IMPROVED IMPELLER FOR SELF-PRIMING PUMP, ASSEMBLY STRUCTURE THEREOF AND SELF-PRIMING PUMP CONTAINING THE SAME Technical Field The present invention relates to an improved impeller for a self-priming pump, an assembly structure thereof, and a self-priming pump containing the same, and more particularly to a multistage impeller for a self-priming pump, an assembly structure thereof, and a self-priming pump containing the same, which can generate high pumping head, high suction pressure, and high exhaust pressure, and has a relatively simple construction and a relatively superior durability.

Background Art In general, a pump is a hydraulic machine, which receives power from a driver, such as a motor, an engine, or a turbine, and transfers fluid such as liquid or gas through a pipe or transfers fluid through a pipe from a container at a low temperature to a container at a high temperature. The pump was initially used for drainage of a colliery, for ships, for water pumping, etc. , and is now widely used for various further<BR> purposes, e. g. , in buildings, for water supply, in drainage systems, for water discharge, for irrigation, for industrial water supply, in power plants, in various other plants. Moreover, a pump is now used in transferring not only water but also special fluid such as petroleum, various chemicals, pulp, and viscous sludge.

Pumps may be classified into reciprocating pumps, rotary pumps, centrifugal pumps, axial flow pumps, friction pumps, and other pumps, according to their structures, or may be classified into pumps for water-

supplying, pumps for deep wells, pumps for shallow wells, etc. , according to their use. Especially, a pump for sucking air or other gas out of a container, thereby causing an interior of the container to be vacuum, is called a vacuum pump.

Further, pumps may be classified into non-self- priming pumps and self-priming pumps. Priming is necessary for initial operation of the non-self-priming pumps and is not necessary for initial operation of the self-priming pumps.

FIG. 10 shows a typical self-priming pump 100' which includes an upper casing 130, a conventional single stage impeller 140, a lower casing 120, and a motor 110. The upper casing 130 includes a suction port 131 and an exhaust port 132. The single stage impeller 140 includes radial blades and a rim. The lower casing 120 has an arcuate groove 121. The motor 110 has a shaft 111 extending through a central portion of the lower casing 120. The shaft 111 has a key 112 inserted in and engaged with a key groove 141 formed in an axial hole 142 of the single stage impeller 140. The shaft 111 is inserted and held in the axial hole 142 by the engagement between the key 112 and the key groove 141.

An assembling screw 135 assembles flanges of the upper casing 130 and the lower casing 120 with each other.

Reference numeral 136 not mentioned above designates a drain cock.

Hereinafter, an operation of the conventional self-priming pump 100'as described above will be described. When the single stage impeller 140 is rotated counterclockwise by the single stage impeller 140, a negative pressure is applied to and water is thusly sucked through an arcuate suction port (not shown) formed at the upper casing 130. The sucked water is carried along the arcuate groove 121 of the lower casing

120 formed at an opposite side of the single stage impeller 140. Then, the water is discharged out of an arcuate exhaust port (not shown) formed at the upper casing 130, and the pressurized water is then exhausted through the exhaust port 132.

The conventional self-priming pump as described above has a simple construction and requires a relatively small space for its installation and no priming for its initial operation. Therefore, it is convenient to use the conventional self-priming pump.

However, since all of the conventional self-priming pumps contain a single stage impeller with an arcuate groove, respectively, the conventional self-priming pump has a relatively small pumping head, a relatively low exhaust pressure, and a relatively small quantity of exhausted fluid.

Therefore, highly required has been a self-priming pump, which has a simple construction, a high exhaust pressure, a large quantity of exhausted fluid, and an improved efficiency, while requiring a small space for its installation.

Disclosure of the Invention Therefore, the present invention has been made in view of the above-mentioned problems, and it is a first object of the present invention to provide an improved impeller for a self-priming pump, which can generate high suction pressure and exhaust pressure and is a non- clog type which can prevent the pump from being blocked during operation of the pump by possible solid alien material or dirt in fluid being transferred.

It is a second object of the present invention to provide an impeller assembly including an improved impeller for a self-priming pump: which can generate high suction pressure and exhaust pressure; which can be

internally inspected for maintenance or repair without being disassembled ; which requires no priming for its initial operation so that it is convenient and reliable to use the pump; and which produces reduced noise and vibration.

