US3286367A

US3286367A - Dryer for photographic type emulsion coated sheets

Info

Publication number: US3286367A
Application number: US313880A
Authority: US
Inventors: Henry N Fairbanks; Daniel H Robbins
Original assignee: Itek Corp
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1963-10-04
Filing date: 1963-10-04
Publication date: 1966-11-22
Anticipated expiration: 1983-11-22
Also published as: CH439965A; GB1083718A; NL6411558A; BE653886A

Description

Nov. 22, 1966 H. N. FAIRBANKS ET AL 3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS Filed Oct. 4, 1963 5 Sheets-Sheet 1 41 CONTROL l F/G. POWER -/7 SOURCE DAN/E L H. ROBBINS HENRY IV. FAIRBANKS I NVENTORS ATTORNEY NOV. 22, 1966 H FMRBANKS ET AL 3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS 5 Sheets-Sheet 2 Filed Oct. 4, 1963 DAN/EL h. ROBBINS HENRY N. FAIRBANKS INVENTORS BY g7 &

ATTORNEY NOV. 22, 1966 FAlRBANKs ET AL 3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS Filed Oct. 4, 1963 5 Sheets-Sheet 3 DAN/E L H. ROBBINS HENRY N FA/RBA/VK5 I NVENTORS ATTORNEY .hydrophilic.

United States Patent p 3 286 367 DRYER FOR rHoToRAPHIO TYPE EMULSION COATED SHEETS Henry N. Fairbanks and Daniel H. Robbins, Rochester,

N.Y., assignors, by mesne assignments, to Itek Corporation, Lexington, Mass., a corporation of Delaware Filed Oct. 4, 1963, Ser. No. 313,880 7 Claims. (Cl.34-123)' The present invention relates to an improved apparatus for drying emulsion coated carrier sheets. More particularly the invention is related to a dryer for photographic processing projection offset plates suchas the typefmarketed by the assignee under the trademark Project-A- Lithf This material is a silver halide emulsion on a support, which upon development results in an image area which is oleophilic and a non-image area which is The automaticprocessor of the type disclosed in the copending application has as one of its features, the ability to produce offset platesat a rapid rate. The device disclosed therein is capable ofproduc'ing offset plates on a continuous basis at the rate of approximately two per minute. In order to maintain a two per minute overall continuous production rate, it is desirable that a compatible dryer operate at the same rate. Coupled with the problem of relatively short drying time is the relatively low maximum temperature at which the offset plate becomes adversely affected. The offset plate is a plastic coated carrier sheet having an emulsion coating on one of the plastic coated sides. Both the plastic and emulsion have relatively low softening temperatures, e.g. in the order of 185 F. If either material is heated above these temperatures it would tackify and stick to the transport and dryer. In addition when the emulsion temperature rises above a critical level, eg l70-l90 F., it discolors, whereby the plate quality is deteriorated. In addition to quality being affected by excessive temperature, it has also been observed to be affected by the uniformity with which drying occurs. Some of the other problems associated with the drying of this type of material arise due to the softness of the emulsion as it emerges from the processor. Therefore, transporting the plate through the dryer must be accomplished without marring or embossing the emulsion surface, whereby the plate quality will be deteriorated. Dryers known in the art do not produce the uniform, rapid drying, at controlled low temperatures, without physical damage to the emulsion that is requiredin the drying of a material such as Proje-ct-A-Lith.

Some prior art devices use heated air for drying photographic type emulsions. One such device is shown in U.S. Patent No. 2,869,246 issued January 20, 1949 to Walter Buschmann and Walter Buhren. Devices of this general type require large volumes of air available at the emulsion surface in order to keep the emulsion temperature relatively low and at the same time drying rapidly to match the Output of an automatic processor of the type disclosed in the assignees copending application. Other dryers for photographic type emulsions, transport the sheet on a web over a heated drum. The web absorbs any chemical left on the surface of the plate after processing. The gradual build-up of these chemicals in the web adversely affects both dryer operation and plate quality (i.e., staining of the emulsion). In addition the fibrous threads, characteristic of the absorbing web, tend to be picked up by the relatively soft emulsion during the drying process. Foreign material attached to the plate 3,286,367 Patented, Nov. 22, 1966 would adversely affect the quality of prints produced from the plates. It is also known in the art, to use heated platen devices for drying. However, it has been observed that drying efiiciency in these devices is affected by uniformity of contact between the material to be dried and the platen. If an air space develops between the material and the platen, drying in the area of the air space is inhibited resulting in non-uniform plates. Thus, prior art dryers do not produce practical, uniform,.rapid drying at controlled low temperatures without physical damage to a relatively soft emulsion coated offset plate material. p i

