Title:
APPARATUS FOR DRYING A WEB BY USE OF AN AIR JET FLOW
United States Patent 3771239
Abstract:
An air-floating type web conveyor and dryer wherein a flexible web with a coating thereon is floated and conveyed by air from a perforated plate spaced therefrom. The size and arrangement of the holes in the plate are such that a substantially uniform static pressure is maintained between the web and the plate so as to uniformly dry the coating on the web and so that the air flow coming from the plate holes is not influenced by the lateral flow of air coming from the central portion of the web.
US Patent References:
APPARATUS FOR GASEOUS TREATMENT OF MOVING WEBS
Brown - August 1970 - 3525164
Float dryer
Flaith et al. - June 1967 - 3324570
Method of changing the moisture content of wood
Milligan et al. - August 1965 - 3199213
MICROWAVE DRYING APPARATUS
Stephansen - June 1972 - 3672066
DRYER FOR A FILM PROCESSING MACHINE
VanBovwel et al. - April 1969 - 3435539
APPARATUS FOR GASEOUS TREATMENT OF MOVING WEBS
Brown - August 1970 - 3525164
Float dryer
Flaith et al. - June 1967 - 3324570
Method of changing the moisture content of wood
Milligan et al. - August 1965 - 3199213
MICROWAVE DRYING APPARATUS
Stephansen - June 1972 - 3672066
DRYER FOR A FILM PROCESSING MACHINE
VanBovwel et al. - April 1969 - 3435539
Inventors:
Minoda, Minoru (Kanagawa, JA)
Yoshida, Tetsuo (Kanagawa, JA)
Chikamasa, Hiroshi (Kanagawa, JA)
Yoshida, Tetsuo (Kanagawa, JA)
Chikamasa, Hiroshi (Kanagawa, JA)
Application Number:
05/213640
Publication Date:
11/13/1973
Filing Date:
12/29/1971
View Patent Images:
Export Citation:
Assignee:
Fuji Photo Film Co., Ltd. (Kanagawa, JA)
Primary Class:
Other Classes:
242/615.110, 226/196.100
International Classes:
F26B13/20; G03D15/02; F26B13/10; B26B13/20; B65H17/32
Field of Search:
34/57R,57B,57A,156,155 226/97
Primary Examiner:
O'dea, William F.
Assistant Examiner:
Devinsky, Paul
Claims:
What is claimed is
1. In an apparatus for conveying and drying a web in which a flexible web having a width of not more than 1.5 m is floated and conveyed by air from a perforated plate without contact, said air having a static pressure of not more than 5 mmH2 O at the central portion of the web width between the web and the perforated plate surface, whereby said coated layer is dried by use of said air, the improvement wherein the air holes provided in the perforated plate have an area of not more than 5 percent of whole area of the plate and satisfy the following dimensional conditions:
2. 3p ≤ 1,
1. In an apparatus for conveying and drying a web in which a flexible web having a width of not more than 1.5 m is floated and conveyed by air from a perforated plate without contact, said air having a static pressure of not more than 5 mmH2 O at the central portion of the web width between the web and the perforated plate surface, whereby said coated layer is dried by use of said air, the improvement wherein the air holes provided in the perforated plate have an area of not more than 5 percent of whole area of the plate and satisfy the following dimensional conditions:
2. 3p ≤ 1,
Description:
BACKGROUND OF THE INVENTION
This invention relates to method of drying a flexible web having a wet layer coated thereon, and more particularly to method of drying a web such as film base, baryta paper and the like having a layer of cooled and set colloidal solution as of a photographic emulsion by the use of an air jet flow provided through a perforated header which conveys the web and causes it to float without contacting the surface thereof.
Nowadays, in the drying process in the manufacture of photographic photosensitive materials, an important problem to be solved has been to prevent surface defects (e.g. abrasion, scratches, press marks, and curling, nicks on the surface of emulsion layer and substrate) and photographic defects (e.g., electrostatic discharge fog, pressure fog, friction fog) caused by the speed of the coating process, thereby to improve the standard of product quality accompanying improvement of production efficiency.
