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Har1c:book . No. Jar1L1ary 1968

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Seecl '- ech:rology Laboratoryl'liRRi88ippi State Ur1i-versitySte.tite College. IVlissisE3ippi

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SEED PROCESSING8r1cl

I---ANDLING

Edited by

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CHALES E. VAUGHABILL R. GREGG

andJAMES C. DE LOUCHE

( Seed Techr1

gy

La.b ra.t ry

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Mississippi S te Ur1i-versity)

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- Sta.te llege. lVississippi

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iii

FOREWORD

In 1954 the Mississippi Agricultural Experiment Station publishedBulletin 520 " SEED PROCESSING EQUIPMENT" . This bulletin was - so faras we know - the first comprehensive consideration of modern seed pro-cessing equipment, principles, and procedures, in this country. Twelvethousand copies were printed (in two printings) and distributed to peoplefrom throughout the U . S . A. and over 40 foreign countries. In tribute tothe pioneering effort represented by Bulletin 520, its coyer design hasbeen used on the cover of tl;e present handbook.

Seed processing was not a new field in 1954. It had long been animportant segment of the commercial seed industry. What was new was adeveloping interest and competence in the field by agronomists andagricultural engineers at one of the Land Grant Universities.

Before 1950, seed processing was largely a skilled craft passedon from craftsman to apprentice. The procedures and techniques usedwere almost completely locked within the experiences of the seed pro-cessing craftsmen in the various seed companies. Indeed , many of thetechniques and procedures were treated as " trade secrets " and, conse-quently, were ' not readily communicated or transmitted to others.

- Seed processing is - at its best - still a skilled craft. But it isan open craft and most of its " secrets " have become public knowledge.A substantial body of written and illustrated material on equipmentprinciples, and techniques has been developed and is available. Withoutthis " body of knowledge " the present handbook would not have beenpossible

Annually since 1951, the Mississippi Seed Technology Laboratory,in cooperation with the manufacturers of seed proce sing and handlingequipment have given a SHORT COURSE FOR SEEDSMEN. And since 1958much of the material presented at the Short Cours-e has been published an annual Proceedings. Although originally published primarily to recordthe transactions of the Short Course, the Proceedings have becomereference books " on seed processing and various other aspects of seed

technology. They have been so widely distributed around the world thatsupplies of most issues have been exhausted.

... .

The Proceedings have served well as reference works on seedprocessing andhandlingi yet, there was still a need for a comphrensivetreatment of these subjects - a treatment that would bring together in onemanual or handbook, pertinent information scattered through the various

- Proceedings and the developing literature on seed proces sing.

It was with this need in mind that the present handbook wasdeveloped. Various members of the staff of the Seed TechnologyLaboratory wrote the several sections. Some served as editors. Allhave drawn heavily on the material presented by the many speakersduring fifteen Short Courses for Seedsmen.

The Seed Technology Laboratory is grateful to the authors ofarticles that first appeared in the Proceedings, the manufacturers ofseed processing and handling equipment, and Jesse. Harmond and hisassociates (USDA), for their assistance and cooperation during thepreparation of this handbook.

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TABLE OF CONTENTS

Section A Introduction and Principles of Seed Processing

" . . .

Introduction

. . . .. . . . . . . . . . . . . . . . . . . . .

Principles of Seed Processing (Bill Gregg)

. . . .

Section B Prec1eaning and Conditioning Equipment.

. . . . . .

Scalpers (Charles E. Vaughan) .Debearders (Charles E. Vaughan) .

.. . . . . . . . . . . .

Huller-Scarifier (Charles E. Vaugban) .

. . . . . . . . . . .

Buckhorn Machine (Bill Gregg) .

Section C Basic Seed Gleaning Equipment

. . . . .

Air-Screen Machine (Charles E. Vaughan) .

. .

Section D Dimensional Sizing Equipment . .

. . . . . . . . .

Width and Thickness Separators (George M. Dougherty)Length Separators (George M. Dougherty) .

. . . . . . . .

Section E Specific Gravity Separators

. . . . . . . . . . . . . .

Specific Gravity Separators (Bill Gregg) . .

. . . . . . . .

Stoners (Bill Gregg) .

.. .,

Section F Surface Texture Separators

. . . . . . . . . . . . .

Roll Mill (George M. Dougherty) .Magnetic Separators (T. Wayne Still)

. . . . . . . . . . .

Inclined Draper (James D. Helmer) .Section G Air Separators

. . . . . . . . . . . . . . . . . . .

Pneumatic Separators (James D. Helmer) .Aspirators (James C. Delouche) . .

. . . . ' . . . . . . . . .

Scalping Aspirators (James C. Delouche) . .

. . . . . . . .

Section H Electronic Separators

. . . . . . . . . . . . . . . .

Electric Color Sorters (A. H. Boyo., Jr.

. . . . . . . . .

ElectrostaUc Separators (T. Wayne Still) .

. . . . . . . .'\ .

Section I Miscellaneous Cleaning Equipment. .

. . . . . . . .

Spiral Separators (James D. Helmer).

. . . . . . . . . .

Polishers (Bill Gregg) .

. . . . . . . . . . . . . . . . . .

Picker Belts (Bill Gregg)

. . . . . . . . . . . . . . . . .

Timothy Bumper Mill (Charles E. Vaughan) .Vibratory Separator (Charles E. Vaughan) . .

. . . . . . . .

Page

113

143

151153161.169

173177179182

185187197

207209212213215216

Section J Seed Treating Equipment

. . . .

0 . . .

. . . . .

Commercial Treaters (Howard C . Potts)

. . . . . . . . .

Farm Treaters (Howard C. Potts) . .

. . . . . . . . . .

Section K Elevating and Conveying Equipment

. . .

. 0

. .

Bucket Elevators (Howard C. Potts)

. . . . . .

. 0 . 0 .Belt Conveyors (Howard C. Potts) .. 0 . 0 . . .

. .

Vibrating Conveyors (Howard C. Potts) .Pneumatic Conveyors (Howard G. Potts) . .

. 0

. .

0 0 .Screw Conveyors (Howard C. Potts) . .

. . . . . . .

. 0Chain Conveyors (Howard C. Potts)

. . . . . . . . . .

Lift Trucks (Howard C. Potts)

. . . . . . . . . . . . . .

Section L Accessory Equipment. 0

. .

0 . 0 . .

. .

. . 0

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Scales (Howard C. Potts) .. 0

. . . . . .

0 0 . . BagClosers (Howard C. Potts) .

. 0

. . . . . . .

0 0Blowers and Vacuum Cleaners oward C. Potts

. . .

Bins (Bill Gregg) . 0 . . . . 0

. . . . . . . . . . . . .

Section M Design and Layout of Processing Plant

. .

. 0

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Seed Plant Layout Planning (Bill Gregg) . . 0 . . .

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Automation (A. H 0 Boyd, Jr.

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Appendix 0 . . . 0 0 . .. 0 0 . .

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Page219221230

233235240243245245246248

251253255261263

26927l291

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Introduction

1 .

New and improved crop varieties become an important agriculturalinput only when seed of such varieties are available to farmers varietallypure, in a viable condition, free of contaminating we d seed and in ade-quate quantities at the right place and time. Seed processing is anintegral part of the technology involved in transforming the geneticengineering of the plant breeder and geneticist into improved seed. In itsbroadest sense seed processing encompasses all the steps involved inthe preparation of harvested seed for marketing - handling shelling, pre-conditioning , drying, cleaning , size-grading,) upgrading, treating andpackaging. In common use however , the terrr seed processing refers

--QDJy to the preconditioning, cleaning, size grading and upgrading of seed.This restricted "definition" of seed processing was adopted in this hand-book with some .expansion of it to incorporate basic considerations ofseed handling and treatment.

