Water inlet connecting structure for medium-lift multi-stage pump and medium-lift multi-stage pump

Abstract

The utility model relates to the field of submersible multi-stage pumps, in particular to a water inlet connecting structure for a medium-lift multi-stage pump and the medium-lift multi-stage pump. The water inlet connecting structure for the medium-lift multi-stage pump comprises a connecting support and a water inlet pipe, wherein the connecting support comprises an outer ring and an inner ring; the outer ring comprises a mounting part, a fixing part and a connecting part; sealing rings are arranged between the mounting part and the outer cover and between the mounting part and the base; a reinforcing plate is formed on the connecting part; bolt holes which are fixedly connected with the lower bearing seat and the guide vane are formed in the inner ring; the lower pump cover comprises a main body fixedly connected with the fixing part, an inner cylinder and a connecting rod; and the middle section is hermetically connected with the fixed part and the main body. According to the water inlet connecting structure for the medium-lift multi-stage pump, an original water inlet section structure is replaced by the connecting support, the middle section and the lower pump cover, the water inlet connecting structure is arranged in a split mode, the structure is simple, the design and manufacturing difficulty is low, and the function of an original water inlet section can be achieved.

Description

Technical Field

[0001] The utility model relates to the field of submersible multistage pumps, in particular to a water inlet connection structure for a medium-lift multistage pump and the medium-lift multistage pump. Background Art

[0002] A multistage submersible pump is a centrifugal pump that can be driven underwater by an electric motor. Depending on the number of impellers, multistage submersible pumps can be divided into low-lift multistage pumps, medium-lift multistage pumps, and high-lift multistage pumps.

[0003] Chinese invention patent application publication number CN108194372A discloses an amphibious vertical sand removal pump. This vertical sand removal pump comprises a cylindrical pump body with a water inlet at the bottom and a water outlet at the top. The pump body is sequentially equipped with a top cover, an upper bearing seat, a middle bearing seat, a lower bearing seat, and a base. An axial-flow impeller is mounted on the end of the rotating shaft of the pump motor. An overflow pipe connected to a water inlet section is located inside the water inlet. However, the pump body and base of this sand removal pump are connected by a water inlet section, a complex, integrated structure that is difficult to design and manufacture.

[0004] Therefore, this field needs a new technical solution to solve the above problems. Summary of the Invention

[0005] In order to improve or solve the technical problem in the prior art that the water inlet section is an integrated structure with a complex structure and great difficulty in design and manufacturing, the utility model provides a water inlet connection structure for a medium-lift multi-stage pump. The water inlet connection structure for a medium-lift multi-stage pump comprises: a connecting bracket, comprising an outer ring, and an inner ring fixedly connected to the outer ring; the outer ring comprises a mounting portion suitable for fixing between the outer cover and the base of the pump body, a fixing portion arranged side by side with the mounting portion, and a connecting portion connecting the mounting portion and the fixing portion; a sealing ring is arranged between the mounting portion and the outer cover and the base; a reinforcing plate suitable for abutting against the base is formed on the connecting portion; bolt holes suitable for forming a fixed connection with the lower bearing seat and the guide vane are opened on the inner ring; a lower pump cover comprises a main body fixedly connected to the fixing portion, an inner cylinder suitable for being sleeved on the circumferential outer side of the impeller, and a connecting rod connecting the main body and the inner cylinder; a middle section is arranged between the fixing portion and the main body and forms a sealed connection with both the fixing portion and the main body.

[0006] The water inlet connection structure for a medium-lift multistage pump comprises a connecting bracket, a lower pump cover, and a middle section. The connecting bracket comprises an outer ring and an inner ring. The outer ring's mounting portion forms a sealed, fixed connection with the pump body, securing the connecting bracket to the pump body. Sealing rings are positioned between the mounting portion, the outer cover, and the base to ensure a tight seal between the outer ring and the pump body. The outer ring's fixing portion forms a fixed connection with the main body of the lower pump cover, securing the lower pump cover. The middle section is secured between the connecting bracket and the lower pump cover, facilitating the installation of the impeller and guide vanes. A reinforcing plate abuts the base, further enhancing the stability of the connection between the connecting bracket and the pump body. Bolt holes are provided on the inner ring for securing the lower bearing seat and guide vanes, respectively, facilitating their installation. With the above arrangement, the water inlet connection structure for a medium-lift multistage pump replaces the existing water inlet joint structure with the connecting bracket, middle section, and lower pump cover. This separate arrangement offers a simple structure, reduced design and manufacturing complexity, and still performs the functions of the existing water inlet joint.

