Digital BW, The Print

Steve,

Surely it is obvious that unless something is done to keep the ink in the 
cartridge, it will simply flow out through the printhead under the influence 
of gravity. The system is open; a hole in the top of the cart, and holes in 
the printhead, so liquid will flow out the bottom if nothing is done to stop 
it. Users of CIS systems often suffer from this. The level of liquid in the 
ink bottles has to be carefully balanced against the level of the printhead. 
Too high and the inks simply runs straight through into the waste chamber. 
Too low and the printhead can't generate enough pressure to lift the ink 
from the bottles.

So the foam in the old carts, and the valves in the new carts, reduce the 
head of ink, and thus the tendency to flow out of the printhead while idle. 
Since the holes in the printhead are very small, surface tension effects may 
help prevent leakage, but given enough head of ink (or touch the printhead 
on the ink pad at rest) and the ink will surely flow if there is a 
sufficient head of ink.

I always thought the long wiggly channels on the top of old carts through 
which the air enters the carts might also have something to do with reducing 
the inflow of air, and thus the tendency of the ink to flow out, but I'm not 
sure on this.

Bob Frost.

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of Steve Kale

OK well for what it's worth the spongeless 21/2200 carts I've been using
don't have any issues with ink leaking out into the printer.  They have two
holes in the top that come shipped with plugs in them.  The stopper for the
primary filling chamber is replaced once the cartridge is full.  The second
stopper over the hole at the top of the spill chamber where air comes in
remains out (and can act as a spare if you lose the one for the filling
chamber).  The carts are certainly considerably more sophisticated than the
MIS ones but not as complicated as Epson's.