Digital printing method and an apparatus therefor

A digital printing method using a digital printer by which images each for one page are consecutively printed on a web of paper for rotary press fed to travel forwards, and in which after printing is suspended temporarily en route, printing is reinitiated on the web of paper fed again to travel forwards, characterized in that it comprises the steps of:

• printing the images and timing marks each for the image with the digital printer while the web of paper is being fed to travel forwards from a paper feed unit to a paper takeup unit with a pair of paper feed roll units which are positioned upstream and downstream, respectively, of the digital printer in a direction of forward feed of the web of paper and which are made able to feed the web of paper to travel both forwards and backwards;
• in reinitiation of printing after printing is temporarily suspended en route, feeding the web of paper to travel backwards so that a series of images and timing marks printed thereon before printing is temporarily suspended moves towards upstream of the digital printer and thereafter feeding the web of paper to travel forwards again, and counting by a mark sensor, upstream of the digital counter, the number of such timing marks moving in each of the backward feed and forward re-feed of the web of paper, respectively;
• when the number of counts of the timing marks counted in the forward re-feed coincides with the number of counts of the timing marks counted in the backward feed, reinitiating to print consecutive images from a position following an image last printed before printing is temporarily suspended;
• and
• rendering said paper feed unit able to feed the web of paper to travel exclusively forwards while it is being braked,
• wherein when the web of paper is fed to travel backwards as aforementioned, the web of paper upstream of said upstream side paper feed roll unit is brought back to and stored in a buffer unit having a paper path whose length is made variable.