US 3675337 A
A drum structure for drying a sheet of material characterized by having means to control the heating profile along the length of the drum and thus control the amount of heat applied across the width of the web or paper being engaged by the drum. To control the heating profile, the rate of heat transfer of the heating medium such as steam is varied along the axial length of the drum by selectively mixing a non-condensible medium with the heating medium to reduce the rate of heat transfer. In one embodiment of the drum structure, the drum is provided with a plurality of sub-chambers formed by axially spaced interior partitions which sub-chambers enable control of the rate of heat transfer to the drum surface associated with each sub-chamber. In another embodiment, the inner surface of the drum is provided with axially spaced grooves and the drum has a second header for a non-condensible medium, which header has means to introduce the non-condensible medium to each groove to control the rate of heat transfer at the groove.
Claims available in
Description (OCR text may contain errors)
United States Patent Duane [451 July 11, 1972 54} DRYER DRUM  ABSTRACT  Inventor. Robert A. Deane, Rockford, Ill.
A drum structure for drying a sheet of material characterized 1 Asslgneei mm by having means to control the heating profile along the length 22 Fred: N of the drum and thus cotrol the amount of heat applied l l M acres the width of the web or paper being engaged by the  Appl. No.: 88,930 drum. To control the heating profile, the rate of heat transfer of the heating medium such as steam is varied along the axial length of the drum by selectively mixing a non-condensible  US. Cl. ..34/4l, 34/124,l|665 /9l(S medium with the Mining Mum m reduce the rate of heat s I] in CI mb 5 transfer. in one embodrme' nt of the drum structure, the drum is provided with a plurality f mh b f d b i ll  dd mil "34/41, I I9, [24, 165/90, 9| spaced inerior partitions which subchambus bk ni l Rd of the rate of heat transfer to the drum surface associated with each sub-chamber. In another embodiment. the inner surface UNITED TATES of the drum is provided with axially spaced grooves and the s PATENTS drum has a second header for a non-condensible medium, 3,492,741 2/1970 Witworth .3411 24 which header has means to introduce the non-condensible 1,594,718 8/1926 Fulton ....34ll24 medium to each groove to control the rate of heat transfer at 2,792,643 5/l957 Guy ....34Il24 the groove. 3.241.251 3/1966 Justus et a1. ..34/124 Primary Examiner-Carroll B. Dority. Jr. 8 Clairm, 3 Drawing figures ArtomeyHill, Sherman, Meroni. Guns 8: Simpson /2 I 1 .zz I I 1 I 1 I I I I I l i i t /7 /l PMENTEDJ L 11 I972 3.675 337 sum 2 nr 2 Fig-'3 DRYER DRUM BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention is directed to a dryer drum and a method of drying sheet material and particularly a web of paper material.
2. Prior Art In presently known devices for drying paper webs or sheets of material, the paper web or the sheet of material is engaged across its width by one or more internally heated drying drums. For various reasons, the drying device does not dry the aper webs across its width with a uniform rate of drying.
SUMMARY OF THE INVENTION The present invention is directed to a dryer drum structure and a method of drying sheet material which utilizes means for controlling the heating profile along the axial length of the drum so that the heat applied across the width of a sheet of paper web by the drum can be controlled to obtain a desired drying profile across the web of paper being dried by the drum. In one embodiment of the invention, the means for control are a plurality of axially spaced partitions forming a plurality of sub-chambers in which the rate of heat transfer of each sub-chamber can be controlled to control the rate of heating of the drum surface. ln another embodiment of the present invention, the means for controlling includes a plurality of axially spaced grooves on the inner surface of the drum with means for supplying a non-condensible medium to the grooves to change the rate of heat transfer in the particular grooves.
Accordingly, it is an object of the present invention to provide a dryer drum having means for controlling a heating profile along the axial length of the drum.
Another object of the present invention is to provide a method of drying sheet material including controlling the profile of the rate of drying of the material across its width.
Other objects, features and advantages of this invention will be readily apparent from the following description of the preferred embodiments taken together in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the scope and spirit of the novel concept of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross sectional view taken along the axis of one embodiment of the dryer drum of the present invention;
FIG. 2 is a partial axial cross section of another embodiment of the dryer drum of the present invention; and
FIG. 3 is a view with portions in elevation for purposes of illustration taken along the line III-III of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the principles of the present invention are of utility for controlling the heating profile of any hollow heating unit, the principles are particularly useful when incorporated in a dryer drum, generally indicated at 10, as illustrated in FIG. 1, utilized to dry at web of paper II during paper making operation.
The dryer drum I has a cylindrical shell 12 which contacts the sheet of material or web of paper II during the drying of the material. The shell 12 at each end has an end plate I3 which is secured to the shell by conventional means such as bolts 14 to define an internal chamber I5. Each of the end plates 13 has a hub portion 16 having bearing surfaces 17 which receive support means for supporting the drum for rotation and the hub may include means for connecting the drum to a source of rotational movement.
