US2689196A

US2689196A - Web drier

Info

Publication number: US2689196A
Application number: US218778A
Authority: US
Inventors: Joseph S Daniels
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-04-02
Filing date: 1951-04-02
Publication date: 1954-09-14
Anticipated expiration: 1971-09-14

Description

p 1954 J. 5. DANIELS 2,689,196

WEB DRIER Filed April 2, 1951 2 Sheets-Sheet l IN V EN TOR.

MSVAM p 1954 J. s. DANIELS WEB DRIER 2 Sheets-Sheet 2 Filed April 2 1951 INVENTOR.

S 0AM 50 lll-vllar/llig s Patented Sept. 14, 1954 I UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to methods and apparatus for drying coated flexible webs of sheet material and more specifically resides in a method and apparatus'in which a web to be dried is passed through a number of lengthwise runs that have a substantial vertical component of travel wherein portions of the web pass over and are guided without contact by drum areas having a plurality of openings from which air is forceably ejected to form a pneumatic cushion between the drum areas and the web that sustains the weight and conveying tension of the vertically extending web portions being dried.

Sheet webs, such as encountered in the manufacture and processing of paper, are at times coated and dried simultaneously on both sides thereof. Some of the coating materials employed must, after application to the web, be kept free of contact with foreign objects until dry, since contact may mar and injure the coated web surface. While it has become desirable in many instances to simultaneously coat both sides of the Web, drying difficulties are increased by the practice. meet these difficulties is to support the web by playing appropriately directed air streams upon the web surfaces from beneath while the web travels in a continuous horizontal run. Due to the drying time required, at practical speeds of operation, the horizontal run required is of considerable length. As a result, extensive floor area is necessary, and the apparatus is large and costly.

It is an object of this invention to dry a coated flexible web of extensive length with the moist portions thereof arranged in several runs that have a substantial vertical directional component of travel, which moist portions are sustained entirely free of harmful contact with surfaces foreign to the web.

It is another object of this invention to provide web drying apparatus wherein the direction of travel of the web is changed by passing the web over a drum at a spaced distance therefrom to avoid damaging contact between the web and the drum, which spaced distance comprises a pneumatic cushion that sustains the weight of the web.

It is a further object of this invention to decrease the ground area requirements for the drying portions of a coating apparatus so that production costs may be minimized by reducing the plant area which has heretofore been required for the housing of horizontally extending drying apparatus.

These and other objects will appear in the description to follow. In the description reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration and not of limitation a specific form in which this invention may be practiced.

In the drawings:

One method which has been employed to Fig. 1 is a schematic view of a web coating and drying apparatus embodying this invention,

Fig. 2 is a view in perspective with parts broken away of a drum forming a part of this invention over which a web to be dried is passed,

Fig. 3 is a view in section of the drum shown in Fig. 2 viewed through the plane 33,

Fig. 4 is an enlarged fragmentary view of the foraminous wall of the drum shown in Fig. 2,

Fig. 5 is an enlarged fragmentary view in section of the foraminous wall of the drum shown in Fig. 2, and

Fig. 6 is a fragmentary view in perspective of the transverse shift restraining web guide mounted upon the drum as shown in Fig. 2.

Referring now to the drawings, there is shown in Fig. 1 a schematic representation of a coating and drying apparatus adapted to apply a coating material to both sides of a flexible web I of paper and to dry the coating material after its application to the surfaces of the web I. The flexible paper web I is unwound from a roll 2 as it enters the coating and drying apparatus. Upon completion of the coating and drying processes it is wound upon the roll 3.

The coating apparatus shown in Fig. 1 comprises coating material trays 4 located both above and below the web I. A supply of coating material 5 is maintained in the trays 4. The coating material 5 may comprise any of the materials used for the treating and coating of surfaces of fabric and paper webs, with particular reference to those materials that must be dried, or substantially dried, before the Web may be permitted to contact other objects without probable damage to the coated surfaces. An example of such a coating material is nitro-cellulose solution that is applied to glassine papers for improving water and grease resistance of the web. This and other coating materials may be applied to the web by any of the suitable means that may be employed to handle the particular coating material chosen. Such means may comprise brush or air coaters in Fig. 1, however, the coating mechanism shown comprises two roll type coaters.