It is a third object of the present invention to provide an improved self-priming pump: which requires no priming fluid for pumping; which can generate high suction pressure and exhaust pressure, so that the pump can effectively transfer not only fluid having a low viscosity but also fluid having a high viscosity; which produces reduced noise and vibration; and which can be easily manufactured.

The first object of the present invention can be effectively achieved by a multistage impeller of an integrated type or a separated type.

The second object of the present invention can be effectively achieved by an impeller assembly, which includes such a multistage impeller for a self-priming pump, arcuate members, and upper and lower casings.

The third object of the present invention can be effectively achieved by a self-priming pump, which includes an impeller assembly having an improved impeller for a self-priming pump, and an impeller rotating means.

The third object of the present invention can also be effectively achieved by an improved eccentric self- priming pump.

Brief Description of the Drawings The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. la is an exploded perspective view of a self- priming pump according to a preferred embodiment of the present invention; FIG. 1b is a detailed side sectional view of an impeller assembly of the self-priming pump shown in FIG. la ; FIG. lc is a perspective view of the multistage impeller which may be preferably employed in the self- priming pump shown in FIG. la according to the first embodiment of the present invention; FIG. ld is a perspective view of an upper casing equipped with an arcuate member employed in the self- priming pump shown in FIG. la ; FIG. le is a bottom view of the upper casing of FIG. 1d equipped with no arcuate member; FIG. 2a is a perspective view of a multistage impeller according to the second embodiment of the present invention, which may be preferably employed in the self-priming pump shown in FIG. la ; FIG. 2b is a perspective view showing a lower surface of the upper casing which can be employed in the pump employing the multistage impeller shown in FIG. 2b; FIG. 3a is an exploded perspective view of a self- priming pump according to another preferred embodiment of the present invention; FIG. 3b is a side sectional view of the impeller assembly shown in FIG. 3a; FIG. 3c is a perspective view of a multistage impeller according to the third embodiment of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 3a ; FIG. 4 is a perspective view of a multistage impeller according to the fourth embodiment of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 3a ;

FIG. 5a is an exploded perspective view of a self- priming pump according to another preferred embodiment of the present invention; FIG. 5b is a perspective view of a multistage impeller according to the fifth embodiment of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 5a; FIG. 5c is a plan view of the multistage impeller shown in FIG. 5b; FIG. 5d is a bottom view of the upper casing for employing the multistage impeller shown in FIG. 5a according to the present invention; FIG. 6a is a perspective view of a multistage impeller according to the sixth embodiment of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 5a; FIG. 6b is a bottom view of the upper casing for employing the multistage impeller shown in FIG. 6a according to the present invention; FIGs. 7a and 7b are perspective views of multistage impellers according to the seventh and eighth embodiments of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 5a ; FIG. 8a is an exploded perspective view of a self- priming pump according to still another preferred embodiment of the present invention; FIGs. 8b to 8d are perspective views of multistage impellers, which may be preferably employed in the self- priming pump shown in FIG. 8a; FIG. 9 is a schematic sectional view of a pump housing containing the impeller shown in FIG. 8b; and FIG. 10 is an exploded perspective view of a typical self-priming pump, which includes a conventional single stage impeller.

Best Mode for Carrying Out the Invention Reference will now be made in detail to the preferred embodiments of the present invention.

FIG. la is an exploded perspective view of a self- priming pump 100 according to a preferred embodiment of the present invention. The self-priming pump 100 according to a preferred embodiment of the present invention includes a multistage impeller 1, an upper casing 20, arcuate members 10 and 10a, a lower casing 30, and an impeller driving means 70.

First, referring to FIG. lc, which is a perspective view of the multistage impeller 1 according to a first embodiment of the present invention, the multistage impeller 1 includes a main impeller 2 and at least one auxiliary impeller 3 assembled with a central portion of at least one side of the main impeller 2. The main impeller 2 of the multistage impeller 1 shown in FIG. la has two separated portions symmetric to and assembled with each other, and the main impeller 2 of the multistage impeller 1 shown in FIG. lc has one integrated body. However, the two main impellers 2 have the same basic construction and thus will not be told from each other in the following description.

