CN114060320A - Pump with heating function - Google Patents

Abstract

The invention discloses a pump with a heating function, which comprises an end cover, an impeller arranged in the end cover and an annular pipe bent into a ring along a plane, wherein the impeller is arranged in the end cover; a heating wire is arranged in the annular pipe in a penetrating way; the annular tube is coiled around the central axis of the impeller and adjacent to the inner wall of the end cover; the diameter of the annular pipe is not larger than the rotating diameter of the impeller. The pump with the heating function adopts the annular pipe with the plane annular structure and the heating wire thereof to heat the fluid in the end cover. On one hand, the installation positions of the annular pipe and the heating wires of the annular pipe in the end cover accord with the flowing characteristic of fluid in the end cover under the action of the impeller, the heating effect of the heating wires can be fully and effectively exerted, the heat exchange efficiency is improved, and the heating requirement is met. On the other hand, the annular pipe reasonably utilizes the gap between the end cover and the impeller, the radial size of the pump cannot be increased, the axial size of the pump cannot be excessively increased, and the overall size and the appearance shape of the pump can be controlled.

Description

Pump with heating function

Technical Field

The invention relates to the field of pumps, in particular to a pump with a heating function.

Background

In order to add a heating function to an existing dishwasher pump, a heating member is generally disposed inside or at an outer periphery of the pump.

For the heating member installed outside the pump, not only the heat exchange efficiency is low, the security is poor, but also the size and the appearance complexity of the pump can be increased. For a heating element installed in the pump, such as a spiral heating pipe, the installation difficulty of other parts in the pump is increased, the size of the shell of the pump is obviously increased, and the hydraulic efficiency of the pump is seriously affected.

Therefore, how to reduce the influence on the size and hydraulic efficiency of the pump on the basis of meeting the heating requirement of the pump becomes a technical problem which needs to be solved urgently by the technical personnel in the field.

Disclosure of Invention

The invention aims to provide a pump with a heating function, which has a simple and exquisite structure and good heat exchange efficiency and hydraulic efficiency.

In order to achieve the aim, the invention provides a pump with a heating function, which comprises an end cover, an impeller arranged in the end cover and an annular pipe bent into a ring along a plane; a heating wire penetrates through the annular pipe; the annular tube is coiled around the central axis of the impeller and proximate to the inner wall of the end cap; the diameter of the annular pipe is not larger than the rotating diameter of the impeller.

Preferably, an upper cavity flow passage and a lower cavity flow passage which are defined by the inner wall and the impeller are arranged in the end cover; the upper cavity flow channel and the lower cavity flow channel are respectively positioned at two axial sides of the impeller and are communicated along the axial direction of the impeller; the upper cavity flow channel and the lower cavity flow channel are both streamlined; the annular pipe is located at the axial communication position of the upper cavity flow passage and the lower cavity flow passage.

Preferably, a straight pipe is connected to the opening of the annular pipe; the straight pipe penetrates through and is fixedly connected with the end cover in a sealing mode.

Preferably, the end cover is provided with a flat head connecting hole and a sealing cover for plugging the flat head connecting hole; the straight pipe and the pressure switch are integrally arranged in the flat joint connecting hole; the pressure switch is electrically connected with the wiring terminal of the heating wire.

Preferably, the end cap is in particular a flame retardant end cap.

Preferably, the straight pipes include a straight pipe I and a straight pipe II extending from the ring opening to a radially outer side of the ring pipe; the sealing cover is provided with mounting holes for the straight pipe I and the straight pipe II to respectively penetrate through; and a positioning bulge is arranged on the inner hole wall of the mounting hole.

Preferably, the end cover is provided with an end cover clamping interface used for being mutually clamped and fixed with the motor shell; the end cover clamping interface is used for a rotating shaft of a power supply machine to penetrate into the impeller.

