US3417484A

US3417484A - Web drying apparatus

Info

Publication number: US3417484A
Application number: US619976A
Authority: US
Inventors: Joseph V Mccarthy
Original assignee: Itek Corp
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1967-03-02
Filing date: 1967-03-02
Publication date: 1968-12-24
Anticipated expiration: 1985-12-24

Description

Dec. 24, 1968 J. v. M CARTHY WEB DRYING APPARATUS Filed March 2, 1967 i BMW/Wi A/R HEATERS Unite States ate 3,417,484 WEB DRYING APPARATUS Joseph V. McCarthy, Needham, Mass., assignor to Itek Corporation, Lexington, Mass., a corporation of Delaware Filed Mar. 2, 1967, Ser. No. 619,976 13 Claims. (Cl. 34156) ABSTRACT OF THE DISCLOSURE Web drying apparatus including a plurality of drying compartments, aligned in the direction of web travel, for receiving the web, an input duct having an input port communicating with each of the compartments for (118- charging a differentially heated fluid medium to its associated compartment and the web segment therein, and means for substantially preventing transfer of the medium and of moisture between the compartments and for facilitating advance of the web between the compartments. Each compartment may include an input nozzle and a web cell, the nozzle having its larger orifice commumcating with the input port and its smaller orifice communicating with the cell, for increasing the heat exchange between the fluid medium and the web. The web may be supported by a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of the web in a plane approximately parallel to the plane of the web, and by an air bearing produced in the cell.

This invention relates to web drying apparatus, and more particularly to such apparatus for drying photographic film including differentially heated compartments and improved air flow chambers.

The speed of conventional photographic processing systems is limited by the dryers which generally operate by pumping hot air over long lengths of film passing through drying tunnels comprising a single large chamber. The temperature of the air in the tunnel can not exceed a recommended limit above which the rate of evaporation of the water at the driest, i.e., most advanced, areas of the film is insufficient to prevent excessive heating of the film, even though the less dry areas of the film, i.e., those just entering the tunnel, could withstand and be more effectually dried by air of a higher tempera ture. Further, the air that reaches the drier areas of the film will be humid and little able to promote evaporation at the drier areas because that air is already saturated by its previous contact with the wetter areas of the film.

Long lengths of film and free, unsupported ends are prone to flutter, causing buckling of the film or permitting it to contact the horizontal surfaces of the drying chamber, either of which actions may mar the film surface. Air currents in these drying tunnels contacting the film at various angles often subject the film to uneven pressures causing it to bow, and drive particles of the water or other solutions across the film surface forming streaks and stains thereon. In addition uneven presures on the film may divert it from its intended path making it difficult to thread.

Although there is a large quantity of hot air flowing in the tunnels, the heat exchange between the air and film, i.e., the drying capacity, is inefficient because of the poor contact between the air mass and the wet film surface: only a small portion of hot dry air ever passes within drying proximity to the film surface.

Attempts to reduce the contact surface of the film with supporting media, such as replacing rollers with stationary support means, such as ridges, have not been successful. Such ridges, if spaced parallel to the directionof film travel, present a constant pressure on the film surface at definite points which mars its surface, and if spaced perpendicular to the direction of film travel cause the film to droop between them, subjecting the film to an undulating forward motion.

Accordingly, it is an object of the invention to provide Web drying apparatus which performs its drying function within a shorter time and/or within a shorter drying tunnel, which supplies hot, dry air to discrete areas of the web to be dried at the optimum permissible drying temperature of each discrete area without endangering or overheating other areas of the web, and which directs the air generally parallel to the film surface, creating even pressure on the upper and lower surfaces of the film promoting vertical centering and inducing self-threading of the film.

It is a further object of the invention to provide Web drying apparatus that compels virtually all of the air supplied to the chamber to contact the film, reduces marring of the film by support media while preventing fluttering, buckling, undulating movement and deleterious pressures on the film, and which removes excess water droplets from the web surface thereby preventing such droplets from being driven across the web by the air and streaking or marring the film.

