Beloit Technologies, Inc.

Rajendra D Deshpande

Jeffrey H Pulkowski

William R McGraw

James P Alfano

A press-to-dryer apparatus is disclosed for pressing and drying a web of paper. The apparatus includes a press for pressing the web of paper and a dryer disposed downstream relative to the press for drying the web. The dryer includes an unfelted drying cylinder disposed immediately downstream relative to the press. The arrangement is such that the web extends from the press to and around the drying cylinder. The dryer also includes a heater which cooperates with the unfelted drying cylinder such that the web is disposed between the drying cylinder and the heater for heating and drying the web. The dryer also includes a single-tier drying section which is disposed downstream relative to the unfelted drying cylinder for completing the drying of the web.

Press-to-dryer apparatus

A press of the Beloit Extended Nip.RTM. type has a nip defined between a backing roll and an elongate shoe. A paper web travels on a dryer felt through the nip and is supported over the shoe by a bearing blanket. The shoe has a rigid concave core to which is fixed a layer of compliant material which defines a concave surface. Lubricant is introduced between the compliant material and the bearing blanket to form a hydrodynamic fluid film. Preferably the rigidity of the compliant material is of the same or lesser order of magnitude than the rigidity of the fluid film at the center of the shoe in the machine direction, such that the fluid film at the nip causes a depression in the compliant material which is filled with lubricant. The thickness of the lubricant is thus greater at the center of the shoe than at regions outward from the shoe center and the escape of lubricant from the shoe is retarded. The compliant material comprises an elastomer with a low coefficient of friction and high abrasion resistance. It has the ability to deform with increased pressure upon it, thus allowing a paper wad or web deformity to pass through the nip without damage to the bearing blanket. Alternatively, the compliant layer may define a plurality of lubricant pockets.

Compliant hydrodynamic/hydrostatic shoe for papermaking press

The dryer section in a papermaking machine has a single tier of all top felted dryer rolls six to nine feet in diameter. Air caps are employed over the dryer rolls to simultaneously dry both sides of the web to prevent curl and to increase drying rates. The air caps employ blown air at a temperature of 250-900 degrees Fahrenheit and air speeds of 8,000-40,000 feet per minute. The dryer fabric employed is foraminous with a permeability of between 300-1,200 cubic feet per minute per square foot and is designed to withstand peak temperatures of up to 900 degrees Fahrenheit and average temperatures of between 500-600 degrees Fahrenheit. A single transfer roll, or more advantageously, two grooved vacuum rolls in a vacuum box are disposed between the dryer rolls to maximize the circumferential wrap of the web and, at the same time, support and transport the web between dryer rolls.

Curl control with dryer aircaps

Method for controlling curl with dryer aircaps

A controlled crown roll utilizes a crown support piston with a glide shoe with a cavity in the face of the glide shoe centered under the nip loading line. The cavity is surrounded by a land area, the majority of which is located away from the nip load. Use of a low viscosity hydraulic fluid, for example, 15.6 cP, with a hydraulic film thickness of 0.002 inches, results in significantly lower friction between the glide shoe and the interior surface of the rotating mantle. Recesses in the piston sides form hydrostatic thrust bearings which perform the centering function for the piston and the glide shoe.

Hydrostatic shoe for controlled crown rolls

A new dryer section or an existing dryer section of the two tier double-felted type has air caps disposed over the upper dryer rolls to simultaneously dry both sides of the web to increase drying rates. The heated pressurized air is blown through multiple air impingement holes in the air cap nozzle plates to impinge the web at a temperature of 500-900 degrees Fahrenheit and air speeds of 20,000-40,000 feet per minute. The dryer fabric employed is foraminous with a permeability of between 400-1,200 cubic feet per minute per square foot and is designed to withstand peak temperatures of up to 900 degrees Fahrenheit and average temperatures of between 500-600 degrees Fahrenheit. The design of the air caps utilizes recirculation of the blowing air to control drying rates.

Air caps for two tier double felted dryer

A vacuum roll apparatus is disclosed for transferring a web supported on a dryer felt from a first to a second drying cylinder of a dryer section. The apparatus includes a rotatable perforate shell having a first and a second end, the shell defining a cavity which extends from the first to the second end of the shell. The arrangement is such that the dryer felt extends from the first dryer around the perforate shell to the second dryer with the web extending contiguously with the dryer felt, and the dryer felt being disposed between the shell and the web. At least one fin is rigidly secured to the shell and is disposed within the cavity such that when the shell is rotated, the fin generates a flow of air through the perforate shell towards the cavity for drawing the web into close conformity with the dryer felt during movement thereof around the vacuum roll apparatus so that the web is restrained against cross-machine directional shrinkage.

Vacuum roll apparatus

The paper dryer section has a single tier of all top felted dryer rolls seven to nine feet in diameter. Air caps are employed over the dryer rolls to simultaneously dry both sides of the web to prevent curl and to increase drying rates. The air caps employ blown air at a temperature of 200-1,000 degrees Fahrenheit and air speeds of 8,000-40,000 feet per minute. The felt employed is foraminous with a permeability of between 300-1,500 cubic feet per minute per square foot and is designed to withstand peak temperatures of up to 1,000 degrees Fahrenheit and average temperatures of between 500-600 degrees Fahrenheit. A single dryer roll, or more advantageously, two vacuum rolls in a vacuum box are disposed between the dryer rolls to maximize the circumferential wrap of the web and, at the same time, support and transport the web between dryers.

Curl control by dryer aircaps in top felted dryer section

A paper drying section utilizes two reversing rolls between each dryer roll to extend the available time for vapor to flash from the web. A vacuum box is disposed between the two reversing rolls to support and dry the felt and paper web as it passes from one reversing roll to another. An air cap is used to blow high velocity air onto the exposed surface of the paper web which is held by the vacuum box. The spacing of the two reversing rolls increases the wrap of the single tier dryer by approximately twenty percent over that of a conventional single tier dryer with a single reversing roll. Another configuration dryer section positions the first of the two reversing rolls downwardly beneath its adjacent dryer roll creating a long draw between the dryer roll and the first reversing roll. This long draw is supported by a vacuum box adjacent the felt. The downward positioning of the first roll increases the length of the draw between the first and second reversing rolls, providing additional area for drying by an air cap.

Single tier dryer section with dual reversing rolls

The dryer of this invention employs a vacuum chamber interposed below and between first and second heated dryer rolls. The vacuum chamber has two sides and a top which overlies two grooved reversing rolls. The vacuum chamber controls all flow of air in the gap between and below the dryer rolls. The dryer-fabric-backed paper web passes from the first dryer roll around the reversing rolls and up to the second dryer roll. The dryer fabric seals the vacuum chamber, and air is drawn therefrom. The provision of the grooved rolls permits a greater wrap of the felt around the dryers and the application of vacuum to hold the web against the felt during movement of the web between the dryers and the grooved rolls and between the grooved rolls.

Growing community of inventors

Rockton, IL, United States of America

Rajendra D Deshpande