Papermaking dryer with pivoting vacuum transfer rolls

Abstract

The top and bottom felts at the web transfer between two dryer sections in a single tier papermaking dryer are spaced by pivoting the vacuum roll over which the felt and web move. The vacuum roll is mounted to two pivot arms which are driven by inflatable air rides to alternately incline the roll toward the downstream felt, forming a sandwich of the two felts and the web, and to a spaced position. The short motion of the vacuum roll allows standard felt stretchers to be used, and permits rapid adjustment of the felt spacing.

I claim: 
     
       1. An apparatus for drying a web, comprising: a frame;   a first dryer roll;   a pivot arm mounted to the frame for pivoting about a cross-machine axis;   a first vacuum roll downstream of the first dryer roll, wherein the first vacuum roll is rotatably mounted to the pivot arm;   a first felt guided about the first dryer roll such that the web is disposed between the first dryer roll and the first felt for drying a first side of the web, wherein the first felt extends over the first vacuum roll;   a second vacuum roll mounted to the frame downstream of the first vacuum roll;   a second dryer roll mounted downstream of the second vacuum roll;   a second felt guided about the second dryer roll such that the web is disposed between the second dryer roll and the second felt for drying a second side of the web, wherein the second felt extends from the second vacuum roll to the second dryer roll, and wherein the web is transferred from the first felt to the second felt between the first dryer roll and the second dryer roll; and   means for pivoting the pivot arm, wherein the pivoting means causes the first vacuum roll to pivot from a first position in which the first felt, the web, and the second felt are engaged, and a second position in which the first felt, the web, and the second felt are not simultaneously engaged.   
     
     
       2. The apparatus of claim 1 wherein the means for pivoting the pivot arm comprises at least one inflatable member connected between the pivot arm and the frame, such that inflation of the member causes a pivoting of the vacuum roller. 
     
     
       3. The apparatus of claim 1 further comprising: a second pivot arm pivotably mounted to the frame, wherein the second vacuum roller is rotatably mounted to the second pivot arm;   a means for pivoting the second pivot arm, wherein the first vacuum roll and the second vacuum roll may both be pivoted toward and away from one another.   
     
     
       4. The apparatus of claim 1 wherein the means for pivoting the pivot arm comprises: a first inflatable member connected between the pivot arm and the frame and extending from the frame upstream to the pivot arm; and   a second inflatable member connected between the pivot arm and the frame and extending from the frame downstream to the pivot arm, such that the inflatable members may be selectably inflated to position the first vacuum roll at a desired inclination.   
     
     
       5. An apparatus for drying a web, comprising: a frame;   a first dryer roll;   a first vacuum roll downstream of the first dryer roll;   a first felt guided about the first dryer roll such that the web is disposed between the first dryer roll and the first felt for drying a first side of the web, wherein the first felt extends over the first vacuum roll;   a second vacuum roll mounted to the frame downstream of the first vacuum roll;   a second dryer roll mounted downstream of the second vacuum roll;   a second felt guided about the second dryer roll such that the web is disposed between the second dryer roll and the second felt for drying a second side of the web, wherein the second felt extends from the second vacuum roll to the second dryer roll, and wherein the web is transferred from the first felt to the second felt between the first dryer roll and the second dryer roll; and   means for pivoting the first vacuum roll from a first position in which the first felt, the web, and the second felt are engaged, and a second position in which the first felt, the web, and the second felt are not simultaneously engaged.   
     
     
       6. The apparatus of claim 5 further comprising a means for pivoting the second vacuum roll from a first position in which the first felt, the web, and the second felt are engaged between the first vacuum roll and the second vacuum roll, and a second position in which the first vacuum roll and the second vacuum roll are pivoted away from one another. 
     
     
       7. An apparatus for drying a web, comprising: a frame;   a first dryer roll rotatably mounted to the frame;   at least one pivot arm mounted to the frame for pivoting about a cross-machine axis,   a first vacuum roll downstream of the first dryer roll, wherein the first vacuum roll is rotatably mounted to the pivot arm;   a first felt guided about the first dryer roll such that the web is disposed between the first dryer roll and the first felt for drying a first side of the web, wherein the first felt extends over the first vacuum roll;   a second vacuum roll mounted to the frame downstream of the first vacuum roll;   a second dryer roll mounted downstream of the second vacuum roll;   a second felt guided about the second dryer roll such that the web is disposed between the second dryer roll and the second felt for drying a second side of the web, wherein the second felt extends from the second vacuum roll to the second dryer roll, and wherein the web is transferred from the first felt to the second felt between the first dryer roll and the second dryer roll; and   an inflatable member connected between the pivot arm and the frame, wherein the inflatable member is inflatable and deflatable to cause the first vacuum roll to pivot between a first position in which the first felt, the web, and the second felt are engaged, and a second position in which the first felt, the web, and the second felt are not simultaneously engaged.   
     
     
       8. The apparatus of claim 7 further comprising a second inflatable member connected between the pivot arm and the frame and extending from the frame downstream to the pivot arm, such that the inflatable members may be selectably inflated to position the first vacuum roll at a desired inclination.