METHOD AND APPARATUS OF NON-CONTACT CONVEYANCE OF A WEB

Abstract: A web conveying apparatus comprising a series of air jetting boxes (3) alternately arranged on opposite sides of a conveyed web (1). Each air jetting box has two outlets (4a, 4b) jetting air toward the web. The outlets are at opposite edges of the air jetting box and direct the air inwardly at an angle of 15° to 45° from the perpendicular of the main or air jetting surface (5) of the box.

Description: This invention relates to a web conveying apparatus for non-contact conveyance of a long belt-shaped support of plastic film, paper or the like (hereinafter referred to as "a web"). More particularly the invention relates to an apparatus for conveying a web in a non-contact manner in the manufacture of a photographic photo-sensitive material such as a photographic film or print paper, a photomechanical material, a magnetic recording material such as a magnetic recording tape, or a recording material such as a pressure-sensitive sheet or heat-sensitive copying sheet. Heretofore, a roller system has been extensively employed to convey a web or plastic film or paper. However, since in the roller system the web is conveyed while being in contact with the rollers, depending on the operating conditions, the web may be scratched or creased, i .e, the product may be damaged. Especially in the case of a web having coated films on both its sides, its quality is lowered when conveyed by the roller system. in order to overcome these difficulties, a method has been employed in which a jetted air stream is applied to a web so that the web is conveyed while being floated, i.e., it is conveyed in a non-contact manner. Fig. 1 is a sectional side view showing a conventional method of conveying a web in a non-contact manner. In the conventional method most extensively employed, as shown in Fig. 1, static pressure support type air jetting boxes 3 are arranged alternately on both sides of a web 1. Air streams are jetted through surfaces 5 of the air jetting boxes which are confronted with the web in such a manner that the jetted air streams are perpendicular to the web 1, thus floating the web in the form of a belt which is wavy in the direction of transport. In the method, in order to convey a web stably, it is essential to carefully design the configuration and dimension of the air jetting boxes 3 and the arrangement or position of air jetting outlets 4. Some of these conditions has been disclosed by Japanese Patent Application (OPI) No. 72847/1979. That is, the air jetting outlets 4 formed along two edges of each air jetting box 3 are slits through which air streams are jetted perpendicular to the air jetting surface. The transport of the web 1 is stabilized when W ≧ P/6 is satisfied. In this expression, W is the distance W between front and rear air jetting outlets 4a and 4b, and P is the distance between two adjacent corresponding postions where the pressure of the air streams act on the web 1 (that is, P is the pitch between two adjacent air jetting boxes on the same side of the web 1). In addition, it has been also disclosed that W should be relatively small (preferably not more that 1/5 of the width of the web). In conclusion, the condition for conveying a web stably is that the distance P is small. A web conveying apparatus of the prior art, accordingly, comprises a plurality of air boxes, said air boxes being alternately arranged in opposite principal sides of said web, each of said air boxes comprising two outlets formed on edges of said enclosed box opposed along the conveying direction and facing said conveyed web, the distance W between said front and said rear air jetting outlets being equal or greater than P/6, P being the pitch between two adjacent air jetting boxes on the same side of the web. As is apparent from the above description, in the conventional web conveying apparatus it is necessary to provide a number of air jetting boxes and accordingly to jet a large quantity of air. As a result, the equipment cost and the running cost are correspondingly increased. It is therefore an object of the present invention to provide a web conveying apparatus in which a web can be stably conveyed with a small quantity of air jetted and in which the equipment cost and running costs can be reduced. This object can be achieved by the characterizing features of claim 1. According to the invention the two outlets have outlet directions inclined towards each other in a direction to said web at an angle of 15° to 45° from the perpendicular of a plane connecting two edges of each air box, said angles being equal to each other, and the two edges of each air box are separated at least 20cm and 30% to 80% of a width of said conveyed web. The sub-claims contain preferred embodiments of the present invention. Further features and advantages will be apparent from the following specification with reference to the drawings, in which: Figure 2 is a perspective view for a description of one example of a web conveying apparatus of the present invention; Fig. 3 is an enlarged cross-section view showing a static pressure support type air jetting box employed in the method of the invention. Fig. 2 is a perspective view showing one example of the method of conveying a web in a non-contact manner according to the invention. Fig. 3 is an enlarged cross-sectional view of an air jetting box 3 employed in the method of the invention. In Fig. 2, jetted air streams are supplied from air pumps to air jetting boxes 3 through ducts 2 running in the direction of movement of a web 1. As the air streams are supplied in the direction of movement of the web 1 as was described above, the internal pressure distribution of the ducts 2 in the widthwise direction of the web 1 is made uniform and the amount of flotation of the web 1 in the widthwise direction becomes constant so that the web 1 can be stably conveyed. In the method of the invention, the distance L between adjacent air jetting boxes can be increased corresponding to an increase in the distance W between the air jetting outlets 4a and 4b provided along two edges of each air jetting box 3. The air jetting boxes in the invention is of the static pressure support type. As shown in Fig. 3, each of the air jetting boxes 3 has the air jetting outlets 4a and 4b formed along the front and rear edges of its surface 5 confronting the web 1 so that the air streams jetted through the air jetting outlets provide static pressure in the space between the web 1 and the air jetting box surface 5 to thereby support the web 1. In the invention, the air jetting outlets 4a and 4b along two edges of each air jetting box need slit guides 6 to direct the jetted air streams. The outlets are preferably in the form of a slit. However, each air jetting outlet may be formed by arranging a number of holes in a line. Furthermore, in each of the air jetting boxes, additional air jetting outlets may be formed between the air jetting outlets provided along the front and rear edges. In the invention, it is essential that the direction of air streams jetted through the air jetting outlets at both edges of each air jetting box is inclined 15° to 45° inwardly of the air jetting surface 5, that is, toward each other, instead of forming right angles with the air jetting surface 5. This permits increasing the distance W between the air jetting outlets 4a and 4b provided along the two edges of the air jetting box 3. However, if the distance W is excessively large, then it becomes difficult to maintain the static pressure between the air jetting surface of the air jetting box 3 and the web 1. Therefore, it is desirable that the distance W is 20 cm or more and 30% to 80% of the web width. As was described above, the air jetting direction of each of the air jetting outlets 4a and 4b at both edges of each static pressure support type air jetting box 3 is inclined by 15° to 45° inwardly of the air jetting box 3 from the plane perpendicular to the air jetting surface 5 of the box 3. Therefore, the static pressure in the space between the central portion of the air jetting surface 5 and the web 1 is held more stably than that in the case where the air jetting angle is 90°. This permits the distance between the air jetting outlets 4a and 4b formed along the front and rear edges of each air jetting box 3 to be at least 20 cm and 30% to 80% of the web width. As a result, the air jetting boxes can be arranged at intervals larger than those in the conventional method. The air jetting box 3 having a large width W according to the invention is substantially equal in the quantity of air jetted to the conventional air jetting box having a small width W. Because of the increased width W, the wavy, stable conveyance of the web can be maintained and the distance L between the adjacent air jetting boxes can be increased. This means that, where the length of conveyance is constant, the number of air jetting boxes to be used can be decreased. Accordingly, the quantity of air jetted for floating the web can be small, when compared with the case of the conventional method. In practice, the intervals of arrangement of the air jetting boxes can be determined according to the material, conveyance condition and object of use of the web. For instance, in the case where the web has a high rigidity, the repetition interval of the air jetting boxes should be made large. In the case, although the quantity of air jetted is greatly decreased, the web can be stably conveyed. In the case where the web has a low rigidity, the width W should be decreased. In this case, while the web can be stably floated, the quantity of air jetted can be decreased. Specific Example The non-contact type web conveying apparatus shown in Fig. 2 was used to provide a transport test for a web of PET 1000 mm in width and 100µm in thickness under the air jetting conditions of ϑ=45° and W=600 mm. The quantity of air jetted was measured under the stable transport condition that the web would not flutter, be creased, be contacted, nor be shifted. It was found that the quantity of air jetted in the method of the invention was 1/3 to 1/4 of that in the conventional method (as disclosed by Japanese Patent Application (OPI) No72847/1979). In addition, the equipment cost of the apparatus of the invention was 1/2 to 2/3 of that of the conventional apparatus (according to Japanese Patent Application (OPI) No. 72847/1979). As is apparent from the above description, because the air jetting direction of each of the air jetting outlets formed along the two edges of each air jetting box is inclined by 15° to 45° inwardly of the air jetting surface from the plane perpendicular to the air jetting surface, the distance between the air jetting outlets can be made large and the pressure of gas for floating the web can be reduced when compared with those in the conventional method. Accordingly, the web is substantially prevented form fluttering and creasing. That is, the web can be stably conveyed. In addition, for the same reason, the intervals of arrangement of the air jetting outlets can be increased, with the result that the number of air jetting boxes can be decreased. Accordingly, the quantity of air jetted (or energy cost) and the equipment cost can be greatly reduced.

