US2458981A

US2458981A - Method of eliminating offset

Info

Publication number: US2458981A
Application number: US619701A
Authority: US
Inventors: Charles B Cotherman
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-10-01
Filing date: 1945-10-01
Publication date: 1949-01-11
Anticipated expiration: 1966-01-11

Description

Patented Jan. 11, 1949 UNITED STATES PATENT OFFICE METHOD OF ELIMINATING OFFSET Charles B. Cotherman, Goshen, Ind.

No Drawing. Application October 1, 1945, Serial No. 619,701

4 Claims. 1

1n the art of printing, one troublesome factor is the tendency of static electricity to interfere with the proper positioning of a sheet of paper on the platen of a printing press, which carries the sheet into printing contact with the type, plate, or printin cylinder. Similarly, static electricity is responsible for considerable difilculty in speedily removing the sheet after it is printed. It also interferes with the jogging of the removed sheets, that is to say, the evening-up of a stack of the printed sheets.

The objects of the present invention are to provide a method of eliminating the adverse efiects usually attributed to static electricity in the art of printing and more specifically, to facilitate the positioning and removal of work on and from the platen of a printing press, to eliminate offsetting, and to facilitate jogging of the printed work.

The platen of a printing press is usually built up with the so-called make ready and covered with a top sheet which is usually referred to as the draw sheet.

According to the present invention, the surface of the draw sheet has applied to it a thin coating of a composition consistin of oil and powdered soapstone. High quality lubricating oil of the grade known as No. (SAE rating) is employed together with the best grade of very finely powdered soapstone (commercially available as No. 1 powdered soapstone), These ingredients are thoroughly mixed in proportions which may vary from about one-half pound to 2 pounds of powdered soapstone to one quart of 011.

For application in the printing art, as already explained, the proportions of about one pound of soapstone to one quart of 011 gives excellent results. Such a mixture is a very thick or viscous mixture, but it has the capacity of being spread into a very thin film so that a very small quantity of the composition is required for covering the entire area of the draw sheet on an average size printing press.

The thin coating of the composition may be wiped over the draw sheet and evenly spread and it will so effectively adhere to the draw sheet that none of it will leave the draw sheet and adhere to the paper placed thereon for printin purposes, or, at least if any of the composition does adhere to the printing paper, it is unnoticeable and hence is negligible.

When the draw sheet of a printing press is coated with the described composition, it is found that the sheets to be printed upon have no tendency to adhere to the draw sheet and that they can be quickly slid across the surface of the draw sheet into their proper position for printing, and then easily withdrawn when the printing is completed. It is sometimes advantageous to adjust the usual sheet gripping means to hold the sheets somewhat more tightly during the travel of the platen carrying the sheet into printing engagement with the type since the elimination of sheet adherence to the draw sheet sometimes results in a tendency for the sheet to be thrown out of place as an incident to its movement with the platen.

In addition to facilitating the insertion and removal of printin sheets from the press, the elimination of static electricity from the printed sheets eliminates ofisetting which results from a pronounced tendency believed to be due to static electricity, for the printed sheets, when piled, too tightly adhere to one another. When the described compound is employed in the manner explained, the printed sheets will form a relatively loose stack so that the ink will set sufiiciently to prevent offset before the printed sheets settle into a tighter stack. This elimination of huddle (sheet to sheet adhesion) also facilitates subsequent jogging, that is to say, evening-up of the stack of sheets, which have been printed and more or less haphazardly assembled in the stack.

Another important benefit of the use of the composition in the printing art as explained, is that the composition protects the draw sheet against excessive wear so that it remains good for use for a much longer period than under ordinary conditions. In ordinary practice, the repeated application and withdrawal of work from the draw sheet covered surface of the platen, appears to be accompanied by a tendency of each printed sheet to remove with it, a certain amount of lint-like fiber from the surface of the draw sheet. This tends to produce a nap-like surface on the draw sheet, which in a short time becomes unfit for further use.

When a draw sheet is coated with the described composition, the tendency of the printed sheets to pick up fibers from the draw sheet appears to be wholly eliminated, and the surface of the draw sheet retains its normal smoothness and hardness for a much longer period than does an untreated sheet.

The mixture described should be thoroughly stirred before it is used because the soapstone ingredient tends to settle out of the oil. The oil, which constitutes a carrier for the soapstone, appears to serve the purpose of adhesively anchoring the soapstone particles to the draw sheet.

The carrier facilitates spreading of the soapstone into a thin and almost imperceptible coat on the surface of the draw sheet. However, the oil may also otherwise contribute to the operativeness of the described method and mixture because of its lubricating properties.

I claim:

1. The method of facilitatin Printing press work positioning and removal which consists in applying to the draw sheet of a printing press platen, a mixture of oil and finely powdered soapstone.

2. The method of facilitating printing press work positioning" and removal which consists in applying" to the draw sheet of sprinting press platen, a mixture of oil and. finely powdered Soapstone, the mixture being in the proportions of from one-half pound to two pounds of soapstone, to about one quart of oil.

3. The method of facilitating printing press work positioning and removal which consists in applying to the draw sheet of a printing press platen, a surface coating of finely powdered soap-,

stone mixed with oil.

4. The method of eliminating the efiects of static electricity on printed work which consists in applying to the draw sheet of the printing press platen on which the work is printed, a mixture of lubricating oil and powdered soapstone.

CHARLES B. COTHERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 110,032 Gorman Dec. 13, 1870 142,930 Muller Sept. 16, 1873 982,726 i Johnson Jan. 24, 1911 1,566,800 MacAurthur Dec. 22, 1925