US1595480A - Method and apparatus for drying sheet material - Google Patents

Description

Aug. 10 1926.

O. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL Original Filed Jan. 20, 1922 5 Sheets-Sheet 1 IAVEgTOR tlnx IORNE Y Xe $40M &

Aug. 10 1926.

' O- MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL 5 Sheets-Sheet 2 Original Filed Jan. 20, 1922 7,, VI W r f gm X a g m4 J y gg ORNE Y Aug. 10 1926.

o. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL 5 Sheets-Sheet 5 5 lzms zvrolg BY Y 6044a Qifiy A ORNEY Aug, 10 1926. 1,595,480

- 0. MlNTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL Original Filed Jan. 2 1922 5 Sheets-Sheet 4 a A/Ja 6 3 a gz 'w fix MW .ORNE Y- Aug. 10 1926, 1,595,480

0. MINTON METHOD AND APPARATUS FOR DRYING SHEET MATERIAL orilinal Filed Jan. 20, 1922 5 Sheets-Sheet 5 7 ,2 7. 0 Q/ 4 y o f N 0 O O O Y 7 O 2/ 6 P7 1261 5 m Patented Aug. 10, 1926.

UNITED STATES OGDEN MINTON, OF GREENWICH, CONNECTICUT.

METHOD AND APPARATUS FOR DRYING SHEET MATERIAL.

- Application filed January 20, 1922, Serial No. 530,665. Renewed February 17, 1926.

The present invention relates to an apparatus and method for the drying of paper and other sheet materials.

My improved method consists in passing 6 the sheet material, which is to be dried, intov a vacuum chamber through a liquid sealing medium which has no afiinity for the material, subjecting it to heat to drive off its contained moisture and then passing the dried material out ofthe chamber through a seal.

' This method may be practiced by the use of various forms of apparatus, some of which are 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 liquid sealing medium which has no allinity 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 and out of the chamber. The heating elelnents within the vacuum chamber, for drying the material, the shape, form, dimensions and location of the liquid .seal containers, and the means for passing the sheet material through the chamber, may all vary.

1 have shown herein a number of varieties which I contemplate using.

This application is a continuation in part of my pending applications Serial Nos.

350,233, filed January 8, 1920, Case A, and Ser. No. 384,212, filed May 25, 1920, Case J.

The accompanyingdrawings, which are partly diagrammatic, illustrate several, but not the only, forms of my apparatus, by the use of which my improved method may be practiced.

Fig. 1 is a vertical section of one form of apparatus by which my improved method may be practiced;

Fig. 2 is a vertical section of one of my improved steam doctors;

Fig. 3 is a vertical section of another form provided with one container, for the sealing medium of such shape and dimensions as to receive revolvingdrums for passing the sheet material:

Fig. 4 is a vertical section of another form similar to that of Fig. 3, provided with endless felts to pass the sheet material through the vacuum chamber;

Fig. 5 is a vertical section on an enlarged scale through a portionof the felts and sheet material as it passes through the sealing medium of Fig. 4;

Fig. 6 is a vertical section through another form of apparatus, provided with two vertical containers for the sealing medium;

Fig. 7 is a vertical section of another form provided with only one container for the sealing medium, but with entrance and exit passages;

Fig. 8 is a vertical section of another form provided with endless felts operating within the chamber for pressing the sheet material into contact with the drying drums;

Fig. 9 is a vertical section of another form provided with endless felts operating partly within'and partly without the vacuum chamber;

Fig. 10 illustrates a form of apparatus in which the heating medium in the vacuum chamber consists of a liquid having neither afiinity for nor deleterious efiect upon the material to be dried.

In the form of apparatus, shown in Fig. 1, for practicing my improved method, the vacuum chamber A is formed between the base member B, the upper body member C, and the side walls, not shown. An entrance passage E into the vacuum chamber is formed between the upturned wall D of the base member and the dependingcurved wall F of the upper body member C, and an exit passage E from the vacuum chamber is formed between the upturned flange D of the base member and the depending curved wall F of the upper body member. The entrance and exit passages are sealed against the admission 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 affinity for the material to be dried.

Within the vacuum chamber are mounted rotating drying cylinders 4, 5, 6, 7 and 8, and rotatin guide drums 9 and 10. The drying cylinders and guide drums are mounted in any suitable manner and provided with any suitable means for causing them to revolve at a required speed, and for heating the drying cylinders.

