US3313462A - Air flotation direction changing roll - Google Patents

Description

p 1957 H. L. SMITH, JR

AIR FLOTATION DIRECTION CHANGING ROLL 2 SheetsSheet 1 Filed June 2, 1966 INVENTOR Horace LSm/ih, Jr:

JAMIE}! H, 1967 H. SMITH, JR

AIR FLOTATION DIRECTION CHANGING ROLL 2 SheetsSheec 2 Filed June 2, 1966 2 haw- 9 a Hi? I? OOOOOOOOOOOO OOOOO W 6 R 4 m M E m 0 V w m a A M C I h m K m -f I LI 1 H M m HUN 4 7 i mm v. d I. //M/ 2 I Q fl M m y 5 1 m m w w W 3 313 452 Am rLorA'rroN nmhciron CHANGING norm Horace L. Smith, J12, Richmond, Va, assignpr to Hupp Corporation, Cleveland, Ohio, a corporation of Virinia g Filed .Iune 2, 1966, Ser. No. 554,842

2 Claims. (6i. 226--97) This application is a continuation-in-part of application No. 289,938, filed June 24, 1963, which is now abandoned.

This invention relates generally to systems for treating continuous web materials, and more specifically to novel methods and apparatus of the type described above including means for changing the direction of travel of continuous web materials during treatment thereof.

As hereinafter employed, the term treating includes drying, printing, coating, impregnating, dusting, sizing, curing, etc., and is therefore applicable, for example, to paper drying, curin. of thermoset resins, coronizing glass fabric, impregnation of materials with plastics, rubber fixation of resin bonded dyes and pigments on web materials, single or multiple pattern dyeing or otherwise treating and developing special designs such as lace or open area effects in fabrics, tapes, Webs, and the like.

Printing, coating, impregnation, etc., of web material, including paper, fabrics, thin sheet metal strips, and like materials is commercially accomplished by completely saturating the web material in a bath or, as in the case of sheet metal, simultaneously wetting or coating both sides by spraying, for example. Subsequently, the web material is passed through treating apparatus to dry or cure the treating material. Heretofore, it has not been possible, at least in commercial installations, to change the direction of travel of the web material during the treating operation since the treating material adhering to the surface of the web is easily transferred to the surface of any member coming in contact therewith, such as a direction-changing roller. In general, such transfer or offsetting is highly undesirable.

To dry or cure such treated material in a single pass, very high drying towers, often six or more stories in height, have been heretofore employed. After bathing or wetting both sides of the web material, the web is directed vertically upward through a drying tower at a rate of speed calculated to fully cure or dry the treating material by the time the treated portion of the web reaches the top of the drying tower. At that point directionchanging rollers reverse the travel of the web and direct it vertically downward to a take-off roll.

In such a process, there is little or no drying or curing of the treating substance during the downward pass. This results in wasted time and, in most cases, wasted heat and, therefore, less elficient operation. In addition, because of the required height of these drying towers, initial plant building and equipment investment is extremely high and any reduction therein is exceptionally desirable.

In general, the objects of the present invention are accomplished by supporting the treated Web material on a thin film of air to space it from a direction changing roller so that the treating material will not be transferred to the roller. Apparatus intended to operate on this principle has heretofore been proposed as shown, for example, by United States Patents Nos. 2,689,196, issued September 14, 1954, to l. S. Daniels for Web Drier; 3,057,079, issued Oct. 9, 1962, to A. G. M. Schmidt for Apparatus for Contactless Guiding and Conveyin of Flexible Sheet- Like Products; and 3,216,638, issued Nov. 9, 1965. to D. I. Brickle et al. for Air Cushion Method and Apparatus.

The novel direction changing apparatus invented by 3,3l3,4b2 Patented Apr. 11, 1967 applicant is of much simpler construction than the heretofore proposed devices disclosed in the foregoing patents and is accordingly significantly cheaper to fabricate and to maintain.

Another important disadvantage of the devices disclosed in the above-mentioned patents is that only a small percentage of the air supplied to the device will flow through the portion of the device around which the supported web is trained. Therefore, these prior art devices are incapable of actually providing a web supporting film of air except, perhaps, when impracticably high flows of air are employed. In the present invention, in contrast, a novel air supply port design permits virtually all of the air supplied to the direction changing apparatus to be gainfully employed in forming a web-supporting air film.

In previously known devices of the same general type as disclosed herein, the air supply ports have been of uniform cross section or have had a relatively large diameter inlet portion followed by a small diameter exit or outlet portion. The disadvantage of these hole configurations is that practically all of the air flows through the ports which are not covered by the web trained around the air flotation device. Accordingly, these previously known devices can be made to operate, if at all, only by supplying impracticably high volumes of air to them.

