US3285169A

US3285169A - Apparatus and method for flexographic printing with doctor roll ink control

Info

Publication number: US3285169A
Application number: US459814A
Authority: US
Inventors: Hans H Hartwig
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-05-28
Filing date: 1965-05-28
Publication date: 1966-11-15
Anticipated expiration: 1983-11-15

Description

Nov. 15, 1966 HARTw 3,285,169

APPARATUS AND M OD FOR FLEX APHIC PRINTING WITH DOCTOR ROLL INK CONTROL Filed May 28, 1955 FIGI HANS H. HARTWIG ATT'YS United States Patent 3,285,169 APPARATUS AND METHOD FOR FLEXOGRAPHIC PRINTING WITH DOCTOR ROLL INK CONTROL Hans H. Hartwig, P.O. Box 723, Appleton, Wis. Filed May 28, 1965, Ser. No. 459,814 9 Claims. (Cl. 101-207) This invention relates to an apparatus and method for flexographic printing and is a continuation-in-part of my co-pending application, Serial No. 379,075, now abandoned, filed June 30, 1964.

The invention makes use of a novel doctor roll or cylinder associated with an indented substantially non-deformable transfer roll to provide a uniform ink film for application to a traveling web. More particularly, the doctor and transfer roll are in light, but positive contact and the surfaces associated with the respective rolls adjacent the contact area are moving in opposite direction.

Through this, a number of heretofore insuperable obstacles have been overcome. Especially vexatious limitation of prior art flexographic presses has been the need to check the operation of the press at the commercial speed, notwithstanding the fact that the operation had been checked at slow speed right after start-up. For example, it was not unusual for the ink film thickness to be measured by an Interchemical Thickness Gauge (manufactured by Gardner Laboratories of Bethesda, Maryland) at 0.0002" at 50 f.p.m. but to find that this thickness increased to 0.0008" at the commercial speed of 400 f.p.m. This then necessitated readjustment of the press and all of the previous checking was wasted effort. Through the invention, the film thickness is controlled so as to remain substantially uniform throughout the range of slow to commercial speed-making rechecking unnecessary. A real advantage to this lies in performing adjustment at slow speed where relatively minor quantities of web have to be thrown away. It is, therefore, a general object of this invention to provide a novel apparatus and method for flexographic printing which avoids the shortcomings of the prior artand a more specific object is to provide such an apparatus and method whereby ink film thickness is substantially independent of press speed.

Another limitation of versatile operation of flexographic presses in the past lay in the character of the plates that were used to receive ink from the transfer roll and deliver the same to a web traveling on an impression cylinder. Heretofore, no more than about 65 lines per inch could be used in plates without loss of printing clarity. Through the invention, plates having as high as 120 lines per inch are satisfactorily employed. The provision of apparatus and method for overcoming this limitation constitutes another object of this invention.

Still another limitation of the prior art resided in the character of the ink used. These inks had to be relatively fluid, i.e., characterized by a viscosity of less than about 25 seconds as measured by a discharge from a No. 2 Zahn cup. According to the present invention, relatively viscose inks (110 seconds discharge from a No. 2 Zahn cup) are applied with satisfactory results. The provision of apparatus and method for overcoming this limitation constitutes still another object of this invention.

Other advantages made possible by the invention include shorter drying times and ease of overprinting particularly from the use of higher solids contents (lower solvents) inks than those heretofore thought possible.

ice

In one embodiment of the invention, I employ a generally resilient smooth control surface in generally lineal contact with a generally rigid, indented transfer surface, the surfaces moving in opposite directions adjacent the line or thin area of contact. Optimally, the surfaces are provided as integral parts of a doctor roll and a transfer roll arranged with their axes in parallel relation, although in some instances it may be advantageous to provide separate surfaces as in the form of belts or blankets. In accordance with conventional practice, the transfer roll delivers a controlled thickness film to the plate cylinder also arranged with its axis parallel to the transfer roll axis. Thereafter, ink film is delivered to a web traveling with and on an impression cylinder having its axis disposed parallel to the previously mentioned axes.

