Monty let me try to explain it in
general terms. Unfortunately, I do not have any detailed pictures.
The pump is working on the positive
displacement principle. It has a piston-cylinder combination with in-out port
control. The port sequence is achieved by rotating the piston in such a way that
the intake is open on the way down, and the outlet is open on the way up. The
stepper motor controls the stroke for more or less pumping.
Here are the physicals. The drive
shaft turns the piston through a 1:1 worm-angle gear. The piston has a wedge
type cut out on the bottom side which is sitting on a cross pin, spring loaded.
When the piston turns, it moves up and down, in and out from the pin. I do not
know exactly how the control pin is hooked to the piston.
I am at this moment making a
replacement for the stepper motor, to do what you described. I believe the pin
is at maximum when it is pushed in, however, I will have a test run on the pump
with my adjuster shortly, and we will know for sure.
I have the same adjustment gadget, in
principle, for the RENESIS pump, ready to sell.
Hope this helps.
Richard Sohn