Seed growers and producers are dependent on the seed processorfor preparation of their seed for market. The quality of the final product regardless of its inherent capacity to produce, is directly related to theproc ssor s ability to remove contaminants and low quality seed, toprop&rly size-grade for precision planting, to treat the seed effectively,and to prevent mechanical mixtures of the seed with those of othervarieties or hybrids. IIi turn, the ,processor s ability to render theseservices efficiently and effectively, is greatly affected by the types ofprocessing and handling equipment available to him, their arrangementwithin the plant, his skill in operating them, and his knowledge of seedcharacteristics and how they relate to processing.

Think of seed processing and you think of equipment and ma-chinery, conveyors and structures. For it is in"conceivable that qualityseed of improved varieties and hybrids could be made.available in thequantities required by farmers without a high degree of mechanization ofthe many steps involved in the processing and preparation of seed. Thus,seed processing involves more mechanical skills and engineering princi-ples than are involved in other area s of seed technology.

A variety of contaminants must be removed from raw seed -particularly seed harvested by a combine - to make it ready for marketingand planting (see chart). Contaminants such as inert material and off-size seed are not, in themselves ; harmful but they do greatly influenceseed flowability and plantability, incidence of insect infestations, andcontribute to storage problems. Other contaminants such as weed seedand seed of other crops and varieties can seriously affect production ofcrops if they are not removed.

INERT MATERIAL

NOXIOUS WEED SEED

DETERIORATED SEED

DAMAGED SEED

HARVESTED SEEDTHRESHEDSHELLEDDRIED

COMMON WEEO SEED

OTHER CROP SEED

OTHER VARIETY SEED

OFF - SIZE SEED

MARKETABLE SEEDCLEANEDGRADEDTREATEDPACKAGEDTESTED

Figure A 1. Flow chart illustrating types of material that are. removed from seed during processing.

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Seeds are processed to remove contaminants to size-grade forplantability, to upgrade quality through removal of damaged or deteri-orated seed, ahd to apply, seeQ tre tment materials. The demands of theseed producer and seed con lmer require that these four objectives beachieved effectively, efficiently and with minimal damage to the seed.

A variety of equipment is available for processing seed. Theyrange from the simple winnowing tray - still used in many areas of theworld - to complex andlI.iQhly uphfstiC9te equipment such as the electricsorting machine. Although variable in type and design, all seed processingequipment have one thing in common: . the ' separations they effect arebased on differences in phYfilcal properties among desirable material(good seed) and undesirable material (contaJIinants). Some machinesseparate good seed ftom c,ontaminants .on the basis of differences inseveral physical properties More often, however satisfactory removalof contaminating mate iqJffpm eeq requires that they be processed in aspecific sequence thrO\1 veral machines -each machine removing acertain portion of the contaminating materiQ,!.

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The choice of a machine or sequence of machines for processingseed depends oil the kind of seed being processed, the nature and kindsof contaminants (weed seed, other crop seed, inert matter, etc. ), thequantity of each in the raw seed, and the quality standards that must bemet. Thus , the processor must be as familiar with seed sta.ndards andseed characteristics ashe . is with processing equIpment.

---!;,

This handbook was prepared as an introduction to seed processingand handling. Various types of equipment are considered. The mainfeatures and component parts , prinCipl s of separation, uses, andoperatio al procedures are di$cussed for each machine. Throughout thehandbook - and specifically in one section - ' an attempt was made toemphasize the concept of l.e "processing line , that is, the combination,proper sequence and arrangement of machines, con\reyors, and proceduresrequired for processing and handling of seed.. For some kinds of seed, asimple processing line cOnsisting of one machine coupled with handlingand bagging equipment is entirely adequate. In the case of other kindsof seed, compl x prQcessing lines consisting of several machinesarranged in sequerice and matched for capacity, many surge and holdingbins, and seve al types of elevators and conveyors are often required forcomplete processing. A processing line should never be static. Flexi-bility is necess;ary so that the line can be tailored and organized tohandle each se dkind and each lot within a Idhd in the most efficientmanner. Considerable attention and thought should be given, therefore,to the spatial arrangement and layout of equipmenLbins, and conveyorswithin the seed plant.

,. .:;..

The arrangement of material in this handbook is progressive likea processing line. The first section is a sort of over-view of the entirespectrum of seed processing equipment and procedures with emphasis fundamental concepts and principles. The next several sections dealwith equipment and procedures basic to all kinds of seed. Then thehighly specialized machines needed for some kinds of seed are discussed.Accessory equipment and seed plant layout and design are considered inthe last sections.

It was stated earlier that this handbook is intended to serve asan introduction to seed processing and handling. That is all that it cbe, for seed processing is a craft, an applied science r and - at its best -an art. The development of operational s kills and expertise can only beattained through exper+ence and constant study.

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PRINCIPLES OF SEED PROCESSING

The modern seed prooessor isbi:Sic l1y interested in five things:(1) Complete separation

- removal of l1 contaminating or undesirablematerial from the seed; (2) Minimum seed loss - some good seed are re- moved along with contaminants in almo t eVt3ry processing operation,but this loss must be kept at a minimum; (3) Upgrading quality - improve-ment of seed quality not only through remov;:lof contaminating seed, butalso removal of rotten, cracked, broken, tnsect damaged or otherwiseinjured or low quality crop s ec;; (4) YticiEmC(Y - the highest capacityconsistent with effectiveness ofseparq;.tipn, qnd (5) Minimum laborrequirement - labor isa direct operating cost and cannot be recovered.

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Seed processing operations can pe broken down into severaldefinite steps that follow in a specific sequence. The first step isRECEIVING - seed arrive at the processing plant in bags, pallet boxes,or in bulk. From the receiving station the seed go into bulk STORAGEto be held for later processing, or directly into the processing line for'cleaning.

The next step in seed processing is CONDITIONING AND PRE-CLEANING. This includes removal of appendages, large pieces of trash,debearding to remove awns, or hulling the seed.

The first actual cleaning and/or upgrading step is BASICCLEANING. The air- screeI: machine is probably the most common basiccleaner. It makes size separations and aspirates the seed. Seed lotsmay come from the field in good condition with feVo contaminating seedsand require cleaning only on the air-screen machine. Most often, how-ever , it is necessary to send the seed through one or more specialSEPARATING OR UPGRADING machInes to remove a specific contaminant.These specii;l machines separate crop and weed seed by differences intheir specific phy ical.characteristics. For effective and efficientseparation, the crop seed must differ from the weed seed sufficiently insome characteristic' so that the machine ca.n differentiate between eachcrop and weed seed.

.,. .

When all possible inert material and weed or other crop seed havebeen removed, the seed are ready for BAGGING. Sometimes a fungicideor insecticide TREATMENT is applied before they are bagged. The seedmay then be shipped directly to other seed companies, or held in STORAGEuntil they are needed.

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Seed processing is based on differenpes in physical propertiesbetween the desirable seed and the contaminating weed or other crop seed. Seed that do not differ in some physical characteristic cannot beseparated. If a difference exists between the seeds and a machine isavailable which can differentiate between them in a consistent manner,they can be separated. Seed processors can choose from a wide selectionof machine that differentiate between seeds differing in SIZ'E, LENGTH,SHAPE , WEIGHT, SURFACE TEXTURE COLOR, AFFINITY FOR LIQUIDS , orCONDUCTIVITY.

