US3553791A

US3553791A - Pneumatic cleaning apparatus for the lickerin section of carding machines

Info

Publication number: US3553791A
Application number: US770356A
Authority: US
Inventors: James F King Jr
Original assignee: Bahnson Co
Current assignee: Bahnson Co
Priority date: 1968-10-24
Filing date: 1968-10-24
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12

Abstract

A SUCTION MANIFOLD STRUCTURE FOR THE LICKERIN SECTION OF A CARDING MACHINE, FORMED OF A SHEET MEMBER TRANSVERSELY SPANNING THE CARDING MACHINE HAVING PLURAL INTEGRALLY CONNECTED AND RELATIVELY INCLINED PLANIFORM PANELS AND END WALLS ADJUSTABLY MOUNTED TO THE CARDING MACHINE AGAINST THE LICKERIN COVER FORMING A SUCTION CHAMBER. THE DISPOSITION OF THE PANELS RELATIVE TO EACH OTHER AND TO THE LICKERIN COVER AND TO OTHER PARTS OF THE CARDING MACHINE IS SUCH AS TO DEFINE READILY ADJUSTABLE ELONGATED SUCTION INTAKE SLOTS LOCATED TO CAPTURE FLY FROM JUNCTION ORIFICES OF THE CARDING MACHINE BETWEEN OPPOSITE EDGES OF THE LICKERIN COVER AND THE FEED ROLL AND BACK KNIFE PLATE.

Description

Jan. 12, 1971 F, Km, ,R 3,553,791

PNEUMATIC CLEANING APPARATUS FOR .THE LIKERIN SECTION OF CARDING MACHINES Filed Oct. 24,- 1968 2 Sheets-Sheet 1 INVENT OR JAME F. Kmci, 3'2.

I. ATTORNEYS 3,553,791 KERIN SECTION Jim J. F. KING. JR

PNEUMATIC CLEANING APPARATUS FOR THE LI OF CARDING MACHINES Filed Oct. 24, 1968 2 Sheets-Sheet 2 m ow c ylllll/llll lll/ INVENTOR JAMES F; Kmo, 32,.

. I I Wasm $wmcQu ATTORNEYS United States Patent() 3,553,791 PNEUMATIC CLEANING APPARATUS FOR THE LICKERIN SECTION OF CARDING MACHINES James E. King, Jr., Winston-Salem, N.C., assignor to The Bahnson Company, Winston-Salem, N.C., a corporation of North Carolina Filed Oct. 24, 1968, Ser. No. 770,356 Int. Cl. D01g 15/76 US. Cl. 19-107 9 Claims ABSTRACT OF THE DISCLOSURE A suction manifold structure for the lickerin se ction of a carding machine, formed of a sheetmember transversely spanning the carding machine having plural integrally connected and relatively inclined planiform panels and end walls adjustably mounted to the carding machine against the lickerin cover forming a suction chamber. The disposition of the panels relative to each other and to the lickerin cover and to other parts of the carding machine is such as to define readily adjustable elongated suction intake slots located to capture fly from junction orifices of the carding machine between opposite edges of the lickerin cover and the feed roll and back knife plate.

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates in general to pneumatic cleaning of carding machines, and more particularly to suction manifold structure for the lickerin section of a carding machine for pneumatically capturing and removing dust-like trash and lint, herein often generally referred to as fly, being discharged from the lickerin region of a carding machine during operation.

Much effort has been devoted to the elimination or reduction of escape of fly, usually in the form of a mixture of short waste fibers and trash, from carding machines, especially as the problem of fiber and trash escape increased with increasing speeds of operation of the card'- ing machines. It is important to eliminate or minimize the escape of such fibers and trash into the air in the textile machinery room, as the resultant contamination would produce unhealthy working conditions forthe operators, impair the quality of the sliver because of intermingling of the airborne trash therewith, and cause deposits of the contaminants on the machinery in the room creating fire hazards and interference with operation of the machinery.