[0007] Furthermore, a limiting ring suitable for abutting against the outer cover is formed on the mounting portion.

[0008] Furthermore, a limiting groove for accommodating a sealing ring is provided on the circumferential inner wall of the fixing portion, and a receiving groove for accommodating a sealing ring is provided on the circumferential inner wall of the middle section; the middle section, the fixing portion and the main body are sealed together through the sealing ring.

[0009] Furthermore, the inner ring includes a first connecting ring suitable for forming a fixed connection with the lower bearing seat, a second connecting ring suitable for forming a fixed connection with the guide vane, and a connecting tube connecting the first connecting ring and the second connecting ring; the first connecting ring and the second connecting ring extend from the connecting tube toward the center line direction of the inner ring.

[0010] Furthermore, connecting pieces are provided between the inner ring and the outer ring to connect the two and are arranged evenly and spaced apart along the circumference of the connecting bracket; some of the connecting pieces are provided with through holes passing through the connecting pieces, and through holes matching the through holes are provided on the connecting tube and the connecting portion.

[0011] Furthermore, a mounting groove for accommodating a sealing ring is provided on one end of the first connecting ring close to the lower bearing seat.

[0012] Furthermore, a receiving groove for accommodating a sealing ring is provided on the circumferential inner wall of the inner cylinder.

[0013] In order to improve or solve the technical problem in the prior art that the water inlet section is an integrated structure with a complex structure and great difficulty in design and manufacturing, the utility model provides a medium-lift multi-stage pump. The medium-lift multi-stage pump comprises a pump body, including an outer cover and a base fixedly connected to the outer cover; a lower bearing seat installed in the pump body; an impeller rotatably installed in the pump body; and a guide vane installed in the pump body. The water inlet connection structure for a medium-lift multi-stage pump described in any of the above items, wherein the mounting portion of the water inlet connection structure forms a sealed fixed connection with the pump body, the reinforcing plate of the water inlet connection structure abuts against the inner circumferential wall of the base, the inner ring of the water inlet connection structure forms a sealed fixed connection with the lower bearing seat and the guide vane, and the main body of the water inlet connection structure abuts against the bottom of the guide vane.

[0014] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The connecting bracket includes an outer ring and an inner ring. The mounting portion of the outer ring forms a sealed fixed connection with the pump body, which is used to fix the connecting bracket on the pump body; a sealing ring is arranged between the mounting portion and the outer cover and the base to ensure the sealing performance between the outer ring and the pump body; the fixing portion of the outer ring forms a fixed connection with the main body of the lower pump cover, which is used to install the lower pump cover and fix the middle section between the connecting bracket and the lower pump cover so as to install the fixed impeller and guide vanes; the reinforcing plate is against the base to further enhance the connection stability between the connecting bracket and the pump body. Bolt holes are provided on the inner ring to form fixed connections with the lower bearing seat and the guide vanes respectively, which facilitates the installation of the lower bearing seat and the guide vanes; the original water inlet section structure is replaced by the connecting bracket, the middle section and the lower pump cover, which are arranged separately, have a simple structure, are easy to design and manufacture, and can realize the function of the original water inlet section.

[0016] (2) The first connecting ring and the second connecting ring extend from the connecting tube toward the center line of the inner ring, which can reduce the material used for the inner ring and reduce the weight of the inner ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0018] Figure 1 It is a schematic diagram of an embodiment of a medium-lift multi-stage pump of the present utility model;

[0019] Figure 2 This is a top view of the connecting bracket in the medium-lift multi-stage pump of the utility model;

[0020] Figure 3 This is a cross-sectional view of a connecting bracket in a medium-lift multi-stage pump of the present invention;

[0021] Figure 4 This is a bottom view of the connecting bracket in the medium-lift multi-stage pump of the utility model;

[0022] Figure 5 This is a top view of the lower pump cover of the medium-lift multi-stage pump of the utility model;

[0023] Figure 6 It is a cross-sectional view of the lower pump cover of the medium-lift multi-stage pump of the utility model.

