US1925429A - Method of drying printed sheets - Google Patents

Description

Sept. 5, 1933. P. AITCHISON ET AL METHOD OF DRYING PRINTED SHEETS Filed Dec. 19, 1930 OZON IZER if an ozorv/z ER a i ATTORNEY.

Patented Sept. 5, 1933 UNITED STATES PATENT? OFFICE METHOD OF DRYING PRINTED SHEETS tion of New York Application December 19, 1930 Serial No. 503,408

3 Claims.

Our invention relates to the method of drying printing sheets, and more particularly to the drying of the ink upon collected printed sheets preparatory to additional work upon said sheets.

5 In printing from engraved, intaglio or undersurface printing plates, inks having an oil vehicle are used, and when stripping the paper from such plates, ink is Withdrawn from the sunken lines of the plate so that as compared with ordinary type printing, the lines of the imgfission contain a considerable quantity of the Following the making of each impression, the printed sheets are collected in a stack or roll, the printed surface of each sheet being separated from the adjacent sheet by a sheet or strip of material coated or impregnated with an oil or wax, one function of which is to avoid offsetting of the impression. So far as the present invention is concerned, such sheets or strips may be considered solely as anti-offset means, although they serve other and desirable purposes well known to the art at the present time.

The drying of printing inks of the character herein referred to is a result of oxidation of the oil vehicle of the ink, and our present invention contemplates the acceleration of such oxidation by the bringing of the oxidizing agent into intimate contact with every portion of the printed sheet, the use of a powerful oxidizing agent and the maintenance of a continued contact of the agent with the vehicle of the ink ,until the oxidation of the oil has progressed to a point where the subsequent handling of the sheets will not result in likelihood of smutting the imprint.

The use of insert sheets or of a web of material acting upon each of the sheets, in the 4 manner above described, has always retarded the drying or oxidation of the ink because of the exclusion of atmospheric air in any substantial volume from about the printed surface of the sheet, and in the practice of the method oftour invention we have found it necessary to relieve the pile or roll containing the printed sheets from external pressure to an extent, which, during the practice of the method, would interfere with the proper introduction of the oxidizing agent within the stack or roll, and the resultant intimate relation of such agent with the ink of the impression upon each print.

The invention consists primarily in the method of drying printed sheets consisting in relieving external pressure upon a stack or roll of collected printed sheets, and introducing an oxidizing agent adjacent the stack or roll while the pressure is thus relieved; and in such other novel steps and practices, and the use of such an oxidizing agent, as are hereinafter set forth and described, and more particularly pointed out in the claims hereto appended.

Referring to the drawing,

Fig. 1 shows conventionally the practice of the method of our invention upon a plurality of printed sheets collected in a roll of anti-ofiset 65. material; I I

Fig. 2 is a'section on the line 2--2 of Fig. I; and

Fig. 3 is a view illustrating the treatment of a stack of sheets with the inserts of anti-offset material.

Like numerals referto like parts throughout the several views.

In printing from engraved, intaglio or undersurface printing plates, two practices are followed when collecting the sheets. By one of these, each printed sheet is placed in a stack and sheets of an anti-offset material are placed upon each sheet. By the other practice, the printed sheets, as they are delivered from the printing machine, are rolled in a web of anti-offset material. When the sheets are stacked, the weight of a large number of sheets results in a fairly heavily compacted stack, while when winding the sheets in the roll of web, the web is subjected to such tension as to form a fairly tight roll.

The effect of both methods of collection is to bring both surfaces of each sheet into close, intimate contact with the anti-offset material, which material extends beyond all edges of the, sheet and serves to exclude atmospheric air from the printed lines upon the sheet, the manner of collecting serving to eifectively express substantially all of the air from between the printed sheet and the anti-ofiset material.

It has been found desirable to employ an antioffset material which is treated with an oil or a Wax which is, in large measure, repellent of the ink used in making the impression, and which has no properties which will tend tocause the adherence of the offset material to the printed sheets, or the absorption of any portion of the vehicle of the ink from the printed lines. These properties are not absolutely necessary in the practice of our present invention, but are highly desirable as tending to facilitate the introduction 105 of the oxidizing agent within the stack or roll, and its introduction between the printed sheet and the antiroffset material.

Upon the completion of a run of a printing machine, it is essential to allow the stack or roll of no duce the finished product.

Prior to our invention, the elapsed interval between succeeding operations upon the printed sheets amounted to several days, and such delays not only interfered with the prompt completion of work, but with the routine necessary to be followed in completing the work and in completing other work.

By the method of our invention, the elapsed time interval between succeeding operations upon a printed sheet may be reduced to a few hours,

thus avoiding delays in the completion of all of the work required upon the sheet, and the interferences with the routine of the factory, which, prior to the invention, were unavoidable.

In the practice of the method or art of our invention, we employ ozone as the oxidizing agent. It is not necessary that the ozone be in a highly concentrated form, although the gaseous mixture used must be rich in ozone. The properties of ozone as an oxidizing agent are well known, and.

its action upon the oil vehicle of printing inks is also well known and has long been known. It is also well known that highly concentrated ozone is highly injurious to health, and particularly to the lung tissues. We have therefore found it essential to utilize the ozone under conditions which will not jeopardize the health of workmen, as well as under conditions which will ensure the effective utilization of the oxidizing properties of the ozone upon the ink of the impressions upon printed sheets collected by one of the two methods above referred to, or the mass treatment of a large number of such sheets. In attempting to so utilize ozone, securing a proper intimate relation between the ozone and the ink of the imprint afforded a serious problem.