The multistage impeller 1 according to the first embodiment of the present invention includes one main impeller 2 and two auxiliary impellers 3 assembled with both sides of the main impeller 2. The main impeller 2 includes a cylindrical core 6, through which an axial hole 7 having a key groove 7a is formed, a first rim 4, and a plurality of first radial blades 5 linearly extending without inclination from an outer cylindrical surface of the cylindrical core 6 to an inner cylindrical surface of the first rim 4. Each of the auxiliary impellers 3 includes a cylindrical core 6, a

second rim 4a having a diameter smaller than that of the first rim 4, and a plurality of second radial blades 5a linearly extending without inclination from an outer cylindrical surface of the cylindrical core 6 to an inner cylindrical surface of the second rim 4a.

In order to increase the pumping head and exhaust pressure, the first and second radial blades 5 and 5a may extend with predetermined curvatures or inclinations, or in a spiral form with both of predetermined curvatures and inclinations, without departing from the scope of the present invention.

The first linear radial blades 5 and the second linear radial blades 5a according to the embodiment shown in FIG. la are aligned to each other in a plan view. However, the scope of the present invention is not limited to such a construction, and instead, the first radial blades and the second radial blades may be disposed to cross each other in a plan view. In general, the number of the first radial blades 5 and the second radial blades 5a may be 4 to 20 and is not restrictive but is selective. However, the number is preferably 8 to 16, more preferably 12 to 14.

Further, in the case in which the multistage impeller 1 according to the first embodiment of present invention is a separated type as shown in FIG. la, separated portions of the multistage impeller 1 may be assembled with each other by screws fitted in a plurality of screw holes formed at the first rim 4, or by a proper assembling means such a laser welding, etc.

In contrast, in the case in which the multistage impeller 1 according to the first embodiment of present invention is an integrated type as shown in FIG. lc, not only the main impeller 2 having a relatively larger diameter has an integrated body, but also the two auxiliary impellers 3 having a relatively smaller

diameter are formed integrally with the main impeller 2.

Also, within the scope of the present invention, the multistage impeller 1 may include an integrated main impeller 2 and two separated auxiliary impellers 3 assembled with both sides of the main impeller 2 by proper assembling means.

Since the multistage impellers 1 to li according to the present invention are members in contact with fluid, it is preferred that they are made from materials, such as stainless steel (SUS) having a superior resistance to corrosion, aluminum or its alloy, engineering plastic or ceramic with high strength and high rigidity, anticorrosive-plated carbon steel with high rigidity, etc.

FIG. 1b is a detailed side sectional view of an impeller assembly 200 of the self-priming pump 100 shown in FIG. la according to the present invention. FIG. 1d and le are perspective and bottom views of the upper casing 20 which may be employed in the self-priming pump shown in FIG. la. Hereinafter, the upper casing 20 will be described with reference to FIGs. la, lb, ld, and le, for convenience of description.

First, the upper casing 20 has an inward protruding flange 25 having a plurality of screw holes 23 formed through the flange 25. Also, the upper casing 20 has a suction port 21 and an exhaust port 22 formed through an upper surface of the upper casing 20, which are interconnected to an arcuate suction opening 21a and an arcuate exhaust opening 22a formed through a bottom surface 28 of the upper casing 20, respectively.

The arcuate member 10a is fixed to a portion of the bottom surface 28 other than the portion through which the arcuate suction opening 21a and the arcuate exhaust opening 22a are formed, specifically, onto a portion of the bottom surface 28 extending in a

direction perpendicular to the direction in which the arcuate suction opening 21a and the arcuate exhaust opening 22a extend, by fixing screws 82 screwed through screw holes 11 of the arcuate member 10a. Therefore, the outer surface of the second rim 4a of the auxiliary impeller 3 (the auxiliary impeller located at the left of the main impeller 2 in FIG. la) of the multistage impeller 1 according to the present invention is opposed to the arcuate inner surface of the arcuate member 10a.

The lower casing 30 has a flange 31 having a plurality of screw holes 32 formed through the flange 31. An axial hole 33 extends through a central portion of a bottom 35 of the lower casing 30. Another arcuate member 10 is fixed to a portion of the bottom 35, corresponding to the arcuate member 10a, by fixing screws 82 screwed through screw holes 11 of the arcuate member 10. Therefore, the outer surface of the first rim 4 of the auxiliary impeller 3 (the auxiliary impeller located at the right of the main impeller 2 in FIG. la) of the multistage impeller 1 according to the present invention is opposed to the arcuate inner surface of the arcuate member 10.

