HIGH-SYMBOL DENSITY PRINTER CARTRIDGE

Abstract: A shuttle matrix printer cartridge has a housing for storing the ribbon (R), an exit arm (16), an entrance arm (18) spaced from the exit arm and a drive mechanism (22) for removing ribbon (R) from the storage chamber (14) through the exit arm (16) into position for printing between a printhead and a substrate and reentry into the cartridge through the entrance arm (18). The entrance arm (18) is flexible in the plane of the cartridge toward and away from the exit arm (16) to facilitate changes in ribbon drag produced during high dot density printing. The cartridge has three spacer legs (70, 88, 180) along its underside for supporting the cartridge on the printer platform (76) in use. Additionally, a post engages a recess in the exit arm to maintain the latter arm rigid during use, while such post, in conjunction with a drive shaft carried by the printer and received in a cartridge drive wheel, positions the cartridge in the printer against lateral movement. A shield (52) is disposed between the drive gears and nip rollers in the drive mechanism to prevent ensnarlment of the ribbon in the drive gears.

Description: BACKGROUND OF THE INVENTION The invention relates to inked ribbon cartridges, and particularly to cartridges for use on printers, such as shuttle matrix printers. Such cartridges are used for storing printing ribbon, such as inked fabric, carbon film, etc. within a storage chamber and from which chamber it may be withdrawn for printing. The invention also relates to a ribbon cartridge constructed to enable control of the position of the ribbon with respect to the print line to accommodate changes in ribbon drag produced during high dot density printing, to facilitate positioning of the cartridge in printing position, and to facilitate ribbon feed into the storage chamber without interference between the ribbon storage mechanism and the ribbon. In high-speed shuttle matrix printer cartridges, ribbon is passed into the nip between a drive roller and driven roller enroute to a storage chamber. Strippers are used to play the ribbon emerging from the nip back and forth between opposite sides of the cartridge storage chamber to provide substantially uniform folds of ribbon throughout the extent of the storage chamber. The drive roller and driven roller also cause the ribbon to be removed from the storage chamber along an exit arm for disposition in a print position for coaction with a printhead having print wires or styli to produce a series of printing dots on the substrate. The ribbon is continuously moved by the drive and driven rollers through the print position and by way of an entrance arm back to the storage chamber. One of the principal problems associated with printers of this type, particularly printers employing a high-speed shuttle matrix printer cartridge, is the capacity to accommodate the changes in ribbon drag caused by the interaction of the print wires and ribbon during high dot density printing when the print wires tend to brake or restrain ribbon movement. When the print wires or styli on the moving printhead impact the ribbon, they instantaneously brake the ribbon movement. As the print density, i.e., dots per inch, increases, this braking action may reach excessive proportions. With a relatively rigid entrance arm, and with the printhead moving in a direction opposite to the direction of movement of the ribbon, the braking or restraining action of the printhead on the ribbon causes the rotating drive wheels to increase the tension on the ribbon. This can cause the ribbon to skew out of alignment and, in an extreme case, cause the ribbon in contact with the print wires to be scraped, punctured or torn. Additionally, the stoppage of the ribbon caused by the interaction of the printhead with the ribbon results in the ribbon slipping on the drive wheel. This adversely affects the tracking of the ribbon into the cartridge, resulting in ribbon creasing, foldover, and twisting or causes the ribbon to be displaced in its own plane up or down the ribbon entrance arm. Twisting of the ribbon also causes the ribbon to track up or down relative to the line of print wires. This results in undesirable folding or wrinkling at the port of the entrance arm, and movement of the ribbon out of the wire printing range. This can lead to a derogation of print performance and ultimately to a failure of the printer to print at all. When the ribbon is snagged or momentarily braked, and the printhead is moving in the direction of the ribbon flow, the printhead assists in advancing the ribbon more rapidly than the advance thereof caused by the drive wheels. This causes an excessive amount of ribbon to be pulled out of the ribbon cartridge and a slack in the ribbon between the printhead and the entrance nip of the drive rollers. This action causes similar results as stated above and may jam the ribbon in the cartridge. It will be appreciated that the printhead moves rapidly back and forth along the print line. The adverse results caused by the interaction of the print wires and the ribbon and the back-and-forth movement of the printhead relative to the unidirectional movement of the ribbon quickly multiply. This results in improper ribbon