These defects are prominent in the case where the photosensitive material has emulsion layers on the opposite surfaces of a substrate and the sensitivity of the emulsion layer is high as in case of X-ray film.
In order to solve the above problem, namely to prevent the surface defects or the like, various methods for conveying and drying the web without contacting the surface thereof by the use of an air stream or the like have been put into practice in the manufacture of photosensitive material. Among the conventional methods of feeding a web without contacting the surface thereof, the most preferable method is to support the web and exert tension thereto by an air jet flow provided through a perforated header, keeping a static pressure between the web and header. By this method, the web can be stably floated without fluttering or causing another surface irregularity while being conveyed. In this case, by utilizing the air which supports the web as the drying air, the air can be used efficiently. Further, in this case, the web can be floated in a stable condition since there is no induced air flow.
In the nozzle jet drying method which is adapted to the air floating methods, air is impinged on the web from slots extending laterally with respect to the web conveying direction and a number of circular small holes uniformly provided in the header perforated plate which has a flat or curved surface.
The ratio of the area of the holes or slits to the whole area of the header perforated plate preferably does not exceed more than 5 percent in order to avoid interaction of air effected in the case where too much air is released out of the holes. In the embodiment of the present invention, the area ratio of the holes to the whole area is made not more than 4 percent, which produces good function of the air impingement.
In the air floating web method, it is necessary and important to establish a uniform air flow distribution in order to stably convey the web. In the case that the area ratio of the air impingement holes to the whole is not more than 4 to 5 percent, the small holes provide more uniform and stable air flow than a slotted nozzle with small amount of air and a simple construction.
However, in the air floating method in which the small holes are used to impinge the web for drying and floating, and a static pressure is maintained between the web and the header having the perforated plate, lateral air flow occurs and some of the air flows out of the air floating portion laterally. Accordingly, the air flow is disturbed at both edge portions of the web. The above lateral flow of air results in the coated layer on the web being unevenly dried.
SUMMARY OF THE INVENTION
In the light of the foregoing description of the prior art, the primary object of the present invention is to provide a method of drying a web by the use of air impingement in which the air flow is not disturbed at the edge portions of the web by compensating for the change of air impingement velocity at the center of the web width.
One object of the present invention is to provide a method of drying a web by the use of air impingement in which the web is conveyed without contacting the header with a perforated plate that may be flat or curved, by means of stable air floatation.
Another object of the present invention is to provide a method of even drying of a coated layer on a web by the use of air impingement in which the web can be conveyed by the air floation, especially in a width smaller than 1.5 m.
A further object of the present invention is to obtain good air impingment efficiency by means of elimination an uneven drying condition by air flow interaction.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects will be made apparent from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawing in which:
FIG. 1 is a longitudinal elevational section of the web floating apparatus embodying the method of the present invention;
FIG. 2 is a plan view of the apparatus shown in FIG. 1; and
FIG. 3 is a schematic view showing the perforated holes for air impingement for drying and floating the web provided in the apparatus shown in FIGS. 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Now referring to FIGS. 1 and 2 of the drawing, the flexible web 1 having a wet coated layer 2 is conveyed in the direction indicated by an arrow A over a header chamber 3 having at the periphery thereof a perforated plate 4 serving as a header provided with a number of holes 5 to discharge air therethrough. The reference numeral 6 shows an air duct through which air is supplied to the header chamber 3 from a suitable air supply unit (not shown).
Referring to FIG. 3, the reference numerals 101, 102, 103 and 104 show air impingement holes arranged on the web guide 4 substantially along a lateral line. The reference numerals 201, 202, 203, and 204 show another line of air holes arranged in parallel with the first air holes 101 to 104. The second line of air holes 201 to 204 is slightly displaced from the first line of air holes 101 to 104 by the distance e in the lateral direction. Similarly, the third and fourth lines of air holes 301 to 304 and 401 to 404 are provided, and are displaced laterally in a manner substantially the same as the air holes 101-104 and 201-204. The angle between the web advancing direction A and the lateral direction in which the line of air holes 101 to 104 extends is indicated at ∠α. The air holes 101, 102, . . . are round and/or oval shaped, and the major axis thereof is inclined at an angle ∠β with the lateral direction. The length of the holes measured along the major axis thereof is indicated at d. The width of the oval holes measured along the minor axis thereof is indicated at s. The interval between the adjacent air holes arranged laterally is indicated at p. The interval between the adjacent lines of air holes arranged laterally is indicated at i.