[0024] List of reference numerals: 1. water inlet connection structure; 11. connecting bracket; 111. outer ring; 1111. mounting portion; 1112. fixing portion; 1113. connecting portion; 1114. reinforcing plate; 1115. limiting ring; 1116. limiting groove; 112. inner ring; 1121. first connecting ring; 1122. second connecting ring; 1123. connecting cylinder; 1124. mounting groove; 1125. reinforcing rib; 113. connecting piece; 1131. through hole; 12. lower pump cover; 121. main body; 122. Inner cylinder; 123, connecting rod; 124, storage groove; 13, middle section; 2, pump body; 21, outer cover; 22, base; 3, motor assembly; 31, motor housing; 32, stator; 33, rotor; 34, rotating shaft; 35, outlet structure; 351, outlet box; 352, cable gland; 353, cable pressure plate; 36, upper bearing seat; 361, terminal; 362, deep groove ball bearing; 4, guide vane; 5, impeller; 6, lower bearing seat; 61, angular contact ball bearing; 62, mechanical seal; 63, sealing chamber cover. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] It should be noted that in the description of this utility model, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the device or component described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, it should not be understood as limiting the utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance.

[0027] Furthermore, it should be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "installed," "set," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0028] In order to improve or solve the technical problems in the prior art that the water inlet section is an integrated structure, has a complex structure, and is difficult to design and manufacture, the present invention provides a water inlet connection structure for a medium-lift multi-stage pump. The water inlet connection structure for a medium-lift multi-stage pump comprises: a connecting bracket 11, comprising an outer ring 111, and an inner ring 112 fixedly connected to the outer ring 111; the outer ring 111 comprises a mounting portion 1111 suitable for fixing between the outer cover 21 and the base 22 of the pump body 2, a fixing portion 1112 arranged side by side with the mounting portion 1111, and a connecting portion 1113 connecting the mounting portion 1111 and the fixing portion 1112; sealing rings are arranged between the mounting portion 1111 and the outer cover 21 and the base 22; and sealing rings are arranged at the connecting portion 1113. A reinforcing plate 1114 is formed on it, which is suitable for abutting against the base 22; bolt holes are opened on the inner ring 112, which are suitable for forming a fixed connection with the lower bearing seat 6 and the guide vane 4 respectively; the lower pump cover 12 includes a main body 121 fixedly connected to the fixing part 1112, an inner cylinder 122 suitable for being sleeved on the circumferential outside of the impeller 5, and a connecting rod 123 connecting the main body 121 and the inner cylinder 122; the middle section 13 is arranged between the fixing part 1112 and the main body 121, and forms a sealing connection with both the fixing part 1112 and the main body 121.

[0029] Figure 1 This is a schematic diagram of an embodiment of a multi-stage pump with a medium lift in the present invention. Figure 1 As shown, in one or more embodiments, the water inlet connection structure of the medium-lift multi-stage pump of the present invention includes a connecting bracket 11, a lower pump cover 12 and a middle section 13.

