US2366484A - Apparatus for applying moisture to paper webs - Google Patents

Description

Jan. 2, 1945. D, BRADNER 2,366,484

APPARATUS FOR APPLYING MOISTURE TO PAPER WEBS Filed July 10, 1941 4 Sheets-Sheet 1 INVENTQR firm/X 8. Edd -42w i Z QLM 4 7662,

ATTORN EY Jan. 2, 1945. D..B. BRADNER 5 APPARATUS FOR APPLYING MQISTURE T0 PAPER WEBS Filed July 10, 1941 4 Sheets-Sheet 2 ATTORNEY Jan. 2, 1945.

APPARATUS D. B. BRADNER 2,366,484

FOR APPLYING MOISTURE TO PAPER WEBS Fi ledJuly 10, 1941' 4 Sheets-Sheet 3 INVENTOR I ATTORNEY Jan. 2, 1945. D. B. BRADNER 2,366,434

, APPARATUS FOR APPLYING MOISTURE To PAPER WEBS Filed July 10, 1941. 4 Sheets-Sheet 4 INVENTOR mal'r/ ATTORN EY Patented a. 2, 1945 APPARATUS ron APPLYING mols'runs mesa wens a Donald B. Bradner, Mount Healthy, Ohio, assignor to The Champion Paper and Fibre Company, Hamilton, Ohio, a corporation of Ohio Application July '10, 1941, Serial N 4o 1'.ss4

. 3 Claims.

This invention relates to the manufacture and handling of paper, cardboard, and similar-ma:

terials and has particular reference to the addition of moisture thereto for controlling their physical properties and/or other characteristics.

In the past, various methods have been used' to apply moisture to moving paper webs for the purpose of increasing their moisture content, of increasing the ease of finishing, of influencing the tendency of the paper to curl, or for other purposes. Various types of sprayshave been used but with these there has been difficulty in securing the uniformity and the freedom from spotting by water drops desired on many types of paper.

Steam showers have often been used instead of water sprays. These have commonly consisted of means for discharging steam into the air in immediate, proximity to, commonly just below. the

7 moving web. They were frequently formed by a series of equally spaced holes in a steam pipe ex-- tending across the width of the web, though various types of refinements in construction were often added to improve the performance of the device. .Such, showers would frequently blow drum of condensate onto the web, thus objectionably marking some types of paper. Though various methom were often adopted to prevent this, such showers seldom gave complete satisfaction. Stray air currents would often disturb or dilute the ascending steam and cause irregular distribution of moisture on the paper. Possibilities of accurate control were lacking and results were not uniformly dependable.

Sweat rolls have also been frequently used, most often at the end of the dryer section of a paper. making machine. These are rolls which are kept cool by internally circulating cooling water, or by other means. and on the surface of which water condenses from the usually humid atmosphere surrounding the machine. As the paper passes around these rolls the mm of condensed moisture is transferred thereto. If the humidity in the room was too low to condense the desired amount ofmoisture on the rolls, steam showers crease the amount of moisture which would condense thereon. This was not always satisfactory .as variable air currents would often blow the steam away from parts of the roll and thus cause close the device to prevent the deleterious enacts of stray air currents resulted in almost pure steam within the enclosure and'therefore often caused the condensation of more-water than was imeven moistening of the web. Attempts t en- I desiredor than could safely be applied to the paper web. a i q The primary object of the present invention is therefore to overcome these and other disad- 8 vantages of the various methods and devices of u the prior art, and to provide a methodand apparatus by which it ispossibie to apply controlled amounts of moisture to-travelling webs of paper and to secure substantially even distribution of the applied moisture over the surface of the web. Another object of the invention, is to provide a method and means by which the amount of moisture being added to the web may be readily and quickly adjusted when adjustment is desired. 15 Other objects of the invention will become apparent fromthe following description. V

