Multi-stage impeller assembly for pump

A pump, comprising:

• a pump housing;
• an input shaft rotatably supported by the pump housing;
• and
• an impeller assembly supported on the input shaft, wherein the impeller assembly includes
• a first impeller portion that is rotationally connected to the input shaft so as to be driven thereby so as to drive a fluid through a fluid conduit;
• a second impeller portion that is movable between a more-rotationally engaged position in which the second impeller portion has a first amount of rotational engagement with the first impeller portion, and a less-rotationally engaged position in which the second impeller portion has a second amount of rotational engagement with the first impeller portion that is less than the first amount of rotational engagement;
• and
• an actuator that is operatively connected to the second impeller portion and is configured to drive movement of the second impeller portion between the more-rotationally engaged position and the less-rotationally engaged position based on a fluid property, wherein the actuator is passive and is engaged with the fluid, and changes shape based on temperature of the fluid so as to be stable in a first position when the temperature of the fluid is at a temperature above a selected threshold temperature and is at a temperature below the selected threshold temperature.

A pump, comprising:

• a pump housing;
• an input shaft rotatably supported by the pump housing;
• and
• an impeller assembly supported on the input shaft, wherein the impeller assembly includes
• a first impeller portion that is rotationally connected to the input shaft so as to be driven thereby so as to drive a fluid through a fluid conduit;
• a second impeller portion that is movable between a more-rotationally engaged position in which the second impeller portion has a first amount of rotational engagement with the first impeller portion, and a less-rotationally engaged position in which the second impeller portion has a second amount of rotational engagement with the first impeller portion that is less than the first amount of rotational engagement;
• and
• an actuator that is operatively connected to the second impeller portion and is configured to drive movement of the second impeller portion between the more-rotationally engaged position and the less-rotationally engaged position, wherein the actuator includes an electromagnetic coil that is stationary, an armature that is connected to the second impeller assembly, and a biasing member that urges the second impeller portion towards the more-rotationally engaged position, and wherein energization of the electromagnetic coil draws the armature and the second impeller portion towards the less-rotationally engaged position against urging by the biasing member.