The invention features web drying apparatus including a plurality of drying compartments, aligned in the direction of web travel, for receiving the web, an input duct having an input port communicating with each of the compartments for discharging a differentially heated fluid medium to its associated compartment and the web segment therein, and means for substantially preventing transfer of the medium and of moisture between the compartments, and facilitating advance of the Web between the compartments.

Each compartment may include an input nozzle and a web cell, the nozzle having its larger orifice communicating with the input port and its smaller orifice communicating with the cell, for increasing the heat exchange between the fluid medium and the web.

The web may be supported by a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of the web in a plane approximately parallel to the plane of the web, and by an air bearing produced in the cell.

Other objects, features, and advantages will appear from the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:

FIG. 1 is an axonometric view of a compartmentalized film dryer with cover removed according to the invention.

FIG. 2 is an enlarged partially broken away View of a chamber used in the compartments of the dryer of FIG. 1.

FIG. 3 is a schematic of the drier of FIG. 2 showing air flow in different directions.

There is shown in FIG. 1 a film dryer 10 formed by end plates 12 having access slots 13 to receive film 14, connected to input duct 16 and exhaust duct 18. Dryer 10 is completed by base 20 and a cover not shown. Between end plates 12 and extending from input duct 16 to exhaust duct 18 transversely to the direction of travel of film 14 are seven vertically disposed pairs of

rollers

22, 24, 26, 28, 30, 32 and 34 independently, synchronously driven by drive means not shown. The lower roller of each pair is in close contact with the upper roller and base 20 and the upper roller is in close contact with the lower roller and the cover, providing six

heat retaining compartments

36, 38, 40, 42, 44 and 46. Contact between rollers in each pair is light but sufficient to direct and advance film 14.

Ballies

48, 50, 52, 54, 56 and 58 in duct 16 direct hot, dry air, pumped into inlet end 60 of duct 16, by means not shown past individually controlled

heaters

62, 64, 66, 68, 70 and 72 and through

ports

74, 76, 78, 80, 82 and 84 into

compartments

36, 38, 40, 42, 44 and 46 and transversely across the segments of film 14 present in those compartments. Bafiies may be used in duct 18 as well to prevent exhaust air from backing up into adjacent compartments.

A corresponding number of

exhaust ports

86, 88, 90, 92, 94 and 96 receive the air from their respective compartments and transport it to exahust duct 18 connected to an exhaust which may be maintained at negative pressure with respect to the compartments.

With all of the inlet ports aligned along one edge of the film in the direction of film travel, and all of the outlet ports similarly aligned along the other edge of the film, the film may be distorted or wrinkled by more rapid drying of the film along the edge adjacent the inlet ports, where at initial entry into the compartments the air is hotter and less humid. To compensate for this the positions of the inlet and outlet ports may be reversed in alternate compartments as shown schematically in FIG. 3. For example,

ports

74, 88, 78, 92, 82 and 96 would be inlet ports,

ports

86, 76, 90, 80, 94, and 84 would be outlet ports and

ducts

16 and 18 would be replaced by a split manifold system capable of exhausting and supplying air to ports on both sides of the film.

Chamber 100 shown in phantom in compartment 44 may be used in each compartment, and consists of a flat, elongated input nozzle 102 and a similarly shaped output nozzle 104 connected with cell 106 and input and

exhaust ducts

16 and 18, respectively, FIG. 2. Nozzle 102 includes an upper 108 and lower 110 wall, which may be formed integrally with upper 112 and lower 114 sections of cell 106, respectively, and which flare outwardly toward duct 16 so that the larger orifice 116 of nozzle 102 connects with port 82 in duct 16 and the smaller orifice 118 connects with cell 106. Nozzle 104 having upper 120 and lower 122 walls has its larger orifice 124 connected to port 94 in duct 18 and its smaller orifice 126 connected to cell 106.

