Abstract:
This invention is directed to a paper-making machine utilizing rotating cylinders, especially dryer cylinders, with a drying felt intertwined about the dryer cylinders to compress the wet paper against the dryer cylinders as the wet paper travels therealong. A threading doctor assembly with a blowpipe air nozzle blowing system is associated with each dryer cylinder. When air is flowing into the blowpipe blowing system, the leading tail of the wet paper is directed from the preceding dryer cylinder to the next. A proximity sensor associated with each threading doctor assembly is in communication with a controller and is positioned to determine if the wet paper is within a detection area. Air valves or solenoids coupled between an air supply system and the blowpipes are also coupled to the controller. As the leading tail of the paper is detected by a proximity sensor to be within the detection area, the next several solenoids associated with the next several threading doctors in the paper advance direction are activated. As well, solenoids associated with the blowpipes of the threading doctors that are more than two or three behind the proximity sensor, relative to the paper advance direction are deactivated. Such sequencing of blowpipes as the leading tail advances through the system reduces the air supply pressure necessary for the system.

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a diagrammatic side view of an embodiment of a dryer section used with a paper making process incorporating the present invention; 
     FIG. 2 is an enlarged side view of a portion of the dryer section of FIG. 1 in accordance with the present invention depicting a detecting area between dryer rolls having a paper tail therein; and 
     FIG. 3 is a diagrammatic view of the air supply system as coupled to the blowpipes of the threading doctors and the associated proximity sensors in communication with a controller. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrate a preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and more particularly to FIG. 1, there is shown a side view of dryer group  10  forming part of a dryer section in a paper-making machine. Dryer group  10  may be one of a plurality of dryer groups which can typically number between three (3) and twelve (12) in a paper-making machine. It should be understood that dryer group  10  is representative of the plurality of such dryer groups that take the moisture out of the paper or other fiber material during the production process. 
     Dryer group  10  is divided into upper dryer group  12  and lower dryer group  14 , which together, move paper or fiber material web  28  therethrough, here, arbitrarily from left to right as indicated by arrow  38 . Upper dryer group  12  includes a plurality of upper dryer cylinders  16   a,    16   b,    16   c,    16   d,  and  16   e,  each being of generally the same size and type as is typical in the art. Each upper dryer cylinder  16   a,    16   b,    16   c,    16   d,  and  16   e  rotates in the direction of their respective arrow. Upper dryer group  12  also includes a plurality of upper felt guide rolls  18   a,    18   b,    18   c,    18   d,    18   e,    18   f,    18   g,  and  18   h  that rotatably support continuous felt sheet  20  and rotate in the direction of their respective arrow. Felt  20  travels in a continuous loop in the direction indicated by arrow  34  and is supported by upper felt guide rolls  18   b,    18   c,    18   d,    18   e,    18   f,  and  18   g  such that felt  20  contacts only the upper portion of each upper dryer cylinder  16   a,    16   b,    16   c,    16   d,  and  16   e.    
     Lower dryer group  14  includes a plurality of lower dryer cylinders  22   a,    22   b,    22   c,    22   d,  and  22   e,  each being of generally the same size and type as is typical in the art. Each lower dryer cylinder  22   a,    22   b,    22   c,    22   d,  and  22   e  rotates in the direction of their respective arrow. Lower dryer group  14  also includes a plurality of lower felt guide rolls  24   a,    24   b,    24   c,    24   d,    24   e,    24   f,    24   g,  and  24   h  that rotatably support continuous felt sheet  26  and rotate in the direction of their respective arrow. Felt  26  travels in a continuous loop in the direction indicated by arrow  36  and is supported by lower felt guide rolls  24   b,    24   c,    24   d,    24   e,    24   f,  and  24   g  such that felt  26  contacts only the lower portion of each lower dryer cylinder  22   a,    22   b,    22   c,    22   d,  and  22   e.    
     Fiber material web  28  enters dryer group  10  between lower felt guide roll  24   b  and lower dryer cylinder  22   a  between felt  26  and lower dryer cylinder  22   a  and is then intertwined in alternating lower and upper dryer cylinders,  16   a,    22   b,    16   b,    22   c,    16   c,    22   d,    16   d,    22   e,  and  16   e.  In this manner, fiber material web  28  is compressed onto the surfaces of the alternating dryer cylinders by respective felts  20  or  26 . In the case of the lower dryer cylinders  22   a,    22   b,    22   c,    22   d,  and  22   e,  fiber web material  28  is compressed between felt  26  and the lower portion surface of the respective lower dryer cylinders. In the case of the upper dryer cylinders  16   a,    16   b,    16   c,    16   d,  and  16   e,  fiber web material  28  is compressed between felt  20  and the upper portion surface of the respective upper dryer cylinders. Additionally, fiber web material  28  has a beginning and end, known in the industry as a leading tail and a trailing tail respectively. The leading tail of fiber web material  28  is designated  40 , while the trailing tail of fiber web material  28  is designated  42 . 
