US3664760A

US3664760A - Centrifugal pump

Info

Publication number: US3664760A
Application number: US68911A
Authority: US
Inventors: Norbert L Reiner
Original assignee: Coleco Industries Inc
Current assignee: SLM Inc
Priority date: 1970-09-02
Filing date: 1970-09-02
Publication date: 1972-05-23
Anticipated expiration: 1989-05-23

Abstract

A CENTIFUGAL PUMP HAS A SYNTHETIC PLASTIC IMPELLER WITH AN ELONGATED PORTION COOPERATIVELY DIMENSIONED AND CONFIGURATED TO ENGAGE AND COVER THE SHAFT OF A MOTOR DRIVING THE PUMP AND WHICH PHYSICALLY AND ELECTRICALLY ISOLATES THE FLUID BEING PUMPED FROM THE MOTOR. THE HOUSING OF THE PUMP HAS A DUMP CHAMBER WITH AN APERATURE THEREIN THROUGH WHICH THE HUB EXTENDS. SEALING MEANS IN PROVIDE ABOUT THE APERATURE, WHICH INCLUDES A RADIAL LIP SEAL AND CYLINDRICAL METALLIC SLEEVE WITH AN INTERIOR ELASTOMERIC COATING PRESS FIT ONTO THE HUB TO INSURE POSITIVE ENGAGEMENT THEREBETWEEN DESPITE VARYING TEMPERATURES AND THE INHERENT DIFFERENT IN THERMAL COEFFICIENTS OF EXPANSION OF THE TWO MATERIALS. A RADIALLY EXTENDING DISC-SHAPED SLINGER IS FIXED ON THE ELONGATED HUB OUTBOARD OF THE IMPELLER AND THE RADIAL SEAL.

Description

May23, 1972 N LREINER Y 3,664,760

- CENTRIFUGAL PUMP Filed Sept. 2, 1970 2 Sheets-Sheet 1 I /1 ven for /Vorer L Eef/1er Hof-Hey May 23, 1972 N. L. REINER 3,664,760

CENTRIFUGAL PUMP 2 Shects-Sheet Filed Sept. "3, 1970 United States Patent O U.S. Cl. 415-170 A 4 Claims ABSTRACT F THE DISCLOSURE A centifugal pump has a synthetic plastic impeller with an elongated portion cooperatively dimensioned and conligurated to engage and cover the shaft of a motor driving the pump and which physically and electrically isolates the uid being pumped from the motor. The housing of the pump has a pump chamber with an aperture therein through which the hub extends. Sealing means is provided about the aperture, which includes a radial lip seal and cylindrical metallic sleeve with an interior elastomeric coating press fit onto the hub to insure positive engagement therebetween despite varying temperatures and the inherent difference in thermal coefficients of expansion of the two materials. A radially extending disc-shaped slinger is fixed on the elongated hub outboard of the impeller and the radial seal.

BACKGROUND OF THE INVENTION Centrifugal pumps are widely used where high volume and relatively small pressure increases are required. Such pumps may be classified in two general classes, namely the volute pumps and diffuser pumps. In the former, the impeller is peripherically surrounded by a spiral case, the outer boundary of which may be a curve called a volute. In the latter, the impeller is rounded by diffuser vanes which provide gradually enlarging passages to effect a gradual reduction in velocity.

Centrifugal pumps are also divided into single-suction pumps and double-suction pumps. Other classifications may be made as to single and multi-stage and also as to the type of impeller, which may `be either of the open or unshrouded type of of the shrouded type. In all of these types various shaft seals of both radial and circumferential design have been employed in the wide range of centrifugal pumps which are known in the art although many are specifically intended for high pressures, temperatures or other special problems.