A single macl1ne cannot separate S eds that differ in all thesecharacteristics. In most instances a different machine must be used tomake separations based on each of these characteristics.

Size

Size is the most common difference among seeds, and betweenseed and undesirable material. Size separations are basic to seedprocessing. The air- screen machine- the basic seed cleaner - uses a

, series of perforated sheet metal or woven wire screens to separate seedof different sizes . One or more air blast separations remove lightmaterial. In a typical air- screen machine, the seed mixture drops throughan air bl. st onto several screens., and then through a second or even athird air blast where remaining light material is removed.

The first screen has perforations large enough to allow the cropseed to drop through. Larger undesirable material does not drop throughthe openings, ' and rides over the screen and out a separate dischargespout. The crop seed then fan onto a second screen which has openingssmaller in size than the crop seed. As the seed passover this screen ,all seed seed pieces, or inert material smaller than the good crop seeddrop through the screen openings into a discharge spout. Good seed rideover this screen and may pass onto additional screens for finer andclos er size separations or be moved to other machines or bagged.

Two types of screen sizings are made: (1) SCALPING, in whichgood seed drop through the screen openings while larger material iscarried over the screen iritoCl separate spout, and (2) GRADING, in whiChthe good seed ride over the screen while smaller particles drop throughthe screen openings. A. series of scalping and grading operations removeall material larger or smaller than the crop seed. The paramount featureof the air-.screen machine is the wide range of available screens - over200 different sizes and shapes of perforations. Seed processors must

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Figure A3. Section view of screens and air system in an air-screen cleaner.

know the characteristics of crop seed and material to be removed, how tooperate the machine and have available all scalping and grading screensneeded to remove undesirable material from the crop.

Width and Thickness

Width and thickness are special size dimensions used in operationssuch as sizing hybrid seed corn into specific widths and thicknesses forspace-planting. Several seed seprations are also made by width orthickness sizing. Width or thickness separations are made by turning theseed on edge or standing it on end to present its width or thickness dimen-sion, to perforations of specific size. ( If the seed is less than theselected width or thickness , it will drop through the perforation; if it isgreater than the selected width or thickness, it will not go through, andwill be discharged into a different spout. A thickness separation ismade by cylindrical or flat screens which have slotted perforations inthe bottom of recessed grooves. The shoulders of the groove turn theseed on edge before it reaches the slotted perforation. Thin seed fallthrough, while thick seed are rejected and go out a separate dischargespout.

Width separations are made by round-hole perforations at thebottom of indents or cup-like depressions in cylindrical or flat screens.

Figure A4. Diagram of thickness separation of corn seedusing a screen with slotted openings.

Shoulders of the indent tilt the seed on end and present its widthdimension to the perforation. lIf the seed is narrow , it drops throughthe perforation; if it is wider than the perforation , it is rejected. Aseries of width and thickness separations can be combined in a single

machine t6 produce several different width and thickness sizes in the

same operation. For example, corn seed can be sized into differentflat and round sizes.

U' .

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Length

Length differences are common among crop seed and weed seed,and are frequently used to upgrade and improve quality. Both the indentedcylinder and the disc separator make length separatiops. The indentedcylinder separator consists principally of a long round cylinder whoseinner surface has thousands of small indents of a precise size. Insidethe cylinder are other parts that help

make the separation, including anauger to keep the seed mass level,

a lifting trough to catch seeds andan auger to remove lifted seed from the trough. Seed are fed into thecylinder as it turns. The seed mass turns as the cylinder revolves sothat. each seed has an opportunity to fit into one of the indents and belifted. The relationship of seed length and center of

gravity to thedepth or size of the indent determines whether the seed will be lifted.Long seed do not fit completely into the indent, so they do not remain

Figure AS. Cross-section of a length separator. A, thecylinder wall with indents stamped into

iti B, theadjustable trough catching short lifted seed; C, theseparating edge of the adjustable trough; and, D, theauger conveyor in the bottom of the cylinder that conveyslong rejected material out of the cvlinder-

in the indents long enough to be lifted as the cylinder revolves. Seedsintermediate in length are lifted slightly above the edge of the seed massby the indents. Shorter seed are lifted higher up the arc of the cylinderrotation, and are dropped into the lifting trough and go out a separatespout. Thus, length of seeds determines their fit in the indents, and howhigh they are lifted.

The disc separator also separates seeds differing in length. Thediscs are cast iron wheels with many small undercut pockets cast intoboth faces. As the disc turns through a mass of seed, each seed has achance to seat in a pocket. If the seed is long, it will fall out; if it isshort , it will seat inside the pocket and be lifted out of the seed masLifted seed are carried up and dropped into a separate discharge spout.Various pockets shapes are available. Square- shaped pockets separatedifferent crop seeds; pockets with rounded lifting edges lift round seed,and pockets with flat lifting edges lift flat- sided or rectangular seed.

The complete disc separator consists of a revolving shaft withmany discs mounted on it. Seed enter the machine at one end, movethrough the center of the discs, and come in contact with the pockets onthe side of each disc. These pockets either reject or lift out seed as themass moves through the machine. By using a series of discs of differentpocket sizes on the same shaft, several length grades can be made in onemachine.

Figure A6 . Disc separator used to separate seed on basis ofdifferences in length.

Shape

Shape varies widely among seeds. The separations made by theair- screen machine are often related to differences in shape especiallywhen triangular-hole screens are used. The indented cylinder and thedisc separator take advantage of shape differences, particularly whenthey are a function of length. There is a machine, however , designedespecially to separate round from flattened seed - the spiral separator.

The spiral separator consists mainly of a simple vertical series

of spiraled flights. A mixture of flat and round seed\ is fed onto theinner spiral at the top of the machine. (As seed move down the spiralsunder the influence of gravity, the velocity of the round free-rollingseed increases to the point where they roll over the inclined edge of the inner flight of spirals, into an outer flight. This outer flight dis-charges into a sepa ate spout. Flattened or irregular- shaped seedslide down rather than roll down the spiral and do not attain sufficientvelocity to roll over the edge of the flight and continue down the flightto the discharge spout. Thus, flat and round seed are separated in thespiral separator by differences in roundness or their ability to roll.

Surface Texture

Relative roughness or smoothness of the seed coat - surface

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Figure A7. Krussow double spiral separator.texture - is a common difference between seeds. The roll or doddermill, the draper belt , the magnetic separator , the buckhorn machineand vibrator separator all effect separations of seeds differing insurface te ure.

The basic unit of the roll mill consists of two long cylinder-like rollers , covered with a ve vet or flannel material , and positionedside by side so that they touch along their entire length forming a troughabove and between the rollers. The long axis of the paired rolls slightly inclined. Tne mixture of smooth and rough seed is fed into thetrough formed by the rolls at the high end. As the rolls revolve inopposite directions up and out from the trough center , (rough seeds arecaught by the nap of the velvet or flannel fabric covering the rollersand are thrown up against the bottom of a curved shieldfmounted justabove the rollers A seed thrown against the shield strikes it at anangle , and rebounds back to the roller at an opposite angle , thus strik-ing the roll at a higher position than that from which it started. It is thenthrown back against the shield. This ricocheting action continues untilthe rough seed is carried over the edge of the rolls and falls into aseparate discharge spout.