The character of the resilient control surface may vary depending upon the geometry of the installation, and the character and film thickness of the ink, web (paper, plastic, textiles, etc.) and the rigid transfer surface. For example, a given Durome-ter cover on the control surface can wipe more deeply into a large cell than into a small cell, thereby removing more of the ink from alarge cell. Since large cells frequently are used for over-all print coverage where substantial amounts of liquid are required, a fairly hard minimum resilient cover is indicated. On the other hand, where small cells are used for sharpness and clarity of character printing, a more resilient rubber cover is indicated. I have found that rubber coverings of the order of one-half inch-one inch thickness with Durometer ratings of the order of 100 can be advantageously used in the practice of the invention.

The rigid transfer surface is advantageously of the form heretofore available in the form of Anilox rolls. Such rolls are characterized by a rigid surface of steel and mechanically worked (milled, knurled, embossed, sandblased, etc.) to provide a plurality of identations or cells. Knurling, for example, provides quad or pyramid cells depending upon their shape and having a depth of the order of 20-100 microns (one micron=0.001 mm.). The conventional desingation of the density of cells is based on the number occurring along a diagonal of a one inch square and the invention can be advantageously practiced with densities of the order of 100200 cells per diagnonal, i.e., per 1.414 inches. The roll may be chrome plated after mechanical working.

The speed of the control surface relative to the trans- V fer surface may vary from about 50% to about 150%.

However, speed less than 100% and of the order of 80% are preferred to avoid developing frictional heat.

Pressures employed are light, but positive, as through the use of positive displacement journal bearings. For example, the bearings may be supported in ways provided as part of the press frame and maintained by threaded studs or adjusting screws providing fine adjustment. In some instances, or like fine adjustment means are advantageously employed. The actual pressure is determined by visual checking of the film by the pressman and may require as little as one-eighth turn of a one-half inch diameter 20 thread per inch stud. In commercial installations, I have found this to be as little as 0.001" movement of the bearing after kissing contact has been achieved.

With a press operating as just described, as the relative speed of the doctor roll increases, the hydraulic pressure tending to force ink through the nip is decreased. Thus, for light printing, relatively high doctor speeds are employed while for heavier printing at the same viscosity, slower speeds are employed.

It will be appreciated that the reversely moving control surface carries liquid away from the nip between the control surface roll and the transfer roll, thereby preventing an accumulation of liquid which would otherwise be pumped through the nip. A higher reverse speed of the control surface roll accentuates this wiping-away effect and minimizes the amount of liquid remaining in the cells and on the transfer surface. Lower speeds in the control surface permit some pumping through of the liquid and thus increases the amount carried by the transverse surface.

In general, lower speeds of the control surface-equipped doctor roll will be employed with low viscosity or highly thixotropic liquid or where more complete print coverage is desired. -On the other hand, higher speed of the control surface doctor roll will be employed with higher viscosity inks or where sharp, fine character printing is desired with minimum ink volume, or in conjunction with light contact pressures for minimum friction and high speed printing. In the present invention, where variable speed control of the control surface doctor roll is provided, the speed of the doctor roll is generally the first adjustment used by the pressman to increase or decrease the amount of ink carried by the transverse surface.

After first adjusting the speed of the doctor roll, the pressman the nmay adjust the amount of the pressure applied between the transfer roll and the doctor roll. As a third method of controlling ink, the ink may be diluted to reduce viscosity. This, however, may be undesirable since dilution of the ink changes the color intensity, increases the drying load and the cost of new materials used. As mentioned previously, the ink is transferred from the indentation of the transfer surface to the receiving surface which is moving at the same speed and in the same direction of the transfer surface. This transfer to .a receiving surface moving at the same speed prevents damage to the rubber printing plate as employed in flexographic printing and avoids halo or build-up of excess ink around the raised portions of the plate.

