Large format printers typically impose upper limits on media width, e.g., 400 to 2000 millimeters (mm), but media lengths tend to be constrained primarily by the amount of media on a roll that feeds the media to the printer. Running out of media part way through a print job can incur costs in wasted media, wasted ink (most large format printers are inkjet or piezo printers), and time. To avoid this waste, some printer manufacturers provide for indications of remaining media length.
Manufacturers of roll media typically label the roll with its dimensions, e.g., 15 meters by 1400 mm. Some printers allow a user to enter a value for roll length into the printer when the roll is installed. During use, the length of media consumed is tracked and subtracted from the nominal roll length to yield an estimate of remaining media length.
There are several problems with this method of tracking remaining media length. First, the nominal lengths are often approximate. Second, some of the length is used to engage the feed mechanism of the printer. Third, the method does not apply well to partially used rolls. In this last case, rolls may be swapped in and out, e.g., to change media types. In theory, a user could note the remaining media length of a roll as it is swapped out and then enter that value into the printer when the roll is swapped in. In practice, the person swapping out a roll may neglect to record the tracked remaining media length. Hence, there is still a need for an approach to determining remaining media length that does not rely on the nominal lengths assigned to a roll of media.
Herein, related art is described to facilitate understanding of the invention. Related art labeled “prior art” is admitted prior art; related art not labeled “prior art” is not admitted prior art.
The figures depict implementations/embodiments of the invention and not the invention itself.
The present invention provides for in-use determinations of roll media dimensions. Media thickness is determined as a function of the relationship between media advance (travel distance) and feed roll rotation. Remaining media length can be determined from the media thickness and a core radius for the roll. This method works despite deviations from nominal roll lengths, variations due to media installation, and swapping of incompletely used media in and out of a printer or other media-handling device.
A media feed system API for a large-format inkjet printer is shown in
Drive subsystem 13 includes a drive roller 31, a nip roller 32, a drive motor 33, including a drive shaft 35, and a drive encoder 39 directly attached to drive roller 32. Drive shaft 35 engages drive roller 31, so that drive roller 31 rotates counterclockwise (given the view of
As drive motor 33 rotates drive roller 31 counter-clockwise (as represented in
Controller 15 implements a method ME1 in accordance with an embodiment of the invention. Immediately below, method ME1 is described conceptually with reference to the flow chart of
With reference to
At method segment M2, media thickness is determined as a function of a correlation between media advance and roll rotation. At subsegment M2A, controller 15 tracks media advance and roll rotation to determine their correlation. For example, feed encoder 29 can be monitored by controller 15 to determine the start and stop times of a single full (360°) rotation of media roll 21. Concurrently, controller 15 can monitor drive encoder 29 to determine the length of media advance during that single full rotation. The media advance during a single full rotation of media roll 21 corresponds to the average (of the diminishing) circumference of roll 21 during the rotation.
In alternative embodiments employing variation of subsegment M2A, media feed systems use intervals smaller or larger than one revolution to track the relationship between media length and roll orientation. Fractional rotations can be used to achieve more rapid estimates of roll radius, while multi-rotational intervals can be used to calculate media thickness. Results from different approaches can be compared to detect anomalous results. At subsegment M2B, the average outer radius of media roll 21 during that rotation can be computed from the average circumference.
At subsegment M2C, controller 15 tracks the outer radius of roll 21 to determine media thickness. For example, the media advance during a second full rotational cycle of media role 21 can be used to calculate a second outer roll radius R1. The first (R0) and second (R1) outer roll radii can be compared. The second is smaller and the difference corresponds to the media thickness. Controller 15 provides for variations of subsegment M2C in which media thickness is determined using fractional or multiple rotations (as opposed to only single full rotations) or plural approaches at once.
At method segment M3, remaining media length is determined as a function of roll core radius, media thickness, and media roll radius. At subsegment M3A, the number (numerosity) of media layers on media roll 21 is determined, e.g., by dividing the difference between the outer radius (determined at subsegment M2B) and the core radius (determined at method segment M1) by the media thickness (determined at subsegment M2C). The numerosity determination may be explicit or implicit in the identification of the layers involved in the length calculations. For each of these layers, an average radius can be determined, e.g., as an integer number times the media thickness added to the core radius or subtracted from the outer roll radius.
At subsegment M3B, the layer lengths (roughly corresponding to circumferences) are calculated using the formula 2πR. At method segment M3B, these layer lengths can be added to provide a measure of remaining media length. This value can be adjusted by the length of media between roll 21 and drive roller 41 to provide a more accurate measure of remaining media length if desired.
A more specific description of an implementation of method ME1 is described below with reference to the flow chart of
R
0
=X*N/(E0−Es)*2π
At method segment S2, the next media thickness calculation point is determined. This is the encoder count E1 that will be achieved after one revolution of media roll 21. This count can be calculated as:
E
1
=E
0
+N.
At method segment S3, media 27 is advanced until the next media calculation point is reached. This point is one media roll revolution past the previous point. At method segment S4, the current roll radius is determined. In the first iteration, the current roll radius is R1; for the ith iteration of method ME1, the current roll radius is Ri.
Method segment S4 involves subsegment S41 of determining the media advance during the last revolution of media roll 21. This media advance is the ith circumference of media roll 21. At subsegment S42, dividing by 2π, yields the ith radius Ri for media roll 21. In practice, the current roll radius can be calculated after every single movement so that we have the last filtered values at S1 and S4. For comparison purposes and to detect anomalous radius determinations, a filtered roll radius can be determined at subsegment S43 according to the following formula.
R
i
=X*s*z/2π+Ri−1*(1−z), where 0<z<1.
The filtered value can be used in place of the unfiltered value, especially where the noise in the measurements is large. The value of z can be determined by trial and error, with 0.3 being typical.
At method segment S5, media thickness is calculated as Ri−Ri−1.
Thus, by tracking encoders 29 and 39, the relationship between media travel and roll rotation can be tracked. This relationship can be used to determine, at any given point during operation, the outer radius of media roll 21.
The media roll radius diminishes as media 27 is drawn from media roll 21. The rate of this change (as a function of media advance) indicates the thickness of media 27. If the core radius of roll 21 is known, the number of media layers between core radius Rc and outer radius Ri can be determined, as can an average radius for each layer. The average radius for each layer can be used to determine a media length for each layer. The sum of the lengths of the media layers corresponds to the length of media remaining on roll 21. This length can be adjusted, e.g., by the distance between media roll 21 and drive roller 31, to provide a precise measure for remaining media length.
At method segment S6, remaining media length is calculated according to the following formula.
MediaLength=ΣR=R
where RC is the roll core radius, and MT is the media thickness.
Media core radius RC can be determined in a variety of ways, e.g., a manual measurement by the user. In the illustrated embodiments, media length advance and roll rotation are tracked using motor position encoders. However, the invention provides for alternatives to these approaches. For example, an optical transmitter and sensor can be applied directly to the media to detect movement. Also, an encoder can detect roll orientation directly, rather than through detection of a motor shaft orientation. This last approach can be used, for example, where a spring is used instead of a feed motor to tension media. These and other variations upon and modifications to the illustrated embodiment are provided for by the present invention, the scope of which is defined by the following claims.
This Utility Patent Application is based on and claims the benefit of U.S. Provisional Application No. 61/054,188, filed on May 19, 2008 the contents of which are hereby incorporated by reference in their entirety.
Number | Date | Country | |
---|---|---|---|
61054188 | May 2008 | US |