J. Phil Thien's Projects

Cole is the guy who made a cone-shaped baffle years before Thien's.  See my link to the earlier design above.  I don't know if Cole's works as well, but I suspect his is the reason Jet made theirs conical.

I think that Jet's design is actually much closer to Phil's than I thought at first glance. Depending on what gets covered, it seems quite plausible his patent would cover Jet's device, even with Cole's prior art.

Cole uses a cone shaped baffle, but draws air from the middle of the baffle. Thien uses a flat baffle, taking air off above. Jet uses a cone shaped baffle, but draws air above.

I can't tell whether Jet's has what I would consider a defining feature of the Thien baffle that I have never encountered anywhere else: a narrow way for the dust to fall below the baffle that is not an even width all the way around the DC, but blocked near the air entry.

Jet  has come out with a DC equipped with something like the Thien baffle.  But presumably to avoid Phil's patent, they based it on an  earlier design.

I think the problem may be that the inlet reaches too far down (up in the picture.)  You need some space below it for the air and crud to circulate.  It is this circulation that holds the dust to the outside edge so clean air can be withdrawn from the center.  There is no need for any space above the inlet, which can touch the top.

In fact, if your inlet were straight instead of a 90 degree curve, and angled through the top without extending in at all, it ought to work even better.  What do you think Phil?

Is it helpful to have both a conical part and the baffle?  Both serve the same purpose -- to allow the dust to drop out without allowing it to be easily kicked back up.

I would add that the reason you don't need to increase the size of the slot for a bigger DC is that you don't have or want much air to go through the slot.  Only the sawdust and chips, held to the outside of the round container by centrifugal force, should go through the slot.  The genius of the baffle is that this does work well to prevent the circulating air from stirring up the dust that's already fallen through.  The more smoothly the air can circulate in the upper part, the cleaner will be the air drawn off from the center.

The circulation region should be round, but that does not mean it's not helpful to have a plywood box around it.  If the round portion is strong enough to maintain its shape under vacuum, then you don't need to surround it.  But a much weaker cylinder would become useful if it were surrounded by a strong leakproof box.  And it might be easier to seal a single box well, and to suspend a cylinder within it, than to seal the cylinder top and bottom to other parts.