Preferably, the end cover clamping interface is provided with a buckle matched with the buckle groove of the motor shell and a plurality of rotary buckles in one-to-one corresponding buckling connection with all the rotary buckle grooves of the motor shell; the buckle is clamped and embedded in the buckle groove when all the rotary buckles buckle fasten all the rotary buckle grooves, and the buckle is used for being matched with the buckle groove in a locking mode along the rotary installation direction of the rotary buckles and the rotary buckle grooves;

any one of the turnbuckles comprises an inlet end and an outlet end which are used for being rotationally buckled in the turnbuckle groove in sequence, and the height of the inlet end is smaller than that of the outlet end; the surfaces of both the inlet end and the outlet end are smoothly transitioned.

Preferably, the matching position of the rotating shaft and the shaft hole of the end cover clamping interface is provided with a mechanical sealing element with a dynamic ring and a static ring.

Preferably, the annular tube is located on the water outlet side of the impeller; the front cover plate of the impeller is tubular; the inner wall is provided with a limiting ring groove surrounding the inlet of the end cover; the front cover plate is nested in the limiting ring groove.

Against the above background, the present invention provides a pump with a heating function, which includes an end cap, an impeller provided in the end cap, and an annular tube bent in a ring along a plane. In the pump with the heating function, a heating wire is arranged in the annular pipe in a penetrating way; the annular tube is coiled around the central axis of the impeller and adjacent to the inner wall of the end cover; the diameter of the annular pipe is not larger than the rotating diameter of the impeller.

The pump adopts a ring-shaped pipe with a plane ring-shaped structure and a heating wire thereof to heat the fluid in the end cover. Based on the relative position relation among the end cover, the impeller and the annular tube, the annular tube and the heating wires thereof can fully and effectively heat fluid in the end cover, and the heat exchange efficiency is improved. The annular pipe has rationally utilized the space between end cover and the impeller, on satisfying aforementioned heat exchange efficiency's basis, neither can cause the obvious increase of size of end cover, also is convenient for dodge other spare parts in the end cover, easily installs, and the whole size and the outward appearance shape of convenient control pump do not influence hydraulic efficiency yet.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a pump with a heating function according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a pump having a heating function provided in accordance with an embodiment of the present invention;

FIG. 3 is a partial schematic diagram of a pump with heating function at a ring tube and a pressure switch according to an embodiment of the present invention;

fig. 4 is a partial cross-sectional view of a pump with heating function provided by an embodiment of the present invention.

The device comprises a motor shell, a 20-impeller, a 30-end cover, a 50-pressure switch, a 70-mechanical sealing element, a 101-rotating shaft, a 201-front cover plate, a 202-blade, a 203-rear cover plate, a 301-inlet, a 302-outlet, a 303-flat head connecting hole, a 304-turn buckle, a 305-buckle, a 306-limit ring groove, a 310-upper cavity flow channel, a 320-lower cavity flow channel, a 400-positioning bulge, a 401-sealing plug, a 402-sealing shell, a 403-sheet metal part, a 405-first connecting terminal, a 406-second connecting terminal, a 407-fuse, a 408-straight pipe I, a 409-straight pipe II, a 411-annular pipe and a 412-heating wire.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1 to 4, fig. 1 is a schematic structural diagram of a pump with a heating function according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of a pump having a heating function provided in accordance with an embodiment of the present invention; FIG. 3 is a partial schematic diagram of a pump with heating function at a ring tube and a pressure switch according to an embodiment of the present invention; fig. 4 is a partial cross-sectional view of a pump with heating function provided by an embodiment of the present invention.

The invention provides a pump with a heating function, which comprises an end cover 30, an impeller 20 arranged in the end cover 30 and a ring-shaped pipe 411 arranged in the end cover 30; wherein, the annular pipe 411 is bent into a ring along a plane, and the shape of the annular pipe 411 can be circular ring or non-circular ring; a heating wire 412 is inserted into the annular pipe 411. Fluid enters from an inlet 301 of the end cover 30, is heated by the rotating work of the impeller 20 and the annular pipe 411, and then flows out from an outlet 302 of the end cover 30.

In this pump with heating function, the annular tube 411 is coiled in close proximity to the inner wall of the end cap 30, that is, at the plane of the annular tube 411, the cross-sectional shape of the inner wall of the end cap 30 is a ring shape surrounding the outer periphery of the annular tube 411, and the distance between the inner wall of the end cap 30 and the annular tube 411 is small, for example, the distance from the annular tube 411 to the inner wall is far smaller than the distance from the annular tube 411 to the center of the end cap 30.

