Abstract: The conductive film (3) of a compliant doctor blade has dispersed particles of molybdenum disulfide, as well as dispersed particles of grit and conductive filler. The molybdenum disulfide eliminates filming of toner. The molybdenum disulfide may be a surface powder since the anti-film action occurs at the pre-nip and therefore is not lost by the molybdenum disulfide wearing away at the nip.

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: Wear on the elements (5) of a printhead (3) is spread by shifting the region of use of the printhead line by line. Font (13) provides information as to whether any character in a line employs the upper three pels or the bottom three pels of a line. For each line which can be printed from different shift positions of the printhead, selection logic controls paper feed (15) to index platen (9) to the least used of a shifted position of printhead. Only those electrodes over the print line in each shifted position are used for printing. This distributes wear without requiring any special ribbon feed. The three pel height is at least as wide as the serifs on most characters, which avoids some electrodes being used for the serifs of given characters in more than one shift position.

Abstract: Member (9) has a tension arm (13) over which ribbon (3) feeds. Biasing arm (17) presses member (9) toward brake surface (7), with slot (21) moved until it encounters stud (23). At low tension of ribbon (3), brake surfaces (11) and (7) press and hold ribbon (3). As feed tension increases tension arm (13) forces member (9) back until stud (23) encounters the opposite end of slot (21), after which slightly higher force further opens the brake and arm (13) continues to provide feed tension. The mechanism is small, efficient, smooth functioning, and suited to incorporation as part of a ribbon cartridge.

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 printhead assembly with a replaceable stylus insert provides for compact connection of contact pads by staggering the contact pads an offset distance that is significantly less than the pad dimension in the direction of offsetting. Preferably the offsets are symmetrically arranged about a reference line and connections are coordinated relative to the reference line so that conductor overlaps are avoided. A compressable means applies pressure to urge the contact pad into intimate engagement and ribs formed in one or both of two clamping sections concentrate pressure along alignments of contact pads.

Abstract: For an electro-thermal printer of the kind that uses a ribbon having a central conducting layer that is covered on one surface by a resistive layer that receives electrical printing currents and on the other surface by a thermally transferrable ink layer, printing current is collected from the conducting layer by an electrically conducting contactor at the ink layer surface of the ribbon. Such contact through the ink layer occurs on the takeup side of a printhead where the integrity of the ink layer is not of concern and voids in the ink layer occur as a result of ink transfers for printing. To increase the quality of the electrical connection, projecting points or barbs may be included on said contactor to penetrate to the conducting layer through intact portions of ink layer.

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.