Title: A Method and Apparatus for Extracting Nut Kernels

Technical field of the invention

THIS INVENTION relates to the extraction of nut kernels from nuts. More particularly, it relates to a method of, and apparatus for, extracting nut kernels from nuts.

Background to the invention

Difficulties are experienced with the extraction of nut kernels from certain nuts, particularly irregularly sized and shaped nuts, such as marula nuts. Traditional methods of extracting marula nut kernels from marula nuts include hitting individual marula nuts with an implement such as a stone or hammer, with blows with the implement being imparted alternatively on each of the perpendicular axes of the nuts. This method of extraction produces a mixture of shell fragments, released whole and broken kernels, and shell fragments with kernels locked in. Thus, manual sorting is thereafter required, as is manual extraction, using a needle-like instrument, of kernels still locked into shell fragments. This manual cracking, sorting and extraction of marula nut kernels is extremely laborious and time consuming, and not very cost efficient. Another traditional method of extraction includes using such an implement to pop out the eyes of the marula nuts, and to extract the kernels through the eyes, using a needle-like instrument. However, this method is similarly laborious and time-consuming. Marula nuts can also be cracked open with nutcrackers such as those in which individual marula nuts are cracked open between two blades, one stationary and the other being one of several mounted to a rotating wheel, with the blades acting in scissors-like fashion to crack open the nut. The output from such a nut cracker includes whole uncracked nuts, partially cracked nuts, shell fragments, kernels locked in shell fragments, whole and broken kernels, and dust. The kernels, shell etc. can then be separated according to size and sorted. Drawbacks of marula nut kernel extraction in this manner include the need to recycle at least once, but more often several times, a substantial portion of uncracked nuts through the

cracker, generation of excessive dust, and the manual extraction of a proportion of nut kernels still locked into shell fragments, or the recycling thereof, with the result that kernel extraction efficiency and cracking throughput are low.

It is accordingly an object of the invention to provide a method of, and apparatus for, extracting nut kernels from nuts, whereby these drawbacks are at least reduced.

General description of the invention

Thus, according to a first aspect of the invention, there is provided a method of extracting nut kernels from nuts, which method includes: repeatedly, and in a single operational step, subjecting a plurality of nuts, having openings in their shells, to impacts in an impact zone, thereby to force the kernels through the openings in the nut shells; and separating the nut shells from the nut kernels.

The method has particular application to nuts, such as marula nuts, which have an eye or eyes in the nut shell, each of which is closed off with an operculum. In one version of the invention, the operculi of the nuts may already have been removed prior to commencing extraction in accordance with the invention, i.e. in a pretreatment step. The pretreatment step may comprise, for example, repeatedly and in a single operational step, subjecting a plurality of nuts to impacts, thereby to create the openings in the nut shells, In particular, operculi may be dislodged by such pretreatment impacts, thereby uncovering eyes (openings) in the nut shells. Instead, the pretreatment step may comprise cutting open the nut shells, to create openings in the nut shells through which the kernels are accessible. The nuts may thus be cut, or sliced, either manually or mechanically, preferably perpendicularly to a long axis of the kernel and tangentially to the operculi. Such pretreatment has the advantage that subsequent separation of kernels from operculi is avoided or at least reduced.

However, in another version of the invention, the method of the invention may include forming the openings in the nut shells in the same operational step as that in which the kernels are forced through the openings in the nut shells. In particular, the openings may be formed by removing, by means of the impacts, operculi thereby uncovering the eyes (openings) of the nuts. By means of one or repeated impacts, the operculi (or micropylar plugs) are thus first dislodged, thereby uncovering the eyes (or microphiles) in the nut shells, whereafter the kernels are expelled, by means of the impacts, through the eyes. The shells thus largely remain intact, thereby facilitating separation of the relatively large shells from the smaller kernels.

The impacts may be imparted randomly to the nuts, and will thus include impacts imparted perpendicularly to the major and minor axes of the nuts, with impacts imparted perpendicularly to the major axes of the nuts being most conducive to 'popping out' of the operculi.

