US2328586A - Printing process and apparatus - Google Patents

Description

Sept. 7, 1943. w. (3. R085 2,328,586

PRINTING PROCESS AND APPARATUS Filed Feb. 12, 1942 3 Sheets-Sheet 1 I j & Q

INVEN+EIRI William C. Ross Sept. 7, 1943. w. c oss 2,328,586

PRINTING PROCESS AND APPARATUS Filed Feb. 12, 1942 3 Sheets-Sheet 2 I l I I I l Q w *URZQI) William C. Ross INVEN+E1RI I William C. Ross @3015... Q.

5 Sheets-Sheet 5 Filed Feb. 12, 1942 W C ROSS PRINTING PROCESS AND APPARATUS Sept. 7, 1943.

paper Patented Sept. 7, 1943 2,328,586 PRINTING PROCESS AND APPARATUS William 0. Ross, Winchester, Mass, assignor to Dewey and Almy Chemical Company, North Cambridge, Mass, a corporation of Massachusetts Application February 12, 1942, Serial No. 430,646 9 Claims. (Cl. 101 417) In textile printing, some dye or color is driven completely through the interstices of the cloth and reaches the backing surface. In printing on a perfecting press, the wet ink of the printing applied to the first side of the sheet runs against the draw sheet of the second impression cylinder. Some of this is picked up by the draw sheet and is offset on to the printed sheet again, thus producing the printing fault known as "second-side offset. Whatever ink or color reaches the surface which backs up the type, plate cylinder or roll, I describe as excess color. Excess color causes the same fundamental trouble whether textile material or paper stock is being printed. If the impression surface becomes dirtied with ink, some color will offset from the-impression surface to the back of the sheet To prevent this, back grays are used in textile printing and smut rolls in web letter-press work. The function of both is to absorb the excess color and carry it away before it can strike through to the blanket or the draw sheet. Smut rolls complicate rotary press work to such an extent and increase the cost of printing to such a degree that they are used only as a last resort and on web of the smut roll and are still commonly used, but, nevertheless, increase the cost of the calico process materially.

In web letter printing, no solution for a dirty draw sheet exists which avoids a smut roll and still prevents secondside offset from the draw sheet. Only expedients such as "skinning the ink, sand paper draw sheets, and stopping and washing-up the press are used to minimize the occurrence of offset on the second side. In textile printing, wash blankets and continuous blanket washers make printing without back greys possible.

But the recent appearance of resin bondedcolors which replace the dyes previously used has driven the textile printing industry back to the use 01' back grays. These colors, as contrasted with the direct vat or basic dyes previously used, do not use a bodier such as deatrine or British gum which is subsequently washed out, but are composed of water-bearing, pulp color suspended in a solvent solution of a thermo-setting resin. The color, therefore, is in suspension in a resin solution which contains water as the internal phase of the emulsion. The water in emulsion behaves in its characteristic water-in-oil manner and stifi'ens the mass into a thick, but workable paste. Bonding of the color to the fiber, upon printing, is no longer a. phenomenon of adsorption or mordanting, but comes about by "advancing" the liquid resin which surrounds the individual textile fibers to an insoluble stage.

Once on the blanket, the emulsion immediately breaks. The resin-in-solvent is not re-emulsified and cannot be removed by present blanket washers. The resin solvents soften and destroy the rubber impregnation of the blanket, and the resin cures in the dryers to a hard and brittle skin.

I have discovered that if the blanket, or draw sheet is coated with an ink or color impermeable coating which is applied immediately before printing, and if the coating together with the ink or color is stripped from th impression surface after printing and a fresh coating applied, not only may incompatible inks be run against blankets or draw sheets which otherwise would be ruined, but a continuously clean, fresh surface is maintained on the impression cylinder which, since it never carries ink as it enters the bite, cannot lay color off on the back of the goods or produce second-side offset. Accordingly, I app y to the supporting surface (impression surface), whether it be a flexible blanket, tympan or draw sheet, a temporary continuous coating which receives the surplus ink, and which is removed periodically and immediately terial which can be form to the supporting surface, will dry or harden quickly, will form that surplus ink will not penetrate to the supporting surface and can be removed easily after printing has taken place. The particular compounds employed are described more fully hereinafter,

Of the numerou adaptations of my process necessary to fit it into existing press installations, I shall describe the process as adapted for textile printing on the wash blanket apparatus as described in the application of McMordie et 9.1., Serial No, 404,209, filed July 26, 1941, but I i tend no limitation thereby, for it is obvious that the processmay be generally used wherever it is desired to maintain a clean impression surface.

