Patent Application
20140311367
The present disclosure relates to a system and method for measuring a change in dimension for a sheet of paper due to operations applying indicia to the paper. In particular, the system and method use a ratio of encoder pulses related to respective movement of oppositely facing sides of the sheet of paper in a process path to determine a dimension change, due to operations on one side of the paper, to adjust application of indicia on the other side of the paper.
When applying indicia to both sides of a sheet of paper, it is desirable to maintain a specified registration between indicia on a front side of the sheet and indicia of the back side of the sheet. The registration noted above assumes a particular dimensionality of the sheet. Known systems and methods for applying indicia, such as xerography, dry ink printing, aqueous ink printing, and lithography, to two sides of a sheet of paper involve operations on the first/top side of the sheet, such as applying heat and pressure, or adding liquid, which can change the dimensions, for example length, of the sheet, for example by changing the moisture content of the sheet or stretching the sheet. When the application of indicia to the top sheet changes the dimensions of the sheet, the assumed dimensionality is no longer accurate and subsequently, the indicia applied to the back side can be out of registration with indicia on the front side.
For example, a xerographic machine passes a sheet through a fuser to fix indicia on a front side of a sheet. The fuser applies heat and pressure which can drive moisture out of the sheet, shrinking the sheet and changing the length of the sheet. Thus, the image magnification for the front side is not appropriate for image magnification for a back side of the sheet, and mis-registration occurs between print on the front and back sides of the sheet. It is known to use a manual measurement procedure to measure mis-registration on a sheet of paper. However, the procedure requires an operator to manually measure a test pattern on both sides of a printed sheet, which is time consuming and prone to operator error.
Many factors contribute to the dimensional change, for example an amount of paper shrinkage through the fuser of a xerographic machine. These factors include: paper type, environmental conditions, and machine settings/conditions. In addition to the time and error problems noted above, the manual measurement described above is only a snapshot in time and needs to be performed again whenever there is a change in any of these factors.
According to aspects illustrated herein, there is provided an apparatus for compensating application of indicia to a sheet of paper according to a change in dimension for the sheet, including: a processor; a measuring system including a plurality of rollers and an encoder connected to a first roller from the plurality of rollers and configured to generate a pulse for each rotation of the first roller by a specified angle; and an indicia system. The apparatus is arranged to perform the following sequence: displace, using the plurality of rollers, a first plurality of sheets along a defined portion of a process path for the apparatus, each sheet having respective first and second sides; generate, using the encoder, a first number of pulses associated with displacement of a first sheet, from the first plurality of sheets, along the defined portion; apply, using the indicia system, first indicia to the respective first side of the first sheet; displace, using the plurality of rollers, the first sheet along the defined portion of the process path; generate, using the encoder, a second number of pulses associated with displacement of the first sheet along the defined portion; calculate, using the processor, a ratio including the first and second numbers and apply, using the indicia system: second indicia to the respective second side of the first sheet; or third indicia to the respective first side of a second sheet from the first plurality of sheets; or fourth indicia to the respective second side of the second sheet. The apparatus is arranged to adjust, using the processor, application of the second, third, or fourth indicia according to the ratio.
According to aspects illustrated herein, there is provided a computer-based method for compensating application of indicia to a sheet according to a change in dimension for the sheet, including: displacing each sheet in a first plurality of sheets through a defined portion of a process path of an apparatus; generating, using an encoder for the apparatus, a first number of encoder pulses associated with displacing a first sheet from the plurality of sheets along the defined portion of the process path; applying first indicia to a first side of the first sheet; displacing the first sheet through the defined portion of the process path of the apparatus; generating, using the encoder, a second number of encoder pulses associated with displacing the first sheet along the defined portion of the process path; calculating, using a processor for the apparatus, a ratio including the first and second numbers; applying second indicia to the respective second side of the sheet or third indicia to the respective first side of a second sheet from the plurality of sheets or fourth indicia to the respective second side of the second sheet; and adjusting, using the processor, application of the second, third, or fourth indicia according to the ratio.