The upper casing 20, the lower casing 30, a connection plate 40 disposed under the lower casing 30, and a housing 50 containing members such as a coupler 60 are assembled with each other by a big assembling screw 81 screwed through them. The impeller driving means 70 such as a motor is installed in the housing 50.

As shown in FIGs. 1d and le, a recess 24 may be formed at a central portion of the upper casing 20, and a nut 83 for a rolling bearing is inserted in the recess 24,'so that one end of a shaft 85 can be located in the recess 24 by means of the nut 83. The shaft 85 is fixed to the multistage impeller 1 of the present invention by a key 84, so that the multistage impeller 1 can rotate

following a rotation of the shaft 85.

A stopper ring 86 is fitted around one end of the shaft 85 inserted through the axial hole 33 formed through the central portion of the bottom 35 of the lower casing 30, and a mechanical seal 87 is fitted under the stopper ring 86 so as to effectively prevent leakage of water or fluid. Bearings 88 are fitted around a portion of the shaft 85 between the connection plate 40 and the housing 50, and a stopper ring 89 is fitted around a portion of the shaft 85 located in the housing 50.

Meanwhile, each of the arcuate members 10 and 10a may have various lengths from a length corresponding to that of a substantially semicircular member extending between portions outside of centers of the arcuate suction opening 21a and the arcuate exhaust opening 22a to a length corresponding to that of a member shaped like a substantially the multistage impeller 1/the auxiliary impeller 3 arc extending between portions outside of ends of the arcuate suction opening 21a and the arcuate exhaust opening 22a. Both ends of each of the arcuate members 10 and 10a may have perpendicular surfaces. Preferably, both ends of each of the arcuate members 10 and 10a may have linearly extending inclined surfaces 12 as shown, in order to ensure smooth flow of fluid and reduction of vibration by the smooth flow of fluid. Otherwise, they may have curvedly inclined surfaces with a predetermined gradient.

In the self-priming pump 100 as shown in FIGs. la to le, when the multistage impeller 1 according to the present invention is rotated by the impeller driving means 70 clockwise in a view from the upper casing 20 toward the lower casing 30, a negative pressure is applied to the arcuate suction opening 21a of the upper casing 20, so that fluid is sucked through the suction

port 21 and the arcuate suction opening 21a from an area located in a 3 o'clock direction of the arcuate member 10a (in a view from the front of the upper casing 20).

The sucked fluid is rotated and pressurized while passing through spaces between the first and second radial blades 5 and 5a of the main impeller 2 and the auxiliary impeller 3 at the left of the main impeller 2 and spaces between the first and second radial blades 5 and 5a of the main impeller 2 and the auxiliary impeller 3 at the right of the main impeller 2. Thereafter, the pressurized fluid is further pressurized by one end of the arcuate member 10 located at a 9 o'clock area of the arcuate member 10 (corresponding to that of the arcuate member 10a), passes sequentially through spaces between the first and second radial blades 5 and 5a and the arcuate exhaust opening 22a of the upper casing 20, and is then exhausted out of the exhaust port 22.

In the self-priming pump 100 shown in FIGs. la to le, both the suction port 21 and the exhaust port 22 are formed at the upper casing 20, the first and second radial blades 5 and 5a of the multistage impeller 1 according to the present invention are blades of the non-clog type, both sides of which are open to prevent foreign material or filth from clogging between the blades, and the arcuate members 10 and 10a are disposed at corresponding locations to be opposed to each other.

FIG. 2a is a perspective view of a multistage impeller la according to the second embodiment of the present invention, which may be preferably employed in the self-priming pump 100 shown in FIG. la, and FIG. 2b is a perspective view showing a lower surface of the upper casing 20 which can be employed in the pump employing the multistage impeller la shown in FIG. 2b.

The second embodiment of the present invention has nearly the same construction as the construction shown

in FIGs. la to le, and thus only the difference between the two embodiments will be described below.

The multistage impeller la shown in FIG. 2a according to the second embodiment of the present invention is an integrated multistage impeller. The multistage impeller la includes'one main impeller 2 and two auxiliary impellers 3 assembled with both sides of the main impeller 2. The main impeller 2 includes the cylindrical core 6 having the axial hole 7 formed through the cylindrical core 6, the first rim 4, and a plurality of first radial blades 5 linearly extending without inclination from an, outer cylindrical surface of the cylindrical core 6 to an inner cylindrical surface of the first rim 4. Each of the auxiliary impellers 3 includes the second rim 4a having a diameter smaller than that of the first rim 4. Each of the auxiliary impellers 3 of the multistage impeller la shown in FIG.