The McMordie et a1. apparatus is modified only by the addition of mechanism which applies a fresh, continuous coating to the diately after the previous-coating which has been stained by the surplus ink has been removed.

In the drawings,

Figure 1 shows a side elevation of an entire a continuous surface so blanket immetextile printing apparatus of the type-described and shows the general location and arrangement of apparatus here necessary for carrying out my invention;

Figure 2 is a sectional view of my apparatus on the line 2-2 of Figure 1;

Figure 3 is a small perspective view of a portion of the blanket after passing under the applicator roll;

Figure 4 is a perspective view of a small portion of the blanket after the coating process is complete;

Figure 5 is a side elevation of the apparatus; and

Figure 6 is a sectional view through the apparatus on the line 6, 6 of Figure 2.

In the McMordie et a1. device, which is shown in Figure 1, the blanket IU' loops around the impression cylinder II and, crossing the guide roll I2, loops through a preliminary washer or muddler 13. Here, in conventional printing, using gum-thickened color, some of the color is removed and the remainder broken up by a counter-running brush I4. The bristles of this brush not only scour the blanket but also act as a pump to raise water from the supply pan and flood the outrunning surface of the blanket with water which is maintained on the blanket surface by the troughlike form given to it by the blanket guides 15. With gum colors, soaking on the outward run softens the color so much that it is removed completely in a single pass through the washer and squeeze dryer l6.

The mechanism for applying the coating material to the blanket I0 is supported from two 2 bar extensions ll-l8 of the main frame member of the dryer [9 by means of two sub-frames 2 l-22 bolted to the 2 bars. The sub-frames are provided with ways 23-24 in which supporting blocks 25-26 may slide vertically. The supporting blocks rest on arms 21-28 which are pivoted at 29-3l, the position of which may be adjusted vertically by means of the screws 32-33 which are threaded through the lugs 34-35 on the subframe. The stop screws 36-31 allow the arm to be locked rigidly in position when vertical adjustment has been secured.

The applicator roll 33 is journaled on pillow blocks 39-41 which are bolted to the supporting blocks 25-26. This is driven at blanket speed and receives its power from a chain 42 led off, as Figure 1 shows, to a live axle of the blanket reversing roll 43. The applicator roll is preferably equipped with a bronze or copper sleeve 44 which bears an all-over engraved pattern of small depressions 45 and, in fact, is quite similar to an all-over textile print roll.

The coating composition, in the form of a plastic but freely movable slurry, is brought up to the applicator roll by the furnisher brush 46 which revolves on journals mounted on the ends of the slurry pan 41. This is not a driven brush but revolves only because of friction between it and the applicator roll. roll by the furnisher brush is scraped off by the doctor blade 48 which is preferably a stiff strip of laminated resin. This is held in the vise blocks 49-5l and is adjusted for bearing against the roll by the screws 52-53 which are threaded through lugs on the doctor blade support arms 54-55. The tubular spreader bar 56 is supported on threaded standards 51-58 which pass through the slotted brackets 59-6I attached to the sub-frames. It may be adjusted to bear against the surface of the blanket.

Excess material applied to the A free running rubber covered roll 62 is journaled on brackets 63-64 mounted on the main frame above the applicator. Its function is merely that of a backing roller and serves to keep pressure on the applicator roll.

In operation, slurry is put into the slurry storage tank 65 and is continuously fed to the slurry pan of the coater by the gear pump 66. All excess runs back through the drain 61 to the tank. The coating first appears on the blanket as a series of small dots or daubs 68 (Figure 3) because the coating is picked out of the depressions 45 of the applicator roll as the blanket l0 passes over the roll. These daubs are smoothed to an even, continuous film 69 (Figure 4) by the spreader bar 56.

On its inward run, the blanket turns at right angles over the guide roll H and enters the dryer 19, which is usually reversed on itself to conserve floor space, and made up of an inrunning tunnel l2 and an outrunning tunnel 13. Air, heated by steam coils in the fan house 14, circulates through both tunnels. The blanket enters the lower tunnel 12 of the dryer l9, and, in passing through the tunnel, the coating is dried or hardened. In the case of a water base coating, all water is evaporated from the coating which dries to a smooth, ink impenetrable and solvent impervious film. Despite its dryness, it remains flexible and coherent and withstands doubling about the reversing rolls of the dryer and the guide rolls of the apparatus without cracking or peeling off.

