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US 5,873,180 AGranted
Papermaking dryer section with partitioned vacuum box for threading
AssigneeBeloit Technologies, Inc.
InventorThomas K. Grunder
Life of this patent
Estimating the term…
Abstract
A single tier dryer system has dryer rolls with a reversing roll positioned between each pair to transfer and wrap the dryer felt and paper web against the next dryer roll. A vacuum box is positioned between the dryer rolls and over the reversing roll to hold the web on the dryer felt by vacuum. Threading of a tail from the web is accomplished by blowing the web tail off a first dryer roll's surface with a jet of air positioned adjacent to the position on the dryer roll where the dryer felt leaves the dryer roll's surface. The vacuum box is divided by a baffle to isolate a portion of the vacuum box near the front of the dryer rolls, and a damper is positioned within the reversing roll to increase the vacuum in the isolated portion of the vacuum box to facilitate threading of the tail.
Claims19
A dryer section having a single tier of dryer rolls with reversing rolls positioned between adjacent dryer rolls, the dryer section having a front end and a back end, and in receiving relation to a tail of a paper web of a width less than the full paper web, the dryer section comprising:
- a plurality of dryer rolls forming an array of dryer rolls, each dryer roll having an axis and a cylindrical surface, wherein the axes of the dryer rolls are in substantially a single plane;
- a plurality of reversing rolls, each reversing roll being positioned between adjacent dryer rolls, and each reversing roll having an axis, the axes of the reversing rolls lying in substantially a single plane which is spaced from and parallel to the plane containing the axes of the dryer rolls, wherein each reversing roll has a cylindrical surface which is closely spaced from the surface of adjacent dryer rolls;
- a dryer felt wrapped around a portion of each dryer roll and each reversing roll and extending between the dryer rolls and the reversing rolls so as to hold a paper web tail against each dryer roll surface, wherein each reversing roll surface is foraminous and wherein each reversing roll has a means for drawing air through the roll foraminous surface;
- a vacuum box positioned between adjacent dryer rolls in vacuum receiving relation to the reversing roll positioned between said adjacent dryer rolls, the vacuum box being defined by seals spaced in the cross machine direction and serving to apply vacuum to the web tail as the felt on which it moves progresses to a reversing roll from a dryer roll and to the adjacent dryer roll from the reversing roll;
- an air jet positioned to blow on each dryer roll on a portion of the dryer roll surface adjacent to where the web and the dryer felt leave the surface of the dryer roll and travel to the closely spaced adjacent reversing roll;
- a baffle dividing the vacuum box into a threading portion and a non-threading portion, the threading portion being positioned adjacent one end of the dryer section;
- and
- fixed shafts on which the reversing rolls are mounted for supplying vacuum to the roll;
- a seal which extends between each fixed shaft and an interior surface of each roll, wherein each seal is positioned beneath the threading baffles and is constructed of a nonmetallic lining material in touching to near touching engagement with the reversing roll, the seal partitioning the interior of the roll into a threading section and a non-threading section;
- a control damper baffle arranged to increase the vacuum applied to the threading section of the reversing roll and hence to the threading portion of the vacuum box the damper baffle being controllable to at least partially close off the non-threading portion of the roll to increase the vacuum in the threading section.
7 more elements
A threading apparatus in a papermaking machine single tier dryer section, the apparatus comprising:
- a first dryer roll;
- a second dryer roll;
- a reversing roll positioned between the first dryer roll and the second dryer roll, wherein the reversing roll has an axis which is positioned below a first dryer roll axis and a second dryer roll axis;
- a felt which is wrapped over a portion of the first dryer roll, beneath the reversing roll, and over a portion of the second dryer roll;
- a web tail which is wrapped between the felt and the first dryer roll, wherein the web tail is narrower than the width of the reversing roll;
- portions of the reversing roll which define a plurality of holes which communicate between the exterior and the interior of the reversing roll;
- a fixed shaft on which the reversing roll is mounted for supplying vacuum to the roll;
- a seal which extends between the fixed shaft and an interior surface of the roll the seal is constructed of a nonmetallic lining material in touching to near touching engagement with the reversing roll, the seal partitioning the interior of the roll into a threading section and a non-threading section;
- a first baffle positioned above the reversing roll at one end of the reversing roll;
- a second baffle spaced in the cross machine direction from the first baffle and positioned above the reversing roll at an end opposite the first baffle;
- a threading baffle positioned between the first baffle and the second baffle to define a threading region between the threading baffle and the first baffle which corresponds approximately to the width of the web tail, and wherein a seal is defined between the first baffle and the threading baffle and the felt;
- and
- a control damper baffle arranged to increase the vacuum applied to the threading section of the reversing roll and hence to the threading portion of the vacuum box, wherein the damper is controllable to at least partially close off the non-threading portion of the roll to increase the level of air drawn from between the threading baffle and the first baffle where the web tail passes on the felt at the threading region, the increased level of air drawn at the threading region thereby creating a region of reduced pressure which draws air through the felt and thereby assists in retaining the web tail on the felt for threading across the reversing roll and onto the second dryer roll.
10 more elements
A threading apparatus in a papermaking machine single tier driver section, the apparatus comprising:
- a first dryer roll;
- a second dryer roll;
- a reversing roll positioned between the first dryer roll and the second dryer roll, wherein the reversing roll has an axis which is positioned below a first dryer roll axis and a second dryer roll axis;
- a felt which is wrapped over a portion of the first dryer roll, beneath the reversing roll, and over a portion of the second dryer roll;
- a web tail which is wrapped between the felt and the first dryer roll, wherein the web tail is narrower than the width of the reversing roll;
- portions of the reversing roll which define a plurality of holes which communicate between the exterior and the interior of the reversing roll;
- means for drawing air from the interior of the reversing roll, and thereby drawing air through the reversing roll holes;
- a first baffle positioned above the reversing roll at one end of the reversing roll;
- a second baffled spaced in the cross machine direction from the first baffle and positioned above the reversing roll at an end opposite the first baffle;
- a threading baffle positioned between the first baffle and the second baffle to define a threading region between the threading baffle and the first baffle which corresponds approximately to the width of the web tail, and wherein a seal is defined between the first baffle and the threading baffle and the felt;
- and
- a means for adjustably increasing the level of air drawn from between the threading baffle and the first baffle where the web tail passes on the felt at the threading region, the increased level of air drawn at the threading region thereby creating a region of reduced pressure which draws air through the felt and thereby assists in retaining the web tail on the felt for threading across the reversing roll and onto the second dryer roll, wherein the means for adjustably increasing the level of air drawn is a damper positioned within the reversing roll, wherein the damper is positioned approximately below the threading baffle, wherein the first baffle comprises a first bracket connected to the cross machine beam, and having a lower arcuate bottom which is positioned above the reversing roll, and wherein the first baffle further comprises a second bracket positioned between the first bracket and the threading baffle, and wherein a portion of brake lining material is affixed beneath the connected first and second brackets to define a rotating seal between the first baffle and the reversing roll.
9 more elements
Dependencies are inferred from the claim text.