Various pneumatic cleaning devices have been proposed to effect suction withdrawal of fly from carding machines or various portions thereof to reduce the escape of the fly into the surrounding atmosphere. Particular effort has been devoted to the design of pneumatic cleaning equipment for preventing or reducing the escape of fly and similar trash from the lickerin region of the carding machine, as especially troublesome discharge of trash occurs in this region. As will be appreciated by those skilled in the art, the lickerin section of the conventional carding machine includes a lickerin cylinder which rotates at high speed beneath a lickerin cover or bonnet and has teeth on its periphery to draw the cotton as fibers or tufts from a lap being fed thereto between a feed roll and feed plate and convey them downwardly in an arcuate path past mote knives, to a main cylinder or swift. There, some of the cotton is transferred directly to the main cylinder, and some of it is impinged against the sharp knife edge of a back knife adjacent the main cylinder periphery and retained momentarily. Any cotton that is not immediately picked up off the knife edge or by the main cylinder 3,553,791 Patented Jan. 12, 1971 is wiped off the knife edge by the rotating lickerin cylinder and is conveyed under the lickerin cover back to its original feed end location. Thus, a large quantity of usable fiber is being conveyed in a circular manner at all times underneath the lickerin cover and any opening in. this cover will allow usable fibers to escape to the atmosphere. Obviously, there is also a large amount of waste spinning around this lickerin cylinder underneath the lickerin cover along with the cotton, and such waste tends to be centrifuged out to the outermost possible location. The slight separation or spacing at the junction between the exit edge of the lickerin cover and the back plate of the card, and at the junction between the feed roll and the adjacent entrance edge of the lickerin cover each constitute junction openings or spaces through which this trash can escape.

Efforts have been made to minimize blowout of cotton and fly at these locations by providing a seal or filler strip at the junction between the lickerin cover and back plate and a rotatable seal roller bearing against the feed roll and overlying the junction between the feed roll and the lickerin cover. Neither of the seals, however, has provided a satisfactory solution to the problem of eliminating escape of trash from these zones. Frequently, lint and trash begin to build up on the surfaces of the filler strip between the lickerin cover and the back plate, and if this strip is shifted slightly by vibration or by hand, some of the contaminants tend to bunch up under the filler strip and cause it to lose its air-tight seal so that air carrying large quantities of trash can find its way into the opening between the bight of the flats and the top of the lickerin cover. In other cases, the machine operators may allow the lickerin cover or the .rear side of the back plate to become bent or damaged so that the filler strip will not satisfactorily seal the junction between these elements. The rotating sealer roller lying in the gap between the lickerin cover and the feed roll also has contamination problems and must be periodically cleaned for satisfactory operation. Buildup of contaminants on the surface of this plush covered sealing roller is not always uniform and frequently trash blows out from unsealed zones that develop as a consequence of this non-uniform buildup of contaminants.

In an effort to solve the problems of contaminant discharge from these lickerin regions, pneumatic cleaning devices in the form of suction manifold structures have been developed to effect suction withdrawal of air from various points in the lickerin region, particularly from the opening between the lickerin cover and back plate and the opening between the feed roll and the lickerin cover, to capture the trash and fly being discharged from these zones. Typical of these is the Reiterer Patent No. 3,115,683; wherein a suction nozzle located immediately above the feed roll draws air from beneath a specially configurated lickerin cover at the end thereof adjacent the feed roll, and optionally another suction duct may communicate with the zone of convergence of the lickerin cover and back plate to effect suction removal of trash. This device re quires special plate constructions to replace the conventional lickerin cover, which in the form applying suction to the zone near the back plate also requires a perforated zone which disturbs the desirable pressure conditions provided by the conventional lickerin cover to retain the usable long fibers on the lickerin teeth, and is quite expensive to produce.

The Bass Patent No. 3,315,320 discloses a subsequent development of a suction manifold designed to be mounted over the conventional lickerin cover and having suction inlet slots positioned immediately above the junction between the lickerin cover entrance edge and the feed roll and between the lickerin cover exit edge and the back plate to capture trash discharged through these junction zones. However, the nature of the Bass construction requires that the size and configuration of the suction intake slots be permanently established at the factory during the construction of the manifold, eliminating the possibility of adjusting the intake slots when the manifold is installed on the carding machine to meet the particular conditions occurring at the carding machine installation. It has been found that'it is necessary to maintain a very exact amount of suction pressure at the junction between the feed roll and lickerin cover and the junction between the lickerin cover and back plate, especially the former, to prevent extraction of reusable cotton fibers while capturing the trash from these junctions and to prevent reduction in the efliciency of the entire carding operation. Therefore, it is mandatory that the manifold suction inlet slots or orifices be adjustable for each particular application or carding installation, to permit attainment ofthe exact suction pressures required to'match the discharge from the particular carding machine and to match the suction pressures available from the primary air handling units applying the suction pressures to the manifold.

