Patent ID: 6196668
Filing Date: 2001-03-06
Classification: B41J

Abstract:
A system for supplying ink to a composite printing head having an upper printhead at a higher elevation than a lower printhead, the upper and lower printheads each having an inlet port in fluid flow communication with a set of orifices, comprising:an upper compartment in fluid flow communication with the upper printhead for supplying ink thereto, said upper compartment having a first outlet, said first outlet opening at a desired height relative to the upper set of orifices that is lower than the height of the upper set of orifices, ink being maintained in the first compartment at the level of said first outlet, thereby defining an upper static height difference between the upper printhead inlet port and the level of ink maintained in the upper compartment to create a back pressure acting on the ink in the inlet port;a lower compartment in fluid flow communication with the lower printhead for supplying ink thereto, said lower compartment being positioned at a lower elevation than the upper compartment and positioned to receive an overflow of ink draining from the outlet opening of the upper compartment, said lower compartment having a second outlet, said second outlet opening at a height relative to the lower set of orifices that is lower than the lower printhead inlet port to define a lower static height difference the same as the upper static height difference, whereby back pressure acting on the ink in the upper printhead orifice is substantially the same as back pressure acting on the ink in the lower printhead orifice;a reservoir for supplying ink to the upper compartment;a supply line for supplying ink from the reservoir to the first compartment; anda pump for delivering the ink via said supply line from the reservoir to the first compartment.