[0030] Figure 2 This is a top view of the connecting bracket in the medium-lift multi-stage pump of the utility model. Figure 3 This is a cross-sectional view of the connecting bracket in the medium-lift multi-stage pump of the utility model. Figure 4 This is a bottom view of the connecting bracket in the medium-lift multi-stage pump of the utility model. Figure 2 、 Figure 3 and Figure 4As shown, the connecting bracket 11 includes an outer ring 111, an inner ring 112, and a connector 113 connecting the inner ring 112 and the outer ring 111. The outer ring 111 is adapted to form a fixed connection with the pump body 2, and the inner ring 112 is adapted to form a fixed connection with the lower bearing seat 6 and the guide vane 4. In one or more embodiments, the outer ring 111 includes a mounting portion 1111 adapted to be fixed between the outer cover 21 and the base 22 of the pump body 2, a fixing portion 1112 arranged side by side with the mounting portion 1111, and a connecting portion 1113 connecting the mounting portion 1111 and the fixing portion 1112. Specifically, the mounting portion 1111 is generally annular and has a plurality of bolt holes arranged evenly and spaced apart along the circumference of the mounting portion 1111. The mounting portion 1111, the outer cover 21, and the base 22 are fixedly connected by bolts. Exemplarily, there are twelve bolt holes. Furthermore, a limiting ring 1115 suitable for abutting against the outer cover 21 is formed on the mounting portion 1111. A sealing ring is provided between the outer circumferential wall of the limiting ring 1115 and the inner circumferential wall of the outer cover 21. Furthermore, a sealing ring is provided between the mounting portion 1111 and the base 22, and the sealing ring is installed on the base 22. Furthermore, the fixing portion 1112 is roughly annular, and the diameter of the fixing portion 1112 is smaller than the diameter of the mounting portion 1111. Specifically, a bolt hole is provided on the fixing portion 1112, and the fixing portion 1112 is fixedly connected to the lower pump cover 12 by bolts. Furthermore, a limiting groove 1116 for accommodating the sealing ring is provided on the circumferential inner wall of the fixing portion 1112, so that the fixing portion 1112 forms a sealed connection with the middle section 13. Further, the connecting portion 1113 connects the fixing portion 1112 and the mounting portion 1111, and the connecting portion 1113 is roughly cylindrical. A reinforcing plate 1114 is provided on the circumferential outer side of the connecting portion 1113. One end of the reinforcing plate 1114, which is away from the connecting portion 1113, abuts against the circumferential inner wall of the base 22. Specifically, a plurality of reinforcing plates 1114 are evenly and spaced apart along the circumference of the connecting portion 1113. For example, four reinforcing plates 1114 are provided.

[0031] Continue to see Figure 2 、 Figure 3 and Figure 4, the connecting piece 113 connects the inner ring 112 and the outer ring 111. In one or more embodiments, the connecting pieces 113 are evenly and spaced apart along the circumference of the connecting bracket 11. Exemplarily, eight connecting pieces 113 are provided. In one or more embodiments, two connecting pieces 113 are provided, one of which is provided with two, the two connecting pieces 113 are arranged opposite to each other, and through holes 1131 passing through the connecting pieces 113 are provided on the two connecting pieces 113. Through holes corresponding to the through holes 1131 are provided on the inner ring 112 and the outer ring 111. Six connecting pieces 113 of another type are provided, and have a smaller diameter. In one or more embodiments, the inner ring 112 includes a first connecting ring 1121 suitable for forming a fixed connection with the lower bearing seat 6, a second connecting ring 1122 suitable for forming a fixed connection with the guide vane 4, and a connecting tube 1123 connecting the first connecting ring 1121 and the second connecting ring 1122. Specifically, the connecting tube 1123 is connected to the connecting member 113, and a first connecting ring 1121 and a second connecting ring 1122 are respectively disposed at each end of the connecting tube 1123. Bolt holes are provided in both the first connecting ring 1121 and the second connecting ring 1122. The first connecting ring 1121 is fixedly connected to the lower bearing seat 6 via bolts, while the second connecting ring 1122 is fixedly connected to the guide vane 4 via bolts. Furthermore, the first connecting ring 1121 and the second connecting ring 1122 extend from the connecting tube 1123 toward the centerline of the inner ring 112. A mounting step is formed at the top of the first connecting ring 1121, protruding from the first connecting ring 1121. Furthermore, a mounting groove 1124 for accommodating a sealing ring is provided on the end of the first connecting ring 1121 proximal to the lower bearing seat 6. Specifically, the mounting groove 1124 is formed on the circumferential inner wall of the mounting step. The first connecting ring 1121 is sealed to the lower bearing seat 6 via the sealing ring. Furthermore, a reinforcing rib 1125 is provided between the first connecting ring 1121 and the second connecting ring 1122, and the reinforcing rib 1125 forms a fixed connection with the first connecting ring 1121, the second connecting ring 1122, and the connecting tube 1123. Exemplarily, four reinforcing ribs 1125 are provided and are evenly and spaced apart along the circumference of the connecting tube 1123.