It is an object of this invention, therefore, to provide an improved apparatus for drying photo-graphic type emulsion coated sheets which avoids one or more disadvantages ofthe prior art.

his a further object of this invention to provide an improved apparatus for drying photographic type emulsion coated sheets at a rapid rate and at relativelylow temperatures. 1

It is a further object of the invention to provide an improved dryer for photographic type emulsion coated sheets that produces uniform dryingacross the face of the emulsion.

It is still a further object of the invention to provide an improved apparatus for drying photographic type emulsion coated sheets wherein the emulsion surface is unmarred during transportationthrough the dryer. I

In accordance with the present invention there is provided an improved apparatus for drying photographic type emulsion coated sheets. The apparatus comprises a housing having an inlet opening and a discharge opening. A heated platen is disposed within the housing. A portion of the platen surface defines a path along which the sheets travel through the dryer. There is provided contact means for holding the sheets in intimate contact with the path defining portion of the platen. The contact means holds the sheets in contact with the platen as the sheets travel along the defined path for causing heat conduction through the sheet to the emulsion coating. The contact means are spaced to permit vaporization of moisture from the emulsion. There are also provided means disposed along the path to accelerate vaporization of moisture from the emulsion coating after the moisture has been initially heated by the platen. Transport means are provided for transporting the sheet in the defined path from the inlet along the platen, to the discharge opening whereby the emulsion coated sheets are dried.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a schematic illustration of the principles of operation of a dryer embodying the present invention;

FIG. 2 is a perspective view, partially cut away of a dryer embodying the present invention;

FIG. 3 is a sectional view taken along line 33 in FIG.

2; and

FIG. 4 is an end view, partially in section, of another embodiment of the present invention.

Referring now in more detail to the drawings and with particular reference to FIG. 1 there is here schematically illustrated the broad principles of operation of the invention. The dryer broadly operates by first conducting heat to the moisture to be removed and then accelerating vaporization by forcing air against the preheated moisture. A typical material to be dried is designated by the numeral 10. This material, by way of example only, has four layers. An emulsion layer 10a, a plastic coating Connects the pulley 41,to the cylinder 34a.

. 3 b, a carrier sheet 100, and a plastic coating 10d. The

sheet 1-0 is fed into the dryer housing 11 'so that the .16 controls the electrical input (i.e., voltage), to the heat source. The platen source is maintained at a substantially constant temperature through a feedback loop consisting of a sensor 14 and control 16. The sensor measures the platen temperature while the control is set for a desired reference temperature. The difference between the two temperatures causes'the control 16 to energize or deenergize the heat source 13. A contact means 18 maintains the sheet in intimate contact with the platen during a portion of its travel in the dryer, thereby preventing air spaces from developing between the platen and the sheet. Any air space would be a local insulator causing nonuniform drying of this sheet. 7 has been found that most of the moisture in'this type of material, as it enters the dryer, is in the emulsion. The material is squeegeed prior to drying, removing most of the moisture from the plastic coated exposed surface. The contact means 18 is provided with perforations 21 for allowing the moisture to escape from the emulsion layer 10a. The emulsion layer is heated by conduction of heat from'the platen 12 through the, layers 10d, 10c, and 10b. The temperature of the emulsion surface rises initiating vaporization of the moisture at the surface. By way of example, the critical temperature beyond which Project-A-Lith emulsion can be heated is in the order of 17()190 F. A blower 19 is mounted in the housing 11 and blows ambient air in the direction A against the emulsion surface to accelerate vaporization of moisture therein. An exhaust system, shown by the exhaust fan 20, may be added to further accelerate vaporization. The exhaust fan continuously removes moisture from the housing 11 in the direction B preventing the humidity level from rising therein.

