This invention relates generally to a liquid ink printing machine and more particularly to a liquid ink printer having a heat and hold drier.
Liquid ink printers of the type frequently referred to as continuous stream or as drop-on-demand, such as piezoelectric, acoustic, phase change wax-based or thermal, have at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in a plurality of channels. Power pulses cause the droplets of ink to be expelled as required from orifices or nozzles at the end of the channels.
In a thermal ink-jet printer, the power pulse is usually produced by a heater transducer or a resistor, typically associated with one of the channels. Each resistor is individually addressable to heat and vaporize ink in the channels. As voltage is applied across a selected resistor, a vapor bubble grows in the associated channel and initially bulges from the channel orifice followed by collapse of the bubble. The ink within the channel then retracts and separates from the bulging ink thereby forming a droplet moving in a direction away from the channel orifice and towards the recording medium whereupon hitting the recording medium a drop or spot of ink is deposited. The channel is then refilled by capillary action, which, in turn, draws ink from a supply container of liquid ink.
The ink jet printhead may be incorporated into either a carriage type printer, a partial width array type printer, or a page-width type printer. The carriage type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead can be sealingly attached to a disposable ink supply cartridge. The combined printhead and cartridge assembly is attached to a carriage which is reciprocated to print one swath of information (having a width equal to the length of a column of nozzles), at a time, on a stationary recording medium, such as paper or a transparency. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath or a portion thereof, so that the next printed swath is contiguous or overlapping therewith. This procedure is repeated until the entire page is printed. In contrast, the page width printer includes a stationary printhead having a length sufficient to print across the width or length of a sheet of recording medium at a time. The recording medium is continually moved past the page width printhead in a direction substantially normal to the printhead length and at a constant or varying speed during the printing process. A page width ink-jet printer is described, for instance, in U.S. Pat. No. 5,192,959.
Many liquid inks and particularly those used in thermal ink jet printing, include a colorant or dye and a liquid which is typically an aqueous liquid vehicle, such as water, and/or a low vapor pressure solvent. The ink is deposited on the substrate to form an image in the form of text and/or graphics. Once deposited, the liquid component is removed from the ink and the paper to fix the colorant to the substrate by either natural air drying or by active drying. In natural air drying, the liquid component of the ink deposited on the substrate is allowed to evaporate and to penetrate into the substrate naturally without mechanical assistance. In active drying, the recording medium is exposed to heat energy of various types which can include infrared heating, conductive heating and heating by microwave energy.
Active drying of the image can occur either during the imaging process or after the image has been made on the recording medium. In addition, the recording medium can be preheated before an image has been made to precondition the recording medium in preparation for the deposition of ink. Preconditioning of the recording medium typically prepares the recording medium for receiving ink by driving out excess moisture which can be present in a recording medium such as paper. Not only does this preconditioning step reduce the amount of time necessary to dry the ink once deposited on the recording medium, but this step also improves image quality by reducing paper cockle and curl which can result from too much moisture remaining in the recording medium.
Various drying mechanisms for drying images deposited on recording mediums are illustrated and described in the following disclosures which may be relevant to certain aspects of the present invention.
In U.S. Pat. No. 4,970,528 to Beaufort et al., a method for uniformly drying ink on paper from an ink jet printer is described. The printer includes a uniform heat flux drier system including a 180xc2x0 contoured paper transport path for transferring paper from an input supply tray to an output tray. During transport, the paper receives a uniform heat flux from an infrared bulb located at the axis of symmetry of the paper transport path. Reflectors are positioned on each side of the infrared bulb to maximize heat transmission from the bulb to the paper during the ink drying process.
U.S. Pat. No. 5,005,025 to Miyakawa et al. describes a printer having means for heating a recording sheet and fixing ink thereon. A fixing means is located adjacently to a recording head or extending from the recording area to ejecting rollers.
U.S. Pat. No. 5,214,442 to Roller describes an adaptive drier for a printing system which obtains values representing mass of ink and/or area coverage of ink on a page.
U.S. Pat. No. 5,274,400 to Johnson et al., describes an ink path geometry for high temperature operation of ink jet printheads. A heating means is positioned close to a print zone for drying of the print medium. The heating means includes a print heater and a reflector which serve to concentrate the heat on the bottom of the print medium through a screen.
U.S. Pat. No. 5,287,123 to Medin et al., describes a color ink jet printer having a heating blower system for evaporating ink carriers from the print medium after ink-jet printing. A print heater halogen quartz bulb heats the underside of the medium via radiant and convective heat transfer through an opening pattern formed in a print zone heater screen.
U.S. Pat. No. 5,500,667 to Schwiebert et al. describes a method and apparatus for heating the print medium in an ink jet printer. The printer includes a print area heater. The printer has a preheater along the medium path, with an unheated area between the print area and the preheater.
In accordance with one aspect of the present invention, there is provided a printing machine for printing an image including colorants, including a liquid carrier, on a recording medium moving along a path through a pre-print zone and a print zone. The printing machine includes a printhead, disposed adjacent the print zone, to deposit the colorants, including the liquid carrier, on the recording medium during movement through the print zone and a pre-print zone drier, disposed adjacent the pre-print zone, to generate a heat energy, towards the recording medium, sufficiently elevated for retention in the recording medium during movement thereof through the print zone.