent to the cutter. In one embodiment, the front edge of the impeller has a front corner located in front of the front edge in the rotational direction of the impeller, the front corner of the impeller extends from the base end of the front corner connected to the boss of the impeller to the tip of the front corner radially outward of the impeller, the front side of the cutter extends from the base end of the front side connected to the pump casing to the tip of the front side radially inward of the impeller, the radial distance of the impeller from the rotational axis of the impeller to the tip of the front side is less than or equal to the radial distance of the impeller from the rotational axis to the base end of the front corner, and the radial distance of the impeller from the rotational axis of the impeller to the base end of the front side is greater than or equal to the radial distance of the impeller from the rotational axis to the tip of the front corner.

[0008] In one embodiment, the pump casing has a suction port, and the cutter protrudes radially inward from the pump casing toward the suction port. In one embodiment, the pump casing further includes a volute chamber having a shape surrounding the impeller and a discharge port connected to the volute chamber, and the cutter is positioned on the opposite side of the discharge port with respect to the center of the suction port. [Effects of the Invention]

[0009] The pump casing is equipped with a cutter facing the leading edge of the impeller. The angle between the front side of the cutter and the leading edge of the impeller as the impeller rotates gradually decreases by an angle less than 90 degrees as the impeller rotates. Therefore, even if foreign matter contained in the liquid is drawn into the pump casing, the foreign matter is trapped and cut between the front side of the cutter and the leading edge of the impeller. As a result, blockage of the pump by foreign matter can be prevented. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows one embodiment of a pump device. [Figure 2] This is a view of the impeller, pump casing, and cutter from an axial direction. [Figure 3] This is a perspective view showing one embodiment of a casing liner and cutter. [Figure 4] This diagram shows the cutter and its leading edge as viewed from the direction of the impeller's rotation axis. [Figure 5] This diagram illustrates how the positional relationship between the front side of the cutter and the leading edge of the impeller changes as the impeller rotates. [Figure 6] Figures 6(a) to 6(c) show the cross-sectional shape of the cutter. [Figure 7] Figure 6(c) is a perspective view of a cutter having a triangular cross-section. [Figure 8] This figure shows one embodiment of the cross-sectional shape of the cutter and its leading edge. [Figure 9] This figure shows another embodiment of the cutter and the leading edge. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a pump device PA. As shown in FIG. 1, the pump device PA includes a pump 1 for transferring a liquid and a motor 2 for driving the pump 1. In the embodiment shown in FIG. 1, the pump 1 is a volute pump for transferring a liquid such as sewage flowing through a sewer pipe.

[0012] The pump 1 includes a rotating shaft 3 connected to the motor 2, an impeller 4 fixed to an end of the rotating shaft 3, and a pump casing 5 for housing the impeller 4. The rotating shaft 3 is rotated by the motor 2, and the impeller 4 rotates together with the rotating shaft 3 inside the pump casing 5. A mechanical seal 6 attached to the rotating shaft 3 is disposed between the motor 2 and the impeller 4. The mechanical seal 6 prevents the liquid sucked into the pump 1 from entering the motor 2.

[0013] The pump casing 5 includes a casing body 10 disposed around the impeller 4 and a casing liner 11 connected to the casing body 10. The casing body 10 has a volute chamber (scroll chamber) 13 formed therein and a discharge port 14 connected to the volute chamber 13. The volute chamber 13 has a shape surrounding the impeller 4. The casing liner 11 has a suction port 12 formed in the central portion thereof.

[0014] The impeller 4 is fixed to the end of the rotating shaft 3 by a fastener 7. When the impeller 4 rotates by driving of the motor 2, the liquid is sucked in from the suction port 12. The liquid is given velocity energy by the rotation of the impeller 4, and further, as the liquid passes through the volute chamber 13, the velocity energy is converted into pressure, and the liquid is pressurized. The pressurized liquid is discharged from the discharge port 14. The blades 15 of the impeller 4 face the inner surface 1 la of the casing liner 11, and a gap having a predetermined size is formed between the blades 15 and the inner surface 11a.

[0015] Figure 2 is a view of the impeller 4, the pump casing 5, and the cutter 30 described later, seen from the axial direction. As shown in Figure 2, the impeller 4 includes a plurality (in this embodiment, two) of blades 15 and a boss portion 16 to which the blades 15 are fixed. The blades 15 rotate together with the rotation axis 3 around the boss portion 16 (see the solid line arrow in Figure 2).

