Abstract:
A direct thermal printer including a latch assembly, a media storage assembly, a media centering assembly, a print assembly, and a temperature sensing member. The latch assembly includes a single latch lever in mechanical communication with latch tabs disposed in the cover of the printer that are received by openings in the base of the printer to engage and disengage the cover from the base. The media storage assembly includes media guides with removable tabs having more than one available position to provide storage of different size media. The media centering assembly includes pulley assemblies that bias the media guides towards each other to secure media between the media guides. The print assembly includes a platen disposed in the base of the printer having cams on each end that are rotatable and positioned to adjust printing characteristic of a printhead disposed in the cover.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from, and the benefit of, U.S. Provisional Application Ser. No. 61/734,406, filed Dec. 7, 2012, the entirety of which is hereby incorporated by reference herein for all purposes. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to printers, and in particular, to a direct thermal printer with a single latch assembly, an adjustable media storage assembly guide, a media centering assembly, a print assembly, and a temperature sensing member. 
         [0004]    2. Description of Related Art 
         [0005]    Direct thermal printers are used to produce a printed image by selectively heating specially coated media as it passes over the printer&#39;s thermal printhead. An image is produced where the media&#39;s coating turns black in the areas where it is heated. Traditional thermal printers include a thermal printhead, which generates heat and effectively prints on the media, a platen, or roller (typically rubber), that feeds the media through the printer, a spring or similar mechanism that urges the thermal printhead toward the media to establish physical contact between the printhead and the media to facilitate thermal printing, and a controller that controls the printer. 
       SUMMARY 
       [0006]    An example embodiment of the present disclosure includes a printer, such as a direct thermal printer, that comprises a housing including a cover and a base connected together with a hinge, a latch assembly disposed in the cover, a media storage assembly disposed in the base, a media centering assembly disposed in the base, a print assembly disposed in the housing, and a temperature sensing member disposed in the base. 
         [0007]    The latch assembly includes a latch lever disposed at least in part on the exterior of the cover in mechanical communication with latch tabs also disposed in the cover such that actuation of the latch lever will simultaneously actuate the first and second latch tabs. Openings in the base of the printer are adapted to receive the latch tabs. Once inserted into the openings, actuation of the latch tabs will move the latch tabs between a locked position and an unlocked position allowing the cover to be selectively engaged and disengaged from the base. 
         [0008]    The media storage assembly includes media guides each having tab slots for receiving removable and repositionable tabs. The media guides also include securing tabs for securing the removable and repositionable tabs in the tab slots. The removable and repositionable tabs include a male feature disposed on the face of each tab. In a first position in the tab slot, the removable and repositionable tab&#39;s male feature is in a position to hold media of a certain size. When the removable and repositionable tab is repositioned to a second position in the tab slot, the removable and repositionable tab&#39;s male feature is in a position to hold media of another inside diameter (ID) core size. 
         [0009]    The media centering assembly includes mounting plates disposed on the media guides and pulley assembly disposed in the base. Each pulley assembly includes a belt that is attached at one end to one media guide and at the other end to the other media guide. An extension spring disposed in the base is secured to the base at a first end and to one of the mounting plates at its other end. The extension spring provides a force to bias the first media guide towards the second media guide. 
         [0010]    The print assembly includes a printhead disposed in the cover and retained by an inner cover frame and positioned by compliant members that apply a force against a platen disposed in the base retained by a bearing and having a cam disposed at both ends of the platen. The compliant members of the printhead provide limited radial movement of the printhead along the printhead&#39;s axis. The platen&#39;s bearing provides radial movement of the platen along the platen&#39;s axis. The print assembly further includes a set screw disposed in the base and a leaf spring disposed on the platen&#39;s bearing and also in contact with the set screw. Rotation of the set screw rotates platen&#39;s cams and this rotation causes contact of the first and second cams with the printhead which positions the printhead forward along the axis of the paper motion. 
         [0011]    The printer optionally includes a temperature sensing member disposed in the base to sense the temperature of certain components. 
