Torque coupling system

An impeller shaft assembly for connection to a drive motor, comprising:

• an elongate shaft having first and second ends, the first end adapted to be connected to the drive motor and the second end adapted to receive an impeller, the second end of the shaft being generally cylindrical;
• an impeller adapted to be connected to the second end of the shaft, the impeller including a generally cylindrical opening into which the second end of the shaft can be placed;
• longitudinally extending openings formed in the impeller and the second end of the shaft at the interface between the second end and the impeller;
• dowels disposed within the openings formed in the impeller and the shaft;
• and
• a torque coupling system for the shaft, said torque coupling system including:
• a hollow coupling having first and second ends and defining a longitudinal axis of rotation, the first end adapted to be connected to the drive motor and the second end adapted to be connected to the first end of the shaft, the second end defining a generally cylindrical opening into which the shaft can be fitted;
• a key disposed within the opening and in engagement with the coupling, the key having a longitudinal axis that is aligned with the longitudinal axis of the coupling;
• compression means for urging the key into contact with the shaft, the compression means being carried by the coupling;
• and
• retaining means for urging the key out of contact with the shaft, the retaining means being carried by the coupling, the retaining means being weaker then the means for urging whereby, upon actuation of the compression means, the key is brought into contact with the shaft but, upon release of the compression means, the key is brought out of contact with the shaft and retained in place relative to the coupling.