Patent Publication Number: US-8976212-B2

Title: Printhead adjustment mechanism for edge justified printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Application No. 61/370,050 filed Aug. 2, 2010, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present inventive subject matter relates generally to the art of printers. Particular relevance is found in connection with edge justified thermal printers, and accordingly the present specification makes specific reference thereto. However, it is to be appreciated that aspects of the present inventive subject matter are also equally amenable to other like applications. 
     BACKGROUND OF THE INVENTION 
     One example of a known thermal printer is disclosed in U.S. Pat. No. 5,947,618 to Keller, et al., is incorporated by reference herein in its entirety. The aforementioned printer is a center justified printer—meaning that label stock or other like print media is centered with respect to a printhead which is used to mark the media. Other printers are known as edge justified printers—meaning that the label stock or other like print media is located to one side or edge of the printhead. 
     In general, the print media is routed or passed between a platen roller and the printhead which marks the media. Achieving good print quality and/or proper printer operation is at least partially dependent upon having an appropriate pressure applied to the printhead so that suitable contact is made with the print media. Conversely, applying excessive pressure to the printhead can cause the printhead to abut the media and/or platen roller with too much force thereby resulting in poor print quality or poor printer operation and/or undue wear on the printhead. 
     In the case of a center justified printer, it is generally acceptable to have a pressure applied to the printhead which is substantially uniform across its width. However, for an edge justified printer, it is often desirable to have a pressure applied to the printhead which is non-uniform across its width, e.g., depending on the width of the media being used at the time. For example, when a media is being used which has a relatively narrow width as compared to the width of the printhead, it may be desirable to have one pressure applied at the end or edge of the printhead to which the media is justified (e.g., an inboard end of the printhead) and relatively less pressure applied at the other end or edge of the printhead (e.g., an outboard end of the printhead). 
     Accordingly, a new and/or improved printhead adjustment mechanism for edge justified printers is disclosed which addresses the above-referenced problem(s) and/or others. 
     BRIEF SUMMARY OF THE INVENTION 
     The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention. 
     The present invention provides a printer having a housing, a mounting assembly that holds printable media and a printhead assembly. The printhead assembly of the present invention may be cantilevered to a mounting member of the printer via a bracket. The printhead assembly is mounted to the mounting member via a bracket. The printer may further comprise pair of pressure adjusting devices wherein each adjusting device includes an adjusting member that is received in the bracket. 
     The present invention also provides an adjusting member having a body that may be cylindrical wherein the body has at least one opening or slot. The adjusting member further comprises an outer member having a plurality of longitudinal extensions. 
     Other features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description of the various embodiments and specific examples, while indicating preferred and other embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These, as well as other objects and advantages of this invention, will be more completely understood and appreciated by referring to the following more detailed description of the presently preferred exemplary embodiments of the invention in conjunction with the accompanying drawings, of which: 
         FIG. 1  is a diagrammatic illustration of an edge justified thermal printer in accordance with aspects of the present inventive subject matter. 
         FIG. 2  shows the printer of  FIG. 1  having an outer housing opened to reveal internal components of the printer, including a printhead assembly mounted in cantilevered fashion to a mounting member. 
         FIG. 3  is a diagrammatic illustration showing an exploded view of the printhead assembly illustrated in  FIG. 2 . 
         FIG. 4  is a diagrammatic illustration showing a partial fragmentary view of the printhead assembly illustrated in  FIG. 3 . 
         FIG. 5  is a diagrammatic illustration showing an enlarged view of the dial or adjustment member illustrated in  FIG. 3 . 
         FIG. 6  is a diagrammatic illustration showing a cross-section view of the printhead assembly illustrated in  FIG. 3  relative to an underlying platen roller. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatuses and methods disclosed in this document are described in detail by way of examples and with reference to the figures. Unless otherwise specified, like numbers in the figures indicate references to the same, similar, or corresponding elements throughout the figures. It will be appreciated that modifications to disclosed and described examples, arrangements, configurations, components, elements, apparatuses, methods, materials, etc. can be made and may be desired for a specific application. In this disclosure, any identification of specific shapes, materials, techniques, arrangements, etc. are either related to a specific example presented or are merely a general description of such a shape, material, technique, arrangement, etc. Identifications of specific details or examples are not intended to be, and should not be, construed as mandatory or limiting unless specifically designated as such. Selected examples of apparatuses and methods are hereinafter disclosed and described in detail with reference made to FIGURES. 
     For clarity and simplicity, the present specification shall refer to structural and/or functional elements, relevant standards and/or protocols, and other components that are commonly known in the art without further detailed explanation as to their configuration or operation except to the extent they have been modified or altered in accordance with and/or to accommodate the preferred embodiment(s) presented herein. 