A convenient, but not the only means for passing the sheet material through the vacuum chamber, consists in the system of endless felts, shown in Fig. 1. The upper felt 11 is caused to move, in the direction of the arrows, on the rollers 12 outside the chamber, and, moving through the entrance opening E and the liquid seal 3, passes around the guide drum 9 to the drying cylinder 4, to the guide roller 13, to the drying cylinder 6, to the guide roller 14, to the drying cylinder 8, to the guide drum 10, through the liquid seal 3 and out of the chamber through the exit opening E. The lower felt 15, is caused to move, in the dH'eCtlOll of the arrows, on the rollers 16, 17 outside the chamber, and, moving through the entrance opening E and the liquid seal 3, passes around the 18, to heating cylin er 5, to guide roller 19, to heating cylinder 7, to guide roller 20, to guide drum 10, through the liquid seal and out of the chamber through the exit opening E.

In its passage through the drying apparatus, the web 1 of paper, or other sheet material, is fed between the felts 11 and 15 and passes between the felts partly around drum 9, the web 1 with the felt 11 passing up to cylinder 4 and the felt 15 passing to roller 18. As the wet web tends to cling to the felt, means 22 may be provided, if desired, at this point to strip the web 1 from the felt 15 and direct it against the felt 11 which with the web 1 passes around cylin der 4, the felt passing to roller 13 and the web, which also tends to cling to the heated surface of the cylinder, may be caused to leave both surfaces and to descend and be caught between the felt 15 and the surface of the cylinder 5. Moving around cylinder 5 the felt 15 moves to roller 19. The web 1 may be caused to leave the felt and the heated surface of the cylinder 5 and to ascend and be caught between the felt l1 and the heated surface of cylinder 6. To over come the tendency of the web to cling to the felts and the heated surfaces of the cylinders and to guide the passage of the end of the web from one cylinder to the next in advance in the series, and particularly from one below to the next above, I may use the steam doctors 22.

One form of steam doctor is shown in Fig. 2 so located as to strip the web from a cylinder 7 and then direct the web in an upward direction. Preferably the doctor is of suflicient length to extend across the cylinder, at least to cover the width of the web and felts. It is provided with a steam supply passage 26, from which extends the port 27 to the toe 28, and the ports 30, 31

uide drum 9 to roller and 32, leading upward toward the head 33 When the doctor is mounted near a heating ploy them the steam issuing from the doctors dries the end of the web and makes it firm so that the web can be more readily threaded through the apparatus. If a steam doctor is employed the steam from the doctor also assists in drying the web in passing through the vacuum chamber.

To assist, if desired, the passage of the web from one cylinder to the next cylinder in advance, I may locate one doctor near the cylinder and another on the opposite side of the web near the felt. The toe jets 27 in each doctor will strip the web from surfaces of the cylinder and felt and the body jets 30, 31 and 32 impinging on both sides of the web will assist in directing its movement and carry the end of the web forward to the next cylinder.

be carried upward from one cylinder to the next in the series located above. a

In Fig. 3 the wet web 1 passes-into the "acuum chamber A through the entrance passage E over the guide roller 36 under the submerging roller 37 in the liquid seal thence in contact with rotating guide drum 9, rotating drying cylinders 4, 6 and 8, then over the rotating guide drum 10 through the seal 3, under the submerging roller 38 and out through the exit passage E and then over the guide roller 39.

In this form of my invention the web 1 is dried by direct contact With the rotating drying cylinders l, 6 and 8, and also the rotating guide drums 9 and 10 should these be heated, without the aid of a felt or felts.

I preferably arrange the rotating guide drums 9 and 10 partially submerged as shown for if a web of paper is fed through a sealing medium unsupported, it has a tendency to wave and flap. If this Waving and flapping is suflicient for the web to engage with the fixed nonmoving portion of the Vacuum chamber, the web is apt to cling to or be retarded by the fixed surface of the chamber with which it contacts. This will cause a break in the web or broke. This serves to foul the machine, requiring rethreading and delays which are very ex- This is adv \'antageous where the end of the web must llh pensive in the manufacture of paper, as

time is one of the most important factors.