         [0012]    In another aspect, the present disclosure is directed to a media centering assembly. The media centering assembly includes a first media guide and a second media guide disposed in slidable opposition to one another and configured to support a roll of media therebetween. The media centering assembly includes a first pulley assembly having a first pulley and a first belt. The first belt is in communication with the first pulley and is operably coupled to the first media guide at a first end of the first belt, and the first belt is operably coupled to the second media guide at a second end of the first belt. The media centering assembly includes a second pulley assembly having a second pulley and a second belt, wherein the second belt is in communication with the second pulley and is operably coupled to the second media guide at a first end of the second belt, and the second belt is operably coupled to the first media guide at a second end of the second belt. An extension spring is operably coupled, at a first end of thereof, to an anchor, and the extension spring operably coupled to the first media guide at a second end of the extension spring. The extension spring is configured to bias the first media guide toward the second media guide. 
         [0013]    In some embodiments, the media centering assembly includes a first mounting plate disposed on the first media guide, and a second mounting plate disposed on the second media guide. In some embodiments, the first belt is fixed to the first mounting plate at a first end of the first belt, and is fixed to the second mounting plate at a second end of the first belt. The second belt is fixed to the second mounting plate at a first end of the second belt, and is fixed to the first mounting plate at a second end of the second belt. 
         [0014]    In some embodiments, the first media guide and the second media guide each include a male protrusion configured for insertion into a support tube of a media roll. In some embodiments, the male protrusion is disposed on a reversible member having a first position wherein the male protrusion is configured for insertion into a support tube of a media roll having a first diameter, and a second, reversed position, wherein the male protrusion is configured for insertion into a support tube of a media roll having a second diameter different from the first diameter. In some embodiments, the first media guide and the second media guide include a tab slot defined therein, and the reversible member includes a tab configured to selectively engage the tab slot of the corresponding first or second media guide. 
         [0015]    In another aspect, the present disclosure is directed to a printer that includes a housing having a cover and a base connected together with a hinge. A latch assembly is disposed in the cover. The latch assembly includes a latch lever disposed at least in part on the exterior of the cover in mechanical communication with a first latch tab and a second latch tab, such that actuation of the latch lever simultaneously actuates the first and second latch tabs. The base includes first and second openings defined therein that are adapted to receive the first and second latch tabs respectively, wherein the actuation of the first and second latch tabs once inserted into the first and second openings will move the latch tabs from a locked position to an unlocked position allowing the cover to be disengaged from the base. The printer includes a print assembly disposed in the housing having a bearing disposed in the base, and an elongate cylindrical platen disposed in the base and rotatable about its longitudinal axis. The platen is retained by the bearing and the bearing facilitates rotation of the platen along the platen&#39;s longitudinal axis. The print assembly includes a first cam disposed on a first end of the platen, and, a temperature sensor disposed in the base. 
         [0016]    In some embodiments, the printer includes a second cam disposed on a second end of the platen, a set screw disposed in the base, and, a leaf spring disposed on the second bearing and in contact with the set screw. Rotation of the set screw rotates the first and second cams and, in turn, rotation of the first and second cams causes contact of the first and second cams with a printhead. In some embodiments, an anchor slot is defined in the base that is configured to receive a portion of the leaf spring. In some embodiments, the leaf spring is configured for deflection in a transverse direction away from the platen to enable the leaf spring to move out of the anchor slot. 
         [0017]    In some embodiments, the bearing is configured for selective removal from the platen by rotating the bearing relative to the platen by a predetermined amount. In some embodiments, the predetermined amount of rotation is about 43 degrees. 
         [0018]    In some embodiments, the printer includes a motor operably coupled to the platen. In some embodiments, the printer includes a temperature sensor configured to sense the temperature of the motor. In some embodiments, the temperature sensor provides closed loop temperature control of the motor. 
         [0019]    In yet another aspect, the present disclosure is directed to a printer that includes a housing having a cover and a base connected together with a hinge. The printer includes a latch assembly disposed in the cover. The latch assembly includes a latch lever disposed at least in part on the exterior of the cover in mechanical communication with a first latch tab and a second latch tab. Actuation of the latch lever simultaneously actuates the first and second latch tabs. The base includes first and second openings defined therein to receive the first and second latch tabs respectively. Actuation of the first and second latch tabs, once inserted into the first and second openings, move the latch tabs from a locked position to an unlocked position thus allowing the cover to be disengaged from the base. The printer includes a media centering assembly disposed in the base. The media centering assembly includes a first media guide and a second media guide disposed in slidable opposition to one another and configured to support a roll of media therebetween. The media centering assembly includes a first pulley assembly having a first pulley and a first belt. The first belt is in communication with the first pulley and is operably coupled to the first media guide at a first end of the first belt, and is operably coupled to the second media guide at a second end of the first belt. The media centering assembly includes a second pulley assembly that includes a second pulley and a second belt. The second belt is in communication with the second pulley and is operably coupled to the second media guide at a first end of the second belt, and operably coupled to the first media guide at a second end of the second belt. The media centering assembly includes an extension spring operably coupled to an anchor at a first end of the extension spring, and is operably coupled to the first media guide at a second end of the extension spring and configured to bias the first media guide toward the second media guide. 
