Abstract: A method and apparatus for extending the useful life of a printing ribbon by controlling the ratio of ink used to ink applied to the ribbon, while maintaining visual clarity of printed characters. A counter accumulates the number of characters printed, and the print density, over a preset period of time. The number of characters printed is compared with predetermined triggering numbers of characters, and the print density is likewise compared with a predetermined triggering print density. As a result of this comparison, the speed of the printer ribbon is increased to allow an increase in the ratio of ink applied to ink used, when the number of characters and print density are high. Conversely, ribbon speed is decreased when the number of characters printed during the preset time period, and the print density, are low, to prevent overinking and fouling of printer hammers. This condition applies when the ribbon is relatively new.

Abstract: A printer ribbon cartridge (10) containing an internal re-inking mechanism (12) for re-inking the ribbon (14) housed in the cartridge is provided. The internal re-inking mechanism (12) comprises a drive assembly (30), pump (24), an eccentric (26), an ink reservoir (22), an ink feeding tube (34), a re-inking ring (30) and a transfer roller (38). As the ribbon (14) is threaded and propelled through the drive assembly (30), the drive assembly drives the pump (24) via the eccentric (26). The pump (24) pumps ink from the ink reservoir (22) to the re-inking ring (36) through the ink feeding tube (34). The ink is transferred from the re-inking ring (36) to the ribbon (14) via the transfer roller (38).

Abstract: An ink reservoir (34) capable of maintaining an even distribution of a single color of ink on a printer ribbon is provided. The ink reservoir is used in ribbon cassettes (10) for typewriters and dot matrix printers. The ink reservoir (34) includes a series of cylindrical ink-carrying elements (50) separated by a series of separating sheets (52). The separating sheets (52) restrict or prevent the flow of ink from one ink-carrying element to another element. This maintains an even distribution of ink throughout the height of the reservoir which, in turn, results in an even transfer of ink from the ink reservoir onto a transfer roller and subsequently onto a ribbon. The even distribution of ink in the ribbon results in an even distribution of ink in the characters printed using the ribbon and, thus, improves print quality.

Abstract: Stored energy print hammer actuators (11) having high efficiency coil posts (19) are disclosed. The coil posts (19) include a cylindrical core (33) mounted on a pin (35). The cylindrical core (33) has high resistivity and, thus, minimizes eddy currents and the power losses created by eddy currents. The cylindrical core (33) also has low hysteresis loss. In one form, the core (33) is formed of layers of a high resistivity material shaped to prevent eddy currents from circulating about the circumference of the posts. Suitable shapes include discrete C-layers and continuous spiral layers. Preferably, the layers are coated with an electrical insulating material that prevents cross-lamination eddy current flow. In another form, the core is formed of a high resistivity homogenous material, such as a ferrite material or a magnetic powder and an adhesive binder.

Abstract: A twin counterweight, shuttle drive (11) for a reciprocably mounted dot matrix line printer carriage (13) that is shock stabilized to: (a) eliminate instability when the printer is bumped; and, (b) maintain the center point of the carriage peak-to-peak travel in the same position even when the printer is inclined, is disclosed. The shuttle drive (11) comprises a pair of equally sized and configured weight unbalanced gears (43) rotatably coupled together and secured to the mounted dot matrix line printer carriage (13). Rotation of the weight unbalanced gears (43) creates a drive force that shuttles the carriage (13). The gears (43) are positioned such that the drive force is aligned with the center of gravity of the carriage (13) and such that the centers of rotation of the gears (43) lie on a line that is perpendicular to the line of shuttle motion.

Abstract: A weight unbalance shuttle drive for flexure mounted carriages (11) is disclosed. The weight unbalance shuttle drive comprises a pair of motors (49) attached to the flexure mounted carriage (11). Mounted on the shaft of each motor is an unbalancing weight (51). When the motors (49) are energized the unbalancing weights (51) produce carriage drive forces in alternating directions resulting in the carriage (11) being shuttled back and forth. The mass and shape of the unbalancing weights (51) is chosen to produce the desired carriage displacement at the desired system operating frequency. The rotary positions of the unbalance weights (51) is chosen to produce the desired force/displacement amplitude.