[0032] Figure 5 This is a top view of the lower pump cover of the medium-lift multi-stage pump of the utility model. Figure 6 This is a cross-sectional view of the lower pump cover of the medium-lift multistage pump of the utility model. Figure 1 、 Figure 5 and Figure 6As shown, in one or more embodiments, the lower pump cover 12 includes a main body 121 fixedly connected to the fixing portion 1112, an inner cylinder 122 sleeved on the circumferential outer side of the impeller 5, and a connecting rod 123 connecting the main body 121 and the inner cylinder 122. Specifically, a receiving groove 124 for accommodating a sealing ring is provided on the circumferential inner wall of the inner cylinder 122. The inner cylinder 122 is connected to the impeller 5 through a sealing ring. Furthermore, the middle section 13 is arranged between the fixing portion 1112 and the main body 121, and a receiving groove for accommodating a sealing ring is provided on the circumferential inner wall of the middle section 13. The middle section 13, the lower pump cover 12, and the connecting bracket 11 are sealed together by the sealing ring.

[0033] In order to improve or solve the technical problems in the prior art that the water inlet section is an integrated structure, has a complex structure, and is difficult to design and manufacture, the present invention provides a medium-lift multistage pump. The medium-lift multistage pump comprises: a pump body 2, including an outer cover 21 and a base 22 fixedly connected to the outer cover 21; a lower bearing seat 6 installed in the pump body 2; an impeller 5 rotatably installed in the pump body 2; and a guide vane 4 installed in the pump body 2. The water inlet connection structure 1 for the medium-lift multistage pump comprises: a mounting portion 1111 of the water inlet connection structure 1 forms a sealed fixed connection with the pump body 2, a reinforcing plate 1114 of the water inlet connection structure 1 abuts against the inner circumferential wall of the base 22, an inner ring 112 of the water inlet connection structure 1 forms a sealed fixed connection with the lower bearing seat 6 and the guide vane 4, and a main body 121 of the water inlet connection structure 1 abuts against the bottom of the guide vane 4.

[0034] See also Figure 1 In one or more embodiments, the medium-lift multi-stage pump of the present invention includes a pump body 2, a motor assembly 3, a water inlet connection structure 1, a lower bearing seat 6, a guide vane 4 and an impeller 5. The water inlet connection structure 1 replaces the original water inlet section.

[0035] Continue to see Figure 1 In one or more embodiments, the pump body 2 includes an outer cover 21 and a base 22 detachably connected to the outer cover 21. A drain port is provided on the outer cover 21 and is located at the top of the outer cover 21. Furthermore, a through hole is provided at the top of the outer cover 21 for extending a cable.

[0036] Continue to see Figure 1In one or more embodiments, the motor assembly 3 includes a motor housing 31 fixedly connected to the pump body 2, a stator 32 installed in the motor housing 31, a rotor 33 installed in the motor housing 31, a rotating shaft 34 rotatably installed in the motor housing 31, and an outlet structure 35 connected to the motor housing 31 and the pump body 2. Specifically, the upper end of the motor housing 31 is connected to an upper bearing seat 36, and the upper bearing seat 36 is fixedly connected to the motor housing 31 by bolts and spring washers. A terminal 361 and a deep groove ball bearing 362 are arranged on the upper bearing seat 36, and the deep groove ball bearing 362 is installed in the upper bearing seat 36 by an upper bearing retaining ring. One end of the rotating shaft 34 is rotatably arranged in the deep groove ball bearing 362. Furthermore, the lower end of the motor housing 31 is connected to a lower bearing seat 6, and the lower bearing seat 6 is sealed and fixedly connected to the motor housing 31 by an O-ring and bolts. An angular contact ball bearing 61 is arranged on the lower bearing seat 6 and is mounted within the lower bearing seat 6 via a lower bearing gland. One end of the rotating shaft 34 passes through the angular contact ball bearing 61 and rotates synchronously with the impeller 5 via a keyway structure. Furthermore, a mechanical seal 62 is arranged between the lower bearing seat 6 and the rotating shaft 34. Below the lower bearing seat 6, a sealing chamber cover 63 is arranged to house the mechanical seal 62. The sealing chamber cover 63 is securely connected to the lower bearing seat 6 via an O-ring and bolts. Furthermore, the outlet structure 35 includes an outlet box 351, a cable gland 352 securely connected to the outlet box 351, and a cable pressure plate 353 mounted on the gland 352. Specifically, the outlet box 351 is securely connected to the upper bearing seat 36 via bolts and a sealing ring. The cable gland 352 is securely connected to the outlet box 351 via bolts. The cable pressing plate 353 presses the cable pressing sleeve 352, thereby fixing the cable in the cable pressing sleeve 352. Furthermore, the end of the cable pressing sleeve 352 away from the outlet box 351 is in a trumpet shape.