         [0020]    In some embodiments, the printer includes a first mounting plate disposed on the first media guide, and a second mounting plate disposed on the second media guide. In some embodiments, the first belt is fixed to the first mounting plate at a first end of the first belt, and is fixed to the second mounting plate at a second end of the first belt. The second belt is fixed to the second mounting plate at a first end of the second belt, and is fixed to the first mounting plate at a second end of the second belt. In some embodiments, the first media guide and the second media guide each include a male protrusion configured for insertion into a support tube of a media roll. In some embodiments, the male protrusion is disposed on a reversible member having a first position wherein the male protrusion is configured for insertion into a support tube of a media roll having a first diameter, and a second, reversed position wherein the male protrusion is configured for insertion into a support tube of a media roll having a second diameter different from the first diameter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The present subject matter may take form in various components and arrangements of components, and in various steps and arrangements of steps. The appended drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the subject matter. 
           [0022]      FIG. 1  is a front perspective view of an assembled thermal printer constructed in accordance with an example embodiment of the present disclosure; 
           [0023]      FIG. 2  is a front perspective view of an assembled thermal printer shown with its cover open and constructed in accordance with an example embodiment of the present disclosure; 
           [0024]      FIG. 3A  is a perspective view of the media storage assembly in accordance with an example embodiment of the present disclosure; 
           [0025]      FIG. 3B  is a perspective view of exemplary media that may be used in an example embodiment of the present disclosure; 
           [0026]      FIG. 4  is a top perspective view of the media centering assembly in accordance with an example embodiment of the present disclosure; 
           [0027]      FIG. 5  is a perspective view of the portion of the print assembly including a portion of the platen and the cam located at one end of the platen constructed in accordance with an example embodiment of the present disclosure; 
           [0028]      FIG. 6  is a side perspective view of the portion of the print assembly including a portion of the platen and the cam located at one end of the platen, the drive train, and a temperature sensing member constructed in accordance with an example embodiment of the present disclosure; and 
           [0029]      FIG. 7  is a circuit drawing of the temperature sensing member constructed in accordance with an example embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Well-known and/or repetitive functions and constructions are not described in detail to avoid obscuring the present disclosure in unnecessary or redundant detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. In addition, as used herein in the description and in the claims, terms referencing orientation, e.g., “top”, “bottom”, “upper”, “lower”, “left”, “right”, and the like, are used with reference to the figures and features shown and described herein. It is to be understood that embodiments in accordance with the present disclosure may be practiced in any orientation without limitation. In this description, as well as in the drawings, like-referenced numbers represent elements which may perform the same, similar, or equivalent functions. 
         [0031]    Turning first to  FIGS. 1 and 2 , according to aspects of the present disclosure, direct thermal printer  100  includes base  110  and cover  120 . Cover  120  is configured for selective engagement with a top portion of base  110  and includes top frame  180 , latch lever  140 , and latch tabs  220 . In the present embodiment, top frame  180  includes an enlarged section of a top surface  121  of cover  120 , and is generally configured to allow cover  120  to couple with base  110  without contacting or interfering with the supply of print media  150  disposed within printer  100 . Additionally, cover  120  may be hingedly attached to a rear portion of the base at hinge  130 . Various structures known in the art to hingedly attach cover  120  to base  110  are also contemplated, for example and without limitation, a conventional hinge-pin arrangement, a living hinge, and so forth. During use, cover  120  may be pivoted or rotated about hinge  130  to enable a user to selectively access the components in base  110 , to load and unload media, and the like. A view of printer  100  with cover  120  open and media inserted is shown in  FIG. 2 . 
