CA1304709C - Color printer - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
In a color printer in which a shuttle assembly con-taining a plurality of impacting print hammers is reciprocated in bidirectional fashion relative to an opposing platen to impact a print paper against the platen through the different color zones of an ink ribbon to print in color, the different color zones of the ribbon are arranged in a repeating pattern along the length thereof enabling the lightest color to be printed first followed by successively darker colors as the ribbon is advanced bidirectionally between the opposite ends thereof. A pair of barrier zones having a blank ribbon zone therebetween are disposed between each adjacent pair of color zones on the ribbon to prevent ribbon contamination due to bleeding of ink between adjacent color zones when the ribbon is wound on a reel. Ribbon contamination is further prevented by the blank ribbon zones which absorb ink that rubs off onto the ribbon guides. The various different color zones are identified by one or more strips which extend across the width of the ribbon adjacent each color one and which identify the color therein in bar code fashion. The color printer may be operated in a manner which provides multiple passes of each color zone through the print station between the shuttle assembly and the platen to prolong the life of the ribbon and to enable the printer to quickly advance to the next color zone with a minimum amount of search time. The print paper which is driven bidirectionally by tractor drives above the print station is held in tension by an arrangement below the print station which employs a torque motor having an elasto-meric wheel engaging a side of the paper opposite arrangement of non-ink absorbing rollers.

Description

13(~7~9 Background of the Invention 1. Field of the Invention The present invention relates to color printers, and more particularly to color printers of the dot matrix impact type in which the different color zones of an ink ribbon are successively impacted to provide printing in color.
This Application is a Division of our Canadian Application Serial No. 478,755 filed April 10, 1985.
2. History of the Prior Art It is known to provide a color printer of the dot matrix impact type in which the different color zones of an ink ribbon are impacted in succession to provide printing in color. Examples of such a printer are provided by United States Patents 4,289,069 and 4,336,751 of Melissa et al. The Melissa et al Patents describe a color printer having an ink ribbon the length of which is basically divided into three different color zones. Printing in color is accomplished by advancing a first one of the color zones of the ribbon to a print station between a platen and a bidirectionally reciprocating shuttle assembly containing impacting hammers. A page or other doc-ument of convenient length is then printed in the color con-tained in the first zone of the ink ribbon. Tractor drives are employed to advance the print paper in a first direction through the print station as the page is printed in the first color. Following printing of the page in the first color, paper advancement is reversed to return the page in preparation for the printing thereof using the second color zone of the ink ribbon which is advanced into the print station. Following printing of the page in the second color, ~3~4'~09 the paper is again reversed in preparation for printing the paqe in a third color usin~ tile tilird color zone o[ the ribbon which is advanced into the print station. By usin~ diEEerent combinations of colors and ~ e dots thatare printed tllerefroln, multi-color printing can be accomplished.
Despite the fact that multi-color printing is pro-vided, the color printer described in the previously referred toMelissa etal patents suEEers Erorna numher of disadvantages.
One such disadvantage relates t:o the arrangement of coior zones on the ink ribbon. It has been found that the best results are achieved if printing is carried out startinq with the lightest colorand then proceeding through the increasingly darker colors. If the darker colors are prirlted Eirst, there is a tendency for the darker ink already deposited on the print paper to rub off onto and tllereby contaminate the lighter color zones of the ribbon as such lighter color zones are used for printing. In the thrce zone ribbon sho~n and described in the Melissa et al patents, it is simp1e enough to arrange the colors of the three zones so that the three colors go become progressively darker as the ribbon is aclvanced along the length thereof in a given direction. Ilo~ever iE the-¦ ribbon is then driven in the opposite direction, the reverse ¦ becomes true and the darkest colors are pre.sented first. The ¦ same problem exists where the basic three color pattern is repeated a plurality of times along the lengtll oE the ribbon.
Again, the desired order oE color presentation is achieved in one direction of ribbon movement, but the reverse is true in the opposite direction. It is desirable t11at the ribbon be driven bidirectionally from end to end during printing in 0 order to optimize speed and efficiency. However, the tllreecolor zone ribbon arrangement of the Melissa et al patents is limite-l to ribbon advancement in a single direction iE
contamination tllereof is to be minimized.
~ ccordingly, it would be desirable to provide a multi-color ribbon in which the ligllter color zones are pre-sented first followed b the c~lrker color ~one.s in either d i r ec t i on o [ r i 1~ l~on d 1 i v ~3~47~9 In the printer s11own and described in tht? previously referred to Melissa et al patents the ril,hon is Eed Erom one reel onto a second reel. lnitially, t~e rioboll is entirely wrapped around the first reel. 1t is then driven in a first direction until it it subs~:antia]ly completely wound around the second reel, whereupon tl1e direction oEdrivin~is reversed and the ribbon is fed from the s~cond reel b1ck 011tO the Eirst reel. The ribbon typically extends throu(Jh a path between the opposite reels including various yuides. As the ribbon is wound onto either oE the reels, portions oE two diEEerent adjacent color zones are disposed in contact with or at least adjacent to one another. It has been found that in time the ink from one color zone can bleed into portions of the adjacent color zone and vice versa, causing contaminatior1ofthe ribbon.
It has also been found that ink From the various color zones tends to be transferred onto the various guides within the ribbon path. Such ink can then ru~ o~E onto color zones of different color, resulting in contamination oE the ribbon.
Accordingly, it would be desirable to provide an in1 ribbon in which contaminc1tiol1 of the various color zones as a result of winding or storage oE the ribbon on each oE
the opposite reels is minimized or eliminated. It would Eurthermore be desirable to provide a ribbon capable of clean-ing some or all of the ink Erom the guides in the ribbon path so as to minimize or e]imin~te contamination of the ribbon.
In the color printer 5hOWrl and described in the previously reEerred to Melissa et al patents the different color zones of the ribbon which are typically welded together to form the ribbon are identified using an arrangement which includes apertures that are provided in the opposite ed~es of the ribbon. In thisway the printeris capahle oEidentifying the particular color being presented at the print station at any given moment. However, while the arrangement of apertures is capable of identifying the diEEerent color zones, it n1ay be desirableto provi~3e a simplerand more reliab1c?arrall~elnellt for identiEying the color zones u~ili%in~ indicia which is easily adrle(3 to t:he ritl)on in conju1lctio1l wit11 a standar-3 coding sche1ne. It would 1lso h?(1esirahle to pr~ide a ribhon which does not have welds or othel jo;nts thel-?in whicll are prone to breaking.
As previously discussed in connoction-~it)-tl-e color printer shown and described in the ~elissa et ai patents the ribbon therein is advanced in a given direction so as to present each of three diEferent color zones oE the ribbon to the print station in succession. It has becn found that the resulting single pass made throuqh each oE the color zones can result in relatively short ribbon life hecause of the uneven depletion of th2 ink that can resuLt. For example the ribbon may be driven at a speed that i~rovides a single pass of a given color zone througll the print station during the time required to print a complete page. Ilowever, if a number of pages are printed in which only the Eirst portion lS of each pagecolltains printed matter, then on]y t~-e correspond-ing first portion of each color zone on the ribbon is used.
This results in depletion of the ink at the Eirst such portion of each color zone while the remaining portioll oE each color zone experiences little or no ink depletion. ~n arrangernent capable of making ribbon use and the reslllting ink depletion more uniform could result in greatly prolonged ribbon life.
Furtilermore, a single pass through each color zone does not always lend itself to East and eEEicient operation, particu-larly where only portions of the pages contain printed matter and the printer must await advanceln~nt oE the ribbon to the next ribbon zone at some nominal ribbon driving speed.
In color printers such as oE the type shown and described in the previously referred to Melissa et al patents, it is necessary to reverse the paper advancement after a page is printed in a first color so that the salne page can be printed in the re;naining colors. One approach is to use pairs of conventional tractor drives both above and be1Ow the print station. This achieves bidirectional paperadvancelnent rather successfully hut at the expense of requiring two separate pairs oE tractor drives. In this connection it woulcl be desirable to provide a paper drivillg arran(3emerlt in which only a single pair of tractol drives is r~quire-l wl)ile at the salne time tlle paper is advlllced bidirectionally urd ra-1esir!d ~3~4709 alnount oE tension so as to mlintain the desired tautness and alignment thereof. This s~lould be done wit~lOUt risk oE the smearing o~ ink on the already printed portiol-s o~ t~le paper.
Brief Description o~ the Inventioll S The present invc?lltion provi~es a color printer in which the ink ribbon is designed and arranged so as to minimize or preventcontamination th,?reof and so as to othelwise prolong useful life of the ribbon. In addition, each color zone of the ribhon is advanced through the prillter in mllltiple passes so as to again prolong ribbolllifeclnd at tlle same time provide for relatively fast and efficient printing in tlle face of the printing of paqes having different amounts of printecl matter less than a Eu11 page thereon. The paper feed within the printer is carried out in bidirectional fashion utilizing either of two relatively simple torque rnotor arranqements that hold the paper under tension without smearing the ink on the already printed portions thereo~.
In one prefcrred arrangement o~ an ink ribbon in accordance with the invention the different color zones which are formed a]ong the length of a continuous, non-welded fabric are arran-3ed in a progression which repeats it~self alony the length of the ribbon. The progression or pattern begins with the lightest color zone at a first end of the ribbon and then progresses through the next darker color zolle to the darkest zone. Thereafter, the next darker color zone is repeated, followed by the lightest color zone to complete tll-?progression or pattern. Accordingly, when aclvancing the ribbon in either direction, it is only necessary that an occasional color zone be skipped. Otherwise, the various color zones are presented at the print station in orclt?rly sequence beginning with the lightestcolorand progressillg througll the increasillglyclarker colors. In one examp1e, the progressioll or pattern begins with yellow anc3 is followed by recl, blue, black alld then red again, where~lpon the progression or patt:t?rll rep(?ats. At the opposite end o~ tht? rib~on a yelLow zon~.? is a~ ?d at the end of the progression or patterll.
Inaccordaocewith tlleir)velltiollcontal~incltion prob-lems due to inks bleedill:~ throll(JIl the ribl)on hetwe(?n color 13i~47~9 -G-zones when the ribbon is stored on a reel are minimized or eliminated by incLuding a pair of barrier zon~?S l~etw(?en each adjacent pair oE color zones on the ribbon. li~e barrier zones are preferably coated with a non-wetting material such as a S fluorochelnical polymer silicone to prevent thc l~leeding of ink therethrou~3h. Each barrier zone preferal~ly has a lt-?ngtll at least equal to the outer circumference of the ribbon reel to insuee that no portion of a color zone on the ribbon overlapsanother portion oE the ribbon other than the adjoining barrier zone. A blank ribbon zone is provided between the pair of barrier zones sep~rating each ad~acent pair of color zones. The bLank zone consists oE a section o~ raw ribbon which rubs against and is eEfective in removing ink which becomes deposited on guides and other elelllents within the ribbon path.
The diEferent color zones of ribbons in accordance Witil the invention may be identified by diEferent groups o indicia consisting oE strips extending across the width of the ribhon and arranged in standard bar code form~t. Each such set oE indicia is preEerably located witllin the barrier zone adjacent an end of each color zone. The indicia includes a desired numb-?r of strips oE selected width so as to identify the color oE tlle zone in bar code fashion as well as tlle opposite ends oE the ribi~on. The stripsare pr?ferably applied to the ribbon by ~oil llot stampinc3. Tlle resulting bar coded information is easily read using optical sensors located within the ribbon path.
Color printers in accordance with the invention are preferably ouerated so that each of the plurality oE color zones along the length oE the ribbon makes a ulurality of difEerent passes through th?L~rint station as tlle color tllereof is printed on a page. ~n odd number of SUCIl passes is required and typically the ribbon undergoes at least two reversals in direction to provide a minimum oE three diEferent passes oE
the color zone throu(311 tll. prillt station. Gre~ter numbers oE p~sses sucll as Eive or s vell C~ l.sol~elli(?,l wh~-?r~? dl?sir(?d.
Tlle use Or rnultiple i)asse h;ls tln? adVtln~..l(Je oC more evenly distributing the wear al~n3 tll(? lt?llg~:ll Or l-~ncil color zone.