Further, the ring pipe 411 is distributed around the center axis of the impeller 20, and the ring diameter of the ring pipe 411 is not larger than the rotation diameter of the impeller 20. The rotation diameter refers to the diameter of the area surrounded by the outer edges of all the blades 202 in the impeller 20, so that all the blades 202 of the impeller 20 are surrounded on the central shaft of the impeller 20; the annular tube 411 and all the blades 202 of the impeller 20 are spaced apart in the axial direction of the impeller 20. Depending on the working characteristics of the impeller 20 on the fluid in the end cover 30 and the flow direction of the fluid, the two sides of all the blades 202 can be regarded as the water inlet side and the water outlet side of the impeller 20, respectively, when viewed along the axial direction of the impeller 20. In the pump with the heating function, the ring pipe 411 may be disposed on the water inlet side of the impeller 20, or may be disposed on the water outlet side of the impeller 20, specifically, depending on the installation space in the end cap 30.

The pump provided by the present invention heats the fluid in the cap 30 using the ring pipe 411 having a planar ring structure and its heating wire 412. On one hand, the installation position of the ring pipe 411 and the heating wire 412 thereof on the end cover 30 conforms to the flow characteristic of the fluid in the end cover 30 under the action of the impeller 20, in other words, based on the relative position relationship among the end cover 30, the impeller 20 and the ring pipe 411, the flow channel of the fluid in the end cover 30 is cut by the plane of the ring pipe 411, and then the shape of the ring pipe 411 and the cross-sectional shape of the fluid are completely or mostly overlapped, so that the ring pipe 411 and the heating wire 412 thereof fully and effectively exert the heating action on the fluid in the end cover 30, and the heat exchange efficiency is improved. On the other hand, the annular tube 411 reasonably utilizes the gap between the end cover 30 and the impeller 20, so that on the basis of meeting the heat exchange efficiency, the radial size of the end cover 30 is not increased, the axial size of the end cover 30 is not obviously increased, and the overall size, the appearance shape and the hydraulic efficiency of the pump are favorably controlled.

In conclusion, the pump with the heating function has the advantages of high integration level, regular shape, small size, high heat exchange efficiency, high water conservancy efficiency and the like on the basis of meeting the heating function.

The pump with heating function provided by the present invention will be further described with reference to the accompanying drawings and embodiments.

In the pump having the heating function, a cavity in which fluid can flow is provided in the head cover 30, and the cavity is divided into an upper cavity flow passage 310 and a lower cavity flow passage 320, which are located on both sides of the impeller 20 in the axial direction, with the impeller 20 as a boundary. The upper chamber flow channel 310 and the lower chamber flow channel 320 are in communication with each other in the axial direction of the impeller 20, and when viewed from the orientation shown in fig. 1, the axial direction of the impeller 20 is vertically distributed, the upper chamber flow channel 310 is located above all the blades 202 of the impeller 20, the lower chamber flow channel 320 is located below all the blades 202 of the impeller 20, and the upper chamber and the lower chamber flow in the vertical direction in fig. 1. The annular tube 411 is disposed at the axial communication position between the upper chamber flow channel 310 and the lower chamber flow channel 320.

In the above embodiment, the upper chamber flow channel 310 and the lower chamber flow channel 320 are both streamlined and connected with each other in a smooth trend, which is beneficial to improving the hydraulic efficiency and the flow capacity of the pump with heating function, and ensures that the fluid can fully contact the annular tube 411 at a high speed after rotating and acting by the impeller 20, thereby improving the heat exchange efficiency.

In the pump with the heating function, the annular pipe 411 can penetrate through the end cover 30 through a straight pipe, so that the heating wire 412 in the annular pipe 411 is connected with an external power supply. The straight tube can be connected to the ring opening of the ring tube 411, and the lumen in the straight tube is communicated with the lumen in the ring tube 411, for example, the ring tube 411 is circular and has a ring opening, and the ring opening is connected with two straight tubes, so the shape of the combined structure of the ring tube 411 and the straight tubes is similar to the outline shape of a microphone or the capital greek letter omega. In the embodiment of the present invention, the straight pipe is often in the same plane as the annular pipe 411.

