US2345179A - Treatment of printing felts - Google Patents

Description

March 28, 1944. J w 1055 ET AL 2,345,179

TREATMENT OF PRINTING FELTS Filed April 10, 1942 POROUS ZONE lMPERV/OUS ZONE,

Patented Mar. 28, 1944 TREATMENT or PRINTING FELTS John W. Close, Lombard, and Clifford H. Hoot,

Chicago, Ill., assignors to United Wall Paper Factories, Inc., a. corporation of Delaware Application April 10, 1942, Serial No. 438,362

1 Claim.

The invention relates to the treatment of printing felts and is of particular value in connection with a type of felt (meaning a continuous belt of flexible porous fabric) which is employed in the printing industry for the purpose of transferring liquid ink or color from a supply source to a printing surface, for example a plate or roll.

The invention is of particular value in connection with the manufacture of wall paper which is generally printed upon a machine which embodies a central platen roll having a plurality of printing stations (sometimes as many as twelve for twelve different colors) around its circumference. Each of these printing stations usually involves a pattern roll which is of the relief type, the relief areas which actually do the printing serving to apply the color to the paper web which is trained around the central platen roll of the machine. With such an arrangement, the color or ink is applied to the relief or printing areas of the pattern roll by means of a porousbelt or felt trained around a set of rollers, usually four in number, which belt receives its ink or color from a suitable ink or color supply.

It has been found that when using the ordinary color transfer belt, generally made of a high quality of wool fabric, that portion of the belt which registers with the printing zone of the pattern roller remains substantially intact and fully efficient for a very long period of time, while the ends or margins of the belt which extend beyond the printing zone deteriorate with relative rapidity, making it necessary to replace the belt frequently, at great expense.

One of the principal difliculties encountered has been the cracking or breaking of the edges of the belt, apparently due to loss of flexibility of the fabric in these marginal zones. We have discovered that this stiffening and consequent cracking of the belt fabric in the marginal zones is due to the fact that, when the belt receives its supply of ink or color from the fountain or other source, the entire width of the belt becomes impregnated with the ink or color and, while the ink in the printing zone of the belt is used up and being constantly replenished with a new supply, the ink in the marginal or non-printing zones of the belt remains in the fabric or structure of the belt in a relatively undisturbed condition over an extended period of time. Apparently, under these conditions, the solid or pigment constituents of the ink or color become concentrated in the fabric of the belt and possibly form a more or less cement-like deposit which materially reduces the flexibility of the fabric in these unused marginal zones and so causes the early break-down before referred to.

Hence, it will be seen that the primary object of the present invention is to provide, in a belt of the character referred to, some method or means by which the flexibility and elasticity of the unusued marginal portions of the felt will be preserved. Further objects are to provide an improved arrangement of the class referred to which does not require any material change, and in most cases no change whatsoever, in the general arrangement of the equipment.

These objects are attained by treating the unused marginal portions of the belt in such a manner that the particles of pigment will not accumulate in the interstices of the fabric, and, to effect this result, these marginal zones of the belt, or at any rate their porous outer surface layers, are charged with a solution or dispersion which, upon drying, leaves the pores of the belt sub stantially filled with a flexible elastic material such as rubber or latex; This material, while not materially interfering with the flexibility of the fabric, serves effectively to bar the entrance of particles of pigment or other unwanted material into the interstices of the fabric.

The drawing accompanying this application illustrates in somewhat diagrammatic form a specific application of the invention to a single station of a wall paper printingpress. In the draw- Fig. 1 represents in diagrammatic form an elevation of the equipment;

Fig. 2 is a section taken on the line 2-2 of Fig. 1; and

Fig. 3 is an enlarged 3--3 of Fig. 1.