In filter pumps for swimming pools and other` applications where persons are in physical contact with the liquid in the system, problems of particular importance are electrical current flow through the metal motor shaft to the pump and thereby through the liquid to the water in a swimming pool or the like, thus presenting a safety hazard. The use of synthetic plastic or other electrically insulating materials for the pump or for the motor shaft has been suggested. However, it is necessary to provide an effective seal about the motor shaft and thus to provide a surface having sufficient wear resistance. Another problem has been the passage of fluid leaking through the shaft seal into the electric motor driving the pump with resultant ill effects thereon. Still another problem has been the corrosion of the motor shaft due to exposure to the water being pumped and particularly to chemicals contained therein. While face seals employed in some centrifugal pumps may be suitable, under certain circumstances they deteriorate rapidly if operated without liquid in the pump to dissipate heat.

It is an object of the invention to provide isolation of the liquid in the centrifugal pump and the electrical current in the motor provided to drive the pump.

It is also an object to provide a pump, wherein water "ice or other liquid may be prevented from flowing into the interior of the motor to prevent damage thereto and wherein there is minimized corrosion of the motor shaft due to exposure to the medium being pumped.

Still another object is to provide a centrifugal pump employing a highly effective shaft seal having excellent wear resistance.

A further object is to provide a relatively low pressure centrifugal water circulating pump which is relatively simple and inexpensive to produce and which is essentially completely sealed from the motor provided to drive the pump.

SUMMARY OF THE INVENTION It has now been found that the foregoing and related objects can be readily attained in a centrifugal pump for a fiuid which is adapted to be driven by a motor having a shaft portion extending therefrom. The pump has a housing providing a chamber of generally circular transverse section, an inlet conduit extending axially from the chamber generally centrally thereof, an outlet conduit, and an aperture extending axially into the chamber 0pposite the inlet conduit. Disposed in the chamber for rotation is a synthetic plastic impeller having a multiplicity of vanes and an integral, elongated generally cylindrical hub extending through the aperture. A coaxial mounting aperture extending into the hub from the end outwardly of the chamber is adapted to engage and enclose the shaft portion of an associated motor, and the outlet conduit has an axis adjacent the periphery of the vanes. Sealing means on the housing engages the elongated hub adjacent the aperture into the chamber so as to prevent substantially fluid flow outwardly of the chamber whereby the elongated hub isolates the associated motor shaft from the fluid in the pump chamber.

In its preferred aspect, the centrifugal pump impeller has a cylindrical metallic sleeve disposed on the elongated hub adjacent the aperture and the sealing means engages the circumferential surface of the sleeve which thus provides a wear resistant surface on the hub. The sleeve will normally have an elastomeric coating on the inner surface thereof to provide a firm press fit on the hub and desirably the sealing means will comprise a dual lip radial seal. A slinger advantageously is disposed on the elongated hub outwardly of the chamber, and it has a radially extending disc portion whereby liquid passing along the elongated hub is centrfugally propelled radially outwardly away from the motor.

In the centrifugal pump employing the present invention, the housing desirably will be fabricated with a c0- axial generally annular recess portion in the chamber about the Iaperture 'and the sealing means is disposed therein. The housing is conventionally comprised of a pair of cooperatively threaded members defining the chamber and having `sealing means engaged therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevational view of a centrifugal pump and motor assembly embodying the present invention;

FIG. 2 is a fragmentary view of the assembly in partial section and to an enlarged scale generally along the line 2 2 of FIG. l showing in detail the relationship of the motor shaft, impeller, hub seal and slinger;

FIG. 3 is a fragmentary sectional view to a still further enlarged scale of the hub seal;

FIG. 4 is a sectional view to a somewhat enlarged scale of the hub seal taken along the line 4 4 of FIG. 2.;

FIG. 5 is a front elevational view of the open-type impeller illustrated in FIG. 2;

FIG. 6 is a side elevational view of an alternate impeller construction of the shrouded type; and

FIG. 7 is a front elevational view of the impeller shown in FIG. 6.

