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...I think I'm beginning to understand: Air can only enter the ink chamber through the vent and through the sponge. For air to pass through the sponge a pressure difference equal to or greater than the capillary force that keeps the ink in the sponge is needed, so if you could measure the pressure in the ink chamber, it would be below atmospheric pressure ? This explains why a not properly sealed top fill hole causes leakage, on the other side: [i]air entering the durchstich refill hole has to pass through the sponge like air from the vent and so causes no leakage.
Me I am understanding it more and more too.
On the dividing wall on the sponge side there are little grooves, going from the passage to the upper sponge, which is not filled with ink. So the air from the sponge chamber can go to the ink chamber through the upper sponge and the grooves, but just enough to fill the lower sponge and not more.
The saturated lower sponge seals the ink chamber from getting more air. And therefore no over saturation and no leaking.
I think every method has its flaws:
german: sometimes difficult to find the way through the sponge, sometimes bad/wrong ink flow from punctured outlet filter,...?
top fill: must be drilled and sealed very properly, ...?
I don't have a clear picture of these sponges. What do they look like and how are they shaped? All I know for sure is that in the picture I posted, one of them looks sort of like a waffle.
And do they have that notch at the top -- that hole between the chambers?
Last edited by ThrillaMozilla (01/27/2011 6:19:18 pm)
On the dividing wall on the sponge side there are little grooves, going from the passage to the upper sponge, which is not filled with ink
Taking a close look at some Canon OEM empty CLI-8 and BCI-6 it looks to me as if the grooves go from the passage to 3-3.5 mm or 1/8 inch below the boundary between the sponges. This distance seems to be very accurately the same on all the carts, so air will have to travel through 1/8 inch of saturated sponge. My guess is that this serves as a kind of pressure regulator. If this is the case, it explains why only Canon OEM carts are well suited for refill, non-OEM carts having only one sponge. I'll try to see if I can take a picture showing this clearly and upload it tomorrow.
I don't have a clear picture of these sponges. What do they look like and how are they shaped?
The sponges are just two regular box shaped pieces of foam are stacked on top of each of each other.The waffle like mark in your picture is an impression mark left by the vent maze I think. In an other thread I uploaded this scanned picture of two Canon CLI-8 carts. You can see the two sponges on top of each other, but the grooves are not visible. Picture is here: http://www.nifty-stuff.com/forum/uploads/6881_cli8c-foam.jpg
Last edited by PeterBJ (01/27/2011 7:42:13 pm)
Ah, yes, a coarse over a fine sponge. Prevents dripping, among other things. Do the aftermarket cartridges also use two sponges? I read that it is patented.
You can see the same with HP cartridges here: http://freedomtoprint.com/2010/06/25/re … pen-chips/ . The groove is in a different place, but it has the same function, to ensure atmospheric pressure, or nearly atmospheric pressure, at the bottom of the sponge chamber.
I have think I have the static pressure behavior reasonably worked out, and will still try to find time to post a description -- even though some of you seem to understand it very well.
No the aftermarkets dont use two.
The groove is in a different place, but it has the same function,
The canon cartridges have these top to bottom grooves as well. I didn't know at first but at a closer look at my empty BCI-6 and CLI-8 cartridges, after seeing your pictures, I found the same grooves on the side walls of the sponge chamber. It is hard to see, but they are there. You can get a hint of it by looking at my scanned CLI-8 picture: http://www.nifty-stuff.com/forum/uploads/6881_cli8c-foam.jpg Look at the cartridge at the bottom of the picture. The vertical groove from the vent chamber to the outlet can be seen as a lighter stripe. It is more easily seen if you are actually looking at the cartridge at an angle, but I have not been able to get a decent picture with my cheap point-and-shoot camera, and my scanner is only good for 2D objects, no depth of field. Only objects in contact with the glass are in focus.
The grooves martin0reg refers to are on the wall between the ink chamber and the sponge chamber. I didn't want to cut open a Canon OEM cart to get a picture of the grooves, these OEM carts are valuable even when empty, but I found a very rare and early 3rd party 2 sponge cartridge. I guess these carts got banned some years ago, being a violation of Canon patent rights. I cut away the ink chamber and did a scan of the wall with the grooves, picture here : http://www.nifty-stuff.com/forum/uploads/6881_grooves_non_oem.jpg You can see the distance between the top of the grooves and the division between sponges. The fact it is not an OEM cartridge is disclosed by the sponges not turning white after flushing the cartridge. But when looked at from the outside Canon cartridges look quite similar with the grooves and the distance.
I cannot figure out the purpose of the grooves from the vent chamber to the outlet. This direct path for air seems to me to defy the purpose of the 1/8 " distance between top of the grooves in the dividing wall and the division between sponges. But maybe the top to bottom grooves do not go all the way to the outlet, and a balance of forces is at play here ?
After reading your last post ThrillaMozilla I do not feel like one of those who seem to understand it very well any more. Am I back to square one ? What is your theory about these cartridges ?
Oh, I think you understand it almost completely, PeterBJ, except for a couple of details. I'm mostly just learning from the explanations I'm reading here, most of which are right on the mark -- plus maybe a little insight of my own. I misunderstood about the configuration of the grooves on the wall, and now that I see your picture, I'm a little puzzled too, at the moment.
I'll try to put together my version in a day or two, although that might be anticlimactic. Not trying to be dramatic, but I'm really stretched for time right now, and besides, I left some notes somewhere else.
Seeing how some people are having trouble visualising how a cartridge is made I thought I'd open one up today and photograph it. I posted my findings here
as a sort of thank you to all those in this forum who first inspired me to use the 'German' method. And, who knows, it may help others who have a problem visualising what is involved:
The upper sponge in Canon OEM cartridges are designed to flow air so that it can easily get to the top of the groves and then down to the hole in the bottom of the wall to allow air to get into the reservoir to replace the ink that is drawn out. That is the major advantage of having two different sponge materials.
Thank you very much for your most excellent photo series, from one of those trying to figure out what is really going on inside a canon cartridge. Your pictures provide a wealth of information.