Patent Application
20180037430
The present disclosure relates generally to airfoils and particularly to active airfoils used to convey sheets of fibrous material through a draw between production areas.
In the manufacture a continuous web of tissue paper or light-weight non-woven fibrous material, a space, commonly known as a draw generally separates the production line's drying area from the production line's winding area. In the case of paper manufacturing, the drying area may have a Yankee cylinder dryer, and the winding area may have one or more spools around which the tissue is wound into rolls. The rolls may be stored in inventory or moved for further processing. The draw is generally long enough to separate the winder from the drying area of the production machine, while allowing equipment to perform intermediate operations on the web as the web travels from the drying area and winding area.
These intermediate operations may include by way of example: calendaring (e.g. passing two or more webs through adjacently disposed rollers to produce webs of uniform thickness), caliper control (e.g. the measurement and adjustment of web unit weight and moisture), quality control (e.g. the real time scanning of web to identify holes and inconsistent fiber distribution), slitting (e.g. cutting the width of web exiting the dryer into multiple narrower widths), and re-pulping that portion of the web which is not being wound, such as the initial web output at production start-up or at a web break.
The web exiting the dryer section of the production machine is generally quite fragile and encounters destabilizing problems as the web moves through some of these intermediate operations. The web generally entrains a layer of air as the web moves through the draw. As the entrained air encounters the equipment that comprises the intermediate operations, the entrained air may become turbulent and create web fluttering. Fluttering can tear the web and generate dust, thereby diminishing the quality of web. While some of the intermediate operations may contribute to stabilizing the web; others can have a net destabilizing effect on the web's position and steadiness.
To account for sections of web instability along the draw, operators have tried to control the web as the web passes from the machine dryer section to the winder. These control devices included bowed pipes or rolls, straight pipes or rolls, and large flat plates or other similar devices. The nature of tissue is such that tissue has a surface being comprised to a multitude of pulp fibers radiating outwardly. As these fibers contact with stationary rigid devices such as rolls or pipes, the rigid devices tend to break these fibers, which results in the production of an extremely fine paper dust. This paper dust presents both a fire hazard situation, as well as a health hazard for the operators through ingestion into the lungs.
Previously, a common method for changing the web path through the tissue manufacturing process involved a rigid pipe. Whether bowed or straight a rigid pipe is generally simple to manufacture and install. However, the pipe method has several inherent problems. The web is generally in firm contact with the pipe, thus requiring additional tension to be applied to the web. Secondly, paper is abrasive, and gradually wears away at the pipe, encouraging periodic replacement. Thirdly, a web has a general tendency to remain attached to the curved surface of the pipe, thus requiring additional tension to break the web loose. Typically, dust particles will collect near the breakaway point, forming an extension of the pipe which eventually breaks off, falling onto the web and either contaminating the web or breaking the web.
Large flat plates were another previously popular web stabilizer and web transport system. Since this large flat plate generally occupies the majority of the draw between the dryer cylinder and the next machine element, the large flat plate is generally moved at time of start-up or web break to provide an unobstructed path for the web traverse to the re-pulper system broke pit. A mechanically driven member generally facilitates plate movement, which adds to the total system complexity. The large flat plate's long machine direction length is such that the web can alternately collapse against the surface of the plate, then pick up from the plate and subsequently collapse again, resulting in the generation of dust due to physical contact, which in turn adds to the total web tension. Additionally, to provide sufficient structural rigidity, the plate is generally made with some finite thickness to accommodate the inclusion of internal structural re-enforcement. As a result of this thickness, the entry and exit ends are shaped (generally rounded) to facilitate smooth entry and exit. The behavior of these curved ends is similar to that of the rigid pipe design, except that the tendency for web attachment to the adjacent surface is typically more aggressive because the radius employed is greater than that of the typical rigid pipe.