     With reference now to  FIGS. 1 and 2 , there is shown an edge justified thermal printer generally indicated at  40  having a two piece housing  41  pivotally joined together at hinges  43 . The housing  41  in one embodiment has more than two pieces. The printer  40  also includes a frame  44  to which the housing  41  is mounted. A roll of label stock or other suitable print media (not shown) is held by the media supply roll mounting assembly  50  mounted on a vertical wall  71  of the frame  44 . For example, the label stock may include a series of individual labels or record members releasably adhered via a pressure sensitive adhesive or the like to a release liner or similar continuous web of material. In any event, the print media is supplied from the roll held by the media supply roll mounting assembly  50  to a thermal printhead  69  (see  FIG. 3 ) for marking thereby. Suitably, the media supply roll mounting assembly  50  provides the print media, or the media is otherwise routed to the printhead  69 , in an edge justified manner, i.e., so that the print media aligns with and/or along one of two opposite ends or edges of the printhead  69 . For example, in the illustrated embodiment, the media aligns with or along the left or inboard end or edge  69 ′ of the printhead  69 . 
       FIG. 2  also shows: an ink ribbon supply spindle  53  for holding a roll of thermal ink ribbon (not shown) from which the ribbon is supplied to the printhead  69 ; and, an ink ribbon take-up spindle  55  for receiving and holding a roll of the spent or used ink ribbon.  FIG. 2  further shows a selectively pivotable mounting member  56  to which the spindles  53  and  55  are mounted in a cantilevered fashion. Further, a printhead assembly  70  containing the printhead  69  is also mounted in a cantilevered fashion to the mounting member  56 . As shown, the selectively pivotable mounting member  56  is positioned upright or vertically, i.e., in the operating position. To facilitate loading and/or threading of the print media and/or ink ribbon between the printhead  69  and a cooperating platen roller  63  (see  FIG. 6 ), the mounting member  56  is selectively tilted back from the upright position thereby raising the cantilevered printhead assembly  70  away from the platen roller  63 . 
     As can be appreciated, suitably the print media is routed and/or guided along a path from the roll carried by the media supply roll mounting assembly  50  to the printhead assembly  70  where it passes (along with an optional ink ribbon from the ink ribbon supply spindle  53 ) between the thermal printhead  69  of the printhead assembly  70  and the cooperating platen roller  63 . 
     With reference now to  FIGS. 3 through 6 , the printhead assembly  70  is mounted via a printhead housing or bracket  59  to the mounting member  56  in cantilevered fashion. The bracket  59  has a plurality of spaced studs  276  which are snugly received in holes or mated recesses (not shown) in the mounting member  56 . The present invention contemplates that more than one bracket may be used to secure the printhead assembly  70  to the mounting member. The bracket  59  has a recess  278  with a rounded projection or pivot edge  279  disposed in the recess  278 . The recess  278  is disposed approximately midway along the width of the bracket  59 . The free end portion  280 ′ of the bracket  59 , which is opposite to end portion  280 , has a latch member  281  which cooperates with a latch member  325  (see  FIG. 2 ) to selectively hold the printhead assembly  70  and the mounting member  56  in the closed or operating position. With particular reference to  FIG. 4 , the bracket  59  has a socket  282  in lateral alignment with the laterally extending projection  279 . The socket  282  receives a ball-shaped member  283  which is secured to a metal mounting member  284  by a screw  285 . The mounting member  284  is generally U-shaped in construction and has a bight  286  and upstanding vertical walls  287  and  288 . The wall  287  has a hole  289  through which a pilot boss  283 ′ of ball-shaped member  283  extends. The wall  288  has a hole  290  laterally aligned with the hole  289  through which a screw driver can be inserted to tighten or loosen the screw  285 . The wall  288  has a bent over tab or flange  291  received in the recess  278 . The underside of the flange  291  contacts the projection  279 . The mounting member  284  is capable of rocking or canting in a vertical plane about the projection  279  where contact is made with the flange  291  and about the place where the socket or pocket  282  receives the ball-shaped member  283 . The mounting member  284  can also adjust in a horizontal plane as the mounting member  56  is moved from its open position to the closed position. In particular, the mounting member  284  has a pair of depending forked locating members  292  each of which has parallel guide walls  293  for receiving and locating on bearings  134  (see  FIG. 6 ) which rotatably support the platen roller  63 . In this way the mounting member  284  and, indeed, the printhead  69  are accurately located in or near parallel with respect to the axis of the platen roller  63 . 