Now the operation of the method and apparatus of the present invention will be described hereinbelow.
Referring to FIGS. 1 to 2, the flexible web 1 having the coated layer 2 is supported or floated by the air impinged upwardly through the holes 5 and conveyed without contacting the header, whereby the coated layer 2 containing moisture is dried by the air.
The air for floating and drying the web is sent to the air blowing out chamber 3 through the air duct 6 from the air supply unit (not shown), and is impinged on the layer 2 coated on the flexible web 1 through the perforated holes 5 provided in the perforated plate 4. Thereafter, the air flows laterally between the web 1 and the perforated plate 4.
The perforated plate 4 forms a flat surface or a curved surface constituting a part of a surface of a cylinder having an axis substantially parallel to the lateral direction of the advancing web or inclined slightly with the lateral direction.
Balanced static air pressure sufficient to float the web 1 having the coated layer 2 thereon is maintained between the web 1 and the perforated plate 4 to convey the web in the floated state without contact.
The coated layer 2 on the flexible web 1 is dried by the air vertically impinging thereon from the holes 5 at the central portion of the web width, and is dried by the air vertically impinged thereon from the perforated holes 5 and air flow laterally between the web 1 and the plate 4 at both side edges thereof.
The size and arrangement of the air impingement holes 5 provided in the plate 4 are such that the ratio of the hole area to the plate area is not more than 5%, and a substantially uniform static pressure is maintained between the web 1 and the plate 4 over the whole area thereof. Further, the arrangement of the holes 5 is required to be so designed that the web 1 is uniformly dried and that the air flow released vertically upwardly out of the holes 5 is not influenced by the lateral flow of the air coming from the central portion of the web width.
The arrangement which fulfils the requirements as described above will now be explained in greater detail hereinbelow referring to FIG. 3. In the case where the width of the flexible web to be floated and dried is not more than 1.5 m in which the optimum result is obtained in accordance with the method of the present invention, and the shape of the holes is circular or any other shape similar thereto, the relationship between
1. the angle between the conveying direction and the line along which the holes are arranged . . . ∠α,
2. the angle between the major axis of the round and/or oval holes and the lateral direction . . . ∠β,
3. the length of the round and/or oval holes measured along the major axis thereof or the representative length thereof . . . d, and
4. the width of the round and/or oval holes measured along the minor axis thereof or the representative width thereof . . . s should satisfy the following conditions:
∠α = 70° to 110°,
∠β = 20°C to 20°,
s = 3 to 7 mm, and
s ≤ d ≤ 3s
Further, the arrangement of the air impingement holes 5 which is optimum from the viewpoint of the present invention is determined by the relation between the volume of air required to dry the web and the volume thereof required to float the web, and by the relation between the interval between the adjacent holes arranged laterally and the interval between the adjacent lines of air holes arranged longitudinally which affects the influence of the lateral flow of air on the vertical air flow blowing at both edge portions of the web. In the case that the ratio of the area of the holes to the whole area of the plate is not more than 5 percent, the relation between the interval p between the adjacent holes and the interval l between the adjacent lines of the holes is required to fulfil the condition of
1.3 p ≤ l
to effect a satisfactory result.
The distance e by which the holes located nearest each other in the adjacent lines of the holes are spaced is determined so that the holes 5 may be distributed substantially uniformly over the whole plate when measured in the direction of the advance of the web.
Further, the method of drying the feeding a web in accordance with the present invention is also applicable to a web treating system in which a web having coated layers on the opposite surfaces thereof is fed and dried.
In accordance with the present invention as described above, various results are effected as follows:
At first, since the air is released out of holes provided in a header perforated plate uniformly, there is no possibility that the flexible web is caused to flutter or slackened while being conveyed and the web can be floated in a remarkably stable condition.