[0016] As shown in Figure 2, the pump casing 5 has a tongue portion 25 that constitutes the start of the spiral of the volute chamber 13. The volute chamber 13 extends along the circumferential direction of the impeller 4, and the liquid flowing through the volute chamber 13 is split at the tongue portion 25. Therefore, most of the liquid flows to the discharge port 14, while a part of the liquid circulates through the volute chamber 13 (see the dotted line arrow in Figure 2).

[0017] In the embodiment shown in Figure 2, the blade 15 is a backward-curved blade. More specifically, the blade 15 has a leading edge portion 20 that spirally extends from the boss portion 16 and a trailing edge portion 21 that spirally extends from the leading edge portion 20. The leading edge portion 20 and the trailing edge portion 21 are connected to each other and are integrally formed.

[0018] The leading edge portion 20 is disposed radially inside the suction port 12. The trailing edge portion 21 faces the inner surface 11a of the casing liner 11 (see Figure). Therefore, when the casing liner 11 is viewed from the direction of the axis CL of the rotation axis 3 (that is, the direction of the rotation axis CL of the impeller 4), the leading edge portion is disposed so as to be exposed from the casing liner 11, and the trailing edge portion 21 is disposed on the back side of the casing liner ));

[0019] As described above, the fluid handled by the pump device PA may contain foreign matter such as fibrous materials and solid materials. The leading edge 20 of the blade 15 is located radially inward of the suction port 12. Therefore, when the fluid is drawn into the suction port 12 by the rotation of the impeller 4, foreign matter may adhere to and accumulate on the leading edge 20. In this state, when the impeller 4 rotates, the foreign matter may become trapped in the gap between the trailing edge 21 and the inner surface 11a of the casing liner 11, potentially causing the pump 1 to become blocked. To prevent the pump 1 from becoming blocked by foreign matter, the pump 1 (more specifically, the pump casing 5) is equipped with a cutter 30 for cutting foreign matter.

[0020] Figure 3 is a perspective view showing one embodiment of a casing liner 11 and a cutter 30. The cutter 30 is fixed to the casing liner 11 of the pump casing 5. More specifically, the cutter 30 is fixed to the inner surface 11a that forms the suction port 12 of the casing liner 11. The cutter 30 protrudes radially inward from the casing liner 11 toward the suction port 12 so as to obstruct the flow path of liquid passing through the suction port 12. In this embodiment, the cutter 30 is made of a different material from the casing liner 11. In one embodiment, the cutter 30 is made of a metal with high hardness such as cast iron, stainless steel, iron, or gunmetal. The cutter 30 is fixed to a cutter mounting portion (not shown) provided on the casing liner 11 by fasteners (not shown). With this configuration, even if the cutter 30 wears out, the operator can easily replace the cutter 30. In one embodiment, the cutter 30 may be a component integrally molded with the casing liner 11.

[0021] The cutter 30 has an upper surface 35 that faces the leading edge 20 of the blade 15 when the impeller 4 is housed in the pump casing 5, a front side surface 36 that constitutes the front side of the cutter 30 in the direction of rotation of the impeller 4 (see arrow in Figure 2), a rear side surface 37 that constitutes the rear side of the cutter 30 in the direction of rotation of the impeller 4, and a lower surface 38 located on the opposite side of the upper surface 35. A gap of a predetermined size is formed between the leading edge 20 of the impeller 4 housed in the pump casing 5 and the upper surface 35 of the cutter 30. The size of this gap is such that foreign matter that could cause blockage of the pump 1 cannot enter. In one embodiment, the gap between the leading edge 20 of the impeller 4 and the upper surface 35 of the cutter 30 is less than 1 mm.

[0022] As shown in Figure 3, the casing liner 11 of the pump casing 5 has grooves 40 formed on its inner surface. In this embodiment, the casing liner 11 has a plurality of (four) grooves 40 arranged along the circumferential direction of the suction port 12. One of the plurality of grooves 40 is located upstream of the cutter 30 in the rotational direction of the impeller 4 and is adjacent to the cutter 30. More specifically, the plurality of grooves 40 are formed on the inner surface 11a of the casing liner 11 and extend from the suction port 12 toward the volute chamber 13. The front side surface 36 of the cutter 30 is connected to the starting end 40a of the groove 40, and the ending end 40b of the groove 40 is connected to the volute chamber 13.

