US3481046A

US3481046A - Process for drying pliable supports

Info

Publication number: US3481046A
Application number: US711239A
Authority: US
Inventors: Motoharu Kuroki; Toshihiro Kato
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1968-03-07
Filing date: 1968-03-07
Publication date: 1969-12-02
Anticipated expiration: 1986-12-02

Description

Dec. 2, 1969 MOTOHARU KUROKI ET 3,481,046

PROCESS FOR DRYING PLIABLE SUPPORTS Filed March '7, 1968 6 O 0 Av O 6 B B 6 6 INVENTORS MOTOHARU KUROKI TOSHEHIRO KATO I 13W, $140,} ,W ATTORNEYS,

United States Patent PROCESS FOR DRYING PLIABLE SUPPORTS Motoharu Kuroki and Toshihiro Kato, Kanagawa,

Japan, assignors to Fuji Shashin Film Kabushiki Kaisha, Kanagawa, Japan Filed Mar. 7, 1968, Ser. No. 711,239 Int. Cl. F26]: 13/16 US. C]. 34-10 3 Claims ABSTRACT OF THE DISCLOSURE Drying solvent-containing coating layers on a continuously moving flexible support by helically wrapping the coated support surface about a perforated cylindrical air chamber with the individual air jets acting as an air bearing for the support while drying the coating layer.

This invention relates to a continuous process for drying continuously moving pliable supports effectively and economically without any contact between the said support and the solid surfaces during the drying step. The process of the present invention is particularly effective for drying solvent-containing coating layers carried by the supports.

For effective drying of solvent-containing coating layers on continuously moving pliable supports, there has been hitherto employed a drying process in which a coated support is supported from the reverse side with respect to its coated surface by spaced supporting rollers located at regular intervals to define a straight, curved or undulated path for the travel of the support. The stream of drying air is blown perpendicularly or substantially perpendicular to the coated surface of the support through perforated or slit plates. In this prior process, however, it is necessary to fabricate the rollers precisely, the surface of the rollers is of mirror-finish and each set of rollers is always adjusted to ensure balanced rotation because, the quality of the supporting rollers has a significant influence on the quality of the dried product. In the manufacture of photosensitive material, so called pressure fog, static fog and an abrasion or scratch are especially fatal defects on the quality of the product and are caused by fine stains on the surface of the supporting rollers, an electrostatic phenomenon due to contact and removal of the support from the supporting rollers and the slip between the supporting rollers and the support, respectively.

There has also been proposed, a process in which a coated support is conveyed without any contact with solid surfaces by blowing drying and supporting air streams onto both sides of the coated support through perforated or slit plates under such conditions that the velocity and quantity of the air stream sustained the support in fixed position. Although all of the defects accompanying the use of the supporting rollers are avoided in this process, it is very expensive because it requires complicated and expensive apparatus including a large capacity air source for supporting the support and with resulting expense in operation of the apparatus.

The present invention eliminates the defects of the prior processes. The present invention consists in an economical process for drying continuously movable, long pliable supports in which the support is not at all in contact with a solid surface and it is unnecessary to use any supporting air streams other than the drying air. In the process of the present invention, drying of the support is performed while passing the support through a helical path by wrapping the support to be dried helically around a tubular air chamber with the surface of the pliable support to be dried facing the outside surface of the air chamber, directing air streams from the peripheral surface of the air chamber in the form of jets to the surface 3,481,046 Patented Dec. 2, 1969 ice to be dried and balancing the tension in the support and the wind pressure of the drying air to support the said support on an air cushion.

The-drying process of the present invention will be illustrated with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of one device for a drying pliable support in accordance with the present invention,

FIG. 2 is an enlarged plan view of the essential parts of the same device, and

FIG. 3 is a plan view of a combination of such devices including the device of FIG. 1 as applied to a single sup port.

A support 1 having a solvent-containing coating layer to be dried is conveyed by winding it'helically around an air chamber 2 and dried in the mannersuch that the surface to be dried faces the surface of the air chamber 2. Drying air passes through an air duct 3 into the air chamber 2. Blown drying air streams exit through a number of holes 4 in the peripheral surface of the air chamber 2 to float the support 1 on the peripheral surface of the air chamber 2. The support 1 is fed by means of, e.g., suction rollers or other suitable means (not shown). The support 1, after completion of drying, is withdrawn under suitable tension by means such as a dancer roller (not shown) to impart tension to the support 1, thereby maintaining an appropriate space between the support 1 and the peripheral surface of the air chamber 2.