The coaters each have a fountain roll 6 partially submerged in a coating tray 4, which roll 6 is in rolling contact with the surface of a distributing roll I. Each distributing roll 1 is in turn in rolling contact with a second distributing roll 8. The distributing rolls 8 are each in rolling contact with a larger application roll 9. The rolls 9 approach one another to form a nip Ii) through which the web I travels. A pair of smoothing rolls I l engage the web I as it passes from the nip ll] of the rolls 9 to the drying section of the apparatus.

Drying air is supplied by a blower l2 having an inlet is and a discharge 14 joined to one end of a main fluid duct l5. Leading from the main fluid duct [5 are feeder ducts l6 each joined with a cylindrical drum ll.

One of the drums I1 is more clearly shown in Figs. 2 and .3. The drum I'I shown therein has two end walls I8 and I9. The wall I8 is joined to the feeder duct I6 serving the drum and the duct I6 opens to the interior of the drum I'I through an opening 29 in the wall I8. Extending between the end walls I8 and I9 of the drum I1 is a cylindrical wall 2I having a cross section configuration which is a circular segment. A flat wall portion 22, also extending between the end walls I3 and I9, joins with the lengthwise edges of the curved wall 2I to complete the enclosure that comprises the drum II.

The paper web I is shown in Figs. 2 and 3 in its relation to the curved cylindrical surface of the drum I'I. It is to be noted in these figures that the web I is separated a slight distance from the surface of the drum I'I so that there is no contact between the web I and the drum I'I. That portion of the web I which is parallel to the curved contour of the drum wall 2I is herein designated as the wrap portion 23 of the web I for purposes of clarity. Substantially vertical run portions 24 of the web I extend between the wrap portions 23 of the web I, as is shown in Fig. l, and are shown as having nearly straight paths of travel. In actual practice the web I may deviate from the precisely straight runs shown in the drawings.

Referring again to Figs. 2 and 3 there extends beneath the wrap 23 of the web I and to either side of the wrap 23 a plurality of small circular openings 25 disposed in the cylindrical wall 2I. The circumferential extent of the openings 25 about the curved wall 2I of the drum [1 extends beyond the termination of the wrap portion 23 of the web I by an amount measured by the angles 26.

A portion of the foraminous exterior surface of the wall 2I is shown in Fig. 4 and an enlarged cross section view of one of the openings 25 is shown in Fig. 5. The openings 25 are countersunk to provide an opening upon the interior of the-drum Ii' larger in diameter than the opening to the atmosphere. To provide a maximum number of the openings 25 within a unit area they are spaced from one another in rows that intersect at angles of sixty degrees. As the openings 25 are shown in Fig. 3 they are slightly enlarged out of scale to the rest of the apparatus for the purpose of clarity.

Extending for the full length of the cylinder IT, as shown in Figs. 2 and 3, are a pair of mounting brackets 21 fastened to the cylindrical wall 2I at-the juncture of the wall 2I with the flat wall portion 22. Mounting slots 28 are provided at the ends of the brackets 21. Fitted over the foraminous areas of the wall 2I which extend transversely beyond the margins of the web I are two felt pads 29 having scalloped side margins 30 that are in facing relation to the edges of the web I. A metal band 3| which has riveted thereto at either end a bracket 32 extends across the top of each of the pads 29. A threaded mounting bolt 33 is threadedly secured within each bracket 32 and extends through an associated slot 28. Wing nuts 34 fasten upon the portion of the bolts 33 that extend through the brackets 21 to secure themetal bands 3| and felts 29 in place.

Referring again to Fig. 1, a large roll 35 engages the web I upon its exit from the drying apparatus. From the roll 35 the web I is led through a plurality of calendering rolls 36 and hence to the roll 3.