Even if the waving or flapping of the web, while passing through the liquid seal and before it is taken u by one of the drying cylinders, is not su cient to cause it to engage with the side of the sealing chamber which might break the web, it causes the fibers to rearrange themselves so that when the paper is dried it has an undesirable crinkle. This crinkle is more or less pronounced depending upon the a" iount 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 9, which is traveling at the same rate of speed as the web. The web will cling to this guide drum during its vertical passage through the seal and until it emerges from the liquid seal 3, in the vacuum chamber A, when almost immediately it passes onto the first of the dryers .4, so that there is no waving or flapping of the web and consequently the liability of Broke from this cause is practically obviated. The undesirable crinkling of the paper is also prevented. Mounting the rotating guide drums so as to be partially submerged in the liquid seal necessitates using only a comparatively little sealing medium 3.

In Fig. 4, I have shown substantially thesame form of apparatus as illustrated in Fig. 3, except that the web 1 is fed over and around the rotating guide drums 9 and 10 and the rotating drying cylinders 4, o and 8.by means of the upper felt 11 and the lower felt 15.

Both felts 11 and 15 meet at the entrance passage E and receive the wet web 1 between them. They then, with the interposed web 1, pass through-the seal 3 over the rotating guide drum 9. The upper felt 11, with the web 1, then passes over the rotating drying cylinder 4, the web being in contact with the cylinder. In leaving the cylinder 4 the web 1 contacts with the drying cylinder 6 being pressed into contact with it by the lower felt 15 which after leaving the drum 9 passes over the guide rollers 41, 42, thence around the rotating guide drum 10, submerging roller 38, out through the exit passage E, over the guide rollers 17, 16

back to the entrance passage E to again engage with the web 1.

The upper felt 11 after passing over the rotating drying drum 4 is led over, but not in contact with, the rotating drying cylinder 6 by passing over the guide rollers 43, 44, 45 and 46, thence around the rotating drying drum 8 in contact with the web 1, thence over the rotating guide drum 10 under the submerging roller 38, out of the exit passage E and over the guide rollers 47 and 48 back to the entrance passage E.

It will, therefore, be seen that in this form of my invention the web 1 passes over the rotating guide drums 9 and 10 interposed between the felts 11 and 15, but in passing over the rotating drying cylinders 4, 6 and 8 it contacts directly with each of said drying cylinders.

Figs. 6, 8 and 9 illustrate other forms of drying apparatus in which the base B is provided with sealing medium containers X formed by vertical walls Y, the U-shaped entrance passage E and exit passage E .to and from the vacuum chamber being formed between the vertical walls of the containers and the depending flanges P of the body member C.

In this form of my invention the web 1 passes over the guide roll 36 through the entrance passage E into the liquid seal 3 under the submerging roll 37 and up into the vacuum chamber and in contact with the rotating heated drying cylinders 4, 5, 6, 7 and 8 and out through the exit seal 103 under the submerging roller 38 over the guide roller 39. and is then preferably immedis-jely rolledinto a finished roll or reel of paper 48.

In Fi 7 is shown a form of vacuum drier provided with a single sealing medium container X, the entrance and exit passages to and from the vacuum chamber belng provided between the vertical walls Y of the container and the depending flanges P of the body member C.

In Fig. 8 both the lower endless felt 15 and the upper endless felt 11 are within the vacuum chamber A and do not pass out through the entrance and exit 1i uid seals 3 and 103 respectively, as in someo the other forms o my invention. The lower felt 15 presses the web 1 against the rotating drying cylinders 5 and 7 and passes over the guide rollers 49, 50, 51, 52 and 53. The upper felt 11 presses the web 1 into contact with the rotating drying cylinders 4, 6 and 8, and passes over the guide rollers 54, 55, 56, 57, 58 and 59.

In Fig. 9, I have shown a form of my invention similar to Fig. 8 except that the endless felts 11 and 15 pass into and out of the vacuum chamber A with the web 1 through the entrance and exit passages E and E, respectively, and through the liquid seals 3 and 103 respectively, protecting each of said passages. After passing under the submerging roller 37 both upper and lower felts, with the interposed web 1, pass up to the guide rollers 60 and 61. The web 1 and the upper felt 11 pass over the rotating drying cylinder 4,the felt pressing the web into contact with the drying cylinder. The

web 1 then passes over the drying cylinder 5, cooperating with the lower endless felt 15. It then passes overthe drying cylinder 6 while in contact with the upper endless felt 11. this felt having passed over the guide rollers 62, 62. The upper felt passes around the drying cylinders 6 and 8 and then in lot contact with theguide roller 65, submerging roller 38, guide rollers 66, 66 back to the entrance passage E, The lower felt after )tISSlIIg over the guide rollers 63, 63 rotating rying cylinder 7, guide roller 64, submerging roller 38 and guide rollers 39, and 67, 67 again passes over the guide roller 36.

