GB2102766A - Ribbon cartridge with tensioning device - Google Patents

Abstract

A cartridge for a daisy wheel type printer includes a supply spool 6, a take-up spool 24 ribbon, two arms 10, 12 which define a path 38 for the ribbon to pass between the paper and the printer, and a leaf spring 101 between the supply spool and a fixed post 105 tension the ribbon as it passes from the supply spool to the take-up spool. The leaf spring has an arcuate shaped distal end which engages the ribbon at all times, the other end being fixed to the cartridge casing. The leaf spring may have a segmented, arcuate profile and may be made of phosphor bronze or of plastics material. The cartridge may include two drive gears which engage one another and enable the cartridge to be used with two different printers having different driving head locations and different directions of driving rotation. <IMAGE>

Description

SPECIFICATION Universal ribbon cartridge This invention relates to a printer cartridge which can be adapted to differing machines wherein the printer cartridge is held at differing locations and provided with a drive ribbon take-up at varied locations and rotating in opposite directions.

High speed printers of the daisy wheel type are known. In such printers a wheel with a protruding group of petals (typically one for each character) is provided. While operating at speeds well beyond human visual discrimination, the printer sequentially registers a wheel petal with a character to be printed thereon over a position on a piece of paper. Once registered, a hammer strikes a petal. Upon striking, the petal moves forward onto the ribbon, leaving an indicia of the desired letter on the paper to be printed.

These daisy wheel type printers commonly employ ribbon cartridges in their design. Such ribbon cartridges have a supply spool with a supply of fresh ribbon on it. They also have a take-up spool for winding the used ribbon around. The cartridge has two arms. The ends of the arms define a path along which the ribbon passes as it is wound onto the take-up spool. A drive shaft from the printer engages the bottom portion of a drive gear. The drive gear has a complementarily-shaped recess for engagement with the driving head of the drive shaft. The drive gear rotates a typically serrated drive wheel.

The ribbon passes between the drive wheel and a biased idler wheel and is thereby advanced along the path between the daisy wheel printer and the paper. The take-up spool is typically rotated by an external drive band, such band being driven by an extension of the drive wheel.

While both the take-up spool and the drive wheel are positively driven, the ribbon supply spool is not positively driven and instead rotates as a result of the ribbon being drawn from the spool by the drive wheel. During the frequent starting and stopping of the drive wheel during the operation of the printer, the inertia of the supply spool can sometimes cause an excess length of ribbon to be discharged therefrom. This, in turn, may cause insufficient tension in the ribbon passing in front of the printer which may cause the print imparted by the daisy wheel to blur.

Such slack might also cause the ribbon to break as the excess length is suddenly drawn in by the drive wheel. It is thus desirable to provide a means for constantly applying a tension on the ribbon as it unwinds from the supply spool so that little or no slack will be present in the ribbon.

A preferred embodiment of the invention to be described in detail hereinafter comprises a cartridge for a daisy wheel type printer. The cartridge is the type which contains two spools. One spool (the supply spool) has wound about it a fresh supply of typing or printing ribbon. The other spool (the take-up spool) is used to wrap the used ribbon on. The cartridge has paired extending arms, including a ribbon exit on one arm and a ribbon entry on the other arm.

These arms define a path for the ribbon to pass there-along. Along such a path the ribbon stands between the paper and the printer mechanism, which is typically of the daisy wheel type. Two drive gears are serially engaged with each other and the ribbon drive means. When the first drive wheel is driven by the printer, the second acts as an idler gear so that the ribbon drive means rotates in the same direction as the drive shaft of the printer. When the second gear is driven, the ribbon drive means is driven directly so that the drive means rotates in the opposite direction as the drive shaft of the printer.

The drive gears are located and their lower portions are configured to engage the respective drive shafts of various printers. The cartridge can accommodate drive shafts which rotate in opposite directions because of their serial engagement. Ribbon take-up can thus occur between varied drives having drive locations of varying spatial location as well as direction of rotation Provision is made to gather the ribbon between an engaged ribbon drive wheel and an idler wheel to the take-up spool. Improved bias of the idler wheel against the drive wheel for ribbon engagement, resulting in improved assembly of the cartridge, is provided.