To address these problems, operators have generally replaced rigid bars and large flat plates with air foils. Air foils generally create lift by exploiting the Bernoulli Principal. In aeronautics, the airfoil is commonly the wing or propeller itself, both of which generally create a majority of lift at the leading edge of the airfoil. In the manufacture of fiber webs, an “airfoil” generally refers to an apparatus that spans the width of the web. These airfoils generally have a slot in the bottom of the airfoil that direct air parallel to both the bottom of the airfoil and the direction of the web movement. Because total pressure of a system remains constant, the high dynamic pressure of the air stream (i.e. the pressure of the air stream flowing horizontally) decreases the static (i.e. atmospheric) pressure vertically between the bottom of the airfoil and the web. As a result, the web, and the air under the web is generally drawn to this low pressure area caused by the horizontal airflow parallel to the web. In this manner, airfoils generally provide web support in the draw while reducing web contact.
Although airfoils address many of the problems of the rigid pipe and large flat plate, airflow instabilities near the web can induce web flutter and subsequent web contact with mechanical parts of the dryer, resulting in a coating disturbance or web damage. Web flutter can manifest in many forms, ranging from a violent flapping of the web to a high frequency drumming. Such flapping may be particularly prominent at the web edges. Increasing production speed demands are increasing instances of flutter. Accordingly, there is a long felt to have an airfoil configured to stabilize webs at increasingly higher speeds.
The problem of web flutter experienced by webs spanning the draw between a drying area of a fiber web manufacturing machine and winder, wherein the web is assisted by airfoils is mitigated by using at least one airfoil having multiple conduits connected to at least one air supply, at least two areas with openings in the form of slots or rows of holes (or elongated openings) are oriented in a direction substantially parallel to the direction of web movement, wherein these openings communicate with the multiple conduits, a Coanda surface disposed adjacent to the openings, and wherein the openings are configured to direct air flowing from the air source through the multiple conduits, through the openings and over the Coanda surface in a direction substantially perpendicular to the direction of web movement.
References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
An exemplary embodiment in accordance with the present disclosure may be used on active airfoils, in which the air entering the airfoil system is compressed air. Without being bounded by theory, Applicant has discovered that by directing air around the Coanda surface, the negative pressure, or under-pressure generated by the fast-flowing airstream may be desirably increased in order to keep a web in the vicinity of the bottom surface of the airfoil and thereby stabilize the web. In this context, a Coanda surface is to be understood as a surface on which a flow medium, which exits from an opening and follows a surface, exhibits the Coanda effect. The Coanda effect is a widely known and proven follower effect whereby a primary media flow is diverted over a Coanda surface. A description of the features of a Coanda surface and also of the effect of the media flow on the Coanda surface can be found in scientific publications. A Coanda surface is also known as a geometric structure with a shape defined by a mathematical curve called a lemniscate. A fluid stream flowing over a Coanda surface tends to adhere to that surface.
Slots, or rows of multiple holes directing air in a direction perpendicular to the direction of web movement, may be disposed at intervals along the width of an airfoil. The width of the airfoil may desirably span the width of the web. In certain exemplary embodiments, the perpendicular airflow may occur at the edges of the airfoil. In other exemplary embodiments, the airfoil may be divided into sectors, wherein perpendicular airflow is directed at the edges of the airfoil sectors such that the airflow curls around the edges of the sectors to stabilize the web.
By using an apparatus in accordance with the present disclosure, operators may be able to stabilize the web with a low pressure fan. In other exemplary embodiments, the fan may be a middle pressure fan. Accordingly, it is an object of the present disclosure to improve web stabilization generally, and particularly at the web edges while minimizing the need to compress air.
It is a further object of the present disclosure to support tail treading and to support spreading the web during or after tail threading to the full width. An exemplary airfoil can be applied to Tissue Machines (“TM”) and Through Air Dryer (“TAD”) machines for an active solution.
