Abstract: A toner cartridge having no toner pump with the toner adding roller (11 ) positioned horizontal to the developer roller (3), the toner chamber (9) located predominantly below the developer roller, the photoconductive drum located 120 degrees from the top of tile developer roller, and the doctor blade (5) is located near the top. The cartridge has a minimal number of operational parts.

Abstract: In a toner cartridge, photoconductor drum (11) is driven by a gear (3) which is in the printer, toner adder roller (48) is driven independently by a face coupling (5) which is in the printer. On the opposite side, a gear train from toner adder roller (48) drives developer roller (42) and toner paddle (52). The two systems permit the cartridge to function in different printers requiring different ratios of speeds. Stiffness requirements of the cartridge are reduced. Movements are more consistent, and space utilization is enhanced.

Abstract: An electrophotographic printer (11) having a base (13) and a top (12), the top (12) being pivotable about an axis (23) between a closed position and an open position. The printer (11) receives a supply cartridge (14) on a shelf (22) which is pivotable about the same axis (23) as the top (12) of the printer (11). A counterbalance spring (34) helps to support the shelf (22) and the cartridge (14) below the top (12) of the printer (11) and above the printer base (13) when the top (12) of the printer (11) is in its open position. When the top (12) of the printer (11) is closed, the cartridge (14) is urged into a position adjacent the printer base (13) and locked into an operative position.

Abstract: Metering roller (3) in the electrophotographic developer cartridge (1) is unsymmetrical along its length. As the metering roller rotates it distributes toner (11) both ways between chamber 13 and chamber 19 to maintain an equilibrium level (31) between the chambers. The unsymmetrical roller simultaneously reduces and increases the area of chamber 11, and possibly also provides a significant open path to chamber 19 across its flat surfaces (35), to inherently eliminate significant pressure build-up in chamber 13. The need for a vent between the chambers is eliminated.

Abstract: A developer apparatus (29) for use in an electrostatic reproduction apparatus includes a large reservoir of toner (34, 44). The toner is located in a supply chamber (39) and is metered to a developer roller chamber (35) from which it is carried by a developer roller (31) past a doctor blade (36) to a photoconductor drum (19) for image development. A toner metering roller (41) rotates with the developer roller (31) to provide a continuous supply of toner from the supply chamber (39) to the developer chamber (35). Once an equilibrium level (65) is reached, the toner metering roller (41) acts to remove toner (34) from the developer chamber (35) to the supply chamber (39) to insure proper operation of the developer roller (31).

Abstract: A thermal printhead, which is pivotally mounted on a carrier, is moved into and out of its printing position by a four bar linkage, which is responsive to the direction in which the carrier is being advanced, rendering a spring, which urges the thermal printhead into its printing position, effective and ineffective. When the carrier is advanced from left to right to print, the linkage responds to a drive mechanism for the carrier to enable movement of the printhead into its printing position by the spring prior to the carrier drive mechanism moving the carrier. When the carrier is to be moved from right to left in the non-printing direction, the linkage responds to the initial motion of the carrier drive mechanism in this direction to render the spring ineffective and to move the printhead out of its printing position prior to the carrier drive mechanism moving the carrier.

Abstract: A symmetrical printer ribbon cartridge which is refillable. An internal, continuous drive belt (15) provides tension to push studs (33, 35) of the supply spool (23) and of a take-up spool (29) to the ends of notches (31, 32) in cartridge wall 1. When the original supply spool is emptied, a new spool need only be moved into place and the free end of the ribbon pulled from the new spool, directed through the ribbon path in the cartridge, and attached to the remaining spool.

Abstract: A wear-resistant ribbon guide surface (11 or 25a, 25b) is added to a thermal printhead (1) to lower the ribbon exit angle after printing or to shift the ribbon exit position away from the printing. The angle past that surface remains large enough for visibility of prior printing. The modification of exit conditions makes the printing darker and significantly improves printhead life.

Abstract: Conservation of ribbon 40 is achieved by underfeeding ribbon 40 relative to movement of thermal printhead 16. Pressure of printhead 16 may be low enough that smearing from a typical ribbon 40 does not occur. Gears 208, 210, 212, 214 and 216 may be positioned in one of two settings by action of bellcrank 230. One position provides a 1.04 to 1 underfeed ratio and the other provides a 5 to 1 underfeed ratio. Control 232 lowers print current for the 5 to 1 ratio. A printer having a single ratio of 1.04 to 1 provides printing of unimpaired quality with significant saving of ribbon.

Abstract: A ribbon loading system for a printer utilizes a ribbon cartridge that includes a container enclosing two coaxially arranged ribbon reels. By providing flexible blades in the floor of the container, the reels are urged toward a top cover where relative movement is restrained. Upon loading of the cartridge, camming arms enter apertures in the container and are moveable to a clamping position to draw the blades from the ribbon reels and allow free rotational movement.For a presently preferred implementation, the structure including the camming arms is coupled through linkages to clear the ribbon threading path and thereby facilitate ribbon insertion.

Abstract: A ribbon feed system for a matrix printer utilizes metering rollers located on the printhead carrier to maintain a substantially zero ribbon velocity relative to the receiving medium with an on-carrier ribbon feed. By coordinating roller rotation with carrier motion, relative motion that would tend to cause smearing during mark formation is avoided. For printers that inject current into the ribbon to cause printing, friction drag is reduced and tension control is simplified by collecting current at the metering rollers for return to the printhead energizing circuitry. Such dual use of the metering rollers takes advantage of the firm intimate contact that exists for metering to establish a high quality electrical connection. A tension controlled brake at the ribbon supply serves to assure tensions are held within a narrow range at the printhead with such a ribbon metering system.

Abstract: In thermal printing the guide (29) positionable toward the platen (3) on a pivoted arm (50) during lift-off correction allows a bond for correction to set before the ribbon (22) is pulled away. The ribbon (22) has an outer layer which adheres to printed characters at somewhat elevated temperatures but is non-tacky at room temperatures. Thermal printing is conducted by setting the switch (44) for heating to temperatures higher than the lift-off temperature.

Abstract: A ribbon feed failure in a printer can cause serious problems, particularly for a printer that uses heat to cause selective ink transfers. Localized heat buildup may injure the printhead and, if allowed to continue, might injure other printer instrumentalities.According to the invention, it is recognized that for ribbons having a degree of electrical conductivity, a mechanical ribbon failure will almost always result in a detectable change of electrical properties. By monitoring the characteristics of an electrical circuit passing through a section of the ribbon around the print point and, preferably, also the printhead-ribbon interface, abnormal electrical parameter values that indicate ribbon failure may be detected to trigger a cessation of printer operation.

Abstract: A printhead assembly for a typewriter of the kind that swipes a printhead along a ribbon in producing marks on a receiving medium, is mounted to pivot and includes a ribbon guide that serves to wrap the ribbon around the trailing side (for a forward printing direction) of the printhead. The assembly is positioned to permit the printhead to be rotated to a normal printing position at a printing line. By so arranging the ribbon path that the ribbon directions for arrival and departure of the assembly intersect the pivot axis, essentially zero resultant torque may be applied to the assembly by ribbon tension forces and the printing pressure at the receiving medium is, accordingly, unaffected by ribbon tension variations.