WO2007149080A1

WO2007149080A1 - Devices and methods for conveying fibers

Info

Publication number: WO2007149080A1
Application number: PCT/US2006/024119
Authority: WO
Inventors: David Herbert Murphy; Kenneth Alan Lewis
Original assignee: Eastman Chemical Company
Priority date: 2006-06-21
Filing date: 2006-06-21
Publication date: 2007-12-27
Also published as: EP2029464A1; JP2009541172A; CN101472818A; MX2008015322A

Abstract

Devices and methods for conveying fibers are disclosed. According to the invention, fibers (1) are conveyed through a conduit (2) using a plurality of in-line flow amplifiers (6, 7, 8, 9) . In this manner, the crimped material may be transported along steep gradients with significantly smaller changes in bulk properties when compared with conventional transport mechanisms that merely pull the crimped material along the line of travel.

Description

DEVICES AND METHODS FOR CONVEYING FIBERS

FIELD OF THE INVENTION

The present invention relates to the production and processing of fibers, and more specifically, to devices and methods suitable for conveying delicate fibers during handling and processing.

BACKGROUND OF THE INVENTION

Wide varieties of fiber products, both natural and synthetic, are available in the marketplace, and they require processing prior to their sale and use. During the processes for producing such fiber products, such as by spinning, a ribbon of oriented fibers is typically produced as an intermediate. In order to increase the bulk of the fibers, they are often crimped. In such processes, a large number of polymer strands are spun, gathered together in a band, and then crimped to add bulk. After crimping, the crimped fiber band is typically spread back and forth on a slow moving drying conveyor to remove any residual solvent. At the end of the conveyor, the crimped fiber band is taken off and transported to a baling machine, where the fiber band is deposited to form a bale for shipment. Acetate tow and polyester tow are typically produced in this manner. Other polymer fibers, such as modacrylics and various types of threads, also may be prepared in similar fashion.

In order to be suitable for its intended purpose, the bulk of the band of crimped fibers is carefully controlled during production. Typical measures of characterizing a fiber's bulk include total denier, crimps/inch, and bandwidth. Spinning characteristics, both the number of filaments and the size of each filament, set total denier. Crimps/inch and bandwidth, however, are functions not just of the spinning process, but also of subsequent fiber band processing.

For example, whether or not intended, bulk may be added to crimped fibers by pulling on them. This effect is quite striking when a band of crimped fibers is pulled in the direction of the length of the band. Thus, while crimping typically adds bulk, that can be defined in part by a discernible increase in bandwidth, when crimping is followed by a pulling of the fibers in the direction of the length of the fiber band, an increase in bandwidth of 200% or more, or 300% or more, or even 500% or more, when compared to a freshly-crimped tow band, may be achieved. This excessive bulking is sometimes described as "blooming," and it is the result in part of the crimps becoming misaligned with respect to one another such that the orientations of the crimps become relatively more random.

Bulk may also be added to a crimped fiber band by subjecting the fiber band to friction, such as by rubbing the band over a surface, or by blowing high-velocity gas on the band. The bulk fiber properties of a band of tow are thus a function of processing at the spinning machine, as well as subsequent work added to the tow band, such as crimping, pulling, and friction, whether or not such bulking is intended. . Conventionally, a band of crimped fibers is pulled from a dryer to a baling machine over a number of stationary guides or rollers. The pulling action associated with moving the weight of the fiber band, and the friction caused by passing the fiber band through the guides, extends the fiber, removes the crimp, and adds unwanted bulk. Unfortunately, this crimp extension is irreversible. That is, the uniformity of the crimp does not return to the band of fibers after the external forces are removed.

The distance the crimped fibers must travel from the dryer to the baling machine varies depending on the relative locations of these two pieces of machinery. Generally speaking, the further the fibers must be transported, the more the crimp in the fibers will be extended. Further, the inlet to the baling machine may be at the same elevation level as the outlet of the dryer, or may be above or below the outlet of the dryer. If the fibers are transported (pulled) uphill, more crimp is removed, and if the fibers are transported (pulled) downhill, less crimp is removed. If there are distance or elevation differences between parallel lines of equipment within a single plant, then the quality of the fiber produced in that plant will be inconsistent.

Thus, in a conventional process, a crimped fiber band irreversibly loses some of its crimp due to the pulling forces used to transport the band and the friction caused by the band sliding across stationary ring guides. The pulling forces and the corresponding crimp loss increase dramatically with the steepness of the gradient that the fiber band must travel from one processing step to another.

During processing and baling of the fiber band, controlled bulking is important to maintain the desired uniformity. With respect to cellulose acetate tow intended for cigarette filter manufacture, controlled bulking is accomplished at the stage of filter manufacture where the tow is removed from a bale and fed to a filter-making machine. It is therefore important to avoid bulking during manufacture and baling of the tow, so that bulking variances are minimized. As a result, methods of conveying tow that may be suitable for removing tow from a bale and conveying the tow to a filter- making machine may be less suitable for use during conveyance of the tow from a dryer to a baler, for example.

To eliminate the problems just described, a belt conveyor or a vibratory shaker conveyor may be used as a fiber transport device. Such a conveyor eliminates the tension (pulling) force required to transport the fibers. However, these devices contain a large number of moving parts, and they are also very expensive, very large, or often unreliable for fiber transport. In addition, the fibers may fall off a single conveyer if the required transport gradient is too steep. The use of two conveyor belts with - A -

the tow sandwiched between them has been suggested (U.S. Pat. No. 3,408,713).

