WO1993013643A1

WO1993013643A1 - Harvesting machine chaff blower

Info

Publication number: WO1993013643A1
Application number: PCT/AU1992/000003
Authority: WO
Inventors: Donald George Brooks; Helen Edith Brooks
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-09-18
Filing date: 1992-01-06
Publication date: 1993-07-22
Anticipated expiration: 1994-07-06
Also published as: AU8385791A; AU639136B2

Abstract

A harvester (10) is provided with a blower (26) and an air distribution manifold (16), which discharges a flow of air generated by the blower (18) as a curtain of air through outlet ports (22 and 23). This curtain of air intercepts and disperses the chaff as the chaff is discharged from the harvester. The outlet ports are disposed so that they impart a component of force to the air flowing from the manifold (18) in a direction transverse to the direction of travel of the harvester and laterally away from the harvester. In a preferred embodiment of the present invention, the air flow from the manifold cooperates with straw spreaders (19) to achieve more even and uniform distribution of the chaff.

Description

HARVESTING MACHINE CHAFF BLOWER

FIELD OF INVENTION

This invention relates to a method and means for distributing chaff behind a harvesting machine.

BACKGROUND OF THE INVENTION

In a grain harvesting machine, such as a wheat harvesting machine, a crop is severed below its heads. The heads are threshed in a thresher and separated out from the straw, and the husks and chaff from the grain. The grain is discharged into a grain container or bin. The straw is moved across the rear of the machine by reciprocating sieves and straw walkers or by rotary screws. The particulate materials, which include chaff, husks, weed seeds, and some grain that was not separated during the threshing process, are left on the ground behind the machine after the grain seeds, and straw have been separated out.

The straw is normally spread on the ground behind the machine over the full width of the machine. While the straw performs a useful function of providing some mulch and retaining topsoil, with existing machines at the time of this invention, the chaff is discharged in a windrow behind the harvesting machine. When plow discs were commonly used, the chaff was turned into the soil upon plowing and little or no problem occurred. The amount of chaff was insufficient substantially to denude the soil of nitrogen and, in any case, the long term effect was roughly equivalent to having straw on the surface functioning as mulch. However, when chemicals are used to kill weeds (as is the practice with most modern farmers), serious disadvantages are encountered if the chaff trail is left as a windrow:

(a) When chemical herbicide is sprayed onto the ground to kill weeds, it can have difficulty penetrating the layer of chaff if the chaff layer is thick. Moreover, weed seeds are concentrated in the chaff trail. Hence, a heavier dosage of herbicide may be required to the chaff trail in order to achieve the same level of weed control as areas having a lower concentration of weed seed. When weeds are heavily concentrated in the chaff trail, a single

SUBSTITUTE SH application of chemical herbicide may not be adequate for control. In certain circumstances, the chemical application rate required effectively to control the weeds is in excess of levels that could harm the crop. In view of this limitation, second, and even third, applications of chemical are frequently required to achieve effective weed control. Moreover, repeated chemical applications must be spaced temporally so that the side effects on the crop are limited and the crop is not impaired. Repeated application of the chemical weed control increases chemical usage as well as the farmer's application costs.

(b) Chaff windrows can cover as much as 20% of the crop area in extreme cases. This can result in decreased yields and further problems for future crops due to a high density of weed seeds.

(c) During the following season's seeding of crop, a tine implement, if used, can be and frequently is blocked up with the rubbish left in the header trail.

(d) When light to medium rain occurs, the windrow of chaff can shed water, so that the ground under the windrow receives less moisture than the ground on each side of the windrow. In prior harvesting equipment, little attention focussed on reducing the effects of chaff windrows. Those prior attempts that have specifically addressed this problem involved different methods than the system of the instant invention. None discloses the use of the unique manifold structure of the present invention to evenly distribute the chaff across the full width of the harvesting machine cut.

For example, Anderson (U.S. Patent No. 4,711,253 for Chaff Blower for Combines) discloses a chaff blower. Anderson uses a split air nozzle 33, centered between the side walls of the harvester on the rear edge of the chaff tray. This structure is located at the point where the chaff is discharged from Anderson's harvester and spreads the chaff sideways, out both sides of the harvester. In other embodiments, Anderson discloses a channel along the rear edge of the chaff tray and a panel that covers the rear exit from the chaff tray, which prevent chaff from being discharged out the rear of Anderson's harvester and direct the chaff out the two sides. Anderson claims that his split nozzle structure spreads the chaff fairly evenly on the ground, preventing the toxic effects of windrows on successive crops.