The apparatus and methods of this invention are primarily concerned with the drying of a coating=and more particularly with the manner of supporting a coated web while undergoing drying. In the form of apparatus shown the drying air applied for this purpose is that which serves also to act as a pneumatic cushion preventing contact with the guiding drums. If desired supplementary drying air may be supplied and the apparatus may be housed to conserve heat or to aid in recovery of volatilized solvent.

The drums I? are alternatively positioned in upper and lower positions such that web I which is carried successively over the drums II travels in substantially vertical runs. As hereinbefore noted, the web I is held from contact with the drums I'z, or from contact with any other substance foreign to the web I, as it is dried. Air or other suitable gaseous fluid supplied to the blower I2 is forceably delivered to the interior of the drums If. This fluid is maintained under pressure within the drums I1 and the escape thereof from the openings 25 within the cylindrical walls 25 of the drums I? is attended with considerable velocity. The resulting impingement of the fluid upon the surface areas of the web I results in formation of a fluid cushion between the web I and drums H which sustains the web I at a distance from the surface areas of the drums H.

The fluid discharged from the openings 25 must necessarily escape from the space between the walls 2| and wrap areas 23 of the web I. This escape occurs at the margin edges of the web I and at those areas where the wrap portions .23 leave the drums i1 and form the run areas 24 of the web 5. This latter escape of fluid tends to entrain portions of the web I near the juncture of the wrap portions 23 and the run portions 24 so as to cause the web I to be deflected toward the surface areas of the wall portions 2|. To overcome the possibility of contact between the web i and the wall portions 2I by reason of such entrainment the circumferential extent about the wall portions 2I of the openings 25 is carried beyond the extent of the wrap portions 23 of the web i by the amount of the angles 26, as hereinbefore described. These angles may vary over a considerable range without impairing proper operation of the apparatus, but it has been found that a five to ten degree angle overcomes undesirable entrainment deflection with a minimum Waste of pressure fluid.

The scalloped margins 30 of the pads 29 are adapted to contact the web I to restrain transverse shift thereof. Fulled felt has been found to be a suitable material for the pads 29. This material has qualities that facilitate guiding of the web I without injury thereto butany other suitable material may be employed. The scalloped margins 39 reduce the extent of contact between the web I and the pads 29 and serve'to permit fluid to escape from beneath the web I by passing between the angular clefts between the projections.

By adjustment of the felt pads 29 axially with respect to the drums I'I, webs of varying width may be accommodated upon the drying apparatus. As the pads 29 are moved to a position to bring the scalloped margins 30 toward theedges of the web I openings 25 extending transverse to the web 4 are sealed by the pads 25 to minimize fluid losses and to increase the economy of operation.

I claim:

1. In an apparatus for drying a coatedweb the combination comprising a plurality of cylindrical drums each vertically displaced vwithzrespect to others of said plurality of drums and aligned with respect to one another to provide guides for a sinuously extending web to be dried wrapped around a portion of the cylindrical surface of each with substantially vertical runs of web extending between and joining successive web wrap portions, foraminous wall areas forming exterior portions of each of said drums facing the wrap areas of the web to be dried, a pair of circumferentially extending lateral web restrainers for each of said drums disposed one to each side of the web to be dried to engagingly restrain transverse shift thereof, a fluid duct having an input opening and outlet openings opening beneath the foraminous wall areas of each of said drums, a blower having a fluid receiving inlet and a discharge outlet joined to the input opening of said fluid duct to forceably discharge fluid under pressure thereinto, and means for drawing the web to be dried successively across said foraminous wall areas of said drums.