Compared with the annular pipe 411, the straight pipe is short in length, so that the end cover 30 can be conveniently penetrated and connected in a sealing manner; the heating wire 412 is not provided in the straight pipe, and only an electric wire connected to the heating wire 412 in the loop pipe 411 is provided, so that an external power source is introduced into the pump having the heating function.

Further, in the pump with the heating function, the end cap 30 is further provided with a flat head connection hole 303, a sealing cover mounted in the flat head connection hole 303, and a pressure switch 50. The flat head connecting hole 303 is communicated with the inside and the outside of the end cover 30, the straight pipe and the pressure switch 50 are both arranged in the flat head connecting hole 303, and the sealing cover is used for plugging the gaps among the flat head connecting hole 303, the straight pipe and the pressure switch 50, so that the straight pipe and the pressure switch 50 are sealed and fixed in the flat head connecting hole 303. The pressure switch 50 may be electrically connected to a terminal of the heating wire 412, so as to control the on/off of a circuit between the terminal and an external power source based on a pressure detection result of the pressure switch 50, and the fuse 407 may be specifically disposed at a connection position of the straight pipe and the circular pipe 411. The sealing cover comprises a sealing plug 401, a sealing shell 402 and a sheet metal part 403, and the sheet metal part 403 can be welded and fixed with the straight pipe.

Further, the end cap 30 is embodied as a flame retardant end cap. In this case, the pump with heating function has triple safety measures, the first is the pressure switch 50, the second is the fuse 407, and the third is the flame-retardant end cap. The pressure switch 50 and the fuse 407 can effectively ensure the operation safety of the annular pipe 411 and the heating wire 412 thereof in the heating process, and the flame-retardant end cover is beneficial to ensuring the service performance of the pump in related products. For example, when the end cap 30 is starved of water, the pressure in the end cap 30 drops, and the pressure switch 50 detects the pressure signal and controls the heating wire 412 to open and close. When the pressure switch 50 fails, the fuse 407 is protected.

In order to improve the structural installation performance of the pump with the heating function, the straight pipes comprise a straight pipe I408 and a straight pipe II409, and the straight pipe I408 and the straight pipe II409 respectively extend from the ring opening of the annular pipe 411 to the radial outer side of the annular pipe 411. Because the straight pipes I408 and II409 are both arranged in the flat head connecting hole 303 in a penetrating way, the sealing cover is correspondingly provided with mounting holes through which the straight pipes I408 and II409 can respectively penetrate. By utilizing the matching relationship between the straight pipe I408 and the straight pipe II409 and the two mounting holes, the mounting strength, the mounting angle and the sealing performance of the annular pipe 411 in the end cover 30 can be effectively maintained. Wherein, the one end that the straight tube is kept away from toroidal tube 411 is equipped with binding post, for example, straight tube I one end outwards is equipped with first binding post 405, and straight tube II409 one end outwards is equipped with second binding post 406.

In particular, the straight tube I408 and the straight tube II409 may be arranged in parallel, and both are located on the same plane with the annular tube 411. At this time, the shape of the combined structure of the straight pipe and the annular pipe 411 is as shown in fig. 1 and fig. 3, the structure is compact, the appearance is exquisite and simple, the integrated installation of the pressure switch 50 and the straight pipe is facilitated, the installation space occupied by the straight pipe in the flat head connection hole 303 can be reduced, and the risk of fluid leakage at the flat head connection hole 303 is reduced.

In addition, in the above embodiment, the inner hole wall of the mounting hole may be provided with a positioning protrusion 400 protruding towards the inside of the mounting hole, and the positioning protrusion 400 is used for clamping the straight pipe, so as to improve the positioning strength of the straight pipe in the axial direction of the mounting hole. The positioning protrusion 400 may be an annular protrusion coaxial with the mounting hole, or may be one or more dot-shaped protrusions. Particularly, when the positioning protrusion 400 is configured as an annular protrusion, the positioning protrusion 400 not only can play a role in positioning, but also can improve the sealing connection effect of the straight pipe and the mounting hole, thereby preventing leakage.

