US1854956A

US1854956A - Paper drier

Info

Publication number: US1854956A
Application number: US436307A
Authority: US
Inventors: Sidney A Reeve
Original assignee: Beloit Iron Works Inc
Current assignee: Beloit Iron Works Inc
Priority date: 1930-03-17
Filing date: 1930-03-17
Publication date: 1932-04-19
Anticipated expiration: 1949-04-19

Description

April 19, 1932. 5 REEVE v 7 1,854,956

PA'PER DRIER Filed March 1'7, 1930 4 Shgets-Sheet l (fidngyfl Baez/e.

April 19, I932. s. A. REEVE PAPER DRIER 4Sheets-Sheet 2 Filed March 17, 1930 YEWZT:

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I April 19, 1932. 5, REEVE 1,854,956

PAPER DRIER Filed March 17, 1930 4 Shegts-Sheet 3 A I \l' Fo nmcocnmmma' Evan/kvr:

April 19, 1932. s. A. REEVE 1,854,956

PAPER DRIER Filed March 17, 1950 4 Sheets-Sheet 4 YEW/532*: fia'drzgz eeuey Patented Apr. 19, 1932 UNITED STATES PATENT OFFICE SIDNEY A. BEEVE, OI ORAN GETOWN, NEW YORK, ASSIgNOR TO BELOI'I IRON WORK S, OF BELOIT, WISCONSIN, A CORPORATION OF WISCONSIN PAPER DRIER This invention relatesto a paper machine and more particularly to a paper machine wherein both the Wet and dry ends of the machine are totally enclosed within a substantially air-tight housing or casing to permit the substantial exclusion of air from Within the casing and permit the effecting of a considerable economy of heat in the drying operation.

The art of drying paper as heretofore practiced may logically be divided into three classifications; (1) drying under purely atmospheric conditions without the application of artificial heat; (2) drying paper 1n an open type drier by contact between the wet Web of paper and traveling heated surfaces, such as drier drums. and (3) dryingrpaper 1n a totally enclosed drier unit under vacuum.

The purely atmospheric type of drier wherein no artificial heat is employed would obviously require a tremendous amount of space in which to complete the drying of the paper, or if unheated rolls were employed for supporting the paper web during the air drying operation. a very large number of such rolls would be necessary to take care of the output of an ordinary present day paper machine.

The use of the steam heated, unenclosed drier, as compared with the purely atmospheric type of drier. would permit a considerable diminution in the number of drier drums required but the fuel efiiciency of the open type of steam drier drum drier unit is relatively low owing to the fact that heat is expended not only in evaporating moisture from the paper web but also in heating the surrounding air. Thus in this type of drier, the size of drier unit is reduced at the expeuse of fuel cost.

In the third type of drier. wherein the.

drying operation is carried out in an enclosed chamber under vacuum. a reduction both in the size of the drier umt. 1. e. in the area of of this type of drier is relatively high due to the necessity of an air-tight casing and seals, vacuum pumps and the like. F urthermore, although a considerable saving in fuel is effected using this vacuum type of drier, as compared with the steam heated, unenclosed type, it is nevertheless evident that,

since all of the water in the paper is evaporated entirely by means of applied heat, the fuel economy is not great as should betheoretically possible, as will later be evident froma consideration of my invention as hereinafter described.

While the development of the paper drier through these three classes or stages represents a very marked progress in the art of drying paper, it is nevertheless pointed out that such progress has been undertaken with reduction in the size of equipment as its main aim and with fuel economy as a secondary gain and without a full recognition of the further possibility for substantial additional savin in fuel both for heating and power purposes, provided the desidera tum of size and first cost of construction be abandoned.

In other words, reviewing past progress the moisture in the paper. In passing from the second stage to the third, the gain has again been primarily in smaller size of drier in paper drying through the three steps just equipment with an incidental reduction of fuel consumption back to about 1.00% of that theoretically required for directly evaporating the moisture in the paper.

The present: invention contemplates sacrificing som'whatwinitial cost of construction and-size of paper machine in order to obtain greater fuel efficiency. In order to dothis I make use of the principle of multiple effect evaporation, a principle which to the best of my knowledge has never heretofore-been applied to the drying of paper. I furthermore compartments, contrasted degrees of pres utilize the coolei atmosphere at the wet end sures may be obtained with substantial exclusion of air or air maybe admitted to one or more compartments with the provision of a heat interchanging air regenerator for utilizing the heat of the air within the casing to preheat the air admitted to the casing.