Referring now in more detail to FIG. 2, there is here shown a perspective view, partially cut away, of the preferred embodiment of a dryer embodying the present invention. The dryer is contained in a housing generally As a practical matter, it

designated by the numeral 30. The housing has an inlet guide 33 for deflecting and guiding the leading edge of the sheet to be dried towards a rotatable cylindrical platen 34. The platen'34 has a cylindrical section 34a and a pair of circular end plates 34b only one of which is shown in FIG. 2. 'Ihe end plates are fastened to the cylindrical section 34a by means of screws 35. The end plates have bearings 36 mounted therein. One bearing is shown in FIG. 2. Associated with each bearing 36 is a snap ring'60 for preventing axial shifting of the platen assembly along shaft 37. The platen assembly is rotatable about stationary shaft 37, which is secured to the housing 30. The assembly is rotated by means of a motor 38 mounted on top of housing 30 in a motor housing 39. A chain drive connects the motor 38 to a sprocket 39 mounted on the end of shaft 40. The opposite end of shaft 40 has a pulley 41 thereon around which is wrapped a garter spring 42. The garter spring 42 p The garter spring 42 is under tension therefore rotating platen 34 as pulley 41 is rotated. Also mounted on shaft 40 is a plurality of spaced rollers 43. As seen more clearly in FIG. 3 which is a vertical section taken along line 33 in FIG. 2, the rollers 43 have endless belts 44 coupled thereto. The endless belts pass over

rollers

45, 46, and 47 mounted on

shafts

48, 49, and 50 respectively. As the pulley 43 is rotated the portion of belt 44 in contact with the platen 34 travels in the same direction as the platen, thus transporting the paper in contact with the platen to allow heating of the sheet by the platen. Since the emulsion surface is soft, it is desirable that the belts 44 do not exert any excessive pressure on the sheet during transport. Therefore, means are provided for adjusting the tension in belts 44 by means of slots 63 disposed in opposite vertical walls of housing 30 (see FIG. 3 wherein one slot is shown). Shaft 49 is provided with the threaded ends 64 which protrude through slots 63 allowing the tension to be adjusted by vertical alignment of shaft 49. Nuts are used to clamp the shaft in place after alignment. For the sake of clarity, the means for rotatably mounting the shafts on the'housing and the means for fixedly mounting the shaft 37 to the housing have not been shown. Any of the means well known in the art for accomplishing the desired result may be used. For example, the rotatable shafts may be mounted in sleeve bearings which are held in trunions on the housing, the trunions for shaft 49 being adjustable vertically as the shaft is adjusted. The stationary shaft 37 may be bolted to the housing. The platen is heated by a heat source 51 which may for example be an infrared lamp, which is coupled toshaft 37 by two brackets on either end of the shaft, one of which is'shown at 52. The belts 44 are preferably porous to allow moisture to pass therethrough,and spaced to leave a maximum area on the sheet material exposed to the housing environment for the purpose of vaporizing moisture from the surface thereof. To accelerate vaporization, a blower 53 is mounted in the housing 30. The blower 53 forces ambientair against the exposed surface of the sheet thus accelerating vaporization of moisture on the exposed surface which. has been initially heated by conduction from platen 34. An exhaust fan 54 may be provided for removing accumulated moisture from the housing 30 thus controlling the humidity level therein. The exhaust fan 54 is also mounted in the housing30. A temperature sensor 60, which may be a thermocouple or thermistor is coupled to the platen for'providing an indication of the platen temperature. This'co-operates with a control device as was explained with reference to FIG. 1. Shaft 40 is provided with a plurality of pulleys 43 supporting endless belts 55 disposed between the belts 44 for transporting paper from the platen towards the exit opening 32. The endless belts 55 are disposed about I The operation of the dryer will be explained with reference to FIGS. 2 and 3.

Prior to use, the platen 34 is preheated by energizing the heat source 51. The motor 38 is energized causing the chain drive to drive sprocket 39 in the direction of arrow C shown on shaft 40. The sprocket 39 in turn drives shaft 40 in the same direction causing belts 44 to move in the direction of arrow E and the platen 34 to rotate in the direction of arrow E. The belts 55 move in the direction of arrow F.

