WO2003069163A1

WO2003069163A1 - Pump casing and pump apparatus

Info

Publication number: WO2003069163A1
Application number: PCT/JP2003/001493
Authority: WO
Inventors: Yoshiaki Miyazaki; Hiroshi Uchida; Kenichi Kajiwara; Yukimasa Nakatsukasa
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2002-02-13
Filing date: 2003-02-13
Publication date: 2003-08-21
Anticipated expiration: 2004-08-13
Also published as: JP2005517860A; AU2003208007A1

Abstract

The present invention relates to a pump casing and a pump apparatus, and more particularly to a pump casing comprising a plurality of plate-like members, and a pump apparatus having such a pump casing. A pump casing (2) comprises at least two plate-like members (3 and 4) formed by press-forming into predetermined shapes, and the at least two plate-like members (3 and 4) are joined together at their circumferential portions by seam welding.

Description

DESCRIPTION

PUMP CASING AND PUMP APPARATUS

Technical Field The present invention relates to a pump casing and a pump apparatus, and more particularly to a pump casing comprising a plurality of plate-like members and a pump apparatus having such a pump casing.

Background Art

Generally, a pump casing constituting a part of a pump apparatus has various shapes and structures depending on the applications of the pump apparatus. For example, there has been known a pump casing, which is used as a part of the pump apparatus for delivering water, comprising a plurality of plate-like members such as sheet metal.

In this type of pump casing, plate-like members are formed into predetermined respective shapes by press-forming, and are then joined together by welding, thus forming a pump casing (i.e. pressed pump casing) .

The plate-like member constituting the pump casing may comprise a stainless steel plate or the like for the purpose of lightweight and reduction in cost. TIG welding (tungsten inert gas arc welding) or MIG welding (metal inert gas welding) is widely used as a welding process for joining the plate-like members pressed by press-forming.

However, in the case where TIG welding or MIG welding process is employed for joining the plate-like members together, such welding process generally requires a long welding time to make the total working time long, and the plate-like members are deformed due to heat generated by welding. Further, in order to prevent such deformation of the plate-like member, the plate-like member for the pump casing is required to be thick to a certain degree. As a result, the pump casing cannot be lightweight.

Disclosure of Invention The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a pump casing which can prevent plate-like members from being deformed at the time of welding by employing a welding process which can reduce the effect of heat on the plate-like members, and can be lightweight and be manufactured in a reduced production time, and to provide a pump apparatus having such a pump casing.

In order to achieve the above object of the present invention, according to a first aspect of the present invention, there is provided a pump casing comprising: at least two plate-like members formed by press-forming into predetermined shapes , the at least two plate-like members being j oined together at their circumferential portions by seam welding.

According to the present invention, because seam welding requires a relatively short welding time, the effect of heat on the plate-like members to be welded can be reduced. In addition, it is possible to supply water onto welding portions of the plate-like members to cool the welding portions when the seam welding is carried out, and hence the effect of heat on the plate-like members can be further reduced. Accordingly, even if a thin plate-like member is used, such plate-like member can be welded without being deformed. Further, according to the present invention, since the thin plate-like member can be used, the pump casing can be lightweight. In a preferred aspect of the present invention, the at least two plate-like members are joined together at their entire circumferential portions .

In a preferred aspect of the present invention, the at least two plate-like members comprise an inner casing serving as a vortex chamber for housing an impeller therein, and an outer casing for enclosing the inner casing so as to form a passage of a liquid between the inner casing and the outer casing. In a preferred aspect of the present invention, the inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of the inner casing. In a preferred aspect of the present invention, the inner casing has a bottom wall projecting downwardly.

In a preferred aspect of the present invention, the outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

In a preferred aspect of the present invention, the closed bottom wall of the outer casing curves upwardly from the outer circumferential portion to the central portion thereof.

In a preferred aspect of the present invention, a cylindrical end portion of the inner casing is fitted into a cylindrical end portion of the outer casing, and the inner casing and the outer casing are j oined together by seam welding at fitted portions .

In a preferred aspect of the present invention, the at least one of the inner casing and the outer casing is formed by bulge forming.