2a does not have a cylindrical core nor a plurality of radial blades, differently from those of the multistage impeller 1 shown in FIGs. la and lc.

FIG. 2b is a perspective view showing a lower surface of the upper casing 20 for employing the multistage impeller la of FIG. 2b. The upper casing 20 has an embossed floor 27 formed in an area defined by the second rim 4a. An arcuate space 27a is formed between an arcuate inner surface of the arcuate member 10a and a portion of a cylindrical outer surface of the embossed floor 27 so that the second rim 4a is rotatably seated in the arcuate space 27a. Meanwhile, the arcuate suction opening 21a and the arcuate exhaust opening 22a are formed through portions symmetrically located around the recess 24 which is formed at a central portion of the embossed floor 27 to receive an end of a shaft.

Further, although not shown, another embossed floor is formed at a bottom of the lower casing 30 also

to define another arcuate space between the embossed floor and another arcuate member, in which the second rim 4a can be rotatably seated.

FIG. 3a is an exploded perspective view of a self- priming pump 100a according to another preferred embodiment of the present invention. The self-priming pump 100a shown in FIG. 3a is substantially equal to the self-priming pump 100 shown in FIG. la, excepting that the suction port 21 and the exhaust port 22 formed at the upper casing 20, and the multistage impeller 1b have different shapes and constructions. Therefore, only the difference between the two pumps will be mainly described below.

FIG. 3a is an exploded perspective view of the self-priming pump 100a including an impeller assembly 200a having a multistage impeller 1b according to the third embodiment of the present invention. The self- priming pump 100a includes a multistage impeller lb, an upper casing 20, arcuate members 10 and 10a, a lower casing 30, and an impeller driving means 70, similarly to the self-priming pumps according to the previous embodiments.

First, referring to FIGs. 2a and 2b, the multistage impeller 1b according to the third embodiment of the present invention includes one main impeller 2 and two auxiliary impellers 3. The main impeller 2 has a plurality of first linear radial blades 5 having a relatively larger length. Each of the auxiliary impellers 3 has a plurality of second linear radial blades 5a having a relatively smaller length. The main impeller 2 is interposed between the two auxiliary impellers 3, and the main impeller 2 and the auxiliary impellers 3 may be either integrally formed or assembled with each other by proper means such as screw jointing or welding.

Otherwise, only one auxiliary impeller 3 may be integrally formed or assembled with only one side of the main impeller 2, within the scope of the present invention.

In the multistage impeller 1b according to the third embodiment of the present invention as shown, each of the first and second radial blades 5 and 5a extends normally outward from an outer surface of the cylindrical core 6, so that they form a radially outward extending shape in total. Each set of one first radial blade 5 and two second radial blades 5a are placed in the same plane.

The multistage impeller 1b according to the third embodiment of the present invention as described above has a difference from the multistage impeller 1 according to the first embodiment of the present invention, in that the multistage impeller 1b has no rim for connecting outer ends of the first and second radial blade 5 and 5a.

FIG. 3b is a side sectional view of the impeller assembly 200a shown in FIG. 3a. The impeller assembly 200a is basically equal to the impeller assembly 200 shown in FIG. lb, excepting that the suction port 21 and the exhaust port 22 formed at the upper casing 20 of the impeller assembly 200a have curved shapes. Therefore, detailed description on the impeller assembly 200a is omitted here.

FIG. 4 is a perspective view of a multistage impeller 1d according to the fourth embodiment of the present invention, which may be preferably employed in the self-priming pump 100a shown in FIG. 3a. The multistage impeller 1d is basically equal to the multistage impeller 1b shown in FIG. 3c, excepting that the first and second radial blades 5 and 5a extend outward from the outer surface of the cylindrical core 6

in spiral shapes in the multistage impeller ld.

Therefore, detailed description on the multistage impeller 1d is omitted here.

The impellers shown in FIGs. 3c and 4 have no rim for connecting outer ends of the first and second radial blades 5 and 5a. The absence of the rim increases not only the capacity of the pump by the volume corresponding to the rim and the quantity of the exhausted fluid but also the lengths of the first and second radial blades 5 and 5a, thereby enabling the exhaust pressure of the pump to be stronger.