Miller, et al. (U.S. Patent No. 4,923,431 for Chaff Spreader) also discloses a chaff spreader for attachment to a harvester combine. Two fans 22 and 24 are mounted at opposite ends of a shroud 18 at the rear chaff discharge from Miller's harvester. The chaff is drawn into the shroud 18 by a suction created by the fans. The back of the shroud prevents the chaff from being expelled straight out the_^rear of Miller's harvester. The two fans 22 and 24 blow the chaff in opposite directions, out the sides of Miller's harvester. Anderson and Miller both disclose systems for spreading chaff.

Although they use different structural means to accomplish this function, both use a blower to accomplish the spreading function. Both blow the chaff out the sides of the harvester, laterally relative to the direction of travel of the harvester. Although the resulting windrows of chaff would likely be less distinct than if no blower were used, both Anderson and Miller may well lead to the formation of windrows of chaff on each side of the path of the harvester. In both, the blower system results in rapid loss of blower pressure. The present invention, in contrast to both Anderson and Miller, uses a curtain of pressurized air exiting from a manifold to distribute chaff across the full width of the cut, in a pattern extending 180° behind the rear, center point of the harvester. In accordance with the invention, the discharge air leaving Applicants' manifold travels at a higher velocity than the air entering the manifold, allowing applicant's invention to more widely disperse the chaff. Moreover, in a preferred embodiment of the present invention, the discharge air operates in conjunction with straw spreaders located at the rear of the harvester. The straw spreaders are disposed immediately to the rear of and above the manifold. In this arrangement, the interaction of the air stream carrying the chaff and the straw spreaders increases the efficiency of spreading the chaff. Applicants believe that their system achieves more effective, and more even, distribution of chaff than would likely result from any of the known prior approaches. Moreover, none of the known prior methods for winnowing and/or spreading chaff suggests the improved manifold system of the present invention, consisting of tubular elements which direct the chaff away from the harvester and evenly spread the chaff, preventing the formation of deep windrows.

SUMMARY OF THE INVENTION The present invention overcomes the problems and disadvantages of the prior art by effectively preventing the formation of windrows behind a harvester.

An object of the present invention is to provide a method and means whereby chaff can be more evenly spread over the surface of the soil, avoiding the formation of windrows.

An additional ob ect of the present invention is to reduce the amount of costly agricultural chemicals needed to control weeds in grain crops.

A further object of the present invention is to reduce the chemical herbicide application rate necessary to control weeds in a grain crop, allowing effective weed control at application rates that do not impair the growing crop.

Another object of the present invention is to eliminate the need for second and third applications of chemical herbicides to agricultural crops, reducing chemical costs as well as application costs.

A further object of the present invention is to minimize the adverse effects of chaff windrows on grain crops, namely decreased yields and problems for future crops due to a high density of weed seeds in the windrows.

Another object of the present invention is to prevent the blocking of tined agricultural implements with rubbish left in the header trail.

Yet another object of the present invention is to minimize the adverse effect on soil moisture caused by the chaff windrow acting to shed water from the ground below the windrow.

Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the instrumentalities and combinations, particularly pointed out in the appended claims.

In one embodiment of the invention a harvester is provided with a blower connected to an air distribution manifold. The manifold discharges a flow of air through outlet ports formed in the manifold. The air entrains the chaff as the chaff is discharged from the harvester and spreads the chaff widely and evenly behind the harvester. The chaff settles on the ground and functions in a manner similar to straw, that is, providing useful mulch. In accordance with the present invention, the chaff is not allowed to settle in a windrow, which would otherwise contain a higher relative concentration of weed seeds.

Moreover, the formation of windrows, which would otherwise impede the penetration of moisture and lower the effectiveness of herbicides, is minimized.

The wide and even distribution of chaff achieved by the present invention allows for more effective and efficient weed kill. Lower chemical application rates are possible. Since less weed seed will be concentrated in the chaff and less of the chemical spray will be blocked by windrows of chaff, less weed control chemical is required.