To heat the dryer drum I0, a steam conduit or pipe 18 extends along the axis of the drum 10. As illustrated, pipe I8 has a plurality of steam nozzles 19 axially spaced therealong and the pipe is supported by bearing means 21 in each of the end plate hubs 16. To prevent the loss of steam from the chamber 15. seal means 22 is provided at the end of one hub and seal means 23 is provided at the end of the other hub to sealingly engage each end of the conduit 18. The bearing means 2I enable the drum I0 to rotate relative to the pipe 18 and thus the pipe 18, as illustrated, is stationary.
The pipe 18 is connected adjacent the seal means 23 to a supply pipe 24 extending to a source of heat transfer steam. At the other end adjacent the seal means 22, the steam pipe or conduit 18 receives a drain line 25 which extends concentrically through the pipe to substantially the center of the chamber 15 where it is connected to a drain means 26 for draining condensate from the chamber 15. The drain means 26 can be a siphon-type drain means and an example of siphon-type drain means is illustrated and described in the U.S. Pat. No. 2,993,282, issued to R. A. Daane and E. J. Justus on July 25, I961.
The steam passed through the nozzles 19 heats the cylindrical shell 12 and the end plates 13 and in the process of heating forms a condensate. The condensate due to the speed of rotation of the drum I0 accumulates as a cylindrical layer adjacent to the interior surface 27 of the shell 11. The siphon or drainage means 26 due to the difference in pressure in the chamber 15 and the pressure in the drain line 25 siphons the condensate from the chamber 15.
When drying a web of paper II with a dryer drum, the rate of drying across the width of the web is not always uniform. For example, the edge portions of the web may dry at a faster rate than the center portion.
To control the rate of drying across the web of the paper, the drum I0 is provided with means for controlling the profile of heating along the axial length. As illustrated in FIG. I, the means for controlling includes a plurality of axially spaced partitions 28 which are attached to the steam pipe I8 to sub divide the chamber I5 into three sub-chambers, a center subchamber 30 between the two partitions 28, and an end subchamber 31 adjacent each of the end plates I3. Each of the partitions 28 is provided with peripheral openings 33 which are illustrated as an annularly extending space between the peripheral edge of the partition 28 and the inner surface of the shell 12.
The means for controlling the profile of heating also includes means for introducing a non-condensible medium such as air into predetermined sub-chambers such as 31. As illus trated, the means for introducing air includes an air supply line 35 extending inwardly from each end of the steam pipe I8 with such line 35 terminating at an air nozzle 36 that discharges into a chamber 31. Each of the air supply lines 35 is connected to a source of air under pressure and has a valve 37 for controlling the amount of air flowing through the line 35 and the nozzle 36 which air is heated by steam in the pipe I8.
By adding a non-condensible medium such as air to the chamber 31 and allowing it to mix with the steam entering through the nozzle I9, the efficiency of the heat transfer of the steam heating the shell I2 is reduced. Thus the adding of air to the chamber 31 lowers the rate of heat transfer to the portion of the shell I2 which is associated with the chamber 31.
The partition 28 maintains the steam or steam and air mixture in each of the sub-chambers 30 and 31; however, the openings 33 allow a portion of condensate to move between the chambers and to the system 26 for removal from the drum. The size of the openings 33 and their coaction with the condensate in each of the sub-chambers 30 and 31 limit the flow of the steam or steam and air mixture across the partition 28 and between the sub-chambers. Thus the heating medium in each of the sub-chambers 30 and 31 is substantially isolated from the heating medium in the adjacent sub-chambers and rate of heating to the portion of the shell I2 associated with each sub-chamber can be controlled and made different from the rate of heating in the other sub-chambers. Thus, by controlling the heating characteristics of the heating medium in each sub-chamber by controlling the amount of air added to the heating medium, will vary the heating profile along the axial length of the dryer drum l0.
In the dryer drum of FIG. I. only the sub-chamber 31 has air nozzles 36. By adding air to the heating medium in each sub chamber 31. the rate of heat transfer in the sub-chamber can be reduced below the rate of heat transfer in the center subchamber 30. By changing the rate of heat transfer, the end portion of the shell associated with the sub-chamber 31 will receive the heat of the steam at a lower rate than the center portion and thus a web of paper 11 which is being engaged by the dryer drum l will have more heat applied to its center portion than to its edge portion. By selecting different rates for heat transfer, the heating profile of the roll along its axial length can be controlled so that the rate of drying of the web or paper ll will be substantially uniform across its width.
As illustrated. the steam pipe 18 supporting the steam nozzles 19, the drain means 26 and the drain line 25 along with the air lines 35, air nozzles 36 are stationary with respect to the rotating shell 12 and end plates 13 of the dryer drum 10. If desired, the end structure of the pipes 18 along with the drain line 25 and the air lines 35 can be provided with appropriate connections to enable relative rotation so that the structure disposed in the chamber of the dryer drum rotates with the dryer drum. If the partitions 28 and steam pipe 18 rotate with the shell 12, the partitions can be provided with connections to the inner surface 27 of the shell 12 to provide additional supports. However. if the partition and the steam pipe 18 are stationary, the peripheral clearance such as the peripheral opening 33 is required to enable the relative rotation between the drum shell ll and the partition 28.