Fig. 10 illustrates a form of my vacuum drier, in which the heating medium for drying the sheet material consists preferably of t acteristic of the so-called loft d1 1n mercury or of any other liquid having neither affinity for, nor deleterious effect upon, the material. As shown, the liquid iscontained within the vacuum chamber, separated from the sealing medium, and is heated byany suitable means. I have shown a device for passing the sheet material through the liquid seals and then through the liquid heating medium. The apparatus shown in Fig. 10 is particularly useful in the manufacture of high grade papers.

In this illustrative embodiment of my invention the web 1 passes over the guide cylinder 36, into the entrance passage E beneath the submerging roller 37 in the liquid seal 3, thence into the vacuum chamber A over the guide rollers 69, 70 and then into the heating liquid bath 71 under the roller 72, thence out over the guide rollers 73, 74 through the exit liquid seal 3 under the subnierging roller 38 and out of the exit passage E. over the guide roller 39, where the web is preferably, though not necessarily, immediately rolled into the finished roll of paper 48.

The roller 7 2, may or may not be heated. Preferably the mercury or equivalent liquid bath 71 is heated by passing steam, products of combustion or other source of heat through the passage 75.

The liquid of the seals 3, 3 may be heated if desired by any suitable means as by steam pipes 76, 76 though these, of course, may be omitted without departing from my invention.

In all forms of my invention the vacuum chamber A is connected with pipes 77, 77, leading to any suitable vacuum apparatus to maintain a partial vacuum. in the Vacuum chamber.

I also preferably provide the casing C of the vacuum chamber with one or more windows 78 that the operator may at all times see within the chamber.

My improved method, particularly adapted, though not confined, to the drying of paper, consists in taking the wet web of paper as it comes from the paper making machine, and either before or after sizing or coloring the web, passing the Web into a vacuum chamber through asealing medium,having neither affinity for, nor del eterious effect upon, the material of the web, and subjecting it while in the .vacuum to direct contact, with the heated surface of rotating cylinders, or with a liquid having neither aflinity for, no deleterious effect upon, the material, whereby the contained moisture is driven off, and then passing the dry material out of the chamber through the sealing medium.

My method possesses many advantages not present in processes heretofore used for many years in the drying of paper.

The evaporation process, which is char 0 paper, has many fully recognize disadvantages, 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 machine, cut into sheets, hung on poles, carried to the drying room where it is subjected to hotair at about 130 F. for about 48 hours, and when dry, each sheet is separately ealendered. Although possessing the advantage of drying at a comparatively low temperature, whereby the moisture is slowly evaporated, loft drying is obviously very inefficient and costly, because it requires many separate manipulations, is extremely 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 such machine, the wet paper as it comes from the paper machine, is passed over many revolving cylinders, heated internally by steam to sufficiently 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 approximately 5.3 pounds gauge pressure, at which the steam has a temperature of 228 F. giving a difference of temperature (228- 212) of only 16 F. With this slight difference of temperature the transfer of heat is extremely slow, and hence it is necessary to employ many drying cylinders, in board machines often one hundred, and in news print machines, forty or more.

Also due to convection and conduction losses, as well as those incident to leaks in the piping system and other inefliciencies, the heat actually required for atmospheric drying of a ton of wet paper, is very much in excess of the theoretical requirement. The thermal efliciency of atmospheric drying by steam heated cylinders is therefore very low. Furthermore, the steam produced from boiling the water out of the paper, is driven off into the operating room. and although fans and exhausters are em ployed, at large expense for power and maintenance, the room atmosphere. is so constantly saturated with moisture as to rust and ultimately destroy all iron and steel materials, and produces an exceedingly disagreeable and unhealthy atmosphere in which to work. It is well' known that the minimum temperature 212, the atmospheric boiling point of water, is positlvely injurious to, and results in oxidizing, the fibres of the paper, the strength of which is vastly improved when the paper 1s dried at lower temperatures, as in loft drying. This atmospheric dryin process requires large initial cost for cy inders, felts, and

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

Some of the modern open air driers are equipped with a blower system by which air, either heated or not, is blown throu h the dryer sections, which will lower t e temperature at which the water is evaporated from the paper much below 212 F. and may, in some cases, reduce the temperature of evaporation as low as 180 F. or lower.