Alternatively, a tow band may be transported using an air plenum device with directional slits. See U.S. Pat. No. 6,402,436 B1. This method reduces the pulling force required to transport the tow band as air pushes the tow band along its transportation path. This method also eliminates the friction associated with pulling a tow band across guides. However, this method does not work well when the tow band must be transported up a steep gradient. U.S. Pat. No. 4,858,809 discloses a process for conveying continuous fiber filaments from a first operational stage to a distant operational stage. The filament bundles, or slivers, are introduced into a first air injector at the front of a conveyor channel, and pneumatically moved through the first air injector and the conveyor channel by creating and maintaining an air flow stream through the channel. The air flow stream is allowed to escape at spaced apart locations along the conveyor channel while air is injected into the channel at these same locations, in order to continue pneumatic movement of the filament bundles through the channel. The filament bundles are mechanically guided by guide means within the conveyor channel and through the conveyor channel until the filaments reach the distant operational stage, and the air flow stream is then terminated and the bundles conveyed mechanically thereafter through the conveyor channels.

U.S. Pat. No. 5,429,575 discloses a conveying system for transporting tow to a filter-making machine, the system comprising a pneumatic duct in which the tow is conveyed with the assistance of air movers.

U.S. Pat. No. 6,543,662 B1 discloses an apparatus for transporting a web that includes a table element provided with an inclined blowing device, at least one rounded hump, and at least one sucking device between the blowing device and the rounded hump. The rounded hump is said to allow the sucking of air without any risk of tearing or breaking the web. The limited amount of air provided is said to ensure high transport forces, and increased efficiency of the transport system. In addition to the fibers already described, there are a variety of other relatively delicate fibers that are difficult to effectively transport, especially lengthwise along significant vertical or horizontal distances, without stretching or breaking the fibers.

There remains a need in the art for improved methods and devices for transporting delicate fibers, such as crimped tow bands, that minimize friction between the transport device and the fibers, and that minimize the need for applying pulling forces to reach the intended destination, such that the fibers are not unduly extended or even destroyed, or any crimp present is not unduly affected, or the width of a fiber band is not unduly increased, or any combination of the foregoing. This need is especially acute when the fibers must be transported to a higher elevation, and at a steep gradient, to either compensate for an undesirable plant layout or to enable a more advantageous one.

BRIEF SUMMARY OF THE INVENTION

The present invention pertains to a device for conveying a fiber band, comprising: a conduit defining a first opening and a second opening; a first in-line flow amplifier provided adjacent to the first opening of the conduit and in fluid communication with the conduit; a second in-line flow amplifier provided adjacent to the second opening of the conduit and in fluid communication with the conduit; and one or more sources of high pressure gas in fluid communication with the first in-line flow amplifier and the second in-line flow amplifier. The present invention also pertains to a method of conveying a fiber band, comprising providing a gas flow to a plurality of in-line flow amplifiers provided along the length of a conduit, to thereby create a flow of air within the conduit to convey the fiber into the conduit via a first opening, through the length of the interior of the conduit, and out a second opening of the conduit, wherein the gas flow is provided at a pressure greater than ambient pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tow-conveying device according to one embodiment of the present invention;

FIG. 2 is a side, cross-sectional view of a portion of a conduit according to an embodiment of the present invention; FIG. 3 is a view of a plant layout that includes an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to the following detailed description of the invention, including the appended figures, and to the examples provided. It is to be understood that this invention is not limited to the specific conditions described. It is also to be understood that the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting.

As used in the specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

By "comprising" or "containing" we mean that at least the named element or material is present, but the terms are not intended to exclude the presence of other elements or materials, even if the other elements or materials have the same function as what is named.

The terms "fiber" and "fibers" as used herein are intended to encompass a variety of natural and synthetic fibers comprised of a variety of materials without limitation, including but not limited to cellulpsic polymers, including cellulose esters such as cellulose acetates, and especially cellulose. acetate tow, such as that used in cigarette filters; polyester polymers such as poly(ethylene) terephthalate and the like; polyalkylenes such as polyethylene, polypropylene, and the like; paper and paper-like materials such as streamers and the like; threads of various types, whether natural or synthetic; and even edible confections such as cotton candy, and the like, that might be suitably conveyed according to the invention.

By the terms "ambient" or "ambient pressure" we mean the pressure generally present in the atmosphere, which is understood to vary based on such factors as elevation and atmospheric phenomena described generally as weather. When the methods and devices according to the invention are implemented in a factory, the ambient pressure may vary slightly from the air pressure outside the factory, based on ventilation systems and air flow patterns within the factory, and in certain controlled environments, the ambient pressure within the factory may vary substantially from ambient outdoor pressure in the vicinity of the factory. Notwithstanding such differences, the ambient pressure will nonetheless differ substantially from the pressure of the high-pressure gas provided to the in-line flow amplifiers useful according to the invention. Thus, in a broad sense, the term "ambient" refers to that pressure around and adjacent the devices according to the invention.