The surfaces of smooth seed do not catch in the nap of the rollfabric, (so they slide down the rollers until they reach the lower end andare discharged. ) The long axis of the rolls usually feeds three bins withdischarge spouts. Near the upper end only rough seed , such as

. '

Figure A8. Roll mill used to separate rough seed from smoothseed.

dodder removed from alfalfa, are thrown over by the rolls. As the seedsmove down the rolls, rough seeds are still being thrown over, but anincreasing percentage of smooth seed will be caught and thrown over.At the lower end of the rolls only smooth seed, such as alfalfa, remainand are sent out the smooth seed spout. Thus, seed discharged at theupper end are all rough, while those discharged at the lower end ar allsmooth. There are, however, intermediate or middling fractions con-sisting of varying proportions of rough and smooth seed.

The inclined draper belt also separates flat from round or roughfrom smooth seed. It 'is essentially a tilted flat-surfaced , endlessbelt that moves in an uphill direction. A mixture of rough and s mootl)seed is fed onto its center. Smooth seed roll or slide relatively easilyon the belt, so they slide downhill under the influence of gravity andfall off the low end. Rough seeds do not roll or slide readily on themoving belt, and are carried over the upper end of the belt where theyare discharged. Extreme differences in surface texture such as the.roughness of dodder and the smoothness of alfalfa are not essential foran effective separation with the draper belt or the roll mill. Sharp edges ,sharp points, or projections on many seed are sufficient to permit theirseparation from smooth seed with the roll mill or the draper belt.

'. .

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FLAT OR ROUGHSEED

DRAPER--ROUND OR SMOOTH

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Figure A9. Diagram of an inclined draper belt separator.

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Color

Many seeds differ in color or reflectivity. Color separations areused more and more in processing, particularly with the larger cropseeds. Electronic color sorters make color separations. These machinespresent each seed to electronic sensing devices which compare the seedwith an electronic pattern or a given color background. If the seed I s colorhue or reflectivity is acceptable, it is allowed to continue to a dischargespout. Seeds not in the acceptable range of color hue or reflectivityare divided from the main stream by compressed air or other devices.

One electronic color separator employs a revolving, endless, u-shaped belt to discharge seed on a calculated trajectory through theelectronic sensing chamber where photoelectric cells compare each seedwith a selected background color. Another color separator picks eachseed up on a vacuum ferrule and passes it through a color sensing cham-ber where photoelectric cells sense its color and either accept or rejectit. Color sorters have relatively low capacity, but their versatilitymakes them unusually valuable for difficult separations on large orvaluable seeds.

Affinity for Liquids

Seeds also differ in their affinity for liquids, or the rate at which

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Figure A10., An 'ESM electric color sorter.

their surface will absorb liquids. The magnetic separator and the buck-horn machine separate seed on the basis of these differences. In themagnetic separator, seed are fed into a mixing chamber where a smallamount of water or other liquid is added to the mixture. Some seeds ab-sorb moisture and become damp, while others do not.

After each seed has had an opportl)nity to absorb moisture, finely-ground iron powder is fed into the mixing chamber and blended in so eachseed has a chance to come in contact with the iron powder. If the seedsurface is moist, the iron powder will stick to the moist seed coat. If theseed surface is not moist, the iron powder will not stick to it. The seedmixture is then passed over a magnetized drum or cyHnder. Seeds whichretain iron powder are attracted by the magnet, stick to the drum, and areseparated from the seed stream. Seeds which do not retain the iron powderdo not react to the magnetic field, and are discharged from the machine .

'. .

The buckhorn machine operates on a similar principle. It wasdesigned specifically to remove buckhorn plantain from clover seed. Theseed mixture is fed into a mixing chamber where moisture is added. Aftereach seed has had an opportunity to absorb moisture, finely-ground hard-wood sawdust or bark is introduced into the mixing chamber. Whenmoisture comes into contact with buckhorn seed, a dried material on theseed surfape becomes mucilaginous and sticky. This sticky material causes

Figure All. Diagram of a drum-type magnetic seed separator.

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the fine sawdust to stick to the seed. Thus , a moistened buckhorn seedends up in the center of a ball of sawdust , and can be removed by agravity separator or an air-screen machine.Weight

Many seeds differ in weight , specific gravity, or relative density.Weight or specific gravity is the effective separation principle in the air-blast separations in air-screen machines. However, the gravity separatorthe stoner, the aspirator and the pneumatic separator are all designed tomake specific separations by differences in weight or specific gravity ofseed.

The specific gravity separator consists basically of a perforateddeck that permits movement of an air stream through it. Seed are fed ontothis deck and into the air stream. The air stream is adjusted to lift lightseed while heavier seed lie on the deck surface. Then the stratified lay-ers of seed are separated so that light seed go to one discharge spout andheavier seed to toa different spout

.! This is accomplished by a recipro-cating motion through the horizontal axis of the deck. Since the decksurface is mounted at a slight angle , '-light seed held up by the air will flowdownhill and discharge from the low side of the deck. Heavier seed lie incontact with the surface of the deck. As the deck reciprocates , this motiontosses heavy seed in an uphill direction. Each time the deck moves theseed are worked slightly uphill.) This motion continues until heavy seed arecarried to the high end of the deck and go out a separate discharge spout.

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Figure A12. Diagram of air flow through seed on the deck ofa specific gravity separator. Seed are stratified into,vertical zones by weight.

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Figure A13. Diagram of gravity separator showing seed flowacross the deck.

FEED

BACKWARD FORWARD

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LIGHT STRATIFYING AREA HEAVY

Figure A14. Section view of a stoner separator.

As the seed move from the feed spout through the stratifyingarea, the light seed flow downhill toward the low corner of the deckand heavier seed move uphill toward the upper corner. Between thepaths of the heaviest seed and the lightest seed, a middling productis formed in the center which contains heavy, light, and intermediatedensity seed. The gravity makes a graded separation from thelightest seed at the lower end of the deck to the heaviest seed at thehigher end of the deck.

The stoner makes only a two component gravity separation - heavy and a light fraction. The seed mixture is fed onto the stonerdeck while an air "Stream moves through it. Air stratifies the seed andcauses light seed to flow to the downhill end. The reciprocatingmotion of the deck moves heavy seed toward the high end of the deck.The stoner is very useful in separating rocks from beans, sand fromclover , or similar separations. Stoners are commonly used to salvagegood seed from waste products coming bff the high end of the gravityseparator.

Aspirators and pneumatic separators also separate seed on thebasis of differences in weight, specific gravity or density. Separationin the aspirator is accomplished by pulling a negative-pressure airstream through a column. Seed fed into the air stream move up or down,

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Figure A15. Small fractionating aspirator.

depending on their terminal velocity. Light seed of low terminal velocitywill be carried along with the air stream and discharged through a spout.Heavy seed with terminal velocity higher than the air stream will passthrough it and fall into a separate discharge spout. Some aspiratorsseparate seed into several fractions, each differing in density.

The pneumatic separator is quite similar to the aspirator. In thismachine, however, separation is accomplished by forcing a positive-pressure air blast through a separating column where light and heavyseeds are separated according to their terminal velocities.

Conductivity

.,.

Seeds also differ in their ability to hold or conduct an electricalcharge. Although many conditions affect a seed I s electrical properties,consistent differences ih such properties can be used to make somedifficult separations. The machine which separates seed on the basisof electrical properties is called an electrostatic separator. A typicalelectrostatic separator consists essentially of a conveyor belt whichcarries a single layer of seed beneath an electrode.