.

~3Q4709 A further ddvantage resides in the ability to print rapidly and efficiently where the pages ~einq printed contain !ess than a Eull page of printed matter. ~ (? amounl: o[ rnatter to be printed on each page is determined, and the ribbon in the meantime is advanced througl1 at least one pas.s oE the color ~one. When printing o ti1e pac3e using tht? color zone is thereaEter completed, the pril1ter is prepare(1 to quickly re-verse the direction oE ribbon drive iE the end of printing occurs during an ev-n numbered pass and then immediately advance the ribbon to the beginning oE the next color zone.
Where desired, the rihbon speed can be increaser] Erom a nominal speed when .searching for the next color zone to Eurther reduce the color selection time.
Inaccordancewith theinventionbidirectional paper advancement can be provided in conjunction with a standard tractor drive using a p.lper tensioning arrangement which engages the paper on the opposite side oE the print station from tlle tractor drive and which Inoves in the samt? direction as the tractor drive but at a different speed so as to maintain the paper in a desired alnoul1t o~ tension througl1 the print station. In a Eirst embodiment thereof, such arrangement may comprisea torquemotorcoupled toa wheelhavinganelastomeric surface whicl1 engages the pril1t paper on a side thereoE
opposite a plurality of rollers rotatably mounted in side-by-side relation. rhe outer urfaces oE the rollers are preEerably of a non-w(?ttiny material such as leflon or Delrin so as to resist the absorbtion oE any ink Erom the already printed portions of tl1e paper wl1ich might otherwise result in contamination. The torque motor and associated ~rive wheel are mounte(T on tl1e lower el1d oE a bracket having an opposite upper el1d pivotally coupled to tl1e tractor drive and an intermediate portion mounting a permanent magnet. The perma~
nent magnet normally clamps itselE onto the back oE the platen to pivot tl1e bracket into a paper engageln(?nt position in which the drive wheel associated with the torque motor presses the paper against ti1e rol]ers. nuring loading al1d ur)loading of the paper~ tllt? platen ma~ b rotated so ac; to call1the permant?l1t magnet awly tl1ereEroll1 ar.1 thereby rotate the 1Ov~er enr1 oE Lhl / tc~lc ~if ,~

~3~4709 - ,3 -bracket: with tlle inciuded tor(.~ue Inotor alld drivf? whee] into a positiondisengaged ~rornthe p"per. The rollr?rsarf?rotatably mounted within a generally rectanc3ular housing which includes opposite paper guides, the ~aper guides converging toward each other inan upward direction to an area or minilnuln spacinc3 therebetween immediately below the rollers r~lld the torque motor and attached lrive wheel.
In an alternative embodiment oE a p~per tensioninc3 arrangement, a torque motor is coupledi to a ~irst roller e~tending across the width o~ the paper on the back thereGf o~ppositea second roller of non-wetting material which extends a~ross the width of the paper on the front thereof. The second roller, w'nich is norlnally biased in a direction to press the paper ac3ainst a resilient sur[ace of the first roller by a pair of springs bearinq against a pair of brackets which rotatably mount the opposite ends of thr? second rolLer, can be moved away from the paper and the ~irst roller to permit loadin~3 and un]oadinc3 of the paper. ~ovelnent o~ the second roller away from the paper is accomplished by hand activation of a lever ex~endinc3 from one oE the pair of brackets so as to rotate the pair of brac'cets and an included rod of square cross-section on which the brackets are mounted in a direction to move the second roller a~ay from the paper against the resistance of the springs. The lever may be locked in the paper load-unload position by disposing it against rl lec'i(3e in a slot in the housin(3 for tlle paper tensioningarrangementfrom whiclltheleverprotrudes. Release of the lever Erom the ledge in the slot allows tile springs to rotate the pair of brackets and thereby cause the second roller to force the paper into contact with the first roller.
'rhe ink ribboll extends througll a ribbon path which includes the print station and one or more c~uidf?s on each side of the print station. ~rhe guide can coln~ri~se roller c~uides, each of which includes a rotatable spool having opposite flanges l:hereon and havin(] an outer surface comprised of generally noll-ink ab~sorbing nlaterial. In ~n alternative embo-'iimentofa ribboncJu:dewllicll avoid.s cer~ ai n disac'ivalltages of both rol:atable gui(l~s all(l fixed gui~`i.s, eacll guide is ~3~47~?~

rotatable through an angular range which is a substantial portion of a revolution of the guide. Upon each reversal in the direction of ribbon drive, any ink which accumulates on the guide at the upstream end of the guide-ribbon interface due to the ribbon being drawn over a non-rotating guide is transferred back onto the ribbon as the guide rotates through a substantial portion of a revolution and thereafter becomes stationary in response to the new direction of ribbon drive.
In accordance with a broad aspect of the invention there is provided a guide for use with an ink ribbon comprising a spool and means for mounting the spool to permit limited rotation of the spool through a predetermined angular range.

Brief Description of the Drawings The foregoing and other objects, features and advant-ages of the invention will be apparent from the following more particular description of a preferred embodiment of the in-vention, as illustrated in the accompanying drawings, in which:
Figure 1 is a perspective view of a color printer in accordance with the invention;
Figure 2 is a plan view of a portion of the printer of Figure 1 together with a block diagram of a servo system for driving the ribbon thereof;
Figure 3 is a representation of a typical prior art ribbon having a plurality of different color zones;
Figure 4 is a representation of a ribbon having color zones arranged to present the colors in descending order of brightness in both directions of ribbon drive in accordance with the invention;

13~47~

-9a- 71772-6D

Figure 5 is a representation of a portion of the ribbon of Figure 4 illustrating the manner in which adjacent color zones are separated by barrier zones and a blank ribbon zone and are identified as to color using strips arranged in bar code format;
Figure 6 is a representation of a portion of the ribbon of Figure 4 illustrating a mode of operation of the color printer of Figure 1 in which each color zone makes plural passes through the print station of the printer;
Figure 7 is a representation of the ribbon of Figure 4 similar to the representation of Figure 6 and showi.ng differ-ent examples of multiple passes of the color zones;
Figure 8 is a representation of a portion of the ribbon of Figure 4 illustrating the manner in which different - 13~47~9 numbers oE plsses of each col~r ZOIIe Can ~)C? empLoyed to eEfect printinc3at di~erent dot densities for a givellllorllinal rihbon speed and color zone size;
Fig. 9 is a representation of a portioll o~ tile ri bon of F`ig. 4 illustrating the mal-ner in w~lich different nul ~bers of passes of a color ~one are selecte(l for different dot densitif?s and numbers o hallllners within the shuttle mechanism or the printer of Fig. 1 for a given nominal ribbon speed and a qiven lenc3th of the color zone;
Fig. 10 is a front view of a portion of the printer of Fig. 1 illustrating an arrangement for maintaining the print paper under desired tension during l~idirectional a~vancement thereof;
Fig. 11 is a sectional view oE the arrangement of lS Fig. 10 in conjunction with a portion oE the prillter oE Fig. l;
[i(3. l2 is a Eront view oE a portioll of the arrange-ment of Fig. 10; and Fig. 13 is a perspective view oE a rolLer guide Eor use in the ribbon path;
~`ig. 14 is a perspective view of all alternative embodimellt of a guide arran~?rnent for use in the ribbon path;
F`ig. 15 is a perspective view of the guide of the arrangement oE Fig. 14;
Fig. 16 is a top view of the guide arrangernellt oE
Fig. 14 with the top portion oE the mollntin(3 Lralne removed therefrom;
Fig. 17 is a top view of a portion of the guide oE
Fig. 15 illustrating the manner in which ink buildup is transferred hack into the rihbon;
Fig. 18 is a perspective view oE an alternative arrangement oE a paper tensioning mechanisln for maintaining tlle print paper under desired tellsioll during bidirectional advancement thereof;
Fig. 19 is a sectional view oE thf? mechanism of Fi~. 18 taken along the line 19-19 tilereof;
Fig. 20 is a view similar to iig. 19 but witl! the second roll-r oE thc?ln(clanism positione3clway rom the Eirst roller thereof to faci]i~nt?L).li~er loadin3 all(l nnl.oa(li ng; all(l ~L3(P47Q~

I'ig. 21 is a perspective view of a portion o~ tlle mechanism oE Fig. 18 which lrovides for temporary positioning of the second roller away Eroln the first rollt?r to ~acilitate paper loading and unloading.
Detailed Description Fi~. 1 depicts a color printer 10 in accordance with the invention. The color printer 10 includes a relatively Elat base 12 thereof mounted on a support pedestal 14. The support ped~stal 14 has a Eront portion 16 thereoE ~or support-ing a stack 18 oE Ean-Eolded edge-per~oratedlllulti-copy print paper 20. The print paper 20 from the stack 18 thereoE is fed upwardly througll a generally rectallgular housillg 22 to a print station 24.
'l'he print station 24 is defined by the interEace between ~n elongated platell 26 and a shuttle assembly 28.
The print pal)er 20 extends througll the print station 24 to a standard traetor drive arrangemellt comprised o~ an opposite pair of tractor drives 30 and 32. The trac~or drives 30 and 32 which are mounted on shaEts 34 and 36 extending between opposite mollnting brackets 38 and 40 generally vertically disposed onthe base 12 engage the perforations in the opposite edges oE the print paper 20 to drive the paper 20 in we]l known fashion. Only portions o~ the opposit:e edyes oE the print paper 20 above the print station 24 are~ shown in Fig. I
for clariLy oE illustration.
~n elongated bracket 42 has an upL)er end 44 thereoE
pivotally mounted on the shaft 36. Coil sprin(~s 46 and 48 disposed around the outer surface of the shaEt 36 between the upper enA 14 oE the bracket 42 and the opposite tractur drives 30 and 32 serve to keep the bracket 42 centered hetween the tractor drives 30 and 32. As described hereaEter the bracket 42 has a torque motor and associated drive wheel mounted thereon (not shown in Fig. ]) [Ol en~aging the print paper 20 at a location below the prillt statioll 24. 'l'he torque motor and associat-ed drive whe~al Inove in the same direction as the tractor drives 30 and 32 hut at a difEerent sp~ed so as to rm~intain a desired allloullt oE tension withill tle print paper 20 within the print st:-llion 24.