The methods and devices of the invention may be used in open systems, in which a conduit is in fluid communication with the environment, such as the open air within a factory, or they may be used in closed systems, in which the conduit is in fluid communication only within a closed system having a controlled environment, whether for contamination purposes, or for purposes of controlling humidity, or if for any other reason the environment adjacent the conduit is in any way controlled. When we use the terms "high-pressure gas" or "high-pressure air" we mean that the pressure of the gas or air is substantially greater than ambient, such that the high-pressure gas or air is sufficient to provide a high volume low pressure flow of air within the conduit of the invention when the high-pressure gas or air is provided to the in-line flow amplifiers used according to the invention. Thus, the higher the pressure of the gas or air provided to the in-line flow amplifiers of the invention, the lower will be the volume needed to induce an equivalent flow of air within the conduit. The flow of air through the conduit, in turn, will be selected to convey the fibers through the conduit without adversely affecting the fibers, which is of course a function of the properties of the fibers themselves.

The terms "gas" and "air" are both used herein to describe the gas or air provided to the in-line flow amplifiers of the invention. The term gas is thus intended to include the term air. Particularly, in those cases in which air may suitably be used or if the use of air will be more economical than most other gases that might be used. When an embodiment is described as using high-pressure air, those skilled in the art will readily appreciate that any other gas may be used that does not, for example, adversely affect the properties of the fiber bands conveyed.

When we say that a flow amplifier is adjacent to an opening of the conduit, we mean that it is relatively near the opening, and in fluid communication with the opening. In any event, the flow amplifier referred to as "adjacent" is in closer proximity to the opening than are other flow amplifiers provided along the length of the conduit. The conduit may be provided at one or both openings of the conduit with a flared mouth to facilitate entry or exit of the fibers. In one aspect, the present invention provides devices for conveying fibers, such as a band of crimped cellulose acetate tow, the devices comprising an open-ended conduit, for example a tube or pipe, such as a cylindrical tube or pipe, provided with a plurality of in-line flow amplifiers along the length of the conduit and in fluid communication with the conduit so as to cause a flow of air within the conduit. By means of these in-line flow amplifiers, a stream of air is created within the conduit that enters the conduit from a first end and exits the conduit from a second end, the flow of air in the conduit being such that, for example, undue blooming of a crimped tow band is avoided. The flow of air exiting the conduit will include the air entering the first opening or entrance of the conduit, and that provided to each of the air amplifiers. In one embodiment, all or substantially all of the air exiting the conduit exits at the second opening, that is, at the functional exit of the conduit from which the fiber band exits the device. In this embodiment, there are no exits or openings that would serve as alternative exits of the air from the conduit.

The in-line flow amplifiers useful according to the invention are provided with a high pressure gas that is caused to flow through an annular gap of the flow amplifiers provided with a Coanda profile, the high pressure gas causing a flow of air through the conduit that is of a greater volume but a lower velocity than that of the high pressure gas provided to the flow amplifiers.

In another aspect, the present invention provides methods for conveying delicate fibers, the methods comprising providing a high pressure gas flow to a plurality of in-line flow amplifiers, for example at least two flow amplifiers, provided along the length of a conduit, to thereby create a flow of air within the conduit to convey the fibers into the conduit via a first opening or entrance, through the length of the interior of the conduit, and out a second opening or exit of the conduit. In yet another aspect, the present invention provides methods for conveying delicate fibers, such as a substantially continuous fiber band, the methods comprising providing a high pressure gas flow through annular gaps of a plurality of in-line flow amplifiers in fluid communication with a conduit through which the fiber band is conveyed, the annular gaps being provided with Coanda profiles along which the gas flows through the annular gap and into the interior of the conduit, to create a flow of air in and through the conduit, to thereby convey the fibers through the conduit.

The devices and methods according to the invention may be used to convey a variety of fibers of various lengths, widths, weights, cross- sectional thicknesses and compositions. By means of the invention, relatively delicate fibers may be conveyed, such as acetate tow bands, for example, comprised of cellulose acetate tow. Alternatively, the fibers may be comprised of a polyester, for example a poly(ethylene) terephthalate. Any other suitable fibers may be likewise conveyed without limitation, the invention being especially suited for use in those cases in which avoidance of undue blooming of crimped fibers during conveyance would be necessary or advantageous. Similarly, delicate fibers that might physically separate from one another or be pulled into separate fragments with the application of a pulling force, likewise may be conveyed while maintaining the integrity of the fibers. While any fibers may be conveyed with the devices and methods according to the invention, fibers not subject to blooming, physical separation, or disintegration might be more economically conveyed simply by pulling the fibers along a series of rollers or ring guides, although the devices and methods of the present invention are nonetheless useful to convey such fiber bands, without limitation as to the physical characteristics of the fibers to be conveyed. Delicate fibers that may be usefully conveyed according to the invention thus include a variety of fibers, without limitation as to their physical characteristics. In some embodiments, the fibers conveyed may be relatively short in length, such as from 1 cm, or even less, up to 25 cm, or more, while in other embodiments, the fibers conveyed may have a length that is at least as long as the conduit through which the fibers are conveyed. Alternatively, the fibers conveyed may be substantially longer than the length of the conduit through which the fibers are conveyed, such as at least twice the length of the conduit, or at least five times the length of the conduit, or the fibers may be substantially continuous, such that interruptions in fiber conveyance and packaging may be minimized. Indeed, the length of the continuous fibers conveyed may be such that the length of the fibers is sufficient to provide a bale or other package containing a single length of fibers, or relatively few separate lengths of fibers, to thereby prevent interruptions in processing the fiber band, and in later removing the fiber band from the packaging to prepare an article such as a cigarette filter rod, for example. In practice, there is no practical limit to the length of the fibers conveyed, and indeed, should it be desirable to do so, a continuous fiber, having no beginning or end, could be conveyed according to the invention in and through the device practically indefinitely.

