Information
-
Patent Grant
-
6267555
-
Patent Number
6,267,555
-
Date Filed
Wednesday, January 12, 200024 years ago
-
Date Issued
Tuesday, July 31, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 415 1991
- 415 1721
- 415 1731
- 415 200
- 415 1821
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International Classifications
-
Abstract
A sheet metal casing for multistage pump and its manufacturing method, the casing includes an outer shell and an inner shell. The outer shell is integrally formed and includes a front end ring, a step positioning ring, an outer shell surface and a positioning end. The inner shell is fixed to the inner side of the outer shell and includes an inner end, an inner shell surface and a step positioning rim. The step positioning rim forms a closed holding space with the outer shell surface for holding and squeezing a seal ring therein. When a plurality of casings being serially mounted on a spindle, the positioning end of a front casing may make contact with the step positioning ring of a rear casing, and the positioning rim of the front inner shell may make contact with the front end ring of the rear outer shell for axially positioning the casings on the spindle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to sheet metal casing for multistage pump and its manufacturing method, and particularly to a sheet metal casing for multistage submerged pump that has simple structure to facilitate fabrication and assembly at low cost, and has improved sealing and pumping efficiency.
2. Description of the Prior Art
Conventional multistage centrifugal pumps (such as submerged pumps) usually includes a plurality of casings with passages and impellers housed therein and mounted serially on a rotationable spindle for pumping fluid by adding pressure. The multistage pump made by casting in the past is heavy and bulky and has lower pump efficiency. It is generally replaced by sheet metal casing pump nowadays.
In the design of multistage sheet metal casing pump, the main considerations include: manufacturing and assembly cost, pump efficiency and passage design, pressure resistance, leakage prevention, etc. These factors are rarely totally met by conventional sheet metal casing multistage pump. For instance, European Pat. Application No. 81110541.0 discloses a sheet metal casing structure for multistage pump shown in FIG.
1
. It has a casing
11
made by punching and a partition member
12
to form a stage
2
for housing an impeller
3
and baffles
20
therein. The casing
11
has a curved portion
19
for engaging a front stage with a rear stage. At the juncture of the engagement, a seal ring
14
is provided. The dimension and precision of the curved portion
19
is difficult to control. When more than one stage being fastened axially, the positioning of the curved portion
19
is even more difficult and is prone to deform. The seal ring
14
tends to malfunction and result in leakage under pressure or vibration. Moreover there is no smooth passage inside the casing
11
and the impeller
13
. It is easy to produce turbulence around the front end
112
during pumping operation and result in lower pump efficiency. In short, it has the drawbacks of poor axial positioning, easy leaking and low pump efficiency.
FIG. 2
illustrates another prior art disclosed in U.S. Pat. No. 5,234,317. It has a pump casing
21
made by punching and pressing. The pump casing
21
has an end rim
211
formed in a U-shaped member for engaging securely with a next stage pump casing. However it has a smaller contact area (sealing surface). The end rim
211
is prone to deform and open outwardly under strong pumping pressure or vibration. Leaking is still not avoidable. Furthermore the pump casing
21
cannot be made by merely punching operation. It needs pressing operation to finish all the fabrication work required. The cost is higher. And there is also no smooth passage inside the casing and may result in turbulence and lower pump efficiency. When two stage pumps are connected, the connection portion forms an S-shaped structure. While it helps to prevent deformation and leakage, it increases production cost.
FIG. 3
shows a still another technique seen in the market place. The pump casing
4
includes a front outer shell
41
, a rear outer shell
42
, a front inner shell
43
, a rear inner shell
44
, a hub
46
, a front seal ring
47
and an impeller (not shown in the figure). The front outer shell
41
includes a front side ring
413
, an axial positioning ring
411
and a radial positioning ring
412
. The rear outer shell
42
includes an axial positioning end
421
and a radial positioning end
422
mating respectively with the rings
411
and
412
. The rear inner shell
44
has a positioning end
441
at the rear end.