Upper and

lower sections

112, 114 of cell 106 contain spaced raised elements 128 providing virtually pressureless support for film 14 passing through. Each element 128 includes a pair of

converging segments

130, 132 which meet in a smooth curved segment 134 forming a chevron-shaped boss pointing in the direction of film travel. Elements 128 may also be formed using only one unilateral oblique segment, or may be formed in chevronlike shapes pointing in the opposite direction of film travel. Many varied shapes may be used such as arcs, zigzags, etc. Preferably, but not essentially, the outer ends of

segments

130, 132 of one element 128 should extend at least as far backward as the curved segment 130 of the next element 128.

In operation film 14 is engaged by rollers 22 as it is threaded through slot 13 in end plate 12 and is vertically centered in alignment with the junction of each pair of rollers by the even pressure .on opposing sides of the film produced by the transverse flow of air from each inlet port, 74, 76, 78, 80, 82 and 84. Since film 14 is vertically aligned with the junction of each pair of rollers, the system is self-threading and the film may be inserted in dryer merely by controlling its forward movement. Each pair of

rollers

22, 24, 26, 28, 30, 32 and 34 is independently, synchronously driven so that film 14 once engaged by rollers 22 is drawn firmly, uniformly through and out of dryer 10.

As film 14 is passing through

successive compartments

36, 38, 40, 42, 44 and 46, air, pumped by an external source, not shown, enters duct 16 at inlet end 60 and is separated into six individual streams of air by

baffles

48, 50, 52, 54 56 and 58 which direct it into

compartments

36, 38, 40, 42, 44 and 46, respectively, in a direction transverse to the path of the film. Each stream of air formed by

battles

48, 50, 52, 54, 56 and 58 passes about an individually controlled

heater

62, 64, 66, 68, 70 and 72, respectively, which heats the stream to the highest temperature that the segment of film 14 in the particular associated compartment is capable of withstanding without injury.

The temperature level that any particular segment can be exposed to is determined by the characteristics of the film and the amount of moisture carried by that segment. Thus, the air directed into compartment 36, which first receives any particular segment of film 14, can be heated to a higher temperature than the air directed into compartment 38, and the air directed into compartment 38 can be at a higher temperature than that directed into compartment 40, and similarly with respect to

compartments

42, 44 and 46. With the film traveling in the direction shown in FIG. 1 then, compartment 36 will receive air at the highest relative temperature, compartment 46 at the lowest. In this manner film 14 may be dried in the most efiicient, hence quickest, manner, and the length of dryer 10 may be shortened.

Air discharged at

inlet ports

74, 76, 78, 80, 82 and 84 moves across the associated compartments channeled by the two pairs of rollers and out the associated one of

exhaust ports

86, 88, 90, 92, 94 and 96 to exhaust duct 18. Thus, the difierentially heated air in each compartment is prevented from flowing into any other compartment by the presence of the roller pairs and the availability of a ready exhaust route. Moreover, humid air from the hotter compartments, the ones nearest the input end of dryer 10, is prevented from flowing into other compartments having less humid atmospheres, and so from hampering evaporation in those compartments. The difierentially heated transverse flow equally divided above and below film 14 maintains an even pressure on the top and bottom surfaces of film 14 preventing buckling, fluttering, and drooping of the film, and because the film 14 has been squeegeed free of water droplets by the preceding noller set the air flow does not drive particles of water or other matter across film 14 streaking or marring its finish. Added prevention of drooping, fluttering, etc. is provided by the relatively closely spaced roller pairs.

Within each of the compartments film 14 may be passed through a chamber 100, FIG. 2, shown in compartment 44. As the air leaves port 82 it encounters the converging outlet area 118 of inlet nozzle 102 which confines the volume and increases the speed of the air flow as it passes into cell 106. After passing through cell 106 the air is exhausted through outlet nozzle 104 whose reduced and enlarged portions, 126, 124, respectively, are reversed with respect to those of nozzle 102 relative to the direction of air flow, for delivering the air to exhaust duct 18 at approximately the same speed and volume at which it was received from input duct 16.

Chamber confines the mass of air so that more air must contact film 14, resulting in a higher heat exchange between the air and film 14, hence faster drying. Contact between the air and film 14 is further increased by the turbulence produced in the air as it strikes elements 128 oblique to the path of the air stream discharged from the ports in input duct 16, and by the increased length of the angled paths defined by adjacent pairs of elements 128 by which the air is partially directed. And since film 14 is carried partially by an air bearing between it and cell 106, the very support for the film is also a drying agent.

