Patent Description:
<CIT> describes a printing system including a movable tray and a fixed tray for holding recording media. The system comprises an optical detector to detect reference marks on a backside of the media. A comparator is to correlate the sensor output signals to media identification signal patterns stored in a look-up table.

<CIT> describes a print apparatus comprising a control unit that controls the motors operatively connected to the roll sheet and the conveying roller of the roller pair such that a substrate tension between the roll sheet and the conveying roller is constant.

Examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:.

Printing systems may be used to print different types of substrates. For each particular type of substrate the printer parameters may be changed to provide for an adequate quality level.

For example, printer parameters can include tension on the substrate throughout the printing process, the amount of print fluid to use in a swath the suction on the print zone, or may be parameters suggesting the use of additional printing accessories, such as absorbent materials below the substrate in case of textile substrates or substrates with high ink absorption.

In cases wherein an additional accessory is needed the setting of the parameter may include prompting a message to the user indicating the need to use such accessory.

<FIG> shows an example of a printing system <NUM> comprising a feeding mechanism <NUM> for feeding a substrate <NUM> from a substrate roll <NUM> to a print zone <NUM> of the printing system <NUM> and a printhead <NUM> wherein, after processing by the printhead <NUM>, a printed substrate <NUM> is obtained.

As mentioned above, the function of the feeding mechanism <NUM> is to manage the feeding of the substrate <NUM> from its loading wherein it is provided in the form of a substrate roll <NUM> until it is fed to the print zone <NUM>. The example feeding mechanism <NUM> of <FIG> comprises a feeding roller <NUM> wherein the substrate roll <NUM> is provided, the feeding roller <NUM> may comprise a motor which speed is controllable and an encoder <NUM> to provide the system with the angular position and/or velocity of the feeding roller <NUM>.

Further, the feeding mechanism <NUM> of <FIG> comprises a media advance mechanism <NUM> comprising a pair of media advance rollers <NUM>, <NUM> being at least one of them powered by a motor and comprising an encoder <NUM> to determine its position and/or speed. The media advance mechanism <NUM> is adapted to receive a substrate <NUM> sheet and it pulls the substrate from the substrate roll <NUM> as to feed it towards the print zone <NUM>. In an example, the feeding roller <NUM> may be configured to maintain a constant tension on the substrate <NUM> by acting upon the substrate <NUM> with a force in a direction opposite to the pulling direction of the media advance mechanism <NUM>.

In an example, a controller <NUM> is provided in the printing system wherein such controller may issue a first command signal <NUM> to control the motor associated to the feeding roller <NUM> and/or a second command signal <NUM> to control the motor associated to the media advance mechanism <NUM>. Further, the controller <NUM> may receive a feeding roller signal <NUM> from the feeding roller encoder <NUM>, that signal may be associated, for example, to the angular position of the feeding roller <NUM> and/or the current speed of the feeding roller <NUM>. Likewise, the controller <NUM> may receive a media advance signal <NUM> originated from the media advance encoder <NUM> associated to the media advance mechanism <NUM> that may be related to the angular position and/or speed of at least one of the media advance rollers <NUM>, <NUM>. Also, the controller <NUM> may further be used to control parameters in the printhead <NUM> (such as ink amount or swath) so it has a bidirectional communication link <NUM> with the printhead <NUM>.

A controller is considered, within the context of this disclosure, as any device comprising a processor and a memory being the processor configured to execute a set of instructions in view of an input (that may be stored in the memory) and issue an actuation signal.

In an example, the feed roller encoder <NUM> and/or the media advance encoder <NUM> may be used for determining parameters of the substrate <NUM>, e.g., the angular position of the rollers may be used for determining the thickness of the substrate, as will be explained in more detail by making reference to <FIG>. Also, the speed of the rollers may be used for estimating an inertia of the substrate roll <NUM>, which is an indication of its mass as will be explained in more detail with reference to <FIG>, <FIG> and <FIG>.

The information from the encoders can, therefore, be used to determine the feeding mechanism parameters, such as angular position or speed and those feeding mechanism parameters may, in turn, be used to calculate (or, at least, estimate) substrate parameters, such as thickness or mass. The substrate parameters can be used also to identify a type of substrate that is loaded on the printing system and such identification may be used to select parameters on the printing system or a set of preset parameters.

In an example, the controller may access a look up table wherein a set of substrate parameters (such as thickness and/or mass) correspond to a determined type of substrate <NUM> and, for each type of substrate a set of parameters are established. In this manner, upon detection of a substrate type, the controller <NUM> may preset several parameters of the printing system which may be, for example, swath, substrate tension, ink quantity to use, print zone suction or may issue alerts to the user indicating the need to use some specific accessories of the printing system, such as, an absorbent below the substrate, a post processing station, a curing station, etc. In the context of the present disclosure, swath is to be understood as the width of each line of print fluid used in a printing pass.

In an example, the substrate parameters may be roughly estimated as there may be no need to identify the properties of a substrate <NUM> in much detail. In a particular example, the substrate determination needs to differentiate between a paper and a textile, since the mass differences are so big, a rough estimation of the mass may be enough to determine the preset conditions for the substrate <NUM>.

