An elongated sheet transport and guidance system including a drive roller mounted for rotation on a frame and adapted to engage and frictionally drive the sheet along its longitudinal axis and a pinch roller engaging the drive roller and mounted for rotation on an axis parallel thereto, the pinch and drive rollers being arranged to straddle and exert a pressure on that portion of the sheet passing therebetween. Also included in the system is a first means for inducing a first pressure level between the pinch and drive rollers in a region adjacent one longitudinal edge of the traveling sheet and a second means for inducing a second pressure level between the pinch and drive rollers in a region adjacent the opposite longitudinal edge of the sheet. In response to the output of a sensing means that senses lateral displacement of the traveling sheet, a control mechanism varies the difference between the first and second pressure levels. The control mechanism causes the first pressure level to increase relative to the second pressure level in response to lateral displacement of the sheet in one sense and causes the second pressure level to increase relative to the first pressure level in response to lateral displacement of the sheet in the opposite sense.
Apparatus for incremental feeding of a paper web from an arborless supply roll over a transverse dancer bar resiliently supported at each end with the respective supports having different and variable spring rates to effect uneven pulling of the web during feeding and thus jogging of the supply roll. This action maintains a tight wrap of the outer layers of web on the roll and aids in maintaining web alignment during feeding.
An arrangement for the lateral positioning of a recording medium (100) in a printer or photocopier comprises a scanning arrangement (S) for establishing the ACTUAL position of the recording medium and a motor-drivable roll arrangement consisting of a counter-roll (201) and a pressure roll (205) which can be pivoted onto and away from the counter-roll (201), between which rolls the recording medium is guided. Furthermore, an apparatus (E) is provided for the controllable adjusting of the pressing force at the feed roll (205) on the counter-roll (201) along its roll length, and a control arrangement (P) which registers the ACTUAL position of the recording medium (100) via the scanning arrangement (S) and adjusts the pressing force of the feed roll (205) via the said apparatus (E) as a function of a predeterminable REFERENCE position. The arrangement is used preferably in the fuser station of an electro-photographic printer for the controllable lateral positioning of the recording medium (100).
A method for positioning a sensor for a web movement control device, in which the sensor executes an edge search process, in order to achieve a rapid and exact positioning of sensors by specifying a relatively early stop threshold for the sensor movement, after-running of the sensor is detected in that after the after-running position is detected by the sensor signal the difference between the preset stop value and the stop value actually reached is formed and specified as the new stop value, after which the edge search process is repeated with the corrected stop value.
Apparatus for controlling the alignment, in a lateral (cross-track) direction, of a web moving along a path to minimize lateral deviation between successive discrete areas of such web. The apparatus includes a steering roller for supporting the web for movement along such path. The steering roller is rotatable about an axis perpendicular to the plane of the span of the web approaching the steering roller. As the web moves along the path, the lateral position of a marginal edge of the web relative to a reference plane is sensed. When such lateral edge position is at either of two spaced predetermined locations relative to such reference plane, signals indicative of the presence of such edge at such locations are produced. The steering roller, in response to such signals, is rotated about the axis perpendicular to the plane of the span of the web approaching the steering roller to steer the web and thereby cause the lateral position of the edge of the web to progress from the predetermined location at which the edge was sensed to the other predetermined location as the web moves along its path.