For the accomplishment of these objects I use steam as the source of moisture. I find that I can control the amount of watercondensed from 20 steam by mixing air therewith in definite, controlled, and preferably adiustableproportions, to form a substantially homogeneous unsaturated mixture. The term "unsaturated as herein used means that the mixture contains less water than 2 it could contain in the form of vapor at that temperature and pressure. The larger the proportion of air the less water will condense from the mixture onto any given obiect, such as a sweat roll or a web of paper, and vice versa. when using such a controlled-mixture instead of steam alone, I find that the condensation is rendered uniform and constant, instead of being unduly increased by the use of enclosing housings which shield the mixture from extraneous air currents. Results are also improved by passing. the mixture over the condensing surface at considerable velocity, that is a velocity sumcient to maintain the quality of the mixture (1. e., the proportions of steam and air therein) at an ai proximately constant value throughout the space adjacent the condensing surface by displacing the mixture as rapidly as its moisture content becomes depleted dueto condensation, by maintaining a turbulent flow to prevent local depletion near the condensing surface, and by preventinB siflniflcant variations in flow due to neighboring air currents, the movements of the surfaces, etc. I also find. it advantageous to heat the mixture and/or its component parts so that the Water vapor therein will be in a somewhat superheated state. and fog and water drops will not be present therein. Water from this mixture will condense upon an" object it touches, which has a temperature below the dew point of the'mixture. This may the p per. In case only temporar moistening, as for the control of the tendency of the paper to. curl, if desired. no cooling isrequired, and when the paper passes from the moistening device into the air the heat of condensation serves to almost immediately evaporate most of the condensed water, leaving the moisture content of the web substantially unchanged. If, on the other hand, it is desired to increase the moisture 'con-' tent of the web, it is necessary to remove the heat of condensation before it has opportunity to cause re-evaporation, This can be accomplished in various ways. For example, when the water is transferred to the paper from a sweat roll, the cooling medium in the roll carries away the heat of condensation; alternatively, the web can be cooled, as by passing over a chilled roll, before it contacts the steam-air mixture. Advantageously, however, a chilled roll, or other cooling medium is used to abstract heat from one side of the web while the other side of the web is in contact with Fig. 3 i a diagrammatic view. of similardevices arranged to increase the moisture content of a web by applying moisture to both sides thereof, showing the connections to steam, air, and coolingwater supplies.

Fig. 4 is a sectional view of another form of device, adapted primarllyfor the temporary application of moisture to one side of a paper web to correct the tendencyof the paper to curl.

Fig. 5 is a sectional view taken on line 5-4 of Fig. 4.

Referring to Fig. 1, a paper web in passes around a roll .II from which heat is abstracted by water which enters and leaves the roll through pipes i2 and i3, respectively, by means of a conventional packing box l4, and under control of valve IS. The steam-air mixture enters through a pipe ii, of ample diameter, and is uniformly distributed across the full width of the web to be treated, by a series of uniformly spaced holes 22, through which it escapes into a housing 23. One

' wall ,24 of this housing lies closely adjacent and roughly parallel to the surface of web ill on roll ii, and is provided with an opening 25 whichextends across the face of the roll, and through which the mixture passes into contact with the extraneous air .currents out of passage 26". Alsobe the paper to be moistened or it may be a sweat roll which transfers the condensed moisture to ends of'the roll ID as shown at 30 in order to keep the passage '28 is made sumciently' thin and the rate of flow of the steam and air through it is maintained sufficiently rapid that turbulence is maintained and extraneous air currentshave substantially no effect on the flow of the mixture over the paper surface. The term thickness as herein used to refer to the passage 28, is used to refer to its least dimension. It is that dimension at right anglesto the direction of flow ofthe steam-air mixture'through the passage whichis measured radially to the roll I I. By the "width" of the passageway is meant that dimension measured at right angles to the direction of iiow of the mixture therethrough, which is measured parallel to the length of roll it and in the samedirection as the width of the paper web. The "length of the passageway 26 is correspondingly the dimension measured in the direction of flow of the mixture therethrough, i. e., circumferentially of the roll ii, and lengthwise of the web. As is clearly shown in the drawings, this length of the passageway is great. in proportion to its thickness in order to give full effective contact pressor 40, or other suitable device, and is delivered through pipe and branch pipes 42 under control of valves to the shower pipes 2|,

alreadydescribed. Means may be provided for heating this air to aid in preventing the formation of fog when steam is added. For this pur- DOSe a steam Jacket 44 may be provided around pipe ll. Steam under pressure is supplied to this web and thence circumferentially around the roll in both directions through passagewa 26 between the roll and the wall 24. The other wall 21 of,housing 23 is advantageously provided with thermal insulation 28 for preventing unnecessary loss of heat and condensation on the wall 21.

Partition members 28 may advantageously be provided in housing 23 (seev Fig. 2) to divide the housing into. sections and thus strengthen the structure and at the same time prevent undesirable cross currents in the steam-air mixture,

bution across the web. The end members-of housing 23 may,--if:.-,uesired. be extended over the .whichnmight'interfere with its uniform distrljacket through pipe "under control of valve 46. Condensate is removed through a pipe 41 and trap 48.

Steam for the mixture is supplied from a steam pipe through pipe Iii and branch pipes 52 which inject steam, under control of valves'lii, into the air flowing through pipes 2. Provision may also be made for superheating this steam to assist in preventing the formation of fog. This superheatenmay also takethe form of asteam Jacket 54' surrounding the pipe-5i. Steam, under higher pressure than that in pipe 50, is supplied to this Jacket through pipe 55 under control of valve 56 and condensate is removed through pipe 61 and trap 58.

