Paper making and fiber liberation – Processes and products – Lead strip forming and/or guiding
Reexamination Certificate
1999-05-26
2001-02-27
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
Lead strip forming and/or guiding
C162S255000, C162S198000, C162S263000, C162S252000, C226S091000, C226S092000, C034S114000, C034S117000
Reexamination Certificate
active
06193845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to paper-making machines and, more particularly, to paper-making machines having air assisted threading doctor elements.
2. Description of the Related Art
Machines for making sheets of material, especially paper, utilize an array of rotating longitudinal cylinders or rolls on which the paper travels. The rolls are used in a variety of different sections during the paper making process. One of the sections is a dryer section, which may consist of several dryer sections, situated one after another. In a dryer section, as the name implies, incoming wet paper is dried by drying rolls.
In most of the various segments of the paper machine, it is known to provide a doctor element, such as a doctor blade, which bears against a roll of the section and cleans the roll by scraping off residual fibers or the like. A water shower is typically provided in association with the doctor blade for lubricating the doctor blade as it bears against the roll. The shower directs a stream of water against the roll across the width of the doctor blade and on the approach side of the doctor blade.
In sections such as a dryer section, it is known to provide a threading doctor at the beginning of a roll in order to direct the paper onto the roll. As the paper advances along the particular section, the threading doctor associated with each roll directs the paper onto the next roll. Generally, such threading doctors have air blowing systems that direct flowing air from nozzles into the region where the paper is to separate from the roll and advance to the next roll. The blowing air forces the paper to travel away from the roll and into a convergence area of the next roll for pickup by that next roll. The use of blowing air is an efficient way to direct the advancing paper since the paper generally advances at 4,000 to 6,000 feet per minute (fpm).
However, the problem with such threading systems is the enormous air pressure required to continuously supply each blowing system associated with each roll. As an example, a typical dryer group of a dryer section includes ten (10) dryer rolls each with a blowing system having an approximate twenty (20) CFM (Cubic Feet per Minute) air flow, yielding approximately two-hundred (200) SCFM. With as many as three (3) to twelve (12) dryer groups per dryer section, this may require an air supply system of six hundred (600) to two-thousand four-hundred (2,400) SCFM.
What is thus needed is an air threading system that utilizes an air supply system of considerably less SCFM.
SUMMARY OF THE INVENTION
In one form, the present invention is a paper-making machine having an air control system. The paper-making machine has a plurality of cylinders with each cylinder having an associated air blowing threading doctor assembly. The control system for the plurality of air blowing threading doctor assemblies includes an air supply system, a controller, a plurality of air valves, and a plurality of proximity sensors. The air valves are associated with each air blowing threading doctor assembly and are in communication with the controller and the air supply system. Each air valve selectively supplies air from the air supply system to the associated air blowing threading doctor assembly upon activation by the controller. Each proximity sensor is associated with each air blowing threading doctor assembly and is in communication with the controller. Each proximity sensor generates a signal upon the detection of a leading tail of the paper within a detection zone associated with each proximity sensor. The controller activates an air valve associated with an air blowing threading doctor assembly associated with a proximity sensor that generated the signal, and additionally activates a next air valve associated with a next air blowing threading doctor assembly associated with a next cylinder relative to a paper advance direction.
Additionally, in accordance with an aspect of the present invention, the air valves to previously activated threading doctors are sequentially turned off as the leading tail of the paper advances.
In another form, the present invention is a method of controlling air blowing threading doctors in a fiber material making machine having a dryer section with a plurality of dryer cylinders, an air supply system. Each of the plurality of dryer cylinders is associated with an air blowing threading doctor that is in communication with the air supply system.
The method includes supplying air from the air supply system to the air blowing threading doctor associated with a first dryer cylinder of the plurality of dryer cylinders. The presence of a leading tail of a web of fiber material being made in the fiber-making machine is detected in a detection zone, wherein a detection zone is defined as between a dryer cylinder emergence area and a next dryer cylinder convergence area relative to a fiber web material advance direction. Air from the air supply system is supplied to the air blowing threading doctors associated with at least the next two dryer cylinders relative to the fiber web material advance direction and the detection zone when the leading tail is detected. The air is shut off to the air blowing threading doctors associated with the dryer cylinders at least twice preceding the detection zone when the leading tail is detected. The detecting, air supplying, and shutting off steps are then repeated until the leading tail is detected in a final dryer cylinder detection zone.
It is an advantage of the present invention that a smaller CFM capacity air supply system can be utilized for the air threading system.
The present invention has particular advantageous use in dryer sections of a paper-making machine.
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Graf Edwin X.
Ricker William B.
Fortuna Jos'e A.
Silverman Stanley S.
Taylor & Aust P.C.
Voith Sulzer Paper Technology North America Inc.
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