It is accordingly an object of the present invention to provide a paper machine that is entirely enclosed and that is divided into different sections or compartments which may be operated under contrasted conditions of pressure to obtain the advantages of multiple efi'ect evaporation.

It is a further lmportant object of this invention to provide an enclosed sectional drier from which air is substantially excluded and in which steam generated from the moisture contained in the paper web in one section is utilized in the drying or heating element of another section, whereby a great economy in heat consumption for effecting the drying of the paper may be realized.

It is a further important object of this invention to provide as one section of the enclosed drier unit, high pressure steam coils in place of the usual drier drums It is a further important object of this invention to provide a paper machine and housing therefor enclosing the entire machine and means for drawing steam generated from the moisture in the paper as it traverses a portion of the driers towards the extreme wet end of the machine to effect a substantial condensation thereof and the heat interchange between such steam and the paper stock on the forming portion of the machine. It is a further object of this invention to save fuel byenclosing all or a part of the drier drums in a substantially air-tight casing, not subjected to vacuum, through which air is circulated, the heat abstracted therefrom'being utilized to preheat the incoming air, instead of to evaporate moisture in drier compartments of lower pressure.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings.

This invention (in apreferred form) is more fully described. On the drawings:

The drawings as a whole represent diagrammatically an entire paper machine embodying the various features of my invention.

Fi ure 1 is a side elevational view, with the side of the casing removed, of afour (lrinier forming part of a paper machine embod ying my invention.

ligure 2 is a continuation of Figure 1 showing the presses, the details of which form no part of my'invention but this figure is included to show a continuous machine.

Figures 3 and 4 are similar continuations' of Figures 1 and 2 showingintermediate drier sections. v

Figure 5 is a side elevational view of a drier section containing high pressure steam coils;

Figure 6 is a continuation of Figure 5 showing l:he end of the drier unit and calender sta-c Figure 7 is a side elevational view of a modified form of the drier compartment shown in Figure 6.

As .shown on the drawings:

The reference numeral 1 indicates as a whole a Fourdrinier paper making machine which is, in accordance with my invention, entirely enclosed within a housing or casing 2. The paper machine '1 comprises the usual main sections of amachine of this type, viz.', a fourdrinier 3, presses 4 and a drier 5. All of these sections are included within the main casing 2, which is itself preferably divided into separate sections or' compartments: compartment A including the forming part 3, the press part 4 and a portion of the drier drums of the drier part 5; a

compartment B constituting the middle drier section; compartment C housing high pres: sure steam coils 6: and compartment D constituting an equalizing chamber from which the paper passes ofl of the paper machine to a calender stack 7 It will be understood that the division of the paper machine housing into compartments is a more or less arbitrary one and that fewer or more compartments may be provided.

v The forming podion of the aper machine, which is supported from a ooring 9, may be of a conventional type, including a head box 10, a Fourdrinier table structure 11, flat stationary suction boxes 12 and a suction couch roll 13. A forming wire 14 is trained in the usual manner around a breast roll 15,

over table rolls 16, the fiat boxes 12 and I around the suction couch roll 13, the under or lower run 'ofthe wire being supported by various idler and tension rolls 17. I

In accordance with'my invention, stock is. admitted into the head box 10 of the paper machine through a piping 18, in which is provided a valve 19 and a loop or sinuous bend 20,

both of which serve to control and throttle down the flow of stock to the head box 10.

The entire compartment A in which is housed the forming part 1,'press part 4 and portion 5 of the drum driers, is maintained under a suitable vacuum, preferably as high as can be practically maintained. It is for this 1'83,"

' suction couch roll 13, water is extracted from the stock to form the moist web of paper, indicated by the reference numeral 22. The white water collecting under the table rolls 16 in a save-all 23 is discharged through a pipe 24 leading into a white water pump (not shown), positioned in the basement.