2. In an apparatus for drying a coated web the combination comprising a plurality of drums each vertically displaced with respect to others of said plurality of drums and disposed with respect to one another to provide guides for a sinuously extending web wrapped around a portion of the surface of each drum, a wall area I for each drum having openings emerging therefrom to the atmosphere forming a perforate surface facing the associated wrap portion of the web and extending circumferentially from to circumferential degrees beyond the points of tangency of the runs of the web merging with the wrap portion of the web, a pair of circumferentially extending lateral web restrainers for each of said drums each disposed to one side of the associated wrap portion of the web, each lateral web restrainer having a scalloped side margin web edge engaging surface, a fluid duct having an input opening and outlet openings opening beneath the perforate surfaces of each of said drums, a blower having a fluid receiving inlet and a discharge outlet joined to the input opening of said fluid duct to forceably discharge fluid under pressure thereinto, and means for drawing the web to be dried successively across said perforate surfaces of said drums.

3. In an apparatus for drying a coated web the combination comprising a plurality of cylindrical drums having parallel axes staggered in alternate vertically disposed upper and lower positions to provide guides for a sinuously extending web to be dried wrapped around a portion of the cylindrical surface of each drum with substantially vertical runs of web extending between and joining successive web wrap portions, each drum being provided with a wall area havin openings emerging therefrom to the atmosphere forming a perforate cylindrical surface facing the associated wrap portion of the web to be dried and extending circumferentially from 5 to 10 circumferential degrees beyond the points of tangency of the respective runs of the web leading to and from the respective drums, a pair of spaced lateral web restrainers for each of said drums extending circumferentially thereof near the ends thereof, said lateral restrainers including means for axially positioning the same with respect to said drums, each lateral web restraining means having a scalloped side margin web edge engaging surface, a fluid duct having an input open-' ing and outlet openings joined to and opening beneath the perforate surfaces of each of said drums, a blower having a fluid receiving inlet and a discharge outlet joined to the input opening of said fluid duct to forceably discharge fluid under pressure thereinto, and means for drawing the web to be dried successively from drum to drum.

4. In an apparatus for drying a coated web the combination comprising a set of upper hollow drums having upwardly facing cylindrical perforate surfaces and a set of lower hollow drums havin downwardly facing cylindrical perforate surfaces to provide guides for a web extending successively and alternately over the drums of said sets to provide a plurality of upwardly and downwardly extending runs of said web intermediate the wrap portions thereof facing the successive drums, each of said drums being substantially closed except for the perforate surfaces thereof and except for an entrance opening, means for supplying air under pressure to said entrance openings at a rate sufficient to establish a pneumatic cushion between the several drums and the adjacent wrap portions of said web to preclude contact of said web wrap portions with said drums, said drums being mounted away from any solid member in position to contact the side of said web opposite the side in contact with said pneumatic cushion, and web feeding and withdrawing means for feeding and withdrawing the web while maintaining the same in alternately oppositely moving runs between said drums with the wrap portions thereof sustained out of contact with said drums by the pneumatic cushions formed on the perforate surfaces thereof, said feedin and withdrawing means acting through the tensile strength of said web to maintain said web against displacement away from said pneumatic cushions.

5. In an apparatus for drying a coated web the combination comprising upper and lower enclosures each having openings therein providing exit passages for a set of upper closely spaced cylindrically disposed air jets joined with an air supply chamber and a set of lower closely spaced cylindrically disposed air jets joined with an air supply chamber to provide guides for a web extending successively and alternately over the jets of said sets to provide a plurality of upwardly and downwardly extending runs of said web intermediate the wrap portions thereof facing the jets, means for supplying air under pressure to said air supply chambers at a rate sufiicient to establish a pneumatic cushion between the enclosures adjacent said jets and the adjacent wrap portions of said web to preclude contact of said web wrap portions with said enclosures, said enclosures bein mounted away from any solid member in position to contact the side of said web opposite the side impinged by jets emerging from said enclosures and web feeding and withdrawing means for feeding and withdrawing the web while maintaining the same in alternately oppositely moving runs between said upper and lower jets with the wrap portions thereof sustained out of contact with said enclosure, said jets emerge forming pneumatic cushions across the outlets of said jets, said feeding and withdrawing means acting through the tensile strength of said web to maintain said web against displacement away from said pneumatic cushions.