According to aspects illustrated herein, there is provided a printer for compensating application of indicia to a sheet according to a change in dimension for the sheet of paper, including: a processor; a plurality of pairs of rollers, each pair of rollers including a respective first roller and a respective second roller arranged to engage each sheet from a plurality of sheets and displace said each sheet along a process path for the printer in a process direction; first and second edge sensors in the process path and separated from each other by a distance in the process direction; an encoder connected to the respective first rollers in the plurality of pairs of rollers and arranged to generate a pulse for each rotation of the respective first rollers by a specified angle; and an indicia system. Said each sheet includes respective first and second sides and respective first and second edges. The plurality of pairs of rollers is arranged to displace, at a first point in time, a first sheet from the plurality of sheets along the process path in the process direction. The first and second edge sensors are configured to detect the respective first and second edges of the first sheet at first and second times, respectively. The encoder is arranged to generate a first number of pulses for a first duration between the first and second times. The indicia system is arranged to print on the respective first side of the first sheet. The plurality of pairs of rollers is arranged to displace, at a second point in time, the first sheet along the process path in the process direction. The first and second edge sensors are configured to detect the first and second edges of the first sheet at third and fourth times, respectively. The encoder is arranged to generate a second number of pulses for a second duration between the third and fourth times. The processor is configured to calculate a ratio including the first and second number of pulses. The indicia system is arranged to print on the respective second side of the first sheet or the respective first side of a second sheet from the plurality of sheets or the respective second side of the second sheet. The processor is configured to adjust a position of print on the respective second side of the first sheet, the respective first side of the second sheet, or the respective second side of the second sheet according to the ratio.
Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawing in which corresponding reference symbols indicate corresponding parts, in which:
Moreover, although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of these embodiments, some embodiments of methods, devices, and materials are now described.
It should be understood that the use of “or” in the present application is with respect to a “non-exclusive” arrangement, unless stated otherwise. For example, when saying that “item x is A or B,” it is understood that this can mean one of the following: (1) item x is only one or the other of A and B; (2) item x is both A and B. Alternately stated, the word “or” is not used to define an “exclusive or” arrangement. For example, an “exclusive or” arrangement for the statement “item x is A or B” would require that x can be only one of A and B.
Apparatus 100 is arranged to perform the following sequence: move another sheet from the plurality of sheets 118, for example sheet 118B, from feed system 127 to path 110; displace sheet 118B along defined portion 120; apply, using the indicia system, indicia 122C to side S1 of sheet 118B; flip sheet 118B in duplex portion 123; displace sheet 118B along portion 120; apply, using system 116, indicia 122D to side S2 of sheet 118B. Apparatus 100 is arranged to adjust, using processor 102, application of indicia 122B, 122C, or 122D according to ratio 124. It should be understood that sheet 118B can be immediately after sheet 118A in a sequence or can be separated from sheet 118A by one or more other sheets in the sequence.
In an example embodiment, measurement system 104 includes edge sensors 126A and 126B separated from each other in process direction PD by distance D, which defines portion 120. PD is the direction in which each sheet 118 is displaced along the process path. That is, portion 120 is the portion of the process path between sensors 126A and 126B. In an example embodiment, system 104 includes at least one pair of rollers 106A/B. One of rollers 106A/B is arranged to apply pressure to grip each sheet 118 between rollers 106A/B and rotate to displace each sheet 118 along path 110 in direction PD. The other of rollers 106A/B is connected to the encoder. For example in
In an example embodiment, to generate N1: sensor 126A is configured to: detect leading edge E1 of sheet 118A, moving in the process direction, at time T1; sensor 126B is configured to detect trailing edge E2 of sheet 118A at time T2, following T1; and sheet 118A is arranged to rotate roller 106B such that encoder 108 generates N1 pulses between T1 and T2. In an example embodiment, to generate N2: sensor 126A is configured to: detect leading edge E2 of sheet 118A, moving in the process direction, at time T3; sensor 126B is configured to detect trailing edge E2 at time T4, following T3; and sheet 118A is arranged to rotate roller 106B such that encoder 108 generates N2 pulses between T3 and T4.
In an example embodiment, ratio 124 is calculated as N1/N2 or N2/N1. In an example embodiment, to make the ratio calculation more robust, a nominal number of pulses N3 from the encoder for distance D are determined by any means known in the art. Then, the ratio is calculated as: [N1+N3]/[N2+N3] or [N2+N3]/[N1+N3]. In an example embodiment, respective positions of indicia 122B, 122C, or 122D are adjusted along respective length L of sheet 118A or sheet 118B.
Apparatus 100, in particular, system 116, can use any process known in the art for applying indicia to a sheet. Such processes can include, but are not limited to: applying heat to the sheet, applying pressure to the sheet, removing moisture from the sheet, adding moisture to the sheet, and stretching the sheet. Such processes can include, but are not limited to xerography, dry ink printing, aqueous ink printing, and lithography. In an example embodiment, application of indicia 122A 122B, 122C, and 122D includes magnifying indicia 122A, 122B, 122C, and 122D, and adjusting application of indicia 122B, 122C, or 122D according to ratio 124 includes adjusting magnification of indicia 122B, 122C, or 122D according to the ratio. Any magnification known in the art can be used with apparatus 100. For example, magnification can be performed by use of hardware, such as lenses; or, magnification can be performed by operating on digital data, for example, digital data obtained from use of a light emitting diode bar.