DETAILED DESCRIPTION OF THE ILLUSTRATE EMBODIMENTS Turning now in detail to FIGS. 1-5 of the attached drawings, therein illustrated is a centrifugal pump embodying the present invention and having a housing comprised of a body member designated by the numeral 10 and a cover member generally designated by the numeral 12. Each has a circular generally planar end wall portion 9, 35 respectively with sidewalls 7, 8 respectively and, when the two are assembled, they deiine a generally circular chamber or cavity 13. The body portion 10 of the housing has an outlet conduit 14 extending secantally of the chamber 13 adjacent the periphery thereof and a detlection member or tongue extending along the length of the sidewall 7 in the chamber 13 adjacent the outlet conduit 14 to cause deflection of iiuid therein. The tongue 15 is generally wedge shaped; one face is aligned with the outlet conduit 14 and one obliquely disposed face is curvilinearly contoured for streamlined relationship with the periphery of the chamber 13. The end Wall 9 of the body member 10 is configured to provide a generally annular recess 18 and has a circular coaxial aperture 20 therein.

The end wall 9 of the body member 10 is provided with four axially extending legs 22 (two not shown) having threaded inserts 22a, the sidewall 7 has an external portion 24 adjacent its free end and which is engaged with the internally threaded portion 30 on the sidewall of the cover member 12. The cover member 12 has a cylindrical inlet conduit on the end wall 35 in coaxial relationship with the circular aperture of the body member 10. The inlet conduit 31 has an enlarged cylindrical portion 32 adjacent the end wall 35 and is supported by the webs 34 integrally formed therewith. On the inner surface of the end wall 35 and are annular rib 38 adjacent the sidewall 8 and an annular channel 39 therebetween generally in alignment with the sidewall 7 of the body member 10. Seated in the channel 39 is a resiliently deformable sealing ring 40 which is formed when the body member 10 and cover member 12 are threaded together tightly as may be seen in FIG. 2.

Supported for rotational movement within the chamber 13 of housing 10 is a synthetic plastic impeller generally designated by the numeral 42 and have a hub generally designated by the numeral 43 and of generally circular cross section. Referring more specifically to FIG. 5, the impeller 42 is integrally formed with the hub portion 43, a disc portion 48 adjacent the end wall 9 and elongated hub portion 43 which are co-planar with shorter vanes 46 extending from the outer peripheral portion thereof toward the central portion. Holes 50 are provided in the disc 48 to ensure a pressure balance between the two generally planar faces thereof.

The elongated hub 43 has a rounded, closed end portion 56 extending from adjacent the end wall 9 beyond the

vanes

14, 46 toward the inlet conduit 31 and a generally cylindrical portion 52 of reduced diameter which extends through the recess 18 and outwardly through the aperture 20 of the end wall 9. Thus, it can be seen that a radially extending shoulder S4 is provided between the

portions

52, 56 of differing diameters and it is located adjacent the recess 18. The elongated hub 43 has an aperture extending coaxially therein from the reduced diameter end portion 52 and which is comprised of a relatively small diameter portion 58 in the closed end portion 56 and relatively large diameter portion 60 in the reduced diameter cylindrical portion 52. In the portion 58, there are two flat surfaces (not shown) spaced about the periphery thereof which are cooperatively dimensioned and configured to mate with the motor shaft 80 and prevent rotation therebetween.

Disposed on the smaller diameter portion 52 is a cylindrical sleeve 62 having press lit relationship therewith and having one end thereof abutting the shoulder 54 of the elongated hub 43. As best seen in FIG. 3, the metallic cylindrical sleeve 62 has a thin layer or coating 64 of elastomeric material extending about its inner periphery to insure positive engagement on the shaft therebetween despite variations in expansion and contraction therebetween resulting from the inherent differences in thermal coetlicients of expansion of the sleeve 62 and the impeller hub 43. The elastomeric coating 64, also seals the interface between the sleeve 62 and the elongated hub 43 to prevent air from being drawin into the pump during operation thereof and to prevent leakage of water out of the pump when the pump is not being operated. The elastomeric coating 64 also thermally isolates the resin of the impeller 42 from frictional heat energy should the pump be operated without water therein. Moreover, the composite construction of the sleeve 62 avoids any need for expensive insert molding which would otherwise be required and which requires special construction of the parts thereof.

