US3744399A - Process and apparatus for removing the outer layer from cereal grains by a wet method - Google Patents

Abstract

A process and apparatus for removing the outer covering from cereal grains by a wet method consisting of subjecting the grains to moisture and to mechanical agitation for mixing the grains and causing them to rub against each other under pressure. The pressure is maintained substantially constant and is uniformly distributed within the mass of the treated grains and in the presence of water equal to between 5 and 15 percent of the dry weight of the grains. The water adheres to the grains by capillary action and penetrates their covers in the course of treatment.

Description

[ 11 3,744,399 July 10, 1973 Szitnkc United States Patent 1 Bonteil thod consisting of d to mechanical agd causing them to rub ainst each other under pressure. The pressure is their cov- Provost........... Tarukawa Carkhuff 4/1901 HooIe Wayne illie G. Abercrombie Blanchard and Flynn ABSTRACT ocess and apparatus for removing the outer covery constant and is uniformly distributed within the mass of the treated grains and in the ual to between 5 and 15 percent the grains. The water adheres to 3/1932 Bloede 1/1969 Wayne 6 Claims, 1 Drawing Figure Primary Examiner-W Attorney-Woodhams,

A pr ing from cereal grains by a wet me subjecting the grains to moisture an itation for mixing the grains an 8 maintained substantiall presence of water eq of the dry weight of the grains by capillary action and penetrates ers in the course of treatment.

Robert C. Bonteil, CIichy I-Iauts-de-Seine, France Societe DEtude et DExploitation de Procedes pour LIndustrie Alimentaire SEPIAL, Clichy (I-Iauts-de-Seine France Oct. 29, 1970 Appl. No.: 84,997

References Cited UNITED STATES PATENTS 2,217,112 10/1940 Hamring.......................... 2,355,810 Loewy Geddes a2 PROCESS AND APPARATUS FOR REMOVING THE OUTER LAYER FROM CEREAL GRAINS BY A WET METHOD [75] Inventor:

[73] Assignee:

[22] Filed:

[30] Foreign Application Priority Data Nov. 24, 1969 France...............................

[51] Int.

[58] Field of Search.....................

PROCESS AND APPARATUS FOR REMOVING THE OUTER LAYER FROM CEREAL GRAINS BY A WET METHOD BACKGROUND OF THE INVENTION The present invention relates in general to a process for removing the outer layer or cover from cereal grains by a wet method in which the grains are subjected to treatment by moisture, followed by mechanical agitation under pressure whereby the grains are caused to rub together.

It is known that a process generally similar to the foregoing is currently used for removing the exterior, cellulose coverings or layers from grains and thereby conserving their ingredients which are rich in proteins. These processes can be applied to wheat, rice, millet sorghum, or to other cereal grains. In the case of wheat, for example, it is desirable to strip the grain of the epidermis or outer layer of the nucellus, but leave on the grain'the protective layer which surrounds the albumen.

In the process of the type described in the foregoing paragraph, the operation of moisturizing the grain consists of making the grains absorb a quantity of water equal to around five percent of their dry weight by gently agitating the grains in the water for about two minutes, after letting the moisture penetrate them for a period of from four to minutes. This way, all the added water penetrates the different epidermic layers of the grains which has the special effect of softening the layer of union separating the epidermis from the epicarp. When the step of moisturizing the grain is ended, the grains are thus nearly dry on the surface and do not carry away water by capillary attraction so that they do not adhere to each other. They are then introduced into a chamber to be skinned by mechanical treatment.

The chambers generally used for this treatment consist of a vertical cylinder having a coaxial shaft rotatably disposed therein and having some stirring vanes thereon. Means are provided for rotating the shaft and, accordingly, the grains within the chamber. The grains are introduced into the top of the chamber and pushed toward the bottom where they are discharged. The grains are thus vertically compressed against each other while they move through the chamber.

However, it is established that with existing types of chambers, in which the tegmens or outer coverings of the grains are sperated according to existing'procedures, the grains are skinned very imperfectly.