[0023] In one embodiment, the casing liner 11 may have a groove 40 adjacent to the cutter 30. In another embodiment, the casing liner 11 may not have a groove 40.

[0024] As the impeller 4 rotates due to the drive of motor 2, foreign matter contained in the liquid is caught and cut between the front side surface 36 of the cutter 30 located at the suction port 12 and the leading edge 20 of the impeller 4. More specifically, as the impeller 4 rotates, the foreign matter is caught between the front side surface 36 of the cutter 30 and the leading edge 20 of the impeller 4 and cut along the radial direction of the impeller 4. As the impeller 4 rotates, the cut foreign matter is guided into a groove 40 formed in the casing liner 11, moves along the groove 40, and is discharged into the volute chamber 13 at the end 40b of the groove 40. The foreign matter is then discharged to the outside through the discharge port 14.

[0025] As shown in Figure 2, the cutter 30 is positioned on the opposite side of the discharge port 14 with respect to the center of the suction port 12. The center of the suction port 12 coincides with the axis CL of the rotation axis 3 (i.e., the rotation axis CL of the impeller 4). The tongue portion 25 is positioned adjacent to the discharge port 14. With this arrangement, foreign matter is discharged into the volute chamber 13 at a position opposite to the tongue portion 25. The foreign matter is then moved through the volute chamber 13 by the flowing liquid while being subjected to centrifugal force. Therefore, the foreign matter is discharged to the outside from the discharge port 14 without getting caught on the tongue portion 25.

[0026] Figure 4 shows the cutter 30 and the leading edge portion 20 as viewed from the rotation axis CL direction of the impeller 4. As shown in Figure 4, the leading edge portion 20 has a front corner portion 27 that constitutes the front side of the leading edge portion 20 in the rotation direction of the impeller 4 indicated by the arrow in Figure 4, and a rear corner portion 28 that constitutes the rear side of the leading edge portion 20 in the rotation direction of the impeller 4. The front corner portion 27 extends from the base end portion 27a of the front corner portion 27 connected to the boss portion 16 to the tip portion 27b of the front corner portion 27, curving radially outward from the impeller 4. The front side surface 36 of the cutter 30 extends from the base end portion 36a of the front side surface 36 connected to the casing liner 11 to the tip portion 36b of the front side surface 36, curving radially inward from the impeller 4.

[0027] The radial distance d1 of the impeller 4 from the rotation axis CL to the tip 36b of the front side surface 36 is less than or equal to the radial distance d3 of the impeller 4 from the rotation axis CL to the base end 27a of the front corner 27. In this embodiment, distance d1 is the same as distance d3, and distances d1 and d3 are equal to the radius of the boss portion 16. Also, the radial distance d2 of the impeller 4 from the rotation axis CL to the base end 36a of the front side surface 36 is greater than or equal to the radial distance d4 of the impeller 4 from the rotation axis CL to the tip 27b of the front corner 27. In this embodiment, distance d2 is the same as distance d4, and distances d2 and d4 are equal to the radius of the suction port 12. With this configuration, the cutter 30 can cut foreign matter sucked in from the suction port 12 by the rotation of the impeller 4, regardless of its position on the front edge portion 20.

[0028] The positional relationship between the cutter 30 and the leading edge portion 20 changes as the impeller 4 rotates. Initially, the tip-side region S1 of the cutter 30, where the tip portion 36b of the cutter 30 is located, faces the base-side region S4 of the leading edge portion 20, where the base portion 27a of the leading edge portion 20 is located. Next, the central region S2 of the cutter 30 faces the central region S5 of the leading edge portion 20. Subsequently, the base-side region S3 of the cutter 30, where the base portion 36a of the cutter 30 is located, faces the tip-side region S6 of the leading edge portion 20, where the tip portion 27b of the leading edge portion 20 is located. The central region S2 of the cutter 30 is located between the tip-side region S1 and the base-side region S3. The central region S5 of the leading edge portion 20 is located between the base-side region S4 and the tip-side region S6.