     A pair of pressure adjusting devices  294  are used to adjust the forces exerted and/or pressure applied from the bracket  59  against the mounting member  284  and in turn which the printhead  69  exerts against the print media and/or the platen roller  63 . In one embodiment a single adjusting device may be utilized  297 . In another embodiment a plurality of adjusting devices  294  are utilized. The adjusting devices  294  each include a dial or adjusting member  295  having a slot  296  and a spring  297  which bears against the upper surface of the bight portion  286 . The projection  279  and the ball-shaped member  283  are preferably located midway between the places where the springs  297  contact the bight portion  286 . 
     The printhead  69  is mounted on the underside of a printhead support plate  298 . The support plate  298  further comprises an upperside (not shown). The plate  298  is preferably constructed of metal such as aluminum and acts as a heat sink. The bight portion  286  has integrally formed depending projections or dimples  299  and  299 ′ received in holes  300  and  300 ′ in the plate  298 . The hole  300 ′ is an elongate slot which extends widthwise of the plate  298 . A connector  301  is secured to the plate  298  by screws  302  passing through holes  303  and threadably received in holes  304  in the plate  298 . The connector  301  is received in a hole or opening  305  in the bight portion  286 . The connector  301  has a perimeter having a plurality of openings around the perimeter and is flexible, resilient, manually deflectable, upstanding spring fingers  306  with projections  307 . The spring fingers  306  extend through the hole  305 . The projections  307  rest on upper edge  287 ′ of the wall  287  and upper portions of the spring fingers  306 , extend through holes  308  located in a recess  309  in the upper surface of the bracket  59 . The spring fingers  306  are manually engageable and when moved to the left or forward as seen in  FIG. 3 , the projections  307  release from the edge  287 ′. Upstanding rigid fingers  306 ′ fit against the outside of the flange or wall  287 . Thus, the wall  287  is straddled by the two spring fingers  306  and by the two rigid fingers  306 ′. As is apparent there is a snap-fit connection to hold the printhead  69 , the plate  298  and the connector  301  to the mounting member  284 . The connector  301  tapers slightly inwardly and upwardly as viewed in  FIG. 3  which allows the connector  301  to be easily inserted into the opening  305 . When the connector  301  is fully inserted into the opening  305 , the connector  301  makes a snug fit with the side edges of the opening  305 . Thus, it is readily apparent that the printhead  69 , the plate  298 , the connector  301  and the mounting member  284  move as a unit on the support  59 . The locating members  292  are guided into place on the bearing  134  as the printhead assembly  70  is moved into its closed or operating position. The aforementioned unit can then gimbal in the horizontal and vertical planes with respect to the support  59 . The bracket  248  and the connector  301  in their assembled condition, are held to the bracket  59  against the forces of the springs  297  by the flange  291  and the ball shaped member  283 . However, when the printhead assembly  70  is brought into the closed or operating position and the forked members  292  are guided by the bearings  134 , the springs  297  compress and the printhead  69  substantially aligns with the axis of the platen roller  63 . 
     As illustrated in  FIG. 5 , each adjusting member  295  is received in an axial bore  310  in the bracket  59 . The adjusting member  295  has a cored out axially extending, right-circular cylindrical body  311  and an outer annular ring or member  312  with a pair of diametrically opposed depending arcuate members, also referred to as a plurality of longitudinal extension  316 . The members  312  receive a portion of the length of the springs  297 . Each spring  297  abuts a lower edge of the respective body  311  within the cored out cylinder. Upper outside ridges or shelves of the members  312  act as cam surfaces  314 . For example, the cam surfaces  314  may define different level settings which progressively increase or decrease in height around the circumference of the body  311 . Suitably, at each preset level, the cam surface  314  may include a depression or recess for holding or retaining a cam follower therein. Suitably, each cam surface  314  may include two or more different preset levels. In one embodiment, each cam surface includes at least four different preset levels. 
     Suitably, each bore  310  has at least one inwardly projecting cam follower (not shown) which rides on and/or otherwise cooperates with the corresponding cam surfaces  314 . Optionally, each bore may include a pair of such cam followers which are located on diametrically opposed sides of the bore  310  and each cam surface  314  may be duplicated on diametrically opposed sides of the dial or adjusting member  295 . For example, the cam followers may be integrally formed with the bracket  59  on the inside surface of each bore  310 . Accordingly, each dial or adjusting member  295  is selectively located in the bore  310  at one of a plurality of different preset depths depending on the rotational position of the member  295  and hence the location at which the cam followers abut their corresponding cam surfaces  314 . 
     Depending on the depth at which each member  295  is located in its respective bore  310 , the corresponding spring  297  may be compressed more or less between the body  311  of each adjusting member  295  and the upper surface of the bight  286 , and hence, more or less pressure respectively may be applied to the corresponding end of the printhead  69 . For example, in one position (as shown by the outboard or right adjusting member  295  in  FIG. 6 ), the adjusting member  295  is located relatively deeper in the bore  310 , thereby causing the underlying spring  297  to exert a higher force against the bight portion  286  and according a higher pressure is applied to the corresponding end of the printhead  69 . Conversely, in another position (as shown by the left or inboard adjusting member  295  in  FIG. 6 ), the adjusting member  295  is located relatively higher in the bore  310 , thereby causing the underlying spring  297  to exert a lower force against the bight portion  286  and accordingly a lower pressure is applied to the corresponding end of the printhead  69 . 
