US3482287A - Method and apparatus for individualizing fibers preparatory to web forming - Google Patents

Description

Dec. 9. 1969 H. M. FLEWWELLING 3,482,237

METHOD AND APPARATUS FOR INDIVIDUALIZING FIBERS PREPARATORY T0 WEB FORMING Filed Nov. 8, 1967 INVENTOR Herbert Martin FLEWWELLING United States Patent METHOD AND APPARATUS FOR INDIVIDUALIZ- lNG FIBERS PREPARATORY TO WEB FORMING Herbert Martin Flewwelling, Pointe Claire, Quebec, Canada, assignor to Domtar Limited, Montreal, Quebec, Canada, a company of Canada Filed Nov. 8, 1967, Ser. No. 689,214 Claims priority, application Canada, Oct. 10, 1967,

Int. Cl. D01g 255/00; D04h 17/00 US. Cl. 19156.3 9 Claims ABSTRACT OF THE DISCLOSURE A head, primarily for individualizing and dry laying of fibers or similar materials, said head having a recirculaton path along which said materials are carried in an air stream, said path having a shape resembling an oval but with an outwardly concave classification section formed in one of the longer sections of the path and an outlet through the outer wall of said path in said concave section ahead of the crest of said concave section in the direction of movement of said material.

provide a system for separating fibers and laying same in the form of a web. The present invention can be used as a device for separating fibers per se or for laying fibers or for both separating and laying of fibers.

The present invention may also be utilized for materials other than fibers, for example fibrids, powders or mixtures thereof (i.e. a powdered adhesive and fibers to form an adhesive bonded fiberboard) or even with different shaped particles such as flakes or the like.

Broadly the present invention comprises a circulation path having an inner and an outer wall, means to introduce a transporting fluid into said path as a jet, said transporting fluid acting to separate said material and to transport same around said path, at least one section concave to said outer wall in said path, means in said concave section ahead of the crest of said section in the direction of travel of said material to permit said material together with transporting fluid to leave said path through said outside wall.

The apparatus of the present invention broadly comprises a confined path having an inside and an outside wall, a dispersion section, a convex curved positioning section and a concave curved classification section in series along said path, means causing fluid to flow in said confined path and to entrain said material, said curved positioning section being shaped to cause said material to move toward and hug said outside wall and said classification section being curved to separate said materials into a retained and a discharge fraction, a discharge duct through said outside wall and positioned to discharge said discharge fraction from said path.

Further features, objects and advantages will be evident from the following detailed description taken in conjunction with the accompanying drawings in which:

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FIG. 1 is a sectional view to scale through one form of the invention.

FIG. 2 is an end view of the apparatus shown in sec tion in FIG. 1.

The apparatus of the present invention comprises a circuitous path or duct 12 defined by an outer wall 14 and an inner wall 16 and a pair of end walls 18. In the illustrated embodiment, the end walls 18 are substantially parallel. The duct 12 has a dispersion zone 20 and an outer concave section or classification zone 22, a positioning zone or bend 24 interconnecting one pair of adjacent ends of the dispersion and classification zones, and a return bend 26 interconnecting the opposite ends of said zones. Both the positioning and return bends extend on an arc of greater than about in the illustrated arrangement. The size and shape of the positioning bend 24 affects the operation of the apparatus as will be more clearly explained hereinbelow. The path or duct 12 resembles an ellipse with one of its sides moved in towards the center to form a concave curved outer section as illustrated at 22.

A material inlet 28 is provided, preferably at the beginning of the dispersion zone 20 adjacent the bend 26. A fluid jet 27 mounted to the rear of the inlet 28 injects fluid (air) at high velocity into the duct or path 12, and this fluid serves as the dispersing and transporting medium for the material entering the path 12. The shear forces in the fluid may cause the material to be separated into smaller segments as it is dispersed. The angle of the inlet jet, the pressure, and the volume may be varied to provide different velocities and turbulences for the dispersion and circulation of the material. A discharge zone or duct 30 is provided in the outer wall 14 towards the end of the concave classification section 22 adjacent the return bend 26, i.e. at a point in advance of the crest of lthe section 22 in the direction of travel of the materia The dispersion zone 20, positioning zone 24, classification zone 22 and discharge zone 30 are the basic elements of the invention and the inter-relationship of the classification zone and discharge zone 30 are of primary importance to the practice of the instant invention.

