What are the wells for in the top of the Canon cartridges?

[ghwellsjr]

Anyone who has looked carefully or removed the label from the top of a Canon BCI-3e, BCI-6, PGI-5, or CLI-8 cartridge has observed a serpentine groove in the air vent path that also has two "wells" along the path. What are they for? Here's my theory:

Due to the daily cyclical change of ambient air pressure, air is constantly forced in and out of the cartridge. This daily change is approximately 0.5% of the total air pressure but can be greater than 1% over a period of many days or weeks.

For this reason, there needs to be a path whose volume is at least 1% of the volume of air in the sponge part of the cartridge. I haven't tried to measure either one of these volumes but it appears to me that without the wells, the volume of the air path would be way too small and so Canon added the wells to increase it to the proper volume.

What if your third-party cartridges don't have this path or don't have the wells or you otherwise bypass the serpentine path in the air vent in Canon carts? The result will be that the water in your ink will dry out at a faster rate than it otherwise would.

 

[mikling]

Good observation and calculations.

It is there to minimize the exchange of air so that the relative humidity remains near 100% above the sponges. That said, if refilling were to somehow block these air channels the potential harm to the printhead should not be overlooked. So sometimes it is a better tradeoff to leave a direct air path.

In my experience the difference has been undetectable but I have never officially measured the difference. Now If I were to look at some other manufacturer cartridges with integrated heads, the volumes are no where close to 1% and they don't appear to suffer. So I wonder sometimes.

But undeniably it is there for the reason stated.

 

[hpnetserver]

Most 3rd party refillable empty cartridges have no cover for the top of the cartridges. The wells and the grooves of the vent become useless. Although there are no immediate impact to the functionality to the cartridges it is true that ink in these cartridges will dry out faster than it should. The only brand of 3rd party empty cartridges I have seen that come with covers as well as labels on the top of the cartridges is Hobbicolors. Not only the wells and the maze on the top of the cartridges are covered as they should be the labels conveniently show the colors of the ink in them. These cartridges are the ones that come with nylon sealing screws. No doubt there are reasons the wells and the maze are covered. I onced removed the label from one cartridge from Hobbicolors. There was another layer of cover that covered the wells and the maze. This layer of cover appeared to be glued on.

 

[WhiteDog]

True about Hobbbicolors, but their cartridges do not have the two-sponge filler of Canon cartridges, and I have discontinued the use of them, though I happily fill up with Hobbicolor ink.

 

[Tin Ho]

Canon's two layer sponge design is patented. I doubt you can find any 3rd party cartridge that has the two layer design. All hp cartridges contain singe piece sponge. I believe singe piece sponge design is adequate to do the job. 2 layer sponge does not mean it will function more similair to Canon's. Canon's bottom sponge is made of laminated layers of fiber running horizonally (the patented design). Stacking two layers of sponge together really doesn't make it much different from one piece.

There are 3 wells on the top of Canon BCI-6 cartridges. The one in the middle is also the vent. The wells are connected through the maze under the label. It is particularily necessary to cover the maze by a label for BCI-3eBK and PGI-5 cartridges. These cartridges contain pigmented ink which is much less tolerant to loss of water vapor through the vent.

If you do not use your printer frequently you really should cover the maze on the top of your cartridges. This helps prevent print head clogs.

 

[ghwellsjr]

Thanks for pointing that out Tin Ho. Yes, there is a third well. I forgot about it because it just looked like part of the vent hole going down into the sponge chamber, but it indeed does add more volume just like the other two wells that don't go anywhere.

You cannot compare Canon's two-sponge design with HP's single-sponge design. HP's cartridges do not have a separate ink reservoir like the Canon cartridges we are talking about here. I agree that stacking two identical sponge materials is no different than having just one (it would be like cutting a sponge in half) and maybe I should have made it clear that the Canon's two-sponge design is superior because the materials are different. The two sponge materials affect the way that air can get down to the hole separating the two compartments which affects the flow of ink out of the reservoir. Follow this link for the complete story:

http://www.nifty-stuff.com/forum/viewtopic.php?pid=9993#p9993

 

[ThrillaMozilla]

I know this is an old threads, but there are some factual errors.

1. HP also uses a two-sponge design. See http://freedomtoprint.com/2010/06/25/review-hp-564-564xl-ink-cartridge-cracked-open-chips/ .

2. The HP XL cartridges DO use a separate ink chamber, like the Canon cartridges. HP also sells smaller, cheaper cartridges that do not have a separate ink chamber. This appears to be a marketing ploy, so they can sell cheap cartridges that contain only a few smudges of ink.

3. I don't understand the odd design of the Canon vent structure. The details of the Canon cartridge are shown here: http://www.nifty-stuff.com/forum/viewtopic.php?id=6221 . The cartridges have a strange, internal air space that is much larger than the external structures. Unless the cartridges are supplied with that air space full of ink, I don't see how the external structure could be of much use for expansion, compared to the internal volume.