Apparatus similar in appearance to that invented by applicant is also shown in United States Patents Nos. 2,753,181 issued to D. R. Andrews et al. Oct. 13, 1959, for Web Reeling System; 2,954,911, issued to H. K. Baumeister et al. Oct. 4, 1960, for Tape Drive; and 2,968,- 702, issued to I. P. Fay Jan. 17, 1961, for Transport Means for a Magnet Recorder-Reproducer. None of these patents, however, suggest that the disclosed apparatus could be used to solve the problems in the heat treating of treated web materials discussed above. The Fay apparatus, for example, through it somewhat resembles applicants invention in appearance, operates in an entirely different manner and, operated as disclosed by the inventor, would be entirely unsuitable for applicants purposes. Thus, in the Pay patent, a perforated drum is employed as a feeding device for a recording tape by evacuating the hollow interior of the drum so that the tape will be forced by air pressure against its outer surface to provide a frictional device connection between the drum and the tape. This apparatus would obviously be unsuitable for altering the direction of web material treated with an easily displaceable treating material which it is desired to prevent from transferring to the direction changim member.

In the Andrews patent a magnetic tape is supported from a direction-changing and guiding member on an air film. However, no utility is disclosed for the Andrews apparatus other than in the stabilizing or guiding of a magnetic tape, and the patent is directed almost entirely to an arran ement of jets or nozzles for producing a fiow pattern that will cause the tape to move to a centered position if it tends to drift along the direction-changing and guiding member.

The purpose and function of the Baumeister et al. patent is even more remote from applicants invention. This patent is much like the Pay patent in that it employs a perforated evacuated cylinder to drive a magnetic tape. While Baumeister et a1. do suggest employing a dynamic flow of air through a perforated cylinder to provide an air cushion, their reason for doing so is merely to permit the tape to move relative to a direction-changing member. There is no suggestion in the Baumeister et al. patent that such an air film could be employed for the purposes to which it has been adapted in the present invention.

Accordingly, it is an important object of the present invention to provide novel improved methods and ap paratus for treating continuous webs which have treating material on both sides of the web.

It is another object of the present invention to provide novel apparatus and methods for changing the direction of travel of a continuous web under treatment while preventing transfer of the treating material to the surface of the apparatus.

Another object of the present invention is to provide novel methods and apparatus for changing the direction of travel of a web material during treatment thereof by means spaced away from the web material.

Still a further specific object of the present invention is to provide air flotation means for changing the direction of the movement of continuous webs having treating materials on both sides thereof by means of a dynamic air flow adjacent the web at the direction'change locale to space the web away from the flotation means on a film or cushion of air and thus prevent transfer of the treating material from the web to the direction changing means.

It is still another object of the instant invention to provide apparatus for treating sheet material which requires substantially less expensive plant facilities than present commercial apparatus.

It is another object of the present invention to provide apparatus and methods for treating sheet material which are faster and more ethcient than present commercial practices,

These and other objectives and advantages of the invention will .be apparent to those conversant with the art from a reading of the following description and subjoined claims in conjunction with the annexed drawings, in which:

FIGURE 1 is a schematic elevation of the method and apparatus of the present invention;

FIGURE 2 is an enlarged elevation, in section, of direction-changing mechanism employed in the apparatus of FIGURE 1;

FIGURE 3 is a plan view of the perforated surface of the direction-changing apparatus of FIGURE 2;

FIGURE 4 is a fragmentary section showing one perforation of the outer surface of the direction-changing apparatus of FIGURE 2; and

FIGURE 5 is a sectional view showing a modified direction-changing apparatus.

FIGURE 1 shows one embodiment of the present invention in the form of a modified tower drier 6, having two passes instead of one and substantially one-half the height of tower driers in commercial use. A standard roll of untreated sheet material 8 is spirally mounted on a mandrel 10 and the combination is rotated unitarily, causing web 12 to travel in the direction of arrow 14. Web 12 may be any standard sheet material including paper, fabric, sheet metal strip, etc. In the embodiment of FIGURE 1, web 12 is directed over roller 16 at station 17 into tank 18, immersed in treating material 20, directed about rollers 22 and 24, respectively, and thereafter moved vertically upward out of tank 18. Station 17 typifies one of several types of treatment apparatus. Coating, dusting, inking, distribution station, etc. are equivalents. Furthermore, station 17 need not necessarily be located in a horizontal attitude, as the invention also encompasses vertical or diagonally oriented stations.