The present invention further employs means for removing excess liquid from the smooth outer surface of the doctor roll. It is desirable that the excess liquid be removed from the control surface roll before it again engages the transfer surface after having first engaged the transfer surface to remove a certain amount of the liquid therefrom. In other words, the reversely moving control surface which approaches the liquid control must be able to receive and carry away excess liquid from the transverse surface. The means for removing excess liquid from the control surface is optionally a doctor blade but may take the form of another reversely turning control surface, cleaning bath or the like.

An embodiment of the invention is shown in the accompanying drawing, in which- FIG. 1 is a diagram of a flexographic printing press;

FIG. 2 is an enlarged fragmentary sectional view of a portion of FIG. 1 and showing details of one ink applicator unit; and

FIG. 3 is a view similar to FIG. 2, but of a different ink applicator unit.

In the illustration given and with reference to FIG. 1, four different colors such as white, yellow, blue and red are printed onto the web W at the four stations indicated at station 11, station 12, station 13 and station 14, the colors being printed onto the web W in various areas and in superposition for additional color tones. The press speed for this type of operation may be approximately 400 feet per minute or more. Stations 11 and 12 are of the type seen in FIG. 2, while

stations

13 and 14 are of the type seen in FIG. 3.

As seen in FIG. 1, a supply roll is indicated at 15 and from this supply roll a web W cellophane, paper, polyethylene, etc., is fed about the

guide roll

16, 17 and 18 to station 11 where it engages a large impression cylinder 19 and is in turn printed on by means of a flexographic plate and plate roll indicated generally by the numeral 21, all of which may be conveniently supported on a frame F, shown only fragmentarily. The web W then continues about the impression cylinder 19 and is engaged succes sively by flexographic plates carried by plate rolls indicated generally by the

reference numerals

21, 22, and 22' at

stations

12, 13 and 14, respectively. The printed web then passes about a guide roll 24 and into an ink dryer 25 of conventional construction. As the web passes out of the dryer 25, it then passes about guide rolls 26, 27 and 28 to a finish roll 29 in the usual manner.

Referring now particularly to FIG. 2 of the drawing, the flexographic plate roll 21 (which also may be the element 21' associated with station 12) includes a metallic cylindrical roll 30 having a flexographic plate 31 cemented or otherwise adhesively secured thereto. The fiexographic plate may be a synthetic rubber in the range of 50 to 60 Durometer and the desired image is molded in the outer surface of the plate.

By means of conventional gearing (not shown), th flexographic plate roll and the indented transfer roll indicated generally by the reference numeral 32 are driven in the directions indicated (i.e., the same direction adjacent the area of contact) and of a surface speed which exactly matches the surface speed of the web being printed and of the impression cylinder. Conventional adjustments (not shown) are provided for setting of the contact between the transfer roll, the plate roll and the web W on the impression cylinder.

The transfer roll 32 comprises a steel shell 33 which is chrome plated as'at 34. The control surface-equipped doctor roll is indicated generally by the reference numeral 34 and includes a substantially cylindrical metallic roll 36 having an outer cover 37 formed preferably of synthetic rubber. A bearing for the control surfaceequipped doctor roll 35 is indicated at 38 and the position of this bearing is governed by means of conventional adjusting screw 39 which is threaded within a fixed bracket member 40 secured to the framework of the machine. By moving the adjusting screw 39 with respect to the bracket 40, the bearing 38 may be moved so as to move the doctor roll 35 toward or away from the transfer roll 32 thereby adjusting the pressure between these rolls. This screw threaded adjustable means provides a means for maintaining a constant light, but positive physical contact between the doctor roll 35 and the transfer roll 32 at all times during operation of the apparatus.