With this arrangement, even in the case where the inner casing or the outer casing is formed into a complicated shape, a single plate-like member can be used to form the inner casing or the outer casing without joining several parts to each other. As a result, the number of components can be reduced and manufacturing processes can be simplified, thus reducing manufacturing cost and shortening manufacturing time. According to a second aspect of the present invention, there is provided a pump casing comprising: an inner casing having a thin plate-like member formed by press-forming into a predetermined shape for housing an impeller therein; and an outer casing having a thin plate-like member formed by press-forming into a predetermined shape; the inner casing and the outer casing being joined together by welding.

According to a third aspect of the present invention, there is provided a method of manufacturing a pump casing comprising: press-forming at least two plate-like members into predetermined shapes; and joining the at least two plate-like members together at their circumferential portions by seam welding.

According to a fourth aspect of the present invention, there is provided a pump apparatus comprising: a pump casing having at least two plate-like members formed by press-forming into predetermined shapes, the at least two plate-like members being joined together at their circumferential portions by seam welding; an impeller housed in the pump casing; a main shaft for supporting the impeller; and a motor for rotating the main shaft and the impeller.

According to a fifth aspect of the present invention, there is provided a pump apparatus comprising: an inner casing having a thin plate-like member formed by press-forming into a predetermined shape for housing an impeller therein; an outer casing having a thin plate-like member formed by press-forming into a predetermined shape; an impeller housed in the inner casing; a main shaft for supporting the impeller; and a motor for rotating the said main shaft and the impeller; the inner casing and the outer casing being joined together by welding.

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a whole structure of a pump apparatus according to an embodiment of the present invention;

FIG. 2 is a plan view showing a pump casing of the pump apparatus shown in FIG. 1; and FIG. 3 is an enlarged cross-sectional view of portion III shown in FIG . 1.

Best Mode for Carrying Out the Invention

A pump casing and a pump apparatus having such a pump casing according to an embodiment of the present invention will be described below with reference to the drawings .

As shown in FIG. 1, according to an embodiment of the present invention, a pump apparatus comprises an impeller 1, a pump casing 2 in which the impeller 1 is housed, a main shaft 5 for supporting the impeller 1, and a motor 6 for rotating the impeller 1 through the main shaft 5.

The impeller 1 is fixed to the end portion of the main shaft 5 by a shaft nut 7 in such a manner that an impeller inlet la faces axially outwardly, and is rotated together with the main shaft 5. The main shaft 5 is rotatably supported by a bearing 8 disposed near the impeller-side end portion of the main shaft 5, and a bearing (not shown in the drawings) disposed in the motor 6. The main shaft 5 is coupled to the motor 6, and hence the impeller 1 is rotated together with the main shaft 5 by energizing the motor 6.

As shown in FIG. 1, the pump casing 2 comprises an inner casing 3 and an outer casing 4, which are composed of a single plate-like member (sheet metal), respectively. The inner casing 3 is formed into a substantially cylindrical cup shape having a circular opening at an upper end portion thereof and a volute portion 3b projecting radially outwardly at a circumferential side wall 3c of the inner casing 3. The inner casing 3 has a bottom wall 3e projecting downwardly and having an open mouth 3d. The outer casing 4 is formed into a substantially cylindrical cup shape having a circular opening at an upper end portion thereof and a closed bottom wall 4b at a lower end portion thereof. The inner casing 3 and the outer casing 4 are joined together by seam welding at their entire circumferential portions (edge portions) . Specifically, a cylindrical upper end portion 3a of the inner casing 3 is fitted into a cylindrical upper end portion 4a of the outer casing 4, and the inner casing 3 and the outer casing 4 are joined together at fitted portions through a seam-welded portion 16 formed by seam welding and extending the respective circumferential portions of the inner casing 3 and the outer casing 4, thus producing the pump casing 2. The inner casing 3 serves as a vortex chamber for housing the impeller 1, and the outer casing 4 is disposed outwardly of the inner casing 3. Both the inner casing 3 and the outer casing 4 are made of stainless steel. The pump casing 2 is fixed to a flange of the motor 6 by a plurality of bolts 9 (one bolt 9 is shown in FIG. 1) .

The inner casing 3 has the volute portion 3b projecting radially outwardly at the circumferential side wall 3c thereof. A discharge nozzle 11 for discharging a liquid to be pumped is fixed to a portion of the volute portion 3b. The volute portion 3b has a substantially spiral shape extending along the circumferential side wall 3c of the inner casing 3 toward the discharge nozzle 11, thus allowing the liquid pressurized by the rotation of the impeller 1 to flow smoothly into the discharge nozzle 11 (see broken lines shown in FIG. 2) .