Two types of electrostatic separations are made. In the " pinningseparation, the electrode sprays a high intensity electrical charge onto

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the seed. Poor-conductors absorb and hold the charge, stick to thegrounded conveyor belt and are carried to a discharge spout. Good-conductors lose their charge readily and are dropped into a separatespout. The " lifting " separation is made by passing seed through anelectrical field created by a different type of electrode. Here, chargeson the seed are rearranged in reaction to this electrical field. Someseeds are attracted to the electrode and lifted into a different flightpath as they fall from the belt or roller. Other seeds which react lessto the electrical field follow a normal flight path to the discharge spout.

Summary

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Many models and types of machines with a wide range capacities are available to the seed processor. . Properly operated,these machines allow him to remove contaminants which differ from thecrop seed in size, length, shape, weight, surface texture, affinity forliquids, color, and electrical conductivity. They can be used to upgradegermination and purity at efficient and economical rates. To use themachines effectively, the processor must know the principle eachmachine uses to separate seeds, how to adjust them for maximumseparation and capacity, and their proper places in the overallprocessing operations.

The processor must also know the physical properties of the cropseed he is processing, and the physical properties of the weed seed andother contaminants in the crop seed.

. After the differences in crop seedand contaminant physical properties are known, the processor can selectthe machine that will make the most efficient separation.

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SCALPERS

Scalping is a precleaning operation in whic;h material larger thanthe crQp seed is femoved from the seed lot. Rough-cleaning, ' on theother hand, is a process

.in which' material both larger qnd smaller thanthe crop seed is removed.

. Scalping or rough-cleaning is now regarded asa basic operation by many seedsmen, because seed harvested withmodern combines are often heaviJ:ycontaminated with foreign materialsuch as stiqks , stems, leaves, trash and weed seeds . This material,which may be as much as 60 to 70 percent of the volume of the combine-run seed lot, needs to be removed before seed can be safely stored,efficiently dried or effectively cleaned.

Since processors I PFeferences and needs differ, there are manydifferent sizes and. types of sealj)rs avaifable from which a unit canbe selected to satisfy a specific need. Sizes range from high cqpacityreceiving scalpers to the small diameter reel scalpers found, as standardequipment, on disc-cylinder separators. Types range from the singlereel or the single flat perforated screen that removes long stems andgreen material to the more complex and fleXible units consisting ofseveral screens or reels with one or more controlled air separations.Near complete removal of fOfeign material is' possible with the unitsthat ine-orporate both screening and aspiration, so they are the most ef-fective in preparipg combine-run seed for further processing.

Parts of the Machine

A description of the more important parts of the various typescalpers follows. Not all parts are found as components of each typescalper.

Feed Hopper

.- The feed hopper receives the seed to be cleaned from the elevatoror some other source and feeds it at a contiolled rate to the cleaningcomponents of the machine. Rate of feed is controlled by a slidinggate Of feed roll at the bottom of the hopper.

.. .

Screens

The bulk of trash or other foreign matter in the seed ot isseparated from the seed by screens. Although the screens in a scalpermay have different overall dimensions than those in an air-screencleaner, perforation sizes and types available are the same. (See the

Figure Bl. Hance Super-Speed scalper Model 36. Scalperhas two screens.

discussion on characteristics of screens in the chapter on Air-ScreenCleaners .

Shoe

The shoe is the vibrating or shaking part of the machine intowhich the screens are placed. A machine may have one or two shoes,depending upon the size of the machine. The shoes are sloped tocause the seed to flow down the screens. In a two- shoe machine, thesloping is in opposite. directions for each shoe, forming a V, so thatthe movement of one shoe counteracts the movement of the other. There-fore, vibration is held to a minimum.

Reel

Certain types of scalpers have a rotating reel screen instead ofa flat vibrating screen. The reel screen may be of perforated metal orof heavy-gauge woven wire mesh.

Fan

Some scalpers have a fan; others do not. 'The air separationwill be made before the seed reach the screens to remove dust andlight material.

Figure B2. Crippen PM2-5472 scalper.

Principles of Operation

Seed to be scalped ar fed into the cleaning area from the bottomof the feed hopper. If the scalper has a fan the seed pas s through theair separation , to remove light chaff and dust before they reach the screensor reel.

Perforations in the scalping screen should be"large enough to per-mit crop seed to drop through readily but small enough to prevent largeforeign material such as stems, sticks, and leaves from dropping throughthe screen.

If the scalper has two screens, the second is used to removematerial smaller than the seed. So, perforations in the second screenshould be small enough to retain all crop seed but large enough to dropforeign material smaller than the seed.

In reel type scalpers the seed fall through the rotating reel anddischarge underneath the reel. Sticks, stems and other large foreignmaterial are rolled out of the machine by the rotating reel.

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Figure B3. A. T. Ferrell, Super 228-D, receiving scalper.Scalper has two screens and an air system.

Adjustment of Equipment

Rate of Feed

When adjusting a scalper, capacity should not be sacrificed infavor of more thorough cleaning, since final cleaning will be made on theair-screen cleaner or other finishing machines. The feed gate should beopened sufficiently sothat a steady, even flow of seed flows from thehopper into the cleaning area.

Screen Selection

Screen openings should not be so close to the size of the seedthat capacity is reduced.

Fan

The air separation should remove most of the light chaff and dustbefore the seed reaches the screens or the scalping reel.

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Figure B4. Carter-Day No. 4 reel type scalper.

Installation

The scalper should, with few exceptions, be the first piece ofequipmeht used when the seed comes in from the field. In order to takefull advantage of the benefits of scalping, many drying and, storagefacilities have receiving scalpers to rough clean all seed lots that areto be dried or stored prior to being finally cleaned. These operatorshave learned that by removing most of the trash and 'green material asthe first step in their operation they will encounter fewer handlingproblems, reduce drying costs and save on storage space.

'. .

Similarly, a scalper in the processing line should also be thefirst piece of equipment used. It should be installed either ahead ofthe main receiving elevator or just ahead of the air-screen cleaner. ahead -of the main elevator it will allow easier and more rapid conveyingof combine-run seed and increase capacity of holding bins.

. Even wheninstalled just ahead of the clir- screen cleaner , a scalper has many advan-tages. Scalping increases the capacity of the air-screen cleaner byminimizing fe d hopper stoppages. . As a result, feeding is more uniformand the operator can make more accurate and sensitive machine adjust-ments .

Scalping with a scalper-aspirator before the seed lot enters theproces,sing area of the seed plant has still another advantage. It willhelp reduce the dust which is both ,a health-and safety problem.

Summary

Scalping is regarded as a basic operation by many seeds men because seed harvested with modern combines are often l:eavily con-taminated with foreign material such a.s sticks. , stems, leaves trashand weed seeds. Thefe are many diffefent sizes and types of scalpersranging ffom high capacity receiving scalpers to small feel scalpersfound as standard equipment on other machines.' Whena. s.calper is used,capacity should not be sacrificed in favor of more thorough cleaning,since final cleaning will be made on the air-screen cleanef or otherfinishing machines. The scalper should, with few exceptions, be thefirst piece of equipment us,ed when the seed comes in from the field, inorder to rough-clean aU s-eed lots that are to be dried or stored prior tobeing finally cleaned.