<FIG> shows a flow diagram wherein a pair of encoders may be used to determine the thickness <NUM> of a substrate roll <NUM>. Initially, an initial radius (R<NUM>) of the substrate roll <NUM> is established and a distance (d) is selected <NUM>, the first radius (R<NUM>) may be a previously known radius, e.g., a previously measured radius and the distance (d) may be a pre-determined length of substrate to perform the thickness calculation.

Then, one of the rollers, for example, one of the rollers from the media advance mechanism <NUM> is actuated <NUM> and the substrate roll <NUM> is pulled by a length of substrate <NUM> corresponding to the distance d, such length may be measured by the media advance encoder <NUM>.

Subsequently, the angular position (a) of the feeding roller <NUM> is measured <NUM>, e.g., by means of the feeding roller encoder <NUM>. Since a determined amount of substrate <NUM> has been withdrawn from the substrate roll <NUM>, its radius has now changed to a new radius (R<NUM>). Such radius can be easily calculated given that the angular position (a) was measured and the arc for such angular position (a) is substantially the distance (d) of substrate <NUM> withdrawn from the substrate roll <NUM>. Then, the new radius (R<NUM>) may be estimated by the equation: <MAT>.

Finally the thickness is estimated <NUM> in view of such radius. In particular the thickness of the substrate <NUM> is proportional to the difference between the initial radius (R<NUM>) and the new radius (R<NUM>).

<FIG> shows a flow diagram wherein a roller may be used to estimate the inertia <NUM> as substrate parameter. In the example of <FIG> a roller, for example, the feeding roller <NUM> may be used. In this example, the controller <NUM> issues a command signal to the motor <NUM> so that the feeding roller <NUM> is moved to a determined speed (V). This speed may be controlled, e.g., by pulse width modulation.

Then, a timer is started <NUM> and the speed increases. A decision block <NUM> determines if the speed has reached a stabilization speed, e.g., <NUM>% of the determined speed (V). If it has not reached this stabilization speed, the timer is maintained and, if it reaches the stabilization speed the timer is stopped <NUM>. As a result a time is obtained <NUM> wherein this time to reach the stabilization speed is related to the inertia of the substrate roll <NUM> as will be explained in more detail with reference to <FIG> and <FIG>.

<FIG> shows a graph that shows the stabilization speed for different substrates <NUM>. In particular, a condition <NUM> with a textile moved by a roller at 24V, another condition <NUM> wherein the textile of the first condition is moved by a roller at 15V, a third condition <NUM> wherein a banner is moved by a roller at 24V and a fourth condition <NUM> wherein the banner of the third condition is moved by a roller at 15V.

From <FIG> it can be seen that, although the nominal speeds of the roller are different (a 24V fed rolled is faster than a 15V fed roller) the stabilization time as <NUM>% of the final speed is very similar. Therefore, an estimation of the inertia based on such measurements can be considered to be robust to the nominal speeds of the rollers, i.e., of the type of roller to use in the printing system.

For these examples, the stabilization speed is considered to be a speed of about <NUM>% of the setting speed issued by the controller <NUM>. Nonetheless, as can be seen from the graph, other percentages may also provide similar results, in particular, the range from <NUM>% to <NUM>% of the setting speed.

Also, <FIG> shows that a rough estimation of the inertia may be enough to differentiate between a textile and a banner. Also, the printing parameters are different between these two types of substrates. On the other hand, some of the printing parameters amongst textiles may be similar so this rough estimation may be enough to establish at least some of the preset parameters.

<FIG> shows a graph wherein the stabilization speed has been correlated to the moment of inertia of the print roll <NUM>. The function <NUM> may be used to calculate the current inertia of the print roll <NUM> to establish the preset to use and, alternatively, provide the user with information about the substrate being used in a printing process.

The thickness of the substrate <NUM> and the inertia of the substrate roll <NUM> are examples of substrate parameters that may be obtained by using existing elements within the print system, such as encoders to determine properties of the substrate. Either one of them may be useful to establish or, at least, estimate the type of substrate that is being loaded to the printing system. In a particular example, both of such parameters are estimated and the type of substrate is determined by the controller <NUM> by identifying in a look-up table the type of substrate on the look-up table that is more similar in view of the estimated substrate parameters. Then the preset parameters configured on the look-up table for such substrate are used throughout the printing process.

In essence, the look-up table comprises preset parameters and a set of substrate parameters. The printing system may select, depending the set of substrate parameters estimated, the preset to be used by the printing system.

Claim 1:
A substrate selection method for a printer wherein the printer comprises a feeding mechanism (<NUM>) including a feeding roller (<NUM>) to receive a substrate roll (<NUM>) and a media advance roller (<NUM>, <NUM>) to receive a substrate (<NUM>) from the substrate roll, the method comprising:
• actuating the feeding roller or the media advance roller;
• measuring a feeding mechanism parameter on the feeding roller or the media advance roller;
• calculating a substrate parameter in view of the feeding mechanism parameter; the method characterized in that:
• determining from a table a substrate type in view of the substrate parameter; and
• selecting a preset of parameters to be used by the printer in view of the substrate type.