US3140930A - Belt conveyor drier for web material - Google Patents

Description

y 14, 1964 E. J. JUSTUS 3,140,930

BELT CONVEYOR DRIER FOR WEB MATERIAL Filed July 20, 1961 4/: 002' 4/! 0v 4/: ml 4/: 007

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United States Patent 3,140,930 BELT CONVEYOR DRIER FOR WEB MATERIAL Edgar J. Justus, Beloit, Wis., assignor to Beloit iron Works, Beloit, Wis, a corporation of Wisconsin Filed July 29, 1961, Ser. No. 125,405 9 Claims. (Cl. 34-456) The present invention relates to an improved mechanism and method for drying a moving paper web after it has left the forming section of a paper making machine.

In the usual paper machine dryer section, there are provided dryer drums such as a Yankee dryer or conventional dryer drums, each of which are cylindrical in shape and have heated outer cylindrical surfaces for carrying the paper web and heating it causing an evaporation of the moisture from the web. The paper web is first formed in the forming section by the deposit of a suspension of paper fibers on a forarninous surface and dewatering the fibers to form a web. After this forming section the traveling web passes to a dryer section which may first include other drying means such as press felts and which usually includes heated dryer drums as above described. The dryer drums necessitate the provision of bulky equipment requiring thermal energy such as provided by steam and require withdrawal of the condensate if steam is used. The rate of drying of the web is de pendent upon the rate of evaporation of water and this in turn is dependent upon the ability of the mechanism to transfer heat energy to the web and to remove the moisture bearing air for increasing evaporation rate. The rate of heat transfer is dependent upon the surface area of the drums in contact with the web. The drums have usually been arranged in a pattern so that the paper passes over their surfaces in a serpentine path inasmuch as it must be held in contact with the surfaces.

It is an object of the present invention to provide an improved method and mechanism for evaporating moisture from a paper web in a drying section of a paper making machine which makes possible the more rapid transfer of thermal energy to the moisture in the web to thereby increase the rate of evaporation and drying rate.

A further object of the invention is to provide a paper web dryer which makes possible the exposure of a greater area of the Web to a heating means in proportion to the volume of equipment required and thereby increases the rate of evaporation of water for a given machine space.

A still further object of the invention is to provide a drying mechanism which avoids the build-up of a layer of air at the surface of the web which is saturated with water vapor or at a high relative humidity which heretofore reduced the drying rate.

A further object of the invention is to provide an improved mechanism for a drying section of a paper machine which eliminates the need for heavy cast iron drying drums, which effects a saving in cost of construction and cost of operation, which obtains more uniform drying across the web, which eliminates the need for high pressure steam supply lines and condensate removal lines, and which is generally more efficient and effective.

As a feature of the invention, the method and mechanism contemplate running a web of paper or board through a dryer section of a paper machine which is constructed so that the web is held against surfaces arranged to provide a greater drying area than heretofore available. The dryer section includes provision of a forarninous surface for supporting the paper web with means for providing a pressure differential across the web such as by applying a suction beneath the forarninous surface, and providing a supply of heated air to the exposed surface of the supported web, which may be confined to the area by providing an enclosure or hood facing the outer surface of the supported area. No heated air passes through ice the web and the suction is utilized solely to hold the web to the supporting surface which can be arranged in a unique path for maximum heat transfer to the web. It has heretofore been necessary to arrange the drying path giving concern to holding the high speed traveling web on the drying rolls, and with heat transfer limited to time of contact with the cylindrical roll surfaces. Heat energy is transmitted to the moisture in the web by the heated air and a layer of saturated air is prevented from building upon the web surface by the moving warm air above the web. The suction holds the web to the foraminous surface permitting the use of long runs of supported Web area.

Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:

FIGURE 1 is a diagrammatic showing of a drying section of a paper machine constructed in accordance with the principles of the present invention; and

FIGURE 2 is a schematic diagram showing the sequence of several sections of a paper making machine.

As shown on the drawings:

As illustrated in FIGURE 2, in a paper making machine a paper web is formed in a forming section 9 which has a forarninous surface for dewatering a suspension of paper fibers supplied at 8. The formed paper web travels into a drying section 10 and on to further sections of the machine where the paper may be finished and may be handled such as by being slit and wound. These sections of the machine are fully appreciated by those skilled in the art and need not be described in detail.

The instant invention pertains to an improved portion of the drying section 10 in which water is taken from the Web of paper or board by evaporation from the surface of the web and it will be understood that the drying meth- 0d and mechanism may be provided as a part of the drying section, or in addition to other drying mechanisms but is well adapted to replacing devices such as dryer drums which take up more space and require more bulky heavier equipment. For example, the drying section 10 may include first water removing mechanism at 10a such as drying felts, and second mechanism at 1012 such as the mechanism shown in FIGURE 1.