flow, adversely affecting print quality, and causes damage to the ribbon and the print wires. Accurate positioning and orientation of the cartridge in the printer is likewise essential for repeated quality printing. In solving the above-identified problems associated with the interaction of the printhead and the ribbon, it is essential that the cartridge at the same time be readily and easily mounted in the printer in proper position and orientation to address the banks of print wires to achieve effective quality printing. Additionally, in those cartridges which employ a drive mechanism for folding ribbon into the storage chamber, there is the tendency, particularly as a result of the above-noted interaction between the printhead and ribbon, for the ribbon to track in the cartridge storage mechanism differently than in its designed track. Often, this locates the ribbon in the drive mechanism per se . Thus, the ribbon may become entangled in its own drive mechanism, causing a complete breakdown of the ribbon flow from the storage chamber into print position and return. It is therefore essential that the ribbon be maintained free and clear of the drive mechanism per se . IBM Technical Disclosure Bulletin, Vol. 27, No. 10B, March 1985, NEW YORK, pages 6356-6357 discloses a ribbon cartridge having self-induced take-up motion. The cartridge comprises a ribbon exit arm and an entrance arm which guide a print ribbon therebetween. One of the arms, the exit arm, is spring-biased. SUMMARY OF THE INVENTION The invention relates to a printer cartridge for carrying a print ribbon for disposition in a print position between a printhead and a print recording medium and including a housing defining a storage chamber for the ribbon; spaced apart ribbon exit and entrance arms extending from said housing for routing the ribbon from the storage chamber along said exit arm into the print position located in the span between said arms and from the print position along said entrance arm to the storage chamber and means for moving the ribbon into said storage chamber thereby displacing the ribbon from the exit arm through the print position and along the entrance arm, said entrance arm comprising a ribbon guide proximate its end remote from said storage chamber for guiding ribbon from said span to said entrance arm, characterized by: a means for minimizing adverse loading on said ribbon during high density printing including forming the entrance arm to flex along the direction of ribbon movement in said span during such high density printing while maintaining the ribbon guide perpendicular to said ribbon movement. Thus, an exemplary ribbon entrance arm embodiment is constructed and dimensioned to enable an angular flexing movement of the end of the arm in the plane and along the direction of the ribbon travel and without substantial rotational or twisting movement of the arm about its linear axis. In one exemplary embodiment, the ribbon entrance arm is provided with cutouts or voids in its upper and lower surfaces dimensioned and configured to permit flexing movement substantially only in the plane of the cartridge. Other embodiments may include relative dimensioning of the walls of the arm both in thickness and in breadth to depth, etc. When the cartridge is mounted in a printer, the entrance arm is relatively free for flexing movement, e.g., such that its entrance port is movable generally toward and away from the opposite exit arm in the plane of the cartridge. By rendering the entrance arm flexible in this plane and by also providing a relatively rigid exit arm for the ribbon, tracking of the ribbon in the cartridge is more accurately and repeatedly maintained substantially without creasing, foldover or twisting or causing the ribbon to track up and down the arms, thereby avoiding the previously stated deleterious effects. To facilitate mounting of the cartridge in the printer, the cartridge may be provided with three spacer legs. One of the legs may constitute a projection along the underside of the ribbon exit arm and in which projection the recess for the mounting post is formed. A second projection along the underside of the cartridge is provided on the flexible entrance arm. A third mounting projection is located on the opposite side of the cartridge, specifically proximate the center of mass of the cartridge and as far as possible from the first and second spacer projections. While it might be preferable to mount this third projection along a transverse line passing through the center of mass of the cartridge and normal to a line interconnecting the first and second projections, to further balance the cartridge, the third projection may be located at the furthest distance from the first and second projections and spaced from the normal line passing through the center of mass. To properly position and orient the cartridge in the printer and to provide an interconnection between a printer drive mechanism and the cartridge drive rollers, the cartridge may have, along its underside, a female receptacle for receiving the splined drive shaft on the printer. Consequently, positioning of the cartridge in a horizontal plane containing the cartridge and the direction of ribbon drive, may be achieved solely