6. In an apparatus for drying a coated web the combination comprising a set of non-rotatable drums having cylindrical perforate surfaces to provide guides for a web extending successively over said drums to provide a plurality of lengthwise extending alternate oppositely moving runs of said web intermediate the wrap portions thereof facing the successive drums, each of said drums being substantially closed except for the perforate surfaces thereof and except for an entrance opening entering therein, means for supplying air under ressure to said entrance openings at a rate sufficient to establish a pneumatic cushion between the several drums and the adjacent wrap portions of said web to preclude contact of said web wrap portions with said drums, said drums being mounted away from any solid member in position to contact the side of said web opposite the side in contact with said pneumatic cushion, and web feeding and withdrawing means for feeding and withdrawing the web while maintaining the same in alternately oppositely moving runs between said drums with the wrap portions thereof sustained out of contact with said drums by the pneumatic cushions formed on the perforate surfaces thereof, said feeding and withdrawing means acting through the tensile strength of said web to maintain said web against displacement away from said pneumatic cushions.

'7. The process of drying a dryable wet coating applied to a traveling web of sheet material without contact of said coating with other than gaseous substances until dryness is attained, which consists in passing said web to and through coating means to apply said wet coating thereto; thereafter passing said web substantially vertically under tension sufficient to ensure substantially straight line travel of said web to a point of near tangency with a first cylindrical array of radially divergent closely spaced rapidly moving streams of air subtending in their angular divergence not less than approximately one semicircle; passing said web around said array of streams in a curved path normal to said streams to cause said streams to impinge on the coating on one side of said web and to apply an are distending force to said web in opposition to and balanced by the tension therein to stabilize the position thereof without contact of the web with any solid member; causing said web thereafter to pass substantially vertically in the opposite sense to a point of near tangency with a second cylindrical array of radially divergent streams similar to the first, facing and impinging on the opposite side of said web; causing said web to pass about said second set of streams while under said tension and while stabilized in position by said streams without contact with any solid member to pass again approximately vertically in the opposite sense; continuing to pass said web in alternate vertical passes and arcuate paths around divergent stream arrays on alternate opposite sides of said web until drying is completed and then withdrawing said web at a rate coordinated with the rate of passage of said web through said coating means while maintaining said tension therein sufficient to ensure substantially straight line travel of said web between the arcuate passes thereof.

8. The process of drying a dryable wet coating applied to both sides of a traveling web of sheet material without contact of said coatings with other than gaseous substances until dryness is attained, which consists in passing said web to and through coating means to apply said wet coating to both sides thereof; thereafter passing said web substantially vertically under tension sufficient to ensure substantially straight line travel of said web to a point of near tangency with'a first cylindrical array of radially divergent closely spaced rapidly moving streams of air subtending in their angular divergence not less than approximately one semicircle; passing said web around said array of streams in a curved path normal to said streams to cause said streams to impinge thereon and to apply an arc distending force to said web in opposition to and balanced by the tension therein to stabilize the position thereof without contact of the web with any solid member; causing said web thereafter to pass substantially vertically in the opposite sense to a point of near tangency with a second cylindrical array of radially divergent streams similar to the first, facing and impinging on the opposite side of said web; causing said web to pass about said second set of streams while under said tension and while stabilized in position by said streams without contact with any solid member to pass again approximately vertically in the opposite sense; continuing to pass said web in alternate vertical passes and arcuate paths around divergent stream arrays on alternate opposite sides of said web until drying is completed and then withdrawing said web at a rate coordinated with the rate of passage of said web through said coating means while maintaining said tension therein sufficient to ensure substantially straight line travel of said web between the arcuate passes thereof.

