Abstract: A high viscosity, high solid volume liquid ink for use in electrophotographic printing systems. A silicone oil carrier material is combined with toner particles (including pigment, binder polymers and charge control agents) in a ratio of about 45% toner particles to 55% carrier liquid. The resultant ink preferably has a viscosity in the range 30000 to 50000 cs. The high viscosity ink of the present invention is preferably applied to a photoconductor material having a latent charged image thereon and a thin pre-wet material applied thereto. The pre-wet material is preferably a low viscosity silicone oil material. The composite layer of the combined low viscosity pre-wet and high viscosity ink permits the polymerized toner particles to migrate toward the latent charged image on the photoconductor surface. The high viscosity ink of the present invention helps maintain uniform dispersion of the toner particles in the liquid carrier.

Abstract: An electrographic printing apparatus comprises a rotatable charge bearing member, a rotatable roller assembly which applies a chargeable pre-wetting oil to the surface of the charge bearing member, a charger assembly which applies uniform charge to the surface of the charge bearing member and/or the pre-wetting oil coating, and a light source which discharges selected areas on the charge bearing member and/or the pre-wetting oil to produce a latent electrostatic image thereon. The electrographic printing apparatus further comprises a liquid development system comprising an ink head assembly which applies liquid toner to the charge bearing member thereby developing the latent electrostatic image, and a rotatable transfer member which receives the developed image from the charge bearing member and then transfers it to a substrate such as paper. The electrographic printing apparatus may also be adapted to produce color images on the substrate.

Abstract: An ink jet printer with a continuous supply of sheet material from a spool contained within an imaging drum. The sheet material is withdrawn from the interior of the drum by a pair of rollers carried by the drum and removably connected to an external drive system. The sheet material travels around the drum and is held by the rollers in that position. The external drive system is then disconnected allowing the drum to rotate while a printing head scans the surface of the sheet material to produce the desired image. After the imaging process, the drum is stopped in a predetermined position and the rollers connected to the external drive. The rollers are then driven to eject the imaged sheet material while a fresh supply is withdrawn from the interior of the drum and wrapped around its outer surface.

Abstract: For requirements where constant velocity is important and positional error must be small and non-cumulative, a bipolar or unipolar, two-phase, permanent magnet stepper motor is driven by sawtooth currents in such manner as to produce a rotating magnetic field that exerts a substantially constant torque on the rotor. When using a bipolar stepper motor with windings electrically offset by 90.degree., two drive currents are generated that increase and decrease in amplitude linearly between predetermined maximum and minimum values. With a unipolar motor, four sawtooth waveforms, of single polarity, are provided. In either case, the currents are displaced by 90.degree. to produce a rotating magnetic field of uniform amplitude.A microprocessor controls the generation of a number of voltage ramps that control current generators for either the bipolar or unipolar stepper motor.

Abstract: An ink jet printer with a roll of paper stored within an imaging drum. The paper through a longitudinal opening in the drum to the outside, passes around the drum, where it is held in place during the imaging process, and then ejected from the drum to the desired length and cut off by a cutter that extends the full width of the paper. While the imaged sheet is being ejected from the drum, the next length of paper is drawn from the interior of the drum and around the outside of the drum in position for the next imaging operation. The length of paper that remains projecting from the drum after the imaged paper has been cut off is then withdrawn into the interior of the drum through the longitudinal opening in the drum surface until only a short stub, which will not interfere with the subsequent imaging operation, remains protruding from the drum. Precise movement of the paper is under the control of a counter that is responsive to the paper movement.

Abstract: An ink jet printer in which a roll of paper is stored within an imaging drum and feeds through a longitudinal opening in the drum to the outside, passes around the drum, where it is held in place during the imaging process, and then ejected from the drum and cut off. While the imaged sheet is being ejected from the drum, the next length of paper is drawn from the interior of the drum and around the outside of the drum in position for the next imaging operation. The paper is withdrawn from the drum by a traction roller that engages only the center portion of the paper to prevent the paper from skewing because of unequal forces applied to the edge portions of the paper. The same traction roller is also used in a reverse mode to tension the paper around the drum.