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DEBEARERS

Important requisites for efficient and effective seed .cleaningare that the seed be completely threshed and as " free flowing " as possible. These requisites are not always met bec'ause of inefficiencyinthreshing.andharvesting equipment and/orpeculiariUesin themorphology .of the seed heads or units. Seed of some forage grassesand 'small grains have awns , beards or glumes that are not completelymoved during threshing. These cause the seeds" to .cling together

and prevent effective size separations. Removal of these appendagesallows more efficient cleaning and accurate planting', an improvesthe test weight. In other cases combine-run seed. ,contains unthreshedpods , seed he'ads. , or clusters of seed, that are much l-argerthan thecompletely threshed seed. To minimize good seed losses, theseclusters , he-ads, or pods must. be completely broken up before the lotis cleaned.

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Manyseedsmen use a machine called .a II Debearder ll to eliminatemany of the difficulties described above and to better prepare the seedfor the various ;cleaning operations. Basicaly, thep.ebearder com-pletesthreshing of unthreshedor partially threshed Hs'eed and removesappendages or hulls that interfere with flow of th.e seed, and preventeffective sizing separations.

Parts of the Machine

Feed Inlet

The . debearder has a feed inlet which controls the flow of seedinto the machine. Usually the feed inlet is offset, so that the com-modityisintroduced to the beaters in the direction of the rotating arm.Rotating Beater Arms

The rotating beater arms are steel barsinstaUed on a centralshaft ata . angle to the perpendicular of the shaft. These rub theseed and convey it through the machine.

Stationary Beater Arms

The stationary beater 'arms are similar in construction to therotating beater arms . They are permanently fixed to the inside of themachine at the same angle

. The rotating beater arms pass betweenthe stat onary. beater arms during operation of the machine.

Figure B5. C!ipper debearder.

Principles of Operation

, Discharge Gate

The discharge gate is a hinged gate at the end of the machineopposite the feed inlet through which the commodity passes after beingsubjected to the action of the beater arms. Attached to the dis-charge gate is a small shaft on which weights can be placed to controlthe length of time the seed remain in the debearder and hence thedebearding action.

Bottom Discharge Slide

A discharge slide located at the bottom of the machine can beopened for complete cleanout of the machine.

Seed are fed through the feed inlet into the machine from abin above the machine. In the machine the seed are subjected tothe action of the beater arms. The rotating beater arms move throughthe seed mass and between the stationary arms at a relatively highspeed. The seed are subjected to a rubbing action which breaks

A. Rotatig beater ann with specialbard coated edges.

B. Stationary beater ann.

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Figue B6. Interal operating parts of a Clipper debearder.

appendages removes hulls threshs seed clusters and in generalpolishes the seed.

The seed are also conveyed to the discharge gate by thebeater arms. When sufficient pressure forces the gate

open seeddischarge out of the machine.

Some seed always remain in the machine after completingthe operation . These are dropped from the machine through thebottom discharge slide.

Adjustments on a DebearderRate of Feed

The feed inlet must have some type of feed control. Thisis necessary so that the rate of flow into the machine can be ad-justedat a rate that will not exceed the discharge capacity of themachine.

Speed of Rotating Beater Arms

An optional variable drive allows control of the speed of the

rotating beater arms . This is extremely useful. because speeds andcapacities are never constant, particularly when more than one kindof seed is handled . Although exapt settings should be determinedduring each run, the following figures may serve as a guide:

Debeard barleyOats - breaks doubles, de-awns

clips glume tipsDe-awn Dill seedBreak-up flax ballsDe-fringe carrot seedDe-awn watergrass (in rice)

550550

500500500350

Position of Weight on Discharge Gate

Changing the position of the shaft weights on the dischargegate will keep material in the machine either more or less time asrequired for adequate debearding.

Uses of the Debearder

Although primarily designed for debearding barley to improveappearance and planting qualities , debearders are now used for manyother kinds of seed. Its principle use today is probably clipping ofseed oats to improve their appearance and to raise the test weight.Clipping refers to the removal of the chaffy tips of the oat hulls thatextend beyond the grain, Other uses include the partial decorticationof sugar beet seed, hulling "whitecaps " in wheat defringing carrotseed polishing and removing mold from pepper balls .' and breakingup flax balls legume pods and seed heads. Another use is de-awn-ing weed seed to permit their separation from crop seeds,

HULLER-SCARIFIER

Following scalping, and possibly debearding, most seed godirectly to the basic air-screen cleaner. Other kinds principallythose of some legumes and grasses may require hulling prior tocleaning and scarification after cleaning.

Hulling and scarifying hastens germination by removal ofgrowth inhibiting parts or by increasing the seed I s permeabilityto water or oxygen. The terms "hulling " and " scarifying " refer totwo different processes. In hulling only the hull or husk sur-rounding the seed is removed whtle the seed itself remains unscathed.It is generally done to improve the seed I s planting characteristicsor to improve the efficiency and effectiveness of subsequent cleaningoperations. In scarification the seedcoat itself is scratched or ruptured to facilitate absorption of water and hasten germination.

Some examples of seed that may require hulling or scarificationor both are:

A. Seeds that may require only hulling

Bermudagrass, Buffalograss , Bahiagrass KoreanLespedeza , Kobe Striate Lespedeza" Common StriateLespedeza, Bicolor Lespedeza

B. Seeds that may require only scarification

Alfalfa White Clover, Sub clover Hairy Indigo, Crotalaria Wild Winter Peas

C. Seeds that may require both hulling and scarification

Sweet Clover , Crown Vetch , Sericea Lespedeza, SourClover, Black Medic

Hulling and scarification may be accomplished in separate orcombined operations. A combination huller-scarifier is the mostcommonly used machine. A huller-scarifier will either hull, scarify,or hull and sc rify.

Parts of the Machine

Feed Hopper

The feed hopper regulates the flow of seed to the machIne.

Figure B7. Clippet, Eddy-Giant, huller-scarifier showing:(1) feed hopper; (2) seed falling from the feed hopper ontothe first rotating, distributing disc; (3) seed flowing downthe funnel-shaped casting to the second rotating, distri-buting disc; (4) seed being blown into the suction chamber; and (5) suction fan removing light dust and the seed beingdischarged at the bottom of the chamber.. '

On some type machines, the feed hopper is funnel-shaped and can beraised or lowered. Other types provide only a feed inlet through whichthe seed pas s .

Rotating Distributing Discs

Rotating distributing discs are corrugated metal discs that rotatein a horizontal plane. These discs throw the seed against the specialhulling and/or scarifying surface by centrifugal force.

Carborundum Concaves

The hulling and scarifying parts are in the form of a largestone ring with a concave inside surface. These stones are similarto abrasive carborundum stones used in grinding.

Rubber Concaves

For less severe action, carborundum stones are replaced hard rubber concaves of the same shape.

Huller-scarifiers have one or two fans. In two fan models,

Fans

DUST DISCHARGE

ABRASIVESEGMENTS

SUCTION FAN

HOPPER

ASPIRATORAIR CONTROL

VARIABLE SPEEDCONTROL

ASPIRATOR1Y. or 2 H.P. Motor

STEEL FRAMEVARIABLE SPEEDDRIVE

Figure B8. Crippen Model S scarifier.

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one fan is located under the lower rotating disc in order to blow theseed into the suction chamber. When the material reaches thesuction chamber , the suction fan removes dust and chaff from theseed. A single fan performs both functions in one-fan models.

Suction Chamber

The suction chamber is a settling type chamber, which allowsthe seed to discharge and the dust and chaff to be pulled away by thesuction fan.