by the printer mounting post and spline connection with the cartridge, i.e., a two-point location is provided. The underside of the cartridge also may have a protruding annular rim which mates with a recessed ring on the platform of the printer receiving the cartridge. The rim does not, however, bottom on the platform. The protruding rim and recessed ring of the cartridge and printer platform, respectively, facilitate centering the driveshaft carried by the printer in the female splined cartridge recess and also minimize oscillation of the cartridge during printing without the rim bottoming on the recessed ring. A high-speed shuttle matrix printer cartridge carrying a print ribbon for disposition in a print position between a printhead and a print recording medium, may include a housing defining a storage chamber for the ribbon, a means (e.g., including exit and entrance arms spaced one from the other and projecting from the housing) for routing the ribbon from the storage chamber along the exit arm into the print position and from the print position along the entrance arm to the storage chamber. Means may also be provided for moving the ribbon into the storage chamber, thereby displacing the ribbon from the exit arm through the print position and along the entrance arm, one of the arms being movable in a plane generally containing the arms in response to changes in ribbon tension produced during printing. Preferably, the movable arm constitutes the entrance arm which has side, upper and lower walls for confining the ribbon therebetween, each of the upper and lower walls having openings therethrough enabling the entrance arm to flex in the plane of the cartridge without twisting. In another preferred embodiment, a ribbon cartridge for attachment to a printer may include a housing defining a ribbon drive and ribbon storage chamber, a pair of spaced-apart arms extending from the cartridge for delivering a substantial span of ribbon from the cartridge via one arm to a print line established between the arms back to the cartridge via the other arm. One of the arms has a ribbon outlet from the cartridge and the other arm has a ribbon inlet to the cartridge. Means are provided for ensuring proper ribbon movement from the outlet arm to the inlet arm and relative to the established print line (e.g., the outlet arm is substantially rigid during ribbon movement when attached to the printer and the inlet arm is configured to be substantially flexible during ribbon movement when attached to the printer). Preferably, the inlet arm is dimensioned to flex substantially in the direction of ribbon movement and means are provided for restraining rotation of the inlet arm relative to the direction of ribbon movement during flexing. The ribbon cartridge also may include a housing defining a ribbon drive chamber and a ribbon storage chamber coupled to the drive chamber and having a smaller width than the drive chamber. In this case, a ribbon drive means may be mounted in the chamber and an inlet arm and an outlet arm extended from the cartridge for delivering a span of ribbon along the print line from the storage chamber and back into the drive chamber in response to an external force applied to the drive means. Means may be provided for maintaining proper ribbon movement in the span between the arms during printhead movement along the print line, including means for maintaining the outlet arm rigid with respect to the print line and the means for maintaining the inlet arm flexible along the direction of the print line without rotation relative to the direction of ribbon movement during flexing of the inlet arm. BRIEF DESCRIPTION OF THE DRAWING FIGURES The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one exemplary embodiment of the invention in which: Figures 1 and 2 are respective bottom and top perspective views of an exemplary ribbon cartridge embodiment constructed in accordance with the present invention; Figures 3 and 4 are respective top and bottom plan views with parts broken out of the ribbon cartridge illustrated in Figure 1; Figure 5 is a side elevational view of the cartridge taken generally about on line 5-5 in Figure 4; Figure 6 is an enlarged view similar to Figure 5 with parts broken out and in cross-section; Figure 7 is an enlarged bottom plan view of the cartridge of Figure 1 with the bottom housing plate removed, illustrating the drive mechanism and storage chamber for the ribbon; Figure 8 is an enlarged top plan view of the inked ribbon cartridge drive assembly forming part of the cartridge illustrated in Figure 1. DETAILED DESCRIPTION OF THE DRAWINGS FIGURES Reference will now be made in detail to the presently preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Generally, an ink ribbon cartridge assembly 10 is intended for use in a shuttle matrix impact printer (not shown except to the extent the printer mounting platform is illustrated in Figure 6). It includes a housing 12 (preferably formed of plastic material) having an elongated storage chamber 14, a laterally enlarged processing chamber 11, and exit (outlet) and entrance (inlet) arms 16 and 18, respectively, at opposite ends of assembly 10. Housing 12 also includes a body section 20 for receiving the inked ribbon