US3614258A

US3614258A - Scavenger plate for pump inlet

Info

Publication number: US3614258A
Application number: US813411A
Authority: US
Inventors: Paul H Scheffler; Jack L Mccabria
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1969-04-04
Filing date: 1969-04-04
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19

Abstract

A plate structure disposed between the end of a pump rotor and an inlet port provided in an associated pump housing, the plate being effective to withdraw liquid from around the outside of the rotor when the rotor is rotated, and direct the liquid radially inwardly towards the axial center of the pump and rotor, and into the flow stream entering the rotor.

Description

provided in an associated pump ective to withdraw liquid from 1' when the rotor is rotated, and rdly towards the axial center of FOREIGN PATENTS 3/1967 White.....

2 1950 10/1919 Switzerland..................

Paul H. Scheffler; Jack L. McCabria, both of Lima, Ohio 813,411 Apr. 4, 1969 [45] Patented Oct. 19, 1971 Westinghouse Electric Corporation Pittsburgh, Pa.

4 Claims, 2 Drawing Figs.

References Cited UNITED STATES PATENTS 6/1948 Unlted States Patent [72] Inventors [21] AppLNo.

[22] Filed [73] Assignee [54] SCAVENGER PLATE FOR PUMP INLET 51] [50] FieldofSearch........,...................................

PATENTEUBU 19 |97| INVENTORS Paul H. Scheffler 0nd r3 ATTORNEY Jock L. McCobrl 2 V 2 m C! WITNESSES SCAVENGER PLATE FOR PUMP INLET BACKGROUND OF THE INVENTION The present invention relates generally to pumps, and particularly to pumps for pumping molten metals.

In copending applications Ser. No. 610,935 filed Jan. 23, 1967 by P. H. Scheffler, and now U.S.'Pat No. 3,459,133, Ser. No. 761,024 filed Sept. 20, 1968 by P. H. Scheffler et al.-, both assigned to the present assignee, there are disclosed pump structures capable of pumping liquid or molten metals in an effective and efficient manner. The disclosed structures include generally an elongated rotor vertically disposed in an associated inlet housing. the lower end of the rotor being located above an inlet port provided in the lower end of the housing. The rotor has an inlet port (or ports) located above the housing inlet port, and internal passageways and vanes extending the length of the rotor, the vanes and passageways providing the pumping action by producing a forced vortex of liquid within the rotor when the rotor is rotated.

Between the inner diameter of the housing and the outer diameter of the rotor is a relatively narrow annular space which fills with the liquid or molten metal when the lower end of the pump is disposed in the vat or container which contains the liquid to be pumped. Liquid from the discharge end of the rotor drains into this annular space during certain modes of operation of the pump since a positive seal is not provided at the rotor discharge. The liquid within the annular space must be removed and continuously scavenged when the rotor is rotating to prevent a self-perpetuating disturbance from acting upon the rotor. This disturbance is produced by an uneven displacement of the liquid within the annular space. If the rotor is displaced a radial distance from the center of the housing, because of vibration or by misalignment or eccentricity in the assembly, a converging passage and a diverging passage are produced in the space around the rotor. The circumferential flow of liquid in the converging passage generates a positive pressure and force in an inward direction towards the center of the rotor, and the flow in the diverging passage generates a negative pressure and force which acts outwardly and away from the center of the rotor. The resultant of these two forces acts through the center of the rotating rotor in a direction perpendicular to the radial displacement of the rotor within the annular space. Thus, the rotor moves in a circumferential direction to a new location where the hydraulic forces will again be directed perpendicular to the new displacement.

The resulting motion of the rotor is therefore self-perpetuating and can be described as a whipping motion about the center of the housing. The mechanism which produces the phenomenon is the same mechanism which produces oil whip or shaft whip in a vertical guide bearing.