Principles of Operation

The seed fall from the feed hopper onto the rotating distribut-ing disc where they are thrown against the hulling and scarifyingsurface by centrifugal force. At this point the seed are hulled and/orscarified. This type action may occur once or twice depending uponthe machine. After this operation the seed are moved into the suctionchamber where the suction fan removes the light, fine dust and theseed discharge at the bottom of the chamber.

" '

Figure B9. Forsberg huller-scarifier.

Adjustments of the Huller-ScarifierRate of Feed

Capacity varies with the kind of seed its conc;ition and thejob to be done. Rate of feed , however , is riot critical. The mainconsideration is not to overload the machine.

Variable Speed Drive

With a variable speed drive, speeds from 500 to 2800 RPMcan be obtained. The rotating distributing discs are driven directlyfrom the variable speed drive. The force with which the seed strikethe concaves is determined by the variable speed drive setting.Position of Concaves

The carborundum rings are concave on the inside and sinceabrasive action only takes place against the upper part of the ringsthe rings can easily be turned over when worn, to give a neV\ abrasive surface, which, of course, adds years of service to eachstone ring .

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Uses of the Huller-Scarifier

It should always be remembered that scarification is a delicateoperation. The severity of the abras ion or the force of the impactmus be accurately controlled to prevent seed damage. Correct ma-chine settings should be determined for each individual seed lot,keeping in mind that seeds with a high moisture content are harderto hull and scarify than dry !:reed.

Scarification should never be attempted until after the seedlot has been over an air-screen cleaner . Clean seed scarifies muchmore uniformly and with less seed damage than uncleaned seed.Therefore, the scarifier should be installed either behind the air-screencleaner or further along the proces sing line. Hullers on the otherhand may be installed either between the scalper and air-screencleane! or further down the processing line. The exact location dependson whether all, or only a portion, of the seed is to be hulled. Thehuller should be located ahead oHhe machine that separates hulled fromunhulled seed if only a portion of the seed is to be hulled.

..:-

Figure BID. Scarifier mounted on rollers to facilitate changeof location.

" ' ::-

BUCKHORN MACHINE

, .

Principle of Operation

The buckhorn machine was designed to remove buckhorn plantainseed from forage legume seed. The principle of separation is based ona characteristic of the seed coat of buckhorn plantain seed. Whenmoistened the seed coat absorbs moisture and becomes sticky andmucilaginous. The mixture of legume and buckhorn seed is introducedinto the mixing chamber of the machine where a small amount of mois-ture is added to the seed. The smooth , hard seed coats of the legumeseed are relatively unaffected, while the seed coats of the buckhornbecome sticky.

Finely- ground sawdust or hardwood bark is then introduced intothe mixing chamber. The legume seed again are not affected, but thefine sawdust sticks to each buckhorn seed so that it emerges from themixing chamber in a ball of sawdust. The buckhorn seed are then largerin size and have a different specific gravity than they had before treat-ment.

The mixture of legume seed and buckhorn-sawdust balls can beseparated with an air- screen cleaner. Legume seed drop through thescreen perforations, while the buckhorn- sawdust balls ride over thescreen; If small buckhorn- sawdust balls drop through with the legumeseed, they can be removed with a gravity separator.

AdjustmentsThe rate of feed, the amount of water and the amount of sawdust

introduced into the mixing chamber can be controlled to obtain completeseparation with a minimum change in seed moisture content and minimumuse of sawdust. The amount of water and sawdust added depends onthe concentration of the buckhorn seed. The higher the concentration ofbuckhorn, the more water needs to be added. The rate of feed should beadjusted to allow the mixture to stay in the mixing chamber until a.llbuckhorn seed are coated with sawdust. A high concentration of buck-horn seed requires slower feeding rates.

In sta lla tion

The buckhorn machine does not effect a separation, it only changesthe physical properties of one component of the seed mixture. Sinceother, separators make the actual separation, the buckhorn machine must

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be installed so that seed can flow from it to an air-screen cleaner orgravity separator. The buckhorn machine may be installed above theseparating unit and feed into it by gravity, or it may be installed on thesame level and feed into the separating unit through an elevator leg.

Uses of the Machine

While the buckhorn machine allows a precise and complete separ-ation of buckhorn and other sticky seeds from small legume seeds withvery little crop seed loss, it is an additional machine in the processingline. Many seed processors have replaced the buc horn machine withmagnetic separators, which make the same separation without a sup-porting air-screen cleaner or gravity separator, and are more versatile.The buckhorn machine , however, is very effective in removing buckhornfrom legume seed, and fills an essential need in plants where this weedis a common problem.

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AIR-SCREEN MAC HINE

The air- screen machine is the basic cleaner in most seed proces-sing plants. Almost all seed must be cleaned by an air-screen cleanerbefore specific separations can be attempted, and many seed lots can becompletely cleaned by this machine. The original hand- powered fanningmills have evolved into many styles and types of air-screen machines.Machine size varies from small, two- screen farm models to largeindustrial cleaners with 7 or 8 screens, 3 or 4 air separations and capac-ities up to 6, 000 pounds of seed per hour. Small, two- screen modelare used on farms, in breeder and foundation seed programs and byexperiment stations for processing small quantities of seed. Three-and four-screen machin s fit into various size operations and are selectedfor precision as well as greater capacity. The 5-8-screen machines areused primarily for processing grain where high capacities are essential.

When selecting a size and type of air- screen cleaner for a parti-cular operation, several factors must be considered, such as powerrequirements, amount and kind of seed to be processed and ease ofcleaning the equipment.

,;..

In order for seed to be separated, cleaned or processed, thecomponents of the lot or mixture must differ in some physical character-istic. In most machines separations are made on the basis .of differencesin only one physical characteristic. The air-screen machine, however,effects separations on the basis of differences in size and weight of seeds.This enables the air screen machine to use three cleaning elements:aspiration , in which light material is removed from the seed mass;scalping in which good seed are dropped through screen openings, butlarger material is carried over the screen into a separate spout; andgrading , in which good crop seed ride over screen openings, whilesmaller particles drop through.

To understand and successfully operate any seed processingmachine, the operator must know three things: (1) the component partsinvolved in the work of the machine and the operations they perform; (2)the flow of seed through the machine; and (3) the adjustments whichaffect the precision of the separation and capacUyof the machine.

Part s of the Machine

Feed Hoppers

Most air- screen machines use one of several general types offeed hoppers

Figure CI. Vac-A-Way, Model 758, seed and grain cleaner.Cleaner has four screens and one air system.

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Roll-feed hopper: The roll- feed hopper consists of three basicparts: (a) a container to receive the seed; (b) hopper flights and augers tospread the seed across the width of the hopper as it is received, and;(c) a revolving fluted roll in the bottom of the hopper that feeds a steady,even flow of seed to the top screen and distributes the seed across thefull screen width . The roll-feed hopper is recommended when cleaningsmall seed that contain very little trash.

Roll-feed brush hopper: The roll-feed brush hopper handlestrashy seed and consists of four main parts: (a) a co'ntainer to receivethe seed; (b) a rotating spiked shaft that pulls trashy seed down to therevolving fluted roll; (c) a revolving, fluted roll, and; (d) a tough fiberbrush. Seed are force-fed between the revolving fluted roll and thisbrush to prevent clogging and to maintain a steady even flow to thescreens.