13(~7(~9 The shuttle assembly 28 is mounted for reciprocating movement in bidirectional fashion relative to the platen 26 as represented by an arrow 50. The shuttle assembly 28 is disposed on the opposite side of a pair of rotatable pulleys from a counterbalancing bar 52. A first one 54 of the pair of pulleys is shown in Figure 1 and is rotatable about a vertical shaft 56. A second one 57 of the pulleys which is not shown in Figure 1 but is shown in Figure 2 is rotatably mounted about a vertical shaft 58 spaced apart from the first vertical shaft 56. The shafts 56 and 58 are journaled within a horizon-tally disposed frame member 60.
As previously noted the shuttle assembly 28 under-goes reciprocating bidirectional motion as represented by the arrow 50. This motion is provided as the shuttle assembly 28 moves over the pair of rotatable pulleys 54 and 57. At the same time the counterbalancing bar 52 which is disposed on the opposite side of the pulleys 54 and 57 from the shuttle assembly 28 undergoes reciprocat.ing motion in an opposite sense from that of the shuttle assembly 28 as represented by an arrow 62.
The shuttle assembly 28 and the counterbalancing bar 52 are coupled to thin, flexible bands ~not shown) which encircle the opposite pulleys 54 and 57 and which together with one or more appropriate magnetic arrangements (not shown) disposed between the shuttle assembly 28 and the counterbalancing bar 52 hold the shuttle assembly 28 and the counterbalancing bar 52 in contact with the pair of pulleys 54 and 57. Such arrangement is shown and described in detail in U.S. Patent 4,359,289 of Barrus et al, Counterbalanced Bidirectional Shuttle Drive Having Linear Motor, which patent is commonly assigned with the present application.

~3~4709 -12a- 71772-6 U.S. Patent 4,359,289 of Barrus et al also describes an appropriate apparatus for driving the arrangement which includes the.shuttle assembly 28 and the counterbalancing bar 52 in bidirectional reciprocating fashion. Such apparatus includes permanent magnets disposed adjacent the inside of the counterbalancing bar 52 for magnetically interacting with a pair of coils 64 and 66 which surround porti.ons of the ~3~47~9 counterbalancing bar 52. ~s des~ribed in i3arrlls et al Patent 4 359 289 the coils 64 and 66 are energi~-?(l by signals which drive the shuttle assembly 28 and the court:erbalallcing bar 52 ata relatively constantvelocity through a~sulstantial portion of the distance oE travel thereoE betweell opposite reversals in direction. In the present example the opposite reversals in direction are provid?d by bumper ass mblies 68 and 70 rnounted on the base 12 and disposed adjac(?llt the ends oE the sllutt1e assernbly 28 an(i tl~e counte-balancing bar 52 respectively. Theshuttll?asseml)ly 28and the counterbalancing bar 52 alternattaly inpact the bumper ass?mblies 68 and 70 to provide reversals in the direction oE move;nent tllereoE.
The shuttle assembly 28 contains a plurality of print hamrners in the form of resilient hammer springs mounted along the length thereoE in side by-side Eashion and each including an impact printing tip for printing a dot on the print paper20. Each hammer spring is operated by an associated print hammer mechanism within the siluttle assembly 28 which employs a l~errnanent magllet to hold tlle hamlner sprin~ in a retract position and a <oil wllicll momentarily overcomes the magnetic elEects of the p?rmanent ma-~net when energized so as to cause the hammer sprin(3 to fly out o~ the retract position and into contact with an ink ribhon 72 disposed hetween the shuttle assembly 28 and the platen 26. This causes the impact printing tip on the hammer spring to impact th? ink ribbon 72 against the print pa[)er 20 as supported by the platen 26 to print a dot on tll? print paper 20. Tllereafter the hammer spring returns to tlle retract position under the inEluence of the permanent magnet. Energi~ing current Eor the various coils oE the difEer~?nt print hammer mechanisms witlin the shuttle assembly 28 is provided by a Elexihle wire bus 74 which extends betweell th~ shuttle assemb~y 28 and a termin(l?
bracket 76 mounted on the trame member 60. ~rom the termillal bracket 76 the various wires oE the wire bus 74 are coupled to appropriate circuitry within a housill~ 73 at the back oE
the print~t?r base 12. Th halnm?r springs an<l a.s.cociate-l print llalnlller m?chanislns Witilil ti~e :;huttle ;I~ lllbly 28 are SllOWIl and described in U.S. Pat nt 3 941 05l of l~-~rru.s ?tal Print-r 13~4709 ~ 71772-6 System which patent is collllllonly assignet] with the r)resent application.
The color printer 10 includes a ribl)oll deck 80 mounted on the base 12 at the forward en;l thereoL. ~rhe ribbon deck 80 has an opposite pair oE reels 82 and 84 rotati?bly mounted thereon and containing the ink ribbon 72. 1'he ribbon 72 extends L'rom the reel E32 throuc3h a ril~bon pAth whicll includes the print station 24 to the opposite r?el 84. ~s L~-?st shown in Fig. 2 the ribbon path inclucles a pair oE guides 86 and 88 disposed at opposite ends of the print statiol- 24.
Eacil of the guides 86 and 88 may contain an electrical sensor for determining when the ond oE the ribbon 72 is present thereat. Each oE the opposite ellds oE thf- ribbon 72 can be provided with a conductive portion which, when present at onc of the guides 86 and 88 provides an indication that the end of the ribbon 72 has been reache~ and that the direction oE
ribbon drive must be reverscd. The ribbon ~ath also includes an opposite pair of guidc?s 90 and 92 disposl?-3 adjacent tht?
guides 86 and 88. A pair of optical sensors 94 and sfi are disposed at the opposite end~s of the print station 24 adjacent and just inside oE the guides 86 and 88. The optical sensors 94 and 96 sense indicia on the ribbon 72 identiEying the color oE various color zones within the ribbon 72. 1'he ribboll 72 can also contain indicia indicating the opposite ends oE tlle ribbon 72, in which event tlle optical sensors 91 and 9G also ~rovide this data in lieu oE electrical sensors within the guides 86 and 88. The color~nd ribbon end identifying indicia and the composition of the ribbon 72 including the layout of the various color zones are described hereaEter.
The reels 82 and 84 are driven by motors 98 and 100 respectively which are shown in L'ig. 2. 'I`lle motors 98 and 100 are Inounted within the ribbollcleck ~30 and lr~ couE~led to a servo system 102 which is also shown in Fig. 2. ~ servo system 102 together with the motors 98 and 100 comprise Eor purposes oE the present e:cample the ribbol) driv? described in U.S. Patent 4 177 731 o~ i~l*ist et aL l'rinter System Qibbon Drive Having Colljt(ll)t: Rib')on Sp?ed anl-l~r-nsion~ ~hic!
piltent is commollly as~ji3n d ~ith th.? L~'''~ a! ~licatioll.

~709 The Kleist et al patent describes a printer system ribbon drive which comprises a servo system having a pair of motors for driving the opposite ribbon reels. The servo system drives the reel motors in response to external command signals so as to provide the ribbon with substantially constant speed and tension.
In like fashion the servo system 102 shown in Figure 2 controls the motors 98 and 100 so as to feed the ribbon 72 between the reels 82 and 84 at a substantially constant speed and under substantially constant tension. With substantially all of the ribbon 72 wound upon one of the reels 82 and 84, the servo system 102 drives the reels 82 and 84 so as to advance the ribbon 72 from the substantially full reel to tne substantially empty reel. Thus, if substantially all of the ribbon 72 is wound upon the reel 82, the servo system 102 drives the reels 82 and 84 to advance the ribbon 72 from the reel 82 to the reel 84. When substantially all of the ribbon 72 has been transferred from the reel 82 to tne reel 84, the optical sensor 94 senses indicia on the ribbon identifying 'J that the end of the ribbon 72 has been reached. This provides an "end of ribbon" signal to the servo system 102, and the servo system 102 responds by reversing tne direction of drive of the reels 82 and 84. This causes transfer of the ribbon 72 from the reel 84 back to the reel 82. When substantially all of the ribbon 72 has been wound on the reel 82, the optical sensor 96 senses indicia at the opposite end of the ribbon 72 indicating that that end of the ribbon 72 has been reached.

The resulting "end of ribbon" signal to the servo system 102 causes the servo system 102 to again reverse the direction of drive of the ribbon 72.
As previously mentioned the optical sensors 94 and 96 sense indicia on the ribbon 72 identifying the different 13~47~9 .
-15a- 71772-6 color zones witnin the ribbon. This enables the servo system 102 to determine the particular ribbon color which is present in the print station 24 at any given instant. It also enables the servo system 102 to drive the reels 82 and 84 so as to provide multiple passes of each color zone through the print station 24 as described hereafter. Such multiple pass 13~47~9 operation rel)restnts a cle~arturt? rrom the <;tal(3;1rd operation in which the ribbon 72 is driven at a nominal sL~eed in the same direction until the end ther~of is reacllt~d. In multiple pass operation the direction oE ribbon drive is reversed a numbt?r of times to provide repeated passes o~ each color zone oE the ribbon 72 through the print station 24 and as described hereaEter the capability exists ~or a~)igh speed ribbon search which can enable the ribbon drive to procee-l at hi~ll speed to the next color zone.
As previously describe(l)lerein and as lescribed in detail in previously referred to U.~S. Patellt 4 359 289 o~
Barrus et al the shuttle assembly 28 is driven along the print station 28 in bidirectiollal reciprocatillg ~ashion by action of a linear motor which includes tile coils 64 and 6G
on the counterb~Lancing ~ar 52. ~s the sl-luttle <ssembly 28 moves alon~ the print station 24 the various print hammers contained therein are s-lectively actuated or Eired by electronic circuitry contained within the housing 78 so as to impact the print paper 20 a~ainst th-? platel- 26 through the ribbon 72 to print dots. The bidirectional reciprocation of the shuttle assembly 28 carries it throuqll a su~icient distance so that the various print halnmers contained therein can print across substantially the entire width oE tl-e print paper 20. The sweep or stroke of the shuttle asseml)ly 28 across the print station 24 is determined in part by the number of print hammers contained within tl-le slluttle assembly 28. Thus, in the case where the ~shuttle assembly 28 contains 17 print hammers, the shuttle assembly 28 must have a str-jke or sweep of 0.8 inches to adequately cover a L~rint paper which is typically 14-7/8 inches wide. Where the shuttle assembly 28 contains 33 print hamlners, the require-l stroke or sweep is 0.4 inches.
Each time the shuttle asselllbly 28 sw-?eps across tlle print paper 20 in either direction, a dot row is printed on the paper 20. During the opposite turnaround interval~s o~
the siluttle assembly 28 wht?n either the bulnp~r asselnbly 68 is impacted by the shutti~ Issemt)~y 28 or tl~e t-llnp~r asselnl-ly 70 is impactl?d by tle c ullterbalancillg l-lr 52 the LaL~er 2() - 13~70g is incremel-ted upwardly by the tractor drivcs 30 and 32 to the next lot row position wl1ich is then printe(1 during the next sweep o~ the shuttle asst?lnbly 28 across the print paper 20. Simultaneously with reciprocation oE the shuttle assembly 528 across the print paper 20 the ribbon 72 is driven through the print station 24 by the servc systen 102 at a desire(1 nominal speed sucll as 3 inches pe1- secon(1 or 6 inches per second. Movement of the ribbon 72 at some nominal ~speed is required to prevent a ~reatly shortel-ed ril~bon life whicl1 would otherwise result Erom depletion oE ink Erom impacted areas oE the ribbon were the ribbon to remain stationary or be driven at too slow a specd.
Color printing requires that the printed matter bt' printed in a plurality oE diEEerent colored inks. A minimum of three colors is usually preferred to provide acceptable color quality and versatility with Eour or five color printin~
being preferred for certain applications to provide greater color quality and variety. Initially a p.l9t-? oE the print paper 20 has the various dot row positions thereo~ through 20the print station 24 by the tractor ~rives 3n and 32 to print a predeter1nined arrangement of dots in a Eirst color on the paper 20. Durin~3 printing oE such first color the servo system 102 insures via signals detected ~y thc optical sensors 94 and 96 that the correct first color on the ribbon 72 is 25present within the print station 24. Following printing oE
the page in the Eirst color the tractor drives 30 and 32 reverse thc direction o[ paper movement and return the print paper 20 to the beginning oE the page in preparation for I printing in a second color. In tl1e meantime the servo system 301 102 advances the ribbon 72 in the high speed search mode so I that a color ~one thereoE containing tl1e second color to he printed is located within the print station 24. The tractor drives 30 and 32 again increment the various dot row positions of thc page throu~l1 the print station 2~ as the reci~rocating 35shuttle assenb]y 28 prints a pre(1eterrl1ined arrangement oE
dots on the page in the second color. The plocess is then ! repeated Eor a thir(l color allcl ally ad-1ition11 colors ~1hich are Lo bu plinted on tl1~ paye. ~h~-n tlls l~st color hna l>een ~.,;

