US2397827A - Method and apparatus for pressing, deaerating, and drying - Google Patents

Description

April 2, 1946. c. w. wlLLiA'Ms 2,397,827

METHOD AND'APPARATUS FOR PRESSING, DEAERATING, AND DRYING I Filed May 25, 1942 ,11% 107m/@5 wv wf//fnms Premessa-.2, 194s r' FFICIl-.

' uarnon Ann Arrmrvs Fon raasslNG. nnanaarma, AND Dama charte w. william., Louisville, xy. Application May 25. 1942, serial' No. 444,340

1 (o1.v i1-sa) subject, each plate being exposed through a standard color nlter, i. e. red, yellow or blue. A black and white printis made from each of the negatives on bromide paper. The bromide prints are contacted with so-called carbon tissues (red, yellow and blue) which have pigmented gelatin on their surfaces. In each case the bromide print, in conjunction with a sensitizer previously soaked into the pigmented gelatin, acts to form a hardened image on the colored gelatin which is identical to the image on the bromide print.. The bromide print is removed from the pigment tissue and the latter pressed onto a sheet of smooth plastic material on which it is washed in hot water to remove the soft gelatin, leaving the hardened image. After the three colored images have been thus secured on three plastic sheets, they are, transferred individually to a single temporary supporting sheet in registry and subsequently -to a sheet oi paper to make the final print.

In the step of applying the pigment tissue to the sheet of plastic, considerable dimculty has been encountered and much time has been wasted due to the inclusion of air bubbles between the contacting surfaces of the sheets, and air apparently included in the gelatin layer, and the necessity for removing these air bubbles. -The existence of the air bubbles or pockets -becomes particularly noticeable when the pigment sheets are immersed in warm water. as is necessary in the processing, because of the expansion of the air under the increased temperature. If the air bubbles are not removed, they cause imperfections in the ilnal print.

Heretofore it has been the practice to squeegee the plastic sheet and the pigment sheet vigorously for an extended period of time in an effort to remove the air bubbles visible at this stage of the process. This causes the pigment sheet to stretch varying amounts in different directions so that it is difficult and sometimes impossible to secure later the exact registration of the three pigment sheets that is required in the iinished print. The

time involved not only representswaste but as'. the time required for squeegeeing the three 'ditferent gelatin prints may be different, the time control of the processing of the three prints is entirely disrupted and is reflected in the :Il nal print.

The application of pressure in connection with this step in the process is highly important.`

While mechanical pressing means andV weights, such as marble slabs, have been employed. they are not only difllcult to handle but are also dilllcut to manipulate to secure the uniform pressure that is required for the best prints. Where marble slabs are used, two or three slabs about "Vg" thick are usually employed, .the pressure obtained thereby being in the order of 0.3# per square inch. Even when perfectly plane surfaces are provided in the press and the pressure is applied with absolute uniformity, which is virtually impossible with the devices now in use, the best prints cannot be secured because of irregularities in the other elements making up the sandwich such as the plastic, the pigmented gelatin and the paper. Such irregularitiescause unequal distribution of pressure to the extent that double the intended pressure may be applied in some spots and only one-half the pressure in other spots.

The drying of the prints at this stage is also important as it has been found that they must be brought to approximately a predetermined water content before they are washed, else the resultant images are not satisfactory.

Similar problems as to air bubbles, pressure. and drying arise in connection with the transfer of the three registered pigment sheets from the temporary support to the nal support. Heretofore considerable time has been required for the vigorous squeegeeing necessary to remove the air bubbles and for the nal drying and difficulty has been experienced in securing even an approximate uniform pressure.

In overcoming the aforesaid disadvantages. it is an object of` my invention to provide novel methods and means wherein steps such as the foregoing can be carried out in a much shorter time than has been possible heretofore and with better results. I

Still a further object of my invention is the provision .,of novel methods and means wherein the steps of removing the air bubbles, reducing the moisture content, and applying uniform pressure can be performed simultaneously in the above procedure and in similar processes with assurance as to the final results.

1n the drawing:

Figure 1 is an exploded view of my invention as embodied in an arrangement for simultaneously de-aerating. drying and pressing a pigment print onto a sheet oi plastic.

Figure 2 is a section taken through one endof the flexible blanket of my invention illustrating the ridge or dam which is provided to insure airtight contact with the supporting base.

Figure 3 isa section through the vacuum connection to the exible blanket. l

Figure 4 is av partialsecuon taxen on the une 4 4 of Figure 5, illustrating the manner in which the flexible blanket embraces the edgesr ofthe Y sheets thereunder.

Figure 6 is a section ora modified table top wherein a groove is formed in the table top to receive the sealing dam on the blanket.

