Abstract: An electrical circuit for measuring the shape of a voltage waveform in a print head of a printer includes an integrated circuit for generating one or more voltage amplitude waveforms. The electrical circuit includes an inkjet drop forming unit including a plurality of inkjet chambers, wherein each of the plurality of inkjet chambers includes a piezoelectric actuator and an ink nozzle, and a connecting circuit between the integrated circuit and the inkjet drop forming unit suitable for applying one of the one or more voltage amplitude waveforms generated by the integrated circuit to the piezoelectric actuator in one of the plurality of inkjet chambers. In order to measure the shape of the one or more generated voltage amplitude waveforms via capacitive crosstalk, the electrical circuit also includes a conductor in physical proximity to the connecting circuit.

Abstract: An electrical circuit for measuring the shape of a voltage waveform in a print head of a printer is provided. The electrical circuit comprises an integrated circuit for generating one or more voltage amplitude waveforms. Further, the electrical circuit comprises an inkjet drop forming unit comprising a plurality of inkjet chambers, wherein each of the plurality of inkjet chambers comprises a piezoelectric actuator and an ink nozzle, and a connecting circuit between the integrated circuit and the inkjet drop forming unit suitable for applying one of the one or more voltage amplitude waveforms generated by the integrated circuit to the piezoelectric actuator in one of the plurality of inkjet chambers. In order to measure the shape of the one or more generated voltage amplitude waveforms via capacitive crosstalk, the electrical circuit also comprises a conductor in physical proximity to the connecting circuit.

Abstract: A method of operating a drop-on demand (DOD) jetting device having a nozzle, a pressure chamber filled with a liquid and connected to the nozzle and an actuator energized by a drive signal, wherein a periodic DOD signal determines whether or not a droplet is jetted out from the nozzle in a given DOD period, and the drive signal has a waveform configured to cause the actuator to excite a pressure wave in the liquid, the method further comprising the steps of a) energizing the actuator with a waveform that has a fixed pattern and extends over a time interval that is longer than the given DOD period; and b) ignoring the DOD signal in at least the first DOD period that follows after said period for which the step a) has been performed.

Abstract: A jetting device includes an ejection unit arranged to eject a droplet of a liquid. The ejection unit includes a nozzle, a liquid duct connected to the nozzle, and an electro-mechanical transducer arranged to create an acoustic pressure wave in the liquid in the duct. The jetting device further includes a filter arranged to filter the liquid being supplied into the duct and a filter status detection system arranged to detect an obstruction status of the filter by measuring a property of the liquid in the duct. The filter status detection system includes a circuit configured for measuring the electric response of the transducer, for recording changes in the electric response that represent pressure fluctuations induced by the acoustic wave in the form of a time-dependent function, and for judging the obstruction status of the filter on the basis of that function.

Abstract: For assessing the functioning of an ejection unit of an inkjet print head, a comparison of a residual pressure wave with a residual pressure wave reference is employed. To enable assessment during printing, multiple residual pressure wave references are provided, each relating to a condition relevant to the residual pressure wave. Such a condition may relate to an actuation status of an adjacent ejection unit which may cause crosstalk, for example. When performing the assessment, the condition during assessment is taken into account, for example for selecting a suitable residual pressure wave reference, such that an appropriate and correct assessment can be performed independent from the conditions during assessment.

Abstract: A method of operating a drop-on demand (DOD) jetting device having a nozzle, a pressure chamber filled with a liquid and connected to the nozzle and an actuator energized by a drive signal, wherein a periodic DOD signal determines whether or not a droplet is jetted out from the nozzle in a given DOD period, and the drive signal has a waveform configured to cause the actuator to excite a pressure wave in the liquid, the method further comprising the steps of a) energizing the actuator with a waveform that has a fixed pattern and extends over a time interval that is longer than the given DOD period; and b) ignoring the DOD signal in at least the first DOD period that follows after said period for which the step a) has been performed.

Abstract: An inkjet print head includes an ejection unit having a liquid chamber for holding an amount of liquid, a electromechanical transducer operatively coupled to the liquid chamber for generating a pressure wave in the amount of liquid and a nozzle in fluid communication with the liquid chamber for enabling a droplet of the amount of liquid to be ejected through the nozzle. A method for detecting an operating state of the ejection unit includes the consecutive steps of actuating the electromechanical transducer to generate a pressure wave in the liquid; actuating the electromechanical transducer to suppress a residual pressure wave in the liquid; sensing an amplitude of the residual pressure wave in the liquid; and based on the result of the sensing step determining that the ejection unit is (i) in an operative state if the amplitude of the residual pressure wave is below a threshold or (ii) in a malfunctioning state if the amplitude of the residual pressure wave is above the threshold.

