US2020177A - Method of manufacturing slip sheets - Google Patents

Description

1935 1... E. GROVE 2,02%17? METHOD OF MANUFACTURING SLIP SHEETS Filed Nov. s, 1935 rove KQQvZQQSHM Patented Nov. 5, 1935 UNITED STATES ME'rnon I or MANUFACTURING snn- SHEETS .0 E. Grove,Hinsdale,Ill. Application November 3, 1933, Serial No.'696,580

2 Claims.

This invention relates particularly to the protection of freshly printed surfaces issuing from a printing-press, or printing-device, and has for its purpose the prevention of smearing, or offsetting,

5 of ink when the freshly printed surface comes in contact with another surface.

While the invention is especially useful in protecting freshly printed artificial cellulose surfaces, or the like, where the ink forming the printed character or design remains mainly on the surface of the sheet, the invention is useful in connection with the preservation of freshly printed surfaces, generally.

In accordance with the present invention, a thin slip-sheet is subjected to a point-embossing operation and in this manner provided on one of its surfaces with a vast number of minute points which are closely associated, but preferably without regularity of position. The point-embossing operation preferably is accomplished by means of a roller having its surface covered with sand-paper of medium coarseness. No. 1% sand-paper is well adapted to the purpose. The embossing roller, covered with sand-paper, coacts with another roller having a yielding surface so that a slip-sheet passed between the rollers will be embossed, without puncturing the slip-sheet.

After the slip-sheet has been produced, it may be used in the ordinary manner as a slip-sheet between successive layers of freshly-printed paper, freshly-printed sheets of cellophane or the like; or the slip-sheet may be wound with the' freshly-printed sheet'upon a suitable take-up roll. In the use of the slip-sheet, the pointembossments are adjacent, the freshly-printed surface and serve to maintain an air film between the freshly-printed surface and the-slip-sheet.

The invention is illustrate in a preferred embodiment in the. accompa ying drawing, in which-- Fig. 1 is a broken plan view of a slip-sheet made in accordance with the invention; Fig. 2, an edge elevational view of the same; Fig. 3, a view illustrating the manner in which the slipsheet is formed; and Fig. 4, a view illustrating one method of applying the slip-sheet to a freshly printed surface.

In the illustration given, A designates the improved slip-sheet; B and B a pair of embossing rolls; 0 and C, a printing-roll and coacting platen-roll;

D, a take-up roll; and E, a guide-roll for directing the slip-sheet into contact with the freshly-printed surface of the sheet being printed, which sheet is designated F.

The slip-sheet may comprise 'a very thin flexible sheetof any suitable material. Itmay be of paper, such as kraft paper, or it may be a very thin sheet of celluloid, or it may be a sheet of fabric produced from viscose, or the like. Preferably, the slip-sheet is rather dense and tough, especially where it is to be used repeatedly. Ordinary thin drafting paper, or tracing paper, may be used. A very loose-fibred, soft paper is not so well adapted to the purpose.

Referring to Fig. 3, the embossing-roll B is shown as having its surface covered with a sheet I of sand-paper or the like which has its outer surface covered with minute sand-projections I. Ordinary sand-paper of medium grade (medium 15 fineness) serves the purpose very well. This may be adhesively joined to the roll B, or otherwise applied.

The coacting impression-roll B preferably is provided with a surface of soft material, desig- 20 nated 2. A felt pad serves the purpose very well. The embossing roller B may be positively rotated by any suitable driving means, and .the coacting impression-roller B' may be an idler. Preferably, the roller B is provided with a heating ele- 25 ment, designated 3. This element may be a steam pipe, a gas burner, or an electric heating element, as desired. It has been found desirable to apply heat during the embossing operation. Where the slip-sheet is of celluloid, the material is softened, 80 I and the embossed points, designated 4, are rather sharply defined and given a permanent set. Inasmuch as most papers contain some sizing, or, something in the nature of a hinder, the same effect, in varying degree, is obtained with various papers. By using minute embossing points on the embossing-roll, puncturing of the paper is avoided. This is especially desirable where the paper fibre is of a character to absorb ink when the paper is punctured. That is, it is desirable 40 to avoid, as far as possible, getting ink upon or absorbed by the slip-sheet, especially where the slip-sheet is to be used repeatedly.

One very useful application of the invention is. to the purpose of preventing smearing or oifsetting of ink in the printing of cellulose tubes, such as are used as artificial sausage casings, or the. like. Cellulose tubes of this character are highly non-absorptive, so that in the printing opera.- tion the ink characters stand upon the surface of the cellulose tube and do not dry quickly. It has been found that danger of smearing is obviated by the use of the improved'slip-sheet.

It is preferred to use a very thin sheet of celluloid, because of its cleanly character and enduring quality. Where paper 'is used, it may be thinly coated with wax after the embossing operation, if desired. This may be done, for. example, by heating the wax and spraying it upon the embossed paper on the side which is provided with the embossed points.

For ordinary printing, where the, slip-sheets are to be used only once, or perhaps a few times, thin krait paper serves the purpose very well.

Preferably, the embossing-roll B is of small diameter, say about 2" in diameter, which gives something approaching a line contact and tends to produce sharpness in the embossed points formed in the slip-sheet. The embossed points need not be raised above the general surface of the slip-sheet more than a very minute traction of an inch, say .0002" to .0006". In ordinary sand-paper, the sand-points are closely but irregularly spaced, and thus the sand-paper serves as a die which will produce irregularly located embossed points in the slip-sheet. This is of some advantage in avoidingcontacts with the ink. The exact height 0! the embossed points on the surface of the slip-sheet is not important,

construed as broadly as permissible, in view oi! the 10 prior art.

What I regard as new and desire to secure by Letters Patent is:

1. A method of producing a slip-sheet for the purpose set forth which comprises passing a thin 7 flexible sheet'between an embossing roll covered with sand-paper and a coacting impression-roll.

2. A method as specified in claim 1, supplemented by applying heat to the zone where the cents arebeing i'o'rmed.

ml. GROVI.

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