As the ribbon is drawn from the supply spool by the ribbon drive wheel and the idler wheel, it must pass through a fixed path and then outward through the exit arm before passing in front of the printing mechanism. The present invention provides a means for maintaining a constant tension on the ribbon as it leaves the supply spool and enters the fixed path. Such means preferably comprises a leaf spring secured at one end to the cartridge body. The distal end of the spring engages the ribbon at a point between the supply spool and the beginning of the fixed path and is disposed so that it takes up any excess ribbon which may leave the supply spool. In this way, tension is constantly maintained on the ribbon regardless of minor variations in the length of ribbon being released by the supply spool.

Constantly providing a tension of the ribbon assures that the ribbon in front of the daisy wheel will be taught and that the print imparted will be sharp and clear. Moreover, by taking up slack in the ribbon, the ribbon is less likely to be broken by the force of the drive wheel suddenly drawing the ribbon onto the take-up spool. An additional advantage afforded by the leaf spring is that the pressure or drag on the supply ribbon applied by the spring helps prevent the ribbon from unwinding in the cartridge before use.

In the accompanying drawings: Figure lisa top or plan view of a preferred embodiment of a ribbon cartridge in accordance with this invention with a daisy wheel printer schematically shown.

Figure 2 is a bottom view of the cartridge shown in Figure 1.

Figure 3 is a top view of the cartridge with the top half of the body removed.

Figure 4 is a detailed view of the ribbon gathering means and the first and second drive gears.

Figure 5 is a view of the first and second driving gears mounted within an elongate hole in the bottom half of the body as seen from the inside of the cartridge.

Figure 6 is a cross-sectional view of the first and second driving gears shown in Figure 5; and Figure 7 is a cross-sectional view of a removable peg.

Atypical daisy wheel printer, the type with which the invention is generally used, will be described first to enable the reader to better understand the invention. Turning nowto FIG. 1, universal ribbon cartridge 2 is shown together with a daisy wheel 1, a petal 3, a hammer 5, and paper 7. Daisy wheel 1, a thin, radially segmented disk-shaped element, carries the characters to be printed on the outermost ends of petals 3 of daisy wheel 1. When a character impression is to be imparted to paper 7, daisy wheel 1 is rotatably indexed at a high rate of speed. Hammer 5 is then activated and strikes the proper petal 3 of daisy wheel 1. The struck petal 3 is driven forward against a ribbon 8 to leave its particular impression on paper 7.The entire printing mechanism including cartridge 2 (and ribbon 8 therewith), wheel 1 and hammer 5 are then indexed for the next impression.

Additionally, ribbon 8 is indexed to provide fresh ribbon 8 for the next impression.

As can be seen from FIGS. 1-3, the universal ribbon cartridge 2 has a body 4, a supply spool 6 on which the ribbon 8 is wound, a ribbon exit arm 10, a ribbon entry arm 12, and a ribbon take-up means 14.

Take-up means 14 includes first and second drive gears 16, 18, a ribbon drive means 20, an idler wheel assembly 22, a take-up spool 24 and an external drive band 26. A gripping surface 28, a mounting means 30, and removal pegs 32 allow the cartridge to be mounted on different printers. Figure 1 shows the gripping means 29 of the printer engaging surface 28 thereby securing cartridge 2 to the printer.

Turning to Figure 3, supply spool 6 is mounted on body 4. Typically a piece of foam 9 is placed between supply spool 6 and body 4 to provide a drag on spool 6 so a proper tension is maintained on ribbon 8. Ribbon 8 wends its way from the supply spool 6 through an exit opening 36 at the end of exit arm 10 and then passes along a path 38 defined between exit and entry arms 10,12 and re-enters body 4 through an entrance opening 40 formed at the end of entrance arm 12. A biasing spring 101 is secured at one end in a slotted pin 103 projecting upward from the cartridge body 4. Ribbon 8 leaving the ribbon pancake mounted on the supply spool 6 must pass around the distal end ofthespring 101 before passing around a fixed post 105.As can be seen, the distal end ofthe spring 101 projects well beyond the line between the fixed post 105 and the centre of the supply spool so that the end will engage the ribbon 8 at all times regardless of the amount of ribbon remaining on the spool 6. The spring 101 is disposed so that it urges the length of ribbon intermediate the ribbon spool and post 105 in the direction of the supply spool 6 as indicated by arrow 106. In this way, the spring 101 will take up any excess ribbon 8 which has left the supply spool 6 during the constant onand-off action of the printer.