Herein, the first and second radial blades 5 and 5a may extend outward either normally from the outer surface of the cylindrical core 6 or slantingly with a predetermined gradient or inclination from the outer surface of the cylindrical core 6. In the latter case, such a predetermined gradient or inclination may be properly selected by one skilled in the art in consideration of a required pumping head, an exhaust <BR> <BR> pressure, a flow quantity, etc. , in relation to the use,<BR> performance, etc. , of the pump, within the scope of the present invention.

The other construction of a pump employing the impeller shown in FIG. 3c or 4 is the same as that of the pump shown in FIG. la, and is thus omitted here.

The multistage impellers 1b and 1d according the third and fourth embodiments of the present invention show a superior efficiency in transferring fluid.

Especially, when the multistage impellers 1b and 1d transfer fluid having a high viscosity, the first and second radial blades 5 and 5a without a rim can naturally prevent the fluid from being sticking to and remaining on peripheral portions of the casing.

Moreover, the multistage impellers 1b and Id can achieve a higher exhaust pressure and a larger quantity of

exhausted fluid.

FIG. 5a is an exploded perspective view of a self- priming pump 100b according to another embodiment of the present invention. The self-priming pump 100b includes the multistage impeller 1, the upper casing 20, the arcuate members 10 and 10a, the lower casing 30, and the impeller driving means 70, similarly to the pumps according to the previous embodiments. The self-priming pump 100b shown in FIG. 5a is nearly the same as the pump shown in FIG. 3a, excepting the slight difference in the shapes of the multistage impeller le and the arcuate members 10 and 10a, only which will be mainly discussed here.

First, referring to not only FIG. 5a but also FIGs. 5b and 5c, which are perspective and plan views of a multistage impeller le according to the fifth embodiment of the present invention, the multistage impeller le includes a main impeller 2 and at least one auxiliary impeller 3 mounted on a central portion of at least one side of the main impeller 2. Herein, FIG. 5a shows the multistage impeller le including two separated symmetric portions assembled with each other, and FIG.

5b shows the multistage impeller le having one integrated body. However, the multistage impellers le have the same basic construction and will not be told from each other in the following discussion.

The multistage impeller le according to the fifth embodiment of the present invention includes one main impeller 2 and two auxiliary impellers 3 assembled with both sides of the main impeller 2. The main impeller 2 includes the cylindrical core 6, through which the axial hole 7 having the key groove 7a is formed, the first rim 4, and a plurality of first radial blades 5 linearly extending without inclination from an outer cylindrical surface of the cylindrical core 6 to an inner

cylindrical surface of the first rim 4. Each of the auxiliary impellers 3 includes the cylindrical core 6, through which the axial hole 7 is formed to be aligned with the axial hole 7 of the main impeller 2, the second rim 4a having a diameter smaller than that of the first rim 4, and a plurality of second radial blades 5a linearly extending without inclination from an outer cylindrical surface of the cylindrical core 6 to an inner cylindrical surface of the second rim 4a.

The first and second radial blades 5 and 5a may extend with predetermined curvatures or inclinations, and may be disposed to cross each other in a plan view.

Especially, the curvatures or inclinations of the second radial blades 5a may be properly selected by one skilled in the art in consideration of a required pumping head, an exhaust pressure, a flow quantity, etc. , in relation<BR> to the use, performance, etc. , of the pump, within the scope of the present invention.

The multistage impeller le according to the fifth embodiment of the present invention further includes extension rims 4b assembled with both sides of the first rim 4, each of which has a diameter equal to the diameter of the first rim 4 and a width equal to the width of the second rim 4a of the auxiliary impeller 3.

Each of the extension rims 4b has an extension flange 4c extending perpendicularly inward from an outer circumference of the extension rim 4b. In the shown embodiment, the extension rim 4b and the extension flange 4c extending toward a center axis from the extension rim 4b constitute an extension section 41.

Also, a plurality of flange pores 4d may be formed through the extension flange 4c with a predetermined space from each other.

The extension section 41 can effectively prevent fluid having a high viscosity from sticking to an inside

portion of the housing through which the fluid passes.