The present invention involves the use of a base member for supporting the prints which are to be pressed, dried and deaerated for transfer or like purposes, and a blanket or cover of flexible air-tight material such as soft rubberwhich is placed over the prints with its sides in contact as a table l I having' a substantially plane smooth` top surface I2 is provided. Taking the step ofl transferring a pigment print onto a sheet of plastic by way of illustration, a plastic sheet is shown at 'I3 and pigment print at I4, the pigmented gelatin being on the underside of the print. Plastic sheet I3 is contacted with pigment print I4, the two laid upon table I I and a blanket I5 of exible air-tight material such as soft rubber placed over the assembled sheets. Blanket I5 is provided with a ridge or dam I6 on its underside and adjacent its edges which is arranged to contact surface I2 of table II outside the area of the plastic sheet and the pigment print as shown in Figure 4 and provide a surrounding air-tight seal. To facilitate the forming of the seal, the top of table II maybe formedwith a shallow groove I2' (Fig. 6) ofv a configuration corresponding to that of dam I6 and into which the lower portion of the dam may be tted when the unit is assembled. y

` To connect the underside of blanket I5 to a source of vacuum such as a conventional aspirator 2| arranged to be operated by city water pressure and a hose connection 22, the blanket is formed with a hole I5 bounded on the upper side of the blanket by a small flange I1 on one end of a connection I1 arranged to receive hose connection 22. A ring 20 .of smaller inside diameter than the outside diameter of flange I1' is itted over connection I1 and suitably sealed to the upperside of blanket I5 by rubber cement as shown at I8. To prevent localization of the vacuum effective through connection I'I and the possible sealing of the inner end of hole I5', a sheet I9 of porous material such as cloth is applied to the underside of the blanket and cemented thereto only about its edges. It is preferred to extend the cloth or like porous material over the entire of dam I5 and seal it to the blanket around its edges only. The provision of such a porous memberlin-eures the access ,of vacuum to all parts of the surface immediately adjacent the blanket, despite the connection of the vacuum at only one point. In lieu of a porous material. the underside of the rubber blanket may be slightly roughened. In operation, the assembly presents the appearance -shown in Figure 5 wherein it will be noted that blanket I5 is drawn'down around its edges so that it conforms closely to the outline of the underneath sheets. By reason-of this conformation ofthe blanket, a channel 23 (Fig. 4) is formed around the periphery oi the sheet of plastic and the pigment sheet so that the vacuum beneath the blanket is effective completely around the periphery of the-contacted sheets. As blotters or similar porous sheets are usually placed between table II and sheet I3 as well as between blanket I5 and pigment print I4, the vacuum is effective through the porous sheets onl all surfaces of the contacted plastic and pigment sheet, this being further assured by porous material I9.

This vacuum not only tends to reduce the moisture to the correct amount for the subsequent washing and to remove the air bubbles but also operates to cause the lblanket to press the print and plastic sheet together with uniform pressure over their entire areas. The pressure obtainable with the well-known aspirator and citywater pressure will run at least 12 lbs. per square inch which is equal to a pile of marble about l0 feet highVv or a pile of steel about 42" high. Such pressure is obtainable with a vacuum of about l25" Hg. In some cases, it has been found possible to secure a vacuum of as high as 28" Hg. with the same means and consequently secure a higher pressure.

Wherev it has heretofore been necessary toV (as is obtainable with three marble slabs of the type usually employed) or more, it is possible with rthe invention to eliminate squecgeeing except what is actually necessary to bring the pigment and plastic sheet into contact and simultaneously dry to the desired degree, de-aerate and press with the desired degree of pressure within the period of 10 minutes. As three pigment sheets must be treated in each processing, this results in a saving of time in excess of 45 minutes for this step alone. Moreover as all the sheets are given uniform treatment for the same period` of time, uniform results are assured and there is no disruption of the time schedule. It has been found in practice that the present invention brings the water content downto the requisite degree of dampness for the subsequent washing with hot water and it is not necessary to required approximately 40 minutes and the application of the considerable pressure to secure a satisfactory transfer. With the treatment of the temporary support andthe final support 'by the method of this invention and the application of vacuum of the order that can be obtained with underside ofthe blanket within the boundaries city water pressure and a conventional aspirator.

i. e., 25" to 28" Hg., it has been found p0Siib1e to cut this time down to 10 minutes and secure better results.

Thus in the tri-color pigment process for a single print, it has been found possible to save in excess of 1 hr. and 15 minutes in actual time in addition to the time and labor involved in the squeegeeing hitherto considered necessary in an attempt to remove the air bubbles, and the additional apparatus required to secure what was hoped to be the desired uniform pressure.'

In the over-al1 process it has been found possible to save as much as three to four and onehalf hours and at the same time improve the character of the prints produced and eliminate any possibility of imperfections due to air bubbles, the application of non-uniform pressure, imper fect register or improperI drying.

Having described my invention, I claim:

An improvement in the art of tri-color pigment printing wherein a sheet supporting a transferable image and a receiving medium to receive the image are brought together in face to face relation to form a, sandwich and then processed to remove water and air from the sandwich and to effect the transfer of the image to the receiving medium comprising: placing the sandwich on a planar air-impervious supporting surface; placing an airtight exible blanket over the sandwich to form, in cooperation with the support, a sealed chamber enclosing the sandwich; and evacuating the chamber to withdraw air and moisture from the sandwich and to cause the blanket to press the sandwich uniformly and firmly against the support to effect the transfer of the image.

CHARLES W. WILLIAMS.

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