In my improved vacuum drying method I contemplate maintaining within the chamber a vacuum of about 28" of mercury, in which water boils at 100 F., and

' supplying the drying cylinders with steam at 5.3 pounds gauge pressure, producing a temperature of 228 F. the temperature difference between the temperature of the steam in the cylinders and that of the paper, is therefore, 128 F. in my vacuum method, or 8 times greater (16 F. 8= 128 F.) than the temperature difference in atmospheric dryin In my improved method the paper dries approximately 8 times faster than in atmospheric drying, and I require only about one-eighth the number of drying cylinders to dry paper at 4 the same rate of speed. I am able to dry paper with 5 cylinders in the sametime required of 40 cylinders drying at atmospheric pressure, resulting 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 efficiency of my vacuum method is very much greater than that of at atmospheric cylinder drying heretofore in universal use for drying paper. Theoretically, it requires about 5287 pounds of steam to dry one ton of paper at atmospheric pressure, but to compensate for convection and conduction losses, and those due to leaks in the piping system, and other ineificiencies, it has been shown in practice that about 10,600 pounds are required.

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 1!. ton of paper by my .method is approximately 5200' pounds.

It is an established fact that paper dried still produce a paper equal in stren h to atmospheric dried paper, in which a igher grade furnish or stock is used. In making newsprint paper, I amab-le to dispense with a considerable portion of the more expensive sulphite pulp, as this can be replaced with the chea er ground wood pulp. By my method I also reduce the number 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 a vacuum chamber which acts on the principle of a thermos bottle, and the steam and vapors driven out of the wet pa or are caughtin the closed vacuum cham er, 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 cost of apparatus and in large savings in cost of operation, maintenance and repairs.

Having thus described this invention in connection with illustrative embodiments thereof, to the details of which I do not desire to be limited, what is claimed as new and what is desired to secure by Letters Patent is set forth in the appended claims.

What I claimis:

1. The method of drying sheet material which consists in passing the wet uncoated sheet material into a vacuum chamber through a liquid sealing medium which has no affinity for the sheet material, subjecting the sheet material in the vacuum chamber to a separate body of heated liquid having no afiinity for the sheet material, and passing the sheet material out through a sealing medium.

2. The method of drying sheet material which consists in passing the wet uncoated sheet material into a vacuum chamber through a liquid sealing medium which has no afiinity for the sheet material, subjecting the sheet material in the chamber to the surface of a heated cylinder, and pass ing the sheet material out through a sealing medium.

3. The method of drying sheet material which consists in passing the wet uncoated sheet material in contact with one or more endless felts into a vacuum chamber through a liquid sealing medium which has no aflinity for the sheet material, subjectlng the sheet material in the'vacuum chamber to heat to drive off the contained moisture, and passing the felts and the dry material out through a sealing medium.

4. The method of drying sheet material which consists in passing the wet uncoated sheet material in contact with one or more endless felts into a vacuum chamber through a liquid sealing medium which hasno affinity for the sheet material, sub ecting the sheet material in the vacuum chamber to heat and to the stripping action of steam ets to strip the wet sheet material from felts and driers and direct its movement, and passing the felts and dry sheet material out through a sealing medium.

The method of drying paper which consists in passing the web of paper into a vacuum chamber through a sealing medium which has no affinity for the paper, subjecting the paper in the vacuum chamber to heat and to the stripping action of steam jets to strip the paper from felts and driers and direct its movement, and passing the dry paper out through a sealing medium.

6. The method of drying paper which consists in passing the web of paper in contact with one or more felts into a vacuum chamber through a liquid sealing medium which has no aflinity for the paper, subjecting the paper in the vacuum chamber to heat and passing the dry paper out through a sealing medium.

7. The method of drying paper which consists-in passing the web of paper in contact with one or more felts into a vacuum chamber through a sealing medium which has no afiinity for the paper, subjecting the, paper in the vacuum chamber to heat and to the stripping action of steam jets to strip the paper from felts and driers and direct its movement, and passing the dry paper out through the sealing medium.

8. The method of drying paper which consists in passing the web of paper in contact with one or more felts into a vacuum chamber through a mercury seal, subjecting the paper in the vacuum chamber to heat to drive off the contained moisture, and passing the felts and dry paper out through a mercury seal.