[0029] Figure 5 illustrates how the positional relationship between the front side surface 36 of the cutter 30 and the leading edge 20 of the impeller 4 changes as the impeller 4 rotates. Positional relationship A in Figure 5 shows the positional relationship where the tip side region S1 of the cutter 30 faces the base side region S4 of the leading edge 20. Positional relationship B in Figure 5 shows the positional relationship where the central region S2 of the cutter 30 faces the central region S5 of the leading edge 20. Positional relationship C in Figure 5 shows the positional relationship where the base side region S3 of the cutter 30 faces the tip side region S6 of the leading edge 20.

[0030] The positional relationship between the cutter 30 and the leading edge 20 changes from positional relationship A to positional relationship B and then to positional relationship C as the impeller 4 rotates. Therefore, when viewed from the direction of the rotation axis CL of the impeller 4, the angle between the front side surface 36 of the cutter 30 and the leading edge 20 of the impeller 4 (more specifically, the front corner 27) includes angle α1 in positional relationship A, angle α2 in positional relationship B, and angle α3 in positional relationship C.

[0031] The angle between the front side surface 36 and the leading edge portion 20 (more specifically, the front corner portion 27) is the angle between the tangent to the front side surface 36 and the tangent to the leading edge portion 20 (more specifically, the front corner portion 27) at the intersection of the front side surface 36 and the leading edge portion 20 (more specifically, the front corner portion 27), when viewed from the direction of the rotation axis CL of the impeller 4.

[0032] In other words, the angle α1 in positional relationship A is the angle between the tangent T1 of the front side surface 36 and the tangent T2 of the front corner portion 27 at the intersection P1 of the tip-side region S1 of the front side surface 36 and the base-side region S4 of the front edge portion 20 (more specifically, the front corner portion 27), when viewed from the direction of the rotation axis CL of the impeller 4.

[0033] Angle α2 in positional relationship B is the angle between the tangent T3 of the front side surface 36 and the tangent T4 of the front corner 27 at the intersection P2 of the central region S2 of the front side surface 36 and the central region S5 of the front edge 20 (more specifically, the front corner 27), when viewed from the direction of the rotation axis CL of the impeller 4. Angle α3 in positional relationship C is the angle between the tangent T5 of the front side surface 36 and the tangent T6 of the front corner 27 at the intersection P3 of the base end region S3 of the front side surface 36 and the tip end region S6 of the front edge 20 (more specifically, the front corner 27), when viewed from the direction of the rotation axis CL of the impeller 4.

[0034] The front side surface 36 of the cutter 30 has a curved shape such that, when viewed from the direction of the rotation axis CL of the impeller 4, the angle between the front side surface 36 and the leading edge 20 gradually decreases as the impeller 4 rotates. More specifically, the front side surface 36 has a curved shape that is concave toward the rear side surface 37 in the central region S2. In one embodiment, when viewed from the direction of the rotation axis CL of the impeller 4, a part of the front side surface 36 of the cutter 30 may have a straight shape. For example, when viewed from the direction of the rotation axis CL of the impeller 4, the front side surface 36 may have a straight shape from the tip side region S1 to the central region S2, and a curved shape from the central region S2 to the base side region S3. The maximum value of the angle between the front side surface 36 and the leading edge 20 is less than 90 degrees. That is, the angle between the front side surface 36 and the leading edge 20 gradually decreases in an angular range greater than 0 degrees and less than 90 degrees as the impeller 4 rotates.

[0035] In this embodiment, the front corner portion 27 of the impeller 4 has a curved shape that, when viewed from the direction of the rotation axis CL of the impeller 4, bulges out in the central region S5 on the opposite side from the rear corner portion 28. The shape of the front side surface 36 of the cutter 30 is appropriately determined according to the shape of the front corner portion 27 of the impeller 4, such that the angle between the front side surface 36 and the leading edge portion 20, when viewed from the direction of the rotation axis CL of the impeller 4, gradually decreases as the impeller 4 rotates.

[0036] In this embodiment, as an example, angle α1 is 50 degrees, angle α2 is 30 degrees, and angle α3 is 25 degrees. Between positional relationship A and positional relationship B, the angle between the front side surface 36 and the leading edge portion 20 gradually decreases from angle α1 to angle α2 as the impeller 4 rotates. Between positional relationship B and positional relationship C, the angle between the front side surface 36 and the leading edge portion 20 gradually decreases from angle α2 to angle α3 as the impeller 4 rotates.