An object of the present invention, therefore, is the provision of a suction manifold structure for use at the lickerin region of carding machines which is of simple and inexpensive construction, which can be easily installed on virtually any conventional carding machine construction, and which defines completely adjustable suction intake orifices for drawing air, and thus capturing trash, from the junctions between the feed roll and lickerin cover and between the lickerin cover and back plate of a carding machine.

, Another object of the present invention is the provision of a novel suction manifold for the lickerin section of carding machines as defined in the immediately preceding paragraph, wherein the manifold structure coacts with the conventional lickerin cover or bonnet of carding machines to define the suction intake slots, and wherein the manifold structure is adjustable and distortable relative to the lickerin cover to define intake slots of various sizes and configurations suited to the discharge conditions and available suction pressures at the particular carding installations.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a fragmentary perspective view of the manifold structure of the present invention installed over the lickerin cover of a conventional carding machine;

'FIG. 2 is a vertical transverse section view, to enlarged scale, of the suction manifold structure installed at the lickerin section of a carding machine, with fragmentary diagrammatic and sectional illustrations of certain carding machine components, and

FIG. 3 is a fragmentary exploded perspective view of the manifold structure and of one of the lickerin cover end plates to which the manifold is mounted.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, the manifold structure of the present invention, indicated in general by the reference character 10, is adapted to be used in conjunction with a conventional flat carding machine including the usual main cylinder or swift 11, shown in its proper relationship and reasonably to scale relative to the other card components, having spiked clothing 12,,which receives cotton fibers from the teeth of the lickerin cylinder 13. The lickerin cylinder 13 is mounted for rotation about a shaft 14, supported by hearings on the usual apron or main frame of the carding machine, with its teeth extending in close proximity to the spiked clothing 12 of the main cylinder 11, and is covered by a lickerin cover or bonnet 15 which terminates on the left hand or entrance side of the lickerin cylinder in close proximity to a serrated feed roll 16. The right hand or exit side of the lickerin bonnet 15 nearer the main cylinder 11 of the card terminates in very close proximity to the back knife plate 17. A filling seal roller 18 is shown at the junction .between the lickerin cover 15 and the feed roll 16, as is generally used on cards to'reduce blowout of short staple cotton and fly at this point. A seal or filler strip 19, conventionally formed of a plush covered wooden wedge orV strip is shown at its conventional position at the junction between the lickerin. cover 15 and the back knife plate 17. This seal 19 is applied or removed according to the desires of the mill personnel.

The incoming lap of cotton enters from the left hand side of FIG. 2 on top of the feed plate 20 and is engaged by rotating feedv roll 16 so as to be driven into the teeth of the lickerin cylinder 13. The cotton is drawn off the lap into the teeth of the lickerin and conveyed downwardly as fibers or tufts past the usual series of mote knives (not shown) or past a fiber retriever of conventional construc-. tion, and thence to the zone immediately below the lower edge of the back knife plate 17 where the fibers are either seated on the spiked clothing of the main cylinder 11 or reconveyed by the lickerin teeth beneath the lickerin cover 15 to the zone of the feed roll 12 FIG. 2 also illustrates a plurality of the flat bars 21 connected serially into a flats chain which negotiates an entrance curve around the flats idler 22 revolving on trunnion '23. As in conventional carding machines, a flats brush 24 is rigidly fixed in place so that it contacts the ends of the flat bars 21 as they move past the bristled surface of the flats brush to wipe them free of lint and dirt before they engage the surface of the card frame over the top of the main cylinder 11.

Contamination of the lickerin area generally takes place from three junction zones or openings which are under pneumatic pressure. These openings or junction zones are indicated at A, B and C in FIG. 2. Opening A between the back knife plate 17 and the flat bars 21 is probably the least objectionable of the trash escape openings, as the majority of blowout from this opening is in the form of pepper trash, such as pieces of cotton stalk and cotton seeds, which constitute only a small amount of residue. Junction B is probably the most troublesome source of trash and fly discharge, as even the seal or filler strip 19 fails to completely eliminate escape of trash from this region for the reasons her'einbefore discussed. Opening C between the entrance end of the lickerin cover 15 and the feed roll 16 in the area occupied by the sealing roller 18 also poses significant contamination problems even with the sealing roller 18 present, because of the difficulty of maintaining a perfect seal in this region.

