Molten metal pump

• US 6,457,940 B1
• Filed: 07/21/2000
• Issued: 10/01/2002
• Est. Priority Date: 07/23/1999
• Status: Expired due to Fees

• Current Assignee: Dale T. Lehman
• Original Assignee: Dale T. Lehman
• Inventors: Lehman, Dale T.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Edgar, Richard A.
• Application Number:
  US09/621,201
• Time in Patent Office: 802 Days
• Field of Search: 415/200, 415/121.2, 415/206, 298/894, 416/247.R, 416/228, 416/235, 416/236.R, 416/182, 416/181, 416/185
• US Class Current: 415/206
• CPC Class Codes: F04D 29/047 hydrostatic; hydrodynamic
• CPC Class Codes: F04D 29/2277 for increasing NPSH or dealing with liquids near boiling-point
• CPC Class Codes: F04D 29/2288 for comminuting, mixing or separating
• CPC Class Codes: F04D 7/06 the fluids being hot or corrosive, e.g. liquid metals
• CPC Class Codes: F04D 7/065 for liquid metal
• CPC Class Codes: Y10T 29/49329 Centrifugal blower or fan

Abstract

An impeller for a molten metal pump includes an exterior bearing mounting surface that is trued about the axis of the impeller and drive shaft assembly. Another impeller arrangement includes a pumping chamber having an axis offset from the impeller axis to achieve a volute pumping arrangement. In a further arrangement, the impeller is provided with peripheral pumping chambers intersecting the peripheral surface of the impeller. In each of the foregoing arrangements, a plate may be fixed to the pump drive shaft at a location axially spaced from the impeller inlet to screen debris and to pump molten metal to the impeller inlet.

Claims

1. A method of making an impeller assembly for a molten metal pump including a casing having a pumping chamber in which said impeller assembly is mounted, said impeller assembly including a shaft having an axis of rotation and opposed first and second shaft ends, an impeller fixed to one of said shaft ends, comprising the steps of mounting said impeller to a trueing shaft to form a trueing assembly, permanently mounting a ring bearing to said impeller, said ring bearing extending about said impeller and having an outer peripheral surface for engaging a casing bearing, and trueing said outer peripheral surface of said ring bearing by rotating said trueing shaft and simultaneously shaping said outer peripheral surface to provide the surface with a circular configuration about said trueing shaft axis.

2. A method as in claim 1, wherein the step of mounting said bearing to said trueing shaft includes rotating said trueing assembly and simultaneously cutting a bearing mounting groove in said impeller having a circular configuration about said trueing shaft axis.

3. A method of making a molten metal pump including a shaft having an axis of rotation and opposed first and second shaft ends, a drive motor operatively connected to said first shaft end, an impeller fixed to said second shaft end and a casing including a pumping chamber having said impeller mounted therein in a volute configuration, comprising the steps of providing said impeller with a plurality of vanes having radial extremities terminating in a circular pattern, fixing said impeller to said shaft to form an assembly, forming said pumping chamber with a circular cross-section having an axis extending through a chamber center in said casing and a sidewall having an inside surface extending about the periphery of said chamber along said circular cross-section with a uniform radial spacing from said chamber axis, forming a pump outlet having an entrance in said pumping chamber and an exit remote of said chamber, mounting said assembly to said casing with said impeller in said casing with said shaft axis off-set from said chamber axis so that the radial spacing and cross-sectional area between the radial extremities of the vanes and the inside surface of the sidewall of the pumping chamber increases in the direction of rotation approaching said entrance of said pump outlet.

4. A pump for pumping molten metal including a casing forming a pumping chamber having a casing inlet for intake of molten metal and a casing outlet for discharge of molten metal, an impeller mounted within said casing, said impeller being mounted to a shaft assembly and including an impeller inlet for receiving molten metal passing through said casing inlet, and a first stage pumping plate secured to said shaft for rotation remote of said casing, said plate including a plurality of plate chambers extending therethrough to pump molten metal into said casing inlet and impeller inlet.

5. An impeller as set forth in claim 4, wherein said plate chambers are inclined into the direction of rotation.

6. An impeller as set forth in claim 5, wherein said plate has opposed first and second plate surfaces, each of said plate chambers communicates between an intake opening in said first plate surface and a discharge opening in said second plate surface, and each of said plate chambers is inclined in the direction of rotation with said intake plate opening leading said discharge plate opening.

7. An impeller as set forth in claim 5, wherein said plate is sized and spaced from said casing to prevent debris contained in the molten metal from passing into said casing inlet.

8. An impeller as set forth in claim 7, wherein said plate has a radial extent substantially coextensive with that of said casing inlet and an axial spacing from said casing selected to inhibit passage therebetween of debris contained in the molten metal.

9. An impeller for a molten metal pump comprising a body portion including an axis of rotation, first and second radial surfaces joined by a peripheral side surface, and a plurality of pumping chambers spaced about the periphery of said body portion, each of said pumping chambers having an elongate, slot-like configuration extending in an axial direction along a chamber length and a cross-sectional area having a major dimension substantially less than said chamber length, an inlet opening in said first radial surface and a discharge opening in said peripheral side surface, and a wall portion inclined in the direction of rotation extending along substantially all of said chamber length to said peripheral side surface and said discharge opening.

10. An impeller as set forth in claim 9, wherein said discharge opening intersects said inlet opening at said first radial surface.

11. An impeller as set forth in claim 10, wherein said pumping chamber has a central axis extending along said pumping chamber length and said central axis extends at an inclined angle relative to the direction of rotation of said impeller.

