CA1299441C - Self metering gravity fed ink dispensing roll - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An ink dispensing roll comprises a generally cylindrical member having a plurality of holes communicating with an interior annular reservoir and a microporous ink impregnated sleeve mounted about the cylindrical member.
The annular reservoir is in liquid communication with a larger reservoir charged with ink that flows by gravity into the annular reservoir and then into the microporous sleeve.

Description

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SE:LF--PIETERI2~G GRAVITY FED INR DISPENSING ROLLER

FIELD OF T~E INV~ION

This invention relate~ to an ink dic~pensing roll for the transfer of ink in a printing apparatus and more particularly to an ink di~pensing roller assembly for the precise metering and transfer of ink for the printing of high quality, optically readable character-~ such as scannable and verifiable bar codes.

9ACKGRO~ND
The prior art is replete with de-scriptions of ink dispensing roll~ with ink metering features. U.S. Patent 4,45B,399 is.4ued July 10, 1984 to Kessler describes the u~ o~ a hori~contally mounted roll cornprised of plurality of coaxially mounted, spaced dlsks positioned within and pres5 fitted again~t ~ perfoeat~d tube about which a sleev~
of porous material is fitted. The spaced disks defined a plurality of chambers which hold ink and permit the flow of ink through the perforations of the tube and into the sleeve. U.S. Patent 4,399,751 issued August 23, 1983 to Kessler discloses still another ~,~

1 ink dispensing roller having a pluralitY of axially aligned thin discs wherein each disc has a series of circumferential grooves and a~ial grooves. The discs are co~ered by a porous sleeYe. Ostensibly, ink flows from the axial grooves to the circumferential grooves and then to the flexible material.
Neither U.S. Patent 4,~58,399 nor 4,399,751 describe how the printing rolls are charged lo with ink.
Another U.S. Patent 3,738,269 issued June 12, 1973 to Wagner describes the structure of a horizontal roller having a porous sleeve of ink-absorbing material with one or more reservoirs of ink within the sleeve. The reservoirs being free of vent~ to the atmos-phere are stated to provide uniform inking.
Industries such as those handling unitary objects and consumer products, e.g., material handling industrie3, have been convert-ing to various types of bar codes readable by scanning devices. Such devices permit the high speed passage of objects to which bar code~ are appended, thus facilitating w~ehousing and inv~ntory control. A major problem, however, h~s been the inability of prlor printing devices to print the sharp bar code imago~ on 0~j2ct~ aa they pass by a printer. Most prior art printers use dye based ink which tend to wick or feather, particularly on corruqat~d boxes, leaving printed codes very difficult or impossible to read by scanners.

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1 Substituting pigment-ba5ed ink, a superior ink for quality printing even on the mo~t difficult qurfaces, hag n~t proven to be viable since such inks are diEficult to uniformily meter and transfer. The pigment-based inks hav-ing s~all particles of pigment suspended or emulsi~ied in liquid as opp~sed to being in solu~ion as in dye based inks, are p~one to clog the transfer structure a~ the g~ruc~ure ac~ a~
a filt~r to the ~uspended pigment particle~.
Thi~ re3ult~ in und~sirabl~ v~riations in print quality.
~he afor~mention~d prior a~t devico~
also hav~ coloplex structu~al require1~ents, ar~
di~ficult to operate consi~tentlyy and do not pro~de th~ conci3e, continuoug and uQlfor~
m~t~ring of ink, particularly ink o th~ pig-m~nted typ2, requircd by 3canning op~rati~ns.

The microporous material i9 initially ink impregnated and consistently transfers ink without substantial loss until the ink supply within is essentially depleted. once depleted, the roll of microporous material is either discarded or impregnated again ~or subsequent u8e. At times it is preferable, however, to utilize such a material to its best advantagas ;n ~ntinuous and extended use. ~he ink feed rollers of the prior art as des-cribed above lack the ability to provide an extended 1 and precise metering of piqmente~ ink to the material for the detailed and prolonged printing required in some circumstances to permit reliable and e~tended printing of fast moving substrate~
with minimal decrease in impression intensity.