The manifold structure 10 of the present invention is designed to establish carefully chosen suction pressures so as to carry away contamination from these three openings A, B and C as fast as contamination develops at these openings. The manifold structure 10 is exceedingly simple in construction and conveniently manufactured, and consists merelyof a broken sheet of light gauge metal 25 bent along spaced parallel lines to provide a series of rectangular panels defining a vertical front wall 25a, a first substantially horizontal upper top wall section 25b, a second downwardly inclined top wall section 250 and a third substantially horizontal, downwardly otfset top wall section 25d.

End walls

26 and 27 formed of similar sheet material are secured to inwardly turned flanges 25' bordering the lateral edges of the sheet 25 to form a downwardly opening hood-like structure adapted to fit over the lickerin cover 15'of the conventional carding machine. One of the end walls, for example, the end wall 26, is also fitted with a nipple 26a for attachment to a source of -air under negativepressure. V 1 I V The manifold structure is rigidly but adjustablyattached to the arcuate, flanges 28a of the conventional lickerin cylinder end plates 28 so that orifices or

suction intake slots

29 and 30 are formedbetween the rnanifold wall and the lickerin cover 15.,The adjustable attachment of the manifold 10 to thelickerin cylinder end plates may be effected by providing enlarged openings 26, 27' at suitable locations in the

end walls

26, 27, for example, /z-inch diameter openings, at appropriate. locations to receive the shanks of smaller diameter headed threaded mounting bolts 31, for example, having shanks of A-inch diameter, which are threaded into tapped openings 32 in the flanges 28a of the lickerin cylinder end plates 28. Washers 31' of larger outer diameter than the

openings

26, 27 may be provided bet-ween the heads of the mounting bolts 31 and the adjacent surfaces of the

end walls

26, 27. By suitably locating the enlarged diameter

mountting bolt openings

26, 27, the manifold10 maybe readily adjusted relative to the lickerin cover 15, before the mounting bolts 31 are tightened to an extent to securely bind the

end walls

26, 27 against the flanges of the lickerin cylinder end plates, to effect a substantial variation in the size and configuration of the

suction intake slots

29, 30. It will be apparent that with this mounting arrangement, either end wall of the manifold may be moved up or down relative to the lickerin cylinder end plates 28, and thus relative to the lickerin cover 15, or the manifold can be slightly warped from end to end to develop variations in the area of the

orifices

29, 30. A recurved lip formation 34 of double thickness defining a smooth, rounded free edge or nose 34a is provided. at the margin of the top wall section 250. nearest the back knife plate 17, terminating if desired in a'downwardly extending terminal flange 34b,

and the manifold is so located within the range of adjustment accommodated by the openings 26', 27' and mounting bolts 31 to space the free edge or nose 34a a slightdistancefrom theback knife plate 17 to providea passage or orifice 35 through which trash falling from the junction A can slide down the surface of the back plate 17 and into the region immediately above the filler strip 19.

It will be apparent that the manifold structure herein.- above described provides a pneumatic suction device wherein a pair of suction intake slots or