The discharge nozzle 11 is connected to a pipe (not shown in the drawings) through a discharge-side flange 12. The liquid pressurized by the rotation of the impeller 1 flows through the discharge nozzle 11, and is discharged into the pipe. The discharge nozzle 11 is made of stainless cast steel.

A liner ring 13 is disposed between the inner casing 3 and the impeller 1. The liner ring 13 is provided so as to prevent the liquid pressurized by the rotation of the impeller 1 from leaking toward a low-pressure side (e.g. the impeller inlet side) . It is preferable to use a so-called floating-type liner ring having such a structure that a ring-shaped liner ring body is housed in a space formed between a liner-ring holder and a liner-ring cover.

As shown in FIG. 1, the outer casing 4 is arranged so as to enclose the inner casing 3, and a passage of the liquid is formed between the inner casing 3 and the outer casing 4. The outer casing 4 has an inlet port 4c at a side thereof for introducing the liquid into the pump casing 2, and the inlet port 4c is connected to a pipe (not shown) through an inlet-side flange 15. The bottom wall 4b of the outer casing 4 has a substantially hemispherical shape such that the bottom wall 4b of the outer casing 4 curves upwardly from the outer circumferential portion to the central portion thereof. With this curved structure of the bottom wall 4b, the strength of the outer casing 4 can be enhanced. Operation of the pump apparatus having the above structure will be described below. First, a liquid is introduced from the inlet port 4c through the pipe into the outer casing 4 by the rotation of the impeller 1. The flow of the liquid is regulated by a regulating vane 10, and the liquid is then sucked through the open mouth 3d of the inner casing 3 and the impeller inlet la into the impeller 1. Thereafter, the liquid is pressurized by the rotation of the impeller 1, and is then discharged through the discharge nozzle 11 to the pipe (not shown) for delivering the pumped liquid. Next, the manufacturing process of the pump casing 2 according to the present invention will be described below. The cylindrical upper end portion 3a of the inner casing 3 is fitted into the cylindrical upper end portion 4a of the outer casing 4. At this state, as shown in FIG. 3, the fitted portions, at which the inner casing 3 and the outer casing 4 are brought into close contact with each other, are joined by seam welding. At this time, the seam-welded portion 16 is formed by the seam welding, and allows the inner casing 3 and the outer casing 4 to be joined together. In this manner, the pump casing 2 is manufactured .

Seam welding is a welding process in which two or more members are joined together by supplying current to a portion of the members to be welded in such a state that the members are clamped and pressed against each other by a pair of rotating disc electrodes for thereby applying successive spot welding to the members . The advantages of seam welding are that the welding time of the seam welding is shorter than that of melting welding process such as TIG welding or MIG welding, and a welded portion has an excellent airtight and liquid-tight capability.

An operation for joining the inner casing 3 and the outer casing 4 with the use of seam welding will be described below.

First, the cylindrical upper end portion 3a of the inner casing 3 is fitted into the cylindrical upper end portion 4a of the outer casing 4, and the fitted portions are joined temporarily by spot welding at certain points (e.g. four points) . In this manner, the fitted portions are temporarily joined in advance, and hence corrugation is prevented from being formed at the fitted portions at the time of later seam welding, and the fitted portions are thus prevented from being separated form each other due to the corrugation.

After the inner casing 3 and the outer casing 4 are temporarily joined together, seam welding is carried out. In this case , it is preferable to supply water onto a welding portion at the same time that or immediately after the seam welding is carried out. By supplying water, the welding portion can be cooled, and hence the effect of heat generated by welding on the welding portion can be reduced, thus preventing strain from being induced in the welding portion. Further, a weld trace (i.e. singe) is hardly formed by supplying water. In the present embodiment, in order to prevent the welding portion from being heated excessively, current is intermittently supplied to the disc electrodes at a predetermined period.

As described above, since the seam welding has the advantage of short welding time, heat generated by welding has little effect on the members to be welded such as the inner casing 3 and the outer casing 4. Accordingly, the inner casing 3 and the outer casing 4 can be welded without being deformed . Further , a thin stainless steel plate can be used for the inner casing 3 and the outer casing 4, and hence the pump casing 2 can be lightweight. Furthermore, the seam-welded portion 16 formed in the inner casing 3 and the outer casing 4 can provide an excellent airtight and liquid-tight capability.

