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jwilson8767 / covid-19-ventilator-concept

Intermittent positive-pressure ventilation to two patients
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Valve arrangment and actuation #2

Open jwilson8767 opened 4 years ago

jwilson8767 commented 4 years ago

(reposting here for visibility)

Rather than 3 on/off valves, why not use 4 valves, all the same, with a "Y" connection to the pressurized air/oxygen input connecting two. Then if the open shut sequence of pairs of valves is made to be break before make, which seems readily guaranteeable if a complementary pair of valves is built as a single unit having a single rotating internal part, it would seem that there would be no need for the one way ball valves (not sure that they work anyways). Then two such dual valves could be stacked on a single keyed shaft (phased appropriately) and one has the basic 4 valve phased operation assemply for this. If driven by a stepping motor and smarts, one would have precise control of duration of each phase. A dumb constant speed motor, perhaps with a few speed options, would give just a few settings for overall periodicity, with the various phase durations set by the internals of the valves (perhaps with build variants). Anyways... time to let a mechanical engineer and a medical professional comment as to whether something so dead simple is actually helpful... Would be nice to imagine a LEGO factory churning out millions of what is needed in just a day or two, if plastic parts would suffice. -- Kevin Huscroft on Agorize

jwilson8767 commented 4 years ago

Using 4 valves is a really good point as it helps even out the fact that the half-circle valves have a momentary gap where the inlet is blocked. The ball valves are important as the half-circle valves have a moment where both outlets are connected to one another and may otherwise backfeed upsetting the balance of pressures (I will however reiterate that I know very little about pneumatics).

I love the idea of stacked valves, but I think that keeping the entire valve manifold relatively flat makes it easier to machine from a single piece of stock material. Additionally, stacked half-circle valve bodies may be much harder to machine, where the current ones could be CNCed in just two stages (one stage from bottom of stock) and one from top.