Coupling and rotor shaft for molten metal devices

Abstract

A coupling has an opening and a protrusion extending downward from the opening. The protrusion has threads that are preferably positioned outside of the opening. A rotor shaft that connects to the coupling has an internal bore with threads that receives and retains the protrusion, such as by a threaded connection between the two, so the protrusion applies driving force to the shaft.

Claims

1. A molten metal pump comprising: (a) a motor having a motor shaft connected thereto, the motor shaft having a first end connected to the motor and a second end having a plurality of fastener apertures therein; (b) a coupling comprising a cylindrical outer surface and having a first end having a plurality of fastener holes extending therethrough aligned with the apertures in the motor shaft for receiving fasteners therein, and a second end of the coupling comprising: (i) a collar having an annular inner sidewall defining a cavity therein concentric with the cylindrical outer surface and having an opening configured to receive an end of a rotor shaft, the cavity defining a top surface at an enclosed end of the cavity; and (ii) a partially threaded cylindrical projection axially protruding through the center of the opening and axially extending outside of the opening, the projection being threaded only outside of the opening such that there are no threads axially within the cavity; and (c) a rotor shaft having (i) a first end positioned at least partly in the cavity of the collar, the first end comprising a bore having a threaded portion that is threadingly connected to the projection outside of the opening to facilitate unthreading of the rotor shaft, and (ii) a second end having a rotor connected thereto.

2. The pump of claim 1, wherein the collar and the projection are comprised of steel.

3. The pump of claim 1, wherein the cavity in the collar is chamfered so that it has a smaller diameter at the top surface than at the opening.

4. The pump of claim 1, wherein the projection protrudes 2 or more from the opening.

5. The pump of claim 1, wherein the projection protrudes 3 or more from the opening.

6. The pump of claim 1, wherein the projection has a first portion configured to be positioned inside of the cavity and a second portion configured to be positioned outside of the opening, the first portion not having any threads.

7. The pump of claim 6, wherein the second portion of the projection has a length, an upper portion and a lower portion, and the lower portion comprises at least ? of the length and having no threads.

8. The pump of claim 1, wherein the threads are square, 1 ACME threads.

9. The pump of claim 1, wherein the projection has an exterior end and the exterior end is chamfered.

10. The pump of claim 9, wherein the exterior end is ? long and has a 45? chamfer.

11. The pump of claim 1, wherein the distance from the top surface to the opening is between 1 and 1.5.

12. The pump of claim 1, wherein the projection includes an interior passage for transferring gas.

13. A rotary degasser comprising: (a) a motor having a motor shaft connected thereto, the motor shaft having a first end connected to the motor and a second end having a plurality of fastener apertures therein; (b) a coupling comprising a cylindrical outer surface and having a first end having a plurality of fastener holes extending therethrough aligned with the apertures in the motor shaft for receiving fasteners therein, and a second end of the coupling comprising: (i) a collar having an annular inner sidewall defining a cavity therein concentric with the cylindrical outer surface and having an opening configured to receive an end of a rotor shaft, the cavity defining a top surface at an enclosed end of the cavity; and (ii) a partially threaded cylindrical projection axially protruding through the center of the opening and axially extending outside of the opening, the projection being threaded only outside of the opening such that there are no threads axially within the cavity; and (c) a rotor shaft having (i) a first end positioned at least partly in the cavity of the collar, the first end comprising a bore having a threaded portion that is threadingly connected to the projection outside of the opening to facilitate unthreading of the rotor shaft, and (ii) a second end having a rotor connected thereto.

14. The degasser of claim 13, wherein the collar and the projection are comprised of steel.

15. The degasser of claim 13, wherein the cavity in the collar is chamfered so that it has a smaller diameter at the top surface than at the opening.

16. The degasser of claim 13, wherein the projection protrudes 2 or more from the opening.

17. The degasser of claim 13, wherein the projection protrudes 3 or more from the opening.

18. The degasser of claim 13, wherein the projection has a first portion configured to be positioned inside of the cavity and a second portion configured to be positioned outside of the opening, the first portion not having any threads.

19. The degasser of claim 18, wherein the second portion of the projection has a length, an upper portion and a lower portion, and the lower portion comprises at least ? of the length and having no threads.