The photographic emulsion is fed into the dryer through the inlet opening 31 with its emulsion side down. The leading edge of the sheet contacts guide 33 and is directed towards the platen 34. The leading edge, thereafter, engages the portion of belts 44 in contact with the platen on the side nearest the inlet opening 31. The sheet is then transported in contact with the rotating platen toward the exit side of the dryer. During transport along the platen, the emulsion surface is away from the platen whereby moisture in the emulsion is heated by heat conduction through the platen to the emulsion surface. As the sheet reaches the vicinity of blower 53 ambient air is forced against the emulsion surface by the blower accelerating vaporization of the moisture that has been preheated by conduction from the platen. In order to achieve maximum vaporization of the moisture from the sheet, belts 44 are porous and spaced. The sheet coutinues to travel in the dryer until the leading edge engages the guide 59 at which point the sheet is directed toward the exit opening 32. The leading edge travels along the guide 59 until it passes between spring 61 and belt 55. The sheet is then driven through the exit opening by the combination of belt 55 and spring 61. The sheet emerges from the dryer with its emulsion side down. An exhaust fan 59 removes air from the housing. The removal of air from the housing lowers the humidity level as well as lowering the housing temperature. Lowering the housing temperature causes a greater temperature drop across the platen and sheet increasing the amount of heat flow therethrough at a given input temperature.

Another embodiment of the invention in FIGS. 2 and 3 is illustrated in FIG. 4. In this embodiment a receiving bin 62 is mounted on the rear wall of the housing 30. As the sheet emerges from the dryer through the exit opening 32, with its emulsion side down, it slides down the rear wall of bin 62. As the sheet lies in the bin, the emulsion side would be facing the discharge of the exhaust blower 54. Although this air from the exhaust blower is slightly damp, it is heated and it has been found to be useful in further drying the sheets.

While we have described what is presently considered a preferred embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the inventive concept, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What is claimed is:

1. In a dryer for drying sheet material:

(a) a curved platen having a sheet contact surface associated therewith;

(b) a plurality of spaced flat sheet transport belts;

(c) means for causing said flat belts to contact the sheet contact surface associated with said curved platen, the ratio of the sum of the widths of said flat belts over the width of said sheet contact surface of said platen being such as to leave wide spaces between said belts for the purpose of vaporizing moisture therefrom;

(d) means for driving said belts to cause said sheet material to be transported through said dryer between said curved platen and said belts, and

(e) means for causing drying gas to pass over at least a portion of said sheet contact surface of said curved platen to accelerate the drying of said sheet material.

2. The combination as set forth in claim 1 wherein said belts are made of non moisture absorbent material having apertures formed therethrough for allowing vapor to escape from said sheets through said apertures.

3. The combination as set forth in claim 1 further including a sheet receptacle means for receiving sheet material emerging from said dryer and means for directing said drying gas from the interior of said dryer to said receptacle to further dry said sheet material present there- 4. The combination as set forth in claim 1 wherein means are provided for heating said curved platen.

5. The combination as set forth in claim 2 wherein means are provided for heating said platen.

6. The combination as set forth in claim 1 wherein said means for driving said belts also drives said platen at the same tangential velocity as the velocity of said belts.

7. The combination as set forth in claim 2 wherein said means for driving said belts also drives said platen at the same tangential velocity as the velocity of said belts.

References Cited by the Examiner UNITED STATES PATENTS 1,794,063 2/1931 Dye 34-ll1 2,596,358 5/1952 Ball 34114 X 2,895,395 7/1959 Gern 34-116 X FREDERICK L. MATTESON, JR., Primary Examiner.

A, D, HERRMANN, Assistant Examiner.

Claims

1. IN A DRYER FOR DRYING SHEET MATERIAL: (A) A CURVED PLATEN HAVING A SHEET CONTACT SURFACE ASSOCIATED THEREWITH; (B) A PLURALITY OF SPACED FLAT SHEET TRANSPORT BELTS; (C) MEANS FOR CAUSING SAID FLAT BELTS TO CONTACT THE SHEET CONTACT SURFACE ASSOCIATED WITH SAID CURVED PLATEN, THE RATIO OF THE SUM OF THE WIDTHS OF SAID FLAT BELTS OVER THE WIDTH OF SAID SHEET CONTACT SURFACE OF SAID PLATEN BEING SUCH AS TO LEAVE WIDE SPACES BETWEEN SAID BELTS FOR THE PURPOSE OF VAPORIZING MOISTURE THEREFROM; (D) MEANS FOR DRIVING SAID BELT TO CAUSE SAID SHEET MATERIAL TO BE TRANSPORTED THROUGH SAID DRYER BETWEEN SAID CURVED PLATEN AND SAID BELTS, AND (E) MEANS FOR CAUSING DRYING GAS TO PASS OVER AT LEAST A PORTION OF SAID SHEET CONTACT SURFACE OF SAID CURVED PLATEN TO ACCELERATE THE DRYING OF SAID SHEET MATERAIL.