[0037] In this specification, "the angle between the front side surface 36 and the leading edge 20 gradually decreases as the impeller 4 rotates" includes cases where the angle between the front side surface 36 and the leading edge 20, as part of the tolerance / error range due to manufacturing conditions, temporarily increases as the impeller 4 rotates. Also, in this specification, "the maximum value of the angle between the front side surface 36 and the leading edge 20 is less than 90 degrees" includes angles greater than 90 degrees as part of the tolerance / error range due to manufacturing conditions, etc.

[0038] If the angle between the front side surface 36 and the leading edge 20 increases with the rotation of the impeller 4, the foreign object may move outward, and the effect of trapping the foreign object between the front side surface 36 and the leading edge 20 may not be sufficient. In particular, if the foreign object is a long fibrous material or a hard solid material, if the angle between the front side surface 36 and the leading edge 20 increases with the rotation of the impeller 4, the foreign object may not be completely cut and may block the pump 1. According to this embodiment, as the angle between the front side surface 36 and the leading edge 20 gradually decreases with the rotation of the impeller 4, the cutter 30 can cut the foreign object while maintaining the effect of trapping it between itself and the leading edge 20. As a result, blockage of the pump 1 by foreign objects can be prevented.

[0039] Figures 6(a) to 6(c) show the cross-sectional shape of the cutter 30. In this embodiment, as shown in Figure 6(a), the front side surface 36 and the rear side surface 37 are connected to the top surface 35 and the bottom surface 38, and the cross-sectional shape of the cutter 30 is rectangular. In this embodiment, the angle θa between the top surface 35 and the front side surface 36 is a right angle (90 degrees).

[0040] In other embodiments, as shown in Figure 6(b), the angle θa between the top surface 35 and the front side surface 36 may be acute. In the embodiment shown in Figure 6(b), the cross-sectional shape of the cutter 30 is trapezoidal. In yet another embodiment, as shown in Figure 6(c), the cutter 30 does not have a bottom surface 38, and the longitudinal cross-sectional shape of the cutter 30 may be triangular. In the embodiment shown in Figure 6(c), the angle θa between the top surface 35 and the front side surface 36 is acute. Although not shown, the angle θa may be obtuse, as long as the cutter 30 is effective in cutting foreign objects.

[0041] Figure 7 is a perspective view of the cutter 30 having the triangular cross-section shown in Figure 6(c). A cutter 30 having such an acute angle θa between the top surface 35 and the front side surface 36 can effectively cut foreign matter between the front side surface 36 and the leading edge 20.

[0042] Figure 8 shows one embodiment of the cross-sectional shape of the cutter 30 and the front edge portion 20. The cutter 30 in this embodiment is the cutter 30 shown in Figure 7. As shown in Figure 8, the angle θb of the cross-section of the front corner portion 27 of the front edge portion 20 of the impeller 4 may be acute. By sandwiching foreign matter between the cutter 30 having an acute angle cross-sectional shape and the front edge portion 20 having an acute angle cross-sectional shape, the foreign matter can be effectively cut.

[0043] Figure 9 shows another embodiment of the cutter 30 and the front edge portion 20. In this embodiment, the cutter 30 has a serrated edge on at least a portion of its front side surface 36. As shown in Figure 9, the front side surface 36 may have a serrated edge over its entire length from the base end 36a to the tip end 36b, or it may have a serrated edge only on a portion of the length from the base end 36a to the tip end 36b. As shown in an enlarged view in Figure 9, the serrated front side surface 36 has a plurality of continuously arranged sawtooths Ta and an edge portion Ea which is the edge of the front side surface 36 on which the plurality of sawtooths Ta are formed. In this embodiment, the sawtooths Ta are triangular in shape, but in one embodiment, the sawtooths Ta may be rectangular or have other shapes (for example, a shape in which part of the sawtooths Ta is curved).

[0044] In this embodiment, the front edge portion 20 has a sawtooth shape on at least a portion of the front corner portion 27. As shown in Figure 9, the front corner portion 27 may have a sawtooth shape over its entire length from the base end portion 27a to the tip end portion 27b, or it may have a sawtooth shape only on a portion of the length from the base end portion 27a to the tip end portion 27b. As shown in an enlarged view in Figure 9, the front corner portion 27 having a sawtooth shape has a plurality of continuously arranged sawtooths Tb and an edge portion Eb which is the edge of the front corner portion 27 on which the plurality of sawtooths Tb are formed. In this embodiment, the sawtooths Tb have a triangular shape, but in one embodiment, the sawtooths Ta may have a rectangular shape or other shape (for example, a shape in which a part of the sawtooth Tb has a curve).