20. The degasser of claim 13, wherein the threads are square, 1 ACME threads.

21. The degasser of claim 13, wherein the projection has an exterior end and the exterior end is chamfered.

22. The degasser of claim 20, wherein the exterior end is ? long and has a 45? chamfer.

23. The degasser of claim 13, wherein the distance from the top surface to the opening is between 1 and 1.5.

24. The degasser of claim 13, wherein the projection includes an interior passage for transferring gas.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a perspective view of a pump for pumping molten metal, which may include a coupling and rotor shaft according to aspects of the invention.

(2) FIG. 2 shows a rotary degasser, which may include a coupling and rotor shaft according to aspects of the invention.

(3) FIG. 3 shows a scrap melter, which may include a coupling and rotor shaft according to aspects of the invention.

(4) FIG. 4 is a side, cross-sectional view of a coupling that can be used in accordance with aspects of the invention.

(5) FIG. 5 is a partial side view of a rotor shaft that may be used according to aspects of the invention.

(6) FIG. 6 is a side view of a coupling that may be used in accordance with aspects of the invention.

(7) FIG. 7 is a side, perspective view of a coupling that may be used in accordance with aspects of the invention.

(8) FIG. 8 is a partial side view of the lower portion of the coupling shown in in FIGS. 6 and 7.

(9) FIG. 9 is a partial, cross-sectional side view of a rotor/coupling connection in accordance with aspects of the invention.

(10) FIG. 10 is a close-up view of Section G of FIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(11) For any device described herein, any of the components that contact the molten metal are preferably formed by a material that can withstand the molten metal environment. Preferred materials are oxidation-resistant graphite and ceramics, such as silicon carbide. Oxidation-resistant graphite is most preferred because of its relatively low cost and ease of manufacturing.

(12) Referring now to the drawing where the purpose is to illustrate and describe different embodiments of the invention, and not to limit same, FIG. 1 shows a molten metal pump 20 in accordance with an aspect of the present invention. Pump 20 is designed for operation in any environment in which molten metal is to be pumped or otherwise conveyed. Pump 20 can be any structure or device for pumping or otherwise conveying molten metal, such as the tangential-discharge pump disclosed in U.S. Pat. No. 5,203,681 to Cooper, or an axial pump having an axial, rather than tangential, discharge. Pump 20 has a pump base 24 submersible in a molten metal bath B. In this embodiment, pump base 24 includes a generally nonvolute pump chamber 26, such as a cylindrical pump chamber or what has been called a cut volute although pump base 24 may have any shape pump chamber suitable of being used, such as a volute-shaped chamber. Chamber 26 may have only one opening, in either its top or bottom, since only one opening is required to introduce molten metal into pump chamber 26, although chamber 26 may have an opening in both its top and bottom. Generally, pump chamber 24 has two coaxial openings of the same diameter and usually one is blocked by a flow blocking plate mounted on the bottom of, or formed as part of, rotor 100. Base 24 further includes a tangential discharge 30 (although another type of discharge, such as an axial discharge, may be used) in fluid communication with chamber 26.

(13) The invention is not limited to any particular type or configuration of pump base, or of even having a base. A pump, rotary degasser or scrap melter used with the invention could be of any size, design or configuration suitable for utilizing a rotor shaft and coupling according to the invention.

(14) In the embodiment shown, one or more support posts 34 connect base 24 to a superstructure 36 of pump 20 thus supporting superstructure 36, although any structure or structures capable of supporting superstructure 36 may be used. Additionally, pump 20 could be constructed so there is no physical connection between the base and the superstructure, wherein the superstructure is independently supported, and/or there is no base. The motor, drive shaft and rotor could be suspended without a superstructure, wherein they are supported, directly or indirectly, to a structure independent of a pump base.

(15) A motor 40, which can be any structure, system or device suitable for driving pump 20, but is preferably an electric, hydraulic or pneumatic motor, is positioned on superstructure 36 and is connected to a drive shaft 42. Drive shaft 42 can be any structure suitable for rotating the impeller 100, and preferably comprises a motor shaft (not shown) that connects to rotor shaft 44 via a coupling 500, which is described further below.

(16) A rotor, also called an impeller, 100 is positioned at least partially within pump chamber 26. Preferred rotor 100 is preferably imperforate, and any type or shape of impeller suitable for use in a molten metal pump, rotary degasser or scrap melter, respectively, may be used to practice aspects of the invention. Rotor 100 has a connecting portion 110 to connect to a second end 44B of rotor drive shaft 44.