The widths of the fibers conveyed may likewise vary within a wide range, for example 1 mm or more, or 5 mm or more, or 1 cm or more, up to 3 cm or more, or up to 5 cm or more, or up to 10 cm, or in certain embodiments, in widths even greater than 10 cm, such as up to 15 cm in width, or up to 25 cm in width, or even greater.

The conduits useful according to the invention may likewise vary within a broad range of lengths and internal diameters, and the internal diameters of the conduits may vary along the lengths of the conduits.

For example, lengths of conduit as short as 50 cm or more, or 1 meter or more, or 2 meters or greater may be used, up to lengths, for example, of 5 meters, or 25 meters, or 50 meters, or even up to 125 meters, or 250 meters or more, can be used, depending upon the length of the area through which the fiber band is to be conveyed.

The internal diameters of the conduits useful according to the invention may likewise vary within a wide range, and the diameters of the conduits may vary along the length of the conduits. For example, if fibers or fiber bands of a relatively narrow width are to be conveyed, for example of a few microns in width, or of one or several millimeters in width, the internal diameter may be, for example, 0.1 cm or more, or 1 cm or more, or 3 cm or more, or 5 cm or more, or 10 cm or more up to, for example, 5 cm or less, or 10 cm or less, or 25 cm or less, or 50 cm or less, or even greater diameters if a fiber band to be conveyed has a relatively wide width, such as several centimeters or more in width.

The conduits useful according to the invention may be straight, substantially straight with small variances not significantly affecting the function or placement of the flow amplifiers, or may be substantially curved, although in those cases in which the conduits are substantially curved, it may be more difficult to determine the appropriate positions to place the flow amplifiers, and it may be necessary or helpful, for example, to provide a flow amplifier at or near the maximum point of curvature. Thus, in many embodiments, the conduits of the invention will be either straight or substantially straight, and substantial changes in the direction in which the tow is to be conveyed may be addressed through some alternative design, such as a guide, a roller, or the like.

The conduits useful according to the invention may be comprised of a wide variety of materials, such as various metals or alloys, or plastics such as PVC, or the like. In those instances in which the fibers may be subject to hanging or catching on small projections, the interior of the conduit may be polished or otherwise smoothed or sanded. Similarly, in those cases in which the fibers may tend to adhere to the conduit upon contact, the conduit may be treated with a substance intended to reduce adhesion, for example poly(tetrafluoroethylene), or the like. When conveying fibers that tend to cause a build-up of static electricity, it may be helpful, for example, to provide a conduit comprised of one or more conductive polymers, or other conductive material, to diffuse the static charge.

The conduits useful according to the invention may have a variety of cross-sectional shapes, from round, to oval, to even roughly square or rectangular, although those skilled in the art will readily comprehend that conduits having a substantially circular or oval cross-section will be more easily fitted with flow amplifiers having substantially annular gaps. Thus, as used herein, the term "annular" need not mean perfectly round, but may instead be substantially oval, although it will be readily appreciated that unless a particular orientation of a fiber band is to be maintained without twisting, or the like, a substantially cylindrical conduit provided with a plurality of flow amplifiers having substantially circular annular gaps will be more easily assembled and used than will one that varies from the circular or cylindrical shapes to any material extent.

The conduits in practice will typically be comprised of separate sections, each of which is in fluid communication with at least one in-line flow amplifier, the length and interior of the conduit thus being defined by the interior of each of the several sections, and by the interior of the in-line flow amplifiers provided along the length of the conduit and through which the sections of the conduit are attached. If there are differences between the diameters of the conduit sections and the interior of the flow amplifiers, the internal diameter of the device may vary along the length of the device.

The devices according to the invention may be used alone or together to span any desired distance or orientation. If a significant distance needs to be spanned, it may be advantageous to use the devices of the invention for vertical scaling, while using more economical devices when horizontal distances need be spanned, such as conveyor belts, roller guides, or the like. In such cases, devices of the invention may be used together with devices suitable for spanning horizontal distances in a series of devices in which fibers are to be conveyed at a distance where both vertical and horizontal distances must be spanned. Alternatively, a single device according to the invention may be used to span a great distance, at substantially any angle between horizontal and vertical, inclusive.

The in-line flow amplifiers useful according to the invention cause a flow of air in the conduit by the Coanda effect phenomenon, as further described below. These flow amplifiers are provided with a source of low volume air at a relatively high pressure, compared to the ambient pressure of the air at the openings of the conduit, causing a relatively large flow of air through the conduit when compared with the volume of high pressure air used to induce the flow. The flow of air through the conduit induced by the in-line flow amplifiers, including both the high pressure air provided to each of the flow amplifiers as well as the flow of air into the first opening (the entrance) of the conduit that is induced by the flow amplifiers, allows the fibers to be conveyed through the conduit without causing significant degradation of the fiber, such as bulking or blooming when the fiber is a crimped tow band, or destruction of the fibers if the fibers are relatively delicate and subject, for example, to being easily pulled apart into separate lengths.