Means as provided for removing excess liquid from the smooth outer surface of the doctor roll 35, this means taking the form of a doctor blade indicated at 41. The doctor blade 41 may be formed either of steel or of synthetic material and is positioned within about of the line of contact C between the

rolls

35 and 32. The blade 41 is oriented to prevent the blade from digging into the rubber cover 37 of the doctor roll 35. Excess liquid is diverted downwardly by the doctor blade 41 into a conventional catch pan 42. The usual shroud including end dams is omitted for sake of clarity of presentation.

A drive sprocket 43 is indicated as being fixed for movement with the transfer roll 32, the second drive sprocket 44 is fixed for rotation with the doctor roll 35. These two

sprockets

43 and 44 are interconnected by means of a chain 45 and trained over the

sprockets

43 and 44. Optionally, the

rolls

32 and 35 may be independently driven in the form of the positive infinitely variable drive shown in FIG. 3.

Alternatively, the speed of rotation of the doctor roll 35 may be controlled by varying the size of the sprocket so as to obtain the desired speed ratio between the

rolls

32 and 35. As illustrated, the drive sprockets are of such a size as to drive the control surface roll at a slightly lower speed than the transfer roll 32. It is accordingly apparent that relative speeds may be adjusted as described, the speed of movement of the smooth outer surface of the doctor roll 35 is preferably within a range as previously described relative to the speed of movement of the transfer roll.

Liquid is supplied through a conduit 46 connected with a suitable source of ink. The conduit discharges ink into the nip between the two

rolls

32 and 35 to form a puddle or pool indicated generally by reference numeral 47. This pool 47 is confined at the ends of the rolls by conventional end dams. A dam-defining wall 48 is provided which carries the doctor blade 41 operating against the outer surface of the roll 35 to prevent most of the liquid from escaping from the puddle. As the machine speed is increased, there is a tendency to develop turbulence in the pool 47. This could entrain and starve the plate cylinder 50. Therefore, I prefer to raise the pool level as speed increases and for this purpose have a wall 48 of substantial height.

A printing ink used may be a polyamide co-solvent type. The solvent may be isopropyl and normal propyl alcohols plus a hydrocarbon such as naphtha. The ink is used without thinning at its original solids content of from about 36-40 percent to as high as about 70 percent. The ink becomes more concentrated during use, but equilibrium is reached and controlled by the addition of more uncut ink or solvent as needed.

The various adjustments of the illustrated embodiment permit very sharp, clear reproduction of the halftone cells of the finished print. Ink remaining on the transfer roll is limited by the doctor roll. This is transferred to the halftone fiexographic plate screen cells without flooding the same by virtue of the precise volume control developed by doctor roll 35. The flexographic plate in turn delivers clearly defined dots of ink to the web W without squashing or smearing.

Referring now to FIG. 3 of the drawing, the ink applicator unit of

stations

13 and 14 is illustrated, and this particular arrangement is particularly designed for the applying of ink to an upwardly traveling portion of the impression cylinder 19. From a consideration of FIG. 2, it will be seen that ink from the pool 47 would be thrown upwardly by the transfer roll 32 if all the roll rotations were reversed as would be the case if the unit of stations 11 and 12 were installed on the upwardly moving side of the impression cylinder 19.

The flexographic plate roll in FIG. 3 indicated generally by the reference numeral 22 (alternately in the element 22) again comprises a synthetic rubber fiexographic plate 49 which is adhesively secured of the plate roll 50.

The transfer roll is indicated generally by the reference numeral 51 and includes a steel shell 52 which is chrome plated as indicated at 53. In this ink applicator unit, the transfer roll 51 dips into an ink fountain pan 54 and picks up an excess amount of ink. A control surface-equipped doctor roll is indicated generally by the reference numeral 55 and includes a rubber covering 56. Roll 55 is journalled within a bearing 57, the position of which is adjusted by means of adjusting screw 58 threaded within a fixed bracket 59 associated with the machine frame.