While the imparting of the impacts can be effected by means of a hammer or another tool or implement and taking care to avoid impacts which have a crushing effect (which can be achieved by allowing the nuts to move freely or to 'bounce'), the impacts of the nuts may, in particular, be achieved by imparting a velocity to the nuts, and allowing the moving nuts to strike an impact surface. The impact surface may be stationary or moving. The imparting of the velocity to the nuts may then be effected by means of a reciprocating or rotating hammer-like, paddle-like or pronged tool, implement or apparatus, pneumatically, by centrifugal force, by elastic force, or by any other suitable means. In particular, the velocity may be imparted to the nuts by means of a rotating pronged rotor, with the rotor prongs striking the nuts, thereby imparting the velocity to the nuts.

The nuts may be allowed to strike a plurality of impact surfaces provided by the rotor prongs as well as by an inner surface of a rotating drum within which the rotor rotates. The drum may be located more or less horizontally, with the rotor mounted axially within the drum, and with nuts which collect at the bottom of the drum being conveyed, as the drum rotates, to a higher zone

from where they drop on to the rotor so that the rotor again imparts velocity to them, with the moving nuts then again striking the drum, so that the nuts are thereby subjected to the repeated impacts. The method may include rotating the rotor at such a speed that the outermost tips of the prongs move at a speed of 7.5 m/s to 28 m/s.

The drum may thus have a cylindrical sleeve defining the impact zone, with the nuts striking the inner surface of the sleeve. The drum may include protrusions extending inwardly from the sleeve, to lift nuts from the bottom of the drum or sleeve to the higher zone.

The prongs may be spaced circumferentially about, as well as longitudinally along, an axle. The rotor may rotate at a rotational speed of at least 800 rpm, and, for marula nuts, typically at about 1200 -3000 rpm, preferably about 1400 to 1800. The rotor may rotate in the same direction as the drum, or in a direction opposite thereto.

The separation of the nut shells from the nut kernels and, where present, the operculi, may be effected by removing the nut kernels and any operculi which have passed through the nut openings, from the impact zone. This may be effected by means of physical separation relying in differences in shape and size of the nuts/kernels and any operculi, and the nut shells, such as sieving; by positive or negative air pressure to achieve a winnowing or cyclone effect; a curtaining effect ahead of potential kernel impacts by changing air density or pressure; and changing of the kernel trajectories away from the impact zone, thereby separating the kernels from the impacting nuts.

In particular, the removal of the nut kernels and any operculi from the impact zone may be effected by allowing them to pass through openings in the drum.

The drum sleeve may be foraminous, thereby to effect separation of the kernels and, when present, the operculi, from the shells, with the kernels and any operculi thus passing through the openings in the drum sleeve and being collected as a combined intermediate product while the shells pass axially

along the sleeve to be discharged at one end thereof. Typically, the openings may be sized and shaped to permit nut kernels having a maximum dimension of about 8mm to pass therethrough.

The method may include separating the kernels from the operculi. This separation may include subjecting the combined intermediate product to cycloning, winnowing, air separation, manual sorting, or density separation e.g. in a salt bath, mechanical sorting, or a combination of two or more of these.

The nuts that are subjected to the method of extraction of the invention, may be as harvested i.e. fresh. However, if desired, the nuts may be conditioned by treating them prior to subjecting them to impacts in accordance with the invention, e.g. to facilitate dislodgement of the operculi and/or the kernels inside the shells or to enhance the effect of the impacts. In one embodiment of the invention, the conditioning may include drying the nuts. In another embodiment of the invention, the conditioning may include, singularly or in combination, partially drying the nuts to a predetermined humidity, heating or cooling the nuts to a particular temperature immediately before subjecting them to the impacts according to the invention, or moistening the nuts. In particular, the conditioning may include imbibition, enzyme treatment, acid or alkaline treatment, or any other physical, chemical or biological treatment that is known to increase germination of seeds (kernels) from nuts by facilitating penetration of the germinating seeds through the eyes of the nuts.

According to a second aspect of the invention, there is provided apparatus for extracting nut kernels from nuts, which apparatus includes a drum comprising a foraminous cylindrical sleeve, and having an inlet for introducing nuts into the sleeve, and an outlet through which nut shells can exit the sleeve; drum drive means for driving the drum to rotate; a rotor mounted rotatably and axially within the drum; and rotor drive means for driving the rotor to rotate at a circumferential speed of at least 7.5 m/s.

