Abstract: In a continuous ink jet printing system a viscosity determining means (12) has a measuring tank (29). An inlet (32) to the tank is connected to the system ink circuit to receive ink under pressure and the inlet has a flow restriction. A vent/return pipe (34) vents the tank and enables ink to be returned to the reservoir. An outlet (33) drains ink from the tank and returns it to the pump, the outlet including a valve (13) to open and close the outlet. A level detector (30,31) in the tank is connected to a timer (38) to determine the time taken for the tank to fill from a first level to a second level detected by the level detector and hence to provide a representation of viscosity of the ink.

Abstract: In a continuous ink jet printing method for printing multiple lines of print (13-15), raster of drops is produced in which the differential charge between drops printed on opposite sides of an interline gap (17,18) is increased in comparison with that between adjacent drops to be printed within a line (13-15). At the same time the number of guard drops is maintained the same or is reduced between the printable drops immediately adjacent to the interline gap, so that the distance between printed drops immediately adjacent to the interline gap is increased without increasing the number of drops in the raster.

Abstract: A discharging head assembly for marking apparatus has a chamber for marking fluid with a plurality of fluid dispensing orifices which are closeable and openable by displaceable closure elements connected via flexible pulling means to respective actuators which are spaced from the chamber, and can therefore be relatively bulky, e.g. strong electromagnets.