An inkjet recording apparatus includes a recording head, an ink tank, a supply flow path, a supply pump located in the supply flow path, a collection flow path, a relief flow path connecting a first position in the supply flow path to a second position in the supply flow path, wherein the first position is located at a downstream side of the supply pump in the supply flow path and the second position located at an upstream side of the supply pump in the supply flow path, and a differential pressure regulating valve located in the relief flow path and configured to, in a case where the pressure of the pumped ink in the supply flow path is larger than a predetermined value, open the relief flow path so as to allow ink in the supply flow path to flow from the first position to the second position.

There is provided a charge electrode for charging ink droplets for continuous ink jet printing. The charge electrode has a generally cylindrical main body defining a generally cylindrical passage for the ink droplets, said passage extending along a travel axis that represents, in use, the position of an ink jet in ingress to the electrode and a direction of travel of the ink droplets once these have detached from the ink jet. The charge electrode comprises two distinct axially disposed regions: a first region for charging the droplets as required; and, a second region for screening the charged droplets from any electric fields which could undesirably affect the trajectory of the ink jet and/or the droplets. The second region may fully surround at least a portion of the travel axis. The invention therefore provides improved screening for the ink jet and/or the droplets. This may in turn enable better control of the charge applied to the charged droplets, and/or of their travel trajectory.

A print head of an ink jet printer comprising: a cavity for the circulation of jets, delimited laterally by side walls, at least one nozzle for producing at least one ink jet in the cavity, at least one generator applying a charge to at least one ink jet, at least one electrode for sorting drops or segments of one or several of the jets intended for printing from drops or segments that are not used for printing, a slot, open onto the exterior of the cavity, a 1.sup.st gutter for recovering drops or segments not intended for printing, a 2.sup.nd gutter for recovering drops or segments that are not deflected and not intended for printing, this 2.sup.nd gutter comprising an input slot and at least one suction channel, an actuator in order to actuate the 2.sup.nd gutter, a 1.sup.st detector to detect an electrical charge of drops recovered in the 2.sup.nd gutter for recovering when the latter is in a closed position and/or a detector to detect, without contact, the passing of charged drops when the 2.sup.nd gutter is in an open position.

A printer includes a transport unit, a first head, a second head disposed downstream of the first head, a first suction unit configured to suction ink mist discharged from the first head, a second suction unit configured to suction ink mist discharged from the second head, and a suction device coupled to the first suction unit and the second suction unit, and configured to generate an airflow for suctioning the ink mist, and a first suction device disposed either one of on a first path from the first suction unit to the suction device, and at the suction device, and configured to adjust a flow rate at the first suction unit, and a second suction device disposed either one of on a second path from the second suction unit to the suction device, and at the suction device, and configured to adjust the flow rate at the second suction unit.

In order to suppress adherence of ink splash to an electrode and ink contamination of surrounding environment, in a printing system, there is provided a continuous type ink jet printer having a nozzle for jetting ink in the form of particles, a charging electrode for electrically charging the jetted ink particles, and a deflection electrode for deflecting the charged ink particles. The system includes a printing section for printing an object to be printed with the ink particles jetted from the nozzle and a charging section configured to charge at least one of the printing object prior to its printing by the printing section and surrounding atmosphere in which the printing on the printing object is to be effected by the printing section with a polarity opposite to a polarity of the charge provided to the ink particles by the charging electrode.

An ink jet recording apparatus includes an ink container in which ink to be used to perform printing on a print target is stored, a nozzle which is connected to the ink container and from which pressurized and supplied ink is jetted, charging electrodes that charge ink particles jetted from the nozzle with electricity, deflecting electrodes that polarize the ink particles charged with electricity by the charging electrodes, a gutter that recovers ink not used for printing, a solvent container in which a solvent is stored, and a liquid nozzle which is connected to the solvent container and from which a pressurized and supplied solvent is jetted. The liquid nozzle includes a liquid flow passage portion that extends from the nozzle in a direction of the gutter, and a liquid jet hole that is formed at an angle allowing the pressurized and supplied solvent to hit the nozzle through the liquid flow passage portion.

The invention provides a method of adding solvent or make-up fluid into the gutter line of a continuous ink printer. During the addition of solvent, the vacuum level in the gutter line is monitored and maintained at a level sufficient to ensure that vacuum is maintained at the gutter. Vacuum level in the gutter line is preferably controlled by controlling the speed of a variable speed gutter pump. Noise in the gutter line is preferably used as a control over pump speed.

Provided is an inkjet recording device, including a print head that includes a head base including: a nozzle from which ink is ejected; charging electrodes that charge the ink ejected from the nozzle; deflection electrodes that deflect the ink charged by the charging electrodes; and a gutter that collects ink not used in printing, and a head cover included in the head base, wherein the head base has a first horizontal uneven side portion, an oblique uneven side portion, and a second horizontal uneven side portion.

A print head of a continuous ink jet printer comprising: a cavity for the circulation of jets, at least one nozzle for producing at least one ink jet or solvent in the cavity, at least one electrode for sorting drops or segments of one or several of the jets intended for printing from drops or segments that are not used for printing, an outlet slot of the cavity, open onto the exterior of the cavity and allowing the exiting of the drops or segments of ink intended for printing, a 1.sup.st gutter for recovering drops or segments not intended for printing, a 2.sup.nd gutter for recovering drops or segments that are not deflected and not intended for printing, this 2.sup.nd gutter being mobile and comprising an input slot and at least one suction channel, a motor, to actuate the 2.sup.nd gutter for recovering in movement between a retracted position, in which it does not close off the outlet slot of the cavity, and a closed position, in which its input slot faces the outlet slot of the cavity; a seal between the print head and the 2.sup.nd gutter for recovering in the closed position of the latter.

The invention discloses various methods of controlling or monitoring the performance of a continuous inkjet printer based on monitoring vacuum levels and/or noise in the gutter line.