In another embodiment, a harvesting machine chaff blower comprises a distribution manifold, attachment means, a blower, conduit means between the blower and manifold, and air flow directing means carried by the manifold arranged to deflect the flow of air discharging from the manifold in a direction which has a large transverse component. The direction can also have a vertical component, and can have a longitudinal component directed toward the rear of the harvester to ensure that the chaff and other paniculate debris being discharged by the machine is spread evenly behind the machine when in operation.

In another preferred embodiment of the invention, the manifold operates in conjunction with the straw spreaders at the rear of the harvester to achieve more evenly distribute the chaff. In this arrangement, the straw spreaders are located immediately to the rear of and above the manifold. The air discharged from the manifold entrains the chaff exiting the rear of the harvester and blows the chaff toward the straw spreaders, where the interaction of the air stream carrying the chaff and the straw spreaders increases the efficiency of spreading the chaff.

To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention manifold means for discharging a flow of air to intercept and distribute the chaff, said manifold means further comprising a surface, an axial direction, and a plurality of outlet apertures formed therein on substantially the same axial surface of said manifold means, attachment means for securing said manifold means to said harvester, and blower means for supplying air to said manifold means under pressure, wherein said air supplied by said blower is discharged from said manifold means through said plurality of outlet apertures resulting in a distributed flow of air discharging from said manifold means across substantially the full axial extent of said manifold means.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate several exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention. While the invention need not necessarily include all of the following details, an embodiment is described hereunder in some further detail with reference to, and as illustrated in, the accompanying drawings.

Figure 1 is a partial section, diagrammatic, side elevation view of the rear portion of a harvester, including a chaff spreader in accordance with the present invention.

Figure 2 is a partial section, cutaway, top elevation view of the embodiment shown in Figure 1, along the line 2-2.

Figure 3 is a partial section, rear elevation of the manifold element of a preferred embodiment of the present invention, corresponding to line 3-3 of Figure 1.

Figure 4 is an oblique view of the manifold element of another embodiment of the present invention, corresponding to line 4-4 of Figure 1.

Figure 5 is a cross-section view of the embodiment depicted in Figure 4, taken along line 5-5.

Figure 6 is a partial section, rear elevation of the manifold element of an embodiment of the present invention corresponding to line 3-3 of Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. A preferred embodiment of the present invention is illustrated in Figs.

1, 2, and 3, and is represented generally by numeral 40.

Reference will now be made to a preferred embodiment of the present invention as depicted in Fig. 1. A harvester 10 of known configuration, suitable for harvesting grain such as wheat, is typically provided with a deflector plate 11, straw walkers 12, and sieves 13. Deflector plate 11 slopes downwardly and rearwardly from straw walkers 12 and sieve 13. It will be apparent to those skilled in the art that various modifications and variations of the deflector plate 11, straw walkers 12, and sieve 13, as well as various other harvester components are known. As an example, although the deflector plate 11 is shown in Fig. 1 to have a saw tooth profile 14, it may also be planar. It is intended that the present invention be compatible with a wide variety of harvester configurations.

In use, when the harvesting machine 10 is reaping a crop, straw is separated, conveyed over straw walkers 12, and discharged over the rotary straw spreader 19. Rotary straw spreaders 19 may comprise one or more discoid-type throwers, as depicted in Figs. 1 and 2. Chaff is separated in sieve 13, conveyed to the rear of the harvester 10, and discharged over deflector plate 11.

In a preferred embodiment of the present invention, the invention comprises manifold means 16, attachment means 17, blower 26, and conduit 27.

Chaff being discharged from harvester 10 is conveyed to the rear edge of deflector plate 11, where it is discharged into the path of a curtain of air 18 which issues from manifold 16.

As depicted in Figs. 2, 3, and 6, in a preferred embodiment of the present invention, manifold 16 has a plurality of apertures formed therein.

Manifold 16 has an inlet aperture 29 and a plurality of outlet ports 22 and 23. In a preferred embodiment of the present invention, manifold 16 is elongated in an axial direction and is disposed with its axis oriented in a substantially transverse direction, across the width of harvester 10, along the lower rear edge of deflector plate 11, as illustrated in the accompanying drawings. In a preferred embodiment of the present invention, outlet ports 22 and 23 are disposed along substantially the same surface 15 of manifold 16, in a plane that is oriented at an angle of substantially 30° relative to the ground. Manifold 16 is attached to harvester 10 by any suitable attachment means 17.