Since the thin stainless steel plate can be used as the plate-like member, the pump casing 2 can easily be formed into a desired shape. For example, in the present embodiment, the inner casing 3 has the volute portion 3b projecting radially outwardly, and such volute portion 3b can easily be formed by bulge forming.

Bulge forming is a process for forming a cylindrical member into a desired shape by pressing the cylindrical member from inside against a female die provided outwardly of the cylindrical member. Specifically, the female die whose inner surface has a recess corresponding to a desired shape is set, and the cylindrical member is inserted into the female die. Thereafter, an internal pressure is applied on an inner surface of the cylindrical member by a fluid or a rubber. As a result, the cylindrical member is bulged outwardly and pressed against the inner surface of the female die, and is thus formed into a desired shape . In the present embodiment, since the thickness of the stainless steel plate used for the inner casing 3 is as thin as about 1.5 mm, the inner casing 3 can easily be bulged by bulge forming. Because the bulge forming is employed, the volute portion 3b can be formed from a single stainless steel plate without being divided into two pieces. Accordingly, the number of components can be reduced and manufacturing processes can be simplified.

Further, the outer casing 4 may be formed into a desired shape by bulge forming.

As described above, according to the present invention, because seam welding is employed for joining the plate-like members constituting the pump casing, these plate-like members can be welded in a short time without being deformed. Further, the thin plate-like members can be used, and hence the pump casing can be lightweight. Furthermore, since bulge forming is employed, even if the plate-like member is formed into a complicated shape, the plate-like member can be formed into a desired shape without being divided into several pieces. As a result, the number of components can be reduced and manufacturing processes can be simplified, thus reducing manufacturing cost.

Industrial Applicability

The present invention is applicable to a pump casing and a pump apparatus, and more particularly to a pump casing comprising a plurality of plate-like members and a pump apparatus having such a pump casing.

Claims

1. A pump casing comprising: at least two plate-like members formed by press-forming into predetermined shapes, said at least two plate-like members being joined together at their circumferential portions by seam welding.

2. A pump casing according to claim 1, wherein said at least two plate-like members are joined together at their entire circumferential portions .

3. A pump casing according to claim 1 or 2 , wherein said at least two plate-like members comprise an inner casing serving as a vortex chamber for housing an impeller therein, and an outer casing for enclosing said inner casing so as to form a passage of a liquid between said inner casing and said outer casing.

4. A pump casing according to claim 3, wherein said inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of said inner casing.

5. A pump casing according to claim 4, wherein said inner casing has a bottom wall projecting downwardly.

6. A pump casing according to any one of claims 3 to 5 , wherein said outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

7. A pump casing according to claim 6 , wherein said closed bottom wall of said outer casing curves upwardly from the outer circumferential portion to the central portion thereof.

8. A pump casing according to any one of claims 3 to 7 , wherein a cylindrical end portion of said inner casing is fitted into a cylindrical end portion of said outer casing, and said inner casing and said outer casing are joined together by seam welding at fitted portions.

9. A pump casing according to any one of claims 3 to 8 , wherein at least one of said inner casing and said outer casing is formed by bulge forming.

10. A pump casing comprising: an inner casing having a thin plate-like member formed by press-forming into a predetermined shape for housing an impeller therein; and an outer casing having a thin plate-like member formed by press-forming into a predetermined shape; said inner casing and said outer casing being joined together by welding.

11. A pump casing according to claim 10 , wherein said inner casing and said outer casing are joined together at their entire edge portions .

12. A pump casing according to claim 10 or 11, wherein said inner casing serves as a vortex chamber, and said outer casing encloses said inner casing so as to form a passage of a liquid between said inner casing and said outer casing.

13. A pump casing according to any one of claims 10 to

12, wherein said inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of said inner casing.

14. A pump casing according to claim 13 , wherein said inner casing has a bottom wall projecting downwardly.

15. A pump casing according to any one of claims 10 to 14, wherein said outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

16. A pump casing according to claim 15, wherein said closed bottom wall of said outer casing curves upwardly from the outer circumferential portion to the central portion thereof.

17. A pump casing according to any one of claims 10 to

16, wherein a cylindrical end portion of said inner casing is fitted into a cylindrical end portion of said outer casing, and said inner casing and said outer casing are joined together by seam welding at fitted portions.