Respective ratios 124 can be calculated for each sheet in a plurality of sheets. In an example embodiment, the processor is configured to calculate running average 128 of the respective ratios 124. That is, as ratio 124 is calculated for a particular sheet, the ratio is averaged with the ratios for the previous sheets in the plurality of sheets. Average 128 can be determined for a particular type of sheet material, a particular process, a particular machine or type of machine, or for sheets coming from particular manufacturing or storage situations. Then, when the same type of sheet is used, the respective average 128 can be used as a default setting for adjusting application of indicia.
As key roller 216 begins to lay down indicia on leading edge E1 of a given sheet 118 (e.g., as the leading edge passes the key roller) with side S1 up, a digital signal is generated and includes a timestamp or other information indicating a time of arrival of the leading edge of the sheet. Since the speed at which the image is traveling on photoreceptor belt 218 is known, and since the distance between imaging stations (e.g., registration points) is known, the system knows when to begin writing with each respective imaging station. Additionally, marker module 204 comprises registration entrance sensor 220 that senses sheet position for adjusting a duplex “eject-to-transfer” time. In an example embodiment, sensor 220 is included in system 104, for example, as sensor 126A or 126B. In an example embodiment, system 104 is proximate sensor 220. A sheet 118 is flipped on duplex path 222, for example, such that side S2 is up.
The following provides further detail regarding apparatus 100. In an example embodiment, apparatus 100 is a xerographic machine and pressure and heat are applied to the sheet as part of xerographic operations on side S1. The pressure and heat can drive moisture from sheet 118A, shrinking the sheet, in particular along length L of the sheet. By using ratio 124, indicia 122B, 122C, or 122D can be adjusted to ensure registration between respective indicia on respective sides S1 and S2. That is, ratio 124 provides automatic adjustment of the registration to accommodate a change in the dimensions of a sheet 118, in particular, a decrease in length L.
In an example embodiment, apparatus 100 is an aqueous ink or lithographic machine and the application of indicia 122A 122B, 122C, and 122D involves adding liquid, for example ink, to each sheet 118 as part of the printing or lithographic process. The addition of a liquid, plus possible stretching of each sheet 118, as part of the process of transporting the sheet and applying the liquid, can result in an increase in L. In this case, by using ratio 124, registration of respective indicia on respective sides S1 and S2 for each sheet 118 is ensured. That is, ratio 124 provides automatic adjustment of the registration to accommodate a change in the dimensions of a sheet 118, in particular, an increase in length L. In general, change in dimension to a sheet due to any chemical processing of the sheet can be accounted for by apparatus 100.
In an example embodiment, operations performed by apparatus 100 include stretching sheet 118, as a result of the architecture for processing upon the sheet. As noted above, the use of ratio 124 enables adjust to account for such stretching and maintain a desired registration between respective indicia on respective sides S1 and S2 for each sheet 118
In an example embodiment, change to width W of a sheet 118 can be determined. For example, a ratio of a change in W with respect to a change in L can be calculated or otherwise obtained and this ratio can be used to determine the change in W when the change in L is known.
Advantageously, apparatus 100 enables real time, dynamic, and constant registration adjustment. For example, dimensional change is measured for a single sheet in real time and registration adjustment is made for that sheet or a subsequent sheet in real time. Thus, there is no lag in the measuring of dimensional change and appropriate adjustment to that change. Further, the real time measurements enable appropriate adjustment responsive to actual conditions and materials.
Apparatus 100 provides the following advantages as well. Apparatus 100 enables accurate correction for side 1 (S1) to side 2 (S2) magnification differences under all conditions, including changing environmental conditions, such as humidity levels and temperature, which affect paper dimensions. Apparatus 100 enables accurate correction for changing sheet media types, such as cover stock and lightweight stock, which change dimensions to differing degrees in the face of varying environmental, such as humidity or temperature, and machine conditions, for instance, fuser setpoints. Apparatus 100 saves operator and service technician time by reducing the time and frequency necessary to perform image to paper registration setup. Apparatus 100 enables registration adjustment for all size sheets supported by a particular embodiment of apparatus 100.
Apparatus 100 enables simple and cost-effective implementation. In some instances, the components of system 104 are already in place and only relatively simple programming adjustments are required. Apparatus 100 reduces front to back show-through error. Apparatus 100 does not depend on accurately measuring an absolute length of the page (an inherent problem with other approaches). Rather, apparatus 100 measures a difference between S1 to S2 and calculates ratio 124. Any error in the S1 measurement is normalized with the same error in the S2 measurement. Apparatus 100 enables, for example through the use of a run-time average, accurate default adjustment.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