cartridge drive assembly, generally designated 22 (Figures 8 and 9). Generally, a continuous inked ribbon R is stored in chamber 14 in multiple, approximately transversely extending uniform folds 24 (Figure 7) extending back and forth across chamber 14. Ribbon R is taken from chamber 14 through an exit slot 25 (Figure 7) and inverted 180° by a mobius loop inverter 110 (for example, as described in U.S. Patent No. 4,630,948). It is then passed about various posts and through exit arm 16 for registry with an impact printing mechanism I (e.g., a shuttle dot matrix printhead, protective cover, air ducts, etc. shown in dotted form in Figure 2), located between arms 16 and 18 and the ribbon R to print on a record medium or substrate M. After use, it is passed into entry arm 18 for return to storage chamber 14 under the action of drive assembly 22. Printing may take place along a print line PL on the medium along a line parallel or skewed with respect to ribbon direction of movement. This may be achieved, for example, by positioning the cartridge on the platform 76 to be at an oblique angle with respect to the print line. As disclosed in the related prior patent application, drive assembly 22 includes drive roller 30 (Figure 8) and driven roller 32. In brief, each of rollers 30 and 31 comprises tiered pinch rollers disposed about a common hub, for example, the pinch rollers 34 and 36 illustrated in Figure 9 for driven roller 32. Drive roller 30 (Figure 6) is suitably driven by a splined post 39 upstanding from the printer platform and which part is received, upon mounting the cartridge on the platform, in a correspondingly splined recess 31 along the underside of cartridge 10. Ribbon R (Figure 8) is therefore received within Processing Chamber II and routed through the nip between the pairs of pinch rollers for introduction into the storage chamber. The drive and driven rollers 30 and 32, respectively, have strippers 38 and 40, respectively, mounted for oscillation about pivot points 42 and 44. Strippers 38 and 40 are generally C-shaped and are mounted for oscillatory movement by rotation of cams 41 and 43, respectively. Thus, upon rotation of rollers 30 and 32, forwardly directed surfaces on the strippers oscillate between positions within and without the confines of the pinch rollers to play the ribbon back and forth between the edges of the storage chamber 14 as the ribbon is advanced. The rollers 30 and 32 are driven by drive wheels 50 and 48, which lie in mesh (one with the other) above the nip formed by the paired pinch rollers. In accordance with one aspect of the present invention, a floating shield 52 (Figure 10) is disposed between the drive wheels 48 and 50 and the uppermost rollers of the pairs of pinch rollers. As illustrated in Figure 10, shield 52 is formed of flat sheet material, preferably stainless steel, having a generally rectangular base portion 54, two semi-cylindrical cutouts 56 and 58 on opposite sides thereof defining a neck 64 therebetween and a pair of arcuately outwardly directed legs 60 and 62 at the end thereof opposite base portion 54. Shield 52 is disposed between drive gears 48 and 50 and the uppermost rollers of the pairs of pinch rollers such that neck 64 thereof is disposed between the meshed gears and the nip formed by the tiered pinch rollers. The uppermost pinch roller of each pair thereof has a radial groove for loosely receiving the margins of the circular cutouts 56 and 58 of shield 52. Referring now to Figures 1-4, the cartridge is specifically constructed to accommodate changes in ribbon drag produced during high dot density printing. To accomplish this, a substantially rigid ribbon exit arm 16 and, in comparison, a flexible ribbon entrance arm 18 is provided. Thus, exit arm 16 has side, top and bottom walls which are solid and continuous to afford rigidity to the arm as it projects from the cartridge. To additionally further rigidify exit arm 16 in use, its underside has a downwardly projecting boss or leg 70, which forms part of the three-point cartridge mounting system described hereinafter. Boss 70 has a recess 72 which, as illustrated in Figure 6, cooperates with a pin 74 carried on the carriage platform 76. When the cartridge is mounted in the printer, pin 74 is located within recess 72 and positions the cartridge relative to the printer. Thus, when the cartridge is mounted in printing position, the structural rigidity of the exit arm 16 is augmented by its securement against movement in the plane of the cartridge by the mounting pin and recess arrangement. Contrary to this rigid construction, the entrance arm 18 is specifically configured for flexing movement in the plane of the cartridge, as particularly illustrated with reference to Figure 3 by a comparison of the full and dashed line configurations of arm 18. The illustration of the flexing motion of arm 18 in Figure 3 is exaggerated. However, arm 18 is specifically constructed to facilitate a flexing movement in the plane of the cartridge by providing openings 80 and 82 in the top and bottom walls 84 and 86 thereof, respectively. A mounting leg or projection 88 is formed along the underside of entry arm 18, as illustrated in Figure 4. However, leg 88 simply rests on, rather than being fixed