Abstract: An adjustable load tear bar mechanism for a friction feed platen (15) that comprises a tear bar assembly (31) and spring loading mechanisms (33) is disclosed. The tear bar assembly (31) comprises a tear bar (51) mounted between a pair of side arms (41, 43) located on opposite ends of the platen (15). The tear bar (51) is an inverted, generally U-shaped channel. Positioned in the channel is a roller shaft (45) on which a plurality of friction feed rollers (47) are mounted. The downstream ends of the side arms (which overlie the platen) are pivotally attached to walls (11, 13) of the printer chassis. The tear bar (51) and roller shaft (45) extend between the upstream ends of the side arms (41, 43). Mounted on the roller shaft (45) so as to be rotatable therewith are arm hooks (53, 55). One of the arm hooks is part of a detent mechanism that includes teeth (125) that co-act with a spring (59) and plunger (57) housed in one of the side arms (43).

Abstract: A print head for a dot matrix serial printer, including a high energy permanent magnet (13) surrounded by a plurality of coil/post combinations (15, 17) each aligned with a print hammer (23), is disclosed. The high energy permanent magnet (13) is centrally mounted on a ferromagnetic base plate (11) having a plurality of outwardly extending arms (41). A coil/post combination (15,17) is mounted on each arm (41). The coil/post combinations (15,17) are surrounded by an apertured spacer ring (19) formed on a nonmagnetic material. The hammers (23) are formed by the inwardly extending arms of a print hammer disc (21) mounted on the spacer ring (19) such that a hammer (23) is aligned with each coil/post combination (15,17). The tips of the hammers overly a stepped pole (25) mounted on the outer end of the high energy permanent magnet (13). When the coils (15) are deenergized, the magnetic flux produced by the permanent magnet (13) stresses the hammers (23) by pulling them against the tips of their related posts (17).

Abstract: An actuating mechanism includes a magnetic circuit formed by a permanent magnet (43), a flux plate (45), a return plate (47), a post (49), and a long release coil (51). The outer end of the release coil (51) terminates slightly short of the tip of the post. Further, the post (49), long coil (51), flux plate (45) and return plate (47) are sized and positioned such that the tip of the post (49) lies coplanar with the outer surface of the return plate (47) and such that the end of the return plate (47) terminates just short of the release coil (51). The head (59) of a hammer (53) is positioned to be attracted to the post tip by the magnetic flux created by the permanent magnet (43). The permanent magnet attraction force bends the head (59) of the hammer (53) across the small gap resulting in the hammer (53) being cocked. When the long release coil (51 ) is energized, it produces a magnetic field that counteracts the permanent magnet attraction force, releasing the cocked hammer.

Abstract: A vibration isolating coupling ideally suited for coupling the bobbin (31) of a linear actuator (23) to a flexure supported printer carriage (11) is disclosed. The two main sources of vibration in a system that includes a flexure (13, 15) supported carriage coupled to a linear actuator (23) are low-frequency vibration resulting from the pivot arc motion of the flexures (13, 15), and high frequency vibration resulting from the change in bobbin shape occurs as AC energy is applied to the bobbin (31). The first source of vibration is reduced by configuring the interface plane between the linear actuator and the flexure supported carriage such that contact occurs at spaced apart points located on either side of the flexure movement plane. Preferably, four contact points equally spaced from the flexure motion plane are used. The region between the contact points and the flexure motion plane is cut out so that no contact occurs in and on either side of the flexure motion plane.