Vacuum is maintained within the casing A by means of one or more suction pumps 100 having a branched intake 101 connected to the flat boxes by means of pipes 27 and 28 and tothe suction chamber of the couch roll 13 by a pipe 29. Said intake'of the pump 100 is likewise connected by a pipe'30 through an automatic reducing valve 31 to the upper extreme end of the casing 2. The reducing valve 31 in the pipe 30 is set to impose asmall difference in pressure between the interior of the suction boxes 12 and of the suction chamber within the couch roll 13, on the one hand, and the interior of the compartment A. Because of this difference being vbut slight, the suction boxes may be given a larger area than usual. The vacuum pump 100 connected to the

pipes

27, 28, 29 and 30 may be regarded as the equivalent of the vacuum pump forming a part of all Fourdrinier machines, being merely somewhat larger for the attainment of a. higher vacuum, but not absorbing necessarily much more power.

Inasmuch as compartment A includes a number of steam heated drier drums 33, there is, of course, a considerable amount of steam or water vapor formed within this compartment from the moisture in the heated web of paper and as all of this water vapor is drawn to the wet end of the compartment A by compartment A and contacts the stock and various showers in the press part 4 and forming part 1. To aid in removing the condensed water and to further insure condensation of the water vapor from the air removed from compartment A, a partition or bafile 34is pro vided above the head box 10 extending the width of the casing and a plurality of conduits 103 are arranged to pass throu h the head box 10 to connect the underneat portion of the Fourdrinier section with the part of the compartment immediately adjacent the pipe 30. In this way, all of themoisture laden air must pass through or around the vari-' ous sprays on the paper machine beforefinding an exit through the pipe 30, with the result that substantially all of the moisture is condensed out and removed. Any moisture condensing in the conduits 103 drains by gravity into the save-all 23.

The paper web 22 passes from the couch roll 13 onto the first press felt 35, through the first set of presses 36 and thence to the second press felt '37. After passingthrough the second set of presses 38, the direction of the web 14 is reversed and the web passed through the third set of presses 39, from which it passes in a relatively dry state into the nip between the first bottom drier drum 40 and the lower drier felt 41- (Figure 3-). The paper web 22 passes around the lower drier drum 40 and between the upper drier felt 42 and first upper drum 43 and thence around the remaining upper and lower drum in the usual maner until it reaches the end of compartment A. Compartment A is divided from compartment B 'by means of upper and lower partitions, 44 and 45 respectively, and seals 46 and 47 joined thereto. Said seals 46 and 47 may suitably comprise flexible metal plates 48 having rounded edges 49 and pivoted to a supporting plate from the partitions 44 and 45 as at 50 and 51, respectively. The particular form and construction of the seals 46 and 47 form no part of the present invention.

The paper web 22 passes in a similar man-' ner over and around the drier drums contained in compartment B and through-a similar sealing mechanism, designated as a whole by the reference numeral 52 into compartment C.

Compartment G houses, in place of the v usual drier drums, a system of high pressure steam coils 6 arranged. in horlzontal tiers. In order to support the paper web in spaced relation to the steam pipes or coils 6, plates ous travel around the various rolls, such as the rolls 54 and 55, in their passage through com-.

partment C. Each of the plates 53 may be formed of wire-reinforced glass or any other suitable translucent material which will serve to. transmit radiant heat.

From compartment C, the web 1s led through 'a seal, designated as a whole by the reference numeral 57 into a, relatively small compartment D in which are housed a plurality of steam drier drums 58. From the compartmentD, the paper web'passes out through a sealing mechanism 59 to the calender stack 7.

Compartment D may be operated as an outying portion of section B or may be operate at its own peculiar pressure with its drums supplied with exhaust steam from any incidental source.

Thearrangement of the drier sections will now be explained. High pressure steam is admitted to the pipes or coils 6 in compartment C through a pipe 60 and after traversing the'various coils of the system, the condensate is discharged through a bottom pipe 61, which may suitably lead to a trap (not shown) for the removal of condensate, and whatever steam may inadvertently escape is to be led by suitable connections (not shown) into pipe 62, thence to the driers 58 in the compartment D. In operation, the steam admitted to the coils 6 in the drying system of com artment C may be superheated and at areliitively high pressure, say 150 to 200 lbs. per sq. in. Heat radiated from the steam pipes 6 causes the evaporation of the mositure contained in the paper web, but at this heat is largely radiant heat, the paper web is not necessarily raised to any high temperature corresponding with that of the steam in'the coils and naturally this is so, as long as the paper web contains any moisture in it at all.