The in-line flow amplifiers useful according to the invention may be provided with individual sources of a gas such as air. Alternatively, the flow amplifiers may use a common source of a gas such as air, distributed for example through a manifold assembly. The gas source used may be a compressed gas such as air, or alternatively, any of various types of blowers may be used as a gas source, or any other known source of gas providing pressures substantially greater than ambient. A typical compressed gas source is a tank of compressed air. To obtain the most economical use of the compressed air, the flow amplifiers may each be calibrated so as to maximize suction flow into each of the air amplifiers. Alternatively, the suction of each may be adjusted such that all of the flow amplifiers function in substantially the same way.

According to the invention, the conveying device is thus provided with a plurality of flow amplifiers along the length of the conduit, for example at least two flow amplifiers, so as to convey the fibers within the conduit at a reduced tension, or even substantially "tension free," when compared with the tension that would be required to pull the fibers along the intended line of travel in the absence of the conveying device. In general, the greater the number of flow amplifiers along the length of the conduit, the lower the compressed gas pressure may be set so as to satisfactorily convey the fibers at a given production speed.

The flow amplifiers useful according to the invention are typically positioned at regular intervals along the conduit, for example with an entry flow amplifier adjacent a first end of the conduit where the fibers enter the conduit, an exit flow amplifier adjacent a second end of the conduit where the fibers exit the conduit, optionally with additional flow amplifiers placed between the two ends, for example at substantially equal intervals along the length of the conduit. If desired, any number of additional flow amplifiers may be included along the length of the conduit between the entrance flow amplifier and the exit flow amplifier.

In view of the present disclosure, one skilled in the art may select the number and placement of the flow amplifiers based on the length of the conduit used, that is of course a function of the distance in which the fiber band is to be conveyed; the cost of the compressed gas provided to the flow amplifiers; the means by which the flow of high pressure gas to each of the flow amplifiers is regulated; and the cost of the flow amplifiers themselves. While it is not necessary that the flow amplifiers be evenly spaced along the conduit, or that the pressure to each of the flow amplifiers be substantially uniform, or that the structure and function of each of the flow amplifiers be the same, in practice it may be desirable that each of the flow amplifiers be functionally equivalent such that the movement of fibers through the conduit may be more quickly normalized along the length of the device. The in-line flow amplifiers useful according to the invention are

Coanda flow amplifiers; that is, they take advantage of the Coanda effect. This effect is well explained in U.S. Pat. No. 5,347,103, the relevant portions of which are incorporated herein by reference, from which the following explanation was derived. The Coanda effect describes the phenomenon in which a jet of fluid exiting a nozzle along a surface tends to follow and adhere to the surface, even if the surface is convexly curved. The jet's entrainment of nearby ambient fluid as it flows depletes the surface fluid. This causes a pressure differential to arise between the side of the jet adjacent the surface, where a partial vacuum or low pressure region arises, and the opposite side of the jet, which is at ambient pressure. This pressure differential is what causes the jet to adhere to the surface. Continual entrainment also causes the thickness of the jet to increase so that eventually, if the surface were long enough, the jet would acquire too much mass and would break up. The optimal curvatures for such surfaces were determined by Henri Coanda, and are referred to as Coanda profiles.

The flow amplifiers useful according to the invention have fluid flow passages, in fluid communication with the conduit of the device, which approximate a Coanda profile. A high pressure gas, such as compressed air under relatively high pressure with respect to ambient conditions, flows radially inwardly into the passage through an annular gap, one surface of which joins and forms a part of the Coanda profile of the passage through the air amplifier. As the high pressure flow exits the gap, it follows the Coanda profile into the passage of the conduit, thereby entraining ambient air, causing it to flow through the conduit. In this manner, a relatively low volume of gas at a relatively high pressure may be used to create a flow of air through the conduit of lower pressure (or velocity) but at a higher volume than the volume of air provided to the air amplifier. Thus, functionally, the flow amplifiers according to the invention use a relatively high pressure gas in relatively low volumes to create a relatively large volume of air flow at relatively low pressure or velocity. It is this large volume of low velocity air through the conduit that conveys the delicate fiber bands through the device without materially affecting the desirable properties of the fiber band. The flow amplifiers according to the invention are in-line flow amplifiers, such that the gap in the flow amplifiers provided with a Coanda profile is a substantially annular gap in fluid communication with the conduit around the entire internal circumference of the conduit. By providing an annular gap, air movement is created uniformly around substantially the entire internal circumference of the conduit, thereby providing an even flow within the conduit. While we do not intend to exclude flow amplifier structures in which the continuity of the annular gap may be interrupted to provide, for example, structural support for the adjacent structures that define the gap, one skilled in the art will readily comprehend that optimal performance is provided with a device in which the annular gap is substantially continuous.

Thus in a broad embodiment, the flow amplifiers useful according to the invention are provided with annular gaps, as just described, in which the gap defines a passage having a surface defining a Coanda profile, the high pressure gas provided to the flow amplifier being conducted through the annular gap adjacent the Coanda profile so as to induce the flow of ambient air within the conduit. The annular gaps of the flow amplifiers of the invention may be distinguished from flow devices provided with a plurality of discrete channels around the circumference of the flow devices. See, for example, U.S. Pat. No. 5,429,575. Thus, in an embodiment of the present invention, the Coanda profile of the flow amplifier provided is functionally adjacent the circumference of the conduit of the device and in fluid communication, such that the flow of air along the Coanda profile of the air amplifier extends from the exit of the flow amplifier along the length of the conduit. The width of the annular gap through which the pressurized gas flows may be selected based upon the pressure of the gas provided, the internal diameter of the conduit, the physical properties of the fiber band including size and weight, and the number and location of the air amplifiers along the conduit. In an embodiment intended to convey crimped bands of cellulose acetate tow having a width, for example, from 1 cm to 3 cm, and in which four or five air amplifiers are provided along the length of a device of twenty feet in length, having an internal diameter from 3 cm to 10 cm, and provided with a high pressure gas at a pressure from 2 psig to 100 psig, the annular gap of the air amplifiers may vary from greater than zero to several thousandths or hundredths of an inch or from 0.025cm to 0.0025cm.