9. The process of drying a dryable wet coating applied to both sides of a traveling web of sheet material without contact of said coating with other than gaseous substance until dryness is attained, which consists in passing said web to and through coating means to apply said wet coating thereto; thereafter passing said web under tension sufiicient to ensure substantially straight line travel of said web to a point of near tangency with a first cylindrical array of radially divergent closely spaced rapidly moving streams of air; passing said web around said array of streams in a curved path normal to said streams to cause said streams to impinge on the same and to apply thereto an arc distending force in opposition to and balanced by the tension in said web to stabilize the position thereof without contactof the web with any solid memher; and then causing said web thereafter to ass substantially vertically without contact with any solid member while drying is continued and then withdrawing said web at a rate coordinated with the rate of passage cf-said web through said coating'means while maintaining said tension therein sufficient to enure substantially straight line travel of said web.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 454,674 Burns Sept. 3, 1895 1,556,057 Wheeler Oct. 6, 1925 1,951,004 Willis Mar. 13, 1934 1,996,020 I-Iurxthal Mar. 26, 1935 2,054,391 Schmidt Sept. 15, 1936 2,138,178 Lang Nov. 29, 1938 2,416,027 Shields Feb. 18, 1947 FOREIGN PATENTS Number Country Date 9.887 Germany May 29, 1880

Claims

7. THE PROCESS OF DRYING A DRYABLE WET COATING APPLIED TO A TRAVELING WEB OF SHEET MATERIAL WITHOUT CONTACT OF SAID COATING WITH OTHER THAN GASEOUTS SUBSTANCES UNTIL DRYNESS IS ATTAINED, WHICH CONSISTS IN PASSING SAID WEB TO AND THROUGH COATING MEANS TO APPLY SAID WET COATING THERETO; THEREAFTER PASSING SAID WEB SUBSTANTIALLY VERTICALLY UNDER TENSION SUFFICIENT TO ENSURE SUBSTANTIALLY STRAIGHT LINE TRAVEL OF SAID WEB TO A POINT OF NEAR TANGENCY WITH A FIRST CYLINDRICAL ARRAY OF RADIALLY DIVERGENT CLOSELY SPACED RAPIDLY MOVING STREAMS OF AIR SUBTENDING IN THEIR ANGULAR DIVERGENCE NOT LESS THAN APPROXIMATELY ONE SEMICIRCLE; PASSING SAID WEB AROUND SAID ARRAY OF STREAMS IN A CURVED PATH NORMAL TO SAID STREAMS TO CAUSE SAID STREAMS TO IMPINGE ON THE COATING ON ONE SIDE OF SAID WEB AND TO APPLY AN ARC DISTENDING FORCE TO SAID WEB IN OPPOSITION TO AND BALANCED BY THE TENSION THEREIN TO STABILIZE THE POSITION THEREOF WITHOUT CONTACT OF THE WEB WITH ANY SOLIDE MEMBER; CAUSING SAID WEB THEREAFTER TO PASS SUBSTANTIALLY VERTICALLY IN THE OPPOSITE SENSE TO A POINT OF NEAR TANGENCY WITH A SECOND CYLINDRICAL ARRAY OF RADIALLY DIVERGENT STREAMS SIMILAR TO THE FIRST, FACING AND IMPINGING ON THE OPPOSITE SIDE OF SAID WEB; CAUSING SAID WEB TO PASS ABOUT SAID SECOND SET OF STREAMS WHILE UNDER SAID TENSION AND WHILE STABILIZED IN POSITION BY SAID STREAMS WITHOUT CONTACT WITH ANY SOLID MEMBER TO PASS AGAIN APPROXIMATELY VERTICALLY IN THE OPPOSITE SENSE; CONTINUING TO PASS SAID WEB IN ALTERNATE VERTICAL PASSES AND ARCUATE PATHS AROUND DIVERGENT STREAMS ARRAYS ON ALTERNATE OPPOSITE SIDES OF SAID WEB UNTIL DRYING IS COMPLETED AND THEN WITHDRAWING SAID WEB AT A RATE COORIDINATED WITH THE RATE OF PASSAGE OF SAID WEB THROUGH SAID COATING MEANS WHILE MAINTAINING SAID TENSION THEREIN SUFFICIENT TO ENSURE SUBSTANTIALLY STRAIGHT LINE TRAVEL OF SAID WEB BETWEEN THE ARCUATE PASSES THEREOF.