SU~ARY OF THE INVENTION
In accordance with the pre~ent inven-tion, the ink dispensing roll compriqes a cylin-dical wall with a plurality of holes extending there through, a thin cavity generally concentric with the wall. The holes communicate with the cavity which in turn communicate with an ink chargeable reservoir having a volume greater than that of the cavity. Poqitioned about the cylindrical ~all over the holes is an ink impreg-nable ~leeve capable of di~pen3ing ink from an exterior surface and absorbing ink through an interior ~urfaoe thereof, thereby providing uniform metering of ink from the reservoir through the exterior surface of the lnk impreg-nable sleeve.
Other features and advantages of the invention will be apparent f rom the following d~cription taken together with the accompanying 2S drawings ~nd appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure l is a side elevation view of an ink dispensing roller as~embly constructed in accordance with one embodiment of the present invention.

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1 Figure 2 is a central longitudinal sectional view of the roller assembly shown in Figure 1 along lines 2-2.
Fiyure 3 is a vertical crOss-sectlona view of the roller assembly of Figure 1 along lines 3-3.
Figure 4 represents a magnified section of the microporous sleeve material as drawn from a photograph.

DETAILED D~SCRIPTION OF PREP~RRED E~ODIM D TS
~igure~ 1 - 3 illustrate an ink roller assembly 10 which is constructed in accordance with the present invention and which includes a sleeve 12 o~ flexible and re~ilient microporous material for the retention and tran~fer of ink as deqcribed below in detail.
Sleeve 12 is mounted about a cylindrical member 14 which maintains ~leeve 12 in a tight fitting relation~hlp. ~Y beqt qe~n in Figure 2, a cylindrical wall 16 of member 14 extends above sleeve 12 and form~ an ink-holding cavity or re~ervoir 1~ capped by integral cover 20. In the r~gion adjacont sl~eve 12, wall 14 is provided wlth a plurality o~ radially extending hole~ 22.
For purpose~ of thiq invention the dia~eter of holes 22 is desirably .001 to .S00 inches, and preferably .040 to .150 inche~.
Positioned internally of wall 16 of member 14 in the region adjacent holes 22, is a second cylindrical member 24 defined by cylin-drical walls 25 and inteyral cover 28 integrally connected to member 14 near the bottom edge by shoulder 23. Members 14 and 24 thus ~orm an annular cavity 26 which is coaxial to sleeve 12 and has a longitudinal length approximately the same as sleeve 12. While the specific radial thickness by annula.r cavity 26 may ke as large as suitable for a particular application, it is desirable in most situations for the radial thickness and volume thereof to be as small as possible to facilitate even transfer of ink and minimize remaining ink when the reservoir is depleted.
Shoulder 23 ~erves as the ~e~led bottom, e.g., a liquid tight seal, of cavity 26 which at the upper end thereof open~ into and communicates directly with reservoir 16.
A hole 30 is de~ined in cover 28 which may be used to charge reservoir 18 with ink and thereafter suitably sealed.
The internal opening 32 formed by cylindri~al member 24 is de~igned to receive bearing mount 34 and shaft 36 (shown in phantom in ~igure 3) for suitable rotation o~ the ink roller assembly 10 in u~e.
When used in operation, assembly 10 is charged with ink and, a~ depicted in ~igure and, is ~ounted vertically with re~ervolr 18 po~itioned above. Ink flowq by geavity into annulat cavit~ 26 ~here un~o~ gravitational pressure and capillary action the ink moves through holes 22 and pores of sleeve 12 impreg-nating sleeve 12. As the ink within sleeve 12 is trans~erred, it is continuously and con-sistently replaced by the metering action of cavity 26 until the ink in reservoir 18 is exhausted so as to maintain as essentially zero ~L29~