orifices

29 and 30,- which are readily adjustable in the field to various sizes and configurations, are appropriately positioned to capture the trash and fly which originate at ..the,junction zones A, B and C of-thecardingmachine. In actual practice, the junction zone B is very carefully established by the machine operators so that it represents a slot of approximately inchfrom end to end. Because of the internal pressure existing in the carding'machine under this zone, a certain amount of blowout carrying trash will exist, but this blowout must be less in air volume than is being handled by the orifice All blowout-from the junction zone B between the lickerin cover and the back knife plate will then be captured by air flowing through the orifice 30 and into the nipple 26a. The trash which falls from the junction zone A slides down the surface of the back knife plate 17 through the orifice and into the region of the pneumatic blowout through the junction zone B, so that it, too, will be carried away by the air moving to and through the orifice 30. The adjustability of the manifold is particularly important, because the orifice 30 must be very carefully adjusted for the air pressure existing within the carding machine relative to the suction pressure available through the nipple 26a, so as to simply nullify the blowout effect at the junction zone B without placing the junction zone B under a negative static pressure. If the orifice 30 is of such size for the particular air pressure existing within the card and the suction pressure available through the nipple as to produce negative static pressure conditions at the junction zone B, it is found that reusable cotton escapes through the slot between the lickerin cover 15 and the back knife plate 17 along with the trash, resulting in a loss of good, usable fiber. Also, the orifice 29, which is in close proximity to the sealing roller 18, needs to be carefully adjusted for the air pressure conditions existing within the card and the suction pressure available through the nipple, since it is essential that the junction opening C bemaintained at atmospheric pressure or negative static pressure not in excess of negative .2 inch of water maximum, whether or not the sealing roller 18 is installed or removed by operating personnel. A generous amount of air moving through the orifice 29 will then capture atmospheric air along with contaminants blown out through the junction opening C, without loss of good, usable fiber. The orifice 29 also needs to have careful adjustment and probably also a proportionately increasing or decreasing area relative to length, so that an equal volume of air will be handled by each longitudinal increment of the orifice 29, even though internal negative static pressure will be decreasing according to known rules at distances away from the suction nipple 26a.

It will also be noted that a hinged baflie plate 36 overlies the zone occupied by the filling seal roller 18 and the feed roll 16 to define an open-ended enclosure above the feed roll, the baffle being mounted to the vertical panel 25a of the manifold by hinge 37, or a plurality of axially aligned hinges. This baflle 36 keeps blowout of material through the orifice C from reaching the room before it engages .a high velocity stream of air entering the manifold through the inlet orifice 29. To facilitate location of the baflie 36 at the downwardly inclined, rest position, a recurved, double thickness lip flange 38 may be provided atthe lowermost edge of the panel 25a to project outwardly from the panel 25a and form a stop for the baflle 36.

What is claimed is: 1. In"a carding machine having a feed roller, a 'main cylinder, a lickerin therebetween, a back knife plate covering a portion of the main cylinder periphery adjacent the lickerin, and a curved .lickerin'cover having end surfaces perpendicular to the lickerin axis and having first and second edges paralleling said axis and located respective ly' adjacent said feed roll and back knife plate, the junction= region between said edges and said feed roll and back knife plate being imperfectly sealed whereby first and second fly escape zones occur at said first and second edges respectively through which fly is discharged; a fly collecting and removing manifold structure'for the lickerin section of the carding machine comprising a sheet member and apair of spaced end walls joined thereto collectively with said lickerin cover 'defining a suction chamber having a main chamberportion overlying the cover, one of said end walls having a nipple extending therethrough' for communication between a source of suction and said. suction chamber, and said sheet member h'avingplural panels generally paralleling said axis including a front wall panel bounding said main chamber portion having a lower edge spaced above the lickerin cover adjacent said first edge defining a suction'intake slot positioned to draw in air and capture fly'from the region of said first fly escape zone and a second wall panel spaced above said second fly escape zone having a free edge adjacent and spaced from said back knife plate and a second edge joined to a third wall panel along an apex therebetween spaced above and closely approaching said lickerin cover defining with said cover a constricted intake throat to said main chamber portion spaced toward said front wall panel from said free edge to draw in air and capture fly from the region of said second fly escape zone, and mounting means adjustably securing lower portions of said end walls to the carding machine against said end surfaces of said lickerin cover for movement through a selected range in plural angular directions in respective planes perpendicular to the axis of the lickerin for adjustment of the vertical size of said intake slots and selective tapering of the slots from end to end.

' 2. The structure as defined in claim 1, wherein the carding machine includes a flats chain whose path defines a bight above said manifold structure wherein the flats pass adjacent said back knife plate defining a junction orifice, the spacing of said free edge of said second wall panel from the back knife plate defining an orifice for gravity discharge of trash from said junction orifice downwardly along the back knife plate into the region immediately above said second fly escape zone for suction withdrawal through said constricted throat.

3. The structure as defined in claim 1, wherein said front wall panel lies in a substantially vertical plane with said lower edge spaced circumferentially of the lickerin from said first edge of the lickerin cover, said second panel lies in a substantially horizontal plane, and said sheet member includes a fourth panel in upwardly offset substantially parallel relation to said second panel joined to the uppermost edge of said first panel, and said third panel is inclined to and interconnects said second and fourth panels.