Web 12 is directed away from station 17 as shown by arrow 26 in FIGURE 1 through rollers 28 and into the upward pass 30 of tower drier 6 between series heaters 32 and 34. Satisfactory series heaters are disclosed in the co-pending application of Horace L. Smith, Ir., Ser. No. 64,965, filed Oct. 25, 1960 (now Patent No. 3,174,228), although other types of heaters may, of course, be employed. Web 12 exits from upward pass 39 at tangent point 36 and thereafter moves in the direction of arrow 38 to tangent point 40, In contrast to the prior art driers in which the treated material is dry when it reaches the upper end of the drier, the treating material adhering to web 12 at tangent point 36 in drier 6 is only partially cured or dried because of the reduced drier height and is readily transferable to any solid coming in contact therewith.

Heretofore, changes in direction of travel of partially treated sheet material was avoided by providing extremely high tower driers facilitating complete treatment during upward travel, and substantially no additional treatment during downward travel of the web. Direction-changing mechanism 42 obviates the need for such extended vertical tower driers, allowing treatment during both upward and downward travel by providing a compressed air chamber 44 which emits compressed air through perforations in cylinder wall 46 to space bend 48 of web 12 away from direction-changing mechanism 42 on an air film 5t).

Thereafter web 12 proceeds vertically downward from tangent point 49 through drier pass 52 between series heaters 54 and 56, similar to series heaters 32 and 34, to complete the treatment of the material adhering to web 12. Subsequently web 12 passes underneath roller 58 in the direction of arrow 61) and is wrapped on mandrel 62 to form a roll of treated material 64.

Direction-changing mechanism 42, best shown in FIG- URE 2, comprises a drum 45 having a cylindrical wall 46 and closed at each end by end wall 47. Appropriate drive means (not shown) are provided for rotating drum 45 on axles 69 about axis of rotation 70 in the direction of arrow 72 which is parallel to the direction of travel of web 12 as shown :by arrow 38 (rotation of the websupporting device is most important in high speed operations as shearing of the air film by the web and the resulting decrease in efiectiveness can be minimized by so rotating the drum that its surface speed matches the web speed).

Web 12 is spaced from cylindrical wall 46 by air film 5% along the 180 angle of curvature shown by line 73. Cylindrical wall 46, in conjunction with its end walls 47, forms a compressed air chamber 44 which receives air under pressure from a suitable source of compressed air (not shown) in any appropriate fashion such as through the passage 69a in axle 69. The source of compressed air and passage 6% form a system for forcingair from chamber 44 to the exterior of cylindrical wall 46, the air flowing to the exterior of wall 46 through perforations or ports 74, which are best shown in FIGURE 3. Air from perforations 74 pressure-bears against web 12 along the 180 angle of curvature indicated by line 73.

For reasons of economy, it is desirable to prevent air flow through the perforations 74 which are not immediately adjacent web 12 at bend 48. Therefore, a shoe member 76 is provided to seal 01f the perforations 74 not adjacent bend 43 of web 12. Shoe member 76 (FIGURE 2) includes, at each end of drum 45, a tubular member 78, journalled on a drum-suporting axle 69 and concentrically located about axis of rotation 70, and hanger members 80 and 82. The two sets of hanger members gravitatingly hold a shield 84 in sealing engagement against cylindrical wall 46 of direction-changing mechanism 42 by seal means 86 and 88 extending longitudinally of cylindrical wall 46 and by end seals (not shown).

Referring to FIGURE 3, additional perforations 74 (not shown), outwardly adjacent rows of perforations 9t) and 92 along edges 94 and 96 of drum 45, respectively, may be required in certain manifestations of the present invention to compensate for pressure drop at the edge of web 12 and/ or to accommodate lateral shifting of web 12 to maintain the longitudinal edges of web 12 away from cylindrical wall 46.

An enlarged fragmentary cross-section of cylindrical wall 46 showing one of a series of relatively large apertures, perforation or ports 74, is shown in FIGURE 4. A tubular orifice or nozzle block 1% is recessedly inserted into perforation 74 so that an equal amount of compressed air is discharged from each perforation 74, resulting in equal pressure distribution across web 12 at bend 48. Compressed air flowing into perforation 74, shown by arrows 101 and 102, engages convergent surface 104 of the nozzle 105 in nozzle block 100 (which is the inlet section of perforation or port 7 4) travels through nozzle passage 106, and out outlet or exit section 108 to thereafter pressure-bear against web 12. This movement of air causes considerable pressure drop through the orifice or nozzle 105, achieving equal distribution of air pressure across the entire surface of web 12 along arrowed line 73 (FIGURE 2).