Preferably, but not essentially, a second high velocity jet 32 is provided at the end of the positioning section 24 and is directed towards the beginning of the concave section 22. This jet 32 accelerates and redirects the material being processed thereby further dispersing and separating the material into smaller segments and positioning the material to facilitate proper classification in the concave section 22. The jet 32 preferably is adjustable in the same manner as the inlet jet 27 referred to above.

The discharging material is received and held in position on a suitable collecting surface. In the illustrated embodiment the collecting surface is formed by a foraminous belt 34 and the material is held in position by a suction box 38 provided on the side of the belt 34 remote from the duct 30. Transporting fluid is drawn through the belt 34 into the suction box 38 to deposit and fix the material in position on the belt.

As shown, particularly in FIG. 2, the width (i.e in the cross-machine direction) of the duct or path 12 may be, and preferably is, maintained substantially constant and equal in width to the mat to be formed on belt 34. Maintaining the path 12 substantially equal in width to the mat permits a more uniform lateral distribution of material. In the illustrated embodiment the duct 30 is shown as having substantially fiat end walls which are merely extensions of the end walls 18 of the path 12, while the front and rear walls are flared slightly in the direction of movement of the belt 34. The end walls may also be flared slightly laterally if desired.

As above indicated, the transverse width of the path 12 is substantially constant and equal to the width of the mat to be formed, but the height of the path 12 may be varied thereby changing the cross-sectional area of the path and the velocity of the circulating fluid and material. The surfaces of the outer and inner walls 14 and 18 respectively facing the path 12 are flat in transverse cross-section as shown in FIGS. 1 and 2.

In operation, material, such as wood pulp, is introduced into the apparatus through inlet 28, While high velocity fluid (air) is introduced through the jets 27 (and 32 if used) and air entrained pulp is removed via the outlet 30. The air flow through the apparatus causes a slight suction force on the inlet 28 which induces flow into the duct through this inlet. As the pulp enters the duct 12 it is entrained in the air flow and traverses the dispersion zone 20 where bundles of fibers are separated and the fibers dispersed by turbulence in the air stream. Next, the pulp travels through the positioning zone or bend 24, which is designed to cause the pulp to move into hugging engagement with the outside wall 24 where it remains until it enters the externally concave classification zone or section 22. As the pulp traverses this zone 22 it is acted upon by forces (i.e. centrifugal force, shear force, etc.) inherent in the flow in the classification section, which forces cause certain particles, e.g. fiber bundles or clumps of fibers not sufliciently broken down into individual fibers, to approach the inner wall quicker than other particles, e.g. the pulp which has been sufiiciently broken down. The outlet duct 30 is positioned relative to the concave classification section 22 to divide the flow into two separate fractions, namely a discharge fraction and a retained fraction. The discharge fraction contains only that pulp broken up to the required degree, while the retained fraction includes pulp not sufficiently broken up to be discharged (i.e. the fiber bundles). The discharge fraction leaves the duct 12 through the outlet duct 30 as a substantially laterally uniform dispersion of fibers, while the retained fraction traverses the return bend 26 and is further subjected to the turbulent air which further reduces the fiber bundles and this circulation continues until the fiber bundles are broken down to the required size for discharge.

By positioning the discharge duct 30 at a point on a concave classification zone 22 of predetermined curvature and by controlling the velocity of the material through this zone 22, the relationship (i.e. quantitative ratio, composition, etc.) between the retained and discharge fractions may, to some extent, be varied.

The function of jet 32 if used, is mainly to accelerate the pulp to ensure that it enters the classification zone 22 with the proper velocity and to aid in properly positioning the pulp in hugging relationship with the outside wall 14.

The quantity of air added, the size of the duct 12, the shape of the ducting, the density, size and shape of the material all contribute in determining the velocity of the material and the forces acting thereon. Thus, the exact configuration of the apparatus and the exact jet velocities and quantities of air will vary with various materials and results desired. When the fibers are to be laid to form a mat it is important to introduce suflicient air so that the volume of air exiting through the duct 30 permits the fibers to leave as substantially non-contacting individual integers.

