Abstract:
A compact ribbon cassette for dispensing and storing a ribbon or tape. The supply and take-up rolls of ribbon or tape are disposed upon a common rotatable shaft mounted for rotation within the housing. A unique chevron disposed adjacent the take-up roll and on the post-printing portion of the cassette causes the dispensed ribbon to reverse direction and change level and be presented for storage upon the take-up roll. The supply roll is under tension because a plurality of spring fingers push against a friction plate, thereby pressing the supply roll against an inner partition plate. The ribbon moves straight off the supply roll without bunching. A spring-loaded ribbon tensioner reduces slack in the ribbon by applying tension to the ribbon.

Description:
RELATED PATENT APPLICATION 
     This application is a continuation-in-part of the copending parent U.S. patent application Ser. No. 09/130,598, filed Aug. 7, 1998, entitled COMPACT RIBBON CASSETTE. The teachings of the parent application are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to ribbon cassettes for storing and dispensing ribbon tapes and, more particularly, to an improved ribbon cassette containing a printing ribbon that is both dispensed from and stored upon a common rotative shaft. A ribbon level change chevron is located on the post-printing portion of the cassette to eliminate ink contamination during printing of the MICR characters. The ribbon is sandwiched between an inner partition and friction plate, disposed between the cassette housing and supply roll. The set of spring fingers interacting with the friction plate provides tension to the ribbon supply roll, pushing it firmly against the inner partition plate. Tension is also provided on the pre-printed ribbon by a dancer arm located proximate the bottom of the supply roll. 
     BACKGROUND OF THE INVENTION 
     In the field of modern Point-of-Sale (POS) transaction printers, the objective is to provide simple, compact machines that are easy both to operate and to load. Axiohm Corporation, the assignee of the present invention, has pioneered the use of drop-loading paper supply rolls and clamshell receipt printers. 
     To save space and to provide faster transaction processing times for customers, many operations heretofore performed on separate pieces of equipment or performed after the actual sales transaction, have been combined into the POS transaction printer. One such feature permits encoding Magnetic Ink Character Recognition (MICR) symbols onto the Amount field of a customer&#39;s check presented in payment for goods or services. MICR encoding requires a high-quality, specialized printer ribbon incorporating magnetic particles which, after deposition on the check, allow magnetization and subsequent reading of the MICR characters. 
     In order to save space and provide easier ribbon loading in the MICR printing devices, the invention of the aforementioned co-pending U.S. patent application Ser. No. 09/130,598, proposed to provide a cassette containing a MICR printing ribbon that is both dispensed and stored upon a common rotative shaft. The compact ribbon cassette replaced cassettes having spaced-apart, individual dispensing and storage rolls that divided the dispensing and storage functions. 
     The aforementioned, prior application described a new style of ribbon cassette for POS printers incorporating a MICR encoder, that vertically stacked the supply roll upon the take-up roll. The supply and take-up rolls were supported upon a common shaft that was rotatively supported within the cassette housing. 
     The ribbon cassette had a cover plate that contained integrally formed leaf springs designed to bear upon a friction plate disposed over the wound supply-ribbon spool. These leaf springs provided biasing against the friction plate, which in turn caused frictional loading of the wound supply ribbon. The friction exerted upon the supply ribbon by the friction plate maintained a tension upon the supply roll of ribbon, so that the ribbon was kept taught as it was dispensed from the supply roll. This eliminated loosely formed intervals in the ribbon as it was dispensed. 
     A uniquely formed chevron, disposed adjacent the supply and take-up rolls, allowed for the ribbon direction to be reversed from the supply roll to the take-up roll and shifted the level of the ribbon from the lower supply spool to the upper take-up spool. Each roll was rotated in a counter-clockwise direction, wherein the ribbon was dispensed from the lower, supply roll, then reversed direction, and was then wound upon the upper, take-up roll. 
     It has been discovered that the MICR printing ribbon that glides over the ribbon level changing chevron becomes wiped of its ink, especially near the edges of the ribbon. The wiped ink may be deposited upon the chevron, and may eventually flake off. These flaked ink particles can be randomly deposited upon the print line near the MICR characters, thereby causing MICR read errors. 
     The present invention reflects the discovery that changing the cassette construction reduces or eliminates the possibility of flaked magnetic ink being deposited upon the printed MICR line. The improved cassette now features a chevron that is located in the post-printing portion of the cassette. Now, if any flaking occurs upon the chevron, it does so after the ribbon has passed through the print window. Therefore, the flaking becomes inconsequential with respect to the printed MICR character quality. However, the flaked ink particles must still be prevented from migrating across the cassette from the post-printing portion to the pre-printing portion. In order to prevent this migration, the pre-printing portion of the cassette is constructed so as to form a sealed chamber. This sealed chamber is created by a plastic partition disposed between the post-printing portion and pre-printing portion of the cassette. 