An embodiment in accordance with the present disclosure may further have a golf ball pattern to improve stability. The golf ball pattern may comprise a series of recesses on the bottom of the airfoil. Without being bounded by theory, air steams may be diverted from a generally horizontal orientation and flow into the series of recesses in accordance with the Coanda Effect. The air moving into the series of recesses may further create areas of low pressure and thereby attract and stabilize the fibrous web. Air flowing over and into the series of recesses that form the golf ball pattern may desirably flow in a direction perpendicular to the direction of web movement, but may also flow in a direction parallel to the web or at other angles.
The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the disclosed embodiments.
The following detailed description of the preferred embodiments is presented only for illustrative and descriptive purposes and is not intended to be exhaustive or to limit the scope and spirit of the invention. The embodiments were selected and described to best explain the principles of the invention and its practical application. One of ordinary skill in the art will recognize that many variations can be made to the invention disclosed in this specification without departing from the scope and spirit of the invention.
Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate embodiments of the present disclosure, and such exemplifications are not to be construed as limiting the scope of the present disclosure.
Operators generally use one or more airfoil web stabilizers 1 in the draw between the drying end of the web-manufacturing machine and the winder. Multiple airfoil web stabilizers 1 in accordance with the present disclosure may span the draw. In other exemplary embodiments, an airfoil web stabilizer 1 with a greater length L may be used in place of multiple airfoil web stabilizers 1 with lesser lengths L.
In an exemplary airfoil web stabilizer 1, air 80 may flow through one or more air inlets 20 communicating with an air source (not depicted). The air source may be a fan, such as a low pressure fan or medium pressure fan. In other exemplary embodiments, the air source may be a repository of compressed air. In still other exemplary embodiments, the air source may be the Yankee dryer hood or other equipment component within the web production line. The air inlets 20 extend through the edge 35 of the airfoil housing 15 and direct air 80 to conduits (90
Without being bounded by theory, the air jet 80′ moving over Coanda surfaces 50 creates areas of low pressure and attracts the web 75 toward the bottom 30 of the airfoil housing 15 due to the Coanda Effect. On the right side of
Without being limited by theory, applicant has discovered that by blowing perpendicular air jets 80′ in opposite directions around the Coanda surfaces 50, the moving air creates areas of low pressure, which attracts the stagnant air located in the etch stabilizing zone 70. The movement of air in the etch stabilizing zone 70 toward the perpendicular air jets 80′ likewise creates areas of low pressure, or under pressure in the etch stabilizing zone 70. This under pressure in the etch stabilizing zone 70 attracts the web moving in a perpendicular direction 95 and stabilizes the web 75 without having the airfoil physically contact the web 75. The movement of air around the corner 33 and edges 35, 37 of the airfoil housing 15 further reduces fluttering at the web edges 72. In active air foils, the air flowing through the slot 45 is desirably at a constant rate of speed and pressure.
Without being bounded by theory, because the under pressure in the stabilizing zone 70 is defined substantially by perpendicular air jets 80′ exiting proximate slots 45 at a constant rate of speed and pressure, expanding air from neighboring slot 45 is less likely to cause pressure variations within the stabilizing zone 70 because the air closer to the slot 45 is more compressed than air further along the width W of the airfoil web stabilizer 1. In the depicted embodiments, the opening 40 is a slot 45. Therefore, the under pressure within the etch stabilizing zone 70 may have greater consistency over conventional designs, and therefore stabilize the web 75 with greater consistency than designs that direct air jets parallel to the direction of web movement 95.
In the depicted embodiment, the slots 45 are not configured to first direct an air jet downwardly toward the web; rather, each slot 45 is configured to direct air flow into a perpendicular air jet 80′ before the air 80 exits the conduit 90 at the bottom 30 of the airfoil housing 15. An exemplary slot 45 may be formed by a top ledge 57 defining a gap 36 over a bottom ledge 54. One side of the conduit 90 may be desirably engaged to an area defining the top ledge 57.