Abstract: A hammer module (11) for a dot matrix line printer including a cantilever mounted multi-arm hammer (23) formed from a single piece of resilient ferromagnetic material is disclosed. The multi-arm hammer (23) comprises a plurality of hammer arms (25) each including a thin spring region (51) and a thick head region (53) that lie in a plane that forms a slight angle with the plane of the base (27) of the multi-arm hammer (23). Each module also includes magnetic circuits for each hammer arm (25) formed by a common permanent magnet (13), a post (19), an arm (29) of a flux plate (15) and an arm (33) of a return plate (17). The post (19) is mounted on the tip of the flux plate arm (29). The flux plate and return plate arms (29 and 33) lie in parallel planes located on opposite sides (poles) of the permanent magnet (13).

Abstract: A linear motor shuttling system for shuttling the print head (11) of a dot matrix line printer is disclosed. The print head (11) is supported by a pair of flexures (13, 15) such that the head is free to move back and forth along a print line. One end of the flexure supported print head is attached to the coil (31) of a voice coil linear motor (23). The linear motor (23) is also flexure (27, 29) supported. The linear motor (23) is positioned such that the axis of coil movement is co-axial with the axis of movement of the print head (11). Further, the resonant vibration frequency of the combination of the linear motor and the linear motor flexure support is tuned to the resonant vibration frequency of the combination of the print head and the print head flexure support.

Abstract: Bi-directional, constant velocity, carriage shuttling mechanisms particularly suitable for use in dot matrix line printers, are disclosed. The carriage shuttling mechanisms comprise a pair of identically sized bi-lobed, second order elliptical gears (41, 45) connected together in a 90.degree. phase relationship either directly or via a belt. One of the bi-lobed gears is rotated at a constant velocity and the other is eccentrically linked (47) to the carriage (11) to be bi-directionally shuttled at a constant velocity.

Abstract: A print hammer actuator system for a dot matrix line printer comprising a plurality of coils greater than the number of dot imprinting hammers to be actuated by the coils is disclosed. The coils (C1, C2 . . . C80 or 61, 62, 63 . . . 69) are mounted side-by-side in a fixed position; and, the hammers (H1, H2 . . . H40 or 51, 53, 55, 57) are oscillated back and forth in the regions where magnetic fields are produced by energized coils. As the hammers are oscillated, the coils are selectively energized and de-energized to actuate the hammers. Energizing the coils attracts the hammers toward the coils, against the spring force of the hammers. De-energizing the coils releases the hammers, whereby the stored spring energy creates a dot. Depending upon the position of the hammers, either one or two coils are energized and de-energized to actuate a single hammer.

Abstract: A rotary/linear shuttle mechanism, particularly suitable for use in shuttling the carriage of a dot matrix line printer, is disclosed. The rotary/linear shuttle mechanism includes a pair of stiff, thin bands--one long and one short (35,41). The bands are formed of an inelastic material, such as steel or titanium. Each band has a centrally located loop (formed by a necked down portion of the band passing through a window in the band), and a pair of outwardly extending arms. The loop (67) in the long band (35) is wrapped around, and affixed to a motor pulley (33). The pulley is mounted on the shaft of a low inertia motor (31), such as a moving coil type DC brush motor. The ends of the arms (66,68) of the long band (35) are affixed to the periphery of a large diameter pulley (37). The large diameter pulley is mounted on a shaft (75) that also supports a small diameter pulley (39).

Abstract: A dot printing mechanism for dot matrix line printers comprising a plurality of hammer modules (45) mounted on a carriage (43) that is shuttled back and forth along a print line is disclosed. Each module includes a plurality of cantilevered print hammers (47) formed of a resilient ferromagnetic material. Each of the print hammers includes an anvil (49) on one face of its cantilevered outer end, adapted to print a dot when the associated hammer is actuated. The modules (45) are mounted on opposite sides of the print line and positioned such that the hammers (47) of juxtaposed modules are interleaved and such that the anvils (49) all lie along the print line. Further, each hammer forms part of a magnetic circuit that includes a permanent magnet (51), a post (57) and ferromagnetic paths between the permanent magnet and post. The post supports a coil (59) and is positioned near the cantilevered end of the print hammer (47), on the side opposite of the anvil (49).