[0045] In this specification, the angle between the front side surface 36 having sawtooth Ta and the front corner 27 having sawtooth Tb is defined as the angle between the edge portion Ea of the front side surface 36 and the edge portion Eb of the front corner 27. In the shape including the contour of the sawtooth Ta of the front side surface 36 and the contour of the sawtooth Tb of the front corner 27, the angle between the front side surface 36 and the leading edge portion 20 may temporarily increase as the impeller 4 rotates. The edge portion Ea of the front side surface 36 of the cutter 30 has a curved shape such that the angle between the edge portion Ea of the front side surface 36 and the edge portion Eb of the leading edge portion 20 gradually decreases as the impeller 4 rotates.

[0046] In one embodiment, the front side surface 36 may have a serrated shape, while the front corner portion 27 may not. In another embodiment, the front corner portion 27 may have a serrated shape, while the front side surface 36 may not.

[0047] According to this embodiment, foreign matter can be effectively cut by the front side surface 36 having serrations Ta and the front edge portion 20 having serrations Tb, which bite into the foreign matter between the front side surface 36 and the front edge portion 20.

[0048] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but should be in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0049] 1 pump 2 motors 3 rotation axes 4-blade wheel 5 Pump casing 6 Mechanical seals 7 Fasteners 10 Casing body 11 Casing Liner 11a Inner Self 12 Inlet 13 Volute Room 14 Outlet 15 wings 16 Boss Section 20 Front edge 21 Trailing edge 25 Tongue 27 Front corner 28 Rear corner 30 cutters 35 Top 36 Front side 37 Rear side 38 Bottom side 40 grooves 40a Starting point 40b termination PA pump system

Claims

1. The impeller and The pump casing comprises the impeller, The pump casing is equipped with a cutter facing the leading edge of the impeller, The cutter has a front side surface that constitutes the front side of the cutter in the direction of rotation of the impeller, When viewed from the direction of the rotation axis of the impeller, the angle between the front side surface of the cutter and the leading edge of the impeller gradually decreases as the impeller rotates. The maximum value of the aforementioned angle is less than 90 degrees for the pump.

2. The pump according to claim 1, wherein the front side surface of the cutter has a curved shape when viewed from the direction of the rotation axis.

3. The pump according to claim 1, wherein the cutter has an upper surface facing the leading edge of the impeller, and the angle between the upper surface of the cutter and the front side surface is acute.

4. The front edge of the impeller has a front corner located on the front side of the front edge in the rotational direction of the impeller. The pump according to claim 1, wherein the front corner portion has an acute-angled cross-section.

5. The pump according to claim 1, wherein at least a portion of the front side surface of the cutter has a serrated shape.

6. The front edge of the impeller has a front corner located on the front side of the front edge in the rotational direction of the impeller. The pump according to claim 1, wherein at least a portion of the front corner portion has a sawtooth shape.

7. The pump casing has grooves formed on its inner surface, The pump according to claim 1, wherein the groove is located adjacent to the cutter.

8. The front edge of the impeller has a front corner located on the front side of the front edge in the rotational direction of the impeller. The front corner portion of the impeller extends from the base end of the front corner portion connected to the boss portion of the impeller to the tip of the front corner portion radially outward of the impeller. The front side of the cutter extends from the base end of the front side connected to the pump casing to the tip of the front side radially inward of the impeller, The radial distance of the impeller from the axis of rotation to the tip of the front side is less than or equal to the radial distance of the impeller from the axis of rotation to the base end of the front corner. The pump according to claim 1, wherein the radial distance of the impeller from the rotation axis to the base end of the front side surface is greater than or equal to the radial distance of the impeller from the rotation axis to the tip of the front corner.

9. The pump casing has a suction port, The pump according to claim 1, wherein the cutter protrudes radially inward from the pump casing toward the suction port.

10. The pump casing is, A volute chamber having a shape that surrounds the impeller, It further has a discharge port connected to the volute chamber, The pump according to claim 9, wherein the cutter is positioned on the opposite side of the discharge port with respect to the center of the suction port.

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