Secondly, since the uniform air flow distribution on the average is effected on the surface of the web, the coated layer thereon is uniformly dried. Accordingly, uneveness in drying which has affected the photographic performance of the emulsion of the film made from the web is improved by this method.
Now the method of the present invention will be described in detail with reference to particular embodiments thereof.
EXAMPLE 1
In an air floating type web conveying and drying device having an air impingement perforated plate of the construction as shown in FIGS. 1 and 2, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in a perforated plate type-A:
the ratio of the area of the holes to the whole area of the plate . . . 2.1 percent
the angle between the conveying direction and the line along which the holes are arranged . . . ∠α = 90°
the angle between the major axis of the holes and the lateral direction . . . ∠β = 0°
the length of the hole . . . d = 6.2mm
the width of the hole . . . s = 6.2mm
the interval between the holes . . . p = 25mm
the interval between the lines of the holes . . . l = 58mm
the deflection of the position of the holes in the adjacent lines of holes . . . e = 6mm
Further, the dimension of the perforated holes as shown in FIG. 3 was determined as follows in another perforated plate type-B:
the ratio of the area of the holes to the whole area of the plate . . . 2.1 percent
the angle between the convey direction and the line of holes . . . ∠α = 90°
the angle between the major axis of the holes and the lateral direction . . . ∠β= 0°
the length of the hole . . . d = 6.2 mm
the width of the hole . . . s = 6.2 mm
the interval between the holes . . . p = 58mm
the interval between the lines of holes . . . l = 25mm
the deflection of the position of the holes in the adjacent lines of holes . . . e = 6mm
The two air impingement perforated plates, type-A and type-B, were used in the web floating and drying device in accordance with the present invention, and a static pressure of 50mmH 2 0 was maintained in the header chamber and a static pressure of 20mmH 2 0 was maintained at the central portion of the web width between the plate and the flexible web. Thus, a polyester film base of 1m wide having a photographic emulsion layer thereon was conveyed without contact and was dried by the air released from the holes.
In a comparison of the two types of plate A and B, it was found that the plate type-A was much superior to the plate type-B in eliminating the un-eveness in drying seen along the lateral direction of the web, in uniformity of drying, in reduction of time required for drying (by 15%), and in floating the flexible web in a stable condition without fluttering, slackness and deforming of the surface thereof.
EXAMPLE 2
In an air floating-type web conveying and drying device having an air impingement perforated plate forming a cylindrical surface as shown in FIGS. 1 and 2, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in a perforated plate of type-C, in which the same reference characters as used in Example 1 are employed for the same dimension:
the ratio of area of the holes to the whole area . . . 2.1 percent
∠α = 90° , ∠β = 0°, d = 9.6mm, s = 4mm, p = 20mm,
l = 72mm, e = 5mm.
Further, in the same device, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in another perforated plate of type-D:
the ratio of area of the holes to the whole . . . 2.1 percent
∠α = 90° , ∠β = 0°, d = s = 6.2mmφ, s = d = 6.2mmφ, p = 72mm, l = 20mm, e = 5mm.
The two air impingement perforated plates type-C and type-D were used in the web floating and drying device in accordance with the present invention, and a static pressure of 50mmH 2 O was maintained in the header chamber and a static pressure of 22mmH 2 O was held at the central portion of the web width between the plate and the flexible web. Thus, a polyester film base of 1 m wide having a photographic emulsion layer thereon was conveyed without contact and was dried by the air impingement out of the holes.
Through the comparison of the two types of plate type-C and type-D, it was found that the plate type-C was much superior to the plate type-D in eliminating the uneveness in drying effect along the lateral direction of the web, in uniformity of drying distribution, in reduction of time required for drying (reduced by 18 percent, and in floating the flexible web in a stable condition without fluttering, slackness and deforming of the surface thereof.
This invention relates to method of drying a flexible web having a wet layer coated thereon, and more particularly to method of drying a web such as film base, baryta paper and the like having a layer of cooled and set colloidal solution as of a photographic emulsion by the use of an air jet flow provided through a perforated header which conveys the web and causes it to float without contacting the surface thereof.