In the arrangement shown in FIGURE 1, the web W, which is a paper web containing moisture and travelling through a paper making machine, is carried through a serpentine path on forarninous support surfaces which are in the form of Wires or belts carried on suction rolls. Suction rolls are provided at 22, 23, 24, 25, 26 and 27 and the web leaves the dryer section shown over a guide roll 28.

A first belt 29 is supported on the suction rolls 22 and 23, a second belt 30 is supported on the suction rolls 24- and 25 and a third belt 31 is supported on the suction rolls 26 and 27. The belts may be driven such as by driving the suction rolls through suitable drives, not shown, or may be driven through engagement with the moving web, and the belt surfaces move at the surface speed of the moving web.

Each of the suction rolls has a forarninous outer surface and is connected to means for applying a suction to the interior thereof. The mechanism for applying a suction may be of various types which will be fully appreciated by those skilled in the art and need not be described in detail. The letter S indicates suction within the rolls such as may be applied by a vacuum pump indicated at P. The belts or wires are also forarninous so that the space within them is subjected to the suction and so that the web W carried on the surface thereof will be subjected to the suction on its lower surface and a pressure dilferential will exist across the web. The suction is for supporting the web on the flat surfaces permitting high speed travel of the webs, with a reversal of their direction of travel without losing control of the web. The web is non-porous with respect to the air and a suction is applied to hold the web on the surface with no flow of air through the web. A suction which would cause any appreciable penetration of the paper or board by the air would effect a disruption of fibers or tearing of the web.

The exposed surface or outer surface of the Web opposite the surface supported by the belts is substantially at atmospheric pressure and is supplied with an atmosphere of heated air by hot air hoods or enclosing caps 32, 34 and 35 and the hoods are shaped so that they form an enclosure to extend over the exposed surfaces of the Web at the areas where the other surface is supported by the foraminous belts.

Thus for its run through the dryer section shown in FIGURE 1, one surface of the web is first subjected to a vacuum while the other surface is subjected to a hot air atmosphere for a portion of its run, and the environment is then reversed. Referring to the surface of the web W, first exposed to the hot air hood 32 as the outer surface, and the surface I, first exposed to the vacuum of the belt 29 as the inner surface, the outer surface 0 when it reaches the suction roll 24 becomes exposed to the suction of the belt 30 and the inner surface I becomes exposed to the heated air supplied by the hood 34. A shield or seal 37 is positioned at the location where the belt 29 runs onto the suction roll 22 so that the Web will be smoothly transferred to the belt 30. The suction roll 22 is provided With an arcuate inner shielding seal 36 to prevent leakage of air into the roll. The roll 24 is similarly provided with a shielding seal 38 on its inner surface to prevent leakage of air into the interior of the roll 24 along its upper surface. The shield 38 extends so that as the Web passes the shield 37 it will become exposed to the vacuum within the belt 30 and roll 24 to smooth the transfer to the belt 30.

The web is supported on the belt 30 and is thereafter smoothly transferred to the belt 31 and a seal 39 within the belt 30 effects a smooth transfer. Suction roll 27 is provided with a shielding seal 40 to prevent the leakage of air and the web smoothly leaves the belt 31 to travel onto the guide roll 28. While on the belt 31, the outer surface 0 of the web W is subjected to an atmosphere of hot air by the hood 35 and the inner surface subjected to suction. Hot air is supplied to the hoods 32, 34 and 35 by suitable air supply mechanism shown schematically by the arrows labelled Air In, and the moisture carrying air leaves as indicated schematically by the arrows labelled Air Out. The interior of the hoods may be kept at atmos pheric pressure or at slightly less than atmospheric pressure to prevent escape of heated air and the edges of the hoods are close to the surface of the moving foraminous belts to prevent escape of air into the room. The air can be heated before entering the hoods or heated within the hoods.

In other words, the first, second and third belts provide a serpentine path with the first belt providing a first surface 2a receiving the web, and reversing over the roll 23 provides a second surface 2%. The second belt 36 provides a continuation second surface 39a which extends in the same direction as the second surface 291) of the first belt and substantially forms a continuation thereof. The surface 36!) of the second belt provides a third surface in the opposite direction of the second surface 30a and the surface 31a of the third belt provides a continuation third surface which is a continuation of the third surface 39b extending in substantially the same direction. This provides for a smooth transfer of the web and a reversal of its path and also a reversal of the surfaces which are exposed to heated air and vacuum, and is repeated through the dryer section. It will be appreciated l that additional rolls and belts may be provided to obtain the drying area necessary and that the position of the rolls and belts may be changed to be horizontal, instead of vertical as shown.