     Generally, the leading tail of a fiber roll is wedge-shaped as is the trailing tail. This is due to the manner in which the paper is cut. As the paper is advancing, a blade or other type of cutter is caused to move transverse to the advancing direction. The blade thus cuts a wedge shape, with the point thereof at one side where the blade starts. 
     Associated with each upper dryer cylinder  16   a,    16   b,    16   c,    16   d,  and  16   e  is a threading doctor assembly  30   a,    30   b,    30   c,    30   d,  and  30   e,  respectively, each of which is positioned on the exit side, relative to paper travel, of the respective dryer cylinder. 
     Associated with each lower dryer cylinder  22   a,    22   b,    22   c,    22   d,  and  22   e  is a threading doctor assembly  32   a,    32   b,    32   c,    32   d,  and  32   e,  respectively, each of which is positioned on the exit side, relative to fiber web travel, of the respective dryer cylinder. 
     With reference now to FIG. 2, there is shown an enlarged view of an area between upper dryer cylinders  16   a  and  16   b,  and lower dryer cylinder  22   b  particularly depicting threading doctor assembly  30   a,  associated with upper dryer cylinder  16   a,  and threading doctor assembly  32   b,  associated with lower dryer cylinder  22   b.    
     Threading doctor assembly  30   a  includes doctor  44  mounted as is typical in the art adjacent the outer surface of upper dryer cylinder  16   a  on the exit side thereof, relative to fiber web material  28  travel through dryer group  10 . Doctor  44  may be mounted so as to be movable toward and away from the cylinder. Doctor  44  extends a portion of the longitudinal length of upper dryer cylinder  16   a.  Mounted to doctor  44  is blowpipe  46 , also extending a portion of the longitudinal length of upper dryer cylinder  16   a,  having a plurality of air nozzles  86  (see FIG. 3) therein. Blowpipe  46 , and thus associated air nozzles  86 , is coupled to a source of compressed or pressurized air  80  (see FIG. 3) via air conduit  48 . Air is directed, forced, or blown into emergence area  70  by air nozzles  86  of blowpipe  46  where upper felt  20  disjoins from upper dryer cylinder  16   a  and fiber web material  28 , compressed between upper felt  20  and the outer surface of upper dryer cylinder  16   a,  emerges. This separates the fiber web material that is compressed against upper dryer cylinder  16   a  therefrom such that the fiber web material can be directed into convergence area  72  to begin travel against lower dryer cylinder  22   b  with the aid of lower felt  26 . 
     Mounted to blowpipe  46  is proximity sensor  50 . Proximity sensor  50  may be any type of sensor, transducer, motion detector or the like that can sense or indicate whether fiber web material  28  is within sensing or detection area  54 . In one form, proximity sensor  50  is an ultrasonic generator/transducer such as a SUPERPROX® proximity sensor manufactured by Hyde Park Electronics, Inc. of Dayton, Ohio. Proximity sensor  50  is adjusted such that only material within sensing or detection area  54  generates a material sensed or detected signal. With additional reference to FIG. 3, proximity sensor  50  is in communication with controller  82  via line  52 . Controller  82  is in communication with air supply system  80  via line  78 . Air supply system  80  is coupled via conduit  78  to air valve or solenoid  76  that is coupled to conduit  48  associated with nozzles  86  of blowpipe  46  via line  78 . Controller  82  is in communication with solenoid  76  via line  90  for activation and deactivation, or on/off, control thereof. When solenoid  76  is actuated by controller  82  via line  90  in accordance with the present invention, compressed or pressurized air is caused to flow from air supply system  80  through conduit  78  and into nozzles  86  of blowpipe  46 . Of course, when solenoid  76  is deactivated or turned off, the air flow into blowpipe  46  is ceased. 
     Threading doctor assembly  32   b  includes doctor  56  mounted as is typical in the art adjacent the outer surface of lower dryer cylinder  22   b  on the exit side thereof, relative to fiber web material  28  travel through dryer group  10 . Doctor  56  may be mounted so as to be movable toward and away from the cylinder. Doctor  56  extends a portion of the longitudinal length of lower dryer cylinder  22   b.  Mounted to doctor  56  is blowpipe  58 , also extending a portion of the longitudinal length of lower dryer cylinder  22   b,  having a plurality of air nozzles  92  (see FIG. 3) therein. Blowpipe  58 , and thus associated air nozzles  92 , is coupled to a source of compressed or pressurized air  80  (see FIG. 3) via conduit  60 . Air is directed into emergence area  74  by air nozzles  92  of blowpipe  58  where lower felt  26  disjoins from lower dryer cylinder  22   b  and fiber web material  28 , compressed between lower felt  26  and the outer surface of lower dryer cylinder  22   b,  emerges. This separates the fiber web material that is compressed against lower dryer cylinder  22   b  therefrom such that fiber web material  28  can be directed into convergence area  88  to begin travel against upper dryer cylinder  16   b  with the aid of upper felt  20 . 