Nowadays, in the drying process in the manufacture of photographic photosensitive materials, an important problem to be solved has been to prevent surface defects (e.g. abrasion, scratches, press marks, and curling, nicks on the surface of emulsion layer and substrate) and photographic defects (e.g., electrostatic discharge fog, pressure fog, friction fog) caused by the speed of the coating process, thereby to improve the standard of product quality accompanying improvement of production efficiency.
These defects are prominent in the case where the photosensitive material has emulsion layers on the opposite surfaces of a substrate and the sensitivity of the emulsion layer is high as in case of X-ray film.
In order to solve the above problem, namely to prevent the surface defects or the like, various methods for conveying and drying the web without contacting the surface thereof by the use of an air stream or the like have been put into practice in the manufacture of photosensitive material. Among the conventional methods of feeding a web without contacting the surface thereof, the most preferable method is to support the web and exert tension thereto by an air jet flow provided through a perforated header, keeping a static pressure between the web and header. By this method, the web can be stably floated without fluttering or causing another surface irregularity while being conveyed. In this case, by utilizing the air which supports the web as the drying air, the air can be used efficiently. Further, in this case, the web can be floated in a stable condition since there is no induced air flow.
In the nozzle jet drying method which is adapted to the air floating methods, air is impinged on the web from slots extending laterally with respect to the web conveying direction and a number of circular small holes uniformly provided in the header perforated plate which has a flat or curved surface.
The ratio of the area of the holes or slits to the whole area of the header perforated plate preferably does not exceed more than 5 percent in order to avoid interaction of air effected in the case where too much air is released out of the holes. In the embodiment of the present invention, the area ratio of the holes to the whole area is made not more than 4 percent, which produces good function of the air impingement.
In the air floating web method, it is necessary and important to establish a uniform air flow distribution in order to stably convey the web. In the case that the area ratio of the air impingement holes to the whole is not more than 4 to 5 percent, the small holes provide more uniform and stable air flow than a slotted nozzle with small amount of air and a simple construction.
However, in the air floating method in which the small holes are used to impinge the web for drying and floating, and a static pressure is maintained between the web and the header having the perforated plate, lateral air flow occurs and some of the air flows out of the air floating portion laterally. Accordingly, the air flow is disturbed at both edge portions of the web. The above lateral flow of air results in the coated layer on the web being unevenly dried.
SUMMARY OF THE INVENTION
In the light of the foregoing description of the prior art, the primary object of the present invention is to provide a method of drying a web by the use of air impingement in which the air flow is not disturbed at the edge portions of the web by compensating for the change of air impingement velocity at the center of the web width.
One object of the present invention is to provide a method of drying a web by the use of air impingement in which the web is conveyed without contacting the header with a perforated plate that may be flat or curved, by means of stable air floatation.
Another object of the present invention is to provide a method of even drying of a coated layer on a web by the use of air impingement in which the web can be conveyed by the air floation, especially in a width smaller than 1.5 m.
A further object of the present invention is to obtain good air impingment efficiency by means of elimination an uneven drying condition by air flow interaction.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects will be made apparent from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawing in which:
FIG. 1 is a longitudinal elevational section of the web floating apparatus embodying the method of the present invention;
FIG. 2 is a plan view of the apparatus shown in FIG. 1; and
FIG. 3 is a schematic view showing the perforated holes for air impingement for drying and floating the web provided in the apparatus shown in FIGS. 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Now referring to FIGS. 1 and 2 of the drawing, the flexible web 1 having a wet coated layer 2 is conveyed in the direction indicated by an arrow A over a header chamber 3 having at the periphery thereof a perforated plate 4 serving as a header provided with a number of holes 5 to discharge air therethrough. The reference numeral 6 shows an air duct through which air is supplied to the header chamber 3 from a suitable air supply unit (not shown).