(17) FIG. 2 shows a preferred gas-release device 200 according to the invention. Device 200 is designed to operate in a molten metal bath B contained within a vessel 1. Device 200 is preferably a rotary degasser and includes a rotor shaft 44, an impeller 300 and a drive source (not shown). Device 200 preferably also includes a coupling 500.

(18) FIG. 3 shows a scrap melter utilizing a coupling 500 and rotor drive shaft 44 in accordance with aspects of the invention.

(19) Turning to FIG. 4, coupling 500 includes a collar 502, which as shown is circular with a flat top 504, an annular outer side wall 506, and a bottom edge 508. Two slots 505 are preferably formed on either side of collar 502 so collar 502 may be easily gripped and turned by a wrench. A passage 509 may be formed in collar 502 to permit gas to transfer therethrough. A cavity 510 is formed within coupling 500 in order to receive a first end 38A of rotor shaft 38, described further below. In one embodiment the coupling 500 is made of steel, has a height of about 2.5-3 and an overall width of about 4?-5?. Cavity 510 has a depth D of about 1-1?, and most preferably about 1?, a diameter of about 3 next to bottom edge 508, and an inner wall 512 that slopes inward at between 5? and 10?, and most preferably about 7?, until it terminates at upper cavity wall 514. Inner wall 512 preferably is not threaded.

(20) A projection 600 extends downward from upper cavity wall 514, through cavity 510 and projects outward therefrom. Projection 600 may be connected to collar 502 in any suitable manner, such as being threadingly received in an opening (not shown) or welded to collar 502. In one embodiment, projection 600 is between 0.800 and 1.000 inches in diameter, and preferably about 0.875 in diameter and extends outward from the bottom of cavity 510 (defined by where cavity 510 aligns with bottom edge 508) by between 2?-3?, and preferably 3?. At the bottom end of projection 600 is preferably a chamfered end 602, that in the embodiment shown is ? long with a 45? chamfer. Projection 600 has an outer surface 604 with threads 606 that are preferably positioned outside of cavity 510. An upper portion 605 of projection 600 is positioned in cavity 510. As shown, the threads 606 preferably begin at a position about ? beneath the lower portion of cavity 510, extend for about 1?, and are 1 ACME threads, although any suitable length and type of thread may be used. Projection 600 may have an internal passage 509 therein for the passage of gas.

(21) Coupling 500 may also include one extended metal portion 650 above coupling Section 502. The extended length of portion 650 reduces the cost of new and replacement rotor shafts (because they are shorter) and portion 650 is preferably between 4.5 and 12 in length. A top plate 660 mates with a known structure, such as a motor shaft with a rotary union, for driving the coupling 500 and injecting gas into it. Apertures 662 permit fasteners (not shown) to pass through and connect to a suitable driving structure, which is known in the art.

(22) As is illustrated in FIGS. 2 and 5, rotor shaft 38 has a first end 38A, a second end 38B, an outer surface 706 (that is preferably annular) and an inner passage 708 (which is optional depending upon the application) for transferring gas. Second end 38B preferably has a structure, such as a threaded end, for connecting to an impeller, although any suitable connection may be used. Shaft 38 may be a unitary structure or may be a plurality of pieces connected together.

(23) First end 38A is dimensioned to receive projection 600 and to fit into cavity 510. First end 38A as shown has a chamfered end 700 that is received in cavity 510 so that top surface 708 is against surface 514 when the rotor shaft 44 and coupling 500 are assembled. First end 38A also has an opening 712 leading to inner passage 708, which includes threads 714 that threadingly engage threads 606. In this embodiment, inner passage 708 extends through, or essentially through, rotor shaft 38 to transfer gas to second end 38B so that gas may be released into molten metal in any suitable manner.

(24) Rotor shaft 38 is connected to coupling 500 by aligning projection 600 with opening 712 and pushing projection into passage 708 until threads 606 meet threads 714, and then screwing rotor shaft 38 onto projection 600. Most preferably the respective threaded portions 606 and 714 are tightened in the same direction as the rotor shaft rotates during operation so that they do not loosen during operation.

(25) Having thus described different embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired result.