printed on the page, the tractor drives 30 and 32 do not return the beginning oE tlle page to the print station 24 but ratiler continue to advance the prillt p.~per 20 in tlle upward direction through the print station 24 as printing of the next page is begun.
The color printer described in previously referred to U.S. Patents 4,289,069 and 4,336 751 oE ~elissa et al utilizes a ribbon divided into tllree c~ifferent color ~ones along t11e length thereof. (`olor printing is ~ccompli~shed by printing a page in a first coLor during whicll the Eirst color zone is advanced through the print station of the printer, followed by printing o~ the same page in a second color as the seconc~ color zone oE the ribbon is advancecl througll the print station and then in a third color as the third color zone oE the ribbon is advanced through the print station. A
similar ribbon arrangelnent involving ~our different colors is sllown in Fig. 3.
Fig. 3 depicts an ink ribbon ]04 which may be used as the ink ribbon 72 in a printer such as the color printer 10 and which is divided into four different color ~ones along the lenqth thereof between opposite first and s~cond ends 106 and 108 respectively. The ribbon 104 includes a Eirst color zone 110 which begins at the first end 106 and which contains yellow ink. The first color zone 110 is Eollowed by a second color zone 112 containing red ink, then a third color zone 114 containing blue ink and tllell a fourth color æone 116 which is at the second end 108 oE the ribbon 104 and which contains black ink. When the ribbon 104 is advanced in a Eirst or "forward" direction between the reels a2 and 84, the resulting forward sequence is to pass the yello~ color zone 110 through tlle print station 24 followed by the red zone ll2, the blue zone 114 and finally the black zone 116. This is a desirable sequence in that it presen~s the lightest color first Eollowed by the other three colors in ~he order of decreasing lightness.
Each time a page on tlle print paper 20 is printed, some of the ink previously printed on the page tends to rub oEE on the ribhon. I~l-ere the previcasly printed in~ is llcl)ter in color than the color presently being printe(1 ~:he rul~ g oEE oE the ` ~3~P47~ ~

lighter colored ink onto the ribbon presellts a relatively minor contamination problem with respect to the ribbon.
However, where the ink previously deposite(3 on the page is darker in color than the color present]y being printed, even very small amounts of the darker ink have the eEfect oE
contamina~ing the lighter colored zone of the ribbon currently being used for printing.
For this reason the Eorward sequence shown in the case of the ribbon 104 oE Fig. 3 is clesirable. Yellow is lighter than red which in turn is lighter than blue which in turn is lighter than black. A ~)roblem arises however when the second end 108 oE the ribbon 104 is reached. Lf the direction of ribbon drive is simply reversed, then the order of printinc3 is reversed with ~lack being printed Eirst, Eol-lowed by blue, then red and then yellow. If the ribbon 104 is driven in one direction only for printing so that the forward sequence is carried out, then the problem is avoided.
However, this requires tllat printing be delayed while tlle ribbon 104 is(lriven in the reverse direction Erom the seconc~
end 108 back to the first end ]06 so that printing can again resume. OtZler problems such as uneven ribbon ~ear a1so result because printing is always colnlnenced at tlle sa:ne end oE each of the color zones 110, 112, 114 and 116. Thus, where the driving speed of the ribbon 104 is timed so as toInove each of the color zones 110, 112, ll4 and 116 thl-ou(~ll the print station 24 in the time that it takes to print a full page froln top to bottom in a given color, then pages containing less th~n a fu11 page of print result in the repeated use oE one end oE
eacll color zone to the e~clusion of the opposite end oE the color zone.
These problelns are avoided in accordance with 'lle invention by arrangin(3 the color zones aLong the length oE
tke ribbon so tllat tlle clesired printing sequence from lighter colors to darker colors is basically observed Eor both direc-tions of ribbon drive. rhis is accomplished by repeatingcertain color %olles in a pl-edetellnined pro(jressio'l or pattern along the lengtll oE the ribbon an(l then skippino certain zones as the ribbon is driven tllro~ h the print station 2~ during - 13~470~ -printing. ~n example o~ such a ribbo~ i is shown in Fig.
4. Tlle ribbon 118 which has opposite rirst and second en(ls 120 and 122 respectively can be assumed to have essentially the same length as the ribbon 104 in Fig. 3. Instead o~
having just four color zones as in the case o~ the ribbon 104 of Fig. 3, the ribbon 118 oE ~ig. 4 llas a considerably greater number o color zones o~ recluced size.
It will be seen that the ribbon ll8 oE Fig. 4 begins atlthe first end 120 with a yellow color zone (Y) 124 followed by a red color zone (R) 12G, a blue color zone (~L) 128 and a black color zone (BK) 130. Such pattern is the same as that found on the ribbon 104 of Fig. 3. ~lowever, be~ore repeating the Y-R-BL-BK sequence along the ribbon 118 an extra red color zone 132 is added. The pattern o~ light to dark then repe~ts itsel~ with a yellow color zone 134, a red color zone 136, a blue color zone 138 and a black color zone 140.
~gain, an extra red color zone l42 is added ~ollowing tlle black color zone 140. ThereaEter, the ligllt to dark pattern repeats with a yellow color zone l44, a red color zone 146, a blue color zone 148 and a black color zone l50. Again, a red color zon~ 152 is added ~ollowing the black color zone 150. Finally, a yellow color zone 154 is added to complete the length of the rib~on 118.
The forward sequence or the ribbon 118 involves passing the yellow color zone 124 througll the print station 24 followed by the red color zone 126, the blue color zone 128 and then the black color zone 130. At this point tlle Eollowing red color zone 132 is quickly advanced through the print station 24 without printing. Printing is then resumed using the yellow color zone 134, the red color zone 136, the blue color zone 138 and then the black color zone 1~0. ~gain, the extra red color zone l42 is quickly passed through the print station 24 without L~rinting. Printin~ is then resumed using the yellow color zol-e 144, the red CO101 z.one 146, the blue color zone 148 and then the black co]or zone 150. ~t this point the red color zone 152 is again skip[)ed an(l printing is again commenced usinl lin~ yellow color 7.0ne 154.