Referring to FIG. 3, the reference numerals 101, 102, 103 and 104 show air impingement holes arranged on the web guide 4 substantially along a lateral line. The reference numerals 201, 202, 203, and 204 show another line of air holes arranged in parallel with the first air holes 101 to 104. The second line of air holes 201 to 204 is slightly displaced from the first line of air holes 101 to 104 by the distance e in the lateral direction. Similarly, the third and fourth lines of air holes 301 to 304 and 401 to 404 are provided, and are displaced laterally in a manner substantially the same as the air holes 101-104 and 201-204. The angle between the web advancing direction A and the lateral direction in which the line of air holes 101 to 104 extends is indicated at ∠α. The air holes 101, 102, . . . are round and/or oval shaped, and the major axis thereof is inclined at an angle ∠β with the lateral direction. The length of the holes measured along the major axis thereof is indicated at d. The width of the oval holes measured along the minor axis thereof is indicated at s. The interval between the adjacent air holes arranged laterally is indicated at p. The interval between the adjacent lines of air holes arranged laterally is indicated at i.
Now the operation of the method and apparatus of the present invention will be described hereinbelow.
Referring to FIGS. 1 to 2, the flexible web 1 having the coated layer 2 is supported or floated by the air impinged upwardly through the holes 5 and conveyed without contacting the header, whereby the coated layer 2 containing moisture is dried by the air.
The air for floating and drying the web is sent to the air blowing out chamber 3 through the air duct 6 from the air supply unit (not shown), and is impinged on the layer 2 coated on the flexible web 1 through the perforated holes 5 provided in the perforated plate 4. Thereafter, the air flows laterally between the web 1 and the perforated plate 4.
The perforated plate 4 forms a flat surface or a curved surface constituting a part of a surface of a cylinder having an axis substantially parallel to the lateral direction of the advancing web or inclined slightly with the lateral direction.
Balanced static air pressure sufficient to float the web 1 having the coated layer 2 thereon is maintained between the web 1 and the perforated plate 4 to convey the web in the floated state without contact.
The coated layer 2 on the flexible web 1 is dried by the air vertically impinging thereon from the holes 5 at the central portion of the web width, and is dried by the air vertically impinged thereon from the perforated holes 5 and air flow laterally between the web 1 and the plate 4 at both side edges thereof.
The size and arrangement of the air impingement holes 5 provided in the plate 4 are such that the ratio of the hole area to the plate area is not more than 5%, and a substantially uniform static pressure is maintained between the web 1 and the plate 4 over the whole area thereof. Further, the arrangement of the holes 5 is required to be so designed that the web 1 is uniformly dried and that the air flow released vertically upwardly out of the holes 5 is not influenced by the lateral flow of the air coming from the central portion of the web width.
The arrangement which fulfils the requirements as described above will now be explained in greater detail hereinbelow referring to FIG. 3. In the case where the width of the flexible web to be floated and dried is not more than 1.5 m in which the optimum result is obtained in accordance with the method of the present invention, and the shape of the holes is circular or any other shape similar thereto, the relationship between
1. the angle between the conveying direction and the line along which the holes are arranged . . . ∠α,
2. the angle between the major axis of the round and/or oval holes and the lateral direction . . . ∠β,
3. the length of the round and/or oval holes measured along the major axis thereof or the representative length thereof . . . d, and
4. the width of the round and/or oval holes measured along the minor axis thereof or the representative width thereof . . . s should satisfy the following conditions:
∠α = 70° to 110°,
∠β = 20°C to 20°,
s = 3 to 7 mm, and
s ≤ d ≤ 3s
Further, the arrangement of the air impingement holes 5 which is optimum from the viewpoint of the present invention is determined by the relation between the volume of air required to dry the web and the volume thereof required to float the web, and by the relation between the interval between the adjacent holes arranged laterally and the interval between the adjacent lines of air holes arranged longitudinally which affects the influence of the lateral flow of air on the vertical air flow blowing at both edge portions of the web. In the case that the ratio of the area of the holes to the whole area of the plate is not more than 5 percent, the relation between the interval p between the adjacent holes and the interval l between the adjacent lines of the holes is required to fulfil the condition of
1.3 p ≤ l
to effect a satisfactory result.
The distance e by which the holes located nearest each other in the adjacent lines of the holes are spaced is determined so that the holes 5 may be distributed substantially uniformly over the whole plate when measured in the direction of the advance of the web.
Further, the method of drying the feeding a web in accordance with the present invention is also applicable to a web treating system in which a web having coated layers on the opposite surfaces thereof is fed and dried.