Abstract: An ink jet printer having an imaging drum with a supply of paper within the drum. The paper is transported by rollers mounted on the imaging drum that are controlled by the transverse position of a cutter mechanism that cuts off the imaged paper. The paper passes from the supply spool in the imaging drum through a longitudinal slot in the drum to the outside, around the exterior of the drum, where it is held in place during the imaging process, and then ejected from the drum to the desired length and cut off. While the imaged sheet is being ejected from the drum, the next length of paper is drawn from the drum and around the outside of the drum in position for the next imaging operation. The length of paper that remains projecting from the drum after the imaged paper has been cut off is then withdrawn into the interior of the drum through the longitudinal opening in the drum surface until only a short stub, which will not interfere with the subsequent imaging operation, remains protruding from the drum.

Abstract: A mechanically balanced pulsed ink droplet mechanism includes a disk or ring of piezoelectric ceramic material positioned within a metal ring of rectangular cross section having an annular channel in its inner surface that is sealed by a thin metal diaphragm to form an annular ink chamber. The piezoelectric transducer is in mechanical engagement with the inner surface of the annular diaphragm, but the ink is electrically insulated from the ceramic. A voltage pulse applied to opposite sides of the disk causes it to expand and eject a droplet of ink from the printing orifice.The ink chamber is shallow and has a ratio of cross section to wetted perimeter or hydraulic radius approximately equal to the diameter of the orifice which quickly damps oscillations resulting from the ejection of each droplet of ink and permitting higher speed operation. The ink chamber is sealed without the use of compliant materials resulting in minimal additional compliance to the liquid.

Abstract: The method of making a print head of the type that includes a piezoelectric transducer positioned within a metal housing having an annular channel in its inner surface that is sealed by a thin metal diaphragm to form an annular ink chamber. The transducer is in mechanical engagement with the inner surface of the diaphragm. The sudden removal of a voltage applied to the transducer expands the disk to reduce the volume of the ink chamber, rupture the meniscus, and force a droplet of ink from the printing orifice.The housing is formed with an internal taper which permits a groove to be cut readily either by a casting or by a tool entering from the larger end of the central opening in the housing. An aluminum mandrel is tapered to match the taper on the inner surface of the housing and provided with an annular groove that corresponds to the groove in the housing. The mandrel is plated with nickel that will later form the diaphragm. The housing and mandrel are then plated with indium.

Abstract: The invention is embodied in a pressurized ink supply system for a three color ink jet printer. In order to provide a relatively large ink supply, three stationary primary ink reservoirs, formed as three long tubular sacks of flexible plastic film, contained in a pressurized disposable cartridge, are connected through flexible plastic umbilical tubes, and three solenoid-operated valves, to three secondary ink reservoirs mounted on the movable carriage of the print head.The pressure in the primary reservoirs, under automatic control, forces the ink to the secondary reservoirs and, under manual control, purges the ink passages and orifices by momentarily opening all of the solenoid valves. The waste ink that is discharged by this purging operation is captured and returned to a separate waste-ink storage chamber in the disposable cartridge. This waste-ink storage chamber is maintained under a slight vacuum by the same pump that provides the pressure for the ink reservoirs.

Abstract: The invention is embodied in a pressurized ink supply system for a three color ink jet printer. In order to provide a relatively large ink supply, three stationary primary ink reservoirs, formed as three long tubular sacks of flexible plastic film, contained in a pressurized disposable cartridge, are connected through flexible plastic umbilical tubes, and three solenoid-operated valves, to three secondary ink reservoirs mounted on the movable carriage of the print head. Automatic ink replenishment and an out-of-ink alarm are controlled entirely from the secondary ink reservoirs.The ink level in each secondary reservoir is maintained within close limits without attention from the operator. When the primary reservoir runs out of ink, as indicated by failure of the secondary reservoir to fill within a specified time period, an alarm alerts the operator to remove and replace the ink cartridge.