The initial displacement of the rotor may be caused by vibration, or by misalignment or eccentricity between the rotor and housing. Accordingly, this initial displacement cannot readily be eliminated. The magnitude of the self-perpetuated whipping motion of the rotor can be such that the rotor will contact and rub against the housing thereby increasing the possibility of damage to both the rotor and the housing. In any case, the magnitude of the deflection is such that the pumping capacity of the pump is appreciably reduced, and the friction generated in the liquid by the whipping rotor increases substantially the power required to drive the rotor.

BRIEF SUMMARY OF THE INVENTION To eliminate the hydraulic forces generated in the liquid metal around the rotor, and thereby maintain rotor alignment and minimum frictional losses within the housing with rotation of the rotor, the present invention includes a stationary scavenger plate disposed between the bottom of the rotor and the bottom wall of the inlet housing. The liquid in the housing can be effectively scavenged" or drawn out from around the rotor by utilizing the rotational velocity imparted to the liquid by the rotor, and by the ejector action of the inlet ports. The bottom surface of the plate is provided with curved bosses or vanes which deflect and direct the rotating liquid radially inwardly towards the eye or axial center of the pump and thus towards the inlet port of the rotor. The ejector action of the port entrains the inwardly directed liquid flow into the rotor through an inlet orifice provided in the plate.

THE DRAWING The invention, along with its objectives and advantages, will better understood upon consideration of the following detailed description in connection with the accompanying drawing, in which:

FIG. 1 is a vertical section of the lower portion of a pump provided with a scavenger plate in accordance with principles of the invention; and

FIG. 2 is a bottom plan view of the plate shown in FIG. ll.

PREFERRED EMBODIMENT Specifically, FIG. I shows, in vertical section, the lower portion of the pump disclosed in the above-mentioned application Ser. No. 761,024, as well as the scavenger plate briefly described above and more particularly described hereinafter.

The portion of the pump shown in FIG. I is generally designated by the numeral 10. The structure of the pump includes an elongated rotor 12 centrally disposed in an elongated inlet housing 14 for rotation therein. Between the rotor and housing is formed a relatively narrow annular space I3. The housing and rotor are provided with inlet ports 16 and 18, respectively, formed by

replaceable orifice structures

20 and 22 suitably secured in the lower ends thereof, though the present invention is not limited thereto. The interior of the rotor is provided with liquid directing passageways or channels 24, the channels being connected in fluid communication with the inlet port 18 by openings 25 provided in an inlet bush ing 26.

As explained in the aforementioned] applications, the pump component parts as thus far described are preferably cast or compacted from a heat and corrosion resistant material such as silicon carbide.

As explained earlier, the portion of the pump 10 shown in FIG. I may be disposed directly in a bath of molten metal (not shown) to perform its pumping function, i.e., to transfer the molten metalfrom a vat or other container (not shown) to another location, to circulate the molten metal within the container, or to circulate it between two or more containers or locations. When the housing 14 is lowered or otherwise disposed in the bath of molten metal, the metal enters the housing through the inlet port 16 to fill the space l3 between the rotor and housing. When it is desired to start the pumping operation, the rotor is rotated causing a flow of the metal into the inlet ports 16 and 18, and through the: rotor channels 24 as indicated by appropriate arrows. The liquid metal is discharged from the pump through a discharge port in the upper portion thereof.

If the rotor 12 is in substantially perfect alignment with the housing I4, and if the surfaces of the housing and rotor forming the annular space 13 are formed or finished in substantially perfect roundness, the hydraulic forces within the space 13 would be essentially balanced and the rotor deflection problem, explained above, would be essentially nonexistent. However, losses due to the friction between the rotor and liquid would remain a problem.

As mentioned above, the component parts of the pump are preferably cast or compacted parts made from hard, ceramic materials which are not easily and economically machined or otherwise finished to a degree providing perfectly round or smooth surfaced components. With such materials and methods of making the pump parts, and particularly the housing and rotor, the probability of some vibration, eccentricity, and misalignment is always present, so that a more simple and economical means is required to effect and insure the balance of the hydraulic forces acting upon the rotor 12.

