Abstract:
An apparatus for gathering a running fiber web into a sliver, includes a web guide element having edge portions defining an outlet opening through which the web passes; a trumpet arranged downstream of the outlet opening of the web guide element as viewed in a direction of web advance, and an arrangement for guiding air, flowing against the direction of web advance and generated by web compression downstream of the web guide element, away from a zone extending between the outlet opening of the web guide element and the outlet opening of the trumpet.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for gathering a fiber web, discharged by a web delivering device of a card, into a sliver, including the step of passing the fiber web through an opening in a fiber web guide element and introducing the gathered fiber web into a trumpet. 
     According to a known method, the gathered fiber web is introduced from the opening in the fiber web guide element directly into the trumpet and leaves the trumpet as a sliver. Upon increasing the delivery speed of the card, for example, to a web speed of 300 m/min., operational disturbances are experienced due to an air backflow at the trumpet. Further, immediately upstream of the trumpet (as viewed in the direction of fiber travel) the fiber web takes up a significantly greater space than the compressed sliver. The environmental air is entrained by the fiber web into the trumpet; the entrained air quantities increase with increasing speed. The air streaming rearwardly from the trumpet, particularly from its constriction, eventually reaches such a high backflow speed that the incoming fiber web is destroyed or is blown back in several zones. If the fiber web is compressed from a large cross section in the trumpet, the backflow velocities were found to be excessively high in case of web speeds above 100 m/min. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved apparatus of the above-outlined type by means of which the discussed disadvantages are eliminated and which thus allow a disturbance-free gathering of the fiber web particularly at high web speeds. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the air which flows backwardly during the compression of the fiber web is guided away from between the opening in the fiber web guide element and the trumpet and/or the location of web entrance into the trumpet. 
     By virtue of guiding away the backflowing air, an accumulation of air in front of the trumpet is prevented and thus a disturbing influence of eddy effects on the fiber web or the pre-densified sliver is avoided. It is thus of importance that the air be removed from the zone--as a rule, the central or mid-zone--where the fiber web is gathered and densified. In this manner, web speeds in excess of 250 m/min. may be achieved for a substantial operational period without experiencing fiber web breakage. Further, fiber webs in the very fine number range, such as an Nm 0.35 may be processed without difficulties. At the same time, dust and short fibers are removed with the air. The method according to the invention is advantageously utilized even in case of lesser fiber web speeds, for example, speed under 180 m/min. The invention ensures that a zone-wise blow-back of the fiber web is eliminated and a breakage of the fiber web in these zones and thus a disadvantageous effect on the uniformity of the fiber web are prevented. 
     The apparatus according to the invention includes an aperture which maintains communication between the ambient atmosphere or an evacuation device and the zone which extends from the outlet opening of the fiber web guide element to the entrance of the trumpet. In this manner, together with the air to be drawn off, dust and short fibers are also eliminated. Expediently, the zone between the outlet opening in the fiber web guide element and the entrance of the trumpet are open in successive zones. In case the fiber web is densified in at least two, but preferably in more successive stages, the web reaches the consecutive trumpet devices with a reduced volume, that is, with lesser air per time unit. In this manner the backflow velocity is reduced to a magnitude at which no operational disturbances occur. 
     Preferably, between the opening in the fiber web guide element and the trumpet there is arranged at least one trumpet-shaped guide element. Expediently, the cross section of the outlet area of each trumpet-shaped guide element is smaller than the cross section of the inlet area of the respective, downstream-arranged trumpet-shaped guide element or the fiber trumpet. According to a further feature of the invention, the trumpet-shaped guide element is at least partially open. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic sectional side elevational view of a preferred embodiment of the invention. 
     FIG. 2a is a schematic sectional side elevational view of another preferred embodiment of the invention. 
     FIG. 2b is a perspective view of a component of the embodiment shown in FIG. 2a. 
     FIG. 3 is a schematic perspective exploded view of a further preferred embodiment of the invention. 
     FIG. 4 is a schematic sectional side elevational view of still another preferred embodiment of the invention. 
     FIG. 4a is a schematic side elevational view of one part of the structure shown in FIG. 4. 
     FIG. 5 is a schematic side elevational view of another preferred embodiment of the invention. 
     FIG. 6 is a schematic sectional side elevational view of another preferred embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to FIG. 1, there are illustrated two crushing rollers 1 and 2 which are supported in a carding machine (not illustrated) and which form the web delivering device thereof. Immediately downstream of the crushing rollers 1 and 2 there is arranged a fiber web guide element 3 (of the type disclosed, for example, in German Pat. No. 2,711,619), a trumpet-shaped guide element 4, a fiber web trumpet 5 and calender rollers 6 and 7. The opening 3a in the fiber web guide element 3 is smaller than the entrance opening 4a of the trumpet-like guide element 4 whose outlet opening 4b, in turn, is smaller than the entrance opening 5a of the trumpet 5. The zones between the outlet opening 3a and the entrance opening 4a as well as between the outlet opening 4b and the entrance opening 5a are discontinuities (openings) 10 and 11 which communicate with the ambient surrounding air. 
