US1762910A - Drying apparatus for gelatin carbon tissue - Google Patents

Description

June 10, 1930. v T. CHESTER 1,762,910

DRYING APPARATUS FOR GELATIN CARBON TISSUE Q File'd Aug. 1, 1928 INVENTOR ATTORNEY Patented 10, 1930 UNITED- TATE FATE-M OFFICE moms cnnsmm, or rrrrsnunez, rmsnvm Y DRYING APPARATUS FOR GEIATIN CARBON TISSUE D Application. filed. August 1, 1928. Serial 1W0." 88,817.

This invention relates to drying apparatus for gelatin carbon tissues, employed in the illustrating process lmown a's rotogravure.

6 The roto'gravure process, as do most of the processes pertaining to the rinting arts, includes a large number of elicate operations a'nd involving the use of the fragile carbon tissues to which reference has been 10 made. Such tissues are well known in the art and comprise thin paper backingscoated with gelatin emulsions, and the rocess of their employment is outlined as ollows:

The tissue as received is not sensitized to light and must be prepared for use by subjection' to a sensitizing potassium' bichro- .mate .bath. The tissue is next squeegeedface down on a polished metal ferrotype I plate on whichit is dried. Thereafter the 0 tissue is peeled from the plate and stored in light-proof means until it is to be used.

Ordinarily several sheets of tissues are so.

sensitized and prepared at once and preferably a relatively short time before their 2 use is intended. 1

When one of the sensitized tissue sheets is to be employed it is printed upon by exposure to light through a photographically obtained positive, developed, fixed and. washed as is usual in the photographic art. Next comes the process wherein the tissue sheet is wrapped-and squeegeed around ,a polished copper cylinder, which is then subected to a hotwater bath for a eriod of indeed, remove part of the gelatin thereof dependent upon the, pattern of the ositive. The cylinder is then dried and sub ected to H a ferric etching solution which lightly etches time sufiicient to: .disintegrate t e paperinto the exposed surface portions of the cop ments are to be printe are of considerable area, running in newspa r work to around 46" x 29"; and the etc 'ng is very light. Further, competition among publishers dictates an extremely high quality of work, and it will beappreciated that very great care must be employed throughout the progress of the carbon tissue. i

Perhaps the most fruitful and least understood souree of inaccuracies in the product 7 is in the drying of the tissue on the ferrotype plates, the general practice in the art heretofore being to use the greatest care and skill in otherwlse handling the tissue sheetbut, inconsistently enough, to dry the same by standin its ferrotype plate on edge and directing t ereagainst the breeze from an electric fan. The result is invariably that some ,of the water with which the 'aper is, saturated works down by avity e ecting a distortion in the tissue. oreover where at-' mospheric or room air is employed, in winter such air is usually so dr that the tissuei'stoo rapidly dried, out wh1le in summer such air is usually too warm and too humid; in either caseproducing still further distortion of the tissue. This method also obviously subjects the tissue backing to all the dust and forei matter in the atmosphere which later fin s its way to produce relatively minute but distinct inaccuracies in the copper printing cylinder. 7

My invention is directed toward the prociess of drying the tissue on the ferrotype plates, and involves 'so controlling the conditions of the drying operation that the same is independent of weatheror room conditions and results in a very substantial super-' iority and exact uniformlty of product.

To this end I provide a chamber in which. the tissue is dried, and arrange'for circulatin the dry medium, such as air, through the cilamber, and forconditioning the me dium before the tissue sheets are exposed thereto, preferably recirculating the same so that outside dust is not accumu ated thereby. Further, in order that a number offerrotype plates with their sheets of tissue may be accomodated, and that each sheet may receive an even distribution of air over its surface, and that the air may find free exit from the sheets, I provide in the chamber through which the air is circulated, a rack of shelves of novel construction as will appear more in detail hereinafter.

The exact nature of the invention to ether with further objects and advantages t ereof will be apparent from the following description, taken in connection with the accompanying drawings, in which Fig. 1 is a plan view of apparatus in which my invention is incorporated; Fig. 2 isa vertical section partly diagrammatic but generally in the plane of line 22, Fig. 1; Fig. 3 is i a detailed vertical section as in the plane 33, Fig. 1; and Fig. l is a detail in perspective of a corner of one of the shelves employed.

Vifith reference now to the drawings, I provide a rack 1 having a number of horizontal rectangular shelves 2 supported as by means of the corner posts 3, each shelf being of suficient supporting area to receive and support a ferrotype plate bearing a sheet of gelatin carbon tissue.

Each of the shelves 2 is hollow, as of sheet metal, and is really an air box, is provided as on its under side as indicated Fig. 4, with a number of relatively small and closely spaced perforations 4, and has on one edge one or more connections 5 whereby a drying fluid may be supplied to the shelf air box.