The operation of the device is as follows: The air supply is turned on and heated as desired by opening steam valve 48. The valves ii are opened to admit cooling water to the roll ii. The paper web II is threaded through the device as shown in the figure. Then steam is admitted by opening valves '3 to the desired amount. The valve 58 may also be opened to provide superheat in the steam. The openings of the valves I5, 43 and 53 are adjusted until the tests of the web show that the desired amount of moisture is being added. Thus, although the-proportions of steam web, it is not necessary to know these proportions. The valves are simply set on the basis of the results obtained. Other things being equal, itis desirable to add the same amount of water to each side ofthe web. Sometimes, however, it may be desirableto add more to one side or the other, or even to moisten one side only, in order to control the tendency of theweb to curl, or for other reasons. This also can be accomplished by setting the valves to give the desired results. If at any time the web breaks and is not immediately re-threaded around the rolls- II, it is desirable to turn oil the sueam so the air comes to rolls Ii warm and dry, and then to turn on the cooling water and stop its circulation through changes in speed would require re-adjustment of the device even though its action were unaffected by the change.

In order to facilitate threading and the rem val of broken paper from the passages 28, the hous-.

ings 23 may, if desired, be swivelled to swing away from rolls ll during the threading and cleanin up operations. Furthermore, in order to prevent broken paper from getting into housings 23 through the openings 25 these openings may be advantageously covered with a screenor grille, notshown. Care should also be taken to see that the steam is admixed with the air in such a manner, and far enough before it reaches the housings 23 that no stratification occurs and the mix:- ture in housings 23 is substantially homogeneous throughout, in order to assure uniform distribution of moisture over the surface of the web.

Figs. 4 and 5 show another embodiment of the invention as applied to the temporary application 'of moisture to one surface of a web in order to control the tendency of the paper tocur'l. In this .case it is-not necessary to abstract heat from the web 80 which, after passing around a roll I,

passes over two fixed. smooth, and substantially co-planar straight edges 82 and which constrain the web to travel in a substantially plane path between them. The steam-air mixture enters through pipe II and is uniformlydistributed across the width of the web by a series of uniformly spaced holes 12. These are here illustrated as formed in a series of corrosion resistant screws is which enter the pipe 1| from below and extend upward for some distance inside of the pipe to entrap any condensate which may come through .pipe I I, especially when start- 'ing operation or the device. One or two screws beyond the edges of the web I are short and ture across the 'web. The mixture then flows downward through a substantially uniform pass'ageway ll between the web 60 and the adjacent exterior wall 82 of the housing 15. and finally escapes into the atmosphere at 83. Steam passages, 8i, and ii are provided for heating plate I8, plate 19 with straight edge-ll, and straight edge '2. respectively, to a temperature above the dew point of the steam-air mixture, in order to prevent condensation of water at points where it might be blown or otherwise transferred onto the paper web. A layer- 81 of thermal insulatin material is provided around the walls of housing "I! to prevent unnecessary heat loss and condensation of moisture onthe insidesurfaces.

The straight edges 82 and 63 serve to exclude a extraneous air currents which might otherwise flow along with the paper and interfere with the uniform-distribution ahdflow of the steam-air mixture in passage ,8! along'the surface oi! the web 80. The entrance of disturbing air currents from the edges is prevented by the end walls 90 of the housing 15. When the web 60 is'narrower than the housing 15 as shown in Fig, 5 adjustable shields 8| (not shown in Fig. 4) are provided for enclosing passage 8i beyond the edges of the web.

This gives a practicallycompletely enclosed passage through which a substantiall uniform'distribution and flow can be maintained. The passage 8! corresponds to the'passages 26 described in connection with Flgs.- l" and 2. The terms length," width. and thickness" are used in a corresponding sense in describing this passageway 8|. It, like passages 28, isat least as wide as the paper web and, as clearly shown in the drawings, .is long in proportionto-its thickness, for analogous reasons.

The steam-air mixture can be formed and sup plied to shower pipe II in the manner described in connection with Fig. 3. An alternative method allow the condensate to be blown out where it will not reach the paper. .The'steam-air jets strike the slanting lower wall ll of housing II and any entrained condensate'flows downward and escapes through a drain "It. flows upward and outward through a narrow slit 11 formed between plates II and" and extending across the full width of'the. web to be treated.

prevent cross currents and eddies "whlchmight The mixture then Such uniformity is ordinarily found where a de- Partition walls serve to maintain the spacing. of plates '18 and I9 and to direct the flow and is illustrated in Figs. 4 and 5. In this modification steam is supplied through pipe it: under control oi! valve III while the air enters through pipe I. under control of valve M. The air maybe supplied by a pump as shown in Fig. 3 V

the two components separately as in the previously described embodiment. Steam is supplied to this jacket through pipe I" provided with valve ill and the condensate is removed through, pipe Ill and trap H2. The pipes I" lead, by

suitableconnections III, to the opposite'ends of shower pipe II, and keep it filled with the mixture under the low but necessary pressure.