_ 13~47~9 ~ rhe yellow color zon~ l5~ whicl~ is at tile seCooc~
end 122 oE the ribbon 11~ can be advanced througll the print station 24 in either the Eorward directioll or tlle reverse direction as convenient. A typical example is to advance the ribbon ll8 to the end 122 t:hereoE Eollowing pl-inting with the black color zone 150, whereupoll tlle drivt? oE the ribbon 118 is reversed and printing is carri?d out within the yellow zone 154.
Printing is then continued in the reverse direction throu(3h th? red zon ? 152 the black æone l50 and the blue zone l48. Although the darker black zone 150 is L~rintecl before tlle sornewha~ ligilter blue zone 148 is printed, the contamination ef~ects arelninimal due to the relatively small differencc? in lightness hetween the blue ink and the black ink. What is signiEicant is th~t printing oE tlle relatively dark bLue ink and the even darker black ink does not preced printing of the lighter r~-~d ink which in turnc1oes not precede printing oE the still ligllter yellow ink.
Following printing within the hluc color ZOI1e 148, tlle red color zone 146 is skipped and the Y-R-BK-~L sequence is tllen reL)eated by printing througll thl? color zones 14~
142, 140 and 138. The red color zone 136 is tllen skipped and printing is again carried out llsing tlle yellow color zone 134, the red color zone 132, the black co]or %one 130 and then the hlue color zone l28. Ihe rt?d color zone 126 is thel-skipped and printing using the yellow color zone 124 is then commenced in either the reverse or the Eorward clirection as convenient .
It will be seen that the ribbon 118 of Fig. 4 l1aS
a repeating progression or pattern which be-3ill~s with tlle lightest color yellow which is then followed by tlle next darker color red and thell Einally 0l1e or Inore zones oE the darkest colors which in this exalnp1e comprise blue and black.
The intermediate color red is then rep,?ated before again commencing the lightest to darkest Se~l]enCe Y-R-BL-BK. The lightest color yellow apL)ears at each o[ tlle 3p!705it':? ends oE the ribhon 118 to insll-~ that printin~7 in botll directions oE rihbon clrive wilL oe3in with the 1il3l~eat c~ lor. ~his is 13~47~g also a(lvalltageous because th? Ii~ test coLoL-s l:en(l to depl?te tle fastest.
The number and length of the various color zones within the ribbon 118 is letermined at l~ast in part by the printinq speed of the color printer 10 and the spee(:l o~ riblon drive. In the case of one example oE the Irinter 10 o[ Lig.
1 having 33 print hammers within tlle shuttle ~sseml)ly 28 approximately 30 milliseconds are required to print each dot row across tlle print papcr 20 witllan adclitional 6 milliseconds being required to accomp1ish turnaround oE the silutt1e ~ssem-b1y 28 and advancement oL~ the print ptiper 20 by one dot row position by the tractor drives 30 and 32. IE printing is at a dot density o~ 100 X 100 per inch then th? time required to plot a page 11 inches loncJ is alproxilnate]y 40 seconds. ~t n lesser dot density of 50 X 50 per inch the time required to piot an 11 inch page is approximately 11.3 seconds. IE the minimum acceptable ribbon speed for reasonable ribbon liEe is determined to be three inches per secon-l then 3-1/3 yards oE ribbon are needed to print an 11 inch pa3e in one color using lO0 X 100 dot density and .945 yards o~ ribbon are needed to print the sam? page in one color using 50 X 50 dot den s i ty .
In a Eurther exalnple oL the color printer 10 the shuttle assembly 28 contai-ls 17 print hammers instead oE 33 print hammers. In that instance the total time required to print a dot row and accomplish t~rnaround becomes 66 milli-seconds. This translates into 73 seconds being required to plot an ll inch page at lO0 X 100 per inch dot density and 25 seconds being required to plot tlle page at 50 X 50 per inch dot density. At a nominal ribbon speed oE tllree inches per second 6 yards of ribbon are required to print the page in one color at 100 X 100 per incll dot dt?nsity and 2.1 yards are required at 50 X 50 per incll dot density.
When a ribbon containill(3 a ~)luralil:y oL di~ferent color zones such as the ribbon ~l8 is wound on thl? spoo1s 82 and 84 there is a t~n(l ncy Lor tht? overl~L;illg portions o~
the ribboll at the int~rr~(e bttw~ell ~:wo ldj(colt color zones to blee-3 ink in!:o eacll ot:.~ r th?l-eby c~(tl~in~ l contalninatio ~3C1 47C~9 problem. ~o prev,?rlt this probl.em ~ e in~:?rElc~ between ~ach adjacent pair of color zones in tl~e ribl)oll ll8 is providcd with at least one barrier zone. One preEerred arr~ngemfllt which is shown in Fiq. 5 places a pair oE barrier ~ones 156 and 158 between each adjacellt pair of color zones 160 an~
162. The coLor zones 160 and 162 could comprise any adjacent pair of color zones within the ribbon 118 S~ICll as the two color zoncs 124 and 126 at the first end 120 oE the ribboll ll8 or the color zones 138 and lq0 at ~n interm~ e portion oE
the ribbon 118. The barrier zone 156 interEaces with the color zone 160, while the barrier zone 158 interEaces wi.th the color zorle 162. A single cleaning zone lG4 consisting oE
a length of blank or raw ribbon is disposed between the two barrier ~ones 156 and 158.
During operation of the ribbon deck 80 shown in Figs. 1 and 2, ink from the various diEferent color zones tends to rub oEf to some extent onto the guides 8G 88, 90 and 92. Such ink can rub onto a color zone oE ditfPrent color so as to create a contaminatioll problem. The cleaning zone 164 minilnizes or eliminates this probleln by rubbil-l(3 ofE or absorb-ing most oE the ink from the guides 86, 88 90 and 92. Thu;, iE the col.or zone 160 is passing over thl.? guides 86, 88, 90 and 92 such that some oE the ink from tlle color zone 160 rub.s onto such elements, the subsec3uellt passa-3e oE the section oE raw ribbon comprising the cleallinc3 %one l64 wipes ofE or otherwise absorbs most or all oE such ink Erom the yuides 86, 88, 90 and 92 prior to passage oE the following color zone 162 throu(3h the print station 24 and over the guides 86, 88, 90 and 92. This prevents contamination of the color zone 162 by ink from the preceding color zone 160.
Each oE the barrier zones 156 and l58 preferably has a lengtll at least equal to the outer circumference oE the reels 82 alld 84. This comp?nsates for the worst case in which the section oE ribbon shown in Fig. 5 is at the outer portion of a ribbon pack wound on one of the reels 82 and 8~ with the ribbon pack Eilling Ul? substalltially the entire reel. By making the bnrrier zon,?s l5G and l58 oC su~ irlil~ m le~
the barrier ~one 15G prev~rlts ally overla!) ol~ the color zo~le `- 13G4709 ! -2~-160 with th(? cleaning zone 164 and the barrier zone 158 prevents any overlap oE the color ~one l62 with the cleaning zone 164. The barrier ~ones 156 and 158 al-i the cleanin(3 zone 164 together prevent any overlapping of the color zones 160 and 162. The barrier zones 156 ~nd 158 are preferably coated with a non-wetting agent such as by spraying with a fluorochemical polymer. This prev-~nts seep~ge oE ink through the barrier zones 156 and 158 between adjacf?nt seglnents of the ribbon.
Unlike certain multi-color ribholls of tlle prior art which are comprised of different segments of fal~ric welded together at the boundaries thereof the ribbon 118 consists of a continuous length of fabric having no welds seams or other joints. This makes the ribbon much less pronc? to breaking pulling apart or otherwise failing.
As seen in ~ig. 5 eacll of the barrier ~ones 156 and 158 has a different set of in3ici~ 166 and 168 thereon. The set of indicia 166 serves to identify the color within the color zone 160 while tie set of inlicia l68 serves to identify the color within the color zone 162. Eacl7 of tile sets of indicia 166 and 168 comprises one or more strips extending across tie width of tlle ribbon between the opposite edges oE
the ribbon. The strips whicil are reflective in nature so as to be detectable by the optical sensors 94 alld 9G and which are preferably applied by foil hot starnpincJ vary in number and can also vary in width as well so as to idelltiEy tlle colors of the various ~ones in conventional bar codt fashion. Tlle use oE Eoil hot stamping pLovides very thin opaque films on the ribbon Witll no signiEicant buildup oE ribbon thickness so as to not obstruct tlle paper path when passing tllrouqh tlle print station. Sets of indicia like th/? sets 166 and 168 can also be used to identify t.lll? opposite ends of the ribbon as previously noted thereby liminating th(? eed for conductive segments at the opposite ellds o~ the ribboll in conjunction with~?l~ctric~l s?nsol-l;wi l:lli.ll tll.?guill?s~Gc~ 88.-ls previolls-ly descri he(l .
(~ne exampl-? or a bar ~ode schl~me Ior idenl:if~ing the four differellt ribl) colol-; of til pr st?ol: ~xampl(?s ~s - 13~470 well as the opposite en~ls oE ~he ribbon uses [ive strips to identify yellow, Eour strips to identiEy re~, three strips to identify blue, two strips to ideotiEy hlack anc1 a single strip to identify the end oE the ribbon.
The ribbons in the present examples are described in terms of the colors ye11Ow, red, blue and bl-ack for conveni-ence of illustration only. ~s previously noted diEferent numbers oE colors and diEEerent comhinations of colors can be used to efEect color printing in accordance with the invention. Also, in the present Eour color e~alnple, the red color is more technically magenta in shade, and the L)lue color is more technically cyan in shade.
The operation oE the color L~rinter 10 h~s thus far been described in terms of a single pass oE ec~tch color zone oE the ribbon through the print station 24 as the ribbon is driven in a given direction. As a result the printing of a given pac3t? is begun at tlle same edge oE each color zone used in printin~3 tilat page for a given direction oE ribbon drive.
If all or substantially all oE the p~ge contains printed matter, then vir~ually all of each color zon? is used t3Urill~3 the printing. IL on the otherlland the page contctins consider-ably less than a full pacJe of printed matter, then only the Eirst portion oE eacl- color zone is used. Because many of the pages heinc3 printed by~-t printer such as the color printer 10 involve less than a Eull page oE printed mattel^, the ribbon tends to wear unevenly. Accordingly, more even utilizatioll oE the ribbon color zones would have the effect of prolongin~3 the useful life oE the ribbon.
A further problem can occur in terms oE the speed or eEficiency of printing when a single pass oE each color zone through the print station is utilize~l. Ag~in, ~here a given page being printed has less tllan a Eull pn(3t? oE printe(3 matter thereon, then only t:he first portion oE the i~ass throuc311 each color zone is accom!)anie,3 b~ printinc3. The prillter must sit idly througll tile latl:.~l- portioll oE each such pass awaiting arrival oE the next COlol-;olle nl: ti~e l,rint sttl:ion ~4 b.Eol-~
L~rintil~(3 in ~ x ~ 1 i rl .

- 13~4709 ~ printing tecl-nilue in accorddnc~ witll the inven-tion which tends to distril)ute~ ribbon wear more uniformly and which at the same time ten~s to make the printing process Easter and Inore efEicient utilizes multiple passes of each color zone oE the ribbon through the print station 24 oE the color printer 10. Such technique is illustrated in ~igs. G
and 7. The example oE Fig. 6 involves three different passes of each color zone through the i~rint station 24. Thus a yellow color zone 170 makes a first pass 172 through the print station 24 in one direction ~ollowed by a secon~ pass 174 through the print station 24 in the opposite direction. The second pass 174 is followed by a third pass 176 which again is in the first direction. A similar sequence o~ three diEferent passes is utilized within each oE the following red blue and black color zones 178 180 and 182 during the continuation o the sequence.
'I`he three diEEerent passes within each color zone such as thc passes 172 174 and 176 within the yellow color zone 170 are accomplished by the servo system 102 which responds to the bar coded signals from tlle optical sensors 94 and 9G indicating when the opposite ends o. the various color zones are reached. Thus in the case oE the yellow color zone 170 the servo system 102 causes the zone 170 to pass throu(3h the print station 24 to complete the Eirst pass 172. When an end 184 oE the yellow col.or zone 170 reaches the print statiol- 24 this con~ition is sensed by one oE the sensors 9~ and 96 and the servo system 102 responds by reversing the direction of ribbon drive to commence the second pass 174. ~he second pass 174 continues until an opposite end 180 of the yellow color zone 170 is reached. When the end 186 is re~ched the associate~ bar co~1e in(1icia is sensed by one of the sensors 9~1 and 96 and the servo system 102 resi?onds by again reversing the dil.-ction oE rihholl lrive to commence the third pass 17G oE the yellow co].or %one 170 through the ~rint station 24. ~t the ~nd of ~ht? third l)ass l7~ the servo systcm l n2 i~]llores ~ ? (~'`CUrr~ l b~c~ls~ oi-the presel)ce of coul)tin~ circui~:ry ~h~ hi 1I di~terlnin(~s that the thrce passes ol lI)e yellow (ol~- ~one I70 i)avc he~?ll !- ~ 3~47~ 9 made. The servo system 102 simply contin~l~?s into th~? red color zone 78 where the thre,? p~ss proc~?ss is rer)eat~d.
It will be seen that the three pasi technique shown in Fig. 6 tends to utilize both ends oE eacll color zone as well as the intermediate portions oE the zone. Such technique also lends itselE to a Easter and mori? eEEicient printing technique as well, as illustrated in Fig. 7 wllich again shows the four color zones 170, 178, 180 and 182 oE tl~e exalnple oE
Fig. 6. In the technique illustrated in Fig. 7 a deterlnination is made with respect to the amount oE inEormation to be printed on a given page. This is easily accomplish.-?d because the information to be printed is typically inputted into and stored within the printer 10 prior to printing as described in connection with the previously referred to U.S. Patent 3,941,051 of Barrus et al. Consequently it can be determined prior to or at least at the end oE the Eirst sweep through the Eirst color zone durillg printing oE a given page whether printing o the page h.lS been complete~ or whetller additional passes are nt?cessary. I`ht? ex~mple shown in th~? lower portion of Fig. 7 assumes a case in JJhich only ti~e very top portion of the given page to be-printed involves printedlnatter. Because the length oE the printed matter is less than 1/3 page, only a single pass is required tl~rough each oE the four color zones 170, 178, 18() an~ 182 ~o accomplished printing oE the page.
This condition is illustra~ed ~y the line 187 in the bottom postion oE Fig. 7. Prior dt?termination o~ the length of the page to be printed enables the servo system 102 to proceed with a single pass through each of the color zones. ~oreover, a higll speed search mode oE opc?ration can be used to advance the ribbon to the next color zone at hic3her speed Eollo~ling termination of printinq.
B cause multiple L>asses througl- each color zone are contemplated in the examples oE li~3. 7, ti~e various color zones oE th--~ rihbon call b. sl~ol-tened ~-r the nominal ri~bon speed call b? increas.<i colnp;1l-ed to ti~(: singl~ pass approach previously d?scril)e(l. Accoriingly, v~n wl~en printing is completed p;lrt ~a~ thl-o~ e.'lCi~ Or tht' COIOI- zcnes 170 178 180 and 182 the time ~ ire(l t) proceed 1--~ Il)e lleXI: coior 13~4709 zone is collsiderably less thln in thr? casl oE the single p3SS
approach .
Fig. 7 illustrates a Eurther -xample at the top portion thereof which involves a determination that the infor-mation to be printed ona given page occupies onlyapproximately1/2 the page. In SUCIl example a Eirst pass 18~ is made througll the yellow color zone 170 followed by a reversal in thc direction of ribbon drive alld the colmnenc*ment of a second pass 190. Approximately halF the way through the second pflSS
190 it is determine(~ that printing oE tlll plge in yellow h~s been completed. At tilat point the direction oF ribbon drive is again reversed and the systeln procee-3s directly to the red color zonc 178 by making a shortened thircl pass 192 through the second half oF the yellow color zone ]70. Ille high speed search mode is preFerably entered so as to accomplist- the third pass 192 at high speed. ~ similar tllr-?e pass procedure is ~ollowed throuc3h eacil of tlle remaining co]or zones 178 180 and 182 to complete the printing o~ the given page.
~t will be seerl thnt where a multiple pass printinl technique is used c~n orlr3 nulnb?r oF p~lS',~:?S is made throu(3h eacll group oE ~our color zones in the rresent examp1e. It is possihle for a single pass to be made through each o~ tile four color zones as shown by tle line 187 oF the example in the lower portion of Fig. 7. Also as shown in Fig. 6 and in the top portion o~ Fig. 7 three diffèrent passes through eacil color zone are also possible in which event tlle passes may be complete passes in the sense o~ coverin-~ ~lle entire length of each color zone as in the case of Fig. 6 or tiley may involve several shortened passes as in the example at the top portion o~ Fig. 7. In any case two direction reversals oF the ribbon drive are involved witllin each color zone except in those instances where only a single pass is r?3uirecl by a page o~
relatively short length.
As c3iscussed h?reafter in connectiol- with Fig. 9 a multiple pass tectlnique o~ operltioll nc?e~l not be limited to three passes but Cflll involve o.h~r o(ld nr~ bel-s oF passes sucl~
flS F i V~?, S~?VC?Il or ni 13(;~4709 Ii~. 8 is useful in e~xl)laining ~:he Inallner in whicll the len~ths oE the various color zones of a rihbon can be chosen so as to provide for a ribbon oE desired overall length in the Eace of different usable dot densities. In the example of a shuttle assembly 28 havin~ 17 print hammera a single pass oE the color zone requires approximately 25 seconds to accomplisll at a ribbon speed oE 2.9 inclles per second iE the color zone is approximatc?ly two yards in length and the printing lensity i.s 50 X 50 dots per inch. When the print density is increased to 100 X lO0 dots per inch, then it can be determined that 73 seconds within the color zone are required iE the color zone is approximately t~o yards lon~
and the rihhon speed is 3 inches per second. l`his can be accomplished without lengthening the two yar(1 long color zone by making tllree passes tllrough the color ~one.
lhus, as il1ustrated in Fig. 8 a co].or zone 194 which has ~-l length of two yards and is movinq at a nomina].
speed of 3 inches per second retluires a singl.e pass thereoE
in the case o~ 50 X 50 dots per inch print dellsity and threr passes th~reof in the case o~ lO0 X 100 dots per inch print density. ~gain, this assumes ~ 17 print llammer slluttle assembly 28.
In the example of a 33 print hammer silutt1e assemb1y 28, the printing speed is virtual1y 3Oubler-3. ilowever e~ch of the color zones such a.s tll2 zone 194 shown in Fig. 8 can be maintained at the two yard 1ell~th sirnply by doubling the nominal ribbon speed to 6 inches per seconcl. Accordin~i.y, the techniques illustrated in Fig. i3 apply to a 33 hammer system as well as a 17 hammer system if tlle nominal ribbon speed is doub1ed to 6 inches per second.
The two yard nominal 1enr3tll oE a color zone can be used to make a ribboll similar to the ribbon 118 sho~/n in Fig.
but havin~ a total oE 26 coLor zones. The 26 color zones require a l:otal of 52 yarcls oE ribbon letlgth alld the interven-ing barrier an(l cl.eani.n-~ zor)es such as sllown ir-l;ig. 5 requirt-approximately 8 ad-3itiollal yclrds oE ril~boll l~ngth. Ihis provides For .~ t:otal riii)orl Lell~Jtll o[ 6() yard- ~hicll is -a stan(3ard ribl)on1?ll~tllu.-;tlilldo~ atri~:L,rin~:~rs ol tilis tyl>e.