In accordance with the present invention, a stationary plate structure 28 is located in the space between the bottom end of the rotor 12 and the end wall 29 of the housing 14 or, more specifically, in a horizontal plane. between the inlet bushing 26 and the orifice member 20.

The bottom surface of the plate 28 is provided with circumferentially spaced apart bosses or raised vane portions 30 which rest on the inside surface of the end wall 29, the vanes being effective to space the main body portion of the plate from said wall and the orifice member 20. in FIG. 2, three vanesare shown, for purposes of illustration only, and the vanes are preferably curved in a radial direction, as shown, for purposes presently to be explained.

The plate 28 is further provided with an inlet orifice 31 located in axial alignment with the ports 16 and 18 of the rotor and housing, respectively. The plate, like the other pump components, is preferably made of a hard, heat resistant material such as silicon carbide.

In operation, upon rotation of the rotor 12, a rotational velocity component is imparted to the liquid in the annular space 13, and, as the pumping action of the rotor draws liquid through the inlet port 16, an ejector action is produced at the port. The direction of the rotational velocity of the liquid is tangential along the fixed, inside surface of the housing 14 so that, without the plate 28, the tendency of the rotating liquid is to remain away from the eye or axial center of the pump and the flow of liquid entering through the port 16. The plate 28, with its vanes 30, however, collects the liquid rotating in the space 13 and redirects it radially inwardly towards the eye of the pump and into the flow of liquid entering through the port 16 to be entrained thereby. The radial curvature of the vanes 30 improves their effectiveness in the directing the flow in a radially inward direction.

In this manner any liquid in the space 13 is moved or scavenged so that friction losses in said liquid, and the possibilityof unevenly displaced liquid existing around the rotor is essentially eliminated, along with the unbalanced hydraulic forces resulting therefrom. In this manner and for this reason,

the rotor is not deflected and the pump structure 10 of the present invention performs effeciently and essentially without vibration with cast components having uneven and unfinished surfaces. And this is accomplished with a simple, economical structure, namely,'the plate 28, the plate providing further savings by permitting the use of pump components having the unfinished surfaces.

Though the invention has been described with a certain degree of particularity, changes may be made therein without departing from the spirit and scope thereof.

We claim:

1. In a pump structure for pumping liquids, said structure including an elongated annular walled rotor having internally axially extending vanes and an elongated walled housing disposed concentrically about said rotor, the rotor being rotatable in the housing about a vertical axis with an annular clearance between the rotor and the housing permitting limited reverse flow 'therebetween, the housing and the rotor having axially aligned restricted inlet ports in their lower ends to admit liquid into the rotor to be pumped axially thereof, and a stationary plate disposed horizontally in the housing between the housing and the lower end of the rotor, said plate having a restricted inlet 'orifice in axial alignment with said rotor inlet port, and said plate having means to direct liquid from said annular clearance through the inlet orifice to the rotor inlet port on the creation of a suction vortex by the rotation of said rotor.

2. The pump structure of claim 1 in which said plate is spaced from the lower end of the housing and said means provides for liquid flow under the plate from the annular clearance to the inlet orifice.

3. The pump structure of claim 1 in which said plate has vanes on its lower surface for supporting the plate in spaced relation to the lower end of the housing, said vanes directing liquid from the annular clearance to flow under the plate to the inlet orifice.

4. The pump structure of claim 3 in which the vanes are curved radially of the plate.

Claims

1. In a pump structure for pumping liquids, said structure including an elongated annular walled rotor having internally axially extending vanes and an elongated walled housing disposed concentrically about said rotor, the rotor being rotatable in the housing about a vertical axis with an annular clearance between the rotor and the housing permitting limited reverse flow therebetween, the housing and the rotor having axially aligned restricted inlet ports in their lower ends to admit liquid into the rotor to be pumped axially thereof, and a stationary plate disposed horizontally in the housing between the housing and the lower end of the rotor, said plate having a restricted inlet orifice in axial alignment with said rotor inlet port, and said plate having means to direct liquid from said annular clearance through the inlet orifice to the rotor inlet port on the creation of a suction vortex by the rotation of said rotor.