US1595484A - Method and apparatus for drying sheet material - Google Patents

Description

Aug. 10 1926. 1,595,484

0. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL.

Original Filed May 25, 1920 g; In mm ,111,,

n I '0 v I] [1111, 6 6 ,101,,

/ I a a law fr AM ATTORNEY Patented Au to, 1926.

UNHTED STATES 1,595,434 PATENT OFFICE.

OGDEN MINTON, 0F GREENWICH, CONNECTICUT.

METHOD APPARATUS FOR DRYING SHEET MATERIAL.

Original application filed May 25, .1920, Serial No 384,212. Divided and this application filed February 4, 1922, Serial No. 534,172.

the sheet materiahwhich is to bedried, into. a vacuum chamber'through a liquid sealing medium which vhas no aflinity for the material, subjecting it to heat to drive off its contained -moisture and then passing the substantially dried material out of the chamber throughaTseal.

This method may be practiced by the use of various formsof apparatus, one of which is herein disclosed; In any form, however,-

it is essential that ,the apparatus be provided with a closed chamber in which a partial vacuum may be maintained. In order that the material to be dried may be continuously passed through the vacuum' chamber, the latter is provided with openings closed to the admission of air by a, t liquidsealing medium which has no afiinity for the material. The liquid seal effectively closes the entrance and exit passages against the admission of air to the chamber, but permits the passage of the material into an out of thechamber.

My invention further relates more particularly to drying a wet web'of paper coming from the wet end of a paper machine usually at high speed, though my invention is also adapted to dry this web at low speeds.

My invention further relates to feeding this web into said vacuum chamber in a manner which will prevent the web flapping or waving as it passes through the liquid seal. l/Vhen paper is dried by my improved method, which eliminates this flapping or waving of the web, the dry paper will notbe crinkled. Where the wet web is permitted to wave or flap the resulting paper is more or less crinkled. Y

My invention further relates to reducing the amount of liquid necessary to form the liquid seall My invention further relates to passing the web over, and in close contact with a guide cylinder partially immersed in the liquid seal.

My invention further relates to drying the web of paper, or similar material, over a plurality of drying drums or cylinders Renewed February 17, 1926: 4

mounted in the vacuum chamber, two of adjacent to the periphery of said guide drums or cylinders or driers (if they are heated) so as to reduce the quantity of liquid necessary to fill the sealing chamber.

My invention further relates to manufacturing paper wherein the fibers are not weakened and the size in the paper is not injured or damaged due to drying at high temperatures.

-. My-invention furtherrelates to manufacturing colored paper and drying it without substantially impairing the coloring matter and mordants used in the paper. Among other advantages this insures that the paper will have bright colors, which will be substaiitially uniform in different runs of paper,

permitting matching of colored paper without any appreciable difference in tone or color.

My invention further relates to certain steps, and combinations of steps, also to certain elements and combinations of elements, whereby the method or processes herein described may be carried out, as well as to certain details of construction, all of which will be more fully hereinafter. described in the specification and pointed out in the claims.

The accompanying drawing which is partially diagrammatic illustrates one, but notthe only, form of my apparatus, by the use of wihich my improved method may be practice The figure is a vertical section of one form of my improved Vacuum apparatus in which 7 the web of paper or similar materiahis fed -which are preferably partially immersed in I chamber A is formed between the base member B, the upper body member C and the side, walls, not shown. An entrance passage E sion of air into the vacuum chamber A, by

the liquid sealing medium 3. I prefer to use mercury for the liquid vacuum seal, but contemplate any liquid Which will effectively seal the openings against the admission of air into the chamber, and which has no aflinity for the material to be dried.

Within the vacuum chamber are mounted rotating drying cylinders 2, 3 and .4 and rotating guide drums or cylinders 5 and 6.

The drying cylinders andguide drums are mounted in any suitable manner and provided with any suitable means for causing them to revolve at the required speed, and for heating the drying cylinders.

In describing my invention I will describe it as applied to sheet material in the form Y of paper, though it is to be distinctly understood that it is equally applicable to and covers drying sheet material in the form of textile fabrics as for example, drying such fabrics after they have been washed or bleached or dyed, or otherwise treated'by' a liquid of some description.

In the ordinary drying .of a web of wet paper such high heat is used as to injuriously affect the fibers of the paper, and in case the paper is colored it will materially affect the coloring matter and 'mordants used. In drying paper in thehigh temperatures used in ordinary practice it often affects the size, so that the resulting paper varies in quality, is not uniform, and is not a perfect product.

