Patent Publication Number: US-10786999-B2

Title: Method and apparatus for protecting a print head in a thermal printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 15/839,267, filed on Dec. 12, 2017, from which this application claims priority. U.S. patent application Ser. No. 15/839,267 is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to thermal printers. More particularly, it relates to a method and device for protecting the print head of a thermal printer. 
     Description of the Prior Art 
     Thermal printers are used for many different label printing operations. They are also used in some industries as label dispensers as well as printers. The direct thermal print heads in these printers are subject to wear when printing labels, and also when not printing labels (i.e., when the printer is being used as a label dispenser for already printed labels) and the thermal printer portion is turned off. In either instance, the abrasive action or friction of the labels or other material traveling against the surface of the direct thermal print head surface will cause damage to the print head. In fact, this abrasive action/friction is the main cause of damage to the thermal print head. Thus, when using the thermal printer as a label dispenser for already printed labels, there is a need to protect the print head from this abrasive action. 
     SUMMARY OF THE INVENTION 
     The present inventions addresses the shortfalls of existing thermal printing machines by providing a protective cover to the direct thermal print head to prevent head wear when the printer is being used to dispense already printed labels. 
     According to one implementation, the thermal printer includes a print head assembly having a printhead, and a cover removably disposed over the printhead and configured to prevent the same from being exposed to a thermal material passing over the same during label dispensing. 
     According to a further implementation, the printhead cover has a low coefficient of friction and is in the form of a sleeve that fits over the entire printhead assembly. 
     Other aspects and features of the present principles will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the present principles, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings wherein like reference numerals denote similar components throughout the views: 
         FIG. 1  is a schematic overview of the print head of a thermal printer and label path with the print head positioned away from the label run, according to an embodiment of the invention; 
         FIG. 2  is a schematic overview of the print head of a thermal printer and label path with the print head positioned against the label run during dispensing, according to an embodiment of the invention; 
         FIG. 3  is an exploded view of the print head with protective sleeve, according to an embodiment of the invention; 
         FIG. 4  is a plan view of the print head with the protective sleeve in place, according to an embodiment of the invention; 
         FIG. 5  is a schematic overview of the print head of a thermal printer with the protective sleeve in place while the print head is positioned away from the label run, according to an embodiment of the invention; 
         FIG. 6  is a schematic overview of the print head of a thermal printer with the protective sleeve in place and label path with the protected print head positioned against the label run during dispensing, according to an embodiment of the invention; and 
         FIG. 7  is a flow chart of the method for protecting/covering the printhead in a thermal printer, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  schematically show the print head assembly  12  having the print head  14  within a thermal printer. The label run  16  includes a plurality of labels  18  spaced thereon. The label run passes around various directional spindles  30 ,  32 ,  34 , etc. to be guided through the printer across the print head  14  when the print head assembly is engaged ( FIG. 2 ). As shown, as the labels  18  pass across the printhead  14  during printing or dispensing. As such, the abrasive action or the friction of the labels  18  passing over the printhead  14  results in damage and wear to the same. Thus, when using the thermal printer for label dispensing and not printing, it will become apparent that such action of running the labels through the printer and across the printhead  14  will ultimately result in increased wear of the printhead, and ultimately shorten the usable life of the same. 
       FIG. 3  shows the printhead assembly  12  (removed from the printer for ease of description) and a protective sleeve  40  according to an embodiment of the present invention. As shown in  FIG. 4 , the sleeve  40  fits over the printhead assembly  12  as shown. Generally speaking the printhead  14  will have a length or size L 1  which essentially dictates the size of the printing area of the same. 
       FIG. 5  shows the printhead assembly  12  with the protective sleeve  40  positioned thereon and before the printhead assembly  12  is engaged for label printing or dispensing.  FIG. 6  shows the printhead assembly  12  with the protective sleeve  40  engaged for label printing or dispensing. As shown, now, as the labels  18  move through the printer, the printhead  14  is protected from the abrasive action caused by the labels moving across the same. When dispensing is completed, the protective sleeve  40  can be removed and the printer used for printing as usual. 
     In accordance with one embodiment, the coefficient of friction of the protective sleeve is very low. Those of skill in the art will appreciate that the coefficient of friction for different materials can be drastically different. As such, and as a guideline, the coefficient of friction for most materials is between 0 and 1, with 0 being the lowest (i.e., no friction). According to the present principles, the printhead cover or sleeve has a low coefficient of friction, preferably 0.3 or less. 
     In accordance with one exemplary embodiment, the protective sleeve  40  is made of an ultra high molecular weight flexible tape (UHMW) having a coefficient of friction in a range of 0.10-0.20, and has a length or size L 2  that does not necessarily have to equal the length or size L 1  of the printhead  14 . In fact, the length or size L 2  can be dictated by the size or width of the label run (thermal material)  16  that would be passing over the printhead  14 . Thus, L 2  will generally be less than L 1  in this instance, but L 2  must always be larger than the width of the label run or thermal material  16 . 
     In accordance with other contemplated embodiments, the protective sleeve  40  can be replaced with other devices that operate in the same manner to shield the printhead  14  from the abrasive action caused by the labels moving across the same. 
     Examples of such other embodiments include a clip on cover that clips onto the printhead  14  or the assembly  12 . In this embodiment, it is envisioned that the clips would engage another portion of the printhead assembly  12  such that a thin strip of material covers the printhead  14 . Another embodiment would include a strip having a removable adhesive that covers the print elements of the print head  14 . This strip could be disposable and be a single use type of product. According to yet another embodiment, the printer could be modified to allow the roller assembly  34  which applies pressure on the back of the thermal material (i.e., label run  16 ) to be retracted away from the printhead  14  such that the thermal material  16  does not come into contact with the same when operating the printer as a label dispenser. 
     In accordance with other embodiment shown in  FIG. 7 , a method  100  for protecting the printhead of a thermal printer is provided. The method includes preparing the thermal printer for dispensing already printed labels (thermal material)— 102 . Once prepared, the printhead is covered with a thin material having a low coefficient of friction— 104 . Once covered, the printer is engaged or activated to dispense the labels— 106 , and the thermal material or label run is run through the printer and over the covered printhead such that the printhead is no longer exposed to the abrasive action causes by the thermal material passing over the same. 
     While there have been shown, described and pointed out fundamental novel features of the present principles, it will be understood that various omissions, substitutions and changes in the form and details of the methods described and devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the same. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the present principles. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or implementation of the present principles may be incorporated in any other disclosed, described or suggested form or implementation as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.