These unsatisfactory results obtained by existing procedures for moist removal of grain coverings is explained by the fact that two necessary conditions for obtaining an effective removal of the outer layers of the grain are not provided: the frictional engagement between the grains is insufficient and the pressures exerted on the grains are not uniformly distributed. In effect, due to the fact that the outer surfaces of the grains are nearly dry and therefore do not adhere to each other when they enter into the treatment chamber, the mechanical treatment produces a gentle rubbing of the grains against each other and this rubbing together of the grains is not sufficient. The grains are not only insufficiently skinned, but the removal of the tegmens is primarily produced by the rubbing of the grains on the walls of the chamber and on the vanes of the shaft. F urthermore, pressures produced in the chamber are exerted primarily in a vertical direction. Thus, as a practical matter, only the horizontal surfaces of the engaging grains are pressed against each other. Moreover, the positions of the grains. in the chamber tend to remain insufficiently changed so that the grains are not only inadequately skinned but also irregularly skinned.

It has been established to the extent necessary that, in existing processes, the grains have to be submitted to additional treatment. For example, in the case of Algerian hard-grained wheat, it has been established that a single operation and mechanical treatment would not permit the obtaining of an appreciable proportion of bran. In order to obtain the extraction of bran in the proportion of 3.7 percent by reference to the weight of the dry grains, it has been necessary to subject the grains to two successive operations of mechanical treatment, similar to that described above, these two supplemental operations being separated by a conditioning of two hours during which the moisture penetrates more deeply into the cellulose layers.

This latter procedure of removing the outer layers of grains is thus long and complicated, due to the fact that it necessitates separate recycles, and it does not always produce entirely satisfactory results.

Accordingly, a primary purpose of the present invention is to remedy these disadvantages in existing processes and apparatus for removing the outer layers from cereal grains.

In order to accomplish this end, the process of removing the outer layers of grains by the wet method according to the invention is characterized inthat the grains are subjected to mechanical treatment or agitation under a controlled substantially constant pressure which is uniformly distributed throughout the mass of the treated grains in the presence of a quantity of water equal to between five and 15 percent of the dry weight of the grains, such water adhering by capillary action to the surface of the grains and penetrating their outer layers in the course of the treatment.

Thus, the water retained on the surface of the grains by capillary action provides the considerable advantage of materially increasing the forces of friction (especially horizontally) that the grains exert on each other during the mechanical treatment. The removal of the tegmens is consequently considerably increased by comparison with the prior art processes and apparatus.

On the other hand, the water which adheres to the grains by capillary action penetrates little by little the exterior layers of the grains during the entire duration of the mechanical treatment. Thus, an important expansion of the grains is achieved at the interior of the mixing chamber. That is, the grains are not only compressed vertically under a controlled pressure, but their expansion makes them exert direct pressures on each other in all directions so that said pressure is uniformly distributed in the mass of the grains in the chamber. Thus, the mass behaves in this respect like a liquid. The forces of removing the tegmens are applied in a uniform manner on all of the surfaces of the grains whereby the removal of the outer layers of the grains is far superior to the removal achieved by the prior art procedures for the same purpose.

At the end of the mechanical treatment, said quantity of water added externally to the dry grains has penetrated the coverings of the grains and the grains thus leave the chamber practically dry again on the surface.

The peeled grains and the torn tegmens can be sorted out later by any type of conventional process.

According to the invention, and before the grains are exposed to mechanical treatment, they are soaked in water during a brief period sufficient for their outer layers to'absorb a small quantity of water, comprising between 2 and 4 percent of the dry weight of the grain.

This small quantity of water saturates the first epidermic layers, so that the removal of the outer layers can be effectively commenced from the moment when the grains are subjected to a mixing action under pressure.

For example, in the case of the hard grained wheat, it has been found advantageous to add to the grains a quantity of water representing 1 1 percent of the grains dry weight, before subjecting the grains to mechanical agitation, and to leave the grains in contact with the water during a time sufficient to absorb about 2.5 percent of the water.

The present invention also concerns an apparatus capable of use in carrying out the process described above, said apparatus including a cylindrical chamber in which the grains are mechanically treated by means of a rotating shaft having stirring vanes for agitating the grains, means for delivery of the grains into the chamber, means for discharging the treated grains, and a pressure control means.