To meet the conditions developed, we found it essential to create a sub-atmospheric pressure about the stack or roll of printed sheets, with their associated anti-offset material, within a closed chamber prior to the introduction of the ozone within said chamber. The creation of this sub-atmospheric pressure is effective in reliev ing the stack or roll from external pressure, so that when the ozone is introduced, it flows readily between the printed sheets and the anti-oilset material, and into intimate contact with the ink of the lines of the impression. The creation of a partial vacuum also removes a very high percentage of the atmospheric air concollected within a web of anti-offset material.

For economys sake it is desirable to limit the capacity of the chamber within the housing 10 to that required to receive the roll 11. The removable cover 12.0f the housing 10 is so constructed as to permit it to be so sealed as to exclude atmospheric air from the chamber when the cover is closed.

In connection withthe housing 10, we use a vacuum pump shown conventionally at 13, the inlet pipe 14 of which communicates with the chamber within the housing 10 and has, in the length thereof, a check valve 15 and a cutoff valve 16. The discharge 17 of the vacuum pump has a check valve 18.

Also communicating with the chamber within the housing 10 is a valve controlled pipe 19 communicating with an ozonizer shown conventionally at 20.

Bearings 21 are provided Within the housing 10 to receive the arbors 22 of the roll 11. A pressure gauge is shown at 23 and a relief valve at 24.

Referring to Fig. 3 of the drawing, the same arrangement of parts is employed as described in connection with Figs. 1 and 2, with the exception that the housing 10a is formed to receive a stack of sheets 25 instead of being curved,

as shown in Figs. 1 and 2, to receive a roll, and

the omission of the bearings 21.

In carrying on the method, the top 12 of the housing 10 is open, and a roll 11 is mounted with its arbors 21 in the bearings 22 as a stack 25 of sheets is placed in said chamber. The cover 12 is then closed and sealed and power is applied to the suction or vacuum pump 13 so as to withdraw air from the chamber within the housing 10. The operation of the pump 13 is continued until substantially all of the air within the housing and between the sheets of printed paper and the associated anti-offset material has been withdrawn. The degree of sub-atmospheric pressure developed is determined largely by the extent to which it is desired to dilute the ozone. For practical purposes, it is desired to extract as much air as possible from the chamber.

When the proper degree of sub-atmospheric pressure has been developed, the cutoff valve 16 is closed, and ozone is delivered to the chamber within the housing 10, thus breaking the sub-atmospheric pressure within such chamber, the ozone rapidly filling the entire chamber as well as freely flowing between the printed sheets and the anti-offset material engaging each sheet. The elimination of external pressure upon the roll or upon the stack facilitates the penetration by the ozone into the space between the convolutions of the roll 11, or the space between the offset sheets of the stack 23 and between each sheet of paper and the contiguous offset material. The pressure ultimately developed by the ozone within the chamber formed by the housing 10 need be little above but one atmosphere, and yet develop conditions where the desired intimate contact of the ozone with the vehicle of the ink upon each printed sheet is secured. When the desired amount of ozone has been delivered within the chamber of the housing 10, the supply of ozone is cut off, and the conditions developed are allowed to continue for the desired length of time to ensure an adequate oxidation of the vehicle of the ink.

By thus introducing the ozone or other oxidizing agent within a closed chamber, likelihood of injury to the health of the workmen is practically eliminated, since if leakage from such chamber should occur, it would be in such small volume as to be negligible in its effect upon the surrounding atmosphere.

When the ink upon the sheets nas been subjected to the ozone for a desired length of time, any desired means, as the pump 13, may be utilized to withdraw the oxidizing agent from the chame ber within the housing 10, and if desired, air may be admitted within said chamber in order to fa-' cilitate the raising of the cover 12, the relief valve 24 being provided for this purpose.

It has been found, in actual practice, that by the use of the method of our invention, it is possible to take the collected sheets, following the days run of each press; and by allowing them to stand over night, to have them in condition for a succeeding run, or for a finishing operation, the following morning. Because of this condition, it is possible to avoid those delays which prior to our invention deferred the making of succeeding impressions, or the performing of succeeding operations, over a period of days. It also permits practically continuous work in the production of the printed sheets or articles using such sheets, since if necessary, following the run of a press in the making of one impression, the press may immediately be made ready for the succeeding impression, utilizing a different plate, thus avoiding all of those difficulties resulting from the interruption of routine work and arising from the necessity of reserving equipment, which might otherwise be used for other purposes, in order to complete a particular job.

It is not our intention to claim broadly the use of ozone as an oxidizing agent for drying printing ink. This property of ozone has long been well known. We believe it, however, to be broadly new to treat printed sheets, en masse,

which printed sheets are separated by anti-offset material, by a procedure, the first step of which is the creation of a sub-atmospheric pressure for the purpose of withdrawing the atmospheric air from about the collected mass of sheets, and from within the mass, so as to facilitate the introduction of ozone or any other desired highly oxidizingagent about and within the mass, and in intimate relation with all of the ink lines of each printed sheet, and we intend to. claim such broad-' Having described the invention, what we claim as new and desire to have protected by Letters Patent, is:

1. The herein described method of drying, or hardening the ink on printed sheets consisting in placing a stack or roll of collected printed sheets in a confined space, creating a sub-atmospheric pressure about said stack or roll and introducing an oxidizing agent within said chamber.

2. The herein described method of drying or hardening the ink on printed sheets consisting in placing a stackor roll of collected printed sheets in a confined space, creating a sub-atmospheric pressure about said stack or roll and introducing a strong concentration of ozone within said chamber.

3. The herein described method of drying or

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