US 4,047,085 A · Method and apparatus for controlling a web handling device

Abstract

A circuit for controlling a graphic display printer wherein a paper sheet is wrapped about a rotating drum and maintained in place thereon by a vacuum. The length of the paper sheet is slightly longer than the circumference of the drum and thus defines a tangentially projecting flap. A sensor detects passage of the flap and in response to the initial detection, a counter is started having a cycle corresponding to one rotation of the drum. Selected states of the counter are digitally compared to the output of the flap sensor. After the rotational position of the flap has been determined twice for each of three successive drum revolutions, a paper validation signal is generated indicating that the paper is properly wrapped about and rotating with the drum. In response to the validation signal, printing is started. The circuit also includes means for preventing writing on the flap by correctly locating the copy with respect to top of paper and for maintaining a straight, first, print line irrespective of the characteristics of the paper edge or its positional sensing variations.

Claims19

Dependent claims

A control circuit for sensing the condition of a web wrapped about a rotating drum displaying an outer surface wherein the web carries a positional indicator comprising:

means fixed with respect to the axis of rotation of the drum for sensing the presence of said web indicator for each passage across a predetermined location and for generating an indicator signal in response thereto,
means responsive to a selected one of said indicator signals for initiating the generation of a first series of positional signals, each signal corresponding to a subsequent predetermined rotational position of the indicator carried by the web;
and
first means for comparing the concurrance of at least one of said indicator signals with at least one of said positional signals so as to ascertain whether said web indicator has rotated a predetermined amount since said selected indicator signal.

1 more element

A graphic printer control circuit for sensing the condition of a sheet of paper wrapped about a rotating cylindrical drum, the paper defining an exposed flap, the plane of said flap being substantially tangent to the surface of the drum, comprising:

means fixed with respect to the axis of the drum for sensing the presence of the paper flap and generating a distinct signal for each passage thereby,
a counter and means responsive to a selected one of said flap sensing signals for enabling said counter in response thereto,
means responsive to the movement of the drum for generating a plurality of clocking signals, said clocking signals serving to advance the counter to successive states thereof,
first means for comparing the occurrence of at least one of said flap signals with a preselected state of said counter so as to ascertain whether said paper has rotated with the drum a predetermined amount since said selected flap signal, and
means for resetting said counter in the absence of a comparison.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling a web handling device

Life of this patent

Method and apparatus for controlling a web handling device

Life of this patent

Abstract

Claims19