JPS61252893A - Sewage and waste pump - Google Patents

Abstract

PURPOSE:To prevent objects from clogging by making the diameter of a suction port defined in a suction cover of a centrifugal pump larger than that of the extream end of an impeller blade so that a counterflow is produced at the portion. CONSTITUTION:A diameter phiD1 of a suction port 3a of a suction cover 3 is larger than a diameter phiD0 of a blade extream end 7a at the suction side of a blade 7 by approximately 10%. Thus, a part of sewage flow A flows toward the suction pot 3a and produces such a counterflow as shown by an arrow B. Foreign elements C are carried by the counterflow B to be get out of the blade extream end 7a and flowingly carried by the flow A together with the sewage from an impeller 5 to a casing 2. As a result, there is no possibility that objects are clogged and reliable operation of a pump is ensured.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a centrifugal pump having an open impeller,
In particular, the present invention relates to a centrifugal pump for sewage and filth in which the gap between the impeller and the suction cover facing the impeller is narrowed.

[Background of the invention]

Many pumps are used in sewage facilities and sewage treatment plants, but these pumps, so-called sewage pumps, can malfunction due to various impurities contained in the flowing water. There must be no

Therefore, various proposals have been made for a long time.

For example, in the device described in Japanese Utility Model Application Publication No. 53-51606, the suction cover is provided with a groove, and the blade is provided with a rotating blade.
This allows foreign matter such as fibers to be cut out, and in the one disclosed in JP-A-57-24491, a gap is provided between the suction cover and the impeller, making it easier for foreign matter to flow away. That's what I do.

However, none of these methods takes into account the removal of fibrous impurities that adhere to the tips of the two blades.

[Purpose of the invention]

The object of the present invention is to eliminate the drawbacks of the prior art described above, and to
To provide a sewage and sewage pump that can be operated with sufficient reliability without causing any functional failure even in flowing water containing many filamentous or string-like impurities such as fibers. It is in. .

[Summary of the invention]

In order to achieve this object, the present invention is characterized in that the diameter of the suction port of the suction cover of the centrifugal pump is made larger than the diameter of the tip of one impeller blade, and a backflow is generated in this portion.

[Embodiments of the invention]

Below, the sewage sewage pump according to the present invention will be described.

This will be explained in detail with reference to the illustrated embodiment.

FIG. 2 shows an entire embodiment of the present invention, in which 1 is a mold, 2 is a casing, 3 is a suction cover, 4 is a strainer, 5 is an impeller, and 6 is a combination of the mold 1 and the impeller 5. A common shaft, 7 is an impeller 6. Figure 1 is an enlarged view of a part of the suction cover 3 and the impeller 5, and Figure 3 is a front view of the impeller 5. As is clear from the figure, in this embodiment, the diameter φD1 of the suction port 3a of the suction cover 3 is increased by about 10% relative to the diameter φDo of the blade tip 7a on the suction port side of the blade 7. Therefore, when this pump is operated, the sewage flowing in from the suction port 3a due to the rotation of the impeller 5 flows through the impeller 7 as shown by arrow A.
It flows into the casing 2, obtains energy through the rotation of the impeller 5, and is sent out to the casing 2.

However, at this time, if the wastewater contains a lot of fibrous impurities such as threads, these impurities may be removed from the blades 7 as shown by C in Figures 1 and 3. Tangle it so that it straddles the tip 7a.

You won't be able to leave. In other words, in this state, the impurities are further pressed against the blade tip 7a by the flow of sewage A, and do not leave the blade tip 7a while the impeller 5 is rotating.

However, in this embodiment, since the diameter φD1 of the suction port 3a of the suction cover 3 is larger than the diameter φDo of the blade tip 7a, a part of the wastewater flow A is transferred to the suction port 3a.
It flows out in the direction a, producing a backflow as shown by arrow B.

As a result, the foreign matter C rides on this backflow B and comes off from the tip 7a of one blade, and rides on the flow A and is washed away from the impeller 5 to the casing 2 together with the dirty water.

Therefore, according to this embodiment, even when handling wastewater containing a large amount of fibrous foreign matter such as threads, there is no risk of foreign matter getting tangled with the tips 7a of the blades, and the pump is always reliably pumped. Able to drive.

By the way, in the present invention, the diameter of the suction port 3a of the suction cover 3 is equal to the blade tip 7 at the end face facing the impeller 5.
As long as the diameter is larger than the diameter of a, the purpose can be achieved by itself.The embodiments of the present invention are not limited to the pumps shown in FIGS. 1 to 3, but for example,
The structure may be as shown in FIGS. 4 to 6. That is, in the embodiment shown in FIG.
The end face facing the impeller 5 is chamfered so that the diameter φDz at this portion is larger than the diameter φDo of the blade tip 7a. Further, in the embodiment shown in FIG. 5, the end face is chamfered with a so-called radius. Further, in the embodiment shown in FIG. 6, a step is provided on one chamfer.

Incidentally, in all of these embodiments, the dimension φDl is set larger than the dimension φDo, thereby reducing the backflow (arrow B).
It is causing Therefore, in these embodiments, a decrease in efficiency can naturally be considered.

However, when we examine the characteristics of these examples, we find that
It looks like Figure 7. In this Figure 7, characteristic a is the characteristic when dimension φD1 is set to be the same as dimension φDo, the figure C is the characteristic when dimension φDl is slightly larger than dimension φDo, and the characteristic C is the characteristic when dimension φDl is set to be the same as dimension φDo. This is the case where it is made about 20% larger than the actual value.

As is clear from the characteristics shown in Fig. 7, even when one dimension φDx is made larger than the dimension φDo, the efficiency decreases not so much, but when the difference reaches about 20%, characteristic C is reached. As can be seen, an inflection point d appears. Therefore, in one embodiment of the present invention, as shown in the above embodiment, the difference between the dimension φDo and the dimension φD1 may be set to 5 to 15%, preferably about 10%.

〔Effect of the invention〕

As explained above, according to the present invention, the simple structure is that the suction port of the suction cover is enlarged.

To easily provide a sewage and sewage pump that can always operate the pump reliably without the risk of clogging, even for sewage mixed with a large amount of fibrous impurities such as threads. be able to.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing an embodiment of a sewage and filth pump according to the present invention, FIG. 2 is a partial sectional view of an example of a sewage and sewage pump, FIG. 3 is a front view of an impeller, and FIG. 4 , FIG. 5, and FIG. 6 are sectional views of main parts showing other embodiments of the present invention, and FIG. 7 is a characteristic diagram of one embodiment of the present invention. l...Moldle, 2...Casing, 3...
・Suction cover, 3a... Suction port, 4... Strainer, 5... Impeller, 6... Common shaft, 7...
・Feather, 7a... Tip of the blade. Figure 1 Figure 2 Figure 3 Δ Figure 5

Claims (1)

[Claims] 1. In a sewage and filth centrifugal pump equipped with an open impeller, the diameter of the suction port is formed to be larger than the diameter of the tip of the suction port blade of the impeller, and the diameter of the suction port blade is A sewage/sewage pump characterized in that it is configured so that backflow occurs in the sewage/sewage pump. 2. The sewage sewage pump according to claim 1, characterized in that the ratio of the diameter of the suction port to the diameter of the tip of the suction port blade of the impeller is 5 to 10%.