1 order rate of loss of ink by s~eeve 12. To help provide this capability, it is d~sirable for economic reasons that the volume of cavity 26 be a small fraction of the volume oE the reservoir 18.
It should be understood that while the de~cription above is directed toward a preferred embodiment in which re~ervoir 18 i5 positioned above cavity 26 as would be the application within a printing apparatus, other po~itioning arrangement~ may be employed depending upon the particular application. IS desired a ho~izontal arrangement could b~ e~ploy~d.
Although Figures 1 through 3 depict an ink roller a~sembly of the dispo-~able or integral type, the a~embly may be advanta-geously constructed so as to have a ~eparat~
cylinder with the reservoir which when exhausted can be replaced by another cylinder.
The microporous material compri4in~
sleeve 12 may be prepared by a method including as its initial step mixing ~rom 8 to 50~ by weight of a pla~tic powder with from about 10 to 90% by w~ight of a water-soluble salt and from about 10 to S0~ by weigh~ of a water-solubl2, pol~r organic sub3tance. Thi3 mixing preferably ~ak~s place in the absence of external h~atl~g, but under vacuum. The purpose of the mixing is to intimately mix the plastic, water-soluble salt and the polar organic liquid. After the mixture is intimately mixed, it is placed in a mold and heat~d with any of a variety of heating _ 7 _ 1 means to a temperature above th~ melting temp-erature of the plastic. This allows the plastic to melt and form a cohesive structure around the salt and polar organic liquid. ~ollowing this meltin~ step, the structure is allowed to cool, and then the salt and polar organic substance are leached from the structur~, preferably with water.
T~e structure is dried and then impregnated with from about 40 to about 903 by weight of an ink.
In the detail~d de~cription of thiQ method which follows, a~ount limitatioos 4hould be con~idered approximat~.
The fir~t ~tep of the pr~ceding method of forming the ~icroporou~ mate~ial u~ed in the present i~vention compri~ mixing ~ro~ 8 to 50~ by w2i~ht of th~ pla~tic po~der with the water-~olubl~ ~lt a~d the w~ter-soluble, polar organic liquid. ~he pla~tic powder preferably ha~ an average particle size withln th~ rang~ o~ fro~ 1 to 80 microns.
~tter re~ult~ are obtained wh~n th~ plastic used to form the structure iq imp~rviou~ tc solvent~ typically uaed in ~ormulatin~ print-ing inks. Suitabl~ pla~tic~ are th~ ther~o-pla~tic poly~er~ such as polyvinyl chlorlde, polyvinyldene chloride, polystyr~ne, acrylon-itr~ butadiene-3tyrene polymers, butadione-~tyrene polymer~, acrylate polymer~ and copolymers such as ethylacrylate, butylacry-late, etc., polyvinyldiene flouride, polyethy-lenel polypropylene, polyethylene vinyl acetate copolymers, polyamides, nylons, polychloro-trifluoroethylene, polyacrylonitril.e, alkyl methacrylate polymers, such as polymethyl methacrylate, etc., cellulose acetate, acetals, polycarbonates, and the like. Preferred polymers include polyethylene, po1ypropylene, polyethylene-vinylacetate copolymers, and mixtures thereof. Although any grade of polyethylene and polypropylene can be used, it is preferred ~o use high density polyethy lene, linear low density polyethylene, mix-ture~ of high density polyethylene with a polyethylene vinylacetate and mixtures of linear low den~ity polyethylene with polyethy-lene vinyl~cetate. The preferred amount of pla~tic powd~r usable in thè ~ethod of the present invention is from about 10 to about 25~ by weight, based on the total weight of the initial mixture including plastlc powder, water-soluble salt and water-~oluble, polar organic liquid.
The ~econd ingredient of the mixture is ~ water-soluble qalt. The salt u~od can be any water-solubl~ 3alt which i9 mi~cable with the plastic powder to be utilized and the ~ater-solublc, polar organic 1iquid. Inorganic salt~, - particularly alkali metal salt5, are pr~ferred.
Su~h salt8 include ~odiu~ nitrate, sodium chloride and the like, o~ which sodium nitrate is pre-Ç~rred. The more water-soluble the salt, the easier it is to remove with the solvent of choice, water. Generally, from about 10 to 90% by weight o~ the water-soluble salt is used in the initial mixture. The greater the amount of water-soluble salt used, the more open or porous the microporous structure becomes. Generally, it is preferred to use between about 40 and 65~ by weight sa~