     As a further precaution against migrating ink particles, the newly designed cassette also contains a wiper pad to remove any stray ink particles from the ribbon before they and it enter the print window. 
     To provide substantially constant tension on the ribbon, spring fingers are molded into the ribbon cassette housing. The spring fingers, acting co-operatively with a friction plate, impose a drag on the supply ribbon pack. The spring fingers and friction plate cause the drag to remain constant, whether the supply spool is full or nearly empty. In addition, a spring-loaded idler roller located adjacent to the supply ribbon spool helps maintain proper ribbon tension as the MICR printing platen is opened and closed. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a ribbon cassette for supplying a printing ribbon for printing MICR characters in a POS transaction printer. The ribbon cassette is constructed with both a supply roll and a take-up roll integrally formed and supported about a common, rotatable shaft. The rotatable shaft is rotatively mounted in the cassette housing. The supply roll and the take-up roll rotate in the same direction about the rotative shaft, but at varying speeds with respect to each other. 
     A uniquely formed chevron, located on the post-printing portion of the cassette, allows for the ribbon direction to be reversed and the level of the ribbon changed. The level change is necessary in order for the supply roll and take-up roll to be compatibly disposed co-axially for rotation upon the common shaft. On the post-printing portion of the cassette, any flaking that occurs upon the level changing chevron will be of minimal consequence, because the ribbon has already been expended in the MICR encoding operation. The flaked ink particles, however, are prevented from migrating across the cassette, from the post-printing portion to the pre-printing portion, by a partition that seals the storage chamber. 
     The partition is disposed between the post-printing portion and the pre-printing portion of the cassette. This partition, along with the friction plate, in cooperation with the spring fingers, provide a predetermined tension on the supply roll. The ribbon moves straight off the supply roll. To prevent slack in the ribbon, a novel spring-loaded ribbon tensioning roller is incorporated into the design of the present invention. A wiper pad disposed adjacent the ribbon entering the print window, effectively removes any stray ink particles that may have found their way to the pre-printing portion. 
     It is an object of the invention to provide an improved ribbon cassette. 
     It is another object of this invention to provide a ribbon cassette that has a partition between supply and take-up rolls that are arranged about a common rotative shaft. 
     It is a further object of the invention to provide a ribbon cassette, the ribbon level change chevron of which is located within the ribbon storage chamber. 
     It is still another object of this invention to provide a plurality of spring fingers that act on a friction plate, exerting tension on a ribbon supply roll, thereby pushing it up against an inner partition. 
     It is yet another object of this invention to incorporate a spring-loaded ribbon tensioning roller to reduce slack in the ribbon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description, in which: 
     FIG. 1 illustrates a schematic, perspective, exploded, frontal view of the improved ribbon cassette of this invention; 
     FIG. 2 depicts a schematic, plan view of the ribbon cassette, shown in FIG. 1; 
     FIG. 3 shows a schematic, cut-away view of the ribbon cassette, illustrated in FIG. 2; and 
     FIG. 4 is a flow chart of the path of travel of the ribbon. 
     For purposes of brevity and clarity, like elements and components will bear the same numbering and designations throughout the figures. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Generally speaking, the invention comprises a compact ribbon cassette for dispensing and storing a ribbon or tape upon co-axial, integrally formed supply and take-up rolls. The supply and take-up rolls are disposed upon a common rotatable shaft mounted for rotation within the housing. A unique chevron contained within the storage compartment causes the dispensed ribbon to change levels and to reverse direction and be presented for storage upon the take-up roll. 
     Now referring to FIGS. 1, 2 and 3, the ribbon cassette 10 of this invention is illustrated in various views, including an exploded, perspective view. The ribbon cassette 10 comprises a housing 12 having a cover 14. A supply roll 16 has a print ribbon 18 wound thereupon, forming a pancake assembly. The supply roll 16 is free to rotate upon a take-up roll 15a. 
     Supply pancake assembly 16 comprises a core 16a and the ribbon 18, and is located immediately below a partitioning plate 6 and a take-up spool 15. Pancake assembly 16 has an inner diameter with a spline 16a&#39; that mates with roll 15a, which is mounted on rotatable shaft 20. The spline 16a&#39; is used in conjunction with appropriate constraining devices, not shown, to prevent rotation during shipping and handling. To prevent adhesive from migrating or oozing from the interface between core 16a and ribbon 18, a paper washer or other suitable low friction material, not shown, can be placed on both sides of the pancake assembly 16. A friction plate 26 with a protrusion 26a also prevents rotation of the pancake assembly 16 relative to the housing 12 both during shipping and during operation of the printer and cassette 10. 