Metering hopper: A third type of hopper is the metering h9,pper.It is designed to feed all kinds of seeds from small clover and grass seedto the largest bean seeds accurately and continuously. It successfullyhandles seed containing considerable trash. It is similar to the roll-feed hopper except that a shaft with specially bent rods is used ratherthan an auger to spread the seed, and the flutes of the revolving roll aremuch deeper.

j .

Roll-Feed Hopper

Corn Hopper

i""

Roll-Feed Brush Hopper

1\'1

Cotton-Seed Hopper

Figure C5. Types of feed hoppers used on Clipper air-screencleaners.

53 Other types of hoppers such as the com hopper and cottonseed

hopper are specifically designed to handle specific crops.

Corn hopper: The corn hopper prevents cracking or chipping ofkernels. It is also used for castor beans, shelled pean ts, and othereasily damaged seed. The fluted roll of this hopper is equipped withwide flights which gently pick up and feed the seed to the top screen inthe machine.

Cottonseed hopper: The cottonseed hopper handles cottonseed,and extremely trashy seed stich as Kobe and Korean Lespedeza, bromeand other non-free flowing grasses. As the large diameter spiked rollrevolves it pulls trashy material down and between the brush on thefront of the roll. See which cling to the roll are removed by a secondbrush installed behind the roll

Screens

Screens in an air- screen machine perform both scalping and grad-ing operations as they separate crop seed from foreign material, othercrop seed and weed seed. Screens are constructed of either perforated

. sheet metal or woven wire mesh 0 Openings in perforated metal screensmay be round, oblong or triangular 0 Openings in wire mesh screens aresquare or rectangular.

There are over 200 different screens available , each identifiedby a number indicating its size and shape.

Perforated metal screens:

(1) Round openings - Round openings in a perforated sheetmetal screen are measured by the diameter of the open-ings 0 Perforations of 5 1/2/64 and larger are designatedin 64ths of an inch and are available in sizes rangingfrom 6/64ths to 80/64ths 0 These screen sizes are com-monly designated by using only the numerator of thefraction, .i. ., 6, 7' 0 0 . . 64 , 72, or 80, thedenominator being understood

Round openings of 5 1/2/64ths or less in diameter aredesignated in fractions of an inch,

1-. o 1 1/12, 1/13,1/14 . 0 . 1/250 Sizes ranging from 1/12th to 1/25thof an inch are readily available.

(2) Oblong openings - Perforated sheet metal screens withoblcmg or slotted openings are designated by twodimensions, the width and length of the opening 0 As

\"\ ,....; ,'..:- \\, \ .

OBLONG HOLES

3/64 x 5/16

ROUND HOLES

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. . . . . . . .

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Figure C6.

Types of screens and perforations used in cleaning

seed.

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screens are fitted are called II shoes " . A shoe usually contains fittingsfor two screens; one for scalping and the other grading. A machine mayhave one or NO shoes, depending upon its size. The shoes are in-clined to allow the seed to flow over the screens. In a machine withtwo shoes, the shoes are inclined in opposite directions forming a V, sothat the movement of one shoe counteracts the movement of the other hold vibration to a minimum.

Eccentrics

The off-center drives on the drive shaft shake the shoes andare called eccentrics. In machines with two shoes the eccentrics of oneshoe are counter-balanced by the eccentrics of the other shoe.Fan

if!

The number of fans in a machine ranges from one in, smallcleaners to as many as four in larger cleaners. Most air- screen ma-chines have two air systems which are desIgnated as upper and lowerair.

The upper air removes light chaff and dust from seed before theyreach the first screen; and is regulated by an adjustable damper in the

. Figure G9. Brushes used to sweep the underside of screensto keep the p'erforations open.

air passage. The lower air blast removes light seed and trash not re-moved by the upper air or screens. When a machine has only one fan it is usually used toremove light seed and trash left after screening.

Air Chest

Air passageways from the fans are connected to the air chest air chamber which allows the material lifted by the air stream to settle.tl)is is done by -decreasing the air velocity as it passes through theair chest. The lifted material settles 'out by gravity , and is spoutedout of the air chest.

Principles of Operation

Although screen arrangement may vary with make, model andnumber pi screens per-machine, a four- screen machine with the follow-ing Screeh arrangement is used as an example in this discussion: firstscreen scalping, second screen grading, third screen close scalping,and fourth screen fine grading.

Seed to be cleaned are fed from the feed hopper by the feed toll,where they pass through the upper air which removes light chaff anddu st .

rop AIR

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ure C 10.

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A -: 334

CLEAN SEED

Figure C 11 Flow

diagram of Crippen A

-334ait-screen cleaner.lit\

DESCRIPTION

1. Main Hopper

2. Repeat Hopper

3.. Repeat Spout4. . Feed Ron5. Feed Lever

6. Repeat Control Board

7. Settling Chamber8. Spiral conveyor. Empties

settling chamber9. Suction Fan

10. 3-Gang Sieve11. 4-Gang Sieve12. Adjustable Screen

13. Repeat Screen with Auto-matic Brush

14. Screen Brush Bracket

15. Reversible Screening

J3)ank16. Adj ustable Tailngs Board17. ' Repeat Elevator Boot18. Direct Blast Fan19. Clean Grain Delivery

20. Brush Pitman

Figure C12. Flow diagram of Cleland Expert air-screen cleaner.

The top screen is used for rough scalping. Its perforations arelarge enough to readily drop the crop seed but small enough to scalp offlarge foreign material such as stems, sticks, dirt or weed seed.

Seed which pass through the first screen are caught on the secondscreen. Perforations in this screen drop out trash, weed seed, and dirtsmaller than the crop seed. Good seed ride over the perforations in thesecond screen and drop onto the third screen. For maximum capacitythe second screen should be kept covered with seed at all times.

The third screen in our example is a clos e scalper. It removeslarge foreign material or contaminating seed that were small enough topass through the first screen.

The crop seed drop through the third screen and go to the fourthscreen for a final close grading. This screen has perforations slightlylarger than those in the second screen. Seed or other material smallerthan the crop seed being cleaned but which were too large to drop throughthe second screen are removed here.

As the crop eed drop off the fourth screen, they fall through thelower air separation. This removes the light seed and trash which wasnot removed by the upper air and the screens. For efficient cleaning,the lower air blast should be strong enough to blowout a few good seed.

Adjustment of EquipmentScreen Selection

Screens must be selected according to the shape of the crop seedbeing cleaned.

(I)

(2)

Round Seeds: A round-hole top screen and a slotted bottomscreen are generally used to clean round- shaped seeds. Theround-hole top screen prevents straw trash, pods and otherlarge and long material from dropping through while the slot-ted bottom screen drops broken seeds and weed seeds thinnerthan the round crop seeds.

Oblong Seeds : An oblong top screen and an oblong bottomscreen are generally used to clean long seeds. The oblongperforations in the top screen separates weed seeds orlarge mater al rounder or thkker than the crop seed. Theoblong bottom screen drops thin weed seed, broken crop seedor hulled crop seed and other material thinner than the cropseed.

SUG

GES

TED

SCRE

ENS-

- FO

UR, S

CREE

N CL

EAN

ERS

Foar ScreeD CleaDera

Use Col. 1 for top screen in top shoe, Co

L 2

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oe,

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r top

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r bot

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reen in bottom shoe.

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ra .

- Us

e Col.

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r top

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. 3 fo

r mid

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ol. 4

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en.

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L I

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1/14

or 1

/18

Ala

ike

Clov

er -