In existing installations of this type, uncontrolled variations in the flow of the grains delivered into the chamber for mechanical treatment are frequently encountered, as are variations in the discharge of the treated grains from the chamber. As a result, substantial variations in the pressure on the grains in the chamber are produced. it follows as a disadvantageous result that, when the pressure is insufficient, removal of the outer layers of the grains is inadequate, and when the pressure is too great, ingredients rich in important nutriments are stripped from the nucellus.

Another object of the invention is to remedy the foregoing disadvantage and, in order to accomplish this, the apparatus according to the invention is characterized by the fact that the pressure control means includes a pressure device which can slide on the agitator shaft, in opposition to a force exercised against it by a resilient member, in response to variations in the pressure developed within the mass of grains in the treatment chamber. The invention is also characterized in that it includes sensing means for detecting the position of said pressure device, said sensing means being adapted to effect interruption in the supply of the grains to the chamber when the pressure devices moves past a predetermined position corresponding to a predetermined pressure in the chamber.

Thus, the means of detecting the position of the pressure means can indicate that the pressure in the chamber is too high and the flow of grains into the chamber is thus automatically stopped during the period of time required to permit the pressure in the chamber to decrease until it again achieves a desired level.

lt is believed that, as a result of this arrangement, the pressure of the grains within the chamber can be automatically maintained at a substantially constant level slightly lower than a predetermined level which corresponds to a precise position of the pressure means.

In effect, after an interruption in the supply of grains, those grains already disposed in the chamber continue to be discharged normally, whereby the pressure of the grains in the chamber is caused to be reduced. The

pressure device is displaced in the opposite direction and, when the pressure in the chamber becomes slightly lower than said predetermined level, the means of detecting the position of said pressure device terminates the operation of the mechanism effecting interruption of the supply; thus, the supply of grains is started again.

It is easy to select, by means of experience, said predetermined level of the pressure and to consequently regulate the force exerted by the resilient member on the pressure device. Thus, it will be seen that by virtue of this arrangement the disadvantages of the prior apparatus are eliminated.

Preferably, in accordance with the invention, said pressure device is comprised of a split disk, including a portion adjacent to the split and sloped with respect to a plane perpendicular to the shaft, and the stirring means are bars extending radially from the shaft to points adjacent the sidewall of the cylindrical chamber.

A preferred embodiment of the invention is disclosed by way of example in the attached drawing in which the single FIGURE represents schematically an apparatus for practicing the process conforming to the invention.

The apparatus illustrated in the FIGURE includes a silo 1 containing the grain to be peeled, such as hard grain wheat 2. A conveyor channel 3 is mounted upon an electric vibrator 4, which is connected by the conductors 5 and 6 to a source of electrical energy, and said channel is placed below the silo l and is arranged in position to collect the grains which flow from the silo. The discharge end of the channel 3 is located above the upper open end of a hopper 7 whose lower open end empties through an opening 8a in the sidewall of the inclined cylinder 8 near the lower or base end thereof in which an Archimedes screw 9 is rotatably disposed. This screw is mounted on a shaft 10 connected to an electric motor 11, which is electrically connected to the supply conductors 5 by the conductors 12. Near its upper end, the inclined cylinder 8 is connected to a water inlet conduit 13 which is in turn connected to a source of water, not shown, by means of an electrical gate valve 14. This electrical gate valve is likewise connected to the supply conductors 5 by means of conductors 15. A conduit for discharging water 16 from the cylinder 8 is connected to and communicates with said cylinder near the lower end thereof.

The cylinder 8 has an opening 8b near its upper end which empties into the upper end of the mechanical treatment chamber 17 which is cylindrical and mounted on a support 18. Within the chamber 17 there is mounted a coaxial shaft 19 upon which are attached the stirring elements 20 which may be comprised of cylindrical bars that extend radially from the shaft 19. The central portion of the shaft 19 is surrounded by a sleeve 21 which is slideably but nonrotatably connected to the shaft by means of a cotter pin 22 which extends through the shaft. The sleeve 21 can slide axially of the shaft due to the fact that there are two lengthwise slots 23 in the sleeve into which the extremities of the cotter pin extend.