Since elements 128 are neither parallel nor perpendicular to the path of film 14, but are oblique to it, whatever support or guidance supplied by them is uniform and non-injurious to film 14 and continuous across the film width. Elements 128 do not permit dropping or undulating motion of film 14 as transverse support members may, and do not permit the distinct and separate streaks on the film emulsion or base caused by the continuous contact of parallel support members. Rather elements 128 provide continuous parallel-type support without longitudinal streaking, and provide the even pressure applied uniformly to the surface of the film by transverse-type support without permitting drooping or undulating motion of the film.

Other embodiments will occur to those skilled in the art and are within the following claims.

What is claimed is:

1. Web drying apparatus comprising:

a plurality of drying compartments, aligned in the line of web travel, for receiving the web, an input duct having an input port communicating with each of said compartments for discharging a differentially heated fluid medium to its associated said compartment and the web segment input;

pairs of rollers between said compartments for substantially preventing transfer of said medium, and of moisture between said compartments, and for facilitating advance of the web between said compartments.

2. The apparatus of claim 1 in which said differentially heated fluid medium is discharged about the web transverse to the path of travel of the web in a plane approximately parallel thereto.

3. The apparatus of claim 1 in which said rollers are driven to advance said web.

4. The apparatus of claim 5 in which said chamber includes a first member having a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of said web in a plane approximately parallel to the plane of said web.

5. Web drying apparatus comprising:

a plurality of drying compartments, aligned in the direction of web travel, for receiving the web;

an input duct having an input port communicating with each of said compartments for discharging a differentially heated fluid medium to its associated compartment and the web segment therein;

a chamber within said compartment including an input nozzle and a web cell, said nozzle having its larger orifice communicating with said input port and its smaller orifice communicating with said cell for increasing the heat exchange between the fluid medium and the web.

6. The apparatus of claim 5 in which said chamber further includes an output nozzles having its smaller orifice communicating with said cell.

7. The apparatus of claim 5 in which said chamber includes a first member having a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of said web in a plane approximately parallel to the plane of said web.

8. The apparatus of claim 7 in which said cell has a second member spaced from said first member and having a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of said web in a plane approximately parallel to the plane of said web.

9. Web drying apparatus comprising:

a plurality of drying compartments aligned in the irection of web travel, for receiving the web, an input duct having an input port communicating with each of said compartments for discharging a differentially heated fluid medium to its associated said compartment and a web segment therein, some of said input ports aligned along one edge of the web and others aligned along the other edge of the Web.

10. The apparatus of claim 9 further comprising an exhaust duct having an output port communicating with each of said compartments for removal of said fluid medrum.

11. Web drying apparatus comprising:

a drying chamber for receiving a web to be dried, and

an input duct with an input port for discharging a heated medium into said chamber generally transversely to the direction of travel of said web,

said chamber having an input nozzle and a web cell,

said input nozzle having its larger orifice communicating with said input port and its smaller orifice communicating with said cell for increasing the heat exchange between said fluid medium and said web.

12. The apparatus of claim 11 in which said chamber includes a first member having a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of said web in a plane approximately parallel to the plane of said web.

13. The apparatus of claim 12 in which said cell has a second member spaced from said first member and having a plurality of raised, spaced elements disposed at an oblique angle to the direction of travel of said web in a plane approximately parallel to the plane of said web.

References Cited UNITED STATES PATENTS 2,338,770 1/ 1944 Leguillon 22697 XR 2,574,844 11/1951 Roden 34159 2,753,766 7/ 1956 Simpson.

2,758,386 8/1956 Cobb 3431 3,098,371 7/1963 Fleissner 34115 XR 3,231,985 2/1966 Smith 341 15 XR 3,308,555 3/1967 Kruger 34155 3,334,908 8/1967 Starbuck 34-242 FREDERICK L. MATTESON, Primary Examiner. ALLAN D. HERRMANN, Assistant Examiner.

US. Cl. X.R.