Abstract: A servo system for compensating for environmental forces acting on, for example, a disk drive. A circuit is provided for causing an electrical current to flow in the voice coil controlling a read/write head; the head is caused to seek a predetermined track; and a device adjusts the current delivered to the voice coil so that the force generated thereby at least approximately balances environmental forces acting upon the voice coil so that the read/write head does not move by more than a predetermined amount from said predetermined track.

Abstract: A predetermined window height at least three times the height of the normal printed characters can be printed in a single horizontal sweep of the printhead across the page. A page of character oriented data is first sorted vertically; the data is then sequentially processed into a "print window" of horizontally sorted characters until a character is reached that will not fit within the current print window. The symbolic data in the print window is converted into bit mapped image data only slightly in advance of the current printhead position. The average throughout is increased by permitting the velocity of the printhead to vary as a function of the complexity of the image formation process. For a thermal process, this is accompanied by an appropriate adjustment in the current passing through the activated printhead electrodes. The vertical positioning of the pixels within the print window is varied to better distribute head wear.

Abstract: An analog servo system suitable for accurately controlling the carriage speed of a high speed printer over a relatively wide range. The system includes an analog tachometer with circuit means which enables the tachometer to operate in either a high gain mode (used at normal or lower carriage speeds) or a low gain mode (used at higher carriage speeds). The tachometer gain mode (or "electronic gear") is controlled by an external command signal such as a single bit supplied by the control microprocessor of the printer. The state of the command signal controls a time constant in the tachometer circuit means which determines the gain mode.

Abstract: A nominal carriage velocity profile is initiated during each carriage positioning interval which enables the carriage to be decelerated and stopped at the proper position for printing. However, the carriage velocity profile can be modified during the positioning interval to avoid decelerating if printing can occur on the fly; i.e., if the print element (and ribbon) are able to complete any necessary positioning by the time the carriage arrives at its printing position. In accordance with the preferred embodiment, the slave microprocessor produces a READY signal in advance of the print wheel arriving at its destination orientation. The READY signal indicates that both the print wheel and ribbon will reach their destinations and be ready for printing within a fixed time interval; e.g., three milliseconds. In response to the READY signal, the master microprocessor inhibits further adjustments in the carriage speed and permits the carriage to assume a "fly" mode.

Abstract: A paper feeder is described, of the type which includes a cylindrical platen (16) and multiple pressure rollers (18,20) that press paper between themselves and the platen, which is of simple and inexpensive construction. The paper feeder includes a shaft (34) of square cross-section, a group of leaf springs (30) with inner ends mounted on the shaft and outer ends lying under the platen, and a group of roller assemblies (38) mounted on the outer ends of the leaf springs. The inner end of each leaf spring has tabs (40,42) on opposite sides, which are bent down at substantially right angles and which have square slots (46) for closely receiving the square shaft. The group of perhaps five leaf springs are mounted on the shaft with their tabs abutting one another, and with grip rings on opposite ends of the shaft to hold the springs in place.

Abstract: A sheet handling path extending from an entrance location to an exit location is provided by a small diameter rotatable roller and several parallel transversely spaced flexible belts. At the exit location, several deflector arms mounted on an actuator shaft initially deflect the leading portion of an exiting sheet towards the forward wall of an underlying receiving tray. An exit roller may also be provided at the exit location. After the leading edge of a sheet has reached the forward wall and the sheet has started to form a buckle, the deflector arms are rotated to a remote position permitting the sheet to be translated rearwardly by friction between the overlying flexible belts and the sheet until a trailing edge of the sheet springs clear of the belts and settles under its own weight into the receiving tray.

Abstract: An improved selector mechanism is described for use in a sheet feeder that has a plurality of bins and a feedout roller shaft associated with each bin, for selecting which of the feedout rollers to rotate, the selection being made by determining the angles at which rotation of a drive member is reversed. Each selector includes a cam assembly connected to the feedout roller shaft by a one-way clutch, and a driven driver which is freely rotatable on the shaft. The driver carries a pivotally mounted arm. The cam assembly has a deflector which moves the arm to a deflected position when the arm rotates in a nonfeed direction, and also carries an arm engager which engages the deflected arm when the driver reverses rotation after the arm is deflected, so the driver rotates the cam and, therefore, the feedout roller shaft in a feed direction. The cam also carries an undeflector which moves the arm back to its undeflected position if the driver rotates too far beyond the point of its encounter with the deflector.