Under these conditions, the temperature of the paper web must remain at about the temperature'of saturated steam correspond-v ing with the pressure Within the chamber C, although the web maybe receiving radiant heat at short range having a temperature 100 or more higher than the aforesaid temperature. Under such conditions, the web is in danger of beingoverheated only should it .come into contact with the high pressure steam coils, but this is precluded by the provision of translucent plates between the steam coils and the traveling web of paper being dried.

There is thus produced an atmosphere of dry steam within the casing C, which steam may or may not be superheated but is preferably kept under a super atmospheric pressure, the pressure being as high as it is practical to build the casing to withstand. The

steam thus generated from the mositure contained in the paper web is conducted from the upper portion of the compartment 5 through a conduit 62 to the drier drums in compartment B. I

The conduit 62 may serve as a header to which the drier drums in section Bare connected by means of individual pipes 63, or

a part of the drier drums in said compart ment B may be connected In series to the conduit 62. A

therefore necessary that compartment B be Steam generated from the web of paper as it passes through compartment B is conducted from saidicompartment by means of a pipe or conduit 64 and branch pipes 65 to the drier drums in compartment A. It is maintained under less pressure than compartment C and under greater pressure than compartment A. For instance, if compart-' ment C is maintained under 30 lbs. gage pressure,-compartment B might be maintained under a pressure varying from atmospheric to a few inches of vacuum and compartment A might be maintained under the highest vacuum practicable. By this arrangement, there is obtained' in substance a multiple effect evaporation of the moisture or water contained in the paper web. Such construction with the accompanying multiple efi'ect mode of operation develops fuel efliciency to the maximum.

Compartment 'D constitutes a kind of equalizing chamber or look between the high pressure compartment 0 and the atmosphere. A pressure relief valve 67 maintains a pressure within compartment D only slightly above atmospheric and from it'steam generated from the paper Web within said compartment may be conducted through a. pipe 68 into the conduit 62 or into the conduit 64. Valves 69 and 7 O are provided for controlling the disposition of the steam passing through the relief valve 67. Any other supplies of steam necessary to the operation of the driers may be conducted to the suitable c01npartmo ment through these same valves. I

It should be noted that the arrangement of graduated ressures in the various compartments an of; seals separating the compartments is conducive to a relaxation of the efficiency of the seals, such as is required in the types of vacuum drier now in use. The primary seal between the highest vacuum, viz. that in compartment A, and the atmosphere, is-maintained by the valve 17 and the no seal .provided by the solid column of Water or stock ahead of said valve 17.- The seal 59, which is the only seal of appreciable dimension which connects the interior of the housing with the atmosphere, is subject 'to internal steam pressure from within the coinpartment D, so that whatever leakage may occur here flows outwardly constituting merely a loss of so much steam. Leakage through the seals between the various compartments n impose an extra load upon the vacuum pump The seals 46, 47 52 and 57 merely seal vapor against vapor. If they leak, neither steam heatnor vacuum is lost thereby but merely a fractionalavailability of the steam I with resultant loss of slight fuel efiiciency. The steam leakage past the seal 59 may take the place, in part, of the usual sweat rolls, which serve to recondition the paper after being dried.

Such a construction as above described would develop fuel efiiciency to the maximum, consuming theoretically only about one-third of the steam consumed by known types of vacuum driers now in use, or about one-quarter of the steam consumption of the usual type of open driers. Furthermore, the incidental operative cost, as for vacuum pump, power, and thelike, would be not more and probably less than the corresponding cost in the operation of the present type of vacuum driers. The size and initial cost of a machine of my invention, however, would 'be relatively large as compared with the present type of vacuum drier, owing to the more drier drums and the enclosing of t e entire paper machine necessity or usin rather than the drier unit only.

As shown in Figure 7, one or more of the compartments of the drier unit, such as the compartment D, may be provided with means for circulating air through the drier compartment and with means for reutilizing the heat of the exit air and gases, which otherwise would be lost, in the preheating of the air admitted to the compartment.

For this purpose, a fan or blower 105, having an intake pipe 106, is connected by means 7 of a discharge pipe 107 through a heat interchanging air regenerating device 108 to the compartment D, preferably to the lower portion of said compartment as at 109. Another pipe 110 leading from near the top of the compartment D, conducts the exit air and gases from said compartment through the heat interchanging device 108 where a por tion or all of the heat of the exit gases is given u to the incoming air. The gases are ally 'scharged from the heat interchanging device 108 through a discharge pipe 111.

