helical gear pump shaft key

[iwate]

Hello everone

This is helical gear pump for turbine.

Why does the upper SHAFT have a ONE key BOTH GEAR FIXED, and the lower SHAFT has FIXED only one GEAR?
The upper&lower herringbone gears is two pieces and same. I want to know whether it's hydrodynamic or mechanical.
And I want to know why making like this???

Have a nice day~

 

[hydtools]

The upper gear key must deliver all driving torque to the pump. The lower gear key must only assure the idler shaft spins in its bushings and not allowing the idler gear to spin on the idler shaft.

Ted

 

[Compositepro]

It may be because it would require almost impossible machining tolerances to get the teeth and keyways perfectly timed for all four gears.

 

[hydtools]

Compositepro, I agree with that reason, too. The one non-keyed gear will permit mismatch that could otherwise lock up the pump or crash the gears.

Ted

 

[iwate]

Thank you for your answers.

At first, I thought the reason for being in one part was to prevent shaft wear. And I thought I could do it at low cost.