US 4,714,340 A · Method and apparatus for inspecting high speed converted web

Abstract

Printed webs leaving a printing press at speeds above 500 feet per minute are inspected with precision across the full width of the web by a stroboscope method and apparatus. Each repetitive image or design imprinted on the high speed web is rendered stationary relative to the eyes of a viewer at a web inspection station by bright short flashes of light emitted by an elongated xenon flash tube or tubes spanning the web transversely of its path of movement. Filtered light flashes are triggered by an improved strobe circuit which is synchronized with the press at all times and permits an inspector to produce from one to six equally spaced images per press cylinder revolution. Additionally, the system can be used in either an image lock mode for side-by-side comparison with a standard or in a controlled pan or scroll mode to allow optimal inspection of entire impression sequences. Also, when desirable, both sides of the web can be inspected by utilizing a second flash tube configuration located behind the web.

Claims19

Dependent claims

A method of inspecting a high speed printed web having spaced repetitive impressions printed thereon, comprising the steps of:

translating said web past a flash tube assembly including at least one flash tube adapted to be stroboscopically excited;
generating trigger pulses which in a first mode of operation are synchronized at a frequency determined by the movement of the web, and in a second mode of operation continue to be synchronized with the web but are periodically advanced in a controlled manner;
exciting said at least one flash tube with the trigger pulses to produce light flashes;
and
directing said light flashes to one surface of the web whereby a stroboscopic effect is produced, such that in said first mode of operation a virtually stationary or locked image of the impression on the web is produced and in said second mode of operation a panned or scrolled image of the impression on the web is produced which is incrementally advanced but which remains synchronized to the web between said advancements.

2 more elements

Apparatus for visually inspecting a high speed printed web being delivered from a printing press having an impression cylinder provided on its outer surface with selectively spaced impression elements, comprising;

at least one linear flash tube extending transversely across one surface of the printed web undergoing inspection;
means for directing light from said flash tube to said one surface;
means for exciting said flash tube upon the application of triggering pulses;
means coupled to said impression cylinder for generating a first train of pulse signals;
means for generating a second train of pulse signals of at least one frequency;
means responsive to said first and second train of pulses for generating a train of trigger pulses wherein in a first mode one trigger pulse is generated for each occurrence of a predetermined total of pulses from said first train of pulse signals, and in a second mode one trigger pulse is generated for each occurence of the same predetermined total of pulses from said first and second train of pulse signals;
and
means for conditioning and coupling said trigger pulses to said means for exciting said flash tube;
wherein said first mode of operation stroboscopically produces a virtually stationary image of the impressions printed on the web and said second mode of operation stroboscopically produces a visually perceptible moving image of the impressions printed on the web in a first controlled rate of movement to provide panning or scrolling of said impressions.

6 more elements

Dependencies are inferred from the claim text.

Method and apparatus for inspecting high speed converted web

Life of this patent

Method and apparatus for inspecting high speed converted web

Life of this patent

Abstract

Claims19