Typewriting machines – Sheet or web
Reexamination Certificate
2000-06-26
2001-11-20
Hilten, John S. (Department: 2854)
Typewriting machines
Sheet or web
C400S582000, C101S484000
Reexamination Certificate
active
06318916
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a method and to an apparatus for the transport of a band-shaped recording medium having a marginal perforation in an electrographic printer, in particular.
Web-shaped, margin-perforated paper is mainly employed in the electrographic high-performance printer field with printing outputs of more than 40 pages per minute. The recording media are usually made of paper and have lateral holes at their longitudinal edges for transport and for monitoring the position of the paper. It is thereby driven by sprocket tractors that engage into the lateral transport holes. These recording media often also have transverse perforations along which the individual pages are separated from one another, or folds with the aid of which they can be folded together or stacked.
The feed of the perforated paper usually occurs in a specific grid corresponding to the hole spacings. Conventional paper webs have hole spacings of ½ inch. The feed can then be accomplished in accordance with 3 steps per hole spacing in a ⅙ inch grid or in accordance with 4 steps per hole spacing in a ⅛ inch grid. The paper web is then not moved continuously but step-by-step by a multiple of the grid spacing.
FIG. 1
shows this type of paper web with a margin perforation. The holes
21
in the margin region of the paper web
5
have a diameter of approx. ⅙ inch and recur at regular intervals of a=½ inch. This hole spacing a is the grid width of the hole spacings. When this kind of paper is ready-made for pages whose length can be divided by ½ inch, the fold, or respectively, the transverse perforation, that defines the beginning of a page is located precisely in the middle between two margin perforations, as represented by line
22
, for example. Given page lengths that can only be divided by ⅙ inch, but not by ½ inch, the fold, or respectively, the transverse perforation, can be located on one of the grid lines
23
. The fold or transverse perforation is then located in a different place relative to the perforations at the beginning of each page.
FIG. 2
illustrates essential components of printers in accordance with the prior art, which are known under the trademark Océ Pagestream®, for example. A tractor drive
24
is provided in these printers. It comprises a step motor
26
, which drives a tractor wheel
25
, whose spindles engage in the margin perforations
21
of the paper web
5
. The step motor
26
is driven by an electronic control unit
27
, which receives clock signals
30
from an image generating unit, on the one hand, and receives clock signals about the current speed of the step motor from a sensor
28
, on the other hand. These signals are formed by sampling a timing disk
29
that is connected to the drive shaft of the step motor. The signals of the timing disk correspond to an advance of ⅙ inch; that is, they correspond exactly to the transport grid. The control unit
27
converts the image generation signals
30
in a fixed frequency ratio into drive signals
31
for the step motor
26
, which effectuate an advance of ⅙ inch on the paper web, respectively. When the printer is turned on, the drive is initialized. For this purpose, the tractor wheel
25
is aligned to the ⅙ inch transport grid. The control unit
27
generates drive signals in steps of {fraction (1/240)} inch until it receives a signal from the sensor
28
indicating that a ⅙ inch marker of the timing disk
29
has been detected at the sensor
28
.
Once the drive
24
has been aligned to the transport grid, the paper web
5
can be advanced in the ⅙ inch grid such that, with each ⅙ inch step, a reference point, for instance the fold
22
, advances exactly from one ⅙ inch increment marker to the next ⅙ inch increment marker on the rule
65
that is fixed to the housing. In the course of initialization, a marker of the paper web
5
, for instance the transverse perforation or the fold, is thus positioned at the corresponding page marker (10″, 11″, 12″ or 13″) of the rule
65
in ⅙ inch increments. The following pages are then automatically exactly positioned on the basis of the restricted guidance by the sprocket tractor.
Margin perforation is employed particularly in the processing of preprinted paper. In this paper, the information that is to be subsequently added, for instance data that are printed into a preprinted form, should be situated optimally precisely in predetermined locations on the blank.
The perforated paper is usually fed in a defined grid corresponding to the hole spacings, for instance in a ½ inch grid or in a ⅙ inch grid. The paper web is moved incrementally by a multiple of the grid spacing.
There is frequently also the demand in the high-performance printing field to be able to employ continuous-form paper that does not comprise such margin perforations in printers for continuous-form paper. Both economic as well as ecological considerations contribute to this demand. Margin-perforated paper is more expensive than paper without margin perforations, since the margin perforations need to be punched in an additional procedure in the course of paper production. An additional processing step is likewise required when printing margin perforated paper for removing the margin strips from the printed page, whereby the waste that thereby arises must be disposed of.
For example, WO 95/19929 A1 discloses a printer that is suitable for processing continuous-form paper without margin perforation which is fed from a roll or stack.
A first seating edge, which prescribes the lateral position of the paper, as well as stabilization rollers, and under-pressure brake and a roller arrangement with a loop-drawing means are provided in this printer for the exact transport of the paper.
Roll papers both with as well as without margin perforation can be fundamentally processed with such a device via a tractorless friction drive. An advantage of this is that paper with margin perforation can still be processed, even though this perforation is not used for transport and guidance of the paper. Papers having margin perforation are frequently still kept in stock in printing centers or are delivered already preprinted. Therefore, it should still be possible to use perforated roll paper in a device which does not necessarily need the margin perforation for transport purposes.
On the other hand, tractorless friction drives have the problem that the transport precision in the feed direction cannot always be adhered to. For example, slippage between the friction roller and the recording medium can contribute thereto.
DE-A-40 39 389 teaches a tractorless drive with which a margin-perforated recording medium can be transported. The transport is controlled by means of a control mechanism, with target positions of the recording medium being computed at reference points and the actual position of the margin holes being detected using a sensor.
SUMMARY OF THE INVENTION
It is an object of the invention to set forth a method and a device for controlling a tractorless drive in a printer, with which web-shaped recording media both with and without margin perforation can be transported in the feed direction with high precision.
This object is achieved by a method for controlling a tractorless drive in an electrographic printer which prints by page on a band-shaped recording medium and wherein a margin-perforated recording medium is first transported in a start mode in increments of a control grid and is fitted in this process into a second grid forming a transport grid which is larger than the control grid, and which corresponds to a fraction of hole spacing. In a drive control target signals as image generating signals of a first frequency are received which are generated by an image generating unit or are synchronous to signals of the generating unit, actual signals of a second frequency being received by a sensor arrangement that continually scans t
Hilten John S.
Nolan, Jr. Charles H.
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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