Engaged with the circumferential surface of the sleeve 62 is a dual radial lip seal generally designated by the numeral 70 and formed of elastomeric material with two lips 72. One of the lips 72 is biased by a stainless steel garter spring 74 against the sleeve 62, and the other lip 72 is extended along the surface of the sleeve 62. The body of the seal 70 is rigidiiied by the metal ring 73, and the circular exterior wall 76 of the seal 70 is pressed into the annular recess 18 of the body member 10 where it is held in fixed position. The relationship of the members is shown in greater detail in the cross sectional view of FIG. 4 wherein are shown the metallic sleeve 62, its elastomer coating 64, the elongated hub 43 and the motor shaft 80. For maximum simplicity, the seal 70 and sleeve 62 in addition to their sealing function also provide the bearing support for the impeller 42 within the pump. This eliminates any alignment problem between the seal and the bearing but makes particularly important the avoidance of wear at the circumferential portion of the elongated hub 43 which contacts the radial seal 70. A dry lubricant (not shown) is carried by the sintered metal sleeve 62 in the pores thereof and optionally in the space between the lips 72 both to avoid slipping and sticking of the seal which would be prejndical to sealing and also to minimize frictional power losses.

The motor shaft 80 of the electric motor `82 is cooperatively configured and dimensioned for engagement with the elongated hub 43. More particularly, the shaft `80 has an end portion of reduced external diameter 84 with two flat portions (not shown) engaged with the ilats (not shown) on the hub 43 impeller aperture portion 58 to prevent relative rotation therebetween. The larger diameter portion -86 has a reduced diameter neck portion 8-8 open along its length to provide an annular recess in which is seated a set screw 90 provided to retain the slinger 92 thereon. As seen in FIG. 2, the slinger 92 has a radially extending disc portion 94 on its axial end adjacent the radial lip seal 70 and it is preferably axially spaced between the seal 70 and the motor 82. The set screw 90 also axially secures the impeller 42 on the shaft 80 since it passes through the aperture 43a of the elongated hub 43, which is best shown in FIG. 3.

In FIGS. 6 and 7, there is illustrated an alternative embodiment of impeller generally designated by the numeral 96. This closed type or shrouded impeller 96 has two parallel radially extending walls 98 of disc-shaped configuration with a coaxial inlet portion 100 of cylindrical conguration adapted to dispose adjacent the inlet of the pump chamber and communicating with the space between walls 98. A multiplicity of wall elements or vanes 102 extend from the center thereof to provide ow channels therebetween. As a result, fluid entering the inlet portion 100 is conveyed into the center of the impeller between the walls 98 and is then centrifugally moved outwardly between the vanes 102.

Turning now to the operation of the pump of the invention, liquid is drawn through the inlet conduit 31 into the chamber 13. The centrifugal action of the

vanes

44, 46, of impeller 42 driven by the motor 82 cause liquid in the chamber 13 to flow into the outlet conduit 16 and thence outwardly of the pump. The radial lip seal 70 bears on the sleeve 4V62 and prevents ow of water between the static pump body member and the elongated hub 43. If any leakage does occur beyond the lipY 72, the uid would continue along the cylindrical section 52 of the elongated hub 43 until it reaches the disc portion 94 of slinger 92 whereupon it will be centrifugally ejected away from the motor 82. Thus, the motor shaft l80 is isolated from and protected from the corrosive action of the uid by the elongated hub 43, which encloses it, and the cooperating structure. Moreover, the structure electively isolates the fluid passing through the pump from the electrical current ow in the motor since the metallic shaft is fully insulated in the area of liquid contact.

