Load sharing spring for tandem thrust bearings of submersible pump assembly

A submersible well pump assembly, comprising:

• a pump operably driven by a motor;
• upper and lower seal sections connected between the pump and the motor;
• upper and lower drive shafts in the upper and lower seal sections, respectively, each extending along a longitudinal axis of the assembly;
• an-upper and lower thrust runners fixed to the upper and lower drive shafts, respectively for rotation therewith;
• upper and lower thrust bearing bases in the upper and lower seal sections, respectively, for rotating engagement by the upper and lower thrust runners, respectively;
• the upper drive shaft configured to undergo an amount of downward movement toward the lower drive shaft in response to wear of the upper thrust bearing base caused by down thrust on the upper drive shaft;
• an internally splined coupling that connects ends of the upper and lower drive shafts together for rotation in unison;
• a spring within the coupling between ends of the upper and lower drive shafts, the spring being configured such that a portion of the down thrust on the upper drive shaft passes through the spring to the lower drive shaft during the amount of downward movement of the upper drive shaft toward the lower drive shaft;
• and
• upper and lower spring plates in the coupling that sandwich the spring between them and are in abutment with the ends of the upper and lower drive shafts, one of the spring plates comprising a rigid stop member having an axial length that is selected to contact the other of the spring plates and stop the amount of downward movement of the upper drive shaft toward the lower drive shaft, and to transfer down thrust from the upper drive shaft to the lower drive shaft directly through the rigid stop member, bypassing the spring, only after the amount of downward movement of the upper drive shaft toward the lower drive shaft has been reached.

A method of operating a submersible well pump assembly having a pump;

• a motor;
• first and second seal sections between the pump and the motor;
• first and second drive shafts in the first and second seal sections, respectively, each extending along a longitudinal axis;
• first and second thrust bearings in the first and second seal sections, respectively;
• and an internally splined coupling that connects ends of the first and second drive shafts together for rotation in unison, the method comprising:
• mounting a spring in the coupling between the ends of the first and second drive shafts;
• mounting a rigid stop member in the coupling between the ends of the first and second drive shafts;
• operating the pump, imposing down thrust from the pump on the first drive shaft and the first thrust bearing and allowing the first drive shaft to undergo movement toward the second drive shaft in response in response to wear of the first thrust bearing;
• during the movement of the first drive shaft toward the second drive shaft, compressing the spring and transferring down thrust on the first drive shaft through the spring to the second drive shaft;
• then
• with the rigid stop member, stopping the movement of the first shaft toward the second shaft and transferring down thrust on the first drive shaft directly through the rigid stop member to the second drive shaft.