The angle of the helix of the support 1 during drying and conveying is determined by both the width of the support 1 and the external diameter of the helical path. The angle is selected as small as possible such that each turn of the support 1 does not overlap the adjacent turns and there is, between the adjacent turns of the support 1, an aperture suflicient to allow escape of the drying air. In the space between the support 1 to be dried and the peripheral surface of the air chamber 2, the static pressure of air is greater than in the circumferential gap surrounding the support 1 and the air chamber 2 due to the resistance to the escape of the drying air. In addition thereto, the support 1 undergoes an internal pressure by the effect of the dynamic pressure of the drying air streams. By suitably choosing the tension applied to the support 1 to balance the tension and the synthetic force of the wind pressure due to said drying air streams, it is possible to sustain the support 1 in a fixed region near the holes 4 where the drying air streams exit to provide maximum drying effect. The components of the force acting on the support 1, in the direction of the axis of the air chamber 2, are balanced in each portion of the support 1, so that the support 1 is conveyed always along a regular path without any deviation therefrom in the direction of the axis of the air chamber 2.

The drying air is supplied to the air chamber 2 through the air duct 3 after being adjusted to the conditions of temperature and humidity required in the drying step and purified by means at drying air sources such as, e.g., blowers, filters, heaters and dehumidifiers. The air is blown through the holes 4 of the air chamber 2 at relatively large velocity to perform effective drying, allowed to diffuse through the aperture between the helical turns of the support 1 into the drying room and recovered by the other exhausting apparatus.

If desired, the conditions of temperature, humidity and the velocity of air streams may be varied by dividing the air chamber longitudinally into sections and supplying the drying air to each section from separate air sources. Alternately, as shown in FIG. 3, a plurality of

air chambers

2, 2', 2" may be provided in parallel at a proper angle as the support to be dried is conveyed successively thereon with supplying the

air chambers

2, 2', 2" with the drying air received through

air ducts

3, 3 and 3", respectively.

In the device as shown in FIG. 1, the width of the support is about 1.2 m., the diameter and length of the air chamber are about 3 m. and about 14 m., respectively, and the angle of the helix is about 9, and the effective length of drying is about 65 m. A support in which the other surface had been previously coated, was coated with an X-ray sensitive photographic emulsion and, after being gelled in the conventional manner to effect cooling and solidification of the coating layer, Was subjected to drying, using this apparatus at a velocity of the drying air of 25 m./sec., and a tension acting on the support of 20 kg. The drying was performed at a rate of 30-35 g./m. min. Without any trouble, e.g., static fog or abrasion fog, and an X-ray film of good quality was obtained. In this case, the drying rate was substantially equal to the drying rate of the prior processes and the capacity of the drying chamber used was from A to /2 of that in the latter effective process.

According to the drying process of the present invention, all of the troubles due to supporting rollers etc., are excluded because drying is performed Without any contact with the solid surface of the support and, in addition, drying is performed economically because it is unnecessary to use any supporting air stream other than the drying air streams. Furthermore, no supporting roller in needed in the drying step, so that the apparatus used is simple and adjustment and maintenance of the apparatus can be made without any difiiculty. As the tension acting on the support during the drying step is uniform, it is unnecessary to use tension adjusting mechanisms such as torque motors common to prior processes in which supporting rollers are used. Moreover, it is possible to make the apparatus compact compared with those used in the prior processes in the manufacture of pliable supports.

What is claimed is:

1. A process for drying continuously moving elongated pliable supports comprising:

providing helical turns to said support with the surface of said support to be dried interiorly thereof, and

directing drying air onto said interior helical surface to dry the same while supporting said helical turns on an air cushion.

2. The process of claim 1 wherein said support is provided with helical turns and dried by wrapping the same about a peripherally perforated cylindrical chamber carrying pressurized drying air.

3. The process of claim 2 further including balancing the tension acting on said continuously moving pliable support with the air cushion wind pressure created by the pressurized drying air exiting through the peripherally perforated chamber.

References Cited UNITED STATES PATENTS 1,473,542 11/1923 Chanier et a1. 34153 2,153,376 4/1939 Kline 34-153 XR 3,102,006 8/1963 Cohn et a1. 34156 XR KENNETH W. SPRAGUE, Primary Examiner U.S. Cl. X.R. 34-153, 156