In Coanda effect devices such as the flow amplifiers of the invention, the output flow rate of the flow amplifier at the exit is a function of the input flow rate of the pressurized gas and the inflow flow rate of ambient gas or air that becomes entrained in the input flow of the flow amplifier. One skilled in the art will readily comprehend that small gaps produce relatively higher output gains but perhaps at the expense of maintaining a relatively uniform, linear flow of air that does not adversely affect the fibers to be conveyed. Based on the present disclosure, the proper gap spacing, air pressure, and number of flow amplifiers, may be selected based upon the intended use and the length of the conduit needed, which is, of course, a function of the distance that the fibers must be conveyed.

The flow amplifiers useful according to the invention are thus in fluid communication with the interior of the conduit of the conveying device. They are attached on the high pressure side with a source of compressed gas such as air, for example, and are provided with an annular gap defining a Coanda profile that is in fluid communication with the conduit so as to draw air into the conduit in the direction of the intended travel of the fibers. By providing a plurality of these flow amplifiers along the length of the conduit, the fibers may be conveyed with little friction or pulling of the band, allowing conveyance at any angle from substantially horizontal to substantially vertical.

Coanda flow amplifiers suitable for use. according to the invention include those available from EXAIR Corporation (Cincinnati, Ohio), O.N. Beck & Co. Ltd. (London, England), and ARTX Ltd. (Cincinnati, Ohio). The flow amplifiers may be provided with a manifold system whereby some or all of the flow amplifiers are in fluid communication with one another through the use of pipes or tubing. Various connection designs are possible, including threaded, welded, or flanged. Each individual flow amplifier may thus be supplied with compressed air through a fitting that is supplied with air via a compressed air plenum that can be another pipe or tube. In addition, each individual flow amplifier may be calibrated so as to achieve maximum or uniform performance prior to installation in the system. The number of individual flow amplifiers in the series may be selected based on the overall length of the system in order to eliminate undue pressure drops between the flow amplifiers.

Compressed air from a compressed air source may thus enter the plenum somewhere along its length, and the plenum may be sized to eliminate undue pressure drops along its length - incrementally longer lengths requiring incrementally larger tubing. Typically, the compressed air supply is regulated via a pressure regulator from some higher pressure to some lower operating pressure that is selectable by the system operator. In a specific embodiment, a fiber band, such as a crimped acetate tow band, typically emerges from a tow dryer on a moving conveyor belt. The tow band is typically in a "criss-cross" lay pattern on the belt, but is quickly refocused as it enters the tow-conveying device. The crimped tow band passes through the entire system at high speed, for example from 200 m/min to 600 m/min, or from 250 m/min to 400 m/min, as it is carried by the air flow inside the device. The tow exits the device in a condition that is substantially the same as that in which it entered, with respect to unwanted bulking, and proceeds onward to the next manufacturing step in the process. The speed at which the tow passes through the device may be controlled by the setting of the regulated air supply, and thus may vary based on overall process requirements.

On start-up, it may be necessary or helpful to increase the pressure of gas provided to the flow amplifiers in order to begin the conveyance of the fibers through the conduit, after which, when the end of the fiber band has traveled in and through the conduit, the pressure may be reduced to obtain the desired speed and condition of the fiber band during substantially continuous operation. The speed of the flow of air within the conduit may vary within a wide range; for example from 100 m/min to 1,500 m/min, or from 150 m/min to 1,000 m/min, or from 250 m/min to 750 m/min.

Similarly, the speed with which the fibers travel through the conduit may vary within a wide range; for example from 150 m/min to 1 ,000 m/min, or from 250 m/min to 400 m/min.

Likewise, the speed the fiber band travels through the conduit may vary with respect to the speed of the air through the conduit within a wide range of ratios. For example, the ratio of the speed of the fiber band to the speed of the air flow may be from 0.1 :1 up to 0.9:1 , or from 0.2:1 to 0.8:1. Turning now to an embodiment depicted in the drawings, Figure 1 depicts a tow-conveying device 12 according to the invention, the device comprising an open-ended tube 2 serving as the conduit that is comprised of separate tube sections 2a, 2b, 2c, 2d of a metal pipe joined with a plurality of in-line, flow amplifiers 6, 7, 8, 9 in fluid communication with the tube 2 and in positions spaced apart along its length. These flow amplifiers 6, 7, 8, 9 are provided with compressed gas supplied from a suitable compressed gas source 3. A regulator 4 regulates the pressure of the compressed gas from its source 3 to a manifold 5. We refer now to Figures 1 and 2, Figure 2 depicting in more detail the flow amplifier 6 of Figure 1 , although in this embodiment each of the flow amplifiers 6, 7, 8, 9 is substantially of the same structure and function. The compressed gas leaves the regulator 4 at a lower, regulated pressure, and flows through manifold 5 to each of the flow amplifiers 6, 7, 8, 9 through compressed gas inlet nozzles 10 in the flow amplifiers 6, 7, 8, 9. The flow of compressed gas through the flow amplifiers causes a partial vacuum in the tube, as a result of the Coanda effect previously described, thereby creating an air flow that conveys the crimped tow band 1 through the tube.

