Abstract: A disposable pen-reservoir unit for a paper-chart recording instrument, includes a reservoir chamber surrounding the pen drive fork, with center of gravity of the unit located between the fork and writing tip, and the center of gravity below the line of bearing of the pen unit knife edge on the drive fork. Pen cross section is minimized. Reservoir diameter to depth ratio is minimized to keep the mass of the reservoir and ink supplies as close to the pen pivot axis as possible, to minimize inertia and dynamic over-shoot of the writing system. A closed system allows maximum utilization of ink supply with virtually no loss to evaporation.

Abstract: A chart recorder has a drawer containing a supply of chart paper fed to the chart marking area, and an accumulation of marked chart paper received from the chart marking area. A flexible curved guide is connected to the drawer and to a permanent fixed guide and assumes different configurations when the drawer is moved from the chart accumulating position during a recording mode of operation, to a chart loading position when the drawer is moved to position for removing an accumulation of marked chart paper and installing and threading a new supply of chart paper during the chart threading mode. The configuration of the flexible guide aids in threading paper onto a drive roll during the threading mode, and aids in guiding the paper around obstructions and onto the roll during the recording mode.