Apparatus For Transferring And Compacting Fiber Material

Abstract

The upper and lower walls of the air duct which conveys fibers from the lickerin to the condenser in a machine for forming random fiber webs are serrated; and the forward side of each serration is provided with apertures through which jets of air operate to compact, stabilize, and advance the airborne fibers which pass through the duct. The jet openings on the forward sides of successive serrations or teeth are preferably arranged in staggered fashion relative to one another.

Description

The present invention relates to apparatus for transferring and compacting fibrous material, and more particularly to apparatus for transferring and compacting fibrous material in the air duct which connects the lickerin with the condenser in a machine for forming random fiber webs.

Apparatus is known for the production of fiber mats and webs in which the fibrous material is opened up by a lickerin or the like and doffed from the lickerin by centrifugal force and the action of an air stream blowing past the lickerin. The doffed fibers are conveyed in the free air stream or in a duct to a rotating suction drum or condenser, on which, the fibers are laid down in the form of a mat or web whose thickness depends on the circumferential speed of the drum or condenser.

Machines are also known where the fibrous material is opened up onto a drum, as on a conventional card, and is then lifted off the drum by an aimed air jet and transferred to one or more suction drums or condensers, the transfer of the mat from the drum to one or both of the suction drums occurring in a free air stream or between baffle plates.

These prior apparatus involve difficulties in depositing the fiber material on the suction drums or condensers, particularly in the case of light mats or webs. Due to the air cushion and air eddies that develop on the surface of the suction drum or condenser, thin mats or webs tend to shimmy and get into folds. This results in irregularities in the layer thickness. The layer thickness is ultimately determining as to the quality of the mat or web; and faults in the layer thickness lead to "clouding" and streaking of the ultimate product.

The primary object of the present invention is to provide apparatus which renders possible easy production of a random fiber web which is of uniform thickness over its whole area, even in the case of a thin web.

Another object of the invention is to provide apparatus of this nature with which the thickness of the web can readily be controlled.

Other objects of the invention will be apparent hereinafter from the specification and the appended claims, particularly when read in conjunction with the accompanying drawing.

In the drawing:

FIG. 1 is a fragmentary, somewhat diagrammatic view illustrating apparatus built according to one embodiment of this invention;

FIG. 2 is a fragmentary, diagrammatic view, showing the serrations at one side of the duct developed into a plane and how they are staggered relative to one another from serration to serration; and

FIG. 3 is a fragmentary longitudinal sectional view through the lower wall of the air duct of FIG. 1.

The purposes of the present invention are achieved by making the lower wall and preferably both the upper and the lower, walls, of the air duct, which connects the lickerin with the condenser, in a random fiber web forming machine, serrated, and providing air jets or nozzles along the front faces of the serrations, which blow into the duct, and compact and stabilize the fibrous material traversing the duct. The air jet or nozzle system produces an air cushion at the bottom, or at both bottom and top of the duct, depending on whether the air jets are disposed in the bottom wall only, or both in the bottom and top walls of the duct, on which the fibers travel from lickerin to condenser. With a bilateral arrangement of the nozzles, the fibers are stabilized in a median position in the duct, and only very shallow waves, if any, can form in the web laid down on the condenser.

At the inlet end of the duct the nozzle system forms a funnel, funneling the fibers into the duct. The nozzle system (duct) widens toward the outlet end of the duct, in order to keep the air velocity practically constant at a constant depth in the duct despite the air flowing into the duct from the nozzles. The nozzle or jet openings of the successive serrations are staggered relative to one another so that a substantially uniform superposition of air currents results. At the outlet end of the duct, the transfer of the fibers to the suction drum or condenser occurs through nozzles whose mouths are arranged tangentially to the circumference of the suction drum or condenser; and the air cushion or cushions is or are lowered by the negative pressure or suction in the drum or condenser.

The doffing of the web from the drum or condenser is effected by a nozzle system which is inclined somewhat out of the tangential direction toward the interior of the suction drum or condenser so that the resulting air cushion lifts the mat off the drum or condenser. The web is then carried off on a conveyor belt for further treatment.

Through use of an adjustable by-pass, the air cushion and its rate of flow can be varied to control the thickness of the web. To avoid the fibers adhering to one another due to electrostatic charge, finely atomized water may be mixed with the nozzle supply air.

Reference now will be had to the drawing by numerals of reference.