The pump construction of the present invention while shown and illustrated with respect to a centrifugal pump having open and shrouded impellers is also adapted for use in centrifugal pumps which may differ in some respects, such as multi-stage pumps. The seal and bearing may be integrated as illustrated or they may be provided by separate elements without departing from the invention. Prevention of relative rotation and axial movement between the impeller and the shaft may be by means of screw threads instead of cooperating fiat surfaces and set screws, or by other suitable mechanical interlocks. Moreover, tbe impeller enclosing the shaft of the associated motor may even be used with a pump utilizing a face seal instead of a radial seal albeit with lesser effectiveness. The material selected for the various parts may vary widely; as for example, the elastomeric coating and the elasomer of the seal material may be selected from various syn thetic elastomers including butadiene copolymers, silicones and polyurethanes; butadiene/acrylonitrile copolymers have been found highly satisfactory. The lubricant used between the sleeve and the radical seal is preferably molybdenum disulfide although other lubricants may be used. The sleeve is preferably made of sintered stainless steel to obtain maximum wear resistance and also to insure optimum lubrication.

The housing elements are constructed of synthetic plastic such as ABS, polycarbonates, polyacetals, polyphenylene oxides (PPO); self-extinguishing ABS compositions are advantageously employed because of easy formability, cost and impact resistance. Similarly, the impeller may be constructed of various synthetic resins including those mentioned for the housing; polycarbonate resins have been found highly satisfactory.

Thus, it can be seen from the foregoing detailed speciiication and drawings that the present invention provides a highly effective pump in which the electric current in the motor is isolated from the fluid in the centrifugal pump. In addition, the coaxially apertured elongated hub enclosing the motor shaft separates it 4from fluids being pumped which might produce corrosion thereof. -Fluid leakage from the pump to the motor is substantially prevented by the use of a sleeve and sealarrangement which is highly durable despite the use of relatively soft synthetic plastic material for the construction of the pump members and particularly the impeller hub. Moreover, this construction is relatively inexpensive and easy to produce and assemble.

vWhat is claimed is:

1. A centrifugal pump for a fluid adapted to be driven by a motor having a shaft portion extending therefrom which comprises:

(a) a housing having walls providing a chamber of generally circular transverse section, an inlet conduit extending axially of said chamber generally centrally thereof, 'an outlet conduit, and an aperture extending axially into said chamber opposite said inlet conduit;

(b) a synthetic plastic impeller having a multiplicity of vanes and an integral, elongated generally cylindrical hub extending through said aperature with a coaxial mounting aperture extending thereinto from the end outwardly of said chamber adapted to engage and enclose the shaft portion, of an associated motor, said outer conduit having an axis adjacent the periphery of said vanes;

(c) a cylindrical metallic sleeve disposed on said elongated hub adjacent said aperture, said sleeve having an elastomeric coating on the inner surface thereof provided resilient frictional engagement on said hub; and

(d) sealing means on said housing engaging the circumferential surface of said sleeve and preventing fluid flow outwardly of said chamber whereby said sleeve provides a wear resistant surface on said hub and said elongated hub isolates the associated motor shaft from fluid in said pump chamber.

2. The centrifugal pump of claim 1 wherein said sealing means comprises a dual lip radial seal.

3. The centrifugal pump of claim 1 wherein said chamber has a coaxial, generally annular recess portion about said aperture in which said sealing means is disposed.

4. The centrifugal pump of claim 3 wherein said housing includes a pairv of cooperatively threaded members defining said chamber and having sealing means therebetween, one of said members providing the sidewall and an end wall through which said hub extends and being adapted to be supported upon the associated motor, the other of said members providing the other end wall of said chamber.

References Cited UNITED STATES PATENTS 2,283,263 5/ 1942 Kates 415-201 2,684,033 7/ 1954 Montgomery et al. 415-214 2,768,849 10/ 1956 Riesing 415-170 A 2,853,021 9/1958 Duble 415-170 A 3,095,821 7/ 1963 Elenbaus 415-214 3,145,912 8/1964 Weis 415-214 3,227,087 l/l966 Albee et al. 415-2l9 3,304,875 2/ 1967 Copeland 415-214 3,335,668 8/1967 Thon 415-214 3,456,875 7/1969 Hein 415-503 3,594,102 7/1971 Oden 417-423 FOREIGN PATENTS 512,223 8/1939 Great Britain 415-196 536,245 5/1941 Great Britain 415-214 652,840 5/ 1951 Great Britain 415-197 HENRY F. RADUAZO, Primary Examiner U.S. Cl. XR.