As before, the adjusting means 57-59 is adapted to roll 55 toward and away from the roll 51 for adjusting the pressure thereb'etween. This adjustment is set so as to maintain a light kiss contact between the control surface doctor roll 55 and the transfer roll 51. The speed of rotation of roll 55 is adjusted so that the surface speed thereof is the same as the surface speed of the roll 35 (FIG. 2). For example, at a press speed of 300 feet per minute, the surface speed of the roll 35 and 55 is of the order of 150-300 feet per minute. A steel doctor blade 60 is provided which bears against the outer surface of covering 56, and excess ink drops downwardly into the fountain 54, the doctor blade 60 6 serving to remove any excess ink from the outer surface of the doctor roll 55.

A drive sprocket 61 is fixed for rotation with roll 51 and is interconnected by means of chain 62 with a drive sprocket 63 in an adjustable variable ratio drive box 64. A drive sprocket 65 of the drive box 64 is connected by means of chain 66 with a sprocket 67 fixed for rotation with roll 55.

This driving arrangement provides a very versatile and practical means for controlling the speed of rotation of roll 55. A given ratio of speed of roll 55 with respect to roll 51 is maintained regardless of changes in press speed. At the same time, the ressman can alter the ratio during operation without the need to stop for sprocket changes as would be required in the arrangement of FIG. 2.

As further illustrative of the invention, two different commercial presses are described as to construction and operation in the examples below.-

EXAMPLE ONE The first commercial press was a four-color press of the arrangement seen in FIG. 1 with stations 11 and 12 having application units of the type illustrated in FIG. 2 and

stations

13 and 14 as illustrated in FIG. 3. In each case, the

plate cylinder

21, 21', 22 and 22 had a finished diameter of 5 inches with a plate of standard thickness of 0.096 inch of 50 Durometer. The face on each plate cylinder was 42 inches, journalled on 60 inch bearing centers and this dimension was employed for all of the transfer rolls 32 and doctor rolls 35. The transfer rolls 32 were five inch diameter as were the doctor rolls, the latter having a inch thickness of synthetic rubber of about 70 Durometer. The speed of the doctor roll 35 was adjusted at 70 percent of the speed of the transfer roll 32, the latter being at the Web or press speed of 320 feet per minute. The transfer roll had indentations (cells) of 50 micron and 150 cells were provided along the diagonal ofa one inch square. The plate cylinders each had lines per inch and an ink of a viscosity of 70 seconds (No. 2 Zahn cup) was used for printing on 0.00 125 inch polyethylene. Ink of the abovementioned polyamide co-solvent type was employed and with this in arrangement, superior printing was achieved, impossible with the same ink and polyethylene using prior art techniques.

EXAMPLE TWO In an other commercial embodiment .of the invention, the drive arrangement of FIG. 3 was employed, utilizing a PIV of link belt manufacture to change the speed. Operating speed of the 84 inch diameter impression cylinder was 35 0400 feet per minute, while adjustments were additional-1y made at 100 feet per minute. The diameter of the doctor roll was 7 inches with a 54 inch base. The transfer roll and plate cylinder eaoh had 54 inch bases with the diameter of the transfer roll being 6.6 inches and the circumference of the plate cylinder 21% inches. The transfer roll had 220 line indentations with 23 micron depth cells while the plate cylinder was of the 85 line per inch variety. With a relatively fluid ink, 25 seconds as measured in discharge from a No. 2 Zahn cup, the ink thickness was 0.0004 inch with a press speed of feet per minute and a doctor roll speed of 35 feet per minute. This corresponds to a ratio of about 35 percent for the speed of the doctor and transfer rolls, somewhat below optimum. Raising the press speed to normal commercial speeds of 350 feet per minute increased the ink thickness .to 0.00075 inoh, the doctor roil speed being feet per minute. Clarity of printing resulted and it was noted that the increase in thickness was within tolerable limits. A [further run using a speed ratio Olf 55 percent and the same relatively fluid ink yielded an increase of ink thickness from 0.000175 to 0.00035 in going from 100 feet per minute to 350 feet per minute press speed. Further runs using 53 second and 45 second inks revealed that with speed ratios of 50 percent (speed of the doctor roll divided by the speed of the transfer roll) revealed the same order of increase in film thickness in going from set-up speed to operating speed. As the speeds were brought closer, i.e., the speed of the doctor roll increased to 70-80 percent of the speed of the transfer roll, the difference in thickness of the film transfer at 100 feet per minute and 350-400 feet per minute did not vary appreciably, the ratio of thicknesses being of the order of less than 1.5, within the limits of measurement and tolerance in printing.