In addition to improving the structural mountability of the pump with heating function based on the straight pipe and its assembly relationship, the shape configuration of the end cap may be adjusted to improve the structural mountability of the pump with heating function.

For example, the end cap 30 has an end cap clip interface, which is used to clip and fix the motor housing 10, for example, the end cap clip interface of the end cap 30 and the motor clip interface of the motor housing 10 are coaxially aligned and spliced, thereby realizing the combined assembly of the pump and the motor; on the other hand, the end cover clamping interface can be used for the rotating shaft 101 of the motor to penetrate, so that the rotating shaft 101 is connected to the impeller 20 of the pump, and the motor drives the impeller 20 to rotate.

In the above example, the end cap 30 and the parts inside the end cap, such as the impeller 20, the annular tube 411, the straight tube, and the pressure switch 50, are separately assembled to form a pump, the motor housing 10 and the rest of the parts of the motor can be separately assembled to form a motor, and finally, the pump and the motor are combined and installed.

A specific snap-fit attachment of the motor 10 and pump is provided below.

The motor casing 10 is provided with an interface I at one side of the rotating shaft 101 penetrating out of the motor casing 10, the end cover 30 is provided with an interface II, and the motor casing 10 and the end cover 30 are fixedly connected at an angle of aligning and inserting the interface I and the interface II.

Interface I is equipped with buckle groove and a plurality of spiral shell knot groove, and interface II is equipped with buckle 305 and a plurality of spiral shell knot 304. When the interface I and the interface II are aligned and spliced, all the turnbuckles 304 are screwed in and fastened to all the turnbuckle grooves in a one-to-one correspondence manner, and meanwhile, the buckles 305 are inserted into the buckle grooves and used for preventing the turnbuckles 304 and the turnbuckle grooves from generating relative movement in the rotating installation direction, so that the fixed connection strength of the interface I and the interface II is further improved. It can be seen that the motor casing 10 and the end cap 30 can be installed quickly and accurately through the interface I and the interface II.

The above-mentioned assembling relationship between the snap 305 and the snap groove can be realized based on the elasticity of the snap 305, for example, the snap 305 can elastically deform in the axial direction of the interface I and the interface II, so as to meet the assembling requirements of the turnbuckle 304 and the turnbuckle groove, and can also play a role in stopping the turnbuckle 304 and the turnbuckle groove.

In addition, any one of the turnbuckles 304 includes an inlet end, which refers to the end that is first screwed into the turnbuckle slot, and an outlet end, which refers to the end that is last screwed into the turnbuckle slot. To facilitate assembly, the height of the inlet end is less than the height of the outlet end, and the surfaces of both the inlet end and the outlet end are smoothly transitioned. In short, the first end of the turnbuckle 304 entering the turnbuckle slot has a smaller size, so that the turnbuckle 304 is easily guided to be inserted into the turnbuckle slot.

Wherein the height of the inlet end and the outlet end refers to the dimension of the turnbuckle 304 in the up-down direction shown in fig. 2.

Further, the pump with heating function further includes a mechanical seal 70 to be disposed between the rotating shaft 101 and the end cap 30. The mechanical seal 70 includes a dynamic ring and a static ring, the dynamic ring and the static ring are sleeved on the rotating shaft 101 and are installed at the shaft hole matching position of the rotating shaft 101 and the end cover 30, so as to ensure the rotation flexibility of the rotating shaft 101 relative to the end cover 30 and ensure the sealing performance of the end cover 30.

The present invention further provides a specific embodiment, which comprises a limiting ring groove 306 arranged on the inner wall of the end cover 30, in addition to the above structural features; the impeller 20 comprises a tubular front cover 201, which is coaxially distributed with all the blades 202. The limiting ring groove 306 can be used for the front cover plate 201 of the impeller 20 to be embedded and sleeved; the aforementioned assembled relationship of the retainer ring groove 306 and the front cover plate 201 facilitates reducing fluid backflow losses and improving volumetric efficiency of the pump with heating function.

