Tensioned support shaft and other molten metal devices
A vertical member, which is preferably a support post used in a molten metal pump, includes a ceramic tube and tensioning structures to add a compressive load to the tube along its longitudinal axis. This makes the tube less prone to breakage. A device, such as a pump, used in a molten metal bath includes one or more of such vertical members.
1. A rotor shaft for use in a molten metal device, the rotor shaft comprising:
an outer tube having a first end, a second end, and an outer surface;
an inner rod having a first end and a second end;
a cap that threads onto the first end of the inner rod, and that has an upper portion configured to be connected to a coupling that drives the rotor shaft; and
a structure that retains the second end of the outer tube;
wherein when the cap is connected to the coupling and the coupling drives the rotor shaft, the rotor shaft moves in a direction that tightens the cap against the first end of the outer tube to apply axial pressure on the outer tube.
2. The rotor shaft of claim 1 , wherein the outer tube is comprised of ceramic.
3. The rotor shaft of claim 2 , wherein the ceramic is silicon carbide.
4. The rotor shaft of claim 1 , wherein the structure that retains the second end of the outer tube is a nut threaded onto the second end.
5. The rotor shaft of claim 1 , wherein the inner rod is formed of steel.
6. The rotor shaft of claim 1 , wherein the upper portion of the cap includes one or more L-shaped openings to connect to the coupling.
7. The rotor shaft of claim 1 , wherein the cap is formed of steel.
8. The rotor shaft of claim 1 , wherein the rotor shaft is configured to attach to a rotor.
9. The rotor shaft of claim 1 is attached to a rotor.
10. The rotor shaft of claim 1 has a first end configured to be retained in the coupling and a second end configured to be connected to a rotor.
11. The rotor shaft of claim 10 , wherein the second end of the rotor shaft is threaded.
12. A molten metal pump comprising the rotor shaft of claim 1 .
13. The molten metal pump of claim 12 that further comprises a motor configured to rotate the rotor shaft, a rotor connected to an end of the rotor shaft, a base that includes a chamber and a discharge, wherein the rotor is positioned in the chamber, a superstructure that supports the motor, and one or more support posts that connect to the base and to the superstructure.