Air flowing out of perforation 74, shown by arrows 112 and 114, embraces web 12 (usually substantially fluid impervious) to space web 12 away from cylindrical wall 46 by dynamic air flow film 110. It is critical that dynamic air fiow film 110 receive a continuous flow of air under substantially uniform pressure from perforations 74; mere static differences in pressure are inadequate for the present invention.

The air flow necessary to provide a web supporting film is sharply reduced from that required in prior art devices by the novel ports of the present invention, which have a small diameter nozzlelike inlet section followed by a large diameter exit section or cavity. In this novel arran ement, the inlet nozzle sections meter or limit the fiow of air through the uncovered ports so that air does not escape through them at a significantly higher rate than it does through the ports covered by the web. Accordingly, in the present invention, there is no large escape of air through the uncovered ports as in previously known devices.

At the same time the enlarged exit cavities make the pressure drop through the covered and uncovered ports much more nearly equal than it is in the prior art devices in which straight sided apertures are employed. Consequently, there is less tendency for the air exiting through the covered ports to escape from beneath the web to the surrounding atmosphere, any flow of this nature being at a low velocity. Consequently, in the present invention, there is a still further reduction in air flow requirements and the formation of a more stable web supporting air film than is provided by prior art devices.

The ratio of the diameters of the inlet and outlet sections of the ports in the present invention may vary from application to application. In one typical application, however, inlet section 106 has a diameter and a cross sectional area of 0.02 sq. in. Outlet section 108 has a 1.25" diameter and a cross section diameter of 1.00 sq. in. By using this port arrangement, the flow of air flow through the uncovered ports was reduced to one thirtyseventh of what there would have been if ports with a one square inch cross section and either of the previously known port constructions discussed above were employed. This provides a substantial overall reduction in the power of the blower necessary and a corresponding decrease in equipment and operating costs.

The pressure of the dynamic air film 50 between web 12 and cylindrical wall 46 required to support the web is, in theory, numerically equal to the tension in web 12, due to its own weight, divided by the surface area of web 12 between tangent points 36 and 40, designated by line 73. For example, assuming the unit weight of web 12 to be pound per square foot which is pound per inch of web width, the vertical run (i.e., the length of web 12 between station 17 and roller 58) to be 30 feet, and the width of web 12 to be 120 inches, the resulting tension in web 12 due to its own weight would be aproximately 60 pounds or 0.3 pound/inch of width. The surface bearing area at bend 48 divided into 60 pounds tension requires an air pressure of approximately 0.05 pound per square inch to support web 12, which requires an air flow at a velocity of 1,300 ft. per minute.

Assuming that drum 45 is 10 feet long and 10 inches in diameter, the total length of escape area for air cushion 50 (assuming also a change of direction) would be approximately 23 feet. Moreover, assuming air film 50 to be 0.01 of an inch thick, the total air escape area would be 0.025 square feet. Using a velocity flow of 2000 ft. per minute, to provide a safety margin, the total volume of air would only be 50 cubic ft. per minute, which is nominal.

In actual practice an air velocity on the order of 4000 feet per minute would be used in an installation with the operating parameters assumed above. The reason for this is that, to insure proper operation of the directionchanging mechanism, the flow between those perforations covered -by web 12 and those that are exposed should be substantially equalized to provide an equal pressure distribution across the span of the direction changing mechanisrn. The difference in flow between the covered and exposed perforations can be reduced to an inconsequential magnitude by maintaining a materially higher pressure in air chamber 44 than in the annular region between direction-changing mechanism 42 and web 12 in addition to employing the novel port configuration described above. This may be done by increasing the flow velocity (which varies with the square of the differential of the pressure on opposite sides of the perforations) to provide a higher pressure differential between the interior and exterior of the direction changing mechanism.

For example, by doubling the calculated flow velocity of 1300 feet per minute and sizing and spacing the perforations to limit the total flow to that sufiicient to provide a pressure of 0.05 p.s.i. under the web, a pressure of 0.20 p.s.i. can be maintained in air chamber 44. To compensate for leakage and other practical factors requiring minor corrections, the pressure in air chamber 44 would preferably be maintained at 0.5 p.s.i. in actual practice so that the flow velocity would be 4000 feet per minute and the pres-sure differential across the perforations would be 0.45 p.s.i.

Under these conditions the flow through the covered and uncovered perforations would be so nearly equal that the small difference in flow could be disregarded.