[0037] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is clearly not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A water inlet connection structure for a medium-lift multistage pump, characterized in that: include: A connecting bracket (11) comprises an outer ring (111) and an inner ring (112) fixedly connected to the outer ring (111); the outer ring (111) comprises a mounting portion (1111) adapted to be fixed between an outer cover (21) and a base (22) of a pump body (2), a fixing portion (1112) arranged side by side with the mounting portion (1111), and a connecting portion (1113) connecting the mounting portion (1111) and the fixing portion (1112); a sealing ring is arranged between the mounting portion (1111) and the outer cover (21) and the base (22); a reinforcing plate (1114) adapted to abut against the base (22) is formed on the connecting portion (1113); and bolt holes adapted to be fixedly connected to the lower bearing seat (6) and the guide vane (4) are provided on the inner ring (112); The lower pump cover (12) comprises a main body (121) fixedly connected to the fixing portion (1112), an inner cylinder (122) adapted to be sleeved on the circumferential outer side of the impeller (5), and a connecting rod (123) connecting the main body (121) and the inner cylinder (122); The middle section (13) is arranged between the fixing portion (1112) and the main body (121), and forms a sealed connection with both the fixing portion (1112) and the main body (121).

2. The water inlet connection structure for a medium-lift multistage pump according to claim 1, characterized in that: A limiting ring (1115) suitable for abutting against the outer cover (21) is formed on the mounting portion (1111).

3. The water inlet connection structure for a medium-lift multistage pump according to claim 2, characterized in that: A limiting groove (1116) for accommodating a sealing ring is provided on the circumferential inner wall of the fixing portion (1112), and a receiving groove for accommodating a sealing ring is provided on the circumferential inner wall of the middle section (13); the middle section (13), the fixing portion (1112), and the main body (121) are sealed together via the sealing ring.

4. The water inlet connection structure for a medium-lift multistage pump according to claim 1, characterized in that: The inner ring (112) includes a first connecting ring (1121) adapted to form a fixed connection with the lower bearing seat (6), a second connecting ring (1122) adapted to form a fixed connection with the guide vane (4), and a connecting tube (1123) connecting the first connecting ring (1121) and the second connecting ring (1122); the first connecting ring (1121) and the second connecting ring (1122) extend from the connecting tube (1123) toward the center line direction of the inner ring (112).

5. The water inlet connection structure for a medium-lift multistage pump according to claim 4, characterized in that: Connecting pieces (113) are provided between the inner ring (112) and the outer ring (111) to connect the two and are arranged uniformly and spaced apart along the circumference of the connecting bracket (11); a portion of the connecting pieces (113) is provided with through holes (1131) passing through the connecting pieces (113), and through holes matching the through holes (1131) are provided on the connecting tube (1123) and the connecting portion (1113).

6. The water inlet connection structure for a medium-lift multistage pump according to claim 4, characterized in that: An installation groove (1124) for accommodating a sealing ring is provided on one end of the first connecting ring (1121) close to the lower bearing seat (6).

7. The water inlet connection structure for a medium-lift multistage pump according to claim 1, characterized in that: A receiving groove (124) for accommodating a sealing ring is provided on the circumferential inner wall of the inner cylinder (122).

8. A medium-lift multistage pump, characterized in that: include: A pump body (2) comprising an outer cover (21) and a base (22) fixedly connected to the outer cover (21); A lower bearing seat (6) is installed in the pump body (2); an impeller (5) rotatably mounted in the pump body (2); a guide vane (4) mounted in the pump body (2); The water inlet connection structure (1) for a medium-lift multistage pump according to any one of claims 1 to 7, wherein the mounting portion (1111) of the water inlet connection structure (1) forms a sealed fixed connection with the pump body (2), the reinforcing plate (1114) of the water inlet connection structure (1) abuts against the inner circumferential wall of the base (22), the inner ring (112) of the water inlet connection structure (1) forms a sealed fixed connection with the lower bearing seat (6) and the guide vane (4), and the main body (121) of the water inlet connection structure (1) abuts against the bottom of the guide vane (4).

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