A split disk 24 is secured to the lower end of the sleeve 21 and includes a portion of a helical ramp which constitutes a pressure member. A disk 25 is soldered to the upper end of the sleeve and is engaged by the lower end of the spring 28. The arm 26, serving as a detector of the position of the disk 25, engages a micro-switch 27 which is connected in series with the electrical supply circuit including the supply conductors 5. The sleeve 21, the pressure member 24 and the disk 25, which are integral, are constantly urged toward the base of the cylinder 17 by the helical spring 28 which surrounds the shaft 19 and is held under compression between the disk and a locking collar 29 which is adjustably mounted on the shaft 19 near the upper end thereof. Finally, the shaft 19 is coupled at its upper end to the output shaft of an electrical motor 30 connected to a source of electrical energy in a conventional manner.

The lower end of the shaft 19 is attached to a circular pan 31 which is disposed directly below the lower end of the chamber 17 and is of slightly less diameter than the diameter of the chamber so that a calibrated discharge space 32 is provided between the pan 31 and the lower edge of the chamber. Below the pan and said space is placed a conventional separation device connected to a source of air under pressure. Said separation device comprises a channel 33 for receiving the peeled grains, and it is situated under a collector 34 in which is located an air discharge head with a back draft 35 connected to a fan 36 by a conduit 37, and a discharge channel for bran 38 disposed below the separation conveyor 39.

OPERATION The apparatus for removing the covers from grain, which has been described above, operates about as follows:

When the chamber 17 for mechanical treatment is empty, prior to operation thereof, any force exerted against the spring 28 is not produced by a force applied to the pressure device 24 and, accordingly, the disk 25 is in its lowermost position so that it does not actuate the arm 26 of the micro-switch 27 which therefore remains closed. The conductors 5 can thus be energized and, when they are, the vibrator 4 and the motor 11 are energized and the electric valve gate 14 is opened. This occurs as soon as the electrical system of the apparatus is connected to a source of energy.

The hard'grain wheat 2 in the silo l flows along the channel 3 away from the silo, under the effect of the vibrations created by the vibrator 4, then into the hopper 7 and thereafter enters the opening 8a at the lower end of the inclined cylinder 8. The motor 11 rotates the Archimedes screw 9 which, accordingly, advances the grains toward the upper end of the cylinder 8 from which they are discharged into the chamber 17 through the opening 8b. The electric gate valve 14, being open, permits water to flow by gravity from the conduit 13 downwardly through the cylinder 8 toward the conduit 16 in a direction opposite to the direction of movement of the grains being transported 'by the screw. The flow of water and the grains is so controlled that the water carried along by the grains into the mechanical treatment chamber represents 11 percent of the dry weight of the grain. The speed of rotation of the Archimedes screw is regulated so that the grains remain for only a brief period of time in the cylinder 8. Thus, most of the water carried by the grains into the treatment chamber is achieved by capillary action, and only a small proportion, such as between 2.5 percent to 3 percent thereof, enters into the bran through the outer layer.

When the chamber 17 is filled with grains to the level of the pressure member 24, said pressure member, carried on the shaft 19 by means of the cotter pin 22 and chamber and these grains flow out through the calibrated space 32. During their movement through the chamber, the grains are submitted to the forces of friction created by rubbing against the wall of the chamber 17 and against the stirring vanes 20. These frictional forces are considerably increased by the fact that the grains are coated with a film of water creating surface tension between the grains.

To the vertical pressure created by the pressure means 24 is added the pressures created by the grains and exerted uniformly within the chamber upon each other as a result of their substantial expansion. In fact, part of the water, which is carried along by the grains by capillary action during entrance of the grains into the mixing chamber, penetrates little by little the several epidermic layers of the grains. This also facilitates the separation of all the tegmens which surround the protective layer. The grains are consequently peeled exactly at the desired level and in a complete and uniform manner, due to the friction exerted because of the expansion on every surface of each grain. During their discharge from the chamber, the peeled grains are separated from the bran by a blast of air and said peeled grains flow through the collector 34 into the channel 33 while the bran flows outwardly along the conveyor 38 in a normal manner.

By means of the process of the invention, one can thus extract an amount of bran representing 4.95 percent of the dry weight of the grain during a single movement of the grain through the chamber 17, which is a result distinctly superior to the outputs produced by prior processes applied to the same hard grain wheat.