For assembly of a single casing
4
, the vane
45
is firstly soldered to the front inner shell
43
. Then the front outer shell
41
, rear outer shell
42
, front inner shell
43
and rear inner shell
44
are assembled together (otherwise the inner shells
43
and
44
cannot be put into the outer shells
41
and
42
). Then circular soldering is made on the solder spots
48
around the outer shell.
For assembly of a multistage pump casing
4
, the positioning end
44
of a front casing
4
will be made contact with the front side ring
413
of a rear casing. The axial and radial positioning end
421
and
422
of the front casing will be made contact with the axial and radial positioning rings
411
and
412
which may couple with a seal ring to prevent leakage. The front and rear inner shells
43
and
44
have curved inside surface to smooth flow passage and enhance pump efficiency.
However there are still disadvantages in this technique, notably:
1. It has too many components and costs too much to produce. Eight components are required, including the front and rear outer shells
41
and
42
front and rear inner shells
43
and
44
, vane
45
, hub
46
, front seal ring
47
and the impeller. The molding cost and assembly time increase greatly. The hub
46
and front seal ring
47
also add to the cost.
2. It needs secondary machining that increases cost and production time. The axial and radial positioning ring
411
and
412
, and the axial and radial positioning end
421
and
422
need high precision machining work to get the accurate dimension for making the required connection. An usual punching operation cannot produce that kind of precision. The machining also unavoidably reduces shell thickness and weaken the structural strength.
3. The circular soldering of the solder spots
48
are much more expensive and time-consuming than conventional spot soldering. It also tends to produce notsightly casing and lower dimension accuracy. Positioning for assembly is more difficult. The soldering property and strength is difficult to control. A secondary machining is needed after the soldering and may reduce casing thickness.
The prior arts set forth above thus cannot totally meet all the design factors such as production and assembly costs, pump efficiency and passage streamline, pressure resistance, leak control and prevention, etc. There are still a lot of room for improvement.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a sheet metal casing for multistage pump and manufacturing method that has lower production and assembly cost, enhanced pressure resistance and improved leakage prevention.
The pump according to this invention consists of a plurality of pump unitsserially mounted on a rotationable spindle. Each pump unit includes a casing, an impeller and a hub. The casing includes an outer shell and an inner shell. The outer shell is integrally formed and includes a front end ring, a step positioning ring, an outer shell surface and a positioning end. The inner shell is located inside the outer shell and includes an inner end, an inner shell surface and a step positioning rim. The positioning rim and the outer shell surface form a holding space inside for holding a seal ring. When a plurality of casings are serially connected, the positioning end of a front casing may contact with the step positioning ring of a rear casing, and the positioning rim of the front casing may contact with front end ring of the rear casing for positioning the casings on the spindle and securing the seal ring in the closed holding space. The front end ring and the inner end are bent and extended forward and are parallel with the spindle with a gap formed therebetween to mate against inlet of the impeller. It also serves sealing function.
The manufacturing method of this invention includes more than one punching operation on a metal sheet to produce the front end ring, step positioning ring and outer shell surface. Then the inner shell is formed by more than one punching operation to form a front half and a rear half sections.
The front half section includes the inner end and about a half of the inner shell surface. The rear half section includes about a half of remaining inner shell surface and the positioning rim. Then the front half section, vane and rear half section are soldered serially to the outer shell. Finally a punching operation is performed on the outer shell to form the positioning end.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention, as well as its many advantages, may be further understood by the following detailed description and drawings, in which:
FIG. 1
is a sectional view of a conventional sheet metal casing for a multistage pump.
FIG. 2
is a fragmentary sectional view of another conventional sheet metal casing for a multistage pump.
FIG. 3
is a fragmentary sectional view of a further conventional sheet metal casing for a multistage pump.