As the coated blanket passes the printing mechanism, here indicated conventionally as an impression cylinder l l, the textile l5, engraved color rolls 16, furnisher brushes TI, and color pans 18, the coating picks up charges of the various colors which are driven through the textile. The blanket then passes through muddling apparatus l3 (Figure 1) where some of the soft color is picked off on the surface of the reversing roll 19 and the blanket is then wet scrubbed by the counter-running brush M. The blanket travels to the rear of the machine while it is submerged beneath a sheet of water onthe top surface of the blanket, this water having been lifted up on to the blanket by the brush l4. During the time that the blanket passes to the rear of the machine, the coating swells in the water, and the swelling disintegrates the film so thoroughly that by the time the blanket reaches the Washer l6 only a colored slime remains on the blanket which is easily removed by the washer. The coating is of such a nature that it absorbs the solvent and the color of resin ink, and clings on to these so tenaciously that the blanket itself remains permanently unaffected by the solvent or the color.

Once this apparatus has been set in operation, the only attendance which it requires is to keep the supply tank filled with the coating slurry and at the end of the day release the wing nuts 8|- 82 which hold the slurry pan in place, wash out the pan and clean out the brush. '1

A dry, fresh printing surface is always presented at the printing station, Excess color is carried away and stripped off from the blanket before the blanket cycle is complete, and since the coating itself absorbs both solvent and color to such an extent that it leaves the blanket free from attack, resin bonded inks can be used. All the advantages of wash blanket printing are retained and the expense of maintaining back grays eliminated.

The coating compositions may vary greatly and may be based on such water-swellable substances as bentonite, caseinates, alpha protein, glue, albumins, etc. In all compositions, a film extender or loading material is helpful. This may be a substance such as whiting, infusorial earth, calcium carbonate or clay. Not only does the extender cheapen the coating greatly and absorb the color and solvent, but, since the materials are capillary active, they draw water into the film so rapidly that a complete break-up of the film in the washing apparatus is assured.

In textile printing bentonite mixed with other clays provides the most economical mix. I prefer to use equal parts (dry weight) of bentonite and a well-refined rubber loading or paper coating clay and add 87 parts of water to produce a suspension having l2 by weight of suspended solids.

.The amount of the coating applied to the blanket I!) may be adjusted by (a) varying the depth of engraving or pattern of the depressions 45 on the applicator roll 38, (b) adjustment of the spreader bar 56, (c) adjustment of the doctor blade 48.

In other applications, coating compositions of a precipitable nature are preferred. For example, a composition of ammonium alginate, whiting and water may be thinly coated on a waterproof draw sheet and coagulated by passing under a licking roller supplied with a coagulant or precipitant, such, for example, as aluminum sulphate, calcium nitrate, etc., which has the efiect of converting the liquid composition into a hard, smooth, continuous film. After leaving the printing station, the whole film may be stripped off the draw sheet by a well adjusted doctor blade. The easy stripping of such coagulated films is surprising.

For simplicity of expression, the word ink used in the claims is intended to cover textile printing colors and dyes as well as oil, water and organosol base inks used on paper.

I claim:

1. In a printing process, the steps which include forming a protective coating on the impression backing surface from a plastic substance, hardening the coating, passing the protected backing surface through the printing station and absorbing excess ink thereon and removing the coating from the backing.

2. In a. printing process, the steps which include forming on the impression backing surface a protective coating composed of a water-swellable colloid and an extender, passing the protected backing surface through the printing station and absorbing excess ink thereon, and removing the coating from colloid.

3. In a textile printing process, the steps which include forming on a wash blanket a protective water-swellable coating, drying the coating, passing the coated blanket through the printing station and absorbing surplus ink onthe coating, and swelling the coating to permit its removal.

4. In a textile printing process, the steps which include forming on a wash blanket a protective coating formed from bentonite and an extender, drying the coating, passing the coated blanket through the printing station and absorbing surblanket, means for washing and means for drying said blanket, and means located aheadof the printing roll to apply a protective coating on said blanket, and means to remove the coating after the blanket leaves the printing roll.

7. The process of printing which includes coating the impression backing surface of a press with coagulable material, coagulating the material to form a protective coating, passing the coated backing surface through the printing station, whereby excess ink is deposited on said coating, and then stripping the coating from the backing.

8. The process of printing which includes coat ing the working surface of an impression cylinder of a press with ammonium alginate, coagulating the alginate, absorbing surplus ink on the alginate by passing the coated working surface through the printing station and removing the alginate from the working surface.

9. In a, printing process, the steps which invclude forming a protective coating on the impression backing surface, hardening the coating, passing the coated backing surface through the printing station and absorbing excess ink thereon and then removing the coating from the backing surface.

WILLIAM C. ROSS.

the backing by swelling the

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