Abstract: A jetting device includes an ejection unit arranged to eject a droplet of a liquid. The ejection unit includes a nozzle, a liquid duct connected to the nozzle, and an electro-mechanical transducer arranged to create an acoustic pressure wave in the liquid in the duct. The jetting device further includes a filter arranged to filter the liquid being supplied into the duct and a filter status detection system arranged to detect an obstruction status of the filter by measuring a property of the liquid in the duct. The filter status detection system includes a circuit configured for measuring the electric response of the transducer, for recording changes in the electric response that represent pressure fluctuations induced by the acoustic wave in the form of a time-dependent function, and for judging the obstruction status of the filter on the basis of that function.

Abstract: An inkjet print head includes an ejection unit having a liquid chamber for holding an amount of liquid, a electromechanical transducer operatively coupled to the liquid chamber for generating a pressure wave in the amount of liquid and a nozzle in fluid communication with the liquid chamber for enabling a droplet of the amount of liquid to be ejected through the nozzle. A method for detecting an operating state of the ejection unit includes the consecutive steps of actuating the electromechanical transducer to generate a pressure wave in the liquid; actuating the electromechanical transducer to suppress a residual pressure wave in the liquid; sensing an amplitude of the residual pressure wave in the liquid; and based on the result of the sensing step determining that the ejection unit is (i) in an operative state if the amplitude of the residual pressure wave is below a threshold or (ii) in a malfunctioning state if the amplitude of the residual pressure wave is above the threshold.

Abstract: For assessing the functioning of an ejection unit of an inkjet print head, a comparison of a residual pressure wave with a residual pressure wave reference is employed. To enable assessment during printing, multiple residual pressure wave references are provided, each relating to a condition relevant to the residual pressure wave. Such a condition may relate to an actuation status of an adjacent ejection unit which may cause crosstalk, for example. When performing the assessment, the condition during assessment is taken into account, for example for selecting a suitable residual pressure wave reference, such that an appropriate and correct assessment can be performed independent from the conditions during assessment.

Abstract: A system for correcting skew of a web of material being fed through a machine includes first and second pinch assemblies placed at a distance transversely to a direction of feeding. First and second stepper motors drive the first and second pinch assemblies, respectively. A control provides first and second pulse trains to drive the first and second stepper motors, respectively. A device determines a value for the skew of the web of material. A method for controlling the system includes establishing first and second corrective pulse train sections for the first and second stepper motors, respectively, in accordance with a determined skew value, and providing first and second pulse trains for driving the first and second stepper motors, respectively.

Abstract: A method of printing a receiving material wherein said receiving material is fed through a printer including a first and a second image-forming unit for substantially simultaneous printing of the front and back of said material in a transfer nip, whereby the two images are brought into register in the lateral direction with the receiving material by determining, prior to the formation of the images, a reference position at the transfer nip; forming the first image in such manner that part of said image which corresponds to the said reference position in the transfer nip substantially coincides therewith; and also forming the second image in such a manner that part of said image which corresponds to the said reference position in the transfer nip substantially coincides therewith; and feeding the receiving material to the transfer nip in such manner that that part of said material which corresponds to the reference position coincides substantially therewith at the transfer nip.

Abstract: An image printing apparatus includes a number of image forming units for forming toner images of different colors in alignment on image receiving material in accordance with electronic image information signals fed to each image forming unit. Each image forming unit includes an image forming element rotatable about an axis of rotation and provided with a dielectric surface layer with adjacent electrode tracks in the direction of rotation. Each image forming unit further includes developing devices which include a linear developing magnet situated near the outer surface and parallel to the axis of rotation of the image forming element, toner feed devices for feeding a complete covering of electrically conductive and magnetically attractable toner powder to the image forming element, electrode track activating devices for applying a first or a second printing voltage between an electrode track and the magnet system in accordance with the image information signals to be fed to the image forming units.

Abstract: A raster image memory which serves as a bit-map memory for the storage of the bit representation of a whole page to be printed for a raster output scanner is connected to a raster image processor by a synchronous raster image bus having a number of data and modification code lines. Each memory element of the bit-map memory corresponds to a position on the page. The raster image processor fills the raster image memory. A logic processing unit is disposed between the raster image bus and the bit-map memory so that one input of the logic processing unit is connected to the data lines of the raster image bus and another input of the logic processing unit is connected to the data outputs of the bit-map memory. The logic processing unit is also capable of performing a number of logic operations on the data presented at the inputs of the logic processing unit in response to the signals on the modification code lines.