In the above example, the front cover plate 201 and the rear cover plate 203 of the impeller 20 are both in the shape of a shaft sleeve and are coaxially arranged; the plurality of blades 202 are radially distributed with the center of the back cover plate 203 as the midpoint. It can be seen that the diameter of the back cover plate 203 of the impeller 20 corresponds to the diameter of rotation of the impeller 20.

The pump with heating function provided by the present invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims (10)

1. A pump with a heating function, comprising an end cover (30) and an impeller (20) provided in the end cover (30), characterized by further comprising an annular tube (411) bent in a ring along a plane; a heating wire (412) penetrates through the annular pipe (411); the annular tube (411) is coiled around the central axis of the impeller (20) and in close proximity to the inner wall of the end cap (30); the diameter of the annular pipe (411) is not larger than the rotating diameter of the impeller (20).

2. The pump with heating function according to claim 1, wherein an upper chamber flow passage (310) and a lower chamber flow passage (320) defined by the inner wall and the impeller (20) are provided in the end cap (30); the upper cavity flow passage (310) and the lower cavity flow passage (320) are respectively positioned at two axial sides of the impeller (20) and are communicated along the axial direction of the impeller (20); the upper cavity flow channel (310) and the lower cavity flow channel (320) are both streamlined; the annular tube (411) is in axial communication with the upper chamber flow channel (310) and the lower chamber flow channel (320).

3. The pump with heating function according to claim 1, wherein a straight pipe is connected to the ring opening of the ring-shaped pipe (411); the straight pipe penetrates through and is fixedly connected with the end cover (30) in a sealing manner.

4. The pump with heating function according to claim 3, wherein the end cap (30) is provided with a flat head connection hole (303) and a sealing cover for sealing the flat head connection hole (303); the straight pipe and the pressure switch (50) are integrally arranged in the flat head connecting hole (303); the pressure switch (50) is electrically connected with the connection terminal of the heating wire (412).

5. Pump with heating function according to claim 4, characterized in that the end cap (30) is in particular a flame-retardant end cap.

6. The pump with heating function according to claim 3, wherein the straight tube includes a straight tube I (408) and a straight tube II (409) extending from the ring opening to a radially outer side of the annular tube (411); the sealing cover is provided with mounting holes for the straight pipe I (408) and the straight pipe II (409) to respectively penetrate through; and a positioning bulge (400) is arranged on the inner hole wall of the mounting hole.

7. The pump with the heating function according to any one of claims 1 to 6, wherein the end cover is provided with an end cover clamping interface for mutually clamping and fixing with the motor shell (10); the end cover clamping interface is used for a rotating shaft (101) of a power supply machine to penetrate through so as to be connected to the impeller (20).

8. The pump with the heating function according to claim 7, wherein the end cover clamping interface is provided with a clamping buckle (305) used for being matched with the clamping buckle groove of the motor casing (10) and a plurality of rotary buckles (304) which are correspondingly buckled and connected with all the rotary buckle grooves of the motor casing (10) one by one; the buckle (305) is clamped and embedded in the buckle groove when all the rotary buckles (304) buckle all the rotary buckle grooves, and the buckle (305) is in stop fit with the buckle groove along the rotary installation direction of the rotary buckles (304) and the rotary buckle grooves;

any one of the turnbuckles (304) comprises an inlet end and an outlet end which are sequentially and rotatably buckled in the turnbuckle groove, and the height of the inlet end is smaller than that of the outlet end; the surfaces of both the inlet end and the outlet end are smoothly transitioned.

9. The pump with the heating function as claimed in claim 7, wherein a mechanical sealing element (70) with a dynamic ring and a static ring is arranged at the matching position of the rotating shaft (101) and the shaft hole of the end cover clamping interface (30).

10. Pump with heating function according to any of claims 1 to 6, characterized in that said annular duct (411) is located on the outlet side of said impeller (20); the front cover plate (201) of the impeller (20) is tubular; the inner wall is provided with a limiting ring groove (306) surrounding an inlet (301) of the end cover (30); the front cover plate (201) is nested in the limiting ring groove (306).

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