9. The method of drying paper which consists in passing the Web of paper in contact with one or more felts into a vacuum chamber through a mercury seal, subjecting the paper in the vacuum chamber to heat and to the action of steam jets to strip the wet sheet material from felts and driers and direct its movement, and passing the d paper and felts out through a mercury sea 10. An apparatus for drying sheet material comprising a closed chamber having entrance and exit passages, means to form a partial vacuum in the chamber, a liquid seal for said passages which has no atlinity for the sheet material, and means located within the chamber and spaced away from the liquid seal for heating the sheet material.

11. An apparatus for drying sheet material comprising a closed chamber having entrance and exit passages, means to form a partial vacuum in the chamber, a liquid seal for said passages which has no afiinity for the sheet material, one or more cylinders within the chamber for heatingthe sheet material, and means for heating the cylinders.

12. An apparatus for drying sheet material comprising a closed chamber having entrance and exit passages, means to form a partial vacuum in the chamber, a liquid seal for said passages which has no afiinity for the sheet material, a liquid within the chamber separate from said liquid seal and having no aflinity for the sheet material, means for heating the said liquid and means for passing the sheet material through said heating liquid.

13. An apparatus for drying paper comprising a closed chamber having entrance and exit passages, means to form a partial vacuum in the chamber, a mercury seal for said passages and Ireans located within the chamber and spaced away from the mercury seal for heating the paper.

sisting of a vacuum chamber and liquid sealing means through which the material passes into and out of said vacuum chamber, the liquid of said sealing means having no afiinity for the sheet material, and one or more heated drying cylinders mounted in the vacuum chamber.

15. An apparatus for drying sheet material consisting of a vacuum chamber and mercury sealing means throu h which the material passes into and out 0 said vacuum chamber, and one or more heated drying cyl inders mounted in the vacuum chamber.

16. An apparatus for drying sheet material consisting of a vacuum chamber and liquid sealing means through which the material passes into and out of said vacuum- 14. An apparatus for drying paper conliquid sealing means through which the material passes into and out of said chamber, the liquid of said sealing means having no affinity for the sheet material, endless felts for passing the sheet material through the said vacuum chamber, means for directing the endless felts, and one or more heated drying cylinders mounted in the vacuum chamber.

18. An apparatus for drying sheet material consisting of a vacum chamber and liquid sealing means through which. the material passes into. and out of said chamber, the liquid of said sealing means having no afiinity for the sheet material, endless felts for passing the sheet material through the vacuum chamber, one or more heated drying cylinders mounted in the vacuum chamber, and means within the chamber for directing jets of steam against the sheet material to strip it from said felts and drying cylinders and direct its movement.

19. An apparatus for dryin sheet material consisting of a vacuum c amber and mercury sealing means through which the material passes into and out of said chamber, endless felts for passing the sheet material through the vacuum chamber and one or more heated drying cylinders mounted in the vacuum chamber.

20. An apparatus for drying sheet material consisting of a vacuum' chamber and mercury sealing means through which the material passes into and out of said chamber, endless felts for passing the sheet material through the vacuum chamber, a heating liquid within said vacuum chamber having no affinity for the sheet material which is passed through it, and means for heating said liquid.

21. An apparatus for drying sheet material consisting of a vacuum chamber and mercury sealing means through which the material passes into and out of said vacuum chamber, endless felts for passing the sheet material through the vacuum chamber, one or more heated drying cylinders mounted in the vacuum chamber, and means within the chamber for directing jets of steam against the sheet material to strip it from said felts and drying cylinders and direct its movement.

22. The method of drying a web of paper consisting in passing it into a vacuum chamber through a liquid seal which has no affinity for said web, passing the web while in the chamber over one or more revolving heated drying drums to dry, flatten, and give a smooth finish to the web, pressing said web of paper into contact with said heated drying drums, and thenpassing said dry, flat and smooth web of paper out of the chamber through a liquid seal which has no aflinity for said web.

23. The method of drying paper consisting in passing the web of the paper in contact with one or more endless felts into a vacuum chamber through a liquid sealing unedium which has no affinity for, or deleterious efiect upon the paper, drying said web in said vacuum and withdrawing the dry web of paper and the felts from the vacuum chamber through a liquid sealing medium having the same charactertistics as that first mentioned.

- OGDEN MINTON.

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