Pattern printing apparatus

Pattern printing apparatus which prints by depositing on a surface to be printed moving relatively to the apparatus successively transverse rows of closely spaced small drops, the apparatus having at least one row of printing guns supplied with printing liquid under pressure to form parallel jets of printing liquid which break up into small drops, charge electrode means for each jet for uniquely charging drops formed in each jet, drop deflection means providing a substantially constant electrostatic field through which the drops formed in the jet path pass, and a drop intercepting device for intercepting drops in each jet which have been charged to a predetermined level, there being further provided signal generating means which make available for application to the charge electrode means a periodic voltage signal the periods of which are of duration sufficient to span the formation of a plurality of drops in each jet path, and, electrical means operative to apply the signal voltage at predetermined voltage levels during each period of the signal voltage to charge electrode means of the printing guns thereby to charge drops formed in the jet path of each gun, the drops from each printing gun which have been charged to the signal voltage level being thereby deposited on the printing surface in the length of a line section, the line sections of the printing guns together being thus occupied by a row of drops extending transversely with respect to the direction of relative movement between the apparatus and the printing surface.