It is apparent from the foregoing discussion that a considerable number of advantages are obtined with the present invention. First concerning print quality, the present invention provides sharp, cleaned up definition of print characters and improved halftone work can be obtained which was formerly very difficult in flexographic printing. Flexographic plates stay clean, thus contributing to clean printing. Less striations occur in the print, these striations having been caused from the prior art by scratches in the plates or cylinders. The present invention also facilitates the maintenance of color match, or in other words, the inks may he thinned for this purpose independently of the viscosity controlled effects. Halos around the printed characters are substantially eliminated, the present speed may be varied without upsetting the press settings, and the invention avoids the necessity of providing excessive nip pressures that previously caused deflection and which gave heavy printing in the center of the press and starved printing on each side. This of course reduces wear on the equipment and eliminates excessive deflection and breakage of the roll journals. Additionally, the rubber surface of the doctor roll is prevented from walking or chattering across the transfer roll surface which occurred in prior art arrangements when nip pressures had been employed and which produced non-uniform transfer and printing.

It is apparent that the arrangement of the present invention results in numerous economic advantages since the power requirements of the press are reduced due to the fact that the drag load is minimized since lower nip pressure has been employed. As mentioned previously, the wear on the equipment is subsatntially reduced. The consumption of solvent and thinner is substantially reduced with the arrangement of the present invention, the drying load is also reduced. Less time is needed to adjust the press and the quality of flexographic plates is less critical. Higher press speeds and widths are possible, and less massive structures are required.

In summary, the apparatus provides a way of controlling the thickness of the ink film transferred to the printing plates from the engraved roll. For a given nip pressure setting, ink viscosity, and press speed, the speed of the doctor roll will determine the thickness of the ink film. Starting at a doctor roll speed of approximately the ink film decreases as the speed of the doctor roll increases. In addition, as the speed of the doctor roll approaches and exceeds 70% of the transfer roll, the tendency for increased press speed and/or increased viscosity to increase the ink film thickness is minimized greatly and ultimately eliminated. Additionally, this permits the development of an ink film having a desired increase or decreased thickness without changing the engraving of the transfer (Anilox) roll.

I claim:

1. An apparatus for ilexographic printing comprising a frame, an impression cylinder rotatably mounted in said frame, means for traveling a web to be printed on said impression cylinder in partial wrapping engagement therewith, a plate cylinder rotatably mounted on said frame and in contact with said web for printing the same, an ink applying unit comprising a rigid cellular surface transfer roll rotatably mounted on said frame for transferring controlled quantities of ink to said plate cylinder, a resilient surface-equipped doctor roll rotatably mounted on said frame in substantial line contact with said transfer roll for controlling the amount of ink on said transfer roll just prior to the transfer thereof to said plate cylinder, doctor blade means associated with said doctor roll for removing excess ink therefrom, means for rotating both of said cylinders and rolls, said rotating means being operative to rotate the surface of said doctor roll in the area of said line contact in the direction opposite to the direction of travel of said transfer roll, means for urging said doctor roll against said transfer roll in light, but positive contact, and means for applying ink to saidtransfer roll for control by said doctor roll.

2. The apparatus of claim 1 in which a plurality of ink applying units and associated plate cylinders are mounted on said frame for applying different colors to said Web.