It will be understood that any conventional type of heat interchanging device may beused for efiecting the utilization of a portion of the heat contained in the exit gases from the compartment D for preheating the incoming air. By this arrangement, eflective air circulation can be maintained within the compartment D without resulting in a loss of heat values such as normally occurs in the open or unenclosed type of steam paper drier units. The compartment D will, of course, be maintained under substantially atmospheric pressure so that there will beno necessity for expensive sealing mechanism or air-tight casing construction.

While the provision of air circulating and heat interchanging means hasbeen shown only in connection with a single compartment, it will be understood that other :com-

partments may be similarly arranged. If

-a housing section enclosin this same principle be applied to the entire machine and the machine enclosed but not provided with evacuatlng devices, with the air circulated through the casing in the manner described, then it is evident that such a drierunit combines the features of the t pe of dr er previously dlscussed wherein no uelis wasted in heating'air and also the advantage of economy in area of drier surface offered by the type of drier wherein the drier unit is composed of steam heated drums not enclosed within a casing. This modified form of drier of my invention eliminates the waste of heat of the open type of drier unit and also the necessity of expensive apparatus as required in the vacuum, enclosed type of drier unit.

I am aware that many changes may be made and numerous details of construction may be varied through'a wide range without departing from the principles of this inven tion, and I, therefore, do not purpose limiting-the patent granted hereon otherwise than necessitated by the prior art. a I

I claim as my invention: a

I. The combination with a paper machine, of a substantially air-tight housing therefor completely enclosing both the wet and dry ends thereof.

2. The combination with a paper machine, of a housing therefor completely enclosin both the wet and dry ends thereof, .sai

said wet end and compelling theflow of white water therefrom. v 4 4. In a completely enclosed paper machine a housin section enclosing the Wet end of the machine and some of the driers.

5. In a completely enclosed paper machine, the wetend of the machine and some 0 the driers and means for creating a vacuum within said housing section.

6. In a completely enclosed paper machine, a housing section enclosing the wet .end of the machine andsome of the driers and means including a vacuum pump connected to fiat suction boxes and a suction couch roll of the machine for creating a vacuum within said housing section.

7 In a paper machine, a sectional housing enclosing the dry end thereof, heatingmeans 8. In a paper machine, a sectional housing enclosingthe dry endthereof, heating means in the compartments of said. housing so formed, means for leading steam generated from the moisture contained in'the paper from one section to the heating means of a passage of paper therethrough and meansfor maintaming said compartments under difierent pressures.

10. In a paper machine, a sectional: hous-.'

ing therefor forming compartments and means for maintaining said compartments under diiierent pressures ranging from subatmospheric at the wet end to super-atmospheric towards the dry end.

11. In a pa er machine, a sectional housingtherefor orming compartments, means for maintaining said compartments under different pressures ranging from a lower pressure at the wet end to a higher pressure towards the dry end, heating means within the compartments of the dry end and means for conducting steam generated from the moisture contained in the paper from one compartment to the heating means in a lower pressure compartment.

12. In a paper machine includin a Fourdrinier section, a press section an a drier section, a housing completely enclosing the paper machine, partitions and seals divlding said housing into compartments, one compartment enclosing the fourdrinier, press section and a group of driers, other compartments enclosing groups of drying elements, and means for maintaining said compartments under contrasted degrees of pressure.

13. In a paper machine including a Fourdrinier section, a press section and a drier section, a housing completely enclosing the paper machine, partitions and seals dividing said housing into com artments, one compartment enclosing the ourdrinier, press section and a group of driers, other compartments enclosing groups of drying elements, means for maintainingv said compartments under contrasted degrees of pressure and means for conducting steam generated in a higher pressure compartment to drying elements in a lower pressure com artment.

14. Inca paper machine inc uding a forming portion and a drier, a housing completely enclosing the forming portion and drier, partitions and seals between groups of the dr ing elements permitting the passage of tli compartment to drying elements in a comnausea paper web through the compartments thus ormed, the drying elements in. one such compail'tment comprising high pressure steam (301 s. 15. In a paper machine including a forming portion and a drier, a housing completely enclosing the forming portion and drier, artitions and seals between groups of the rye ing elements permitting the passage of the paper web through the compartments thus '75 formed, the drying elements in one such compartment comprising high pressure steam coils and means for conducting steam generatedfrom paper passing through said one partment of lower pressure.