Claims: A web conveying apparatus comprising a plurality of air boxes (3), said air boxes (3) being alternately arranged in opposite principal sides of said web (1), each of said air boxes (3) comprising two outlets (4a,4b) formed on edges of said enclosed box opposed along the conveying direction and facing said conveyed web (1), the distance W between said front and said rear air jetting outlets (4a,4b) being equal or greater than P/6, P being the pitch between two adjacent air jetting boxes (3) on the same side of the web (1), characterized in that said two outlets (4a,4b) having outlet directions inclined towards each other in a direction to said web (1) at an angle (ϑ) of 15° to 45° from the perpendicular of a plane connecting two edges of each air box (3), said angles being equal to each other, and that said two edges of each air box (3) are separated by at least 20 cm and 30% to 80% of a width of said conveyed web (1). A web conveying apparatus according to claim 1, wherein said plane connecting said two edges is a planar surface (5) facing said web (1). A web conveying apparatus according to claim 1 or 2, wherein said outlets (4a,4b) are channel slits (6) extending perpendicularly to said conveying direction along said planar surface (5). A web conveying apparatus according to claim 1 or 2, wherein each of said outlets is a series of apertures arranged perpendicular to said conveying direction along said planar surface (5).

Inventors: FUKUHARA, SANSHIROU, KAWARADA, MASAYUKI, NAKASHIMA, HIROSHI
Applicants: FUJI PHOTO FILM CO., LTD.
Application year: 1987
Main classification: B65H20
IPC codes: B65H20, F26B13, B65H23