Ink jet printing apparatus and process

DETAILED DESCRIPTION It is, therefore, an object of the present invention to provide an ink jet printing apparatus suitable for printing large size alpha-numeric characters on a moving surface which apparatus is simple and dependable in operation and economical to construct.
Another object of the invention is to provide an ink jet printing process which utilizes an ink matched to the apparatus to provide satisfactory wetting of the printing substrate without drying in the apparatus nozzles.
The improved ink jet printing apparatus of this invention includes a source of pressurized ink and a plurality of valves, each of the valves having an input port which is in fluid communication with the pressurized ink source and an output port.
A plurality of jeweled orifice nozzles are provided, each of which is in fluid communication with a select one of the output ports of the valves.
Control means control the output of the ink from the valves to the nozzles.
In the preferred embodiment, an ink manifold communicates with the pressurized ink source.
A plurality of solenoid valves have input ports which are connected by means of fluid conduits to the ink manifold.
The output ports of the solenoid valves are connected by means of fluid conduits to the jeweled nozzles.
The nozzle orifices are in the range of 0.
025 mm to 0.
215 mm in diameter.
In the ink jet printing process, a source of pressurized water-based ink is prepared which comprises 60 to 95 percent by weight water, 0.
05 to 25 percent by weight dye, and 2.
5 to 20 percent by weight glycol ether.
The pressurized ink source is connected to a plurality of solenoid valves which are in turn connected to individual jeweled orifice nozzles.
An electrical control means controls the output of the solenoid valves to the nozzles.
The glycol ether is preferably a mixture of 2 to 8 percent by weight butyl cellosolve and 2 to 8 percent by weight butyl carbitol, said percentages being based on the total weight of the water-based ink.
The relative proportions of the glycol ethers are selected to produce an ink having a viscosity in the range of 1