The pressure upon the grains in the chamber 17 is automatically maintained at a substantially constant level in the following way:

When, for example, as a result of a decrease in the discharge of the grains from the lower end of chamber 17 or as a result of an increase in the flow of the dry grains being supplied, the pressure of the grains in the chamber 17 increases, the pressure member 24, the sleeve 21 and the disk 25 are pushed upwardly toward the upper end of the chamber 17. The spring 28 is compressed by the upward movement of the disk 25 and the sleeve 21 is permitted to move relative to the extremities of the cotter pin 22 by virtue of the slots 23 in said sleeve.

When the pressure within the chamber 17 reaches a specified level, the disk 25 reaches a position where it actuates the arm 26 which in turn opens the microswitch 27. The collar 29 is adjusted so that the amount of the pressure within the chamber 17 has reached a predetermined value before the disk 25 actuates the switch 27. While said pressure is equal to'or in excess of said predetermined value, the-vibrator 4 and motor 11 are deenergized and the water valve 14 is closed. Thus, the supply of moist grains into the chamber 17 is interrupted. The motor 30, however, continues to operate normally so that the treated grains continue, nevertheless, to discharge from the lower end of the chamber 17 and, accordingly, the pressure of the grains within the chamber 17 decreases. As soon as they pressure be comes lower than said predetermined value, the disk 25 is below the point where it causes the arm 26 to open the switch 27. Thus, the switch 27 is closed whereby theflow of moist grains into the chamber 17 again.

It is thus seen that the pressure of the grains in the chamber is maintained at a substantially constant level which is slightly lower than the predetermined pressure value. An important factor in the mechanical treatment of the grains is thus automatically controlled whereby the high quality of the treatment of the grains is additionally assured. It is to be noted that the regulation of the pressure within the chamber 17 does not disturb the flow of treated grains discharged into the channel 33 since such discharge in the chamber is never interrupted.

In one particular embodiment of the invention, the inflow of grains into the chamber 17 is interrupted when the pressure on the grains in said chamber reaches approximately 150 grams per square centimeter.

Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:

1. A process for removing the outer layer from cereal grains, comprising the steps of:

subjecting said grains to a quantity of water for a brief period of time during which said grains absorb a small amount of said water and a larger amount of said water clings to the outer surface of said grains;

moving said grains and said water into the upper end of a chamber for creating a mass of grains within said chamber;

maintaining the mass of grains in said chamber in a moist condition, the total amount of water absorbed by and clinging to said grains being in the range of from to percent of the dry weight of said grains;

applying a substantially constant compressive pressure to the mass of moist grains within said chamber so that a substantially uniform compressive pressure is applied on the grains throughout said mass;

agitating said mass of moist grains within said chamber by mechanical means for removing the outer layer from said grains;

discharging said grains from the lower end of said chamber; and

interrupting the movement of said grains and said water into said chamber whenever the pressure within said mass exceeds a predetermined level.

2. A process according to claim 1, comprising the step of subjecting said grains to said quantity of water for a sufficient period of time to cause said grains to absorb an amount of water equal to between 2 and 4 percent of their dry weight before they enter said chamber, and subjecting said grains to said quantity of water for a sufficient period of time to cause the total amount of water absorbed by and clinging to said grains to be begins equal to approximately I l percent of the dry weight-of said grains.

3. An apparatus for removing the tegmens from cereal grains, comprising:

means defining an upright agitation chamber for receiving moist grains, said chamber having an inlet opening at the upper end thereof and a discharge opening at the lower end thereof;

an inclined conveyor having an upper end discharging into the upper end of said chamber;

receiver means near the lower end of said conveyor adapted to be connected to a source of grains for guiding said grains onto the conveyor;

a source of water and conduit means for guiding said water into engagement with said grains on said conveyor, whereby a certain amount of said water is absorbed by said grains and another. amount clings to the outer surfaces of said grains;

agitation means within said chamber for moving the grains therein;

pressure means engageable with said grains within said chamber for applying to said grains a substantially constant and uniform compressive pressure while simultaneously permitting a varying supply of grain into said chamber;

drive means for operating said conveyor and valve means controlling the flow of said water; and

sensing means responsive to said pressure means for deactivating said drive means and closing said valve means when said pressure in said chamber exceeds a predetermined amount and for activating said drive means and opening said valve means when said pressure in said chamber falls below said predetermined amount.