         [0032]    Latch lever  140  can be mechanically connected to latch tabs  220  which can be disposed on opposing sides of cover  120 . Latch tabs  220  can be normally biased for engaging slots  230  located in base  110 . Actuation of latch lever  140  can simultaneously actuate latch tabs  220 , which overcomes the bias such that latch tabs  220  do not engage slots  230  in base  110  and cover  120  can be pivoted about hinge  130  or separated from base  110 . Conversely, the normal bias of latch tabs  220  urges latch tabs  220  to engage a portion of slots  230  thereby securing cover  120  to base  110 . 
         [0033]    Front plate  160  of base  110  provides an exit surface over which media  150  passes as it exits printer  100 . Front plate  160  may be pulled away from base  110  to provide space for the attachment of optional accessories, such as a label peeler and/or a cutter, to base  110 . 
         [0034]    Printer  100  can be supplied with power from an electrical source (not shown). The electrical source of energy can be AC or DC depending on the desired configuration of printer  100 . Switches or buttons  170  can be positioned on the top face of cover  120  and can be in electrical communication with a control circuit (not shown) that is disposed within printer  100 . The control circuit can be a printed circuit board or any control circuit known in the art sized to fit in printer  100 . Buttons  170  can control operation of printer  100  such as pause, resume, and feed. 
         [0035]    Media storage assembly  300 , which can be seen only partially in  FIG. 2 , is shown in further detail in  FIGS. 3A and 4 . Media storage assembly  300  includes spaced apart media guides  310  each having tab slots  320  for receiving removable tabs  330  which may be selectively positioned within tab slots  320 . Media guides  310  can also include securing tabs  340  for securing removable tabs  330  in tab slots  320 . Removable tabs  330  can include disc-shaped male features  350  disposed on the face of removable tabs  330 . Male features  350  are adapted for engaging a portion of the inside diameter of media supply roll  152 . Various types of media  150  may have an inside diameter of varying sizes. For example, as illustrated in  FIG. 3B , media supply roll  152   a  has an inside diameter  360   a  of diameter d a , while media supply roll  152   b  has an inside diameter  360   b  of diameter d b  that is greater than diameter d a . 
         [0036]    Media supply roll  152 , media supply roll  152   a , and/or media supply roll  152   b  may include a support tube  151 , support tube  151   a , and/or support tube  151   b , respectively, that engages male feature  350  such that media supply roll  152  is rotatable on male features  350 , thereby allowing media  150  to be fed from media supply roll  152  toward printhead  510 . Media guides  310  can be repositioned within tab slots  320  to allow for media supply rolls  152  of different inside diameters to fit in printer  100 . In a first position in tab slot  340 , which is indicated by  330   a , removable tab&#39;s  330  male feature  350  is in a position to hold media rolls of a certain size, for example, a media supply roll having a width of 1.5 inches. When removable tab  330  is removed, rotated  180  degrees, and reinserted in a second position, which is indicated by  330   b , in the tab slot, removable tab&#39;s  330  male feature  350  is placed in a position suitable to hold media of another size, for example, 1.0 inches wide. 
         [0037]    Turning now to  FIG. 4 , media centering assembly  400  is shown in further detail. Media centering assembly  400  may include mounting rails (not shown) disposed in base  110 , first and second mounting plates  410  disposed on first and second media guides  310 , and pulley assemblies  415   a  and  415   b  disposed in base  110 . Pulley assembly  415   a  includes pulley  420   a  and belt  430   a . As shown in  FIG. 4 , belt  430   a  can be attached to a first mounting plate  410  with fastener  440   a  and to a second mounting plate  410  with fastener  440   b . Pulley assembly  415   b  includes pulley  420   b , belt  430   b , and extension spring  450 . As shown in  FIG. 4 , belt  430   b  is joined to one of mounting plates  410  with fastener  440   c  and to the other media of mounting plates  410  with another fastener (not shown). Although fasteners are illustrated here, any attaching mechanisms known in the art are contemplated by the present disclosure, including without limitation, threaded fasteners, rivets, clips, adhesive, integral forming, overmolding, intermolding, and so forth. Mounting plates  410  are slidably mounted to the mounting rails (not shown) such that movement of mounting plates  410  and guides  310  is directed in a transverse linear path. Extension spring  450  is disposed between one of mounting plates  410  and an anchor  451  situated on a portion of base  110  that is opposite mounting plate  410 , such as the platen bracket (not shown), an interior wall of base  110 , or any other suitable position. Extension spring  450  is biased for pulling media guides  310   a ,  310   b  towards each other. 