Although only two partitions 28 are illustrated to create three subchambers. additional partitions could be used to increase the number of sub-chambers. Each sub-chambers can be provided with means for adding a non-condensible medium such as air and means to control the amount of air added could be provided for each of the sub-chambers.
Another structural embodiment of a dryer drum having means for controlling the heating profile along the axial length of the drum is generally indicated at 50 in F165. 2 and 3 and has a cylindrical shell 51. The drum 50 can either be constructed with a structure similar to the drum 10 of FIG. 1 with end plates, steam lines. air lines and drain lines or constructed with a structure similar to the drum illustrated and disclosed in U.S. Pat. No. 3,241.25 l issued to E. l. Justus and R. A. Daane on Mar. 22, l966.
The shell 51 has a plurality of axially spaced grooves 52 on the inner surface and the steam condenses in the grooves 52 to heat the portion of the shell 5] associated with each of the grooves. Each groove 52 has a a root surface 53 and radially extending side walls 54.
To remove the condensate from the grooves, a drain means having a header 55, which is connected by a conduit 56 to a drain line of the drum has a plurality of small tubes 57 with a tube extending into each of the grooves 52. The small tubes 57 remove the condensate from each of the grooves 52 and the condensate is then drawn into the header 55 and then through the conduit 56 to the drain line.
To control the heating profile along the axial length of the drum 50, a second header 60 which is connected by a conduit 61 to a source of non-condensible medium such as air supplied to the interior of the drum 50 by an air line similar to 35 of FIG. I. is provided and extends parallel to the axis of the drum 50. The header 60 has a plurality of axially spaced tubes 62 which are arranged with one tube extending into each groove 52. The tubes 62 act as an air nozzle for discharging air into each groove 52 at the root surface 53. The air discharged into the groove 52 will be concentrated at the root surface 53 and the side walls 54 of the groove will limit the fiow of the air into the adjacent grooves. By appropriate means such as providing a construction in the tubes 62, the amount of air discharge from each tube 62 into its respective groove 52 can be selectively varied.
As in the previously described embodiment, the addition of air to the steam in the grooves 52 will lower the rate of heat transfer and enable a change in the amount of heat transferred through the root surface 53 to the shell 51 adjacent the groove 52. By varying the amount of air discharged into each groove 52, the heating profile of the shell 51 can be varied. Thus. by arranging each tube 62 to discharge the desired amount of air for a given air pressure in the header 60, the heating profile along the length of the drum 50 can be controlled to be a predetermined profile which is best suited to achieve the desired uniformity of drying of the web of paper.
Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.
I claim as my invention:
1. A dryer drum comprising:
a cylindrical shell;
end plate heads secured to the shell to provide a closed chamber;
means for supporting the drum for rotation;
means for delivering heat transfer steam to the chamber along the axial length thereof; and
means for controlling the heating profile along the axial length of the shell including means for supplying a noncondensible medium to predetermined portions of the closed chamber to lower the rate of heat transfer of the steam in the predetermined portions.
2. A dryer drum according to claim 1. wherein said controlling means include means dividing said chamber into a plurality of sub-chambers and wherein said means for supplying a non-condensible medium introduces the non-condensible medium to predetermined sub-chambers to lower the rate of heat transfer of the steam in the predetermined sub-chambers.
3. A dryer drum according to claim 2. which further include means for removing condensate from the inner surface of the shell and said means for removing condensate is disposed in the sub-chamber which is equally spaced from each of said end plates and said means dividing said chamber includes means enabling transfer of condensate between the su b-chambers while limiting the transfer of the steam and non-condensible medium between said sub-chambers.
4. A dryer drum according to claim 2, wherein said means dividing said chamber comprises:
partitions extending transverse to the axis of said shell. said partitions having means defining openings adjacent the inner surface of said cylindrical shell for transfer of condensate between the sub-chambers whereby during operation, the condensate in said sub-chambers blocks said opening means to limit the flow of steam and noncondensible medium across said partitions.
5. A dryer drum according to claim 1, wherein said controlling means includes a plurality of axially spaced grooves provided on the inner surface of the cylindrical shell and wherein said means for supplying a non-condensible medium is arranged to introduce the non-condensible medium at a predetermined rate to each of said grooves so that the rate of heat transfer at each of the grooves is varied by the rate of introduction of the non-condensible medium thereto.
6. A dryer drum according to claim 5, wherein each of the grooves is provided with means for removing the condensate therefrom.
7. A dryer drum according to claim 5, wherein said means for supplying a non-condcnsible medium includes a header disposed in the chamber and extending parallel to the axis of the shell. said header being connected to a source of non-condensible medium and having a plurality of tubes extending therefrom, each of said tubes extending to one of the grooves and terminating adjacent the root thereof so that the non-condensible medium can be discharged adjacent the root of the respective groove.
8. A method of drying a web of sheet material by surface contact with a steam heated, horizontally disposed rotating cylinder drum comprising the steps of heating the cylinder drum by distributing steam to the interior of the drum to provide a supply of uncondensed portions to lower the rate of heat transfer at these portions to obtain the desired heating profile along the length of the drum to insure the desired application of heat across the width of the web of material to control the rate of drying across the width of the web of material.
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