Insure proper ink tank venting

[Tom Hock]

Canon ink tank vent on clear tanks #3, #5, #6, #8 and maybe others.

Sometimes when using the German refill method the syringe needle will push the sponge tightly against the surface that separates the ink chamber from the sponge chamber and into the vent path along this wall leading to the top serpentine vent area. This can block the air flow and prevent the ink from flowing into the sponge, resulting in ink starvation, poor printing and maybe print head failure.

This doesnt happen often, and when it does, if it is noticed, the suggested fix is to tap the ink tank on a hard surface with the sponge side down in hopes of causing the sponge to move away from the vent path. Proper venting is critical, and this method seems hit-or-miss.

I may have a better method as shown in the pictures. By drilling a 1/16 inch hole in the top of the tank just inside the sponge chamber, a wire, or the syringe needle can be feed along this vent wall to move the sponge away to insure proper venting, which is essential. This hole can be sealed with tape so as not to interfere with the serpentine vent structure.

During the next few months I will be using tanks that I have tried this method on, but It looks good on paper so I thought I would pass it on for your critique.

 

[turbguy]

Is there an intended "slot" on this wall to admit air into the reservoir?

Wayne

 

[The Hat]

Tom Hock

Thats a very new and interesting take on the German refill method all right,
while there are some who are having problems maintaining this refill method
and then some who are not for whatever reason.

Maybe you have hit on something and only time and testing will tell
so I will look forward to hearing back on your progress and results..

 

[Tom Hock]

There are five slots, or depressions in the wall just above the opening between the sponge side and reservoir side that run up the wall for 3/8 inches. These depressions are intended to provide an air (vent) path from the top sponge where it freely connect to the serpentine vent. What sometimes happens with the German method of filling is the lower sponge is pushed into, and closes off, these five vents so the air can not get into the reservoir. This will prevent the ink from flowing out of the reservoir, thus, ink starvation. My idea is to move the sponge back where it belongs to open this vent. Like I said in my firs posting, this is an infrequent situation.

 

[barfl2]

Makes sense to me and well worthwhile trying say on a particular cart which the user may have had problems. I am one of those who have reported occasional problems with the German method and poor feeding as a result. Mind you having a clear cart makes it a lot easier in getting the hole in the exact right spot.

In general not keen on adding additional holes but if you have a cart which seems to play up regularly this method well worth a try.

 

[Tudor]

Doesn't that wire leave a groove in the sponge all the way to the top?

 

[Grandad35]

It is certainly true that it is a bad thing when the sponge is pressed into the vertical grooves. However, IMHO the sponge must be tight against the vertical wall above the grooves for proper operation. When the ink level in the sponge(s) is above the top of the grooves, air is blocked from entering the grooves and ink will be pulled from the sponge(s) before any ink can be pulled from the ink tank. When the ink level in the sponges drops below the top of the grooves, air can be pulled into the grooves and ink will be pulled from the tank until it empties. After the tank empties, enough ink remains in the lower sponge to continue printing for another CC or two (thus the "ink empty" signal comes after the "ink low" signal).

If there is an open air path when the sponges are full, the tank will start to empty immediately, reducing the effective ink capacity by several CCs.

 

[Tom Hock]

Grandad35; Interesting theory on the way the sponges control ink flow. I guess a lot more experimentation is required on my part to see if my idea has any merit. The one ink tank I did refill (the tank pictured) did have a permanent groove in the sponge, as Tudor observed in posting #6. When this tank was left lying on it's side over night I observed a slight weeping of ink from the vent and the top of the sponge was saturated with ink .not what we want to see. The groove in the sponge was caused by the blunt end of the large paper clip I pushed between the sponge and the wall. It did not just push the sponge aside, it cut the groove. I will try putting a chisel edge on the wire which may eliminate the permanent groove. I would expect the sponge to be resilient enough to move back into full contact with the wall. I have not dismantled one of these tanks to get a feel of the sponge properties.

I have observed that when filling a tank in which the sponge is depleted of ink, there is a strong steady stream of air bubbles entering the ink chamber after the tank is placed right side up, and as much as one half of the newly filled chamber will be absorbed by the sponge in less than a minute. The question I must answer is where is this air coming from? If it is coming through the serpentine vent then it is also passing through the top sponge freely, which may conflict with your theory. However, the air may enter the tank outlet port or the hole used for the German fill method. I will have to experiment some more. No hurry on my part and this may have to wait a while.

 

[Tudor]

A post about the construction of bci-6: http://www.nifty-stuff.com/forum/viewtopic.php?id=6221 The sponge is not like the ones used in cleaning or upholstery, it's made of fibers.
How the sponge absorbs ink:
- vent opened: http://www.youtube.com/watch?v=I8ot2hKfAvo
- vent plugged: http://www.youtube.com/watch?v=yyv9PBaqyhY
It doesn't matter if the system is closed on the sponge side, there will be an air-ink transfer between the sponge and ink chamber until something stops it. When ink fills the first sponge it creates a seal above the grooves and the system is in equilibrium. The sponge wants to absorb more ink, but there is negative pressure in the ink chamber and air can't enter to replace it because of the "seal". If you put a vertical groove in the sponge it will fail in creating that "seal" and the system will achieve equilibrium only when the sponge is filled with ink. It depends on how large the groove is, I think, but that's the theory.

Ha! Finally found that post: http://www.nifty-stuff.com/forum/viewtopic.php?pid=46685#p46685 . See this for more info about how the cartridge works and how the sponges look like.

 

[Tom Hock]

This was not such a good idea. Do not try it. The one tank I tried it on, and pictured in the first posting, leaks.