Device for controlling and regulating an ink and processing thereof in a continuous ink jet printer

Claim 1

Device for controlling and regulating ink in a continuous ink jet printer in which a continuous ink jet (J) leaves a nozzle (2), comprising: means (4, 5) for breaking-up said ink (J) by formation of said ink jet (J) into equidistant and equidimensional droplets (G); a charging electrode (6) where said droplets are selectively electrostatically charged; a charged drop speed detector (8); deflecting electrodes (10) where said droplets (G) are deflected as a function of charge, wherein said detector (8) comprises firstly a central conducting element (8c) of length (L), in two symmetrical parts with respect to an axis of a path of the droplets (G), spaced by a distance (R), said conducting element (8c) being protected by a insulating element (8 i ) of total length (L i ) from an influence of an external conducting element (8e) connected electrically to ground, satisfying the relations: R<L.sub.e and L.sub.e =L+L.sub.i /2 L e being an effective length of said detector (8) and wherein said device further comprises an electric drop speed detection circuit (9) including means for measuring a charge per unit length (σ x ) according to the equation: ##EQU3## where Qg is a charge on the droplets and x i is a position of the droplets in the detector (8); means for measuring an evolution of a total charge Q carried by the conductive element (8c) of effective length (Le) according to the equation: ##EQU4## means for measuring the evolution of said total charge Q with respect to a time f(t) according to the following: Q=f(t) means for measuring a first derivative I(t) and a second derivative J(t) with respect to the time of total charge Q means for calculating the drop speed V with the two inflexion points of the function Q=f(t) corresponding to time T 1 and T 2 , by the relation: V=Le/(T.sub.2 -T.sub.1).