FIG. 4
is a fragmentary sectional view of this invention for a single pump casing.
FIG. 5
is fragmentary sectional view of this invention for a two-stage pump.
FIG. 6
is a fragmentary sectional view of a positioning end for holding a seal ring.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIGS. 4 and 5
, the sheet metal casing of this invention consists of a plurality of pump casings
6
serially mounted on a rotationable spindle
5
. Each of the pump casings
6
includes a casing, an impeller
7
and a vane
8
. The structure of the spindle
5
, impeller
7
and vane
8
, and their constructional relationship are known in the art and form no part of this invention, thus will be omitted hereinafter.
This invention mainly focuses the pump casing structure and will be described in the following.
The pump casing includes an outer shell
61
, an inner shell
62
and a seal ring
9
. The outer shell
61
is made by punching a sheet metal (such as stainless steel) with more than one operation to form an integrated annular shell shape. It includes (from left to right in
FIG. 4
) a first front end
611
which extends approximately parallel with the spindle
5
for a selected length, a front end ring
612
extending outward and normal to the spindle
5
, a step positioning ring
613
extending outward from the front end ring
612
, an outer shell surface
614
extending parallel with the spindle
5
and a positioning end
615
extending inward and nearly normal to the spindle
5
as shown in FIG.
6
). The step positioning ring
613
also has a normal or near normal angle.
The inner shell
62
is fixed inside the outer shell
61
and houses the vane
8
therein. The inner shell
62
includes a second front end
621
approximately parallel with the spindle
5
, an inner end
622
extending outward and normal to the spindle
5
, an inner shell surface
623
approximately parallel with the spindle
5
below the outer shell surface
614
and forms a step elbow inward toward the spindle
5
at a fist curved bend
627
, and a positioning rim
624
parallel with the spindle
5
. The positioning rim
624
and positioning end
615
form a holding space for holding the seal ring
9
therein. The juncture between the inner end
622
and inner shell surface
623
also forms a second curved bend
626
which couples with the first curved bend
627
to form a smooth fluid passage guide to enable pumping fluid to flow smoothly from the impeller
7
to the vane
8
without producing turbulence.
Referring to
FIG. 5
, when a plurality of pump casings
6
are assembled serially, the front casing
6
(at the left side in
FIG. 5
) has its positioning end
615
making contact with the step positioning ring
613
of the rear casing (at the right side in FIG.
5
). The positioning rim
624
of the front casing makes contact with the front ending
612
of the rear casing, so that the pump casing
6
may be positioned on the spindle
5
and the space
625
may become closed. The seal ring
9
held in the closed space
625
is squeezed and may prevent leakage effectively. As the positioning end
615
of the front casing engages with a slightly tilted step positioning ring
613
of the rear casing, the deformation of the positioning end
615
under pressure may be minimized and may further prevent leakage from taking place. Furthermore the first front end
611
and second front end
621
form a gap mating with the inlet
71
of the impeller
7
and may also provide impeller sealing function.
FIG. 6
shows another embodiment of the positioning end
615
of this invention. Same or similar components will be marked by same numerals suffixed with a character. The positional end
615
a
is bent slightly larger than 90 degree for wedging with the step positioning ring
613
a
. It forms a more secured sealing and anti-leaking effect than the one shown in FIG.
5
. However it needs more precise machining.
The manufacturing method of this invention may include the following steps:
a. punching a sheet metal more than once to form the outer shell
61
, including the first front end
611
, front end ring
612
, step positioning ring
613
and outer shell surface
614
;
b1. Punching two metal sheets more than once to form the front and rear half section of the inner shell
62
. The front half section includes the second front end
621
, inner end
622
and about a half of the inner shell surface
623
. The rear half, section includes about a half of the inner shell surface
623
and positioning rim
624
.
b2. Placing the front half section of the inner shell
62
and the vane
8
into the outer shell
62
from a rear end thereof, soldering the vane
8
to the front half section.
b3. Placing the rear half section of the inner shell
62
into the outer shell
61
from the rear end thereof;
Soldering the front and rear half section together to form a complete inner shell
62
and fixing the inner shell
62
to the inner side of the outer shell surface
614
.
c. punching the outer shell surface
614
to form the positioning end
615
.