A plurality of nozzles 20 and 31 are disposed along the inner surface of manifold 16, forming a plurality of outlet ports 22 and 23. In a preferred embodiment of the present invention, first outlet ports 22 and second outlet ports 23 are formed by the intersection of nozzles 20 and 31, respectively, with the top surface 15 and end surfaces 34 of manifold 16, respectively.

In a preferred embodiment of the present invention, shown in Figs. 2 and 3, nozzles 20 and 31 comprise short lengths of tubing of relatively small diameter, disposed along the length of manifold 16. As depicted in Figs. 2 and 3, in a preferred embodiment of the present invention, as viewed from the rear of the harvester, first nozzles 20 are disposed at an angle relative to the vertical in order to cause the air being discharged 18 from manifold 16 through first outlet ports 22 to have a transverse component of direction, relative to the direction of travel of the harvester. In this configuration, the intersection of nozzles 20 and manifold surface 15 forms elliptical outlet ports 22. As shown in Figs. 2 and 3, in a preferred embodiment of the present invention, first outlet ports 22 are disposed in two rows, one row having nozzles 20 disposed to create a transverse component of direction of the discharge air 18 to the left of the direction of travel, and the other row- disposed to create a component of force to the right of the direction of travel, of harvester 10.

In a preferred embodiment of the invention, nozzles 31 are disposed in the ends 34 of manifold 16, forming second outlet ports 23. Nozzles 31 discharge streams of air 18 out opposite ends of manifold 16, to ensure as wide as possible a dispersion of materials discharged as chaff from the harvester 10. In a preferred embodiment of the present invention, outlet ports 22 and

23 cooperate with straw spreader 19 to achieve wide dispersion of the straw and chaff. Specifically, the chaff exiting deflector plate 11 is entrained in air flow 18 and mixes with straw being discharged and spread by straw spreaders 19. In this way, the interaction of the discharge air and straw spreader 19 achieves a wider and more even distribution of straw and chaff than would otherwise be possible.

There is a tendency for discharging material exiting deflector plate 11 to be concentrated at the center of the harvester 10. In order to prevent the formation of "dead spots" in the curtain of air 18 being discharged from manifold 16, as shown in Figs 2, and 3, in a preferred embodiment of the invention, the rows of nozzles 20 overlap in a central region 21 of top surface 15 of manifold 16. Specifically, in a preferred embodiment, outlet ports 22 are arranged in two horizontal rows. Each row of openings covers about two- thirds of the width of manifold 34. These rows overlap substantially at central region 21. This overlap creates a region having transverse components of force in both lateral directions relative to the direction of harvester travel, and reduces substantially the tendency for the material being discharged to form a windrow behind the harvester. It will be apparent to those skilled in the art that various modifications and variations can be made to the chaff winnowing apparatus of the present invention and, in particular, in the construction of manifold 16 and attachment means 17, without departing from the scope or spirit of the invention. For example, the angle at which nozzles 20 and 31 are disposed within manifold 16, the number and arrangement of outlet ports 22 and 23 on the surface of manifold 16, and the extent and position of the overlapping region 21, may be varied.

Figures 3, 4, and 6, for example, depict variations in the arrangement and configuration of outlet ports 22 and 23. As a further example, as shown in Figs. 4 and 5, a series of slots 32 and vanes 33 can replace nozzles 20 of the present invention. This modification allows the angle at which the air discharging from the outlet ports 22 to be varied by the operator as appropriate. For example, even distribution of the chaff may be impaired in crosswinds. To overcome this problem, in one embodiment of the present invention, the top surface 15 of manifold 16 may have one or more slots 32 formed therein. Each slot 32 is provided with a plurality of vanes 33. As was the case with nozzles 20 and outlet ports 22, vanes 33 are disposed at an angle relative to the vertical in order to cause the air to be discharged from manifold 16 through slot 32 to have a transverse component of direction, relative to the direction of travel of the harvester.

As shown in Figs. 4 and 5, in a preferred embodiment of the present invention, slots 32 are disposed in two rows. In one row, the vanes 33 are disposed to create a transverse component of direction of the discharge air 18 to the left of the direction of travel; while the vanes 33 in the other row other row are disposed to create a component of force to the right of the direction of travel of harvester 10. As shown in Figs. 4 and 5, in a preferred embodiment of the invention, the two rows of slots and vanes overlap in a central region 21 of manifold 16. As did outlet ports 22, slots 32 overlap at a region 21 on the top surface of manifold 16 to eliminate any "dead spots" in the curtain of air 18 discharging from manifold 16.