The flange pores 4d formed through the extension flange 4c cause the high viscosity fluid to undergo turbulent flow, thereby preventing the high viscosity fluid from remaining in the housing and ensuring the fluid to be smoothly transferred.

FIG. 5d is a bottom view of the upper casing 20 for employing the multistage impeller le shown in FIG.

5a according to the fifth embodiment of the present invention. The upper casing 20 shown in FIG. 5d has a construction basically equal to that shown in FIG. ld, excepting that a stepped groove 13 is formed at an outer lower portion of each of the arcuate members 10 and 10a and a spacing groove 29 is formed between an outer arcuate surface of each of the arcuate members 10 and 10a and an inner cylindrical surface of the upper casing 20 or the lower casing 30, so repetition of description on the same construction will be omitted.

In the multistage impeller le according to the fifth embodiment of the present invention, each of the arcuate members 10 and 10a is fixed by a fixing means such as the fixing screws 82 while being spaced from the inner cylindrical surface of the upper casing 20 or the lower casing 30 by such a distance to form the spacing groove 29 (as shown in FIGs. 5d and 6b) having a width slightly larger than the thickness of the extension rim 4b. The stepped groove 13 formed at an outer lower portion of each of the arcuate members 10 and 10a enables the extension flange 4c of the multistage impeller le to be rotatably located in the stepped groove 13. Of course, it is possible to fix the arcuate member 10 or 10a by forming screw holes through an outer surface of the arcuate member 10 or 10a, differently from the shown embodiment.

FIGs. 6a, 7a, and 7b are perspective views of

multistage impellers according to the sixth and seventh embodiments of the present invention, which are modified from the multistage impeller le shown in FIG. 5b according to the fifth embodiment of the present invention.

The only difference between a multistage impeller lf according to the sixth embodiment of the present invention shown in FIG. 6a and the multistage impeller le shown in FIG. 5a is that the first rim 4 of the multistage impeller lf has only the extension rim 4b of the same diameter without the extension flange 4c.

Therefore, as noted from FIG. 6b, which is a bottom perspective view of the upper casing 20 employing the multistage impeller lf of FIG. 6a, each of the arcuate members 10 and 10a is fixed by a fixing means such as the fixing screws 82 while being spaced from the inner cylindrical surface of the upper casing 20 or the lower casing 30 by such a distance to form the spacing groove 29 (as shown in FIGs. 5d and 6b) having a width slightly larger than the thickness of the extension rim 4b, but each of the arcuate members 10 and 10a has no such a stepped groove 13 as shown in FIG. 5d.

FIGs. 7a and 7b are perspective views of multistage impellers lg and 1h according to the seventh and eighth embodiments of the present invention, which may be preferably employed in the self-priming pump shown in FIG. 5a. The multistage impeller lg and Ih can be produced by eliminating the auxiliary impeller 3 from the multistage impellers le and lf according to the fifth and sixth embodiments of the present invention, respectively. Instead, the multistage impeller Ig has the extension section 41 including the extension rim 4b and the extension flange 4c (see FIG. 7a), and the multistage impeller 1h has only the extension rim 4b (see FIG. 7b).

FIG. 8a is an exploded perspective view of a self- priming pump 100c according to a preferred embodiment of the present invention. Basically, the self-priming pump 100c includes an impeller assembly 200c and the impeller driving means 70 such as a motor. The impeller assembly 200c includes the upper casing 20, a typical impeller 1', and the lower casing 30 having an eccentric axial hole 33a.

The self-priming pump 100c shown in FIG. 8a is different from the self-priming pumps 100, 100a, and 100b shown in FIGs. la, 3a, and 5a, in that the typical impeller 1'or 1", or the multistage impeller li is eccentrically seated in the housing defined by the upper casing 20 and the lower casing 30, and instead the self- priming pump 100c has no arcuate member (see the arcuate members 10 and 10a in FIGs. la, 3a, and 5a).

Referring to FIG. 8b, which is a perspective view of the typical impeller 1', the typical impeller 1' includes a cylindrical core 6 having an axial hole 7 and a plurality of first radial blades 5 extending radially outward from an outer cylindrical surface of the cylindrical core 6.

Further, another typical impeller 1"shown in FIG.

8c has nearly the same construction as that of the typical impeller 1'shown in FIG. 8b, excepting that the typical impeller 1"has a plurality of curved radial blades 5'extending outward in spiral shapes with a predetermined gradient instead of the linearly extending blades 5.