According to this invention, the outer shell
61
and inner shell
62
have relatively simple form. They are simpler to produce and assemble at lower cost. The positioning end
615
is formed after the inner shell
62
is fixed in the outer shell
61
. It may be made with simpler mold at higher precision. It thus can sustain high pressure without deformation or leakage. The engagement of the positioning end
615
with the step positioning ring
613
is also more secure, and can effectively prevent leakage under high pressure even with less than perfect fabrication precision of the pump casing. The seal ring
9
held in a closed space
625
can further improve anti-leaking effect. The curved bend
626
and
627
provide smooth passage guide to streamline fluid flow without generating turbulence and thus may enhance pump efficiently. Almost all the shortcomings resulting from conventional pump casing thus may be overcome by means of this invention. In summary, this invention offers the following advantages:
1. Small number of components.
As shown in
FIGS. 4 and 5
, the pump casing
6
of this invention includes an outer shell
61
, an inner shell
62
(with a front and a rear section), a vane
8
and an impeller. It takes only five components comparing with eight in the conventional pump casing mentioned before. Positioning and assembly become much easier. At least four molds may be saved for producing the components. Production cost thus may be greatly reduced. The sealing between the hub and the front seal ring may be done without additional features. It also helps to drive cost down.
2. No need for secondary high precision machining.
The sealing effect from the positioning end
615
and step positioning ring
613
and the seal ring
9
is simple and effective with no need of precision machining. The production cost becomes lower.
3. No need for circular soldering.
The outer shell
61
is one piece made integrally. Spot soldering is sufficient to accomplish required bonding strength. It costs lower, makes sightly appearance and stronger structural strength. Spot soldering also has less impact on pump casing deformation and mechanical strength of the material, it thus makes secondary machining for the step positioning ring
613
and positioning end
615
unnecessary.
It may thus been seen that the objects of the present invention set forth herein, as well as those made apparent from the foregoing description, are efficiently attained. While the preferred embodiment of the invention has been set forth for purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skill in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
Claims
- 1. A sheet metal casing for multistage pump which consists a plurality of pump casings serially mounted on a rotationable spindle, the pump casing includes a casing, an impeller and a vane, the casing comprising;an annular outer shell made by integral forming including at least, starting from one end thereof, a front end ring approximately normal to the spindle and extending outward, a step positioning ring having one end thereof connecting with the front end ring, an outer shell surface extending nearly parallel with the spindle and a positioning end connecting with an end of the outer shell surface and extending toward the spindle; an inner shell fixedly located in the outer shell and housed the vane therein, including at least, starting from an end adjacent the front end ring, an inner ring approximately normal to the spindle and extending outward, an inner shell surface approximately parallel with the spindle, and a step positioning end connection with inner shell surface at one end thereof, the step positioning end forming a holding space with the outer shell surface; and a seal ring held in the holding space; wherein the front end ring has a first front end bent parallel with the spindle and extending forward, the inner end has a second front end bent parallel with the spindle and extending forward, the first and second front ends form a gap therebetwen mating with an inlet of the impeller for sealing the impeller.
- 2. The sheet metal casing for multistage pump of claim 1, wherein the positioning end of a front pump casing makes contact with the step positioning ring of a rear pump casing, and the positioning rim of the front pump casing makes contact with the front end ring of the rear pump casing to form a closed space to hold the squeezed seal ring therein for preventing leakage.
- 3. The sheet metal casing for multistage pump of claim 1, wherein the positioning end has a surface formed an approximately ninety degree angle radially against the outer shell surface for mating and contacting with the step positioning ring of the rear adjacent pump casing to prevent leaking under high pumping pressure.