Moreover, the disposition of the plane formed by outlet ports 22 and 23, in top surface 15 of manifold 16 relative to the horizontal can vary. Depending on the arrangement of other harvester components and the desired distribution pattern of the chaff, this angle may vary from about 30° in a preferred embodiment of the invention, up to about 70 to 80° from the horizontal.

Moreover, various attachment means 17 can be employed. In a preferred embodiment of the invention, attachment means 17 comprises known fasteners.

Appropriate variations and modifications and variations in the construction of these various manifold and attachment means components will depend, at least in part, on the configuration, spacing, and disposition of the other elements of the invention, as well as of certain known harvester elements, such as the deflector plate 11 and straw walkers 19. These variations, as well as others, can be used to control the precise pattern of distribution of the chaff. Thus, it is intended that the present invention cover the modifications and variations of these elements provided they come within the scope of the appended claims and their equivalents.

In a preferred embodiment, the manifold is supplied with air by blower 26 through conduit 27. In most instances, drive for blower 26 can be effected from a shift existing on the harvester machine 10. If such a shift is not available, or is not conveniently located, an engine 24 is mounted on a side wall of harvester 10. Engine 24 is connected by a belt drive 25 to blower 26. In a preferred embodiment of the present invention, air is delivered to manifold 16 by blower 26 through a flexible conduit 27. Flexible conduit 27 is connected to manifold 16 by a diverting air inlet deflector 28, which communicates with air inlet aperture 29 formed in manifold 16.

In a preferred embodiment of the present invention, inlet aperture 29 of manifold 16 is larger in cross-sectional area than the sum of the cross- sectional areas of the various outlet ports 22, 23, and/or 34. This difference in cross-sectional area between the inlet and outlet apertures of manifold 16, allows manifold 16 to function as an "air chest". As a result, the velocity of the air discharged 18 from manifold 16 will be higher at the outlet ports 22, 23, and/or 34 than is velocity of air flowing entering manifold 16 at inlet aperture 29. This resulting increase in velocity aids in achieving wide and even dispersal of the chaff and other discharge materials.

It will be apparent to those skilled in the art that various modifications and variations can be made to the chaff winnowing apparatus of the present invention and, in particular, in the construction of blower 26, conduit 27, diverting air inlet deflector 28, and inlet aperture 29, without departing from the scope or spirit of the invention. For example, in a preferred embodiment of the invention, depending on the configuration and size of blower 26 and conduit 27, the velocity of air discharged 18 from manifold 16 would be higher than the air velocity in conduit 27, as well as being higher than the velocity at inlet aperture 29. In a preferred embodiment of the present invention, blower 26 is a centrifugal blower. Other types of blowers could be substituted, provided they are capable of delivering air at an appropriate volume, velocity, and pressure.

As a further example, variations in drive could be employed. Blower

26 can be driven by an engine, an electric motor, or the harvester machine main engine. It may also be driven hydraulically. Conduit 27 can be formed from a flexible or semi-flexible hose. It may also be provided with an air control butterfly or other type of air speed control means. Thus, it is intended that the present invention cover the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents.

It will be apparent to those skilled in the art that various modifications and variations in addition to those specifically mentioned can be made to the present invention, without departing from the scope or spirit of the invention.

It is intended that the present invention cover all such modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalents.

Claims

We claim: 1. Means for distributing chaff being discharged from a grain harvester, comprising: an air distribution manifold, attachment means for securing said air distribution manifold to the harvester to he adjacent to the path of chaff discharge, an inlet conduit in air flow communication with said manifold, a plurality of outlet ports opening from the manifold oriented so that air discharging from the outlet ports deflects the discharging chaff laterally, an air blower on the harvesting machine in air flow communication with said conduit, and drive means coupled to the air blower.

2. Means according to claim 1, wherein said air distribution manifold is elongate and extends in a lateral direction across the grain harvesting machine, and the outlet ports comprise two groups oriented to direct discharging air laterally outwardly in respective opposite directions, the manifold being so mounted that chaff discharged from the harvesting machine is discharged into said discharging air.