13~4709 I:i(3. 9 provi-3es a Eurtller illustr.ltion oE tilf? manner in which multiple pass operation can be utili%ed in con jurlction with a nominal ribbon spee(l and color zone lellgtl7 to mak~-? the salne ribbon usable at different dot densities anc=i within 5 printers having difEerent nurnbers of print h~ammers. In tilf?
examp1e of Fig. 9 the ribbon is driven at ~1 nominctl speed oE
8 inches per second, and a color ~one 196 shown therein hcts a lengtll or two yards. The approximate times requir-?(l to make one, three, five, seven and nine passes thl-oucih sucll 10 color zone are il1ustratr?~. Based on this i t can l?e determined tl-at a 17 hammer printer requires three oasses tilrou(JIl eacll color zone for a dot density of 50 X 50 dots per incll and nine passes through eacll color ZOn(? for a dot densi ty of 100 X 100 3Ots per inch. A 33 hammer printer requi rcs a single pass throu~h e~ch color zone Eor ~-t diot (1ensity of 50 X 50 dot:s per inch, and five passes eacll color ~one Eor a dot df?llsity ot 100 X 100 dots per inch.
As ~reviously noted the tractor drives 30 and 32 increment the print paper 20 in an upward direction through each oE the successive dot row positions of a E?agf? durin~
L?rintin~J thereol in a giv n color, folLowinci whicll the p-tp-~r is dciven in the reverse diirection to return to t~le beginning of the page in preparation for printing oE tile next color. T t is desirable to be ab1e to llold tile print paper 20 in tension as it moves through the print statioll 2~ in eithf?r direction.
This is accolnp1ishecl by the arrallyement showl- i n l igs. 10-12 which includes the elongated bracket 42 and th~.? rectan~u1ar housing 22 previously noted in connecti on ~i tll ~ig . l . A~s noted in connection with Fig. 1 the e1Ongated bracket 42 is pivotally coupled to the shaft 36 of the tractor clrives 30 and ? 32 at the u[?per end 44 thereoE. The pivota1 Inoulltin~3 is accomplished by a hinge Inelnber 198 couple('i to t'hf-? upper elld 4q oE the bracket 42 and llnvi ng a~l a~er~ e 200 tllc?rein tor receivin~ the shaft 36.
A torcjlle motol^ 2()2 is moulltl?d On tlle hricket 42 at a lower endi 2011 thel-eor ! ~o;i~:~ the Ul p ~r erl(3 44. Tlle torc~ue motor 202 llds a cirive whe 1 2i)G couple(l t o h~ rotlt lhly (irivell tllerel)y. 'I'l~e drivc ~ e~l ;'()G h;l; all eln~ eric nlltc?r sl!rrace ~3~4'7~

sucll ~.s oC ruL~b--r to l~roviclt? tr;lctioll bt?tw¢?t?rl til? wileel 206 and the pri~t L~aper 20. A r~ctan3ular-shape.1E)ernanent mactnet 208 is mounted on the br~cket 42 at ~n in~eL^Illediate portion thereof between the upper end 44 and the lower en~ 204. The permanent magnet 208 normally attaches to the back of the platen 26 by magnetic attraction to hold tlle pivotal bracket 42 in all operative position in whicll the drive wlleel 206 oE
the torquemotor202 engac3es the back side oEthe print paper20.
Witil tlle bracket 42 in the operativ-? position, the drive wheel 206 presses the print paper 20 against an arrange-ment oE rol1ers 210. Tll~ rollers 210 are rotatab1y mounted in side-by-side fashion along the length oE a sllact 212 extending between and mounted on the opposite ends oE the rectangular housing 22. Consequently, the various rollers 210 extend across the width of tl-e print paper 20. The various~
rollers 210 are rnade oc a non-wetting mat¢?rial 5UCIl asl)elrin so as to have an outer surface which does not absorb ink. This is important ~ecause the ro]lers 210 come in contact with portions oE the print paper 20 which have already l~een printed in one or more colors when the paper 20 is reversed ancllnov¢d downwardly to return to the top of a givel- pac3¢? beillg printel in prepar~tion for printing in the next ¢olor. The driv¢
wheel 206 which pushes the back oE the print paper 20 against the rollers 210 need not have a non-wetting outer surEace a~s it contacts a side o~ the paper which does not contain ink.
In operation the torque motor 202 is driven in the same direction as tl~e tractor drives 30 and 32 ~ut at a different rate. Whell the print paper 2n is driven in an upward direction by the tractor drives 30 ancl 32, the torque motor 202 causes the drive wheel 206 to rotate in tlle direction of upward paper movement at a slower ra~e. This creates a desire¢1 alnount oE tension in the print paper 20 within tle print statioll 24. When ~h.-? prillt p;~ r 2() is driv¢?n in -a downwar;l direction hy th¢? ~ractor driv s ~() al-d 32 the tor~3u?
motor 202 is ¢driven so ~; ~o ro(ate tl~¢lriv wll el 20G in a directi.on o~ downwar~ ap,?r m;)ve:nent .'1~' n s].i Jhtly EasteL-rate thall tllat provillo(l i.y l:he tractor dliv~; 30 nl-(l 32. Ihi.s i ~3~47()9 acts to maillt3in tlle clesire-3 L nsion withill tlc paper 20 at the print station 24.
As previously noted the permanentlna(]net 208 clamps to the back oE the platen 26 to hold tlle bracket 42 in the operative position in which tile drive wheel 206 presses the print paper 20 against the rol]ers 210. Ti~e bracket 42 may be pivoted out oE the operativ~ position to move the drive wheel 206 away from the print paper 20 and tl-reby facilitate loading and unloading of ti~e papfr witilin the printer 10.
This is accomplished by action oE a relatively Elat cam 214 which is mounted on the top of til? platen 26 and which has an edge of slightly tapered thickness that engages the permanent magnet 208 so as to push the magnet 208 and the attached bracket 42 outwal-dly when the platen 26 is rotated. The lS platen 26 is made rotatable about a shaft 216 therethrough as shown by an arrow 2l8. Because the shaft 216 is of~-center relative to the platel- 26 rotation of the platen 26 pulls it away ~rom the shuttle assembly 28 to Eacilitate loading and unloading of the urint paper 20. Thus at the same time ti~at the platen 26 is rotated to open such space the cam 214 engages the permanent magnet 208 to push the bracket 42 outwardly and thereby move the drive wheel 206 wllictlis coupled to the torque motor 202 away froln the rollers 210.
The rectangular housing 22 includes a paper guide arrangement having an opposite pair of pape~l guides 220 and 222. The paper guides 220 and 222 which extend along the length of the rectangular llousing 22 at the inside o the housing 22 extend upwardly in a direction toward the drive wheel 206 and the rollers 210. The paper cJIlides 220 and 222 conver~e toward each other as tiley extend upwardly until tlley reach an area of minimum s-paration tllerebetween immediately below the drive wheel 206 an~ the rollers 210 as shown in Fig. ll.
The paper guides 220 alld 222 fc~cilitate loading of the print paper into ~lle cf)lor printer 10 As sllown in Fig. 1 a pap-r stack lf3 is l)~ lllllly disposecl on tln~ Eront portion 16 of the suLL~ort pef.lestn~ hl~ st~ k lf~ (~olllpri;~s a fol-l 1 length oE tlle print pal)~ r 2() . Tlle pri l-t pal)er 2() i.s loa~ed ~3~7~9 by pulling it upwar-ily anl in-;~r~in-3 it in~:o the bottom of the rectangular housing 22. At this point the paL~er guides 220 and 222 serve to guide the edc3e of the r~aL~er as it is ~ moved upwardly between the drive whee1 206 an(1 the rollers 1 210, through an opening in the base 12 between tl1e platen 26 ! and the shuttle assembly 28 and into the tractor drives 30 and 32.
Fir3. 13 illustrates a roller guidf? which can be used as tll? guides 86 88 90 and 92 sl1owr1 in Fig. 2. Lhe guides u~ied in a ribbon dec`~ oE tl1is type normally comprise a fixed mel11bt?r or post around whicl1 the rib~on is ~rawn. Tl1e practical result is that Som? of the ink from th(? ribt~on rub.s onto the guide. l`his is not a particular prohlem in tl1e case oE an all black ribbon used in black and white printing. In the case of color printing however ink Erol11 one color ZOllC
which is deposited on a gui-ie and ther~aEter rul~s off on a diEferent color zone creates a contamination problem.
Such problem c~n 1>.- minimized by use oE the roller guicde 224 shown in Fig. 13. rLhe roller guir1e 224 comprises a spool 226 having opposite Elang-?s 228 and 230 of greater diameter and which is rotat.1bly mounte-3 on ~3 v;-rtical shaEt 232 which in turn is mollnte(l on the deck 80. Ihe rotatably mounted spool 226 is free to rotate with the ribbon 72 as the ribbon 72 is hidirectionally driven. Rotation ot~ the spool 226 with the ribbon 72 acts to greatly minimi~.e the amount of ink from the ribbon 72 which is deposited thereon, when contrasted with the fixcd ribbon guides of the prior art.
Moreover, the outer surEace of the spool 226 is comprised oE
a non-wetting material such as reflon~w11ich does not absorb ink from the ribbon 72. Ti1is also 3reatly minimi~es the amount of ink Erom the ribbon 72 which is deposited on the spool 226.
As noted above in col1ncetio11 witl1 ~ig. 13 the guides used in a rihhon drive mecl1al1isn1 oL th-- type ~shown in t;~ig. 2 normally compris(? a fixed m?ll1ber Ol- L)ost around which tl1e ribbon is drav~r). 1he l)roi)lem with ;UCi1 fixed gui(1es lies in the subst~ntill al11ounti,l inl~ w1lich c1l) rub onto tlle gUid(?
Erom the ribb~n. I~1i.s ii ot: n l~arti(ula~ prot)1en in tl1e casc ~ T~ k 13~9~7~3~