The above described example of the instant invention has primarily dealt with pulp fibers and FIG. 1 is a drawing to scale of the first model of the invention, and has been found suitable for use with wood pulp fibers. The actual dimensions of the duct 12, and the curvature of the positioning bend 24, and classification zone 22, and discharge duct 30, can all be altered to adapt the characteristics of the device for optimum results with a given material to be processed. As above indicated, the present invention is not to be limited to use with fibers or to the exact specific shape disclosed.

Similarly, only air has been referred to as the fluid medium, however, other fluids may also be used provided they permit the required positioning and classification of the material. Also the fluid may serve other functions than for separation and conveying of the material, such functions including treating, drying and otherwise affecting the characteristics of the fibers.

Modifications may be made to the invention as disclosed without departing from the spirit of same as defined in the appended claims.

What is claimed is: 1. An apparatus for separating material comprising means including an inside and an outside wall defining a continuous confined circuitous path having its longitudinal center line lying in a plane and including in series a dispersion section, a convex curved positioning section connected directly to a concave curved classification section, means defining an inlet for introducing said material into said path without disrupting the operation of said positioning and classification sections, jet means for introducing entraining fluid into said path, said dispersion section being interposed between said jet means and said convex curved positioning section, and means defining a discharge duct opening through said outside wall in said classification section on the side of the crest of said concave curved classification section remote from said positioning section.

2. An apparatus as defined in claim 1 further comprising; fluid injecting means for introducing fluid into said duct adjacent the junction of said positioning section with said classification section.

3. An apparatus as defined in claim 1 wherein the surface of said outside wall facing said path in said convex curved positioning section and said concave curved classification section is substantially flat in transverse crosssection.

4. An apparatus for laying materials to form a mat comprising; means including curved inner and outer walls defining a continuous, confined, circuitous path having its longitudinal center line in a plane and including in series a dispersion section and a convex curved positioning section connected directly to a concave curved classification section, means defining an inlet for introducing said material into said path without disrupting the operation of said positioning and classification sections, the surface of said outside wall facing said path in said convex curved positioning section and said concave curved classification section being substantially flat in transverse cross-section, jet means to introduce fluid into said path, said dispersion section of said path being interposed between said jet means and said convex curved positioning section, means defining a discharge duct opening through said outside wall in said classification section on the side of the crest of said classification section remote from said positioning section, a receiving surface positioned across said duct and means mounting said receiving surface from movement across said duct.

5. An apparatus as defined in claim 4 further comprising; second means to introduce fluid, said second means being located adjacent the junction of said positioning and classification sections.

6. A method of forming a uniform web from material having fiber bundles therein comprising;

introducing said material including said fiber bundles into a confined path between an inside and an outside wall which define a dispersion section, a convex curved positioning section and a concave curved classification section having a crest therein in said path, said path having its longitudinal center line in a plane,

controllably introducing conveying fluid into said path at the end of said dispersion section remote from said positioning section at a rate whereby turbulence is generated in said dispersion section to tend to separate said fiber bundles and to generate a fluid velocity in said path sufficient to entrain said material and move said material through said path at a velocity to permit centrifugal positioning and classification of said material in said positioning and classification sections,

withdrawing a fraction of said material substantially free of said fiber bundles through said outside wall in said classification section on the side of said crest remote from said positioning section,

continuously collecting said withdrawn fraction in the form of a substantially flat web, and

recirculating said material including fiber bundles not sufficiently dispersed and fluid not withdrawn from said classification section back to said dispersion section.

7. A method as defined in claim 6 wherein said fluid is air.

8. A method as defined in claim 7 further comprising introducing further fluid into said path adjacent the junction of said positioning and classification sections at a rate suflicient to increase the velocity of said material through said classification section.

References Cited UNITED STATES PATENTS Stephanoff 2415 Step-hanoff 2145 Stephanofl. 24139 X Boesch 209143 Meiler 19156.3

Oja 19156.3 Kidwell 24139 Novotny 19200 FRANK W. LUTTER, Primary Examiner US. Cl. X.R.

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