Claims
- 1. A method of forming a non-woven web of fibers comprising the steps of:
- feeding a source of fiber stock into engagement with a rotating toothed cylinder;
- rotating the cylinder at such a speed that the stock is opened so as to form individual fibers moving with the cylinder in induced air stream;
- deflecting the individual fibers from the cylinder in the form of a stream of fibers by positioning one end of a deflector plate adjacent to the peripheral surface of the cylinder and another remote end away from the cylinder, so a guiding surface of the deflector plate guides the fibers from the cylinder;
- keeping the cylinder free of air streams other than said induced air streams which would tend to doff the fibers from the cylinder;
- keeping the stream of fibers free of confining ducts; and
- intercepting the stream of fibers with a moving conveyor and accumulating the fibers on the conveyor to form a web material.
- 2. The method as claimed in claim 1, wherein the step of feeding involved simultaneously feeding two different laterally spaced stocks to the cylinder.
- 3. The method as claimed in claim 1, further including the step of protecting the peripheral surface of the cylinder with a cover extending from the deflector plate to the feed means on the side of the cylinder opposite the fiber stream.
- 4. The method as claimed in claim 1, further including the step of creating a vacuum of less than 5 inches of water through perforations in the conveyor.
- 5. The method as claimed in claim 1, further including the step of providing a porous substrate on the moving conveyor prior to intercepting the stream of fibers with the conveyor, such that the web of material is formed on the substrate.
- 6. The method as claimed in claim 1, further including the step of locating at least one open tray of particulate material adjacent the cylinder so that the material is drawn to the cylinder due to its rotation and is blended with the fibers for deflection by the deflector plate.
- 7. The method as claimed in claim 6, further including the step of providing a taper to the deflector plate away from the guiding surface at the remote end of the plate such that the fibers and the particulate material are deflected at different angles.
- 8. A uniform fluff web product produced by the method of claim 1, having a length, width and thickness wherein the web is substantially free of shingle effect.
- 9. The product as claimed in claim 8, wherein the fibers of one lateral portion of the web differ from the fibers of another lateral portin.
- 10. The product as claimed in claim 8, wherein at least one type of particulate material is uniformly blended in the product.
- 11. The product as claimed in claim 8, wherein different particulate materials are blended with fibers at different lateral portions of the web.
- 12. The product as claimed in claim 8, wherein the particulate material predominates at one level of thickness of the web.
TECHNICAL FIELD
This is a continuation-in-part application of copending application Ser. No. 75,708, filed July 20, 1987.
The present invention relates to methods and apparatus for forming non-woven structures of fibers and, more particularly, to the efficient formation of uniform webs from fiber materials, such as pulp board stock or fiber batts.
Non-woven fabrics are structures consisting of accumulations of fibers typically in the form of a web. Such fabrics have found great use in disposable items, such as hand towels, table napkins, curtains, hospital caps, draperies, etc., because they are far less expensive to make than conventional textile fabrics made by weaving and knitting processes.
There exist many different processes for forming non-woven structures. The processes, however, when used to generate uniform pulp fluff structures from pulp board stock, generally involve introducing the individualized pulp fibers into an air stream, such that the fibers are conveyed at high velocity and high dilution rates to a moving condensing screen upon which the fibers are accumulated in the form of a continuous web. The individualized pulp fibers may be generated through the use of various hammer mills. As an alternative, the fibers may be generated by using a lickerin or wire-wound roll to grind or shred pulp board. An air stream is tangentially passed over the fiber-laden lickerin, or about the mill, to doff or remove the fibers and entrain them in the air stream. Typically the air stream with the fibers is contained within a duct from the point of grinding to the point of deposition upon the condenser screen. In order to maintain the air streams in the duct at velocities high enough to ensure a uniform flow and deposition of the fibers upon the condensing screen, as well as to assure that the fibers do not adhere to the duct walls, it is necessary to employ a fan or other suction device beneath the condensing screen to create a pressure of at least 20 inches of water, and often up to 100 inches of water.
U.S. Pat. No. 3,512,218 of Langdon discloses apparatus for forming non-woven webs with two lickerins. The fibers are doffed from the lickerins by a single air stream formed by a suction box below the condensing screen. U.S. Pat. No. 3,535,187 of Woods discloses a similar arrangement wherein two air streams are used to doff the fibers from the lickerin. According to U.S. Pat. No. 3,772,739 of Lovgren both pulp fibers and longer textile fibers are individualized and blended in apparatus using high speed lickerins rotating at different speeds. As in the other references, the individualized fibers are doffed from their respective lickerins by separate air streams produced by a suction fan located in the condenser section of the apparatus. A baffle plate inserted between two lickerins for controlling the degree of mixing of fibers doffed by air streams passing over separate lickerins is described in U.S. Pat. No. 3,768,118 of Ruffo et al. and U.S. Pat. No. 3,740,797 of Farrington.