     Suitably, adjustments are selectively made by inserting a coin or a screw driver in the slot  296  to turn the corresponding dial or adjusting member  295  to the desired preset level. By rotating the members  295  until the corresponding cam followers abut or rest on a given preset level of the cam surfaces  314 , as the case may be, the spring force adjustments are made. In this manner, adjustments can be selectively made to accommodate print media of different thicknesses and/or widths. For wider print media, for example, four inches in width or sufficiently close to the full width of the printhead  69 , relatively higher force is generally desired and thus the members  295  may be set relatively deeper in the bores  310 . For narrower print media, for example, two inches in width or sufficiently less than the width of the printhead  69 , relatively lower force is generally desire and thus the members  295  may be set relatively higher in the bores  310 . 
     As seen, the adjusting devices  294  are individually adjustable and there are a plurality of registration marks (e.g., such as marks  321  and  322 ) on the bracket  59  around the bores  310  to show at which preset level each adjusting device  294  is set. During use of the printer  40 , depending on the width of the print media, suitably the adjusting members  295  are set so that the springs  297  will exert unequal spring forces against the bight portion  286  and hence uneven pressure will be applied across the width of the printhead  69 . Alternately, again depending on the width of the print media, the adjusting members  295  may be set so that the springs  297  will exert substantially equal spring forces against the bight portion  286  and hence even pressure will be applied across the width of the printhead  69 . 
     For example, assuming that the print media is justified or aligned under the left end or inboard edge of the printhead  69 , when using a narrower width print media (e.g., two inches or sufficiently less than the width of the printhead  69 ), suitably the spring force exerted by the right or outboard adjusting device  294  is set relatively lower than the spring force exerted by the left or inboard adjusting device  294 , and hence, the pressure applied to the right or outboard end of the printhead  69  is relatively lower than the pressure applied to the left or inboard end of the printhead  69 . Alternately, assuming again that the print media is still justified or aligned under the left end or inboard edge of the printerhead  69 , when using a wider width print media (e.g., four inches or sufficiently close to the full width of the printhead  69 ), suitably the spring force exerted by the right or outboard adjusting device  294  is set substantially equal to the spring force exerted by the left or inboard adjusting device  294 , and hence, the pressure applied to the right or outboard end of the printhead  69  is substantially equal to the pressure applied to the left or inboard end of the printhead  69 . 
     In one suitable embodiment, each cam surface  314  is substantially continuous around the circumference of the cylindrical body  311  and the dial or adjusting member  295  is free to rotate 360 degrees or greater within the bore  310 . While rotating the dial or member  295 , to help eliminate or alleviate resistance which would otherwise be experienced due to the cam follower meeting a steep or substantially vertical incline on the cam surface  314 , a user may optionally apply a downward force on the dial or member  295  to overcome the back pressure of the underlying spring  297  and hence permit the cam follower to more easily ride or pass over the incline. 
     In any event, it is to be appreciated that in connection with the particular exemplary embodiment(s) presented herein certain structural and/or function features are described as being incorporated in defined elements and/or components. However, it is contemplated that these features may, to the same or similar benefit, also likewise be incorporated in other elements and/or components where appropriate. It is also to be appreciated that different aspects of the exemplary embodiments may be selectively employed as appropriate to achieve other alternate embodiments suited for desired applications, the other alternate embodiments thereby realizing the respective advantages of the aspects incorporated therein. 
     It is also to be appreciated that certain elements described herein as incorporated together may under suitable circumstances be stand-alone elements or otherwise divided. Similarly, a plurality of particular functions described as being carried out by one particular element may be carried out by a plurality of distinct elements acting independently to carry out individual functions, or certain individual functions may be split-up and carried out by a plurality of distinct elements acting in concert. Alternately, some elements or components otherwise described and/or shown herein as distinct from one another may be physically or functionally combined where appropriate. 
     In short, the present specification has been set forth with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the present specification. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. 
     It will thus be seen according to the present invention a highly advantageous. adjustment mechanism for an adjustment mechanism has been provided. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it will be apparent to those of ordinary skill in the art that the invention is not to be limited to the disclosed embodiment, and that many modifications and equivalent arrangements may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims so as to encompass all equivalent structures and products. 
     The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of their invention as it pertains to any apparatus, system, method or article not materially departing from but outside the literal scope of the invention as set out in the following claims.