In operation, the web W in FIGURES 1 or 2 arrives from the forming section 9, FIGURE 2, at the drying section 10, and the mechanism of FIGURES 1 and 2 provides at least a part of the drying section. The web is supported alternately on its inner and outer surfaces on a foraminous surface provided by the suction rolls 22-27 of FIGURE 1, or by the foraminous belts 29, 30 and 31 of FIGURE 1. One surface of the web is supported on the foraminous surface and subjected to a vacuum which holds the web on the surface, and the other exposed surface of the web is subjected to a flow of hot air from hood to transfer thermal energy and increase the temperature of the moisture in the web for evaporation, and the air will flow out of the hoods after flowing over the web and will carry away evaporating moisture. The hood is close to the web at its sides but not sealed thereto.

It is contemplated that the belts may be of varying lengths, and a suflicient number of belts will be employed in sequence to effect the drying necessary. It is further contemplated as being within the scope of the invention that the belts provided a preferred form of foraminous support, the surfaces do not have to be straight and surfaces of other types such as cylinders may be employed.

Thus it will be seen that I have provided an improved unique mechanism and method for the drying section of a paper making machine which meets the objectives and advantages above set forth. The mechanism can be constructed without the bulk of heavy cast iron drying rolls and will require reduced machine volume and will obtain rapid moisture evaporation from the paper web.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

1. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belt with the rolls for each belt spaced apart for carrying the belt and forming linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said belts positioned close together so that the second run of the first belt travels toward the first run of the second belt and in the same direction and has a delivery end spaced close to a receiving end of the first run of the second belt to transfer the web from the first to the second belt at the end of the second run of the first belt, means for creating a suction within said belts along said runs to hold the Web thereon, a first U-shaped hood position over the first belt and having sides extending along said first and second runs, a second U-shaped hood extending over said second belt with the sides extending along said first and second runs said hoods extending over the ends of the belts between said first and second runs, means for directing a flow of heated air from the first hood onto the first belt, and means for directing a flow of heated air from the second hood onto the second belt.

2. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belts with the rolls for each belt spaced apart vertically for carrying the belt and forming vertical linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said runs positioned close together so that the second run of the first belt travels toward the first run of the second belt and in the same direction and is close thereto to transfer the web from the first to the second belt at the end of the second run of the first belt, means for creating a suction within said belt to hold the web thereon, and a heated air source on the exposed surface of the web on said runs and over the end of the belts between the first and second runs for evaporating moisture from the web.

3. In a paper machine dryer section for drying a Wet paper web, first, second and third closed loops of foraminous flexible belts, a first pair of vertically spaced support rolls for the first looped belt defining first and second linear runs for carrying the paper web, a second pair of vertically spaced support rolls supporting said second loop defining first and second linear runs between them With said first run of said second belt positioned to receive the web from said second run of the first belt and being closely spaced thereto and traveling in the same direction, a third pair of vertically spaced support rolls for the third looped belt defining first and second linear Web supporting runs between them with the first run of the third belt positioned to receive the web from the second run of the second belt and being closely spaced thereto and traveling in the same direction, said web transferring from the first to the second belt and from the second to the third belt at the end of said second runs, means for applying a suction within each of the loops of said belts for holding the web on said runs, and a heated air source on the exposed surface of the web over said first and said second runs and over the end of the belt loop therebetween evaporating moisture from the web.

4. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belts with the rolls for each belt spaced apart for carrying the belt and forming linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said belts posi tioned close together so that the second run of the first belt travels toward the first run of the second belt and has a delivery end spaced close to a receiving end of the first run of the second belt to transfer the web from the first to the second belt and said second run of the first belt and first run of the second belt traveling in the same direction, said web transferring from the first to the second belt at the end of the second run of the first belt, means for creating a pressure differential across said belts along said runs to hold the web thereon, and a heated air source on the exposed surface of the web on said first and second runs and over the end of the belts between the runs for evaporating moisture from the web.

5. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belts with the rolls for each belt spaced apart for carrying the belt and forming linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said belts positioned close together so that the second run of the first belt travels toward the first run of the second belt to transfer the web from the first to the second belt at the end of the second run of the first belt, said second run of the first belt and first run of the second belt traveling in the same direction, means for creating a suction Within each of said belts for holding the web on the outer surface of the belts on said runs, and a heated air source on the exposed surface of the web on said first and second runs and over the end of the belts therebetween for evaporating moisture from the web.

6. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, pairs of spaced support rolls respectively within said first and second belts with each pair having first and second rolls spaced apart for carrying the belt and forming linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the'first belt and thereafter over the first and second runs of the second belt, said first run extending from the first to the second roll, said second run extending from the second to the first roll, said belts positioned close together so that the second run of the first belt travels toward the first run of the second belt and in the same direction to transfer the web from the first to the second belt at the end of the second run of the first belt, said second rolls each being foraminous, means for creating a suction within said belts and within said second rolls for holding the web to the belts and to the second rolls as the web passes from the first to the second runs, and a heated air source on the exposed surface of the web on said first and second runs and over the ends of the belts between the first and second runs for evaporating moisture for the web.

7. In a paper machine dryer section for drying a paper web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belts with the rolls for each belt spaced apart for carrying the belt and forming linear runs therebetween, each pair of rolls including first and second rolls with the first run extending from the first to the second roll and the second run extending from the second to the first roll, said runs extending substantially parallel to each other, said runs defining a paper web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said belts positioned close together so that the second run of the first belt travels toward the first run of the second belt and in the same direction to transfer the web from the first to the second belt at the end of the second run, said second rolls each being foraminous, means for creating a suction within said belts and within said second rolls for holding the webs to the belts and to the second rolls as the web passes from the first to the second runs, U-shaped air hoods projecting over said belts on said first and second runs and over the belts on said second rolls between the first and second runs, and means for circulating heated air through said hoods over the exposed surface of the moving web.

8. In a paper machine dryer section for drying a paper Web, first and second closed loops of foraminous flexible belts, first and second pairs of spaced support rolls respectively within said first and second belts with the rolls for each belt spaced apart for carrying the belt and forming linear runs therebetween, said runs extending substantially parallel to each other, said runs defining a paper Web supporting path extending sequentially over the first and second runs of the first belt and thereafter over the first and second runs of the second belt, said belts positioned close together so that the second run of the first belt travels toward the first run of the second belt and in the same direction to transfer the web from the first to the second belt at the end of the second run, means for creating a suction within said belts for holding the web to the belt, and means for creating a flow of heated air over the exposed web of the paper along said first and second runs and over the end of the belts between said first and second runs at sufficiently low pressure so that the air does not penetrate the Web.

9. In a paper machine dryer section for drying a paper 1 web, a closed looped foraminous flexible belt, first and second spaced support rolls for the looped belt defining first and second linear runs between them, means for creating a pressure differential across said belt to hold the web on said runs, means for holding the Web on said belt as it travels around the second support roll from the first to the second run, web carrying means traveling in the same direction as the second run positioned immediately adjacent the end of the second run and receiving the web from said second run at the end of the second run, and a heated air source on the exposed surface of the web along said first and second runs and over the end of the belts between said first and second runs evaporating moisture from the web.

References Cited in the file of this patent UNITED STATES PATENTS 1,701,878 Freegard Feb. 12, 1929 1,996,020 Hurxthal Mar. 26, 1935 2,091,805 Chuse Aug. 31, 1937 2,760,410 Gillis Aug. 28, 1956 2,981,007 Fleissner Apr. 25, 1961 FOREIGN PATENTS 1,104,438 Germany Apr. 6, 1961

Claims (1)

1. IN A PAPER MACHINE DRYER SECTION FOR DRYING A PAPER WEB, FIRST AND SECOND CLOSED LOOPS OF FORAMINOUS FLEXIBLE BELTS, FIRST AND SECOND PAIRS OF SPACED SUPPORT ROLLS RESPECTIVELY WITHIN SAID FIRST AND SECOND BELT WITH THE ROLLS FOR EACH BELT SPACED APART FOR CARRYING THE BELT AND FORMING LINEAR RUNS THEREBETWEEN, SAID RUNS EXTENDING SUBSTANTIALLY PARALLEL TO EACH OTHER, SAID RUNS DEFINING A PAPER WEB SUPPORTING PATH EXTENDING SEQUENTIALLY OVER THE FIRST AND SECOND RUNS OF THE FIRST BELT AND THEREAFTER OVER THE FIRST AND SECOND RUNS OF THE SECOND BELT, SAID BELTS POSITIONED CLOSE TOGETHER SO THAT THE SECOND RUN OF THE FIRST BELT TRAVELS TOWARD THE FIRST RUN OF THE SECOND BELT AND IN THE SAME DIRECTION AND HAS A DELIVERY END SPACED CLOSE TO A RECEIVING END OF THE FIRST RUN OF THE SECOND BELT TO TRANSFER THE WEB FROM THE FIRST TO THE SECOND BELT AT THE END

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