-My invention is particularly adapted to dry the wet web of paper as it comes from the wet end of a paper machine, and will be so described in this application. In the manufacture of some classes of paper the web is fed, as for example, in the manufacture of news, at the rate of about 500 to 700 feet a minute. This web has to be dried as fast as it is fed from the paper machine. If

it is not, or if any breaks occur, which are known 1n shop parlance as broke, the web will pile up to the ceiling in a short time,- foul the machine, require the stopping of the as the case may he, passes over the guide roll 7, and into the liquid seal 3 through the and an exit passage entrance passage E under the guide roll 8, and thence in contact with the surface of the guide drum 5, while it is traveling in a vertical direction through the seal 3. It then leaves the guide drum 5 at the point 9, at a tangent to the guide drum 5 and in a horizontal plane, and almost immediately engages with the drying steam heated cylinder 2. It is completely dried by this and the other heated drying cylinders 3 and 4 and passes out of the vacuum chamber A around the guide drum 6, through the seal 3, be-

neath the guide roll 10, out through the seal 3 may be of any suitable material which has no affinity for or deleterious effect on the web to be dried. Preferably I employ a seal of mercury but any amalgam, or other liquid having the characteristics above set forth may be used. The interior of the sealing chamber 12 is preferably formed in arcs of circles, the center of which are the axles of the cylinders 5 and 6 respectively. These guide drums 5 and 6 may actsimply to guide the paper, or in addition thereto they may be heated in any manner, as by steam, when they perform the additional function of heating the paper and in effect become one of the drying cylinders, the same as 2, 3 and 4.

When a Web of paper is fed through a sealing medium unsupported, it hasa tendency to wave and flap. If this waving and flapping is suflicient for the web to engage with the fixed non-moving portion of the vacuum chamber, as for example, a portion of the ill) as time is one of the most important factors.

Even if the waving or flapping of theweb, while passing through the liquid seal and before it is taken up by one of the drying cylinders, is not sufficient to cause it to engage with the side of the sealing chamber-which might breakthe web, it causes the fibers to rearrange themselves so that when the paper is dried it has an undesirable crinkle. This crinkle, as previously described, is more or less pronounced depending upon the amount of the waving or flapping of the web in its passage into the vacuum apparatus.

By my invention the web 1 is fed almost immediately on its entrance into the liquid seal 3 into contact with the rotating guide drum or cylinder 5, which is traveling at the same rate of speed as the web. The web will cling to this guide drum during its vertical passagefthrough the seal and until it emerges from the liquid seal 3, in

the vacuum chamber A, when almost"immediately itpasses onto the first of the driers 2, so that there'is' no waving or flapping of the' web and consequently the lia-' ility of broke from this cause is ractically obviated. The undesirable crink ing'of the paper is also prevented. I i

The required degree of vacuum within.-

the vacuum chamber 8, preferably about 28 inches is maintained in any suitable-manner, such as by connecting the pipes 12, 12-

with any suitable vacuum apparatus.

Almost all paper mills are located on a stream of water or other abundant supply.

of water. With such a supply of cold Water a barometric .condenser or eductor type of condenser may be used to maintain the vacuum without the use of'an air pump. The cost of maintaining the, vacuum is. practically negligible and the cost'of the apparatus itself is very low. a p

My method possesses manyladvanta es not present in processes .heretoforeused or many years in the drying of paper.- The evaporation process, which is charact'eristic of the so-called loft drying of paper, has manyfully recognized disad-,

39 vantages, and yet it is used today and has been in use for many years. In this method the wet paper is taken from the paper ma-.

chine, cut into sheets, hung on poles, car

ried'to the drying'room where it is subjected to hot air at about 130 F. for about mw arately calendered'. Although .possessing.

' such machine, the wet paper as it comes from the paper machine, is passed over many 48 hours, and when dry, eachsheetis septhe a'dvantage of drying at a comparatively low temperature, whereby the moisture is slowly evaporated, loft drying is obviously very ineflicient and costly, because it requires many separate manipulations, is ex.-'

tremely slow, uses extensive floor space and wastes heat.

The process which is employed in the ordinary paper machine in common use, is likewise subject to many disadvantages. In

revolving cylinders, heated internally by steam to sufiiciently high degree of heat, to raise the temperature of the water in the paper to 212 F., the atmospheric boiling point of water. It is customary to supply the drying cylinders with steam at approxt 1 losses, as well as those incident to leaks in the iping system and other ineificiencies, the cat actually required for atmospheric drying of a ton of wet paper, is very much in excess of the theoretical requirement.