     The take-up spool 15 stores the ribbon 18 dispensed from the supply roll 16, allowing the ribbon 18 to wind thereupon, as shown in FIG. 3. The supply roll 16 and take-up spool 15 are mounted upon take-up roll 15a (FIG. 1). The cover 14 is affixed to the housing 12, through which the take-up roll 15a is disposed. The thin-walled partitioning plate 6 is disposed between the supply roll 16 and the take-up spool 15. The partitioning plate 6 prevents any ink particles, not shown, that flake off a ribbon reversing chevron 5 (to be described hereinafter) from entering the upper cavity 23 containing the take-up roll 15a. 
     The partitioning plate 6 comprises detents 46 and 48 which snap into apertures, not shown, in the housing 12 or inner wall 74 in aperture 76. The supply roll 16 is biased against the partitioning plate 6 by the spring fingers 47 acting on friction plate 26. The spring fingers 47 apply a predetermined amount of force on the friction plate 26, thereby, causing the friction plate 26 to exert tension or drag on the supply roll 16, pushing the supply roll 16 up against the partitioning plate 6. This novel construction exerts the appropriate amount of force on the supply roll 16 to maintain uniform pre-printing tension on the ribbon 18, thereby assuring optimum tension for good print quality. The spring fingers 47 provide a constant force on the ribbon supply roll 16, independent of the amount of ribbon 18 remaining on supply roll 16. 
     Tension is also applied to the pre-printing portion of ribbon 18 by a ribbon tensioning roller 52 on tensioning arm 72. Ribbon tensioning arm 72 is disposed below the supply roll 16 and is anchored at point 70 to inner wall 74 of housing 12, thereby allowing the ribbon tensioning arm 72 to flex. This removes any post-printing slack in the ribbon 18 caused by movement of the printhead (not shown) away from the print platen (not shown). 
     A lower right pivot pin 50 is operatively connected to the ribbon tensioning arm 72. Roller 52 is rotatively attached to the lower right pivot pin 50. When the ribbon 18 moves off the supply roll 16 and around the lower right roller 52, the ribbon 18 exerts an upward force on the ribbon tensioning arm 72. The ribbon tensioning arm 72, by design, exerts a counteracting, downward force on the ribbon 18 looped around the lower right roller 52, thereby reducing slack in the ribbon 18 when the MICR printhead, not shown, is retracted. 
     The printing ribbon 18 is fed past (arrow 19) the printing window 11 into a lower storage cavity 21. A chevron 5, disposed in lower storage cavity 21, adjacent the take-up roll 15a, reverses the direction and the level of the printing ribbon 18, as previously described in the aforementioned parent patent application. The ribbon 18 rides over the lower diagonal surface 32, and is then guided over the upper diagonal surface 22 of chevron 5. In so traversing the lower and upper surfaces 32, 22 of the chevron 5, the ribbon 18 is caused to reverse direction and change level. The reversed, level-shifted printing ribbon 18 is now fed (arrow 36) between locating flanges 35 of take-up spool 15, as shown in FIGS. 1 and 3. 
     The chevron 5 is affixed between the cover 14 and the housing 12, by means of upper and lower tenons 38 and 40, respectively. The upper tenon 38 fits into mortise 42 in the cover 14; the lower tenon 40 fits into a similar mortise (not shown) in the housing 12. 
     The used ribbon 18 is guided to the take-up spool 15 through two meshing gears 37 and 37&#39;. Gear 37 mates with an external gear 37&#39; to provide positive ribbon drive. These meshing gears positively capture the used ribbon 18, thus causing the ribbon 18 to be positively advanced without slippage along its passage through the cassette 10 to the take-up spool 15. 
     A felt wiper pad 27 (FIG. 2) is disposed within the slots of abutments 28 and 29. The advancing print ribbon 18 is guided past the wiper pad 27 in order to remove any extraneous ink particles from the ribbon 18 prior to its transit past print window 11. 
     Now referring also to FIG. 4, the path of travel of the ribbon 18 is described in detail. The ribbon 18 first winds off the supply roll 16 in a clockwise direction, step 100. The ribbon next moves around the lower right roller 52, rotatively connected to the lower right pivot pin 50. Then the ribbon 18 moves towards the upper right roller 54, rotatively connected to the upper right support shaft 56, step 102. Next, the ribbon 18 moves past the print window 11, step 104. After passing across the print window 11, the ribbon 18 moves around the upper left roller 60, rotatively connected to the upper left support shaft 58, down past the gear 37, and along the front surface 68 of the chevron 5, step 106. Now, the ribbon 18 moves around the lower diagonal surface 32 to the back surface 64 until it reaches the upper diagonal surface 22, step 108, and then proceeds up the front surface 68 of the chevron 5 towards the left roller 66, rotatively connected to the left support shaft 52, step 110. From this point, the ribbon 18 moves onto the take-up spool 15 and winds in a clockwise direction thereon, step 112. 
     Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 
     Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.