-In this case, for any given-mixture of s'team and air, the amount of water condensed is dependent primarily on the available temperature rise in the web and is therefore relatively independent of variations in the speed of the web, a but dependent on the temperature at which the web reaches the device. 'Uniiormity or results. therefore, depends on substantial uniformity of temperature of the web coming to the device.

vice of this type is used, but changes in web temperature may be'made and will ordinarily require a re-adjustmentor the percentages of steam and air in the mixture, if changes are not desired in V the amount or moisture added,

In'caso it shouldbodesiredto use the device in ing the moisture content of the web instead of for the mere temporary addition of moisture,

means may be provided for removing heat. For example, the web may be pre-cooledby providing cooling for'the roll II. similar to that used in rolls H (Figs, 1+3).

posed to the steam air mixture in passage ll.

Alternatively the member" and passage ll may be made curved to follow paper on the surface ofrollll.

Whatever form the device may take, however, I

find that the present invention fumishes a simple Or heat'removal could be accomplishedby passing acurrent of cooled airover the side of the web N; oppositeto that ex-' and eflective method and apparatus for uniformly and either temporarily or permanently adding moisture to fibrous websfsuch as paper, and for accurately controlling the operation 'to give, within limits, whateverdegree of moistening maybe required.

I claim: Y

l. A device for applying a controlled amount of moisture to a moving web of paper by a process involving condensation of the required moisture from an unsaturated mixture of steam-and air,

which comprises: means for constraining the web to travel in a fixed path at the location wherethe moisture is to be applied thereto; means for continuously forming an unsaturated mixture of steam and air; means for adjusting the proportions of steam and air mixed. by said mixing means; a housing extending across the widthof the paper web, for maintaining a quantity of said mixture under pressure slightly above that of the surrounding atmosphere; conduit means for continuously conducting said mixture from said p asse ses the form illustrated in Figs. 4 and 5 for increascooling' said roll; means for continuously forming an unsaturated mixture of steam and air; means for adjusting the proportions of steam and air mixed by said mixing means; a housing extending across thewidth of-the paper web, for maintaining a quantity of said mixture under pressure slightly above that of the surrounding atmosphere; conduit means for continuously conducting said mixture from said mixing means to said housing; a wall member associated with said housing and disposed closely adjacent and substantiallyparallel to the surface of said roll,-said walland the surface of said roll defining a thin passageway which is long in proportion to its thickness and at least as wide as the paper web, forconducting a stream of said mixture circum-- recting and confining said stream of. mixture to.

and excluding extraneous air from,said passageway; and escape means in said housing, extending uniformly across the width of the web and mixing means to said housing; a wall member 1 associated with the housing and disposed closely adjacent and substantially parallel to the position of the condensing surface, said wall and said condensing surface defining a. thin passageway, which is long in proportion to its thickness and at least as wide as the paper web, for conducting a stream of said mixture along said condensing surface lengthwise of the web, said wall member further constituting means for directing and confining saidstream of mixture to, and excluding extraneous air from, said passageway and escape means in said housing, extending uniformly across the width of the web and communicating with said passageway, through which said mixture flows, uniformly distributed across the width of the web, from said housinginto said passageway.

2. A device for applying a controlled amount of moisture to a moving web of paper by a process involving condensation ofthe required moisture from an unsaturated mixture ofsteam and air, which comprises: a roll in contact with which the moving web travels; means for continuously communicating with said passageway, through, which said mixture flows, uniformly distributed across the widthof the web, from said housing into said passageway.

3. A device for applyin a controlled amount of moisture to a moving web of paper by -con-. densation thereon of the-required moisture from an unsaturated mixture of steam and air, which comprises: twoflxed smooth straight edges over which the paper travels and which constrain the web to travel in a substantially plane path therebetween; means for continuously forming an unsaturated mixture of steam and air; means for adjusting the proportions of steam and air mixed by said mixing means; a: housing extending across the width of the paper web, forimaintaining a quantity of said mixture under pressure slightly-above that of the surrounding atmosphere; conduit means for continuously conducti'ng said mixture from said mixing meansv to said housing; a wall member associated with said housing and disposed closely adjacent and substantially parallel to the surface of the web as it passes between said straight edges, said wall and the surfaceof the paper web between said straight edges defining a thin passageway which is long in proportion to its thickness and at least as wide as the paper web, for conducting a stream of said mixture lengthwise along the surface of the web, said wall member further constituting means for directing" and confining said stream of mixture to, and excluding extraneous air from,- said passageway; and escape means in said hous-' ing, extending uniformly across the width of the web and communicating with said passageway,-

- through which said mixture iiows, uniformly disnonaw B. mm.

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