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[Bill Jones <billj AT harborside.com>]

Bill Jones wrote:

> The only remaining (easy) task is to come up with a circuit that will 
> turn on a 3-way solenoid valve (or off, depending on which type of valve 
> it is), to turn off the air pressure when the pressure switch cuts out, 
> and then delay for a fixed length of time before resetting, to allow the 
> top ball to fall and the chamber to refill.
>
>  
That will definitely work, but today I mastered the secret of pure 
mechanical control.  When the pressure rises, indicating that the 
chamber is full of air and ready to reset, a pressure-relief valve 
releases the air from the line.  This would work by itself, but poorly.  
My buddy Orlando was happy with this arrangement, but I see only 
inefficiency as the air blows uncontrollably, first out the valve, and 
then out the top of the chamber, whose top ball will have now fallen, 
perhaps even interfering with the top ball as it tries to seat itself.

So I had an idea to use a valve that would shut when the air flow goes 
above a certain rate.  It would be like the pneumatic equivalent of a 
circuit breaker, one that resets itself.  It turns out that the valve I 
need is precisely the one that James was talking about for the hydraulic 
ram pump a few months back.  It's actually a one-way valve, the 
pneumatic equivalent of a diode, placed backwards in the line, which 
allows only a low rate of flow in the "wrong" direction.  This one has 
to work for air, but it's the same principle.

The one tiny problem remaining is how to make this valve reset.  It 
stays shut until the pressure on both sides nearly equalizes, I would 
think.  Well, here's how to solve that problem.  A second air tube is 
connected directly from the pressure supply to the chamber, bypassing 
the "circuit breaker" valve, but through a valve that barely leaks air 
in at all (the pneumatic equivalent of a large electrical resistance).  
This way, very little air is wasted during the reset of the system, but 
when the top ball plugs the hole, only a little air needs to seep in 
through the second tube to repressurize the chamber, and that allows the 
built-in spring to reset the fancy valve, allowing air to flow freely 
into the now sealed chamber.

Mr. Stauffer deserves a patent for this device, unlike so many other 
patents I've been embarrassed to learn of.  After all, it took me ten 
years of off-and-on cogitating to figure it all out.  But the hour is 
late, and the ecovillagers don't deserve to starve to death because they 
can't afford $800 for a water pump.  Wasn't all that *simplicity* 
supposed to help lower the price?  So now I'm happy to announce that 
anyone can build one for under $100.

Bill
S. Oregon coast