The multistage impeller li according to the ninth embodiment of the present invention as shown in FIG. 8d includes a first rim 4 connecting ends of the curved radial blades 5"and extension flanges 4c perpendicularly extending toward a center axis from both sides of the first rim 4, in addition to the

construction of the typical impeller 1"shown in FIG.

8c. Here, the extension flange 4c may have a plurality of the flange pores 4d formed through the extension flange 4c.

The same description can be given on the extension flange 4c and the flange pore 4d, as that on those in FIGs. 5a and 5b.

FIG. 9 is a schematic sectional view of a pump housing containing the typical impeller 1"shown in FIG.

8b, which shows that the typical impeller 1"is rotatably and eccentrically seated in the upper casing 20.

In FIG. 9, reference numerals 21a, 22a, and 5'not described above designate an arcuate suction opening, an arcuate exhaust opening, and a radial blade, respectively.

Hereinafter, the operation of the self-priming pump 100c according to the present invention will be described with reference to FIGs. 8a and 9.

When the typical impeller 1'or 1", or the multistage impeller li is rotated by the impeller driving means 70 counterclockwise in a view from the upper casing 20 toward the lower casing 30, a negative pressure is applied to the arcuate suction opening 21a located at 9 o'clock of the upper casing 20 and fluid is strongly sucked through the arcuate suction opening 21a.

The sucked fluid is rotated and pressurized while passing through spaces between the radial blades 5 or 5', and is then exhausted through the arcuate exhaust opening 22a located at 3 o'clock of the upper casing 20 opposed to the lower casing 30.

As noted from FIG. 9, the typical impeller 1'or 1"or the multistage impeller li is rotated counterclockwise while being located relatively adjacent to the upper end of the housing and relatively far from

the lower end of the housing, so that the fluid is pressurized with a higher pressure at the upper end and with a lower pressure at the lower end of the housing.

Therefore, the fluid sucked through the eccentric arcuate suction opening 21a located at 9 o'clock of the upper casing 20 is transferred from a relatively'narrow area to a relatively wide area while its pressure is reduced. Therefore, the fluid can be easily introduced.

The introduced fluid is pressurized by the lower casing 30 while being rotated and passing through the spaces between the blades 5 or 5'. When the pressurized fluid passes through the eccentric arcuate exhaust opening 22a located at 3 o'clock of the upper casing 20, the fluid is transferred from a relatively wide area to a relatively narrow area, so that the fluid can be exhausted with a higher pressure. Moreover, the eccentricity of the typical impeller 1'or 1"or the multistage impeller li enables the typical impeller 1' or 1"or the multistage impeller li to pump a larger quantity of fluid in comparison with the size of the typical impeller 1'or 1"or the multistage impeller li.

Further, the self-priming pump 100c according to the present invention may employ the multistage impeller li according to the ninth embodiment of the present invention as shown in FIG. 8d, so that the spiral blades 5'can further improve the transfer efficiency of the fluid and the first rim 4, the extension flange 4c, the flange pore 4d can efficiently prevent fluid having a high viscosity from sticking to and remaining at a circumferential portion of the housing.

Industrial Applicability As can be seen from the foregoing, an improved impeller for a self-priming pump according to the present invention can generate high suction pressure and

exhaust pressure through its rotation. Aeover, since the impeller according to the present invention is non- clog type or semi-clog type, the impeller can prevent a pump employing the impeller from being blocked by alien material or dirt, which may exists in the fluid being transferred. Moreover, a pump assembly containing the impeller can be directly connected in series with a driving means such as a motor. Therefore, the impeller of the present invention not only can reduce noise and vibration but also achieve a relative large pumping head and a highly increased exhaust pressure and flow, even with a relatively simple construction. Furthermore, a pump employing the impeller can be internally inspected for maintenance or repair even without being disassembled. In addition, a pump employing the impeller can be used in an easy and simple manner and has a high reliability since it requires no priming for its initial operation. Further, an extension section, which may be formed at the impeller, can increase a contact area between the impeller and the fluid and enables fluid having a high viscosity to be smoothly transferred without clinging to inner corners of the housing constituted by the upper casing and the lower casing.

Therefore, an improved impeller according to the present invention, which has such an extension section, is proper especially for transferring fluid having a high viscosity.

While this invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.