18. A pump casing according to any one of claims 10 to

17, wherein at least one of said inner casing and said outer casing is formed by bulge forming.

19. A method of manufacturing a pump casing, comprising: press-forming at least two plate-like members into predetermined shapes; and joining said at least two plate-like members together at their circumferential portions by seam welding.

20. A method of manufacturing a pump casing according to claim 19 , wherein said at least two plate-like members are j oined together at their entire circumferential portions by seam welding.

21. A method of manufacturing a pump casing according to claim 19 or 20, wherein said at least two plate-like members comprise an inner casing serving as a vortex chamber for housing an impeller therein, and an outer casing for enclosing said inner casing so as to form a passage of a liquid between said inner casing and said outer casing.

22. A method of manufacturing a pump casing according to claim 21, wherein said inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of said inner casing, and said outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

23. A method of manufacturing a pump casing according to any one of claims 19 to 22, wherein a cylindrical end portion of said inner casing is fitted into a cylindrical end portion of said outer casing, and said inner casing and said outer casing are joined together by seam welding at fitted portions.

24. A method of manufacturing a pump casing according to any one of claims 21 to 23, wherein at least one of said inner casing and said outer casing is formed by bulge forming.

25. A pump apparatus comprising: a pump casing having at least two plate-like members formed by press-forming into predetermined shapes, said at least two plate-like members being joined together at their circumferential portions by seam welding; an impeller housed in said pump casing; a main shaft for supporting said impeller; and a motor for rotating said main shaft and said impeller.

26. A pump apparatus according to claim 25, wherein said at least two plate-like members are joined together at their entire circumferential portions.

27. A pump apparatus according to claim 25 or 26, wherein said at least two plate-like members comprise an inner casing serving as a vortex chamber for housing said impeller therein, and an outer casing for enclosing said inner casing so as to form a passage of a liquid between said inner casing and said outer casing.

28. A pump apparatus according to claim 27, wherein said inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of said inner casing.

29. A pump apparatus according to claim 28, wherein said inner casing has a bottom wall projecting downwardly.

30. A pump apparatus according to any one of claims 27 to 29, wherein said outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

31. A pump apparatus according to claim 30, wherein said closed bottom wall of said outer casing curves upwardly from the outer circumferential portion to the central portion thereof.

32. A pump apparatus according to any one of claims 27 to 31 , wherein a cylindrical end portion of said inner casing is fitted into a cylindrical end portion of said outer casing, and said inner casing and said outer casing are joined together by seam welding at fitted portions.

33. A pump apparatus according to any one of claims 27 to 32, wherein at least one of said inner casing and said outer casing is formed by bulge forming.

34. A pump apparatus comprising: an inner casing having a thin plate-like member formed by press-forming into a predetermined shape for housing an impeller therein; an outer casing having a thin plate-like member formed by press-forming into a predetermined shape; an impeller housed in said inner casing; a main shaft for supporting said impeller; and a motor for rotating said main shaft and said impeller; said inner casing and said outer casing being joined together by welding.

35. A pump apparatus according to claim 34, wherein said inner casing and said outer casing are joined together at their entire edge portions.

36. A pump apparatus according to claim 34 or 35, wherein said inner casing serves as a vortex chamber, and said outer casing encloses said inner casing so as to form a passage of a liquid between said inner casing and said outer casing.

37. A pump apparatus according to any one of claims 34 to 36, wherein said inner casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a volute portion projecting radially outwardly at a circumferential side wall of said inner casing.

38. A pump apparatus according to claim 37, wherein said inner casing has a bottom wall projecting downwardly.

39. A pump apparatus according to any one of claims 34 to 38, wherein said outer casing is formed into a substantially cylindrical cup shape having an opening at an upper end portion thereof and a closed bottom wall at a lower end portion thereof.

40. A pump apparatus according to claim 39, wherein said closed bottom wall of said outer casing curves upwardly from the outer circumferential portion to the central portion thereof.

41. A pump apparatus according to any one of claims 34 to 40, wherein a cylindrical end portion of said inner casing is fitted into a cylindrical end portion of said outer casing, and said inner casing and said outer casing are joined together by seam welding at fitted portions.

42. A pump apparatus according to any one of claims 34 to 41, wherein at least one of said inner casing and said outer casing is formed by bulge forming.