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1 although in certain situations, where a very porous ink roll is required, up to 90~ wt. can be utilized.
The third component is a watPr-soluble, polar organic liquid. As such liquid, an alcohol such as an alkanediol can be used, preferably one having from 2 to 6 carbon atoms. The boiling point of the polar organic liquid must be higher than the meltin~ point of ~he particular pla~tic to be u~ed becau~e the polar organic liquid must remain in a liquid state while the plastic i~
beiny mel~ed to form the microporou~ cohesiYe structure. Suitable alkanediols include propylene glycol, 1, 4-butanediol, 1,5-pentanediol, 1,6-hepandiol and the like. Generally, from 10 to 50% by weight of the water-soluble li~uid i~
used, and preferably fro~ 20 to 40~ by weight, based on the total weight of the initial mixture.
The water-soluble, polar organic liquid improve~ the proce3sing of the micro-porous ~truCture at room te~perature. ~ow-ever, the prime reason for using the water-soluble, polar organic liquid is to enh~nce the ~low char~cterl3tic3 o~ the high d~n3ity iDage-producing ink from the microporou~
structure which ia ~ormed. The water-soluble, polar organic liquid coat~ the salt par~icles and smooth~ ~round) their rough edge3 during the molding process to take place. This allows the formation of a microporous struc-ture having a smooth, rounded internal surface which dramatically lowers the internal surEace ~L2~

1 area of the structure. Microporous struc-tures with a high intern~l surface area act to hold the ink within the structure and the structure may actually ~ilter the pigment out S of the ink, a circumstance to be avoided.
Thus, proper careful control permit~ an ea~e of tailoring appropriate ~urface characteri3-tic~.
The use of the water-soluble, polar organic liquid acts on the mold~d plastic to Eorm an open-celled ~tructure of interconnected, often ~pheroidal or ovoid cavitie~ with ~mooth internal ~urface~ essentially f~ee o~ ~ibrow type projections~ Thi5 3tructure ha~ a "0"
(i.e., zero) order ink lOss rate rather than a flrst order i~k loss rat~, a~ 1~ typical of othe~
microporou5 structure~. Th~ pract~cal effect of a "0~ order ink los~ rate is the structure di~-penses sub5tantially the ~ame amount of ink upon repetitive contract with a ~urface ~ver mo8t of it3 u~e~ul liEe, i.e. the ~a~ a~ount between 2000-3000 impre~sion5 as betw~en 8000-9000 impres--~ion~
A method for making microporous material suitable or use in the invention is as follows:
The plastic powder, ~alt and water-soluble, polar organic liquid are mixed together ln any order to Porm a thick vi~cous paste~ The mixing step is carried out over a period of at least about 10 minute5. Thi~ mixing is to be done without application of heat, but preferably under sub-atmospheric (~., vacuum) or such other condi-tions so that air is not introduced into the mixture. The thick mixture is then placed in an ~4~

1 appropriate mold by pu~ping, manual trans~er or the like. Suitable molds can include cylindrical pipe shaped molds, bar molds, etc. The plastic is then heated and ~coled. rt beevmes firm and hard, and is then removed from the mold. After molding and cooling, the salt and liquid are leached out. One method of leaching is to place the structure in water and allow it to stand.
Dep~nding upon the temperature and the movement oÇ the water, the ~alt and water-soluble liquid can be leached out of the structure in as little as one hour. After the water and soluble liquid and salt are removed, a pliable, microporou~
qtructur~ remains. ~his structure is then dried and the high denqity image-producing ink, a~
described in detail below, i~ impregnated th~rein.
In one application of th2 preceding general ~ethod, th~ powdered plastic, water-soluble, polar organic liquid and water-solubl~
salt ar~ mixed for from lO to 45 minute~ to for~
an inti~ate mixture of the components. The mix-ing al~o rounds the sharp edyes of th~ particles during molding. Mixing can be accompli~hed by conventional mixing equip~nt without supplying ho~t ~ur~ng the mixing step. The re~ulting ~at~ri~l can be easily handled.
After the mixture of plastic, water-soluble liquid and smoothed water~soluble salt particles is formed, it i~ then transfarred by any conventional means to a mold, such as pumping if the mixture is pumpable, or manual trans~er, 4~

