canonfodder
Printer Guru
First, know that the Canon Pixma printers must have a negative ink pressure at the point of ink input to the print head. The print head operation depends on that negative pressure.
The needed negative pressure is why the ink cartridges have sponge material just above the ink output port. The sponge material generates a negative pressure through capillary action. If you wish to delve into how capillary action works, go to a website like wikipedia.org and read up. If you want to read about the Canon sponged cartridges and their negative pressure, go to google.com/patents and look up U. S. Patent 6,145,972.
Measurements made on CLI-8 cartridges show that they produce ink output pressures from about 1.1 to 2.5 inch water column. Printing tests with a Pixma iP4200 show that the print head will function normally with ink input pressure as weak as 0.3 inch water column, but it would be sensible to operate with pressure closer to 1.0 inch water column. Limiting it to that level protects the cartridge-to-print head seals from overstress.
The benefits of a constant pressure are the prevention of a positive pressure which results in printing gaps and cross contamination, and the prevention of too great a negative pressure causing possible seal leaks and the attendant printing failures.
In operation, the print head sucks in the ink it needs. If it has to suck the ink upward against the force of gravity, a negative pressure will be formed in the tube that carries the ink. To establish a negative 1 inch water column pressure, the ink needs to be sucked upward 1 inch. This means that with a CIS and its tubing connecting to the external bottles, the surface level of the ink in the external bottles needs to be 1 inch below the print head ink entrance. If the surface level of the ink can be kept at 1 inch below the print head ink entrance elevation, the pressure will stay constant.
It has been suggested before that floating the CIS bottles somehow could help make a more constant operating pressure. What is shown here is a practical and simple method of "floating" the CIS bottles resulting in the constant negative pressure desired.
Note that the quantity of magenta ink is distinctly less than the others, but its surface level is the same as the others. The spring lifts the bottle by the correct amount as the ink is consumed.
Each bottle is supported by a coil spring in compression. The spring rate of the compression springs matches the ink weight rate of the bottles. The weight of one inch of ink in the bottle is matched by the force required to compress the spring one inch. The result is that the ink surface is kept at a constant elevation. Since the printer tolerates a spread of the negative pressure, great perfection is not required. If the spring rate accuracy is within 10%, operation will be fine.
Full construction details of this Spring Float CIS will be entered soon.
The needed negative pressure is why the ink cartridges have sponge material just above the ink output port. The sponge material generates a negative pressure through capillary action. If you wish to delve into how capillary action works, go to a website like wikipedia.org and read up. If you want to read about the Canon sponged cartridges and their negative pressure, go to google.com/patents and look up U. S. Patent 6,145,972.
Measurements made on CLI-8 cartridges show that they produce ink output pressures from about 1.1 to 2.5 inch water column. Printing tests with a Pixma iP4200 show that the print head will function normally with ink input pressure as weak as 0.3 inch water column, but it would be sensible to operate with pressure closer to 1.0 inch water column. Limiting it to that level protects the cartridge-to-print head seals from overstress.
The benefits of a constant pressure are the prevention of a positive pressure which results in printing gaps and cross contamination, and the prevention of too great a negative pressure causing possible seal leaks and the attendant printing failures.
In operation, the print head sucks in the ink it needs. If it has to suck the ink upward against the force of gravity, a negative pressure will be formed in the tube that carries the ink. To establish a negative 1 inch water column pressure, the ink needs to be sucked upward 1 inch. This means that with a CIS and its tubing connecting to the external bottles, the surface level of the ink in the external bottles needs to be 1 inch below the print head ink entrance. If the surface level of the ink can be kept at 1 inch below the print head ink entrance elevation, the pressure will stay constant.
It has been suggested before that floating the CIS bottles somehow could help make a more constant operating pressure. What is shown here is a practical and simple method of "floating" the CIS bottles resulting in the constant negative pressure desired.
Note that the quantity of magenta ink is distinctly less than the others, but its surface level is the same as the others. The spring lifts the bottle by the correct amount as the ink is consumed.
Each bottle is supported by a coil spring in compression. The spring rate of the compression springs matches the ink weight rate of the bottles. The weight of one inch of ink in the bottle is matched by the force required to compress the spring one inch. The result is that the ink surface is kept at a constant elevation. Since the printer tolerates a spread of the negative pressure, great perfection is not required. If the spring rate accuracy is within 10%, operation will be fine.
Full construction details of this Spring Float CIS will be entered soon.
Although I'm wondering if I've missed some obvious Eureka principle regarding the water level.. Hmm..