oE a single color ribbon, but in the case oE a rnulticolor ribbon at least some of the ink deposited on tllt? ~uide can be transferred to a different color zone, even where the ribbon is provided with an interveninq cleaning zone such as tlle zone 164, thereby resulting in contamination. ']`he roller guide 224 shown in Fig. 13 minimizes this problem by providin~
a spool 226 tht?reof which is free to rotate with the ribbon 72 as the ribbon 72 is bidirectionally driven ~ 3Owever the roller guide 224 o~ ~`ig. 13 is not without one possible probleln of its own If the central axis oE the spool 226 about which the guide 224 rotates is precisely located relative to the passing ribbon, then the ribbon tends to roll over theguide 224 in smooth, continuousant3nondistort-ing fashion. However, there is a tendency for the rotatin~
spool 226 oE the guide 224 as in the case oE any rotatable ribbon guide to steer or guide the ribbon thereover, and this can result ina tendency on the part oE the ribbon to eventually fold over on itself or run complete7y oEf of the guide in certain extrelne cases, particularly where the central axis oE the spool 226 is not precisely located. Ttlis is not a problem in tlle case of stationary guides which do not rotate However, as noteri above stationary guides have the problem of eventual ink buildup with possible contamination oE other color zones in the case of a multi-color ribhon.
Figs. 14-17 illustrate an alterllative embodiment of a ribbon guide 240 which avoids the problem of ribbon steering or guiding present in the case of rotatable ribbon guides while at the Saln~-? time minimizing the possibility of contaminationwhen used with a ribbon comprised ofa succession ofdiEferentcolorzones. The ribbonguide240 is characterized by its ability to rotate thl-ough a limited ran~e oE angular motion which in the present example is a subst~ntial portion of one complete revolution of the ribbon guide 240. Accord-ingly, upon each reversal in the direction oE ribbon drive, the ribbonguide240 thereaEter rotates with the ribbon through a substantial portion oE a complete revolutioll, Eollowing 'which the ribboll guide 2~10 remains statiollary co as to cause the ribbon l:o slide thel-eover.

~3~47~

As ~shown in ~i(3. l4 the partially rotat~ble ribbon guide 240 is carried by a stationary mounting Erame 242 having opposite top and bottorn portions 244 and 246 respectively and an intermediate portion 248 extendin~ between the top and bottom portions 244 and 246. The top portion 244 has an aperture 250 therein for receiving the ribbon guide 240. ~hl?
bottom portion 246 has a similar aperture tl1erein (not shown) for receiving the ribbon guide 210. qhe intermedilte portion 246 is oE generally elongated conEiguratiol1 al1d terminates in a roun~3t?d lorward edc~2 252 adjacent the ribbon guide 240.
The details of the ribbon guide 240 are shown in Fig. 15. As seen in Fig. 15 tl1e ribhon guide 240 includes an elongated, generally cylindrical spool 25-1disposed betwe?l1 an opposite pair of Elanges 256 and 258. ~ stop member 260 has a generally disk-shaped portion thereoE mounted on the flange 1 256 opposite the spool 254 and a protrusionor tab 262 extending ¦ outwardly tl1ereEroln. A shaft 264 whici1 extends outwardly from the stop member 260 oppo~site the flan~(- 256 h~s a central axis thereof coincident with a central axis oE the spool 254.
~ secon-~ shaEt 266 whicl1 also l1;1S a central axis coincident with the central axis of the spool 254 is disp()sed on the opposite side of the lower flange 258 from the spool 254.
The shaft 264 is rotatably received witl1il~ tht? aperture 250 in the top portion 244 of the mounting Erame 242. ll)e op~osit( shaft 266 is rotatably received within the ar)erture in the bottom portion 246 of the mounting frame 242.
The ribbon guide 240 is conEigured ~o receive an ink ribbon such as the ribhon 72 on the sL~ool 254 between the opposite Elanges 256 and 258 thereof. In ti1e abs~-?nce oE the stop member 260, the ribbon guide 240 would i>e [ree to rotate continuously in response to movemel1t oE the ink ribbon.
However, as sl1own in Fig. L6 in which ti1e toL~ portion 244 oE
the mounting fralne 242 is omitted for clarity of illustration the stop member 260 with its included tab 262 conEines rota-tional motion oE the ribhon guide 240 to an angular range which is less thani) complete re~olution tl)ert?oE. This is due to enyagement oE opL)osit~ sides oE tht inten-1?diate portion 248 of th mountin~ rale 242 by the tal) 2fi2 1i the rihho ` ~3~47~9 guide 240 rotate~s in op[)osite directions. At one extreme of movelnent, the tab 262 ~n~3ages a first side 26~ o[ the Eorward edge 252 oE the intermediate portiol) 48 as si)own in solid outline in Fig. 16. ~t the other extreme the tah 262 engages an opposite second side 270 of the forward C?d9e 252 oE the intermediate portion 248 as shown in dotted nutline in ~ig.
16. An arrow 272 i11ustrates that tlle ribboll guide 240 is capable oE rotating between the opposite limit positions sllown in whicll tlle tab 262 enga~Jes one or the other of tl)e sides 26 and 270 of the forward edge 252 of theintermediate portion 248.
Because oE tlle limited range oE rotationa] movement of the ribbon guide 240, it will be appre~ciated that tl)e problem of ribbon steering or guidin;3 typically present in the case of freely rotatable guides is minimal or nonexistent.
Upon each reversal in the direction of ribbon drive, the ribbon guide 240 thereaEter undergoes rotation through a substantial portion of a revolution to tlle opposite limit position, whereupon the ribbon guide 240 becomesand thereaEter remains stationary witi~ the ribbon slidiny thereover in the manner oE a Eixed or nonrotatable ribbon gui-3e. When tlle direction o~ ribbon guide is once against reversed, the ribbon guide 240 again rotates with the ribbon through a substantial portionoEa revolution thereof to the opposite limit position, at which point the ribbon guide 240 becomes and thereaEter remains stationary with the ribbon sliding thereover. Because the ink ribbon has a tendency to fold over on itself or run completely oEf of tlle guide only after many rotations o~ the guide, such a problem is virtually nonexistent with the ribbon guide 240 which has a limitecd range of possible rotation. ~t the same time the small amount oE rotation permitted the ribbon guicle 240 greatly minimi~es ribbon contlminatioll prob-lems which would otl~erwise be present with a stationary or nonrotatinrJ guic~e, as explained in connection with Fig. 17.
Fig. 17 illustrates ~he spool 254 o~ the ribbon guide 240 with a length oE ink ribbon such as the ribbon 72 wound therearound. It is assUlllec~ that the ribbon 72 is being driven in the direction repres nted by arrows 274 and that the ribbon guide 240 !~as be~n ro~ate(l so ~hat the tab 2G2 of `-~ 13~47~9 the sto~ mc~lnber 2G0 resides against tlle first sid2 258 oE the forward edge 252 of the intermediate portion 248. ~ 1ine 276 on the spool 254 represents the orientation oE the tab 262 when in such position. As the ribbon 72 continues to be driven in the direction oE the arrows 274 with the spool 2,4 remaining stationary, the squeegee eEEect o the ribbon 72 patsing over the stationary spool 254 causes a quantity oE
ink 278 to be formed at the upstream end o[ the interace between the ribbon 72 and the spool 2S4. IE the direction of drive oE the ribbon 72 were no~l reversed with the spool 254 continuing to remain stationary the quantity of ink 278 which is contained essentially on the spool 254 would remain.
This is of no consequence so long as the same color zone oE
the ink ribbon 72 continues to be drawn over the spool 254.
However, at such time as a diEferent color ~one of the ribbon 72 is drawn up to and over the spool 254, at 1east some oE
the quantity o~ ink 278 is transferred onto such different color zone resulting in contamination thereof.
In the case oE tlle ribbon ~uide 2~0, reversal in tlle direction o~ drive of the rihbon 72 from that silown by the arrows 274 causes the ribbon guide 240 and the included spool 254 to rotate throut~h a substantial portion oE a revolu-tion as represented by an arrow 280. Durint~ such rotation the tab 262 moves from the orientation represented by the line 276 to an opposite position at the second side 270 of the forward edge 252 of the intermediate portion 248 as represented by a dashed line 282 in Fig. 17. As the spool 254 rotates in this fashion in response to reversa1 in the direction oE drive of the ribbon 72, the quantity oE ink 278 previously deposited on the spool 254 is caused to rotate around to a point 284 at the opposite end o[ tlle interface between the ribbon 72 and the spool 254. ThereaEter, as the spool 254 continues to un-lert3O the sma11 alnount oE rotation necessary to complete itsmovement hetween theopposite]imits the quantity oE ink 278 on the spooL 25~ moves into contact with the ri~hon 72, causin~ mo;~ or substarl~:ia11y all o~ the quantity o~ ink 278 to bt ~ransE~rrt?-l h-l-`k OlltO l-llc rihhon 13~70~
-3~-72. ~ecaus? the sam~ co1Or ~one Or tl1~ rihl~ 72 is .still present at the ribbon gui-le 240 thi.s is of no consequellce IE the ribbon 72 therea~ter contin~es to l~e dl-iven in a direction opposite that si1own by tl-~arrow-; 27~ rnov-ment s o~ the ribbon 72 over tl)e stationary sl)ool 2~4 resu].ts in a quantity oE ink being built up on the surr3~- oF the spool 254 at the point 284. If the ribi)on 72 is now r~ve1~s!(i so as to again be driven in the direction o~ the arrows 27-1 the ribbon guide 2~0 and the included spool 25~ rotates s() as to carry such quantity of ink around an(i then into con~-act with tl1e ribbon 72 so as to transr-er such quantity o~ ink t~ack onto the ribbon 72.
The advanta~es o~ the limited rc~l:ati.ona1 movelnel1t provided by tlle rihbon ~3uide 2~iO are best uti1.i~c.~d where the ribbon 72 is driven in a manner 50 as to provide a plul-ality of diE~erent pa.sses of each color zone oE ~he ribbon throuc3i-) the print stati.on 24 adjacent the ribbon guide 240. Such multi-pass operation has been ~ound to pro(.iuce relativ*ly large quantities oE in~ at tl1e inter~ace o~ the ribhon 72 and the spool 254, which quantities are not complet*ly relnoved ~rom the spool 254 by the intervening cleallin~3 zone l6~ of the ribbon 72 prior to movel-lent oE the next color zone onto thespool 254. Ininstances wllere the ribbon 72 is continuously driven from one end thereoE to the other so as to pLOViCiea but a single pass of each color zonc over the ribbon guidè 240 and through the print station 24 tl1e spool 254 remains stationary as each succecc1ing color zone is adval1ced to the ribbon guide 240. In such instances l~owever, t:he buildu~
of ink at the interface between the ribbon 72 anci the spool 254 has been ~ound to be mi.nimal, an(l ~uch qual1tities o~ ink are usually reduced or eIiminated by the interveninc3 cleaning zones on tile ribbon 72 so that contal~1inatiol1 does not becorne a problem.
~ `he previous description o~ l.ig. I included re~er-ence to a paper tensionin~3 mechanism which is.contained in a rectanc3u].ar housin~3 22 and which is descLibefi in detail in connection witl) ~i(3s. 1(:-1.2. .~`n al.t*l-n;lti.ve ~n(i somewhat simpler arr.ln(~ement o[ a p.ll) r ten.siol1in(3 m?(~l1nnisll1 i.n 13(:! 47C~9 -3)-accordance with th? invel)tion is illustr3ted in l~ s. 18-21.
~igs. 18-21 illustrate a paper tensioninc3 meci~anism 290 which is contained withina genera]ly rectan(3ullrllolsi~ 292adapte(1 to be coup]ed to tlle underside oE the base 12 o[ tle color printer 10 in the Eashion oE tlle rectangular housing 22 shown in ri9. 1.
I`ontained witllin the hollsing 292 is -l torque motor 294 havin~ a shaft 296 coup~e(l tv a fir~st roll~r 29l3. An end of the first roLler 298 opposite the torque motor 294 is provided witll a shaEt 300 ~hicil i~ rotatal~ly receiv?-l within the housin3 292 so as to mount the Eirs~ r~l~er 298 ~or rotation under control oE the torque motor 234. rhe first roller 298 which extends acros.s the widtll oE;I ]-n~tll oE print paper 302 at the back side thereof is principally compriâed oE foam ruhher so as to have a resiliellt out(?r surEace. ~he resilient outer surface oE the Eirst roller 298 Eacilitates engagement oE the print paper 302 by the first roller 298 ~:o drive thc print paper 302 in response to opel-ation oE the torque motor 294.
~ second roller 301 extends acl~o;; the width and contacts the print paper 302 on the opposite sid oE the print paper 302 Erom the Eirst roller 298. As in t:he case of tll?
rollers 210 of tlle prior embodiment as shown in lig. 10 the second roller 304 is comprisel oE a non-ink w tting material so as not to disturb ink alrea~y transferred onto the adjacent surface of the ~rint paper 302. The second roller 30~ is rotatably mounted between an opposite pair oE brackets 306 and 308 which in turn are pivotally mounted witllin the housing 292 as descrii)edllereaEter. A coil spring 310 ext?nds between an inner wall of the housing 292 and the bracket 306 so as to normall~ ur-~e the bracket 306 in a directioll toward the print paper 302 and the first roller 298. ~ coil spring 312 which extends between the inner wall oE the housing 292 and the bracket 308 normally urges the bracket 3()8 in a directioll toward the ~rint paper 302 an(l the Eirst roller ~98. In this fashion the coil springs 110 and 3l2 bias tll( second roller 304 so as to mailltaill the ?rint pll-r 3n2 i,- en~ ~1ement: wi th the first roller 298. Ihic p)sitiollisillll;t~ 1in~ .19.