The openings in the sleeve may be sized and shaped to allow passage therethrough of nut kernels and operculi based on physical differences in shape and size of the nut kernels and operculi on the one hand, and the nut shells on the other hand. In the case of marula nuts, the openings may be oblong or elongated, with a width of about 8mm. Thus, kernels and operculi having one dimension of up to about 8mm will pass through the openings, while nut shells, which have a minimum dimension in all their planes greater than about 8mm, will be unable to pass through the openings.

In particular, the openings may be in the form of gaps or spaces between adjacent ring-like sections of the drum sleeve. The gaps or spaces thus extend circumferentially, i.e. the openings are of elongated form. The openings may be about 8mm wide.

The drum drive means and the rotor drive means may be adapted to drive the drum and the rotor to rotate in the same direction, or in opposite directions.

The rotor may comprise an axle from which protrudes a plurality of prongs.

The prongs may be spaced circumferentially about the axle, as well as longitudinally along the axle. While prongs of differing lengths may be provided with shorter prongs being located closer to the drum nut inlet, and longer prongs being located closer to the drum nut shell outlet, for marula nuts the prongs may be of the same length, typically about 70mm i.e. the prongs may protrude a distance of about 70mm from the axle.

The circumferential speed is thus the circumferential speed of the outermost tips of the prongs.

The prongs may be staggered along the length of the rotor. In particular, the prongs may be arranged to form at least one partial helix along the length of the rotor. Adjacent prongs may be staggered, when the rotor is viewed end on, 1° to 5° relative to each other, e.g. about 2.5° relative to each other. Instead, however, the prongs may be arranged linearly along the axle, i.e. in one or more straight lines along the axle, or even circumferentially, i.e. the

prongs are arranged in groups spaced along the axle, with the prongs in each group being aligned when the rotor is viewed from the side.

More particularly, the rotor drive means may be adapted to drive the rotor at such a speed so that outermost tips of the prongs will move at a speed in excess of 7.5 m/s.

Description of the embodiments of the invention

The invention will now be described in more detail with reference to the accompanying diagrammatic drawings.

In the drawings

Figure 1 shows a three dimensional view of apparatus for extracting marula nut kernels from marula nuts, according to the second aspect of the invention;

Figure 2 shows a similar three dimensional view of the apparatus of Figure 1, with a side panel removed to show the drum of the apparatus;

Figure 3 shows, in part, a three dimensional view of the rotor of the apparatus of Figure 1 ; Figure 4A shows a sectional view through IV-IV, of the rotor of Figure 3;

Figure 4B shows a sectional view similar to that of Figure 4B ₁ but showing two pairs of prongs only;

Figure 5 shows an exploded view of one of the sections of the drum of the apparatus of Figure 1 ; and Figure 6 shows, in part, an exploded view of the rotor and drum of the apparatus of Figure 1.

In the drawings, reference numeral 10 generally indicates apparatus for extracting marula nut kernels from marula nuts, in accordance with the second aspect of the invention.

The apparatus 10 includes a base 12 having legs 14 supporting the base with clearance above the ground. An enclosure, generally indicated by reference

numeral 16, is mounted on the base 12. The enclosure comprises an upper panel 18, side panels 20, 22, and end panels 24, 26.

An opening 28 is provided in the end panel 24 and is closed off with an open ended box 30 which defines a marula nut inlet chute.

The base 12 is provided with an opening (not shown) which is covered by a chute (not shown) defining a collection zone for marula nut kernels and operculi.

An opening is also provided in the end panel 26, at a low level, with this opening defining an outlet through which marula nut shells can be discharged from the apparatus 10.

The apparatus 10 also includes a horizontal drum, generally indicated by reference numeral 32, rotatably mounted within the enclosure 16. The drum 32 is driven to rotate by drum drive means comprising an electric motor 34, a belt 36 passing around a pulley mounted to an axle of the electric motor 34, an axle (not shown) rotatably mounted to the base 12 and provided, at its one end, with a cooling fan 38 housed within a housing 40, a sprocket wheel (not shown) mounted to this axle, another sprocket wheel (not shown) mounted to an end flange (not shown) of the drum 32, and a chain (not shown) passing around the two sprocket wheels.

The drum 32 comprises a sleeve made up of a plurality of sleeve sections, each generally indicated by reference numeral 50. Each sleeve section 50 comprises a cast ring, generally indicated by reference numeral 52.

