Abstract: In a continuous ink jet printer for use with pigmented ink, the entrance to the ink path (81), (35) from the interior of the ink tank (27) to the ink pump (31) is made up of a plurality of small inlet openings, which may be provided by nozzles 85 formed in a shroud 83 that fits around an ink filter (33) in the ink tank (27). The openings are provided at the bottom of the ink tank (27), close to the floor, and face parallel to the floor or at least partially towards it. If the ink pump (31) is driven in reverse, any ink in the ink path is driven at speed out through the inlet openings into the interior of the ink tank (27), followed by air. This tends to disperse pigment that may have settled to the bottom on the ink tank (27).

Abstract: Either during message selection in an industrial printer (e.g. ink jet or laser marking) for printing onto objects carried past it on a conveyor, or during printing, or both, a printer displays an image associated with the message proposed for printing or being printed. The image may be a picture (e.g. a photograph) of the object on which the message should be printed or the intended customer/end user or the intended use of the object on which the message should be printed. Since a human operator can usually identify an object or intended customer/use more quickly and accurately from a picture than from text, this reduces errors in message selection and/or helps the detection of an incorrect message during printing. The image may be displayed with the associated message or without it.

Abstract: A continuous inkjet printer has an ink circuit comprising an ink tank, an ink pump and a Venture suction device. The Venturi is used to suck an extra solvent or ink as required. However, if the ink tank is empty, no ink can be pumped through the Venture and so it will not develop suction and thus, cannot be used to suck in an initial supply of ink to an empty tank. A removable ink container may be connected to the ink tank or elsewhere in the ink circuit, for example, between the Venturi outlet and the pump inlet. Compressing the ink container manually will force ink into the ink circuit. When enough ink has been added, the pump will drive ink through the Venturi and suction will be generated.

Abstract: An electrostatic deflection inkjet printer has a main printer body separated by a vapor barrier into an electrical region and a fluid region. Electrically operated valves are provided in the fluid region. Control circuitry for deciding when to operate the valves is provided in the electrical region. Valve drive circuitry, for generating drive currents for the valves, is provided in the fluid region and is in data communication with the control circuitry via wiring, which may be a serial bus, that passes through the vapor barrier. This reduces the number of electrical connections that need to pass through the vapor barrier. A circuit carrier for the valve drive circuitry may be mounted on a valve block for the valves, and an electrically insulating material may cover the circuit carrier. The electrically insulating material may extend partially or wholly around the valve block.

Abstract: A non-contact printer controls the sensitivity of sensors provided upstream of a print head, to detect the approach of an object. In a calibration operation to set the sensitivity level of the sensors before a printing operation, the printer displays instructions to guide the operator and adjusts the sensor sensitivity to find detection threshold levels for a background (object absent) condition and when the object is present. The calibration results may be stored in association with data identifying the conveyor and the type of object used in the calibration operation. If the same conveyor and/or object type is used again in a later printing operation, the sensitivity level of the sensors can be set using the stored calibration results so that a further calibration operation is not necessary.

Abstract: A continuous inkjet printer has an ink circuit comprising an ink tank, an ink pump and a Venture suction device. The Venturi is used to suck an extra solvent or ink as required. However, if the ink tank is empty, no ink can be pumped through the Venture and so it will not develop suction and thus, cannot be used to suck in an initial supply of ink to an empty tank. A removable ink container may be connected to the ink tank or elsewhere in the ink circuit, for example, between the Venturi outlet and the pump inlet. Compressing the ink container manually will force ink into the ink circuit. When enough ink has been added, the pump will drive ink through the Venturi and suction will be generated.

Abstract: A cap 13, 15, for the print face 9 of a drop-on-demand ink jet printer moves between a closed position, in which it covers the print nozzles on the print face 9, and an open position in which the print nozzles are uncovered, without requiring movement of the print face 9. In the open position, the cap is recessed relative to the front surface 21 of the printhead. For at least part of the movement of the cap, it is further forward than the print face 9, so that it does not slide across and damage the print nozzles. The drop-on-demand ink jet printer may be used to print onto objects 3 conveyed past it, for example on a packing line. The cap 13, 15, does not obstruct the path of the objects 3 even if they pass very close (e.g. 0.5 mm) to the print face 9 because its uncapped position is further back than the front surface 21 of the printhead.

Abstract: A cap 13, 15, for the print face 9 of a drop-on-demand ink jet printer moves between a closed position, in which it covers the print nozzles on the print face 9, and an open position in which the print nozzles are uncovered, without requiring movement of the print face 9. In the open position, the cap is recessed relative to the front surface 21 of the printhead. For at least part of the movement of the cap, it is further forward than the print face 9, so that it does not slide across and damage the print nozzles. The drop-on-demand ink jet printer may be used to print onto objects 3 conveyed past it, for example on a packing line. The cap 13, 15, does not obstruct the path of the objects 3 even if they pass very close (e.g. 0.5 mm) to the print face 9 because its uncapped position is further back than the front surface 21 of the printhead.