Direction-changing mechanism 42, appearing in FIG- URES 1-4, is only one manifestation of the present invention for changing the direction of travel of a partially treated substance adhering to web 12. FIGURE 5 shows a second manifestation, stationary direction-changing mechanism 120, which includes a drum structure 121 unitarily formed of a semi-cylindrical wall 122, base walls 124 and 126, tubular air inlet member 128, and end walls (not shown). The direction of travel of web 12, having partially treated substance adhering thereto, is changed by compressed air proceeding into chamber 130, out perforations 132, preferably of the type discussed above, to pressure-bear against Web 1 2 and space it from cylindrical wall 122 by air cushion 134 in the manner described previously in conjunction with the embodiment of FIGURE 1. Consequently, no solid material touches the material adhering to web 12 while the traveling direction of web 12 is selectively changed.

While only two manifestations of the present directionchanging mechanism have been shown, namely, directionchanging mechanisms 42 and 120, other types of dynamic air fiow pressure-bearing mechanisms are comprehended by this invention employing the principles discussed above.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description.

What is claimed and desired to be secured by Letters Patent is:

1. Apparatus for changing the direction of travel of a web during processing thereof in which the web is supported on a film of air, comprising:

(a) a single hollow drum having a wall of substantial thickness, said drum being rotatably supportable and being adapted to have the web trained thereover; and

(b) ports through said wall providing communication between the interior and exterior of the drum, Whereby air may be forced from the interior of said drum to the exterior thereof to provide a filrnlike cushion of air between the drum and the web, said ports each having an inlet section of relatively small crosssectional area for metering the flow of air through the ports and an outlet section communicating with said inlet section, said outlet section having a substantially larger cross-sectional area than the inlet section; and

(c) means for sealing off the perforations through the portion of the drum other than those over Which the web is trained comprising:

(1) an arcuate shield member within said drum cooperating with the inner surface thereof; (2) support means mounting said shield for free rotational movement about an axis coincident with the axis of rotation of said drum, and

(3) seal means extending along opposite edges of said shield and disposed between said shield and said drum for preventing escape of air through perforations underlying the shield.

2. The apparatus of claim 1, wherein the inlet sections of said ports are formed in nozzle blocks disposed in apertures through the wall of said structure, the outlet sections of said ports being provided by said apertures.

References Cited by the Examiner UNITED STATES PATENTS 2,717,710 9/1955 Baker et a1 22695 X 3,075,679 1/1963 VVadey 22697 X 3,097,778 7/1963 Pendleton 226-97 X 3,142,428 7/1964 Faeber 22695 3,151,795 10/1964 Gwillim 22695 M. HENSON WOOD, JR., Primary Examiner.

ALLEN N. KNOWLES, Examiner.

Claims (1)

1. APPARATUS FOR CHANGING THE DIRECTION OF TRAVEL OF A WEB DURING PROCESSING THEREOF IN WHICH THE WEB IS SUPPORTED ON A FILM OF AIR, COMPRISING: (A) A SINGLE HOLLOW DRUM HAVING A WALL OF SUBSTANTIAL THICKNESS, SAID DRUM BEING ROTATABLY SUPPORTABLE AND BEING ADAPTED TO HAVE THE WEB TRAINED THEREOVER; AND (B) PORTS THROUGH SAID WALL PROVIDING COMMUNICATION BETWEEN THE INTERIOR AND EXTERIOR OF THE DRUM, WHEREBY AIR MAY BE FORCED FROM THE INTERIOR OF SAID DRUM TO THE EXTERIOR THEREOF TO PROVIDE A FILMLIKE CUSHION OF AIR BETWEEN THE DRUM AND THE WEB, SAID PORTS EACH HAVING AN INLET SECTION OF RELATIVELY SMALL CROSSSECTIONAL AREA FOR METERING THE FLOW OF AIR THROUGH THE PORTS AND AN OUTLET SECTION COMMUNICATING WITH SAID INLET SECTION, SAID OUTLET SECTION HAVING A SUBSTANTIALLY LARGER CROSS-SECTIONAL AREA THAN THE INLET SECTION; AND (C) MEANS FOR SEALING OFF THE PERFORATIONS THROUGH THE PORTION OF THE DRUM OTHER THAN THOSE OVER WHICH THE WEB IS TRAINED COMPRISING: (1) AN ARCUATE SHIELD MEMBER WITHIN SAID DRUM COOPERATING WITH THE INNER SURFACE THEREOF; (2) SUPPORT MEANS MOUNTING SAID SHIELD FOR FREE ROTATIONAL MOVEMENT ABOUT AN AXIS COINCIDENT WITH THE AXIS OF ROTATION OF SAID DRUM, AND (3) SEAL MEANS EXTENDING ALONG OPPOSITE EDGES OF SAID SHIELD AND DISPOSED BETWEEN SAID SHIELD AND SAID DRUM FOR PREVENTING ESCAPE OF AIR THROUGH PERFORATIONS UNDERLYING THE SHIELD.

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