In accordance with the present invention as described above, various results are effected as follows:
At first, since the air is released out of holes provided in a header perforated plate uniformly, there is no possibility that the flexible web is caused to flutter or slackened while being conveyed and the web can be floated in a remarkably stable condition.
Secondly, since the uniform air flow distribution on the average is effected on the surface of the web, the coated layer thereon is uniformly dried. Accordingly, uneveness in drying which has affected the photographic performance of the emulsion of the film made from the web is improved by this method.
Now the method of the present invention will be described in detail with reference to particular embodiments thereof.
EXAMPLE 1
In an air floating type web conveying and drying device having an air impingement perforated plate of the construction as shown in FIGS. 1 and 2, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in a perforated plate type-A:
the ratio of the area of the holes to the whole area of the plate . . . 2.1 percent
the angle between the conveying direction and the line along which the holes are arranged . . . ∠α = 90°
the angle between the major axis of the holes and the lateral direction . . . ∠β = 0°
the length of the hole . . . d = 6.2mm
the width of the hole . . . s = 6.2mm
the interval between the holes . . . p = 25mm
the interval between the lines of the holes . . . l = 58mm
the deflection of the position of the holes in the adjacent lines of holes . . . e = 6mm
Further, the dimension of the perforated holes as shown in FIG. 3 was determined as follows in another perforated plate type-B:
the ratio of the area of the holes to the whole area of the plate . . . 2.1 percent
the angle between the convey direction and the line of holes . . . ∠α = 90°
the angle between the major axis of the holes and the lateral direction . . . ∠β= 0°
the length of the hole . . . d = 6.2 mm
the width of the hole . . . s = 6.2 mm
the interval between the holes . . . p = 58mm
the interval between the lines of holes . . . l = 25mm
the deflection of the position of the holes in the adjacent lines of holes . . . e = 6mm
The two air impingement perforated plates, type-A and type-B, were used in the web floating and drying device in accordance with the present invention, and a static pressure of 50mmH 2 0 was maintained in the header chamber and a static pressure of 20mmH 2 0 was maintained at the central portion of the web width between the plate and the flexible web. Thus, a polyester film base of 1m wide having a photographic emulsion layer thereon was conveyed without contact and was dried by the air released from the holes.
In a comparison of the two types of plate A and B, it was found that the plate type-A was much superior to the plate type-B in eliminating the un-eveness in drying seen along the lateral direction of the web, in uniformity of drying, in reduction of time required for drying (by 15%), and in floating the flexible web in a stable condition without fluttering, slackness and deforming of the surface thereof.
EXAMPLE 2
In an air floating-type web conveying and drying device having an air impingement perforated plate forming a cylindrical surface as shown in FIGS. 1 and 2, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in a perforated plate of type-C, in which the same reference characters as used in Example 1 are employed for the same dimension:
the ratio of area of the holes to the whole area . . . 2.1 percent
∠α = 90° , ∠β = 0°, d = 9.6mm, s = 4mm, p = 20mm,
l = 72mm, e = 5mm.
Further, in the same device, the dimension of the air impingement holes as shown in FIG. 3 was determined as follows in another perforated plate of type-D:
the ratio of area of the holes to the whole . . . 2.1 percent
∠α = 90° , ∠β = 0°, d = s = 6.2mmφ, s = d = 6.2mmφ, p = 72mm, l = 20mm, e = 5mm.
The two air impingement perforated plates type-C and type-D were used in the web floating and drying device in accordance with the present invention, and a static pressure of 50mmH 2 O was maintained in the header chamber and a static pressure of 22mmH 2 O was held at the central portion of the web width between the plate and the flexible web. Thus, a polyester film base of 1 m wide having a photographic emulsion layer thereon was conveyed without contact and was dried by the air impingement out of the holes.
Through the comparison of the two types of plate type-C and type-D, it was found that the plate type-C was much superior to the plate type-D in eliminating the uneveness in drying effect along the lateral direction of the web, in uniformity of drying distribution, in reduction of time required for drying (reduced by 18 percent, and in floating the flexible web in a stable condition without fluttering, slackness and deforming of the surface thereof.