to, platform 76 when the cartridge is mounted in the printer and is thus adapted for sliding movement relative to the printer. Consequently, angular flexing movement of entrance arm 18 in the plane of ribbon travel and without substantial rotational or twisting movement thereof about its linear axis or out of such plane is provided. By providing an entrance arm 18 flexible in the plane of the cartridge and a rigid exit arm, tracking of the ribbon in the cartridge is accurately and repeatedly maintained without ribbon foldover or twisting or causing the ribbon to track up and down the arms. To further facilitate maintaining the ribbon in proper position relative to the printhead, i.e., the line of print, the guide surfaces at the ends of the entrance and exit arms are specifically shaped to assist in maintaining the ribbon in the plane of the cartridge. Particularly, the guide surface 90 at the tip of the exit arm 16 tapers from its opposite ends inwardly to a reduced diameter central or middle portion 92. The guide surface 94 at the tip of the entrance arm 18 tapers from a larger diameter mid-portion 96 in opposite directions towards its smaller diameter opposite ends. To facilitate mounting of the cartridge in the printer, a three-point mounting system is provided for supporting the cartridge on the printer platform 76. To accomplish this, first, second and third spacer legs 70, 88 and 100 are provided along the underside of the cartridge 10. Spacer legs 70, 88 and 100 project downwardly from the underside of cartridge 10 and support the cartridge on printer platform 76. It will be appreciated that two of the spacer legs, i.e., 70 and 88, lie adjacent the extremities of the exit and entrance arms 16 and 18, respectively, projecting from the bottom of the cartridge. The third mounting leg 100 projects from the bottom of the cartridge and proximate the center of mass C.M. and spaced from mounting legs 70 and 88. Because of the dimensioning of chamber 11, leg 100 is selected to lie to one side of an imaginary line 103 through the center of mass C.M. and normal to an imaginary line interconnecting legs 70 and 88 for purposes of locating leg 100 as far from legs 70 and 88 as possible and hence afford substantial stability to the cartridge when mounted in the printer. As illustrated in Figures 5 and 6, the chamber 11 has an annular rim 102 coincident with the center line of the drive wheel 30 and projects downwardly from the underside of cartridge 10. The rim 102 is disposed about the splined post 39 of the printer and mates with a recessed ring 111 in the printer platform surrounding the drive shaft. The rim 102 mates with the ring 111 concentrically to assist in centering the cartridge when the cartridge is installed on the platform. To install the cartridge in the printer, the cartridge is oriented relative to the printer platform such that the drive post 39 is received in the drive roller splined recess 31 and the post 74 is received in the recess 72 of mounting leg 70. The cartridge is then lowered onto the platform such that legs 70, 88 and 100 engage platform 76. Thus, the cartridge is mounted against rotation in the plane of the cartridge by engagement of post 74 in recess 72 and drive shaft 39 in recess 31 of the drive wheel 30, with the entire support for the cartridge derived from the three spacer legs 70, 88 and 100 engaging platform 76. In this latter mounted condition, the rim 102 does not bottom on the platform ring 111 but rather only concentrically engages the recessed ring carried by the platform. Upon installation, it may be necessary to advance the ribbon drive mechanism in a direction to draw the ribbon taut. This facilitates feeding the ribbon between the printheads and the print medium, and minimizes the likelihood of ribbon jam due to tracking misalignment because of excess ribbon. To overcome this likelihood, it is common to provide a knob, such as 112 shown in Figure 2. This knob engages a drive wheel shaft. By rotating the knob in the proper direction, the ribbon in the span is drawn taut by being fed into the storage chamber. In certain instances, as where a wide ribbon is involved (such as 35 mm (1-3/8'') in the case of one shuttle printer) and the ribbon in the storage chamber is uniformly fan-folded (broad folds) rather than random folded (small, irregular folds), it is vital that the knob not be turned in the wrong direction, such as to undesirably draw ribbon from the storage chamber to the inlet arm. In so doing, the combination of the wide ribbon and the back pressure of the wide folds results in ribbon clumping at the nip (in the reverse ribbon drive direction). Also, drawing ribbon back toward the span by the drive wheels from the storage chamber results in undesirable ribbon foldover and buckling at the nip between the wheels and beyond, introducing excessive torque loading on or jamming the drive wheels for printing. To avoid these undesirable shortcomings, the knob is coupled to the drive wheel shaft by a one-way clutch by the serrated teeth on the knob and the shaft. This ensures that under no circumstances will the operator be able to draw ribbon back to the span from the storage chamber. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment.