I arrange the rack 1 within an enclosure having its left and right side walls 6 and 7 and rear wall 8 well spaced from the rack. Above the rack I arrange a container or, as indicated in the drawings and by the partitioning members 9, 10 and 11, a compartment or subenclosure. Extending downwards of the right-hand wall 10 and between the rear wall of the compartment and the front wall thereof is a partition 12 having openings 13 corresponding with the connections 5' of the shelves 2, the connections 5 being secured in these openings as indicated Fig. 2. The space bounded by the walls 7 8 and partitions l0 and 12 thus forms a chamber B through which access may be had with the chamber A in which the rack 1 is located, by way of the openings 13, connections 5, the hollows of the shelves 2 and the perforations 4, free exit from between the shelves being had on all sides thereof.

Upper and lower doors 14 and 15 are-provided as indicated Fig. 3, which together with the parts already described, substantially form of the interior of the enclosure, the chambers A and B as set forth and the chamber 0 in the upper portion thereof.

A blower 16 as of the centrifugal type indicated, and driven by a motor 17 and which may be located above the enclosure is provided, and by means of the fan outlet duct 18 is arranged to deliver a drying medium such as air, through an inlet opening 19 to the chamber B. i

The up er portion of the chamber A lying between t e wall 6 and partition 9 has an outlet opening 20, and a fan inlet duct 21 is arranged as indicated. Thus, with the doors closed operation of the fan will cause a circulation from the chamber 13 to the chamber A by way of the shelves so that a drying medium will be directed downwards upon carbon tissue mounted on ferrotype plates resting upon the shelves, the perforations insuring even distribution over the tissue sheets.

The partition 11 is provided with an open- .ing 22 by which communication is had between the compartments A and C, and the compartment C has communication with the duct ,21 by Way of an opening 23 in the upper wall of the enclosure and a branch duct 24; whereby communication between the chamber A and the fan is had by the two paths described, one including the chamber C and each forming a by-pass for the other.

Within the chamber C are arranged a number of coils 25 interspaced by baffle plates 26 and having connection as by pipe 27 with a source of refrigerant with which the coils form a refrigerating unit.

' Within the branch duct 24 are coils 28 having connections as by pipe 29 with a source of heating medium such as steam, the steam supply to the coils 28 being conveniently controlled by a thermostatic valve 80 actuated by a thermostatic unit 31 in the fan outlet duct 18, although it will be understood that the unit 31 might be located in the fan inlet duct 21.

Operation of the apparatus in drying carbon tissue placed on the shelves 2, access to which for the purpose is had through the door 15, will be evident. Operation of the fan 16 effects circulation and recirculation as already described causing a draft of air evenly downwards upon the tissue sheets and away therefrom in all directions. The pro-j portions are preferably such that about 10% of this air passes through the chamber C. In the chamber C presuming the coils 25 actively refrigerant, this portion of the air is caused to drop its moisture as will be understood; and as this air subsequently passes over the heating coils 28 it is again brought to the desired temperature, which I find to be about 68 F., the proper heating coil temperature being maintained by the thermally responsive valve 30.

The portion of air thus conditioned is mixed in the fan 16 with that portion of the circulating air by-passed around-the chamber 0 the tissue sheets being subjected to this mixture as will be well understood by one familiar with the air conditioning art; however, the whole of the recirculating air is substantially constantly maintained in the proper conditions of temperature and humidity to produce a constant drying efi'ect entirely independent of weather or other general atmospheric conditions.

What I claim is:

1. Apparatus of the. character described and comprising means for supporting plates to be dried, means for directing a drying medium upon said lates, means arranged about said parts to ormva drying chamber within which the parts are located, means providing a second chamber, said directin means having supply connectionwith sai second chamber, means providin a third chamber communicating with said rst chamber, refrigerant means having a cooling surface in said third chamber, means eifecting circulation from said first. and third chambers to said second chamber and hence from the second to the first chamber through said directing means, and heatin means ar-' ranged 1n the flow of circulation from the third to the second chamber.

2. Apparatus of the character described and including a plurality of shelves each adapted to support a ferrotype plate bearing a sheet of tissue, said shelves being hollow and perforate each on one side, and

their hollows having connection with a source of drying medium, the arrangement being such that said medium will be directed from a shelf and against the tissue on the 1 adjacent shelf.

3. Apparatus of the character described and including a rack of shelves each adapted to support a ferrotype plate bearing a sheet of tissue, said shelves being hollow and perforate each on one side, and having connection with a source of drying medium, the

arrangement being such that said medium will be directed vertically from a shelf and against the tissue on the adjacent shelf, an enclosure for said rack, means for conditioning said medium, and means for circulating the same through said conditioning means, said shelves and said enclosure.l

4. Apparatus of the character described and including a rack of shelves each adapted to support a ferrotype plate bearing a sheet of tissue, said shelves being hollow and perforate each on one side and having connection with a source of drying medium, the arrangement being such that said mediun'iwill be directed vertically from a shelf and againstthe tissue on the adjacent shelf,

- an enclosure for said'rack and having walls spaced from said shelves whereby said medium may find 'exit from between the shelves on all sides thereof, means for conditioning said medium, and means for circulating the same through said conditioning means, said shelves and said enclosure,

5. Apparatus of the character described and including a rack of shelves each adapted

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