1 The mold can be of any desired shape. For form-ing ink rolls, a mold of 4" outside diameter and 3.5" inside diameter by 12~' in l~ngth is suitable.
After the mixture is placed in the mold, the mold and mixture are heated by conven-tional means, for instance, a hot oil bath, microwave radia~ion or forced air. The exact temperature depends on the components used. The temperature ~hould be above the melting tempera-ture of the pla~tic but below the boiling point of the water-soluble, polar organic liquid. For typical mixtures, a temperature within the range of from 170 to 200 P maintained for 10 to 40 minute~ i3 ~Ui table.
The mold i~ then allowed to cool and the resulting structure is re~oved from the mold.
The structure i3 then placed in a solvent, pr~-ferably an aqueous ~olvent ~uch a~ water, to leach out the water-soluble, polar organic liquid ~0 and the water-soluble salt. Any conventional leaching m~thod ~ay be u~ed. One convenient method i~ to u e war~ (120-140 P) water which i~ agitat~d. The ~tructure i5 left for up to 24 hours, although shorter periods can be used, such a~ 4 to ~ hours for a ~tructur~ of sm~ller ~iz~. Th~ water can be changed periodically to decr.e~se the leaching ti~o.
After leaching, the structure is dried by any conventional means, such as a forced air oven. A drying period of 20-24 hours at 120-1~0 F will typically dry the structure and xender it ready for use as a sleeve in an ink dispensing roller assembly. Occas.ionally, it 1 may further be desirable to grind the outer sur-Eace o~ the struc~ure to adjust the dimension~
of the structure to a desired size. Thiq grind-ing has no substan~ial effect on the release rate oE the ink from the structure if adjusted.
The ext~rior surface of the structu~e thus pre-pared ~with or without grinding) lack~ a skin which mu~t be removed, or through which the ink mu~t permeate.
The averag~ pore ~ize of ~icroporous material is at least 10 microns, gen~rally in the r~nge of approximately 10 to 250 ~icrons.
Within the 10-250 micron rang~, individual pore sizea are seldom more than 50 miCrons larger or ~aller tha~ the average pore size. Po~e~ com-pri~ interconn~cted cavities or cell , generally of ~phero~dal or ovoid 3hape, or of other ~hap~, which are smooth-walled and rounded. Thi~ con-figuration is depicted in ~igure 4, a drawing r~nd~tlon of a ~agnified portion o~ a ~ur~ac~ o~
sleev~ 12. A~ will be noted the cavitie~ or pores shown gene~ally a~ numeral 38 h~ve rounded wall~ ~3hown ge~erally a5 40) which giv2 the por~ 38 a 3pher~1dal or ovlod shap~.
~ Pores smaller than 10 microns are undesirable becau~e particle~ of pigment in the ink have particle sizes typlcally up to about 10 microns, and may thu~ become lodged in a pore and clog it. Inks preferable for use in the invention have an average pigment particle size of le~s than about 5 microns, particularly less than about 3 microns, for this reason. As referred to herein, pore and particle sizes refer ~29~

1 to the diameter thereof, or to th~ largest dimen-sion thereof if not spheriodal.
The following example, which is for the purpo~e of illustration and is not in any way to be construed as limiting, depiGts one method of forming the microporous ma~erial.

EXAMPL
To a ~05S Interplanatary mixer is add~d 60.0 pounds of sodium nitr~te, particle ~ize 50-150 micron~, 15.0 pound~ oE FE-53? Microthene plastic powder, 10-80 microns, 90~ Ethylene/10 vinylacetate copolymer Erom USI Chem~cal, and 20.0 pounds of 1,4-but~nediol. Th~ above is mixed at low speed undær vacuum for 10 ~nutes.
At that time, an additional 5.0 pounds of 1,4-but~nediol i~ added and the mixture i3 mixed at high speed for 15 minut~3 under v~cuu~. The re~ulting slurry is re~oved Erom the mixer and pumped to an aluminum mold. The mold is a cylinder having a core and end caps.
The mold forms a part having a 4H out-~ide dia~eter and a 3.5 inch inside diamcter by 12 inch~3 long. The mold iS seal~d and pl~ced in ~ hot oll bath at 280 ~ for 20 ~inut~3.
After heating, the mold is removed and placed in water for 1.5 to 20 minutes to cool. The part is then removed from the mold and placed in agitated warm ~120-140F) water. After 1 hour, the water is changed and the part is left to soak for an added 6 hours. The part is removed from the water and dried in a forced air oven at 120-140 F for 24 hours. After removal from the oven, ~2~9~