         [0038]    During use, in order to insert a media roll  152  on male features  350 , a user pushes apart media guides  310  thus extending extension spring  450  to overcome the bias thereof. After media roll  152  is positioned on media guides  310 , e.g., male features  350  are inserted into support tube  151  of media roll  15 , the user releases media guides  310 , which, in turn, causes extension spring  450  to contract, thus allowing the media guides  310  to pull towards each other and thereby hold media roll  152  in place. Advantageously, the interaction of belt  430   a  and pulley  420   a  with left media guide  310   a  and right media guide  310   b , the interaction of belt  430   b  and pulley  420   b  with left media guide  310   a  and right media guide  310   b , together with the inward bias of extension spring  450 , enables media guides  310  to move in a reciprocal manner about the centerline A-A ( FIG. 2 ) of printer  100 , which, in turn, enables media guides  310  to retain media roll  152  in a centered position relative to printhead  510 . In this manner, centering of the print media roll  152  may be achieved without the bulk and friction typically encountered with conventional rack and pinion arrangements. 
         [0039]    Print assembly  500 , which is shown partially in  FIG. 2 , is disposed within base  110  and/or within cover  120 . A portion of print assembly  500  that may be disposed in cover  120  includes inner cover  562 , compliant members (such as compression springs—not shown) and printhead  510 . Inner cover  562  and compliant members can retain printhead  510  providing limited radial movement of printhead  510  along printhead  510 &#39;s axis. 
         [0040]    The portion of print assembly  500  is shown in further detail in  FIG. 5 . Bearing  550  retains platen  520  and facilitates axial rotation of platen  520  along a longitudinal axis thereof. A cam  530  is disposed at each end of platen  520 . An adjustment set screw  560  is disposed in base  110 . Leaf spring  540  is disposed at a first end  541  on the bearing  550  and at a second end  542  in slot  545 . When positioned in slot  545 , leaf spring  540  contacts a set screw  560 . Rotation of set screw  560  engages leaf spring  540 , which, in turn, rotates cam  530 . As cam  530  rotates, printhead  510  is translated in a longitudinal direction (e.g., along axis A-A). In this manner, the position of printhead  510  may be adjusted to achieve optimal printing. Set screw  560  includes a tool engaging feature  561 , such as a slot, Phillips head, Pozidrive head, hex head, Torx head, and the like to facilitate the adjustment thereof with a screwdriver or other suitable tool. In some embodiments, set screw  560  may be knurled to enable adjustment using only the fingers. Leaf spring  540  is biased inward, e.g., toward platen  520 , to retain platen  520  in association with bearing  550 . During use, leaf spring  540  may be deflected in a transverse direction away from platen  540  (e.g., orthogonal to axis A-A) to allow leaf spring  540  to move out of its anchor position in base  110 . Once bearing  550  is rotated a predetermined amount, for example, about 43 degrees, bearing  550  may be removed from the platen bracket (not shown) to facilitate the removal and replacement of platen  520 , bearing  550 , leaf spring  540  and/or set screw  560 . 
         [0041]    Printer  100  also includes motor  605  as shown in  FIG. 6 . Motor  605 , which may be a stepper motor, a DC motor, an AC motor, or any suitable motor now or in the future known, is operatively coupled to platen roller  520  via drive train  620  such that a full step of motor  605  corresponds to a predetermined length of media  150  movement. Temperature sensor  610 , which may include a thermistor, and drive train  620 , are shown in  FIG. 6 . Temperature sensor  610  is disposed in base  110  and is configured to sense and/or monitor the temperature of motor  605 , providing closed loop temperature control of motor  605  which, in turn, allows printer  100  to run at higher duty cycles and protect the printer  100  and/or motor  605  from overheating. 
         [0042]      FIG. 7  shows a stepper motor interface  700  which illustrates the electrical connections of the temperature sensor  610  to an analog-to-digital converter (ADC) input  612  of the printer controller (not shown), which is used to determine motor temperature. In the illustrated embodiment, motor  605  employs a four-wire arrangement in which the relative timing of the phase A  614  and phase B  616  motor drive signals, as provided by the controller, determines the rotational output of motor  605  and thus, the advancement of media  150 . 
         [0043]    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. Further variations of the above-disclosed embodiments and other features and functions, or alternatives thereof, may be made or desirably combined into many other different systems or applications 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.