The compressed gas flows into each of the flow amplifiers 6, 7, 8, 9 at inlet 10 along the arrows indicated at inlet 10 which is in fluid communication with an annular gap 13 defined by a main body 14 of the flow amplifier and an inner body 15 of the flow amplifier and is rotatably attached to the main body 14 of the flow amplifier 6 via threadings 17 that allow the gap 13 to be adjusted and thereafter locked at the desired position via locking ring 18. The inner body 15 of the flow amplifier 6 defines a lip 16 along the annular gap 13 in the form of a Coanda profile. The flow of air through the annular gap 13 along the Coanda profile lip 16 causes a flow of air along and through the tube 2 in the direction of the arrows. The flow amplifier 6 is rotatably connected with tube section 2b via the threadings 17 and with tube section 2a via threadings 19, and each of the tube sections 2a, 2b is locked at the desired positions by means of locking nuts 20, 21 respectively to form a substantially air-tight seal between the flow amplifier and the sections 2a, 2b that form portions of the tube 2 adjacent the flow amplifier 6. Those skilled in the art will readily appreciate that the means of connecting a flow amplifier with the sections of a tube include, but are not limited to, threadings, flanges, or welding. Referring again to Figure 2, ambient air indicated at arrows 24 is caused to flow into and through the tube 2 by the air exiting the annular gap 13 of the flow amplifier 6 along the Coanda profile lip 16. The flow of air conveys a crimped tow band 1 into and through the tube 2. As previously described, the ambient gas flowing into the tube 2 can be room air, an inert gas source, or a fiber band conditioning gas source. Room air is most economical.

Similarly, the compressed gas provided from the compressed gas source 3 can be air, an inert gas, or a conditioning gas, such as one having controlled humidity or one or more other intentionally selected properties. By inert gas, we mean a gas that does not substantially affect the physical or chemical properties of the conveyed fibers so as to make them unfit for the intended use. A conditioning gas is one selected to provide one or more desirable properties to the tow band, such as a particular humidity selected to provide or maintain the desired water content in the fibers.

Alternatively, an anti-static solution can be metered into the air amplifier to prevent the generation or to further dissipate the presence of static electricity in the process.

Although the device shown in Figure 1 is provided with a single compressed air source 3 providing air to each of the flow amplifiers, alternatively each flow amplifier may be provided with a separate source of compressed air. Of course, the flow amplifiers will be aligned to move gas in the same direction, such as left to right in Figure 2, and likewise, the air flowing through the conduit will exit at the same opening from which the tow exits the conduit. Although the number of gas amplifiers may vary, the air flow is desirably maintained through the conduit at a velocity sufficient to offset the weight and pulling forces on the tow, while not substantially affecting the bulk fiber properties. In other words, compressed gas flow into the flow amplifiers should ordinarily be such that locally high gas velocities are not present because they might affect the bulk properties of the fiber band, or even tear the fibers.

The flow amplifiers useful according to the invention may be calibrated on a performance basis by any suitable means. That is, instead of simply setting the internal annular gap in the flow amplifier to a specified distance, the flow amplifiers may be calibrated to provide maximum suction, to get the most performance for the amount of compressed air used, or to the same amount of suction, so as to avoid variability in flow rate within and through the conduit.

Figure 3 depicts an embodiment of the invention described in the examples. A tow band 1 leaves a dryer apron 24 at position A. The tow is transported through the conveying device. The total length of the vacuum conveyer is 6 meters. Thus the tow travels 6 meters from position A to position B. After leaving the vacuum conveyer, the tow travels over a guide 25. The guide can be a roller guide or a stationary guide. The tow continues horizontally through a number of guides 26 from 3 meters to 15 meters in the horizontal direction. The final measurements for tow characteristics are taken at position C just before the tow enters the bale 22.

EXAMPLES

In the examples, a crimped cellulose acetate fiber tow band, having a total denier of 30,000 and an initial bandwidth of 7/8 inch, is transported vertically 15-25 feet (or 4.6-7.6 meters) from point A and then 4-7 feet (or 1.2-2.2 meters) horizontally to point B, and afterward transported substantially horizontally for an additional variable distance from 10-40 feet (or 3.1-12.2 meters) to point C. The final bandwidth is then measured at point C. Example 1 (comparative)

A crimped acetate tow band as just described is transported under tension (pulled) from point A to point B using from 1-3 stationary ring guides with variable wrap angles in a non-linear fashion and then to point C using 1-4 rings guides that are positioned horizontally 10 feet (or 3.1 meters) apart. The bandwidth increases, as a result, to a width of 1.76 inches or by 100 %. .

Example 2 (inventive)

A crimped acetate tow band is transported from point A to point B through a 20 foot tube, having approximately a 2-inch nominal diameter, provided with 4 in-line flow amplifiers (O.N. Beck & Co. Ltd., model RJ405C (London, England)), and then transported under tension (pulled) to position C. The pressure of the compressed air provided to each of the air amplifiers is 8.5 psig. The air amplifiers are calibrated for maximum suction. The width of the crimpled acetate tow filter band increases to 1.1 inches, or by 26%. A further improvement is achieved when a light weight roller guide is provided at position B, with the bandwidth increasing to only 1.0 inches or by 14%.