12. An impeller as set forth in claim 11, wherein said inclined angle is a linear angle.

13. An impeller as set forth in claim 11, wherein said inclined angle is a non-linear angle.

14. The impeller of claim 9, wherein said pumping chamber includes a second wall portion that also extends to said discharge opening, said second wall portion opposing said first mentioned wall portion and also being inclined in the direction of rotation at substantially the same angle as said first mentioned wall portion.

15. The impeller of claim 9, wherein said wall portion imposes an intake vector force on molten metal entering said inlet opening along substantially all of said chamber length and said impeller also imposes a centrifugal force to radially discharge molten metal through said discharge opening during rotation of said impeller.

16. The impeller of claim 9, wherein said peripheral side surface has an axial length, and said pumping chamber and discharge opening extend along a substantial portion of the axial length of said peripheral side surface.

17. The impeller of claim 9, wherein said first and second wall portions are joined remote of said discharge opening and cooperate to provide said pumping chamber with a channel-shape having a bight that opens in said peripheral side surface to form said discharge opening and opposed first and second axial extremities spaced along said pumping chamber length, said first axial extremity opening in said first radial surface to form said inlet opening and said second axial extremity comprising a chamber end wall adjacent said second radial surface.

18. The impeller of claim 17, wherein said inlet opening intersects said discharge opening at said first radial surface.

19. The impeller of claim 18, wherein said peripheral side surface has an axial length, and said pumping chamber and discharge opening extend along a substantial portion of the axial length of said peripheral side surface.

20. The impeller of claim 19, wherein said pumping chamber has a central axis inclined in the direction of rotation from about 1°

to about 60°

.

21. The impeller of claim 20, wherein said pumping chamber channel-shape is a generally cylindrical shape and said wall portions comprise an arcuate wall.

22. The impeller of claim 20, wherein said pumping chamber channel-shape is a generally rectangular shape and said wall portions comprise planar or flat shape walls.

23. The impeller of claim 9, wherein said pumping chamber cross-sectional area intersects said peripheral side surface to form said discharge opening along substantially all of said chamber length.

24. The impeller of claim 23, wherein said impeller includes from about three to about eight of said pumping chambers, said pumping chambers being equally angularly spaced about said axis of rotation.

25. The impeller of claim 23, wherein said impeller has a generally cylindrical shape, and said pumping chambers are substantially-located in the outer one-third of the diametrical extent of the impeller.

26. The impeller of claim 9, wherein said impeller body portion has a generally cylindrical shape, said peripheral side surface including said discharge openings form a circle in a plane extending at a right angle to said axis of rotation and through said peripheral side surface, and the total of the arcuate dimensions of said discharge openings as measured along said circle is less than one-half of the circumference of said circle.

27. The impeller of claim 9, wherein said pumping chamber has a central axis extending along said pumping chamber length, said pumping length being measured along said central axis of the pumping chamber, said cross-sectional major dimension being measured in a plane extending at a right angle to said central axis, the ratio of said chamber length to said major dimension being in the range of from about 3:

1 to 20;

1.

28. The impeller of claim 23, wherein said impeller body portion has a polygonal cross-section including axially extending side faces, at least one of said side faces being radially inwardly inclined in a direction extending toward said base.

29. The impeller of claim 28, wherein said at least one side face is inclined at an angle in the range of from about 1°

to about 60°

.

30. The impeller of claim 29, wherein all side faces of said body portion are radially inwardly inclined.

31. A method of pumping molten metal by rotating an impeller submerged below the surface of the molten metal, said impeller having an axis of rotation and including a plurality of angularly spaced pumping chambers having associated intake openings in a first radial surface and discharge openings in a peripheral side surface that extends to a second radial surface, each of said pumping chambers having a chamber length and a wall portion inclined in the direction of rotation extending along substantially all of said chamber length to said peripheral side surface and said discharge opening, comprising the steps of imposing an intake force vector along said wall portion upon molten metal within said pumping chamber to cause intake flow of molten into said intake openings, and imposing centrifugal force upon molten metal within said pumping chamber to cause discharge of molten metal through said discharge openings.

32. The method of claim 31, wherein said pumping chamber and discharge opening are axially coextensive to continuously impose an intake force vector on said molten metal within said pumping chamber until it is ejected through said discharge opening.

33. An impeller for a molten metal pump comprising a body portion including an axis of rotation, first and second radial surfaces joined by an axially extending peripheral side surface, and a plurality of pumping chambers spaced about the periphery of said body portion, each of said pumping chambers having an elongate, slot-like configuration extending in an axial direction along a chamber length and a cross-sectional area having a major dimension substantially less than said chamber length, an inlet opening in said first radial surface and a discharge opening in said peripheral side surface, each of said pumping chambers including substantially equally spaced and opposed walls that extend along substantially all of said chamber length to said peripheral side surface to form said discharge opening, said opposed walls directing molten metal flow along a straight flow path through said pumping chamber.

34. An impeller as set forth in claim 33, wherein said opposed walls are inclined in the direction of rotation.

35. An impeller as set forth in claim 34, wherein said pumping chamber axially extends from said inlet opening in said first radial surface to a radially extending chamber end wall extending to said peripheral surface adjacent said second radial surface, and said discharge opening intersects said inlet opening at said first radial surface and axially extends to said chamber end wall.

36. An impeller as set forth in claim 35, wherein said opposed walls are flat or planar and cooperate to form a chamber interior surface remote of said discharge opening that directs molten metal in a single flow direction through said pumping chamber.

37. An impeller as set forth in claim 34, wherein said opposed walls have an arcuate-shape that forms a chamber interior surface remote of said discharge opening that directs molten metal in a single flow direction through said pumping chamber.