Patent Application
20060180737
1. Field of the Invention
The present invention relates generally to thermal demand printing, and more particularly, to detection of print area edges in label printing.
2. Description of the Prior Art
Thermal demand printing has been in use for years where speed is required. Such applications include printing receipts, facsimiles and adhesive shipping labels. Generally, a thermal demand printer uses media coated with a thermal-reactive layer, which darkens with exposure to heat above a threshold temperature. The printer is equipped with a print head having a heating element configured to apply direct heat at or above the threshold temperature to an area of the thermal media, which is usually dimensioned as a roll of media. The threshold temperature is usually set at a temperature high enough not to be encountered by the media accidentally in a typical storage environment but below the flashpoint of the media, i.e., the point at which the media would combust.
In the specific case of adhesive label printing, the media used has a multitude of adhesive labels placed side-by-side on a substrate or backing and allows the labels to be readily peeled off individually. These labels come in a variety of sizes. The range of available label sizes and separation between labels gives rise to a significant printing issue.
The problem encountered with label printing involves correctly aligning the individual label for printing. Since the printing area is not continuous throughout the roll, i.e., the printing area is defined by the dimensions of the individual label and not by the dimensions of the media roll, the printer must detect when one label ends and the next one begins so that the printer is able to render the print within the bounds of the printable area of each label.
The criticality of this is best demonstrated by a hypothetical case wherein shipping labels are printed. In such a case, if the label is misaligned, the address may not be fully and clearly printed on the one label. In an automated shipping process, this inadequate shipping label may still end up on a package, but because the address is incomplete, the package cannot be efficiently delivered to its destination.
Therefore, a need exists for techniques for detecting an edge of each label on a media roll. Preferably, such a detection means should detect the label edge of commonly used label rolls, regardless of the presence, or lack thereof, of an edge indicator on the media.
The present disclosure provides a system and method for detecting an edge of a label on a media roll. The system includes a first light source positioned along a media feed path and a photodetector positioned opposite the first light source so that the media feed path is positioned between the photodetector and the first light source. A second light source is positioned adjacent and on the same side of the media feed path as the photodetector.
Additionally, a controller is in electrical communication with the first and second light sources and the photodetector. The controller is configured for selectively activating the first light source and/or the second light source and for receiving feedback from the photodetector. A media feed mechanism is also provided for advancing media of a label roll, e.g., an adhesive label roll, along the media feed path. The media feed mechanism is controllable by the controller using the received feedback.
Further, the present disclosure provides a method for detecting a label edge. In the disclosed method, a first light source is positioned along a media feed path, with a photodetector positioned opposite the first light source, on either side of the media feed path. A second light source is positioned adjacent and on the same side of the media feed path as the photodetector. One of either the first light source or the second light source is selected for illuminating a media roll supporting the label as the media moves along a point on the media feed path. At least a portion of the illumination is received by the photodetector, wherein the portion has previously impacted the media. It is determined that an edge of the adhesive label has been encountered based on at least one characteristic of the illumination received by the photodetector.
These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:
a and 3b illustrate two prior art label media types employed in accordance with the present disclosure; and
Referring to
Additionally, a second light source 110 is positioned along side and at an angle to the photodetector 106. The second light source 110 is angled so as to illuminate a spot on the media backing of the label sheet as it moves through the media feed path 108 in a manner in which the light reflected by portions of the media impacts the photodetector 106. This reflection mode is appropriately used when the adhesive label roll separates individual labels with a black or absorptive marking or strip on a side of the media opposite the labels, e.g., the backing, thus light is reflected to the photodetector 106 by the underside of the labels but little or no light is reflected to the photodetector 106 by the portions of the media (or web as the label supporting media is known in the art) between the labels having the black or absorptive marking.
a and 3b illustrate two types of label media. Referring to
An enclosing protective shell 114 having a slot aperture 116 formed thereon may be positioned to encase the photodetector 106 and second light source 110. The shell 114 provides two functions, the first being to protect the photodetector 106 and second light source 110 from damage, while also providing an increased sensitivity to smaller gap widths between labels by the use of the slot aperture 116 above the photodetector 106, which reduces the area of the focal plane normal to the relative motion of the gap between labels as it moves past the sensor.
The various components of the present embodiment, e.g., the first light source 102, second light source 110, and photodetector 106 are in electronic communication with a controller (not shown). The controller provides the activation inputs to the two light sources 102 and 110 and receives an output signal from the photodetector 106.
The controller also controls calibration components and the media feed mechanism using the output signal from the photodetector 106 as the control signal. The controller may analyze the control signal to determine the intensity of the light produced by the light sources 102 and 110, and increase or decrease the output power of the light sources, adjusting the edge detection sensitivity. For example, a typical calibration sequence may include removing media from the paper feed path, adjusting the light source (e.g., LED) current in steps from minimum to maximum and recording the sensor reading for each step; next, inserting the backing, i.e., with no label, into the feed path, adjusting LED current in steps from minimum to maximum and recording the sensor reading for each step; and lastly, inserting the backing with at least one label into the feed path, adjusting LED current in steps from minimum to maximum and recording the sensor reading for each step. The recorded data may then be used to determine a current setting for the LED that yields the best separation for label/backing to backing to media out conditions. Additionally, the data may be used to select edge detection thresholds based on the determined current setting. Alternatively, voltage levels of the light sources may be adjusted to calibrate the system.
As shown in
In transmissive mode light detection step 204a, the detected light intensity needs to be above a predetermined intensity threshold in order for the determination of edge detection to have occur at which point, printing begins in step 206; less then the threshold intensity value results in a ‘no edge detected’ determination and the media is advanced in step 205. Upon completion of step 205, the process loops back to step 204a until an edge is detected.
Alternatively in the reflective mode light detection step 204b, the detected light intensity needs to be below a predetermined intensity threshold in order for the determination of edge detection to have occur at which point, printing begins in step 206; detected light intensity greater then the threshold intensity value results in a ‘no edge detected’ determination and the media is advanced in step 205. Upon completion of step 205, the process loops back to step 204b until an edge is detected.
The present disclosure is dimensioned as a component installable, either during manufacture or as an after-market option, on commercially available label printers such as the modular printer disclosed in U.S. Pat. No. 6,616,362 issued on Sep. 9, 2003 and incorporated herein by reference in its entirety.
Briefly, modular printer 10 includes a media take-up assembly 12 including a hub assembly 14 configured to support a media take-up roll (not shown), a support block assembly 16, a printhead assembly 18, a stepper motor assembly 20, a media sensor assembly 24 (see
As discussed above, printer 10 has a display assembly 32. Display assembly 32 includes a module 150 having an LED display and a casing 152. Module 150 is positioned between diametrically opposed guide brackets 154 formed on support body 34. Opposite corners of module 150 are subsequently secured to support body 34 by screws. Casing 152 includes a plurality of flexible brackets 156, which can be snap fit to support body 34 over module 150. Support body 34 includes receiving structure 158 formed therein. Alternately, other known fastening devices may be used to secure module 150 and casing 152 to support body 34.
Referring again to
The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.