16. 1n a paper machine, a sectional housing therefor, high pressure steam coils in one section thereof and translucent means for supporting the paper web adjacent to but spaced from said coils.

' 17. In a paper machine, a sectional housing therefor, high pressure steam coils in one section thereof, means for supportingthe paper web adjacent to but spaced from said coils, drier drums in another section of said housing and means for conducting steam generated from the paper web in the one section into said dried drums.

18..In a paper machine, an enclosed drier section from'which air is substantially exeluded, partitions and seals dividing said drier section into a plurality of compartments, heating elements in each compartment and means for maintaining said compartments under graduated pressures.

19. In a paper machine, an enclosed drier section from which air is substantially excluded, partitions .and seals dividing said drier section into a plurality of compartments, heating elements in each compartment, means for maintaining said compartments under graduated pressures ranging from sub to super atmospheric toward the dry end and means for leading steam generated from 0 moisture in the paper in a higher pressure compartment to the heating elements in a lower pressure compartment.

20. In a paper machine,.an enclosed drier section from which air is substantially exeluded, partitions and seals dividing said drier section into a plurality of compartments, heating, elements in each compartment, means for maintaining said compartments under contrasted pressures graduated from sub to super atmospheric toward the dry end, high pressure steam coils in a su eratmospheric compartment and means leadlng steam generated from moisture in the paper in said -superatm0spheric compartment into a.pre-

ceding lower pressure compartment.

- 21. In a paper machine, an enclosed drier section from which air is substantially e xeluded, partitions and seals dividing said drier section into a plurality of compart-- mimosa ments, heating elements in each compartment, means for maintaining said compartments under contrasted pressures graduated from sub to super atmospheric toward the dry end, high pressure steam coils in a superatmospheric compartment, steam drier drums in a preceding sub-atmospheric compartment and a conduit leading steam generated from moisture in the paper Web in said superatmospheric compartment into said drier drums.

22. In a Fourdrinier paper machine including a wet and dry end, a substantially air tight casing completely enclosing said wet and dry ends and sealing means at the ends of said casing against the admission of air thereinto.

23. In a Fourdrinier paper machine including a Wet and dry end, a substantially air tight casing completely enclosing said wet and dry ends, sealing means at the ends of said casing against the admission of air thereinto and means for creating contrasted degrees of pressure within said casing.

24. In a Fourdrinier paper machine including a wet and dry end, a substantially airtight casing enclosing the entire machine,

partitions and seals dividing said easing into compartments, one compartment enclosing the wet end and a portion of the driers 1n the dry end, and means for partially evacuating said compartment.

25. In a Fourdrinier paper machine includinga wet and dry end, a substantially alrtight casing enclosing the entire machine, partitions and seals dividing said easing into compartments, one compartment enclosing the wet end and a portion of the driers in the dry end, means for partially evacuating said compartment, another compartment enclosing a portion of the drier drums, means for maintaining a lesser vacuum in said second compartment and means conducting steam generated from moisture contained in.

paper in said second compartment into the drier drums of said first compartment.

26. A paper machine including a Fourdrinier having flat suction boxes and a suction couch roll, comprising a substantially air-tight casing for said machine, a vacuum pump, a branched intake thereto connected in parallel to said suction boxes, couch roll and to the wet end of saidcasing and a constant pressure difierence valve in the connecexchanging contact with the wet end of the machine.

29. A .paper machine, a casing therefor, driers at the dry end thereof for evaporating moisture from the paper web, a head box for incoming stock and conduits traversing said head box opening at their ends near the top and bottom'of said casing to drain condensate into the bottom of said casing. I

30. In a paper drier, a casing enclosing all or a part of the drier rolls, a heat interchanging air regenerator, and a fan blowing air through said regenerator into said casin at substantially atmospheric pressure, an then out, of said casing through said regenerator again, to impart its heat to the incom- 1110 an.

In testimony whereof I have hereunto subriybed my name at Nyack, Rockland County, SIDNEY A. REEVE;

tion leading from said pump to wet end of I said casing.

27. A paper machine, a substantially airtight easing therefor, including the wet end and a portion of the driers, a vacuum ump and a conduit connecting the intake 0 said pump to the wet end of said casing,

28. A paper machine, a substantially airtight casing therefor, driers therein at the dry end of the machine for evaporating the moisture from the paperweb and means for conducting the vapor thus formed into @heat