     Mounted to blowpipe  58  is proximity sensor  62 . Proximity sensor  62  may be any type of sensor, transducer, motion detector or the like that can sense or indicate whether paper  28  is within sensing or detecting area  66 . In one form, proximity sensor  62  is an ultrasonic generator/transducer such as a SUPERPROX® proximity sensor manufactured by Hyde Park Electronics, Inc. of Dayton, Ohio. Proximity sensor  62  is adjusted such that only material within sensing or detecting area  66  generates a material sensed or detected signal. With additional reference to FIG. 3, proximity sensor  50  is in communication with controller  82  via line  64 . Controller  82  is in communication with air supply system  80  via line  84 . Air supply system  80  is coupled via conduit  96  to air valve or solenoid  94  that is coupled to conduit  60  associated with nozzles  92  of blowpipe  58 . Controller  82  is in communication with solenoid  94  via line  98  for activation and deactivation, or on/off, control thereof. When solenoid  94  is actuated by controller  82  via line  98  in accordance with the present invention, compressed or pressurized air is caused to flow from air supply system  80  through conduit  96  and into nozzles  92  of blowpipe  58 . Of course, when solenoid  94  is deactivated or turned off, the air flow into blowpipe  58  is ceased. 
     In like manner to threading doctor assemblies  30   a  and  32   b  depicted in FIG. 2, threading doctor assemblies  30   b,    30   c,    30   d,    30   e,    32   a,    32   c,    32   d,  and  32   e  each include a blowpipe having air nozzles in air communication with an air valve or solenoid that is in air communication with air supply system  80 , and a proximity sensor in communication with controller  82 . Each solenoid is in communication with the controller  82 . This is indicated by the several partial blowpipes depicted in FIG. 3 which represent a plurality of threading doctor assemblies in accordance with the present invention. 
     In operation, fiber web material  28  initially enters dryer group  10  and, in particular, lower dryer group  14  between lower felt  26  coming from lower felt guide roll  24   b  and lower dryer cylinder  22   a  traveling in the direction indicated by arrow  38 . Fiber web material  28  is compressed against lower dryer cylinder  22   a  between lower felt  26  and the outer surface of the lower portion of lower dryer cylinder  22   a,  then exits on the opposite side of lower dryer cylinder  22   a  towards upper dryer cylinder  16   a.  At upper dryer cylinder  16   a,  fiber web material  28  becomes compressed against upper dryer cylinder  16   a  between upper felt  20  and the outer surface of the upper portion of upper dryer cylinder  16   a.  This compression scheme of the fiber web material between alternating lower and upper dryer cylinders continues until the fiber web material exits from the last dryer cylinder, here upper dryer cylinder  16   e.  In order to direct the fiber web material into the convergence area or entry point, defined as between the particular upper or lower felt and the particular upper or lower respective dryer cylinder, pressurized air from air supply  80  is directed through the blowpipe associated with the particular dryer cylinder. 
     Generally, before leading tail  40  of fiber web material  28  enters the first dryer cylinder, here lower dryer cylinder  22   a,  controller  82  activates at least the threading doctor blowpipe associated with that cylinder, and preferably, the next one (1) or two (2) blowpipes in the fiber web material advancing direction. All other threading doctor blowpipes are not active since the solenoids associated therewith are off or deactivated. With reference to FIG. 2, as leading tail  40  of fiber web material  28  rolls off of upper dryer cylinder  16   a  into emergence area  70  and begins to travel downwardly, proximity sensor  50  determines that leading tail  40  has entered sensing area  54 . Proximity sensor  50  then sends a signal to controller  82  via line  52 . As indicated above, controller  82  has preferably already activated solenoid  76  such that air from air supply system  80  is already flowing into blowpipe  46  and thus from nozzles  86 . However, in accordance with an alternative approach, the moment proximity sensor  50  detects leading tail  40  within sensing area  54 , sensor  50  indicates such presence to controller  82  which signals solenoid  76 , via line  90 , to activate and allow air to flow into blowpipe  46 . 
     As leading tail  40  emerges from emergence area  74  into sensing or detecting area  66 , proximity sensor  62  of threading doctor  32   b  detects the presence of leading tail  40 . Proximity sensor then generates and sends a detection signal via line  64  to controller  82 . Upon receipt of the detection signal from proximity sensor  62 , controller  82  activates the solenoids of the next two ( 30   b,  and  32   c ) or three ( 30   b,    32   c,  and  30   c ) threading doctors in the paper advance direction. As well, controller  82  sends a signal via respective lines to deactivate the solenoids of any threading doctors which are previous or behind, relative to the fiber web material advance direction, more than two or three threading doctors before proximity sensor  62 . In this manner, controller  82  sequences the activation and deactivation of threading doctors as the leading tail of the fiber web material advances. 
     In another form, it is possible to utilize a single proximity sensor disposed at the first or second threading doctor, or several proximity sensors disposed on the beginning several threading doctors, to detect when the leading tail of the paper enters the system. Since the rotational velocity of the dryer cylinders is generally known, the controller can be programmed or determine on the fly with the aid of one or more rotational velocity sensors, when to activate the next blowpipes of the threading doctors as the fiber web material advances, and as well determine when to deactivate any preceding blowpipes that were activated. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.