The etch stabilizing zone 70 is disposed between the two oppositely disposed slots 45 directing air jets 80′ in opposite substantially horizontal directions, but also in a direction substantially perpendicular to the direction of web movement 95.
Affixing receptacles 23 are attached to the edge 35 and opposite edge 37 of the airfoil housing 15. A bar 29 extends into the affixing receptacles 23 to position the airfoil web stabilizer 1 along the draw.
The perpendicular air jets 80′ curve into the golf ball divots 25 thereby increasing the rate of air speed in the golf ball divots 25, thereby creating multiple areas of low pressure to stabilize the web 75. The golf ball patterns may provide sufficient low pressure areas and stability, that a passive airfoil may be used. In certain exemplary embodiments, the bottom 30 of the airfoil housing 15 may be curved in a convex shape. The curved orientation may facilitate web movement 95 with air flow.
An exemplary airfoil web stabilizer comprises: an airfoil housing having a top and a bottom, an air inlet extending into the airfoil housing, wherein the air inlet is in fluid communication with a conduit disposed inside the airfoil housing along a length of the airfoil housing, wherein the conduit is in fluid communication with an area of the bottom of an airfoil housing defining an opening in the bottom of the airfoil housing, a Coanda surface disposed on the bottom of the airfoil housing adjacent to the area defining the opening in the bottom of the airfoil housing, wherein the opening is configured to direct air horizontally over the Coanda surface along a width of the bottom of the airfoil housing, wherein the width is perpendicularly disposed to the length of the airfoil housing.
An exemplary airfoil web stabilizer may have an airfoil housing further comprising sloped surfaces. In another exemplary airfoil web stabilizer, the opening may be a slot. In still other exemplary airfoil web stabilizers, the opening may be a series of holes. In yet other exemplary embodiments, the airfoil web stabilizer may further comprise an air source fluidly communicating with the air inlet.
In an exemplary airfoil web stabilizer, the area defining the opening in the bottom of the airfoil housing may further comprise a top ledge oppositely disposed a bottom ledge, wherein the top ledge and bottom ledge define a gap between the top edge and bottom ledge and wherein the gap extends the length of the airfoil housing. In another exemplary embodiment, the airfoil web stabilizer may have multiple areas defining openings in the bottom of the airfoil housing, wherein each opening is configured to direct air over a Coanda surface in a direction perpendicular to the length of the airfoil housing.
Another exemplary airfoil web stabilizer may further comprise a series of golf ball divots at the bottom of the airfoil housing. The golf ball divot in the series of golf ball divots may be disposed proximate to a Coanda surface such that air jets exiting the opening flows over the Coanda surface before flowing across the golf ball divot.
In yet another exemplary embodiment, a web stabilizing system may comprise: an airfoil comprising an airfoil housing having a top and a bottom, an air inlet extending into the airfoil housing, wherein the air inlet fluidly communicates with a conduit within the airfoil housing, an area in the bottom of the airfoil housing defining an opening, wherein the conduit is in fluid communication with the area of the bottom of the airfoil housing defining an opening, a Coanda surface on the bottom of the airfoil housing, wherein the Coanda surface is adjacently disposed to the opening in the bottom of the airfoil housing, a web suspended under the bottom of the airfoil housing, wherein the web moves in a direction parallel to a length of the bottom of the airfoil housing, wherein air flowing through the opening flows over the Coanda surface in a direction perpendicular to the direction of web movement.
An exemplary web stabilizing system may further comprise multiple openings in the bottom of the airfoil housing, wherein half of the openings direct air perpendicular to the direction of web movement toward an edge of the airfoil housing and wherein half of the openings direct air perpendicular to the direction of web movement toward an opposite edge of the airfoil housing.
While this invention has been particularly shown and described with references to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
This application claims the benefit of U.S. provisional patent application 62/131,399, filed on Mar. 11, 2015, the entirety of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/055255 | 3/11/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62131399 | Mar 2015 | US |