Abstract: A cap 13, 15, for the print face 9 of a drop-on-demand ink jet printer moves between a closed position, in which it covers the print nozzles on the print face 9, and an open position in which the print nozzles are uncovered, without requiring movement of the print face 9. In the open position, the cap is recessed relative to the front surface 21 of the printhead. For at least part of the movement of the cap, it is further forward than the print face 9, so that it does not slide across and damage the print nozzles. The drop-on-demand ink jet printer may be used to print onto objects 3 conveyed past it, for example on a packing line. The cap 13, 15, does not obstruct the path of the objects 3 even if they pass very close (e.g. 0.5 mm) to the print face 9 because its uncapped position is further back than the front surface 21 of the printhead.

Abstract: A cap 13, 15, for the print face 9 of a drop-on-demand ink jet printer moves between a closed position, in which it covers the print nozzles on the print face 9, and an open position in which the print nozzles are uncovered, without requiring movement of the print face 9. In the open position, the cap is recessed relative to the front surface 21 of the printhead. For at least part of the movement of the cap, it is further forward than the print face 9, so that it does not slide across and damage the print nozzles. The drop-on-demand ink jet printer may be used to print onto objects 3 conveyed past it, for example on a packing line. The cap 13, 15, does not obstruct the path of the objects 3 even if they pass very close (e.g. 0.5 mm) to the print face 9 because its uncapped position is further back than the front surface 21 of the printhead.

Abstract: An ink/air separator for an ink jet printer has one or more plates 77, 79, 81, 83 over which an ink/air mixture can spread. Preferably there is more than one plate, and the mixture overflows from one plate to the next. Preferably adjacent plates are spaced so that as the mixture passes between two plates it contacts the surface above it as well as the surface below it. The plates may be separated by a gap of 10 mm or less, e.g. a gap of 2 mm to 5 mm, where they overlap Preferably some or all of the plate surfaces contacted by the mixture are roughened. Interaction between the ink/air mixture and the plate surface tends to slow the flow of very small air bubbles and encourage them to accumulate and/or merge, so that they separate from the ink more quickly than individual small bubbles. The ink/air separator may be connected in the path of unused ink returned from the gutter 27 of a continuous ink jet printer to an ink tank 39, or may be placed inside the ink tank 39.

Abstract: A continuous ink jet printer has a line (69a) for venting at least some of the air that has been sucked along the gutter line (17), and a line (69b) for recirculating back to the printhead (25) at least some of the air that has been sucked down the gutter line (17). Preferably the relative proportions of vented air and recirculated air can be varied, so as to reduce solvent loss during normal operation but allow increased solvent loss if the ink is over-dilute. Preferably the air recirculated to the printhead is connected directly into the flow path from the gutter orifice to the source of gutter suction, without opening into the space containing the ink jet. This reduces the tendency of solvent in the recirculated air condense on the printhead electrodes.

Abstract: A gutter line of a continuous inkjet printer which includes a variable flow restrictor fitted into the gutter line, and a pressure transducer for measuring the pressure in the gutter line downstream of the variable flow restrictor, where the variable flow restrictor is controlled in response to the output of the pressure transducer to maintain a downstream pressure substantially constant. Airflow along the gutter line has a lower flow resistance than a slug of ink. Accordingly, the system responds dynamically to restrict the flow of air along the gutter line when no ink is passing along it, thereby reducing the volume of air sucked along the gutter line while maintaining adequate suction to reliably clear ink away from the gutter so that the amount of solvent lost from the ink is reduced during operation of an inkjet printer.

Abstract: A continuous ink jet printer has a line (69a) for venting at least some of the air that has been sucked along the gutter line (17), and a line (69b) for recirculating back to the printhead (25) at least some of the air that has been sucked down the gutter line (17). Preferably the relative proportions of vented air and recirculated air can be varied, so as to reduce solvent loss during normal operation but allow increased solvent loss if the ink is over-dilute. Preferably the air recirculated to the printhead is connected directly into the flow path from the gutter orifice to the source of gutter suction, without opening into the space containing the ink jet. This reduces the tendency of solvent in the recirculated air condense on the printhead electrodes.

Abstract: A continuous ink jet printer comprising an ink gun for forming an ink jet; an arrangement of electrodes for trapping electric charges on ink drops of the ink jet and for creating an electrostatic field for deflecting drops carrying trapped electric charges; and a gutter having an ink-receiving orifice for receiving ink drops of the ink jet which are not used for printing; a gutter flow path for flow of ink from the ink-receiving orifice of the gutter, through and away from the gutter; an air recirculation line for conveying at least some of any air that has passed with the ink along at least a part of the gutter flow path so as to re-enter the gutter flow path either through the ink-receiving orifice or through a connection into the gutter flow path downstream of the ink-receiving orifice; and a vent for venting at least some of the air that has passed with the ink along at least a part of the gutter flow path so as not to re-enter the gutter flow path.