     In operation, the fiber web 8 delivered by the crushing rollers 1 and 2 is gathered by the fiber web guide element 3 and thereafter passed through the opening 3a and is admitted, as a pre-compressed fiber material, into the trumpet-like guide element 4 and therefrom it is introduced into the fiber trumpet 5 from which it is drawn by the calender rollers 6 and 7 as a sliver 9. Thus, the fiber web is densified in several stages. By gathering the material by the fiber web guide element 3 and upon passage through the opening 3a the fiber web 8 is first pre-compressed. Thereafter, a more pronounced densification takes place in the trumpet-like guide element 4 whereupon eventually the final densification occurs in the trumpet 5 from which the sliver emerges. During the compression (densification) of the sliver 9 in the trumpet 5 air is liberated which streams backwardly in the direction of the entrance opening 5a and enters into the ambient atmosphere through the aperture 11. One part of the backflowing air may enter the fiber material and thus may slightly inflate the same. The trumpet-like guide element 4 therefore also has the purpose to hold together the pre-compressed fiber material. A further purpose of the trumpet-like guide element 4 is to additionally compress the fiber material which leaves the opening 3a. Air which passes through the entrance opening 4a during this process is guided away through the aperture 10. 
     Turning now to FIGS. 2a and 2b, the trumpet-like guide element 4 has an opening 4c in its wall, that is, the wall is partially open, starting from the entrance opening 4a. By virtue of the opening 4c, a greater quantity of backflowing air may be guided away from the trumpet-like guide element 4. Further, by virtue of the opening 4c it is feasible to predetermine the direction of air removal (upward, in the embodiment shown in FIGS. 2a and 2b). 
     Turning now to FIG. 3, between the fiber web guide element 3 and the trumpet 5 there are provided two trumpet-like guide elements 4 and 4&#39;. The guide element 4 is fully open in the downward direction whereas the guide element 4&#39; is fully open in an upwardly oriented direction. 
     Turning now to FIG. 4, there is illustrated a preferred embodiment wherein the zones between the opening 3a of the fiber web guide element 3 and the entrance opening 5a of the trumpet 5 are only partially open as indicated at 10&#39; and 11&#39;. One part of the edge defining the opening 3a has an upwardly open extension 3b (also see FIG. 4a) which projects partially into the entrance opening 4a of the trumpet-like guide element 4. The terminal edge of the extension 3b partially contacts and seals the inner face of the trumpet-like guide element 4 along its lower zone as viewed in FIG. 4. In the upward direction no such contacting takes place, whereby the opening 10&#39; is formed. One part of the edge defining the outlet opening 4b has an extension 4d projecting into the entrance opening 5a of the trumpet 5, whereby the terminal edge of the extension 4d partially contacts and seals the inner face of the trumpet 5 along its upper zone, as viewed in FIG. 4. In the downward direction no such contacting takes place whereby the opening 11&#39; is formed. 
     Turning now to FIG. 5, downstream of the crushing rollers 1 and 2 there is arranged a fiber web guide element 3&#39; of the type disclosed in U.S. Pat. No. 4,272,866. The opening 3a&#39; of the guide element 3&#39; is slightly bent and reaches into a guide element 12 which is a generally U-shaped sheet metal component. The outlet zone 12b of the guide element 12 is obturated by a cover 3b&#39;. The guide element 12 has an upwardly oriented opening 12a. To the end of the guide element 12 there is mounted, with the intermediary of a disc 13, the trumpet 5 followed downstream by the calender rollers 6 and 7. The opening 12a serves for guiding away the backflowing air emanating from the trumpet 5. A contacting of the pre-compressed fiber material is thus not effected by the guide element 12. The edge defining the opening 3a&#39; may have an extension similarly to the structure shown in FIG. 4a and it is also feasible that a like extension projects into the entrance opening 5a of the trumpet 5. In this embodiment, the pre-compressed material leaving the opening 3a&#39; is supported from below by the cover 3b&#39;. 
     In FIG. 6 there is illustrated a trumpet-shaped guide element 4&#34; which is inserted into the entrance opening 5a&#39; of the trumpet 5&#39; in such a manner that an intermediate space 14 having the configuration of a truncated cone jacket is formed between the outer surface of the trumpet-like guide element 4&#34; and the inner surface of the trumpet 5&#39;. The intermediate space 14 communicates with the outlet opening 5b&#39; of the trumpet 5&#39;. Thus, the entrance openings of the trumpet-like guide element 4&#34; and the trumpet 5&#39; merge into one another. The intermediate space 14 is sealed in the zone of the contact between the trumpet-like guide element 4&#34; and the trumpet 5&#39;. In the lower wall zone of the trumpet 5&#39; there is provided a throughgoing opening 15 which connects the intermediate space 14 with a vacuum device (not shown) and which functions as an air sluice. The opening 15 is arranged between the entrance opening 5a&#39; of the trumpet 5&#39; and the outlet opening 4b&#34; of the trumpet-like guide element 4&#34; in such a manner that it is shielded by the latter, so that no fiber material may be introduced into the opening 15. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.