The ring 52 includes three radially inwardly protruding formations 62, which are also spaced equidistantly apart. Each formation 62 defines a sleeve 64. The sleeves 64 are internally screw threaded. Threaded rods 66 engage the threads of the sleeves 64. By means of suitable sleeve-like spacers or nuts (not shown) on the rods and located between adjacent rings 52, the distances between the rings 52 can be set to a particular gap size for optimal

separation, for a particular nut species, of nut shells from nut kernels during passage through the drum, as described hereunder. For marula nuts, the gap is typically about 8mm.

The outer component 54 also includes a plurality of inwardly directed protrusions 72 which are spaced circumferentially apart.

The rings 52 are relatively thin, so that the gaps defined between adjacent rings are located relatively closely together; this assists in inhibiting crushing of nut kernels.

The apparatus 10 also includes a rotor, generally indicated by reference numeral 80. The rotor 80 is mounted axially within the drum 32, and is driven to rotate by rotor drive means comprising an electric motor 82, a pulley mounted to the output shaft of the motor 82, and a belt 84 interconnecting that pulley and a pulley (not shown) mounted to an axle 86 of the rotor.

The rotor 86 includes a plurality of prongs 90 mounted to a second portion 88 of the axle 86. Each prong 90 is made up of a length of round bar 92 which extends through a transverse passageway 94 in the axle portion 88 and is held in place with a grub screw 96.

The prongs 90 are spaced longitudinally apart along the axle portion 88, with adjacent prongs being spaced equidistantly apart along the rotor. Adjacent prongs 90 are spaced 2.5° apart circumferentially, as indicated most clearly in Figures 3 and 4. The prongs 90 are all of the same length. In another version of the invention (not shown), at least some of the prongs can be of differing lengths.

The helical arrangement of the prongs 90 along the axle assists in moving the nuts along the drum 32 from its inlet end (end panel 24) towards its outlet end (end panel 26). If necessary, the drum 32 can be slanted downwardly (not shown) from its inlet end to its outlet end to assist in passage of nuts along the drum.

Typically, the lengths of round bar 92 that are used are 180 mm. Instead of round bar, flat or angled bar can be used.

The electric motor 82 and dimension of the pulleys associated with it and with the rotor 80 are such that the rotor 80 is driven to rotate at a speed greater than 800rpm, and typically at between 1200 and 3000 rpm for marula nuts.

The following dimensions apply to the apparatus 10:

Effective internal diameter of the drum 32, that is, the internal diameter of the rings - 374mm radius R of the rings 52 - 187mm diameter of the axle portion 88 - 45mm length of round bars 92 used for the prongs 90 -180mm total number of round bars 92 - 30 number of prongs 90 having length L of 68mm - 60 spacing between adjacent prongs 90 when rotor is viewed end on - 2.5° distance between adjacent prongs 90 when rotor is viewed side on - 20 mm speed of outer tips of prongs 90 whose length L is 68mm - 11.3 - 28.3 m/s at 1200 - 3000 rpm

In use, marula nuts enter the drum 32, which is driven by the electric motor 34 to rotate at a speed of 15-30 rpm, through the opening 28. The rotor 80 is driven, by the electric motor 82, to rotate at a speed of 1200 - 3000 rpm. The nuts move along the inside of the drum 80. As the nuts move along the drum 80, they are subjected, in a single continuous operation, to repeated random impacts on striking against the rotating prongs 90, especially the prong tips, as well as on striking the inner surface of the drum shell. The inside of the drum 80 thus defines an impact zone. The protrusions 62 and 72 act to pick up nuts from the bottom of the drum and drop them on the rotating prongs for further impacting thereof. In this fashion, the nuts are automatically subjected to a large number of impacts on all portions of their shells including along their major and minor axes. This causes the operculi of the nuts to 'pop-out' and the nut kernels to pass through the eyes which are thus uncovered. The operculi and nut kernels pass through the drum openings 70 while the empty

nut shells pass along the drum to be discharged at the outlet end of the drum. The operculi and kernels are collected in the chute attached to the base 12 of the apparatus 10.

The Applicant believes that the method of, and apparatus for, extracting marula nut kernels from marula nuts, according to the invention, will provide advantages over existing methods outlined above, such as ease of extraction of the kernels from the shells, ease of separation of the kernels from the empty shells, and ease of separation of the kernels from the operculi.

It is to be appreciated that the invention is not limited to the precise constructional details hereinbefore described with reference to the accompanying drawings.