3. Means according to claim 2 wherein each said group of outlet ports comprises a plurality of nozzles opening along a top portion of said mamfold.

4. Means according to claim 2 wherein each said group of outlet ports comprises a laterally extending slot opening along a top portion of said manifold, and a plurality of deflecting vanes bridging that said slot and sloping so as to effect said orientation to direct the discharging air outwardly.

5. Means according to claim 2 further comprising nozzles in respective ends of the manifold arranged to direct air flow laterally outwardly from said means.

6. Means according to claim 2 wherein said outlet ports of the two groups overlap near the center of the manifold.

1. Means according to claim 2 wherein said harvesting machine is of the kind having a deflector plate sloping downwardly and rearwardly of straw walkers and sieves, and also includes a rotary straw spreader, said securing means comprising fasteners securing the manifold to the rear edge of said deflector plate in a position wherein said discharging air also intercepts straw being spread by the spreader.

8. Means according to claim 2 wherein said drive means comprises an engine on the harvesting machine.

9. An apparatus for dispersing chaff being discharged from the rear of a grain harvester, comprising: an air distribution manifold disposed adjacent the chaff discharge of the harvester, comprising a surface, an axial direction, end portions, an inlet aperture, and a plurality of outlet ports formed in said manifold for discharging a flow of air to intercept and distribute the chaff, said outlet ports being disposed on substantially the same axial surface of said manifold means, attachment means for securing said manifold means to said harvester,

blower means in communication with said inlet aperture of said manifold for supplying air to said mamfold means under pressure, and conduit means for connecting said blower to said inlet aperture of said manifold in air flow communication therewith, wherein said air- supplied by said blower is discharged from said manifold means through said plurality of outlet apertures resulting in a distributed flow of air being discharged from said manifold means across substantially the full axial extent of said manifold means, wherein said outlet apertures impart a transverse direction of flow to said air flow from said manifold in a direction transverse to the direction of travel of the harvester.

10. The apparatus of claim 9, wherein said plurality of outlet apertures comprise two rows of outlet apertures, each of said rows extending more than half but less than the full axial extent of said mamfold, and wherein said rows of outlet apertures overlap for at least some portion of their axial extent.

11. The apparatus of claim 9, wherein said rows of outlet apertures comprise first and second rows, said first row being disposed to impose a first component of direction on the flow of air transverse to a direction of travel of the harvester, and said second row being disposed to impose a second component of direction on the flow of air transverse to the direction of travel of the harvester and opposite said first transverse direction.

12. The apparatus of claim 9, wherein said mamfold means further comprises outlet apertures formed in said opposite ends of said mamfold means.

13. The apparatus of claim 9, wherein said outlet apertures comprise slots formed in an axial surface of said manifold means.

14. The apparatus of claim 13, wherein said outlet apertures further comprise vanes disposed in each of said slots.

15. The apparatus of claim 14, wherein said vanes are disposed to impose a component of force on said flow of air in a direction transverse to the direction of travel of the harvester.

16. The apparatus of claim 14, wherein said slots comprise first and second rows of slots, said first row being disposed to impose a first component of direction on the flow of air transverse to a direction of travel of the harvester, and said second row being disposed to impose a second component of direction on the flow of air transverse to a direction of travel of the harvester and opposite said first transverse direction.

17. The apparatus of claim 13, wherein said plurality of outlet apertures further comprise outlet apertures formed in said opposite ends of said manifold means.

18. The apparatus of claim 17, wherein the cross-sectional area of said manifold inlet aperture is larger than sum of the cross-sectional areas of all of said manifold outlet apertures, resulting in the air at said outlet apertures being delivered at a higher velocity than the air entering said mamfold at said inlet aperture.

19. The apparatus of claim 9, wherein the cross-sectional area of said manifold inlet aperture is larger than sum of the cross-sectional areas of all of said mamfold outlet apertures, resulting in the air at said outlet apertures being delivered at a higher velocity than the air entering said manifold at said inlet aperture.

20. The apparatus of claim 12, wherein the cross-sectional area of said manifold inlet aperture is larger than sum of the cross-sectional areas of all of said manifold outlet apertures, resulting in the air at said outlet apertures being delivered at a higher velocity than the air entering said manifold at said inlet aperture.