In'the drawing, it will be seen that the paper web H1 is supported on a platen which takes the form of a cylinder Ii, positively driven by means not shown. It will be understood that the pattern roll 12 is also positively driven and rotates at such speed that the circumference travels at the same linear speed as the circumference of the platen cylinder l l In the multi-color printing press a portion of which is herein illustrated, the printing area is in relief as shown at I3, it being understood that these relief areas or elevations I3 are the only portions of the roller l2 which make contact with the paper [0, and, of course, these relief areas are of the proper shape or configuration and size to produce upon the paper an impression in that particular color at the places desired in the complete wall paper pattern.

section taken on the line The relief areas in the printing zone of the pattern roller l2 receive their supply of ink and color from a belt [4 which, except as otherwise described, is the usual endless wool fabric belt of such lateral width that the ends of marginal zones project beyond the ends of the printing zone of the pattern roller l2, as shown best in Figs. 2 and 3, and preferably overhang slightly the ends of the cylindrical portions of the belt rollers l5, l6, l1 and I8, as shown best in Fig. 2. In accordance with the usual practice, the belt roller I6 is driven so as to effect the necessary movement of the belt past, and in contact with, the pattern roll l2. However, it need not necessarily be particularly well synchronized with the drive for the pattern roll l2 and platen cylinder II. The lower roll 18 serves as the upper roll of a pair which also include the color pick-up roll I 9 dipping into a trough 20 containing a supply of suitable liquid color 2|. As is usual in modern wall paper manufacture, the ink or color 2i is of the water dispersion type. It will be understood that, as the belt travels in the nip of th two rolls I8 and I9, it will receive color from the circumference of the roll l9, which amount of color picked up by the belt is, to a certain extent, determined by the relative pressure between the rolls [8 and I9. Ordinarily, it will be found advisable to pick up an excess of color which may be doctored off the front or contact surface of the belt H by means of any suitable doctoring arrangement indicated at 22.

The arrangement so far described is such as is understood to have been common practice in this art for a long time.

In printing press arrangements of the character described, the belts are usually about two or three inches wider than the face length of the pattern roll. For example a pattern roll having a printing face 22 inches to 24 inches long can usually be served with a belt which is 2.4 inches to 28 inches wide, so that there will be at each margin of the belt an unused or non-printing portion from 1 to 2 inches in width. This is the part of the belt that gives the trouble according to the heretofore existing practice.

To overcome this difliculty, before a new belt is installed in the equipment, we measure off the length of face of the printing zone of the pattern roller and compare that length with the total width of the belt, and thus determine how wide the unused marginal zones of the belt will be under the particular conditions. The new belt is then rolled up into a fairly compact coil and one end of the .coil or roll, holding the axis of the coil vertical, is lowered into a suitable fiatbottomed receptacle which contains a suflicient depth of the proper impregnating material to soak the unused marginal portion of the belt.

After one edge of the belt has been impregnated in this manner, the coil is reversed and the opposite edge of the belt is similarly treated.

After both edges of the belt have been impregnated in this manner, the belt is unwound or stretched out, and the impregnated marginal zones are allowed to dry.

Preferably, the impregnating liquid consists of a commercial type of latex dispersion in Water, containing about 36% rubber, and an accelerator and a vulcanizer of the cold type.

Using a latex dispersion of the type described, it is found that the material will penetrate the belt fabric for a distance equal to about onequarter of the thickness of the belt, so that, when the margins of the belt are treated in the foregoing manner, there will be a relatively untreated central layer representing about one-half of the whole thickness of the belt. According to our practice, we have not found it necessary to impregnate this central layer or core of the belt.

In certain cases, it may prove to be advisable to treat the entire non-working or inside face of the belt with the same type of solution, using a brush or roller applicator. In this case, sufficient material is applied to penetrate into the face of the belt for a distance equal to about onequarter of its thickness. This is of advantage sometimes when the belt is used to apply colors containing certain red pigments or micaceous materials. Furthermore, this treatment of the non-- working face of the belt is of some value in preventing the loss or waste of color caused by the ink passing completely through the belt and naturally simplifies the clean-up problem.

Whereas the old type of untreated belt usually is found to break down after having been used for printing about 300,000 twenty-four foot rolls of wall paper, precisely the same type of belt, when subjected to our improved preliminary treatment, is still efiective after having been used for the printing of more than 1,000,000 of such rolls of wall paper.

The invention is capable of certain modifications which will be apparent to those skilled in the art, and the scope of the invention should be determined by reference to the appended claim.

We claim:

An endless wool fabric or felt belt for feeding to a wallpaper printing roller surfacing fluid comprising a Water-dispersion of insolubilizabl ingredients, said belt having the border surface layers thereof outwardly of the area of engagement of said belt and roller treated with a rubber-like, water-resistant material so as to immunize said border surface layers against impregnation by said surfacing fluid.

JOHN W. CLOSE. CLIFFORD H. HOOT.

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