3. The apparatus of claim 1 in which a plurality of ink applying units and associated plate cylinders are mounted on said frame for applying different colors to said web, some of said units being on one vertical side of said impression cylinder and the remainder on the other vertical side, the units on the vertical side wherein the surface of the impression cylinder is traveling downwardly being equipped with dam means defining a pool of ink between said doctor and transfer roll and above the axis of said doctor roll associated therewith, the units on the other vertical side wherein the surface of the impression cylinder is traveling upwardly being equipped with darn means below the transfer roll associated therewith.

4. The apparatus of claim 1 in which the doctor blade means associated with said doctor roll is positioned to contact the said doctor roll within about of said line contact in the direction of the rotation of said doctor roll.

5. The apparatus of claim 1 in which said means for applying ink includes a delivery conduit having an outlet generally vertically above said line contact, said transfer cylinder surface in the area of said line contact moving downwardly.

6. The apparatus of claim 1 in which the doctor roll surface has the lineal speed of the order of about 50-100 percent of the speed of the transfer roll surface.

7. A method of fiexographic printing providing an indented transfer surface of substantially non-deformable surface material capable of receiving and transferring liquids, moving said transfer surface in a certain direction, applying an excess quantity of liquid to said transfer surface, providing a smooth resilient doctor control surface, moving said resilient doctor control surface in a direction opposite to the direction of movement of said transfer surface, maintaining said smooth resilient control doctor surface in light, but positive physical contact with said transfer surface during operation of the apparatus to remove excess liquid from said transfer surface while removing excess liquid from said control surface and while transferring a portion of the liquid from said transfer surface to a receiving surface moving in substantially the same direction and at substantially the same speed as said transfer surface.

8. The method of claim 7 in which a pool of ink is maintained between said transfer and-doctor control roll surfaces, a depth of said pool being maintained at a level to prevent air-entraining turbulence as the speed of said receiving surface is increased.

9. The method of claim 7 in which the thickness of ink film carried by said transfer surface to said receiving surface is measured at relatively low speed and thereafter the speed thereof is increased to a predetermined operatingspeed without further measure.

References Cited by the Examiner UNITED STATES PATENTS 1,780,695 11/1930 Alger 101350 2,185,859 1/1940 Massey 118262 X 2,406,057 8/ 1946 Barrett et al 118-262 X (Other references on following page) UNITED STATES PATENTS 2,987,993 6/1961 Giori 101-167 X 7 1950 B it t 113 2 2X ,4 7 7/19 Tyma 101-350 1950 1332 1 5: 1 101 350 3,163,109 12/1964 SteHing 101349 X 10/1952 Brodie 101-426 X 9/1954 Burroughs 101 178 5 ROBERT E. PULFREY', Primary Examzner.

7/1958 Pumper 118262 X DAVID KLEIN, Exammer- 1/1960 Nitcher a1 101 35O X J. R. FISHER, Assistant Examiner.

Claims

1. AN APPARATUS FOR FLEXOGRAPHIC PRINTING COMPRISING A FRAME, AN IMPRESSION CYLINDER ROTATABLY MOUNTED IN SAID FRAME, MEANS FOR TRAVLING A WEB TO BE PRINTED ON SAID IMPRESSION CYLINDER IN PARTIAL WRAPPING ENGAGEMENT THEREWITH, A PLATE CYLINDER ROTATABLY MOUNTED ON SAID FRAME AND IN CONTACT WITH SAID WEB FOR PRINTING THE SAME, AN INK APPLYING UNIT COMPRISING A RIGID CELLULAR SURFACE TRANSFER ROLL ROTATABLY MOUNTED ON SAID FRAME FOR TRANSFERRING CONTROLLED QUANTITIES OF INK TO SAID PLATE CYLINDER, A RESILIENT SURFACE-EQUIPPED DOCTOR ROLL ROTATABLY MOUNTED ON SAID FRAME IN SUBSTANTIAL LINE CONTACT WITH SAID TRANSFER ROLL FOR CONTROLLING THE AMOUNT OF INK ON SAID TRANSFER