Claims: A printer cartridge (10) for carrying a print ribbon (R) for disposition in a print position between a printhead and a print recording medium and including a housing (12) defining a storage chamber (14) for the ribbon (R); spaced apart ribbon exit and entrance arms (16, 18) extending from said housing (12) for routing the ribbon (R) from the storage chamber (14) along said exit arm (16) into the print position located in the span between said arms and from the print position along said entrance arm (18) to the storage chamber (14) and means (22) for moving the ribbon into said storage chamber thereby displacing the ribbon from the exit arm through the print position and along the entrance arm (18), said entrance arm (18) comprising a ribbon guide (94) proximate its end remote from said storage chamber (14) for guiding ribbon from said span to said entrance arm (18), characterized by: a means (80, 82, 88) for minimizing adverse loading on said ribbon during high density printing including forming the entrance arm (18) to flex along the direction of ribbon movement in said span during such high density printing while maintaining the ribbon guide (94) perpendicular to said ribbon movement. A cartridge according to Claim 1 wherein said entrance arm (18) has a side wall and upper and lower walls for confining the ribbon (R) therebetween, each of said upper and lower walls having openings (80, 82) therethrough enabling said entrance arm to flex without substantial rotation. A cartridge according to Claim 1 or 2 wherein said cartridge is elongated in a longitudinal direction, at least three spacers (70, 88, 100) projecting from said cartridge along one side thereof, two of said spacers projecting from said entrance (18) and exit (16) arms, respectively, the third space (100) being located between said two spacers (70, 88) and spaced therefrom on the opposite side of the center of mass of said cartridge. A cartridge according to one of Claims 1-3 including means adjacent the tip of said exit arm (16) defining an aperture (72) for receiving a mounting post on a printer platform to maintain the exit arm (16) substantially rigid relative to said printhead and said flexible entrance arm (18). A cartridge according to one of Claims 1 to 4 wherein said moving means includes a wheel within said cartridge having a female splined gear for coupling with a ribbon drive mechanism having a splined post (39) carried by the printer. A cartridge according to one of Claims 1 to 5 wherein the guide (94) of said entrance arm (18) about which the ribbon is routed for movement about an axis generally normal to said ribbon movement and for ribbon entry into said entrance arm has a central portion of greater lateral extent relative to said axis than the lateral extent of said guide adjacent opposite ends thereof. A cartridge according to one of Claims 1 to 6 wherein said exit arm (16) includes a guide (90) adjacent its distal end about which the ribbon is routed for movement about an axis generally normal to ribbon movement, said guide (90) having a central portion thereof of lesser lateral extent relative to said axis than the lateral extent of said guide adjacent opposite ends thereof. A cartridge according to one of Claims 1 to 7 wherein said moving means includes a pair of rollers defining a nip for receiving the ribbon, a pair of gears on one side of said rollers with said gears meshing one with the other adjacent said nip, and means for preventing displacement of the ribbon in the nip in a direction toward the meshed gears.

Inventors: KARALEVICZ, JOHN M., MILLISER, CHARLES E., QUICK, HARRY C.
Applicants: GENICOM CORPORATION
Application year: 1989
Main classification: B41J32
IPC codes: B41J33, B41J32