- 4. The sheet metal casing for multistage pump of claim 1, wherein the inner shell surface forms respectively with the inner end and positioning rim a first and a second curved bend to become curved passage guide to streamline fluid flow from the impeller to the vane for preventing turbulence.
- 5. The sheet metal casing for multistage pump of claim 1, wherein the positioning end forms an angle with the outer shell surface larger than ninety degree, the step positioning ring has a bending angle less than ninety degree for mating and contacting with the positioning end so that the positioning end wont deform outward under high pumping pressure.
- 6. The sheet metal casing for multistage pump of claim 1, wherein the vane is fixedly located on the inner end within the inner shell.
- 7. A manufacturing method for fabricating the sheet metal casing of claim 1, comprising the following steps:a. punching a sheet metal more than once to form the front end ring, step positioning ring and the outer shell surface; b. placing the inner shell which has the vane located therein into the outer shell through a rear end thereof and soldering the inner shell to the outer shell; and c. punching a rear end of the outer shell surface to form the positioning end.
- 8. The manufacturing method of claim 7, wherein the step b further includes the following:b1. Punching more than once two separate metal sheets to form a front and a rear section of the inner shell, the front section including at least the inner end and approximately a half of the inner shell surface, the rear section including at least approximately a half of the inner shell surface and the positioning end; b2. Placing the front section and a front end of the vane into the outer shell at a selected location behind an inside end of the outer shell, the vane being soldered to the front section before being moved into the outer shell; and b3. Placing the rear section into the outer shell to connect with the front section by soldering to form the inner shell, fixing the inner shell to an inner side of the outer shell surface.
- 9. A sheet metal casing for multistage pump which consists a plurality of pump casings serially mounted on a rotationable spindle, the pump casing includes a casing, an impeller and a vane, the casing comprising;an outer shell engaged with an inner shell; an annular outer shell made by integral forming including at least, starting from one end thereof, a front end ring approximately normal to the spindle and extending outward, a step positioning ring having one end thereof connecting with the front end ring, an outer shell surface extending nearly parallel with the spindle and a positioning end connecting with an end of the outer shell surface and extending toward the spindle; an inner shell fixedly located in the outer shell and housed the vane therein, including at least, starting from an end adjacent the front end ring, an inner ring approximately normal to the spindle and extending outward, an inner shell surface approximately parallel with the spindle, and a step positioning end connection with inner shell surface at one end thereof, the step positioning end forming a holding space with the outer shell surface; and wherein the front end ring has a first front end bent parallel with the spindle and extending forward, the inner end has a second front end bent parallel with the spindle and extending forward, the first and second front ends form a gap therebetwen mating with an inlet of the impeller for sealing the impeller.
- 10. The sheet metal casing for multistage pump of claim 9 further having a seal ring located in the holding space, the seal ring being squeezed when the pump casings being serially mounted for preventing leakage.
- 11. The sheet metal casing for multistage pump of claim 9 wherein the positioning end has a surface formed an approximately ninety degree angle radially against the outer shell surface for mating and contacting with the step positioning ring of the rear adjacent pump casing to prevent leaking under high pumping pressure.
- 12. The sheet metal casing for multistage pump of claim 9, wherein the inner shell surface forms respectively with the inner end and positioning rim a first and a second curved bend to become curved passage guide to streamline fluid flow from the impeller to the vane for preventing turbulence.
- 13. The sheet metal casing for multistage pump of claim 9, wherein the positioning end forms an angle with the outer shell surface larger than ninety degree, the step positioning ring has a bending angle less than ninety degree for mating and contacting with the positioning end so that the positioning end wont deform outward under high pumping pressure.
- 14. The sheet metal casing for multistage pump of claim 9, wherein the vane is fixedly located on the inner end within the inner shell.
US Referenced Citations (6)