4. An apparatus according to claim 3, wherein said pressure means includes a split disc positioned within said chamber and disposed for engaging the mass of grains in said chamber for compressing same, said pressure means including means biasing said split disc into engagement with said mass of grains for urging same toward said discharge opening, said split disc including a helically sloped portion disposed directly adjacent the split, the sloped portion extending at an angle relative to a plane substantially perpendicular to the longitudinally extending direction of said chamber.

5. An apparatus according to claim 4, wherein said agitation means incudes a rotatable agitator member disposed within said chamber, said agitator member having an elongated rotatable shaft disposed substantially centrally within said chamber and extending 1ongitudinally thereof; and

said split disc being disposed substantially in surrounding relationship to said shaft adjacent the upper end of said chamber, and resilient means coacting with said disc for resiliently urging same downwardly into engagement with the upper portion of the mass of grains contained within said chamber.

6. An apparatus according to claim 5, further including means for nonrotatably connecting said split disc to said shaft while permitting said disc to slideably move axially relative to said shaft.

Claims (6)

1. A process for removing the outer layer from cereal grains, comprising the steps of: subjecting said grains to a quantity of water for a brief period of time during which said grains absorb a small amount of said water and a larger amount of said water clings to the outer surface of said grains; moving said grains and said water into the upper end of a chamber for creating a mass of grains within said chamber; maintaining the mass of grains in said chambeR in a moist condition, the total amount of water absorbed by and clinging to said grains being in the range of from 5 to 15 percent of the dry weight of said grains; applying a substantially constant compressive pressure to the mass of moist grains within said chamber so that a substantially uniform compressive pressure is applied on the grains throughout said mass; agitating said mass of moist grains within said chamber by mechanical means for removing the outer layer from said grains; discharging said grains from the lower end of said chamber; and interrupting the movement of said grains and said water into said chamber whenever the pressure within said mass exceeds a predetermined level.

2. A process according to claim 1, comprising the step of subjecting said grains to said quantity of water for a sufficient period of time to cause said grains to absorb an amount of water equal to between 2 and 4 percent of their dry weight before they enter said chamber, and subjecting said grains to said quantity of water for a sufficient period of time to cause the total amount of water absorbed by and clinging to said grains to be equal to approximately 11 percent of the dry weight of said grains.

3. An apparatus for removing the tegmens from cereal grains, comprising: means defining an upright agitation chamber for receiving moist grains, said chamber having an inlet opening at the upper end thereof and a discharge opening at the lower end thereof; an inclined conveyor having an upper end discharging into the upper end of said chamber; receiver means near the lower end of said conveyor adapted to be connected to a source of grains for guiding said grains onto the conveyor; a source of water and conduit means for guiding said water into engagement with said grains on said conveyor, whereby a certain amount of said water is absorbed by said grains and another amount clings to the outer surfaces of said grains; agitation means within said chamber for moving the grains therein; pressure means engageable with said grains within said chamber for applying to said grains a substantially constant and uniform compressive pressure while simultaneously permitting a varying supply of grain into said chamber; drive means for operating said conveyor and valve means controlling the flow of said water; and sensing means responsive to said pressure means for deactivating said drive means and closing said valve means when said pressure in said chamber exceeds a predetermined amount and for activating said drive means and opening said valve means when said pressure in said chamber falls below said predetermined amount.

4. An apparatus according to claim 3, wherein said pressure means includes a split disc positioned within said chamber and disposed for engaging the mass of grains in said chamber for compressing same, said pressure means including means biasing said split disc into engagement with said mass of grains for urging same toward said discharge opening, said split disc including a helically sloped portion disposed directly adjacent the split, the sloped portion extending at an angle relative to a plane substantially perpendicular to the longitudinally extending direction of said chamber.

5. An apparatus according to claim 4, wherein said agitation means incudes a rotatable agitator member disposed within said chamber, said agitator member having an elongated rotatable shaft disposed substantially centrally within said chamber and extending longitudinally thereof; and said split disc being disposed substantially in surrounding relationship to said shaft adjacent the upper end of said chamber, and resilient means coacting with said disc for resiliently urging same downwardly into engagement with the upper portion of the mass of grains contained within said chamber.

6. An apparatus according to claim 5, further including means for nonrotatably connecting said split disc to said shaft whiLe permitting said disc to slideably move axially relative to said shaft.

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