Preferably, the distal end of the spring 101 is rounded to assure a smooth passage of the ribbon thereabout, and the spring includes one or more arcuate segments which impart additional resilience beyond that which would be obtained from a straight spring formed of the same material. The preferred material of the spring is a resilient plastic.

As shown best at FIG. 4 in conjunction with FIGS. 1 and 3, ribbon 8 is driven along its path by passing between the serrated surfaces of idler wheel 42 and ribbon drive wheel 44. Wheel 44 is mounted on a common shaft with a ribbon drive gear 46. Ribbon drive wheel 44 and ribbon drive gear 46 comprise ribbon drive means 20. Gear 46 rotatably engages and is driven by second drive gear 18.

Also mounted on a common shaft with ribbon drive gear 46 and extending outwardly past a top half 48 of body 4 is an extension 50 defining a circular groove 52 into which drive band 26 is seated.

Band 26 also seats within a like extension 54 extending from take-up spool 24. Rotation of drive wheel 44 thus results in the rotation of spool 24. As the amount of ribbon 8 on spool 24 increases, band 26 slips so that the travel of ribbon 8 along path 38 is determined by the rotational speed of serrated wheel 44 and not by the rotational speed of take-up spool 24.

As seen best at FIGS. 2,4 and 5, first and second drive gears 16, 18 are mounted on a bottom half 56 of body 4 with second gear 18 serially engaging both first gear 16 and drive gear 46. Gears 16,18 are located to overlay respective ribbon drive shafts from differing types of printers. Gears 16, 18 have complementarily-shaped recesses 16a and 18a, respectively for positive rotational engagement with their respective ribbon drive shafts, as seen at FIG. 2.

In the preferred embodiment gears 16 and 18 are of the same size; however, depending upon the particular requirements of the printer used, gears 16, 18 may be of differing sizes. Also, in the preferred embodiment the serial alignment of gears 16, 18 allows the universal ribbon cartridge 2 to be used on printers with printer drives which rotate in opposite directions. This advantage exists because when first drive gear 16 is driven by the driving head of the printer drive shaft, second drive gear 18 acts as a direction reverse so that ribbon drive gear46turns in the same direction as the printer drive shaft. When the driving head of the printer drive shaft engages and drives the second drive gear 18, ribbon drive gear 46 turns in the opposite direction as the printer drive shaft.

Turning now to FIGS. and 6, drive gears 16,18 are mounted on bottom half 56 in a convenient manner. An elongate hole 58 having semi-circular ends is formed in bottom half 56. Gears 16,18 are relatively thin, cylindrical elements having teeth 60 around the circumference of one end, a groove 62 defined medialy within the circumference of gears 16, 18, and a retaining shoulder 64 defining the circumference of the other end. The entry end 66 of hole 58 is slightly larger than the remaining portion thereby allowing shoulder 64 to be passed therethrough but not so large as to allow teeth 60 to pass therethrough. Gear 16 is then slid along hole 58 past detents 68. Gear 18 is likewise positioned in hole 58 and engages gear 16. Some slight pressure is necessary to get gears 16, 18 past detents 68.Gears 16, 18 are retained in positioned by the engagement ofthe sides of hole 58 with groove 62 and by detents 68.

Idler wheel assembly 22, as shown in FIGS. 3 and 4, includes an idler wheel carrying arm 70 pivotally connected to body 4 at a pivot point 72 at one end thereof. Idler wheel 42 is rotatably connected to arm 70 at a central portion of arm 70. At the end opposite pivot point 72, arm 70 includes a flat spring 74 extending outwardly therefrom. Spring 74 is configured to rest against an inside surface of body 4 at a point near an aperture 76 thereby biasing idler wheel 42 against ribbon drive wheel 44. During assembly spring 74 extends through aperture 76 so that no force is exerted by idler wheel 42 on ribbon drive wheel 44. After assembly with top and bottom halves 48,56 of body 4 secured spring 74 is urged inwardly through aperture 76, thus biasing idler wheel 42 against ribbon drive wheel 44.Using this method, lateral forces on pivot point 72 and ribbon drive wheel and gear 44,46 are greatly reduced thus promoting alignment of components and easing assembly considerably.