In these references, and generally in the prior art, the high speed air streams impel the fibers against the moving condenser screen at such a speed that there is a compression of the resulting web. In addition, the particles, after leaving the lickerin or rotating cylinder, are conducted to the condensing screen by a duct structure which confines their travel and, due to the air pressure, accelerates their travel. In order to assure that the air pressure is not reduced, seal means are provided where the duct structure engages the moving condenser screen. This may be in the form of floating or rolling seals, which further act to compress the fiber web as it is withdrawn from the condenser on the moving screen.
Because of the substantial pressure which must be generated in order to create the high speed air streams, the prior art methods of producing non-woven webs require a great deal of energy. In addition, the resulting web is compressed both by the air stream and the seals that are used to maintain the pressure for the air stream. Thus it would clearly be advantageous to the production of fluff fiber structures, or staple length fiber structures, if they could be created with much less energy and with less compression, i.e. much greater loft.
The present invention is directed to a method and apparatus for (1) forming high loft fiber structures without the use of high speed air streams and duct structure, such that much less energy is needed and a more lofty web is formed, and (2) blending other fibers or particulate matter into the fiber structure.
In an illustrative embodiment of the invention, a frame structure is used which has an endless conveyor screen in its lower section. This screen enters the frame structure at one end and exits it at the other. At the locations where the conveyor screen enters and leaves the frame, the frame is open to the atmosphere.
At an upper portion of the frame there is a feeding means for feeding fiber stock, e.g. pulp stock, rayon or cotton, into engagement with a high speed rotating cylinder, i.e. lickerin. The feeding means essentially comprises a feed roller, which forces the stock against the lickerin, and a nose bar that holds the stock in place as its end is shredded by the wire projections of the lickerin or other rough objects on the surface of a cylinder.
It has been found that in the absence of a high speed air stream, the individualized fibers created by the rotating cylinder tend to follow the peripheral direction of the cylinder. However, if a deflector plate is positioned parallel to the axis of the cylinder, but closely spaced from its peripheral surface, the fibers are directed from the cylinder in a stream toward the conveyor screen located in the lower portion of the frame.
At the conveyor screen, the individual particles are accumulated into a non-woven fiber structure. As the screen is moved, a continuous fiber structure is formed, which structure extends out of the open end of the frame to other processing equipment.
If desired, a relatively low air pressure may be created in a suction chamber below the screen. This acts to keep dust particles at a minimum and to improve the lateral placement of the fibers in forming the web. However, this low pressure is insufficient to doff the individual fibers from the lickerin. In particular, the suction pressures can be less than 5 inches of water, and are preferably in the range of 1/2 to 1 inch of water, as opposed to 20 to 100 inches of water as in prior art processes.
Pulp webs formed by this new process are typically more lofty than webs formed using a conventional process because of the lower compression effect resulting from the elimination of the high velocity depositing stream and the absence of seals positioned at the exit of the conveyor screen from the frame.
Other materials can be blended with the fibrous stream deflected from the cylinder. This is accomplished by mounting a feed tray beneath and parallel to the nose bar. The rotation of the cylinder creates a high velocity airstream in proximity to the rotating surface which draws particulate or fibrous materials in a tray toward the cylinder, where it is blended with the fiber stream. This results in the creation of unique blended non-woven fiber products.
When two materials of different densities are combined through the use of a feed tray, it is also possible to control the relative positioning of the two components in the resulting fiber structure by varying the shape of the discharge edge of the deflector plate. A sharp-edged, straight plate will yield a uniformly blended web. However, a discharge edge that is angled or curved away from the normal direction of flow, will create a wall attachment effect that causes light weight particles to follow the contour of the wall, while heavy particles, under inertial influence, continue in a straight line. The result is a preponderance of heavy particles in the lower layers of the fiber structure, and light particles in the upper layers.
US Referenced Citations (8)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 2192010 |
Dec 1987 |
GBX |
Non-Patent Literature Citations (2)
| Entry |
| Cotton Manufacturing Pt. 1 E. A. Posselt, p. 142. |
| Cotton, Pickers, Cards, Drawing Rolls, Combers, Fly Frames International Library of Technology, p. 14, Seat 18. |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
75708 |
Jul 1987 |
|
Patent Grant
5093962