Example 3 (inventive)

A crimped acetate tow band as already described is transported from point A to point B through a 20 foot pipe, having a 2 inch nominal internal diameter, provided with 4 in-line air amplifiers, and afterward pulled under tension to variable position C. The air pressure of the compressed air provided to each air amplifier is 5 psig. The air amplifiers are calibrated for maximum suction. The acetate tow bandwidth increases to 1.4 inches or by 60%. Further improvement is achieved when the tow travels over a roller guide provided at point B, with the bandwidth increasing to only 1.3 inches, or by 48%.

Example 4 (inventive)

The crimping in this example is decreased by some amount to produce a slightly looser tow band initially. The acetate tow band, as previously, described is transported from point A to point B through a 20 foot tube, with a nominal internal diameter of 1.88 inches, and then transported under tension (pulled) through 1-4 stationary ring guides to point C. The pressure of the compressed air used is 4-5 psig. The air amplifiers are specially calibrated for maximum suction. The bandwidth of the acetate tow band increased to 1.5 inches, or by 70%. Further improvement is achieved when the tow travels over a roller guide at point B, with the bandwidth increasing to only 1.4 inches or by 60%.

The invention has been described in detail with particular reference to preferred embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. In the specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only, and not for purposes of limitations, the scope of the invention being set forth in the following claims.

Claims

We claim:

1. A device for conveying a fiber band, comprising: a conduit defining a first opening and a second opening; a first in-line flow amplifier provided adjacent to the first opening of the conduit and in fluid communication with the conduit; a second in-line flow amplifier provided adjacent to the second opening of the conduit and in fluid communication with the conduit; and one or more sources of high pressure gas in fluid communication with the first in-line flow amplifier and the second in-line flow amplifier.

2. The device according to claim 1 , wherein the device further comprises one or more intermediate in-line flow amplifiers provided along the length of the conduit between the first flow amplifier and the second flow amplifier, and in fluid communication with the conduit.

3. The device according to claim 1 , wherein the conduit has an internal length from 0.5 meters to 250 meters.

4. The device according to claim 1 , wherein the conduit has an internal length from 1 meter to 100 meters.

5. The device according to claim 1 , wherein the conduit has an internal length from 5 meters to 50 meters.

6. The device according to claim 1 , wherein there is one or more sources of compressed air that provides air at a pressure from 2 psig to 100 psig.

7. The device according to claim 1 , wherein the conduit has an internal diameter from 0.1 cm to 50 cm.

8. The device according to claim 1, wherein the conduit has an internal diameter from 1 cm to 25 cm.

9. The device according to claim 1, wherein the device further comprises a manifold in fluid communication with the one or more sources of compressed air and with the plurality of air amplifiers.

10. The device according to claim 1 , wherein the conduit has a substantially circular cross-section.

11. The device according to claim 1 , wherein the conduit has a substantially square or rectangular cross-section.

12. The device according to claim 1 , wherein each of the in-line flow amplifiers is provided with a high pressure gas that flows through an annular gap of the flow amplifiers, the high pressure gas causes a flow of air through the conduit that is of a greater volume but a lower velocity than that of the high pressure gas provided to the flow amplifiers.

13. The device according to claim 1, wherein each of the in-line flow amplifiers cause a flow of air in the conduit by the Coanda effect.

14. The device according to claim 1 , wherein each of the in-line flow amplifiers is provided with a source of low volume air at a relatively high pressure, compared to the ambient pressure of the air at the openings of the conduit, thereby causing a relatively large flow of air through the conduit when compared with the volume of high pressure air used to induce the flow.

15. A method of conveying a fiber band, comprising providing a gas flow to a plurality of in-line flow amplifiers provided along the length of a conduit, to thereby create a flow of air within the conduit to convey the fiber into the conduit via a first opening, through the length of the interior of the conduit, and out a second opening of the conduit, wherein the gas flow is provided at a pressure greater than ambient pressure.

16. The method of claim 14, wherein the fiber comprises one or more of: a cellulosic polymer; a polyester polymer; a polyalkylene polymer; paper; a natural or synthetic thread; or an edible confection.

17. The method of claim 14, wherein the fiber comprises cellulose acetate tow.

18. A method of conveying a fiber band, comprising providing a gas flow through annular gaps of a plurality of in-line flow amplifiers in fluid communication with a conduit through which the fiber band is conveyed, the gas flows through the annular gaps and into the interior of the conduit, to create a flow of air in and through the conduit, to thereby convey the fiber band through the conduit.

19. The method of claim 18, wherein the speed of the flow of air within the conduit is from 100 m/min to 1,500 m/min.

20. The method of claim 18, wherein the speed of the flow of air within the conduit is from 150 m/min to 1000 m/min.

21. The method of claim 18, wherein the speed of the flow of air within the conduit is from 250 m/min to 750 m/min.

22. The method of claim 18, wherein the speed the fibers travel through the conduit is from 150 m/min to 1 ,000 m/min.

23. The method of claim 18, wherein the speed the fibers travel through the conduit is from 250 m/min to 400 m/min.

24. The method of claim 18, wherein the flow of air through the conduit is selected to convey the fibers through the conduit without adversely affecting the fibers.

25. The method of claim 18, wherein the fibers are conveyed any distance and at any angle from substantially horizontal to substantially vertical.