10 denotes a conventional lickerin which in its rotation combs fibers from a mat or batt that may be fed to the lickerin in conventional fashion by a feed roll (not shown) over the nose of a feed plate (not shown). The fibers are doffed from the lickerin into the air duct 11, which connects the lickerin 10 with a conventional rotary condenser 12, by the centrifugal force generated through the high speed rotation of the lickerin and by the force of an air jet directed tangentially at the rotating lickerin from the nozzle 14. The condenser may be of conventional construction and comprise a rotary screen 22 and a fixed drum 23 which has a slot 24 extending across its full width. Air is drawn through the screen into the drum through the slot by a suction fan (not shown).

The upper and lower walls 20,21 of the duct 11, in the embodiment of the invention illustrated, are serrated; and the front faces 15 of the teeth or serrations 16 have jet or nozzle openings 17 in them directed inwardly of the duct but forwardly in the direction of air flow therein. Each tooth or serration has a plurality of jet openings 17 therein spaced laterally along the front face of the tooth from side to side thereof; and the jet openings in one tooth front face are staggered with reference to those in the adjacent front tooth face as illustrated in FIG. 2.

The duct at its inlet end 18 is funnel-shaped; and it widens toward its outlet end 19, as shown in FIG. 1 to keep the air velocity practically constant at constant depth of the duct. Through the bilateral arrangement of the air jets 17, the fibers flowing in the duct 11 ride on air cushions at the top and bottom of the duct and the stream of fibers F is stabilized in a median position in the duct as shown in FIG. 1.

At the outlet end 19 of the duct, the nozzle or jet openings 17 extend tangentially of the condenser 12 so that the fibers are deposited on the condenser by degrees. Removal of the web from the condenser 12 is effected with the assistance of a conventional doffing plate 25, which delivers the web onto the conveyor belt 28 that travels over roller 29.

The quantity of air in the duct may be controlled through a by-pass 26, which communicates with the duct near its inlet end and which may have an adjustable damper 27 in it for control of the amount of air exhausting at this point from the duct.

To avoid static, an atomizer 30 is connected to the by-pass to discharge finely atomized water into the duct.

While the invention has been described in connection with one embodiment thereof, it will be understood that it is capable of further modification; and this application is intended to cover any modifications of the invention that come within the scope or the limits of the appended claims.

Claims

We claim:

1. In apparatus for forming a random fiber web,

a duct through which fibers suspended in air may be conveyed,

said duct having a top wall and a bottom wall,

said walls diverging from one another longitudinally of the duct,

each wall being serrated and having serrations extending crosswise of the duct,

a rotary lickerin disposed adjacent the inlet end of the duct for combing fibers from a mat fed to the lickerin,

a movable foraminous condenser disposed adjacent the outlet end of the duct, and

means for directing an air stream tangentially of said lickerin so that fibers are doffed therefrom by centrifugal force and by the force of said air stream and the doffed fibers are conveyed through the duct by the air steam from the lickerin for deposit on said condenser,

said serrations having nozzle openings through their front faces, and means for directing air through said openings forwardly of the duct for compacting and stabilizing the fibers as they flow through the duct.

2. Apparatus as claimed in claim 1, wherein the openings through the front faces of the serrations are staggered from serration to serration.

3. Apparatus as claimed in claim 1, wherein a by-pass is connected to said duct adjacent its inlet opening, and

adjustable means is provided to control the amount of air exhausting from said duct through said by-pass, and

means is provided connecting said by-pass at least with the jets in the bottom wall of said duct.

4. Apparatus as claimed in claim 3, wherein an atomizer is connected to said by-pass to supply atomized water droplets to at least the air supplied to the jets in said bottom wall.

5. In apparatus for forming a random fiber web, having

a duct through which fibers are conveyed in an air stream, said duct having an inlet opening at one end and an outlet at its other end,

means for directing an air stream with fibers suspended therein into said inlet opening,

and a movable foraminate condenser disposed at the outlet end of said duct on which the fibers are deposited,

said duct having at least its bottom wall serrated with the serrations extending crosswise of the duct,

said serrations having air jet openings through their front faces for directing air streams forwardly of the duct for conveying fibers through the duct and for forming an air cushion on which the fibers ride as they flow with the stream through the duct, and by which the fibers are stabilized in a median position of the duct as they travel through the duct.

6. Apparatus as claimed in claim 5, wherein the jet openings in the front walls of successive serrations are staggered, relative to one another.