The preferred embodiment of universal ribbon cartridge 2 is adapted for mounting on at least two types or classes of printers A first type engages cartridge 2 at gripping surface 28, shown at FIG. 1, which surface is defined along the edge of top half 48 of body4 between arms 10,12. A second type grips bottom half 56 at gripping means 30, shown at FIG. 3. Means 30 is a narrow planar extension located within a notch 78 medially along both sides 80. Cartridge 2 also has removable pegs 32, as seen at FIGS. 2 and 7, positioned within bottom half 56 for registry with corresponding apertures in the second type printer. Other means, such as pivotable pegs, not shown, could also be used in lieu of the removable pegs 32.

In the preferred embodiment all elements, except drive band 26 and ribbon 8, are made of plastic, however other suitable materials can be used.

Spring 74 could, for example, be made of phosphor bronze as well as nylon.

Claims (12)

1. In a ribbon cartridge including a body, a supply spool upon which a ribbon is wound, a means for gathering the ribbon as it passes from the supply spool and around a fixed exit point, wherein the supply spool rotates substantially freely as the ribbon is drawn therefrom, an improved ribbon feeding apparatus comprising: a leaf spring having one end secured to the cartridge body and the other end projecting into the space between the supply spool and the fixed exit point so that the ribbon must pass around the distal end of the spring as it leaves the spool and so that the position of the distal end defines a path of variable length.

2. An improved ribbon feeding apparatus as in claim 1, wherein the distal end of the leaf spring has an arcuate shape to facilitate passage of the ribbon therearound.

3. An improved ribbon feeding apparatus as in claim 1, wherein the leaf spring has a segmented, arcuate profile.

4. An improved ribbon feeding apparatus as in claim 1, wherein the fixed point is a post projecting from the cartridge body.

5. A ribbon feed mechanism for use in a ribbon cartridge, said mechanism comprising: a cartridge body; a spirally-wound ribbon pancake rotatably mounted within the cartridge body; means for defining a fixed ribbon path; means for gathering the ribbon so that the ribbon passes through the fixed ribbon path; a biasing spring mounted within the cartridge so that a distal end of the spring engages the ribbon at a point after it leaves the ribbon pancake and before it enters the fixed path, the spring being biased so that it defines a variable-length path between the ribbon pancake and the fixed path and so that the path length increases as the ribbon tension decreases.

6. A ribbon feed mechanism as in claim 5, wherein the means for defining a fixed ribbon path includes a fixed post secured to the cartridge body, and wherein the distal end of the spring engages the ribbon after it emerges from the pancake and before it passes around the post.

7. A ribbon feed mechanism as in claim 5, wherein the biasing spring has a segmented arcuate profile, including an arcuate portion at its distal end to facilitate passage of the ribbon therearound.

8. A ribbon cartridge for use on more than one type of printer, each printer including a drive shaft with a driving head at the end thereof, the driving heads of the printers located in different positions and rotating in different directions, said cartridge comprising: a body; a supply spool having a supply of ribbon mounted within the body; said body having a ribbon exit arm and a ribbon entrance arm, said arms defining a path therebetween for passage of ribbon from said supply spool, out through the exit arm, along said path, and in through the entrance arm; a first drive gear mounted in the body in a first position; a second drive gear mounted in the body in a second position, said second gear rotatably engaged with said first drive gear so that said first drive gear rotates in a first direction while said second drive gear rotates in a second direction;; means for gathering ribbon, said gathering means mounted in the body and having a ribbon drive gear mounted in rotative engagement with the first drive gear; said first and second drive gears arranged and located for driven engagement with the driving head of a printer whereby said cartridge is adaptable for use with printers having different driving head locations and different directions of driving rotation; a take-up spool mounted in the body and rotatably coupled to said gathering means so that said gathered ribbon is collected on said take-up wheel; and a biasing spring secured to the body at one end so that a distal end of the spring engages the ribbon at a point between its emergence from the supply spool and its passage out through the exit arm, whereby slack in the ribbon is taken up.

9. The device of claim 8 wherein the printer drives the first drive gear.

10. The device of claim 8, wherein the printer drives the second drive gear.

11. The device of claim 8, wherein said ribbon gathering means further comprises: means for rotatably engaging said ribbon drive gear; and means for biasing said rotatable engaging means against said ribbon drive gear so that the ribbon which passes therebetween is positively advanced from the supply spool to the take-up spool by the action of the printer rotating a drive gear.

12. The device of claim 8, wherein the biasing spring has a segmented arcuate profile, including an arcuate portion at the distal end to facilitate passage of the ribbon therearound.