1 the part is a soft microporou5 ~trUcture ready to be inked and mounted about cylinder 14 in a tight fit rela~ionship.
Thus, ~he positioning of a sl2eve of m~terial as de~cribed above about the outer cylindrical member 14 and the placement of members 14 and 24 so a~ to form the thin annular cavity 26 communicating with ink charged r~s~r-voir 18 are important to the prop~r oper~tion of the in~ntion. Additionally~ ~he voluo~ of the cavity in relation3hip to the re~ervoir ig important to the cont~olled met~ring o~ lnk.
The c~vity and th~ juxtapo~ed reservoir en~ur~
a uni~orm and con~tant ~upply of ink to th~
slecv~ and mini~i~es variablo3 as~ociated ~ith horizontally positioned res2rvoir~. The lnk ~upply ~eters under gr~vity into the c~vity cont~olled by thQ radial width/s~ll volume of the cavity, and move~ by gravi~y and capillary action, conai~tently and unieormly, through the holes in the ~lrst ~omber. ~t i9 th~n trans-~err~d by the microporous stru~tur~ of the sle~ve to the out~r periphery thereof with minimu~ rate o~ tr~n3~r lo~ ~or conta~ with a ~r2n~r sub~tr~t~ in a printin~ operation. Th~ ink will contlnu~ to move in t~i~ m2nner as long a3 th~
r~3crvoir contalns ink. ~ecause th2 volu~ o~
ink held by the cavity is ~mall compared to the volume of ink contained by the reqervoir, the cavity will be uniEormly fi].led and in contact with the microporous ink retaining material until the supply of ink is virtually exhausted.

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1 While a preferred embo~iment of the invention has been sho~n and described, it w.ill be understood th~t the invention may take on other embodiments without departing from the scope and spirit of the appended claim-~.

Claims (13)

1. An ink dispensing roll, comprising:
(a) a first hollow and substantially cylindrical member with a plurality of holes extending therethrough only in a defined region located near one end of said first member;
(b) a second substantially cylindrical member defining with said first member an annularly shaped cavity volume extending along the entire width of said defined region and terminating substantially at the end of said region and directed away from said one end of said first member;
(c) said first member also defining a reservoir volume for ink positioned in fluid communication with said cavity volume, said reservoir volume being substantially greater than said cavity volume; and (d) ink impregnable means secured to and around the outer surface of said first cylindrical member only over said defined region for absorbing ink flowing through said holes from said cavity volume into the interior of said ink impregnable means and for dispensing ink from an exterior surface of said ink impregnable means upon contact with an ink receiving surface.

2. The ink dispensing roll of claim 1, wherein said cavity is of annular shape and said reservoir communicates with said cavity at an end portion thereof.

3. The ink dispensing roll of claim 2, wherein said reservoir is generally cylindrical and is coaxial with said cavity.

4. The ink dispensing roll of claim 1, wherein said ink impregnable means comprises a tubular sheath of an ink impregnated, microporous material disposed in close conforming contact with said cylindrical wall.

5. The ink dispensing roll of claim 1 is which said reservoir volume is at least twice said cavity volume.

6. The ink dispensing roll of claim 5 in which a ratio of said reservoir volume to said cavity volume is between about 5 to 1 and 20 to 1.

7. The ink dispensing roll of claim 5 in which said cavity has a radial thickness of about 0.050" to 0.500".

8. The ink dispensing roll of claim 7 in which said annular cavity has a radial thickness of about 0.100" to 0.125".

9. An ink dispensing roll capable of uniformly metering and transferring ink to a surface comprising:
(a) a first hollow cylindrical member and an integral first top enclosing one end of said first member, said first Member having a plurality of holes extending therethrough only in a defined region near the other end of said first member;
(b) a second cylindrical member and an integral second top positioned within said first cylindrical member, said first and second members defining an annular cavity therebetween and extending the width of said defined region and terminating at the end of said region toward said first top, said members being sealed together along a lower region of each, said first and second tops and said first member defining a reservoir capable of receiving ink and in communication with said annular cavity, said reservoir having a volume at least twice the volume of said annular cavity; and (c) ink impregnable means mounted about said first cylindrical wall only along the defined region thereof for uniformly transferring ink moving from said reservoir into said cavity and through said plurality of holes to an exterior surface in contact with said ink impregnable means.

10. The ink dispensing roll of claim 9 in which said first and second cylindrical walls are aligned substantially coaxially.

11. The ink dispensing roll of claim 9 in which a ratio of said reservoir volume to said annular cavity volume is between about 5 to 1 and 50 to 1.

12. The ink dispensing roll of claim 11 in which said annular cavity has a radial thickness of between about 0.050"
to 0.500".

13. The ink dispensing roll of claim 12 in which said annular cavity has a radial thickness of between about 0.100"
to 0.250".