The thermal efficiency of atmospheric drying by steam heated cylinders is therefore very low. Furthermore, the steam pro- "duced from boiling the water out of the paper, is driven off into the. operating room, and although fans and exhausters are employed, at large expense for power and maintenance, the room atmosphere is so constantly saturated with moisture as to rust I 'andultim'ately destroy all iron and steel materials, and produces an exceedingly dis agreeable and unhealthy atmosphere in which to work. It is well .known that the minimum temperature 212, the atmospheric boiling point of water, is positively injurious to, and results in oxidizing, the fibres of the paper, the strength of which is vastly improved when the paper is dried at lower temperatures, as in loft drying.

This atmospheric drying process requires large initial cost for cylinders, felts, and

other necessary equipment, and extensive floor space, and resultsin the consumption of large amounts of power, and great cost for operation, maintenance and repairs.

In my improved vacuum drying method I contemplate m'aintainingwithin the chamher a vacuum of about 28" of mercury, in

which waterboils at F., and supplying the drying cylinders with. steam at 5.3 pounds gaugepressure, producing a temperature of 228 F. The temperature difference between the temperature of the steam in the cylinders and that ofthe paper, is therefore, 128 F. in my vacuum method, or '8 times greater (16 F. 8::128 F.) than the temperature difference in atmospheric drying. In my im roved method the paper dries approximate y 8 times faster than in atmospheric drying, and I require,

only about one-eighth the number of drying cylinders to dry paper at the same rate of speed. I am able to dry paper with 5 cylinders in the same timerequired of 40 cylinders drying at atmospheric pressure, re-

sulting in, great economies in cost of the machine,,floor space and of necessary piping,

felts, auxiliary equipment, and particularly in power and maintenance charges.

The thermal efliciency of my vacuum method is very much greater than that of the atmospheric cylinder drying heretofore in universal usev for drying paper. ically, it requires about 5287 pounds of steam to dry one ton of paper at atmospheric pres-' sure, but to compensate for convection and conduction losses, and those due to leaks in the piping system, and other inefficiencies, it has been shown in practice that about 10,600 pounds are required.

Theoret- In my method, using a vacuum of about 28", the convection, conduction and piping losses are exceedingly small and the total steam required to dry 2. ton of paper by my method is approximately 5200 pounds.

It is an established fact that paper dried at low temperatures is much stronger than when it is dried at the high temperatures used in paper machine atmospheric drying. Paper dried in a vacuum of 28", or at a temperature of about 100 'F., as in my method, is very much stronger than paper dried at atmospheric pressure, when the steam in the driers is at 228 F. WVhen paper is dried by my method, therefore, a cheaper furnish can be used and still produce a paper equal in strength to atmospheric dried paper, in which a higher grade furnish is used. In making newsprint paper, I am able to dispense with a considerable portion of the more expensive sulphite pulp, as this can be replaced with the cheaper ground wood pulp. By my method I also reduce thenumber of breaks in the web as it passes over the cylinder.

Furthermore, in my method, there is a great saving of heat (or steam) because the process is carried on in avacuum chamber which acts on the principle of a thermos b'ot-. tle, and the steam and vapors driven out of the wet paper are caught in the closed vacuum chamber, and conducted away to the condenser. The operating room is free from steam, humidity and heat, and fans, and exhausters are dispensed with. In the use of my method the apparatus is at all times operating under definite humidity, the control of the drying can be closely standardized, and the moisture content in the paper carefully regulated.

Having pointed out the many advantages of my method and apparatus Over those heretofore used, it will be apparent that the use of my invention results in great economy in the initial costof apparatus and in large savings in cost of operation,'maintenance and repairs.

Having thus described this invention "and'adapted to guide the web in a vertical seal, and then out of said seal into the vacu- --ping and waving of the web and crinkling of the paper, said method consisting in passing the web into the liquid of the seal and into contact with the partly immersed cylinder and then out of said liquid while still in con-v tact with the cylinder.

.2. The method of feeding a wet web of $5 paper or similar material into a vacuum drying chamber consisting in feeding it through and out of a liquid seal of the vacuum chamber while in contact with a rotating heated guiding and drying member.

3. The combination in a vacuum drier, of liquid seal, a vacuum chamber, driers, and rigid means to prevent the material to be dried from flapping or Waving while passing through the liquid seal into the vacuum chamber. v

4. The combination in a vacuum drier of a liquid seal, a vacuum chamber, driers, and guide drum partially immersed in the seal direction while in contact with said drum and through the seal into the vacuum chamher to prevent flapping or waving of the web while passing through the seal.

5. The method of drying a web of paperand preventing the flapping and waving of the web and crinkling of the paper, consisting in passing it into the seal and into contact with a cylinder partly immersed in the um chamber while still in contact with the cylinder, drying the web in the vacuum chamber, and withdrawing the web through the liquid seal while in contact with another guide cylinder partly immersed in the seal.

OGDEN MINTON.

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