4. The structure as defined in claim 1, wherein said sheet member is formed of a broken sheet of light gauge metal bent to define a plurality of integrally connected rectangular sections forming said panels, said front wall panel lies in a substantially vertical plane with said lower edge spaced circumferentially of the lickerin from said first edge of the lickerin cover, said second panel lies in a substantially horizontal plane, and said sheet member includes a fourth panel in upwardly otfset substantially parallel relation to said second panel joined to the uppermost edge of said first panel and said third panel is inclined to and interconnects said second and fourth panels.

5. The structure as defined in claim 1, wherein said mounting means for the end walls of the manifold structure includes fastening means for securing said end walls to stationary portions of the carding machine at spaced locations along each end wall providinga range of movement of each end wall in all directions in a vertical plane.

6. The structure as defined in claim 1, wherein the carding machine includes a pair of stationary lickerin end plate members at opposite ends of the lickerin adjacent said end surfaces of the lickerin cover, said mounting means for the end walls of the manifold structure including headed fastening members having shank portions extending along shank axes through said end walls into said end plates to bind the end walls thereagainst at variable positions of adjustment, said end walls having oversized apertures through which said shank portions extend to accommodate a selected range of relative adjustment of the end walls in any radial direction from the axis of each of said shank portions.

7. The structure as defined in claim 2, wherein the carding machine includes a pair of stationary lickerin end plate members at opposite ends of the lickerin adjacent said end surfaces of the lickerin cover, said mounting means for the end walls of the manifold structure including headed fastening members having shank portions extending along shank axes through said end walls into said end plates to bind the end walls thereagainst at variable positions of adjustment, said end walls having oversized apertures through which said shank portions extend to accommodate a selected range of relative adjustment of the end walls in any radial direction from the axis of each Of said shank portions.

8. The structure as defined in claim 3, wherein the carding machine includes a pair of stationary lickerin end plate members at opposite ends of the lickerin adjacent said end surfaces of the lickerin cover, said mounting means for the end walls of the manifold structure including headed fastening members having shank portions extending along shank axes through said end walls into said end plates to bind the end walls thereagainst at variable positions of adjustment, said end walls having oversized apertures through which said shank portions extend to accommodate a selected range of relative adjustment of the end walls in any radial direction from the axis of each of said shank portions.

9. In a carding machine having a feed roller, a main cylinder, a lickerin therebetween, a back knife plate covering a portion of the main cylinder periphery adjacent the lickerin, and a curved lickerin cover having end surfaces perpendicular to the lickerin axis and having first and second edges paralleling said axis and located respectively adjacent said feed roll and back knife plate, the junction region between said edges and said feed roll and back knife plate being imperfectly sealed whereby first and second fly escape zones occur at said first and second edges respectively through which fly is discharged; a fly collecting and removing manifold structure for the lickerin section of the carding machine comprising an elongated upper sheet member having a top wall portion and downwardly extending longitudinal side wall portions spaced above said lickerin cover and a pair of spaced end walls joined to said sheet member collectively with said sheet member defining a downwardly opening hood structure, mounting means for securing lower portions of said end walls against said lickerin cover to surmount said hood structure over said lickerin cover in position to collectively form a suction chamber therewith having a main chamber portion, said hood structure including coupling nipple means for communicating a source of suction to said main chamber portion, said side wall portions having longitudinal edges spaced above the lickerin cover at a pair of circumferentially spaced positions relative to the lickerin including a first position adjacent said first edge defining a first suction intake slot between said lickerin cover and one of said longitudinal edges to draw in air and capture fly from the region of said first fly escape zone and a second position spaced toward said back knife plate from said first position defining a constricted intake throat to said main chamber portion between said lickerin cover and another of said longitudinal edges to draw in air and capture fly from the region of said second fly escape zone, said mani fold structure including means for varying the effective cross-sectional size of said suction intake slot and said throat when said hood structure is mounted over said lickerin cover to vary the suction pressure conditions at said slot and throat, said last-mentioned means comprising means for varying the vertical spacing of each of said longitudinal edges from said lickerin cover and for varying the relative vertical position of diflerent longitudinal portions of each of said longitudinal edges.

References Cited UNITED STATES PATENTS 2,774,994 12/1956 Hayes 19-109X 3,315,320 4/ 1967 Bass et al 19107 DORSEY NEWTON, Primary Examiner