Abstract: Apparatus to support an inked ribbon cartridge and/or daisywheel motor and assembly. The cartridge has a paper shield integral therewith that is notched to expose the ribbon to the paper, whereby a daisywheel petal carrying a type font may be struck by a print hammer to type a character. The cartridge has a detent to lock the daisywheel motor support in a fixed position. The motor support may be adjusted in position relative to the platen.

Abstract: A disc is provided which centers itself on motor shafts that vary somewhat in diameter. The disc is formed of a single sheet of material with a central hole for receiving the shaft and with a group of fingers projecting slightly into the hole to engage a shaft. The fingers are formed by pairs of slots that extend from the edge of the central hole and radially outward to form fingers of considerable length which can be bent out of the plane of the disc to engage shafts of varying size. The radially inner tips of the fingers lie precisely on an imaginary circle which is slightly smaller than the minimum diameter of a shaft, and the fingers deflect uniformly to hold the shaft centered on the axis of the disc.

Abstract: A printer having a print wheel rotatable on a carriage. The carriage is guided for movement parallel to a platen. The printer may print at either a fast speed for draft quality output, or a slower speed for highest quality output. The lesser quality of output produced at the fast speed is more than adequate for draft documents.

Abstract: In a printer having a sheet feeder associated therewith, means are provided for feeding only the top sheet in a stack of sheets to the printer platen. A feed roller is positioned in contact with the top sheet and is energized a plurality of times prior to the paper clearing two corner separators associated with the sheet feeder, the acceleration and stopping of the feed roller having a tendency to jerk the first sheet of paper out of the stack while leaving the subsequent sheets in the stack. Although several methods can be utilized to energize the feed roller, control signals for energizing the feed roller are preferably generated by the printer microprocessor.

Abstract: A cartridge which contains two spools. The supply spool has wound about it a printing ribbon and the take-up spool being used for wrapping the used ribbon. The cartridge has a ribbon exit at one location and a ribbon entry at a remote location to define a path for the ribbon to pass therealong. Two drive gears are engaged with each other and a pressure roller. The drive gears are located and their lower portions are configured to engage the respective drive shafts of various printers. When the first drive gear is driven by a printer, the second gear, which includes the drive wheel, rotates in the opposite direction of the drive shaft of the printer. When the second gear is driven, the integral drive wheel rotates in the same direction as the drive shaft of the printer. The pressure roller is provided with internal flexible spokes, or springs, and provides a self-adjusting bias against the drive wheel to drive the ribbon and provides an extremely efficient pinching action.

Abstract: A daisywheel printer having interchangeable modules for different respective communications with alternate corresponding plug-in connections.

Abstract: Apparatus used in conjunction with printer document feed mechanisms for allowing the dynamic adjustment of the feed mechanisms while paper feed is occurring, thus adjusting paper tension. The apparatus has a linear adjustment capability over its total range. In particular, adjusting levers are attached to the feed mechanism support shaft, pinions being attached to each end of the shaft. The pinion teeth mesh with the teeth of racks attached to each side plate of the feed mechanism. As the adjusting levers are moved, the support shaft and pinions rotate. The rotation of the pinion meshing with the rack causes the support shaft (and feed mechanism) to move, changing the distance between the feed mechanism and the printer platen. This distance, and paper tension, vary linearly with the angular position of the levers. The paper tension can be adjusted while the feed mechanism is operative.

Abstract: A sheet feeder for an impact daisywheel type printer is interconnected with an existing system by reconnecting the ASCII type data cable to the sheet feeder. The internal logic of the sheet feeder is cabled to the printer and provides for all necessary automatic control. The sheet feeder also includes a mechanical bail control which opens the bail to allow for automatic feeding of the paper around the platen.