13(~47(~9 -41)-~ rlt mannf?r in whicll tlle ~)rac~e~s 30~ an(l 3()8 arf~
pivotally mounted within tl)e hoIsin] 292 is illl~strntef7 in Fig. 21. ~acll oE the brackets 306 and 3()8 wl)i(l~ rotltc~lly mounts a diEferent end oE the seconc7 rolltr 3n4 at an upper end thereo{ has a lower end mounted on a sllaft 3l4 oL generally square cro~ss-section. rile shaft 314 ha~s a first end 3l6 thereoE af;7jacent the bracket 306 which is rotlt.l!~Iy receive(3 within an aperture 318 in a bracket 320. An opL~)osite second end 322 oE the shaEt 3l4 is rotatably r~ceiv~-l witllin an aperture 324 in a bracket 326. The opposite hra(kets 320 an(1 326aremountedwithin oppositf* ends of the rectan(l~llar71ousin~
292 to mount the shaft 314 the brackets 306 cnl~(7 308 arld tlle second roller 30~7 witllin the rectangu1ar 11ousin(3 292.
~s pl-fviously mentioned the coil spril-~3s 310 and ]5 312 normalIy urge the upper ends of the brackets 306 and 308 and the inclutl d second rol1er 304 in a direction to press the print paper 302 against the Eirst roller 298 as illust:rated in Fig. 19. ilowever tl~e second rol1er 304 call 1)? Inovf;?d away froln tlle print pa;)er 302 anfl the fir~st roller 2~8 ~gainst tlle resistancf-~oE the coil springs 310 and 312 hy down~ r(1lnovemf?llt o~ a lever 32~3 forming a part oE tl~f~? Iower end ol the brac7;et 306 and which extends tllrouf3il a slot 330 in ti)~-~ r-ctarcJuldr housing 292 as shown in Fig. l8. I)ownwar~7 Inovellellt oE the lever 328 cluses rotation oE the bracket 306 against the resistance of the coil sprilJ 310 ~o move the uppf~r end of tll~ braeket 306 and the associatf?-l end o~ tl~? second roller 304 in a direction away Eroln the print ua~er 302 and the first roller 298 a~3ainst the resistance ol- tile coil spring 310. 4t the same time the sh~Et 3l4 wi)ich i5 secured to tile lowf2r end of the bracket 306 rotates within the aperture- 318 and 324 in the brackets 320 and 32G. l7~is results in ro~:atiol) of tl~e bracket 308 in t71e same direction an~l7 by substantia11y the same amount a.s the rotation oE thf? bracket 306 against the resistance oE ti~ coil sprin(l 312. Consequently tl)l second roller 304 mov-s away ~roln ~ e print paper 302 and t71e Eirst roller 298 in y nfral1y ulli[orlll pc-~rallf;?l fashio~ ir- r spons to downwar(l mov;~;nent oE Illf? l--ver 328. 'l'hia iC illll'str~t~
in Fif3. 20 an;l is tl)e pl~SitiOIl wl~ich thf s~coll roIl~r 3n1 130~7G'~

assumes to lermit loadi.ng alld unloadin(3 oE the prilt paper 302. The second roller 304 and thc brackets 30~ and 308 can ! be locked in the position sllown in Fig. 20 by E]-?xure oE th(?
lever 328 to ~he lefthand ~)ortion o~ tlle slot 330 slown in Fig. 18 so that the lever 328 engages a Ledge 332 within the slot 330.
j As shown in Figs. 19 and 20 as we].l a.s in Fig. 18 the paper tensioning mechanism 290 is provided witn o~posite conver3ing paper guides 334 and 3~6 whicl ~unction in a manner similar to the paper guides 220 and 222 silown in the ~)revious arrangem(?nt o Figs. 10-12 t:o Eaci.litate the in.sel-tion oE the print paper 302 into and throu-3h the pap-?rtt?llsi~lilg mecllanism 230. Upon installation of the pl.int paper 3()2 within l:tle paper tensioning mecllanisln 290 the secon(3 rollt?r 304 and the lS bracket~ 306 and 308 are returned to tle position shown in Fig. 19 ~y movement of th-? lever 328 to tile ri~lt within the slot 330 sllown i.n Fig. l8 so as to clear tlle ].edge 332. This allows the .lever 328 to IllOVe upwardly within tlle .slot 330 as the coil springs 310 an(l 3L2 ur~e the upL~ r ends of the ~rackets 306 and 308 ~nd the include3second roLler 304 towarl and tl)en into contact Witil the print paper 302 pt~osite tle ~irst rol].-r 298.
In operation th(? t.orqu(?lnotvr 299 is enel-gized so as to drive the print ~aper 302 via the first roll.er 298 in the same direction as and at a slightly differel-t speed than the tractor drives 30 an3 32 shown in Fig. 1. ;~iere the ~rint paper 302 is being advanced in all upward 3irection by tl~e tractor drives 30 and 32 the torqu? motor 294lnoves the first roller 298 in a direction to all.ow upward movelnent of the pr.int paper 302 but at a sli3htly slower spr.?e(3 so as to maintain a desired amount oC ten:iion in t:he print paper 302 in the region of the print stati.ol 24. Converst?ly wllen til-?
: tra.ctor drives 30 and 32 are driving th-.? pl-int lap~?r 302 in a downward direction the ~.orqn? motor 29~ 3rives the ~irst roller 29~ in a direction and at -a rate to move the print paper 302 lownwardly at.l~sli(3l~ly astt?r sp?ed a(3ain provid-ing or a lesired amo~ o[ tensiol~ in the irin~ laler 302 in . tilt? r~?~iolloE tlle[)rillt ;tlti(>ll24. Unli.kt?tit ~ rtt?ll.Siolilg ~3~47(:~9 mbchanism sllown in Fi(~s. 10-12 wilich is aulolm;ltically caused to assum? th-?paper loading and unloadin~3~ ition in response to rotation oE the platen 26 the paper tellsioninc3 mechanisln 290 of Figs. 18-21 re~uire separate act atioll o~ tlle lever 328 to move the second rol]er 304 into the E)aper loading and unloading pOSitiOIl showll in Fig. 20. ~t ~lle salne time, however the paper tensioningllecl-arlism 29~ is ol~ considera`oly simpler construction and operation.
~hile the invention has been particularly sl-own and described with re~er?nce to preferred emho(lilnerlts thereof it will be understood by those skilled in the at-t that various changes in form and details may be mad~-? therein without departing i-rom the spirit and scope of the invention.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A guide for use with an ink ribbon comprising a spool and means for mounting the spool to permit limited rotation of the spool through a predetermined angular range.

2. The invention set forth in claim 1, wherein the means for mounting is operative to permit rotation of the spool which is limited to a substantial portion of a revolut-ion of the spool.

3. The invention set forth in claim 1, wherein the means for mounting the spool includes means for rotatably mounting the spool, a protrusion extending from a portion of the spool and a stationary member positioned in the path of the protrusion.

4. The invention set forth in claim 1, wherein the spool has a pair of flanges coupled to opposite ends thereof and a pair of shafts extending outwardly from the opposite ends thereof outside of the flanges, and the means for mounting includes a mounting frame having opposite top and bottom portions and an intermediate portion extending between the top and bottom portions, each of the top and bottom portions having an aperture therein for receiving a different one of the pair of shafts to rotatably mount the spool therebetween, and a tab mounted on one of the pair of flanges and extending out-wardly from the spool, the tab being operative to engage opposite sides of the intermediate portion of the mounting frame to limit rotation of the spool to the predetermined angular range.